Transparent shrinkage-free functional film and production process thereof

Abstract

The invention discloses a transparent shrinkage-free functional film and a production process thereof, and belongs to the technical field of high polymer material film production.A chain extender and a molecular regulator synergistically regulate and control a polyvinyl chloride molecular chain cross-linked structure to enhance the strength of the film, and a migration type slipping agent and an environment-friendly dispersing agent are combined for compounding to achieve long-acting surface slipping; meanwhile, a water freezing rapid shaping process is innovatively adopted to replace a polluting powder scattering technology, and a pre-stretching and anti-rolling dynamic stress eliminating technology is integrated, so that the problems that a traditional functional thin film is too high in shrinkage rate, insufficient in transparency, declined in smoothness and production pollution are systematically solved; the synergistic breakthrough of near-zero shrinkage, high transparency, lasting smoothness and green production is achieved for the first time in the field of ultrathin semi-hard films.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material film production, in particular to a transparent non-shrinkage functional film and a production process thereof. Background Art

[0002] With the continuous development of functional films, consumers' requirements for functional films are getting higher and higher. Traditional functional films have many shortcomings in shrinkage performance, transparency and feel, and cannot fully meet market demand.

[0003] At the same time, the production process also faces technical bottlenecks: first, the existing process is difficult to balance the molecular weight distribution and crystallinity, resulting in excessive shrinkage in a water bath / heating environment, affecting dimensional stability; second, the reliance on a powdering process for anti-sticking leads to increased haze on the film surface, and the slip agent migrates quickly and lacks durability. The powdering process also generates dust pollution, and plasticizers such as phthalates pose environmental risks. Finally, the traditional winding process cannot eliminate thermal stress on the film surface, and subsequent processing is prone to warping and shrinkage fluctuations. The above problems jointly restrict the application of ultra-thin semi-rigid functional films in high-end scenarios such as high-precision packaging and electronic protective films. Summary of the Invention

[0004] The main purpose of the present invention is to provide a transparent non-shrinkage functional film and a production process thereof, which can effectively solve the problems mentioned in the background technology.

[0005] To achieve the above object, the technical solution adopted by the present invention is: A transparent non-shrinkage functional film and its production process, comprising the following components and parts by weight: 100 parts of PVC resin (K value 800); 15-25 parts of dioctyl terephthalate (DOTP); Molecular regulator tert-dodecyl mercaptan (C 12 H 26 S) 1-2 servings; Chain extender 2-ethyl-2-hydroxymethyl-1,3-propanediol (C6H 14 O3) 0.5-1.5 parts; Migration type lubricant stearamide (C 18 H 37 NO) 0.5-1 part; Modified perfluoropolyether diffusing agent (PFPE-606) 0.5-1.5 parts; Nano-silicon dioxide (particle size 10-30nm) 0.5-1 part; 3-4 parts of odorless calcium zinc stabilizer; 5-10 parts of CPE impact modifier; 1-3 parts of acrylic core-shell particles.

[0006] By synergistically regulating the cross-linking degree of PVC molecular chains through chain extenders and molecular regulators, the semi-rigid properties can be ensured while reducing the amount of plasticizers, thus resolving the contradiction between the strength and shrinkage of traditional films.

[0007] Preferably, the polymerization degree of the PVC resin is 700-800, and the particle size is 0.1-0.2 mm; the modified perfluoropolyether diffusing agent is a short-chain perfluoropolyether with a carbon chain length ≤ C6.

[0008] Preferably, the film has a thickness of 0.05 ± 0.005 mm, a heat shrinkage of ≤ 1.5% (100°C x 30 min), a water bath shrinkage of ≤ 3% (70°C x 30 min), and a coefficient of friction of ≤ 0.08 (ASTM D1894). Nano-silica and stearamide form a micro-convex surface structure, reducing the coefficient of friction and suppressing shrinkage fluctuations.

[0009] A production process for a transparent non-shrinkage functional film comprises the following steps: S1, step-by-step mixing: S1.1. Place 100 parts by weight of PVC resin (K value 800), 15-25 parts by weight of DOTP, and 3-4 parts by weight of odorless calcium zinc stabilizer into a high-speed mixer and mix at a low speed of 750±50rpm until the temperature reaches 105-110℃; S1.2. Add 1-2 parts by weight of tert-dodecyl mercaptan, 5-10 parts by weight of CPE, and 0.5-1 part by weight of stearamide, increase the speed to 1500±100 rpm and mix at high speed until the temperature reaches 125-135°C; S1.3, add 0.5-1.5 parts by weight of modified perfluoropolyether diffusant and 0.5-1 parts by weight of nano-silicon dioxide, reduce the speed to 750±50rpm, and cool to 120℃ before discharging; S2, catalytic plasticization: S2.1, mix the mixture, 0.5-1.5 parts by weight of chain extender (C6H 14 O3), 1-3 parts by weight of acrylic acid core-shell particles are put into an internal mixer; S2.2. Plasticize at 160-180°C and a rotor speed of 30-40 rpm for 5-8 minutes to trigger in-situ crosslinking of the chain extender and the PVC molecular chain; S3, calendering-water-passing collaborative molding: S3.1. The plasticized material is calendered on a four-roll calender. The roller temperatures are set as follows: upper roller 180±5℃, middle roller 185±5℃, lower roller 170±5℃, side roller 175±5℃, and roller speed ratio 1:1.2-1.5; S3.2. Immediately place the formed base film into a 2±1°C ice water tank at a cooling rate of ≥50°C / s for 3-5 seconds. S3.3. After exiting the tank, the product is evenly covered with a deionized water film by an ultrasonic atomization spray system, with a water mist particle size of 5-10 μm and a flow rate of 100 ± 20 mL / min; S4, dynamic stress relief: The film passes through the pre-stretching roller group (tension 0.3-0.5kgf / cm 2 ) and reverse winding unit (tension 0.5±0.1kgf / cm 2 ), winding speed 20-25m / min.

[0010] Step temperature control prevents decomposition of lubricants, and chilled water cooling inhibits molecular chain rearrangement, eliminating thermal stress at the source.

[0011] Preferably, the heating rate of the high-speed mixing in S1 is 8-10°C / min, and the cooling rate is 5-7°C / min.

[0012] Preferably, the chain extender in S2 is activated above 160° C. to form an ether bond cross-linking network with the chlorine atoms at the ends of the PVC molecules.

[0013] Preferably, the cooling medium in the ice water tank in S3 is a 20-30 wt% ethylene glycol aqueous solution with a freezing point of ≤ -10°C. The frequency of the ultrasonic atomization spray system is 1.5-2.5 MHz. This allows for precise atomization to cover the micropores on the film surface, improving optical smoothness (haze ≤ 2%) and replacing polluting powdering processes.

[0014] Preferably, the reverse winding unit in S4 includes a tension closed-loop control system, which monitors the stress fluctuation of the film surface in real time and adjusts the winding torque by feedback, controlling the tension fluctuation to ≤±0.05kgf / cm 2 Dynamically adjust the winding torque to offset the residual shrinkage potential energy and ensure that the shrinkage rate approaches zero.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes innovative formulation design and collaboratively optimized production processes. The introduction of a synergistic system of chain extenders and molecular regulators achieves in-situ crosslinking and strengthening of polyvinyl chloride (PVC) molecular chains. Simultaneously, a process combining rapid freezing and water-setting with dynamic stress relief replaces traditional powdering techniques. This method simultaneously achieves an ultra-thin film with zero shrinkage, optical clarity, and long-lasting smoothness, while significantly improving production cleanliness and efficiency. This overcomes the technical challenge of balancing low shrinkage with high strength in the field of functional films. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a schematic diagram of the production process of a transparent non-shrinkage functional film. DETAILED DESCRIPTION

[0017] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0018] like Figure 1 The production process of the transparent non-shrinkable functional film shown is schematically illustrated and described below in conjunction with a detailed embodiment.

[0019] 1. Raw material formula (parts by weight): PVC resin (K value 800, particle size 0.15mm): 100 parts DOTP plasticizer: 20 parts Tert-dodecyl mercaptan (molecular regulator): 1.5 parts 2-Ethyl-2-hydroxymethyl-1,3-propanediol (chain extender): 1.0 part Stearamide (slip agent): 0.8 parts Modified perfluoropolyether PFPE-606 (diffuser): 1.0 part Nano-silicon dioxide (particle size 20nm): 0.8 parts Odorless calcium zinc stabilizer: 3.5 parts CPE impact modifier: 8 parts Acrylate core-shell particles: 2 parts 2. Production process Step 1: Stepwise Mixing Operation: Put PVC resin, DOTP and calcium zinc stabilizer into high-speed mixer and mix at low speed of 750 rpm; When the temperature reaches 108°C (heating rate 8°C / min), tert-dodecyl mercaptan, CPE, and stearamide are added; Increase the speed to 1500 rpm and mix until the temperature reaches 130°C (stearamide is completely melted at this time); Add PFPE-606 and nano-silica, reduce the speed back to 750 rpm, and cool to 120°C for discharge.

[0020] Principle: Temperature is controlled in stages to avoid agglomeration of nanoparticles (agglomeration occurs at temperatures above 135°C), and stearamide is evenly dispersed into the PVC matrix in a molten state at 125-130°C.

[0021] Step 2: Catalytic plasticization Operation: Put the mixture, chain extender and acrylic core-shell particles into the internal mixer; Set the rotor speed to 35 rpm, the temperature to 170°C, and plasticize for 6 minutes; Take samples to detect the plasticization end point (the material is in a uniform viscous flow state without any granular feeling).

[0022] Reaction mechanism: Chain extender C6H 14O3 is activated at ≥160℃ and reacts with the chlorine atoms at the ends of the PVC molecules: PVC-Cl+HO-CH2-C(CH2OH)(C2H5)-CH2OH→ PVC-O-CH2-C(CH2OH)(C2H5)-CH2OH + HCl.

[0023] Form an ether bond cross-linking network to enhance the strength of the molecular chain.

[0024] Step 3: Calendering Operation: The plasticized material is conveyed to the four-roll calender, and the roller temperature settings are: upper roller: 180℃, middle roller: 185℃, lower roller: 172℃, side roller: 175℃.

[0025] The roller gap was adjusted to 0.05 mm, the roller speed ratio was 1:1.3, and the base film linear speed was 22 m / min; Real-time monitoring of film thickness fluctuation (±0.003mm).

[0026] The middle roller has the highest temperature (185°C) to ensure material fluidity and avoid the rough surface caused by the lower roller temperature being too low.

[0027] Step 4: Rapid cooling of the frozen water tank Operation: The basement membrane is immediately placed in a freezing water tank (medium: 25% ethylene glycol aqueous solution, temperature 2°C); Cooling time 4s, cooling rate 55℃ / s; The membrane surface temperature dropped to 25℃ after leaving the tank.

[0028] The molecular chains are "frozen" under ultra-fast cooling, inhibiting crystal rearrangement (traditional slow cooling easily forms crystal regions and causes shrinkage).

[0029] Step 5: Ultrasonic atomization spraying Operation: Use a 2.0MHz ultrasonic atomizer to atomize deionized water into 8μm particle size water mist; flow rate 110mL / min, double-sided spraying to cover the membrane surface; Use a hot air knife (50°C) to blow away excess water film.

[0030] Micron-level water mist fills the microscopic depressions on the film surface (Ra is reduced from 0.2μm to 0.05μm), and the light transmittance is increased to 92.5%.

[0031] Step 6: Dynamic Stress Relief Operation: The film is passed through a pre-stretching roller group (tension 0.4kgf / cm 2 ) Release calendering stress; Enter the reverse winder, set the tension to 0.5kgf / cm 2 ; Closed-loop system monitors membrane surface tension fluctuations in real time (±0.03kgf / cm 2), automatically adjust the winding torque.

[0032] Principle: Reverse winding allows the film to curl in a relaxed state, offsetting the potential energy of thermal shrinkage (traditional winding will accumulate interlayer stress).

[0033] The performance test results are shown in the following table

[0034] The above examples show that this solution strengthens the molecular structure by catalyzing the in-situ cross-linking of PVC molecular chains with a chain extender, inhibits crystallization shrinkage by combining ultra-rapid cooling in a freezing water tank, and replaces the powdering process with ultrasonic atomization spraying to achieve optically smooth film surfaces. At the same time, the dynamic closed-loop control of pre-stretching and reverse winding completely eliminates residual stress on the film surface, thereby achieving for the first time in the field of ultra-thin semi-rigid films the technical effects of zero shrinkage, high transparency, long-lasting smoothness, and green production. This systematically overcomes the long-standing industry problems of functional films, namely, the inability to achieve both strength and shrinkage, and the mutual exclusion of smoothness and environmental protection.

[0035] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A transparent non-shrinkage functional film, characterized by: It includes the following components and parts by weight: 100 parts of PVC resin; 15-25 parts of dioctyl terephthalate; 1-2 parts of molecular regulator tert-dodecyl mercaptan; Chain extender 2-ethyl-2-hydroxymethyl-1,3-propanediol 0.5-1.5 parts; 0.5-1 part of migrating lubricant stearamide; 0.5-1.5 parts of modified perfluoropolyether diffusing agent; 0.5-1 part of nano silicon dioxide; 3-4 parts of odorless calcium zinc stabilizer; 5-10 parts of CPE impact modifier; 1-3 parts of acrylic core-shell particles.

2. The transparent non-shrinkable functional film according to claim 1, characterized in that: The polymerization degree of the PVC resin is 700-800, and the particle size is 0.1-0.2 mm; the modified perfluoropolyether diffusing agent is a short-chain perfluoropolyether with a carbon chain length of ≤C6.

3. The transparent non-shrinkable functional film according to claim 1, characterized in that: The thickness of the film is 0.05±0.005 mm; the shrinkage rate when heated is ≤1.5%, the shrinkage rate when water bath is ≤3%; and the friction coefficient is ≤0.

08.

4. A process for producing the film according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, step-by-step mixing: S1.

1. Place 100 parts by weight of PVC resin, 15-25 parts by weight of dioctyl terephthalate, and 3-4 parts by weight of odorless calcium zinc stabilizer in a high-speed mixer and mix at a low speed of 750±50 rpm until the temperature reaches 105-110°C; S1.

2. Add 1-2 parts by weight of tert-dodecyl mercaptan, 5-10 parts by weight of CPE, and 0.5-1 part by weight of stearamide, increase the speed to 1500±100 rpm and mix at high speed until the temperature reaches 125-135°C; S1.3, add 0.5-1.5 parts by weight of modified perfluoropolyether diffusant and 0.5-1 parts by weight of nano-silicon dioxide, reduce the speed to 750±50rpm, and cool to 120℃ before discharging; S2, catalytic plasticization: S2.

1. Place the mixture, 0.5-1.5 parts by weight of chain extender, and 1-3 parts by weight of acrylate core-shell particles into an internal mixer; S2.

2. Plasticize at 160-180°C and a rotor speed of 30-40 rpm for 5-8 minutes to trigger in-situ crosslinking of the chain extender and the PVC molecular chain; S3, calendering-water-passing collaborative molding: S3.

1. The plasticized material is calendered on a four-roll calender. The roller temperatures are set as follows: upper roller 180±5℃, middle roller 185±5℃, lower roller 170±5℃, side roller 175±5℃, and roller speed ratio 1:1.2-1.5; S3.

2. Immediately place the formed base film into a 2±1°C ice water tank at a cooling rate of ≥50°C / s for 3-5 seconds. S3.

3. After exiting the tank, the product is evenly covered with a deionized water film by an ultrasonic atomization spray system, with a water mist particle size of 5-10 μm and a flow rate of 100 ± 20 mL / min; S4, dynamic stress relief: The film passes through the pre-stretching roller group and the reverse winding unit in sequence, with a winding speed of 20-25m / min.

5. The process for producing a transparent non-shrinkable functional film according to claim 4, characterized in that: The high-speed mixing in S1 has a heating rate of 8-10°C / min and a cooling rate of 5-7°C / min.

6. The process for producing a transparent non-shrinkable functional film according to claim 4, characterized in that: The chain extender in S2 is activated above 160° C. to form an ether bond cross-linking network with the chlorine atoms at the ends of the PVC molecules.

7. The process for producing a transparent non-shrinkable functional film according to claim 4, wherein: The cooling medium of the ice water tank in S3 is a 20-30wt% ethylene glycol aqueous solution with a freezing point of ≤-10°C; the frequency of the ultrasonic atomization spraying system is 1.5-2.5MHz.

8. The process for producing a transparent non-shrinkable functional film according to claim 4, wherein: The reverse winding unit described in S4 includes a tension closed-loop control system that monitors the stress fluctuation of the film surface in real time and adjusts the winding torque through feedback to control the tension fluctuation to ≤±0.05kgf / cm 2 .

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