Method for eliminating oriented crystallization of polyolefin-based film

Abstract

The invention relates to the technical field of polyolefin-based membranes, and provides a method for eliminating directional crystallization of a polyolefin-based membrane, which comprises the following steps: S1, photoinitiator pretreatment: mixing a photoinitiator and first solvent oil, heating and melting to obtain a premixed solution; s2, mixing the premixed solution with second solvent oil to obtain a mixed solution; s3, melting polyolefin resin, mixing the molten polyolefin resin with the mixed solution, extruding to form a film, and cross-linking to obtain a polyolefin base film; the first solvent oil and the second solvent oil respectively and independently comprise mineral oil. According to the technical scheme, the problem that the acupuncture strength of the polyolefin-based film is poor due to directional crystallization of the polyolefin-based film in the related technology is solved.

Description

Technical Field

[0001] The invention relates to the technical field of polyolefin-based films, and in particular to a method for eliminating directional crystallization of polyolefin-based films. Background Art

[0002] Polyolefin-based films, such as polyethylene (PE) films, are widely used in packaging, battery separators, electronic materials, etc. However, traditional polyolefin-based films often need to be stretched horizontally and vertically during the preparation process to enhance their physical properties. Although this step can significantly improve certain properties of the film, it also leads to directional crystallization in the horizontal and vertical directions inside the film. Uneven directional crystallization will make the film very easy to tear along the stretching direction when subjected to external forces, resulting in a decrease in the needle puncture strength of the film, which greatly limits its application range and lifespan.

[0003] In order to solve the above problems, the industry has been looking for new methods to improve the performance of polyolefin-based films, so as to eliminate the problem of directional crystallization of polyolefin-based films and improve the needle puncture strength of polyolefin-based films. Summary of the invention

[0004] The present invention provides a method for eliminating directional crystallization of a polyolefin base film, which solves the problem in the related art that the polyolefin base film has poor needle puncture strength due to the existence of directional crystallization.

[0005] The technical solution of the present invention is as follows: The present invention provides a method for eliminating directional crystallization of a polyolefin-based film, comprising the following steps: S1, photoinitiator pretreatment: mixing the photoinitiator and the first solvent oil, heating and melting, to obtain a premixed liquid; S2, mixing the premixed liquid with a second solvent oil to obtain a mixed liquid; S3, mixing the melted polyolefin resin with the mixed solution, extruding into a film, and cross-linking to obtain a polyolefin-based film; The first solvent oil and the second solvent oil each independently comprise mineral oil.

[0006] As a further technical solution, the thickness of the polyolefin-based film is 3-9 μm.

[0007] As a further technical solution, the photoinitiator includes one or more of 2-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 4-chlorobenzophenone, 4,4-bis(diethylamino)benzophenone, 2-ethylanthraquinone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and the like.

[0008] As a further technical solution, the photoinitiator is 2,4-diethylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide in a mass ratio of 1:9 to 9:1.

[0009] In the present invention, the photoinitiator is synergistically compounded with 2,4-diethylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, thereby further improving the needle puncture strength and heat resistance of the polyolefin-based film.

[0010] As a further technical solution, the photoinitiator is 2,4-diethylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide in a mass ratio of 5:1-5.

[0011] In the present invention, in the polyolefin-based film, the photoinitiator uses 2,4-diethylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide in a mass ratio of 5:1-5, which further improves the needle puncture strength and heat resistance of the polyolefin-based film.

[0012] As a further technical solution, the mass ratio of the first solvent oil and the second solvent oil to the polyolefin resin and the photoinitiator is 70-85:15-30:0.001-0.02; The mass ratio of the first solvent oil to the second solvent oil is 1:1-3; The weight average molecular weight of the polyolefin resin is 600,000 to 800,000.

[0013] As a further technical solution, in step S3, silicon dioxide is also added during the mixing; the mass ratio of silicon dioxide to polyolefin resin is 8-15:100.

[0014] As a further technical solution, the silicon dioxide is silicon dioxide modified by a modifier; the modifier includes acetamide phenyl sulfone.

[0015] In the present invention, silicon dioxide modified by acetamide phenyl sulfone is added to the polyolefin base film, so as to further improve the needle puncture strength and heat resistance of the polyolefin base film.

[0016] As a further technical solution, the modifier includes acetamide phenyl sulfone and a silane coupling agent in a mass ratio of 8:2-5.

[0017] As a further technical solution, the silane coupling agent includes one or both of dodecyltrimethoxysilane and hexadecyltrimethoxysilane.

[0018] In the present invention, when the modifier modifies silicon dioxide, the modifier uses acetamide phenyl sulfone and a silane coupling agent to cooperate with each other, thereby further improving the needle puncture strength and heat resistance of the polyolefin-based film.

[0019] As a further technical solution, the preparation method of the modifier-modified silica comprises the following steps: mixing silica and a modifier in a solvent, and drying to obtain the modifier-modified silica; The mass ratio of the silicon dioxide, the modifier and the solvent is 10:1:40-50.

[0020] The working principle and beneficial effects of the present invention are: In the present invention, when preparing the polyolefin base film, the photoinitiator is first pretreated, and then the cross-linking reaction initiated by the photoinitiator inside the base film effectively eliminates the transverse and longitudinal directional crystallization phenomenon caused by the traditional stretching process, so that the base film is not easy to tear when subjected to external force; at the same time, the occurrence of the cross-linking reaction forms a tighter network structure between the molecular chains of the base film, thereby significantly improving the puncture resistance, tensile strength, and tear strength of the base film; the uniform distribution of the photoinitiator and the effective cross-linking reaction also effectively reduce the deformation and shrinkage rate of the base film during the processing, improve the dimensional stability and processing efficiency of the product, and significantly improve the needle puncture strength and heat resistance of the polyolefin base film, with excellent comprehensive performance, and can be widely used in packaging, battery separators, electronic materials and other fields that have higher requirements for material strength, toughness, and heat resistance, which is of great significance for promoting the performance improvement and application expansion of polyolefin base film materials. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the following examples and comparative examples, The weight average molecular weight of polyethylene is 600,000, and the particle size of silica is 50 nm.

[0023] Example 1 The method for eliminating directional crystallization of a polyolefin-based film comprises the following steps: S1. Photoinitiator pretreatment: 0.001 parts of 2-isopropylthioxanthone and 35 parts of white oil are mixed and heated to melt to obtain a premixed solution; S2, mixing the premixed liquid and 35 parts of white oil to obtain a mixed liquid; S3, 30 parts of polyethylene resin are melted and mixed with the mixed solution, extruded into a film, and cross-linked to obtain a polyolefin-based film with a thickness of 5 μm.

[0024] Example 2 The method for eliminating directional crystallization of a polyolefin-based film comprises the following steps: S1. Photoinitiator pretreatment: 0.01 parts of 2,4-diethylthioxanthone and 42.5 parts of white oil are mixed and heated to melt to obtain a premixed solution; S2, mixing the premixed liquid and 42.5 parts of white oil to obtain a mixed liquid; S3, 15 parts of polyethylene resin are melted and mixed with the mixed solution, extruded into a film, and cross-linked to obtain a polyolefin base film with a thickness of 3 μm.

[0025] Example 3 The method for eliminating directional crystallization of a polyolefin-based film comprises the following steps: S1. Photoinitiator pretreatment: 0.01 parts of 2,4-diethylthioxanthone, 0.01 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 20 parts of white oil are mixed and heated to melt to obtain a premixed solution; S2, mixing the premixed liquid and 60 parts of white oil to obtain a mixed liquid; S3, 20 parts of polyethylene resin are melted and mixed with the mixed solution, extruded into a film, and cross-linked to obtain a polyolefin base film with a thickness of 7 μm.

[0026] Example 4 The difference between this example and Example 2 is that 2,4-diethylthioxanthone is replaced by 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0027] Example 5 The only difference between this example and Example 2 is that one tenth of the mass of 2,4-diethylthioxanthone is replaced by an equal amount of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0028] Example 6 The only difference between this example and Example 2 is that nine-tenths of the mass of 2,4-diethylthioxanthone is replaced by an equal amount of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0029] Example 7 The only difference between this embodiment and embodiment 2 is that one sixth of the mass of 2,4-diethylthioxanthone is replaced by an equal amount of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0030] Example 8 The difference between this example and Example 2 is that half the mass of 2,4-diethylthioxanthone is replaced by an equal amount of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0031] Example 9 The difference between this embodiment and embodiment 8 is that step S3 of the method for eliminating directional crystallization of the polyolefin base film is: melting the polyethylene resin, mixing it with the mixed solution and silicon dioxide, extruding it into a film, and cross-linking it to obtain a polyolefin base film with a thickness of 3 μm; The mass ratio of silica to polyethylene resin is 8:100.

[0032] Example 10 The difference between this embodiment and embodiment 9 is that the silicon dioxide is replaced by the modifier-modified silicon dioxide; The preparation method of modifier-modified silica comprises the following steps: mixing silica and acetamide phenyl sulfone in ethanol with a volume fraction of 70%, and drying to obtain modifier-modified silica; Among them, the mass ratio of silicon dioxide, acetamide phenyl sulfone and ethanol is 10:1:45.

[0033] Embodiment 11 The difference between this embodiment and embodiment 9 is that acetamide phenyl sulfone is replaced by dodecyltrimethoxysilane.

[0034] Example 12 The difference between this embodiment and embodiment 9 is that two tenths of the mass of acetamide phenylsulfone is replaced by dodecyltrimethoxysilane.

[0035] Embodiment 13 The difference between this embodiment and embodiment 9 is that 5 / 13 of the mass of acetamide phenylsulfone is replaced by dodecyltrimethoxysilane.

[0036] Embodiment 14 The only difference between this embodiment and embodiment 13 is that the mass ratio of modifier-modified silica to polyethylene resin is 8:100.

[0037] Comparative Example 1 The method for preparing a polyolefin-based film comprises the following steps: 30 parts of polyethylene resin were melted and mixed with 70 parts of white oil, and extruded into a film to obtain a polyolefin-based film with a thickness of 5 μm.

[0038] Comparative Example 2 The method for preparing a polyolefin-based film comprises the following steps: 15 parts of polyethylene resin were melted and mixed with 85 parts of white oil, and extruded into a film to obtain a polyolefin-based film with a thickness of 3 μm.

[0039] Comparative Example 3 The method for preparing a polyolefin-based film comprises the following steps: 20 parts of polyethylene resin were melted and mixed with 80 parts of white oil, and extruded into a film to obtain a polyolefin-based film with a thickness of 7 μm.

[0040] Comparative Example 4 The method for preparing a polyolefin-based film comprises the following steps: 15 parts of polyethylene resin were melted, mixed with 0.01 parts of 2,4-diethylthioxanthone and 85 parts of white oil, extruded into a film, and cross-linked to obtain a polyolefin-based film with a thickness of 3 μm.

[0041] The polyolefin-based films prepared in Examples 1 to 14 and Comparative Examples 1 to 4 were tested for heat resistance and needle puncture strength: Heat resistance: The polyolefin base film was placed in an oven at 105°C for 1 hour in its natural state, and then the transverse (TD) shrinkage and longitudinal (MD) shrinkage of the battery separator were measured; Puncture strength: Use a needle with a diameter of 1 mm and a tip bending radius of 0.5 mm to puncture the polyolefin base film at a speed of 2 mm / sec to measure the puncture strength; The results are shown in Table 1 below.

[0042] Table 1 Test results of polyolefin-based film properties

[0043] Compared with Comparative Examples 1 to 4, the polyolefin base films prepared in Examples 1 to 14 have lower shrinkage and higher needle puncture strength, indicating that when preparing the polyolefin base film, the photoinitiator is first pretreated, and then the cross-linking reaction initiated by the photoinitiator inside the base film significantly improves the needle puncture strength and heat resistance of the polyolefin base film.

[0044] Compared with Example 2 and Example 4, the polyolefin-based films prepared in Examples 5 to 8 have lower shrinkage and higher puncture strength, indicating that the photoinitiator is synergistically compounded with 2,4-diethylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, which further improves the puncture strength and heat resistance of the polyolefin-based film.

[0045] Compared with Examples 5-6, the polyolefin-based films prepared in Examples 7-8 have lower shrinkage and higher puncture strength, indicating that in the polyolefin-based films, the photoinitiator uses 2,4-diethylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide in a mass ratio of 5:1-5, which further improves the puncture strength and heat resistance of the polyolefin-based films.

[0046] Compared with Examples 8 to 9, the polyolefin-based film prepared in Example 10 has a lower shrinkage rate and a higher needle puncture strength, indicating that silica modified with acetamide phenyl sulfone is also added to the polyolefin-based film, which further improves the needle puncture strength and heat resistance of the polyolefin-based film.

[0047] Compared with Examples 10 to 11, the polyolefin-based films prepared in Examples 12 to 14 have lower shrinkage and higher needle puncture strength, indicating that when the modifier modifies silica, the modifier uses acetamide phenyl sulfone and silane coupling agent to synergistically improve the needle puncture strength and heat resistance of the polyolefin-based film.

[0048] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for eliminating directional crystallization of a polyolefin-based film, characterized in that: The following steps are involved: S1, photoinitiator pretreatment: mixing the photoinitiator and the first solvent oil, heating and melting, to obtain a premixed liquid; S2, mixing the premixed liquid with a second solvent oil to obtain a mixed liquid; S3, mixing the melted polyolefin resin with the mixed solution, extruding into a film, and cross-linking to obtain a polyolefin-based film; The first solvent oil and the second solvent oil each independently comprise mineral oil.

2. A method for eliminating directional crystallization of a polyolefin-based film according to claim 1, characterized in that: The thickness of the polyolefin-based film is 3-9 μm.

3. A method for eliminating directional crystallization of a polyolefin-based film according to claim 1, characterized in that: The photoinitiator includes one or more of 2-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 4-chlorobenzophenone, 4,4-bis(diethylamino)benzophenone, 2-ethylanthraquinone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and the like.

4. A method for eliminating directional crystallization of a polyolefin-based film according to claim 3, characterized in that: The photoinitiator is 2,4-diethylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide in a mass ratio of 1:9 to 9:

1.

5. A method for eliminating directional crystallization of a polyolefin-based film according to claim 4, characterized in that: The photoinitiator is 2,4-diethylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide in a mass ratio of 5:1-5.

6. The method for eliminating directional crystallization of a polyolefin-based film according to claim 1, characterized in that: The mass ratio of the first solvent oil and the second solvent oil to the polyolefin resin and the photoinitiator is 70-85:15-30:0.001-0.02; The mass ratio of the first solvent oil to the second solvent oil is 1:1-3; The weight average molecular weight of the polyolefin resin is 600,000 to 800,000.

7. The method for eliminating directional crystallization of a polyolefin-based film according to claim 1, characterized in that: In step S3, silicon dioxide is also added during the mixing; the mass ratio of silicon dioxide to polyolefin resin is 8-15:

100.

8. A method for eliminating directional crystallization of a polyolefin-based film according to claim 7, characterized in that: The silicon dioxide is modifier-modified silicon dioxide; the modifier includes acetamide phenyl sulfone.

9. A method for eliminating directional crystallization of a polyolefin-based film according to claim 8, characterized in that: The modifier comprises acetamide phenyl sulfone and a silane coupling agent in a mass ratio of 8:2-5.

10. A method for eliminating directional crystallization of a polyolefin-based film according to any one of claims 8 to 9, characterized in that: The preparation method of the modifier-modified silica comprises the following steps: mixing silica and a modifier in a solvent, and drying to obtain the modifier-modified silica; The mass ratio of the silicon dioxide, the modifier and the solvent is 10:1:40-50.

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