High-temperature thermal expansion microsphere with rapid foaming response and preparation method thereof

Abstract

The invention provides a high-temperature thermal expansion microsphere with rapid foaming response and a preparation method of the high-temperature thermal expansion microsphere. The high-temperature thermal expansion microsphere comprises an olefinic unsaturated monomer, the olefinic unsaturated monomers comprise the following components in percentage by weight: 40 to 60 percent of acrylonitrile monomers, 10 to 20 percent of acrylic acid monomers, 10 to 20 percent of acrylamide monomers and 5 to 30 percent of cage type polysilsesquioxane monomers containing double-bond monofunctional groups; the double-bond monofunctional polyhedral oligomeric silsesquioxane monomer is used for participating in polymerization to form a microsphere shell. The foaming response speed of the microspheres can be remarkably improved, and the microspheres have high foam breaking temperature and high expansion performance.

Description

Technical Field

[0001] The invention relates to the field of manufacturing expandable particles, in particular to a high-temperature thermal expansion microsphere with rapid foaming response and a preparation method thereof. Background Art

[0002] The heat-expandable microsphere having a structure of enclosing a foaming agent in its interior as an outer shell using a thermoplastic resin is commonly referred to as a heat-expandable microcapsule. As a thermoplastic resin, vinylidene chloride copolymers, acrylonitrile copolymers, acrylate copolymers can be used usually. In addition, as a foaming agent, mainly alkanes such as isooctane or isopentane are used.

[0003] Methods for preparing various heat-expandable microspheres have been disclosed in patents such as WO2007 / 142593A1, EP1149628A1, EP1811007A1, EP1302239A1, EP0486080, EP112807B1, EP0348372A2, WO2004 / 0566549A1, US4287308 and EP1592733B1.

[0004] For heat-expandable microspheres, it is important to have both a high foaming temperature and a fast foaming response characteristic. Among them, high-temperature heat-expandable microspheres usually have a high starting foaming temperature of 150-180°C, which can be applied to the injection molding of thermoplastic materials, such as PP, PC, PA, ABS and other plastics. During the injection molding process, the microspheres expand due to heat, achieving controllable foaming, helping various thermoplastic materials to generate a uniform closed cell structure, while reducing the density and improving the surface structure, thereby improving the stability of the finished product. In the field of thermosensitive devices and explosives, the strong impact force generated instantly when the microspheres foam quickly is required. Therefore, developing a high-temperature foaming microsphere with the characteristic of rapid response to high temperature is an important issue in the industry.

[0005] In order to improve the foaming temperature and rapid foaming response time of microspheres, the study found that CN117069996B discloses a method for synthesizing epoxy resins, and introduces the resin into expandable microspheres, thereby improving the high-temperature durability of the microspheres. However, the above method has the disadvantages of long foaming time and slow temperature response. CN201410362784.2 discloses a fast-foaming thermoplastic expandable microsphere, in which vinyl acetate is used as a modified monomer to overcome the limitations of long foaming time and large temperature difference in the past. The temperature difference required from the beginning of expansion to the maximum foaming is extremely small, generally around 10°C, but the microspheres prepared by it will break quickly after reaching the maximum expansion, and the durability will be greatly reduced. CN202410666163.7 reported that by regulating the type of foaming agent and the phase transition temperature of the shell, the microspheres have achieved full gasification of the foaming agent before the phase transition, so as to achieve rapid expansion of the microspheres when they reach the phase transition, and the shell does not break. The shortcoming of this patent is that the foaming temperature of the microspheres is too low (90-120°C), and it cannot be applied to research in the medium and high temperature fields. Summary of the invention

[0006] In view of the defects in the prior art, the purpose of the present invention is to provide a high-temperature heat-expandable microsphere with a rapid foaming response and a preparation method thereof, wherein the heat-expandable microsphere has the advantages of a high bubble breaking temperature (>180°C), a rapid foaming speed and extended durability.

[0007] According to one aspect of the present invention, a high-temperature heat-expandable microsphere with a fast foaming response is provided, comprising an ethylenically unsaturated monomer (i.e., an olefinic unsaturated monomer), wherein the ethylenically unsaturated monomer comprises the following components by weight percentage: 40-60% of an acrylonitrile monomer, 10-20% of an acrylic acid monomer, 10-20% of an acrylamide monomer, and 5-30% of a double-bond monofunctional cage-type polysilsesquioxane (POSS) monomer, wherein the monofunctional group refers to a functional group structure having an active site, which may be a vinyl alkyl group, a butylate functional group, or an acrylate alkyl group, etc.; the double-bond monofunctional cage-type polysilsesquioxane monomer is used to participate in polymerization to form a microsphere shell, thereby improving the foaming response speed and the bubble breaking temperature.

[0008] Optionally, the cage-type polysilsesquioxane monomer containing a double bond monofunctional group is any one of a cage-type tetramer silsesquioxane containing a double bond monofunctional group, a cage-type hexamer silsesquioxane containing a double bond monofunctional group, a cage-type octamer silsesquioxane containing a double bond monofunctional group, a cage-type decamer silsesquioxane containing a double bond monofunctional group, and a cage-type dodecamer silsesquioxane containing a double bond monofunctional group.

[0009] Preferably, the double bond-containing monofunctional cage-type polysilsesquioxane monomer is a double bond-containing monofunctional cage-type octamer silsesquioxane, whose structural formula is as follows:

[0010]

[0011] In the formula, X = any one of (meth)acrylic acid, acrylic acid ester, olefin and its derivatives containing double bonds, R 1-7 =Any one of an alkyl group, an aromatic group derivative, an epoxy group, and a carboxyl group.

[0012] Optionally, the double bond-containing monofunctional cage-type polysilsesquioxane monomer can be selected from any one or more of (meth)acryloxypropyl heptaisobutyl polysilsesquioxane, (meth)acryloxypropyl heptaphenyl silsesquioxane, acryloxypropyl heptacarboxyl polysilsesquioxane, (meth)acryloxypropyl nonacyclic epoxypropyl polysilsesquioxane, propyleneethyl nonaisopropyl polysilsesquioxane, (meth)acryloxypropyl undecylisobutyl and vinylpropyl undecylpropyl polysilsesquioxane.

[0013] Optionally, the acrylonitrile monomer is any one or more of acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile and crotononitrile. Preferably, it is one of acrylonitrile and methacrylonitrile or a mixture of the two.

[0014] Optionally, the acrylic monomer is a carboxyl-containing methacrylic monomer, including a carboxyl-containing methacrylic monomer and / or a carboxyl metal salt-containing methacrylic monomer. The above-mentioned carboxyl-containing methacrylic monomer is not particularly limited, and exemplarily, is methacrylic acid, methacrylic acid metal salt, etc. The above-mentioned methacrylic monomer containing carboxyl metal salt (methacrylic acid metal salt) is exemplarily magnesium methacrylate, calcium methacrylate, zinc methacrylate, etc. These carboxyl-containing methacrylic monomers can be used alone or in combination of two or more.

[0015] Optionally, the acrylamide monomer is any one or more of N-isopropyl acrylamide, N-hydroxymethyl acrylamide, N-methoxymethyl acrylamide, N,N-dimethyl acrylamide, N,N-diethyl acrylamide and acryloyl morpholine, preferably N,N-dimethyl acrylamide.

[0016] The present invention adopts a double-bond monofunctional cage-type polysilsesquioxane (POSS) monomer, which can be miscible with other acrylic acid (ester) and acrylonitrile monomers, and directly participate in the free radical reaction of the double bond, and the reaction is completed in one step without post-addition. At the same time, the silicon-containing monomer is evenly dispersed in the body of the microsphere shell, and the content can be adjusted at will. As the content increases, the inorganic silicon content increases, which greatly improves the foaming response speed and the bubble breaking temperature.

[0017] Optionally, the microspheres further include a foaming agent, a cross-linking agent, an initiator, a dispersion stabilizer, a dispersion stabilization aid and a dispersion medium. By weight percentage, the ethylenically unsaturated monomer accounts for 50-70% of the oil phase, the foaming agent accounts for 20-30% of the oil phase, the cross-linking agent accounts for 0.1-0.6% of the oil phase, the initiator accounts for 0.6-1% of the oil phase, the dispersion stabilizer accounts for 8-15% of the water phase, the dispersion stabilization aid accounts for 0.5-2% of the water phase, and the dispersion medium accounts for 60-80% of the water phase.

[0018] Optionally, the foaming agent is a liquid having a boiling point not higher than the softening temperature of the thermoplastic polymer shell. The foaming agent is a hydrocarbon or halogenated hydrocarbon compound having 5 to 8 carbon atoms, specifically including any one or more of n-pentane, isopentane, n-hexane, isohexane, n-octane, and isooctane, and the boiling point of the foaming agent is 25 to 127°C, preferably 70 to 100°C.

[0019] The foaming agent is wrapped inside the microspheres and is liquid at room temperature, forming a core structure. As the temperature rises, the liquid begins to volatilize, and the internal pressure gradually increases in the sealed shell. When a certain pressure is reached, the microspheres begin to expand. Generally speaking, the higher the boiling point of the foaming agent, the higher the foaming temperature of the microspheres. However, the expansion effect (expansion rate) of the microspheres also needs to consider whether the composition of the microsphere shell matches the type and content of the foaming agent. In addition, it is also affected by the pressure difference between the inside and outside of the microspheres at a specific temperature. Using the above substances as foaming agents can achieve microsphere expansion at high temperatures and maintain an excellent expansion rate.

[0020] Crosslinking agents are crosslinking monomers having two or more polymerizable double bonds. These monomers crosslink linear copolymers containing the above-mentioned monomers to extend the elastic range of the copolymer and give thermal stability. These monomers include: ethylene glycol (meth) diacrylate, diethylene glycol di(meth) acrylate, dipropylene glycol di(meth) acrylate, 1,4-butanediol di(meth) acrylate, 1,6-hexanediol diacrylate, neopentyl glycol di(meth) acrylate, glycerol dimethacrylate, polyethylene glycol (200) dimethacrylate, polyethylene glycol (400) dimethacrylate, polyethylene glycol (600) dimethacrylate, trimethylolpropane tri(meth) acrylate, trimethylolpropane tri(meth) acrylate, divinyl ether, triethylene glycol divinyl ether, butanediol divinyl ether, etc., but are not limited thereto. They can be used alone or in combination of two or more.

[0021] Preferably, the crosslinking agent is any one or more of polyethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, ethylene glycol (400) dimethacrylate, polyethylene glycol (600) dimethacrylate, and trimethylolpropane tri(meth)acrylate.

[0022] The type and content of the crosslinking agent affect the expansion ratio and temperature of the microspheres. When the crosslinking agent content is low, the microspheres have poor foam stabilization performance, poor heat resistance, and shrink quickly after expansion. When the crosslinking agent content is high, the degree of crosslinking is dense. Although the heat resistance will be moderately improved, the expansion effect will be worse. Generally, trifunctional crosslinking agents have a higher degree of crosslinking than difunctional crosslinking agents. If the crosslinking agent is a trifunctional compound, the amount of the crosslinking agent is 0.01 to 2 wt% of the ethylenically unsaturated monomer.

[0023] If the crosslinking agent is a difunctional compound, the amount of the crosslinking agent is 0.1 to 3 wt % of the ethylenically unsaturated monomer.

[0024] Optionally, the initiator is an oil-soluble cleavage-type thermal initiator, and may be dimethyl azobisisobutyrate, benzoyl peroxide, dibenzoic acid peroxide, lauroyl peroxide, dilauric acid peroxide, tert-butyl perlaurate, 2,2'-azobisisobutyronitrile, 2,2'-azobis((2,4-dimethylvaleronitrile)), etc., but is not limited thereto and may be used alone or in combination of two or more.

[0025] Optionally, the dispersion medium is deionized water, or deionized water containing a hydrophilic organic solvent such as alcohol.

[0026] Optionally, the dispersion stabilizer is an insoluble salt, oxide or hydroxide of a metal such as calcium, magnesium, barium, iron, zinc, nickel or manganese; it can also be a polymer dispersion stabilizer, including a condensation product of diethanolamine and aliphatic dicarboxylic acid, polyvinyl pyrrolidone, polyethylene oxide, polyvinyl alcohol, methyl cellulose, agar powder, hydroxypropyl methyl cellulose, carboxymethyl cellulose, silica sol, colloidal clay, etc., but not limited thereto. They can be used alone or in combination of two or more.

[0027] According to the selection of the dispersion stabilizer, the pH value of the dispersion medium is controlled. For example, the dispersion stabilizer is selected from insoluble salts, oxides or hydroxides of metals such as metal calcium, magnesium, barium, iron, zinc, nickel or manganese, such as calcium phosphate, calcium carbonate, magnesium hydroxide, magnesium oxide, calcium oxalate, and one or more of zinc, nickel or manganese hydroxides, and the pH value is controlled at 5 to 12, preferably 6 to 10; the dispersion stabilizer is selected from polymer type, such as methylcellulose, agar powder, hydroxypropyl methylcellulose, carboxymethylcellulose, silica sol, colloidal clay, then the pH value is selected from 1 to 6, the pH value of the dispersion medium affects the viscosity and thixotropy of the suspension, and then affects the dispersion stability of the suspension, that is, the uniformity of the oil droplets, and the collision rate between the oil droplets during the reaction process (low viscosity-low thixotropy, the oil droplets are easy to merge with each other to form large oil droplets), thereby affecting the particle size and dispersion uniformity (CV value) of the final microspheres. In addition, high viscosity-high thixotropy will affect the workability. In the case of high viscosity, the stirring power is large and the energy consumption is high. Preferably, the pH value of the dispersion medium is 3-5.

[0028] Optionally, the auxiliary stabilizer can be selected from the following substances: condensation products of diethanolamine and aliphatic dicarboxylic acids, condensation products of urea and formaldehyde, water-soluble nitrogen-containing compounds, polyethylene oxide, tetramethylammonium hydroxide, gelatin, methylcellulose, polyvinyl alcohol, dioctyl sulfosuccinate, dehydrated sorbitan esters, various emulsifiers, etc.

[0029] The water-soluble nitrogen-containing compound may be, for example, polyvinyl pyrrolidone, polyethyleneimine, polyoxyethylene alkylamine, polyacrylamide, polycationic acrylamide, polyamine, polyallylamine, etc.; polydimethylaminoethyl methacrylate, polydimethylaminoethyl acrylate, polydialkylaminoalkyl (meth)acrylate, polydimethylaminopropyl acrylamide, polydimethylaminopropyl methacrylamide, etc., polydialkylaminoalkyl (meth)acrylamide, etc. may also be used. Preferably, the water-soluble nitrogen-containing compound is polyvinyl pyrrolidone.

[0030] When the auxiliary stabilizer is added to the aqueous dispersion medium, the amount of the auxiliary stabilizer added can be appropriately determined according to the target average particle size of the heat-expandable microcapsules.

[0031] For example, when the condensation product or the water-soluble nitrogen-containing compound is used as the auxiliary stabilizer, the amount of the auxiliary stabilizer added is preferably 0.05 parts by weight and 2 parts by weight, based on 100 parts by weight of all monomer components in the monomer mixture.

[0032] The combination of the above-mentioned dispersion stabilizer and the above-mentioned auxiliary stabilizer is not particularly limited, and examples thereof include: a combination of colloidal silica and a condensation product, a combination of colloidal silica and a water-soluble nitrogen-containing compound, a combination of magnesium hydroxide or calcium phosphate and an emulsifier, etc. Among these, a combination of colloidal silica and a condensation product is preferred, and as the condensation product, a condensation product of diethanolamine and an aliphatic dicarboxylic acid is preferred, and a condensation product of diethanolamine and adipic acid, and a condensation product of diethanolamine and itaconic acid are particularly preferred.

[0033] According to another aspect of the present invention, there is provided a method for preparing the above-mentioned high-temperature thermal expansion microspheres with rapid foaming response, comprising:

[0034] The ethylenically unsaturated monomer, the crosslinking agent, the initiator and the blowing agent are mixed to prepare an oil phase for suspension polymerization;

[0035] Mixing a dispersion stabilizer, a dispersion stabilization aid and a dispersion medium to prepare an aqueous phase for suspension polymerization;

[0036] After the water phase and the oil phase are emulsified into a suspension, the suspension is stirred in a high-pressure reactor to carry out a suspension polymerization reaction, thereby obtaining slurry-like high-temperature heat-expandable microspheres.

[0037] Furthermore, the aqueous phase also includes an electrolyte, which is selected from sodium chloride, potassium chloride, lithium chloride, magnesium chloride, sodium bicarbonate, lithium sulfate, sodium sulfate, potassium sulfate, ammonium sulfate, sodium carbonate or benzoic acid; relative to 100 parts by weight of the dispersion medium, the amount of electrolyte is 0.1 to 50 parts by weight. The electrolyte can effectively reduce the solubility of polar monomers in the aqueous phase, reduce the probability of polymerization nucleation in the aqueous phase, effectively improve the uniformity of particle size, ensure that polar monomers efficiently participate in the formation of shell wall polymers, enhance the interaction between shell wall polymers, and improve the heat resistance of microspheres, thereby improving the high-temperature foam stability of microspheres.

[0038] Optionally, the emulsification method of the oil phase and the water phase is selected from a dispersion method such as a stirring method using a homogenizer, a homogenizer, a static dispersion method using a static mixer, a membrane emulsification method, an ultrasonic dispersion method or a microchannel method.

[0039] The suspension polymerization method refers to using water as a medium, dispersing the monomer into fine particles and suspending them in water through mechanical stirring, and then thermally initiating polymerization.

[0040] The reaction temperature of suspension polymerization is determined by the initiation temperature of the initiator. If the temperature is too high, the reaction rate will be faster, the molecular weight of the polymer in the microsphere shell will increase, and the foaming effect will be affected. In addition, the temperature will also affect the properties and morphology of the microspheres. The pressure affects the gas-liquid equilibrium of the monomer and the foaming agent. The appropriate pressure allows a certain amount of the foaming agent to be wrapped inside the microspheres. The reaction time is determined according to the half-life of the initiator at a certain temperature to ensure that the monomer is fully converted.

[0041] Optionally, the suspension polymerization reaction temperature is 40-100°C, preferably 50-90°C; more preferably 60-80°C.

[0042] Optionally, the suspension polymerization reaction pressure is 0 to 5.0 MPa, preferably, 0.1 to 0.3 MPa; more preferably, 0.2 to 2.0 MPa.

[0043] Optionally, the suspension polymerization reaction time is 18 to 22 hours.

[0044] Optionally, to control the pH value of the aqueous phase, the acid added is an organic acid or an inorganic acid, for example, the organic acid is selected from oxalic acid, tartaric acid, oxalic acid, malic acid, citric acid, ascorbic acid (i.e., vitamin C), etc., and there are also aromatic organic acids such as benzoic acid, salicylic acid, caffeic acid, etc., and the inorganic acid is selected from sulfuric acid, hydrochloric acid, phosphoric acid, etc., but is not limited thereto. They can be used alone or in combination of two or more.

[0045] Furthermore, the preparation method further comprises dehydrating the slurry-like high-temperature heat-expandable microspheres to obtain wet cake-like heat-expandable microspheres; or washing, dehydrating and drying to obtain dispersed heat-expandable microspheres.

[0046] The dehydration method includes bed filtration, pressure filtration, liquid filtration, rotary filtration, suction filtration or centrifugal separation; the drying method includes spray drying, bracket drying, tunnel drying, rotary drying, drum drying, ventilation drying, turbine bracket drying, disc drying or fluidized bed drying.

[0047] The invention provides a method for preparing heat-expandable microspheres. In an aqueous dispersion medium containing a dispersion stabilizer and in the presence of a foaming agent, a mixture of ethylenically unsaturated monomers is subjected to suspension polymerization to prepare an outer shell of a thermoplastic copolymer with a high glass transition temperature, and the foaming agent is sealed inside the outer shell to obtain heat-expandable microspheres.

[0048] The volume average particle size of the high temperature heat-expandable microspheres (i.e., heat-expandable microcapsules) of the present invention preferably has a lower limit of 10 μm and an upper limit of 50 μm; the more preferred lower limit of the above volume average particle size is 15 μm and the more preferred upper limit is 35 μm. When the above volume average particle size is less than 10 μm, for example, when the heat-expandable microcapsules are used for foaming, the bubbles of the obtained foaming molded body are too small, and sometimes the lightweight becomes insufficient. When the above volume average particle size exceeds 50 μm, for example, when the heat-expandable microcapsules are used for foaming, the bubbles of the obtained foaming molded body become too large, and sometimes it becomes a problem in terms of strength, etc.

[0049] The present invention provides a high-temperature heat-expandable microsphere with excellent durability, and the preparation method thereof comprises the following steps: water phase preparation, oil phase preparation, and suspension polymerization. The microsphere has a structure in which a foaming agent is enclosed in an outer shell formed by a polymer, and a silicon-containing acrylate monomer participates in the formation of the outer shell of the microsphere, and the microsphere has better durability and foam stabilization performance. The microsphere is synthesized by a one-pot copolymerization-suspension polymerization method, and the heat-expandable microsphere has a smooth surface and a perfect core-shell structure; the particle size of the microsphere is uniformly controlled, and the particle size can be controlled between 10 and 50 microns. The present invention can significantly improve the foaming response speed and bubble breaking temperature of the microsphere.

[0050] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0051] The high-temperature heat-expandable microspheres provided by the present invention introduce a double-bond monofunctional group cage-type polysilsesquioxane (POSS) monomer and other monomers to participate in the formation of the microsphere shell through copolymerization reaction, which can significantly improve the foaming response speed of the microspheres. The microspheres have a higher bubble breaking temperature (180-220° C.) and higher expansion performance.

[0052] The invention adopts a one-pot copolymerization-suspension polymerization method to synthesize microspheres. The prepared thermal expansion microspheres have smooth surfaces and perfect core-shell structures. The particle size of the microspheres is evenly controlled and can be controlled between 10 and 50 microns. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0054] Figure 1 The figure is a schematic flow chart of the method for preparing high temperature thermal expansion microspheres in an embodiment of the present invention. DETAILED DESCRIPTION

[0055] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0056] Example 1

[0057] Reference Figure 1 As shown, the method for preparing high temperature thermal expansion microspheres in this embodiment comprises the following steps:

[0058] S1. Add 90 g acrylonitrile, 30 g methacrylic acid, 15 g N,N-dimethylacrylamide, 15 g (meth)acryloxypropyl heptaisobutyl polysilsesquioxane, 15 g ethanol, 0.8 g ethylene glycol dimethacrylate, 25 g isopentane, 35 g isooctane and 1.6 g AIBME in sequence to obtain an oil phase for suspension polymerization.

[0059] S2. 300 g of deionized water, 72 g of sodium chloride, 50.4 g of silica sol, 1.6 g of citric acid, 0.1 g of sodium nitrite, and 4 g of a dispersant (adipic acid-diethanolamine polymer) were added in sequence to obtain a water phase for suspension polymerization.

[0060] S3, the oil phase and the water phase are mixed, stirred at 10000rpm for 5 minutes by a homogenizer, emulsified and dispersed, thereby preparing a suspension solution. The suspension is injected into a 1.0L autoclave, the air is replaced by nitrogen, and the autoclave is pressurized to an initial pressure of 0.3MPa. Then, the reaction is carried out at 70°C for 20 hours, the temperature is lowered, and the pressure is released. Then, the mixture is washed, filtered, and dried in an oven at 50°C to obtain white or slightly yellow thermoplastic microspheres.

[0061] Example 2

[0062] Reference Figure 1As shown, the method for preparing high temperature thermal expansion microspheres in this embodiment comprises the following steps:

[0063] S1, sequentially adding 75g acrylonitrile, 30g methacrylic acid, 15g N,N-dimethylacrylamide, 30g (meth)acryloxypropyl heptaisobutyl polysilsesquioxane, 15g ethanol, 0.8g ethylene glycol dimethacrylate, 25g isopentane, 35g isooctane, and 1.6g AIBME to obtain an oil phase for suspension polymerization;

[0064] Step S2 and step S3 are the same as in Example 1.

[0065] Example 3

[0066] Reference Figure 1 As shown, the method for preparing high temperature thermal expansion microspheres in this embodiment comprises the following steps:

[0067] S1, sequentially adding 90g acrylonitrile, 30g methacrylic acid, 15g N,N-dimethylacrylamide, 15g (meth)acryloxypropyl heptaphenylsilsesquioxane, 15g ethanol, 0.8g ethylene glycol dimethacrylate, 25g isopentane, 35g isooctane, and 1.6g AIBME to obtain an oil phase for suspension polymerization;

[0068] Step S2 and step S3 are the same as in Example 1.

[0069] Example 4

[0070] Reference Figure 1 As shown, the method for preparing high temperature thermal expansion microspheres in this embodiment comprises the following steps:

[0071] S1, add 75g acrylonitrile, 30g methacrylic acid, 15g N,N-dimethylacrylamide, 30g (meth)acryloxypropyl heptaphenylsilsesquioxane, 15g ethanol, 0.8g ethylene glycol dimethacrylate, 25g isopentane, 35g isooctane, and 1.6g AIBME in sequence to obtain an oil phase for suspension polymerization;

[0072] Step S2 and step S3 are the same as in Example 1.

[0073] Example 5

[0074] Reference Figure 1 As shown, the method for preparing high temperature thermal expansion microspheres in this embodiment comprises the following steps:

[0075] S1, add 75g acrylonitrile, 30g methacrylic acid, 15g N,N-dimethylacrylamide, 30g vinyl propyl undecyl polysilsesquioxane, 15g ethanol, 0.8g ethylene glycol dimethacrylate, 25g isopentane, 35g isooctane, and 1.6g AIBME in sequence to obtain an oil phase for suspension polymerization;

[0076] Step S2 and step S3 are the same as in Example 1.

[0077] Example 6

[0078] Reference Figure 1 As shown, the method for preparing high temperature thermal expansion microspheres in this embodiment comprises the following steps:

[0079] S1, add 75g acrylonitrile, 30g methacrylic acid, 15g N, N-dimethylacrylamide, 30g single tube POSS-nonaisopropyl, 15g ethanol, 0.8g ethylene glycol dimethacrylate, 25g isopentane, 35g isooctane, 1.6g AIBME in sequence to obtain an oil phase for suspension polymerization;

[0080] Step S2 and step S3 are the same as in Example 1.

[0081] Comparative Example 1

[0082] Reference Figure 1 As shown, the method for preparing high temperature thermal expansion microspheres in this embodiment comprises the following steps:

[0083] S1, adding 90g acrylonitrile, 30g methacrylic acid, 30g N,N-dimethylacrylamide, 15g ethanol, 0.8g ethylene glycol dimethacrylate, 25g isopentane, 35g isooctane, and 1.6g AIBME in sequence to obtain an oil phase for suspension polymerization;

[0084] Step S2 and step S3 are the same as in Example 1.

[0085] Comparative Example 2

[0086] Reference Figure 1 As shown, the method for preparing high temperature thermal expansion microspheres in this embodiment comprises the following steps:

[0087] S1, add 75g acrylonitrile, 30g methacrylic acid, 45g N,N-dimethylacrylamide, 15g ethanol, 0.8g ethylene glycol dimethacrylate, 25g isopentane, 35g isooctane, and 1.6g V65 in sequence to obtain an oil phase for suspension polymerization;

[0088] Step S2 and step S3 (different temperature, 50° C. reaction) are the same as in Example 1.

[0089] Comparative Example 3

[0090] Reference Figure 1 As shown, the method for preparing high temperature thermal expansion microspheres in this embodiment comprises the following steps:

[0091] S1, add 75g acrylonitrile, 30g methacrylic acid, 15g N, N-dimethylacrylamide, 30g single tube POSS-heptaisobutyl, 15g ethanol, 0.8g ethylene glycol dimethacrylate, 25g isopentane, 35g isooctane, 1.6g V65 in sequence to obtain an oil phase for suspension polymerization;

[0092] Step S2 and step S3 (different temperature, 50° C. reaction) are the same as in Example 1.

[0093] Comparative Example 4

[0094] Reference Figure 1 As shown, the method for preparing high temperature thermal expansion microspheres in this embodiment comprises the following steps:

[0095] S1, add 75g acrylonitrile, 30g methacrylic acid, 15g N, N-dimethylacrylamide, 30g single tube POSS-heptylphenyl, 15g ethanol, 0.8g ethylene glycol dimethacrylate, 25g isopentane, 35g isooctane, 1.6g V50 in sequence to obtain an oil phase for suspension polymerization;

[0096] Step S2 and step S3 (different temperature, 50° C. reaction) are the same as in Example 1.

[0097] Comparative Example 5

[0098] Reference Figure 1 As shown, the method for preparing high temperature thermal expansion microspheres in this embodiment comprises the following steps:

[0099] S1, add 75g acrylonitrile, 30g methacrylic acid, 15g N, N-dimethylacrylamide, 30g single tube POSS-nonaisopropyl, 15g ethanol, 0.8g ethylene glycol dimethacrylate, 25g isopentane, 35g isooctane, 1.6g V50 in sequence to obtain an oil phase for suspension polymerization;

[0100] Step S2 and step S3 (different temperature, 50° C. reaction) are the same as in Example 1.

[0101] The performance tests of the high temperature heat expandable microspheres in the above embodiments and comparative examples are as follows:

[0102] 1. Particle size distribution characteristics

[0103] Particle size test of microspheres Take about 1-2g of washed and dried sample, add 20-30ml of deionized water, stir evenly and ultrasonicate for 2 minutes; turn on the laser particle size analyzer and the analysis software on the computer, and then pour in the ultrasonicated sample. The analyzer and the analysis software can be used to obtain the average particle size, the percentage of particles within each size range and the particle size distribution curve.

[0104] The particle size distribution calculation formula is: CV value = (standard deviation / average diameter) × 100%.

[0105] 2. Foaming performance test of microspheres

[0106] Use a microscope and a thermostat to test. Take a small amount of the product on a glass slide and place it on a hot stage. Then, according to the particle size, use different objective lenses and eyepieces to observe (objective lens x4, x10, x40, x80; eyepiece x10). Connect the camera to the microscope, select the appropriate heating rate of the hot stage, observe and record the foaming process of the heat-expandable microspheres, and take pictures of the foaming at different stages. At the same time, correctly record the starting foaming temperature T according to the number on the thermostat. start , Maximum foaming temperature T max , bubble breaking temperature T break , foaming ratio and foam stability.

[0107] 3. Foaming response time test

[0108] The prepared 0.4-0.5g microspheres were placed in an oven at 190°C, and the start time, concentrated foaming time, and foam breaking time of the microspheres were recorded. The time required for the microspheres to foam from the beginning to the maximum foaming was the foaming response speed.

[0109] The microsphere components and performance test results in the above embodiments and comparative examples are shown in Table 1.

[0110] Table 1 Performance test results of high temperature thermal expansion microspheres

[0111]

[0112]

[0113]

[0114] In Table 1, AN: acrylonitrile; MMA: methyl methacrylate; MAA: methacrylic acid; DMAA: N,N-dimethylacrylamide; single-tube MA-POSS-heptaisobutyl: (meth)acryloxypropyl heptaisobutylsilsesquioxane; single-tube MA-POSS-phenyl: (meth)acryloxypropyl heptaphenylsilsesquioxane; single-tube MA-POSS-nona-glycidyl: (meth)acryloxypropyl nona-glycidylsilsesquioxane; AIBME: dimethyl azobisisobutyrate; V50: 2,2'-azobisisobutylamidine dihydrochloride; V65: 2,2'-azobisisoheptanoonitrile.

[0115] The above-mentioned embodiment 1-embodiment 5 all introduce the cage type polysilsesquioxane (POSS) monomer containing double bond monofunctional group to participate in polymerization at 70 ℃, and the comparative example does not introduce POSS monomer or reacts at a lower temperature after introducing POSS. According to the results such as the initial foaming time, the maximum foaming time, and the bubble breaking time in Table 1, the cage type polysilsesquioxane (POSS) containing double bond monofunctional group participates in the polymerization of the microsphere shell as a monomer, accelerates the foaming time of the microsphere, improves the bubble breaking temperature and the heat-resistant lasting time, and the microsphere in the above-mentioned embodiment of the present invention has excellent foaming response speed and stable foam performance, and the prepared microsphere is more sensitive to the temperature reaction, which can meet the different needs in industrial production.

[0116] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or variations within the scope of the claims, which does not affect the essence of the present invention. The above preferred features can be used in any combination without conflicting with each other.

Claims

1. A high temperature thermal expansion microsphere with rapid foaming response, characterized in that: The invention comprises ethylenically unsaturated monomers, wherein the ethylenically unsaturated monomers comprise the following components by weight percentage: 40-60% acrylonitrile monomers, 10-20% acrylic acid monomers, 10-20% acrylamide monomers, and 5-30% double-bond monofunctional cage-type polysilsesquioxane monomers; the double-bond monofunctional cage-type polysilsesquioxane monomers are used to participate in polymerization to form the microsphere shell.

2. The high temperature thermal expansion microsphere with rapid foaming response according to claim 1, characterized in that: The cage-type polysilsesquioxane monomer containing a double bond monofunctional group is any one of a cage-type tetramer silsesquioxane containing a double bond monofunctional group, a cage-type hexamer silsesquioxane containing a double bond monofunctional group, a cage-type octamer silsesquioxane containing a double bond monofunctional group, a cage-type decamer silsesquioxane containing a double bond monofunctional group, and a cage-type dodecamer silsesquioxane containing a double bond monofunctional group.

3. The high temperature thermal expansion microspheres with rapid foaming response according to claim 1, characterized in that: The double bond-containing monofunctional cage-type polysilsesquioxane monomer is a double bond-containing monofunctional cage-type octamer silsesquioxane.

4. The high temperature thermal expansion microspheres with rapid foaming response according to claim 3, characterized in that: The structural formula of the double bond-containing monofunctional cage-type octamer silsesquioxane is as follows: In the formula, X = any one of (meth)acrylic acid, acrylic acid ester, olefin and its derivatives containing double bonds, R 1-7 =Any one of an alkyl group, an aromatic group derivative, an epoxy group and a carboxyl group.

5. The high temperature thermal expansion microspheres with rapid foaming response according to claim 1, characterized in that: The double bond-containing monofunctional cage-type polysilsesquioxane monomer is selected from any one or more of (meth)acryloxypropyl heptaisobutyl polysilsesquioxane, (meth)acryloxypropyl heptaphenyl silsesquioxane, acryloxypropyl heptacarboxyl polysilsesquioxane, (meth)acryloxypropyl nona-glycidyl polysilsesquioxane, (meth)acryloxypropyl undecylisobutyl and vinylpropyl undecylpropyl polysilsesquioxane.

6. The high temperature thermal expansion microspheres with rapid foaming response according to claim 1, characterized in that: The microspheres also include a foaming agent, a cross-linking agent, an initiator, a dispersion stabilizer, a dispersion stabilization aid and a dispersion medium. By weight percentage, the ethylenically unsaturated monomer accounts for 50-70% of the oil phase, the foaming agent accounts for 20-30% of the oil phase, the cross-linking agent accounts for 0.1-0.6% of the oil phase, the initiator accounts for 0.6-1% of the oil phase, the dispersion stabilizer accounts for 8-15% of the water phase, the dispersion stabilization aid accounts for 0.5-2% of the water phase, and the dispersion medium accounts for 60-80% of the water phase.

7. A method for preparing high-temperature thermal expansion microspheres with rapid foaming response according to any one of claims 1 to 6, characterized in that: include: The ethylenically unsaturated monomer, the crosslinking agent, the initiator and the blowing agent are mixed to prepare an oil phase for suspension polymerization; Mixing a dispersion stabilizer, a dispersion stabilization aid and a dispersion medium to prepare an aqueous phase for suspension polymerization; After the water phase and the oil phase are emulsified into a suspension, the suspension is stirred in a high-pressure reactor to carry out a suspension polymerization reaction, thereby obtaining slurry-like high-temperature heat-expandable microspheres.

8. The method for preparing high temperature thermal expansion microspheres with rapid foaming response according to claim 7, characterized in that: The suspension polymerization reaction temperature is 40-100°C.

9. The method for preparing high temperature thermal expansion microspheres with rapid foaming response according to claim 7, characterized in that: The pressure of the suspension polymerization reaction is 0-5.0 MPa.

10. The method for preparing high temperature thermal expansion microspheres with rapid foaming response according to claim 7, characterized in that: The suspension polymerization reaction time is 18 to 22 hours.

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