A biodegradable wrapping film and a preparation method and application thereof

Abstract

The application provides a biodegradable wrapping film and a preparation method and application thereof. The biodegradable wrapping film comprises a self-adhesive layer and a supporting layer coated on the surface of the self-adhesive layer. The self-adhesive layer comprises 10-20 parts of PPC dihydric alcohol, 60-80 parts of PPC and 10-20 parts of inorganic powder by weight. The supporting layer comprises 10-20 parts of PPC, 78-89 parts of PBAT, 0.5-1.5 parts of a compatibilizer and 0.5-1 part of an opening agent by weight. The PPC dihydric alcohol provides self-adhesion, the PPC provides elastic recovery capability, and the PBAT provides mechanical support. The application adopts a double-layer design, and adds PPC and a compatibilizer in the supporting layer, which is beneficial to adjusting the melt flowability of the self-adhesive layer and the supporting layer to be close, so that the self-adhesive layer and the supporting layer have better adhesion, and the biodegradable wrapping film has higher self-adhesion and a rebound recovery value.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable plastics technology, specifically relating to a biodegradable stretch film, its preparation method, and its application. Background Technology

[0002] Stretch film is a packaging film that can be stretched and tightly wrapped around a packaged item at room temperature and sealed at the end. Because stretch film packaging does not require heating, its process is simpler and more practical than that of heat shrink film. Stretch film also features high tensile strength, good self-adhesion, and ease of use, and is currently widely used in industrial and agricultural packaging. Currently, my country's demand for stretch film is approximately 78,000 tons per year. However, as a composite film, stretch film is difficult to recycle and reuse. Therefore, the continued high-intensity and large-scale use of stretch film easily leads to white pollution.

[0003] Biodegradable stretch film can degrade in the environment, which can fundamentally solve the white pollution problem caused by stretch film. However, after years of development, in addition to its high price, biodegradable stretch film still has two performance problems. First, the self-adhesion of biodegradable stretch film is still low, making it difficult to seal after wrapping. At present, most of them increase self-adhesion by adding polyisobutylene, but polyisobutylene is not biodegradable. Second, the resilience of biodegradable stretch film is low, and permanent deformation will occur after wrapping, resulting in it not being able to wrap tightly and becoming loose. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a biodegradable stretch film, its preparation method, and its application. The biodegradable stretch film has high self-adhesion and resilience, and is fully biodegradable.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a biodegradable wrapping film, comprising a self-adhesive layer and a support layer covering the surface of the self-adhesive layer;

[0007] The self-adhesive layer comprises, by weight, 10-20 parts of PPC diol, 60-80 parts of PPC, and 10-20 parts of inorganic powder;

[0008] The support layer comprises, by weight, 10-20 parts PPC, 78-89 parts PBAT, 0.5-1.5 parts compatibilizer and 0.5-1 part opening agent.

[0009] Wherein, PPC is the abbreviation for polypropylene carbonate, and PPC diol is the abbreviation for polypropylene carbonate diol.

[0010] Preferably, the PPC diol has a number-average molecular weight of 1800–2000 g / mol, a molecular weight distribution of 1.2–1.6, a polycarbonate content of 30–50%, and a viscosity of 40–60 Pa·s at 22°C.

[0011] Preferably, the PPC has a number-average molecular weight of 100-150 kg / mol, a molecular weight distribution of 2.2-3, and a melt index of 0.3-1.5 g / 10 min (170 °C, 2.160 kg).

[0012] Preferably, the PBAT has a number-average molecular weight of 60-80 kg / mol, a molecular weight distribution of 2.2-3, and a melt index of 3-5 g / 10 min (190°C, 2.160 kg).

[0013] Preferably, the compatibilizer is a terpolymer of carbon dioxide, propylene oxide, and a functional monomer, wherein the functional monomer is selected from allyl glycidyl ether or glycidyl methacrylate.

[0014] Preferably, the inorganic powder is calcium carbonate and / or talc.

[0015] Preferably, the opening agent is erucamide and / or oleamide.

[0016] Preferably, the mass ratio of the self-adhesive layer to the support layer is 1:(1 to 1.5).

[0017] Preferably, the thickness of the biodegradable wrapping film is 50–60 μm.

[0018] Secondly, the present invention provides a method for preparing the above-mentioned biodegradable wrapping film, comprising the following steps:

[0019] S1: After mixing PPC diol with inorganic powder evenly, the resulting mixture is then mixed evenly with PPC. The resulting product is then melt-granulated using a twin-screw extruder to obtain the self-adhesive layer material. PPC, PBAT, compatibilizer, and opening agent are mixed evenly, and the resulting product is then melt-granulated using a twin-screw extruder to obtain the support layer material.

[0020] S2: Add the self-adhesive layer material and the support layer material to the conveying screw of the double-layer casting machine to cast and prepare a biodegradable wrapping film.

[0021] Preferably, the mixing of PPC diol and inorganic powder specifically involves: first, stirring the PPC diol and inorganic powder at 50-70 r / min for 1-5 min, and then stirring at 550-600 r / min for 1-5 min.

[0022] Preferably, the temperature of the twin-screw melt granulation process for obtaining the self-adhesive layer material is 120–150°C.

[0023] Preferably, during the process of obtaining the support layer material, the temperature of the twin-screw melt granulation is 140–165°C.

[0024] Preferably, in step S2, the inner screw temperature of the double-layer casting machine is 140-155°C, the outer screw temperature is 140-165°C, and the die head temperature is 170-175°C.

[0025] Thirdly, the present invention provides a packaging film composed of the biodegradable wrapping film involved in the above-mentioned technical solution.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention provides a biodegradable stretch film, comprising a self-adhesive layer and a support layer covering the surface of the self-adhesive layer. In this invention, the self-adhesive layer comprises, by weight, 10-20 parts of PPC diol, 60-80 parts of PPC, and 10-20 parts of inorganic powder; the support layer comprises, by weight, 10-20 parts of PPC, 78-89 parts of PBAT, 0.5-1.5 parts of compatibilizer, and 0.5 parts of opening agent. PPC diol itself has high viscosity and can precipitate at room temperature, providing self-adhesion for the biodegradable stretch film, and also exhibits good biodegradability. Since PPC diol itself is very viscous and difficult to process, this invention adds inorganic powder as a carrier for PPC diol, facilitating feeding and processing. Simultaneously, to ensure good resilience of the biodegradable stretch film, this invention adds PPC to the self-adhesive layer. PPC has a low glass transition temperature (around 30°C), and shrinks easily upon low-temperature heating, significantly improving elastic recovery. To ensure the performance of the biodegradable stretch film, this invention also prepares a support layer, which forms a bilayer film with the self-adhesive layer. PBAT provides mechanical support, and the addition of PPC to the support layer improves the compatibility between the support and self-adhesive layers. The addition of a compatibilizer ensures more uniform mixing of PPC and PBAT in the support layer, facilitating the adjustment of the melt flow of the self-adhesive and support layers to be similar, resulting in better adhesion and preventing delamination. An opening agent can precipitate on the surface of the stretch film, solving the problem of the stretch film roll being difficult to open. In packaging applications, simply heating the stretch film allows it to tightly wrap the packaged items, thus solving the application bottleneck problems encountered by existing biodegradable stretch films.

[0028] Tests show that the biodegradable wrapping film provided by this invention has a transverse tensile strength (N) of not less than 7±0.2N, a longitudinal tensile strength (N) of not less than 11±0.2N, a transverse elongation at break of not less than 587±12%, a longitudinal elongation at break of not less than 291±7%, a viscosity of not less than 1.8±0.1N, and an elastic recovery rate of not less than 36±3%. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] To address the issues of poor self-adhesion and resilience of existing biodegradable stretch films, this invention provides a biodegradable stretch film comprising a self-adhesive layer and a support layer covering the surface of the self-adhesive layer.

[0031] In this invention, the self-adhesive layer comprises, by weight, 10-20 parts of PPC diol, which can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 parts; 60-80 parts of PPC, which can be 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, or 80 parts; and 10-20 parts of inorganic powder, which can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 parts.

[0032] The PPC diol can be prepared according to the literature "Selective synthesis of oligo(carbonate-ether)diols from copolymerization of CO2 and propylene oxide under zinc-cobalt double metalcyanide complex." J PolymRes (2012) 19:9878. The PPC diol itself has high viscosity and can precipitate at room temperature, thus providing self-adhesion for the biodegradable wrapping film and exhibiting good biodegradability. In this invention, the number-average molecular weight of the PPC diol is preferably 1800–2000 g / mol, more preferably 1900 g / mol; the molecular weight distribution is preferably 1.2–1.6, more preferably 1.3–1.5; the polycarbonate content is preferably 30–50%, more preferably 40%; and the viscosity at 22°C is preferably 40–60 Pa·s, more preferably 50 Pa·s.

[0033] Because PPC diol itself is highly viscous and difficult to process, this invention adds inorganic powder as a carrier for the PPC diol to the raw materials for preparing the self-adhesive layer, facilitating feeding and processing. The inorganic powder is calcium carbonate and / or talc. The calcium carbonate has an average particle size of 4 μm and a particle size distribution of 2–8 μm; the talc has an average particle size of 5 μm and a particle size distribution of 3–6.5 μm. This invention does not have special restrictions on the source of the inorganic powder and it can be obtained commercially.

[0034] Meanwhile, to ensure good resilience of the biodegradable wrapping film, this invention adds PPC to the self-adhesive layer. PPC has a low glass transition temperature (around 30°C), making it prone to shrinkage upon low-temperature heating, thus significantly improving elastic recovery. This invention does not impose any special restrictions on the source of PPC; it can be obtained commercially. The number-average molecular weight of the PPC is preferably 100–150 kg / mol, more preferably 120–130 kg / mol; the molecular weight distribution is 2.2–3, more preferably 2.4–2.6; and the melt flow index is 0.3–1.5 g / 10 min, more preferably 0.5–1.0 g / 10 min. The melt flow index is preferably measured at a temperature of 170°C with a weight mass of 2.160 kg.

[0035] In this invention, the support layer comprises, by weight, 10-20 parts of PPC (which can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 parts, etc.); 78-89 parts of PBAT (which can be 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, or 89 parts, etc.); 0.5-1.5 parts of compatibilizer (which can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5 parts, etc.); and 0.5-1 part of opening agent (which can be 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 parts, etc.).

[0036] In this invention, adding a relatively small amount of PPC to the support layer can improve the compatibility between the support layer and the self-adhesive layer, and adjust the melt flow rates of the support layer and the self-adhesive layer to be similar. This invention does not have special restrictions on the source of PPC; it can be obtained commercially. It should be noted that if PPC is not added to the support layer, a cast film cannot be prepared. The addition of PPC can better regulate the melt flow rates of the two layers. If PBAT material alone is used as the support layer, firstly, the casting processing temperature needs to be above 190°C, which is incompatible with the processing temperatures of the support layer and the self-adhesive layer; secondly, insufficient compatibility between the support layer and the self-adhesive layer will result in delamination.

[0037] The PBAT mentioned is a thermoplastic biodegradable plastic, a copolymer of butylene adipate and butylene terephthalate, possessing characteristics of both polybutylene adipate (PBA) and polybutylene terephthalate (PBT). It exhibits good ductility and elongation at break, as well as good heat resistance and impact resistance, and also excellent biodegradability. In this invention, PBAT is used as the main component of the support layer to provide mechanical support. The number-average molecular weight of the PBAT is preferably 60–80 kg / mol, more preferably 70 kg / mol; the molecular weight distribution is preferably 2.2–3, more preferably 2.4–2.6; and the melt index is 3–5 g / 10 min, more preferably 4 g / 10 min. The melt index is preferably measured at a temperature of 190°C and a weight mass of 2.160 kg.

[0038] In this invention, the compatibilizer (referred to as "branched PPC") is a terpolymer of carbon dioxide, propylene oxide, and a functional monomer, wherein the functional monomer is selected from allyl glycidyl ether or glycidyl methacrylate. The compatibilizer can be prepared according to the literature High-Performance Biodegradable PBAT / PPC Composite Film Through Reactive Compatibilizer. Chinese Journal of Polymer Science (2022) 8:411 or Chinese invention patent "A branched PPC base film and its preparation method" (authorization number CN113683764B). In this invention, by adding a compatibilizer to the support layer, the PPC and PBAT in the support layer can be mixed more uniformly, which is beneficial for adjusting the melt flow of the self-adhesive layer and the support layer to be similar, and makes the self-adhesive layer and the support layer have better adhesion, preventing delamination.

[0039] In this invention, the opening agent is erucamide and / or oleamide, which can precipitate on the surface of the winding film, solving the problem of the winding film roll being difficult to open. This invention does not have special restrictions on the source of the opening agent and it can be obtained commercially.

[0040] In this invention, the preferred mass ratio of the self-adhesive layer to the support layer is 1:(1-1.5), which can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5, etc. The PPC diol in the self-adhesive layer can precipitate at room temperature, improving the self-adhesion of the biodegradable wrapping film. PPC has a low glass transition temperature, making it prone to shrinkage upon low-temperature heating. When combined with PBAT to form a bilayer film, PBAT provides mechanical support, while PPC provides thermal shrinkage resistance, significantly improving elastic recovery. In some embodiments of this invention, the thickness of the prepared biodegradable wrapping film is preferably 50-60 μm, which can be 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm, 59 μm, or 60 μm, etc.

[0041] The present invention also provides a method for preparing the above-mentioned biodegradable wrapping film, comprising the following steps:

[0042] S1: After mixing PPC diol with inorganic powder evenly, the resulting mixture is then mixed evenly with PPC. The resulting product is then melt-granulated using a twin-screw extruder to obtain the self-adhesive layer material. PPC, PBAT, compatibilizer, and opening agent are mixed evenly, and the resulting product is then melt-granulated using a twin-screw extruder to obtain the support layer material.

[0043] S2: Add the self-adhesive layer material and the support layer material to the conveying screw of the double-layer casting machine to cast and prepare a biodegradable wrapping film.

[0044] According to this invention, PPC diol and inorganic powder are first mixed evenly, and then the resulting mixture is mixed evenly with PPC. The resulting product is then melt-granulated using a twin-screw extruder to obtain a self-adhesive layer material. The selection and proportions of PPC diol, inorganic powder, and PPC are as described in the aforementioned technical solutions and will not be repeated here. In some embodiments of this invention, the mixing of PPC diol and inorganic powder specifically involves: first, stirring the PPC diol and inorganic powder at a low speed of 50–70 r / min for 1–5 min, preferably at 60 r / min for 2–3 min; then, stirring at a high speed of 550–600 r / min for 1–5 min, preferably at 580 r / min for 2–3 min. This invention first mixes PPC diol and inorganic powder at low speed, and then mixes them at high speed to ensure uniform mixing of the PPC diol and inorganic powder. Without high-speed mixing, large agglomerates of PPC diol encapsulated in inorganic powder can easily form, which is detrimental to subsequent processing. After the PPC diol and inorganic powder are uniformly mixed, the resulting mixture is preferably mixed uniformly with PPC. This mixing is preferably carried out under stirring conditions, with a stirring speed of 40–70 r / min, preferably 50 r / min, and a stirring time of 1–5 min, preferably 2–3 min. In this invention, the mixing and stirring are preferably carried out in a high-speed mixer. Then, the obtained product is melt-granulated using a twin-screw extruder to obtain the self-adhesive layer material. In this step, the aspect ratio of the twin screws in the twin-screw melt-granulation is preferably (40–52):1, more preferably 48:1; the temperature is preferably 120–150°C. In some embodiments of the present invention, the temperature of the twin-screw is set as follows: Zone 1: 120°C; Zone 2: 125°C; Zone 3: 135°C; Zone 4: 140°C; Zone 5: 140°C; Zone 6: 140°C; Zone 7: 145°C; Zone 8: 145°C; Zone 9: 150°C; Zone 10: 150°C; Zone 11: 145°C; and the die head: 140°C. In the present invention, after obtaining the self-adhesive layer material, it is preferably stored in an environment below 4°C to avoid premature precipitation of PPC diol.

[0045] According to this invention, PPC, PBAT, a compatibilizer, and an opening agent are mixed evenly, and the resulting product is melt-granulated using a twin-screw extruder to obtain the support layer material. The selection and dosage ratio of PPC, PBAT, the compatibilizer, and the opening agent are as described in the relevant sections of the above-mentioned technical solutions and will not be repeated here. In some embodiments of this invention, the mixing of PPC, PBAT, the compatibilizer, and the opening agent is preferably carried out at 50–70 r / min, more preferably 60 r / min, and the stirring time is preferably 1–5 min, more preferably 2–3 min. The stirring is preferably carried out in a high-speed mixer. Then, the evenly mixed product is melt-granulated using a twin-screw extruder to obtain the support layer material. In this step, the length-to-diameter ratio of the twin screws in the twin-screw melt-granulation is preferably (40–52):1, more preferably 48:1; the temperature is preferably 140–165°C. In some embodiments of the present invention, the temperature of the twin screw is set to 140°C in zone 1, 145°C in zone 2, 150°C in zone 3, 155°C in zone 4, 160°C in zone 5, 165°C in zone 6, 165°C in zone 7, 165°C in zone 8, 160°C in zone 9, 160°C in zone 10, 155°C in zone 11, and 155°C at the die head.

[0046] After obtaining the self-adhesive layer material and the support layer material, according to the present invention, preferably, the self-adhesive layer material and the support layer material are added to the conveying screw of a double-layer casting machine to prepare a biodegradable wrapping film by casting. In some embodiments of the present invention, the self-adhesive layer material is added to the inner conveying screw of the casting machine, and the support layer material is added to the outer conveying screw of the casting machine, and then a biodegradable wrapping film is prepared by casting. The present invention does not impose any particular limitation on the casting method; conventional techniques known to those skilled in the art can be used. In the present invention, the inner screw temperature of the double-layer casting machine is 140–155°C, the outer screw temperature is 140–165°C, and the die head temperature is 170–175°C. In some embodiments of the present invention, the inner screw temperature is set to 140°C in zone one, 150°C in zone two, and 155°C in zone three; the outer screw temperature is set to 140°C in zone one, 155°C in zone two, and 165°C in zone three; and the die head temperature is 170°C.

[0047] The preparation method of the above-mentioned biodegradable wrapping film provided by the present invention is simple, convenient, easy to implement, and conducive to large-scale production.

[0048] This invention also provides a packaging film composed of the biodegradable stretch film described in the above-mentioned technical solutions. When used in packaging, the biodegradable stretch film only requires heating (e.g., using a hair dryer) to tightly wrap the packaged items, thus solving the application bottleneck problems encountered by existing biodegradable stretch films.

[0049] Tests showed that the biodegradable stretch film provided by this invention has a transverse tensile strength (N) of not less than 7±0.2N, a longitudinal tensile strength (N) of not less than 11±0.2N, a transverse elongation at break of not less than 587±12%, a longitudinal elongation at break of not less than 291±7%, an adhesiveness of not less than 1.8±0.1N, and an elastic recovery rate of not less than 36±3%. These data indicate that the biodegradable stretch film has high self-adhesion and resilience, and exhibits good performance.

[0050] It should be noted that the point values ​​listed above in this invention are merely for illustrative purposes and are not limited thereto. Other point values ​​within the numerical range are also applicable and will not be elaborated upon here.

[0051] To further illustrate the present invention, the following examples provide a detailed description. The PPC diol used in the following examples was prepared according to the literature *Selective synthesis of oligo(carbonate-ether)diols from copolymerization of CO2 and propylene oxide under zinc-cobalt doublemetalcyanide complex.* J PolymRes (2012) 19:9878; the compatibilizer was prepared according to the corresponding method in patent CN113683764B, wherein the functional monomer was glycidyl methacrylate. PBAT and PPC were purchased from Zhejiang Huafeng Environmental Protection Materials Co., Ltd.; erucamide and oleamide were purchased from Jiangxi Beier Gaoke New Materials Co., Ltd.; calcium carbonate filler was purchased from Guangxi Hezhou Kelong Powder Co., Ltd.; and talc filler was purchased from Liaoning Jinghua New Materials Co., Ltd. In the following examples, the length-to-diameter ratio of the twin screws was 48:1, and the length-to-diameter ratio of the inner and outer conveying screws of the casting machine was 48:1.

[0052] Example 1

[0053] This embodiment provides a biodegradable wrapping film, the preparation method of which is as follows:

[0054] (1) Place 2 kg of PPC diol with a number average molecular weight of 2000 g / mol, a molecular weight distribution of 1.48, and a polycarbonate content of 42% and 1 kg of talc powder in a high-speed mixer. Stir at 50 r / min for 1 minute, then at 600 r / min for 1 minute. Then add 7 kg of PPC with a number average molecular weight of 102 kg / mol and a molecular weight distribution of 2.6. Stir at 50 r / min for 2 minutes. Take out the mixture and add it to a twin-screw extruder. Set the twin-screw temperature to 120℃ in zone 1, 125℃ in zone 2, 135℃ in zone 3, 140℃ in zone 4, 140℃ in zone 5, 140℃ in zone 6, 145℃ in zone 7, 145℃ in zone 8, 150℃ in zone 9, 150℃ in zone 10, 145℃ in zone 11, and 140℃ at the die head. Granulate to obtain the inner layer modified material. Store the inner layer modified material in an environment below 4℃ to avoid premature precipitation of PPC diol.

[0055] (2) Place 1 kg of PPC with a number-average molecular weight of 102 kg / mol and a molecular weight distribution of 2.6, 8.8 kg of PBAT with a number-average molecular weight of 67 kg / mol and a molecular weight distribution of 2.4, 0.15 kg of branched PPC with a number-average molecular weight of 34 kg / mol and a molecular weight distribution of 4.1, and 0.05 kg of erucamide in a mixer and stir at 50 r / min for 3 minutes. Take out the mixture and add it to a twin-screw extruder. Set the twin-screw temperature to 140℃ in zone 1, 145℃ in zone 2, 150℃ in zone 3, 155℃ in zone 4, 160℃ in zone 5, 165℃ in zone 6, 165℃ in zone 7, 165℃ in zone 8, 160℃ in zone 9, 160℃ in zone 10, 155℃ in zone 11, and 155℃ at the die head. Granulate to obtain the outer modified material.

[0056] (3) The outer and inner modified materials were added to the inner and outer conveying screws of the casting machine, respectively. The inner screw temperature was 140℃ in zone 1, 150℃ in zone 2, and 155℃ in zone 3. The outer screw temperature was 140℃ in zone 1, 155℃ in zone 2, and 165℃ in zone 3. The die head temperature was 170℃. The mass ratio of the inner and outer layers was 1:1.5. A 50μm thick biodegradable winding film was prepared. The performance test results are shown in Table 1. The test standard refers to BB / T0024-2018.

[0057] Example 2

[0058] This embodiment provides a biodegradable wrapping film, the preparation method of which is as follows:

[0059] (1) Place 1 kg of PPC diol with a number average molecular weight of 2000 g / mol, a molecular weight distribution of 1.48, and a polycarbonate content of 42% and 2 kg of calcium carbonate powder in a high-speed mixer. Stir at 50 r / min for 1 minute, then at 600 r / min for 1 minute. Then add 7 kg of PPC with a number average molecular weight of 102 kg / mol and a molecular weight distribution of 2.6. Stir at 50 r / min for 2 minutes. Take out the mixture and add it to a twin-screw extruder. Set the twin-screw temperature to 120℃ in zone 1, 125℃ in zone 2, 135℃ in zone 3, 140℃ in zone 4, 140℃ in zone 5, 140℃ in zone 6, 145℃ in zone 7, 145℃ in zone 8, 150℃ in zone 9, 150℃ in zone 10, 145℃ in zone 11, and 140℃ at the die head. Granulate to obtain the inner layer modified material. The inner layer modified material should be stored below 4℃ to avoid premature precipitation of PPC diol.

[0060] (2) 2 kg of PPC with a number-average molecular weight of 102 kg / mol and a molecular weight distribution of 2.6, 7.8 kg of PBAT with a number-average molecular weight of 67 kg / mol and a molecular weight distribution of 2.4, 0.15 kg of branched PPC with a number-average molecular weight of 34 kg / mol and a molecular weight distribution of 4.1, and 0.05 kg of oleic acid amide were placed in a mixer and stirred at 50 r / min for 3 minutes. The mixture was then removed and added to a twin-screw extruder. The twin-screw extruder temperature was set to 140℃ in zone 1, 145℃ in zone 2, 150℃ in zone 3, 155℃ in zone 4, 160℃ in zone 5, 165℃ in zone 6, 165℃ in zone 7, 165℃ in zone 8, 160℃ in zone 9, 160℃ in zone 10, 155℃ in zone 11, and 155℃ at the die head. Granulation was performed to obtain the outer modified material.

[0061] (3) Add the outer and inner modified materials to the inner and outer conveying screws of the casting machine, respectively. The inner screw temperature is 140℃ in zone 1, 150℃ in zone 2, and 155℃ in zone 3. The outer screw temperature is 140℃ in zone 1, 155℃ in zone 2, and 165℃ in zone 3. The die head temperature is 170℃. The mass ratio of the inner and outer layers is 1:1. Prepare a 60μm thick biodegradable winding film. The performance test is shown in Table 1. The test standard refers to BB / T0024-2018.

[0062] Example 3

[0063] This embodiment provides a biodegradable wrapping film, the preparation method of which is as follows:

[0064] (1) 2 kg of PPC diol with a number-average molecular weight of 1800 g / mol, a molecular weight distribution of 1.28, and a polycarbonate content of 49% and 1 kg of talc powder were placed in a high-speed mixer and stirred at 50 r / min for 1 minute, followed by stirring at 600 r / min for 1 minute. Then, 7 kg of PPC with a number-average molecular weight of 102 kg / mol and a molecular weight distribution of 2.6 was added and stirred at 50 r / min for 2 minutes. The mixture was then removed and added to a twin-screw extruder. The twin-screw extruder temperature was set as follows: Zone 1: 120℃, Zone 2: 125℃, Zone 3: 135℃, Zone 4: 140℃, Zone 5: 140℃, Zone 6: 140℃, Zone 7: 145℃, Zone 8: 145℃, Zone 9: 150℃, Zone 10: 150℃, Zone 11: 145℃, and die head: 140℃. Granulation was performed to obtain the inner layer modified material. The inner layer modified material was stored in an environment below 4℃ to avoid premature precipitation of PPC diol.

[0065] (2) Place 1 kg of PPC with a number-average molecular weight of 102 kg / mol and a molecular weight distribution of 2.6, 8.8 kg of PBAT with a number-average molecular weight of 67 kg / mol and a molecular weight distribution of 2.4, 0.15 kg of branched PPC with a number-average molecular weight of 34 kg / mol and a molecular weight distribution of 4.1, and 0.05 kg of erucamide in a mixer and stir at 50 r / min for 3 minutes. Take out the mixture and add it to a twin-screw extruder. Set the twin-screw temperature to 140℃ in zone 1, 145℃ in zone 2, 150℃ in zone 3, 155℃ in zone 4, 160℃ in zone 5, 165℃ in zone 6, 165℃ in zone 7, 165℃ in zone 8, 160℃ in zone 9, 160℃ in zone 10, 155℃ in zone 11, and 155℃ at the die head. Granulate to obtain the outer modified material.

[0066] (3) Add the outer and inner modified materials to the inner and outer conveying screws of the casting machine, respectively. The inner screw temperature is 140℃ in zone 1, 150℃ in zone 2, and 155℃ in zone 3. The outer screw temperature is 140℃ in zone 1, 155℃ in zone 2, and 165℃ in zone 3. The die head temperature is 170℃. The mass ratio of the inner and outer layers is 1:1. Prepare a 50μm thick biodegradable winding film. The performance test is shown in Table 1. The test standard refers to BB / T0024-2018.

[0067] Example 4

[0068] This embodiment provides a biodegradable wrapping film, the preparation method of which is as follows:

[0069] (1) Place 2 kg of PPC diol with a number average molecular weight of 2000 g / mol, a molecular weight distribution of 1.48, and a polycarbonate content of 42% and 1 kg of talc powder in a high-speed mixer. Stir at 70 r / min for 1 minute, then at 550 r / min for 2 minutes. Then add 7 kg of PPC with a number average molecular weight of 138 kg / mol and a molecular weight distribution of 2.9. Stir at 70 r / min for 3 minutes. Take out the mixture and add it to a twin-screw extruder. Set the twin-screw temperature to 120℃ in zone 1, 125℃ in zone 2, 135℃ in zone 3, 140℃ in zone 4, 140℃ in zone 5, 140℃ in zone 6, 145℃ in zone 7, 145℃ in zone 8, 150℃ in zone 9, 150℃ in zone 10, 145℃ in zone 11, and 140℃ at the die head. Granulate to obtain the inner layer modified material. The inner layer modified material should be stored below 4℃ to avoid premature precipitation of PPC diol.

[0070] (2) Place 1 kg of PPC with a number-average molecular weight of 138 kg / mol and a molecular weight distribution of 2.9, 8.8 kg of PBAT with a number-average molecular weight of 67 kg / mol and a molecular weight distribution of 2.4, 0.15 kg of branched PPC with a number-average molecular weight of 34 kg / mol and a molecular weight distribution of 4.1, and 0.05 kg of erucamide in a mixer and stir at 70 r / min for 3 minutes. Take out the mixture and add it to a twin-screw extruder. Set the twin-screw temperature to 140℃ in zone 1, 145℃ in zone 2, 150℃ in zone 3, 155℃ in zone 4, 160℃ in zone 5, 165℃ in zone 6, 165℃ in zone 7, 165℃ in zone 8, 160℃ in zone 9, 160℃ in zone 10, 155℃ in zone 11, and 155℃ at the die head. Granulate to obtain the outer modified material.

[0071] (3) The outer and inner modified materials were added to the inner and outer conveying screws of the casting machine, respectively. The inner screw temperature was 140℃ in zone 1, 150℃ in zone 2, and 155℃ in zone 3. The outer screw temperature was 140℃ in zone 1, 155℃ in zone 2, and 165℃ in zone 3. The die head temperature was 170℃. The mass ratio of the inner and outer layers was 1:1.5. A 50μm thick biodegradable winding film was prepared. The performance test results are shown in Table 1. The test standard refers to BB / T0024-2018.

[0072] Comparative Example 1

[0073] This comparative example provides a winding film, the preparation method of which is as follows:

[0074] (1) 1 kg of talc powder and 9 kg of PPC with a number average molecular weight of 102 kg / mol and a molecular weight distribution of 2.6 were stirred at 50 r / min for 2 minutes. The mixture was then taken out and added to a twin-screw extruder. The twin-screw extruder temperature was set to 120℃ in zone 1, 125℃ in zone 2, 135℃ in zone 3, 140℃ in zone 4, 140℃ in zone 5, 140℃ in zone 6, 145℃ in zone 7, 145℃ in zone 8, 150℃ in zone 9, 150℃ in zone 10, 145℃ in zone 11, and 140℃ at the die head. Granulation was performed to obtain the inner layer modified material.

[0075] (2) Place 1 kg of PPC with a number-average molecular weight of 102 kg / mol and a molecular weight distribution of 2.6, 8.8 kg of PBAT with a number-average molecular weight of 67 kg / mol and a molecular weight distribution of 2.4, 0.15 kg of branched PPC with a number-average molecular weight of 34 kg / mol and a molecular weight distribution of 4.1, and 0.05 kg of erucamide in a mixer and stir at 50 r / min for 3 minutes. Take out the mixture and add it to a twin-screw extruder. Set the twin-screw temperature to 140℃ in zone 1, 145℃ in zone 2, 150℃ in zone 3, 155℃ in zone 4, 160℃ in zone 5, 165℃ in zone 6, 165℃ in zone 7, 165℃ in zone 8, 160℃ in zone 9, 160℃ in zone 10, 155℃ in zone 11, and 155℃ at the die head. Granulate to obtain the outer modified material.

[0076] (3) The outer and inner modified materials were added to the inner and outer conveying screws of the casting machine, respectively. The inner screw temperature was 140℃ in zone 1, 150℃ in zone 2, and 155℃ in zone 3. The outer screw temperature was 140℃ in zone 1, 155℃ in zone 2, and 165℃ in zone 3. The die head temperature was 170℃. The mass ratio of the inner and outer layers was 1:1.5. A 50μm thick biodegradable winding film was prepared. The performance test results are shown in Table 1. The test standard refers to BB / T0024-2018.

[0077] Comparative Example 2

[0078] This comparative example provides a winding film, the preparation method of which is as follows:

[0079] (1) Place 1 kg of PPC with a number-average molecular weight of 102 kg / mol and a molecular weight distribution of 2.6, 8.8 kg of PBAT with a number-average molecular weight of 67 kg / mol and a molecular weight distribution of 2.4, 0.15 kg of branched PPC with a number-average molecular weight of 34 kg / mol and a molecular weight distribution of 4.1 and 0.05 kg of erucamide in a mixer and stir at 50 r / min for 3 minutes. Take out the mixture and add it to a twin-screw extruder. Set the twin-screw temperature to 140℃ in zone 1, 145℃ in zone 2, 150℃ in zone 3, 155℃ in zone 4, 160℃ in zone 5, 165℃ in zone 6, 165℃ in zone 7, 165℃ in zone 8, 160℃ in zone 9, 160℃ in zone 10, 155℃ in zone 11, and 155℃ at the die head. Granulate to obtain the modified material.

[0080] (2) Add the modified material to the casting machine. The screw temperature is 140℃ in zone 1, 155℃ in zone 2, and 165℃ in zone 3. The die head temperature is 170℃. Prepare a 50μm thick biodegradable wrapping film. The performance test results are shown in Table 1. The test standard is based on BB / T 0024-2018.

[0081] In this invention, the corresponding test standards for the biodegradable stretch film prepared in the examples and the stretch film prepared in the comparative examples were all performed in accordance with BB / T 0024-2018. Specifically, the data for the adhesion test were obtained by placing the biodegradable stretch film prepared in the examples and the stretch film prepared in the comparative examples at room temperature for more than 48 hours to allow the PPC diol to precipitate and generate adhesion. The data for elastic recovery were obtained by stretching the biodegradable stretch film prepared in the examples and the stretch film prepared in the comparative examples and placing them at 50°C for 3 minutes.

[0082] The test results are shown in Table 1 below:

[0083] Table 1

[0084]

[0085] As shown in Table 1, the tensile strength and elongation at break of the biodegradable wrapping film obtained in the examples are not significantly different from those in the comparative examples. Furthermore, the addition of PPC diol may even reduce tensile mechanical properties. However, comparing the viscosity data of the examples and the comparative examples reveals that PPC diol plays a major role. The biodegradable wrapping film obtained in the examples has the lowest viscosity at 1.8 ± 0.18 N, significantly higher than that of the comparative example. Comparing the elastic recovery data of the examples and the comparative example shows that the two-layer design of PPC and PBAT is significantly beneficial to elastic recovery. The wrapping film in Comparative Example 2, which uses a single outer modified material, not only lacks viscosity but also has an elastic recovery value far lower than that of the examples.

[0086] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A biodegradable wrapping film, characterized in that, It includes a self-adhesive layer and a support layer covering the surface of the self-adhesive layer; The self-adhesive layer comprises, by weight, 10-20 parts of PPC diol, 60-80 parts of PPC, and 10-20 parts of inorganic powder; The support layer comprises, by weight, 10-20 parts PPC, 78-89 parts PBAT, 0.5-1.5 parts compatibilizer and 0.5-1 part opening agent.

2. The biodegradable wrapping film according to claim 1, characterized in that, The PPC diol has a number-average molecular weight of 1800–2000 g / mol, a molecular weight distribution of 1.2–1.6, a polycarbonate content of 30–50%, and a viscosity of 40–60 Pa·s at 22°C. The PPC has a number-average molecular weight of 100–150 kg / mol, a molecular weight distribution of 2.2–3, and a melt index of 0.3–1.5 g / 10 min. The PBAT has a number-average molecular weight of 60–80 kg / mol, a molecular weight distribution of 2.2–3, and a melt index of 3–5 g / 10 min.

3. The biodegradable wrapping film according to claim 1, characterized in that, The compatibilizer is a terpolymer of carbon dioxide, propylene oxide and a functional monomer, wherein the functional monomer is selected from allyl glycidyl ether or glycidyl methacrylate. The inorganic powder is calcium carbonate and / or talc. The opening agent is erucamide and / or oleamide.

4. The biodegradable wrapping film according to claim 1, characterized in that, The mass ratio of the self-adhesive layer to the support layer is 1:(1~1.5).

5. The biodegradable wrapping film according to claim 1, characterized in that, The thickness of the biodegradable wrapping film is 50–60 μm.

6. A method for preparing a biodegradable wrapping film as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1: After mixing PPC diol with inorganic powder evenly, the resulting mixture is then mixed evenly with PPC. The resulting product is then melt-granulated using a twin-screw extruder to obtain the self-adhesive layer material. PPC, PBAT, compatibilizer, and opening agent are mixed evenly, and the resulting product is then melt-granulated using a twin-screw extruder to obtain the support layer material. S2: Add the self-adhesive layer material and the support layer material to the conveying screw of the double-layer casting machine to cast and prepare a biodegradable wrapping film.

7. The preparation method according to claim 6, characterized in that, The specific mixing of PPC diol and inorganic powder is as follows: first, PPC diol and inorganic powder are stirred at 50-70 r / min for 1-5 min, and then stirred at 550-600 r / min for 1-5 min.

8. The preparation method according to claim 6, characterized in that, During the process of obtaining the self-adhesive layer material, the temperature of the twin-screw melt granulation is 120-150℃. During the process of obtaining the support layer material, the temperature of the twin-screw melt granulation is 140-165℃.

9. The preparation method according to claim 6, characterized in that, In step S2, the inner screw temperature of the double-layer casting machine is 140-155℃, the outer screw temperature is 140-165℃, and the die head temperature is 170-175℃.

10. A packaging film, characterized in that, The composition comprises the biodegradable stretch film according to any one of claims 1 to 5 or the biodegradable stretch film prepared by the preparation method according to any one of claims 6 to 9.

Images