A nano-conductive liquid based on environmentally friendly water-based adhesive and its preparation method

Abstract

This invention relates to the field of semiconductive materials for cables, and discloses a nano-conductive liquid based on an environmentally friendly water-based adhesive and its preparation method. The nano-conductive liquid comprises a water-based polyurethane-acrylate composite emulsion containing glycidyl methacrylate structural units, aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes, a polymer dispersant, additives, and water; wherein the aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes are the sole nano-conductive filler, and the epoxy functional groups in the composite emulsion pair with the amino functional groups on the surface of the grafted carbon nanotubes. This invention can improve the dispersion stability of conductive fillers in aqueous systems, enhance the interfacial bonding between the conductive layer and the fiber substrate, and improve the adhesion, dust resistance, bending resistance, and conductivity stability after thermal aging of the semiconductive tape, making it suitable for preparing semiconductive tapes for cables.

Description

Technical Field

[0001] This invention belongs to the technical field of semiconductive materials for cables, specifically relating to a nano-conductive liquid based on environmentally friendly water-based adhesive and its preparation method. Background Technology

[0002] In existing technologies, semi-conductive wrapping tapes for cables are typically obtained by applying a conductive liquid to the surface of a fiber substrate and then drying it to form a semi-conductive layer. The focus of disclosures on this type of technology is mostly concentrated on the dispersion of conductive fillers and colloidal film formation. CN102385951A discloses a conductive liquid for high-performance nano-semi-conductive wrapping tapes, which is composed of halogen-free nano-sized conductive hollow carbon nanotubes, acrylic emulsion, dispersant, leveling agent, and water. The halogen-free nano-sized conductive hollow carbon nanotubes account for 20-30%, the acrylic emulsion for 10-20%, the dispersant for 3-5%, the leveling agent for 3-5%, and the water for 40-50%. The disclosure also specifies a spraying amount of 90-120 g / m³. 2 And a layering process at 150-180℃. CN105625034A further applies the impregnation route of nano-hollow carbon nanotubes, acrylic emulsion, leveling agent, dispersant, and water to the semi-conductive nonwoven fabric scenario, and provides tensile strength > 50 N / cm, surface resistivity < 500 Ω, and volume resistivity < 1 × 10⁻⁶. 4 The performance anchor point is Ω·cm.

[0003] However, the aforementioned disclosures primarily address how to fabricate usable semiconductive tapes. They lack detailed designs focusing on functional group reaction pairing and interfacial bridging to address issues such as the interfacial adhesion mechanism of fiber substrates, resistance retention after repeated bending, resistance drift after thermal aging, and the amount of conductive powder detachment. Particularly on fiber substrates such as nylon, polyester, and nonwoven tapes, a single acrylic adhesive phase is more prone to problems such as insufficient conductive layer adhesion, localized crack propagation after bending, powder detachment, and instability of the conductive network after thermal aging.

[0004] On the other hand, several unit technologies have been disclosed in adjacent technical fields. CN104974313A discloses the introduction of glycidyl methacrylate chemical bonds into waterborne polyurethane, so that the resulting system retains epoxy functional groups that can react with amines; CN101906192A discloses a method for preparing waterborne polyurethane-acrylate composite emulsions without the addition of external emulsifiers, the resulting composite emulsion having a solid content higher than 45% and high storage stability; CN107398188A discloses a route for multi-walled carbon nanotubes to be carboxylated and acylchlorinated with mixed acids, and then grafted with amino-containing organosilanes; CN104119728A discloses the idea of ​​introducing waterborne polyurethane, waterborne acrylic resin and epoxy silane coupling agent into a waterborne conductive system.

[0005] Therefore, it is still necessary to provide a water-based nano-conductive liquid technology solution that does not stop at replacing conductive fillers or adhesives, but rather improves adhesion, dust resistance, bending resistance and conductivity stability after thermal aging in an environmentally friendly water-based system through the synergistic pairing between the functionalization of the conductive filler surface and the built-in reactive functional groups in the colloidal phase. Summary of the Invention

[0006] The purpose of this invention is to provide a nano-conductive liquid based on environmentally friendly water-based adhesive and its preparation method, which solves the technical problem in the prior art of simultaneously improving adhesion, anti-dust properties, bending resistance and conductivity stability after thermal aging in an environmentally friendly water-based system through the synergistic pairing between the functionalization of the conductive filler surface and the built-in reactive functional groups in the adhesive phase.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a nano-conductive liquid based on an environmentally friendly water-based adhesive. The water-based nano-conductive liquid comprises, by weight, 20-35 wt% of a water-based polyurethane-acrylate composite emulsion containing glycidyl methacrylate structural units, 5-10 wt% of aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes, 0.3-1.5 wt% of a polymer dispersant, 0-1.5 wt% of additives, and the balance being water. The aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes are the only conductive filler in the aqueous nano-conductive liquid. The waterborne polyurethane-acrylate composite emulsion contains epoxy functional groups derived from glycidyl methacrylate in its resin solids, and the epoxy value of the resin solids is 0.15-0.50 mmol / g. The surface of the aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes contains amino functional groups that can pair with the epoxy functional groups, and the amino value is 0.08-0.30 mmol / g. Based on the epoxy value of the resin solid and the amino value of the grafted multi-walled carbon nanotubes, the molar ratio of the epoxy functional group to the amino functional group is 1.0:1-4.0:1.

[0008] The molar ratio of epoxy functional groups to amino functional groups is determined as follows: the number of epoxy functional groups is the product of the solid resin mass and the epoxy value of the solid resin in the waterborne polyurethane-acrylate composite emulsion; the number of amino functional groups is the product of the mass of aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes and their amino value; the epoxy value of the solid resin is determined by the hydrochloric acid-acetone method, and the amino value is determined by a non-aqueous titration method.

[0009] Furthermore, the aminoalkoxysilane is an aminoalkoxysilane containing at least two nitrogen-containing active sites in its molecule, specifically N-(2-aminoethyl)-3-aminopropyltrimethoxysilane or N-(2-aminoethyl)-3-aminopropyltriethoxysilane.

[0010] Furthermore, the aminoalkoxysilane grafted with carboxylated multi-walled carbon nanotubes is obtained by acylation of the carboxylated multi-walled carbon nanotubes and then reacting them with the aminoalkoxysilane. The surface of the grafted multi-walled carbon nanotubes retains free amino functional groups that can be measured by non-aqueous titration.

[0011] Furthermore, the waterborne polyurethane-acrylate composite emulsion is obtained by polymerizing a waterborne polyurethane dispersion with an acrylate monomer containing glycidyl methacrylate.

[0012] Furthermore, the nano-conductive liquid does not contain graphene, graphene oxide, conductive carbon black, or acetylene black; the additives include one or more of wetting agents, defoamers, leveling agents, and pH adjusters.

[0013] This invention also provides a method for preparing the above-mentioned nano-conductive liquid based on environmentally friendly water-based adhesive, comprising the following steps: (1) Multi-walled carbon nanotubes are oxidized to obtain carboxylated multi-walled carbon nanotubes; (2) The carboxylated multi-walled carbon nanotubes are grafted with aminoalkoxysilane to obtain aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes. (3) Prepare an aqueous polyurethane-acrylate composite emulsion containing glycidyl methacrylate structural units; (4) The aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes, polymer dispersant and water were pre-dispersed to obtain a pre-dispersed solution; (5) Add the waterborne polyurethane-acrylate composite emulsion to the pre-dispersion liquid, and add the additives and the balance water; by controlling the amount of resin solids added to the composite emulsion and the amount of grafted multi-walled carbon nanotubes added, the molar ratio of the epoxy functional group to the amino functional group is 1.0:1-4.0:1, and the waterborne nano-conductive liquid is obtained.

[0014] Furthermore, the oxidation treatment in step (1) is a mixed acid oxidation treatment, wherein the mixed acid is composed of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 2:1-4:1, the oxidation temperature is 80-110℃, and the reaction time is 4-8h.

[0015] Furthermore, in step (2), the carboxylated multi-walled carbon nanotubes are first subjected to acylation treatment using a thionyl chloride / dimethylformamide system, and then grafted with the aminoalkoxysilane in an organic solvent; the pre-dispersion in step (4) includes high-speed shear dispersion and / or ultrasonic dispersion; the waterborne polyurethane-acrylate composite emulsion in step (5) is added after the pre-dispersion.

[0016] The present invention also provides the application of the above-mentioned nano-conductive liquid in the preparation of semi-conductive wrapping tape for cables. The nano-conductive liquid is applied to the surface of a fiber substrate and dried to obtain a semi-conductive wrapping tape for cables. The fiber substrate is a nylon tape, a polyester tape, or a non-woven tape.

[0017] Furthermore, the nano-conductive liquid is applied to the surface of the fiber substrate by means of impregnation, spraying or scraping; the fiber substrate is subjected to corona treatment or plasma treatment before the nano-conductive liquid is applied; the drying temperature is 130-160℃ and the drying time is 1-5min.

[0018] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: (1) In this invention, aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes are used as the sole nano-conductive filler, so that the surface of the multi-walled carbon nanotubes simultaneously has amino functional groups and alkoxysilane groups. Compared with ungrafted carboxylated multi-walled carbon nanotubes, this grafting structure can improve the dispersion stability of multi-walled carbon nanotubes in aqueous systems, reduce the agglomeration of conductive fillers, and enhance the interfacial bonding between conductive fillers and aqueous colloidal phases and fiber substrates, thereby improving the adhesion and anti-dust properties of the conductive layer.

[0019] (2) This invention uses an aqueous polyurethane-acrylate composite emulsion containing glycidyl methacrylate structural units as an environmentally friendly aqueous colloidal phase, which retains epoxy functional groups that can react with amino groups in the colloidal phase. These epoxy functional groups can form hydrogen bonds, dipole interactions, or interfacial entanglements with nitrogen-containing polar groups on the surface of grafted multi-walled carbon nanotubes, silane structures, and polar segments in the colloidal phase, thereby forming a more stable bonding network between the conductive filler and the colloidal phase. Compared with the WPUA system without GMA structural units, the conductive layer obtained by this invention has better film integrity, bending resistance, and conductivity stability after thermal aging.

[0020] (3) This invention controls the ratio between epoxy functional groups and amino functional groups to enable synergistic pairing of functional groups between grafted multi-walled carbon nanotubes and WPUA composite emulsion containing GMA structural units. This design differs from the existing technology that relies solely on conductive filler dispersion and ordinary adhesive film formation. It can improve the structural stability of the conductive network during bending, wrapping, and thermal aging while maintaining the water-based environmentally friendly system, and reduce cracking, debonding, and pulverization of the conductive layer.

[0021] (4) The nano-conductive liquid of the present invention is applicable to various fiber substrates for cables, such as nylon tape, polyester tape, and non-woven tape. By impregnation, spraying, or scraping followed by drying, a continuous and stable semi-conductive layer can be formed on the surface of the fiber substrate. Furthermore, when the fiber substrate is subjected to corona treatment or plasma treatment before coating, the wetting and interfacial bonding of the aqueous conductive liquid to the substrate can be improved, thereby further improving the adhesion and durability of the conductive layer. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the preparation method of the nano-conductive liquid of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The original multi-walled carbon nanotubes used in this invention have an outer diameter of 10-15 nm, a length of 5-8 μm, and a purity of approximately 96%. The N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropyltriethoxysilane used are commercially available industrial products. The polymer dispersant used is a polyurethane-type polymeric dispersant. The wetting agent used is a polyether-modified siloxane wetting agent. The defoamer used is a mineral oil-type defoamer.

[0026] In this invention, the aminoalkoxysilane is preferably an aminoalkoxysilane containing at least two nitrogen-containing active sites in its molecule, including N-(2-aminoethyl)-3-aminopropyltrimethoxysilane or N-(2-aminoethyl)-3-aminopropyltriethoxysilane. After the carboxylated multi-walled carbon nanotubes treated with acyl chloride react with the aminoalkoxysilane, some of the nitrogen-containing active sites form amide linkages with the acyl chloride groups on the surface of the carbon nanotubes, while the other part of the nitrogen-containing active sites are retained as amino functional groups that can undergo ring-opening reactions or strong interactions with epoxy functional groups. Thus, the surface of the grafted multi-walled carbon nanotubes simultaneously possesses a silane structure and an amino functional group that can pair with epoxy functional groups.

[0027] Example 1 See Figure 1 As shown in the figure, this embodiment provides several methods for preparing grafted multi-walled carbon nanotubes, as detailed below: (1) Preparation of grafted multi-walled carbon nanotubes A 100g of raw multi-walled carbon nanotubes were added to a mixed acid consisting of 1500mL concentrated sulfuric acid and 500mL concentrated nitric acid, and reacted at 95℃ for 6h. After the reaction, the mixture was filtered and repeatedly washed with deionized water until the pH of the filtrate was 6.5-7.0, and then vacuum dried at 80℃ for 12h to obtain carboxylated multi-walled carbon nanotubes. The carboxyl content was determined to be 2.1wt% by potentiometric titration. Take 60g of the above carboxylated multi-walled carbon nanotubes, add 600mL of thionyl chloride and 6mL of dimethylformamide, and react at 75℃ for 12h for acylation treatment; after removing excess thionyl chloride under reduced pressure, wash the resulting solid once with anhydrous toluene, then disperse it in 800mL of anhydrous toluene, add 18g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and react at 95℃ for 12h under nitrogen protection; after the reaction, wash with toluene and anhydrous ethanol successively, and dry under vacuum at 60℃ for 10h to obtain grafted multi-walled carbon nanotube A; characterization shows that the amino value of the grafted multi-walled carbon nanotube A is 0.16mmol / g and the silicon content is 0.62wt%.

[0028] (2) Preparation of grafted multi-walled carbon nanotubes B The grafting process was carried out using the same method as for grafted multi-walled carbon nanotubes A, but the amount of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane added was adjusted from 18g to 20g, and the grafting reaction time was adjusted from 12h to 14h to obtain grafted multi-walled carbon nanotubes B. Characterization showed that the amino value of grafted multi-walled carbon nanotubes B was 0.18mmol / g, and the silicon content was 0.68wt%.

[0029] (3) Preparation of grafted multi-walled carbon nanotubes C The grafting was carried out using the same method as grafted multi-walled carbon nanotubes A, but N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was replaced with 16g of N-(2-aminoethyl)-3-aminopropyltriethoxysilane. The grafting reaction temperature was 90℃ and the grafting reaction time was 10h to obtain grafted multi-walled carbon nanotubes C. Characterization showed that the amino value of grafted multi-walled carbon nanotubes C was 0.14mmol / g and the silicon content was 0.56wt%.

[0030] Example 2 See Figure 1 As shown in the figure, this embodiment provides several methods for preparing WPUA composite emulsions containing GMA structural units, as detailed below: (1) Preparation of WPUA composite emulsion A 120g of polycarbonate diol and 18g of polytetrahydrofuran ether diol were added to a reactor and dehydrated under vacuum at 110℃ for 1h. After cooling to 80℃, 35g of isophorone diisocyanate and 0.06g of dibutyltin dilaurate were added, and the mixture was stirred for 3.5h. Then, 7.0g of dimethylolbutyric acid was added, and the reaction was continued for 2h. Next, 4.0g of hydroxyethyl methacrylate was added, and the reaction was carried out for 1h to obtain a polyurethane prepolymer with double bonds at the end groups. After cooling to 60℃, 5.1g of triethylamine was added for neutralization for 20min, and then 285g of deionized water was added for self-emulsification. The stirring speed was 400r / min, and the emulsification time was 20min. Subsequently, 2.6g of ethylenediamine was dissolved in 20g of deionized water and slowly added to the reactor, and the chain extension was carried out for 30min to obtain an aqueous polyurethane dispersion. Separately, 24g of butyl acrylate, 14g of methyl methacrylate, and 8g of glycidyl methacrylate were mixed, and 0.65g of ammonium persulfate and 20g of deionized water were added to prepare a monomer / initiator mixture system. This mixture system was added dropwise to the above-mentioned aqueous polyurethane dispersion at 79-86℃ over 3 hours. After the addition was complete, the mixture was kept at this temperature for another 3 hours, cooled, and discharged to obtain WPUA composite emulsion A. The solid content of emulsion A was determined to be 42.3wt%, and the epoxy value of the resin solids was 0.29mmol / g.

[0031] (2) Preparation of WPUA composite emulsion B The same method was used for WPUA composite emulsion A, but the amount of glycidyl methacrylate was increased from 8g to 10g, while the amount of methyl methacrylate was reduced from 14g to 12g to obtain WPUA composite emulsion B. The solid content was determined to be 43.1wt%, and the resin solid epoxy value was 0.36mmol / g.

[0032] (3) Preparation of WPUA composite emulsion C The same method was used for WPUA composite emulsion A, but glycidyl methacrylate was replaced with an equal mass of methyl methacrylate to obtain WPUA composite emulsion C without GMA structural units; its solid content was determined to be 42.1 wt%, and the resin solid epoxy value was approximately 0.00 mmol / g.

[0033] Example 3 See Figure 1 As shown, this embodiment combines the grafted multi-walled carbon nanotubes prepared in Example 1 and the WPUA composite emulsion prepared in Example 2 to provide a method for preparing a nano-conductive liquid, and a method for preparing a semi-conductive tape using the nano-conductive liquid, specifically including the following steps: Take 260.0g of WPUA composite emulsion A, 72.0g of grafted multi-walled carbon nanotubes A, 9.0g of polyurethane-type polymeric dispersant, 0.8g of polyether-modified siloxane wetting agent, 0.5g of mineral oil-type defoamer, 0.5g of 25wt% ammonia water, and 657.2g of deionized water.

[0034] First, grafted multi-walled carbon nanotubes (MWCNTs) A, a polymer dispersant, and 400 g of deionized water were added to a dispersion vessel and pre-wetted at 1000 rpm for 5 min. Then, the flow rate was increased to 2000 rpm for 20 min of high-speed shearing. Next, ultrasonic dispersion was performed using a 600 W probe for 30 min, with circulating cooling to ensure the system temperature did not exceed 35°C during dispersion. The remaining deionized water was then added, and the D90 of the conductive phase aggregates formed by the nano-conductive filler was measured to be 5.8 μm. Then, WPUA composite emulsion A was slowly added at 600 rpm below 35°C, and stirring was continued for 15 min after addition. Wetting agent, defoamer, and ammonia were then added to adjust the pH to 7.8. Finally, the mixture was aged for 6 h to obtain the nano-conductive liquid. The viscosity at 25°C was measured to be 950 mPa·s. Calculations showed that the mass ratio of the composite emulsion resin solid to the grafted MWCNTs was 1.53:1, and the molar ratio of epoxy groups to amino groups was approximately 2.75:1.

[0035] A nylon tape with a thickness of approximately 0.16 mm was selected as the substrate. Before coating, a corona treatment machine was used for surface treatment at a power of 1.2 kW and a linear speed of 12 m / min. The surface tension after a single treatment was 43.2 mN / m. The aforementioned nano-conductive liquid was applied to the surface of the nylon tape using a doctor blade, with the dry coating amount controlled at 60 g / m². After pre-drying at 80 °C for 1 min, it was then dried at 145 °C for 3 min to obtain a semi-conductive tape.

[0036] Example 4 See Figure 1 As shown, this embodiment combines the grafted multi-walled carbon nanotubes prepared in Example 1 and the WPUA composite emulsion prepared in Example 2 to provide a method for preparing a nano-conductive liquid, and a method for preparing a semi-conductive tape using the nano-conductive liquid, specifically including the following steps: Take 240.0g of WPUA composite emulsion A, 65.0g of grafted multi-walled carbon nanotubes A, 8.0g of polyurethane-type polymeric dispersant, 0.8g of polyether-modified siloxane wetting agent, 0.4g of mineral oil-type defoamer, 0.4g of 25wt% ammonia water, and 685.4g of deionized water.

[0037] The solution preparation process was the same as in Example 3. The conductive phase aggregate formed by the nano-conductive filler in the obtained nano-conductive liquid had a D90 of 6.1 μm, a pH of 7.7, and a viscosity of 840 mPa·s at 25°C. Calculations showed that the mass ratio of the composite emulsion resin solid to the grafted multi-walled carbon nanotubes was approximately 1.56:1, and the molar ratio of epoxy groups to amino groups was approximately 2.83:1.

[0038] A polyester tape with a thickness of approximately 0.14 mm was selected as the substrate. Before coating, it was treated with atmospheric pressure air plasma at a power of 320 W and a linear speed of 18 m / min, resulting in a surface tension of 44.1 mN / m. The nano-conductive liquid was applied to the surface of the polyester tape using a doctor blade, with a dry coating amount controlled at 55 g / m². After pre-drying at 85 °C for 1 min, it was dried at 150 °C for 2 min to obtain the semi-conductive polyester tape.

[0039] Example 5 See Figure 1 As shown, this embodiment combines the grafted multi-walled carbon nanotubes prepared in Example 1 and the WPUA composite emulsion prepared in Example 2 to provide a method for preparing a nano-conductive liquid, and a method for preparing a semi-conductive tape using the nano-conductive liquid, specifically including the following steps: Take 300.0g of WPUA composite emulsion A, 80.0g of grafted multi-walled carbon nanotubes A, 10.0g of polyurethane-type polymeric dispersant, 1.0g of polyether-modified siloxane wetting agent, 0.5g of mineral oil-type defoamer, 0.6g of 25wt% ammonia water, and 607.9g of deionized water.

[0040] The solution preparation process was the same as in Example 3. The conductive phase aggregate formed by the nano-conductive filler in the obtained nano-conductive liquid had a D90 of 6.6 μm, a pH of 7.9, and a viscosity of 1180 mPa·s at 25°C. Calculations showed that the mass ratio of the composite emulsion resin solid to the grafted multi-walled carbon nanotubes was approximately 1.59:1, and the molar ratio of epoxy groups to amino groups was approximately 2.87:1.

[0041] A nonwoven fabric tape with a thickness of approximately 0.21 mm was selected as the substrate. Before coating, it was treated with a corona generator at a power of 1.0 kW and a linear speed of 10 m / min, resulting in a surface tension of 42.6 mN / m. The nano-conductive liquid was applied to the nonwoven fabric tape using an impregnation-roller-drying method, with a roller linear pressure of 0.25 MPa and a dry coating amount of 70 g / m². After pre-drying at 90°C for 1 min, it was dried at 140°C for 4 min to obtain the semi-conductive nonwoven fabric tape.

[0042] Example 6 See Figure 1As shown, this embodiment combines the grafted multi-walled carbon nanotubes prepared in Example 1 and the WPUA composite emulsion prepared in Example 2 to provide a method for preparing a nano-conductive liquid, and a method for preparing a semi-conductive tape using the nano-conductive liquid, specifically including the following steps: Take 0.0g of WPUA composite emulsion B23, 8.0g of grafted multi-walled carbon nanotubes B5, 8.5g of polyurethane-type polymeric dispersant, 0.8g of polyether-modified siloxane wetting agent, 0.5g of mineral oil-type defoamer, 0.5g of 25wt% ammonia water, and 701.7g of deionized water.

[0043] The solution preparation process was the same as in Example 3. The conductive phase aggregate formed by the nano-conductive filler in the obtained nano-conductive liquid had a D90 of 5.5 μm, a pH of 7.6, and a viscosity of 920 mPa·s at 25°C. Calculations showed that the mass ratio of the composite emulsion resin solid to the grafted multi-walled carbon nanotubes was approximately 1.71:1, and the molar ratio of epoxy groups to amino groups was approximately 3.42:1, which is near the upper limit of the preferred functional group pairing range of this invention.

[0044] Using the same nylon tape as in Example 3 as the substrate, the tape was treated with atmospheric pressure plasma at a power of 280W and a linear speed of 15m / min before coating, resulting in a surface tension of 45.0mN / m. The nano-conductive liquid was applied to the surface of the nylon tape using a doctor blade, with a dry coating amount controlled at 50g / m². After pre-drying at 85℃ for 1min, it was dried at 150℃ for 2min to obtain a semi-conductive tape.

[0045] Example 7 See Figure 1 As shown, this embodiment combines the grafted multi-walled carbon nanotubes prepared in Example 1 and the WPUA composite emulsion prepared in Example 2 to provide a method for preparing a nano-conductive liquid, and a method for preparing a semi-conductive tape using the nano-conductive liquid, specifically including the following steps: Take 250.0g of WPUA composite emulsion A, 70.0g of grafted multi-walled carbon nanotubes C, 8.5g of polyurethane-type polymeric dispersant, 0.8g of polyether-modified siloxane wetting agent, 0.5g of mineral oil-type defoamer, 0.5g of 25wt% ammonia water, and 669.7g of deionized water.

[0046] First, the grafted multi-walled carbon nanotubes C were pre-wetted, subjected to high-speed shearing, and ultrasonically dispersed in the same manner as in Example 3; the D90 of the conductive phase aggregate formed by the nano-conductive filler was measured to be 6.0 μm. Then, WPUA composite emulsion A was added below 35°C, and the pH was adjusted and aged for 6 hours in the same manner as in Example 3 to obtain a nano-conductive liquid. The resulting nano-conductive liquid had a pH of 7.7 and a viscosity of 910 mPa·s at 25°C. Calculations showed that the mass ratio of the composite emulsion resin solid to the grafted multi-walled carbon nanotubes was approximately 1.51:1, and the molar ratio of epoxy groups to amino groups was approximately 3.13:1.

[0047] A polyester tape of the same specifications as in Example 4 was selected as the substrate and corona treated to a surface tension of 43.8 mN / m. The nano-conductive liquid was applied to the surface of the polyester tape by a doctor blade, with the dry coating amount controlled at 58 g / m². After pre-drying at 85°C for 1 min, it was dried at 148°C for 2.5 min to obtain a semi-conductive polyester tape.

[0048] Comparative Example 1 The difference between Comparative Example 1 and Example 3 is that the conductive liquid was changed to a single acrylic emulsion / hollow carbon nanotube route: 250.0 g of hollow carbon nanotubes, 150.0 g of acrylic emulsion, 40.0 g of dispersant, 40.0 g of leveling agent, and 520.0 g of deionized water were taken and stirred at 1500 r / min for 30 min to obtain the conductive liquid, instead of the process of pre-dispersing grafted multi-walled carbon nanotubes and then adding WPUA composite emulsion. The resulting conductive liquid had a pH of 7.4, a viscosity of 1480 mPa·s at 25°C, and a D90 of 14.8 μm. The remaining substrates used the same nylon tape and the same corona pretreatment as in Example 3, but the dry coating amount was adjusted to 100 g / m², and the drying conditions were 160°C × 3 min.

[0049] Comparative Example 2 The only difference between Comparative Example 2 and Example 3 is that the grafted multi-walled carbon nanotubes A in Example 1 are replaced with an equal mass of ungrafted carboxylated multi-walled carbon nanotubes. The remaining amounts of WPUA composite emulsion A, dispersant, wetting agent, defoamer, pH adjustment, substrate, dry coating amount, and drying conditions are the same as in Example 3.

[0050] Comparative Example 3 The only difference between Comparative Example 3 and Example 3 is that the WPUA composite emulsion A in Example 1 is replaced with an equal mass of WPUA composite emulsion C without GMA structural units. The remaining amounts of grafted multi-walled carbon nanotubes A, dispersant, wetting agent, defoamer, pH adjustment, substrate, dry coating amount and drying conditions are the same as in Example 3.

[0051] Comparative Example 4 The only difference between Comparative Example 4 and Example 3 is that: WPUA composite emulsion A was added to the dispersion vessel along with grafted multi-walled carbon nanotubes A, polymer dispersant and water at the beginning of dispersion; the high-speed shear time, ultrasonic power, ultrasonic time, cooling conditions, additive addition method, pH adjustment method and aging time were the same as in Example 3.

[0052] Comparative Example 5 The only difference between Comparative Example 5 and Example 3 is that the substrate was not subjected to corona treatment, and the nano-conductive liquid obtained in Example 3 was directly applied to the untreated nylon tape; the surface tension of the nylon tape was 35.8 mN / m. The remaining formulation, liquid preparation process, dry coating amount, and drying conditions were the same as in Example 3.

[0053] Performance testing The amino value of grafted multi-walled carbon nanotubes was determined by non-aqueous titration, and the silicon content was determined by X-ray fluorescence method; the epoxy value of WPUA composite emulsion resin solid was determined by hydrochloric acid-acetone method. The D90 of the conductive phase aggregate was determined using a laser particle size analyzer; the viscosity of the nano-conductive liquid at 25°C was determined using a rotational viscometer, and the pH was determined using a calibrated pH meter; the storage stability was determined by measuring the viscosity change rate after being sealed and placed at 25°C for 30 days, and observing whether hard sedimentation occurred. Before the surface resistance test, the sample was placed at 23±2℃ and 50±5% relative humidity for 24 hours; a 50mm wide sample strip was taken, and the surface resistance value of the sample strip was measured using parallel electrodes. The average value of five parallel samples was used as the result; the volume resistivity was obtained after measurement under the same temperature and humidity conditions. For tensile strength testing, a 15mm wide sample bar with a clamping distance of 100mm was stretched at a speed of 300mm / min, and the average value of five parallel samples was taken. During the 180° peel strength test, the coated semiconductive layer was laminated with the standard test tape, and a 25mm wide strip was peeled at 180°. The test speed was 300mm / min, and the average value of five parallel samples was taken and converted to N / cm. During the reciprocating bending test, 1000 reciprocating bends were performed with a bending radius of 10mm, and then the surface resistance was measured. The resistance change rate was calculated as the percentage of the difference between the surface resistance after bending and before bending to the surface resistance before bending. During the thermal aging test, the sample was placed in a forced-air drying oven at 125±2℃ for 168 hours, and the surface resistance was measured after cooling to room temperature. The resistance change rate was calculated as the percentage of the difference between the surface resistance after aging and the surface resistance before aging to the surface resistance before aging. In the powder shedding test, a pre-weighed white cotton cloth was placed over a 100cm² sample surface. The sample was rubbed back and forth 50 times under a 500g load. The shed powder was collected and weighed, and the results were expressed as mg / 100cm². 2This indicates that the average value of three parallel samples is taken.

[0054] The specific performance test data are shown in Tables 1 and 2: Table 1. Characterization and storage stability test results of nano-conductive liquid and key components Table 2. Test results of semiconductive tape performance As shown in Table 1, the D90 of the conductive phase aggregates formed by the nano-conductive fillers in the nano-conductive liquids obtained in Examples 3-7 was all controlled below 6.6 μm, and the viscosity change rate after 30 days of sealed storage at 25°C was no greater than 8.4%, with no visible hard sedimentation. In contrast, the D90 of Comparative Example 1 reached 14.8 μm, Comparative Example 2 reached 11.0 μm, and Comparative Example 4 reached 9.8 μm, and all showed varying degrees of sedimentation. This indicates that the combination of pre-dispersing grafted multi-walled carbon nanotubes and then adding WPUA composite emulsion in this invention not only improves the initial dispersion state but also significantly enhances the storage stability of the aqueous system.

[0055] Furthermore, Example 3 differs from Comparative Example 2 by only one key feature: whether the conductive phase is grafted with aminoalkoxysilane. Under the same conditions of adhesive phase, substrate, dry coating amount, and drying conditions, the D90 of Example 3 decreased from 11.0 μm in Comparative Example 2 to 5.8 μm, the 180° peel strength increased from 1.34 N / cm to 2.18 N / cm, the powder shedding decreased from 4.8 mg / 100 cm² to 1.0 mg / 100 cm², and the resistivity change rate after 1000 bends decreased from 22.1% to 9.6%. This indicates that the first distinguishing feature does not merely bring about a slight improvement in dispersion, but rather significantly improves the conductive phase agglomeration, interfacial adhesion, and anti-powder shedding performance while maintaining a single nano-conductive filler route. The mechanism is that the amino and alkoxysilane structures introduced on the surface of carboxylated multi-walled carbon nanotubes improve the compatibility between the conductive phase and the aqueous colloidal phase, and promote hydrogen bonding / condensation-type interfacial bridging with polar groups on the substrate surface during the drying process, thereby reducing the probability of powder detachment and bending delamination.

[0056] The only key difference between Example 3 and Comparative Example 3 is the second key difference: whether GMA structural units are introduced into the adhesive phase and reactive epoxy functional groups are retained. Both examples share the same conductive phase type, pre-dispersion method, substrate, and drying conditions, and their D90 values ​​are very similar, at 5.8 μm and 6.5 μm respectively. However, Example 3 exhibits a significant difference: its 180° peel strength increases from 1.30 N / cm to 2.18 N / cm, its resistivity change rate after 1000 bends decreases from 24.8% to 9.6%, and its resistivity change rate after 125°C × 168 h of heat aging decreases from 35.2% to 14.2%. This indicates that the second key difference is not primarily reflected in the initial dispersion, but rather in the improved durability after film formation and during service. The effect is not simply a linear improvement from replacing acrylic acid with ordinary WPUA, but rather a more pronounced synergistic enhancement in the presence of a conductive phase containing grafted amino groups. The mechanism is that the epoxy functional groups in the WPUA composite emulsion undergo a ring-opening reaction with the amino groups on the surface of the grafted multi-walled carbon nanotubes to form a more stable flexible covalent network, which not only improves the adhesion strength between the conductive layer and the substrate, but also slows down the damage to the conductive pathways during bending and thermal aging.

[0057] The only third distinguishing feature between Example 3 and Comparative Example 4 is whether the process sequence of pre-dispersing the conductive phase followed by adding the composite emulsion is adopted. The formulations of both are identical, but in Example 3, the D90 decreased from 9.8 μm to 5.8 μm, the 30-day viscosity change rate decreased from 16.7% to 6.3%, the 180° peel strength increased from 1.57 N / cm to 2.18 N / cm, and the resistivity change rate after 125°C × 168 h of heat aging decreased from 22.8% to 14.2%. This indicates that the process sequence is not merely an arbitrarily chosen workshop parameter, but directly affects the microscopic distribution of the conductive phase in the colloidal phase, ultimately influencing interfacial adhesion and long-term stability. The mechanism is as follows: if the conductive phase is directly mixed with the composite emulsion before it has fully depolymerized, the resin coating will inhibit the subsequent effective depolymerization, resulting in larger agglomerates being locked in the colloidal phase; however, the present invention first disperses the grafted multi-walled carbon nanotubes to the target particle size and then introduces them into the WPUA composite emulsion, which can enable the conductive phase to form a more uniform and continuous conductive network in the subsequent film formation.

[0058] Comparative Example 1, using a single acrylic emulsion, hollow carbon nanotubes, dispersant, leveling agent, and water, achieved a surface resistivity still below 500 Ω, but required a higher dry coating weight (100 g / m²). Its 180° peel strength was only 1.04 N / cm, with a resistivity change rate of 39.2% after 1000 bends, a resistivity change rate of 50.8% after 125°C × 168 h of heat aging, and a powder shedding rate of 8.9 mg / 100 cm². In contrast, Example 3 achieved a surface resistivity of 208 Ω, a peel strength of 2.18 N / cm, a 9.6% resistivity change rate after bends, a 14.2% resistivity change rate after heat aging, and a powder shedding rate of 1.0 mg / 100 cm² with a lower dry coating weight. This improvement exceeds what is generally reasonably expected when replacing known materials side-by-side. In other words, the combination of distinguishing features of the present invention does not result in a mild improvement in a single performance point, but rather in a simultaneous improvement in conductivity, adhesion, dust resistance, and durability.

[0059] Furthermore, Example 3 still achieves a tensile strength of 66 N / cm, a surface resistivity of 265 Ω, and a strength of 4.2 × 10⁻⁶ on a nonwoven fabric substrate. 3 The volume resistivity is measured in Ω·cm. This result is not only comparable to, but also surpasses, the nonwoven anchor point data disclosed in CN105625034A. Furthermore, it supplements the 180° peel strength, resistance change rate after bending, resistance change rate after thermal aging, and dust shedding indicators that were not quantified or not fully quantified in the prior art. Therefore, the beneficial effects of this invention are not only reflected in achieving the basic conductivity indicators of existing semi-conductive nonwoven fabrics, but also in further improving interfacial adhesion and long-term stability based on similar conductivity indicators.

[0060] For a further preferred measure of substrate surface treatment, Example 3 and Comparative Example 5 used the same conductive liquid, but Comparative Example 5 did not undergo corona treatment. Its 180° peel strength decreased from 2.18 N / cm to 1.63 N / cm, the powder shedding increased from 1.0 mg / 100 cm² to 2.5 mg / 100 cm², and the rate of change in resistance after 1000 bends increased from 9.6% to 16.5%. This indicates that substrates with a surface tension of 42 mN / m or higher are more conducive to leveraging the interfacial advantages of the conductive liquid of the present invention, and therefore this preferred feature can be used as a further limitation in the application claims.

[0061] In summary, the present invention has the following outstanding beneficial effects: Firstly, the distinguishing feature of aminoalkoxysilane-grafted multi-walled carbon nanotubes compared to ungrafted multi-walled carbon nanotubes is that they result in smaller conductive phase aggregates, higher peel strength, lower powder shedding, and better resistance retention after bending. Secondly, the distinguishing feature is that, compared with the WPUA composite emulsion without GMA structural units, the WPUA composite emulsion containing GMA structural units still significantly improves the peel strength and significantly reduces the resistance drift after bending and thermal aging, even when the conductive phase dispersion state is similar. Third, the characteristic conductive phase is pre-dispersed and the colloidal phase is added later, which, compared to a one-step mixing process, significantly reduces D90 and improves storage stability, adhesion and thermal aging stability under the same formulation.

[0062] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0063] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A nano-conductive liquid based on environmentally friendly water-based adhesive, characterized in that, Based on the total weight of the aqueous nano-conductive liquid, it includes 20-35 wt% of an aqueous polyurethane-acrylate composite emulsion containing glycidyl methacrylate structural units, 5-10 wt% of aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes, 0.3-1.5 wt% of a polymer dispersant, 0-1.5 wt% of an additive, and the balance being water. The aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes are the only conductive filler in the aqueous nano-conductive liquid. The waterborne polyurethane-acrylate composite emulsion contains epoxy functional groups derived from glycidyl methacrylate in its resin solids, and the epoxy value of the resin solids is 0.15-0.50 mmol / g. The surface of the aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes contains amino functional groups that can pair with the epoxy functional groups, and the amino value is 0.08-0.30 mmol / g. Based on the epoxy value of the resin solid and the amino value of the grafted multi-walled carbon nanotubes, the molar ratio of the epoxy functional group to the amino functional group is 1.0:1-4.0:

1.

2. The nano-conductive liquid based on environmentally friendly water-based adhesive according to claim 1, characterized in that, The aminoalkoxysilane is an aminoalkoxysilane containing at least two nitrogen-containing active sites in its molecule, specifically N-(2-aminoethyl)-3-aminopropyltrimethoxysilane or N-(2-aminoethyl)-3-aminopropyltriethoxysilane.

3. The nano-conductive liquid based on environmentally friendly water-based adhesive according to claim 2, characterized in that, The aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes are obtained by acylation of the carboxylated multi-walled carbon nanotubes and then reacting them with the aminoalkoxysilane. The surface of the grafted multi-walled carbon nanotubes retains free amino functional groups that can be measured by non-aqueous titration.

4. The nano-conductive liquid based on environmentally friendly water-based adhesive according to claim 1, characterized in that, The waterborne polyurethane-acrylate composite emulsion is obtained by polymerizing a waterborne polyurethane dispersion with an acrylate monomer containing glycidyl methacrylate.

5. The nano-conductive liquid based on environmentally friendly water-based adhesive according to claim 1, characterized in that, The nano-conductive liquid does not contain graphene, graphene oxide, conductive carbon black, or acetylene black; the additives include one or more of wetting agents, defoamers, leveling agents, and pH adjusters.

6. A method for preparing a nano-conductive liquid based on an environmentally friendly water-based adhesive according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Multi-walled carbon nanotubes are oxidized to obtain carboxylated multi-walled carbon nanotubes; (2) The carboxylated multi-walled carbon nanotubes are grafted with aminoalkoxysilane to obtain aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes. (3) Prepare an aqueous polyurethane-acrylate composite emulsion containing glycidyl methacrylate structural units; (4) The aminoalkoxysilane-grafted carboxylated multi-walled carbon nanotubes, polymer dispersant and water were pre-dispersed to obtain a pre-dispersed solution; (5) Add the waterborne polyurethane-acrylate composite emulsion to the pre-dispersion liquid, and add the additives and the balance water; by controlling the amount of resin solids added to the composite emulsion and the amount of grafted multi-walled carbon nanotubes added, the molar ratio of the epoxy functional group to the amino functional group is 1.0:1-4.0:1, and the waterborne nano-conductive liquid is obtained.

7. The method for preparing a nano-conductive liquid based on an environmentally friendly water-based adhesive according to claim 6, characterized in that, The oxidation treatment in step (1) is a mixed acid oxidation treatment, wherein the mixed acid is composed of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 2:1-4:1, the oxidation temperature is 80-110℃, and the reaction time is 4-8h.

8. The method for preparing a nano-conductive liquid based on an environmentally friendly water-based adhesive according to claim 6, characterized in that, In step (2), the carboxylated multi-walled carbon nanotubes are first subjected to acylation treatment using a thionyl chloride / dimethylformamide system, and then grafted with the aminoalkoxysilane in an organic solvent; the pre-dispersion in step (4) includes high-speed shear dispersion and / or ultrasonic dispersion; the waterborne polyurethane-acrylate composite emulsion in step (5) is added after the pre-dispersion.

9. The application of the nano-conductive liquid according to any one of claims 1-5 in the preparation of semi-conductive wrapping tape for cables, characterized in that, The nano-conductive liquid is applied to the surface of a fiber substrate and dried to obtain a semi-conductive wrapping tape for cables; the fiber substrate is a nylon tape, a polyester tape, or a non-woven tape.

10. The application of the nano-conductive liquid according to claim 9 in the preparation of semi-conductive wrapping tape for cables, characterized in that, The nano-conductive liquid is applied to the surface of the fiber substrate by immersion, spraying or scraping; the fiber substrate is subjected to corona treatment or plasma treatment before the nano-conductive liquid is applied; the drying temperature is 130-160℃ and the drying time is 1-5 min.

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