Thermally expandable microspheres prepared from bio-based monomers
The present disclosure provides thermally expandable microspheres at least partially prepared from bio-based monomers and a process of their manufacture. The microspheres include a thermoplastic polymer shell encapsulating a blowing agent. The thermoplastic polymer shell includes a copolymer of an itaconate dialkylester and at least one aliphatic or aromatic mono-ethylenically unsaturated comonomer. The itaconate dialkylester has the formula (1): where each of R 1 and R 2 , separately from one another, is an alkyl group having 1-4 carbon atoms, and the copolymer includes 0-50 wt. % of vinyl aromatic comonomers, based on the total weight of the comonomers. The present disclosure further provides expanded microspheres usable in a variety of applications.
1. Thermally expandable microspheres comprising a thermoplastic polymer shell encapsulating a blowing agent, wherein the thermoplastic polymer shell comprises a copolymer of an itaconate dialkylester and at least one aliphatic or aromatic mono-ethylenically unsaturated comonomer, wherein the itaconate dialkylester is according to formula (1):
wherein each of R 1 and R 2 , separately from one another, is an alkyl group having from 1 to 4 carbon atoms, and
wherein the copolymer includes from 0 to 50 wt. % of vinyl aromatic comonomers, based on the total weight of the comonomers.
2. The microspheres according to claim 1 , wherein the itaconate dialkylester is selected from dimethyl itaconate (DMI), diethyl itaconate (DEI), di(n-propyl) itaconate, diisopropyl itaconate, and dibutyl itaconate (DBI).
3. The microspheres according to claim 1 , wherein the copolymer includes less than 50 wt. % of the itaconate dialkylester monomer, based on the total weight of the comonomers.
4. The microspheres according to claim 1 , wherein the copolymer includes less than 10 wt. % of the vinyl aromatic comonomers.
5. The microspheres according to claim 1 , wherein the at least one aliphatic or aromatic mono-ethylenically unsaturated comonomer is selected from unsaturated lactones, acrylonitrile, methacrylonitrile, methyl methacrylate, vinylidene chloride, methyl acrylate, (meth)acrylic acid and (meth)acrylamide.
6. The microspheres according to claim 5 , wherein the unsaturated lactone is selected from α-methylene-γ-valerolactone (MVL), β-methyl-α-methylene-γ-butyrolactone (MMBL), and α-methylene-γ-butyrolactone (MBL).
7. The microspheres according to claim 1 , wherein the blowing agent is a hydrocarbon.
8. A process for the manufacture of the thermally expandable microspheres of claim 1 , comprising the step of polymerizing ethylenically unsaturated monomer(s) by aqueous suspension polymerization using a free-radical initiator in the presence of a blowing agent, wherein at least one ethylenically unsaturated monomer is the itaconate dialkylester according to the formula (1).
9. The process according to claim 8 , further comprising the step of stabilizing the suspension with SiO 2 , optionally modified with one or more organosilane groups, or Mg(OH) 2.
10. Expanded microspheres obtained by thermal expansion of the microspheres according to claim 1 .
11. A process for the manufacture of expanded microspheres, comprising heating the thermally expandable microspheres according to claim 1 such that the thermally expandable microspheres expand.
12. The microspheres according to claim 1 , wherein the copolymer is free of the vinyl aromatic comonomers.
13. The microspheres according to claim 7 , wherein the hydrocarbon is selected from n-butane, isobutane n-pentane, isopentane, cyclopentane, neopentane, hexane, isohexane, neo-hexane, cyclohexane, heptane, isoheptane, octane, isooctane, decane, dodecane, isododecane, and any combination thereof.