JPS6225190B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of a rodent-proof paint for coating electric wires and cables to which cycloheximides are added. Conventionally, the rat-proofing effect of cycloheximides was utilized by dissolving them in various resin solutions to form a solution, and then applying the solution to the coating layer (sheath) of electric wires and cables to form a rat-proofing coating. is already known to form. However, the main elements for forming a film containing cycloheximides, that is, vehicles, are polyethylene resins, polyvinyl chloride resins, ethylene-vinyl acetate resins, polyamide resins, polycarbonate resins, etc., which are conventionally used as sheath materials for electric wires and cables. The paint used is a 10% concentration of dissolved in an organic solvent. However, at present, when a rodent-proofing paint made of this type of resin is applied to a cable, there are several major drawbacks, and there are significant limitations in practical use. First, one of the drawbacks is that the cable sheath may be destroyed if the coating film formed directly on the cable itself is subjected to excessive pressing force. In other words, when forming a coating film on a cable sheath, the cable that has gone through the coating-drying process is
The cable is wound around a cable drum, and when it is used it is pulled out from the drum again, but as is well known, when the cable is wound around the drum, a considerable amount of tension is applied to the wound cable so that there is no slack, and the cable is wound in layers. . Therefore, the cables wound around the drum are left in close contact with each other and under pressure, and in this case, in the case of cables after the rat-proof coating has been formed, the coatings are in close contact with each other. becomes. At this time, if the adhesive strength between the coating films is excessive, there is a risk that the cable sheath (generally made of polyvinyl chloride) will rupture due to peeling action during unwinding. In other words, among the rat-proofing paints available on the market, those made mainly of vinyl acetate resin, for example, polyvinyl acetate-based resin, have improved adhesion to coated wires and are excellent in forming a rat-proof coating. However, since the adhesive strength between the coatings is also high, cables coated with this coating produce high adhesive strength when they come into contact with each other. This adhesive force manifests itself in a peel strength that is higher than the mechanical properties of the vinyl sheath when the cable is unwound, and as a result, either one of the vinyl sheaths, which is the cable sheath, is torn and the cable becomes unusable. The state will be as follows. This phenomenon becomes noticeable when the cable is left at a high temperature even temporarily before use, and then rewound in a low temperature environment. For example, if a cable coated with the above-mentioned vinyl acetate resin-based rodent-proof paint is left at around 80℃ and then the temperature drops to about 5 to 10℃, it is almost always necessary to remove the cable from the drum. Cracks and tears occur in the cable sheath layer. This is because the polyvinyl acetate resin, which is the vehicle for rodent-proof paint, softens due to temperature dependence, and the coatings on the stacked cable sheaths fuse together to form an integrated structure, resulting in even stronger adhesion at low temperatures. It's all about demonstrating your power. Moreover, this tendency is a serious drawback not only in the above-mentioned polyvinyl acetate resin, but also in all commercially available rat-proof paints using polyvinyl chloride resins, polyamide resins, etc. as vehicles. Another drawback is that coatings formed from conventional rodent-resistant paints reduce the low-temperature embrittlement resistance of the cable sheath when applied. In other words, regardless of whether or not the cable sheath peels off due to adhesion as described above, if the low-temperature embrittlement temperature of the resin, which is the main element forming the coating film, is high, when such a coating film is applied on the cable sheath, the low temperature of the cable sheath The embrittlement temperature rises to the low-temperature embrittlement temperature of the coating, or at least becomes embrittled at a temperature so high that the low-temperature embrittlement temperature of the cable sheath itself cannot be maintained. This is because when a coating film that absorbs little impact energy is closely interposed as an epithelial layer against impact impact at low temperatures, the underlying cable sheath receives the shock waves and loses its inherent low-temperature embrittlement. It will get worse. As an example, if a chlorinated rubber-based coating is formed on a vinyl-sheathed cable, the low temperature embrittlement temperature of the cable sheath (PVC) (ASTMD
746-73), which is originally -23°C, in this case it is -15°C, a significant decrease. Therefore, even if the vehicle does not cause peeling failure of the sheath material due to adhesion, which is the first drawback, it is not practical to use a material (resin) that increases the low-temperature embrittlement temperature of the sheath material. This is not a good thing. Furthermore, in chlorinated organic solvents that have traditionally been used as solvents for resin solutions due to their low risk of flammability, cycloheximide, a medicinal ingredient for rodent repellency, has poor stability and a significantly low residual rate. has become known. That is, when cycloheximide is dissolved in trichlorethylene, which is a typical example of a chlorinated organic solvent, a residual rate of 32% when stored at room temperature for one month and 0% when stored at 35°C has been obtained. This is because cycloheximide is presumed to form isomers in chlorinated organic solvents, which exerts a certain degree of repellent effect on rats, but the use of chlorinated organic solvents with low residual cycloheximide yields a more reliable rat-repellent effect. That's not a good thing. As a result of intensive research in order to solve these drawbacks of conventional paints, the present inventors have succeeded in guaranteeing adhesion to the cable sheath material (PVC) and maintaining the original performance of the cable sheath in terms of low-temperature embrittlement. We have now found a rodent-proofing paint for electric wires and cables that has a high persistence of cycloheximide, an effective rodent-proofing ingredient, without impairing the rodent-proofing properties. That is, the rodent-proof paint for applying to electric wires and cables of the present invention is a rodent-proof paint made by dissolving a film-forming resin and cycloheximide in an organic solvent, and uses an acrylic acid-based synthetic rubber containing butyl acrylate as the main component as the film-forming resin. In the case of a cable coated with a rodent-proof paint characterized by the use of a rodent-proof paint, the cable sheath may be destroyed due to mutual adhesion of the paint films on the sheath, as seen in the use of conventional rodent-proof paints. It has been found that an excellent rodent-proofing effect can be obtained without deteriorating the low-temperature embrittlement of the cable sheath due to coating film formation. In the present invention, organic solvents for dissolving the film-forming resin and cycloheximide include toluene, cyclohexane, etc., since cycloheximide has a particularly high rat repellent effect compared to conventional chlorinated organic solvents such as trichlorethylene. It is desirable to use a non-chlorinated organic solvent such as a hydrocarbon solvent such as, a ketone solvent such as acetone or methyl ethyl ketone, or an alcohol solvent such as isopropyl alcohol or ethyl alcohol. In addition, the acrylic acid-based synthetic rubber containing butyl acrylate as the main component used as the film-forming resin is a block copolymer formed by irregular arbitrary bonds with other monomers such as acrylonitrile, vinyl chloride, vinylidene chloride, butadiene, or side chains. An example of this acrylic acid-based synthetic rubber is one manufactured by Toa Paint Co., Ltd. under the trade name "Toa Acron PS".
#200, #210, #250, etc. are commercially available. Further, the content of this film-forming resin is used within a range of 0.5% to 20% by weight in the paint. If the resin content does not reach 0.5% by weight, it will be difficult to maintain the rodent-proof coating on the cable sheath, and if it exceeds 20% by weight, there will be no particular merit in forming the coating, and some peeling may occur. This is because the embrittlement properties deteriorate. In addition, the content of cycloheximide in the paint is 0.1
Add and dissolve so that the content is ~5% by weight. This is because if the content of cycloheximide does not reach 0.1%, a sufficient rat repellent effect cannot be obtained in the resulting coating film. The upper limit is not particularly limited, but if it exceeds 5% by weight, there is no significant difference in the rat repellent effect from adding up to 5% by weight, which only increases the cost of the paint and has little merit.
The present invention will be further described below with reference to Examples. Examples 1 to 6 Comparative Examples 1 to 3 Acrylic acid-based synthetic rubber made of a copolymer of butyl acrylate and acrylonitrile (trade name TOA ACRON PS #250, manufactured by Toa Paint Co., Ltd.) as a film-forming resin and comparison Therefore, various rodent-proof paints using ethylene-vinyl acetate copolymer and vinyl acetate-vinyl chloride copolymer and having the composition shown in Table 1 were applied onto the VV cable sheath immediately after the paint was manufactured and one year after the manufacture. A feeding damage experiment was conducted using brown rats on each of the cables subjected to such treatment. Examples 1 to 5 did not suffer from feeding damage, but Example 6 used trichlorethylene as the solvent.
has suffered some damage. Comparative Examples 1 and 2 use a chlorinated organic solvent, so the rat repellent effect of cycloheximide is reduced. We also investigated the peelability of the coating between cable sheaths. As shown in FIGS. 1 to 3, the peel force test method involves molding test specimens 1 in which strips 3 (length A+B, width C) of vinyl resin composition for cable sheath are laminated and bonded. From this, the peeling load when both strips are peeled off is measured. After applying each paint adjusted as described above to one side of each strip with a brush, it was heated to 80°C. After drying at temperature for 5 minutes, the two sheets were stacked and placed on a smooth bottom plate 4 as shown in Figure 3, and a weight of 20 kg/50 mm x 20 mm was placed from above through a presser plate 5.
Apply a load 6 of (= length x width = coated area) to adhere the adhesive layer 2 to the B (50 mm) part of the sample body 1.
was formed. Both strips were then peeled off using a tensile testing machine under a condition where a load was applied and the temperature was maintained at a constant temperature as shown below, and the load at the time of peeling was measured. (See Figure 4) The measurement conditions are as follows. Load holding temperature: 5°C 10°C 20°C Load holding time: 3 hours Pulling speed: 500 mm/min Table 1 also lists the measured values obtained using the coatings of the example and comparative examples using the above method. In the above test method, a cable coated with rodent-proof paint is wound around a drum and left in a multilayered state. At this time, since the wires are subjected to tightening pressure, the adhesive strength of the coating film is further affected by this tightening.
A clear difference in peeling force can be seen from Comparative Examples 1 and 2, which simulate this relationship and do not use acrylic acid-based synthetic rubber. The speed at which the cable is unwound (typically 15
The peeling loads shown in Comparative Examples 1 and 2 at (m/min) suggest that the adhesive force is sufficient to cause peeling rupture in the cable sheath, and the lower the temperature, the stronger the coating film becomes There is a strong tendency for the load to increase. This imposes excessive restrictions on actual work as it affects the environment during unwinding of the cable. On the other hand, although the product of this example is slightly temperature dependent, the load at the time of peeling is such that it does not impose any restrictions on the unwinding of the cable. Next, the effect on the low-temperature embrittlement of the cable sheath to which the coating of the present invention was applied was investigated. The results of the embrittlement temperature test conducted in accordance with ASTMD 746-73 are also listed in Table 1. Examples 1 to 4 and 6 containing 20% by weight or less of acrylic acid-based synthetic rubber were compared to Comparative Example 3. Shows the same embrittlement temperature as a blank. In contrast, 30% by weight of acrylic acid-based synthetic rubber
In Example 5, in which acrylic acid-based synthetic rubber was mixed, and in Comparative Examples 2 and 3, in which no acrylic acid-based synthetic rubber was used, the embrittlement temperature was clearly higher than that of the blank. This shows that since the coating of the present invention has excellent flexibility at low temperatures, it does not have any effect even if a coating film is formed on the cable sheath. The results obtained above are summarized in Table 1. 【table】

[Brief explanation of the drawing]

FIG. 1 is a schematic front cross-sectional view of a test specimen for which the load during peeling is to be measured in an example of the present invention, FIG. 2 is a schematic side cross-sectional view thereof, and FIG. Furthermore, FIG. 4 is a schematic cross-sectional view showing a test specimen torn off by a tensile testing machine. 1...Test specimen, 2...Adhesive paint layer, 3...Strip-shaped vinyl for cable sheath, 4...Bottom plate, 5...Pressure plate, 6...Load, A...Length of surface of test sample 1 on which no coating film is formed (50 mm), B... Length of the coating surface of test specimen 1 (50 mm), C... Width of the coating film forming surface of specimen 1 (20
mm), P...Tension.

Claims (1)

[Scope of Claims] 1. A rat-proofing paint made by dissolving a film-forming resin and cycloheximide in an organic solvent, characterized in that an acrylic acid-based synthetic rubber containing butyl acrylate as a main component is used as the film-forming resin. Rodent-proof paint for electric wires and cables. 2. The rodent-proof coating for electric wires and cables according to claim 1, comprising 0.5 to 20% by weight of acrylic acid-based synthetic rubber, 0.1 to 5% by weight of cycloheximide, and the balance being an organic solvent. 3. The rat-proof paint for applying to electric wires and cables according to claim 1, wherein the organic solvent is a non-chlorine organic solvent.