Composition for coating wire seal and method for sealing coated wire

Abstract

Provided are a coated electric cable sealing composition which has excellent sealing properties even under conditions of cold / hot cycle and high temperature and humidity, for example, and a method for sealing a coated electric cable. This coated electric cable sealing composition, for sealing a core wire connecting portion formed by electrically connecting a plurality of core wires that are exposed from a plurality of coated electric cables, is characterized in that when the part in which the core wires are exposed, including the core wire connecting portion, and a boundary part between the coated portions and the exposed portions of the core wires are immersed vertically into the coated electric cable sealing composition, which has a curing time of 10 minutes or less at 130°C and with which a resin cap has been filled, and curing is performed by heating, the composition penetrates to a height of at least 5 mm inside the coated electric cables when cured.

Description

Technical Field

[0001] The present invention relates to a sealing composition and a sealing method for a coated electric wire having excellent sealing properties even under conditions such as a thermal cycle, high temperature and high humidity, and is widely used as a sealing agent and a sealing method for coated electric wires in wiring of various electrical systems such as automobiles, home appliances, and OA equipment.

Background Art

[0002] Wires such as wire harnesses used as automotive electrical components may electrically connect a plurality of wires at their ends for branched wiring. The connection is made, for example, by peeling the coatings of the end portions of a plurality of coated electric wires to expose the core wires, and bonding the exposed plurality of core wires. Such a connection portion of the core wires needs to be insulated from the outside to enhance the reliability of the circuit and sealed to prevent water ingress, and various sealing methods have been conventionally studied.

[0003] Conventionally, it is known to seal a core wire connection portion with a thermosetting resin. However, in order to make the seal perfect, the thermosetting resin must sufficiently penetrate into narrow gaps such as the gaps between the core wires, the gaps between the coated electric wires, and the gaps between the core wire and its coating at the core wire connection portion. For this purpose, it is necessary that the viscosity of the thermosetting resin is low. Generally, when manufacturing a product using a thermosetting resin, it can be cured at a relatively high temperature from the viewpoint of improving productivity. However, in this application, since the curing reaction proceeds and the viscosity increases before the thermosetting resin sufficiently penetrates into the gaps, curing at a high temperature has been impossible.

[0004] On the other hand, Patent Document 1 discloses a sealing method for resin-sealing a core wire connection portion formed by electrically connecting a plurality of core wires exposed from a plurality of coated electric wires, wherein the core wire connection portion is immersed in a thermosetting resin, and the thermosetting resin is cured in a temperature range in which the resin viscosity of the thermosetting resin is maintained at 1 Pa·sec or less for at least 1 minute.

[0005] In this sealing method, the core wire connection part is immersed in a thermosetting resin heated in a temperature range where the progress of curing is relatively slow, and cured in that temperature range, so that a relatively long time can be ensured before the viscosity rapidly increases due to curing. Therefore, the thermosetting resin has the characteristic that it can sufficiently penetrate into narrow gaps such as the gaps between core wires at the core wire connection part, the gaps between coated electric wires, and the gaps between the core wire and its coating.

[0006] However, the invention described in Patent Document 1 immerses the core wire connection part in a thermosetting resin heated in a temperature range where the progress of curing is relatively slow, and cures it in that temperature range, so that a relatively long time can be ensured before the viscosity rapidly increases due to curing. Eventually, it took a long time to cure. Specifically, according to the examples, it took more than 10 minutes for the curing of the curable resin, so there was a problem of poor production efficiency.

[0007] Therefore, in sealing the core wire connection part using a thermosetting resin, in order to improve production efficiency, it was not known to adopt curing at a high temperature and the means to perfect the sealing in this case.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The problem to be solved by the present invention is to provide a sealing composition and a sealing method for a coated electric wire that are excellent in sealing performance even under conditions such as cold and heat cycles and high temperature and high humidity. The sealing composition can be cured in a short time within 10 minutes for the sealing operation of the coated electric wire, and the production efficiency of the operation can be improved.

Means for Solving the Problems

[0010] Means for solving the above problems include the following aspects. <1> A composition for coating wire seal for sealing a wire connection portion formed by electrically connecting a plurality of core wires exposed from a plurality of coated wires, having a curing time at 130 ° C of 10 minutes or less, and when the composition for coating wire seal filled in a resin cap is vertically immersed in a portion where the core wire including the core wire connection portion is exposed and a boundary portion between the coated portion and the exposed portion of the core wire and heat-cured, it penetrates to a height of 5 mm or more inside the coated wire at the time of curing. A composition for coating wire seal characterized by the above. <2> The composition for coating wire seal according to <1>, characterized in that the curing time at 130 ° C is 4 minutes or less. <3> The composition for coating wire seal according to <1> or <2>, comprising an epoxy component and a curing component. <4> The composition for coating wire seal according to <3>, wherein the epoxy component is mainly composed of an epoxy resin having 4 or less epoxy groups per molecule. <5> The composition for coating wire seal according to <3> or <4>, wherein the epoxy component is mainly composed of bisphenol A type epoxy resin and / or bisphenol F type epoxy resin. <6> The composition for coating wire seal according to <3>, characterized in that the curing component is an amine compound or a mercapto compound. <7> The composition for coating wire seal according to any one of <3> to <6>, further containing a reactive diluent. <8> The composition for coating wire seal according to any one of <3> to <7>, further containing a coupling agent. <9> A step of filling the resin cap with the composition for coating wire seal according to any one of <1> to <8>; a step of immersing a portion where the core wire including the core wire connection portion is exposed and a boundary portion between the coated portion and the exposed portion in the composition for coating wire seal; a step of heating the resin cap and curing the composition for coating wire seal; A method for sealing a coated wire including the above steps. A wire coated with a cured product of the composition for coating wire seal according to any one of <10> <1> to <8>.

Advantages of the Invention

[0011] According to the composition for coating wire seal and the sealing method of the present invention, the sealing property of the coated wire can be maintained even under conditions such as cold and heat cycles and high temperature and high humidity, and it can be cured within 10 minutes, so it is excellent in productivity.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0013] The present invention will be specifically described below.

[0014] The sealing method of the present invention is a method of sealing a core wire connection portion formed by electrically connecting a plurality of core wires exposed from a plurality of coated wires with a composition for sealing, wherein the core wire connection portion is immersed in the composition for sealing and can be cured by heating at 130°C within 10 minutes.

[0015] The sealing composition of the present invention has a curing time of 10 minutes or less at 130°C. When the coating wire sealing composition filled in the resin cap is vertically immersed in the exposed portion of the core wire including the core wire connection portion and the boundary portion between the coated portion and the exposed portion of the core wire and heat-cured, it penetrates into the interior of the coated wire, that is, between the coating and the core wire, to a height of 5 mm or more at the boundary portion between the coated portion and the exposed portion during curing, and thereby exhibits the effects of the present invention. Here, the boundary portion between the coated portion and the exposed portion is substantially parallel to the sealing composition as shown in FIGS. 1 and 2. Note that the sealing composition of the present invention does not necessarily have to be cured at 130°C, and it may be cured at a temperature lower than this.

[0016] As the coating wire sealing composition of the present invention, if the curing time at 130°C is 7 minutes or less, it is more preferably highly productive, and more preferably 4 minutes or less. Here, curing refers to the state in which the evaluation of heat curability shown in the examples is ○, and the curing time is the shortest time until the composition in a liquid state at room temperature is heated and cured according to the procedure of the examples.

[0017] The core wire connection portion in which a plurality of core wires exposed from a plurality of coated wires used in the present invention are electrically connected is formed by electrically connecting a plurality of core wires exposed at the end portions of the plurality of coated wires by methods such as bonding, welding, caulking, etc., as shown in FIG. 1, and those known in the art are used without particular limitation. Here, in FIG. 1, 1 represents a coated wire, 2 represents an exposed portion of the core wire, and 3 represents a connection portion (bonding portion) where a plurality of core wires are electrically connected.

[0018] As the coating wire sealing composition of the present invention, a so-called two-component type thermosetting epoxy resin composed of an epoxy component and a curing component is preferable because cracks and the like are less likely to occur in the sealed portion after curing.

[0019] The epoxy component in the coating wire sealing composition of the present invention preferably contains, as a main component, an epoxy resin having 4 or less epoxy groups per molecule. When the number of epoxy groups exceeds 4, the crosslinking density with the curing component increases extremely rapidly within a short time. When the core wire connection part is vertically immersed in the coating electric wire sealing composition of the present invention, the composition will not penetrate into the interior of the coating electric wire to a height of 5 mm or more, and as a result, there is a risk that the effects of the present invention cannot be obtained. Here, the main component refers to occupying 50% by mass or more of all epoxy components, and more preferably 80% by mass or more.

[0020] Examples of the epoxy component in the coating electric wire sealing composition of the present invention include glycidyl ether-based epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, 1,4-cyclohexanedimethanol diglycidyl ether, and o-phthalate diglycidyl ether, and glycidyl ester-based epoxy resins such as tetrahydrophthalic acid diglycidyl ester and hexahydrophthalic acid diglycidyl ester. However, since the effect of improving the adhesion to the core wire and the coating material of the coating electric wire is great, those mainly composed of bisphenol A type epoxy resin and / or bisphenol F type epoxy resin are preferred.

[0021] The bisphenol A type epoxy resin is preferably liquid at room temperature (25 °C), its viscosity is preferably 40 Pa·s or less, and more preferably 25 Pa·s or less. Also, the epoxy equivalent of the bisphenol A type epoxy resin is preferably 225 or less. On the other hand, the bisphenol F type epoxy resin is also preferably liquid at room temperature (25 °C), its viscosity is preferably 15 Pa·s or less, and more preferably 5 Pa·s or less. Also, the epoxy equivalent of the bisphenol F type epoxy resin is preferably 190 or less.

[0022] The curing component in the coating electric wire sealing composition of the present invention is preferably an amine-based compound or a mercapto-based compound. By using these compounds, it becomes easier to obtain the effect that the formulation cures within 10 minutes under heating conditions of 130°C. Examples of the amine compound include linear aliphatic polyamines, cycloaliphatic polyamines, aromatic polyamines, modified amines, and polyaminoamides (polyamide resins). From the reasons of good compatibility with epoxy resins and excellent safety, modified amines obtained from aliphatic polyamines and polyamide resins are preferred. These compounds are preferably of a type that uniformly disperses or dissolves in the epoxy component. The compounding amount of these compounds is preferably 0.5 to 1.5 moles of the amino group or mercapto group contained in these compounds with respect to 1 mole of the epoxy group contained in the epoxy component.

[0023] In the composition for coating wire seal of the present invention, it is preferably further contained with a reactive diluent in addition to the epoxy resin and the curing component. The reactive diluent is one that reduces the viscosity without impairing the properties of the epoxy resin. For the composition for coating wire seal of the present invention, it reduces the viscosity thereof and has an effect of improving the penetrability when the core wire connection part is immersed in the composition for coating wire seal. Examples of the reactive diluent include alkyl monoglycidyl ether, alkyl diglycidyl ether, etc. The reactive diluent is preferably of a type that is uniformly mixed or dissolved with the epoxy resin.

[0024] In the composition for coating wire seal of the present invention, it is preferably further contained with a coupling agent. The coupling agent may be, for example, a silane coupling agent having one or more alkoxysilyl groups in one molecule. Examples of the silane coupling agent include alkylalkoxysilanes, aminoalkoxysilanes, epoxyalkoxysilanes, vinylalkoxysilanes, and alkoxysilyl group-containing (meth)acrylates. The coupling agent has an effect of improving the adhesion to the core wire and the coating material of the coated wire. The coupling agent is preferably of a type that is uniformly mixed with or dissolved in the epoxy component. The coupling agent is preferably blended in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of the epoxy component.

[0025] As a method for sealing a coated electric wire using the composition for coating electric wire seal of the present invention, various methods can be mentioned, but a method including the following steps is preferable for reasons of ensuring water stoppage and insulation properties. (1) A step of filling the composition for coating electric wire seal into a resin cap (2) A step of immersing a portion where the core wire including the core wire connection portion is exposed and a boundary portion between the coated portion and the exposed portion of the core wire in the composition for coating electric wire seal (3) A step of heating the resin cap to cure the composition for coating electric wire seal

[0026] Examples of the resin cap used in this step include a resin cap made of a vinyl chloride resin and a heat-shrinkable cap made of a polyolefin resin or the like. The composition for coating electric wire seal is filled into the resin cap using a dispenser or the like. The filling amount needs to be an amount that sufficiently immerses the entire portion where the core wire including the core wire connection portion is exposed and the boundary portion between the coated portion and the exposed portion of the core wire. Next, the cap filled with the composition for coating electric wire seal is immersed so that the entire portion where the core wire including the core wire connection portion is exposed and the boundary portion between the coated portion and the exposed portion of the core wire are covered with the composition. The resin cap has a function of protecting the connection portion of the coated electric wire. By putting the composition for coating electric wire seal into the resin cap and immersing the entire portion where the core wire including the core wire connection portion is exposed and the boundary portion between the coated portion and the exposed portion of the core wire, and curing the composition for coating electric wire seal, a protective cap can be attached to the connection portion of the coated electric wire.

[0027] Next, the resin cap is heated to cure the composition for coating electric wire seal. Examples of the heating means include a heater, infrared rays, a laser, microwaves, dielectric heating, etc. Among these, a heater using a heating element is preferred because the device is simple, and it is more preferable to use a block heater (registered trademark) adapted to the shape of the resin cap. In the present invention, the heating temperature was measured by putting a test tube containing oil into a block heater and inserting a thermocouple into the oil.

[0028] Note that heating can also be performed after immersing the portion where the core wire including the core wire connection portion is exposed and the boundary portion between the coated portion and the exposed portion of the core wire in the coating wire sealing composition filled in the resin cap. However, in order to shorten the curing time, it is preferable to pre-heat the resin cap. The portion where the core wire including the core wire connection portion is exposed and the boundary portion between the coated portion and the exposed portion of the core wire are preferably immersed in a direction substantially perpendicular to the liquid level of the coating wire sealing composition in the resin cap. Although it is possible to provide an inclination during immersion, it is more preferable to be perpendicular in order for the coating wire sealing composition to penetrate to a uniform height inside a plurality of coated wires. The angle at which the coated wire is immersed with respect to the liquid level of the coating wire sealing composition is preferably in the range of 85 to 95°, and within this range, it can be regarded as perpendicular.

[0029] The coating wire sealing composition of the present invention satisfies the following conditions: (1) it cures within 10 minutes at 130°C, and (2) when the coating wire sealing composition filled in the resin cap is heated and cured by immersing the portion where the core wire including the core wire connection portion is exposed and the boundary portion between the coated portion and the exposed portion of the core wire vertically therein, the composition penetrates to a height of 5 mm or more inside the coated wire during curing. If only the condition of (2) is satisfied, the viscosity of the composition for coating wire seal may be lowered and the heating temperature may be suppressed, but the workability was poor. On the other hand, as the composition cures by heating, its viscosity rapidly increases, and since the rate of increase depends on temperature, at high temperatures the time until complete curing is too short to penetrate into narrow gaps such as the gap between the core wires, the gap between the coated wires, and the gap between the core wire and its coating at the core wire connection part, and it has been considered that an incomplete coating is formed. Therefore, the conditions for forming a complete coating at a curing temperature as high as 130 °C have not been considered. Also, since the resin cap undergoes thermal deformation at temperatures exceeding 130 °C, 130 °C is preferable.

[0030] The coated wire with the core wire connection part thus sealed has high airtightness and is preferably used for automotive wire harnesses, overhead power transmission products, OA equipment, etc. used in harsh environments.

Examples

[0031] The present invention will be described more specifically by the following examples. Note that the present invention is not limited to the examples at all.

[0032] (Example 1) To 100 parts by mass of bisphenol A type epoxy resin, 40 parts by mass of modified aliphatic polyamine as a curing component and 1 part by mass of 3-aminopropyltriethoxysilane as a coupling agent were blended to prepare a composition for coating wire sealability. Next, as shown in Fig. 1, 0.7 g of the composition was injected into a polyvinyl chloride cap with a diameter of 12 mm. The cap was placed in a heat block with an opening diameter of 13 mm Φ that conforms to its shape. On the other hand, the coating at the end of a wire in which a core wire with a total diameter of 1.5 mm was coated with a 0.3 mm thick vinyl chloride resin was peeled off, and 5 ends of the wire were bonded together (hereinafter referred to as "wire A") was prepared. Next, as shown in FIG. 2, the tip portion of 3.5 cm of wire A (the exposed portion of the core wire including the core wire connection portion and the boundary portion between the covering portion and the exposed portion of the core wire) was immersed in the covering wire sealing composition in the polyvinyl chloride cap, heated at 130° C. for 5 minutes through the heat block, and then cooled at room temperature for 1 hour, which was used as a sample for the penetration length and sealing property test.

[0033] Similarly, the tip portion of wire A was immersed in the composition for covering wire sealing in the polyvinyl chloride cap, and the heat curability was confirmed at the time of heating at 130° C. for 4 minutes and 7 minutes through the heat block, and it was described in Table 1. In the table, ○, Δ, and × indicate the following meanings. ○: When lifting the wire in the cap, the position of the wire does not shift and the cap comes off the heat block together. Δ: When lifting the wire in the cap, the wire comes off the heat block together with the cap while the position of the wire shifts. ×: When lifting the wire in the cap, the wire comes out of the cap.

[0034] Regarding the sample for the penetration length and sealing property test, the penetration length was measured by the following method and described in Table 1. (Penetration length) Peel off the polyvinyl chloride covering of the wire after the sealing treatment, unwind the core wire, and measure the length penetrated by the sealing composition.

[0035] Regarding the sample, the sealing property was evaluated by the following evaluation method, and the results were described in Table 1. (Initial sealing property evaluation) From the side where the covered wire is not sealed, compressed air of 0.5 kg / cm 2 was sent, and the tip of the sealed covered wire was dipped in water to check for air leakage. In the table, ○ and × indicate the following meanings. ○: No air leakage ×: Air leakage exists

[0036] (Sealing property evaluation after the durability test) (1) Heat resistance test The coated electric wire after sealing treatment was left in a 120°C environment for 100 hours, and then the presence or absence of air leakage was examined in the same manner as the initial sealing property evaluation. (2) Damp heat resistance test The coated electric wire after sealing treatment was left in an 80°C × 95% RH environment for 100 hours, and then the presence or absence of air leakage was examined in the same manner as the initial sealing property evaluation. (3) Thermal shock test The coated electric wire after sealing treatment was subjected to 100 cycles of a temperature cycle of -40°C × 30 minutes to 120°C × 30 minutes, and then the presence or absence of air leakage was examined in the same manner as the initial sealing property evaluation.

[0037] (Example 2) Except that the type of electric wire was changed to an electric wire (Wire B) in which the coating at the end of an electric wire with a core wire having a total diameter of 2.5 mm coated with a 0.3 mm thick vinyl chloride resin was peeled off and two were bonded together, a coated electric wire with the end of the coated electric wire sealed in the same manner as in Example 1 was produced, and various tests were conducted. The results are shown in Table 1.

[0038] (Examples 3 to 10, Comparative Examples 1 and 2) Except that the composition of the composition for sealing the coated electric wire was changed to the composition shown in Table 1, a coated electric wire with the end of the coated electric wire sealed in the same manner as in Example 2 was produced, and various tests were conducted. The results are shown in Table 1.

[0039]

Table 1

[0040] As is clear from Table 1, in the composition for sealing the coated electric wire in Examples 1 to 10, the curing time at 130°C was 7 minutes or less, and in the process of vertically immersing and heat-curing the part where the core wire including the core wire connection part was exposed and the boundary part between the coated part and the exposed part of the core wire in the composition for sealing the coated electric wire filled in the resin cap, it penetrated to a height of 5 mm or more inside the coated electric wire at the time of curing, and the sealing property in the initial and durability tests was good.

[0041] The composition of Comparative Example 1 uses an acid anhydride as the curing component, and since its curability is slower than that of amine-based or mercapto-based ones, the curing time at 130 °C exceeds 7 minutes, resulting in poor initial sealing performance. On the other hand, for the composition of Comparative Example 2, as the epoxy component, a material having about 6 epoxy groups per molecule is used. Therefore, the curing is too fast and the resin does not penetrate into the coated wire interior, resulting in poor initial sealing performance.

Explanation of Signs

[0042] 1 Coated wire 2 Portion where the core wire is exposed 3 Bonding processed portion where a plurality of core wires are electrically connected 4 Resin cap 5 Composition for coating wire sealing 6 Block heater

Claims

1. A composition for coating wire seal for sealing a core wire connection part formed by electrically connecting a plurality of core wires exposed from a plurality of coated wires, wherein the curing time at 130 ° C is 10 minutes or less, and the liquid composition for coating wire seal filled in a resin cap, the portion where the core wire including the core wire connection part is exposed and the boundary part between the coated part and the exposed part of the core wire are immersed vertically with respect to the liquid surface, and when the composition for coating wire seal is heated to 130 ° C and cured, it penetrates to a height of 5 mm or more from the boundary part between the coated part and the exposed part of the coated wire into the coated part at the curing time. A composition for coating wire seal, characterized by the above.

2. The composition for coating wire seal according to claim 1, wherein the curing time at 130 ° C is 4 minutes or less.

3. The composition for coating wire seal according to claim 1 or 2, comprising an epoxy component and a curing component.

4. The composition for coating wire seal according to claim 3, wherein the epoxy component is mainly composed of an epoxy resin having 4 or less epoxy groups per molecule.

5. The composition for coating wire seal according to claim 3 or 4, wherein the epoxy component is mainly composed of bisphenol A type epoxy resin and / or bisphenol F type epoxy resin.

6. The composition for coating wire seal according to claim 3, wherein the curing component is an amine compound or a mercapto compound.

7. The composition for coating wire seal according to any one of claims 3 to 6, further containing a reactive diluent.

8. The composition for coating wire seal according to any one of claims 3 to 7, further containing a coupling agent.

9. A method for sealing a coated wire, comprising the steps of: filling a resin cap with the composition for coating wire seal according to any one of claims 1 to 8; immersing the portion where the core wire including the core wire connection part is exposed and the boundary part between the coated part and the exposed part of the core wire in the composition for coating wire seal; heating the resin cap to cure the composition for coating wire seal.

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