JP3156260B2 - Core material for optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core material for an optical fiber . More specifically, optical fiber
The present invention relates to core materials for buses .

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 63-256902 discloses that a (meth) acrylic acid ester having an ester group such as an alkyl group or a dicyclopentenyl group and a general formula CH ₂ CRCRCO (OCH ₂ CH ₂ ) nOC
An optical transmitter made of a synthetic resin, which is composed of a copolymer with di (meth) acrylate in which OCR = CH ₂ [R: H, CH ₃ ] is described.

However, this synthetic resin optical transmission body molded as a core material or the like is prepared by injecting the above (meth) acrylate and di (meth) acrylate as a monomer mixture into a tube serving as a cladding material. Because of the heat polymerization in the tube, volumetric shrinkage occurs due to the progress of the polymerization, causing "sink" in the tube, the surface of the polymer serving as the core material loses smoothness, and the roundness is lost. It is stated in the publication that when the monomer mixture is injected, the pump must be injected at an extremely low speed or the pump must be kept running for the purpose of pressurization.

[0004] Such a polymerization operation is not only complicated but also inhomogeneous due to gelation.
In addition, unreacted monomers clearly remain, and scattering caused by non-uniformity of the refractive index caused by such a problem causes a problem that the transparency of the light transmitting body is low.

In conventional acrylic acrylate-based transparent acrylic rubber compositions such as ethyl acrylate polymers, tertiary hydrogen is present in the main chain of the polymer. When exposed, for example 130 ° C
When exposed to the air for 50 hours, a decomposition reaction occurs in the main chain of the polymer starting from the oxidation reaction of the tertiary hydrogen, resulting in a decrease in the molecular weight of the polymer and coloring of the polymer by the decomposition products Leads to.

[0006] As described above, the conventional transparent acrylic rubber composition has a problem in heat resistance, and is colored in high-temperature air so that light transmittance, which is a characteristic of the optical fiber core material , is reduced. become.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a non-reacted monomer, a non-uniform refraction caused by the presence of a gel or microphase separation, a high crosslinking density, and excellent shape retention. An object of the present invention is to provide a core material for an optical fiber comprising a crosslinked product of a transparent acrylic rubber composition that gives a flexible crosslinked product.

Another object of the present invention is to provide an optical fiber comprising a crosslinked product of a transparent acrylic rubber composition having excellent thermal decomposition resistance.
An object of the present invention is to provide a core material for iva .

[0009]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
Alkyl (meth) acrylate and general formula [I] CH ₂ CRCR ₁ COOR
₂ or CH ₂ CRCR ₁ COO (CH ₂ ) nOR ₂ (where R ₁ is a hydrogen atom or a methyl group, R ₂ is a dicyclopentenyl group, and n is 1 or 2) Copolymer with dicyclopentenyl (meth) acrylate or dicyclopentenyloxyalkyl (meth) acrylate and general formula
[II] CH ₂ CC (CH ₃ ) CO (OCH ₂ CHR ₃ ) mOCOC (CH ₃ ) = CH ₂ (where R ₃ is a hydrogen atom or a methyl group, and m is an integer of 1 to 10. An optical fiber comprising a crosslinked product of a transparent acrylic rubber composition containing a dimethacrylate compound represented by
Achieved by iva core material .

The alkyl (meth) acrylate which forms the main component of the copolymer includes alkyl having 1 to 12 carbon atoms such as methyl, ethyl, n-butyl, isobutyl, 2-ethylhexyl, octyl and dodecyl. An acrylate or an alkyl methacrylate having an alkyl group having 6 to 12 carbon atoms, such as hexyl, octyl, decyl, and dodecyl, is used. The carbon number of methacrylate
It is limited to 6 or more because of the relationship with the glass transition point, and within a range where a copolymer exhibiting rubber-like elasticity at room temperature can be obtained, alkyl methacrylate having 5 or less carbon atoms is 3 or less.
There is no problem even if copolymerization is carried out over the starting material.

The (meth) acrylate represented by the general formula [I], which is copolymerized with these alkyl (meth) acrylates, is used as a crosslinking point-forming monomer in the copolymer in an amount of about 1%.
3030 mol%, preferably about 5-20 mol%.

In order to improve the thermal decomposition resistance of the transparent acrylic rubber composition, alkyl methacrylate is used as a main component of the copolymer, and methacrylate is also used for the compound represented by the above general formula [I]. . As described above, by using a methacrylate compound and substituting the tertiary hydrogen in the polymer main chain with a methyl group, the thermal decomposition resistance is improved. Further, in the copolymer of such a combination, in order to take a rubber state at room temperature (glass transition point Tg is 0 ° C. or less), the alkyl group of the alkyl methacrylate has 6 or more carbon atoms, preferably 8 or more. Used.

[0013] The copolymerization reaction is carried out by a solution polymerization method, an emulsion polymerization method, or the like. Since it is essential that gelation does not occur, the solution polymerization method is optimal. that time,
It is preferable to use a chain transfer agent represented by an organic mercapto compound in an amount of about 2% by weight or less based on the monomer mixture, thereby effectively preventing gelation of the copolymer. After the completion of the polymerization reaction, the copolymer is purified by a method such as reprecipitation to remove unreacted monomers, oligomers and other impurities.

The dimethacrylate compound represented by the above general formula [II] is added to the copolymer as a co-crosslinking agent. Such a co-crosslinking agent has close reactivity with the cross-linking group in the copolymer derived from the dicyclopentenyl group, thereby reducing microphase separation due to homopolymerization of the co-crosslinking agent, that is, reduction in transparency due to light scattering. Preventing. The co-crosslinking agent is equivalent to the crosslinking point in the copolymer in an equivalent ratio of about 0.5 to 1.5,
It is preferably used at a ratio of about 0.6 to 0.75.

On the other hand, when a diacrylate compound corresponding to the dimethacrylate compound represented by this general formula is used as a co-crosslinking agent, the acrylate group has higher reactivity than the dicyclopentenyl group, and The homopolymerization of the diacrylate itself proceeds considerably, and the compatibility with the copolymer is reduced, so that microphase separation is likely to occur.

A composition comprising a copolymer and a dimethacrylate compound co-crosslinking agent is crosslinked by heating, irradiation with active energy rays, or the like. At this time, the composition is crosslinked by a crosslinking initiator generally using an organic peroxide. The crosslinking initiator is used at a ratio of about 2 parts by weight or less per 100 parts by weight of the copolymer, but when a radical is generated without using a crosslinking initiator and a crosslinking reaction is performed, even if a crosslinking initiator is not used. Good.

[0017]

According to the present invention, a copolymer of an alkyl (meth) acrylate having a crosslinkable group and dicyclopentenyl (meth) acrylate or dicyclopentenyloxyalkyl (meth) acrylate is co-cross-linked, and the reaction of the co-cross-linking agent at that time. By selecting the property, that is, by selecting a dimethacrylate compound that is less reactive than the diacrylate compound, foaming and partial gelation due to excessive reaction heat, preventing uneven refractive due to microphase separation, uniform and high transparency A crosslinked acrylic rubber can be obtained.

This transparent acrylic rubber composition is an optical fiber.
It can be used effectively as fiber core material . The production of an optical fiber using this composition is performed by an extrusion coating method, a double extrusion method, or the like, in addition to the method using a clad material tube.

Further, when a copolymer of an alkyl methacrylate having an alkyl group having 6 or more, preferably 8 or more carbon atoms and dicyclopentenyl methacrylate or dicyclopentenyloxyalkyl methacrylate is used, a sufficient amount of rubber can be obtained at room temperature. While showing the state, the effect of remarkably improving the thermal decomposition resistance can be obtained.

[0020]

Next, the present invention will be described with reference to examples.

Example 1 Ethyl acrylate 900 g Dicyclopentenyl acrylate 100 g Azobisisobutyronitrile 2.0 g 2-Mercaptoethanol 1.5 g Methyl ethyl ketone 1000 g The mixture was heated to 55 ° C. and copolymerized to a conversion of 35%. This was purified by reprecipitation in a 70% aqueous methanol solution, and ethyl acrylate-dicyclopentenyl (molar ratio: 90:10)
330 g of a copolymer was obtained.

A viscous liquid material prepared by adding 33 g of tetraethylene glycol dimethacrylate and 1.65 g of an organic peroxide (Nippon Oil & Fats product, Perhexa 3M) to the total amount of the copolymer was added to a Teflon tube (inner diameter 2 mm, wall thickness). 1 mm) and cross-linked at 140 ° C. for 4 minutes under pressure to produce an optical fiber using Teflon as a cladding material. The light transmittance of the obtained optical fiber at a wavelength of 700 nm was 50% / m.

Example 2 In Example 1, 24.2 g of diethylene glycol dimethacrylate was used instead of tetraethylene glycol dimethacrylate. The light transmittance of the obtained optical fiber was 48% / m.

Example 3 In Example 1, 50.6 g of octaethylene glycol dimethacrylate was used instead of tetraethylene glycol dimethacrylate. The light transmittance of the obtained optical fiber was 51% / m.

Example 4 n-Butyl acrylate 800 g Dicyclopentenyl acrylate 100 g Benzoyl peroxide 1.8 g Octyl mercaptan 2.0 g Methyl ethyl ketone 1000 g The above mixture was heated to 55 ° C. and copolymerized to a conversion of 35%. This was purified by reprecipitation in a 70% aqueous methanol solution, and n-
Butyl acrylate-dicyclopentenyl acrylate
(Molar ratio: 85:15) 300 g of a copolymer was obtained.

A viscous liquid prepared by adding 30 g of tetraethylene glycol dimethacrylate and 1.65 g of an organic peroxide (Nippon Oil & Fats product, Perhexa 3M) to the total amount of the copolymer was added to a Teflon tube (inner diameter 2 mm, wall thickness). 1 mm) and cross-linked at 140 ° C. for 4 minutes under pressure to produce an optical fiber using Teflon as a cladding material. The light transmittance of the obtained optical fiber at a wavelength of 700 nm was 51.5% / m.

Example 5 N-dodecyl methacrylate 1000 g Dicyclopentenyl methacrylate 120 g Benzoyl peroxide 1.8 g Octyl mercaptan 2.0 g Methyl ethyl ketone 1100 g A mixture of at least 58 ° C. was heated to 58 ° C. and copolymerized to a conversion of 35%. This was purified by reprecipitation in a mixture of methanol and methyl ethyl ketone (70:30) to give a copolymer of n-dotesyl methacrylate-dicyclopentenyl methacrylate (molar ratio 88:12).
360g was obtained.

A viscous liquid prepared by adding 30 g of tetraethylene glycol dimethacrylate and 1.65 g of organic peroxide (Perhexa 3M) to the total amount of this copolymer was placed in a Teflon tube (inner diameter 2 mm, wall thickness 1 mm). And press under pressure 14
Crosslinking was performed at 0 ° C. for 4 minutes to produce an optical fiber using Teflon as a cladding material. The light transmittance of the obtained optical fiber at a wavelength of 700 nm was 49.0% / m.

Example 6 In Example 5, when 115 g of dicyclopentenyl acrylate was used instead of dicyclopentenyl methacrylate, an optical fiber having a light transmittance of 49.5% / m at a wavelength of 700 nm was obtained.

Comparative Example 1 Ethyl acrylate, dicyclopentenyl acrylate and azobisisobutyronitrile used in Example 1 were put in a small plunger pump in the same Teflon tube immersed in a constant temperature water bath at a water temperature of 80 ° C. Press in with 80
Polymerization was performed at 2 ° C. for 2 hours. Thereafter, the mixture was heated and polymerized at 120 ° C. for 15 hours to produce an optical fiber using Teflon as a cladding material. The obtained light transmittance was 15% / m.

Comparative Example 2 An optical fiber was manufactured in the same manner as in Example 1 except that tetraethylene glycol diacrylate was used instead of tetraethylene glycol dimethacrylate. The light transmittance of the obtained optical fiber was 28% / m.

The optical fiber obtained in each of the above Examples and Comparative Example 2 had a core material having a glass transition point Tg-2.
Since it is a rubber-like elastic body at 0 ° C., even if it is bent until the Teflon tube exceeds the buckling limit, the core material portion has such flexibility that there is no change.

Example 7 Alkyl methacrylate 95 parts by weight Dicyclopentenyl (oxyalkyl) methacrylate 5 〃 azobisisobutyronitrile 0.05 〃 2-mercaptoethanol 0.06 メ チ ル methyl ethyl ketone 150 をCopolymerized to 40%. These are treated with methanol-methyl ethyl ketone (70: 3
0) Reprecipitation purification was performed in the mixed solution to obtain copolymers I to VI, respectively. Copolymer I: n-dodecyl methacrylate-dicyclopentenyloxymethyl methacrylate copolymer II: n-dodecyl methacrylate-dicyclopentenyloxyethyl methacrylate copolymer III: n-dodecyl methacrylate-dicyclopentenyl methacrylate Copolymer 〃 IV: 2-ethylhexyl methacrylate-dicyclopentenyloxymethyl methacrylate copolymer 〃 V: 2-ethylhexyl methacrylate-dicyclopentenyloxyethyl methacrylate copolymer 〃 VI: 2-ethylhexyl methacrylate-dicyclopentenyl Methacrylate copolymer

To 100 parts by weight of these copolymers, a co-crosslinking agent was added.
CH as_Two= C (CH_Three) CO (OCH_TwoCH_Two)_FourOCOC (CH_Three) = CH_Two[TEG
DM] or CH_Two= C (CH_Three) CO (OCH_TwoCH (CH_Three)]₉OCOC (CH_Three)
= CH_Two(Shin Nakamura Chemical NK Ester 9PG) 10 parts by weight and
Composition containing 1 part by weight of organic peroxide (Perhexa 3M)
Is heated at 130 ° C for 10 minutes and crosslinked or 400W high-pressure water
UV irradiation from a distance of 20 cm with a silver lamp for 1 minute to crosslink,
A 1.6 mm thick crosslinked sheet was formed into a quartz cell.Composition Copolymer Co-crosslinking agent Crosslinking method Crosslinked product Tg (° C)  1 I TEGDM Heat crosslink -50 2 II 加熱 Heat crosslink ３ 3 III 〃 Heat crosslink ４ 4 IV 架橋 Heat crosslink 架橋 5.5 V -5 Heat crosslink 〃 6 VI 加熱 Heat crosslink 〃 7 I NK ester UV crosslink -50 8 II 紫外線 UV Crosslinking 〃 9 III 紫外線 Ultraviolet crosslinking 〃 10 IV 紫外線 Ultraviolet crosslinking -5 11 V 架橋 Ultraviolet crosslinking 〃 12 VI 〃 Ultraviolet crosslinking 〃

When the light transmittance of each of the crosslinked sheets in the above quartz cell before and after exposure to air at 130 ° C. for 150 hours was measured, the light transmittance was as small as 93% / cm before heating to 75% / cm. Had stayed low. In addition, the increase in absorbance at 400 nm also increased from 0 to 0.005 to 0.02 before and after heating for 150 hours.
To a slight rise.

Reference Example In Example 7, the same amounts of ethyl acrylate and dicyclopentenyl acrylate were used in place of alkyl methacrylate and dicyclopentenyl methacrylate, respectively, to obtain an ethyl acrylate-dicyclopentenyl acrylate copolymer. Was.

A composition obtained by adding 10 parts by weight of TEGDM and 1 part by weight of an organic peroxide to 100 parts by weight of this copolymer was crosslinked by a heat crosslinking method to form a 1.6 mm thick crosslinked sheet (Tg: -1).
(5 ° C.) was molded into a quartz cell.

When the light transmittance before and after exposure to air at 130 ° C. for 150 hours and the absorbance at 400 nm were measured in the same manner as in Example 7, the light transmittance was greatly reduced from 93% / cm to 0.02% / cm. And the absorbance increased greatly to 0.005 to 0.6.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-8124 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/00 C08F 265/06

Claims (1)

(57) [Claims] 1. An alkyl (meth) acrylate having the general formula CH
₂ CRCR ₁ COOR ₂ or CH ₂ 1CR ₁ COO (CH ₂ ) nOR ₂ (where R ₁ is a hydrogen atom or a methyl group, R ₂ is a dicyclopentenyl group, and n is 1 or 2 And a general formula CH ₂で C (CH ₃ ) CO (OC
_{H 2 CHR 3) mOCOC (CH} 3) = CH 2 ( wherein, R ₃ is a hydrogen atom or a methyl group, m is transparent acrylic containing dimethacrylate compound represented by a is) an integer from 1 to 10 Rubber
An optical fiber core material comprising a crosslinked product of the composition .