PBT (Polybutylene Terephthalate) material for secondary coating of optical communication micro cable and preparation method of PBT material

Abstract

The invention discloses a PBT (polybutylene terephthalate) material for secondary coating of an optical communication micro cable and a preparation method of the PBT material. The PBT material is prepared from the following components in percentage by weight: 98.5-99.6% of PBT resin; 0.2%-0.8% of a crystallizing agent, wherein the crystallizing agent is an organic acid salt or nano clay or an inorganic mineral; 0.2%-0.7% of a lubricant; the crystallizing agent is one or more of sodium benzoate or sodium phenyl phosphate or sodium stearate or talcum powder or organic modified montmorillonite. According to the preparation method of the PBT material, the crystallization nucleus is added at a low-temperature stage, so that the crystallization efficiency of the PBT resin is improved from 60% to 90% or above, the performance of the material is improved, rapid shaping of the material in micro-cable high-speed extrusion production is ensured due to the high crystallization speed, and the problems that a thin-wall pipe is difficult to form and easy to deform are solved; the adding amount of the crystallizing agent is strictly controlled, and the excess length of the optical fiber is accurately controlled within 0.02%-0.04%.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a PBT material and its preparation method for secondary coating of optical communication microcables. Background Technology

[0002] With the dense deployment of fiber-to-the-home (FTTH) and 5G networks, higher demands are being placed on the diameter, weight, and laying efficiency of optical cables, leading to the emergence of microcable technology. The core of microcables lies in reducing the diameter of their fiber core tubes from the traditional 2.0mm or more to 1.0-1.6mm. This places extremely stringent requirements on the performance of the tube material, PBT: while significantly reducing the wall thickness, its mechanical properties must be maintained or even improved, with a lateral compressive strength ≥800N, fiber excess length controlled within the range of 0.02%~0.04%, and excellent formability to ensure stable production and performance compliance of the microcable tubes.

[0003] Currently, the PBT material commonly used in optical cables on the market typically has a crystallinity of around 60%, resulting in insufficient material hardness and poor lateral pressure resistance, generally below 600N. This fails to meet the production requirements of micro-cable thin-walled bundle tubes. The fundamental reason is that conventional PBT lacks sufficient nucleation points, resulting in slow crystallization and incomplete crystallization. This leads to large shrinkage and poor dimensional stability after the material is laid, making it difficult to control the excess fiber length. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art by providing a PBT material and preparation method for secondary coating of optical communication microcables. The prepared PBT material has sufficient hardness and strong resistance to lateral pressure while ensuring thin-wall forming, and the excess length of the bundle tube is between 0.02% and 0.04%.

[0005] To achieve the above objectives, the technical solution adopted by this invention is: a PBT material for secondary coating of optical communication microcables, composed of the following components by weight percentage:

[0006] PBT resin: 98.5% ~ 99.6%;

[0007] Crystallizing agent: 0.2% ~ 0.8%, wherein the crystallizing agent is an organic acid salt, nano-clay, or inorganic mineral;

[0008] Lubricant: 0.2% ~ 0.7%.

[0009] Furthermore, the crystallizing agent is one or more of sodium benzoate, sodium phenyl phosphate, sodium stearate, talc, or organically modified montmorillonite.

[0010] Furthermore, the particle size of the crystallizing agent is no greater than 10 μm.

[0011] Furthermore, the lubricant is polyethylene wax or calcium stearate.

[0012] A method for preparing PBT material for secondary coating of optical communication microcables includes the following steps:

[0013] S1. Weigh each component according to the following weight percentages: PBT resin: 98.5% ~ 99.6%; crystallizer: 0.2% ~ 0.8%; lubricant: 0.2% ~ 0.7%

[0014] S2. Vacuum dry the PBT resin at 110℃-130℃ for 4-6 hours, and mix the dried PBT resin and crystallizer in a low-speed mixer at room temperature for 20-40 minutes.

[0015] S3. Feed the mixed material into a twin-screw reactive extruder for melt thickening. Set the extruder temperature from zone one to zone five to 220℃-245℃, and the die head temperature to 235℃-250℃. Inert protective gas is then introduced into the melt.

[0016] S4. Lubricant is accurately added in the middle and rear section of the extruder via a side feeder;

[0017] S5. After melt extrusion, stretching, and cooling in a cooling water tank, the material is pelletized, sieved, and packaged to obtain PBT material.

[0018] Furthermore, the inert protective gas is high-purity nitrogen.

[0019] Furthermore, the sieve mesh size is 20 to 4 mesh.

[0020] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0021] The present invention relates to a PBT material and preparation method for secondary coating of optical communication microcables. By adding crystal nuclei at a low temperature stage, the crystallinity of PBT resin is increased from about 60% to over 90%, thereby improving performance parameters. At the same time, the high crystallization rate ensures rapid shaping of the material in the high-speed extrusion production of microcables, solving the problems of difficult molding and easy deformation of thin-walled tubes.

[0022] Secondly, by strictly controlling the addition of crystallizer in the range of 0.2%-0.8%, the crystallinity is stabilized within the optimal range, avoiding the problem of excessive shrinkage caused by excessive crystallinity, thereby precisely controlling the fiber excess length within the range of 0.02%-0.04%. The entire process from low-temperature mixing to high-temperature reaction ensures that the crystallizer is evenly dispersed and well coated in the PBT matrix, avoiding performance defects caused by agglomeration. Attached Figure Description

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings:

[0024] Figure 1 This is a flowchart illustrating the preparation process of the present invention. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0026] For ease of understanding, the specific process in the embodiments of this application is described below. A PBT material for secondary coating of optical communication microcables in the embodiments of this application is composed of the following components by weight percentage: PBT resin: 98.5% ~ 99.6%; crystallizer: 0.2% ~ 0.8%, wherein the crystallizer is an organic acid salt, nano clay, or inorganic mineral; lubricant: 0.2% ~ 0.7%.

[0027] Furthermore, the crystallizing agent is one or more of sodium benzoate, sodium phenyl phosphate, sodium stearate, talc, or organically modified montmorillonite.

[0028] Furthermore, the particle size of the crystallizer is no greater than 10 μm, which provides a sufficient number of effective nucleation sites to ensure uniform material properties and obtain a fine and uniform crystal structure.

[0029] Furthermore, the lubricant is polyethylene wax or calcium stearate, which can improve the processing performance of the material and reduce friction and wear during extrusion. The amount of lubricant added is between 0.2% and 0.7%; a lubricant content of 0.2% ensures that the lubricant can effectively play its role and improve processing performance, but the content should not exceed 0.7%, thereby avoiding the negative impact of excessive lubricant on material properties, such as reduced mechanical strength.

[0030] This invention relates to PBT materials used in the secondary coating of optical communication microcables. The addition of a crystallizing agent can significantly improve the crystallization speed and degree of PBT resin. This crystallizing agent acts as a nucleus for PBT crystallization, enabling PBT to crystallize rapidly after molding. Compared with ordinary PBT materials, the crystallization efficiency of the PBT material of this invention can reach more than 90%, while the crystallization efficiency of ordinary PBT materials is usually only about 60%, which significantly improves the hardness and lateral pressure resistance of PBT materials.

[0031] based on Figure 1 The present invention also discloses a method for preparing PBT material for secondary coating of optical communication microcables, comprising the following steps:

[0032] S1. Weigh each component according to the following weight percentages: PBT resin: 98.5% ~ 99.6%; crystallizer: 0.2% ~ 0.8%; lubricant: 0.2% ~ 0.7%

[0033] S2. Vacuum dry the PBT resin at 110℃-130℃ for 4-6 hours. Mix the dried PBT resin and crystallizer in a low-speed mixer at room temperature for 20-40 minutes to ensure that the crystallizer is uniformly attached to the surface of the PBT particles.

[0034] S3. The mixed material is fed into a twin-screw reactive extruder for melt thickening. The extruder temperature is set from zone one to zone five to 220℃-245℃, and the die head temperature is 235℃-250℃. An inert protective gas is introduced into the melt; wherein the inert protective gas is high-purity nitrogen (purity ≥99.99%). This effectively prevents the material from oxidizing and degrading at high temperatures, ensuring the quality and performance of the material. The nitrogen flow rate is controlled at 10~20 L / min to ensure the protective effect.

[0035] S4. Lubricant is accurately added in the middle and rear section of the extruder via a side feeder;

[0036] S5. After melt extrusion, stranding, and cooling in a cooling water tank, the material is pelletized, sieved, and packaged to obtain PBT material. The cooling water temperature is between 20℃ and 30℃ to ensure that the material does not generate stress due to excessive temperature differences during cooling. Furthermore, the sieve mesh size is 20 to 4 mesh.

[0037] Several embodiments are listed below for illustration.

[0038] Example 1

[0039] A method for preparing PBT material for secondary coating of optical communication microcables includes the following steps:

[0040] S1. Weigh each component according to the following weight percentages: PBT resin: 99.2%; sodium benzoate: 0.3%; calcium stearate: 0.5%.

[0041] S2. Vacuum dry the PBT resin at 110°C for 4 hours, and mix the dried PBT resin and crystallizer in a low-speed mixer at room temperature for 20 minutes.

[0042] S3. Feed the mixed material into a twin-screw reactive extruder for melt thickening. Set the extruder temperature from zone one to zone five to 220°C and the die head temperature to 235°C. Inert protective gas is then introduced into the melt.

[0043] S4. Lubricant is accurately added in the middle and rear section of the extruder via a side feeder;

[0044] S5. After melt extrusion, stretching, and cooling in a cooling water tank, the material is pelletized, sieved, and packaged to obtain PBT material.

[0045] Example 2

[0046] A method for preparing PBT material for secondary coating of optical communication microcables includes the following steps:

[0047] S1. Weigh each component according to the following weight percentages: PBT resin: 99.0%; Sodium benzoate: 0.5%; Calcium stearate: 0.5%.

[0048] S2. Vacuum dry the PBT resin at 130°C for 6 hours, and mix the dried PBT resin and crystallizer in a low-speed mixer at room temperature for 40 minutes.

[0049] S3. Feed the mixed material into a twin-screw reactive extruder for melt thickening. Set the extruder temperature from zone one to zone five to 245°C and the die head temperature to 250°C. Inert protective gas is then introduced into the melt.

[0050] S4. Lubricant is accurately added in the middle and rear section of the extruder via a side feeder;

[0051] S5. After melt extrusion, stretching, and cooling in a cooling water tank, the material is pelletized, sieved, and packaged to obtain PBT material.

[0052] Example 3

[0053] S1. Weigh the components according to the following weight percentages: PBT resin: 98.7%; sodium benzoate: 0.8%; calcium stearate: 0.5%;

[0054] S2. Vacuum dry the PBT resin at 120°C for 5 hours, and mix the dried PBT resin and crystallizer in a low-speed mixer at room temperature for 30 minutes.

[0055] S3. Feed the mixed material into a twin-screw reactive extruder for melt thickening. Set the extruder temperature from zone one to zone five to 235°C and the die head temperature to 240°C. Inert protective gas is then introduced into the melt.

[0056] S4. Lubricant is accurately added in the middle and rear section of the extruder via a side feeder;

[0057] S5. After melt extrusion, stretching, and cooling in a cooling water tank, the material is pelletized, sieved, and packaged to obtain PBT material.

[0058] Comparative Example 1

[0059] The difference between Comparative Example 1 and Examples 1, 2 and 3 is that sodium benzoate was not added, and its content was PBT resin: 99.5%; calcium stearate: 0.5%.

[0060] The performance parameters of the PBT materials obtained in Examples 1, 2, and 3, and Comparative Example 1 are compared as follows:

[0061] Comparative Example 1 Example 1 Example 2 Example 3 Yield strength (MPa) 50.8 55.5 57.2 58 Shore hardness (D Scale) 77 80 82 84 Lateral pressure resistance of the bundled tube (N / 100mm) 600 850 980 1020 Bundle tube excess length (%) 0.05% 0.025% 0.030% 0.045% Crystallization efficiency ~60% ~85% ~92% ~95%

[0062] As shown in the table above, the yield strength, Shore hardness, and lateral pressure resistance of PBT materials are greatly improved after the addition of sodium benzoate. The lateral pressure resistance is significantly improved, from 600N in the comparative example to over 980N, which fully meets and exceeds the 800N standard required for micro-cables. Moreover, the higher the sodium benzoate content, the stronger the lateral pressure resistance.

[0063] In Examples 1 and 2, the excess length was precisely controlled within the ideal range of 0.02% to 0.04%; the excess length in Example 3 (0.045%) slightly exceeded the upper limit, indicating that higher surface crystallinity is not always better. Excessive crystallinity (>95%) can lead to increased material shrinkage in the later stages, resulting in a larger excess length and affecting the signal transmission performance of the optical cable.

[0064] Secondly, the lateral pressure resistance of Example 3 is better than that of Examples 1 and 2, indicating that the content of crystallizing agent is not necessarily better the more it is.

[0065] Example 4

[0066] The difference between this embodiment and Embodiment 2 is that the crystal nucleus is sodium phenyl phosphate.

[0067] Example 5

[0068] The difference between this embodiment and Embodiment 2 is that the crystal nucleus is sodium stearate.

[0069] The performance parameters of the PBT materials prepared in Comparative Examples 1, 2, 4, and 5 are compared in the table below:

[0070] Comparative Example 1 (without crystallizing agent) Example 2 (0.5% Sodium Benzoate) Example 4 (0.5% Sodium Phenylated Phosphate) Example 5 (0.5% Sodium Stearate) Yield strength (MPa) 50.8 57.2 58.3 56.0 Shore hardness (D Scale) 77 82 83 80 Lateral pressure resistance of the bundled tube (N / 100mm) 600 980 1020 900 Bundle tube excess length (%) 0.05% 0.030% 0.028% 0.032%

[0071] From the table above, we can see that:

[0072] Sodium phenyl phosphate exhibits the best performance among all crystallizing agents. It has the highest lateral compressive strength (1020 N) and hardness (83), while maintaining the excess length (0.028%) within the optimal range. The molecular structure of sodium phenyl phosphate is highly compatible with PBT, providing the most effective heterogeneous nucleation sites and significantly increasing the crystallization temperature and rate (highest DSC peak temperature). This allows the material to solidify instantly after leaving the mold, resulting in the highest crystallization efficiency and optimal overall performance.

[0073] Example 6

[0074] The difference between this embodiment and Embodiment 2 is that the crystallization nucleus is added in zone four of the extruder. The final parameters and properties of the PBT material prepared in Embodiment 2 are shown in the table below.

[0075] Example 2 Example 6 Yield strength (MPa) 57.2 53.5 Shore hardness (D Scale) 82 78 Lateral pressure resistance of the bundled tube (N / 100mm) 980 720 Bundle tube excess length (%) 0.030% 0.038%

[0076] As shown in the table above, even with the exact same type and dosage of crystallizer, the performance of the final product varied significantly simply due to the different timing of its addition. This invention mixes powdered crystallizer with PBT resin particles at room temperature, allowing the crystallizer particles to adhere uniformly to the surface of the PBT particles. During the subsequent extrusion and melting process, each crystallizer particle is encapsulated by the molten PBT, thus forming an effective nucleation point at its location, achieving uniform and efficient heterogeneous nucleation.

[0077] In Example 6 (added at high temperature in Zone 4), the crystallizer is directly added to the PBT melt that is already in a high-temperature molten state. At this time, the high viscosity melt makes it difficult to disperse the crystallizer particles quickly and evenly, which easily leads to the crystallizer particles agglomerating and failing to provide uniform and effective nucleation sites. The particles are difficult to be fully wetted by the PBT molecular chains, and the nucleation efficiency is greatly reduced, resulting in a decrease in performance.

[0078] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A PBT material for secondary coating of optical communication microcables, characterized in that, It consists of the following components by weight percentage: PBT resin: 98.5% ~ 99.6%; Crystallizing agent: 0.2% ~ 0.8%, wherein the crystallizing agent is an organic acid salt, nano-clay, or inorganic mineral; Lubricant: 0.2% ~ 0.7%.

2. The PBT material for secondary coating of optical communication microcables as described in claim 1, characterized in that: The crystallizing agent is one or more of sodium benzoate, sodium phenyl phosphate, sodium stearate, talc, or organically modified montmorillonite.

3. The PBT material for secondary coating of optical communication microcables as described in claim 1, characterized in that: The particle size of the crystallizing agent is no greater than 10 μm.

4. The PBT material for secondary coating of optical communication microcables as described in claim 1, characterized in that: The lubricant is polyethylene wax or calcium stearate.

5. A method for preparing PBT material for secondary coating of optical communication microcables, characterized in that, Includes the following steps: S1. Weigh each component according to the following weight percentages: PBT resin: 98.5% ~ 99.6%; crystallizer: 0.2% ~ 0.8%; lubricant: 0.2% ~ 0.7% S2. Vacuum dry the PBT resin at 110℃-130℃ for 4-6 hours, and mix the dried PBT resin and crystallizer in a low-speed mixer at room temperature for 20-40 minutes. S3. Feed the mixed material into a twin-screw reactive extruder for melt thickening. Set the extruder temperature from zone one to zone five to 220℃-245℃, and the die head temperature to 235℃-250℃. Inert protective gas is then introduced into the melt. S4. Lubricant is accurately added in the middle and rear section of the extruder via a side feeder; S5. After melt extrusion, stretching, and cooling in a cooling water tank, the material is pelletized, sieved, and packaged to obtain PBT material.

6. The method for preparing PBT material for secondary coating of optical communication microcables as described in claim 5, characterized in that: The inert protective gas is high-purity nitrogen.

7. The method for preparing PBT material for secondary coating of optical communication microcables as described in claim 5, characterized in that: The sieve mesh size is 20 to 4 mesh.

Images