JPH06278787A - Method for transporting and storing polycarbonate resin - Google Patents

Abstract

PURPOSE:To reduce generation of dust by using a metal material subjected to electrolytic polishing as a material for a tube and a storage container. CONSTITUTION:A metal material made of austenite stainless steel subjected to electrolytic polishing is used as a material for a tube and a storage container. Normally, dust in polycarbonate resin powder exists according to a specific particle size distribution, wherein when dust of 0.5 to 1.0mum size is 1.0X10<4> per gram or less, the amount of dust of 1.0 to 10mum size is 500 per gram or less, and the amount of dust of 10 to 50mum size is 1 to 2 per gram or less. Polycarbonate resin with such amounts of dust can be sufficiently applied to optic application. Using this tube and storage container can minimize contamination caused on the polycarbonate powder or pellets during tubing or transportation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an optical disc, a lens,
The present invention relates to a method of transporting and storing dust-reduced polycarbonate resin for manufacturing optical molded articles such as prisms. More specifically, it uses an electrolytically polished metal material as a material for piping and a storage container. The present invention relates to a method for transporting and storing a polycarbonate resin in which dust generation is reduced.

[0002]

2. Description of the Related Art For transporting and storing a polycarbonate resin, a method is generally used in which a pipe made of a mechanically polished corrosion resistant metal material is pneumatically transported by pressure feeding or suction, and then stored and transported in a container of the same material as the pipe. Is common. However, this method is not problematic for general grades or colored products, but may deteriorate quality when used for optical applications.

[0003] Usually, a pipe or a container made of a corrosion-resistant metal material is ground with a mineral abrasive as a surface finish. The surface finish by this method is a mirror finish in terms of visual appearance, but microscopically minute polishing streaks exist on the entire polishing surface. In the recess of this polishing striation,
The fine metal powder is bitten like a wedge, and it is difficult to completely remove the fine metal powder by ordinary cleaning. When the material or powder of the polycarbonate resin is transported or stored using the pipe or container made of such a material, fine metal powder on the inner surface of the container or the pipe is mixed into the polycarbonate resin for a long period of time. This phenomenon deteriorates the quality for optical applications.

[0004]

Polycarbonate resins used for optical applications are required to have dust reduced as much as possible, and the increase of dust in the transportation and storage steps has been a problem to be solved immediately. Up until now, it was recognized that the increase in dust due to transportation and storage was largely due to the surface finish of the corrosion-resistant metal materials used for piping and containers, but until now it has not been sufficiently resolved. is there. Accordingly, the present invention provides a method for transporting and storing a polycarbonate resin with reduced dust generation.

[0005]

[Means for Solving the Problems] As a result of intensive investigations by the inventors of the present invention, the materials for pipes and containers used for the transportation and storage of optical polycarbonate resins and the prevention of dust generation due to surface finishing have been investigated. The inventors have found that the amount of dust generated is significantly reduced by carrying out the method, and have reached the present invention.

That is, the present invention relates to a method of transporting and storing polycarbonate resin pellets, characterized in that a metal material made of austenitic stainless steel subjected to electrolytic polishing is used as a material for piping and a storage container.

The term "polycarbonate resin powder" as used in the present invention means a powder which has been dried in a conventional process for producing an optical aromatic polycarbonate resin, or a substance which has been separated from a refined aromatic polycarbonate resin solution. It is an undried powder containing non-solvent, water and the like. The amount of dust in such powder may be increased by any subsequent process, but is not decreased. In the case of polycarbonate resin powder or pellets used for optical applications, it is desirable that the amount of dust is as small as possible, and dust of at least 0.5 to 1.0 μm is 1.0 × 1.
It is necessary to set it to 0 ⁴ pieces / g or less.

Usually, the dust in the polycarbonate resin powder is present according to a specific particle size distribution, and is 0.5 to 1.0.
If the dust with a size of μm is 1.0 × 10 ⁴ particles / g or less, the amount of dust with a size of 1.0 to 10 μm is 500 /
The amount of dust having a size of g or less and 10 to 50 μm is 1 to 2 pieces / g or less. This amount of dust is sufficiently applicable as a raw material powder for optical use.

In the actual manufacturing process, the aromatic polycarbonate resin powder is generally obtained through the following steps. First, the polycarbonate resin solution is separated from the polymerization solution and purified, and then fine dust is removed by microfiltration, centrifugation, etc. to obtain a purified good solvent solution of the polycarbonate resin. Then, a method of concentrating the resin solution as it is or by adding a poor solvent to the resin solution to such an extent that precipitation does not occur or by condensing the resin solution into warm water and distilling off the solvent The "concentration method", which is a so-called "warm water dropping method", and the "precipitation method", which is a method of dropping the resin solution into a poor solvent or dropping the poor solvent into the resin solution, Separate and
Dry to a dry powder.

Alternatively, a wet powder produced by adding water to the wet powder obtained by the "warm water dropping method" or the powder obtained by the precipitation method and heating the mixture while appropriately wet-milling to distill off the solvent. It is also possible to obtain a polycarbonate resin powder as a powder.

When pelletizing the above polycarbonate resin powder, the polycarbonate resin powder is mixed into an extruder with a vent having one or more or more uniaxial or one or more vents to prevent dust from entering from the outside. And pellets are produced while distilling off the volatile components in the resin from the vent.

After the production and granulation steps, the powders and pellets are transported to a storage tank by an air transportation system by suction or pressure feeding. In the case of pressure feeding, it is pneumatically transported in the corrosion-resistant metal pipe at a pressure of 1 to 7 kg / cm ² and in the case of suctioning at a pressure of −500 mmAq to −1000 mmAq. The powder or pellets move at a flow rate of 3 to 20 m / sec in this air transportation pipe. Usually, a corrosion-resistant metal pipe whose inner surface is finished by mechanical polishing is used for the air transportation pipe.

By the way, as described above, generally, in mechanical polishing, polishing is performed by using a mineral abrasive according to the finishing accuracy, and the surface finish is a mirror finish in terms of visual appearance, but it is microscopically fine. Abrasive scratches exist on the entire polishing surface. The fine metal powder of the polishing agent is wedged into the concave portion of the polishing streak. When the powder or pellets having the above-mentioned flow velocity collide with the polished surface, the mineral particles are mixed in the polycarbonate resin powder or pellets to cause contamination.

The powder or pellets are filled in an airtight corrosion-resistant metal container and shipped. If the shipping container is also mechanically polished, vibration caused by transportation causes the same contamination.

The austenitic stainless steel of the material used for the piping and storage container of the present invention is preferably an alloy having the following components.

Alloy 1 C: 0.03 wt% or less Si: 1.0 wt% or less Mn: 2.0 wt% or less P: 0.045 wt% or less S: 0.03 wt% or less Ni: 8.0 ~ 12.0 wt% Cr: 18.0 to 20.0 wt%

Alloy 2 C: 0.03 wt% or less Si: 1.0 wt% or less Mn: 2.0 wt% or less P: 0.045 wt% or less S: 0.03 wt% or less Ni: 10.0 〜14.0% by weight Cr: 16.0 to 3.0% by weight Mo: 2.0 to 3.0% by weight

In the present invention, the above contamination is prevented by adopting electrolytic polishing as the surface finish of the corrosion resistant metal. In the present invention, the surface roughness after electrolytic polishing preferably has a maximum height Rmax of 0.8 μm.

In the electropolishing of the present invention, an anode for direct current is connected to the object to be polished, and an external current is caused to flow in the electrolytic solution so as to face the cathode, whereby the uneven portion of the object to be polished is electrochemically treated. It dissolves and removes fine particles that cause contamination.

[0020]

[Examples] The following test was conducted to confirm the effect of reducing the dust of the electrolytic polishing treatment material on the optical polycarbonate resin. As a test container, the following three types of different materials, and a closed container with a surface finish are prepared.

(1) Material: SUS304 Inner surface: Electropolish finish (2) Material: SUS316 Inner surface: Buff # 400 Polish finish (3) Material: SUS316 Inner surface: No finish (2B material equivalent)

The inner surface of each container is washed with a surfactant and ultrapure water. After the containers are dried in a class 100 clean booth, the optical polycarbonate resin powder or pellets are placed in each container and sealed, and the containers are fixed on a shaker. The frequency of the shaker was set to three levels of 3 times / second, 4 times / second, and 5 times / second, and shaking was performed for a maximum of 5 hours, and the change in the number of dust increases with time was measured. The optical polycarbonate resin powder or pellet used in the test is 0.5 to
The dust having a size of 1.0 μm is 1.0 × 10 ⁴ particles / g or less.

FIGS. 1 to 6 show the results of measuring the change in the number of dusts over time with the number of shakes of each container. The dust number was measured by using a light scattering type particle size sensor in a solution of 1 g of polycarbonate resin dissolved in 100 cc of methylene chloride.

As shown in FIGS. 1 to 6, when the material produced by the method according to the present invention is used, the dust increase is remarkably suppressed. On the other hand, it is easily understood that the increase of dust is remarkable when the material produced by the conventional method is used, and the stable production of the polycarbonate resin for optical use is adversely affected.

[0025]

Industrial Applicability The polycarbonate resin powder or pellets are pneumatically transported using the electrolytically polished metal pipe subjected to the electropolishing treatment of the present invention, and are stored in a container of the same material, so that the polycarbonate resin powder or pellets can be stored in a pipe or during transportation. It is useful for transportation and storage of optical polycarbonate resin powders and pellets, which require minimal dusting.

[Brief description of drawings]

FIG. 1 is a diagram showing a time-dependent change in the number of dust in each container when pellets of the same quality are hermetically sealed in each container, set on a shaker and shaken 3 times / sec.

FIG. 2 is a diagram showing a time-dependent change in the number of dust in each container when pellets of the same quality are sealed in each container, set in a shaker, and shaken 4 times / sec.

FIG. 3 is a diagram showing a time-dependent change in the number of dust in each container when pellets of the same quality are hermetically sealed in each container and set in a shaker and shaken 5 times / sec.

FIG. 4 is a diagram showing a time-dependent change in the number of dust in each container when the same quality material powder is sealed in each container and set in a shaker and shaken 3 times / sec.

FIG. 5 is a diagram showing a time-dependent change in the number of dusts in each container when the same quality material powder is sealed in each container and set in a shaker and shaken 4 times / sec.

FIG. 6 is a view showing a time-dependent change in the number of dust in each container when the same quality material powder is sealed in each container and set in a shaker and shaken 5 times / sec.

Claims (3)

[Claims] 1. A method for transporting and storing polycarbonate resin pellets, characterized in that a metal material made of austenitic stainless steel subjected to electrolytic polishing is used as a material for the pipe and the storage container. 2. The method according to claim 1, wherein the polycarbonate resin powder or pellets are transported and stored in a sealed state without contact with the outside air. 3. The method according to claim 1, wherein the surface roughness of the electrolytically-polished metal material has a maximum height Rmax of 0.8 μm.