JP4825123B2 - Cleaning method for fiber spinning nozzle - Google Patents

Description

  The present invention relates to a method for cleaning a fiber spinning nozzle used when producing a fibrous product such as an optical fiber by a melt spinning method.

Conventionally, optical fibers such as plastic optical fibers are manufactured by melt spinning. FIG. 2 is a partial cross-sectional view schematically showing an example of the melt spinning process. Reference numeral 1 denotes a fiber spinning nozzle (hereinafter also simply referred to as “nozzle”), and 2 denotes an optical fiber. In the melt spinning process, as shown in FIG. 2, a resin 2 a used as a core material or a clad material is supplied to a fiber spinning nozzle 1, and an optical fiber 2 shaped into a fiber shape from the tip of the nozzle 1. Is discharged.
However, in the melt spinning step, as schematically illustrated in FIG. 3, the core material or the clad material may remain as the resin carbide 3 in the nozzle 1. If the amount of the resin carbide 3 increases with time, the flow path of the resin 2a may be inhibited to cause the resin 2a to stay, or the resin carbide 3 may be mixed into the staying resin 2a. Further, when the resin carbide 3 adheres in the vicinity of the outlet of the nozzle 1, there is a problem in that the outer shape abnormality in which the two diameters of the ejected optical fiber fluctuate locally is caused and the optical characteristics of the optical fiber 2 deteriorate.

  Therefore, when producing optical fibers by the melt spinning method, in order to maintain good quality of the optical fibers over a long period of time, the inside of the nozzle is periodically cleaned, and the resin carbide adhering or remaining in the nozzle is removed. Need to be removed. Conventionally, such a nozzle cleaning method includes a cleaning method using an organic solvent such as acetone, a cleaning method by heat treatment, a heating cleaning method using an alkaline solution, and the like.

Further, when a fluorine-containing resin is used as a clad material for optical fibers, the inner wall of the nozzle 1 may corrode. When such corrosion occurs, a portion where the resin (cladding material) 2a is likely to stay in the nozzle 1 is generated, and the phenomenon that the optical properties of the optical fiber deteriorate due to the staying and deteriorated resin being mixed, The problem is that the flow state of the resin fluctuates and the outer diameter of the optical fiber becomes abnormal.
Therefore, when corrosion occurs in the nozzle, it is preferable to remove the corroded portion before the corrosion proceeds.

  However, in the conventional method of cleaning using an organic solvent, it is difficult to sufficiently remove the resin carbide and corroded portion adhering in the nozzle.

  On the other hand, in the cleaning method by heat treatment, it is difficult to sufficiently remove the resin carbide adhering to the inside of the nozzle, and the corroded portion cannot be removed. When a thin nozzle used for melt spinning is washed, the fiber spinning nozzle may be deformed by heat. Furthermore, when a fluororesin is used as the optical fiber cladding material, hydrogen fluoride may be generated during the heat treatment, which may promote corrosion of the nozzle itself.

  Further, the heat cleaning method using an alkaline solution has a problem that an appropriate disposal of the alkaline solution and the cleaning liquid is required.

  The present invention has been made in view of the above circumstances, and provides a method for cleaning a fiber spinning nozzle that can sufficiently remove deposits and corroded portions in the nozzle without causing deformation of the fiber spinning nozzle. The purpose is to do.

In order to solve the above-mentioned problems, the method for cleaning a fiber spinning nozzle according to the present invention includes an injection step of injecting, into the nozzle, an abrasive having abrasive particles attached to the surface of core particles made of an elastic material. And
It is preferable to have a preliminary cleaning step of cleaning the inner surface of the nozzle with a solvent before the spraying step.
In the spraying step, spraying may be performed a plurality of times by changing the particle diameter of the abrasive grains.

  According to the cleaning method of the present invention, deposits in the nozzle can be sufficiently removed without causing deformation of the melt fiber spinning nozzle, and the corroded portion can be easily removed even when corrosion occurs on the inner wall of the nozzle. It can be removed by polishing.

  Embodiments of the present invention will be described below. In the following, as an example of a fiber spinning nozzle, a nozzle used when producing optical fibers by the melt spinning method will be described. However, the method of the present invention uses a fiber spinning method other than optical fibers by the melt spinning method. The present invention can also be applied to a fiber spinning nozzle used for manufacturing.

[Preliminary washing process]
First, a preliminary cleaning process is performed in which the inner surface of the nozzle is cleaned with a solvent to remove a part of the residue and deposits. In the present invention, the pre-cleaning step is not essential, but when there are many residues and deposits to be removed, it is preferable to perform the pre-cleaning step prior to the spraying step. Specifically, the nozzle can be immersed in a solvent.
As the solvent, a solvent that dissolves the residue to be removed and the deposit can be appropriately selected and used. In the case of a nozzle for optical fiber production, the main residue and deposit are resin carbides, and an organic solvent such as acetone is suitable as the solvent.

[Injection process]
(Abrasive)
Next, cleaning is performed by a method of spraying an abrasive into the nozzle (a spraying step). In the present invention, an abrasive having abrasive particles attached to the surface of core particles made of an elastic material is used.
FIG. 1 is a cross-sectional view schematically showing a preferred embodiment of an abrasive. In the abrasive of this embodiment, an adhesive layer 12 is provided on the outer periphery of the core particle 11, and abrasive grains 13 are attached to the adhesive layer 12.
In the present invention, the phrase “abrasive grains are attached to the surface of the core particles” means that the core particles and the abrasive grains are in a state of flowing integrally. Therefore, in the abrasive of the present embodiment, “abrasive grains 13 adhering to the adhesive layer 12” are not in contact with the adhesive layer 12 in addition to the abrasive grains 13 in contact with the adhesive layer 12. Also included are abrasive grains 13 that are in contact with the abrasive grains 13 that are in contact with the layer 12 by cohesive force or the like, and as a result, are in a state of flowing integrally with the core particles 11. From the viewpoint of the durability of the abrasive, it is preferable that the adhesive layer 12 and the abrasive grains 13 of the entire company are in physical contact.

The core particle 11 is made of an elastic material and has an indefinite shape. As the elastic material, an elastically deformable polymer material is used. Specific examples include isoprene rubber, chloroprene rubber, silicone rubber, acrylic rubber, acrylic elastomer, styrene elastomer, and polyester elastomer.
If the abrasive core particles are made of an elastic material, when the abrasive material collides with the deposit in the nozzle, it will collapse due to elastic deformation and the collision area will increase. It is considered that the effect of removing the deposits is enhanced by promoting the peeling.
The particle diameter of the core particles is preferably in the range of 0.1 to 0.6 mm, and more preferably in the range of 0.3 to 0.6 mm.
In one type of abrasive, the particle size of the core particles may not be uniform and may vary within the above range. The variation is preferably small.

The adhesive layer 12 is made of a material having adhesiveness to both the core particles 11 and the abrasive grains 13.
The adhesive layer 12 is preferably provided so as to cover the entire outer peripheral surface of the core particle 11. The thickness of the adhesive layer 12 should just be more than the thickness from which favorable adhesiveness is obtained.

The abrasive grains 13 are made of a material having a polishing ability with respect to deposits to be removed and corroded portions on the inner surface of the nozzle. Specific examples include diamond, silicon carbide, alumina and the like.
Among these, diamond is particularly preferable because it has a very high polishing ability, so that the polishing time is short and the core particles 11 are easy to last.
Silicon carbide is preferable because it has a high polishing ability and is inexpensive. Alumina is suitable for surface finishing to reduce the surface roughness of the nozzle inner wall.
The particle diameter of the abrasive grains is preferably 10 μm or less, and more preferably 5 μm or less.
In one type of abrasive, the particle size of the abrasive grains may not be uniform and may vary within the above range. The variation is preferably small.

(Injection device)
As a device for injecting the abrasive into the nozzle, a known injection device can be used as appropriate. For example, an apparatus known as a shot blasting apparatus can be used. As the shot blasting apparatus, an air blasting apparatus that uses compressed gas as injection power, an impeller type that uses a blade that rotates at high speed, and the like are well known. For example, if an apparatus having an elevator and an elevator mechanism for circulating the injected abrasive as described in Japanese Patent No. 3588284 is used, the injection and cleaning equipment should be small and maintainable. Can do.

(Injection method)
The step of injecting the abrasive into the nozzle may be performed by (1) a method of injecting one type of abrasive once or twice, or (2) injecting a plurality of times by changing the particle diameter of the abrasive grains. You may carry out by the method to perform, ie, the method of spraying once or twice each using 2 or more types of abrasives from which the particle diameter of an abrasive grain differs.
In the method (2), first, a coarse abrasive having a large grain size of abrasive grains is sprayed to perform the first injection step, and then a finished abrasive having a grain size of abrasive grains smaller than the coarse abrasive. It is preferable to select the abrasive so that the particle size of the abrasive grains is sequentially reduced, for example, by performing the second injection step. According to this method, even when there is a large amount of deposits remaining on the inner surface of the nozzle after preliminary cleaning, the deposits can be sufficiently removed, and the surface roughness of the nozzle inner surface is reduced so that resin carbides are less likely to adhere. Surface finish is possible.
The coarse abrasive preferably has a core particle diameter in the range of 0.4 to 0.6 mm and an abrasive grain diameter in the range of 4 to 5 μm.
The finish abrasive preferably has a core particle diameter in the range of 0.3 to 0.5 mm and an abrasive grain diameter of 1 μm or less. By using abrasive grains having a particle diameter of 1 μm or less, the inner surface of the nozzle can be mirror-finished, and thereby it is possible to satisfactorily suppress the adhesion of resin carbide and the like after cleaning.

  On the other hand, when the amount of deposits remaining on the nozzle inner surface after the preliminary cleaning is relatively small, the deposits can be sufficiently removed even using the method (1). In this case, it is preferable to perform the removal of deposits and the surface finishing of the inner surface of the nozzle at the same time using the above-mentioned finish abrasive.

According to this embodiment, resin carbide or the like remaining or adhering in the nozzle can be sufficiently removed by polishing. In addition, since the inner surface of the nozzle can be polished, the surface roughness of the inner surface of the nozzle can be reduced to suppress adhesion of resin carbide, etc., and even when light corrosion occurs on the inner surface of the nozzle, the corroded portion is removed by polishing, Further surface finishing can be performed.
Therefore, by cleaning the inside of the nozzle periodically or as necessary with the cleaning method of the present embodiment, a stable quality optical fiber with no abnormal outer diameter or optical characteristics is produced by a melt spinning method over a long period of time. It becomes possible to do.
In addition, since the nozzle can be satisfactorily cleaned without going through the step of heating the nozzle or the step of using an alkaline solution, the alkaline solution is discarded without worrying about nozzle deformation or hydrogen fluoride generation. This complicated operation is also unnecessary.

The following examples illustrate the invention. Various evaluations were performed by the following methods.
[Evaluation of optical characteristic abnormality] A plastic optical fiber (hereinafter abbreviated as POF) was manufactured, and the obtained POF was subjected to transmission loss using light of wavelength 650 nm and NA = 0.1 by the 25-5 m cutback method. And the number of times that a sudden increase in transmission loss occurred was measured. When resin carbide or the like is mixed into POF, a rapid increase in transmission loss occurs. Therefore, a small number of occurrences indicates that there is little mixing of resin carbide or the like.

  The abrasives used in the following examples are shown in Table 1 below. Both have the configuration shown in FIG.

  In the following examples and comparative examples, as a nozzle for cleaning, a nozzle used for discharging a single-core plastic optical fiber having a certain amount of resin carbide adhered on the inner surface is used. It was.

Example 1
A pre-cleaning step was performed by immersing the nozzle in acetone. After roughly removing the resin carbide inside the nozzle by the preliminary cleaning step, an injection step was performed using an injection device. First, as a first spraying step, a coarse abrasive (D) was sprayed into the nozzle.
Then, the finishing abrasive (D) was injected into the nozzle as a second injection step.
When the inner wall of the nozzle was observed after the second injection step was completed, no resin carbide adhered.

Next, using the nozzle cleaned by the above method, the core is made of polymethyl methacrylate (PMMA) and the clad is made of vinylidene fluoride / tetrafluoroethylene copolymer (molar ratio; 80/20 mol%). A POF having a diameter of 0.5 mm was produced over about 50 km, and the number of occurrences of abnormal optical properties and abnormal outer diameters of the obtained POF was measured by the above method.
The results are shown in Table 2 together with main production conditions.

(Example 2)
In Example 1, the nozzle was cleaned in the same manner as in Example 1 except that the coarse abrasive (S) was used in the first spraying step. Using the nozzle thus cleaned, a POF was prepared in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Table 2 together with main production conditions.

(Example 3)
In Example 1, the nozzle was cleaned in the same manner as in Example 1 except that the finish abrasive (A) was used in the second spraying step. Using the nozzle thus cleaned, a POF was prepared in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Table 2 together with main production conditions.

(Comparative Example 1)
In Example 1, a POF was prepared and evaluated in the same manner as in Example 1 except that a nozzle that had been subjected only to the preliminary cleaning step using acetone was used. The results are shown in Table 2 together with main production conditions.

(Comparative Example 2)
Using a heating furnace, the nozzle was heat-treated at 500 ° C. A POF was prepared and evaluated in the same manner as in Example 1 except that the nozzle thus cleaned was used. The results are shown in Table 2 together with main production conditions.

(Comparative Example 3)
The nozzle that had been pre-cleaned in the same manner as in Example 1 was heat-cleaned by a method of immersing it in an alkaline solution. A POF was prepared and evaluated in the same manner as in Example 1 except that the nozzle thus cleaned was used. The results are shown in Table 2 together with main production conditions.

  From the results in Table 2, in Examples 1 to 5, stable POFs having no outer diameter abnormality and optical characteristic abnormality were obtained. This shows that the nozzle has been sufficiently cleaned. On the other hand, in Comparative Examples 1 to 3, the occurrence of abnormal outer diameters and optical characteristics are more frequent than in Examples 1 to 5, and it can be seen that the cleaning of the nozzle is insufficient.

It is a schematic sectional drawing which shows one Embodiment of the abrasive | polishing material concerning this invention. It is a partial cross section schematic diagram for demonstrating a melt spinning process. It is a partial cross section schematic diagram for demonstrating the problem in a melt spinning process.

Explanation of symbols

11 ... Core particles,
12 ... Adhesive layer,
13 ... abrasive.

Claims (3)

  A method for cleaning a fiber spinning nozzle, comprising: an injection step of injecting an abrasive having abrasive particles attached to the surface of core particles made of an elastic material into the nozzle.   2. The method for cleaning a fiber spinning nozzle according to claim 1, further comprising a preliminary cleaning step of cleaning the inner surface of the nozzle with a solvent before the jetting step.   3. The method for cleaning a fiber spinning nozzle according to claim 1, wherein in the spraying step, spraying is performed a plurality of times while changing the particle diameter of the abrasive grains.

Images