A needle-punched, resin-impregnated, reinforced composite adhesive material and method of making the same

Abstract

This invention relates to the field of polymer composite materials technology, specifically to a needle-punched and impregnated reinforced composite adhesive material and its preparation method. The needle-punched and impregnated reinforced composite adhesive material is formed by first needle-punching natural fibers and chemical fibers to create a nonwoven substrate, which is then impregnated in an adhesive. A second needle-punching is then performed while the adhesive is still uncured, followed by drying and curing. The adhesive contains a waterborne polyurethane / acrylate hybrid and an adhesion promoter whose molecules simultaneously contain trimethoxysilylpropyl, phosphonic acid, secondary amino, and hydroxyl groups. This invention, by designing and introducing an adhesion promoter, significantly improves the initial adhesion of the needle-punched and impregnated reinforced composite adhesive material to commonly used automotive substrates such as aluminum alloys and polyurethane foams, as well as its adhesion durability after thermal cycling, effectively avoiding failure problems such as delamination and blistering.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a needle-punched and impregnated reinforced composite adhesive material and its preparation method. Background Technology

[0002] With the development of lightweight, environmentally friendly, and high-end automotive interiors, higher demands are being placed on the comprehensive performance of interior materials. Needle-punched nonwoven fabrics, due to their advantages such as high designability, sound absorption and heat insulation, lightweight and environmental friendliness, are often combined with dissimilar substrates such as aluminum alloy skeletons and polyurethane foams to manufacture multi-layer structural components such as door panels, dashboards, and seats. However, reliable bonding between these dissimilar materials is a key challenge in achieving structural integration and long-term durability.

[0003] Currently, the industry commonly uses waterborne adhesives such as waterborne polyurethane, acrylate, or their blends for impregnation and lamination to balance performance and environmental requirements. However, traditional waterborne adhesive systems often suffer from insufficient interfacial adhesion when simultaneously bonding multiple substrates with significant differences in surface energy and chemical properties. Especially in automotive environments, materials are subjected to long-term thermal cycling, vibration, and humidity changes, which can easily lead to interfacial failure, resulting in delamination, blistering, or detachment, severely impacting the safety, aesthetics, and lifespan of components. Summary of the Invention

[0004] The purpose of this invention is to provide a needle-punched and impregnated reinforced composite adhesive material and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a needle-punched and impregnated reinforced composite adhesive material, wherein the needle-punched and impregnated reinforced composite adhesive material is formed by first needle punching natural fibers and chemical fibers to form a non-woven substrate, then impregnating it in an adhesive, subsequently performing a second needle punching in the uncured state of the adhesive, and finally drying and curing to obtain the final product;

[0006] The adhesive comprises the following components by mass percentage: 40%–60% waterborne polyurethane / acrylate hybrid, 0.3%–0.6% adhesion promoter, 3%–8% pigments and fillers, 2%–5% film-forming aid, 0.5%–2.0% crosslinking agent, 0.1%–0.5% wetting and leveling agent, and the balance being deionized water;

[0007] The adhesion promoter is an organic compound containing trimethoxysilylpropyl, phosphonic acid, secondary amino, and hydroxyl groups in its molecule, wherein the trimethoxysilylpropyl and phosphonic acid groups are linked by alkylene chains containing secondary amino and hydroxyl groups.

[0008] Optionally, the natural fiber is selected from at least one of flax fiber, jute fiber, sisal fiber, or coconut shell fiber, and the chemical fiber is selected from at least one of polyester fiber, polypropylene fiber, low melting point copolyester fiber, or polylactic acid fiber; the mass ratio of the natural fiber to the chemical fiber is (30-70):(70-30).

[0009] Optionally, the method for preparing the adhesion promoter includes the following steps:

[0010] (1) Take 100 parts by weight of 3-glycidoxypropyltrimethoxysilane and mix it with 680 to 700 parts by weight of anhydrous 2-methyltetrahydrofuran. Stir at 22 to 27°C until the system is homogeneous to prepare a silane solution.

[0011] (2) Under a nitrogen protective atmosphere, 52-55 parts by mass of 2-aminoethylphosphonic acid were added to a dry reaction vessel. The reaction temperature was controlled at 22-27°C and the stirring rate was 60-90 rpm. The silane solution was slowly added dropwise. After the addition was completed, the reaction was continued for 1.5-2.5 h under the same temperature and stirring conditions to obtain a homogeneous reaction solution.

[0012] (3) Cool the homogeneous reaction solution in an ice bath at 2-5°C. First, adjust the pH of the system to 1.8-2.2 with an 8-10 wt% hydrochloric acid aqueous solution cooled in an ice bath. Then, slowly raise the temperature to 22-27°C and stir at 120-180 rpm for 40-60 min. Then, adjust the pH to 6.0-6.5 with a saturated sodium bicarbonate solution. Extract with ethyl acetate. Collect the organic phase and filter it through 0.45 μm and 0.22 μm polytetrafluoroethylene filter membranes in sequence. Finally, place it in a vacuum distillation apparatus and distill it under vacuum at 45-55°C and -0.08--0.10 MPa to obtain the concentrated product.

[0013] (4) Add 0.05% to 0.10% of disodium ethylenediaminetetraacetate and 0.01% to 0.04% of 2,6-di-tert-butyl-p-cresol by mass to the concentrated product, stir evenly, and then filter through a 0.45 μm polytetrafluoroethylene filter membrane to obtain a light yellow transparent liquid, which is the adhesion promoter.

[0014] Optionally, based on a total mass of 100 parts of pigments and fillers, the pigments and fillers include the following components: 63.0 to 79.5 parts of titanium dioxide, 20 to 35 parts of zinc phosphate, and 0.5 to 2.0 parts of zinc phytate;

[0015] The preparation method of the pigment and filler includes the following steps: dissolving zinc phytate in ethanol or isopropanol to prepare a zinc phytate alcohol solution with a concentration of 10-20 wt%; spraying the zinc phytate alcohol solution into a mixed powder of titanium dioxide and zinc phosphate under stirring; vacuum drying at 60-80℃ for 2-4 h, and then pulverizing by airflow to D50≤0.5 μm to obtain the pigment and filler.

[0016] Optionally, the film-forming aid is any one of dipropylene glycol methyl ether, dipropylene glycol butyl ether, or 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate.

[0017] Optionally, the crosslinking agent is an aziridine crosslinking agent or a carbodiimide crosslinking agent.

[0018] Optionally, the wetting and leveling agent is a polyether-modified polysiloxane or a fluorocarbon-modified acrylic copolymer.

[0019] On the other hand, the present invention provides the following technical solution: the preparation method of the above-mentioned needle-punched and impregnated reinforced composite adhesive material includes the following steps:

[0020] S1. Natural fibers and chemical fibers are mixed in a certain proportion, and after opening, carding and web laying, a web is formed with a basis weight of 200-800 g / m². 2 Fiber webs with a thickness of 1–5 mm;

[0021] S2. Perform the first needle punching on the fiber web, controlling the needle punching density to be 300-800 needles / in. 2 The needle-punching depth is 8-15 mm to obtain a nonwoven substrate;

[0022] S3. The nonwoven substrate is impregnated in the adhesive by a two-roller impregnation method, and the liquid content is controlled to be 80% to 150%. The impregnated nonwoven substrate is pre-dried at 50 to 60°C until no free adhesive drips from the surface but the adhesive has not yet cross-linked and cured.

[0023] S4. In the uncrosslinked and uncured state of the adhesive, the pre-dried nonwoven substrate is subjected to a second needle-punching treatment, with the needle-punching density controlled at 50-250 needles / in. 2 The needle insertion depth is 3–8 mm;

[0024] S5. The nonwoven substrate after the second needle punching is first dried at 90-110℃ for 3-8 min, and then heat-cured and dried at 130-150℃ for 10-20 min to obtain the needle-punched and impregnated reinforced composite adhesive material.

[0025] Optionally, the needle used for the first acupuncture is of type #36 to #40; the needle used for the second acupuncture is of type #40 to #42.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention designs and introduces a multifunctional adhesion promoter containing trimethoxysilylpropyl, phosphonic acid, secondary amino, and hydroxyl groups in its molecule. This promoter significantly improves the initial adhesion of needle-punched and impregnated composite adhesive materials to commonly used automotive substrates such as aluminum alloys and polyurethane foams in waterborne polyurethane / acrylate hybrid adhesive systems, as well as the adhesion durability after thermal cycling, effectively avoiding failure problems such as delamination and blistering.

[0028] 2. This invention sprays zinc phytate in the form of ethanol or isopropanol solution onto the surface of a mixture of titanium dioxide and zinc phosphate pigments and fillers, and combines vacuum drying and airflow ultrafine grinding processes to form a uniform and stable active coating layer on the surface of the pigment and filler particles. This not only improves the dispersibility and storage stability of highly filled pigments and fillers in aqueous systems, but also allows the polyphosphonic acid structure in its molecules to chelate with the metal substrate, synergistically releasing corrosion-inhibiting ions with zinc phosphate, thus achieving a dual anti-corrosion mechanism of physical barrier and chemical passivation, significantly improving the long-term performance of the material in harsh environments such as humidity and salt spray.

[0029] 3. The needle-punched and impregnated reinforced composite adhesive material prepared by this invention has excellent initial tack, peel strength and tensile strength. The material has good flexibility and strong impact resistance, and can withstand cold bending, hot pressing and assembly stress in automobile manufacturing. It effectively overcomes the defects of traditional nonwoven composite materials, such as easy cracking, insufficient adhesion or weak cohesion. At the same time, the product adopts a natural fiber and water-based adhesive system, with low VOC emissions and good recyclability, which is in line with the development trend of automotive lightweighting and green manufacturing. It is an ideal high-performance adhesive composite material for automotive parts such as door panel liners, headliner substrates, trunk liners and other lightweight building materials. Attached Figure Description

[0030] Figure 1 The chemical structural formula of the adhesion promoter of this invention is shown below;

[0031] Figure 2 The Fourier transform infrared spectrum of the adhesion promoter prepared in Example 1;

[0032] Figure 3 The adhesion promoter prepared in Example 1 1 H NMR spectrum (D2O, 400 MHz);

[0033] Figure 4 The adhesion promoter prepared in Example 1 31 P NMR spectrum (D2O, 162 MHz). Detailed Implementation

[0034] 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.

[0035] Example 1

[0036] This embodiment provides a needle-punched and impregnated reinforced composite adhesive material. The material is made by first needle-punching natural fibers and chemical fibers to form a nonwoven substrate, which is then impregnated in an adhesive. A second needle-punching is then performed while the adhesive is still uncured, followed by drying and curing. The natural fiber is flax fiber, and the chemical fiber is polyester fiber, with a mass ratio of 60:40.

[0037] The adhesive comprises the following components by mass percentage: 55.0% waterborne polyurethane / acrylate hybrid, 0.5% adhesion promoter, 6.0% pigments and fillers, 4.0% dipropylene glycol methyl ether, 1.8% aziridine crosslinking agent, 0.3% polyether-modified polysiloxane, and the balance being deionized water.

[0038] Figure 1 The chemical structural formula of the adhesion promoter of the present invention is shown below. The adhesion promoter is an organic compound containing trimethoxysilylpropyl, phosphonic acid, secondary amino, and hydroxyl groups in its molecule, wherein the trimethoxysilylpropyl and phosphonic acid groups are linked by alkylene chains containing secondary amino and hydroxyl groups. The preparation method of the adhesion promoter includes the following steps:

[0039] (1) Take 100 parts by weight of 3-glycidoxypropyltrimethoxysilane and mix it with 690 parts by weight of anhydrous 2-methyltetrahydrofuran. Stir at 25°C until the system is homogeneous to prepare a silane solution.

[0040] (2) Under a nitrogen protective atmosphere, 53 parts by mass of 2-aminoethylphosphonic acid were added to a dry reaction vessel. The reaction temperature was controlled at 25°C and the stirring rate was 75 rpm. Silane solution was slowly added dropwise. After the addition was completed, the reaction was continued for 2.0 h under the same temperature and stirring conditions to obtain a homogeneous reaction solution.

[0041] (3) The homogeneous reaction solution was cooled in an ice bath at 4°C. The pH of the system was first adjusted to 2.0 with a 10 wt% hydrochloric acid aqueous solution cooled in an ice bath. Then the temperature was slowly increased to 25°C and stirred at 150 rpm for 45 min. The pH was then adjusted to 6.2 with a saturated sodium bicarbonate solution. The solution was extracted with ethyl acetate. The organic phase was collected and filtered through 0.45 μm and 0.22 μm polytetrafluoroethylene filter membranes in sequence. Finally, the solution was placed in a vacuum distillation apparatus and distilled under vacuum at 50°C and -0.09 MPa to obtain the concentrated product.

[0042] (4) Add 0.075% by mass of disodium ethylenediaminetetraacetate and 0.025% by mass of 2,6-di-tert-butyl-p-cresol to the concentrated product, stir evenly, and then filter through a 0.45 μm polytetrafluoroethylene filter membrane to obtain a light yellow transparent liquid, which is the adhesion promoter.

[0043] The pigment and filler comprise the following components: 71 parts titanium dioxide, 27.5 parts zinc phosphate, and 1.5 parts zinc phytate. The preparation method of the pigment and filler includes the following steps: dissolving zinc phytate in ethanol to prepare a 15 wt% zinc phytate alcohol solution; spraying the zinc phytate alcohol solution into the mixed powder of titanium dioxide and zinc phosphate under stirring; vacuum drying at 70°C for 3 h, and then pulverizing by air jet to D50≤0.5 μm to obtain the pigment and filler.

[0044] The method for preparing the adhesive includes the following steps:

[0045] S1. Add deionized water to the dispersion vessel, add dipropylene glycol methyl ether and polyether-modified polysiloxane sequentially while stirring at 300 rpm, stir for 15 min until uniform, then slowly add pigments and fillers while stirring at 450 rpm, then increase the speed to 1000 rpm and disperse for 45 min to obtain pigment and filler slurry.

[0046] S2. Add the waterborne polyurethane / acrylate hybrid to the pigment and filler slurry and stir at 500 rpm for 25 min to obtain the base material;

[0047] S3. While stirring at 400 rpm, slowly add the adhesion promoter and aziridine crosslinking agent to the base material, continue stirring until the system is uniform, let it stand to defoam, and then filter it through a 150-mesh filter to obtain the adhesive.

[0048] This embodiment also provides a method for preparing the above-mentioned needle-punched and impregnated reinforced composite adhesive material, including the following steps:

[0049] S1. Natural fibers and chemical fibers are mixed in a certain proportion, and after opening, carding and web laying, a web is formed with a basis weight of 500 g / m². 2 A fiber mesh with a thickness of 3 mm;

[0050] S2. Perform the first needle punching on the fiber web, controlling the needle punching density to 600 needles / in. 2 A nonwoven substrate was obtained by using a needle penetration depth of 10 mm and a needle type of #38.

[0051] S3. The nonwoven substrate is impregnated in the adhesive by a two-roller impregnation method, the liquid coverage is controlled at 120%, and the impregnated nonwoven substrate is pre-dried at 55°C until no free adhesive drips from the surface but the adhesive has not yet cross-linked and cured.

[0052] S4. Before the adhesive has cross-linked and cured, perform a second needle-punching treatment on the pre-dried nonwoven substrate, controlling the needle-punching density to be 150 needles / in. 2 The needle insertion depth is 5 mm, and the needle type is #41.

[0053] S5. The nonwoven substrate after the second needle punching is dried at 100℃ for 5 min, and then heat-cured and dried at 140℃ for 15 min to obtain the needle-punched and impregnated reinforced composite adhesive material.

[0054] Example 2

[0055] This embodiment provides a needle-punched and impregnated reinforced composite adhesive material. The material is made by first needle-punching natural fibers and chemical fibers to form a nonwoven substrate, which is then impregnated in an adhesive. A second needle-punching is then performed while the adhesive is still uncured, followed by drying and curing. The natural fiber is jute fiber, and the chemical fiber is polylactic acid fiber, with a mass ratio of 50:50.

[0056] The adhesive comprises the following components by mass percentage: 40.0% waterborne polyurethane / acrylate hybrid, 0.3% adhesion promoter, 8.0% pigments and fillers, 4.0% dipropylene glycol butyl ether, 0.5% aziridine crosslinking agent, 0.1% fluorocarbon modified acrylic copolymer, and the balance being deionized water.

[0057] The preparation method of the adhesion promoter includes the following steps:

[0058] (1) Take 100 parts by weight of 3-glycidoxypropyltrimethoxysilane and mix it with 680 parts by weight of anhydrous 2-methyltetrahydrofuran. Stir at 22°C until the system is homogeneous to prepare a silane solution.

[0059] (2) Under a nitrogen protective atmosphere, 52 parts by mass of 2-aminoethylphosphonic acid were added to a dry reaction vessel. The reaction temperature was controlled at 22°C and the stirring rate was 60 rpm. Silane solution was slowly added dropwise. After the addition was completed, the reaction was continued for 1.5 h under the same temperature and stirring conditions to obtain a homogeneous reaction solution.

[0060] (3) The homogeneous reaction solution was cooled in an ice bath at 2°C. The pH of the system was first adjusted to 1.8 with an 8 wt% hydrochloric acid aqueous solution cooled in an ice bath. Then the temperature was slowly increased to 22°C and stirred at 120 rpm for 40 min. The pH was then adjusted to 6.0 with a saturated sodium bicarbonate solution. The solution was extracted with ethyl acetate. The organic phase was collected and filtered through 0.45 μm and 0.22 μm polytetrafluoroethylene filter membranes in sequence. Finally, the solution was placed in a vacuum distillation apparatus and distilled under vacuum at 45°C and -0.08 MPa to obtain the concentrated product.

[0061] (4) Add 0.05% by mass of disodium ethylenediaminetetraacetate and 0.01% by mass of 2,6-di-tert-butyl-p-cresol to the concentrated product, stir evenly, and then filter through a 0.45 μm polytetrafluoroethylene filter membrane to obtain a light yellow transparent liquid, which is the adhesion promoter.

[0062] The pigment and filler comprise the following components: 63.0 parts titanium dioxide, 35 parts zinc phosphate, and 2.0 parts zinc phytate. The preparation method of the pigment and filler includes the following steps: dissolving zinc phytate in ethanol to prepare a 10 wt% zinc phytate alcohol solution; spraying the zinc phytate alcohol solution into the mixed powder of titanium dioxide and zinc phosphate under stirring; vacuum drying at 60℃ for 2 h, and then pulverizing by air jet to D50≤0.5 μm to obtain the pigment and filler.

[0063] The method for preparing the adhesive includes the following steps:

[0064] S1. Add deionized water to the dispersion vessel, add dipropylene glycol butyl ether and fluorocarbon modified acrylic copolymer in sequence under stirring at 200 rpm, stir for 10 min until uniform, then slowly add pigments and fillers under stirring at 300 rpm, then increase the speed to 800 rpm and disperse for 30 min to obtain pigment and filler slurry.

[0065] S2. Add the waterborne polyurethane / acrylate hybrid to the pigment and filler slurry and stir at 400 rpm for 20 min to obtain the base material;

[0066] S3. While stirring at 300 rpm, slowly add the adhesion promoter and aziridine crosslinking agent to the base material, continue stirring until the system is uniform, let it stand to defoam, and then filter it through a 100-mesh filter to obtain the adhesive.

[0067] Furthermore, this embodiment also provides a method for preparing the above-mentioned needle-punched impregnation-reinforced composite adhesive material, including the following steps:

[0068] S1. Natural fibers and chemical fibers are mixed in a certain proportion, and after opening, carding and web laying, a web is formed with a basis weight of 200 g / m². 2 A fiber mesh with a thickness of 1 mm;

[0069] S2. Perform the first needle punching on the fiber web, controlling the needle punching density to 300 needles / in. 2 A nonwoven substrate was obtained by using a needle punching depth of 8 mm and a needle type of #36.

[0070] S3. The nonwoven substrate is impregnated in the adhesive by a two-roller impregnation method, the liquid content is controlled at 80%, and the impregnated nonwoven substrate is pre-dried at 50°C until no free adhesive drips from the surface but the adhesive has not yet cross-linked and cured.

[0071] S4. Before the adhesive has cross-linked and cured, perform a second needle-punching treatment on the pre-dried nonwoven substrate, controlling the needle-punching density to 50 needles / in. 2 The needle insertion depth is 3 mm, and the needle type is #40.

[0072] S5. The nonwoven substrate after the second needle punching is dried at 90℃ for 8 min, and then heat-cured and dried at 130℃ for 20 min to obtain the needle-punched and impregnated reinforced composite adhesive material.

[0073] Example 3

[0074] This embodiment provides a needle-punched and impregnated reinforced composite adhesive material. The material is made by first needle-punching natural fibers and chemical fibers to form a nonwoven substrate, which is then impregnated in an adhesive. A second needle-punching is then performed while the adhesive is still uncured, followed by drying and curing. The natural fiber is sisal fiber, and the chemical fiber is polypropylene fiber, with a mass ratio of natural fiber to chemical fiber of 30:70.

[0075] The adhesive comprises the following components by mass percentage: 60.0% waterborne polyurethane / acrylate hybrid, 0.4% adhesion promoter, 3.0% pigments and fillers, 2.0% 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, 1.0% carbodiimide crosslinking agent, 0.5% polyether-modified polysiloxane, and the balance being deionized water.

[0076] The preparation method of the adhesion promoter includes the following steps:

[0077] (1) Take 100 parts by weight of 3-glycidoxypropyltrimethoxysilane and mix it with 700 parts by weight of anhydrous 2-methyltetrahydrofuran. Stir at 27°C until the system is homogeneous to prepare a silane solution.

[0078] (2) Under a nitrogen protective atmosphere, 55 parts by mass of 2-aminoethylphosphonic acid were added to a dry reaction vessel. The reaction temperature was controlled at 27°C and the stirring rate was 90 rpm. Silane solution was slowly added dropwise. After the addition was completed, the reaction was continued for 2.5 h under the same temperature and stirring conditions to obtain a homogeneous reaction solution.

[0079] (3) Cool the homogeneous reaction solution in an ice bath at 2-5°C. First, adjust the pH of the system to 2.2 with a 10 wt% hydrochloric acid aqueous solution cooled in an ice bath. Then, slowly raise the temperature to 27°C and stir at 180 rpm for 60 min. Then, adjust the pH to 6.5 with a saturated sodium bicarbonate solution. Extract with ethyl acetate. Collect the organic phase and filter it through 0.45 μm and 0.22 μm polytetrafluoroethylene filter membranes in sequence. Finally, place it in a vacuum distillation apparatus and distill it under vacuum at 55°C and -0.10 MPa to obtain the concentrated product.

[0080] (4) Add 0.10% by mass of disodium ethylenediaminetetraacetate and 0.04% by mass of 2,6-di-tert-butyl-p-cresol to the concentrated product, stir evenly, and filter through a 0.45 μm polytetrafluoroethylene filter membrane to obtain a light yellow transparent liquid, which is the adhesion promoter.

[0081] The pigment and filler comprises the following components: 79.5 parts titanium dioxide, 20 parts zinc phosphate, and 0.5 parts zinc phytate. The preparation method of the pigment and filler includes the following steps: dissolving zinc phytate in isopropanol to prepare a 20 wt% zinc phytate alcohol solution; spraying the zinc phytate alcohol solution into the mixed powder of titanium dioxide and zinc phosphate under stirring; vacuum drying at 80℃ for 4 h, and then pulverizing by air jet to D50≤0.5 μm to obtain the pigment and filler.

[0082] The method for preparing the adhesive includes the following steps:

[0083] S1. Add deionized water to a dispersion vessel, and add 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate and polyether-modified polysiloxane sequentially while stirring at 400 rpm. Stir for 20 min until homogeneous, then slowly add pigments and fillers while stirring at 600 rpm. Increase the speed to 1200 rpm and disperse for 60 min to obtain a pigment and filler slurry.

[0084] S2. Add the waterborne polyurethane / acrylate hybrid to the pigment and filler slurry and stir at 600 rpm for 30 min to obtain the base material;

[0085] S3. While stirring at 500 rpm, slowly add the adhesion promoter and carbodiimide crosslinking agent to the base material, continue stirring until the system is uniform, let it stand to defoam, and then filter it through a 200-mesh filter to obtain the adhesive.

[0086] Furthermore, this embodiment also provides a method for preparing the above-mentioned needle-punched impregnation-reinforced composite adhesive material, including the following steps:

[0087] S1. Natural fibers and chemical fibers are mixed in a certain proportion, and after opening, carding and web laying, a web is formed with a basis weight of 800 g / m². 2 A fiber mesh with a thickness of 5 mm;

[0088] S2. Perform the first needle punching on the fiber web, controlling the needle punching density to 800 needles / in. 2 A nonwoven substrate was obtained by using a needle penetration depth of 15 mm and a needle type of #40.

[0089] S3. The nonwoven substrate is impregnated in the adhesive by a two-roller impregnation method, the liquid coverage is controlled at 150%, and the impregnated nonwoven substrate is pre-dried at 60°C until no free adhesive drips from the surface but the adhesive has not yet cross-linked and cured.

[0090] S4. Before the adhesive has cross-linked and cured, perform a second needle-punching treatment on the pre-dried nonwoven substrate, controlling the needle-punching density to be 250 needles / in. 2 The needle depth is 8 mm and the needle type is #42;

[0091] S5. The nonwoven substrate after the second needle punching is dried at 110°C for 3 min, and then heat-cured and dried at 150°C for 10 min to obtain the needle-punched and impregnated reinforced composite adhesive material.

[0092] Example 4

[0093] This embodiment provides a needle-punched and impregnated reinforced composite adhesive material. The material is made by first needle-punching natural fibers and chemical fibers to form a nonwoven substrate, which is then impregnated in an adhesive. A second needle-punching is then performed while the adhesive is still uncured, followed by drying and curing. The natural fiber is coconut shell fiber, and the chemical fiber is selected from low-melting-point copolyester fiber. The mass ratio of natural fiber to chemical fiber is 70:30.

[0094] The adhesive comprises the following components by mass percentage: 50.0% waterborne polyurethane / acrylate hybrid, 0.6% adhesion promoter, 5.0% pigments and fillers, 3.5% dipropylene glycol methyl ether, 1.5% carbodiimide crosslinking agent, 0.2% fluorocarbon modified acrylic copolymer, and the balance being deionized water.

[0095] The preparation method of the adhesion promoter includes the following steps:

[0096] (1) Take 100 parts by weight of 3-glycidoxypropyltrimethoxysilane and mix it with 685 parts by weight of anhydrous 2-methyltetrahydrofuran. Stir at 24°C until the system is homogeneous to prepare a silane solution.

[0097] (2) Under a nitrogen protective atmosphere, 53 parts by mass of 2-aminoethylphosphonic acid were added to a dry reaction vessel. The reaction temperature was controlled at 24°C and the stirring rate was 80 rpm. Silane solution was slowly added dropwise. After the addition was completed, the reaction was continued for 2.2 h under the same temperature and stirring conditions to obtain a homogeneous reaction solution.

[0098] (3) The homogeneous reaction solution was cooled in an ice bath at 3°C. The pH of the system was first adjusted to 2.1 with a 9 wt% hydrochloric acid aqueous solution cooled in an ice bath. Then the temperature was slowly increased to 24°C and stirred at 160 rpm for 55 min. The pH was then adjusted to 6.4 with a saturated sodium bicarbonate solution. The solution was extracted with ethyl acetate. The organic phase was collected and filtered through 0.45 μm and 0.22 μm polytetrafluoroethylene filter membranes in sequence. Finally, the solution was placed in a vacuum distillation apparatus and distilled under vacuum at 52°C and -0.085 MPa to obtain the concentrated product.

[0099] (4) Add 0.08% by mass of disodium ethylenediaminetetraacetate and 0.022% by mass of 2,6-di-tert-butyl-p-cresol to the concentrated product, stir evenly, and filter through a 0.45 μm polytetrafluoroethylene filter membrane to obtain a light yellow transparent liquid, which is the adhesion promoter.

[0100] The pigment and filler comprise the following components: 67.2 parts titanium dioxide, 32 parts zinc phosphate, and 1.8 parts zinc phytate. The preparation method of the pigment and filler includes the following steps: dissolving zinc phytate in isopropanol to prepare a zinc phytate alcohol solution with a concentration of 18 wt%; spraying the zinc phytate alcohol solution into the mixed powder of titanium dioxide and zinc phosphate under stirring; vacuum drying at 75°C for 2.5 h, and then pulverizing by air jet milling to D50≤0.5 μm to obtain the pigment and filler.

[0101] The method for preparing the adhesive includes the following steps:

[0102] S1. Add deionized water to the dispersion vessel, add dipropylene glycol methyl ether and fluorocarbon modified acrylic copolymer in sequence while stirring at 360 rpm, stir for 18 min until uniform, then slowly add pigments and fillers while stirring at 540 rpm, then increase the speed to 900 rpm and disperse for 45 min to obtain pigment and filler slurry.

[0103] S2. Add the waterborne polyurethane / acrylate hybrid to the pigment and filler slurry and stir at 540 rpm for 25 min to obtain the base material;

[0104] S3. While stirring at 420 rpm, slowly add the adhesion promoter and carbodiimide crosslinking agent to the base material, continue stirring until the system is uniform, let it stand to defoam, and then filter it through a 180-mesh filter to obtain the adhesive.

[0105] Furthermore, this embodiment also provides a method for preparing the above-mentioned needle-punched impregnation-reinforced composite adhesive material, including the following steps:

[0106] S1. Natural fibers and chemical fibers are mixed in a certain proportion, and after opening, carding and web laying, a web is formed with a basis weight of 600 g / m². 2 A fiber mesh with a thickness of 4 mm;

[0107] S2. Perform the first needle punching on the fiber web, controlling the needle punching density to 600 needles / in. 2 A nonwoven substrate was obtained by using a needle penetration depth of 12 mm and a needle type of #39.

[0108] S3. The nonwoven substrate is impregnated in the adhesive by a two-roller impregnation method, the liquid coverage is controlled at 130%, and the impregnated nonwoven substrate is pre-dried at 58°C until no free adhesive drips from the surface but the adhesive has not yet cross-linked and cured.

[0109] S4. Before the adhesive has cross-linked and cured, perform a second needle-punching treatment on the pre-dried nonwoven substrate, controlling the needle-punching density to be 200 needles / in. 2 The needle depth is 6 mm and the needle type is #42;

[0110] S5. The nonwoven substrate after the second needle punching is dried at 105℃ for 4 min, and then heat-cured and dried at 145℃ for 12 min to obtain the needle-punched and impregnated reinforced composite adhesive material.

[0111] Compare with Example 1

[0112] It is basically the same as Example 1, except that the adhesion promoter is replaced with an equal amount of deionized water.

[0113] Compare with Example 2

[0114] The example is essentially the same as Example 1, except that the adhesion promoter is replaced with an equal amount of 3-glycidoxypropyltrimethoxysilane.

[0115] Compare with Example 3

[0116] The process is basically the same as in Example 1, except that the pigments and fillers are made by directly and physically mixing titanium dioxide, zinc phosphate and zinc phytate in the same proportion, without alcohol solution spraying and vacuum drying.

[0117] Test Example 1: Adhesion and Adhesion Retention Performance After Thermal Cycling

[0118] 1. Test materials

[0119] (1) Substrate

[0120] Standard aluminum foil: 30 μm thick, surface degreased by acetone wiping and air-dried naturally;

[0121] Polyurethane foam material: density 30 kg / m³ 3 The surface is corona treated, and the surface tension is 48 mN / m.

[0122] (2) Coating samples

[0123] The adhesives prepared in Examples 1-4 and Comparative Examples 1-3.

[0124] 2. Experimental Content and Methods

[0125] (1) Coating preparation

[0126] The coating samples were uniformly coated on the surfaces of the two substrates mentioned above and dried in an oven at 60℃ for 2 hours to form a dry film. The thickness of the dry film was measured using an eddy current thickness gauge, and a dry film thickness of 35±3 μm was taken as qualified. The samples were then placed in an environment of 23℃ / 50% RH for 3 days as test samples for future use.

[0127] (2) Initial adhesion test

[0128] According to the test method published in GB / T 9286-2021, in an environment of 23℃ / 50% RH, first use a cross-cutting knife to cut out a grid of 1 mm × 1 mm (aluminum foil) or 2 mm × 2 mm (polyurethane foam) on the coating, then apply standard pressure-sensitive tape tightly and quickly tear it off vertically. Rating is based on grades 0 to 5. Each group of test samples is repeated 3 times and the average grade is taken.

[0129] (3) Adhesion test after thermal cycling

[0130] Another batch of test samples prepared in the same batch were placed in a high and low temperature alternating test chamber for thermal cycling treatment. The procedure was as follows: high temperature section: 40℃ / holding for 2 h; low temperature section: -30℃ / holding for 2 h; heating and cooling rate ≤3℃ / min; a total of 5 complete thermal cycles were completed.

[0131] After the cycle was completed, the sample was conditioned in an environment of 23℃ / 50% RH for 2 hours, and then the cross-cut adhesion test was performed in the same way as in (2) above. Each group was tested in parallel for 3 times, and the average grade was taken.

[0132] The test results are recorded in Table 1.

[0133] Table 1

[0134]

[0135] As shown in Table 1, the adhesives prepared in the examples exhibited good initial adhesion (grade 0-1) and excellent adhesion retention (grade 0-1) after thermal cycling on both aluminum foil and polyurethane foam substrates. Examples 1 and 4 showed the best performance, achieving grade 0 adhesion on both substrates without degradation after cycling. The control examples showed significantly poorer initial adhesion (grade 2-4), which further deteriorated to grade 3-5 after thermal cycling. This indicates that the multifunctional structure of the adhesion promoter and the pigment / filler spray coating with zinc phytate alcohol solution play a crucial role in improving the interfacial bonding between the coating and the aluminum foil / polyurethane foam, as well as its resistance to environmental aging.

[0136] Therefore, the needle-punched and impregnated reinforced composite adhesive material using the adhesive prepared in the examples not only possesses excellent cohesive strength and structural stability in practical applications, but also significantly improves the interfacial adhesion performance between the material and heterogeneous substrates such as aluminum alloy body panels and polyurethane foam core layers due to the presence of multifunctional adhesion promoters and zinc phytate-modified anti-corrosion pigments and fillers in the adhesive system. Even after experiencing harsh temperature alternation environments (such as -30°C to 40°C), it can still maintain high adhesion (0-1 grade), effectively avoiding delamination, bulging, or peeling failure. This characteristic makes the composite adhesive material of the present invention particularly suitable for the manufacture of lightweight automotive parts with high requirements for adhesion reliability, weather resistance, and environmental protection.

[0137] Experimental Example 2: Low Temperature Flexibility Test

[0138] 1. Test materials

[0139] Aluminum foil: 0.25 mm thick, surface degreased by acetone wiping and air-dried naturally;

[0140] The adhesives prepared in Examples 1-4 and Comparative Examples 1-3.

[0141] 2. Experimental Content and Methods

[0142] (1) Coating preparation: The adhesive is uniformly coated on the surface of the aluminum foil and dried in an oven at 60℃ for 2 h to form a dry film. The thickness of the dry film is measured by an eddy current thickness gauge. The thickness of the dry film is 35±3 μm as qualified. The film is placed in an environment of 23℃ / 50% RH for 3 days as a test sample.

[0143] (2) Flexibility test: According to the test method disclosed in GB / T 1731–2022, the coating surface is facing upward and bent 180° around cylindrical shafts with diameters of 2 mm, 3 mm, 4 mm and 5 mm in sequence. Observe whether the coating cracks or peels off. Judgment criteria: The smallest shaft diameter that does not produce visible cracks is used as the flexibility index. The smaller the diameter, the better the flexibility.

[0144] (3) Impact resistance test: According to the test method published in GB / T 1732-2022, a heavy hammer impact tester was used, with a fixed punch diameter of 8 mm. The impact was dropped freely from different heights (corresponding to impact energy: 10 kg·cm, 20 kg·cm, 30 kg·cm, 40 kg·cm, 50 kg·cm) to impact the back of the coating (substrate side), causing the coating to be stretched and deformed; the judgment standard was: the maximum impact energy (kg·cm) of the coating without cracking, peeling or obvious whitening was used as the impact resistance performance index.

[0145] The test results are recorded in Table 2.

[0146] Table 2

[0147]

[0148] As shown in Table 2, the adhesives in the examples all exhibited good flexibility and impact resistance. Examples 1 and 4 showed the best flexibility and an impact resistance of up to 50 kg·cm; Example 3 was second best, with an impact resistance of 45 kg·cm. Example 2, due to its lower resin content and higher proportion of pigments and fillers, had relatively lower flexibility and impact resistance. In contrast, the control examples, lacking a dedicated adhesion promoter or with ineffective surface treatment of pigments and fillers, suffered from weak coating cohesion and poor interfacial bonding, resulting in significantly reduced flexibility. The minimum shaft diameter was 4–5 mm, and the impact resistance was only 20–25 kg·cm, far lower than the examples. The results indicate that the synergistic effect of multifunctional adhesion promoters and zinc phytate-coated pigments and fillers can significantly improve the processing adaptability and mechanical reliability of the adhesives.

[0149] Therefore, the needle-punched and impregnated reinforced composite adhesive material using the adhesive prepared in the examples exhibits excellent low-temperature flexibility and impact resistance. The material is not prone to cracking, delamination, or loss of adhesion during bending, stamping, or assembly. It can withstand mechanical impacts during cold bending, hot pressing, and transportation and installation in automobile manufacturing, making it particularly suitable for automotive parts with stringent requirements for deformation adaptability and structural integrity, such as: complex curved interior parts, lightweight sandwich panels, and exterior auxiliary structural parts.

[0150] Experimental Example 3: Viscosity and Strength Properties Test

[0151] 1. Test materials

[0152] The needle-punched and impregnated reinforced composite adhesive materials prepared in Examples 1-4 and Comparative Example 2 were cut into test strips with a width of 25 mm and a length of 150 mm.

[0153] 2. Experimental Content and Methods

[0154] (1) Initial tack test: According to the test method disclosed in GB / T 4852-2002, the test strip is fixed horizontally on a standard inclined plate (inclination angle 30°), and the steel ball is released and rolled down from the top. The number of the largest steel ball that can be stuck to the test strip is recorded. Each group is tested 5 times and the average value is taken.

[0155] (2) 180° peel strength test: According to the test method published in GB / T 2792-2014, the test strip was bonded to a standard cold-rolled steel sheet at 23℃ and 50% RH, rolled back and forth twice with a 2 kg rubber roller, and allowed to stand for 20 min. Then, it was peeled at 180° at a speed of 300 mm / min on a universal testing machine. The peel force was recorded in N / 25 mm. Five parallel samples were tested in each group, and the average value was taken.

[0156] (3) Tensile strength test: According to the test method disclosed in GB / T 3923.1-2013, the test specimen was clamped in a universal testing machine, the tensile speed was 100 mm / min, and the maximum breaking strength was recorded in N / 25 mm. Five parallel specimens were tested in each group, and the average value was taken.

[0157] 3. The test results are recorded in Table 3.

[0158] Table 3

[0159]

[0160] As shown in Table 3, the needle-punched and impregnated reinforced composite adhesive material prepared in Example 1 exhibits excellent comprehensive performance in terms of initial tack, peel strength, and tensile strength. This indicates that by constructing a fiber web using flax fiber and polyester fiber at a mass ratio of 60:40, and combining it with appropriate basis weight, needle-punching density, and liquid retention, excellent interfacial adhesion characteristics can be achieved while ensuring good structural strength. In contrast, although Comparative Example 2 used the common silane coupling agent 3-glycidoxypropyltrimethoxysilane, it only contains epoxy and trimethoxysilane groups and lacks multiple functional groups such as phosphonic acid groups, secondary amino groups, and hydroxyl groups. This makes it difficult to simultaneously form synergistic chemical reactions with metal oxides, polyurethane foams, and waterborne hybrid resins, resulting in insufficient interfacial bonding and low coating cohesive strength. Compared to other examples, Example 1 achieves a better balance between adhesion and mechanical strength, making it particularly suitable for the manufacture of automotive interior parts where high requirements are placed on processing adaptability, bonding reliability, and cost control.

[0161] Depend on Figure 1 It can be seen that the Fourier transform infrared spectrum of the adhesion promoter provided by the present invention shows that: in the range of 3200–3500 cm⁻¹ -1The broad absorption band in region one, attributed to the stretching vibrations of OH and NH, indicates that the molecule contains both hydroxyl and secondary amino groups. Furthermore, at 1640 cm⁻¹... -1 The absorption peak at 1180 cm⁻¹ corresponds to the NH bending vibration of the secondary amine, further confirming the presence of the secondary amine; -1 A strong absorption peak was observed at 1050 cm⁻¹, which is attributed to the stretching vibration of the P=O bond in the phosphonic acid group, indicating that the phosphonic acid group is intact and preserved in the molecular structure; -1 and 850 cm -1 The characteristic absorption peaks appearing at the respective locations can be attributed to the asymmetric stretching vibration of Si-OC and the symmetric stretching vibration of Si-O-CH3, confirming that the molecule contains a trimethoxysilylpropyl structure.

[0162] The above results demonstrate that the Fourier transform infrared spectroscopy data fully prove that the adhesion promoter is an organosilicon phosphonic acid derivative that simultaneously contains trimethoxysilylpropyl, phosphonic acid, secondary amino, and hydroxyl groups.

[0163] Depend on Figure 2 It can be seen that the adhesion promoter provided by the present invention... 1 The 1H NMR spectrum showed a sharp, strong singlet in the δ = 3.3–3.5 ppm region, consistent with the characteristic signal of nine equivalent methoxy protons in the trimethoxysilane structure; multiplets were observed in the δ = 2.0–2.7 ppm region, which could be attributed to the ortho-methylene protons of the phosphonate group and the ortho-methylene protons of the amino group, respectively, and their splitting mode was consistent with the spin-spin coupling relationship between adjacent methylene groups; multiplets were observed in the δ = 3.5–4.0 ppm region, corresponding to the methine protons linked by the hydroxyl group, which was due to coupling by the methylene protons on both sides; in addition, multiple sets of coupling peaks appeared in the aliphatic region of δ < 2.0 ppm, and their splitting characteristics were consistent with the expected spin coupling mode of the propylsilane chain.

[0164] The above results show that the characteristic proton signals of all key structural units in the adhesion promoter molecule were clearly observed, and the chemical shift and splitting behavior are in line with theoretical expectations, further confirming the successful synthesis of the adhesion promoter.

[0165] secondary phosphonic acid (R-PO(OH)2) 31 The characteristic chemical shift range of P NMR is δ≈15~25 ppm. Figure 3 shown 31As seen in the 1NMR spectrum, the adhesion promoter provided by this invention exhibits a single, sharp characteristic signal peak at δ=19.29 ppm, which falls precisely within the typical chemical shift range of the secondary phosphonic acid group. This phenomenon indicates that the phosphonic acid group in the molecule is in a single chemical environment, and no characteristic signals of phosphate esters, phosphine oxides, or other phosphorus-containing byproducts were detected in the spectrum, fully confirming that the target product has been successfully synthesized with good purity and no obvious side reactions.

[0166] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A needle-punched and impregnated reinforced composite adhesive material, characterized in that, The needle-punched and impregnated reinforced composite adhesive material is made by first needle-punching natural fibers and chemical fibers to form a non-woven substrate, then impregnating it in an adhesive, then performing a second needle-punching while the adhesive is not cured, and finally drying and curing it. The adhesive comprises the following components by mass percentage: 40%–60% waterborne polyurethane / acrylate hybrid, 0.3%–0.6% adhesion promoter, 3%–8% pigments and fillers, 2%–5% film-forming aid, 0.5%–2.0% crosslinking agent, 0.1%–0.5% wetting and leveling agent, and the balance being deionized water; The adhesion promoter is an organic compound containing trimethoxysilylpropyl, phosphonic acid, secondary amino, and hydroxyl groups in its molecule, wherein the trimethoxysilylpropyl and phosphonic acid groups are linked by alkylene chains containing secondary amino and hydroxyl groups.

2. The needle-punched impregnation-reinforced composite adhesive material according to claim 1, characterized in that, The natural fiber is selected from at least one of flax fiber, jute fiber, sisal fiber, or coconut shell fiber, and the chemical fiber is selected from at least one of polyester fiber, polypropylene fiber, low melting point copolyester fiber, or polylactic acid fiber; the mass ratio of the natural fiber to the chemical fiber is (30-70):(70-30).

3. The needle-punched and impregnated reinforced composite adhesive material according to claim 1, characterized in that, The method for preparing the adhesion promoter includes the following steps: (1) Take 100 parts by weight of 3-glycidoxypropyltrimethoxysilane and mix it with 680 to 700 parts by weight of anhydrous 2-methyltetrahydrofuran. Stir at 22 to 27°C until the system is homogeneous to prepare a silane solution. (2) Under a nitrogen protective atmosphere, 52-55 parts by mass of 2-aminoethylphosphonic acid were added to a dry reaction vessel. The reaction temperature was controlled at 22-27°C and the stirring rate was 60-90 rpm. The silane solution was slowly added dropwise. After the addition was completed, the reaction was continued for 1.5-2.5 h under the same temperature and stirring conditions to obtain a homogeneous reaction solution. (3) Cool the homogeneous reaction solution in an ice bath at 2-5°C. First, adjust the pH of the system to 1.8-2.2 with an 8-10 wt% hydrochloric acid aqueous solution cooled in an ice bath. Then, slowly raise the temperature to 22-27°C and stir at 120-180 rpm for 40-60 min. Then, adjust the pH to 6.0-6.5 with a saturated sodium bicarbonate solution. Extract with ethyl acetate. Collect the organic phase and filter it through 0.45 μm and 0.22 μm polytetrafluoroethylene filter membranes in sequence. Finally, place it in a vacuum distillation apparatus and distill it under vacuum at 45-55°C and -0.08--0.10 MPa to obtain the concentrated product. (4) Add 0.05% to 0.10% of disodium ethylenediaminetetraacetate and 0.01% to 0.04% of 2,6-di-tert-butyl-p-cresol by mass to the concentrated product, stir evenly, and then filter through a 0.45 μm polytetrafluoroethylene filter membrane to obtain a light yellow transparent liquid, which is the adhesion promoter.

4. The needle-punched and impregnated reinforced composite adhesive material according to claim 1, characterized in that, Based on a total mass of 100 parts, the pigments and fillers include the following components: 63.0 to 79.5 parts of titanium dioxide, 20 to 35 parts of zinc phosphate, and 0.5 to 2.0 parts of zinc phytate; The preparation method of the pigment and filler includes the following steps: dissolving zinc phytate in ethanol or isopropanol to prepare a zinc phytate alcohol solution with a concentration of 10-20 wt%; spraying the zinc phytate alcohol solution into a mixed powder of titanium dioxide and zinc phosphate under stirring; vacuum drying at 60-80℃ for 2-4 h, and then pulverizing by airflow to D50≤0.5 μm to obtain the pigment and filler.

5. The needle-punched and impregnated reinforced composite adhesive material according to claim 1, characterized in that, The film-forming aid is any one of dipropylene glycol methyl ether, dipropylene glycol butyl ether, or 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate.

6. The needle-punched impregnation-reinforced composite adhesive material according to claim 1, characterized in that, The crosslinking agent is a aziridine crosslinking agent or a carbodiimide crosslinking agent.

7. The needle-punched and impregnated reinforced composite adhesive material according to claim 1, characterized in that, The wetting and leveling agent is a polyether-modified polysiloxane or a fluorocarbon-modified acrylic copolymer.

8. A method for preparing a needle-punched impregnation-reinforced composite adhesive material as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Natural fibers and chemical fibers are mixed in a certain proportion, and after opening, carding and web laying, a web is formed with a basis weight of 200-800 g / m². 2 Fiber webs with a thickness of 1–5 mm; S2. Perform the first needle punching on the fiber web, controlling the needle punching density to be 300-800 needles / in. 2 The needle-punching depth is 8-15mm to obtain a nonwoven substrate; S3. The nonwoven substrate is impregnated in the adhesive by a two-roller impregnation method, and the liquid content is controlled to be 80% to 150%. The impregnated nonwoven substrate is pre-dried at 50 to 60°C until no free adhesive drips from the surface but the adhesive has not yet cross-linked and cured. S4. In the uncrosslinked and uncured state of the adhesive, the pre-dried nonwoven substrate is subjected to a second needle-punching treatment, with the needle-punching density controlled at 50-250 needles / in. 2 The needle insertion depth is 3–8 mm; S5. The nonwoven substrate after the second needle punching is first dried at 90-110℃ for 3-8 min, and then heat-cured and dried at 130-150℃ for 10-20 min to obtain the needle-punched and impregnated reinforced composite adhesive material.

9. The method for preparing the needle-punched impregnation-reinforced composite adhesive material according to claim 8, characterized in that, The needles used for the first acupuncture were of type #36 to #40; the needles used for the second acupuncture were of type #40 to #42.

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