JP2001264599A - Polyethylene resin composition for manufacture of spacer of optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyethylene resin composition which is suitable for the spacer of an optical fiber cable by hetero-extrusion forming and which realizes improvement in the surface smoothness of the molded spacer, decrease in color changes and suppression of production of contaminant. SOLUTION: The composition contains a polyethylene resin as the main component and a fluorocarbon resin as an additive component, and the polyethylene resin has 0.01 to 0.3 g/10 minutes melt index(MI) and 0.94 to 0.96 g/cm3 density. The fluorocarbon resin has 100 to 300 deg.C melting point and >=50 wt.% fluorine content. The content of the fluorocarbon resin is 0.01 to 2 parts by mass to 100 parts by mass of the polyethylene resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyethylene resin composition suitable for producing a spacer for an optical fiber cable.

[0002]

2. Description of the Related Art In modern life, information exchange plays an important role, and various information is transmitted through various communication means. As for the communication means, they are roughly classified into those using electric signals and those using optical signals. Of these, the so-called optical communication using an optical signal is a newer technology than the telecommunication using an electric signal in the past, but is rapidly spreading with the progress of optical fiber as a communication medium.

[0003] An optical fiber used for optical communication is generally a fibrous transmission medium made of glass or transparent resin, and has a structure in which a high refractive index core (core wire) is covered by a low refractive index clad. It is used as a single strand or as a cable composed of a plurality of wires. In addition, the optical fiber is lightweight, has a low loss property and can be used for a long repeater section, and has a wide band, which enables high-speed transmission. It has excellent characteristics such as being capable of communication and being made of a non-metallic material, having high insulation properties and ignoring a ground potential difference.

[0004] An optical fiber cable (or simply an optical cable) in which a plurality of optical fibers are assembled is roughly classified into four types, a layered type cable, a unit type cable, a tape type cable, and a spacer type cable, from the viewpoint of the basic structure. In the spacer type cables, various spacers are used to protect the fiber strands or the core wires from external force. As an example, a spacer with a spiral groove is shown in FIGS. 1 (A) and 1 (B). The spacer 11 has a groove 13 for storing an optical fiber formed in a spiral shape on its surface, and is manufactured by extruding a polymer material such as polyethylene into a deformed shape. Reference numeral 15 in the drawing denotes a member called a tensile strength member, which has a function of allowing an optical fiber (not shown) stored in the groove 13 to withstand the tension at the time of laying a cable. Is done. Although the optical cable spacer shown in FIGS. 1 (A) and 1 (B) is provided with only one spiral groove, one spacer may be provided with two or more spiral grooves.

In order to manufacture the spacer 11 having such a complicated structure by profile extrusion molding, generally, a polymer material having a high melt viscosity which is advantageous for the dimensional stability of a molded product is used. As a measure of the melt viscosity of a polymer material, there is a melt index (MI), and a material having a lower MI has a higher viscosity (lower fluidity) when melted. Extrusion molding of the spacer 11 of FIG.
Polyethylene for less than 10 minutes is used.

However, when such a low-MI polyethylene is used for profile extrusion, unless the extrusion processing speed (generally called "linear speed") is reduced, the following problems occur. (1) Since the viscosity at the time of molding is high, the back pressure is too high. (2) Melt fracture (a phenomenon in which parallel flow lines are not formed on the die land because the flow rate into the die orifice of the extrusion molding machine is too high, and the resulting surface roughness of the molded product occurs) occurs.

[0007] Among them, a fatal problem for the optical cable spacer which is an extruded product is the occurrence of melt fracture. The occurrence of melt fracture
This means that the smoothness of the wall forming the groove of the spacer for storing the optical fiber cable is reduced. Therefore, if the optical fiber is stored in the groove of the spacer where the melt fracture occurs, a problem in transmission characteristics occurs. The reason is that the optical fiber core wire stored in the groove of the spacer is in direct contact with the wall of the groove of the spacer, and when the surface smoothness of the spacer is reduced, the micro fiber bending of the optical fiber fiber called microbending is reduced. This is because bending occurs, causing transmission loss.

Conventionally, in order to solve such a problem, a fluorine rubber-based additive has been added to a polyethylene resin as a spacer material for an optical cable (Japanese Patent Application Laid-Open No. 9-40816). By using this additive, even if a low MI polyethylene resin material was used, the melt viscosity could be reduced, the occurrence of melt fracture could be suppressed, and the surface smoothness of the spacer could be improved. .

However, when a polyethylene resin material is extruded and formed by using the fluororubber additive, when the processing temperature or the resin temperature rises, the heat resistance of the fluororubber additive is low, so that the discoloration of the molded product is reduced. And may cause. Generally, polyethylene resin is a fatty acid salt-based lubricant (for example, calcium stearate, magnesium stearate, zinc stearate, etc., and particularly calcium stearate is often used).
In many cases, when such a lubricant is used in combination with a fluororubber-based additive, their interaction (reaction)
As a result, the discoloration of the extruded product is remarkably increased, and further, the resin material staying in the screw of the extruder may be changed to a black foreign substance. Such foreign matter may cause a contaminant called "eyes" to be generated on the lip portion of the die, or may cause an excessive load on the extruder to hinder extrusion.

[0010]

SUMMARY OF THE INVENTION Accordingly, the present invention is intended to improve the surface smoothness of the spacer of a molded product even when the spacer is molded at an increased extrusion processing speed (linear speed) during the production of an optical fiber cable spacer by profile extrusion molding. Polyethylene resin useful for the manufacture of spacers for optical fiber cables, which can be improved, can reduce discoloration of molded products, and can be extruded while suppressing the occurrence of eyes even when used in combination with a lubricant. It is intended to provide a composition.

[0011]

SUMMARY OF THE INVENTION
The Tylene resin composition is used as a spacer for optical fiber cables.
A composition used for the production of polyethylene
Fat as a main component, and fluororesin as an additive component.
In addition, the polyethylene resin has a melt index (M
I) is 0.01 to 0.3 g / 10 min, and the density is 0.94 to
0.96 g / cm ^ThreeWherein the fluororesin is
Melting point: 100-300 ° C, fluorine content: 50 wt% or less
Above, and the content of the fluororesin is
0.01 to 2 parts by mass per 100 parts by mass of polyethylene resin
Part of the polyethylene resin composition.

Preferably, the fluororesin has a melting point of 1
Use one having a temperature of 10 to 230 ° C. Again, preferably
A fluorine resin having a fluorine content of 66% by weight or more is used.

More preferably, a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer is used as the fluororesin.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The main component in the composition of the present invention is
Polyethylene resin, which is 0.01-0.3 g /
MI of 10 minutes and 0.94-0.96 g / cm^ThreeDensity
Having. Polyethylene resin MI is 0.01 g / 10
If less, optical cable manufactured by profile extrusion
Spacers for metal do not have sufficient surface smoothness.
If it exceeds g / 10 minutes, the fluidity of the composition at the time of molding is high.
Dimensional stability of spacers formed by
You. The polyethylene resin has a density of 0.94 g / cm.
^ThreeIf it is less than, the rigidity of the molded spacer is insufficient
And the density is 0.96 g / cm^ThreeOver, the spacer
The surface smoothness is reduced.

The fluororesin used as an additive component in the composition of the present invention has a higher heat resistance than a fluororubber conventionally used as an additive component for a polyethylene resin composition as a raw material for producing an optical cable spacer. It has been found that it is excellent and has little interaction with lubricants widely used in polyethylene resin compositions. Fluororesin and fluororubber are both polymers containing a fluorine atom in the molecule, but both have differences as described below.

Generally, a substance called "rubber" (or "elastomer") is a polymer that exhibits entropy elasticity (rubber elasticity) in a rubber state. The rubber state is defined as an amorphous (non-crystalline, amorphous) polymer liquid state among the possible states of a substance.
The rubber state of a specific substance is on the higher temperature side than the glass transition temperature (Tg) of the substance, and the entropy elasticity (rubber elasticity) refers to an undeformed state in which a system that has been deformed and has reduced entropy has a large entropy. Elasticity based on voluntary return. The entropy elasticity is characterized by an elongation usually up to several 100% and a small elastic modulus of the order of 10 ⁶ N / m ² . Few substances exhibit permanent elasticity due to entanglement of physical macromolecules, and many of them are elasticized by a method of crosslinking. According to the definition of the ASTM, entropic elasticity means that a substance is stretched twice in length at room temperature (18 to 29 ° C.) in an undiluted state and held for 1 minute before loosening, but after 1 minute, It shrinks to less than 1.5 times its original length.

On the other hand, "resin" is not an amorphous polymer but a polymer having crystallinity and exhibiting no elasticity at room temperature. Simply put, among the high-molecular substances, all that are not rubber can be considered as resins.

More specifically, an amorphous polymer (rubber) shows a glass transition point (Tg) but does not show a melting point, and a resin shows a melting point but the glass transition point becomes difficult to understand. Does not show Tg when it becomes a crystalline resin. Generally, a polymer having a temperature of Tg or lower has a glass-like property, and is hard and easily broken.

At present, the fluororubbers used industrially are limited, and vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-propylene copolymer and tetrafluoroethylene-vinylidene fluoride-hexafluoropropylene are used. Mainly copolymers. These have a Tg of about −35 ° C. to −5 ° C., are in the rubber elastic region at room temperature, and do not show a melting point even at a high temperature.

As described above, in the present invention, a fluororesin having a melting point is used unlike fluororubber. Examples of such a fluororesin include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-hexa. Fluoropropylene-perfluoroalkyl vinyl ether copolymer (EPA), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVD)
F), tetrafluoroethylene-propylene copolymer (TFE / P), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (T
HV) and the like. The fluororesin used as an additive in the polyethylene resin composition of the present invention has better heat resistance than fluororubber, and when used in combination with a stearate-based lubricant, interaction (reaction) with the lubricant. Can be reduced.

The fluororesin used in the present invention comprises 1
It is important to show a melting point in the range from 00 to 300 ° C. If the melting point of the fluororesin is less than 100 ° C., the dispersibility of the fluororesin used is too low, which is not preferable.
That is, in order to obtain the effect of the additive, it is necessary that the fluororesin is uniformly dispersed in the polyethylene and the dispersed particle diameter is small. In order to obtain such dispersibility, it is necessary that the fluororesin is melted at the time of polyethylene processing and molding, and for that purpose, the melting point is preferably 100 ° C. or more. If the temperature exceeds 300 ° C., the molding temperature becomes 30
The temperature is 0 ° C. or higher, so that the polyethylene itself is liable to be decomposed, so that it is difficult to sharply form. A more preferable range of the melting point of the fluororesin is 110 to 230 ° C.
It is. Of the fluororesins mentioned above as examples, those having a melting point of 100 to 300 ° C. are FEP, PCTFE, E
TFE, PVDF, TFE / P, THV and the like. Further, among these, those having a melting point of 110 to 230 ° C.
PVDF, TFE / P, THV and the like. Considering the reactivity between the fluororesin and the stearate-based lubricant in the polyethylene resin composition and the stability of the fluororesin itself, THV is most suitable.

The tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer is also used in the polyethylene resin composition described in JP-A-9-40816 described above. Is a "fluoroelastomer". "Elastomer" is a general term for substances that exhibit rubber elasticity at around room temperature. As already clarified, fluorine-based elastomers have a Tg of about -35 ° C to -5 ° C and are in the rubber elasticity range at room temperature. Since it does not show a melting point, it is clearly distinguished from the "fluororesin" used in the present invention.

In order to obtain a spacer for an optical cable having improved surface characteristics from the polyethylene resin composition of the present invention to which a fluororesin is added by profile extrusion molding, the fluorine content of the fluororesin is preferably 50 wt% or more. When the fluorine content is less than 50 wt%, not only the heat resistance of the fluororesin is hardly obtained, but also the compatibility with polyethylene is exhibited, so that the effect of the present invention cannot be sufficiently obtained. More preferably, the fluororesin is 6
Contains 6 wt% or more of fluorine.

In the polyethylene resin composition of the present invention, the fluororesin is used in an amount of 0.01 to 2 parts by mass per 100 parts by mass of the main component polyethylene resin. If the amount of the fluororesin is less than 0.01 part by mass, the effect of addition cannot be obtained, and if it exceeds 2 parts by mass, it becomes easy to slip between the polyethylene resin composition and the screw, and it is difficult to uniformly extrude. Become.

As already mentioned, in the polyethylene resin composition of the present invention, a fatty acid salt-based lubricant may be used. Representative examples of fatty acid salt-based lubricants include calcium stearate, magnesium stearate, zinc stearate and the like.

In addition to the lubricant, the composition of the present invention may contain various additives as required. Examples of such additives include antioxidants, ultraviolet absorbers, fungicides, colorants (pigments, dyes), antiblocking agents,
Examples include an antistatic agent and an antirust agent. Still further, a filler (for example, calcium carbonate, silica, or the like) can be used.

In order to prepare the composition of the present invention, any generally known method of adding various additives to the main component resin to prepare the composition may be employed. A mixer (eg, a ribbon blender, a Henschel mixer, a Banbury mixer, a kneader, a two-roll machine, etc.) is usually used for uniform mixing of each component. Is subjected to granulation.

[0028]

Next, the present invention will be further described with reference to examples, but it goes without saying that the present invention is not limited to these examples.

Example 1 A tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer having a melting point of 165 ° C. and a fluorine content of 73 wt% (T
Thermogravimetric analysis (TGA) of HV) (powder (powder) form)
Is made by Rigaku Corporation Thermo PlusTG8120
I went using. The obtained TGA chart is shown in FIG. The melting point of THV was measured by a measuring method based on ASTM D 4591, and the fluorine content was measured by a quantitative method using FT-IR.

(Comparative Example 1) Dynamer FX-9613, a typical fluororubber-based additive conventionally used (manufactured by Dyneon Inc., containing granular, about 10% inorganic filler)
Was performed using the same measuring instrument as used in Example 1. The obtained TGA chart is shown in FIG.

From the comparison of the TGA charts of FIGS. 2 and 3, it can be seen that the THV resin additive of the present invention has a higher temperature at which thermal decomposition starts to be decomposed than the fluororubber additive of the comparative example and is thermally stable. I understand. Note that the additive of Example 1 is in powder form, whereas the additive of Comparative Example 1 is in granular form, and that the former contains no filler whereas the latter contains filler. It is also important. This has a difference that the thing of Example 1 is fluorine "resin" and the thing of Comparative Example 1 is fluorine "rubber". Therefore, the latter is easy to form a lump because it is sticky at normal temperature. The former reflects the fact that inorganic fillers are included as antiblocking agents, while the former do not require such fillers.

Example 2 and Comparative Example 2 In these examples, the discoloration of the fluorine-based additive itself due to heating is examined. 5 g of a THV additive having a melting point of 120 ° C. and a fluorine content of 69% (Dynamer FX-5911X manufactured by Dyneon Co., Ltd.) was placed in a Petri dish, and placed in an oven at 220 ° C.
After a minute, the degree of discoloration of the additive was observed (Example 2). Furthermore, a fluoro rubber-based additive (Dynamer F manufactured by Dyneon Co., Ltd.)
X-9613) was compared under the same conditions (Comparative Example 2). Table 1 shows the results.

[0033]

[Table 1]

From the results, it was found that the THV resin additive of Example 2 did not discolor even when heated, and
It was confirmed that the additive is less likely to cause a problem thermally as compared with the fluororubber-based additive.

(Example 3 and Comparative Examples 3A and 3B) In these examples, discoloration due to the interaction between the fluorine-based additive and the lubricant due to heating is examined. THV resin having a melting point of 120 ° C. and a fluorine content of 69% (Dynamar FX-591)
1X) and the interaction between calcium stearate (CaSt) used as a lubricant was verified by the degree of discoloration after heating. 5 g of each of THV and calcium stearate were placed in a Petri dish and stirred well. Next, the petri dish was placed in an oven at 220 ° C., and the degree of discoloration after 30 minutes was observed (Example 3). For comparison, a fluororubber-based additive (Dynamer FX-9613) and calcium stearate each taken in a 5 g petri dish (Comparative Example 3A) and a calcium stearate alone in a 5 g petri dish (Comparative Example 3B) A similar experiment was performed. Table 2 shows the obtained results.

[0036]

[Table 2]

Comparative Example 3A is an example for comparing the interaction between a conventional fluororubber-based additive and a lubricant, calcium stearate, with that of the present invention. On the other hand, Comparative Example 3
B was performed only with calcium stearate. In this case, the white powder before heating turned brown by heating, but this was not due to the interaction with the fluorine-based additive, but calcium stearate itself was used. This is the discoloration that occurs and corresponds to the phenomenon shown when the polyethylene resin is blended alone as a lubricant without a fluorine-based additive. That is, this comparative example simulates the case where only a lubricant was added to a polyethylene resin without adding a fluorine-based additive (resin (Example 3) or rubber (Comparative Example 3A)). This is an example serving as a reference for Comparative Example 3A.

From the results in Table 2, it can be seen that in the situation where calcium stearate was added, the color of the THV resin additive (Example 3) was the same as that of calcium stearate alone (Comparative Example 3B) even when heated. Therefore, it can be seen that there is no difference in the discoloration ratio in the resin composition to which they are added. On the other hand, in the case of the fluororubber-based additive (Comparative Example 3A), the color after heating becomes black, and the interaction between the fluororubber-based additive and calcium stearate causes a significant discoloration of the polyethylene resin composition. It can be seen. This also indicates that the use of the composition containing the fluororesin additive of the present invention makes it possible to suppress the occurrence of eyes and marks due to the discoloration of the molded article due to the combined use of a lubricant.
Thus, it was confirmed that THV, which is the fluororesin additive used in the present invention, is an additive that is less likely to cause a thermal problem as compared with the conventional fluororubber-based additive.

Example 4 and Comparative Example 4 Polyethylene resin (melt index: 0.06 g / 10 min, density: 0.1)
THV resin having a melting point of 120 ° C. and a fluorine content of 69% in 954 g / cm ³ ) (Dynamer FX-5911X)
Was added to prepare a composition to which 0.1 wt% was added. With respect to this composition, the apparent viscosity of the resin composition was measured at a temperature of 220 ° C. with a capillary rheometer while changing the shear rate (according to JIS K 7199), and the surface state of the emerging capillary was observed (Example 4). ). For comparison, a similar experiment was performed on a polyethylene resin to which no THV resin was added (Comparative Example 4). The results are shown in FIGS.

[0040]

[Table 3]

As can be seen from FIG. 3, the composition containing the fluororesin (THV) additive of the present invention (dashed line data) is compared with the case of polyethylene resin alone (solid line data).
Shows a considerably low apparent viscosity at the same shear rate, indicating that the extrudability is improved.

Table 4 summarizes the surface states of the extruded capillaries at various shear rates. The actual surface states are shown in FIGS. 5A (invention) and 5B.
(Comparative Example)

From these results, it can be confirmed that the addition of the fluororesin (THV) additive to the polyethylene resin can increase the shear rate at the time of extrusion molding and can also improve the surface condition (improvement of smoothness). Was.

[0044]

As described above, by using the polyethylene resin composition of the present invention to which a fluororesin additive has been added, it is possible to improve the surface smoothness of a spacer formed by profile extrusion. Can be reduced, and even when a lubricant is used in combination with this additive, extrusion can be performed while suppressing the occurrence of eye burns.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view for explaining a spacer having a spiral groove for an optical fiber cable, wherein (A) is a partially broken top view thereof, and (B) is a cross-sectional view taken along the line BB of (A).

FIG. 2 is a TGA chart of a fluororesin additive used in the present invention.

FIG. 3 is a TGA chart of a conventional fluororubber-based additive.

FIG. 4 is a graph showing the results of Example 4 and Comparative Example 4.

FIGS. 5A and 5B are photographs showing the surface states of the extruded products obtained in Example 5 and Comparative Example 5, in which FIG. 5A is that of Example 5, and FIG.

[Explanation of symbols]

 11 ... Spiral grooved spacer 13 ... Spiral groove 15 ... Strength member

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 27/20 C08L 27/20

Claims (4)

[Claims] 1. A polyethylene resin as a main component and a fluorine resin as an additive component, and the polyethylene resin has a melt index (MI) of 0.01 to 0.3 g.
/ 10 minutes, the density is 0.94 to 0.96 g / cm ³ , and the fluororesin has a melting point of 100 to 300 ° C.,
A polyethylene resin composition for producing a spacer for an optical fiber cable, wherein the fluorine content is 50 wt% or more, and the content of the fluororesin is 0.01 to 2 parts by mass with respect to 100 parts by mass of the polyethylene resin. 2. The melting point of the fluororesin is 110 to 230.
The polyethylene resin composition according to claim 1, wherein the temperature is ° C. 3. The fluorine content of the fluororesin is 66 watts.
The polyethylene resin composition according to claim 1 or 2, which is at least t%. 4. The polyethylene resin composition according to claim 1, wherein the fluororesin is a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer.