Thermal expansion microsphere and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to the field of IPC C08J9, and more specifically relates to a thermal expansion microsphere and a preparation method thereof. Comprising a water phase and an oil phase, and the water phase comprises the following components in parts by weight: 0.1-2 parts of polyol, 0.1-1 part of a surfactant, 2-10 parts of a dispersion stabilizer, 0.5-2 parts of a water phase polymerization inhibitor, 0.1-1 part of metal salt and 300-500 parts of deionized water; the oil phase comprises 50-100 parts of nitrile monomers, 10-50 parts of acrylic monomers, 0.1-2 parts of an initiator, 0.1-1 part of a cross-linking agent and 20-60 parts of a foaming agent. The expansion rate of the microspheres is 60-80 times, and the microspheres are cured after being cooled, do not retract, have good supporting performance, yellowing resistance and particle fluidity, and can be applied to the fields of shoe materials, wallpaper, automobile sealing, light weight and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to the field of IPC C08J9, and more specifically to a thermal expansion microsphere and a preparation method thereof. Background Art

[0002] Heat-expandable microspheres have good physical and chemical properties. They are microspheres composed of polymer copolymers with diameters ranging from 1 micron to 100 microns. Heat-expandable microspheres are coated with low-boiling-point alkanes in the shell of polymer copolymers. Under heating conditions, the shell softens, the alkanes vaporize, and the microspheres expand. Heat-expandable microspheres are composed of wall materials of polymer copolymers and core materials of low-boiling-point alkanes. Excellent heat-expandable microspheres should have the characteristics of suitable foaming temperature, wide stable foaming range, high foaming rate, high foaming ratio, no shrinkage after cooling, bright white color, non-toxic and odorless. The strength and mechanical properties of the foamed materials prepared by heat-expandable microspheres are much better than those of simple gas foaming. The foamed materials prepared by expanded microspheres have uniform and delicate pores and good mechanical properties. Heat-expandable microspheres not only increase the specific volume of the material, but also have the advantages of light weight, insulation, noise elimination, etc., and at the same time have the characteristics of improving the optical properties of the material such as refractive index and transparency. They are widely used in industries such as construction, automobiles, aircraft materials and special materials.

[0003] CN105949494B discloses a heat-expandable microsphere and a preparation method and application thereof. The heat-expandable microsphere is prepared by a reverse polymerization method at room temperature and pressure. Specifically, the heat-expandable microsphere is made of a core material of a sodium hydroxide aqueous solution wrapped with a wall material obtained by condensation of diacyl chloride and diamine. The prepared heat-expandable microsphere has a diameter of about 25 μm, a foaming volume ratio of 2-6 times, and uniform and fine foaming pores. The heat-expandable microsphere is prepared by reverse suspension polymerization at room temperature and pressure with a sodium hydroxide aqueous solution as the core material, which is environmentally friendly and low in cost. The prepared heat-expandable microsphere is more environmentally friendly and low in cost, but the foaming performance is still not high enough. Summary of the invention

[0004] The first aspect of the present invention provides a heat-expandable microsphere, comprising an aqueous phase and an oil phase, wherein the aqueous phase comprises, by weight, 0.1-2 parts of a polyol, 0.1-1 parts of a surfactant, 2-10 parts of a dispersion stabilizer, 0.5-2 parts of an aqueous phase inhibitor, 0.1-1 parts of a metal salt and 300-500 parts of deionized water; and the oil phase comprises 50-100 parts of a nitrile monomer, 10-50 parts of an acrylic monomer, 0.1-2 parts of an initiator, 0.1-1 parts of a cross-linking agent and 20-60 parts of a foaming agent.

[0005] Preferably, the weight ratio of the nitrile monomer to the acrylic monomer is (2-4):1.

[0006] More preferably, the weight ratio of the nitrile monomer to the acrylic monomer is (2-3):1.

[0007] Preferably, the polyol comprises polyethylene glycol and an alkyl alcohol with a carbon chain length of 12-20, and the weight ratio of the polyethylene glycol to the alkyl alcohol with a carbon chain length of 12-20 is 1:(1-2.5).

[0008] Further preferably, the polyol comprises polyethylene glycol and an alkyl alcohol with a carbon chain length of 12-20, and the weight ratio of the polyethylene glycol to the alkyl alcohol with a carbon chain length of 12-20 is 1:(1-1.8).

[0009] The applicant has found that the weight ratio of the nitrile monomer to the acrylic monomer is (2-4):1, which can increase the foaming ratio of the microspheres to 60-80 times. The microspheres that expand when heated are composed of two layers, an inner layer and an outer layer, wherein the outer layer is a polymer copolymer. The three-dimensional structure formed by compounding the nitrile monomer and the acrylic monomer in a specific ratio effectively improves the plasticity of the outer layer. Further research has found that the nitrile monomers include acrylonitrile and methacrylonitrile, and the weight ratio of acrylonitrile to methacrylonitrile is (4-6):1. While achieving excellent mechanical properties, the yellowing resistance of the microspheres can be further improved. This may be because the specific structure avoids the occurrence of oxidation and ring formation reactions of the nitrile group.

[0010] Preferably, the alkyl alcohol with a carbon chain length of 12-20 includes at least one of dodecanol, tetradecanol, hexadecanol, octadecanol and eicosanol.

[0011] The nitrile monomer includes at least one of acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile or fumaronitrile.

[0012] Preferably, the nitrile monomers include acrylonitrile and methacrylonitrile, and the weight ratio of acrylonitrile to methacrylonitrile is (4-6):1.

[0013] More preferably, the nitrile monomers include acrylonitrile and methacrylonitrile, and the weight ratio of acrylonitrile to methacrylonitrile is (5-6):1.

[0014] The surfactant includes at least one of sodium dodecyl sulfate, span, allyl polyethylene glycol, allyl sulfoalkoxy succinic acid diester sodium salt, and polyoxyethylene nonylphenol ether acrylate.

[0015] The metal salt includes at least one of sodium chloride, potassium chloride, magnesium chloride, sodium sulfate, potassium sulfate and magnesium sulfate.

[0016] The dispersion stabilizer includes at least one of montmorillonite, colloidal silicon dioxide, colloidal calcium carbonate, magnesium hydroxide, calcium phosphate, aluminum hydroxide, iron hydroxide, calcium sulfate, calcium oxalate, calcium carbonate, barium carbonate, magnesium carbonate, and aluminum hydroxide sol.

[0017] The acrylic monomer includes at least one of methyl acrylate, methacrylic acid, ethyl acrylate, butyl acrylate, dicyclopentenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and isobornyl methacrylate.

[0018] The initiator includes at least one of dihexadecyl peroxydicarbonate, di(4-tert-butylcyclohexyl), peroxydicarbonate, dioctanoic acid peroxide, dibenzoic acid peroxide, dilauric acid peroxide, didecanoic acid peroxide, tert-butyl peracetate, tert-butyl perlaurate, tert-butyl peroxybenzoate, benzoyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ethyl cumene peroxide, dicyclohexyl peroxycarbonate, azobisisobutyronitrile, diisopropyl hydroxydicarboxylate, 2,2'-azobis((2,4-dimethylvaleronitrile), 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), dimethyl 2,2,-azobis(2-methylpropionate), and 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propyl epoxy.

[0019] The crosslinking agent includes 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, At least one of acrylate, triallyl formal tri(meth)acrylate, allyl methacrylate, ethylene glycol dimethacrylate, trimethylolpropane tri(meth)acrylate, tributylene glycol di(meth)acrylate, di(meth)acrylate, ethylene glycol diacrylate, di(meth)acrylate, di(meth)acrylate, 3-acryloyl glycol monoacrylate, triacyl formal, triallyl isocyanate, triallyl isocyanurate, divinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, and tetraethylene glycol divinyl ether.

[0020] The foaming agent includes at least one of butane, isobutane, isopentane, neopentane, n-hexane, heptane, isooctane, octane and petroleum ether.

[0021] The second aspect of the present invention provides a method for preparing heat-expandable microspheres, comprising the following steps:

[0022] S1, adding a dispersing stabilizer into deionized water, then adding other aqueous phase components and mixing, cooling to 5-15°C while stirring, to obtain an aqueous phase for use;

[0023] S2, mixing all the ingredients of the oil phase and stirring them evenly to obtain the oil phase for later use;

[0024] S3, mixing the water phase and the oil phase, homogenizing them, and then adding them into the reactor, stirring them to react. After the reaction is completed, the temperature is cooled to room temperature, and the pressure is discharged, filtered, dried, and crushed in sequence to obtain heat-expandable microspheres.

[0025] The reaction pressure in step S3 is 0.2-0.6 MPa, and the reaction time is 14-20 h.

[0026] The reaction in step S3 includes a first stage and a second stage. The reaction time of the first stage is 4-8 hours and the reaction temperature is 50-60°C. The reaction time of the second stage is 10-12 hours and the reaction temperature is 60-70°C.

[0027] The D50 particle size of the heat-expandable microspheres is 20-50 microns, and the expansion ratio is 60-80 times.

[0028] The heat-expandable microspheres are used as additives in the fields of shoe materials, wallpapers, and automobile seals, and the added amount of the heat-expandable microspheres is 0.7-1 wt %.

[0029] Beneficial effects:

[0030] 1. The heat-expandable microspheres prepared in this application can be used as additives in the fields of shoe materials, wallpapers, and automotive seals, and can effectively improve the mechanical properties and optical properties of the products on the basis of a relatively low addition amount (0.7-1wt%).

[0031] 2. The microspheres prepared in this application have a wide operating temperature range (140-210°C).

[0032] 3. The weight ratio of the nitrile monomer to the acrylic monomer is (2-4):1, which can increase the microsphere foaming ratio to 60-80 times.

[0033] 4. The microspheres prepared in the present application solidify after cooling, do not shrink, and have excellent support stability.

[0034] 5. The weight ratio of acrylonitrile to methacrylonitrile is (4-6):1, which can further improve the yellowing resistance of the microspheres while achieving excellent mechanical properties.

[0035] 6. The microspheres prepared in the present application are resistant to non-polar solvents, ethanol, methanol, and basically resistant to water. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a photo of the microspheres prepared in Example 1.

[0037] Figure 2 These are photos of microspheres after aging in Example 1 and Example 4, where the right side corresponds to Example 1.

[0038] Figure 3 This is a micrograph of the microparticles of Example 1.

[0039] Figure 4 This is a micrograph of the cells of Example 1. DETAILED DESCRIPTION

[0040] Example 1

[0041] A heat-expandable microsphere comprises a water phase and an oil phase, and the formula is as follows:

[0042] Water Phase

[0043] 400g-deionized water

[0044] 0.2164g-Polyol (Polyethylene glycol 2000) Jiangyin Haolin Chemical Co., Ltd.

[0045] 0.320g-polyol (hexadecanol)

[0046] 0.162g-Surfactant (sodium dodecyl sulfate)

[0047] 0.0972g-Surfactant (Siban)

[0048] 6.054g-Dispersion stabilizer (montmorillonite) (Shanghai Shisi Hewei Chemical Co., Ltd.)

[0049] The dispersion stabilizer (montmorillonite) was soaked in 50g of water for 12h before being added to obtain a montmorillonite gel solution.

[0050] 0.7568g-water phase inhibitor (sodium nitrite)

[0051] 0.324g-Metal salt (sodium chloride)

[0052] oil phase

[0053] 70.25g-Nitrile monomer (acrylonitrile)

[0054] 12.4g-Nitrile monomer (methacrylonitrile)

[0055] 13.10g-Acrylic monomer (methyl acrylate)

[0056] 25.10g-Acrylic acid monomer (methacrylic acid)

[0057] 1g-Initiator (azobisisobutyronitrile)

[0058] 0.5268g- Crosslinker (ethylene glycol diacrylate)

[0059] 42g-foaming agent (isopentane)

[0060] A method for preparing heat-expandable microspheres comprises the following steps:

[0061] S1. Preparation of aqueous phase: Add montmorillonite gel solution into deionized water, then add other aqueous phases and mix, cool to 15°C while stirring, and set aside;

[0062] S2. Preparation of oil phase: Mix all ingredients of the oil phase and stir evenly, and refrigerate at 5°C before using isopentane;

[0063] S3. After mixing the water phase and the oil phase, homogenize them at 10000 r / min for 300 seconds. The microscopic photograph of the particles is as follows: Figure 3 As shown, then add it into the reactor, pressurize it to 0.4MPa, stir and react for 18h, the reaction temperature is 60℃ for the first 6 hours and 65℃ for the last 12 hours, and after the reaction, cool it to room temperature, then release the pressure, filter, dry and crush to obtain Figure 1 The microscopic photograph of the heat-expanded microspheres and cells is shown in Figure 4 shown.

[0064] Example 2

[0065] The specific implementation is the same as in Example 1; the difference is that in Example 2, no hexadecanol is added.

[0066] Example 3

[0067] The specific implementation is the same as in Example 1; the difference is that in Example 3, no sodium nitrite is added.

[0068] Example 4

[0069] The specific implementation is the same as in Example 1; the difference is that in Example 4, the amount of methacrylonitrile added is 6.2 g.

[0070] Performance testing methods and data

[0071] The microspheres prepared in the examples were subjected to performance tests, and the test data are listed in Table 1.

[0072] Bubble temperature and bubble stabilization temperature: slowly increase the temperature through a microscopic melting point apparatus and observe the changes in the microspheres. The temperature when most of the microspheres begin to expand is recorded as the bubble temperature, and the temperature when the microspheres break in an orderly manner is recorded as the bubble stabilization temperature.

[0073] Expansion ratio: 0.4 g of microsphere powder with a density of 0.4 g / ml was spread on the bottom of a 100 ml beaker and placed in a 200°C oven. The peak volume after expansion within 10 minutes was recorded as the expansion ratio.

[0074] Yellowing resistance: Figure 2 As shown, Example 1 does not turn yellow after aging, while Example 4 turns yellow after aging. The microspheres are tested for whiteness after 5 minutes from the start of foaming at 200°C. Whiteness above 80 is considered to be qualified for yellowing resistance, while whiteness below 80 is considered to be unqualified for yellowing resistance.

[0075] Solvent resistance: The microspheres are completely immersed in the solvent for 10 minutes, then filtered, dried, crushed, and then subjected to a foaming test. If the expansion ratio is less than 60% of the original, it is judged to be intolerant to the solvent. If it is higher than 60% and lower than 80%, it is judged to be basically tolerant. If it is higher than 80%, it is judged to be tolerant to the solvent.

[0076] Table 1

[0077]

Claims

1. A heat-expandable microsphere, characterized in that: The invention comprises a water phase and an oil phase. The water phase comprises, by weight, 0.1-2 parts of a polyol, 0.1-1 parts of a surfactant, 2-10 parts of a dispersion stabilizer, 0.5-2 parts of a water phase inhibitor, 0.1-1 parts of a metal salt and 300-500 parts of deionized water; the oil phase comprises 50-100 parts of a nitrile monomer, 10-50 parts of an acrylic monomer, 0.1-2 parts of an initiator, 0.1-1 parts of a cross-linking agent and 20-60 parts of a foaming agent.

2. The heat-expandable microspheres according to claim 1, characterized in that: The weight ratio of the nitrile monomer to the acrylic monomer is (2-4):

1.

3. The heat-expandable microspheres according to claim 2, characterized in that: The polyol comprises polyethylene glycol and an alkyl alcohol with a carbon chain length of 12-20, and the weight ratio of the polyethylene glycol to the alkyl alcohol with a carbon chain length of 12-20 is 1:(1-2.5).

4. The heat-expandable microspheres according to claim 3, characterized in that: The nitrile monomer includes at least one of acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile and fumaronitrile.

5. The heat-expandable microspheres according to claim 4, characterized in that: The nitrile monomers include acrylonitrile and methacrylonitrile, and the weight ratio of acrylonitrile to methacrylonitrile is (4-6):

1.

6. The heat-expandable microspheres according to claim 1, characterized in that: The acrylic monomer includes at least one of methyl acrylate, methacrylic acid, ethyl acrylate, butyl acrylate, dicyclopentenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and isobornyl methacrylate.

7. A method for preparing heat-expandable microspheres according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, adding a dispersing stabilizer into deionized water, then adding other aqueous phase components and mixing, cooling to 5-15°C while stirring, to obtain an aqueous phase for use; S2, mixing all the ingredients of the oil phase and stirring them evenly to obtain the oil phase for later use; S3, mixing the water phase and the oil phase, homogenizing them, and then adding them into the reactor, stirring them to react. After the reaction is completed, the temperature is cooled to room temperature, and the pressure is discharged, filtered, dried, and crushed in sequence to obtain heat-expandable microspheres.

8. The method for preparing heat-expandable microspheres according to claim 7, characterized in that: The reaction pressure in step S3 is 0.2-0.6 MPa, and the reaction time is 14-20 h.

9. The method for preparing heat-expandable microspheres according to claim 8, characterized in that: The reaction in step S3 includes a first stage and a second stage. The reaction time of the first stage is 4-8 hours and the reaction temperature is 50-60°C. The reaction time of the second stage is 10-12 hours and the reaction temperature is 60-70°C.

10. The method for preparing heat-expandable microspheres according to claim 9, characterized in that: The D50 particle size of the heat-expandable microspheres is 20-50 microns, and the expansion ratio is 60-80 times.

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