RU2320590C2 - Optical fiber with hardened polymer coat - Google Patents

Abstract

FIELD: manufacture of optical fibers with hardened polymer coats.

SUBSTANCE: proposed optical fiber has glass part and at least one layer of protective coat which embraces glass part. Layer of protective coat is characterized within temperature range of from -40 C to +60 C by magnitude of modulus of elasticity between 5 Mpa and 600 Mpa; difference (V₁) between modulus of elasticity measured at temperature of -40 C and that measured at temperature +60 C does not exceed 495 Mpa for protective layer. It is preferable that modulus of elasticity does not exceed 500 Mpa and more preferable 450 Mpa and most preferable 300 Mpa. It is preferable that layer of protective coat is made in form of single layer which is brought in contact with glass part.

EFFECT: enhanced protection of optical fiber; reduced attenuation of signal due to availability of micro-bends.

51 cl, 3 dwg, 5 tbl, 14 ex

Description

The present invention relates to a cured polymer coated optical fiber.

More specifically, the present invention relates to an optical fiber with at least one layer of protective coating, characterized by reduced attenuation of the transmitted signal.

In addition, the present invention relates to an optical fiber with at least one layer of protective coating obtained by curing a radiation-curable composition containing at least one ethylenically unsaturated polyurethane and at least one polyfunctional reactive diluting monomer, as well as the radiation curable composition used therein.

In addition, the present invention also relates to a method for controlling attenuation losses of a signal transmitted over an optical fiber due to the presence of microbends.

Optical fibers typically consist of a glass part (usually with a diameter of approximately 125 μm) within which the transmitted optical signal is enclosed, and of a coating, usually polymeric, located around the glass part mainly for protection purposes. This protective coating typically includes a first coating layer located directly on the surface of the glass, known as the "primary coating layer" or "primary coating" for short, usually having a thickness in the range of from about 25 microns to about 35 microns. In turn, this primary coating is generally coated with a second coating layer, known as a “secondary coating layer” or “secondary coating” for short, typically having a thickness in the range of from about 10 μm to about 30 μm.

These polymer coatings can be obtained from compositions containing oligomers and monomers, which are generally crosslinked by UV radiation in the presence of a suitable photoinitiator. The two coating layers described above, among other things, differ in the elastic modulus of the crosslinked material. Actually, one of the problems encountered when using coating layers that adhere to the glass surface of an optical fiber is caused by the difference in glass and coating layer in response to temperature changes, which contributes to the attenuation of the signal in the fiber due to the presence of microbends, features when falling into the range of very low temperatures. To minimize this problem during the formation of the primary coating mentioned above, a coating layer is selected that is characterized by a very low elastic modulus. Therefore, in order to ensure that the primary coating has a desired low modulus of elasticity, it will be necessary to sacrifice the desired hardness and stiffness of the coating layer that is in contact with the glass, so that it becomes necessary to apply the aforementioned secondary coating over the primary coating. The combination of the above two coating layers provides the proper mechanical protection of the optical fiber.

An optical fiber arranged in this way is typically characterized by a total diameter of approximately 250 microns. However, for specific applications, this total diameter may also be smaller; in this case, a coating layer with a reduced thickness is usually applied.

However, the need to use two coating layers having different characteristics can lead to certain disadvantages. For example, there may be problems associated with adhesion between the primary and secondary coatings: therefore, it is necessary to choose polymeric materials that will be compatible with each other, but which will have different values of the elastic modulus, in order to avoid microbending and to ensure proper mechanical protection.

In order to eliminate the aforementioned disadvantages, certain efforts have been made in the prior art to obtain coating compositions that can be used as an individual coating layer for optical fibers.

For example, US Pat. No. 4,806,574 describes a UV curable liquid coating composition which, when cured by ultraviolet radiation in the presence of a suitable photoinitiator, provides a coating adapted to the requirements for coating optical fiber. This coating composition as an essential component contains a polyurethane oligomer with terminal acrylate groups based on a polyfunctional core, which is at least trifunctional and which has one branch for each functionality on the core. In accordance with the claims made in the patent, the said coating composition can be used as a top coating, as well as a coating directly applied to the surface of a glass fiber, in order to obtain a low value of tensile modulus at low operating temperatures with which collide in order to counter the appearance of microbends. In one embodiment, said cured coating composition is characterized by a modulus value under tension equal to 6410 lbs / ⁱⁿ² (approximately 44 MPa) when measured at 25 ° C and a modulus value of tensile equal to 96971 lbs / ⁱⁿ² (approximately 669 MPa) when measured at -40 ° C.

US 4,682,850 describes an optical fiber including a core and an outer sheath. On the shell is coated as a single curable material to ultraviolet radiation characterized by a tensile modulus in the range of from about 1,000 to about 10,000 lb / ⁱⁿ² (about 7 MPa to about 70 MPa). Preferably, the modulus is about 7,800 lb / ⁱⁿ² (about 53.8 MPa) as measured at 25 ° C, and the material is characterized by the Shore A hardness ranging from about 70 to about 75. In accordance with the statement made in this patent , said individual coating satisfactorily protects the optical fiber, it is easy to apply to the fiber, and it minimizes losses due to the presence of microbends over a wide temperature range.

Other documents, such as, for example, US 4,690,501, US 4,690,502, US 4,798,852, US 4,932,750, describe optical fiber coating compositions adapted to the requirements of either a primary coating or an individual (single) coating, generally mentioning that the compositions are suitable for minimizing the occurrence of microbends. In addition, no specific value of tensile modulus for coating compositions measured either at + 25 ° C or at -40 ° C is given in the referenced documents.

However, despite the efforts made to obtain suitable individual coating layers, no satisfactory solution has yet been found. In particular, despite the fact that the documents mentioned above emphasize the need to prevent microbending at low operating temperatures (i.e. at -40 ° C), most of these documents do not give any details regarding the mechanical properties of the coating layers used at such low temperatures. As a matter of fact, only the aforementioned US Pat. No. 4,806,574 describes an example of a coating layer characterized by a tensile modulus of approximately 668 MPa when measured at -40 ° C. However, the applicant noted that this value is still excessively high in order to significantly prevent the occurrence of phenomena associated with microbending.

In addition to this, the applicant noted that the said coating layer has a modulus of tensile elasticity upon transition from room temperature (+ 25 ° C) to low operating temperatures of the order of -40 ° C undergoes an excessive change, where this change, in turn, determines for an optical fiber an excessive and uncontrolled change in signal attenuation due to the presence of microbends.

In order to obtain the value of the modulus of elasticity of about 60 MPa when measured at 25 ° C in accordance with what is proposed in the above paper US 4,682,850, the Applicant has observed the behavior of both (A) commercial individual coating DeSolite ^® 3471-3 -7 (from DSM), and (B) an individual single coating obtained by mixing 63% of the commercial primary coating DeSolite ^® 3471-1-129 (from DSM) and 37% of the commercial secondary coating DeSolite ^® 3471-2- 136 (from DSM): however, two individual demonstration coatings an excessively high increase in the value of the elastic modulus when measured at -40 ° C was shown, which is shown in the attached figure 3 (the abscissa axis reportedly shows the temperature (T) in ° C, while the ordinate axis reportedly modulus of elasticity (E ') in MPa). The said value of the modulus of elasticity is the value of the modulus of tensile elasticity, and it is measured using the apparatus for DMTA (dynamic mechanical thermal analysis) (Dynamic Mechanical Thermal Analyzer from Reometrics Inc.), which operates, as will be described in more detail below.

The applicant further noted that the tensile modulus of the coating layer must be controlled in a wider range than that indicated in the prior art (from -40 ° C to + 25 ° C). Actually, under normal operating conditions, an optical fiber can easily be exposed to temperatures of approximately + 40 ° C, and in some cases up to approximately 60 ° C. Thus, in order to appropriately protect the glass portion of the optical fiber, it is important that the tensile modulus of the coating layer remains high enough also at such high operating temperatures.

Thus, the applicant found that in order to have an acceptable amount of microbend at low operating temperatures (-40 ° C) and to prevent the occurrence of excessive changes in signal attenuation due to the presence of microbends, the value of the elastic modulus measured at -40 ° C should be relatively low (that is, not exceeding 500 MPa), in particular, the mentioned value of the elastic modulus should be relatively constant in the range from -40 ° C to + 60 ° C in order to minimize the change in signal attenuation la due to the presence of microbending; Of course, the aforementioned relatively low value of the elastic modulus should not adversely affect the mechanical protection of the optical fiber. In addition to this, the applicant has discovered that the material of said protective coating layer must have a sufficiently high equilibrium modulus (i.e., exceeding 5 MPa) in order to provide satisfactory protection of the optical fiber from mechanical stresses at high operating temperatures.

The applicant has discovered that a coating layer, in particular a single coating layer intended for an optical fiber, which is able to provide satisfactory protection of the optical fiber and minimize signal attenuation due to the presence of microbends in a wide temperature range, in particular in the temperature range from -40 ° C to + 60 ° C, can be obtained using a radiation-curable composition containing at least one polyurethane with an unsaturation of ethylene type and at least one polyfunctional acrylate monomer.

In particular, the Applicant has found that a suitable radiation-curable composition may contain at least one ethylene-type unsaturated polyurethane having a glass transition temperature not exceeding -40 ° C and at least one polyfunctional reactive diluting monomer.

More specifically, the applicant found that the use of ethylene-type unsaturated polyurethane, characterized by a low glass transition temperature, affects the value of the elastic modulus of the cured composition at low temperatures, in particular, makes it possible to obtain a coating that does not exhibit an excessively high increase in the value of the elastic modulus at a decrease in temperature (for example, the value of the elastic modulus is still relatively small at -40 ° C). Regarding the use of a multifunctional reactive diluting monomer, the Applicant has found that its use can appropriately modulate the value of the modulus of elasticity, in particular by keeping it at a sufficiently high level at elevated operating temperatures without excessively increasing its value at lower operating temperatures.

In accordance with a first aspect, the present invention relates to an optical fiber, comprising:

- glass part;

- at least one layer of protective coating, placed so as to directly cover said glass portion;

wherein said protective coating layer in the range from -40 ° C to + 60 ° C is characterized by a modulus of elasticity ranging from 5 MPa to 600 MPa, preferably not exceeding 500 MPa, more preferably not exceeding 450 ° MPa, much more preferably not exceeding 300 ° MPa. Preferably, said elastic modulus value is not less than 8 MPa, more preferably more than 12 MPa.

According to a preferred embodiment, said protective coating layer is placed in contact with said glass portion.

According to a particularly preferred embodiment, said optical fiber includes a glass portion and a single protective coating layer that is placed in contact with said glass portion.

In accordance with another aspect, the present invention relates to a method for controlling attenuation losses of a signal transmitted through an optical fiber including an inner glass portion due to microbending, which comprises providing at least one layer of a protective coating arranged to cover said glass portion, wherein said protective coating layer in the range from -40 ° C to + 60 ° C is characterized by a modulus of elasticity falling in the range from 5 MPa to 600 MPa, the preferred but not exceeding 500 MPa, more preferably not exceeding 450 MPa, much more preferably not exceeding 300 ° MPa. Preferably, said elastic modulus value is not less than 8 MPa, more preferably more than 12 MPa.

In the present description and in the claims that follow, the term "optical fiber comprising a single layer of protective coating" means that the mechanical protection of the optical fiber from external loads, which can lead to increased signal attenuation due to the presence of microbends, is essentially ensured by the presence of said single layer of cured polymer material. Thus, this definition includes, for example, also such embodiments in which the optical fiber is coated with a single protective layer of cured polymeric material directly applied to the glass part, where this coating, in turn, is covered by an outer coating, which does not make any significant contribution to protecting the fiber from external loads, such as, for example, a marking layer of paint applied for identification purposes. Typically, in the case of an outer layer applied to said single protective coating layer (for example, an external marking layer), the protective layer comprises at least 80% of the total polymer coating thickness of the optical fiber, preferably at least about 85%, more preferably about 90% ± 2%. For example, in the case of a single protective coating having a thickness of approximately 60 μm, the thickness of the outer layer (printing ink) may be in the range of about 5 μm to 7 μm.

In addition, in the present description and in the claims that follow, the term "single layer of protective coating" includes in its meaning a coating in the form of a polymeric material, applied either as a separate single layer or as several layers superimposed Each other.

According to another preferred embodiment, the difference (V ₁ ) between the value of the elastic modulus measured at -40 ° C and the value of the elastic modulus measured at + 60 ° C for said protective coating layer does not exceed 495 MPa, preferably does not exceed 320 MPa, more preferably does not exceed 150 MPa.

In accordance with yet another embodiment, said protective coating layer is characterized by an equilibrium modulus (EM) of more than 5 MPa.

In accordance with another preferred embodiment, said optical fiber in the range of -40 ° C to + 60 ° C is characterized by a change in signal attenuation due to the presence of microbends (V ₂ ), measured as a result of winding a fiber with a length of 100 m with a tension of 5 g per 300 mm expandable metal bobbin coated with a rough material not exceeding 20 (dB / km) / (g / mm), preferably not exceeding 15 (dB / km) / (g / mm), more preferably not exceeding 6 ( dB / km) / (g / mm).

The said value of the modulus of elasticity and the said value of the equilibrium modulus are assumed to correspond to the "modulus of elasticity in tension", and they are measured using an apparatus for DMTA (Dynamic Mechanical Thermal Analyzer from Reometrics Inc.) at a frequency of 1 Hz and at a heating rate of 2 ° C / min : Further details regarding the analysis method will be described in the examples given later in this document.

Preferably, said protective coating layer at room temperature has a refractive index exceeding the refractive index of the glass portion (approximately 1.46).

Preferably, said protective coating layer, in particular when used as an individual protective coating layer, has a thickness in the range of 20 μm to 70 μm, more preferably 30 μm to 60 μm.

In accordance with another preferred embodiment, said protective coating layer can be obtained by curing a radiation curable composition comprising:

(a) at least one ethylene-type unsaturated polyurethane characterized by a glass transition temperature (T _g ) falling in the range from -40 ° C to -100 ° C, preferably from -50 ° C to -85 ° C;

(b) at least one polyfunctional reactive diluting monomer.

The glass transition temperature mentioned can be measured in accordance with known methods, such as, for example, differential scanning calorimetry (DSC): further details regarding DSC analysis will be described in the examples below.

According to another preferred embodiment, said radiation-curable composition also comprises at least one polymerization initiator (c).

According to yet another preferred embodiment, said radiation curable composition also comprises at least one monofunctional reactive diluting monomer (d).

According to yet another preferred embodiment, said radiation curable composition also comprises at least one adhesion promoter (e).

In accordance with another aspect, the present invention relates to a radiation curable composition comprising:

(a) based on the total weight of said radiation-curable composition, from 50% (mass.) to 95% (mass.), preferably from 75% (mass.) to 90% (mass.) of at least one polyurethane with an ethylene-type unsaturation characterized by a glass transition temperature (T _g ) in the range of from -40 ° C to -100 ° C, preferably from -50 ° C to -85 ° C;

(b) based on the total weight of said radiation-curable composition, from 5% (mass.) to 50% (mass.), preferably from 10% (mass.) to 35% (mass.) of at least one multifunctional reactive diluting monomer.

In accordance with yet another preferred embodiment, said radiation curable composition has a Brookfield viscosity in the temperature range of 20 ° C. to 80 ° C., having a value in the range of 1000 ° m · Pa · s to 4000 ° m · Pa · s, preferably in the range of 2000 m · Pa · s to 3000 m · Pa · s.

The Brookfield viscosity is measured using a Brookfield viscometer, model DV-III, equipped with a configuration of 29.

According to a preferred embodiment, ethylene unsaturated polyurethane of type (a) is obtained by reaction between the following compounds:

(A) at least one polyol as one compound, including a structural unit described by the following formula (I):

where n is an integer in the range from 0 to 4 inclusive; R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ , which may be identical to each other or different from each other, represent a hydrogen atom or a C ₁ -C ₄ alkyl group;

(B) at least one polyisocyanate compound; and

(C) at least one (meth) acrylate derivative having at least one hydroxyl group.

Compounds (A) related to the type of polyols that may be suitable in accordance with the present invention may include any other structural units, provided that the compound will include at least the structural unit described by formula (I).

Specific examples of the structural unit described by formula (I) are as follows:

and

Compounds (A) of the type of polyols, particularly preferred in accordance with the present invention, are as follows: compounds obtained by polymerization of at least one compound selected from the group consisting of ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, tetramethylene glycol, 2-alkyl-1,4-butanediol and 3-alkyl-1,4-butanediol; compounds obtained by ring-opening polymerization of 2-alkyltetrahydrofuran or 3-alkyltetrahydrofuran; compounds resulting from the copolymerization of 2-alkyltetrahydrofuran, 3-alkyltetrahydrofuran or 2-alkyl-1,4-butanediol and a cyclic ether such as ethylene oxide, propylene oxide and tetrahydrofuran; and the like, or mixtures thereof. If the compound (A) of the polyol type will include a structural unit other than the structural unit described by formula (I), then the structural unit described by formula (I) will preferably be present in an amount of at least 5% (mass .), more preferably at least 10% (mass.), based on the weight of the compound (A). More preferably, the polyol-type compound (A) is selected from polytetramethylene glycol, polypropylene glycol, tetramethylene glycol copolymer or polypropylene glycol.

Preferably, said polyol-type compound (A) is characterized by an average (number average) molecular weight in the range of 200 to 6000, preferably 400 to 4000.

The aforementioned average (number average) molecular weight can be determined by known methods, such as, for example, gel permeation chromatography (GPC).

Other compounds (A ') related to the type of polyols that do not include the structural unit described by formula (I), either as such or in a mixture with at least one compound (A) of the type of polyols, can be used to advantage . Alternatively, said polyol (A ') type compounds can be copolymerized with at least one polyol (A) type compound.

Specific examples of the mentioned other compounds (A ′) of the type of polyols that can be used in accordance with the present invention are as follows: polybutadiene having a terminal hydroxyl group, hydrogenated polybutadiene having a terminal hydroxyl group, polyisobutylene polyol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, bisphenol A, bisphenol F, alkylene oxide adducts of bisphenol A, alkylene oxide adducts of bisphenol F, dimethylated derivative of dicyclopentadiene, polyether diols ve esters, polycaprolactone diol, polycarbonate diols and the like or mixtures thereof. Preferably, the other polyol-type compounds (A ′) mentioned have an average (number average) molecular weight in the range of 200 to 8000, preferably 400 to 4000.

The polyisocyanate compounds (B) that can be used in accordance with the present invention can be selected from: polyisocyanates, such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 1,5 naphthalenediisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, 3,3'-dimethyl-4,4'-diphenylmethanediisocyanate, 4,4'-diphenylmethanediisocyanate, 3,3'-dimethylphenylenediisocyanate, 4,4'-biphenylenediisocyanate hexamethylene diisocyanate, isophorondiisocyanate, methylene bis (4-cyclohexyl isocyanate), 2,2,4-trimethylhexamethy endiizotsianat, 2,4,4-trimethylhexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, bis (2-izotsianatoetil) fumarate, 6-isopropyl-1,3-phenyl diisocyanate, 4-difenilpropanizotsianat, lysine diisocyanate and the like or mixtures thereof. Preferred are 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, isophorone diisocyanate.

(Meth) acrylate derivatives (C) having at least one hydroxyl group that can be used in accordance with the present invention can be selected from the group consisting of: 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, propanediol (meth) acrylate, 1,4-butanediolmono (meth) acrylate, 2-hydroxyalkyl (meth) acryloyl phosphate, 4-hydroxycyclohexyl (meth) acrylate, 1,6- hexanediolmono (meth) acrylate, neopentyl glycolmono (meth) acrylate, trimethylolpropanedi (meth) acrylate, trimethylol ethanedi (meth) acrylate, pentaerythritol (meth) acrylate, dipentaerythritol (meth) acrylate, (meth) acrylates described by the following formulas (II) or (III):

where R ₅ represents a hydrogen atom or a methyl group, and n represents an integer in the range from 1 to 15, inclusive; and the like, or mixtures thereof. Preferred are 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate.

In addition, a compound obtained by carrying out an addition reaction between a compound having a glycidyl group, such as, for example, alkyl glycidyl ether, aryl glycidyl ether and glycidyl (meth) acrylate, and (meth) acrylic acid, can be used to advantage.

As described above, ethylene unsaturated polyurethane type (a) used in accordance with the present invention can be obtained by reacting the aforementioned polyol as one compound (A) or (A ′), a polyisocyanate compound (B) and (meth) an acrylate derivative having at least one hydroxyl group (C). More specifically, it can be obtained by carrying out a reaction between the isocyanate group of said polyisocyanate compound (B) and the hydroxyl group of said polyol compound (A) or (A ') and said (meth) acrylate derivative having at least one hydroxyl group, (C).

The reaction may be carried out by co-loading the polyol as one compound (A) or (A ′), the polyisocyanate compound (B) and the (meth) acrylate derivative (C). Alternatively, it can be carried out by first carrying out the reaction between the polyol as one compound (A) or (A ′) and the polyisocyanate compound (B), and after that, carrying out the reaction between the resulting compound and the (meth) acrylate derivative (C) having at least one hydroxyl group. More specifically, the latter method involves the reaction between the hydroxyl group of the polyol as one compound (A) or (A ′) and the isocyanate group of the polyisocyanate compound (B) under such reaction conditions that an excess amount of isocyanate may be present in the reaction system with respect to the amount of the hydroxyl group, and then the reaction between the remaining amount of the isocyanate group and the hydroxyl group of the (meth) acrylate derivative (C). In addition, polyurethane with an unsaturation of ethylene type (a) can also be obtained by first carrying out the reaction between the polyisocyanate compound (B) and the (meth) acrylate derivative (C) and after that carrying out the reaction between the polyol compound (A) or (A ') and the resulting product, that is, as a result of the reaction between the hydroxyl group of the (meth) acrylate derivative (C) and the isocyanate group of the polyisocyanate compound (B) under such reaction conditions that, in the reaction system, an excessive amount of the isocyanate group is present in relation to the amount of the hydroxyl group, and after that, the reaction between the remaining amount of the isocyanate group and the hydroxyl group of the polyol as one compound (A) or (A ′).

The used ratio of the amounts of polyol as one compound (A) or (A '), polyisocyanate compound (B) and (meth) acrylate derivative (C) is preferably determined so that the amount of isocyanate group present in the polyisocyanate compound (B) and the amount of hydroxyl group, available in the (meth) acrylate derivative (C) could be in the range of 1.1 to 2 equivalents and in the range of 0.5 to 1.5, respectively, based on 1 equivalent of the hydroxyl group present in the polyol compound ( A) or (A ').

The urethaneisation catalyst, such as, for example, copper naphthenate, cobalt naphthenate, zinc naphthenate, dibutyltin dilaurate, triethylamine and the like, in an amount in the range from 0.01 mass parts to 1.0 mass parts based on 100 mass parts of the total amount of raw materials. The reaction temperature is in the range from 10 ° C to 90 ° C, preferably from 30 ° C to 80 ° C.

Polyurethanes with ethylenically unsaturated (a) which may be used in accordance with the present invention are commercially available, e.g., under the trade names Ebecryl ^® 230 from the company UCB Chemical or BR ^® 304 from the company Bomar Specialties or can be synthesized according to the method described in the following examples.

The radiation curable composition of the present invention may also contain other radiation curable polymers that can be selected from the group consisting of: polyurethane with an unsaturated ethylene type other than polyurethane with an unsaturated ethylene type (A) or (A '), polyester (meth) acrylates based on esters, epoxy (meth) acrylates, polyamide (meth) acrylates, diene type polymers having (meth) acryloxy groups, siloxane polymers having (meth) acryloxy groups, and the like either x blends.

According to a preferred embodiment, an ethylenically unsaturated polyurethane of type (a) does not crystallize during cooling down to -20 ° C. In the case when the polyurethane with ethylene unsaturation (a) crystallizes during cooling, the coating layer on the optical fiber can be carried out by performing operations at a temperature of at least 10 ° C higher than the melting temperature of the mentioned polyurethane with ethylene unsaturation type (a), and not allowing any cooling during application.

According to a preferred embodiment, the multifunctional reactive diluting monomer (b) can be selected from monomers having at least two reactive functional groups that are capable of reacting with reactive functional groups present in ethylene unsaturated polyurethane type (a). Preferably, said at least two reactive functional groups are (meth) acrylate groups.

Specific examples of the multifunctional reactive diluent monomers (b) that can be used in accordance with the present invention are: ethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, propanedioldi (meth) acrylate, 1,4-butanediol (meth) acrylate, trimethylolpropanedi (meth) acrylate, trimethylolpropantri (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanedioldi (meth) acrylate, 1,6-hexamethylene dihydroxy (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol di (meth) acry ester derived from hydroxypivalic acid and neopentyl glycol, trimethylol propane (meth) acrylate, trimethylol propane trioxyethyl (meth) acrylate, tricyclodecane dimethanoldi (meth) acrylate, dicyclopentadienedi (meth) acrylate, pentaerythritol (pentaerythritol) ) acrylate, pentaerythritol tetraoxyethyl (meth) acrylate, di (meth) acrylate diol, such as an addition product (adduct) of ethylene oxide or propylene oxide and bisphenol A, hydrogenated bisphenol A, glycidyl ether of bisphenol A, and the like, or mixtures thereof. 1,6-hexanediol diacrylate, pentaerythritol triacrylate and a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate are preferred.

Polyfunctional reactive diluent monomers (b) which are commercially available in accordance with the present invention, such as, for example, a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (PETIA) or 1,6-hexanediol diacrylate (HDDA), which are commercially available, for example, are commercially available. UCB Chemicals.

As stated above, the radiation curable composition of the present invention also contains at least one polymerization initiator (c). Irradiation can be carried out using ultraviolet radiation or ionizing radiation.

Specific examples of the polymerization initiators (c) that can be used in accordance with the present invention can be selected from the group consisting of: benzophenone, benzoin, benzoinisobutyl ether, benzyl, benzoin ethyl ether, 2,2-dimethoxy-2-phenylacetophenone, xanton, fluorenone, 4-chlorobenzophenone, triphenylamine, carbazole, 3-methylacetophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, Michler ketone, benzoinpropyl ether, acetophenone diethyl ketal, benzoinethyl ether, 1-hydroxy idroksi-2-methylpropiophenone (such as Darocure ^® 1173 or Irgacure ^® 819, manufactured by Ciba Specialty Chemicals), 4'-isopropyl-2-hydroxy-2-methylpropiophenone, α, α-dichloro-4-fenoksiatsetofenona, benzyl dimethyl ketal, 2, dietoksiatsetofenonhlortioksantona-2, 2-isopropylthioxanthone, diethylthioxanthone, 3,3-dimethyl-4-methoxybenzophenone, 2-methyl-1- [4- (methylthio) phenyl] -2-morfolinopropanona, α-hydroxycyclohexyl (such as Irgacure ^® 184, produced by by Ciba Specialty Chemicals), 2,4,6-trimethylbenzoyldiphenylphosphine (such as Lucirin ^® TPO, manufactured by Basf) the like or mixtures thereof. Preferred are α-hydroxycyclohexyl phenyl ketone (such as Irgacure ^® 184, manufactured by Ciba Specialty Chemicals), 2-hydroxy-2-methylpropiophenone (such as Darocure ^® 1173 or Irgacure ^® 819, manufactured by Ciba Specialty Chemicals), and 2,4,6-trimethylbenzoyldiphenylphosphine (such as Lucirin ^® TPO manufactured by Basf).

In addition to the polymerization initiator (c), at least one photosensitizer (f) may be added to the radiation curable composition of the present invention.

The photosensitizer (f) can be selected from: amines, ureas, phosphorus compounds, sulfur compounds, nitriles and the like, or mixtures thereof. Particular examples of photosensitizers that may be used in accordance with the present invention are: triethylamine, diethylaminoethyl methacrylate, N-methyldiethanolamine, 4-dimetilaminoetilbenzoat, 4-dimetilaminoizoamilbenzoat, 4,4'-bisdietilaminobenzofenon, Ubecryl ^® P104 (high molecular weight tertiary amine derivative produced by UCB Chemicals) and the like, or mixtures thereof.

In the radiation curable composition of the present invention, said polymerization initiator (c) and said photosensitizer (f) may be present in the total amount in the range from 0.01% (mass.) To 10% (mass.), Preferably from 0, 05% (mass.) To 8% (mass.), Calculated on the total weight of the mentioned radiation-curable composition.

If the radiation curable composition of the present invention is crosslinked using ionizing radiation, then the polymerization initiator (c) is absent.

As stated above, the radiation curable composition of the present invention also contains at least one monofunctional reactive diluting monomer (d).

According to a preferred embodiment, the monofunctional reactive diluting monomer (d) can be selected from monomers having one reactive functional group that is capable of reacting with reactive functional groups present in ethylene unsaturated polyurethane type (a). Preferably, said reactive functional group is a (meth) acrylate group.

Specific examples of monofunctional reactive diluent monomers (d) that can be used in accordance with the present invention are: 2-hydroxyethyl (meth) acrylate; 2-hydroxypropyl (meth) acrylate; 2-ethylhexyl (meth) acrylate; butoxyethyl (meth) acrylate; tetrahydrofurfuryl (meth) acrylate; linear or branched alkyl (meth) acrylates, such as, for example, butyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, isodecyl (meth) acrylate; n-hexyl (meth) acrylate; cyclohexyl (meth) acrylate; invented (meth) acrylate; ethoxylated alkyl (meth) acrylates, such as, for example, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, 2- (2-ethoxyethoxy) ethyl (meth) acrylate; dicyclopentenyl (meth) acrylate; diethylene glycol (meth) acrylate; ethoxyethylene glycol (meth) acrylate; benzyl (meth) acrylate; polyethylene glycol (meth) acrylate; polypropylene glycol (meth) acrylate; methoxypolyethylene glycol (meth) acrylate; methoxypolypropylene glycol (meth) acrylate; 2-phenoxyethyl (meth) acrylate; phenoxypolyethylene glycol (meth) acrylate; alkylphenoxyethyl (meth) acrylate, such as, for example, nonylphenoxyethyl (meth) acrylate; alkylphenoxypolyalkylene glycol (meth) acrylate; 2-hydroxy-3-phenyloxypropyl (meth) acrylate; tetrahydrofurfuryloxypropylalkylene glycol (meth) acrylate; dicyclopentenyloxypolyalkylene glycol (meth) acrylate; 2-hydroxyalkyl (meth) acryloyl phosphate; polyfluoroalkyl (meth) acrylate; N-vinylpyrrolidone; N-vinylcaprolactam; diacetone (meth) acrylamide; isobutoxymethyl (meth) acrylamide; N, N-dimethylacrylamide; tert-octyl (meth) acrylamide; dialkylaminoethyl (meth) acrylate; (meth) acryloylmorpholine; and the like, or mixtures thereof. Ibornyl acrylate, 2-phenoxyethyl acrylate, nonylphenoxyethyl acrylate, C ₈ -C ₁₃ alkyl acrylates, lauryl acrylate, isodecyl acrylate are preferred. Due to the low glass transition temperature (T _g ) of their homopolymer, particularly preferred are: 2-phenoxyethyl acrylate, nonylphenoxyethyl acrylate, C ₈ -C ₁₃ alkyl acrylates, lauryl acrylate, isodecyl acrylate.

In the radiation curable composition of the present invention, said monofunctional reactive dilution diluent monomer (d) may be present in an amount in the range of from 3% (mass) to 25% (mass), preferably from 5% (mass) to 20% (mass.), based on the total weight of the aforementioned radiation-curable composition. It should be noted that if the glass transition temperature (T _g ) of the homopolymer of said monofunctional reactive monomer is relatively high (for example, exceeding approximately 90 ° C), then the amount of the latter will preferably not exceed approximately 20% (mass.) based on the total weight of said radiation-curable composition: in fact, a higher content of said monofunctional reactive diluting monomer (d) may entail current curing the coating layer at low temperatures.

Monofunctional reactive diluent monomers (d) are commercially available that can be used in accordance with the present invention, such as, for example, isobornyl acrylate (IBOA), a mixture of octyl acrylate and decyl acrylate (ODA), or 2-phenoxyethyl acrylate (REA), which are commercially available, for example, UCB Chemicals.

As stated above, the radiation curable composition of the present invention may also contain at least one adhesion promoter (e).

According to a preferred embodiment, the adhesion promoter (e) is an organofunctional silane.

For the purposes of the present description and claims, the term "organofunctional silane" refers to a silyl compound having functional groups that facilitate chemical or physical bonding between the surface of the glass and silane, which ultimately leads to increased or improved adhesion between the coating and the glass fiber.

Specific examples of the organofunctional silanes that can be used in accordance with the present invention are: octyltriethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, tris (3-trimethoxysilylpropyl) isocyanurate, vinyltriethoxysilane, vinylmethylethoxyloxymethyloxymethyloxymethyloxymethyryloxymethyryloxymethryloxy - (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, organically modified polydimethyl siloxane, γ-ureidopropyltrialkoxysilane, γ-ureidopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane and the like, or mixtures thereof. Particularly preferred are γ-mercaptopropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane.

Other examples of organofunctional silanes that can be used in the present invention can be described, for example, by the following structural formula (IV):

where R groups, which may be identical to each other or different from each other, are selected from: alkyl, alkoxyl or aryloxy groups or halogen atoms, provided that at least one of the R groups is an alkoxy or aryloxy group ; n is an integer in the range from 1 to 6, inclusive; X represents a group selected from the groups: nitroso, mercapto, epoxy, vinyl, imido, chlorine, - (S) _m C _n H _2n -Si- (R) ₃ , where m and n are integers ranging from 1 up to 6, inclusive, and the R groups are determined as was done above. Among them, bis (3-trimethoxysilylpropyl) disulfane and bis (3-triethoxysilylpropyl) disulfane are particularly preferred.

Adhesion promoters (e) that can be used in the present invention are commercially available, for example under the trademarks Dynasylan ^® MTMO and Dynasylan ^® MEMO from Degussa Company and Si ^® 266 from the company Degussa-Hüls.

In the radiation curable composition of the present invention, the adhesion promoter (e) is preferably present in an amount in the range from 0.1% (mass.) To 2.5% (mass.), More preferably from 0.3% (mass. ) up to 1.5% (mass.), calculated on the total weight of the aforementioned radiation-curable composition.

In addition to this, in order to improve the fundamental characteristics of the above radiation-curable compositions, commonly used additives can be added. For example, solvents, plasticizers, surfactants that can improve the wettability ("wetting") of the coating on the glass part of the optical fiber, additives that help remove volatile substances, additives that improve the rheological properties, antioxidants, UV stabilizers that can not influence the operations that take place during curing. In the aforementioned radiation curable composition, said commonly used additives may be present in an amount in the range from 0.1% (mass.) To 20% (mass.), Preferably from 0.5% (mass.) To 10% (mass. ), based on the total weight of said radiation-curable composition.

If the same cable has several optical fibers inside, then the operator should be able to confidently distinguish between different fibers, so it is convenient to color different fibers in different identifying colors. Accordingly, the coating composition may further comprise commonly used dyes and / or pigments to impart the desired color to the material.

Instead of coloring the protective coating layer, the optical fiber according to the present invention can be identified by color by covering the protective coating layer with an additional colored polymer layer, commonly referred to as “marking”, typically having a thickness in the range of about 2 μm to 10 μm, preferably about 5 microns to 8 microns. Examples of said colored resin layer spread on a commercial basis under the tradename Cablelite ^® by DSM.

The present invention can be realized with greater clarity when using the link to the following accompanying figures:

figure 1 is a cross section of an optical fiber in accordance with the present invention;

figure 2 is a General diagram of a system (exhaust tower), designed to produce an optical fiber in accordance with the present invention.

Fig. 1 shows an optical fiber (1) according to the present invention, comprising a glass portion (2) that includes a core and a shell, the core having a higher refractive index compared to the shell that the protective coating layer (3) covers.

An optical fiber according to the present invention can be obtained in accordance with conventional drawing methods using, for example, a system such as that schematically illustrated in FIG.

This system, commonly known as the “exhaust tower," typically includes a firebox (302), inside which a preform for optical fiber to be drawn is placed. The lower part of said preform is heated to a softening temperature and stretched to produce an optical fiber (301). After that, the fiber is preferably cooled to a temperature of at least 60 ° C, preferably in a suitable cooling tube (303) of the type described, for example, in patent application WO 99/26891, and passed through a diameter measuring device (304). This device by means of a microprocessor (307) is connected to a pulley (310), which controls the speed of drawing; in case of any change in fiber diameter, the microprocessor (307) adjusts the speed of rotation of the pulley (310) so as to keep the diameter of the optical fiber constant. After that, the fiber is passed through the coating layer apparatus (305) containing the coating composition in liquid form, and the fiber formed by the composition is coated on the fiber to a thickness of approximately 60 μm. The coated fiber is then passed through a UV curing chamber (or through a series of cameras) (306) where the coating layer cures.

Alternatively, the protective coating layer may be applied in two successive steps. In this case, the fiber is first coated with a first coating layer with a thickness of approximately 30 μm, and then the coated fiber is passed through a second coating device (not shown in FIG. 2), where a second fiber is applied a coating layer of the same material with a thickness of approximately 30 μm, and then crosslinking is carried out in an appropriate UV curing chamber (or in a series of chambers) (not shown in FIG. 2). In this case, to ensure the required identification of the optical fiber, it may be advantageous to find the dye and / or pigment only in the coating composition in the second coating layer, if desired.

In the case where it will be necessary to apply an external colored coating layer, the optical fiber is passed through a printing ink sprayer and a corresponding UV curing chamber (not shown in FIG. 2).

After coating and curing this coating layer in order to reduce the PMD (“polarization mode dispersion”) value of a given fiber, the fiber can optionally be passed through a device capable of imparting a predetermined twist to the fiber, for example, through a device of the type described in international patent application WO 99/67180. A pulley (310), located along the process after the devices illustrated earlier, controls the speed of the fiber draw. After this exhaust pulley, the fiber is passed through a device (308) capable of adjusting the fiber tension of the type described, for example, in patent application EP 1112979, and finally collected on a spool (309).

The optical fiber thus obtained can be used in the manufacture of optical cables. The fiber can be used either as such or in the form of tapes comprising several fibers combined together due to the presence of a common coating.

Hereinafter, the present invention will be further illustrated using several examples of its embodiment, which are offered solely as a guide and do not constitute a limitation on the invention.

EXAMPLES 1-9

Got nine coating compositions. The number of components for each composition (% (mass.)) Are shown in table 1.

Table 1 EXAMPLE one 2 3 (*) four 5 6 7 8 9 HEA-IPDI-PolyTHF 2900-IPDI-HEA (a) 58.5 - - - - - - - Ebecryl ^® 230 (a) - 83.0 - - - - - - - BR ^® 304 (a) - - - 63.5 58.5 83.0 73.3 73.3 73.3 HEA-IPDI- (PolyTHF 650-TDI) ₂ -HEA (a) - - 65 - - - - - - PETIA (b) - 14.6 - 14.6 - 14.6 14.6 14.6 24.3 HDDA (b) 29.4 - 24.4 - 29.4 - - - - IBOA (d) - - - 19.5 - - 9.7 - - ODA (d) 9.7 - 9.7 - 9.7 - - - - PEA (d) - - - - - - - 9.7 - Irgacure ^® 184 (s) 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 Dynasylan ^® MTMO (e) 1.46 1.46 1.46 1.46 1.46 1.46 1.46 1.46 1.46 (*): for comparison

HEA-IPDI-PolyTHF 2900-IPDI-HEA (oligomer): the oligomer was prepared as follows: 0.024 ° mole of polytetramethylene glycol, characterized by an average (number average) molecular weight of 2900 (PolyTHF), 0.048 mol of isophorondiisocyanate, which was IPOPH (IPTHI) diisate, was charged into a three-necked flask. 150 ppm of dibutyltin dilaurate was slowly added dropwise: the resulting mixture was kept under mechanical stirring at 55 ° C in an inert atmosphere (argon) for 2 hours. After that, 0.048 mol of hydroxyethyl acrylate (HEA) was slowly added and the mixture was kept under mechanical stirring at 55 ° C in an inert atmosphere (argon) for 18 hours to obtain the desired oligomer.

Ebecryl ^® 230 (oligomer): ether based aliphatic polyether urethane di-acrylate, characterized by an average (number average) molecular weight of 5000 from UCB Chemicals;

BR ^® 304 (oligomer): aromatic polyether urethanediacrylate based on ethers, characterized by an average (number average) molecular weight exceeding 4000 from Bomar Specialty;

HEA-IPDI- (PolyTHF 650-TDI) _2- HEA (oligomer): the oligomer was prepared as follows: 0.024 moles of polytetramethylene glycol, characterized by an average (number average) molecular weight of 650 (PolyTHF), 0.048 moles of isophorone diisocyanate, were loaded into a three-necked flask. which were slowly added dropwise and 150 ppm of dibutyltin dilaurate: the resulting mixture was kept under mechanical stirring at 55 ° C in an inert atmosphere (argon). After that, 0.048 mol of hydroxyethyl acrylate (HEA) was slowly added and the mixture was kept under mechanical stirring at 55 ° C in an inert atmosphere (argon) for 18 hours to obtain the desired oligomer.

PETIA (polyfunctional monomer): a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate from UCB Chemicals;

HDDA (polyfunctional monomer): 1,6-hexanediol diacrylate from UCB Chemicals;

IBOA (monofunctional monomer): isobornyl acrylate from UCB Chemicals;

ODA (monofunctional monomer): a mixture of octyl acrylate and decyl acrylate from UCB Chemicals;

PEA (monofunctional monomer): 2-phenoxyethyl acrylate from UCB Chemicals;

Irgacure ^® 184 (polymerization initiator): α-hydroxycyclohexyl from the company Ciba Specialties;

Dynasylan ^® MTMO (adhesion promoter): gamma-mercaptopropyltrimethoxysilane from Degussa.

The above oligomers (a) were subjected to differential scanning calorimetry (DSC) analysis in order to measure both the glass transition temperature (T _g ) and the melting temperature (T _m ): the results are shown in table 2. DSC analysis was performed in the following way.

Preliminary stages:

- temperature scan: heating from + 25 ° C to + 80 ° C at a heating rate of 10 ° C / min;

- isotherm: keeping for 5 min at + 80 ° С;

- temperature scan: cooling from + 80 ° C to + 25 ° C at a cooling rate of 10 ° C / min.

The preliminary steps described above are necessary to eliminate the thermal history if the oligomer has a melting point.

First stage:

- temperature scan: cooling from + 25 ° C to -100 ° C at a cooling rate of 10 ° C / min.

Second stage:

- isotherm: keeping for 2 min at -100 ° С.

Third stage:

- temperature scan: heating from -100 ° C to + 80 ° C at a heating rate of 10 ° C / min.

table 2 HEA-IPDI-PolyTHF 2900-IPDI-HEA Ebecryl ^® 230 BR 304 HEA-IPDI- (PolyTHF 650-TDI) ₂ -HEA T _g (° C) -71.2 -54.5 -61.0 -28.0 (T _m ) (° C) + 25 ° C - - -

The above multifunctional monomers (b) and monofunctional monomer (d) were analyzed by differential scanning calorimetry (DSC) in order to measure the glass transition temperatures (T _g ) of their homopolymer: the DSC analysis was performed as described in Sartomer Application Bulletin, No. 4013, published in October 1999. The results are shown in table 3.

Table 3 PETIA HDDA IBOA ODA Pea T _g (° C) +103 +43 +88 -thirty +5

The components shown in table 1 were placed in a 100 ml beaker and kept under mechanical stirring at 40 ° C for 2 hours. After this, the composition was left to stand for at least 12 hours at room temperature so as to obtain a homogeneous composition without bubbles.

Example 12

Analysis of mechanical and chemical-physical properties

The compositions of examples 1-9 were subjected to the following types of analysis of mechanical and chemical-physical properties.

By comparison:

(A): commercial single coating DeSolite ^® 3471-3-7 (from DSM) (example 10); and

(B): a mixture of 63% of the commercial primary coating DeSolite ^® 3471-1-129 (from DSM) and 37% of the commercial secondary coating DeSolite ^® 3471-2-136 (from DSM) (example 11)

subjected to the same types of analysis of mechanical properties.

Viscosity

The temperatures at which the uncured compositions obtained in accordance with Examples 1 to 9 reached a Brookfield viscosity of 2000 m · Pa · s were determined using a Brookfield type viscometer, model DV-III, equipped with a configuration of 29, operating at 150 rpm / min The results are shown in table 3.

The value of the modulus of elasticity

Films were prepared from the above compositions, proceeding as follows. A film with dimensions of 120 mm × 150 mm and a thickness of 70 μm was applied to a glass plate using a Doctor Blade filmography at a speed of 2 m per minute; curing of the film was carried out using a Fusion UV curing System, model F600 device and a lamp with spectrum D, exposed to a UV dose of 1.5 J / cm ² when irradiated in an inert nitrogen atmosphere. After curing, the films were removed from the glass plate.

The films thus obtained were conditioned for 24 hours at 25 ° C. and 50% relative humidity, and then they were measured for tensile modulus using a DMTA apparatus (Dynamic Mechanical Thermal Analyzer from Reometrics Inc.) at a frequency of 1 Hz and at a heating rate of 2 ° C / min in the temperature range from -60 ° C to 120 ° C. The smallest value of the modulus of elasticity, measured as described above, was taken as the equilibrium modulus. The results are shown in table 4.

Table 4 EXAMPLE one 2 3 (*) four 5 6 7 8 9 10 (*) eleven (*) Brookfield Viscosity: 200 mPa / s
(temperature: ° C) 40 56 45 35 fifty 51 42 36 48 - - DMTA ANALYSIS (MPa) -40 ° C 300 390 1510 449 254 113 237 104 253 1800 1600 + 25 ° С fifty 29.4 53 19 44 19.5 fourteen 8.5 32 150 60 + 60 ° C 28 eighteen 31 11.3 23 fifteen 9.5 7 25 fourteen 9 E. M. ⁽¹⁾ twenty 17 eighteen 6.8 16 10 7 5.5 fifteen 12 8 V ₁ ⁽²⁾ 272 372 1479 437.7 231 98 227.5 97 228 1786 1591 (*): for comparison;
⁽¹⁾ : equilibrium modulus;
⁽²⁾ : the difference between the value of the modulus of elasticity measured at -40 ° C and the value of the modulus of elasticity measured at + 60 ° C.

The data shown in table 4 demonstrate that the radiation-curable compositions corresponding to the present invention (example 1, 2, 4, 5, 6, 7, 8 and 9), have better properties compared with comparative compositions. In particular, the above data indicate that:

- the use of an oligomer characterized by an excessively high glass transition temperature (T _g ), (example 3), leads to an excess increase in the value of the elastic modulus at low temperature (-40 ° C);

- as a commercial individual coating (example 10), and a mixture of two commercial coatings (example 11) show an excessive increase in the value of the modulus of elasticity at low temperature (-40 ° C, which is also shown in the attached figure 3).

EXAMPLE 13

Optical Fiber Production

Dyed optical fibers were obtained in accordance with methods known in the art. Four optical glass fibers including a glass portion having a diameter of 125 μm were individually coated with a thickness of 60 μm using radiation-curable compositions of the present invention (compositions of examples 1, 2 and 7) and, by comparison, the composition of example 11 .

On individual coating obtained as described above from the compositions of Examples 1, 2 and 7 were coated with a printing ink based on acrylate with a thickness of 7 micrometers (Cablelite ^® from DSM company).

EXAMPLE 14

Microbend test

The attenuation of the signal due to the presence of microbends for the optical fiber obtained as described in example 12 (individual coating obtained from the compositions of examples 1, 2, 7 and 11) was determined by the "method using a sliding bobbin", described, for example, in work G Grasso and F. Meli in: "Microbending losses of cabled single-mode fibers", ECOC '88, pp.526-ff or defined by IEC standard 62221 (Optical fibers - Measurement methods - Microbending sensitivity - Method A, Expandable drum; October 2001).

The test was conducted when winding the optical fiber with a length of 100 m at a tension of 55 g on a sliding metal bobbin of 300 mm diameter coated with a roughened coating material (grade 3M Imperial ^® PSA, 40 microns).

The bobbin was connected to a personal computer that controlled:

- increase in bobbin volume (expressed through a change in fiber length); and

- transmission loss for fiber.

After that, the bobbin volume was gradually increased while monitoring the dependence of transmission loss for the fiber on fiber deformation.

The pressure acting on the fiber was calculated from the relative elongation of the fiber according to the following formula:

p = EAε / R,

where E is the value of the modulus of elasticity of the glass, A is the area of the coated fiber, ε is the elongation of the fiber, and R is the radius of the bobbin.

For each optical fiber, the MAC (mass attenuation coefficient) was determined as follows:

MAC = MFD / λ _co ,

where MFD (mode field diameter as defined by Petermann) at 1550 nm and λ _co (lambda-critical wavelength for fiber - 2 m length) were determined in accordance with ITUT G650 standard.

As a result of measuring the signal attenuation due to the presence of microbends at different temperatures, for the coated optical fibers according to Example 12, corresponding curves of the signal attenuation due to the presence of microbends on temperature were obtained. Table 5 shows the values for signal attenuation due to the presence of microbends obtained from the mentioned curves at various temperatures in the range from -40 ° C to + 60 ° C.

Table 5 Example one 2 7 eleven (*) Signal attenuation due to microbending (dB / km) / (g / cm) -40 ° C 14.5 9.8 5.3 28,2 -20 ° C 8.9 7.5 3.6 14.3 -10 ° C 7.0 6.8 3.0 - + 0 ° С 3.3 6.5 2,5 10.7 + 10 ° С 2.7 6.5 2,3 - + 25 ° С 2.6 5.8 2.0 6.2 + 60 ° C 2,5 4.2 1.8 4.6 MAS 8 7.9 7.5 8.3 V ₂ ⁽¹⁾ 12.0 5,6 3,5 23.6

(*): for comparison;

⁽¹⁾ : change in signal attenuation due to the presence of microbends in the range from -40 ° C to + 60 ° C.

Claims (51)

1. Optical fiber comprising a glass portion; at least one layer of polymer protective coating, placed so that it covers said glass portion; wherein said protective coating layer is characterized by a modulus of elasticity at a temperature of from -40 ° C to + 60 ° C in the range from 5 MPa to 600 MPa, the difference (V ₁ ) between the value of the modulus of elasticity measured at -40 ° C, and the value of the elastic modulus, measured at + 60 ° C, for the protective coating layer does not exceed 495 MPa. 2. The optical fiber according to claim 1, where the value of the modulus of elasticity does not exceed 500 MPa. 3. The optical fiber according to claim 2, where the value of the modulus of elasticity does not exceed 450 MPa. 4. The optical fiber according to claim 3, where the value of the elastic modulus does not exceed 300 MPa. 5. The optical fiber according to claim 1, where the value of the elastic modulus is not less than 8 MPa. 6. The optical fiber according to claim 4, where the value of the elastic modulus is greater than 12 MPa. 7. The optical fiber according to any one of claims 1 to 6, wherein the protective coating layer is placed in contact with said glass portion. 8. The optical fiber according to any one of claims 1 to 6, wherein the protective coating layer is a single protective coating layer that is placed in contact with said glass portion. 9. The optical fiber according to claim 1, where the difference (V ₁ ) between the value of the elastic modulus measured at -40 ° C and the value of the elastic modulus measured at + 60 ° C for the protective coating layer does not exceed 320 MPa. 10. The optical fiber according to claim 9, where the difference (V ₁ ) between the value of the modulus of elasticity measured at -40 ° C and the value of the modulus of elasticity measured at + 60 ° C for the protective coating layer does not exceed 150 MPa. 11. The optical fiber according to claim 1, where the protective coating layer is characterized by the value of the equilibrium module (EM), exceeding 5 MPa. 12. The optical fiber according to claim 1, where in the temperature range from -40 ° C to + 60 ° C, the signal attenuation changes due to the presence of microbends (V ₂ ), measured as a result of winding a fiber with a length of 100 m with a tension of 5 g per a sliding metal bobbin with a diameter of 300 mm with a coating of rough material, does not exceed 20 (dB / km) / (g / mm). 13. The optical fiber according to item 12, where in the temperature range from -40 ° C to + 60 ° C, the signal attenuation due to the presence of microbends (V ₂ ), measured as a result of winding a fiber with a length of 100 m with a tension of 5 g per a sliding metal bobbin with a diameter of 300 mm coated with a material of rough material, does not exceed 15 (dB / km) / (g / mm). 14. The optical fiber according to item 13, where in the temperature range from -40 ° C to + 60 ° C the change in signal attenuation due to the presence of microbends (V ₂ ), measured as a result of winding a fiber with a length of 100 m with a tension of 5 g per a sliding metal bobbin with a diameter of 300 mm coated with a material of rough material, does not exceed 6 (dB / km) / (g / mm). 15. The optical fiber according to claim 1, where the protective coating is obtained by curing a radiation-curable composition containing (a) at least one ethylene-type unsaturated polyurethane characterized by a glass transition temperature (T _g ) in the range of -40 ° C to -100 ° C; (b) at least one polyfunctional reactive diluting monomer. 16. The optical fiber according to clause 15, where the polyurethane with an unsaturation of ethylene type (a) is characterized by a glass transition temperature (T _g ) in the range from -50 ° C to -85 ° C. 17. The optical fiber according to clause 15, where the polyurethane with unsaturation of ethylene type (a) is obtained by carrying out reactions between the following compounds: (A) at least one polyol as one compound, including the structural unit described by the following formula (I)

where n is an integer in the range from 0 to 4 inclusive; R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ , which may be identical to each other or different from each other, represent a hydrogen atom or a C ₁ -C ₄ alkyl group; (B) at least one polyisocyanate compound; and (C) at least one (meth) acrylate derivative having at least one hydroxyl group. 18. The optical fiber according to 17, where the polyol-related compounds (A) are selected from compounds obtained by polymerization of at least one compound selected from the group consisting of ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, tetramethylene glycol, 2 -alkyl-1,4-butanediol and 3-alkyl-1,4-butanediol; compounds obtained by ring-opening polymerization of 2-alkyltetrahydrofuran or 3-alkyltetrahydrofuran; compounds obtained by the copolymerization of 2-alkyltetrahydrofuran, 3-alkyltetrahydrofuran or 2-alkyl-1,4-butanediol and a cyclic ether such as ethylene oxide, propylene oxide and tetrahydrofuran, or mixtures thereof. 19. The optical fiber according to claim 17, wherein the polyol-containing compound (A) is selected from the group consisting of polybutadiene having a terminal hydroxyl group, hydrogenated polybutadiene having a terminal hydroxyl group, polyisobutylene polyol, 1,6-hexanediol, neopentyl glycol, 1, 4-cyclohexanedimethanol, bisphenol A, bisphenol F, alkylene oxide adducts of bisphenol A, alkylene oxide adducts of bisphenol F, dimethylated derivative of dicyclopentadiene, polyester diols based on esters, polycaprolactone diols, polycarboxy natdiolov or mixtures thereof. 20. The optical fiber according to claim 17, wherein the polyisocyanate compound (B) is selected from polyisocyanates, such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 1,5-naphthalenediisocyanate , m-phenylenediisocyanate, p-phenylenediisocyanate, 3,3'-dimethyl-4,4'-diphenylmethanediisocyanate, 4,4'-diphenylmethanediisocyanate, 3,3'-dimethylphenylenediisocyanate, 4,4'-biphenylenediisiocyanate, 1,6-hexamethylene isophorondiisocyanate, methylene bis (4-cyclohexyl isocyanate), 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene zotsianat, 1,4-hexamethylene diisocyanate, bis (2-izotsianatoetil) fumarate, 6-isopropyl-1,3-phenyl diisocyanate, 4-difenilpropanizotsianat, lysine diisocyanate or mixtures thereof. 21. The optical fiber according to claim 17, wherein the (meth) acrylate derivative (C) having at least one hydroxyl group is selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate , 2-hydroxy-3-phenyloxypropyl (meth) acrylate, propanediol (meth) acrylate, 1,4-butanediolmono (meth) acrylate, 2-hydroxyalkyl (meth) acryloyl phosphate, 4-hydroxycyclohexyl (meth) acrylate, 1,6-hexanediolmono (meth) acrylate, neopentyl glycolmono (meth) acrylate, trimethylolpropanedi (meth) acrylate, trimethylol ethanedi (meth) acrylate, pentaerythritol (meth) acrylate, dip Pentaerythritol (meth) acrylate, (meth) acrylates described by the following formulas (II) or (III)

where R ₅ represents a hydrogen atom or a methyl group, and n represents an integer in the range from 1 to 15, inclusive; or mixtures thereof. 22. The optical fiber according to clause 15, where the multifunctional reactive diluting monomer (b) is selected from the group consisting of ethylene glycol (meth) acrylate, tetraethylene glycol (meth) acrylate, propanedioldi (meth) acrylate, 1,4-butanediol (meth) acrylate , trimethylolpropanedi (meth) acrylate, trimethylolpropanetri (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanedioldi (meth) acrylate, 1,6-hexamethylene dihydroxy (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene di (meth) acrylate ester hydroxypival of new acid and neopentyl glycol, trimethylol propane (meth) acrylate, trimethylol propane trioxyethyl (meth) acrylate, tricyclodecane dimethanoldi (meth) acrylate, dicyclopentadienedi (meth) acrylate, pentaerythritol (meth) acrylate, pentaerythritol (pentaerythritol) ) acrylate, di (meth) acrylate diol, such as an addition product (adduct) of ethylene oxide or propylene oxide and bisphenol A, hydrogenated bisphenol A, glycidyl ether of bisphenol A, or mixtures thereof. 23. The optical fiber of claim 15, wherein the multifunctional reactive diluting monomer (b) is 1,6-hexanediol diacrylate, pentaerythritol triacrylate, or a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate. 24. The optical fiber according to clause 15, where the radiation-curable composition contains at least one polymerization initiator (s). 25. The optical fiber according to paragraph 24, where the polymerization initiator (c) is selected from the group consisting of benzophenone, benzoin, benzoinisobutyl ether, benzyl, benzoin ethyl ether, 2,2-dimethoxy-2-phenylacetophenone, xanton, fluorenone, 4-chlorobenzophenone , triphenylamine, carbazole, 3-methylacetophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, Michler ketone, benzoinpropyl ether, acetophenone diethyl ketal, benzoin ethyl ether, 1-hydroxycyclohexylphenyl ketone, 2-hydroxycyclohexylphenyl ketone, 2-hydroxycyclohexylphenylketone, 2-hydroxycyclohexylphenyl ketone, 2-hydroxycyclohexylphenylketone -2-hydroxy-2-methylpropiophenone , α, α-dichloro-4-phenoxyacetophenone, benzyldimethyl ketal, 2,2-diethoxyacetophenone chlorothioxantone, 2-isopropylthioxantone, diethylthioxantone, 3,3-dimethyl-4-methoxybenzophenone, 2-methyl-1- [4- (methylthio) phenyl] 2-morpholinopropanone, α-hydroxycyclohexylphenylketone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, or mixtures thereof. 26. The optical fiber according to paragraph 24, where the radiation-curable composition contains at least one photosensitizer (f). 27. The optical fiber according to claim 26, wherein the photosensitizer (f) is selected from amines, ureas, phosphorus compounds, sulfur compounds, nitriles, or mixtures thereof. 28. The optical fiber according to p. 26, where in the radiation-curable composition, the polymerization initiator (c) and the photosensitizer (f) are present in a total amount of from 0.01 wt.% To 10 wt.% Based on the total weight of said radiation-curable composition. 29. The optical fiber according to clause 15, where the radiation-curable composition contains at least one monofunctional reactive diluting monomer (d). 30. The optical fiber according to clause 29, where the monofunctional reactive diluting diluting monomer (d) is selected from the group consisting of 2-hydroxyethyl (meth) acrylate; 2-hydroxypropyl (meth) acrylate; 2-ethylhexyl (meth) acrylate; butoxyethyl (meth) acrylate; tetrahydrofurfuryl (meth) acrylate; linear or branched alkyl (meth) acrylates such as butyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, isodecyl (meth) ) acrylate; n-hexyl (meth) acrylate; cyclohexyl (meth) acrylate; invented (meth) acrylate; (ethoxylated alkyl) (meth) acrylates such as methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, 2- (2-ethoxyethoxy) ethyl (meth) acrylate; dicyclopentenyl (meth) acrylate; diethylene glycol (meth) acrylate; ethoxydiethylene glycol (meth) acrylate; benzyl (meth) acrylate; polyethylene glycol (meth) acrylate; polypropylene glycol (meth) acrylate; methoxypolyethylene glycol (meth) acrylate; methoxypolypropylene glycol (meth) acrylate; 2-phenoxyethyl (meth) acrylate; phenoxypolyethylene glycol (meth) acrylate; alkylphenoxyethyl (meth) acrylate such as nonylphenoxyethyl (meth) acrylate; alkylphenoxypolyalkylene glycol (meth) acrylate; 2-hydroxy-3-phenyloxypropyl (meth) acrylate; tetrahydrofurfuryloxypropylalkylene glycol (meth) acrylate; dicyclopentenyloxypolyalkylene glycol (meth) acrylate; 2-hydroxyalkyl (meth) acryloyl phosphate; polyfluoroalkyl (meth) acrylate; N-vinylpyrrolidone; N-vinylcaprolactam; diacetone (meth) acrylamide; isobutoxymethyl (meth) acrylamide; N, N-dimethylacrylamide; tert-octyl (meth) acrylamide; dialkylaminoethyl (meth) acrylate; (meth) acryloylmorpholine; or mixtures thereof. 31. The optical fiber according to claim 30, wherein the monofunctional reactive diluting monomer (d) is isobornyl acrylate, 2-phenoxyethyl acrylate, nonyl phenoxyethyl acrylate, C ₈ -C ₁₃ alkyl acrylates, lauryl acrylate, isodecyl acrylate. 32. The optical fiber according to clause 29, where in the radiation-curable composition, a monofunctional reactive diluting monomer (d) is present in an amount in the range from 3 wt.% To 25 wt.% Based on the total weight of said radiation-curable composition. 33. The optical fiber according to clause 15, where the radiation-curable composition contains at least one adhesion promoter (e). 34. The optical fiber according to claim 33, wherein the adhesion promoter (e) is an organofunctional silane selected from the group consisting of octtriethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, tris- (3-trimethoxysilylpropyl) isocyanurate, vinyltriethoxylisan, 2-vinyltriethoxysilane, -methoxyethoxy) silane, vinylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, organo-modified polyide tilsiloksana, γ-ureidopropyltrialkoxysilanes, γ-ureidopropiltrimetoksisilana, γ-isocyanatopropyltriethoxysilane, or mixtures thereof. 35. The optical fiber according to claim 33, wherein the adhesion promoter (e) is described by the following structural formula (IV)

where the R groups, which may be identical to each other or different from each other, are selected from alkyl, alkoxyl or aryloxy groups or halogen atoms, provided that at least one of the R groups is an alkoxy or aryloxy group; n is an integer ranging from 1 to 6 inclusive; X represents a group selected from the groups: nitroso, mercapto, epoxy, vinyl, imido, chlorine, - (S) _m C _n H _2n -Si- (R) ₃ , where m and n are integers ranging from 1 up to 6, inclusive, and the R groups are determined as described above. 36. The optical fiber according to clause 33, where in the radiation-curable composition, the adhesion promoter (e) is present in an amount in the range from 0.1 wt.% To 2.5 wt.% Based on the total weight of said radiation-curable composition. 37. Radiation-curable composition containing (a) from 50 wt.% to 95 wt.%, calculated on the total weight of said radiation-curable composition of at least one polyurethane with an ethylene-type unsaturation characterized by a glass transition temperature (T _g ) in the range of -40 ° C to -100 ° C; (b) from 5 wt.% to 50 wt.%, calculated on the total weight of said radiation-curable composition of at least one polyfunctional reactive diluting diluting monomer. 38. The radiation-curable composition according to clause 37, where the polyurethane with an unsaturation of ethylene type (a) is determined according to any one of paragraphs.17-21. 39. The radiation-curable composition according to clause 37 or 38, where the multifunctional reactive diluting diluting monomer (b) is determined according to clause 22 or 23. 40. The radiation-curable composition according to clause 37, which contains at least one polymerization initiator (C), which is determined according to paragraph 24 or 25. 41. The radiation-curable composition according to claim 40, which contains at least one photosensitizer (f), which is defined according to any one of claims 26 to 28. 42. The radiation-curable composition according to clause 37, which contains at least one monofunctional reactive diluting monomer (d), which is defined according to any one of paragraphs.29-32. 43. The radiation-curable composition according to clause 37, which contains at least one adhesion promoter (e), which is defined according to any one of claims 33-36. 44. The radiation-curable composition according to clause 37, characterized by Brookfield viscosity, in the temperature range from 20 ° C to 80 ° C, component from 1000 m · PA · s to 4000 m · PA · s. 45. A method for controlling attenuation losses of a signal transmitted through an optical fiber including an inner glass portion caused by the presence of microbends, which comprises providing at least one layer of a polymer protective coating characterized by an elastic modulus value at a temperature of from -40 ° C to + 60 ° C in the range from 5 MPa to 600 MPa, and the difference (V ₁ ) between the value of the elastic modulus measured at -40 ° C and the value of the elastic modulus measured at + 60 ° C for the protective coating layer does not exceed 495 MPa . 46. The method according to item 45, where in the temperature range from -40 ° C to + 60 ° C, the value of the elastic modulus does not exceed 500 MPa. 47. The method according to item 46, where in the temperature range from -40 ° C to + 60 ° C, the value of the elastic modulus does not exceed 450 MPa. 48. The method according to clause 47, where in the temperature range from -40 ° C to + 60 ° C, the value of the elastic modulus does not exceed 300 MPa. 49. The method according to item 45, where in the temperature range from -40 ° C to + 60 ° C, the value of the elastic modulus is not less than 8 MPa. 50. The method according to 49, where in the temperature range from -40 ° C to + 60 ° C, the value of the elastic modulus is more than 12 MPa. 51. The method according to any one of claims 46-50, wherein said protective coating layer is defined according to any one of claims 15 to 36.

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