JPS6367163B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a synthetic resin optical transmission fiber having a core-sheath structure. Conventionally, inorganic glass fibers have been known as optical transmission fibers that have excellent optical transmission properties over a wide range of wavelengths, but they are not only difficult to process and susceptible to bending stress, but also expensive. , optical transmission fibers based on synthetic resin have been developed. Optical transmission fibers made of synthetic resin are known to use polystyrene and methyl methacrylate polymers as core materials, but methyl methacrylate polymers have been used because of their superior optical transmission performance. things are commonly used. As a sheath material for optical transmission fibers using methyl methacrylate polymer as a core material,
methacrylic acid and fluorinated alcohols as described in Japanese Patent Publication No. 56-8321, Japanese Patent Publication No. 56-8322, Japanese Patent Publication No. 56-8323, and Japanese Patent Publication No. 53-60243. Those made by polymerizing esters and those made of a copolymer of vinylidene fluoride and tetrafluoroethylene as described in Japanese Patent Publication No. 53-42260 are known. The optical transmission performance of an optical transmission fiber is closely related to absorption and scattering of the core material and sheath material, reflectance at the core-sheath interface, and the like. Polymers mainly composed of esters made of methacrylic acid and fluorinated alcohols, which have traditionally been used as sheath materials, have extremely low absorption and scattering, so although optical transmission loss due to such factors is small, However, it has the disadvantage of poor adhesion to the core material, methyl methacrylate polymer, and high transmission loss at the core-sheath interface. on the other hand,
Although the copolymer consisting of vinylidene fluoride and tetrafluoroethylene as described in Japanese Patent Publication No. 53-42260 has excellent adhesion with polymethyl methacrylate polymer, it is crystalline. , the disadvantage is that the transmission loss due to scattering is large. As a result of intensive studies to improve the optical transmission loss of optical transmission fibers using such methyl methacrylate polymer as a core material, the present inventors have developed the following general formula. (In the formula, X is composed of a random bond of tetrafluoroethylene (T) and vinylidene fluoride (V), and the total number of constituents of (T) and (V) forming X is 2 to 6, and A chain with a constituent number ratio (T)/(V) of 1/5 to 5, n
indicates 1 or 2. ) By using a polymer mainly composed of esters of fluorinated alcohols and methacrylic acid as the sheath material, the light transmission performance has improved adhesion to the methyl methacrylate polymer of the core material. The present invention was achieved by discovering that the improvement in That is, the gist of the present invention is that a methyl methacrylate polymer containing at least 90 mol % of methyl methacrylate units in terms of monomer mol % is used as a core material, and the general formula (In the formula, X is composed of a random bond of tetrafluoroethylene (T) and vinylidene fluoride (V), and the total number of constituents of (T) and (V) forming X is 2 to 6, and A chain with a constituent number ratio (T)/(V) of 1/5 to 5, n
An optical transmission fiber characterized in that the sheath material is a polymer consisting of at least one fluoroalkyl methacrylate represented by (1 or 2) or a copolymer containing the compound () as a main component. be. The methyl methacrylate polymer used as the core material of the optical transmission fiber of the present invention is a polymer in which at least 90 mol %, calculated as monomer mol %, consists of methyl methacrylate units. Suitable monomers that can be copolymerized with methyl methacrylate in an amount not exceeding 10 mol % include methyl acrylate and ethyl acrylate.
These comonomers improve the processability and heat resistance of methyl methacrylic polymers, but addition of large amounts tends to reduce optical transmission performance, so comonomers should be added within 10 mol%. Preferably, it is polymerized. The fluoroalkyl methacrylate used as the main component of the sheath material of the optical transmission fiber of the present invention has the following general formula: (In the formula, X is composed of a random bond of tetrafluoroethylene (T) and vinylidene fluoride (V), and the total number of constituents of (T) and (V) forming X is 2 to 6, and A chain with a constituent number ratio (T)/(V) of 1/5 to 5, n
represents 1 or 2), which is a methacrylic ester represented by: tetrafluoroethylene and vinylidene fluoride;
It is easily synthesized from fluoroalkyl alcohol and methacrylic acid chloride produced by telomerization reaction with ethyl alcohol and methyl alcohol. However, if the number of tetrafluoroethylene or vinylidene fluoride structural units constituting X of the alcohol component of the fluoroalkyl methacrylate exceeds 6 units in terms of the number of monomers, the heat resistance deteriorates and it becomes unsuitable as a sheath material. ,
Also, tetrafluoroethylene (T) constituting X
When the composition ratio (T)/(V) of the structural units of vinylidene (V) fluoride becomes less than 1/5, the refractive index increases and the difference from the refractive index of the methyl methacrylate polymer, which is the core material, becomes small. Since the aperture angle becomes smaller, the amount of transmitted light decreases. On the other hand, (T)/
When the value of (V) exceeds 5, the structural units of vinylidene fluoride (V) contained in decreases.
Therefore, it is preferable that the structure of X is within a range where (T)/(V) satisfies the above-mentioned composition ratio. The sheath material of the optical transmission fiber of the present invention has the general formula ()
It may be a single or mutual copolymer of two or more fluoroalkyl methacrylates represented by, or these and other acrylate or methacrylate monomers, such as Japanese Patent Publication No. 43-8978
The following general formula described in the publication (In the formula, X' represents a hydrogen atom, a fluorine atom, or a chlorine atom, n represents an integer of 2 to 10, m represents an integer of 1 to 6, and Y represents a hydrogen atom or a methyl group.) Fluoroalkyl methacrylate monomer, 2,2,2-trifluoroethyl methacrylate, 1,1,1,3,3,3-hexafluoro-2-propyl methacrylate, perfluoro-
It may also be a copolymer with a fluoroalkyl methacrylate monomer such as t-butyl methacrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, or the like.
However, if the content of the copolymerized monomer becomes too large, the adhesion with the methyl methacrylate polymer used as the core material may decrease, the refractive index difference between the core and the sheath becomes small, and the amount of transmitted light decreases. Therefore, it is preferable to carry out copolymerization in a range of 50 mol % or less in terms of monomer mol %. The optical transmission fiber of the present invention can be produced by melt-spinning the core material and sheath material polymers from a core-sheath spinneret, or by applying a solution containing the sheath material to the surface of the melt-spun core material and drying it. can be manufactured. Hereinafter, the present invention will be explained in more detail with reference to Examples. Examples 1 to 8, Comparative Examples 1 to 4 Optical transmission fibers were manufactured by the route shown below. (i) Production of methyl methacrylate polymer rod Purification of the monomer used in polymerization is carried out by preparing a module made of porous polypropylene with a pore diameter of 700 Å as measured by the mercury porosimeter method, for example, as shown in Figures 1 and 2. It was incorporated into a purification apparatus as shown and purified by a gas phase filtration method. G-t
-Butyl peroxide and t-butyl mercaptan were used after being filtered through a Teflon membrane module having a pore size of 0.1 μm. The formulation of monomers and additives is based on the pore size measured by mercury porosimeter method.
The experiments were carried out in a clean room filled with clean air passed through a module made of 700 Å porous polypropylene hollow fibers. The methyl methacrylate polymer was prepared using a module made of porous polypyrene hollow fibers with a pore diameter of 700 Å measured by the mercury porosimeter method, washed with distilled water, and dried in a clean room with an inner diameter of 10 mm and a wall thickness of 1 mm. After charging the monomer composition prepared under the conditions shown in Table 1 into a Pyrex glass tube with a length of 350 mm in a clean room, the mixture was heated to 10 ^-2 using a refrigerant consisting of dry ice and methanol. After repeating freezing and degassing three times under a reduced pressure of mmHg to remove dissolved air, the tube was sealed under reduced pressure and then immersed in an oil bath at 140° C. for 4 hours for polymerization. By this polymerization method, the inner diameter of 10 mmφ and the length of about 200 mm as shown in Table 1 is obtained.
mm of methyl methacrylate polymer rod ~
I got it.

[Table] An example of a purification apparatus preferable for carrying out the present invention is shown in FIG. The material is Pyrex glass. 1 is a container for containing the liquid to be purified;
Heat appropriately using electric heat, etc. 2 is used when distilling under reduced pressure with a capillary. 3 and other connections use SPC joints (manufactured by Shibata Kagakukiki Co., Ltd.) to prevent dust from entering.
4 is a rectification column, and 5 is a filter section. To prevent gas from condensing in this filter section, a tape heater 6 was wrapped around the outside to heat it. The gas is passed through the filter 5 and condensed in the cooling section 7, and only the liquid is stored in the container 8. In the case of a liquid with a high boiling point, 9 is a Teflon pot connected to 10 with a vacuum pump to maintain the system at reduced pressure. Figure 2 is 5
In the cross-sectional view of the filter shown in the section, thin porous hollow fibers 11 are bundled in a glass tube and both ends 12 and 13 are hardened with epoxy resin. is open. In the apparatus shown in FIGS. 1 and 2, gas passes through the porous membrane from the outer wall of the hollow fiber, passes through the hollow portion, and is released from the open end 12 thereof. It is also possible to supply the gas to be treated from inside the hollow fiber. Also, the filter may be placed vertically instead of horizontally. Furthermore, the hollow fiber may be opened at the terminal 13 as well, and gas may be allowed to enter and exit from both 12 and 13. (ii) Production of fluoroalkyl methacrylate polymer General formula (In the formula, X is a chain composed of random bonds with tetrafluoroethylene (T) and vinylidene fluoride (V), and the total number of (T) and (V) forming , and a chain in which the number ratio (T)/(V) of both is 1/5 to 5, where n represents 1 or 2) The synthesis of fluoroalkyl methacrylate is carried out by the route shown below. Ta. First, 0 to 100 parts by weight of tetrafluoroethylene, 0 to 100 parts by weight of vinylidene fluoride, methanol or ethanol.
500 parts by weight of di-t-butyl peroxide and 2 parts by weight of di-t-butyl peroxide were poured into a stainless steel autoclave and subjected to a telomerization reaction at 140°C to 150°C and a pressure of 500 to 700 kg/cm ² to form a fluoroalkyl alcohol. After that, it was fractionated by distillation, elemental analysis, and NMR to determine the composition ratio of tetrafluoroethylene and vinylidene fluoride that constitute the fluoroalkyl chain. Next, 100 to 200 parts by weight of these fluoroalkyls, 100 parts by weight of methacrylic acid chloride, and 5 parts by weight of p-methoxyphenol were charged into a flask, and the mixture was reacted by heating under reflux for 4 hours.
A fluoroalkyl methacrylate derivative was prepared by fractional distillation. The fluoroalkyl methacrylate polymer was produced by adding 0.1 part of azobisisobutyronitrile and 0.3 part of n-dodecylmercaptan to 100 parts by weight of the total monomers, and carrying out bulk polymerization at 80°C for 10 hours. The charging composition and the refractive index of the obtained polymer are
Shown in the table.

【table】

[Table] (iii) Manufacture of optical transmission fiber The optical transmission fiber was manufactured using the spinning apparatus shown in FIG. This spinning device includes a rod attachment chuck portion 14 that can slide at a constant speed on a monorail;
Pore diameter measured by mercury porosimeter method is 700Å
A rod end heater 15 filled with clean nitrogen gas passed through a module made of porous polypropylene hollow fibers, a cooling section 16 surrounded by a polycarbonate cylinder, and a container 1 for coating the sheath material.
7, a coating yarn drying tower 18, a take-off nip roller 19, and a winding machine 20. Nitrogen gas is passed through an air filter 21 and sent to the cooling section 16 . After the methyl methacrylate polymer rod 22 polymerized in step (i) is attached to the chuck portion 14, the chuck descending speed, the nip roller winding speed, and the heating temperature are adjusted so that the conditions do not cause fiber orientation. After stretching and spinning with appropriate adjustment, an ethyl acetate solution containing 20% by weight of each of Polymers A to G is applied and dried to obtain a light transmission fiber. By this method, optical transmission fibers having an outer diameter of 1 mm shown in Examples 1 to 8 and Comparative Examples 1 to 4 were manufactured. (iv) Evaluation of optical transmission loss The transmission loss of the obtained optical transmission fiber was measured using the apparatus shown in FIG. Light emitted from a halogen lamp 102 driven by a stabilized power source 101 is made into parallel light beams by a lens 103 and then monochromated by an interference filter 104 and has a numerical aperture equal to that of the light transmission fiber 100. The light is focused at the focal point of the lens 105. The light is made to enter the optical transmission fiber 100 by adjusting the incident end face 106 of the optical transmission fiber to be located at this focal point.
The light incident from the input end face 106 is attenuated and exits from the output end face 107. This emitted light is converted into a current by a photodiode 108 having a sufficiently large area, amplified by a current-voltage conversion type amplifier 109, and then read as a voltage value by a voltmeter 110. Measurement of transmission loss shall be carried out using the following procedure. First, the optical transmission fiber 100 is cut to a length of lo, with both end faces cut at right angles to the fiber axis and finished with a smooth surface.
The above device has an input end face 106 and an output end face 10.
7 so that it does not move during measurement. Read the reading on the voltmeter in a dark room. Let this voltage value be ₁ . Next, the room light is turned on, the output end face 107 is removed from the device, and the optical transmission fiber 100 is cut from this end face at a point 111 of length l. Then, the end face of the optical fiber that is attached to the device is finished to a surface perpendicular to the fiber axis in the same way as the first one, and this is installed as a new output end face in the device. During these operations,
In order to keep the amount of incident light constant, care must be taken not to move the incident end face 106. Return to the dark room, read the reading on the voltmeter, and set it to ₂ . Optical transmission loss (α) is calculated using the following formula. α=10/l log( _2/1 )(dB/ _Km ) where l: Length of optical fiber (Km) ₁ , ₂ : Light amount (voltmeter reading) The measurement conditions in the present invention are as follows. It is as follows. Interference filter (dominant wavelength): 646nm lo (total length of optical fiber): 15ml (cutting length): 10m D (diameter of bobbin): 190mm The bobbin is used here to make the device compact. The remaining optical transmission fibers are wound around a bobbin (not shown) such that the distance between the incident end face 106 and the outgoing end face 107 is approximately 1 m. Table 2 shows the results of each example and comparative example.

【table】 [Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a monomer purification device of the present invention, FIG. 2 is a diagram showing an example of a filter for monomer purification of the present invention, and FIG. 3 is an explanation of a spinning device for producing optical transmission fibers. 4 are explanatory diagrams of a transmission loss measuring device for optical transmission fibers. In the figure, 1: liquid container to be treated, 4: rectification column, 5: filter, 8: purified liquid container, 11:
Porous hollow fiber, 14: chuck part for rod attachment, 15: rod tip heater, 17: container for coating sheath material, 18: drying tower, 19: nip roller for take-up, 100: optical transmission fiber, 102: halogen Lamp, 104: Interference filter, 10
6: incident end face, 107: exit end face, 108: photodiode, 109: amplifier, 110: voltmeter.

Claims (1)

[Claims] 1. At least 90 mol% in terms of monomer mol%
The core material is a methyl methacrylate polymer containing methyl methacrylate units with the general formula (In the formula, X is composed of a random bond of tetrafluoroethylene (T) and vinylidene fluoride (V), and the total number of constituents of (T) and (V) forming X is 2 to 6, and A chain with a constituent number ratio (T)/(V) of 1/5 to 5, n
An optical transmission fiber characterized in that the sheath material is a polymer made of at least one fluoroalkyl methacrylate represented by (1 or 2) or a copolymer containing the compound () as a main component.