LASER TRANSPARENT COMPOSITIONS AND METHODS OF LASER WELDING
Laser transparent compositions that may be black in color. The laser transparent compositions may include a matrix material that includes a polypropylene, a dye system that includes one, and optionally two or more, polar organic compounds, a plurality of glass fibers, and a UV stabilizer. Methods of laser welding, which may include irradiating a laser absorbing composition that contacts a laser transparent composition at an interface.
1 . A laser transparent composition having a black color, the laser transparent composition comprising:
a matrix material comprising a polypropylene;
a dye system, wherein the dye system is (i) dispersed in the matrix material, and (ii) present at an amount of about 0.05% to about 0.5%, by weight, based on the weight of the laser transparent composition;
a compatibilizer, wherein the compatibilizer is (i) dispersed in the matrix material, and (ii) present at an amount of about 0.1% to about 10%, by weight, based on the weight of the laser transparent composition;
a plurality of glass fibers, wherein the plurality of glass fibers is (i) dispersed in the matrix material, and (ii) present at an amount of about 1% to about 40%, by weight, based on the weight of the laser transparent composition; and
a UV stabilizer, wherein the UV stabilizer is (i) dispersed in the matrix material, and (ii) present at an amount of about 0.1% to about 2%, by weight, based on the weight of the laser transparent composition;
wherein the laser transparent composition has a laser transparency of at least 50%.
2 . The laser transparent composition of claim 1 , wherein the laser transparent composition has a laser transparency of at least 65%.
3 . The laser transparent composition of claim 1 , wherein the dye system comprises two or more polar organic compounds.
4 . The laser transparent composition of claim 3 , wherein the two or more polar organic compounds of the dye system comprise a red dye and a green dye, and wherein the red dye and the green dye are present in the dye system at a weight ratio of about 40:60 (red dye:green dye) to about 60:40 (red dye:green dye).
5 . The laser transparent composition of claim 4 , wherein (i) the red dye comprises MACROLEX® Red EG dye, (ii) the green dye comprises MACROLEX® Green 5B, or (iii) the red dye comprises MACROLEX® Red EG dye and the green dye comprises MACROLEX® Green 5B.
6 . The laser transparent composition of claim 1 , wherein the compatibilizer comprises a modified polypropylene homopolymer, wherein the modified polypropylene homopolymer comprises
(i) a polypropylene homopolymer, and
(ii) a monomer comprising a polar functional group;
wherein the monomer comprising the polar functional group is (a) grafted to the polypropylene homopolymer, and (b) present at an amount of about 3 mole % to about 10 mole % relative to the moles of polypropylene monomer in the polypropylene homopolymer.
7 . The laser transparent composition of claim 6 , wherein the compatibilizer has (i) a density of about 0.8 g/cm 3 to about 1 g/cm 3 , (ii) a melt flow rate of about 30 g/10 minutes to about 50 g/10 minutes, or (iii) a combination thereof.
8 . The laser transparent composition of claim 6 , wherein the compatibilizer has (i) a density of about 0.91 g/cm 3 , (ii) a melt flow rate of about 42 g/10 minutes, or (iii) a combination thereof.
9 . The laser transparent composition of claim 6 , wherein the polar functional group comprises a carboxylic acid.
10 . The laser transparent composition of claim 9 , wherein the monomer comprising the polar functional group comprises acrylic acid, maleic anhydride, or a combination thereof.
11 . The laser transparent composition of claim 1 , wherein the plurality of glass fibers has an average filament diameter of about 10 p.m to about 25 p.m, and an average length of about 1 mm to about 10 mm.
12 . The laser transparent composition of claim 1 , wherein the plurality of glass fibers is present at an amount of about 10% to about 30%, by weight, based on the weight of the laser transparent composition.
13 . The laser transparent composition of claim 1 , wherein the plurality of glass fibers comprises THERMOFLOW® EC14-738 glass fibers.
14 . The laser transparent composition of claim 1 , wherein the UV stabilizer is present at an amount of about 0.5% to about 0.7%, by weight, based on the weight of the laser transparent composition.
15 . The laser transparent composition of claim 1 , wherein the UV stabilizer comprises HOSTAVIN® N 30 UV stabilizer, CHIMASSORB®-LS119 UV stabilizer, SABOSTAB® UV 62 UV stabilizer, or a combination thereof.
16 . The laser transparent composition of claim 1 , wherein the laser transparent composition is UV stable up to at least 2000 KJ/m 2 .
17 . The laser transparent composition of claim 1 , wherein the polypropylene of the matrix material comprises EXXONMOBIL® PP1105E1 polypropylene, EXXONMOBIL® ACHIEVE® Advanced PP1605 polypropylene, or a combination thereof.
18 . A method of laser welding, the method comprising:
providing (i) the laser transparent composition of claim 1 , and (ii) a laser absorbing composition that is black in color, wherein the laser transparent composition and the laser absorbing composition contact each other at an interface; and
directing laser irradiation through the laser transparent composition to heat at least a portion of the laser absorbing composition at the interface for a time effective to liquefy at least part of (i) the portion of the laser absorbing composition at the interface, (ii) a portion of the laser transparent composition at the interface, or (iii) a combination thereof.
19 . The method of claim 18 , further comprising solidifying (i) the portion of the laser absorbing composition at the interface, (ii) the portion of the laser transparent composition at the interface, or (iii) a combination thereof to weld the laser transparent composition and the laser absorbing composition together at the interface.
20 . The method of claim 18 , wherein the laser absorbing composition comprises carbon black.