Expandable microsphere with improved water resistance and preparation method thereof

Abstract

The preparation method comprises the following steps: mixing a monomer, an initiator, a cross-linking agent, a volatile foaming agent and an auxiliary agent to obtain an oil phase; mixing a water-based dispersion medium, inorganic salt, a dispersion stabilizer and a dispersion stabilizing aid to obtain a water phase; stirring the oil phase and the water phase to disperse the oil phase and the water phase to obtain a suspension solution; the expandable microspheres are prepared through a suspension polymerization method. The water resistance of the prepared expandable microspheres is obviously improved, meanwhile, the foaming performance of the expandable microspheres is not affected, and the application field of the expandable microspheres is widened.

Description

Technical Field

[0001] The invention relates to the field of polymer materials, and in particular to expandable microspheres with improved water resistance and a preparation method thereof. Background Art

[0002] Expandable microspheres are microspheres with a core-shell structure, which are composed of a thermoplastic polymer as a shell and an expandable substance such as a volatile expander such as aliphatic hydrocarbons. Expandable microspheres have been successfully applied to the fields of plasticine, printing paste, plastics, elastomers, etc. as a light and heavy filler. However, due to the composition defects of the microspheres without methacrylonitrile system, the foaming performance of the microspheres is easily affected or destroyed in various applications in water environment or aqueous solution environment.

[0003] In the currently disclosed patent technologies, methacrylonitrile system microspheres with good water resistance or water resistance are usually used. However, methacrylonitrile system microspheres require the use of methacrylonitrile, which has a relatively high raw material cost, and the cost of preparing the microspheres is relatively high. In order to broaden the application range of heat-expandable microspheres and maintain the maximum foaming temperature of expandable microspheres above 180°C, non-methacrylonitrile system microspheres usually need to use heat-resistant monomers to replace methacrylonitrile, that is, cheap and easily available methacrylic acid monomers. Due to the strong water solubility of methacrylic acid monomers and their homopolymers, non-methacrylonitrile system microspheres are subject to the penetration and swelling of water molecules in a long-term aqueous solution environment, and the expansion performance of the microspheres is easily greatly affected or destroyed. Summary of the invention

[0004] The purpose of the present invention is to provide an expandable microsphere with improved water resistance and a preparation method thereof, so as to overcome the defects of the prior art.

[0005] On one hand, the present invention provides a method for preparing microspheres with improved water resistance, comprising mixing a monomer, an initiator, a crosslinking agent, a volatile foaming agent and an auxiliary agent to obtain an oil phase; mixing an aqueous dispersion medium, an inorganic salt, a dispersion stabilizer and a dispersion stabilizing auxiliary agent to obtain a water phase; stirring the oil phase and the water phase to disperse the oil phase and the water phase to obtain a suspension solution; and preparing expandable microspheres by suspension polymerization.

[0006] A method for preparing microspheres with improved water resistance comprises the following steps:

[0007] (1) Mixing monomers, initiators, crosslinking agents, volatile foaming agents, and additives to obtain an oil phase;

[0008] (2) mixing an aqueous dispersion medium, an inorganic salt, a dispersion stabilizer, and a dispersion stabilization aid to obtain an aqueous phase;

[0009] (3) stirring the oil phase and the water phase to disperse the oil phase and the water phase to obtain a suspension solution;

[0010] (4) subjecting the obtained suspension solution to polymerization reaction for 15 to 25 hours at 40 to 80° C. and 0.1 to 0.5 MPa in an inert atmosphere, lowering the temperature of the microsphere slurry to room temperature, filtering and drying to obtain water-resistant expandable microspheres;

[0011] The auxiliary agent is butyl rubber containing polybutadiene chain segments.

[0012] Furthermore, the butyl rubber includes one or more of chloroprene rubber, nitrile rubber, and styrene-butadiene rubber.

[0013] Furthermore, the expandable microspheres include a thermoplastic shell and a volatile expansion agent wrapped in the thermoplastic shell.

[0014] Furthermore, the monomer comprises the following components in parts by weight:

[0015] 40-90 parts of nitrile monomer;

[0016] Acrylic monomer 0-60 parts;

[0017] 5-50 parts of acrylic acid ester monomer.

[0018] Furthermore, the nitrile monomer is one or more of acrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile or fumaronitrile; the acrylic monomer is one or more of acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, α-methylcinnamic acid, maleic acid, itaconic acid, fumaric acid and citraconic acid; the acrylate monomer is one or more of methyl acrylate, ethyl acrylate, butyl acrylate, dicyclopentenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate or isobornyl methacrylate.

[0019] Furthermore, the boiling point of the volatile expansion agent is not higher than the softening temperature of the thermoplastic shell, and the volatile expansion agent is a C4-C12 aliphatic hydrocarbon compound.

[0020] Preferably, the volatile expansion agent is a C4-C8 straight-chain or branched saturated hydrocarbon compound.

[0021] Furthermore, the volatile expansion agent is one or more of isooctane, isopentane, isobutane, neopentane, n-hexane, heptane, petroleum ether and other low molecular weight hydrocarbons, tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, trimethyl-n-propylsilane.

[0022] Preferably, the volatile expansion agent is one or more of isooctane, isopentane, isobutane, n-hexane and petroleum ether.

[0023] Preferably, based on the total weight of the nitrile monomers and the acrylate monomers, the thermoplastic shell further comprises the following components in percentage by weight:

[0024] Cross-linking agent 0.1wt%~5wt%;

[0025] Initiator 1 wt%~5 t%;

[0026] Additives 0.1wt%~0.5wt%;

[0027] Dispersion stabilizer 0.1~0.5%;

[0028] Dispersing and stabilizing agent 0.1~0.5%;

[0029] Inorganic salt 1%-3%.

[0030] Further, the crosslinking agent is divinylbenzene, ethylene glycol di(meth)acrylate, di(ethylene glycol) di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, glycerol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, One of 1,2-dimethylolpropane tri(meth)acrylate, 1,2-dimethylolpropane tri(meth)acrylate, 1,2-dimethylolpropane di ... or several; the initiator is di(hexadecyl) peroxydicarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, dioctanoic acid peroxide, di-(2-ethylhexyl) peroxydicarbonate, dibenzoic acid peroxide, dilauric acid peroxide, didecanoic acid peroxide, tert-butyl peracetate, tert-butyl perlaurate, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, diisopropyl hydroxydicarboxylate, 2,2'-azobis((2,4-dimethylvaleronitrile), 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), dimethyl 2,2,-azobis( The dispersion stabilizer is one or more of colloidal silicon dioxide, colloidal clay, calcium carbonate, calcium phosphate, calcium sulfate, calcium oxalate or barium carbonate; the dispersion stabilizing agent is one or more of methyl cellulose, methyl hydroxypropyl cellulose, polyvinyl alcohol, gelatin, polyvinyl pyrrolidone, polyethylene oxide, dialkyl dimethyl ammonium chloride, alkyl trimethyl ammonium chloride, alkyl sodium sulfate, alkyl sodium sulfonate, alkyl dimethyl amino acetate betaine or alkyl dihydroxyethyl amino acetate betaine.

[0031] Preferably, the thermoplastic shell is suspended and polymerized in an aqueous dispersion medium containing a dispersion stabilizer and / or a dispersion stabilizing aid, the aqueous dispersion medium is water, and an inorganic salt may be added thereto, the inorganic salt being sodium chloride or sodium sulfate.

[0032] Another aspect of the present invention provides expandable microspheres with improved water resistance, wherein the expandable microspheres with improved water resistance are prepared by the above method.

[0033] The expandable microspheres with improved water resistance provided by the present invention can be used in various applications in water-containing environments, and specific applications include: prepregs of glass fiber thermoplastics, water-based printing paste, papermaking, ultra-light clay, lightweight cement, etc.

[0034] The inventors have found that after the additive is introduced into the oil phase, the butadiene segment contained in the additive has a carbon-carbon unsaturated double bond. After the oil phase initiator decomposes to generate free radicals, the primary free radicals can react well with the double bonds of the butadiene segment to form a cross-linked polymer and quickly precipitate at the oil-water interface. A shell layer with a high butadiene segment content is formed on the surface of the microsphere, and finally expandable microspheres with improved water resistance are obtained.

[0035] The beneficial effects of the present invention are:

[0036] The invention significantly improves the water resistance and does not affect the foaming performance of the expandable microspheres, thereby broadening the application field of the expandable microspheres. DETAILED DESCRIPTION

[0037] The present invention is further described below by way of examples. In the examples listed, unless otherwise specified, all parts and percentages in the examples are parts and percentages by weight, and the analysis of the heat-expandable microspheres was performed using the following methods and instruments:

[0038] (1) Particle size distribution characteristics analysis:

[0039] The particle size distribution of the microspheres was measured by a particle size distribution laser diffraction analyzer LS13320 produced by Bekman Coulter, and the average diameter was measured as the volume average particle size.

[0040] (2) Foaming characteristics analysis:

[0041] The characteristic of heat-expandable microsphere is measured by the thermomechanical analyzer TMA Q-400 produced by TA Instrument company.The 1.0mg heat-expandable microsphere prepared sample by the aluminum pan of diameter 6.7mm and depth 4.5mm.Then, the aluminum pan of diameter 6.5mm and depth 4.0mm is sealed.According to the TMA extended probe type, the sample temperature is increased to 280 ℃ from ambient temperature with the heating rate of 20 ℃ / min, and the power of 0.1N is applied by probe.Analysis is carried out by measuring the vertical displacement of probe.

[0042] - Expansion initial temperature (Tstart): The temperature at which the probe displacement starts to increase (°C);

[0043] - Maximum foaming temperature (Tmax): the temperature (°C) when the probe displacement reaches the maximum;

[0044] - Foaming density (Dmin): the ratio of the amount of microspheres added to the volume after foaming (kg / m3).

[0045] (3) Evaluation method of microsphere water resistance:

[0046] 1 gram of microsphere dry powder was added to 9 grams of deionized water to prepare microsphere slurry, which was filtered and dried after storage at room temperature for 30 days. The dried microspheres were subjected to TMA test. We will compare the blank example with Examples 1 to 5.

[0047] Example of Preparation of Blank Expandable Microspheres

[0048] Aqueous phase:

[0049] 280 g water (aqueous dispersion medium)

[0050] 10g sodium chloride (inorganic salt)

[0051] 0.5g 50 wt% silica aqueous solution (dispersion stabilizer)

[0052] 0.5g 5 wt% aqueous solution of methyl hydroxypropyl cellulose (average molecular weight 26000g / mol) (dispersion stabilizing agent)

[0053] 0.2g sodium dodecyl sulfate (dispersion stabilizing agent)

[0054] Oil phase:

[0055] 150g acrylonitrile (monomer)

[0056] 50g Methacrylic acid (monomer)

[0057] 30g Methyl methacrylate (monomer)

[0058] 4g dodecyl peroxide (initiator)

[0059] 0.6g Trimethylolpropane tri(meth)acrylate (crosslinking agent)

[0060] 50g isopentane (volatile expansion agent)

[0061] Under the condition of 0.5Mpa, the oil phase and the water phase were dispersed by stirring at 7000rpm for 2 minutes with a homogenizer to prepare a suspension solution. The suspension solution was immediately injected into a 1-liter autoclave, the air was replaced by nitrogen, and the autoclave was pressurized to reach an initial pressure of 0.6MPa. Then, the polymerization reaction was carried out at 50-70°C for 20 hours. After the polymerization was completed, the basic expandable microspheres were obtained by filtering, washing and drying. The relevant properties of the microspheres are shown in Table 1.

[0062] Table 1

[0063]

[0064] In Table 1, (nitrile monomer) AN: acrylonitrile, (acrylic acid monomer) MAA: methacrylic acid, (acrylate monomer) MMA: methyl methacrylate, TMPDMA: trimethylolpropane trimethacrylate, LPO: dodecyl peroxide, IP: isopentane.

[0065] Example 1

[0066] Preparation of Blank Example 0.35 g of chloroprene rubber was added to the oil phase of the reaction and dispersed at room temperature for 1 hour, and then water-oil phase emulsification and suspension polymerization were performed. The obtained product was filtered and dried to obtain water-resistant expandable microspheres. The relevant test data are listed in Table 2.

[0067] Example 2

[0068] Preparation of Blank Example 0.7 g of chloroprene rubber was added to the oil phase of the reaction and dispersed at room temperature for 1 hour, and then water-oil phase emulsification and suspension polymerization were performed. The obtained product was filtered and dried to obtain water-resistant expandable microspheres. The relevant test data are listed in Table 2.

[0069] Example 3

[0070] Preparation of Blank Example 1.05 g of chloroprene rubber was added to the oil phase of the reaction and dispersed at room temperature for 1 hour, and then water-oil phase emulsification and suspension polymerization were performed. The obtained product was filtered and dried to obtain water-resistant expandable microspheres. The relevant test data are listed in Table 2.

[0071] Example 4

[0072] Preparation of Blank Example 0.75 g of nitrile rubber was added to the oil phase of the reaction and dispersed at room temperature for 1 hour, and then water-oil phase emulsification and suspension polymerization were performed. The obtained product was filtered and dried to obtain water-resistant expandable microspheres. The relevant test data are listed in Table 2.

[0073] Example 5

[0074] Preparation of Blank Example 0.75 g of styrene-butadiene rubber was added to the oil phase of the reaction and dispersed at room temperature for 1 hour, and then water-oil phase emulsification and suspension polymerization were performed. The obtained product was filtered and dried to obtain water-resistant expandable microspheres. The relevant test data are listed in Table 2.

[0075] Through the data in Table 2, we first found that the addition of butyl rubber to the oil phase had no significant effect on the expansion properties of the microspheres.

[0076] Through the blank example and implementation 1, experimental example 2, and experimental example 3 in Table 2, we can find that after adding chloroprene rubber to the oil phase, the water resistance of the microspheres is significantly improved, and as the amount of chloroprene rubber added increases, the resistance performance of the microspheres is significantly improved.

[0077] By comparing Implementation 2, Experimental Example 4, and Experimental Example 5, we can also find that under the condition of the same amount of butyl rubber added, adding nitrile rubber in the oil phase can obtain expandable microspheres with excellent foaming performance and water resistance.

[0078] Table 2

[0079]

[0080] According to the method given in the above description, a person skilled in the art can think of various modifications and other embodiments of the present invention. Therefore, the protection scope of the present invention is not limited to the disclosed embodiments, and any appropriate changes or modifications made by a person skilled in the art should be deemed to be within the scope of the patent of the present invention.

Claims

1. A method for preparing expandable microspheres with improved water resistance, comprising the following steps: (1) Mixing monomers, initiators, crosslinking agents and volatile foaming agents to obtain an oil phase; (2) mixing an aqueous dispersion medium, an inorganic salt, a dispersion stabilizer, and a dispersion stabilization aid to obtain an aqueous phase; (3) stirring the oil phase and the water phase to disperse the oil phase and the water phase to obtain a suspension solution; (4) After the obtained suspension solution is polymerized for 15 to 25 hours in an inert atmosphere at 40 to 80° C. and a pressure of 0.1 to 0.5 MPa, the temperature of the microsphere slurry is lowered to room temperature, filtered and dried to obtain temperature-resistant expandable microspheres; The auxiliary agent is butyl rubber containing polybutadiene chain segments.

2. The method for preparing expandable microspheres according to claim 1, characterized in that: The butyl rubber includes one or more of chloroprene rubber, nitrile rubber and styrene-butadiene rubber.

3. The method for preparing expandable microspheres according to claim 1, characterized in that: The expandable microspheres include a thermoplastic shell and a volatile expansion agent wrapped in the thermoplastic shell.

4. The method for preparing expandable microspheres according to claim 1, characterized in that: The monomer comprises the following components in parts by weight: 40-90 parts of nitrile monomer; 5-50 parts of acrylamide monomer; 5-50 parts of acrylic acid ester monomer.

5. The method for preparing expandable microspheres according to claim 1, characterized in that: The volatile expansion agent is one or more of isooctane, isopentane, isobutane, neopentane, n-hexane, heptane, petroleum ether and other low molecular weight hydrocarbons, tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, trimethyl-n-propylsilane.

6. An expandable microsphere for improving water resistance, characterized in that: The expandable microspheres are prepared by the method according to any one of claims 1 to 5.

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