CN114539911A - High-transmittance ultraviolet optical fiber internal coating with high crosslinking density and preparation method thereof - Google Patents

Abstract

The invention discloses a high-transmittance ultraviolet optical fiber internal coating with high crosslinking density and a preparation method thereof. The high-transmittance ultraviolet optical fiber internal coating with high crosslinking density comprises the following raw materials in percentage by weight: 50-99% of polymerizable multifunctional acrylate organic silicon resin prepolymer, 0-50% of reactive diluent and 0.5-3 wt% of photoinitiator. The polymerizable multifunctional acrylate organic silicon resin in the high-transmittance ultraviolet optical fiber internal coating with high crosslinking density can be used as both resin and crosslinking agent, no small-molecule crosslinking agent is required to be added additionally, the curing rate is high, the obtained coating still has high crosslinking density, the coating has better mechanical property, and the ultraviolet transmittance is obviously improved.

Description

High-transmittance ultraviolet optical fiber inner coating coating with high cross-linking density and preparation method thereof

technical field

The invention relates to the technical field of optical fiber inner coating paint, in particular to a high cross-linking density and high transmission ultraviolet optical fiber inner coating paint and a preparation method thereof.

Background technique

In recent years, UV-transmitting optical fiber inner coating has extremely important application value in the preparation process of fiber grating. During the straightening process of the optical fiber, because the optical fiber is thin and brittle, it is extremely vulnerable to external influences or damages, resulting in defects, which will lead to signal transmission loss during use. Therefore, it is necessary to apply an optical fiber coating on the surface of the optical fiber to improve the mechanical properties of the optical fiber and protect the optical fiber from damage. In addition, in the subsequent production process, during the laser writing process of the fiber grating, it is necessary to carry out partial peeling off the grating writing and subsequent overmolding or metal sheathing of the coated coating. This not only makes the fiber grating easily damaged during processing, but also causes uneven stress on the grating part due to material differences, which affects the sensitivity, signal transmission quality and stability of the fiber grating during use.

At present, the inner layer coatings of UV-transmitting optical fibers are mainly thermal-curing coatings and light-curing coatings. Heat-curable coatings require high temperature treatment during use, which is easy to damage the optical fibers, and at the same time, the curing rate is relatively slow, which is not conducive to the rapid production of optical fibers. For light-curing UV-transmitting optical fiber coatings, most of the materials used are resin materials with only two unsaturated bonds at the end groups. To cure quickly, a large amount of small molecular cross-linking agent needs to be added, resulting in low transmittance in the ultraviolet region and affecting fiber gratings. laser writing efficiency.

Therefore, it is necessary to provide an optical fiber inner coating coating with high UV transmittance and fast curing with ultraviolet light, so as to avoid the above disadvantageous factors and improve the production efficiency of optical fibers.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the above-mentioned technical deficiencies, and to propose a high-crosslinking density high-transmission UV optical fiber inner coating coating and a preparation method thereof, so as to solve the problem that the UV-transparent optical fiber inner coating in the prior art cannot take into account both rapid curing and high UV Technical issues of light transmittance.

In order to achieve the above technical purpose, a first aspect of the present invention provides a high-crosslinking density high-transmittance UV optical fiber inner coating, in terms of weight percentage, the raw materials include: 50-99% polymerizable polyfunctionality Acrylate silicone resin prepolymer, 0-50% reactive diluent and 0.5%-3 wt% photoinitiator; unsaturated double bond functionality of the above polymerizable multifunctional acrylate silicone resin prepolymer ≥3.

A second aspect of the present invention provides a method for preparing a high-crosslinking density high-transmittance UV optical fiber inner coating, comprising the following steps:

Mix the polymerizable multifunctional acrylate silicone resin prepolymer, reactive diluent and photoinitiator evenly, then heat to 40-50℃ under the protection of dark nitrogen until the photoinitiator is completely dissolved, filter to remove insoluble matter, A high-transmission UV optical fiber inner coating with high cross-linking density is obtained.

Compared with the prior art, the beneficial effects of the present invention include:

The polymerizable multifunctional acrylate organosilicon resin in the high cross-linking density high-transmittance ultraviolet optical fiber inner coating coating of the present invention can be used as both a resin and a cross-linking agent, and no additional small molecule cross-linking is required. agent, the curing rate is fast, and the obtained coating still has a high crosslinking density, better mechanical properties, and significantly improved UV transmittance.

Description of drawings

Fig. 1 is the structure diagram of different functional silicone urethane acrylate prepolymer;

Fig. 2 is the UV transmittance test curve after curing of different optical fiber inner coating coatings; wherein, a is the transmittance test curve of Comparative Example 2, b is the transmittance test curve of Example 1, and c is Example 2 The transmittance test curve of ;

Fig. 3 is the mechanical property test curve diagram of different optical fiber inner coating coatings after curing; wherein, a is the stress-strain curve of comparative example 2, b is the stress-strain curve of embodiment 1, and c is the stress-strain curve of embodiment 2;

Fig. 4 is the optical time domain reflectometry of continuously writing 5m spaced fiber gratings on about 2000m ultraviolet-transparent optical fiber by using an online continuous grating writing device;

FIG. 5 is an enlarged view of FIG. 4 at a measurement length of 2400 meters.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present 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 only used to explain the present invention, but not to limit the present invention.

The first aspect of the present invention provides a high-crosslinking density high-transmittance UV optical fiber inner coating, the raw materials of which include: 50-99% polymerizable multifunctional acrylate silicone resin pre- polymer, 0-50% reactive diluent and 0.5%-3wt% photoinitiator. In some specific embodiments of the present invention, the raw materials of the above-mentioned high-transmittance UV optical fiber inner coating with high crosslinking density, by weight percentage, include: 78-90% of polymerizable multifunctional acrylate silicone Resin prepolymer, 8-20% reactive diluent and 1%-2wt% photoinitiator. Further, the above-mentioned high-crosslinking density high-transmittance UV optical fiber inner coating, in terms of weight percentage, its raw materials include: 88-90% polymerizable multifunctional acrylate silicone resin prepolymer, 9 ~10% reactive diluent and 1% ~ 2wt% photoinitiator. The raw material of the high-crosslinking density high-transmittance UV optical fiber inner coating material of the present invention does not need to add additional small-molecule cross-linking agent.

Please refer to FIG. 1. In the present invention, the main resin used is a polymerizable multifunctional acrylate silicone resin prepolymer, and the unsaturated double bond functionality of the polymerizable multifunctional acrylate silicone resin prepolymer is ≥ 3, further from 4 to 12, for example, the unsaturated double bond functionality can be four, six, eight, ten and twelve. Further, the terminal group of the polymerizable multifunctional acrylate silicone resin prepolymer is acrylate or methacrylate; the preferred molecular weight of the multifunctional acrylate silicone resin is 1000-3000 g/mol.

The polymerizable multifunctional acrylate organosilicon resin in the high cross-linking density high-transmittance ultraviolet optical fiber inner coating coating of the present invention can be used as both a resin and a cross-linking agent, and no additional small molecule cross-linking is required. agent, the curing rate is fast, and the obtained coating still has a high crosslinking density, better mechanical properties, and significantly improved UV transmittance.

In some embodiments of the present invention, the polymerizable multifunctional acrylate silicone resin prepolymer is a multifunctional silicone urethane acrylate prepolymer.

Further, the preparation method of multifunctional organosilicon urethane acrylate prepolymer is as follows:

Method 1: Mix the diisocyanate A and the catalyst, heat up to 40-50°C, add dropwise double-ended hydroxypropyl silicone oil, keep the temperature for reaction until the -NCO drops to half of the added amount, then heat up to 60-70°C, add dropwise and expand Chain agent, continue to heat preservation reaction until the -NCO content is less than 0.1%; then add diisocyanate B dropwise, continue to heat preservation reaction until -NCO drops to half of the added amount, then add end capping agent and polymerization inhibitor, continue to heat preservation reaction to -NCO When the content is less than 0.1%, a multifunctional organosilicon urethane acrylate prepolymer is obtained. In this process, the chain extender used is polyol or polyamine, such as diethanolamine, isopropanol, pentaerythritol, etc.; the end group of the end capping agent is preferably at least one of acrylate or methacrylate. For example, it can be hydroxyethyl acrylate, hydroxyethyl methacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, etc.; It is 1: (1.8-2.2): (1.8-2.2): (4-12); The molar ratio of blocking agent and diisocyanate B is 1: (0.9-1.2).

Method 2: Mix the diisocyanate A and the catalyst, heat up to 40-50°C, add dropwise double-terminated hydroxypropyl silicone oil, keep the temperature for reaction until the -NCO drops to half of the added amount, then heat up to 60-70°C, add dropwise end capping agent and a polymerization inhibitor, and continue the heat preservation reaction until the -NCO content is less than 0.1% to obtain a multifunctional organosilicon urethane acrylate prepolymer. In this process, the end group of the end-capping agent is preferably at least one of acrylate or methacrylate, such as hydroxyethyl acrylate, hydroxyethyl methacrylate, pentaerythritol triacrylate, dipentaerythritol pentaerythritol Acrylate, etc.; the molar ratio of double-terminated hydroxypropyl silicone oil to diisocyanate A and blocking agent is 1:(1.8-2.2):(1.8-2.2).

Wherein, diisocyanate A and diisocyanate B are isophorone diisocyanate; the molecular weight of double-terminated hydroxypropyl silicone oil is 500～10000g/mol, further is 1000～3000g/mol, and further is 1500g/mol; the catalyst is Stannous octoate, the amount of catalyst added is 0.01% to 0.2% of the mass of the double-terminated hydroxypropyl silicone oil; the polymerization inhibitor is p-methoxyphenol, and the added amount of the polymerization inhibitor is 0.05% of the mass of the double-terminated hydroxypropyl silicone oil ~0.5%.

The present invention does not limit the specific types of reactive diluents, and those skilled in the art can select them according to actual conditions. Examples of reactive diluents are isobornyl acrylate, isooctyl acrylate, 4-acryloylmorpholine, gamma-methacryloyloxypropyltrimethoxysilane, gamma-methacryloyloxypropyltriethyl Oxysilane, methacryloyloxypropyltris(trimethylsiloxane)silane, vinyltriethoxysilane, γ-methacryloyloxypropyltriisopropoxysilane, and the like.

The present invention does not limit the specific types of photoinitiators, and those skilled in the art can select them according to actual conditions. For example, the photoinitiator can be 1-hydroxycyclohexyl phenyl ketone (184), 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (2959), 2,4, Ethyl 6-trimethylbenzoylphosphonate (TPO-L), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), etc.

A second aspect of the present invention provides a method for preparing a high-crosslinking density high-transmittance UV optical fiber inner coating, comprising the following steps:

Mix the polymerizable multifunctional acrylate silicone resin prepolymer, reactive diluent and photoinitiator evenly, then heat to 40-50℃ under the protection of dark nitrogen until the photoinitiator is completely dissolved, filter to remove insoluble matter, A high-transmission UV optical fiber inner coating with high cross-linking density is obtained. The obtained high-crosslinking density high-transmittance ultraviolet optical fiber inner coating is a colorless and transparent solution, which is protected from light for future use.

Example 1

Synthesis of tetrafunctional silicone urethane acrylate prepolymer: 88.92 g of isophorone diisocyanate (IPDI) and 0.58 g of stannous octoate (0.15 wt %) were added to a three-necked bottle with a thermometer and placed in an oil bath After being heated to 45 ℃ in the middle, 300g (molecular weight 1500) dehydrated hydroxypropyl silicone oil was added dropwise to the there-necked flask through a constant pressure funnel within 30 minutes, and the di-n-butylamine method was adopted after being incubated for 2.5 to 3 hours. Measure the isocyanate content; after the isocyanate content is half of the added amount, the system is heated to 60-65°C, and 42.1 g of dried diethanolamine is added dropwise to the there-necked flask within half an hour, and the temperature is kept for 2.5 to 3 hours. To the NCO content less than 0.1%; then add 117.8g IPDI dropwise to the three-necked bottle within half an hour, keep warm for 2.5 to 3 hours until the NCO content reaches half of the added amount; add 0.4g p-methoxyphenol to the flask; In the three-necked bottle, then 95.2 g of hydroxyethyl acrylate was added dropwise to the three-necked bottle within half an hour, kept for 3 to 3.5 hours until the NCO content was less than 0.1%, cooled and transferred to the bottle for later use.

Preparation of optical fiber inner coating: 90 g of tetrafunctional silicone urethane acrylate prepolymer, 10 g of isobornyl acrylate and 1.5 g of photoinitiator TPO were mixed uniformly, and the resulting mixture was heated under the protection of nitrogen gas. To 50 ℃ until the photoinitiator is completely dissolved, filter to remove the insoluble matter, the paint is a colorless and transparent solution, keep away from light for future use.

A 500W ultraviolet lamp is used to perform ultraviolet curing on the above-mentioned coating, and the coating can be cured in 8 seconds, and the coating thickness is about 40-50 microns. The fiber curing experiment was carried out at 10 m/min and 20 m/min drawing speed. The coating thickness on one side was about 20 μm. At 10 m/min drawing speed, the surface was not sticky; at 20 m/min drawing speed, the surface was not sticky. Not sticky (see Table 1 for details).

After curing, the transmittance at 248 nm of the coating was 71.9% (Fig. 2) (the coating thickness was 45 microns), the strength of the coating was improved, and the tensile properties were decreased (Fig. 3).

Example 2

Synthesis of six-functional silicone urethane acrylate prepolymer: 88.92 g of isophorone diisocyanate (IPDI) and 0.58 g of stannous octoate (0.15 wt%) were added to a three-necked bottle with a thermometer and placed in an oil bath After being heated to 45 ℃ in the middle, 300g (molecular weight 1500) dehydrated hydroxypropyl silicone oil was added dropwise to the there-necked flask through a constant pressure funnel within 30 minutes, and the di-n-butylamine method was adopted after being incubated for 2.5 to 3 hours. Measure the isocyanate content; after the isocyanate content is half of the added amount, the system is heated to 65-70 ° C, 0.4 g of p-methoxyphenol is added to the there-necked bottle, and then 119.3 g of pentaerythritol triacrylate is added within half an hour. Add dropwise to the three mouths, keep warm for 3 to 3.5 hours until the NCO content is less than 0.1%, then lower the temperature and transfer it to a bottle for use.

Preparation of optical fiber inner coating: Mix 90 g of six-functional silicone urethane acrylate prepolymer, 10 g of isobornyl acrylate and 1.5 g of photoinitiator TPO, and heat the resulting mixture under the protection of nitrogen gas in the dark To 50 ℃ until the photoinitiator is completely dissolved, filter to remove the insoluble matter, the paint is a colorless and transparent solution, keep away from light for future use.

A 500W ultraviolet lamp is used to perform ultraviolet curing on the above-mentioned coating, and the coating can be cured in 8 seconds, and the coating thickness is about 40-50 microns. The fiber curing experiment was carried out at 10 m/min and 20 m/min drawing speed. The coating thickness on one side was about 20 μm. At 10 m/min drawing speed, the surface was not sticky; at 20 m/min drawing speed, the surface was not sticky. Not sticky (see Table 1 for details).

After curing, the transmittance at 248 nm of the coating was 70.8% (Fig. 2) (the coating thickness was 45 microns), the strength of the coating was improved, and the toughness was decreased (Fig. 3).

Example 3

Synthesis of ten-functional silicone urethane acrylate prepolymer: 88.92 g of isophorone diisocyanate (IPDI) and 0.58 g of stannous octoate (0.15 wt %) were added to a three-necked bottle with a thermometer and placed in an oil bath After being heated to 45 ℃ in the middle, 300g (molecular weight 1500) dehydrated hydroxypropyl silicone oil was added dropwise to the there-necked flask through a constant pressure funnel within 30 minutes, and the di-n-butylamine method was adopted after being incubated for 2.5 to 3 hours. Determine the isocyanate content; after the isocyanate content is half of the added amount. The system is heated to 65～70℃, 0.8g p-methoxyphenol is added into the three-necked bottle, then 209.8g of dipentaerythritol pentaacrylate is added dropwise to the three-necked flask within half an hour, and the temperature is kept for 3～3.5 hours After the NCO content is less than 0.1%, the temperature is lowered and transferred to a bottle for use.

Preparation of optical fiber inner coating: Mix 80 g of ten-functional silicone urethane acrylate prepolymer, 20 g of isobornyl acrylate and 1.5 g of photoinitiator TPO, and heat the resulting mixture under the protection of nitrogen in the dark To 50 ℃ until the photoinitiator is completely dissolved, filter to remove the insoluble matter, the paint is a colorless and transparent solution, keep away from light for future use.

Example 4

Synthesis of twelve-functional silicone urethane acrylate prepolymer: 88.92 g of isophorone diisocyanate (IPDI) and 0.58 g of stannous octoate (0.15 wt %) were added to a three-necked bottle with a thermometer, and in oil After being heated up to 45 ℃ in the bath, 300g (molecular weight 1500) dehydrated hydroxypropyl silicone oil was added dropwise to the there-necked flask through a constant pressure funnel within 30 minutes, and di-n-butylamine was used after being incubated for 2.5 to 3 hours. The isocyanate content was determined by the method; after the isocyanate content was half of the added amount. Then, after heating the system to 60-65°C, 42.1 g of dried diethanolamine was added dropwise to the three ports within half an hour, and the temperature was kept for 2.5-3 hours until the NCO content was less than 0.1%. Then 117.8g IPDI was added dropwise to the three-necked bottle within half an hour, and the temperature was kept for 2.5 to 3 hours until the NCO content reached half of the added amount; The triacrylate is added dropwise to the three mouths within half an hour, kept for 3 to 3.5 hours until the NCO content is less than 0.1%, then cooled and transferred to a bottle for use.

Preparation of optical fiber inner coating: Mix 80 g of 12-functional silicone urethane acrylate prepolymer, 20 g of isobornyl acrylate and 1.5 g of photoinitiator TPO evenly, and put the resulting mixture under the protection of light-proof nitrogen. Heat to 50°C until the photoinitiator is completely dissolved, and filter to remove insoluble matter. The paint is a colorless and transparent solution, which should be stored in the dark for future use.

Comparative Example 1

Synthesis of difunctional silicone urethane acrylate prepolymer: 88.92 g of isophorone diisocyanate (IPDI) and 0.58 g of stannous octoate (0.15 wt %) were added to a three-necked bottle with a thermometer and placed in an oil bath After being heated to 45 ℃ in the middle, 300g (molecular weight 1500) dehydrated hydroxypropyl silicone oil was added dropwise to the there-necked flask through a constant pressure funnel within 30 minutes, and the di-n-butylamine method was adopted after being incubated for 2.5 to 3 hours. Determination of isocyanate content; after the isocyanate content is half of the added amount, the system is heated to 65-70 ° C, 0.2 g of p-methoxyphenol is added to the there-necked bottle, and then 47.6 g of hydroxyethyl acrylate are added within half an hour. Add dropwise to three mouths, keep warm for 3 to 3.5 hours until the NCO content is less than 0.1%, then lower the temperature and transfer it to a bottle for use.

Preparation of optical fiber inner coating: 90 g of difunctional silicone urethane acrylate prepolymer, 10 g of isobornyl acrylate and 1.5 g of photoinitiator TPO were mixed uniformly, and the resulting mixture was heated under the protection of nitrogen in the dark To 50 ℃ until the photoinitiator is completely dissolved, filter to remove the insoluble matter, the paint is a colorless and transparent solution, keep away from light for future use.

The above coatings were UV-cured using a 500W UV lamp. The coating can only be fully cured after 1 minute of UV irradiation, because the crosslinking density is low, the film is fragile, and it is not easy to obtain a film with complete properties.

Comparative Example 2

Synthesis of difunctional silicone urethane acrylate prepolymer: 88.92 g of isophorone diisocyanate (IPDI) and 0.58 g of stannous octoate (0.15 wt %) were added to a three-necked bottle with a thermometer and placed in an oil bath After being heated to 45 ℃ in the middle, 300g (molecular weight 1500) dehydrated hydroxypropyl silicone oil was added dropwise to the there-necked flask through a constant pressure funnel within 30 minutes, and the di-n-butylamine method was adopted after being incubated for 2.5 to 3 hours. Determination of isocyanate content; after the isocyanate content is half of the added amount, the system is heated to 65-70 ° C, 0.2 g of p-methoxyphenol is added to the there-necked bottle, and then 47.6 g of hydroxyethyl acrylate are added within half an hour. Add dropwise to three mouths, keep warm for 3 to 3.5 hours until the NCO content is less than 0.1%, then lower the temperature and transfer it to a bottle for use.

Preparation of optical fiber inner coating: 80 g of difunctional silicone urethane acrylate prepolymer, 10 g of isobornyl acrylate, 10 g of hexanediol diacrylate (small molecular crosslinking agent) and 1.5 g of photoinitiator The TPO was mixed evenly, and the resulting mixture was heated to 50° C. under the protection of nitrogen in the dark until the photoinitiator was completely dissolved, and the insolubles were removed by filtration.

The above coatings were UV-cured using a 500W UV lamp. The coating can be cured in 20 seconds, and the coating thickness is about 40-50 microns. The fiber curing experiment was carried out at 10 m/min and 20 m/min drawing speed. The coating thickness on one side was about 20 μm. At 10 m/min drawing speed, the surface was not sticky; at 20 m/min drawing speed, the surface was not sticky. Slightly sticky (see Table 1 for details).

After curing, the transmittance at 248 nm of the coating was 57% (Fig. 2) (the coating thickness was 45 microns), and the coating had a certain toughness (Fig. 3).

The performance results of the above optical fiber inner coating coatings are summarized in Table 1.

Table 1

It can be seen from Table 1 that the high-crosslinking density high-transmission UV optical fiber inner coating has a higher curing rate, which is more conducive to the rapid production of optical fiber coatings. Further comparing the results of writing with coating and writing without coating, we can see that grating can be written on optical fiber through coating. Since the coating itself is not 100% transmittance, the strength of grating with coating is weaker than that of stripping coating. Some, but had the least effect on the coating inscription of the coated optical fiber ribbon formed by the coating of Example 2.

It can be seen from the results in FIG. 2 and FIG. 3 that the transmittance formed by the example of the present invention is significantly higher than that of the comparative example 2; and the multifunctional silicone urethane acrylate prepolymer enables the optical fiber coating to have higher tensile strength Elongation, with the increase of functionality, the film strength increases and the elongation decreases.

Using the preparation method published in the patent 201710042159.3, on the coated optical fiber of the present invention, the grating structure is continuously written on-line on about 2000 m of UV-transparent coated optical fiber every 5 m interval, as shown in Figure 4 and Figure 5 for details. It can be seen from FIG. 4 and FIG. 5 that after the coating of the present invention is cured, the optical fiber can be directly inscribed with a laser without peeling off the layer, which simplifies the grating preparation process and the reliable performance.

To sum up, the high-crosslinking density high-transmittance UV optical fiber inner coating prepared by the present invention has high curing rate (8s fast curing, 20m/s curing rate on optical fiber curing machine), high crosslinking density and high depth. Ultraviolet transmittance (the transmittance can reach 71.9% when the film thickness at 248nm is 45 microns), after curing, the optical fiber can be directly inscribed with laser, without the need to peel off the layer, which simplifies the grating preparation process and reliable performance.

The specific embodiments of the present invention described above do not limit the protection scope of the present invention. Any other corresponding changes and modifications made according to the technical concept of the present invention shall be included in the protection scope of the claims of the present invention.

Claims (10)

1. The high-transmittance ultraviolet optical fiber internal coating with high crosslinking density is characterized by comprising the following raw materials in percentage by weight: 50-99% of polymerizable multifunctional acrylate organic silicon resin prepolymer, 0-50% of reactive diluent and 0.5-3 wt% of photoinitiator; the unsaturated double bond functionality of the polymerizable multifunctional acrylate organic silicon resin prepolymer is more than or equal to 3.

2. The UV-high fiber internal coating having a high crosslinking density according to claim 1, wherein the polymerizable multifunctional acrylate silicone resin prepolymer has an unsaturated double bond functionality of 4 to 12.

3. The uv undercoating with high crosslinking density of claim 1 wherein the polymerizable multifunctional acrylate silicone resin prepolymer has an end group of acrylate or methacrylate.

4. The uv fiber undercoating coating with high crosslink density of claim 1, wherein said polymerizable multifunctional acrylate silicone resin prepolymer is a multifunctional silicone urethane acrylate prepolymer.

5. The high-transmittance ultraviolet optical fiber inner coating with high crosslinking density as claimed in claim 4, wherein the preparation method of the multifunctional organosilicon polyurethane acrylate prepolymer comprises the following steps: mixing diisocyanate A and a catalyst, heating to 40-50 ℃, dropwise adding double-end hydroxypropyl silicone oil, carrying out heat preservation reaction until-NCO is reduced to half of the added amount, then heating to 60-70 ℃, dropwise adding a chain extender, and continuing the heat preservation reaction until the-NCO content is less than 0.1%; then, dropwise adding diisocyanate B, continuing to perform heat preservation reaction until the-NCO content is reduced to half of the added amount, then adding a blocking agent and a polymerization inhibitor, and continuing to perform heat preservation reaction until the-NCO content is less than 0.1% to obtain a multifunctional organosilicon polyurethane acrylate prepolymer; wherein the chain extender is a polyol or a polyamine; the end group of the end capping agent is at least one of acrylate or methacrylate.

6. The high-transmittance ultraviolet optical fiber inner coating with high crosslinking density as claimed in claim 4, wherein the preparation method of the multifunctional organosilicon polyurethane acrylate prepolymer comprises the following steps: mixing diisocyanate A and a catalyst, heating to 40-50 ℃, dropwise adding double-end hydroxypropyl silicone oil, carrying out heat preservation reaction until-NCO is reduced to half of the added amount, then heating to 60-70 ℃, dropwise adding a blocking agent and a polymerization inhibitor, and continuing heat preservation reaction until-NCO content is less than 0.1% to obtain a multifunctional organic silicon polyurethane acrylate prepolymer; wherein the end group of the end capping agent is at least one of acrylate or methacrylate.

7. The high transmission ultraviolet optical fiber undercoating having a high crosslinking density as set forth in claim 1, wherein the reactive diluent is at least one of isobornyl acrylate, isooctyl acrylate, 4-acryloylmorpholine, γ -methacryloyloxypropyltrimethoxysilane, γ -methacryloyloxypropyltriethoxysilane, methacryloyloxypropyltris (trimethylsiloxy) silane, vinyltriethoxysilane, γ -methacryloyloxypropyltriisopropoxysilane; the photoinitiator is at least one of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-4' - (2-hydroxyethoxy) -2-methyl propiophenone, 2,4, 6-trimethyl benzoyl ethyl phosphonate and 2,4, 6-trimethyl benzoyl diphenyl phosphine oxide.

8. The high-transmittance ultraviolet optical fiber inner coating paint with high crosslinking density as claimed in claim 1, is characterized in that the high-transmittance ultraviolet optical fiber inner coating paint with high crosslinking density comprises the following raw materials in percentage by weight: 78-90% of polymerizable multifunctional acrylate organic silicon resin prepolymer, 8-20% of reactive diluent and 1-2 wt% of photoinitiator.

9. The high-transmittance ultraviolet optical fiber internal coating material with high crosslinking density as claimed in claim 1, wherein the high-transmittance ultraviolet optical fiber internal coating material with high crosslinking density comprises the following raw materials in percentage by weight: 88-90% of polymerizable multifunctional acrylate organic silicon resin prepolymer, 9-10% of reactive diluent and 1-2 wt% of photoinitiator.

10. The preparation method of the high-transmittance ultraviolet optical fiber internal coating with high crosslinking density as claimed in any one of claims 1 to 9, which is characterized by comprising the following steps:

uniformly mixing the polymerizable multifunctional acrylate organic silicon resin prepolymer, the active diluent and the photoinitiator, heating to 40-50 ℃ under the protection of light-proof nitrogen until the photoinitiator is completely dissolved, and filtering to remove insoluble substances to obtain the high-transmittance ultraviolet optical fiber internal coating with high crosslinking density.

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