Full-dry loose tube optical unit, preparation method thereof and full-dry optical cable

Abstract

The invention belongs to the field of optical communication, and particularly relates to a full-dry loose tube optical unit, a preparation method thereof and a full-dry optical cable. The water-blocking microspheres with the water-blocking powder surface coated with the modified material are used for preparing the full-dry type loose tube optical unit, powder can be uniformly discharged through powder spraying equipment, the phenomenon that a powder spraying air pipe is blocked is effectively avoided, meanwhile, the water-blocking microspheres blown into the inner cavity of the loose tube can be attached to the inner wall of the loose tube, and the water-blocking effect is good. The modified material wrapping the surfaces of the water-blocking microspheres melts to form a buffer layer adhered to the inner wall of the loose tube, and meanwhile, the water-blocking powder in the water-blocking microspheres is uniformly dispersed on the periphery of the light guide element, so that the problem of accumulation of the water-blocking powder is effectively solved, and an excellent water-blocking effect is achieved. In addition, the buffer layer adhered to the inner wall of the loose tube can effectively solve the problem that optical fiber attenuation is increased due to small-radius bending of the optical fiber caused by friction accumulation of the light guide element on the inner wall of the loose tube, additional attenuation is effectively reduced, and the consistency of the excess length of the optical fiber is good.

Description

Technical Field

[0001] This application belongs to the field of optical communication. More specifically, it relates to a fully dry loose tube optical unit, a preparation method thereof, and a fully dry optical cable. Background Art

[0002] There is no grease filling in the fully dry optical cable, so there is no grease pollution during the manufacturing and construction processes, and it is not necessary to clean the grease, which is very convenient. The water blocking materials of the fully dry optical cable mainly include two categories: water blocking yarn and water blocking powder. When using water blocking yarn to prepare the loose tube optical unit of the fully dry optical cable, problems such as poor consistency of the fiber slack length and accumulation of fibers against the wall lead to the inability to further reduce the size of the tube. At the same time, when using ordinary water blocking powder to prepare the loose tube optical unit of the fully dry optical cable, the ordinary water blocking powder is prone to getting damp and caking, resulting in uneven powder spraying, and even blocking the air pipe of the powder spraying equipment, seriously affecting the production efficiency and product quality. Summary of the Invention

[0003] Aiming at the defects of the prior art, the purpose of this application is to provide a fully dry loose tube optical unit, a preparation method thereof, and a fully dry optical cable, aiming to solve the problems that when ordinary water blocking powder is used to prepare the fully dry loose tube optical unit, it is prone to getting damp and caking, uneven powder spraying, blocking the air pipe of the powder spraying equipment, poor water blocking effect, high additional attenuation value of the obtained fully dry loose tube optical unit, and poor consistency of the fiber slack length.

[0004] To achieve the above purpose, in the first aspect, this application provides a fully dry loose tube optical unit, including an optical guiding element and a loose tube for accommodating the optical guiding element. A buffer layer is adhered to the inner wall of the loose tube, and water blocking powder is dispersed on the outer periphery of the optical guiding element; The buffer layer is formed by melting a modified material coating the surface of water blocking microspheres and adhering it to the inner wall of the loose tube. At the same time, the water blocking powder inside the water blocking microspheres is dispersed on the outer periphery of the optical guiding element; The modified material is an elastomer modified by a compatibilizer, and the elastic modulus of the elastomer is 50 MPa to 500 MPa.

[0005] Preferably, the average particle size of the water blocking microspheres is 50 μm to 200 μm.

[0006] Preferably, the compatibilizer is a maleic anhydride-based compatibilizer, preferably one or more of maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene, maleic anhydride grafted POE, and maleic anhydride grafted SEBS.

[0007] Preferably, the elastomer is thermoplastic polyurethane and / or thermoplastic elastomer.

[0008] Preferably, the dosage of the compatibilizer is 1 wt% to 10 wt% of the mass of the elastomer.

[0009] Preferably, the water blocking powder is sodium polyacrylate and / or acrylamide, and the particle size is 10 μm to 50 μm.

[0010] Preferably, the method for preparing the water blocking microspheres includes the following steps: Blend and melt-extrude a compatibilizer and an elastomer to obtain a modified material, then mix a solution containing the water blocking powder with an organic solution of the modified material, and after stirring and drying, obtain microspheres with the modified material coated on the surface of the water blocking powder, that is, water blocking microspheres.

[0011] Preferably, the mass ratio of the modified material to the water blocking powder is (5 - 8):(2 - 5).

[0012] Preferably, the material of the loose tube is one or more of polyamide, polycarbonate, dibutyl terephthalate, and polypropylene.

[0013] Preferably, the outer diameter of the loose tube is 1.5 mm to 15 mm, the wall thickness is 0.1 mm to 1.0 mm, and the elastic modulus is 1000 MPa to 3000 MPa.

[0014] Preferably, the optical guiding element is a single-mode optical fiber, a multi-mode optical fiber, a loose fiber, an optical fiber ribbon, an optical fiber ribbon array, or a flexible optical fiber ribbon.

[0015] In a second aspect, the present application provides a method for preparing the above-mentioned all-dry loose tube optical unit, including the following steps: S1. Extrude the loose tube forming material outside the bundled optical guiding elements to form a loose tube substrate; S2. Blow the above-mentioned water blocking microspheres into the inner cavity of the loose tube substrate. The water blocking microspheres adhere to the inner wall of the loose tube substrate. The modified material coated on the surface of the water blocking microspheres melts to form a buffer layer adhering to the inner wall. At the same time, the water blocking powder inside the water blocking microspheres is dispersed around the optical guiding elements, and then cooling and shaping are carried out, so that the loose tube substrate is cooled and shaped into a loose tube, and the above-mentioned all-dry loose tube optical unit is prepared.

[0016] Preferably, the temperature of the inner wall of the loose tube substrate is 10 °C to 50 °C higher than the melting point of the modified material.

[0017] In a third aspect, the present application provides an all-dry optical cable, which includes the above-mentioned all-dry loose tube optical unit or an all-dry loose tube optical unit prepared by the above-mentioned preparation method Preferably, the above-mentioned all-dry optical cable includes a central tube optical cable or a stranded optical cable.

[0018] Generally speaking, compared with the prior art through the above technical solutions conceived by the present application, the main technical advantages are as follows: In this application, by using microspheres with a surface-coated modified material for water-blocking powder (i.e., water-blocking microspheres) to prepare a fully dry loose tube optical unit, powder can be evenly discharged through a powder spraying device, effectively avoiding the phenomenon that the powder spraying air pipe is blocked due to the damp caking of the water-blocking powder. Further, the water-blocking microspheres blown into the inner cavity of the loose tube through the powder spraying device can adhere to the inner wall of the loose tube, and the modified material coated on the surface of the water-blocking microspheres melts to form a buffer layer adhering to the inner wall of the loose tube. At the same time, the water-blocking powder inside the water-blocking microspheres is evenly dispersed on the outer periphery of the optical guiding element, which can effectively solve the problem of water-blocking powder accumulation and exert an excellent water-blocking effect. In addition, the buffer layer adhering to the inner wall of the loose tube substrate can effectively solve the problem that the optical guiding element causes small-radius bending of the optical fiber due to friction and accumulation on the inner wall of the loose tube, resulting in an increase in optical fiber attenuation, effectively reducing the additional attenuation, and the optical fiber surplus length has good consistency. In practical applications, the size of the loose tube can be further reduced, and the optical fiber density can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic cross-sectional view of a preparation device for a fully dry loose tube optical unit provided by an embodiment of the present application; Figure 2 is a schematic cross-sectional structure view of the fully dry loose tube optical unit provided by Application Examples 1-2, 4-7 of the present application; Figure 3 is a schematic cross-sectional structure view of the fully dry loose tube optical unit provided by Application Example 3 of the present application; In all the drawings, the same reference numerals are used to represent the same elements or structures, where: 1 is an extrusion die; 1.1 is a die cover; 1.2 is a die core; 2 is a cluster powder spraying composite die; 2.1 is a powder spraying device; 2.2 is an optical guiding element introducing needle; 3 is a cooling water tank; 4.1 is an optical guiding element; 4.2 is a buffer layer; 4.3 is water-blocking powder; 4.4 is a loose tube. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] In the description of the present application, it should be understood that the term "and / or" is an association relationship describing associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. The symbol " / " in this article represents an "or" relationship between associated objects, for example, A / B represents A or B.

[0022] In the description and claims of the present application, terms such as "first" and "second" are used to distinguish different objects, rather than to describe a specific order of objects, and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features.

[0023] In the description of the embodiments of the present application, words such as "exemplary" or "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0024] In the description of the embodiments of the present application, unless otherwise specified, the meaning of "a plurality" refers to two or more.

[0025] The present application provides a fully dry loose tube optical unit, including an optical guiding element and a loose tube for accommodating the optical guiding element; wherein, a buffer layer is adhered to the inner wall of the loose tube, and a water blocking powder is dispersed on the outer periphery of the optical guiding element; The buffer layer is formed by melting a modified material coated on the surface of water blocking microspheres and adhering it to the inner wall of the loose tube. At the same time, the water blocking powder inside the water blocking microspheres is dispersed on the outer periphery of the optical guiding element; The modified material is an elastomer modified by a compatibilizer, and the elastic modulus of the elastomer is 50 MPa to 500 MPa.

[0026] In some embodiments, the preparation method of the water blocking microspheres includes the following steps: blending and melt-extruding a compatibilizer and an elastomer to obtain a modified material, then mixing a solution containing a water blocking powder and an organic solution of the modified material, and stirring and drying to obtain microspheres with a modified material coated on the surface of the water blocking powder, that is, water blocking microspheres. It can be understood that those skilled in the art can select other methods to prepare water blocking microspheres according to laboratory conditions, which are all applicable to the present application.

[0027] By using microspheres with a modified material coated on the surface of the water blocking powder (i.e., water blocking microspheres) to prepare a fully dry loose tube optical unit, the present application can evenly powder through a powder spraying device such as a spray gun, avoiding the phenomenon that the powder spraying air pipe is blocked due to the damp caking of the water blocking powder. At the same time, the blown water blocking microspheres can adhere to the inner wall of the loose tube under the action of the compatibilizer, and the modified material wrapped on the surface of the water blocking microspheres melts and forms a buffer layer adhered to the loose tube. At the same time, the water blocking powder inside the water blocking microspheres is evenly dispersed on the outer periphery of the optical guiding element, which can effectively solve the problem of water blocking powder accumulation and achieve an excellent water blocking effect. In addition, the buffer layer adhered to the inner wall of the loose tube can effectively solve the problem that the friction and accumulation of the optical guiding element on the inner wall of the loose tube cause small-radius bending of the optical fiber and increase the optical fiber attenuation, and the optical fiber surplus length has good consistency.

[0028] In some embodiments, the above-mentioned modified material is an elastomer modified by a compatibilizer, which can enable the water-blocking microspheres to adhere well to the inner wall of the loose tube, preventing the water-blocking microspheres from falling off the inner wall. Further, the modified material coated on the surface of the water-blocking microspheres melts to form a buffer layer, which plays a buffering role between the optical waveguide element and the loose tube. In some embodiments, the elastic modulus of the above-mentioned elastomer is 50 MPa to 500 MPa, and it can be selected from thermoplastic polyurethane (TPU) or thermoplastic elastomer (TPE). When the modulus of the elastomer is too low, it is difficult to prepare the water-blocking microspheres, and it is not easy to form spheres, and a modified material coating cannot be formed on the surface of the water-blocking powder; when the modulus of the elastomer is too high, the buffer layer formed on the inner wall of the loose tube cannot play a good buffering role, and the problem of small-radius bending of the optical fiber cannot be effectively improved, and the optical fiber attenuation increases.

[0029] Generally, the above-mentioned compatibilizer is a maleic anhydride-based compatibilizer, which can be but is not limited to one or more of maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene, maleic anhydride grafted POE, and maleic anhydride grafted SEBS. In some embodiments, the dosage of the above-mentioned compatibilizer is 1 wt% to 10 wt% of the mass of the above-mentioned elastomer. When the dosage of the compatibilizer is too small, the adhesion between the water-blocking microspheres and the inner wall of the loose tube is not firm; when the dosage of the compatibilizer is too large, the mechanical properties of the elastomer material are affected.

[0030] It can be understood that the present application has no special limitation on the material of the above-mentioned water-blocking powder, and the water-blocking powders reported in the prior art applicable to the preparation of all-dry loose tube optical units or all-dry optical cables are applicable to the present application, including but not limited to sodium polyacrylate, acrylamide, etc. In some embodiments, the average particle size of the above-mentioned water-blocking powder is 10 µm to 50 µm. When the particle size of the water-blocking powder is too small, it is easy to agglomerate together, and it is difficult to prepare the water-blocking microspheres; when the particle size of the water-blocking powder is too large, it is not easy to disperse in the solution.

[0031] In some embodiments, the mass ratio of the above-mentioned modified material to the above-mentioned water-blocking powder is (8 to 5):(5 to 2). To achieve a better coating effect, the dosage of the modified material needs to be more than that of the water-blocking powder, so as to form the effect of coating the modified material on the surface of the water-blocking powder. When the dosage of the modified material is less, some of the water-blocking powder is not coated, and the prepared water-blocking microspheres are prone to moisture absorption and caking, which does not meet the use requirements.

[0032] In some embodiments, the above solution containing the water blocking powder is formed by uniformly mixing the water blocking powder and a first solvent. The above first solvent may be, but is not limited to, water, alkaline solution, etc. It can be understood that the present application does not limit the above mixing method, such as, but not limited to, mechanical stirring, ultrasonic mixing, etc. Further, those skilled in the art can adaptively adjust the rotation speed and time of mechanical stirring, the time of ultrasonic mixing, etc. as long as a modified material coating layer can be formed on the surface of the water blocking powder, which is within the protection scope of the present application. The present application does not limit the ratio of the water blocking powder and the first solvent, as long as the water blocking powder can be uniformly mixed in the first solvent, which is within the protection scope of the present application. In some embodiments, in order to make the water blocking powder better dissolve in the first solvent, in the above solution containing the water blocking powder, the concentration of the water blocking powder may be, but is not limited to, 30wt% - 50wt%.

[0033] In some embodiments, the above organic solution of the modified material is formed by uniformly mixing the modified material and an organic solvent. The above organic solvent includes, but is not limited to, dimethylformamide (DMF), tetrahydrofuran (THF), toluene, chloroform, dichloromethane, etc. The present application does not limit the ratio of the modified material and the organic solvent, as long as the modified material can be uniformly mixed in the organic solvent, which is within the protection scope of the present application. In some embodiments, in the above organic solution of the modified material, the concentration of the modified material may be, but is not limited to, 5wt% - 10wt%.

[0034] In some embodiments, the above water blocking powder solution is added in a dropwise manner.

[0035] In some embodiments, the average particle size of the above water blocking microspheres is 50μm - 200μm, and they can uniformly powder through common powder spraying devices such as spray guns.

[0036] It can be understood that the present application does not limit the number of layers of the loose tube in the above all-dry loose tube optical unit, and the above loose tube can be a single-layer structure or a multi-layer structure. The present application does not make special limitations on the material type of the above loose tube, and the materials reported in the prior art applicable to the preparation of the loose tube are all applicable to the present application. In some embodiments, the material of the above loose tube is one of polyamide (PA), polycarbonate (PC), polybutylene terephthalate (PBT), polypropylene (PP), a mixture of multiple ones, or a composite of multiple ones. In some embodiments, the outer diameter of the above loose tube is 1.5mm - 15mm, the wall thickness is 0.1mm - 1.0mm, and the elastic modulus is 1000MPa - 3000MPa, having excellent mechanical properties.

[0037] In some embodiments, the above optical guiding element is a single-mode optical fiber, a multi-mode optical fiber, a loose fiber, a fiber ribbon, a fiber ribbon array, a flexible fiber ribbon, etc.

[0038] Those skilled in the art can select an appropriate filling amount of water-blocking microspheres according to the actual application scenarios of the all-dry loose tube optical unit and the inner diameter of the loose tube, etc. In some embodiments, in the above all-dry loose tube optical unit, the ratio of the filling amount of water-blocking microspheres to the length of the loose tube is 0.02 g / m to 6 g / m.

[0039] On the other hand, the present application also provides a method for preparing the above all-dry loose tube optical unit, including the following steps: S1. Extrude the loose tube forming material outside the bundled optical guiding elements to form a loose tube base material; S2. Blow the above water-blocking microspheres into the inner cavity of the above loose tube base material. The water-blocking microspheres adhere to the inner wall, and the modified material coated on the surface of the water-blocking microspheres melts to form a buffer layer adhering to the inner wall. At the same time, the water-blocking powder inside the water-blocking microspheres is dispersed on the outer periphery of the above optical guiding elements, and then cooling and shaping are carried out to make the above loose tube base material cool and shape into a loose tube, thus obtaining the above all-dry loose tube optical unit.

[0040] In some embodiments, it is prepared by using the preparation device of the all-dry loose tube optical unit as shown in Figure 1 . The preparation device includes an annular extrusion die 1 and a tubular cluster powder spraying composite die 2; the extrusion die 1 is nested coaxially with the cluster powder spraying composite die 2 as the center. Among them, the extrusion die 1 is composed of a die cover 1.1 and a die core 1.2 to form an annular extrusion port; the cluster powder spraying composite die 2 is composed of a powder spraying device 2.1 on the outer side and an optical guiding element introducing needle 2.2 on the inner side. The powder spraying device 2.1 and the optical guiding element introducing needle 2.2 form an annular cavity, and the annular cavity has an inclination angle obliquely outward. This inclination angle is the included angle between the annular cavity and the axis of the sleeve. The included angle between the annular cavity and the axis of the sleeve is 5° to 30° so that the water-blocking microspheres can be evenly blown into the inner cavity of the loose tube. The powder spraying device 2.1 is provided with one or more water-blocking microsphere filling ports. The preparation device also includes a cooling water tank 3.

[0041] In some embodiments, using the above device to prepare the all-dry loose tube optical unit includes the following steps: (1) Bundle the optical guiding elements through the optical guiding element introducing needle, and at the same time extrude the loose tube forming material through the extrusion die outside the bundled optical guiding elements to form a loose tube base material; (2) Blow the water-blocking microspheres into the inner cavity of the above loose tube base material through the powder spraying device. The water-blocking microspheres adhere to the inner wall of the loose tube base material. The modified material coated on the surface of the water-blocking microspheres melts to form a buffer layer adhering to the inner wall. At the same time, the water-blocking powder inside the microspheres is dispersed on the outer periphery of the above optical guiding elements, and then cooling and shaping are carried out to make the above loose tube base material cool and shape into a loose tube, that is, the all-dry loose tube optical unit is obtained.

[0042] In some embodiments, the temperature of the inner wall of the loose tube substrate is 10°C to 50°C higher than the melting point of the above-mentioned modified material, so that the water-blocking microspheres blown into the inner cavity of the loose tube substrate melt after adhering to the inner wall to form a buffer layer. When the temperature of the inner wall of the loose tube substrate is too high, the water-blocking microspheres melt before adhering to the inner wall after being blown into the inner cavity of the loose tube substrate, and a buffer layer cannot be formed.

[0043] The present application also provides a fully dry optical cable, which includes the above-mentioned fully dry loose tube optical unit.

[0044] In some embodiments, the above-mentioned fully dry optical cable includes a central tube optical cable or a stranded optical cable.

[0045] In some embodiments, the above-mentioned central tube optical cable includes the above-mentioned fully dry loose tube optical unit, other possible components, and an outer sheath; wherein, the above-mentioned outer sheath is coated on the outside of the above-mentioned fully dry loose tube optical unit. Those skilled in the art can select appropriate outer sheath materials according to the application scenarios of the optical cable, including but not limited to polyethylene, elastomeric materials, etc.

[0046] In some embodiments, the above-mentioned stranded optical cable includes a plurality of the above-mentioned fully dry loose tube optical units, a central strength member, other possible components, and an outer sheath; wherein, the plurality of the above-mentioned fully dry loose tube optical units are stranded and wound around the above-mentioned central strength member and are embedded in the inner side of the above-mentioned outer sheath. Those skilled in the art can select appropriate outer sheath materials according to the application scenarios of the optical cable, including but not limited to polyethylene, elastomeric materials, etc.

[0047] It should be understood that materials with the same or similar types, models, qualities, properties, or functions as the reagents and instruments used in the following embodiments can be used to implement the present application. The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments can be obtained from commercial sources unless otherwise specified.

[0048] The following are examples and comparative examples: Example 1 The preparation method of the water-blocking microspheres provided in this embodiment includes the following steps: (1) High-speed stirring of 97 wt% TPE (elastic modulus of 200 MPa) and 3 wt% maleic anhydride for blending, and then subjecting the blended material to twin-screw melting and shearing, followed by extrusion, drawing, pelletizing, and drying processes to prepare a modified TPE material for standby.

[0049] (2) Dissolve the above-mentioned modified material in dichloromethane to form an oil phase, where the concentration of the modified material is 5 wt%. Dissolve sodium polyacrylate with an average particle size of 30 µm in a sodium hydroxide solution to form an aqueous phase, where the concentration of sodium polyacrylate is 30 wt%. Then, drop the aqueous phase into the oil phase, where the mass ratio of the modified TPE material to sodium polyacrylate is 7:3, stir to form a reaction solution with the oil phase coating the aqueous phase, and then evaporate, wash, and dry to obtain microspheres with the modified material coated on the surface of the water-blocking powder, that is, water-blocking microspheres, with an average particle size of 120 µm.

[0050] Example 2 The preparation method of the water-blocking microspheres provided in this example includes the following steps: (1) High-speed stir 95 wt% TPE (with an elastic modulus of 500 MPa) and 5 wt% maleic anhydride for blending, and then subject the blended material to twin-screw melt shearing, followed by extrusion, strand drawing, pelletizing, and drying processes to prepare a modified TPE material for standby.

[0051] (2) Dissolve the above-mentioned modified material in dichloromethane to form an oil phase, where the concentration of the modified material is 8 wt%. Dissolve sodium polyacrylate with an average particle size of 30 µm in a sodium hydroxide solution to form an aqueous phase, where the concentration of sodium polyacrylate is 40 wt%. Then, drop the aqueous phase into the oil phase, where the mass ratio of the modified TPE material to sodium polyacrylate is 5:5, stir to form a reaction solution with the oil phase coating the aqueous phase, and then evaporate, wash, and dry to obtain microspheres with the modified material coated on the surface of the water-blocking powder, that is, water-blocking microspheres, with an average particle size of 150 µm.

[0052] Example 3 The preparation method of the water-blocking microspheres provided in this example includes the following steps: (1) High-speed stir 99 wt% TPE (with an elastic modulus of 200 MPa) and 1 wt% maleic anhydride for blending, and then subject the blended material to twin-screw melt shearing, followed by extrusion, strand drawing, pelletizing, and drying processes to prepare a modified TPE material for standby.

[0053] (2) Dissolve the above-mentioned modified material in dichloromethane to form an oil phase, where the concentration of the modified material is 10 wt%. Dissolve sodium polyacrylate with an average particle size of 30 µm in a sodium hydroxide solution to form an aqueous phase, where the concentration of sodium polyacrylate is 30 wt%. Then, drop the aqueous phase into the oil phase, where the mass ratio of the modified TPE material to sodium polyacrylate is 8:5, stir to form a reaction solution with the oil phase coating the aqueous phase, and then evaporate, wash, and dry to obtain microspheres with the modified material coated on the surface of the water-blocking powder, that is, water-blocking microspheres, with an average particle size of 130 µm.

[0054] Example 4 The preparation method of the water-blocking microspheres provided in this example includes the following steps: (1) High-speed stir 90 wt% TPE (with an elastic modulus of 50 MPa) and 10 wt% maleic anhydride for blending. Then, subject the blended material to twin-screw melt shearing, followed by extrusion, strand pelletization, and drying processes to prepare a modified TPE material for standby use.

[0055] (2) Dissolve the above-mentioned modified material in dichloromethane to form an oil phase, where the concentration of the modified material is 5 wt%. Dissolve sodium polyacrylate with an average particle size of 30 µm in a sodium hydroxide solution to form an aqueous phase, where the concentration of sodium polyacrylate is 50 wt%. Then, drop the aqueous phase into the oil phase, where the mass ratio of the modified TPE material to sodium polyacrylate is 8:2. Stir to form a reaction solution with the oil phase coating the aqueous phase, and then evaporate, wash, and dry to obtain microspheres with the modified material coated on the surface of the water-blocking powder, i.e., water-blocking microspheres, with an average particle size of 90 µm.

[0056] Application Examples 1 - 7 Adopt the preparation device of the all-dry loose tube optical unit as Figure 1 shown, and use the water-blocking microspheres prepared in Examples 1 - 4 to prepare the all-dry loose tube optical unit. This preparation device includes an annular extrusion die 1 and a tubular cluster powder spraying composite die 2; the extrusion die 1 is nested coaxially with the cluster powder spraying composite die 2 as the center. Among them, the extrusion die 1 consists of a die cover 1.1 and a die core 1.2, forming an annular extrusion outlet; the cluster powder spraying composite die 2 consists of a powder spraying device 2.1 and an optical fiber element introducing needle 2.2. The powder spraying device 2.1 and the optical fiber element introducing needle 2.2 form an annular cavity, which has an inclination angle obliquely outward, and the angle between the annular cavity and the axis of the sleeve is 10°. The powder spraying device 2.1 is provided with one or more water-blocking microsphere charging ports. This preparation device also includes a cooling water tank 3.

[0057] The design parameters of the all-dry loose tube optical units in Application Examples 1 - 7 and Comparative Example 1 are shown in Table 1, and the preparation method includes the following steps: (1) Bundle the optical fiber elements 4.1 through the optical fiber element introducing needle 2.2, and at the same time extrude the loose tube forming material through the extrusion die 1 outside the bundled optical fiber elements 4.1 to form a loose tube substrate. (2) Blow the prepared water-blocking microspheres into the inner cavity of the above-mentioned loose tube substrate through the powder spraying device 2.1. The water-blocking microspheres adhere to the inner wall of the loose tube substrate, where the modified material coated on the surface of the water-blocking microspheres melts to form a buffer layer 4.2 adhering to the inner wall. At the same time, the water-blocking powder 4.3 inside the microspheres is dispersed on the outer periphery of the bundled optical fiber elements 4.1. Then, perform cooling and shaping to make the above-mentioned loose tube substrate cool and shape into a loose tube 4.4, that is, the all-dry loose tube optical unit is prepared.

[0058] The structures of the all-dry loose tube optical units prepared in Application Examples 1 - 2 and Application Examples 4 - 7 are asFigure 2 As shown in the figure, it includes a loose tube 4.4, a buffer layer 4.2 adhered to the inner wall of the loose tube, a bundle of optical waveguide elements 4.1 accommodated in the loose tube, and a water blocking powder 4.3 dispersed on the outer periphery of the optical waveguide elements; among them, the optical waveguide element 4.1 is a single-mode optical fiber.

[0059] The structure of the all-dry loose tube optical unit prepared in Application Example 3 is as Figure 3 shown in the figure, it includes a loose tube 4.4, a buffer layer 4.2 adhered to the inner wall of the loose tube, a bundle of optical waveguide elements 4.1 accommodated in the loose tube, and a water blocking powder 4.3 dispersed on the outer periphery of the optical waveguide elements; among them, the optical waveguide element 4.1 is an optical fiber ribbon.

[0060] The structure of the all-dry loose tube optical unit prepared in Comparative Example 1 is as Figure 2 shown in the figure. The design parameters of the all-dry loose tube optical unit are the same as those in Application Example 7, except that the water blocking powder used in Comparative Example 1 is a common water blocking powder, that is, sodium polyacrylate with an average particle size of 90 µm.

[0061] Table 1 Design parameters of the all-dry loose tube optical unit

[0062] The performance of the all-dry loose tube optical unit prepared above was tested, and the test method is as follows: 1) Water blocking performance: Refer to GB / T 7424.22-2021 "General specification for optical cables - Part 22: Basic test methods for optical cables - Environmental performance test methods" to conduct a water seepage test to test the water blocking performance of the all-dry loose tube optical unit. Specifically, take a 3m sample of the all-dry loose tube optical unit and place it on a test bench with a 1m water column, and observe whether water seeps or leaks from the end face within 24h.

[0063] 2) Additional attenuation: Test according to GB / T 15972.40.

[0064] 3) Slack length: Accurately measure the optical fiber slack length of the all-dry loose tube optical unit through an automated optical fiber slack length test bench.

[0065] The test results are shown in Table 2.

[0066] Table 2 Performance of the all-dry loose tube optical units prepared in Application Examples 1 - 7 and Comparative Example 1

[0067] The test results show that by using microspheres with a surface-coated modified material for water-blocking powder (i.e., water-blocking microspheres) in the preparation of all-dry loose tube optical units in this application, the powder can be evenly discharged through the powder spraying device, effectively avoiding the phenomenon that the powder spraying air pipe is blocked due to the damp caking of the water-blocking powder. Further, the water-blocking microspheres blown into the inner cavity of the loose tube through the powder spraying device can adhere to the inner wall of the loose tube, and the modified material coated on the surface of the water-blocking microspheres melts to form a buffer layer adhering to the inner wall of the loose tube. At the same time, the water-blocking powder inside the water-blocking microspheres is evenly dispersed on the outer periphery of the optical waveguide element, which can effectively solve the problem of water-blocking powder accumulation and achieve an excellent water-blocking effect.

[0068] Compared with the all-dry loose tube optical unit prepared with ordinary water-blocking powder in Comparative Example 1, the additional attenuation of the all-dry loose tube optical unit prepared in this application is significantly reduced. The reason may be that the buffer layer adhering to the inner wall of the loose tube can effectively solve the problem that the optical waveguide element rubs and accumulates on the inner wall of the loose tube, causing the small-radius bending of the optical fiber and increasing the optical fiber attenuation. In addition, the optical fiber surplus length consistency of the all-dry loose tube optical unit prepared in this application is good. In practical applications, the size of the loose tube can be further reduced, and the optical fiber density can be increased.

[0069] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A fully dry loose tube optical unit, comprising a light guide element and a loose tube for accommodating the light guide element, characterized in that: A buffer layer is adhered to the inner wall of the loose tube, and water-blocking powder is dispersed on the outer periphery of the optical guide element; The buffer layer is formed by the modified material coated on the surface of the water-blocking microspheres and then adhered to the inner wall of the loose tube after melting, and the water-blocking powder inside the water-blocking microspheres is dispersed on the periphery of the light-guiding element; The modified material is an elastomer modified by a compatibilizer, and the elastic modulus of the elastomer is 50MPa-500MPa.

2. The fully dry loose tube optical unit according to claim 1, characterized in that: The average particle size of the water-blocking microspheres is 50 μm to 200 μm.

3. The fully dry loose tube optical unit according to claim 1, characterized in that: The compatibilizer is a maleic anhydride compatibilizer, preferably one or more of maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene, maleic anhydride grafted POE and maleic anhydride grafted SEBS; and / or, The elastomer is thermoplastic polyurethane and / or thermoplastic elastomer; and / or, The amount of the compatibilizer is 1wt% to 10wt% of the mass of the elastomer; and / or, The water-blocking powder is sodium polyacrylate and / or acrylamide, and has a particle size of 10 μm to 50 μm.

4. The fully dry loose tube optical unit according to any one of claims 1 to 3, characterized in that: The preparation method of the water-blocking microspheres comprises the following steps: The compatibilizer and the elastomer are blended and melt-extruded to obtain a modified material, and then a solution containing water-blocking powder and an organic solution of the modified material are mixed, stirred and dried to obtain microspheres with the modified material coated on the surface of the water-blocking powder, namely water-blocking microspheres.

5. The fully dry loose tube optical unit according to claim 4, characterized in that: The mass ratio of the modified material to the water-blocking powder is (5-8):(2-5).

6. The fully dry loose tube optical unit according to claim 1, characterized in that: The material of the loose tube is one or more of polyamide, polycarbonate, polybutylene terephthalate, and polypropylene; Preferably, the outer diameter of the loose tube is 1.5 mm to 15 mm, the wall thickness is 0.1 mm to 1.0 mm, and the elastic modulus is 1000 MPa to 3000 MPa.

7. The fully dry loose tube optical unit according to claim 1, characterized in that: The optical waveguide element is a single-mode optical fiber, a multi-mode optical fiber, a loose fiber, an optical fiber ribbon, an optical fiber ribbon array or a flexible optical fiber ribbon.

8. A method for preparing a fully dry loose tube optical unit according to any one of claims 1 to 7, characterized in that: The steps include: S1, extruding a loose tube forming material outside the bundled optical waveguide element to form a loose tube substrate; S2, blowing the water-blocking microspheres into the inner cavity of the loose tube substrate, the water-blocking microspheres adhere to the inner wall of the loose tube substrate, wherein the modified material coated on the surface of the water-blocking microspheres melts to form a buffer layer adhered to the inner wall, and at the same time, the water-blocking powder inside the water-blocking microspheres is dispersed on the periphery of the optical waveguide element, and then cooled and shaped, so that the loose tube substrate is cooled and shaped into a loose tube, and the fully dry loose tube optical unit is obtained.

9. The preparation method according to claim 8, characterized in that: The temperature of the inner wall of the loose tube substrate is 10° C. to 50° C. higher than the melting point of the modified material.

10. A fully dry optical cable, characterized in that: It comprises the fully dry loose tube optical unit as described in any one of claims 1 to 7 or the fully dry loose tube optical unit prepared by the preparation method as described in claim 8 or 9.

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