1. A preparation method of an all-silicon-based optical fiber internal coating is characterized by comprising the following steps:

mixing diisocyanate 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 60-65 ℃, adding a hydroxyl acrylate monomer and a polymerization inhibitor, and continuing heat preservation reaction until-NCO content is less than 0.1% to obtain an organosilicon polyurethane acrylate prepolymer;

mixing 50-70 parts of the organic silicon polyurethane acrylate prepolymer, 10-40 parts of double-end acrylate organic silicon resin, 10-30 parts of single-end acrylate organic silicon resin and 0.5-2 parts of photoinitiator, heating in a dark place until the photoinitiator is completely dissolved, and filtering to obtain the all-silicon-based optical fiber inner coating.

2. The method for preparing the internal coating of the all-silica-based optical fiber according to claim 1, wherein the diisocyanate is isophorone diisocyanate; the hydroxyl acrylate monomer is at least one of hydroxyethyl acrylate and hydroxyethyl methacrylate.

3. The method for preparing the internal coating of the all-silica-based optical fiber according to claim 1, wherein the molecular weight of the bis-hydroxypropyl methyl silicone oil is 1000-3000 g/mol.

4. The method for preparing the internal coating of the all-silica-based optical fiber according to claim 1, wherein the molar ratio of the diisocyanate to the hydroxypropyl silicone oil at both ends and the hydroxyl acrylate monomer is 1: (0.4-0.6): (0.9-1.1).

5. The method for preparing the internal coating of the all-silica-based optical fiber according to claim 4, wherein the molar ratio of the diisocyanate to the hydroxypropyl silicone oil at both ends and the hydroxyl acrylate monomer is 1: 0.5: 1.01.

6. the preparation method of the all-silica-based optical fiber inner coating paint according to claim 1, wherein the catalyst is stannous octoate, and the addition amount of the catalyst is 0.01-0.2% of the mass of the hydroxypropyl silicone oil at the two ends.

7. The method for preparing the internal coating of the all-silica-based optical fiber according to claim 1, wherein the polymerization inhibitor is p-methoxyphenol, and the amount of the polymerization inhibitor added is 0.3 to 0.5 percent of the mass of the hydroxyl acrylate monomer.

8. The method of claim 1, wherein the terminal group of the double-terminal acrylate silicone resin and the single-terminal acrylate silicone resin is at least one of acrylate or methacrylate.

9. The method of claim 1, wherein the photoinitiator is one or two of 1-hydroxycyclohexyl phenyl ketone, ethyl 2,4, 6-trimethylbenzoylphosphonate, 2-methyl-1- [4- (methylthio) phenyl ] -2- (4-morpholinyl) -1-propanone, 2,4, 6-trimethylbenzoyl-diphenylphosphine oxide, and 2-hydroxy-4' - (2-hydroxyethoxy) -2-methyl phenylpropanone.

10. An all-silicon-based optical fiber inner coating paint, which is obtained by the preparation method of the all-silicon-based optical fiber inner coating paint according to any one of claims 1 to 9.

Background

In recent years, with the wide application of optical fiber technology in the fields of optical fiber communication, optical fiber imaging, optical fiber sensors, military and the like, the preparation technology of the optical fiber grating is rapidly developed. The preparation of the fiber grating is to form a space phase grating in a fiber core by utilizing the photosensitivity of a fiber material to form a narrow-band filter or a reflector, and the fiber grating is used for detecting fiber sensors and various fiber sensing networks of various parameters such as stress, strain, temperature and the like. Currently, fiber gratings are mainly prepared by 248nm or 266nm laser writing technology, and 248nm laser has higher energy and is more selected for being more beneficial to preparing fiber gratings.

At present, the preparation of the fiber grating is mainly to strip part of a coating after the coating is finished and then write, and then to perform plastic sheathing or metal sheath treatment after the preparation is finished, so that the grating is damaged in the processing process, and the subsequent protection treatment also causes uneven stress on the grating part in the fiber, thereby affecting the sensitivity and the signal transmission quality of the grating. In particular applications, fiber gratings are required to have particular temperature flexibility, e.g., high temperature resistance, to prevent their stability during use in particular environments.

The xu Weiqi et al synthesizes aliphatic polyurethane acrylic ester by one-step method by using polytetrahydrofuran ether glycol, hydroxypropyl acrylate and isophorone isocyanate as raw materials. The polysiloxane acrylate is prepared by taking hydrogen-terminated silicone oil and 1, 6-hexanediol diacrylate as raw materials and carrying out hydrogen-terminated addition reaction under the action of an organic platinum catalyst. And compounding the two resins, adjusting the dosage of the resins, and adding a photoinitiator and an active diluent to prepare the UV photocuring fiber grating coating. The coating had a light transmission of 75% at 248nm (film thickness 60 μm). In the method, an organic platinum catalyst is adopted, the catalyst is difficult to prepare and expensive, and the addition reaction of silicone oil and acrylate is slow, so that the production cost is high.

Zhang Chang et al disclose a method for preparing high ultraviolet transmittance optical fiber coating, which comprises reacting hydroxyl silicone oil with isophorone isocyanate to prepare polysiloxane polyurethane, preparing hydroxyl acrylic resin from hydroxyl acrylate monomer and acrylic acid monomer, and modifying the polysiloxane polyurethane with hydroxyl acrylic resin to prepare high ultraviolet transmittance acrylic polyurethane coating. The resin prepared by the method has the light transmittance of 85 percent at the position of 248nm and good heat resistance (5 percent of thermal weight loss rate is 280 ℃). However, the coating is unstable and must be stored hermetically at room temperature and in the dark. the-NCO in the coating is easy to hydrolyze when meeting water, amino and carbon dioxide gas are generated, the amino reacts with isocyanate groups, the viscosity of a system is increased, even self-crosslinking and curing are caused, the performance of the coating is influenced, sometimes, the coating can not be continuously used, and the specific reaction formula is as follows:

meanwhile, the coating is a two-component coating which is prepared before use, needs to be used as soon as possible after preparation, cannot be mixed and placed for a long time, and the mixed placement causes the two components of the coating to slowly react and be cured, so that the coating effect is influenced.

Disclosure of Invention

In view of the above, it is necessary to provide an all-silica-based optical fiber inner coating and a preparation method thereof, so as to solve the technical problems of high production cost and poor long-term storage stability of the optical fiber coating with high ultraviolet transmittance in the prior art.

The first aspect of the invention provides a preparation method of an all-silicon-based optical fiber inner coating, which comprises the following steps:

mixing diisocyanate 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 60-65 ℃, adding a hydroxyl acrylate monomer and a polymerization inhibitor, and continuing heat preservation reaction until-NCO content is less than 0.1% to obtain an organosilicon polyurethane acrylate prepolymer;

mixing 50-70 parts of organic silicon polyurethane acrylate prepolymer, 10-40 parts of double-end acrylate organic silicon resin, 10-30 parts of single-end acrylate organic silicon resin and 0.5-2 parts of photoinitiator, heating in a dark place until the photoinitiator is completely dissolved, and filtering to obtain the all-silicon-based optical fiber inner coating.

The second aspect of the present invention provides an all-silica-based optical fiber inner coating paint obtained by the method for preparing the all-silica-based optical fiber inner coating paint provided by the first aspect of the present invention.

Compared with the prior art, the invention has the beneficial effects that:

the polymerizable acrylate organic silicon resin is selected as the main material to prepare the all-silicon-based optical fiber inner coating under the condition of the photoinitiator, so that the preparation process is simple, the reaction is rapid, the raw materials are easy to obtain, the cost is low, and the industrial production is facilitated; the obtained all-silicon-based optical fiber inner coating does not contain other heteroatoms and unsaturated bonds, and has weak ultraviolet absorption, so that the all-silicon-based optical fiber inner coating has higher ultraviolet transmittance and can meet the writing requirement of grating coating; meanwhile, the coating system is stable, does not need to be prepared for use, can not react with water, can be stored for a long time under the conditions of normal temperature and light resistance, can be rapidly solidified into a film under the condition of ultraviolet light, and has very high practical value.

Drawings

In FIG. 1, a to c are respectively the UV transmittance curves of the coating formed by curing the all-silica-based optical fiber inner coating prepared in examples 2 to 4 of the present invention; the thickness of the coating is 62-63 mu m;

in FIG. 2, a to c are respectively the UV transmittance curves of the coating formed by curing the all-silica-based optical fiber inner coating prepared in examples 2 to 4 of the present invention; the thickness of the coating is 30 mu m;

FIG. 3 is a graph showing the thermal weight loss of a coating layer formed after curing of an all-silica based optical fiber undercoating prepared in example 2 of the present invention;

FIG. 4 is a graph of the write strength of a coated and stripped fiber grating prepared from the inner coating of a fully silica-based optical fiber prepared in example 4 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The first aspect of the invention provides a preparation method of an all-silicon-based optical fiber inner coating, which comprises the following steps:

s1, mixing diisocyanate 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 60-65 ℃, adding a hydroxyl acrylate monomer and a polymerization inhibitor, and continuing the heat preservation reaction until-NCO content is less than 0.1% to obtain an organic silicon polyurethane acrylate prepolymer;

s2, mixing 50-70 parts of organic silicon polyurethane acrylate prepolymer, 10-40 parts of double-end acrylate organic silicon resin, 10-30 parts of single-end acrylate organic silicon resin and 0.5-2 parts of photoinitiator, heating in a dark place until the photoinitiator is completely dissolved, and filtering to obtain the all-silicon-based optical fiber inner coating.

The polymerizable acrylate organic silicon resin is selected as the main material to prepare the all-silicon-based optical fiber inner coating under the condition of the photoinitiator, so that the preparation process is simple, the reaction is rapid, the raw materials are easy to obtain, the cost is low, and the industrial production is facilitated; the obtained all-silicon-based optical fiber inner coating does not contain other heteroatoms and unsaturated bonds, and has weak ultraviolet absorption, so that the all-silicon-based optical fiber inner coating has higher ultraviolet transmittance and can meet the writing requirement of grating coating; meanwhile, the coating system is stable, does not need to be prepared for use, can not react with water, can be stored for a long time under the conditions of normal temperature and light resistance, can be rapidly solidified into a film under the condition of ultraviolet light, and has very high practical value.

The single-end acrylate organic silicon resin can be used as a diluent, and does not need to be added with a micromolecular diluent, so that monomer volatilization is prevented, and the environmental safety and health in the production process are ensured.

In the invention, the diisocyanate is isophorone diisocyanate; the hydroxyl acrylate monomer is at least one of hydroxyethyl acrylate and hydroxyethyl methacrylate. By selecting the raw materials, the end group of the obtained organosilicon polyurethane acrylate prepolymer is at least one of acrylate or methacrylate.

In the invention, the molecular weight of the dihydroxypropyl methyl silicone oil is 1000-3000 g/mol, preferably 1500 g/mol.

In the invention, the molar ratio of diisocyanate to the double-end hydroxypropyl silicone oil and the hydroxyl acrylate monomer is 1: (0.4-0.6): (0.9 to 1.1), preferably 1: 0.5: 1.01. within the above ratio range, the isocyanate can be fully reacted, and the instability of the system due to the residual isocyanate in the long-term storage process can be avoided.

In the invention, the catalyst is stannous octoate, and the addition amount of the catalyst is 0.01-0.2% of the mass of the hydroxypropyl silicon oil at the two ends.

In the invention, the polymerization inhibitor is p-methoxyphenol, and the addition amount of the polymerization inhibitor is 0.3-0.5% of the mass of the hydroxyl acrylate monomer.

In the invention, the mixture of the hydroxyl acrylate monomer and the polymerization inhibitor is added into the system in a dropwise manner.

In the present invention, the terminal group of the double-terminal acrylate silicone resin and the single-terminal acrylate silicone resin is at least one of acrylate or methacrylate.

In some embodiments of the present invention, the molecular weight of the double-ended acrylate silicone resin is 1000 to 2000g/mol, preferably 1000 g/mol; the molecular weight of the single-ended acrylate organic silicon resin is 400-1000 g/mol, preferably 500 g/mol.

In the invention, the photoinitiator is one or two of 1-hydroxycyclohexyl phenyl ketone (184), 2,4, 6-trimethyl benzoyl ethyl phosphonate (TPO-L), 2-methyl-1- [4- (methylthio) phenyl ] -2- (4-morpholinyl) -1-acetone (907), 2,4, 6-trimethyl benzoyl diphenyl phosphine oxide (TPO) and 2-hydroxy-4' - (2-hydroxyethoxy) -2-methyl phenylpropyl ketone (2959).

In the invention, the temperature for mixing and heating in a dark place is 40-60 ℃, and preferably 50 ℃.

The second aspect of the present invention provides an all-silica-based optical fiber inner coating paint obtained by the method for preparing the all-silica-based optical fiber inner coating paint provided by the first aspect of the present invention.

Example 1

This example provides a method for preparing a silicone polyurethane acrylate prepolymer, including the following steps:

74.1g of isophorone diisocyanate (IPDI) and 0.49g of stannous octoate were added to a three-necked flask with a thermometer, and after the temperature was raised to 45 ℃, 250g of dehydrated double-end hydroxypropyl silicone oil (M)_W1500) is added into the system, and after heat preservation is carried out for 2-2.5 hours, the content of isocyanate is measured by adopting a di-n-butylamine method; and (3) after the-NCO content is reduced to half of the adding amount, heating the system to 60-65 ℃, dissolving 0.15g of polymerization inhibitor p-methoxyphenol in 40.0g of hydroxyethyl acrylate (98%), dropwise adding the polymerization inhibitor p-methoxyphenol into the system, keeping the temperature for 3-3.5 hours until the-NCO content is less than 0.1%, cooling, transferring the bottle, and placing the bottle in a refrigerator for later use.

Example 2

50g of the silicone polyurethane acrylate prepolymer prepared in example 1 was weighed and 40g of a double-terminal acrylate silicone resin (M) was added_W1000), 10g of a single-ended acrylate silicone resin (M)_W500), 0.5g of photoinitiator TPO-L and 0.5g of photoinitiator 2959, the mixture was heated to 50 ℃ in the dark until the photoinitiator was completely dissolved, the insoluble matter was removed by filtration, and the resulting coating was a colorless transparent solution and was stored in the dark until use.

The above coatings were coated on a substrate and UV cured using a 1kW UV lamp to prepare samples having coating thicknesses of 62 microns and 30 microns. Referring to FIG. 1a, the transmittance at 248nm of the cured coating with a thickness of 62 μm is 69.1%, and the coating remains transparent after heating at 200 ℃ for 24 hours, with a transmittance of 60.5%; referring to fig. 3, the heat stability temperature of the coating layer at 5% weight loss after curing is 280 ℃, and the heat stability temperature of the heat-treated coating layer after curing is 293 ℃; referring to FIG. 2a, the transmittance at 248nm after curing of a coating having a thickness of 30 μm is 80.1%.

Example 3

65g of the silicone polyurethane acrylate prepolymer prepared in example 1 was weighed and 15g of a double-terminal acrylate silicone resin (M) was added_W1000), 30g of a single-ended acrylate silicone resin (M)_W500), 0.5g of photoinitiator TPO-L and 0.5g of photoinitiator 184, the mixture was heated to 50 ℃ in the dark until the photoinitiator was completely dissolved, and insoluble matter was removed by filtration, and the resulting coating was a colorless transparent solution and was stored in the dark until use.

The above coatings were coated on a substrate and UV cured using a 1kW UV lamp to prepare samples having coating thicknesses of 63 microns and 30 microns. Referring to FIG. 1b, the transmittance at 248nm of the cured coating with a thickness of 63 μm was 64.3%, and the coating remained transparent after heating at 200 ℃ for 24 hours, with a transmittance of 59.4%; referring to FIG. 2b, the transmittance at 248nm after curing of the coating with a thickness of 30 μm is 77.6%.

Example 4

70g of the silicone polyurethane acrylate prepolymer prepared in example 1 was weighed and 10g of a double-terminal acrylate silicone resin (M) was added_W1000), 20g of a single-ended acrylate silicone resin (M)_W500), 0.5g of photoinitiator TPO and 0.5g of photoinitiator 907, the mixture was heated to 50 ℃ in the dark until the photoinitiator was completely dissolved, insoluble materials were removed by filtration, and the resulting coating was a colorless transparent solution and was stored in the dark for later use.

The above coatings were coated on a substrate and UV cured using a 1kW UV lamp to prepare samples having coating thicknesses of 62 microns and 30 microns. Referring to FIG. 1c, the transmittance at 248nm of the cured coating of 62 μm was 56.8%, and the coating remained transparent after heating at 200 ℃ for 24 hours, with a transmittance of 55.0%; referring to FIG. 2c, the transmittance at 248nm after curing of the coating with a thickness of 30 μm is 73.5%.

The coating of the embodiment 4 is used for preparing a G652 optical fiber by utilizing an online ultraviolet curing and wire drawing process, the thickness of a single-layer coating of the G652 optical fiber is 30 microns, grating writing is carried out on the single-mode fiber with the ultraviolet-transmitting coating after being drawn by utilizing a 248nm excimer laser and a 1068nm phase mask plate, and the grating writing strength of the fiber with the coating and the stripped coating is compared under 50mJ single-pulse exposure energy. Referring to FIG. 4, the single pulse lower grating strength of the coated fiber is only 3dB lower than that of the stripped fiber, which can fully meet the application requirements of the fiber grating array.

Compared with the prior art, the invention has the beneficial effects that:

the optical fiber coating can be used at a high temperature of 200 ℃ for a long time to keep the coating stable, the transmittance of a sample with the thickness of 30 micrometers at the position of 248nm of the wavelength of common grating writing ultraviolet laser can reach 80.1 percent, and the normal use of the optical fiber under a special environment can be met;

the coating is an all-silicon-based coating, does not contain small molecular reagents, is not volatilized in the using process, has excellent high-temperature resistance and has important value in special fields;

the optical fiber coating provided by the invention has excellent mechanical properties, high-temperature stability and high transparency in a deep ultraviolet region (240 nm), and the coating can be directly subjected to laser writing without peeling, so that the grating preparation process is simplified, and the strength of an optical fiber and the use reliability under special conditions are improved.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.