EVA / polyolefin film and preparation method thereof

Abstract

The invention provides an EVA / polyolefin film and a preparation method thereof, and relates to the technical field of polyolefin films. The EVA / polyolefin film comprises a surface layer and a core layer, the surface layer comprises EVA and magnetic master batch, and the core layer comprises polyolefin; and the magnetic master batch comprises Fe3O4 and EVA (Ethylene Vinyl Acetate). The magnetic master batch is added into the EVA layer, so that polar groups on EVA are combined with magnetic particles, and the magnetic particles are induced to move through an external magnetic field, so that non-polar chain segments of the EVA material at the interface of the EVA and the polyolefin material are aggregated, and the acting force at the interface of the EVA and the polyolefin material is enhanced.

Description

Technical Field

[0001] This invention relates to the field of polyolefin film technology, and more particularly to an EVA / polyolefin film and its preparation method. Background Technology

[0002] EVA / polyolefin film is a high-performance film made by combining EVA and polyolefin. The adhesion between EVA and polyolefin materials is a processing challenge for EVA / polyolefin film products. This is mainly because EVA material has polar segments, while polyolefin material only has non-polar segments, making it difficult to prepare EVA / polyolefin films with high VA content. Summary of the Invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes an EVA / polyolefin film and its preparation method.

[0004] The present invention proposes an EVA / polyolefin film, comprising a surface layer and a core layer, wherein the surface layer comprises EVA and a magnetic masterbatch, and the core layer comprises polyolefin; the magnetic masterbatch comprises Fe3O4 and EVA.

[0005] Preferably, the mass ratio of Fe3O4 to EVA in the magnetic masterbatch is (2-3):(7-8).

[0006] Preferably, the preparation of the magnetic masterbatch includes: uniformly mixing Fe3O4 and EVA; the mixing temperature is 180-200℃ and the mixing speed is 100-120 rpm.

[0007] By controlling the temperature and speed of the mixing process and repeatedly mixing, the dispersion effect of Fe3O4 in EVA materials can be improved.

[0008] Preferably, the mass of the magnetic masterbatch is 0.1%-5% of the total mass of the surface raw materials.

[0009] Preferably, the thickness ratio of the surface layer to the core layer is (15-25):(75-85).

[0010] Preferably, the VA content in the EVA is 30%-40%.

[0011] Preferably, the polyolefin is selected from one or more of polyethylene and polypropylene.

[0012] This invention also proposes a method for preparing EVA / polyolefin films, comprising the following steps:

[0013] S1. Mix the raw materials of the surface layer and the core layer evenly and extrude them to obtain the surface layer melt and the core layer melt;

[0014] S2. The surface melt and core melt are cast through a die, cast into sheets, biaxially stretched, and cooled to obtain an EVA / polyolefin film.

[0015] Preferably, in S1, the extrusion temperature is 210-250℃.

[0016] Preferably, in S2, a magnetic chuck is mounted above the mold head.

[0017] Preferably, in step S2, when the surface melt passes through the die head, the magnetic chuck above the die head magnetically induces the magnetic masterbatch in the surface melt to move.

[0018] By controlling the magnetic force in the magnetic chuck to induce the movement of the magnetic masterbatch, the bonding between the surface layer and the core layer is enhanced.

[0019] More preferably, the magnetic field strength of the magnetic chuck is 500-10000GS.

[0020] Preferably, in S2, the bidirectional tension includes longitudinal tension and transverse tension; the longitudinal tension has a tension ratio of 3-7; and the transverse tension has a tension ratio of 6-10.

[0021] More preferably, the longitudinal stretching temperature is 110-130°C, and the transverse stretching temperature is 150-165°C.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention prepares a magnetic masterbatch by using magnetic nanoparticles, and adds the magnetic masterbatch to an EVA layer. This allows the polar groups on the EVA to combine with the magnetic particles. By inducing the movement of the magnetic particles through an external magnetic field, the non-polar segments of the EVA material at the interface between the EVA and polyolefin materials are aggregated, thereby enhancing the effect at the interface between the EVA and polyolefin materials. The technical solution of this invention can prepare EVA / polyolefin films with high VA content through unilateral enhancement.

[0024] This invention incorporates a magnetic chuck at the die head position. The chuck is an electrically driven magnetic chuck, whose magnetic field strength can be adjusted by controlling the current, creating a directional magnetic field at the die head position. Magnetic particles are used to induce the movement of the VA segment within the EVA material, thereby enhancing the composite strength of the EVA material with the polyolefin material. Detailed Implementation

[0025] The technical solution of the present invention will be described in detail through specific embodiments.

[0026] Unless otherwise specified, all materials and reagents used in the following examples and comparative examples are commercially available.

[0027] Example 1

[0028] An EVA / polyolefin film includes a surface layer and a core layer, the surface layer having a thickness of 50 μm and the core layer having a thickness of 200 μm; wherein the surface layer comprises EVA and magnetic masterbatch, and the core layer is polypropylene; wherein the mass of the magnetic masterbatch is 0.1% of the total mass of the raw materials in the surface layer;

[0029] The preparation of the magnetic masterbatch includes mixing Fe3O4 and EVA in a mass ratio of 3:7 until homogeneous; the mixing temperature is 190℃ and the mixing speed is 120rpm.

[0030] A method for preparing an EVA / polyolefin film includes the following steps:

[0031] S1. Mix the raw materials of the surface layer and the core layer evenly, and extrude them at 230℃ to obtain the surface layer melt and the core layer melt;

[0032] S2. The surface melt and core melt are cast through a die head. A magnetic chuck is installed above the die head. When the surface melt passes through the die head, the magnetic chuck above the die head magnetically induces the magnetic masterbatch in the surface melt to move, enhancing the bonding between the surface and core layers. Cast sheet, biaxially stretched: the longitudinal stretching ratio is 5, the transverse stretching ratio is 8, the longitudinal stretching temperature is 120℃, and the transverse stretching temperature is 160℃. Cooling yields an EVA / polyolefin film; the VA content in the EVA is 38%; the magnetic field strength of the magnetic chuck is 2000GS.

[0033] Example 2

[0034] An EVA / polyolefin film includes a surface layer and a core layer, the surface layer having a thickness of 50 μm and the core layer having a thickness of 200 μm; wherein the surface layer comprises EVA and magnetic masterbatch, and the core layer is polypropylene; wherein the mass of the magnetic masterbatch is 0.5% of the total mass of the raw materials in the surface layer;

[0035] The preparation of the magnetic masterbatch includes mixing Fe3O4 and EVA in a mass ratio of 3:7 until homogeneous; the mixing temperature is 190℃ and the mixing speed is 120rpm.

[0036] A method for preparing an EVA / polyolefin film includes the following steps:

[0037] S1. Mix the raw materials of the surface layer and the core layer evenly, and extrude them at 230℃ to obtain the surface layer melt and the core layer melt;

[0038] S2. The surface melt and core melt are cast through a die head. A magnetic chuck is installed above the die head. When the surface melt passes through the die head, the magnetic chuck above the die head magnetically induces the magnetic masterbatch in the surface melt to move, enhancing the bonding between the surface and core layers. Cast sheet, biaxially stretched: the longitudinal stretching ratio is 5, the transverse stretching ratio is 8, the longitudinal stretching temperature is 120℃, and the transverse stretching temperature is 160℃. Cooling yields an EVA / polyolefin film; the VA content in the EVA is 38%; the magnetic field strength of the magnetic chuck is 2000GS.

[0039] Example 3

[0040] An EVA / polyolefin film includes a surface layer and a core layer, the surface layer having a thickness of 50 μm and the core layer having a thickness of 200 μm; wherein the surface layer comprises EVA and magnetic masterbatch, and the core layer is polypropylene; wherein the mass of the magnetic masterbatch is 1% of the total mass of the raw materials in the surface layer;

[0041] The preparation of the magnetic masterbatch includes mixing Fe3O4 and EVA in a mass ratio of 3:7 until homogeneous; the mixing temperature is 190℃ and the mixing speed is 120rpm.

[0042] A method for preparing an EVA / polyolefin film includes the following steps:

[0043] S1. Mix the raw materials of the surface layer and the core layer evenly, and extrude them at 230℃ to obtain the surface layer melt and the core layer melt;

[0044] S2. The surface melt and core melt are cast through a die head. A magnetic chuck is installed above the die head. When the surface melt passes through the die head, the magnetic chuck above the die head magnetically induces the magnetic masterbatch in the surface melt to move, enhancing the bonding between the surface and core layers. Cast sheet, biaxially stretched: the longitudinal stretching ratio is 5, the transverse stretching ratio is 8, the longitudinal stretching temperature is 120℃, and the transverse stretching temperature is 160℃. Cooling yields an EVA / polyolefin film; the VA content in the EVA is 38%; the magnetic field strength of the magnetic chuck is 2000GS.

[0045] Example 4

[0046] An EVA / polyolefin film includes a surface layer and a core layer, the surface layer having a thickness of 50 μm and the core layer having a thickness of 200 μm; wherein the surface layer comprises EVA and magnetic masterbatch, and the core layer is polypropylene; wherein the mass of the magnetic masterbatch is 5% of the total mass of the raw materials in the surface layer;

[0047] The preparation of the magnetic masterbatch includes mixing Fe3O4 and EVA in a mass ratio of 3:7 until homogeneous; the mixing temperature is 190℃ and the mixing speed is 120rpm.

[0048] A method for preparing an EVA / polyolefin film includes the following steps:

[0049] S1. Mix the raw materials of the surface layer and the core layer evenly, and extrude them at 230℃ to obtain the surface layer melt and the core layer melt;

[0050] S2. The surface melt and core melt are cast through a die head. A magnetic chuck is installed above the die head. When the surface melt passes through the die head, the magnetic chuck above the die head magnetically induces the magnetic masterbatch in the surface melt to move, enhancing the bonding between the surface and core layers. Cast sheet, biaxially stretched: the longitudinal stretching ratio is 5, the transverse stretching ratio is 8, the longitudinal stretching temperature is 120℃, and the transverse stretching temperature is 160℃. Cooling yields an EVA / polyolefin film; the VA content in the EVA is 38%; the magnetic field strength of the magnetic chuck is 2000GS.

[0051] Example 5

[0052] An EVA / polyolefin film includes a surface layer and a core layer, the surface layer having a thickness of 50 μm and the core layer having a thickness of 200 μm; wherein the surface layer comprises EVA and magnetic masterbatch, and the core layer is polypropylene; wherein the mass of the magnetic masterbatch is 1% of the total mass of the raw materials in the surface layer;

[0053] The preparation of the magnetic masterbatch includes mixing Fe3O4 and EVA in a mass ratio of 3:7 until homogeneous; the mixing temperature is 190℃ and the mixing speed is 120rpm.

[0054] A method for preparing an EVA / polyolefin film includes the following steps:

[0055] S1. Mix the raw materials of the surface layer and the core layer evenly, and extrude them at 230℃ to obtain the surface layer melt and the core layer melt;

[0056] S2. The surface melt and core melt are cast through a die head. A magnetic chuck is installed above the die head. When the surface melt passes through the die head, the magnetic chuck above the die head magnetically induces the magnetic masterbatch in the surface melt to move, enhancing the bonding between the surface and core layers. Cast sheet, biaxially stretched: the longitudinal stretching ratio is 5, the transverse stretching ratio is 8, the longitudinal stretching temperature is 120℃, and the transverse stretching temperature is 160℃. Cooling yields an EVA / polyolefin film; the VA content in the EVA is 38%; the magnetic field strength of the magnetic chuck is 500GS.

[0057] Example 6

[0058] An EVA / polyolefin film includes a surface layer and a core layer, the surface layer having a thickness of 50 μm and the core layer having a thickness of 200 μm; wherein the surface layer comprises EVA and magnetic masterbatch, and the core layer is polypropylene; wherein the mass of the magnetic masterbatch is 1% of the total mass of the raw materials in the surface layer;

[0059] The preparation of the magnetic masterbatch includes mixing Fe3O4 and EVA in a mass ratio of 3:7 until homogeneous; the mixing temperature is 190℃ and the mixing speed is 120rpm.

[0060] A method for preparing an EVA / polyolefin film includes the following steps:

[0061] S1. Mix the raw materials of the surface layer and the core layer evenly, and extrude them at 230℃ to obtain the surface layer melt and the core layer melt;

[0062] S2. The surface melt and core melt are cast through a die head. A magnetic chuck is installed above the die head. When the surface melt passes through the die head, the magnetic chuck above the die head magnetically induces the magnetic masterbatch in the surface melt to move, enhancing the bonding between the surface and core layers. Cast sheet, biaxially stretched: the longitudinal stretching ratio is 5, the transverse stretching ratio is 8, the longitudinal stretching temperature is 120℃, and the transverse stretching temperature is 160℃. Cooling yields an EVA / polyolefin film; the VA content in the EVA is 38%; the magnetic field strength of the magnetic chuck is 1000GS.

[0063] Example 7

[0064] An EVA / polyolefin film includes a surface layer and a core layer, the surface layer having a thickness of 50 μm and the core layer having a thickness of 200 μm; wherein the surface layer comprises EVA and magnetic masterbatch, and the core layer is polypropylene; wherein the mass of the magnetic masterbatch is 1% of the total mass of the raw materials in the surface layer;

[0065] The preparation of the magnetic masterbatch includes mixing Fe3O4 and EVA in a mass ratio of 3:7 until homogeneous; the mixing temperature is 190℃ and the mixing speed is 120rpm.

[0066] A method for preparing an EVA / polyolefin film includes the following steps:

[0067] S1. Mix the raw materials of the surface layer and the core layer evenly, and extrude them at 230℃ to obtain the surface layer melt and the core layer melt;

[0068] S2. The surface melt and core melt are cast through a die head. A magnetic chuck is installed above the die head. When the surface melt passes through the die head, the magnetic chuck above the die head magnetically induces the magnetic masterbatch in the surface melt to move, enhancing the bonding between the surface and core layers. Cast sheet, biaxially stretched: the longitudinal stretching ratio is 5, the transverse stretching ratio is 8, the longitudinal stretching temperature is 120℃, and the transverse stretching temperature is 160℃. Cooling yields an EVA / polyolefin film; the VA content in the EVA is 38%; the magnetic field strength of the magnetic chuck is 5000GS.

[0069] Example 8

[0070] An EVA / polyolefin film includes a surface layer and a core layer, the surface layer having a thickness of 50 μm and the core layer having a thickness of 200 μm; wherein the surface layer comprises EVA and magnetic masterbatch, and the core layer is polypropylene; wherein the mass of the magnetic masterbatch is 1% of the total mass of the raw materials in the surface layer;

[0071] The preparation of the magnetic masterbatch includes mixing Fe3O4 and EVA in a mass ratio of 3:7 until homogeneous; the mixing temperature is 190℃ and the mixing speed is 120rpm.

[0072] A method for preparing an EVA / polyolefin film includes the following steps:

[0073] S1. Mix the raw materials of the surface layer and the core layer evenly, and extrude them at 230℃ to obtain the surface layer melt and the core layer melt;

[0074] S2. The surface melt and core melt are cast through a die head. A magnetic chuck is installed above the die head. When the surface melt passes through the die head, the magnetic chuck above the die head magnetically induces the magnetic masterbatch in the surface melt to move, enhancing the bonding between the surface and core layers. Cast sheet, biaxially stretched: the longitudinal stretching ratio is 5, the transverse stretching ratio is 8, the longitudinal stretching temperature is 120℃, and the transverse stretching temperature is 160℃. Cooling yields an EVA / polyolefin film; the VA content in the EVA is 38%; the magnetic field strength of the magnetic chuck is 10000GS.

[0075] Comparative Example 1

[0076] An EVA / polyolefin film includes a surface layer and a core layer, wherein the surface layer has a thickness of 50 μm and the core layer has a thickness of 200 μm; wherein the surface layer is EVA and the core layer is polypropylene;

[0077] A method for preparing an EVA / polyolefin film includes the following steps:

[0078] S1. Mix the raw materials of the surface layer and the core layer evenly, and extrude them at 230℃ to obtain the surface layer melt and the core layer melt;

[0079] S2. The surface melt and core melt are cast through a die head, which is equipped with a magnetic chuck with a magnetic field strength of 2000GS. The casting is then biaxially stretched: the longitudinal stretching ratio is 5, the transverse stretching ratio is 8, the longitudinal stretching temperature is 120℃, and the transverse stretching temperature is 160℃. After cooling, an EVA / polyolefin film is obtained; the VA content in the EVA is 38%.

[0080] Comparative Example 2

[0081] An EVA / polyolefin film includes a surface layer and a core layer, the surface layer having a thickness of 50 μm and the core layer having a thickness of 200 μm; wherein the surface layer comprises EVA and magnetic masterbatch, and the core layer is polypropylene; wherein the mass of the magnetic masterbatch is 1% of the total mass of the raw materials in the surface layer;

[0082] The preparation of the magnetic masterbatch includes mixing Fe3O4 and EVA in a mass ratio of 3:7 until homogeneous; the mixing temperature is 190℃ and the mixing speed is 120rpm.

[0083] A method for preparing an EVA / polyolefin film includes the following steps:

[0084] S1. Mix the raw materials of the surface layer and the core layer evenly, and extrude them at 230℃ to obtain the surface layer melt and the core layer melt;

[0085] S2. The surface melt and core melt are cast through a die, cast into a sheet, and then biaxially stretched: the longitudinal stretching ratio is 5, the transverse stretching ratio is 8, the longitudinal stretching temperature is 120℃, and the transverse stretching temperature is 160℃; after cooling, an EVA / polyolefin film is obtained; wherein the VA content in the EVA is 38%.

[0086] The percentage of the magnetic masterbatch mass to the total mass of the surface raw materials in Examples 1-8 and Comparative Examples 1-2, and the magnetic field strength of the magnetic chuck are shown in Table 1.

[0087] Table 1

[0088]

[0089] The tensile strength (test standard GB / T 27740-2011), elongation at break (test standard GB / T 27740-2011), composite strength (test standard GB / T 8808-1988), and light transmittance / haze (test standard GB / T 27740-2011) of the above EVA / polyolefin film were tested. The test results are shown in Table 2.

[0090] Table 2

[0091]

[0092] As shown in Table 2, the EVA / polyolefin film prepared by this invention exhibits high tensile strength, elongation at break, composite strength, and transmittance / haze. Examples 1-4 show that while the tensile strength and elongation at break of the EVA / polyolefin film slightly decrease with increasing magnetic masterbatch, the composite strength significantly increases. This demonstrates that the technical solution of this application can improve the bonding force between the surfaces of high-VA-content EVA materials and polyolefin materials, making it suitable for large-scale film manufacturing. Examples 5-8 show that the composite strength gradually increases with increasing magnetic field strength.

[0093] In summary, the EVA / polyolefin film provided by this invention has excellent mechanical properties and strong adhesion between EVA and the polyolefin surface.

[0094] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An EVA / polyolefin film, characterized in that, It includes a surface layer and a core layer, wherein the surface layer includes EVA and magnetic masterbatch, and the core layer includes polyolefin; the magnetic masterbatch includes Fe3O4 and EVA.

2. The EVA / polyolefin film according to claim 1, characterized in that, The mass ratio of Fe3O4 to EVA in the magnetic masterbatch is (2-3):(7-8).

3. The EVA / polyolefin film according to claim 1 or 2, characterized in that, The preparation of the magnetic masterbatch includes: uniformly mixing Fe3O4 and EVA; the mixing temperature is 180-200℃ and the mixing speed is 100-120 rpm.

4. The EVA / polyolefin film according to claim 1, characterized in that, The mass of the magnetic masterbatch is 0.1%-5% of the total mass of the surface raw materials.

5. The EVA / polyolefin film according to claim 1, characterized in that, The thickness ratio of the surface layer to the core layer is (15-25):(75-85); the VA content in the EVA is 30%-40%; the polyolefin is selected from one or more of polyethylene and polypropylene.

6. A method for preparing an EVA / polyolefin film according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Mix the raw materials of the surface layer and the core layer evenly and extrude them to obtain the surface layer melt and the core layer melt; S2. The surface melt and core melt are cast through a die, cast into sheets, biaxially stretched, and cooled to obtain an EVA / polyolefin film.

7. The preparation method according to claim 6, characterized in that, In S2, a magnetic chuck is installed above the mold head.

8. The preparation method according to claim 7, characterized in that, In S2, when the surface melt passes through the die head, the magnetic chuck above the die head magnetically induces the magnetic masterbatch in the surface melt to move; the magnetic field strength of the magnetic chuck is 500-10000GS.

9. The preparation method according to claim 6, characterized in that, In S1, the extrusion temperature is 210-250℃.

10. The preparation method according to claim 6, characterized in that, In S2, bidirectional tension includes longitudinal tension and transverse tension; the longitudinal tension has a tension ratio of 3-7; the transverse tension has a tension ratio of 6-10; the longitudinal tension temperature is 110-130℃, and the transverse tension temperature is 150-165℃.

Images