Highly transparent biodegradable polyethylene film and its use

Abstract

The application relates to the technical field of plastic processing, and discloses a high-transmittance biodegradable polyethylene film and application thereof, which comprises an antibacterial coating, an inner layer, an intermediate layer and a surface layer, the intermediate layer and the surface layer are co-extrusion blow molded, the inner layer is laminated on the side surface of the intermediate layer, the antibacterial coating is a BPTCA-N antibacterial coating which is sprayed and solidified on the surface of the inner layer, and the antibacterial coating is sprayed on the surface of the inner layer by using a BPTCA-N alkaline solution while hot; the inner layer components are linear low-density polyethylene, high-density polyethylene, starch, glycerol, talcum powder, sodium polyacrylate and appropriate water; during processing, starch is gelatinized by using high temperature, and then the gelatinized starch is high-temperature melted into plasticized starch by the synergistic plasticizing effect of glycerol and sodium polyacrylate. The plasticized starch is added into the inner layer, the demand for petroleum products is reduced, the market demand for biodegradable plastics is met, the sustainable development of the industry is promoted, and the prepared composite film has good mechanical properties and excellent antibacterial activity.

Description

[0001] The application is a divisional application of the invention application with the invention name of "Polyethylene composite packaging bag and its processing technology", the parent application number is 202111672888.X, and the parent application date is December 31, 2021. TECHNICAL FIELD

[0002] The application belongs to the technical field of plastic processing, and particularly relates to a high-transmittance biodegradable polyethylene film and application thereof. BACKGROUND

[0003] The polyethylene film, namely PE film, is a film produced by PE and can be divided into low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE) and cross-linked polyethylene. In packaging materials, low-density polyethylene and linear low-density polyethylene are generally used to make the heat-sealing layer of the composite film, and then the heat-sealing layers of the composite film are oppositely heat-sealed to achieve the sealing effect. However, the adhesion of low-density polyethylene and linear low-density polyethylene is very large, and once the heat-sealing is performed on the two layers of the composite film, a strong binding force is generated between the two layers of the composite film, so that the consumer is difficult to separate the two layers of the composite film under the general force, which is inconvenient to use.

[0004] In the prior art, a Chinese patent with the authorization announcement number CN102423942B discloses a food packaging plastic base film and its production process, which comprises three layers of inner layer, intermediate layer and outer layer; the inner layer is made of low-density polyethylene LDPE and metallocene linear low-density polyethylene m-LLDPE, the intermediate layer is made of low-density polyethylene LDPE and linear low-density polyethylene LLDPE, and the outer layer is made of low-density polyethylene LDPE and linear low-density polyethylene LLDPE; the production process comprises the steps of mixing feeding, extrusion, film blowing, shaping, traction cutting and the like, and the film can improve the high barrier property, high air tightness, anti-pollution, high heat-sealing strength and good heat-sealing performance.

[0005] However, with the large-scale manufacturing and consumption of plastic products in industry and life, the waste after use has brought serious environmental problems and caused great pollution to the environment, and the "white pollution" has occurred, and millions of tons of organic polymer waste are generated every year in the world. However, the biodegradability of the existing polyethylene film is very poor, and the antibacterial performance is also a performance requirement of the packaging film material, so it is urgent to develop a polyethylene composite packaging film with good mechanical properties and antibacterial properties. SUMMARY

[0006] The application aims to provide a high-transmittance biodegradable polyethylene film and application thereof.

[0007] To achieve the above object, the technical scheme adopted by the present application is:

[0008] The processing technology of the polyethylene composite packaging bag specifically comprises the following steps:

[0009] S1, batching: the surface layer raw material, the intermediate layer raw material and the inner layer raw material are weighed according to the formula, wherein:

[0010] The surface layer comprises the following components in parts by weight: low-density polyethylene 20-30 parts, linear low-density polyethylene 70-75 parts, antistatic agent 0.3-0.5 parts, slip agent 0.2-0.5 parts, opening agent 0.5-1.5 parts, color masterbatch 0-5 parts;

[0011] The intermediate layer comprises the following components in parts by weight: low-density polyethylene 70-80 parts, polybutylene adipate terephthalate 25-35 parts;

[0012] The inner layer comprises the following components in parts by weight: linear low-density polyethylene 4-8 parts, high-density polyethylene 25-45 parts, starch 20-30 parts, glycerol 5-10 parts, talc 15-25 parts, sodium polyacrylate 4-6 parts and appropriate amount of water;

[0013] S2, preparing a blown film body: the surface layer raw material and the intermediate layer raw material are placed in a co-extrusion blown film machine to be melted into melts respectively, the surface layer melt temperature is 200-220℃, the intermediate layer melt temperature is 240-260℃, then blown, cooled, and drawn to be shaped to obtain a blown film body;

[0014] S3, laminating the inner layer by coating: the inner layer raw material is mixed and kneaded in an internal mixer at a kneading temperature of 120-150℃, then the sheet is opened and sent to a coating machine, the melt temperature is 160-180℃, extrusion coating is performed on the inner surface of the blown film body, BPTCA-N alkaline solution is sprayed while hot, then cooled, rolled, and the surface layer is subjected to corona treatment, thereby obtaining a polyethylene composite packaging film, the thickness ratio of the inner layer, the intermediate layer and the surface layer is 1:3-4:0.8-1.2;

[0015] S4, winding, slitting and bag making.

[0016] Preferably, the antistatic agent in the surface layer is antistatic agent SP or antistatic agent 609.

[0017] Preferably, the slip agent in the surface layer is erucamide or oleamide.

[0018] Preferably, the opening agent in the surface layer is silica powder with a particle size of 4-10μm.

[0019] Preferably, the concentration of the BPTCA-N alkaline solution is 15 g / L to 30 g / L, and the spraying amount is 0.8 g / m². 2 ~1.5g / m 2 .

[0020] Preferably, the linear low-density polyethylene in the inner layer has a density of 0.915 g / cm³. 3 ~0.920g / cm 3 The melt flow index is 0.9 g / 10 min to 1.1 g / 10 min, and the density of the high-density polyethylene in the inner layer is 0.955 g / cm³. 3 ~0.965g / cm 3 The melt index is 0.8 g / 10 min to 1.2 g / 10 min.

[0021] Preferably, the low-density polyethylene in the intermediate layer has a density of 0.920 g / cm³. 3 ~0.925g / cm 3 The melt index is 1.8 g / 10 min to 2.0 g / 10 min; the melt index of poly(butylene adipate) / terephthalate in the intermediate layer is 2.3 g / 10 min to 2.8 g / 10 min.

[0022] Preferably, the low-density polyethylene in the surface layer has a density of 0.923 g / cm³. 3 ~0.926g / cm 3 The melt flow index is 0.5 g / 10 min to 0.8 g / 10 min; the density of the linear low-density polyethylene in the surface layer is 0.915 g / cm³. 3 ~0.920g / cm 3 The melt index is 0.9 g / 10 min to 1.1 g / 10 min.

[0023] Preferably, the roller pressing pressure in step S3 is 6MPa to 8MPa.

[0024] The present invention also provides a polyethylene composite packaging bag manufactured using the above-described processing technology.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention adds an appropriate amount of poly(butylene adipate / terephthalate) to the intermediate layer raw material and plasticized starch to the inner layer, thereby reducing the demand for petroleum industrial products, meeting the market demand for biodegradable plastics, promoting the sustainable development of the industry, and producing a composite film with good mechanical properties and excellent antibacterial activity.

[0027] This invention incorporates glycerol, sodium polyacrylate, talc, starch, and linear low-density polyethylene (LDPE) and high-density polyethylene (HDPE) into the inner layer. This reduces the amount of polyethylene used and utilizes specific amounts of LPE and HDPE to achieve an anti-adhesion effect on the inner surface of the film. Furthermore, the inner layer raw materials are first mixed in a mixer and then sheeted. High temperature gelatinizes the starch, and then, with the synergistic plasticizing effect of appropriate amounts of glycerol and sodium polyacrylate, the gelled starch is melted again at high temperature in a coating machine to form plasticized starch, which disperses with the LPE and HDPE to ensure mechanical requirements are met. Additionally, the sprayed BPTCA-N alkaline solution binds to the inner layer surface through electrostatic attraction with the anionic groups of sodium polyacrylate, thereby endowing the film with excellent photoinduced antibacterial activity. Detailed Implementation

[0028] Example 1

[0029] This embodiment provides a polyethylene composite packaging bag, which is made by cutting and packaging a polyethylene composite packaging film. The polyethylene composite packaging film includes an antibacterial coating, an inner layer, an intermediate layer, and a surface layer. The intermediate layer and the surface layer are co-extruded and blown to form a blown film. The inner layer is laminated onto the inner surface of the blown film (i.e., the side of the intermediate layer away from the surface layer). The antibacterial coating is a BPTCA-N antibacterial coating that is sprayed and cured on the surface of the inner layer. The thickness ratio of the inner layer, intermediate layer, and surface layer is 1:3.5:1.2.

[0030] The processing technology of the polyethylene composite packaging film in this embodiment specifically includes the following steps:

[0031] S1. Ingredients: Weigh the surface layer, middle layer, and inner layer ingredients according to the formula. The surface layer includes the following components by weight: density 0.925 g / cm³. 3 25 parts of low-density polyethylene with a melt flow index of 0.8 g / 10 min and a density of 0.918 g / cm³. 3 The mixture comprises 75 parts of linear low-density polyethylene with a melt index of 1.0 g / 10 min, 0.4 parts of antistatic agent SP, 0.35 parts of erucamide, and 1 part of silica powder with a particle size of 4 μm to 10 μm. The intermediate layer consists of the following components in parts by weight: density 0.923 g / cm³. 3 The inner layer comprises 75 parts of low-density polyethylene with a melt index of 1.8 g / 10 min and 30 parts of polybutylene adipate terephthalate (PBAT) with a melt index of 2.5 g / 10 min, provided by Juyou Chemical. The inner layer consists of the following components in parts by weight: density 0.915 g / cm³. 3 Six parts of linear low-density polyethylene with a melt flow index of 1.1 g / 10 min and a density of 0.960 g / cm³. 3 40 parts of high-density polyethylene with a melt flow index of 0.8 g / 10 min and a density of 1.5 g / cm³3 corn starch 20 parts, glycerin 5 parts, talc 15 parts, sodium polyacrylate 5 parts and appropriate amount of water.

[0032] S2, preparing the blown film body: placing the surface layer raw material and the intermediate layer raw material in a co-extrusion blown film machine to melt into melt respectively, the surface layer melt temperature is 200℃, the intermediate layer melt temperature is 260℃, then blowing, cooling, and drawing to form the blown film body.

[0033] S3, laminating the inner layer: mixing and kneading the inner layer raw material in the internal mixer, the kneading temperature is 125℃, then opening the sheet and feeding into the film laminating machine, the melt temperature is 180℃, extruding and coating on the inner surface of the blown film body, spraying the BPTCA-N alkaline solution with a concentration of 15g / L while hot, the spraying amount is 1.5g / m 2 , then cooling, 6MPa rolling, and then corona treating the surface layer, the corona value is 40-42 dyne, thus obtaining the polyethylene composite packaging film.

[0034] S4, winding, slitting, and bag making.

[0035] Example 2

[0036] The polyethylene composite packaging bag is made by slitting the polyethylene composite packaging film. The polyethylene composite packaging film comprises an antibacterial coating layer, an inner layer, an intermediate layer, and a surface layer, the intermediate layer and the surface layer are co-extruded and blown to form a blown film body, the inner layer is laminated on the inner surface of the blown film body (i.e. the side of the intermediate layer away from the surface layer), the antibacterial coating layer is the BPTCA-N antibacterial coating layer sprayed and solidified on the surface of the inner layer, and the thickness ratio of the inner layer, the intermediate layer, and the surface layer is 1:4:1.1.

[0037] The processing technology of the polyethylene composite packaging film of the example comprises the following steps:

[0038] S1, batching: weighing the surface layer raw material, the intermediate layer raw material, and the inner layer raw material according to the formula, wherein: the surface layer comprises the following components in parts by weight: low density polyethylene with a density of 0.926g / cm 3 , melt index of 0.6g / 10min 20 parts, talc 15 parts, sodium polyacrylate 5 parts and appropriate amount of water. 3 , linear low density polyethylene with a density of 0.915g / cm 3low density polyethylene with melt index of 1.8 g / 10 min 80 parts, polybutylene adipate-co-terephthalate (PBAT) with melt index of 2.3 g / 10 min 25 parts provided by Poly Union Chemical Industry Co., Ltd. The inner layer comprises the following components in parts by weight: corn starch 25 parts, glycerol 10 parts, talc 20 parts, sodium polyacrylate 4 parts, and appropriate amount of water. 3 linear low density polyethylene with melt index of 0.9 g / 10 min 4 parts, and 3 high density polyethylene with melt index of 1.0 g / 10 min 25 parts, and 3 density 1.38 g / cm

[0039] S2, preparing a blown film body: placing the surface layer raw material and the middle layer raw material into a co-extrusion blown film machine to melt into a melt respectively, the surface layer melt temperature is 220℃, the middle layer melt temperature is 240℃, then blowing, cooling, and drawing to form a blown film body.

[0040] S3, laminating the inner layer: mixing the inner layer raw material in an internal mixer, the mixing temperature is 140℃, then opening the sheet and feeding into a film laminating machine, the melt temperature is 160℃, extruding and coating on the inner surface of the blown film body, while hot spraying a BPTCA-N alkaline solution with a concentration of 30 g / L, the spraying amount is 1 g / m 2 , then cooling, rolling at 8 MPa, and then corona treating the surface layer, the corona value is 40-42 dyne, to obtain a polyethylene composite packaging film.

[0041] S4, winding, slitting, and bag making.

[0042] Example 3

[0043] The present example provides a polyethylene composite packaging bag made by slitting a polyethylene composite packaging film. The polyethylene composite packaging film comprises an antibacterial coating layer, an inner layer, a middle layer, and a surface layer, the middle layer and the surface layer are co-extruded to form a blown film body, the inner layer is laminated on the inner surface of the blown film body (i.e. the side of the middle layer away from the surface layer), the antibacterial coating layer is a BPTCA-N antibacterial coating layer sprayed and solidified on the surface of the inner layer, and the thickness ratio of the inner layer, the middle layer, and the surface layer is 1:3:0.8.

[0044] The processing technology of the polyethylene composite packaging film of the present example specifically comprises the following steps:

[0045] S1, batching: weighing the surface layer raw material, the middle layer raw material, and the inner layer raw material according to the formula, wherein: the surface layer comprises the following components in parts by weight: low density polyethylene with density of 0.923 g / cm 3 linear low density polyethylene with melt index of 0.5 g / 10 min 30 parts, and 3linear low density polyethylene with a melt index of 1.1 g / 10 min 70 parts, antistatic agent SP 0.5 part, erucic acid amide 0.2 part, silica powder with a particle size of 4 μm to 10 μm 1.2 parts, color master 2 parts. The intermediate layer comprises the following components in parts by weight: linear low density polyethylene with a density of 0.920 g / cm 3 low density polyethylene with a melt index of 2.0 g / 10 min 70 parts, polybutylene adipate-co-terephthalate PBAT with a melt index of 2.8 g / 10 min provided by Polyone Chemical Industry 35 parts. The inner layer comprises the following components in parts by weight: linear low density polyethylene with a density of 0.918 g / cm 3 linear low density polyethylene with a melt index of 0.9 g / 10 min 8 parts, linear low density polyethylene with a density of 0.965 g / cm 3 high density polyethylene with a melt index of 1.2 g / 10 min 45 parts, high density polyethylene with a density of 1.45 g / cm 3 corn starch 30 parts, glycerol 10 parts, talc 25 parts, sodium polyacrylate 6 parts, and an appropriate amount of water.

[0046] S2, preparing a blown film body: placing the surface layer raw material and the intermediate layer raw material into a co-extrusion blown film machine to melt into a melt respectively, the surface layer melt temperature is 210°C, the intermediate layer melt temperature is 260°C, then blowing, cooling, and drawing to form a blown film body.

[0047] S3, laminating the inner layer by coating: mixing and kneading the inner layer raw material in an internal mixer, the kneading temperature is 120°C, then opening the sheet and feeding into a coating machine, the melt temperature is 170°C, extruding and coating on the inner surface of the blown film body, while hot spraying a BPTCA-N alkaline solution with a concentration of 25 g / L, the spraying amount is 0.8 g / m 2 , then cooling, rolling at 6 MPa, and then carrying out corona treatment on the surface layer, the corona value is 40-42 dyne, to obtain a polyethylene composite packaging film.

[0048] S4, winding, slitting, and bag making.

[0049] Comparative Example 1

[0050] This comparative example provides a polyethylene composite packaging film, which is different from the above-mentioned Example 1 only in that the inner layer contains high density polyethylene in an amount of only 20 parts.

[0051] Comparative Example 2

[0052] This comparative example provides a polyethylene composite packaging film, which is different from the above-mentioned Example 1 only in that glycerol is not added to the inner layer raw material.

[0053] Comparative Example 3

[0054] This comparative example provides a polyethylene composite packaging film, which is different from the above-mentioned Example 1 only in that sodium polyacrylate is not added to the inner layer raw material.

[0055] The polyethylene composite packaging films prepared in the above Examples 1-3 and Comparative Examples 1-3, respectively, were subjected to tensile strength, elongation at break, impact strength, light transmittance, antibacterial rate and anti-blocking comparison tests, and the test results are shown in Table 1.

[0056] In the table, the tensile strength and elongation at break were tested according to GB / T13022-1991 "Test method for tensile properties of plastic films", the impact strength was tested according to A method in GB9639 / T-2008 "Free falling dart tester for plastic films", and the light transmittance was tested according to GB / T2410-2008 "Determination of light transmittance and haze of transparent plastics".

[0057] The bacteria used for the antibacterial rate test were Staphylococcus aureus and Escherichia coli. Two pieces of packaging film with a size of 3.5 cm x 3.5 cm were sterilized at 121°C for 15 min, then placed in a sterilized culture medium, 300 μL of 10 5 CFU / mL bacterial solution was added on the packaging film, and irradiated under ultraviolet light (365 nm) for 60 min. The irradiated packaging film was taken out and immersed in 30 mL of sterile PBS buffer solution, and uniformly oscillated for 3 min. After oscillation, 100 μL was taken out and diluted three times in succession, and dropped onto four areas of sterile culture medium, respectively. Then the culture medium was placed in a 37°C constant temperature incubator for a certain period of time, and then taken out to calculate the antibacterial rate.

[0058] In the anti-blocking test, two film samples each with a size of 100 mm x 200 mm were closely contacted with their inner surfaces contacting each other, and then a load of 1 kg was applied to an area of 80 mm x 80 mm at 60°C for 72 hours to compress and contact them. Thereafter, one end of them was clamped to the upper load sensor of a tensile tester, while a PTFE-coated brass rod was inserted between the uncompressed parts of the film samples, and the brass rod itself was connected to a metal frame which was mounted on the lower clamp of the tensile tester. When the lower clamp of the tensile tester was lowered, the brass rod would separate the 80 mm x 80 mm compressed parts of the film samples from each other, and the average force applied by pulling the brass rod downward was the force required to separate the two layers of film or the blocking force of the film.

[0059] Table 1: Experimental data table of Examples 1-3 and Comparative Examples 2-3 of the present application

[0060]

[0061] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A high-transparency biodegradable polyethylene film, characterized in that: The polyethylene film comprises an antibacterial coating, an inner layer, an intermediate layer and a surface layer, the inner layer is laminated on the side of the intermediate layer away from the surface layer, the antibacterial coating is a BPTCA-N antibacterial coating sprayed and solidified on the surface of the inner layer, and the antibacterial coating is sprayed on the surface of the inner layer with a BPTCA-N alkaline solution while hot; The inner layer comprises the following components in parts by weight: linear low density polyethylene 4-8 parts, high density polyethylene 25-45 parts, starch 20-30 parts, glycerol 5-10 parts, talc 15-25 parts, sodium polyacrylate 4-6 parts and appropriate amount of water; The surface layer comprises the following components in parts by weight: low density polyethylene 20-30 parts, linear low density polyethylene 70-75 parts, antistatic agent 0.3-0.5 parts, slip agent 0.2-0.5 parts, opening agent 0.5-1.5 parts, color masterbatch 0-5 parts; The intermediate layer comprises the following components in parts by weight: low density polyethylene 70-80 parts, polybutylene adipate terephthalate 25-35 parts; The intermediate layer and the surface layer are co-extrusion blown into a blown film body, the surface layer melt temperature is 200-220℃, and the intermediate layer melt temperature is 240-260℃; The laminated inner layer is specifically prepared as follows: the inner layer raw materials are mixed and kneaded in a kneader, the kneading temperature is 120-150℃, then the sheet is sent into a laminating machine, starch is gelatinized by high temperature, and the gelatinized starch is melted into plasticized starch again by the synergistic plasticizing effect of glycerol and sodium polyacrylate, the melt temperature is 160-180℃, the plasticized starch is extrusion coated on the inner surface of the blown film body, BPTCA-N alkaline solution is sprayed while hot, then the surface layer is subjected to corona treatment after cooling and rolling, and the polyethylene film is obtained; The thickness ratio of the inner layer, the intermediate layer and the surface layer is 1:3-4:0.8-1.

2.

2. The high-transparency biodegradable polyethylene film according to claim 1, characterized by: The corona value of the surface layer is 40-42 dynes.

3. The high-transparency biodegradable polyethylene film according to claim 1, characterized by: the density of the low density polyethylene in the skin layer is 0.923 g / cm 3 ~ 0.926 g / cm 3 , and the melt index is 0.5 g / 10 min ~ 0.8 g / 10 min; the density of the linear low density polyethylene in the skin layer is 0.915 g / cm 3 ~ 0.920 g / cm 3 , and the melt index is 0.9 g / 10 min ~ 1.1 g / 10 min.

4. The high-transparency biodegradable polyethylene film according to claim 1, characterized by: The low density polyethylene in the intermediate layer has a density of 0.920 g / cm 3 ~ 0.925 g / cm 3 and a melt index of 1.8 g / 10 min to 2.0 g / 10 min; the polybutylene adipate terephthalate in the intermediate layer has a melt index of 2.3 g / 10 min to 2.8 g / 10 min.

5. The high-transparency biodegradable polyethylene film according to claim 1, characterized by: density of the linear low density polyethylene in the inner layer is 0.915 g / cm 3 ~ 0.920 g / cm 3 density of the high density polyethylene in the inner layer is 0.955 g / cm 3 ~ 0.965 g / cm 3 melt index is 0.8 g / 10 min ~ 1.2 g / 10 min.

6. The high-transparency biodegradable polyethylene film according to claim 1, characterized by: The concentration of the BPTCA-N alkaline solution is 15g / L-30g / L, and the spraying amount is 0.8g / m 2 ~1.5g / m 2 .

7. Use of the high-transmittance biodegradable polyethylene film according to any one of claims 1 to 6 in the preparation of a polyethylene composite packaging bag.

Images