Dual color blow molding process
An example extrusion blow molding (EBM) method includes extruding first and second colors of plastic to form a parison that includes an inner layer of the first color of plastic, and an outer layer of the second color of plastic. The parison is placed in a mold, the mold is closed, and the parison is inflated to create a blow molded structure. A portion of an interior of the blow molded structure is formed of the first color of plastic, and a portion of an exterior of the blow molded structure is formed of a blend of the first color of plastic and the second color of plastic.
1. A method, comprising:
extruding plastic of a first color and plastic of a second color to form a parison comprising melted plastic, wherein the parison includes an inner layer comprising the plastic of the first color, and the parison also includes an outer layer comprising the plastic of the second color, and wherein during and/or after the extruding, the plastic of the first color blends together with the plastic of the second color so that a portion of the parison comprises a blend of the plastic of the first color and the plastic of the second color;
placing the parison in a mold; and
inflating the parison to create a blow molded structure.
2. The method as recited in claim 1 , wherein a portion of the outer layer of the parison comprises the blend.
3. The method as recited in claim 1 , wherein a portion of an exterior of the blow molded structure comprises the blend.
4. The method as recited in claim 1 , wherein the inner layer and the outer layer each vary in thickness, but the overall thickness of a cross-section of the blow-molded structure is substantially constant.
5. The method as recited in claim 1 , wherein one of the plastic of the first color and the plastic of the second color includes regrind.
6. The method as recited in claim 5 , wherein the regrind comprises a combination of the plastic of the first color and the plastic of the second color.
7. The method as recited in claim 1 , wherein the plastic of the first color and the plastic of the second color are not blended with each other until after exiting a diverter.
8. The method as recited in claim 1 , wherein a portion of an exterior of the blow molded structure includes one or more randomly distributed irregularities in one or more of color, color gradient, tone, color depth, and color distribution.
9. The method as recited in claim 1 , wherein a portion of an interior of the blow molded structure is defined by the inner layer of the parison, and a portion of an exterior of the blow molded structure is defined by the outer layer of the parison.
10. The method as recited in claim 1 , wherein a feed rate of the plastic of the first color is different from a feed rate of the plastic of the second color.
11. The method as recited in claim 1 , wherein the blow molded structure is a watercraft.
12. The method as recited in claim 1 , wherein the extrusion process is performed by an extrusion machine that includes an accumulator head and a double heart diverter.
13. The method as recited in claim 1 , wherein the blow molded structure is other than a watercraft.
14. The method as recited in claim 1 , wherein the inner layer of the parison and the outer layer of the parison extend over an entire length of the parison.
15. The method as recited in claim 1 , wherein a feed rate of the plastic of the first color to an extrusion die is the same as a feed rate of the plastic of the second color to the extrusion die.
16. The method as recited in claim 1 , wherein the plastic of the first color and the plastic of the second color are the same physically and chemically identical polymer.
17. The method as recited in claim 1 , wherein the blow molded structure is created without the use of a preform or an overmold.
18. The method as recited in claim 1 , wherein the inner layer and the outer layer are attached to each other.
19. The method as recited in claim 1 , wherein a portion of the blend is created during extrusion.
20. The method as recited in claim 1 , wherein the blow molded structure is created without the use of injection molding, stretch blow molding, rotomolding, or twin sheet molding.
21. A method, comprising:
extruding a plastic of a first color and a plastic of a second color to form a parison comprising melted plastic, wherein during and/or after the extruding, plastic of the first color blends together with plastic of the second color so that a portion of the parison comprises a blend of the plastic of the first color and the plastic of the second color;
placing the parison in a mold; and
inflating the parison to create a blow molded structure.
22. The method as recited in claim 21 , wherein a portion of an interior of the blow molded structure comprises the plastic of the first color.
23. The method as recited in claim 21 , wherein the portion of the parison that comprises the blend forms a portion of an exterior of the blow molded structure, and the portion of the exterior has a third color that is different from the first color and the second color.
24. The method as recited in claim 21 , wherein extrusion of the plastic of the first color overlaps in time with extrusion of the plastic of the second color.
25. The method as recited in claim 21 , wherein the blend comprises high density polyethylene (HDPE) plastic.
26. The method as recited in claim 21 , wherein the plastic of the second color comprises high density polyethylene (HDPE) plastic.
27. The method as recited in claim 21 , wherein a portion of an exterior of the blow molded structure has a low surface gloss.
28. The method as recited in claim 21 , wherein the plastic of the first color and the plastic of the second color both comprise high density polyethylene (HDPE) plastic.
29. The method as recited in claim 1 , wherein the blend is formed by bleed through of one of the plastic of the first color and the plastic of the second color into the other of the plastic of the first color and the plastic of the second color.