Thermally expandable microcapsules having good electrical conductivity and a process for their preparation

Abstract

The present application relates to the technical field of thermal expansion microcapsule, and especially relates to a thermal expansion microcapsule with good conductivity and a preparation method thereof. The thermal expansion microcapsule is prepared by polymerization of raw materials including the following components by weight: 100 parts of ethylenically unsaturated monomer, 10-100 parts of conductive monomer, 0.01-10 parts of crosslinking agent, 0.01-10 parts of initiator, 10-60 parts of foaming agent, 0.01-5 parts of dispersion stabilizer, 0.01-5 parts of dispersion stabilizing aid, and 0.5-10 parts of inorganic salt. The thermal expansion microcapsule has excellent conductivity, and meanwhile, the foaming performance of the microcapsule is not affected, so that the application field of the thermal expansion microcapsule is widened.

Description

Technical Field

[0001] This invention relates to the field of thermal expansion microcapsule technology, and in particular to a thermal expansion microcapsule with good electrical conductivity and its preparation method. Background Technology

[0002] Thermally expandable microcapsules have a closed outer shell and a gas-generating core material, which can produce an expansion effect. Functionalized thermally expandable microcapsules refer to the grafting of some functional groups or substances onto the surface of thermally expandable microcapsules, or the preparation of functional carbon materials by pyrolysis of thermally expandable microcapsules as precursors. They are novel functional materials with unique new functions or great potential for development.

[0003] Currently, the functionalization of thermally expandable microcapsules involves two approaches. The first approach is pretreatment, which involves copolymerizing monomers containing specific functional groups with the original monomer to encapsulate a core material, forming a functional polymer. Alternatively, a core with different functions is introduced into the reaction system, encapsulating it within a polymer-based shell to form a functional polymer. Common methods for this approach include emulsion polymerization, dispersion polymerization, and suspension polymerization. Pretreatment methods often employ copolymerization modification, commonly introducing functional groups such as double bonds, carboxyl groups, hydroxyl groups, amino groups, and acyl chloride groups. However, copolymerization modification has limited application due to its complex and difficult-to-control copolymerization conditions between functional monomers and the original monomer, as well as its high cost.

[0004] The second approach is the post-processing method, which involves first preparing thermally expandable microcapsules, and then grafting functional groups or substances onto the surface of the microcapsules through a chemical reaction. Post-processing modification utilizes forces such as hydrogen bonds, electrostatics, and covalent bonds to capture functional groups or substances and encapsulate them on the surface of the thermally expandable microcapsules.

[0005] Conductive thermal expansion microcapsules mainly consist of conductive polymers or inorganic metals encapsulated on the surface of thermal expansion microcapsules, thereby forming conductive medium / thermal expansion microcapsule composite microcapsules. Summary of the Invention

[0006] The purpose of this invention is to provide a thermally expandable microcapsule with good electrical conductivity and its preparation method, so as to overcome the defects of the prior art.

[0007] To address the aforementioned technical problems, the present invention provides a thermally expandable microcapsule with good electrical conductivity, which is a thermally expandable microsphere composed of a shell formed from a thermoplastic resin and a foaming agent contained within the shell and vaporized by heating, using a conductive monomer as the starting material.

[0008] Furthermore, the thermally expandable microcapsule with good electrical conductivity comprises a shell formed of thermoplastic resin and a foaming agent contained within the shell and vaporized by heating.

[0009] Furthermore, the thermally expandable microcapsules with good electrical conductivity comprise the following raw materials in parts by weight:

[0010]

[0011]

[0012] Preferably, the raw materials comprise the following parts by weight:

[0013]

[0014] Furthermore, the olefinic unsaturated monomer comprises the following components in weight percentages:

[0015] 15-80 parts of acrylic monomers

[0016] 40-90 parts of nitrile monomers

[0017] 20-70 parts of acrylate monomers

[0018] Preferably, the olefinic unsaturated monomer comprises the following components by weight percentage:

[0019] 20-70 parts of acrylic monomers

[0020] 50-80 parts of nitrile monomers

[0021] 30-60 parts of acrylate monomers

[0022] Further, the acrylic monomers are one or two of methacrylic acid and acrylic acid; the nitrile monomers are one or more of acrylonitrile, methacrylonitrile, 2-methyl-2-acrylonitrile, 2-chloroacrylonitrile, 2-ethoxyacrylonitrile, 2-butenonitrile, and trans-1,2-dicyanoethylene; and the acrylate monomers are one or more of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, methyl methacrylate, ethyl methacrylate, isobornyl methacrylate, hydroxyethyl acrylate, and glycidyl methacrylate.

[0023] Preferably, the acrylic monomer is one or two of methacrylic acid and acrylic acid; the nitrile monomer is one or two of acrylonitrile and methacrylonitrile; and the acrylate monomer is methyl methacrylate.

[0024] Furthermore, the conductive monomer is one or more of naphthalene-based monomers, carbazole-based monomers, and acridine-based monomers.

[0025] Further, the naphthalene monomer is one or more of 2-vinylnaphthalene, 2-vinylanthracene, 2-vinylquinone, and 2,6-2-vinylnaphthalene; the carbazole monomer is one or more of 9-phenylcarbazole, 3-methyl-9-phenylcarbazole, 9-(4-methylphenyl)-9H-carbazole, and 9,9'-P-phenylenecarbazole; and the acridine monomer is one or more of 9-phenylacridine, 10-methyl-9-phenylacridine perchlorate, 9-methylacridine, and 2-acridineamine.

[0026] Preferably, the naphthalene monomer is 2-vinylnaphthalene; the carbazole monomer is 9-phenylcarbazole; and the acridine monomer is 9-methylacridine.

[0027] Further, the crosslinking agent is one or more of the following: dicumyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, diethylenetriamine, divinylbenzene, ethylene glycol divinyl ether, divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, ethylene glycol di(meth)acrylate, di(ethylene glycol) di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, triacylformaldehyde, triallyl isocyanate, and triallyl isocyanurate.

[0028] Preferably, the crosslinking agent is one or more of dicumyl peroxide and triethylene glycol divinyl ether.

[0029] Further, the initiator is one or more of azobisisobutyronitrile, benzoic acid peroxide, didecanoic acid peroxide, dilauric acid peroxide, percarbonate peroxide, tert-butyl peroxide benzoate, tert-butyl perlaurate, and tert-butyl peracetate.

[0030] Preferably, the initiator is azobisisobutyronitrile.

[0031] Furthermore, the foaming agent is a C4-C8 straight-chain or branched saturated hydrocarbon compound.

[0032] Furthermore, the C4-C8 straight-chain or branched saturated hydrocarbon compound is one or more of the following: n-butane, isobutane, n-pentane, isopentane, n-hexane, n-heptane, n-octane, isooctane, and petroleum ether.

[0033] Preferably, the foaming agent is one or more of isooctane, isopentane, and petroleum ether.

[0034] Further, the dispersant stabilizer is one or more of the following: calcium phosphate, calcium carbonate, magnesium carbonate, magnesium hydroxide, magnesium oxide, barium sulfate, barium carbonate, barium hydroxide, zinc hydroxide, nickel hydroxide, manganese hydroxide, starch, methylcellulose, hydroxypropyl methylcellulose, hydroxymethylcellulose, colloidal silica, aluminum oxide, aluminum hydroxide, iron oxide, and iron hydroxide.

[0035] Preferably, the dispersant stabilizer is one or more of magnesium hydroxide and colloidal silica.

[0036] Furthermore, the dispersion stabilizing agent is one or more of polyvinylpyrrolidone, methylcellulose, polyvinyl alcohol, polyethylene oxide, alkyltrimethylammonium chloride, and dialkyldimethylammonium chloride.

[0037] Preferably, the dispersion stabilizing agent is polyvinylpyrrolidone.

[0038] Furthermore, the inorganic salt is one or more of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate.

[0039] Preferably, the inorganic salt is sodium chloride.

[0040] The specific technical solution of this invention is as follows: It includes the following steps:

[0041] Step (1): Mix the dispersant stabilizer, dispersant stabilizing aid, dispersion medium and inorganic salt to obtain an aqueous phase;

[0042] Step (2): Mix the olefinic unsaturated monomer, conductive monomer, crosslinking agent, initiator and foaming agent to obtain the oil phase;

[0043] Step (3): Stir and disperse the oil and water phases evenly to obtain a suspension solution;

[0044] Step (4): The obtained suspension is subjected to polymerization reaction for 10 to 25 hours in an inert atmosphere (including one or more of nitrogen or argon) at 40 to 90°C and a pressure of 0.05 to 1 MPa.

[0045] Step (5): After the reaction is completed, the microcapsules are obtained by filtration and washing with deionized water. After drying, the microcapsules with good electrical conductivity are obtained.

[0046] Preferably, the polymerization reaction temperature is 50–80°C, the pressure is 0.1–0.8 MPa, and the polymerization reaction time is 12–20 hours.

[0047] The inventors have discovered that by introducing conductive monomers into thermally expandable microcapsules and polymerizing them under certain conditions, thermally expandable microcapsules with good conductivity can be obtained.

[0048] The beneficial effects of this invention are:

[0049] The thermally expandable microcapsules of this invention have excellent electrical conductivity without affecting their foaming properties, thus broadening the application fields of thermally expandable microcapsules. Detailed Implementation

[0050] The present invention will be further explained and illustrated below through specific embodiments, but these do not constitute any limitation on the present invention.

[0051] The following methods and instruments were used to analyze all thermally expanded microcapsules in the examples:

[0052] The average particle size was measured using a nanolaser particle size analyzer from Zetasizer Nano.

[0053] The foaming properties of the microcapsules were tested using a Mettler TMA841 micrometer, with a heating rate of 5 °C / min and a load of 0.06 N. start It is the temperature at which expansion begins, T max It is the temperature at which the maximum expansion is achieved.

[0054] Its resistivity was determined according to the national standard GB / T 1410-2006.

[0055] Example 1

[0056] Step (1): Mix 3g magnesium hydroxide, 2g polyvinylpyrrolidone, 120g water and 8g sodium chloride to prepare an aqueous phase;

[0057] Step (2): Mix 100g of methacrylonitrile, 30g of 2-vinylnaphthalene, 3g of dicumyl peroxide, 1g of azobisisobutyronitrile and 45g of isopentane to obtain an oil phase;

[0058] Step (3): Stir and disperse the oil and water phases evenly to obtain a suspension solution;

[0059] Step (4): The obtained suspension was subjected to polymerization reaction at 60°C and 0.5 MPa for 15 hours in an inert atmosphere (nitrogen in this case);

[0060] Step (5): After the reaction is complete, the microcapsules are obtained by filtration and washing with deionized water. After drying, thermally expanded microcapsules with good electrical conductivity are obtained. The obtained microcapsules have a core-shell structure, with the outer shell being a thermoplastic polymer and the interior being a low-boiling-point foaming agent, with a wall thickness of 2-10 micrometers.

[0061] Example 2

[0062] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 1, 3g of colloidal silica, 2g of polyvinylpyrrolidone, 120g of water and 8g of sodium chloride were mixed to obtain an aqueous phase.

[0063] Example 3

[0064] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 1, 3g of magnesium hydroxide, 1g of polyvinylpyrrolidone, 120g of water and 8g of sodium chloride were mixed to obtain an aqueous phase.

[0065] Example 4

[0066] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 2, 100g of acrylonitrile, 30g of 2-vinylnaphthalene, 3g of diisopropylbenzene peroxide, 1g of azobisisobutyronitrile and 45g of isopentane were mixed to obtain an oil phase.

[0067] Example 5

[0068] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 2, 100g of methacrylonitrile, 30g of 9-phenylcarbazole, 3g of diisopropylbenzene peroxide, 1g of azobisisobutyronitrile and 45g of isopentane were mixed to obtain an oil phase.

[0069] Example 6

[0070] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 2, 80g of methacrylonitrile, 30g of 9-phenylcarbazole, 3g of diisopropylbenzene peroxide, 1g of azobisisobutyronitrile and 45g of isopentane were mixed to obtain an oil phase.

[0071] Example 7

[0072] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 2, 80g of methacrylonitrile, 30g of 9-phenylcarbazole, 3g of triethylene glycol divinyl ether, 1g of azobisisobutyronitrile and 45g of isopentane were mixed to obtain an oil phase.

[0073] Example 8

[0074] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 2, 100g of methacrylonitrile, 30g of 9-phenylcarbazole, 3g of diisopropylbenzene peroxide, 1g of azobisisobutyronitrile and 30g of isooctane were mixed to obtain an oil phase.

[0075] Example 9

[0076] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 2, 100g of methacrylonitrile, 30g of 9-phenylcarbazole, 3g of diisopropylbenzene peroxide, 1g of azobisisobutyronitrile, 25g of isopentane, and 25g of isooctane were mixed to obtain an oil phase.

[0077] Example 10

[0078] Thermally expandable microcapsules were prepared according to the method of Example 10, except that in step 4, the obtained suspension was subjected to polymerization reaction for 20 hours at 50°C and 0.5 MPa under an inert atmosphere.

[0079] The above embodiments are some implementations of the present invention, but the implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and are included within the protection scope of the present invention.

[0080] Comparative Example 1

[0081] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 1, 2g of polyvinylpyrrolidone, 120g of water and 8g of sodium chloride were mixed to obtain an aqueous phase.

[0082] Comparative Example 2

[0083] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 1, 3g of magnesium chloride, 2g of polyvinyl alcohol, 120g of water and 8g of sodium chloride were mixed to obtain an aqueous phase.

[0084] Comparative Example 3

[0085] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 2, 100g of 3-pentenonitrile, 30g of 2-vinylnaphthalene, 3g of diisopropylbenzene peroxide, 1g of azobisisobutyronitrile and 45g of isopentane were mixed to obtain an oil phase.

[0086] Comparative Example 4

[0087] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 2, 100g of acrylonitrile, 3g of diisopropylbenzene peroxide, 1g of azobisisobutyronitrile and 45g of isopentane were mixed to obtain an oil phase.

[0088] Comparative Example 5

[0089] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 2, 100g of methacrylonitrile, 5g of 9-phenylcarbazole, 3g of diisopropylbenzene peroxide, 1g of azobisisobutyronitrile and 45g of isopentane were mixed to obtain an oil phase.

[0090] Comparative Example 6

[0091] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 2, 80g of methacrylonitrile, 30g of 9-phenylcarbazole, 1g of azobisisobutyronitrile and 45g of isopentane were mixed to obtain an oil phase.

[0092] Comparative Example 7

[0093] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 2, 100g of methacrylonitrile, 30g of 9-phenylcarbazole, 3g of diisopropylbenzene peroxide and 1g of azobisisobutyronitrile were mixed to obtain an oil phase.

[0094] Comparative Example 8

[0095] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step 2, 100g of methacrylonitrile, 30g of 9-phenylcarbazole, 3g of diisopropylbenzene peroxide, 1g of azobisisobutyronitrile and 5g of isopentane were mixed to obtain an oil phase.

[0096] Comparative Example 9

[0097] Thermally expandable microcapsules were prepared according to the method of Example 10, except that in step 4, the obtained suspension was subjected to polymerization reaction for 30 hours at 30°C and 2 MPa under an inert atmosphere.

[0098] The results of comparing the examples and comparative examples are shown in Tables 1 and 2 below:

[0099] Table 1

[0100]

[0101]

[0102] Table 2

[0103]

[0104] Compared with the comparative examples, the examples show better electrical conductivity and excellent foaming properties. Compared with Example 1, Examples 2 and 3 changed the type and amount of dispersant, resulting in a slight decrease in the conductivity of the thermally expanded microcapsules; Examples 4 and 5 changed the type of monomer, resulting in a slight decrease in the resistivity of the microcapsules; Example 7 changed the type of crosslinking agent, resulting in a decrease in the foaming performance of the microcapsules; Examples 8 and 9 changed the type and amount of foaming agent, resulting in a decrease in the pressure and foaming ratio of the microcapsules during foaming; Example 10 changed the polymerization temperature and time, and also obtained thermally expanded microcapsules with good electrical conductivity.

[0105] From the comparative examples, Comparative Example 1 removed the dispersant; Comparative Example 2 changed the type of dispersant (using a non-optimal dispersant), resulting in uneven dispersion during polymerization and reduced foaming and conductivity; Comparative Example 3 changed the nitrile monomer (using a non-optimal monomer), resulting in microcapsules that could not withstand high temperatures and had poor conductivity; Comparative Example 4 did not add a conductive monomer, resulting in microcapsules that lacked conductivity; Comparative Example 5 reduced the amount of conductive monomer (a non-optimal ratio), resulting in reduced conductivity of the microcapsules; Comparative Example 6 did not add a crosslinking agent, leading to low crosslinking degree of the microcapsule shell, poor rigidity, and poor foaming performance; Comparative Example 7 did not add a foaming agent, and Comparative Example 8 reduced the amount of foaming agent (a non-optimal ratio), resulting in microcapsules with very poor foaming performance; Comparative Example 9 changed the polymerization temperature and time (non-optimal temperature and time), resulting in low microcapsule formation rate and poor foaming and conductivity.

[0106] The thermally expandable microcapsules with good electrical conductivity described in this invention can be used as fillers in antistatic composite materials. Foamed materials have wide applications in automotive interiors and packaging, but they are prone to generating static electricity hazards during use. Researching and preparing foamed materials with antistatic properties can avoid this problem. The thermally expandable microcapsules with good electrical conductivity obtained in Example 1 were foamed by heating at 210°C for 5 minutes and then used as conductive fillers to fill biaxially oriented polypropylene (BOP) antistatic composite materials. The resistivity was measured to be 0.25 Ω·m according to the national standard GB / T 1410-2006.

Claims

1. A thermally expandable microcapsule with good electrical conductivity, characterized in that, It is a thermally expandable microcapsule made from conductive monomers as starting materials; It is produced by polymerization reaction using raw materials comprising the following parts by weight: 100 parts of olefinic unsaturated monomers 10-100 parts of conductive monomer Crosslinking agent 0.01~10 parts Initiator 0.01~10 parts 10-60 parts of foaming agent Dispersant stabilizer 0.01~5 parts Dispersion stabilizer 0.01~5 parts Inorganic salts 0.5-10 parts; The olefinic unsaturated monomer comprises the following components by weight percentage: 15-80 parts of acrylic monomers 40-90 parts of nitrile monomers 20-70 parts of acrylate monomers The acrylic monomer is one or both of methacrylic acid and acrylic acid; The nitrile monomers are one or more selected from acrylonitrile, methacrylonitrile, 2-methyl-2-acrylonitrile, 2-chloroacrylonitrile, 2-ethoxyacrylonitrile, 2-butenonitrile, and trans-1,2-dicyanoethylene; The acrylate monomers are one or more selected from methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, methyl methacrylate, ethyl methacrylate, isobornyl methacrylate, hydroxyethyl acrylate, and glycidyl methacrylate. The conductive monomer is one or more of naphthalene monomers, carbazole monomers, and acridine monomers; The naphthalene monomer is 2-vinylnaphthalene; The carbazole monomer is 9-phenylcarbazole; The acridine monomers are one or more selected from 9-phenylacridine, 10-methyl-9-phenylacridine perchlorate, 9-methylacridine, and 2-acridineamine; The crosslinking agent is dicumyl peroxide; The initiator is azobisisobutyronitrile; The foaming agent is a C4~C8 straight-chain or branched saturated hydrocarbon compound; The C4-C8 straight-chain or branched saturated hydrocarbon compounds are one or more of the following: n-butane, isobutane, n-pentane, isopentane, n-hexane, n-heptane, n-octane, isooctane, and petroleum ether. The dispersing stabilizer is one or more of the following: calcium phosphate, calcium carbonate, magnesium carbonate, magnesium hydroxide, magnesium oxide, barium sulfate, barium carbonate, barium hydroxide, zinc hydroxide, nickel hydroxide, manganese hydroxide, starch, methylcellulose, hydroxypropyl methylcellulose, hydroxymethylcellulose, colloidal silica, aluminum oxide, aluminum hydroxide, iron oxide, and iron hydroxide. The dispersion stabilizing agent is one or more of the following: polyvinylpyrrolidone, methylcellulose, polyvinyl alcohol, polyethylene oxide, alkyltrimethylammonium chloride, and dialkyldimethylammonium chloride; The inorganic salt is one or more of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate.

2. A method for preparing thermally expandable microcapsules with good electrical conductivity as described in claim 1, characterized in that, Includes the following steps: Step (1): Mix the dispersant stabilizer, dispersant stabilizing aid, dispersion medium and inorganic salt to obtain an aqueous phase; Step (2): Mix the olefinic unsaturated monomer, conductive monomer, crosslinking agent, initiator and foaming agent to obtain the oil phase; Step (3): Stir and disperse the oil phase and aqueous phase evenly to obtain a suspension solution; Step (4): The obtained suspension is subjected to polymerization reaction at 40~90℃ and 0.05~1MPa pressure for 10~25 hours in an inert atmosphere; Step (5): After the reaction is completed, the microcapsules are obtained by filtration and washing with deionized water. After drying, the microcapsules with good electrical conductivity are obtained.

3. The method for preparing thermally expandable microcapsules with good electrical conductivity according to claim 2, characterized in that, The dispersion medium is water.

4. The application of the thermally expandable microcapsule with good electrical conductivity as described in claim 1, characterized in that, It is used as a filler in antistatic composite materials, and its thermal expansion temperature range is 120~230℃.

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