Optical fiber cable with dimensionally stable polymeric component
View Patent ↗An optical fiber cable having a polymeric component, in particular a buffer tube, suitable for both terrestrial and undersea uses. The polymeric material forming the component has a copolymer of propylene with a C 4 -C 8 α-olefin and preferably a nucleating agent disbursed therein. The obtained component shows improved dimensional stability, which guarantees its non-deformability, and high transparency and can be extruded at lower extrusion temperatures.
1. An optical fiber cable comprising a cable component, wherein the cable component is made of a polymeric material comprising a crystalline random copolymer derived from monomers selected from the group consisting of propylene and C 4 -C 8 α-olefin monomers, wherein said crystalline random copolymer is derived from propylene with at least one C 4 -C 8 α-olefin.
2. The optical fiber cable according to claim 1 , wherein the cable component is a buffer tube defined by a peripheral polymeric wall and containing at least one optical fiber housed therein.
3. The optical fiber cable according to claim 2 , wherein a longitudinal reinforcing element is embedded in the peripheral wall of the buffer tube.
4. The optical fiber cable according to claim 1 , wherein the cable component is substantially made of the copolymer.
5. The optical fiber cable according to claim 1 , wherein the at least one C 4 -C 8 α-olefin is an olefin of the formula CH 2 ═CH—R, where R is a linear or branched alkyl containing 2 to 6 carbon atoms.
6. The optical fiber cable according to claim 1 , wherein the at least one C 4 -C 8 α-olefin is selected from 1 -butene, 1 -pentene, 3-methyl-1 -butene, 4-methyl-1-pentene, 1 -hexene, 3,4-dimethyl-1 -butene, 1 -octene or a mixture thereof.
7. The optical fiber cable according to claim 1 , wherein the at least one C 4 -C 8 α-olefin is 1-butene.
8. The optical fiber cable according to claim 1 , wherein the copolymer contains from about 1 to about 12 weight percent of the at least one C 4 -C 8 α-olefin, with respect to the total weight of the copolymer.
9. The optical fiber cable according to claim 1 , wherein the copolymer contains from about 4 to about 10 weight percent of the at least one C 4 -C 8 α-olefin, with respect to the total weight of the copolymer.
10. The optical fiber cable according to claim 1 , wherein the copolymer has a melting point of from about 140° C. to about 156° C.
11. The optical fiber cable according to claim 1 , wherein the copolymer has a crystallization point from about 90° C. to 120° C.
12. The optical fiber cable according to claim 1 , wherein the copolymer has a content of fractions insoluble in xylene at 25° C. higher than about 93%.
13. The optical fiber cable according to claim 12 , wherein the copolymer has a content of fractions insoluble in xylene at 25° C. higher than about 95%.
14. The optical fiber cable according to claim 1 , wherein the copolymer has a Melt Flow Index (MFI) in the range from 1 to 15 g/10 min. measured at 190° C. (ASTM 1238).
15. The optical fiber cable according to claim 1 , wherein the copolymer has a Melt Flow Index (MFI) in the range from 1 to 10 g/10 min. measured at 190° C. (ASTM 1238).
16. The optical fiber cable according to claim 1 , wherein the polymeric material has a flexural modulus (method ISO 178) of at least about 500 MPa.
17. The optical fiber cable according to claim 1 , wherein the polymeric material has a flexural modulus (method ISO 178) in the range of about 800 to 1500 MPa.
18. The optical fiber cable according to claim 1 , wherein the transmittance of the polymeric material is above 70%.
19. The optical fiber cable according to claim 1 , wherein the transmittance of the polymeric material is above 80%.
20. The optical fiber cable according to claim 1 , wherein the copolymer is in admixture with at least a second olefin polymer.
21. The optical fiber cable according to claim 20 , wherein the second olefin polymer is selected from a propylene homopolymer or a crystalline propylene copolymer containing from 1% to 3% by weight of ethylene.
22. The optical fiber cable according to claim 20 , wherein the amount of the second olefin polymer is in the range of from about 10% to about 40%, with respect to the total weight of said crystalline random copolymer derived from propylene and C 4 -C 8 α-olefin monomers.
23. The optical fiber cable according to claim 20 , wherein the amount of the second olefin polymer is in the range of from about 10% to about 30%, with respect to the total weight of said crystalline random copolymer derived from propylene and C 4 -C 8 α-olefin monomers.
24. The optical fiber cable according to claim 1 , wherein a nucleating agent is disbursed into the polymeric material.
25. The optical fiber cable according to claim 24 wherein the nucleating agent is in the range of 0.05% to 1% by weight, with respect to the total weight of the copolymer.
26. The optical fiber cable according to claim 24 , wherein the nucleating agent is in the range of 0.1% to 0.5% by weight, with respect to the total weight of the copolymer.
27. The optical fiber cable according to claim 24 , wherein the nucleating agent is selected from inorganic materials, D-sorbitol derivatives, salts of aliphatic monobasic or dibasic acids, aralkyl acids, or alkali metal or aluminum salts of aromatic or alicyclic carboxylic acids, talc, or a mixture thereof.
28. The optical fiber cable according to claim 24 , wherein the nucleating agent is a D-sorbitol derivative of the following formula:
wherein R and R 1 are independently a
group, wherein R 2 represents a C 1 - 6 alkyl or alkoxy group and n is 1, 2 or 3.
29. The optical fiber cable according to the claim 28 , wherein R and R 1 are a
group, R 2 being a C 1 -C 6 alkyl group and n being 1, 2 or 3.
30. An optical fiber cable component comprising a polymeric material comprising a crystalline random copolymer derived from monomers selected from the group consisting of propylene and C 4 -C 8 α-olefin monomers, wherein said crystalline random copolymer is derived from propylene with at least one C 4 -C 8 α-olefin.
31. An optical fiber cable component according to claim 30 , which is a buffer tube.