Secondary foaming polyurethane polishing pad as well as preparation method and application thereof
The secondary foaming process forms a uniform cell structure, which solves the problem of low porosity in polyurethane polishing pads, improves polishing efficiency and quality, and is suitable for polishing mobile phone glass covers.
Patent Information
- Application Number
- CN202511939285.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-22
- Publication Date
- 2026-03-20
AI Technical Summary
In the prior art, polyurethane polishing pads have a low open porosity and an unsatisfactory pore structure, resulting in insufficient storage and distribution of polishing fluid in the pad, which affects polishing efficiency and surface quality.
A two-stage foaming process is adopted, which involves mixing isocyanate prepolymer, polishing abrasive, N,N-dimethylformamide solution and foaming additives, allowing it to stand for foaming, and then heating it for a second foaming process to form a uniform cell structure, thereby improving the open cell ratio and oxygen content.
It improves the workpiece removal rate during the polishing process, reduces surface scratches, and enhances polishing efficiency and quality. It is suitable for polishing various mobile phone glass covers.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to the field of grinding and polishing technology, and in particular to a secondary foamed polyurethane polishing pad, its preparation method, and its application. Background Technology
[0002] Mobile phone glass covers play a crucial role in the protection and touch control of electronic devices such as smartphones and tablets, and their surface quality directly affects the product's display effect and user experience. To achieve consistent thickness, surface smoothness, and gloss in glass covers, chemical mechanical polishing (CMP) technology is widely used. CMP is a precision machining method that combines chemical etching and mechanical abrasion, enabling the achievement of high flatness and low surface roughness while ensuring material removal rates.
[0003] In the CMP process, polyurethane polishing pads are a key consumable, serving to support the polishing slurry, uniformly transmit grinding pressure, and regulate polishing speed. Currently, most polyurethane polishing pads used for polishing mobile phone glass covers employ traditional molding foaming technology. This process is typically a one-step foaming method, where foaming is completed in a mold in a single step, resulting in a block-shaped foam. Subsequently, the block-shaped foam needs to be cut into the required sheet-shaped polishing pads using a slicing process to fit glass substrates of different sizes and shapes.
[0004] However, traditional molding foaming processes have several limitations. First, because it is difficult to precisely control conditions such as temperature and pressure during the foaming process, significant differences in the physical properties of the upper and lower layers of the polishing pad, such as inconsistent hardness and elastic modulus, occur, affecting the uniformity and stability of the polishing process. Second, polishing pads produced by traditional processes have a low open-cell ratio and an imperfect pore structure, resulting in insufficient storage and distribution of polishing fluid within the pad, affecting polishing efficiency and surface quality. Furthermore, the blocky foam is prone to edge burrs or structural damage during cutting, further reducing the lifespan of the polishing pad and the polishing effect.
[0005] Therefore, there is an urgent need to develop a new polyurethane polishing pad preparation process to improve its structural uniformity, increase porosity and liquid storage capacity, thereby improving the stability, removal rate and surface quality of the polishing process, and meeting the higher requirements of high-end mobile phone glass cover plates for precision machining. Summary of the Invention
[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a secondary foamed polyurethane polishing pad, its preparation method, and its application. The polyurethane polishing pad described in this application solves the problems of low open-cell ratio and unsatisfactory pore structure in existing polyurethane polishing pads, which result in insufficient storage and distribution of polishing fluid within the pad, affecting polishing efficiency and surface quality.
[0007] To achieve the above and other related objectives, the present invention is obtained through the following technical solution.
[0008] The first aspect of this invention discloses a method for preparing a secondary foamed polyurethane polishing pad, the method comprising the following steps:
[0009] 1) Based on the total mass of the raw materials of the polishing pad, the raw materials include 50-65 wt% isocyanate prepolymer, 15-30 wt% polishing abrasive, 10-20 wt% N,N-dimethylformamide solution containing 3,3'-dichloro-4,4'-diaminodiphenylmethane, and 2-9 wt% foaming additive. The raw materials are mixed and coated, and then allowed to stand to foam to obtain a preliminary foamed polishing pad.
[0010] 2) Heat the initially foamed polishing pad to perform secondary foaming, thereby obtaining the polyurethane polishing pad;
[0011] Based on the total mass of the isocyanate prepolymer, the isocyanate prepolymer contains 7-12 wt% isocyanate groups and has a weight-average molecular weight of 900-1300 g / mol; the mass ratio of 3,3'-dichloro-4,4'-diaminodiphenylmethane to N,N-dimethylformamide is (0.5-1):1; the foaming additive includes sodium bicarbonate and water.
[0012] In this application, N,N-dimethylformamide can form strong intermolecular hydrogen bonds with the amine groups on the 3,3'-dichloro-4,4'-diaminodiphenylmethane molecule through its highly polar carbonyl group, making 3,3'-dichloro-4,4'-diaminodiphenylmethane liquid at room temperature. After being dissolved by N,N-dimethylformamide, the amine groups of 3,3'-dichloro-4,4'-diaminodiphenylmethane are encapsulated, resulting in decreased reactivity, slower viscosity increase, and sufficient operating time. Furthermore, the slow and stable reaction leads to a more uniform pore structure and more consistent physical properties.
[0013] Preferably, the isocyanate prepolymer is selected from one or more of toluene diisocyanate prepolymer, diphenylmethane diisocyanate prepolymer, terephthalic diisocyanate prepolymer, and dimethylbiphenyl diisocyanate prepolymer.
[0014] More preferably, the isocyanate prepolymer is a toluene diisocyanate prepolymer.
[0015] In one specific embodiment, the isocyanate prepolymer is a toluene diisocyanate prepolymer, wherein the isocyanate group content is 9.6-9.8 wt% and the weight-average molecular weight is 1100 g / mol.
[0016] Preferably, the polishing abrasive is selected from one or more of cerium oxide, zirconium oxide, aluminum oxide, and barium sulfate.
[0017] Preferably, the particle size of the polishing abrasive is 1.5 to 3.5 μm.
[0018] Preferably, the D of the polishing abrasive 50 The thickness is 2.0–2.5 μm, D 100 It is 3.0–3.5 μm.
[0019] Preferably, the sodium bicarbonate content is 2-4 wt% based on the total mass of the raw materials.
[0020] Preferably, the water content is 0.15 to 0.2 wt% based on the total mass of the raw materials.
[0021] Preferably, the foaming additive further includes one or more of 1,4-butanediol, a cell opener, a foam stabilizer, and a catalyst.
[0022] More preferably, the content of 1,4-butanediol is 3 to 4 wt% based on the total mass of the raw materials.
[0023] More preferably, the pore-opening agent is selected from one or more of the following: polyoxyolefin-polysiloxane copolymer, polypropylene-ethylene oxide copolymer, polyethylene glycol, polypropylene glycol, paraffin oil, polybutadiene, dimethyl silicone oil, and polyether-modified siloxane.
[0024] In one specific embodiment, the pore-opening agent is a polyoxyolefin-polysiloxane copolymer, specifically O-501 manufactured by Evonik Specialty Chemicals AG, Germany.
[0025] More preferably, the content of the pore-opening agent is 0.3 to 0.5 wt% based on the total mass of the raw materials.
[0026] More preferably, the foam stabilizer is selected from one or more of non-hydrolyzable silicone surfactants and silicone surfactants.
[0027] In one specific embodiment, the foam stabilizer is a non-hydrolyzable silicone surfactant, specifically manufactured by Momentive, Inc. silicone L-1500.
[0028] More preferably, the content of the foam stabilizer is 0.3 to 0.5 wt% based on the total mass of the raw materials.
[0029] More preferably, the catalyst is selected from one or more of triethylenediamine, N,N,N',N”,N”-pentamethyldiethylenetriamine, dimethylethanolamine, dimethylaminoethyl ether, tetramethylethylenediamine, stannous octoate, dibutyltin dilaurate, and N,N-dimethylethanolamine.
[0030] In one specific embodiment, the catalyst is triethylenediamine, specifically A33, which is a 33% triethylenediamine solution prepared by dissolving solid triethylenediamine in a diol such as dipropylene glycol (CAS No.: 280-57-9, molecular formula C6H). 12 N2).
[0031] More preferably, the content of the catalyst is 0.3 to 0.5 wt% based on the total mass of the raw materials.
[0032] Preferably, in step 1), the mixing temperature is 70–80°C.
[0033] Preferably, before step 1), a step of preheating the isocyanate prepolymer is also included.
[0034] More preferably, the preheating temperature is 50–70°C.
[0035] More preferably, the preheating time is 10 to 14 hours.
[0036] Preferably, in step 1), the coating thickness is 1 to 6 mm.
[0037] Preferably, in step 1), the coating tool is a coating head.
[0038] Preferably, in step 1), the coating plate is a polytetrafluoroethylene plate.
[0039] Preferably, in step 1), the time for standing foaming is 3 to 15 minutes.
[0040] Preferably, in step 2), the heating includes a first stage and a second stage, wherein the temperature of the first stage is 50-70°C and the time is 3-5 hours; and the temperature of the second stage is 100-120°C and the time is 16-24 hours.
[0041] Preferably, step 2) is followed by a post-processing step, which includes surface polishing.
[0042] The second aspect of this application also discloses a polyurethane polishing pad prepared according to the above method.
[0043] Preferably, the thickness of the polishing pad is 1.5 to 4.5 mm.
[0044] Preferably, the moisture content of the polishing pad is 19.00–26.31 mL / cm³. 3 .
[0045] The capacity mentioned in this application refers to the amount of polishing fluid that a unit volume polishing pad can hold.
[0046] Preferably, the porosity of the polishing pad is 53-60%.
[0047] The porosity refers to the percentage of the total volume of the polishing pad material that is interconnected and communicates with the external environment. A high porosity results in better chip removal capability, higher polishing fluid transfer efficiency, and longer pad life.
[0048] Preferably, the pore size of the polishing pad is 40–200 μm.
[0049] The third aspect of this application discloses the use of a polyurethane polishing pad as described above in polishing glass plates.
[0050] Preferably, the glass plate is a glass cover for an electronic device.
[0051] Compared with the prior art, the present invention has the following beneficial effects:
[0052] 1) In the preparation method of the polishing pad described in this application, N,N-dimethylformamide makes 3,3'-dichloro-4,4'-diaminodiphenylmethane liquid at room temperature. Compared with molten 3,3'-dichloro-4,4'-diaminodiphenylmethane, the reactivity decreases and the viscosity increases slowly, providing sufficient operating time; and the reaction proceeds slowly and steadily, resulting in a more uniform cell structure and more consistent physical properties.
[0053] 2) The polishing pad preparation method described in this application involves secondary foaming, which increases the porosity and moisture content of the polishing pad, significantly improving the workpiece removal rate during the polishing process, while reducing surface scratches, improving polishing efficiency, and reducing defects.
[0054] 3) The polishing pad preparation method described in this application makes the number of bubbles and the open area ratio of the polishing pad suitable for polishing various mobile phone glass covers.
[0055] 4) The preparation method of the polishing pad described in this application is highly operable and has good application results, providing a basis for further development of high polishing efficiency.
[0056] The high efficiency and high stability of the material provide new ideas and have great research significance and promising prospects. Attached Figure Description
[0057] Figure 1 The figures shown are viscosity test curves for Embodiment 2 and Comparative Example 2 of this application.
[0058] Figure 2 The diagram shows a density comparison between Example 1 and Comparative Examples 1-2 of this application.
[0059] Figure 3 The image shown is a surface SEM image of the polishing pad prepared in Example 1 of this application.
[0060] Figure 4 The image shown is a surface SEM image of the polishing pad prepared in Comparative Example 1 of this application.
[0061] Figure 5 The image shows a comparison of the removal rates during the polishing process of Example 1 of this application, Comparative Example 1, and competing products.
[0062] Figure 6 The diagram shows a comparison of the open area ratios of Embodiment 1 and Comparative Example 1 of this application. Detailed Implementation
[0063] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.
[0064] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.
[0065] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.
[0066] This application addresses the technical problem in existing polyurethane polishing pads where the open-cell ratio is low and the pore structure is not ideal, resulting in insufficient storage and distribution of polishing fluid within the pad, thus affecting polishing efficiency and surface quality. The applicant provides a secondary foamed polyurethane polishing pad, its preparation method, and its application. The preparation method of the polyurethane polishing pad described in this application provides sufficient operating time, allowing the foaming reaction to proceed slowly and steadily, resulting in a more uniform pore structure and more consistent physical properties. The secondary foaming process increases the open-cell ratio and fluid retention capacity of the polishing pad, significantly improving the workpiece removal rate during polishing, while simultaneously reducing surface scratches, increasing polishing efficiency, and reducing defects.
[0067] Specifically, this invention provides a specific polyurethane polishing pad and its preparation method, wherein the preparation method includes the following steps: 1) Based on the total mass of the raw materials of the polishing pad, the raw materials include 50-65 wt% isocyanate prepolymer, 15-30 wt% polishing abrasive, 10-20 wt% N,N-dimethylformamide solution of 3,3'-dichloro-4,4'-diaminodiphenylmethane, and 2-9 wt% foaming additive; the raw materials are mixed and coated, and then allowed to stand for foaming. 1) Foaming to obtain a preliminary foamed polishing pad; 2) Heating the preliminary foamed polishing pad for secondary foaming to obtain the polyurethane polishing pad; Based on the total mass of the isocyanate prepolymer, the isocyanate group content in the isocyanate prepolymer is 7-12 wt%, and the weight average molecular weight is 900-1300 g / mol; The mass ratio of 3,3'-dichloro-4,4'-diaminodiphenylmethane to N,N-dimethylformamide is (0.5-1):1; The foaming additive includes sodium bicarbonate and water.
[0068] 3,3'-Dichloro-4,4'-diaminodiphenylmethane, as a chain extender and crosslinking agent, can rapidly react with the isocyanate groups in the prepolymer, linking the prepolymer molecular chains together and rapidly increasing the molecular weight. Simultaneously, it forms a three-dimensional network structure, stabilizing the bubbles generated during the foaming reaction and preventing cell collapse or merging, ultimately resulting in a uniform and dense cell structure. However, 3,3'-dichloro-4,4'-diaminodiphenylmethane is a solid particle that requires heating and melting (melting point around 120℃) before use. Maintaining this molten state during use results in a very short gel and foaming reaction time for polyurethane, causing the viscosity to rise exponentially within a short period. This makes thorough mixing difficult, leading to uneven and irregular cell structures, potentially resulting in macropores, cross-cells, and closed cells. Furthermore, 3,3'-dichloro-4,4'-diaminodiphenylmethane is highly susceptible to oxidation under long-term high-temperature environments, leading to a significant decrease in the mechanical strength, hardness, and wear resistance of the final product.
[0069] In this application, N,N-dimethylformamide can form strong intermolecular hydrogen bonds with the amine groups on the 3,3'-dichloro-4,4'-diaminodiphenylmethane molecule through its highly polar carbonyl group, making 3,3'-dichloro-4,4'-diaminodiphenylmethane liquid at room temperature. After being dissolved by N,N-dimethylformamide, the amine groups of 3,3'-dichloro-4,4'-diaminodiphenylmethane are encapsulated, resulting in decreased reactivity, slower viscosity increase, and sufficient operating time. Furthermore, the slow and stable reaction leads to a more uniform pore structure and more consistent physical properties.
[0070] The content of each raw material component in this application can be adjusted according to actual polishing and production needs.
[0071] The content of the isocyanate prepolymer can be 50-51 wt%, 51-52 wt%, 52-53 wt%, 53-54 wt%, 54-55 wt%, 55-56 wt%, 56-57 wt%, 57-58 wt%, 58-59 wt%, 59-60 wt%, 60-61 wt%, 61-62 wt%, 62-63 wt%, 63-64 wt%, or 64-65 wt%.
[0072] The content of the polishing abrasive can be 15-18 wt%, 18-21 wt%, 21-24 wt%, 24-27 wt%, or 27-30 wt%.
[0073] The content of the N,N-dimethylformamide solution of 3,3'-dichloro-4,4'-diaminodiphenylmethane can be 10-12 wt%, 12-14 wt%, 14-16 wt%, 16-18 wt%, or 18-20 wt%.
[0074] The content of the foaming additive can be 2-3 wt%, 3-4 wt%, 4-5 wt%, 5-6 wt%, 6-7 wt%, 7-8 wt%, or 8-9 wt%.
[0075] The isocyanate group content in the isocyanate prepolymer can be 7-8 wt%, 8-9 wt%, 9-10 wt%, 10-11 wt%, or 11-12 wt%.
[0076] The mass ratio of 3,3'-dichloro-4,4'-diaminodiphenylmethane to N,N-dimethylformamide can be (0.5-0.6):1, (0.6-0.7):1, (0.7-0.8):1, (0.8-0.9):1, or (0.9-1):1.
[0077] The weight-average molecular weight of the isocyanate prepolymer can be 900–1000 g / mol, 1000–1100 g / mol, 1100–1200 g / mol, or 1200–1300 g / mol.
[0078] In one specific embodiment, the mixing sequence is as follows: first, water, alumina powder, dispersant, and lubricant are mixed evenly; then, an aqueous solution of suspending agent is added and mixed evenly; finally, a pH adjuster is added and mixed evenly to adjust the pH of the mixture to 12-14.
[0079] In one specific embodiment, the isocyanate prepolymer is selected from one or more of toluene diisocyanate prepolymer, diphenylmethane diisocyanate prepolymer, terephthalic diisocyanate prepolymer, and dimethylbiphenyl diisocyanate prepolymer.
[0080] In a more specific embodiment, the isocyanate prepolymer is a toluene diisocyanate prepolymer.
[0081] In one specific embodiment, the isocyanate prepolymer is a toluene diisocyanate prepolymer, wherein the isocyanate group content is 9.6–9.8 wt%, and the weight-average molecular weight is 1100 g / mol. Both excessively high and low isocyanate group content are detrimental to obtaining polishing pads with suitable hardness. The isocyanate group content described in this application helps to balance the grinding removal rate and defect rate, achieving a high removal rate while avoiding an excessively high defect rate.
[0082] In one specific embodiment, the polishing abrasive is selected from one or more of cerium oxide, zirconium oxide, aluminum oxide, and barium sulfate.
[0083] In one specific embodiment, the particle size of the polishing abrasive is 1.5–3.5 μm. For example, it can be 1.5–2.0 μm, 2.0–2.5 μm, 2.5–3.0 μm, or 3.0–3.5 μm.
[0084] In one specific embodiment, the D of the polishing abrasive 50 The thickness is 2.0–2.5 μm, D 100 It is 3.0–3.5 μm. For example, D... 50 The micrometers can be 2.0–2.1 μm, 2.1–2.2 μm, 2.2–2.3 μm, 2.3–2.4 μm, or 2.4–2.5 μm. D 100 The micrometers can be 3.0–3.1 μm, 3.1–3.2 μm, 3.2–3.3 μm, 3.3–3.4 μm, or 3.4–3.5 μm.
[0085] It should be noted that the composition and particle size of the polishing abrasive can be adjusted according to the actual polishing object and polishing effect.
[0086] In one specific embodiment, the sodium bicarbonate content is 2-4 wt% based on the total mass of the raw materials. For example, it can be 2-2.4 wt%, 2.4-2.8 wt%, 2.8-3.2 wt%, 3.2-3.6 wt%, or 3.6-4 wt%. It should be noted that the sodium bicarbonate content can be adjusted according to the required number of cells in the final polyurethane polishing pad; more sodium bicarbonate is added if a higher number of cells is required, and vice versa.
[0087] In one specific embodiment, the water content is 0.15–0.2 wt% based on the total mass of the raw materials. For example, it can be 0.15–0.16 wt%, 0.16–0.17 wt%, 0.17–0.18 wt%, 0.18–0.19 wt%, or 0.19–0.2 wt%.
[0088] In one specific embodiment, the secondary foaming additive further includes one or more of 1,4-butanediol, a cell opener, a foam stabilizer, and a catalyst.
[0089] In a more specific embodiment, the content of 1,4-butanediol is 3-4 wt% based on the total mass of the raw materials. For example, it can be 3-3.2 wt%, 3.2-3.4 wt%, 3.4-3.6 wt%, 3.6-3.8 wt%, or 3.8-4.0 wt%.
[0090] In a more specific embodiment, the pore-opening agent is selected from one or more of the following: polyoxyolefin-polysiloxane copolymer, polypropylene-ethylene oxide copolymer, polyethylene glycol, polypropylene glycol, paraffin oil, polybutadiene, dimethyl silicone oil, and polyether-modified siloxane.
[0091] In one specific embodiment, the pore-opening agent is a polyoxyolefin-polysiloxane copolymer, specifically O-501 manufactured by Evonik Specialty Chemicals AG, Germany.
[0092] In a more specific embodiment, the content of the pore-opening agent is 0.3 to 0.5 wt% based on the total mass of the raw materials. For example, it can be 0.3 to 0.35 wt%, 0.35 to 0.4 wt%, 0.4 to 0.45 wt%, or 0.45 to 0.5 wt%.
[0093] In a more specific embodiment, the foam stabilizer is selected from one or more of non-hydrolyzable silicone surfactants and silicone surfactants.
[0094] In one specific embodiment, the foam stabilizer is a non-hydrolyzable silicone surfactant, specifically manufactured by Momentive, Inc. silicone L-1500.
[0095] In a more specific embodiment, the content of the foam stabilizer is 0.3–0.5 wt% based on the total mass of the raw materials. For example, it can be 0.3–0.35 wt%, 0.35–0.4 wt%, 0.4–0.45 wt%, or 0.45–0.5 wt%.
[0096] In a more specific embodiment, the catalyst is selected from one or more of triethylenediamine, N,N,N',N”,N”-pentamethyldiethylenetriamine, dimethylethanolamine, dimethylaminoethyl ether, tetramethylethylenediamine, stannous octoate, dibutyltin dilaurate, and N,N-dimethylethanolamine.
[0097] In one specific embodiment, the catalyst is triethylenediamine, specifically A33, which is a 33% triethylenediamine solution prepared by dissolving solid triethylenediamine in a diol such as dipropylene glycol (CAS No.: 280-57-9, molecular formula C6H). 12 N2).
[0098] In a more specific embodiment, the catalyst content is 0.3–0.5 wt% based on the total mass of the raw materials. For example, it can be 0.3–0.35 wt%, 0.35–0.4 wt%, 0.4–0.45 wt%, or 0.45–0.5 wt%.
[0099] In one specific implementation, in step 1), the mixing temperature is 70–80°C.
[0100] It should be noted that the mixing time can be adjusted according to the actual equipment and its power, as long as the raw materials are mixed evenly.
[0101] In one specific embodiment, before step 1), a step of preheating the isocyanate prepolymer is also included.
[0102] In a more specific embodiment, the preheating temperature is 50–70°C.
[0103] In a more specific embodiment, the preheating time is 10 to 14 hours.
[0104] In one specific embodiment, in step 1), the coating thickness is 1 to 6 mm.
[0105] In one specific implementation, in step 1), the coating tool is a coating head.
[0106] In one specific embodiment, in step 1), the coated plate is a polytetrafluoroethylene plate.
[0107] In one specific implementation, in step 1), the time for standing foaming is 3 to 15 minutes.
[0108] In one specific implementation, step 2) includes a first stage and a second stage. The temperature of the first stage is 50-70°C and the time is 3-5 hours. The temperature of the second stage is 100-120°C and the time is 16-24 hours.
[0109] In one specific implementation, step 2) is followed by a post-processing step, which includes surface polishing.
[0110] This application also discloses a polyurethane polishing pad prepared according to the above method.
[0111] In one specific embodiment, the thickness of the polishing pad is 1.5 to 4.5 mm.
[0112] In one specific embodiment, the moisture content of the polishing pad is 19.00–26.31 mL / cm³. 3 .
[0113] The capacity mentioned in this application refers to the volume of polishing fluid that a unit volume polishing pad can hold.
[0114] In one specific embodiment, the porosity of the polishing pad is 53-60%. For example, it can be 53-54%, 54-55%, 55-56%, 56-57%, 57-58%, 58-59%, or 59-60%.
[0115] The porosity refers to the percentage of the total volume of the polishing pad material that is interconnected and communicates with the external environment. A high porosity results in better chip removal capability, higher polishing fluid transfer efficiency, and longer pad life.
[0116] In one specific embodiment, the pore size of the polishing pad is 40–200 μm. For example, it can be 40–45 μm, 45–50 μm, 50–55 μm, 55–60 μm, 60–65 μm, 65–70 μm, 70–80 μm, 80–90 μm, 90–100 μm, 100–120 μm, 120–140 μm, 140–170 μm, or 170–200 μm. In the polishing pad described in this application, more than 50% of the pores have a size of 40–100 μm.
[0117] This application discloses the use of the polyurethane polishing pad described above in polishing glass plates.
[0118] In one specific implementation, the glass plate is a glass cover for an electronic device.
[0119] The technical solution and effects of the present invention will be further illustrated and explained through the following specific embodiments and implementation effects.
[0120] The following embodiments of this application:
[0121] D 50 and D 100 The particle size was obtained using a Malvern particle size analyzer and Zetasizer Advance Series-Lab.
[0122] Viscosity was obtained by testing with a Borelfeld viscometer;
[0123] The cell size was obtained by SEM imaging and statistical analysis;
[0124] The open area ratio was obtained by testing in accordance with GB / T 10799-2008;
[0125] Wear test method: Take a sample with a diameter of 110 mm and a thickness of 3.0 mm, at a density of 1.3 g / cm³. 3 After immersing in a cerium oxide polishing solution with a pH of 7-8 for 30 minutes, heat at 100℃ for 2 hours until constant weight is achieved, and record the mass as M1. Test the wear using a Taber abrasion tester, using an H-18 ceramic grinding wheel with a load of 1.5 kg, rotate 2000 times at 60 rpm, and record the mass as M2; the mass reduction M1-M2 is the wear amount.
[0126] Cultivation capacity test method: Take a sample with a diameter of 110 mm and a thickness of 3.0 mm, weigh it, and record its mass as M3. At a density of 1.3 g / cm³... 3 After soaking in a cerium oxide polishing solution with a pH of 7-8 for 30 minutes, its mass is recorded as M4; the increase in mass, M3-M4, is the retention capacity.
[0127] Scratch test method: Thoroughly clean the surface of all polished glass covers with a lint-free cloth and alcohol to ensure there is no dust, fingerprints, or oil. Place them in a standard light source box (HL-DFL-F280CH from Hikari-ya, Japan) and observe them from multiple angles at a distance of 30-40cm. Bright lines longer than 2cm are considered scratches, and the number of scratches is recorded.
[0128] TTV test method: After polishing, thoroughly clean the surface of all glass covers with a lint-free cloth and alcohol to ensure that there is no dust, fingerprints and oil stains. Use a dial indicator to test the thickness. From all the measurement point data, find the maximum thickness (Tmax) and minimum thickness (Tmin) and calculate it according to the formula TTV = Tmax - Tmin.
[0129] Removal rate calculation method:
[0130] Wherein, RR is the removal rate, in μm / min; H0 is the initial thickness of the polished workpiece, in μm; H1 is the thickness of the workpiece after polishing, in μm; T is the polishing time, in min; the polishing was performed on a 2-inch mobile phone glass cover (Kunlun Glass) using a Zhejiang Mingzheng 6B double-sided polishing machine; the polishing solution was cerium oxide polishing powder with a particle size of 1.0-1.2 μm, a density of 1.2 g / mL, and a pH of 7.5. The polishing pressure was 160 g / cm³. 2 Lower plate rotation speed: 35 rpm, upper plate rotation speed: 15 rpm, polishing fluid flow rate: 1200 ml / min.
[0131] In the following specific embodiments, the coating plate is a polytetrafluoroethylene plate, the cell opener is O-501 manufactured by Evonik Specialty Chemicals AG (Germany), and the foam stabilizer is manufactured by Momentive Chemicals (USA). silicone L-1500; the catalyst is A33, which is a 33% triethylenediamine solution, prepared by dissolving solid triethylenediamine in a diol such as dipropylene glycol (CAS No.: 280-57-9, molecular formula C6H). 12 N2).
[0132] Example 1
[0133] In this embodiment, a specific polyurethane polishing pad and its preparation method are provided. The preparation method includes the following steps:
[0134] 1) Take 5000g of toluene diisocyanate prepolymer with an NCO content of 9.6% and a weight-average molecular weight of 1100g / mol, and heat it in an oven at 60℃ for 12h, which is recorded as A; Take 700g of N,N-dimethylformamide, add 500g of 3,3'-dichloro-4,4'-diaminodiphenylmethane, and stir with a mixer at 2000rpm for 3 minutes until the 3,3'-dichloro-4,4'-diaminodiphenylmethane is completely dissolved, which is recorded as B1; Take 250g of 1,4-butanediol, and add 25g of cell opener O-501, 25g of foam stabilizer L-1500, 200g of sodium bicarbonate, 2.5g of A33 catalyst, and 12g of water in sequence, and stir with a mixer at 2000rpm for 3 minutes until fully mixed, which is recorded as B2.
[0135] 2) Add 1700g of cerium oxide abrasive to A, and stir at 2000rpm for 10 minutes until uniformly mixed. Then add B1 and B2 to the uniformly mixed material in sequence, and stir at 2000rpm for 50 seconds. Invert the uniformly mixed material onto the coating plate of the coating machine (the coating plate is a polytetrafluoroethylene plate), adjust the coating gap to 1.5mm, and start coating. After coating is completed, let it stand for 10 minutes to allow the water to react with the toluene diisocyanate prepolymer and complete the initial foaming.
[0136] 3) Place the coated product, along with the coated plate, into an oven at 60°C for 4 hours to allow N,N-dimethylformamide to slowly evaporate and the slurry to initially gel. Then, raise the temperature to 110°C and place for 20 hours to decompose the previously added sodium bicarbonate, causing it to expand and foam. This allows any remaining N,N-dimethylformamide in the system to completely evaporate, forming the pre-defined cell structure. Simultaneously, this allows the polyurethane slurry to fully react and mature.
[0137] 4) Remove the cured and molded product from the coating substrate and use a sanding machine to sand the surface, removing 0.2mm to obtain a final product with a thickness of 3mm. The sandpaper used in the sanding machine is 240 grit.
[0138] Example 2
[0139] In this embodiment, a specific polyurethane polishing pad and its preparation method are provided. The difference between the preparation method and that in Example 1 is that the weight of sodium bicarbonate in step 1) is 175g.
[0140] Example 3
[0141] In this embodiment, a specific polyurethane polishing pad and its preparation method are provided. The difference between the preparation method and that in Example 1 is that the weight of N,N-dimethylformamide in step 1) is 850g.
[0142] Comparative Example 1
[0143] This comparative example provides a specific polyurethane polishing pad and its preparation method, including the following steps:
[0144] 1) Weigh 20,000g of toluene diisocyanate prepolymer into a 60L container. Add 100g of O-501 and 100g of L1500 sequentially, and stir with a mixer for 5 minutes at 2000rpm. Add 6800g of cerium oxide to the stirred material, and stir with a mixer for another 10 minutes at 2000rpm. Then add 10g of A33, 48g of water, 2000g of molten 3,3'-dichloro-4,4'-diaminodiphenylmethane at 120℃, and 1000g of 1,4-butanediol sequentially, and stir with a mixer for 50 seconds at 2000rpm.
[0145] The mixed material is quickly poured into a foaming mold with a thickness of 50mm.
[0146] 2) After 1 hour, open the mold and remove the product. Place the demolded product in an oven at 110℃ and heat for 20 hours to cure and shape.
[0147] 3) Cut the cured product into 3mm thick sheets using a slicer to obtain the final product.
[0148] Comparative Example 2
[0149] In this comparative example, a specific polyurethane polishing pad and its preparation method are provided. The difference between the preparation method and Example 1 is that in step 1), 500g of 3,3'-dichloro-4,4'-diaminodiphenylmethane is taken and heated in an oven at 120°C for 2 hours until the 3,3'-dichloro-4,4'-diaminodiphenylmethane is completely dissolved, which is denoted as B1.
[0150] Comparative Example 3
[0151] In this comparative example, a specific polyurethane polishing pad and its preparation method are provided. The difference between the preparation method and Example 1 is that in step 1), B2 does not include sodium bicarbonate.
[0152] Application Example 1
[0153] The viscosity of the slurry obtained by mixing the raw materials in step 2) of Example 2 and Comparative Example 2 was measured every 10 seconds. A Borelfeld viscometer was used for the test, and the test was conducted according to GB / T 2794-2022. The results are as follows: Figure 1 As shown.
[0154] Test Results Data Explanation: In Example 2 of this application, N,N-dimethylformamide was used to dissolve 3,3'-dichloro-4,4'-diaminodiphenylmethane, compared to Comparative Example 2, which melted 3,3'-dichloro-4,4'-diaminodiphenylmethane at 120°C. Clearly, the viscosity increase in Example 2 was slower, indicating a more gradual reaction and providing sufficient operating time for more uniform cell structure formation and more consistent physical properties of the polishing pad.
[0155] Application Example 2
[0156] Example 1: Five polishing pads were continuously prepared, and the density value of each pad was measured after polishing. Comparative Example 1: The density values of the top, middle, and bottom layers were measured after slicing. Comparative Example 2: Five polishing pads were continuously prepared, and the density value of each pad was measured after polishing. The testing methods were performed according to GB / T 6343-2009, and the results are as follows: Figure 2 As shown.
[0157] Test results data: In Comparative Example 1, 3,3'-dichloro-4,4'-diaminodiphenylmethane was melted and prepared using a molding foaming slicing process. The density of the upper, middle, and lower layers exhibited a "smile curve" distribution, with significant density differences. In Comparative Example 2, 3,3'-dichloro-4,4'-diaminodiphenylmethane was melted and prepared using a coating process. No density difference was observed, and the stability was good, but the density was significantly increased. In Example 1 of this application, N,N-dimethylformamide was used to dissolve 3,3'-dichloro-4,4'-diaminodiphenylmethane and then coated to prepare a polishing pad. Compared to the above comparative examples, the density was stable and low.
[0158] Application Example 3
[0159] Figures 3-4 The images shown are SEM images of the surfaces of the polishing pads prepared in Example 1 and Comparative Example 2, respectively.
[0160] Test result data explanation: such as Figure 3 As shown, the polishing pad prepared in Example 1 has a significantly higher number of surface pores and significantly smaller pore sizes, ranging from 40 to 200 μm, with the vast majority distributed between 40 and 100 μm, exhibiting greater uniformity. In contrast, the polishing pad prepared in Comparative Example 2 has surface pore sizes ranging from 50 to 360 μm, with fewer pores, a wider distribution range, and unevenness. Therefore, the polishing pad of Example 1 can distribute the polishing liquid more evenly during the polishing process, enabling more uniform transmission of polishing pressure and resulting in a better polished surface.
[0161] Application Example 4
[0162] Using the above polishing process and calculation method, a comparison chart of removal rates during the polishing process of Example 1, Comparative Example 1, and competing products was obtained, as shown below. Figure 5 As shown. The competing product is a commonly used polishing pad on the market, manufactured by Universal Optics Inc. in the United States, model LP66.
[0163] Test results data: Example 1 showed a 20% increase in removal rate compared to Comparative Example 1 and a 9% increase compared to competing products, with a significant increase in polishing efficiency.
[0164] Application Example 5
[0165] Example 1 and Comparative Examples 1-3 were tested for open area ratio according to GB / T 10799-2008, and the results are as follows. Figure 6 As shown.
[0166] Test results data description: Compared with Comparative Examples 1 to 3, which used molten 3,3'-dichloro-4,4'-diaminodiphenylmethane or did not add sodium bicarbonate, Example 1 using the preparation method of this application showed a significant improvement in porosity, which means improved chip removal capacity of the polishing pad, improved polishing fluid transmission efficiency, and longer pad life.
[0167] Application Example 6
[0168] The wear, moisture retention, scratches, and TTV of Examples 1-3 and Comparative Examples 1-3 were tested using the above method, and the results are shown in Table 1.
[0169] Test results data: Compared with Comparative Examples 1-3, which used molten 3,3'-dichloro-4,4'-diaminodiphenylmethane or did not add sodium bicarbonate, Examples 1-3 using the preparation method of this application showed significantly reduced wear, increased moisture retention, fewer scratches, and lower TTV. In other words, the polishing pad's chip removal capacity, liquid storage capacity, and polishing fluid transfer efficiency were improved, resulting in longer pad life and better polishing effect.
[0170] Table 1
[0171] sample Wear amount (mg) Nutritional capacity (mg) Scratches (strips) TTV(μm) Example 1 160 750 1 2 Example 2 160 660 0 2 Example 3 150 810 0 2 Comparative Example 1 250 480 3 4 Comparative Example 2 210 550 2 3 Comparative Example 3 200 560 2 3
[0172] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A method for preparing a secondary foamed polyurethane polishing pad, characterized in that, The preparation method includes the following steps: 1) Based on the total mass of the raw materials of the polishing pad, the raw materials include 50-65 wt% isocyanate prepolymer, 15-30 wt% polishing abrasive, 10-20 wt% N,N-dimethylformamide solution containing 3,3'-dichloro-4,4'-diaminodiphenylmethane, and 2-9 wt% foaming additive. The raw materials are mixed and coated, and then allowed to stand to foam to obtain a preliminary foamed polishing pad. 2) Heat the initially foamed polishing pad to perform secondary foaming, thereby obtaining the polyurethane polishing pad; Based on the total mass of the isocyanate prepolymer, the isocyanate prepolymer contains 7-12 wt% isocyanate groups and has a weight-average molecular weight of 900-1300 g / mol; the mass ratio of 3,3'-dichloro-4,4'-diaminodiphenylmethane to N,N-dimethylformamide is (0.5-1):1; the foaming additive includes sodium bicarbonate and water.
2. The preparation method according to claim 1, characterized in that, The isocyanate prepolymer is selected from one or more of toluene diisocyanate prepolymer, diphenylmethane diisocyanate prepolymer, terephthalic diisocyanate prepolymer, and dimethyl biphenyl diisocyanate prepolymer; And / or, the polishing abrasive is selected from one or more of cerium oxide, zirconium oxide, aluminum oxide, and barium sulfate; And / or, the particle size of the polishing abrasive is 1.5 to 3.5 μm; And / or, the D of the polishing abrasive 50 The diameter is 2.0–2.5 μm, D 100 The thickness is 3.0–3.5 μm. And / or, based on the total mass of the raw materials, the content of sodium bicarbonate is 2 to 4 wt%; And / or, based on the total mass of the raw materials, the water content is 0.15 to 0.2 wt%.
3. The preparation method according to claim 2, characterized in that, The isocyanate prepolymer is toluene diisocyanate prepolymer.
4. The preparation method according to claim 1, characterized in that, The foaming additive also includes one or more of 1,4-butanediol, a cell opener, a foam stabilizer, and a catalyst.
5. The preparation method according to claim 4, characterized in that, Based on the total mass of the raw materials, the content of 1,4-butanediol is 3-4 wt%. And / or, the pore-opening agent is selected from one or more of the following: polyoxyolefin-polysiloxane copolymer, polypropylene-ethylene oxide copolymer, polyethylene glycol, polypropylene glycol, paraffin oil, polybutadiene, dimethyl silicone oil, and polyether-modified siloxane. And / or, based on the total mass of the raw materials, the content of the pore-opening agent is 0.3 to 0.5 wt%; And / or, the foam stabilizer is selected from one or more of non-hydrolyzable silicone surfactants and silicone surfactants; And / or, based on the total mass of the raw materials, the content of the foam stabilizer is 0.3 to 0.5 wt%; And / or, the catalyst is selected from one or more of triethylenediamine, N,N,N',N”,N”-pentamethyldiethylenetriamine, dimethylethanolamine, dimethylaminoethyl ether, tetramethylethylenediamine, stannous octoate, dibutyltin dilaurate, and N,N-dimethylethanolamine; And / or, based on the total mass of the raw materials, the content of the catalyst is 0.3 to 0.5 wt%.
6. The preparation method according to claim 1, characterized in that, In step 1), the mixing temperature is 70–80°C; And / or, before step 1), a step of preheating the isocyanate prepolymer is also included; And / or, in step 1), the coating thickness is 1 to 6 mm; And / or, in step 1), the coated plate is a polytetrafluoroethylene plate; And / or, in step 1), the standing foaming time is 3 to 15 minutes; And / or, in step 2), the heating includes a first stage and a second stage, wherein the temperature of the first stage is 50-70°C and the time is 3-5 hours; and the temperature of the second stage is 100-120°C and the time is 16-24 hours. And / or, step 2) may be followed by a post-processing step, which may include surface polishing.
7. The preparation method according to claim 6, characterized in that, The preheating temperature is 50–70°C; And / or, the preheating time is 10 to 14 hours.
8. A polyurethane polishing pad prepared by the preparation method according to any one of claims 1 to 7.
9. The polyurethane polishing pad according to claim 8, characterized in that, The thickness of the polishing pad is 1.5–4.5 mm; And / or, the porosity of the polishing pad is 53-60%; And / or, the pore size of the polishing pad is 40–200 μm; And / or, the moisture content of the polishing pad is 19.00–26.31 mL / cm³. 3 .
10. Use of a polyurethane polishing pad as described in any one of claims 8 to 9 in polishing glass plates.