Food packaging bag and preparation method thereof

Abstract

The invention provides a food packaging bag and a preparation method thereof. The food packaging bag comprises the following raw materials in parts by mass: 50 parts of polylactic acid, 50-100 parts of poly (butylene adipate-co-terephthalate), 5-10 parts of a plasticizer and 5-10 parts of a modified filler, wherein the modified filler comprises a multi-arm grafted filler, the end group of each arm is an acyl chloride group, and each arm comprises a polyethylene glycol chain segment. According to the food packaging bag, polylactic acid and poly (butylene adipate-co-terephthalate) are used as main materials, meanwhile, the brittleness of the food packaging bag is further reduced and the flexibility of the food packaging bag is improved by using a plasticizer, and in addition, by adding a modified filler comprising a multi-arm grafted filler, the food packaging bag is more environment-friendly. The multi-arm grafted filler can improve the barrier property of the food packaging bag on the premise of not deteriorating the flexibility of the food packaging bag, so that the obtained food packaging bag has good flexibility and barrier property.

Description

Technical Field

[0001] This application relates to the technical field of food packaging materials, and specifically relates to a food packaging bag and a preparation method thereof. Background Art

[0002] With the continuous improvement of environmental awareness and the popularization of the concept of sustainable development, biodegradable materials have gradually become alternatives to traditional plastics. Among many biodegradable plastics, polylactic acid (PLA) has been gradually widely used in the food packaging field due to its characteristics such as being derived from renewable resources, good biodegradability, non-toxic and harmless. However, as a thermoplastic plastic, PLA faces some problems during its application, especially in the food packaging field.

[0003] PLA has poor flexibility, especially being prone to embrittlement at low temperatures. And due to its relatively high glass transition temperature, PLA shows high rigidity and low toughness at room temperature, which makes it easy to crack or tear in actual applications, thus affecting its application effect in food packaging. In addition, the barrier performance of PLA is limited, especially its barrier property to gases such as water vapor and oxygen is poor. Food packaging materials need to have high gas barrier performance to effectively extend the shelf life of food and prevent the penetration of moisture and oxygen. However, due to the characteristics of its structure, PLA has poor barrier performance to these gases, which makes it perform poorly in food packaging with high humidity or requiring a long shelf life.

[0004] Therefore, when using PLA to prepare food packaging bags, it is necessary to modify the PLA material accordingly to improve its flexibility and barrier performance to be suitable for the food packaging field.

[0005] Patent CN117799272A discloses a bio-based food packaging bag and a preparation method thereof. The bio-based food packaging bag includes the following weight components: The outer layer includes the following components in parts by weight: 100 parts of PLA, 5 - 25 parts of silicate; the middle layer includes the following components in parts by weight: 100 parts of PLA, 5 - 25 parts of silicate, 2 - 5 parts of 2 - methoxycinnamaldehyde; the inner layer includes the following components in parts by weight: 100 parts of PLA, 5 - 25 parts of silicate, 2 - 5 parts of 2 - methoxycinnamaldehyde. This patent forms a blend by adding silicate to PLA, improving the gas barrier performance of PLA; and by adding 2 - methoxycinnamaldehyde, the compatibility of PLA and silicate is improved, thereby enhancing the toughness of the bio-based food packaging bag.

[0006] The above patent improves the toughness and barrier properties of bio-based food packaging bags through multi-layer design and the modification of PLA materials using silicate and 2-methoxycinnamaldehyde. The problem is that it mainly improves the barrier properties of bio-based food packaging bags through multi-layer design, which has little effect on the barrier properties of the material itself, and at the same time, the multi-layer design will increase the production cost of food packaging bags.

[0007] Therefore, there is a need to provide a food packaging bag with good barrier properties. Summary of the Invention

[0008] This application provides a food packaging bag and a preparation method thereof. The food packaging bag has good barrier properties and flexibility through optimizing the components of the raw materials.

[0009] In the first aspect, this application provides a food packaging bag, which includes the following raw materials in parts by mass:

[0010] 50 parts of polylactic acid, 50 - 100 parts of polybutylene adipate / terephthalate (PBAT), 5 - 10 parts of plasticizer, 5 - 10 parts of modified filler; wherein, the modified filler includes multi-arm grafted filler, the end groups of the arms are acyl chloride groups, and the arms include polyethylene glycol segments.

[0011] According to this application, the food packaging bag uses polylactic acid and polybutylene adipate / terephthalate (PBAT) as the main materials. Polybutylene adipate / terephthalate is also a biodegradable polymer material, which will not affect the biodegradable performance of the food packaging bag. At the same time, it has good flexibility and a low glass transition temperature, and has good compatibility with polylactic acid. Therefore, using the two as the main materials can effectively improve the flexibility of the food packaging bag; at the same time, by using a plasticizer, the brittleness of the food packaging bag is further reduced and its flexibility is improved; in addition, by adding a modified filler including multi-arm grafted filler, the arms of the multi-arm grafted filler are polyethylene glycol segments with acyl chloride groups at the end, and the multi-arm grafted filler can improve the barrier properties of the food packaging bag without deteriorating its flexibility, so that the obtained food packaging bag has good flexibility and barrier properties.

[0012] In some embodiments, it includes the following raw materials in parts by mass:

[0013] 50 parts of polylactic acid, 50 - 75 parts of polybutylene adipate / terephthalate, 5 - 8 parts of plasticizer, 5 - 8 parts of modified filler.

[0014] In some embodiments, the preparation method of the multi-arm grafted filler includes the following steps:

[0015] S1: React polyethylene glycol with a weight-average molecular weight of 300 - 1000 and succinic anhydride in toluene, so that the hydroxyl groups at both ends of the polyethylene glycol react with succinic anhydride, and carboxyl groups are grafted onto both ends of the polyethylene glycol to obtain carboxylated polyethylene glycol;

[0016] S2: React carboxylated polyethylene glycol with thionyl chloride in toluene, so that the carboxyl groups at both ends of the carboxylated polyethylene glycol react with thionyl chloride, and acyl chloride groups are grafted onto both ends of the carboxylated polyethylene glycol to obtain acyl chlorinated polyethylene glycol;

[0017] S3: React the filler with an amino-silane coupling agent in an aqueous ethanol solution, so that a branched chain containing an amino group is grafted onto the surface of the filler to obtain an amino-functionalized filler; the amino-silane coupling agent includes N-phenyl-γ-aminopropyltrimethoxysilane;

[0018] S4: React acyl chlorinated polyethylene glycol with the amino-functionalized filler in toluene, wherein the amino group on the surface of the modified filler reacts with acyl chlorinated polyethylene glycol, and acyl chlorinated polyethylene glycol is grafted onto the surface of the filler to obtain a multi-arm grafted filler.

[0019] In some embodiments, S1 specifically includes:

[0020] Disperse 10 parts by mass of polyethylene glycol with a weight-average molecular weight of 300 - 1000 and 5 - 10 parts by mass of succinic anhydride in 150 - 300 parts by mass of toluene, and react at 60 - 80 °C for 5 - 12 h to obtain carboxylated polyethylene glycol.

[0021] In some embodiments, S2 specifically includes:

[0022] Disperse 10 parts by mass of carboxylated polyethylene glycol and 10 - 30 parts by mass of thionyl chloride in 100 - 200 parts by mass of toluene, and react at 75 - 90 °C for 18 - 36 h to obtain acyl chlorinated polyethylene glycol.

[0023] In some embodiments, S3 specifically includes:

[0024] Disperse 5 parts by mass of the filler and 40 - 60 parts by mass of the amino-silane coupling agent in 200 - 300 parts by mass of an aqueous ethanol solution, and react at 75 - 90 °C for 0.5 - 2 h to obtain an amino-functionalized filler.

[0025] In some embodiments, the filler includes graphene oxide and oxidized carbon nanotubes, and the mass ratio of graphene oxide to oxidized carbon nanotubes is 1:0.1 - 0.5.

[0026] In some embodiments, S4 specifically includes:

[0027] Disperse 10 parts by mass of acyl chlorinated polyethylene glycol and 1 - 5 parts by mass of the amino-functionalized filler in 100 - 200 parts by mass of toluene, and react at 80 - 90 °C for 6 - 12 h to obtain a multi-arm grafted filler.

[0028] In some embodiments, the weight-average molecular weight of the polylactic acid is 100,000 - 200,000.

[0029] In some embodiments, the weight-average molecular weight of the polybutylene adipate / terephthalate is 150,000 - 300,000.

[0030] In some embodiments, the plasticizer includes at least one of glyceryl triacetylcitrate, tributyl citrate, triethyl citrate, poly(butylene adipate), and epoxidized soybean oil.

[0031] In some embodiments, it further includes 0.5 - 2 parts of an antioxidant; the antioxidant includes at least one of 2,6-di-tert-butyl-p-cresol, dilauryl thiodipropionate, and vitamin E.

[0032] In a second aspect, the present application provides a method for preparing a food packaging bag, including:

[0033] Providing the raw materials in the food packaging bag according to any one of the embodiments in the first aspect;

[0034] Drying the raw materials, then melt-blending, extruding, pelletizing, and blow-molding to obtain a food packaging bag.

[0035] According to the present application, since it is prepared by using the raw materials in the food packaging bag according to any one of the embodiments in the first aspect, it has the beneficial effects of the first aspect. Specific Embodiments

[0036] In this specification, the embodiments or implementation schemes are described in a progressive manner, and each embodiment focuses on the differences from other embodiments.

[0037] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0038] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of this application, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0039] This application provides a food packaging bag and a preparation method thereof. The food packaging bag has good flexibility and barrier properties by optimizing its raw material components. The following provides a detailed description of the specific embodiments provided by this application.

[0040] In a first aspect, this application provides a food packaging bag, including the following raw materials in parts by mass:

[0041] 50 parts of polylactic acid, 50 - 100 parts of polybutylene adipate / terephthalate (PBAT), 5 - 10 parts of plasticizer, 5 - 10 parts of modified filler; wherein, the modified filler includes multi-arm grafted filler, the end groups of the arms are acyl chloride groups, and the arms include polyethylene glycol segments.

[0042] According to this application, the food packaging bag uses polylactic acid and polybutylene adipate / terephthalate (PBAT) as the main materials. Polybutylene adipate / terephthalate is also a degradable polymer material, which does not affect the degradable performance of the food packaging bag. At the same time, it has good flexibility and a low glass transition temperature, and has good compatibility with polylactic acid. Therefore, using the two as the main materials can effectively improve the flexibility of the food packaging bag; at the same time, by using a plasticizer, the brittleness of the food packaging bag is further reduced and its flexibility is improved; in addition, by adding a modified filler including multi-arm grafted filler, the end groups of the arms of the multi-arm grafted filler are reactive acyl chloride groups, and at the same time the arms include polyethylene glycol segments. The multi-arm grafted filler can improve the barrier performance of the food packaging bag without deteriorating its flexibility, so that the obtained food packaging bag has good flexibility and barrier properties.

[0043] Specifically, in the related art, by adding fillers to food packaging bags, during the melt extrusion process, the fillers can improve the crystallinity of the matrix material through heterogeneous nucleation effect, thereby improving the barrier performance of the food packaging bags. However, the improvement of crystallinity will deteriorate the flexibility of the food packaging bags, making it impossible for the food packaging bags to have both good flexibility and barrier performance. Based on this, the inventor prepared a multi-arm grafted filler, which is a star-shaped grafting of multiple reactive arms on the surface of the filler. The end groups of the arms are acyl chloride groups, and the acyl chloride groups have good reactivity with the end groups (hydroxyl groups and / or carboxyl groups) of PLA and PBAT. During the melt blending process, the multi-arm grafted filler can utilize its reactivity, use the multi-arm grafted filler as a crosslinking center to increase the crosslinking density of the matrix material, and cooperate with the physical barrier effect in the filler system to extend the gas diffusion path, effectively improving the barrier performance of the food packaging bags. At the same time, the inventor found that the improvement of crosslinking density will also reduce the flexibility of the food packaging bags. Grafting polyethylene glycol segments on the arms can effectively reduce the impact of the multi-arm grafted filler on the flexibility of the food packaging bags. This may be because in the crosslinked product of the multi-arm grafted filler and the matrix material, the filler and the matrix material are connected through the arms, and the polyethylene glycol segments on the arms can effectively disperse the stress received by the food packaging bags, thereby effectively reducing the impact of the multi-arm grafted filler as a crosslinking center on the flexibility of the food packaging bags. The resulting food packaging bags have both good flexibility and barrier performance.

[0044] In some embodiments, the raw materials include the following parts by mass:

[0045] 50 parts of polylactic acid, 50 - 75 parts of polybutylene adipate / terephthalate, 5 - 8 parts of plasticizer, 5 - 8 parts of modified filler.

[0046] In the above-mentioned some embodiments, by further optimizing the content of each component of the raw materials, the obtained food packaging bags have better flexibility and barrier performance.

[0047] In some embodiments, the preparation method of the multi-arm grafted filler includes the following steps:

[0048] S1: React polyethylene glycol with a weight average molecular weight of 300 - 1000 and succinic anhydride in toluene, so that the hydroxyl groups at both ends of the polyethylene glycol react with succinic anhydride, and carboxyl groups are grafted at both ends of the polyethylene glycol to obtain carboxylated polyethylene glycol;

[0049] S2: React carboxylated polyethylene glycol with thionyl chloride in toluene, so that the carboxyl groups at both ends of the carboxylated polyethylene glycol react with thionyl chloride, and acyl chloride groups are grafted at both ends of the carboxylated polyethylene glycol to obtain acyl chlorinated polyethylene glycol;

[0050] S3: React the filler with an amino-silane coupling agent in an ethanol aqueous solution to graft a branched chain containing an amino group onto the filler surface, obtaining an aminated filler; the amino-silane coupling agent includes N-phenyl-γ-aminopropyltrimethoxysilane;

[0051] S4: React the acyl chlorinated polyethylene glycol with the aminated filler in toluene, wherein the amino group on the surface of the modified filler reacts with the acyl chlorinated polyethylene glycol to graft the acyl chlorinated polyethylene glycol onto the filler surface, obtaining a multi-arm grafted filler.

[0052] In some of the above embodiments, the multi-arm grafted filler is obtained by the above preparation method. Specifically, in step S1, polyethylene glycol with a weight average molecular weight of 300 to 1000 is subjected to end-group carboxylation modification using succinic anhydride. The inventor found that the weight average molecular weight of polyethylene glycol has a certain influence on the flexibility and barrier properties of food packaging bags. When the weight average molecular weight is within the above range, an appropriate chain length can, on the one hand, effectively improve the compatibility of the multi-arm grafted filler, making the multi-arm grafted filler more easily and evenly dispersed, and more uniformly improving the crosslinking density in the system, thereby improving the flexibility and barrier properties; on the other hand, it can also reduce the influence of too long polyethylene glycol chain segments on the crosslinking density. Preferably, the weight average molecular weight of polyethylene glycol in step S1 is 400 to 600;

[0053] In step S2, the carboxylated polyethylene glycol is further subjected to end-group acyl chlorination modification using thionyl chloride, so that both ends of the polyethylene glycol chain segment are grafted with acyl chloride groups, thus having good reactivity with hydroxyl groups and carboxyl groups;

[0054] In step S3, an amino-silane coupling agent is used to graft a branched chain containing an amino group onto the filler surface, obtaining an aminated filler; the amino-silane coupling agent includes N-phenyl-γ-aminopropyltrimethoxysilane. The inventor found that by using an amino-silane coupling agent to graft a branched chain containing an amino group onto the filler surface, the residue after hydrolysis of the amino-silane coupling agent is also grafted onto the filler surface as a branched chain. The multi-arm grafted fillers obtained using different amino-silane coupling agents have a certain influence on the performance of food packaging bags. When using N-phenyl-γ-aminopropyltrimethoxysilane as the amino-silane coupling agent, the food packaging bag has better barrier properties; the reason may be that the residue grafted by N-phenyl-γ-aminopropyltrimethoxysilane on the filler surface has stronger rigidity and hydrophobicity compared to other amino-silane coupling agents, such as γ-aminopropyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane. The hydrophobic residues near the filler surface can increase the crystallization rate of the heterogeneous nucleus, reduce the free energy required to form the critical nucleus, thereby increasing the crystallinity, and further improving the barrier properties of the food packaging bag. At the same time, since the polyethylene glycol chain segment is grafted subsequently, this residue does not affect the dispersion of the multi-arm grafted filler in the system and has little influence on the flexibility of the food packaging bag.

[0055] In step S4, the aminated filler is grafted and modified with chlorinated polyethylene glycol, so that a polyethylene glycol chain segment with an acyl chloride group at the end is grafted onto the filler surface; it can be understood that after the reaction between chlorinated polyethylene glycol and the aminated filler, due to steric hindrance, the acyl chloride groups grafted on the filler surface are less likely to further react with the unreacted amino groups on the surfaces of other fillers. Therefore, the fillers are not likely to agglomerate and crosslink, and the obtained multi-arm grafted filler has better dispersibility and reactivity.

[0056] It should be noted that the amino groups described in this application, unless otherwise specified, include primary amino groups and secondary amino groups that are reactive with acyl chloride groups.

[0057] In some embodiments, S1 specifically includes:

[0058] 10 parts by mass of polyethylene glycol with a weight average molecular weight of 300 to 1000 and 5 to 10 parts by mass of succinic anhydride are dispersed in 150 to 300 parts by mass of toluene and reacted at 60 to 80 °C for 5 to 12 h to obtain carboxylated polyethylene glycol. Based on the above embodiments, under the above conditions, the hydroxyl groups at both ends of polyethylene glycol can react with succinic anhydride to obtain carboxylated polyethylene glycol.

[0059] In some embodiments, S2 specifically includes:

[0060] 10 parts by mass of carboxylated polyethylene glycol and 10 to 30 parts by mass of thionyl chloride are dispersed in 100 to 200 parts by mass of toluene and reacted at 75 to 90 °C for 18 to 36 h to obtain chlorinated polyethylene glycol. Based on the above embodiments, under the above conditions, the carboxyl groups at both ends of carboxylated polyethylene glycol can react with thionyl chloride to obtain chlorinated polyethylene glycol.

[0061] In some embodiments, S3 specifically includes:

[0062] 5 parts by mass of the filler and 40 to 60 parts by mass of an amino silane coupling agent are dispersed in 200 to 300 parts by mass of an ethanol aqueous solution and reacted at 75 to 90 °C for 0.5 to 2 h to obtain an aminated filler.

[0063] In the above-mentioned some embodiments, under the above conditions, branched chains containing amino groups can be fully grafted onto the filler surface to obtain an aminated filler.

[0064] In some embodiments, the filler includes at least one of nano calcium carbonate, graphene oxide, and carbon nanotubes oxidized.

[0065] It is understandable that graphene oxide and oxidized carbon nanotubes have the meanings well-known in the art, that is, graphene and carbon nanotubes after oxidation treatment, and the surface after oxidation treatment may include hydroxyl groups and / or carboxyl groups. For example, oxidized carbon nanotubes include, but are not limited to, hydroxylated carbon nanotubes or carboxylated carbon nanotubes.

[0066] In some embodiments, the filler includes graphene oxide and oxidized carbon nanotubes, and the mass ratio of graphene oxide to oxidized carbon nanotubes is 1:0.1 - 0.5.

[0067] In some of the above embodiments, the inventors found that when the filler includes graphene oxide and oxidized carbon nanotubes in the above mass ratio, the obtained food packaging bag has better barrier properties; the possible reason is that by using the above composite filler, graphene oxide and oxidized carbon nanotubes act as crosslinking centers in the system to crosslink the matrix material, and the two-dimensional graphene oxide and one-dimensional oxidized carbon nanotubes form a complex spatial network structure in the system, which can further reduce the diffusion of moisture and gas in the food packaging bag, thereby further improving the barrier properties of the food packaging bag.

[0068] In some embodiments, S4 specifically includes:

[0069] Disperse 10 parts by mass of acyl chloride polyethylene glycol and 1 - 5 parts by mass of amino-functionalized filler in 100 - 200 parts by mass of toluene, and react at 80 - 90 °C for 6 - 12 h to obtain multi-armed grafted filler.

[0070] In some of the above embodiments, under the above conditions, acyl chloride polyethylene glycol can fully graft acyl chloride polyethylene glycol chain segments onto the surface of the amino-functionalized filler, and at the same time can further reduce the crosslinking between the fillers by acyl chloride polyethylene glycol, so that the obtained multi-armed grafted filler has better dispersibility and reactivity, thereby making the obtained food packaging bag have good flexibility and barrier properties.

[0071] In some embodiments, the weight-average molecular weight of polylactic acid is 100,000 - 200,000. Based on the above embodiments, polylactic acid with the above weight-average molecular weight can better balance flexibility and degradability. As an example, in one embodiment of the present application, polylactic acid with a weight-average molecular weight of 150,000 is used.

[0072] In some embodiments, the weight-average molecular weight of polybutylene adipate / terephthalate is 150,000 - 300,000. Based on the above embodiments, polybutylene adipate / terephthalate with the above weight-average molecular weight can make the food packaging bag have better flexibility. As an example, in one embodiment of the present application, polybutylene adipate / terephthalate with a weight-average molecular weight of 200,000 is used.

[0073] In some embodiments, the plasticizer includes at least one of glyceryl triacetylcitrate, tributyl citrate, triethyl citrate, poly(butylene adipate), and epoxidized soybean oil. As an example, glyceryl triacetylcitrate is used as the plasticizer in an embodiment of the present application.

[0074] In some embodiments, 0.5 to 2 parts of an antioxidant are further included; the antioxidant includes at least one of 2,6-di-tert-butyl-p-cresol, dilauryl thiodipropionate, and vitamin E. Based on the above embodiments, further adding an antioxidant can reduce the oxidative decomposition of the main material and improve the service life of the food packaging bag. As an example, 2,6-di-tert-butyl-p-cresol is used as the antioxidant in an embodiment of the present application.

[0075] In a second aspect, the present application provides a method for preparing a food packaging bag, including:

[0076] Providing the raw materials in the food packaging bag according to any one of the embodiments of the first aspect;

[0077] Drying the raw materials and then melt-blending, extruding, granulating, and blow molding to obtain a food packaging bag.

[0078] According to the present application, since it is prepared by using the raw materials in the food packaging bag according to any one of the embodiments of the first aspect, it has the beneficial effects of the first aspect.

[0079] In some embodiments, specifically including: drying 50 parts of polylactic acid, 50 to 100 parts of poly(butylene adipate-co-terephthalate), and 5 to 10 parts of modified filler, then adding 5 to 10 parts of plasticizer and 0.5 to 2 parts of antioxidant and dispersing them evenly, using a twin-screw extruder to extrude and granulate, and blow molding to obtain a food packaging bag.

[0080] In some embodiments, the temperature of the feeding zone of the twin-screw extruder is 140 to 150 °C, the temperature of the melting zone is 160 to 180 °C, the temperature of the homogenizing zone is 180 to 190 °C, the temperature of the extrusion zone is 170 to 180 °C, and the screw shear rate is 20 to 60 rpm.

[0081] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. For those without specific technical or conditions noted in the embodiments, the techniques or conditions described in the literature in the art or according to the product specifications are followed. Those reagents or instruments without the manufacturer noted are all conventional products that can be obtained through commercial procurement.

[0082] Graphene oxide, which is carboxylated graphene purchased from Jiangsu Xianfeng Nano Materials, has a thickness of 0.8 to 1.2 nm and a carboxyl content of about 5 wt%;

[0083] Carbon nanotubes, which are carboxylated multi-walled carbon nanotubes purchased from Jiangsu Xianfeng Nano Materials, with a diameter of 10 - 20 nm, an inner diameter of 5 - 10 nm, a length of 0.5 - 2 μm, and a carboxyl content of 2 wt%.

[0084] Example 1

[0085] Preparation of food packaging bags:

[0086] 50 parts by mass of polylactic acid with a weight-average molecular weight of 150,000, 70 parts by mass of polybutylene adipate / terephthalate with a weight-average molecular weight of 200,000, and 6 parts by mass of multi-arm grafted filler are dried, then 8 parts by mass of triacetyl citrate glycerol ester and 1 part by mass of 2,6-di-tert-butyl-p-cresol are added and uniformly dispersed. They are extruded and granulated using a twin-screw extruder and then blow-molded to obtain food packaging bags.

[0087] Among them, the multi-arm grafted filler is prepared by the following method:

[0088] 10 parts by mass of polyethylene glycol with a weight-average molecular weight of 400 and 6 parts by mass of succinic anhydride are dissolved in 200 parts by mass of toluene, heated and reacted at 75 °C for 9 h, extracted with chloroform and then dried. After removing chloroform by rotary evaporation, it is dissolved in ether and then dried to obtain carboxylated polyethylene glycol;

[0089] 10 parts by mass of carboxylated polyethylene glycol and 20 parts by mass of thionyl chloride are dissolved in 150 parts by mass of toluene, heated and reacted at 85 °C for 24 h, and dried by rotary evaporation to obtain polyethylene glycol acyl chloride;

[0090] 5 parts by mass of filler is ultrasonically dispersed in 200 parts by mass of ethanol aqueous solution (volume ratio of ethanol to water is 1:1), then 50 parts by mass of N-phenyl-γ-aminopropyltrimethoxysilane is added, heated and reacted at 85 °C for 1 h. After the reaction, it is centrifuged, separated, washed and dried to obtain amino-functionalized filler;

[0091] 10 parts by mass of polyethylene glycol acyl chloride and 4 parts by mass of amino-functionalized filler are dispersed in 150 parts by mass of toluene, ultrasonically dispersed for 15 min, heated and reacted at 85 °C for 8 h, and centrifuged and dried to obtain multi-arm grafted filler;

[0092] Among them, the filler is a mixture of graphene oxide and carbon nanotubes with a mass ratio of 1:0.2.

[0093] Example 2

[0094] Preparation of food packaging bags:

[0095] It is substantially the same as Example 1, with the only difference being that in the preparation process of the multi-arm grafted filler, the filler is graphene oxide.

[0096] Example 3

[0097] Preparation of food packaging bag:

[0098] It is substantially the same as Example 1, except that in the preparation process of the multi-arm grafted filler, the filler is carbon dioxide nanotubes.

[0099] Example 4

[0100] Preparation of food packaging bag:

[0101] It is substantially the same as Example 1, except that in the preparation process of the multi-arm grafted filler, polyethylene glycol with a weight average molecular weight of 600 is used.

[0102] Example 5

[0103] Preparation of food packaging bag:

[0104] It is substantially the same as Example 1, except that in the preparation process of the multi-arm grafted filler, polyethylene glycol with a weight average molecular weight of 300 is used.

[0105] Example 6

[0106] Preparation of food packaging bag:

[0107] It is substantially the same as Example 1, except that in the preparation process of the multi-arm grafted filler, polyethylene glycol with a weight average molecular weight of 1000 is used.

[0108] Example 7

[0109] Preparation of food packaging bag:

[0110] It is substantially the same as Example 1, except that in the preparation process of the multi-arm grafted filler, γ-aminopropyltrimethoxysilane is used as the amino silane coupling agent.

[0111] Example 8

[0112] Preparation of food packaging bag:

[0113] It is substantially the same as Example 1, except that in the preparation process of the multi-arm grafted filler, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is used as the amino silane coupling agent.

[0114] Example 9

[0115] It is substantially the same as Example 1, except that the multi-arm grafted filler is prepared by the following method:

[0116] Dissolve 10 parts by mass of polyethylene glycol with a weight average molecular weight of 400 and 6 parts by mass of succinic anhydride in 200 parts by mass of toluene, heat and react at 75 °C for 9 h, add chloroform for extraction and then dry, remove chloroform by rotary evaporation, dissolve with ether and then dry to obtain carboxylated polyethylene glycol;

[0117] Dissolve 10 parts by mass of carboxylated polyethylene glycol and 20 parts by mass of thionyl chloride in 150 parts by mass of toluene, heat and react at 85 °C for 24 h, and rotary evaporate and dry to obtain polyethylene glycol acyl chloride;

[0118] Ultrasonically disperse 10 parts by mass of polyethylene glycol acyl chloride and 4 parts by mass of filler in 150 parts by mass of toluene, ultrasonically disperse for 15 min, heat and react at 85 °C for 8 h, and centrifuge and dry to obtain multi-arm grafted filler;

[0119] Among them, the filler is a mixture of graphene oxide and carbonized carbon nanotubes with a mass ratio of 1:0.2.

[0120] Comparative Example 1

[0121] Preparation of food packaging bag:

[0122] Dry 50 parts by mass of polylactic acid with a weight average molecular weight of 150,000, 70 parts by mass of polybutylene adipate / terephthalate with a weight average molecular weight of 200,000, and 6 parts by mass of graphene acyl chloride, then add 5 parts by mass of polyethylene glycol with a weight average molecular weight of 400, 8 parts by mass of triacetyl citrate glycerol ester and 1 part by mass of 2,6-di-tert-butyl-p-cresol and disperse evenly, use a twin-screw extruder to extrude and granulate, and blow molding to obtain a food packaging bag.

[0123] Among them, the graphene acyl chloride is prepared by the following method:

[0124] Ultrasonically disperse 10 parts by mass of graphene oxide in 200 parts by mass of toluene, then add 20 parts by mass of thionyl chloride, heat and react at 85 °C for 24 h, centrifuge and separate, and dry to obtain graphene acyl chloride.

[0125] Testing part

[0126] Measure the oxygen transmission rate (OT value) of the food packaging bags obtained in the above examples and comparative examples with reference to GB / T 1038-2022 "Test Method for Gas Permeability of Plastics, Films and Sheets - Differential Pressure Method"; measure the maximum tensile stress with reference to GB / T 1040-2006 "Determination of Tensile Properties of Plastics"; the results are shown in Table 1.

[0127] Table 1

[0128] <![CDATA[OT value [cm 3 / (m 2 ·d·Pa)]]]> Maximum tensile stress / N Example 1 632 60.7 Example 2 696 55.3 Example 3 719 52.9 Example 4 641 61.2 Example 5 677 54.4 Example 6 698 58.6 Example 7 703 61.1 Example 8 689 60.3 Example 9 722 60.9 Comparative Example 1 843 45.2

[0129] According to Table 1, the OT value of the food packaging bags obtained in each example is smaller and the maximum tensile stress is greater than that of the comparative example, indicating that the food packaging bags obtained in this application have better barrier properties and flexibility. The reason may be that the compatibility between the filler and the matrix material used in Comparative Example 1 is poor. Although it has reactivity with the matrix material, due to poor compatibility, it cannot uniformly increase the crosslinking density of the material, and the additional addition of polyethylene glycol cannot effectively improve the compatibility of the filler, resulting in poor barrier properties and flexibility of the obtained food packaging bags.

[0130] According to Examples 1 to 3, it can be seen that the multi-arm grafted fillers obtained using different fillers have a certain impact on the barrier properties and flexibility of food packaging bags. Among them, using a certain proportion of graphene oxide and carbonized carbon nanotubes as fillers to modify the multi-arm grafted fillers, the obtained food packaging bags have better barrier properties and flexibility than those using single fillers in Examples 2 and 3. The reason may be that the more complex three-dimensional structure formed by two-dimensional graphene oxide and one-dimensional carbonized carbon nanotubes in the system can further improve its flexibility and further reduce the penetration of oxygen in the material, thereby further improving its barrier properties. In addition, the multi-arm grafted filler obtained using graphene oxide in Example 3 is better than that in Example 2.

[0131] According to Examples 1, 4 to 6, it can be seen that the length of the polyethylene glycol chain segment on the surface of the multi-arm grafted filler also has a certain impact on the barrier properties and flexibility of food packaging bags. The barrier properties and flexibility of Examples 1 and 4 are better. The reason may be that the shorter polyethylene glycol chain segment in Example 5 may affect its dispersibility, thereby affecting the barrier properties and flexibility of the food packaging bag; the longer polyethylene glycol chain segment in Example 6 may affect the crosslinking density of the material, thereby affecting the barrier properties and flexibility of the food packaging bag. Therefore, during the preparation process of the multi-arm grafted filler, using polyethylene glycol with a weight average molecular weight of 400 to 600 results in better barrier properties and flexibility of the obtained food packaging bags.

[0132] According to Examples 1, 7 to 9, it can be seen that the multi-arm grafted fillers obtained using different types of amino silane coupling agents or without using amino silane coupling agents have a certain impact on the barrier properties and flexibility of food packaging bags. It can be seen that the flexibility of the food packaging bags obtained in Examples 1, 7 to 9 has little difference, but the barrier properties of the food packaging bag obtained in Example 1 are significantly better than those of other examples, indicating that during the preparation process of the multi-arm grafted filler, using N-phenyl-γ-aminopropyltrimethoxysilane to modify the filler and then further grafting results in better barrier properties of the obtained food packaging bag and does not significantly deteriorate its flexibility.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A food packaging bag, characterized in that: The invention comprises the following raw materials in parts by weight: 50 parts of polylactic acid, 50-100 parts of polybutylene adipate / terephthalate, 5-10 parts of plasticizer, 5-10 parts of modified filler; Wherein, the modified filler comprises a multi-arm grafted filler, the end groups of the arms are acyl chloride groups, and the arms comprise polyethylene glycol segments.

2. The food packaging bag according to claim 1, characterized in that: The invention comprises the following raw materials in parts by weight: 50 parts of polylactic acid, 50-75 parts of polybutylene adipate / terephthalate, 5-8 parts of plasticizer, and 5-8 parts of modified filler.

3. The food packaging bag according to claim 1 or 2, characterized in that: The preparation method of the multi-arm grafted filler comprises the following steps: S1: reacting polyethylene glycol having a weight average molecular weight of 300 to 1000 with succinic anhydride in toluene, so that the hydroxyl groups at both ends of the polyethylene glycol react with the succinic anhydride, and grafting carboxyl groups on both ends of the polyethylene glycol to obtain carboxylated polyethylene glycol; S2: reacting carboxylated polyethylene glycol with thionyl chloride in toluene, so that the carboxyl groups at both ends of the carboxylated polyethylene glycol react with thionyl chloride, grafting acyl chloride groups on both ends of the carboxylated polyethylene glycol, and obtaining acyl chloride polyethylene glycol; S3: reacting the filler with an aminosilane coupling agent in an ethanol aqueous solution to graft an amino-containing side chain onto the surface of the filler to obtain an amino filler; the aminosilane coupling agent includes N-phenyl-γ-aminopropyltrimethoxysilane; S4: reacting the chlorinated polyethylene glycol with the amino filler in toluene, wherein the amino groups on the surface of the modified filler react with the chlorinated polyethylene glycol, grafting the chlorinated polyethylene glycol on the surface of the filler, and obtaining a multi-arm grafted filler.

4. The food packaging bag according to claim 3, characterized in that: The S1 specifically includes: 10 parts by weight of polyethylene glycol with a weight average molecular weight of 300 to 1000 and 5 to 10 parts by weight of succinic anhydride are dispersed in 150 to 300 parts by weight of toluene, and reacted at 60 to 80° C. for 5 to 12 hours to obtain carboxylated polyethylene glycol.

5. The food packaging bag according to claim 3, characterized in that: The S2 specifically includes: 10 parts by weight of carboxylated polyethylene glycol and 10 to 30 parts by weight of thionyl chloride are dispersed in 100 to 200 parts by weight of toluene, and reacted at 75 to 90° C. for 18 to 36 hours to obtain acyl chloride polyethylene glycol.

6. The food packaging bag according to claim 3, characterized in that: The S3 specifically includes: 5 parts by weight of filler and 40-60 parts by weight of aminosilane coupling agent are dispersed in 200-300 parts by weight of ethanol aqueous solution, and reacted at 75-90° C. for 0.5-2 hours to obtain an amino filler.

7. The food packaging bag according to claim 3 or 6, characterized in that: The filler comprises graphene oxide and oxidized carbon nanotubes, and the mass ratio of the graphene oxide to the oxidized carbon nanotubes is 1:0.1-0.

5.

8. The food packaging bag according to claim 3, characterized in that: The S4 specifically includes: 10 parts by weight of acyl chloride polyethylene glycol and 1 to 5 parts by weight of the amino filler are dispersed in 100 to 200 parts by weight of toluene, and reacted at 80 to 90° C. for 6 to 12 hours to obtain a multi-arm grafted filler.

9. The food packaging bag according to claim 1 or 2, characterized in that: The food packaging bag satisfies at least one of the following conditions: 1) The weight average molecular weight of the polylactic acid is 100,000 to 200,000; 2) The weight average molecular weight of the polybutylene adipate / terephthalate is 150,000 to 300,000; 3) The plasticizer includes at least one of triacetyl citrate, tributyl citrate, triethyl citrate, polybutylene adipate, and epoxidized soybean oil; 4) It also includes 0.5 to 2 parts of an antioxidant; the antioxidant includes at least one of 2,6-di-tert-butyl-p-cresol, dilaurylthiopropionate, and vitamin E.

10. A method for preparing a food packaging bag, characterized in that: include: Providing a raw material in a food packaging bag according to any one of claims 1 to 9; The raw materials are dried, melt-blended, extruded, granulated, and blow-molded to obtain food packaging bags.