Modified heat-expandable microspheres and preparation method thereof, foamed silicone rubber and preparation method thereof

Abstract

The present application discloses a modified heat-expandable microsphere and a preparation method thereof, a foamed silicone rubber and a preparation method thereof, and belongs to the technical field of organic materials. The modified heat-expandable microsphere comprises a heat-expandable microsphere matrix and a photoluminescent modification layer, the photoluminescent modification layer is arranged on the surface of the heat-expandable microsphere matrix, and the photoluminescent modification layer comprises a spiro compound having a photoluminescent effect. The modified heat-expandable microsphere of the present application can improve the luminescence uniformity of the foamed silicone rubber.

Description

Technical Field

[0001] The present application relates to the technical field of organic materials, and in particular to a modified thermally expandable microsphere and a preparation method thereof, and a foamed silicone rubber and a preparation method thereof. Background Art

[0002] Foaming materials are a type of high-performance composite materials with a porous structure. They have good shock absorption and noise reduction, sound insulation and heat preservation, and resilience, and are light and high-strength. The preparation of foaming materials usually adopts physical foaming, chemical foaming and hollow microsphere filling foaming methods.

[0003] Currently, the materials with photoluminescent effects on the market are mostly made by adding fluorescent agents or fluorescent powders to the raw materials. Through physical blending and addition, nano-scale fluorescent powders are dispersed in polymers, but local agglomeration and uneven dispersion are very likely to occur. When irradiated with UV or other light sources, it is easy to produce uneven luminescence such as brighter spots or darker spots in some locations. Moreover, after the polymer containing fluorescent agents is physically or chemically foamed, the internal pores are hollow, which leads to the weakening of the overall luminescence effect of the material and the aggravation of the unevenness.

[0004] Therefore, the current foaming materials with fluorescent effects still have the problem of poor uniformity of light emission. Summary of the invention

[0005] The main purpose of the present application is to provide a modified thermally expandable microsphere and a preparation method thereof, a foamed silicone rubber and a preparation method thereof, in order to solve the technical problem of poor luminous uniformity of the foamed material.

[0006] To achieve the above-mentioned purpose, the present application provides a modified heat-expandable microsphere, which comprises a heat-expandable microsphere matrix and a photoluminescent modification layer, wherein the photoluminescent modification layer is arranged on the surface of the heat-expandable microsphere matrix, and the photoluminescent modification layer comprises a spiro compound having a photoluminescent effect.

[0007] In some embodiments, the spirocyclic compound includes at least one of octamethylcycloeicosatetraeneoctone, heterocyclic compounds of 2,5-dihydropyrrole and 3-aminofuran, dihydroxycyclodextrin derivatives, rhodamine B-β-cyclodextrin derivatives, benzisoselenazolone β-cyclodextrin derivatives, heptakis(2,3,6-tri-O-ethyl)-β-cyclodextrin, and 2-alkyl-3-boryl heterocyclic compounds.

[0008] In some embodiments, the modified heat-expandable microspheres have a diameter before expansion of 1 μm-100 μm.

[0009] In some embodiments, the expansion temperature of the modified heat-expandable microspheres ranges from 80°C to 220°C.

[0010] In addition, to achieve the above-mentioned purpose, the present application also provides a method for preparing modified heat-expandable microspheres, which is used to prepare the modified heat-expandable microspheres as described above, comprising:

[0011] preparing a heat-expandable microsphere matrix, and performing surface amino modification on the heat-expandable microsphere matrix to obtain surface amino-modified heat-expandable microspheres;

[0012] The spiro compound solution and the surface-amino-modified heat-expandable microspheres are uniformly mixed, and the mixed materials are washed and filtered to obtain modified heat-expandable microspheres.

[0013] In some embodiments, the step of performing surface amino modification on the heat-expandable microsphere matrix to obtain surface amino-modified heat-expandable microspheres comprises:

[0014] Adding the heat-expandable microsphere matrix into a hydroxylamine aqueous solution, stirring and heating;

[0015] The reaction was carried out for 5 minutes to 15 minutes to obtain the heat-expandable microspheres with surface amino groups.

[0016] In some embodiments, the stirring and heating temperature is less than or equal to 70°C.

[0017] In addition, to achieve the above-mentioned purpose, the present application also provides a foamed silicone rubber, which includes, by mass, 100 parts of silicone rubber base, 0.001-1 parts of catalyst, 0.001-1 parts of cross-linking agent, 0.001-0.1 parts of inhibitor and 1-10 parts of modified heat-expandable microspheres, and the modified heat-expandable microspheres are the modified heat-expandable microspheres described above.

[0018] In addition, to achieve the above-mentioned purpose, the present application also provides a method for preparing a foamed silicone rubber, which is used to prepare the foamed silicone rubber as described above, comprising:

[0019] Mixing silicone rubber base, catalyst, cross-linking agent, inhibitor and modified heat-expandable microspheres;

[0020] The molding mold temperature is set to 110°C-170°C, and foamed silicone rubber is obtained after molding.

[0021] In some embodiments, the molding pressure of the molding die is 3MPa-12MPa; and / or the molding time is 1min-5min.

[0022] The embodiment of the present application provides a modified heat-expandable microsphere and a preparation method thereof, a foamed silicone rubber and a preparation method thereof, wherein the modified heat-expandable microsphere comprises a heat-expandable microsphere matrix and a photoluminescent modification layer, wherein the photoluminescent modification layer is arranged on the surface of the heat-expandable microsphere matrix, and the photoluminescent modification layer comprises a spiro compound having a photoluminescent effect. In the technical scheme of the present application, the spiro compound in the photoluminescent modification layer enables it to have a photoluminescent effect, and can re-radiate photons after absorbing photons under a light source of a certain wavelength, showing fluorescence, and the heat-expandable microsphere matrix has a thermal expansion effect, and volume expansion can occur during the vulcanization process of the silicone rubber, generating pores, and since the spiro compound is arranged on the surface of the heat-expandable microsphere matrix, the luminescent area can be dispersed in the foamed silicone rubber following the position of the modified heat-expandable microsphere, reducing the probability of uneven luminescence caused by agglomeration of the luminescent substance, thereby improving the luminescence uniformity of the foamed material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present drawings or related technologies, the drawings required for use in the embodiments or related technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0024] Figure 1 A schematic diagram of the expansion process of the heat-expandable microsphere matrix provided in an embodiment of the present application;

[0025] Figure 2 A schematic diagram of the preparation process of the modified heat-expandable microspheres provided in the embodiments of the present application.

[0026] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0027] It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0028] Hereinafter, the modified heat-expandable microspheres and their preparation methods, foamed silicone rubber and their preparation methods of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0029] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0030] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0031] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0032] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and understandable, the technical solution of the present application is further described below in conjunction with the accompanying drawings and embodiments. However, the present application is not limited to the listed embodiments, and should also include any other known changes within the scope of the rights claimed in the present application.

[0033] Foaming materials are a type of high-performance composite materials with a porous structure. They have good shock absorption and noise reduction, sound insulation and thermal insulation performance, and resilience, and are light and high-strength. Physical foaming, chemical foaming, and hollow microsphere filling and foaming methods can be used to prepare foaming materials. Physical foaming and chemical foaming methods generate gas in polymers to form a hollow cell structure, but this foaming process is prone to cause gas residue in the material, poor foaming uniformity, and difficult to control the cell size and foaming ratio. The phenomenon of uneven cells cannot meet the increasingly stringent environmental protection requirements, and due to its porous structure, the mechanical properties and strength of the foamed material are significantly reduced. While it achieves lightweight, it causes the strength to fail to meet the use requirements. The hollow microsphere filling method, whose process is different from the chemical foaming method and the physical foaming method, is special in that there is no foaming process. The foaming ratio, pore size and distribution can be controlled by controlling the amount and type of microspheres added and the temperature. The method has good controllability. In addition, the method does not generate gas and has no gas leakage or residue problems. The foamed material prepared by the microsphere filling method has good support in its pore structure due to the presence of microspheres, so that the material as a whole has good mechanical properties, dimensional stability and thermal stability.

[0034] Currently, the materials with photoluminescent effects on the market are mostly made by adding fluorescent agents or fluorescent powders to the raw materials. Through physical blending and addition, nano-scale fluorescent powders are dispersed in polymers, which are prone to local agglomeration and uneven dispersion. When irradiated with UV or other light sources, it is easy to produce uneven luminescence such as brighter spots or darker spots in some locations. Moreover, after the polymer containing fluorescent agents is physically or chemically foamed, the internal pores are hollow, which weakens the overall luminescence effect of the material and exacerbates the unevenness.

[0035] Silicone rubber has excellent high and low temperature resistance, excellent oil resistance, solvent resistance, UV resistance, radiation resistance, good aging resistance, excellent electrical insulation and chemical stability, as well as physiological inertness. Foamed silicone rubber is a porous polymer elastic material formed by silicone rubber after foaming. It is a multifunctional silicone rubber material. In addition to the excellent properties of silicone rubber itself, it also has the advantages of light weight, damping effect and good insulation performance. It also has the advantages of high and low temperature resistance, weather resistance and environmental protection that other foam materials do not have. At present, most silicone rubber materials are formed by adding chemical foaming agents or self-reaction gas production to form foamed silicone rubber, and the strength is significantly reduced.

[0036] In view of the above problems, an embodiment of the present application provides a modified heat-expandable microsphere. After surface treatment of the heat-expandable microsphere matrix, the surface is modified with a spiro compound having photoluminescent properties to obtain photoluminescent modified heat-expandable microspheres. The microspheres can emit light of different colors under a light source in a specific wavelength range. The microspheres are added to silicone rubber and, after vulcanization, a foamed silicone rubber having a photoluminescent effect is obtained.

[0037] The embodiment of the present application provides a modified heat-expandable microsphere, which comprises a heat-expandable microsphere matrix and a photoluminescent modification layer. The photoluminescent modification layer is arranged on the surface of the heat-expandable microsphere matrix. The photoluminescent modification layer comprises a spiro compound having a photoluminescent effect.

[0038] It can be understood that the heat-expandable microsphere matrix in the embodiment of the present application can use commercially available expandable microspheres, and its shell is a thermoplastic shell with good airtightness, and the inside of the shell encapsulates permeable low-boiling point hydrocarbons. Figure 1 The schematic diagram of the expansion process of the heat-expandable microsphere matrix provided in the embodiment of the present application is as follows: Figure 1 As shown, the heat-expandable microsphere matrix before expansion contains foaming gas inside and is wrapped by a polymer shell outside. The heat-expandable microsphere matrix will expand after heating to become a core-shell particle with a hollow structure. The heat-expandable microsphere matrix has the advantages of controlled size change and good compressibility. However, since the heat-expandable microsphere matrix is ​​a thermoplastic polymer material, its surface is electrically neutral and it is difficult to adsorb metals or other organic groups. Therefore, a spirocyclic compound can be grafted on the surface of the heat-expandable microsphere matrix by surface modification to form a photoluminescent modification layer, which produces a photoluminescent effect after being illuminated by light of a specific wavelength.

[0039] Spiro compounds refer to polycyclic compounds in which two monocyclic rings share one carbon atom. Spiro compounds have a rigid structure, and their chiral ligands have a large specific rotation, so many types of spiro compounds can produce photoluminescence effects. The spiro compounds used in the embodiments of the present application may include carbon rings and / or heterocycles, and two conjugated molecular groups are connected by spiro atoms to avoid the adverse effects of intramolecular interactions and improve the processability of the material.

[0040] In some embodiments of the present application, the spiro compound includes at least one of octamethylcycloeicosatetraene octane, 2,5-dihydropyrrole and 3-aminofuran heterocyclic compounds, dihydroxycyclodextrin derivatives, rhodamine B-β-cyclodextrin derivatives, benzisoselenozolide β-cyclodextrin derivatives, heptadecanol (2,3,6-tri-O-ethyl)-β-cyclodextrin, and 2-alkyl-3-boryl heterocyclic compounds. It is understood that the above-mentioned types of spiro compounds can be modified on the surface of the heat-expandable microsphere matrix to form a photoluminescent modification layer. As the heat-expandable microsphere matrix expands, the photoluminescent modification layer is stably surrounded by the outer layer of the heat-expandable microsphere matrix, and produces a fluorescence-like effect after illumination of a specific wavelength.

[0041] In some embodiments of the present application, the diameter of the modified heat-expandable microsphere before expansion is 1 μm-100 μm, for example, 1 μm, 5 μm, 10 μm, 30 μm, 50 μm, 80 μm, 100 μm or within the range of any of the above values. It is understandable that the larger the diameter of the modified heat-expandable microsphere before expansion, the larger the size of the pores produced after expansion. The smaller the diameter of the modified heat-expandable microsphere before expansion, the smaller the diameter of the pores can be. The internal pressure required for the modified heat-expandable microspheres with a smaller diameter before expansion is greater, and higher temperature and pressure are required during the expansion process. Therefore, according to the requirements for the pore size and porosity in the foamed silicone rubber, the modified heat-expandable microspheres with different diameters before expansion can be selected to regulate the comprehensive properties of the foamed silicone rubber.

[0042] In some embodiments of the present application, the expansion temperature range of the modified heat-expandable microspheres is 80°C-220°C, for example, 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 220°C or within the range composed of any of the above values. It is understandable that the expansion temperature range is related to the type and composition of the low-boiling hydrocarbons encapsulated in the matrix of the heat-expandable microspheres. By selecting a suitable low-boiling hydrocarbon substance for encapsulation, modified heat-expandable microspheres that expand within a certain temperature range can be obtained. The lower the boiling point of the encapsulated hydrocarbon substance, the lower the temperature required for expansion. The smaller the diameter of the modified heat-expandable microspheres before expansion, the higher the temperature conditions will be required, so that the expansion temperature range is increased. The embodiment of the present application selects modified heat-expandable microspheres within the above expansion temperature range, which can complete the process of thermal expansion and foaming during the vulcanization of the foamed silicone rubber, and the manufacturing process is simplified.

[0043] In this embodiment, the spiro compound in the photoluminescent modification layer enables it to have a photoluminescent effect, and it can re-radiate photons after absorbing photons under a light source of a certain wavelength, showing fluorescence. The heat-expandable microsphere matrix has a thermal expansion effect, and volume expansion can occur during the vulcanization process of the silicone rubber to produce bubbles. Since the spiro compound is arranged on the surface of the heat-expandable microsphere matrix, the luminous area can be dispersed in the foamed silicone rubber following the position of the modified heat-expandable microspheres, reducing the probability of uneven luminescence caused by agglomeration of the luminescent substance, thereby improving the luminescence uniformity of the foamed material.

[0044] The present application also provides a method for preparing modified heat-expandable microspheres, which may include the following steps S10 to S20:

[0045] Step S10, preparing a heat-expandable microsphere matrix, and performing surface amino modification on the heat-expandable microsphere matrix to obtain surface amino-modified heat-expandable microspheres;

[0046] The heat-expandable microsphere matrix can be selected from commercially available expanded microspheres. Since the expanded microsphere is a thermoplastic polymer material, its surface is electrically neutral, so it can be modified by surface amination, and amino groups are first introduced on its surface to obtain surface aminated heat-expandable microspheres as intermediates, and the characteristics of the higher reactivity of the amino group are utilized, and then the spiro compound is introduced by the amino group. It is understandable that the amination modification process can adopt an aminating agent to react with the heat-expandable microspheres, so that the surface of the heat-expandable microsphere matrix is ​​converted into an amino-modified state by electrical neutrality. In the aminating agent, except the amino group, other active groups can also be included so that the amino group can be grafted to the surface of the heat-expandable microsphere matrix under certain reaction conditions.

[0047] In some embodiments of the present application, the step of performing surface amino modification on the heat-expandable microsphere substrate to obtain the surface amino-modified heat-expandable microspheres may include the following steps S11 to S12:

[0048] Step S11, adding the heat-expandable microsphere matrix into the hydroxylamine aqueous solution, stirring and heating;

[0049] A 1 mol / L hydroxylamine aqueous solution may be prepared, and then 0.1 g of the heat-expandable microsphere matrix may be added, stirred and heated, and reacted. Optionally, the stirring and heating temperature may be controlled to be less than or equal to 70° C. so that the hydroxylamine can remain dissolved in the aqueous solution and does not volatilize due to excessively high temperature.

[0050] Step S12, react for 5 min-15 min to obtain heat-expandable microspheres with surface amino groups.

[0051] The reaction time can be 5min, 8min, 10min, 12min, 15min or within the range of any of the above values. If the reaction time is too short, the degree of amination on the surface of the heat-expandable microspheres may be low, resulting in less introduction of spiro compounds, weak luminescence intensity, and poor luminescence effect. If the reaction time is too long, the degree of amination is not significantly improved, affecting production efficiency. During the reaction, hydroxylamine is grafted to the surface of the heat-expandable microsphere matrix through the hydroxyl group, retaining the amino group to form surface-aminated heat-expandable microspheres.

[0052] Step S20, uniformly mixing the spiro compound solution and the surface amino-modified heat-expandable microspheres, washing and filtering the mixed materials to obtain modified heat-expandable microspheres.

[0053] A suitable solvent can be selected to dissolve the spiro compound to form a spiro compound solution. For example, the solvent that can be used includes ethanol, methanol, or isopropanol. After dissolution, ultrasonic dispersion is performed for 10 minutes to make the substances in the spiro compound solution more uniformly dispersed. 0.2g of the spiro compound can be dissolved in the solvent, and the formed spiro compound solution is added to the surface amino-modified heat-expandable microspheres in the above step, heated and stirred, and the temperature is controlled not to exceed 50°C. After cooling and standing, deionized water is used to wash and filter to obtain photoluminescent modified heat-expandable microspheres.

[0054] Figure 2 The schematic diagram of the preparation process of the modified heat-expandable microspheres provided in the embodiment of the present application is as follows: Figure 2 As shown, after the heat-expandable microsphere matrix with amino groups grafted on the surface reacts with the spiro compound, the spiro compound is grafted to the site where the amino group is located. After heating and expansion, the volume of the modified heat-expandable microsphere becomes larger. After UV irradiation, the photoluminescent modification layer on the surface of the modified heat-expandable microsphere can produce a photoluminescent effect.

[0055] In this embodiment, the surface of the heat-expandable microsphere substrate is modified by amino modification, and then the spirocyclic compound is grafted onto the amino group site to obtain modified heat-expandable microspheres, which have a photoluminescent effect and are added to foamed silicone rubber to improve the luminescence uniformity of the foamed silicone rubber.

[0056] The embodiment of the present application also provides a foamed silicone rubber, which includes, by mass, 100 parts of silicone rubber base, 0.001-1 parts of catalyst, 0.001-1 parts of cross-linking agent, 0.001-0.1 parts of inhibitor and 1-10 parts of modified heat-expandable microspheres as described in the embodiment of the present application.

[0057] The amount of modified heat-expandable microspheres added can be 1-10 parts, for example, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc. It can be understood that the more the amount of modified heat-expandable microspheres added, the more pores will be formed in the structure of the foamed silicone rubber, and the size and porosity of the pores will affect its performance in terms of shock absorption, noise reduction, sound insulation, heat preservation, and strength. If the amount of modified heat-expandable microspheres added is too little, the foaming degree of the silicone rubber may not be enough, which will also affect the performance in terms of shock absorption, noise reduction, sound insulation, and heat preservation. The appropriate amount of addition can be selected according to the actual requirements for the pore size and porosity, so that the foamed silicone rubber has good comprehensive properties.

[0058] Silicone rubber base is the basic substance in foamed silicone rubber. Optionally, the silicone rubber base used can be vinyl silicone rubber base. The introduction of a small amount of vinyl can improve the heat aging resistance and high temperature compression deformation resistance of the foamed silicone rubber.

[0059] The amount of catalyst added can be 0.001-1 part, for example, 0.001 part, 0.005 part, 0.01 part, 0.05 part, 0.1 part, 0.5 part, 1 part, etc. The catalyst can be used to promote the cross-linking of silicone rubber. It is understandable that too little catalyst may lead to incomplete cross-linking; too much catalyst may cause too fast reaction, which is difficult to control, or produce oversulfurization, resulting in a decrease in the performance of the foamed silicone rubber. Optionally, the catalyst of this embodiment can be a platinum catalyst.

[0060] The amount of cross-linking agent added can be 0.001-1 part, for example, 0.001 part, 0.005 part, 0.01 part, 0.05 part, 0.1 part, 0.5 part, 1 part, etc. The cross-linking agent can undergo a cross-linking reaction. Alternatively, the cross-linking agent of the present embodiment can be a hydrogen-containing silicone oil. There is a Si-H bond in the hydrogen-containing silicone oil, which can undergo a cross-linking reaction with other functional groups in the silicone rubber, thereby forming a cross-linked structure between the silicone rubber molecular chains. This cross-linked structure can not only enhance the mechanical properties of the silicone rubber, but also improve its heat resistance and weather resistance.

[0061] The amount of the inhibitor added can be 0.001-1 part, for example, 0.001 part, 0.005 part, 0.01 part, 0.05 part, 0.1 part, 0.5 part, 1 part, etc. The inhibitor can be used to improve the stability of silicone rubber in a high temperature environment and avoid the silicone rubber base from curing too quickly. It is understandable that in the process of preparing foamed silicone rubber, the inhibitor and the catalyst are added separately to avoid direct curing of the silicone rubber base. If the amount of the inhibitor added is too little, the inhibitory effect is not obvious, and if the amount is too much, the mechanical properties and heat resistance of the foamed silicone rubber will be reduced. Optionally, the inhibitor selects an acetylene alcohol inhibitor. The inhibitory effect of acetylene alcohol inhibitors is strong. The acetylene alcohol inhibitors that can be used in this embodiment include ethynyl cyclopentanol, methyl butynol, methyl pentynol, etc.

[0062] The foamed silicone rubber of the embodiment of the present application has modified heat-expandable microspheres added as foaming materials. The volume expansion of the modified heat-expandable microspheres generates pores in the silicone rubber to form a porous structure. The surface of the modified heat-expandable microspheres includes a photoluminescent modification layer, which can produce a photoluminescent effect under specific light. Compared with the addition of fluorescent agents, the modified heat-expandable microspheres are not easy to agglomerate, and the luminescence uniformity is improved.

[0063] The present application also provides a method for preparing a foamed silicone rubber, which may include the following steps A10 to A20:

[0064] Step A10, mixing the silicone rubber base, the catalyst, the cross-linking agent, the inhibitor and the modified thermal expansion microspheres;

[0065] It is understandable that the above raw materials can be added in batches, wherein the catalyst and the inhibitor are added separately, mixed and then cured and molded. The foamed silicone rubber can be molded by injection molding or hot pressing molding.

[0066] Step A20, setting the molding mold temperature to 110° C.-170° C., and obtaining foamed silicone rubber after molding.

[0067] The above-mentioned prepared raw materials are injected into a molding mold, and the temperature of the molding mold is set within a temperature range of 110°C-170°C, for example, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, etc. After molding for a certain period of time, a foamed silicone rubber with a photoluminescent effect is obtained. If the temperature of the molding mold is too high, the prepared raw materials may solidify too quickly, resulting in bubble defects, which may cause the foamed silicone rubber to break easily. If the temperature of the molding mold is too low, the time required for curing will be extended, affecting production efficiency and easily leading to insufficient foaming. By controlling the temperature of the molding mold within an appropriate range, a foamed silicone rubber with good molding quality can be obtained.

[0068] In some embodiments of the present application, the molding pressure of the molding die is 3MPa-12MPa, for example, 3MPa, 5MPa, 8MPa, 10MPa, 12MPa, etc. It is understandable that if the molding pressure is too high, the silicone rubber product may be deformed and the size may be inaccurate. If the molding pressure is too low, the silicone rubber may not fill the mold enough, resulting in a lack of glue and affecting its appearance. By selecting a suitable molding pressure, a foamed silicone rubber product with good molding quality can be obtained.

[0069] In some embodiments of the present application, the molding time is 1 min-5 min, for example, 1 min, 2 min, 3 min, 4 min, 5 min, etc. It is understandable that if the molding time is too long, the brittleness of the foamed silicone rubber increases, and it is easy to be damaged or broken. If the molding time is too short, the foamed silicone rubber may not be fully cured and the quality is poor. Selecting a suitable molding time can obtain a foamed silicone rubber product of good quality.

[0070] In this embodiment, the raw materials for preparing the foamed silicone rubber include modified heat-expandable microspheres. The volume expansion of the modified heat-expandable microspheres can produce pores in the silicone rubber to form a porous structure, and the surface of the modified heat-expandable microspheres includes a photoluminescent modification layer, which can produce a photoluminescent effect under specific light. Compared with the addition of fluorescent agents, the modified heat-expandable microspheres are not easy to agglomerate, and the luminescence uniformity is improved.

[0071] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A modified heat-expandable microsphere, characterized in that: The modified heat-expandable microspheres include a heat-expandable microsphere matrix and a photoluminescent modification layer. The photoluminescent modification layer is arranged on the surface of the heat-expandable microsphere matrix, and the photoluminescent modification layer includes a spiro compound with a photoluminescent effect.

2. The modified heat-expandable microspheres according to claim 1, characterized in that: The spirocyclic compound includes at least one of octamethylcycloeicosatetraeneoctone, heterocyclic compounds of 2,5-dihydropyrrole and 3-aminofuran, dihydroxycyclodextrin derivatives, rhodamine B-β-cyclodextrin derivatives, benzisoselenazolone β-cyclodextrin derivatives, heptakis(2,3,6-tri-O-ethyl)-β-cyclodextrin, and 2-alkyl-3-boryl heterocyclic compounds.

3. The modified heat-expandable microspheres according to claim 1, characterized in that: The modified heat-expandable microspheres have a diameter before expansion of 1 μm to 100 μm.

4. The modified heat-expandable microspheres according to claim 1, characterized in that: The expansion temperature range of the modified heat-expandable microspheres is 80°C-220°C.

5. A method for preparing modified heat-expandable microspheres, characterized in that: For preparing the modified heat-expandable microspheres according to any one of claims 1 to 4, comprising: preparing a heat-expandable microsphere matrix, and performing surface amino modification on the heat-expandable microsphere matrix to obtain surface amino-modified heat-expandable microspheres; The spiro compound solution and the surface-amino-modified heat-expandable microspheres are uniformly mixed, and the mixed materials are washed and filtered to obtain modified heat-expandable microspheres.

6. The method for preparing modified heat-expandable microspheres according to claim 5, characterized in that: The step of performing surface amino modification on the heat-expandable microsphere substrate to obtain the surface amino-modified heat-expandable microspheres comprises: Adding the heat-expandable microsphere matrix into a hydroxylamine aqueous solution, stirring and heating; The reaction was carried out for 5 minutes to 15 minutes to obtain the heat-expandable microspheres with surface amino groups.

7. The method for preparing modified heat-expandable microspheres according to claim 6, characterized in that: The stirring and heating temperature is less than or equal to 70°C.

8. A foamed silicone rubber, characterized in that: In parts by mass, the foamed silicone rubber comprises 100 parts of silicone rubber base, 0.001-1 parts of catalyst, 0.001-1 parts of cross-linking agent, 0.001-0.1 parts of inhibitor and 1-10 parts of modified heat-expandable microspheres, wherein the modified heat-expandable microspheres are the modified heat-expandable microspheres described in any one of claims 1 to 4.

9. A method for preparing foamed silicone rubber, characterized in that: For preparing the foamed silicone rubber as claimed in claim 8, comprising: Mixing silicone rubber base, catalyst, cross-linking agent, inhibitor and modified heat-expandable microspheres; The molding mold temperature is set to 110°C-170°C, and foamed silicone rubber is obtained after molding.

10. The method for preparing foamed silicone rubber according to claim 9, characterized in that: The molding pressure of the molding die is 3MPa-12MPa; and / or the molding time is 1min-5min.

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