Moulding compositions based on vinylaromatic copolymers for 3D printing
Thermoplastic moulding composition for 3D printing containing a polymer mixture A made of components a and b: a being from 30 to 95% by weight of at least one vinylaromatic copolymer a with average molar mass Mw from 150 000 to 360 000 g/mol, b being from 5 to 70% by weight of at least one impact modifier b, where the viscosity of the moulding composition (measured in accordance with ISO 11443) at shear rates of from 1 to 10 l/sec and at a temperature of 250° C. is not higher than 1×10 5 Pa*s and the Melt Volume Rate (MVR, measured in accordance with ISO 1133 for 220° C. and 10 kg load) is more than 6 ml/10 min.
1. A thermoplastic molding composition for 3D printing, comprising a polymer mixture A composed of components a and b:
a: 30 to 95 wt % of at least one polymer a having an average molar mass Mw of 150 000 to 360 000 g/mol, selected from:
vinylaromatic copolymers selected from the group consisting of: styrene-acrylonitrile copolymers, α-methylstyrene-acrylonitrile copolymers, styrene-maleic anhydride copolymers, styrene-phenylmaleimide copolymers, styrene-methyl methacrylate copolymers, styrene-acrylonitrile-maleic anhydride copolymers, styrene-acrylonitrile-phenylmaleimide copolymers, α-methylstyrene-acrylonitrile-methyl methacrylate copolymers, α-methylstyrene-acrylonitrile-tert-butyl methacrylate copolymers, and styrene-acrylonitrile-tert-butyl methacrylate copolymers, and
b: 5 to 70 wt % of at least one impact modifier b, built up from components b1 and b2:
b1: 20-90 wt % of a graft base made from one or more monomers, consisting of:
b11: 70 to 100 wt % of at least one conjugated diene, and
b12: 0 to 30 wt % of styrene, and,
b2: 10 to 80 wt % of a graft made from one or more monomers, consisting of:
b21: 65 to 95 wt % of at least one vinylaromatic monomer,
b22: 5 to 35 wt % of acrylonitrile and/or methacrylonitrile, and
b23: 0 to 30 wt % of at least one further monoethylenically unsaturated monomer selected from: MMA, MAN, and N-PMI;
where the sum of components a and b totals 100 wt %,
characterized in that the viscosity (measured to ISO 11443) of the molding composition at shear rates of 1 to 10 1/s and at temperatures of 250° C. is not higher than 1×10 5 Pa*s and the melt volume rate (MVR, measured to ISO 1133 at 220° C. and 10 kg load) is more than 6 ml/10 min;
wherein the residual monomer content is not more than 2000 ppm and the solvent content is not more than 1000 ppm; and
the impact modifier b has a trimodal particle size distribution and is a mixture of ABS graft copolymers b′, b″, and b′″ where the graft base b1′ of the ABS graft polymer b′ has an average particle diameter d 50 of 25 to 200 nm, the graft base b1″ of the ABS graft copolymer b″ has an average particle diameter d 50 of 230 to 330 nm, and the graft base b1′″ of the ABS graft copolymer b′″ has an average particle diameter d 50 of 340 to 480 nm.
2. The molding composition as claimed in claim 1 , characterized in that additionally there is
at least one further polymer b, selected from polycarbonates, polyamides, poly(meth)acrylates, polyesters, and styrene-butadiene block copolymers; and/or
customary additives; and/or
auxiliaries c.
3. The molding composition as claimed in claim 1 , characterized in that at least half of the polymers present in the molding composition are amorphous polymers.
4. The molding composition as claimed in claim 1 , comprising:
40 to 100 wt % of polymer mixture a,
0 to 60 wt % of polymer b, and
0 to 40 wt % of minerals as auxiliaries c,
based in each case on the overall molding composition, and where the sum of a, b and c is 100 wt %.
5. The molding composition as claimed in claim 1 , characterized in that the particle size of the impact modifier b is at least 50 nm and at most 10 μm.
6. The molding composition as claimed in claim 1 , characterized in that polymer a is a styrene-acrylonitrile copolymer (SAN) comprising 18 to 35 wt % acrylonitrile and 82 to 65 wt % styrene.
7. The molding composition as claimed in claim 1 , characterized in that the impact modifier b has bimodal, trimodal or multimodal particle size distributions.
8. The molding composition as claimed in claim 1 , characterized in that the impact modifier b is an ABS impact modifier b built up from:
b1: 40 to 90 wt % of a graft base consisting of:
b11: 70 to 100 wt % of butadiene, and
b12: 0 to 30 wt % of styrene, and
b2: 10 to 60 wt % of a graft consisting of:
b21: 65 to 95 wt % of styrene,
b22: 5 to 35 wt % of acrylonitrile, and
b23: 0 to 30 wt % of MMA.
9. The molding composition as claimed in claim 1 , characterized in that in the polymer mixture A, the fraction of the polymer a is 75 to 95 wt % and the fraction of the impact modifier b is 5 to 25 wt %.
10. The molding composition as claimed in claim 1 , characterized in that in the polymer mixture A, the fraction of the polymer a is 65 to 95 wt % and the fraction of the impact modifier b is 5 to 35 wt %.
11. The molding composition as claimed in claim 1 , characterized in that in the polymer mixture A, the fraction of the polymer a is 30 to 60 wt % and the fraction of the impact modifier b is 40 to 70 wt %.
12. The molding composition as claimed in claim 1 , characterized in that the coefficient of linear thermal expansion is less than 100×10 −6 1/K.
13. The molding composition as claimed in claim 1 , characterized in that the transition metal content is not more than 500 ppm.
14. A method of 3D printing comprising the step of extruding the molding composition as claimed in claim 1 to produce an object.
15. A method of 3D printing comprising the step of extruding the molding composition as claimed in claim 11 to produce a filament.
16. A method of 3D printing comprising the step of extruding the molding composition as claimed in claim 1 to produce an object for home application.
17. A method for producing 3-dimensional moldings from the molding composition as claimed in claim 1 by fused deposition modeling, where, in a 3D printer with a heating nozzle freely movable in the fabrication plane, a supplied filament of the molding composition is fluidized, and the fluidized molding composition is extruded, applied layer by layer, and consolidated.
18. The method as claimed in claim 17 , characterized in that filaments of the molding composition melted in a 3D printer having a heating nozzle diameter of 0.3 to 0.8 mm at a nozzle temperature of 200 to 270° C., and the melted molding composition is extruded at an extrusion rate of 60 to 180 mm/s.
19. A method for determining the print quality of a 3-dimensional molding produced as claimed in claim 17 , characterized in that the ratio of the width of the extruded strand to minimum edge length or of the width of the extruded strand to minimum diameter of the 3-dimensional molding is at least 1:20.