Antistatic stretch film and preparation method thereof

Abstract

The invention discloses an antistatic stretched film and a preparation method thereof, and belongs to the technical field of films. The raw materials comprise, by mass, 70-90 parts of PET resin and 3-5 parts of polyethylene glycol as an inner layer, 30-40 parts of PET resin, 10-15 parts of an antistatic filler, 4-14 parts of an antistatic auxiliary agent and 2-4 parts of a processing auxiliary agent as an antistatic functional layer; pET resin is used as a main raw material, so that the film is endowed with good transparency and mechanical properties; wherein the antistatic filler has good compatibility with a matrix, and the antistatic performance of the matrix can be greatly enhanced; wherein the molecules of the antistatic auxiliary agent contain a plurality of functional groups, so that the antibacterial property, the mechanical property and the antistatic property of the matrix can be remarkably improved; in conclusion, the prepared film is high in transparency and excellent in mechanical property, also has efficient antibacterial property and antistatic property, and has important application value in the technical field of films.

Description

Technical Field

[0001] The invention belongs to the technical field of films, and in particular relates to an antistatic stretched film and a preparation method thereof. Background Art

[0002] As a functional material, stretch film has broad application prospects in modern industry and daily life. With the continuous development of science and technology, people's requirements for packaging materials are no longer limited to basic protection and sealing performance, but are gradually developing towards high performance and multi-functions. Traditional plastic films are prone to static electricity accumulation due to friction during use. The static electricity phenomenon is caused by the uneven distribution of charges on the surface of the material, and this phenomenon is particularly common in plastic products. Ordinary plastic films are usually made of polymer materials such as polyethylene, polypropylene, and polyester. These materials themselves have high resistivity, which makes it difficult for charges to dissipate quickly. This will not only cause the film to absorb dust and impurities, affecting its appearance and use effect, but may also cause damage to sensitive items such as electronic components.

[0003] At present, there are some antistatic film products on the market, but they still have certain limitations in performance and preparation process. Traditional antistatic methods are mainly divided into two types: external coating type and internal addition type. External coating antistatic agents achieve antistatic effect by coating a layer of conductive material on the surface of the film. This method is simple to operate and low in cost, but its antistatic performance is often not durable enough and is easily invalidated by environmental factors (such as humidity changes) or mechanical wear. In addition, the external coating may affect the optical properties and mechanical strength of the film, limiting its scope of application. Internal addition antistatic agents directly mix antistatic substances into the plastic substrate and improve the overall antistatic performance by uniform dispersion. The advantage of this method is that the antistatic effect is more durable and does not significantly change the appearance and mechanical properties of the film. However, the selection and dispersion technology of internal addition antistatic agents is still a difficult point, especially how to ensure antistatic performance without affecting other performance indicators. In addition, bacteria exist in large quantities in the environment, and the spread of epidemic diseases caused by bacteria is getting faster and faster, and the scope of influence is getting larger and larger. Conventional antistatic films do not have antibacterial properties, and bacteria are easy to breed on the surface of the film, endangering people's health. In summary, there is an urgent need to invent a stretch film with both antistatic and antibacterial properties to meet higher requirements in the field of film technology. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide an antistatic stretched film and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions: An antistatic stretch film comprises an inner layer and an antistatic functional layer; The inner layer comprises raw materials in the following parts by weight: 70 - 90 parts of PET resin and 3 - 5 parts of polyethylene glycol; The antistatic functional layer comprises raw materials in the following parts by weight: 30 - 40 parts of PET resin, 10 - 15 parts of antistatic filler, 4 - 14 parts of antistatic auxiliary and 2 - 4 parts of processing aid.

[0006] Further, the processing aid is one of stearic acid, white paraffin wax and polyethylene wax.

[0007] A preparation method of an antistatic stretched film comprises the following steps: Adding PET resin and polyethylene glycol into a single - screw extruder for melting, then adding PET resin, antistatic filler, antistatic auxiliary and processing aid into a twin - screw extruder for melting. The melt is extruded through a co - extrusion die head, cooled, then longitudinally stretched and transversely stretched, heat - set, and wound up to obtain the antistatic stretched film.

[0008] Further, the temperature of the longitudinal stretching is 80 - 100 °C, and the stretching ratio is 4.0 - 4.2 times.

[0009] Further, the temperature of the transverse stretching is 100 - 120 °C, and the stretching ratio is 3.8 - 4.0 times.

[0010] Further, the temperature of the heat - setting is 150 - 180 °C.

[0011] Using PET resin as the main raw material endows the film with good transparency and mechanical properties; adding polyethylene glycol as a nucleating agent can promote the rapid growth of crystals and improve the toughness and processing performance of the film simultaneously.

[0012] Further, the antistatic filler is prepared through the following steps: Mixing γ - aminopropyltrimethoxysilane with an ethanol aqueous solution, adding acetic acid solution to adjust the pH of the system to 4 - 5, stirring at room temperature for 15 min to fully hydrolyze γ - aminopropyltrimethoxysilane; then adding indium tin oxide into the system, reacting in a constant - temperature water bath at 60 °C for 5 h, continuously stirring during the reaction. After the reaction is completed, centrifugally separated, washed with absolute ethanol for many times, vacuum - dried and ground to obtain the antistatic filler.

[0013] Further, the dosage ratio of γ - aminopropyltrimethoxysilane, ethanol aqueous solution and indium tin oxide is 5.3 g:100 mL:1 g.

[0014] Indium tin oxide is a transparent conductive material. After hydrolysis, γ-aminopropyltrimethoxysilane can form strong chemical bonds with indium tin oxide, significantly improving the compatibility between indium tin oxide and the polyester matrix, promoting the dispersion of indium tin oxide in the matrix, reducing the agglomeration phenomenon and the impact on the mechanical and processing properties of the matrix, and greatly enhancing the antistatic performance of the matrix.

[0015] Furthermore, the antistatic aid is prepared through the following steps: Step 1: Add 4-aminopyridine, stearic acid, and N,N-dimethylformamide into a three-necked flask equipped with a magnetic stirrer. Stir magnetically at room temperature for 10 min, then add dicyclohexylcarbodiimide. Then place the device in a water bath and stir and react at a constant water bath temperature of 50 °C for 3 h. After the reaction is completed, pour the mixed solution into ice water, extract with ethyl acetate, combine the organic phases, wash with saturated sodium bicarbonate solution, dry with anhydrous sodium sulfate, rotary evaporate to remove ethyl acetate, and obtain intermediate product 1. Using dicyclohexylcarbodiimide as a dehydrating agent, the amino group of 4-aminopyridine and the carboxyl group of stearic acid undergo an amidation reaction to form intermediate product 1. The specific reaction process is as follows:

[0016] Step 2: Add intermediate product 1 and dichloroethane into a three-necked flask equipped with a thermometer, a spherical condenser, and a magnetic stirrer. Stir and mix evenly, heat until the temperature reaches 65 °C, maintain this temperature, and reflux and react for 5 h. After the reaction is completed, distill off part of the solvent under reduced pressure, and then purify by silica gel column chromatography (the eluent is petroleum ether and ethyl acetate, and their volume ratio is 5:1). Rotary evaporate to remove the eluent, and dry under vacuum to obtain intermediate product 2. Intermediate product 1 and dichloroethane undergo a quaternization reaction. Dichloroethane not only participates in the reaction but also serves as a solvent to reduce the occurrence of side reactions and is in excess to ensure that only one chloro group of dichloroethane participates in the reaction, obtaining intermediate product 2. The specific reaction process is as follows:

[0017] Step 3: Add intermediate product 2 and N,N-dimethylformamide into a three-necked flask equipped with a magnetic stirrer, a condenser, and a thermometer. Dissolve alizarin and sodium hydroxide in N,N-dimethylformamide and distilled water respectively, stir and mix evenly, and then add them into the flask in sequence. Heat the device. When the temperature reaches 70 °C, keep the temperature unchanged and stir and react for 5 h. After the reaction is completed, distill off part of the solvent under reduced pressure, and then purify by silica gel column chromatography (the eluent is petroleum ether and ethyl acetate, and their volume ratio is 5:1). Rotary evaporate to remove the eluent, and dry under vacuum to obtain the antistatic aid. Sodium hydroxide can react with the hydroxyl group at the 2'-position in the alizarin molecule to form a phenolate with stronger nucleophilicity. The hydroxyl group at the 1'-position forms a hydrogen bond with the carbonyl group and is not easily broken. The phenolate can attack the carbon atom connected to the chlorine atom in intermediate 2 to form an ether bond. By adjusting the molar ratio of alizarin to intermediate 2 to be close to 1:1 (with alizarin being slightly in excess), an antistatic agent is produced. The specific reaction process is as follows:

[0018] The prepared antistatic agent molecule contains anthraquinone, pyridinium quaternary ammonium salt, and a long carbon chain structure. Among them, anthraquinone compounds have excellent antibacterial effects. The carbonyl group (C=O) in the quinone molecule has strong electrophilicity and can covalently bind to nucleophilic groups (such as sulfhydryl groups and amino groups) in microbial cells, destroying the cells and enhancing the antibacterial performance of the matrix. Pyridinium quaternary ammonium salt is a new type of quaternary ammonium salt antibacterial agent. The positive charge in its molecular structure is more concentrated, and it can more efficiently bind to the negatively charged components on the bacterial cell membrane, thereby destroying the integrity of the cell membrane and causing bacterial death. This efficient bactericidal mechanism not only significantly improves the antibacterial ability but also reduces the possibility of bacteria developing drug resistance, thus effectively avoiding the drug resistance problem caused by the large - scale and long - term use of traditional quaternary ammonium salt antibacterial agents. It can act synergistically with anthraquinone to greatly enhance the antibacterial performance of the matrix, and the pyridinium quaternary ammonium salt structure can also enhance the antistatic performance of the matrix. Finally, the molecule contains a long carbon chain structure, which can not only toughen the matrix but also interpenetrate into the macromolecular chains of the matrix to improve the stability of the antistatic agent molecule.

[0019] Furthermore, in step 1, the dosage ratio of 4 - aminopyridine, stearic acid, N,N - dimethylformamide, and dicyclohexylcarbodiimide is 9.4 g:28.4 g:100 mL:20.6 g.

[0020] Furthermore, in step 2, the dosage ratio of intermediate 1 to dichloroethane is 35.9 g:100 mL.

[0021] Furthermore, in step 3, the dosage ratio of intermediate 2, N,N - dimethylformamide, alizarin, sodium hydroxide, and distilled water is 42.3 g:120 mL:24.1 g:3.9 g:50 mL.

[0022] The beneficial effects of the present invention: 1. The film prepared by the present invention uses PET resin as the main raw material, endowing the film with good transparency and mechanical properties; 2. Adding polyethylene glycol as a nucleating agent improves the toughness and processing performance of the film; 3. By modifying indium tin oxide, compared with ordinary indium tin oxide, it has better compatibility with the matrix and can greatly enhance the antistatic performance of the matrix; 4. An antistatic additive is prepared through three-step reactions. The additive molecule contains multiple functional groups, which can significantly improve the antibacterial property, mechanical property, and antistatic property of the matrix. In summary, the film prepared by the present invention has high transparency, excellent mechanical properties, as well as high antibacterial and antistatic properties, and has important application value in the field of film technology. Specific Embodiments

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. Example 1

[0024] Preparation of antistatic filler: Mix 5.3 g of γ-aminopropyltrimethoxysilane with 100 mL of an ethanol aqueous solution (volume ratio of ethanol / water is 9:1), add acetic acid solution (mass fraction 9%) to adjust the pH of the system to 4 - 5, stir at room temperature for 15 min to fully hydrolyze γ-aminopropyltrimethoxysilane; then add 1 g of indium tin oxide to the system, and react in a constant temperature water bath at 60 °C for 5 h with continuous stirring during the reaction. After the reaction is completed, centrifuge and separate, wash with absolute ethanol multiple times, dry under vacuum, and grind to obtain the antistatic filler. Example 2

[0025] Preparation of antistatic additive: Step 1. Add 9.4 g of 4-aminopyridine, 28.4 g of stearic acid, and 100 mL of N,N-dimethylformamide to a three-necked flask equipped with an electromagnetic stirrer, stir magnetically at room temperature for 10 min, then add 20.6 g of dicyclohexylcarbodiimide, and place the device in a water bath. Stir and react at a constant temperature of 50 °C for 3 h. After the reaction is completed, pour the mixed solution into ice water, extract with ethyl acetate, combine the organic phases, wash with saturated sodium bicarbonate solution, dry with anhydrous sodium sulfate, and rotary evaporate to remove ethyl acetate to obtain Intermediate Product 1. Step 2. Add 35.9 g of Intermediate Product 1 and 100 mL of dichloroethane to a three-necked flask equipped with a thermometer, a spherical condenser, and an electromagnetic stirrer, stir and mix evenly, heat until the temperature reaches 65 °C, maintain this temperature, and reflux for 5 h. After the reaction is completed, distill off part of the solvent under reduced pressure, then purify by silica gel column chromatography (the eluent is petroleum ether and ethyl acetate, with a volume ratio of 5:1), rotary evaporate to remove the eluent, and dry under vacuum to obtain Intermediate Product 2. Step 3: Add 42.3 g of Intermediate 2 and 80 mL of N,N-dimethylformamide into a three-necked flask equipped with a magnetic stirrer, a condenser and a thermometer. Then dissolve 24.1 g of alizarin and 3.9 g of sodium hydroxide in 40 mL of N,N-dimethylformamide and 50 mL of distilled water respectively. After stirring and mixing evenly, add them into the flask in sequence. Heat the device. When the temperature reaches 70 °C, keep the temperature unchanged and stir for 5 h. After the reaction is completed, remove part of the solvent by vacuum distillation, and then purify it by silica gel column chromatography (the eluent is petroleum ether and ethyl acetate, and the volume ratio of the two is 5:1). Rotate and evaporate to remove the eluent, and dry it in vacuum to obtain the antistatic additive. Example III

[0026] Melt 70 g of PET resin and 3 g of polyethylene glycol (molecular weight 1000) in a single-screw extruder. Then add 30 g of PET resin, 10 g of the antistatic filler prepared in Example I, 4 g of the antistatic additive prepared in Example II and 2 g of stearic acid into a twin-screw extruder to melt. The melt is extruded through a coextrusion die head, cooled, longitudinally stretched at 80 °C (the stretching multiple is 4.0 times), transversely stretched at 100 °C (the stretching multiple is 3.8 times), heat-set at 150 °C, and wound up to obtain the antistatic stretched film. Example IV

[0027] Melt 80 g of PET resin and 4 g of polyethylene glycol (molecular weight 1000) in a single-screw extruder. Then add 35 g of PET resin, 12.5 g of the antistatic filler prepared in Example I, 9 g of the antistatic additive prepared in Example II and 3 g of white paraffin into a twin-screw extruder to melt. The melt is extruded through a coextrusion die head, cooled, longitudinally stretched at 90 °C (the stretching multiple is 4.1 times), transversely stretched at 110 °C (the stretching multiple is 3.9 times), heat-set at 165 °C, and wound up to obtain the antistatic stretched film. Example V

[0028] Melt 90 g of PET resin and 5 g of polyethylene glycol (molecular weight 1000) in a single-screw extruder. Then add 40 g of PET resin, 15 g of the antistatic filler prepared in Example I, 14 g of the antistatic additive prepared in Example II and 4 g of polyethylene wax into a twin-screw extruder to melt. The melt is extruded through a coextrusion die head, cooled, longitudinally stretched at 100 °C (the stretching multiple is 4.2 times), transversely stretched at 120 °C (the stretching multiple is 4.0 times), heat-set at 180 °C, and wound up to obtain the antistatic stretched film.

[0029] Comparative Example I Use the same mass of unmodified indium tin oxide to replace the antistatic filler in Example V, and the remaining steps are the same as those in Example V to prepare the film.

[0030] Comparative Example 2 Replace the antistatic aid in Example 5 with a commercially available antistatic agent of the same quality, and the remaining steps are the same as those in Example 5 to prepare a film.

[0031] Comparative Example 3 Use a commercially available antistatic film.

[0032] Make the corresponding shapes of Examples 3, 4, 5 and Comparative Examples 1, 2, 3 according to different test standards, and conduct the following performance tests: Determine the tensile strength according to the national standard GB / T 16958-2008 "Testing of Biaxially Oriented Polyester Films for Packaging"; Determine the resistance according to the national standard GB / T 33398-2016 "Optical Functional Films - Polyethylene Terephthalate (PET) Films - Determination Method of Surface Resistance"; Determine the antibacterial property according to the national standard GB / T 31402-2015 "Plastics - Test Method for Antibacterial Property of Plastic Surfaces"; The measured results are shown in the following table:

[0033] As can be seen from the above table, the film prepared in the embodiment of the present invention has good mechanical properties, and excellent antibacterial and antistatic properties. Therefore, the present invention has important application value in the field of film technology.

[0034] In the description of the specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0035] The above content is only an example and explanation of the present invention. Those skilled in the art of the present technology make various modifications or supplements to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should all belong to the protection scope of the present invention.

Claims

1. An antistatic stretched film, characterized in that: It includes an inner layer and an antistatic functional layer; The inner layer comprises the following raw materials in parts by weight: 70-90 parts of PET resin and 3-5 parts of polyethylene glycol; the antistatic functional layer comprises the following raw materials in parts by weight: 30-40 parts of PET resin, 10-15 parts of antistatic filler, 4-14 parts of antistatic additive and 2-4 parts of processing aid.

2. The antistatic stretch film according to claim 1, characterized in that: The antistatic auxiliary agent is prepared by the following steps: Step 1, 4-aminopyridine, stearic acid and N,N-dimethylformamide were stirred at room temperature, dicyclohexylcarbodiimide was added, and the mixture was reacted at 50° C. for 3 h. After the reaction was completed, an intermediate product 1 was obtained; Step 2, adding the intermediate product 1 and dichloroethane into a flask, stirring and mixing, reacting at 65° C. for 5 h, and completing the reaction to obtain the intermediate product 2; Step 3: Add the intermediate product 2 and N,N-dimethylformamide into a flask, dissolve alizarin and sodium hydroxide in N,N-dimethylformamide and distilled water respectively, stir and mix, add the mixture into the flask, and react at 70°C for 5h. The reaction is completed to obtain an antistatic additive.

3. An antistatic stretch film according to claim 2, characterized in that: In step 1, the ratio of 4-aminopyridine to stearic acid is 9.4 g:28.4 g.

4. The antistatic stretch film according to claim 2, characterized in that: In step 2, the ratio of the amount of intermediate product 1 to that of dichloroethane is 35.9 g:100 mL.

5. The antistatic stretch film according to claim 2, characterized in that: In step 3, the ratio of the amount of intermediate product 2, alizarin and sodium hydroxide is 42.3g:24.1g:3.9g.

6. The antistatic stretched film according to claim 1, characterized in that: The antistatic filler is prepared by the following steps: γ-aminopropyltrimethoxysilane was mixed with ethanol aqueous solution, the pH of the system was adjusted to 4-5, and stirred at room temperature for 15 minutes. Then, indium tin oxide was added and reacted at 60° C. for 5 hours. The reaction was completed to obtain an antistatic filler.

7. The antistatic stretched film according to claim 6, characterized in that: The usage ratio of γ-aminopropyltrimethoxysilane, ethanol aqueous solution, and indium tin oxide is 5.3 g:100 mL:1 g.

8. The antistatic stretched film according to claim 1, characterized in that: The processing aid is one of stearic acid, white paraffin and polyethylene wax.

9. The method for preparing an antistatic stretched film according to claim 1, characterized in that: The following steps are involved: PET resin and polyethylene glycol are added to a single-screw extruder for melting, and then PET resin, antistatic filler, antistatic additive and processing aid are added to a twin-screw extruder for melting. The melt is extruded through a co-extrusion die head, cooled, and then longitudinally stretched and transversely stretched, heat-set, and rolled to obtain an antistatic stretch film.

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