Unsaturated polyester resin for reinforced core of optical cable and preparation method of unsaturated polyester resin

Abstract

The invention discloses unsaturated polyester resin for an optical cable reinforcing core and a preparation method thereof, and belongs to the technical field of unsaturated polyester resin. The composition is composed of the following components: PG, IPA, a catalyst, maleic anhydride, AA, styrene, an antioxidant, a first polymerization inhibitor, a second polymerization inhibitor and a third polymerization inhibitor. The ratio of alcohol to acid is (1.08-1.12): 1; the activity is (3.4-3.8): 1; the molar ratio of AA to IPA is 1: (12-16); the preparation method comprises the following steps: 1) uniformly mixing propylene glycol, a catalyst and isophthalic acid; 2) raising the temperature, preserving the heat and raising the temperature again; cooling, sequentially adding a first polymerization inhibitor, maleic anhydride and adipic acid, heating, keeping the temperature, and heating again; 3) cooling and adding a second polymerization inhibitor, and 4) cooling and adding styrene, a third polymerization inhibitor and an antioxidant, uniformly mixing, and cooling to less than or equal to 60 DEG C to obtain the unsaturated polyester resin for the optical cable reinforcing core. The unsaturated polyester resin for the optical cable reinforcing core has the characteristics of high bending strength and high temperature resistance.

Description

Technical Field

[0001] This invention belongs to the field of unsaturated resin technology, specifically relating to an unsaturated polyester resin for optical cable reinforcing cores and its preparation method. Background Technology

[0002] In the field of optical cable manufacturing, the optical cable reinforcing core is a core component that ensures the structural stability of the optical cable, and its performance directly determines the service life and reliability of the optical cable in complex environments. As the "skeleton" of the optical cable, the reinforcing core needs to have both excellent bending strength and outstanding heat resistance to cope with various harsh working conditions such as underground burial, high-altitude installation, and severe temperature differences.

[0003] Currently, the industry standard for preparing resins for optical cable reinforcing cores involves blending unsaturated polyester resin and vinyl ester resin in a specific ratio. Vinyl ester resin, with its unique cross-linking system, enhances the high-temperature resistance of the composite material, ensuring structural stability of the reinforcing core. However, this blending method has unavoidable drawbacks. First, the relatively high cost of vinyl ester resin increases the production cost of optical cable reinforcing cores, becoming a major obstacle to cost reduction and efficiency improvement for companies in the context of continuously shrinking profit margins in the optical cable industry. Second, the compatibility of the two resins requires precise control of stirring rate, temperature gradient, and curing time. The mixing process alone necessitates additional precision monitoring equipment, which not only extends the production cycle but may also introduce defects such as bubbles and delamination due to fluctuations in operating parameters, leading to a lower product yield.

[0004] A Chinese invention patent entitled "A method for preparing a heat-resistant unsaturated polyester resin", publication number CN111253557A, describes the preparation of a heat-resistant unsaturated polyester resin by using phthalic anhydride, maleic anhydride, isophthalic acid, etc. as raw materials and reacting them in a stepwise heating manner under the action of a specific composite catalyst and polymerization inhibitor. However, the resin has insufficient flexural strength and toughness, and the high reaction temperature leads to high energy consumption.

[0005] The function of the fiber optic cable reinforcing core is to provide overall rigidity for the cable, preventing it from sagging due to its own weight during long-distance laying (such as aerial cables), while also ensuring the stability of the cable's cross-sectional shape for easy splicing and maintenance. High-altitude installations must withstand high temperatures from daytime sunlight, plus the heat generated by the fiber optic cable itself, thus requiring strict requirements for heat resistance and bending strength. Low bending strength will fail to provide adequate support, and poor heat resistance will easily lead to cracking when heated.

[0006] As can be seen from the above records, the existing resins used for optical cable reinforcing cores have problems such as low bending strength and poor heat resistance. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an unsaturated polyester resin for optical cable reinforcing core and its preparation method. The present invention has the characteristics of high bending strength and high temperature resistance.

[0008] To achieve the above objectives, the present invention provides an unsaturated polyester resin for optical cable reinforcing cores, comprising, by weight, the following components: 600-760 parts propylene glycol, 254.6-290.6 parts isophthalic acid, 0.26-1.45 parts catalyst, 553.6-692.7 parts maleic anhydride, 15.9-18.7 parts adipic acid, 0.038-0.046 parts first polymerization inhibitor, 0.17-0.21 parts second polymerization inhibitor, 790-911 parts styrene, 0.034-0.041 parts third polymerization inhibitor, and 0.34-0.41 parts antioxidant; the molar ratio of total alcohol to total acid is 1.08-1.12:1; the molar ratio of unsaturated acid to saturated acid is 3.4-3.8:1; and the molar ratio of adipic acid to isophthalic acid is 1:12-16. Propylene glycol (PG), maleic anhydride (abbreviated as maleic anhydride), isophthalic acid (abbreviated as IPA), and adipic acid (abbreviated as AA).

[0009] The first, second, and third polymerization inhibitors are at least one of methylhydroquinone, hydroquinone, and copper naphthenate; the catalyst is monobutyltin oxide or zinc acetate, and the zinc acetate used in this application is zinc acetate dihydrate. The antioxidant is butylated hydroxytoluene, abbreviated as BHT. The copper naphthenate in this application is 8% copper naphthenate, where 8% copper naphthenate indicates that the mass percentage of copper content is 8%. Preferably, the first polymerization inhibitor is methylhydroquinone, the second polymerization inhibitor is hydroquinone, and the third polymerization inhibitor is copper naphthenate.

[0010] The molar ratio of total alcohol to total acid, also known as the alcohol-acid ratio, is crucial. A molar ratio between 1.08 and 1.12:1 allows for the complete reaction of alcohols and acids to form high-molecular-weight polymers with intact molecular chain structures. This imparts high tensile strength and toughness to the reinforcing core of the optical cable, meeting the cable's requirements for resisting tensile and bending mechanical stresses in complex environments. A molar ratio that is too low or too high leads to lower molecular weight, insufficient resin crosslinking density, decreased mechanical properties, and negatively impacts the long-term stability of the optical cable.

[0011] The activity is determined by the molar ratio of unsaturated acid to saturated acid. A molar ratio of 3.4 to 3.8:1 can optimize the mechanical properties and thermal stability of the optical cable reinforcing core by regulating the molecular chain structure and crosslinking density. A higher ratio of unsaturated to saturated acid results in greater activity, higher mechanical strength, and a higher heat distortion temperature, but also decreased toughness, brittleness, and lower elongation at break. Therefore, neither too high nor too low activity is necessarily better. The activity of this application balances mechanical strength and elongation at break, meeting the performance requirements of unsaturated polyester resin for optical cable reinforcing cores. Excessive activity leads to a violently exothermic reaction due to excess maleic anhydride, increasing the risk of gelation; insufficient activity results in insufficient crosslinking and prolonged curing time.

[0012] The molar ratio of adipic acid to isophthalic acid is controlled at 1:12-16. Adipic acid enhances toughness, while isophthalic acid primarily strengthens strength and heat resistance. By regulating the molecular chain structure, a synergistic balance of high rigidity, heat resistance, and moderate toughness required for the optical cable reinforcing core is achieved. High flexural strength and high temperature resistance of the material can be achieved using unsaturated polyester resin. This achievement effectively solves the problems of high cost and complex processes caused by the use of mixed resins in existing technologies. This application avoids the use of expensive vinyl ester resins, using only unsaturated polyester resin for optical cable reinforcing cores as raw materials, significantly reducing the production cost of the optical cable reinforcing core. Compared with traditional mixed resins, the cost of this application can be reduced by 20-30%. The proportion of isophthalic acid reaches 12-16 times that of adipic acid. The high proportion of isophthalic acid constructs a rigid framework, and its symmetrical benzene ring structure significantly improves the regularity and packing density of the molecular chain, enabling the cured resin to form a highly cross-linked rigid network. The high thermal stability of the benzene ring effectively resists the thermal stress of the optical cable operating environment, preventing high-temperature softening and deformation. Adipic acid has a toughening effect by breaking up excessively rigid structures, absorbing external impact energy, increasing fracture elongation, and preventing brittle fracture.

[0013] By weight, it consists of the following components: 640-720 parts propylene glycol, 264.6-282.6 parts isophthalic acid, 0.53-1.13 parts catalyst, 553.6-692.7 parts maleic anhydride, 15.9-18.7 parts adipic acid, 0.038-0.046 parts primary polymerization inhibitor, 0.17-0.21 parts secondary polymerization inhibitor, 790-911 parts styrene, 0.034-0.041 parts tertiary polymerization inhibitor, and 0.34-0.41 parts antioxidant.

[0014] Preferably, the molar ratio of total alcohol to total acid is 1.09~1.11:1; this ensures sufficient esterification of carboxyl groups and avoids hydrolytic degradation caused by residual acid; it also improves the uniformity of molecular chain length, reduces oligomer residue, and lowers curing shrinkage stress. The unsaturated polyester resin for optical cable reinforcing cores obtained at this ratio exhibits excellent heat distortion temperature, tensile strength, flexural strength, and toughness.

[0015] Preferably, the molar ratio of unsaturated acid to saturated acid is 3.5~3.7:1; the balance between crosslinking density and molecular chain flexibility is optimized to achieve the best mechanical strength, heat resistance and reactivity.

[0016] Preferably, the molar ratio of adipic acid to isophthalic acid is 1:13~15; by adjusting the ratio of rigid and flexible segments of the molecular chain, the optimal balance of mechanical strength, heat resistance and toughness is achieved.

[0017] Preferably, the composition includes 680 parts propylene glycol, 273.9 parts isophthalic acid, 0.82 parts catalyst, 623.8 parts maleic anhydride, 17.2 parts adipic acid, 0.04 parts first polymerization inhibitor, 0.19 parts second polymerization inhibitor, 851 parts styrene, 0.038 parts third polymerization inhibitor, and 0.38 parts antioxidant; the molar ratio of total alcohol to total acid is 1.10:1; the molar ratio of unsaturated acid to saturated acid is 3.6:1; the molar ratio of adipic acid to isophthalic acid is 1:14; and the catalyst is monobutyltin oxide.

[0018] This invention also provides a method for preparing unsaturated polyester resin for optical cable reinforcing cores, comprising the following steps: (1) Add propylene glycol, catalyst and isophthalic acid to the reaction vessel according to the weight parts and mix well; (2) Heat the product obtained in step (1), keep it at the temperature, and then heat it again to react until the acid value is 15~20mgKOH / g; after cooling down, add the first polymerization inhibitor, maleic anhydride and adipic acid in sequence according to the weight parts, heat it, keep it at the temperature, and then heat it again to react until the acid value is 10~15mgKOH / g. (3) After cooling the product obtained in step (2), add the second polymerization inhibitor according to the weight parts; (4) After cooling down the product obtained in step (3), add styrene, third polymerization inhibitor and antioxidant by weight, mix well, and then cool down to ≤60℃ to obtain unsaturated polyester resin for optical cable reinforcing core.

[0019] The reactions described in steps (1) and (2) are both carried out under inert gas protection. Inert gas protection can prevent oxidative degradation and discoloration, reduce hydrolysis and free radical side reactions, inhibit monomer volatilization, isolate water vapor and pollutants, and improve the rigidity, heat resistance and toughness consistency of the final product. The inert gas used in steps (1) and (2) is nitrogen.

[0020] The specific operation of step (1) is to add propylene glycol, catalyst and isophthalic acid to the reaction vessel according to the weight parts, and mix them under the protection of inert gas; the stirring rate of step (1) is 110~130r / min.

[0021] The specific operation of step (2) is as follows: under the protection of an inert gas, the product obtained in step (1) is heated to 185~190℃ to react and produce water, and then kept at this temperature for 0.5~1h. The temperature is then increased to 200~205℃ at a rate of 15~18℃ / h to react until the acid value reaches 15~20 mgKOH / g. After cooling to 135~140℃, the first polymerization inhibitor, maleic anhydride, and adipic acid are added sequentially according to their weight proportions. The temperature is then increased to 165~170℃ to react and produce water, and then kept at this temperature for 0.5~1h. The temperature is then increased to 205~210℃ at a rate of 15~18℃ / h to react until the acid value reaches 10~15 mgKOH / g. The stirring speed in step (2) is 230~250 r / min. The 165~170℃ holding stage can promote the ring-opening of maleic anhydride and the initial esterification reaction with adipic acid; the heating rate of 15~18℃ / h to 205~210℃ can reduce the loss caused by the volatilization of alcohol and acid during the synthesis process, ensuring economic benefits.

[0022] The specific operation of step (3) is to cool down to 150~160℃ and then add the second polymerization inhibitor according to the weight. The stirring speed of step (3) is 230~250r / min.

[0023] Step (4) After cooling the product obtained in step (3) to 120~130℃, add styrene, the third polymerization inhibitor, and the antioxidant according to the weight parts, stir and mix well, and then stir and cool to ≤60℃ to obtain unsaturated polyester resin for optical cable reinforcing core. The stirring speed in step (4) is 390~410r / min; 150~160℃ is the temperature window in which the polymerization inhibitor can effectively play its role, which can both inhibit the premature polymerization of maleic anhydride residual double bonds and avoid the decomposition and failure of the polymerization inhibitor due to high temperature. 120~130℃ can ensure that it is uniformly mixed and does not volatilize, providing an active diluent for subsequent crosslinking and curing.

[0024] The cooling rate at each step of this application will not affect the flexural strength and temperature resistance of the final product. The first polymerization inhibitor is added to prevent the risk of uncontrollable or even curing caused by excessively rapid self-polymerization of the resin during synthesis. The second polymerization inhibitor is suitable for a temperature window of 150-160℃. Its addition prevents premature cross-linking of the system due to residual active free radicals during cooling, which would lead to gelation risks. The third polymerization inhibitor is added simultaneously with styrene at 120-130℃. Styrene is easily polymerized by heat or light; the addition of the third inhibitor avoids gelation problems caused by localized overheating during dilution and cooling stages, ensuring that the reaction proceeds as expected at each stage. Adding the second and third polymerization inhibitors simultaneously would affect the resin's gel time.

[0025] The phased addition of the polymerization inhibitor in this application ensures the stability of the resin synthesis process, allowing the total alcohol and total acid to fully react and form a high molecular weight polymer, while simultaneously ensuring a balance in the crosslinking density of unsaturated and saturated acids. This results in a well-ordered resin molecular chain and a reasonable packing density. The symmetrical benzene ring structure of isophthalic acid significantly enhances heat resistance, while adipic acid effectively strengthens toughness, achieving a synergistic effect of high flexural strength and high temperature resistance. Both isophthalic acid and adipic acid are relatively low-reactivity raw materials; adding them simultaneously would lead to slow synthesis speed, excessively long cycle time, and difficulty in completing the reaction. An excessively long reaction cycle not only causes the resin to darken, affecting the product's appearance, but also increases production costs, hindering economic efficiency. Incomplete reaction leads to reduced mechanical properties and heat resistance of the product; an excessively long reaction cycle not only increases production costs, hindering economic efficiency, but also causes the resin to darken, affecting the product's appearance.

[0026] Compared with the prior art, the beneficial effects of this invention are: 1. The present invention discloses an unsaturated polyester resin for optical cable reinforcing cores, which features high flexural strength and high temperature resistance. Adipic acid plays a role in improving toughness, while isophthalic acid mainly enhances strength and heat resistance. By regulating the molecular chain structure, a synergistic balance of high rigidity, heat resistance, and moderate toughness required for optical cable reinforcing cores is achieved. High flexural strength and high temperature resistance of the material can be achieved using only unsaturated polyester resin for optical cable reinforcing cores. The total alcohol to total acid molar ratio ensures the formation of high molecular weight polymers, guaranteeing tensile strength and toughness. The unsaturated acid to saturated acid molar ratio balances mechanical strength, elongation at break, and thermal stability, avoiding the risk of gelation or delayed curing caused by excessively high or low ratios. The present invention discloses an unsaturated polyester resin for optical cable reinforcing core with tensile strength of 85.08~98.48MPa, tensile modulus of elasticity of 3623.0~3926.5MPa, elongation at break of 2.61~3.55%, flexural strength of 132.1~138.8MPa, flexural modulus of elasticity of 3765.4~3920.3MPa, and heat distortion temperature of 133.6~139.3℃.

[0027] 2. The unsaturated polyester resin for optical cable reinforcing core of the present invention has a simple process, low cost, stable performance without the need to mix other resins, and saves raw materials and energy consumption. Detailed Implementation

[0028] Example 3 is the preferred embodiment of the present invention. The present invention will be further described below with reference to specific embodiments and comparative examples.

[0029] The chemical additives used in the embodiments and comparative examples of this invention are all commercially available, and the specific information is as follows: Propylene glycol: purchased from Cangzhou Jinzhan Chemical Co., Ltd.; isophthalic acid: purchased from Jiangsu Zhaohua Chemical Co., Ltd.; Monobutyltin oxide: purchased from Changzhou Yurong Chemical Co., Ltd.; Zinc acetate dihydrate: purchased from Guangzhou Yuansu Chemical Technology Development Co., Ltd.; Methylhydroquinone: purchased from Changzhou Yurong Chemical Co., Ltd.; Hydroquinone: Industrial grade, purchased from Changzhou Yurong Chemical Co., Ltd.; 8% Copper naphthenate: purchased from Shanghai Taoyuan Cobalt Co., Ltd.; BHT: Industrial grade, purchased from Changzhou Yurong Chemical Co., Ltd. maleic anhydride: purchased from Wanhua Chemical Group Petrochemical Sales Co., Ltd.; Adipic acid: purchased from Ningbo Zhongxing New Material Technology Co., Ltd.; Styrene: Purchased from Shenyang Jinhua Petrochemical Co., Ltd.; Cobalt isooctanoate, model EC-12: purchased from J.P. Chemical (Shanghai) Co., Ltd.; Methyl ethyl ketone peroxide: purchased from Qingdao Feiyang Trading Co., Ltd.

[0030] Table 1. Raw materials for the embodiments (by weight). .

[0031] Example 1 A method for preparing unsaturated polyester resin for optical cable reinforcing cores comprises the following steps: (1) Add propylene glycol, catalyst and isophthalic acid to the reaction vessel according to the weight parts, and mix them under the protection of nitrogen; the stirring rate in step (1) is 130 r / min; (2) Under the protection of nitrogen, the product obtained in step (1) is heated to 185°C and reacted to produce water. After the water is produced, the temperature is maintained for 0.5 h. Then, the temperature is increased to 200°C at a rate of 15°C / h and reacted until the acid value is 15 mg KOH / g. The temperature is lowered to 135°C and the first polymerization inhibitor, maleic anhydride and adipic acid are added in sequence according to the weight parts. After stirring and heating to 165°C, the water is produced. After the water is produced, the temperature is maintained for 0.5 h. Then, the temperature is increased to 205°C at a rate of 15°C / h and reacted until the acid value is 10 mg KOH / g. The stirring rate in step (2) is 250 r / min. (3) After cooling the product obtained in step (2) to 150°C, add the second polymerization inhibitor according to the weight parts. The stirring rate in step (3) is 250 r / min. (4) After the product obtained in step (3) is cooled to 120°C, styrene, third polymerization inhibitor and antioxidant are added according to the weight parts, mixed evenly, and then cooled to ≤60°C to obtain unsaturated polyester resin for optical cable reinforcing core; the stirring rate in step (4) is 410r / min.

[0032] Example 2 A method for preparing unsaturated polyester resin for optical cable reinforcing cores comprises the following steps: (1) Add propylene glycol, catalyst and isophthalic acid to the reaction vessel in parts by weight and mix them under nitrogen protection. The stirring rate in step (1) is 110 r / min. (2) Under the protection of nitrogen, the product obtained in step (1) is heated to 190°C and reacted to produce water. After holding the temperature for 1 hour, the temperature is increased to 205°C at a rate of 18°C / h and reacted until the acid value is 20 mg KOH / g. The temperature is then lowered to 140°C and the first polymerization inhibitor, maleic anhydride and adipic acid are added in sequence according to the weight parts. Under the protection of nitrogen, the temperature is increased to 170°C and reacted to produce water. After holding the temperature for 1 hour, the temperature is increased to 210°C at a rate of 18°C / h and reacted until the acid value is 15 mg KOH / g. The stirring rate in step (2) is 230 r / min. (3) After cooling the product obtained in step (2) to 160°C, add the second polymerization inhibitor according to the weight parts. The stirring rate in step (3) is 230 r / min. (4) After cooling the product obtained in step (3) to 130°C, add styrene, third polymerization inhibitor and antioxidant by weight, mix well, and then cool to ≤60°C to obtain unsaturated polyester resin for optical cable reinforcing core; the stirring rate in step (4) is 390r / min.

[0033] Example 3 A method for preparing unsaturated polyester resin for optical cable reinforcing cores comprises the following steps: (1) Add propylene glycol, catalyst and isophthalic acid to the reaction vessel according to the weight parts, and mix them under the protection of nitrogen; the stirring rate in step (1) is 120 r / min; (2) Under the protection of nitrogen, the product obtained in step (1) is heated to 187°C and reacted to produce water. After the water is produced, the temperature is maintained for 0.7 h. Then, the temperature is increased to 203°C at a rate of 16°C / h and reacted until the acid value is 18 mg KOH / g. The temperature is lowered to 137°C and the first polymerization inhibitor, maleic anhydride and adipic acid are added in sequence according to the weight parts. After the water is produced, the temperature is increased to 177°C and reacted to produce water. After the water is produced, the temperature is maintained for 0.7 h. Then, the temperature is increased to 207°C at a rate of 17°C / h and reacted until the acid value is 13 mg KOH / g. The stirring rate in step (2) is 240 r / min. (3) After cooling the product obtained in step (2) to 155°C, add the second polymerization inhibitor according to the weight parts; the stirring rate in step (3) is 240 r / min; (4) After cooling the product obtained in step (3) to 125°C, add styrene, third polymerization inhibitor and antioxidant by weight, mix well, and then cool to ≤60°C to obtain unsaturated polyester resin for optical cable reinforcing core; the stirring rate in step (4) is 400r / min.

[0034] Example 4 A method for preparing unsaturated polyester resin for optical cable reinforcing cores comprises the following steps: (1) Add propylene glycol, catalyst and isophthalic acid to the reaction vessel according to the weight parts, and mix them under the protection of nitrogen; the stirring rate in step (1) is 120 r / min; (2) Under nitrogen protection, the product obtained in step (1) was heated to 187°C and reacted to produce water. After holding the temperature for 0.7 h, the temperature was increased to 203°C at a rate of 16°C / h and reacted until the acid value was 18 mg KOH / g. The temperature was then lowered to 137°C and the first polymerization inhibitor, maleic anhydride and adipic acid were added in sequence according to the weight parts. Under nitrogen protection, the temperature was increased to 177°C and reacted to produce water. After holding the temperature for 0.7 h, the temperature was increased to 207°C at a rate of 17°C / h and reacted until the acid value was 11 mg KOH / g. The stirring rate in step (2) was 240 r / min. (3) After cooling the product obtained in step (2) to 155°C, add the second polymerization inhibitor according to the weight parts; the stirring rate in step (3) is 240 r / min; (4) After cooling the product obtained in step (3) to 125°C, add styrene, third polymerization inhibitor and antioxidant by weight, mix well, and then cool to ≤60°C to obtain unsaturated polyester resin for optical cable reinforcing core; the stirring rate in step (4) is 400r / min.

[0035] Example 5 A method for preparing unsaturated polyester resin for optical cable reinforcing cores comprises the following steps: (1) Add propylene glycol, catalyst and isophthalic acid to the reaction vessel according to the weight parts, and mix them under the protection of nitrogen; the stirring rate in step (1) is 120 r / min; (2) Under nitrogen protection, the product obtained in step (1) was heated to 187°C and reacted to produce water. After the water was produced, the temperature was maintained for 0.7 h. Then, the temperature was increased to 203°C at a rate of 16°C / h and reacted until the acid value was 18 mg KOH / g. The temperature was lowered to 137°C and the first polymerization inhibitor, maleic anhydride and adipic acid were added in sequence according to the weight parts. Under nitrogen protection, the temperature was increased to 177°C and reacted to produce water. After the water was produced, the temperature was maintained for 0.7 h. Then, the temperature was increased to 207°C at a rate of 17°C / h and reacted until the acid value was 14 mg KOH / g. The stirring rate in step (2) was 240 r / min. (3) After cooling the product obtained in step (2) to 155°C, add the second polymerization inhibitor according to the weight parts. The stirring rate in step (3) is 240 r / min. (4) After cooling the product obtained in step (3) to 125°C, add styrene, third polymerization inhibitor and antioxidant by weight, mix well, and then cool to ≤60°C to obtain unsaturated polyester resin for optical cable reinforcing core; the stirring rate in step (4) is 400r / min.

[0036] Comparative Example 1 The preparation method of the unsaturated polyester resin for the optical cable reinforcing core described in this comparative example is the same as that in Example 3, except that the alkyd-acid ratio is too low. For the specific formula, please refer to Table 2.

[0037] Comparative Example 2 The preparation method of the unsaturated polyester resin for the optical cable reinforcing core described in this comparative example is the same as that in Example 3, except that the alkyd-acid ratio is too high. For the specific formula, please refer to Table 2.

[0038] Comparative Example 3 The preparation method of the unsaturated polyester resin for the optical cable reinforcing core described in this comparative example is the same as that in Example 3, except that the activity is too low. For the specific formula, please refer to Table 2.

[0039] Comparative Example 4 The preparation method of the unsaturated polyester resin for optical cable reinforcing core described in this comparative example is the same as that in Example 3, except that the activity is too high. For the specific formula, please refer to Table 2.

[0040] Comparative Example 5 The preparation method of the unsaturated polyester resin for the optical cable reinforcing core described in this comparative example is the same as that in Example 3, except that the molar ratio of adipic acid and isophthalic acid is too low. For the specific formula, please refer to Table 2.

[0041] Comparative Example 6 The preparation method of the unsaturated polyester resin for the optical cable reinforcing core described in this comparative example is the same as that in Example 3, except that the molar ratio of adipic acid and isophthalic acid is too high. For the specific formula, please refer to Table 2.

[0042] Comparative Example 7 The formulation of the unsaturated polyester resin for the optical cable reinforcing core described in this comparative example is the same as that in Example 3, except that (1) propylene glycol, catalyst, isophthalic acid and adipic acid are added to the reaction vessel in parts by weight and mixed under nitrogen protection.

[0043] Table 2 shows the raw materials (by weight) for Comparative Examples 1-6. .

[0044] Performance testing The performance of the unsaturated polyester resin used for the optical cable reinforcing core prepared in the examples and comparative examples was tested, and the specific test results are shown in Table 3.

[0045] 1% cobalt isooctanoate accelerator was added to the unsaturated polyester resin for optical cable reinforcing core prepared in the examples and comparative examples, and stirred evenly. Then, 1.5% methyl ethyl ketone peroxide initiator was added and stirred evenly. The mixture was poured into a steel mold with dimensions of 350mm×300mm×5mm and cured at 21~25℃ for 24 hours to obtain an unsaturated polyester resin casting for optical cable reinforcing core.

[0046] Tensile strength was tested in accordance with standard GB / T2567-2021; The tensile modulus of elasticity was tested in accordance with the standard GB / T2567-2021; The elongation at break was tested in accordance with the standard GB / T2567-2021; Bending strength was tested in accordance with standard GB / T2567-2021; The flexural modulus of elasticity was tested in accordance with standard GB / T2567-2021; The heat distortion temperature was tested in accordance with the standard GB / T2567-2021.

[0047] Table 3 Performance test results of the examples and comparative examples .

[0048] As shown in Table 3, the tensile strength of Examples 1-5 is 85.08-98.48 MPa, the tensile modulus of elasticity is 3623.0-3926.5 MPa, the elongation at break is 2.61-3.55%, the flexural strength is 132.1-138.8 MPa, the flexural modulus of elasticity is 3765.4-3920.3 MPa, and the heat distortion temperature is 133.6-139.3℃, which meets the requirements for optical cable reinforcing core materials. Adipic acid plays a role in improving toughness, while isophthalic acid mainly enhances strength and heat resistance. By regulating the molecular chain structure, a synergistic balance of high rigidity, heat resistance, and moderate toughness required for optical cable reinforcing cores is achieved. The flexural strength of Example 3 reaches 138.8 MPa, and the heat distortion temperature reaches 139.3℃.

[0049] The heat distortion temperature range of 133.6~139.3℃ in this application is because optical cables erected at high altitudes are subject to high temperatures from daytime sunlight, coupled with the heat generated during communication, leading to a rapid temperature increase. For optical cables facing underground burial and high-altitude installations (due to day / night / seasonal temperature differences), a heat distortion temperature of 133.6~139.3℃ helps prevent performance degradation caused by temperature changes. A heat distortion temperature that is too low will cause the resin to soften under high-temperature conditions, making it unable to maintain structural rigidity, resulting in cracks and loss of support; bending strength will decrease with increasing temperature, making it unable to withstand the cable's own weight, causing the overhead optical cable to sag and deform; a low heat distortion temperature will also cause cracks to accelerate the intrusion of moisture and contaminants, triggering resin hydrolysis or degradation, while increasing the difficulty of cable splicing and maintenance, and shortening its service life.

[0050] The results of Comparative Examples 1 and 2 show that when the alkyd-acid ratio exceeds the range of this application, esterification will be incomplete, the molecular chain crosslinking density will be insufficient, and the tensile strength and heat distortion temperature will be reduced. Only when the alkyd-acid ratio is within the range of this application can the optimal tensile strength and heat distortion temperature be obtained.

[0051] The results of Comparative Examples 3 and 4 show that when the activity exceeds the range of this application, the elongation at break and the heat distortion temperature will decrease; only when the activity is within the range of this application can the optimal elongation at break and the heat distortion temperature be obtained.

[0052] The excessive adipic acid in Comparative Example 5 led to a decrease in heat distortion temperature, and the excessive rigidity in Comparative Example 6 led to stress concentration and easy fracture. The results of Comparative Examples 5 and 6 show that only when the molar ratio of adipic acid to isophthalic acid is within the range of this application can toughness and heat resistance be balanced.

[0053] In Comparative Example 7, the simultaneous addition of isophthalic acid and adipic acid resulted in a decrease in both mechanical properties and heat distortion temperature. This is because the simultaneous addition of both leads to a slower synthesis rate and incomplete reaction. Therefore, it is evident that only by following the preparation steps of this application can the technical effects of this application be achieved.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An unsaturated polyester resin for the reinforcing core of an optical cable, characterized in that, By weight, it consists of the following components: 600-760 parts propylene glycol, 254.6-290.6 parts isophthalic acid, 0.26-1.45 parts catalyst, 553.6-692.7 parts maleic anhydride, 15.9-18.7 parts adipic acid, 0.038-0.046 parts primary polymerization inhibitor, 0.17-0.21 parts secondary polymerization inhibitor, 790-911 parts styrene, 0.034-0.041 parts tertiary polymerization inhibitor, and 0.34-0.41 parts antioxidant; the molar ratio of total alcohol to total acid is 1.08-1.12:1; the molar ratio of unsaturated acid to saturated acid is 3.4-3.8:1; and the molar ratio of adipic acid to isophthalic acid is 1:12-16.

2. The unsaturated polyester resin for optical cable reinforcing core according to claim 1, characterized in that, The first, second, and third polymerization inhibitors are at least one of methylhydroquinone, hydroquinone, and copper naphthenate.

3. The unsaturated polyester resin for optical cable reinforcing core according to claim 1, characterized in that, By weight, it consists of the following components: 640-720 parts propylene glycol, 264.6-282.6 parts isophthalic acid, 0.53-1.13 parts catalyst, 553.6-692.7 parts maleic anhydride, 15.9-18.7 parts adipic acid, 0.038-0.046 parts primary polymerization inhibitor, 0.17-0.21 parts secondary polymerization inhibitor, 790-911 parts styrene, 0.034-0.041 parts tertiary polymerization inhibitor, and 0.34-0.41 parts antioxidant.

4. The unsaturated polyester resin for optical cable reinforcing core according to claim 1, characterized in that: The molar ratio of total alcohol to total acid is 1.09 to 1.11:

1.

5. The unsaturated polyester resin for optical cable reinforcing core according to claim 1, characterized in that, The molar ratio of the unsaturated acid to the saturated acid is 3.5~3.7:

1.

6. The unsaturated polyester resin for optical cable reinforcing core according to claim 1, characterized in that, The molar ratio of adipic acid to isophthalic acid is 1:13~15.

7. A method for preparing an unsaturated polyester resin for an optical cable reinforcing core according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Add propylene glycol, catalyst and isophthalic acid to the reaction vessel according to the weight parts and mix well; (2) Heat the product obtained in step (1), keep it at the temperature, and then heat it again to react until the acid value is 15~20mgKOH / g; after cooling down, add the first polymerization inhibitor, maleic anhydride and adipic acid in sequence according to the weight parts, heat it, keep it at the temperature, and then heat it again to react until the acid value is 10~15mgKOH / g. (3) After cooling the product obtained in step (2), add the second polymerization inhibitor according to the weight parts; (4) After cooling down the product obtained in step (3), add styrene, third polymerization inhibitor and antioxidant by weight, mix well, and then cool down to ≤60℃ to obtain unsaturated polyester resin for optical cable reinforcing core.

8. The method for preparing unsaturated polyester resin for optical cable reinforcing core according to claim 7, characterized in that, The specific operation of step (1) is to add propylene glycol, catalyst and isophthalic acid to the reaction vessel in parts by weight and mix them under the protection of inert gas.

9. A method for preparing an unsaturated polyester resin for an optical cable reinforcing core according to claim 7, characterized in that, The specific operation of step (2) is as follows: under the protection of an inert gas, the product obtained in step (1) is heated to 185~190℃ to react and produce water, and then kept at the temperature for 0.5~1h. Then, the temperature is increased to 200~205℃ at a rate of 15~18℃ / h to react until the acid value is 15~20mgKOH / g. After cooling to 135~140℃, the first polymerization inhibitor, maleic anhydride and adipic acid are added in sequence according to the weight parts. After the temperature is increased to 165~170℃ to react and produce water, it is kept at the temperature for 0.5~1h. Then, the temperature is increased to 205~210℃ at a rate of 15~18℃ / h to keep at the temperature to react until the acid value is 10~15mgKOH / g.

10. A method for preparing an unsaturated polyester resin for an optical cable reinforcing core according to claim 7, characterized in that, The specific operation of step (4) is to cool the material obtained in step (3) to 120~130℃, add styrene, third polymerization inhibitor and antioxidant according to the weight, mix well, and then cool to ≤60℃ to obtain unsaturated polyester resin for optical cable reinforcing core.