JPH0249005A - Vent type extruder - Google Patents

Abstract

PURPOSE:To obtain a vent type extruder capable of providing a plastic optical fiber having excellent corrosion resistance and good light transmission properties by using a metal alloy having specific Cr and Ni content and high Rockwell hardness as a material for cylinder and screw. CONSTITUTION:Methyl methacrylate(MMA) purified by vacuum distillation is stored in a storage tank 1, fed to a polymerization reaction tank 3, polymerized by heating under nitrogen atmosphere introduced from a nitrogen introduction line 7 and fed to a vent type extruder 10 using a metal alloy having 10-25% Cr content and <=2% Ni content and >=40 Rockwell C scale hardness as a material for cylinder 14 and screw 15 and unreacted monomer in the polymer is removed from plural vent ports 11 by raising the temperature in the vent type extruder to 180 deg.C in the inlet and 230 deg.C in the extruding part and then the resultant polymer is introduced to a composite spinning machine and spun using a fluorine-containing methacrylate copolymer as a sheath component to provide the optical fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vent extruder. More specifically, the present invention relates to a vent extruder for removing unreacted monomers from a methacrylic polymer that is a core component of plastic optical fibers when the polymer is produced.

[Prior Art] As a method for industrially manufacturing plastic optical fibers, for example, as proposed in Japanese Patent Publication No. 53-42261, continuous bulk polymerization/continuous polymerization of a methacrylic polymer as a core material is used. The monomer method is known. Further, as the manufacturing apparatus thereof, a tank type reaction vessel and a vent extruder are known as proposed in the same publication. Further, as proposed in Japanese Patent Application Laid-Open No. 61-275705, the device is constructed of materials with corrosion resistance in mind.

[Problems to be Solved by the Invention] However, even these devices are still insufficient. In other words, in the equipment proposed in Japanese Patent Publication No. 53-4226"l, sufficient consideration was not given to the occurrence of thermal oxidative deterioration during demonomer treatment, and when materials with insufficient corrosion resistance were used, the equipment Impurities caused by the material are mixed in, making it impossible to obtain a satisfactory light transmission performance.In addition, the device proposed in JP-A No. 61-275705 has excellent corrosion resistance, so heavy It is possible to suppress the incorporation of thermal oxidation degraded products of coalescence and corrosion-resistant material powder due to thermal oxidation degradation reactions, and a considerable improvement is recognized, but since the hardness is not very large, abrasion particles from sliding friction between the cylinder and screw are generated. It is not possible to easily produce a core material for plastic optical fibers that has excellent translucency.

The purpose of the present invention is to solve the above-mentioned problems of the conventional bent extruder, which is an apparatus for manufacturing optical fibers, and to further improve the rigidity, corrosion resistance, and abrasion resistance of the conventional bent extruder material. To provide a bent extruder for producing a core material of plastic optical fiber, which achieves excellent light transmission performance.

[Means to solve the problem] The present invention has the following configuration.

The configuration of the present invention will be explained in detail below.

(1) In the vent extruder that removes unreacted monomers from the polymer, Cylinder is added to the material of the cylinder and screw.
The r content is 10% or more and 25% or less, the Ni content is 2% or less, and the hardness is 40 on the Rockwell C scale.
A vent extruder characterized in that the above metal alloy is used.

(2) The vent extruder according to claim (1), wherein the hardness of the cylinder is greater than the hardness of the screw by 5 or more on the Rockwell C scale.

(3) The vent extruder according to claim (1) or (2), wherein the extruder comprises a single screw.

The present invention will be explained in detail below.

The metal material constituting the vent extruder of the present invention is
It is necessary that the metal alloy has a Cr content of 10% or more and 25% or less, and a Ni content of 2% or less. When producing a methacrylic polymer required for the core material of optical fibers, it is common to use a mercaptan compound as a chain transfer agent in addition to methyl methacrylate, which is the main component.

However, the mercaptan compound has a strong chemical corrosive effect, and when selecting a vent extruder to be used in the demonomerization process that removes unreacted monomers from the reaction solution at high temperatures, it is necessary to pay special attention to the corrosion resistance of the mercaptan compound. There is. - Aluminum, titanium, glass, etc. are known as materials with good corrosion resistance against mercaptan compounds for boat fishing. However, due to rigidity, workability, etc., it is not possible to manufacture a vent extruder using the above materials.

In addition, a Cr alloy with a Cr content of more than 25% reacts with a mercaptan compound in an oxygen atmosphere, precipitating a chromium sulfide compound and mixing it into the polymer, which significantly deteriorates the light-transmitting performance of the polymer.

Furthermore, in a Ni alloy with a N content exceeding 2%, it reacts with a mercaptan compound at high temperatures, precipitating a nickel sulfide compound, which is mixed into the polymer and significantly deteriorates the light-transmitting performance of the polymer.

Note that carbon steel containing Fe and C as main components reacts with methyl methacrylate at high temperatures, causing corrosion.

From the above, metal materials containing the above elements as main components cannot be used alone because they corrode mercaptan compounds or methyl methacrylate. however,
Surprisingly, the above-mentioned corrosion phenomenon was not observed at all in the alloy in which the mixing ratio of these elements was controlled, and it was found that the alloy had excellent corrosion resistance against the mercaptan compound and methyl methacrylate.

In other words, as a constituent material for a vent extruder that removes unreacted monomers and chain transfer agents from a methacrylic polymer at high temperatures, the Cr content is 10% to 25%.
A Cr alloy having a Ni content of 2% or less is suitable.

Next, the material of the vent extruder must have a hardness of 40 or more on the Rockwell C scale.

As is well known, the vent extruder purifies the polymer by sequentially removing unreacted monomers from a vent section provided in the cylinder when the polymer is transported by rotating a screw inside the cylinder. . Therefore, when the hardness of the vent extruder material is low, abrasion occurs due to sliding between the cylinder and the screw, and abrasion powder is mixed into the polymer, deteriorating the light-transmitting performance of the polymer.

To maintain excellent light transmission performance, the allowable concentration of metal wear particles in the polymer is 100% for any metal.
It is necessary to keep it below ppb. In order to create such a situation, it is necessary that the hardness of BentEx[-Ruda is 40 or more on the Rockwell C scale. In addition, in order to further suppress sliding wear between the cylinder and screw, it is effective to differentiate the hardness of the two.In this case, for economical reasons, the hardness of the cylinder is equal to the hardness of the screw. 5 on the Rockwell C scale.
It is preferable to increase the amount more than that.

A metal material that satisfies these requirements is 5US420J2 (Cr12-14%,
Ni0.6% or less), 5US440C (Cr16~18
%, Ni0.6% or less), 5KD-11 (Crl 1~
13%, NiO), HPM-38 (Cr15.5~
17.5%, N1% or less) (manufactured by Hitachi Metals).

By using the above metal material, thermal oxidative deterioration of the polymer in the vent extruder, corrosion of the metal material, and 1) dynamic wear are suppressed, and the produced polymer has extremely excellent light-transmitting performance. However, in order to further improve the light transmitting performance, it is preferable that the vent extruder is constructed from a single screw. This is because, in the case of a single-screw, the mechanism is to transport the polymer forward while the screw groove scrapes off the polymer adhering to the cylinder wall, whereas with a multi-screw, such as a biaxial screw, This is because the mechanism is such that the polymer pooled in the screw groove is transported forward by the meshing of the teeth of each screw, so multi-screws are more likely to cause wear due to contact between the screws.

The methacrylic polymer produced by the vent extruder of the present invention includes a polymer containing methyl methacrylate as a main component, and more preferably a methacrylic polymer containing 80% by weight or more of methyl methacrylate. is used.

In addition, the volatilized unreacted monomer removed by the vent extruder is not particularly limited; This is determined by taking into account process stability and economic efficiency including the polymerization process, and 3 in the methacrylic polymer reaction solution.
The present invention will be explained in more detail based on the following examples in which the content is preferably 0 to 60% by weight.

[Example] Examples 1 to 2, Comparative Example 1 The content of the polymerization reaction storage tank was 40ff and the screw diameter was 40
A methyl methacrylate polymer, which is a core component of an optical fiber, was produced using a polymerization reaction apparatus shown in FIG. 1, which was equipped with a single-layer screw vent extruder having a screw diameter of 1200# and a five-stage vent. Here, the barrel and screw of the bent extrusion were manufactured using various metal alloys as shown in Table 1.

MMA purified under reduced pressure and temperature is stored in a monomer storage tank, and 5 to 3/3
was fed into the polymerization reactor at a rate of 1 hour. Azo-1-octane 0.0045% by weight (relative to MMA') as a polymerization initiator
and 0.1 n-butyl mercaptan as chain transfer agent.
75% by weight (based on MMA) of MM to the polymerization reaction tank.
A line mix was added to the A supply piping. Nitrogen was supplied to the polymerization reactor and the reaction pressure was adjusted to 4'j/cm gauge.

Further, the heating system was adjusted so that the reaction temperature was 135°C. The liquid level was controlled so that the average residence time in the polymerization reaction tank was 4 hours, and the reaction product was weighed at 5 kg using a metering pump.
/hour and fed into a vent extruder.

The inlet temperature of the vent extruder is 180°C, the stomach is gradually warmed from the first vent part to the fifth vent part, and the temperature is 230°C at the extrusion part.
It was set to ℃.

The vacuum degree of the first vent part to the fifth vent part is 250°50.
It was set to increase in steps of 50, 20, and 5↑orr.

The polymer discharged from the vent extruder was introduced into a composite spinning machine, and a fluorine-containing methacrylate copolymer having a composition of tetrafluoropropyl methacrylate/methyl methacrylate = 90/10 was spun as a sheath component to obtain an optical fiber.

The spinning temperature was 242°C, and the weight ratio of the core component to the sheath component was 92:8. The core component was discharged at a discharge rate of 6.59/min per hole, and the take-up rate was 2 C) m1m group.

Table 1 shows the metal content in the 1q optical fiber and the optical properties of the fiber in comparison with the composition of the metal alloy constituting the vent extruder.

[Effect of the invention] The present invention has the following effects.

■ Since a metal material with excellent corrosion resistance is used as the constituent material of the vent extruder, there is no precipitation of chemical reaction products with unreacted monomers.

(2) Therefore, a methacrylic polymer with excellent optical properties can be obtained, and a plastic optical fiber containing the methacrylic polymer as a core component has excellent light-transmitting performance.

■ Since a highly hard metal material is used as the component of the vent extruder, it is possible to suppress the generation of friction powder between the cylinder and screw to an extremely small amount.
The light transmission performance of the plastic optical fiber containing the obtained methacrylic polymer as a core component is extremely excellent.

■ It is economical because the vent extruder can be constructed using general metal materials.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet diagram showing one aspect of the polymerization reaction process of a core component polymer used for manufacturing an optical fiber incorporating an extruder according to the present invention. 1° Monomer storage tank 2: Metering pump 3: Polymerization reaction tank 4: Upper jacket 5: Lower jacket 6
:Li stirrer, 7゛nitrogen introduction line 8:Pressure control valve 9
°Measuring pump, 10: Vent extruder 11: Multiple vents 12: Distillation system 13 Ni line 14 Niji cylinder 15: Screw

Claims (3)

[Claims] (1) In the vent extruder that removes unreacted monomers from the polymer, Cylinder is added to the material of the cylinder and screw.
The r content is 10% or more and 25% or less, the Ni content is 2% or less, and the hardness is 40 on the Rockwell C scale.
A vent extruder characterized in that the above metal alloy is used. (2) The vent extruder according to claim (1), wherein the hardness of the cylinder is greater than the hardness of the screw by 5 or more on the Rockwell C scale. (3) The vent extruder according to claim (1) or (2), wherein the extruder comprises a single screw.