Functional film and production process thereof

Abstract

The invention discloses a functional film and a production process thereof, and belongs to the technical field of film production process.In formula design, polyvinyl chloride resin with the ultralow polymerization degree is adopted, a plasticizer is compounded in a specific proportion, a rare earth optical agent is introduced to achieve the spontaneous bright sheet effect, and a nanoscale surface modifier is added to optimize interface characteristics; according to the production process, a stepped embossing technology is adopted, shallow-layer grains are formed through coordinated regulation and control of temperature and pressure, and ultraviolet light online excitation treatment is synchronously combined; in the aspect of equipment, a non-contact air flotation winding device is designed, a thin film is wound in a suspended mode through directional airflow, and constant-pressure winding is achieved in cooperation with dynamic tension control. According to the scheme, on the basis of maintaining high light transmittance and excellent elasticity of the film, the durability of the paillette effect is remarkably improved, the deformation defect of the coiled material is effectively eliminated, meanwhile, the processing energy consumption is reduced, and the method is suitable for manufacturing high-end home decoration materials.

Description

Technical Field

[0001] This invention relates to the field of thin film manufacturing technology, and in particular to a functional thin film and its manufacturing process. Background Technology

[0002] High-brightness, elastic functional films widely used in home decoration primarily achieve their dazzling visual effect through a combination of polyvinyl chloride (PVC) materials and glitter embossing. However, existing technologies, in order to obtain sufficient glitter refraction, generally employ deep embossing (typically up to 3mm), leading to stress concentration within the film substrate. This results in irreversible indentation deformation during subsequent winding and storage, severely impacting product yield and appearance consistency. Simultaneously, plasticizer migration in traditional formulations reduces film transmittance and flexibility, while the high temperature and pressure conditions required for deep embossing not only increase energy consumption but also accelerate the decay of the glitter pattern, causing a significant decline in visual appeal after six months of use. Furthermore, conventional contact winding processes, where mechanical pressure acts directly on the film surface, inevitably lead to edge deformation of the roll material. Although the industry has attempted to mitigate these defects by optimizing embossing roller design or adjusting winding tension, a fundamental solution to the trade-off between optical performance, mechanical strength, and processing efficiency has yet to be found. Summary of the Invention

[0003] The main objective of this invention is to provide a functional thin film and its manufacturing process, which can effectively solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A functional thin film comprising the following components by mass percentage: 75%-78% ultra-low degree of polymerization PVC resin, degree of polymerization DP=800; 6%-7% of compound plasticizer, composed of DOTP and epoxidized soybean oil in a mass ratio of 2:1; 3.5% nano-sized modified silica slip agent, particle size ≤50nm; 5% hydrogenated SBS star elastomer; 0.5%-2% rare earth europium complex optical enhancer; The 4%-6% composite stabilizer is composed of calcium-zinc stabilizer and hydrotalcite in a mass ratio of 2:1.

[0005] Ultra-low degree of polymerization PVC resin (DP=800) has a short molecular chain, which improves melt flow by 30% and avoids yellowing caused by high-temperature shear degradation. DOTP in the compound plasticizer provides flexibility, and epoxidized soybean oil bonds with the polar groups of PVC to form a molecular-level water-locking structure, which inhibits the increase in haze caused by the migration of plasticizer to the surface.

[0006] Preferably, the rare-earth europium complex is excited at a wavelength of 365 nm, producing a self-illuminating glitter effect under natural light, with a transmittance ≥92%. The rare-earth europium complex contains Eu... 3+ Ionic 5 D0→ 7 The F2 transition produces 615nm red fluorescence, which, when superimposed with the specular reflection light from the physical embossing, creates an interference enhancement effect in the visible light band; its excited state lifetime reaches 0.8ms, ensuring that it maintains afterglow brightness even after leaving the ultraviolet region.

[0007] Preferably, the nano-modified silica slip agent forms a uniform molecular layer on the film surface, resulting in a surface friction coefficient ≤0.15. The alkyl chains (C18) grafted onto the nano-silica surface are directionally enriched at the interface during film cooling via entropy-driven effects, forming a molecular brush structure; its surface energy is reduced to 18 mN / m, thus reducing the interlayer peel force of the roll material to 0.2 N / cm.

[0008] A process for manufacturing a functional thin film includes the following steps: S1. Raw material blending: Mix ultra-low polymerization degree PVC resin, compound plasticizer, nano-grade modified silica slip agent, hydrogenated SBS star elastomer, rare earth europium complex and composite stabilizer in a high-speed mixer at 80-90℃ for 10-15 minutes. S2, Melt Calendering: The mixture is melted and plasticized at 160-180℃ using a twin-screw extruder, and then calendered into a base film using a calender. S3, stepped embossing: S3.1 Preheating stage: Hot pressing at 150-160℃ and 5MPa pressure for 10s; S3.2 Main embossing stage: Press at 175±2℃ and 15MPa pressure for 8s to form a sequined texture with a depth of 1.5mm; S3.3 Fixation stage: Processing at 185℃ and 8MPa pressure for 5s, while simultaneously exciting fluorescence online with 365nm ultraviolet light; S4. Air-floating winding: An air-floating winding device is used, in which 0.3-0.5MPa compressed air is introduced into the shaft core to form an air film. Winding is performed under dynamic tension control, with an initial tension of 1.2kgf / cm. 2 The pressure decreased linearly to 0.8 kgf / cm² as the roll diameter increased to 50%. 2 In the above process, 175℃ is close to the high elasticity transition point of PVC. Applying a pressure of 15MPa at this temperature can cause the molecular chains to align along the embossing direction. At the same time, the styrene hard segments of hydrogenated SBS form physical cross-linking points under pressure, locking the 1.5mm shallow deformation. Online ultraviolet excitation avoids chain segment relaxation caused by secondary heating.

[0009] Preferably, in step S3, an embossing roller is used for embossing. The embossing roller has a double-layer cooling structure, including an internal circulating water cooling system and a surface air cooling nozzle. Within 10 seconds after embossing, the film temperature is reduced to below 80°C. The internal water cooling (10°C) quickly removes heat from the roller, while the surface air cooling (-5°C nitrogen) rapidly cools the film surface, allowing it to pass through the temperature range of the maximum crystallization rate of PVC (120-90°C) within 10 seconds, controlling the crystallinity to below 5% and eliminating texture rebound.

[0010] Preferably, the dynamic tension control in S4 satisfies the following relationship:

[0011] in Real-time tension, unit is kgf / cm 2 , This represents the percentage of the current roll diameter to the initial roll diameter. The formula is derived based on the principle of conservation of thin film strain energy, ensuring that the elastic deformation energy density of the inner and outer layers of the roll material is consistent; the coefficient 0.008 has been verified by finite element simulation to ensure that the interlayer pressure gradient is ≤3%.

[0012] Preferably, the air-floating winding device in S4 includes: Hollow metal shaft core with uniformly distributed micropores on the surface, with a pore size of 50-100μm; The compressed air supply system supplies air to the inner cavity of the shaft core through a rotary joint; Tension sensor and closed-loop control system to adjust the speed of the take-up motor in real time; The distribution density of the micropores is 20-30 per cm. 2 The airflow direction forms a 45° angle with the film's motion direction.

[0013] The 45° angled micro-orifice jet airflow forms a Bernoulli low-pressure zone on the core surface, generating a 0.25MPa lift to offset the film's own weight; 20-30 pores / cm 2 Density matching the film yield strength avoids resonance induced by airflow disturbance.

[0014] Preferably, the surface of the shaft core is coated with a diamond-like carbon coating with a surface hardness ≥ HV2000. Diamond-like carbon coating sp 3 Hybridization content > 80%, surface energy < 15 mJ / m 2 This ensures that the contact angle of the slip agent is >110°, preventing nanoparticles from embedding into the micropores through the hydrophobic effect; the HV2000 hardness ensures that the micropores deform <1μm under a radial load of 10kN.

[0015] Compared with the prior art, the present invention has the following beneficial effects: In terms of functional film formulation design, this invention uses a combination of ultra-low polymerization degree PVC resin and a specific proportion of plasticizer to improve material fluidity, while introducing rare earth optical agents to achieve a self-illuminating sequin effect, and using nano-slip agents to optimize surface properties; in terms of production process, it adopts stepped embossing technology combined with online photoexcitation treatment, and uses an air-floating winding device to achieve non-contact winding; ultimately, while maintaining the film's high light transmittance and excellent elasticity, it significantly reduces processing energy consumption, effectively eliminates the problem of roll indentation and deformation, and greatly extends the durability of the sequin decorative effect. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the production process of the functional thin film of the present invention. Detailed Implementation

[0017] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0018] like Figure 1 The schematic diagram of the functional thin film production process is shown below, and will be explained in conjunction with a detailed embodiment.

[0019] I. Raw material preparation (based on a total mass of 100kg) According to the formula ratio, accurately weigh the following raw materials: Ultra-low degree of polymerization PVC resin: 76kg (DP=800). This degree of polymerization was chosen because its molecular chains are short and its flowability is good, allowing it to quickly fuse with plasticizers and avoid uneven plasticization during subsequent melting.

[0020] Compound plasticizer: 6.5 kg (DOTP and epoxidized soybean oil compounded at a mass ratio of 2:1). This includes 4.33 kg of DOTP (dioctyl terephthalate) and 2.17 kg of epoxidized soybean oil. DOTP improves the film's flexibility and temperature resistance, while epoxidized soybean oil enhances the compatibility of the plasticizer with PVC and reduces later migration (plasticizer migration leads to film hardening and decreased light transmittance).

[0021] Nanoscale modified silica slip agent: 3.5 kg (particle size 30 nm). The particle size must be controlled below 50 nm to form a uniform molecular layer on the film surface (if the particle size is too large, local agglomeration will occur, resulting in fluctuations in the surface friction coefficient).

[0022] Hydrogenated SBS star-shaped elastomer: 5kg. The star-shaped structure of hydrogenated SBS can form an "elastic support network" between PVC molecules, improving the tensile resilience of the film (tests show that after adding this elastomer, the film's elongation at break can be increased to over 300%).

[0023] Rare earth europium complex optical enhancer: 1.2 kg (excitation wavelength 365 nm). This complex produces a self-illuminating glitter effect under natural light, with a light transmittance of 92%.

[0024] Composite stabilizer: 5.8 kg (calcium-zinc stabilizer and hydrotalcite are compounded at a mass ratio of 2:1). Of this, 3.87 kg is calcium-zinc stabilizer and 1.93 kg is hydrotalcite. The calcium-zinc stabilizer prevents PVC from decomposing during high-temperature processing, while the hydrotalcite adsorbs hydrogen chloride gas generated during processing, further enhancing stability.

[0025] II. Raw material blending Add the weighed raw materials to a high-speed mixer (e.g., SHR-500), set the temperature to 85℃ and the speed to 800r / min, and mix for 12min.

[0026] Explanation of the principle: A temperature of 80-90℃ allows the plasticizer to gradually penetrate into the PVC resin particles, while high-speed stirring uses shear force to disperse the raw materials evenly. If the temperature is too low (e.g., below 80℃), the plasticizer cannot fully wet the PVC, which will lead to "fish eyes" (unplasticized particles) appearing during the later melting process; if the time is too short (e.g., less than 10 minutes), the nano-slip agent may be unevenly dispersed, affecting the surface slip effect.

[0027] After mixing, take a sample for observation. The material should be a uniform powder with no obvious lumps (if there are lumps, the mixing time needs to be extended by 2-3 minutes).

[0028] III. Melt rolling Melting and plasticizing: The mixed material is fed into a twin-screw extruder (model such as TE-65). The barrel temperature is set to 160℃, 170℃ and 180℃ from the feed section to the die head (gradually increasing the temperature to avoid local overheating and decomposition of PVC). The screw speed is 30r / min. The material melts and plasticizes in the barrel to become a uniform melt.

[0029] Calendering: The melt enters the calender (four-roll calender, roll temperature 170℃) through the extruder head and is rolled into a base film with a thickness of 0.3mm by the rolls. During the calendering process, the roll speed is controlled at 15m / min (too fast a speed will cause uneven base film thickness, while too slow a speed will cause the film to yellow due to excessive residence time).

[0030] Because 160-180℃ is the optimal melting range for PVC: below 160℃, the melt viscosity is high and it cannot be molded smoothly; above 180℃, it may cause PVC to decompose (producing hydrogen chloride gas, which causes black spots to appear on the film).

[0031] IV. Stepped embossing (core technology) The base film is fed into the embossing unit and processed in the following three stages: Preheating stage: The embossing roller and the pressure roller are hot-pressed at 155℃ and 5MPa for 10 seconds.

[0032] Principle: Preheating softens the base film, reducing stress concentration during subsequent main embossing (if preheating is not performed, direct high-pressure pressing can easily lead to cracking at the edges of the base film).

[0033] Main embossing stage: Switch to the main embossing roller and press for 8 seconds at 175℃ and 15MPa pressure to form a 1.5mm deep sequin pattern on the base film surface (the pattern is hexagonal honeycomb, and each sequin has a side length of 2mm).

[0034] By adjusting the pattern of the embossing roller, sequins of different shapes (such as circles and squares) can be formed, but the pattern depth must be kept at 1.5mm (shallower than the 3mm of the existing technology, which can reduce stress concentration and reduce the risk of indentation).

[0035] Light fixation stage: The embossed film is sent into the light fixation device and treated at 185℃ and 8MPa pressure for 5s. At the same time, a 365nm ultraviolet lamp (power 100W) is turned on to excite rare earth europium complex online.

[0036] Principle: A temperature of 185℃ can set the texture, and ultraviolet light excitation can "solidify" the fluorescence effect of rare earth europium complex (which can then continue to glow under natural light); tests show that after this treatment, the luminescence persistence of the glitter can be increased to 18 months (current technology does not use online excitation, and the brightness usually decreases by 30% after 6 months).

[0037] Auxiliary cooling: After embossing, the film temperature is reduced to 70°C within 10 seconds by the double-layer cooling structure of the embossing roller (5°C circulating water in the inner cavity and 10m / s air speed of the surface air-cooling nozzles) to avoid residual heat causing deformation of the pattern.

[0038] V. Air-floating winding The air-float type winding device is used for winding, and the specific operation is as follows: Air film formation: Compressed air at 0.4 MPa is introduced into the hollow metal shaft core (surface coated with diamond-like carbon, hardness HV2200). The air passes through the micropores on the surface of the shaft core (pore size 80 μm, distribution density 25 pores / cm). 2 The air is ejected and forms an air film between the shaft and the film (the airflow direction is 45° to the film movement direction, which can reduce the friction between the film and the shaft).

[0039] Dynamic tension control: Initial tension set to 1.2 kgf / cm 2 When the roll diameter increases to 50% of the initial roll diameter (e.g., from an initial roll diameter of 300 mm to 450 mm), the tension decreases linearly to 0.8 kgf / cm according to the formula. 2 .

[0040] Principle: If the tension remains unchanged when the roll diameter increases, the inner film will be deformed by pressure; linear tension reduction can ensure that the film is subjected to uniform force during the winding process and avoid indentations (traditional contact winding is prone to edge wrinkles due to the lack of air film and dynamic tension).

[0041] Rewinding complete: When the roll diameter reaches 1000mm, stop rewinding to obtain the finished roll material.

[0042] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A functional thin film, characterized in that: Includes the following components by mass percentage: 75%-78% ultra-low degree of polymerization PVC resin, degree of polymerization DP=800; 6%-7% of compound plasticizer, composed of DOTP and epoxidized soybean oil in a mass ratio of 2:1; 3.5% nano-sized modified silica slip agent, particle size ≤50nm; 5% hydrogenated SBS star elastomer; 0.5%-2% rare earth europium complex optical enhancer; The 4%-6% composite stabilizer is composed of calcium-zinc stabilizer and hydrotalcite in a mass ratio of 2:

1.

2. The functional thin film according to claim 1, characterized in that: The rare earth europium complex is excited at a wavelength of 365nm, produces a self-illuminating glitter effect under natural light, and has a transmittance of ≥92%.

3. A functional thin film according to claim 2, characterized in that: The nanoscale modified silica slip agent forms a uniform molecular layer on the film surface.

4. A manufacturing process for a functional thin film as described in any one of claims 1-3, characterized in that: Includes the following steps: S1. Raw material blending: Mix ultra-low polymerization degree PVC resin, compound plasticizer, nano-grade modified silica slip agent, hydrogenated SBS star elastomer, rare earth europium complex and composite stabilizer in a high-speed mixer at 80-90℃ for 10-15 minutes. S2, Melt Calendering: The mixture is melted and plasticized at 160-180℃ using a twin-screw extruder, and then calendered into a base film using a calender. S3, stepped embossing: S3.1 Preheating stage: Hot pressing at 150-160℃ and 5MPa pressure for 10s; S3.2 Main embossing stage: Press at 175±2℃ and 15MPa pressure for 8s to form a sequined texture with a depth of 1.5mm; S3.3 Fixation stage: Processing at 185℃ and 8MPa pressure for 5s, while simultaneously exciting fluorescence online with 365nm ultraviolet light; S4. Air-floating winding: An air-floating winding device is used, in which 0.3-0.5MPa compressed air is introduced into the shaft core to form an air film. Winding is performed under dynamic tension control, with an initial tension of 1.2kgf / cm. 2 The pressure decreased linearly to 0.8 kgf / cm² as the roll diameter increased to 50%. 2 .

5. The manufacturing process of a functional thin film according to claim 4, characterized in that: In S3, an embossing roller is used for embossing. The embossing roller has a double-layer cooling structure, including an internal circulating water cooling system and a surface air cooling nozzle. The film temperature is reduced to below 80°C within 10 seconds after embossing.

6. The manufacturing process of a functional thin film according to claim 4, characterized in that: The dynamic tension control in S4 satisfies the following relationship:

7. Among them Real-time tension, unit is kgf / cm 2 , This is the percentage value of the current roll diameter compared to the initial roll diameter.

8. The manufacturing process of a functional thin film according to claim 4, characterized in that: The air-float type winding device in S4 includes: Hollow metal shaft core with uniformly distributed micropores on the surface, with a pore size of 50-100μm; The compressed air supply system supplies air to the inner cavity of the shaft core through a rotary joint; Tension sensor and closed-loop control system to adjust the speed of the take-up motor in real time; The distribution density of the micropores is 20-30 per cm. 2 The airflow direction forms a 45° angle with the film's motion direction.

9. The manufacturing process of a functional thin film according to claim 7, characterized in that: The surface of the shaft core is coated with a diamond-like carbon coating with a surface hardness ≥ HV2000.

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