CN116171306A

CN116171306A - Foaming material and preparation method and application thereof

Info

Publication number: CN116171306A
Application number: CN202280004127.3A
Authority: CN
Inventors: 李敏; 邹海良
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-07-31
Filing date: 2022-08-01
Publication date: 2023-05-26
Also published as: CN115678086A; WO2023011410A1

Abstract

The application relates to the field of foaming materials, and provides a foaming material, a preparation method thereof, application of the foaming material and an abrasive material. The foaming material comprises an unfoamed structure and foaming structures dispersed in the unfoamed structure, wherein multiple cells are arranged in the foaming structure, and the average distance between the foaming structures is larger than the average distance between the cells. The foaming material that this application provided, foaming structure have better particle diameter homogeneity and dispersion homogeneity, can avoid foaming material to form skin core structure, reduce foaming material top layer and sandwich layer because the different temperature difference that leads to of heat dissipation to give foaming material performance even advantage.

Description

Foaming material and preparation method and application thereof

The present application claims priority to chinese patent application filed at month 7 and 31 of 2021, application No. 202110877145.X, application name "polymer foam and method for preparing same, application of polymer foam, polishing material", and claims priority to chinese patent application filed at month 7 and 15 of 2022, application No. 202210837183.7, application name "a foam and method for preparing same, and application thereof", which are incorporated herein by reference in their entirety.

Technical Field

The application belongs to the technical field of foaming materials, and particularly relates to a foaming material, a preparation method thereof and application of the foaming material.

Background

A foamed material is a microporous material based on a polymer (plastic, rubber, elastomer or natural high molecular material) and having cells therein. The foaming material is widely used in household daily necessities, traffic tools, insulating materials, packaging materials, electric appliances, sports facilities, electronic products, chemistry, textile and other fields due to the characteristics of light weight, heat insulation, sound insulation and the like. For example, the foamed materials are used in the electronic industry technology for polishing parts of electronic industry products or industrial materials which need to be planarized, i.e. the polymer is foamed to form a polishing material.

The foaming material can be prepared by foaming polymer microspheres, but in the preparation process, the polymer microspheres are difficult to uniformly disperse and have wide particle size distribution, so that the application of the foaming material is affected. Taking an abrasive material as an example, as shown in fig. 1, a technician uses foaming microspheres to prepare a polyurethane polishing pad, and the process for preparing the polyurethane polishing pad by the method comprises the following steps: firstly, preparing polyacrylonitrile microspheres through high-pressure suspension polymerization, wherein the interior of the microspheres generally contains low-boiling hydrocarbon substances; then heating to make the shell polymer reach above Tg, and heating and gasifying and expanding the inner layer low boiling point substance to form hollow foaming microsphere; finally, the hollow microspheres are mixed into a mixture of isocyanate and a cross-linking agent, and are subjected to pouring molding and rapid solidification to form the microporous material. However, the grinding pad prepared by the method has complex microsphere preparation process, and the pore size and distribution of the obtained material cells are uneven; because of the density difference between polyurethane and microspheres, the microspheres are difficult to disperse uniformly in the pouring process, and the uniformity of the product is poor; the addition amount of the microspheres is limited by the limitation of the stirring process, so that the porosity adjustment range of the product is small. Another method of making a polyurethane polishing pad is shown in fig. 2, comprising: firstly, synthesizing a thermoplastic polyurethane material substrate, and forming the substrate to obtain a polyurethane sheet, wherein the size of the sheet is larger than that of a grinding pad (800 mm multiplied by 2 mm); then heating the sheet to above Tg, introducing supercritical gas, and impregnating the sheet; finally, the supercritical gas immersed in the sheet is gasified and expanded through rapid decompression to form a cell structure. The polyurethane grinding pad obtained by the method has uniform size and distribution of the foaming microspheres, and the material is easy to form a sheath-core structure with uneven heat dissipation, the uniformity of cells is difficult to control, and the open pore structure is more, as shown in the right diagram of fig. 2.

Therefore, it is important to develop a polymer material with uniform size and distribution of the foaming microsphere.

Disclosure of Invention

The purpose of the application is to provide a foaming material, a preparation method thereof, application of the foaming material and an abrasive material, and aims to solve the problems of nonuniform size and distribution of foaming microspheres in the existing foaming material. When the material is foamed, the material has smaller size, can effectively control heat dissipation, and can effectively control the nucleation and diffusion speed of the air holes. Thereby obtaining the porous particle material with uniform pore diameter. And the material properties of the grinding materials obtained by splicing the particles are the same in the middle edge region, and the material properties obtained between the upper layer and the lower layer are the same in the sheets.

In order to achieve the purposes of the application, the technical scheme adopted by the application is as follows:

a first aspect of the present application provides a foamed material comprising a plurality of foamed structures having a plurality of cells therein, wherein an average distance between the foamed structures is greater than an average distance between the cells. The size of each foaming structure in the foaming material is small, heat transfer and mass transfer in the foaming process are effectively controlled, the size of foam holes of the foaming structure is better controlled in a relatively uniform range, the existence of large foam holes is reduced, and defects are reduced. Because the foaming conditions are consistent among different foaming structures, the performance difference of each foaming structure is small, so that the performance difference of the whole foaming material is small, and the material performance is uniform.

The particle size of the foaming material provided by the application is 50-30000 micrometers, and the particle size of the foaming structure has better uniformity compared with the foaming material; meanwhile, the distance between adjacent foaming structures is 2-10000 microns, so that the foaming structures are uniformly dispersed in the foaming material. In addition, as the foaming structure is dispersed in the unfoamed material of the continuous phase, the whole foaming material has better fusion property, and the particle size and the dispersion uniformity of the foaming structure can be stabilized. In conclusion, the foaming material provided by the application has the advantages that the foaming structure has good particle size uniformity and dispersion uniformity, the foaming material can be prevented from forming a skin-core structure, the temperature difference between the surface layer and the core layer of the foaming material due to different heat dissipation is reduced, and therefore the foaming material is endowed with uniform heat dissipation.

As one possible implementation of the foaming material of the present application, the particle size of the foaming structures is 100 to 5000 micrometers, and the average distance between adjacent foaming structures is 50 to 1000 micrometers.

As a possible implementation manner of the foaming material, the foaming material is characterized in that the particle size of the foaming structures is 200-3500 micrometers, and the average distance between adjacent foaming structures is 50-500 micrometers.

As a possible implementation manner of the foaming material, the foaming material is characterized in that the particle size of the foaming structures is 1500-3500 micrometers, and the average distance between adjacent foaming structures is 50-500 micrometers.

As one possible implementation of the foamed material of the present application, the average pore size of the cells is 1 to 200 micrometers, and the distance between adjacent cells is 1 to 500 micrometers. Under the condition, the foaming structure in the foaming material has foam holes with uniform particle size and uniform distribution, which is beneficial to maintaining the performance stability of each area of the foaming material and improving the overall stability of the foaming material. By way of example, when the foaming material is used as the grinding material, since the foam cells in the foaming structure have better particle size uniformity and dispersion uniformity, the aggregation of grinding particles by the large-cell structure can be avoided, and further the aggregated grinding particles are prevented from scratching workpieces to be ground such as wafers, and the yield of the workpieces to be ground is influenced.

As one possible implementation of the foamed material of the present application, the average pore size of the cells is 1 to 60 micrometers, and the average distance between adjacent cells is 1 to 60 micrometers. In this case, the presence of large pore size is avoided in the foamed material, and the internal grinding is reduced, so that the aggregation is reduced, and polishing defects are reduced.

As one possible implementation of the foamed material of the present application, the average pore size of the cells is 10 to 40 micrometers, and the distance between adjacent cells is 2 to 40 micrometers. In this case, the particle size distribution of the foaming structure in the foaming material is more concentrated, and the dispersion of the cells in the foaming structure is more uniform, so that the overall performance of the foaming material is uniform and stable, thereby giving the foaming material excellent performance. Under the condition, the cell structure of the material can be more uniform, and the stability of different parts, different layers and different batches of the material can be realized.

As a possible implementation of the foamed material of the present application, the polymer constituting the unfoamed structure and the polymer of the foamed structure may be the same or different.

As one possible implementation manner of the foaming material, the particle size of the foaming structures is 200-3500 micrometers, and the interval between adjacent foaming structures is 50-500 micrometers. In this case, the particle size distribution of the foaming structure in the foaming material is more concentrated, and the dispersion of the foaming structure in the foaming material is more uniform, so that the foaming material can exert more uniform and stable properties such as heat dissipation uniformity, scratch resistance and the like.

As a possible implementation of the foamed material of the present application, the polymer constituting the unfoamed continuous phase is the same as the polymer constituting the foamed structure. In this case, the fusion of the whole foam material is further enhanced, the particle diameter of the foam structure and the stability of uniform dispersion are improved, and the scratch resistance of the foam material is enhanced.

As one possible implementation of the foamed material of the present application, the polymer is a thermoplastic polymer, a thermosetting polymer, or a mixture of a thermoplastic polymer and a thermosetting polymer. In this case, since the type of the foaming material is not limited, the type of the foaming material can be enriched, so that the application scene of the foaming material can be expanded, and for example, the foaming material provided by the application can be used as an abrasive material, a heat insulating material, a packaging material, a vibration damping material, a noise reducing material, a model material and the like. Moreover, the material can firstly form polymer microspheres, then form an internally foamed core-shell structure by using a supercritical carbon dioxide foaming technology, and then form a continuous phase outside the foamed structure by hot pressing or bonding, thereby being beneficial to improving the integral fusion property of the foamed material and enhancing the scratch resistance of the foamed material.

As one possible implementation of the foam of the present application, the polymer is selected from one of thermoplastic elastomers, polyolefin, polycarbonate, polyvinyl alcohol, polyamide, rubber, polyaromatic, fluoropolymer, polyimide, polyacrylate, polyether urea, polyisocyanurate, thermoset polyurethane, polyurea, polyurethane urea.

As one possible implementation of the foam of the present application, the polymer is selected from a copolymer or a mixture of at least two of thermoplastic elastomers, polyolefins, polycarbonates, polyvinyl alcohol, polyamides, rubbers, polyaromatic compounds, fluoropolymers, polyimides, polyacrylates, polyether ureas, polyisocyanurate, thermoset polyurethanes, polyureas, polyurethane ureas.

As one possible implementation of the foaming material of the present application, the polymer includes at least one selected from thermoplastic elastomer, polyolefin, polycarbonate, polyvinyl alcohol, polyamide, rubber, polyaromatic, fluoropolymer, polyimide, polyacrylate, polyether urea, polyisocyanurate, thermosetting polyurethane, polyurea, polyurethane urea, and copolymers formed from at least two selected from thermoplastic elastomer, polyolefin, polycarbonate, polyvinyl alcohol, polyamide, rubber, polyaromatic, fluoropolymer, polyimide, polyacrylate, polyether urea, polyisocyanurate, thermosetting polyurethane, polyurea, polyurethane urea.

The foaming materials provided by the three implementation modes can adjust the types of the polymers according to the application requirements of the foaming materials, so that the foaming materials with different performances are obtained, and the application fields of the foaming materials are further expanded.

As one possible implementation of the foamed material of the present application, in the foamed structure, 95% or more of the cells are closed cells. The higher closed pore rate ensures that the foaming material is rich in a large number of foam cells with uniform particle size and uniform dispersion, thereby endowing the foaming material with excellent foaming micropore characteristics and being beneficial to improving the performance of the foaming material in the use of specific application scenes. If the foaming material is used as an abrasive material, the planarization effect is improved due to the high closed cell rate; when the foaming material is used as a heat insulation material and a heat preservation material, the high closed porosity effectively prevents a large number of foam holes in the foaming structure from heat circulation, so that the heat insulation and heat preservation effects are improved; when the foaming material is used as a noise reducing material, the high closed porosity can reduce the circulation of noise, and the like.

The second aspect of the present application provides a method for preparing a foaming material, comprising the steps of:

adding polymer microspheres with the particle size of 20-3000 micrometers into water, and mixing to obtain a mixture; placing the mixture in a high-pressure reaction kettle, injecting supercritical carbon dioxide into the high-pressure reaction kettle, heating and stirring, performing heat preservation treatment after the pressure and the temperature are stable, and releasing pressure after the heat preservation is finished, so that the polymer microspheres are foamed to obtain polymer foamed microspheres, wherein the polymer foamed microspheres are of a core-shell structure and comprise unfoamed shell layers and foamed cores;

Injecting the polymer foaming microsphere into a mould, carrying out hot pressing treatment, and demoulding to obtain a foaming material; or mixing the adhesive raw material with the polymer foaming microsphere, injecting the mixture into a mold, heating the mixture for reaction, and demolding the mixture to obtain the foaming material, wherein the foaming material comprises an unfoamed continuous phase and foaming structures dispersed in the unfoamed continuous phase, and the foaming structures are internally provided with foam cells, wherein the particle size of the foaming structures is 50-3500 microns, and the interval between adjacent foaming structures is 20-500 microns.

The preparation method of the foaming material provided by the application has the following advantages:

firstly, polymer microspheres with the particle size of 20-3000 micrometers are selected for foaming to form polymer foaming microspheres, and the microspheres with overlarge particle size difference are prevented from being introduced at the front end of the process, so that the microspheres form a foaming structure with relatively uniform particle size after foaming, the problem of uneven distribution of the foaming structure in the foaming microsphere forming process is effectively controlled, and the temperature difference between the surface layer and the core layer of the foaming material caused by different heat dissipation is avoided, so that the foaming material has the advantage of uniform heat dissipation. Meanwhile, as the size and the dispersion uniformity of the polymer microspheres are improved, the size and the dispersion uniformity of the foam holes in the foaming structure are also improved. Therefore, the foaming structure and the foaming material with improved size uniformity and distribution uniformity of the foaming holes can avoid structural difference between the surface and the core layer, and further improve the uniformity of the foaming material.

Secondly, the foaming process of the polymer microsphere and the forming process of the foaming material are carried out in two steps, so that the problem that the size and the distribution of foam holes formed by foaming are uneven due to heating and heat dissipation in the process of one-step material integrated forming can be effectively avoided, and the uniformity and the distribution uniformity of the size of the foam holes of the foaming structure and the size of the foam holes are further improved.

Thirdly, compared with the method for directly preparing the foaming microsphere by adopting the polymer raw material, the method adopts supercritical carbon dioxide to foam the polymer microsphere to prepare the polymer foaming microsphere, so that the size difference of the pore bubbles caused by the non-uniform size of the microsphere is avoided, and the large-aperture pore holes are formed.

Fourth, the present application uses hot pressing or bonding techniques to form the foam. The heat pressing method fuses the surface shells of the polymer foaming microspheres to form a continuous phase through heating, so that the overall fusion of the foaming material is improved, and the foaming structure is favorably improved to maintain good dispersion uniformity of the foaming material. According to the bonding method, the adhesive raw material is added, so that the shell layers on the surfaces of the polymer foaming microspheres are bonded to form a continuous unfoamed structure, and the foamed structure is kept to maintain good dispersion uniformity in the foaming material.

As one possible implementation manner of the preparation method of the foaming material, the polymer microsphere is at least one of thermoplastic elastomer microsphere, polyolefin microsphere, polycarbonate microsphere, polyvinyl alcohol, polyamide microsphere, rubber microsphere, polyaromatic microsphere, fluoropolymer microsphere, polyimide microsphere, polyacrylate microsphere, polyether urea microsphere, polyisocyanurate microsphere, thermosetting polyurethane microsphere, polyurea microsphere and polyurethane urea microsphere.

As one possible implementation of the method for preparing a foamed material of the present application, the polymeric microspheres are selected from copolymer microspheres formed from at least two of thermoplastic elastomers, polyolefins, polycarbonates, polyvinyl alcohols, polyamides, rubbers, polyaromatic compounds, fluoropolymers, polyimides, polyacrylates, polyether ureas, polyisocyanurate, thermoset polyurethanes, polyureas, polyurethane ureas.

As one possible implementation of the method for preparing a foamed material of the present application, the polymer microsphere includes at least one of thermoplastic elastomer microsphere, polyolefin microsphere, polycarbonate microsphere, polyvinyl alcohol, polyamide microsphere, rubber microsphere, polyaromatic microsphere, fluoropolymer microsphere, polyimide microsphere, polyacrylate microsphere, polyether urea microsphere, polyisocyanurate microsphere, thermosetting polyurethane microsphere, polyurea microsphere, polyurethane urea microsphere, and copolymer microsphere formed of at least two selected from thermoplastic elastomer, polyolefin, polycarbonate, polyvinyl alcohol, polyamide, rubber, polyaromatic, fluoropolymer, polyimide, polyacrylate, polyether urea, polyisocyanurate, thermosetting polyurethane, polyurea, polyurethane urea.

The polymer microsphere provided by the three implementation modes can be subjected to foaming treatment through supercritical carbon dioxide, and the formed cells have good pore diameter uniformity and dispersion uniformity; moreover, the polymer foaming microsphere formed by the material can be formed by hot pressing or bonding of similar polymer binders, so that the fusion property of the foaming material is improved. The foaming material formed by the method has the advantages that the mechanism difference and the material difference of different areas are reduced, and the consistency of the performance of the material surface and the performance of the material inside is improved, so that the performance of the foaming material is improved and stabilized. In addition, according to the type of the polymer of the application demand adjustment of the foaming material, can obtain the foaming material that the performance is different, and then expand the application field of foaming material.

As one possible implementation manner of the preparation method of the foaming material, the polymer microsphere is a polyurethane microsphere, and the preparation method of the polyurethane microsphere is as follows: preparing an organic solution of polymer polyol, adding isocyanate into the organic solution of the polymer polyol, mixing, standing and reacting to obtain the polyurethane microsphere. The polyurethane microsphere is used as a polymer microsphere, and the formed foaming material has excellent planarization effect as an abrasive material; moreover, after the polyurethane microsphere is subjected to supercritical carbon dioxide foaming treatment, the polyurethane grinding material is formed through hot pressing or bonding, the pore size of the foam holes is good in uniformity, and the grinding material can be prevented from being locally aggregated on the grinding material to damage a workpiece to be ground.

As a possible implementation manner of the preparation method of the foaming material, in the step of adding isocyanate into the organic solution of the polymer polyol, the molar ratio of isocyanate groups to hydroxyl groups is 1: (1-1.05) adding isocyanate to the organic solution of the polymer polyol. In the application, in the polymerization reaction of polymer polyol and isocyanate polyol, polymer polyol with a molar content slightly more than that of isocyanate is introduced, so that more stable isocyanate polyol is used as an end group, and stable polymer microspheres are obtained, and the polymer blocked by isocyanate is prevented from being unstable under the conditions of water and the like, and the formation of a foaming material is prevented from being influenced in the supercritical carbon dioxide foaming process.

As a possible implementation manner of the preparation method of the foaming material, the step of adding isocyanate into the organic solution of the polymer polyol further comprises: a catalyst is added to the organic solution of the polymer polyol, the catalyst being used to catalyze the polymerization reaction between the polymer polyol and the isocyanate. By adding a catalyst, the rate of formation of polymer microspheres from polymer polyols and isocyanates can be accelerated.

As a possible implementation of the method for preparing a foamed material according to the present application, the average thickness of the shell layer is 10 to 30 micrometers, and the particle size of the core is 20 to 500 micrometers. Under the condition, the foaming structure is uniform in size, and as the average thickness of the shell layers is relatively uniform, after hot pressing or bonding molding, the shell layers form a continuous phase and have relatively uniform distances between adjacent foaming structures, so that the foaming structures can be uniformly dispersed in the foaming material, and the foaming material can exert more uniform and stable performances such as heat dissipation uniformity, scratch resistance and the like.

As a possible implementation manner of the preparation method of the foaming material, the polymer foaming microsphere is injected into a mold, and the step of hot pressing treatment comprises the following steps:

heating the polymer expanded microspheres to a temperature T of the microsphere polymer _g Above T _m The following are set forth;

and injecting the heated polymer foaming microsphere into a mould, and pressurizing to form.

In this case, the shell layers of the polymer foam microspheres are fused to form a continuous phase, and the cores of the foam microspheres are fixed therein to form a foam structure of the foam material by heat treatment. The size uniformity and the distribution uniformity of the foaming structure of the foaming material are improved, the structural difference of different areas of the foaming material can be reduced, the consistency of the performance of the surface of the material and the performance of the interior of the material is improved, and the foaming material can maintain stable performance.

As a possible implementation manner of the preparation method of the foaming material, the steps of mixing the binder raw material with the polymer foaming microsphere, injecting the mixture into a mold, and heating and reacting include:

mixing the binder raw material with the polymer foaming microsphere to obtain a mixed solution;

and injecting the mixed solution into a mould, and heating to form.

In this case, the binder raw material forms a binder under heating conditions, the shell layers of the polymer foam microspheres are fused to form a continuous phase, and the cores of the foam microspheres are fixed therein to form a foam structure of the foam material. The size uniformity and the distribution uniformity of the foaming structure of the foaming material are improved, the structural difference of different areas of the foaming material can be reduced, the consistency of the performance of the surface of the material and the performance of the interior of the material is improved, and the foaming material can maintain stable performance. In addition, the porosity of the foaming material can be regulated and controlled by the added adhesive, so that the foaming material is suitable for the use requirements of different scenes.

As one possible implementation manner of the preparation method of the foaming material, the polymer foaming microsphere is a polyurethane foaming microsphere; the raw materials of the adhesive are isocyanate prepolymer, polymer polyol and cross-linking agent. In this case, the binder formed by the isocyanate prepolymer, the polymer polyol and the crosslinking agent is also polyurethane, and can be fused with the shell layer of the polymer foam microsphere to form a continuous phase with good fusion, so that the structural and material uniformity of the foam material is improved.

A third aspect of the present application provides the use of the foam of the first aspect or the foam produced by the method of the second aspect as an abrasive material, a thermal insulation material, a packaging material, a vibration damping material, a noise reduction material, a modeling material.

The foaming material provided in the first aspect or the foaming material prepared by the method provided in the second aspect has better particle size uniformity and dispersion uniformity, and the non-foaming structure forms a continuous phase, so that structural difference of the foaming material can be reduced, uniformity of performance of the material surface and the material interior is improved, stability of performance of the foaming material is facilitated, such as uniform heat dissipation, heat insulation performance, vibration reduction performance, noise reduction performance, scratch prevention performance and the like of the foaming material is endowed, and the foaming material can be used as an abrasive material, a heat insulation material, a packaging material, a vibration reduction material, a noise reduction material and a model material.

In a fourth aspect, the present application provides an abrasive material, which is the foamed material according to the first aspect or the foamed material produced by the method according to the second aspect.

The abrasive material that this application provided, foaming structure disperse in continuous phase non-foaming structure, and have better particle diameter homogeneity and dispersion uniformity in whole abrasive material to can reduce abrasive material top layer and sandwich layer structure difference, and avoid abrasive material to form skin core structure, reduce the abrasive material top layer and sandwich layer because the temperature difference that the difference leads to of heat dissipation gives the even advantage of foaming material heat dissipation. Moreover, the foaming structure with uniform particle size is beneficial to improving the uniformity of pore diameters of cells, so that aggregation of grinding particles by cells with large pore diameters is avoided, scratches of a workpiece to be ground such as a wafer by the grinding material are reduced, and planarization effect is improved. In addition, the porosity of the grinding material can be adjusted by providing the polymer microsphere size, the supercritical carbon dioxide foaming multiplying power and the like in the method provided by the second aspect, so that the requirements of different workpieces to be ground on the porosity of the grinding material can be better met.

Drawings

FIG. 1 is a schematic flow chart of a polyurethane polishing pad prepared by using foaming microspheres according to the prior art;

FIG. 2 is a process flow diagram of supercritical carbon dioxide foaming of polyurethane sheet materials provided in the prior art;

FIG. 3 is a schematic view of a foam material provided in an embodiment of the present application;

fig. 4 is a flowchart of a process for preparing a foaming material according to an embodiment of the present application;

fig. 5 is a schematic flow chart of a hot-pressing foaming material preparation provided in the embodiment of the application;

FIG. 6 is a schematic flow chart of a bonding preparation foaming material provided in the embodiment of the present application;

Detailed Description

in order to make the technical problems, technical schemes and beneficial effects to be solved by the present application more clear, the present application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.

In this application, the term "and/or" describes an association relationship of an association object, which means that there may be three relationships, for example, a and/or B may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship.

In the present application, "at least one" means one or more, and "a plurality" means two or more. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple, respectively.

It should be understood that, in various embodiments of the present application, the sequence number of each process does not mean that the sequence of execution is sequential, and some or all of the steps may be executed in parallel or sequentially, where the execution sequence of each process should be determined by its functions and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The term "CMP" is abbreviated as "Chemical mechanical planarization" and refers to chemical mechanical polishing, a technique used in the fabrication of semiconductor devices to planarize silicon or other substrate material while it is in process. The basic principle is that under the condition of a certain pressure and the existence of grinding liquid (mixed liquid composed of superfine grinding particles, chemical oxidant and liquid medium), a workpiece to be ground rotates relative to a grinding pad, and the material on the surface of the workpiece is removed by the mechanical grinding of the grinding particles and the corrosion action of the chemical oxidant, so that a smooth surface is obtained.

The term "Tg" is an abbreviation for "glass transition temperature" and refers to the glass transition temperature, which refers to the temperature at which a polymer changes from a glassy state to a highly elastic state. Tg is the lowest temperature at which molecular segments can move and is a relaxation of amorphous portions of a polymer from a frozen state to a thawed state.

The term "Tm" is an abbreviation for "Melting Temperature" and refers to the melting temperature, also referred to as the melting point, for crystalline polymers, to refer to the temperature at which the three-dimensional remote ordered state of the macromolecular chain structure is converted to a disordered viscous state. Tm is the lower temperature limit of the crystalline polymer molding process.

The term "TPU" is abbreviated as "Thermoplastic polyurethanes" and refers to a thermoplastic polyurethane elastomer, which is a polymer material formed by the joint reaction and polymerization of diisocyanate molecules such as diphenylmethane diisocyanate (MDI) or Toluene Diisocyanate (TDI) and macromolecular polyol, and low-molecular polyol (chain extender), and can be melted by heating.

The term TSU is abbreviated as thermeset polyurethane elastomer and refers to a thermosetting polyurethane elastomer which is a polyurethane elastomer formed by chemical reaction under the action of heat, catalyst, pressure, ultraviolet light and the like, and is not melted again when heated and is decomposed when heated strongly.

The foaming material has the characteristics of light weight, heat insulation, sound insulation and the like, and can be widely used in various industries, and the foaming material is exemplified as an abrasive material, a heat insulation material, a heat preservation material, a packaging material, a vibration reduction material, a noise reduction material, a model material and the like, but is not limited to the above. Wherein, the foaming structure plays a role in light weight, heat insulation, sound insulation and the like of the foaming material. In particular, the size difference and the dispersion performance of the foaming structure in the foaming material directly influence the structural uniformity and the performance uniformity of the foaming material, thereby influencing the performance of the foaming material. Taking the grinding material as an example, the size difference and the dispersion uniformity of the foaming structure in the foaming material will be briefly described, and the influence on grinding will be described.

The polishing pad formed by foaming polyurethane has excellent planarization effect on the patterned semiconductor wafer. However, since the polymeric microspheres have a very wide particle size distribution, it is difficult to uniformly disperse, so that the polishing pad forms a large cell structure, and the large cell structure is easy to aggregate the polishing particles in the polishing liquid, and the aggregated polishing particles are extremely easy to scratch a workpiece to be polished, such as a wafer, so that the workpiece to be polished is defective or even scrapped.

In view of this, the embodiments of the present application provide a foamed material that improves dimensional uniformity and dispersion uniformity of a foamed structure. It should be understood that the foaming material provided by the embodiment of the application can be used as an abrasive material, and can also be used as a heat insulation material, a heat preservation material, a packaging material, a vibration damping material, a noise reduction material and a model material, and the use performance of the foaming material when the foaming material is used as the material is correspondingly improved by improving the foaming structure size and the dispersion uniformity of the foaming material.

Specifically, as shown in fig. 3, the foamed material provided in the embodiment of the present application includes an unfoamed continuous phase and a foamed structure dispersed in the unfoamed continuous phase, where the unfoamed continuous phase forms a honeycomb-like structure. As the foaming structure is dispersed in the unfoamed material of the continuous phase, the whole foaming material has better fusion property, and the foaming structure can be stabilized, so that the foaming material has better particle size and dispersion uniformity.

In the embodiments of the present application, the unfoamed continuous phase and the foamed structure are both polymer materials, and the polymer constituting the unfoamed continuous phase is the same as or different from the polymer constituting the foamed structure.

In one embodiment, the polymer comprising the unfoamed continuous phase is the same as the polymer comprising the foamed structure. In this case, the fusion between the unfoamed continuous phase and the foamed structure is higher, the fusion of the whole foamed material is enhanced, the stability of the whole material is improved, and the scratch resistance of the foamed material is enhanced. When the foaming material is an abrasive material, the consistency of the abrasive material can be improved, the planarization effect of the abrasive material can be improved, and the scratch risk of the abrasive material to a workpiece to be ground can be reduced when the polymer forming the unfoamed continuous phase is the same as the polymer forming the foaming structure.

In one possible implementation, the polymer that comprises the unfoamed continuous phase and the foamed structure is a thermoplastic polymer, a thermosetting polymer, or a mixture of a thermoplastic polymer and a thermosetting polymer. In this case, since the type of the foaming material is not limited, the type of the foaming material can be enriched, so that the application scene of the foaming material can be expanded, for example, the foaming material provided in the embodiment of the application can be respectively selected to be suitable polymer materials according to different application fields, so that the foaming material can be used as an abrasive material, a heat insulation material, a heat preservation material, a packaging material, a vibration reduction material, a noise reduction material, a model material and the like. Moreover, the material can firstly form polymer microspheres, then form an internally foamed core-shell structure by using a supercritical carbon dioxide foaming technology, and then form a continuous phase outside the foamed structure by hot pressing or bonding, thereby being beneficial to improving the integral fusion property of the foamed material and enhancing the scratch resistance of the foamed material.

In one possible implementation, the polymer is selected from one of thermoplastic elastomers, polyolefins, polycarbonates, polyvinyl alcohols, polyamides, rubbers, polyaromatic compounds, fluoropolymers, polyimides, polyacrylates, polyether ureas, polyisocyanurate, thermoset polyurethanes, polyureas, polyurethaneureas. In this case, the polymer constituting the unfoamed continuous phase and the polymer constituting the foamed structure are selected from one of the above polymers, and the obtained foamed material is a thermoplastic elastomer foamed material, a polyolefin foamed material, a polycarbonate foamed material, a polyvinyl alcohol foamed material, a polyamide foamed material, a rubber foamed material, a polyaromatic foamed material, a fluorine foamed material, a polyimide foamed material, a polyacrylate foamed material, a polyether urea foamed material, a polyisocyanurate foamed material, a thermosetting polyurethane foamed material, a polyurea foamed material, a polyurethane urea foamed material.

In one possible implementation, the polymer is selected from a copolymer or mixture of at least two of thermoplastic elastomers, polyolefins, polycarbonates, polyvinyl alcohols, polyamides, rubbers, polyaromatic compounds, fluoropolymers, polyimides, polyacrylates, polyether ureas, polyisocyanurate, thermoset polyurethanes, polyureas, polyurethane ureas. In this case, the polymer constituting the unfoamed continuous phase and the polymer constituting the foamed structure are selected from the same copolymer or the same mixture of the above polymers, and the corresponding foamed material is a foamed material formed of a copolymer of at least two of thermoplastic elastomer, polyolefin, polycarbonate, polyvinyl alcohol, polyamide, rubber, polyaromatic, fluoropolymer, polyimide, polyacrylate, polyether urea, polyisocyanurate, thermosetting polyurethane, polyurea, polyurethane urea; or the foaming material is a mixed foaming material formed by at least two of thermoplastic elastomer, polyolefin, polycarbonate, polyvinyl alcohol, polyamide, rubber, polyaromatic compound, fluorine polymer, polyimide, polyacrylate, polyether urea, polyisocyanurate, thermosetting polyurethane, polyurea and polyurethane urea.

In one possible implementation, the polymer comprises at least one selected from thermoplastic elastomers, polyolefins, polycarbonates, polyvinyl alcohols, polyamides, rubbers, polyaramids, fluoropolymers, polyimides, polyacrylates, polyether ureas, polyisocyanurates, thermoset polyurethanes, polyureas, polyurethaneureas, and copolymers of at least two selected from thermoplastic elastomers, polyolefins, polycarbonates, polyvinyl alcohols, polyamides, rubbers, polyaramids, fluoropolymers, polyimides, polyacrylates, polyether ureas, polyisocyanurates, thermoset polyurethanes, polyureas, polyurethane ureas.

In one possible embodiment, the foamed material is an abrasive material and the polymer comprising the foamed structure is a thermoplastic material. The thermoplastic material increases the cold flow of the material and can effectively reduce scratches on the workpiece to be ground, such as a wafer. In addition, the thermoplastic material can be melted after being heated, so that good recycling can be realized, and environmental pollution is reduced.

In one possible implementation, the foaming material is used as the grinding material, the polymer forming the unfoamed continuous phase and the polymer forming the foaming structure are polyurethane, and the grinding material formed by the foaming material has better planarization effect on the workpiece to be ground; on the basis, through regulating and controlling the particle size and the dispersion uniformity of the foaming structure, the dispersion uniformity and the pore size uniformity of the pores in the foaming structure can be further improved, the formation of the pores with large pore diameters in the foaming structure is avoided, the damage to the workpiece to be ground caused by the aggregation of grinding particles is avoided, and the yield of the workpiece to be ground is improved. Polyurethane abrasive materials have excellent planarization, particularly for patterned semiconductor wafers.

It will be understood, of course, that the polymer comprising the unfoamed continuous phase and the polymer comprising the foamed structure may not be identical. Illustratively, the polymer comprising the foamed structure is polyurethane, the polymer comprising the unfoamed continuous phase is a mixture of polyurethane and other polymers, e.g., the polymer comprising the foamed structure is TPU, and the polymer comprising the unfoamed continuous phase is a mixture of TPU and TSU.

In the embodiment of the application, the particle size of the foaming structures is 50-3500 micrometers, and meanwhile, the distance between adjacent foaming structures is 20-500 micrometers. In this case, the particle size of the foamed structure has a good uniformity with respect to the foamed material; meanwhile, the foaming structure can be uniformly dispersed in the foaming material, so that the structural difference of the foaming material on the surface and the core layer can be avoided, and the consistency of the performance of the surface of the foaming material and the performance of the inside of the foaming material can be improved. For example, the foaming material provided by the embodiment of the application can avoid uneven heat dissipation caused by the difference of the surface layer and the core layer structure, so that the foaming material has the advantage of even heat dissipation; the foaming material provided by the embodiment of the application can also avoid the influence of the difference of the surface layer and the core layer structure on the planarization effect of the workpiece to be ground. Because the thickness dimension of the polymer abrasive material in the application process can be millimeter (such as an abrasive pad), the excessive size of the foaming structure of the foaming material or the excessive spacing between adjacent foaming structures can reduce the micropore characteristics of the foaming material and even lose the micropore effect.

By way of example only, and not by way of limitation, the particle size of the foaming structure in the foaming material can be 50-300 micrometers, 50-400 micrometers, 50-500 micrometers, 50-600 micrometers, 50-800 micrometers, 50-1000 micrometers, 50-1500 micrometers, 50-2000 micrometers, 50-2500 micrometers, 50-3000 micrometers, 50-3500 micrometers, 100-500 micrometers, 100-600 micrometers, 100-800 micrometers, 100-1000 micrometers, 100-1500 micrometers, 100-2000 micrometers, 100-2500 micrometers, 100-3000 micrometers, 100-3500 micrometers, 150-500 micrometers, 150-600 micrometers, 150-800 micrometers, 200-1000 micrometers, 200-1500 micrometers, 200-2000 micrometers, 200-2500 micrometers, 200-3000 micrometers, 200-3500 micrometers, 300-800 micrometers, 300-1000 micrometers, 300-1500 micrometers, 300-2000 micrometers, 300-2500 micrometers, 300-3000 micrometers, 300-3500 micrometers 400-1000 microns, 400-1500 microns, 400-2000 microns, 400-2500 microns, 400-3000 microns, 400-3500 microns, 500-1000 microns, 500-1500 microns, 500-2000 microns, 500-2500 microns, 500-3000 microns, 500-3500 microns, 600-1000 microns, 600-1500 microns, 600-2000 microns, 600-2500 microns, 600-3000 microns, 600-3500 microns, 800-1200 microns, 800-1500 microns, 800-2000 microns, 800-2500 microns, 800-3000 microns, 800-3500 microns, 1000-1500 microns, 1000-2000 microns, 1000-2500 microns, 1000-3000 microns, 1000-3500 microns, 1500-2000 microns, 1500-2500 microns, 1500-3000 microns, 1500-3500 microns, 2000-3000 microns, 2000-3500 microns, 50-30000 microns. It should be understood that the smaller the particle size range of the foamed structure in the foamed material, the better the uniformity of the particle size of the foamed structure, thereby being more beneficial to reducing the difference of cells in the foamed structure, and obtaining the foamed material with uniform performance.

Exemplary spacing between adjacent foam structures may range from 20 to 100 microns, 20 to 150 microns, 20 to 200 microns, 20 to 250 microns, 20 to 300 microns, 20 to 350 microns, 20 to 400 microns, 20 to 450 microns, 20 to 500 microns, 50 to 100 microns, 50 to 150 microns, 50 to 200 microns, 50 to 250 microns, 50 to 300 microns, 50 to 350 microns, 50 to 400 microns, 50 to 450 microns, 50 to 500 microns, 80 to 150 microns, 80 to 200 microns, 80 to 250 microns, 80 to 300 microns, 80 to 350 microns, 80 to 400 microns, 80 to 450 microns, 80 to 500 microns, 100 to 150 microns, 100 to 200 microns, 100 to 250 microns, 100 to 300 microns, 100 to 350 microns, 100 to 400 microns, 100 to 450 microns, 100 to 500 microns, 150 to 200 microns, 150 to 250 microns, 150 to 300 microns, 150 to 350 microns, 150 to 400 microns, 150 to 450 microns, 150 to 500 microns, 200 to 250 microns, 200 to 300 microns, 200 to 400 microns, 400 to 400 microns, 500 to 250 microns, 500 to 300 microns, 400 to 400 microns, 500 to 250 microns, 500 microns, 400 to 300 microns, 500 microns, 400 to 400 microns, 500 to 300 microns, etc. It should be understood that the smaller the spacing range of adjacent foam structures in the foam, the smaller the structural difference between the foam skin and core layers, and the better the uniformity of material properties. In addition, the smaller the spacing range of adjacent foam structures, the higher the porosity of the foam structures; conversely, the larger the spacing range of adjacent foam structures, the lower the foam structure porosity. In some embodiments, the foaming material is obtained by foaming polymer microspheres by supercritical carbon dioxide and then hot-pressing or bonding and molding, so that the foaming degree of the foaming microspheres, namely the ratio of the foamed core to the unfoamed shell, can be controlled by controlling the technological parameters in the foaming process of the polymer microspheres according to the requirement of the foaming material on the porosity, and the foaming material with different porosities is obtained.

In some embodiments, the larger the particle size range of the foamed structures in the foamed material, the larger the spacing range of adjacent foamed structures; accordingly, the smaller the particle size range of the foam structure in the foam material, the smaller the spacing range of adjacent foam structures. Illustratively, when the particle size of the foam structures in the foam material is less than 500 microns, the spacing between adjacent foam structures is preferably less than 100 microns.

In one possible implementation, the foam structures have a particle size of 100 to 500 microns and the spacing between adjacent foam structures is 50 to 100 microns. Under the condition, the particle size distribution of the foaming structure in the foaming material is more concentrated, and the dispersion of the foaming structure in the foaming material is more uniform, so that the overall uniformity of the foaming material is improved, and the foaming material can exert more uniform and stable performances such as heat dissipation uniformity, scratch resistance and the like.

In the embodiment of the application, foam holes are formed in the foaming structure, so that the foaming material is endowed with excellent foaming micropore performance, such as grinding, heat preservation, noise reduction, vibration reduction and the like.

In one possible implementation, the cells have an average pore size of 1 to 60 microns and the distance between adjacent cells is 1 to 20 microns. In this case, the foaming structure in the foaming material has foam holes with uniform particle size and uniform distribution, which is beneficial to improving the foaming micropore characteristic of the foaming material; in addition, the foaming structure has better size uniformity and dispersion uniformity, so that the performance stability of each area of the foaming material is maintained, and the overall stability of the foaming material is improved. By way of example, when the foaming material is used as the grinding material, since the foam cells in the foaming structure have better particle size uniformity and dispersion uniformity, the aggregation of grinding particles by the large-cell structure can be avoided, and further the aggregated grinding particles are prevented from scratching workpieces to be ground such as wafers, and the yield of the workpieces to be ground is influenced.

In one possible implementation, the cells have an average pore size of 10 to 20 microns and the distance between adjacent cells is 2 to 8 microns. In this case, the particle size distribution of the foaming structure in the foaming material is more concentrated, and the dispersion of the cells in the foaming structure is more uniform, so that the overall performance of the foaming material is uniform and stable, thereby giving the foaming material excellent performance.

In one possible implementation, the foam structure has cells with an average pore size of 1 to 60 microns, a distance between adjacent cells of 1 to 20 microns, and more than 95% of the cells are closed cells. Under the condition, the high closed pore rate enables the foaming material to be rich in a large number of foam cells with uniform particle size and uniform dispersion, so that the foaming material is endowed with excellent foaming micropore characteristics, and the performance of the foaming material in the use of specific application scenes is improved. If the foaming material is used as an abrasive material, the planarization effect is improved due to the high closed cell rate; when the foaming material is used as a heat insulation material and a heat preservation material, the high closed porosity effectively prevents a large number of foam holes in the foaming structure from heat circulation, so that the heat insulation and heat preservation effects are improved; when the foaming material is used as a noise reducing material, the high closed porosity can reduce the circulation of noise, and the like.

In one possible implementation, the foam structure has cells with an average pore size of 10 to 20 microns, a distance between adjacent cells of 2 to 8 microns, and more than 98% of the cells are closed cells. In this case, the foaming material has more excellent foaming microcellular characteristics, thereby better improving the performance of the foaming material.

With the rapid development of the electronic industry, electronic industry product parts or industry materials, including silicon wafers, flat panel displays, memory disks, and the like, that need to be planarized are increasing. Chemical mechanical polishing is a common method of planarization, and polishing pads have received much attention as a key material in the planarization process. During the polishing process, the polishing pad needs to have a certain mechanical strength to maintain a certain polishing speed; at the same time, stable polishing performance is also required to reduce the polishing variation from wafer to wafer. In addition, the polishing pad needs to have as small polishing defects as possible to maintain high-performance planarization quality. Therefore, it is very important to find an abrasive material having a good planarization effect. In addition to the above embodiments, as a first embodiment, a foaming material is used as an abrasive material. In this case, by improving the foaming structure size and dispersion uniformity of the foaming material, the structural difference of the surface layer and the core layer of the abrasive material is reduced, and the heat dissipation uniformity of the abrasive material is improved. Meanwhile, the foaming structure has better size and dispersion uniformity, and the pore diameter uniformity of the cells in the foaming structure is correspondingly improved, so that large cells in the foaming structure can be avoided. Since large cells are easy to gather grinding particles in the grinding fluid, and the surface of a workpiece to be ground such as a wafer is scratched, the anti-scratch performance of the grinding material provided by the embodiment of the application is improved.

As a second embodiment, a foam material is used as the heat insulating material. In this case, by improving the size and dispersion uniformity of the foamed structure of the foamed material, the difference in the flow path of heat in the heat insulating material is reduced, the uniformity of the heat insulating performance between the material surface and the material interior is improved, and the heat insulating performance of the heat insulating material is further improved.

As a third embodiment, a foam material is used as the heat insulating material. In this case, the heat insulation performance of the heat insulation material is improved by improving the size and dispersion uniformity of the foaming structure of the foaming material, and the heat insulation effect of the heat insulation material is improved.

As a fourth embodiment, a foam material is used as a vibration damping material. In this case, by improving the size and dispersion uniformity of the foaming structure of the foaming material, the transmission effect of the vibration damping material on vibration is improved, and the vibration damping difference of materials in different areas is reduced, thereby improving the vibration damping performance of the vibration damping material.

As a fifth embodiment, a foam material is used as the noise reducing material. In this case, by improving the size and dispersion uniformity of the foaming structure of the foaming material, the noise absorption effect of the noise reduction material is improved, the noise reduction difference of the materials in different areas is reduced, and the noise reduction performance of the vibration reduction material is improved.

As a sixth embodiment, since the foaming structure size and dispersion uniformity of the foaming material are improved, when the foaming material is used as a packaging material, the material structure difference can be reduced, thereby improving the overall performance of the material.

As a seventh embodiment, since the foaming structure size and dispersion uniformity of the foaming material are improved, when the foaming material is used as a mold material, the material structure difference can be reduced, thereby improving the overall performance of each material.

The foaming material provided by the embodiment of the application can be prepared by the following method.

Correspondingly, as shown in fig. 4, the embodiment of the application provides a preparation method of a foaming material, which comprises the following steps:

s10, adding polymer microspheres with the particle size of 20-3000 microns into water, and mixing to obtain a mixture; placing the mixture in a high-pressure reaction kettle, injecting supercritical carbon dioxide into the high-pressure reaction kettle, heating and stirring, performing heat preservation treatment after the pressure and the temperature are stable, and releasing pressure after the heat preservation is finished, so that the polymer microsphere is foamed to obtain the polymer foamed microsphere, wherein the polymer foamed microsphere is in a core-shell structure and comprises an unfoamed shell layer and a foamed core.

In this step, the polymeric microspheres are solid microspheres resulting from the polymerization of the polymerized monomers. In one possible implementation, the polymeric microspheres are at least one of thermoplastic elastomer microspheres, polyolefin microspheres, polycarbonate microspheres, polyvinyl alcohol, polyamide microspheres, rubber microspheres, polyaromatic microspheres, fluoropolymer microspheres, polyimide microspheres, polyacrylate microspheres, polyether urea microspheres, polyisocyanurate microspheres, thermoset polyurethane microspheres, polyurea microspheres, polyurethane urea microspheres.

In one possible implementation, the polymeric microspheres are selected from copolymer microspheres formed from at least two of thermoplastic elastomers, polyolefins, polycarbonates, polyvinyl alcohols, polyamides, rubbers, polyaromatic compounds, fluoropolymers, polyimides, polyacrylates, polyether ureas, polyisocyanurate, thermoset polyurethanes, polyureas, polyurethane ureas.

In one possible implementation, the polymeric microspheres include thermoplastic elastomer microspheres, polyolefin microspheres, polycarbonate microspheres, polyvinyl alcohol, polyamide microspheres, rubber microspheres, polyaromatic microspheres, fluoropolymer microspheres, polyimide microspheres, polyacrylate microspheres, polyether urea microspheres, polyisocyanurate microspheres, thermoset polyurethane microspheres, polyurea microspheres, polyurethane urea microspheres, and copolymer microspheres formed from at least two of thermoplastic elastomers, polyolefin, polycarbonate, polyvinyl alcohol, polyamide, rubber, polyaromatic, fluoropolymer, polyimide, polyacrylate, polyether urea, polyisocyanurate, thermoset polyurethane, polyurea, polyurethane urea.

The polymer microsphere provided by the three implementation modes can be subjected to foaming treatment through supercritical carbon dioxide, and the formed cells have good pore diameter uniformity and dispersion uniformity; moreover, the polymer foaming microsphere formed by the material can be formed by hot pressing or bonding of similar polymer binders, so that the fusion property of the foaming material is improved. The foaming material formed by the method has the advantages that the mechanism difference and the material difference of different areas are reduced, so that the performance of the foaming material is improved and stabilized. In addition, according to the type of the polymer of the application demand adjustment of the foaming material, can obtain the foaming material that the performance is different, and then expand the application field of foaming material.

In the embodiment of the application, polymer microspheres with the particle size of 20-3000 microns are selected for foaming to form polymer foaming microspheres. Under the condition, the size of the polymer microsphere can be controlled at the front end of the preparation process of the foaming material, so that the polymer microsphere forms a foaming structure with relatively uniform particle size after foaming, thereby effectively controlling the problem of uneven distribution of the foaming structure in the forming process of the foaming microsphere, further reducing the difference between the surface layer and the core layer of the foaming material, improving the consistency of the performance of the surface and the inner part of the material, and ensuring that the prepared foaming material has uniform and stable performance. By adopting polymer microspheres with particle diameters less than or equal to 3000 micrometers for foaming, the structural difference between the surface layer and the core layer in the forming process is effectively reduced, and the temperature difference caused by different heat dissipation of the surface layer and the internal material is avoided.

By way of example only, and not by way of limitation, the particle size range of the polymeric microspheres may be 20 to 200 microns, 20 to 300 microns, 20 to 400 microns, 20 to 500 microns, 20 to 600 microns, 20 to 800 microns, 20 to 1000 microns, 20 to 1500 microns, 20 to 2000 microns, 20 to 2500 microns, 20 to 3000 microns, 40 to 200 microns, 40 to 300 microns, 40 to 400 microns, 40 to 500 microns, 40 to 600 microns, 40 to 800 microns, 40 to 1000 microns, 40 to 1500 microns, 40 to 2000 microns, 40 to 2500 microns, 40 to 3000 microns, 60 to 200 microns, 60 to 300 microns, 60 to 400 microns, 60 to 500 microns, 60 to 600 microns, 60 to 800 microns, 60 to 1000 microns, 60 to 1500 microns, 60 to 2000 microns, 60 to 2500 microns, 60 to 3000 microns, 100 to 200 microns, 100 to 300 microns, 100 to 400 microns, 100 to 500 microns, 100 to 600 microns, 100 to 800 microns, 100 to 1000 microns, 100 to 1500 microns, 100 to 2000 microns 100 to 2500 microns, 100 to 3000 microns, 200 to 300 microns, 200 to 400 microns, 200 to 500 microns, 200 to 600 microns, 200 to 800 microns, 200 to 1000 microns, 200 to 1500 microns, 200 to 2000 microns, 200 to 2500 microns, 200 to 3000 microns, 300 to 400 microns, 300 to 500 microns, 300 to 600 microns, 300 to 800 microns, 300 to 1000 microns, 300 to 1500 microns, 300 to 2000 microns, 300 to 2500 microns, 300 to 3000 microns, 400 to 500 microns, 400 to 600 microns, 400 to 800 microns, 400 to 1000 microns, 400 to 1500 microns, 400 to 2000 microns, 400 to 2500 microns, 400 to 3000 microns, 500 to 600 microns, 500 to 800 microns, 500 to 1000 microns, 500 to 1500 microns, 500 to 2000 microns, 500 to 2500 microns, 500 to 3000 microns, 600 to 800 microns, 600 to 1000 microns, 600 to 1500 microns, 600 to 2000 microns, 600 to 2500 microns, 600-3000 microns, 800-1000 microns, 800-1500 microns, 800-2000 microns, 800-2500 microns, 800-3000 microns, 1000-1500 microns, 1000-2000 microns, 1000-2500 microns, 1000-3000 microns, 1200-1500 microns, 1200-2000 microns, 1200-2500 microns, 1200-3000 microns, 1500-2000 microns, 1500-2500 microns, 1500-3000 microns, 2000-2500 microns, 2000-3000 microns, 2500-3000 microns, 50-30000 microns, etc. It should be understood that the smaller the particle size range of the foamed structure in the foamed material, the better the uniformity of the particle size of the foamed structure, thereby being more beneficial to reducing the difference of cells in the foamed structure, and obtaining the foamed material with uniform performance.

In one possible implementation, the polymeric microspheres have a particle size of 100 to 5000 microns. In this case, the polymer microspheres are foamed to form a foamed structure having better uniformity of particle size and uniformity of dispersion.

In the embodiment of the application, the polymer microsphere with proper size can be obtained through screening. The polymer microsphere can be prepared by suspension polymerization, precipitation polymerization, emulsion polymerization, suspension polymerization, glass film emulsification method, interfacial polymerization, precipitation polymerization, extrusion granulation and cutting grinding. In one possible implementation, the polymer microspheres with the particle size of 20-3000 microns can be directly prepared through suspension polymerization and precipitation polymerization. Moreover, the polymer microsphere prepared by suspension polymerization has better dispersibility and is not easy to adhere; the polymer microsphere prepared by precipitation polymerization has the advantage of low cost.

In one possible implementation, the polymeric microspheres are polyurethane microspheres, and the polyurethane microspheres are prepared by: preparing an organic solution of polymer polyol, adding isocyanate into the organic solution of the polymer polyol, mixing, standing and reacting to obtain the polyurethane microsphere. The polyurethane microsphere is used as a polymer microsphere, and the formed foaming material has excellent planarization effect as an abrasive material; moreover, after the polyurethane microsphere is subjected to supercritical carbon dioxide foaming treatment, the polyurethane grinding material is formed through hot pressing or bonding, the pore size of the foam holes is good in uniformity, and the grinding material can be prevented from being locally aggregated on the grinding material to damage a workpiece to be ground.

In the implementation mode, the polymer polyol solution is prepared in the organic solution of the polymer polyol, the concentration of the polymer polyol is reduced, and then isocyanate is added, so that the problem that severe reaction occurs due to overhigh local concentration when the polymer polyol and the isocyanate are added simultaneously is avoided.

In some embodiments, the polymer polyol is subjected to a drying process prior to the preparation of the organic solution of the polymer polyol; before adding isocyanate, the isocyanate is dried to avoid introducing water into the reaction system and interfering the polymerization reaction. The drying method and the drying atmosphere are not strictly limited, and a vacuum atmosphere may be used, or an inert atmosphere or air may be used. Illustratively, the isocyanate and polymer polyol are dried under heat and vacuum. Wherein the heating temperature is less than the glass transition temperature Tg to prevent the adhesion between isocyanate and polymer polyol; drying efficiency is promoted by vacuum conditions.

In one embodiment, in the step of adding isocyanate to the organic solution of polymer polyol, the molar ratio of isocyanate groups to hydroxyl groups is 1: (1 to 1.05), and adding isocyanate into the organic solution of the polymer polyol. In the application, in the polymerization reaction of polymer polyol and isocyanate polyol, polymer polyol with a molar content slightly more than that of isocyanate is introduced, so that more stable isocyanate polyol is used as an end group, and stable polymer microspheres are obtained, and the polymer blocked by isocyanate is prevented from being unstable under the conditions of water and the like, and the formation of a foaming material is prevented from being influenced in the supercritical carbon dioxide foaming process.

In one embodiment, the step of adding isocyanate to the organic solution of polymer polyol further comprises: a catalyst is added to the organic solution of the polymer polyol, the catalyst being used to catalyze the polymerization reaction between the polymer polyol and the isocyanate. By adding a catalyst, the rate of formation of polymer microspheres from polymer polyols and isocyanates can be accelerated. Illustratively, the catalyst is an organic amine, such as triethylamine.

Adding isocyanate into the organic solution of polymer polyol or adding isocyanate and catalyst into the organic solution of polymer polyol, mixing, standing for reaction for a period of time to make the conversion rate of the reaction monomer reach above 90%. The method of the mixing treatment is not limited, and a manual shaking method may be used, but is not limited thereto.

An exemplary method for preparing the polyurethane microsphere is as follows: drying the isocyanate and the polymer polyol under heating and vacuum conditions; fully dissolving polyol in acetonitrile through ultrasonic, uniformly mixing, adding isocyanate, uniformly mixing, and standing for reaction; and after the reaction is finished, centrifugally separating the mixture, washing the obtained solid with acetonitrile, and heating and drying to obtain the thermoplastic polyurethane microspheres.

In the embodiment of the application, polymer microspheres (solid microspheres) are subjected to foaming treatment by using supercritical carbon dioxide to prepare the polymer foaming microspheres. Compared with a method for gasifying, expanding and foaming by means of low-boiling-point hydrocarbon stored in a polymer, supercritical gas is adopted for foaming, so that the pore difference caused by uneven pore size of microspheres in the gasifying, expanding and foaming process can be avoided, large-pore cells are avoided in the foaming process, and the pore size and dispersion uniformity of the cells are improved. Particularly, when the supercritical carbon dioxide is used for preparing the grinding material, as the foaming process is not easy to form large-aperture cells, the damage to a workpiece to be ground caused by the aggregation of grinding particles in the large-aperture cells can be avoided, if the existence of the large aperture can cause the aggregation of the grinding particles in the wafer grinding process, and wafer scratches are formed.

In the embodiment of the application, before the supercritical carbon dioxide foaming is performed, the polymer microspheres are added into water to be mixed to obtain a mixture, so that the polymer microspheres are prevented from being adhered. Then placing the mixture into a high-pressure reaction kettle, injecting supercritical carbon dioxide into the high-pressure reaction kettle, heating and stirring, and preserving heat after the pressure and the temperature are stable, so that the supercritical carbon dioxide is fully infiltrated into the polymer microspheres. In the embodiment of the application, when supercritical carbon dioxide is used for foaming, the foaming temperature is higher than Tg of the polymer microsphere base material, and Tm of the polymer microsphere base material is low.

And (3) performing pressure relief treatment after heat preservation is finished, and changing the supercritical carbon dioxide into gaseous carbon dioxide through rapid pressure relief. The gaseous carbon dioxide formed in the polymer microsphere has high diffusion resistance and is aggregated to form cells; the carbon dioxide on the surface of the polymer microsphere escapes, and the epidermis forms a structure with less pores, namely a skin structure, which is also called an unfoamed shell layer. Thus, polymer expanded microspheres are formed by supercritical carbon dioxide. The polymer foaming microsphere is in a core-shell structure and comprises a foaming core and a shell layer coated on the surface of the core, wherein the shell layer is an unfoamed shell layer. The polymer foam microsphere is formed by supercritical carbon dioxide, the pores of the shell layer are large and small in number, and the cells formed in the core are small and large in number. After the hot pressing or bonding forming treatment is carried out in the following steps, the shell layer materials are fused to form a continuous phase, and the foam structure is formed by uniformly dispersed cores with pore sizes of cells, so that the material structure difference caused by inconsistent cell sizes and distribution on the surface and the inside of the foam microsphere is eliminated, and the foam structure is prevented from forming a core-skin structure with structure difference.

In one possible implementation, the average thickness of the shell layer is 10 to 30 microns and the particle size of the core is 20 to 500 microns. Under the condition, the foaming structure is uniform in size, and as the average thickness of the shell layers is relatively uniform, after hot pressing or bonding molding, the shell layers form a continuous phase and have relatively uniform distances between adjacent foaming structures, so that the foaming structures can be uniformly dispersed in the foaming material, and the foaming material can exert more uniform and stable performances such as heat dissipation uniformity, scratch resistance and the like.

In one embodiment, the polymeric microspheres are thermoplastic polyurethane microspheres and the method of foaming the thermoplastic polyurethane microspheres is: adding thermoplastic polyurethane microspheres into water, mixing, and placing into a high-pressure reaction kettle; injecting supercritical carbon dioxide with certain pressure into a high-pressure reaction kettle through a high-pressure flowmeter, heating and stirring, and preserving heat for a certain time after the pressure and the temperature are stable; finally, the thermoplastic polyurethane foaming microsphere is obtained through rapid decompression.

S20, injecting the polymer foaming microspheres into a mold, carrying out hot pressing treatment, and demolding to obtain a foaming material; or mixing the binder raw material with the polymer foaming microsphere, injecting the mixture into a mold, heating the mixture for reaction, and demolding the mixture to obtain the foaming material, wherein the foaming material comprises an unfoamed continuous phase and foaming structures dispersed in the unfoamed continuous phase, the foaming structures are internally provided with foam holes, the particle size of the foaming structures is 50-3500 microns, and the distance between adjacent foaming structures is 20-500 microns.

This step provides two methods for forming polymeric expanded microspheres to produce a foamed material.

In a first possible implementation, a method for preparing a foamed material by shaping polymeric foamed microspheres includes: injecting the polymer foaming microsphere into a mould, carrying out hot pressing treatment, and demoulding to obtain the foaming material. Through hot pressing treatment, the surface shell layers of the polymer foaming microsphere are fused to form a continuous phase to cover the core, so that a foaming structure is formed, the integral fusion property of the foaming material can be improved, and the foaming structure can be favorably improved to maintain good dispersion uniformity of the foaming material.

In one embodiment, as shown in fig. 5, the step of hot pressing to prepare the foaming material includes:

In this case, the shell layers of the polymer foam microspheres are fused to form a continuous phase, and the cores of the foam microspheres are fixed therein to form a foam structure of the foam material by heat treatment. The size uniformity and the distribution uniformity of the foaming structure of the foaming material are improved, and the structural difference of different areas of the foaming material can be reduced, so that the foaming material can maintain stable performance.

In this embodiment, the product after the hot press molding is cooled and demolded, and a foaming material can be obtained.

In a second possible implementation, a method for preparing a foamed material by shaping polymeric foamed microspheres includes: mixing the adhesive raw material with the polymer foaming microsphere, injecting into a mold, heating for reaction, and demolding to obtain the foaming material. According to the method, the adhesive raw material is added, so that the shell layers on the surfaces of the polymer foaming microspheres are bonded to form a continuous unfoamed structure, and the foaming structure is kept to maintain good dispersion uniformity in the foaming material. In addition, the content of the adhesive can be regulated by the method, so that the porosity of the foaming material can be regulated.

In one possible implementation, the step of mixing the binder raw material with the polymer expanded microspheres and injecting into a mold, and heating the reaction comprises:

mixing the raw material of the adhesive with polymer foaming microspheres to obtain a mixed solution;

and injecting the mixed solution into a mold, and heating to form.

In this case, the binder raw material forms a binder under heating conditions, the shell layers of the polymer foam microspheres are fused to form a continuous phase, and the cores of the foam microspheres are fixed therein to form a foam structure of the foam material. The size uniformity and the distribution uniformity of the foaming structure of the foaming material are improved, and the structural difference of different areas of the foaming material can be reduced, so that the foaming material can maintain stable performance. In addition, the porosity of the foaming material can be regulated and controlled by the added adhesive, so that the foaming material is suitable for the use requirements of different scenes. In particular, since it is difficult to prepare a foamed material having a low porosity by supercritical carbon dioxide foaming (due to the difficulty of the supercritical carbon dioxide of the first concentration entering the substrate itself, it is possible to reduce the porosity of the material by increasing the content of the continuous phase by adding a binder.

In this embodiment, the foamed material can be obtained by cooling and demolding the product after the bonding molding.

In one embodiment, the polymeric foam microspheres are polyurethane foam microspheres; the raw materials of the adhesive are isocyanate prepolymer, polymer polyol and cross-linking agent. At this time, as shown in fig. 6, the binder raw material and the polymer foam microspheres are mixed and then injected into a mold, and the heating reaction step includes: and uniformly mixing the isocyanate prepolymer, the polymer polyol, the cross-linking agent and the polyurethane foaming microsphere, injecting the mixture into a mold, heating the mixture to be molded, cooling and demolding the molded product to obtain the foaming material. In this case, the binder formed by the isocyanate prepolymer, the polymer polyol and the crosslinking agent is also polyurethane, and can be fused with the shell layer of the polymer foam microsphere to form a continuous phase with good fusion, so that the structural and material uniformity of the foam material is improved.

According to the embodiment of the application, the foaming process of the polymer microsphere and the forming process of the foaming material are carried out in two steps, so that the problem that the size and the distribution of foam holes formed by foaming are uneven due to heating and heat dissipation in the process of one-step material integrated forming can be effectively avoided, and the uniformity and the distribution uniformity of the size of the foam holes of the foaming structure and the size of the foam holes are further improved.

According to the embodiment of the application, the porosity can be controlled by adjusting the size of the microspheres, controlling the content of the binder and adjusting and controlling the supercritical carbon dioxide foaming multiplying power, so that the preparation of foaming materials with various porosities can be realized, and the porosity adjustable range of the materials is widened. The foaming material prepared by the method provided by the embodiment of the application can be applied as grinding materials, heat insulation materials, heat preservation materials, packaging materials, vibration reduction materials, noise reduction materials and model materials.

In an embodiment of the present application, an abrasive material is also provided. The abrasive material is the foam of the first aspect or the foam produced by the second aspect. The obtained grinding material has the advantages that the foaming structure is dispersed in the continuous phase non-foaming structure, and the particle size uniformity and the dispersion uniformity are good in the whole grinding material, so that the difference of the surface layer and the core layer of the grinding material can be reduced, the skin-core structure of the grinding material is avoided, the temperature difference of the surface layer and the core layer of the grinding material caused by different heat dissipation is reduced, and the foaming material has the advantage of uniform heat dissipation. Moreover, the foaming structure with uniform particle size is beneficial to improving the uniformity of pore diameters of cells, so that aggregation of grinding particles by cells with large pore diameters is avoided, scratches of a workpiece to be ground such as a wafer by the grinding material are reduced, and planarization effect is improved. In addition, the porosity of the grinding material can be adjusted by providing the polymer microsphere size, the supercritical carbon dioxide foaming multiplying power and the like in the method provided by the second aspect, so that the requirements of different workpieces to be ground on the porosity of the grinding material can be better met.

The polishing material provided by the embodiment of the application can be used for polishing workpieces waiting to be polished, such as semiconductor substrates, optical substrates and magnetic substrates, and at the moment, products formed by the polishing material are called polishing pads. Illustratively, the workpiece to be abraded is to be a semiconductor substrate, wafer, metallurgy, storage disk surface, optical element, lens, wafer template.

Illustratively, a wafer in chip processing is polished by using a polishing pad. During the polishing process, the polishing pad is mounted on the polishing platen and rotates with the polishing platen. The polishing head fixes the wafer, and the wafer is turned upside down to be contacted with the polishing pad, and a certain pressure is applied. And adding grinding fluid on the surface of the grinding pad, starting the grinding head and the grinding table, and enabling the grinding head to rotate relative to the grinding table along with the wafer, wherein the surface of the wafer and the grinding pad relatively move. And (3) polishing the wafer through the polishing liquid on the surface of the polishing pad. It should be understood that when the workpiece to be abraded is another workpiece, the workpiece to be abraded is illustratively a semiconductor substrate, a wafer, a metallurgy, a memory disk surface, an optical element, a lens, a wafer template, or the like, and the wafer is replaced with another workpiece to be abraded, and the abrasion of the workpiece to be abraded is achieved by the same principle.

The following description is made with reference to specific embodiments.

Example 1

A method of making an abrasive material comprising the steps of:

(1) Preparing TPU microspheres by a precipitation method: diphenylmethane diisocyanate (MDI) and polytetrahydrofuran ether-650 (PTMG-650) were dried in vacuo at 95 ℃ for 3 hours. Acetonitrile (100 g) and PTMG-650 (32.5 g, about 100. Mu. Mol of hydroxyl group) were added to a 500mL reaction flask, and the mixture was subjected to ultrasonic dispersion to completely dissolve PTMG-650; MDI (13.2 g, about 100 μmol of isocyanate groups) and triethylamine (TEA, 1.28 g) were added to the solution; after hand shaking and mixing evenly, the reaction bottle is sealed and placed in a constant temperature water bath at 40 ℃ for reaction for 5 hours. After the reaction, the mixture was centrifuged, and the obtained solid was washed with acetonitrile for 3 times and dried at 50℃for 24 hours to obtain polyurethane microspheres.

The polyurethane microsphere prepared by the step has a particle size ranging from 20 to 300 microns and an average particle size of about 100 microns through SEM test.

(2) Preparing TPU foaming microspheres: 50g of the TPU solid microspheres synthesized in step (1) were weighed, mixed with 2500mL of medium water, and placed in an autoclave reaction chamber provided with a perforated plate at the bottom. 12MPa CO is injected into the reaction chamber through a high-pressure fluid metering pump ₂ Air in the reaction kettle is discharged; at the same time, the autoclave controller was turned on to heat the material system to 108℃with a stirring rate of 300rpm. After the pressure and the temperature are stable, the heat preservation and pressure maintaining stage is started for 2 hours. Closing the high-pressure fluid metering pump, quickly opening the ball valve connected with the discharge pipe, and enabling the suspension medium to enter the collecting barrel. And closing the reactor controller, and stopping heating and stirring. The kettle cover was opened, the foam beads were taken out from the reaction chamber, and the initial expansion ratio was measured. The obtained expanded beads were washed and left at room temperature and pressure for 48 hours or more to obtain cured beads.

The TPU expanded microsphere prepared by the step has the particle size range of 20-500 microns, the average particle size of about 200 microns, the average thickness range of an unfoamed structure (shell layer) of 10-30 microns, the average thickness of the shell layer of about 20 microns, the distance range between adjacent cells of 1-20 microns, the average distance between adjacent cells of about 5 microns, the pore size range of about 1-60 microns and the average pore size of about 10 microns.

(3) Compression molding of TPU:

preheating the TPU foaming microsphere prepared in the step (2) at the temperature of 90 ℃, placing the preheated TPU foaming microsphere in a preheated die (110 ℃), continuously heating the die, maintaining the temperature at 105-115 ℃, applying pressure to the die, and maintaining the temperature for 10 minutes. The mold was slowly cooled to room temperature (30 minutes), and the abrasive material, i.e., the polishing pad substrate, was obtained by taking out the mold.

The grinding material prepared by the step is tested by SEM, the distance between adjacent foaming structures is 20-60 micrometers, and the average distance is about 40 micrometers; the honeycomb of the honeycomb-like unfoamed structure (foamed structure) had a diameter in the range of 30 to 500 μm and an average diameter of about 200. Mu.m. The distance between adjacent cells is in the range of 1-20 microns, the average distance between adjacent cells is about 5 microns, the pore size of the cells is in the range of about 1-60 microns, and the average pore size is about 10 microns.

The abrasive material prepared in example 1 has an average pore size of about 10 microns, more than 95% of the pores are closed-cell, the cells are uniformly distributed, and the hardness of the abrasive material is more adjustable. This is due to: the foaming process and the molding process of the grinding material are carried out in two steps, so that the problem of non-uniformity of cells caused by uneven heating and heat dissipation in the gas heating expansion foaming process is effectively avoided; meanwhile, the introduction of microspheres with a second structure is avoided, and the process difficulty is reduced. The abrasive material prepared in example 1 had uniform cell distribution between the upper and lower layers, the middle and the edges. The final abrasive material had a hardness of about 30D and an abrasive material density of about 0.76g/cm ³ The compression ratio was about 1.3.

Example 2

A method of making an abrasive material comprising the steps of:

(3) Compression molding TPU and TSU:

480g of TPU foamed solid microspheres prepared in the step (2) are weighed, 300g of a prepolymer (isocyanate end-capped) of TDI and PTMG (Mn=650) are added, a mixture of polyether polyol 4110 and para-di-o-chloroaniline methane (NCO: OH molar ratio of 2.2:1) is added, the mixture is uniformly mixed and degassed, the mixture is injected into a mold, the temperature is maintained at about 80 ℃, the reaction is maintained for about 24 hours, the reaction is carried out for 30 minutes, the reaction is cooled to room temperature, the mold is removed, and the polishing pad substrate is taken out of the mold.

The grinding material prepared by the step is tested by SEM, the distance between adjacent foaming structures is 22-80 microns, and the average distance is about 50 microns; the honeycomb of the honeycomb-like unfoamed structure (foamed structure) had a diameter in the range of 30 to 500 μm and an average diameter of about 230. Mu.m. The distance between adjacent cells is in the range of 1-20 microns, the average distance between adjacent cells is about 5 microns, the pore size of the cells is in the range of about 1-60 microns, and the average pore size is about 10 microns.

The abrasive material prepared in example 2 had an average pore size of about 100 microns and over 95% of the cells were closed cell structure and uniformly distributed. This is due to: the foaming process and the molding process of the grinding material are carried out in two steps, so that the problem of non-uniformity of cells caused by uneven heating and heat dissipation in the gas heating expansion foaming process is effectively avoided; meanwhile, the introduction of microspheres with a second structure is avoided, and the process difficulty is reduced. After the polishing material prepared in example 2 was cut into a polishing pad, cells were uniformly distributed between the upper and lower layers, the middle and the edge of the polishing pad. The final abrasive material had a hardness of about 35D and an abrasive material density of about 0.97g/cm ³ The compression ratio was about 0.9.

In contrast to example 1, the abrasive material prepared in example 2 incorporates a thermoset polyurethane material such that the continuous unfoamed phase is a mixture of thermoplastic and thermoset polyurethane, but the foamed structure is still a thermoplastic polyurethane material. The technology can expand the material selection range of the grinding material, realize the performance adjustment of wide distribution of grinding performance, and is more beneficial to the realization of the grinding material with various performance characteristics.

Example 3

A method of making an abrasive material comprising the steps of:

(1) Preparing TPU foaming microspheres: 50g of the TPU solid microspheres extruded and pelletized were weighed, mixed with 2500mL of medium water and placed in an autoclave reaction chamber equipped with a perforated plate at the bottom. 12MPa CO is injected into the reaction chamber through a high-pressure fluid metering pump ₂ Air in the reaction kettle is discharged; at the same time, the autoclave controller was turned on to heat the material system to 108℃with a stirring rate of 300rpm. After the pressure and the temperature are stable, the heat preservation and pressure maintaining stage is started for 2 hours. Closing the high-pressure fluid metering pump, quickly opening the ball valve connected with the discharge pipe, and enabling the suspension medium to enter the collecting barrel. Closing the reactor controller and stopping Heating and stirring. The kettle cover was opened, the foam beads were taken out from the reaction chamber, and the initial expansion ratio was measured. The obtained expanded beads were washed and left at room temperature and pressure for 48 hours or more to obtain cured beads.

The TPU expanded microsphere prepared by the step has the particle size range of 2000-3000 microns, the average particle size of about 2800 microns, the average thickness of an unfoamed structure (shell layer) is 10-50 microns, the average thickness of the shell layer is about 30 microns, the distance between adjacent cells is 1-20 microns, the average distance between adjacent cells is about 10 microns, the pore size of the cells is about 1-60 microns, and the average pore size is about 30 microns.

(2) Compression molding TPU and TSU:

and (2) weighing 520g of TPU foaming solid microspheres prepared in the step (1), adding 300g of a mixture of the adhesive A and the adhesive B, uniformly mixing, degassing, injecting into a mould, maintaining the temperature at about 80 ℃, reacting for about 24 hours, cooling to room temperature within 30 minutes, taking out of the mould, and taking out the grinding pad substrate from the mould.

The grinding material prepared by the step is tested by SEM, the distance between adjacent foaming structures is 20-200 micrometers, and the average distance is about 50 micrometers; the unfoamed structure had a diameter in the range of 2800-3500 microns with an average diameter of about 3000 microns. The distance between adjacent cells is in the range of 1-20 microns, the average distance between adjacent cells is about 10 microns, the pore size of the cells is in the range of about 1-60 microns, and the average pore size is about 30 microns.

The abrasive material prepared in example 3 had an average pore size of about 30 microns and over 95% of the cells were closed cell structure and uniformly distributed. This is due to: the foaming process and the molding process of the grinding material are carried out in two steps, so that the problem of non-uniformity of cells caused by uneven heating and heat dissipation in the gas heating expansion foaming process is effectively avoided; meanwhile, the introduction of microspheres with a second structure is avoided, and the process difficulty is reduced. After the polishing material prepared in example 3 was cut into a polishing pad, cells were uniformly distributed between the upper and lower layers, the middle and the edge of the polishing pad. The final abrasive had a hardness of about 45D and an abrasive density of about 0.89g/cm ³ The compression ratio was about 0.8.

In contrast to example 1, the abrasive material prepared in example 3 incorporates a thermoset polyurethane material such that the continuous unfoamed phase is a mixture of thermoplastic and thermoset polyurethane, but the foamed structure is still a thermoplastic polyurethane material. The technology can expand the material selection range of the grinding material, realize the performance adjustment of wide distribution of grinding performance, and is more beneficial to the realization of the grinding material with various performance characteristics.

The abrasive material prepared in example 3, incorporating a lower molecular weight polyol, resulted in a harder abrasive material than in example 2.

Example 4

A method of making an abrasive material comprising the steps of:

(1) Preparing TPU foaming microspheres: 50g of the TPU solid microspheres extruded and pelletized were weighed, mixed with 2500mL of medium water and placed in an autoclave reaction chamber equipped with a perforated plate at the bottom. 12MPa CO is injected into the reaction chamber through a high-pressure fluid metering pump ₂ Air in the reaction kettle is discharged; at the same time, the autoclave controller was turned on to heat the material system to 108℃with a stirring rate of 300rpm. After the pressure and the temperature are stable, the heat preservation and pressure maintaining stage is started for 2 hours. Closing the high-pressure fluid metering pump, quickly opening the ball valve connected with the discharge pipe, and enabling the suspension medium to enter the collecting barrel. And closing the reactor controller, and stopping heating and stirring. The kettle cover was opened, the foam beads were taken out from the reaction chamber, and the initial expansion ratio was measured. The obtained expanded beads were washed and left at room temperature and pressure for 48 hours or more to obtain cured beads.

(2) Compression molding TPU and TSU:

80g of TPU foamed solid microspheres prepared in the step (2) are weighed, 400g of a prepolymer (isocyanate end-capped) of TDI and PTMG (Mn=650) are added, a mixture of polyether polyol 4110 and para-di-o-chloroaniline methane (NCO: OH molar ratio of 2.2:1) is added, the mixture is uniformly mixed and degassed, the mixture is injected into a mold, the temperature is maintained at about 80 ℃, the reaction is maintained for about 24 hours, the temperature is cooled to room temperature within 30 minutes, the mold is removed, and the polishing pad substrate is taken out of the mold.

The grinding material prepared by the step is tested by SEM, the distance between adjacent foaming structures is 20-500 micrometers, and the average distance is about 100 micrometers; the unfoamed structure had a diameter in the range of 2800-3800 microns and an average diameter of about 3300 microns. The distance between adjacent cells is in the range of 1-20 microns, the average distance between adjacent cells is about 10 microns, the pore size of the cells is in the range of about 1-60 microns, and the average pore size is about 30 microns.

The abrasive material prepared in example 4 had an average pore size of about 3 microns and over 95% of the cells were closed cell structure and uniformly distributed. This is due to: the foaming process and the molding process of the grinding material are carried out in two steps, so that the problem of non-uniformity of cells caused by uneven heating and heat dissipation in the gas heating expansion foaming process is effectively avoided; meanwhile, the introduction of microspheres with a second structure is avoided, and the process difficulty is reduced. After the polishing material prepared in example 4 was cut into a polishing pad, cells were uniformly distributed between the upper and lower layers, the middle and the edge of the polishing pad. The final abrasive material had a hardness of about 55D and an abrasive material density of about 1.18g/cm ³ The compression ratio was about 0.5.

The abrasive materials prepared in example 4 have reduced expanded microsphere content (binder added) compared to examples 1-3, and the resulting abrasive materials have greater hardness, higher density, and lower compressibility.

Finally, it should be noted that: the foregoing is merely a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical scope of the present disclosure should be covered in the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

A foamed material comprising a plurality of foamed structures having a plurality of cells therein, wherein an average distance between the foamed structures is greater than an average distance between the cells.
The foam material of claim 1, wherein the foam structure has a particle size of 50 to 30000 microns and an average spacing between adjacent foam structures is 2 to 10000 microns.
The foam of claim 1, wherein the foam structures have a particle size of 100 to 5000 microns and an average spacing between adjacent foam structures is 50 to 1000 microns.
The foam of claim 1, wherein the foam structures have a particle size of 200 to 3500 microns and an average spacing between adjacent foam structures is 50 to 500 microns.
The foamed material of claim 1, wherein said cells have an average pore size of 1 to 200 microns and an average distance between adjacent ones of said cells is 1 to 500 microns.
The foamed material of claim 1, wherein said cells have an average pore size of 1 to 60 microns and an average distance between adjacent ones of said cells is 1 to 60 microns.
The foamed material of claim 1, wherein said cells have an average pore size of 10 to 40 microns and an average distance between adjacent ones of said cells is 2 to 40 microns.
The foam of claim 1, wherein the foam comprises unfoamed structures dispersed in the foamed structure.
The foamed material according to any one of claims 1 to 7, wherein the polymer constituting the unfoamed structure and the polymer of the foamed structure may be the same or different.
The foamed material of claims 1 to 8, wherein at least one of the unfoamed polymer and the foamed polymer is a thermoplastic polymer, a thermosetting polymer, or a mixture of a thermoplastic polymer and a thermosetting polymer.
The foamed material of claim 10, wherein the foamed structure is a thermoplastic polymer and the unfoamed structure is a thermoset polymer.
The foamed material of claim 10, wherein at least one of the unfoamed polymer and the foamed polymer is selected from one of thermoplastic elastomers, polyolefin, polycarbonate, polyvinyl alcohol, polyamide, rubber, polyaromatic, fluoropolymer, polyimide, polyacrylate, polyether urea, polyisocyanurate, thermoset polyurethane, polyurea, polyurethane urea, and/or the polymer is selected from a copolymer or mixture of at least two of thermoplastic elastomers, polyolefin, polycarbonate, polyvinyl alcohol, polyamide, rubber, polyaromatic, fluoropolymer, polyimide, polyacrylate, polyether urea, polyisocyanurate, thermoset polyurethane, polyurea, polyurethane urea.
The foamed material of any of claims 1-7, wherein greater than 95% of the cells in the foamed structure are closed cells.
The foam material according to any one of claims 1 to 7, wherein the density of the material is in the range of 0.3 to 1.1g/cm3.
The foam material according to any one of claims 1 to 7, wherein the density of the material is in the range of 0.6-1g/cm3.
The cell of claim 1, wherein the cell walls and the polymer between adjacent cells are of the same material in the same foamed structure.
The unfoamed structure of claim 1, wherein the cell content is <10%.
The unfoamed structure of claim 1, wherein the number of voids having a size > 200 μm is less than the number of foamed structures.
The preparation method of the foaming material is characterized by comprising the following steps:

adding polymer microspheres with the particle size of 20-3000 micrometers into water, and mixing to obtain a mixture; placing the mixture in a high-pressure reaction kettle, injecting supercritical gas into the high-pressure reaction kettle, heating and stirring, performing heat preservation treatment after the pressure and the temperature are stable, and releasing pressure after the heat preservation is finished, so that the polymer microspheres are foamed to obtain polymer foamed microspheres, wherein the polymer foamed microspheres are of a core-shell structure and comprise unfoamed shell layers and foamed cores;

injecting the polymer foaming microsphere into a mould, carrying out hot pressing treatment, and demoulding to obtain a foaming material; or mixing the adhesive raw material with the polymer foaming microsphere, injecting the mixture into a mold, heating the mixture for reaction, and demolding the mixture to obtain the foaming material, wherein the foaming material comprises an unfoamed continuous phase and foaming structures dispersed in the unfoamed continuous phase, and the foaming structures are internally provided with foam cells, wherein the particle size of the foaming structures is 50-3500 microns, and the interval between adjacent foaming structures is 20-500 microns.
The method of producing a foamed material according to claim 19, wherein the polymer microsphere is at least one of a thermoplastic elastomer microsphere, a polyolefin microsphere, a polycarbonate microsphere, a polyvinyl alcohol, a polyamide microsphere, a rubber microsphere, a polyaromatic microsphere, a fluoropolymer microsphere, a polyimide microsphere, a polyacrylate microsphere, a polyether urea microsphere, a polyisocyanurate microsphere, a thermosetting polyurethane microsphere, a polyurea microsphere, a polyurethane urea microsphere, and/or

The polymer microsphere is a copolymer microsphere formed by at least two of thermoplastic elastomer, polyolefin, polycarbonate, polyvinyl alcohol, polyamide, rubber, polyaromatic compound, fluorine polymer, polyimide, polyacrylate, polyether urea, polyisocyanurate, thermosetting polyurethane, polyurea and polyurethane urea.
The method of claim 19, wherein the polymer microsphere is a polyurethane microsphere, and the method of preparing the polyurethane microsphere comprises: preparing an organic solution of polymer polyol, adding isocyanate into the organic solution of the polymer polyol, mixing, standing and reacting to obtain the polyurethane microsphere.
The method for producing a foamed material according to claim 19, wherein in the step of adding isocyanate to the organic solution of the polymer polyol, the molar ratio of isocyanate groups to hydroxyl groups is 1: (1-1.05) adding isocyanate to the organic solution of the polymer polyol.
The method of producing a foamed material according to claim 21, wherein the step of adding isocyanate to the organic solution of the polymer polyol further comprises:

a catalyst is added to the organic solution of the polymer polyol, the catalyst being used to catalyze the polymerization reaction between the polymer polyol and the isocyanate.
The method for preparing a foamed material according to any one of claims 19 to 23, wherein the average thickness of the shell layer is 10 to 30 μm and the particle diameter of the core is 20 to 500 μm.
A method of preparing a foamed material according to any one of claims 19 to 23, wherein the step of injecting the polymeric foamed microspheres into a mould and hot pressing comprises:

heating the polymer expanded microspheres to a temperature above the Tg and below the Tm of the microsphere polymer;

and injecting the heated polymer foaming microsphere into a mould, and pressurizing to form.
A method of preparing a foamed material according to any one of claims 19 to 23, wherein the step of mixing a binder material with the polymeric foam microspheres and injecting the mixture into a mold, and the step of heating the mixture to react comprises:

mixing the binder raw material with the polymer foaming microsphere to obtain a mixed solution;

and injecting the mixed solution into a mould, and heating to form.
The method of claim 26, wherein the polymeric foam microspheres are polyurethane foam microspheres; the raw materials of the adhesive are isocyanate prepolymer, polymer polyol and cross-linking agent.
Use of a foamed material according to any one of claims 1 to 18 or a foamed material produced by a method according to any one of claims 19 to 27 as an abrasive material, a heat insulating material, a packaging material, a vibration damping material, a noise reducing material, a model material.
An abrasive material, characterized in that the abrasive material is a foamed material according to any one of claims 1 to 18 or a foamed material produced by the method according to any one of claims 19 to 27.