PMMA-based cast polymers having improved mechanical properties
A composition can be used for producing a PMMA-based cast polymer with a low styrene content using urea (derivatives) as a formulation constituent, and a hydrophilic inorganic compound as a filler. It is possible to produce PMMA-based cast polymers and mouldings having surprisingly high mechanical stability from the composition.
1. A composition for producing a poly(methyl methacrylate)-based (PMMA-based) cast polymer, wherein the composition contains:
1% to 10% by weight of urea and/or a urea derivative,
0.001% to 2.0% by weight of an initiator,
0% to 20% by weight of a further non-polymerizable blowing agent,
0% to 5% by weight of a chain-transfer agent,
0.5% to 10% by weight of a hydrophilic inorganic compound essentially not soluble in the composition, and
53% to 98.498% by weight of a monomer mixture consisting of
60% to 95% by weight of methyl methacrylate (MMA),
5% to 40% by weight of acrylic acid, methacrylic acid, and/or itaconic acid,
and 0% to 35% by weight of a further MMA-copolymerizable monomer other than urea derivatives,
wherein the hydrophilic inorganic compound has a methanol wettability of less than 30% by volume of methanol in a methanol/water mixture,
the monomer mixture contains essentially no styrene, α-methylstyrene, and/or chlorostyrene and excludes methacrylamide, N-alkyl(meth)acrylamides and N,N-dialkylmethacrylamides, and
the hydrophilic inorganic compound is selected from the group consisting of silica, a metal oxide, a metal hydroxide, a metal silicate, talcum, and a mixture thereof,
wherein a PMMA-based cast polymer produced from the composition has an elastic modulus of at least 4,500 MPa, measured at room temperature.
2. The composition according to claim 1 , wherein the composition contains:
2% to 8% by weight of the urea and/or the urea derivative,
0.002% to 1.0% by weight of the initiator,
0% to 20% by weight of the further non-polymerizable blowing agent,
0% to 5% by weight of the chain-transfer agent,
1% to 8% by weight of the hydrophilic inorganic compound, and
57% to 96.999% by weight of the monomer mixture consisting of
70% to 90% by weight of the MMA,
10% to 30% by weight of the acrylic acid, the methacrylic acid, and/or the itaconic acid,
and
0% to 35% by weight of the further MMA copolymerizable monomer other than urea derivatives.
3. The composition according to claim 1 , wherein the hydrophilic inorganic compound has an average diameter d50 of between 5 and 1000 nm, determined according to ASTM 690-1992.
4. The composition according to claim 1 , wherein the monomer mixture contains at least 0.01% by weight of the further MMA-copolymerizable monomer, and wherein the further MMA-copolymerizable monomer is a crosslinker.
5. The composition according to claim 1 , wherein the urea derivative is selected from the group consisting of an N-alkylurea, an N,N′-dialkylurea, a 2-imidazolidone, a 1-methyl-2-imidazolidinone, and a mixture thereof.
6. The composition according to claim 1 , wherein the urea derivative is at least partly copolymerizable with MMA urea derivatives.
7. The composition according to claim 1 , wherein the monomer mixture contains between 5% and 10% by weight of tert-butyl methacrylate, isopropyl methacrylate, tert-butyl acrylate, and/or isopropyl acrylate.
8. A PMMA-based cast polymer, obtainable by polymerization of the composition according to claim 1 .
9. A process for producing a PMMA-based cast polymer, the process comprising:
polymerizing the composition according to claim 1 at a temperature between 20° C. and 100° C.
10. A PMMA-based foam, obtainable by foaming the PMMA-based cast polymer according to claim 8 .
11. The PMMA-based foam according to claim 10 , wherein the PMMA-based foam has a density of between 30 kg/m 3 and 350 kg/m 3 , determined according to DIN EN ISO 1183.
12. A process for producing a PMMA-based foam, the process comprising:
polymerizing the composition according to claim 1 at a temperature between 20° C. and 100° C., and subsequently foaming at a temperature between 130° C. and 250° C.
13. The process according to claim 12 , wherein the polymerizing and foaming are carried out at least partly simultaneously.
14. The composition according to claim 4 , wherein the further MMA-copolymerizable monomer is ethylene glycol dimethacrylate, triallyl cyanurate, triallyl isocyanurate, allyl methacrylate, or a mixture thereof.
15. The composition according to claim 6 , wherein the urea derivative is at least partly copolymerizable with N-(2-methacryloyloxyethyl)ethyleneurea.
16. A PMMA-based foam, obtainable by foaming the composition according to claim 1 , which is at least partly polymerized.