Polyurethane and preparation method thereof, polishing composite material and preparation method thereof, and polishing pad

Abstract

The embodiment of the invention provides polyurethane and a preparation method thereof, a polishing composite material and a preparation method thereof, and a polishing pad. The polyurethane provided by the embodiment of the invention is prepared from diisocyanate and polyether polyol, wherein the polyether polyol comprises polyether polyol of which the number-average molecular weight is less than or equal to 500g / mol; the number-average molecular weight of the polyurethane is greater than or equal to 18000 g / mol, and the molecular weight distribution index of the polyurethane is 1-3. The polyurethane provided by the embodiment of the invention has relatively high hardness and certain elasticity, and can be used for providing a polishing composite material with relatively high hardness, good compression performance and relatively high uniformity.

Description

Technical Field

[0001] The present application relates to the technical field of polymer materials, and in particular to polyurethane and a preparation method thereof, a composite material for polishing and a preparation method thereof, and a polishing pad. Background Art

[0002] In the semiconductor industry, the surface treatment of wafers is very important. At present, the mainstream technology for wafer surface flattening is chemical mechanical polishing, and the performance of the polishing pad used in the above process is very critical. Polishing pads commonly used in the industry include polyurethane polishing pads, for example, foamed types and non-woven composite types. In the related art, in order to take into account the elasticity and hardness of non-woven polyurethane polishing pads, it is usually dependent on the composite of polyurethane and other resins. In this way, not only the preparation process is complicated, but also the compatibility of different resins with non-woven fabrics needs to be considered. The essence of the above technical problem is the lack of a polyurethane with high hardness and certain elasticity. Summary of the invention

[0003] In view of this, the embodiments of the present application provide polyurethane and preparation method thereof, composite material for polishing and preparation method thereof, and polishing pad. The polyurethane provided in the embodiments of the present application has both high hardness and certain elasticity, and can be used to provide a composite material for polishing with high hardness, good compression performance and high uniformity.

[0004] In a first aspect, an embodiment of the present application provides a polyurethane, wherein the polyurethane is prepared by diisocyanate and polyether polyol, wherein the polyether polyol comprises a polyether polyol having a number average molecular weight of ≤500 g / mol;

[0005] The number average molecular weight of the polyurethane is ≥18000 g / mol, and the molecular weight distribution index of the polyurethane is 1-3.

[0006] The polyurethane provided in the embodiment of the present application has a high number average molecular weight, a narrow molecular weight distribution, good uniformity, and no low molecular weight segment structure affects the mechanical properties of the polyurethane in the polishing composite material, so the polishing composite material polyurethane can have a high polishing removal rate. In addition, the soft segment in the molecular chain of the polishing composite material polyurethane includes a segment structure obtained by reacting a polyether polyol with a number average molecular weight of ≤500g / mol with an isocyanate group, so the molecular segment length of the soft segment in its molecular chain is short, which can effectively improve the rigidity of the polyurethane. Therefore, the above polyurethane can be used to provide a polishing composite material with high hardness, good compression performance and high uniformity.

[0007] A second aspect of the present application provides a method for preparing polyurethane, comprising:

[0008] Mixing diisocyanate, polyether polyol and solvent to obtain a first mixture, and reacting at a first temperature for a first time to obtain a solution containing a first prepolymer; the polyether polyol includes a polyether polyol having a number average molecular weight of ≤500 g / mol;

[0009] Adding a chain extender to the solution containing the first prepolymer to obtain a second mixture, and reacting at a second temperature for a second time to obtain a solution containing the second prepolymer; wherein the chain extender comprises one or more of a diol, a diamine and a diolamine;

[0010] adding diisocyanate to the solution containing the second prepolymer to obtain a third mixture, and reacting for a third time to obtain a solution containing the third prepolymer;

[0011] A capping agent is added to the solution containing the third prepolymer to obtain a fourth mixture, and the mixture is reacted for a fourth time to obtain a solution containing polyurethane; the number average molecular weight of the polyurethane is ≥18000 g / mol, and the molecular weight distribution index of the polyurethane is 1-3.

[0012] The above preparation method decomposes the chain extension reaction in the polyurethane preparation process into multiple steps, which can effectively increase the molecular weight of the final polyurethane and control its molecular weight fraction within a narrow range; in addition, the above multi-step chain extension method can also effectively increase the proportion of the structural unit obtained after the reaction of the chain extender and the diisocyanate in the polyurethane group, so it can effectively increase the proportion of the hard segment in the polyurethane molecular chain and improve the rigidity of the polyurethane molecular chain. The use of polyether polyols with a number average molecular weight of ≤500g / mol can also effectively improve the rigidity of the soft segment in the polyurethane molecular chain, thereby improving the rigidity of the polyurethane molecular chain.

[0013] The third aspect of the embodiment of the present application provides a composite material for polishing, including a polishing layer; the polishing layer includes the aforementioned polyurethane provided in the embodiment of the present application, or includes a polyurethane prepared according to the preparation method of the aforementioned polyurethane provided in the embodiment of the present application. Due to the use of the polyurethane provided in the embodiment of the present application, the polishing layer can have a high hardness, a certain elasticity and a high uniformity.

[0014] The fourth aspect of the embodiment of the present application provides a method for preparing the aforementioned composite material for polishing, comprising:

[0015] The polyurethane solution is prepared by the polyurethane preparation method provided in the second aspect of the embodiment of the present application, and the non-woven fabric is immersed in the polyurethane solution, extruded, and dried to form the polishing layer.

[0016] A fifth aspect of the present application provides a polishing pad, which is made from the composite material for polishing provided in the present application. In some embodiments of the present application, the polishing pad is a chemical mechanical polishing pad. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1A The surface scanning electron microscope (SEM) photograph of the polishing layer prepared in Example 1;

[0018] Figure 1B This is a SEM photograph of the surface of the polishing layer obtained in Example 1;

[0019] Figure 2 This is a surface photograph of a silicon carbide wafer polished by the polishing composite material of Example 1;

[0020] Figure 3 These are photos of a process of polishing a silicon carbide wafer using the polishing composite material of Example 1. DETAILED DESCRIPTION

[0021] The embodiment of the present application provides a polyurethane, wherein the polyurethane is prepared by diisocyanate and polyether polyol, wherein the polyether polyol comprises a polyether polyol having a number average molecular weight of ≤500 g / mol;

[0022] The number average molecular weight of the polyurethane is ≥18000 g / mol, and the molecular weight distribution index of the polyurethane is 1-3.

[0023] In the present application, polyurethane refers to a polymer containing a carbamate group (-NHCOO-) in the molecular structure. It is understandable that the molecular structure of polyurethane includes a soft segment and a hard segment, and the soft segment can give polyurethane a certain elasticity, and the hard segment can give polyurethane hardness. In the present application, matrix-assisted laser desorption flight mass spectrometry (MALDI-TOF) can be used to test polyurethane to characterize the number average molecular weight of the polyether polyol used to prepare polyurethane.

[0024] In the embodiments of the present application, nuclear magnetic resonance (NMR), pyrolysis-gas chromatography-mass spectrometry (PY-GC / MS), infrared, or X-ray fluorescence spectroscopy (XRF) can be used to characterize the chemical composition of the polyurethane. Molecular weight distribution index Wherein, Mw is the weight average molecular weight of polyurethane, and Mn is the number average molecular weight of polyurethane. Gel Permeation Chromatography (GPC) can be used to characterize the number average molecular weight and molecular weight distribution index of polyurethane. Specifically, the molecular weight distribution index of polyurethane can be, for example, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, etc.

[0025] The polyurethane provided in the embodiment of the present application has a high number average molecular weight, and its molecular weight distribution is narrow, and the uniformity is good. There is no low molecular weight substance that affects the mechanical properties of the polyurethane, so the polyurethane can have good mechanical properties. In addition, the soft segment in the polyurethane molecular chain includes a structural unit obtained by reacting a polyether polyol with a number average molecular weight of ≤500g / mol with an isocyanate group, so the molecular segment length of the soft segment in its molecular chain is short, which can effectively improve the rigidity of the polyurethane. The above-mentioned polyurethane can be used to provide a high wear-resistant polishing composite material having high hardness, good compression performance, good resilience, and high uniformity. In addition, due to the above-mentioned properties of the above-mentioned polyurethane, when it is used to prepare a non-woven composite polishing composite material, it is not necessary to introduce other resins to obtain a highly wear-resistant non-woven composite polishing composite material.

[0026] In the embodiments of the present application, the number average molecular weight of the polyether polyol with a number average molecular weight ≤ 500 g / mol may be, but is not limited to, 100 g / mol, 200 g / mol, 300 g / mol, 400 g / mol, 500 g / mol, etc.

[0027] In some embodiments of the present application, the polyether polyol with a number average molecular weight of ≤500 g / mol includes, but is not limited to, one or more of polytetramethylene glycol (PTMG) and its derivatives, polypropylene glycol (PPG) and its derivatives, polyethylene glycol (PEG) and its derivatives. Specifically, the above-mentioned derivatives of PTMG, derivatives of PPG, and derivatives of PEG can be PTMG, PPG, and PEG substituted with substituents, respectively; the above-mentioned substituents are independently selected from amine groups, halogen atoms, etc.

[0028] For the convenience of description, the polyether polyol with a number average molecular weight of ≤500g / mol is referred to as "low molecular weight polyether polyol" hereinafter, and the polyether polyol with a number average molecular weight>500g / mol is referred to as "high molecular weight polyether polyol". In some other embodiments of the present application, the above-mentioned polyether polyol includes the above-mentioned low molecular weight polyether polyol and the high molecular weight polyether polyol, and the mass proportion of the low molecular weight polyether polyol in the polyether polyol is ≥50%. In this way, the average chain length of the soft segment in the molecular structure of the polyurethane can also be controlled to be shorter, and the hardness of the polyurethane can be higher while having a certain elasticity, so that the compression rate of the polishing composite material finally obtained is relatively slightly higher. Specifically, the mass proportion of the above-mentioned low molecular weight polyether polyol in the polyether polyol can be, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc.

[0029] In some embodiments of the present application, diisocyanates include, but are not limited to, one or more of 4,4'-diphenylmethane diisocyanate (4,4'-MDI) or its derivatives, 2,4'-diphenylmethane diisocyanate (2,4'-MDI) or its derivatives, 2,2'-diphenylmethane diisocyanate (2,2'-MDI) or its derivatives, meta-xylylene diisocyanate (XDI) or its derivatives, 1,5-naphthalene diisocyanate (NDI) or its derivatives. In this way, the polyurethane has good processability, which is beneficial to its subsequent application.

[0030] It is understandable that the molecular structure of the polyurethane may also include a molecular chain end active group after the chain extender reacts with the isocyanate. In some embodiments of the present application, the polyurethane includes a polymer of a diisocyanate, a polyether polyol and a chain extender, and the chain extender is selected from a diamine, a small molecule diol amine or a diol. In some specific embodiments, the chain extender is selected from a small molecule diamine, a small molecule diol amine or a small molecule diol, specifically, for example, diethyltoluenediamine, 4,4'-methylenebis(2-chloroaniline), and ethanolamine. In this way, it is beneficial to improve the hardness of the polyurethane. In some specific embodiments, the chain extender is selected from aliphatic small molecule diols, including but not limited to ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, etc. One or more.

[0031] In some embodiments of the present application, polyurethane is obtained by polymerization reaction of diisocyanate, polyether diol and chain extender, and the chain extender is selected from diol and / or diamine, diol amine. In this way, the polyurethane is a thermoplastic polyurethane, which is more conducive to application; for example, it is more conducive to compounding with non-woven fabrics, improving the uniform mixing degree between it and non-woven fabric fibers at the micro interface and the macro interface, thereby facilitating the improvement of the performance of the final polishing composite material; in other words, it can reduce the difficulty of uniformly mixing polyurethane and non-woven fabric fibers at the micro and macro interfaces, reducing the difficulty and cost of production.

[0032] The present application also provides a method for preparing polyurethane, comprising:

[0033] S01, mixing diisocyanate, polyether polyol and solvent to obtain a first mixture, reacting at a first temperature for a first time to obtain a solution containing a first prepolymer; the polyether polyol includes a polyether polyol having a number average molecular weight of ≤500 g / mol;

[0034] S02, adding a chain extender to the solution containing the first prepolymer to obtain a second mixture, reacting at a second temperature for a second time to obtain a solution containing a second prepolymer; the chain extender comprises one or more of a diol, a diamine and a diolamine;

[0035] S03, adding diisocyanate to the solution containing the second prepolymer to obtain a third mixture, and reacting for a third time to obtain a solution containing the third prepolymer;

[0036] S04. Adding a capping agent to the solution containing the third prepolymer to obtain a fourth mixture, and reacting for a fourth time to obtain a solution containing polyurethane; the number average molecular weight of the polyurethane is ≥18000 g / mol, and the molecular weight distribution index of the polyurethane is 1-3.

[0037] In the embodiments of the present application, considering the subsequent application of the polyurethane, the solvent in the solution containing the polyurethane may not be removed first, but the solution containing the polyurethane may be directly applied.

[0038] The above preparation method decomposes the chain extension reaction in the polyurethane preparation process into multiple steps, which can effectively increase the molecular weight of the final polyurethane and control its molecular weight fraction within a narrow range; in addition, the above multi-step chain extension method can also effectively increase the proportion of functional groups in the polyurethane group in the molecular chain after the reaction of the chain extender and the diisocyanate, so it can effectively increase the proportion of hard segments in the polyurethane molecular chain and improve the rigidity of the polyurethane molecular chain. The use of polyether polyols with a number average molecular weight of ≤500g / mol can also effectively improve the rigidity of the soft segments in the polyurethane molecular chain, thereby improving the rigidity of the polyurethane molecular chain. In some embodiments of the present application, the mass proportion of polyether polyols with a number average molecular weight of ≤500g / mol in the polyether polyol is ≥50%.

[0039] In the related art, in order to reduce the reaction barrier and accelerate the polymerization reaction, a catalyst is often introduced into the raw materials for preparing polyurethane. In the preparation method provided in this embodiment, the viscosity of the system during the reaction is more controllable. The polymerization experiment of the above preparation method has good controllability, less by-products, and the product performance is stable and can be repeatedly achieved.

[0040] In some embodiments of the present application, in step S01, the solvent includes but is not limited to N,N-dimethylformamide or N,N-dimethylacetamide.

[0041] In some embodiments of the present application, in step S01, the first temperature is 50°C-100°C, and the first duration is 1h-3h. A suitable reaction temperature is conducive to the reaction and the reaction rate can be controlled within a suitable range, which is conducive to the control of the reaction process and the viscosity of the system. Specifically, the above-mentioned first temperature can be, for example, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc. Specifically, the first duration can be, for example, 1h, 1.5h, 2h, 2.5h, 3h, etc.

[0042] In some embodiments of the present application, in step S01, mixing diisocyanate, polyether polyol and solvent comprises:

[0043] Mix the polyether polyol and the solvent, and add diisocyanate thereto at room temperature to 80°C and in a protective atmosphere. This is conducive to improving the uniformity of the system. Specifically, when diisocyanate is added to the mixture of solvent and polyether polyol, the temperature of the system can be, for example, 25°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, etc. In the embodiments of the present application, room temperature refers to 25±2°C.

[0044] It is understandable that before mixing the diisocyanate, polyether polyol and solvent, the polyether polyol and solvent are subjected to a dehydration treatment, which can be specifically performed by dehydrating the mixture of the polyether polyol and the solvent, using a dehydration method commonly used in the industry, such as keeping the mixture at 100° C. for a certain period of time.

[0045] In some embodiments of the present application, in step S01, in the first mixture, the molar ratio of isocyanate group to hydroxyl group is (1-2): 1. This is beneficial to the control of subsequent reactions, thereby facilitating the preparation of polyurethane with high molecular weight and narrow molecular weight distribution. Specifically, in the first mixture, the molar ratio of isocyanate group to hydroxyl group can be, for example, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, etc.

[0046] In some embodiments of the present application, the solid content of the first mixture is 30%-40%. This is conducive to controlling the viscosity of the system within a suitable range, facilitating the progress and control of the reaction, and thus making it easy to produce polyurethane with a narrow molecular weight distribution. Specifically, the solid content of the first mixture can be, for example, 30%, 32%, 35%, 38%, 40%, etc.

[0047] In some embodiments of the present application, in step S02, in the second mixture, the molar ratio of the isocyanate group to the first reactive group is (0.9-1):1, and the first reactive group includes a hydroxyl group and / or an amine group. Similarly, this is conducive to the preparation of a polyurethane with a higher molecular weight and a narrower molecular weight distribution. Specifically, in the second mixture, the molar ratio of the isocyanate group to the first reactive group can be, for example, 0.9:1, 0.92:1, 0.95:1, 0.98:1, 1:1.

[0048] In some embodiments of the present application, the solid content of the second mixture is 30%-40%. Specifically, the solid content of the second mixture can be, for example, 30%, 32%, 35%, 38%, 40%, etc.

[0049] In some embodiments of the present application, in step S02, the second temperature is 50°C-80°C, and the second duration is 1h-4h. In this way, it is beneficial to obtain a polyurethane with a higher molecular weight and a narrower molecular weight distribution. Specifically, the second temperature can be, for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc., and the second duration can be, for example, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, etc.

[0050] In some embodiments of the present application, in steps S02 to S04, the temperature of the reaction system is controlled to be 50° C.-80° C. during the reaction process. The reaction temperatures of the systems in steps S02, S03, and S04 may be the same or different.

[0051] In some embodiments of the present application, in the third mixture, the molar ratio of the isocyanate group to the second reactive group is (1-1.2): 1, and the second reactive group includes a hydroxyl group and / or an amine group. Specifically, in the third mixture, the molar ratio of the isocyanate group to the second reactive group can be, for example, 1: 1, 1.12: 1, 1.15: 1, 1.18: 1, 1.2: 1, etc. In some embodiments of the present application, the solid content of the third mixture is 30%-35%. Specifically, the solid content of the third mixture can be, for example, 30%, 31%, 32%, 33%, 34%, 35%, etc.

[0052] In some implementations of the present application, in step S03, the third reaction time is 0.5h-3h. Specifically, the third reaction time can be, for example, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, etc.

[0053] In some embodiments of the present application, the end-capping agent is selected from an end-capping agent containing an amine group or a hydroxyl group, and the end-capping agent containing an amine group or a hydroxyl group includes one or more of phenol, p-chlorophenol, ethanol, dibutylamine, and 2-isopropylamine. In some specific embodiments, the end-capping agent is selected from a monofunctional end-capping agent containing a hydroxyl group or an amino group.

[0054] In some embodiments of the present application, in the fourth mixture, the molar ratio of the isocyanate group to the third reactive group is less than 1, and the third reactive group includes a hydroxyl group and / or an amine group, and a group in the capping agent that can react with the isocyanate group. Specifically, the molar ratio of the isocyanate group to the third reactive group can be, for example, 0.9:1, 0.8:1, 0.7:1, 0.6:1, 0.5:1, 0.3:1, etc. In this way, it is not only conducive to the preparation of polyurethane with a higher molecular weight and a narrower molecular weight distribution, but also the content of the isocyanate group in the polyurethane-containing solution finally obtained is very small, which can effectively reduce the risk of the isocyanate group reacting with water during the storage process of the solution, thereby effectively improving the storage stability of the polyurethane-containing solution. In some embodiments of the present application, the solid content of the fourth mixture is 20%-35%. Specifically, the solid content of the fourth mixture can be, for example, 20%, 22%, 25%, 28, 30%, 32%, 35%, etc.

[0055] In the embodiments of the present application, the molar ratio of isocyanate groups to hydroxyl groups in the first mixture, the second mixture, the third mixture and the fourth mixture can be tested by titration; or, the molar ratio of the above functional groups in the system can be tested by infrared spectroscopy, ultraviolet spectroscopy, nuclear magnetic resonance and the like.

[0056] In some embodiments of the present application, in step S04, the fourth reaction time is 0.1h-3h. Specifically, the fourth reaction time can be, for example, 0.1h, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, etc.

[0057] In some specific embodiments, in the first mixture, the molar ratio of isocyanate group to hydroxyl group is (1-2):1; the solid content of the first mixture is 30%-40%; in the second mixture, the molar ratio of isocyanate group to first reactive group is (0.9-1):1; the solid content of the second mixture is 30%-40%; in the third mixture, the molar ratio of isocyanate group to second reactive group is (1-1.2):1; the solid content of the third mixture is 30%-35%; in the fourth mixture, the molar ratio of isocyanate group to third reactive group is less than 1; the solid content of the fourth mixture is 20%-35%. In this way, it is easy to control the number average molecular weight of the final polyurethane within the range of 18000g / mol-40000g / mol.

[0058] In some embodiments of the present application, the viscosity of the polyurethane-containing solution at room temperature is 5000 cP-40000 cP. This is beneficial for subsequent applications, for example, for the preparation of a composite material for polishing.

[0059] Of course, the polyurethane provided in the embodiments of the present application can also be used in other products.

[0060] An embodiment of the present application also provides a composite material for polishing, including a polishing layer; the polishing layer includes the aforementioned polyurethane provided in the embodiment of the present application, or includes a polyurethane prepared according to the preparation method of the aforementioned polyurethane provided in the embodiment of the present application.

[0061] Due to the use of the polyurethane provided in the embodiment of the present application, the polishing layer can have higher hardness, certain elasticity and higher uniformity.

[0062] In the embodiment of the present application, the polishing layer can be a composite layer of polyurethane and non-woven fabric. Due to the use of the polyurethane provided in the embodiment of the present application, it has good compatibility with the non-woven fabric and a high degree of uniform mixing at the microscopic interface and the macroscopic interface, which is conducive to improving the performance of the final polishing composite material; in other words, the difficulty of uniform mixing of the two at the microscopic and macroscopic interfaces is reduced, the process is simple, and the production cost is low.

[0063] In some embodiments of the present application, the polishing layer further has a groove structure. The present application embodiment does not impose any restrictions on the shape, size and distribution of the groove structure, which can be determined according to actual production conditions.

[0064] In some embodiments of the present application, in addition to the polishing layer, the polishing composite material may also have other layer structures. For example, a glue layer, etc. In some embodiments of the present application, the polishing composite material includes a polishing layer and a glue layer stacked, and the glue layer is used to fix the polishing composite material in the polishing device. In the embodiments of the present application, the material and parameters of the glue layer are not limited. Those skilled in the art can make a selection according to actual production conditions.

[0065] In some embodiments of the present application, the polishing layer includes non-woven fabric and polyurethane. In the embodiments of the present application, the parameters and materials of the non-woven fabric are not limited. Any non-woven fabric known in the art that is suitable for composite materials for polishing can be used, and the size parameters of the non-woven fabric are determined according to actual production conditions. In some embodiments of the present application, the material of the non-woven fabric includes but is not limited to one or more of polypropylene, polyester, polyamide, polyacrylonitrile, polyethylene, polyvinyl chloride, and viscose fiber, but is not limited thereto. The material of the non-woven fabric can be any material known in the art that is insoluble in polyurethane solution and polishing liquid.

[0066] In some embodiments of the present application, polyurethane is coated on the surface of the fibers in the non-woven fabric; and the surface and interior of the polishing layer have a porous structure, so that the polishing liquid can be carried and transported.

[0067] In some specific embodiments, the polishing composite material is composed of a glue layer and a polishing layer, and the polishing layer is composed of non-woven fabric and polyurethane. The polishing composite material with the above structure can avoid the problem of uneven polishing caused by reduced interlayer bonding force in the multi-layer structure of the polishing composite material in the related art, and does not contain other resins, and is easy to prepare.

[0068] In some embodiments of the present application, in the polishing layer, the mass proportion of the non-woven fabric is 25%-60%, and the mass proportion of the polyurethane is 40%-75%. Specifically, the mass proportion of the non-woven fabric in the polishing layer can be, for example, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%; the mass proportion of the polyurethane polishing composite material can be, for example, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, etc. By controlling the mass proportions of the two respectively within the above ranges, the hardness of the polishing layer can be controlled within a suitable range, which can achieve a higher material removal rate and a lower risk of scratching the surface of the workpiece to be polished; in addition, during its application, the polishing layer has a strong ability to carry the polishing liquid, a strong ability to store and transport the polishing liquid, and a good polishing effect and high efficiency. In the embodiments of the present application, thermogravimetric analysis (TG) can be used to test the mass proportion of the non-woven fabric and the polyurethane in the polishing layer.

[0069] In some embodiments of the present application, the apparent density of the polishing layer is 0.25 g / cm 3 -0.6g / cm 3 Because the true density of the non-woven fabric and the polishing polyurethane is constant, the apparent density of the polishing layer is controlled within the above range, which can reflect the porosity of the polishing layer from the side. In this way, the polishing layer has a better polishing liquid carrying capacity and transportation capacity. Specifically, the apparent density of the polishing layer can be, for example, 0.25 g / cm 3 , 0.30g / cm 3 , 0.40g / cm 3 , 0.45g / cm 3 , 0.50g / cm 3 , 0.55g / cm 3 , 0.60g / cm 3 In the examples of the present application, the apparent density of the polishing layer can be tested by referring to GB / T24218.1-2009 "Test methods for textile nonwovens - Part 1: Determination of mass per unit area".

[0070] In some embodiments of the present application, the number average molecular weight of the polyurethane is 18000 g / mol-40000 g / mol. In this way, it is also beneficial to control the hardness of the polishing layer to be more appropriate, which is beneficial to improve the higher material removal rate and reduce the risk of scratching the workpiece surface due to high hardness. Specifically, the number average molecular weight of the polyurethane for the polishing layer can be, for example, 18000 g / mol, 20000 g / mol, 22000 g / mol, 25000 g / mol, 28000 g / mol, 30000 g / mol, 32000 g / mol, 35000 g / mol, 38000 g / mol, 40000 g / mol.

[0071] In some embodiments of the present application, the Shore hardness of the polishing layer is 70A-110A. Specifically, the Shore hardness of the polishing layer can be, for example, 70A, 75A, 80A, 85A, 90A, 95A, 100A, 105A, 110A. In the embodiments of the present application, the Shore hardness of the polishing layer can be tested with reference to GB / T2411-2008 "Determination of indentation hardness (Shore hardness) of plastics and hard rubber using a hardness tester".

[0072] In some embodiments of the present application, the compression rate of the polishing layer is 2%-17%. A good compression rate is conducive to the storage and transportation of the polishing liquid, and can also effectively avoid the problem of scratching the surface of the workpiece. Specifically, the compression rate of the polishing layer can be, for example, 2%, 5%, 8%, 10%, 12%, 15%, 17%, etc. In the embodiments of the present application, the compression rate of the polishing layer can be tested with reference to GB / T 24442.1-2009 "Determination of compression properties of textiles Part 1: Constant method".

[0073] In some embodiments of the present application, the water absorption rate of the polishing layer is 80%-400%. In this way, during the application of the composite material for polishing, the polishing layer has a strong ability to carry the polishing liquid. Specifically, the water absorption rate of the polishing layer can be, for example, 80%, 100%, 150%, 200%, 250%, 300%, 350%, 400%. In the embodiment of the present application, the polishing layer can be placed in deionized water and squeezed to absorb water until the weight no longer changes. Water absorption rate = (mass after water absorption - mass before water absorption) / mass before water absorption * 100%.

[0074] In some embodiments of the present application, the surface roughness of the polishing layer is 10 μm-22 μm. In this way, the polishing effect of the polishing layer is better and it is not easy to damage the surface of the workpiece to be polished. Specifically, the surface roughness of the composite material for polishing can be, for example, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, etc. In the embodiment of the present application, a surface roughness meter can be used to test the surface roughness of the polishing layer.

[0075] In some embodiments of the present application, the thickness of the polishing layer is 1.2 mm to 2.3 mm, which is beneficial to its application and has a longer service life for the polishing composite material.

[0076] The present application also provides a method for preparing a composite material for polishing, comprising:

[0077] The polyurethane solution is prepared by the polyurethane preparation method provided in the embodiment of the present application, and the non-woven fabric is immersed in the polyurethane solution, squeezed, and dried to form a polishing layer.

[0078] The preparation method is simple and easy to implement, has high production efficiency, and is suitable for large-scale industrial production.

[0079] In some embodiments of the present application, the non-woven fabric is immersed in the solution containing polyurethane, and the extrusion and drying include:

[0080] The non-woven fabric is placed in a solution containing polyurethane, and is continuously squeezed to allow the solution to fully penetrate the non-woven fabric. Excess solution on the surface of the non-woven fabric is scraped off, and the non-woven fabric is dried to remove the solvent to form a polishing layer.

[0081] In some specific embodiments, after the above-mentioned drying, the polishing layer is further subjected to grinding, groove carving, forming a glue layer on its surface, cutting and other processes to obtain a composite material for polishing.

[0082] In the embodiment of the present application, the non-woven fabric may be a needle-punched non-woven fabric or a spunlace non-woven fabric.

[0083] The present application also provides a polishing pad, which is made by the polishing pad provided in the present application. In some embodiments of the present application, the polishing device is a chemical mechanical polishing pad.

[0084] The polishing pad can be made by cutting the composite material for polishing provided in the embodiment of the present application.

[0085] In some embodiments of the present application, the polishing pad includes a polishing layer and a back adhesive layer, and the polishing layer can be a composite layer of polyurethane and non-woven fabric provided in the embodiments of the present application.

[0086] In some embodiments of the present application, the polishing layer further has a groove structure. The present application embodiment does not impose any restrictions on the shape, size and distribution of the groove structure, which can be determined according to actual production conditions.

[0087] In some embodiments of the present application, in addition to the polishing layer, the polishing pad may also have other layer structures. For example, a glue layer, etc. In some embodiments of the present application, the polishing pad includes a polishing layer and a glue layer arranged in a stacked manner, and the glue layer is used to fix the polishing pad in the polishing device. In the embodiments of the present application, the material and parameters of the glue layer are not limited. Those skilled in the art can make a selection according to actual production conditions.

[0088] It can be understood that the polishing pad is made of the composite material for polishing provided in the embodiment of the present application. The relevant descriptions about the composite material for polishing in the foregoing text are all applicable to the polishing pad provided in the embodiment of the present application and will not be repeated here.

[0089] The technical solution of the present application is further illustrated by multiple embodiments below.

[0090] Example 1

[0091] (1) Mixing polyether polyol (specifically PTMG250 with a number average molecular weight of 250 g / mol) and solvent (specifically N,N-dimethylacetamide, DMF), and removing water; controlling the temperature of the mixed solution to 40° C., adding diisocyanate (specifically 2,4′-MDI) under a protective atmosphere to obtain a first mixture, wherein the solid content of the first mixture is 33%, wherein the molar ratio of isocyanate group to hydroxyl group is 1.03:1. The first mixture is reacted at 50° C. for 1.5 hours to obtain a solution containing a first prepolymer.

[0092] (2) adding a chain extender (specifically ethylene glycol) to the solution containing the first prepolymer to obtain a second mixture; in the second mixture, the molar ratio of isocyanate group to the first reactive group (specifically hydroxyl group) is 0.93:1, and the solid content of the second mixture is 32%; reacting the second mixture at 58° C. for 1 hour to obtain a solution containing the second prepolymer;

[0093] (3) adding diisocyanate (specifically 2,4′-MDI) to the solution containing the second prepolymer to obtain a third mixture; the solid content of the third mixture is 30%, and the molar ratio of isocyanate group to the second active group (specifically hydroxyl group) in the third mixture is 1.01:1; the third mixture is reacted at 64° C. for 0.5 h to obtain a solution containing the third prepolymer;

[0094] (4) adding a blocking agent (specifically phenol) to the solution containing the third prepolymer to obtain a fourth mixture; the solid content of the fourth mixture is 30%, and the molar ratio of the isocyanate group to the third active group (specifically hydroxyl group) in the fourth mixture is 0.95:1; reacting the fourth mixture at 50° C. for 0.5 h to obtain a solution containing polyurethane;

[0095] (5) Immersing a non-woven fabric (specifically, a needle-punched polyester non-woven fabric) in the above-mentioned polyurethane-containing solution, continuously squeezing it, scraping off excess polyurethane-containing solution on its surface, and drying it to obtain a polishing layer; wherein the mass proportion of the non-woven fabric is 40%, and the mass proportion of the polyurethane is 60%.

[0096] Example 2

[0097] (1) Mixing polyether polyol (specifically 80 wt.% of PEG200 with a number average molecular weight of 200 g / mol and 20 wt.% of PTMG3000 with a number average molecular weight of 3000 g / mol) and solvent (specifically DMAC), and removing water; controlling the temperature of the mixed solution to 40° C., adding diisocyanate (specifically 2,4′-MDI) under a protective atmosphere to obtain a first mixture, wherein the solid content of the first mixture is 33%, wherein the molar ratio of isocyanate group to hydroxyl group is 1.05:1. The first mixture is reacted at 80° C. for 1 hour to obtain a solution containing a first prepolymer.

[0098] (2) adding a chain extender (specifically 1,3-propylene glycol) to the solution containing the first prepolymer to obtain a second mixture; in the second mixture, the molar ratio of isocyanate group to the first reactive group (specifically hydroxyl group) is 0.99:1, and the solid content of the second mixture is 33%; reacting the second mixture at 60° C. for 1.5 hours to obtain a solution containing the second prepolymer;

[0099] (3) adding diisocyanate (specifically 2,4′-MDI) to the solution containing the second prepolymer to obtain a third mixture; the solid content of the third mixture is 32%, and the molar ratio of isocyanate group to the second active group (specifically hydroxyl group) in the third mixture is 1.05:1; the third mixture is reacted at 80° C. for 1.5 hours to obtain a solution containing the third prepolymer;

[0100] (4) adding a capping agent (specifically 2-isopropylamine) to the solution containing the third prepolymer to obtain a fourth mixture; the solid content of the fourth mixture is 30%, and the molar ratio of the isocyanate group to the third active group (specifically hydroxyl group and amine group) in the fourth mixture is 0.99:1; reacting the fourth mixture at 55° C. for 3 hours to obtain a solution containing polyurethane;

[0101] (5) Immersing a non-woven fabric (specifically, a needle-punched polyester non-woven fabric) in the above-mentioned polyurethane-containing solution, continuously squeezing it, scraping off excess polyurethane-containing solution on its surface, and drying it to obtain a polishing layer; wherein the mass proportion of the non-woven fabric is 25%, and the mass proportion of the polyurethane is 75%.

[0102] Example 3

[0103] (1) Mix polyether polyol (specifically 70wt.% of polypropylene glycol with a number average molecular weight of 400g / mol and 30wt.% of tetrahydrofuran-propylene oxide copolymer glycol with a number average molecular weight of 1200g / mol) and solvent (specifically DMF), and remove water; control the temperature of the above mixed solution to 25°C, add diisocyanate (specifically 2,4′-MDI) under a protective atmosphere to obtain a first mixture, the solid content of the first mixture is 40%, wherein the molar ratio of isocyanate group to hydroxyl group is 1.2:1. The above first mixture is reacted at 80°C for 2h to obtain a solution containing a first prepolymer.

[0104] (2) adding a chain extender (specifically 1,3-propylene glycol) to the solution containing the first prepolymer to obtain a second mixture; in the second mixture, the molar ratio of isocyanate group to the first reactive group (specifically hydroxyl group) is 0.95:1, and the solid content of the second mixture is 38%; reacting the second mixture at 80° C. for 3 hours to obtain a solution containing the second prepolymer;

[0105] (3) adding diisocyanate (specifically 2,4′-MDI) to the solution containing the second prepolymer to obtain a third mixture; the solid content of the third mixture is 35%, and the molar ratio of isocyanate group to the second active group (specifically hydroxyl group) in the third mixture is 1.1:1; the third mixture is reacted at 75° C. for 2 hours to obtain a solution containing the third prepolymer;

[0106] (4) adding a blocking agent (specifically p-chlorophenol) to the solution containing the third prepolymer to obtain a fourth mixture; the solid content of the fourth mixture is 32%, and the molar ratio of the isocyanate group to the third active group (specifically hydroxyl group) in the fourth mixture is 0.95:1; reacting the fourth mixture at 60° C. for 2 hours to obtain a solution containing polyurethane;

[0107] (5) Immersing a non-woven fabric (specifically, a needle-punched polyester non-woven fabric) in the above-mentioned polyurethane-containing solution, continuously squeezing it, scraping off excess polyurethane-containing solution on its surface, and drying it to obtain a polishing layer; wherein the mass proportion of the non-woven fabric is 40%, and the mass proportion of the polyurethane is 60%.

[0108] Example 4

[0109] (1) Mix polyether polyol (specifically 60wt.% of polyethylene glycol with a number average molecular weight of 200g / mol and 40wt.% of tetrahydrofuran-propylene oxide copolymer with a number average molecular weight of 1100g / mol) and solvent (specifically N,N-dimethylacetamide, DMF), and remove water; control the temperature of the above mixed solution to 70°C, add diisocyanate (specifically 4,4′-MDI) under a protective atmosphere to obtain a first mixture, the solid content of the first mixture is 40%, wherein the molar ratio of isocyanate group to hydroxyl group is 1.3:1. The above first mixture is reacted at 70°C for 3h to obtain a solution containing a first prepolymer.

[0110] (2) adding a chain extender (specifically 1,6-hexanediol) to the solution containing the first prepolymer to obtain a second mixture; in the second mixture, the molar ratio of isocyanate group to the first reactive group (specifically hydroxyl group) is 0.98:1, and the solid content of the second mixture is 31%; reacting the second mixture at 75° C. for 4 hours to obtain a solution containing the second prepolymer;

[0111] (3) adding diisocyanate (specifically 4,4′-MDI) to the solution containing the second prepolymer to obtain a third mixture; the solid content of the third mixture is 29%, and the molar ratio of isocyanate group to the second active group (specifically hydroxyl group) in the third mixture is 1.1:1; reacting the third mixture at 80° C. for 3 hours to obtain a solution containing the third prepolymer;

[0112] (4) adding a blocking agent (specifically phenol) to the solution containing the third prepolymer to obtain a fourth mixture; the solid content of the fourth mixture is 27%, and the molar ratio of the isocyanate group to the third active group (specifically hydroxyl group) in the fourth mixture is 0.95:1; reacting the fourth mixture at 80° C. for 1.5 hours to obtain a solution containing polyurethane;

[0113] (5) Immersing a non-woven fabric (specifically, a needle-punched polyester non-woven fabric) in the above-mentioned polyurethane-containing solution, continuously squeezing it, scraping off excess polyurethane-containing solution on its surface, and drying it to obtain a polishing layer; wherein the mass proportion of the non-woven fabric is 45%, and the mass proportion of the polyurethane is 55%.

[0114] Example 5

[0115] (1) Mixing polyether polyol (specifically 50wt.% of polytetramethylene glycol with a number average molecular weight of 250g / mol and 50wt.% of polytetramethylene glycol with a number average molecular weight of 650g / mol) and solvent (specifically N,N-dimethylacetamide, DMF), and removing water; controlling the temperature of the above-mentioned mixed solution to 50°C, adding diisocyanate (specifically 2,4′-MDI and 4,4′-MDI) under a protective atmosphere to obtain a first mixture, the solid content of the first mixture is 35%, wherein the molar ratio of isocyanate group to hydroxyl group is 1.08:1. The above-mentioned first mixture is reacted at 60°C for 2.5h to obtain a solution containing a first prepolymer.

[0116] (2) adding a chain extender (specifically 1,4-butanediol) to the solution containing the first prepolymer to obtain a second mixture; in the second mixture, the molar ratio of isocyanate group to the first reactive group (specifically hydroxyl group) is 0.97:1, and the solid content of the second mixture is 32%; reacting the second mixture at 55° C. for 2 hours to obtain a solution containing the second prepolymer;

[0117] (3) adding diisocyanate (specifically 2,4′-MDI and 4,4′-MDI) to the solution containing the second prepolymer to obtain a third mixture; the solid content of the third mixture is 31%, and the molar ratio of isocyanate group to the second active group (specifically hydroxyl group) in the third mixture is 1.2:1; the third mixture is reacted at 64° C. for 1 hour to obtain a solution containing the third prepolymer;

[0118] (4) adding a capping agent (specifically ethanol) to the solution containing the third prepolymer to obtain a fourth mixture; the solid content of the fourth mixture is 30%, and the molar ratio of the isocyanate group to the third active group (specifically hydroxyl group) in the fourth mixture is 0.97:1; reacting the fourth mixture at 64° C. for 0.2 h to obtain a solution containing polyurethane;

[0119] (5) Immersing a non-woven fabric (specifically, a needle-punched polyester non-woven fabric) in the above-mentioned polyurethane-containing solution, continuously squeezing it, scraping off excess polyurethane-containing solution on its surface, and drying it to obtain a polishing layer; wherein the mass proportion of the non-woven fabric is 32%, and the mass proportion of the polyurethane is 68%.

[0120] Example 6

[0121] (1) Mix polyether polyol (specifically 65wt.% of polypropylene glycol with a number average molecular weight of 400g / mol and 35wt.% of polytetramethylene glycol with a number average molecular weight of 1000g / mol) and solvent (specifically N,N-dimethylacetamide, DMF), and remove water; control the temperature of the above mixed solution to 40°C, add diisocyanate (specifically 2,4′-MDI and 4,4′-MDI) under a protective atmosphere to obtain a first mixture, the solid content of the first mixture is 33%, wherein the molar ratio of isocyanate group to hydroxyl group is 1.44:1. The above first mixture is reacted at 100°C for 1.5h to obtain a solution containing a first prepolymer.

[0122] (2) adding a chain extender (specifically ethylene glycol) to the solution containing the first prepolymer to obtain a second mixture; in the second mixture, the molar ratio of isocyanate group to the first reactive group (specifically hydroxyl group) is 1:1, and the solid content of the second mixture is 32%; reacting the second mixture at 64° C. for 1 hour to obtain a solution containing the second prepolymer;

[0123] (3) adding diisocyanate (specifically 2,4′-MDI and 4,4′-MDI) to the solution containing the second prepolymer to obtain a third mixture; the solid content of the third mixture is 31%, and the molar ratio of isocyanate group to the second active group (specifically hydroxyl group) in the third mixture is 1.06:1; the third mixture is reacted at 60° C. for 1 hour to obtain a solution containing the third prepolymer;

[0124] (4) adding a capping agent (specifically ethanol) to the solution containing the third prepolymer to obtain a fourth mixture; the solid content of the fourth mixture is 20%, and the molar ratio of the isocyanate group to the third active group (specifically hydroxyl group) in the fourth mixture is 0.9:1; reacting the fourth mixture at 64° C. for 1 hour to obtain a solution containing polyurethane;

[0125] (5) Immersing a non-woven fabric (specifically, a needle-punched polyester non-woven fabric) in the above-mentioned polyurethane-containing solution, continuously squeezing it, scraping off excess polyurethane-containing solution on its surface, and drying it to obtain a polishing layer; wherein the mass proportion of the non-woven fabric is 40%, and the mass proportion of the polyurethane is 60%.

[0126] In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

[0127] Comparative Example 1

[0128] The difference from Example 1 is that step (3) and step (4) are not performed, and a solution containing polyurethane is obtained after step (2) is completed; a non-woven fabric (specifically a needle-punched polyester non-woven fabric, the same as in Example 1) is immersed in the product obtained in the above step (2), continuously squeezed, excess polyurethane solution on its surface is scraped off, and dried to obtain a polishing layer; wherein the mass proportion of the non-woven fabric is 45%, and the mass proportion of the polyurethane is 55%.

[0129] Comparative Example 2

[0130] The difference from Example 1 is that in step (1), the polyether polyol is polytetrahydrofuran ether diol with a number average molecular weight of 2000 g / mol.

[0131] Parameter Characterization

[0132] The number average molecular weight and molecular weight distribution index of the polyurethanes prepared in various examples and comparative examples were tested by GPC, and the results are summarized in Table 1.

[0133] Morphology test

[0134] The surface and cross section of the polishing layer prepared in each embodiment and comparative example were observed under SEM. The surface SEM photos of the polishing layer of Example 1 are shown in Figure 1A and Figure 1B .

[0135] Performance Testing

[0136] (1) The room temperature viscosity of the polyurethane-containing solutions (or, polyurethane-containing solutions) of each embodiment and comparative example was tested using a cone-plate rotational viscometer, and the results are summarized in Table 2; and the solutions were stored at room temperature and the changes were observed, and the results are summarized in Table 2.

[0137] (2) Referring to GB / T24218.1-2009 “Test methods for textile nonwovens - Part 1: Determination of mass per unit area”, the apparent density of the polishing layer was tested; specifically, 5 samples with a size of 300 mm*300 mm were cut from the polishing layer of each embodiment and comparative example, and the apparent density was calculated by measuring the weight per unit area and the thickness, and the average value was obtained; the results are summarized in Table 3.

[0138] (3) The Shore hardness of the polishing layer of each embodiment and comparative example was tested with reference to GB / T2411-2008 "Determination of indentation hardness (Shore hardness) of plastics and hard rubber using a hardness tester". Specifically, multiple polishing layer samples were stacked to make the test thickness greater than 4 mm, and the Shore hardness of five locations was tested using a Shore hardness tester and the average value was taken. The results are summarized in Table 3.

[0139] (4) The compression rate and rebound rate of the polishing layer of each embodiment and comparative example were tested with reference to GB / T 24442.1-2009 “Determination of compression properties of textiles Part 1: Constant method”. The results are summarized in Table 3.

[0140] (5) The polishing layer of each embodiment and comparative example was placed in deionized water and squeezed to absorb water until the weight no longer changed. Water absorption rate = (mass before water absorption - mass after water absorption) / mass before water absorption * 100%. The results are summarized in Table 3.

[0141] Table 1

[0142]

[0143]

[0144] Table 2

[0145] Case Viscosity(cP) Storage conditions Example 1 8000 Stablize Example 2 25600 Stablize Example 3 18400 Stablize Example 4 6582 Stablize Example 5 10120 Stablize Example 6 9481 Stablize Comparative Example 1 3563 Stablize Comparative Example 2 14000 Stablize

[0146] Table 3

[0147]

[0148] Wafer polishing test

[0149] The polishing layer prepared in each embodiment and comparative example is subjected to surface grinding treatment, groove engraving, and a glue layer is formed on one side of the surface to obtain a polishing composite material, and the thickness of the polishing layer in each polishing composite material is controlled to be consistent. The polishing composite materials prepared in each embodiment and comparative example are cut into polishing pads of appropriate sizes and respectively installed in polishing equipment. After continuously polishing the carbon surface or silicon surface of the silicon carbide wafer for 2 hours, the thickness removal per unit time of each surface of the wafer is tested, which is the removal rate. Figure 2 This is a surface photograph of a silicon carbide wafer polished by the polishing composite material of Example 1; Figure 3 These are photos of a process of polishing a silicon carbide wafer using the polishing composite material of Example 1.

[0150] Wafer surface test: A three-dimensional white light profilometer was used to test each surface of the wafer before and after polishing. The results are summarized in Table 4.

[0151] Table 4

[0152]

[0153] Combining the results of Tables 1 to 4, it can be seen that the polyurethane-containing solution provided in the embodiment of the present application has stable properties and good storage performance, and the polishing composite material prepared therefrom has good comprehensive performance, which can be specifically manifested as high material removal rate, good rebound rate, and no damage to the wafer. In addition, the high material removal rate and good rebound rate also indicate that the polyurethane provided in the embodiment of the present application has both high hardness and certain elasticity.

[0154] The above is an exemplary embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present application. These improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A polyurethane, characterized in that The polyurethane is prepared by diisocyanate and polyether polyol, and the polyether polyol includes a polyether polyol with a number average molecular weight of ≤500 g / mol; The number average molecular weight of the polyurethane is ≥18000 g / mol, and the molecular weight distribution index of the polyurethane is 1-3.

2. The polyurethane according to claim 1, characterized in that The mass proportion of the polyether polyol having a number average molecular weight of ≤500 g / mol in the polyether polyol is ≥50%.

3. The polyurethane according to claim 1 or 2, characterized in that The polyurethane is obtained by polymerization reaction of diisocyanate, polyether diol and chain extender, and the chain extender is selected from one or more of diol, diamine and diol amine.

4. A method for preparing polyurethane, characterized in that: include: Mixing diisocyanate, polyether polyol and solvent to obtain a first mixture, and reacting at a first temperature for a first time to obtain a solution containing a first prepolymer; the polyether polyol includes a polyether polyol having a number average molecular weight of ≤500 g / mol; Adding a chain extender to the solution containing the first prepolymer to obtain a second mixture, and reacting at a second temperature for a second time to obtain a solution containing the second prepolymer; wherein the chain extender comprises one or more of a diol, a diamine and a diolamine; adding diisocyanate to the solution containing the second prepolymer to obtain a third mixture, and reacting for a third time to obtain a solution containing the third prepolymer; A capping agent is added to the solution containing the third prepolymer to obtain a fourth mixture, and the mixture is reacted for a fourth time to obtain a solution containing polyurethane; the number average molecular weight of the polyurethane is ≥18000 g / mol, and the molecular weight distribution index of the polyurethane is 1-3.

5. The preparation method according to claim 4, characterized in that: In the first mixture, the molar ratio of isocyanate group to hydroxyl group is (1-2):1; the solid content of the first mixture is 30%-40%; and / or, in the second mixture, the molar ratio of isocyanate group to first reactive group is (0.9-1):1, the first reactive group includes hydroxyl group and / or amine group; the solid content of the second mixture is 30%-40%; And / or, in the third mixture, the molar ratio of isocyanate group to second reactive group is (1-1.2):1, and the second reactive group includes hydroxyl group and / or amine group; the solid content of the third mixture is 30%-35%; And / or, in the fourth mixture, the molar ratio of isocyanate group to the third reactive group is less than 1, the third reactive group includes hydroxyl group and / or amine group, and the group in the capping agent that can react with isocyanate group; the solid content of the fourth mixture is 20%-35%.

6. The preparation method according to claim 4 or 5, characterized in that: The mixed diisocyanate, polyether polyol and solvent include: The polyether polyol and the solvent are mixed, and the diisocyanate is added thereto at 10° C. to 80° C.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The first temperature is 50°C-100°C, and the first time is 1h-3h; And / or, the second temperature is 50°C-80°C, and the second time period is 1h-4h; And / or, the third duration is 0.5h-3h; And / or, the fourth duration is 0.1h-3h.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The solvent includes N,N-dimethylformamide or N,N-dimethylacetamide; And / or, the end-capping agent is selected from an end-capping agent containing an amino group or a hydroxyl group, and the end-capping agent containing an amino group or a hydroxyl group includes one or more of phenol, p-chlorophenol, ethanol, dibutylamine, and 2-isopropylamine.

9. A composite material for polishing, characterized in that: Comprising a polishing layer; the polishing layer comprises the polyurethane as described in any one of claims 1-3, or comprises the polyurethane prepared by the preparation method of the polyurethane as described in any one of claims 4-8.

10. The composite material for polishing according to claim 9, characterized in that: The polishing layer also includes non-woven fabric; in the polishing layer, the mass proportion of the non-woven fabric is 25%-60%, and the mass proportion of the polyurethane is 40%-75%.

11. The composite material for polishing according to claim 10, characterized in that: The polyurethane is coated on the surface of the fibers in the non-woven fabric; the surface and the interior of the polishing layer have a pore structure.

12. The composite material for polishing according to claim 10 or 11, characterized in that: The number average molecular weight of the polyurethane is 18000 g / mol-40000 g / mol.

13. The composite material for polishing according to any one of claims 9 to 12, characterized in that: The Shore hardness of the polishing layer is 70A-100A; and / or the compression rate of the polishing layer is 2%-17%; And / or, the apparent density of the polishing layer is 0.25 g / cm 3 -0.6g / cm 3 ; And / or, the surface roughness of the polishing layer is 10 μm-22 μm; and / or, the water absorption rate of the polishing layer is 80%-400%; And / or, the polishing layer has a thickness of 1.2 mm to 2.3 mm.

14. A method for preparing the composite material for polishing according to any one of claims 9 to 13, characterized in that: include: The polyurethane-containing solution is prepared by the preparation method according to any one of claims 4 to 8, the non-woven fabric is immersed in the polyurethane-containing solution, extruded, and dried to form the polishing layer.

15. A polishing pad, characterized in that: The polishing composite material is prepared according to any one of claims 9 to 13.

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