High-strength and high-toughness photocuring outer coating for small-diameter polarization maintaining optical fiber

Abstract

The invention provides a high-strength and high-toughness photocuring outer coating for a thin-diameter polarization-maintaining optical fiber. The coating comprises the following components: 60-80% of a modified acrylate oligomer; 20-40% of an acrylate monomer; 0.5 to 6% of a photoinitiator; 0.05-1% of an antioxidant; the modified acrylate oligomer is formed by polymerizing oligosaccharide, alkyl acid, (methyl) acrylic acid, an acid catalyst and a polymerization inhibitor, the main chain of the oligosaccharide has a continuous pyranoid ring structure and the polymerization degree is 2-10, and carboxyl in the alkyl acid and hydroxyl on a pyranoid ring are subjected to esterification reaction so as to be grafted on the oligosaccharide to form an alkyl side chain. The high-strength and high-toughness photocuring outer coating for the small-diameter polarization maintaining optical fiber has the advantages of high strength and high flexibility, the curing speed is high by adopting a photocuring mode, and the raw materials are cheap and easy to obtain.

Description

Technical Field

[0001] This invention relates to the field of optical fiber coating technology, specifically to a high-strength, high-toughness photocurable outer coating for small-diameter polarization-maintaining optical fibers. Background Technology

[0002] Fiber optic gyroscopes are one of the most important achievements in the field of fiber optic sensing. They have advantages such as no moving parts, simple manufacturing process, wide accuracy coverage, large dynamic range, fast start-up, long life, shock resistance, and overload resistance. They have broad development prospects in military fields such as aviation, aerospace, navigation, and weaponry, as well as civilian fields such as geology and oil exploration.

[0003] The sensitive loop wound with polarization-maintaining fiber is a key component in fiber optic gyroscope systems, with panda-type polarization-maintaining fiber being the most widely used. The rapid development of fiber optic gyroscopes has placed higher demands on the performance of polarization-maintaining fibers. Currently, fiber optic gyroscope systems are developing towards miniaturization, high precision, and high stability. To adapt to this trend, the development of polarization-maintaining fibers is also moving towards smaller diameters, higher precision, longer lengths, higher stability, and better adaptability to complex environments. Small-diameter polarization-maintaining fiber products employ a unique fine-coating control technology, reducing the fiber diameter from 165μm to 135μm or even 100μm while keeping the fiber quartz cladding diameter constant. This effectively increases the winding length within the same volume, solving the miniaturization problem of fiber optic gyroscope devices and providing a new solution for manufacturing high-precision fiber optic gyroscopes.

[0004] The outer coating of optical fibers, acting as a protective layer against external environmental factors, generally possesses a certain level of mechanical strength and toughness. As the thickness of the outer coating decreases in narrow-diameter polarization-maintaining fibers, higher mechanical strength is required. Simultaneously, during fiber winding, significant stress is generated due to fiber bending; to prevent brittle fracture, the outer coating also needs good toughness. Conventional optical fiber outer coatings are typically blends of epoxy acrylate and polyurethane acrylate. While epoxy acrylate possesses high mechanical strength, it is also brittle and prone to fracture. To balance its mechanical strength and toughness, it is often blended with polyurethane acrylate. However, a small amount of polyurethane acrylate results in poor toughening, while a large amount significantly reduces mechanical strength, making it difficult to obtain high-strength, high-toughness products; therefore, it is only suitable for conventional optical fiber coatings. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a high-strength and high-toughness photocurable outer coating for fine-diameter polarization-maintaining optical fibers. It possesses both high strength and high flexibility, and the photocuring method ensures fast curing speed and uses inexpensive and readily available raw materials.

[0006] The technical solution adopted to achieve the above-mentioned objectives of this invention is as follows:

[0007] A high-strength, high-toughness photocurable outer coating for small-diameter polarization-maintaining optical fibers, the coating comprising the following components by weight percentage:

[0008] Modified acrylate oligomers 60-80%;

[0009] 20-40% acrylate monomers;

[0010] Photoinitiator 0.5~6%;

[0011] Antioxidant 0.05~1%;

[0012] The modified acrylate oligomer is polymerized from oligosaccharides, alkyl acids, (meth)acrylic acid, acidic catalysts and polymerization inhibitors. The oligosaccharide backbone has a continuous pyran ring structure and a degree of polymerization of 2 to 10. The carboxyl group in the alkyl acid undergoes esterification with the hydroxyl group on the pyran ring to graft onto the oligosaccharide to form an alkyl side chain.

[0013] Furthermore, the molar ratio of the oligosaccharide, alkyl acid, and (meth)acrylic acid is 1:(2a~3a):(2~4), where a is the degree of polymerization of the oligosaccharide.

[0014] Furthermore, the molecular weight of the oligosaccharide is 400-2000.

[0015] Furthermore, the alkyl acid has 6 to 18 carbon atoms.

[0016] Furthermore, the modified acrylate oligomer is prepared by the following method: oligosaccharides, alkyl acids, (meth)acrylic acid, acidic catalysts and polymerization inhibitors are added to a reaction apparatus equipped with a stirrer and a reflux condenser, heated to 105~110°C, and the reaction is stopped after full reaction under stirring; then the reaction solution is added to deionized water under stirring, and after sufficient settling, the supernatant is removed, and the bottom product is washed with deionized water until the pH of the washing solution is neutral. After vacuum drying, the modified acrylate oligomer is obtained.

[0017] Furthermore, the acidic catalyst is one or more of sulfuric acid, hydrochloric acid, and p-toluenesulfonic acid.

[0018] Furthermore, the polymerization inhibitor is one or more of tert-butylhydroquinone, p-hydroxyanisole, hydroquinone, or o-methylhydroquinone.

[0019] Furthermore, the acrylate monomer is one or more of the following: isobornyl (meth)acrylate, 3,3,5-trimethylcyclohexyl acrylate, dicyclopentyl methacrylate, tricyclodecanediethanol diacrylate, laurate acrylate, stearate acrylate, isodeoxy acrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, and trimethylolpropane tri(meth)acrylate.

[0020] Furthermore, the photoinitiator is selected from one or more of Irgacure1173, Irgacure184, IrgacureTPO-L and Irgacure819.

[0021] Furthermore, the antioxidant is selected from one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], Irganox L135, Irganox L57, and Irganox 1035.

[0022] Compared with existing technologies, the high-strength and high-toughness photocurable outer coating for small-diameter polarization-maintaining optical fibers provided by this invention has the following advantages:

[0023] 1. The optical fiber outer coating of this invention is made of modified acrylate oligomer as the main resin. The oligosaccharides in the modified acrylate oligomer have a continuous six-membered ring (pyran ring) structure on the main chain, which gives it high rigidity. At the same time, it is modified by esterification with long-chain alkyl acid, and alkyl side chains with good flexibility are introduced into the main chain. While retaining its rigidity, its toughness is improved, so that the final product has the advantages of high strength and high flexibility. As an outer coating layer, it can provide good protection for small diameter polarization-maintaining optical fibers.

[0024] 2. The introduction of acrylic acid in this invention gives it the characteristics of photocuring, and under the action of the initiator, the final product also has the advantage of fast curing speed.

[0025] 3. The present invention uses oligosaccharides and alkyl acids as the main components, which are inexpensive and readily available; at the same time, the overall synthesis process is simple and does not require complicated operation steps, so the manufacturing cost of the final product is low. Detailed Implementation

[0026] The present invention will now be described in detail with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0027] Example 1

[0028] At room temperature, 1 mol of maltotriose, 6 mol of dodecyl acid, 3 mol of acrylic acid, 1 g of p-toluenesulfonic acid, and 1 g of tert-butylhydroquinone were added to a reaction flask equipped with a stirrer and a reflux condenser. The mixture was heated to 105-110°C and stirred for 3 hours, after which heating was stopped. The liquid in the flask was added to deionized water under stirring, allowed to stand, and the supernatant was removed. The bottom product was washed with deionized water until the pH of the washing solution was neutral. The product was then vacuum dried to obtain the modified acrylate oligomer (material L1).

[0029] Take 65g of material L1, 30g of 1,6-hexanediol diacrylate, 4g of TPO-L, and 0.5g of Irganox L135, stir and mix well, and filter to obtain composition A1.

[0030] Example 2

[0031] At room temperature, 1 mol of maltotriose, 6 mol of octadecyl acid, 3 mol of acrylic acid, 1 g of p-toluenesulfonic acid, and 1 g of tert-butylhydroquinone were added to a reaction flask equipped with a stirrer and a reflux condenser. The mixture was heated to 105-110°C and stirred for 3 hours, after which heating was stopped. The liquid in the flask was added to deionized water under stirring, allowed to stand, and the supernatant was removed. The bottom product was washed with deionized water until the pH of the washing solution was neutral. The product was then vacuum dried to obtain the modified acrylate oligomer (material L2).

[0032] Take 65g of material L2, 30g of 1,6-hexanediol diacrylate, 4g of TPO-L, and 0.5g of Irganox L135, stir and mix well, and then filter to obtain composition A2.

[0033] Example 3

[0034] At room temperature, 1 mol of maltopentose, 10 mol of dodecyl acid, 3 mol of acrylic acid, 1 g of p-toluenesulfonic acid, and 1 g of tert-butylhydroquinone were added to a reaction flask equipped with a stirrer and a reflux condenser. The mixture was heated to 105-110°C and stirred for 3 hours, after which heating was stopped. The liquid in the flask was added to deionized water under stirring, allowed to stand, and the supernatant was removed. The bottom product was washed with deionized water until the pH of the washing solution was neutral. The product was then vacuum dried to obtain the modified acrylate oligomer (material L3).

[0035] Take 65g of material L3, 30g of 1,6-hexanediol diacrylate, 4g of TPO-L, and 0.5g of Irganox L135, stir and mix well, and then filter to obtain composition A3.

[0036] Example 4

[0037] At room temperature, 1 mol of maltoctaose, 20 mol of hexanoic acid, 3.5 mol of acrylic acid, 1.5 g of sulfuric acid, and 1.5 g of hydroquinone were added to a reaction flask equipped with a stirrer and a reflux condenser. The mixture was heated to 105-110°C and stirred for 3 hours, after which heating was stopped. The liquid in the flask was added to deionized water under stirring, allowed to stand, and the supernatant was removed. The bottom product was washed with deionized water until the pH of the washing solution was neutral. The product was then vacuum dried to obtain the modified acrylate oligomer (material L4).

[0038] Take 56g of material L4, 38g of 1,6-hexanediol diacrylate, 5g of 1173, and 0.5g of Irganox L57, stir and mix well, and then filter to obtain composition A4.

[0039] Example 5

[0040] At room temperature, 1 mol of maltotriose, 7 mol of decanoic acid, 3 mol of acrylic acid, 1 g of p-toluenesulfonic acid, and 1 g of tert-butylhydroquinone were added to a reaction flask equipped with a stirrer and a reflux condenser. The mixture was heated to 105-110°C and stirred for 3 hours, after which heating was stopped. The liquid in the flask was added to deionized water under stirring, allowed to stand, and the supernatant was removed. The bottom product was washed with deionized water until the pH of the washing solution was neutral. The product was then vacuum dried to obtain the modified acrylate oligomer (material L4).

[0041] Take 60g of material L4, 32g of tripropylene glycol diacrylate, 4.5g of 184, and 0.5g of Irganox L1035, stir and mix well, and filter to obtain composition A5.

[0042] Comparative Example 1

[0043] At room temperature, 1 mol of maltotriose, 3 mol of acrylic acid, 1 g of p-toluenesulfonic acid, and 1 g of tert-butylhydroquinone were added to a reaction flask equipped with a stirrer and a reflux condenser. The mixture was heated to 105-110°C and stirred for 3 hours, after which heating was stopped. The liquid in the flask was added to deionized water under stirring, allowed to stand, and the supernatant was removed. The bottom product was washed with deionized water until the pH of the washing solution was neutral. The product was then vacuum dried to obtain the acrylate oligomer (material LL1). This comparative example differs from Example 1 in that the oligomer was not esterified with an alkyl acid.

[0044] Take 65g of material LL1, 30g of 1,6-hexanediol diacrylate, 4g of TPO-L, and 0.5g of Irganox L135, stir and mix well, then filter to obtain composition B1. Unlike Example 1, material LL1 was not alkylated.

[0045] Comparative Example 2

[0046] Take 65g of bisphenol A epoxy acrylate, 30g of 1,6-hexanediol diacrylate, 4g of TPO-L, and 0.5g of Irganox L135, stir and mix well, then filter to obtain composition B2. Unlike Example 1, the oligomer is bisphenol A epoxy acrylate.

[0047] Comparative Example 3

[0048] Take 65g of a bisphenol A epoxy acrylate and polyurethane acrylate blend (mass ratio 5:1), 30g of 1,6-hexanediol diacrylate, 4g of TPO-L, and 0.5g of Irganox L135, stir and mix well, then filter to obtain composition B3. Unlike Example 1, the oligomer is a bisphenol A epoxy acrylate and polyurethane acrylate blend.

[0049] The compositions (A1, A2, A3, B1, B2, B3) prepared in Examples 1-3 and Comparative Examples 1-3 were coated with a 200 μm film and irradiated under an electrodeless lamp with an energy of 500 mJ / cm². 2 The cured film was then cured. The mechanical properties (tensile strength, elongation at break, and 2.5% modulus of deformation) of the cured film were tested, and the results are shown in the table below:

[0050]

[0051] The test results above show that, compared to B2, compositions A1, A2, A3, and B2 exhibit a very high elongation at break, and the 2.5% modulus of deformation is around 1200 MPa. This indicates that the modified acrylate, compared to epoxy acrylate, possesses both high strength and high toughness, meeting the performance requirements of the outer coating for small-diameter polarization-maintaining optical fibers. Compared to B1, compositions A1, A2, A3, and B1 show that while the acrylate oligomer complex without long-chain alkyl acid modification has high strength, its toughness is poor, failing to meet the performance requirements of the outer coating for small-diameter polarization-maintaining optical fibers. Composition B3 is a blend of epoxy acrylate and polyurethane acrylate. Although the addition of polyurethane acrylate somewhat improves its toughness and increases the elongation at break, its strength still falls short of the performance requirements for the outer coating of small-diameter polarization-maintaining optical fibers, only meeting the requirements for the outer coating of ordinary optical fibers.

Claims

1. A high-strength, high-toughness photocurable outer coating for small-diameter polarization-maintaining optical fibers, characterized in that: The coating comprises the following components by weight percentage: Modified acrylate oligomers 60-80%; 20-40% acrylate monomers; Photoinitiator 0.5~6%; Antioxidant 0.05~1%; The modified acrylate oligomer is polymerized from oligosaccharides, alkyl acids, (meth)acrylic acid, acidic catalysts and polymerization inhibitors. The oligosaccharide backbone has a continuous pyran ring structure and a degree of polymerization of 2 to 10. The carboxyl group in the alkyl acid undergoes an esterification reaction with the hydroxyl group on the pyran ring, thereby grafting onto the oligosaccharide to form an alkyl side chain.

2. The high-strength, high-toughness photocurable outer coating for fine-diameter polarization-maintaining optical fibers according to claim 1, characterized in that: The molar ratio of the oligosaccharide, alkyl acid, and (meth)acrylic acid is 1:(2a~3a):(2~4), where a is the degree of polymerization of the oligosaccharide.

3. The high-strength, high-toughness photocurable outer coating for fine-diameter polarization-maintaining optical fibers according to claim 1, characterized in that: The oligosaccharide has a molecular weight of 400-2000.

4. The high-strength, high-toughness photocurable outer coating for fine-diameter polarization-maintaining optical fibers according to claim 1, characterized in that: The alkyl acid has 6 to 18 carbon atoms.

5. The high-strength, high-toughness photocurable outer coating for small-diameter polarization-maintaining optical fibers according to claim 1, characterized in that: The modified acrylate oligomer was prepared by the following method: oligosaccharides, alkyl acids, (meth)acrylic acid, acidic catalysts and polymerization inhibitors were added to a reaction apparatus equipped with a stirrer and a reflux condenser, heated to 105-110°C, and the reaction was carried out under stirring until the reaction was complete, after which the heating was stopped; then the reaction solution was added to deionized water under stirring, and after sufficient settling, the supernatant was removed, and the bottom product was washed with deionized water until the pH of the washing solution was neutral. After vacuum drying, the modified acrylate oligomer was obtained.

6. The high-strength, high-toughness photocurable outer coating for small-diameter polarization-maintaining optical fibers according to claim 1, characterized in that: The acidic catalyst is one or more of sulfuric acid, hydrochloric acid, and p-toluenesulfonic acid.

7. The high-strength, high-toughness photocurable outer coating for small-diameter polarization-maintaining optical fibers according to claim 1, characterized in that: The polymerization inhibitor is one or more of tert-butylhydroquinone, p-hydroxyanisole, hydroquinone, and o-methylhydroquinone.

8. The high-strength, high-toughness photocurable outer coating for fine-diameter polarization-maintaining optical fibers according to claim 1, characterized in that: The acrylate monomer is one or more of the following: isobornyl (meth)acrylate, 3,3,5-trimethylcyclohexyl acrylate, dicyclopentyl methacrylate, tricyclodecanediethanol diacrylate, laurate acrylate, stearate acrylate, isodeoxy acrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, and trimethylolpropane tri(meth)acrylate.

9. The high-strength, high-toughness photocurable outer coating for small-diameter polarization-maintaining optical fibers according to claim 1, characterized in that: The photoinitiator is selected from one or more of Irgacure1173, Irgacure184, IrgacureTPO-L and Irgacure819.

10. The high-strength, high-toughness photocurable outer coating for small-diameter polarization-maintaining optical fibers according to claim 1, characterized in that: The antioxidant is selected from one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], Irganox L135, Irganox L57, and Irganox 1035.

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