Laser sintering powder, laser sintering article, and a method of making a laser sintering article
The present invention comprises a laser sintering powder composition comprising: greater than 30 to 90 wt. % of a hydrogenated styrene-butadiene/styrene-styrene (S(EB/S)S) block copolymer or a hydrogenated styrene-butadiene-styrene (SEBS) block copolymer, or a mixture thereof; 10 to less than 70 wt. % of a C 3 to C 8 polyolefin, or a mixture of two or more polyolefins, 0 to 20 wt. % mineral oil, 0.2 to 1 wt. % of one or more antioxidants, 0 to 5 wt. % colorant, 0 to 20 wt. % surface modifying agent, wherein the total of the above ingredients is 100 wt. %, and optionally 0 to 5 parts by weight of a powder flow agent, based on 100 weight parts of the laser sintering powder composition. The composition has a melt flow rate of at least 20 grams/10 min. at 190° C./2.16 kg mass. The invention also comprises laser sintered articles and methods for making the same.
1. A laser sintering powder composition comprising:
a) greater than 35 to 80 wt. % of SEBS or S(EB/S)S or a mixture thereof,
b) 20 to less than 65 wt. % of C3-C8 polyolefin, or a mixture of two or more polyolefins,
c) 1 to 15 wt. % mineral oil,
d) 0.2 to 1 wt. % antioxidant(s),
e) 0 to 5 wt. % colorant, and
f) 0.5 to 15 wt. % of surface modifying agent,
wherein the total of all components (a to f) is 100 wt. % of said composition, and 0.1 to 5 wt. % powder flow agent wherein said powder flow agent is hydrophobic fumed silica or a metal oxide, based on 100 weight parts of said laser sintering powder composition, wherein the particle size of said composition is less than about 150 μm, and wherein the laser sintering powder composition has a melt flow rate of at least 20 grams/10 min. at 190° C/2.16 kg mass according to ASTM D1238;
wherein the polystyrene content of the SEBS ranges from 10 to 30 wt. % based on the total weight of the block copolymer; and
wherein the laser sintering powder composition has a Shore A hardness ranging from 70 to 95 measured on injection molded plates.
2. The laser sintering powder composition of claim 1 wherein said SEBS or S(EB/S)SS-EB/S-S is radially coupled and takes the form (S-EB)nX or (S-EB/S)nX, wherein S is styrene, EB is ethylene butadiene (hydrogenated butadiene), n is between 1.5 and 6.0, and X is the residue of a coupling agent.
3. The laser sintering powder composition of claim 1 wherein said polyolefin or mixture of two or more polyolefins is polypropylene homopolymer or copolymer, respectively.
4. The laser sintering powder composition of claim 1 wherein said polyolefin or said mixture of two or more polyolefins has a melt point less than about 170° C.
5. The laser sintering powder composition of claim 1 wherein said powder flow agent is applied to said laser sintering powder composition in an amount of 0.1 to 3 parts by weight based on 100 weight parts of said laser sintering powder composition.
6. The laser sintering powder composition of claim 1 wherein said antioxidants include primary and secondary antioxidants.
7. The laser sintering powder composition of claim 6 , further comprising a colorant.
8. The laser sintering powder composition of claim 1 comprising a mixture of SEBS and S(EB/S)S in a weight ratio ranging from 1/3 to 3/1.
9. A laser sintered article comprising the laser sintering powder composition of claim 1 .
10. The laser sintered article of claim 9 wherein said polyolefin before sintering is polypropylene homopolymer or copolymer.
11. The laser sintered article of claim 9 further including a surface modifying agent present in an amount of 0.5 to 10 wt. %, based on weight of the article.