Self-cleaning oil-repellent nylon film and production process thereof

Abstract

The application provides a self-cleaning oil-proof nylon film and a production process thereof. The application adopts a three-layer co-extrusion structure, an outer layer is compounded with fluorine compounds and hydrophobic nano-SiO2, a low-surface-energy hydrophobic and oleophobic system is constructed, the problems of easy oil stain, easy fingerprint and difficult cleaning of a traditional nylon film are effectively improved, 100% pure PA6 is used as a supporting layer in a middle layer, the light and thin film and high light transmittance are realized, and the overall mechanical strength and size stability of the film are ensured, functional components are directly blended with resins and integrally formed through extrusion, no coating layer is needed in the later stage, the problems of easy peeling and delamination of the coating layer are solved, the oil-proof function is more durable, and the friction resistance is stronger, an anti-blocking additive is added in an inner layer, the film is prevented from being adhered during winding, good composite adhesion is reserved, and the poor adaptability of subsequent printing and composite processing is improved, the film can be produced by using a conventional two-way stretching process, no complex equipment needs to be newly added, continuous industrial mass production is realized, and the production difficulty and cost are reduced.

Description

Technical Field

[0001] This invention relates to the field of feature-functional thin film technology, specifically to a self-cleaning, oil-resistant nylon film and its manufacturing process. Background Technology

[0002] Biaxially oriented polyamide 6 (PA6) nylon film (BOPA) is a core substrate for flexible packaging, electronic protection, and home film due to its excellent mechanical strength, puncture resistance, oil resistance, high light transmittance, and printability. However, PA6 contains a large number of polar amide groups, resulting in high surface energy and strong oleophilic and hydrophilic properties, which presents significant challenges in practical applications. When used for packaging fried foods and sauces, it is easily soaked and adhered to by oil, affecting not only the packaging appearance but also causing oil penetration and reduced barrier properties. When used for protective films for electronic devices and touch panels, it is prone to fingerprints and oil stains, making cleaning difficult and severely impacting the user experience and light transmittance.

[0003] In existing technologies, solutions to improve the oil and fingerprint resistance of nylon films mainly fall into two categories: one is the surface coating method, which involves coating the surface of the nylon film with an organosilicon or fluorocarbon anti-fouling coating. Although this method can achieve oil and dirt resistance in the short term, it suffers from poor adhesion between the coating and the nylon substrate. After friction, bending, and high-temperature treatment, the coating is prone to peeling off, and the anti-fouling function quickly fails. At the same time, the coating affects the light transmittance of the nylon film and the subsequent printing and lamination performance. The other is the blending modification method, which involves blending anti-fouling functional fillers with PA6 resin to form a film. Although this method can solve the coating peeling problem, in existing technologies, the functional fillers have poor compatibility with the PA6 substrate and are prone to agglomeration. This not only causes crystal points and film breakage in the film, but also leads to a significant decrease in the film's light transmittance and mechanical strength. It is impossible to balance ultra-thin thickness, high light transmittance, and anti-fouling performance, making it difficult to meet the needs of industrial production and high-end applications.

[0004] Therefore, there is a need in the current environment to design a self-cleaning, oil-resistant nylon membrane and its manufacturing process to solve the technical problems mentioned in the background. Summary of the Invention

[0005] This invention provides a self-cleaning, oil-resistant nylon film and its manufacturing process to solve the technical problems mentioned in the background section.

[0006] The technical solution of the present invention is: a self-cleaning and oil-resistant nylon film and its production process, wherein the nylon film is divided into a three-layer co-extruded biaxially stretched structure, which consists of a self-cleaning and oil-resistant outer layer, a supporting middle layer, and a composite inner layer.

[0007] Optionally, the self-cleaning and oil-resistant outer layer comprises the following raw material components: 70-85 parts of PA6 resin, 5-10 parts of fluorine compound, 2-5 parts of hydrophobic nano-SiO2, and 2-5 parts of dispersant; the supporting middle layer comprises the following raw material components: 100wt% PA6 resin; and the composite inner layer comprises the following raw material components: 80-95 parts of PA6 resin and 5-10 parts of anti-blocking agent.

[0008] Optionally, the fluorinated compound is at least one of perfluoroalkyl ethyl acrylate copolymer, polytetrafluoroethylene micropowder, and fluorinated modified polyacrylate.

[0009] Optionally, the hydrophobic nano-SiO2 is fumed silica modified with hexamethyldisilazane and has a particle size of 10-50 nm.

[0010] Optionally, the dispersing agent is at least one of polyethylene wax, zinc stearate, and ethylene-acrylate copolymer.

[0011] Optionally, the anti-blocking agent is at least one of erucamide, oleamide, and micron-sized spherical silica.

[0012] Optionally, the total thickness of the nylon membrane is 8-30 μm, wherein the thickness of the self-cleaning and oil-resistant outer layer accounts for 15-25%, the thickness of the supporting middle layer accounts for 50-70%, and the thickness of the composite inner layer accounts for 15-25%.

[0013] Optionally, the raw materials of the self-cleaning and oil-resistant outer layer are, by weight: 78-82 parts PA6 resin, 7-9 parts fluorine compound, 3-4 parts hydrophobic nano-SiO2, and 2-3 parts dispersant; the raw materials of the composite inner layer are, by weight: 88-92 parts PA6 resin and 6-8 parts anti-blocking agent.

[0014] Optionally, a method for preparing a self-cleaning, oil-resistant nylon film includes the following steps: (1) Raw material pretreatment: Weigh each raw material according to the formula ratio of the self-cleaning oil-proof outer layer, the supporting middle layer and the composite inner layer, and dry them respectively; (2) Blending and plasticizing: The raw materials of the dried self-cleaning oil-proof outer layer, the supporting middle layer and the composite inner layer are blended at high speed and uniformly, and then sent to the corresponding extruders for melt mixing, vacuum degassing and melt filtration to obtain the molten melt of each layer; (3) Co-extrusion casting: The three layers of molten melt are quantitatively delivered to the three-layer co-extrusion flat die head through a precision metering pump, and molten three-layer co-extrusion sheet is formed by extrusion. The sheet is attached to the surface of the cooling roller for rapid cooling and shaping by a combination of air knife and high pressure classical adsorption to obtain amorphous casting sheet. (4) Biaxial stretching: The casting is stretched longitudinally and transversely in sequence to obtain a biaxially stretched nascent film; (5) Heat setting and cooling: The nascent film is subjected to gradient heat setting to eliminate internal stress, followed by cooling and tension balancing treatment; (6) Online testing and winding: The film performance is tested online. Qualified products are corona-treated, edge-trimmed, wound, and slit to obtain the finished product.

[0015] The beneficial effects of this invention are as follows: 1. Adopting a three-layer co-extrusion structure, the outer layer is compounded with fluorine compounds and hydrophobic nano-SiO2 to construct a low surface energy hydrophobic and oleophobic system, which effectively improves the problems of traditional nylon films being easy to stick to oil stains, easy to leave fingerprints, and difficult to clean; 2. The middle layer uses 100% pure PA6 as the support layer, which ensures the overall mechanical strength and dimensional stability of the film while achieving thinness and high light transmittance. 3. Functional components are directly blended with resin and extruded into one piece without a post-coating layer, which solves the problem of easy coating peeling and delamination, making the anti-oil and anti-friction function more durable and the friction resistance stronger. 4. An anti-blocking agent is added to the inner layer to prevent the film from sticking together during winding, while maintaining good composite adhesion and improving the problem of poor compatibility in subsequent printing and lamination processes. 5. It can be produced using conventional biaxial stretching technology without the need for additional complex equipment, enabling continuous industrial mass production and reducing production difficulty and costs. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It should be understood that the specific embodiments described herein are only for explaining the present invention and not for limiting the present invention. Furthermore, it should be noted that, for ease of description, only the parts related to the present invention are shown, not all structures. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0017] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0018] The preferred process parameters in the production process are as follows: (1) Raw material pretreatment: Dry at 75-85℃ for 10-16 hours, and control the moisture content of the raw material after drying to ≤300ppm; (2) Blending and plasticizing: The length-to-diameter ratio of the extruder is 36-48; the main machine speed is 200-400 r / min; the extrusion temperature range is 230-260℃; and the melt filtration adopts a 200-300 mesh double-layer filter screen. (3) Co-extrusion casting: The temperature of the chiller roll is controlled at 15-25℃; (4) Biaxial stretching: Longitudinal stretching preheating temperature 50-65℃, stretching temperature 55-70℃, stretching ratio 2.8-3.5 times; Transverse stretching preheating temperature 80-95℃, stretching temperature 90-105℃, stretching ratio 3.0-4.0 times. (5) Heat setting and cooling: Heat setting temperature 180-220℃, setting time 5-15s, and cooling to 20-30℃ after setting.

[0019] The methods for testing the oil and fingerprint resistance performance are as follows (the finished film product needs to undergo oil and fingerprint resistance performance testing): (1) Cut a 100mm×100mm sample, fix the self-cleaning oil-proof outer layer with the top facing up, and use a contact angle measuring instrument to measure the static contact angle between water and soybean oil. (2) Add 2 drops of soybean oil to the surface of the sample, and gently touch the simulated fingerprint with a clean finger cot to observe the state of oil stains and fingerprint residue; (3) Tilt the sample at 45°, rinse it with deionized water at a flow rate of 30L / min for 5s, and after drying, test the change in transmittance and calculate the oil residue rate and removal rate. Example 1

[0020] The self-cleaning and oil-resistant nylon membrane provided in this embodiment has a total thickness of 15μm, and the thickness ratio of the three-layer structure is as follows: 20% for the self-cleaning and oil-resistant outer layer, 60% for the supporting middle layer, and 20% for the composite inner layer.

[0021] Raw materials for each layer, by weight: Self-cleaning and oil-resistant outer layer: 80 parts PA6 resin, 8 parts perfluoroalkyl ethyl acrylate copolymer, 3 parts hydrophobic nano SiO2 (30nm, modified with hexamethyldisilazane), and 2 parts polyethylene wax dispersant; Supporting middle layer: 100wt% PA6 resin; Composite inner layer: 90 parts PA6 resin, 3 parts erucamide, and 5 parts micron-sized spherical silica (3μm).

[0022] Production process steps: (1) Raw material pretreatment: vacuum drying at 80℃ for 12h; (2) Blending and plasticizing: After high-speed mixing, the mixture is plasticized by a twin-screw extruder at a temperature of 235-255℃; (3) Co-extrusion casting: extruded by a three-layer co-extrusion die, and cast by quenching at 20°C; (4) Biaxial tension: 3.2 times in the longitudinal direction and 3.8 times in the transverse direction; (5) Heat setting: Gradient setting at 190-210℃ for 10 seconds; (6) Detection, corona treatment, and winding. Example 2

[0023] The total thickness is 8μm, with a 25% self-cleaning and oil-resistant outer layer, a 50% support middle layer, and a 25% composite inner layer.

[0024] Self-cleaning and oil-resistant outer layer: 70 parts PA6, 10 parts polytetrafluoroethylene micro powder, 5 parts hydrophobic nano SiO2, and 5 parts zinc stearate; Supporting middle layer: 100wt% PA6 resin; Composite inner layer: 80 parts PA6, 3 parts oleamide, and 7 parts silica. Example 3

[0025] Total thickness 30μm, self-cleaning and oil-resistant outer layer 15%, support middle layer 70%, composite inner layer 15%.

[0026] Self-cleaning and oil-resistant inner layer: 85 parts PA6, 5 parts fluorinated modified polyacrylate, 2 parts hydrophobic nano-SiO2, and 3 parts ethylene-acrylate copolymer. Supporting middle layer: 100wt% PA6 resin; Composite inner layer: PA6 95 parts, erucamide 2 parts, silicon dioxide 3 parts.

[0027] Comparative Example 1 The film is made of commercially available 15μm biaxially oriented nylon and has a conventional three-layer co-extrusion structure. The upper and lower surface layers are made of PA6 resin with a slip and anti-blocking agent, and the core layer is made of 100wt% PA6 resin. No oil-proof or fingerprint-proof modification treatment has been applied. It is prepared using conventional BOPA film production process.

[0028] Performance testing The nylon films prepared in Examples 1, 2, and 3, as well as the commercially available nylon film of Comparative Example 1, were simultaneously tested for appearance, mechanical properties, surface function, and composite performance. The specific test results are as follows: Example 1: The film has a total thickness of 15 μm, a visible light transmittance of 92.3%, a longitudinal tensile strength of 186 MPa, a transverse tensile strength of 279 MPa, a water static contact angle of 142°, a soybean oil static contact angle of 118°, an oil removal rate of 97.6%, no fingerprint residue on the surface, and a peel strength with CPP film of 3.8 N / 15 mm. After 500 cycles of rubbing, the oil removal rate remains at 92.1%. Example 2: The film has a total thickness of 8 μm, a visible light transmittance of 93.1%, a longitudinal tensile strength of 178 MPa, a transverse tensile strength of 268 MPa, a water static contact angle of 148°, a soybean oil static contact angle of 125°, an oil removal rate of 98.9%, no fingerprint residue on the surface, and a peel strength with CPP film of 3.8 N / 15 mm. The peel strength of the composite film is 3.6 N / 15 mm. After 500 cycles of reciprocating friction, the oil removal rate remains at 90.5%. In Example 3, the total film thickness is 30 μm, the visible light transmittance reaches 91.5%, the longitudinal tensile strength is 195 MPa, the transverse tensile strength is 292 MPa, the static contact angle of water is 135°, the static contact angle of soybean oil is 112°, the oil removal rate is 95.2%, and slight fingerprints on the surface can be easily wiped off. The peel strength of the composite film with CPP film is 3.9 N / 15 mm. After 500 cycles of reciprocating friction, the oil removal rate remains at 91.3%. In Comparative Example 1, the total thickness of a commercially available film is 15 μm, the visible light transmittance is 92.0%, the longitudinal tensile strength is 188 MPa, the transverse tensile strength is 282 MPa, the static contact angle of water is only 66°, the static contact angle of soybean oil is only 30°, the oil removal rate is only 20.3%, and there is serious fingerprint residue on the surface. After 500 cycles of reciprocating friction, the oil removal rate drops to 18.7%.

[0029] The test results above show that the self-cleaning, oil-resistant nylon film prepared by this invention can achieve an ultra-thin thickness of 8-30μm while maintaining a high visible light transmittance of over 91.5%. Its mechanical tensile properties are comparable to those of ordinary nylon films, with no significant decrease. The outer layer exhibits excellent hydrophobic and oleophobic properties, with an oil removal rate exceeding 95%. It also demonstrates outstanding anti-fingerprint effects, maintaining a stable function retention rate of over 90% after repeated rubbing, ensuring long-lasting functionality. The inner layer exhibits excellent composite adhesion, meeting the required strength for bonding with conventional packaging substrates. It is fully compatible with subsequent printing and lamination processes, effectively solving the core pain point in existing technologies where anti-fouling performance cannot be balanced with basic mechanical and optical properties. Overall, its performance is far superior to that of ordinary unmodified nylon films.

[0030] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A self-cleaning, oil-resistant nylon film, characterized in that, The nylon membrane is composed of a three-layer co-extruded biaxially stretched structure, consisting of a self-cleaning and oil-resistant outer layer, a supporting middle layer, and a composite inner layer.

2. The self-cleaning, oil-resistant nylon membrane according to claim 1, characterized in that, The self-cleaning and oil-resistant outer layer comprises the following raw material components: 70-85 parts PA6 resin, 5-10 parts fluorine compound, 2-5 parts hydrophobic nano SiO2, and 2-5 parts dispersant. The supporting middle layer comprises the following raw material components: 100wt% PA6 resin. The composite inner layer comprises the following raw material components: 80-95 parts PA6 resin and 5-10 parts anti-blocking agent.

3. The self-cleaning, oil-resistant nylon membrane according to claim 2, characterized in that, The fluorinated compound is at least one of perfluoroalkyl ethyl acrylate copolymer, polytetrafluoroethylene micro powder, and fluorinated modified polyacrylate.

4. The self-cleaning, oil-resistant nylon membrane according to claim 2, characterized in that, The hydrophobic nano-SiO2 is fumed silica modified with hexamethyldisilazane, with a particle size of 10-50 nm.

5. The self-cleaning, oil-resistant nylon membrane according to claim 2, characterized in that, The dispersing agent is at least one of polyethylene wax, zinc stearate, and ethylene-acrylate copolymer.

6. The self-cleaning, oil-resistant nylon membrane according to claim 2, characterized in that, The anti-adhesion agent is at least one of erucamide, oleamide, and micron-sized spherical silica.

7. The self-cleaning, oil-resistant nylon membrane according to claim 1, characterized in that, The total thickness of the nylon membrane is 8-30μm, of which the thickness of the self-cleaning and oil-resistant outer layer accounts for 15-25%, the thickness of the supporting middle layer accounts for 50-70%, and the thickness of the composite inner layer accounts for 15-25%.

8. The self-cleaning, oil-resistant nylon membrane according to claim 1, characterized in that, The raw materials of the self-cleaning and oil-resistant outer layer are, by weight: 78-82 parts PA6 resin, 7-9 parts fluorine compound, 3-4 parts hydrophobic nano SiO2, and 2-3 parts dispersant; the raw materials of the composite inner layer are, by weight: 88-92 parts PA6 resin and 6-8 parts anti-blocking agent.

9. A method for preparing a self-cleaning, oil-resistant nylon film, applicable to the self-cleaning, oil-resistant nylon film described in claims 1-8, characterized in that, Includes the following steps: (1) Raw material pretreatment: Weigh each raw material according to the formula ratio of the self-cleaning oil-proof outer layer, the supporting middle layer and the composite inner layer, and dry them respectively; (2) Blending and plasticizing: The raw materials of the dried self-cleaning oil-proof outer layer, the supporting middle layer and the composite inner layer are blended at high speed and uniformly, and then sent to the corresponding extruders for melt mixing, vacuum degassing and melt filtration to obtain the molten melt of each layer; (3) Co-extrusion casting: The three layers of molten melt are quantitatively delivered to the three-layer co-extrusion flat die head through a precision metering pump, and molten three-layer co-extrusion sheet is formed by extrusion. The sheet is attached to the surface of the cooling roller for rapid cooling and shaping by a combination of air knife and high pressure classical adsorption to obtain amorphous casting sheet. (4) Biaxial stretching: The casting is stretched longitudinally and transversely in sequence to obtain a biaxially stretched nascent film; (5) Heat setting and cooling: The nascent film is subjected to gradient heat setting to eliminate internal stress, followed by cooling and tension balancing treatment; (6) Online testing and winding: The film performance is tested online. Qualified products are corona-treated, edge-trimmed, wound, and slit to obtain the finished product.