A fiber-filled surface high-strength polyamide wet coating slurry, its preparation method and application

Abstract

This invention discloses a high-strength polyamide wet coating slurry for fiber-filled surfaces, its preparation method, and its application. The method includes: preparing a ternary solvent from metal halide salt A, alcohol B, and deionized water; placing waste nylon fibers C into the solvent system and dissolving them fully under specific temperature conditions; then adding a certain amount of filler fiber D to the system and dispersing it uniformly using mechanical stirring; coating the resulting polyamide wet coating slurry onto the surface of a composite yarn of a specific size using a double-sided coating method; and then performing a film-forming treatment under a water bath condition with added cationic polyelectrolyte E to obtain a high-strength polyamide wet coating for fiber-filled surfaces.

Description

Technical Field

[0001] This invention relates to the field of polyamide coating slurries, specifically to a high-strength polyamide wet coating slurry for fiber-filled surfaces, its preparation method, and its application. Background Technology

[0002] The polyamide wet coating process is an important means of recycling and reusing waste nylon (PA) using the dissolution / reprecipitation method. This process usually involves dissolving waste PA fibers in a special solvent system, adding appropriate fillers, coating the fabric, and then performing water bath exchange to obtain the corresponding polyamide wet-coated fabric.

[0003] The performance of polyamide coatings is closely related to their structural morphology, and the filler and the water bath exchange process are the two biggest influencing factors on the coating structure. Commonly used inorganic powder fillers mainly include calcium carbonate, kaolin, and hydrotalcite. The addition of fillers can optimize the performance of coated fabrics to a certain extent, but their functions are often limited. Therefore, the industry often uses modification methods to endow fillers with richer properties. For example, patent CN202111119777.6 describes the grafting modification of inorganic lightweight calcium carbonate powder and its application in polyamide wet coating, which gives the coated fabric certain excellent properties. Although such methods have achieved some success, the inherent limitations of powder fillers cannot be solved.

[0004] In recent years, fiber-reinforced composite materials have attracted widespread attention due to their generally high specific strength and good durability. Various fibers have been incorporated as reinforcing fillers into various matrix materials, achieving desirable results. For example, patent CN202110398462.3 (CN113119243A) describes a carbon fiber reinforced panel. This panel uses a fiber reinforcement method, laying carbon fiber composite materials within it, and employs a hot-pressing process to prepare a lightweight, high-strength panel, overcoming the problem of low strength-to-weight ratio in existing plywood panels. Patent CN104114619A discloses a preparation process for a fiber-reinforced resin composite. This reinforcing material is prepared by adding cellulose nanofibers to a matrix resin, exhibiting excellent bending and impact resistance properties.

[0005] Furthermore, the methanol precipitation rate during water bath exchange has a significant impact on the coating morphology, but previous studies have not described this issue extensively. This invention also addresses this issue by specially treating the aqueous phase components to stabilize the precipitation of substances such as methanol and calcium chloride through temperature and ion concentration adjustments.

[0006] In summary, fiber reinforcement technology can potentially solve the problems faced by traditional powder fillers. Therefore, this invention introduces ultrafine fibers as a reinforcing filler into the preparation process of polyamide wet coatings. Utilizing the lightweight and high-strength characteristics of fiber materials significantly reduces the amount of filler required, solves the defects caused by slurry viscosity, and imparts excellent wear resistance and other mechanical properties to the coating. Furthermore, the fiber material itself does not have hydrolysis issues, eliminating the need to consider pH levels and meeting environmentally friendly production requirements.

[0007] Traditional polyamide wet coating processes are highly dependent on fillers. However, powder fillers have a significant impact on slurry viscosity. To ensure the performance of the fabric, only one type of filler can often be added in industrial production, resulting in a single function of the coated fabric. Furthermore, the coated fabric has limitations such as low surface layer strength, filler hydrolysis, easy filler deposition, and uneven slurry coating leading to defects. Therefore, it is necessary to introduce a new type of filler material.

[0008] Fiber reinforcement is a highly effective method for strengthening materials. Ultrafine fibers themselves possess characteristics such as lightweight, high strength, high wear resistance, and high water and oil absorption. Even a very small amount of ultrafine fibers combined with the matrix material can produce a synergistic reinforcing effect, significantly improving the mechanical properties of the composite material. Therefore, the preparation of fiber-reinforced polyamide wet coatings is feasible. Summary of the Invention

[0009] To address the aforementioned problems, this invention provides a method for preparing a polyamide wet coating using ultrafine fibers as flexible reinforcing fillers.

[0010] In this invention, a ternary solvent is prepared using metal halide salt A, alcohol B, and deionized water. Waste nylon fibers C are placed in the solvent system and fully dissolved under specific temperature conditions. Then, a certain amount of filler fiber D is added to the system and dispersed uniformly using mechanical stirring. The resulting polyamide wet coating slurry is coated onto the surface of a composite yarn of a specific size using a double-sided coating method. A film-forming treatment is then performed in a water bath with added cationic polyelectrolyte E to obtain a high-strength polyamide wet coating on the fiber-filled surface.

[0011] To address the above problems, the present invention provides the following series of technical solutions:

[0012] A method for preparing a high-strength polyamide wet coating on a fiber-filled surface, wherein the mass fraction ratio of each component in the coating slurry is as follows:

[0013] drug quality score Nylon waste yarn 10～15％ Metal halide salts 25～30％ Monohydric alcohol 20～26％ Deionized water 30～40％ microfiber 1～3％

[0014] A method for preparing a wet-process coating slurry for fiber-filled surfaces using high-strength polyamide includes the following steps:

[0015] Step 1. Weigh a certain amount of metal halide salt, monohydric alcohol and deionized water, put the three into a 250ml three-necked flask, stir at low speed at room temperature until calcium chloride is completely dissolved, and the ternary solution system is obtained.

[0016] Step 2. Weigh a certain amount of waste nylon fibers and place them into the ternary dissolution system described in Step 1. Let the reaction stand until the waste nylon fibers are fully dissolved.

[0017] Step 3. After the nylon waste fibers have been dissolved, a certain amount of filler fibers that have been pre-shredded are placed into the system and stirred and dispersed to obtain the coating slurry;

[0018] In step 2, the temperature for the static reaction is 55-65°C, and the reaction time is 40-60 min. More preferably, the system temperature is 60°C and the reaction time is 50 min.

[0019] In step 3, the stirring and dispersing operation is carried out for 20 to 40 minutes at a speed of 100 to 300 r / min. More preferably, the stirring and dispersing operation is carried out for 30 minutes at a speed of 200 r / min.

[0020] A method for preparing a fiber-filled surface high-strength polyamide wet-coated film and coated fabric includes the following steps:

[0021] Step 1. Pour an appropriate amount of the prepared polyamide coating slurry into a polytetrafluoroethylene mold with grooves, then perform water bath exchange to form a film in a specific aqueous phase, and dry it thoroughly in an oven to obtain the coating film.

[0022] Step 2. Take a polyester / spandex blended base fabric, cut it to a certain size, and then fully immerse it in the coating slurry;

[0023] Step 3. Take out the fabric that is fully soaked in the sizing agent, scrape the sizing agent on both sides and place it in a specific water phase water bath. After the water bath is completely replaced, take out the fabric, wash it with deionized water and fix it flat on the needle plate. Then dry it thoroughly in the oven to obtain the coated fabric.

[0024] In step 1, the dimensions of the polytetrafluoroethylene mold groove should be 100mm×100mm×2mm, and the water bath exchange time should be 15-30s.

[0025] In step 2, the fabric specifications should be 70D, 200mm×50mm, the sizing temperature should be 40℃~50℃, and the soaking time should be 10~15s;

[0026] In step 3, the water bath exchange time should be 5-10 seconds, and the drying temperature should be 60℃-80℃.

[0027] The solution system used is a ternary system, consisting of a metal halide salt, a monohydric alcohol, and water, with a molar ratio of 1:2:8.

[0028] The metal halide salts used are one or more of calcium chloride, magnesium chloride, barium chloride, calcium bromide, and magnesium bromide, and their mass fraction in the slurry components is 25-30%.

[0029] The monohydric alcohol used is one or more of methanol, ethanol, n-propanol, isopropanol, and n-butanol, and its mass fraction in the slurry composition is 20-26%.

[0030] The filler used is one or more of ultrafine natural fibers (silk, cellulose fibers, etc.) and ultrafine synthetic fibers (polyester, polyamide, polyacrylonitrile, polypropylene, polytetrafluoroethylene, glass fiber, etc.), with a length-to-diameter ratio (L / D) of 5.1, a fiber length of 300-500 μm in the slurry, and a mass fraction of 1-3% for this component;

[0031] The filler fiber dispersion method in the preparation of polyamide coating slurry is mechanical stirring. The resulting slurry is milky white and has a viscosity of 220-300 mPa / s.

[0032] During the water bath exchange process of polyamide wet coating, one or more cationic polyelectrolytes such as polyethyleneimine, polyethyleneamine, and polyvinylpyridine should be added to a specific aqueous phase, with an addition amount of 10-20 g / L, and the aqueous phase temperature should be 1-5℃.

[0033] The resulting coated fabric has a double-layer structure. The upper surface functional layer is 5–7 mil thick, the lower honeycomb support layer is 5–8 mil thick, the total thickness of the single-sided coating film is 10–15 mil, the whiteness of the coated fabric is 105–108, the total thickness of the coated fabric is 1.1–1.3 mm, and the weight is 125–128 g / m². 2 .

[0034] Furthermore, the preparation process of a high-strength polyamide wet coating on a fiber-filled surface specifically includes the following steps:

[0035] Step 1. Weigh a certain amount of metal halide salt, monohydric alcohol and deionized water, put the three into a 250ml three-necked flask, stir at low speed at room temperature until calcium chloride is completely dissolved, and the ternary solution system is obtained.

[0036] Step 2. Weigh a certain amount of waste nylon fibers and place them into the ternary dissolution system described in Step 1. Let the mixture stand at 60°C for 50 minutes until the waste nylon fibers are fully dissolved.

[0037] Step 3. After the nylon waste fibers have been dissolved, a certain amount of filler fibers that have been pre-shredded are placed into the system and continuously stirred and dispersed at 200 r / min for 30 min to obtain the coating slurry.

[0038] Step 4. Take an appropriate amount of the prepared polyamide coating slurry and pour it into a polytetrafluoroethylene mold with a groove of 100mm×100mm×2mm. Then, perform water bath exchange in a specific aqueous phase for 15-30 seconds to form a film. Dry it thoroughly in an oven to obtain the coating film.

[0039] Step 5. Take a 70D polyester / spandex blended base fabric, cut it into 200mm×50mm pieces, and then fully impregnate it in a sizing solution at 40℃~50℃ for 10~15s.

[0040] Step 6. Take out the fabric that is fully soaked in the sizing agent, scrape the sizing agent on both sides, and place it in a specific water phase water bath for 5-10 seconds. After the water bath is completely replaced, take out the fabric, wash it with deionized water 2-3 times, and then flatten and fix it on the needle plate. Then dry it thoroughly in an oven at 60℃-80℃ to obtain the coated fabric.

[0041] In step 1, the molar ratio of the metal halide, monohydric alcohol and deionized water should be 1:2:8.

[0042] In step 1, the metal halide salt is one or more of calcium chloride, magnesium chloride, barium chloride, calcium bromide, and magnesium bromide.

[0043] In step 1, the alcohols are small molecule monohydric alcohols, such as one or more of methanol, ethanol, n-propanol, isopropanol, and n-butanol.

[0044] The ternary solvent system greatly promoted the dissolution of waste nylon fibers. The metal ions (such as Ca²⁺) released from the ionization of metal halide salts in the system... 2+ The nucleophile will form a complex with the carbonyl group in the nylon molecule, thereby breaking the hydrogen bond, reducing the crystallinity of the nylon molecule, and causing it to transform from a crystalline state to an amorphous state, thus promoting the dissolution of nylon waste fibers. The alcohol-water solvent system provides a polar environment, which intensifies the attack of the nucleophile group on the positively charged component in the reaction substrate, thereby promoting the nucleophilic reaction and accelerating the dissolution rate of the nylon molecule in the system.

[0045] In step 1, the mass fraction of metal halide salts in the slurry components is 25-30%, and the mass fraction of monohydric alcohols in the slurry components is 20-26%.

[0046] In step 3, the filler fiber is one or more of the following: ultrafine natural fibers (silk, cellulose fibers, etc.) and ultrafine synthetic fibers (polyester, polyamide, polyacrylonitrile, polypropylene, polytetrafluoroethylene, glass fiber, etc.).

[0047] Microfibers possess high aspect ratios and orientation ratios, along with a large specific surface area, resulting in exceptionally superior mechanical properties that significantly enhance various properties of the substrate. The high strength of microfibers in small quantities minimizes their impact on slurry viscosity, reducing defects during coating application. Furthermore, they migrate to the surface during water bath exchange, forming a high-strength, dense upper layer. In addition, microfibers act as bridging agents within the coating, dispersing external stresses, reducing microcrack formation, improving the coating's mechanical properties, and enhancing structural stability.

[0048] In step 3, the filler fiber accounts for 1-3% of the mass fraction of the slurry composition;

[0049] The specific aqueous phase mentioned in steps 4 and 6 is a water bath environment with added cationic polyelectrolyte, and the cationic polyelectrolyte is one or more of polyethyleneimine, polyethyleneamine, polyvinylpyridine, etc.

[0050] Film formation in a cationic polyelectrolyte solution can stabilize the water bath exchange process and reduce the degree of swelling inside the coating. The cationic polyelectrolyte can regulate the ion concentration in the water exchange system, which can optimize the surface and internal structure of the polyamide coating. If the ion concentration in the water exchange system is too low, calcium chloride will precipitate out in large quantities along with methanol molecules during the aqueous phase exchange, thereby affecting the microstructure of the coating and causing defects such as powdering. At the same time, the addition of cationic polyelectrolyte can also improve the surface smoothness of the coating after phase inversion, which is beneficial for subsequent inkjet printing and other specific applications.

[0051] In steps 4 and 6, the amount of cationic polyelectrolyte added in the specific water bath environment is 10-20 g / L.

[0052] In steps 4 and 6, the water phase temperature is 1-5℃, and the water bath exchange time is 15-30s and 5-10s, respectively.

[0053] The microstructure of the coating is greatly affected by the water bath exchange time. Keeping the water bath temperature at a low level can slow down the precipitation of methanol. In addition, if the water bath exchange time is insufficient, the coating film will not be formed sufficiently and cannot be used later. If the water bath exchange time is too long, the honeycomb structure inside the coating will be too obvious and cracks will appear on the surface, which will directly affect the various performance indicators of the coated fabric.

[0054] In step 5, the slurry temperature should be maintained between 40°C and 50°C.

[0055] The viscosity and rheological properties of polyamide wet coating slurry are greatly affected by temperature. If the temperature is too low, the slurry viscosity will be high and the rheological properties will be poor, which will easily cause uneven distribution of filler during the coating process.

[0056] Compared with the prior art, the present invention has the following advantages:

[0057] 1. The reinforcing material used in this invention differs from the traditional preparation process of polyamide wet coating. By introducing lightweight and high-strength ultrafine fibers, it solves various defects existing in traditional powder fillers at present.

[0058] 2. The dissolution system used in this invention is different from the traditional polyamide wet coating preparation process. It is a ternary system of metal halide salt-alcohol-water. Using this system to dissolve nylon waste fibers can achieve better dissolution rate and effect.

[0059] 3. This invention can construct a special polyamide wet coating upper surface layer by controlling the water bath exchange process. The resulting surface layer has a different density than the underlying honeycomb structure, which can give the coated fabric better abrasion resistance. Attached Figure Description

[0060] Figure 1 Surface morphology (SEM) of ultrafiber-filled polyamide wet coating;

[0061] Figure 2 The morphology of the ultrafine fibers within the coating (SEM);

[0062] Figure 3 The surface morphology (SEM) of the bottom surface of the functional layer is shown.

[0063] Figure 4 The surface morphology (SEM) of the honeycomb support layer;

[0064] Figure 5 This is a schematic diagram of a two-layer structure (the upper layer is the surface functional layer, and the lower layer is the honeycomb support layer). Detailed Implementation

[0065] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto. Unless otherwise specified, all percentages in the embodiments and comparative examples are mass percentages.

[0066] Preparation processes of Examples 1-5 and Comparative Examples 1-3:

[0067] (1) Weigh calcium chloride (CaCl2, Zhejiang Kairuibo Technology Co., Ltd.), ethanol (analytical grade, CH3CH2OH, Shanghai Aladdin Reagent Co., Ltd.) and water according to Table 1 below. Stir the three substances at low speed in a flask at room temperature (25°C) to prepare a ternary solution system.

[0068] (2) Weigh a certain amount of waste nylon filaments (Zhejiang Kairuibo Technology Co., Ltd.) according to Table 1 below, put them into the ternary dissolution system, and let them stand at 60°C for 50 minutes until the waste nylon filaments are fully dissolved;

[0069] (3) After the nylon waste fibers have been dissolved, different fillers (polyamide ultrafine synthetic fibers, raw material length-to-diameter ratio (L / D) of 5.1:1, fiber length in slurry of 300-500μm) are placed into the system according to Table 1. The coating slurry is obtained by stirring and dispersing continuously at 200r / min for 30min.

[0070] (4) Take 70D polyester / spandex blended base fabric, cut it into 200mm×50mm size, and then carry out fabric impregnation, water bath exchange and drying operations under the process conditions in Table 2.

[0071] The resulting coated fabric has a double-layer structure. The upper surface functional layer is 5–7 mil thick, the lower honeycomb support layer is 5–8 mil thick, the total thickness of the single-sided coating film is 10–15 mil, the whiteness of the coated fabric is 105–108, the total thickness of the coated fabric is 1.1–1.3 mm, and the weight is 125–128 g / m². 2 .

[0072] Table 1. Polyamide wet coating paste formulation (%)

[0073]

[0074] Note: The remaining components are ethanol and water, with a molar ratio of 2:8.

[0075] Table 2. Process conditions for preparing coated fabrics

[0076]

[0077] The samples obtained in the above steps all need to be tested as follows:

[0078] Rubbing fastness test: The test was conducted in accordance with GB / T 3920-2008 "Textiles - Tests for color fastness - Color fastness to rubbing".

[0079] Whiteness test: The test was conducted in accordance with GB / T8424.4-2001 "Method for First-Stage Evaluation of Whiteness of Textiles";

[0080] Coating thickness testing: Measured using a thickness gauge (coating thickness gauge from Shanghai Litao Automation Technology Co., Ltd.);

[0081] Acid release test: The test was conducted in accordance with GB / T 7573-2009 "Determination of pH value of water extract of textiles".

[0082] Ink absorption performance is compared using ink absorption time:

[0083] Cut five 25×25mm coated fabric samples. Add 0.04ml of commercial ink 1cm above the sample and observe the time it takes for the ink to completely penetrate the sample and stop spreading. Record the time and repeat 5 times to take the average value.

[0084] Stiffness test: The test was conducted in accordance with GB / T 7689.4-2013 "Test methods for reinforced woven fabrics - Part 4: Determination of bending stiffness";

[0085] Table 3. Test results for the examples and comparative examples.

[0086]

[0087] As shown in Table 1, the polyamide wet coatings obtained in Examples 1 to 5 of the present invention can achieve good dry and wet rubbing fastness, whiteness, and ink absorption on fabrics, and the fabrics are lighter and thinner, and the pH value is stable when exposed to water.

[0088] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. The application of a fiber-filled surface high-strength polyamide wet coating slurry in the preparation of coated films and coated fabrics, characterized in that, Includes the following steps: Step 1. Pour the prepared high-strength polyamide wet coating slurry for the fiber-filled surface into a mold with grooves, then perform water bath exchange to form a film in an aqueous phase, and dry it thoroughly in an oven to obtain the coating film. Step 2. Take the blended base fabric and immerse it in the high-strength polyamide wet coating slurry on the fiber-filled surface until fully impregnated; Step 3. Take out the fabric that is fully soaked in the sizing agent, scrape the sizing agent on both sides and place it in an aqueous phase water bath. After the water bath is completely replaced, take out the fabric, wash it with water and fix it flat on the board. Then dry it thoroughly in the oven to obtain the coated fabric. In steps 1 and 2, the high-strength polyamide wet coating slurry for the fiber-filled surface uses the following raw materials in the following mass percentages: 10-15% waste nylon fibers; Metal halide salts 25-30%; Monohydric alcohols 20-26%; 30-40% deionized water; Filler fiber 1~3%; The filler fiber is one or more of ultrafine natural fiber and ultrafine synthetic fiber, with a length-to-diameter ratio of 4.5~5.5:1 and a length of 300~500μm in the slurry; In steps 1 and 3, the aqueous phase is a water bath environment with added cationic polyelectrolyte, which is one or more of polyethyleneimine, polyethyleneamine, and polyvinylpyridine. In steps 1 and 3, the water phase temperature is 1~5℃, and the water bath exchange time is 15~30s and 5~10s, respectively.

2. The application according to claim 1, characterized in that, In step 2, the temperature of the high-strength polyamide wet coating slurry on the fiber-filled surface is 40℃~50℃, and the wetting time should be 10~15s; In step 3, the oven temperature is 60℃~80℃.

3. The application according to claim 1, characterized in that, The metal halide salt is one or more of calcium chloride, magnesium chloride, barium chloride, calcium bromide, and magnesium bromide.

4. The application according to claim 1, characterized in that, The monohydric alcohol is one or more of methanol, ethanol, n-propanol, isopropanol, and n-butanol.

5. The application according to claim 1, characterized in that, The method for preparing the high-strength polyamide wet coating slurry for fiber-filled surfaces includes the following steps: Step 1. Weigh out the metal halide salt, monohydric alcohol and deionized water, stir the three at low speed until the calcium chloride is completely dissolved, and you will get the ternary solution system. Step 2. Weigh out the waste nylon fibers and place them into the ternary dissolution system from Step 1. Let the reaction stand until the waste nylon fibers are fully dissolved. Step 3. After the nylon waste fibers have completely dissolved, place the pre-shredded filler fibers into the system and stir to disperse them to obtain the coating slurry.

6. The application according to claim 5, characterized in that, In step two, the temperature for the static reaction is 55~65℃, and the reaction time should be 40~60 min.

7. The application according to claim 5, characterized in that, In step three, the stirring and dispersing operation is carried out for 20 to 40 minutes at a speed of 100 to 300 r / min.

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