RU2644891C1 - Coatings of fibre light guides from aromatic polyamides and method of their manufacture - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: coating of formula I with a molecular weight of 35,000 to 85,000 is proposed:

, where x:y = 0-1: 1-0; R₁,

R₃=

R₂, R₄=

The method involves pulling the light guide from the workpiece. Stretching it through a spinneret containing a solution of a polyamide of formula I with a viscosity of 2400-18000⋅ mPac in an aprotic dipolar solvent of an amide type, and removing the solvent by heating in an oven.

EFFECT: high thermal stability and satisfactory adhesion to fibre, easy removal with the help of organic solvents of amide type.

3 cl, 2 dwg, 1 tbl, 8 ex

Description

The invention relates to fiber optics, namely to primary protective heat-resistant coatings of fiber optical fibers from aromatic polyamides (PA) and a method for their manufacture.

The invention can most effectively be used in the manufacture of optical fibers for use in aerospace technology, the oil and gas and automotive industries, energy and medicine.

Polyamides belong to the class of organic polymers widely used as primary protective coatings of optical fibers because of their hydrophobicity, mechanical strength, and the necessary adhesion to the fiber [A. Laptev The application of polymer shells on fiber optical fibers made of quartz glass: Dis. ... cand. Chem. sciences. Nizhny Novgorod, 1992]. Unfortunately, most applications and patents for inventions devoted to such coatings do not contain information about the structure of the claimed PAs and how to apply them to optical fibers. It can only be stated that the most popular are aliphatic (for example, commercially available PA 6, PA 6,6, PA 12) and semi-aromatic homo- and copolyamides and various compositions based on them, and the main method of their application is extrusion [JP S5928101 (A ), 1984; W02001040841; JP 2000098195 (A); JP H11241018 (A), 1999; JP S59188603 (A), 1984; JP 2003227975 (A); JPS6125114 (A), 1986]. Aliphatic and semi-aromatic PAs have the advantage of good processability, and the main disadvantage is their low heat resistance.

L. High-performance aromatic polyamides. progress in Polymer Science, 2010, 35(5), 623-686;

M.,

P.,

N.,

A.,

F.C., Serna F., de la

J.L.,

J.M. Recent patents on aromatic polyamides. Recent Patents on Materials Science, 2009, 2 (3), 190-208]. Правда, из таких полимеров изготавливают синтетические волокна и ткани, мембраны и фильтры, а использование их для получения покрытий, в том числе волоконных световодов, ограничено вследствие низкой термопластичности и плохой растворимости.There is a need for thermostable coatings, which can be provided with aromatic PAs, since they are widely applicable as high-strength materials with excellent thermal properties [Garcia JM, Garcia FC, Sema R.,

L. High-performance aromatic polyamides. progress in Polymer Science, 2010, 35 (5), 623-686;

M.,

P.,

N.,

A.,

FC, Serna F., de la

JL,

JM Recent patents on aromatic polyamides. Recent Patents on Materials Science, 2009, 2 (3), 190-208]. True, synthetic polymers and fabrics, membranes and filters are made from such polymers, and their use for coatings, including optical fibers, is limited due to low thermoplasticity and poor solubility.

A technical solution is known for creating an inexpensive fiber-optic cable with high heat and frost resistance by coating a fiber with a finished aramid film with a thickness of 2-20 μm, characterized by high tensile strength, low coefficient of thermal expansion in the longitudinal direction (3.5 × 10 ^-5 / ° C) and a shrink rate of ≤5.0% at 250 ° C [Japanese Patent Application JP H02280106 (A), 1990]. However, this solution does not describe the method of fixing the aramid film and its stability on the surface of the fiber, nor does it describe the properties of the obtained fiber-optic cable.

Closest to the claimed method, the analogue is a method for producing coatings of optical fibers, which consists in applying a solution containing aromatic PA with hydroxyl groups, an epoxy resin, a curing accelerator and an organic solvent to the fiber, and then curing the solution on the surface of the fiber with heating [JP patent application JP 2010-004611].

In aromatic PA

Ar ₁ and Ar ₃ are aromatic groups; Ar ₂ is a hydroxyl-containing aromatic radical; n / (m + n)>0.05; 0 <m + n≤200.

There is a low temperature of molding of coatings and their excellent thermal stability and fire resistance.

The disadvantages of the prototype method include: the use of a mixture of components to form a coating; the simultaneous occurrence of two processes in this case - the condensation of the epoxy resin with hydroxyl-containing PA and the removal of the solvent; formation of a coating insoluble in organic solvents.

The objective of the invention is the creation of heat-resistant soluble aromatic polyamide coatings of optical fibers and the development of a method for their manufacture from solutions of the corresponding PA in organic solvents.

The problem is solved by the claimed heat-resistant soluble coatings of optical fibers from homo- and copolyamides of the general formula I

,

,

where x: y = 0-1: 1-0;

And also the problem is solved by the method of their preparation, including pulling the fiber from the preform, pulling it through a die containing a solution of polyamide of formula I with a viscosity of 2400-18000 mPa⋅s, and removing the solvent when heated in an oven at 250-350 ° C. Amide aprotic dipolar solvents are used to prepare the polyamide solution, such as N-methyl-2-pyrrolidone (N-MP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAA).

The inventive coatings are soluble in N-MP, DMF, DMAA and have high performance characteristics, determined by the properties used for their manufacture of aromatic polyamides and films obtained from them. The heat resistance (T _c ) of all polyamides of formula I exceeds 300 ° C, and the heat resistance is more than 400 ° C (see table), which makes it possible to use coatings from them under extreme conditions. The breaking strength of the films formed by polyamides I is 100-140 MPa (see table).

The adhesion of coatings made of polyamides I is sufficient to effectively protect the optical fibers from mechanical and thermal stresses without the use of resins. The loss of strength of the coated fiber in bending after holding at 300 ° C for 3 hours in the worst case is 30% (see Fig. 2).

The most important distinguishing feature of the proposed polyamide coatings of optical fibers compared to those used and described previously is the use of aromatic polyamides, rather than aliphatic or semi-aromatic polyamide resins, which provides significant thermal stability of the coatings.

A method of manufacturing coatings according to the invention involves applying a solution of a PA of formula I to the surface of a fiber drawn from a preform by pulling it through a die and then removing the solvent (Fig. 1). The advantage of the proposed method is its compatibility with existing technological installations for the manufacture of heat-resistant polyimide coatings [Semenov S.L., Sapozhnikov D.A., Erin D.Yu., Zabegaeva ON, Kushtavkina I.A., Nishchev K.N. , Vygodsky Ya.S., Dianov E.M. High temperature polyimide coating for optical fibers. Quantum Electronics, 2015, 45 (4), 330-332].

To prepare aromatic PA solutions applied to the fiber, amide solvents are used: N-MP, DMF and DMAA. The solubility in such solvents of the homo- and copolyamides of the present invention is due to their carbohydrate (fluorene or phthalide), Cl or HOC (O) groups.

A solution of (co) polyamide is prepared by dissolving the synthesized and isolated polymer in a suitable solvent or using a solution of synthesized PA without isolation (in situ) if the polycondensation is carried out, for example, in N-MP or DMAA. In all cases, the solution is adjusted to a viscosity of 2400-18000 mPa⋅s. In this viscosity range, a smooth uniform coating forms on the fiber. At lower viscosity values, droplets have time to form on the fiber during its drawing, and at higher values, the probability of the formation of other defective regions, for example, “scallops”, increases. The value of the viscosity of the solution is determined by the molecular weight of the polyamide, its concentration, the nature of the solvent and temperature. In the inventive method, polyamides with a wide range of molecular weights from 35,000 to 85,000 are applicable, which corresponds to a logarithmic viscosity of the polymer from 0.4 to 1.2 dl / g.

In FIG. 1 shows a diagram of an installation for manufacturing a polymer coated fiber, where 1 is a blank, 2 is a furnace, 3 is a die, 4 is a furnace, 5 is a coil.

In FIG. 2 shows the change in the strength of the coatings in bending, depending on the temperature and time of heat exposure; ln {ln [1 / (1-F)]} is the Weibull function, where F is the cumulative probability of fiber destruction.

The novelty of the proposed method consists in applying to the fiber not a polymer melt, traditionally used to form coatings based on aliphatic polyamides, but a polyamide varnish, followed by removal of the solvent.

The results of the invention are the development of heat-resistant soluble coatings of optical fibers from a variety of aromatic polyamides and their manufacture by applying a solution of the corresponding PA to the optical fiber with subsequent removal of the solvent by heat treatment.

The invention is illustrated by the following examples and drawings.

General procedure for the manufacture of polyamide coatings

Aromatic polyamides are obtained by low-temperature polycondensation in a solution of dichlorohydrides of aromatic dicarboxylic acids with aromatic diamines [Vinogradova SV, Vasnev VA, Vygodsky Ya.S. Cardiovascular polyheteroarylenes. Synthesis, properties and originality. Advances in Chemistry, 1996, 65 (3), 266-296]. After synthesis is complete, PAs are usually isolated, purified and dried, then dissolved in a selected solvent until a solution viscosity of 2400-18000 mPaПs is reached and applied to a fiber.

During polycondensation in N-MP or DMAA, the stage of PA release can be eliminated. Obtained during the synthesis of the polymer solution is diluted to the desired viscosity and applied to the fiber.

In the installation for manufacturing a polymer coated fiber (Fig. 1), a fiber with a diameter of about 110-150 μm is drawn from a preform 1 heated in a furnace 2 and pulled through a die 3 with a hole diameter of 200-250 μm containing a solution of the corresponding PA. Then, the fiber with the applied solution enters the furnace 4, where the solvent is removed within 3-8 s. The temperature in the oven (250-350 ° C) depends on the boiling point of the solvent used. It is selected in such a way as to ensure the most complete removal of the solvent. After exiting the furnace, a fiber with a finished polyamide coating is wound on a coil 5, the rotation frequency of which determines the diameter of the optical fiber, the thickness of the coating and the drying time. The difference between the diameter of the hole of the die and the diameter of the drawn fiber determines the thickness of the applied layer of the polyamide solution. The thickness of the manufactured layer of the polyamide coating of the fiber for 1 cycle of application of the solution reaches 5-10 microns.

Example 1

From a pre-synthesized, isolated and purified polyamide Ia based on terephthalic acid dichloride and 9.9-bis- (4'-aminophenyl) fluorene, a 15-20% solution in N-MP is prepared corresponding to the required viscosity range. The solution is filtered and poured into a die through which the optical fiber is pulled according to the general procedure. The temperature in the furnace where the solvent is removed is 300-350 ° C.

The polymer coating of the present structure has a glass transition temperature of about 390 ° C and a temperature of 10% weight loss in air of about 510 ° C. Film polymer samples demonstrate tensile strength of the order of 115 MPa, tensile modulus of 2350 MPa, tensile elongation of about 8% (table).

A fiber with a coating of polyamide Ia is resistant to prolonged thermal effects: exposure for 120 h at 250 ° C leads to a 10% loss in bending strength, at 300 ° C - 30% (Fig. 2).

Example 2

The coating is made from a solution of copolyamide Ib based on terephthalic acid dichloride (1.0 mol), 9.9-bis- (4'-aminophenyl) fluorene (0.5 mol) and 2-chloro-1,4-diaminobenzene (0, 5 mol) in N-MP. The temperature in the oven is 300-350 ° C.

The coating has a glass transition temperature of about 390 ° C and a temperature of 10% weight loss in air of about 470 ° C. The tensile strength of film samples is about 140 MPa, the tensile modulus is 2060 MPa with a tensile elongation of 10% (table). The exposure of a fiber coated with copolyamide Ib for 3 hours at 250 and 300 ° C reduces its bending strength by no more than 15 and 30%, respectively (Fig. 2).

Example 3

The coating is made from a solution of copolyamide Ic based on terephthalic acid dichloride (1.0 mol), 9.9-bis- (4'-aminophenyl) fluorene (0.3 mol) and 2-chloro-1,4-diaminobenzene (0, 7 mol) in N-MP. The temperature in the oven is 300-350 ° C.

The coating has properties comparable to those described in example 2.

Example 4

The coating is made from a solution of copolyamide Id based on terephthalic acid dichloride (1.0 mol), 9.9-bis- (4'-aminophenyl) fluorene (0.5 mol) and 3,5-diaminobenzoic acid (0.5 mol) in N-MP. The temperature in the oven is 300-350 ° C.

The polymer coating of the present structure has a glass transition temperature of about 360 ° C and a temperature of 10% weight loss in air of about 440 ° C. Film polymer samples exhibit tensile strength of the order of 135 MPa, tensile modulus of 1600 MPa and tensile elongation of about 11% (table).

Optical fibers coated with Id copolyamide are resistant to significant thermal effects. The flexural strength of a fiber with a coating of such a polymer does not decrease after exposure for 72 and 3 hours at 250 and 300 ° C, respectively (Fig. 2).

Example 5

The coating is made from a solution of copolyamide Ie based on 3,3-bis - [(4'-chlorocarbonyl) phenyl] phthalide and 2-chloro-1,4-diaminobenzene in N-methyl-2-pyrrolidone. The temperature in the oven is 300-350 ° C.

The coating is characterized by a glass transition temperature of about 360 ° C and a temperature of 10% weight loss in air of about 470 ° C. Films from polyamide Ie have a tensile strength of about 100 MPa, a tensile modulus of 1700 MPa, and an elongation of about 18% (table). The bending strength of a fiber with a coating of such a polymer does not decrease after exposure for 1 h at 350 ° C and decreases by no more than 10% after exposure for 72 hours at 300 ° C (Fig. 2).

Example 6

The manufacture of the coating from polyamide Ia described in Example 1 is carried out similarly, but N, N-dimethylformamide is used to prepare the polyamide solution, and the oven temperature is 250-300 ° C. The properties of the coating are similar to the properties of the coating described in example 1 (see table).

Example 7

The manufacture of the coating from polyamide Ia described in Example 1 is carried out similarly, but N, N-dimethylacetamide is used to prepare the polyamide solution, and the oven temperature is 250-300 ° C. The properties of the coating are similar to the properties of the coating described in example 1 (see table).

Example 8

The synthesis of polyamide Ia used in example 1 is carried out in N-methyl-2-pyrrolidone. The resulting synthesis solution is diluted to the desired viscosity and used without isolating the polymer (in situ) in accordance with the procedure described in example 1. The properties of the coating are similar to the properties of the coating described in example 1 (see table).

All polyamide coatings obtained in examples 1-8 are soluble in N-MP, DMF and DMAA.

EFFECT: new heat-resistant coatings of fiber optical fibers from soluble aromatic homo- and copolyamides, a convenient method for their manufacture from solution, and the possibility of removal using an appropriate solvent.

The claimed invention has the following advantages:

- the resulting coatings of fiber optic fibers are thermostable and easily removed from the surface due to the use of soluble aromatic homo- and copolyamides in their manufacture with high heat and heat resistance;

- for the manufacture of coatings and their removal from the surface of the fiber, you can use a wide range of organic solvents of the amide type;

- after applying the polyamide solution to the fiber to form the final coating, it is only necessary to remove the solvent when heated (there are no chemical transformations during the formation of the coating, which involves the prototype method);

- the required coating thickness of 5-10 microns is achieved as a result of a single application;

- it is possible to obtain polyamide coatings of optical fibers from carded and other aromatic homo- and copolyamides with variable properties;

- the resulting coatings have the necessary adhesion to the surface of the fiber and are firmly held on its surface, which leads to high bending strength after heat treatment, in contrast to the aramid film used as a thermostable coating.

Claims (7)

1. Heat-resistant soluble fiber coating of an aromatic homo- or copolyamide of formula I with a molecular weight of from 35,000 to 85,000:

, where x: y = 0-1: 1-0;

2. A method of manufacturing a coating according to claim 1, including pulling the fiber from the preform, pulling it through a die containing a solution of a polyamide of formula I with a viscosity of 2400-18000 mPa · s, and removing the solvent when heated in an oven at 250-350 ° C. 3. The method according to claim 2, characterized in that aprotic dipolar solvents such as N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide are used to prepare a solution of the polyamide of formula I.

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