High-toughness conductive polyurethane synthetic leather and preparation method thereof

Abstract

The present invention discloses a high-toughness conductive polyurethane synthetic leather and a preparation method thereof. The polyurethane synthetic leather comprises, from the outside to the inside, a surface layer, an intermediate layer, an adhesive layer, and a base fabric layer laminated sequentially. The surface layer slurry comprises an aqueous surface layer resin and an aqueous carbon nanotube dispersion, and the intermediate layer slurry comprises an aqueous intermediate layer resin and an aqueous carbon nanotube dispersion. The preparation method of the aqueous carbon nanotube dispersion comprises the following steps: S1: adding hydroxyl-modified carbon nanotubes to isocyanate or a prepolymer formed by isocyanate and polyol, ball milling to uniformly disperse them under nitrogen protection, to obtain an oil phase; S2: preparing a PVA solution as the aqueous phase; S3: quickly pouring the oil phase into the aqueous phase, emulsifying to obtain a uniform emulsion without a significant oil phase, and then pouring the emulsion into a reactor for reaction to obtain an emulsion with an easily breakable capsule core structure containing the modified carbon nanotubes, namely the aqueous carbon nanotube dispersion. The polyurethane synthetic leather of the present invention has excellent conductivity and improved toughness.

Description

Technical Field

[0001] The invention belongs to the technical field of synthetic leather production, and in particular relates to high-toughness conductive polyurethane synthetic leather and a preparation method thereof. Background Art

[0002] After years of development, traditional polyurethane synthetic leather has reached a bottleneck in raw material sourcing and production methods. Future development focuses not only on replacing environmentally friendly raw materials and corresponding production processes, but also on functional development. Polyurethane synthetic leather is an excellent base material, making it easy to add various functional materials during the production process to achieve functional development goals. Currently, the most advanced functional materials are almost entirely developed in the laboratory, with only a few truly reaching production volume, requiring significant resource allocation.

[0003] Carbon nanotubes (CNTs) have long been a hot topic and a popular material. After years of development, they have become a substantial industry with numerous mature applications in daily life. However, their application in synthetic leather remains largely unexplored. While the dispersion problem of CNTs has been solved, dilution stability in practical applications remains a significant issue. Summary of the Invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a high-toughness conductive polyurethane synthetic leather and a preparation method thereof. The synthetic leather prepared by this method has good conductivity and improved toughness.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a high-toughness conductive polyurethane synthetic leather, which comprises a surface layer, an intermediate layer, an adhesive layer and a base fabric layer laminated in sequence from the outside to the inside, wherein the surface layer is made of a surface layer slurry, and the intermediate layer is made of an intermediate layer slurry;

[0007] The surface layer slurry includes an aqueous surface layer resin and an aqueous carbon nanotube dispersion, and the intermediate layer slurry includes an aqueous intermediate layer resin and the aqueous carbon nanotube dispersion.

[0008] The water-based surface layer resin and the water-based middle layer resin are both polyether-type water-based polyurethane resin with an aliphatic solid content of 30-40wt% or one or more of water-based acrylate resin, water-based epoxy resin, and water-based unsaturated acrylic modified polyurethane resin.

[0009] The preparation method of the aqueous carbon nanotube dispersion comprises the following steps:

[0010] S1: Adding hydroxyl-modified carbon nanotubes to isocyanate or a prepolymer formed by isocyanate and polyol, and uniformly dispersing them by ball milling under nitrogen protection to obtain an oil phase;

[0011] S2: Prepare a PVA solution with a certain solid content as the aqueous phase;

[0012] S3: The oil phase is quickly poured into the water phase, and after emulsification for a certain period of time, a uniform emulsion without obvious oil phase is obtained, which is then poured into a reactor and reacted for a certain period of time to obtain an emulsion with an easily breakable core structure containing modified carbon nanotubes, which is the aqueous carbon nanotube dispersion.

[0013] In the above technical solution, in S1, the viscosity of the aqueous carbon nanotube dispersion is 100-300 mPs, the viscosity is 3000-8000 cps / 25°C, the particle size of the microspheres is 10-100 μm, the content of the hydroxyl-modified carbon nanotubes is 1-10 wt%, the tube diameter is 5-20 nm, and the tube length is 5-15 μm.

[0014] In the above technical solution, in S1, the NCO group content in the isocyanate or the prepolymer formed by isocyanate and polyol is controlled to be 8-40 wt%.

[0015] In the above technical solution, in S3, the mass ratio of the oil phase to the water phase is 1:1-1:3.

[0016] In the above technical solution, in S3, the emulsification process is carried out under ice bath insulation conditions, and the reaction conditions in the reactor are 50°C for 2 hours and then 70°C for 2 hours.

[0017] In the above technical solution, the surface layer slurry and the intermediate layer slurry further include a water-based leveling agent, a water-based defoaming agent and a water-based color paste;

[0018] The weight proportions of the components in the surface layer slurry are: 100 parts of aqueous surface layer resin, 0.1-1 parts of aqueous leveling agent, 0.1-0.5 parts of aqueous defoamer, 3-20 parts of aqueous color paste, and 0.1-50 parts of aqueous carbon nanotube dispersion.

[0019] The weight proportions of the components in the intermediate layer slurry are as follows: 100 parts of aqueous intermediate layer resin, 0.1-1 parts of aqueous leveling agent, 0.1-0.5 parts of aqueous defoamer, 3-20 parts of aqueous color paste, and 0.1-50 parts of aqueous carbon nanotube dispersion.

[0020] The bonding layer is a solvent-free bonding layer, which is composed of bonding layer resin, water-based leveling agent, water-based defoaming agent and catalyst. The weight proportions of the components are: 100 parts of bonding layer resin, 0.1-1 parts of water-based leveling agent, 0.1-0.5 parts of water-based defoaming agent and 0.1-0.5 parts of catalyst.

[0021] In the above technical solution, the adhesive layer resin is a solvent-free two-component, polyether-type polyurethane resin with an aliphatic solid content of 40%-60%, the water-based leveling agent is a polyether-modified polysiloxane leveling agent, the water-based defoaming agent is a polyether and mineral oil compound defoaming agent, and the catalyst is a tertiary amine catalyst for polyurethane.

[0022] The present invention also provides a method for preparing high-toughness conductive polyurethane synthetic leather, comprising the following steps:

[0023] Step 1: adding the aqueous carbon nanotube dispersion to the surface layer slurry and stirring evenly, coating on release paper and drying, and transferring the texture of the release paper to the surface to form the surface layer of synthetic leather;

[0024] Step 2: adding the aqueous carbon nanotube dispersion to the intermediate layer slurry and stirring evenly, coating it on the surface layer, and drying to obtain the intermediate layer;

[0025] Step 3: Apply the adhesive layer to the surface of the middle layer, dry it for a certain period of time until it is semi-dry, and then laminate it with the base fabric layer and squeeze it hard;

[0026] Step 4: Place the bonded base fabric layer, adhesive layer, middle layer, surface layer and release paper into an oven for curing, then roll the finished product onto a winding rack and place it in a constant temperature room for curing, then separate the release paper from the base fabric layer to obtain the high-toughness conductive polyurethane synthetic leather.

[0027] In the above technical solution, in step 3, the drying temperature before lamination is controlled at 70-90°C;

[0028] In step 4, the aging process temperature is set at 90-140° C., the drying time is 5-15 minutes, the temperature of the constant temperature chamber is 50-80° C., and the aging placement time is 24-48 hours.

[0029] The above technical solution also includes step 5: connecting positive and negative electrodes at a certain distance on the surface of the prepared high-toughness conductive polyurethane synthetic leather, testing the conductivity of the synthetic leather surface, and measuring the 100% modulus of the corresponding film.

[0030] The beneficial effects of the present invention are:

[0031] 1. The present invention disperses hydroxyl-modified carbon nanotubes in isocyanate or its prepolymer to form an oil phase. After the oil phase is dispersed in the aqueous phase, interfacial polymerization reaction occurs for a period of time to form a very thin film on the surface of the oil droplets, thereby preventing leakage of the material in the core material. At the same time, during the reaction, the hydroxyl-modified carbon nanotubes are cross-linked with the NCO in the isocyanate to prevent the carbon nanotubes from settling during the subsequent storage process, thereby ensuring that the carbon nanotubes are uniformly dispersed in the oil phase.

[0032] 2. During the synthetic leather molding process, the fragile capsule core structure is crushed by normal lamination and rolling, releasing the substance in the core material, and further cross-linking with water-based polyurethane during subsequent high-temperature drying; the synthetic leather prepared by this method has good conductivity and improved toughness. DETAILED DESCRIPTION

[0033] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. The present invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the present invention to those skilled in the art. The present invention will be limited only by the claims.

[0034] The invention provides a high-toughness conductive polyurethane synthetic leather, which comprises a surface layer, an intermediate layer, an adhesive layer and a base fabric layer laminated in sequence from the outside to the inside. The surface layer and the intermediate layer are water-based coatings, the adhesive layer is a solvent-free adhesive layer, and the base fabric layer is ultrafine fiber.

[0035] The surface layer is made of surface layer slurry, and the middle layer is made of middle layer slurry. The components of the surface layer, middle layer and adhesive layer are shown in Table 1 below.

[0036] Table 1 Composition of surface layer, middle layer and adhesive layer

[0037]

[0038]

[0039] The water-based surface layer resin and the water-based middle layer resin are both polyether-based water-based polyurethane resins with an aliphatic solids content of 30-40% by weight. Besides water-based polyurethane, other resins such as water-based acrylates, water-based epoxy resins, and water-based unsaturated acrylic-modified polyurethanes can also be used. The adhesive layer resin is a solvent-free, two-component polyether-based polyurethane resin with an aliphatic solids content of 40%-60%.

[0040] The water-based leveling agent is a polyether-modified polysiloxane leveling agent. The water-based defoamer is a compound defoamer of polyether and mineral oil. The catalyst is a tertiary amine polyurethane catalyst, such as bis(dimethylaminoethyl) ether and triethylenediamine.

[0041] The aqueous carbon nanotube dispersion has a viscosity of 100-300 mPs, a modified carbon nanotube content of 1-10 wt%, a microsphere particle size of 10-100 μm, a dispersant of 1-10 wt%, water of 60-70 wt%, a viscosity of 3000-8000 cps / 25°C, a modified carbon nanotube diameter of 5-20 nm, and a tube length of 5-15 μm.

[0042] The carbon nanotubes used in the present invention are hydroxylated carbon nanotubes obtained by modification and dispersed in isocyanate or isocyanate prepolymer, dispersed into uniform oil droplets under high-speed stirring conditions, and heated to react for a period of time to form an easily breakable capsule core structure containing the modified carbon nanotubes.

[0043] The preparation method of the aqueous carbon nanotube dispersion comprises the following steps:

[0044] S1: Adding hydroxyl-modified carbon nanotubes to isocyanate or a prepolymer formed by isocyanate and polyol, and uniformly dispersing them by ball milling under nitrogen protection to obtain an oil phase;

[0045] S2: Prepare a PVA solution with a certain solid content as the aqueous phase;

[0046] S3: The oil phase is quickly poured into the water phase, and after emulsification for a certain period of time, a uniform emulsion without obvious oil phase is obtained, which is then poured into a reactor and reacted for a certain period of time to obtain an emulsion with an easily breakable core structure containing modified carbon nanotubes, which is an aqueous carbon nanotube dispersion.

[0047] As one embodiment, the hydroxyl-modified carbon nanotubes in S1 are purchased from Shenzhen Guosen Linghang Technology Co., Ltd., with a tube diameter range of 5-20 nm and a tube length of 5-15 μm.

[0048] The oil phase is one or more of an isocyanate or its prepolymer. The isocyanate can be TDI, MDI, IPDI, etc. The polyol used in the prepolymer can be polyethylene glycol, polyhexylene glycol, etc. The NCO group content is controlled at 8-40wt% to maximize the activity of the prepolymer.

[0049] The solid content of the aqueous PVA solution in S2 is generally controlled at 1-10 wt %. The dosage is determined based on the particle size requirements of the microspheres. Generally, the higher the PVA content, the smaller the particle size. PVA brand is 1799, etc.

[0050] The mass ratio of oil phase to water phase in S3 is 1:1-1:3. The emulsification process is carried out in an ice bath using a homogenizer. The emulsified microspheres are as large and fragile as possible, with no visible oil droplets. The reaction conditions in the autoclave are 50°C for 2 hours, followed by 70°C for 2 hours.

[0051] Since the carbon nanotubes are hydroxyl-modified and have multiple hydroxy groups on their surface, they can form crosslinks with a certain structure with isocyanate or its prepolymer during the subsequent reaction process, thereby preventing the carbon nanotubes from being deposited during the placement of the finished product.

[0052] The present invention also provides a method for preparing high-toughness conductive polyurethane synthetic leather, comprising the following steps:

[0053] Step 1: Add the aqueous carbon nanotube dispersion to the surface layer slurry and stir evenly, apply it on the release paper and dry it, and transfer the texture of the release paper to the surface to form the surface layer of the synthetic leather;

[0054] Step 2: Add the aqueous carbon nanotube dispersion to the intermediate layer slurry and stir evenly, apply it to the surface layer, and dry it to obtain the intermediate layer;

[0055] Step 3: Apply the adhesive layer to the surface of the middle layer, dry it for a certain period of time until it is semi-dry, and then laminate it with the base fabric layer and squeeze it hard;

[0056] Step 4: Place the bonded base fabric layer, adhesive layer, middle layer, surface layer and release paper into an oven for curing. Then roll the finished product onto a winding rack and place it in a constant temperature room for curing. Then separate the release paper from the base fabric layer to obtain high-toughness conductive polyurethane synthetic leather.

[0057] As one embodiment, the drying temperature before lamination in step 3 is controlled at 70-90° C. Experimental comparison shows that this temperature range can effectively control the degree of slurry penetration during lamination and improve the peel strength.

[0058] In step 4, the aging process temperature is set at 90-140° C., the drying time is 5-15 minutes, the temperature of the constant temperature chamber is 50-80° C., and the aging placement time is 24-48 hours.

[0059] As one embodiment, step 5 is added after step 4: positive and negative electrodes are connected at a distance of 10 cm on the surface of the prepared high-toughness conductive polyurethane synthetic leather to test the conductivity of the synthetic leather surface in Ω; at the same time, the 100% modulus of the corresponding film (the coating film that is not attached to the base fabric when making the sample) is measured.

[0060] It should be noted that the purpose of the vigorous squeezing in step 3 is to rupture the hydroxyl-modified carbon nanotube microspheres, allowing the isocyanate or its prepolymer and the hydroxyl-modified carbon nanotubes in the capsule core to flow out simultaneously and continue to cross-link with the waterborne polyurethane and the solvent-free polyurethane in the adhesive layer, thereby achieving toughening, reinforcement, and conductivity. The conductivity of the synthetic leather is also adjusted based on the amount of aqueous carbon nanotube dispersion added.

[0061] The following examples were prepared using the above preparation method, with the only difference being the amount of aqueous carbon nanotube dispersion added. The performance of each example was tested, and the test methods and results are shown in Table 2.

[0062] Table 2 Performance test results of polyurethane synthetic leather of Examples 1-7

[0063]

[0064]

[0065] As can be seen from Table 2 above, the conductivity and toughness of the finished synthetic leather prepared by adding the aqueous carbon nanotube dispersion to the slurry of the surface layer and the middle layer are greatly improved.

[0066] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A high-toughness conductive polyurethane synthetic leather comprising, from the outside to the inside, a surface layer, an intermediate layer, an adhesive layer, and a base fabric layer laminated sequentially, the surface layer being made of a surface layer slurry, and the intermediate layer being made of an intermediate layer slurry; characterized in that: The surface layer slurry includes an aqueous surface layer resin and an aqueous carbon nanotube dispersion, and the intermediate layer slurry includes an aqueous intermediate layer resin and the aqueous carbon nanotube dispersion. The aqueous surface layer resin and the aqueous intermediate layer resin are both polyether-type aqueous polyurethane resins with an aliphatic solid content of 30-40 wt% or one or more of aqueous acrylate resins, aqueous epoxy resins, and aqueous unsaturated acrylic modified polyurethane resins. The preparation method of the aqueous carbon nanotube dispersion comprises the following steps: S1: adding hydroxyl-modified carbon nanotubes to isocyanate or a prepolymer formed by isocyanate and polyol, and uniformly dispersing by ball milling under nitrogen protection to obtain an oil phase; wherein the NCO group content in the isocyanate or the prepolymer formed by isocyanate and polyol is controlled to be 8-40wt%; S2: Prepare a PVA solution with a certain solid content as the aqueous phase; S3: quickly pouring the oil phase into the water phase, emulsifying for a certain period of time to obtain a uniform emulsion without a significant oil phase, and then pouring it into a reactor to react for a certain period of time to obtain an emulsion with an easily breakable core structure containing hydroxyl-modified carbon nanotubes, which is the aqueous carbon nanotube dispersion; During the synthetic leather forming process, the breakable core structure is broken by normal lamination and rolling.

2. The high-toughness conductive polyurethane synthetic leather according to claim 1, characterized in that: In S1, the viscosity of the aqueous carbon nanotube dispersion is 100-300 mPa·s, the microsphere particle size is 10-100 μm, the content of the hydroxyl-modified carbon nanotubes is 1-10 wt %, the tube diameter is 5-20 nm, and the tube length is 5-15 μm.

3. The high-toughness conductive polyurethane synthetic leather according to claim 1, characterized in that: In S3, the mass ratio of the oil phase to the water phase is 1:1-1:

3.

4. The high-toughness conductive polyurethane synthetic leather according to claim 1, characterized in that: In S3, the emulsification process was carried out in an ice bath, and the reaction conditions in the reactor were 50° C. for 2 h and then 70° C. for 2 h.

5. The high-toughness conductive polyurethane synthetic leather according to claim 1, characterized in that: The surface layer slurry and the intermediate layer slurry also include a water-based leveling agent, a water-based defoaming agent and a water-based color paste; The weight proportions of the components in the surface layer slurry are: 100 parts of aqueous surface layer resin, 0.1-1 parts of aqueous leveling agent, 0.1-0.5 parts of aqueous defoamer, 3-20 parts of aqueous color paste, and 3-50 parts of aqueous carbon nanotube dispersion. The weight proportions of the components in the intermediate layer slurry are: 100 parts of aqueous intermediate layer resin, 0.1-1 parts of aqueous leveling agent, 0.1-0.5 parts of aqueous defoamer, 3-20 parts of aqueous color paste, and 3-50 parts of aqueous carbon nanotube dispersion. The bonding layer is a solvent-free bonding layer, which is composed of bonding layer resin, water-based leveling agent, water-based defoaming agent and catalyst. The weight proportions of the components are: 100 parts of bonding layer resin, 0.1-1 parts of water-based leveling agent, 0.1-0.5 parts of water-based defoaming agent and 0.1-0.5 parts of catalyst.

6. The high-toughness conductive polyurethane synthetic leather according to claim 5, characterized in that: The adhesive layer resin is a solvent-free two-component, polyether-type polyurethane resin with an aliphatic solid content of 40%-60%. The water-based leveling agent is a polyether-modified polysiloxane leveling agent. The water-based defoaming agent is a polyether and mineral oil compound defoaming agent. The catalyst is a tertiary amine catalyst for polyurethane.

7. The method for preparing the high-toughness conductive polyurethane synthetic leather according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: adding the aqueous carbon nanotube dispersion to the surface layer slurry and stirring evenly, coating on release paper and drying, and transferring the texture of the release paper to the surface to form the surface layer of synthetic leather; Step 2: adding the aqueous carbon nanotube dispersion to the intermediate layer slurry and stirring evenly, coating it on the surface layer, and drying to obtain the intermediate layer; Step 3: Apply the adhesive layer to the surface of the middle layer, dry it for a certain period of time until it is semi-dry, and then laminate it with the base fabric layer and squeeze it hard; Step 4: Place the bonded base fabric layer, adhesive layer, middle layer, surface layer and release paper into an oven for curing, then roll the finished product onto a winding rack and place it in a constant temperature room for curing, then separate the release paper from the base fabric layer to obtain the high-toughness conductive polyurethane synthetic leather.

8. The method for preparing high-toughness conductive polyurethane synthetic leather according to claim 7, characterized in that: In step 3, the drying temperature before lamination is controlled at 70-90°C; In step 4, the aging process temperature is set at 90-140° C., the drying time is 5-15 minutes, the temperature of the constant temperature chamber is 50-80° C., and the aging placement time is 24-48 hours.

9. The method for preparing high-toughness conductive polyurethane synthetic leather according to claim 7, characterized in that: The method also includes step 5: connecting positive and negative electrodes at a certain distance from the surface of the prepared high-toughness conductive polyurethane synthetic leather to test the conductivity of the synthetic leather surface and simultaneously measuring the 100% modulus of the corresponding film.

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