PBT-doped double-layer composite optical cable sleeve, optical cable and preparation method of PBT-doped double-layer composite optical cable sleeve
By doping PBT into PET material, a double-layer composite structure of the PET modified layer and the PBT layer is prepared, which solves the problems of retraction and extrusion deformation of the optical cable casing, and achieves a low retraction and good rebound force optical cable casing , suitable for applications with high tensile strength.
Patent Information
- Application Number
- CN202310877416.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-17
- Publication Date
- 2025-01-17
AI Technical Summary
The existing optical cable casing material PBT has strong retraction, which causes optical fiber to retract, increasing the residual length of the fiber, causing fiber attenuation and line failure. The casing is easily extruded and deformed by using PET materials alone, and it is difficult to make the casing. Solve these problems.
By doping PBT with a specific proportion of PET materials, a double-layer composite structure between the PET modified layer and the PBT layer is prepared. The low retraction property of the PET modified layer and the rebound force of the PBT layer are used to form a double-layer composite optical cable sleeve. , the double-layer co-extruder head is prepared, the temperature and pressure parameters are adjusted to ensure that the inner and outer layer materials are sticky and tight.
It significantly reduces the retractability of the optical cable casing, improves the tensile resistance of the casing, avoids extrusion deformation, reduces the preparation cost, and forms an optical cable casing with low retraction and good rebound force.
Smart Images
Figure CN119322398A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of optical cable preparation, and more specifically, to a PBT-doped double-layer composite optical cable casing, an optical cable and a preparation method thereof. Background Art
[0002] The optical cable casing is formed by extruding a layer of plastic protective tube after covering several optical fibers or water-blocking materials. It mainly provides direct protection for optical fibers. Tensile strength and anti-compression performance indicators are important performance indicators of loose casing. Stranded optical cable is composed of multiple casings containing optical fibers twisted around the central reinforcement member to form a round cable core. The metal or non-metal reinforcement member is located in the center of the optical cable, and the loose casing containing the optical fiber is arranged around the reinforcement member. PBT is the main raw material for loose casing of optical cables at present, with good mechanical, chemical and processing properties. However, the optical fiber covered by PBT casing often has serious retraction problems. The retraction of the casing increases the excess length of the optical fiber, thereby increasing the attenuation of the optical fiber. The retraction length of the optical fiber ranges from several centimeters to more than ten centimeters. Severe retraction may even cause the optical fiber covered by the PBT casing to slide off the optical fiber connector fixing plate, causing line failure and other problems.
[0003] PET (polybutylene terephthalate) is the most important type of thermoplastic polyester, mainly used in the preparation of heat shrinkable tubes. Its shrinkage is significantly better than that of PBT. However, due to its strong memory and poor resilience, it is not suitable for the preparation of optical cable sheaths alone, which will cause the optical cable sheaths to be easily squeezed and deformed. This is a defect that needs to be overcome. At present, there are still few related research reports on the application of PET materials with excellent shrinkage performance in the preparation of optical cable sheaths. It is very difficult to use PET materials to prepare optical cable sheaths with excellent performance. Summary of the invention
[0004] In view of at least one defect or improvement need of the prior art, the present invention provides a PBT-doped multilayer optical cable sheath, an optical cable and a preparation method thereof, wherein the PET is modified by doping PBT into a PET material with low shrinkage in a specific proportion to obtain a PET modified layer, and the PET modified layer is composited with the PBT layer in layers of different thicknesses to prepare a double-layer composite optical cable sheath, which greatly reduces the shrinkage of the traditional PBT single-layer sheath, making it have the characteristics of low shrinkage, not easy to be squeezed and deformed, and good resilience, while reducing the preparation cost.
[0005] To achieve the above object, according to one aspect of the present invention, there is provided a PBT-doped multi-double-layer composite optical cable casing, the composite optical cable casing comprising an outer PBT layer and an inner PET modified layer, the thickness ratio of the PBT layer to the PET modified layer in the radial direction is in the range of 1:(3-4), and the PET modified layer comprises a blended material of PET and PBT;
[0006] The composite optical cable sheath is prepared by a double-layer co-extrusion die head, and the ratio of the axial distribution section length of the inner layer diverter to the outer layer diverter of the double-layer co-extrusion die head is (1.2-1.4):1; the temperature of the inner layer extruder head is consistent with that of the outer layer extruder head, and the temperature ratio of the inner layer extruder body to that of the outer layer extruder body is (1.2-1.4):1, so that the composite optical cable sheath can be extruded and formed.
[0007] Preferably, the molar ratio of the PET blend material to the PBT blend material is in the range of (4-6):1.
[0008] Preferably, the body temperature of the inner layer extruder is 260-270°C, the body temperature of the outer layer extruder is 240-260°C, and the head temperature of the inner layer extruder and the head temperature of the outer layer extruder are 240-250°C.
[0009] Preferably, the thickness of the PBT layer in the radial direction is 0s.08-0.15cm.
[0010] Preferably, the PET blend material includes terephthalic acid and ethylene glycol, and the molar ratio of each component is 1:(1:5-2.5); the PBT blend material includes terephthalic acid and butanediol, and the molar ratio of each component is 1:(1:1-2.5).
[0011] According to another aspect of the present invention, there is also provided a PBT-doped double-layer composite sheath optical cable, comprising a stranded cable core, a reinforcing core being arranged in the middle of the stranded cable core, a plurality of PBT-doped double-layer composite optical cable sheaths as claimed in any one of claims 1 to 5 being distributed in an annular manner around the outer portion of the reinforcing core, a plurality of optical fibers being arranged inside the sheath, and a sheath tube being coated on the outer circumference of the sheath.
[0012] According to another aspect of the present invention, there is also provided a method for preparing a PBT-doped double-layer composite optical cable casing, comprising the following steps:
[0013] The PBT material components are added to the outer layer splitter of the double-layer co-extrusion die head, and the catalyst tetrabutyl titanate is added; the blended material components of PBT and PET are added to the inner layer splitter of the double-layer co-extrusion die head, and the catalyst tetrabutyl titanate and antimony trioxide are added; the ratio of the axial distribution section length of the inner layer to the outer layer splitter is (1.2-1.4):1;
[0014] The temperature of the inner layer extruder head and the outer layer extruder head are controlled to be consistent, and the temperature ratio of the inner layer extruder body and the outer layer extruder body is controlled to be (1.2-1.4):1. The inner layer of the composite optical cable sheath is formed by the inner layer outlet die, and the outer layer of the composite optical cable sheath is formed by the outer layer outlet die.
[0015] Preferably, the molar ratio range of the PET blend material component and the PBT blend material component is (4-6):1, the PET blend material component includes terephthalic acid and ethylene glycol, and the molar ratio of each component is 1:(1:5-2.5); the PBT material component includes terephthalic acid and butanediol, and the molar ratio of each component is 1:(1:1-2.5).
[0016] Preferably, the body temperature of the inner layer extruder is 260-270°C, the body temperature of the outer layer extruder is 240-260°C, and the head temperature of the inner layer extruder and the head temperature of the outer layer extruder are 240-250°C.
[0017] Preferably, the screw compression ratio of the inner layer extruder and the outer layer extruder is (2.4-2.6):1.
[0018] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:
[0019] (1) The present invention provides a PBT-doped double-layer composite optical cable sheath, wherein the inner PET modified layer is modified by doping PET with small shrinkage with a specific ratio of PBT material, and the modified PET is more suitable for preparing optical cable sheaths. It fully utilizes the advantage of small shrinkage of PET material and greatly reduces the shrinkage of optical cable sheaths. The outer PBT layer can make up for the defect of poor resilience caused by the single PET material, so that the sheath still maintains good resilience. The double-layer composite structure solves the problem of large shrinkage of traditional PBT single-layer sheaths in the prior art by compounding the inner and outer layers with different thicknesses, and overcomes the defects of preparing optical cable sheaths with PET alone, and finally obtains an optical cable sheath with low shrinkage and good resilience.
[0020] (2) The present invention provides a PBT-doped double-layer composite optical cable casing, which is prepared by a double-layer co-extrusion method. By adjusting the temperature and pressure parameters of the inner and outer layer co-extrusion heads, the inner and outer layer materials can be better adhered together to avoid stratification of the double-layer casing, and finally a tightly combined two-dimensional composite structure is formed. In addition to improving the shrinkage problem of the casing, the double-layer composite optical cable casing of the present invention has better tensile properties than ordinary PBT casings and is more suitable for casing molds with greater tensile strength. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 is a schematic diagram of a PBT-doped double-layer composite optical cable provided in an embodiment of the present invention; DETAILED DESCRIPTION
[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0023] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.
[0024] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.
[0025] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0026] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.
[0027] The effect of optical cable casing is to protect the optical fiber that it is stored, and generally requires good tensile and compressive properties, with higher elongation at break and tensile strength. For the retraction problem of the most commonly used PBT casing at present, existing research and patent mainly increase the friction between casing and sheath to alleviate casing retraction by making the loose casing outer surface and the sheath inner surface into a concave-convex chelate structure, but this structure does not solve the problem of casing retraction from physical nature, when casing retracts significantly in a short time, sheath does not retract to the same degree, then the concave-convex chelate structure will fail, and the effect envisioned in the patent cannot be reached. The inventive concept of the present invention is to adopt the PET material preparation casing that retracts significantly less than PBT from the material itself, improve its retraction problem.
[0028] To this end, the present invention adopts PET (polybutylene terephthalate) material which is not easy to shrink and has a shrinkage amount significantly smaller than PBT. In order to overcome the shortcomings of PET material that it is easy to be extruded and deformed and has poor resilience, the present invention modifies PET by adding an appropriate amount of PBT into it in an optimal ratio to prepare a PET modified layer, and designs a double-layer composite structure of an outer PBT layer and an inner PET modified layer, wherein the inner PET modified layer is doped with PBT and PET in a specific ratio to ensure that the sleeve is not easy to shrink, and the outer PBT layer ensures the lateral pressure resistance of the sleeve, so that it has good resilience and is not easy to be extruded and deformed. Such a multi-layer sleeve structure ensures the excellent performance of the sleeve in all aspects, and at the same time, due to the relatively low cost of PET, the production cost is greatly reduced.
[0029] Specifically, the composite optical cable sleeve includes an outer PBT layer and an inner PET modified layer, the thickness ratio of the PBT layer to the PET modified layer in the radial direction is 1:(3-4), the PET modified layer includes a blend of PET and PBT. The thickness of the PBT layer in the radial direction is 0.08-0.15 cm.
[0030] The doping ratio of the PBT and PET blended material components in the PET modified layer is crucial to the performance of the PET modified layer. If the doping ratio of PBT is too large, it will not improve the shrinkage performance of the sleeve, while if the doping ratio of PBT is too small, the mechanical properties of the sleeve will be reduced and it will be easy to be compressed and deformed. After repeated experiments and ratio adjustments, the present invention finally determined that the molar ratio range is 4:1 to 6:1.
[0031] The PET blend material components include terephthalic acid and ethylene glycol, and the molar ratio of each component is 1: (1: 5-2.5); the PBT material components include terephthalic acid and butanediol, and the molar ratio of each component is 1: (1: 1-2.5).
[0032] Furthermore, the composite optical cable sheath layer is prepared by a double-layer co-extrusion head, which has two layers of diverters in the head: an inner diverter and an outer diverter. The inner diverter and the outer diverter are respectively connected to the inner extruder and the outer extruder. After the material components are added to the diverter, they are extruded through the extruder and then formed into the inner and outer layers of the composite optical cable sheath through the outlet die.
[0033] In order to better fuse the outer PBT layer and the inner PET modified layer together and obtain the best inner and outer layer adhesion effect, it is necessary to adjust the double-layer co-extrusion head and extruder parameters, among which the extrusion pressure and extruder temperature have an important influence on the formation of a stable double-layer composite structure in the present invention. Through testing, it is found that the best ratio of the axial distribution section length of the inner layer and the outer layer diverter of the double-layer co-extrusion head is 1.2:1~1.4:1. This setting can increase the pressure in the fusion area of the inner and outer materials, so that the inner and outer layers are better adhered. At the same time, in order to facilitate the molding of the double-layer sleeve, the temperature of the inner layer extruder head and the outer layer extruder head are controlled to be consistent, and the ratio of the temperature of the inner layer extruder body to the temperature of the outer layer extruder body is 1.2:~1.4, so that the composite optical cable sleeve can be extruded. In order to verify the effect of extrusion molding, masterbatches of different colors were added to the inner and outer extruders respectively, and the adhesion effect was determined by the end face of the sleeve sample obtained by the final extrusion. The optimal effect was that the two colors of the inner and outer layers were partially fused, and the colors of the inner and outer layers were clearly distinguished.
[0034] The present invention provides a method for preparing a PBT-doped double-layer composite optical cable casing, comprising the following steps:
[0035] The PBT material components are added to the outer layer splitter of the double-layer co-extrusion die head, and the catalyst tetrabutyl titanate is added; the blended material components of PBT and PET are added to the inner layer splitter of the double-layer co-extrusion die head, and the catalyst tetrabutyl titanate and antimony trioxide are added; the ratio of the axial distribution section length of the inner layer to the outer layer splitter is (1.2-1.4):1;
[0036] The temperature of the inner layer extruder head and the outer layer extruder head are controlled to be consistent, and the temperature ratio of the inner layer extruder body and the outer layer extruder body is controlled to be (1.2-1.4):1. The inner layer of the composite optical cable sheath is formed by the inner layer outlet die, and the outer layer of the composite optical cable sheath is formed by the outer layer outlet die.
[0037] Specifically, the molar ratio of the PET blend material component to the PBT blend material component is in the range of (4-6):1, the PET blend material component includes terephthalic acid and ethylene glycol, and the molar ratio of each component is 1:(1:5-2.5); the PBT material component includes terephthalic acid and butanediol, and the molar ratio of each component is 1:(1:1-2.5)
[0038] Specifically, the temperature of the inner layer extruder body is 260-270°C, the temperature of the inner layer extruder head is 240-250°C, the temperature of the outer layer extruder body is 240-260°C, and the temperature of the outer layer extruder head is 240-250°C.
[0039] Specifically, the screw compression ratio of the inner layer extruder and the outer layer extruder is 2.4:1-2.6:1, and the ratio of the axial distribution section lengths of the inner layer and the outer layer splitters is (1.2-1.4):1.
[0040] The following are examples:
[0041] Example 1
[0042] 1 part of PBT material component (phthalic acid and butanediol molar ratio of 1:1.2) is added to the outer layer splitter of the double-layer co-extrusion die head, and a catalyst of tetrabutyl titanate is added; 4 parts of PET blended material components (phthalic acid and ethylene glycol molar ratio of 1:1.5) and 1 part of PBT blended material component (phthalic acid and butanediol molar ratio of 1:1.2) are added to the inner layer splitter of the double-layer co-extrusion die head, and catalysts of tetrabutyl titanate and antimony trioxide are added; the ratio of the axial distribution section length of the inner layer to the outer layer splitter is 1.2:1;
[0043] A universal BM screw is used, wherein the screw compression ratio is 2.4:1 to 2.6:1; the temperature of the inner layer extruder head and the outer layer extruder head is 240°C, the temperature of the inner layer extruder body is 260°C, the temperature of the outer layer extruder body is 240°C, the inner layer of the composite optical cable sheath is formed through the inner layer outlet die, and the outer layer of the composite optical cable sheath is formed through the outer layer outlet die.
[0044] Example 2
[0045] 1 part of PBT material component (phthalic acid and butanediol molar ratio of 1:1.2) is added to the outer layer splitter of the double-layer co-extrusion die head, and a catalyst of tetrabutyl titanate is added; 5 parts of PET blended material components (phthalic acid and ethylene glycol molar ratio of 1:1.5) and 1 part of PBT blended material component (phthalic acid and butanediol molar ratio of 1:1.2) are added to the inner layer splitter of the double-layer co-extrusion die head, and catalysts of tetrabutyl titanate and antimony trioxide are added; the ratio of the axial distribution section length of the inner layer to the outer layer splitter is 1.2:1;
[0046] A universal BM screw is used, wherein the screw compression ratio is 2.4:1 to 2.6:1; the temperature of the inner layer extruder head and the outer layer extruder head is 240°C, the temperature of the inner layer extruder body is 270°C, the temperature of the outer layer extruder body is 250°C, the inner layer of the composite optical cable sheath is formed through the inner layer outlet die, and the outer layer of the composite optical cable sheath is formed through the outer layer outlet die.
[0047] Example 3
[0048] 1 part of PBT material component (phthalic acid and butanediol molar ratio of 1:1.2) is added to the outer layer splitter of the double-layer co-extrusion die head, and the catalyst tetrabutyl titanate is added; 6 parts of PET blended material components (phthalic acid and ethylene glycol molar ratio of 1:1.5) and 1 part of PBT blended material component (phthalic acid and butanediol molar ratio of 1:1.2) are added to the inner layer splitter of the double-layer co-extrusion die head, and the catalysts tetrabutyl titanate and antimony trioxide are added; the ratio of the axial distribution section length of the inner layer to the outer layer splitter is 1.2:1;
[0049] A universal BM screw is used, wherein the screw compression ratio is 2.4:1 to 2.6:1; the temperature of the inner layer extruder head and the outer layer extruder head is 250°C, the temperature of the inner layer extruder body is 260°C, the temperature of the outer layer extruder body is 250°C, the inner layer of the composite optical cable sheath is formed through the inner layer outlet die, and the outer layer of the composite optical cable sheath is formed through the outer layer outlet die.
[0050] Example 4
[0051] 1 part of PBT material component (phthalic acid and butanediol molar ratio of 1:1.2) is added to the outer layer splitter of the double-layer co-extrusion die, and the catalyst tetrabutyl titanate is added; 5 parts of PET blended material components (phthalic acid and ethylene glycol molar ratio of 1:2) and 1 part of PBT blended material component (phthalic acid and butanediol molar ratio of 1:1.5) are added to the inner layer splitter of the double-layer co-extrusion die, and the catalysts tetrabutyl titanate and antimony trioxide are added; the ratio of the axial distribution section length of the inner layer to the outer layer splitter is 1.2:1;
[0052] A universal BM screw is used, wherein the screw compression ratio is 2.4:1 to 2.6:1; the temperature of the inner layer extruder head and the outer layer extruder head is 250°C, the temperature of the inner layer extruder body is 260°C, the temperature of the outer layer extruder body is 250°C, the inner layer of the composite optical cable sheath is formed through the inner layer outlet die, and the outer layer of the composite optical cable sheath is formed through the outer layer outlet die.
[0053] Ordinary pure PBT single-layer casing and multi-layer casing in Examples 1-4 were stored in 23℃, 70℃ and 80℃ environments with a length of 1m. The wire was taken up and relaxed on a tray. The shrinkage of the casing was observed when it was stored at 23℃ and 70℃ for 120h and when it was stored at 80℃ for 1h. The shrinkage of the casing was measured, and the tensile strength of the casing was also measured. The test data are shown in the following table.
[0054]
[0055]
[0056] It can be seen from the shrinkage data in the above table that, compared with ordinary pure PBT single-layer casing, the multi-layer casing obtained by the method of the present application has the smallest shrinkage during storage when stored in an environment of 23°C, 70°C and 80°C, and its shrinkage is significantly improved compared with ordinary pure PBT single-layer casing. At the same time, the casing also has good tensile strength.
[0057] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A PBT-doped double-layer composite optical cable casing, characterized in that: The composite optical cable sleeve comprises an outer PBT layer and an inner PET modified layer, the thickness ratio of the PBT layer to the PET modified layer in the radial direction is in the range of 1:(3-4), and the PET modified layer comprises a blended material of PET and PBT; The composite optical cable sheath is prepared by a double-layer co-extrusion die head, and the ratio of the axial distribution section length of the inner layer diverter to the outer layer diverter of the double-layer co-extrusion die head is (1.2-1.4):1; the temperature of the inner layer extruder head is consistent with that of the outer layer extruder head, and the temperature ratio of the inner layer extruder body to that of the outer layer extruder body is (1.2-1.4):1, so that the composite optical cable sheath can be extruded and formed.
2. The PBT-doped double-layer composite optical cable casing according to claim 1, characterized in that: The molar ratio of the PET blend material to the PBT blend material is in the range of (4-6):
1.
3. The PBT-doped double-layer composite optical cable casing according to claim 1, characterized in that: The body temperature of the inner layer extruder is 260-270°C, the body temperature of the outer layer extruder is 240-260°C, and the head temperature of the inner layer extruder and the head temperature of the outer layer extruder are 240-250°C.
4. The PBT-doped double-layer composite optical cable casing according to claim 1, characterized in that: The thickness of the PBT layer in the radial direction is 0.08-0.15 cm.
5. The PBT-doped double-layer composite optical cable casing according to claim 1, characterized in that: The PET blend material includes terephthalic acid and ethylene glycol, and the molar ratio of each component is 1:(1:5-2.5); the PBT blend material includes terephthalic acid and butanediol, and the molar ratio of each component is 1:(1:1-2.5).
6. A PBT-doped double-layer composite sheathed optical cable, characterized in that: It comprises a layer-twisted cable core, wherein a reinforcing core is arranged in the middle of the layer-twisted cable core, and a plurality of PBT-doped double-layer composite optical cable sheaths as claimed in any one of claims 1 to 5 are distributed in an annular manner around the reinforcing core, wherein a plurality of optical fibers are arranged inside the sheath, and the outer periphery of the sheath is covered with a sheath tube.
7. A method for preparing a PBT-doped double-layer composite optical cable casing, characterized in that: The steps include: The PBT material components are added to the outer layer splitter of the double-layer co-extrusion die head, and the catalyst tetrabutyl titanate is added; the blended material components of PBT and PET are added to the inner layer splitter of the double-layer co-extrusion die head, and the catalyst tetrabutyl titanate and antimony trioxide are added; the ratio of the axial distribution section length of the inner layer to the outer layer splitter is (1.2-1.4):1; The temperature of the inner layer extruder head and the outer layer extruder head are controlled to be consistent, and the temperature ratio of the inner layer extruder body and the outer layer extruder body is controlled to be (1.2-1.4):
1. The inner layer of the composite optical cable sheath is formed by the inner layer outlet die, and the outer layer of the composite optical cable sheath is formed by the outer layer outlet die.
8. The method for preparing the PBT-doped double-layer composite optical cable casing according to claim 7, characterized in that: The molar ratio of the PET blend material component to the PBT blend material component is in the range of (4-6):1, the PET blend material component includes terephthalic acid and ethylene glycol, and the molar ratio of each component is 1:(1:5-2.5); the PBT blend material component includes terephthalic acid and butanediol, and the molar ratio of each component is 1:(1:1-2.5).
9. The method for preparing the PBT-doped double-layer composite optical cable casing according to claim 7, characterized in that: The body temperature of the inner layer extruder is 260-270°C, the body temperature of the outer layer extruder is 240-260°C, and the head temperature of the inner layer extruder and the head temperature of the outer layer extruder are 240-250°C.
10. The method for preparing the PBT-doped double-layer composite optical cable casing according to claim 7, characterized in that: The screw compression ratio of the inner layer extruder and the outer layer extruder is (2.4-2.6):1.