Preservative film and production process thereof

Abstract

The invention discloses a preservative film and a production process, and the preservative film is prepared from the following formula materials in percentage by weight: 44%-48% of high-pressure LDPE-35B, 30%-35% of high-pressure LDPE-2426K and 20%-23% of high-pressure LLDPE-5199. According to the invention, the preservative film produced by mixing the three raw materials according to a specific proportion has good ductility and light transmittance, so that the preservative film disclosed by the invention also has good ductility under the condition that a plasticizer is not used, and the risk of incorrectly adding the plasticizer in production is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of cling film processing, in particular to a cling film and a production process. Background Art

[0002] Cling film is a plastic packaging product, usually made of ethylene as a masterbatch through polymerization reaction. It is mainly used for microwave food heating, refrigerator food preservation, fresh and cooked food packaging, etc. It is widely used in family life, supermarkets, hotels and restaurants, and industrial production of food packaging. According to the different types of ethylene masterbatch, cling film can be divided into three categories. The first is polyethylene, referred to as PE, which is mainly used for food packaging. The film used for fruits and vegetables we usually buy, including semi-finished products purchased from supermarkets, is made of this material; the second is polyvinyl chloride, referred to as PVC, which can also be used for food packaging, but it has a certain impact on human safety; the third is polyvinylidene chloride, referred to as PVDC, which is mainly used for the packaging of some cooked food, ham and other products.

[0003] Among these three types of cling film, those made of PE and PVDC are safe for the human body and can be used with confidence. However, due to the high cost and difficulty in processing of PVDC cling film, its market share is not high, so most of the cling films on the market are PE cling film.

[0004] Existing PE cling film is generally made of LDPE and LLDPE. In order to improve the ductility of the cling film in the existing technology, plasticizers need to be added. However, plasticizers cannot be used casually in food packaging. Their content must comply with the "Food Safety Standard for the Use of Additives in Food Contact Materials and Products" (GB9685-2016). If improper operation is performed during the production process, excessive addition of plasticizers may easily cause harm to the human body. Summary of the invention

[0005] The purpose of the present invention is to provide a cling film and a production process, so that the cling film has good ductility without adding plasticizer, so as to solve the problem of excessive addition of plasticizer due to improper operation mentioned in the background technology, which causes harm to the human body.

[0006] In order to solve the above technical problems, the present invention provides: In a first aspect, a cling film is provided, wherein, based on 100% by weight, the formula material comprises 44%-48% of high pressure LDPE-35B, 30%-35% of high pressure LDPE-2426K and 20%-23% of high pressure LLDPE-5199.

[0007] Furthermore, based on 100% by weight, the formula includes 46% high pressure LDPE-35B, 33% high pressure LDPE-2426K and 21% high pressure LLDPE-5199.

[0008] In a second aspect, a production process of a cling film is provided, which is used to prepare a cling film as in the first aspect, and comprises the following steps: S1. Prepare materials: first prepare the masterbatch of each formula material in the first aspect, that is, obtain raw materials; S2, mixing: adding a thickening masterbatch to the raw materials, putting them into a mixing device for mixing, mixing evenly, and drying to obtain a premix; S3, secondary granulation: the premix is ​​fed into a preheated extruder, and granulated and modified again through high-temperature melting and screw extrusion, and each formula material is fully integrated to obtain secondary granulation material; S4, film blowing: putting the secondary granulated material into a film blowing machine for film blowing to form a semi-finished film; S5, cutting and coiling: The cooled semi-finished film is subjected to slitting, point-breaking, and coiling processes to produce a cling film that meets the performance indicators.

[0009] Furthermore, in the step S2, the weight ratio of the viscosity-enhancing masterbatch to the raw material is 1.5-3.5:100.

[0010] Furthermore, in the step S2, the mixing device maintains the temperature at 90-100°C when mixing.

[0011] Furthermore, in the film blowing machine in step S4, the set temperature of the conveying section is 142-148°C, the set temperature of the melting section is 148-152°C, the set temperature of the mixing rubber section is 152-158°C, the set temperature of the exhaust pipe section is 152-158°C, and the set temperature of the homogenizing section is 148-152°C.

[0012] Furthermore, in the film blowing machine, the material residence time in the conveying section is 55-65 min, the residence time in the melting section is 55-65 min, the residence time in the mixing rubber section is 55-65 min, the residence time in the exhaust pipe section is 85-95 min, and the residence time in the homogenizing section is 85-95 min.

[0013] Furthermore, in the film blowing machine, the material temperature needs to be maintained at 145°C for 18-22 minutes in the conveying section, at 150°C for 18-22 minutes in the melting section, at 155°C for 18-22 minutes in the mixing rubber section, at 155°C for 18-22 minutes in the exhaust pipe section, and at 150°C for 18-22 minutes in the homogenizing section.

[0014] The beneficial effects of the present invention are: 1. The 35B-LDPE high pressure used in the present invention is 35B type low-density high-pressure polyethylene, which is a linear material and has the property of increasing the longitudinal and transverse tension of the product; the 2426K-LDPE high pressure is 2426K type low-density high-pressure polyethylene, which is an adhesive material, so that the product has self-adhesiveness and better sealing and preservation effect; the 5199-LLDPE high pressure is 5199 type linear low-density high-pressure polyethylene, which makes the product more transparent. The cling film produced by mixing the three raw materials in a specific proportion has good ductility and light transmittance. The product of the present invention can be used in the cling film without using plasticizers, and the cling film of the present invention also has good ductility, reducing the risk of incorrectly adding plasticizers in production.

[0015] 2. The present invention can promote the mixing of raw materials by preheating the mixing of raw materials, ensure uniform mixing, and at the same time increase the temperature of the raw materials to make them easier to melt, reduce the energy required for melting, and thus improve production efficiency. In addition, the water that may exist in the raw materials can also be evaporated to reduce the moisture content in the materials, thereby improving the quality and preservation performance of the cling film. Extruder preheating can increase the temperature of the extruder, so that it can melt and plasticize the raw materials faster, thereby improving the production efficiency of the cling film.

[0016] 3. In the mixing process of the present invention, a viscosity-enhancing masterbatch is added to increase the viscosity of the plastic wrap. The masterbatch is used instead of a liquid additive to better integrate with the raw materials, thereby retaining the original ecology of the material to the maximum extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is an experimental data table of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiment is only one embodiment 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 creative work are within the protection scope of the present invention.

[0019] In order to make the objectives, technical solutions and advantages of the present application more clear, the present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0020] In the following description, references to "one embodiment", "an embodiment", "an example", "an example", etc. indicate that the embodiment or example described in this way may include specific features, structures, characteristics, properties, elements or limitations, but not every embodiment or example necessarily includes the specific features, structures, characteristics, properties, elements or limitations. In addition, repeated use of the phrase "according to one embodiment of the present application" may refer to the same embodiment, but does not necessarily refer to the same embodiment.

[0021] In a first aspect, the present invention discloses a cling film, wherein the formula comprises 44%-48% of high pressure LDPE-35B, 30%-35% of high pressure LDPE-2426K and 20%-23% of high pressure LLDPE-5199, calculated by weight percentage of 100%. The best formula is 46% of high pressure LDPE-35B, 33% of high pressure LDPE-2426K and 21% of high pressure LLDPE-5199.

[0022] The high-pressure LDPE-35B high-pressure used in the present invention is a 35B type low-density high-pressure polyethylene, which is a linear material and has the property of increasing the longitudinal and transverse tensile force of the product; the high-pressure LDPE-2426K is a 2426K type low-density high-pressure polyethylene, which is an adhesive material, so that the product has self-adhesiveness and better sealing and preservation effect; the high-pressure LLDPE-5199 is a 5199 type linear low-density high-pressure polyethylene, which makes the product more transparent. The cling film produced by mixing the three raw materials in a specific proportion has good ductility and light transmittance. The product of the present invention can be used in the cling film without using a plasticizer, and the cling film of the present invention also has good ductility, reducing the risk of incorrectly adding plasticizers in production.

[0023] In a second aspect, a production process of a cling film is provided, which is used to prepare a cling film as in the first aspect, and comprises the following steps: S1. Prepare materials: first prepare the masterbatch of each formula material in the first aspect, that is, obtain raw materials; S2, mixing: add thickening masterbatch to the raw materials, put them into the mixing device for mixing, mix them evenly, and dry them to obtain premix. Use H01 thickening masterbatch instead of liquid additives to increase the viscosity of the cling film, better integrate it with the raw materials, and retain the original ecology of the material to the maximum extent; S3. Secondary granulation: The premix is ​​fed into a preheated extruder, and granulated and modified again through high-temperature melting and screw extrusion. Each formula material is fully integrated to obtain secondary granulation material; the formula material is granulated and modified again through high-temperature melting and screw extrusion. Each formula material is fully integrated to ensure a perfect combination of various properties.

[0024] S4, film blowing: put the secondary granulated material into the film blowing machine, blow the film to form a semi-finished film; S5, cutting and winding: the cooled semi-finished film is cut, cut, rolled and other processes to produce a fresh-keeping film that meets the performance indicators.

[0025] Furthermore, in the step S2, the weight ratio of the tackifying masterbatch to the raw material is 1.5-3.5:100, and the tackifying masterbatch is model H01. The optimal weight ratio of the tackifying masterbatch to the raw material is 2:100.

[0026] Furthermore, in the step S2, when the mixing device is mixing, the temperature is maintained at 90-100°C, and the optimal temperature is 92°C.

[0027] Putting the raw materials into the mixing device for mixing and preheating can promote the mixing of raw materials and ensure uniform mixing. At the same time, it can increase the temperature of the raw materials, make them easier to melt, reduce the energy required for melting, and thus improve production efficiency. In addition, it can also evaporate the water that may exist in the raw materials, reduce the moisture content in the materials, and thus improve the quality and preservation performance of the cling film. At the same time, preheating the extruder can increase the temperature of the extruder, so that it can melt and plasticize the raw materials faster, thereby improving the production efficiency of the cling film.

[0028] Furthermore, in the step S4, the film blowing machine adopts the model ST75, and the main engine speed (20HZ) and the traction (10HZ) fan speed (20HZ) are set. Note that the blocked filter should be replaced before starting the machine.

[0029] In the film blowing machine, the set temperature of the conveying section is 142-148°C, the set temperature of the melting section is 148-152°C, the set temperature of the mixing rubber section is 152-158°C, the set temperature of the exhaust pipe section is 152-158°C, and the set temperature of the homogenizing section is 148-152°C.

[0030] Furthermore, in the film blowing machine, the material residence time in the conveying section is 55-65 min, the residence time in the melting section is 55-65 min, the residence time in the mixing rubber section is 55-65 min, the residence time in the exhaust pipe section is 85-95 min, and the residence time in the homogenizing section is 85-95 min.

[0031] Furthermore, in the film blowing machine, the material temperature needs to be maintained at 145°C for 18-22 minutes in the conveying section, at 150°C for 18-22 minutes in the melting section, at 155°C for 18-22 minutes in the mixing rubber section, at 155°C for 18-22 minutes in the exhaust pipe section, and at 150°C for 18-22 minutes in the homogenizing section.

[0032] In the above data, in the blow molding machine, in each section: the material residence time in the conveying section is 1 hour, and the temperature is maintained at 142-148°C, and the constant temperature is maintained at 145°C for 20 minutes; the residence time in the melting section is 1 hour, and the temperature is maintained at 148-152°C, and the constant temperature is maintained at 150°C for 20 minutes; the residence time in the mixing rubber section is 1 hour, and the temperature is maintained at 152-158°C, and the constant temperature is maintained at 155°C for 20 minutes; the residence time in the exhaust pipe section is 1.5 hours, and the temperature is maintained at 152-158°C, and the constant temperature is maintained at 155°C for 20 minutes; the residence time in the homogenizing section is 1.5 hours, and the temperature is maintained at 148-152°C, and the constant temperature is maintained at 150°C for 20 minutes.

[0033] Finally, a film with a width of 300 mm and a thickness of 0.01 mm was obtained in the film blowing machine, and the weight of the film per meter was kept at 5.7 grams.

[0034] After the film blowing machine blows the film, quality inspection is carried out: 1. The product has no impurities, no color difference, and the end surface of the film roll is flat; 2. Whether the horizontal and vertical tensions meet the national standards; 3. Whether the self-adhesion is within the qualified range; 4. Visually, there are no fish eyes or dead blocks.

[0035] Contents of the comparative experiment: On the basis of the above-mentioned embodiments, this embodiment provides the influence of whether or not a plasticizer is added to the cling film during preparation on the oxygen permeability, moisture permeability, tensile strength, nominal strain at break, light transmittance, haze, and self-adhesion (shear peel strength) of the cling film. The specific experimental contents are as follows: Experimental group 1: The formula material includes 44% high-pressure LDPE-35B, 30% high-pressure LDPE-2426K and 20% high-pressure LLDPE-5199, and then a viscosity-enhancing masterbatch is added to the formula material at a weight ratio of 1.5:100 to the formula material, and then processed according to the process of the second aspect.

[0036] Experimental Group 2: The formula includes 46% high-pressure LDPE-35B, 33% high-pressure LDPE-2426K and 21% high-pressure LLDPE-5199, and then a viscosity-enhancing masterbatch is added to the formula in a weight ratio of 2:100 to the formula, and then processed according to the best solution in the process of the second aspect.

[0037] Experimental Group 3: The formula includes 48% high-pressure LDPE-35B, 35% high-pressure LDPE-2426K and 23% high-pressure LLDPE-5199, and then a viscosity-enhancing masterbatch is added to the formula in a weight ratio of 3.5:100 to the formula, and then processed according to the process of the second aspect.

[0038] Control group: existing cling film with added plasticizer, whose specific common formula is 85 parts of common food grade LDPE, 15 parts of common food grade LLDPE and 5 parts of plasticizer, processed according to the common scheme.

[0039] Experimental steps: The performance test is carried out in accordance with the requirements of GB / T 10457-2021 General rules for quality of plastic self-adhesive cling film for food, including: The oxygen permeability is measured in accordance with the provisions of GB / T 1038.

[0040] The tensile strength nominal strain at break shall be determined in accordance with the provisions of GB / T1040.3-2006.

[0041] The transmittance and haze are measured in accordance with the provisions of GB / T 2410-2008.

[0042] The self-adhesion (shear peel strength) shall be measured in accordance with the provisions of GB / T 10457-2021.

[0043] The experimental results are as follows Figure 1 It can be seen from the table that the experimental groups 1-3 and the control group all meet the national standards, and the experimental data of the cling film of the present invention and the existing cling film with added plasticizer in terms of oxygen permeability, moisture permeability, tensile strength, nominal strain at break, light transmittance, haze, self-adhesion (shear peel strength), etc. are not much different, and the experimental data of the cling film of the present invention in some aspects are better than the existing cling film with added plasticizer.

[0044] Therefore, the cling film made by mixing 46% high-pressure LDPE-35B, 33% high-pressure LDPE-2426K and 21% high-pressure LLDPE-5199 can make the cling film of the present invention have good ductility without using a plasticizer, thereby reducing the risk of incorrectly adding plasticizers during production. At the same time, the present invention has good light transmittance, haze and self-adhesion, so that the present invention is easy to use and has a good preservation effect.

[0045] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A fresh-keeping film, characterized in that: Based on 100% by weight, the formula includes 44%-48% of high-pressure LDPE-35B, 30%-35% of high-pressure LDPE-2426K and 20%-23% of high-pressure LLDPE-5199.

2. A cling film according to claim 1, characterized in that: Based on 100% by weight, the formula includes 46% high pressure LDPE-35B, 33% high pressure LDPE-2426K and 21% high pressure LLDPE-5199.

3. A production process for a cling film, for preparing a cling film as claimed in claim 1 or 2, characterized in that: The steps include: S1. Prepare materials: first prepare the masterbatch of each formula material in claim 1 or 2, that is, obtain raw materials; S2, mixing: adding a thickening masterbatch to the raw materials, putting them into a mixing device for mixing, mixing evenly, and drying to obtain a premix; S3, secondary granulation: the premix is ​​fed into a preheated extruder, and granulated and modified again through high-temperature melting and screw extrusion, and each formula material is fully integrated to obtain secondary granulation material; S4, film blowing: putting the secondary granulated material into a film blowing machine for film blowing to form a semi-finished film; S5, cutting and coiling: the semi-finished film after cooling is cut, cut and rolled to produce the cling film that meets the performance indicators.

4. The production process of a fresh-keeping film according to claim 3, characterized in that: In the step S2, the weight ratio of the viscosity-enhancing masterbatch to the raw material is 1.5-3.5:

100.

5. The production process of a fresh-keeping film according to claim 3, characterized in that: In the step S2, the mixing device is used to mix the materials at a temperature of 90-100°C.

6. The production process of a fresh-keeping film according to claim 3, characterized in that: In the film blowing machine in step S4, the set temperatures of the conveying section are 142-148°C, the melting section are 148-152°C, the mixing section are 152-158°C, the exhaust pipe section are 152-158°C, and the homogenizing section are 148-152°C.

7. The production process of a fresh-keeping film according to claim 6, characterized in that: In the film blowing machine, the material residence time in the conveying section is 55-65 minutes, the residence time in the melting section is 55-65 minutes, the residence time in the mixing rubber section is 55-65 minutes, the residence time in the exhaust pipe section is 85-95 minutes, and the residence time in the homogenizing section is 85-95 minutes.

8. The production process of a fresh-keeping film according to claim 7, characterized in that: In the film blowing machine, the material temperature needs to be maintained at 145°C for 18-22 minutes in the conveying section, at 150°C for 18-22 minutes in the melting section, at 155°C for 18-22 minutes in the mixing rubber section, at 155°C for 18-22 minutes in the exhaust pipe section, and at 150°C for 18-22 minutes in the homogenizing section.

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