Preparation method of fully-degradable non-woven fabric capable of being dispersed

Abstract

The preparation method of the fully-degradable non-woven fabric capable of being dispersed comprises the following steps: providing a non-woven fabric matrix capable of being dispersed, and the matrix comprises 10-18% of PLA (Polylactic Acid) fiber; heating through high-temperature airflow; performing secondary fluffy treatment through hot steam; performing low-temperature setting treatment through low-temperature airflow; according to the preparation method, the PLA fibers are subjected to surface blowing treatment through normal-temperature airflow, and the hydrogen-bond interaction among the fibers can be accurately controlled while the PLA fibers are softened and the fluffy structure is fixed, so that the prepared non-woven fabric has excellent fluffy softness, proper dry and wet strength, rapid water dispersibility and low powder falling rate, is completely biodegraded, and has a good application prospect. And the technical contradiction of stiffness and difficulty in dispersion caused by the PLA fiber in the traditional process is effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a fully degradable flushable non-woven fabric. BACKGROUND

[0002] Flushable non-woven fabric is widely used in wet wipes, sanitary products and other fields as an environmentally friendly material. Its core requirement is to disperse quickly in water after use to avoid pipe blockage. With the strengthening of environmental protection regulations, the introduction of fully biodegradable materials such as polylactic acid (PLA) has become a trend. However, after adding PLA fibers to the flushable non-woven fabric, the PLA fibers are more stiff than wood pulp fibers and viscose fibers, which makes the hand feeling of the flushable non-woven fabric decrease. Especially when the addition amount of PLA fibers is more than 10%, the bulkiness, softness and hand feeling of the flushable non-woven fabric decrease significantly, affecting the user experience.

[0003] Therefore, the surface of these flushable non-woven fabrics that can achieve full degradation needs to be treated to improve the bulkiness, softness and hand feeling of the flushable non-woven fabric. In document CN114808327A, a preparation method of fluffy non-woven fabric is proposed, which can increase the thickness and softness by high-temperature airflow heating combined with low-temperature airflow rapid cooling and setting. However, this method is mainly for synthetic fibers such as polyolefin and hot air non-woven fabric. It is found in practice that direct application of hot air treatment combined with rapid cooling and setting can exacerbate the brittleness of PLA fibers, leading to fiber shedding and increased dust during production. On the other hand, this treatment method has limited effect on the surface bulkiness improvement of water jet process flushable non-woven fabric.

[0004] Therefore, there is an urgent need in the art for an innovative preparation method that can improve the surface bulkiness, softness and hand feeling of flushable non-woven fabric containing PLA fibers while maintaining the flushable and fully degradable properties. SUMMARY

[0005] Therefore, the present application provides a preparation method of a fully degradable flushable non-woven fabric to solve the above technical problems.

[0006] A preparation method of a fully degradable flushable non-woven fabric, comprising: S10: providing a flushable non-woven fabric base body, the base body comprising 10% to 18% PLA fibers; S20: heating the flushable non-woven fabric base body by high-temperature airflow, the high-temperature airflow temperature being 115 to 125°C, the wind pressure being 1500 to 2500 Pa, and the high-temperature airflow passing in a direction substantially perpendicular to the flushable non-woven fabric base body; S30: performing secondary fluffy treatment on the flushable non-woven fabric base body by hot steam, the hot steam temperature being 95 to 105°C, the humidity being 5 to 8%, and the treatment time being 1 to 3 seconds; S40: low-temperature setting treatment of the dispersible nonwoven fabric substrate by low-temperature airflow, low-temperature airflow temperature: 5-20°C, treatment time: ≤3s; S50: surface blowing treatment of the dispersible nonwoven fabric substrate by normal-temperature airflow, normal-temperature airflow temperature: 25-45°C, the normal-temperature airflow flows in a direction substantially parallel to the dispersible nonwoven fabric substrate.

[0007] The PLA fiber has a length of 3-10 mm, a fineness of 1-3 denier, and a melting point of 165-175°C.

[0008] In step S20, the air pressure is 1800-2200 Pa.

[0009] In step S30, when the PLA fiber content in the substrate is 10-12%, the temperature of the hot steam is 95-98°C, when the PLA fiber content in the substrate is 13-16%, the temperature of the hot steam is 99-102°C, and when the PLA fiber content in the substrate is 17-18%, the temperature of the hot steam is 103-105°C.

[0010] In step S40, when the PLA fiber content in the substrate is 10-12%, the temperature of the low-temperature airflow is 15-20°C, when the PLA fiber content in the substrate is 13-16%, the temperature of the low-temperature airflow is 10-15°C, and when the PLA fiber content in the substrate is 17-18%, the temperature of the low-temperature airflow is 5-10°C.

[0011] In step S30, when the substrate basis weight is less than or equal to 30 g / m2, the treatment time is 1-1.5 s, when the substrate basis weight is 30-50 g / m2, the treatment time is 1.5-2.5 s, and when the substrate basis weight is greater than or equal to 50 g / m2, the treatment time is ≥2.5 s.

[0012] In step S40, the low-temperature airflow is dry cold air, and the dew point temperature is lower than -10°C.

[0013] The PLA fiber has a trilobal cross-sectional shape, and the PLA fiber has a crimped form with a crimp number of 6-10 / 25 mm.

[0014] In step S50, the air speed of the normal-temperature airflow is 8-15 m / s.

[0015] The high-temperature airflow passes through the dispersible non-woven fabric substrate in a direction substantially perpendicular to the dispersible non-woven fabric substrate, and the angle between the flow direction of the high-temperature airflow and the plane direction of the substrate is 80-100°.

[0016] The application provides a preparation method of a fully degradable dispersible non-woven fabric. Specifically, the dispersible non-woven fabric substrate can be prepared through the following steps.

[0017] The application provides a preparation method of a fully degradable dispersible non-woven fabric, and specifically comprises the following steps.

[0018] S10: providing a dispersible non-woven fabric substrate, wherein the substrate comprises 10-18% of PLA fibers.

[0019] Specifically, the dispersible non-woven fabric substrate can be prepared through the following steps.

[0020] S101: providing fiber raw materials.

[0021] The fiber raw materials comprise 60-70% of wood pulp fibers, 15-20% of viscose fibers and 10-18% of PLA fibers.

[0022] The wood pulp fiber is 2.0-4.5 mm of conifer wood pulp fiber, preferably, the average fiber length of the conifer wood fiber is 2.5-3.7 mm, so that the conifer wood pulp fiber has better water dispersibility and longer length, so that the flushable non-woven fabric has sufficient strength and meets the flushable requirement, and when the conifer wood pulp fiber is used, the freeness of the formed conifer wood pulp is preferably 200-700 cc, and the freeness is measured by the Canadian standard freeness measurement method.

[0023] The viscose fiber includes round viscose fiber and flat viscose fiber, and the proportion of the viscose fiber in the fiber mixture is 15%-20%, wherein the proportion of the round viscose fiber is 10%-15%, and the proportion of the flat viscose fiber is 5%-10%. It can be understood that the flat viscose fiber can be obtained by dissolving natural fibers in a corresponding solvent and then wet spinning. Compared with the round viscose fiber, the flat viscose fiber has smaller bending stiffness and is more prone to entanglement. At the same time, the fiber can be entangled by its own physical properties, and the entanglement is a frictional holding action. Since the flat viscose fiber can be entangled using less external force than the round viscose fiber, the flat viscose fiber is more easily dispersed in water than the round viscose fiber.

[0024] In the embodiment, the round viscose fiber has a length of 4-20 mm, a denier of 1-3 deniers, and a length-diameter ratio of ≥3000, so as to provide entanglement strength and softness. In a specific embodiment, the round viscose fiber with a length of 6 mm, 12 mm or 18 mm can be used.

[0025] The flat viscose fiber has a length of 5-15 mm, a denier of 0.5-2 deniers, and a length-diameter ratio of ≥4000, so as to utilize the flat cross section to deform easily in water flow and enhance dispersibility.

[0026] Preferably, the width-thickness ratio of the flat viscose fiber is ≥2:1, and more preferably, the width-thickness ratio of the flat viscose fiber is 2.5:1-4:1, so as to improve dispersibility and softness while ensuring sufficient wet strength.

[0027] The viscose fiber can be lyocell fiber, which has a length of 8-15 mm and a linear density of 1.2-1.8 deniers. Lyocell fiber has excellent wet strength and biodegradability, which helps to improve the flushable characteristics of the product. It can be understood that the length is the average length, and the linear density is the average linear density.

[0028] In the embodiment, the PLA fiber has a length of 3-10 mm and a fineness of 1-3 deniers.

[0029] Further, the PLA fiber has a cross-sectional shape of a circle or a trilobal shape, and the PLA fiber has a crimped form with a number of crimps of 6-10 per 25 mm. Preferably, the PLA fiber has a cross-sectional shape of a trilobal shape, and the trilobal shape increases the friction and cohesion between the fibers, thereby enhancing the strength of the fiber web without using additional adhesive. Meanwhile, the special angular structure is more prone to stress concentration when subjected to shear force of water flow, thereby accelerating the disintegration of the fiber network. In addition, the crimped form of the PLA fiber greatly improves the bulkiness and entanglement of the fiber, so that the formed non-woven fabric is softer and more elastic.

[0030] Further, the PLA fiber has a melting point of 165-175°C.

[0031] Further, in order to improve the interfacial bonding between the polylactic acid staple fiber and the hydrophilic cellulose fiber, the polylactic acid staple fiber can also be subjected to surface hydrophilization pretreatment, such as atmospheric plasma treatment, or 0.5%-1.5% hydrophilic masterbatch can be added during spinning.

[0032] S102: Fiber web formation.

[0033] The fiber web formation process can adopt wet web formation. In the web formation process, the basis weight of the fiber web is controlled in the range of 30-150 grams per square meter, and the web formation speed is maintained at 50-200 meters / min.

[0034] Further, the fiber web formation can be performed by an inclined screen former, which comprises a headbox and a forming wire. The forming wire is configured in a endless loop shape and is supported and moved by a plurality of rolls, wherein the rolls include a breast roll located upstream of the headbox. A portion of the forming wire downstream of the breast roll is configured to be inclined upward relative to the horizontal direction, and this inclined upward portion is referred to as a forming section. The headbox applies the mixed pulp formed by the fiber raw material from above to the forming section, and the pulp is dewatered and formed into a wet fiber web.

[0035] S103: Hydroentanglement reinforcement.

[0036] Specifically, the wet fiber web can be subjected to hydroentanglement reinforcement by a hydroentanglement unit, which comprises a plurality of hydroentanglement assemblies arranged in sequence along the running direction of the wet fiber web. Preferably, the plurality of hydroentanglement assemblies comprises a pre-entanglement assembly, a main entanglement assembly, and a micro-entanglement assembly.

[0037] The pre-entanglement assembly is used for preliminary compaction and entanglement of the wet fiber web, wherein the pre-entanglement assembly comprises 1-2 hydroentanglement heads, and the hydroentanglement pressure is 20-30 Bar. When hydroentanglement is performed, the wet fiber web is sprayed from top to bottom.

[0038] The main needling assembly is used to make the fibers produce intense displacement, insertion, bending and entanglement, so as to form a main body network structure, wherein the main needling assembly comprises 3-5 water needling heads, the water needling pressure is 50-80 Bar, and the water needling heads of the main needling assembly can be arranged on the upper and lower sides of the wet fiber web to spray from the upper and lower sides of the wet fiber web at the same time.

[0039] The micro needling assembly is used to entangle and arrange the surface and internal of the fiber web through ultra-high pressure and extremely fine water needles, so as to micro-adjust and surface finish the wet fiber web through micro needling. The micro needling assembly comprises a micro needling water needle plate, the micro needling water needle plate comprises holes with a diameter of 0.08-0.1 mm, and the water pressure is 100-130 Bar during micro needling. The high-energy fine water needles can penetrate deep into the fiber web during the micro needling process, so as to fix the fibers that have not been completely entangled, especially the middle fibers, after main needling. In addition, the micro needling can eliminate the fiber fluff generated on the surface of the fiber web in the pre-needling and main needling steps, so as to make the material surface smooth and flat, thereby improving the hand feeling and avoiding the phenomenon of fluff and powder falling. In addition, the micro needling can optimize the structure, that is, optimize the fluffy structure and pore structure of the fiber network, so as to balance the strength, softness and dispersibility of the material.

[0040] S104: Dehydrating, primary drying and forming a primary dried substrate.

[0041] It can be understood that the substrate reinforced by water needling can be dehydrated in the form of negative pressure dehydration, and the dehydrated substrate can be dried. In the embodiment, the drying temperature is controlled in the range of 80-140°C, and the drying time is 0.5-5 min.

[0042] S20: Heating the flushable non-woven fabric substrate by high-temperature airflow, the temperature of the high-temperature airflow is 115-125°C, the wind pressure is 1500-2500 Pa, and the high-temperature airflow passes in a direction substantially perpendicular to the flushable non-woven fabric substrate.

[0043] It is found that the glass transition temperature (Tg) of PLA is about 55-60°C, and the melting point (Tm) is 160-180°C. The temperature interval of 115-125°C of the high-temperature airflow is located in the high-elasticity region of the PLA fiber, which can reduce the stiffness of the PLA fiber, and will not cause the fiber to soften excessively or even partially melt. Compared with the traditional high-temperature treatment above 130°C, the energy consumption is reduced by 15-20%.

[0044] Further, the wind pressure is 1800-2200 Pa, which is the best fluffy interval, the fibers can be fully separated without damage, and the processing consistency of the whole width can be further ensured in this range. In addition, when the wind pressure is greater than 2500 Pa, excessive impact will cause the fiber to break and generate excessive dust.

[0045] The high-temperature gas flow passes through the dispersible nonwoven fabric substrate in a direction substantially perpendicular to the substrate, specifically, the angle between the flow direction of the high-temperature gas flow and the plane direction of the substrate is 80°-100°.

[0046] S30: The dispersible nonwoven fabric substrate is subjected to secondary lofting treatment by hot steam, the temperature of the hot steam is 95-105°C, the humidity is 5-8%, and the treatment time is 1-3 s.

[0047] It can be understood that the hot steam used in the secondary lofting treatment is slightly wet superheated steam. By mixing the steam into the hot gas flow, a mixed gas flow with controllable temperature and humidity is formed. In the case where the temperature of the hot steam is 95-105°C and the humidity is 5-8%, the temperature is higher than the glass transition temperature of PLA fiber, which can effectively soften the PLA molecular chain, so that it is flexible and fluffy. However, the temperature is much lower than the melting point of the fiber, thereby avoiding fiber melting and bonding to ensure the flushability of the final product. It is found that in the case where the humidity is 5-8%, suitable water molecules can be provided as lubricants to penetrate into the amorphous region of the PLA fiber, reduce its glass transition temperature, and make it more easily stretched and deformed. However, it is not enough to cause melting or bonding. At the same time, it can balance the lofting degree, softness, strength, and flushability. More specifically, when the humidity is further increased, the wood pulp fibers and viscose fibers in the substrate absorb water and swell, which leads to the destruction of hydrogen bonds. Although it is soft, the wet strength is lost, and after drying, it is easy to appear hardening phenomenon.

[0048] Further, when the content of PLA fiber in the substrate is 10-12%, the temperature of the hot steam is 95-98°C; when the content of PLA fiber in the substrate is 13-16%, the temperature of the hot steam is 99-102°C; and when the content of PLA fiber in the substrate is 17-18%, the temperature of the hot steam is 103-105°C.

[0049] Further, when the basis weight of the substrate is less than or equal to 30 g / m2, the treatment time is 1-1.5 s; when the basis weight of the substrate is 30-50 g / m2, the treatment time is 1.5-2.5 s; and when the basis weight of the substrate is greater than or equal to 50 g / m2, the treatment time is ≥2.5 s.

[0050] S40: The dispersible nonwoven fabric substrate is subjected to low-temperature setting treatment by a low-temperature gas flow, the temperature of the low-temperature gas flow is 5-20°C, and the treatment time is ≤3 s.

[0051] Further, when the content of PLA fiber in the substrate is 10-12%, the temperature of the low-temperature gas flow is 15-20°C; when the content of PLA fiber in the substrate is 13-16%, the temperature of the low-temperature gas flow is 10-15°C; and when the content of PLA fiber in the substrate is 17-18%, the temperature of the low-temperature gas flow is 5-10°C.

[0052] Further, the low-temperature airflow is dry cold air, and the dew point temperature is lower than -10°C, which can avoid water vapor condensation on the relatively cold substrate surface, thereby preventing unnecessary temporary water bridges between fibers and affecting the dryness and strength of the final product.

[0053] It can be understood that the low-temperature setting treatment can fix the shape of the wood pulp fibers and the viscose fibers, preventing them from falling off in large quantities and forming dust during the subsequent surface blowing treatment.

[0054] S50: Surface blowing treatment of the dispersible non-woven fabric substrate by a normal-temperature airflow, the normal-temperature airflow temperature: 25-45°C, the normal-temperature airflow flows in a direction substantially parallel to the dispersible non-woven fabric substrate.

[0055] It can be understood that the surface blowing treatment by the normal-temperature airflow minimizes the temperature difference between the airflow and the substrate, avoids the influence of thermal shock on the set fluffy structure, and naturally connects with the conventional production environment temperature without the need for additional energy consumption for temperature adjustment. The surface blowing treatment in a direction substantially parallel to the dispersible non-woven fabric substrate can effectively remove loose fibers and dust, and can also avoid the penetrating disturbance of the vertical airflow to the fluffy structure, preventing the fiber from falling off after the fluffy treatment and causing the basis weight or thickness to change.

[0056] The normal-temperature airflow flows in a direction substantially parallel to the dispersible non-woven fabric substrate, which means that the included angle between the flow direction of the normal-temperature airflow and the surface of the substrate is 0-8°.

[0057] Further, the wind speed of the normal-temperature airflow is 8-15 m / s.

[0058] The fully degradable dispersible non-woven fabric of the present application will be described below in conjunction with specific examples. Example

[0059] Step S10: Fiber raw material: wood pulp fiber 67% + viscose fiber 18% + PLA fiber 15%; Among them, the wood pulp fiber is coniferous wood pulp fiber with an average length of 2.8 mm; the viscose fiber is 10% round viscose fiber + 18% flat viscose fiber; the PLA fiber is trilobal cross-section PLA fiber with a length of 6 mm, a denier of 1.8 denier, a crimp number of 8 / 25 mm, and a hydrophilic pretreatment.

[0060] Basis weight: 45 g / m2.

[0061] Step S20: using 120°C high temperature air flow, air pressure 2000Pa, vertically through the substrate.

[0062] Step S30: using 100°C, 6% humidity, micro-wet superheated steam treatment for 2 seconds.

[0063] Step S40: using 11°C dry cold air (dew point <-10°C) treatment for 2.5 seconds.

[0064] Step S50: using 35°C normal temperature air flow, blowing treatment in the direction of 5° angle with the substrate surface.

[0065] Comparative Example 1: The same as step S10 of Example 1, without the treatment of steps S20-S50.

[0066] The specific test results are as follows: Test index Unit Example 1 Comparative Example 1 Test method Basis weight g / ㎡ 45 45 GB / T 24218.1-2009 Bulkness cm³ / g 24.5 15.2 GB / T 24218.2-2009 MDT N / m 390 427 GB / T 12914.3 MDT-wet N / m 102 113 GB / T 12914.3 Water dispersibility s 180 220 EDANA / INDA shaking box Dust fall rate mg / ㎡ 0.06 0.11 EDANA ERT 130.2-02 Biodegradability % 90 / ISO 14855 From the test results, Example 1 compared to Comparative Example 1, the moisture dispersion performance is greatly improved, the powder drop rate is greatly reduced, at the same time, the strength is basically maintained, and the bulkiness is greatly increased, the performance is obviously improved compared with the existing product.

[0067] The above is only an embodiment of the present application, and does not limit the patent scope of the present application, any equivalent structure or equivalent flow transformation using the content of the present application specification, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a fully biodegradable, washable nonwoven fabric, characterized in that, include: S10: Provide a washable nonwoven fabric matrix, said matrix comprising 10% to 18% PLA fibers; S20: The buoyant nonwoven fabric substrate is heated by a high-temperature airflow, wherein the temperature of the high-temperature airflow is 115-125°C and the air pressure is 1500-2500Pa, and the high-temperature airflow passes through in a direction approximately perpendicular to the buoyant nonwoven fabric substrate. S30: The washable nonwoven fabric matrix is ​​subjected to a secondary fluffing treatment by hot steam. The hot steam temperature is 95-105°C, the humidity is 5-8%, and the treatment time is 1-3 seconds. S40: Low-temperature shaping treatment of the washable nonwoven fabric matrix is ​​carried out by low-temperature airflow. Low-temperature airflow temperature: 5~20°C, treatment time: ≤3s; S50: The surface of the nonwoven fabric substrate is treated by blowing air at room temperature. The temperature of the air is 25-45°C and the air flows in a direction roughly parallel to the nonwoven fabric substrate.

2. The preparation method according to claim 1, characterized in that, The PLA fiber has a length of 3-10 mm, a fineness of 1-3 denier, and a melting point of 165-175℃.

3. The preparation method according to claim 2, characterized in that, In step S20, the wind pressure is 1800-2200 Pa.

4. The preparation method according to claim 3, characterized in that, In step S30, when the PLA fiber content in the matrix is ​​10-12%, the temperature of the hot steam is 95-98°C; when the PLA fiber content in the matrix is ​​13-16%, the temperature of the hot steam is 99-102°C; and when the PLA fiber content in the matrix is ​​17-18%, the temperature of the hot steam is 103-105°C.

5. The preparation method according to claim 4, characterized in that, In step S40, when the PLA fiber content in the matrix is ​​10-12%, the temperature of the low-temperature airflow is 15-20°C; when the PLA fiber content in the matrix is ​​13-16%, the temperature of the low-temperature airflow is 10-15°C; and when the PLA fiber content in the matrix is ​​17-18%, the temperature of the low-temperature airflow is 5-10°C.

6. The preparation method according to claim 5, characterized in that, In step S30, when the matrix weight is less than or equal to 30 g / m², the processing time is 1 to 1.5 s; when the matrix weight is 30 to 50 g / m², the processing time is 1.5 to 2.5 s; and when the matrix weight is greater than or equal to 50 g / m², the processing time is ≥2.5 s.

7. The preparation method according to claim 6, characterized in that, In step S40, the low-temperature airflow is dry and cold air, and its dew point temperature is below -10°C.

8. The preparation method according to claim 7, characterized in that, The PLA fiber has a trilobal cross-sectional shape and is crimped, with 6 to 10 crimps per 25 mm.

9. The preparation method according to claim 8, characterized in that, In step S50, the wind speed of the ambient temperature airflow is 8 to 15 m / s.

10. The preparation method according to claim 1, characterized in that, The high-temperature airflow passing through the nonwoven fabric substrate in a direction approximately perpendicular to it means that the angle between the flow direction of the high-temperature airflow and the plane of the substrate is 80° to 100°. The normal-temperature airflow flowing in a direction approximately parallel to the nonwoven fabric substrate means that the angle between the flow direction of the normal-temperature airflow and the surface of the substrate is 0° to 8°.