Inner-layer coating for marine optical fiber and preparation method of inner-layer coating

Abstract

The invention discloses an inner coating for a marine optical fiber, which belongs to the technical field of optical fiber coatings and comprises the following raw materials in parts by weight: 80-120 parts of polyurethane acrylate prepolymer, 10-130 parts of bifunctional acrylate active monomer diluent, 1-16 parts of photoinitiator and 0-7 parts of assistant. The invention also discloses a preparation method of the polyurethane acrylate prepolymer. According to the invention, the polyurethane acrylate prepolymer is matched with the bifunctional polyurethane acrylate to prepare the inner-layer coating, the inner-layer coating has lower modulus and good flexibility after being cured, and the stress brought by the harder outer-layer coating can be fully released; meanwhile, the cohesive energy density of the coating is improved on the basis of low modulus, so that the coating has relatively high strength and can be suitable for a seabed high-pressure environment.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber coating technology, specifically relating to a method for preparing an inner layer coating for marine optical fibers and a polyurethane acrylate prepolymer. Background Technology

[0002] Over the past thirty years, civilian communication technology has made rapid progress. Among them, submarine optical cables, due to their characteristics such as long transmission distance, strong anti-interference ability, high security and good confidentiality, have gradually replaced coaxial cables, satellite communication and other technologies, and have become one of the main media for global information transmission today.

[0003] At the fiber optic level, due to the need for long-distance transmission, higher strength and lower loss are required. In the applicant's earlier patent application CN119736013A, a partially crystalline outer coating for optical fibers was prepared. Through matching with the fiber drawing process, the drawn optical fiber possessed good strength and water resistance. However, the rigid outer coating also places higher demands on the performance of the inner coating, requiring the inner coating to better function as a buffer layer. The characteristics of marine optical fibers also determine that they are more sensitive to external stress than ordinary optical fibers.

[0004] Commercially available inner coatings, designed to achieve low attenuation and low microbending loss in optical fibers, often possess very low strength and modulus. While this design effectively relieves stress and contributes to the low attenuation performance of marine optical fibers, its low strength poses a risk of failure in the high-pressure environment of the seabed. Therefore, it is necessary to design an inner coating that is both flexible and possesses sufficient strength, while also maintaining good flexibility at low temperatures to meet the environmental requirements of marine optical fibers. Summary of the Invention

[0005] In view of one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides a method for preparing marine optical fiber inner layer coating and polyurethane acrylate prepolymer. The coating improves the strength while maintaining a low modulus, so that it can meet the requirements of use in high-pressure environments on the seabed.

[0006] To achieve the above objectives, according to one aspect of the present invention, an inner layer coating for marine optical fibers is provided, wherein the raw materials of the inner layer coating, by weight, include: 80-120 parts of polyurethane acrylate prepolymer, 10-130 parts of difunctional acrylate reactive monomer diluent, 1-16 parts of photoinitiator, and 0-7 parts of additives.

[0007] As a further improvement of the present invention, the difunctional acrylate reactive monomer diluent includes one or more of the following: Lankeluo polyurethane acrylate 6212, Changxing polyurethane acrylate 61369, Changxing polyurethane acrylate 6101, Changxing polyurethane acrylate DR-161, polyethylene glycol dimethacrylate, bisphenol A dimethacrylate oxyacetylene oxide, 2-methyl-1,3-propanediol diacrylate oxyacetylene oxide, 1,9-nonanediol dimethacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, and neopentyl glycol diacrylate oxyacetylene oxide. More preferably, it is Lankeluo polyurethane acrylate 6212 and / or Changxing polyurethane acrylate 61369, and more preferably, it is Lankeluo polyurethane acrylate 6212.

[0008] As a further improvement of the present invention, the raw materials of the polyurethane acrylate prepolymer, by weight, include 50-100 parts of polyol, 3-20 parts of isocyanate, 1-10 parts of (meth)acrylate hydroxy ester, 0.05-0.2 parts of catalyst, and 0.05-0.2 parts of polymerization inhibitor.

[0009] As a further improvement of the present invention, the method for preparing the polyurethane acrylate prepolymer includes: After mixing polyol, isocyanate and catalyst, react at 60±2℃ for 2~2.5 hours, then add (meth)acrylate hydroxyl ester and polymerization inhibitor, and continue to react at 65±2℃ for 2~3 hours until the isocyanate is completely consumed, thus obtaining the polyurethane acrylate prepolymer.

[0010] As a further improvement of the present invention, the polyol includes one or more of polyether polyols, polyolefin polyols, and polysiloxane polyols. More preferably, it is a polyether polyol, and more preferably, it is polypropylene glycol.

[0011] The isocyanate includes one or more of toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, phenyldimethyl diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, lysine diisocyanate, diethyl transbutadiene diisocyanate, methylcyclohexyl diisocyanate, dicyclohexylmethane diisocyanate, and tetramethylphenyldimethyl diisocyanate; preferably isophorone diisocyanate.

[0012] The catalyst comprises one or more of the following: dibutyltin dilaurate, bismuth carboxylate, bismuth isooctanoate, N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, N,N,N',N'-tetramethylalkylene diamine, triethylamine, N,N-dimethylbenzylamine, steramine, N-ethylmorpholine, N,N'-diethylpiperazine, triethanolamine, dimethylaminoethanol, pyridine, and N,N'-dimethylpyridine; preferably dibutyltin dilaurate.

[0013] As a further improvement of the present invention, the (meth)acrylate hydroxy ester is one or more selected from the following: hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, 2-hydroxyoctyl (meth)acrylate, pentaerythritol tri(meth)acrylate, glycerol di(meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, trimethylolpropane di(meth)acrylate, and trimethylolethane di(meth)acrylate; and / or, The polymerization inhibitor is one or more of hydroquinone and p-hydroxyanisole.

[0014] As a further improvement of the present invention, the photoinitiator includes one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylbenzophenone, benzoin dimethyl ether, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 2-methyl-1-(4-methylthiophenyl)-2-morpholine-1-propanone.

[0015] As a further improvement of the present invention, the additives include one or more of defoamers, leveling agents, antioxidants and stabilizers.

[0016] According to another aspect of the present invention, a method for preparing a polyurethane acrylate prepolymer is provided for preparing the polyurethane acrylate prepolymer in the inner layer coating for marine optical fibers, characterized by comprising the following steps: After mixing polyol, isocyanate and catalyst, react at 60±2℃ for 2~2.5 hours, then add (meth)acrylate hydroxyl ester and polymerization inhibitor, and continue to react at 65±2℃ for 2~3 hours until the isocyanate is completely consumed, thus obtaining the polyurethane acrylate prepolymer.

[0017] This invention utilizes polyether polyols to prepare polyurethane acrylate prepolymers, achieving a balance between flexibility and water resistance, making them suitable as oligomeric materials for the inner coating of marine optical fibers. Polyether polyols (such as polypropylene glycol) have regular structures and controllable molecular weights. Polyurethane acrylate prepolymers synthesized using polyether polyols exhibit better molecular chain flexibility, effectively buffering mechanical stress caused by changes in seabed pressure and preventing damage to the optical fiber due to deformation. Simultaneously, the strong hydrophobicity of the ether bonds in polyether polyols effectively blocks seawater penetration, reducing the risk of moisture absorption or corrosion of the internal optical fiber.

[0018] Marine optical fiber is an ultra-low attenuation fiber, but its application environment differs from that of ordinary ultra-low attenuation optical fiber. The high-pressure environment on the seabed requires the inner coating to maintain low modulus and high elongation at break while also possessing a certain compressive strength. This invention, based on the aforementioned polyurethane acrylate prepolymer, further enhances the cohesiveness of the coating after curing by adding a bifunctional acrylate diluent (generally, monofunctional acrylate diluents are used for inner coatings). This improves the strength and compressive strength. Simultaneously, the bifunctional structure forms a denser network, effectively blocking seawater penetration and protecting the optical fiber from moisture and corrosion, further improving its water resistance.

[0019] However, conventional bifunctional diluents result in coatings with high modulus after curing, making them unsuitable for inner layer coatings. For the inner layer material of marine optical fibers, the selection of bifunctional acrylate diluents needs to balance flexibility and low-temperature performance, while also considering their dilution capacity and curing shrinkage (bifunctional diluents generally have a higher curing shrinkage than monofunctional diluents; excessively high curing shrinkage can introduce stress and affect fiber attenuation). Therefore, this invention preferably uses bifunctional acrylate diluents Lankel 6212 and Changxing 61369 in combination with polyurethane acrylate prepolymers to prepare the inner layer coating. Lankel 6212 and Changxing 61369, as bifunctional polyurethane acrylate diluents, exhibit good flexibility at both room temperature and low temperature, and have lower viscosity than conventional bifunctional polyurethane acrylates (Lankel 6212 being superior), and also possess lower curing shrinkage (Lankel 6212 being superior). According to coating performance testing, the inner layer coating of the optical fiber of the present invention has low modulus, high elongation at break, and good flexibility; at the same time, according to optical fiber performance testing, the optical fiber prepared with the inner layer coating of the present invention has strong compressive strength and is suitable for marine optical fiber.

[0020] Furthermore, to adapt to complex temperature environments, the coating needs to have a low modulus at low temperatures to maintain low attenuation of the optical fiber. This invention, by formulating a prepolymer with excellent low-temperature performance and combining it with a bifunctional acrylate diluent with good low-temperature performance, enables the coating to maintain a low modulus at low temperatures. This invention simulates a high-pressure environment on the seabed by conducting low-temperature tests on optical fiber ribbons at -40°C. The results show that the optical fiber prepared using the inner coating formulation of this invention maintains low attenuation at low temperatures, exhibits low-temperature resistance, and is suitable for marine optical fibers.

[0021] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art: (1) The present invention prepares an inner coating by combining a polyurethane acrylate prepolymer with a difunctional polyurethane acrylate. It has a low modulus and good flexibility after curing, which can fully release the stress brought by the hard outer coating. At the same time, the cohesive energy density of the coating is increased on the basis of low modulus, so that the coating has high strength and can be used in the high pressure environment of the seabed.

[0022] (2) The present invention formulates a prepolymer with excellent low-temperature performance and combines it with a difunctional acrylate diluent with good low-temperature performance. While maintaining the high strength of the coating, the low-temperature performance is optimized so that it can maintain a low modulus in a low-temperature environment to maintain the low attenuation of the optical fiber.

[0023] (3) The high cohesive energy density of the inner coating and the modulus stability at low temperature of the present invention simultaneously improve the environmental weather resistance of the optical fiber. The test results show that the optical fiber’s resistance to damp heat aging and its resistance to low temperature under high pressure are significantly improved. Attached Figure Description

[0024] Figure 1 These are microscope images taken after fiber compression testing in Example 1. Figure 2 This is a microscope image of the optical fiber compression test in Comparative Example 1. Figure 3 This is a microscope image of the fiber compression test in Comparative Example 2; Figure 4 This is a microscope image of the optical fiber compression test in Comparative Example 3. Figure 5 This is a microscope image of the optical fiber compression test in Comparative Example 4; Figure 6 This is a microscope image of the fiber optic cable after the fiber compression test in Comparative Example 5. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] With regard to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. Unless otherwise stated, the techniques used in the embodiments are conventional methods well known to those skilled in the art, and the materials, reagents, etc., used are commercially available products.

[0029] Examples 1 to 4 (1) Preparation of polyurethane acrylate prepolymer: In a three-necked flask equipped with a mechanical stirrer, a constant pressure funnel, and a thermometer, polyol, isocyanate, and catalyst were added sequentially, and the temperature was raised to 60±2℃ and maintained for 2~2.5 hours. Then, (meth)acrylate hydroxyl ester and polymerization inhibitor were added dropwise through the constant pressure funnel, and the reaction was continued at 65±2℃ for 2~3 hours. The isocyanate group content was measured by sampling until the content was zero, thus obtaining the polyurethane acrylate prepolymer. The raw materials and mass fractions of the polyurethane acrylate prepolymer are shown in Table 1.

[0030] Table 1. Raw materials and mass fractions of the prepolymer

[0031] (2) Preparation of inner layer coating for marine optical fiber: The polyurethane acrylate prepolymer prepared in step (1) is mixed with difunctional acrylate reactive monomer diluent, photoinitiator and additives to obtain the inner layer coating for marine optical fiber. The specific raw materials and mass fractions are shown in Table 2.

[0032] Table 2 Raw materials and mass fractions of inner coating

[0033] Comparative Examples 1 to 5 (1) The polyurethane acrylate prepolymers in Comparative Examples 1, 2, 3, and 5 were prepared according to the method described in the above examples. The raw materials and mass fractions of the polyurethane acrylate prepolymers are shown in Table 3. The prepolymer in Comparative Example 4 was Changxing polyurethane acrylate oligomer DR-U168.

[0034] Table 3 Raw materials and mass fractions of prepolymer

[0035] (2) The inner coating was prepared according to the method of the above embodiment. The specific raw materials and mass fractions are shown in Table 4.

[0036] Table 4 Raw materials and mass fractions of inner coating

[0037] Furthermore, the performance of the inner coatings and optical fibers prepared in the examples and comparative examples was tested. The performance testing methods are as follows: Elongation at break of the cured coating film and tensile modulus of the cured coating film at 2.5% strain: tested in accordance with GB / T 1040.2-2022; Energy storage modulus E': Tested in accordance with ISO 6721-4; Fiber attenuation, fiber tensile strength (including after aging), and additional attenuation from immersion testing: Tested in accordance with IEC 60793-1; -40℃ Low Temperature Test with Reel: The optical fiber is not loosely wound, and the attenuation data is tested directly on the reel at a low temperature of -40℃.

[0038] Fiber pressure test: (1) Place the clean fiber horizontally on the stage of the self-made pressure test equipment. The metal cylinder above moves towards the fiber at a constant speed. After contact, apply a pressure of 50N and return the machine. (2) Observe the microstructure of the fiber that has been pressured under a microscope.

[0039] The test results are shown in Tables 5 and 6.

[0040] Table 5 Performance test results of the coatings and optical fibers in the examples

[0041] Table 6 Performance test results of the comparative coatings and optical fibers

[0042] The test results show that this invention, through the combination of polyurethane acrylate prepolymer and bifunctional polyurethane acrylate, achieves a coating formulation with suitable mechanical properties. Furthermore, the coating's modulus remains low even at -40℃, indicating good low-temperature flexibility. Through the design of the coating's properties, excellent optical fiber attenuation, strength, water resistance, low-temperature resistance, and compressive strength are further achieved.

[0043] In Examples 1 to 3, polyurethane acrylate prepolymers were synthesized using polypropylene glycols of different molecular weights. These prepolymers were then combined with Lancolu bifunctional polyurethane acrylate 6212 to obtain an inner coating for marine optical fibers. All three coating formulations achieved high coating strength and elongation at break while maintaining a low modulus. In Example 4, 6212 in Example 1 was replaced with Changxing bifunctional polyurethane acrylate 61369. The target coating and optical fiber performance were also achieved. However, the curing shrinkage rate of 61369 was higher than that of 6212. Furthermore, due to its higher viscosity and larger addition amount in the formulation, the impact was amplified, resulting in a slight increase in optical fiber attenuation.

[0044] In Comparative Example 1, the difunctional acrylate 6212 in Example 1 was replaced with a monofunctional acrylate (propoxylated nonylphenol acrylate). The coating strength and elongation at break decreased, as did the optical fiber strength, water resistance, low-temperature performance, and compressive strength. This may be because the coating system obtained using a monofunctional monomer has insufficient cohesion after curing, resulting in insufficient coating strength. Consequently, the inner coating layer is insufficient to resist external stress during fiber compression testing, leading to defects (such as…). Figure 2 (As shown). Similarly, since the tape reel low-temperature test introduces tension on top of the conventional loosely wound optical fiber low-temperature test, insufficient coating strength will also cause an increase in the additional attenuation of the tape reel low-temperature test. In addition, insufficient cohesion will also make it easier for water vapor to enter, thus increasing the additional attenuation of the immersion test. It can be seen that the formulation of Comparative Example 1 cannot meet the requirements for use in the high-pressure environment of the seabed.

[0045] Comparative Example 2 replaced the bifunctional acrylate 6212 in Example 1 with polypropylene glycol (700) diacrylate. The coating strength decreased, causing the inner coating to be insufficient to resist external stress during fiber compression testing, resulting in defects (such as...). Figure 3 As shown in the figure, this may be due to the low cohesiveness of the coating formulation obtained using polypropylene glycol (700) diacrylate after curing; and because polypropylene glycol (700) diacrylate has poor water resistance, the additional attenuation of the optical fiber increases sharply after immersion in water; at the same time, because the curing shrinkage rate of polypropylene glycol (700) diacrylate is higher than 6212, it leads to a slight increase in optical fiber attenuation. It can be seen that although polypropylene glycol (700) diacrylate is a bifunctional acrylate, it is not suitable for use in the coating for marine optical fibers of the present invention.

[0046] Comparative Example 3 replaced the bifunctional acrylate 6212 in Example 1 with the commonly used bifunctional photocurable diluent tripropylene glycol diacrylate. Due to its high brittleness, the resulting coating formulation had an excessively high modulus, making it unsuitable as an inner layer coating for optical fibers. Therefore, the fiber attenuation and low-temperature performance failed to meet requirements. Furthermore, due to the high inner layer modulus, the adhesion to the glass decreased significantly, resulting in noticeable separation between the inner coating and the glass during fiber compression testing, leading to poor compressive strength (e.g., ...). Figure 4 (As shown).

[0047] Comparative Example 4 replaced the polyurethane acrylate prepolymer prepared in the examples with Changxing polyurethane acrylate oligomer DR-U168. Because this oligomer is more brittle than the prepolymer prepared in this invention, the coating strength and elongation at break both decreased, while the modulus increased, leading to increased fiber attenuation. The increased brittleness of the inner coating prevented it from fully releasing stress, resulting in defects in the fiber compression test (e.g., ...). Figure 5 (As shown). At the same time, the replacement of the prepolymer significantly increases the modulus of the coating at low temperatures, which in turn leads to an increase in the additional attenuation of the optical fiber at low temperatures.

[0048] In Comparative Example 5, the polypropylene glycol (PPG) in the examples was replaced with polycaprolactone diol 2000 (PCL2000). Because PCL2000 itself has high strength but poor flexibility, the resulting coating, while having high strength, exhibits low elongation at break, excessively high modulus at both room and low temperatures, and high brittleness. This leads to high fiber attenuation, poor low-temperature performance, and poor compressive strength (e.g., ...). Figure 6 (As shown).

[0049] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. An inner coating for marine optical fibers, characterized in that, The raw materials of the inner coating, by weight, include: 80-120 parts of polyurethane acrylate prepolymer, 10-130 parts of difunctional acrylate reactive monomer diluent, 1-16 parts of photoinitiator, and 0-7 parts of additives.

2. The inner coating for marine optical fibers according to claim 1, characterized in that, The difunctional acrylate reactive monomer diluent includes one or more of the following: Lankeluo polyurethane acrylate 6212, Changxing polyurethane acrylate 61369, Changxing polyurethane acrylate 6101, Changxing polyurethane acrylate DR-161, polyethylene glycol dimethacrylate, bisphenol A dimethacrylate ethoxylate, 2-methyl-1,3-propanediol diacrylate ethoxylate, 1,9-nonanediol dimethacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, and neopentyl glycol diacrylate ethoxylate.

3. The inner coating for marine optical fibers according to claim 2, characterized in that, The diluent for the bifunctional acrylate reactive monomer is Lankelu polyurethane acrylate 6212 and / or Changxing polyurethane acrylate 61369.

4. The inner coating for marine optical fibers according to any one of claims 1-3, characterized in that, The raw materials of the polyurethane acrylate prepolymer, by weight, include 50-100 parts of polyol, 3-20 parts of isocyanate, 1-10 parts of (meth)acrylate hydroxy ester, 0.05-0.2 parts of catalyst, and 0.05-0.2 parts of polymerization inhibitor.

5. The inner coating for marine optical fibers according to claim 4, characterized in that, The method for preparing the polyurethane acrylate prepolymer includes: After mixing polyol, isocyanate and catalyst, react at 60±2℃ for 2~2.5 hours, then add (meth)acrylate hydroxyl ester and polymerization inhibitor, and continue to react at 65±2℃ for 2~3 hours until the isocyanate is completely consumed, thus obtaining the polyurethane acrylate prepolymer.

6. The inner coating for marine optical fibers according to claim 4, characterized in that, The polyol includes one or more of polyether polyols, polyolefin polyols, and polysiloxane polyols; and / or The isocyanate comprises one or more of toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, phenylenediamine diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, lysine diisocyanate, diethyl transbutadiene diisocyanate, methylcyclohexyl diisocyanate, dicyclohexylmethane diisocyanate, and tetramethylphenyl diisocyanate; and / or, The catalyst comprises one or more of the following: dibutyltin dilaurate, bismuth carboxylate, bismuth isooctanoate, N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, N,N,N',N'-tetramethylalkylene diamine, triethylamine, N,N-dimethylbenzylamine, steramine, N-ethylmorpholine, N,N'-diethylpiperazine, triethanolamine, dimethylaminoethanol, pyridine, and N,N'-dimethylpyridine.

7. The inner coating for marine optical fibers according to claim 6, characterized in that, The polyol is a polyether polyol, and / or the isocyanate is isophorone diisocyanate, and / or the catalyst is dibutyltin dilaurate.

8. The inner coating for marine optical fibers according to claim 4, characterized in that, The hydroxy methacrylate is one or more of the following: hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dipentaerythritol monohydroxypentamethacrylate, 2-hydroxyoctyl methacrylate, pentaerythritol trimethacrylate, glycerol dimethacrylate, 4-hydroxycyclohexyl methacrylate, trimethylolpropane dimethacrylate, and trimethylolethane dimethacrylate; and / or, The polymerization inhibitor is one or more of hydroquinone and p-hydroxyanisole.

9. The inner coating for marine optical fibers according to any one of claims 1-3 and 5-8, characterized in that, The photoinitiator comprises one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylbenzophenone, benzoin dimethyl ether, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 2-methyl-1-(4-methylthiophenyl)-2-morpholine-1-propanone; and / or, The additives include one or more of defoamers, leveling agents, antioxidants, and stabilizers.

10. A method for preparing a polyurethane acrylate prepolymer, used to prepare the polyurethane acrylate prepolymer in the inner coating for marine optical fibers according to any one of claims 1-9, characterized in that, Includes the following steps: After mixing polyol, isocyanate and catalyst, react at 60±2℃ for 2~2.5 hours, then add (meth)acrylate hydroxyl ester and polymerization inhibitor, and continue to react at 65±2℃ for 2~3 hours until the isocyanate is completely consumed, thus obtaining the polyurethane acrylate prepolymer.

Images