Sealing cover film for yoghourt plastic cup

Abstract

The invention relates to the technical field of inner-layer materials of yogurt cover films, and discloses a yogurt plastic cup sealing cover film which is prepared by compounding an outer-layer PET film, a middle-layer aluminum foil and an inner-layer hydrophobic heat-sealing film through a dry method. The invention discloses an inner-layer hydrophobic heat-sealing film of a yoghourt plastic cup sealing cover film. The inner-layer hydrophobic heat-sealing film comprises the following raw materials: ultralow-density polyethylene resin, low-density polyethylene resin, linear low-density polyethylene resin and an organic-inorganic composite hydrophobic composition, the organic-inorganic composite hydrophobic composition is prepared from low-density polyethylene resin, linear low-density polyethylene resin, long alkyl chain functionalized nano silicon dioxide and maleic anhydride grafted polyethylene resin. According to the prepared inner-layer hydrophobic heat-sealing film for the sealing cover film of the yoghourt plastic cup, the residual rate of yoghourt is reduced to 10% or below while it is guaranteed that the heat-sealing strength meets the use requirement.

Description

Technical Field

[0001] The invention relates to the technical field of inner layer materials of yogurt cover films, in particular to a sealing cover film for a yogurt plastic cup. Background Art

[0002] Currently, the common packaging forms of yogurt on the market are mainly bottles, cups and bags. When the sealing cover of cup yogurt is opened before eating, a thick layer of milk cap will appear on the cover film. The milk cap is actually formed on the cover film when the yogurt is shaken back and forth in the cup.

[0003] The sealing capping films for cup yogurt on the market are mainly made of composite materials. The outer layer material is usually selected from materials with good mechanical strength, heat resistance, good printing performance, and good optical performance. The middle layer material is usually used to strengthen a certain characteristic of the composite structure, such as barrier properties, light-shielding properties, fragrance retention, strength and other properties. The most critical function of the inner layer material is sealing. The inner layer structure is in direct contact with the inner object, so it is required to be non-toxic, odorless, water-resistant and oil-resistant. At present, the inner layer material of the sealing capping film of cup yogurt often adopts the same structure as the general beverage cap, which mainly plays a sealing role on the bottle body. However, since the concentration of yogurt is greater than that of general beverages, residues are common after drinking, so the development of yogurt capping film that does not stick to yogurt has very important industrial application value. Summary of the invention

[0004] The present invention independently develops an inner layer hydrophobic heat-sealing film product of a yogurt plastic cup sealing cover film, and the film product has the beneficial technical effect of significantly reducing the residual amount of yogurt in the inner layer of the sealing cover film.

[0005] A sealing cover film for a yogurt plastic cup, wherein the sealing cover film for the yogurt plastic cup is prepared by dry-compounding an outer PET film, an intermediate aluminum foil and an inner hydrophobic heat-sealing film; The inner layer hydrophobic heat-sealing film of the sealing cover film of the yogurt plastic cup comprises the following raw materials in parts by weight: 5-10 parts of ultra low density polyethylene resin VLLDPE; 40-60 parts of low-density polyethylene resin LDPE; 20-40 parts of linear low density polyethylene resin LLDPE; 15-30 parts of an organic-inorganic composite hydrophobic composition; The formula of the organic-inorganic composite hydrophobic composition is: 30-50wt% low-density polyethylene resin LDPE, 30-50wt% linear low-density polyethylene resin LLDPE, 10-25wt% long alkyl chain functionalized nano-silica and 0.5-5wt% maleic anhydride grafted polyethylene resin PE-g-MAH; Long alkyl chain functionalized nano-silica is obtained by modifying the surface of hydroxylated nano-silica with a long alkyl chain silane coupling agent; The long alkyl chain silane coupling agent is mono-cardanol ester trimethoxy silane or bis-cardanol ester trimethoxy silane.

[0006] Preferably, the synthesis method of the monocardanol ester trimethoxysilane is: Cardanol methacrylate is generated by a nucleophilic addition reaction between the acyl chloride functional group of methacryloyl chloride and the phenolic hydroxyl functional group of cardanol; The NH2 functional group of the silane coupling agent KH-540 and the α,β-unsaturated olefin functional group of cardanol methacrylate undergo an amine-ene addition reaction, and the molar ratio of the silane coupling agent KH-540 and the cardanol methacrylate participating in the reaction is controlled to be (1.01-1.09):1 to obtain monocardanol ester-based trimethoxysilane.

[0007] Preferably, the synthesis method of the bis-cardanol ester-based trimethoxysilane is: using the NH2 functional group of the silane coupling agent KH-540 and the α,β-unsaturated olefinic functional group of cardanol methacrylate to undergo an amine-ene addition reaction, and controlling the molar ratio of the silane coupling agent KH-540 and the cardanol methacrylate involved in the reaction to be 1:(2.01-2.09) to obtain bis-cardanol ester-based trimethoxysilane.

[0008] Preferably, the preparation method of the organic-inorganic composite hydrophobic composition is: preparing ingredients according to the formula of the organic-inorganic composite hydrophobic composition, adding the formulated raw materials into a high-speed mixer and mixing them evenly, and extruding and granulating them through a twin-screw extruder to prepare the organic-inorganic composite hydrophobic composition.

[0009] Preferably, the process parameters of the twin-screw extruder are set as follows: the temperatures of zones 1-6 are 160-170°C, 165-170°C, 170-180°C, 175-185°C, 175-185°C, 180-185°C, respectively, and the screw speed is 250-400r / min.

[0010] Preferably, the preparation method of the inner layer hydrophobic heat-sealing film of the yogurt plastic cup sealing cover film is: ingredients are prepared according to the formula of the inner layer hydrophobic heat-sealing film of the yogurt plastic cup sealing cover film, the formulated raw materials are added into a mixing device and mixed thoroughly, and the inner layer hydrophobic heat-sealing film of the yogurt plastic cup sealing cover film is prepared through an extrusion blow molding process.

[0011] Preferably, the parameters of the extrusion blow molding process are set as follows: barrel temperature zone 1 155-165°C, zone 2 165-170°C, zone 3 170-175°C, zone 4 175-185°C, and screw speed 35-50r / min.

[0012] Preferably, the thickness of the inner hydrophobic heat-sealing film of the yogurt plastic cup sealing cover film is 50-100 μm.

[0013] Compared with the prior art, the present invention has the following beneficial technical effects: The invention firstly synthesizes a long alkyl chain silane coupling agent with a hydrophobic function, which specifically comprises mono-cardanol ester trimethoxy silane and bis-cardanol ester trimethoxy silane; Then, the surface of hydroxylated nano-silica is modified by using a long alkyl chain silane coupling agent with hydrophobic function to obtain long alkyl chain functionalized nano-silica; Long alkyl chain functionalized nano-silica is used as a hydrophobic functional filler and is compounded with a low-density polyethylene resin, a linear low-density polyethylene resin and a maleic anhydride grafted polyethylene resin to obtain an organic-inorganic composite hydrophobic composition; An organic-inorganic composite hydrophobic composition is introduced into polyethylene resin, and an inner layer hydrophobic heat-sealing film for the sealing cover film of a yogurt plastic cup is prepared through an extrusion blow molding process. While ensuring that the heat-sealing strength meets the use requirements, the yogurt residue rate is reduced to less than 10%. DETAILED DESCRIPTION Embodiment 1:

[0014] A yogurt plastic cup sealing cover film, which is prepared by dry compounding of an outer PET film, an intermediate aluminum foil and an inner hydrophobic heat-sealing film; The inner hydrophobic heat-sealing film is the inner hydrophobic heat-sealing film a or the inner hydrophobic heat-sealing film b. Embodiment 2:

[0015] The inner layer hydrophobic heat-sealing film a of the sealing cover film of the yogurt plastic cup in Example 1 comprises the following raw materials in parts by weight: 8 parts of ultra-low density polyethylene resin VLLDPE; ultra-low density polyethylene resin VLLDPE was purchased from Dongguan Hongkuo Plastic Co., Ltd., brand VL8005; 50 parts of low-density polyethylene resin LDPE; the low-density polyethylene resin LDPE was purchased from Shanghai Handar New Materials Co., Ltd., brand Q281; 30 parts of linear low-density polyethylene resin LLDPE; linear low-density polyethylene resin LLDPE was purchased from Dongguan Hongkuo Plastic Co., Ltd., brand LL6201RQ; 25 parts of an organic-inorganic composite hydrophobic composition; The formula of the organic-inorganic composite hydrophobic composition is: 40wt% low-density polyethylene resin LDPE, 40wt% linear low-density polyethylene resin LLDPE, 18wt% hydrophobic nano-silica (which is monocardanol ester-based nano-silica) and 2wt% maleic anhydride grafted polyethylene resin PE-g-MAH; Monocardanol ester-based nano-silica is a homemade raw material of the present invention, and its preparation method is described in Experimental Example 1; Maleic anhydride grafted polyethylene resin PE-g-MAH was purchased from Dongguan Taotao Plastic Raw Materials Co., Ltd., brand 18410P. Embodiment three:

[0016] The method for preparing the inner hydrophobic heat-sealing film a of the sealing cover film of the yogurt plastic cup in Example 2 comprises the following steps: Step 1, preparation of monocardanol ester-based nano-silica: using monocardanol ester-based trimethoxysilane to modify the surface of hydroxylated nano-silica, the specific experimental process is: prepare 50mL of a mixed solvent (composed of equal volume portions of anhydrous ethanol and deionized water), add ammonia water to adjust the pH value of the mixed solution to 9; add 10g of nano-silica (7nm) to the mixed solvent, ultrasonically disperse for 10min, stir in a water bath at 80°C for 20min, add 10mL of anhydrous ethanol solution containing 0.25g of cardanol ester-based trimethoxysilane, stir in a water bath at 80°C for 2h, filter, wash, and obtain monocardanol ester-based nano-silica; Step 2, preparing an organic-inorganic composite hydrophobic composition: according to the formula of the organic-inorganic composite hydrophobic composition, the ingredients are prepared, the formula raw materials are added to a high-speed mixer and mixed evenly, and the mixture is extruded and granulated by a twin-screw extruder. The process parameters of the twin-screw extruder are set as follows: the temperatures of zones 1-6 are 165°C, 170°C, 175°C, 180°C, 180°C, and 185°C, respectively, and the screw speed is 300r / min, to prepare an organic-inorganic composite hydrophobic composition; Step three, prepare the hydrophobic heat-sealing film a: prepare the ingredients according to the formula of the inner layer hydrophobic heat-sealing film of the yogurt plastic cup sealing cover film, add the formulated raw materials into the mixing equipment and mix them evenly, and then undergo the extrusion blow molding process. The extrusion blow molding process parameters are: barrel temperature zone 160°C, zone 2 165°C, zone 3 175°C, zone 4 185°C, screw speed 40r / min, and prepare the inner layer hydrophobic heat-sealing film a of the yogurt plastic cup sealing cover film with a thickness of 70μm. Embodiment 4:

[0017] The inner layer hydrophobic heat-sealing film b of the yogurt plastic cup sealing cover film in Example 1 is prepared. The formula and preparation method of the inner layer hydrophobic heat-sealing film b are different from the formula and preparation method of the inner layer hydrophobic heat-sealing film a of the yogurt plastic cup sealing cover film in that the hydrophobic nano-silica is bis-cardanol ester-based nano-silica; Biscardanol ester-based nano-silica is a self-made raw material of the present invention, and its preparation method is described in Experimental Example 2. Embodiment five:

[0018] The performance test of the inner hydrophobic heat-sealing film of the yogurt plastic cup sealing cover film in Example 1 was carried out, and the test method was as follows: 1. The HSG-C heat sealer was used to conduct heat sealing experiments on the samples. The sealing knife area was 15 cm × 1 cm, the heat sealing temperature was set to 160 ° C, the heat sealing pressure was 0.2 MPa, and the heat sealing time was 1.0 s. According to QB / T 2358-1998 "Test Method for Heat Seal Strength of Plastic Film Packaging Bags", the heat seal performance of the heat seal sample was tested at a test speed of 300mm / min and a clamp spacing of 50mm. The heat seal strength of the sample was recorded. 2. Weigh the initial weight of the film m0 and the weight of yogurt (Mengniu Pure Yogurt) M, drop the yogurt on the surface of the film, observe the flow of the yogurt, and weigh the weight of the film m1 again after the yogurt slides on the film surface for 30 seconds. The ratio of the weight of the yogurt remaining on the film to the total weight of the yogurt dropped on the film is the residual rate of the yogurt, and the formula is: residual rate = [(m1-m0) / M] × 100%; The above experimental results are shown in Table 1 below; Table 1 Performance test results of the inner hydrophobic heat-sealing film of the yogurt plastic cup sealing cover film

[0019] Note: The formula and preparation method of the inner hydrophobic heat-sealing film 1 are different from the formula and preparation method of the inner hydrophobic heat-sealing film a of the yogurt plastic cup sealing cover film only in that the hydrophobic nano-silicon dioxide (7nm) is replaced by the directly purchased raw material; The formula of the inner layer hydrophobic heat-sealing film 2 is: 8 parts of ultra-low density polyethylene resin VLLDPE; ultra-low density polyethylene resin VLLDPE was purchased from Dongguan Hongkuo Plastic Co., Ltd., brand VL8005; 60 parts of low-density polyethylene resin LDPE; the low-density polyethylene resin LDPE was purchased from Shanghai Handar New Materials Co., Ltd., brand Q281; 40 parts of linear low-density polyethylene resin LLDPE; linear low-density polyethylene resin LLDPE was purchased from Dongguan Hongkuo Plastic Co., Ltd., brand LL6201RQ; 5 parts of maleic anhydride grafted polyethylene resin PE-g-MAH; The preparation method of the inner layer hydrophobic heat-sealing film II is as follows: ingredients are prepared according to the formula of the inner layer hydrophobic heat-sealing film II, the formula raw materials are added into a mixing device and mixed evenly, and the inner layer hydrophobic heat-sealing film II is prepared by an extrusion blow molding process, wherein the extrusion blow molding process is controlled as follows: the barrel temperature is 160° C. in the first zone, 165° C. in the second zone, 175° C. in the third zone, and 185° C. in the fourth zone, and the screw speed is 40 r / min, thereby preparing the inner layer hydrophobic heat-sealing film II with a thickness of 70 μm; From the experimental results, we can know that: The heat sealing strength of the inner layer hydrophobic heat sealing film of the yogurt plastic cup sealing cover film prepared by the present invention is significantly greater than the technical requirement of JB / T 9086-2007 "Plastic Bag Hot Press Sealing Machine" on the sealing strength ≥10N (material thickness R, 0.04mm≤R<0.08mm); In addition, the inner layer hydrophobic heat-sealing film product of the yogurt plastic cup sealing cover film prepared by the present invention achieves the beneficial technical effect of significantly reducing the amount of yogurt residue. Experimental Example 1:

[0020] The specific synthesis process of synthesizing monocardanol ester trimethoxysilane is as follows: Synthesis of cardanol methacrylate: cardanol methacrylate is generated by a nucleophilic addition reaction between the acyl chloride functional group of methacryloyl chloride and the phenolic hydroxyl functional group of cardanol. The specific experimental steps are as follows: 6.08 g of cardanol, 3 mL of triethylamine and 80 mL of dichloromethane are added to a three-necked flask, and magnetic stirring is performed at room temperature. A mixed solution of 2 mL of methacryloyl chloride and 20 mL of dichloromethane is slowly added dropwise with a constant pressure dropping funnel. After the addition is completed, the mixture is refluxed at 38° C. for 2 h. After the reaction is completed, the mixture is filtered and distilled under reduced pressure to obtain cardanol methacrylate, and its chemical structure is as follows: ; Synthesis of mono-cardanol ester trimethoxysilane: The NH2 functional group of 3-aminopropyl trimethoxysilane (silane coupling agent KH-540) and the α,β-unsaturated olefin functional group of cardanol methacrylate are used to undergo an amine-ene addition reaction, and the molar ratio of 3-aminopropyl trimethoxysilane (silane coupling agent KH-540) to cardanol methacrylate participating in the reaction is controlled to be 1.07:1 to obtain mono-cardanol ester trimethoxysilane. The specific experimental steps are as follows: Under the protection of a nitrogen atmosphere, 1.5 mL of 3-aminopropyl trimethoxysilane (silane coupling agent KH-540), 3 g of cardanol methacrylate and 25 mL of anhydrous ethanol are added to a three-necked flask, and the reaction is stirred for 12 h under reflux, the solvent is evaporated by a rotary evaporator, and the mono-cardanol ester trimethoxysilane is obtained. Its chemical structure is: ; The hydrogen spectrum characterization results of monocardanol ester trimethoxysilane are as follows: 1H NMR (400MHz, DMSO-d6, δ, ppm): 0.60-0.75 (m, 2H), 0.87-0.92 (t, 3H), 1.09-1.10 (d, 3H), 1.19-1.39 (m, 24H), 1.50-1.63(m, 4H), 2.42-2.48(m, 1H), 2.53-2.75(m, 5H), 2.97-3.08(m, 2H), 3.57(s, 9H), 6.86-7.31(m, 4H). Experimental Example 2:

[0021] Synthesis of bis-cardanol trimethoxysilane: The NH2 functional group of 3-aminopropyl trimethoxysilane (silane coupling agent KH-540) and the α,β-unsaturated olefin functional group of cardanol methacrylate are used to undergo an amine-ene addition reaction, and the molar ratio of 3-aminopropyl trimethoxysilane (silane coupling agent KH-540) to cardanol methacrylate participating in the reaction is controlled to be 1:2.08 to obtain bis-cardanol trimethoxysilane. The specific experimental steps are as follows: Under the protection of a nitrogen atmosphere, 1 mL of 3-aminopropyl trimethoxysilane (silane coupling agent KH-540), 4.4 g of cardanol methacrylate and 25 mL of anhydrous ethanol are added to a three-necked flask, and the reaction is stirred for 12 h under reflux, and the solvent is evaporated by a rotary evaporator. The mixture is vacuum dried at 60°C for 12 h to obtain bis-cardanol trimethoxysilane, and its chemical structure is as follows: ; The hydrogen spectrum characterization results of bis-cardanol ester trimethoxysilane are as follows: 1 H NMR (400MHz, DMSO-d6, δ, ppm): 0.62-0.78 (m, 2H), 0.86-0.92 (t, 6H), 1.18-1.36 (m, 54H), 1.53-1.62(m, 6H), 2.54-2.66(m, 8H), 2.86-3.00(m, 4H), 3.57(s, 9H), 6.87-7.33(m, 8H).

Claims

1. A sealing cover film for a yogurt plastic cup, characterized in that: The sealing cover film of the yogurt plastic cup is prepared by dry compounding of an outer PET film, an intermediate aluminum foil and an inner hydrophobic heat-sealing film; The inner layer hydrophobic heat-sealing film of the sealing cover film of the yogurt plastic cup comprises the following raw materials in parts by weight: 5-10 parts of ultra low density polyethylene resin VLLDPE; 40-60 parts of low-density polyethylene resin LDPE; 20-40 parts of linear low density polyethylene resin LLDPE; 15-30 parts of an organic-inorganic composite hydrophobic composition; The formula of the organic-inorganic composite hydrophobic composition is: 30-50wt% low-density polyethylene resin LDPE, 30-50wt% linear low-density polyethylene resin LLDPE, 10-25wt% long alkyl chain functionalized nano-silica and 0.5-5wt% maleic anhydride grafted polyethylene resin PE-g-MAH; Long alkyl chain functionalized nano-silica is obtained by modifying the surface of hydroxylated nano-silica with a long alkyl chain silane coupling agent; The long alkyl chain silane coupling agent is mono-cardanol ester trimethoxy silane or bis-cardanol ester trimethoxy silane.

2. The sealing cover film for a yogurt plastic cup according to claim 1, characterized in that: The chemical structural formula of the monocardanol ester trimethoxysilane is: 。 3. The sealing cover film for a yogurt plastic cup according to claim 2, characterized in that: The synthesis method of the monocardanol ester trimethoxysilane is: Cardanol methacrylate is generated by a nucleophilic addition reaction between the acyl chloride functional group of methacryloyl chloride and the phenolic hydroxyl functional group of cardanol; The NH2 functional group of the silane coupling agent KH-540 and the α,β-unsaturated olefin functional group of cardanol methacrylate undergo an amine-ene addition reaction, and the molar ratio of the silane coupling agent KH-540 and the cardanol methacrylate participating in the reaction is controlled to be (1.01-1.09):1 to obtain monocardanol ester-based trimethoxysilane.

4. The sealing cover film for a yogurt plastic cup according to claim 1, characterized in that: The chemical structural formula of the bis-cardanol ester trimethoxysilane is: 。 5. The sealing cover film for a yogurt plastic cup according to claim 4, characterized in that: The synthesis method of the bis-cardanol ester-based trimethoxysilane is as follows: an amine-ene addition reaction is carried out by using the NH2 functional group of the silane coupling agent KH-540 and the α,β-unsaturated olefin functional group of cardanol methacrylate, and the molar ratio of the silane coupling agent KH-540 and the cardanol methacrylate participating in the reaction is controlled to be 1:(2.01-2.09), thereby obtaining the bis-cardanol ester-based trimethoxysilane.

6. The sealing cover film for a yogurt plastic cup according to claim 1, characterized in that: The preparation method of the organic-inorganic composite hydrophobic composition comprises: preparing ingredients according to the formula of the organic-inorganic composite hydrophobic composition, adding the formula raw materials into a high-speed mixer and mixing them evenly, and extruding and granulating them through a twin-screw extruder to prepare the organic-inorganic composite hydrophobic composition.

7. The sealing cover film for a yogurt plastic cup according to claim 6, characterized in that: The process parameters of the twin-screw extruder are set as follows: the temperatures of zones 1-6 are 160-170°C, 165-170°C, 170-180°C, 175-185°C, 175-185°C, 180-185°C, respectively, and the screw speed is 250-400r / min.

8. The sealing cover film for a yogurt plastic cup according to claim 1, characterized in that: The preparation method of the inner hydrophobic heat-sealing film of the yogurt plastic cup sealing cover film comprises the following steps: preparing ingredients according to the formula of the inner hydrophobic heat-sealing film of the yogurt plastic cup sealing cover film, adding the formulated raw materials into a mixing device and mixing them evenly, and preparing the inner hydrophobic heat-sealing film of the yogurt plastic cup sealing cover film through an extrusion blow molding process.

9. The sealing cover film for a yogurt plastic cup according to claim 8, characterized in that: The parameters of the extrusion blow molding process are set as follows: barrel temperature zone 1 155-165°C, zone 2 165-170°C, zone 3 170-175°C, zone 4 175-185°C, and screw speed 35-50r / min.

10. A sealing cover film for a yogurt plastic cup according to any one of claims 1 to 9, characterized in that: The thickness of the inner hydrophobic heat-sealing film of the yogurt plastic cup sealing cover film is 50-100 μm.

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