A single material heat-sealed temperature gradient co-extruded cast film

Abstract

The present invention provides a single-material heat-seal temperature gradient co-extruded cast film, which is a composite film formed by co-extruded casting of four layers, namely, a printing layer, a first core layer, a second core layer, and a sealing layer from the outside to the inside. The printing layer and the sealing layer of the present invention are the surface layer and the inner layer of the film, respectively, and the two layers are composed of medium-density linear metallocene polyethylene and low-density linear metallocene polyethylene. The flame retardant content of the printing layer, that is, the content of polyetheramine, is increased. At the same time, the sealing layer uses a modified polyester material to reduce its temperature resistance, so that the produced printing layer and the sealing layer have a temperature difference of 10°C to 20°C during the heat-sealing process, forming a heat-sealing temperature gradient, thereby achieving the effect of heat-sealing the sealing layer without burning the edges.

Description

Technical Field

[0001] The invention relates to a single-material heat-sealed temperature gradient co-extruded cast film, belonging to the field of films for kitchen paper towel packaging. Background Art

[0002] Cast film is a non-stretched, non-directional flat extruded film produced by quenching the melt. Kitchen paper towels are also wrapped with cast film, especially roll-packed kitchen paper towels, such as Figure 1 As shown, area A is a cast film that is packaged after stacking 4 layers, and area B is a single layer of cast film. During packaging, due to material problems, when the heat sealing strength of area A is good, a relatively high heat sealing temperature needs to be set. However, this heat sealing temperature can easily cause the film in area B to be burned.

[0003] In this regard, the existing published application number is 201810759553.3, and the name of the patent application is a three-layer co-extruded cast film and its preparation method. It discloses that the three-layer co-extruded cast film is prepared by the casting method. The three-layer co-extruded cast film has good processing performance, can be repeatedly heated and shaped, can be repeatedly printed many times, and can maintain structural stability and invariance within a wide temperature range. However, the raw materials of the surface layer and the inner layer of the cast film are the same, and the performance of the surface layer and the inner layer of the prepared cast film are consistent. When heat sealing is performed, the inner layer melts and fits, and the surface layer will also melt at the same time. When used to wrap kitchen rolls, the side packaging film will still be burned.

[0004] The existing published application number is 202311740606.4, and the patent application name is a high-temperature resistant low-shrinkage film and its preparation method. It reveals that the invention abandons the single-component polyethylene, polyester and other packaging film materials in the existing technology, and uses four-layer co-extrusion casting to prepare a packaging film with good performance. It not only has excellent mechanical properties, but also has excellent high-temperature shrinkage rate. It meets the conditions of 121°C steam sterilization for 15 minutes, 115°C steam sterilization for 30 minutes, and 110°C steam / water boiling sterilization for 60 minutes. The shrinkage rate of the protective film is less than 0.5%, which properly optimizes the technical problems of poor heat resistance and easy shrinkage of the protective film in the existing technology. However, the first core layer and the second core layer of the invention both use a combined layer of polypropylene and ethylene elastomer. Polypropylene has poor compatibility with polyethylene, and it is not a single-material polyethylene material. The performance of its recycled material is significantly lower than that of a single-material polyethylene material. Although polypropylene has ethylene elastomer added, it feels stiff and has poor puncture resistance.

[0005] The existing application number is 202110920994.9, and the name of the patent application is a drinking water packaging film and its preparation method. The four resin layers are processed and produced using polyethylene raw materials, and then made using a four-layer co-extrusion casting process. It is a single material, and the film treated in a water bath removes low-molecular polymers on the surface of the film, and performs secondary cleaning on the film to remove odors on the surface of the film, meeting the requirements of drinking water packaging for the odor sensitivity of packaging materials; the four-layer co-extruded film takes into account the cost advantages in the design of the interlayer ratio, making the processing cost lower, but in actual use, the invention only stacks two layers for heat sealing. If it is used for the packaging of kitchen rolls, there are also problems of side burns or non-fitting heat seals in area A.

[0006] Therefore, the present invention provides a single-material, multi-layer heat-sealed co-extruded cast film with a heat-sealing temperature gradient and no edge burns. Summary of the Invention

[0007] The present invention provides a single-material heat-sealed temperature gradient co-extruded cast film, which can effectively solve the above problems.

[0008] The present invention is achieved in that:

[0009] A single material heat-sealed temperature gradient co-extruded cast film is a composite film formed by co-extrusion casting of four layers from the outside to the inside: a printing layer, a first core layer, a second core layer and a sealing layer;

[0010] The raw materials of the printing layer include 20 to 30 parts of medium-density linear metallocene polyethylene, 30 to 50 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 to 2 parts of lubricant and 1 to 2 parts of opening agent, and 2 to 3 parts of polyetheramine in parts by weight;

[0011] The raw materials of the first core layer and the second core layer include 20-30 parts of high-density polyethylene, 30-50 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1-2 parts of antistatic agent, and 0.5-1 part of polyetheramine in parts by weight;

[0012] The raw materials of the sealing layer include 20 to 30 parts of low-density linear metallocene polyethylene, 30 to 50 parts of metallocene polyethylene, and 100 parts of low-density polyethylene as a base material, with 1 to 2 parts added by weight.

[0013] A method for preparing a cast film, based on the single-material heat-sealing temperature gradient co-extruded cast film, comprises the following steps:

[0014] S1, raw material preparation: prepare the raw materials for the printing layer, the first core layer, the second core layer and the sealing layer;

[0015] S2, melt extrusion: each layer of the prepared material is sequentially placed into a melter for melting at a melting temperature of 100°C to 130°C. The molten polyethylene enters the extruder sequentially according to the number of layers from the inside to the outside or from the outside to the inside of the film, is fused and compressed by the screw of the extruder, and is pushed into the die under high temperature and high pressure. The extruder is preheated in advance for 30 minutes to 60 minutes.

[0016] S3, die extrusion: molten polyethylene is extruded through the nozzle of the die to form a continuous film;

[0017] S4, cooling and stretching: The film is quickly cooled by cold air or cold water to reduce the film temperature and solidify it. The film is then drained to the stretching rollers through the traction rollers. The distance between the stretching rollers is adjusted to stretch the film.

[0018] S5, winding: After stretching is completed, the film thickness is detected in real time by an infrared film thickness gauge, and the film is wound into a roll through a winding mechanism.

[0019] The beneficial effects of the present invention are:

[0020] ① The printing layer and sealing layer of the present invention are the surface layer and inner layer of the film. These two layers are respectively composed of medium-density linear metallocene polyethylene and low-density linear metallocene polyethylene. The flame retardant content of the printing layer, that is, the content of polyetheramine, is increased. At the same time, the sealing layer uses a modified polyester material to reduce its temperature resistance. As a result, there is a temperature difference of 10°C to 20°C between the produced printing layer and the sealing layer during the heat sealing process, forming a heat sealing temperature gradient, thereby achieving multi-layer heat sealing without edge burns.

[0021] ② Except for a small amount of additives, 90% of the four-layer material of the cast film of the present invention is polyethylene, which is a single material. When it is used and recycled, there is no need to consider material separation and it can be directly recycled, which is green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 It is a structural diagram of the background technology of the present invention.

[0024] Figure 2 It is a schematic diagram of the principle of providing a single-material heat-sealing temperature gradient co-extruded cast film according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention for which protection is sought, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0027] Reference Figure 2 As shown, a single-material heat-sealed temperature gradient co-extruded cast film is a composite film formed by co-extrusion casting of four layers from the outside to the inside: a printing layer, a first core layer, a second core layer, and a sealing layer;

[0028] The raw materials of the printing layer include 20 to 30 parts of medium-density linear metallocene polyethylene, 30 to 50 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 to 2 parts of lubricant and 1 to 2 parts of opening agent, and 2 to 3 parts of polyetheramine in parts by weight;

[0029] The raw materials of the first core layer and the second core layer include 20-30 parts of high-density polyethylene, 30-50 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1-2 parts of antistatic agent, and 0.5-1 part of polyetheramine in parts by weight;

[0030] The raw materials of the sealing layer include 20-30 parts of low-density linear metallocene polyethylene, 30-50 parts of metallocene polyethylene, and 100 parts of low-density polyethylene as a base material, 1-2 parts of a slip agent, 1-2 parts of an opening agent, and 0.5-1 part of a modified polyester material.

[0031] The printing layer and sealing layer of the present invention are the surface layer and inner layer of the produced film. These two layers are respectively composed of medium-density linear metallocene polyethylene and low-density linear metallocene polyethylene. The flame retardant content of the printing layer, that is, the content of polyetheramine, is increased. At the same time, the sealing layer uses a modified polyester material to reduce its temperature resistance. As a result, there is a temperature difference of 10°C to 20°C between the produced printing layer and the sealing layer during the heat sealing process, forming a heat sealing temperature gradient. Except for a small amount of additives, 90% of the four layers of the cast film are polyethylene, which is a single material. During use and recycling, there is no need to consider material separation and can be directly recycled, which is environmentally friendly.

[0032] The modified polyester material refers to a long-spacing aliphatic model polyester synthesized by the acyclic diene metathesis copolymerization of undec-10-ene-1-acyl undec-10-enoate and undec-1,10-diene, followed by exhaustive hydrogenation. The modified polyester material is added to our sealing layer. The polyester obtained during the thermoplastic process contains 52.6 to 0.9 ester groups per 1000 methylene units, which are randomly distributed on the polyethylene main chain; thereby reducing the melting point.

[0033] The metathesis copolymerization described here refers to ADMET, a special type of olefin metathesis reaction that can form new double bonds in either cis or trans form, and the cis-trans ratio depends on the structures of the monomer and the catalyst.

[0034] The polyetheramines in the printing layer and the first and second core layers include amino-terminated polyoxypropylene ether and amino-terminated polyoxyethylene ether, etc., which contain ether bonds in their molecular structure. The ether bonds increase the flexibility of the polyetheramine molecules, increase the physical entanglement between the first and second core layers and the polyethylene molecules, and improve the supporting effect of the first and second core layers, as well as the temperature resistance of the printing layer.

[0035] More specifically, the density of the medium density linear metallocene polyethylene is 0.936 g / cm 3 , melt index is 4.5g / 10min, Vicat softening temperature is 118℃; model is Exxon 4536PA B l own.

[0036] More specifically, the density of the high-density polyethylene is 0.957 g / cm 3 , the material with a melt index of 7.69g / 10mi, model is Dushanzi 8008h.

[0037] More specifically, the density of the low-density linear metallocene polyethylene is 0.903 g / cm 3 , melt index is 3.8g / 10min; model is Japan Mitsui SP540.

[0038] More specifically, the density of the metallocene polyethylene is 0.927 g / cm3 , melt index is 0.3g / 10min, Vicat softening temperature is 115℃, model is Exxon 2703mc.

[0039] The polyethylene in the above printing layer, the first core layer, the second core layer and the sealing layer are all made of materials with similar melt index. When heat sealing, the temperature of the film is transferred one by one from the inside to the outside or from the outside to the inside, and the effect works at the same time. In the production process, during co-extrusion, the connection between the layers will be tighter and it is less likely to produce gaps.

[0040] More specifically, the thickness of the composite film is 50-51 μm, and the thickness of the film is enhanced to improve the puncture resistance.

[0041] In more detail, the percentages of the printed layer, the first core layer, the second core layer and the sealing layer in the film thickness are 10-20%, 30-40%, 30-40% and 10-20% respectively, and the first core layer and the second core layer account for 60-80% of the total thickness. During the heat sealing process, the temperature resistance of the core layer is enhanced, the printing layer and the sealing layer account for a small proportion, and the higher the proportion of the first core layer and the second core layer, the better the heat resistance of the produced film.

[0042] Furthermore, the introduction of high-density polyethylene in the first core layer and the second core layer will also improve the heat resistance of the film.

[0043] A method for preparing a cast film, based on the single-material heat-sealing temperature gradient co-extruded cast film, comprises the following steps:

[0044] S1, raw material preparation: prepare the raw materials for the printing layer, the first core layer, the second core layer and the sealing layer;

[0045] S2, melt extrusion: each layer of the prepared material is sequentially placed into a melter for melting at a melting temperature of 100°C to 130°C. The molten polyethylene enters the extruder sequentially according to the number of layers from the inside to the outside or from the outside to the inside of the film, is fused and compressed by the screw of the extruder, and is pushed into the die under high temperature and high pressure. The extruder is preheated in advance for 30 minutes to 60 minutes.

[0046] S3, die extrusion: molten polyethylene is extruded through the nozzle of the die to form a continuous film;

[0047] S4, cooling and stretching: The film is quickly cooled by cold air or cold water to reduce the film temperature and solidify it. The film is then drained to the stretching rollers through the traction rollers. The distance between the stretching rollers is adjusted to stretch the film.

[0048] S5, winding: After stretching is completed, the film thickness is detected in real time by an infrared film thickness gauge, and the film is wound into a roll through a winding mechanism.

[0049] More specifically, the pulling force of the pulling roller is 20N / m 2 ~40N / m 2 .

[0050] More specifically, in step S2, the high temperature and high pressure refers to a temperature of 185° C. to 190° C. and a pressure of 150 to 350 MPa.

[0051] Example 1

[0052] A single material heat-sealed temperature gradient co-extruded cast film is a composite film formed by co-extrusion casting of four layers from the outside to the inside: a printing layer, a first core layer, a second core layer and a sealing layer;

[0053] The raw materials of the printing layer include 20 parts of medium-density linear metallocene polyethylene, 30 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 part of lubricant and 1 part of opening agent, and 0.5 parts of polyetheramine by weight;

[0054] The raw materials of the first core layer and the second core layer include 20 parts of high-density polyethylene, 30 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 part of antistatic agent, and 0.5 part of polyetheramine in parts by weight;

[0055] The raw materials of the sealing layer include 20 parts of high-density linear metallocene polyethylene, 30 parts of metallocene polyethylene, and 100 parts of low-density polyethylene as a base material, 1 part of a slip agent, 1 part of an opening agent, and 0.5 parts of polyetheramine.

[0056] A method for preparing a cast film, based on the single-material heat-sealing temperature gradient co-extruded cast film, comprises the following steps:

[0057] S1, raw material preparation: prepare the raw materials for the printing layer, the first core layer, the second core layer and the sealing layer;

[0058] S2, melt extrusion: each layer of the prepared material is sequentially placed into a melter for melting at a melting temperature of 100°C to 130°C. The molten polyethylene enters the extruder sequentially according to the number of layers from the inside to the outside or from the outside to the inside of the film, is fused and compressed by the screw of the extruder, and is pushed into the die head at a temperature of 185°C to 190°C and a pressure of 150 to 350 MPa. The extruder is preheated in advance for 30 to 60 minutes.

[0059] S3, die extrusion: molten polyethylene is extruded through the nozzle of the die to form a continuous film;

[0060] S4, cooling and stretching: The film is quickly cooled by cold air or cold water to reduce the film temperature and solidify it. The film is then drawn to the stretching roller by a traction roller. The distance between the stretching rollers is adjusted to stretch the film. The traction force of the traction roller is 20N / m 2 ~40N / m 2 ;

[0061] S5, winding: After stretching is completed, the film thickness is detected in real time by an infrared film thickness gauge. The thickness of the composite film is 50-51 μm. After reaching the standard, the film is wound into a roll through a winding mechanism.

[0062] Example 2

[0063] A single material heat-sealed temperature gradient co-extruded cast film is a composite film formed by co-extrusion casting of four layers from the outside to the inside: a printing layer, a first core layer, a second core layer and a sealing layer;

[0064] The raw materials of the printing layer include 20 parts of medium-density linear metallocene polyethylene, 30 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 part of a slip agent, 1 part of an opening agent, and 2 parts of polyetheramine in parts by weight;

[0065] The raw materials of the first core layer and the second core layer include 20 parts of high-density polyethylene, 30 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 part of antistatic agent, and 0.5 part of polyetheramine in parts by weight;

[0066] The raw materials of the sealing layer include 20 parts of high-density linear metallocene polyethylene, 30 parts of metallocene polyethylene, and 100 parts of low-density polyethylene as a base material, 1 part of a slip agent, 1 part of an opening agent, and 0.5 parts of polyetheramine.

[0067] A method for preparing a cast film, based on the single-material heat-sealing temperature gradient co-extruded cast film, comprises the following steps:

[0068] S1, raw material preparation: prepare the raw materials for the printing layer, the first core layer, the second core layer and the sealing layer;

[0069] S2, melt extrusion: each layer of the prepared material is sequentially placed into a melter for melting at a melting temperature of 100°C to 130°C. The molten polyethylene enters the extruder sequentially according to the number of layers from the inside to the outside or from the outside to the inside of the film, is fused and compressed by the screw of the extruder, and is pushed into the die head at a temperature of 185°C to 190°C and a pressure of 150 to 350 MPa. The extruder is preheated in advance for 30 to 60 minutes.

[0070] S3, die extrusion: molten polyethylene is extruded through the nozzle of the die to form a continuous film;

[0071] S4, cooling and stretching: The film is quickly cooled by cold air or cold water to reduce the film temperature and solidify it. The film is then drawn to the stretching roller by a traction roller. The distance between the stretching rollers is adjusted to stretch the film. The traction force of the traction roller is 20N / m 2 ~40N / m 2 ;

[0072] S5, winding: After stretching is completed, the film thickness is detected in real time by an infrared film thickness gauge. The thickness of the composite film is 50-51 μm. After reaching the standard, the film is wound into a roll through a winding mechanism.

[0073] Example 3

[0074] A single material heat-sealed temperature gradient co-extruded cast film is a composite film formed by co-extrusion casting of four layers from the outside to the inside: a printing layer, a first core layer, a second core layer and a sealing layer;

[0075] The raw materials of the printing layer include 20 parts of medium-density linear metallocene polyethylene, 30 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 part of a slip agent, 1 part of an opening agent, and 2 parts of polyetheramine in parts by weight;

[0076] The raw materials of the first core layer and the second core layer include 20 parts of high-density polyethylene, 30 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 part of antistatic agent, and 0.5 part of polyetheramine in parts by weight;

[0077] The raw materials of the sealing layer include 20 parts of low-density linear metallocene polyethylene, 30 parts of metallocene polyethylene, and 100 parts of low-density polyethylene as a base material, 1 part of a slip agent, 1 part of an opening agent, and 0.5 parts of polyetheramine.

[0078] A method for preparing a cast film, based on the single-material heat-sealing temperature gradient co-extruded cast film, comprises the following steps:

[0079] S1, raw material preparation: prepare the raw materials for the printing layer, the first core layer, the second core layer and the sealing layer;

[0080] S2, melt extrusion: each layer of the prepared material is sequentially placed into a melter for melting at a melting temperature of 100°C to 130°C. The molten polyethylene enters the extruder sequentially according to the number of layers from the inside to the outside or from the outside to the inside of the film, is fused and compressed by the screw of the extruder, and is pushed into the die head at a temperature of 185°C to 190°C and a pressure of 150 to 350 MPa. The extruder is preheated in advance for 30 to 60 minutes.

[0081] S3, die extrusion: molten polyethylene is extruded through the nozzle of the die to form a continuous film;

[0082] S4, cooling and stretching: The film is quickly cooled by cold air or cold water to reduce the film temperature and solidify it. The film is then drawn to the stretching roller by a traction roller. The distance between the stretching rollers is adjusted to stretch the film. The traction force of the traction roller is 20N / m 2 ~40N / m 2 ;

[0083] S5, winding: After stretching is completed, the film thickness is detected in real time by an infrared film thickness gauge. The thickness of the composite film is 50-51 μm. After reaching the standard, the film is wound into a roll through a winding mechanism.

[0084] Example 4

[0085] A single material heat-sealed temperature gradient co-extruded cast film is a composite film formed by co-extrusion casting of four layers from the outside to the inside: a printing layer, a first core layer, a second core layer and a sealing layer;

[0086] The raw materials of the printing layer include 20 parts of medium-density linear metallocene polyethylene, 30 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 part of a slip agent, 1 part of an opening agent, and 2 parts of polyetheramine in parts by weight;

[0087] The raw materials of the first core layer and the second core layer include 20 parts of high-density polyethylene, 30 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 part of antistatic agent, and 0.5 part of polyetheramine in parts by weight;

[0088] The raw materials of the sealing layer include 20 parts of low-density linear metallocene polyethylene, 30 parts of metallocene polyethylene, and 100 parts of low-density polyethylene as a base material, 1 part of a slip agent, 1 part of an opening agent, and 0.5 parts of a modified polyester material.

[0089] A method for preparing a cast film, based on the single-material heat-sealing temperature gradient co-extruded cast film, comprises the following steps:

[0090] S1, raw material preparation: prepare modified polyester material, and configure raw materials for the printing layer, the first core layer, the second core layer, and the sealing layer;

[0091] S2, melt extrusion: each layer of the prepared material is sequentially placed into a melter for melting at a melting temperature of 100°C to 130°C. The molten polyethylene enters the extruder sequentially according to the number of layers from the inside to the outside or from the outside to the inside of the film, is fused and compressed by the screw of the extruder, and is pushed into the die head at a temperature of 185°C to 190°C and a pressure of 150 to 350 MPa. The extruder is preheated in advance for 30 to 60 minutes.

[0092] S3, die extrusion: molten polyethylene is extruded through the nozzle of the die to form a continuous film;

[0093] S4, cooling and stretching: The film is quickly cooled by cold air or cold water to reduce the film temperature and solidify it. The film is then drawn to the stretching roller by a traction roller. The distance between the stretching rollers is adjusted to stretch the film. The traction force of the traction roller is 20N / m 2 ~40N / m 2 ;

[0094] S5, winding: After stretching is completed, the film thickness is detected in real time by an infrared film thickness gauge. The thickness of the composite film is 50-51 μm. After reaching the standard, the film is wound into a roll through a winding mechanism.

[0095] The modified polyester material is prepared by using acyclic diene metathesis copolymerization of undec-10-ene-1-acyl undec-10-enoate and undec-1,10-diene, and then exhaustively hydrogenating to synthesize a long-spacing aliphatic model polyester, which is the modified polyester material.

[0096] Comparative Example

[0097] A cast film is a composite film formed by co-extrusion casting of four layers, namely, a printing layer, a first core layer, a second core layer and a sealing layer from outside to inside; the printing layer and the sealing layer are made of the same material;

[0098] The raw materials of the printing layer include 20 parts of high-density linear metallocene polyethylene, 30 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 part of lubricant and 1 part of anti-blocking agent, and 0.5 parts of polyetheramine by weight;

[0099] The raw materials of the first core layer and the second core layer include 20 parts of high-density polyethylene, 30 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 part of antistatic agent, and 0.5 part of polyetheramine in parts by weight;

[0100] The raw materials of the sealing layer include 20 parts of high-density linear metallocene polyethylene, 30 parts of metallocene polyethylene, and 100 parts of low-density polyethylene as a base material, 1 part of a slip agent, 1 part of an opening agent, and 0.5 parts of polyetheramine.

[0101] A method for preparing a cast film, based on the single-material heat-sealing temperature gradient co-extruded cast film, comprises the following steps:

[0102] S1, raw material preparation: prepare the raw materials for the printing layer, the first core layer, the second core layer and the sealing layer;

[0103] S2, melt extrusion: each layer of the prepared material is sequentially placed into a melter for melting at a melting temperature of 100°C to 130°C. The molten polyethylene enters the extruder sequentially according to the number of layers from the inside to the outside or from the outside to the inside of the film, is fused and compressed by the screw of the extruder, and is pushed into the die head at a temperature of 185°C to 190°C and a pressure of 150 to 350 MPa. The extruder is preheated in advance for 30 to 60 minutes.

[0104] S3, die extrusion: molten polyethylene is extruded through the nozzle of the die to form a continuous film;

[0105] S4, cooling and stretching: The film is quickly cooled by cold air or cold water to reduce the film temperature and solidify it. The film is then drawn to the stretching roller by a traction roller. The distance between the stretching rollers is adjusted to stretch the film. The traction force of the traction roller is 20N / m 2 ~40N / m 2 ;

[0106] S5, winding: After stretching is completed, the film thickness is detected in real time by an infrared film thickness gauge. The thickness of the composite film is 50-51 μm. After reaching the standard, the film is wound into a roll through a winding mechanism.

[0107] Experimental testing

[0108] The single-material heat-seal temperature gradient co-extruded cast films prepared in Examples 1 to 4 and the comparative example were subjected to the standard QB / T 1130-1991 plastic right-angle tear performance test method to prepare standard specimens. The physical properties of the films were tested to see whether they changed when subjected to a certain load. The test results are shown in Table 1.

[0109] Table 1

[0110]

[0111] As shown in Table 1, the comparison results of Example 4 in which the modified polyester material is added to the sealing layer and Example 3 in which the modified polyester material is not added show that the physical properties of the film are enhanced by 2% after the modified polyester material is added, and the film is less likely to be burned during thermal synthesis.

[0112] As shown in Table 1, the tear strength at both the horizontal and vertical right angles of Example 2 and Example 1, in which the polyetheramine content in the printed layer is increased, is increased by 5%, indicating that the high polyetheramine content enhances the flame retardancy of the printed layer. The printed layer is not ruptured before the sealing layer is heat-melted, thereby enhancing the physical properties of the film.

[0113] As can be seen from Table 1, compared with Example 3 in which low-density polyethylene is added, Example 1 shows that the sealing layer and the printing layer with the addition of low-density polyethylene form an internal and external temperature difference of 10 to 20 degrees. When the sealing layer has been hot-melted, the printing layer has not been burned and is not easy to tear, and the physical properties are improved by 2%.

[0114] As shown in Table 1, the comparative example in which the amount of polyetheramine was not increased and the sealing layer of modified polyester material and low-density polyethylene was not added, compared with Example 4 in which polyetheramine, modified polyester material and low-density polyethylene were added, the test results of Example 4 showed that the physical properties of the film were enhanced by 10%. This indicates that under the same temperature and heat-sealing strength, increasing the amount of polyetheramine and adding modified polyester material and low-density polyethylene to the sealing layer can achieve the effect of preventing the edge of a single-layer film from being scalded when applied to a multi-layer heat seal.

[0115] The density gradient difference between the medium-density linear metallocene polyethylene and the low-density linear metallocene polyethylene in the printing layer and the sealing layer, as well as the addition of modified polyester materials and flame retardants, enhance the physical properties of the film, making it difficult to be torn, that is, not easy to be burned.

[0116] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A single material heat-sealed temperature gradient co-extruded cast film, characterized in that: It is a composite film formed by co-extrusion casting of four layers, namely the printing layer, the first core layer, the second core layer and the sealing layer. The raw materials of the printing layer include, by weight, 20 to 30 parts of medium-density linear metallocene polyethylene, 30 to 50 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1 to 2 parts of a slip agent, 1 to 2 parts of an anti-blocking agent, and 2 to 3 parts of polyetheramine. The raw materials of the first core layer and the second core layer include 20-30 parts of high-density polyethylene, 30-50 parts of metallocene polyethylene, 100 parts of low-density polyethylene, 1-2 parts of antistatic agent, and 0.5-1 part of polyetheramine in parts by weight; The raw materials of the sealing layer include 20-30 parts of low-density linear metallocene polyethylene, 30-50 parts of metallocene polyethylene, 100 parts of low-density polyethylene as a base material, 1-2 parts of a slip agent, 1-2 parts of an opening agent and 0.5-1 part of a modified polyester material. The modified polyester material is a long-spacing aliphatic polyester synthesized by performing acyclic diene metathesis copolymerization of undec-10-ene-1-acyl undec-10-enoate and undec-1,10-diene, followed by exhaustive hydrogenation.

2. The single-material heat-seal temperature gradient co-extruded cast film according to claim 1, characterized in that: The density of the medium density linear metallocene polyethylene is 0.936 g / cm 3 , melt index is 4.5 g / 10 min, and Vicat softening temperature is 118℃.

3. The single material heat-seal temperature gradient co-extruded cast film according to claim 1, characterized in that: The density of the high-density polyethylene is 0.957 g / cm 3 , the melt index is 7.69 g / 10 min.

4. The single-material heat-seal temperature gradient co-extruded cast film according to claim 1, characterized in that: The density of the low-density linear metallocene polyethylene is 0.903 g / cm 3 , the melt index is 3.8 g / 10 min.

5. The single material heat-seal temperature gradient co-extruded cast film according to claim 1, characterized in that: The density of the metallocene polyethylene is 0.927 g / cm 3 , melt index is 0.3 g / 10 min, and Vicat softening temperature is 115℃.

6. The single-material heat-seal temperature gradient co-extruded cast film according to claim 1, characterized in that: The thickness of the composite film is 50-51 μm.

7. The single-material heat-seal temperature gradient co-extruded cast film according to claim 5, characterized in that: The percentages of the printing layer, the first core layer, the second core layer and the sealing layer in the thickness of the film are 10-20%, 30-40%, 30-40% and 10-20% respectively.

8. A method for preparing a cast film, based on the single-material heat-sealable temperature gradient co-extruded cast film according to any one of claims 1 to 6, characterized in that: The steps include: S1, raw material preparation: prepare the raw materials for the printing layer, the first core layer, the second core layer and the sealing layer; S2, melt extrusion: each layer of the prepared material is sequentially placed into a melter for melting at a melting temperature of 100°C to 130°C. The molten polyethylene enters the extruder sequentially according to the number of layers from the inside to the outside or from the outside to the inside of the film, is fused and compressed by the screw of the extruder, and is pushed into the die under high temperature and high pressure. The extruder is preheated in advance for 30 min to 60 min. S3, die extrusion: molten polyethylene is extruded through the nozzle of the die to form a continuous film; S4, cooling and stretching: The film is quickly cooled by cold air or cold water to reduce the film temperature and solidify it. The film is then drained to the stretching rollers through the traction rollers. The distance between the stretching rollers is adjusted to stretch the film. S5, winding: After stretching is completed, the film thickness is detected in real time by an infrared film thickness gauge, and the film is wound into a roll through a winding mechanism.

9. The single-material heat-seal temperature gradient co-extruded cast film according to claim 8, characterized in that: The pulling force of the pulling roller is 20 N / m 2 ~40 N / m 2 .

10. The single-material heat-seal temperature gradient co-extruded cast film according to claim 8, characterized in that: In step S2, the high temperature and high pressure refers to a temperature of 185° C. to 190° C. and a pressure of 150 to 350 MPa.

Images