CN-122018100-A - Low-shrinkage full-dry loose tube optical unit for bridging fixed water-blocking powder, preparation method thereof and optical cable

CN122018100ACN 122018100 ACN122018100 ACN 122018100ACN-122018100-A

Abstract

The application belongs to the technical field of optical communication, and particularly relates to a low-shrinkage full-dry loose tube optical unit of bridging fixed water-blocking powder, a preparation method thereof and an optical cable. The application adopts the modified copolyester material with reduced crystallinity as the sleeve substrate, introduces the reactive group on the surface of the water-blocking powder by the chemical grafting technology, realizes the covalent bonding of the water-blocking powder and the sleeve material, greatly improves the shrinkage condition after the sleeve, simultaneously remarkably reduces the additional attenuation of the optical fiber because the water-blocking powder is not in direct contact with the optical fiber, and ensures that the water-blocking powder fixed by the chemical grafting is not easy to fall off and the water-absorbing expansion rate of the water-blocking powder is obviously improved.

Inventors

TANG SIYI
CHEN CHANGCHENG
HU HAIFENG
RUAN YUNFANG
ZHAN HAO
QI LIN

Assignees

长飞光纤光缆股份有限公司

Dates

Publication Date: 20260512
Application Date: 20251231

Claims (10)

1. A low shrinkage full dry loose tube light unit of bridging fixed water blocking powder, characterized by comprising a light guiding element and a loose tube containing the light guiding element; The loose tube comprises an outer thermoplastic layer and an inner water-absorbing thermoplastic resin layer which is in chemical bridging connection with the thermoplastic layer to fix water-blocking powder, wherein the outer thermoplastic layer and the inner water-absorbing thermoplastic resin layer are prepared by a double-layer coextrusion process; The outer thermoplastic layer is thermoplastic modified PBT copolyester, the modified PBT copolyester is obtained by introducing an amorphization comonomer to participate in copolymerization in the PBT synthesis process, and the amorphization comonomer participates in the copolymerization of the PBT to reduce the molecular chain structural regularity of the PBT; The extrusion raw material of the inner water-absorbing thermoplastic resin layer contains the modified PBT copolyester, a monomer containing methacryloxy groups and epoxy groups, and chemical grafting modified water-blocking powder obtained by activating sodium polyacrylate by polymerizable double bonds, and a photoinitiator; And then under the irradiation of ultraviolet light, decomposing a photoinitiator to generate free radicals, and initiating the copolymerization reaction of the grafted methacryloxy on the modified PBT copolyester and polymerizable double bonds on the surface of the modified water-blocking powder to form firm chemical bridging to obtain the low-shrinkage all-dry loose sleeve of the bridged fixed water-blocking powder.
2. The all-dry loose tube light unit according to claim 1, wherein the amorphized comonomer is one or more of cyclohexanedimethanol, dimethyl sebacate and sebacic acid, and/or, In the process of the modified PBT copolyester copolymerization, the monomers participating in the reaction comprise, by weight, 100 parts of dimethyl terephthalate and/or terephthalic acid, 40-50 parts of 1, 4-butanediol, 8-15 parts of cyclohexanedimethanol and 5-12 parts of dimethyl sebacate and/or sebacic acid.
3. The all-dry sleeve light unit of claim 1 wherein said methacryloxy and epoxy group containing monomer is one or more of glycidyl methacrylate, glycidyl acrylate, and 3, 4-epoxycyclohexylmethyl methacrylate.
4. The all-dry loose tube light unit according to claim 1, wherein the sodium polyacrylate water-blocking powder is modified by adopting a silane coupling agent containing methacryloxy groups to obtain the chemical grafting modified water-blocking powder obtained by activating sodium polyacrylate by polymerizable double bonds.
5. The all-dry loose tube light unit according to claim 1, wherein the mass ratio of the modified PBT copolyester, the monomer containing methacryloxy group and epoxy group, the chemical grafting modified water-blocking powder obtained by activating sodium polyacrylate with polymerizable double bond and the photoinitiator in the extrusion raw material of the water-absorbing thermoplastic resin layer is (75-80): 2-5): 15-20): 0.5-1.
6. A method of producing a full dry loose tube light unit as claimed in any one of claims 1 to 5, comprising the steps of: (1) Co-extrusion plasticizing, namely simultaneously extruding the slice of the modified PBT copolyester and the extrusion raw material for forming the water-absorbing thermoplastic resin layer outside the bunched photoconductive element through a main extruder and a sub extruder respectively to obtain a plasticized molten pipe; (2) And then the semi-solidified loose tube passes through a shaped ultraviolet irradiation cavity, under the irradiation of ultraviolet light, a photoinitiator is decomposed to generate free radicals, the methacryloxy grafted on the modified PBT copolyester and the polymerizable double bond on the surface of the modified water-blocking powder are initiated to generate a copolymerization reaction, firm chemical bridging is formed, and the tube blank is sized by a vacuum sizing sleeve and enters a cooling water tank to be cooled and solidified to obtain the low-shrinkage full-dry loose tube of the bridging fixed water-blocking powder.
7. The method of claim 6, wherein the main extruder in step (1) is melt plasticized at 220-230 ℃ and the sub-extruder is melt blended plasticized at 210-220 ℃.
8. The method of claim 6, wherein the mass ratio of the slice of the modified PBT copolyester of step (1) to the extrusion raw material of the water-absorbent thermoplastic resin layer is 3-5:1.
9. The process of claim 6 wherein step (1) further comprises adding a plasticizer to the slices of the modified PBT copolyester and extruding the slices through a main extruder.
10. An optical cable comprising an outer jacket and a cable core received therein, the cable core comprising the all-dry loose tube light unit of any one of claims 1 to 5.

Description

Low-shrinkage full-dry loose tube optical unit for bridging fixed water-blocking powder, preparation method thereof and optical cable Technical Field The application belongs to the technical field of optical communication, and particularly relates to a low-shrinkage full-dry loose tube optical unit of bridging fixed water-blocking powder, a preparation method thereof and an optical cable. Background Today, where optical communication networks are developed at a high speed, the performance of optical fiber cables as physical carriers for information transmission directly affects the communication quality and the network reliability. The optical fiber sleeve is used as a core component of the optical cable, and protects the precise and vulnerable optical fiber from mechanical stress, moisture penetration and environmental change. Currently, the traditional casing materials widely used in the industry, in particular polybutylene terephthalate (PBT), are favored for their semi-crystalline nature and good processability. However, this material suffers from two technical difficulties in practical application, which are persistent and interrelated. The post-casing shrinkage problem stems from the semi-crystalline nature of the PBT material. During extrusion, the polymer molecular chains are in a high Wen Moxu state, while during the cooling solidification phase, the molecular chains begin to arrange in order to form crystalline regions. This process is not done instantaneously after extrusion, but continues for subsequent storage and use, resulting in slow but significant shrinkage (i.e. "post-shrinkage") of the sleeve dimensions in the axial and radial directions. Research shows that the shrinkage rate of the traditional PBT sleeve can reach 0.8-1.5% within 168 hours after extrusion. This constant dimensional change can create constant compressive stress on the internal optical fiber or ribbon, which can lead to macrobending and microbending losses in the fiber, manifesting as a significant increase in optical signal attenuation (additional attenuation), directly affecting the stability and reliability of the transmission. The additional attenuation problem caused by the water-blocking powder is not ignored. To ensure the water blocking performance of the cable, and prevent water from diffusing longitudinally along the fiber, the inside of the jacket is usually filled with water blocking powder (SAP). However, conventional physical filling means allow the water-blocking powder particles to be in direct, random contact with the surface of the optical fiber. Under vibration, bending and temperature changes during the cable laying, operation, these hard and loose water-blocking powder particles can rub against the surface of the optical fiber and even form local stress points, causing significant microbending losses. Industry test data shows that the direct contact of the water-blocking powder with the optical fiber can increase the additional attenuation by 0.03-0.08 dB/km, and the value can be further increased in a low-temperature environment. Several attempts are currently made by the industry to address these issues. The full-dry type optical cable technology replaces the traditional ointment by using dry type water blocking materials such as water blocking yarns, water blocking strips and the like, so that the problem of difficult cleaning of the ointment is truly solved, and the connection efficiency is improved. There are patent documents that adopt a method of adsorbing and fixing water-blocking powder on the inner wall of the loose tube, and the problems of powder flying and accumulation of the water-blocking powder are reduced by controlling the friction coefficient of the inner surface of the loose tube within the range of 0.21-0.34. More recently, it has been proposed to form a resin layer containing uniformly distributed water-blocking powder inside the loose tube to optimize the distribution of the water-blocking powder. However, these solutions do not fundamentally solve the problem of post-shrinkage of the material itself, nor do they realize efficient combination of the water-blocking powder and the sleeve material, so that the friction loss between the water-blocking powder and the optical fiber cannot be effectively eliminated. Disclosure of Invention Aiming at the defects of the prior art, the application aims to provide a low-shrinkage full-dry loose tube optical unit with water-blocking powder fixed in a bridging way, a preparation method thereof and an optical cable, and aims to solve the technical problems that the shrinkage is serious after the full-dry loose tube optical unit is made of a sleeve material, and the water-blocking powder is rubbed with an optical fiber to cause the optical cable loss in the prior art. To achieve the above object, in a first aspect, the present application provides a low shrinkage full dry loose tube light unit of a bridged fixed water-blocking powder, compris