CN104772956B - A kind of light-weight packed film and preparation method thereof - Google Patents

Abstract

The invention discloses a lightweight packaging film and a preparation method thereof. The lightweight packaging film is a three-layer composite structure, which is divided into an outer film layer, a middle film layer and an inner film layer; the composition of the outer film layer is as follows: Polypropylene; the composition of the middle film layer is linear low density polyethylene and low density polyethylene; the composition of the inner film layer is metallocene linear low density polyethylene, low density polyethylene and polyolefin elastomer. The light-weight packaging film has excellent performance, simple production process, and no knife sticking during the heat-sealing process. It is especially suitable for high-speed FFS packaging. The production speed can be increased from the original 10/min to 40 packs/min, greatly improving Productivity.

Description

A kind of lightweight packaging film and preparation method thereof

technical field

The invention relates to the field of packaging films, in particular to a lightweight packaging film and a preparation method thereof.

Background technique

In recent years, the FFS three-layer co-extruded packaging film industry has developed vigorously, and various packaging films have emerged continuously. However, the existing light-weight packaging film used for packaging objects weighing less than 0.8 kg is easy to stick to the knife during the heat-sealing process. After a period of production, it needs to be shut down to clean the knife edge, which greatly reduces the production efficiency.

Therefore, the prior art still needs to be improved and developed.

Contents of the invention

In view of the above deficiencies in the prior art, the present invention provides a lightweight packaging film and a preparation method thereof. The lightweight packaging film is a three-layer co-extruded film suitable for packaging objects weighing less than 0.8 kg, aiming to solve the current Some packaging films tend to stick to the knife during the heat sealing process.

Technical scheme of the present invention is as follows:

A lightweight packaging film, wherein the lightweight packaging film is a three-layer composite structure, which is divided into an outer film layer, a middle film layer and an inner film layer;

The raw material composition of the outer film layer is polypropylene;

The raw material composition of the middle film layer is linear low-density polyethylene and low-density polyethylene;

The raw material composition of the inner film layer is metallocene linear low density polyethylene, low density polyethylene and polyolefin elastomer.

The light-weight packaging film, wherein, the raw material composition of the middle film layer is calculated in parts by mass, the content of linear low-density polyethylene is 70-80 parts, and the content of low-density polyethylene is 20-30 parts.

The lightweight packaging film, wherein, the raw material composition of the inner film layer is calculated in parts by mass, the content of metallocene linear low-density polyethylene is 40-60 parts, the content of low-density polyethylene is 10-30 parts and The content of the polyolefin elastomer is 20-40 parts.

The lightweight packaging film, wherein the polypropylene has a density of 0.900-0.910g/cm ³ and a melt index of 8g/10min.

The lightweight packaging film, wherein the density of the linear low-density polyethylene in the middle film layer is 0.918g/cm ³ , and the melt index is 2g/10min; the density of the low-density polyethylene in the middle film layer is 0.92g/cm ³ , the melt index is 4g/10min.

The lightweight packaging film, wherein the density of the metallocene linear low-density polyethylene in the inner film layer is 0.918g/cm ³ , and the melt index is 1g/10min; the density of the low-density polyethylene in the inner film layer is 0.92g/cm ³ , the melt index is 4g/10min; the density of the polyolefin elastomer in the inner film layer is 0.870g/cm ³ , and the melt index is 1g/10min.

The lightweight packaging film, wherein, the total thickness of the lightweight packaging film is 60 μm to 80 μm; the thickness of the outer film layer accounts for 28% to 35% of the total thickness; the thickness of the inner film layer accounts for 20% of the total thickness 40% to 50%; the balance is the thickness of the middle film layer.

A method for preparing a lightweight packaging film as described above, comprising the following steps:

Pour polypropylene into the screw extruder of the outer film layer and knead; after fully mixing linear low density polyethylene and low density polyethylene in proportion, pour it into the screw extruder of the middle film layer and knead; metallocene After linear low-density polyethylene, polyolefin elastomer and low-density polyethylene are fully mixed in proportion, they are poured into the screw extruder of the inner film layer for mixing;

The fluidized three-layer film raw material after kneading is simultaneously transported to the film head of the three-layer co-extrusion extruder to be melted and extruded, and kneaded to form a bubble embryo. Cooling and molding under the action of the ring.

The preparation method of the lightweight packaging film, wherein, the screw temperature of the outer film layer screw extruder is 180-190°C, and the head temperature is 185-200°C; the screw temperature of the middle film layer screw extruder is It is 155-165°C, and the head temperature is 185-200°C; the screw temperature of the inner film layer screw extruder is 155-165°C, and the head temperature is 185-200°C.

The preparation method of the lightweight packaging film, wherein the screw speeds of the outer film layer screw extruder, the middle film layer screw extruder and the inner film layer screw extruder are all 20-40r/min, The extrusion processing pressure is 25-35MPa.

Beneficial effects: the light-weight packaging film provided by the present invention is a three-layer co-extruded packaging film. Through the matching of different materials in each layer, the light-weight packaging film of the present invention has superior performance, simple production process, and no heat sealing process. There will be knife sticking, especially suitable for high-speed FFS packaging, the production speed can be increased from the original 10/min to 40 packs/min, which greatly improves the production efficiency. The lightweight packaging film is suitable for packaging objects weighing less than 0.8 kg, such as clothing accessories, Rifeng pipes, etc. Moreover, the production cost is low, the composite film is about 20,000/ton, while the light-weight packaging film of the present invention is about 10,000/ton.

Description of drawings

Fig. 1 is a schematic structural view of the lightweight packaging film of the present invention.

detailed description

The present invention provides a light-weight packaging film and a preparation method thereof. In order to make the purpose, technical solution and effect of the present invention clearer and clearer, the present invention will be further described in detail below. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

A kind of lightweight packaging film provided by the present invention, as shown in Figure 1, is formed by three-layer co-extrusion of an outer film layer 1, a middle film layer 2 and an inner film layer 3, and air cooling. Wherein, the composition of the outer film layer 1 is polypropylene (PP). The composition of middle film layer 2 is linear low density polyethylene (LLDPE) and low density polyethylene (LDPE), and the mass parts of LLDPE and LDPE are respectively 70～80 parts, 20～30 parts; The composition of inner film layer 3 The ingredients are metallocene linear low-density polyethylene (m-LLDPE), low-density polyethylene (LDPE) and polyolefin elastomer (POE), and the mass parts between m-LLDPE, LDPE and POE are 40-60 parts , 10-30 parts, 20-40 parts.

The total thickness of the lightweight packaging film is 60 μm to 80 μm, the thickness of the outer film layer accounts for 22% to 28% of the total thickness; the inner film layer is a heat seal layer, and its thickness accounts for 40% to 50% of the total thickness ; The balance is the thickness of the middle film layer.

The polypropylene used as the material of the outer film layer is because the density of polypropylene is the lowest among the five general-purpose plastics, so choosing polypropylene can achieve the light weight of the film, and it also has the advantages of heat resistance and corrosion resistance, which improves the The outer layer of the packaging film is resistant to heat and temperature, which solves the problem that the packaging film will stick to the knife during heat sealing. The middle film layer provides strength. The material is linear low density polyethylene, which has a high softening temperature and melting temperature. It has high tensile strength, high tear strength, environmental stress cracking resistance, low temperature resistance, heat resistance and heat resistance. The puncture performance is particularly superior, and it is resistant to chemical reagents, etc. Low-density polyethylene has good molding processability and is suitable for various molding processes of thermoplastic molding processing, and can be used to improve the processing stability of the middle film layer and the inner film layer. The material of the inner film layer reduces the heat sealing temperature, and the metallocene linear low density polyethylene is selected, which has excellent tensile strength, impact strength and puncture resistance. These excellent strength properties together with good drawing properties make it a general-purpose packaging film resin. Since the melt index of metallocene low-density polyethylene is relatively low, it is necessary to add polyolefin elastomer and low-density polyethylene to the inner film layer to improve the processing performance. Preferably, the metallocene linear low-density polyethylene containing an antiblocking agent and a slip agent can be selected, and its performance is more excellent. The content of the anti-blocking agent and the slipping agent is an appropriate amount, and the content of different manufacturers or different models will be different, so I will not repeat them and limit them here.

Preferably, among the materials of the outer film layer, the density of the polypropylene is 0.900-0.910 g/cm ³ (ISO1183), and the melt index MI is 8g/10min (ISO1133, 230°C/2.16kg).

In the material of the middle film layer, the density of the linear low-density polyethylene LLDPE is 0.918g/cm ³ (ASTMD-1928), and the melt index MI is 2g/10min (ASTM D-1238); the low-density polyethylene LDPE The density is 0.92g/cm ³ (ISO1183), and the melt index MI is 4g/10min (ISO1133, 230°C/2.16kg).

Among the materials of the inner film layer, the density of the metallocene linear low density polyethylene m-LLDPE is 0.918g/cm ³ , and the melt index MI is 1g/10min (ASTM D-1238); the low density polyethylene LDPE The density is 0.923g/cm ³ (ISO1183), and the melt index MI is 4g/10min (ISO1133, 230°C/2.16kg). The polyolefin elastomer POE has a density of 0.870 g/cm ³ (ASTM D-1505), and a melt index of 1 g/10 min (ASTM D-1238, 190° C./2.16 kg).

The present invention also provides a method for preparing the lightweight packaging film, which specifically includes the following steps:

S1. Preparation of outer film layer film: Pour polypropylene PP directly into the outer film layer screw extruder for mixing. Wherein, the screw temperature of the outer film layer screw extruder is 180-190°C, and the head temperature of the screw extruder is 185-200°C. The rotation speed of the screw is 20-40r/min, and the extrusion processing pressure is 25-35MPa.

S2. Preparation of middle layer film layer film: after fully mixing linear low density polyethylene LLDPE and low density polyethylene LDPE in proportion, pour into middle layer film layer screw extruder for mixing. Wherein, the screw temperature of the middle film layer screw extruder is 155-165°C, and the head temperature of the screw extruder is 185-200°C. The rotation speed of the screw is 20-40r/min, and the extrusion processing pressure is 25-35MPa.

S3. Preparation of the inner film layer film: After fully mixing metallocene linear low density polyethylene m-LLDPE, polyolefin elastomer POE and low density polyethylene LDPE in proportion, pour it into the inner film layer screw extruder to mix refining. Wherein, the screw temperature of the inner film layer screw extruder is 155-165°C, and the head temperature of the screw extruder is 185-200°C. The rotation speed of the screw is 20-40r/min, and the extrusion processing pressure is 25-35MPa.

S4. Extrusion molding and co-extrusion upper blowing cooling: the three-layer film raw materials in a fluid state after mixing are transported to the membrane head of the three-layer co-extrusion machine at the same time, and the three fluid raw materials are in the extrusion head. Co-melting and extruding, kneading to form a bubble embryo, through the traction of the upper traction rotary tractor, the film bubble is cooled and formed under the action of the cooling air ring. Finally, the lightweight packaging film is curled by a winding device.

The present invention will be further described below by specific examples.

Example 1

The lightweight packaging film is prepared according to the above process. In this embodiment, the total thickness of the lightweight packaging film is 60 μm, the thickness of the outer film layer is 13.2-16.8 μm, the thickness of the middle film layer is 13.2-22.8 μm, and the thickness of the inner film layer is 13.2-22.8 μm. The layer thickness of the film layer is 24-30 μm (because the thickness of the co-extruded film cannot be measured accurately, the values given in the examples are ranges). Wherein, the composition of the middle film layer is LLDPE and LDPE, and the mass parts are 75 parts and 25 parts respectively; the composition of the inner film layer is m-LLDPE, LDPE and POE, and the mass parts are 50 parts, 20 parts, and 30 parts. The main technical indicators of this embodiment are shown in Table 1.

Example 2

The lightweight packaging film is prepared according to the above process. In this embodiment, the total thickness of the lightweight packaging film is 80 μm, the thickness of the outer film layer is 17.6-22.4 μm, the thickness of the middle film layer is 17.6-30.4 μm, and the inner film layer is 17.6-30.4 μm. The thickness of the thin film layer is 32-40 μm. Wherein, the composition of the middle film layer is LLDPE and LDPE, and the mass parts are 75 parts and 25 parts respectively; the composition of the inner film layer is m-LLDPE, LDPE and POE, and the mass parts are 60 parts, 20 parts, and 20 parts.

The main technical indicators of this embodiment are shown in Table 1.

Example 3

The lightweight packaging film is prepared according to the above process. In this embodiment, the total thickness of the lightweight packaging film is 70 μm, the thickness of the outer film layer is 15.4-19.6 μm, the thickness of the middle film layer is 15.4-26.6 μm, and the thickness of the inner film layer is 15.4-26.6 μm. The thickness of the thin film layer is 28-35 μm. Wherein, the composition of middle layer film layer is LLDPE and LDPE, and mass parts are respectively 80 parts, 20 parts; The composition of inner layer film layer is m-LLDPE, LDPE and POE, and mass parts are respectively 60 parts, 20 parts, 20 parts.

The main technical indicators of this embodiment are shown in Table 1.

Example 4

The lightweight packaging film is prepared according to the above process. In this embodiment, the total thickness of the lightweight packaging film is 60 μm, the thickness of the outer film layer is 13.2-16.8 μm, the thickness of the middle film layer is 13.2-22.8 μm, and the thickness of the inner film layer is 13.2-22.8 μm. The thickness of the thin film layer is 24-30 μm. Wherein, the composition of middle layer film layer is LLDPE and LDPE, and mass parts are respectively 70 parts, 30 parts; The composition of inner layer film layer is m-LLDPE, LDPE and POE, and mass parts are respectively 50 parts, 25 parts, 25 parts.

The main technical indicators of this embodiment are shown in Table 1.

Table 1 Performance test results of the packaging films of Examples 1 to 4

In summary, the lightweight packaging film provided by the present invention is a three-layer co-extruded packaging film. Through the matching of different materials in each layer, the lightweight packaging film of the present invention has superior performance, simple production process, and no heat sealing process. There will be knife sticking, especially suitable for high-speed FFS packaging, the production speed can be increased from the original 10/min to 40 packs/min, which greatly improves the production efficiency. The lightweight packaging film is suitable for packaging objects weighing less than 0.8 kg, such as clothing accessories, Rifeng pipes, etc. Moreover, the production cost is low, the composite film is about 20,000/ton, while the light-weight packaging film of the present invention is about 10,000/ton.

It should be understood that the application of the present invention is not limited to the above examples, and those skilled in the art can make improvements or transformations according to the above descriptions, and all these improvements and transformations should belong to the protection scope of the appended claims of the present invention.

Claims (4)

1. A lightweight packaging film, characterized in that the lightweight packaging film is a three-layer composite structure, which is divided into an outer film layer, a middle film layer and an inner film layer; The raw material composition of the outer film layer is polypropylene; The raw material composition of the middle film layer is linear low-density polyethylene and low-density polyethylene; The raw material composition of the inner film layer is metallocene linear low-density polyethylene, low-density polyethylene and polyolefin elastomer; The raw material composition of the middle film layer is calculated in parts by mass, the content of linear low-density polyethylene is 70-80 parts, and the content of low-density polyethylene is 20-30 parts; The raw material composition of the inner film layer is calculated in parts by mass. The content of metallocene linear low-density polyethylene is 40-60 parts, the content of low-density polyethylene is 10-30 parts and the content of polyolefin elastomer is 20-40 parts. share; The total thickness of the lightweight packaging film is 60 μm to 80 μm; the thickness of the outer film layer accounts for 28% to 35% of the total thickness; the thickness of the inner film layer accounts for 40% to 50% of the total thickness; the balance is the middle layer film layer thickness; The polypropylene has a density of 0.900-0.910g/cm ³ and a melt index of 8g/10min; The linear low-density polyethylene in the middle film layer has a density of 0.918g/cm ³ and a melt index of 2g/10min; the density of the low-density polyethylene in the middle film layer is 0.92g/cm ³ and a melt index of 4g/10min; The metallocene linear low density polyethylene in the inner film layer has a density of 0.918g/cm ³ and a melt index of 1g/10min; the density of low density polyethylene in the inner film layer is 0.92g/cm ³ and a melt index of 4g /10min; the density of the polyolefin elastomer in the inner film layer is 0.870g/cm ³ , and the melt index is 1g/10min. 2. a preparation method of lightweight packaging film as claimed in claim 1, is characterized in that, comprises the following steps: Pour polypropylene into the screw extruder of the outer film layer and knead; after fully mixing linear low density polyethylene and low density polyethylene in proportion, pour it into the screw extruder of the middle film layer and knead; metallocene After linear low-density polyethylene, polyolefin elastomer and low-density polyethylene are fully mixed in proportion, they are poured into the screw extruder of the inner film layer for mixing; The fluidized three-layer film raw material after kneading is simultaneously transported to the film head of the three-layer co-extrusion extruder to be melted and extruded, and kneaded to form a bubble embryo. Cooling and molding under the action of the ring. 3. The preparation method of lightweight packaging film according to claim 2, characterized in that, the temperature of the screw of the outer layer film layer screw extruder is 180-190°C, and the temperature of the machine head is 185-200°C; The screw temperature of the layer screw extruder is 155-165°C, and the head temperature is 185-200°C; the screw temperature of the inner film layer screw extruder is 155-165°C, and the head temperature is 185-200°C . 4. the preparation method of lightweight packaging film according to claim 2 is characterized in that, the rotating speed of the screw of outer layer film layer screw extruder, middle layer film layer screw extruder and inner layer film layer screw extruder Both are 20-40r/min, and the extrusion processing pressure is 25-35MPa.