Polymethacrylimide thermal expansion microsphere and preparation method thereof
阅读说明：本技术 一种聚甲基丙烯酰亚胺热膨胀微球及其制备方法 (Polymethacrylimide thermal expansion microsphere and preparation method thereof ) 是由 张竞 周一凡 吴义民 汤继俊 张娇霞 于 2019-10-15 设计创作，主要内容包括：本发明公开一种聚甲基丙烯酰亚胺热膨胀微球及其制备方法,通过Pickering乳液悬浮聚合,由不饱和烯烃类单体包裹烷烃发泡剂制成,以不饱和烯烃类单体100wt％为计算基准,丙烯腈(AN)占60wt％～85wt％,甲基丙烯酸(MAA)占10wt％～30wt％,丙烯酰胺类单体5wt％～15wt％,丙烯酸酯类占2wt％～10wt％；该制备方法简单,反应条件温和,易于控制,在微球的膨胀过程中相邻的丙烯腈和甲基丙烯酸链节形成了具有耐高温特性的六元酰亚胺环结构,制备的聚甲基丙烯酰亚胺微球在具有耐高温特性的基础上不含甲基丙烯腈(MAN),成本低廉,易于工业化。(The invention discloses a polymethacrylimide thermal expansion microsphere and a preparation method thereof, wherein the polymethacrylimide thermal expansion microsphere is prepared by suspending and polymerizing Pickering emulsion and coating AN alkane foaming agent by AN unsaturated olefin monomer, wherein 100 wt% of the unsaturated olefin monomer is taken as a calculation reference, Acrylonitrile (AN) accounts for 60-85 wt%, methacrylic acid (MAA) accounts for 10-30 wt%, AN acrylamide monomer accounts for 5-15 wt%, and acrylates account for 2-10 wt%; the preparation method is simple, the reaction condition is mild, the control is easy, the adjacent acrylonitrile and methacrylic acid chain links form a six-membered imide ring structure with high temperature resistance in the expansion process of the microsphere, the prepared polymethacrylimide microsphere does not contain Methacrylonitrile (MAN) on the basis of high temperature resistance, the cost is low, and the industrialization is easy.)
1. The preparation method of the polymethacrylimide thermal expansion microsphere is characterized by mainly comprising the following steps:
1) uniformly mixing an unsaturated olefin monomer, a cross-linking agent, an alkane foaming agent and an oil-soluble initiator, and magnetically stirring for 5-10 min to obtain an oil phase;
2) homogenizing and emulsifying inorganic dispersant, emulsifier, inorganic salt, aqueous phase polymerization inhibitor and deionized water at 10000rpm for 3min to obtain aqueous phase;
3) slowly dripping the oil phase obtained in the step (1) into the water phase obtained in the step (2), and fully and uniformly mixing by mechanically stirring for 15-35 min to obtain an oil-in-water emulsion;
4) injecting the emulsion obtained in the step (3) into a high-pressure reaction kettle, heating to 55-80 ℃ under the nitrogen atmosphere, polymerizing at 0.4-0.6 MPa for 18-25 h, washing the obtained product with deionized water, filtering, and drying to obtain the thermal expansion microspheres;
wherein, the unsaturated olefin monomer and the cross-linking agent used in the step 1 are shell materials of the microspheres, and the alkane foaming agent with low boiling point is a core material of the microspheres;
the unsaturated olefin monomer consists of acrylonitrile, methacrylic acid, acrylamide monomers and acrylate monomers, wherein 100 wt% of the unsaturated olefin monomer is taken as a reference, the acrylonitrile accounts for 60-85 wt%, the methacrylic acid accounts for 10-30 wt%, the acrylamide monomers account for 5-15 wt%, and the acrylate monomers account for 2-10 wt%.
2. The method of claim 1, wherein the acrylic acid ester comprises at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and glycidyl methacrylate.
3. The method for preparing polymethacrylimide thermal expansion microspheres as claimed in claim 1, wherein the alkane blowing agent used in step 1 is 10 wt% to 40 wt% of the unsaturated olefin monomer, and the alkane blowing agent is selected from alkanes having 4 to 8 carbon atoms and a boiling point higher than 20 ℃.
4. The method for preparing polymethacrylimide thermal expansion microspheres as claimed in claim 1, wherein the cross-linking agent used in step 1 is one or more of ethylene glycol dimethacrylate, trimethylolpropane triacrylate, 1, 6-hexanediol dimethacrylate, 1, 4-butanediol vinyl diether, and the amount of the cross-linking agent is 0.01 wt% to 1 wt% of the amount of the unsaturated olefin monomer; the oil-soluble initiator used in the step 1 is one or more of azobisisobutyronitrile, azobisisoheptonitrile, benzoyl peroxide and lauroyl peroxide.
5. The method for preparing polymethacrylimide heat expandable microspheres as claimed in claim 1, wherein the inorganic salt used in step 2 is sodium chloride; the inorganic dispersant used in the step 2 is one or more of nano silicon dioxide, nano titanium dioxide, halloysite and lithium magnesium silicate; the emulsifier used in the step 2 is one or more of polyvinylpyrrolidone, polyvinyl alcohol and sodium dodecyl sulfate.
6. The method for preparing polymethacrylimide thermal expansion microspheres as claimed in claim 1, wherein the suspension polymerization temperature in step 3 is 60-70 ℃.
7. The method for preparing polymethacrylimide thermal expansion microspheres as claimed in claim 1, wherein acrylonitrile in the unsaturated olefin monomers used in step 1 accounts for 65 wt% -80 wt%; the unsaturated olefin monomer used in the step 1 contains 15-25 wt% of methacrylic acid.
8. The method for preparing polymethacrylimide heat expandable microspheres as claimed in claim 3, wherein the alkane blowing agent is selected from one of isopentane, n-pentane, isohexane, n-hexane, and isoheptane.
9. The method for preparing polymethacrylimide thermal expansion microspheres as claimed in claim 4, wherein the amount of the cross-linking agent is 0.1 wt% to 0.5 wt% of the amount of the unsaturated olefin monomers.
10. The polymethacrylimide thermally expandable microspheres prepared by the method for preparing polymethacrylimide thermally expandable microspheres according to any one of claims 1 to 9, wherein the microsphere shell contains a polymethacrylimide structure, the shell takes MAA/AN copolymer as a main body, and the core is a foaming agent.
Technical Field
The invention relates to the field of high polymer foaming materials, in particular to polymethacrylimide thermal expansion microspheres and a preparation method thereof.
Background
Thermally expandable microspheres are polymeric particles having a core-shell structure, the shell of which is typically composed of a thermoplastic polymer and the interior of which is typically encapsulated with a low boiling alkane. After heating, the polymer shell is softened, the vapor pressure generated by the foaming agent in the polymer shell enables the microspheres to expand, and the diameter of the expanded microspheres can be increased by 3-5 times. After cooling, the microspheres may remain in their expanded state. Due to its unique properties, thermally expandable microspheres have been widely used in various fields such as printing inks, ceramics, composite materials, and the like.
The Polymethacrylimide (PMI) foam is a thermosetting hard foam material, and the molecular structure of the Polymethacrylimide (PMI) foam has a unique six-membered imide ring structure, so that the Polymethacrylimide (PMI) foam has excellent mechanical property and thermal deformation temperature (180-220 ℃).
The expanded microsphere with excellent heat resistance has higher initial foaming temperature (T)start) Generally, at 150-180 ℃, the patent CN 201910023650.0 adds the high-temperature resistant thermal expansion microspheres into crystalline polymers such as polyvinyl chloride and the like to prepare the automobile bottom coating with low density and excellent corrosion resistance.
Disclosure of Invention
The invention aims to solve the defects in the prior art and provide a thermal expansion microsphere which does not contain methacrylonitrile, adopts acrylonitrile and methacrylic acid as main monomers to prepare a polymethacrylimide shell structure and has higher foaming capacity.
The technical scheme of the invention is as follows: a preparation method of polymethacrylimide thermal expansion microspheres mainly comprises the following steps:
1) uniformly mixing an unsaturated olefin monomer, a cross-linking agent, an alkane foaming agent and an oil-soluble initiator, and magnetically stirring for 5-10 min to obtain an oil phase;
2) homogenizing and emulsifying inorganic dispersant, emulsifier, inorganic salt, aqueous phase polymerization inhibitor and deionized water at 10000rpm for 3min to obtain aqueous phase;
3) slowly dripping the oil phase obtained in the step (1) into the water phase obtained in the step (2), and fully and uniformly mixing by mechanically stirring for 15-35 min to obtain an oil-in-water emulsion;
4) and (3) injecting the emulsion obtained in the step (3) into a high-pressure reaction kettle, heating to 55-80 ℃ under the nitrogen atmosphere, polymerizing at 0.4-0.6 MPa for 18-25 h, washing the obtained product with deionized water, filtering, and drying to obtain the thermal expansion microspheres.
In the
Preferably, the unsaturated olefin monomer used in
Preferably, the unsaturated olefin monomer used in
The acrylic ester includes at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and glycidyl methacrylate.
The dosage of the alkane foaming agent used in the
Preferably, the alkane blowing agent is selected from one of isopentane, n-pentane, isohexane, n-hexane, and isoheptane.
The cross-linking agent used in the
Preferably, the amount of the crosslinking agent is 0.1 to 0.5 wt% based on the amount of the unsaturated olefin monomer.
The oil-soluble initiator used in the
The inorganic salt used in the
The inorganic dispersant used in the
The emulsifier used in the
In the
A polymethacrylimide thermal expansion microsphere is provided, wherein the microsphere shell contains a polymethacrylimide structure, MAA/AN copolymer is taken as a main body of the shell, a core is taken as a foaming agent, and the microsphere shell has excellent heat resistance.
The invention has the beneficial effects that:
1. according to the preparation method, a Pickering emulsion suspension polymerization method is adopted, acrylonitrile, methacrylic acid and acrylamide compounds are used as monomers, acrylate compounds are used as modified monomers to prepare the polymethacrylimide thermal expansion microsphere, the thermal expansion microsphere prepared by the method is good in foaming performance and not easy to agglomerate, adjacent acrylonitrile and methacrylic acid chain links form a six-membered imide ring structure in the expansion process of the microsphere, and the six-membered imide ring structure has a high temperature resistance characteristic;
2. the preparation method disclosed by the invention is simple, mild in reaction condition and easy to control;
3. the method completely replaces methacrylonitrile with cheap acrylonitrile monomer, has higher economic value and is easy to industrialize.
Drawings
FIG. 1 is a scanning electron microscope image of the thermally expandable microspheres prepared in example 1;
FIG. 2 is a graph of static thermomechanical analysis of thermally expanded microspheres prepared in example 1;
FIG. 3 is an infrared spectrum of the thermally-expansible microballs prepared in example 1;
FIG. 4 is a graph showing TG and DTG profiles of the thermally-expansible microballs prepared in example 1;
FIG. 5 is a table showing the data statistics of the thermal mechanical analysis test of the thermally expandable microspheres prepared in examples 1 to 4.
Detailed Description
The following examples further illustrate the present invention but are not to be construed as limiting the invention. Modifications and substitutions to methods, procedures, or conditions of the invention may be made without departing from the spirit of the invention.