Hot melt adhesive film for vehicle FFC wire, and preparation method therefor

Abstract

Disclosed in the present invention is a hot melt adhesive film for a vehicle FFC wire. The hot melt adhesive film comprises a base material and a hot melt adhesive layer, which are sequentially connected from bottom to top, the hot melt adhesive layer being coated on the upper surface of the base material by means of a hot melt adhesive. The hot melt adhesive comprises, in percentages by mass: 18-22% of a polyurethane resin, 1-2% of an epoxy resin, 18-25% of a flame retardant, 1-2% of titanium dioxide and 50-60% of a solvent, wherein the softening point of the polyurethane resin is 180-200°C. The hot melt adhesive film for a vehicle FFC wire provided in the present invention has both excellent bonding performance and hot-pressing fitting performance, such that it is ensured that the hot melt adhesive film can be used in a high-humidity and high-temperature environment, and it is also ensured that the hot melt adhesive film can effectively coat a tinned flat copper wire, thereby reducing the difficulty of the preparation of a vehicle FFC wire, and overcoming the defects in the prior art.

Description

Hot melt adhesive film for automotive FFC wire and preparation method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application with application number 202311856627.2 filed with the China Patent Office on December 29, 2023, entitled "A hot melt adhesive film for automotive FFC wire and its preparation method", the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present invention relates to the technical field of hot melt adhesive films, and in particular to a hot melt adhesive film for automotive FFC wires and a preparation method thereof. Background Art

[0004] FFC (Flexible Flat Cable) is made by hot-pressing a hot-melt adhesive film and extremely thin tinned flat copper wire on a substrate using an automatic roller-pressing laminating machine. It is soft and bendable, compact and lightweight, and has a high degree of wiring harness integration. It is widely used not only in traditional fields such as printers, plotters, and copiers, but also in emerging fields such as laptops, plotters, and automobiles.

[0005] The automotive FFC wires in cars will bend and move frequently with the movement of the car's onboard moving parts, and they often need to be used in high-humidity and high-heat environments. Their application environment is much harsher than traditional application scenarios such as printers. Therefore, higher requirements are placed on the performance of automotive FFC wires, and higher requirements are also placed on the hot melt adhesive film of automotive FFC wires.

[0006] Specifically, on the one hand, the hot melt adhesive film is required to have good bonding properties to ensure adhesion to the tinned flat copper wire, so that it can be twisted and bent at will in a hot and humid environment without falling off; on the other hand, the hot melt adhesive film is required to have hot pressing bonding properties to avoid its high fluidity during hot pressing bonding, which makes it unable to effectively wrap the tinned flat copper wire, which increases the difficulty of preparing automotive FFC wires; on the other hand, due to the failure to effectively wrap the tinned flat copper wire, the bonding performance of the hot melt adhesive film to the tinned flat copper wire is reduced.

[0007] Hot-melt adhesive films for automotive FFC filaments primarily consist of a base material and a hot-melt adhesive layer coated on the base material. Therefore, the adhesive and hot-press lamination performance of the hot-melt adhesive film depends primarily on the layer formed by coating the hot-melt adhesive on the base material. Existing hot-melt adhesive formulations typically use unsaturated polyester resin as the base resin and incorporate hydrogen peroxide as a curing agent to achieve these goals. On the one hand, since the ester group in the unsaturated polyester resin is easily hydrolyzed, it is easy to swell under the action of water vapor in the natural environment, which reduces the bonding performance of the hot melt adhesive film. On the other hand, since the softening point of the unsaturated polyester resin is usually between 50 and 60°C, its softening point is relatively low, resulting in greater high-temperature fluidity during hot pressing. Even if a curing agent is added to the formula to cross-link and cure the unsaturated polyester resin, the degree of curing of the unsaturated polyester resin is affected by many factors such as curing time, curing temperature and type of curing agent, resulting in the difficulty in ensuring the degree of cross-linking and curing of the unsaturated polyester resin, that is, it is difficult to ensure the improvement of the softening point of the hot melt adhesive, and thus the hot pressing bonding performance of the hot melt adhesive film is still difficult to ensure; at the same time, it also affects the bonding performance of the hot melt adhesive film.

[0008] Summary of the Invention

[0009] The purpose of the present invention is to propose a hot melt adhesive film for automotive FFC wire, which has excellent bonding properties and hot pressing bonding properties. On the one hand, it ensures that it can be used in high humidity and heat environments. On the other hand, it ensures that it can effectively wrap tinned flat copper wire, reducing the difficulty of preparing automotive FFC wire, so as to overcome the shortcomings of the existing technology.

[0010] The second purpose of the present invention is to propose a method for preparing a hot melt adhesive film for automotive FFC wire. The preparation method is simple and easy to operate, ensuring that the obtained automotive FFC wire has excellent bonding properties and hot pressing bonding properties, meeting actual use requirements.

[0011] To achieve this object, the present invention adopts the following technical solutions:

[0012] A hot melt adhesive film for automotive FFC wires, comprising a substrate and a hot melt adhesive layer connected sequentially from bottom to top, wherein the hot melt adhesive layer is coated on the upper surface of the substrate by hot melt adhesive;

[0013] Calculated by mass percentage, the hot melt adhesive includes 18-22% polyurethane resin, 1-2% epoxy resin, 18-25% flame retardant, 1-2% titanium dioxide and 50-60% solvent; wherein the softening point of the polyurethane resin is 180°C to 200°C.

[0014] Furthermore, the molecular weight of the epoxy resin is 1000-3000.

[0015] Furthermore, the polyurethane includes at least one of polycaprolactone polyurethane, polyalkylalkanoate polyurethane and polyaliphatic ester polyurethane.

[0016] Furthermore, the epoxy resin includes at least one of E44 epoxy resin and E51 epoxy resin.

[0017] Furthermore, the substrate is a PET film;

[0018] The thickness of the PET film is 25 to 50 μm; the thickness of the hot melt adhesive layer is 18 to 20 μm.

[0019] Furthermore, the flame retardant includes at least one of decabromodiphenylethane, antimony trioxide, octabromoether, nitrogen-based flame retardant, phosphorus-based flame retardant, magnesium hydroxide and aluminum hydroxide.

[0020] Furthermore, the titanium dioxide is at least one of rutile titanium dioxide, anatase titanium dioxide or brookite titanium dioxide.

[0021] Furthermore, the solvent includes at least one of methyl acetate, ethyl acetate, phenyl acetate, methyl benzoate, butyl acetate and octyl acrylate.

[0022] A method for preparing a hot melt adhesive film for an automotive FFC wire, for preparing the hot melt adhesive film for the above-mentioned automotive FFC wire, comprises the following steps:

[0023] A. Mix and disperse the formulated amount of polyurethane resin, epoxy resin and solvent evenly, add the formulated amount of flame retardant and titanium dioxide during the dispersion process, and grind to obtain a hot melt adhesive;

[0024] B. performing a corona treatment on the substrate, and coating the hot melt adhesive obtained in step A on the corona treated substrate to form a hot melt adhesive layer, thereby preparing a hot melt adhesive film for automotive FFC wires.

[0025] Furthermore, in step B, the corona current in the corona treatment step is 3 to 5A.

[0026] The technical solutions provided by the embodiments of the present application may have the following beneficial effects:

[0027] 1. Polyurethane resin has thermoplasticity and can melt at high temperature under hot pressing temperature, which makes the hot melt adhesive film have low fluidity under hot pressing temperature, ensuring the hot pressing bonding performance of the hot melt adhesive film, so that the hot melt adhesive film can effectively wrap the tinned flat copper wire, reducing the difficulty of preparing automotive FFC wire, and at the same time does not affect the bonding performance of the hot melt adhesive film; In addition, the hot melt adhesive film wrapping the tinned flat copper wire can protect the tinned flat copper wire, isolate it from external dust and water vapor, and extend its service life; In addition, the groups such as carbamate and allophanate in the polyurethane resin are regularly and spaced to form rigid segments, so the rubber obtained has The regular network structure ensures the bonding performance of the hot melt adhesive layer, and thus ensures the bonding performance of the hot melt adhesive film; in addition, the carbamate group and allophanate group in the polyurethane resin give it higher cohesive energy, further improving its adhesion. Adding them to the formula not only makes the hot melt adhesive layer obtained after the hot melt adhesive is coated have strong adhesion to the substrate, but also increases the bonding performance of the hot melt adhesive film, ensuring the adhesion of the hot melt adhesive film to the tinned flat copper wire, so that the tinned flat copper wire can be twisted and bent at will without falling off; in addition, the hydrolysis resistance of the carbamate group and the allophanate group is higher than that of the ester group, which improves the hydrolysis resistance of the hot melt adhesive film and makes it more suitable for high temperature and hot use environment.

[0028] 2. This technical solution replaces the unsaturated polyester resin used in existing technologies by combining epoxy and polyurethane resins. The softening point of the polyurethane resin and the dosage of epoxy and polyurethane resins are controlled to ensure the hot-melt adhesive layer's excellent adhesion and lamination properties to tinned flat copper wire. Furthermore, since this technical solution does not include the addition of a curing agent, it avoids the numerous factors that require control when cross-linking and curing with a curing resin, which can increase the difficulty of hot-melt adhesive film preparation and lead to poor performance stability. DETAILED DESCRIPTION

[0029] The present technical solution provides a hot melt adhesive film for automotive FFC wires, comprising a substrate and a hot melt adhesive layer connected sequentially from bottom to top, wherein the hot melt adhesive layer is coated on the upper surface of the substrate by hot melt adhesive;

[0030] Calculated by mass percentage, the hot melt adhesive includes 18-22% polyurethane resin, 1-2% epoxy resin, 18-25% flame retardant, 1-2% titanium dioxide and 50-60% solvent; wherein the softening point of the polyurethane resin is 180°C to 200°C.

[0031] In order to ensure that the hot melt adhesive layer has both adhesive and hot-pressing properties, this technical solution proposes a hot melt adhesive film for automotive FFC wires, comprising a substrate and a hot melt adhesive layer connected sequentially from bottom to top. By optimizing the hot melt adhesive formula, the hot melt adhesive film for automotive FFC wires has both excellent adhesive and hot-pressing properties. This ensures that it can be used in high-humidity and high-heat environments, and that it can effectively wrap tinned flat copper wires, reducing the difficulty of preparing automotive FFC wires. Furthermore, because this technical solution does not add a curing agent, it avoids the need to control too many factors when using a curing agent resin for cross-linking and curing, which can easily increase the difficulty of preparing the hot melt adhesive film and, on the other hand, lead to poor performance stability of the resulting hot melt adhesive film.

[0032] Specifically, existing hot melt adhesive formulations generally use unsaturated polyester resin as the base resin and add hydrogen peroxide curing agents to the hot melt adhesive formulation to achieve the corresponding purpose. On the one hand, because the ester group in the unsaturated polyester resin is easily hydrolyzed, it easily swells under the influence of water vapor in the natural environment, which also reduces the adhesive properties of the hot melt adhesive film. On the other hand, because the softening point of unsaturated polyester resin is generally between 50 and 60°C, its low softening point leads to greater high-temperature fluidity during hot pressing. Even if a curing agent is added to the formulation to crosslink and cure the unsaturated polyester resin, the degree of curing of the unsaturated polyester resin is affected by various factors such as curing time, curing temperature, and type of curing agent. As a result, it is difficult to ensure the degree of crosslinking and curing of the unsaturated polyester resin, that is, it is difficult to ensure the improvement of the softening point of the hot melt adhesive, and thus the hot pressing and laminating properties of the hot melt adhesive film are still difficult to ensure. At the same time, it also affects the adhesive properties of the hot melt adhesive film.

[0033] The raw materials of the hot melt adhesive of the present technical solution include polyurethane resin. The polyurethane resin has thermoplasticity and can be melted at high temperature at the hot pressing temperature, so that the hot melt adhesive film has low fluidity at the hot pressing temperature, ensuring the hot pressing bonding performance of the hot melt adhesive film, so that the hot melt adhesive film can effectively wrap the tinned flat copper wire, reducing the difficulty of preparing automotive FFC wire, and at the same time not affecting the bonding performance of the hot melt adhesive film; in addition, the hot melt adhesive film wrapping the tinned flat copper wire can protect the tinned flat copper wire, isolate it from external dust and water vapor, and extend its service life; in addition, the groups such as carbamate and allophanate in the polyurethane resin are regularly and spaced to form rigid segments Therefore, the rubber produced has a regular network structure, which ensures the bonding performance of the hot melt adhesive layer, and then ensures the bonding performance of the hot melt adhesive film; in addition, the carbamate group and allophanate group in the polyurethane resin give it higher cohesive energy, further improving its adhesion. When added to the formula, the hot melt adhesive layer obtained after the hot melt adhesive is coated has strong adhesion to the substrate, and can also increase the bonding performance of the hot melt adhesive film, ensuring the adhesion of the hot melt adhesive film to the tinned flat copper wire, so that the tinned flat copper wire can be twisted and bent at will without falling off; in addition, the hydrolysis resistance of the carbamate group and the allophanate group is higher than that of the ester group, which improves the hydrolysis resistance of the hot melt adhesive film, making it more suitable for high temperature and hot use environment.

[0034] Because hot-melt adhesive films require high adhesion in high-humidity and high-heat environments, maintaining such performance can be challenging when using only polyurethane resin as the base resin. Therefore, this technical solution incorporates epoxy resin into the formulation. Epoxy resin exhibits excellent adhesion to tinned flat copper wire. This combination of epoxy and polyurethane resin replaces the unsaturated polyester resin used in existing technologies, ensuring the hot-melt adhesive layer's excellent adhesion and lamination properties. Furthermore, this technical solution eliminates the need for a curing agent to cure the resin, ensuring the hot-melt adhesive film's stable performance.

[0035] Furthermore, the softening point of the polyurethane resin is 180°C to 200°C, so that the softening point of the obtained hot melt adhesive film is ≥180°C, which matches the hot pressing bonding temperature (160°C to 200°C) during the preparation of automotive FFC wires, thereby ensuring the bonding performance of the hot melt adhesive film. When the softening point of the polyurethane resin is too low, the fluidity of the hot melt adhesive film at the hot pressing bonding temperature will be greatly increased, making it difficult to effectively wrap the tinned flat copper wire, increasing the difficulty of preparing automotive FFC wires, and also causing the bonding performance of the hot melt adhesive film to decrease; when the softening point of the polyurethane resin is too high, the hot melt adhesive film will have no fluidity or too little fluidity at the hot pressing bonding temperature, and it will also be difficult to effectively wrap the tinned flat copper wire, making it difficult to prepare automotive FFC wires, and also causing the bonding performance of the hot melt adhesive film to decrease.

[0036] Furthermore, the addition amount of polyurethane resin is limited to 18-22%. When the addition amount of polyurethane resin is greater than 22%, the hot melt adhesive film will have too low high-temperature fluidity under the hot pressing bonding temperature and hot pressing bonding pressure, making it difficult to effectively wrap the tinned flat copper wire; when the addition amount of polyurethane resin is less than 18%, the hot melt adhesive film will have too high high-temperature fluidity under the hot pressing bonding temperature and hot pressing bonding pressure, making it difficult to effectively wrap the tinned flat copper wire. At the same time, it will also lead to a decrease in the bonding strength of the hot melt adhesive film and a decrease in the bonding performance to the tinned flat copper wire.

[0037] At the same time, the present technical solution limits the addition amount of epoxy resin to 1-2%. Since the softening point of epoxy resin is lower than that of polyurethane resin, when the addition amount of epoxy resin is greater than 2%, the softening point of the hot melt adhesive film will drop significantly, and its hot pressing bonding performance cannot be guaranteed, which also leads to a decrease in the bonding performance of the hot melt adhesive film; when the addition amount of epoxy resin is less than 1%, it has limited effect on improving the bonding performance of the hot melt adhesive film, which will lead to the bonding performance of the hot melt adhesive film cannot be guaranteed.

[0038] Therefore, this technical solution replaces the unsaturated polyester resin used in existing technologies by combining epoxy and polyurethane resins. The softening point of the polyurethane resin and the dosage of epoxy and polyurethane resins are controlled to ensure the hot-melt adhesive layer's adhesion and lamination properties to tinned flat copper wire. Furthermore, since this technical solution does not add a curing agent, it avoids the numerous factors that require control when using a curing resin for cross-linking and curing, which can increase the difficulty of hot-melt adhesive film preparation and lead to poor performance stability of the resulting hot-melt adhesive film.

[0039] It is further explained that the molecular weight of the epoxy resin is 1000 to 3000.

[0040] Since the molecular weight of epoxy resin is related to its softening point, the larger the molecular weight, the higher the softening point, and the smaller the molecular weight, the lower the softening point. Therefore, in a preferred embodiment of the present technical solution, the molecular weight of the epoxy resin is limited to 1000-3000 to further ensure the hot pressing bonding performance of the hot melt adhesive film.

[0041] It is further specified that the polyurethane includes at least one of polycaprolactone polyurethane, polyalkylalkanoate polyurethane and polyaliphatic ester polyurethane.

[0042] Since polyester polyurethane is harder, more wear-resistant and more resistant to high temperatures than polyether polyurethane, in a preferred embodiment of the present technical solution, polyurethane is limited to polyester polyurethanes such as polycaprolactone polyurethane, polyalkyl alkanoate polyurethane and polyaliphatic ester polyurethane, to ensure that the obtained hot melt adhesive film can meet the use requirements in high humidity and heat environments.

[0043] It is further specified that the epoxy resin includes at least one of E44 epoxy resin and E51 epoxy resin.

[0044] In a preferred embodiment of the present technical solution, the epoxy resin includes E44 epoxy resin and E51 epoxy resin. E44 epoxy resin has high temperature resistance and excellent bonding properties, and E51 epoxy resin has good bonding, insulation and high strength, thereby ensuring the bonding strength of the hot melt adhesive film in a high humidity and heat environment.

[0045] It is further described that the substrate is a PET film;

[0046] The thickness of the PET film is 25 to 50 μm; the thickness of the hot melt adhesive layer is 18 to 20 μm.

[0047] In a preferred embodiment of the present technical solution, the substrate is a PET film (polyethylene terephthalate film). The PET film has high strength, low heat shrinkage, high temperature resistance and high stability. Hot melt adhesive is applied thereon, so that the obtained hot melt adhesive film not only has excellent hot pressing bonding and adhesion properties, but also has the characteristics of high strength, low heat shrinkage, high temperature resistance and high stability of the PET film itself, and is more suitable for use in high humidity and heat environments.

[0048] In another preferred embodiment of this technical solution, the PET film has a thickness of 25-50 μm, providing support and ensuring the strength and hardness of the hot-melt adhesive film. The hot-melt adhesive layer has a thickness of 18-20 μm, allowing it to encapsulate the tinned flat copper wire, a metallic conductor, preventing it from being exposed to air and affecting the performance of the FFC cable. Furthermore, the thickness of the PET film and hot-melt adhesive layer is limited to ensure a relatively thin automotive FFC cable, avoiding excessive thickness that would increase production and transportation costs, while also meeting the requirements for use in confined spaces.

[0049] It is further specified that the flame retardant includes at least one of decabromodiphenylethane, antimony trioxide, octabromoether, nitrogen-based flame retardant, phosphorus-based flame retardant, magnesium hydroxide and aluminum hydroxide.

[0050] In a preferred embodiment of the present technical solution, the flame retardant includes at least one of decabromodiphenylethane, antimony trioxide, octabromoether, nitrogen-based flame retardant, phosphorus-based flame retardant, magnesium hydroxide and aluminum hydroxide to meet the flame retardant requirements of automotive FFC wire.

[0051] It should be noted that the phosphorus-based flame retardants include triphenyl phosphate, ethylphenyl phenyl phosphate, tert-butylphenyl diyl phosphate, tetraarylarylene bisphosphate, resorcinol phosphate and tetraphenyl bisphenol A-diphosphate, which are not limited here.

[0052] It should be further explained that the nitrogen-based flame retardant may be melamine and its derivatives and related heterocyclic compounds, which are not limited here.

[0053] To further illustrate, the titanium dioxide is at least one of rutile titanium dioxide, anatase titanium dioxide or brookite titanium dioxide.

[0054] In a preferred embodiment of the present technical solution, the titanium dioxide is at least one of rutile titanium dioxide, anatase titanium dioxide or brookite titanium dioxide, which shields the tinned flat copper wire to ensure its aesthetics.

[0055] It is further specified that the solvent includes at least one of methyl acetate, ethyl acetate, phenyl acetate, methyl benzoate, butyl acetate and octyl acrylate.

[0056] In a preferred embodiment of the present technical solution, the solvent is preferably an environmentally friendly solvent such as methyl acetate, ethyl acetate, phenyl acetate, methyl benzoate, butyl acetate and octyl acrylate, which reduces pollution to the environment and ensures the environmental friendliness of the product.

[0057] A method for preparing a hot melt adhesive film for an automotive FFC wire, for preparing the hot melt adhesive film for the above-mentioned automotive FFC wire, comprises the following steps:

[0058] A. Mix and disperse the formulated amount of polyurethane resin, epoxy resin and solvent evenly, add the formulated amount of flame retardant and titanium dioxide during the dispersion process, and grind to obtain a hot melt adhesive;

[0059] B. performing a corona treatment on the substrate, and coating the hot melt adhesive obtained in step A on the corona treated substrate to form a hot melt adhesive layer, thereby preparing a hot melt adhesive film for automotive FFC wires.

[0060] This technical solution also proposes a method for preparing a hot melt adhesive film for automotive FFC wire. The preparation method is simple and easy to operate, ensuring that the obtained automotive FFC wire has excellent bonding properties and hot pressing bonding properties, meeting actual use requirements.

[0061] Specifically, in step A, the solid content of the prepared hot melt adhesive is 20-30%, which ensures the processability and film-forming effect of the hot melt adhesive. If the solid content of the hot melt adhesive is too low, the difficulty of film formation will increase, and the film thickness will be too thin, and the performance of the hot melt adhesive film cannot be ensured; at the same time, if the solid content of the hot melt adhesive is too high, the difficulty of coating the hot melt adhesive will increase, and the uniformity of the obtained hot melt adhesive layer will also be affected, which will also affect the performance of the hot melt adhesive film.

[0062] Preferably, in step A, the mixing and dispersing step is performed at a speed of 100-200 rpm / min for a time of 20-30 minutes; and the grinding step is performed for a time of 25-30 minutes. By optimizing each of the above steps, uniform dispersion of the hot melt adhesive is ensured, and agglomeration and precipitation are avoided, which could affect the performance of the hot melt adhesive film.

[0063] Further description, in step B, the corona current in the corona treatment step is 3 to 5A.

[0064] Since hot-melt adhesive films consist of a substrate and a hot-melt adhesive layer, and the substrate, serving as the base film of the hot-melt adhesive film, needs to be bonded to the hot-melt adhesive layer, forming the hot-melt adhesive layer by coating the hot-melt adhesive on the substrate, this technical solution limits the corona treatment current to 3-5A, ensuring a surface tension of the PE film greater than 46mN / m, facilitating adhesion to the hot-melt adhesive layer and ensuring the performance of the hot-melt adhesive film.

[0065] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0066] Performance testing:

[0067] (1) Appearance: After the hot melt adhesive is applied to the surface of the substrate, it is qualified if there are no bubbles, pinholes or particles in the hot melt adhesive layer.

[0068] (2) Hot pressing bonding performance: The fluidity of the hot melt adhesive film is measured under the conditions of hot pressing temperature of 160°C and pressure of 300KPa. If the fluidity of the hot melt adhesive film is 1.0~3.0um / min, the hot pressing bonding performance is qualified.

[0069] (3) Difficulty of pressing: The hot melt adhesive film was pressed onto a tinned flat copper wire with a thickness of 0.035 mm and a width of 0.3 mm at a hot pressing temperature of 160°C and a pressure of 300 kPa for 10 seconds to test the difficulty of pressing.

[0070] (3) Adhesion performance: The hot melt adhesive film is pressed onto a tinned flat copper wire with a thickness of 0.035 mm and a width of 0.3 mm under the conditions of a hot pressing temperature of 160°C and a pressure of 300 kPa for 10 seconds. After being pressed into an FFC wire, the adhesion of a single tinned flat copper wire is tested at the window position of the FFC wire at a room temperature of 25°C using a tensile testing machine. The peeling speed is 300 mm / min, and the peeling value is greater than 40 N / mm, which is considered qualified.

[0071] (4) Flame retardancy: Flame retardancy is tested according to the “U.S. Flame Retardant Material UL94 Standard and Test Method”.

[0072] Example 1

[0073] In this embodiment, calculated by mass percentage, the hot melt adhesive includes 20% polyurethane resin, 1% epoxy resin, 20% flame retardant, 2% titanium dioxide and 57% solvent; wherein, the polyurethane resin is polycaprolactone polyurethane, the epoxy resin is E44 epoxy resin, the flame retardant is decabromodiphenyl ethane, the titanium dioxide is rutile titanium dioxide, and the solvent is ethyl acetate; wherein, the softening point of the polyurethane resin is 180°C, and the molecular weight of the epoxy resin is 1000.

[0074] The method for preparing a hot melt adhesive film for an automotive FFC wire in this embodiment includes the following steps:

[0075] A. Mix and disperse the formulated amount of polyurethane resin, epoxy resin, and solvent at a speed of 100 rpm / min for 30 minutes. During the dispersion process, add the formulated amount of flame retardant and titanium dioxide, and grind for 30 minutes to obtain a hot melt adhesive;

[0076] B. A PET film with a thickness of 25 μm was corona treated using a corona current of 3 A, and the hot melt adhesive obtained in step A was coated on the corona-treated PET film to obtain a hot melt adhesive layer with a thickness of 18 μm, thereby preparing a hot melt adhesive film for automotive FFC wires.

[0077] Example 2

[0078] In this embodiment, calculated by mass percentage, the hot melt adhesive includes 22% polyurethane resin, 2% epoxy resin, 21% flame retardant, 2% titanium dioxide and 53% solvent; wherein, the polyurethane resin is polyalkyl alkanoate polyurethane, the epoxy resin is E44 epoxy resin, the flame retardant is triphenyl phosphate, the titanium dioxide is anatase titanium dioxide, and the solvent is butyl acetate; wherein, the softening point of the polyurethane resin is 200°C, and the molecular weight of the epoxy resin is 3000.

[0079] The method for preparing a hot melt adhesive film for an automotive FFC wire in this embodiment includes the following steps:

[0080] A. Mix and disperse the formulated amount of polyurethane resin, epoxy resin, and solvent at a speed of 150 rpm / min for 25 minutes. During the dispersion process, add the formulated amount of flame retardant and titanium dioxide, and grind for 25 minutes to obtain a hot melt adhesive;

[0081] B. A PET film with a thickness of 30 μm was corona treated using a corona current of 4 A, and the hot melt adhesive obtained in step A was coated on the corona-treated PET film to obtain a hot melt adhesive layer with a thickness of 20 μm, thereby preparing a hot melt adhesive film for automotive FFC wires.

[0082] Example 3

[0083] In this embodiment, calculated by mass percentage, the hot melt adhesive includes 22% polyurethane resin, 1% epoxy resin, 25% flame retardant, 2% titanium dioxide and 50% solvent; wherein, the polyurethane resin is a polyaliphatic ester type polyurethane, the epoxy resin is E51 epoxy resin, the flame retardant is magnesium hydroxide, the titanium dioxide is brookite type titanium dioxide, and the solvent is methyl benzoate; wherein, the softening point of the polyurethane resin is 190°C, and the molecular weight of the epoxy resin is 2000.

[0084] The method for preparing a hot melt adhesive film for an automotive FFC wire in this embodiment includes the following steps:

[0085] A. Mix and disperse the formulated amount of polyurethane resin, epoxy resin, and solvent at 200 rpm / min for 20 minutes. During the dispersion process, add the formulated amount of flame retardant and titanium dioxide. Grind for 25 minutes to obtain a hot melt adhesive.

[0086] B. A PET film having a thickness of 40 μm was corona treated using a corona current of 5 A, and the hot melt adhesive obtained in step A was coated on the corona-treated PET film to obtain a hot melt adhesive layer having a thickness of 20 μm, thereby preparing a hot melt adhesive film for automotive FFC wires.

[0087] Example 4

[0088] In this embodiment, calculated by mass percentage, the hot melt adhesive includes 18% polyurethane resin, 1% epoxy resin, 19% flame retardant, 2% titanium dioxide and 60% solvent; wherein, the polyurethane resin is polycaprolactone polyurethane, the epoxy resin is E51 epoxy resin, the flame retardant is ethylphenyl phenyl phosphate, the titanium dioxide is rutile titanium dioxide, and the solvent is butyl acetate; wherein, the softening point of the polyurethane resin is 200°C, and the molecular weight of the epoxy resin is 3000.

[0089] The method for preparing a hot melt adhesive film for an automotive FFC wire in this embodiment includes the following steps:

[0090] A. Mix and disperse the formulated amount of polyurethane resin, epoxy resin, and solvent at 200 rpm / min for 25 minutes. During the dispersion process, add the formulated amount of flame retardant and titanium dioxide. Grind for 30 minutes to obtain a hot melt adhesive.

[0091] B. A PET film with a thickness of 50 μm was corona treated using a corona current of 4 A, and the hot melt adhesive obtained in step A was coated on the corona-treated PET film to obtain a hot melt adhesive layer with a thickness of 20 μm, thereby preparing a hot melt adhesive film for automotive FFC wires.

[0092] Comparative Example 1

[0093] The hot melt adhesive used in Comparative Example 1 was replaced with a conventional hot melt adhesive. The hot melt adhesive comprised, by weight, 20% unsaturated polyester resin, 1% curing agent, 20% flame retardant, 2% titanium dioxide, and 57% solvent. The unsaturated polyester resin was a phthalate resin, the curing agent was dibenzoyl peroxide, the flame retardant was decabromodiphenylethane, the titanium dioxide was rutile titanium dioxide, and the solvent was ethyl acetate.

[0094] Comparative Example 2

[0095] The preparation method and raw materials of Comparative Example 2 were the same as those of Example 1, except that the ratio of the raw materials in the hot melt adhesive was different from that in Example 1. The hot melt adhesive comprised 16% polyurethane resin, 2% epoxy resin, 23% flame retardant, 1% titanium dioxide, and 58% solvent, calculated by mass percentage.

[0096] Comparative Example 3

[0097] The preparation method and raw materials of Comparative Example 3 were the same as those of Example 1, except that the ratio of the raw materials in the hot melt adhesive was different from that in Example 1. The hot melt adhesive comprised 24% polyurethane resin, 1% epoxy resin, 18% flame retardant, 2% titanium dioxide, and 505% solvent, calculated by mass percentage.

[0098] Comparative Example 4

[0099] The preparation method and raw materials of Comparative Example 4 were the same as those of Example 1, except that the ratio of the raw materials in the hot melt adhesive was different from that in Example 1. The hot melt adhesive comprised 20% polyurethane resin, 0.5% epoxy resin, 20.5% flame retardant, 2% titanium dioxide, and 57% solvent, calculated by mass percentage.

[0100] Comparative Example 5

[0101] The preparation method and raw materials of Comparative Example 5 were the same as those of Example 1, except that the ratio of the raw materials in the hot melt adhesive was different from that in Example 1. The hot melt adhesive comprised 20% polyurethane resin, 2.5% epoxy resin, 18.5% flame retardant, 2% titanium dioxide, and 57% solvent, calculated by mass percentage.

[0102] The hot melt adhesive films prepared in the above examples and comparative examples were subjected to performance tests, and the specific test results are shown in Table 1 below:

[0103] Table 1 Test results of relevant properties of hot melt adhesive film

[0104] From the test results in Table 1, it can be seen that compared with the hot melt adhesive in the prior art of Comparative Example 1, the hot melt adhesive film prepared by the present technical solution has excellent hot pressing bonding performance and adhesion performance. On the one hand, it ensures that it can be used in high humidity and heat environments. On the other hand, it also ensures that it can effectively wrap tinned flat copper wire, reducing the difficulty of preparing automotive FFC wire.

[0105] In Comparative Example 2, due to the low amount of polyurethane resin added, the hot melt adhesive film has excessive high-temperature fluidity at the hot pressing temperature and pressure, making it difficult to effectively wrap the tinned flat copper wire. At the same time, it will also lead to a decrease in the bonding performance of the hot melt adhesive film to the tinned flat copper wire.

[0106] In Comparative Example 3, due to the excessive addition of polyurethane resin, the hot melt adhesive film has too low high-temperature fluidity under the hot pressing bonding temperature and hot pressing bonding pressure, making it difficult to effectively wrap the tinned flat copper wire. At the same time, it will also cause the bonding performance of the hot melt adhesive film to the tinned flat copper wire to be reduced.

[0107] In Comparative Example 4, since the amount of epoxy resin added is too small, its effect on improving the bonding performance of the hot melt adhesive film is limited, which will lead to a decrease in the bonding performance of the hot melt adhesive film.

[0108] In Comparative Example 5, due to the excessive addition of epoxy resin, the softening point of the hot melt adhesive film is greatly reduced, and its hot pressing bonding performance cannot be guaranteed. At the same time, it will also lead to a decrease in the bonding performance of the hot melt adhesive film to the tinned flat copper wire.

[0109] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and are not to be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will readily conceive of other specific embodiments of the present invention without inventive effort, and such embodiments will fall within the scope of protection of the present invention.

Claims

1. A hot melt adhesive film for vehicle FFC wire harness, characterized in that: It includes a base material and a hot melt adhesive layer connected in sequence from bottom to top, and the hot melt adhesive layer is coated on the upper surface of the base material by hot melt adhesive; Calculated by mass percentage, the hot melt adhesive includes 18-22% of polyurethane resin, 1-2% of epoxy resin, 18-25% of flame retardant, 1-2% of titanium dioxide and 50-60% of solvent; among them, the softening point of the polyurethane resin is 180°C - 200°C.

2. The hot melt adhesive film of a vehicle FFC wire according to claim 1, characterized in that: The molecular weight of the epoxy resin is 1000 - 3000.

3. The hot melt adhesive film of a vehicle FFC wire according to claim 1, wherein: The polyurethane includes at least one of polycaprolactone type polyurethane, polyhydroxyalkanoate type polyurethane and polyaliphatic ester type polyurethane.

4. The hot melt adhesive film for a vehicle FFC wire according to claim 2, characterized in that: The epoxy resin includes at least one of E44 epoxy resin and E51 epoxy resin.

5. The hot melt adhesive film for a vehicle FFC wire according to claim 1, characterized in that: The base material is a PET film; The thickness of the PET film is 25 - 50μm; the thickness of the hot melt adhesive layer is 18 - 20μm.

6. The hot melt adhesive film for a vehicle FFC wire according to claim 1, characterized in that: The flame retardant includes at least one of decabromodiphenylethane, antimony trioxide, octabromoether, nitrogen-based flame retardant, phosphorus-based flame retardant, magnesium hydroxide and aluminum hydroxide.

7. The hot melt adhesive film for a vehicle FFC wire according to claim 1, wherein: The titanium dioxide is at least one of rutile type titanium dioxide, anatase type titanium dioxide or brookite type titanium dioxide.

8. The hot melt adhesive film of a vehicle - used FFC wire according to claim 1, characterized in that: The solvent includes at least one of methyl acetate, ethyl acetate, phenyl acetate, methyl benzoate, butyl acetate and octyl acrylate.

9. A preparation method of a hot melt adhesive film for a vehicle-used FFC wire harness, characterized in that: A hot melt adhesive film for preparing a vehicle FFC wire harness according to any one of claims 1 - 8, comprising the following steps: A. Mix and disperse the formulated amounts of polyurethane resin, epoxy resin and solvent evenly, and add the formulated amounts of flame retardant and titanium dioxide during the dispersion process, and obtain a hot melt adhesive after grinding; B. Perform corona treatment on the base material, and coat the hot melt adhesive obtained in step A on the corona-treated base material to form a hot melt adhesive layer, thereby obtaining a hot melt adhesive film for a vehicle FFC wire harness.

10. The preparation method of a hot melt adhesive film for a vehicle FFC wire according to claim 9, characterized in that: In step B, the corona current in the corona treatment step is 3 - 5A.

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