A high-heat-resistant hot melt adhesive screen for a vehicle and a method of manufacturing the same

Abstract

The application discloses a high-heat-resistance hot melt adhesive screen for vehicles and a preparation method thereof. The raw materials of the screen include the following components in mass fractions: 50-70 parts of high-melting-point copolyamide, 18-25 parts of low-melting-point copolyamide, 10-20 parts of copolyester, 0.3-1.5 parts of latent multifunctional epoxy chain extender, 2-6 parts of talcum powder, 0.1-0.5 parts of barium stearate, 1-5 parts of solid glass microbeads, 0.2-1.0 parts of oxidized paraffin soap, 0.3-0.8 parts of hindered phenolic antioxidant, 0.2-0.6 parts of phosphite antioxidant, 0.5-1.5 parts of polycarbodiimide hydrolysis-resistant agent and 0.2-0.5 parts of zinc stearate. The heat retention performance of the screen under the 80-90 DEG C vehicle exposure environment is remarkably improved through the component compounding, meanwhile, the screen retains good bonding properties for polar substrates such as leather, cloth and polyurethane foam, has low VOC volatilization, is not prone to yellowing and has good hydrolysis resistance.

Description

Technical Field

[0001] This invention relates to the field of hot melt adhesive bonding materials, and in particular to a high heat-resistant hot melt adhesive web for vehicles and its preparation method. Background Technology

[0002] Hot melt adhesive web is a type of hot melt adhesive material with a porous mesh structure. Compared to dense, thin-film hot melt adhesives, it offers advantages such as better breathability, softer adhesion, and less tendency for adhesive droplet accumulation. It has been widely used in composite bonding processes in clothing, footwear, automotive interiors, and filter materials. In vehicle interior manufacturing, hot melt adhesive web is commonly used to laminate substrates of different polarities, such as polyurethane foam, PVC artificial leather, leather, fabric, cotton cloth, and ethylene-vinyl acetate copolymer, for components like seats, headliners, door panels, and dashboard linings.

[0003] In related technologies, the base material of hot melt adhesive webs for vehicles is often low-melting-point copolyamide or low-melting-point copolyester. These materials have advantages such as low melting point, low bonding temperature, no damage to the substrate, and high adhesion strength to polar substrates, which meet the process requirements of heat-sensitive substrates in vehicle interior composite processes. However, these webs have gradually revealed insufficient heat resistance during long-term use: the interior temperature of a vehicle can rise to 80-90°C when it is stationary and exposed to the sun, while the softening temperature of the aforementioned hot melt adhesive webs is usually only 60-80°C, close to or lower than the interior sun exposure temperature. This causes the bonded composite interior parts to soften under long-term high-temperature conditions, resulting in a significant decrease in peel strength or even debonding failure, seriously affecting the service life and safety performance of the vehicle interior.

[0004] In addition, previous solutions also attempted to improve heat resistance by increasing the molecular weight of the base material or by using high-melting-point polymers (such as nylon 6 and nylon 66). However, increasing the molecular weight would significantly deteriorate the fluidity of the melt, making it difficult to operate the melt spinning web process stably. The resulting webs would have uneven filament diameters and disordered mesh distribution. Using high-melting-point polymers would raise the bonding temperature to over 160°C, which would easily damage heat-sensitive substrates such as polyurethane foam and would also cause the loss of adhesion properties to polar substrates, resulting in a significant reduction in bonding strength.

[0005] In summary, how to significantly improve the heat resistance of hot melt adhesive webs under 80-90°C exposure in a vehicle interior while ensuring the stability of the web forming process and maintaining good adhesion to various polar substrates such as leather, fabric, and polyurethane foam is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In order to improve the problem of softening of adhesive layer and failure of bonding of hot melt adhesive web for vehicles under exposure to 80~90℃ in the interior of a vehicle, and at the same time take into account the good bonding characteristics to various polar substrates, this application provides a high heat-resistant hot melt adhesive web for vehicles and its preparation method.

[0007] To achieve the above technical objectives, this application adopts the following technical solution: Firstly, this application provides a high heat-resistant hot melt adhesive mesh for vehicles, which adopts the following technical solution: A high-heat-resistant hot melt adhesive web for vehicles is prepared from the following raw materials by melt blending and hot melt blow molding process: 50-70 parts of high-melting-point copolyamide, 18-25 parts of low-melting-point copolyamide, 10-20 parts of copolyester, 0.3-1.5 parts of latent multifunctional epoxy chain extender, 2-6 parts of talc, 0.1-0.5 parts of barium stearate, 1-5 parts of solid glass microspheres, and 0. 2-1.0 parts, hindered phenolic antioxidant 0.3-0.8 parts, phosphite antioxidant 0.2-0.6 parts, polycarbodiimide anti-hydrolysis agent 0.5-1.5 parts, zinc stearate 0.2-0.5 parts; wherein, the high melting point copolyamide has a melting point of 130-150℃, the low melting point copolyamide has a melting point of 90-110℃, and the copolyester has a melting point of 100-120℃.

[0008] By adopting the above technical solution, since high-melting-point copolyamide is used as the main base material (accounting for about 60-70% of the total base material), its melting point is 130-150℃. In the product, it acts as a continuous phase and crystalline skeleton, which is significantly higher than the upper limit of 90℃ for exposure temperature inside the vehicle. Therefore, it can still maintain the integrity of the crystalline phase in an environment of 80-90℃, thereby maintaining the cohesive strength of the adhesive layer. At the same time, low-melting-point copolyamide and copolyester are dispersed in the high-melting-point copolyamide matrix during melt blending. They melt preferentially at lower temperatures in the web forming and subsequent bonding processes, and are responsible for achieving good adhesion to polar substrates such as leather, polyurethane foam, and fabric. This overcomes the defects of high bonding temperature and poor adhesion to polar substrates caused by simply using high-melting-point copolyamide. Furthermore, due to the synergistic introduction of talc and solid glass microspheres, talc, as a layered silicate mineral, has a certain epitaxial matching relationship between the lattice parameters of its (001) crystal plane and the polyamide matrix. It can play a role in heterogeneous crystallization nucleation of high-melting-point copolyamide, improving its crystallization rate and crystallinity, and further increasing the heat-resistant softening temperature of the product. Meanwhile, solid glass microspheres, as rigid inorganic fillers, are dispersed in the adhesive network and form a rigid skeleton at a high temperature of 80~90℃. Even if a small amount of low-melting-point components soften, the rigid skeleton can still maintain the overall dimensional stability of the adhesive layer, effectively preventing deformation and debonding failure in the peeling direction. The latent multifunctional epoxy chain extender is styrene containing more than three epoxy functional groups per molecule. - Acrylic ester-based multifunctional epoxy oligomers react further with the abundant end groups in the matrix during the preparation process, forming a locally branched-slightly cross-linked network structure in situ at and near the bonding interface. This in-situ network connects and locks the linear macromolecular chains that would otherwise creep and untangle at high temperatures. This further improves the cohesive strength and peel strength retention of the adhesive layer at long-term high temperatures of 80-90°C without increasing the bonding temperature, damaging the heat-sensitive substrate, or sacrificing the adhesion to polar substrates. Therefore, a high-heat-resistant hot melt adhesive web for vehicles is obtained, exhibiting high peel strength retention at 80-90°C under vehicle interior exposure, good adhesion to various polar substrates, and excellent comprehensive performance in terms of moisture and solvent resistance.

[0009] Preferably, the weight ratio of the high-melting-point copolyamide to the low-melting-point copolyamide is (2.5~3.5):1.

[0010] By adopting the above technical solution, within this weight ratio range, the high-melting-point copolyamide component forms a continuous matrix phase, while the low-melting-point copolyamide exists in the form of a dispersed phase. This is beneficial for the low-melting-point component to melt and penetrate into the pores on the substrate surface to form mechanical interlocking during the bonding process, without destroying the continuity of the high-melting-point matrix. If the proportion of high-melting-point copolyamide is too low, the continuous phase will be incomplete, and the heat resistance will decrease. If the proportion is too high, the low-melting-point component will not be able to wet the substrate, and the bonding strength will decrease.

[0011] Preferably, the median particle size D50 of the talc powder is 1~3μm, and it has undergone stearic acid surface activation treatment.

[0012] By adopting the above technical solution, ultrafine talc powder with a median particle size of 1~3μm has a high specific surface area, which is beneficial to uniformly disperse in the polyamide matrix during melt blending. It serves as a nucleation center for heterogeneous crystallization, promoting the crystallization of high-melting-point copolyamide and improving its crystallinity. The talc powder treated with stearic acid has improved surface oleophilicity and increased compatibility with polyamide and copolyester matrices, avoiding problems such as coarsening of the mesh fiber diameter and decline in mechanical properties caused by filler agglomeration.

[0013] Preferably, the solid glass microspheres have a median particle size D50 of 10~25μm and a true density of 2.4~2.6g / cm³. 3 .

[0014] By adopting the above technical solution, solid glass microspheres have the advantages of pressure resistance and high dimensional stability compared with hollow glass microspheres. They can maintain their integrity under the shearing action of twin-screw melt blending and high-speed hot air stretching. Solid glass microspheres with a median particle size of 10~25μm are evenly distributed inside the mesh filaments after forming the web, forming a rigid support in the high temperature environment of 80~90℃ inside the machine and inhibiting the creep of the adhesive layer. At the same time, the spherical appearance of the glass microspheres does not significantly affect the melt flowability, ensuring the stable operation of the web forming process.

[0015] Preferably, the weight ratio of the talc powder to the solid glass microspheres is (1.2~2.0):1.

[0016] By adopting the above technical solution, talc powder is used as a nucleating agent for fine-particle layered silicates, and solid glass microspheres are used as spherical large-particle rigid fillers. The two are compounded in the above weight ratio to form a dual heat-resistant enhanced structure in the microstructure of the network film, which is a highly crystalline matrix phase initiated by layered nucleation centers and a supporting skeleton composed of spherical rigid fillers. The synergistic effect of the two is significantly better than that of a single filler, and the heat retention performance is maximized without significantly affecting the melt flowability.

[0017] Furthermore, this application introduces barium stearate as an organic nucleating agent in addition to talc. The long-chain alkyl structure of barium stearate gives it good compatibility with the polyamide matrix, enabling uniform dispersion at the molecular scale and providing additional heterogeneous nucleation centers. Simultaneously, the metal ion terminals of barium stearate can coordinate with the amide groups of the polyamide molecular chains, further inducing a regular arrangement of the molecular chains. Talc (inorganic nucleating agent) and barium stearate (organic nucleating agent), supplemented with oxidized paraffin soap as a dispersant and auxiliary nucleating agent, constitute a ternary composite nucleation system. This system is complementary in its nucleation mechanism—talc provides a layered epitaxial growth surface, while barium stearate provides molecular-scale nucleation sites. Their synergistic effect significantly improves the crystallization rate and crystallinity of the high-melting-point copolyamide, resulting in a more complete and dense matrix crystalline framework and a further increase in the product's heat softening temperature.

[0018] Preferably, the weight ratio of the talc powder to the barium stearate is (8~20):1.

[0019] Preferably, the hindered phenolic antioxidant is at least one of antioxidant 1010, antioxidant 1098, or antioxidant 245; and the phosphite antioxidant is antioxidant 168 or antioxidant 626.

[0020] By adopting the above technical solution, hindered phenolic antioxidants serve as the main antioxidants, which inhibit the oxidative degradation of polymers during high-temperature processing and long-term exposure by capturing free radicals; phosphite antioxidants serve as auxiliary antioxidants, which can decompose peroxide intermediates; the combination of the two produces a synergistic effect, which significantly inhibits the yellowing and degradation of the membrane during vehicle production, transportation and long-term use, ensuring low VOC emissions and color stability of the product.

[0021] Preferably, the basis weight of the mesh is 6~120 g / m³. 2 The wire diameter is 5~40μm.

[0022] By adopting the above technical solution, the weight and filament diameter range enable the mesh to have suitable porosity and bonding area, which can be adjusted according to different vehicle interior composite application scenarios (such as headliner, seats, door interior panels, etc.), ensuring good breathability and soft feel while ensuring bonding strength.

[0023] Secondly, this application provides a method for preparing a high heat-resistant hot melt adhesive web for vehicles, using the following technical solution: S1. Raw material pretreatment: High-melting-point copolyamide, low-melting-point copolyamide, and copolyester are vacuum dried at 80-95℃ for 4-8 hours respectively, so that the moisture content is less than 0.05wt%. S2. Masterbatch preparation: The dried high-melting-point copolyamide, latent multifunctional epoxy chain extender, talc, barium stearate, solid glass microspheres, oxidized paraffin soap, hindered phenolic antioxidant, phosphite antioxidant, polycarbodiimide anti-hydrolysis agent, and zinc stearate are added to a twin-screw extruder according to the formula. The mixture is melt-blended, extruded, and granulated at a barrel temperature of 150~210℃ and a screw speed of 250~350rpm to obtain the functional masterbatch. S3. Blending and granulation: The functional masterbatch and the remaining low-melting-point copolyamide and copolyester are added to a twin-screw extruder. The mixture is melt-blended and extruded under the conditions of barrel temperature of 140~200℃ and screw speed of 200~300rpm, water-cooled and pelletized to obtain composite modified granules. S4. Web forming: The composite modified adhesive particles are fed into a meltblown or melt-blown screen equipment. Under the conditions of melt temperature of 160~210℃ and die temperature of 170~200℃, the particles are melt-spun and hot-air drawn, and randomly deposited on the receiving roller to form a porous mesh structure. After cooling and winding, the high heat-resistant hot melt adhesive web for vehicles is obtained.

[0024] By adopting the above technical solution, functional components such as latent multifunctional epoxy chain extenders, talc, solid glass microspheres, and oxidized paraffin soap are first prepared with high-melting-point copolyamide through twin-screw extrusion at a relatively high temperature to prepare functional masterbatch. This ensures the full dispersion of inorganic fillers and oxidized paraffin soap in the high-melting-point matrix. The oxidized paraffin soap, as a dispersing aid, further promotes the uniform dispersion of talc and solid glass microspheres. The chain extender is added during the masterbatch preparation step to ensure its effective dispersion in the high-melting-point copolyamide matrix containing high-end... The matrix is ​​pre-blended with uniform distribution and limited chain extension branching, and the residence time in the secondary blending and web forming stages is short, so the chain extender does not react excessively. Then, the functional masterbatch is blended with low-melting-point copolyamide and copolyester to avoid excessive thermal degradation of low-melting-point components at a lower temperature, while achieving uniform distribution of each component. Finally, the web is formed by melt-blowing or melt blowing process to obtain the high heat-resistant hot melt adhesive web film described in this application, and the chain extender forms a local network in situ in the subsequent hot pressing and laminating process.

[0025] In summary, this application has the following beneficial effects: 1. Because this application uses a ternary matrix compound system with high-melting-point copolyamide as the main body and low-melting-point copolyamide and copolyester as auxiliary adhesive components, the high-melting-point copolyamide (melting point 130~150℃) maintains the integrity of the crystalline phase and provides a heat-resistant skeleton under exposure at 80~90℃. The low-melting-point component is responsible for achieving high-strength adhesion to polar substrates. This results in good initial adhesion performance with a peel strength greater than 5N / cm and no tearing on polar substrates such as leather, PVC, cloth, cotton, and EVA. At the same time, after 7 days of damp heat aging at 85℃ and 85%RH, the peel strength retains more than 85% of the durability performance.

[0026] 2. In this application, a dual-filler synergistic system of talc powder and solid glass microspheres is preferred. Talc powder acts as a heterogeneous nucleating agent to improve the crystallinity of high-melting-point copolyamide, while solid glass microspheres act as a rigid skeleton to inhibit high-temperature creep. A latent multifunctional epoxy chain extender with regulated reactivity is introduced so that it does not impair melt flowability and filamentation during the network formation stage. During the hot pressing bonding stage, a locally branched-slightly cross-linked network is formed in situ, locking the matrix macromolecular chains together and further improving the heat retention performance.

[0027] 3. The method of this application, through a step-by-step processing strategy of first preparing functional masterbatch and then secondary blending, effectively solves the process problem of inorganic fillers being difficult to disperse in a low-melting-point matrix, and obtains the process effect of uniform wire diameter, stable basis weight, good processing performance, and large-scale continuous production. At the same time, due to the optimized antioxidant and anti-hydrolysis agent compound system, the product has the comprehensive advantages of low VOC volatile matter, non-yellowing, and good hydrolysis resistance. Detailed Implementation

[0028] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0029] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0030] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0032] Unless otherwise explicitly defined and specified herein, all technical and scientific terms used in this application shall have the generally accepted meanings understood by one of ordinary skill in the field of chemical and chemical materials technology (including but not limited to polymer chemistry, inorganic chemistry, organic synthesis, catalysis chemistry, materials processing, and chemical unit operations) based on their professional knowledge and conventional practice. The use of any terminology herein is intended to describe the specific embodiments of this application in the clearest and most accurate manner, so as to fully disclose the technical solution. Such use shall not in any way be construed as a limitation on the scope of the claims, nor does it imply the exclusion of equivalent technical solutions that could be reasonably known by one of skill in the art based on the concept of this application.

[0033] The terms "comprising," "including," "having," "containing," and any grammatical variations or similar expressions used in the specification and claims of this application are all open-ended and non-exhaustive descriptive terms. Their purpose is to explicitly describe the existence of the stated technical features, components, steps, or parts, while explicitly allowing and covering the possibility that other features, components, steps, parts, or any combinations thereof not explicitly listed may exist or be added to the technical solution, as long as such additions do not destroy the integrity and inventiveness of the original technical solution.

[0034] When the terms "embodiments," "some embodiments," or "specific embodiments" are mentioned in the specification, they refer to examples that, in conjunction with the specific parameters, materials, steps, and results described in that section, constitute one or a group of examples for implementing the technical solutions of this application. These embodiments are used for full disclosure and illustrative purposes, not for exhaustive enumeration. Those skilled in the art should understand that, without departing from the overall inventive concept of this application, the various technical features disclosed in different embodiments can be combined, substituted, modified, or deleted to form other implementation methods that are not listed one by one in the specification but also fall within the protection scope of this application.

[0035] Unless otherwise expressly specified and limited, all terms related to chemical process operations, material preparation, processing and analytical testing involved in this application shall be interpreted in the broadest sense based on the conventional understanding of those skilled in the art.

[0036] Regarding performance testing and structural characterization, all testing and characterization methods involved in this application, unless otherwise specified, refer to conventional methods known in the art. Specific testing conditions may be selected and adjusted according to the sample properties and relevant national standards, international standards, or industry-standard methods. Test items may include mechanical properties (such as tensile, bending, and impact strength), thermal properties (such as DSC and TGA analysis), and chemical stability (such as solvent resistance and acid / alkali corrosion resistance). Structural characterization methods may include FT-IR, NMR, XRD, SEM, TEM, and BET. All test results should be understood to be within the allowable range of conventional experimental errors.

[0037] Regarding numerical values ​​and ranges, all parameter ranges expressed in this application in the form of "from a certain value to a certain value" should be understood as explicitly disclosing the endpoints of the range, each specific numerical point between the endpoints, and all sub-ranges formed by any two numerical points within the range. For example, "30℃ to 80℃" discloses 30, 31, ..., 80℃, as well as sub-ranges such as 30-50℃, 45-70℃, etc. When a numerical value is preceded by "about," "approximately," or similar words, it indicates that the numerical value is allowed to have reasonable errors recognized in the art under the measurement or control conditions, which can generally be understood as the deviation allowed by relevant standards or a normal fluctuation range of ±5% or ±10%.

[0038] The inventive concept of this application is as follows: In related technologies, hot melt adhesive webs for vehicles are prone to softening and adhesion failure under 80-90°C exposure conditions inside a vehicle. The applicant has conducted extensive research on this phenomenon and found that the softening temperature of existing low-melting-point copolyamide webs is only 60-80°C, close to or below the upper limit of vehicle exposure temperature, which is the direct cause of exposure failure. Increasing the molecular weight of the base material or replacing it with high-melting-point nylon will damage the stability of the web-forming process or cause loss of low-temperature bonding ability. Based on this finding, the applicant proposes a composite modification approach of "high-melting-point skeleton phase + low-melting-point adhesive phase + inorganic rigid skeleton": Specifically, a high-melting-point copolyamide with a melting point of 130-150℃ is used as the main continuous phase to provide a crystalline framework that exceeds the upper limit of the temperature for exposure inside a vehicle. Low-melting-point copolyamide with a melting point of 90-110℃ and copolyester with a melting point of 100-120℃ are used as adhesive phases, which preferentially melt during low-temperature bonding to ensure good adhesion to polar substrates such as leather, polyurethane foam, and fabric. At the same time, talc powder with a median particle size of 1-3μm is introduced as a heterogeneous nucleating agent, which utilizes its layered silicate structure to improve the crystallinity of the high-melting-point copolyamide. Solid glass microspheres with a median particle size of 10-25μm are introduced as a rigid framework to inhibit the creep of the adhesive layer at high temperatures of 80-90℃. Combined with hindered phenol / phosphite composite antioxidants and polycarbodiimide anti-hydrolysis agents, comprehensive properties such as heat resistance, damp heat resistance, hydrolysis resistance, and low yellowing are obtained. This approach fully leverages the synergistic effects of different components, utilizes readily available commercial raw materials, and can be achieved through a purely physical melt blending process. The process is mature and suitable for large-scale industrial production. This application is based on the aforementioned findings.

[0039] Source of raw materials The raw materials used in the embodiments and comparative examples of this application are all commercially available and well-known substances. The specific technical parameters and sources are as follows: (1) High melting point copolyamide: PA6 / 66 / 12 ternary copolyamide. In this application, the grade with a melting point (differential scanning calorimetry DSC test, heating rate 10℃ / min) of 140℃ is selected. This type of copolyamide is a commonly used industrial-grade known product in the hot melt adhesive field and can be purchased through conventional chemical raw material market channels.

[0040] (2) Low melting point copolyamide: PA6 / 66 / 610 ternary copolyamide. The grade with a melting point of about 100°C was selected in the embodiments of this application. This type of copolyamide is also a commonly known industrial-grade product in the hot melt adhesive field and can be purchased through conventional chemical raw material market channels.

[0041] (3) Copolyester: It is a semi-crystalline copolyester with terephthalic acid, isophthalic acid and ethylene glycol as polymer monomers. The grades with a melting point of about 110°C are selected in the embodiments of this application. This type of copolyester is a commonly known industrial-grade product in the field of hot melt adhesives and can be purchased through conventional chemical raw material market channels.

[0042] (4) Talc: Ultrafine talc, the main component of which is hydrated magnesium silicate (CAS No. 14807-96-6), has a layered silicate crystal structure; the embodiment of this application selects a grade with a median particle size D50 of 2μm, and it is treated with stearic acid surface activation, with a whiteness ≥90; this type of ultrafine modified talc is a commonly known industrial-grade product in the field of plastic fillers, and can be purchased through conventional mineral product market channels.

[0043] (5) Solid glass microspheres: solid spherical microparticles made of sodium calcium silicate glass. In this application, the grade with a median particle size D50 of 15 μm is selected. This type of solid glass microsphere is a commonly known industrial-grade product in the field of plastic fillers and can be purchased through conventional chemical raw material market channels.

[0044] (6) Hindered phenolic antioxidants: Antioxidant 1010, chemical name is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], CAS number 6683-19-8, this compound is a well-known commercial antioxidant.

[0045] (7) Phosphite antioxidants: Antioxidant 168, chemical name is tris(2,4-di-tert-butylphenyl) phosphite, CAS number 31570-04-4, this compound is a well-known commercial antioxidant.

[0046] (8) Polycarbodiimide anti-hydrolysis agents: Polycarbodiimide compounds are well-known anti-hydrolysis stabilizers for engineering plastics, suitable for melt processing of polymers such as PA, PET, PBT, EVA, and TPU.

[0047] (9) Zinc stearate: CAS No. 557-05-1, industrial grade, used as a processing aid and lubricant.

[0048] (10) Calcium carbonate (used in Comparative Example 4): Heavy calcium carbonate, CAS No. 471-34-1, median particle size D50 is 2μm, industrial grade known product.

[0049] (11) Hollow glass microspheres (used in Comparative Example 5): Hollow spherical microparticles made of sodium calcium silicate glass with a median particle size D50 of 15 μm, an industrial-grade known product.

[0050] (12) Latent multifunctional epoxy chain extender: a copolymer of styrene (ST), methyl methacrylate (MMA) and glycidyl methacrylate (GMA), purchased from Qingdao Zhenguang Functional Materials Technology Co., Ltd., chain extender 3700; CAS: 1191261-43-4.

[0051] All of the above raw materials are commercially available products known in the field and can be purchased through conventional channels. This application does not limit the specific supplier brand.

[0052] Example 1 A high-heat-resistant hot melt adhesive mesh for vehicles is made from the following raw materials in parts by weight: 50 parts high-melting-point copolyamide, 20 parts low-melting-point copolyamide, 15 parts copolyester, 0.6 parts latent multifunctional epoxy chain extender, 0.2 parts barium stearate, 3 parts talc, 0.2 parts oxidized paraffin soap, 2 parts solid glass microspheres, 0.4 parts antioxidant 1010, 0.3 parts antioxidant 168, 0.8 parts polycarbodiimide anti-hydrolysis agent, and 0.3 parts zinc stearate. In this embodiment, the weight ratio of high-melting-point copolyamide to low-melting-point copolyamide is 2.5:1, and the weight ratio of talc to solid glass microspheres is 1.5:1.

[0053] The preparation method is as follows: S1. Raw material pretreatment: Place 50 parts of high melting point copolyamide, 20 parts of low melting point copolyamide and 15 parts of copolyester in a vacuum drying oven and vacuum dry at 90°C for 6 hours to make the moisture content less than 0.05wt%.

[0054] S2. Masterbatch preparation: 50 parts of dried high-melting-point copolyamide, 0.6 parts of latent multifunctional epoxy chain extender, 3 parts of talc, 0.2 parts of barium stearate, 2 parts of solid glass microspheres, 0.4 parts of antioxidant 1010, 0.3 parts of antioxidant 168, 0.8 parts of polycarbodiimide anti-hydrolysis agent, and 0.3 parts of zinc stearate are premixed in a high-speed mixer for 2 minutes, and then added to a twin-screw extruder with a screw length-to-diameter ratio of 44:1. The barrel temperature along the material flow direction is set to 8 temperature zones of 155℃, 170℃, 185℃, 200℃, 205℃, 200℃, 195℃, and 190℃, the die temperature is 190℃, and the screw speed is 300 rpm. The mixture is melt-blended, extruded, water-cooled, and pelletized to obtain the functional masterbatch. S3. Blending and Granulation: The prepared functional masterbatch is premixed with 20 parts of low-melting-point copolyamide and 15 parts of copolyester in a high-speed mixer for 2 minutes, and then added to a twin-screw extruder. The temperature of the barrel along the material flow direction is set to 145℃, 160℃, 175℃, 185℃, 195℃, 195℃, 190℃ and 185℃ in sequence, the die temperature is 185℃ and the screw speed is 250 rpm. The mixture is melt-blended, extruded, water-cooled and pelletized to obtain composite modified granules.

[0055] S4. Web Forming: The prepared composite modified granules are fed into a melt-blowing machine with a melt temperature of 195℃, a die temperature of 190℃, a hot air temperature of 210℃, a hot air pressure of 0.4MPa, and a receiving distance of 20cm. After melt spinning and hot air drawing, a porous network structure is randomly deposited on the receiving roller. After cooling and winding, a basis weight of 40g / m² is obtained. 2 High heat-resistant hot melt adhesive mesh for vehicles with a wire diameter of approximately 25μm.

[0056] Example 2 A high-heat-resistant hot melt adhesive mesh for vehicles differs from Example 1 only in the raw material ratio. This example uses: 60 parts high-melting-point copolyamide, 20 parts low-melting-point copolyamide, 15 parts copolyester, 0.8 parts latent multifunctional epoxy chain extender, 4 parts talc, 0.3 parts barium stearate, 2.5 parts solid glass microspheres, 1.0 part oxidized paraffin soap, 0.5 parts antioxidant 1010, 0.4 parts antioxidant 168, 1.0 part polycarbodiimide anti-hydrolysis agent, and 0.3 parts zinc stearate. In this example, the weight ratio of high-melting-point copolyamide to low-melting-point copolyamide is 3.0:1, and the weight ratio of talc to solid glass microspheres is 1.6:1. The remaining raw material types and preparation methods are the same as in Example 1. The resulting mesh has a basis weight of 40 g / m². 2 The wire diameter is approximately 25 μm.

[0057] Example 3 A high-heat-resistant hot melt adhesive mesh for vehicles differs from Example 1 only in the raw material ratio. This example uses: 70 parts high-melting-point copolyamide, 20 parts low-melting-point copolyamide, 12 parts copolyester, 1.0 part latent multifunctional epoxy chain extender, 5 parts talc, 0.5 parts oxidized paraffin soap, 0.5 parts barium stearate, 3 parts solid glass microspheres, 0.6 parts antioxidant 1010, 0.5 parts antioxidant 168, 1.2 parts polycarbodiimide anti-hydrolysis agent, and 0.4 parts zinc stearate. In this example, the weight ratio of high-melting-point copolyamide to low-melting-point copolyamide is 3.5:1, and the weight ratio of talc to solid glass microspheres is approximately 1.67:1. The remaining raw material types and preparation methods are the same as in Example 1. The resulting mesh has a basis weight of 40 g / m². 2 The wire diameter is approximately 25 μm.

[0058] Example 4 A high-heat-resistant hot melt adhesive web for vehicles differs from Example 2 only in that: in this example, solid glass microspheres with a median particle size D50 of 10 μm are used instead of the solid glass microspheres with a median particle size D50 of 15 μm in Example 2; the other raw material types, proportions, and preparation methods are the same as in Example 2. The resulting web has a basis weight of 40 g / m². 2 The wire diameter is approximately 25 μm.

[0059] Comparative Example 1 A hot melt adhesive web for vehicles uses a conventional low-melting-point copolyamide web formulation in related technologies: 100 parts of low-melting-point copolyamide (melting point 100℃), 0.4 parts of antioxidant 1010, 0.3 parts of antioxidant 168, 0.8 parts of polycarbodiimide anti-hydrolysis agent, and 0.3 parts of zinc stearate. The preparation method is as follows: All the above-mentioned low-melting-point copolyamides were vacuum dried at 80°C for 6 hours, then premixed with each functional additive for 2 minutes using a high-speed mixer. The mixture was then added to a twin-screw extruder. The barrel temperatures along the material flow direction were sequentially set to 120°C, 135°C, 150°C, 160°C, 170°C, 170°C, 165°C, and 160°C. The die temperature was 160°C, and the screw speed was 250 rpm. The mixture was melt-blended, extruded, water-cooled, and pelletized to obtain granules. These granules were then fed into a meltblown fabric to form a web, following the same process as step S4 of Example 1 (the melt temperature was adjusted to 170°C). The resulting web had a basis weight of 40 g / m². 2 The wire diameter is approximately 25 μm.

[0060] Comparative Example 2 A hot melt adhesive mesh for vehicles differs from Example 2 only in that it does not contain solid glass microspheres (0 parts), while the other raw material types, proportions, and preparation methods are the same as in Example 2.

[0061] Comparative Example 3 A hot melt adhesive mesh for vehicles differs from Example 2 only in that: no talc powder (0 parts) is added, while the other raw material types, proportions, and preparation methods are the same as in Example 2.

[0062] Comparative Example 4 A hot melt adhesive mesh for vehicles differs from Example 2 only in that an equal amount of heavy calcium carbonate (median particle size D50 of 2 μm) is used to replace the talc powder in Example 2, while the other raw material types, proportions, and preparation methods are the same as in Example 2.

[0063] Comparative Example 5 A hot melt adhesive mesh for vehicles differs from Example 2 only in that it uses an equal amount of hollow glass microspheres (median particle size D50 of 15 μm and true density of 0.4 g / cm³). 3 The solid glass microspheres in Example 2 are replaced, and the other raw materials, proportions and preparation methods are the same as in Example 2.

[0064] Comparative Example 6 A hot melt adhesive mesh for vehicles differs from Example 2 only in that the weight ratio of high-melting-point copolyamide to low-melting-point copolyamide is reduced to 1:1.

[0065] Comparative Example 7 A hot melt adhesive mesh for vehicles differs from Example 2 only in that it does not contain a latent multifunctional epoxy chain extender.

[0066] Performance testing The performance of the hot melt adhesive webs for vehicles prepared in Examples 1-4 and Comparative Examples 1-7 was tested according to the following method: Detection method: (1) Initial peel strength: Referring to GB / T 2791-1995 "Test method for T-peel strength of adhesives, flexible materials to flexible materials", the prepared mesh was placed between polyvinyl chloride artificial leather and polyurethane foam respectively. The composite was laminated under the conditions of a lamination temperature of 130℃, a lamination pressure of 0.3MPa, and a lamination time of 30 seconds to obtain a composite sample with a width of 25mm. A universal tensile testing machine was used to conduct a T-peel test at a tensile rate of 100mm / min to test the peel strength, which was recorded as the initial peel strength (N / cm). Five samples of the same sample were tested, and the average value was taken. The test required that the sample did not break in the substrate itself.

[0067] (2) Peel strength retention rate after baking at 90℃: The above-mentioned bonded composite sample was placed in a constant temperature oven at 90℃ and baked for 7 days. After taking it out, it was equilibrated at 23℃ and 50%RH for 4 hours. Then, the peel strength was tested according to method (1). The ratio of the peel strength to the initial peel strength is the peel strength retention rate (%) after baking at 90℃. It was also observed whether the sample delaminated during the baking process.

[0068] (3) Peel strength retention rate after 85℃ / 85%RH damp heat aging: The laminated composite sample was placed in a constant temperature and humidity test chamber at 85℃ and 85%RH for 7 days. After being taken out, it was equilibrated at 23℃ and 50%RH for 4 hours. Then, the peel strength was tested according to method (1). The ratio of the peel strength to the initial peel strength is the peel strength retention rate (%) after 85℃ / 85%RH damp heat aging.

[0069] (4) 60℃ water immersion cycle test: Immerse the bonded composite sample in a 60℃ constant temperature water bath for 30 minutes, take it out and dry it in a 23℃ environment for 30 minutes, which is recorded as 1 cycle; repeat 20 cycles and observe whether the sample delaminates during the cycle.

[0070] (5) VOC emissions: Referring to VDA 277 "Determination of volatile organic compounds in non-metallic materials for automotive interior parts", accurately weigh about 1.0 g of the mesh sample, place it in a 10 mL headspace vial and seal it. Heat it at 120 °C for 5 hours to allow the headspace gas to reach gas-solid equilibrium. Then, take a quantitative amount of headspace gas for injection. Use gas chromatography-flame ionization detector (GC-FID) with acetone as the calibrator to perform quantification and determine the total volatile organic compound emissions of the mesh sample. The total volatile organic compound emissions are expressed as equivalent carbon content per unit mass of sample (μgC / g).

[0071] (6) Change in yellowing index (ΔYI): Referring to GB / T 2409-1980 "Test method for yellow index of plastic", the yellow index YI of the film sample before and after baking in a constant temperature oven at 90℃ for 7 days was measured by a colorimeter. The difference between the two was calculated as ΔYI = YI (after baking) - YI (before baking).

[0072] (7) Web forming quality: Observe the stability of the web forming process, measure the basis weight uniformity of the web (take 5 samples from different positions of the same roll of web to measure, calculate the relative standard deviation of basis weight, %) and the wire diameter (μm, measured by optical microscope).

[0073] The performance test results of the membranes prepared in each embodiment and comparative example are shown in Table 1: Table 1 Performance test results of the membranes prepared in the examples and comparative examples

[0074] The data in Table 1 are all arithmetic mean of 5 parallel samples. The standard deviation (SD) of each test item is within a reasonable range (peel strength SD ≤ ±0.3 N / cm, retention rate SD ≤ ±2.0%). The data reliability meets the general requirements for precision of standards such as GB / T 2791 and VDA 277.

[0075] Combining Examples 1-4 and Comparative Example 1, it can be seen that although the conventional low-melting-point copolyamide web film (Comparative Example 1) in the related technology can achieve an initial peel strength of 5.4 N / cm, its peel strength retention rate is only 32% after baking at 90℃ for 7 days, resulting in severe delamination; after 7 days of damp heat aging at 85℃ / 85%RH, the peel strength retention rate is only 41%; and in the 60℃ water immersion cycle test, delamination occurs after only 5 cycles. This is because the softening temperature of its base material is only 60~80℃, which is close to or lower than the test temperature, causing the adhesive layer to soften significantly at high temperatures and the cohesive strength to decrease severely. The meshes of Examples 1-4 of this application, while maintaining a good initial peel strength of 5.4-5.8 N / cm, retain 88-94% of their peel strength after baking at 90℃ for 7 days without delamination. After 7 days of damp heat aging at 85℃ / 85%RH, their peel strength retains 86-91%. They also do not delaminate after 20 cycles of immersion in water at 60℃. Their overall heat resistance and damp heat resistance are significantly better than those of Comparative Example 1.

[0076] Combining Example 2 and Comparative Examples 2, 3, and 4, and referring to Table 1, it can be seen that the key role of the synergistic effect of talc powder and solid glass microspheres as dual fillers is evident: Comparative Example 2 (lacking solid glass microspheres alone) maintained a peel strength retention rate of 71% after baking at 90℃ for 7 days, but delamination occurred after 15 cycles of water immersion at 60℃, indicating that the rigid skeleton formed by the solid glass microspheres plays a crucial role in inhibiting high-temperature creep and maintaining the dimensional stability of the adhesive layer; Comparative Example 3 (lacking talc alone) maintained a peel strength retention rate of 76% after baking at 90℃ for 7 days, which is also significantly lower than that of Comparative Example 4. The 92% yield in Example 2 demonstrates that the heterogeneous nucleation effect of talc effectively enhances the crystallinity of the high-melting-point copolyamide matrix, which is indispensable for improving heat resistance. Comparative Example 4 (using an equal amount of calcium carbonate instead of talc) showed a peel strength retention rate of only 74% after baking at 90℃ for 7 days, similar to Comparative Example 3. This is because the calcite crystal structure of calcium carbonate lacks epitaxial crystal plane matching with the copolyamide matrix, resulting in a much lower heterogeneous crystallization nucleation efficiency than talc with its layered silicate structure. This further proves the irreplaceable role of talc as a nucleating agent. In summary, the combination of talc and solid glass microspheres at a weight ratio of 1.2~2.0:1 produces a significant synergistic effect. The absence or equal replacement of any component significantly reduces heat resistance. The dual-filler synergistic system of this application is a key innovation in improving heat resistance.

[0077] Combining Example 2 and Comparative Example 5, we can see the key difference between solid glass microspheres and hollow glass microspheres: Comparative Example 5 used an equal amount of hollow glass microspheres (true density only 0.4 g / cm³). 3The hollow glass microspheres, instead of solid glass microspheres, only retained 67% of their peel strength after baking at 90℃ for 7 days, and delamination occurred after 12 cycles of immersion in water at 60℃. This is because hollow glass microspheres have thin walls and low compressive strength, making them prone to breakage under the high shear forces of twin-screw extrusion and hot air stretching. After breakage, they cannot form a complete spherical rigid skeleton, thus losing their rigid support function. This further proves the inventiveness of the design using solid glass microspheres in this application.

[0078] Combining Example 2 and Comparative Example 6, we can see the crucial role of the preferred weight ratio of high-melting-point copolyamide to low-melting-point copolyamide: Comparative Example 6 uses a 1:1 weight ratio, and although the initial peel strength reaches 6.0 N / cm, slightly higher than the Example, its peel strength retention rate after baking at 90℃ for 7 days is only 58%, far lower than the Example, and local delamination occurs. This is because the proportion of low-melting-point copolyamide is too high, and a continuous high-melting-point skeleton phase cannot be formed in the microstructure of the product, thus showing a clear overall softening trend at 80~90℃. However, when the weight ratio of high-melting-point to low-melting-point copolyamide falls within the preferred range of (2.5~3.5):1 (Examples 1~3), it ensures both the continuity of the high-melting-point skeleton phase and provides sufficient heat resistance support, while also ensuring an appropriate amount of low-melting-point adhesive phase, achieving good adhesion to polar substrates such as leather, PVC, and polyurethane foam during low-temperature bonding.

[0079] Combining Examples 1-3 with Table 1, we can see the progressive effect of the preferred embodiments of this application: From Example 1 to Example 3, with the increase in the proportion of high-melting-point copolyamide (high:low weight ratio from 2.5:1 → 3.0:1 → 3.5:1) and the slight increase in the amount of inorganic filler, the peel strength retention rate after baking at 90℃ for 7 days increased from 88% to 94%, and the retention rate after damp heat aging at 85℃ / 85%RH increased from 86% to 91%; at the same time, the initial peel strength decreased slightly from 5.6 N / cm to 5.4 N / cm, which is due to the relatively reduced proportion of low-melting-point adhesive phase, but it still meets the requirement of being greater than 5 N / cm and not breaking the substrate, demonstrating that the technical solution of this application has achieved a good balance between heat resistance and adhesion; Example 3 is the optimal embodiment of this application.

[0080] Combining Examples 2 and 4, we can see the effect of the particle size of solid glass microspheres: In Example 4, the median particle size of solid glass microspheres was adjusted from 15 μm to 10 μm, and its peel strength retention rate after baking at 90℃ for 7 days was 90%, which is slightly lower than 92% in Example 2. This is because the rigid skeleton structure formed by the smaller particle size glass microspheres is relatively loose, but it is still in the range of 10~25 μm, and its heat resistance is still significantly better than that of the comparative example.

[0081] Combining Example 2 and Comparative Example 7, it can be seen that the heat resistance retention rate of Example 2 is further improved compared with Comparative Example 7. The latent multifunctional epoxy chain extender is beneficial to further improve the heat resistance without increasing the bonding temperature or impairing the web formation and bonding performance.

[0082] Furthermore, the TVOC emissions of the embodiments in this application are all 22~26 μgC / g, which is significantly lower than the 31 μgC / g of Comparative Example 1; the yellowing index change ΔYI after baking at 90℃ for 7 days is only 1.1~1.4, which is significantly lower than the 3.8 of Comparative Example 1. This indicates that the hindered phenolic antioxidant / phosphite antioxidant compound system and the polycarbodiimide antihydrolysis agent used in this application synergistically exert excellent antioxidant and antihydrolysis effects, giving the product the advantages of low VOC emissions and low yellowing, which fully meets the high requirements of vehicle interior for environmental performance and appearance stability.

[0083] In summary, the high heat-resistant hot melt adhesive web for vehicles provided in this application significantly improves the heat retention performance of the product under exposure to sunlight at 80~90℃ inside a vehicle through the synergistic compounding of ternary base materials of high melting point copolyamide / low melting point copolyamide / copolyester and the synergistic design of dual fillers of heterogeneous nucleation of talc powder and rigid skeleton of solid glass microspheres. At the same time, it retains good low-temperature adhesion characteristics to polar substrates such as leather, cloth, and polyurethane foam, overcoming the technical contradiction of difficulty in balancing heat resistance and adhesion in related technologies. It has outstanding substantive features and significant progress.

[0084] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high heat-resistant hot melt adhesive web for vehicles, characterized in that: Its raw materials include the following components in parts by weight: 50-70 parts of high-melting-point copolyamide, 18-25 parts of low-melting-point copolyamide, 10-20 parts of copolyester, 0.3-1.5 parts of latent multifunctional epoxy chain extender, 2-6 parts of talc, 0.1-0.5 parts of barium stearate, 1-5 parts of solid glass microspheres, 0.2-1.0 parts of oxidized paraffin soap, 0.3-0.8 parts of hindered phenolic antioxidant, 0.2-0.6 parts of phosphite antioxidant, 0.5-1.5 parts of polycarbodiimide anti-hydrolysis agent, and 0.2-0.5 parts of zinc stearate; The high-melting-point copolyamide has a melting point of 130~150℃, the low-melting-point copolyamide has a melting point of 90~110℃, and the copolyester has a melting point of 100~120℃.

2. The high heat-resistant hot melt adhesive web for vehicles according to claim 1, characterized in that: The weight ratio of the high-melting-point copolyamide to the low-melting-point copolyamide is (2.5~3.5):

1.

3. The high heat-resistant hot melt adhesive web for vehicles according to claim 1, characterized in that: The talc powder has a median particle size D50 of 1~3μm and is surface activated by stearic acid.

4. The high heat-resistant hot melt adhesive web for vehicles according to claim 1, characterized in that: The solid glass microspheres have a median particle size D50 of 10–25 μm and a true density of 2.4–2.6 g / cm³. 3 .

5. The high heat-resistant hot melt adhesive web for vehicles according to claim 1, characterized in that: The weight ratio of the talc powder to the solid glass microspheres is (1.2~2.0):

1.

6. The high heat-resistant hot melt adhesive web for vehicles according to claim 1, characterized in that: The hindered phenolic antioxidant is at least one of antioxidant 1010, antioxidant 1098, or antioxidant 245; the phosphite antioxidant is antioxidant 168 or antioxidant 626.

7. The high heat-resistant hot melt adhesive web for vehicles according to claim 1, characterized in that: The basis weight of the membrane is 6~120g / m². 2 The wire diameter is 5~40μm.

8. The high heat-resistant hot melt adhesive web for vehicles according to claim 1, characterized in that: The high-melting-point copolyamide is PA6 / 66 / 12 ternary copolyamide; the low-melting-point copolyamide is PA6 / 66 / 610 ternary copolyamide; the copolyester is a semi-crystalline copolyester with terephthalic acid, isophthalic acid and ethylene glycol as polymerizing monomers; the latent multifunctional epoxy chain extender is a copolymer of styrene, methyl methacrylate and glycidyl methacrylate.

9. A method for preparing a high heat-resistant hot melt adhesive web for vehicles as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Raw material pretreatment: High-melting-point copolyamide, low-melting-point copolyamide, and copolyester are vacuum dried at 80-95℃ for 4-8 hours respectively, so that the moisture content is less than 0.05wt%. S2. Masterbatch preparation: 0.3-1.5 parts of dried high-melting-point copolyamide, latent multifunctional epoxy chain extender, talc, barium stearate, solid glass microspheres, oxidized paraffin soap, hindered phenolic antioxidant, phosphite antioxidant, polycarbodiimide anti-hydrolysis agent, and zinc stearate are added to a twin-screw extruder according to the formula. The mixture is melt-blended, extruded, and granulated under the conditions of barrel temperature of 150-210℃ and screw speed of 250-350rpm to obtain the functional masterbatch. S3. Blending and granulation: The functional masterbatch and the remaining low-melting-point copolyamide and copolyester are added to a twin-screw extruder. The mixture is melt-blended and extruded under the conditions of barrel temperature of 140~200℃ and screw speed of 200~300rpm, water-cooled and pelletized to obtain composite modified granules. S4. Web forming: The composite modified adhesive particles are fed into a meltblown or melt-blown screen equipment. Under the conditions of melt temperature of 160~210℃ and die temperature of 170~200℃, the particles are melt-spun and hot-air drawn, and randomly deposited on the receiving roller to form a porous mesh structure. After cooling and winding, the high heat-resistant hot melt adhesive web for vehicles is obtained.

10. The method for preparing a high heat-resistant hot melt adhesive web for vehicles according to claim 9, characterized in that: The twin-screw extruder described in step S2 has a screw length-to-diameter ratio of 40:1 to 48:

1. The barrel is divided into 8 to 10 temperature zones along the material flow direction. The temperatures from the feeding section to the discharge die are set sequentially as follows: 150 to 160°C, 165 to 175°C, 180 to 190°C, 195 to 205°C, 200 to 210°C, 195 to 205°C, 190 to 200°C, and 185 to 195°C.

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