Lightweight tear-resistant PVC lamp box fabric

Abstract

The invention discloses a light-weight tear-resistant PVC (polyvinyl chloride) lamp-box fabric, which belongs to the technical field of layered products and comprises a base layer, a middle reinforcing layer and a surface functional layer. The preparation method of the middle enhancement layer comprises the following steps: dopamine modification and gum dipping; the dopamine modification method comprises the following steps: orthogonally weaving aramid fibers and ultra-high molecular weight polyethylene fibers into a grid structure, dipping the grid structure in a dopamine solution, carrying out oscillation treatment at room temperature for 6-8 hours, taking out the grid structure, washing the grid structure with water for 2-3 times, and carrying out vacuum drying at 60-70 DEG C for 1-1.5 hours, so that a polydopamine coating formed on the surfaces of the fibers is cured; a fiber network modified by dopamine is obtained; according to the light-weight tear-resistant PVC lamp box fabric, light weight is guaranteed, mechanical optimization of tear resistance is achieved, tensile strength, elongation at break, trapezoidal tear strength and interlayer peel strength are improved, and the tear strength recovery rate is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of laminated products, and particularly relates to a lightweight and tear-resistant PVC light box cloth. Background Art

[0002] With the continuous progress of society and the increasing abundance of commodities, the advertising industry has developed rapidly, which puts forward higher requirements for advertising media. The emergence of light box cloth has replaced hard materials such as neon lights, plastic films, and plexiglass that once dominated the advertising media, and has gradually become the preferred material for making light boxes. The advantages of light box cloth are manifested in that the light boxes made are brightly colored, have a long service life, are convenient for transportation, are safe to use, can be pasted with light-transmitting instant stickers on the light box, and can also be subjected to heat transfer printing, super heat printing, computer photo printing, etc., and can be made into large or extra-large light boxes, with arbitrary shapes of plane and curved surfaces, and are widely used.

[0003] Traditional light box cloth faces many challenges during outdoor use. On the one hand, its tear resistance is insufficient. In outdoor complex environments, such as strong winds and external force collisions, it is prone to tearing, and even the light box may be damaged. When there is a slight tear in the light box cloth, a light-transmitting gap is formed at the tear, affecting the advertising display effect, and the exposed fibers accelerate aging, shortening the overall service life. On the other hand, traditional light box cloth is relatively heavy, which brings inconvenience to transportation and installation, increases the construction cost and difficulty, and in some large outdoor advertising projects, due to the heavy weight of the light box cloth, more manpower and equipment are required for installation, and problems such as deformation caused by weight are likely to occur during the installation process.

[0004] In the prior art, although attempts have been made to improve the strength by adding calcium carbonate or fibers, problems such as an increase in grammage or a poor strength improvement effect will occur, and it is difficult to balance lightweight and tear resistance. Therefore, it is of great practical significance to develop a lightweight PVC light box cloth with excellent tear resistance. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a lightweight and tear-resistant PVC light box cloth, which realizes the mechanical optimization of the tear resistance while ensuring lightweight, improves the tensile strength, elongation at break, trapezoidal tear strength, and interlayer peel strength, and has a high tear strength recovery rate.

[0006] To solve the above technical problems, the technical solutions adopted by the present invention are as follows: A lightweight and tear-resistant PVC light box cloth, comprising a base layer, an intermediate reinforcing layer, and a surface functional layer; The preparation method of the base layer is to mix hollow polyester fibers and chopped carbon fibers, impregnate with PVC emulsion after needle punching molding, and dry at 100 - 120 °C; The basis weight of the base layer is 110-130 g / m 2 , and the porosity is 30%-40%; The mass ratio of the hollow polyester fiber to the short carbon fiber is 10:1.5-2; The length of the short carbon fiber is 3-6 mm.

[0007] The preparation method of the intermediate reinforcing layer includes the following steps: dopamine modification and dipping; The method of dopamine modification is to orthogonally weave aramid fiber and ultra-high molecular weight polyethylene fiber into a grid structure, immerse it in dopamine solution, oscillate at room temperature for 6-8 hours, take it out and rinse it with water 2-3 times, and dry it in vacuum at 60-70 °C for 1-1.5 hours to cure the polydopamine coating formed on the fiber surface, and obtain a dopamine-modified fiber network; The linear density of the aramid fiber is 200-300 D; The linear density of the ultra-high molecular weight polyethylene fiber is 150-200 D; The mass ratio of the aramid fiber to the ultra-high molecular weight polyethylene fiber is 1:0.8-1; The warp and weft density of the grid structure is 10×10 roots / cm-14×14 roots / cm; The dopamine solution is prepared by dissolving dopamine hydrochloride in Tris buffer solution with a pH of 8.2-8.8, and the concentration of dopamine in the dopamine solution is 2-2.5 g / L; The concentration of the Tris buffer solution is 12-20 mmol / L; The method of dipping is to add oxidized micro carbon fiber into N,N-dimethylacetamide, ultrasonically treat it for 20-30 min, then add polyurethane prepolymer, stir at a speed of 600-800 rpm for 2-3 h to obtain a glue solution, immerse the dopamine-modified fiber network in the glue solution, take it out after dipping for 5-8 min, and dry it at 70-80 °C for 15-20 min to make the glue solution initially gel, and then thermocompression laminate it with the base layer; The mass ratio of the polyurethane prepolymer, oxidized micro carbon fiber, and N,N-dimethylacetamide is 100:5-7:20-30; The number average molecular weight of the polyurethane prepolymer is 500-1000; The frequency of the ultrasonic wave is 50-70 kHz; The preparation method of the oxidized micro carbon fiber is to disperse the micro carbon fiber in a 60-65 wt% nitric acid solution, reflux at 75-80 °C for 3-4 h, filter, wash, and dry to obtain oxidized short carbon fiber; The length of the micro carbon fiber is 80-120 μm; The temperature of the hot pressing composite is 150 - 170 °C, and the pressure is 4 - 6 MPa.

[0008] The preparation method of the surface functional layer is as follows: 5 - 8 wt% of anti - tearing microcapsules are added to PVC resin, and granulation is carried out by twin - screw extrusion. Then, it is calendered into a film at 170 - 180 °C, and the film thickness is 0.2 - 0.3 mm. It is then secondarily hot - pressed and compounded with the middle reinforcing layer, cooled and wound up to obtain the PVC light - box cloth. The temperature of the hot pressing composite is 150 - 170 °C, and the pressure is 4 - 6 MPa.

[0009] The preparation method of the anti - tearing microcapsules is as follows: Modified nano - silica and polycaprolactone prepolymer are mixed evenly, dispersed in N,N - dimethylformamide, and initiator benzoyl peroxide is added. The reaction is carried out at 80 - 100 °C for 8 - 10 h, then 4,4 - dithiobutyric acid is added, and the stirring reaction is carried out at 60 - 70 °C for 4 - 5 h. After the reaction, the anti - tearing microcapsules are prepared by spray drying. The number - average molecular weight of the polycaprolactone prepolymer is 500 - 1500. The mass ratio of the modified nano - silica, polycaprolactone prepolymer, benzoyl peroxide, 4,4 - dithiobutyric acid, and N,N - dimethylformamide is 10:20 - 30:0.2 - 0.4:2 - 3:60 - 80. During the spray - drying process, the inlet air temperature is 100 - 120 °C, the outlet air temperature is 60 - 70 °C, the atomization pressure is 0.3 - 0.5 MPa, and the feeding rate is 5 - 8 mL / min. The modified nano - silica is obtained by surface - modifying nano - silica with γ - aminopropyltriethoxysilane. The preparation method of the modified nano - silica is as follows: Nano - silica is dispersed in a mixed solution of ethanol and water, γ - aminopropyltriethoxysilane is added, and the reaction is carried out at 75 - 85 °C for 2 - 3 h. After the reaction, it is filtered, washed, and dried to obtain the modified nano - silica. The mass ratio of the nano - silica, γ - aminopropyltriethoxysilane, and the mixed solution is 10:0.4 - 0.6:100 - 150. The mass ratio of ethanol and water in the mixed solution is 10:1 - 2. The particle size of the nano - silica is 20 - 50 nm.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The lightweight anti - tearing PVC light - box cloth of the present invention has a three - dimensional gradient reinforcement structure. Based on the multi - layer composite design and the directional arrangement of high - strength fibers, the mechanical optimization of the anti - tearing performance is realized. The hollow polyester fibers in the base layer significantly reduce the material density through the internal cavity structure. The doped short carbon fiber cuttings have high modulus characteristics that can enhance the flexural stiffness of the base layer. The short carbon fiber cuttings are dispersed in the gaps between the polyester fibers, forming a "micro-pile array" at the interface to inhibit crack propagation and form local strengthening points. The intermediate layer realizes multi-scale strengthening through dopamine modification and micron composite dipping. The polydopamine coating is rich in catechol groups, forming strong hydrogen bonds and π-π conjugation with the polyurethane solution to enhance the interfacial bonding strength. After ultrasonic dispersion, the oxidized micron carbon fibers form an interpenetrating network with the polyurethane prepolymer. During hot pressing, the carbon fibers are oriented along the stress direction to form a "pinning effect", increasing the strength and toughness of the adhesive layer.

[0011] (2) For the lightweight and tear-resistant PVC light box cloth of the present invention, the surface layer endows the PVC light box cloth with dynamic repair ability through dynamic bond microcapsules to inhibit the propagation of microcracks. During the preparation of the tear-resistant microcapsules, γ-aminopropyltriethoxysilane hydrolyzes in an ethanol / water mixed solution to generate silanol, which condenses and dehydrates with the surface hydroxyl groups of nano-SiO 2 to form Si-O-Si covalent bonds. Benzoyl peroxide thermally decomposes at 80-100 °C to generate benzoyloxy radicals, which attack the polycaprolactone prepolymer chain segments to initiate chain growth reactions. The modified SiO 2 surface amino groups undergo condensation reactions with the carboxyl groups at the ends of the polycaprolactone chains. Free radical polymerization causes the polycaprolactone chains to graft and grow on the SiO 2 surface. Subsequently, the added 4,4-dithiobutyric acid undergoes a crosslinking reaction with the polycaprolactone to form a core-shell microcapsule structure with SiO 2 as the core and the crosslinked product of polycaprolactone and 4,4-dithiobutyric acid as the shell. When the material is torn by external force, the microcapsules rupture to release the repair agent. After treatment at 50-70 °C for 20-30 min, the polycaprolactone containing S-S bonds fills the cracks through thermoplastic flow. The S-S bonds break to generate sulfur radicals, and the radicals migrate to the crack interface to recombine, achieving crack interface healing. Among them, the nano-SiO 2 acts as a physical crosslinking point to play a supplementary strengthening role, improving the tear strength recovery rate of the light box cloth.

[0012] (3) For the lightweight and tear-resistant PVC light box cloth of the present invention, the weight per unit area is 418-425 g / m 2 , the radial tensile strength is 2560-2630 N / 5 cm, the weft tensile strength is 2180-2240 N / 5 cm, the radial elongation at break is 16.5-16.8%, the weft elongation at break is 22.3-23.1%, the trapezoidal tear strength is 620-650 N, the interlayer peel strength is 5.5-5.8 N / mm, and the tear strength recovery rate in the scratch test is 89-90%. Specific embodiments

[0013] To have a clearer understanding of the technical features, objectives, and effects of the present invention, the specific implementation manners of the present invention will now be described.

[0014] Example 1 A lightweight and tear-resistant PVC light box cloth, comprising a base layer, an intermediate reinforcing layer, and a surface functional layer; A preparation method of a lightweight and tear-resistant PVC light box cloth comprises the following steps: (1) Preparation of the base layer Mix hollow polyester fibers and chopped carbon fibers in a mass ratio of 10:1.5, impregnate with PVC emulsion after needle punching molding, and dry at 100 °C; The basis weight of the base layer is 110 g / m 2 , and the porosity is 40%; The length of the chopped carbon fibers is 3 mm.

[0015] (2) Preparation of the intermediate reinforcing layer A. Dopamine modification Orthogonally weave aramid fibers with a linear density of 200 D and ultra-high molecular weight polyethylene fibers with a linear density of 150 D into a grid structure. The warp and weft densities of the grid structure are 10×10 roots / cm. Immerse it in a dopamine solution, perform oscillating treatment at room temperature for 6 hours, take it out and rinse it with water 2 times, and vacuum dry it at 60 °C for 1.5 hours to cure the polydopamine coating formed on the fiber surface, obtaining a dopamine-modified fiber network; The mass ratio of the aramid fibers to the ultra-high molecular weight polyethylene fibers is 1:0.8; The dopamine solution is prepared by dissolving dopamine hydrochloride in a Tris buffer solution with a pH of 8.2, and the concentration of dopamine in the dopamine solution is 2 g / L; The concentration of the Tris buffer solution is 12 mmol / L.

[0016] B. Impregnation with glue Add oxidized micro carbon fibers to N,N-dimethylacetamide, perform ultrasonic treatment for 30 min, add polyurethane prepolymer, stir at a rotation speed of 600 rpm for 2 h to obtain a glue solution. Immerse the dopamine-modified fiber network in the glue solution, take it out after impregnation for 5 min, and dry it at 70 °C for 20 min to preliminarily gel the glue solution, and then thermocompression bond it with the base layer at 150 °C and 4 MPa; The mass ratio of the polyurethane prepolymer, oxidized micro carbon fibers, and N,N-dimethylacetamide is 100:5:20; The number average molecular weight of the polyurethane prepolymer is 1000; The frequency of the ultrasonic wave is 50 kHz; The preparation method of the oxidized micro carbon fiber is as follows: disperse the micro carbon fiber in a 60 wt% nitric acid solution, reflux at 75 °C for 4 h, filter, wash, and dry to obtain oxidized short carbon fibers; The length of the micro carbon fiber is 80 μm.

[0017] (3)Prepare the surface functional layer Add 5 wt% of anti-tear microcapsules to the PVC resin, granulate by twin-screw extrusion, then calender into a film at 170 °C, the film thickness is 0.2 mm, and secondarily thermocompound with the middle reinforcement layer, the temperature of the thermocompounding is 150 °C, the pressure is 4 MPa, wind up after cooling to obtain the PVC light box cloth; The preparation method of the anti-tear microcapsules is as follows: mix the modified nano-silica and the polycaprolactone prepolymer evenly, disperse in N,N-dimethylformamide, add the initiator benzoyl peroxide, react at 80 °C for 10 h, then add 4,4-dithiobutyric acid, stir and react at 60 °C for 5 h, and make anti-tear microcapsules by spray drying after the reaction ends; The number-average molecular weight of the polycaprolactone prepolymer is 500; The mass ratio of the modified nano-silica, polycaprolactone prepolymer, benzoyl peroxide, 4,4-dithiobutyric acid, and N,N-dimethylformamide is 10:20:0.2:2:60; During the spray drying process, the inlet air temperature is 100 °C, the outlet air temperature is 60 °C, the atomization pressure is 0.3 MPa, and the feeding rate is 5 mL / min; The preparation method of the modified nano-silica is as follows: disperse the nano-silica with a particle size of 20 nm in a mixed solution of ethanol and water, add γ-aminopropyltriethoxysilane, react at 75 °C for 3 h, filter, wash, and dry after the reaction ends to obtain the modified nano-silica; The mass ratio of the nano-silica, γ-aminopropyltriethoxysilane, and the mixed solution is 10:0.4:100; The mass ratio of ethanol and water in the mixed solution is 10:1.

[0018] Example 2 A lightweight anti-tear PVC light box cloth, including a base layer, a middle reinforcement layer, and a surface functional layer; A preparation method of a lightweight anti-tear PVC light box cloth includes the following steps: (1)Prepare the base layer Mix the hollow polyester fiber and the short carbon fiber according to a mass ratio of 10:1.8, impregnate with a PVC emulsion after needle punching molding, and dry at 110 °C; The gram weight of the base layer is 120 g / m 2 , and the porosity is 35%; The length of the chopped carbon fiber is 5 mm.

[0019] (2)Prepare the intermediate reinforcing layer A. Dopamine modification Aramid fibers with a linear density of 250 D and ultra-high molecular weight polyethylene fibers with a linear density of 180 D are orthogonally woven into a grid structure. The warp and weft densities of the grid structure are 12×12 pieces / cm. The woven structure is immersed in a dopamine solution and subjected to oscillating treatment at room temperature for 7 hours. After taking out, it is rinsed with water 3 times and vacuum dried at 65 °C for 1.2 hours to cure the polydopamine coating formed on the fiber surface, obtaining a dopamine-modified fiber network; The mass ratio of the aramid fiber to the ultra-high molecular weight polyethylene fiber is 1:0.9; The dopamine solution is prepared by dissolving dopamine hydrochloride in a Tris buffer solution with a pH of 8.5. The concentration of dopamine in the dopamine solution is 2.2 g / L; The concentration of the Tris buffer solution is 16 mmol / L.

[0020] B. Impregnation with glue Add oxidized micro carbon fibers to N,N-dimethylacetamide, perform ultrasonic treatment for 25 min, add a polyurethane prepolymer, and stir at a speed of 700 rpm for 2.5 h to obtain a glue solution. Immerse the dopamine-modified fiber network in the glue solution, take it out after impregnation for 6 min, and dry it at 75 °C for 18 min to preliminarily gel the glue solution, and then perform hot pressing and compounding with the base layer at 160 °C and 5 MPa; The mass ratio of the polyurethane prepolymer, oxidized micro carbon fibers, and N,N-dimethylacetamide is 100:6:25; The number average molecular weight of the polyurethane prepolymer is 1200; The frequency of the ultrasonic wave is 60 kHz; The preparation method of the oxidized micro carbon fibers is to disperse the micro carbon fibers in a 62 wt% nitric acid solution, reflux at 78 °C for 3.5 h, filter, wash, and dry to obtain oxidized chopped carbon fibers; The length of the micro carbon fibers is 100 μm.

[0021] (3)Prepare the surface functional layer Add 6 wt% of tear-resistant microcapsules to the PVC resin, extrude and granulate through a twin-screw extruder, and then calender into a film at 175 °C. The film thickness is 0.25 mm, and it is secondarily hot-pressed and compounded with the intermediate reinforcing layer. The temperature of the hot-pressing and compounding is 160 °C, the pressure is 5 MPa, and after cooling, it is wound up to obtain a PVC light box cloth; The preparation method of the tear-resistant microcapsules is as follows: Mix the modified nano-silica and the polycaprolactone prepolymer evenly, disperse them in N,N-dimethylformamide, add benzoyl peroxide as the initiator, react at 90 °C for 9 h, then add 4,4-dithiobutyric acid, and stir and react at 65 °C for 4.5 h. After the reaction, the tear-resistant microcapsules are prepared by spray drying; The number-average molecular weight of the polycaprolactone prepolymer is 1000; The mass ratio of the modified nano-silica, the polycaprolactone prepolymer, benzoyl peroxide, 4,4-dithiobutyric acid, and N,N-dimethylformamide is 10:25:0.3:2.5:70; During the spray drying process, the inlet air temperature is 110 °C, the outlet air temperature is 65 °C, the atomization pressure is 0.4 MPa, and the feeding rate is 6 mL / min; The preparation method of the modified nano-silica is as follows: Disperse nano-silica with a particle size of 30 nm in a mixed solution of ethanol and water, add γ-aminopropyltriethoxysilane, react at 80 °C for 2.5 h, and after the reaction, filter, wash, and dry to obtain the modified nano-silica; The mass ratio of the nano-silica, γ-aminopropyltriethoxysilane, and the mixed solution is 10:0.5:120; The mass ratio of ethanol and water in the mixed solution is 10:1.5.

[0022] Example 3 A lightweight tear-resistant PVC light box cloth includes a base layer, an intermediate reinforcing layer, and a surface functional layer; A preparation method of a lightweight tear-resistant PVC light box cloth includes the following steps: (1) Prepare the base layer Mix hollow polyester fibers and chopped carbon fibers according to a mass ratio of 10:2, impregnate them with PVC emulsion after needle punching molding, and dry at 120 °C; The basis weight of the base layer is 130 g / m 2 , and the porosity is 30%; The length of the chopped carbon fibers is 6 mm.

[0023] (2) Prepare the intermediate reinforcing layer A. Dopamine modification Orthogonally weave aramid fibers with a linear density of 300 D and ultra-high molecular weight polyethylene fibers with a linear density of 200 D into a grid structure. The warp and weft densities of the grid structure are 14×14 roots / cm, impregnate them in a dopamine solution, perform room temperature oscillation treatment for 8 hours, take them out and rinse 3 times with water, and vacuum dry at 70 °C for 1 hour to cure the polydopamine coating formed on the fiber surface to obtain a dopamine-modified fiber network; The mass ratio of the aramid fiber to the ultra-high molecular weight polyethylene fiber is 1:1; The dopamine solution is prepared by dissolving dopamine hydrochloride in a Tris buffer solution with a pH of 8.8, and the concentration of dopamine in the dopamine solution is 2.5 g / L; The concentration of the Tris buffer solution is 20 mmol / L.

[0024] B. Impregnation with glue Add the oxidized micro carbon fiber into N,N-dimethylacetamide, ultrasonically treat for 20 min, add the polyurethane prepolymer, stir at a rotation speed of 800 rpm for 3 h to obtain a glue solution, immerse the dopamine-modified fiber network in the glue solution, take it out after impregnation for 8 min, and dry it at 80 °C for 15 min to preliminarily gel the glue solution, and then perform hot pressing and compounding with the base layer at 170 °C and 6 MPa; The mass ratio of the polyurethane prepolymer, the oxidized micro carbon fiber, and N,N-dimethylacetamide is 100:7:30; The number-average molecular weight of the polyurethane prepolymer is 1500; The frequency of the ultrasonic wave is 70 kHz; The preparation method of the oxidized micro carbon fiber is to disperse the micro carbon fiber in a 65 wt% nitric acid solution, reflux at 80 °C for 3 h, filter, wash, and dry to obtain oxidized short carbon fiber; The length of the micro carbon fiber is 120 μm.

[0025] (3) Preparation of the surface functional layer Add 8 wt% of anti-tear microcapsules to the PVC resin, extrude and granulate through a twin-screw extruder, and then calender into a film at 180 °C. The film thickness is 0.3 mm, and it is secondarily hot-pressed and compounded with the middle reinforcing layer. The temperature of the hot pressing and compounding is 170 °C, the pressure is 6 MPa, and it is wound up after cooling to obtain the PVC light box cloth; The preparation method of the anti-tear microcapsules is to mix the modified nano-silica and the polycaprolactone prepolymer evenly, disperse them in N,N-dimethylformamide, add the initiator benzoyl peroxide, react at 100 °C for 8 h, then add 4,4-dithiobutyric acid, stir and react at 70 °C for 4 h, and after the reaction is completed, make anti-tear microcapsules by spray drying; The number-average molecular weight of the polycaprolactone prepolymer is 1500; The mass ratio of the modified nano-silica, the polycaprolactone prepolymer, benzoyl peroxide, 4,4-dithiobutyric acid, and N,N-dimethylformamide is 10:30:0.4:3:80; During the spray drying process, the inlet air temperature is 120 °C, the outlet air temperature is 70 °C, the atomization pressure is 0.5 MPa, and the feeding rate is 8 mL / min; The preparation method of the modified nano-silica is as follows: disperse nano-silica with a particle size of 50 nm in a mixed solution of ethanol and water, add γ-aminopropyltriethoxysilane, react at 85 °C for 2 h, filter, wash and dry after the reaction to obtain the modified nano-silica; The mass ratio of the nano-silica, γ-aminopropyltriethoxysilane and the mixed solution is 10:0.6:150; The mass ratio of ethanol and water in the mixed solution is 10:2.

[0026] Example 4 A lightweight and tear-resistant PVC light box cloth includes a base layer, an intermediate reinforcing layer and a surface functional layer; The preparation method of a lightweight and tear-resistant PVC light box cloth includes the following steps: (1) Prepare the base layer Mix hollow polyester fibers and chopped carbon fibers in a mass ratio of 10:1.8, impregnate with PVC emulsion after needle punching molding, and dry at 110 °C; The basis weight of the base layer is 120 g / m 2 , and the porosity is 35%; The length of the chopped carbon fibers is 5 mm.

[0027] (2)Prepare the intermediate reinforcing layer Aramid fibers with a linear density of 250 D and ultra-high molecular weight polyethylene fibers with a linear density of 180 D are orthogonally woven into a fiber network with a grid structure. The warp and weft density of the fiber network is 12×12 roots / cm. Add oxidized micro-carbon fibers to N,N-dimethylacetamide, perform ultrasonic treatment for 25 min, add polyurethane prepolymer, stir at 700 rpm for 2.5 h to obtain a glue solution. Immerse the fiber network in the glue solution, take it out after 6 min of impregnation, and dry at 75 °C for 18 min to make the glue solution preliminarily gel, and then thermocompression bond with the base layer at 160 °C and 5 MPa; The mass ratio of the aramid fibers to the ultra-high molecular weight polyethylene fibers is 1:0.9; The mass ratio of the polyurethane prepolymer, oxidized micro-carbon fibers and N,N-dimethylacetamide is 100:6:25; The number average molecular weight of the polyurethane prepolymer is 1200; The frequency of the ultrasonic wave is 60 kHz; The preparation method of the oxidized micro-carbon fibers is as follows: disperse micro-carbon fibers in a 62 wt% nitric acid solution, reflux at 78 °C for 3.5 h, filter, wash and dry to obtain oxidized chopped carbon fibers; The length of the micro-carbon fibers is 100 μm.

[0028] (3) Preparation of surface functional layer Add 6 wt% of anti - tear microcapsules to PVC resin, granulate by twin - screw extrusion, then calender into a film at 175 °C. The film thickness is 0.25 mm, and it is thermocompression - laminated with the middle reinforcing layer for the second time. The temperature of thermocompression - lamination is 160 °C, the pressure is 5 MPa, and it is wound up after cooling to obtain PVC light - box cloth; The preparation method of the anti - tear microcapsules is as follows: Mix modified nano - silica and polycaprolactone prepolymer evenly, disperse them in N,N - dimethylformamide, add initiator benzoyl peroxide, react at 90 °C for 9 h, then add 4,4 - dithiobutyric acid, stir and react at 65 °C for 4.5 h. After the reaction, the anti - tear microcapsules are made by spray drying; The number - average molecular weight of the polycaprolactone prepolymer is 1000; The mass ratio of the modified nano - silica, polycaprolactone prepolymer, benzoyl peroxide, 4,4 - dithiobutyric acid, and N,N - dimethylformamide is 10:25:0.3:2.5:70; During the spray - drying process, the inlet air temperature is 110 °C, the outlet air temperature is 65 °C, the atomization pressure is 0.4 MPa, and the feeding rate is 6 mL / min; The preparation method of the modified nano - silica is as follows: Disperse nano - silica with a particle size of 30 nm in a mixed solution of ethanol and water, add γ - aminopropyltriethoxysilane, react at 80 °C for 2.5 h. After the reaction, filter, wash, and dry to obtain modified nano - silica; The mass ratio of the nano - silica, γ - aminopropyltriethoxysilane, and the mixed solution is 10:0.5:120; The mass ratio of ethanol and water in the mixed solution is 10:1.5.

[0029] Example 5 A lightweight anti - tear PVC light - box cloth, including a base layer, a middle reinforcing layer, and a surface functional layer; A preparation method of a lightweight anti - tear PVC light - box cloth includes the following steps: (1) Preparation of the base layer Mix hollow polyester fiber and chopped carbon fiber according to a mass ratio of 10:1.8, impregnate with PVC emulsion after needle punching molding, and dry at 110 °C; The basis weight of the base layer is 120 g / m 2 , and the porosity is 35%; The length of the chopped carbon fiber is 5 mm.

[0030] (2) Preparation of the middle reinforcing layer A. Dopamine modification Aramid fibers with a linear density of 250 D and ultra-high molecular weight polyethylene fibers with a linear density of 180 D are orthogonally woven into a grid structure. The warp and weft densities of the grid structure are 12×12 roots / cm. It is impregnated in a dopamine solution, treated with shaking at room temperature for 7 hours, taken out and rinsed with water 3 times, and vacuum dried at 65 °C for 1.2 hours to cure the polydopamine coating formed on the fiber surface, obtaining a dopamine-modified fiber network; The mass ratio of the aramid fibers to the ultra-high molecular weight polyethylene fibers is 1:0.9; The dopamine solution is prepared by dissolving dopamine hydrochloride in a Tris buffer solution with a pH of 8.5. The concentration of dopamine in the dopamine solution is 2.2 g / L; The concentration of the Tris buffer solution is 16 mmol / L.

[0031] B. Impregnation with glue Mix the polyurethane prepolymer and N,N-dimethylacetamide, stir at a speed of 700 rpm for 2.5 h to obtain a glue solution. Immerse the dopamine-modified fiber network in the glue solution, take it out after impregnation for 6 min, and dry it at 75 °C for 18 min to preliminarily gel the glue solution, and then thermocompression laminate it with the base layer at 160 °C and 5 MPa; The mass ratio of the polyurethane prepolymer to N,N-dimethylacetamide is 100:25; The number average molecular weight of the polyurethane prepolymer is 1200; The frequency of the ultrasonic wave is 60 kHz.

[0032] (3)Preparation of the surface functional layer Add 6 wt% of anti-tear microcapsules to the PVC resin, extrude and granulate through a twin-screw extruder, and then calender into a film at 175 °C. The film thickness is 0.25 mm, and it is thermocompression laminated with the middle reinforcing layer for the second time. The thermocompression lamination temperature is 160 °C, the pressure is 5 MPa, and it is wound up after cooling to obtain a PVC light box cloth; The preparation method of the anti-tear microcapsules is as follows: Mix the modified nano-silica and the polycaprolactone prepolymer evenly, disperse them in N,N-dimethylformamide, add the initiator benzoyl peroxide, react at 90 °C for 9 h, then add 4,4-dithiobutyric acid, and stir and react at 65 °C for 4.5 h. After the reaction, it is made into anti-tear microcapsules by spray drying; The number average molecular weight of the polycaprolactone prepolymer is 1000; The mass ratio of the modified nano-silica, the polycaprolactone prepolymer, benzoyl peroxide, 4,4-dithiobutyric acid, and N,N-dimethylformamide is 10:25:0.3:2.5:70; During the spray drying process, the inlet air temperature is 110 °C, the outlet air temperature is 65 °C, the atomization pressure is 0.4 MPa, and the feeding rate is 6 mL / min; The preparation method of the modified nano-silica is as follows: disperse nano-silica with a particle size of 30 nm in a mixed solution of ethanol and water, add γ-aminopropyltriethoxysilane, and react at 80 °C for 2.5 h. After the reaction, filter, wash, and dry to obtain the modified nano-silica; The mass ratio of the nano-silica, γ-aminopropyltriethoxysilane, and the mixed solution is 10:0.5:120; The mass ratio of ethanol and water in the mixed solution is 10:1.5.

[0033] Example 6 A lightweight tear-resistant PVC light box cloth includes a base layer, an intermediate reinforcing layer, and a surface layer; A preparation method of a lightweight tear-resistant PVC light box cloth includes the following steps: (1) Prepare the base layer Mix hollow polyester fibers and short carbon fibers in a mass ratio of 10:1.8, impregnate with PVC emulsion after needle punching, and dry at 110 °C; The basis weight of the base layer is 120 g / m 2 , and the porosity is 35%; The length of the short carbon fibers is 5 mm.

[0034] (2) Prepare the intermediate reinforcing layer A. Dopamine modification Orthogonally weave aramid fibers with a linear density of 250 D and ultra-high molecular weight polyethylene fibers with a linear density of 180 D into a grid structure. The warp and weft densities of the grid structure are 12×12 roots / cm. Immerse in dopamine solution, oscillate at room temperature for 7 hours, take out and rinse with water 3 times, and vacuum dry at 65 °C for 1.2 hours to cure the polydopamine coating formed on the fiber surface to obtain a dopamine-modified fiber network; The mass ratio of the aramid fibers to the ultra-high molecular weight polyethylene fibers is 1:0.9; The dopamine solution is prepared by dissolving dopamine hydrochloride in Tris buffer with a pH of 8.5. The concentration of dopamine in the dopamine solution is 2.2 g / L; The concentration of the Tris buffer is 16 mmol / L.

[0035] B. Impregnation The oxidized micro carbon fibers were added to N,N-dimethylacetamide and ultrasonically treated for 25 min. Then, the polyurethane prepolymer was added, and the mixture was stirred at 700 rpm for 2.5 h to obtain a glue solution. The dopamine-modified fiber network was immersed in the glue solution, taken out after 6 min of impregnation, and dried at 75 °C for 18 min to preliminarily gel the glue solution. Then, it was hot-pressed and compounded with the base layer at 160 °C and 5 MPa. The mass ratio of the polyurethane prepolymer, oxidized micro carbon fibers, and N,N-dimethylacetamide is 100:6:25. The number-average molecular weight of the polyurethane prepolymer is 1200. The frequency of the ultrasonic treatment is 60 kHz. The preparation method of the oxidized micro carbon fibers is as follows: The micro carbon fibers were dispersed in a 62 wt% nitric acid solution, refluxed at 78 °C for 3.5 h, filtered, washed, and dried to obtain oxidized short-cut carbon fibers. The length of the micro carbon fibers is 100 μm.

[0036] (3)Preparation of the surface layer The PVC resin was calendered into a film at 175 °C with a film thickness of 0.25 mm, and then hot-pressed and compounded with the middle reinforcing layer for the second time. The temperature of the hot-pressing and compounding was 160 °C, and the pressure was 5 MPa. After cooling, it was wound up to obtain the PVC light box cloth.

[0037] Test Example 1 The PVC light box cloths prepared in Examples 1-6 were tested for tensile strength, trapezoidal tear strength, and interlayer peel strength. The test results are shown in Table 1.

[0038] Table 1 Strength performance

[0039] As can be seen from Table 1, in Example 4, when preparing the middle reinforcing layer, the fibers were directly impregnated with glue, omitting the dopamine modification layer, and the tensile strength, elongation at break, trapezoidal tear strength, and interlayer peel strength all decreased. This shows that the dopamine modification layer in the middle reinforcing layer can enhance the tensile strength, elongation at break, trapezoidal tear strength, and interlayer peel strength of the light box cloth. In Example 5, in the impregnation step during the preparation of the middle reinforcing layer, the glue solution used was a mixture of polyurethane prepolymer and N,N-dimethylacetamide. Compared with Example 2, the oxidized micro carbon fibers were omitted, indicating that the oxidized micro carbon fibers in the glue solution have the effect of enhancing the tensile strength, elongation at break, trapezoidal tear strength, and interlayer peel strength of the light box cloth during the preparation of the middle reinforcing layer.

[0040] Test Example 2 The tear strength recovery performance of the PVC light box fabrics prepared in Examples 1-3 and Example 6 was detected. The detection method was as follows: Use a micro-scratch tester to create a standard crack with a length of 5 mm and a depth of 0.1 mm, heat it at 60 °C for 30 minutes, compare the trapezoidal tear strength before and after repair, calculate the tear strength recovery rate, and observe the crack closure situation. The detection results are shown in Table 2.

[0041] Table 2 Tear Strength Recovery Performance

[0042] As can be seen from Table 2, the tear strength recovery rate of Example 6 is significantly lower than that of Example 2, and the crack closure effect is also poor. For the PVC light box fabric prepared in Example 6, the surface layer does not add anti-tear microcapsules, indicating that the anti-tear microcapsules added to the surface layer can significantly improve the tear strength recovery performance of the PVC light box fabric.

[0043] Test Example 3 The weight per unit area of the PVC light box fabrics prepared in Examples 1-6 was detected. The detection results are shown in Table 3.

[0044] Table 3 Weight per Unit Area

[0045] As can be seen from Table 3, the weight per unit area of the PVC light box fabrics prepared in Examples 1-6 is less than 430 g / m 2 , achieving the lightweight of the light box fabric.

[0046] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A lightweight tear-resistant PVC light box cloth, characterized in that: The light box cloth comprises a base layer, an intermediate reinforcement layer and a surface functional layer; The preparation method of the intermediate reinforcement layer comprises the following steps: dopamine modification and resin dipping; The dopamine modification method comprises: orthogonally weaving aramid fibers and ultra-high molecular weight polyethylene fibers into a grid structure, immersing the fibers in a dopamine solution, shaking the solution at room temperature for 6-8 hours, taking the solution out and rinsing the solution with water for 2-3 times, and vacuum drying the solution at 60-70° C. for 1-1.5 hours to solidify the polydopamine coating formed on the fiber surface, thereby obtaining a fiber network modified with dopamine; The dipping method comprises the following steps: adding oxidized micron carbon fiber to N,N-dimethylacetamide, ultrasonically treating the carbon fiber for 20-30 minutes, adding a polyurethane prepolymer, stirring the mixture at a speed of 600-800 rpm for 2-3 hours to obtain a glue solution, dipping the fiber network modified by dopamine into the glue solution, taking the fiber network out after dipping for 5-8 minutes, drying the fiber network at 70-80°C for 15-20 minutes to preliminarily gel the glue solution, and then hot-pressing the fiber network with the base layer.

2. The lightweight tear-resistant PVC light box cloth according to claim 1, characterized in that: In the dopamine modification step, the dopamine solution is prepared by dissolving dopamine hydrochloride in a Tris buffer having a pH of 8.2-8.8, and the concentration of dopamine in the dopamine solution is 2-2.5 g / L; the concentration of the Tris buffer is 12-20 mmol / L.

3. The lightweight tear-resistant PVC light box cloth according to claim 2, characterized in that: In the dopamine modification step, The linear density of aramid fiber is 200-300D; The linear density of ultra-high molecular weight polyethylene fiber is 150-200D; The mass ratio of aramid fiber to ultra-high molecular weight polyethylene fiber is 1:0.8-1; The warp and weft density of the grid structure is 10×10 strands / cm-14×14 strands / cm.

4. The lightweight tear-resistant PVC light box cloth according to claim 1, characterized in that: In the dipping step, The mass ratio of polyurethane prepolymer, oxidized micron carbon fiber and N,N-dimethylacetamide is 100:5-7:20-30; The number average molecular weight of the polyurethane prepolymer is 500-1000.

5. The lightweight tear-resistant PVC light box cloth according to claim 1, characterized in that: In the step of dipping, the preparation method of the oxidized micron carbon fiber is to disperse the micron carbon fiber in a 60-65wt% nitric acid solution, reflux at 75-80°C for 3-4h, filter, wash and dry to obtain the oxidized chopped carbon fiber; The length of the micron carbon fiber is 80-120 μm.

6. The lightweight tear-resistant PVC light box cloth according to claim 1, characterized in that: The preparation method of the surface functional layer is as follows: 5-8wt% of tear-resistant microcapsules are added to PVC resin, granulated by twin-screw extrusion, and then calendered into a film at 170-180°C with a film thickness of 0.2-0.3mm, and then hot-pressed and compounded with the middle reinforcement layer for a second time, and rolled up after cooling to obtain the PVC light box cloth.

7. The lightweight tear-resistant PVC light box cloth according to claim 6, characterized in that: The preparation method of the tear-resistant microcapsules comprises the following steps: uniformly mixing modified nano-silica and polycaprolactone prepolymer, dispersing the mixture in N,N-dimethylformamide, adding initiator benzoyl peroxide, reacting the mixture at 80-100° C. for 8-10 hours, then adding 4,4-dithiodibutyric acid, stirring the mixture at 60-70° C. for 4-5 hours, and preparing the tear-resistant microcapsules by spray drying after the reaction is completed.

8. The lightweight tear-resistant PVC light box cloth according to claim 7, characterized in that: In the preparation step of the tear-resistant microcapsules, The number average molecular weight of the polycaprolactone prepolymer is 500-1500; The mass ratio of the modified nano-silica, polycaprolactone prepolymer, benzoyl peroxide, 4,4-dithiodibutyric acid, and N,N-dimethylformamide is 10:20-30:0.2-0.4:2-3:60-80; The modified nano silicon dioxide is obtained by surface modification of nano silicon dioxide by gamma-aminopropyltriethoxysilane.

9. The lightweight tear-resistant PVC light box cloth according to claim 7, characterized in that: In the preparation step of the tear-resistant microcapsules, during the spray drying process, the inlet air temperature is 100-120° C., the outlet air temperature is 60-70° C., the atomization pressure is 0.3-0.5 MPa, and the feed rate is 5-8 mL / min.

10. The lightweight tear-resistant PVC light box cloth according to claim 1, characterized in that: The preparation method of the base layer is as follows: hollow polyester fibers are mixed with short-cut carbon fibers, and after needle punching, the mixture is impregnated with PVC emulsion and dried at 100-120°C. The mass ratio of the hollow polyester fiber to the chopped carbon fiber is 10:1.5-2; The length of the chopped carbon fibers is 3-6 mm.

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