CN114002794A

CN114002794A - Layer-stranded air-blown micro-cable with high fiber core density, and preparation method and application of outer layer thereof

Info

Publication number: CN114002794A
Application number: CN202111360402.9A
Authority: CN
Inventors: 阮云芳; 胡海峰; 刘宏超; 郑磊; 王佳; 詹浩; 祁林; 王俊; 肖毅
Original assignee: Yangtze Optical Fibre and Cable Co Ltd
Current assignee: Yangtze Optical Fibre and Cable Co Ltd
Priority date: 2021-11-17
Filing date: 2021-11-17
Publication date: 2022-02-01
Anticipated expiration: 2041-11-17
Also published as: CN114002794B

Abstract

The invention discloses a layer-stranded air-blown micro cable with high fiber core density, which comprises a sheath and a cable core, wherein the cable core comprises a bundle yarn, a central reinforced core and a plurality of optical fiber units; the mixture for preparing the outer layer mainly comprises polyformaldehyde, molybdenum disulfide, a compatilizer, an antioxidant, an aldehyde absorbing agent, a light shielding agent and a low-density polyethylene grafting material; the invention greatly saves nonrenewable pipe hole resources, breaks through the limitation that the duty ratio between the optical cable and the micro-pipe is generally not more than 60% in the traditional air-blowing construction, has good air-blowing effect even if the duty ratio reaches 65-70% in the air-blowing construction, and mainly greatly reduces the surface friction coefficient of the layer-stranded air-blowing micro-cable on the outer layer of the sheath and combines the flexibility of the inner layer of the sheath, thereby greatly improving the air-blowing distance of products, improving the construction efficiency and enabling the air-blowing laying under high duty ratio to be possible.

Description

Layer-stranded air-blown micro-cable with high fiber core density, and preparation method and application of outer layer thereof

Technical Field

The invention belongs to the field of optical communication, and particularly relates to a layer stranded air-blown micro cable with high fiber core density, and a preparation method and application of an outer layer of the layer stranded air-blown micro cable.

Background

The air-blown micro-pipe micro-cable technology for air-blown laying communication has been widely applied to the 5G network construction process at home and abroad at present due to the construction standardization, mechanization and high efficiency, and the advantages of saving pipe hole resources, being capable of managing intellectualization and the like. However, in some big cities and extra-large cities, along with network upgrading and transformation, the contradiction of insufficient pipe hole resources is increasingly prominent, and meanwhile, along with the increasing standardization and strictness of city management, new pipe holes are more and more difficult to dig and lay on the road surface, and the improvement of the pipe hole resource utilization rate becomes the most urgent requirement of each operator. Therefore, the development of the air-blowing micro cable with high core density and/or the air blowing of the air-blowing micro cable in the air-blowing micro tube for communication with high duty ratio are the optimal options.

On one hand, the development of the air-blown micro-cable with high fiber core density means that new challenges are provided for optical fiber design, optical cable manufacturing process and design so as to ensure stable optical fiber transmission performance in the laid optical cable. On the other hand, the air-blown micro-cable with good air-blowing performance (meeting the standard requirement of IEC 60794) under the condition of high duty ratio is developed so as to accommodate more optical cables with the same core number in the pipeline with the same specification. However, almost all the existing air-blowing micro-cable sheaths are made of high-density polyethylene (HDPE), the friction coefficient of an air-blowing micro-cable product produced by the air-blowing micro-cable sheath is different from 0.12 to 0.35, the air-blowing micro-cable sheath is mainly related to the grade and the processing technology of the sheath material selected by each manufacturer, and under a high duty ratio, a good air-blowing effect is difficult to achieve by using the friction coefficient, so that the duty ratio (which can be considered as the area of the outer edge of the cross section of the micro-cable/the area of the inner edge of the cross section of the air-blowing micro-tube for communication) of the micro-cable/the air-blowing micro-tube for communication in an air-blowing instruction manual is required to be less than 60%, and the limit is also known in the industry, and the duty ratio is 40% -50% in a general case to be a better choice.

Some producers do some changes in product appearance structure for making up the not enough of air-blowing micro cable sheath coefficient of friction, if set up some recesses etc. on the sheath surface, can reduce product coefficient of friction objectively, but when actual air-blowing, because the wearing and tearing of sheath surface material in the air-blowing in-process and the HDPE material softening production under the high temperature high pressure air-blowing condition with the gluing of air-blowing microtube wall for communication, actual air-blowing effect improves not greatly, hardly have big breakthrough on the air-blowing distance, be difficult to satisfy the requirement of customer air-blowing distance and high-efficient construction, touch the condition of a little complicated construction route and hot day gas a little, the air-blowing construction progress will be influenced greatly.

In addition, when the air-blowing micro cable taking HDPE as the sheath material rubs with the HDPE material as the same material of the air-blowing micro pipe for communication, the fluctuation range of the friction coefficient is very large, and the air-blowing effect is reflected that the air-blowing speed is unstable and suddenly slow, so that the air-blowing construction safety is influenced.

Another difficult problem to solve with high core density air blown micro-cables is the environmental resistance of the product. The surplus length is beneficial to bending of the loose tube, and attenuation of the optical fiber is not influenced within a proper tension range. As shown in fig. 1a and 1b, the front equipment of the extruder includes an optical fiber pay-off rack 112, a fiber paste injection system 111, and an extruder system 113, the optical fiber unit in the conventional air-blown micro cable includes an optical fiber 101, a fiber paste 102, and a PBT loose tube 103, the optical fiber 101 is directly placed in the PBT loose tube 103 and affected by material shrinkage, the optical fiber 101 forms an extra length in the PBT loose tube 103 in a sine wave manner, the extra length is beneficial to the requirement of bending the PBT loose tube 103, the optical fiber 101 is in the approximate sine wave form, the wall of the PBT loose tube 103 and the optical fiber 101 must have a sufficient gap to ensure normal attenuation of the optical fiber 101, and therefore, the diameter of the conventional high-fiber core density loose tube is difficult to be made small. Under the condition that the fiber core density is not high enough and the air ratio in the PBT loose tube 103 is sufficient, the optical fiber attenuation is normal, once the air ratio in the PBT loose tube 103 is reduced, the fiber core density is improved, the excess length of the optical fiber 101 in the PBT loose tube 103 is not easy to obtain, when the PBT loose tube material is contracted in a water tank, the optical fiber 101 in the PBT loose tube 103 can form internal extrusion stress, when the PBT loose tube 103 is bent on a disc or stranded to form a cable core, the optical fiber 101 close to the outer wall of the tube can be subjected to bending tensile force, the optical fiber 101 close to the inner wall of the tube can be subjected to extrusion force, and meanwhile, the outer wall of the PBT loose tube 103 can also form extrusion force for the directly contacted outer edge optical fiber 101, so that the microbending and macrobending losses of the optical fiber 101 are increased at the same time, and the attenuation of the optical fiber 101 is increased. Therefore, the PBT loose tube 103 has to have enough gap between the tube wall and the optical fiber 101 to ensure the normal attenuation of the optical fiber 101, so the conventional high-core-density loose tube has a difficult diameter to be small.

Particularly, in the air-blown micro cable, shrinkage and elongation of loose sleeve materials and a sheath HDPE (high-density polyethylene) sheath occur due to changes of ambient temperature, and for the laid cable, the shrinkage and elongation of the sheath caused by changes of high and low temperatures can cause the deterioration of the transmission performance of the optical fiber.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides a layer stranded air-blown micro cable with high fiber core density, and a preparation method and application of an outer layer thereof, wherein low-density polyethylene is used for the inner layer of an air-blown micro cable sheath to ensure the smoothness of the air-blown micro cable, so that the air-blown micro cable is suitable for the bending requirement of an optical cable during air blowing, an ultra-low friction coefficient material is developed as the outer layer of the sheath to ensure that the air-blown micro cable can be applied to long-distance air blowing in a pipeline with the duty ratio (the area of the outer edge of the cross section of the micro cable/the area of the inner edge of the cross section of the micro tube) of 65-70 percent, and the air-blown effect meets the standard requirement of IEC-60794; by using the SZ twisting principle of the sleeve in the cabling process in the optical cable production process, the twisting principle is applied to two processes of high-fiber-core-density loose tube production for the first time, a new high-fiber-core-density loose tube surplus length control mode is developed, the problem of bending stress of optical fibers in the high-fiber-core-density loose tube is solved, the diameter of the loose tube can be made smaller, and the fiber core density of a product can be maximized. The product has the obvious advantages of extremely low friction coefficient, excellent high and low temperature environment resistance, greatly improved fiber core density in unit area, greatly saved pipe hole resources, low comprehensive cost and the like.

To achieve the object of enabling long-distance air-blown applications in pipelines with duty ratios of 65% to 70%, according to one aspect of the present invention, there is provided a high-core-density ultra-low-friction-coefficient layer-stranded air-blown micro-cable, comprising a sheath and a cable core disposed in the sheath, the cable core comprising a binder yarn, a central reinforcing core and a plurality of optical fiber units, each of the optical fiber units comprising a loose tube and an optical fiber bundle disposed in the loose tube, the optical fiber units being stranded around the central reinforcing core, the binder yarn being bound to the stranded optical fiber units, the sheath having an inner layer and an outer layer sheathed on the inner layer, the inner layer being made of low-density ethylene; the mixture for preparing the outer layer mainly comprises polyformaldehyde, molybdenum disulfide, a compatilizer, an antioxidant, an aldehyde absorbing agent, a light shielding agent and a low-density polyethylene grafting material;

in the mixture, the mass parts of polyformaldehyde are 85-95 parts, the mass parts of molybdenum disulfide are 3-12 parts, and the mass parts of low-density polyethylene grafting material are 1-2 parts.

Preferably, the mass parts of other components are as follows: 0.05 to 0.2 portion of compatilizer, 0.05 to 0.2 portion of antioxidant, 0.03 to 0.1 portion of aldehyde absorbing agent and 2 to 3 portions of light shielding agent.

Preferably, the optical fiber bundles in the loose tube of each optical fiber unit are in an SZ stranded state in the loose tube.

Preferably, the core density of each optical fiber unit is more than 14.17 cores/mm²The stranding pitch of the optical fibers in the loose tube is greater than 1000 mm.

Preferably, the friction coefficient of the sheath with respect to the communication air-blown microtube of HDPE material is lower than 0.1, with a preferred value of 0.045.

Preferably, the antioxidant is one or more of polyphenol hindered phenol antioxidant, phosphorous acid antioxidant and hindered amine.

Preferably, the light-shielding agent is a nanoscale conductive carbon black or a hindered amine.

Preferably, the polyethylene grafting material is prepared by uniformly mixing low-density polyethylene, Maleic Anhydride (MAH) and 2, 5-dimethyl-2, 5-bis (tert-butylperoxy) hexane (commonly called as a bis-penta initiator) at normal temperature, and then mixing and granulating at 160-180 ℃ by using an extensional rheological extruder, wherein the mass part ratio of the low-density polyethylene, the Maleic Anhydride (MAH) and the 2, 5-dimethyl-2, 5-bis (tert-butylperoxy) hexane (commonly called as a bis-penta initiator) is (97-99): (1-2): (0.5-1).

Preferably, the core density of the layer-stranded air-blown micro-cable is more than 8.47 cores/mm²。

For the purpose of realizing high core density, the term "high core density" used in the present invention has two meanings, i.e. on the layer of a single optical fiber unit, the core density of the single optical fiber unit is high and can be more than 14.17 cores/mm²And the purpose of high density of the single-tube fiber core is achieved. (ii) a Secondly, the fiber core density of the layer stranded air-blown micro cable is more than 8.47 cores/mm on the whole air-blown micro cable layer surface²

Preferably, long-flying small-diameter optical fibers (the diameter of the optical fibers is 192um +/-5um) are used, 36 optical fibers are in an SZ stranded state in a single loose tube, and the stranded pitch of the optical fibers in the loose tube is more than 1000 mm.

Preferably, the loose tube of the single optical fiber unit has an outer diameter of 1.6mm to 1.8mm, preferably 1.7 mm.

Preferably, the inner and outer layers of the sheath are bonded tightly and the bond is greater than 0.5N/mm.

According to another aspect of the invention, the preparation method of the sheath material of the outer layer of the sheath is further provided, which is characterized by comprising the following steps:

1) putting polyformaldehyde and molybdenum disulfide into a mixing kettle of a high-speed mixer, uniformly mixing, then adding a compatilizer, an antioxidant, an aldehyde absorbing agent, a light shielding agent and a low-density polyethylene grafting material, and uniformly mixing to form a mixture;

in the mixture, the mass parts of polyformaldehyde are 85-95 parts, the mass parts of molybdenum disulfide are 3-12 parts, and the mass parts of low-density polyethylene grafting material are 1-2 parts;

2) the mixture is transferred into a double-screw extruder for mixing, and then the sheath material is obtained after extrusion, cooling, granulation and drying in sequence, wherein the extrusion temperature of the double-screw extruder is 180-190 ℃;

3) and extruding the sheath material through an extruder to form the outer layer of the sheath of the optical cable.

According to another aspect of the invention, the application of the high-fiber-core-density ultra-low-friction-coefficient layer-stranded air-blown micro-cable is also provided, and the layer-stranded air-blown micro-cable is laid in a pipeline with the duty ratio of 65% -70% in an air-blown mode.

One of the base materials consisting of the low-friction sheath is polyformaldehyde, which is widely used for manufacturing various sliding and rotating mechanical parts, almost no report is available for optical cable sheath materials at present, the base material has the hardness, strength and rigidity similar to those of metals, has better wear resistance, can be used for a long time at the temperature of minus 40 ℃ to 100 ℃, and has good self-lubricating property, good fatigue resistance and extremely low friction coefficient (the friction coefficient is 0.012 to 0.018 under the condition of lubrication) under the conditions of wide temperature and humidity; the second base material is molybdenum disulfide which is generally used as a solid lubricant, the molybdenum disulfide is in a 2H crystal form and has a special layered structure, and all the layers are mutually connected by extremely tiny molecular force. Molybdenum disulfide is separated from layer to layer easily, consequently has good lubricating property, is honored as high-grade solid lubricating oil, mixes under lower proportion, and molybdenum disulfide forms the interfacial lubrication film between micro cable sheath surface and microtubule, makes the friction part between sheath surface and the microtubule convert into intermolecular and slides, plays and reduces sheath surface friction coefficient and improves the effect of sheath stand wear and tear ability.

The low-density polyethylene graft material is used as an additive, and due to the existence of a polar unit, the affinity of the low-density polyethylene graft material and polyformaldehyde is enhanced, the intermolecular acting force is enhanced, the inner layer of the sheath and the outer layer of the sheath are easy to be tightly bonded into a whole, and the impact resistance, torsion resistance, bending resistance and other aspects of the polyformaldehyde can be improved by times.

The antioxidant is one or more of polyphenol hindered phenol antioxidant, phosphorous acid antioxidant and hindered amine, and preferably the mass fraction in the mixture is as follows: the combination of 0.01 percent of polyphenol hindered phenol antioxidant, 0.01 percent of phosphorous acid antioxidant and 0.02 percent of high molecular weight hindered amine has good use effect.

The compatilizer is preferably a mixture of Maleic Anhydride (MAH) and 2, 5-dimethyl-2, 5-bis (tert-butylperoxy) hexane (commonly known as bis-dipenta-vulcanizing agent), and the mass part ratio of the Maleic Anhydride (MAH) to the bis-dipenta-vulcanizing agent is (1-2): (0.5-1), preferably 2:1, so as to ensure that the molybdenum disulfide and each additive are well compatible with the polyformaldehyde, and the molybdenum disulfide and the polyformaldehyde can play a role in linking molecules on an interface, namely a compatibility role.

The light shielding agent is conductive carbon black, preferably nanoscale conductive carbon black, not only can shield ultraviolet rays, but also can enable the sheath to have antistatic property, can eliminate the influence of electrostatic adsorption generated by plastic friction in the air blowing process on the air blowing effect and the influence of ultraviolet resistance and the like of the optical cable, and for the optical cable required by the non-black sheath, the use of hindered amine light stabilizer as the light shielding agent is not excluded.

The formaldehyde absorbent is preferably formic acid absorbent, and is used for inhibiting formaldehyde gas generation of the sheathing compound during extrusion.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

1) the high-fiber-core-density air-blown micro cable greatly saves nonrenewable pipe hole resources, breaks through the limitation that the duty ratio (the area of the outer edge of the cross section of the micro cable/the area of the inner edge of the cross section of the micro pipe) between an optical cable and a pipeline is generally not more than 60% in the traditional air-blown construction, has good air-blown effect even if the duty ratio reaches 65% -70% in the air-blown construction, and meets the requirements of IEC-60794 standards. The outer layer of the mixture mainly comprises polyformaldehyde, molybdenum disulfide, a compatilizer, an antioxidant, an aldehyde absorbing agent, a light shielding agent, a low-density polyethylene grafting material and the like, and the mixture is extruded after blending, so that the surface friction coefficient of the layer-stranded air-blown micro-cable is greatly reduced, and the flexibility of the inner layer of the sheath is combined, so that the air-blown distance of the product can be greatly increased, the construction efficiency is improved, and the air-blown laying under high duty ratio is possible.

2) Compared with the friction coefficient of an air-blown plastic micro-tube for communication in the industry, the twisted layer air-blown micro-cable sheath with high fiber core density has the advantages that the fluctuation range is smaller than 0.01 in the test process, is almost a straight line and is far smaller than the fluctuation range of the friction coefficient of a conventional air-blown micro-cable made of HDPE sheath materials, so that the air-blown speed is stable and ordered, the condition of suddenly fast and suddenly slow can not occur, and the construction safety is ensured.

3) The optical fibers of the optical fiber units in the high-fiber-core-density air-blown micro cable are in an SZ twisted state in the loose tube, when the loose tube is bent, the optical fibers are hardly subjected to the pressure/tensile stress generated by the length difference of the inner edge and the outer edge of the tube due to the existence of the twisted surplus length, and the optical fibers are not subjected to the pressure of the tube wall even in a very small hollow space of the tube, so that the optical fibers are hardly influenced by macrobending and microbending, and the attenuation of the optical fibers is ensured to meet the requirements; because the hollow space in the sleeve can be made very small, and the diameter of the loose sleeve can also be made very small, the density of the fiber core in the sleeve can be increased, and the propagation capacity of optical signals can be effectively improved.

4) The outer layer of the sheath of the high-fiber-core density air-blown micro cable has stable environment resistance, the crystallinity reaches more than 70 percent in the processing process, and particularly, the low-density polyethylene material of the inner layer is softer than high-density polyethylene and softer than the high-density polyethylene under the low-temperature (-40 ℃) environment, so that the attenuation performance of the optical fiber is better, and the problem of stable transmission performance of the optical fiber is solved.

Drawings

FIGS. 1a and 1b are schematic diagrams of conventional extruder head-end equipment and a representation of conventional layer-stranded air-blown micro-cable excess length, respectively;

fig. 2a and 2b are schematic diagrams of the extruder head-end and layer-twisted air-blown micro-cable extra length representations, respectively, of the present invention.

FIG. 3 is a schematic diagram illustrating the construction of a 720-core stranded air-blown micro-cable according to the present invention;

FIG. 4 is a graph showing the results of the coefficient of friction test of example 3 (sample # 7);

FIG. 5 is a graph showing the results of the coefficient of friction test of example 5 (sample # 9);

FIG. 6 is a graph showing the results of the coefficient of friction test of example 4 (sample # 8);

FIG. 7 is a graph showing the results of the coefficient of friction test of example 6 (sample # 10);

fig. 8 is a graph showing the results of the friction coefficient test of comparative example 3 (sample # 3).

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Referring to fig. 3, a 720-core stranded air-blown micro cable structure according to the present invention relates to a high-core-density ultra-low-friction-coefficient layer-stranded air-blown micro cable, which includes a sheath and a cable core disposed in the sheath, where the cable core includes a binder yarn, a central reinforcing core 1 and a plurality of optical fiber units stranded around the central reinforcing core, the binder yarn is bound to the stranded optical fiber units, the central reinforcing core is preferably a water-blocking non-metallic central reinforcing core, and each high-core-density loose tube 2 preferably contains 36 optical fibers therein to form an optical fiber bundle 3; the 20 loose tubes are stranded around the central reinforced core 1, the 20 loose tubes are arranged in an inner ring and an outer ring, wherein the inner ring is provided with 7 loose tubes, the outer ring is provided with 13 loose tubes, and the loose tubes are bundled by binding yarns to form a cable core; the cable core is covered with a sheath, and at least one mooring rope 6 is arranged under the sheath; the sheath comprises inlayer and skin, and wherein inlayer 4 is low density polyethylene material, and outer 5 has ultralow coefficient of friction, and wherein inlayer 4 thickness accounts for whole sheath thickness proportion and is not more than 80%, and the inlayer combines closely, guarantees the air-blowing micro cable pliability when the air-blowing turns round, obtains good air-blowing effect under the high duty cycle. The inner layer 4 and the outer layer 5 are formed together in a double-layer co-extrusion mode.

The layer-stranded air-blowing micro cable can be applied to air blowing in 16/12mm (outer diameter is 16mm, inner diameter is 12mm) pipelines with duty ratio of 65-70%.

The whole forming process of the layer-stranded air-blowing micro cable comprises the following steps:

1) ring spraying and coloring: the optical fiber with long flying and small fiber diameter (the diameter of the optical fiber is 192um +/-5um, and the optical fiber is colored and sprayed with rings according to a certain rule for distinguishing.

2) Secondary plastic coating: the process is one of key processes of the invention, the same as the normal casing paying-off process, 36 optical fibers are put on a paying-off rack, before entering a mould of two sets of extruders, the 36 optical fibers are arranged according to a certain rule and penetrate into a twisting device capable of SZ twisting, the speed of the twisting device is synchronous with that of a production line, in the casing production process, a twisting head rotates according to the twisting pitch set by the process, the ratio of the equivalent cross section of the optical fibers in the casing to the inner diameter cross section of the casing is more than 90%, the optical fibers in the casing form the twisting excess length along the SZ twisting direction, when the casing is bent, the optical fibers have the twisting excess length, the stress is small, the optical fiber attenuation meets the requirement, the outer diameter of the produced high-fiber-core-density loose casing is 1.6mm-1.8mm, the center value of the produced high-fiber-core-density loose casing is 1.7mm, and the fiber-core density of the loose casing is more than 14.17 cores/mm²Preferably 15.8 cores/mm²The optical fiber is in an SZ twisted state in the loose tube, and the twisting pitch is 1000 mm. .

3) Cabling procedure: the (inner 7+ outer 13) sleeves are stranded around the water-blocking nonmetal central reinforcing core (water-blocking FRP), aramid fibers with extremely low shrinkage rate are used as binding yarns, and the sleeves are bound into a cable core. The non-metal central reinforced core of the layer-stranded air-blowing micro cable is a water-blocking FRP reinforced core coated to 2.25mm from 2.2mm in diameter, the surface of the FRP body is provided with a layer of water-blocking substance with the uniform curing thickness not exceeding 0.05mm, the water-blocking substance can absorb water, expand and block water, and the mode of using FRP and water-blocking yarns to block water is not excluded.

4) A sheath forming procedure: the sheath is extruded to the micro cable by adopting a double-layer co-extrusion mode outside the cable core, wherein the inner layer adopts low-density polyethylene, the outer layer adopts ultra-low friction coefficient sheath material, the inner layer of the sheath accounts for not more than 80% of the thickness of the whole sheath and is tightly combined with the outer layer of the sheath, the bonding force between the inner layer and the outer layer is more than 0.5N/mm, and a cable-opening rope is arranged between the inner layer of the sheath and the cable core and used for stripping the cable core.

The outer layer material for preparing the sheath is mainly prepared by blending and extruding materials such as polyformaldehyde, molybdenum disulfide, a compatilizer, an antioxidant, an aldehyde absorbing agent, a light shielding agent, a low-density polyethylene graft material and the like.

The co-extrusion processing temperature of the inner layer and the outer layer of the sheath is lower than 200 ℃.

Referring to fig. 2, a schematic diagram of the production of a high-core-density loose tube and the surplus length thereof according to an embodiment of the present invention is shown, an optical fiber unit includes an optical fiber 201, a fiber paste 202 and a PBT loose tube 203, but the optical fiber 201 is stranded in the PBT loose tube 203 in an SZ manner, all the optical fibers 201 are stranded around the center of the PBT loose tube 203 to generate the surplus length, the optical fibers 201 in the PBT loose tube 203 are more compact, the surplus length generated by the SZ stranding satisfies the bending requirement of the optical fiber unit, and an excessive gap is not required to be reserved between the tube wall of the PBT loose tube 203 and the optical fibers 201, so that the diameter of the PBT loose tube 203 can be made very small, and the optical fibers 201 generate the surplus length in the loose tube in a spiral manner. The extruder front-end equipment comprises the following components: an optical fiber pay-off stand 212, a stranding assembly 214, a paste injection system 211, and an extruder system 213, which are based on the extruder pre-equipment of fig. 1, and a stranding assembly is arranged after the optical fiber pay-off stand and before the paste injection system to strand the optical fiber 201.

The core density of the high core density loose tube of the present invention is described in further detail below with reference to example a and comparative example a, but the embodiments of the present invention are not limited thereto.

Comparative example a ordinary air-blown micro-cable 36F/T (F/T means the number of optical fibers in a single loose tube)

1) Fiber diameter 200um (+/-10um)

2) Secondary plastic coated optical fiber direct laying

3) Loose tube diameter 1.95mm (+/-0.05mm)

4) The wall thickness of the loose tube is 0.15mm

5) Core density of optical fiber unit: outer edge area of fiber core number/loose tube cross section

6) Sample number a # of labeled fiber unit

Example a high core Density Loose tube 36F/T

1) Fiber diameter 192um (+/-5um)

2) The optical fiber in the secondary plastic coating loose sleeve is SZ twisted

3) Loose tube diameter 1.7mm (+/-0.05mm)

4) The wall thickness of the loose tube is 0.14mm

6) Sample number b # of labeled fiber unit

TABLE 1 parameter table of air-blown optical cable

As can be seen from table 1, in the example a (sample a #) compared to the comparative example a (sample b #), the loose tube twisted by the optical fibers SZ in the step 2) can be made smaller in inner diameter due to the extra twist length, and the outer diameter of the loose tube can be relatively reduced, and the small-diameter optical fiber having a more uniform long flight diameter is objectively more favorable for reducing the diameter, so that the core density of the loose tube is increased, and the core density is increased by about 30% compared to the comparative example.

High-fiber-core-density ultra-low-friction-coefficient layer stranded air-blown micro cable

According to another aspect of the present invention, there is also provided a method for preparing an outer layer of a sheath of the high core density ultra-low friction coefficient layer-stranded air-blown micro-cable, comprising the steps of:

2) the mixture is transferred into a double-screw extruder for mixing, and then the sheath material is obtained after extrusion, cooling, granulation and drying in sequence;

Wherein, the mass part ratio and other technical parameters of the raw materials added in the step 1) are shown in the following examples 1-10 in the table 2.

The HDPE materials and preparation methods of the sheaths of comparative examples 1-4 in Table 2 employ existing conventional techniques.

The preparation method of the outer layer of the sheath of comparative examples 5 to 8 in table 2 is substantially the same as that of the present invention, except that the mass part ratio of each raw material in step 1) and the parameter collocation such as extrusion temperature are different.

Table 2 table of raw materials and test results of the relevant verification examples and comparative examples

The raw material ratios of the low density polyethylene graft materials used in examples 1 to 10 are shown in Table 3.

TABLE 3 raw material ratio table of low density polyethylene graft material

Step one:

as can be seen from table 2:

1) the core density of the air-blown micro cable of the No. 6 sample can reach 9.35 cores/mm²。

2) As can be seen from the samples No. 6/7/8/17/18, the amount of the additive added in the given range slightly affects the friction coefficient, and the grafting material mainly affects the bonding strength between the inner layer and the outer layer of the sheath, thereby being beneficial to production and processing and slightly affecting the friction coefficient of the sheath.

2) From the 2# sample and the 5# sample, it can be seen that in the same specification air-blowing pipeline, even under high duty ratio, the air-blowing effect is obviously much better due to the adoption of the material with ultra-low friction coefficient, and the core capacity is increased by 33%.

3) It can be seen from the 4# sample that the HDPE sheath air-blowing micro-cable is adopted, the air-blowing performance can barely meet the requirement that the IEC standard is larger than 1000m under the condition that the duty ratio is close to 60%, and great uncertainty exists, and it can be seen from the 3# sample that the HDPE sheath air-blowing micro-cable is adopted, the air-blowing performance can not meet the requirement that the IEC standard is larger than 1000m basically under the condition that the duty ratio is larger and 60% to 65%.

4) From the sample No. 4 and the sample No. 6, under the condition of meeting the air blowing requirement, in the air-blowing micro-tube for air-blowing communication with the same specification, the fiber core density of the air-blowing micro-cable is improved by 100% on the same scale, and the tube hole resource is greatly saved.

And (2) a summary II:

the test comparisons of the friction coefficients in the 16/12 mm-sized pipes of the air-blown microtube for air-blown communication, example 3 (sample # 7)/example 6 (sample # 10)/example 9 (sample # 13) and comparative example 3 (sample # 3)/comparative example 6 (sample # 16) of the micro cable, are made, and are shown in the test charts.

Comparing example 3 (sample # 7)/example 6 (sample # 10)/example 9 (sample # 13) of the micro cable with comparative example 3 (sample # 3)/comparative example 6 (sample # 16) of the micro cable, the friction coefficient in the pipe of the air-blown micro tube 16/12mm for air-blown communication can be seen: 1) the friction coefficient of the air-blowing micro cable with the ultralow friction coefficient is reduced by about 60% compared with that of a polyethylene sheath; 2) the air-blowing micro cable with ultralow friction coefficient is adopted, so that the fluctuation range of the friction coefficient is very small and is extremely balanced; 3) when the addition amount of the molybdenum disulfide is increased to a certain component ratio, the friction coefficient is not continuously reduced, but tends to be increased.

And (3) a summary III:

as can be seen from example 2 (sample # 6)/sample # 5 (sample # 9)/sample # 8 (sample # 12) and comparative example 7 (sample # 17)/sample # 8 (sample # 18), the addition of low density polyethylene graft materials in different component ratios promotes the adhesive strength between the outer layer and the inner layer of the sheath, and when the addition amount is more than 1 part, the adhesive strength is substantially satisfied to be more than 0.5N/mm, and when the addition amount is more than 1.5 parts, the adhesive strength must be more than 0.5N/mm.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. The layer-stranded air-blown micro cable with high fiber core density comprises a sheath and a cable core arranged in the sheath, wherein the cable core comprises a binding yarn, a central reinforced core and a plurality of optical fiber units, each optical fiber unit comprises a loose tube and an optical fiber bundle arranged in the loose tube, the optical fiber units are stranded around the central reinforced core, the binding yarn is bound on the stranded optical fiber units, the sheath is provided with an inner layer and an outer layer sleeved on the inner layer, and the inner layer is made of low-density ethylene;

the mixture for preparing the outer layer mainly comprises polyformaldehyde, molybdenum disulfide, a compatilizer, an antioxidant, an aldehyde absorbing agent, a light shielding agent and a low-density polyethylene grafting material;

2. The stranded air-blown micro cable with high fiber core density according to claim 1, wherein the mass parts of other components are as follows: 0.05 to 0.2 portion of compatilizer, 0.05 to 0.2 portion of antioxidant, 0.03 to 0.1 portion of aldehyde absorbing agent and 2 to 3 portions of light shielding agent.

3. The high core density layer stranded air blown micro cable of claim 1, wherein the optical fiber bundles within the loose tube of each optical fiber unit are in an SZ stranded state within the loose tube.

4. According toThe high core density stranded air blown micro-cable of claim 3, wherein each fiber unit has a core density greater than 14.17 cores/mm²And the stranding pitch of the optical fiber bundle of each optical fiber unit in the loose tube is more than 1000 mm.

5. The high core density layer stranded air blown micro cable of claim 1, wherein the friction coefficient of the sheath relative to the communication air blown micro tube of HDPE material is less than 0.1.

6. The high core density layer stranded air blown micro cable of claim 1, wherein said antioxidant is one or more of a polyphenol hindered phenolic antioxidant, a phosphorous acid antioxidant, a hindered amine.

7. The high core density layer stranded air blown micro cable of claim 1, wherein said light shielding agent is carbon black or hindered amine.

8. The layer-stranded air-blown micro-cable with high fiber core density according to claim 1, wherein the low-density polyethylene graft material is prepared by uniformly mixing low-density polyethylene, Maleic Anhydride (MAH) and 2, 5-dimethyl-2, 5-bis (tert-butylperoxy) hexane at normal temperature, and then mixing and granulating the mixture at 160-180 ℃ by using an extensional rheological extruder, wherein the mass part ratio of the low-density polyethylene to the Maleic Anhydride (MAH) to the 2, 5-dimethyl-2, 5-bis (tert-butylperoxy) hexane (commonly called as a bis-penta initiator) is (97-99): (1-2): (0.5-1).

9. The high core density stranded air blown micro-cable of claim 1, wherein the core density of the stranded air blown micro-cable is greater than 8.47 cores/mm²。

10. The high core density stranded air blown micro cable of claim 1, wherein the inner and outer layers of the jacket are tightly bonded and the bond is greater than 0.5N/mm.

11. The method for preparing the outer layer of the sheath of the layer stranded air blown micro cable with high core density as claimed in any one of claims 1 to 10, comprising the steps of:

12. The use of the high core density ultra-low friction coefficient layer-stranded air-blown micro-cable of any one of claims 1 to 10, wherein the air-blown laying is carried out in a pipeline with a duty cycle of 65% to 70%.