A recyclable low-temperature heat-seal packaging composite film and a preparation process thereof

Abstract

The present application relates to the development of multifunctional sauce packaging material technical field, specifically to a kind of easy recovery low temperature heat sealing packaging composite film and preparation process, comprising: setting packaging composite film is eleven layer coextrusion film;Using the silane crosslinking agent containing phenolic hydroxyl functional group and methoxyl functional group is crosslinked to hydroxyl-terminated polydimethylsiloxane Processing, obtain the antisticking modifier;With metallocene polyethylene resin, low-density polyethylene resin and antisticking modifier as raw material synthesis heat sealing layer, using eleven layer coextrusion blow molding process, obtain the thickness 50~200 μm easy recovery low temperature heat sealing packaging composite film, it not only significantly reduces the adhesion amount of sauce on the surface of packaging composite film, and under the low temperature heat sealing of 100 ℃, obtain the beneficial technical effect that heat sealing strength is greater than 15N / 15mm, it has the effect of energy saving and consumption reduction in packaging link, can be used to package sauce product, play the role of antiadhesion.

Description

TECHNICAL FIELD

[0001] The present application relates to the development of multifunctional sauce packaging materials, specifically to an easy-to-recycle low-temperature heat-seal packaging composite film and its preparation process. BACKGROUND

[0002] Sauce is a daily-use seasoning product, which is often used to add color and flavor in diet and cooking. The packaging forms of sauce are various, including canned packaging and bagged packaging for easy carrying. Bagged packaging sauce is usually packaged with plastic soft film.

[0003] The emergence of small-bag packaged sauce is the result of market demand. It can provide various conveniences to consumers. Compared with large canned sauce, which is bulky and not easy to carry, small-bag packaged sauce is more suitable for use in travel, fast food, and other situations where the amount of use is small. This makes the use of sauce packets remain high. With the increase of use, the problems generated during use become significant, typically manifested as sauce, as a viscous liquid food, will always have some sauce adhering to the surface of the packaging material after being eaten, causing waste.

[0004] In addition, heat sealing is a process that uses external heating conditions (electric heating, high-frequency induction heating, ultrasonic waves, etc.) to make the sealing part of the plastic substrate film become a viscous flow state, and with the help of the pressure between the heat sealing tools, the upper and lower two layers of film are fused into one, and after cooling, a certain strength is maintained. The main factor affecting the heat sealing property of the film is the melting point of the film. The film with a lower melting point generally requires a lower temperature during heat sealing. Among several commonly used heat-sealable films, EVA film, ionic polymer, and metallocene polyethylene have lower heat-sealing temperatures than PE film. Among them, the melting point of metallocene polyethylene is lower than that of traditional polyethylene, so under the same density, its heat-sealing temperature is also lower, but the heat-sealing strength is higher.

[0005] In addition, the packaging material of a single material does not need to be classified for recycling and can be recycled and reused, gradually becoming the development trend of plastic soft packaging. SUMMARY

[0006] The present application utilizes hydrophobic siloxane polymer to optimize the hydrophobic properties of the polyethylene matrix, and on the other hand, by blending low-melting-point metallocene polyethylene, the low-temperature heat-sealing properties of the polyethylene matrix are optimized. An easy-to-recycle low-temperature heat-seal packaging composite film is prepared by co-extrusion blow molding process.

[0007] A preparation process of an easy-to-recycle low-temperature heat-seal packaging composite film, comprising the following steps:

[0008] Step one: set the film layer structure of eleven-layer co-extruded film, the structure is as follows: surface layer (6-1), support layer (5-1), support layer (4-1), adhesive layer (3-1), barrier layer (2-1), barrier layer (1), barrier layer (2-2), adhesive layer (3-2), support layer (4-2), support layer (5-2), heat-seal layer (6-2);

[0009] Step two: prepare the raw materials of eleven-layer co-extruded film:

[0010] The raw material of surface layer (6-1) is 60-80wt% low-density polyethylene resin and 20-40wt% linear low-density polyethylene resin;

[0011] The raw material of support layer (5-1), support layer (4-1), support layer (5-2) and support layer (4-2) is 30-50wt% high-density polyethylene resin and 50-70wt% low-density polyethylene resin;

[0012] The raw material of adhesive layer (3-1) and adhesive layer (3-2) is 100wt% maleic anhydride grafted polyethylene resin;

[0013] The raw material of barrier layer (2-1) and barrier layer (2-2) is 95-99wt% low-density polyethylene resin and 1-5wt% ethylene-vinyl alcohol copolymer resin;

[0014] The raw material of barrier layer (1) is 90-99wt% low-density polyethylene resin and 1-10wt% ethylene-vinyl alcohol copolymer resin;

[0015] The raw material of heat-seal layer (6-2) is 15-25wt% low-density polyethylene resin, 65-85wt% metallocene polyethylene resin and 1-10wt% anti-sticking modifier;

[0016] Among them, the preparation method of anti-sticking modifier is: using silane crosslinking agent containing phenolic hydroxyl functional group and methoxyl functional group to crosslink hydroxyl-terminated polydimethylsiloxane to obtain;

[0017] Step three: according to the raw material in step two, eleven-layer co-extruded blown film process is used to prepare easy-to-recycle low-temperature heat-seal packaging composite film with thickness of 50-200μm.

[0018] Preferably, the mass ratio of the surface layer (6-1), the support layer (5-1), the support layer (4-1), the adhesive layer (3-1), the barrier layer (2-1), the barrier layer (1), the barrier layer (2-2), the adhesive layer (3-2), the support layer (4-2), the support layer (5-2), and the heat-sealing layer (6-2) in the packaging composite film is (5-15): (5-15): (5-15): (1-5): (5-15): (3-10): (5-15): (1-5): (5-15): (5-15): (10-30).

[0019] Preferably, the preparation method of the silane crosslinker containing phenolic hydroxyl functional groups and methoxy functional groups is as follows: a basic catalyst is used to catalyze a nucleophilic addition reaction between the alkenyl functional group of 1 molar equivalent of magnolol and the mercapto functional group of (2.01-2.05) molar equivalents of 3-mercaptopropyltrimethoxysilane to prepare a silane crosslinker containing phenolic hydroxyl functional groups and methoxy functional groups.

[0020] Preferably, the alkaline catalyst is one of sodium hydroxide, sodium carbonate and sodium ethoxide.

[0021] Preferably, the preparation method of the anti-sticking modifier is as follows: on the one hand, a silanol functional group generated by a hydrolysis reaction of a silane crosslinker containing a phenolic hydroxyl functional group and a methoxy functional group undergoes a condensation reaction with a hydroxyl functional group of a hydroxyl-terminated polydimethylsiloxane; and on the other hand, a hydrogen bond is generated between the phenolic hydroxyl functional group of the silane crosslinker containing a phenolic hydroxyl functional group and a methoxy functional group and the hydroxyl-terminated polydimethylsiloxane to prepare the anti-sticking modifier.

[0022] Preferably, the mass ratio of the silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups to the hydroxyl-terminated polydimethylsiloxane in the anti-sticking modifier is 1:(2-10).

[0023] Preferably, the number average molecular weight of the hydroxyl-terminated polydimethylsiloxane is 1000-4000.

[0024] The easily recyclable low-temperature heat-sealable packaging composite film prepared according to the above process has a heat-seal strength of ≥15N / 15mm under the condition of a heat-seal temperature of 100°C.

[0025] The easily recyclable low-temperature heat-sealed packaging composite film prepared according to the above process is used to package sauce products and has an anti-adhesion effect.

[0026] Beneficial effects:

[0027] A silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups is synthesized using the bioactive compounds magnolol and 3-mercaptopropyl trimethoxysilane extracted from the bark of Magnolia officinalis as raw materials, and a hydroxyl-terminated polydimethylsiloxane (hydrophobic agent) is crosslinked using the silane crosslinking agent, and then added to polyethylene containing a metallocene polyethylene (low-temperature heat sealing performance resin) in the formula to prepare a packaging composite film, which not only significantly reduces the amount of sauce adhering to the surface of the packaging composite film, but also achieves a heat sealing strength greater than 15 N / 15 mm at a low temperature of 100 ℃, thereby achieving energy saving and consumption reduction in the packaging process. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Product structure diagram of the packaging composite film;

[0029] Among them, the numbers 1, 2-1 and 2-2 are barrier layers, the numbers 3-1 and 3-2 are adhesive layers, the numbers 4-1, 4-2, 5-1 and 5-2 are support layers, the number 6-1 is a surface layer, and the number 6-2 is a heat sealing layer. DETAILED DESCRIPTION

[0030] Example 1:

[0031] Preparation of a silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups: a nucleophilic addition reaction occurs between the alkyl functional groups of 1 mole equivalent of magnolol and the mercapto functional groups of (2.01-2.05) mole equivalents of 3-mercaptopropyl trimethoxysilane catalyzed by a basic catalyst to generate a silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups, and the chemical structural formula is:

[0032]

[0033] Among them, the basic catalyst is one of sodium hydroxide, sodium carbonate and sodium ethoxide; sodium ethoxide is selected for use in this experimental example;

[0034] The specific experimental steps for preparing the silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups are as follows: 2.7 g of magnolol, 0.5 g of sodium ethoxide and 30 mL of anhydrous ethanol are added to a three-necked flask, stirred at room temperature until completely dissolved, then 4 mL of 3-mercaptopropyl trimethoxysilane is added dropwise to the three-necked flask, heated to 70 ℃ and stirred for 6 h, cooled to room temperature, washed with deionized water, dried with anhydrous magnesium sulfate, removed the solvent by rotary evaporation, and vacuum dried to obtain the silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups;

[0035] The nuclear magnetic resonance hydrogen spectrum of the silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups is characterized as: 1H NMR (CDC13, 400 MHz) δ: 0.78-0.82 (t, 4H), 1.65-1.72 (m, 4H), 1.85-1.92 (m, 4H), 2.52-2.58 (m, 8H), 2.82-2.86 (t, 4H), 3.57 (s, 18H), 6.90-7.09 (m, 6H, Ar-H).

[0036] Example 2:

[0037] The anti-sticking modifier is prepared by crosslinking treatment of hydroxyl-terminated polydimethylsiloxane with a silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups.

[0038] The crosslinking mechanism of the silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups to the hydroxyl-terminated polydimethylsiloxane is that, on the one hand, the silanol functional groups generated by the hydrolysis reaction of the hydrolysis functional groups of the silane crosslinking agent and the hydroxyl functional groups of the hydroxyl-terminated polydimethylsiloxane undergo condensation reaction, and on the other hand, the phenolic hydroxyl functional groups of the silane crosslinking agent and the hydroxyl-terminated polydimethylsiloxane produce hydrogen bonding.

[0039] The specific experimental steps for preparing the anti-sticking modifier are as follows: 5 g of hydroxyl-terminated polydimethylsiloxane, 80 mL of dichloromethane and 20 mL of deionized water are added to a beaker, heated to 40°C and stirred until completely dissolved and uniform, then 1 g of a silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups and 2 drops of glacial acetic acid are added to the beaker in turn, and the temperature is continued to be raised to 60°C and stirred for 5 h, then cooled to room temperature, rotary evaporation to remove the solvent, vacuum drying to obtain the anti-sticking modifier.

[0040] The hydroxyl-terminated polydimethylsiloxane is purchased from Wuhan Kemik Biomedical Technology Co., Ltd., and its specification is: average Mn ~ 2000.

[0041] Example 5:

[0042] The packaging composite film is prepared by using an eleven-layer co-extrusion film blowing machine set, and a packaging composite film with a thickness of 80 μm is prepared, as shown in the following table: Figure 1 The film structure of the packaging composite film is in turn: surface layer 6-1, support layer 5-1, support layer 4-1, adhesive layer 3-1, barrier layer 2-1, barrier layer 1, barrier layer 2-2, adhesive layer 3-2, support layer 4-2, support layer 5-2, heat-seal layer 6-2, and the mass ratio of the film structure is 10:10:10:2.5:10:5:10:2.5:10:10:20.

[0043] The raw material of the surface layer 6-1 is 70wt% low-density polyethylene resin and 30wt% linear low-density polyethylene resin; the raw material of the support layer 5-1, the support layer 4-1, the support layer 5-2 and the support layer 4-2 is 40wt% high-density polyethylene resin and 60wt% low-density polyethylene resin; the raw material of the heat-sealing layer 6-2 is 20wt% low-density polyethylene resin, 75wt% metallocene polyethylene resin and 5wt% anti-sticking modifier;

[0044] The process parameters of the corresponding screw extruder of the surface layer 6-1, the support layer 5-1, the support layer 4-1, the support layer 5-2, the support layer 4-2 and the heat-sealing layer 6-2 are set as follows: the temperatures of 1-3 zones are 120℃, 150℃ and 170℃ respectively, the runner temperature is 165℃, and the rotating speed is 30r / min;

[0045] The raw material of the barrier layer 1 is 95wt% low-density polyethylene resin and 5wt% ethylene-vinyl alcohol copolymer resin, and the process parameters of the corresponding screw extruder are set as follows: the temperatures of 1-3 zones are 150℃, 170℃ and 190℃ respectively, the runner temperature is 185℃, and the rotating speed is 40r / min;

[0046] The raw material of the barrier layer 2-1 and the barrier layer 2-2 is 97wt% low-density polyethylene resin and 3wt% ethylene-vinyl alcohol copolymer resin, and the process parameters of the corresponding screw extruder are set as follows: the temperatures of 1-3 zones are 140℃, 160℃ and 180℃ respectively, the runner temperature is 175℃, and the rotating speed is 40r / min;

[0047] The raw material of the adhesive layer 3-1 and the adhesive layer 3-2 is 100wt% maleic anhydride grafted polyethylene resin, and the process parameters of the corresponding screw extruder are set as follows: the temperatures of 1-3 zones are 115℃, 145℃ and 160℃ respectively, the runner temperature is 150℃, and the rotating speed is 15r / min;

[0048] The low-density polyethylene resin is purchased from Jiangsu Rantai Plastic Co., Ltd., and its brand is LD 150DW; the linear low-density polyethylene resin is purchased from Yuyao Hongyang Plastic Co., Ltd., and its brand is 2045G; the high-density polyethylene resin is purchased from Dongguan Longhang Plastic Raw Material Co., Ltd., and its brand is FB5600; the metallocene polyethylene resin is purchased from Dongguan Jinshixiang Plastic Raw Material Co., Ltd., and its brand is SP4020; the maleic anhydride grafted polyethylene resin is purchased from Dongguan Taota Plastic Raw Material Co., Ltd., and its brand is 4288.

[0049] Comparative example:

[0050] Preparation of the composite film a: referring to the preparation experiment of the packaging composite film, the difference is only that the anti-sticking modifier is not used, and the composite film a is prepared, which is used as Comparative Example 1;

[0051] Preparation of composite film b: Refer to the preparation experiment of the packaging composite film, the difference is only that no anti-sticking modifier is used, and the raw material of the heat-sealing layer 6-2 is 100 wt% low-density polyethylene resin, and the composite film b is prepared as Comparative Example 2.

[0052] Performance test:

[0053] (1) Heat-sealing performance test: The HSG-C type heat-sealing instrument is used to perform the heat-sealing experiment on the sample, the sealing knife area is 15 cm x 1 cm, the heat-sealing temperature is 100°C, the heat-sealing pressure is 0.2 MPa, and the heat-sealing time is 2.0 s; the heat-sealing performance of the sample is tested according to QB / T 2358-1998;

[0054] (2) Barrier performance test: The barrier performance of the sample is tested according to GB / T 1038-2000 and GB / T 1037-2021 respectively;

[0055] (3) Mechanical property test: The mechanical property of the sample is tested according to GB / T 13022-91;

[0056] (4) Anti-sticking performance test: The anti-sticking performance is analyzed by testing the residual amount of sauce on the sample, and the specific test steps are as follows: a sample of 3 cm x 2 cm is fixed on a clamp plate with a length x width of 5 cm x 4 cm, a drop of sauce (Sousaku soy sauce) is injected to the top end of the sample with a 20 mL range syringe filled with sauce, the initial sauce mass is weighed, then the test sample is placed at an angle of 45° with the horizontal plane, after the sauce flows down, it is placed for 20 s, the residual sauce mass after tilting is recorded, and the sauce residual amount is calculated, the specific method is as follows:

[0057] Sauce residual amount (%) = residual sauce mass on the sample after tilting / initial sauce mass on the sample;

[0058] (5) Hygienic performance: The hygienic performance of the sample is tested according to GB / T 5009.60-2003;

[0059] The above test results are shown in Tables 1 and 2;

[0060] Table 1 Performance test results of packaging composite film

[0061]

[0062] Table 2 Performance test results of composite film

[0063]

[0064] Note: the physicochemical indexes of the experimental results are in accordance with GB / T 5009.58-2003 "Analysis Method of Polyethylene Resin Hygienic Standard for Food Packaging";

[0065] By comprehensively analyzing the above experimental results, the following conclusions can be drawn:

[0066] Conclusion 1: The heat sealing strength of the packaging composite film prepared by the application is greater than 15 N / 15 mm at a heat sealing temperature of 100 DEG C. According to the national standards and the use requirements of the enterprise users, the packaging composite film prepared by the application belongs to a low-temperature heat sealing type packaging material.

[0067] Conclusion 2: The adhesion-resistant modifier prepared by cross-linking treatment of hydroxyl-terminated polydimethylsiloxane with a silane cross-linking agent containing phenolic hydroxyl functional groups and methoxyl functional groups can significantly reduce the sauce residue of the packaging composite film, and has a very significant effect on the improvement of the adhesion resistance of the packaging composite film.

[0068] Conclusion 3: The packaging composite film prepared by the application exhibits relatively excellent barrier properties and mechanical properties.

Claims

1. A process for the preparation of a recyclable low temperature heat sealable packaging composite film, characterized in that, The method comprises the following steps: Step one: setting the film layer structure of the eleven-layer co-extruded film, and the structure is specifically as follows: surface layer (6-1), support layer (5-1), support layer (4-1), adhesive layer (3-1), barrier layer (2-1), barrier layer (1), barrier layer (2-2), adhesive layer (3-2), support layer (4-2), support layer (5-2), heat-sealing layer (6-2); Step two: preparing the raw materials of the eleven-layer co-extruded film: The raw material of the surface layer (6-1) is 60-80 wt% low-density polyethylene resin and 20-40 wt% linear low-density polyethylene resin; The raw material of the support layer (5-1), the support layer (4-1), the support layer (5-2) and the support layer (4-2) is 30-50 wt% high-density polyethylene resin and 50-70 wt% low-density polyethylene resin; The raw material of the adhesive layer (3-1) and the adhesive layer (3-2) is 100 wt% maleic anhydride grafted polyethylene resin; The raw material of the barrier layer (2-1) and the barrier layer (2-2) is 95-99 wt% low-density polyethylene resin and 1-5 wt% ethylene-vinyl alcohol copolymer resin; The raw material of the barrier layer (1) is 90-99 wt% low-density polyethylene resin and 1-10 wt% ethylene-vinyl alcohol copolymer resin; The raw material of the heat-sealing layer (6-2) is 15-25 wt% low-density polyethylene resin, 65-85 wt% metallocene polyethylene resin and 1-10 wt% anti-sticking modifier; The preparation method of the anti-sticking modifier is as follows: a silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups is used to crosslink hydroxyl-terminated polydimethylsiloxane to obtain the anti-sticking modifier; The chemical structural formula of the silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups is as follows: Step three: according to the raw material formula in step two, an eleven-layer co-extruded blown film process is used to prepare an easy-to-recycle low-temperature heat-sealing packaging composite film with a thickness of 50-200 μm.

2. The process for the preparation of a recyclable low temperature heat sealable packaging composite film according to claim 1, characterized in that, The mass ratio of the surface layer (6-1), the support layer (5-1), the support layer (4-1), the adhesive layer (3-1), the barrier layer (2-1), the barrier layer (1), the barrier layer (2-2), the adhesive layer (3-2), the support layer (4-2), the support layer (5-2) and the heat-sealing layer (6-2) in the packaging composite film is (5-15):(5-15):(5-15):(1-5):(5-15):(3-10):(5-15):(1-5):(5-15):(5-15):(10-30).

3. The process for preparing a recyclable low-temperature heat-seal packaging composite film according to claim 1, characterized in that, The preparation method of the silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups is as follows: under the catalysis of an alkaline catalyst, 1 mole equivalent of the alkenyl functional groups of magnolol reacts with (2.01-2.05) mole equivalents of the mercapto functional groups of 3-mercaptopropyltrimethoxysilane to obtain the silane crosslinking agent containing phenolic hydroxyl functional groups and methoxy functional groups.

4. The process for preparing a recyclable low-temperature heat-seal packaging composite film according to claim 3, characterized in that, The alkaline catalyst is one of sodium hydroxide, sodium carbonate and sodium ethoxide.

5. The process for preparing a recyclable low-temperature heat-seal packaging composite film according to claim 1, characterized in that, The preparation method of the anti-sticking modifier is: on one hand, the condensation reaction of the silicon hydroxyl functional groups generated by the hydrolysis reaction of the hydrolysis functional groups of the silane crosslinking agent containing phenolic hydroxyl functional groups and methoxyl functional groups and the hydroxyl functional groups of the hydroxyl-terminated polydimethylsiloxane, and on the other hand, the hydrogen bonding of the phenolic hydroxyl functional groups of the silane crosslinking agent containing phenolic hydroxyl functional groups and methoxyl functional groups and the hydroxyl-terminated polydimethylsiloxane, to obtain the anti-sticking modifier.

6. The process for preparing a recyclable low-temperature heat-seal packaging composite film according to claim 5, characterized in that, The mass ratio of the silane crosslinking agent containing phenolic hydroxyl functional groups and methoxyl functional groups in the anti-sticking modifier to the hydroxyl-terminated polydimethylsiloxane is 1:(2-10).

7. The process for preparing a recyclable low-temperature heat-seal packaging composite film according to claim 5, characterized in that, The number average molecular weight of the hydroxyl-terminated polydimethylsiloxane is 1000-4000.

8. A recyclable low temperature heat sealable packaging composite film prepared by the process as claimed in any one of claims 1 to 7, wherein, The heat sealing strength of the packaging composite film is greater than or equal to 15 N / 15 mm at a heat sealing temperature of 100 DEG C.

9. A recyclable low temperature heat seal packaging composite film according to claim 8, characterized in that, The packaging composite film is used for packaging sauce products and plays an anti-sticking role.

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