Use of polyalkyl(meth)acrylate bead polymers and moulding material for producing extruded moulded parts with a matt surface
View Patent ↗The invention relates to the use of polyalkyl(meth)acrylate bead polymers with an average particle size V 50 that ranges between 30 and 70 μm for improving the stress cracking resistance of moulding materials containing polyalkyl(meth)acrylate. The invention also relates to moulding materials comprising: a) at least 50 wt. % of an impact resistance modifying agent, which contains at least one polyalkyl(meth)acrylate phase; b) at least 8 wt. % of a polyalkyl(meth)acrylate bead polymer with an average particle size V 50 that ranges between 30 and 70 μm; and c) between 0 and 42 wt. % of a polyalkyl(meth)acrylate with a molecular weight ranging between 20,000 and 350,000 g/mol, whereby the wt. % of the components a) to c) amounts to 100 wt. %, and to moulded bodies that can be obtained from said materials.
1. A molding composition, comprising:
a) at least 70% by weight of an impact modifier which comprises at least one polyalkyl(meth)acrylate phase capable of thermoplastic processing,
b) at least 8% by weight of a polyalkyl(meth)acrylate bead polymer whose median particle size V 50 is in the range from 30 to 70 μm, and
c) from 0 to 42% by weight of a polyalkyl(meth)acrylate whose weight average molar mass is in the range from 20,000 to 350,000 g/mol, wherein a sum of the % by weight of components a) to c) is 100% by weight;
wherein the impact modifier comprises a hard phase A) whose glass transition temperature Tg is >25° C. comprising at least 70% by weight of methyl methacrylate, and a tough phase B) obtained from monomers the polymers of which have a glass transition temperature Tg of <25° C.,
wherein the impact modifier is prepared by an at least two-stage polymerization process,
wherein, in a first stage, said hard phase A) whose glass transition temperature Tg is >25° C. comprising at least 70% by weight of methyl methacrylate is polymerized to yield a hard phase A), and
then, in a second stage, said monomers of the tough phase B), polymers of which have said glass transition temperature Tg of <25° C., are added to the polymerized hard phase A) and polymerized with the polymerized hard phase A).
2. The molding composition as claimed in claim 1 , wherein the impact modifier comprises a polyalkyl(meth)acrylate phase whose glass transition temperature Tg is greater than 25° C.
3. The molding composition as claimed in claim 1 , wherein the polymerization of the hard phase A) in the first stage takes place in the presence a) of an oil-soluble free-radical initiator, and b) of an organic sulfur compound having at least two thiol groups in the molecule.
4. The molding composition as claimed in claim 1 , wherein the polymerization of the monomers of the tough phase B) in the second stage takes place with use of a graft-linking agent in the presence of the hard phase first formed.
5. A molding, comprising:
a molding composition comprising
a) at least 70% by weight of an impact modifier which comprises at least one polyalkyl(meth)acrylate phase capable of thermoplastic processing,
b) at least 8% by weight of a polyalkyl(meth)acrylate bead polymer whose median particle size V 50 is in the range from 30 to 70 μm, and
c) from 0 to 42% by weight of a polyalkyl(meth)acrylate whose weight average molar mass is in the range from 20,000 to 350,000 g/mol, wherein a sum of the % by weight of components a) to c) is 100% by weight;
wherein the impact modifier comprises a hard phase A) whose glass transition temperature Tg is >25° C. comprising at least 70% by weight of methyl methacrylate, and a tough phase B) obtained from monomers the polymers of which have a glass transition temperature Tg of <25° C.,
wherein the impact modifier is prepared by an at least two-stage polymerization process,
wherein, in a first stage, said hard phase A) whose glass transition temperature Tg is >25° C. comprising at least 70% by weight of methyl methacrylate is polymerized to yield a hard phase A), and
then, in a second stage, said monomers of the tough phase B), polymers of which have said glass transition temperature Tg of <25° C., are added to the polymerized hard phase A) and polymerized with the polymerized hard phase A).
6. The molding as claimed in claim 5 , wherein the molding comprises at least 80% by weight of said molding composition.
7. The molding as claimed in 5 , which is produced via extrusion,
said molding having a thickness of 3 mm, a width of 3.5 cm and a length of 55 cm,
said molding having at most 4 fractures, after 5 minutes in a flexed condition at 23° C. in an ethanol/water mixture (ratio by volume: 90/10).
8. The molding as claimed in claim 5 , wherein the molding has a modulus of elasticity greater than or equal to 1000 MPa according to ISO 527-2.
9. The molding as claimed in claim 5 , wherein the molding has a Vicat softening point greater than or equal to 75° C.
10. The molding as claimed in claim 5 , wherein the molding has an average surface roughness R Z of the sheet in the range from 4 to 70 μm.
11. The molding composition as claimed in claim 1 , wherein component c) is present.
12. The molding as claimed in claim 5 , wherein component c) is present.