Dimensionally stable acrylic alloy for 3-D printing
The invention relates to an acrylic alloy composition that can be 3-D printed by a material extrusion additive manufacturing process, to an acrylic filament that has a very uniform diameter useful in the extrusion additive manufacturing process, to acrylic articles made from the acrylic alloy composition by a material extrusion additive process, and to a material extrusion additive manufacturing process for producing the acrylic articles. The acrylic alloy composition is an alloy of an acrylic polymer, and a low melt viscosity polymer, such as polylactic acid. The alloy may optionally be impact modified, preferably with hard core core-shell impact modifiers.
1. An acrylic article made by a material extrusion additive manufacturing process, using an acrylic alloy composition, said acrylic composition comprising:
a polymer matrix blend comprising:
1) one or more acrylic polymers having a weight average molecular weight of from 50,000 to 300,000 g/mol,
2) 5 to 60 weight percent of one or more low viscosity polymers that are compatible, semi-miscible, or miscible with the acrylic polymer, said low viscosity polymers having a melt flow rate of greater than 10 g/10 minutes, as measured by ASTM D1238 at 230° C./10.4 kg of force,
3) optionally 0 to 60 weight percent of impact modifiers,
wherein said acrylic composition has a viscosity at a shear of 1 sec −1 of less than 100,000 Pa-sec at a temperature of 230° C., and a viscosity of 20 to 2,000 Pa-s at a shear rate of 100 sec −1 at a temperature of 230° C., as measured by a rotational viscometer according to ASTM C965.
2. The article of claim 1 , wherein said article has one or more of the following properties:
a) a tensile elongation as measured by ASTM D638 of greater than 10 percent,
b) a fill density of greater than 85 percent,
c) a stress at yield of greater than 35 MPa when measured by ASTM D638,
d) a transmittance of greater than 50% when measured on a 2.1 mm thick sample using ASTM D1003.
3. A filament for 3-D printing comprising an acrylic alloy composition, wherein the filament varies by less than +/−5% in diameter over ten feet of length, said acrylic composition comprising:
a polymer matrix blend comprising:
1) one or more acrylic polymers having a weight average molecular weight of from 50,000 to 300,000 g/mol,
2) 5 to 60 weight percent of one or more low viscosity polymers that are compatible, semi-miscible, or miscible with the acrylic polymer, said low viscosity polymers having a melt flow rate of greater than 10 g/10 minutes, as measured by ASTM D1238 at 230° C./10.4 kg of force,
3) optionally 0 to 60 weight percent of impact modifiers,
wherein said acrylic composition has a viscosity at a shear of 1 sec −1 of less than 100,000 Pa-sec at a temperature of 230° C., and a viscosity of 20 to 2,000 Pa-s at a shear rate of 100 sec −1 at a temperature of 230° C., as measured by a rotational viscometer according to ASTM C965.
4. The filament of claim 3 wherein said filament is a coextruded, multiphase filament.
5. The filament of claim 3 , wherein said multiphase filament comprises a special effect composition that provides visual effects as one of the phases.
6. A process for forming an extrusion additive (3D) acrylic article, comprising the steps of:
presetting the software of a 3D printer to a set volume flow and line spacing for the printing of said article;
feeding an acrylic alloy composition in the form of filament, pellets or powder into the 3D printer;
feeding by the printer of the acrylic composition melt to a heated nozzle;
depositing the acrylic composition melt at the set location, line spacing and flow rate set by the software, to form an article,
said acrylic composition comprising:
a polymer matrix blend comprising:
1) one or more acrylic polymers having a weight average molecular weight of from 50,000 to 300,000 g/mol,
2) 5 to 60 weight percent of one or more low viscosity polymers that are compatible, semi-miscible, or miscible with the acrylic polymer, said low viscosity polymers having a melt flow rate of greater than 10 g/10 minutes, as measured by ASTM D1238 at 230° C./10.4 kg of force,
3) optionally 0 to 60 weight percent of impact modifiers,
wherein said acrylic composition has a viscosity at a shear of 1 sec −1 of less than 100,000 Pa-sec at a temperature of 230° C., and a viscosity of 20 to 2,000 Pa-s at a shear rate of 100 sec −1 at a temperature of 230° C., as measured by a rotational viscometer according to ASTM C965.
7. The process of claim 6 , wherein the flow rate and/or line spacing represents an overflow of from 1-10 percent.
8. The process of claim 6 , wherein said nozzle is heated to between 190° C. and 250° C.