JPH044355B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyurethane sealing material that has excellent sealing effects and heat dissipation properties, and is easy to disassemble after application.

Conventionally, connections, terminals, and penetrations (through walls, floors, etc.) of electric wires and cables are sealed using various compounds.

Sealing parts made of asphalt-based compounds have drawbacks such as asphalt tends to flow out when the temperature rises, thermal expansion and contraction is large, and components migrate and have poor heat dissipation properties that adversely affect cable materials.

Sealing parts using polyester resin or epoxy resin have large reaction shrinkage when the resin hardens, heat shrinkage after an exothermic reaction, hardening progresses over time, and is easy to peel off due to heat cycles, vibrations, and shocks, and is strong. There are drawbacks such as the sealing part cannot be easily disassembled because it hardens.

The present invention has been made in view of the above points, and provides a polyurethane sealing material that has excellent sealing effects and heat dissipation properties, is easy to remove as necessary after application, and is easy to branch and repair cables. It is something.

The main points of the present invention are as described in the claims.
(1) It is a mixture of isocyanate compounds with a molecular weight of 200 or more, and 5 to 40% of the isocyanate groups contained therein belong to monoisocyanate compounds,
Isocyanate component (2), polyol component (3), of which 95-60% belongs to the polyisocyanate compound, inorganic powder and/or organic powder are essential components, and the inorganic and/or organic powder is 30-75% by weight in the total composition.
Contains polyurethane sealant.

The present invention is mainly applied and constructed at locations where electric wires and cables are laid, and the sealing material used therein must be one that can be safely handled on site. The isocyanate component of the polyurethane sealing material used in the present invention is a mixture of a monoisocyanate having a molecular weight of 200 or more and a polyisocyanate having two or more isocyanate groups in view of handling safety.

Its content ratio is as described above. molecular weight
The reason for limiting the number to 200 or higher is that isocyanate compounds with a molecular weight of 200 or less tend to emit harmful vapors even at room temperature, and if special care is not taken when handling them, there is a high risk of health problems during work. be.

In other words, tolylene diisocyanate with a molecular weight of 174 is designated as a specified class 2 substance under the Ministry of Labor Ordinance No. 39 (Showa 47.9) Ordinance on Prevention of Hazards Due to Specified Chemical Substances, and tolylene diisocyanate and its 1%
Items containing the above require special consideration in manufacturing, handling, management, health examinations, protective equipment, etc.

When using an isocyanate compound with a molecular weight of 200 or more, less vapor is released at room temperature, making it easier to ensure work safety.

Monoisocyanates that can be used in the present invention include tridecyl isocyanate (molecular weight 235) and octadecyl isocyanate (molecular weight 295).

Furthermore, a monoisocyanate having a molecular weight of 200 or more obtained by subjecting a polyisocyanate to an addition reaction with a monohydric alcohol can also be used in the present invention. Suitable monohydric alcohols for the addition reaction include methanol, ethanol, propanol, butanol, octanol, decanol, and tridecanol.

Polyisocyanates having two or more isocyanate groups that can be used in the present invention include liquefaction-modified methylene diphenyl diisocyanate (molecular weight approximately 250), polymethylene polyphenyl polyisocyanate, and prepolymers of these and polyhydric alcohols. .

A mixture of the above-mentioned monoisocyanate and polyisocyanate is used in the present invention, and the appropriate ratio of the two is such that 5 to 40% of the isocyanate groups belonging to the monoisocyanate compound are included in the total isocyanate groups.

Incidentally, a mixture obtained by reacting the polyisocyanate and monohydric alcohol in such a ratio that the ratio of both falls within this range may be used as is as the isocyanate component.

The advantage of using such a mixture is that by adding a monohydric alcohol to a portion of the polyisocyanate, the vapor pressure is further reduced and toxicity is alleviated, and that the polyol and other components can be used in cable connections etc. The curing reaction when mixed and injected becomes gentle, and temperature rise and thermal expansion and contraction due to reaction heat are reduced.

The reason why the present invention uses a monoisocyanate compound and a polyisocyanate compound as the isocyanate component of the polyurethane sealing material is to prevent the sealing material from becoming a hard cured product, maintain plasticity over a long period of time, and improve the sealing effect. This is to enable maintenance, and to enable the seal portion to be easily dismantled with a screwdriver or other simple jig if necessary.

If the content of isocyanate groups in the monoisocyanate compound is less than 5%, the plasticity effect will be insufficient, and if it exceeds 40%, there will be a problem that the monoisocyanate compound tends to flow when the temperature is increased.

The polyurethane sealant of the present invention is inorganic and/or
Or organic powder is contained in the total composition in an amount of 30 to 75% by weight. The reason for blending inorganic powder is to increase the thermal conductivity of the sealing material, improve heat dissipation, reduce thermal expansion and contraction, and also provide the effect of facilitating disassembly.

Organic powder is added as a halogen-based powder flame retardant when flame retardancy is required, or used to facilitate disassembly. If the amount of powder blended is less than 30% by weight, the above effects will be insufficient, and if it is more than 75% by weight, construction will be difficult.

Examples of the polyol component used in the present invention include polyether polyols such as polypropylene glycol, castor oil which is a natural polyol, liquid polybutadiene having a hydroxyl group, liquid chloroprene having a hydroxyl group, and polyester polyols.

These may be mixed alone or in combination with the isocyanate component, and the mixing ratio of the polyol component and the isocyanate component is preferably in the range of 1:1 to 0.4:1 of hydroxyl group and isocyanate group.

Other additives such as antifoaming agents, colorants, and antioxidants may be added to the polyurethane sealing material used in the present invention.

The present invention will be specifically explained below using Examples and Application Examples.

Example 1 As shown in Table 1, polymethylene polyphenyl isocyanate [trade name] was used as the isocyanate component.
A mixture of 30 parts by weight of MDI-CR200 manufactured by Mitsui Nisso Urethane Co., Ltd. and 10 parts by weight of octadecyl isocyanate is used.

100 parts by weight of castor oil as a polyol component;
460 parts by weight of alumina powder is used as the inorganic powder.
The alumina powder is mixed with castor oil in advance, and immediately before use, the isocyanate component is added thereto and stirred and mixed uniformly.

The initial viscosity of this composition after mixing is at 25℃
It is 6000cps. After one day at room temperature, it hardens into a gel-like state,
It does not flow even when heated to 100℃. The result of measuring the thermal conductivity of the cured product is 25×10 ^-4 Cal/cm・sec・
℃, and the thermal resistance was 96cm・℃/W.

For comparison, a composition obtained by removing alumina powder from the above composition was cured and its thermal conductivity was measured to be 4.5×10 ^-4 Cal/cm・sec・℃, thermal resistance 530cm,
The temperature was ℃/W.

Next, the above composition containing alumina powder was applied to a model of an end seal portion of an inorganic insulated wire shown in FIG.

In other words, the wire has a structure in which a core conductor 1 with a diameter of 1.5 mm is coated with an inorganic insulator 2, and is further covered with a metal sheath 3 with a diameter of 8 mm, with the core conductor at both ends exposed. The bottom end is a polyurethane sealing material 5 in a container 4 with a volume of 300 c.c.
It's embedded inside. This sealing material 5 is the composition of Example 1.

After curing for one day, the upper part was filled with water 6 and heat cycled 10 times at 60℃ for 5 hours and at room temperature for 19 hours.
The change in insulation resistance between the metal sheath and the core conductor was measured using an insulation resistance meter 7.

Insulation resistance is both initial value and after heat cycle.
Sealing performance was maintained at 2000MΩ or higher. This cured product could be dismantled relatively easily using a metal spatula, knife, or the like.

Example 2 Using a polyurethane sealant having the composition of Example 2 shown in Table 1, the ends of inorganic insulated wires were sealed in the same manner as in FIG. 1, and a similar heat cycle test was conducted. The insulation resistance before and after the test was over 2000MΩ, and good sealing performance was maintained. The cured product was soft and could be easily dismantled with the tip of a screwdriver.

Example 3 A polyurethane sealing material having the composition of Example 3 shown in Table 1 was used, and this was applied to a model of a wall penetrating portion of an electric wire shown in FIG.

That is, five polyvinyl chloride sheathed electric wires 21 with a diameter of 10 mm were passed through a conduit pipe 22 with a diameter of 120 mm, and after sealing the lower end with a putty material 23 to a thickness of 10 mm, Polyurethane sealing material 24 was injected to a thickness of 50 mm and cured at room temperature for one day.

After removing the putty material on the bottom edge, heat at 100℃ for 6 hours.
A heat cycle of 20°C for 18 hours was repeated 10 times.
After this heat cycle, the upper part of the conduit pipe was filled with water 25, and water leakage was examined, and watertightness was maintained.

This sealant is highly flame retardant and has an oxygen index of 35.

The flame of a Bunsen burner adjusted to an inner flame of 30 mm and an outer flame of 17 mm was applied to the polyurethane seal at the lower end of the conduit pipe shown in Figure 2, and a combustion test was conducted at 1000℃ for 30 minutes. The PVC sheath of the wire was protected from the spread of fire by forming a solid layer.

This polyurethane sealing material can be easily dismantled using a screwdriver or the like.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the case where the polyurethane sealant of the present invention is applied to a model of the end seal part of an electric wire, and Figure 2 is an explanatory diagram of the case where the polyurethane sealant of the present invention is applied to a model of the wall penetration part of an electric wire. It is a diagram. 1... Core conductor, 2... Inorganic insulator, 3... Metal sheath, 4... Container, 5... Polyurethane sealing material.

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Claims (1)

[Scope of Claims] 1 (1) A mixture of isocyanate compounds having a molecular weight of 200 or more, in which 5 to 40% of all isocyanate groups contained therein belong to monoisocyanate compounds, and 95 to 60% belong to polyisocyanate compounds. A polyurethane sealing material which contains isocyanate component (2), polyol component (3), inorganic and/or organic powder as essential components, and contains 30 to 75% by weight of the above (3) in the total composition.