JPH1078513A - Production of rodlike polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a rodlike polymer having uniform outer diameter without including bubbles in the center part. SOLUTION: This rodlike polymer is produced by filling a cylindrical container 12 comprising a polymer which forms the outer peripheral part of the rodlike polymer with monomers to form the inner part of the rodlike polymer, and then polymerizing the monomers. In this production method, a material which shrinks without heat, for example, a spiral spring 1, a heat-resistant rubber tube or a combination of a spiral spring and a protective sleeve is wound around the outer surface of the cylindrical container 2 so that the monomers are polymerized while the cylindrical container 2 is tightened by the shrinking member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rod-shaped polymer such as a preform for a plastic optical fiber. More specifically, the center of the rod-shaped polymer,
For example, the present invention relates to a method for producing a rod-shaped polymer in which the core of a plastic optical fiber preform contains no air bubbles.

[0002]

2. Description of the Related Art As a method for producing a preform for a gradient index plastic optical fiber, WO 93/08488 is known.
Discloses a method of forming a refractive index distribution by promoting polymerization of a monomer from the inner wall of a cylindrical container made of a polymer. Specifically, a polymethyl methacrylate (PMMA) tube is used as a cylindrical container, and a core is formed in a hollow portion of the PMMA tube. The PMMA tube is manufactured by heating and polymerizing a monomer tube containing a methyl methacrylate (MMA) monomer solution while rotating the glass tube, and the core is made of a PMM solution containing a non-polymerizable compound.
A preform having a refractive index distribution can be prepared by injecting into a tube A and performing heat polymerization while rotating. The obtained preform is drawn by heating and melting to obtain an optical fiber having a predetermined diameter. However, when the core monomer solution is polymerized by the above-mentioned method, the volume may be reduced somewhat at that time, and the core may contain air bubbles.

One method for preventing the generation of bubbles during the polymerization of such a core monomer is disclosed in JP-A-8-11041.
No. 9 discloses this. In the disclosed method, the outer periphery of the clad is coated with a heat-shrinkable tube, and the polymerization in the longitudinal direction is performed in multiple stages, whereby the shrinkable tube is shrunk in accordance with the shrinkage caused by the shrinkage of the core, thereby generating bubbles. Has been prevented.

[0004] However, the heat-shrinkable tube described in JP-A-8-110419 has such a property that the higher the applied temperature, the greater the degree of shrinkage, and the shrinkage occurs locally in a portion softened by heating. However, when polymerizing the core monomer for the preform, the temperature distribution in the longitudinal direction is non-uniform due to the temperature distribution of the heating furnace and the reaction heat of the polymerization reaction of the monomer. It is difficult to shrink.
In particular, when monomers are polymerized in multiple stages as described in JP-A-8-110419, it may not be possible to heat the heat-shrinkable tube equally over the entire length.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a cylindrical container made of a polymer forming an outer peripheral portion of a rod-shaped polymer,
When filling the monomer for forming the inside of the rod-shaped polymer and polymerizing the monomer to produce the rod-shaped polymer, the cylindrical container can be uniformly compressed from the outside, and furthermore, using a member that does not excessively compress, It is intended to provide a method for polymerizing a monomer while compressing a container.

[0006]

In order to solve the above-mentioned problems, the present invention uses a member that shrinks non-heatably as a member capable of uniformly compressing a cylindrical container. In a preferred embodiment of the present invention, a spiral leaf spring, a heat-resistant rubber tube, or a combination of a spiral spring and a protective sleeve is used as the non-heat-shrinkable member.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The cylindrical container of a polymer used in the production method of the present invention may be a cylindrical container formed of a polymer, and the production method is not limited. It may be formed by hollowing out the inside of a cylindrical polymer, or may be formed by filling a cylindrical polymerization container with a monomer and performing polymerization to a predetermined thickness from the container wall toward the inside.

In the first embodiment of the manufacturing method of the present invention, a spiral leaf spring 1 as shown in FIG. 1 is used as a contracting member, and is wound around a cylindrical container 2. The inner diameter of the spiral leaf spring is set in accordance with the outer diameter of the cylindrical container after contraction. As shown in FIG. 2, the spiral leaf spring 1 contracts up to the set inner diameter, but does not contract any more. In addition, since the contraction force is constant in the longitudinal direction, the cylindrical container is uniformly compressed in the longitudinal direction. Therefore, the outer shape of the obtained rod-shaped polymer does not become distorted, and the outer shape does not vary in the longitudinal direction.

In the second embodiment, a heat-resistant rubber tube 3 as shown in FIG.
And wrap it around. The inner diameter of the heat-resistant rubber tube 3 is also
Set according to the outer diameter of the cylindrical container after contraction. The rubber tube shrinks up to the set inner diameter, but does not shrink any more, and thus has the same effect as the spiral leaf spring.

As the heat resistant rubber, any known heat resistant rubber can be used. Preferred examples of the heat-resistant rubber include fluorine rubber (for example, tetrafluoroethylene-perfluoromethylvinyl ether copolymer rubber), acrylic rubber, hydrin rubber, silicone rubber, ethylene-propylene copolymer rubber, and halogenated butyl rubber.

In the third embodiment, a combination of a spiral spring 4 and a protective sleeve 5 as shown in FIG. 3 is used as a contracting member. In this case, a film or sheet of a polymer or other suitable material is wrapped around the cylindrical container 2 to form a protective sleeve 5, from which the spiral spring 5 is wrapped. The inner diameter of the spiral spring 5 is also set according to the outer diameter of the cylindrical container after contraction. The pitch of the spiral spring is preferably small in order to compress the cylindrical container as uniformly as possible. However, if the protective sleeve has an appropriate hardness and the compressive force of the spring is appropriately dispersed and a uniform compressive force is transmitted to the cylindrical container, the pitch of the spiral spring may be somewhat large. . The spiral spring contracts up to the set inner diameter, but does not contract any further. Therefore, the combination of the spiral spring and the protective sleeve has the same effect as the spiral plate spring or the heat-resistant rubber tube.

In a preferred embodiment, the monomer which forms the interior of the rod-shaped polymer is placed in the internal space of a polymer cylindrical container, and while the container is held horizontally and rotated, the monomer is polymerized to produce a plastic light. A rod-shaped polymer such as a fiber preform is manufactured.

The type of the polymer forming the cylindrical container and the type of the polymer forming the inside of the rod-shaped polymer are not limited.
This will be described by taking a plastic optical fiber preform as an example. As the polymer forming the clad portion of the preform, a colorless and highly transparent plastic conventionally used for a plastic optical fiber can be used. Examples of monomers that provide such plastics include the following methacrylates, styrene compounds, fluorinated acrylates, fluorinated methacrylates, and the like: (a) methacrylate and acrylic acid Esters Methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, t-butyl methacrylate, benzyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, diphenylmethyl methacrylate, etc .; methyl acrylate, ethyl acrylate, t-butyl acrylate (B) styrene-based compounds styrene, α-methylstyrene, chlorostyrene, bromostyrene, dichlorostyrene, dibromostyrene, etc .; (c) fluorinated acrylate 2,2,2-trif Oro ethyl acrylate; (d) a fluorinated methacrylate ethyl 1,1,2-trifluoroethyl methacrylate.

To such a monomer, a polymerization initiator and, if desired, an additive (eg, a chain transfer agent) are added, and an appropriate amount is placed in a polymerization vessel. While the polymerization container is being rotated by a motor, the monomer is polymerized on the inner wall of the polymerization container by heating with a heating device to form a clad portion. The amount of the monomer may be determined from the size of the polymerization vessel and the thickness of the clad. Alternatively, an excessive amount of monomer may be added, polymerization may be stopped when a clad portion having a desired thickness is formed, and unnecessary monomer may be discharged from the polymerization container.

The solution serving as the raw material of the polymer for forming the core is adjusted by mixing a monomer used for forming the clad with a compound for adjusting the refractive index. To form the core, to the mixture of the monomer and the compound for adjusting the refractive index as described above, a polymerization initiator and a chain transfer agent and the like are added, put in a cylindrical container serving as a clad, and while rotating the container, Heat to polymerize. The polymerization is terminated when a core having a predetermined thickness is formed.

[0016]

When the core is formed, the volume decreases and shrinks as the polymerization of the monomer progresses. In the present invention, since the shrinking member is disposed around the cylindrical container (cladding portion), the container is compressed according to the decrease in volume by the compressive force, and no void is generated in the core portion. No bubbles are generated. In addition, since the non-heat-shrinkable member is used, the degree of shrinkage of the shrinkable member does not depend on the temperature, so that the shrinkable member can uniformly compress the cylindrical container. Therefore, there is no variation in the outer diameter in the longitudinal direction.

[0017]

The present invention will be specifically described below with reference to examples. Example 1 One end of a resin tube made of methyl methacrylate resin having an outer diameter of 18.4 mm, an inner diameter of 12.0 mm, and a length of 500 mm is closed, and a methyl methacrylate monomer and a non-polymerizable hetero-refractive index substance (dopant) are contained therein. A liquid in which diphenyl sulfide was mixed at a weight ratio of 5: 1 was sealed, and partially heated externally with a dedicated heater set at 90 ° C. to carry out polymerization. At this time, polyethylene terephthalate (PTF)
E) The film was wound, and a plate-shaped spring having a thickness of 0.2 mm was covered over the film over a length of 400 mm. Both ends other than the contraction region wound by the plate spring are also exposed from the PTFE so as to bend into an unpolymerized state, and excessive polymerization shrinkage and large bubbles are driven to both ends.

After the polymerization was carried out for 20 hours, the formed optical fiber preform was taken out. The preform is
Only the portion covered with the spring was finely deformed, and the outer diameter of the resin tube was 17.8 mm. This means that it contracted about 3.3% in diameter. When the leaf spring was unfolded and removed, and the pulled out optical fiber preform was observed, there was no bubble in the resin inside the cladding tube, and no change was observed in the outer diameter dimension in the length direction.

EXAMPLE 2 One end of a resin tube made of methyl methacrylate resin and having an outer diameter of 18.4 mm, an inner diameter of 12.0 mm and a length of 500 mm was closed, and a methyl methacrylate monomer and a non-polymerizable hetero-refractive index material were placed therein. (Dopant) A liquid in which diphenyl sulfide was mixed at a weight ratio of 5: 1 was sealed, and partially heated externally with a special heater set at 90 ° C. to polymerize. At this time, a polyethylene (PE) film was wound around the center of the resin tube, and a heat-resistant silicone rubber tube having a thickness of 1.5 mm was placed over the film over a length of 400 mm. Both ends were exposed to form an unpolymerized state locally, and excessive polymerization shrinkage and large bubbles were driven to both ends.

After the polymerization was carried out for 20 hours, the formed optical fiber preform was taken out. The preform is
Only the portion covered with the tube was thinly deformed, and the outer diameter of the resin tube was 17.8 mm. This is about 3.3% in diameter
It means shrinking. The optical fiber preform pulled out of the rubber tube by unrolling the rubber tube had no bubbles inside the clad tube, and no change was observed in the outer diameter in the length direction.

EXAMPLE 3 One end of a resin tube made of methyl methacrylate resin having an outer diameter of 18.4 mm, an inner diameter of 12.0 mm and a length of 500 mm was closed, and a methyl methacrylate monomer and a non-polymerizable hetero-refractive index material were placed therein. (Dopant) A liquid in which diphenyl sulfide was mixed at a weight ratio of 5: 1 was sealed, and partially heated externally with a special heater set at 90 ° C. to polymerize. At this time, a PE film was wound around the center of the resin tube, and a 0.3 mm-thick spiral processed leaf spring having a width of 40 cm was covered over the PE film. Both ends were exposed to form an unpolymerized state locally, and excessive polymerization shrinkage and large bubbles were driven to both ends.

After the polymerization was carried out for 20 hours, the formed optical fiber preform was taken out. The preform is
Only the portion covered with the leaf spring / PTFE film was finely deformed, and the outer diameter was 17.8 mm. This means that it contracted about 3.3% in diameter. The optical fiber preform pulled out by expanding and removing the leaf spring had no bubbles inside the cladding tube, and no change was observed in the outer diameter in the length direction.

EXAMPLE 4 One end of a resin tube made of methyl methacrylate resin having an outer diameter of 18.4 mm, an inner diameter of 12.0 mm, and a length of 500 mm was closed, and a methyl methacrylate monomer and a non-polymerizable hetero-refractive material were placed therein. (Dopant) A liquid in which diphenyl sulfide was mixed at a weight ratio of 5: 1 was sealed, and partially heated externally with a special heater set at 90 ° C. to polymerize. At this time, a PTFE film was wound around the center of the resin pipe, and a spiral spring having a wire diameter of 1.0 mm was covered over the PTFE film over a length of 400 mm. Both ends other than the shrinking region wound at a pitch of 10 mm were also exposed from PTFE to locally form an unpolymerized state, so that excessive polymerization shrinkage and large bubbles were driven to both ends.

In the optical fiber preform taken out after 20 hours, only the portion covered with the spring / PTFE film was thinly deformed and had an outer diameter of 17.8 mm. This means that it contracted about 3.3% in diameter. The optical fiber preform pulled out by expanding and removing the leaf spring had no bubbles inside the cladding tube, and no change was observed in the outer diameter in the length direction.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state in which a spiral leaf spring is wound around a polymer cylindrical container as a member that shrinks non-heatably in a production method of the present invention.

FIG. 2 is a diagram showing the cylindrical container and the spiral spring of FIG. 1 after contraction.

FIG. 3 is a diagram showing a state in which a heat-resistant rubber tube is wound around a polymer cylindrical container as a member that shrinks non-heatably in the production method of the present invention.

FIG. 4 is a diagram showing a state in which a combination of a spiral spring and a protective sleeve is wound around a polymer cylindrical container as a member that shrinks non-heatably in the production method of the present invention.

Claims (2)

[Claims] 1. A method for producing a rod-shaped polymer by charging a monomer for forming the interior of the rod-shaped polymer into a cylindrical container made of a polymer forming an outer peripheral portion of the rod-shaped polymer, and polymerizing the monomer. A method for producing a rod-shaped polymer, comprising: wrapping a non-heat-shrinkable member around the outer periphery of a cylindrical container, and polymerizing the monomer while tightening the cylindrical container with the shrinkable member. 2. The method according to claim 1, wherein the shrinkable member is a spiral leaf spring, a heat-resistant rubber tube, or a combination of a spiral spring and a protective sleeve.