High-temperature anti-fog film, preparation method and packaging bag

Abstract

The application provides a high-temperature anti-fog film, a preparation method and a packaging bag. The film comprises an outer layer base film, a middle layer base film and an inner layer base film which are tightly attached from outside to inside. The outer layer base film comprises 20% by weight of a first low-density polyethylene, 50% by weight of a metallocene linear polyethylene, 29% by weight of a linear low-density polyethylene and 1% by weight of an anti-fog agent. The middle layer base film comprises 30% by weight of a medium-density polyethylene and 70% by weight of a metallocene linear polyethylene. The inner layer base film comprises 30% by weight of a second low-density polyethylene, 69% by weight of a metallocene linear low-density polyethylene and 1% by weight of an anti-fog agent. The high-temperature anti-fog film prepared by the above components and process has good high-temperature anti-fog performance on the inner and outer layers. The inner layer base film prepared by blending the second low-density polyethylene and the metallocene linear low-density polyethylene has a smooth surface and high toughness, and can ensure that water droplets automatically slide on the film surface even under internal pressure.

Description

Technical Field

[0001] The present invention belongs to the technical field of packaging films, and in particular relates to a high-temperature anti-fog film, a preparation method and a packaging bag. Background Art

[0002] As society develops, people's requirements for food packaging are becoming increasingly stringent. For example, when using packaging bags to hold liquids or heatable contents, the contents of the transparent bag can generate mist when exposed to ambient temperature fluctuations or when heated in an oven. This mist adheres to the inner layer of the bag, blurring the view. Alternatively, external steam can adhere to the outside of the bag, making it impossible to clearly see the contents or the printed text on the bag.

[0003] While existing anti-fog packaging film technologies exist, they generally address the misting caused by temperature differences in natural environments. If packaging bags are placed in a steam-heated environment, their anti-fog effectiveness deteriorates due to high temperatures on both sides and increased internal pressure. Therefore, developing a packaging film with excellent anti-fog performance at high temperatures is crucial. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a high-temperature anti-fog film, a preparation method and a packaging bag, which solve the defects of the prior art packaging film such as poor anti-fog effect at high temperatures.

[0005] In a first aspect, the present invention provides a high-temperature anti-fog film, comprising an outer base film, a middle base film, and an inner base film that are tightly bonded from the outside to the inside;

[0006] The outer base film comprises 20% by weight of a first low-density polyethylene, 50% by weight of a metallocene linear polyethylene, 29% by weight of a linear low-density polyethylene and 1% by weight of an anti-fogging agent;

[0007] The middle base film comprises 30% by weight of medium-density polyethylene and 70% by weight of metallocene linear polyethylene;

[0008] The inner base film includes 30 weight percent of a second low-density polyethylene, 69 weight percent of a metallocene linear low-density polyethylene, and 1 weight percent of an anti-fogging agent.

[0009] In some embodiments, the thickness ratio of the inner base film, the middle base film, and the outer base film is 3:4:3.

[0010] In some embodiments, the first low-density polyethylene is Shell LDPE 2420D, the second low-density polyethylene is Shell LDPE 2426K, the metallocene linear low-density polyethylene is Primex MLLDPE SP0540, and the metallocene linear polyethylene is Exxon Chemical 8Carbon MLLDPE 1327CA.

[0011] In some embodiments, the anti-fog agent is CJXF001.

[0012] In some embodiments, the anti-fog agent comprises a first anti-fog component and a second anti-fog component, the first anti-fog component has better hydrophilic property than the second anti-fog component, the second anti-fog component has better lipophilic property than the first anti-fog component, and the first anti-fog component has more weight parts than the second anti-fog component.

[0013] In a second aspect, the present application provides a preparation method of the high-temperature anti-fog film according to any one of the preceding embodiments, characterized by the following steps:

[0014] 20% by weight of the first low-density polyethylene, 50% by weight of the metallocene linear polyethylene, 29% by weight of the linear low-density polyethylene, and 1% by weight of the anti-fog agent are uniformly mixed and then fed into the outer layer hopper of the three-layer co-extrusion film blowing machine;

[0015] 30% by weight of the medium-density polyethylene and 70% by weight of the metallocene linear polyethylene are uniformly mixed and then fed into the middle layer hopper of the three-layer co-extrusion film blowing machine;

[0016] 30% by weight of the second low-density polyethylene, 69% by weight of the metallocene linear low-density polyethylene, and 1% by weight of the anti-fog agent are uniformly mixed and then fed into the inner layer hopper of the three-layer co-extrusion film blowing machine;

[0017] The working temperature of each screw extrusion mechanism in the three-layer co-extrusion film blowing machine is set, a three-layer film structure is formed by extrusion through the screw extrusion mechanism, and film blowing is performed, air is introduced from the extrusion die to perform inflation and cooling, the condensation line height of the film is 30-40 mm, and the high-temperature anti-fog film is formed after traction, rolling, and winding.

[0018] In some embodiments, the components of the inner layer base film, the middle layer base film, and the outer layer base film are fed according to a weight ratio of 3:4:3.

[0019] In some embodiments, a film tube with a three-layer film structure is co-extruded from the screw extrusion mechanism, and the film tube is water-cooled, wherein the water temperature of the water cooling treatment is 1-4℃, and the flow rate is 36-40 L / min.

[0020] In some embodiments, the operating temperature range of the inner screw extrusion structure is 145-150°C, the operating temperature range of the middle screw extrusion structure is 210-215°C, the operating temperature range of the outer screw extrusion structure is 205-210°C, and the extrusion die head blowing operating temperature range of the co-extrusion film blowing machine is 215-220°C.

[0021] In a third aspect, the present invention further provides a high-temperature anti-fog packaging bag, which is prepared using the high-temperature anti-fog film described in any of the above embodiments.

[0022] Compared with the prior art, the beneficial effects of the present invention include at least:

[0023] The high-temperature anti-fog film produced by the above components and processes has excellent high-temperature anti-fog performance in both its inner and outer layers. The inner base film, made of a blend of second low-density polyethylene and metallocene linear low-density polyethylene, has a smooth surface and strong toughness, ensuring that water droplets can automatically slide off the film surface even under internal pressure.

[0024] In order to ensure the anti-fog effect under continuous high temperature, this anti-fog agent is composed of two components. The first anti-fog component with better hydrophilicity has a better anti-fog effect in the initial heating stage, and the second anti-fog component with better lipophilicity has a longer-lasting anti-fog effect during the continuous high-temperature heating process, thereby achieving excellent anti-fog effect under continuous high temperature.

[0025] By controlling the condensation line height at 30-40 mm during film making, the surface of the formed film becomes glossier and smoother. The smooth surface plays the same role as the anti-fog agent, reducing the amount of anti-fog agent used and avoiding excessive adverse effects on the heat sealing strength of the film. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solution of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be noted that terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" to indicate positions or relationships are used solely to facilitate description and simplify the present invention. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific manner. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of the present invention, when a specific device is described as being located between a first device and a second device, an intervening device may or may not be present between the specific device and the first device or the second device. When a specific device is described as being connected to another device, the specific device may be directly connected to the other device without an intervening device, or may be directly connected to the other device but with an intervening device.

[0029] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0030] The applicant's research found that:

[0031] In the prior art, when a packaging bag is used to carry liquids that already have a certain temperature or hot contents, or when a heatable content is loaded and heated, the surface of the transparent packaging bag is easily fogged, and water mist may form on the inner or outer surface of the packaging bag. For example, the Chinese medicine that is packaged and boiled in a Chinese medicine store has a certain temperature and will carry hot air. After the Chinese medicine bag is taken home, it needs to be heated in a steamer before it can be consumed. Water mist will be formed in both processes. Currently, there is no film that can meet the anti-fog requirements of at least the above two application scenarios.

[0032] In view of this, in a first aspect, the present disclosure provides a high-temperature anti-fog film, comprising an outer base film, a middle base film, and an inner base film that are tightly attached from the outside to the inside;

[0033] The outer base film comprises 20% by weight of a first low-density polyethylene, 50% by weight of a metallocene linear polyethylene, 29% by weight of a linear low-density polyethylene and 1% by weight of an anti-fogging agent;

[0034] The middle base film comprises 30% by weight of medium-density polyethylene and 70% by weight of metallocene linear polyethylene;

[0035] The inner base film includes 30 weight percent of a second low-density polyethylene, 69 weight percent of a metallocene linear low-density polyethylene, and 1 weight percent of an anti-fogging agent.

[0036] It should be noted that the high-temperature anti-fog film has a three-layer structure, which includes an outer base film, a middle base film and an inner base film from the outside to the inside. The specific components of each layer are different. In order to achieve the anti-fog function of the base film that is in direct contact with water mist, an anti-fog agent is added to the outer base film and the inner base film. In order to achieve the high strength of the packaging bag even when a small amount of anti-fog is added, the middle base film contains a larger weight portion of metallocene linear polyethylene, which can provide basic high strength after mixing with medium-density polyethylene. In the inner and outer base films, low-density polyethylene and metallocene linear low-density polyethylene / metallocene linear polyethylene are used to form a base film with a smooth surface. The smooth surface plays the same role as the anti-fog agent, reduces the amount of anti-fog agent, and avoids excessive adverse effects on the heat sealing strength of the film.

[0037] As an embodiment, the thickness ratio of the inner base film, the middle base film and the outer base film is 3:4:3. The high-temperature anti-fog film composed of this thickness ratio has better performance, lower cost and better effect. The middle base film is thicker, thereby providing a more solid foundation strength.

[0038] Example 1:

[0039] In this embodiment 1, the first low-density polyethylene in the outer base film is CNOOC Shell LDPE 2420D, with a melt index of 4 g / 10 min and a melting point of 110-112°C; the metallocene linear polyethylene is Exxon Chemical 8-carbon MLLDPE1327CA, with a melt index of 1.3 g / 10 min and a melting point of 122°C; the linear low-density polyethylene is Dow MP188.11, with a melt index of 1.6 g / 10 min and a melting point of 122°C; and the anti-fog agent is CJXF001, with a melt index of 2 g / 10 min and a melting point of 105-110°C.

[0040] The medium-density polyethylene in the middle base film is Borealis MDPE FB2230 with a melting index of 0.2 g / 10 min and a melting point of 125-129°C; the metallocene linear polyethylene is Exxon Chemical 8-carbon MLLDPE1327CA with a melting index of 1.3 g / 10 min and a melting point of 122°C.

[0041] The second low-density polyethylene in the inner base film is CNOOC Shell LDPE 2426K, with a melt index of 4 g / 10 min and a melting point of 110-112°C; the metallocene linear low-density polyethylene is Japan Prime MLLDPE SP0540, with a melt index of 3.8 g / 10 min and a melting point of 88°C; the anti-fog agent is CJXF001, with a melt index of 2 g / 10 min and a melting point of 105-110°C.

[0042] Example 2:

[0043] In this embodiment 2, based on the embodiment 1, the anti-fog agent is replaced with the following embodiment: the anti-fog agent includes a first anti-fog component and a second anti-fog component, the hydrophilicity of the first anti-fog component is better than that of the second anti-fog component, the lipophilicity of the second anti-fog component is better than that of the first anti-fog component, and the weight portion of the first anti-fog component is more than that of the second anti-fog component.

[0044] In order to ensure the anti-fog effect under continuous high temperature, the anti-fog agent in this embodiment is composed of two components, wherein the first anti-fog component with better hydrophilicity has a better anti-fog effect in the initial stage of heating, and the second anti-fog component with better lipophilicity has a longer-lasting anti-fog effect during the continuous high-temperature heating process, thereby achieving a superior anti-fog effect under continuous high temperature, with good initial anti-fog effect and long-lasting anti-fog performance.

[0045] Optionally, in the inner / outer base film, the first anti-fog component is 0.7% by weight, and the second anti-fog component is 0.3% by weight.

[0046] Optionally, the first anti-fog component is polyethylene glycol 400 monolaurate, PEG400ML; the second anti-fog component is sorbitan monooleate, Span 80.

[0047] Example 3:

[0048] In this embodiment 3, based on the embodiment 1 or embodiment 2, further material limitations are made. More specifically, an ethylene-α-olefin copolymer is added to the first low-density polyethylene or the second low-density polyethylene. The ethylene-α-olefin copolymer has monomer units based on ethylene and monomer units based on α-olefins with 3 to 20 carbon atoms. The melt flow rate (MFR) of the ethylene-α-olefin copolymer is 0.01 to 100 g / 10 minutes and the density is 860 to 970 kg / m 3 , the molecular weight distribution (Mw / Mn) is 4.5 to 13, the activation energy (Ea) is 40 to 100 kJ / mol, and the characteristic relaxation time (T) satisfies the following relationship:

[0049] T<3.25×MFR -0.6675

[0050] After the ethylene-α-olefin copolymer is added to the first low-density polyethylene or the second low-density polyethylene, a lower heat-sealing temperature can be achieved, and good mechanical strength can be maintained under low-temperature heat sealing.

[0051] In a second aspect, the present disclosure provides a method for preparing the high-temperature anti-fog film described in any of the above embodiments, which is prepared according to the following steps:

[0052] 20% by weight of the first low-density polyethylene, 50% by weight of the metallocene linear polyethylene, 29% by weight of the linear low-density polyethylene and 1% by weight of the anti-fogging agent are uniformly mixed and then fed into the outer layer hopper of a three-layer co-extrusion film blowing machine;

[0053] 30% by weight of medium-density polyethylene and 70% by weight of metallocene linear polyethylene were uniformly mixed and fed into the middle layer hopper of a three-layer co-extrusion film blowing machine;

[0054] 30% by weight of the second low-density polyethylene, 69% by weight of the metallocene linear low-density polyethylene and 1% by weight of the anti-fog agent were uniformly mixed and fed into the inner layer hopper of a three-layer co-extrusion film blowing machine;

[0055] The working temperature of each screw extrusion mechanism in the three-layer co-extrusion film blowing machine is set, and a three-layer film structure is formed by extrusion through the screw extrusion mechanism and the film is blown. Air is introduced from the extrusion die head for inflation and cooling. The height of the condensation line of the film is 30 to 40 mm. After traction, flattening and winding, a high-temperature anti-fog film is formed.

[0056] It should be noted that after the raw material particles of the inner layer are mixed evenly according to the formulation ratio, they are fed into the inner layer hopper of the three-layer co-extrusion film blowing machine. The working temperature of the corresponding screw extrusion mechanism is set according to the melting point of the raw material combination, and the inner layer base film of the three-layer film structure of the heavy packaging film is formed through screw extrusion;

[0057] Similarly, the raw material particles of the middle layer are mixed evenly according to the formulation ratio and fed into the middle layer hopper of the three-layer co-extrusion film blowing machine. The working temperature of the corresponding screw extrusion mechanism is set according to the melting point of the raw material combination, and the middle layer base film of the three-layer film structure of the heavy packaging film is formed through screw extrusion;

[0058] Similarly, after the raw material particles of the outer layer are mixed evenly according to the preparation ratio, they are fed into the outer layer hopper of the three-layer co-extrusion film blowing machine. The working temperature of the corresponding screw extrusion mechanism is set according to the melting point of the raw material combination, and the outer layer base film in the three-layer film structure of the heavy packaging film is formed through screw extrusion.

[0059] After the inner, middle and outer three-layer base film is extruded from the screw, air is introduced into the blown film bubble through the die head for inflation and cooling, then it is shaped by a herringbone plate and pulled by a traction roller, and finally flattened and wound by a winding device. During film making, the height of the condensation line of the film is controlled at 30-40mm in order to improve the smoothness of the blown film surface, thereby ensuring the water droplet sliding effect and reducing the use of anti-fog agent.

[0060] In this embodiment, the components of the inner base film, the middle base film and the outer base film are added in a weight ratio of 3:4:3.

[0061] Example 4:

[0062] In this embodiment 4, when preparing a high-temperature anti-fog film, the operating temperature range of the inner layer screw extrusion structure is controlled to be 145-150°C, the operating temperature range of the middle layer screw extrusion structure is 210-215°C, the operating temperature range of the outer layer screw extrusion structure is 205-210°C, the extrusion die head blowing operating temperature range of the co-extrusion film blowing machine is 215-220°C, the blowing ratio of the film is 1.5:2.5; the traction ratio of the film is 1:7-15, the corona voltage is 300-400V, the condensation line height of the film is 40mm, and the wetting tension of the film is increased to greater than 40 dynes / square centimeter through corona treatment.

[0063] Example 5:

[0064] In this embodiment 5, a film tube having a three-layer film structure is co-extruded from a screw extruder mechanism, and the film tube is water-cooled, wherein the water temperature of the water cooling treatment is 1-4° C. and the flow rate is 36-40 L / min.

[0065] The membrane tube is rapidly cooled by water cooling so that the formation of crystals can be controlled by quenching, which is beneficial to the orientation of molecular segments and thus achieves the purpose of reducing the haze of the finished product.

[0066] Moreover, during the preparation process, the blowing ratio and pulling ratio after cooling are controlled to match the crystallinity of the film tube, which effectively prevents the phenomenon of film wrinkles caused by excessive blowing ratio and pulling ratio causing unstable film bubbles and excessive shrinkage.

[0067] On the third aspect, the present disclosure provides a high-temperature anti-fog packaging bag, which is prepared using the high-temperature anti-fog film described in any of the above embodiments. In high-temperature application scenarios, both the inner and outer base films have long-lasting and superior anti-fog effects, and the heat sealing strength of the packaging bag remains unchanged. Even if the internal pressure increases, the structure will not fail.

[0068] In addition, a barrier layer can be added in the outer direction of the outer base film. The barrier layer is made of ethylene-vinyl alcohol copolymer (EVOH) and has a thickness of 5% of the total thickness. It can prevent the bag from emitting a strong irritating smell during long-term use in high-temperature anti-fog packaging bags, thereby improving user experience.

[0069] Compared to the prior art, the present invention provides a high-temperature anti-fog film, a preparation method, and a packaging bag. The high-temperature anti-fog film produced by the above components and process has excellent high-temperature anti-fog performance in both the inner and outer layers. The inner base film, made from a blend of second low-density polyethylene and metallocene linear low-density polyethylene, has a smooth and tough surface, ensuring that water droplets can automatically slide off the film surface even under internal pressure.

[0070] In order to ensure the anti-fog effect under the continuous high temperature, the anti-fog agent is composed of two components, the first anti-fog component with better hydrophilic property has better anti-fog effect in the initial heating stage, and the second anti-fog component with better lipophilic property has longer anti-fog effect in the continuous high temperature heating process, so as to realize superior anti-fog effect under the continuous high temperature;

[0071] By controlling the condensation line height at 30-40mm during film making, the surface of the formed film is more glossy and smooth, the smooth surface plays the same role as the anti-fog agent, the amount of the anti-fog agent is reduced, and the excessive adverse effect on the heat sealing strength of the film is avoided.

[0072] Finally, it should be emphasized that the present application is not limited to the above embodiments, the above is only the preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A high temperature resistant anti-fog film, characterized in that: It includes the outer basement membrane, the middle basement membrane and the inner basement membrane that fit tightly from the outside to the inside; The outer base film comprises 20% by weight of a first low-density polyethylene, 50% by weight of a metallocene linear polyethylene, 29% by weight of a linear low-density polyethylene and 1% by weight of an anti-fogging agent; The middle base film comprises 30% by weight of medium-density polyethylene and 70% by weight of metallocene linear polyethylene; The inner base film comprises 30% by weight of a second low-density polyethylene, 69% by weight of a metallocene linear low-density polyethylene, and 1% by weight of an anti-fog agent; The thickness ratio of the inner basement membrane, the middle basement membrane and the outer basement membrane is 3:4:3; The first low-density polyethylene is CNOOC Shell LDPE 2420D, the second low-density polyethylene is CNOOC Shell LDPE 2426K, the metallocene linear low-density polyethylene is Japan Prime MLLDPE SP0540, and the metallocene linear polyethylene is Exxon Chemical 8-carbon MLLDPE1327CA; The anti-fog agent comprises a first anti-fog component and a second anti-fog component, the first anti-fog component has better hydrophilicity than the second anti-fog component, the second anti-fog component has better lipophilicity than the first anti-fog component, and the first anti-fog component has more parts by weight than the second anti-fog component; In the inner / outer base film, the first anti-fog component is 0.7% by weight, and the second anti-fog component is 0.3% by weight; the first anti-fog component is polyethylene glycol 400 monolaurate, i.e. PEG400ML; the second anti-fog component is sorbitan monooleate, i.e. Span 80.

2. A method for preparing a high temperature resistant anti-fog film according to claim 1, characterized in that: Prepare as follows: 20% by weight of the first low-density polyethylene, 50% by weight of the metallocene linear polyethylene, 29% by weight of the linear low-density polyethylene and 1% by weight of the anti-fogging agent were uniformly mixed and fed into the outer layer hopper of a three-layer co-extrusion film blowing machine; 30% by weight of medium-density polyethylene and 70% by weight of metallocene linear polyethylene were uniformly mixed and fed into the middle layer hopper of a three-layer co-extrusion film blowing machine; 30% by weight of the second low-density polyethylene, 69% by weight of the metallocene linear low-density polyethylene and 1% by weight of the anti-fog agent were uniformly mixed and fed into the inner layer hopper of a three-layer co-extrusion film blowing machine; Set the working temperature of each screw extrusion mechanism in the three-layer co-extrusion film blowing machine, extrude a three-layer film structure through the screw extrusion mechanism and blow the film, introduce air from the extrusion die head for blowing and cooling, the condensation line height of the film is 30~40mm, and after pulling, flattening and winding, a high-temperature resistant anti-fog film is formed.

3. The preparation method according to claim 2, wherein The components of the inner base film, the middle base film and the outer base film are added in a weight ratio of 3:4:

3.

4. The preparation method according to claim 3, wherein A membrane tube having a three-layer membrane structure is co-extruded from a screw extruder mechanism, and the membrane tube is water-cooled, wherein the water temperature of the water cooling treatment is 1-4°C and the flow rate is 36-40 L / min.

5. The preparation method according to claim 4, wherein The operating temperature range of the inner screw extrusion structure is 145~150℃, the operating temperature range of the middle screw extrusion structure is 210~215℃, the operating temperature range of the outer screw extrusion structure is 205~210℃, and the extrusion die head blowing operating temperature range of the co-extrusion film blowing machine is 215~220℃.

6. A high temperature resistant anti-fog packaging bag, characterized in that: It is prepared using the high-temperature resistant anti-fog film as claimed in claim 1.