JPH0124006B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an underground power cable protection tube formed by molding a resin composition mainly composed of polyvinyl chloride resin. It is already well known that molded products of synthetic resin such as polyvinyl chloride resin (hereinafter abbreviated as PVC) are used as power cable protection tubes, and vinyl chloride tubes reinforced with impact strength agents (hereinafter referred to as high-impact tubes) are already known. ) has already been used in some areas as protective tubes for cables with small power capacities that do not require much heat resistance. For this purpose, the advantages of high-impact tubes, such as being lightweight, easy to work with, and having impact resistance, are utilized. However, this material has limitations in terms of physical properties. In other words, PVC's unique property of heat deformation resistance (hereinafter simply referred to as heat resistance) (heat compression resistance of the pipe body) is limited, and it can only be used as a protective tube for cables with small power capacity and low heat generation. It's just that it's done. When used as a protective tube for a cable with a large power capacity, it becomes soft due to the heat generated and cannot withstand earth pressure or live loads such as trucks, and it virtually ceases to function as a protective tube. It's put away. For this reason, the actual situation is that steel pipes, humid pipes, etc. are used as protection pipes for conduits that require a large power capacity. Although steel pipes and humid pipes each have their own advantages and are useful, they also have a number of drawbacks. Steel pipes are heavy (approximately 15 kg/m for GP130), making on-site work such as piping, connecting, and cutting extremely difficult, and requires a lot of manpower to handle. Huyum pipes are heavy (approximately 25 kg/m for HP130), making field work difficult, requiring a wide excavation width to tighten the pipe joints, and being extremely vulnerable to impacts from pickaxes, etc., resulting in damage to the cable. It has drawbacks such as not being able to prevent accidents. The present invention is directed to such conventional high-impact pipes,
It was completed as a result of intensive study to solve the shortcomings of steel pipes, humid pipes, etc. all at once.It has excellent impact resistance and heat resistance, and is lightweight (about 1 inch lighter than steel pipes) as a cable protection pipe for underground cables. /3, 1/5 the weight of hume pipes) and is a synthetic resin pipe with excellent installation workability. The polyvinyl chloride resin composition according to the present invention is a composition containing PVC, a heat-resistant ABS resin (hereinafter referred to as heat-resistant ABS), and a weather-resistant impact strengthener. Only by properly combining them will it be possible to obtain an underground cable protection tube with practical performance. In general, PVC has flame resistance and moderate impact resistance, but it has poor heat resistance.Adding an impact strengthener increases the impact strength, but the heat resistance further decreases, and the flame resistance also decreases. do. On the other hand, heat-resistant ABS has extremely good heat resistance, but has extremely poor weather resistance and flame resistance. Regarding impact resistance, although initial strength is excellent, weather resistance deteriorates significantly. This is because polybutadiene rubber, which has poor weather resistance, is used as the main component of the graft copolymer. Therefore, PVC, which has the above advantages and disadvantages,
By mixing appropriate amounts of three types of resin, which are a combination of heat-resistant ABS and an impact strengthener with excellent weather resistance,
It has been discovered that a molding resin with excellent heat resistance, flame resistance, and impact resistance can be obtained by taking advantage of the strengths and compensating for the weaknesses of each. In addition, the above heat-resistant ABS
It was also observed that when mixed with PVC, the processability was improved compared to when PVC was used alone. In other words, when heat-resistant ABS is mixed with PVC, PVC
Heat-resistant ABS and heat-resistant ABS tend to form a relatively uniform phase, and in particular, the mixture of heat-resistant ABS, which also acts as a processability improver for PVC, helps PVC to gel easily, resulting in a more uniform heat-resistant phase. It has been found that not only is it easy to form a phase and improve heat resistance, but also that the impact strength agent is easily and uniformly dispersed in the matrix phase, resulting in improved impact resistance even with a relatively small amount of blending. The fact that the amount of impact toughener can be reduced also has the effect of reducing the decrease in tensile strength and heat resistance of the molded article. The molded product obtained in this way has excellent impact resistance, heat resistance, and flame resistance, and has performance that cannot be obtained with conventional high-impact pipes. This made it possible to use it as a protective pipe for underground cables, which was especially needed. Below, a detailed description will be given of the cable protection tube for underground wires that is molded from a resin composition containing PVC, heat-resistant ABS, an impact strengthener, and other additives used in the present invention. PVC used in the present invention can be produced by suspension polymerization method or
It is produced by a known method such as emulsion polymerization and has an average degree of polymerization in the range of 800 to 1,500. Those with an average degree of polymerization lower than this have insufficient impact resistance, and those with an average degree of polymerization higher than this have high melt viscosity, poor processability, and poor physical properties. The heat-resistant ABS used in the present invention is a copolymer () obtained by emulsion polymerization of a mixture of acrylonitrile, α-methylstyrene, and methyl methacrylate, and contains styrene in a composition range suitable for diene-based synthetic rubber. Alternatively, it is a thermoplastic resin composition to which an appropriate amount of a graft copolymer () obtained by emulsion polymerization of methyl methacrylate that may contain styrene and acrylonitrile is added. This heat resistant
ABS manufacturing methods are already known, and can be manufactured, for example, by the method described in Japanese Patent Publication No. 46-37415. The manufacturing method will be explained in more detail using an example. First, the heat-resistant copolymer () contains 3 to 30% by weight of acrylonitrile and 30% by weight of α-methylstyrene.
~80% by weight and 5-50% by weight of methyl methacrylate
It can be obtained by emulsion polymerization of a mixture of. Emulsion polymerization may be carried out according to a conventional method. The graft copolymer () is obtained by graft copolymerizing about 35 to 65% by weight of diene-based synthetic rubber and about 65 to 35% by weight of styrene or methyl methacrylate, which may contain styrene and acrylonitrile, by an emulsion polymerization method. Manufactured. For example, a diene-based synthetic rubber latex may be treated with a monomer in an aqueous dispersion in the presence of a radical polymerization initiator. Examples of diene-based synthetic rubber include polybutadiene, polyisoprene, polychloroprene-butadiene-styrene copolymer, butadiene-acrylonitrile copolymer, isoprene-isobutylene copolymer, etc., but mainly polybutadiene, butadiene-styrene copolymer, etc. Polymers, butadiene-acrylonitrile copolymers, and other materials containing butadiene as a constituent are used. The heat resistance and impact resistance of the above composition, ie, heat-resistant ABS, depend not only on the respective compositions of the copolymer () and the graft copolymer (), but also on their mixing ratio. Therefore, the mixing ratio may be appropriately selected depending on the desired heat resistance and impact resistance, but it is recommended to mix the diene synthetic rubber so that it accounts for about 5 to 30% by weight in the mixed composition. desirable. Mixing may be performed by a method known per se. The impact strengthener used in the present invention is a multicomponent resin obtained by graft polymerizing monomers such as methyl methacrylate, styrene, and acrylonitrile to a copolymer rubber mainly composed of acrylic acid ester. The method for producing this multi-component resin is already known, for example, Japanese Patent Publication No. 51-5674, Japanese Patent Publication No. 51-28117,
JP-A-50-88168, JP-A-50-88169, JP-A-50-
It can be manufactured by the method described in 98951 etc. The manufacturing method will be explained in more detail using an example. For the acrylic ester that is the main component of the copolymer rubber, at least 80% by weight of an acrylic alkyl ester or an acrylic alkyl ester in which the alkyl group has 2 to 8 carbon atoms is used, and monovinylidene that can be copolymerized with this is used. A compound and a polyfunctional crosslinker are reacted to first form an aqueous dispersion of a rubbery copolymer. Next, a methacrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms, a vinyl aromatic compound, an unsaturated nitrile, and A multicomponent resin is obtained by graft polymerization of 20 to 80 parts by weight of all or a mixture of 2 to 3 monomers containing a monovinylidene group copolymerizable with these monomers. This type of resin not only has particularly excellent performance in terms of weather resistance, but because of the slippery properties of molecules that are unique to acrylic resins, PVC resins containing this type of impact strengthener are It has the characteristic that it can also improve the processability of the composition. In the present invention, the ratio of heat-resistant ABS to PVC in the polyvinyl chloride resin composition and impact reinforcement agent is based on 100 parts by weight of a resin composition in which 5-50 parts by weight of heat-resistant ABS is mixed with 95-50 parts by weight of PVC. , the impact toughener ranges from 5 to 20 parts by weight. If the amount of impact strengthener added is less than 5 parts by weight, impact resistance will hardly be improved, and if it exceeds 20 parts by weight, heat resistance will deteriorate.
The effect of improving heat resistance and tensile strength by mixing ABS will be lost. All or part of various known heat and light stabilizers, lubricants, fillers, pigments, etc. may be added to the resin composition as referred to in the present invention, if necessary. Then, they are mixed using a known mixing device such as a roll mill, ribbon blender, Henschel mixer, or Banbury mixer, and further molded into a desired molded product using a known kneading processing machine such as an extruder. The cable protection pipe for underground cables as used in the present invention refers to all tubular molded products obtained by extrusion molding the above-mentioned resin composition, as well as bent pipes, sleeve products, connecting pipes, etc. obtained by secondary molding them. This is a general term that includes the following, and does not refer only to the protective tube as a mere primary molded product. Next, the main practical performances required of the underground cable protection pipe of the present invention are impact resistance, heat resistance, weather resistance, and flame resistance. The required performances and test methods will be explained in detail below. First, regarding impact resistance, when a worker accidentally hits the pipe with all his might with a pickaxe during actual protection pipe installation work or re-excavation work on the pipe that has already been buried or its surrounding area. The pipe needs to be free from cracks and deformation that would impede wire passage, and the tip of the pickaxe must not be exposed on the inner surface of the pipe. Furthermore, when the above-mentioned work is carried out, the temperature of the pipe body ranges from around 0°C to approximately 0°C when buried and energized.
Since the temperature range is up to 75℃ (for heat-resistant cables), extremely strict conditions are required regarding the test temperature. As mentioned above, as a test method for impact resistance performance,
In addition to the above-mentioned impact test using a practical pickaxe, a mechanized impact tester is used to facilitate quantification. This impact tester is a tester that complies with the impact load test method in section 7.14 of JIS C3801 (Insulator Test Method).As shown in Figure 1, the end of arm 1, which is rotatable and has a length of 1m, has a load capacity of 16.16Kg. A load 2 (the tip 3 is in the shape of a pickaxe) is attached and allowed to fall naturally from an angle of 95 degrees, and the test tube 4 (tube body cut into a length of approximately 30 cm) fixed perpendicularly to the center of the arm axis with a fixture 5 is placed at 0.
Blow at a temperature range of ~75°C. The level required for this test is the same as in the case of the impact test with a practical pickaxe under the above test temperature conditions, that the pipe does not develop cracks or deformation that would impede wire passage, and that the tip 3 of the testing machine is on the inner surface of the pipe. It is important not to expose yourself to Regarding heat resistance, the heating of the pipe takes into account the earth pressure that is applied to the pipe body when it is actually energized as an underground cable protection pipe, and the allowable limit of the flatness of the pipe, which is determined by the temperature of the pipe body at that time. Evaluated by heat compression resistance by compression test and buried current test. The load acting on the top of a buried pipe 1.2m underground under normal conditions is 0.64Kg/cm ² as earth pressure (backfill earth pressure + earth equivalent to the live load when a 20-ton vehicle passes over the buried ground). The amount of flattening of the tube when this load is applied must be 2.5% or less of the inner diameter of the tube so as not to impede the wire passage. moreover,
According to the results of the buried energization test, the temperature of the tube body when energized is
Since the temperature is around 75°C, the heating compression test is conducted in the following manner. That is, a tubular test piece with a length of 50 mm was cut from the test tube, conditioned for 1 hour in an atmosphere of 75°C, and then placed between the flat plates of a testing machine (Autograph).
After 5 minutes when the temperature of the test machine reaches 75℃, the tube is compressed at a speed of 10 mm/min perpendicular to the tube axis, and the amount of flatness of the tube is measured when a load of 20.7 kg is applied. In addition, as a buried energization test method, first, a test tube is wired and buried as shown in FIGS. 2a and 2b.
The load is adjusted so that the earth pressure acting on the upper end of the upper pipe, which is installed in two layers and two layers, is 0.64Kg/cm ² , and the cable core wire temperature is always 100℃, for a short time (5 hours) 130
℃ for more than 1 month (for a short time,
Conduct a energization test (continuous heat cycle for 2 days). After the test, the test tube 1 is excavated and the outer diameters in two directions, top, bottom, left and right, are measured at the central portion between the nozzles 3 and at the contact portion with the nozzles 3. Regarding heat compression resistance, the amount of deformation of the tube is required to be 2.5% or less of the inner diameter of the tube in all tests. Weather resistance refers to the weather resistance while the pipe is left in the field before it is buried as an underground cable protection pipe, and the required performance is a Charpy impact test on accelerated exposed test pieces. When the impact value is 14.5Kg・cm/cm ² or more. The weather resistance test method was to set the test piece cut from the test tube in the WS type accelerated exposure test device specified in JIS A1415 (accelerated exposure test method for plastic building materials), and spray at a black panel temperature of 63±3℃ for 18 minutes. Exposure for 100 hours at /120 minutes. After exposure, test according to JIS K7111 (Hard Plastic Shalpey Impact Test Method). Regarding flame resistance, it is necessary to sufficiently withstand cable short-circuit accidents, and performance equivalent to the flame resistance specified in JIS C8430 (rigid vinyl conduit) is required. Next, the features of the present invention regarding the required performance of underground cable protection tubes as described above will be explained. That is, the first feature of the protective tube of the present invention is that the temperature dependence of the amount of thermal compression deformation is significantly smaller than that of conventional high-impact tubes. The difference between the two is especially significant when the tube body temperature is around 75℃, which is required for power cable protection tubes (heat resistance). Furthermore, it has better impact resistance and heat resistance than high impact tubes,
The second feature is that it also has excellent weather resistance. As described above, the greatest advantage of the present invention is that the main performances as a cable protection tube are balanced at a high level, and this is unprecedented. Hereinafter, the present invention will be further specifically explained using Examples. Example 1 (A) Production of impact toughener (acrylic multi-component resin) Production of a rubbery polymer aqueous dispersion; 98 parts by weight of butyl acrylate was added while stirring the components listed in Table 1 at a temperature of 30°C. A mixed solution of 2 parts by weight of allyl methacrylate and 0.2 parts by weight of kyumene hydroperoxide (hereinafter referred to as CHP) was added over 4 hours to proceed with polymerization. Table 1 Water 250 parts by weight Sodium oleate 3 Sodium formaldehyde condensed naphthalene sulfonate 0.2 Sodium formaldehyde sulfoxylate (hereinafter referred to as Rongarit) 0.4 〃 Disodium ethylenediaminetetraacetate (hereinafter referred to as EDTA・2Na) 0.01 〃 Ferrous sulfate - Heptahydrate 0.005 After the monomer addition was completed, the temperature was maintained for 1 hour to complete the polymerization, and the polymerization rate was 96%. Production of graft polymer: An aqueous dispersion of a rubbery polymer and the components shown in Table 2 were charged and kept at 60°C. However, the amount of water is 250 parts by weight, which is the sum of the water from the aqueous dispersion and the amount required for adding acetic acid and caustic potash described later, and while stirring, add 40 parts by weight of 1% acetic acid aqueous solution and mix for 15 minutes. After this period, 20 parts by weight of a 2% aqueous solution of potassium hydroxide was added to stabilize the dispersion. Table 2 Rubbery polymer dispersion (as polymer solid content) 60 parts by weight Water 250 〃 SPS 0.2 〃 EDTA・2Na 0.01 〃 Ferrous sulfate heptahydrate 0.005 〃 Subsequently, methacrylic acid was added while stirring at 60°C. A mixture consisting of 40 parts by weight of methyl and 0.2 parts by weight of CHP was added over a period of 4 hours, and then maintained for 1 hour to complete the polymerization. The obtained graft copolymer dispersion was salted out and coagulated by adding hydrochloric acid, then heated and granulated, dehydrated, washed and dried to obtain a powdered resin. (B) Production of heat-resistant ABS Production of copolymer (): In a reactor equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, add 250 parts of water, 3.0 parts of sodium oleate, and 0.2 parts of ascorbic acid. , 0.0025 part of ferrous sulfate hydrate, and 0.01 part of disodium ethylenediaminetetraacetate were added, and after deoxygenation, the mixture was heated and stirred at 60°C in a nitrogen stream. Next, a monomer mixture of a certain composition (a mixture of acrylonitrile, α-methylstyrene, and methyl methacrylate) in which 0.3 parts of kyumene hydroperoxide and 0.3 parts of tertiary dodecyl mercaptan were dissolved was prepared at 100%
of the mixture was placed in a dropping funnel and added continuously over a period of 5 hours. After the addition was completed, stirring was continued for an additional hour at 60°C. The copolymer latex produced is coagulated with common salt and hydrochloric acid, and the particles are agglomerated by heating.
A powdered resin was obtained by washing separately with water and drying. Production of graft copolymer (): In the same reactor as above, large-particle high-temperature polymerization polybutadiene rubber latex (manufactured by Nippon Gosei Rubber Co., Ltd.) was added.
JSRO700 latex) 84.7 parts (solid content 50 parts), water
Add 215.3 parts of ascorbic acid, 0.2 parts of ascorbic acid, 0.0025 parts of ferrous sulfate hydrate, and 0.01 parts of disodium ethylenediaminetetraacetate, and after deoxidizing, under a nitrogen stream.
The mixture was heated to 60°C and stirred. Next, 50 parts of a monomer mixture of a certain composition (styrene or methyl methacrylate which may contain styrene and acrylonitrile) in which 0.2 parts of kyumene hydroperoxide and 0.15 parts of third mixed mercaptan were dissolved was placed in the dropping funnel. It was continuously added dropwise over a period of 3 hours. When half the amount is dropped, sodium oleate (1.0 part) is added to 10
% solution. After the dropwise addition was completed, stirring was continued for an additional hour at 60°C. The resulting graft copolymer latex was coagulated with common salt and hydrochloric acid, heated to aggregate the particles, and then washed and dried to obtain a powdered resin. The copolymer () and graft copolymer () produced as described above were blended together with other ingredients at the mixing ratio shown in (A) of (C) and used. (C) Molding of cable protection tube Graft polymer (multicomponent resin) manufactured in (A)
was used as a weather-resistant impact strengthener, polyvinyl chloride resin and heat-resistant ABS manufactured from (B) were blended in the following formulation using a 300 Henschel mixer in a conventional manner, and then extruded using an 80φ bidirectional twin-screw extruder. A tubular molded body with an inner diameter of 130 φmm and a wall thickness of 8.5 to 9.3 mm was extruded using the same. The formulation and molding conditions were as follows. (B) Compounding conditions Part by weight polyvinyl chloride resin (Kanevinyl, average degree of polymerization: 1300) 90 Heat-resistant ABS resin (copolymer (): graft copolymer () = 8:2)
10 Impact strengthener (acrylic-multicomponent resin) 7 Tin stabilizer 2 Wax lubricant 1.7 Pigment 0.2 (b) Molding conditions cylinder temperature (℃) C ₁ C ₂ C ₃ C ₄ C ₅ AD 185 175 165 160 150 165 Die temperature (℃) D ₁ D ₂ D ₃ D ₄ 175 180 185 190 Screw temperature (℃) 100 The extrusion results were as follows. Screw rotation speed 28rpm Back pressure 12 tons (1000Kg) Discharge rate 125Kg/Hr The extruded tubular body has tensile strength and impact resistance (pickaxe impact strength), which are the main performances required for underground cable protection pipes. ), heat resistance (heat compression resistance), weather resistance, and flame resistance were investigated. The results are summarized in Table-1.
Table 1 shows two types of commercially available polyvinyl chloride pipes (a 125φ general pipe and a high-impact pipe) and a known composition for high-impact pipes, which are molded in the same manner as in Example 1, as reference examples. The physical property values of the pipe of the same size (130φ) are taken as Reference Example 3,
Furthermore, the physical property values of a 130φ pipe molded in the same manner as in Example 1 using only chlorinated polyvinyl chloride resin (hereinafter abbreviated as CPVC), which is a typical heat-resistant resin, and an impact strengthener are also shown as Reference Example 4. The blending conditions for Reference Example 3 and Reference Example 4 were as follows. Compound of Reference Example 3 Part by weight PVC (average degree of polymerization of Kanevinyl: 1300) 100 Impact strengthener (acrylic-based multi-component resin) 7 Lead-based stabilizer 1.0 Lead stearate 1.5 Metal soap-based lubricant 1.5 Pigment 0.2 Reference example 4 combination CPVC (heat-resistant Kanevinyl, chlorine content 67%) 100 Impact strength agent (acrylic-based multi-component resin) 30 Workability improver (Kane Ace PA) 2.0 Tin-based stabilizer 2.0 Lead stearate 2.5 Metal adhesive system Lubricant 1.5 Pigment 0.2 As is clear from the results in Table 1, the protective tube of the present invention is superior to commercially available vinyl chloride tubes (general tubes and high impact tubes) shown as reference examples and reference examples 3 and 4. It can be seen that it has superior performance in impact resistance, heat resistance, and weather resistance compared to the prototype high-impact tube shown above. In addition, the impact-strengthened CPVC pipe of Reference Example 4 requires a particularly large amount of impact-strengthening agent to improve impact resistance, and as a result,
Workability and heat resistance have been sacrificed considerably, but impact resistance has not been improved much. Next, the temperature dependence of the amount of thermal compression deformation at around 75°C was investigated for two types of tubes, Example 1 and Reference Example 3. As a result, it was found that the protective tube of the present invention (Example 1) not only had a smaller amount of thermal compression deformation than the conventional high-impact tube, but also had a significantly smaller rate of change due to temperature. This means that it is less susceptible to changes in the temperature of the tube due to fluctuations in the amount of current when energizing the tube, as well as to temperature increases around the tube. From the above points, it can be seen that the product of the present invention has much better performance than any of the pipes shown in the reference examples as cable protection pipes for underground cables. Example 2 A tubular molded body was extruded in the same manner as in Example 1 using the following formulation. The formulation and molding conditions were as follows. (a) Compounding conditions PVC (Kanevinyl, average degree of polymerization: 1300)
90 parts by weight heat-resistant ABS resin (copolymer (): graft copolymer () = 8:2) 10 〃 Impact strengthener (acrylic-based multi-component resin) 12 〃 Lead-based stabilizer 2.0 〃 Lead stearate 1.0 〃 Metal soap-based lubricant 0.5 〃 Wax-based lubricant 1.0 〃 Pigment 0.2 〃 (B) Molding conditions Cylinder temperature (℃) C ₁ C ₂ C ₃ C ₄ C ₅ AD 180 175 170 165 160 165 Die temperature (℃) D ₁ D ₂ D ₃ D ₄ 175 185 185 190 Screw temperature (°C) 100 The extrusion results were as follows. Screw rotation speed 28rpm Back pressure 12.0 tons (1000Kg) Extrusion amount 130Kg/Hr Example 1 Regarding the extruded tubular body
The same physical property tests as in the case were carried out and the results are shown in the table below.
They are summarized in 1. Regarding the performance of the pipe, although it is slightly inferior to Example 1 in terms of weather resistance, it has strength equal to or higher than the level of the reference example, and in terms of heat resistance, it has excellent performance equivalent to or higher than Example 1. Indicated.

【table】 - -
Example 3 The pipes of Example 2 and Reference Example 3 were subjected to a buried energization test as underground cable protection pipes.
The burial test was conducted in accordance with the method described above. In this test, in order to be able to test the above two types of pipes under the same conditions, the test pipes were placed in the lower two examples of the buried cross-sectional view shown in Figure 2a, and the specified energization [cable core wire Adjust the amount of current so that the temperature is always 100℃ and short time (5 hours) 130℃ (2 days continuous heat cycle), and the earth pressure acting on the upper end of the upper pipe is 0.64Kg/cm ² 1 below
A power test was conducted for several months. After the test, the test tube was excavated and the outer diameter in two directions, top, bottom, left and right, was measured at the center between the nozzles and at the contact area with the nozzle, and the amount of deformation of the tube was investigated. Table 2 summarizes the results of these measurements regarding the central part of the tube immediately under the load with the largest amount of internal deformation and the contact part with the nozzle closest to that part.

[Table] As is clear from the results in Table 2, the conventional high-impact tube type of Reference Example 3 has a 3.25
Compared to the case where the deformation exceeds 2.5% (2.5%), the amount of deformation in the present invention of Example 1 is far less than 2.5%, and it has extremely excellent heat resistance with high practicality. It has been proven that.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the impact testing machine, FIG. 2a is a buried cross-sectional view of the buried energization test, and FIG. 2b is a side view of the piping. 1... Arm, 2... Load, 3... Pickaxe-shaped tip, 4... Test tube, 5... Fixture, 6... Cable,
7... Nozzle stand, 8... River sand, 9... Original soil, 10... Thermocouple (for recording core wire temperature), 11... Earth pressure gauge.

Claims (1)

[Claims] 1 Heat-resistant ABS resin 5-50 parts by weight and degree of polymerization 800-
For 100 parts by weight of a resin composition mixed with 95 to 50 parts by weight of polyvinyl chloride resin of
A cable protection tube for underground wires that is formed by molding a polyvinyl chloride resin composition containing ~20 parts by weight and has excellent heat deformation resistance, impact resistance, and weather resistance.