JP2007058047A - Core material for plastic optical fiber and plastic optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a core material for a POF (Plastic Optical Fiber) for obtaining the POF that excels in heat resistance and transmission properties. <P>SOLUTION: The core material for the POF is composed of a copolymer (X) which has a lactone ring structure expressed in general formula (1) and formed by copolymerizing α-(hydroxy alkyl) acrylic ester monomer (A) with a monomer mixture containing this monomer (A) and a vinyl-polymerizable monomer (B) and then by giving cyclic condensation reaction, and which has a glass transition temperature in the range of 115-160°C, wherein the number of foreign substances having size of ≥0.5 μm measured by a particle counter and contained in the copolymer (X) is ≤20,000 pieces/g. In general formula (1), R<SP>1</SP>, R<SP>2</SP>and R<SP>3</SP>denote organic residues that can independently contain hydrogen atoms or oxygen atoms of carbon contents 1-20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a core material having transparency, low transmission loss, and excellent heat resistance, and a plastic optical fiber using the core material.

  Plastic optical fibers (hereinafter abbreviated as “POF”) have been put to practical use in lighting, FA, and communication fields, taking advantage of their low cost, light weight, flexibility, and large diameter. The one using a system called “PMMA” is the mainstream.

  POF with PMMA as a core material has a glass transition temperature (Tg) of PMMA of about 110 ° C., so that the actual usable temperature is about 110 ° C. even when a higher heat resistant polymer is coated on the outside. It is an upper limit. For this reason, use of a material having higher heat resistance than PMMA as a core material is being studied in applications where further heat resistance is required.

  For example, polycarbonate (Patent Document 1), (Patent Document 2), amorphous polyolefin having an alicyclic group with high heat resistance in the main chain (Patent Document 3), (Patent Document 4), (Non-Patent Document 1) There have been proposed POFs having various materials as core materials.

  However, POF using polycarbonate as the core material has difficulty in refining the core material, removing foreign matter, and the like, and light scattering loss due to density fluctuation of the polymer itself has a finite size. Compared with POF as a core material, transmission characteristics are greatly inferior.

  In addition, a polymer having an alicyclic group in the main chain marketed by each company is difficult to purify, and POF using these as a core material is the same as the POF using polycarbonate as a core material. Since the light scattering loss derived from the above has a finite size, the transmission performance is inferior.

  In order to solve such problems, a copolymer of methacrylate having an alicyclic group in the side chain such as bornyl methacrylate, adamantyl methacrylate, tricyclodecanyl methacrylate and the like and methyl methacrylate (hereinafter referred to as “MMA”) is used. POFs having relatively good transmission characteristics as core materials have been proposed (Patent Document 5) and (Patent Document 6).

However, a polymer having a monomer unit of (meth) acrylate having an alicyclic side chain as described above tends to have low thermal decomposition resistance. For this reason, the POF using the polymer as a core material has a problem in that transmission characteristics are deteriorated and spinning stability is extremely inferior because the core material is significantly deteriorated when the POF is spun by melt spinning.
JP-A-6-200004 JP-A-6-200005 JP-A-4-365003 JP 2001-174647 A Japanese Patent Laid-Open No. 63-74010 JP-A 63-163306 Tanaka Akira, 8th POF Consortium Lecture Collection, POF Consortium, April 26, 1995, p. 7-15

  An object of the present invention is to find a resin capable of reducing the content of foreign matters and impurities contained in a resin, and to use this resin to reduce transmission loss and to obtain a plastic optical fiber having excellent heat resistance. It is to provide a core material for plastic optical fiber.

  The present inventors have synthesized a polymer having a lactone ring formed in a main chain by copolymerization of an α-hydroxymethyl acrylate monomer and a vinyl polymerizable monomer and then a cyclization condensation reaction. Despite having an alicyclic structure that has been difficult to purify and has a large optical transmission loss in the past, coalescence can be used as a core material for optical fibers because it can reduce the content of foreign substances and impurities. In this case, the light scattering loss can be reduced, and since the polymer has a high glass transition temperature, the knowledge that it can be suitably used as a core material of an optical fiber placed in a high temperature environment, Based on this knowledge, the present invention has been accomplished.

  That is, the present invention relates to an α- (hydroxyalkyl) acrylic acid ester monomer (A) and a monomer (B) capable of vinyl polymerization with the α- (hydroxyalkyl) acrylic acid ester monomer (A). Formed by copolymerization of a monomer mixture containing the following general formula (1):

(Wherein R ^1, R ² , and R ³ independently represent a hydrogen atom or an organic residue that may contain an oxygen atom having 1 to 20 carbon atoms). A core material for a plastic optical fiber comprising a copolymer (X) having a glass transition temperature in the range of 115 ° C. to 160 ° C.,
The present invention relates to a plastic optical fiber core material characterized in that the number of foreign matters of 0.5 μm or more measured with a particle counter contained in copolymer (X) is 20000 / g or less.

  Further, the present invention provides a compound represented by the general formula (2)

In the formula, R ^{4 to} R ⁸ independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a hydroxyl group, or an alkoxy group having 1 to 5 carbon atoms. Monomer containing α- (hydroxyalkyl) acrylate monomer (A), α- (hydroxyalkyl) acrylate monomer (A) and vinyl polymerizable monomer (B) Formed by copolymerizing the mixture and then subjecting it to a cyclization condensation reaction, general formula (1)

(Wherein R ^1, R ² , and R ³ independently represent a hydrogen atom or an organic residue that may contain an oxygen atom having 1 to 20 carbon atoms). , A plastic optical fiber core material comprising a copolymer (X) having a glass transition temperature in the range of 115 ° C. to 160 ° C.,
The plastic optical fiber, wherein the content of the compound represented by the general formula (2) in the α- (hydroxyalkyl) acrylate monomer (A) contained in the monomer mixture is 100 ppm or less Related to core material.

  Moreover, this invention is comprised from the core part containing the core material for plastic optical fibers in any one of Claims 1-6, and the clad part which has a refractive index 1% or more lower than the refractive index of a core part, 25-5m The present invention relates to a plastic optical fiber characterized in that the transmission loss measured by the cut back method is 400 dB / Km or less.

  The plastic optical fiber core material of the present invention can reduce the transmission loss and obtain a plastic optical fiber with excellent heat resistance by using a resin capable of reducing foreign substances and impurities contained therein.

  The core material for plastic optical fibers of the present invention comprises an α- (hydroxyalkyl) acrylate monomer (A) and a monomer capable of vinyl polymerization with the α- (hydroxyalkyl) acrylate monomer (A). Formed by copolymerizing a monomer mixture containing the product (B) and then subjecting it to a cyclization condensation reaction.

(Wherein R ^1, R ² , and R ³ independently represent a hydrogen atom or an organic residue that may contain an oxygen atom having 1 to 20 carbon atoms). , A core material for plastic optical fibers made of a copolymer (X) having a glass transition temperature in the range of 115 to 160 ° C., measured by a particle counter contained in the copolymer (X) of 0.5 μm or more. The number of foreign matters is 20000 pieces / g or less.

  Moreover, the core material for plastic optical fibers of the present invention has the general formula (2)

In the formula, R ^{4 to} R ⁸ independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a hydroxyl group, or an alkoxy group having 1 to 5 carbon atoms. Monomer containing α- (hydroxyalkyl) acrylate monomer (A), α- (hydroxyalkyl) acrylate monomer (A) and vinyl polymerizable monomer (B) Formed by copolymerizing the mixture and then subjecting it to a cyclization condensation reaction, general formula (1)

(Wherein R ^1, R ² , and R ³ independently represent a hydrogen atom or an organic residue that may contain an oxygen atom having 1 to 20 carbon atoms). , A plastic optical fiber core material comprising a copolymer (X) having a glass transition temperature in the range of 115 ° C. to 160 ° C.,
The content of the compound represented by the general formula (2) in the α- (hydroxyalkyl) acrylate monomer (A) contained in the monomer mixture is 100 ppm or less.
[Α- (hydroxyalkyl) acrylic acid ester monomer (A)]
The α- (hydroxyalkyl) acrylic acid ester monomer (A) used for the plastic optical fiber core material of the present invention can be represented by the general formula (3).

In the formula, R ² and R ³ independently represent a hydrogen atom or an organic residue that may contain an oxygen atom having 1 to 20 carbon atoms.

In general formula (3), the organic residue which may contain an oxygen atom having 1 to 20 carbon atoms represented by R ² and R ³ is an alkyl group having 1 to 20 carbon atoms or an alkoxy having 1 to 20 carbon atoms. Group, an alkoxycarbonyl group having 1 to 20 carbon atoms, an acyl group having 1 to 20 carbon atoms, and the like.

  Examples of the compound represented by the general formula (3) include methyl α- (hydroxymethyl) acrylate, ethyl α- (hydroxymethyl) acrylate, isopropyl α- (hydroxymethyl) acrylate, α- (hydroxymethyl). ) N-butyl acrylate, t-butyl α- (hydroxymethyl) acrylate, 2-ethylhexyl α- (hydroxymethyl) acrylate, and the like, among these, α- (hydroxymethyl) methyl acrylate , Α- (hydroxymethyl) ethyl acrylate is preferable, and among them, α- (hydroxymethyl) methyl acrylate is particularly preferable because the effect of improving heat resistance is remarkable. These may be used alone or in combination of two or more.

  Here, the α- (hydroxyalkyl) acrylic acid ester is very easily polymerized and polymerizes and solidifies when left at room temperature or higher. Therefore, the α- (hydroxyalkyl) acrylic acid ester has a general formula when stored. (2)

(Wherein R ^{4 to} R ⁸ each independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a hydroxyl group, or an alkoxy group having 1 to 5 carbon atoms) was added in a predetermined amount. Those are preferred. Examples of the compound represented by the general formula (2) include hydroquinone monomethyl ether (methoquinone), hydroquinone monoethyl ether, 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, 2-tert- Butyl-4-methoxyphenol, 2,4,6-trimethylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert -Butyl-4-hydroxytoluene, 2,4,6-tri-tert-butylphenol and the like can be mentioned.

  In the core material for plastic optical fibers of the present invention, the monomer (A) stored by adding the compound represented by the general formula (2) is used in a monomer mixture of a copolymer. The content of the compound represented by the general formula (2) is 100 ppm or less. More preferably, it is 60 ppm or less, More preferably, it is 30 ppm or less. When the content of the compound represented by the general formula (2) is 100 ppm or less, the polymerizability is not significantly reduced, and when the POF is spun during polymerization or after polymerization, the polymer is not colored and the POF In the core material, an increase in transmission loss can be suppressed even in an initial and high temperature environment, which is preferable.

  In order to reduce the content of the compound represented by the general formula (2) in the α- (hydroxyalkyl) acrylate ester to 100 ppm or less, distillation or adsorption treatment is performed immediately before the polymerization with the monomer (B). And a method of carrying out copolymerization by mixing with the monomer (B) immediately after setting the content of the compound represented by the general formula (2) to 100 ppm or less.

The amount of α- (hydroxyalkyl) acrylic acid ester used is in the total monomer mixture for obtaining the vinyl copolymer (x) as the precursor of the copolymer (X) having a lactone ring structure. The content of can be 10 to 60% by mass, preferably 20 to 55% by mass, and more preferably 30 to 50% by mass. When the content of the α- (hydroxyalkyl) acrylic acid ester is 10% by mass or more, a copolymer (X) having a sufficiently formed lactone ring unit can be obtained, and a copolymer having heat resistance ( X) can be obtained to obtain a plastic optical fiber that can be used at high temperatures. When the content of the α- (hydroxyalkyl) acrylic acid ester is 20% by mass or more and 30% by mass or more, such an effect can be obtained more remarkably. Further, when the content of α- (hydroxyalkyl) acrylic acid ester is 60% by mass or less, the copolymer (X) can be stably molded without increasing the viscosity, and maintains transparency. can do. When the content of the α- (hydroxyalkyl) acrylic acid ester is 55% by mass or less and 50% by mass or less, such an effect can be obtained more remarkably.
[Monomer (B)]
The unit (A) of the α- (hydroxyalkyl) acrylate monomer and the monomer (B) capable of vinyl polymerization preferably include (meth) acrylate (B1) as a main component, In addition, the monomer (B2) which has an acid group can be mentioned, Furthermore, the other vinyl polymerizable monomer (B3) may be included as needed.

  Examples of the (meth) acrylic acid ester (B1) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylic acid. n-butyl, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 2- (meth) acrylate 2- Hydroxyethyl and the like can be mentioned. Among these, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n (meth) acrylate Those having a small number of carbon atoms in the ester group such as -butyl, isobutyl (meth) acrylate, and t-butyl (meth) acrylate are preferred. These may be used alone or in combination of two or more.

  The ratio of the (meth) acrylic acid ester (B1) in the monomer component is not particularly limited, but is preferably 50 to 80% by weight in the total monomer components.

  Examples of the monomer (B2) having an acid group include monomers having a carboxyl group such as (meth) acrylic acid, itaconic acid, maleic acid monoester, and itaconic acid monoester, and acids such as maleic anhydride and itaconic anhydride. Monomers having an anhydride group, monomers having a phosphoric acid group, monomers having a sulfonic acid group, monomers having a phenol group, and the like are mentioned. Among them, (meth) acrylic acid is the heat resistance of the copolymer (X). This is preferable from the viewpoint of excellent improvement effect. These may be used alone or in combination of two or more.

  The ratio of the monomer (B2) having an acid group in the monomer component is in the range of 1 to 10% by mass, preferably 1 to 5% by mass in the total monomer components. If the content of the monomer component (B2) having an acid group in the monomer component is 10% by mass or less, the copolymer (X) having excellent molding stability and suppressing the increase in viscosity Can be obtained. On the other hand, when the content is 1% by mass or more, lactone cyclization of the polymerization precursor (x) is efficient, and the copolymer (X) can be made excellent in heat resistance.

  Specific examples of the other copolymerizable monomer (B3) include styrene, vinyl toluene, α-methyl styrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, vinyl chloride, and vinyl acetate. Can do. Among these, styrene, α-methylstyrene, and acrylonitrile are preferable in that the heat resistance can be further improved. In addition, these may use only 1 type or may use 2 or more types together.

The ratio of the copolymerizable monomer (B3) in the monomer component is not particularly limited, but is preferably 30% by weight or less in the total monomer component.
[Monomer mixture]
As a monomer mixture in the core material for plastic optical fibers of the present invention, any one may be used as long as it contains the α- (hydroxyalkyl) acrylate monomer (A) and the monomer (B). However, depending on the polymerization method, it may optionally contain a solution, a polymerization initiator, a chain transfer agent, and other functions are added to the copolymer obtained as necessary. It may contain a functional substance.
[Copolymerization of monomer mixture]
As a method of copolymerizing the monomer mixture to obtain the vinyl copolymer (x) which is a precursor of the copolymer (X), solution polymerization or bulk polymerization is preferable, and solution polymerization is particularly preferable.

  The solvent used in the solution polymerization is not particularly limited. For example, a solvent used in a normal radical polymerization reaction can be used, and ketones such as methyl ethyl ketone (MEK) and methyl isobutyl ketone; aromatics such as toluene, xylene, and ethylbenzene. Group hydrocarbons; ethyl esters such as ethyl acetate and butyl acetate; chloroform, DMSO, tetrahydrofuran and the like. Also, if the boiling point of the solvent used is too high, the residual volatile content in the resin after deaeration will increase, so that the polymer is dissolved at the treatment temperature and the boiling point is in the range of 50 to 200 ° C. For example, preferable examples include ketones such as methyl ethyl ketone and aromatic hydrocarbons such as toluene.

  The amount of the solvent to be contained in the monomer mixture of the solution polymerization reaction may be in a range where the concentration of the monomer in the polymerization reaction mixture is 10 to 80% by mass, preferably 20 to 70% by mass, More preferably, it is 30-60 mass%. If the concentration of the monomer in the polymerization reaction mixture is 10% by mass or more, volatilization of the solvent can be suppressed, and the polymerization reaction can proceed efficiently. If the concentration of the monomer is 20% by mass or more and 30% by mass or more, the above effect can be obtained more remarkably. On the other hand, if the monomer concentration is 80% by mass or less, the increase in polymerization viscosity can be suppressed, so that handling becomes easy, and if the monomer concentration is 70% by mass or less and 60% by mass or less, it takes. The effect can be obtained more remarkably.

  An initiator may be added to the solution polymerization reaction mixture as necessary. The initiator is not particularly limited. For example, 2,2′-azobis (2-methylpropionate), 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexanecarbonitrile) 2,2′-azobis (2,4-divaleronitrile), 2,2′-azobis (dimethyl isobutyrate), 2,2′-azobis (cyanovaleric acid), 2,2′-azobis (2, And azo compounds such as 4,4-trimethylpentane) and organic peroxides such as t-butylperoxyisopropyl carbonate and t-amylperoxy-2-ethylhexanoate. These may be used alone or in combination of two or more. Among these, 2,2′-azobis (2-methylpropionate) or 2,2′-azobis (dimethyl isobutyrate) is particularly preferable in terms of improving the optical properties of the obtained polymer. The usage-amount of these polymerization initiators can be made into the range of 0.001-3 mass parts with respect to 100 mass parts of said monomer components, for example.

  Furthermore, you may add a chain transfer agent to the said mixture of the solution polymerization reaction as needed. Although it does not specifically limit as a chain transfer agent, For example, alkyl mercaptans, such as n-propyl mercaptan, n-butyl mercaptan, t-butyl mercaptan, n-hexyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, can be mentioned. . Of these, alkyl mercaptans having 3 to 6 carbon atoms such as n-butyl mercaptan and t-butyl mercaptan are preferable, and n-butyl mercaptan is particularly preferable because of low boiling point and easy volatilization removal. These chain transfer agents can be used in an amount of, for example, 3 parts by mass or less with respect to 100 parts by mass of the monomer component.

The temperature and polymerization time in the solution polymerization reaction can be appropriately selected according to the type of monomer used, the ratio of use, etc., and can be set to a polymerization temperature of 0 to 150 ° C. and a polymerization time of 0.5 to 20 hours. The polymerization time is preferably 80 to 140 ° C. and the polymerization time is 1 to 10 hours. Under such conditions, a copolymer in which the monomer is polymerized can be obtained. The obtained copolymer can be purified by a known method, and a vinyl copolymer (x) which is a precursor of the copolymer (X) having a lactone ring unit can be obtained.
[Cyclocondensation reaction]
After obtaining the precursor vinyl copolymer (x), the structural unit derived from the α- (hydroxyalkyl) acrylate ester in the vinyl copolymer (x) is then cyclized and condensed almost quantitatively. By carrying out the reaction (lactone cyclization reaction), a copolymer (X) having a lactone ring unit represented by the general formula (1) can be obtained.

In the formula, R ^1, R ² and R ³ independently represent a hydrogen atom or an organic residue which may contain an oxygen atom having 1 to 20 carbon atoms.

  The cyclocondensation reaction is adjacent to a hydroxyl group derived from an α- (hydroxyalkyl) acrylate monomer (A) unit in a molecular chain formed by polymerizing the monomer component. an ester group derived from an α- (hydroxyalkyl) acrylic acid ester monomer (A) unit, or an ester group (B1) or acid group (B2) derived from a monomer (B) unit copolymerizable therewith; Is a reaction in which a lactone ring is formed in the molecular chain of the polymer (in the main skeleton of the polymer), and water and alcohol are by-produced by lactone cyclization. Thus, by using a polymer having a lactone ring structure formed in the main skeleton of the polymer as the core material, the performance required for the POF core material such as transparency and heat resistance can be improved. The copolymer (X) is a polymer in which the α- (hydroxyalkyl) acrylate monomer (A) unit is lactone-cyclized almost quantitatively. It is not necessary for all of the units of the monomer (A) to be lactone cyclized, and the lactone cyclization rate is preferably 90 mol% or more, more preferably 95 mol% or more.

As a method for obtaining a copolymer (X) having a lactone ring structure by lactone cyclization of the vinyl copolymer (x), a vinyl copolymer (x ) And a solvent,
(I) A method in which a catalyst is added and heat-reacted without applying pressure or under pressure (ii) A method in which a heat-reaction is carried out without using a catalyst and without applying pressure or under pressure.

  In this lactone cyclization condensation step, the “mixture containing the vinyl copolymer (x) and the solvent” used in the cyclization condensation reaction may be a mixture of the polymerization reaction products obtained in the solution polymerization step. Further, after removing the solvent from these, a solvent suitable for the cyclization condensation reaction may be added again.

  As the catalyst used in the above method (i), known catalysts can be used, and generally used esterification catalysts or transesterification catalysts such as p-toluenesulfonic acid, organic acids, organic phosphorus compounds, basic compounds, Examples thereof include organic carboxylates and carbonates. When the monomer (B2) having an acid group is used in the vinyl copolymerization reaction, the monomer having an acid group and / or the resulting polymer is converted into a lactone cyclization reaction of the vinyl copolymer (x). Since it sometimes acts as a catalyst, it is possible to carry out the lactone cyclization reaction simultaneously with the vinyl polymerization reaction without adding a separate catalyst for the lactone cyclization.

  The catalyst may be added at the beginning of the reaction or in the middle of the reaction, or may be added in two or more portions. The addition amount of the catalyst can be 0.001 to 10% by mass, preferably 0.01 to 5% by weight, based on the precursor vinyl copolymer (x). As the heating temperature and the heating time in method (i), it is preferable to select a range in which a sufficient lactone cyclization rate is obtained and the resin is not colored or decomposed. The heating time is, for example, 1 to 20 hours, preferably 2 to 10 hours.

  Examples of the method (ii) include a method in which a mixture of polymerization reaction products obtained in the solution polymerization reaction step is heated as it is using a pressure-resistant kettle or the like. As the heating temperature and the heating time, it is preferable to select a range in which a sufficient lactone cyclization rate is obtained and the resin is not colored or decomposed. As the heating temperature, for example, 100 ° C. or more can be mentioned, Preferably it is 150 degreeC or more. As heating time, 1 to 20 hours can be mentioned, for example, Preferably it is 2 to 10 hours.

  Both the above methods (i) and (ii) can be performed under pressure depending on the conditions.

  Here, the copolymer (X) having a lactone ring unit obtained by the above method includes a solvent, volatile components of residual monomers, and alcohol and water by-produced by condensation cyclization reaction of lactone cyclization reaction. However, if the amount of volatile components remaining in the copolymer (X) increases, coloring, bubbles, silver streaks, etc. occur, resulting in a decrease in transmission characteristics. Since problems arise, it is preferable to remove volatile components. As a method for removing volatile components, a method for removing them under reduced pressure heating conditions can be cited as necessary. As a device for performing this method, a vacuum device, a heating furnace having a degassing device, a reaction device, An extruder with a volatilizer can be used.

  As a method for removing the volatile component, it is preferable to perform the lactone cyclization condensation reaction in the presence of a solvent and also use a degassing treatment in combination. By carrying out the cyclization condensation reaction in the presence of a solvent, it is possible to carry out a high-yield reaction and forcibly remove the alcohol and water by-produced by the cyclization condensation reaction. This is advantageous because it moves to the production side. Furthermore, the process cost can be reduced as compared with the method in which the condensation cyclization reaction and the deaeration treatment are individually performed.

  In the case of a form in which the cyclization condensation reaction and the degassing treatment are used in combination, as a device to be used, a degassing device equipped with a heat exchanger and a degassing tank, an extruder with a vent, these degassing devices and an extrusion device are used. Although the apparatus which has arrange | positioned the machine in series can be used, it is preferable to use the deaeration apparatus provided with the heat exchanger and the deaeration tank, and the extruder with a vent.

  In the case of using a degassing apparatus comprising this heat exchanger and degassing tank, the reaction / treatment temperature can be appropriately selected depending on the vaporization temperature of the monomer used, and can be in the range of 150 to 350 ° C., for example. , Preferably it is the range of 200-300 degreeC. If the said temperature is 150 degreeC or more, a condensation cyclization reaction will advance and reduction of a residual volatile matter can be aimed at, and if it is 350 degrees C or less, decomposition | disassembly of a product will be suppressed and coloring etc. will be suppressed. Can do. The pressure during the reaction / treatment is preferably in the range of 931 to 1.33 hPa (700 to 1 mmHg), and more preferably in the range of 798 to 66.5 hPa (600 to 50 mmHg). If the said pressure is 1.33 hPa or more, the residual amount of volatile matters including alcohol and water can be reduced, and if it is 931 hPa or less, industrial implementation can be made possible.

  When using an extruder with a vent, the number of vents may be one, but it is preferable to have a plurality of vents. The reaction / treatment temperature in the extruder with a vent can be appropriately selected depending on the vaporization temperature of the monomer used, and can be, for example, in the range of 150 to 350 ° C., preferably in the range of 200 to 300 ° C. . If the said temperature is 150 degreeC or more, a condensation cyclization reaction will advance and reduction of a residual volatile matter can be aimed at, and if it is 350 degrees C or less, decomposition | disassembly of a product will be suppressed and coloring etc. may be suppressed. Can do. The pressure during the reaction / treatment is preferably in the range of 931 to 1.33 hPa (700 to 1 mmHg), and more preferably in the range of 798 to 13.3 hPa (600 to 10 mmHg). If the said pressure is 1.33 hPa or more, the residual amount of volatile matters including alcohol and water can be reduced, and if it is 931 hPa or less, industrial implementation can be made possible.

  When both the cyclization condensation reaction and the deaeration process are performed simultaneously, for example, when heat treatment is performed at a high temperature near 250 ° C. or higher using a twin-screw extruder, the difference in thermal history As described above, there is a possibility that some decomposition occurs before the condensation cyclization reaction occurs, and that the physical properties of the copolymer (X), which is a reaction product, may change due to the severe conditions. It is preferable to use a catalyst for a dealcoholization reaction and under a mild condition as much as possible using an extruder with a vent.

  Furthermore, when a cyclization condensation reaction and a degassing treatment are used in combination, the degassing treatment is not allowed to proceed simultaneously throughout the condensation cyclization reaction process, but only in part of the condensation cyclization reaction process. You can also. For example, a copolymer (X) in which only the condensation cyclization reaction proceeds in advance to produce a lactone ring unit in part is produced, and then the condensation cyclization reaction and the deaeration treatment are performed simultaneously, The form in which the reaction is completed by performing the production is preferable because the reaction conditions when used in combination with the degassing treatment can be relaxed and deterioration of physical properties can be suppressed. At this time, the cyclization condensation reaction performed in advance before the degassing treatment can be 50% or more, preferably 60% or more, more preferably 70% or more, using the lactone cyclization rate as a guide. . If the lactone cyclization rate is 50% or more, the resulting copolymer (X) can be highly prevented from being altered, and if the lactone cyclization rate is 60% or 70% or more, such an effect is obtained. Can be obtained more remarkably. Specifically, the condensation cyclization reaction is allowed to proceed to a certain reaction rate in the presence of a solvent in advance using a kettle-type reactor, and then a reactor equipped with a degassing device, for example, a heat exchanger And a deaeration device comprising a deaeration tank, an extruder with a vent, and the like that complete the condensation cyclization reaction. At this time, the condensed cyclization reaction is more preferably performed in the presence of a catalyst. The copolymer (X) obtained in such a form that precedes such a condensation cyclization reaction and then combines the condensation cyclization reaction and the deaeration reaction has a higher glass transition temperature and a higher cyclization condensation reaction rate. It will be excellent in heat resistance.

  The removal of the volatile component by the degassing treatment is such that the volatile content remaining in the copolymer (X) is 3.0% by mass or less, preferably 1.5% by mass or less, more preferably 0.5% by mass or less. It is preferable to carry out until it becomes. When the residual volatile content of the volatile component is 3.0% by mass or less, the initial transmission characteristics of POF and the transmission characteristics in a heat-resistant environment are excellent.

The lactone cyclization rate can also be determined from the hydroxyl group remaining rate in the copolymer (X), and the hydroxyl group remaining rate in the copolymer (X) is preferably 10 mol% or less, more preferably 5 mol. % Or less. The hydroxyl group residual ratio in the copolymer (X) can be determined from dynamic TG measurement shown in Examples.
[Copolymer (X)]
The molecular weight of the copolymer (X) thus obtained is not particularly limited, but the polystyrene equivalent molecular weight measured by GPC (gel permeation chromatography) is preferably 50,000 or more and 150,000 or less, More preferably, it is 70,000 or more and 125,000 or less. When the molecular weight is 50,000 or more, the POF is not broken when bent, and when the molecular weight is 150,000 or less, the molding stability of the POF is not lowered.

  The copolymer (X) has a glass transition temperature in the range of 115 to 160 ° C., and POF using the copolymer (X) having such a glass transition temperature is a sensor in the semiconductor field and food field. It can be placed in a space where the environmental temperature is 115 ° C. or higher, such as for use or safety control in an in-vehicle LAN. In such a case, Tg of the copolymer (X) is preferably 125 ° C. or higher, more preferably 145 ° C. or higher. When the Tg of the copolymer (X) is 160 ° C. or less, the copolymer (X) can be prevented from becoming brittle, and an increase in the cost of the POF material can be avoided. In the above copolymer (X), the glass transition temperature is appropriately adjusted within the above range by adjusting the composition of the monomer (A) and the monomer (B) and adjusting the molecular weight. Can do. For example, copolymer (X) is obtained by copolymerizing a unit of α-hydroxymethyl acrylate monomer (A) as a monomer unit and a MMA unit as a unit of monomer (B). In the case of a polymer obtained by cyclization condensation of the obtained precursor (x), the unit of α-hydroxymethyl acrylate monomer (A) is used in order to make the glass transition temperature 115 ° C. or higher Is preferably contained in an amount of 10% by mass or more, and if it is contained in an amount of 25% by mass or more, and further 40% by mass or more, a POF having better transmission characteristics, mechanical strength, and heat resistance can be obtained. Specifically, in the case of methyl α-hydroxymethyl acrylate / MMA = 40/60 (mass%), Tg of the copolymer (X) is 150 ° C., and POF using this as a core material is Not only is it excellent in transmission characteristics and mechanical strength, but also heat resistance is dramatically improved compared to POF using PMMA as a core material. Moreover, in the copolymer (X), in order to prevent the problem of POF being thermally contracted, it is preferable to appropriately select the glass transition temperature and the molecular weight within the above-described numerical ranges.

  The copolymer (X) thus obtained has a content of foreign matter having a particle diameter of 0.5 μm or more, measured by a light scattering method using a particle counter, of 20000 pieces / g or less. Preferably it is 10,000 pieces / g or less, More preferably, it is 6000 pieces / g or less, Most preferably, it is 3000 pieces / g or less. If the number of foreign matters of 0.5 μm or more is 20000 pieces / g or less, it is possible to suppress an increase in light scattering loss of the core material, and the POF has excellent transmission characteristics. As the content of foreign matters having a particle diameter of 0.5 μm or more is 10,000 / g or less, 6000 / g or less, and 3000 / g or less, such an effect can be obtained more remarkably. As a method of setting the number of foreign matters in the copolymer (X) to 20000 pieces / g or less, a raw material monomer, a solvent, etc. to be subjected to polymerization are subjected to filter filtration, or a polymerization facility is used before the polymerization operation. Use a solvent that contains a small amount of foreign matter, or use raw materials such as monomer and solvent in the polymerization equipment until the copolymer (X) is taken out to block the foreign matter from the outside. The method of lowering as much as possible can be mentioned.

  Further, the general formula (2) contained in the copolymer (X).

(In the formula, each of R ^{4 to} R ⁸ independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a hydroxyl group, or an alkoxy group having 1 to 5 carbon atoms). Is preferable, and 10 ppm or less is more preferable. When the content is 20 ppm or less, in the POF, coloring due to the compound can be suppressed, and deterioration of initial transmission characteristics and transmission characteristics under a high temperature environment can be suppressed.

  The amount of residual sulfur compound contained in the copolymer (X) is preferably 20 ppm or less, and more preferably 10 ppm or less. If it is 20 ppm or less, coloring can be suppressed and reduction of optical transmission loss can be suppressed in POF placed under high temperature, and excellent transmission characteristics can be obtained. In order to adjust the amount of the residual sulfur compound to 10 ppm or less, the addition amount of the mercaptan compound used as the chain transfer agent and the polymerization conditions (temperature, time, etc.) can be appropriately adjusted. The residual sulfur compound includes a mercaptan compound in a free state in the copolymer (X), a disulfide compound, a compound in which a monomer and a mercaptan are bonded, and the like.

Furthermore, when copolymer (X) contains a MMA unit, it is preferable that content of the MMA dimer contained in copolymer (X) is 5 ppm or less, and it is more preferable that it is 1 ppm or less. If it is 5 ppm or less, coloring can be suppressed and reduction of optical transmission loss in POF can be suppressed, and excellent transmission characteristics can be obtained. In order to reduce the content of MMA dimer to 5 ppm or less, as a pretreatment for performing a vinyl polymerization reaction, a method of reducing dissolved oxygen in the monomer by bubbling the monomer mixture with nitrogen gas or the like, or a monomer mixture Known techniques such as a method of adding a known antioxidant or the like can be applied.
[Optical fiber]
The plastic optical fiber of the present invention comprises a core part including the core material for a plastic optical fiber of the present invention and a clad part having a refractive index lower by 1% or more than the refractive index of the core part, and a 25-5 m cutback method. As long as the transmission loss measured by the above is 400 dB / Km or less, there is no particular limitation.

  The plastic optical fiber of the present invention is provided with a clad composed of a polymer having a refractive index lower by 1% or more than the refractive index of the core material on the outer periphery of the core, and is 1% or higher than the refractive index of the core material. By providing a clad material having a low refractive index, it is possible to increase the aperture angle, reduce the light leakage when the POF is bent, and improve the transmission characteristics.

  The clad provided on the outer peripheral portion of the POF core material of the present invention is not limited to a single-layer structure, and may have a multilayer structure of two or more layers.

  As a clad material used for the POF of the present invention, a known fluoropolymer can be used. Specific examples include fluorine-containing olefin resins and fluorinated methacrylate copolymers. As such a fluorine-containing olefin resin, specifically, a copolymer comprising a vinylidene fluoride unit (VdF) and a tetrafluoroethylene unit (TFE), a copolymer of VdF and a hexafluoropropylene unit (HFP), Copolymer of VdF, TFE and HFP, Copolymer of VdF, TFE, HFP and (perfluoro) alkyl vinyl ether, Copolymer of VdF and hexafluoroacetone, Copolymer of VdF and trifluoroethylene And a copolymer of VdF, TFE, and hexafluoroacetone, and a copolymer of ethylene, TFE, and HFP.

On the other hand, specific examples of the fluorinated methacrylate copolymer include the following general formula (i):
_{CH 2 = CX-COO (CH} 2) m (CF 2) n Y (i)
(Wherein X represents a hydrogen atom, a fluorine atom or a methyl group, Y represents a hydrogen atom or a fluorine atom, m represents 1 or 2, and n represents an integer of 1 to 12). A copolymer of 15 to 90% by mass of the fluoroalkyl (meth) acrylate unit (a) and 10 to 85% by mass of another copolymerizable monomer (b) is preferred. In order to ensure that the glass transition temperature of the clad material satisfies the appropriate conditions, a monomer component that does not decrease transparency is used as another copolymerizable monomer (b) within the above-described monomer composition range. Can be used.

Examples of such monomers include (meth) acrylic acid alkyl esters such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate;
(Meth) acrylic acid (1-methyltricycloheptyl), cyclohexyl (meth) acrylate, methyl cyclohexyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, etc. (Meth) acrylic acid cycloalkyl ester of
(Meth) acrylic acid alicyclic ester having an alicyclic group such as (meth) acrylic acid tricyclodecanyl, (meth) acrylic acid (1-methylhexacyclododecyl) in the side chain;
(Meth) acrylic acid aromatic esters such as phenyl (meth) acrylate and benzyl (meth) acrylate; branched fluorinated alkyl groups such as hexafluoroneopentyl (meth) acrylate and hexafluoroisobutyl (meth) acrylate (Meth) acrylic acid fluorinated ester having in the side chain;
N-substituted maleimides such as N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-cyclohexylmaleimide and N-phenylmaleimide;
α-fluoroacrylic acid esters such as methyl α-fluoroacrylate, α-fluoroacrylic acid 2,2,2-trifluoroethyl, α-fluoroacrylic acid 2,2,3,3,3-pentafluoropropyl, etc. Can be mentioned. Appropriate selection of at least one monomer selected from these monomers, and the physical properties required for POF use such as refractive index, transparency, mechanical strength, and heat decomposability in the polymer. Can be copolymerized by the blending ratio and polymerization method.

  The POF of the present invention may be a sea-island type multi-core POF in which a plurality of island portions are separated from each other and integrated by a common sea portion in addition to the SI-type POF. In the sea-island type multi-core POF, the entire island portion can be a core, or the island portion can be composed of a core and a clad.

  As a method for producing the POF of the present invention, a known method can be used. For example, a solution obtained by dissolving a cladding material in a solvent such as ethyl acetate, dimethylformamide, dimethylacetamide or the like can be obtained by a coating method or a dipping method. A clad can be formed by covering the surface of a separately molded core. In addition, when manufacturing SI type POF, the copolymer (X) and the clad material are supplied to a composite spinning nozzle directly connected to a degassing extruder, and the core and clad are extruded and molded to form POF. The obtained composite spinning method is preferable in terms of excellent spinning stability and productivity.

  The POF of the present invention may have a protective layer on the outer periphery of the clad. Examples of the material of the protective layer include a copolymer of VdF and TFE, a copolymer of VdF, TFE, and HFP, a copolymer of VdF, TFE, HFP, and perfluoro (fluoro) alkyl vinyl ether, and VdF. Copolymer of TFE and perfluoro (fluoro) alkyl vinyl ether, copolymer of ethylene, TFE and HFP, copolymer of TFE and HFP, copolymer of VdF, TFE and hexafluoroacetone, etc. Can be mentioned.

  The protective layer can be formed on the outer periphery of the clad in the same manner as when the clad is formed on the outer periphery of the core. That is, the protective layer can be formed by using a coating method or a dipping method, or by extruding the core, the clad and the protective layer using a composite spinning nozzle. As for the sea-island type POF, a protective layer can be formed on the outer periphery of the POF using a known composite spinning nozzle or the like.

  Furthermore, the POF of the present invention can be made into a POF cable by providing a coating layer in close contact with the outer periphery of the cladding or the outer periphery of the protective layer in order to improve the bending resistance and the heat and moisture resistance. Since the coating layer does not directly contact the core, no particular problem occurs even if the transparency is reduced by crystallization. As a material of the coating layer, various thermoplastic resins generally used as a POF coating material can be used. For example, depending on the environment in which the POF cable is used, polyamide resin, polyethylene resin, polypropylene resin, polyvinylidene chloride resin, chlorinated polyethylene resin, polyurethane resin, vinylidene fluoride resin, various UV / ultraviolet rays One type or a mixture of two or more types selected from the group consisting of cured resins can be used. The method for forming the covering material can be appropriately selected depending on the physical properties of the covering material. A method of coating the POF using a T-type die that pours and coats the melted coating material from the side surface of the traveling POF is preferable because of excellent workability.

  The POF of the present invention, which has a transmission characteristic with a transmission loss of 400 dB / Km or less measured by a 25-5 m cutback method, is used for sensors in the semiconductor field and the food field, or for safety control in an automotive LAN. It can be used for applications.

EXAMPLES Next, although an Example demonstrates this invention concretely, the technical scope of this invention is not limited by these. The abbreviations of monomers used in each Example and Comparative Example indicate the following compounds.
MMA: methyl methacrylate,
RHMA: methyl α- (hydroxymethyl) acrylate MAA: methacrylic acid,
α3FA: α-fluoroacrylic acid 2,2,2-trifluoroethyl,
αFMe: methyl α-fluoroacrylate,
VdF: vinylidene fluoride,
TFE: tetrafluoroethylene,
HFP: hexafluoropropylene,
PFPVE: perfluoropropyl vinyl ether,
PC: Polycarbonate resin (manufactured by Idemitsu Petrochemical Co., Ltd., trade name: Toughlon A1700)
PMMA: Polymethyl methacrylate (Mitsubishi Rayon Co., Ltd.)
PA12: nylon 12 (manufactured by Daicel Degussa, trade name: Daiamide L1640)
[Refractive index]
Using the obtained polymer (pellet), a film-shaped test piece having a thickness of 200 μm was formed by a melt press, and the refractive index (n _D ²⁵ ) of sodium D-line at 25 ° C. was measured using an Abbe refractometer. It was measured.
[Glass transition temperature (Tg)]
A differential scanning calorimeter (DSC) manufactured by Rigaku Corporation, apparatus name: DSC-8230) was used. About 10 mg of the obtained polymer (pellet) was collected in an aluminum pan cell for DSC measurement, and the temperature was raised to 220 ° C. at a temperature rising rate of 10 ° C./min under the condition of a nitrogen flow of about 50 ml / min. After holding for 5 minutes to melt, the temperature is lowered to 0 ° C. at 10 ° C./min, the temperature is raised again at a rate of temperature rise of 10 ° C./min, held for 5 minutes, and the temperature is lowered at 10 ° C./min. The time Tg was determined.
[Dynamic TG]
The obtained polymer (or polymer solution or pellet) was dissolved or diluted in tetrahydrofuran, and then poured into excess hexane or methanol for reprecipitation. Volatile components and the like are removed by vacuum drying (1 mmHg (1.33 hPa), 80 ° C., 3 hours or longer) of the taken out precipitate, and the obtained white solid resin is treated by the following method (dynamic TG method). ).
Measuring apparatus: ThermoPlus2 TG-8120 DynamicTG (manufactured by Rigaku Corporation)
Measurement conditions: Sample amount 5-10 mg
Temperature increase rate: 10 ° C / min
Atmosphere: Nitrogen flow 200ml / min
Method: Step-like isothermal control method (controlled at a weight reduction rate value of 0.005% / sec or less between 60 ° C. and 500 ° C.)
[Lactone cyclization rate]
The lactone cyclization rate was determined by the formula (I).

The lactone cyclization rate was determined based on the amount of weight loss that occurred when all hydroxyl groups were dealcoholated as methanol from the polymer composition obtained by polymerization, and from 150 ° C. before the weight loss began in dynamic TG measurement, It calculated | required from the weight reduction by the dealcoholization reaction to 300 degreeC before decomposition | disassembly started.

Specifically, the weight loss rate between 150 ° C. and 300 ° C. is measured in the dynamic TG measurement of the polymer having a lactone ring structure, and the actually measured weight loss rate is defined as (X).
On the other hand, from the composition of the polymer, the theoretical weight loss rate when assuming that all the hydroxyl groups contained in the polymer composition become alcohols because they are involved in the formation of lactone rings (ie, on the composition) The weight reduction rate calculated on the assumption that a 100% dealcoholization reaction has occurred is defined as (Y). More specifically, the theoretical weight reduction rate (Y) is the molar ratio of raw material monomers having a structure (hydroxyl group) involved in the dealcoholization reaction in the polymer, that is, the raw material monomers in the polymer composition. It can calculate from the content rate of. These values (X) and (Y) are calculated from the dealcoholization formula:

The value was determined by substituting into, and the lactone cyclization rate was determined in%.

In the pellet obtained in Example 1, the ratio of the lactone ring structure was calculated. The theoretical weight loss rate (Y) of this polymer was determined. The molecular weight of methanol is 32, the molecular weight of methyl 2- (hydroxymethyl) acrylate is 116, and the content (weight ratio) in the polymer of methyl 2- (hydroxymethyl) acrylate is 40.0 in terms of composition. Since it is% by weight, (32/116) × 40.0≈11.03% by weight. On the other hand, the actual weight loss rate (X) by dynamic TG measurement was 0.43% by weight. When these values are applied to the above-mentioned dealcoholization calculation formula, since 1 (0.43 / 11.03) ≈0.961, 96.1% was obtained as the lactone cyclization rate.
[Hydroxyl group residual ratio]
The hydroxyl group remaining rate was determined by the following formula (II).

  The residual hydroxyl group amount (P) derived from the α- (hydroxyalkyl) acrylic acid ester unit in 1 g of the polymer is obtained by dividing the actual weight loss rate (X) obtained by the dynamic TG measurement of the polymer by the molecular weight of the alcohol that is eliminated. And asked.

The hydroxyl group residual ratio in the pellet obtained in Example 1 was calculated. The amount [mol] of α- (hydroxyalkyl) acrylic acid ester in 1 g of all monomer components of this polymer is 116 molecular weight of methyl 2- (hydroxymethyl) acrylate, and 2- (hydroxymethyl) acrylic Since the content (weight ratio) of methyl acid in all monomers is 40.0% by weight, 1 × (40/100) /116≈3.45 mmol. On the other hand, since the actual weight loss rate (X) by dynamic TG measurement is 0.43% by weight and the molecular weight of methanol to be eliminated is 32, it is derived from α- (hydroxyalkyl) acrylate unit in 1 g of polymer. The residual hydroxyl group amount (P) was 1 × (0.43 / 100) /32≈0.134 mmol, and the residual hydroxyl group ratio was (0.134 / 3.45) × 100 = 3.9%.
[Weight average molecular weight]
The weight average molecular weight of the polymer was measured using gel permeation chromatography (GPC) (GPC system manufactured by Tosoh Corporation) and determined as a molecular weight in terms of polystyrene.
[Quantification method of polymerization inhibitor]
The amount of the polymerization inhibitor (methoquinone) in the polymer was determined according to the following procedure. Polymer pellets dissolved in methyl 2- (hydroxymethyl) acrylate or dimethylformamide were dissolved in glacial acetic acid solvent, and a saturated sodium nitrite aqueous solution was added to cause color development. Absorbance was measured with a spectrophotometer (wavelength 420 nm), and the amount of methoquinone was quantified using a calibration curve prepared in advance.
[Measurement of the number of foreign objects using a particle counter]
In the case of pellets, 100 g of dimethylacetamide (DMAc) is added to 1 g of pellets, and after standing overnight to dissolve sufficiently, a particle counter device (manufactured by Pacific Scientific, device name: ARS-2) The number of foreign matters having a size of 0.5 μm or more was measured. In the case of the polymer solution, 90 g of DMAc was added to 10 g of the polymer solution, and the number of foreign matters was measured by the same procedure as above. In addition, after confirming that the number of foreign matters having a size of 0.5 μm or more in DMAc is equal to or less than 100 pieces / g, DMAc is obtained by filtering a commercially available product with a Teflon filter (caliber 0.22 μm). It used for the measurement.
[Quantification of MMA dimer]
The obtained polymer (polymer solution or POF / pellet) was dissolved in methylene chloride, and MMA dimer was measured by gas chromatography (manufactured by Shimadzu Corporation, apparatus name: GC-8A). The MMA dimer was quantified using a calibration curve prepared in advance.
[Quantitative determination of residual sulfur compounds]
The obtained polymer (POF / pellet) was dissolved in methylene chloride, and the remaining sulfur compound was analyzed by gas chromatography (Shimadzu Corporation, apparatus name: GC-8A) equipped with an SCD detector (Sulfur Chemiluminescence Detector). Was measured.
[Transmission characteristics of POF]
The transmission loss of POF at an excitation NA of 0.1 and a measurement wavelength of 650 nm was measured by a 25m-5m cutback method.
[POF heat resistance test]
The transmission loss (dB / km) when the POF cable was left in an oven at a temperature of 125 ° C. for 1000 hours was measured by a 25 m-5 m cutback method. Light having a measurement wavelength of 650 nm and an excitation NA of 0.1 was used.
[Example 1]
A 2 m ³ pressure-resistant reaction kettle equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen inlet pipe is washed with methyl ethyl ketone (MEK) that has passed through a filter, and the amount of foreign matter of 0.5 μm or more in the kettle is 1000 pieces / g. It was as follows. In this reaction kettle, 92.0 kg of methyl 2- (hydroxymethyl) acrylate, 126.5 kg of methyl methacrylate, 11.5 kg of methacrylic acid, 11.5 kg of methacrylic acid, and MEK224. 0 kg and 0.46 kg of n-butyl mercaptan were charged through a filter. This was bubbled with nitrogen for 30 minutes, so that the dissolved oxygen amount in the kettle was 0.2 mg / L. When this was heated to 90 ° C. and refluxed, a solution consisting of 0.23 kg of 2,2′-monoazobis (2-methylpropionate) as an initiator and 6 kg of MEK was added dropwise over 5 hours under reflux (about Solution polymerization was performed at 80 ° C. to 90 ° C., and the reaction vessel was pressurized for 1 hour at normal pressure, and further aged at 90 to 95 ° C. for 3 hours.

  A part of the obtained reaction solution was taken out and the dynamic TG was measured by the method described above. As a result, a weight loss of 2.68% was detected, and the lactone cyclization rate was 76%.

Next, the polymer solution obtained by the above cyclization condensation reaction was prepared with a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1 and a forevent number of 4 It is introduced into a bent type screw twin screw extruder (caliber 29.75 mm, L / D = 30) at a processing rate of 2.5 kg / hour in terms of resin amount, and cyclization condensation reaction and devolatilization are carried out in the extruder. By extruding, transparent pellets were obtained.
When the obtained pellet was measured for dynamic TG, a weight reduction rate of 0.43% was detected, the lactone cyclization rate was 96.0%, and the hydroxyl group residual rate was 3.9%. Moreover, the weight average molecular weight of this pellet was 66000, the glass transition temperature was 149 degreeC, and the refractive index was 1.510. Metoquinone contained in this pellet was 1.1 ppm, MMA dimer was 1.4 ppm, and the residual sulfur compound was 8 ppm.
[Example 2]
The polymer solution obtained in Example 1 is supplied as a polymer for the core material to the vent type screw twin-screw extruder described in Example 1, and the screw single-screw extruder (15 mm in diameter, L / D = 20) Supplied with pellets of VdF / TFE / HFP copolymer (trade name: THV415, manufactured by Sumitomo 3M Co., Ltd., refractive index 1.360) as a polymer for clad material, and two layers directly connected to these two extruders The polymer was simultaneously extruded from a composite spinning nozzle having a structure to produce a POF having a core / cladding structure. The temperature of the composite spinning nozzle at this time was 225 ° C. This POF was passed through a stretched portion heated to 170 ° C. and stretched 2.4 times to finally produce an SI type POF. This POF had a diameter of 1 mm, a cladding thickness of 10 μm, and a core diameter of 980 μm.

  The obtained POF was cut to an appropriate length and left overnight in methylene chloride to dissolve only the core material polymer, and then the number of foreign matters in the methylene chloride was measured with a particle counter. The number of foreign matters of 0.5 μm or more contained in 1 g of the polymer of the core material was 4500 / gr.

The transmission loss of POF at an excitation NA of 0.1 and a measurement wavelength of 650 nm was measured by the 25m-5m cutback method to be 390 dB / km. Further, the loss increase after leaving this POF in an atmosphere of 125 ° C. for 1000 hours was 110 dB / km.
[Examples 3 and 4]
A POF was produced in the same manner as in Example 2 except that the clad material shown in Table 1 was used. Various characteristics of the obtained POF were evaluated, and the results are shown in Table 1.
[Examples 5 to 7]
A POF was produced in the same manner as in Example 2 except that the core material and the clad material shown in Table 2 were used. Various physical properties of the obtained POF core material polymer were evaluated, and the results are shown in Table 2. Further, various properties of the obtained POF were evaluated, and the results are shown in Table 1.
[Examples 8 to 10]
Polyamide 12 resin (trade name: Daiamide-L1640, manufactured by Daicel Degussa Co., Ltd.) is coated on the outer periphery of the POFs of Example 2 and Example 4 using a coating die to produce a POF cable having a diameter of 1.5 mm. And evaluated. The results are shown in Table 3.
[Comparative Examples 1 and 2]
An SI-type POF was prepared and evaluated in the same manner as in Example 2 except that the core material and the clad material shown in Table 1 were used. The results are shown in Table 1.
[Results of Examples 2 to 10 and Comparative Examples 1 and 2]
As shown in Examples 2 to 7 of Table 1, when the POF core material is composed of the copolymer (X) having a lactone ring structure, the initial transmission characteristics and heat resistance of the obtained POF are It was good. As shown in Examples 8 to 10 in Table 2, the POF cable in which the polyamide 12 resin was provided on the coating layer had good initial transmission characteristics.

  As described in Comparative Example 1, when the POF core material was made of PMMA, the POF contracted in a curled shape during a heat resistance test at 125 ° C., and measurement was impossible. In addition, as described in Comparative Example 2, when the POF core material is made of a polycarbonate resin, the POF cable has inferior initial transmission characteristics.

  The POF of the present invention is used in a space where the environmental temperature is 115 ° C. or higher, such as a sensor application in the semiconductor field or food field, or a safety control application in an in-vehicle LAN.

Claims (7)

Monomer containing α- (hydroxyalkyl) acrylate monomer (A), α- (hydroxyalkyl) acrylate monomer (A) and vinyl polymerizable monomer (B) Formed by copolymerizing the mixture and then subjecting it to a cyclization condensation reaction, general formula (1)

(Wherein R ^1, R ² , and R ³ independently represent a hydrogen atom or an organic residue that may contain an oxygen atom having 1 to 20 carbon atoms). A core material for a plastic optical fiber comprising a copolymer (X) having a glass transition temperature in the range of 115 ° C. to 160 ° C.,
A core material for plastic optical fibers, wherein the number of foreign matters of 0.5 μm or more measured with a particle counter contained in the copolymer (X) is 20000 pieces / g or less. General formula (2)

In the formula, R ^{4 to} R ⁸ independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a hydroxyl group, or an alkoxy group having 1 to 5 carbon atoms. Monomer containing α- (hydroxyalkyl) acrylate monomer (A), α- (hydroxyalkyl) acrylate monomer (A) and vinyl polymerizable monomer (B) Formed by copolymerizing the mixture and then subjecting it to a cyclization condensation reaction, general formula (1)

(Wherein R ^1, R ² , and R ³ independently represent a hydrogen atom or an organic residue that may contain an oxygen atom having 1 to 20 carbon atoms). , A plastic optical fiber core material comprising a copolymer (X) having a glass transition temperature in the range of 115 ° C. to 160 ° C.,
The plastic optical fiber, wherein the content of the compound represented by the general formula (2) in the α- (hydroxyalkyl) acrylate monomer (A) contained in the monomer mixture is 100 ppm or less Core material. The plastic optical fiber core material according to claim 2, wherein the content of the compound represented by the general formula (2) contained in the copolymer (X) is 20 ppm or less. The core material for plastic optical fibers according to any one of claims 1 to 3, wherein the content of the sulfur compound contained in the copolymer (X) is 20 ppm or less. The plastic optical fiber according to any one of claims 1 to 4, wherein the α- (hydroxyalkyl) acrylic acid ester monomer (A) and the vinyl polymerizable monomer (B) are methyl methacrylate. Core material. 6. The plastic optical fiber core material according to claim 5, wherein the content of the methyl methacrylate dimer contained in the copolymer (X) is 5 ppm or less. It is comprised from the core part containing the core material for plastic optical fibers in any one of Claims 1-6, and the clad part which has a refractive index lower 1% or more than the refractive index of a core part, and is measured by the cut-back method of 25-5m A plastic optical fiber characterized by having a transmission loss of 400 dB / Km or less.