A coating composition, its preparation method and its use

Abstract

This invention discloses a coating composition comprising the following parts by weight: (1) 20-60 wt% modified polyalkane emulsion; (2) 2-15 wt% lubricant; (3) 5-25 wt% wax emulsion; (4) 0.1-3 wt% mixture of silica and graphene; (5) 1-10 wt% crosslinking agent; (6) 0.1-3 wt% leveling agent; and (7) the balance being water. This invention also discloses a method for preparing the coating composition and its use in preparing lubricated BOPP films.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a thin film coating composition, its preparation method, and its use in preparing lubricating BOPP films. Background Technology

[0002] Biaxially oriented polypropylene (BOPP) film is widely used in packaging, printing, and other industries due to its excellent properties. However, its high coefficient of friction makes it prone to jamming and wrinkling during high-speed processing. Existing solutions include adding inorganic or organic lubricants, coating with silicone oil or fluorinated materials, but these have drawbacks such as reduced transparency, unstable migration, reduced printability, and high cost. Therefore, the market needs a new lubricating coating with superior overall performance. This invention is proposed to address this need. Summary of the Invention

[0003] The present invention aims to provide a thin film coating composition, its preparation method, and its use in preparing lubricating BOPP films; the ultra-smooth BOPP film prepared by the present invention has a coating that does not affect the film's transparency, printability, and composite performance, and has high stability.

[0004] The technical solution of the present invention is as follows:

[0005] The first aspect of the present invention discloses a coating composition comprising the following parts by weight: (1) 20-60 wt% modified polyalkane emulsion; (2) 2-15 wt% lubricant; (3) 5-25 wt% wax emulsion; (4) 0.1-3 wt% mixture of silica and graphene; (5) 1-10 wt% crosslinking agent; (6) 0.1-3 wt% leveling agent; and (7) the balance being water.

[0006] Preferably, the silica is nano-hydrophobic silica and the graphene is monolayer graphene oxide; the particle size of the silica or graphene is 5-40 nm; and the mass ratio of silica to graphene is 19:(0.5-5).

[0007] Preferably, the solid content of the modified polyalkane emulsion is 35-40 wt%.

[0008] Preferably, the solid content of the wax emulsion is 30-40 wt%; the wax is one or more of PE wax, PP wax or Fischer-Tropsch wax, and the particle size is not greater than 100 nm.

[0009] Preferably, the lubricant is a siloxane-polyether copolymer.

[0010] Preferably, the crosslinking agent is an isocyanate or an amino compound; the leveling agent is a polyether-modified polydimethylsiloxane.

[0011] The second aspect of the present invention discloses a method for preparing the coating composition, comprising the following steps: diluting a modified polyalkane emulsion with water; adding a wax emulsion and dispersing it under shear conditions for 15–30 minutes; adding a mixture of silica and graphene and ultrasonically or dispersing it for 5–15 minutes; adding a crosslinking agent and a leveling agent, and stirring until homogeneous to obtain the coating composition.

[0012] A third aspect of the present invention discloses the use of the coating composition in the preparation of a lubricated BOPP film.

[0013] Preferably, the method for preparing the lubricated BOPP film is as follows: the coating composition is coated using a coating machine, microgravure coating, rod coating, or spray coating, at a concentration of 0.2-1.0 g / m². 2 The coating amount is applied to the surface of the BOPP film; dried at 60-110℃ for 10-60 seconds; cooled to room temperature to obtain the lubricated BOPP film.

[0014] Preferably, the coefficient of friction of the lubricated BOPP film is 0.15-0.25.

[0015] The beneficial effects of this invention are as follows:

[0016] The lubricating BOPP film obtained by this invention has a coefficient of friction of 0.15-0.25, which is much lower than that of BOPP film without coating composition; the optical properties of the film are basically unaffected; the lubrication performance is stable, and the coating composition does not migrate over time. The coating process of this invention is simple and can be implemented online; the cost is controllable, making it suitable for large-scale production. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the preparation method and coating process of the coating composition of the present invention.

[0018] Figure 2 This is a scanning electron microscope (SEM) schematic diagram of the coating of the present invention.

[0019] Figure 3 The diagram on the right shows the HDI crosslinking agent anchoring at the interface in the coating of this invention; the diagram on the left shows a prior art coating. In the diagrams: 1. Traditional slip agent; 2. BOPP film; 3. HDI anchoring point. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Example 1: Preparation of coating composition and thin film coating.

[0022] The coating composition was prepared as follows: (1) Modified polyalkane emulsion: 40wt%; the modified polyalkane emulsion was a nonionic maleic anhydride grafted polypropylene emulsion (Michem Emulsion 94340), with a solid content of 35wt%~40wt%, a softening point of 140℃~160℃, and an average particle size of 100nm-200nm; (2) Organosilicon-polyether lubricant: 8wt%; the organosilicon-polyether lubricant was a polyether modified polysiloxane (BYK-307), with an EO / PO (ethylene oxide / propylene oxide) molar ratio of (2-4):1, an effective active ingredient content of 100%, and a viscosity (25℃) of 500-1500cSt; (3) PE wax emulsion: 15wt%; it was an anionic oxidized high-density polyethylene wax emulsion (BYK Aquacer). 531), solid content 30wt%-40wt%, pH value of emulsion 9.0-10.0, melting point 125℃-135℃, particle size 50-90nm; (4) Silica and graphene mixture: total 0.5wt%; the mixture is made by mixing hydrophobically modified fumed silica (particle size 15-20nm) and monolayer graphene oxide (particle size 15-20nm) at a mass ratio of 19:1; and pre-dispersed in deionized water; (5) HDI crosslinking agent: 5wt%; the HDI crosslinking agent is sulfonate modified hydrophilic aliphatic polyisocyanate (Covestro Bayhydur 305), of which the NCO group content is 18%-22%, and the viscosity is 2000~3500mPa·s at 23℃; (6) leveling agent: 0.5 wt%; the leveling agent is a polyether-modified silicone surface additive (BYK-333), with a surface tension of <25 mN / m; (7) deionized water: the remainder is deionized water.

[0023] according to Figure 1 The flowchart shows the preparation steps: Modified polyalkane emulsion is mixed with deionized water; lubricant and wax emulsion are added and dispersed under high-speed shear for 20 minutes; a mixture of silica and graphene is added and ultrasonicated for 10 minutes; a crosslinking agent and leveling agent are added, and the mixture is stirred until homogeneous to obtain the coating composition. The coating composition is then coated onto the surface of a BOPP film; Coating method: On an 8.2 m wide BOPP production line, a microgravure coating method is used, with a coating density of 0.6 g / m². 2 The coating composition of the present invention is applied online and dried at 90°C for 20 seconds; the lubricated BOPP film is obtained by cooling to room temperature.

[0024] Figure 2 This is a scanning electron microscope (SEM) schematic diagram of the coating of the present invention; the spherical structures are nanoscale silicon dioxide, and the sheet-like structures are monolayer graphene oxide. Figure 2It is evident that the spherical nanoscale silica and sheet-like monolayer graphene oxide in the coating form a microscopic "ball bearing" and "skateboard" structure, significantly reducing the physical contact area. Simultaneously, the polyether segments of the lubricant (typically polyethylene glycol or polypropylene glycol) impart water solubility, while the polysiloxane segments provide extremely low surface energy. This structure causes it to tend to align on the outermost surface of the coating during drying, forming a durable lubricating film. The coefficient of friction on the BOPP film surface is significantly reduced. The granular wax particles, spherical nanoscale silica, and sheet-like monolayer graphene oxide in the coating all contribute to reducing the coefficient of friction on the BOPP film surface.

[0025] Table 1 below shows a comparison of the performance of the BOPP film before and after coating in this embodiment:

[0026]

[0027] The resulting BOPP film exhibits no jamming during processing, increasing the speed by 15-25%.

[0028] As can be seen from the data comparison in Table 1, the friction coefficient of the lubricated BOPP film obtained by this invention is 0.19, which is much lower than the 0.35 of the BOPP film without the coating composition; the optical properties of the film are basically unaffected (the light transmittance is similar). The lubrication performance is stable, and the coating composition basically does not migrate over time; for example... Figure 3 As shown, the reason is that the crosslinking agent HDI tightly anchors the silicone-polyether lubricant to the polyalkane matrix and the BOPP surface, fundamentally solving the drawback of traditional slip agents (such as erucamide) migrating to the surface over time and causing printing failure. Since the coating of this invention is a water-based system (meeting environmental requirements), the HDI used must be ionized or non-ionic modified to ensure its dispersion in water; it can crosslink with the hydroxyl or carboxyl groups in the polyalkane emulsion to form a dense network structure, improving the adhesion of the coating.

[0029] Example 2: Preparation of coating composition and thin film coating.

[0030] The coating composition was prepared in the same manner as in Example 1, except that (4) hydrophobically modified fumed silica and monolayer graphene oxide were mixed at a mass ratio of 19:2. The preparation and coating were the same as in Example 1. The coating properties of the obtained BOPP film are shown in Table 2 below.

[0031]

[0032] The resulting BOPP film also exhibits no jamming during processing, increasing the speed by 15-25%.

[0033] Example 3: Preparation of coating composition and thin film coating.

[0034] The coating composition was prepared in the same manner as in Example 1, except that (4) hydrophobically modified fumed silica and monolayer graphene oxide were mixed at a mass ratio of 19:3. Preparation and coating were performed in the same manner as in Example 1. The coating properties of the obtained BOPP film are shown in Table 3 below.

[0035]

[0036] The resulting BOPP film also exhibits no jamming during processing, increasing the speed by 15-25%.

[0037] The above embodiments are not intended to limit the present invention, nor is the present invention limited to the examples described above. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the present invention are also within the protection scope of the present invention.

Claims

1. A coating composition characterized in that, The product comprises the following parts by weight: (1) 20-60 wt% modified polyalkane emulsion; (2) 2-15 wt% lubricant; (3) 5-25 wt% wax emulsion; (4) 0.1-3 wt% mixture of silica and graphene; (5) 1-10 wt% crosslinking agent; (6) 0.1-3 wt% leveling agent; and (7) the remainder is water.

2. The coating composition of claim 1, wherein, The silica is nano-hydrophobic silica, and the graphene is monolayer graphene oxide; the particle size of silica or graphene is 5-40 nm; the mass ratio of silica to graphene is 19:(0.5-5).

3. The coating composition of claim 1, wherein, The solid content of the modified polyalkane emulsion is 35-40 wt%.

4. The coating composition of claim 1, wherein, The solid content of the wax emulsion is 30-40 wt%; the wax is one or more of PE wax, PP wax or Fischer-Tropsch wax, and the particle size is not greater than 100 nm.

5. The coating composition of claim 1, wherein, The lubricant is a siloxane-polyether copolymer.

6. The coating composition of claim 1, wherein, The crosslinking agent is an isocyanate or an amino compound; the leveling agent is a polyether-modified polydimethylsiloxane.

7. The method of making the coating composition according to any one of claims 1-6, wherein, The process includes the following steps: diluting the modified polyalkane emulsion with water; adding the wax emulsion and dispersing it under shear conditions for 15–30 minutes; adding a mixture of silica and graphene and ultrasonicating or dispersing it for 5–15 minutes; adding a crosslinking agent and a leveling agent, and stirring until homogeneous to obtain the coating composition.

8. Use of the coating composition according to any one of claims 1-6 for the preparation of a lubricated BOPP film.

9. Use according to claim 8, characterized in that, The method for preparing the lubricant type BOPP film is as follows: the coating composition is coated on the surface of the BOPP film by means of coating machine, micro gravure coating, bar coating or spray coating, with a coating amount of 0.2-1.0 g / m 2 ; dried at 60-110 °C for 10-60 seconds; cooled to room temperature to obtain the lubricant type BOPP film.

10. The use according to claim 8, characterized in that, The coefficient of friction for lubricated BOPP films is 0.15-0.25.

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