阅读说明：本技术 一种食品用重复封合包装膜及其制备方法 (Repeated sealing packaging film for food and preparation method thereof ) 是由 陆锦霞 陈宝昆 董亮亮 陈伟 王雪飞 于 2020-08-03 设计创作，主要内容包括：本发明公开了一种食品用重复封合包装膜,包括由外至内依次叠加的外层、中间层、冷粘层和热封层,所述冷粘层包括重量份数计的30-50份的热塑性弹性体、10-20份的增粘树脂、18-20份的丙烯酸共聚物、10-12份的偶联剂改性碳酸钙中空颗粒、15-18份的共聚酯胶、3-4份的助剂；所述热封层包括重量份数为50-58份的LLDPE、40-50份的LDPE、1-1.5份的开口剂、0.3-0.5份的爽滑剂。本发明的食品用重复封合包装膜通过对包装膜的冷粘层的配方进行设计,添加了偶连改性碳酸钙中空颗粒、共聚酯胶和各种其他组分,各组分与主机之间的协同增效作用,使得食品包装膜具有了优异的耐低温性能,且在经过多次低温冷藏或者冷冻后还能够保持重复多次封合的密封效果。(The invention discloses a repeated sealing packaging film for food, which comprises an outer layer, an intermediate layer, a cold-bonding layer and a heat-sealing layer which are sequentially overlapped from outside to inside, wherein the cold-bonding layer comprises 30-50 parts by weight of thermoplastic elastomer, 10-20 parts by weight of tackifying resin, 18-20 parts by weight of acrylic acid copolymer, 10-12 parts by weight of coupling agent modified calcium carbonate hollow particles, 15-18 parts by weight of copolyester adhesive and 3-4 parts by weight of auxiliary agent; the heat sealing layer comprises 50-58 parts by weight of LLDPE, 40-50 parts by weight of LDPE, 1-1.5 parts by weight of a mouth-opening agent and 0.3-0.5 part by weight of a slipping agent. According to the repeated sealing packaging film for the food, the formula of the cold-bonding layer of the packaging film is designed, the coupling modified calcium carbonate hollow particles, the copolyester adhesive and various other components are added, and the components and the host have synergistic interaction, so that the food packaging film has excellent low-temperature resistance, and can keep the sealing effect of repeated sealing after multiple times of low-temperature refrigeration or freezing.)

1. A repeated sealing packaging film for food is characterized by comprising an outer layer, an intermediate layer, a cold-bonding layer and a heat-sealing layer which are sequentially overlapped from outside to inside, wherein the cold-bonding layer comprises 30-50 parts by weight of thermoplastic elastomer, 10-20 parts by weight of tackifying resin, 18-20 parts by weight of acrylic acid copolymer, 10-12 parts by weight of coupling agent modified calcium carbonate hollow particles, 15-18 parts by weight of copolyester adhesive and 3-4 parts by weight of auxiliary agent; the heat sealing layer comprises 50-58 parts by weight of LLDPE, 40-50 parts by weight of LDPE, 1-1.5 parts by weight of a mouth-opening agent and 0.3-0.5 part by weight of a slipping agent.

2. The reclosable packaging film for food products of claim 1, wherein said copolyester adhesive is prepared by esterification of a dibasic acid with a dibasic alcohol; the dibasic acid is formed by mixing sebacic acid and dimer acid; the dihydric alcohol is formed by mixing butanediol, isosorbide and castor oil, wherein the molar ratio of sebacic acid to dimer acid in the dibasic acid is 1-1.2: 2, the molar ratio of butanediol, isosorbide and castor oil in the dihydric alcohol is 1: 0.8-1: 0.008-0.015.

3. The re-sealing packaging film for food as claimed in claim 2, wherein the copolyester adhesive is prepared by adding selected dibasic acid, glycol and catalyst in proportion into a reaction kettle for esterification reaction, wherein the initial reaction temperature is 160 ℃, the temperature is gradually increased to 220 ℃, and when the water amount generated by the reaction reaches 95% or more of the theoretical water yield, the esterification reaction is finished; controlling the temperature at 230-250 ℃, controlling the vacuum at 100-150 Pa for polycondensation reaction, and finishing the polycondensation reaction after 2 h.

4. The repetitive sealing packaging film for food according to claim 3, wherein said thermoplastic elastomer comprises 6-10 parts of natural rubber, 6-12 parts of SIS, 6-12 parts of SBS, 6-12 parts of EVA and 6-15 parts of nitrile rubber with 18-20% acrylonitrile content.

5. The reclosable packaging film for food products of claim 4, wherein said cold-stick layer further comprises ethylene thiourea in an amount of 1-2 parts and zinc oxide in an amount of 2-6 parts.

6. The food re-sealing packaging film as claimed in claim 5, wherein the acrylic copolymer is methyl methacrylate or butyl methacrylate, the auxiliary agent is a softener, an antioxidant and an anti-aging agent, and the weight part ratio of the softener, the antioxidant and the anti-aging agent in the auxiliary agent is 1-2:1: 1.

7. The reclosable packaging film of claim 6, wherein said softener is a phthalate type softener; the antioxidant is microcrystalline wax and propyl gallate; the anti-aging agent is N, N-dibutyl zinc dithiocarbamate and zinc ethyl phenyl dithiocarbamate.

8. The reclosable packaging film for food products as claimed in claim 7, wherein said outer layer and said middle layer comprise, in parts by weight, 40-50 parts of LLDPE, 20-30 parts of LDPE, 10-20 parts of HDPE, and 3-5 parts of antioxidant.

9. A method of making the cold-stick layer of claim 8, comprising the steps of: step one, weighing various components and auxiliaries of the thermoplastic elastomer according to the formula amount, and putting the components and the auxiliaries into an internal mixer for mixing, wherein the mixing temperature is 90-110 ℃; and step two, putting the mixed material obtained in the step one into a stirrer, and then adding tackifying resin, acrylic copolymer, coupling agent modified calcium carbonate hollow particles, copolyester adhesive, ethylene thiourea and zinc oxide in a formula amount, and stirring at the temperature of 140-.

10. A method for preparing the food-use re-sealing packaging film of claim 8, comprising the steps of preparing the outer layer and the intermediate layer of the packaging film by co-extrusion film blowing, coating the cold-bond layer material on the inner side of the intermediate layer by gravure coating, and then compounding the outer layer, the intermediate layer, the cold-bond layer and the heat-seal layer by a dry compounding machine at a traveling speed of 70-90m/min, wherein the coating amount of the cold-bond layer is 3-5g/m²。

Technical Field

The invention relates to the technical field of food packaging films, in particular to a repeated sealing packaging film for food and a preparation method thereof.

Background

In recent years, the development of packaging containers for various foods and packaging films has been rapid, and tear films, tear-off films and packaging films that can be repeatedly sealed have been developed. The packaging film that can repeat the involution carries out the heat-seal through inside heat-seal layer and seals, when opening for the first time, the cold layer of gluing of heat-seal layer and packaging film separates, and when sealing for the next time, only need press hard and reveal the preceding heat-seal region in position, need not to heat the involution, especially can not eat up to some once, need the food of sealed package once more, and the packaging film that can repeat the involution improves the convenience and the ease of this kind of food to a higher level.

However, many foods which are not eaten for one time or a plurality of times and need to be sealed and sealed again, such as chocolate, ice cream or jujube cake, need to be sealed and sealed again, and need to be refrigerated or frozen for preservation again besides being sealed and sealed again, and many current packaging films which can be sealed repeatedly are refrigerated or frozen for a plurality of times, the repeated sealing performance of the packaging films is seriously reduced, and even the second sealing or the third sealing cannot be carried out.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a repeated sealing packaging film for food, which is resistant to low temperature and can keep repeated sealing effect after low temperature.

In order to achieve the purpose, the technical scheme of the invention is to design a repeated sealing packaging film for food, which comprises an outer layer, a middle layer, a cold-bonding layer and a heat-sealing layer which are sequentially overlapped from outside to inside, wherein the cold-bonding layer comprises 30-50 parts by weight of thermoplastic elastomer, 10-20 parts by weight of tackifying resin, 18-20 parts by weight of acrylic copolymer, 10-12 parts by weight of coupling agent modified calcium carbonate hollow particles, 15-18 parts by weight of copolyester adhesive and 3-4 parts by weight of auxiliary agent; the heat sealing layer comprises 50-58 parts by weight of LLDPE, 40-50 parts by weight of LDPE, 1-1.5 parts by weight of a mouth-opening agent and 0.3-0.5 part by weight of a slipping agent. The preparation method of the coupling agent modified calcium carbonate hollow particles comprises the steps of immersing dried calcium carbonate hollow particles with the particle size of 10-30 microns in absolute ethyl alcohol, conducting ultrasonic dispersion for 30-40min, heating to 85-90 ℃ after ultrasonic treatment, preserving heat, stirring for 8-12min at the rotating speed of 600 plus materials and 1000rpm, adding an aqueous solution of an aminosilane coupling agent, heating to 95 ℃, preserving heat, stirring for 0.5-1h at the rotating speed of 600 plus materials and 1000rpm, taking out, washing for 5 times with the absolute ethyl alcohol, drying in a vacuum drying oven for 90 ℃, and drying for 6-8h to obtain the coupling agent modified calcium carbonate hollow particles, wherein the weight of the coupling agent is 12-15% of that of the calcium carbonate hollow particles. The hollow particles may be made of other materials such as silica hollow particles or mica hollow particle powder.

The calcium carbonate hollow particles are inorganic particles with hollow structures, are uniformly dispersed in the cold adhesive layer, and other components of the cold adhesive layer are filled in holes of the hollow particles to play a heat preservation effect similar to that of a snow digging hole, so that the other components of the cold adhesive layer are contained and preserved, and the cold adhesive layer has better mechanical property and thermal insulation property, and can effectively prevent the cold adhesive layer from being damaged by an external low-temperature environment; meanwhile, the surface of the hollow calcium carbonate particles presents hydrophilicity due to the existence of hydroxyl groups, the surface of the hollow calcium carbonate particles is modified by a coupling agent, partial hydroxyl groups on the surface of the hollow calcium carbonate particles react with an organic chain of the coupling agent, the hydrophilicity is changed into hydrophobicity and lipophilicity, so that the modified hollow calcium carbonate particles can be uniformly dispersed in an organic matrix of the cold-bonding layer, and a strong interface is formed between the modified hollow calcium carbonate particles and the organic matrix for bonding, so that a good reinforcing effect is achieved, the low-temperature toughness of the cold-bonding layer is improved, and the low-temperature resistance of the cold-bonding layer is obviously improved; the copolyester adhesive with good low-temperature resistance and flexibility is added into the components of the cold-bonding layer, so that the low-temperature resistance and the flexibility of the cold-bonding layer are improved, and the cold-bonding layer can also have excellent bonding performance and mechanical performance after being refrigerated for many times.

The preferable technical proposal is that the copolyester adhesive is prepared by esterification reaction of dibasic acid and dibasic alcohol; the dibasic acid is formed by mixing sebacic acid and dimer acid; the dihydric alcohol is formed by mixing butanediol, isosorbide and castor oil, wherein the molar ratio of sebacic acid to dimer acid in the dibasic acid is 1-1.2: 2, the molar ratio of butanediol, isosorbide and castor oil in the dihydric alcohol is 1: 0.8-1: 0.008-0.015; the preparation method of the copolyester adhesive comprises the steps of adding selected dibasic acid, dihydric alcohol and a catalyst into a reaction kettle in proportion to carry out esterification reaction, wherein the initial reaction temperature is 160 ℃, gradually raising the temperature to 220 ℃, and finishing the esterification reaction when the water generated by the reaction reaches 95% or more of the theoretical water yield; controlling the temperature at 230-250 ℃, controlling the vacuum at 100-150 Pa for polycondensation reaction, and finishing the polycondensation reaction after 2 h. The unique proportion of the dimer acid and the sebacic acid for preparing the copolyester adhesive can reduce the glass transition temperature and the melting point of a polyester reaction system, and the addition of the castor oil containing the appropriate hydroxyl functionality is used for improving the crosslinking density of the esterification reaction system and improving the low-temperature resistance and the flexibility of the product copolyester adhesive, so that the copolyester adhesive has excellent bonding performance and mechanical performance, and the low-temperature resistance of a cold-bonded layer is further improved.

The further preferred technical scheme is that the thermoplastic elastomer comprises 6-10 parts of natural rubber, 6-12 parts of SIS, 6-12 parts of SBS, 6-12 parts of EVA and 6-15 parts of nitrile rubber with the acrylonitrile content of 18-20%. The nitrile rubber has excellent oil resistance, and avoids the phenomenon that the repeated adhesion performance of the cold adhesion layer is influenced by the fact that the grease of the packing material is leached to the cold adhesion layer; the acrylonitrile-butadiene rubber with low acrylonitrile content with the content of 18-20% is adopted, the lower the acrylonitrile content in the acrylonitrile-butadiene rubber is, the higher the butadiene content is, the more flexible the acrylonitrile-butadiene rubber molecules are, the better the low-temperature effect is, and the low-temperature resistance of the cold-bonded layer is further improved.

The further preferable technical scheme is that the cold-bonding layer also comprises 1-2 parts of ethylene thiourea and 2-6 parts of zinc oxide. The ethylene thiourea and the zinc oxide have a synergistic effect, and the crosslinking degree of each component in the cold-bonding layer is matched with the modified calcium carbonate hollow particles, so that the strength and the bonding property of the cold-bonding layer are further improved, and the stability and the freezing resistance of the cold-bonding layer in a low-temperature state are improved in a phase-changing manner.

According to a further preferable technical scheme, the acrylic copolymer is methyl methacrylate or butyl methacrylate, the auxiliary agent is a softening agent, an antioxidant and an anti-aging agent, and the weight part ratio of the softening agent, the antioxidant and the anti-aging agent in the auxiliary agent is 1-2:1: 1. Methyl methacrylate or butyl methacrylate with low glass transition temperature is selected as one of the materials of the cold bonding layer, the bonding strength of the cold bonding layer is reduced, and the cold bonding layer and ethylene thiourea and zinc oxide which are used for improving the bonding strength of the cold bonding layer in the cold bonding layer are mutually cooperated and promoted, so that the bonding strength of the cold bonding layer is balanced, the cold bonding layer can keep proper bonding performance at low temperature, and has proper bonding strength at normal temperature, and the peeling of the packaging film is facilitated.

The further preferable technical proposal is that the softener is phthalate softener; the antioxidant is microcrystalline wax and propyl gallate; the anti-aging agent is N, N-dibutyl zinc dithiocarbamate and zinc ethyl phenyl dithiocarbamate.

The further preferable technical scheme is that the outer layer and the middle layer comprise 40-50 parts of LLDPE, 20-30 parts of LDPE, 10-20 parts of HDPE and 3-5 parts of antioxidant in parts by weight.

The invention also designs a method for preparing the cold-bonding layer, which comprises the following steps: step one, weighing various components and auxiliaries of the thermoplastic elastomer according to the formula amount, and putting the components and the auxiliaries into an internal mixer for mixing, wherein the mixing temperature is 90-110 ℃; and step two, putting the mixed material obtained in the step one into a stirrer, and then adding tackifying resin, acrylic copolymer, coupling agent modified calcium carbonate hollow particles, copolyester adhesive, ethylene thiourea and zinc oxide in a formula amount, and stirring at the temperature of 140-.

The invention also designs a method for preparing the repeated sealing packaging film for food, which comprises the following steps of firstly preparing the outer layer and the middle layer of the packaging film by co-extrusion film blowing, then coating the cold bonding layer material on the inner side of the middle layer in a gravure coating mode, and then compounding the outer layer, the middle layer, the cold bonding layer and the heat sealing layer by a dry compounding machine at the advancing speed of 70-90m/min, wherein the coating amount of the cold bonding layer is 3-5g/m²。

The invention has the advantages and beneficial effects that: the repeated sealing packaging film for the food is designed according to the formula of the cold-bonding layer of the packaging film, the coupling modified calcium carbonate hollow particles, the copolyester adhesive of the dibasic acid and the dihydric alcohol, other components and auxiliaries are added, and the synergistic interaction between the components and the auxiliaries ensures that the food packaging film has excellent low-temperature resistance, can keep the sealing effect of repeated sealing after repeated low-temperature refrigeration or freezing, and prolongs the food service cycle while having good moisture and oxygen insulation performance. The preparation method of the cold-bonding layer and the preparation method of the repeated sewing packaging film for the food are simple, short in flow, convenient to implement and wide in application prospect.

Detailed Description

The following further describes embodiments of the present invention with reference to examples. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.