Method for manufacturing micro-foamed bulk hot air nonwoven fabric

Abstract

The application discloses a kind of micro-foaming fluffy hot air nonwoven fabric production methods, belong to nonwoven fabric production technical field, comprising the following steps: S1, polyethylene is heated to melt after adding crosslinking agent, foaming master batch, dispersing agent, antioxidant is uniformly mixed and stirred to obtain first component;S2, polypropylene is heated to melt to obtain second component;S3, first component and second component are only made into composite fiber silk and then only made into composite fiber web;S4, by hot air, composite fiber silk is mutually adhered, then the temperature of hot air is increased, and foaming master batch is foamed into micro-foaming fiber silk to polyethylene fiber silk, to obtain micro-foaming fiber web;S5, to micro-foaming fiber web is cured, cooling forming after obtaining hot air nonwoven fabric;The hot air nonwoven fabric of the application has good structural stability, tensile strength, fluffiness, comfort, hygroscopicity and air permeability due to micro-foaming fiber silk.

Description

A method for producing micro-foamed fluffy hot air nonwoven fabric Technical Field

[0001] This invention relates to the field of nonwoven fabric manufacturing technology, specifically to a method for manufacturing micro-foamed fluffy hot air nonwoven fabric. Background Technology

[0002] Hot-air nonwoven fabric is produced by carding fibers and then using hot air from a drying device to penetrate the fiber web, causing it to melt. Because the melting and bonding caused by the hot air penetrating the fiber web is point-like rather than regional, hot-air nonwoven fabric has advantages such as good bulkiness and breathability. Furthermore, the production process of hot-air nonwoven fabric is simple, efficient, and has low production costs. However, due to the characteristics of the materials used in making hot-air nonwoven fabric and the structure of the internal fibers, hot-air nonwoven fabric is usually made of one or more of polyethylene, polypropylene, and polyethylene terephthalate. Its material has a relatively obvious plastic texture, resulting in a harder feel. The texture of hot-air nonwoven fabric is not as delicate and soft as spunlace nonwoven fabric, and its moisture absorption is also not as good as spunlace nonwoven fabric or meltblown nonwoven fabric, which limits the application scenarios of hot-air nonwoven fabric.

[0003] Chinese Patent CN104988660A discloses a method for producing three-dimensional hot air nonwoven fabric, the steps of which include: Step 1, opening process, in which the fibers are opened; Step 2, carding process, in which the opened fibers are carded into a fiber web; Step 3, hot air setting process, in which the fiber web is sent into an oven for hot air penetration and setting, so that the fibers adhere to each other to form a planar hot air nonwoven fabric; Step 4, three-dimensional forming process, in which the three-dimensional forming equipment consists of a pair of heatable interlocking concave and convex rollers, the protrusions on the convex rollers are needles, the three-dimensional forming equipment is located at the outlet of the oven in Step 3, and a hot air nonwoven fabric preheating equipment is provided before the three-dimensional forming equipment; Step 5, winding process.

[0004] The aforementioned hot-air nonwoven fabric achieves a three-dimensional effect through a three-dimensional molding process, giving it a larger surface area and porosity, resulting in better bulkiness, moisture absorption, and breathability. However, the three-dimensional molding process affects the structural stability of the hot-air nonwoven fabric, reduces its tensile strength, and makes it difficult to maintain the three-dimensional effect under certain temperatures or pressures. Furthermore, the three-dimensional effect is achieved through surface protrusions forming a three-dimensional structure, which increases the surface roughness and further emphasizes the material's hardness, thus reducing its tactile feel and overall comfort. Therefore, there is still room for improvement. Summary of the Invention

[0005] To address the technical deficiencies in the background technology, this invention proposes a method for manufacturing micro-foamed fluffy hot air nonwoven fabric, which solves the aforementioned technical problems and meets practical needs. The specific technical solution is as follows:

[0006] A method for producing a micro-foamed, fluffy hot-air nonwoven fabric includes the following steps:

[0007] S1. Heat 15-50 parts of polyethylene by weight until melted, then add 0.5-3 parts of crosslinking agent, 0.1-1 parts of foaming masterbatch, 0.02-0.2 parts of dispersant, and 0.01-0.1 parts of antioxidant, mix and stir evenly to obtain the first component;

[0008] S2. Heat 50-100 parts by weight of polypropylene until melted to obtain the second component;

[0009] S3. The first component and the second component are spun into composite fiber filaments through a composite spinning equipment. The composite fiber filaments are composed of polyethylene fiber filaments and polypropylene fiber filaments with several foaming masterbatches dispersed inside. The composite fiber filaments are opened and combed to obtain a composite fiber web.

[0010] S4. By heating the polyethylene fiber filaments to a molten state through hot air penetrating the composite fiber mesh, the composite fiber filaments are bonded together. Then, the temperature of the hot air is increased to decompose the foaming masterbatch and generate foaming gas. The foaming gas causes the molten polyethylene fiber filaments to foam and form several pores on the surface. The polyethylene fiber filaments are foamed to obtain micro-foamed fiber filaments. The micro-foamed fiber filaments and polypropylene fiber filaments together form a micro-foamed fiber mesh.

[0011] S5. After the micro-foamed fiber web is cured and cooled to form a hot air nonwoven fabric composed of micro-foamed fiber filaments and polypropylene fiber filaments, a hot air nonwoven fabric is obtained.

[0012] As a further technical solution of the present invention, in step S1, the polyethylene is heated to a melting temperature of 120-130°C.

[0013] As a further technical solution of the present invention, the crosslinking agent is selected as dicumyl peroxide.

[0014] As a further technical solution of the present invention, the foaming masterbatch is modified sodium bicarbonate, and the foaming temperature of the foaming masterbatch is 140-155℃.

[0015] As a further technical solution of the present invention, the foaming masterbatch is prepared by the following method: 1 part by weight of epoxy resin is dissolved in sufficient anhydrous ethanol under the action of ultrasound, followed by the addition of 4-5 parts of sodium bicarbonate powder, 0.1 part of surfactant, and 0.1 part of curing agent, and then the mixture is stirred evenly to obtain a mixture. The mixture is then heated to allow the epoxy resin to react and cure. After the reaction is completed, the mixture is filtered to obtain a solid product. The solid product is washed and dried to obtain a foaming masterbatch of sodium bicarbonate coated with epoxy resin.

[0016] As a further technical solution of the present invention, the surfactant is selected from one or more of sodium dodecylbenzenesulfonate, sodium tetrapolypropylenebenzenesulfonate, sodium diisooctyl succinate sulfonate, and sodium dibutylnaphthalenesulfonate; the curing agent is selected from one of diethylenetriamine, triethylenetetramine, and diethylaminopropylamine.

[0017] As a further technical solution of the present invention, the dispersant is selected from one or more of polyvinyl alcohol, sodium polyacrylate, polyvinylpyrrolidone, and hydroxypropyl methylcellulose.

[0018] As a further technical solution of the present invention, the antioxidant is selected from one or more of butylated hydroxytoluene, AO-1010, AO-1076, AO-3114, and AO-330.

[0019] As a further technical solution of the present invention, in step S2, the polypropylene is heated to a melting temperature of 165-180°C.

[0020] As a further technical solution of the present invention, in step S4, the hot air temperature for heating the polyethylene fiber filaments to the melting point is 125-135°C, and the hot air temperature for decomposing the foaming masterbatch to generate foaming gas is 140-155°C.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention uses polyethylene and polypropylene to form a core-sheath composite fiber filament through spinning. The polyethylene fiber filament, serving as the sheath, contains foaming masterbatch. Hot air melts the polyethylene fiber filaments, causing them to bond together. Simultaneously, the foaming masterbatch decomposes, generating gas. This gas causes the polyethylene fiber filaments to slightly foam, creating micro-foamed fiber filaments. The hot-air nonwoven fabric consists of a fiber structure where several micro-foamed fiber filaments wrap around polypropylene fiber filaments. The large contact area between the bonded micro-foamed fiber filaments gives the hot-air nonwoven fabric good structural stability and tensile strength. Furthermore, because each fiber structure surface is composed of foamed micro-foamed fiber filaments, the hot-air nonwoven fabric exhibits good bulkiness and comfort. Additionally, the numerous pores on the surface of the micro-foamed fiber filaments provide excellent moisture absorption and breathability. Detailed Implementation

[0023] The embodiments of the present invention will be described below with reference to relevant examples. The embodiments of the present invention are not limited to the following examples, and the present invention relates to relevant necessary components in this technical field, which should be regarded as well-known technology in this technical field and can be known and mastered by those skilled in this technical field.

[0024] A method for producing a micro-foamed, fluffy hot-air nonwoven fabric includes the following steps:

[0025] S1. Heat 15-50 parts of polyethylene by weight until melted, then add 0.5-3 parts of crosslinking agent, 0.1-1 parts of foaming masterbatch, 0.02-0.2 parts of dispersant, and 0.01-0.1 parts of antioxidant, mix and stir evenly to obtain the first component;

[0026] S2. Heat 50-100 parts by weight of polypropylene until melted to obtain the second component;

[0027] S3. The first component and the second component are spun into composite fiber filaments through a composite spinning equipment. The composite fiber filaments are composed of polyethylene fiber filaments and polypropylene fiber filaments with several foaming masterbatches dispersed inside. The composite fiber filaments are opened and combed to obtain a composite fiber web.

[0028] S4. By heating the polyethylene fiber filaments to a molten state through hot air penetrating the composite fiber mesh, the composite fiber filaments are bonded together. Then, the temperature of the hot air is increased to decompose the foaming masterbatch and generate foaming gas. The foaming gas causes the molten polyethylene fiber filaments to foam and form several pores on the surface. The polyethylene fiber filaments are foamed to obtain micro-foamed fiber filaments. The micro-foamed fiber filaments and polypropylene fiber filaments together form a micro-foamed fiber mesh.

[0029] S5. After the micro-foamed fiber web is cured and cooled to form a hot air nonwoven fabric composed of micro-foamed fiber filaments and polypropylene fiber filaments, a hot air nonwoven fabric is obtained.

[0030] This invention discloses a method for manufacturing a two-component hot-air nonwoven fabric. In step S1, polyethylene is the low-melting-point component of the hot-air nonwoven fabric, and in step S2, polypropylene is the high-melting-point component. Polyethylene, as the internal adhesive structure of the hot-air nonwoven fabric, has good adhesive properties, low-temperature resistance, and chemical stability. It can effectively bond polypropylene fibers together to form a stable and continuous nonwoven fabric structure, which is beneficial to improving the tensile strength and stability of the hot-air nonwoven fabric. Polypropylene has good acid and alkali resistance, high-temperature resistance, air permeability, and antibacterial properties. The two-component hot-air nonwoven fabric formed by polyethylene and polypropylene has good chemical stability, air permeability, and antibacterial properties.

[0031] In step S1, a crosslinking agent, foaming masterbatch, dispersant, and antioxidant are added to the polyethylene. The dispersant improves the dispersibility of the foaming masterbatch in the first component by adsorbing onto the surface of the foaming masterbatch to form a protective film and reacting with the groups on the surface of the foaming particles, thereby ensuring the uniform distribution of the foaming masterbatch in the polyethylene melt. The foaming masterbatch is used to allow the polyethylene to foam and expand during the bonding and molding of the hot-air nonwoven fabric. The uniform distribution of the foaming masterbatch is beneficial for the uniform foaming of polyethylene to form a foam with a uniform cell structure. The crosslinking agent increases the viscosity, elasticity, and melt strength of the polyethylene melt through a crosslinking reaction, giving the polyethylene melt sufficient strength to... Foaming enhances the strength of the foamed material. Antioxidants prevent oxidative degradation of polyethylene at high temperatures, improving the durability of hot-air nonwoven fabrics. It's important to note that the foaming temperature of the foaming masterbatch needs to be higher than the melting temperature of polyethylene but lower than the melting temperature of polypropylene. This prevents the masterbatch from foaming in the first component, maintaining a stable melt structure. Furthermore, during the subsequent process of bonding the composite fibers together to form a nonwoven fabric by heating polyethylene to a melt, the polypropylene fibers will not be in a molten state during the foaming process, keeping them solid and improving the stability of the bonded hot-air nonwoven fabric structure.

[0032] In step S3, the first component is mainly composed of polyethylene melt, and the second component is polypropylene melt. The first and second components are spun into composite fiber filaments by a composite spinning device. The first and second components can be spun out through parallel spinnerets to form composite fiber filaments composed of parallel polyethylene fiber filaments and polypropylene fiber filaments, or they can be spun out through coaxial spinnerets to form a core-sheath structure composite fiber filament with polyethylene fiber filaments as the sheath and polypropylene fiber filaments as the core. The composite fiber filaments of the present invention preferably have a core-sheath structure. After being spun out through the spinnerets, the composite fiber filaments are continuously formed under the traction of airflow, and then collected by a receiving device. After the composite fiber filaments are cooled, they are opened and combed to form a composite fiber web composed of several composite fiber filaments. The composite fiber web has a non-woven fabric structure.

[0033] In step S4, since the composite fiber filaments have a core-sheath structure, the hot air, after penetrating the composite fiber web, heats the surface polyethylene to a molten state. The composite fiber filaments adhere to each other through the molten polyethylene. If the composite fiber web is cooled at this point to solidify the polyethylene, a conventional two-component core-sheath structure hot-air nonwoven fabric will be obtained. However, in this invention, the temperature of the hot air needs to be further increased to raise the temperature of the foaming masterbatch inside the polyethylene fiber filaments to the foaming temperature. The foaming masterbatch will decompose and generate gas. Since the polyethylene fiber filaments are in a molten state, this gas will cause the polyethylene fiber filaments to expand internally or escape to the surface of the polyethylene fiber filaments, thereby causing the polyethylene fiber filaments to expand and... Several foam structures are formed, that is, polyethylene fiber filaments are foamed into foam body through foaming masterbatch. The foam body is micro-foamed fiber filaments wrapped on the outer surface of polypropylene fiber. At this time, the fibers inside the composite fiber network are still in a core-sheath structure, with the sheath layer being micro-foamed fiber filaments and the core layer being polypropylene fiber filaments. Several core-sheath structure fiber filaments are bonded together by micro-foamed fiber filaments to form a micro-foamed fiber network. After the polyethylene fiber filaments are foamed into micro-foamed fiber filaments, the thickness increases, and the contact area of ​​the micro-foamed fiber filaments bonding together in the micro-foamed fiber network increases, ensuring the bonding strength of the micro-foamed fiber network. This allows the final hot-air nonwoven fabric to have good structural stability and tensile strength.

[0034] In step S5, the microfoamed fiber web is placed in an environment with a certain temperature for curing. During the curing process, the polyethylene molecular structure inside the microfoamed fiber filaments will rearrange and cross-link, forming a more compact and ordered structure, which is beneficial to improving the heat resistance, chemical resistance, and mechanical properties of the microfoamed fiber filaments. After curing and cooling, the polypropylene fiber filaments are firmly wrapped inside and together form a core-sheath fiber filament structure. Several core-sheath fiber filaments are bonded together by the microfoamed fibers on the surface to form a hot-air nonwoven fabric. It should be noted that the amount of foaming masterbatch added in the first component is small, and the amount of gas generated by the foaming masterbatch during the foaming process is small. The polyethylene fiber filaments will only produce slight foaming during the foaming process, so that the foamed microfoamed fiber filaments can still maintain their fibrous shape. The diameter of the foamed fiber filaments is approximately twice that of the polyethylene fiber filaments, while the diameter of the core-sheath fiber filaments is approximately 1.2-1.5 times that of the composite fiber filaments. The gaps between the fibers in the composite fiber web do not disappear due to the foaming of the polyethylene fiber filaments. Therefore, the hot-air nonwoven fabric still has a fiber web structure, and there are still a large number of gaps between the core-sheath fiber filaments to maintain a certain degree of air permeability. The surface of each core-sheath fiber filament is a micro-foamed fiber filament formed by foaming, which has good softness and fluffiness, giving the hot-air nonwoven fabric a good feel and improving its comfort. Furthermore, the micro-foamed fiber filaments have many pore structures, and the gaps between the fiber filaments are increased during the foaming process to maintain good air permeability. At the same time, the hot-air nonwoven fabric exhibits strong capillary action when in contact with liquid through these pores, thus having good moisture absorption.

[0035] In summary, this invention uses polyethylene and polypropylene to form a core-sheath structure composite fiber filament through spinning. The polyethylene fiber filament, serving as the sheath, contains foaming masterbatch. Hot air melts the polyethylene fiber filaments, causing them to bond together. Simultaneously, the foaming masterbatch decomposes to generate gas, which slightly foams the polyethylene fiber filaments into micro-foamed filaments. The hot-air nonwoven fabric consists of a fiber structure where several micro-foamed filaments wrap around polypropylene fiber filaments. The large contact area between the bonded micro-foamed filaments gives the hot-air nonwoven fabric good structural stability and tensile strength. Furthermore, since each fiber structure surface is composed of foamed micro-foamed filaments, the hot-air nonwoven fabric exhibits good bulkiness and comfort. Additionally, the numerous pores on the surface of the micro-foamed filaments provide excellent moisture absorption and breathability.

[0036] In one of the preferred embodiments of the present invention, in step S1, the polyethylene is heated to a melting temperature of 120-130°C.

[0037] The melting temperature of polyethylene is 110-130℃. In step S1 of this invention, heating polyethylene to 120-130℃ is to make polyethylene completely molten and have good fluidity and plasticity. Good fluidity makes it easier for the foaming masterbatch to be evenly dispersed in the first component. Good plasticity allows the first component to be reshaped into fibrous polyethylene fibers through the spinning process.

[0038] As one of the preferred embodiments of the present invention, dicumyl peroxide is selected as the crosslinking agent.

[0039] Because polyethylene has a high gas permeability, the foaming gas produced by the decomposition of the foaming agent can easily penetrate the polyethylene melt and escape, thus reducing the foaming effect. After adding a crosslinking agent to polyethylene, the crosslinking agent will react with polyethylene to increase the viscosity, elasticity and strength of the polyethylene melt, making it difficult for the foaming gas to penetrate the polyethylene melt and escape. This allows the polyethylene fiber filaments to foam and form several cell structures, resulting in micro-foamed fiber filaments. Diisopropylbenzene oxide decomposes to generate active free radicals. These active free radicals take hydrogen from the polyethylene carbon chain and form macromolecular free radicals, which in turn produce carbon-carbon coupling crosslinks to form a network structure.

[0040] As one of the preferred embodiments of the present invention, the foaming masterbatch is modified sodium bicarbonate, and the foaming temperature of the foaming masterbatch is 140-155℃.

[0041] The foaming masterbatch of this invention uses modified sodium bicarbonate that is heated to 140-155°C before it begins to decompose and produce carbon dioxide. Since the foaming masterbatch needs to be added to the polyethylene melt and mixed with other additives as the first component, and polyethylene needs to be heated to 120-130°C to become molten, the foaming masterbatch can be prevented from being decomposed by heat during this process. Thus, during the hot air bonding process of the composite fiber network, the foaming temperature of the foaming masterbatch can be used to make the polyethylene fiber filaments become molten and at the same time, the foaming masterbatch decomposes to produce carbon dioxide, thereby foaming the polyethylene fiber filaments into micro-foamed fiber filaments.

[0042] As one of the preferred embodiments of the present invention, the foaming masterbatch is prepared by the following method: 1 part by weight of epoxy resin is dissolved in sufficient anhydrous ethanol under the action of ultrasound, followed by the addition of 4-5 parts of sodium bicarbonate powder, 0.1 part of surfactant, and 0.1 part of curing agent, and the mixture is stirred until homogeneous to obtain a mixture. The mixture is then heated to allow the epoxy resin to react and cure. After the reaction is complete, the mixture is filtered to obtain a solid product. The solid product is washed and dried to obtain a foaming masterbatch of sodium bicarbonate encapsulated in epoxy resin.

[0043] The foaming masterbatch of this invention consists of microcapsules of sodium bicarbonate encapsulated in epoxy resin. During the preparation of the foaming masterbatch, the epoxy resin is dissolved in anhydrous ethanol using ultrasound to obtain an epoxy resin solution. Then, micron-sized sodium bicarbonate powder, a surfactant, and a curing agent are added. The sodium bicarbonate powder is difficult to dissolve in the epoxy resin solution but disperses within it, while the surfactant and curing agent dissolve. The surfactant reduces the surface tension of the epoxy resin solution and increases the wettability and dispersibility of the sodium bicarbonate powder. The epoxy resin solution is then stirred and heated to 60-80°C to allow the curing agent to promote the epoxy resin's dispersibility. The epoxy resin undergoes a curing reaction. After curing, the epoxy resin cannot dissolve further in anhydrous ethanol and precipitates on the surface of sodium bicarbonate powder. After all the epoxy resin has cured, a number of epoxy resin-coated sodium bicarbonate powder particles are dispersed in the solution. The solution is then filtered to obtain a solid product. After washing and drying, the solid product is used to obtain foaming masterbatch. The foaming temperature of the foaming masterbatch obtained after the sodium bicarbonate is modified by epoxy resin coating is 140-155℃, which is suitable for foaming the polyethylene fiber filaments of the present invention. Moreover, the foaming masterbatch consists of micron-sized particles, which ensures that after being mixed in the polyethylene melt, it can be used to form polyethylene fiber filaments through the spinning process.

[0044] As one of the preferred embodiments of the present invention, the surfactant is selected from one or more of sodium dodecylbenzenesulfonate, sodium tetrapropylenebenzenesulfonate, sodium diisooctyl succinate sulfonate, and sodium dibutylnaphthalene sulfonate; the curing agent is selected from one of diethylenetriamine, triethylenetetramine, and diethylaminopropylamine.

[0045] The surfactant of this invention can form a thin film on the surface of the epoxy resin solution, thereby reducing the surface tension of the epoxy resin solution and making it easier to flow and disperse. The surfactant can also be adsorbed on the interface between the epoxy resin solution and sodium bicarbonate powder, acting as an intermediary between the two immiscible substances, improving their compatibility, and thus promoting the uniform dispersion of sodium bicarbonate powder in the epoxy resin solution. Heating the epoxy resin solution promotes the curing agent and epoxy resin to undergo a condensation reaction to generate a cross-linked structure, thereby forming a fixed three-dimensional spatial network structure and a hardened epoxy resin. The cured epoxy resin cannot dissolve in anhydrous ethanol and precipitates on the surface of sodium bicarbonate powder, thus obtaining a foaming masterbatch composed of epoxy resin encapsulating sodium bicarbonate powder.

[0046] As one of the preferred embodiments of the present invention, the dispersant is selected from one or more of polyvinyl alcohol, sodium polyacrylate, polyvinylpyrrolidone, and hydroxypropyl methylcellulose.

[0047] In the dispersants of this invention, polyvinyl alcohol and sodium polyacrylate are nonionic dispersants. These dispersants react with the carbonyl structure in the epoxy resin on the surface of the foaming masterbatch through their functional groups, which helps the foaming masterbatch to be uniformly dispersed in the polyethylene melt. Sodium polyacrylate, polyvinylpyrrolidone, and hydroxypropyl methylcellulose are polymeric dispersants. These dispersants can form a protective film on the surface of the foaming masterbatch by adsorption, so that the foaming masterbatch forms a stable dispersion system in the polyethylene melt.

[0048] As one of the preferred embodiments of the present invention, the antioxidant is selected from one or more of butylated hydroxytoluene, AO-1010, AO-1076, AO-3114, and AO-330.

[0049] The antioxidant of this invention provides antioxidant protection by inhibiting thermal oxidative degradation and the reaction of free radicals with oxygen during the heating and processing of polyethylene. This improves the thermal stability and weather resistance of polyethylene, prevents thermal degradation from causing a decline in the performance and shortening the lifespan of polyethylene materials, and enables polyethylene to maintain good physical and chemical properties in high-temperature environments, thereby increasing the service life of polyethylene materials.

[0050] In one of the preferred embodiments of the present invention, in step S2, the polypropylene is heated to a melting temperature of 165-180°C.

[0051] In this invention, polypropylene fiber filaments are the main component of hot-air nonwoven fabric. Their melting temperature is higher than that of foaming masterbatch. When polyethylene fiber filaments bond the composite fiber filaments together and when foaming microparticles are foamed, the polypropylene fiber filaments are in a solid state. The polypropylene fiber filaments can serve as a skeleton structure in this process, so that the composite fiber web can maintain the stability of its original structure and ensure the stability of the hot-air nonwoven fabric structure after bonding and foaming.

[0052] As one of the preferred embodiments of the present invention, in step S4, the hot air temperature for heating the polyethylene fiber filaments to the melting point is 125-135°C, and the hot air temperature for decomposing the foaming masterbatch to generate foaming gas is 140-155°C.

[0053] The melting temperature of polyethylene is 110-130℃, and the hot air heating temperature is 125-135℃, which allows polyethylene to be completely molten, giving it good fluidity and plasticity. This allows the composite fiber filaments to bond together through the molten polyethylene fiber filaments. When the hot air temperature rises to 140-155℃, the sodium bicarbonate inside the foaming masterbatch will gradually decompose to produce carbon dioxide. The carbon dioxide will cause the molten polyethylene fiber filaments to foam into micro-foamed fiber filaments. The foaming temperature of the foaming masterbatch is higher than the melting temperature of polyethylene but lower than the melting temperature of polypropylene, so that the foaming masterbatch will not foam in the first component but will foam when the composite fiber filaments are bonded together. This results in a hot air nonwoven fabric with good bulkiness, comfort, moisture absorption and breathability.

[0054] The present invention will be further illustrated below through examples and comparative examples.

[0055] Example 1

[0056] S1. Heat 20 parts by weight of polyethylene until it melts, then add 1 part of crosslinking agent, 0.3 parts of foaming masterbatch, 0.08 parts of dispersant, and 0.03 parts of antioxidant, mix and stir evenly to obtain the first component;

[0057] S2. Heat 80 parts by weight of polypropylene until melted to obtain the second component;

[0058] S3. The first component and the second component are spun together by a composite spinning equipment to obtain a core-sheath composite fiber filament. The composite fiber is then opened and combed to obtain a composite fiber web.

[0059] S4. By heating the polyethylene fiber filaments to a molten state through hot air penetrating the composite fiber mesh, the composite fiber filaments are bonded together. Then, the temperature of the hot air is increased to decompose the foaming masterbatch and generate foaming gas. The foaming gas causes the molten polyethylene fiber filaments to foam and form several pores on the surface. The polyethylene fiber filaments are foamed to obtain micro-foamed fiber filaments. The micro-foamed fiber filaments and polypropylene fiber filaments together form a micro-foamed fiber mesh.

[0060] S5. After the micro-foamed fiber web is cured and cooled to form a hot air nonwoven fabric composed of micro-foamed fiber filaments and polypropylene fiber filaments, a hot air nonwoven fabric is obtained.

[0061] Example 2

[0062] S1. Heat 35 parts by weight of polyethylene until it melts, then add 1.8 parts of crosslinking agent, 0.55 parts of foaming masterbatch, 0.15 parts of dispersant, and 0.06 parts of antioxidant and mix thoroughly to obtain the first component;

[0063] S2. Heat 65 parts by weight of polypropylene until melted to obtain the second component;

[0064] S3. The first component and the second component are spun together by a composite spinning equipment to obtain a core-sheath composite fiber filament. The composite fiber is then opened and combed to obtain a composite fiber web.

[0065] S4. By heating the polyethylene fiber filaments to a molten state through hot air penetrating the composite fiber mesh, the composite fiber filaments are bonded together. Then, the temperature of the hot air is increased to decompose the foaming masterbatch and generate foaming gas. The foaming gas causes the molten polyethylene fiber filaments to foam and form several pores on the surface. The polyethylene fiber filaments are foamed to obtain micro-foamed fiber filaments. The micro-foamed fiber filaments and polypropylene fiber filaments together form a micro-foamed fiber mesh.

[0066] S5. After the micro-foamed fiber web is cured and cooled to form a hot air nonwoven fabric composed of micro-foamed fiber filaments and polypropylene fiber filaments, a hot air nonwoven fabric is obtained.

[0067] Example 3

[0068] S1. Heat 50 parts by weight of polyethylene until it melts, then add 2.5 parts of crosslinking agent, 0.8 parts of foaming masterbatch, 0.2 parts of dispersant, and 0.08 parts of antioxidant, mix and stir evenly to obtain the first component;

[0069] S2. Heat 50 parts by weight of polypropylene until melted to obtain the second component;

[0070] S3. The first component and the second component are spun together by a composite spinning equipment to obtain a core-sheath composite fiber filament. The composite fiber is then opened and combed to obtain a composite fiber web.

[0071] S4. By heating the polyethylene fiber filaments to a molten state through hot air penetrating the composite fiber mesh, the composite fiber filaments are bonded together. Then, the temperature of the hot air is increased to decompose the foaming masterbatch and generate foaming gas. The foaming gas causes the molten polyethylene fiber filaments to foam and form several pores on the surface. The polyethylene fiber filaments are foamed to obtain micro-foamed fiber filaments. The micro-foamed fiber filaments and polypropylene fiber filaments together form a micro-foamed fiber mesh.

[0072] S5. After the micro-foamed fiber web is cured and cooled to form a hot air nonwoven fabric composed of micro-foamed fiber filaments and polypropylene fiber filaments, a hot air nonwoven fabric is obtained.

[0073] Comparative Example 1

[0074] 20 parts by weight of polyethylene and 80 parts by weight of polypropylene are heated to a molten state and then spun through a composite spinning equipment to obtain a core-sheath composite fiber filament. The composite fiber is then opened and combed to obtain a composite fiber web. Hot air is passed through the composite fiber web to heat the polyethylene fiber filament to a molten state, causing the composite fiber filament to bond together. After cooling and molding, a hot air nonwoven fabric is obtained.

[0075] Comparative Example 2

[0076] 35 parts by weight of polyethylene and 65 parts by weight of polypropylene are heated to a molten state and then spun through a composite spinning equipment to obtain a core-sheath composite fiber filament. The composite fiber is then opened and combed to obtain a composite fiber web. Hot air is passed through the composite fiber web to heat the polyethylene fiber filament to a molten state, causing the composite fiber filament to adhere to each other. After cooling and molding, a hot air nonwoven fabric is obtained.

[0077] Comparative Example 3

[0078] 50 parts by weight of polyethylene and 50 parts by weight of polypropylene are heated to a molten state and then spun through a composite spinning equipment to obtain a core-sheath composite fiber filament. The composite fiber is then opened and combed to obtain a composite fiber web. Hot air is passed through the composite fiber web to heat the polyethylene fiber filament to a molten state, causing the composite fiber filament to bond together. After cooling and molding, a hot air nonwoven fabric is obtained.

[0079] According to Part 3: Determination of breaking strength and elongation at break, Part 6: Determination of absorbency, and Part 15: Determination of air permeability of the hot-air nonwoven fabrics obtained in the above examples and comparative examples, the breaking strength, liquid absorption, and air permeability were tested respectively. To more intuitively compare the absorbency of the hot-air nonwoven fabrics, the water absorption rate was calculated based on the dry weight of the hot-air nonwoven fabric before the test after obtaining the liquid absorption amount from the absorbency test. The test results are shown in Table 1 below.

[0080]

[0081] Table 1

[0082] According to the data in Table 1, the tensile strength of the hot-air nonwoven fabric in Examples 1-3 first increased and then decreased with the increase of polyethylene addition. This is because the fibers in the hot-air nonwoven fabric are bonded and fixed together by polyethylene, and the polyethylene exists in a foamed state. Increasing the amount of polyethylene added will increase the contact area between the fibers, thereby increasing the bonding strength between the fibers. However, the tensile strength of polyethylene foam is low, and the higher its content, the lower the tensile strength of the hot-air nonwoven fabric. Therefore, the amount of polyethylene added needs to be within a reasonable range, and the polyethylene addition ratio in Example 2 is relatively reasonable. The water absorption rate of the hot-air nonwoven fabric in Examples 1-3 increased with the increase of polyethylene addition. This is because polyethylene exists in a foamed state. The body exists in a state with many pore structures and absorbs and locks in a large amount of liquid through capillary action. Therefore, increasing the amount of polyethylene added is beneficial to improving the moisture absorption of hot air nonwoven fabric. In Examples 1-3, the air permeability of hot air nonwoven fabric decreases slightly with the increase of polyethylene addition. This is because the fibers in hot air nonwoven fabric are bonded and fixed to each other by polyethylene. The higher the amount of polyethylene added, the tighter the bonding and fixing between the internal fibers will be, resulting in a reduction in the gap between the fibers. Polyethylene will increase the gap between the fibers during the foaming process. Moreover, the polyethylene foam has several pore structures. Therefore, the air permeability of hot air nonwoven fabric will not decrease significantly with the increase of polyethylene addition, thus maintaining good air permeability.

[0083] Comparing the data from the embodiments and comparative examples in Table 1, although the hot-air nonwoven fabrics prepared with the same ratio are compared, the hot-air nonwoven fabrics obtained in the embodiments have lower tensile strength, but better moisture absorption and breathability, especially with a significant improvement in moisture absorption. In addition, when the hot-air nonwoven fabrics are touched, the hot-air nonwoven fabrics obtained in the embodiments have a finer texture and better softness. Its touch, softness, and moisture absorption are comparable to common spunlace nonwoven fabrics on the market, while the hot-air nonwoven fabrics obtained in the comparative examples continue the disadvantage of the relatively stiff touch of traditional hot-air nonwoven fabrics. It can be seen that the hot-air nonwoven fabrics obtained based on the technical solution of the present invention improve the defects of traditional hot-air nonwoven fabrics such as poor texture and poor moisture absorption. Combined with the relatively simple production process and high production efficiency of hot-air nonwoven fabrics, hot-air nonwoven fabrics can be applied to more products and fields.

[0084] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a micro-foamed, fluffy hot-air nonwoven fabric, characterized in that, Includes the following steps: S1. 15-50 parts by weight of polyethylene are heated to melt, then 0.5-3 parts of crosslinking agent, 0.1-1 parts of foaming masterbatch, 0.02-0.2 parts of dispersant, and 0.01-0.1 parts of antioxidant are added and mixed evenly to obtain the first component; the foaming masterbatch is modified sodium bicarbonate, and the foaming temperature of the foaming masterbatch is 140-155℃; the foaming masterbatch is prepared by the following method: 1 part by weight of epoxy resin is dissolved in sufficient anhydrous ethanol under ultrasonic action, then 4-5 parts of sodium bicarbonate powder, 0.1 parts of surfactant, and 0.1 parts of curing agent are added and stirred evenly to obtain a mixture. The mixture is then heated to allow the epoxy resin to react and cure. After the reaction is complete, the mixture is filtered to obtain a solid product. The solid product is washed and dried to obtain a sodium bicarbonate foaming masterbatch coated with epoxy resin; S2. ... S3. 50-100 parts of polypropylene are heated to melt to obtain the second component; S4. The first and second components are spun into composite fiber filaments through a composite spinning device. The composite fiber filaments are composed of polyethylene fiber filaments and polypropylene fiber filaments with several foaming masterbatches dispersed inside. The composite fiber filaments are opened and combed to obtain a composite fiber web; S5. The polyethylene fiber filaments are heated to a molten state by hot air penetrating the composite fiber web to make the composite fiber filaments stick together. Then the temperature of the hot air is increased to decompose the foaming masterbatch to generate foaming gas. The foaming gas causes the molten polyethylene fiber filaments to foam and form several pores on the surface. The polyethylene fiber filaments are foamed to obtain micro-foamed fiber filaments. The micro-foamed fiber filaments and polypropylene fiber filaments together form a micro-foamed fiber web; S6. The micro-foamed fiber web is cured, cooled and shaped to obtain a hot air nonwoven fabric composed of micro-foamed fiber filaments and polypropylene fiber filaments.

2. The method for producing micro-foamed fluffy hot air nonwoven fabric according to claim 1, characterized in that, In step S1, the polyethylene is heated to a melting temperature of 120-130°C.

3. The method for producing micro-foamed fluffy hot air nonwoven fabric according to claim 1, characterized in that, The crosslinking agent is dicumyl peroxide.

4. The method for producing micro-foamed fluffy hot air nonwoven fabric according to claim 1, characterized in that, The surfactant is selected from one or more of sodium dodecylbenzenesulfonate, sodium tetrapolypropylenebenzenesulfonate, sodium diisooctyl succinate sulfonate, and sodium dibutylnaphthalene sulfonate; the curing agent is selected from one of diethylenetriamine, triethylenetetramine, and diethylaminopropylamine.

5. The method for producing micro-foamed fluffy hot air nonwoven fabric according to claim 1, characterized in that, The dispersant is selected from one or more of polyvinyl alcohol, sodium polyacrylate, polyvinylpyrrolidone, and hydroxypropyl methylcellulose.

6. The method for producing micro-foamed fluffy hot air nonwoven fabric according to claim 1, characterized in that, The antioxidant is selected from one or more of butylated hydroxytoluene, AO-1010, AO-1076, AO-3114, and AO-330.

7. The method for producing micro-foamed fluffy hot air nonwoven fabric according to claim 1, characterized in that, In step S2, the polypropylene is heated to a melting temperature of 165-180°C.

8. The method for producing micro-foamed fluffy hot air nonwoven fabric according to claim 1, characterized in that, In step S4, the hot air temperature for heating the polyethylene fiber filaments to the melting point is 125-135℃, and the hot air temperature for decomposing the foaming masterbatch to generate foaming gas is 140-155℃.

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