Preparation method of long-acting bacteriostatic multi-layer composite fresh-keeping packaging film

Abstract

This invention belongs to the field of packaging material technology, specifically disclosing a method for preparing a long-lasting antibacterial multilayer composite preservation packaging film, comprising the following steps: mixing starch, glycerin, a crosslinking agent, and polybutylene terephthalate (PET), melting, extruding, and granulating to obtain thermoplastic starch-based granules; melting, extruding, and granulating PET, a crosslinking agent, and a polyguanidine bactericide to obtain antibacterial polyester granules; extruding the thermoplastic starch-based granules using a blown film process to obtain a blown starch-based film; extruding the antibacterial polyester granules using a molding process to obtain a hot-pressed polyester film; sandwiching the blown starch-based film between the hot-pressed polyester film and then molding the film to obtain the preservation packaging film. This invention utilizes the above-mentioned method for preparing a long-lasting antibacterial multilayer composite preservation packaging film, and the prepared composite film material can maintain its antibacterial properties for a long time without experiencing a reduction in the leaching of effective components.

Description

Technical Field

[0001] This invention relates to the field of packaging technology, and in particular to a method for preparing a long-lasting antibacterial multilayer composite preservative packaging film. Background Technology

[0002] While the plastic films currently on the market offer excellent performance and convenience, most of their raw materials are non-degradable and non-renewable. This not only wastes a significant amount of resources but also causes substantial "white pollution" to the environment. To meet environmental protection requirements, the demand for biodegradable plastic products is growing.

[0003] Most food packaging films currently on the market are made from polyethylene, polypropylene, and other plastics. These plastics are difficult to degrade and easily pollute the environment. Furthermore, antibacterial materials prepared with antibacterial agents such as chitosan and metal ions (such as silver and copper ions) have short lifespans, are expensive, and lack long-lasting antibacterial effects. Conventional plasticized starch food packaging films are low-cost, widely available, and have good biodegradability. However, they contain a large number of hydroxyl groups, making them highly absorbent and prone to rupture. They also have poor mechanical properties and are easily contaminated by bacteria and other microorganisms during packaging and transportation. Spoiled food can seriously endanger human health, causing symptoms ranging from diarrhea and vomiting to life-threatening conditions. These drawbacks greatly limit the application of starch films in the food packaging field. The purpose of this invention is to provide a long-lasting antibacterial multilayer composite preservation packaging film that possesses both excellent antibacterial and biodegradable properties. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a long-lasting antibacterial multilayer composite preservation packaging film. The prepared composite film material can maintain its antibacterial properties for a long time. The antibacterial agent is coupled and connected with the polybutylene terephthalate (PBAT) matrix, and there will be no phenomenon of reduced leaching of effective ingredients. At the same time, it greatly reduces the risk of starch material being damaged due to excessive water absorption.

[0005] To achieve the above objectives, the present invention provides a method for preparing a long-lasting antibacterial multilayer composite preservative packaging film, comprising the following steps:

[0006] Step 1: Mix starch, glycerol, crosslinking agent and polybutylene terephthalate, premix evenly, and then melt, extrude and granulate through a twin-screw extruder to obtain thermoplastic starch-based granules;

[0007] Step 2: Polybutylene terephthalate, crosslinking agent, and polyguanidine bactericide are mixed and stirred evenly, and then melted, extruded and granulated by a twin-screw extruder to obtain antibacterial polyester granules.

[0008] Step 3: The thermoplastic starch-based granules prepared in Step 1 are subjected to a blown film process to obtain a blown starch-based film;

[0009] Step 4: The antibacterial polyester particles prepared in Step 2 are subjected to a molding process to obtain a hot-pressed polyester film.

[0010] Step 5: The blown starch-based film prepared in step 3 is sandwiched between the hot-pressed polyester film prepared in step 4, and then subjected to a molding process again to obtain a long-lasting antibacterial multilayer composite fresh-keeping packaging film.

[0011] Preferably, in step 1, 50-60g of starch, 13-18g of glycerol, 0.1-1g of crosslinking agent and 25-35g of polybutylene terephthalate are added in the following weight proportions.

[0012] Preferably, in step 1, the crosslinking agent is an ADR epoxy chain extender.

[0013] Preferably, in step 1, the starch is tapioca starch.

[0014] Preferably, in step 1, the temperature control ranges of the twin-screw extruder in the barrel electric heating zone ①, ②, ③, ④, and ⑤ are 100℃-110℃, 110℃-120℃, 120℃-130℃, 130℃-135℃, and 130℃-135℃, respectively. The die head temperature range of the twin-screw extruder is 130℃-135℃, the screw length-to-diameter ratio is 1:40, and the screw speed range is 50rpm-70rpm.

[0015] Preferably, in step 2, 92-99 parts by weight of polybutylene terephthalate, 0-7 parts of crosslinking agent, and 1 part of polyguanidine bactericide are added.

[0016] Preferably, in step 2, the temperature control ranges of the composite material in the electric heating zone ①, ②, ③, ④, and ⑤ of the barrel of the twin-screw extruder are 100℃-110℃, 110℃-120℃, 125℃-130℃, 135℃-140℃, and 135℃-140℃, respectively. The die head temperature range of the twin-screw extruder is 130℃-135℃, the screw length-to-diameter ratio is 1:40, and the screw speed range is 50rpm-70rpm.

[0017] Preferably, in step 2, the polyguanidine bactericide is polyhexamethylene guanidine hydrochloride.

[0018] Preferably, in step 2, the crosslinking agent is one of ADR epoxy chain extender and epoxidized soybean oil.

[0019] Preferably, in step 3, the thickness of the blown starch base film is 0.04~0.06mm.

[0020] The advantages and beneficial effects of the above-mentioned method for preparing a long-lasting antibacterial multilayer composite preservative packaging film are as follows:

[0021] This invention involves mixing glycerin, starch, a crosslinking agent, and polybutylene terephthalate (PBAT) to prepare thermoplastic starch-based granules, which are then blown into a blown starch-based film. Next, PBAT, a crosslinking agent, and an antibacterial component are mixed to prepare thermoplastic antibacterial granules, which are then hot-pressed into a long-lasting antibacterial hot-pressed polyester film. The "sandwich" structure is created by hot-pressing the polyester film, the blown starch-based film, and the hot-pressed polyester film in that order. This long-lasting antibacterial composite film prevents bacterial adsorption and efficiently and rapidly kills bacteria on its surface. Furthermore, the "sandwich" structure effectively prevents the starch component in the film from being damaged due to excessive water absorption, thus avoiding loss of preservation effect.

[0022] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0023] The technical solution of the present invention will be further described below through embodiments.

[0024] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0025] The following examples are not intended to limit the invention, but are only for illustration. Unless otherwise specified, the experimental methods used in the following examples are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0026] Example 1

[0027] A method for preparing a long-lasting antibacterial multilayer composite preservative packaging film includes the following steps:

[0028] Step 1: 53.5g of tapioca starch, 16g of glycerol, 0.5g of crosslinking agent ADR epoxy chain extender, and 30g of polybutylene terephthalate (PBAT) were mixed sequentially for 30 minutes. After uniform premixing, the mixture was melted, extruded, and granulated using a twin-screw extruder to obtain thermoplastic starch-based granules. The temperature control ranges of the electric heating zones ①, ②, ③, ④, and ⑤ of the twin-screw extruder were 100℃-110℃, 110℃-120℃, 120℃-130℃, 130℃-135℃, and 130℃-135℃, respectively. The die head temperature range of the twin-screw extruder was 130℃-135℃, the screw length-to-diameter ratio was 1:40, and the screw speed range was 50rpm-70rpm.

[0029] Step 2: Dry PBAT at 80℃ for 24 hours. Mix 98.9g of PBAT, 0.1g of crosslinking agent ADR epoxy chain extender, and 1g of polyhexamethylene guanidine hydrochloride by weight, stir until homogeneous, and then melt, extrude, and granulate using a twin-screw extruder to obtain antibacterial polyester granules. The temperature control ranges of the composite material in the electrically heated barrel zones ①, ②, ③, ④, and ⑤ of the twin-screw extruder are 100℃-110℃, 110℃-120℃, 125℃-130℃, 135℃-140℃, and 135℃-140℃, respectively. The die head temperature range of the twin-screw extruder is 130℃-135℃, the screw length-to-diameter ratio is 1:40, and the screw speed range is 50rpm-70rpm.

[0030] Step 3: Before preparing the thermoplastic starch-based granules obtained in Step 1 into a film, they are dried at 80℃ for 12 hours, and then blown into a starch-based film using a blown film process. The temperatures of the blown film machine from the feeder to the die are set to 100℃-110℃, 125℃-135℃, 130℃-140℃, 135℃-145℃, 140℃-130℃, and 130℃-125℃, respectively. The screw speed is 30rpm~40rpm, the screw diameter (D) is 20mm, the screw length-to-diameter ratio is 1:28, the blown film die diameter is 30mm, the traction speed is 2m / min~2.5m / min, and the cooling air flow rate is 30L / min. The extrusion-blowing process of the obtained film samples remains continuous and stable. The thickness of the obtained film is 0.04~0.06mm.

[0031] Step 4: Before preparing the antibacterial polyester particles obtained in Step 2 into a film, dry them at 80℃ for 12 hours, and then obtain a hot-pressed polyester film through a molding process. The parameters of the flat vulcanizing machine are: temperature 140℃, preheating time 5 min, venting times 5 times, venting time: 10 s, pressurization time 5 min, and cold pressing time 5 min.

[0032] Step 5: Sandwich the blown starch-based film prepared in Step 3 between the hot-pressed polyester film prepared in Step 4, and then perform a molding process again to obtain a long-lasting antibacterial multi-layer composite preservation packaging film. Sandwiching the blown starch-based film between two hot-pressed polyester films and then hot-pressing them again in a flat vulcanizing machine results in a long-lasting antibacterial multi-layer composite preservation packaging film with a "hot-pressed polyester film-blown starch-based film-hot-pressed polyester film" structure. The "sandwich" structure, created by hot-pressing the hot-pressed polyester film, blown starch-based film, and hot-pressed polyester film in that order, effectively prevents the starch component in the film from being damaged due to excessive water absorption, thus avoiding loss of preservation effect.

[0033] Cassava starch contains 27% amylose and 73% amylopectin. The polyhexamethylene guanidine hydrochloride (PHMG) powder has a molecular weight of 1000 g / mol, a purity of 99%, and a PBAT melt index range of ≤5.0 g / 10 min.

[0034] Tapioca starch (27% amylose, 73% amylopectin) and polybutylene terephthalate (PBAT, melt index ≤5.0g / 10min) both have good biodegradability, and PBAT can improve the mechanical properties of starch films.

[0035] Plasticizer: Glycerin, used to reduce the intermolecular forces of starch molecules and improve the flexibility of the film.

[0036] Crosslinking agent: ADR epoxy chain extender or epoxidized soybean oil (ESO), which enhances the structural stability of the membrane and reduces water absorption through crosslinking reaction.

[0037] Antibacterial component: Polyhexamethylene guanidine hydrochloride (PHMG, molecular weight 1000 g / mol, purity 99%), which has broad-spectrum antibacterial properties and can couple with the PBAT matrix to prevent the leaching of active ingredients.

[0038] Example 2

[0039] Unlike Example 1, in step 1, 55g of tapioca starch, 18g of glycerol, 0.3g of crosslinking agent ADR epoxy chain extender, and 25g of polybutylene terephthalate (PBAT) were mixed in sequential parts by weight for 30 minutes. In step 2, 98.7g of PBAT, 0.3g of crosslinking agent ADR epoxy chain extender, and 1g of polyhexamethylene guanidine hydrochloride were mixed and stirred until homogeneous. The rest of the process was the same as in Example 1.

[0040] Example 3

[0041] The difference from Example 1 is that in step 1, 58g of tapioca starch, 14g of glycerol, 0.6g of crosslinking agent ADR epoxy chain extender and 28g of polybutylene terephthalate (PBAT) are mixed in the following order for 30 minutes. In step 2, 98.5g of PBAT, 0.5g of crosslinking agent ADR epoxy chain extender and 1g of polyhexamethylene guanidine hydrochloride are mixed in the following order and stirred until homogeneous. The rest of the process is the same as in Example 1.

[0042] Example 4

[0043] Unlike Example 1, in step 1, 60g of tapioca starch, 13g of glycerol, 1g of crosslinking agent ADR epoxy chain extender and 31g of polybutylene terephthalate (PBAT) were mixed for 30 minutes. In step 2, 98.3g of PBAT, 0.7g of crosslinking agent ADR epoxy chain extender and 1g of polyhexamethylene guanidine hydrochloride were mixed and stirred until homogeneous. The rest of the process was the same as in Example 1.

[0044] Example 5

[0045] Unlike Example 1, in step 1, 60g of tapioca starch, 14g of glycerol, 0.1g of crosslinking agent ADR epoxy chain extender and 35g of polybutylene terephthalate (PBAT) were mixed for 30 minutes. In step 2, 98g of PBAT, 1g of epoxy soybean oil crosslinking agent and 1g of polyhexamethylene guanidine hydrochloride were mixed and stirred evenly. The rest of the process was the same as in Example 1.

[0046] Example 6

[0047] Unlike Example 1, in step 1, 56g of tapioca starch, 17g of glycerol, 0.8g of crosslinking agent ADR epoxy chain extender and 35g of polybutylene terephthalate (PBAT) were mixed for 30 minutes. In step 2, 96g of PBAT, 3g of epoxy soybean oil crosslinking agent and 1g of polyhexamethylene guanidine hydrochloride were mixed and stirred evenly. The rest of the process was the same as in Example 1.

[0048] Example 7

[0049] The difference from Example 1 is that in step 1, 52g of tapioca starch, 15g of glycerol, 0.5g of crosslinking agent ADR epoxy chain extender and 30g of polybutylene terephthalate (PBAT) are mixed for 30 minutes. In step 2, 94g of PBAT, 5g of epoxy soybean oil crosslinking agent and 1g of polyhexamethylene guanidine hydrochloride are mixed and stirred evenly. The rest of the contents are the same as in Example 1.

[0050] Example 8

[0051] The difference from Example 1 is that in step 1, 59g of tapioca starch, 16g of glycerol, 0.7g of crosslinking agent ADR epoxy chain extender and 34g of polybutylene terephthalate (PBAT) are mixed for 30 minutes. In step 2, 92g of PBAT, 7g of epoxy soybean oil crosslinking agent and 1g of polyhexamethylene guanidine hydrochloride are mixed and stirred evenly. The rest of the contents are the same as in Example 1.

[0052] Comparative Example 1

[0053] Unlike Example 1, in step 2, 99g of PBAT and 1g of polyhexamethylene guanidine hydrochloride were mixed and stirred until homogeneous. The rest of the steps were the same as in Example 1.

[0054] The required amounts of each component for the antibacterial ester particles in step 2 of Examples 1-8 and Comparative Example 1 were statistically analyzed, and the results are shown in Table 1. The performance of the long-lasting antibacterial multilayer composite preservative packaging film prepared according to the methods of Examples 1-8 and Comparative Example 1 was tested, and the test results are shown in Table 2.

[0055] Table 1. Amounts of each component required for preparing antibacterial polyester particles in the examples and comparative examples.

[0056]

[0057] Table 2 Test Results

[0058]

[0059] The comparative data in Table 2 shows that the addition of the crosslinking agent improved both the tensile strength and elongation at break. However, with the increase of the crosslinking agent ADR epoxy chain extender content, both the tensile strength and elongation at break decreased. In Example 2, the tensile strength was 7.5 MPa and the elongation at break was 654%. In Examples 6-8, with the increase of the crosslinking agent epoxidized soybean oil (ESO) content, the tensile strength remained almost unchanged, while the elongation at break decreased. In Example 6, the tensile strength was 11.5 MPa and the elongation at break was 1420%. Through a simple melt reaction grafting reaction of the polyguanidine salt antibacterial agent, the composite membrane material achieved a 90% inhibition rate against Staphylococcus aureus and Escherichia coli. Furthermore, after soaking in water for 7 days, the antibacterial rate of the polyester composite membrane remained above 90%. This composite membrane material can also maintain its antibacterial properties for a long time. The antibacterial agent can be coupled and connected to the PBAT matrix without any reduction in the leaching of effective components. At the same time, it greatly reduces the risk of starch material breakage due to excessive water absorption.

[0060] Therefore, this invention employs the aforementioned method for preparing a long-lasting antibacterial multilayer composite preservative packaging film, using starch and PBAT as the main raw materials, both of which are biodegradable in the natural environment, avoiding "white pollution." Compared to traditional polyethylene packaging films, it complies with national plastic pollution control policies, and there are no harmful pollutant emissions during the production process. After adding a crosslinking agent, the tensile strength and elongation at break of the composite film are significantly improved. The PHMG in the composite film is coupled and connected to the PBAT matrix through melt reaction grafting, without any effective component leaching. After soaking in water for 7 days, the antibacterial rate remains above 90%, and the inhibitory effect on common food contaminants such as Staphylococcus aureus and Escherichia coli is long-lasting, effectively extending the shelf life of food and reducing the risk of microbial contamination.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a long-lasting antibacterial multilayer composite preservative packaging film, characterized in that, Includes the following steps: Step 1: Mix starch, glycerol, crosslinking agent and polybutylene terephthalate (PET), premix evenly, and then melt, extrude and granulate through a twin-screw extruder to obtain thermoplastic polyester composite granules and thermoplastic starch-based granules; the crosslinking agent is ADR epoxy chain extender. Step 2: Polybutylene terephthalate, crosslinking agent, and polyguanidine bactericide are mixed and stirred evenly, and then melted, extruded and granulated through a twin-screw extruder to obtain antibacterial polyester granules; the crosslinking agent is one of ADR epoxy chain extender and epoxidized soybean oil. Step 3: The thermoplastic polyester composite particles and thermoplastic starch-based particles obtained in Step 1 are blown into a starch-based film through a blown film process. Step 4: The antibacterial polyester particles prepared in Step 2 are subjected to a molding process to obtain a hot-pressed polyester film. Step 5: The blown starch-based film prepared in step 3 is sandwiched between the hot-pressed polyester film prepared in step 4, and then subjected to a molding process again to obtain a long-lasting antibacterial multilayer composite fresh-keeping packaging film.

2. The method for preparing a long-lasting antibacterial multilayer composite preservative packaging film according to claim 1, characterized in that: In step 1, add 50-60g of starch, 13-18g of glycerin, 0.1-1g of crosslinking agent and 25-35g of polybutylene terephthalate.

3. The method for preparing a long-lasting antibacterial multilayer composite preservative packaging film according to claim 1, characterized in that: In step 1, the starch is tapioca starch.

4. The method for preparing a long-lasting antibacterial multilayer composite preservative packaging film according to claim 1, characterized in that: In step 1, the temperature control ranges of the twin-screw extruder in the barrel electric heating zone ①, ②, ③, ④, and ⑤ are 100℃-110℃, 110℃-120℃, 120℃-130℃, 130℃-135℃, and 130℃-135℃, respectively. The die head temperature range of the twin-screw extruder is 130℃-135℃, the screw length-to-diameter ratio is 1:40, and the screw speed range is 50rpm-70rpm.

5. The method for preparing a long-lasting antibacterial multilayer composite preservative packaging film according to claim 1, characterized in that: In step 2, add 92-99 parts by weight of polybutylene terephthalate, 0-7 parts of crosslinking agent, and 1 part of polyguanidine bactericide.

6. The method for preparing a long-lasting antibacterial multilayer composite preservative packaging film according to claim 1, characterized in that: In step 2, the temperature control ranges of the composite material in the electric heating zone ①, ②, ③, ④, and ⑤ of the barrel of the twin-screw extruder are 100℃-110℃, 110℃-120℃, 125℃-130℃, 135℃-140℃, and 135℃-140℃, respectively. The die head temperature range of the twin-screw extruder is 130℃-135℃, the screw length-to-diameter ratio is 1:40, and the screw speed range is 50rpm-70rpm.

7. The method for preparing a long-lasting antibacterial multilayer composite preservative packaging film according to claim 1, characterized in that: In step 2, the polyguanidine bactericide is polyhexamethylene guanidine hydrochloride.

8. The method for preparing a long-lasting antibacterial multilayer composite preservative packaging film according to claim 1, characterized in that: In step 3, the thickness of the blown starch-based film is 0.04~0.06mm.

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