CN113970821A - Air-blowing micro cable capable of being used under large duty ratio, and preparation method and application of outer layer of air-blowing micro cable - Google Patents

Abstract

The invention discloses an air-blowing micro cable capable of being used under a large duty ratio, which comprises a sheath and a cable core arranged in the sheath, wherein the cable core comprises a binding yarn, a central reinforcing core and a plurality of optical fiber units; the mixture for preparing the outer layer mainly comprises polyformaldehyde, TPU, 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 pipeline 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

Air-blowing micro cable capable of being used under large duty ratio, and preparation method and application of outer layer of air-blowing micro cable

Technical Field

The invention belongs to the field of optical communication, and particularly relates to an air-blowing micro cable capable of being used under a large duty ratio, and a preparation method and application of an outer layer of the air-blowing 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 the air-blown micro cable which can be used under a large duty ratio, and the preparation method and the application of the outer layer thereof, wherein the inner layer of the air-blown micro cable sheath is made of low-density polyethylene, so that the smoothness of the air-blown micro cable is ensured, the air-blown micro cable is suitable for the bending requirement of an optical cable during air blowing, an ultralow-friction-coefficient material is developed as the outer layer of the sheath, the air-blown micro cable can be ensured to be applied in a long-distance air blowing manner in a pipeline with the duty ratio of 65-70%, and the air-blown effect meets the IEC-60794 standard requirement; 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 layer stranded air-blown micro-cable with high core density and large duty ratio, 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, TPU, a compatilizer, an antioxidant, an aldehyde absorbing agent, a light shielding agent and a low-density polyethylene grafting material;

in the mixture, the mass portion of the polyformaldehyde is 80-90 parts, and the mass portion of the TPU is 5-15 parts.

Preferably, the mass parts of the components are as follows: 1 to 3 portions of compatilizer, 0.05 to 0.2 portion of antioxidant, 0.03 to 0.1 portion of aldehyde absorbing agent, 2 to 3 portions of light shielding agent and 0.5 to 1.5 portions of low-density polyethylene graft material.

Preferably, the low-density 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 bis-penta vulcanizing agent) 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 is (97-99): (1-2): (0.5-1).

Preferably, the friction coefficient of the sheath with respect to the communication air-blown micro tube made of HDPE material is lower than 0.1, which is preferably 0.06.

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.

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/mm²(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-fly small-diameter optical fibers (fiber diameter 192um (+/-5 um)) 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 in a single optical fiber unit is more than 1000 mm.

Preferably, the outer diameter of the single loose tube in the sheath is 1.6mm-1.8mm, preferably 1.7mm, and the density of the optical fiber unit formed by the single loose tube and the optical fiber in the single loose tube is more than 14.17 cores/mm²And the purpose of high density of the single-tube fiber core is achieved.

Preferably, the plurality of sleeves are stranded in a certain way to realize that the density of the unit fiber core of the layer stranded air-blown micro cable is more than 8.47 cores/mm²。

The invention also provides a preparation method of the outer layer of the sheath, which is characterized by comprising the following steps:

1) putting polyformaldehyde and TPU 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 polyethylene grafting material, and uniformly mixing to form a mixture;

in the mixture, the mass part of polyformaldehyde is 80-90 parts, and the mass part of TPU is 5-15 parts;

2) mixing the mixture in a double-screw extruder, and then sequentially carrying out extrusion, cooling, granulation and drying to obtain the sheath material, 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 layer-stranded air-blown micro-cable with high fiber core density and capable of being used under a large duty cycle is further provided, and the layer-stranded air-blown micro-cable is laid in a pipeline with the duty cycle 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 Thermoplastic Polyurethane (TPU) with hardness of more than 60HA, preferably TPU with hardness of 65HA, mainly because part of ether bonds in polyformaldehyde molecules and TPU form hydrogen bonds, have certain compatibility, are easier to blend and extrude and process, are dispersed more uniformly in polyformaldehyde, have smaller dispersed phase size, can effectively dissipate energy when being subjected to external force, can improve the toughness of polyformaldehyde, and increase the capabilities of impact resistance, torsion resistance, bending and the like, especially are added according to a certain proportion, can further reduce the friction coefficient effect of the surface of the sheath, and according to the difference of the adding proportion, the abrasion resistance and the friction coefficient are slightly different, and the proportion of lower friction coefficient is preferably about 10% in the invention. The sheath can not be adhered to the pipe wall under the condition of laying the high-temperature high-pressure air-blowing strips.

The compatilizer is maleic anhydride, and promotes the dispersed phase TPU to be uniformly dispersed in the polyformaldehyde, so that the polyformaldehyde and the TPU well form a uniform sea-island structure; a physical or chemical or both physical and chemical region similar to an interpenetrating network structure can be formed between polyformaldehyde and TPU molecules, so that the impact strength of the TPU is greatly improved, and the sea-island structure is one of the real reasons that the friction coefficient of the sheath is extremely low and the fluctuation range is extremely small.

The antioxidant is polyphenol hindered phenol antioxidant, phosphorous acid antioxidant and high molecular weight hindered amine, preferably the weight ratio of the polyphenol hindered phenol antioxidant 0.01% + phosphorous acid antioxidant 0.01% + high molecular weight hindered amine in the mixture is the combination, and the using effect is good.

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.

The polyethylene grafting material enables the outer layer of the sheath and the inner layer of the sheath to be tightly combined and difficult to peel and separate.

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 traditional air-blown construction, is generally limited in that the duty ratio between the optical cable and the pipeline is not more than 60%, can have a good air-blown effect even if the duty ratio of the air-blown construction reaches 65% -70%, and meets the requirements of IEC-60794 standards. The sheath outer layer is formed by blending and extruding materials such as polyformaldehyde, Thermoplastic Polyurethane (TPU), a compatilizer, an antioxidant, an aldehyde absorbing agent, a light shielding agent and a polyethylene grafting material, the surface friction coefficient of the layer-stranded air-blown micro cable is greatly reduced, and the flexibility of the sheath inner layer 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 fiber in the high fiber core density air-blown micro cable is in an SZ twisted state in the loose tube, when the loose tube is bent, the optical fiber is hardly subjected to the pressure/tensile stress generated by the length difference of the inner edge fiber and the outer edge fiber of the tube because of the twisted surplus length, and the optical fiber is not subjected to the pressure of the tube wall in time in a small hollow space of the tube, so that the optical fiber is hardly influenced by macrobending and microbending, and the attenuation of the optical fiber is ensured to meet the requirement; 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, in the low-temperature (-40 ℃) environment, the low-density polyethylene is softer than the high-density polyethylene and softer than the high-density polyethylene, 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 tests for sample # 7, sample # 10 and sample # 13;

FIG. 5 is a graph of the results of the coefficient of friction test for sample # 16;

fig. 6 is a graph showing the results of the coefficient of friction test for 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 layer-stranded air-blown micro-cable capable of being used at a large duty ratio, 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, each of the optical fiber units includes a loose tube and an optical fiber bundle disposed in the loose tube, the optical fiber units are 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 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:

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

Secondary plastic coating: the process is one of key processes of the invention, like a normal casing paying-off process, 36 optical fibers are placed on a paying-off rack, the 36 optical fibers are arranged according to a certain rule before entering a mould of two sets of extruders, and penetrate into a twisting device capable of carrying out 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 a twisting pitch set by a process, the ratio of the equivalent cross section of the optical fibers in the casing to the inner diameter sectional area of the casing is more than 90%, and the optical fibers in the casing form twisting residue along the SZ twisting directionThe length is long, when the sleeve is bent, the optical fiber has surplus twisting length, the stress is small, the attenuation of the optical fiber is ensured to meet the requirement, the outer diameter of the produced high-fiber-core-density loose sleeve is 1.6-1.8 mm, the central value of the produced high-fiber-core-density loose sleeve is 1.7mm, and the fiber core density of the loose sleeve 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. .

Cabling procedure: 20 sleeve pipes (the inner 7 optical fiber units and the outer 13 optical fiber units) are stranded around the water-blocking nonmetal central reinforced core (water-blocking FRP), aramid fibers with extremely low shrinkage rate are used as binding yarns, and the sleeve pipes are bound into a cable core. The non-metal central reinforcement of layer stranded air-blown micro cable is excellent, 2.2mm coats the FRP reinforcing core that blocks water of 2.25mm, and its FRP body surface has the even solidification thickness to be no more than 0.05 mm's of a layer material that blocks water, but the expansion that absorbs water blocks water, does not exclude to use FRP to add the yarn mode that blocks water to block water and block water.

Sheathing: and extruding a sheath for 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 is extruded with a sheath material with an ultralow friction coefficient, 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, and an open cable is arranged between the inner layer of the sheath and the cable core.

The sheath outer layer material is mainly prepared by blending and extruding materials such as polyformaldehyde, TPU (thermoplastic polyurethane), compatilizer, antioxidant, aldehyde absorbing agent, light shielding agent, 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 high core density loose tube of the present invention will be described in further detail below with reference to examples and comparative examples, 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) Marker cannula sample number a #

Example a high core Density Loose tube 36F/T

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

2) Secondary plastic coated optical fiber SZ twisted into loose tube

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

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

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

6) Sample number b # of labeled cannula

TABLE 1 parameter table of air-blown optical cable

As can be seen from table 1, in the example a, compared with the comparative example 1, the loose tube twisted by the optical fiber SZ is used for the sample a #, the inner diameter of the loose tube can be made smaller due to the extra twisting length, the outer diameter of the loose tube can be reduced compared with the sample b #, and the diameter can be objectively reduced by selecting the small-diameter optical fiber with more uniform long flying diameter, so that the core density of the loose tube is increased, and the core density is increased by nearly 30% compared with the comparative example a.

According to another aspect of the present invention, there is also provided a method for preparing an outer layer of a sheath of a layer-twisted air-blown micro-cable with a high core density and a large duty cycle, comprising the steps of:

1) putting polyformaldehyde and TPU 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 polyethylene grafting material, and uniformly mixing to form a mixture;

2) mixing the mixture in a double-screw extruder, and then sequentially carrying out extrusion, cooling, granulation and drying to obtain a sheath material;

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

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

The 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 7 in table 2 is substantially the same as that of the present invention except that the mixing ratio of the raw materials in parts by mass and the extrusion temperature in step 1) 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

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) From the 2# sample and the 5# sample, it can be seen that in the same-specification pipeline, even at a high duty ratio, the air blowing effect is obviously much better due to the adoption of the material with the ultralow 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 friction coefficients of the micro-cable example 3 (sample # 7)/example 6 (sample # 10)/example 9 (sample # 13) and the micro-cable comparative example 3 (sample # 3)/comparative example 6 (sample # 16) in the 16/12mm sized air-blown micro-tube for air-blown communication were compared for test, and are shown in fig. 4 to 6.

Comparing the friction coefficients of the micro cable example 3 (sample # 7)/example 6 (sample # 10)/example 9 (sample # 13) and the micro cable comparative example 3 (sample # 3), the comparative example 5 (sample # 15), and the comparative example 6 (sample # 16) in the air-blown micro tube 16/12mm comparative pipe for air-blown communication, it can be seen that: 1) the friction coefficient of the air-blowing micro cable with the ultralow friction coefficient is reduced by about 1/2 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) after TPU with different component proportions is added, the surface friction coefficient can be improved, and when the addition amount is increased to a certain component proportion, the friction coefficient is not continuously reduced but tends to be increased; 4) comparing the sample No. 6/7/9/12 of the micro cable example with the sample No. 17 of the micro cable, it can be seen that the adhesive strength between the outer layer and the inner layer of the sheath is promoted by adding the low-density polyethylene graft materials with different component ratios, when the adding amount is more than 0.5 part, the adhesive force is basically more than 0.5N/mm, when the adding amount is more than 1 part, the adhesive force is definitely more than 0.5N/mm, and the adhesive force between the inner layer and the outer layer of the sheath without the graft materials is basically not existed.

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 (12)

1. The air-blowing micro cable capable of being used under the large duty ratio 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 twisted around the central reinforced core, the binding yarn is bound on the twisted 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, TPU, a compatilizer, an antioxidant, an aldehyde absorbing agent, a light shielding agent and a low-density polyethylene grafting material;

in the mixture, the mass portion of the polyformaldehyde is 80-90 parts, and the mass portion of the TPU is 5-15 parts.

2. The blown micro cable usable at a large duty cycle according to claim 1, wherein the mass fraction of each component is as follows: 1 to 3 portions of compatilizer, 0.05 to 0.2 portion of antioxidant, 0.03 to 0.1 portion of aldehyde absorbing agent, 2 to 3 portions of light shielding agent and 0.5 to 1.5 portions of polyethylene grafting material.

3. The air-blown micro-cable for use at high duty cycles of claim 1, wherein the optical fibers within each loose tube are in an SZ stranded state within the loose tube.

4. The air-blown micro-cable for use at high duty cycles of claim 3, wherein the core density of the optical fiber unit consisting of the single loose tube inside the sheath and the optical fibers inside the single loose tube is greater than 14.17 cores/mm²And the stranding pitch of each optical fiber in the corresponding loose tube is more than 1000 mm.

5. The air-blown micro-cable for use at a high duty cycle according to claim 1, wherein the friction coefficient of the sheath with respect to the HDPE air-blown communication micro-tube is less than 0.1.

6. The air-blown micro-cable of claim 1, wherein the antioxidant is one or more of a polyphenol hindered phenol antioxidant, a phosphorous acid antioxidant, and a hindered amine.

7. A blown micro-cable usable at high duty cycles according to claim 1, wherein said light shielding agent is carbon black or a hindered amine.

8. The air-blowing micro cable capable of being used at a large duty ratio 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 (commonly called as a bis-penta initiator) at normal temperature, and then mixing and granulating the mixture at 160-180 ℃ by using a stretching 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).

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

10. The air-blown micro-cable of claim 1, wherein the inner and outer layers of the jacket are tightly bonded, and the bonding strength between the inner and outer layers is greater than 0.5N/mm.

11. The method for preparing the outer layer of the sheath of the air-blown micro-cable capable of being used under the large duty cycle according to any one of claims 1 to 10, which is characterized by comprising the following steps:

1) putting polyformaldehyde and TPU 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 polyethylene grafting material, and uniformly mixing to form a mixture;

in the mixture, the mass part of polyformaldehyde is 80-90 parts, and the mass part of TPU is 5-15 parts;

2) mixing the mixture in a double-screw extruder, and then sequentially carrying out extrusion, cooling, granulation and drying to obtain the sheath material, 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.

12. Use of an air-blowing micro-cable according to any one of claims 1 to 10, wherein the air-blowing micro-cable is laid in an air-blowing micro-tube made of HDPE material with a duty ratio of 65% to 70% for air-blowing communication.

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