Apparatus for preparation of synthetic wood

• US 3,881,984 A
• Filed: 01/09/1973
• Issued: 05/06/1975
• Est. Priority Date: 08/07/1969
• Status: Expired due to Term

• Current Assignee: Motoshige Hayashi, Shigenari Soda, Shigeru Daiguji, Tatsujiro Seki
• Original Assignee: Motoshige Hayashi, Shigenari Soda, Shigeru Daiguji, Tatsujiro Seki
• Inventors: Soda, Shigenari, Seki, Tatsujiro, Hayashi, Motoshige, Daiguji, Shigeru
• Primary Examiner(s): Weston, Caleb
• Application Number:
  US05/322,130
• Time in Patent Office: 847 Days
• Field of Search: 156/244,500 264/46,51,53,211,232,321 425/66,72,109,113,114,130,131,324,325,326,376,378,380,382,463,464,465,466
• US Class Current: 156/500
• CPC Class Codes: B29C 44/468 in a plurality of parallel streams which unite during the foaming

Abstract

A synthetic wood being an elongated microporous article formed of a plurality of coalesced, foamed resin strands, each being in intimate contact with each other, and each having a higher density in its outer surface and lower density in its inner portion. Thus, the cross section of the synthetic wood comprises a frame distributed in a reticulate form. The synthetic wood of the invention is produced by extruding softened thermoplastic resin containing expanding agents into a plurality of expandable strands by passing the same through a die at the discharge end of an extruder, the die having a number of apertures and coalescing the strands into a microporous article having a desired crosssectional area while the strands are still in a softened state, wherein the space in which each individual strand is allowed to expand is restricted to provide each of the strands with a higher density outer surface.

Claims

1. In an apparatus for preparing synthetic wood which includes an extruding means for extruding softened thermoplastic resin containing expanding agents, die means disposed at the discharge end of said extruding means adapted to permit the extruded thermoplastic resin to pass therethrough to form a plurality of expanded strands, said die means including a first chamber and at least one plate having a plurality of apertures therethrough disposed on the outlet side of said chamber, and coalescing means disposed at the outlet side of said die means for coalescing said plurality of expanded strands into a microporous article having a desired cross-sectional area while said strands are still in a softened state, the improvement comprising at least one of said die and said coalescing means being constructed to restrict the space in which each individual strand is allowed to expand to provide each of said strands with a higher density outer surface.

2. The improvement according to claim 1 further comprising a cooling element positioned and arranged so as to effect cooling of the outer surface the plurality of expanded strands at a point near the point of emergence of the expanded strands from the die means.

3. The improvement according to claim 1 wherein the apertures of said first plate of said die means have different land lengths to provide equal resin flow therethrough.

4. The improvement accordIng to claim 1 further comprising resin temperature regulator means disposed between said extruding means and said die means.

5. The improvement according to claim 1 wherein said die means further includes a second chamber disposed on the outlet side of said first plate and a second plate having a plurality of apertures therethrough disposed on the outlet side of said second chamber.

6. The improvement according to claim 1 wherein at least some of said apertures are different from the remaining apertures.

7. The improvement according to claim 6 wherein said apertures differ in length.

8. The improvement according to claim 6 wherein said apertures differ in cross-sectional area.

9. The improvement according to claim 6 wherein said apertures are substantially cylindrical and exhibit different diameters.

10. The improvement according to claim 6 wherein at least one of said apertures has a small area opening at one end and a large area at the other end.

11. The improvement according to claim 1 wherein said plate is provided with a variable density of apertures.

12. The improvement according to claim 1 wherein the total cross-sectional area of said apertures is relatively small in relation to the expanding ability of said thermoplastic resin such that each of the resultant strands exhibits a high density outer surface and a low density interior.

13. The improvement according to claim 1 wherein said apertures are constructed such that different strands have different densities.

14. The improvement according to claim 1 wherein said plate is constructed to yield substantially identical strands each having low density interiors and high density skins.

15. The improvement according to claim 14 wherein said chamber increases in cross-sectional area from the end adjacent said extruding means to said plate, said apertures being constructed to produce an overall pressure drop distribution compensating for the variance in the pressure drop produced by the change in the cross-sectional area of said chamber.

16. The improvement according to claim 15 wherein a second, uniformly aperture plate is disposed on the outlet side of the first plate.

17. The improvement according to claim 15 wherein at least a portion of said apertures have the same length and have enlarged and smaller portions, the apertures closest to the periphery having enlarged sections of greater length than those nearer the center.

18. The improvement according to claim 1 wherein said apertures are constructed to produce a lower pressure drop in the center apertures and a higher pressure drop in the peripheral apertures.

19. The improvement according to claim 18 wherein the center apertures have larger cross-sectional areas than those of the peripheral apertures.

20. The improvement according to claim 18 wherein the plate is thinner in the center than in the periphery.

21. The improvement according to claim 1 wherein the inlet sides of at least a number of the individual apertures have a relatively small cross-sectional portion and the outlet sides have a relatively large cross-sectional portion, the size of the relatively large cross-sectional portions being such the expansion of said strands is restricted thereby.

22. The improvement according to claim 1 wherein peripheral apertures have enlarged inlet portions the lengths of which diminish toward the center apertures, the center apertures exhibiting constant diameters.

23. The improvement according to claim 1 wherein said coalescing means includes at least one pair oppositely disposed, non-driven rolls rotatable by frictioned contact with said strands.

24. The improvement according to claim 23 wherein said coalescing means includes a plurality of pairs of said rollers positioned such that said strands are nipped and compressed on all four sides bordering the moving path of said strands.

25. The improvement according to claim 23 wherein said coalescing means further comprises a tapered frame engaging opposite siDes of the group of strands in advance of said rollers.

26. The improvement according to claim 1 wherein said coalescing means comprises a tapered frame engaging and compressing opposite sides of the group of strands leaving said die means.

27. The improvement according to claim 1 further comprising blower means positioned at the outlet end of said die means for cooling said strands.

28. The improvement according to claim 1 further comprising heat exchange means positioned at the outlet side of said die means for cooling said strands.

29. An apparatus for preparing synthetic wood comprising an extruding means for extruding softened thermoplastic resin containing expanding agents, die means disposed at the discharge end of said extruding means adapted to permit the extruded thermoplastic resin to pass therethrough to form a plurality of expanded strands, said die means including a first chamber, at least one plate having a plurality of apertures therethrough disposed on the outlet side of said chamber, a second chamber disposed on the outlet side of said first plate and a second plate having a plurality of apertures therethrough disposed on the outlet side of said second chamber, and coalescing means disposed at the outlet side of said die means for coalescing said plurality of expanded strands into a microporous article having a desired cross-sectional area while said strands are still in a softened state, at least one of said die and said coalescing means being constructed to restrict the space in which each individual strand is allowed to expand to provide each of said strands with a higher density outer surface.

30. The apparatus according to claim 29 further comprising resing temperature regulator means disposed between said extruding means and said die means.

31. The apparatus according to claim 29 wherein the apertures of said first plate of said die means have different land lengths to provide equal resin flow therethrough.

32. The apparatus according to claim 29 further comprising a cooling element positioned and arranged so as to effect cooling of the outer surface the plurality of expanded strands at a point near the point of emergence of the expanded strands from the die means.

33. The apparatus according to claim 29 wherein said coalescing means includes a plurality of pairs of said rollers positioned such that said strands are nipped and compressed on all four sides bordering the moving path of said strands.