Preparation method of high-transmittance anti-yellowing self-adhesive film

Abstract

The present application relates to the technical field of protective film, and particularly relates to a preparation method of high-transmittance anti-yellowing self-adhesive film, which comprises the following steps: first, preparing outer layer, middle layer and inner layer blending materials respectively, wherein the outer layer blending material is obtained by mixing low-density polyethylene, unwinding master batch and ultraviolet absorber, the middle layer blending material is a mixture of low-density polyethylene and light stabilizer, and the inner layer blending material is obtained by mixing self-adhesive material and antioxidant; then, feeding the three-layer blending materials into a three-layer co-extrusion blowing machine according to a specific ratio and controlling corresponding heating temperature, and obtaining a self-adhesive film blank through co-extrusion molding; finally, cooling the film blank to normal temperature in a specific temperature environment, and cutting and winding after standing. Through the three-layer functional partition design, the prepared self-adhesive film has high transmittance, excellent anti-yellowing performance and stable mechanical properties, and can meet the use requirements of various scenes.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of protective films, in particular to a preparation method of a high-transmittance anti-yellowing self-adhesive film. BACKGROUND

[0002] The adhesive polyethylene protective film is also called a PE protective film, and as a high-efficiency and environment-friendly surface protection material, plays an irreplaceable role in the fields of industrial manufacturing, electronic products, building decoration and public health. Compared with traditional adhesive films, the self-adhesive PE protective film realizes glue-free bonding relying on the viscoelastic properties of the material itself, has core advantages such as no residual glue risk, stable adhesion, low cost and environmental friendliness, and has become a mainstream protection material in the market. With the diversification of application scenarios and the refinement of functional requirements, the technical development of the self-adhesive PE protective film presents three trends of multilayer co-extrusion structuring, functional compounding and performance long-acting, and the innovative design not only expands the application range of the material, but also shows important value in emerging fields.

[0003] At present, the PE self-adhesive film is widely used in the household appliance and building material industries, but the household appliances and building materials covered with the PE self-adhesive film will appear yellowing and the performance of the protective film will become poor after long-term exposure to the outdoors or long-term direct sunlight, which directly affects the user experience.

[0004] The self-adhesive film products on the market at present mostly adopt single-layer or simple multi-layer structure design, and the material functional integration degree is low. In order to realize the anti-yellowing performance, some products will add ultraviolet absorbers, light stabilizers and other additives in the base material, but the full-layer mixed addition method is often used. This method not only easily leads to uneven distribution of the additives in the material, produces local agglomeration, and then reduces the transmittance of the film and affects the transparency requirement, but also may weaken the functional effects of different additives due to the interaction between different additives in the full layer, and it is difficult to form an efficient anti-aging system. SUMMARY

[0005] In order to solve the foregoing technical problems, the application provides a preparation method of a high-transmittance anti-yellowing self-adhesive film, which realizes the accurate distribution and cooperation of each subarea through three-layer functional subarea design, solves the problems of low transmittance, poor anti-yellowing effect, easy thermal oxidation aging of the self-adhesive material, and difficult balance between mechanical properties and transmittance, and the like, and is specifically realized through the following technical scheme.

[0006] The preparation method of the high-transmittance anti-yellowing self-adhesive film comprises the following steps:

[0007] Step 1: uniformly mix low-density polyethylene, unwinding master batch and ultraviolet absorber through a mixer to obtain outer-layer blended material for standby;

[0008] Step 2: uniformly mix the low-density polyethylene, light stabilizer through the mixer to obtain the middle layer blend ready for use;

[0009] Step 3: uniformly mix the self-adhesive material, antioxidant through the mixer to obtain the inner layer blend ready for use;

[0010] Step 4: respectively add the outer layer blend, the middle layer blend, and the inner layer blend to the first, second, and third feeding ports of the three-layer co-extrusion blow molding machine, respectively heat to the set temperature to make each layer of the blend in a molten state, then simultaneously extrude the three layers of the molten blend through the die to obtain a three-layer structure of the self-adhesive film parison;

[0011] Step 5: transfer the self-adhesive film parison to an environment of 20-40℃ and cool to room temperature, stand for 1-2 hours, then cut and roll to obtain the high-transmittance yellowing-resistant self-adhesive film.

[0012] Preferably, in step 1, the mass ratio of the low-density polyethylene, the unwinding master batch, and the ultraviolet absorber is 95%-99%:1%-4%:0.05%-0.5%.

[0013] Preferably, in step 1, the ultraviolet absorber is compounded from benzophenone ultraviolet absorber, benzotriazole ultraviolet absorber, and triazine ultraviolet absorber according to a molar ratio of 0.8-1.2:0.8-1.2:0.8-1.2.

[0014] Preferably, in step 1, the unwinding master batch contains 50%-70% of carrier resin, 25%-45% of opening agent, and 5%-10% of auxiliary agent.

[0015] The carrier resin is linear low-density polyethylene or low-density polyethylene, the opening agent is calcium hydrogen phosphate, and the auxiliary agent is stearic acid and silane coupling agent in equal mass ratio.

[0016] Preferably, in step 2, the light stabilizer is a hindered amine light stabilizer, and the addition amount is 0.05%-0.5% of the total mass of the middle layer.

[0017] Preferably, in step 3, the self-adhesive material is compounded from polyisobutylene, modified polyethylene, and thermoplastic elastomer according to a molar ratio of 0.7-1.3:0.7-1.3:0.7-1.3.

[0018] Preferably, in step 3, the antioxidant is compounded from phenolic antioxidant, amine antioxidant, phosphite antioxidant, and sulfide antioxidant according to a molar ratio of 0.8-1.2:0.8-1.2:0.8-1.2:0.8-1.2, and the addition amount of the antioxidant is 0.01%-0.1% of the total mass of the inner layer.

[0019] Preferably, the mass ratio of the first, second and third feeding ports of the three-layer co-extrusion blow molding machine in step 4 is 3-4:3-4:2-4.

[0020] Preferably, the heating temperature of the outer layer blend in step 4 is 150-200 DEG C, the heating temperature of the middle layer blend is 160-230 DEG C, and the heating temperature of the inner layer blend is 160-200 DEG C.

[0021] After the above technical scheme is adopted, the beneficial effects of the present application are:

[0022] 1. By the three-layer functional partition design, the ultraviolet absorber is concentrated in the outer layer, the light stabilizer is distributed in the middle layer, and the antioxidant is placed in the inner layer, so that the precise distribution and synergistic effect of each functional additive are realized, and the yellowing resistance and aging resistance of the self-adhesive film are significantly improved.

[0023] 2. The outer layer adopts a specific proportion of unwinding master batch and ultraviolet absorber, which effectively inhibits the invasion of ultraviolet rays while ensuring high light transmission, the middle layer light stabilizer inhibits free radical chain reaction, and the inner layer antioxidant prevents thermal oxidative degradation, thereby prolonging the service life of the film as a whole.

[0024] 3. The three-layer structure is based on a low-density polyethylene system with good compatibility, strong interlayer bonding force, no interface separation phenomenon, excellent mechanical properties, and high levels of tensile strength and elongation.

[0025] 4. By the pre-mixing and stepwise feeding process, the uniform dispersion of the additives in the matrix is ensured, the light scattering or uneven performance caused by local aggregation is avoided, and the overall light transmission and functional stability of the film are ensured.

[0026] 5. The overall preparation process is simple and controllable, suitable for industrial production, and can adjust the thickness and additive proportion of each layer according to actual needs, with good popularization prospect and application flexibility. DETAILED DESCRIPTION

[0027] The features and exemplary embodiments of various aspects of the present application will be described in detail below, in order to make the purposes, technical solutions and advantages of the present application more clear, the present application will be further described in detail below in combination with specific embodiments. It should be understood that the specific embodiments described herein are configured to explain the present application, and are not configured to limit the present application. The present application can be implemented without some of these specific details by those skilled in the art. The following description of the embodiments is merely to provide a better understanding of the present application by showing examples of the present application.

[0028] The present application provides a preparation method of a high-transmittance anti-yellowing self-adhesive film, which specifically comprises the following steps:

[0029] Step 1

[0030] Low density polyethylene (LDPE), unwinding master batch, ultraviolet absorber are mixed evenly through a mixer as the outer layer blend for standby.

[0031] The mass ratio of low density polyethylene, unwinding master batch and ultraviolet absorber in the above process is 95%-99%:1%-4%:0.05%-0.5%.

[0032] The ultraviolet absorber is compounded from benzophenone ultraviolet absorber, benzotriazole ultraviolet absorber and triazine ultraviolet absorber according to a molar ratio of 0.8-1.2:0.8-1.2:0.8-1.2.

[0033] The unwinding master batch includes 50%-70% carrier resin, 25%-45% opening agent and 5%-10% auxiliary agent, wherein the carrier resin is linear low density polyethylene (LLDPE) and low density polyethylene (LDPE), the opening agent is calcium hydrogen phosphate, and the auxiliary agent is stearic acid and silane coupling agent in a mass ratio.

[0034] The outer layer is the layer directly contacting with the external environment as a self-adhesive film. In this step, different functional components are uniformly dispersed in the low density polyethylene matrix by physical blending, and the synergistic effect of each component is used to endow the outer layer with excellent ultraviolet aging resistance, good processing fluidity and opening performance.

[0035] The low density polyethylene has good optical properties, processing fluidity and flexibility, and is the basic matrix material for constituting the outer layer, providing the basic physical structure and light transmission properties for the self-adhesive film.

[0036] The core function of the unwinding master batch is to solve the sticking problem of the film during production, storage and use. The carrier resin adopts LLDPE or LDPE, which has good compatibility with the outer layer matrix LDPE and can uniformly disperse the opening agent and auxiliary agent. The opening agent calcium hydrogen phosphate forms small protrusions on the film surface to reduce the contact area and friction between the films. The stearic acid in the auxiliary agent can further reduce the surface tension of the film, and the silane coupling agent can improve the interfacial bonding force between calcium hydrogen phosphate and the resin matrix.

[0037] The ultraviolet absorber can selectively absorb ultraviolet rays in external light and convert them into harmless heat energy, thereby preventing the degradation of high molecular materials by ultraviolet rays and delaying the yellowing and performance degradation of the film. Different types of ultraviolet absorbers have slightly different wavelength ranges for absorbing ultraviolet rays, so the use of compound can further broaden the ultraviolet spectrum band and improve the anti-yellowing effect.

[0038] In this step, the components are added to a mixer in a specific ratio, and mechanical stirring is used to achieve uniform dispersion of the solid particles, ensuring that the functional components in the ultraviolet absorber and the uncoiling master batch are evenly distributed on the surface of the low-density polyethylene particles and in the particle gaps, laying the foundation for uniform distribution of the components during subsequent extrusion molding.

[0039] Step 2

[0040] The low-density polyethylene and light stabilizer are mixed uniformly by a mixer as a middle layer blend for standby.

[0041] The amount of light stabilizer added is 0.05% to 0.5% of the total mass of the middle layer.

[0042] The light stabilizer is a hindered amine light stabilizer.

[0043] During the mixing of low-density polyethylene and light stabilizer, the light stabilizer is first mixed uniformly with a small amount of low-density polyethylene, and then the remaining low-density polyethylene is added to complete the final mixing.

[0044] The middle layer serves as a functional reinforcement layer for the self-adhesive film, mainly assisting the outer layer in improving anti-aging performance while maintaining the structural stability and light transmittance of the film.

[0045] The low-density polyethylene in the middle layer is consistent with the outer layer matrix, ensuring better compatibility between the middle layer and the outer layer, and avoiding a decrease in interlayer strength due to material differences. At the same time, the high light transmittance and flexibility of low-density polyethylene ensure that the middle layer does not affect the overall optical and physical properties of the self-adhesive film.

[0046] In addition, the introduction of light stabilizer in the middle layer can synergistically work with the ultraviolet absorber in the outer layer to form an anti-aging system. The main function of the ultraviolet absorber in the outer layer is to absorb ultraviolet light, while the hindered amine light stabilizer does not directly absorb ultraviolet light, but captures hydroxyl, alkyl, and other free radicals generated during the degradation process of the polymer material, inhibits the chain reaction of free radicals, and prevents further degradation of the material.

[0047] In addition, the hindered amine light stabilizer can also decompose hydrogen peroxide, which is extremely destructive during material oxidation, into relatively stable and harmless substances, thereby cutting off the chain degradation reaction that leads to a decrease in material performance. In addition, the nitrogen-oxygen free radical in the hindered amine light stabilizer can be regenerated continuously, allowing it to work repeatedly and thus play a long-term anti-aging role.

[0048] In the step, the low-density polyethylene and the hindered amine light stabilizer are added into a mixer, and uniformly dispersed by mechanical stirring. Since the amount of the light stabilizer is very low, to avoid agglomeration, the light stabilizer is usually pre-mixed with a small amount of low-density polyethylene, and then mixed with a large amount of low-density polyethylene, to ensure that the light stabilizer is fully dispersed in the middle layer blend, and to avoid the decrease of film light transmittance due to the local high concentration.

[0049] Step 3

[0050] The self-adhesive material and the antioxidant are mixed uniformly by a mixer, as the inner layer blend for standby.

[0051] The self-adhesive material is composed of polyisobutylene, modified polyethylene, and thermoplastic elastomer, with a molar ratio of 0.7-1.3:0.7-1.3:0.7-1.3.

[0052] The amount of the antioxidant is 0.01%-0.1% of the total mass of the inner layer.

[0053] The antioxidant is composed of phenolic antioxidant, amine antioxidant, phosphite antioxidant, and sulfide antioxidant, with a molar ratio of 0.8-1.2:0.8-1.2:0.8-1.2:0.8-1.2.

[0054] The inner layer, as the layer directly contacting the adherend of the self-adhesive film, must have good self-adhesion, compatibility, and thermal-oxidative aging resistance.

[0055] The self-adhesive material is a high-molecular material with low glass transition temperature and high flexibility, and its molecular chain segments have strong activity, which can tightly contact the surface of the adherend under certain pressure, to generate self-adhesion through van der Waals force, hydrogen bond, and other interactions, to ensure that the self-adhesive film can be firmly pasted on the surface of the adherend.

[0056] The main function of the antioxidant is to inhibit the thermal-oxidative aging of the self-adhesive material during processing and use, to avoid the molecular chain breakage or crosslinking caused by degradation of the self-adhesive material, to ensure the long-term stability of the self-adhesion of the inner layer, and to meet the use requirements of the self-adhesive film.

[0057] In the above step, due to the strong adhesion of the self-adhesive material, a step-by-step mixing method can be used, i.e., the antioxidant is pre-mixed with a small amount of self-adhesive material, and then added into a large amount of self-adhesive material, to ensure that the antioxidant is uniformly distributed in the self-adhesive material, and to avoid the oxidative degradation of the self-adhesive material during high-temperature processing due to the local absence of the antioxidant.

[0058] In addition, during the mixing of the self-adhesive material and the antioxidant, the temperature and stirring speed need to be controlled, on the one hand to avoid the agglomeration of the self-adhesive material due to high temperature, and on the other hand to ensure that the antioxidant is uniformly dispersed in the adhesive matrix, to avoid agglomeration.

[0059] Step 4

[0060] The outer layer blend, the middle layer blend and the inner layer blend are respectively placed in the first, second and third feeding ports of a three-layer co-extrusion blow molding machine, and the outer layer blend, the middle layer blend and the inner layer blend are respectively heated to 150-200℃, 160-230℃ and 160-200℃, and the three-layer melt state blends are simultaneously extruded through a die to obtain a three-layer self-adhesive film web.

[0061] The first, second and third feeding ports are fed according to a mass ratio of 3-4:3-4:2-4.

[0062] In the above step, the outer layer blend, the middle layer blend and the inner layer blend are respectively melt plasticized in different extruders, and then the three-layer melt streams are compounded, extruded and molded through a three-layer co-extrusion die to finally obtain a three-layer structure film web. Through the three-layer co-extrusion blow molding process, the functions of the outer layer, the middle layer and the inner layer are combined to prepare a three-layer structure integrated self-adhesive film web, so that the film has comprehensive properties such as anti-yellowing, high light transmission and self-adhesion.

[0063] In addition, the heating temperature of each layer is accurately controlled in the process to ensure that the temperatures of the three layers match when the melts are compounded, so as to avoid poor interlayer bonding force caused by temperature difference. By accurately controlling the feeding ratio of each layer, the product thickness is uniform, and problems such as interlayer delamination, excessive thickness deviation and film defects are avoided.

[0064] Step 5

[0065] The self-adhesive film web obtained in step 4 is transferred to an environment of 20-40℃ and cooled to room temperature, and after standing for 1-2 hours, it is cut and wound to obtain a high light transmission and anti-yellowing self-adhesive film.

[0066] In the above step, after the self-adhesive film web comes out of the blow molding machine, there is still some residual heat inside, and the molecular chain arrangement has not yet completely stabilized. By transferring it to an environment of 20-40℃ and cooling it to room temperature, the molecular chains inside the film can be fully relaxed and the crystal structure can be stabilized, avoiding size shrinkage or performance changes of the film in subsequent processing or use due to residual heat.

[0067] In order to facilitate further understanding of the present application, several embodiments and comparative examples of the present application are given below.

[0068] Example 1

[0069] The present embodiment provides a preparation method of a high light transmission and anti-yellowing self-adhesive film, which specifically comprises the following steps:

[0070] Step 1

[0071] Linear low density polyethylene, low density polyethylene, calcium hydrogen phosphate, stearic acid, silane coupling agent were prepared into an open roll master batch according to a mass ratio of 5:5:6:1:1, benzophenone-3, methylphenyl triazone siloxane, octyl triazone ketone were compounded into an ultraviolet absorber according to a molar ratio of 1:1:1, and low density polyethylene, the open roll master batch, and the ultraviolet absorber were uniformly mixed by a mixer according to a mass ratio of 96:3.5:0.5, serving as an outer layer blend material for standby.

[0072] Step 2

[0073] Low density polyethylene and bis(2,2,6,6-tetramethyl-4-piperidine) sebacate were uniformly mixed by a mixer according to a mass ratio of 99.5:0.5, serving as a middle layer blend material for standby.

[0074] Step 3

[0075] Polyisobutylene, modified polyethylene, and thermoplastic elastomer were compounded into a self-adhesive material according to a molar ratio of 1:1:1, bisphenol A, diphenylamine, tris(nonylphenyl) phosphite, and dilauryl thiodipropionate were compounded into an antioxidant according to a molar ratio of 1:1:1:1, and the self-adhesive material and the antioxidant were uniformly mixed by a mixer according to a mass ratio of 99.9:0.1, serving as an inner layer blend material for standby.

[0076] Step 4

[0077] The outer layer blend material, the middle layer blend material, and the inner layer blend material were respectively placed in the first, second, and third feeding ports of a three-layer co-extrusion blow molding machine, the first, second, and third feeding ports were fed according to a mass ratio of 3.5:3.5:3, and the outer layer, the middle layer, and the inner layer blend materials were heated to 170℃, 200℃, and 180℃ respectively, and the three-layer melt state blend materials were simultaneously extruded through a die to obtain a three-layer self-adhesive film parison.

[0078] Step 5

[0079] The self-adhesive film parison obtained in step 4 was transferred to an environment of 30℃ and cooled to room temperature, and after standing for 1.5 hours, it was cut and wound to obtain a high-transmittance and yellowing-resistant self-adhesive film.

[0080] Example 2

[0081] This example is based on example 1, and the addition ratio of each component in step 1 is adjusted, specifically:

[0082] Step 1

[0083] Linear low density polyethylene, low density polyethylene, calcium hydrogen phosphate, stearic acid, silane coupling agent were prepared into an open roll master batch according to a mass ratio of 5:5:6:1:1, benzophenone-3, methylphenyl glycidyl ether trisiloxane, octyl triazine ketone were compounded into an ultraviolet absorber according to a molar ratio of 1:1:1, and low density polyethylene, the open roll master batch, and the ultraviolet absorber were uniformly mixed by a mixer according to a mass ratio of 98:1.8:0.2, serving as an outer layer blend material for standby.

[0084] The remaining steps were completely the same as those in Example 1.

[0085] Example 3

[0086] This example was based on Example 1, and the addition ratio of each component in step 2 was adjusted, specifically as follows.

[0087] Step 2

[0088] Low density polyethylene and bis(2,2,6,6-tetramethyl-4-piperidine) sebacate were uniformly mixed by a mixer according to a mass ratio of 99.8:0.2, serving as a middle layer blend material for standby.

[0089] The remaining steps were completely the same as those in Example 1.

[0090] Example 4

[0091] This example was based on Example 1, and the addition ratio of each component in step 3 was adjusted, specifically as follows.

[0092] Step 3

[0093] Polyisobutylene, modified polyethylene, and thermoplastic elastomer were compounded according to a molar ratio of 1:1:1 to form a self-adhesive material, bisphenol A, diphenylamine, tris(nonylphenyl) phosphite, and dilauryl thiodipropionate were compounded according to a molar ratio of 1:1:1:1 to form an antioxidant, and the self-adhesive material and the antioxidant were uniformly mixed by a mixer according to a mass ratio of 99.95:0.05, serving as an inner layer blend material for standby.

[0094] The remaining steps were completely the same as those in Example 1.

[0095] Example 5

[0096] This example was based on Example 1, and the ratio of the first, second, and third feeding ports in step 4 was adjusted, specifically as follows.

[0097] Step 4

[0098] The outer layer blend, the middle layer blend and the inner layer blend were respectively placed in the first, the second and the third feeding ports of a three-layer co-extrusion blow molding machine, the first, the second and the third feeding ports were fed according to a mass ratio of 4:4:2, and the outer layer blend, the middle layer blend and the inner layer blend were respectively heated to 170℃, 200℃ and 180℃, and the three-layer melt state blend was simultaneously extruded through a die to obtain a three-layer self-adhesive film parison.

[0099] The remaining steps were exactly the same as those in Example 1.

[0100] Comparative Example 1

[0101] In this comparative example, the outer layer and the middle layer in Example 1 were exchanged, and the blending and heating parameters were correspondingly adjusted, specifically as follows:

[0102] Step 1

[0103] Linear low density polyethylene, low density polyethylene, calcium hydrogen phosphate, stearic acid and silane coupling agent were prepared into an unwinding master batch according to a mass ratio of 5:5:6:1:1, benzophenone-3, methylphenyl triazone siloxane and octyl triazone ketone were compounded into an ultraviolet absorber according to a molar ratio of 1:1:1, and low density polyethylene, the unwinding master batch and the ultraviolet absorber were uniformly mixed by a mixer according to a mass ratio of 96:3.5:0.5 to serve as the middle layer blend for standby.

[0104] Step 2

[0105] Low density polyethylene and bis(2,2,6,6-tetramethyl-4-piperidine) sebacate were uniformly mixed by a mixer according to a mass ratio of 99.5:0.5 to serve as the outer layer blend for standby.

[0106] Step 4

[0107] The outer layer blend, the middle layer blend and the inner layer blend were respectively placed in the first, the second and the third feeding ports of a three-layer co-extrusion blow molding machine, the first, the second and the third feeding ports were fed according to a mass ratio of 3.5:3.5:3, and the outer layer blend, the middle layer blend and the inner layer blend were respectively heated to 200℃, 170℃ and 180℃, and the three-layer melt state blend was simultaneously extruded through a die to obtain a three-layer self-adhesive film parison.

[0108] The remaining steps were exactly the same as those in Example 1.

[0109] Comparative Example 2

[0110] In this example, ultraviolet absorbers, light stabilizers and antioxidants were added to the outer layer, the middle layer and the inner layer, and the total amount was the same as that in Example 1, specifically as follows:

[0111] Step 1

[0112] The benzophenone-3, the cresol trisiloxane, and the octyl triazone are compounded into an ultraviolet absorber according to a molar ratio of 1:1:1, the bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate is used as a light stabilizer, the bisphenol A, the diphenylamine, the tris(nonylphenyl) phosphite, and the dilauryl thiodipropionate are compounded into an antioxidant according to a molar ratio of 1:1:1:1, and the ultraviolet absorber, the light stabilizer, and the antioxidant are uniformly mixed into an additive according to a mass ratio of 35:35:6 to be used as a standby additive.

[0113] Step 2

[0114] The linear low-density polyethylene, the low-density polyethylene, the calcium hydrogen phosphate, the stearic acid, and the silane coupling agent are prepared into an uncoiling master batch according to a mass ratio of 5:5:6:1:1, the low-density polyethylene, the uncoiling master batch, and the additive are uniformly mixed by a mixer according to a mass ratio of 96:3.5:0.5 to be used as an outer layer blend material.

[0115] Step 3

[0116] The low-density polyethylene and the additive are uniformly mixed by a mixer according to a mass ratio of 99.5:0.5 to be used as a middle layer blend material.

[0117] Step 4

[0118] The polyisobutylene, the modified polyethylene, and the thermoplastic elastomer are compounded into a self-adhesive material according to a molar ratio of 1:1:1, and the self-adhesive material and the additive are uniformly mixed by a mixer according to a mass ratio of 99.9:0.1 to be used as an inner layer blend material.

[0119] Step 5

[0120] The outer layer blend material, the middle layer blend material, and the inner layer blend material are respectively placed in first, second, and third feeding ports of a three-layer co-extrusion blow molding machine, the first, second, and third feeding ports are fed according to a mass ratio of 3.5:3.5:3, and the outer layer, the middle layer, and the inner layer blend materials are respectively heated to 170℃, 200℃, and 180℃, and the three layers of melt blend materials are simultaneously extruded through a die to obtain a three-layer self-adhesive film parison.

[0121] Step 6

[0122] The self-adhesive film parison obtained in step 5 is transferred to an environment of 30℃ and cooled to a normal temperature state, and after standing for 1.5 hours, a high-transmittance and yellowing-resistant self-adhesive film is obtained by slitting and winding.

[0123] Comparative Example 3

[0124] This comparative example is based on the comparative example 1, and the use amount of the additive in steps 2, 3, and 4 is adjusted, specifically:

[0125] Step 2

[0126] Linear low density polyethylene, low density polyethylene, calcium hydrogen phosphate, stearic acid, silane coupling agent were prepared into an open roll master batch according to a mass ratio of 5:5:6:1:1, and low density polyethylene, open roll master batch, and additive were mixed uniformly by a mixer according to a mass ratio of 95.5:3.5:1 to serve as an outer layer blend for standby.

[0127] Step 3

[0128] Low density polyethylene and additive were mixed uniformly by a mixer according to a mass ratio of 99:1 to serve as a middle layer blend for standby.

[0129] Step 4

[0130] Polyisobutylene, modified polyethylene, and thermoplastic elastomer were compounded according to a molar ratio of 1:1:1 to form a self-adhesive material, and the self-adhesive material and additive were mixed uniformly by a mixer according to a mass ratio of 99.8:0.2 to serve as an inner layer blend for standby.

[0131] The remaining steps were exactly the same as those of Comparative Example 1.

[0132] According to the step method in the above examples and comparative examples, the corresponding self-adhesive film samples were respectively prepared, and the light transmittance detection and yellowing resistance detection were respectively performed on each self-adhesive film sample, and the tensile strength and elongation of each self-adhesive film sample were respectively measured.

[0133] Among them, the light transmittance detection adopts the spectrophotometric method, and the light transmittance of the 380-780nm waveband is measured according to the GB / T 2410-2008 standard.

[0134] The yellowing resistance detection determines the yellowing resistance effect of the corresponding sample by detecting the color difference value before and after ultraviolet aging, and the aging test is carried out according to the GB / T 14522-2008 standard, and the test is carried out by using a yellow index tester, and the specific parameters are:

[0135] The ultraviolet lamp type of ultraviolet aging is UVA-313, and the irradiance is 0.71W / m 2 During the irradiation process, 60℃ irradiation for 4 hours plus 50℃ cooling for 4 hours is a cycle, and the cycle cumulative time is 300 hours to complete the test; the yellow index YI of the corresponding sample before and after ultraviolet aging is measured, and the yellowing index ΔYI is calculated by difference.

[0136] The tensile strength and elongation detection are completed by using a tensile testing machine, and the strength data and elongation size of the sample at the time of tensile fracture are recorded, the strength data at the time of fracture is the tensile strength, and the elongation data and the size ratio of the original sample are the elongation.

[0137] The samples of each example and comparative example were detected by the above detection and measurement methods, and the results are shown in the following table:

[0138]

[0139] From the above data, the following conclusions can be drawn:

[0140] In terms of light transmittance, Examples 1-5 all adopt a three-layer functional zoning design, the outer layer and the middle layer use high-transmittance LDPE as the matrix, and the ultraviolet absorber, light stabilizer, and antioxidant added in each layer are uniformly dispersed through pre-mixing and other processes, and there is basically no problem of light transmittance reduction caused by local agglomeration, and the light transmittance is maintained above 92%.

[0141] In Comparative Example 1, the light stabilizer in the middle layer is distributed easily to cause slight light scattering on the surface when the middle layer containing the light stabilizer is used as the outer layer, and the ultraviolet absorber in the outer layer is absorbed to a certain extent when the outer layer containing the ultraviolet absorber is used as the middle layer, resulting in a light transmittance of 85.6%; in Comparative Examples 2 and 3, various additives are added in each layer, and there is slight interaction between the additives, increasing light scattering and absorption, so the light transmittance is lower than that of the examples, and the light transmittance of Comparative Example 3 is slightly lower than that of Comparative Example 2 due to the higher amount of additives.

[0142] In terms of yellowing resistance, in Examples 1-5, the ultraviolet absorber in the outer layer and the light stabilizer in the middle layer form a synergistic anti-aging system, which can effectively inhibit ultraviolet damage and free radical chain reactions, so the color difference change value ΔYI after ultraviolet aging and heat aging is small.

[0143] In Example 2, the amount of ultraviolet absorber added in the outer layer is reduced, and the ultraviolet absorption capacity is weakened, so the ΔYI is higher than that of Example 1; in Example 3, the amount of light stabilizer added in the middle layer is reduced, and the ability to inhibit free radical reactions is decreased, so the ΔYI is slightly higher than that of Example 1; in Example 4, the amount of antioxidant added in the inner layer is reduced, although it mainly affects the thermal-oxidative aging of the inner layer, a small amount of free radicals diffuse to the middle layer and the outer layer, resulting in a ΔYI slightly higher than that of Example 1; in Example 5, the proportion of the outer layer and the middle layer is increased, and the anti-aging functional layer is thicker, so the anti-yellowing effect is better, and the ΔYI is slightly lower than that of Example 1.

[0144] In Comparative Example 1, the light stabilizer in the outer layer cannot effectively absorb ultraviolet light due to the misplacement of functions between layers, and the ultraviolet absorber in the middle layer has weak inhibitory capacity for internal free radicals, so the anti-aging system is ineffective, and the ΔYI increases significantly; in Comparative Example 2, the synergistic effect is weakened due to the mixed addition of additives, and the anti-aging capacity decreases, so the ΔYI is higher than that of the examples; in Comparative Example 3, the amount of additives is increased, although it can improve part of the anti-aging capacity, but the interaction between the additives is intensified, and the anti-aging system is imbalanced in some areas, so the ΔYI is lower than that of Comparative Example 1 but higher than that of the examples.

[0145] For the strength performance, in the examples 1-5, the three-layer material has good compatibility, and each additive is uniformly dispersed without destroying the molecular chain structure, so that the tensile strength is maintained at 18.2-19.0 MPa, and the elongation is maintained at 505%-525%.

[0146] Examples 2-4 have little effect on the molecular chain structure of the material due to the adjustment of the amount of single additive, so the mechanical properties are close to example 1; Example 5 has slightly higher tensile strength and elongation than example 1 due to the increase of the proportion of the outer layer and the middle layer, and the overall structure of the material is more stable.

[0147] Comparative example 1 has slightly decreased interlayer bonding force due to the exchange of interlayer function, and the slight degradation of the material due to the decline of the anti-aging ability, so the mechanical properties are significantly reduced; Comparative examples 2 and 3 have lower mechanical properties than examples due to the mixed addition of additives, some additives have a slight crosslinking effect on the molecular chain, and the uneven distribution of additives between the layers will affect the bonding force, and the mechanical properties of comparative example 3 are slightly lower than those of comparative example 2 due to the higher amount of additive added, and the crosslinking and interface effect are more obvious.

[0148] According to the above embodiments of the present application, these embodiments do not describe all the details and are not limited to the specific embodiments of the present application. Obviously, according to the above description, many modifications and changes can be made. The present description selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well utilize the present application and make modifications and uses on the basis of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a high-transmittance, yellowing-resistant, self-adhesive film, characterized by, The method comprises the following steps: Step 1: uniformly mix low-density polyethylene, unwinding master batch and ultraviolet absorber through a mixer to obtain outer layer blend material for standby; Step 2: uniformly mix low-density polyethylene and light stabilizer through a mixer to obtain middle layer blend material for standby; Step 3: uniformly mix self-adhesive material and antioxidant through a mixer to obtain inner layer blend material for standby; Step 4: correspondingly add the outer layer blend material, the middle layer blend material and the inner layer blend material into the first, the second and the third feeding ports of a three-layer co-extrusion blow molding machine respectively, heat them to the set temperature to make each layer of blend material in a molten state, and then extrude the three layers of molten blend material through a die at the same time to obtain a three-layer structure of self-adhesive film blank; Step 5: transfer the self-adhesive film blank to an environment with a temperature of 20-40℃ to cool to room temperature, and then stand for 1-2 hours before being cut and rolled to obtain the high-transmittance yellowing-resistant self-adhesive film. In step 1, the mass ratio of low-density polyethylene, unwinding master batch and ultraviolet absorber is 95%-99%:1%-4%:0.05%-0.5%, the unwinding master batch contains 50%-70% carrier resin, 25%-45% opening agent and 5%-10% auxiliary agent, the carrier resin is linear low-density polyethylene or low-density polyethylene, the opening agent is calcium hydrogen phosphate, and the auxiliary agent is stearic acid and silane coupling agent in equal mass ratio; In step 2, the addition amount of light stabilizer accounts for 0.05%-0.5% of the total mass of the middle layer; In step 3, the self-adhesive material is compounded by polyisobutylene, modified polyethylene and thermoplastic elastomer in a molar ratio of 0.7-1.3:0.7-1.3:0.7-1.3; In step 3, the addition amount of antioxidant accounts for 0.01%-0.1% of the total mass of the inner layer.

2. The preparation method of the high-transmittance yellowing-resistant self-adhesive film according to claim 1, wherein in step 1, the ultraviolet absorber is compounded by benzophenone ultraviolet absorber, benzotriazole ultraviolet absorber and triazine ultraviolet absorber in a molar ratio of 0.8-1.2:0.8-1.2:0.8-1.

2.

3. The preparation method of the high-transmittance yellowing-resistant self-adhesive film according to claim 1, wherein in step 2, the light stabilizer is hindered amine light stabilizer.

4. The preparation method of the high-transmittance yellowing-resistant self-adhesive film according to claim 1, wherein in step 3, the antioxidant is compounded by phenolic antioxidant, amine antioxidant, phosphite antioxidant and sulfide antioxidant in a molar ratio of 0.8-1.2:0.8-1.2:0.8-1.2:0.8-1.

2.

5. The preparation method of the high-transmittance yellowing-resistant self-adhesive film according to claim 1, wherein in step 4, the feeding mass ratio of the first, the second and the third feeding ports of the three-layer co-extrusion blow molding machine is 3-4:3-4:2-4.

6. The preparation method of the high-transmittance yellowing-resistant self-adhesive film according to claim 1, wherein in step 4, the heating temperature of the outer layer blend material is 150-200℃, the heating temperature of the middle layer blend material is 160-230℃, and the heating temperature of the inner layer blend material is 160-200℃. ​ ​ ​ ​ ​

Images