An ultra-high gloss and ultra-low haze blown PE film and its preparation process

Abstract

This application relates to the field of thin film technology, and specifically discloses a blow-molded PE film with ultra-high gloss and ultra-low haze and its preparation process. The blow-molded PE film with ultra-high gloss and ultra-low haze successively includes an outer layer, a middle layer and an inner layer from outside to inside; the inner layer is made of the following raw materials: metallocene linear low density polyethylene, metallocene linear ultra-low density polyethylene, low density polyethylene, metallocene polyethylene, antiblocking agent, slip agent, PPA additive; the middle layer is made of the following raw materials: high density polyethylene, metallocene linear medium density polyethylene, polypropylene, PPA additive, nucleating agent; the outer layer is made of the following raw materials: metallocene linear low density polyethylene, metallocene linear ultra-low density polyethylene, low density polyethylene, metallocene polyethylene, PPA additive. The blow-molded PE film with ultra-high gloss and ultra-low haze of this application has the advantages of high gloss, low haze, excellent mechanical properties and strong barrier properties.

Description

Technical Field

[0001] The present application relates to the field of thin film technology, and more specifically, it relates to a blow-molded PE film with ultra-high gloss and ultra-low haze and its preparation process. Background Art

[0002] As an essential packaging form in today's society, plastic flexible packaging is widely used in the packaging of various categories of goods. The main reasons are that plastic flexible packaging can meet the requirements of diverse protection of goods, has a simple packaging process, is convenient to operate and use, and has many advantages such as affinity. Polyethylene is divided into high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene, and one of its main uses is film application.

[0003] In the prior art, a Chinese invention patent document with the application number... disclosed a PE film, which includes an inner layer, a middle layer, and an outer layer stacked in sequence. The inner layer includes 10wt% - 45wt% of low-density polyethylene, 50wt% - 85wt% of linear low-density polyethylene, and 3wt% - 10wt% of myrcene; the middle layer includes 10wt% - 45wt% of low-density polyethylene, 50wt% - 85wt% of linear low-density polyethylene, and 3wt% - 10wt% of myrcene; the outer layer includes 10wt% - 50wt% of low-density polyethylene and 50wt% - 90wt% of linear low-density polyethylene.

[0004] However, regarding the above-mentioned related technology, the inventor found that in the high-pressure low-density polyethylene / linear low-density polyethylene (LDPE / LLDPE) blended resin in the inner layer, the LLDPE resin is composed of ethylene and 1-butene copolymerized under low pressure by a Ziegler-Natta catalyst following the coordination polymerization mechanism. Its molecular structure is linear, with short side chains and a wide distribution on the main chain, and many macromolecules. Therefore, during the blown film processing, when the resin transforms from the molten state to the glassy state, large-sized crystal grains are easily formed and the crystal regions are unevenly distributed, resulting in irregular light refraction and light scattering on the film surface, causing high haze and poor transparency of the LLDPE film. In addition, during the blown film process, due to low cooling efficiency, the transparency of the film will further decrease. Summary of the Invention

[0005] In order to improve the gloss and transparency of the blow-molded PE film and reduce the haze, the present application provides a blow-molded PE film with ultra-high gloss and ultra-low haze and its preparation process.

[0006] In the first aspect, the present application provides a blow-molded PE film with ultra-high gloss and ultra-low haze, adopting the following technical scheme:

[0007] A blow-molded PE film with ultra-high gloss and ultra-low haze includes an outer layer, a middle layer, and an inner layer from outside to inside in sequence;

[0008] The inner layer is made of raw materials including the following parts by weight: 30-50 parts of metallocene linear low density polyethylene, 30-50 parts of metallocene linear ultra low density polyethylene, 5-15 parts of low density polyethylene, 5-15 parts of metallocene polyethylene, 1-3 parts of antiblocking agent, 1.5-2.5 parts of slip agent, and 0.5-1.5 parts of PPA additive;

[0009] The middle layer is made of raw materials including the following parts by weight: 30-50 parts of high density polyethylene, 20-40 parts of metallocene linear medium density polyethylene, 20-40 parts of polypropylene, 0.5-1.5 parts of PPA additive, and 4-6 parts of nucleating agent;

[0010] The outer layer is made of raw materials including the following parts by weight: 30-50 parts of metallocene linear low density polyethylene, 30-50 parts of metallocene linear ultra low density polyethylene, 5-15 parts of low density polyethylene, 5-15 parts of metallocene polyethylene, and 0.5-1.5 parts of PPA additive.

[0011] By adopting the above technical solution, in the middle layer, PP-3988 type nucleating agent is used, thus greatly reducing the crystal size in the blown film cooling and forming process, greatly reducing the influence of cooling and forming on haze. In cooperation with polypropylene, it can effectively improve the gloss of HDPE. In addition, metallocene linear medium density polyethylene is also used in the middle layer, which can not only maintain the rigidity of HDPE, but also has the flexibility and creep resistance of LDPE. And metallocene linear ultra low density polyethylene is used in the outer layer and the inner layer, thus improving the transmittance of the PE film, improving the glossiness of the PE film by increasing the refraction and reducing the haze. The metallocene polyethylene in the outer layer is a thermoplastic with excellent performance and one of the most important technological advances in the polyolefin industry. It has the characteristics of narrow molar mass distribution, uniform distribution of comonomers, and good three-dimensional control of the polyolefin microstructure. However, its shear sensitivity is low and the melt mass flow rate is low. Therefore, it is blended with low density polyethylene, but the two are thermodynamically incompatible systems. During the melt extrusion process, periodic and self-similar small ridges will appear on the extruded film, that is, the sharkskin phenomenon appears. Therefore, metallocene polyethylene, PPA additive, etc. are used to inhibit the sharkskin phenomenon, so that the produced PE film has a high gloss, and the middle layer contains PP and HDPE with high barrier properties, which can reduce the precipitation amount of the slip agent in the inner layer to the outer layer and reduce the friction coefficient of the outer layer.

[0012] Optionally, it sequentially includes an outer layer, a middle layer and an inner layer from outside to inside;

[0013] The inner layer is made of raw materials including the following parts by weight: 40 parts of metallocene linear low density polyethylene, 40 parts of metallocene linear ultra low density polyethylene, 10 parts of low density polyethylene, 10 parts of metallocene polyethylene, 2 parts of antiblocking agent, 2 parts of slip agent, and 1 part of PPA additive;

[0014] The middle layer is made of raw materials including the following parts by weight: 40 parts of high-density polyethylene, 30 parts of metallocene linear medium-density polyethylene, 30 parts of polypropylene, 1 part of PPA additive, and 5 parts of nucleating agent;

[0015] The outer layer is made of raw materials including the following parts by weight: 40 parts of metallocene linear low-density polyethylene, 40 parts of metallocene linear ultra-low-density polyethylene, 10 parts of low-density polyethylene, 10 parts of metallocene polyethylene, and 1 part of PPA additive.

[0016] By adopting the above technical solution, the dosage of each raw material of the outer layer, middle layer and inner layer is more accurate, and the haze of the produced PE film can be lower and the transparency can be better.

[0017] Optionally, the slip agent is erucamide.

[0018] By adopting the above technical solution, erucamide is prepared from single unsaturated C22 erucic acid, has good thermal stability, strong antioxidant ability, less volatile matter generated during processing, is more suitable for processing under high-temperature conditions, has high processing productivity, and the quality of the produced film product is high. It migrates to the film surface due to incompatibility with the polymer, improves antistatic and lubricating properties, can also improve moisture-proof performance, can significantly reduce the friction coefficient and adhesion resistance, improve the blown film efficiency, effectively prevent the adhesion between films and the adhesion between pellets, and can increase the smoothness of the film surface and prevent dust from adhering to the product film.

[0019] Optionally, the middle layer further contains 10-15 parts by weight of a barrier enhancer, and the preparation method of the barrier enhancer is as follows: (1) Melt PVC, cast it to form a PVC film, soak the PVC film in an aqueous solution of polyvinyl alcohol with a concentration of 10-12 wt% for 1-2 min, take out the PVC film, and hang it until no aqueous solution of polyvinyl alcohol flows down;

[0020] (2) Immerse cellophane in a chitosan acetate solution with a concentration of 1.5-2 wt% for 1-2 min, take out the cellophane, and hang it until no chitosan acetate solution flows down;

[0021] (3) Bond the product obtained in step (1) on both sides of the product obtained in step (2), dry it under vacuum, and crush it to an average length of 10-20 μm.

[0022] By adopting the above technical solution, since the slip agent in the inner layer is likely to precipitate onto the outer layer, the friction coefficient of the corona surface of the outer layer is small, making it difficult to compound and print. Therefore, a barrier modifier is added to the middle layer to improve the barrier properties of the middle layer to the slip agent, water vapor and gas, reduce the precipitation amount of the slip agent, and improve the friction coefficient of the outer layer. A PVC film with polyvinyl alcohol adhered to both sides is used as the outer side, and a glassine paper with chitosan adhered to both sides is used as the inner side for lamination. The PVC film has high tensile strength and good elongation at break, but poor barrier properties. An aqueous solution of polyvinyl alcohol is adhered to the PVC film. Polyvinyl alcohol has good film-forming properties and can be evenly and densely distributed on the PVC film, helping the polyvinyl alcohol film and the PVC film to jointly bear the external force, thereby further improving the tensile strength of the PVC film. The glassine paper has high oxygen barrier properties, large longitudinal strength and small transverse strength. Adhering a chitosan solution to its surface can not only improve the tensile strength and elongation at break of the glassine paper, but also enhance the barrier properties of the glassine paper to water vapor. When the PVC film adhered with polyvinyl alcohol is laminated with the glassine paper adhered with chitosan, there is a strong hydrogen bond between chitosan and polyvinyl alcohol, which can improve the lamination stability of the PVC film and the glassine paper. Therefore, polyvinyl alcohol and chitosan not only act as a barrier layer, but also act as an adhesive layer. Moreover, both PVC and glassine paper have high transparency, and adding a barrier modifier made in the middle layer has little effect on the transparency of the PE film.

[0023] Optionally, the aqueous solution of polyvinyl alcohol further contains nano-silica pretreated with a silane coupling agent, and the mass ratio of nano-silica to the aqueous solution of polyvinyl alcohol is 0.2 - 0.3:1.

[0024] By adopting the above technical solution, since the raw materials in the middle layer are substances such as high-density polyethylene and polyethylene, and polyvinyl alcohol, which is the outermost barrier modifier, has poor compatibility with these polymers, nano-silica is added to the polyvinyl alcohol solution. The nano-silica treated by the silane coupling agent can be evenly dispersed in the aqueous solution of polyvinyl alcohol. After the aqueous solution of polyvinyl alcohol containing nano-silica adheres to the PVC film and is cured into a film, the nano-silica increases the roughness of the polyvinyl alcohol film, thereby increasing the interfacial strength between the polyvinyl alcohol film on the PVC film and each raw material in the middle layer, and also enhancing the bonding fastness between the PVC film and the glassine paper.

[0025] Optionally, the particle size of the anti-blocking agent is 7 - 8 μm.

[0026] By adopting the above technical solution, the anti-blocking performance of the PE film can be effectively improved, preventing the PE film from sticking together and being difficult to open.

[0027] Optionally, in the middle layer, the mass ratio of polypropylene to high-density polyethylene is 3 - 4:4 - 3.

[0028] By adopting the above technical solution, when using polypropylene and high-density polyethylene at this mass ratio, the gloss of HDPE can be effectively enhanced.

[0029] Optionally, the thickness ratio of the middle layer, outer layer and inner layer is 1:0.5 - 1:0.5 - 1.

[0030] By adopting the above technical solution, with a suitable thickness ratio, the EP film can have high transparency and gloss, and the haze of the film can be reduced.

[0031] In a second aspect, the present application provides a preparation process for a blow-molded PE film with ultra-high gloss and ultra-low haze, adopting the following technical solution:

[0032] A preparation process for a blow-molded PE film with ultra-high gloss and ultra-low haze includes the following steps:

[0033] Ingredient preparation: Mix the raw materials of the outer layer, middle layer and inner layer separately in proportion for later use;

[0034] Temperature increase: Adopt a method of continuous temperature increase in zones. Heat the inner layer main machine to 195 - 210 °C, the middle layer main machine to 195 - 210 °C, the outer layer main machine to 195 - 208 °C, and the die head to 200 - 210 °C;

[0035] Blow molding: Place the prepared raw materials of each layer into the corresponding main machine respectively, and after blowing, cooling and forming, evenly pull up the film bubble; Rewinding: Corona treat the film bubble and then cut it into two pieces, and package it after rewinding.

[0036] By adopting the above technical solution, using German Reifen equipment and precisely controlling the temperature, through measures such as heating, traction and cooling and shaping of the film, the flatness of the film is greatly improved, wrinkles during film blowing are prevented, and the film tension of the PE film is increased; If the main machine temperature is too high, the resin is prone to decomposition, the PE film is brittle, and the longitudinal tensile strength is low. If the main machine temperature is too low, the resin is poorly plasticized, reducing the tensile strength, surface gloss and transparency of the PE film.

[0037] Optionally, in the blow molding step, the rotational speed of the outer layer main machine is 50 - 55 r / min, the rotational speed of the middle layer main machine is 30 - 35 r / min, the rotational speed of the inner layer main machine is 40 - 45 r / min, the blow-up ratio is 2 - 3, and the traction speed is 20 - 25 m / min.

[0038] By adopting the above technical solutions, the rotation speeds of the outer layer host and the inner layer host are faster than that of the middle layer host, which can enhance the mixing state of the raw materials in the outer layer and the inner layer. The rotation speed of the middle layer host is slightly lower, which can increase the plasticization time of the raw materials in the middle layer, extend the residence time of the raw materials in the middle layer, and improve the reaction degree. Ensure that the traction speed is 20 - 25 m / min, which can prevent the traction speed from being too fast. When the traction speed is too fast, the longitudinal tensile strength of the PE film increases and the thickness decreases. It can also prevent the traction speed from being too slow. When the traction speed is too slow, the longitudinal tensile strength of the PE film decreases and the thickness increases. The blow-up ratio refers to the ratio of the diameter of the blown film bubble to the diameter of the non-blown pipe diameter. Increasing the blow-up ratio will increase the transverse strength of the PE film, but if the blow-up ratio is too large, the film bubble will be unstable and the film is prone to wrinkles. Therefore, it is appropriate to control the blow-up ratio between 2 and 3.

[0039] In summary, the present application has the following beneficial effects:

[0040] 1. Since metallocene linear ultra-low density polyethylene is used in the outer layer and the inner layer of the PE film of the present application, and metallocene linear medium density polyethylene is used in the middle layer, and PP is added as a nucleating agent, it can reduce the crystal size during film blowing and cooling, and improve the refractive index of PE, thereby improving the glossiness of the PE film and reducing the haze.

[0041] 2. In the present application, an opening agent with an appropriate particle size and an appropriate thickness ratio of the middle layer, outer layer and inner layer are preferably adopted, so that the haze of the prepared PE film is lower and the glossiness is increased.

[0042] 3. In the present application, a PVC film adhered with polyvinyl alcohol and a glass paper adhered with chitosan are preferably compounded and then ground into micron-sized flakes, which are uniformly dispersed in the middle layer as a barrier modifier. The barrier property of the thus prepared PE film is improved, and the amount of the slip agent in the inner layer precipitating outwards can be reduced, thereby improving the friction coefficient of the outer layer and enhancing the printability and compoundability. Specific Embodiments

[0043] Preparation Examples 1 - 8 of Barrier Modifier

[0044] Preparation Example 1: (1) Heat PVC to 180 °C for melting, cast it onto a glass substrate, dry it at 40 °C for 48 h, separate the glass substrate, and make a PVC film with a thickness of 50 nm. Immerse the PVC film in an aqueous solution of polyvinyl alcohol with a concentration of 12 wt% for 1 min, take out the PVC film, scrape off the excess aqueous solution of polyvinyl alcohol, and hang it until no aqueous solution of polyvinyl alcohol flows down;

[0045] (2) Immerse cellophane with a thickness of 10 μm in a chitosan acetate solution with a concentration of 1.5 wt% for 2 min. Take out the cellophane, scrape off the excess chitosan acetate solution, and hang it until no chitosan acetate solution drips. The concentration of the acetate solution is 0.5 wt%; (3) Attach the product obtained in step (1) with a thickness of 80 nm on both sides of the product obtained in step (2) with a thickness of 15 μm, vacuum dry at 40 °C for 72 h, and crush it to an average length of 20 μm.

[0046] Preparation Example 2: (1) Heat PVC to 180 °C for hot melting, cast it onto a glass substrate, dry at 40 °C for 48 h, separate the glass substrate, and make a PVC film with a thickness of 50 nm. Immerse the PVC film in an aqueous solution of polyvinyl alcohol with a concentration of 10 wt% for 2 min. Take out the PVC film, scrape off the excess aqueous solution of polyvinyl alcohol, and hang it until no aqueous solution of polyvinyl alcohol drips;

[0047] (2) Immerse cellophane with a thickness of 10 μm in a chitosan acetate solution with a concentration of 2 wt% for 1 min. Take out the cellophane, scrape off the excess chitosan acetate solution, and hang it until no chitosan acetate solution drips. The concentration of the acetate solution is 0.5 wt%;

[0048] (3) Attach the product obtained in step (1) with a thickness of 80 nm on both sides of the product obtained in step (2) with a thickness of 15 μm, vacuum dry at 40 °C for 72 h, and crush it to an average length of 30 μm.

[0049] Preparation Example 3: The difference from Preparation Example 1 is that the product obtained in step (1) is attached only on one side of the product obtained in step (2).

[0050] Preparation Example 4: The difference from Preparation Example 1 is that the product obtained in step (1) is not attached on both sides of the product obtained in step (2).

[0051] Preparation Example 5: The difference from Preparation Example 1 is that the product obtained in step (1) is crushed to an average particle size of 20 μm as a barrier modifier.

[0052] Preparation Example 6: The difference from Preparation Example 1 is that the cellophane is not immersed in the chitosan acetate solution.

[0053] Preparation Example 7: The difference from Preparation Example 1 is that the PVC film is not immersed in the aqueous solution of polyvinyl alcohol.

[0054] Preparation Example 8: The difference from Preparation Example 1 is that nano-silica pretreated with silane coupling agent KH550 is added to the aqueous solution of polyvinyl alcohol in step (1), and the mass ratio of nano-silica to the aqueous solution of polyvinyl alcohol is 0.3:1.

[0055] Examples

[0056] The models and manufacturers of the raw materials in the examples are shown in Table 1.

[0057]

[0058] Example 1: A high-gloss and ultra-low haze blown PE film, including an outer layer, a middle layer and an inner layer from outside to inside. The thickness ratio of the outer layer, the middle layer and the inner layer is 0.5:1:0.5. The raw material usage of the outer layer, the middle layer and the inner layer is shown in Table 2. Among them, the particle size of the antiblocking agent is 7μm, the slip agent is erucamide, the melt index of the metallocene linear low density polyethylene is 0.92g / cm 3 , and the melt index is 1g / 10min. The density of the metallocene linear ultra-low density polyethylene is 0.903g / cm 3 , and the melt index is 3.8g / 10min. The density of the low density polyethylene is 0.923g / cm 3 , and the melt index is 1.9g / 10min. The density of the metallocene polyethylene is 0.925g / cm 3 , and the melt index is 1.9g / 10min. The density of the high density polyethylene is 0.956g / cm 3 , and the melt index is 1g / 10min. The density of the metallocene linear medium density polyethylene is 0.937g / cm 3 , and the melt index is 1.8g / 10min.

[0059] The preparation process of the above high-gloss and ultra-low haze blown PE film includes the following steps:

[0060] S1. Batching: Mix the raw materials of the outer layer, the middle layer and the inner layer separately according to the ratio for standby;

[0061] S2. Heating: Use the method of continuous heating in zones to heat the main machines of the inner layer, the outer layer and the middle layer. The temperatures of each zone of the inner layer main machine are: Zone 1 195°C, Zone 2 205°C, Zone 3 205°C, Zone 4 210°C, Zone 5 210°C, Zone 6 210°C. The temperatures of each zone of the middle layer main machine are: Zone 1 195°C, Zone 2 210°C, Zone 3 215°C, Zone 4 220°C, Zone 5 215°C, Zone 6 210°C. The temperatures of each zone of the outer layer main machine are: Zone 1 195°C, Zone 2 200°C, Zone 3 205°C, Zone 4 210°C, Zone 5 210°C, Zone 6 208°C. The temperatures of each zone of the die head are: Zone 1 220°C, Zone 2 220°C, Zone 3 215°C, Zone 4 215°C, Zone 5 210°C. After the heating is completed, keep warm for 30 minutes and then start blowing. And the start-up time intervals of the main machines of the outer layer, the middle layer and the inner layer are 4 minutes. Before starting up, replace the filters of each layer, turn on the fan, and clean the die lip of the die head;

[0062] S3. Blow molding: Place the prepared raw materials for each layer into the corresponding main machine. The rotational speed of the outer-layer main machine is 51.5 r / min, the rotational speed of the middle-layer main machine is 34.6 r / min, and the rotational speed of the inner-layer main machine is 44.4 r / min. Turn on the cold air blower, maintain the inlet air temperature at 20 °C, the blower frequency at 40 Hz, pull upward and quickly knead the molten glue, inject compressed air into the die head, control the blow-up ratio to be 2, and form it through blow-up and cooling. Evenly pull up the film bubble, and the traction speed is 23 m / min;

[0063] S4. Rewinding: Corona-treat the film bubble and then cut it into two pieces, and package it after rewinding.

[0064] Table 2 Raw material consumption of PE films in Examples 1 - 3

[0065]

[0066]

[0067] Example 2: A blow-molded PE film with high gloss and ultra-low haze, including an outer layer, a middle layer, and an inner layer from outside to inside. The thickness ratio of the outer layer, middle layer, and inner layer is 1:1:1. The raw materials used for the outer layer, middle layer, and inner layer are shown in Table 2. Among them, the particle size of the anti-blocking agent is 8 μm, the slip agent is erucamide, the melt index of metallocene linear low-density polyethylene is 0.92 g / cm 3 , the melt index is 1 g / 10 min, the density of metallocene linear ultra-low-density polyethylene is 0.903 g / cm 3 , the melt index is 3.8 g / 10 min, the density of low-density polyethylene is 0.923 g / cm 3 , the melt index is 1.9 g / 10 min, the density of metallocene polyethylene is 0.925 g / cm 3 , the melt index is 1.9 g / 10 min, the density of high-density polyethylene is 0.956 g / cm 3 , the melt index is 1 g / 10 min, the density of metallocene linear medium-density polyethylene is 0.937 g / cm 3 , the melt index is 1.8 g / 10 min.

[0068] The preparation process of the above-mentioned blow-molded PE film with high gloss and ultra-low haze includes the following steps:

[0069] S1. Batching: Mix the raw materials for the outer layer, middle layer, and inner layer separately according to the ratio for standby;

[0070] S2. Heating: The inner, outer, and middle layer main machines are heated by means of continuous zone heating. The temperatures of each zone of the inner layer main machine are: Zone 1: 190 °C, Zone 2: 200 °C, Zone 3: 200 °C, Zone 4: 205 °C, Zone 5: 205 °C, Zone 6: 210 °C. The temperatures of each zone of the middle layer main machine are: Zone 1: 190 °C, Zone 2: 205 °C, Zone 3: 210 °C, Zone 4: 215 °C, Zone 5: 210 °C, Zone 6: 205 °C. The temperatures of each zone of the outer layer main machine are: Zone 1: 190 °C, Zone 2: 200 °C, Zone 3: 200 °C, Zone 4: 205 °C, Zone 5: 205 °C, Zone 6: 208 °C. The temperatures of each zone of the die head are: Zone 1: 220 °C, Zone 2: 220 °C, Zone 3: 215 °C, Zone 4: 215 °C, Zone 5: 210 °C. After the heating is completed, keep warm for 30 min and then start the blow molding machine. The start-up time intervals of the outer, middle, and inner layer main machines are 3 min. Before starting, replace the filters of each layer, turn on the fan, and clean the die lip of the die head;

[0071] S3. Blow molding: Place the prepared raw materials of each layer into the corresponding main machine respectively. The rotation speed of the outer layer main machine is 55 r / min, the rotation speed of the middle layer main machine is 35 r / min, and the rotation speed of the inner layer main machine is 45 r / min. Turn on the cold air blower, keep the inlet air temperature at 20 °C, the fan frequency at 40 Hz, pull upward and quickly knead the molten glue, inject compressed air into the die head, control the blow-up ratio to be 2, form by blow-up and cooling, and evenly pull up the film bubble. The traction speed is 25 m / min;

[0072] S4. Rewinding: Corona treat the film bubble and then cut it into two pieces, and then wind it up and package it.

[0073] Example 3 - 5: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that the raw material dosages are as shown in Table 1.

[0074] Example 6: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that the middle layer further includes 15 kg of a barrier modifier prepared from Preparation Example 1.

[0075] Example 7: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that the middle layer further includes 10 kg of a barrier modifier prepared from Preparation Example 2.

[0076] Example 8: A high-gloss and ultra-low haze blown PE film, which is different from Example 6 in that the barrier modifier in the middle layer is prepared from Preparation Example 3.

[0077] Example 9: A high-gloss and ultra-low haze blown PE film, which is different from Example 6 in that the barrier modifier in the middle layer is prepared from Preparation Example 4.

[0078] Example 10: A high-gloss and ultra-low haze blown PE film, which is different from Example 6 in that the barrier modifier in the middle layer is made from Preparation Example 5.

[0079] Example 11: A high-gloss and ultra-low haze blown PE film, which is different from Example 6 in that the barrier modifier in the middle layer is made from Preparation Example 6.

[0080] Example 12: A high-gloss and ultra-low haze blown PE film, which is different from Example 6 in that the barrier modifier in the middle layer is made from Preparation Example 7.

[0081] Example 13: A high-gloss and ultra-low haze blown PE film, which is different from Example 6 in that the barrier modifier in the middle layer is made from Preparation Example 8.

[0082] Comparative Example

[0083] Comparative Example 1: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that the nucleating agent in the middle layer is calcium stearate.

[0084] Comparative Example 2: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that in the middle layer, low-density polyethylene of model 2420H is used to replace metallocene linear medium-density polyethylene of model SP4020 in equal amount.

[0085] Comparative Example 3: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that in the inner layer, high-density polyethylene of model F920A is used to replace metallocene linear ultra-low density polyethylene of model SP0540 in equal amount.

[0086] Comparative Example 4: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that in the outer layer, high-density polyethylene of model F920A is used to replace metallocene linear ultra-low density polyethylene of model SP0540 in equal amount.

[0087] Comparative Example 5: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that in the middle layer, the dosage of high-density polyethylene is 10 kg, and the dosages of the remaining raw materials remain unchanged.

[0088] Comparative Example 6: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that in the middle layer, the dosage of high-density polyethylene is 70 kg, and the dosages of the remaining raw materials remain unchanged.

[0089] Comparative Example 7: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that the dosage of high-density polyethylene is 20 kg and the dosage of polypropylene is 50 kg.

[0090] Comparative Example 8: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that the mass of high-density polyethylene is 60 kg and the dosage of polypropylene is 10 kg.

[0091] Comparative Example 9: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that the dosage of nucleating agent is 1 kg.

[0092] Comparative Example 10: A high-gloss and ultra-low haze blown PE film, which is different from Example 1 in that the dosage of nucleating agent is 10 kg.

[0093] Comparative Example 11: A low-temperature polyethylene film is prepared by co-extrusion blow molding of three layers of films, namely an inner layer, a middle layer and an outer layer. The inner layer is made of linear low-density polyethylene FK1828, metallocene polyethylene 1881G and low-density polyethylene 2426H in a weight percentage of 25%:55%:20%. The middle layer is made of linear low-density polyethylene 35B, linear low-density polyethylene 222WT and low-density polyethylene 2420H in a weight percentage of 40%:40%:20%. The outer layer is made of linear low-density polyethylene 35B and low-density polyethylene 2426H in a weight percentage of 80%:20%. The processing temperature of the inner layer is 140 °C, the processing temperature of the middle layer is 150 °C, and the processing temperature of the outer layer is 160 °C. The co-extrusion blow molding is carried out by a three-layer co-extrusion blow molding machine. The die head temperature of the three-layer co-extrusion blow molding machine is 160 °C. The thickness ratio of the inner layer, the middle layer and the outer layer is 40%:35%:25%. The heat sealing pressure of the low-temperature polyethylene film is 0.4 mpg and the time is 0.7 s.

[0094] Performance Detection Test

[0095] Prepare PE films according to the above method, and use a commercially available blown PE film as a control group. Cut the made PE films into specimens with a length of 1040 mm and a thickness of 80 μm. Under the environment of 23 °C and 50% relative humidity, refer to the following methods for performance detection, and record the detection results in Table 3.

[0096] 1. Transmittance and haze: Detect according to GB / T2410-2008 "Test Method for Transmittance and Haze of Transparent Plastics";

[0097] 2. Glossiness: Measure according to ASTM D523 "Test Method for Specular Gloss", and the incident angle is 60 degrees;

[0098] 3. Tensile strength at break and elongation at break: Detect according to GB13022-1991 "Test Method for Tensile Properties of Plastic Films";

[0099] 4. Tear strength: Tested in accordance with GB / T 16578 "Test Method for Tear Resistance of Plastic Films and Sheets - Trouser Tear Method".

[0100] 4. Coefficient of friction: Tested in accordance with GB / T 10006 - 1988 "Determination Method of Coefficient of Friction for Plastics and Sheets".

[0101] 5. Impact strength: Tested in accordance with GB9639A "Test Method for Impact Resistance of Plastic Films by Free - Falling Dart Method".

[0102] 6. Heat - seal strength: Tested in accordance with QB - 75041166 - 9 - 02.

[0103] 7. Water vapor transmission rate (g / (m 2 ·24h)): Tested in accordance with GB / T 26253 - 2010 "Determination of Water Vapor Transmission Rate of Plastic Films and Sheets - Infrared Detector Method", using a BASIC301 water vapor transmission rate tester at a temperature of 23°C and a relative humidity of 85%.

[0104] 8. Oxygen transmission rate (cm 3 / (m 2 ·24h·0.1MPa)): Tested using a VACV1 type oxygen transmission rate tester at a temperature of 23°C and a relative humidity of 0%.

[0105] Table 3 Performance test results of PE films

[0106]

[0107]

[0108] Continued Table 3

[0109]

[0110]

[0111]

[0112] In Examples 1 - 5, the raw material dosages of the inner layer, middle layer, and outer layer are different. The PE films produced have a light transmittance of over 90%, a haze of 7% or less, lower haze, higher light transmittance, better gloss, and higher mechanical strength compared to commercially available PE films.

[0113] In Example 6 and Example 7, the barrier modifiers prepared in Preparation Example 1 and Preparation Example 2 were respectively used in the middle layer. Compared with Example 1, the PE films prepared in Example 6 and Example 7 had higher tensile strength at break, elongation at break and tear strength, higher mechanical strength, and improved barrier properties to water vapor and oxygen. In addition, the friction coefficient of the corona surface increased, and the precipitation amount of the slip agent decreased.

[0114] Compared with Example 1, in Example 8, the barrier modifier prepared in Preparation Example 3 was used. The properties such as light transmittance and haze of the PE film changed little, but the mechanical properties such as elongation at break and tear strength decreased significantly, and the transmittance of water vapor and oxygen increased, and the friction coefficient of the outer layer decreased, indicating a decrease, and the precipitation amount of the slip agent increased.

[0115] In Example 9, the barrier modifier prepared in Preparation Example 4 was used, and the glass paper fragments adhered with chitosan on both sides were used as the barrier modifier. As shown in Table 3, the light transmittance, haze and glossiness of the PE film changed little, but the mechanical strength and barrier property were worse than those in Example 8, and the friction coefficient decreased further.

[0116] In Example 10, the barrier modifier prepared in Preparation Example 5 was used. In Preparation Example 5, the PVC film adhered with polyvinyl alcohol on the surface was used as the barrier modifier. The data in Table 3 showed that compared with Example 6, the mechanical strength of the PE film prepared in Example 10 decreased, the barrier ability decreased, and the friction coefficient of the outer corona surface decreased.

[0117] Compared with Example 6, in Example 11, the barrier modifier prepared in Preparation Example 6 was used. In Preparation Example 6, the chitosan aqueous solution was not adhered on the PVC film. The barrier property of the film prepared in Example 11 decreased significantly, the surface friction coefficient increased, and the mechanical properties decreased to some extent.

[0118] In Example 12, the barrier modifier prepared in Preparation Example 7 was used. In Preparation Example 7, the polyvinyl alcohol aqueous solution was not adhered on the PVC film, and it was directly compounded with the glass paper adhered with chitosan. Compared with Example 6, the barrier property of the PE film prepared in Example 12 decreased, the mechanical strength decreased slightly, and the surface friction coefficient decreased.

[0119] In Example 13, the barrier modifier prepared in Preparation Example 8 was used. In Preparation Example 8, nano-silica was also added to the polyvinyl alcohol aqueous solution. Compared with Example 6, the barrier property of the PE film prepared in Example 13 to water vapor and oxygen was further enhanced, the friction coefficient of the corona surface increased, and the mechanical properties of the film were improved to some extent.

[0120] In Comparative Example 1, calcium stearate was used as a nucleating agent in the middle layer. Compared with Example 1, the haze of the PE film prepared in Comparative Example 1 increased, the light transmittance decreased, and the mechanical properties such as tensile strength decreased.

[0121] In Comparative Example 2, the metallocene linear medium density polyethylene in the middle layer was replaced with low density polyethylene. As shown in Table 3, the light transmittance of the PE film made in Comparative Example 2 decreased, the haze increased, the transparency decreased, and the mechanical strength weakened.

[0122] In Comparative Example 3 and Comparative Example 4, high density polyethylene was used to equally replace the metallocene linear ultra low density polyethylene in the inner layer and the outer layer respectively. As can be seen from Table 3, the haze of the PE films made in Comparative Example 3 and Comparative Example 4 increased, the transparency decreased, and the mechanical strengths such as the tensile strength weakened.

[0123] In Comparative Example 5 and Comparative Example 6, the amount of high density polyethylene in the middle layer was decreased and increased respectively. Compared with Example 1, the transparency of the PE films prepared in Comparative Example 5 and Comparative Example 6 decreased, the friction coefficient of the corona surface of the outer layer decreased, and the barrier properties to water vapor and oxygen weakened. It shows that changing the amount of high density polyethylene will reduce the barrier property of the inner layer, resulting in an increase in the precipitation amount of the slip agent.

[0124] Compared with Example 1, in Comparative Example 7 and Comparative Example 8, although the total amount of high density polyethylene and polypropylene was considered to be 70 kg, the amount of high density polyethylene in Comparative Example 7 decreased, and the amount of high density polyethylene in Comparative Example 8 increased. As can be seen from the test data in Table 3, the transparency and mechanical strength of the films prepared in Comparative Example 7 and Comparative Example 8 weakened, and the friction coefficient of the corona surface of the outer layer decreased. It shows that changing the dosage ratio of high density polyethylene and polypropylene will cause a decrease in the barrier property of the film, an increase in the precipitation amount of the slip agent, and a weakening of the barrier property.

[0125] In Comparative Example 9 and Comparative Example 10, the amount of the nucleating agent was decreased and increased respectively. The transparency of the film decreased and the haze increased. It can be seen that the amount of the nucleating agent has a great influence on the transparency and gloss of the film.

[0126] Comparative Example 11 is a polyethylene film prepared by the prior art. It has a high light transmittance, but the haze reaches 12.7%, which is inferior to Example 1 of the present application.

[0127] The control group is a polyethylene film prepared by the prior art. It has a high haze, a low light transmittance, and poor transparency.

[0128] This specific embodiment is only an explanation of the present application, and it is not a limitation of the present application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A blow-molded PE film with ultra-high gloss and ultra-low haze, characterized in that, It includes an outer layer, a middle layer and an inner layer from outside to inside in sequence; The inner layer is made of raw materials including the following parts by weight: 30-50 parts of metallocene linear low density polyethylene, 30-50 parts of metallocene linear ultra low density polyethylene, 5-15 parts of low density polyethylene, 5-15 parts of metallocene polyethylene, 1-3 parts of antiblocking agent, 1.5-2.5 parts of slip agent, 0.5-1.5 parts of PPA additive; The middle layer is made of raw materials including the following parts by weight: 30-50 parts of high density polyethylene, 20-40 parts of metallocene linear medium density polyethylene, 20-40 parts of polypropylene, 0.5-1.5 parts of PPA additive, 4-6 parts of nucleating agent, 10-15 parts of barrier enhancer; The outer layer is made of raw materials including the following parts by weight: 30-50 parts of metallocene linear low density polyethylene, 30-50 parts of metallocene linear ultra low density polyethylene, 5-15 parts of low density polyethylene, 5-15 parts of metallocene polyethylene, 0.5-1.5 parts of PPA additive; The preparation method of the barrier enhancer is as follows: (1) Melt PVC, cast it to form a PVC film, soak the PVC film in an aqueous solution of polyvinyl alcohol with a concentration of 10-12wt% for 1-2min, take out the PVC film, and hang it until no aqueous solution of polyvinyl alcohol flows down; (2) Immerse glassine paper in a chitosan acetate solution with a concentration of 1.5-2wt% for 1-2min, take out the glassine paper, and hang it until no chitosan acetate solution flows down; (3) Bond the product obtained in step (1) on both sides of the product obtained in step (2), dry it in vacuum, and crush it to an average length of 10-20μm; The density of the metallocene linear low density polyethylene is 0.92 g / cm 3 , the melt index is 1 g / 10 min, the density of the metallocene linear ultra-low density polyethylene is 0.903 g / cm 3 , the melt index is 3.8 g / 10 min, the density of the low density polyethylene is 0.923 g / cm 3 , the melt index is 1.9 g / 10 min, the density of the metallocene polyethylene is 0.925 g / cm 3 , the melt index is 1.9 g / 10 min, the density of the high density polyethylene is 0.956 g / cm 3 , the melt index is 1 g / 10 min, the density of the metallocene linear medium density polyethylene is 0.937 g / cm 3 , the melt index is 1.8 g / 10 min.

2. The ultra-high gloss and ultra-low haze blown PE film according to claim 1, wherein The slip agent is erucamide.

3. The ultra-high gloss and ultra-low haze blown PE film according to claim 1, characterized in that, The aqueous solution of polyvinyl alcohol also contains nano-silica pretreated by a silane coupling agent, and the mass ratio of nano-silica to the aqueous solution of polyvinyl alcohol is 0.2-0.3:

1.

4. The ultra-high gloss and ultra-low haze blown PE film according to claim 1, characterized in that, The particle size of the antiblocking agent is 7-8μm.

5. The ultra-high gloss and ultra-low haze blown PE film according to claim 1, characterized in that, Inside the middle layer, the mass ratio of polypropylene to high density polyethylene is 3-4:4-3.

6. The ultra-high gloss and ultra-low haze blown PE film according to claim 1, characterized in that, The thickness ratio of the middle layer, the outer layer and the inner layer is 1:0.5-1:0.5-1.

7. The preparation process of the ultra-high gloss and ultra-low haze blown PE film according to any one of claims 1-6, characterized in that, It includes the following steps: Ingredient preparation: Mix the raw materials of the outer layer, the middle layer and the inner layer separately according to the ratio and set aside; Temperature rising: Adopt the method of continuous temperature rising in zones, raise the temperature of the inner layer main machine to 195-210°C, raise the temperature of the middle layer main machine to 195-210°C, raise the temperature of the outer layer main machine to 195-208°C, and raise the temperature of the die head to 200-210°C; Blow molding: Place the prepared raw materials of each layer into the corresponding main machine respectively, form them by blowing and cooling, and pull up the film bubble at a constant speed; Rewinding: Corona treat the film bubble and then cut it into two pieces, and rewind and package it.

8. The preparation process of the ultra-high gloss and ultra-low haze blown PE film according to claim 7, characterized in that, In the blow molding step, the rotation speed of the outer layer main machine is 50-55r / min, the rotation speed of the middle layer main machine is 30-35r / min, the rotation speed of the inner layer main machine is 40-45r / min, the blow-up ratio is 2-3, and the traction speed is 20-25m / min.

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