Preparation method and application of silica opening agent for plastic film

Abstract

This invention relates to the field of plastic film additives, specifically to a method for preparing and applying a silica opening agent for plastic films. The method for preparing the silica opening agent includes the following steps: S1, adding mesoporous silica and a silane coupling agent to an aqueous ethanol solution, stirring and reacting to obtain pretreated mesoporous silica; S2, adding the pretreated mesoporous silica, a catalyst, and a long-chain alkyl modifier to toluene, reacting, filtering, washing, and drying to obtain modified silica; S3, adding the modified silica obtained in step S2 and a polyether-type dispersant to an aqueous ethanol solution, stirring at room temperature, and then spray-drying to obtain the silica opening agent. The silica opening agent for plastic films prepared by this invention has the advantage of good dispersibility, effectively reducing the haze of plastic films, and good opening properties, which can meet the requirements for good application in plastic films.

Description

Technical Field

[0001] This invention relates to the field of plastic film additives, and specifically to a method for preparing and applying a silica opening agent for plastic films. Background Technology

[0002] Plastic films (such as polyethylene (PE), polypropylene (PP), and polyester (PET)) are prone to interlayer adhesion during production, winding, storage, and use due to intermolecular forces, electrostatic adsorption, or vacuum bonding caused by smooth surfaces. This can lead to difficulties in opening, unwinding, or tearing during stretching. To address this issue, the industry commonly uses the addition of "opening agents." Silica, due to its chemical inertness, good thermal stability, and refractive index close to that of polymers, is one of the most widely used opening agents. Its mechanism of action involves forming microscopic protrusions on the film surface, reducing the contact area and thus preventing adhesion.

[0003] In the prior art, patent CN121470501A discloses a method for preparing highly transparent and highly dispersible silica for PE opening agents, specifically relating to a method for preparing highly transparent and highly dispersible silica for PE opening agents. This invention involves simultaneously adding water glass solution and sulfuric acid solution dropwise to a reaction vessel under controlled pH and temperature conditions. After aging, the silica is filtered, washed, spray-dried, and subjected to airflow crushing to obtain highly specific surface area and highly dispersible transparent silica for PE opening agents. The resulting product has characteristics such as high transparency, high dispersibility, and high specific surface area. Furthermore, the method provided by this invention is simple, low-cost, and the resulting product is safe and non-toxic, suitable for large-scale industrial production. However, this method mainly focuses on the synthesis of the silica bulk, and the control of the interfacial compatibility between the particle surface and the polymer matrix remains insufficient.

[0004] Patent CN117586558A discloses a method for developing a silica opening agent, using a modulus of 3.0. 3.5% solid sodium silicate is used to prepare a certain volume of solution with a concentration of 15%. A 20wt% sodium silicate solution is prepared to a certain volume with a concentration of 15. A 20wt% sulfuric acid solution was used, with sodium fatty alcohol hydroxyethyl sulfonate selected as the reaction structure directing agent. This agent features high specific surface area, small average pore size, and low oil absorption value, resulting in strong anti-blocking properties, reduced film haze, improved light transmittance, and excellent opening effect. However, sodium fatty alcohol hydroxyethyl sulfonate may adsorb into the silica pores after the reaction. If washing is incomplete, the residual organic components can easily cause yellowing, affecting the transparency of the plastic.

[0005] Therefore, there is an urgent need in the market for a silica opening agent for plastic films that has good dispersibility and does not affect the transparency of plastics. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to obtain a silica opening agent for plastic films with good dispersibility and which affects the transparency of plastics.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing a silica opening agent for plastic films, comprising the following steps: S1. Add mesoporous silica and silane coupling agent to an aqueous ethanol solution and stir at 50-80℃ for 2-4 hours to obtain pretreated mesoporous silica. S2. Add the pretreated mesoporous silica, catalyst and long-chain alkyl modifier obtained in step S1 to toluene, heat to 80-120℃, continue the reaction for 4-8 hours, filter, wash and dry to obtain modified silica. S3. Add the modified silica and polyether dispersant obtained in step S2 to an ethanol aqueous solution, stir at room temperature for 1-3 hours, and spray dry to obtain the silica opening agent.

[0008] Preferably, the concentration of the ethanol aqueous solution in steps S1 and S3 is 85-95 wt%.

[0009] Preferably, the ratio of mesoporous silica to aqueous ethanol solution is 1g:(8-12)ml.

[0010] Preferably, the catalyst is p-toluenesulfonic acid.

[0011] Preferably, the mass ratio of the pretreated mesoporous silica to the catalyst in step S2 is 1:(0.001-0.003).

[0012] Preferably, the ratio of pretreated mesoporous silica to toluene in step S2 is 1g: (8-12)ml.

[0013] Preferably, the ratio of modified silica to ethanol aqueous solution in step S3 is 1g: (8-12)ml.

[0014] This application improves the dispersion performance of mesoporous silica by modifying it with silane coupling agents, long-chain alkyl modifiers, and polyether dispersants. Specifically, silane coupling agents introduce reactive anchor points on the silica surface, long-chain alkyl modifiers can be chemically grafted onto these anchor points to form flexible segments compatible with the polyolefin matrix, and polyether dispersants are physically adsorbed or partially chemically bonded to the shell surface, providing steric stabilization. The synergistic effect of these components enhances the dispersion performance of the silica-opening agent.

[0015] This application constructs a core-shell structure. The core is made of mesoporous silica with a specific pore size, ensuring the "skeleton" effect of the opening agent in forming microscopic protrusions. The presence of the mesoporous core not only reduces the density and cost of the opening agent itself, but more importantly, its channels can accommodate some modifiers. In the molten state during processing, these stored modifiers or matrix molecular chains may exhibit a weak "anchoring-release" behavior, which helps to form a more stable micro-rough structure at the film interface, giving the opening agent long-lasting performance. The shell, through chemically grafted long-chain alkyl groups, greatly improves the compatibility with the plastic film matrix, allowing the opening agent to be uniformly distributed at the nanoscale in the matrix without agglomeration. This avoids light scattering caused by agglomerates and minimizes the impact of haze.

[0016] This application employs a dual modification strategy of "chemical bonding + physical adsorption". First, a silane coupling agent is used as a "bridge" to covalently link long-chain alkyl groups to the silica surface, ensuring the durability of the modified layer and preventing desorption during high-temperature extrusion processing. Second, the polyether-type dispersant introduced into the outer layer provides additional steric hindrance, effectively preventing the particles from re-agglomerating during storage and processing.

[0017] In some embodiments, the average particle size of the mesoporous silica is 2-6 μm.

[0018] In some embodiments, the silane coupling agent is selected from one or more of KH550, KH560, and KH570.

[0019] In some embodiments, the long-chain alkyl modifier is a saturated or unsaturated fatty acid, a fatty amine, or a derivative thereof, with 12-22 carbon atoms.

[0020] Preferably, the long-chain alkyl modifier is one or more of erucamide, stearic acid, n-octadecylamine, and palmitoleic acid.

[0021] In some embodiments, the polyether-type dispersant is one or more of polyethylene glycol, polypropylene glycol, and polyoxyethylene-polyoxypropylene block copolymer.

[0022] In some embodiments, the mass ratio of the mesoporous silica to the silane coupling agent is 1:(0.025-0.035).

[0023] In some embodiments, the mass ratio of the mesoporous silica to the long-chain alkyl modifier is 1:(0.05-0.1).

[0024] In some embodiments, the mass ratio of the modified silica to the polyether dispersant is 1:(0.03-0.06).

[0025] Another aspect of the present invention provides an application of a silica opening agent for plastic films, comprising the following steps: mixing the silica opening agent with a plastic matrix resin, and then processing it through melt extrusion, casting, blow molding or biaxial stretching processes to obtain a plastic film with a thickness of 10-50 μm.

[0026] In some embodiments, the mass ratio of the silica opening agent to the plastic matrix resin is (0.001-0.01):1.

[0027] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention prepares a silica opening agent with a core-shell structure by modifying mesoporous silica with silane coupling agent, long-chain alkyl modifier and polyether dispersant, which can improve its dispersion performance and prevent yellowing.

[0028] (2) The present invention uses mesoporous silica with a specific pore size as the core, which not only reduces the density and cost of the opening agent itself, but also allows its pores to accommodate some modifiers. In the molten state of processing, these stored modifiers or matrix molecular chains may have a weak "anchoring-release" behavior, which helps to form a more stable micro-rough structure at the film interface, giving the opening agent long-lasting effect and improving its opening performance.

[0029] (3) The present invention first pretreats mesoporous silica with silane coupling agent and then covalently links long-chain alkyl groups to the silica surface, which ensures the durability of the modified layer and makes it less prone to desorption during high-temperature extrusion processing; secondly, the polyether dispersant introduced in the outer layer provides additional steric hindrance effect, which effectively prevents the particles from agglomerating again during storage and processing. Detailed Implementation

[0030] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0031] The compounds and related reagents used in the following examples and comparative examples are all commercially available. The mesoporous silica has an average particle size of 3 μm and was purchased from Qinghe County Chaotai Metal Materials Co., Ltd. The number average molecular weight of polyethylene glycol is 400.

[0032] Example 1 A method for preparing a silica opening agent for plastic films includes the following steps: S1. Add 10g of mesoporous silica and 0.3g of KH-560 silane coupling agent to 100ml of 90wt% ethanol aqueous solution, and stir at 65℃ for 3h to obtain pretreated mesoporous silica. S2. Add 10g of the pretreated mesoporous silica obtained in step S1, 0.02g of p-toluenesulfonic acid and 0.7g of erucamide to 100ml of toluene, heat to 100℃, continue to react for 6h, filter, wash with anhydrous ethanol, and dry at 60℃ to obtain modified silica. S3. Add 10g of the modified silica obtained in step S2 and 0.45g of polyethylene glycol to 100ml of 90wt% ethanol aqueous solution, stir at room temperature for 2h, and spray dry under the conditions of feed temperature of 200℃ and discharge temperature of 100℃ to obtain silica opening agent.

[0033] Example 2 A method for preparing a silica opening agent for plastic films includes the following steps: S1. Add 10g of mesoporous silica and 0.25g of KH-560 silane coupling agent to 80ml of 90wt% ethanol aqueous solution, and stir at 50℃ for 4h to obtain pretreated mesoporous silica. S2. Add 10g of the pretreated mesoporous silica obtained in step S1, 0.01g of p-toluenesulfonic acid and 0.5g of erucamide to 80ml of toluene, heat to 80℃, continue to react for 8h, filter, wash with anhydrous ethanol, and dry at 60℃ to obtain modified silica. S3. Add 10g of the modified silica obtained in step S2 and 0.3g of polyethylene glycol to 80ml of 90wt% ethanol aqueous solution, stir at room temperature for 1h, and spray dry under the conditions of feed temperature of 200℃ and discharge temperature of 100℃ to obtain silica opening agent.

[0034] Example 3 A method for preparing a silica opening agent for plastic films includes the following steps: S1. Add 10g of mesoporous silica and 0.35g of KH-560 silane coupling agent to 120ml of 90wt% ethanol aqueous solution, and stir at 80℃ for 2h to obtain pretreated mesoporous silica. S2. Add 10g of the pretreated mesoporous silica obtained in step S1, 0.03g of p-toluenesulfonic acid and 1g of erucamide to 120ml of toluene, heat to 100℃, continue to react for 6h, filter, wash with anhydrous ethanol, and dry at 60℃ to obtain modified silica. S3. Add 10g of the modified silica obtained in step S2 and 0.6g of polyethylene glycol to 120ml of 90wt% ethanol aqueous solution, stir at room temperature for 3h, and spray dry under the conditions of feed temperature of 200℃ and discharge temperature of 100℃ to obtain silica opening agent.

[0035] Example 4 A method for preparing a silica opening agent, the specific implementation method is the same as in Example 1, except that the amount of KH-560 silane coupling agent added is 0.5g.

[0036] Example 5 A method for preparing a silica opening agent, the specific implementation method is the same as in Example 1, except that the amount of erucamide added is 1.5g.

[0037] Example 6 A method for preparing a silica opening agent is described, with the specific implementation method being the same as in Example 1, except that the amount of polyethylene glycol added is 0.8g.

[0038] Example 7 A method for preparing a silica opening agent, the specific implementation method is the same as in Example 1, except that erucamide is replaced with decylamine in equal amounts.

[0039] Comparative Example 1 A method for preparing a silica opening agent for plastic films includes the following steps: S1. Add 10g of mesoporous silica and 0.3g of KH-560 silane coupling agent to 100ml of 90wt% ethanol aqueous solution, and stir at 65℃ for 3h to obtain pretreated mesoporous silica. S2. Add 10g of the pretreated mesoporous silica obtained in step S1, 0.02g of p-toluenesulfonic acid and 0.7g of erucamide to 100ml of toluene, heat to 100℃, continue the reaction for 6h, filter, wash with anhydrous ethanol, and dry at 60℃ to obtain silica opening agent.

[0040] Comparative Example 2 A method for preparing a silica opening agent for plastic films includes the following steps: S1. Add 10g of mesoporous silica and 0.3g of KH-560 silane coupling agent to 100ml of 90wt% ethanol aqueous solution, and stir at 65℃ for 3h to obtain pretreated mesoporous silica. S1. Add 10g of pretreated mesoporous silica obtained in step S1 and 0.45g of polyethylene glycol to 100ml of 90wt% ethanol aqueous solution, stir at room temperature for 2h, and spray dry under the conditions of feed temperature of 200℃ and discharge temperature of 100℃ to obtain silica opening agent.

[0041] Performance testing The silica opening agents obtained in the above embodiments and comparative examples were tested: (1) Sample preparation Each silica opening agent was mixed with LLDPE (Dow 1220P) at a mass ratio of 0.5:99.5. Plastic film samples with a thickness of 30 μm were prepared by blow molding machine with an extrusion temperature of 170℃, a blow ratio of 3, and a traction ratio of 5.

[0042] (2) Performance testing 1. Haze: The haze was tested in accordance with GB / T 2410-2008 "Determination of Light Transmittance and Haze of Transparent Plastics"; 2. Opening property: After the film is pressed, it is placed at 50℃ and 0.5MPa pressure for 24 hours, and then the opening force is tested by an electronic tensile testing machine at a speed of 200-300mm / min.

[0043] Table 1

[0044] As shown in Table 1, the plastic film samples with the addition of the materials from Examples 1-3 of this invention exhibited lower haze and tensile strength, indicating that the silica opening agent possesses excellent opening and dispersing properties. A comparison between Example 4 and Example 1 shows that changing the ratio of mesoporous silica to silane coupling agent may result in an excessively thick organic layer on the silica, weakening the micro-rough structure, thus reducing the opening performance of the opening agent and increasing the tensile strength of the plastic film. A comparison between Example 5 and Example 1 shows that changing the ratio of mesoporous silica to long-chain alkyl modifier may lead to excessive erucamide, resulting in an excessive migration layer on the film surface, causing surface enrichment and increasing the haze of the plastic film. A comparison between Example 6 and Example 1 shows that changing the ratio of modified silica to polyether dispersant... In comparison, the hydrophilicity of the opening agent surface may be enhanced, its compatibility with hydrophobic resins may be reduced, and the risk of agglomeration may increase, leading to an increase in haze. At the same time, larger agglomerates reduce surface micro-roughness, thereby increasing the tensile strength of the plastic film. The comparison between Example 7 and Example 1 shows that replacing erucamide with decylamine may reduce the migration of organic segments on the silica opening agent, resulting in a decrease in the dispersibility of the opening agent and an increase in haze. The comparison between Comparative Example 1 and Example 1 shows that without the use of polyethylene glycol-modified silica, the dispersion performance of the opening agent decreases, leading to an increase in the haze and tensile strength of the plastic film. The comparison between Comparative Example 2 and Example 1 shows that without the use of long-chain alkyl modifiers to modify silica, the dispersion performance of the silica opening agent decreases, leading to an increase in the haze and tensile strength of the plastic film.

[0045] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a silica opening agent for plastic films, comprising the following steps: S1. Add mesoporous silica and silane coupling agent to an aqueous ethanol solution and stir at 50-80℃ for 2-4 hours to obtain pretreated mesoporous silica. S2. Add the pretreated mesoporous silica, catalyst and long-chain alkyl modifier obtained in step S1 to toluene, heat to 80-120℃, continue the reaction for 4-8 hours, filter, wash and dry to obtain modified silica. S3. Add the modified silica and polyether dispersant obtained in step S2 to an ethanol aqueous solution, stir at room temperature for 1-3 hours, and spray dry to obtain the silica opening agent.

2. The method for preparing the silica opening agent for plastic film according to claim 1, characterized in that, The average particle size of the mesoporous silica is 2-6 μm.

3. The method for preparing the silica opening agent for plastic film according to claim 1, characterized in that, The silane coupling agent is selected from one or more of KH550, KH560, and KH570.

4. The method for preparing the silica opening agent for plastic film according to claim 1, characterized in that, The long-chain alkyl modifier is a saturated or unsaturated fatty acid, a fatty amine, or its derivative, with 12-22 carbon atoms.

5. The method for preparing the silica opening agent for plastic film according to claim 1, characterized in that, The polyether-type dispersant is one or more of polyethylene glycol, polypropylene glycol, and polyoxyethylene-polyoxypropylene block copolymer.

6. The method for preparing the silica opening agent for plastic films according to claim 1, characterized in that, The mass ratio of the mesoporous silica to the silane coupling agent is 1:(0.025-0.035).

7. The method for preparing the silica opening agent for plastic films according to claim 1, characterized in that, The mass ratio of the mesoporous silica to the long-chain alkyl modifier is 1:(0.05-0.1).

8. The method for preparing the silica opening agent for plastic film according to claim 1, characterized in that, The mass ratio of the modified silica to the polyether dispersant is 1:(0.03-0.06).

9. The application of a silica opening agent obtained by the preparation method according to any one of claims 1-8, characterized in that, The process includes the following steps: mixing the silica opening agent with a plastic matrix resin, and then processing the mixture through melt extrusion, casting, blow molding, or biaxial stretching to obtain a plastic film with a thickness of 10-50 μm.

10. The application of the silica opening agent for plastic films according to claim 9, characterized in that, The mass ratio of the silica opening agent to the plastic matrix resin is (0.001-0.01):1.

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