PMMA-based cast polymers having improved mechanical properties

Abstract

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.

Claims

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, 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 5% to 40% by weight of acrylic acid, methacrylic acid, and/or itaconic acid, less than 4% by weight of styrene, α-methylstyrene, and/or chlorostyrene, 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.

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-poly erizah e l lowing agent, 0% to 5% by weight of the chain-transfer agent, 1% to 8% 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 α-methacylic acid, and/or the itaconic acid, less than 2% by weight of the styrene, the α-methylstyrene, and/or the chlorostyrene, 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 monomer mixture contains essentially no styrene, α-methylstyrene and/or chlorostyrene.

4. The composition according to claim 1, wherein 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.

5. The composition according to claim 1, wherein the hydrophilic inorganic compound has an average diameter dso of between 5 and 1000 nm, determined according to ASTM 690-1992.

6. The composition according to claim 1, wherein the monomer mixture contains at least 0.01% by weight of the further MMA-copolymeriable monomer, and wherein the further MMA-copolymerizable monomer is a crosslinker.

7. 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.

8. The composition according to claim 1, wherein the urea derivative is at least partly copolymerizable with MMA urea derivatives.

9. The composition according to claim 1, wherein the monomer mixture contains between 5% and 10% by weight of tert-butyl methacrylate, isopropyl methacrylate, tert-buty1 acrylate, and/or isopropyl acrylate.

10. A PMMA-based cast polymer, obtainable by polymerization of the composition according to claim 1.

11. 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.

12. A PMMA-based foam, obtainable by foaming the PMMA-based cast polymer according to claim 10.

13. The PMMA-based foam according to claim 12, wherein the PMMA-based foam has a density of between 30 kg/m.sup.3 and 350 kg/m.sup.3. determined according to DIN EN ISO 1183.

14. 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.

15. The process according to claim 14. wherein polymerizing and foaming are carried out at least partly simultaneously.

16. The composition according to claim 6, wherein the further MMA-copolymerizable monomer is ethylene glycol dimethacrylate, triallyl cyanurate, isocyanurate, allyl methacrylate, or a mixture thereof.

17. The composition according to claim 8, wherein the urea derivative is at least partly copolymerizable with N-(2-metbacryloyloxyethypethyleneurea.

18. A PMMA-based foam, obtainable by foaming the composition according to claim 1, which is at least partly polymerized.

Description

EXAMPLES

[0068] The PMMA polymers were produced in the casting process. To this end, glass chambers consisting of 2 glass plates (400×300 mm) held apart and sealed by a sealing tape (13 mm thickness) were filled with the monomer solution.

[0069] To produce the monomer solution, the ingredients were added together according to the formulations recited below (Tables 1-4) and stirred until all constituents were dissolved.

[0070] The thus produced and filled glass chambers were stored in a water bath at 40° C. for the polymerization. After about 27 h the glass chambers were end-polymerized at 115° C. The glass plates and the sealing rope were then removed. A hard and translucent polymer was obtained in all cases.

[0071] AEROSIL® OX50 (manufacturer: Evonik Resource Efficiency GmbH) was used as a hydrophilic inorganic compound.

[0072] Tensile tests for determining the elastic modulus of the polymers were performed using a Zwick/Roell Z030 instrument. Measurements were carried out at standard conditions of 23° C. and 50% humidity. The samples were stored for at least 16 hours at identical conditions (23° C-50% humidity) prior to measurement. The results are shown in Table 5.

TABLE-US-00001 TABLE 1 Example 1 Example 1 wt % Methyl methacrylate 69.45 Methacrylic acid 20.00 Butyl acrylate 1.00 Urea 5.00 Silica (AEROSIL ® OX50) 4.00 2,2′-Azobis(2,4-dimethylvaleronitrile) 0.05 2-Ethylhexyl thioglycolate 0.50

TABLE-US-00002 TABLE 2 Comparative Example 1 Comparative Example 1 wt % Methyl methacrylate 63.45 Methacrylic acid 20.00 Butyl acrylate 1.00 Styrene 6.00 Urea 5.00 Silica (AEROSIL ® OX50) 4.00 2,2′-Azobis(2,4-dimethylvaleronitrile) 0.05 2-Ethylhexyl thioglycolate 0.50

TABLE-US-00003 TABLE 3 Comparative Example 2 Comparative Example 2 wt % Methyl methacrylate 74.45 Methacrylic acid 20.00 Butyl acrylate 1.00 Silica (AEROSIL ® OX50) 4.00 2,2′-Azobis(2,4-dimethylvaleronitrile) 0.05 2-Ethylhexyl thioglycolate 0.50

TABLE-US-00004 TABLE 4 Comparative Example 3 Comparative Example 3 wt % Methyl methacrylate 74.45 Methacrylic acid 20.00 Butyl acrylate 1.00 Urea 4.00 2,2′-Azobis(2,4-dimethylvaleronitrile) 0.05 2-Ethylhexyl thioglycolate 0.50

TABLE-US-00005 TABLE 5 Elastic moduli Elastic modulus Elastic modulus comparison (MPa) Example 1 (with urea and SiO.sub.2) 4900 Comparative example 1 (with urea, SiO.sub.2 and styrene) 4400 Comparative example 2 (no urea, with SiO.sub.2) 3600 Comparative example 3 (with urea, no SiO.sub.2) 4500

[0073] Table 5 shows the results of the measurement of the elastic moduli of the polymers prepared in Example 1 and comparative examples 1-3. The polymer prepared without the use of urea as a blowing agent and silica as a filler (comparative example 2), shows the lowest elastic modulus. The use of both urea and silica, but no styrene (example 1) shows the best results. The use of urea, silica and styrene leads to inferior results (comparative example 1) than in example 1, as well as the use of urea without silica (comparative example 3).