US20130040053A1

US20130040053A1 - Ripcord of optic cables and method of manufacturing the same

Info

Publication number: US20130040053A1
Application number: US13/655,885
Authority: US
Inventors: Chang-Bae Lee; Tae-Hak Park; Jin-woo Kim
Original assignee: Kolon Industries Inc
Current assignee: Kolon Industries Inc
Priority date: 2007-05-08
Filing date: 2012-10-19
Publication date: 2013-02-14
Also published as: EP2142952A1; US20100129655A1; WO2008136650A1; JP5400035B2; WO2008136649A1; JP2010526347A; ES2576463T3; CN101681007B; CN101681007A; EP2142952B1; EP2142952A4

Abstract

Disclosed are a ripcord for optic cable and a method of manufacturing the same. The ripcord for optic cable has a coating layer formed by applying a coating solution, which includes a binder and a colorant dispersed in the binder, to a surface of a folded and twisted yarn formed by folding and twisting together wholly aromatic polyamide filaments.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 12/598,998 filed Jan. 14, 2010, which is a National Stage of International Application No. PCT/KR2008/002597 filed May 8, 2008, claiming priority based on Korean Patent Application Nos. 10-2007-0044420, 10-2007-0044422, 10-2007-0044426 and 10-2007-0044430 filed May 8, 2007, the contents of all of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a ripcord for optic cables and a method of manufacturing the same, and more particularly, to a ripcord for optic cable which comprises a folded and twisted yarn formed by folding and twisting together wholly aromatic polyamide filaments and a coating layer containing a coloring agent formed on a surface of the folded and twisted yarn, so that the ripcord can be easily distinguished from reinforcing materials for the optic cable at installation or repairs of the optic cable, thereby enhancing workability thereof and, in addition, a method of manufacturing the same.

BACKGROUND ART

A ripcord for optic cable is so called “a cutting fiber,” which helps a resin coating film of an optic cable to be easily cut and removed.
As shown in FIG. 1, the optic cable generally includes an optic fiber 1 at a center of the optic cable, a reinforcing material 2 covering and protecting the optic fiber 1, ripcords 3 mixed in the reinforcing material 2, and a resin coating layer 4 formed outside both of the reinforcing material 2 and the ripcords 3.
FIG. 1 is a schematic cross-sectional view of a conventional optic cable.
As the reinforcing material 2, a bundle of wholly aromatic polyamide filaments is mostly used, which is typically formed by folding and twisting together a plurality of wholly aromatic polyamide filaments in non-twisted states. Such a filament bundle may be called “folded and twisted yarn.”
The reinforcing material 2 is used for protecting the optic fiber 1.
The ripcords 3 function to easily remove the resin coating layer 4 of the optic cable for repairing or the like. More particularly, with regard to management or repairs of the optic cable, a resin coating layer 4 of the optic cable can be easily stripped from the optic cable by pulling the ripcords 3.
In order to simply cut and remove the resin coating layer 4 of the optic cable during repairing, the ripcords 3 are desirably distinguished from the reinforcing material 2.
Conventional ripcords for optic cables mostly include folded and twisted yarns, each of which is usually produced by folding and twisting together a plurality of wholly aromatic polyamide filaments. However, since such ripcord comprises the wholly aromatic polyamide filaments only, this has disadvantages including, for example, poor dyeing properties, reduced dyeing intensity, low dyeing fastness, high production cost, etc. in spite of excellent mechanical properties such as modulus.
Especially, the known ripcord 3 for optic cable with poor dyeing properties and dyeing fastness involved a problem that the ripcord is difficult to distinguish from the reinforcing material 2 of the optic cable during repairing.
As another ripcord for optic cable, Korean Patent Registration No. 0373235 proposed a ripcord for optic cable with 1,500 to 12,000 denier produced by folding and twisting together polyester yarns with the number of twists ranging from 200 to 500 per meter. This ripcord consists of polyester yarns only, and thus, has favorable dyeing properties enough to easily distinguish the ripcord from other materials. However, when comparing it with a ripcord formed of wholly aromatic polyamide fibers, this ripcord needs higher denier and larger weight to have desired mechanical properties such as modulus.
A further technique described in Japanese Patent Laid-Open No. 2005-148150 is that a ripcord is produced by covering an outer side of a fibrous material with a resin such as polytetrafluoroethylene resin, silicon dispersed polyethylene resin, silicon grafted polyethylene resin or fluoride resin dispersed polyethylene resin. US Patent Laid-Open No. 2005-036750 proposed a ripcord with improved smoothness coated with silicon oil or wax in order to prevent damage of the ripcord. However, although these techniques can improve smoothness and abrasion resistance of a ripcord, there is still a problem that the ripcord is difficult to distinguish from reinforcing materials 2 used therein.
Additionally, US Patent Laid-Open No. 2003-095763 disclosed a colored buffer tube for a ripcord in order to easily distinguish the ripcord from other materials. Korean Utility Model Registration No. 0352977 suggested a multiple linear core type cable that comprises (i) a linear core unit assembly including a linear core assembly and a unit jacket enclosing the same and (ii) a cable jacket covering the linear core unit assembly in a longitudinal direction, and includes a marker tape with marking codes between the linear core assembly and the unit jacket. But, the above known arts cannot enhance abrasion resistance although these allow the ripcord or the linear unit to be easily distinguished from other materials.
As described above, conventional techniques concerning ripcords for optic cables involve a disadvantage in simultaneously exhibiting an effect of easily distinguishing the ripcord from other materials as well as excellent abrasion resistance and mechanical properties of the ripcord.

DISCLOSURE OF THE INVENTION

Technical Problem

Accordingly, the present invention is directed to solve the problems described above in regard to conventional methods and an object of the present invention is to provide a ripcord for optic cable which has a coating layer containing a colorant on a surface of a folded and twisted yarn formed by folding and twisting together wholly aromatic polyamide filaments, so that the ripcord is easily distinguished from reinforcing materials of the optic cable during installation and repairs of the optic cable and shows excellent mechanical properties and, in addition, a method for manufacturing the same.
Another object of the present invention is to provide a method of manufacturing a ripcord for optic cable that has a coating layer containing a colorant on a surface of a folded and twisted yarn formed by folding and twisting together wholly aromatic polyamide filaments so that a diluent portion contained in the coating layer can be sufficiently and easily evaporated and removed, thereby resulting in improvement of productivity and effectively preventing reduction of coating fastness and mechanical properties caused by a residue of the diluent, in view of manufacturing the ripcord with excellent mechanical properties and capable of being easily distinguished from reinforcing materials of the optic cable at installation or repairs of the optic cable.
A further object of the present invention is to provide a hybrid type ripcord for optic cable, comprising a folded and twisted yarn formed by folding and twisting together wholly aromatic polyamide filaments and additional functional filaments for industrial use, so as to exhibit excellent mechanical properties simultaneously with additional properties such as dyeing properties.

Technical Means to Solve the Problem

Hereinafter, the present invention will be described in more detail with reference to accompanying drawings.
In order to accomplish the above objects, the present invention provides a ripcord for optic cable that has a coating layer containing a binder and a colorant dispersed in the binder, which is formed on a surface of a folded and twisted yarn formed by folding and twisting together wholly aromatic polyamide filaments.
The present invention also provides a method of manufacturing a ripcord for optic cable, which includes applying a coating solution containing a binder and a colorant dispersed in the binder to a surface of a folded and twisted yarn formed by folding and twisting together wholly aromatic polyamide filaments to form a coating layer on the folded and twisted yarn, drying and winding the coated yarn over a winding machine.
The colorant dispersed in the binder preferably includes pigment or dye.
The colorant has an average particle size ranging from 0.01 to 100 μm and, preferably, 0.1 to 10 μm.
If the average particle size is less than 0.01 μm, the colorant is scattered and makes it difficult to conduct the coating process. On the other hand, with an average particle size of more than 100 μm, the colorant is difficult to disperse in the binder.
Using a laser particle size analyzer Model LS 13320 (Tornado) available from BECKMAN a particle size of the colorant was measured five (5) times and the average value was calculated from the measured values for the particle size except upper and lower limits.
The binder may comprise at least one polymer selected from (i) glycol based polymers with a number average molecular weight ranging from 100 to 1,000 and (ii) aqueous polymers.
The glycol based polymers include a polymer selected from a group consisting of polyethyleneglycol, polypropyleneglycol and polytetramethyleneglycol, while the aqueous polymers include a resin selected from a group consisting of aqueous acrylic resin, aqueous urethane resin, aqueous phenol resin and aqueous epoxy resin.
If the binder is the glycol polymer, this is naturally hardened without drying thus more economically advantageous than the aqueous polymer in view of production cost.
When the number average molecular weight of the glycol polymer based binder is beyond the desired range, it shows a viscosity so high or low that it may cause poor coating of the folded and twisted yarn.
If the binder is the aqueous polymer, this needs a drying process to remove water as a solvent.
In order to improve strength and dyeing properties of a ripcord for optic cable, the folded and twisted yarn formed by folding and twisting together wholly aromatic polyamide filaments preferably comprises (i) 50 to 99 wt. % of the wholly aromatic polyamide filaments and (ii) 1 to 50 wt. % of additional functional filaments for industrial use (hereinafter referred to as “functional industrial filament”) selected from a group consisting of polyester filaments, polyamide filaments, polyvinylalcohol filaments, rayon filaments, polyolefin filaments and polybenzonite filaments.
If an amount of the wholly aromatic polyamide filaments in the ripcord for the optic cable according to the present invention is less than 50 wt. %, in other words, an amount of the functional industrial filaments exceeds 50 wt. %, mechanical properties such as modulus of the ripcord are lowered.
On the other hand, the ripcord does not effectively show additional properties such as dyeing properties and/or bulkiness in case that the amount of the functional industrial filaments is less than 1 wt. %.
More particularly, polyamide filaments or rayon filaments can improve dyeing properties and dyeing fastness while polyethylene filaments with higher molecular weight enhance mechanical properties such as modulus of the ripcord.
The inventive ripcord for optic cable preferably has strength ranging from 50 to 100 kgf and total fineness ranging from 3,000 to 5,000 denier.
With the strength and the total fineness exceeding the above ranges, respectively, it is easier to remove a resin coating layer from the optic cable. But the ripcord is more difficult to manage or handle as it becomes stiff, and may cause increase in production cost. If both of the strength and the total fineness are less than the desired ranges, the ripcord has low mechanical properties and may cause the ripcord to snap when cutting and stripping the resin coating layer from the optic cable.
The method of manufacturing a ripcord for optic cable according to the present invention includes: applying a coating solution, which contains a binder and a colorant, to a surface of a folded and twisted yarn formed by folding and twisting together wholly aromatic polyamide filaments to form a coating layer; and drying and winding the coated yarn over a winding machine.
The coating solution preferably includes a diluent as an additive.
The diluent may include water alone, a combination of water and an evaporation promoter (hereinafter referred to as “promoter”) with a lower boiling point than that of water and/or the promoter alone.
As the diluent, the combination of the promoter and water preferably includes 1 to 20 wt. % of the promoter and 80 to 99 wt. % of water.
In case that an amount of the promoter is less than 80 wt % relative to total weight of the combination, it is difficult to effectively prevent decrease in mechanical properties and/or coating fastness of the ripcord caused by a diluent portion remained in the coating layer.
The promoter with a lower boiling point than that of water includes, for example, ethanol, methylethylketone, ether, tetrahydrofuran, acetone, methylalcohol, etc.
The promoter functions to evaporate and remove the diluent contained in the coating solution leading to improved productivity and to effectively prevent reduction of mechanical properties or coating fastness.
In order to apply the coating solution to a surface of a folded and twisted yarn A comprising wholly aromatic polyamide filaments, there may be used, a method shown in FIG. 2 that passes the folded and twisted yarn A over a rotational coating roller C partially immersed in a tank B containing the coating solution, or a method shown in FIG. 3 that passes the folded and twisted yarn A over a coating roller fed with the coating solution from a tank G containing the coating solution by an injector H.
As shown in FIG. 2, it is preferable to adopt a squeezing roller C′ mounted on a top of the coating roller C to squeeze the folded and twisted yarn A after applying the coating solution.
The folded and twisted yarn A coated with the coating solution is processed at 150 to 240° C. with a speed ranging from 5 to 1,000 m/min and, preferably, 10 to 800 m/min.
Next, a method of manufacturing a ripcord for optic cable according to the present invention will be described in more detail with reference to FIG. 2 and FIG. 3.
FIG. 2 and FIG. 3 are schematic views for illustrating a method of manufacturing a ripcord for optic cable according to the present invention.
As shown in FIG. 2, the inventive method comprises: passing a folded and twisted yarn A formed by folding and twisting together wholly aromatic polyamide filaments over a rotational coating roller C partially immersed in a tank B that contains a coating solution to apply the coating solution to a surface of the folded and twisted yarn A; drying the coated yarn by means of a dryer D; and winding the dried yarn over a winder E to produce a ripcord for optic cable, which has a coating layer containing a colorant on a surface of the ripcord.
More preferably, a squeezing roller C′ is mounted on a top of the coating roller C to squeeze the coated folded and twisted yarn.
As shown in FIG. 3, an alternative embodiment of the inventive method comprises: passing a folded and twisted yarn A formed by folding and twisting together wholly aromatic polyamide filaments over a coating roller C fed with a coating solution from a tank H that contains the coating solution by means of an injector H to apply the coating solution to a surface of the folded and twisted yarn A; drying the coated yarn by means of a dryer D; and winding the dried yarn over a winder E to produce a ripcord for optic cable, which has a coating layer containing a colorant on a surface of the ripcord.

Advantageous Effects

A ripcord for optic cable according to the present invention has a coating layer containing a colorant on a surface of a folded and twisted yarn formed by folding and twisting together wholly aromatic polyamide filaments, so as to easily distinguish the ripcord from reinforcing materials of the optic cable at installation and repairs of the optic cable and have excellent mechanical properties such as high strength owing to inherent properties of the wholly aromatic polyamide filaments. Especially, the inventive ripcord which has a coating layer containing fluorescent ingredients can be simply distinguished from the reinforcing materials of the optic cable even in a dark place such as a tunnel.
The present invention can easily evaporate a diluent ingredient contained in the coating layer to improve productivity of the ripcord, and effectively prevent reduction of mechanical properties or coating fastness due to a residue of the diluent ingredient.
The inventive ripcord exhibits additional properties such as dyeing properties as well as mechanical properties such as modulus. Alternatively, the ripcord for optic cable produced according to the present invention has various advantages such as less decrease of strength in dyeing, superior dyeing fastness and dyeing properties, convenience in distinguishing the ripcord from other materials during repairs of the optic cable, and economical benefit in production.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects, features and advantages of the present invention will become more apparent to those skilled in the related art in conjunction with the accompanying drawings. In the drawings:

FIG. 1 is a cross-sectional view of an optic cable;

FIG. 2 and FIG. 3 are schematic views illustrating a method of manufacturing a ripcord for optic cable according to the present invention.


Description of symbols for
major parts in drawings

	1: optic fiber	2: reinforcing material
	3: ripcord	4: resin coating layer


	A:	bobbin for folded and twisted yarn comprising
		wholly aromatic polyamide filaments

B:	coating solution bath	C:	coating roller
C′:	squeezing roller	D:	dryer
E:	winder	F:	guide roller
G:	coating solution tank	H:	injector

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail from the following examples and comparative examples with reference to the accompanying drawings.
However, these are intended to illustrate the invention as preferred embodiments of the present invention and do not limit the scope of the present invention.

Example 1

A folded and twisted yarn A with total fineness of 3,000 denier was prepared, which consisted of two strands of wholly aromatic polyamide filament each comprising 1,000 mono filaments with mono fineness of 1.5 denier.
As shown in FIG. 2, the prepared folded and twisted yarn was passed over a rotational coating roller C that was partially immersed in a tank B containing a coating solution which included (i) a polyethyleneglycol binder having a number average molecular weight of 400 and (ii) a colorant having an average particle size of 5 μm dispersed in the binder to apply the coating solution to a surface of the folded and twisted yarn A to form a coating layer. Following this, the coated yarn was wound over a winder E to produce a ripcord 3 for optic cable.
The coating roller C was equipped with a squeezing roller C′ at the top of the roller C.
After covering an optic fiber 1 with the produced ripcord 3 together with a reinforcing material 2 made of a folded and twisted yarn comprising wholly aromatic polyamide filaments, a resin coating layer 4 was formed over the prepared optic fiber to produce an optic cable with a cross section shown in FIG. 1.
Strength of the ripcord and convenience in distinguishing the ripcord from the optic cable were evaluated and the results are shown in the following Table 1.

Example 2

A folded and twisted yarn A with total fineness of 4,500 denier was prepared, which consisted of three strands of wholly aromatic polyamide filament each comprising 1,000 mono filaments with mono fineness of 1.5 denier.
As shown in FIG. 3, the prepared folded and twisted yarn was passed over a coating roller C fed with a coating solution which included (i) a polytetramethyleneglycol binder having a number average molecular weight of 600 and (ii) a colorant having an average particle size of 5 μm dispersed in the binder, from a tank B containing the coating solution by means of an injector H to apply the coating solution to a surface of the folded and twisted yarn A to form a coating layer. Following this, the coated yarn was wound over a winder E to produce a ripcord 3 for optic cable.
After covering an optic fiber 1 with the produced ripcord 3 together with a reinforcing material 2 made of a folded and twisted yarn comprising wholly aromatic polyamide filaments, a resin coating layer 4 was formed over the prepared optic fiber to produce an optic cable with a cross section shown in FIG. 1.
Strength of the ripcord and convenience in distinguishing the ripcord from the optic cable were evaluated and the results are shown in the following Table 1.

Example 3

A ripcord for optic cable and an optic cable with a cross section shown in FIG. 1 were produced under the same conditions described in Example 1 except that an alternative coating solution which included (i) an aqueous acrylic resin binder, (ii) a pigment having an average particle size of 5 μm dispersed in the binder and (iii) water as a diluent was used instead of the coating solution described in Example 1 and, after applying the coating solution to a surface of the folded and twisted yarn A to form a coating layer, the coated yarn was first passed through a dryer D at 200° C. with a speed of 20 m/min before winding the yarn over a winder E.
Strength of the ripcord and convenience in distinguishing the ripcord from the optic cable were evaluated and the results are shown in the following Table 1.

Example 4

A ripcord for optic cable and an optic cable with a cross section shown in FIG. 1 were produced under the same conditions described in Example 2 except that an alternative coating solution which included (i) an aqueous acrylic resin binder, (ii) a pigment having an average particle size of 5 μm dispersed in the binder and (iii) a diluent comprising a combination of water and ethanol as an evaporation promoter was used instead of the coating solution described in Example 2 and, after applying the coating solution to a surface of the folded and twisted yarn A to form a coating layer, the coated yarn was first passed through a dryer D at 200° C. with a speed of 20 m/min before winding the yarn over a winder E.
Strength of the ripcord and convenience in distinguishing the ripcord from the optic cable were evaluated and the results are shown in the following Table 1.

Example 5

A ripcord for optic cable and an optic cable with a cross section shown in FIG. 1 were produced under the same conditions described in Example 1 except that an alternative coating solution which included (i) an aqueous urethane resin binder, (ii) a dye having an average particle size of 5 μm dispersed in the binder and (iii) an evaporation promoter comprising methylethylketone was used instead of the coating solution described in Example 1 and, after applying the coating solution to a surface of the folded and twisted yarn A to form a coating layer, the coated yarn was first passed through a dryer D at 200° C. with a speed of 20 m/min before winding the yarn over a winder E.
Strength of the ripcord and convenience in distinguishing the ripcord from the optic cable were evaluated and the results are shown in the following Table 1.

Example 6

A ripcord for optic cable and an optic cable with a cross section shown in FIG. 1 were produced under the same conditions described in Example 1 except that a folded and twisted yarn A which consisted of (i) a strand of wholly aromatic polyamide filament with 1,500 denier comprising 1,000 mono filaments with mono fineness of 1.5 denier and (ii) another strand of polyethylene filament with total fineness of 1,500 denier was used instead of the folded and twisted yarn described in Example 1.
Strength of the ripcord and convenience in distinguishing the ripcord from the optic cable were evaluated and the results are shown in the following Table 1.

Example 7

A ripcord for optic cable and an optic cable with a cross section shown in FIG. 1 were produced under the same conditions described in Example 1 except that an alternative coating solution which included (i) aqueous phenol resin as a binder, (ii) a dye having an average particle size of 10 μm dispersed in the binder and (iii) an acetone evaporation promoter was used instead of the coating solution described in Example 1 and, after applying the coating solution to a surface of the folded and twisted yarn A to form a coating layer, the coated yarn was first passed through a dryer D at 200° C. with a speed of 20 m/min before winding the yarn over a winder E.
Strength of the ripcord and convenience in distinguishing the ripcord from the optic cable were evaluated and the results are shown in the following Table 1.

Example 8

A ripcord for optic cable and an optic cable with a cross section shown in FIG. 1 were produced under the same conditions described in Example 1 except that an alternative coating solution which included (i) aqueous epoxy resin as a binder, (ii) a dye having an average particle size of 20 μm dispersed in the binder and (iii) a hydrofurane as a evaporation promoter was used instead of the coating solution described in Example 1 and, after applying the coating solution to a surface of the folded and twisted yarn A to form a coating layer, the coated yarn was first passed through a dryer D at 200° C. with a speed of 20 m/min before winding the yarn over a winder E.
Strength of the ripcord and convenience in distinguishing the ripcord from the optic cable were evaluated and the results are shown in the following Table 1.

Example 9

A ripcord for optic cable and an optic cable with a cross section shown in FIG. 1 were produced under the same conditions described in Example 1 except that a folded and twisted yarn A which consisted of (i) two strands of wholly aromatic polyamide filament with 1,000 denier, each comprising 1,000 mono filaments with mono fineness of 1.0 denier and (ii) two strands of polyethylene filament with total fineness of 1,500 denier was used instead of the folded and twisted yarn described in Example 1.
Strength of the ripcord and convenience in distinguishing the ripcord from the optic cable were evaluated and the results are shown in the following Table 1.

COMPARATIVE EXAMPLE 1

A folded and twisted yarn A with total fineness of 4,500 denier was prepared, which consisted of three strands of wholly aromatic polyamide filament each comprising 1,000 mono filaments with mono fineness of 1.5 denier. The prepared folded and twisted yarn A was used to produce a ripcord for optic cable.
After covering an optic fiber 1 with the produced ripcord 3 together with a reinforcing material 2 made of a folded and twisted yarn comprising wholly aromatic polyamide filaments, a resin coating layer 4 was formed over the prepared optic fiber to produce an optic cable with a cross section shown in FIG. 1.
Strength of the ripcord and convenience in distinguishing the ripcord from the optic cable were evaluated and the results are shown in the following Table 1.

COMPARATIVE EXAMPLE 2

A ripcord for optic cable and an optic cable with a cross section shown in FIG. 1 were produced under the same conditions described in Example 1 except that the binder in the coating solution described in Example 1 was changed to polyethyleneglycol having a number average molecular weight of 80.
Strength of the ripcord and convenience in distinguishing the ripcord from the optic cable were evaluated and the results are shown in the following Table 1.

COMPARATIVE EXAMPLE 3

A ripcord for optic cable and an optic cable with a cross section shown in FIG. 1 were produced under the same conditions described in Example 1 except that the binder in the coating solution described in Example 2 was changed to polytetramethyleneglycol having a number average molecular weight of 1,150.
Strength of the ripcord and convenience in distinguishing the ripcord from the optic cable were evaluated and the results are shown in the following Table 1.

TABLE 1

Evaluation results of mechanical properties of ripcords

	Strength of ripcord for	Convenience in distinguishing
Section	optic cable (kgf)	ripcord from optic cable

Example 1	83	Easy
Example 2	92	Easy
Example 3	84	Easy
Example 4	91	Easy
Example 5	83	Easy
Example 6	74	Easy
Example 7	85	Easy
Example 8	84	Easy
Example 9	83	Easy
Comparative	92	Difficult
example 1
Comparative	92	Easy
example 2
Comparative	91	Easy
example 3

From the above Table 1, the strength of a ripcord for optic cable was determined using a sample with a length of 250 mm at a tension speed of 300 mm/min according to ASTM D 885.
The convenience in distinguishing a ripcord from an optic cable was identified by ten (10) panels through sensory evaluation. When the ripcord was easily distinguished from the optic cable by at least eight (8) among them, it was defined as “easy.” Conversely, the ripcord which was not easily distinguished by seven (7) or less of the panels was defined as “difficult.”
For Comparative Examples 2 and 3, each of the binders has a number average molecular weight beyond a range of 100 to 1,000. Accordingly, these comparative examples show significantly lowered processing effects in application of the coating solutions to the folded and twisted yarns A, compared to Examples 1 and 2.

INDUSTRIAL APPLICABILITY

As described in detail above, a method of folding and twisting multiple filaments according to the present invention is useful for producing a wholly aromatic polyamide folded and twisted filament used to cover optic fibers in manufacturing optic cables.
The present invention can effectively produce a ripcord for optic cable which is useful for easily cutting and stripping a resin coating layer out of the optic cable.
While the present invention has been described with reference to the accompanying drawings, it will be understood by those skilled in the art that various modifications and variations may be made therein without departing from the scope of the present invention as defined by the appended claims.

Claims

1. A method of manufacturing a ripcord suitable for an optic cable comprising:

applying a coating solution, which includes a binder and a colorant dispersed in the binder, to a surface of an assembled and twisted yarn formed by assembling and twisting together wholly aromatic polyamide filaments to form a coating layer; and

winding the coated yarn over a winding machine.

2. The method according to claim 1, further comprising a diluent in the coating solution.

3. The method according to claim 2, wherein the diluent is a combination of water and an evaporation promoter having a boiling point lower than that of water.

4. The method according to claim 2, wherein the diluent is a combination of 1 to 20 wt. % of an evaporation promoter and 80 to 99 wt. % of water.

5. The method according to claim 2, wherein the diluent is at least one selected from the group consisting of an evaporation promoter and water.

6. The method according to claim 3, wherein the evaporation promoter is at least one selected from the group consisting of ethanol, methylethylketone, ether, tetrahydrofuran, acetone and methylalcohol.

7. The method according to claim 1, wherein the coating solution is applied to the surface of the assembled and twisted yarn by passing the assembled and twisted yarn over a rotational coating roller, wherein said rotational coating roller is partially immersed in a tank containing the coating solution.

8. The method according to claim 7, wherein a squeezing roller is mounted on a top of the rotational coating roller to squeeze the assembled and twisted yarn coated with the coating solution.

9. The method according to claim 1, wherein the coating solution is applied to the surface of the assembled and twisted yarn by passing the assembled and twisted yarn over a coating roller fed with the coating solution from a tank containing the coating solution by means of an injector.

10. The method according to claim 1, wherein the assembled and twisted yarn formed by assembling and twisting together wholly aromatic polyamide filaments,

wherein said yarn comprises (i) 50 to 99 wt. % of the wholly aromatic polyamide filaments and (ii) 1 to 50 wt. % of at least one selected from the group consisting of a polyester filament, polyamide filament, polyvinylalcohol filament, rayon filament, polyolefin filament and polybenzonite filament.

11. The method according to claim 1, wherein the assembled and twisted yarn is dried after forming the coating layer on the surface of the assembled and twisted yarn and before winding the same.

12. The method according to claim 11, wherein the drying process is conducted with a speed ranging from 5 to 1,000 m/min at 150 to 240° C.

13. The method according to claim 11, wherein the drying process is conducted at a speed ranging from 10 to 800 m/min at 150 to 240° C.

14. The method according to claim 4, wherein the evaporation promoter is at least one selected from the group consisting of ethanol, methylethylketone, ether, tetrahydrofuran, acetone and methylalcohol.

15. The method according to claim 5, wherein the evaporation promoter is at least one selected from the group consisting of ethanol, methylethylketone, ether, tetrahydrofuran, acetone and methylalcohol.