Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
  • G02B1/045—Light guides
  • G02B1/046—Light guides characterised by the core material
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/05—Filamentary, e.g. strands
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/15—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor incorporating preformed parts or layers, e.g. extrusion moulding around inserts
  • B29C48/154—Coating solid articles, i.e. non-hollow articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/30—Extrusion nozzles or dies
  • B29C48/32—Extrusion nozzles or dies with annular openings, e.g. for forming tubular articles
  • B29C48/34—Cross-head annular extrusion nozzles, i.e. for simultaneously receiving moulding material and the preform to be coated
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D11/00—Producing optical elements, e.g. lenses or prisms

Definitions

• the present invention relates to a method for manufacturing an index gradient optical fiber, as well as an optical fiber obtained by this method.
• Plastic optical fibers with an index gradient which can be used in a spectral range covering the visible to the near infrared, are advantageous because they can be applied to broadband access networks.
• a graded index plastic optical fiber comprises at least one basic polymer and another compound, called dopant, comprising one or more monomers or polymers.
• the proportion of the base polymer is substantially the same over the entire fiber and the proportion of the dopant varies from the core to the periphery of the fiber so as to form the desired index gradient.
• the manufacture of such plastic optical fibers is delicate, because it is necessary to distribute the dopant varying from the heart to the periphery of a plastic optical fiber.
• the fiber must have a refractive index profile of the gradient index type as regular as possible, the variation of refractive index between the center and the periphery of the fiber is generally between 0.01 and 0.03.
• document EP-1 067 222 discloses a process for manufacturing a plastic optical fiber with an index gradient, the index of which varies continuously between the center and the periphery of the fiber.
• the fiber is made from at least one polymer P and at least one reactive diluent D1 serving as a dopant making it possible to vary its refractive index.
• This process comprises the following stages: preparation of two compositions of different refractive index, the difference in refractive index between the two compositions being at least 5.10 ⁇ 3 , each comprising at least the polymer P, one of the compositions, known as the first composition, further comprising at least the reactive diluent D1, a radical polymerization initiator being present in at least one of the compositions,
• the polymer P and the reactive diluent D1 are also chosen such that:
• the polymer P is of molar mass between 1000 and 20000 g. moles "1 and the reactive diluent D1 has a molar mass of between 100 and 1000 g. moles " 1 ,
• the reactive diluent D1 comprises at least one reactive unsaturated group vis-à-vis UV chosen from the group formed by vinyl groups and acrylic groups,
• the polymer P comprises at least one unsaturated group reactive with respect to UV rays chosen from the group formed by vinyl groups and acrylic groups, at least one of the two compounds P and D1 is at least mono-functional , the other of the two compounds P and D1 is at least bi-functional.
• molar masses mentioned above are number average molar masses. This is also the case for the molar masses mentioned in all that follows.
• a preferred base polymer is of the poly ( ⁇ fluoro) methacrylate type, and more generally of the PMMA (polymethylmethacrylate) type.
• the aim of the present invention is therefore to develop a process for manufacturing an index gradient optical fiber making it possible to obtain plastic optical fibers capable of operating at wavelengths greater than 500 nm without causing prohibitive attenuation of the transmitted optical signal.
• the present invention provides a method for manufacturing a plastic optical fiber with an index gradient, the index of which varies continuously between the center and the periphery of the fiber, from at least one polymer P and at least one reactive diluent D1 making it possible to vary the refractive index of said fiber, said method comprising the following steps:
• compositions with different refractive index preparation of two compositions with different refractive index, the difference in refractive index between the two compositions being at least 5.10 "3 , each comprising at least polymer P, one of the compositions, known as the first composition, comprising in addition at least the reactive diluent D1, a radical polymerization initiator being present in at least one of the compositions,
• R 1 is an atom of H, F, Cl or Br or a carbon group comprising from 1 to 10 carbon atoms partially or completely fluorinated
• - Y 1 and Y 2 are taken either from the group of atoms comprising H, F, Cl and Br, or from the family of carbon groups comprising from 1 to 10 carbon atoms - Y 3 is a group carbonyl or a divalent carbon group
• Z 1 , Z 2 , Z 3 are hydrogen or fluorine atoms, carbon groups comprising from 1 to 10 carbon atoms
• - n is equal to 0 or 1 - A is an ester function, an oxygen or sulfur atom
• R 2 is taken from the group comprising divalent hydrocarbon groups of 2 to 8 carbon atoms and divalent carbon groups of 2 to 8 carbon atoms, partially halogenated
• - B x is an unsaturated reactive function - i, j, and k correspond to a repetitive number of units, the content of units P3 in the terpolymer being between 2 and 40% by mole, preferably between 10 and 20% and the molar ratio of units P1 / P2 being between 0.5 and 5.5, preferably between 1 and 2, said terpolymer being transparent, of amorphous nature and having a glass transition temperature (Tg) greater than 25 T.
• Tg glass transition temperature
• plastic optical fibers can be obtained with an index gradient having a lower attenuation than that of the fibers obtained from polymers of the prior art of PM ⁇ A type.
• This polymer is obtained from the radical copolymerization of monomers available on the market which does not require the use of dangerous reagents for their transformation.
• this functional polymer of an ethylenic group makes it crosslinkable at any time by simple photochemical or heat treatment.
• the crosslinking of this functional terpolymer, in the presence of photoinitiator allows the preparation of optical components such as optical fibers.
• the fibers obtained by the method according to the invention are particularly suitable for applications at wavelengths greater than 500 nm, typically in the transmission windows located around 650, 850, 1300 and 1550 nm.
• the crosslinking is a photo-crosslinking and the initiator is a photoinitiator.
• the molar mass of the polymer P is between 1000 and 20000 g. moles "1 and the reactive diluent D1 has a molar mass of between 100 and 1000 g. moles " 1 .
• These choices limit the viscosity of the composition and facilitate spinning.
• the polymer P and the reactive diluent D1 each comprise at least one unsaturated group reactive with respect to UV rays chosen from the group formed by vinyl groups and acrylic groups.
• the glass transition temperature of the terpolymer is between approximately 60 and 90 ° C. when the content of P2 units in the terpolymer is between about 20 and 50 mol%.
• the molar mass (Mn) of the terpolymer is between 500 and 10 5 g. moles “1 , preferably between 10 3 and 10 4 g.moles " 1 and more particularly between 2.10 3 and 5.10 3 g. moles "1 .
• the repeating unit P1 is obtained from the polymerization of a monomer M1 of the following general formula:
• TFE tetrafluoroethylene
• M1 is chlorotrifluoroethylene (CTFE).
• CTFE chlorotrifluoroethylene
• M1 can also be a compound of which
• repeating unit P2 results from the polymerization of a monomer M2 of cyclic structure having the following general formula: ⁇ l ⁇ 2
• M2 can be vinylene carbonate (VCA) in which Y 3 is a carbonyl group and Y 1 and Y 2 are hydrogen atoms.
• VCA vinylene carbonate
• Y 3 is either a carbonyl group or a divalent carbon group such as for example: -CH 2 -, -CH (CH 3 ) - and -C (CH 3 ) 2-.
• the repeating unit P3 results from the polymerization followed by a chemical transformation of a monomer M3 of the following general formula:
• A is an ester function such that M3 corresponds to one of the two formulas M3 'or M3 "below, where R ⁇ M3:
• R 2 is taken from the group comprising divalent alkyl groups of 2 to 8 carbon atoms and partially halogenated alkyl groups F and / or Cl and divalent of 2 to 8 carbon atoms.
• B x can be equal to B 1 taken from the group comprising a chlorine, bromine, iodine atom, a hydroxyl function and a hydroxyl function modified by a protective group which may for example be a trimethylsilane group or a mesityl group.
• M3 can be ethylene glycolvinyl ether (EGVE) or butanediolvinyl ether (BDVE) or their protected form.
• EGVE ethylene glycolvinyl ether
• BDVE butanediolvinyl ether
• the transformation of the group B 1 into an acrylic function, when B 1 is a hydroxyl function, can be obtained according to the conventional routes of organic synthesis from acid chlorides, anhydrides or alternatively by transesterification reaction with ( meth) methyl or ethyl acrylate or alternatively by direct esterification of the acid with alcohol B 1 with elimination of the water formed.
• An active mixture according to the process of the invention is a mixture which is helped to form, that is to say which is not produced only by diffusion; this active mixture can be obtained statically by forcing by a static diffusion means the mixture of the two compositions, most often by forced flow, or by dynamic means which actively produces such a mixture.
• Such a method has the advantage of being rapid, in particular much faster than if only the diffusion between the compositions is used, and of making it possible to obtain a concentration gradient and therefore a continuous refractive index and practically smoothed.
• the crosslinking kinetics are generally such that, under maximum exposure and complete transformation of the initiator, the gel time is less than 10 s, preferably less than 2 s.
• the spinning of the index gradient mixture is followed by a photochemical or thermal crosslinking leading to the production of a three-dimensional network.
• This process advantageously makes it possible to at least partially freeze the components of the plastic optical fiber.
• the plastic optical fiber thus obtained and its index gradient therefore have stability over time and stability in temperature.
• at least one of the two compositions comprises a monomer; in addition, at least one of the two compositions comprises at least one radical polymerization initiator, and preferably each of the two compositions comprises at least one radical polymerization initiator.
• the radical polymerization initiator is a compound which makes it possible to generate initiator radicals by thermal or photo-chemical decomposition.
• the second composition comprises at least one reactive diluent D2 also making it possible to vary the refractive index, the reactive diluent D2 being of refractive index substantially different from the refractive index of D1, having a molar mass of between 100 and 1000 g. moles "1 , and comprising at least one UV-reactive unsaturated group chosen from the group formed by vinyl groups and acrylic groups.
• the reactive diluents D1 and D2 have practically identical respective viscosities and the proportion by mass of the polymer P relative to the constituents of the composition is practically constant for each of the compositions.
• the process is easier to implement because the variation of the proportion by diluting reagent (s) D1 and / or D2, mainly allowing to modulate the refractive index, does not significantly influence the viscosity compositions.
• the mixing of the two compositions is carried out at a temperature such that the viscosity at 20 ° C. of each of the two compositions is between 1 and 25 Pa.s, preferably between 1 and 15 Pa.s. This advantageously makes it possible to facilitate the implementation of the method according to the invention, because such a viscosity makes it possible to mix relatively fluid compositions.
• the spinning is carried out at a temperature such that the viscosity of each of the two compositions is greater than 500 mPa.s, preferably greater than 1000 mPa.s.
• the reactive groups carried by the constituents D1 and D2 as well as by the polymer P are chosen from the group formed by vinyl groups and acrylic groups, that is to say from acrylates, methacrylates, vinyl ethers or propenyl ethers, these compounds possibly being at least partially halogenated, most often fluorinated and / or chlorinated.
• any component of one of the compositions is an at least partially halogenated material, most often fluorinated and / or chlorinated.
• one of the two reactive diluents D1 or D2 is at least partially fluorinated and the other of the two reactive diluents D2 or D1 is at least partially chlorinated or chloro-fluorinated, and therefore has a refractive index substantially higher than that of the at least partially fluorinated monomer.
• the present invention also relates to a plastic optical fiber with an index gradient obtained by the method according to the invention, as well as an optical waveguide obtained by the method according to the invention.
• a plastic optical fiber with an index gradient obtained by the method according to the invention as well as an optical waveguide obtained by the method according to the invention.
• FIG. 2 shows a schematic view of the index profile of an optical fiber obtained by means of the device of Figure 1
• FIG. 3 shows the glass transition temperature Tg as a function of the molar concentration of vinylene carbonate (VGA) in the terpolymer P used in the process of the invention.
• two compositions are prepared, each comprising a terpolymer P.
• One of these compositions also comprises at least one reactive diluent D1, which is preferably a monomer.
• the other composition comprises at least one reactive diluent D2, which is also preferably a monomer.
• the concentration of D1 is different in each of the two compositions, which gives a different refractive index to each composition.
• the two values of refraction index thus obtained constitute the maximum and the minimum of the parabolic index gradient gradient curve that one seeks to obtain for the plastic optical fiber resulting from the process (see FIG. 2).
• the terpolymer P used in the process of the invention is as defined above, that is to say that it comprises at least three repeating units P1, P2 and P3 of the following general formulas:
• any polymerization process known to a person skilled in the art can be used: in a solvent medium, in suspension or in emulsion in water for example. It is generally preferable to work in a solvent medium in order to control the exothermicity of the polymerization and to favor an intimate mixture of the different monomers.
• solvents commonly used there may be mentioned: ethyl acetate, methyl or butyl acetate, chlorinated or chlorofluorinated solvents such as, for example, F141 b® (CFCl 2 -CH 3 ) or CF 3 - CH 2 -CF 2 -CH 3 .
• radical polymerization initiator it is possible to use free radical generators such as peroxides, hydroperoxides, percarbonate or even diazo compounds such as azobisisobutyronitrile (AIBN) or its functionalized derivatives which then make it possible to introduce an acrylic group at the end of the chain . It is also possible, in the case of processes carried out in an aqueous medium, to use inorganic free radical generators such as persulfates or so-called redox combinations.
• free radical generators such as peroxides, hydroperoxides, percarbonate or even diazo compounds such as azobisisobutyronitrile (AIBN) or its functionalized derivatives which then make it possible to introduce an acrylic group at the end of the chain .
• AIBN azobisisobutyronitrile
• inorganic free radical generators such as persulfates or so-called redox combinations.
• the polymerization temperature is generally dictated by the decomposition rate of the initiator chosen and is generally between 0 and 200 ° C, more particularly between 40 and 120 ° C.
• the pressure is generally between atmospheric pressure and a pressure of 50 bars, more particularly between 2 and 20 bars.
• the reaction can be carried out in the presence of a stabilizer of the functional monomer M3, without prejudice to the invention.
• the stabilizers are hydrogen type compounds or dihydrogenphosphate, hydrogencarbonate or any other epoxide-like compound which may prevent this side reaction.
• This stabilizer is present in amounts of the order of 0.01 to 10 mol% relative to the monomer M3.
• Control of the molar mass of terpolymer P is obtained by controlling the length of the terpolymer chain.
• the purpose of this control is to allow the adjustment of the solubility of the terpolymer chain in a solvent or diluent acrylic or vinyl reactive and also to control the final viscosity of this mixture in order to obtain viscosity values compatible with the subsequent process for using the terpolymer.
• chain limiter In order to control the length of macromolecular chains, comprising the entities P1, P2 and P3, it is possible to add, during the copolymerization of the monomers M1, M2 and M3, an agent called chain limiter or transfer agent whose role is well known in radical polymerization.
• the solvent used can also have a role of chain limiter depending on its chemical nature.
• chain limiters known to those skilled in the art there may be mentioned, for example, halogen derivatives such as CCl, CHCl 3 , phosphites such as H-PO (OEt) 2 , alcohols or ethers having hydrogens on the alpha carbon of the oxygen atom, esters such as ethyl acetate.
• the polymer P according to the invention has a molar mass (Mn) of between 500 and 10 5 g. moles "1 , preferably between 10 3 and 10 4 g. moles " 1 and very particularly between 2.10 3 and 5.10 3 g. moles ' 1 .
• Mn molar mass
• the content of functional P3 units in the terpolymer comprising the units P1, P2 and P3, that is to say the molar percentage expressed by (k / (i + j + k) x 100), can vary between 2 and 40 % by mole and preferably between 10 and 20%. This content determines the degree of crosslinking at the time of implementation.
• the ratio of the units P1 / P2 that is to say the ratio (i / d), can vary from 0.5 to 5.5, and is preferably between 1 and 2. This ratio, and more particularly the content of pattern P2, influences the glass transition temperature (Tg) of the polymer.
• EGVE-TMS CH2 CH-O-CH2-CH2-O-Si (CH3) 3
• VCA vinylene carbonate
• TBPP 75% tert-butyl perpivalate in isododecane
• EMHQ 4-methoxy-phenol
• DAROCUR 1173® 2-hydroxy-2-methylpropiophenone Tg Glass transition temperature Mn: number average molecular weight Mn (number average molecular weights) were determined by analysis CES (exclusion chromatography sté ⁇ 'that). An apparatus from the company Spectra Physic "Winner Station” is used. Detection is carried out by refractive index. The column is a 5 micron mixed C PL gel column from the company Polymer Laboratory and the solvent used is THF at a flow rate of 0.8 ml / min. The molar masses in number (Mn) are expressed in g. moles ' 1 compared to a polystyrene standard.
• the Tg glass transition temperatures are determined by differential scanning calorimetry (DSC). A first temperature rise is carried out at 20 ° C / min followed by cooling and then a second temperature rise during which the Tg or Tf (melting temperatures) are noted.
• the temperature range is either from -20 ° C to 80 ° C if the Tg is below 60 ° C, or from 50 ° C to 200 ° C if the Tg is above 60 ° C.
• the chlorine levels are determined conventionally by mineralization in a PARR bomb with Na 2 ⁇ 2 followed by determination of the chlorides by argentimetry.
• the assays of the hydroxyl functions are carried out by the method of Bryant et al (J. Am. Chem. Soc. Vol 62, 1, 1940) described by Stig Veibel in “The Determination of Hydroxyl Groups ed. R. Belcher and DMW ANDERSON, Académie Press, London and New York, 1972 (p 86 and 129) ”.
• the alcohol functions are acetylated by a BF 3 / CH 3 COOH complex, then the water formed is assayed in return by a potentiometric titration of the Karl Fisher type.
• the solvent, paradioxane, mentioned in the method has been replaced by acetonitrile.
• the results are expressed in milli-equivalents of OH function per gram of polymer (meq / g).
• a Fusion UV LC-6 conveyor is used fitted with a Fusion F300S UV treatment system which is fitted with a 214 W “bulb H” lamp (wavelength from 351 to 400 nm) .
• the conveyor running speed corresponds to an exposure time of 300 ms to ultra violet radiation for one passage.
• Comparative example 1 [M1 / M3: CTFE / EGVE]
• the operation is carried out in a 160 ml stainless steel reactor. Once the reactor is closed, two to three purges are carried out with 5 bars of nitrogen. The reactor is then placed under vacuum (approximately 100 mbar) and 50 ml of an ethyl acetate solution containing 0.4 ml of TBPP initiator (1.5 mmol) and 3.8 gd are then introduced by suction. 'EGVE (M3; 43 mmol). 5 g of CTFE (M1; 43 mmol) are then introduced. The reactor is closed and the temperature is brought to 70 ° C. for 4 hours with stirring, the initial pressure is approximately 5 bars. After reaction, the contents of the autoclave are evaporated until a volume of approximately 10-20 ml is obtained, then the reaction mass is precipitated with n-heptane. The precipitated terpolymer is separated and then dried under vacuum.
• the operation is carried out in a 160 ml stainless steel reactor.
• the reactor is closed and then two to three purges are carried out with 5 bars of nitrogen.
• the reactor is then placed under vacuum (approximately 100 mbar) and 50 ml of an ethyl acetate solution containing 0.4 ml of TBPP initiator (1.5 mmol), 2.1 g of is introduced by suction.
• EGVE-TMS M3; 13 mmol
• VCA M2; 30 mmol
• 5 g of CTFE (M1; 43 mmol) are then introduced.
• the reactor is closed and the temperature is brought to 70 ° C. for
• Example 2 A second experiment similar to that of Example 2 made it possible to measure a chlorine level equal to 18.0% with a ratio of comparable P2 / P3 units (equal to 0.25), which leads to a molar composition in P1 / P2 / P3 units, for the terpolymer of Example 2, estimated at 52/10/38.
• CTFE / VCA / EGVE-TMS M1 / M2 / M3 in ethyl acetate
• the operation is carried out in a 160 ml stainless steel reactor.
• the reactor is closed and then two to three purges are carried out with 5 bars of nitrogen.
• the reactor is then placed under vacuum (approximately 100 mbar) and 50 ml of an ethyl acetate solution containing 0.4 ml of TBPP initiator (1.5 mmol), 2.1 g of is introduced by suction.
• EGVE-TMS M3; 13 mmol
• 5.03 g of VCA M2; 58 mmol
• CTFE 7 g of CTFE (M1; 60 mmol) are introduced.
• the temperature is brought to 70 ° C. for 4 h with stirring with an initial pressure of approximately 5 bars.
• the contents of the autoclave are evaporated until a volume of about 10-20 ml is obtained and 50 ml of methanol are added to deprotect the alcohol function of P3.
• the mixture is left under stirring for 12 h at room temperature then the reaction mass is again evaporated until a volume of approximately 20 ml is obtained. It is precipitated with n-heptane.
• the precipitated P1 / P2 / P3 terpolymer is separated and then dried under vacuum. 5 g of terpolymer soluble in the usual solvents (acetonitrile, THF) are thus obtained.
• the analyzes of the terpolymer obtained are reported below:
• the operation is carried out in a 300 ml stainless steel reactor.
• the reactor is closed, then two to three purges are carried out with 5 bars of nitrogen.
• the reactor is then placed under vacuum (approximately 100 mbar) and 150 ml of a solution of F141 b® containing 1.5 ml of TBPP initiator (5.6 mmol), 12.6 g of EGVE are introduced by suction.
• -TMS M3; 78 mmol
• 15.6 g of VCA M2; 182 mmol
• 7.2 g of diethyl phosphite 52 mmol
• 30.5 g of CTFE (M1; 257 mmol) are then introduced.
• the reactor is closed and the temperature is brought to 70 ° C.
• the graph in FIG. 3 represents the glass transition temperature (Tg) in ° C as a function of the% of vinylene carbonate (VCA) incorporated in the terpolymer according to the invention. It is found that the Tg increases with the% of VCA and that it is between approximately 60 and 90 ° C. when the content of motif P2 is between approximately 20 and 50 mol%.
• Infrared analysis shows the appearance of the characteristic acrylate bands.
• DAROCUR 1173® About 1 ml of this solution is deposited in a aluminum dish (diameter 5 cm) then the solvent is evaporated in order to prepare a film. This film is then exposed under UV. After three passages for 300 ms, the disappearance of the acrylate bands is observed in infrared analysis. The product thus obtained becomes insoluble in the usual solvents (acetone), which indicates crosslinking of the matrix.
• a control reaction carried out without a photoinitiator, shows that the oligomer does not crosslink, the acrylate bands are always present on the infrared spectrum and the product remains soluble in acetone after UV exposure. Similarly, a check carried out on this polymer shows that the acrylate bands remain stable at 54 ° C. for 4 hours. This clearly demonstrates that the polymer crosslinks by photochemical initiation and not by a thermal or degradation process.
• a mixture comprising by mass 50% of the polymer resulting from the first step of Example 7 above and 50% of trifluoroethyl acrylate is used as reactive diluent.
• the two products form a mixture of a transparent and liquid resin.
• This mixture is dissolved in 1, 1, 2 trichloroethane in the presence of the same photoinitiator as in the third step of Example 7. After a single passage under UV for 300 ms, crosslinking is observed leading to disappearance infrared acrylate bands and an insolubility of the product obtained after UV irradiation.
• the two compositions C1 and C2 are prepared, making it possible to produce a fiber according to the invention.
• Two different compositions comprising a commercial photoinitiator, the reactive terpolymer P of Example 7 above, and a reactive diluent composed of two monomers in different proportions according to the composition, the two monomers being (D1) and (D2).
• the photo-initiator can for example be a hydroxyketone (IRGACURE 184, DAROCUR 1173), a mono acyl phosphine (DAROCUR TPO) or a bis acyl phosphine (IRGACURE 819).
• D1 and D2 can be monomers having at least one acrylic, methacrylic, ⁇ -fluoroacrylic,, ⁇ -difluoroacrylic or vinyl function comprising halogen groups (fluorinated and chlorinated).
• compositions C1 and C2 prepared from the mixture of reactive terpolymer P of Example 7, the reactive diluent D1 being trifluoroethyl acrylate (including the homopolymer at 20 ° C has a refractive index equal to 1.407), and the reactive diluent D2 being trifluoroethyl methacrylate (the homopolymer of which at 20 ° C. has a refractive index equal to 1.437).
• the photoinitiator is from the class of bis acyl phosphines (BAPO - IRGACURE 819). The quantities are calculated for 700 grams of composition.
• the ratio, in% by weight, of terpolymer P to the sum of the constituents of each composition is constant, while within the reactive diluent the relative proportion, in% by mass of D1 relative to the sum of D1 and D2 , varies from composition to composition. This allows control the viscosity of the two compositions while varying the refractive index of each of these compositions.
• the continuous index variation is created by producing an active mixture of the two starting compositions C1 and C2.
• a mixing means which can be a static or dynamic type mixer. This implementation is explained in detail in the document
• EP-1 067 222 which is incorporated here by reference. We will therefore not return here more to the operation of the static or dynamic mixer used in the method according to the invention, and we will be content to simply describe the method of the invention in its implementation using the 'one of the static mixers described in document EP-1 067 222.
• FIG. 1 represents a very schematic sectional view, in a plane comprising a central axis X, of a device for manufacturing an optical fiber according to the method of the invention.
• the device 10 comprises a static mixer 1.
• the compositions C1 and C2 of the table above are mixed there.
• the mixer 1 comprises two concentric cylinders 3 and 4 serving as reservoirs for the compositions C1 and C2. It is the cylindrical enclosure 8 of the mixer 1 which serves as a reservoir 4 for the composition C2.
• the composition C1 with the highest refractive index is placed in the central reservoir 3.
• the enclosure 8 comprises a sealed upper closure 8d which has two respective inlets 8g and 8f making it possible to ensure a controlled pressure in each of the respective tanks 3 and 4, for example by means of two positive displacement pumps (not shown).
• the enclosure 8 also includes an area 8e where the two reservoirs 3 and 4 are concentric, isolated from one another, as well as an area 8a whose upper limit is the bottom of the central reservoir 3 and whose lower limit is the bottom of the peripheral reservoir 4.
• Zone 8a corresponds to a zone for mixing the two compositions C1 and C2 by the mixer 1, namely a set 2 of plates (2a, 2b) superimposed and perforated with holes 12.
• the enclosure 8 also includes a conical zone 8b where a homothetic variation of the section occurs, and finally a calibrated zone 8c comprising a die 15, which gives the desired order of magnitude to the diameter of a plastic optical fiber with index gradient 6 obtained.
• the fiiere 15 is an insert, which allows the calibration to be easily changed without having to change the mixer 1.
• the mixer 1 has in its zone 8a at least two, and here seven, perforated plates (2a, 2b) superimposed one above the other.
• This set 2 of plates (2a, 2b) is placed at the lower end of the central reservoir 3 so as to ensure a radial mixing of the compositions C1 and C2.
• a mixture 5 is obtained having a concentration gradient of compositions C1 and C2, in zone 8a.
• the mixture 5 is formed by the superposition of the plates (2a, 2b).
• Each plate 2a (respectively 2b) has holes 12, generally arranged in opposition with respect to each other from a plate 2a to an adjacent plate 2b (respectively from a plate 2b to an adjacent plate 2a).
• the mixture 5 thus obtained is brought to the calibrated die 15 from the zone 8c of the enclosure 8 by the conical zone 8b, the upper limit of which is the lower end of the last plate 2a.
• This variation homothetic makes it possible to preserve the form of the variation in concentration of the compositions C1 and C2.
• the wire obtained which is a plastic optical fiber with an index gradient, 6, is drawn by a capstan 10.
• the plastic optical fiber 6 is hardened by photocrosslinking with using a source 7 of ultraviolet (UV) rays in a polymerized plastic optical fiber 9.
• UV ultraviolet
• the plastic optical fiber 9 is wound on a reel 11.
• the diameter of the fiber 9 is given by the die 15, but it can be refined according to the strength of the spinning carried out by means of the capstan 10.
• FIG. 2 shows a schematic view of the index profile obtained for an optical fiber manufactured by the device of Figure 1.
• the profile of the refractive index n of the optical fiber 6 of Figure 1 practically smoothed so as to form a gradient of parabolic shape, as a function of the distance r from the center of the fiber 6, which is on the axis X.
• compositions and examples given are for information only, and they can be modified without departing from the scope of the invention as long as the terpolymer P retains the general characteristics mentioned above.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Manufacturing & Machinery (AREA)
• Health & Medical Sciences (AREA)
• Ophthalmology & Optometry (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Macromonomer-Based Addition Polymer (AREA)

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• 2001
  • 2001-11-19 FR FR0115037A patent/FR2832515B1/fr not_active Expired - Fee Related
• 2002
  • 2002-11-18 EP EP02803434A patent/EP1451004A1/de not_active Withdrawn
  • 2002-11-18 CN CNA028229797A patent/CN1589198A/zh active Pending
  • 2002-11-18 KR KR10-2004-7006776A patent/KR20040066803A/ko not_active Withdrawn
  • 2002-11-18 WO PCT/FR2002/003931 patent/WO2003043804A1/fr not_active Ceased
  • 2002-11-18 US US10/493,998 patent/US7099546B2/en not_active Expired - Fee Related
  • 2002-11-18 JP JP2003545463A patent/JP2005509911A/ja not_active Withdrawn

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