High-barrier polyethylene milk bottle cap and preparation method thereof

Abstract

The application discloses a high-barrier polyethylene milk bottle cap and a preparation method thereof, and relates to the technical field of polyethylene. The preparation method of the high-barrier polyethylene milk bottle cap comprises the following steps: uniformly mixing high-density polyethylene, modified polyethylene, polyethylene elastomer, modified montmorillonite, an antioxidant, an initiator and a color masterbatch, feeding into a spiral extruder, melt extruding, injection molding, and obtaining the high-barrier polyethylene milk bottle cap. The modified polyethylene and the modified montmorillonite are prepared and added in the polyethylene milk bottle cap, the barrier property of the milk bottle cap is significantly improved, the processing property is improved, the friction coefficient of the bottle cap surface after processing is significantly reduced, and the smoothness of the bottle cap in use is improved.

Description

Technical Field

[0001] This invention relates to the field of polyethylene technology, specifically to a high-barrier polyethylene milk bottle cap and its preparation method. Background Technology

[0002] In the packaging industry, polyethylene is often used as a raw material for making milk bottle caps due to its excellent chemical stability and suitable mechanical properties. However, traditional polyethylene milk bottle caps still have some shortcomings that affect the shelf life and quality of milk: for example, the barrier properties of polyethylene bottle caps are limited, and oxygen and moisture can easily pass through the cap into the bottle, causing the nutrients in the milk to be broken down and reducing the shelf life of the milk; in addition, milk bottle caps have high static friction, poor ease of opening, and low smoothness, which affects the opening experience of consumers, especially the elderly and children.

[0003] In conclusion, solving the above problems and developing a high-barrier polyethylene milk bottle cap is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a high-barrier polyethylene milk bottle cap and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A high-barrier polyethylene milk bottle cap comprises the following raw materials, by weight: 80 parts high-density polyethylene, 10-15 parts modified polyethylene, 4-6 parts polyethylene elastomer, 4-6 parts modified montmorillonite, 0.04-0.06 parts antioxidant, 0.01-0.02 parts initiator, and 0.8-1 parts color masterbatch.

[0007] Preferred method for preparing modified polyethylene includes the following steps: (1) mixing high-density polyethylene masterbatch, 5-hexenylmethyldichlorosilane, benzoyl peroxide and xylene evenly, stirring at 100~105℃ for 2.5~3h, filtering, washing with acetone, drying to obtain dichlorosilane modified polyethylene;

[0008] (2) Dichlorosilane-modified polyethylene, 5-hexenylmethyldichlorosilane, and (3,3,3-trifluoropropyl)dichloromethylsilane were added to deionized water and mixed evenly. The mixture was stirred at 95~100℃ for 25~30 min, filtered, washed, and dried to obtain fluorinated polyethylene.

[0009] (3) Fluorine-modified polyethylene, 1,2-epoxyoctadecane and stannous octoate are added to toluene and mixed evenly. The mixture is stirred at 110~120℃ for 12~24h, the solvent is evaporated, and the mixture is washed with acetone and dried to obtain modified polyethylene.

[0010] More preferably, the fluorinated modified polyethylene comprises dichlorosilane modified polyethylene, 5-hexenylmethyldichlorosilane, and (3,3,3-trifluoropropyl)dichloromethylsilane in a mass ratio of 10:2~3:4~6.

[0011] Preferably, the dichlorosilane-modified polyethylene comprises the following raw materials, in parts by weight: 8-10 parts high-density polyethylene masterbatch, 18-20 parts 5-hexenylmethyldichlorosilane, 0.03-0.04 parts benzoyl peroxide, and 1-2 parts xylene;

[0012] The modified polyethylene comprises the following raw materials, by mass parts: 8-10 parts of fluorinated modified polyethylene, 10-15 parts of 1,2-epoxyoctadecane, 0.02-0.03 parts of stannous octoate, and 8-10 parts of toluene.

[0013] Preferably, the high-density polyethylene masterbatch has a particle size of 2-3 mm.

[0014] Preferred method for preparing modified montmorillonite includes the following steps: (1) calcining montmorillonite at 200-250°C for 2-3 hours, grinding, and passing through an 800-1000 mesh sieve to obtain activated montmorillonite;

[0015] (2) Activated montmorillonite was added to an ethanol aqueous solution and ultrasonically dispersed evenly. 3-(2,3-epoxypropoxy)propyltrimethoxysilane was added and stirred at 80~90℃ for 20~24h. After centrifugation, washing, grinding, and passing through an 800~1000 mesh sieve, epoxy-modified montmorillonite was obtained.

[0016] (3) Mix epoxy-modified montmorillonite, hydroxyl fluorosilicone oil and stannous octoate evenly, stir at 130~135℃ for 20~24h, centrifuge, wash and dry to obtain modified montmorillonite.

[0017] More preferably, the epoxy-modified montmorillonite comprises the following raw materials, by mass parts: 2-3 parts activated montmorillonite, 100 parts 60% ethanol aqueous solution, and 3-4 parts 3-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0018] The modified montmorillonite comprises the following raw materials, by mass: 2-3 parts epoxy-modified montmorillonite, 10-12 parts hydroxyl fluorosilicone oil, and 0.01-0.02 parts stannous octoate.

[0019] A preferred embodiment of the method for preparing a high-barrier polyethylene milk bottle cap includes the following steps: mixing high-density polyethylene, modified polyethylene, polyethylene elastomer, modified montmorillonite, antioxidant, initiator, and color masterbatch evenly, feeding them into a screw extruder, melt extruding, and injection molding to obtain a high-barrier polyethylene milk bottle cap.

[0020] Preferably, during the melt extrusion process, the temperatures of each zone are 140~160℃, 165~170℃, 165~170℃, 170~180℃, 180~190℃, 180~190℃, 190~210℃, and 215~220℃ respectively.

[0021] Preferably, during the injection molding process, the injection pressure is 80~100 bar, and the temperatures of each temperature zone are 180~190℃, 190~200℃, 200~210℃, and 210~220℃.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: by preparing and adding modified polyethylene and modified montmorillonite to the polyethylene milk bottle cap, the present invention significantly improves the barrier performance of the milk bottle cap, improves the processing performance, significantly reduces the coefficient of friction of the bottle cap surface after processing, and improves the smoothness of the bottle cap during use.

[0023] The modified polyethylene is prepared by grafting the vinyl group of 5-hexenylmethyldichlorosilane onto the surface of the polyethylene masterbatch with macromolecular free radicals under the initiation of benzoyl peroxide, thereby obtaining dichlorosilane-modified polyethylene. Further, based on the hydrolysis of dichlorosilane to form Si-OH, and the co-hydrolysis of 5-hexenylmethyldichlorosilane and (3,3,3-trifluoropropyl)dichloromethylsilane in deionized water to form a polysiloxane structure, fluorinated modified polyethylene containing multiple olefin crosslinking points is obtained. Further, the Si-OH at the chain ends of the polysiloxane structure in the fluorinated modified polyethylene and the epoxy groups of 1,2-epoxyoctadecane are grafted under the action of stannous octoate as a ring-opening promoter to obtain modified polyethylene.

[0024] The polysiloxane segments have low surface energy, which facilitates migration from the matrix to the substrate surface, thereby reducing the coefficient of friction of the polyethylene matrix, improving processing performance, and enhancing the smoothness of the bottle cap surface. Furthermore, the fluorinated silanes increase the contact angle of the bottle cap, preventing milk residue from clinging to the bottle walls. Vinyl silanes can crosslink with the polyethylene segments to form a micro-crosslinked structure, increasing barrier properties and fixing the polysiloxane segments, thus enhancing lubrication durability. However, the ratio of fluorinated silanes to vinyl silanes needs to be controlled. Excessive vinyl silane content leads to over-crosslinking in the matrix, reducing crystallization perfection and decreasing barrier properties. The introduced octadecane structure has high chain end mobility, which helps reduce the coefficient of friction and fills defects on the matrix surface, further improving barrier properties.

[0025] The preparation method of modified montmorillonite is as follows: after talc powder is activated at high temperature, it is grafted onto the surface of talc powder by condensation after hydrolysis of 3-(2,3-epoxypropoxy)propyltrimethoxysilane to obtain epoxy-modified talc powder, and further grafted with hydroxyl fluorosilicone oil under the action of stannous octoate as a ring-opening promoter to obtain modified talc powder.

[0026] Montmorillonite, with its layered structure, can form a labyrinthine barrier in the matrix, significantly extending the diffusion path of molecules and improving the barrier properties of polyethylene bottle caps. However, montmorillonite is highly polar, differing from the non-polar nature of the polyethylene matrix, resulting in poor dispersibility. Conventional organic intercalation modification involves ion exchange between quaternary ammonium salt cations and the metal cations in montmorillonite, followed by intercalation into the interlayer and the introduction of organic segments, which can effectively improve the dispersibility and interfacial properties of montmorillonite. However, during melt extrusion processing, the temperature is typically 200-250℃, and the relatively poor stability of quaternary ammonium salts makes them prone to decomposition, disrupting the interface between them and the polymer. Therefore, this invention first employs high-temperature activation treatment of montmorillonite to remove some of the bound water between montmorillonite molecules, exposing activated hydroxyl groups. Further modification with 3-(2,3-epoxypropoxy)propyltrimethoxysilane generates covalent bonds, improving the interfacial properties between montmorillonite and the polyethylene matrix during high-temperature processing, thereby enhancing barrier properties. Furthermore, the fluorosilicone oil structure introduced through epoxy groups further reduces surface energy, improves hydrophobicity and compatibility, and enhances barrier properties. On the other hand, it has a partially similar structure to modified polyethylene, constructing a dense hydrophobic network that improves barrier properties while reducing the coefficient of friction. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that the following quantities are by weight. There are no special restrictions on the manufacturers of the raw materials involved in this invention. Exemplary examples include: high-density polyethylene (HD2200JP), manufactured by PTT; color masterbatch (8001), brand: Dude Plastics; polyolefin elastomer (8003), brand: Dow Chemical; antioxidant, antioxidant 1010; montmorillonite, particle size 400-800 mesh; CAS number: 90054-19-6 for 5-hexenylmethyldichlorosilane; CAS number: 94-36 for benzoyl peroxide. -0; Xylene CAS No.: 1330-20-7; (3,3,3-trifluoropropyl)dichloromethylsilane CAS No.: 675-62-7; 1,2-epoxyoctadecane CAS No.: 7390-81-0; Stannous octoate CAS No.: 301-10-0; 3-(2,3-epoxypropoxy)propyltrimethoxysilane CAS No.: 2530-83-8; Hydroxyfluorosilicone oil is designated as DFO-MF, brand is Shanghai Guishan; In the following examples, parts are by weight, and all the above and other raw materials used but not mentioned are commercially available.

[0029] Example 1: A method for preparing a high-barrier polyethylene milk bottle cap, comprising the following steps:

[0030] Step 1: Preparation of modified polyethylene: (1) Mix 10 parts of high-density polyethylene masterbatch, 20 parts of 5-hexenylmethyldichlorosilane, 0.03 parts of benzoyl peroxide and 1.5 parts of xylene evenly, stir at 105℃ for 2.5h, filter, wash with acetone, and dry to obtain dichlorosilane modified polyethylene; (2) Add 10 parts of dichlorosilane modified polyethylene, 2.5 parts of 5-hexenylmethyldichlorosilane and 5 parts of (3,3,3-trifluoropropyl)dichloromethylsilane to deionized water and mix evenly, stir at 100℃ for 30min, filter, wash, and dry to obtain fluorinated modified polyethylene; (3) Add 10 parts of fluorinated modified polyethylene, 12 parts of 1,2-epoxyoctadecane and 0.02 parts of stannous octoate to 10 parts of toluene and mix evenly, stir at 115℃ for 18h, evaporate the solvent, wash with acetone, and dry to obtain modified polyethylene;

[0031] Step 2: Preparation of modified montmorillonite: (1) Calcine montmorillonite at 250℃ for 2h, grind, and pass through an 800-mesh sieve to obtain activated montmorillonite; (2) Add 2.5 parts of activated montmorillonite to 100 parts of 60% ethanol aqueous solution and ultrasonically disperse evenly, add 3.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, stir at 85℃ for 24h, centrifuge, wash, grind, and pass through an 800-mesh sieve to obtain epoxy-modified montmorillonite; (3) Mix 2.5 parts of epoxy-modified montmorillonite, 10 parts of hydroxyl fluorosilicone oil, and 0.01 parts of stannous octoate evenly, stir at 135℃ for 20h, centrifuge, wash, and dry to obtain modified montmorillonite;

[0032] Step 3: Preparation of high-barrier polyethylene milk bottle cap: Mix 80 parts high-density polyethylene, 12 parts modified polyethylene, 5 parts polyethylene elastomer, 5 parts modified montmorillonite, 0.05 parts antioxidant, 0.01 parts initiator, and 1 part color masterbatch evenly, and put them into a screw extruder. Set the temperature of each zone to 150℃, 170℃, 170℃, 180℃, 180℃, 190℃, 200℃, and 220℃ respectively, and perform melt extrusion. Set the injection pressure to 100 bar and the temperature of each zone to 190℃, 200℃, 210℃, and 220℃ for injection molding to obtain a high-barrier polyethylene milk bottle cap.

[0033] Example 2: A method for preparing a high-barrier polyethylene milk bottle cap, comprising the following steps:

[0034] Step 1: Preparation of modified polyethylene: (1) Mix 10 parts of high-density polyethylene masterbatch, 20 parts of 5-hexenylmethyldichlorosilane, 0.03 parts of benzoyl peroxide and 1.5 parts of xylene evenly, stir at 105℃ for 2.5h, filter, wash with acetone, and dry to obtain dichlorosilane modified polyethylene; (2) Add 10 parts of dichlorosilane modified polyethylene, 2.5 parts of 5-hexenylmethyldichlorosilane and 5 parts of (3,3,3-trifluoropropyl)dichloromethylsilane to deionized water and mix evenly, stir at 100℃ for 30min, filter, wash, and dry to obtain fluorinated modified polyethylene; (3) Add 10 parts of fluorinated modified polyethylene, 12 parts of 1,2-epoxyoctadecane and 0.02 parts of stannous octoate to 10 parts of toluene and mix evenly, stir at 115℃ for 18h, evaporate the solvent, wash with acetone, and dry to obtain modified polyethylene;

[0035] Step 2: Preparation of modified montmorillonite: (1) Calcine montmorillonite at 250℃ for 2h, grind, and pass through an 800-mesh sieve to obtain activated montmorillonite; (2) Add 2.5 parts of activated montmorillonite to 100 parts of 60% ethanol aqueous solution and ultrasonically disperse evenly, add 3.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, stir at 85℃ for 24h, centrifuge, wash, grind, and pass through an 800-mesh sieve to obtain epoxy-modified montmorillonite; (3) Mix 2.5 parts of epoxy-modified montmorillonite, 10 parts of hydroxyl fluorosilicone oil, and 0.01 parts of stannous octoate evenly, stir at 135℃ for 20h, centrifuge, wash, and dry to obtain modified montmorillonite;

[0036] Step 3: Preparation of high-barrier polyethylene milk bottle cap: Mix 80 parts high-density polyethylene, 10 parts modified polyethylene, 4 parts polyethylene elastomer, 4 parts modified montmorillonite, 0.05 parts antioxidant, 0.01 parts initiator, and 1 part color masterbatch evenly, and put them into a screw extruder. Set the temperature of each zone to 150℃, 170℃, 170℃, 180℃, 180℃, 190℃, 200℃, and 220℃ respectively, and perform melt extrusion. Set the injection pressure to 100 bar and the temperature of each zone to 190℃, 200℃, 210℃, and 220℃ for injection molding to obtain a high-barrier polyethylene milk bottle cap.

[0037] Example 3: A method for preparing a high-barrier polyethylene milk bottle cap, comprising the following steps:

[0038] Step 1: Preparation of modified polyethylene: (1) Mix 10 parts of high-density polyethylene masterbatch, 20 parts of 5-hexenylmethyldichlorosilane, 0.03 parts of benzoyl peroxide and 1.5 parts of xylene evenly, stir at 105℃ for 2.5h, filter, wash with acetone, and dry to obtain dichlorosilane modified polyethylene; (2) Add 10 parts of dichlorosilane modified polyethylene, 2.5 parts of 5-hexenylmethyldichlorosilane and 5 parts of (3,3,3-trifluoropropyl)dichloromethylsilane to deionized water and mix evenly, stir at 100℃ for 30min, filter, wash, and dry to obtain fluorinated modified polyethylene; (3) Add 10 parts of fluorinated modified polyethylene, 12 parts of 1,2-epoxyoctadecane and 0.02 parts of stannous octoate to 10 parts of toluene and mix evenly, stir at 115℃ for 18h, evaporate the solvent, wash with acetone, and dry to obtain modified polyethylene;

[0039] Step 2: Preparation of modified montmorillonite: (1) Calcine montmorillonite at 250℃ for 2h, grind, and pass through an 800-mesh sieve to obtain activated montmorillonite; (2) Add 2.5 parts of activated montmorillonite to 100 parts of 60% ethanol aqueous solution and ultrasonically disperse evenly, add 3.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, stir at 85℃ for 24h, centrifuge, wash, grind, and pass through an 800-mesh sieve to obtain epoxy-modified montmorillonite; (3) Mix 2.5 parts of epoxy-modified montmorillonite, 10 parts of hydroxyl fluorosilicone oil, and 0.01 parts of stannous octoate evenly, stir at 135℃ for 20h, centrifuge, wash, and dry to obtain modified montmorillonite;

[0040] Step 3: Preparation of high-barrier polyethylene milk bottle cap: Mix 80 parts high-density polyethylene, 15 parts modified polyethylene, 6 parts polyethylene elastomer, 6 parts modified montmorillonite, 0.05 parts antioxidant, 0.01 parts initiator, and 1 part color masterbatch evenly, and put them into a screw extruder. Set the temperature of each zone to 150℃, 170℃, 170℃, 180℃, 180℃, 190℃, 200℃, and 220℃ respectively for melt extrusion. Set the injection pressure to 100 bar and the temperature of each zone to 190℃, 200℃, 210℃, and 220℃ for injection molding to obtain the high-barrier polyethylene milk bottle cap.

[0041] Comparative Example 1: Based on Example 1, (3,3,3-trifluoropropyl)dichloromethylsilane was added alone to the modified polyethylene process, while the rest of the process was the same as in Example 1, as follows:

[0042] Step 1: Preparation of modified polyethylene: (1) Mix 10 parts of high-density polyethylene masterbatch, 20 parts of 5-hexenylmethyldichlorosilane, 0.03 parts of benzoyl peroxide and 1.5 parts of xylene evenly, stir at 105℃ for 2.5h, filter, wash with acetone, and dry to obtain dichlorosilane modified polyethylene; (2) Add 10 parts of dichlorosilane modified polyethylene and 7.5 parts of (3,3,3-trifluoropropyl)dichloromethylsilane to deionized water and mix evenly, stir at 100℃ for 30min, filter, wash, and dry to obtain fluorinated modified polyethylene; (3) Add 10 parts of fluorinated modified polyethylene, 12 parts of 1,2-epoxyoctadecane and 0.02 parts of stannous octoate to 10 parts of toluene and mix evenly, stir at 115℃ for 18h, evaporate the solvent, wash with acetone, and dry to obtain modified polyethylene;

[0043] Step 2: Preparation of modified montmorillonite: (1) Calcine montmorillonite at 250℃ for 2h, grind, and pass through an 800-mesh sieve to obtain activated montmorillonite; (2) Add 2.5 parts of activated montmorillonite to 100 parts of 60% ethanol aqueous solution and ultrasonically disperse evenly, add 3.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, stir at 85℃ for 24h, centrifuge, wash, grind, and pass through an 800-mesh sieve to obtain epoxy-modified montmorillonite; (3) Mix 2.5 parts of epoxy-modified montmorillonite, 10 parts of hydroxyl fluorosilicone oil, and 0.01 parts of stannous octoate evenly, stir at 135℃ for 20h, centrifuge, wash, and dry to obtain modified montmorillonite;

[0044] Step 3: Preparation of high-barrier polyethylene milk bottle cap: Mix 80 parts high-density polyethylene, 12 parts modified polyethylene, 5 parts polyethylene elastomer, 5 parts modified montmorillonite, 0.05 parts antioxidant, 0.01 parts initiator, and 1 part color masterbatch evenly, and put them into a screw extruder. Set the temperature of each zone to 150℃, 170℃, 170℃, 180℃, 180℃, 190℃, 200℃, and 220℃ respectively, and perform melt extrusion. Set the injection pressure to 100 bar and the temperature of each zone to 190℃, 200℃, 210℃, and 220℃ for injection molding to obtain a high-barrier polyethylene milk bottle cap.

[0045] Comparative Example 2: Based on Example 1, the ratio of 5-hexenylmethyldichlorosilane to (3,3,3-trifluoropropyl)dichloromethylsilane was exchanged in the modified polyethylene process, while the rest of the process was the same as in Example 1, as detailed below:

[0046] Step 1: Preparation of modified polyethylene: (1) Mix 10 parts of high-density polyethylene masterbatch, 20 parts of 5-hexenylmethyldichlorosilane, 0.03 parts of benzoyl peroxide and 1.5 parts of xylene evenly, stir at 105℃ for 2.5h, filter, wash with acetone, and dry to obtain dichlorosilane modified polyethylene; (2) Add 10 parts of dichlorosilane modified polyethylene, 5 parts of 5-hexenylmethyldichlorosilane and 2.5 parts of (3,3,3-trifluoropropyl)dichloromethylsilane to deionized water and mix evenly, stir at 100℃ for 30min, filter, wash, and dry to obtain fluorinated modified polyethylene; (3) Add 10 parts of fluorinated modified polyethylene, 12 parts of 1,2-epoxyoctadecane and 0.02 parts of stannous octoate to 10 parts of toluene and mix evenly, stir at 115℃ for 18h, evaporate the solvent, wash with acetone, and dry to obtain modified polyethylene;

[0047] Step 2: Preparation of modified montmorillonite: (1) Calcine montmorillonite at 250℃ for 2h, grind, and pass through an 800-mesh sieve to obtain activated montmorillonite; (2) Add 2.5 parts of activated montmorillonite to 100 parts of 60% ethanol aqueous solution and ultrasonically disperse evenly, add 3.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, stir at 85℃ for 24h, centrifuge, wash, grind, and pass through an 800-mesh sieve to obtain epoxy-modified montmorillonite; (3) Mix 2.5 parts of epoxy-modified montmorillonite, 10 parts of hydroxyl fluorosilicone oil, and 0.01 parts of stannous octoate evenly, stir at 135℃ for 20h, centrifuge, wash, and dry to obtain modified montmorillonite;

[0048] Step 3: Preparation of high-barrier polyethylene milk bottle cap: Mix 80 parts high-density polyethylene, 12 parts modified polyethylene, 5 parts polyethylene elastomer, 5 parts modified montmorillonite, 0.05 parts antioxidant, 0.01 parts initiator, and 1 part color masterbatch evenly, and put them into a screw extruder. Set the temperature of each zone to 150℃, 170℃, 170℃, 180℃, 180℃, 190℃, 200℃, and 220℃ respectively, and perform melt extrusion. Set the injection pressure to 100 bar and the temperature of each zone to 190℃, 200℃, 210℃, and 220℃ for injection molding to obtain a high-barrier polyethylene milk bottle cap.

[0049] Comparative Example 3: Based on Example 1, the modified polyethylene process does not involve grafting octadecyl oxide; the remaining processes are the same as in Example 1, as detailed below:

[0050] Step 1: Preparation of modified polyethylene: (1) Mix 10 parts of high-density polyethylene masterbatch, 20 parts of 5-hexenylmethyldichlorosilane, 0.03 parts of benzoyl peroxide and 1.5 parts of xylene evenly, stir at 105℃ for 2.5h, filter, wash with acetone, and dry to obtain dichlorosilane modified polyethylene; (2) Add 10 parts of dichlorosilane modified polyethylene, 2.5 parts of 5-hexenylmethyldichlorosilane and 5 parts of (3,3,3-trifluoropropyl)dichloromethylsilane to deionized water and mix evenly, stir at 100℃ for 30min, filter, wash and dry to obtain modified polyethylene;

[0051] Step 2: Preparation of modified montmorillonite: (1) Calcine montmorillonite at 250℃ for 2h, grind, and pass through an 800-mesh sieve to obtain activated montmorillonite; (2) Add 2.5 parts of activated montmorillonite to 100 parts of 60% ethanol aqueous solution and ultrasonically disperse evenly, add 3.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, stir at 85℃ for 24h, centrifuge, wash, grind, and pass through an 800-mesh sieve to obtain epoxy-modified montmorillonite; (3) Mix 2.5 parts of epoxy-modified montmorillonite, 10 parts of hydroxyl fluorosilicone oil, and 0.01 parts of stannous octoate evenly, stir at 135℃ for 20h, centrifuge, wash, and dry to obtain modified montmorillonite;

[0052] Step 3: Preparation of high-barrier polyethylene milk bottle cap: Mix 80 parts high-density polyethylene, 12 parts modified polyethylene, 5 parts polyethylene elastomer, 5 parts modified montmorillonite, 0.05 parts antioxidant, 0.01 parts initiator, and 1 part color masterbatch evenly, and put them into a screw extruder. Set the temperature of each zone to 150℃, 170℃, 170℃, 180℃, 180℃, 190℃, 200℃, and 220℃ respectively, and perform melt extrusion. Set the injection pressure to 100 bar and the temperature of each zone to 190℃, 200℃, 210℃, and 220℃ for injection molding to obtain a high-barrier polyethylene milk bottle cap.

[0053] Comparative Example 4: Based on Example 1, montmorillonite was modified by intercalation treatment using octadecyltrimethylammonium chloride. The remaining processes were the same as in Example 1, as follows:

[0054] Step 1: Preparation of modified polyethylene: (1) Mix 10 parts of high-density polyethylene masterbatch, 20 parts of 5-hexenylmethyldichlorosilane, 0.03 parts of benzoyl peroxide and 1.5 parts of xylene evenly, stir at 105℃ for 2.5h, filter, wash with acetone, and dry to obtain dichlorosilane modified polyethylene; (2) Add 10 parts of dichlorosilane modified polyethylene, 2.5 parts of 5-hexenylmethyldichlorosilane and 5 parts of (3,3,3-trifluoropropyl)dichloromethylsilane to deionized water and mix evenly, stir at 100℃ for 30min, filter, wash, and dry to obtain fluorinated modified polyethylene; (3) Add 10 parts of fluorinated modified polyethylene, 12 parts of 1,2-epoxyoctadecane and 0.02 parts of stannous octoate to 10 parts of toluene and mix evenly, stir at 115℃ for 18h, evaporate the solvent, wash with acetone, and dry to obtain modified polyethylene;

[0055] Step 2: Preparation of modified montmorillonite: (1) Grind 2.5 parts of montmorillonite, pass through an 800-mesh sieve, add 100 parts of deionized water and ultrasonically disperse evenly, add 1.5 parts of octadecyltrimethylammonium chloride, stir at 80℃ for 8 hours, centrifuge, wash, and dry to obtain modified montmorillonite;

[0056] Step 3: Preparation of high-barrier polyethylene milk bottle cap: Mix 80 parts high-density polyethylene, 12 parts modified polyethylene, 5 parts polyethylene elastomer, 5 parts modified montmorillonite, 0.05 parts antioxidant, 0.01 parts initiator, and 1 part color masterbatch evenly, and put them into a screw extruder. Set the temperature of each zone to 150℃, 170℃, 170℃, 180℃, 180℃, 190℃, 200℃, and 220℃ respectively, and perform melt extrusion. Set the injection pressure to 100 bar and the temperature of each zone to 190℃, 200℃, 210℃, and 220℃ for injection molding to obtain a high-barrier polyethylene milk bottle cap.

[0057] Performance testing: (1) The static friction coefficient of each sample was tested according to GB / T 10006-2021; (2) The oxygen permeability coefficient of each sample was tested according to GB / T 1038.1-2022 at a test temperature of 23℃; (3) Samples were prepared according to GB / T1040.3-2006, and the tensile yield strength was measured at a tensile speed of 50mm / min; the experimental data are shown in the table below.

[0058]

[0059] Conclusion: As shown in the table, this invention significantly improves the barrier properties and processing performance of milk bottle caps by preparing and adding modified polyethylene and modified montmorillonite to the polyethylene milk bottle cap, significantly reduces the coefficient of friction of the bottle cap surface after processing, and improves the smoothness of the bottle cap during use.

[0060] In Comparative Example 1, the addition of (3,3,3-trifluoropropyl)dichloromethylsilane alone resulted in a lack of micro-crosslinked structure, leading to reduced barrier properties and mechanical properties. In Comparative Example 2, the ratio of 5-hexenylmethyldichlorosilane to (3,3,3-trifluoropropyl)dichloromethylsilane was changed, resulting in an over-crosslinked structure in the matrix, which reduced barrier properties and mechanical properties. In Comparative Example 3, the modified polyethylene process did not involve grafting octadecyl oxide, which increased the friction coefficient and somewhat reduced barrier properties. In Comparative Example 4, the use of octadecyltrimethylammonium chloride for intercalation modification of montmorillonite resulted in partial decomposition during processing, decreased interfacial properties, and significantly reduced performance.

[0061] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high barrier polyethylene milk bottle cap characterized by: The product contains the following raw materials, by weight: 80 parts high-density polyethylene, 10-15 parts modified polyethylene, 4-6 parts polyethylene elastomer, 4-6 parts modified montmorillonite, 0.04-0.06 parts antioxidant, 0.01-0.02 parts initiator, and 0.8-1 parts color masterbatch; The method for preparing the modified polyethylene includes the following steps: (1) mixing high-density polyethylene masterbatch, 5-hexenylmethyldichlorosilane, benzoyl peroxide, and xylene evenly, stirring at 100~105℃ for 2.5~3h, filtering, washing with acetone, and drying to obtain dichlorosilane modified polyethylene; (2) adding dichlorosilane modified polyethylene, 5-hexenylmethyldichlorosilane, and (3,3,3-trifluoropropyl)dichloromethylsilane to deionized water and mixing evenly, stirring at 95~100℃ for 25~30min, filtering, washing, and drying to obtain fluorinated modified polyethylene; (3) adding fluorinated modified polyethylene, 1,2-epoxyoctadecane, and stannous octoate to toluene and mixing evenly, stirring at 110~120℃ for 12~24h, evaporating the solvent, washing with acetone, and drying to obtain modified polyethylene; The fluorinated modified polyethylene comprises dichlorosilane-modified polyethylene, 5-hexenylmethyldichlorosilane, and (3,3,3-trifluoropropyl)dichloromethylsilane in a mass ratio of 10:2~3:4~6. The preparation method of the modified montmorillonite includes the following steps: (1) calcining montmorillonite at 200~250℃ for 2~3h, grinding, and passing through an 800~1000 mesh sieve to obtain activated montmorillonite; (2) adding activated montmorillonite to an ethanol aqueous solution and ultrasonically dispersing it evenly, adding 3-(2,3-epoxypropoxy)propyltrimethoxysilane, stirring at 80~90℃ for 20~24h, centrifuging, washing, grinding, and passing through an 800~1000 mesh sieve to obtain epoxy-modified montmorillonite; (3) mixing epoxy-modified montmorillonite, hydroxyl fluorosilicone oil, and stannous octoate evenly, stirring at 130~135℃ for 20~24h, centrifuging, washing, and drying to obtain modified montmorillonite.

2. A high barrier polyethylene milk bottle cap according to claim 1, characterized in that: The dichlorosilane-modified polyethylene comprises the following raw materials, by mass parts: 8-10 parts high-density polyethylene masterbatch, 18-20 parts 5-hexenylmethyldichlorosilane, 0.03-0.04 parts benzoyl peroxide, and 1-2 parts xylene; The modified polyethylene comprises the following raw materials, by mass parts: 8-10 parts of fluorinated modified polyethylene, 10-15 parts of 1,2-epoxyoctadecane, 0.02-0.03 parts of stannous octoate, and 8-10 parts of toluene.

3. A high barrier polyethylene milk bottle cap according to claim 1, characterized in that: The high-density polyethylene masterbatch has a particle size of 2-3 mm.

4. The high barrier polyethylene milk bottle cap according to claim 1, characterized in that: The epoxy-modified montmorillonite comprises the following raw materials, by mass parts: 2-3 parts activated montmorillonite, 100 parts 60% ethanol aqueous solution, and 3-4 parts 3-(2,3-epoxypropoxy)propyltrimethoxysilane. The modified montmorillonite comprises the following raw materials, by mass: 2-3 parts epoxy-modified montmorillonite, 10-12 parts hydroxyl fluorosilicone oil, and 0.01-0.02 parts stannous octoate.

5. The preparation method of the high-barrier polyethylene milk bottle cap according to any one of claims 1-4, characterized in that: The process includes the following steps: mixing high-density polyethylene, modified polyethylene, polyethylene elastomer, modified montmorillonite, antioxidant, initiator, and color masterbatch evenly, feeding them into a screw extruder, melting and extruding them, and injection molding them to obtain a high-barrier polyethylene milk bottle cap.

6. The method of claim 5, wherein the high barrier polyethylene milk bottle cap is prepared by the steps of: (1) preparing a high barrier polyethylene milk bottle cap by the method of claim 1; (2) coating the high barrier polyethylene milk bottle cap with a coating layer; and (3) drying the coating layer. During the melt extrusion process, the temperatures of each zone are 140~160℃, 165~170℃, 165~170℃, 170~180℃, 180~190℃, 180~190℃, 190~210℃, and 215~220℃, respectively.

7. The method of claim 5, wherein the high barrier polyethylene milk bottle cap is prepared by the steps of: (1) preparing a high barrier polyethylene milk bottle cap by the method of claim 1; (2) coating the high barrier polyethylene milk bottle cap with a coating layer; and (3) drying the coating layer. During the injection molding process, the injection pressure is 80~100 bar, and the temperatures in each temperature zone are 180~190℃, 190~200℃, 200~210℃, and 210~220℃.

Images