CN112759961A

CN112759961A - Low-refractive-index optical fiber coating and preparation method thereof

Info

Publication number: CN112759961A
Application number: CN202110176043.5A
Authority: CN
Inventors: 沈亚汝; 郑超
Original assignee: Shanghai Xianquan Optical Fiber Technology Co ltd
Current assignee: Shanghai Xianquan Optical Fiber Technology Co ltd
Priority date: 2021-02-09
Filing date: 2021-02-09
Publication date: 2021-05-07
Anticipated expiration: 2041-02-09
Also published as: CN112759961B

Abstract

The invention discloses a low-refractive-index optical fiber coating and a preparation method thereof. The raw materials of the optical fiber coating comprise fluorinated acrylic resin, 1H,1H, 11H-perfluoroundecyl acrylate, trimethylolpropane triacrylate, 1-3 parts of a photoinitiator, mercaptopropyl trimethoxy silane, phosphorus-based polyurethane acrylate and trimethoxy propyl silane acrylate. Has the advantages that: (1) the phosphorus-based polyurethane acrylate is prepared, so that the movement of the fluorine-containing alkyl is inhibited, the difference of the internal and external refractive indexes of the coating is reduced, the toughness of the coating is improved, and the flame retardance of the coating is improved; (2) a macromolecular photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-acetone is used for increasing compatibility, inhibiting migration and volatilization behaviors and increasing curing uniformity; (3) the compatibility of each phase in the coating is good, and the increase of the refractive index after multiphase mixing is inhibited.

Description

Low-refractive-index optical fiber coating and preparation method thereof

Technical Field

The invention relates to the technical field of optical fiber coatings, in particular to a low-refractive-index optical fiber coating and a preparation method thereof.

Background

The optical fiber is a light-conducting material made of glass, but it is brittle and easily broken; and the optical fiber can affect the transmission of signals due to the surface adhesion of pollutants, so that the optical fiber needs to be protected by a coating. The coating used by the coating has very important influence on the mechanical strength and the transmission performance of the optical fiber. In the existing coating with low refractive index and good flexibility, the photocureable coating is widely applied due to environmental protection, no pollution, high curing speed and moderate viscosity.

In the low-refraction light-cured coating, the refractive index of the acrylic coating which is commercialized in the market at present is higher than that of quartz glass or slightly lower than that of the quartz glass, in actual use, when the energy optical fiber transmits energy, partial coating energy leaks into an inner coating to cause coating failure, and finally, the optical fiber fails. And when the content of the fluorinated monomer is too high, the compatibility of the fluorinated monomer with polyurethane is affected, and microphase separation is generated, thereby increasing the refractive index. In addition, due to compatibility problems, very little flame retardant is added to the optical fiber coating, making the optical fiber coating non-flame retardant.

In conclusion, the preparation of the low-refractive-index optical fiber coating with flame retardance and good compatibility has important significance.

Disclosure of Invention

The invention aims to provide a low-refractive-index optical fiber coating and a preparation method thereof, so as to solve the problems in the background technology.

In order to solve the technical problems, the invention provides the following technical scheme:

a low-refractive-index optical fiber coating comprises the following raw materials: by weight, 50-60 parts of fluorinated acrylic resin, 20-30 parts of 1H,1H, 11H-perfluoroundecyl acrylate, 5-18 parts of trimethylolpropane triacrylate, 1-3 parts of a photoinitiator, 2-3 parts of mercaptopropyl trimethoxy silane, 8-12 parts of phosphorus-based polyurethane acrylate and 0.5-1 part of trimethoxy propyl silane acrylate.

Preferably, the raw materials of the phosphorus-based polyurethane acrylate comprise the following components: 10-25 parts of ethylene glycol, 22-35 parts of hexamethylene diisocyanate, 10-20 parts of trimethylolpropane triacrylate and 2-5 parts of a phosphorus triazole compound.

Preferably, the raw materials of the phosphorus-based triazole compound comprise the following components: 18-20 parts of 2-chloro-5, 5-dimethyl-1, 3, 2-dioxaphosphorinane-2-oxide, 8-10 parts of 3-amino-1, 2, 4-triazole and 0.01-0.05 part of triethylamine.

Preferably, the photoinitiator is a macrophotoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone.

Preferably, the fluorinated acrylate is prepared by polymerizing 1H,1H, 11H-perfluoroundecyl acrylate and methacrylate under an initiator.

Preferably, the preparation method of the optical fiber coating with low refractive index is characterized by comprising the following steps: the method comprises the following steps:

s1: preparation of the photoinitiator: dissolving 2-hydroxy-2-methyl-1-phenyl-1-acetone in acetone to obtain a solution A for later use; sequentially adding toluene-2, 4-diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate trimer and a catalyst into a reaction kettle, slowly adding the solution A, and heating to 60 ℃ for reaction for a period of time; dropwise adding trimethylolpropane triacrylate, setting the temperature to be 70 ℃, continuing the reaction, and stopping the reaction when the-NCO content is lower than 0.3% to obtain a photoinitiator;

s2: preparation of phosphorus-based polyurethane acrylate:

(1) dissolving 2-chloro-5, 5-dimethyl-1, 3, 2-dioxaphosphorinane-2-oxide in a solvent to obtain a solution B for later use; sequentially adding 3-amino-1, 2, 4-triazole and triethylamine into a reaction kettle, dropwise adding the solution B, and reacting at the reaction temperature of 80-85 ℃ for a period of time to obtain a phosphorus-based triazole compound for later use;

(2) adding ethylene glycol into a reaction kettle, adding a catalyst and hexamethylene diisocyanate, keeping the reaction system at 50-55 ℃, adding a phosphorus-based triazole compound after-NCO reaches a theoretical value in the reaction, heating to 70-80 ℃ for reaction for a period of time, adding trimethylolpropane triacrylate and the catalyst, continuing the reaction, and stopping the reaction when the content of free-NCO is lower than 0.3% to obtain phosphorus-based polyurethane acrylate;

s3: preparing an optical fiber coating: weighing fluorinated acrylic resin, 1H,1H, 11H-perfluoroundecyl acrylate, trimethylolpropane triacrylate, mercaptopropyl trimethoxy silane, phosphorus-based polyurethane acrylate and trimethoxy propyl silane acrylate, sequentially adding into a reaction kettle, and uniformly stirring; adding the photoinitiator and stirring uniformly to obtain the optical fiber coating.

Preferably, the specific step of step S1 is: dissolving 2-hydroxy-2-methyl-1-phenyl-1-acetone in acetone to obtain a solution A for later use; sequentially adding toluene-2, 4-diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate trimer and a catalyst into a reaction kettle, setting the stirring speed to be 200-500 rmp, uniformly mixing, setting the temperature to be 35-40 ℃, slowly adding the solution A, heating to 60 ℃, and reacting for 3-4 hours; and (3) dropwise adding trimethylolpropane triacrylate within 1 hour, continuously reacting for 2-4 hours at the set temperature of 70 ℃, stopping the reaction when the-NCO content is lower than 0.3%, dissolving the mixture in petroleum ether, washing and extracting, drying with anhydrous sodium sulfate, and performing rotary evaporation to obtain the photoinitiator.

Preferably, the specific step of step S2 is: (1) dissolving 2-chloro-5, 5-dimethyl-1, 3, 2-dioxaphosphorinane-2-oxide in acetonitrile to obtain a solution B for later use; sequentially adding 3-amino-1, 2, 4-triazole, triethylamine and acetonitrile into a reaction kettle, setting the stirring speed to be 200-500 rmp, dropwise adding the solution B, setting the reaction temperature to be 80-85 ℃ after dropwise adding, reacting for 10-12 hours, washing, filtering and drying to obtain a phosphorus-based triazole compound for later use; (2) adding ethylene glycol into a reaction kettle, setting the temperature at 120 ℃ for 2 hours of decompression dehydration, cooling to 50-60 ℃, adding a catalyst and hexamethylene diisocyanate, keeping the reaction system at 50-55 ℃, adding a phosphorus-based triazole compound after-NCO reaches a theoretical value in the reaction, heating to 70-80 ℃ for reaction for 1-2 hours, adding trimethylolpropane triacrylate and the catalyst, continuing the reaction for 2-4 hours, and stopping the reaction when the content of free-NCO is lower than 0.3% to obtain the phosphorus-based polyurethane acrylate.

Preferably, the specific step of step S3 is: weighing fluorinated acrylic resin, 1H,1H, 11H-perfluoroundecyl acrylate, trimethylolpropane triacrylate, mercaptopropyl trimethoxy silane, phosphorus-based polyurethane acrylate and trimethoxy propyl silane acrylate, sequentially adding the materials into a reaction kettle, setting the stirring speed to be 500-800 rmp, heating to 80-85 ℃, and stirring for 30-60 minutes; and cooling to 40-50 ℃, adding a photoinitiator, continuously stirring for 20-30 minutes, cooling and degassing to obtain the optical fiber coating.

Preferably, in step S2 (2), the theoretical value of-NCO reached during the reaction is 10% to 13%.

In the technical scheme, fluorinated acrylic resin is used as a main body, a phosphorus-based polyurethane acrylate auxiliary body, 1H, 11H-perfluoroundecyl acrylate is used as a fluorine-containing monomer, mercaptopropyl trimethoxy silane is used as a silane coupling agent, a prepared macroinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-acetone is used as a photoinitiator, and trimethoxy propyl silane acrylate is used as a compatilizer to prepare an optical fiber coating, wherein the prepared optical fiber coating has a lower refractive index which is as low as 1.376; the flame-retardant polyester has good hydrophobicity of 95-100 degrees, good flame retardance and an extreme oxygen index of 31%.

First, the low refractive index and low optical loss are usually achieved by replacing hydrogen atoms with fluorine atoms to avoid the combination of O-H and N-H. Therefore, in the formula of the scheme, fluorinated acrylate prepared by polymerizing 1H,1H, 11H-perfluoroundecyl acrylate and trimethylolpropane triacrylate under an initiator is taken as a main body, and simultaneously, 1H, 11H-perfluoroundecyl acrylate is taken as a fluorine-containing monomer to lay a low-refractive-index kerbstone of the optical fiber coating. However, the fluorine-containing alkyl group is easy to move, so that the surface of the coating contains more fluorine and the content of fluorine in the coating is low, so that the refractive index distribution is uneven, transmitted light is influenced, the transmitted light is refracted and scattered at the intersection interface of different refractive indexes, the optical loss is increased, and the optical transmission is influenced. Therefore, the addition of polyurethane is required to suppress the occurrence of this problem, principle: the polyurethane can form a stable cross-linked structure with the fluorine-containing group, and movement of the fluorine-containing alkyl group is inhibited, so that movement of internal fluorine to the surface is reduced, and distribution difference between the surface layer and the internal fluorine is reduced.

However, when the content of the fluorinated monomer is too high, the compatibility of the fluorinated monomer with polyurethane is affected, and microphase separation is generated to increase the refractive index, so that we prepared the phosphorus-based polyurethane acrylate to increase the compatibility by the similar compatibility principle. Wherein, the phosphorus-containing hybridization is connected to the triazole by utilizing the substitution reaction that the substitution of-Cl in 2-chloro-5, 5-dimethyl-1, 3, 2-dioxaphosphorinane-2-oxide is positioned in imino (-HN) in 3-amino-1, 2, 4-triazole to form the phosphorus-based triazole compound, and then the amino (-NH) on the phosphorus-based triazole compound is utilized₂) And the phosphorus-based polyurethane acrylate is grafted on the prepared polyurethane acrylate in the preparation process through nucleophilic reaction with-NCO on hexamethylene diisocyanate, so that the flame retardance of the coating is improved. In addition, the prepared aliphatic chain polyurethane can reduce the rigidity of the coating, increase the toughness and inhibit yellowing.

In addition, in the scheme, a commonly used photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-acetone is pre-reacted with isocyanate and trimethylolpropane triacrylate to form a copolymer by utilizing a nucleophilic reaction between-NCO and-OH, the copolymer is a macromolecular photoinitiator, and the compatibility of the initiator in the coating is increased according to a similar compatibility principle. Meanwhile, 2-hydroxy-2-methyl-1-phenyl-1-acetone is fixed in the polymer in advance, so that the mobility and the volatility of the polymer are inhibited, and the uniformity of curing reaction is improved.

The same compatilizer trimethoxy propyl silane acrylate is added to increase the compatibility of the mercaptopropyl trimethoxy silane in the coating, thiol click reaction is generated between the mercapto group in the structure of the compatilizer trimethoxy silane and the double bond in the fluorinated resin under the action of a photoinitiator, the curing is carried out to form a film, the crosslinking degree is increased, and therefore the toughness of the cured coating is increased.

Among them, it should be noted that the reason why such importance is attached to compatibility in this scheme is that: the coating forms a multiphase mixture after mixing, and due to the different viscosity and interfacial properties of the phases, the polymer generates a hazy mixture, so that dispersed liquid drops in the multiphase mixture are larger, and the refractive index is increased. The higher the compatibility, the smaller the dispersed droplets formed by the multiple phases, the lower the haze produced, and the increase in the refractive index after the multiple phases are mixed is suppressed.

Compared with the prior art, the invention has the following beneficial effects: (1) the phosphorus-based polyurethane acrylate is prepared, so that the movement of the fluorine-containing alkyl is inhibited, the difference of the internal and external refractive indexes of the coating is reduced, the toughness of the coating is improved, and the flame retardance of the coating is improved; (2) the macromolecular photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-acetone is used for increasing compatibility, inhibiting migration and volatilization behaviors and increasing curing uniformity; (3) the compatibility of each phase in the coating is good, the increase of the refractive index of the coating after multi-phase mixing is inhibited, and the whitening of the coating is inhibited; (4) thiol click reaction is generated between the added mercaptopropyl trimethoxy silane and partial double bonds in the coating, the crosslinking degree is increased, and the toughness is increased.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1:

s1: preparation of the photoinitiator: dissolving 2-hydroxy-2-methyl-1-phenyl-1-acetone in acetone to obtain a solution A for later use; sequentially adding toluene-2, 4-diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate trimer and a catalyst into a reaction kettle, setting the stirring speed to be 350rmp, uniformly mixing, setting the temperature to be 38 ℃, slowly adding the solution A, and heating to 60 ℃ for reaction for 3.5 hours; and (3) dropwise adding trimethylolpropane triacrylate within 1 hour, continuously reacting for 3 hours at the set temperature of 70 ℃, stopping the reaction when the-NCO content is lower than 0.3%, dissolving the mixture in petroleum ether, washing and extracting, drying with anhydrous sodium sulfate, and performing rotary evaporation to obtain the photoinitiator.

S2: preparation of phosphorus-based polyurethane acrylate: (1) dissolving 19 parts of 2-chloro-5, 5-dimethyl-1, 3, 2-dioxaphosphorinane-2-oxide in acetonitrile to obtain a solution B for later use; adding 9 parts of 3-amino-1, 2, 4-triazole, 0.03 part of triethylamine and acetonitrile into a reaction kettle in sequence, setting the stirring speed to be 350rmp, dropwise adding the solution B, setting the reaction temperature to be 82 ℃ after dropwise adding, reacting for 11 hours, washing, filtering and drying to obtain a phosphorus-based triazole compound for later use; (2) adding 18 parts of ethylene glycol and ethylene glycol into a reaction kettle, carrying out reduced pressure dehydration for 2 hours at the set temperature of 120 ℃, cooling to 55 ℃, adding a catalyst and 28 parts of hexamethylene diisocyanate, keeping the reaction system at 52 ℃, adding 4 parts of phosphorus-based triazole compound when-NCO reaches a theoretical value of 12% in the reaction, heating to 75 ℃ for reaction for 1.5 hours, adding 15 parts of trimethylolpropane triacrylate and the catalyst, continuing the reaction for 3 hours, and stopping the reaction when the content of free-NCO is lower than 0.3% to obtain the phosphorus-based polyurethane acrylate.

S3: preparing an optical fiber coating: weighing 55 parts of fluorinated acrylic resin, 25 parts of 1H,1H, 11H-perfluoroundecyl acrylate, 11.5 parts of trimethylolpropane triacrylate, 2.5 parts of mercaptopropyl trimethoxy silane, 8-12 parts of phosphorus-based polyurethane acrylate and 0.8 part of trimethoxy propyl silane acrylate, sequentially adding the materials into a reaction kettle, setting the stirring speed to be 650rmp, heating to 82 ℃, and stirring for 45 minutes; and cooling to 45 ℃, adding 2 parts of photoinitiator, continuously stirring for 25 minutes, cooling and degassing to obtain the optical fiber coating.

Example 2:

s1: preparation of the photoinitiator: dissolving 2-hydroxy-2-methyl-1-phenyl-1-acetone in acetone to obtain a solution A for later use; sequentially adding toluene-2, 4-diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate trimer and a catalyst into a reaction kettle, setting the stirring speed to be 200rmp, uniformly mixing, setting the temperature to be 35 ℃, slowly adding the solution A, and heating to 60 ℃ for reaction for 3 hours; and (3) dropwise adding trimethylolpropane triacrylate within 1 hour, continuously reacting for 2 hours at the set temperature of 70 ℃, stopping the reaction when the-NCO content is lower than 0.3%, dissolving the mixture in petroleum ether, washing and extracting, drying with anhydrous sodium sulfate, and performing rotary evaporation to obtain the photoinitiator.

S2: preparation of phosphorus-based polyurethane acrylate: (1) dissolving 18 parts of 2-chloro-5, 5-dimethyl-1, 3, 2-dioxaphosphorinane-2-oxide in acetonitrile to obtain a solution B for later use; sequentially adding 8 parts of 3-amino-1, 2, 4-triazole, 0.01 part of triethylamine and acetonitrile into a reaction kettle, setting the stirring speed to be 200rmp, dropwise adding the solution B, setting the reaction temperature to be 80 ℃ after dropwise adding, reacting for 10 hours, washing, filtering and drying to obtain a phosphorus-based triazole compound for later use; (2) adding 10 parts of ethylene glycol and ethylene glycol into a reaction kettle, carrying out reduced pressure dehydration for 2 hours at the set temperature of 120 ℃, cooling to 50 ℃, adding a catalyst and 22 parts of hexamethylene diisocyanate, keeping the reaction system at 50 ℃, adding 2 parts of phosphorus-based triazole compound when-NCO reaches the theoretical value of 10% in the reaction, heating to 70 ℃ for reaction for 1 hour, adding 10 parts of trimethylolpropane triacrylate and the catalyst, continuing the reaction for 2 hours, and stopping the reaction when the content of free-NCO is lower than 0.3%, thus obtaining the phosphorus-based polyurethane acrylate.

S3: preparing an optical fiber coating: weighing 50 parts of fluorinated acrylic resin, 20 parts of 1H,1H, 11H-perfluoroundecyl acrylate, 5 parts of trimethylolpropane triacrylate, 2 parts of mercaptopropyl trimethoxy silane, 8 parts of phosphorus-based polyurethane acrylate and 0.5 part of trimethoxy propyl silane acrylate, sequentially adding the materials into a reaction kettle, setting the stirring speed to be 500rmp, heating to 80 ℃, and stirring for 30 minutes; and cooling to 40 ℃, adding 1 part of photoinitiator, continuously stirring for 20 minutes, cooling and degassing to obtain the optical fiber coating.

Example 3:

s1: preparation of the photoinitiator: dissolving 2-hydroxy-2-methyl-1-phenyl-1-acetone in acetone to obtain a solution A for later use; sequentially adding toluene-2, 4-diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate trimer and a catalyst into a reaction kettle, setting the stirring speed to be 500rmp, uniformly mixing, setting the temperature to be 40 ℃, slowly adding the solution A, and heating to 60 ℃ for reaction for 4 hours; and (3) dropwise adding trimethylolpropane triacrylate within 1 hour, continuously reacting for 4 hours at the set temperature of 70 ℃, stopping the reaction when the-NCO content is lower than 0.3%, dissolving the mixture in petroleum ether, washing and extracting, drying with anhydrous sodium sulfate, and performing rotary evaporation to obtain the photoinitiator.

S2: preparation of phosphorus-based polyurethane acrylate: (1) dissolving 20 parts of 2-chloro-5, 5-dimethyl-1, 3, 2-dioxaphosphorinane-2-oxide in acetonitrile to obtain a solution B for later use; sequentially adding 10 parts of 3-amino-1, 2, 4-triazole, 0.05 part of triethylamine and acetonitrile into a reaction kettle, setting the stirring speed to be 500rmp, dropwise adding the solution B, setting the reaction temperature to be 85 ℃ after dropwise adding, reacting for 12 hours, washing, filtering and drying to obtain a phosphorus-based triazole compound for later use; (2) adding 25 parts of ethylene glycol and ethylene glycol into a reaction kettle, carrying out reduced pressure dehydration for 2 hours at the set temperature of 120 ℃, cooling to 60 ℃, adding a catalyst and 35 parts of hexamethylene diisocyanate, keeping the reaction system at 55 ℃, adding 5 parts of phosphorus-based triazole compound when-NCO reaches a theoretical value of 13% in the reaction, heating to 80 ℃ for reaction for 2 hours, adding 20 parts of trimethylolpropane triacrylate and the catalyst, continuing the reaction for 4 hours, and stopping the reaction when the content of free-NCO is lower than 0.3%, thus obtaining the phosphorus-based polyurethane acrylate.

S3: preparing an optical fiber coating: weighing 60 parts of fluorinated acrylic resin, 30 parts of 1H,1H, 11H-perfluoroundecyl acrylate, 18 parts of trimethylolpropane triacrylate, 3 parts of mercaptopropyl trimethoxy silane, 12 parts of phosphorus-based polyurethane acrylate and 1 part of trimethoxy propyl silane acrylate, sequentially adding the materials into a reaction kettle, setting the stirring speed to be 800rmp, heating to 85 ℃, and stirring for 60 minutes; and cooling to 50 ℃, adding 3 parts of photoinitiator, continuously stirring for 30 minutes, cooling and degassing to obtain the optical fiber coating.

Example 4: the phosphorus-based triazole compound is not added in the process of replacing phosphorus-based polyurethane acrylate with polyurethane; the rest is the same as in example 1.

Example 5: no phosphorus-based polyurethane acrylate is added; the rest is the same as in example 1.

Example 6: the procedure of example 1 was repeated except that 2-hydroxy-2-methyl-1-phenyl-1-propanone was used in place of the macrophotoinitiator.

Example 7: no mercaptopropyl trimethoxysilane was added; the rest is the same as in example 1.

Experiment: the low-refractive-index optical fiber coating prepared in the embodiment 1-7 is coated on a quartz glass plate, and is cured by an ultraviolet lamp to form a film, and the basic performance of the coating is tested. Measuring the refractive index of a magnetic yoke amount coating by using an Abbe refractometer in three points, and taking an average value; secondly, testing the tensile strength of the coating by adopting a universal mechanical testing instrument according to a T1731-93 standard method; thirdly, testing the adhesive force of the coating by adopting a pull-off method adhesive force measuring instrument; fourthly, performing flame retardance test on the coating by adopting a limit oxygen index test method; the data obtained are shown in the following table:

and (4) conclusion: as can be seen from the examples 1 to 3, the prepared optical fiber coating has better adhesive force which is between 2.1 and 2.7 MPa; easy to strip and suitable for secondary processing of optical fiber coating. The low-refractive-index glass has a low refractive index which is 1.37 at the lowest and excellent performance; the tensile strength is more than 1.7, and the low-refraction coating material is suitable for optical fiber drawing. And the extreme oxygen index is higher and reaches 31 percent, and the flame retardant property is excellent.

The data from comparative example 4 shows that: the flame retardance is reduced linearly, which shows that the phosphorus-containing group grafted on the polyurethane is a source of flame retardance; ② the refractive index is increased because when the content of the fluorinated monomer is too high, the compatibility of the fluorinated monomer with polyurethane is affected, microphase separation is generated, thereby increasing the refractive index. ③ the tensile strength is slightly reduced, the acrylic acid group is reduced, and the crosslinking degree is slightly reduced. Comparing the data of example 5 again, it can be found that: all data were subject to a substantial reduction except for adhesion. The reason for the decrease in flame retardancy is the same as in example 4; ② the reason of the refractive index rising, the problem of processing compatibility, and also because the polyurethane can form a stable cross-linking structure with the fluorine-containing group, the movement of the fluorine-containing alkyl group is inhibited, thereby reducing the movement of the internal fluorine to the surface and reducing the distribution difference of the surface layer and the internal fluorine. And the tensile strength is reduced because the addition of the polyurethane can reduce the rigidity of the coating and increase the toughness of the coating.

The data of comparative example 6 can find that: the refractive index is increased, the tensile strength is increased because of the macromolecular photoinitiator, the compatibility is increased, the migration and volatilization behaviors are inhibited, and the curing uniformity is increased.

The data of comparative example 7 can find that: the tensile strength is reduced because the added mercaptopropyl trimethoxy silane and partial double bonds in the paint generate mercaptan click reaction, the crosslinking degree is increased, and the toughness is increased.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A low index optical fiber coating, comprising: the raw materials of the optical fiber coating comprise the following components: by weight, 50-60 parts of fluorinated acrylic resin, 20-30 parts of 1H,1H, 11H-perfluoroundecyl acrylate, 5-18 parts of trimethylolpropane triacrylate, 1-3 parts of a photoinitiator, 2-3 parts of mercaptopropyl trimethoxy silane, 8-12 parts of phosphorus-based polyurethane acrylate and 0.5-1 part of trimethoxy propyl silane acrylate.

2. A low index optical fiber coating according to claim 1, wherein: the raw materials of the phosphorus-based polyurethane acrylate comprise the following components: 10-25 parts of ethylene glycol, 22-35 parts of hexamethylene diisocyanate, 10-20 parts of trimethylolpropane triacrylate and 2-5 parts of a phosphorus triazole compound.

3. A low index optical fiber coating according to claim 2, wherein: the raw material of the phosphorus-based triazole compound comprises the following components: 18-20 parts of 2-chloro-5, 5-dimethyl-1, 3, 2-dioxaphosphorinane-2-oxide, 8-10 parts of 3-amino-1, 2, 4-triazole and 0.01-0.05 part of triethylamine.

4. A low index optical fiber coating according to claim 1, wherein: the photoinitiator is a macromolecular photoinitiator based on 2-hydroxy-2-methyl-1-phenyl-1-propanone.

5. A low index optical fiber coating according to claim 1, wherein: the fluorinated acrylate is prepared by polymerizing 1H,1H, 11H-perfluoroundecyl acrylate and methacrylate under an initiator.

6. A preparation method of a low-refractive-index optical fiber coating is characterized by comprising the following steps: the method comprises the following steps:

s2: preparation of phosphorus-based polyurethane acrylate:

7. The method of claim 6, wherein the method comprises the steps of: the specific steps of step S1 are: dissolving 2-hydroxy-2-methyl-1-phenyl-1-acetone in acetone to obtain a solution A for later use; sequentially adding toluene-2, 4-diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate trimer and a catalyst into a reaction kettle, setting the stirring speed to be 200-500 rmp, uniformly mixing, setting the temperature to be 35-40 ℃, slowly adding the solution A, heating to 60 ℃, and reacting for 3-4 hours; and (3) dropwise adding trimethylolpropane triacrylate within 1 hour, continuously reacting for 2-4 hours at the set temperature of 70 ℃, stopping the reaction when the-NCO content is lower than 0.3%, dissolving the mixture in petroleum ether, washing and extracting, drying with anhydrous sodium sulfate, and performing rotary evaporation to obtain the photoinitiator.

8. The method of claim 6, wherein the method comprises the steps of: the specific steps of step S2 are: (1) dissolving 2-chloro-5, 5-dimethyl-1, 3, 2-dioxaphosphorinane-2-oxide in acetonitrile to obtain a solution B for later use; sequentially adding 3-amino-1, 2, 4-triazole, triethylamine and acetonitrile into a reaction kettle, setting the stirring speed to be 200-500 rmp, dropwise adding the solution B, setting the reaction temperature to be 80-85 ℃ after dropwise adding, reacting for 10-12 hours, washing, filtering and drying to obtain a phosphorus-based triazole compound for later use; (2) adding ethylene glycol into a reaction kettle, setting the temperature at 120 ℃ for 2 hours of decompression dehydration, cooling to 50-60 ℃, adding a catalyst and hexamethylene diisocyanate, keeping the reaction system at 50-55 ℃, adding a phosphorus-based triazole compound after-NCO reaches a theoretical value in the reaction, heating to 70-80 ℃ for reaction for 1-2 hours, adding trimethylolpropane triacrylate and the catalyst, continuing the reaction for 2-4 hours, and stopping the reaction when the content of free-NCO is lower than 0.3% to obtain the phosphorus-based polyurethane acrylate.

9. The method of claim 6, wherein the method comprises the steps of: the specific steps of step S3 are: weighing fluorinated acrylic resin, 1H,1H, 11H-perfluoroundecyl acrylate, trimethylolpropane triacrylate, mercaptopropyl trimethoxy silane, phosphorus-based polyurethane acrylate and trimethoxy propyl silane acrylate, sequentially adding the materials into a reaction kettle, setting the stirring speed to be 500-800 rmp, heating to 80-85 ℃, and stirring for 30-60 minutes; and cooling to 40-50 ℃, adding a photoinitiator, continuously stirring for 20-30 minutes, cooling and degassing to obtain the optical fiber coating.

10. The method of claim 6, wherein the method comprises the steps of: in step S2 (2), the theoretical value of-NCO reached in the reaction is 10% to 13%.