Anti-fog master batch for polypropylene film and anti-fog polypropylene film

Abstract

The invention discloses an anti-fog master batch for a polypropylene film. The anti-fog master batch is prepared from the following raw material components: polypropylene, maleic anhydride grafted polypropylene, sorbitan monopalmitate and polyimide. Secondly, the invention also discloses an antifogging polypropylene film, which is prepared by the following steps: preparing an antifogging master batch from polypropylene, maleic anhydride grafted polypropylene, polyimide and sorbitan monopalmitate; and uniformly mixing the anti-fog master batch with polypropylene, extruding the mixture into a strip-shaped or tubular film by adopting a screw extruder, and rolling and pulling the film to form the required width and thickness, thereby obtaining the anti-fog polypropylene film. According to the anti-fog polypropylene film, polyimide, maleic anhydride grafted polypropylene and sorbitan monopalmitate cooperate with one another and serve as a whole to jointly improve the hydrophilic performance of the anti-fog polypropylene film, so that the anti-fog performance of the anti-fog polypropylene film is greatly improved, and the water contact angle of the anti-fog polypropylene film can be lower than 10 degrees.

Description

Technical Field

[0001] The present invention relates to an anti-fog masterbatch for polypropylene film and an anti-fog polypropylene film. Background Art

[0002] In the application of plastic greenhouses, due to the temperature difference inside and outside the greenhouse, it is extremely easy to form fog droplets on the plastic film of the plastic greenhouse. These fog droplets will refract sunlight, reduce the light transmittance of the plastic film, thereby reducing the photosynthesis of crops in the greenhouse, and thus reducing the yield and quality of crops and affecting agricultural income.

[0003] To reduce the influence of fog droplets on the light transmittance, it is necessary to add an anti-fogging agent to the plastic or coat an anti-fogging layer on the surface of the plastic film to improve the hydrophilicity of the film, so that the fog droplets attached to the film spread along the surface of the film to form a water film, thereby reducing the refraction of light.

[0004] As a general material, polypropylene material is also used as a material for agricultural films. However, due to its non-polar nature, its anti-fog performance is poor, which limits its scope of use. To improve the anti-fog performance of polypropylene film, an anti-fogging agent is usually coated on the surface of the plastic film. However, under the action of sunlight and the absorption of the anti-fogging agent by fog droplets, the retention time of the anti-fogging agent is reduced, and it is necessary to apply the anti-fogging agent by spraying on the film, but its uniformity cannot be guaranteed, reducing the anti-fogging effect of the film. Therefore, it is necessary to prepare a polypropylene material with its own anti-fogging function for the production of plastic films with anti-fogging effects. Summary of the Invention

[0005] To solve the problem that polypropylene film is prone to fogging, the present application first proposes an anti-fog masterbatch for polypropylene film, and its raw material components include polypropylene, maleic anhydride grafted polypropylene, sorbitan monopalmitate and polyimide.

[0006] Specifically, the mass percentages of each component are as follows: polypropylene accounts for 30 - 45%, maleic anhydride grafted polypropylene accounts for 6 - 12%, polyimide accounts for 35 - 50%, and sorbitan monopalmitate accounts for 5 - 15%.

[0007] Specifically, in maleic anhydride grafted polypropylene, the grafting rate of maleic anhydride is 0.8 - 1.2%.

[0008] Secondly, the present application also discloses an anti-fog polypropylene film, and its preparation method includes the following steps: (1) Mix 30-45% polypropylene, 6-12% maleic anhydride grafted polypropylene, 35-50% polyimide, and 5-15% sorbitan monopalmitate by mass percentage using a high-speed mixer. After that, extrude the melt at 170-220°C through a twin-screw extruder. The melt is pelletized, dried, and cooled to produce an anti-fog masterbatch. (2) Mix the anti-fog masterbatch with polypropylene evenly, and then extrude it using a screw extruder to form a molten material. The molten material is extruded through the screw and die head of the extruder to form a strip-shaped or tubular film. At the same time, the film is formed to the required width and thickness through roll pressing and traction to obtain an anti-fog polypropylene film. The thickness of the anti-fog polypropylene film is 0.5-0.8 mm.

[0009] Specifically, the extrusion temperature of the molten material is 170-200°C.

[0010] In this application, polyimide, maleic anhydride grafted polypropylene (PP-g-MAH), and sorbitan monopalmitate are added to the anti-fog masterbatch as modifiers to improve the hydrophilicity of the anti-fog polypropylene film. Maleic anhydride grafted polypropylene can enhance the compatibility between polypropylene and polyimide. In this application, polyimide, maleic anhydride grafted polypropylene (PP-g-MAH), and sorbitan monopalmitate synergistically improve the hydrophilic performance of the anti-fog polypropylene film as a whole. Currently, sorbitan monopalmitate is the main component of spray-type anti-fogging agents. However, when it is added alone to polypropylene (PP) materials, although the resulting film has certain anti-fogging properties, its water contact angle is still above 80°, and the anti-fogging performance of the film is limitedly improved. After adding polyimide and maleic anhydride grafted polypropylene (PP-g-MAH) as auxiliary anti-fogging agents to the polypropylene material, they can act together with sorbitan monopalmitate to greatly improve the anti-fogging performance of the anti-fog polypropylene film, and the water contact angle of the anti-fog polypropylene film can be lower than 10°.

[0011] Polyimide contains a large number of amino groups, and these amino groups can react with the anhydride in PP-g-MAH to form amide bonds. Amide bonds are a kind of strong polar bonds, which can effectively improve the polarity of the anti-fog polypropylene film and are beneficial to improving the hydrophilicity of the anti-fog polypropylene film. The amino groups in polyimide can also form hydrogen bonds with the hydroxyl groups of sorbitan monopalmitate. The three components of sorbitan monopalmitate, polyimide, and maleic anhydride grafted polypropylene all have strong polarity, which greatly improves the polarity of the anti-fog polypropylene film. During the use of the anti-fog polypropylene film, sorbitan monopalmitate located inside the film will migrate outwards to supplement the lost sorbitan monopalmitate to maintain the stability of the sorbitan monopalmitate content on the film surface, thereby maintaining the stability of the anti-fogging performance of the anti-fog polypropylene film.

[0012] For the anti-fog polypropylene film in this application, its light transmittance is maintained above 70%, ensuring the normal needs of photosynthesis of crops. Brief Description of the Drawings

[0013] Figure 1 It is the detection diagram of the migration of sorbitan monopalmitate in the 1# film in Example 1. Detailed Description of the Invention

[0014] In the following examples and comparative examples, the Mn of polypropylene (PP) is 8500 Da. In the following examples and comparative examples, the thickness of the prepared hydrophilic polypropylene film is 0.06 mm. Examples

[0015] Preparation of anti-fog polypropylene film: (1) Mix 45% by mass of polypropylene, 12% of maleic anhydride grafted polypropylene, 38% of polyimide and 5% of sorbitan monopalmitate using a high-speed mixer, and then extrude the melt at 220 °C through a twin-screw extruder. After pelletizing, drying and cooling the melt, an anti-fog masterbatch is made; (2) Mix polypropylene particles and the anti-fog masterbatch evenly according to a mass ratio of 1:0.8, and then extrude at 180 °C using a screw extruder to form a molten material. Let the molten material be extruded through the screw and die head of the extruder to extrude into a strip-shaped or tubular film. At the same time, roll and draw the film to form the required width and thickness to obtain an anti-fog polypropylene film, marked as 1# film, and the thickness of the 1# film is 0.7 mm. In the maleic anhydride grafted polypropylene, the grafting rate of maleic anhydride is 1.2%. Examples

[0016] Preparation of anti-fog polypropylene film: (1) Mix 40% by mass of polypropylene, 8% of maleic anhydride grafted polypropylene, 42% of polyimide and 10% of sorbitan monopalmitate using a high-speed mixer, and then extrude the melt at 200 °C through a twin-screw extruder. After pelletizing, drying and cooling the melt, an anti-fog masterbatch is made; (2) Mix polypropylene particles and the anti-fog masterbatch evenly according to a mass ratio of 1:1, and then extrude at 195 °C using a screw extruder to form a molten material. Let the molten material be extruded through the screw and die head of the extruder to extrude into a strip-shaped or tubular film. At the same time, roll and draw the film to form the required width and thickness to obtain an anti-fog polypropylene film, marked as 2# film, and the thickness of the 2# film is 0.7 mm. In the maleic anhydride grafted polypropylene, the grafting rate of maleic anhydride is 1.1%. Examples

[0017] Preparation of anti-fog polypropylene film: (1) Mix 30% polypropylene, 10% maleic anhydride grafted polypropylene, 45% polyimide and 15% sorbitan monopalmitate by mass percentage using a high-speed mixer. After that, extrude the melt at 170 °C through a twin-screw extruder. The melt is pelletized, dried and cooled to make the anti-fog masterbatch; (2) Mix polypropylene particles and the anti-fog masterbatch evenly according to a mass ratio of 1:1.1. Then extrude at 170 °C using a screw extruder to form a molten material. The molten material is extruded through the screw and die head of the extruder into a strip-shaped or tubular film. At the same time, the film is formed to the required width and thickness through roll pressing and traction to obtain the anti-fog polypropylene film, marked as Film 3#. The thickness of Film 3# is 0.7 mm. In the maleic anhydride grafted polypropylene, the grafting rate of maleic anhydride is 0.8%.

[0018] Comparative Example 1 Preparation of anti-fog polypropylene film: Extrude polypropylene particles at 195 °C using a screw extruder to form a molten material. The molten material is extruded through the screw and die head of the extruder into a strip-shaped or tubular film. At the same time, the film is formed to the required width and thickness through roll pressing and traction to obtain Film 4#. The thickness of Film 4# is 0.7 mm. In this example, only polypropylene particles are used as raw materials, and the prepared Film 4# is a pure PP film.

[0019] Comparative Example 2 Preparation of anti-fog polypropylene film: This comparative example is basically the same as Example 2, except that polyimide and sorbitan monopalmitate are cancelled. Marked as Film 5#.

[0020] Comparative Example 3 Preparation of anti-fog polypropylene film: This comparative example is basically the same as Example 2, except that maleic anhydride grafted polypropylene and polyimide are cancelled. Marked as Film 6#.

[0021] Comparative Example 4 Preparation of anti-fog polypropylene film: This comparative example is basically the same as Example 2, except that sorbitan monopalmitate is cancelled. Marked as Film 7#.

[0022] Comparative Example 5 Preparation of anti-fog polypropylene film: This comparative example is basically the same as Example 2, except that polyimide is cancelled. Marked as Film 8#.

[0023] Detection: Detect the water contact angle of the film.

[0024] The water contact angles of the films in Examples 1-3 and Comparative Examples 1-5 were measured. The water contact angles of the films in Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Comparative Example 5, Example 1, Example 2, and Example 3 were 104.6°, 89.3°, 81.2°, 63.2°, 81.5°, 9.8°, 8.9°, and 7.5°, respectively. From the above data, it can be seen that the antifog masterbatch prepared by using maleic anhydride grafted polypropylene or sorbitan monopalmitate alone as the antifog component can reduce the water contact angle of the film, but the reduction amplitude is limited; while the antifog masterbatch prepared by using a two-component of maleic anhydride grafted polypropylene and sorbitan monopalmitate or a two-component of maleic anhydride grafted polypropylene and polyimide for antifogging cannot significantly reduce the water contact angle of the film formed.

[0025] When maleic anhydride grafted polypropylene, polyimide, and sorbitan monopalmitate are used simultaneously as the antifog component, the formed antifog masterbatch can significantly reduce the water contact angle of the film, so that the fog droplets on the film can spread quickly to form a water film, reducing the refraction of sunlight.

[0026] During the use of the film, the sorbitan monopalmitate on the film surface will be lost with the fog droplets or water film. It is necessary for the sorbitan monopalmitate inside the film to migrate outward to the film surface to maintain the antifog performance of the film. Therefore, the migration of sorbitan monopalmitate in the film was measured. The specific measurement method was as follows: Prepare sorbitan monopalmitate / 10% ethanol-distilled water solutions with different concentrations, and use an ultraviolet-visible spectrophotometer to determine the maximum wavelength corresponding to the absorbance peak of sorbitan monopalmitate as a comparison table. Immerse the 2# film in a 10% ethanol-distilled water solution at 60°C, take a fixed amount of solution every 1 hour and supplement the same volume of standard solution to keep the total solution volume constant. Use an ultraviolet-visible spectrophotometer to measure the absorbance of the solution at the determined wavelength to obtain Figure 1 the attached figure shown.

[0027] According to Figure 1, as the soaking time extends, the absorbance of the solution gradually increases. However, over time, the concentration of sorbitan monopalmitate in the solution increases rapidly at the beginning stage, but the rate of concentration increase gradually slows down. The reason may be that at the beginning stage, sorbitan monopalmitate on the film surface quickly dissolves into the solution. However, as sorbitan monopalmitate on the film surface dissolves, sorbitan monopalmitate inside the film needs a certain migration time to diffuse to the film surface, resulting in a slower increase in absorbance. This is because the anhydride groups of PP-g-MAH and the amino groups of polyimide can adsorb sorbitan monopalmitate molecules through hydrogen bonding or ionic interactions, delaying its migration rate, achieving stable and slow release, and extending the anti-fog life of the film.

[0028] The light transmittance of the 1#-4# films is 86.1%, 85.3%, 84.6% and 88.7% respectively. Compared with the pure PP film (4# film), the light transmittance of the films prepared in this application all shows a small decrease, but the decrease range is limited and all can meet the use requirements.

[0029] The anti-fog properties of the films were detected using GB / T31726—2015 "Test Method for Anti-fogging Property of Plastic Films". The anti-fog properties of the 1#-8# films are Class 1, Class 1, Class 1, Class 5, Class 4, Class 4, Class 2, and Class 4 in sequence.

[0030] Due to the strong enhancement effect of maleic anhydride grafted polypropylene in this application, the mechanical strength of the films in this application has also been greatly improved. The corresponding test samples were made from the raw materials of the 1#-5# films, and their tensile strength, elongation at break and impact strength were detected. The specific test data are as follows: The tensile strength of the materials of the 1#-5# films is 38.1 MPa, 37.4 MPa, 36.8 MPa, 36.1 MPa and 34.9 MPa respectively. The elongation at break of the materials of the 1#-5# films is 1251%, 1211%, 1082%, 635% and 896% respectively. The impact strength of the materials of the 1#-5# films is 9.27 KJ / m 2 , 9.55 KJ / m 2 , 9.61 KJ / m 2 , 4.75 KJ / m 2 and 4.46 KJ / m 2。It can be seen from the above data that the tensile strength of each film is within the same level range with little difference, but the difference in elongation at break and impact strength is relatively large. Among them, the elongation at break and impact strength of the materials of the 1#-3# films are significantly higher than those of the materials of the 4# and 5# films. When sorbitan monopalmitate is added alone, due to its certain plasticizing effect, the elongation at break of the material is increased, and the impact strength is slightly decreased. However, when sorbitan monopalmitate, PP-g-MAH and polyimide are added simultaneously, both the elongation at break and the impact strength are significantly increased. The reason may be that the hydroxyl group of sorbitan monopalmitate can form hydrogen bonds with the anhydride group of PP-g-MAH and the amino group of polyimide, and the anhydride group of PP-g-MAH and the amino group of polyimide generate amide groups, enhancing the interfacial strength between the components and reducing phase separation; sorbitan monopalmitic acid is a compound with a flexible long chain, which has a plasticizing effect and can also enhance the interfacial bonding, thus making the stress distribution more uniform and delaying crack propagation. However, the content of sorbitan monopalmitate should not be too large. When the content of sorbitan monopalmitate is too large, the tensile strength and elongation at break of the material will also decrease. This is because the excessive sorbitan monopalmitate can exist in the form of an independent phase, becoming the crack initiation point, reducing the strength and toughness. Secondly, the hydroxyl group of the excessive sorbitan monopalmitate may form hydrogen bonds with the amino group of polyimide or the carboxylic acid group of PP-g-MAH, resulting in a reduction in the effective interaction between polyimide and PP-g-MAH and weakening the interfacial strengthening effect. Therefore, the dosage of sorbitan monopalmitate should not be too high.

Claims

1. An anti-fog masterbatch for polypropylene film, characterized in that, Its raw material components include polypropylene, maleic anhydride grafted polypropylene, sorbitan monopalmitate, and polyimide.

2. The anti-fog masterbatch according to claim 1, characterized in that, The mass percentages of each component are as follows: Polypropylene accounts for 30 - 45%, maleic anhydride grafted polypropylene accounts for 6 - 12%, polyimide accounts for 35 - 50%, and sorbitan monopalmitate accounts for 5 - 15%.

3. The anti - fog masterbatch according to claim 1, wherein In the maleic anhydride grafted polypropylene, the grafting rate of maleic anhydride is 0.8 - 1.2%.

4. A fog-proof polypropylene film, characterized in that, Its preparation method includes the following steps: (1) Mix 30 - 45% by mass of polypropylene, 6 - 12% of maleic anhydride grafted polypropylene, 35 - 50% of polyimide, and 5 - 15% of sorbitan monopalmitate using a high - speed mixer. After that, extrude the melt at 170 - 220 °C through a twin - screw extruder. After the melt is pelletized, dried, and cooled, an anti - fog masterbatch is made; (2) Mix the polypropylene particles and the anti - fog masterbatch evenly, and then extrude at 170 - 200 °C using a screw extruder to form a molten material. Let the molten material be extruded through the screw and die head of the extruder to extrude into a strip - shaped or tubular film. At the same time, through roll pressing and traction, the film is formed to the required width and thickness to obtain an anti - fog polypropylene film, and the thickness of the anti - fog polypropylene film is 0.5 - 0.8 mm.

5. The anti - fog polypropylene film according to claim 1, wherein The mass ratio of the polypropylene particles to the anti - fog masterbatch is 1:(0.8 - 1.1).

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