JP7288648B2 - Sheath-core composite monofilament - Google Patents

Description

TECHNICAL FIELD The present invention relates to monofilaments, and more particularly to monofilaments having excellent adhesiveness to polyolefin resins.

In recent years, with the spread of the Internet and the increase in video distribution, etc., there is a demand for high-speed distribution of a huge amount of information. expanding. Various types of optical cables are used to bring optical fibers into offices and ordinary homes from optical cables installed in the air.

An optical cable accommodates delicate optical fibers, and must be devised so that it can withstand practical use indoors and outdoors. Generally, in order to increase toughness, it is made up of an optical fiber, a sheath material, and a tension member, making it an optical cable that is less susceptible to external forces, has stable transmission characteristics, and is easy to lay. It is required to do.

Tension members used in optical cables are mainly used to protect and reinforce optical fibers from tension applied during laying, and conventionally, steel and glass fibers have been widely used. However, the tension member using steel has problems of electromagnetic induction and the problem that the specific gravity is large and the fiber becomes heavy, and the tension member using glass fiber has problems with impact resistance and flexibility of the material.

Tension members using ceramic fibers, carbon fibers, aromatic polyester fibers, aramid fibers, polybenzazole fibers, etc. have also been proposed, but all of them are rigid and lack flexibility, making them difficult to fabricate optical cables. There is a problem in that the workability is inferior during installation, the optical cable may be damaged, and the handleability in laying work is also inferior.

The applicant of the present application has found that polyolefin resin can be suitably used as a reinforcing material for cables and cords in which a polyolefin resin is used as a sheath material, for example, as a tension member provided together with an optical fiber in an optical cable, and has excellent adhesiveness to polyolefin resin. As a monofilament, a monofilament having a core-sheath structure described in Patent Document 1 was proposed.

JP 2015-175077 A

INDUSTRIAL APPLICABILITY The present invention can be suitably used as a reinforcing material for cables and cords in which a polyolefin resin is used as a sheath material, for example, as a tension member provided together with an optical fiber in an optical cable, and has even better adhesion to the polyolefin resin. An object is to provide a monofilament.

The present inventors arrived at the present invention as a result of studies for solving the above problems.
That is, the present invention provides a core-sheath composite monofilament,
The core is made of a polyamide resin, and 90% by mass or more of the polyamide resin is nylon MXD6,
The sheath part is a polyethylene resin having a melt index of 0.5 to 30 g/10 min at 190° C. and a melt index of 0.5 to 30 g/10 min. Consists of a blend body in which 10 to 35% by mass of an acid -modified polyethylene resin is blended,
The core-sheath composite monofilament is characterized in that the area ratio of the core portion to the fiber cross section of the monofilament is 60 to 95%.

The present invention will be described in detail below.

First, the monofilament of the present invention is a core-sheath composite monofilament, the core portion is composed of a polyamide resin, and 90% by mass or more of the polyamide resin is nylon MXD. Nylon MXD6 occupies 90% by mass or more of the polyamide resin arranged in the core, and is excellent in mechanical strength, dry heat shrinkage, flexibility, runnability at the time of melt spinning, etc., making it possible to obtain a monofilament. can. Within a range not exceeding 10% by mass, in order to exhibit desired functions such as viscosity modifiers, plasticizers, compatibilizers, weathering agents, flame retardants, antioxidants, light stabilizers, lubricants, fillers, colorants, etc. may contain resins other than nylon MXD, additives, and the like.

In the core-sheath composite monofilament of the present invention, the resin constituting the sheath part is 65 to 90% by mass of a polyethylene resin having a melt index of 0.5 to 30 g/10 minutes at 190 ° C. and 2.16 kg, and the above polyethylene It is composed of a blend obtained by blending 10 to 35% by mass of an acid -modified polyethylene resin having a melt index difference of 5 g/10 minutes or less from the resin.

The polyethylene resin is unmodified polyethylene, and includes high-density polyethylene, medium-density polyethylene, and low-density polyethylene. Linear low-density polyethylene can be preferably used. By using linear low-density polyethylene, there is little damage due to rubbing during the process, and the obtained fibers and fiber structures using the same are flexible and easy to handle.

The polyethylene resin used has a melt index of 0.5 to 30 g/10 minutes at 190° C. and 2.16 kg. If the melt index is less than 0.5 g/10 minutes, the viscosity is too high, resulting in insufficient spinnability during monofilament spinning and insufficient fluidity of the sheath component during thermal processing. On the other hand, if the melt index exceeds 30 g/10 minutes, the viscosity is too low, the wire diameter stability during monofilament spinning decreases, and the sheath component flows and spreads over a wider area than necessary during heat processing, causing contamination. and machining defects.

The sheath is composed of a blend of unmodified polyethylene resin and acid -modified polyethylene resin, and the blend ratio (% by mass) is polyethylene resin: acid -modified polyethylene resin=65 to 90:35. ~10. By increasing the ratio of the polyethylene resin in the blend to 65 to 90, the performance of the acid -modified polyethylene resin, which is inferior in terms of durability and physical properties, is covered by the non-modified polyethylene resin, and the spinning operation and handleability as a monofilament. , has the advantage of being excellent in mechanical properties. If the blend amount of the acid -modified polyethylene resin is less than 10% by mass, the effect of blending the acid -modified polyethylene resin is not exhibited, and the interfacial affinity between the core and the sheath and the interfacial affinity between the sheath and other materials. A problem arises in that the adhesive force between them is not improved.

The difference in melt index between the unmodified polyethylene resin and the acid -modified polyethylene resin should be within 5 g/10 minutes. By setting the melt index difference within 5 g/10 minutes, the two can be blended well and uniformly, and the wire diameter and adhesion performance can be stabilized.

An acid- modified polyethylene resin is a polyethylene resin that has been copolymerized or graft-modified with an acid or an acid anhydride.

Examples of acids that modify polyethylene resins include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, α-ethylacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and tetrahydrophthalic acid. These may be used singly or in combination of two or more. Examples of acid anhydrides that modify polyethylene resins include unsaturated carboxylic acid anhydrides such as maleic anhydride, citraconic anhydride, itaconic anhydride, tetrahydrophthalic anhydride, nadic anhydride, and methyl nadic anhydride. These may be used singly or in combination of two or more. Among the above acid-modified polyethylene resins, maleic anhydride-modified polyethylene resin graft-modified with maleic anhydride is particularly preferably used.

The acid -modified polyethylene resin may be a copolymer obtained by copolymerizing other components as long as it is mainly composed of acid -modified polyethylene.

The sheath may contain viscosity modifiers, plasticizers, compatibilizers, weathering agents, flame retardants, antioxidants, light stabilizers, lubricants, and fillers within a range that does not impair the performance of the polyethylene resin and acid-modified polyethylene resin. Other resins and additives may be added to achieve desired functions such as agents, colorants, and the like.

In the core-sheath composite monofilament of the present invention, the area ratio of the core portion to the fiber cross section is 60 to 95%. By setting the area ratio of the core to 60 to 95%, the ratio of nylon MXD6 in the core to the fiber is increased, and the monofilament has excellent mechanical strength, dry heat shrinkage, and flexibility, and the monofilament can be used as a tension member. It is also excellent in handleability and workability when applied as a material, and the obtained cables can be sufficiently reinforced, and the toughness of the cables can be further increased when used indoors and outdoors. By setting the area ratio of the core to 95% or less, when the monofilament is applied as a tension member, the adhesiveness and bondability between the polyethylene resin blend, which is the sheath of the monofilament, and the sheath material of the optical cable are improved. Thus, it is possible to obtain an optical cable in which the tension member is not likely to fall off from the cable and is excellently integrated.

When the core-sheath composite monofilament is used as a tension member, it is required to have high strength in order to reinforce cables well, and also to be stable against heat and humidity. Therefore, the core-sheath composite monofilament should preferably have a tensile strength of 350 MPa or more and a dry heat shrinkage rate (140° C. atmosphere×10 minutes) of 3% or less.

The tensile strength of the core-sheath composite monofilament is measured at a gripping distance of 25 cm and a tensile speed of 30 cm/min based on the standard time test for tensile strength and elongation of JIS L1013. When the strength of the monofilament is less than 350 MPa, the strength is insufficient, and the cables may be broken during production or use, and the cables tend not to be sufficiently reinforced.

The dry heat shrinkage rate of the core-sheath composite monofilament was measured by the following method. That is, a load of 0.01 MPa is applied to the sample (for example, a load of 0.4 g for a sample of 0.7 mmφ), 500 mm is accurately measured and two points are placed, and with the load applied, 140 ° C. After being left in the atmosphere for 10 minutes, it was taken out and cooled to room temperature. The sample was scored at 5 points, and the average value was taken as the dry heat shrinkage rate.

In the present invention, if the dry heat shrinkage rate exceeds 3%, for example, when a cable and a monofilament are coated with a sheath material to prepare a cable, the resin constituting the sheath material is melt-coated. Due to the heat treatment for this purpose, the monofilament shrinks greatly, and the sheath material breaks or cracks.

In addition, the core-sheath composite monofilament of the present invention should have an adhesive pull-out strength of 100 MPa or more, taking into consideration the adhesiveness to polyethylene, as an indicator of excellent adhesiveness and jointability to the sheath material when used as a tension member. It is preferably 110 MPaN or more, more preferably 110 MPaN or more.

The adhesive pull-out strength is measured as follows. 10 g of polyethylene chips are placed in an aluminum cup (No. 5) with a hole in the bottom for passing the monofilament in advance, and melted by heat treatment at 190° C. for 20 minutes. Before the polyethylene solidifies, the monofilament is passed from below and solidified by cooling at 25° C. for 60 minutes. After that, the bottom of the container is turned up, the container is fixed so that it does not move when it is pulled out, and it is installed in a tensile tester. While pulling out the monofilament at a pulling speed of 50 mm/min, the strength at the time of drawing was measured, and the value obtained by dividing the maximum value of this strength by the cross-sectional area of the fiber was taken as the adhesion drawing strength. The sample was given a score of 5, and the average value was taken as the adhesive pull-out strength.

Since polyethylene is often used for the sheath material of optical cables, when using a monofilament as a tension member, the adhesive pull-out strength, which indicates the adhesion to polyethylene, is considered to be an important characteristic value. The core-sheath composite monofilament of the present invention has a blend of unmodified polyethylene resin with a specific melt viscosity and acid -modified polyethylene resin with a specific melt viscosity on the filament surface. Although it is not clear, the adhesive pull-out strength can be improved, and the adhesive pull-out strength of 100 MPa or more can be obtained.

The diameter of the core-sheath composite monofilament of the present invention may be appropriately selected depending on the application and required performance, and is not particularly limited, but is preferably about 0.4 mm to 1.5 mm.

Next, an example of the method for producing the core-sheath composite monofilament of the present invention will be described. Each chip is prepared so that nylon MXD6 is arranged in the core part and the blend of the above-described unmodified polyethylene resin and acid -modified polyethylene resin is arranged in the sheath part, and the spinning temperature is set to about 255 to 285 ° C. and extruder type Using a spinning device, melt-spinning from a spinneret while blending two resins in the sheath, and cooling the spun yarn in a hot water bath at about 40 to 60°C to obtain an undrawn yarn. . The undrawn yarn is subjected to the first stage drawing (drawing ratio of about 2.5 to 4.5 times) in a water bath of about 60 to 90 ° C., and then to the second stage in a hot air atmosphere of 100 to 300 ° C. (stretching ratio of about 1.1 to 2.5 times) is performed. Subsequently, a relaxation heat treatment of about 2.5 to 30% is performed in a hot air atmosphere of about 150 to 300° C. to obtain the core-sheath composite monofilament of the present invention.

The core-sheath composite monofilament of the present invention has nylon MXD6 in the core and a blend of two types of polyethylene resins having a specific melt viscosity in the sheath. It is sufficiently high, and when used as a tension member, it is excellent in adhesion and bonding properties with the sheath material, and the work environment and operability during manufacturing are good.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples.
Example 1
In order to obtain a filament with a composite core-sheath cross section, nylon MXD6 chips (manufactured by Mitsubishi Chemical Co., Ltd. "S6007" relative viscosity 2.7) placed in the core and linear low-density polyethylene chips ( "Novatec LL UJ960" (melt index: 5.0) manufactured by Nippon Polyethylene Co., Ltd. and acid-modified linear low-density polyethylene resin chips ("ADMER NE827" manufactured by Mitsui Chemicals, Inc. (melt index: 5.6)) were prepared. Then, it was melt-spun at a temperature of 275° C. using an ordinary extruder-type melt-spinning apparatus. In addition, the spinning was carried out by weighing so that the volume ratio of the core part and the sheath part was 2.8/1 (core/sheath). Furthermore, the two types of resin chips of the sheath are blended in an extruder so that the ratio of linear low-density polyethylene chips is 90% by mass and acid-modified linear low-density polyethylene chips are 10% by mass. Melt spun. The spun monofilament was cooled in a hot water bath at 60°C to obtain an undrawn yarn. Without taking up the undrawn yarn, it is first drawn in a hot water bath at 90°C at a draw ratio of 3.7 times, and then heated in a 215°C heating zone so that the total draw ratio is 5.5 times. The filament was drawn in the second stage (drawing ratio of 1.5 times) while passing through the filament, and then passed through a heating zone at 240° C. for relaxation heat treatment of 0.8 times to obtain a core-sheath composite monofilament. The resulting core-sheath composite monofilament had a diameter of 0.7 mm and a core/sheath area ratio in the cross section of 2.8/1.

Example 2
In Example 1, except that the blend ratio of the sheath was changed to 70% by mass of linear low-density polyethylene chips and 30% by mass of acid-modified linear low-density polyethylene chips. A core-sheath composite monofilament was obtained in the same manner as in 1. The resulting core-sheath composite monofilament had a diameter of 0.7 mm and a core/sheath area ratio in the cross section of 2.8/1.

Example 3
In Example 2, in the same manner as in Example 2, except that melt spinning was performed while measuring so that the volume ratio of the core part and the sheath part was core/sheath = 4/1 during melt spinning, A core-sheath composite monofilament was obtained. The resulting core-sheath composite monofilament had a diameter of 0.7 mm and a core/sheath area ratio of 4/1 in the cross section.

Example 4
In Example 3, maleic anhydride-modified polyethylene obtained by copolymerizing acrylate ("Rekspearl ET220X" melt index: 8.5, manufactured by Nippon Polyethylene Co., Ltd.) was used as the modified polyethylene in the blend of the sheath. obtained a core-sheath composite monofilament in the same manner as in Example 3. The resulting core-sheath composite monofilament had a diameter of 0.7 mm and a core/sheath area ratio of 4/1 in the cross section.

Example 5
A core-sheath composite monofilament was obtained in the same manner as in Example 2, except that "S6121" (relative viscosity: 3.5) manufactured by Mitsubishi Chemical Corporation was used as nylon MXD6 for the core. The resulting core-sheath composite monofilament had a diameter of 0.7 mm and a core/sheath area ratio in the cross section of 2.8/1.

Comparative example 1
In Example 1, instead of the blended body of the sheath, only linear low-density polyethylene chips (manufactured by Nippon Polyethylene Co., Ltd. "Novatec LL UJ960" melt index: 5.0) were used. A core-sheath composite monofilament was obtained in the same manner. The resulting core-sheath composite monofilament had a diameter of 0.7 mm and a core/sheath area ratio in the cross section of 2.8/1.

Comparative example 2
In Example 5, instead of the blended body of the sheath, only linear low-density polyethylene chips ("Novatec LL UJ960" melt index: 5.0 manufactured by Japan Polyethylene Co., Ltd.) were used. A core-sheath composite monofilament was obtained in the same manner. The resulting core-sheath composite monofilament had a diameter of 0.7 mm and a core/sheath area ratio in the cross section of 2.8/1.

Comparative example 3
A single-phase monofilament was obtained by melt spinning using only nylon MXD6 (Mitsubishi Chemical Co., Ltd. "S6121" relative viscosity 3.5). The melt spinning conditions, drawing conditions, etc. were the same as in Example 1. The resulting monofilament had a diameter of 0.7 mm.

The physical properties of the obtained monofilaments of Examples 1 to 5 and Comparative Examples 1 to 3 were measured and shown in Table 1. The methods for measuring physical properties are as described above. The elongation was defined as the maximum elongation obtained when the tensile strength was measured. As is clear from Table 1, the monofilaments of Examples were practical and had excellent mechanical strength and elongation, had high adhesive pull-out strength, and had very excellent adhesive strength.

Claims (2)

A core-sheath composite monofilament,
The core is made of a polyamide resin, and 90% by mass or more of the polyamide resin is nylon MXD6,
The sheath part is a polyethylene resin having a melt index of 0.5 to 30 g/10 min at 190° C. and a melt index of 0.5 to 30 g/10 min. Consists of a blend body in which 10 to 35% by mass of an acid -modified polyethylene resin is blended,
A core-sheath composite monofilament, characterized in that the area ratio of the core portion to the fiber cross section of the monofilament is 60 to 95%.
The core-sheath composite monofilament according to claim 1, wherein the polyethylene resin in the sheath is linear low-density polyethylene having a melting point of 70°C or higher.