KR100471541B1 - Telecommunication Cable Covering Resin Composition - Google Patents

Abstract

The present invention relates to a black resin composition for coating a communication cable containing a carbon black, a crosslinking agent, and a polypropylene resin based on a linear low density polyethylene resin, wherein the crosslinking agent in the composition generates a long chain branch in the compound to produce a critical shear stress (melt flop). It increases the extrusion stress during the cable coating process by increasing the extruded load and resin pressure of the compound whose molecular weight is large due to the formation of long chain branches. It is related with the improved resin composition.

Description

Resin composition for communication cable coating

The present invention relates to a resin composition for coating a communication cable. More specifically, the present invention relates to a black resin composition for coating a communication cable containing a carbon black, a crosslinking agent, and a polypropylene resin based on a linear low density polyethylene resin, wherein the crosslinking agent in the composition is formed by producing a long chain branch in the compound. It increases shear stress (shear stress caused by melt flexure) and polypropylene decreases the extrusion load and resin pressure of compound whose molecular weight is large due to the formation of long chain branches. The present invention relates to a resin composition in which the extrusion appearance is significantly improved.

Communication line cables are typically made by coating polyolefins or expandable polyolefins on a core wire to make primary telephone wires, wrapping these telephone wires with steel or aluminum tape, and then covering them with a covering black polyethylene composition.

The quality of communication line generally requires long-term reliability of 20-30 years or more with respect to the call quality. To satisfy such reliability, the physical and chemical action that is first encountered from the outside when the communication line is installed underground or on the ground The black covering forming the outermost layer of the cable should be safe. Therefore, the development process of communication cable is a cable coating material development process that has long-term stability against the physicochemical action that the cable can receive.

Weatherproofness and mechanical properties should be good because it requires at least 20 to 30 years of durability when exposed to the wire covering polyethylene outdoors, and the stress environment cracking resistance of the coating black resin composition should be excellent because the wire shape is cylindrical. . In particular, in self-supporting cables, adhesion to aluminum tape and heat deformation are important. When the adhesion is weak and the heat deformation is large, triangular voids appear on the telephone line, and jelly filling is prevented to prevent moisture penetration due to external deformation and damage. This can cause fatal defects in the cable. Recently, in order to improve problems such as stress cracking, mechanical properties and triangular voids, the base resin of the black compound for communication cable coating has been changed from the existing low density polyethylene to the linear low density polyethylene. I can satisfy you. However, the linear low density polyethylene has excellent mechanical properties, stress environment cracking properties, aluminum tape adhesion, and heat resistance deformation, but molecular weight distribution due to the presence of branched comonomers such as butene or hexene in ethylene polymers having unsaturated hydrocarbons Due to its narrowness, very poor extrusion processability is pointed out as a disadvantage. Therefore, since the appearance roughness due to the generation of the melt-fold during the coating process occurs, there is a problem that must be carried out by lowering the extrusion flux.

Specifically, the recent efforts to supplement the extrusion processability of the black coating compound for communication cable using linear low density polyethylene as a base resin are as follows.

Since the magnitude of the critical shear stress generated by the melt complex is closely related to the molecular weight of the base resin, the molecular weight is extruded when the molecular weight is lowered, that is, the melt index (MI) is increased to 3.0 to be used as the base resin of the black coating compound. Processability is somewhat improved, but mechanical properties and stress environment cracking characteristics are deteriorated due to low molecular weight.

Several methods have been used to increase the extrusion processability while satisfying the mechanical properties and stress cracking characteristics. One of them is the use of additives. It is a method to make the extrusion appearance smooth during the process. However, the black compound for communication cable coating contains a large amount of inorganic additives such as carbon black, and it has little effect of improving workability when a small amount is added and the coating time in the extruder barrel is required for a long time, and the processing aid is 100 parts by weight of base resin. The effect can be obtained only by adding 0.3 parts by weight or more. The problem is that the cost of the processing aid is very expensive. In the case of the commercial fluorine-based processing aid, 3M dynama and DuPont bezon, the economic burden is high at about 20,000 won per Kg.

Another method to improve the extrudability of black coated compounds is to improve the extrusion processability of the base resin by melt extrusion under oxygen atmosphere (general air) with no additives in the production of the base resin of the communication cable coating compound. The critical shear shear stress of the base resin is remarkable because the double bond portion present in the linear low density polyethylene is decomposed by heat and shear force in the extruder to generate radicals, and the generated radicals are grafted to the linear low density polyethylene molecules to form long chain branches. It is possible to increase the extrusion processability of the compound. However, there is a problem in applying this method to commercial plants. There is a risk of carbide generation in the extruder when melt extruding in an oxygen atmosphere due to the absence of antioxidants, and there is a high risk of contamination of the product by carbides. In addition, there is a possibility of misuse due to carbide residue in the extruder in the production of other products after the completion of production, it is very difficult to apply commercial plants. However, when the pellet manufacturing process is not carried out in a commercial plant and the linear polyethylene in powder form is separately collected and melt-extruded in an oxygen atmosphere in a twin screw extruder, the original purpose can be achieved. However, in this case, there is an economic problem such as an additional process that needs to separately receive the linear low density polyethylene powder and an increase in cost due to the passage of the compounding extruder.

The present inventors have made diligent efforts to improve the extrudability (especially the extrusion appearance), which is a problem of the black coating compound of the communication cable manufactured by using the linear low density polyethylene as a base resin, and composed of a linear low density polyethylene and a carbon black masterbatch when manufacturing the compound. By adding a small amount of crosslinking agent and polypropylene at the same time to the composition, it has developed a black resin composition for communication cable coating, which has excellent mechanical strength and stress resistance, and has excellent extrusion processability.

The resin composition of the present invention comprises 100 parts by weight of linear low density polyethylene, 5 to 30 parts by weight of carbon black, 0.05 to 0.1 parts by weight of a crosslinking agent generated at 160 to 220 ° C for 1 minute half-life, and 0.05 to 15 parts by weight of polypropylene. It features.

The crosslinking agent used in the present invention significantly improves the critical shear stress of the compound by artificially making the long-chain branch in the linear low density polyethylene, and thereby improves the extrusion processability of the compound during the cable coating process. One minute half-life which generate | occur | produces at 160-220 degreeC, Tert- butyl cumyl peroxide, 2, 5-bis (tert- butyl peroxy) -2, 5- dimethyl hexane; 2,5-bis (tert-butylperoxy) -2,5-dimethylhexine-3; 1,1-bis-tert-butylperoxy-3,3,5-trimethylcyclohexane; Di-tert-butylperoxide; Or α, α-bis (tert-butylperoxyisopropyl) benzene. It is preferable that the quantity added at the time of manufacturing a black coating compound is 0.05-0.1 weight part with respect to 100 weight part of base resins. If the added content is less than 0.05 parts by weight, long chain branching in the linear low-density polyethylene is insignificant, and there is little effect of improving the extrudability of the compound during the coating process. The workability is lowered. In addition, if the 1 minute half-life of the crosslinking agent is less than 160 ° C, decomposition may occur at the sample transfer site in the extruder during the production of the black coating compound. The product's uniformity may be degraded because it falls and creates locally excessive long chain branches. If the one-minute half-life exceeds 220 ° C, since the residence time of the resin mixture in the extruder is usually about 30 seconds to 1 minute at about 210 ° C, the decomposition reaction may be delayed, resulting in the smell of the crosslinker in the final product. The smell of the cross-linking agent can be prevented to some extent when working at a high temperature of 230 ° C. or higher, but there may be a problem of non-uniformity of extrusion amount during the communication cable coating process due to the sticking phenomenon of two or more pellets sticking together.

When artificially creating long chain branches by adding a crosslinking agent to the black coating compound made of linear low density polyethylene and carbon black masterbatch, the critical shear stress is dramatically increased and the extrusion appearance is improved. Since the resin pressure and the extrusion load are increased, it may be a problem in the high-speed coating process. In order to solve this problem, the present invention can reduce the extrusion load and the resin pressure of the black coating compound by simultaneously injecting polypropylene having a melt index of 8 or more together with a crosslinking agent when preparing the compound. At this time, the amount of polypropylene to be added is 0.05 to 15 parts by weight with respect to 100 parts by weight of the base resin, the optimum effect is 5 parts by weight. When the polypropylene is less than 0.05 parts by weight relative to 100 parts by weight of the base resin in the black coating compound, there is no improvement effect, and when mixed in excess of 15 parts by weight, there is little kneading with the linear low density polyethylene. Accompanying the deterioration of properties, the extrusion amount may be uneven due to surging phenomenon due to phase separation during extrusion.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

<Method>

Manufacturing method of black resin for communication cable coating

In order to manufacture black compound for coating communication cable, carbon black masterbatch, crosslinking agent, and polypropylene resin are melt-extruded at 190 ~ 220 ℃ with biaxial screw extruder using linear low density polyethylene as base resin. To prepare.

<Evaluation of Extrusion Processability by Experimental Equipment>

Measuring equipment: HAAK5 single screw extruder (rheocode 90) screw L / D = 2/1

Die Type: Capillary Die L / D = 1O / 1

Extruder Temperature Arrangement: C1 / C2 / C3 / HEAD / DIE = 18O ℃ / 19O ℃ / 2OO ℃ / 21O ℃ / 22O ℃

Screw RPM: 6O / 1OO / 12O

Measurement items: extrusion appearance, resin pressure, extrusion load, odor

* Extrusion appearance is taken by SEM after cutting strand made in HAAKE single screw extruder into 1cm size.

<Measurement of Rheological Molecular Weight by Experimental Device>

Measuring equipment: rheometers (rheometrics dynamic spectrometer)

Measurement mode: dynamic mode, frequency sweep, strain 5, measurement temperature 230 ℃

Parallel plate, Radius 12.5mm, Gap size: 2.0mm

Measurement item: Viscosity (zero shear viscosity)

Example 1

8 parts by weight of carbon black masterbatch, tert-butyl based on 100 parts by weight of linear low density polyethylene (melt index 2.4g / 10min, Samsung Total Chemical: trade name 4142W) according to the method for manufacturing black compound for communication cable coating presented in the above method. 0.1 parts by weight of cumyl peroxide and 5 parts by weight of polypropylene were melt-extruded in a twin screw extruder to prepare a compound for coating a communication cable, followed by extrusion processing test and rheological molecular weight measurement. Among the test results, the resin pressure, the extruded load, and the odor of the compound are shown in Table 1, the appearance of the extrusion is shown in FIG. 1, and the rheological molecular weight is shown in FIG.

Comparative Example 1

8 parts by weight of the same carbon black masterbatch with 100 parts by weight of the same base resin as in Example 1 was prepared in the same manner as in Example 1, and a black compound for coating a communication cable was subjected to the extrusion process in the same manner. Each test result is shown in Table 1, FIG. 1, and FIG.

Comparative Example 2

8 parts by weight of the same carbon black masterbatch and 0.1 parts by weight of tert-butyl cumyl peroxide in 100 parts by weight of the same base resin as in Example 1 were prepared in the same manner as in Example 1 to prepare a black compound for communication cable coating and then tested for extrusion processability. It was. The test results are shown in Table 1.

Comparative Example 3

8 parts by weight of the same carbon black masterbatch, 0.03 parts by weight of tert-butyl cumyl peroxide and 5 parts by weight of polypropylene were prepared in the same manner as in Example 1 to prepare a black compound for coating a communication cable. After the rheological molecular weight was measured in the same manner as in Example 1. The test results are shown in FIG.

Comparative Example 4

8 parts by weight of the same carbon black masterbatch, 0.2 parts by weight of tert-butyl cumyl peroxide, and 5 parts by weight of polypropylene were prepared in the same manner as in Example 1 to prepare a black compound for coating a communication cable. After the extrusion process and rheological molecular weight was measured in the same manner. Each test result is shown in Table 1, FIG. 1, and FIG.

Comparative Example 5

8 parts by weight of the same carbon black masterbatch, 0.1 parts by weight of dicumyl peroxide, and 5 parts by weight of polypropylene in 100 parts by weight of the same base resin as in Example 1 were prepared in the same manner as in Example 1 to produce a black compound for communication cable coating. Processability was tested. The test results are shown in Table 1.

Table 1. Extrusion processability evaluation results

1 is a photograph showing the results of the extrusion processability test for the communication cable coating resin prepared according to the Examples and Comparative Examples of the present invention.

2 is a graph showing the results of measuring the rheological molecular weight of the resin for communication cable coating prepared by the Examples and Comparative Examples of the present invention.

Claims (2)

100 parts by weight of linear low density polyethylene, 5 to 30 parts by weight of carbon black, 0.05 to 0.1 parts by weight of a crosslinking agent generated at 160 to 220 ° C. for 1 minute, and 0.05 to 15 parts by weight of polypropylene. Resin composition. The method of claim 1, The crosslinking agent is tert-butyl cumyl peroxide, 2,5-bis (tert-butylperoxy) -2,5-dimethylhexane; 2,5-bis (tert-butylperoxy) -2,5-dimethylhexine-3; 1,1-bis-tert-butylperoxy-3,3,5-trimethylcyclohexane; Di-tert-butylperoxide; Or α, α-bis (tert-butylperoxyisopropyl) benzene.

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