Full-biodegradable composite film as well as preparation method and application thereof

Abstract

The invention relates to the field of biodegradation, and discloses a full-biodegradable composite film as well as a preparation method and application thereof. The composite film comprises a barrier layer, a protective layer and a bonding layer, the protective layer is arranged on the surface layer of the composite film, and the barrier layer and the protective layer are bonded through the bonding layer; matrix resin B of the bonding layer is selected from degradable resin grafted polar monomers and / or degradable resin grafted monomers containing groups capable of reacting with hydroxyl; the matrix resin C of the barrier layer at least contains polyglycolic acid with multimodal molecular weight distribution. The composite film provided by the invention has excellent barrier property and biodegradability, and also has good interlayer peel strength and heat sealing strength.

Description

Technical Field

[0001] The present invention relates to the technical field of biodegradation, and in particular to a fully biodegradable composite film and a preparation method and application thereof. Background Art

[0002] The market for barrier packaging films is enormous, but the vast majority currently suffer from poor biodegradability, making rapid and complete degradation difficult, thus causing environmental pollution. The few biodegradable barrier films that do exist are often produced as blends, making it difficult for the barrier material to form a continuous phase. Consequently, their barrier properties are insufficient to meet the demands of high-barrier applications.

[0003] CN102007001B (China National Offshore Oil Corporation, September 13, 2009) discloses a biodegradable composite oxygen barrier film and its application. The barrier layer of the invention is polycarbonate 1,2-propylene glycol (i.e., propylene carbonate, PPC) and nano-montmorillonite-modified polycarbonate 1,2-propylene glycol, and its oxygen and water vapor permeability are as low as 17.8 cm 3 / (m 2 ·day·atm) and 135g / (m 2 · 24h), the total thickness of the composite film is 70μm. The barrier properties of this invention, especially water barrier properties, are still not excellent enough to meet the application fields of high barrier properties.

[0004] CN111959080A (Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, August 24, 2020) and CN112874099A (Dongguan Pukai Plastic Technology Co., Ltd., December 31, 2020) disclose a biodegradable multilayer composite barrier film and its preparation method, respectively. The barrier layers in both inventions are polyvinyl alcohol (PVA), whose backbone is a polyolefin, which has poor biodegradability and requires stringent biodegradation conditions.

[0005] However, PGA itself also has issues with easy hydrolysis and low melt strength, resulting in poor blow molding processability, making it difficult to effectively utilize its barrier properties. Therefore, in practical applications, a gas resin with a certain degree of water barrier properties is required as a protective layer to delay the hydrolysis of the PGA barrier layer and extend its shelf life and service life.

[0006] CN108377821B (Zhejiang University, March 24, 2020) discloses a biodegradable barrier mulch film. The barrier layer of this mulch film is a PGA blend, not pure PGA. PGA does not form a homogeneous continuous phase, resulting in poor oxygen and water barrier properties. Consequently, the resulting multi-layer co-extruded biaxially stretched film does not meet the requirements for high barrier properties.

[0007] In addition, PGA has poor compatibility with other common biodegradable materials, so an adhesive layer is required to improve the adhesion between the protective layer and the PGA barrier layer.

[0008] CN113211920A (Hunan Aerospace Magnetism and Electricity Co., Ltd., 2021.05.27) discloses a multi-layer co-extruded fully degradable high-barrier packaging film and its preparation method. First of all, the outer protective layer and the inner heat-sealing layer of the invention have not been modified by chain extension, and cannot have sufficient melt strength at the processing temperature of PGA (about 230°C), and the film blowing property is poor. Secondly, the PGA used in its PGA barrier layer has not been modified in any way, and usually has the problem of low melt strength, which also leads to poor film blowing properties. At the same time, the adhesive layer of the invention selects a blend of polylactic acid and a multi-active functional group compatibilizer. The multi-active functional group compatibilizer itself will be consumed and lost by the polylactic acid in the adhesive layer, and it is difficult to complete the compatibilization reaction in a short time of melt compounding of the multi-layer film, so the bonding effect of its adhesive layer is general.

[0009] CN116512721A (China Shenhua Coal to Oil Chemical Co., Ltd., 2023.05.19) discloses a degradable multi-layer high-barrier film, its preparation method and application. Its barrier layer is pure PGA, but the outer layer and adhesive layer are both PBAT / PGA blends. PGA itself is easily hydrolyzed, and usually requires an outer layer with certain water-blocking properties to protect it. The outer layer of the multi-layer film obtained by this invention itself contains more PGA, the overall hydrolysis rate is faster, the lifespan is shorter, and the effect of a simple PGA blend as an adhesive layer is also average. In addition, since the invention adopts a casting molding method rather than blow molding, the melt strength requirements of the PGA used in the inner layer are not high, and blow molding has high production efficiency, low equipment investment and low material loss, which are incomparable to the casting process. Summary of the Invention

[0010] The present invention aims to overcome the problems of existing high-barrier packaging films, such as poor biodegradability, low melt strength, poor heat sealability, and easy hydrolysis of PGA, which make it difficult to directly meet the application requirements of barrier materials. Furthermore, the poor compatibility of PGA with other biodegradable plastics leads to poor interlayer adhesion during multilayer composites. The present invention provides a fully biodegradable composite film, its preparation method, and its application. This composite film offers advantages such as a long shelf life, high gas barrier properties, and biodegradability.

[0011] In order to achieve the above-mentioned objectives, the first aspect of the present invention provides a fully biodegradable composite film, comprising a barrier layer, a protective layer and an adhesive layer, wherein the surface layer of the composite film is a protective layer, and the barrier layer and the protective layer are bonded to each other through an adhesive layer; the matrix resin B of the adhesive layer is selected from a degradable resin grafted with a polar monomer and / or a degradable resin grafted with a monomer containing a group that can react with a hydroxyl group; the matrix resin C of the barrier layer contains at least polyglycolic acid with a multimodal molecular weight distribution.

[0012] A second aspect of the present invention provides a method for preparing the fully biodegradable composite film of the present invention, which comprises: melting, compressing, and extruding a protective layer material, an adhesive layer material containing a matrix resin B, and a barrier layer material containing a matrix resin C, respectively, and then separately forming a barrier layer, a protective layer, and an adhesive layer through film-forming, and then hot pressing; or melting and compressing the protective layer material, the adhesive layer material containing a matrix resin B, and the barrier layer material containing a matrix resin C, respectively, and then co-extruding and distributing them to form a film.

[0013] The third aspect of the present invention provides applications of the fully biodegradable composite film of the present invention in food packaging bags, agricultural films, medical packaging, and the electronics field.

[0014] Compared with the prior art, the present invention has at least the following advantages:

[0015] (1) The barrier layer of the present invention uses a multimodal molecular weight distribution polyglycolic acid, which has both gas barrier properties and biodegradability. Its oxygen permeability coefficient and water vapor permeability coefficient are lower than those of common barrier materials such as ethylene-vinyl alcohol copolymer (EVOH), polyvinylidene chloride (PVDC), polyethylene terephthalate (PET) and polyamide (PA), and its barrier properties are less affected by ambient temperature.

[0016] (2) The polyglycolic acid with multimodal molecular weight distribution used in the present invention does not require any post-modification step and can be well drawn to obtain qualified products. It can be directly blown with protective layer materials and adhesive layer materials to obtain composite films. Compared with other film preparation methods, this blown film method has simple equipment, low investment, rapid results, and is more likely to produce wide-width films.

[0017] (3) The multimodal molecular weight distribution polyglycolic acid of the present invention has better performance than films made of other barrier materials or films made of conventional polyglycolic acid and polyglycolic acid blends;

[0018] (4) The barrier layer, protective layer and adhesive layer in this application all have good biodegradability, so the entire multilayer film also has good biodegradability, which complies with the degradation requirements for biodegradable plastics and products in GB / T 41010-2021 "Degradation Performance and Labeling Requirements for Biodegradable Plastics and Products".

[0019] (5) The composite film of the present invention can be compounded with multimodal molecular weight distribution polyglycolic acid with high barrier properties and other biodegradable polyesters by multi-layer co-extrusion, thereby obtaining a fully biodegradable composite film with high barrier properties and a longer life than that of PGA single-layer film. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1is a GPC curve diagram of the polyglycolic acid particles in Example 1, Example 4, and Comparative Example 2;

[0021] Figure 2 This is a flow chart of preparing a composite film in a multi-layer co-extrusion blown film preparation device with a uniaxial stretching device;

[0022] Figure 3 This is a flow chart of preparing a composite film in a multi-layer co-extrusion cast film preparation device with a uniaxial stretching device;

[0023] Figure 4 Schematic diagram of the structure of the fully biodegradable composite membrane in Example 1.

[0024] Description of Reference Numerals

[0025] 10a, 10b, 10c: Hoppers 20a, 20b, 20c: Single-screw extruders

[0026] 30a, 30b, 30c: melt pumps 40a: feed pipe

[0027] 40b: Coextrusion distributor 50a: Film blowing die

[0028] 50b: air ring 50c: casting die

[0029] 60: Herringbone splint 70a: Clamp roller

[0030] 80: Unidirectional stretching device 90: Winding roller

[0031] 01a: Membrane vesicle 01b: Precursor membrane

[0032] 01c: Film after stretching DETAILED DESCRIPTION

[0033] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0034] The first aspect of the present invention provides a fully biodegradable composite film, comprising a barrier layer, a protective layer and an adhesive layer. The surface layer of the composite film is a protective layer, and the barrier layer and the protective layer are bonded to each other via an adhesive layer. The matrix resin B of the adhesive layer is selected from a degradable resin grafted with a polar monomer and / or a degradable resin grafted with a monomer containing a group that can react with a hydroxyl group. The matrix resin C of the barrier layer contains at least polyglycolic acid with a multimodal molecular weight distribution.

[0035] The matrix resin B of the adhesive layer in the present invention is selected from a degradable resin grafted with a polar monomer and / or a degradable resin grafted with a monomer containing a group reactive with a hydroxyl group, and the matrix resin C of the barrier layer contains at least polyglycolic acid with a multimodal molecular weight distribution. The fully biodegradable composite film not only has excellent barrier properties and biodegradability, but also has good interlayer peel strength and heat sealing strength.

[0036] In the present invention, the barrier layer, the protective layer and the adhesive layer are all prepared from their respective corresponding base resins according to a process capable of obtaining corresponding film layers.

[0037] In the present invention, the terms "degradable" and "biodegradable" refer to biodegradable products well known in the art, that is, the mass proportion of biodegradable components in the composite film is not less than 90%, preferably not less than 98%; referring to the conditions specified in GB / T41010-2021, the relative biodegradation rate of the composite film within 6 months is not less than 90%, and the absolute biodegradation rate of a single organic component greater than or equal to 1% is greater than or equal to 60%.

[0038] According to the present invention, the surface layer of the composite film refers to the outermost layer of the composite film (i.e., the upper surface layer and the lower surface layer of the composite film), that is, the outermost layer of the composite film is the protective layer, the barrier layer is the film layer that has a barrier function, the protective layer is the film layer that protects the barrier layer and prevents the barrier layer function from decreasing, the adhesive layer is the film layer that has the function of enhancing the adhesion between the protective layer and the barrier layer, and the adhesive layer is located between the adjacent barrier layer and the protective layer to enhance the adhesion between the protective layer and the barrier layer. For example, the fully biodegradable composite film is arranged from the inner surface to the outer surface in sequence as a protective layer, an adhesive layer, a barrier layer, an adhesive layer, a protective layer, or a protective layer, an adhesive layer, a barrier layer, a protective layer, an adhesive layer, a barrier layer, an adhesive layer, a protective layer, etc.

[0039] According to the present invention, in some embodiments, the number of barrier layers is at least 1, such as 1, 2 or 3 layers. In the present invention, the types of the barrier layers may be the same or different, and the thicknesses of the barrier layers may be the same or different. Preferably, the thickness of each single barrier layer is independently 1 to 50 μm, preferably 5 to 40 μm.

[0040] According to the present invention, in some embodiments, the number of layers of the protective layer is at least 2, such as 2 layers, 3 layers, 5 layers, 7 layers, 9 layers, preferably 2 to 7 layers. The types of the protective layers in the present invention may be the same or different, and the thicknesses of the protective layers may be the same or different. Preferably, the thicknesses of the single protective layers are independently 3 to 80 μm, preferably 20 to 60 μm.

[0041] According to the present invention, it can be understood that the adhesive layer is a film layer used to enhance the bonding function between the protective layer and the barrier layer. The specific number of adhesive layers is determined according to the specific number of protective layers and barrier layers. The thickness of each adhesive layer may be the same or different. Preferably, the thickness of each single adhesive layer is independently 0.5 to 30 μm, preferably 3 to 20 μm.

[0042] According to the present invention, in some embodiments, the total thickness of the composite film is 8 to 270 μm, preferably 15 to 200 μm.

[0043] The number of layers and thickness of each layer of the film of the present invention can be measured and characterized by photographing the cross section of the multilayer film using an optical microscope or a scanning electron microscope.

[0044] According to the present invention, in some embodiments, the melt strength of the multimodal molecular weight distribution polyglycolic acid at 235°C is not less than 4 cN, preferably not less than 8 cN, such as 8 cN, 10 cN, 12 cN, 15 cN, 18 cN, 20 cN, 22 cN, or any range consisting of two of these values. Using these embodiments, the barrier layer can be better formed by film blowing, resulting in a composite film with improved barrier properties.

[0045] The melt strength of the multimodal molecular weight distribution polyglycolic acid described herein can be measured using methods known in the art, such as, but not limited to, the following method: The test was conducted on a Rosand RH7 high-pressure capillary rheometer from Malvern Panalytical, China. The model number was Haul Off (diameter: 2.0 mm, length: 20 mm), the barrel push rod downward speed was 15 mm / min, the test temperature was 235°C, the initial draw speed was 3 mm / min, the final draw speed was 50 mm / min, and the acceleration time was 3 minutes.

[0046] According to the present invention, in some embodiments, the weight average molecular weight of the multimodal molecular weight distribution polyglycolic acid is 200,000 to 1.5 million g / mol, for example, it can be 200,000 g / mol, 250,000 g / mol, 300,000 g / mol, 350,000 g / mol, 400,000 g / mol, 450,000 g / mol, 500,000 g / mol, 800,000 g / mol, 1 million g / mol, 1.5 million g / mol, and an interval consisting of any two of the above values, preferably 250,000 to 500,000 g / mol.

[0047] According to the present invention, in some embodiments, the molecular weight distribution index of the multimodal molecular weight distribution polyglycolic acid is 1.5 to 20.0, for example, it can be 1.5, 1.8, 2.0, 2.1, 2.0, 3.5, 4.0, 6.0, 7.0, 9.0, 10.0, 12.0, 14.0, 16.0, 20.0, and the interval consisting of any two of the above values, preferably 2.0 to 3.5.

[0048] According to the present invention, in some embodiments, the melt flow rate (MFR) of the multimodal molecular weight distribution polyglycolic acid at 230°C / 2.16kg is not higher than 20g / 10min, preferably 0.01-20g / 10min, such as 0.01g / 10min, 0.1g / 10min, 0.5g / 10min, 1g / 10min, 2g / 10min, 3g / 10min, 4g / 10min, 5g / 10min, 6g / 10min, 7g / 10min, 8g / 10min, 9g / 10min, 10g / 10min, 13g / 10min, 15g / 10min, 20g / 10min, and intervals consisting of any two of the above values, more preferably 0.5-10g / 10min. The composite film prepared under the aforementioned embodiment has better comprehensive properties.

[0049] The melt flow rate in the present invention can be measured using methods known in the art, such as, but not limited to, the following method: The test is conducted on a CEAST MF20 melt flow rate tester (Instron, USA). The test temperature is 230°C, the load weight is 2.16 kg, and the preheating time is 4 minutes.

[0050] According to the present invention, in some embodiments, the multimodal molecular weight distribution polyglycolic acid is a homogeneous continuous phase. Using these embodiments, the composite film exhibits superior barrier properties, interlayer peel strength, and heat seal strength, and its barrier performance is far superior to films made of other barrier materials or films of polyglycolic acid blends in which conventional polyglycolic acid is a discontinuous phase. The composite film of the aforementioned embodiment exhibits superior barrier properties.

[0051] The homogeneous continuous phase in the present invention means that the volume proportion of its main phase is not less than 95%, preferably not less than 99%, and its phase structure is continuous. The phase structure can be measured by methods well known in the art, for example: after the sample is quenched at low temperature, its cross section is observed by scanning electron microscopy.

[0052] According to the present invention, in some embodiments, the multimodal molecular weight distribution polyglycolic acid contains 2 to 4 peaks, for example including but not limited to 2 or 3 peaks.

[0053] The number of molecular weight distribution peaks in the present invention can be detected by gel permeation chromatography (GPC).

[0054] According to the present invention, in some embodiments, the multimodal molecular weight distribution polyglycolic acid comprises a polyglycolic acid graft copolymer and a polyglycolic acid homopolymer. In such embodiments, the multimodal molecular weight distribution polyglycolic acid comprising two polyglycolic acid components with different chemical structures can better prepare composite films with excellent barrier properties, interlaminar peel strength, and heat seal strength.

[0055] According to the present invention, in some preferred embodiments, the weight average molecular weight of the polyglycolic acid graft copolymer is greater than the weight average molecular weight of the polyglycolic acid homopolymer. Using the above embodiment, the composite film has better barrier properties, interlayer peel strength and heat sealing strength.

[0056] According to the present invention, in some preferred embodiments, the weight-average molecular weight of the polyglycolic acid graft copolymer is 500,000 to 10 million g / mol, for example, 500,000 g / mol, 1 million g / mol, 1.5 million g / mol, 2 million g / mol, 3 million g / mol, 4 million g / mol, 5 million g / mol, 6 million g / mol, 10 million g / mol, and an interval consisting of any two of the above values, preferably 1 million to 6 million g / mol.

[0057] According to the present invention, in some preferred embodiments, the weight average molecular weight of the polyglycolic acid homopolymer is 50,000 to 350,000 g / mol, for example, 50,000 g / mol, 100,000 g / mol, 120,000 g / mol, 140,000 g / mol, 160,000 g / mol, 180,000 g / mol, 200,000 g / mol, 300,000 g / mol, 350,000 g / mol, preferably 100,000 to 200,000 g / mol.

[0058] According to the present invention, in some preferred embodiments, the molecular weight polydispersity index of the polyglycolic acid graft copolymer is 1.01 to 3.0, preferably 1.05 to 1.5.

[0059] According to the present invention, in some preferred embodiments, the molecular weight polydispersity index of the polyglycolic acid homopolymer is 1 to 3, preferably 1.4 to 2.9.

[0060] According to the present invention, in some preferred embodiments, the mass ratio of the polyglycolic acid graft copolymer to the polyglycolic acid homopolymer is 2:98 to 60:40, preferably 3:97 to 10:90.

[0061] In the present invention, parameters such as the weight-average molecular weight of the multimodal molecular weight distribution polyglycolic acid, the molecular weight distribution index of the multimodal molecular weight distribution polyglycolic acid, the number of molecular weight distribution peaks of the multimodal molecular weight distribution polyglycolic acid, the weight-average molecular weight of the polyglycolic acid graft copolymer, the molecular weight polydispersity index of the polyglycolic acid graft copolymer, the molecular weight polydispersity index of the polyglycolic acid homopolymer, the mass fraction of the polyglycolic acid graft copolymer, and the mass fraction of the polyglycolic acid homopolymer can be measured by gel permeation chromatography (GPC). Specific detection methods can employ conventional detection parameters in the art. For example, but not limited to, the following method is employed: the test instrument is a PL-GPC50 gel permeation chromatograph from Angilent, USA, and the processing software is GPC offline. During the test, the mobile phase is hexafluoroisopropanol containing 5 mmol / L sodium trifluoroacetate, the flow rate is 1 mL / min, the column temperature is 40°C, the injection volume is 100 μL, the standard sample is PMMA, and the sample concentration is 1 mg / mL. The specific values of the above parameters are obtained using analytical methods known in the art.

[0062] According to the present invention, in some preferred embodiments, the backbone of the polyglycolic acid graft copolymer comprises ethylene-vinyl alcohol copolymer segments derived from ethylene-vinyl alcohol copolymer and / or polyvinyl alcohol segments derived from polyvinyl alcohol, and the side chains comprise grafted segments derived from glycolic acid monomer derivatives, glycolic acid oligomers, or glycolic acid polymers. The composite films of these embodiments exhibit superior heat seal strength, interlayer peel strength, and barrier properties.

[0063] According to the present invention, the backbone structure of the polyglycolic acid graft copolymer of the present invention can be random, block, or alternating. The specific form of the backbone structure depends on the raw materials and / or polymerization method used to provide the structural units, but is generally random. In an exemplary embodiment, the structure of the glycolic acid graft copolymer is shown in structural formula (I):

[0064]

[0065] In the structural formula (I), x and m are positive integers, and y1, y2 and z are natural numbers.

[0066] According to the present invention, in some more preferred embodiments, in structural formula (I), the sum of x, y1, y2 and z is not less than 50, for example, 50, 100, 150, 200, 300, 500, 1000, 1500, 1700, 2000, 2500, 3000, 4000, 5000, 6000, and the interval consisting of any two of the above values, preferably 50-6000, more preferably 200-2500.

[0067] According to the present invention, in some more preferred embodiments, in structural formula (I), m is not less than 50, for example, 50, 80, 100, 150, 200, 250, 300, 400, 500, 600, 800, 1000, and an interval consisting of any two of the above values, preferably 50 to 1000.

[0068] According to the present invention, the sum of x+y1+y2+z is the degree of polymerization of the ethylene-vinyl alcohol copolymer and / or polyvinyl alcohol, which can be calculated by providing the number average molecular weight of the raw material ethylene-vinyl alcohol copolymer and / or polyvinyl alcohol of the corresponding segment on the main chain, and z is related to the ethylene content in the ethylene-vinyl alcohol copolymer; and the ratio of x to y2 can be calculated by the integrated area of the corresponding peak of the nuclear magnetic hydrogen spectrum.

[0069] The parameters of the ethylene-vinyl alcohol copolymer in the present invention are known parameters of the raw materials before leaving the factory, and can also be obtained by various detection methods in the art such as nuclear magnetic resonance and near infrared.

[0070] According to the present invention, in some more preferred embodiments, the proportion of z in x+y1+y2+z is 0% to 50%, for example, 0%, 1%, 5%, 10%, 15%, 20%, 30%, 40%, 50%, and the interval consisting of any two of the above values.

[0071] According to the present invention, when z in structural formula (I) is 0, the main chain of the polyglycolic acid graft copolymer contains a polyvinyl alcohol segment. Preferably, when z in structural formula (I) is 0, the ratio of y1 to x+y1+y2 is 0.1% to 32%.

[0072] When z in the structural formula (I) of the present invention is not 0, the main chain of the polyglycolic acid graft copolymer contains an ethylene-vinyl alcohol copolymer segment. Preferably, in the structural formula (I), the proportion of z in the sum of x+y1+y2+z is 1% to 50%, preferably 20% to 45%, and the proportion of y1 in the sum of x+y1+y2 is preferably 0.1% to 6%.

[0073] According to the present invention, the m value in formula (I) has a wide range of selection. In some preferred embodiments, m is not less than 50, preferably 50 to 1000. According to the examples below, it is calculated that the m value of the obtained polymers is greater than 50.

[0074] According to the present invention, the value of m can be measured and calculated using conventional methods in the art, for example, m = (number average molecular weight of the polyglycolic acid graft copolymer - number average molecular weight of the ethylene-vinyl alcohol copolymer and / or polyvinyl alcohol) / (x * molecular weight of the PGA repeating unit). To directly obtain the high-molecular-weight PGA graft copolymer structure described in the present invention, it can be fully hydrolyzed, the initiator collected, its structure analyzed, and then tested using the above method. According to the examples described below, the values of m in the resulting polymers were calculated to be greater than 50.

[0075] The structure of the polyglycolic acid homopolymer is shown in structural formula (II):

[0076]

[0077] In the structural formula (II), n1, n2, ..., n i are all natural numbers; M1, M2, ..., M i Each is an imino group, a secondary amino group or an ether bond; i is an integer not less than 1; R is H, an alkane group or an aromatic hydrocarbon group with a molecular weight of 14 to 1000 g / mol.

[0078] According to the present invention, in some preferred embodiments, the range of i in structural formula (II) is 1 to 20, for example, 1, 2, 3, 4, 5, 6, 8, 10, 15, 18, 20, preferably 1 to 6.

[0079] According to the present invention, in some preferred embodiments, when i is greater than 1, R is an alkane group or an aromatic hydrocarbon group with a molecular weight of 14 to 1000 g / mol; when i=1, R is H, an alkane group or an aromatic hydrocarbon group with a molecular weight of 14 to 1000 g / mol.

[0080] According to the present invention, in some preferred embodiments, n1, n2, ..., n i The sum of is not less than 50, preferably 50 to 5000, for example, 50, 100, 500, 1500, 2000, 3000, 4000, 5000, and any interval consisting of any two of the above values.

[0081] In the structural formula (II) of the present invention, n1, n2, ..., n i The sum of the values can be calculated by dividing the number average molecular weight of the polyglycolic acid homopolymer in the GPC results by the molecular weight of the repeating units in the polyglycolic acid homopolymer. According to the embodiments of the present invention, it is calculated that n1, n2, ..., n i The sum of the values is greater than 100.

[0082] The multimodal molecular weight distribution polyglycolic acid in the present invention is preferably a homogeneous continuous phase. The content of each segment in the multimodal molecular weight distribution polyglycolic acid is analyzed as a whole. Preferably, relative to 100 parts by mass of the polyglycolic acid segment, The multimodal molecular weight distribution polyglycolic acid contains 0.001 to 10 parts by mass of ethylene-vinyl alcohol copolymer segments. Contains 0.001 to 10 parts by mass

[0083] According to the present invention, in some preferred embodiments, relative to 100 parts by mass of polyglycolic acid segments The multimodal molecular weight distribution polyglycolic acid contains 0.01 to 1 parts by mass of ethylene-vinyl alcohol copolymer segments. Contains 0.01 to 1 parts by mass The mass content of each of the above segments can be detected by methods known in the art, or can be calculated based on the amount of raw materials added during the preparation process.

[0084] The multimodal molecular weight distribution polyglycolic acid of the present invention can be prepared by copolymerization methods in the art. According to the present invention, the structural selection of the multimodal molecular weight distribution polyglycolic acid can provide monomers, initiators and other raw materials of the corresponding structural units and the feed ratio of each raw material. In some preferred embodiments, the preparation method of the multimodal molecular weight distribution polyglycolic acid comprises: polymerizing the polyglycolic acid segments The present invention relates to a method for melt polymerization of monomers, ethylene-vinyl alcohol copolymer (and / or polyvinyl alcohol) and optionally a small molecule co-initiator in the presence of a catalyst and optionally an antioxidant.

[0085] According to the present invention, polyglycolic acid segments can be provided The monomers are suitable for preparing the multimodal molecular weight distribution polyglycolic acid of the present invention. In some preferred embodiments, the polyglycolic acid segments can be provided. The monomer includes at least one of methyl glycolate, glycolic acid and glycolide, preferably glycolide.

[0086] According to the present invention, in some preferred embodiments, the content of ethylene segments in the ethylene-vinyl alcohol copolymer is 25 to 50 mol%, for example, it can be 25 mol%, 35 mol%, 45 mol%, 50 mol%, and an interval consisting of any two of the above values.

[0087] According to the present invention, in some preferred embodiments, the degree of polymerization of the ethylene-vinyl alcohol copolymer is 50 to 6000, preferably 300 to 2000, for example, 300, 500, 1000, 1500, 2000, and intervals consisting of any two of the above values.

[0088] According to the present invention, in some preferred embodiments, the alcoholysis degree of the polyvinyl alcohol is 68% to 100%, for example, 68%, 75%, 85%, 95%, 99%, 100%, and intervals consisting of any two of the above values.

[0089] According to the present invention, in some preferred embodiments, the melt flow rate of the polyvinyl alcohol at 190° C. / 2.16 kg is 0.1 to 50 g / 10 min.

[0090] According to the present invention, the small molecule co-initiator is selected from a compound that can provide an imino group, a secondary amino group or an ether bond. Preferably, the small molecule co-initiator is a small molecule substance containing a hydroxyl group or an amino group with a boiling point greater than 160°C. Preferably, the molecular weight of the small molecule co-initiator is not greater than 1000 g / mol; preferably 60 to 300 g / mol. Examples of small molecule initiators include ethylene glycol, butanediol, glycerol, serinol, leucinol, pentaerythritol, sorbitol, xylitol, amino acids, phenol, hydroquinone, resorcinol, benzyl alcohol, aniline, benzylamine, p-phenylenediamine, m-phenylenediamine, hexamethylenediamine, dodecanediamine, etc.

[0091] The catalyst for melt polymerization of the present invention can be a conventional melt polymerization initiator in the art, and the present invention has no special limitation thereto. Sn salt, specifically stannous octoate, is used as the catalyst in the present invention, but the present invention is not limited thereto.

[0092] When preparing polyglycolic acid with a multimodal molecular weight distribution according to the present invention, the amount of each raw material can be selected according to the number of each structural unit of the polyglycolic acid with a multimodal molecular weight distribution. Preferably, the amount of the ethylene-vinyl alcohol copolymer (and / or polyvinyl alcohol) is 0.001 to 10 parts by mass, preferably 0.01 to 1 part, relative to 100 parts of monomers; preferably, the amount of the small molecule co-initiator is 0.001 to 10 parts by mass, preferably 0.01 to 1 part, relative to 100 parts of monomers; preferably, the amount of the catalyst is 0.005 to 1 part by mass, preferably 0.01 to 0.2 parts by mass, relative to 100 parts of monomers; preferably, the amount of the antioxidant is 0 to 2 parts by mass, preferably 0.01 to 1 part (phr), relative to 100 parts of monomers.

[0093] When preparing polyglycolic acid with a multimodal molecular weight distribution in the present invention, the melt polymerization conditions can be selected from conditions that are conducive to the occurrence of the polymerization reaction. The preferred melt polymerization temperature is 160 to 250° C., preferably 200 to 240° C.; the preferred melt polymerization time is 0.5 to 60 min, preferably 1 to 10 min.

[0094] The melt polymerization in the present invention can be carried out in a conventional melt mixing device in the art, such as a kettle reactor, a tubular reactor, an internal mixer, a Farrel continuous mixer, a Banbury mixer, a single-screw extruder, a multi-screw extruder and a reciprocating single-screw extruder. The above melt mixing devices can be used alone or in combination in series of the same or different types. In the present invention, a twin-screw extruder is preferably used for melt polymerization.

[0095] According to the present invention, in some preferred embodiments, the melt polymerization in the present invention is carried out in a twin-screw extruder, preferably with an aspect ratio of 30 to 80, preferably 40 to 70; preferably with a total feed rate of 10-20 kg / h, and preferably with a screw speed of 100-200 rpm.

[0096] The matrix resin B, matrix resin C, etc. in the present invention are only for distinction, so B, C, etc. are used for identification. In essence, they are still the corresponding resin matrices of the corresponding film layers.

[0097] According to the present invention, the adhesive layer is prepared from the corresponding adhesive layer containing the matrix resin B according to the preparation method of the film layer.

[0098] According to the present invention, in some preferred embodiments, the grafting rate of the base resin B is 0.1% to 5%.

[0099] The graft ratio in the present invention refers to the mass of the grafted side chains (monomers) in the graft copolymer / the mass of the graft copolymer×100%.

[0100] According to the present invention, the grafting rate can be detected by methods known in the art, for example, first purifying the grafted copolymer by dissolution-precipitation or the like, then obtaining the amount of grafted side chains (monomers) by quantitative analysis methods such as nuclear magnetic resonance and infrared, and finally calculating the grafting rate.

[0101] According to the present invention, in some more preferred embodiments, the base resin B includes poly(butylene terephthalate-co-adipate) grafted glycidyl methacrylate, poly(butylene terephthalate-co-adipate) grafted glycidyl acrylate, poly(butylene terephthalate-co-adipate) grafted methyl methacrylate, poly(butylene terephthalate-co-adipate) grafted hydroxyethyl methacrylate, poly(butylene terephthalate-co-adipate) grafted hydroxypropyl methacrylate, poly(butylene terephthalate-co-adipate) grafted hydroxyethyl acrylate, poly(butylene terephthalate-co-adipate) grafted dimethylaminoethyl methacrylate, poly(butylene terephthalate-co-adipate) grafted dodecafluoroheptyl methacrylate, poly(butylene terephthalate-co-adipate) grafted maleic anhydride, Polybutylene terephthalate-co-adipate grafted dibutyl maleate, Polybutylene terephthalate-co-adipate grafted dimethylmaleic anhydride, Polybutylene terephthalate-co-adipate grafted itaconic anhydride, Polybutylene terephthalate-co-adipate grafted acrylamide, Polybutylene terephthalate-co-adipate grafted acrylonitrile, Polybutylene terephthalate-co-adipate One or more blends of grafted N-ethylacrylamide, poly(butylene terephthalate-co-adipate) grafted p-styrenesulfonic acid, poly(butylene terephthalate-co-succinate) grafted maleic anhydride, poly(lactic acid) grafted maleic anhydride, poly(propylene carbonate) grafted maleic anhydride, poly(caprolactone) grafted maleic anhydride, starch grafted maleic anhydride, poly(hydroxyalkanoate) grafted maleic anhydride, and poly(glycolic acid) grafted maleic anhydride. The present invention lists one or more specific base resins B in the examples below, which should not be construed as limiting the present invention by those skilled in the art.

[0102] The degradable resin grafted polar monomer or the degradable resin grafted monomer containing a group reactive with hydroxyl in the present invention can be obtained commercially or homemade, and the preparation method can be a conventional polymer grafting method in the art. Preferably, the preparation method of the degradable resin grafted polar monomer or the degradable resin grafted monomer containing a group reactive with hydroxyl of the adhesive layer includes: in the presence of a free radical initiator, grafting polymerization of the degradable resin, the grafted monomer and a processing aid optionally containing an antioxidant.

[0103] According to the present invention, the degradable resin includes, but is not limited to, polybutylene terephthalate-co-adipate, polybutylene terephthalate-co-succinate, polylactic acid, polypropylene carbonate, polycaprolactone, starch, polyhydroxyalkanoate, and polyglycolic acid.

[0104] According to the present invention, the grafting monomer is a compound containing an unsaturated double bond and having a high polarity or containing a group that can react with a hydroxyl group, and the grafting monomer includes but is not limited to glycidyl methacrylate, glycidyl acrylate, maleic anhydride, itaconic anhydride, diethyl maleate, dibutyl maleate, methyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, dimethylaminoethyl methacrylate, dodecafluoroheptyl methacrylate, 4-penten-1-ol, 5-hexen-1-ol, undecenol, undecylenic acid, erucic acid, acrylamide, acrylonitrile, N-ethylacrylamide and p-styrenesulfonic acid.

[0105] According to the present invention, as long as the purpose of the present invention can be achieved, the type of the free radical initiator is not particularly limited. Initiators that can generate free radicals by heat in the art are all suitable for the system of the present invention, preferably azo compounds, organic peroxides, inorganic peroxides, including but not limited to azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, di-tert-butyl peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide isopropyl benzene, benzoyl peroxide, dibenzoyl peroxide, ditoluoyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, lauroyl peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, acetylcyclohexanesulfonyl peroxide, ammonium persulfate, and potassium persulfate.

[0106] In the present invention, when preparing a degradable resin grafted with a polar monomer or a degradable resin grafted with a group reactive with a hydroxyl group, the amount of the grafting monomer can be selected according to the required grafting rate of the degradable resin grafted with a polar monomer or the degradable resin grafted with a group reactive with a hydroxyl group. Preferably, the amount of the grafting monomer is 0.5 to 20 parts by mass relative to 100 parts of the degradable resin, for example, 0.5 parts, 2 parts, 3 parts, 5 parts, 7 parts, 10 parts, 15 parts, 20 parts, and preferably 3 to 10 parts.

[0107] According to the present invention, the amount of the free radical initiator used is sufficient to allow the graft polymerization to proceed smoothly. Preferably, the amount of the free radical initiator used is 0.1 to 2 parts by mass, preferably 0.15 to 0.25 parts by mass, relative to 100 parts by mass of the degradable resin.

[0108] According to the present invention, when preparing a degradable resin grafted with a polar monomer or a degradable resin grafted with a group reactive with a hydroxyl group, preferably a degradable polyester grafted with a polar group reactive with a hydroxyl group, a person skilled in the art may need to choose to add or not add components such as an antioxidant. Preferably, the amount of the antioxidant is 0 to 1 part, preferably 0.3 to 0.6 parts, relative to 100 parts of the degradable resin, by mass.

[0109] According to the present invention, the processing aids may also include dispersants, anti-hydrolysis agents, and the like.

[0110] According to the present invention, the graft polymerization temperature is preferably 120 to 210° C., preferably 120 to 180° C.; the graft polymerization time is preferably 0.5 to 10 min;

[0111] The graft polymerization in the present invention can be carried out in conventional reaction equipment in the art, such as in a twin-screw extruder, preferably with a feed rate of 1 to 5 kg / h, preferably 2 to 4 kg / h; preferably, a screw speed of 120 to 250 rpm, preferably 150 to 200 rpm.

[0112] According to the present invention, the protective layer is a film layer that protects the barrier layer and prevents the barrier layer from decreasing in function. In some preferred embodiments, the water vapor permeability coefficient of the protective layer is not greater than 20,000 g·μm / (m 2 ·day·atm). The composite film of the aforementioned embodiment has more excellent barrier properties.

[0113] According to the present invention, the protective layer is prepared by a protective layer material containing a corresponding base resin A according to a film preparation method. Preferably, the base resin A of the protective layer is the same as the degradable resin in the degradable resin grafted polar monomer / or the degradable resin grafted monomer containing a group reactive with a hydroxyl group.

[0114] According to the present invention, in some preferred embodiments, the base resin A of the protective layer is selected from polyester biodegradable resins.

[0115] The polyester biodegradable resin in the present invention can be any one or more of those known in the art. Preferably, the polyester biodegradable resin is selected from any one or more of poly(butylene terephthalate-co-adipate), poly(butylene terephthalate-co-succinate), poly(ethylene terephthalate-co-adipate), poly(ethylene terephthalate-co-succinate), poly(butylene succinate), poly(butylene adipate), polylactic acid, poly(propylene carbonate), poly(hydroxyalkanoate), and thermoplastic starch. When the base resin of the protective layer in the present invention uses multiple different types of polyester biodegradable resins, it can be referred to as a blend.

[0116] In the present invention, polybutylene terephthalate-co-adipate refers to a copolymer of butylene adipate and butylene terephthalate; polybutylene terephthalate-co-succinate refers to a copolymer of butylene succinate and butylene terephthalate; poly(ethylene terephthalate-co-adipate) refers to a copolymer of ethylene adipate and ethylene terephthalate; poly(ethylene terephthalate-co-succinate) refers to a copolymer of ethylene succinate and ethylene terephthalate.

[0117] According to the present invention, in some preferred embodiments, the matrix resin A contains at least polybutylene terephthalate-co-adipate and / or polybutylene terephthalate-co-succinate.

[0118] According to the present invention, in some preferred embodiments, the base resin A is polybutylene terephthalate-co-adipate.

[0119] According to the present invention, in some preferred embodiments, the base resin A is a binary blend of polybutylene terephthalate-co-adipate and polylactic acid, and the ratio of polybutylene terephthalate-co-adipate to polylactic acid is not particularly limited. Preferably, the mass ratio is (60-80): (20-40), for example, 80:20, 60:40, etc.

[0120] According to the present invention, in some preferred embodiments, the matrix resin A is a binary blend of polybutylene terephthalate-co-adipate and polypropylene carbonate, and the mass ratio of polybutylene terephthalate-co-adipate and polypropylene carbonate is not particularly limited. Preferably, the mass ratio is (60-80): (20-40), for example, 80:20, 60:40, etc.

[0121] According to the present invention, in some preferred embodiments, the matrix resin A is a binary blend of polybutylene succinate and polylactic acid. The mass ratio of polybutylene succinate to polylactic acid is not particularly limited, and preferably the mass ratio is (60-80): (20-40), for example, 80:20, 60:40, etc.

[0122] According to the present invention, in some preferred embodiments, the polyester biodegradable resin is a ternary blend of polybutylene terephthalate-co-adipate, polypropylene carbonate and polylactic acid.

[0123] According to the present invention, the base resin A of the protective layer serves as the raw material composition of the protective layer. When the base resin A is used to prepare the corresponding protective layer, a chain extender may be added to the raw material composition of the protective layer as needed to improve the mechanical properties and process properties of the base resin A. Preferably, the amount of the chain extender added is 0.1 to 1 part by mass (phr) based on 100 parts by mass of the base resin. For example, at least one of an epoxy chain extender, an isocyanate chain extender, an anhydride chain extender, and an amine chain extender may be added, such as a polycyclic polymer (such as polymethyl methacrylate / glycidyl methacrylate copolymer, JONCRYL ADR4468, chain extender ADR 4370, etc.), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), and lysine diisocyanate (LDI).

[0124] According to the present invention, in order to increase the openness of the film layer, inorganic fillers can be added to the raw material composition of the protective layer as needed. The inorganic fillers can mainly act as inorganic opening agents, and can also improve the water barrier properties. Preferably, the amount of inorganic fillers added is 0 to 10 parts by mass based on 100 parts by mass of the base resin A, for example, 1 part by mass, 2 parts by mass, 4 parts by mass, 5 parts by mass, 6 parts by mass, 7 parts by mass, 8 parts by mass or 10 parts by mass, wherein the inorganic fillers include but are not limited to silica, talc, calcium carbonate, calcium sulfate, diatomaceous earth, montmorillonite, kaolin, wollastonite, mica, and bentonite.

[0125] According to the present invention, an antioxidant may be added to the raw material composition of the protective layer as needed, preferably 0 to 1 part by mass of the antioxidant based on 100 parts by mass of the base resin A.

[0126] According to the present invention, the protective layer is located at the outermost layer. In order to increase the light aging resistance of the film layer, a light stabilizer can be added to the raw material composition of the protective layer as needed. Preferably, the amount of the light stabilizer added is 0 to 1 part by mass based on 100 parts by mass of the base resin A. The light stabilizer is selected from at least one of salicylates, benzoates, benzophenones, benzotriazoles, triazines, substituted acrylonitriles, oxamides, organic nickel complexes and hindered amine light stabilizers, including but not limited to di(2,2,6,6-tetramethyl-3-piperidinylamino)-isophthalamide, N-(2-ethoxyphenyl)-N'-(4-ethylphenyl)-oxalamide, N-(5-(1,1)dimethylethyl)-2-ethoxyphenyl)- N'-(2-ethylphenyl)ethanedimide, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol) succinate, poly{[6-[(1,1,3,3-tetramethylbutyl)amino]]-1,3,5-triazine-2,4-[(2,2,6,6,-tetramethyl-piperidinyl)imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]}, poly[(6-morpholinyl-1,3,5-triazine-2,4-yl)-((2,2,6,6-tetramethyl-4-piperidinyl)imino)hexane-((2,2,6,6-tetramethyl-4-piperidinyl)imino)].

[0127] According to the present invention, in order to increase the comprehensive properties of the film layer such as hydrolysis resistance, an anti-hydrolysis agent may be added to the raw material composition of the protective layer as needed. Preferably, the amount of the anti-hydrolysis agent added is 0 to 1 part by mass based on 100 parts by mass of the base resin A. The anti-hydrolysis agent includes monomeric carbodiimides, polymeric carbodiimides, isocyanates, oxazoline compounds, epoxy compounds and acid anhydride compounds, such as N,N'-di(2,6-diisopropylphenyl)carbodiimide and polycarbodiimide.

[0128] According to the present invention, in order to increase the stability during the preparation of the film layer, a dispersant may be added to the raw material composition of the protective layer as needed. Preferably, the amount of the dispersant added is 0 to 1 part by mass based on 100 parts by mass of the base resin A, for example, 0.1 part by mass, 0.2 part by mass, 0.5 part by mass, or 1 part by mass; the dispersant is selected from at least one of oleamide, erucamide, stearamide, natural paraffin, and ethylene bisstearamide (EBS).

[0129] According to the present invention, in order to increase the stability and other properties of the base resin A, an ester exchange inhibitor may be added to the raw material composition of the protective layer as needed. Preferably, the amount of the ester exchange inhibitor added is 0 to 1 part by mass based on 100 parts by mass of the base resin A. The ester exchange inhibitor includes but is not limited to sodium pyrophosphate, disodium dihydrogen pyrophosphate, sodium dihydrogen phosphate, zinc dihydrogen phosphate, alkyl phosphate, triphenyl phosphite, and calcium phosphate.

[0130] In the present invention, when forming the corresponding protective layer, the base resin A of the protective layer can be first melt-blended with other additives (such as chain extenders, inorganic fillers, dispersants, oxidants, etc.) to form the corresponding protective layer material (for example, the base resin A, chain extenders, inorganic fillers, dispersants, and oxidants are melt-extruded and granulated, the melting temperature can be 140-250° C., the melt extrusion granulation can be carried out in a screw extruder, the feeding rate can be 10-18 kg / h, and the screw speed can be 120-180 rpm), and then the protective layer material containing the base resin A is used to prepare the composite film.

[0131] The antioxidants used in the protective layer, adhesive layer, and barrier layer of the present invention can each be a conventional antioxidant in the art, and the present invention does not make any special limitation thereto. The antioxidants in the protective layer, adhesive layer, and barrier layer are each selected from hindered phenol antioxidants and / or phosphite antioxidants. Examples of hindered phenol antioxidants include antioxidant BHT, antioxidant TMBTB, antioxidant 2246, antioxidant 259, antioxidant 1010, antioxidant 1024, antioxidant 1098, antioxidant 1076, antioxidant 330, and the like; examples of phosphite antioxidants include antioxidant TBP, antioxidant TBNPA, antioxidant DPIOP, antioxidant BDIPP, antioxidant PDOP, antioxidant DPD, antioxidant 168, antioxidant 686, antioxidant 626, and the like.

[0132] In the present invention, the barrier layer containing multimodal molecular weight distribution polyglycolic acid, and the composite film obtained by compounding it with the protective layer and the adhesive layer has excellent heat sealing strength. In some preferred embodiments, the heat sealing strength of the composite film is not less than 3.0N / 15mm, for example, 3.0N / 15mm, 4.4N / 15mm, 6.3N / 15mm, 8.7N / 15mm, 9.0N / 15mm. The interval formed by any two of the above values is preferably not less than 5.0N / 15mm.

[0133] In the present invention, the barrier layer containing multimodal molecular weight distribution polyglycolic acid, the composite film obtained by compounding it with the protective layer and the adhesive layer has excellent interlayer peel strength. In some preferred embodiments, the interlayer peel strength of the composite film is not less than 1.0N / 15mm, for example, 1.0N / 15mm, 1.5N / 15mm, 1.9N / 15mm, 2.5N / 15mm, 2.8N / 15mm. The interval formed by any two of the above values is preferably not less than 2.0N / 15mm.

[0134] In the present invention, the barrier layer containing polyglycolic acid with multimodal molecular weight distribution, the composite film obtained by compounding it with the protective layer and the adhesive layer has excellent barrier properties. In some preferred embodiments, the oxygen transmission rate of the composite film at 23±0.5°C and relative humidity of 65%±5% is not more than 6cm 3 / (m 2 ·day·atm), for example, 1.24cm 3 / (m 2 ·day·atm)、2cm 3 / (m 2 ·day·atm)、2.67cm 3 / (m 2 ·day·atm)、3.84cm 3 / (m 2 ·day·atm)、4.84cm 3 / (m 2 ·day·atm)、5.84cm 3 / (m 2 ·day·atm)、6cm 3 / (m 2 ·day·atm), and the range of any two of the above values, preferably not more than 2cm 3 / (m 2 ·day·atm).

[0135] According to the present invention, in some preferred embodiments, the oxygen permeability coefficient of the composite membrane at 23±0.5°C and relative humidity 65%±5% is not greater than 1500 cm 3 μm / (m 2 ·day·atm), for example, 223cm 3 μm / (m 2 ·day·atm)、267cm 3 μm / (m 2 ·day·atm)、500cm 3 μm / (m 2 ·day·atm)、576cm 3μm / (m 2 ·day·atm)、1500cm 3 μm / (m 2 ·day·atm), and the range of any two of the above values, preferably not more than 500cm 3 μm / (m 2 ·day·atm).

[0136] According to the present invention, in some preferred embodiments, the water vapor transmission rate of the composite film is not greater than 30g / (m 2 ·day·atm), for example, 6.80g / (m 2 ·day·atm)、10.81g / (m 2 ·day·atm)、12.81g / (m 2 ·day·atm)、15g / (m 2 ·day·atm)、30g / (m 2 ·day·atm), and the range of any two values above, preferably not more than 15g / (m 2 ·day·atm).

[0137] According to the present invention, in some preferred embodiments, the water vapor permeability coefficient of the composite film is not greater than 2000 g·μm / (m 2 ·day·atm), for example, 1081g·μm / (m 2 ·day·atm)、1224g·μm / (m 2 ·day·atm)、1922g·μm / (m 2 ·day·atm)、2000g·μm / (m 2 ·day·atm), and the range of any two values above, preferably not more than 1500g·μm / (m 2 ·day·atm).

[0138] A second aspect of the present invention provides a method for preparing the fully biodegradable composite film of the present invention, which comprises: melting, compressing, and extruding an adhesive layer material containing a matrix resin B and a barrier layer material containing a matrix resin C, respectively, and then separately forming a barrier layer, a protective layer, and an adhesive layer through film-forming, and then hot pressing; or melting and compressing the protective layer material, the adhesive layer material containing the matrix resin B, and the barrier layer material containing the matrix resin C, respectively, and then co-extruding and distributing them to form a film.

[0139] In the present invention, a barrier layer material containing polyglycolic acid with a multimodal molecular weight distribution is used to prepare the barrier layer, and a degradable resin matrix is used to prepare the corresponding protective layer and adhesive layer. The composite film finally prepared not only has excellent barrier properties and biodegradability, but also has good interlayer peel strength and heat sealing strength.

[0140] In the present invention, as long as the purpose of the present invention can be achieved, the equipment for preparing the composite film is not particularly limited, for example, melting and extrusion are carried out in a screw extruder (single-screw extruder or twin-screw extruder).

[0141] According to the present invention, in some preferred embodiments, the screw speed of the screw extruder is independently 10 to 200 rpm; the screw speed when the protective layer material is melted is preferably 40 to 60 rpm, the screw speed when the barrier layer material containing multimodal molecular weight distribution polyglycolic acid is melted is preferably 30 to 40 rpm, and the screw speed when the adhesive layer material is melted is preferably 8 to 12 rpm.

[0142] According to the present invention, in some preferred embodiments, the temperatures of the polyglycolic acid with multimodal molecular weight distribution, the protective layer material and the adhesive layer material when they are melted are 180° C. to 260° C. respectively.

[0143] In the present invention, as long as the purpose of the present invention can be achieved, the film-making method can be a film-making method commonly used in the art, and the film-making method is blown film or cast film, and the molds for film making can each be a blown film mold or a cast film mold.

[0144] According to the present invention, in order to improve production efficiency and reduce equipment investment and material loss, the film-making method is preferably blown film.

[0145] Regardless of which method is used, the film-making method can be blown film or cast film; in the present invention, after film blowing or casting, it can be cooled and wound up, preferably stretched before winding up, and finally the corresponding film product is obtained, that is, after film blowing or casting, cooling, stretching, and winding up are performed to finally prepare the corresponding film product. Cooling, stretching, and winding up are conventional methods in the art. For example, stretching is to orient the film in one or more directions to further improve the orientation degree and reduce the thickness; specifically, the film can be heated to a temperature lower than the melting point of one or more polymers in the film (higher than the glass transition temperature) by heating with guide rollers. The heated temperature enables the film to be continuously and controllably stretched, and the gradually increasing speed of adjacent rollers serves to stretch the film; some guide rollers can also be used as preheating rollers; wherein, the guide rollers can be multiple guide rollers (for example, from 5 to 8), which are arranged to stretch the film in the machine direction (MD) The film is gradually stretched in the machine direction (MD) and thinned. The specific number of guide rollers can be selected as needed, which is related to the desired stretching ratio and the degree of stretching between each roller. During stretching, the heated "softened" film can be stretched step by step by guide rollers rotating at different speeds to stretch it to the desired stretch ratio in the machine direction (MD). In addition, various additional potential processing and / or finishing steps, such as slitting, processing, perforating, printing graphics or laminating, can be performed on the film having other layers without departing from the spirit and scope of the present invention. In the present invention, as long as the purpose of the present invention can be achieved, the conditions for preparing the composite film are not particularly limited. For example, when blowing the film, gases such as air can be used to expand the film bubble formed by the extruded polymer through the annular die. Specifically, the blowing ratio and film thickness can be controlled by adjusting the pressure of the gas in the film bubble. The greater the pressure, the larger the film bubble, the lower the thickness of the film, and the higher the degree of transverse orientation of the film. In the present invention, the blowing ratio during film blowing is preferably (1 to 6):1, preferably (2 to 5):1; wherein the blowing ratio refers to the ratio of the diameter of the film bubble to the diameter of the film blowing machine die, and the preferred draw ratio during film blowing is 1 to 3, preferably 1.3 to 2.5.

[0146] According to the present invention, in some embodiments, Figure 2The composite film is prepared in the multi-layer co-extrusion blown film preparation device with a unidirectional stretching device shown in the figure. The preparation method of the composite film includes: adding the protective layer material, the adhesive layer material and the barrier layer material into the hopper 10a of the single screw extruder 20a, the hopper 10b of the single screw extruder 20b and the hopper 10c of the single screw extruder 20c respectively, and then entering the corresponding single screw extruder 20a, the single screw extruder 20b and the single screw extruder 20c respectively for melting and extruding to the melt pump 30a, the melt pump 30b and the melt pump 30c respectively. The pump 30c is pressurized and then enters the co-extrusion distributor 40b through the feed pipe 40a for distribution. The distributed material melts and enters the film blowing die 50a, where it is inflated by gas (such as air) through the air ring 50b and pulled upward to cool to form a film bubble 01a. After cooling, the film bubble 01a is guided by the herringbone splint 60 and squeezed by the clamping roller 70a to obtain a precursor film 01b. The precursor film 01b is stretched by the unidirectional stretching device 80 to obtain a stretched film 01c. The stretched film 01c is wound and collected on the winding roller 90.

[0147] According to the present invention, in some embodiments, Figure 3 The multi-layer co-extrusion cast film preparation device with a unidirectional stretching device shown is used to prepare a composite film. The preparation method of the composite film includes: adding the protective layer material, the adhesive layer material and the barrier layer material into the hopper 10a of the single-screw extruder 20a, the hopper 10b of the single-screw extruder 20b and the hopper 10c of the single-screw extruder 20c respectively, and then entering the corresponding single-screw extruder 20a, the single-screw extruder 20b and the single-screw extruder 20c for melting and extrusion respectively to the melt pump 30a, the melt pump 30b and the melt pump 30c for pressurization, and then entering the co-extrusion distributor 40b through the feed pipe 40a for distribution, and the distributed material melt material enters the cast die 50c for extrusion and casting, and then is cooled by the cooling roller 70b to obtain the precursor film 01b, and then the precursor film 01b is stretched by the unidirectional stretching device 80 to obtain the stretched film 01c, and the stretched film 01c is wound and collected on the winding roller 90.

[0148] In the present invention Figure 2 and Figure 3 Part of the structure of the preparation device is the same, so the same part of the structure and other parts in the present invention use the same figure marks.

[0149] The film blowing, cooling, stretching, and winding in the present invention are conventional technical means in this field. There are no special requirements for the process conditions, as long as a film layer of corresponding thickness can be prepared. Therefore, the specific conditions in the present invention and the embodiments are not described in detail, and those skilled in the art can choose according to their needs.

[0150] The third aspect of the present invention provides applications of the fully biodegradable composite film of the present invention in food packaging bags, agricultural films, medical packaging, and the electronics field.

[0151] The fully biodegradable composite film of the present invention has excellent biodegradability, interlayer peeling strength, heat sealing strength and barrier properties, and has excellent performance when used in food packaging bags, agricultural films, medical packaging and electronic fields.

[0152] The present invention performs performance measurement according to the following method:

[0153] Melt flow rate measurement: Tests were conducted on a CEAST MF20 melt flow tester (Instron, USA). The test temperature was 230°C, the load was 2.16 kg, and the preheating time was 4 minutes.

[0154] Gel Permeation Chromatography (GPC): Testing was performed on a PL-GPC50 gel permeation chromatograph (Angilent, USA), using GPC offline software. The mobile phase consisted of hexafluoroisopropanol containing 5 mmol / L sodium trifluoroacetate, at a flow rate of 1 mL / min, a column temperature of 40°C, and an injection volume of 100 μL. The standard sample was PMMA, with a sample concentration of 1 mg / mL.

[0155] Melt strength testing: Tests were conducted on a Rosand RH7 high-pressure capillary rheometer from Malvern Panalytical, China. The model number was Haul-Off (2.0 mm diameter, 20 mm length), the barrel push rod downward speed was 15 mm / min, the test temperature was 235°C, the initial draw-down speed was 3 mm / min, the final draw-down speed was 50 mm / min, and the acceleration time was 3 minutes.

[0156] Thickness testing of each layer of a multilayer film: Images were taken using a Japanese HIROX KH-1300M 3D video microscope. The film was fixed with a homemade film fixture and cut with a blade. The cross-section was observed at 400x magnification, and the thickness was measured using the software's built-in measurement tool.

[0157] Interlayer Peel Strength Test: Referring to Method A in GB 8808-1988, the multilayer film was cut into strips 15 mm wide and 200 mm long. After peeling off 50 mm of one section, a tensile test was conducted on an Instron 3344 materials testing machine (USA). The unpeeled section formed a T-shape with the tensile direction, and the tensile rate was 300 mm / min.

[0158] Heat seal strength: refer to QB / T2358-1998, sample width is 15mm, fixture spacing is 50mm, test speed is 300mm / min.

[0159] Oxygen barrier performance testing: A MOCON OX-TRAN Model 2 / 22 oxygen transmission rate tester was used. According to international standard ISO 15105-2, film samples were cut using a circular sampler and their thickness was measured. High-vacuum sealant was applied along the sealing ring on one side of the sample and the sample was secured in a test chamber. The test temperature was 23°C and the relative humidity (RH) was 65%.

[0160] Water Vapor Barrier Performance Test: Film samples were tested using a MOCON PERMATRAN-W Model 3 / 61 water vapor transmission rate tester, in accordance with international standard ISO 15106-2, using an infrared detector method. Circular film samples were taken with a sampler and their thickness measured. The test temperature was 38°C, the humidity was 90%, and the pressure was 1 standard atmosphere (atm). The test lasted 24 hours.

[0161] The present invention will be described in detail below by way of examples. In the following examples:

[0162] Glycolide was purchased from Shenzhen Boli Biomaterial Co., Ltd. with a purity of ≥99.5%.

[0163] Stannous octoate and 1,4-butanediol were purchased from Sinopharm Chemical Reagent Co., Ltd. The purity of stannous octoate was AR grade, and the purity of 1,4-butanediol was CP grade.

[0164] Antioxidant 1010 was purchased from BASF (China) Co., Ltd.; antioxidant 626 was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., with a purity of ≥95%.

[0165] Chain extender (polyepoxide polymer), brand: JONCRYL ADR 4370, purchased from BASF (China) Co., Ltd.; EBS dispersant (ethylene bisstearamide) was purchased from Nanjing Baitong New Materials Co., Ltd.; talc powder (5000 mesh) was purchased from Suzhou Mingjiang Fine Chemical Co., Ltd.; di-tert-butyl peroxide isopropyl benzene (BIBP) was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., purity: 96%.

[0166] Maleic anhydride (maleic anhydride) and glycidyl methacrylate were purchased from Shanghai MacLean Biochemical Technology Co., Ltd. with purities of AR and 97%, respectively.

[0167] Ethyl methacrylate was purchased from Sinopharm Reagent, purity: CP, ≥98%.

[0168] Polybutylene terephthalate-co-adipate (PBAT), brand: A400 NC901, was purchased from Zhuhai Jinfa Biomaterial Co., Ltd.; polybutylene terephthalate-co-succinate (PBST), brand: TS-159, was purchased from Sinopec Yizheng Chemical Fiber Co., Ltd.; polylactic acid (PLA), brand: REVODE 110, was purchased from Zhejiang Hisun Biomaterial Co., Ltd.

[0169] Ethylene-vinyl alcohol copolymer (EVOH) was purchased from Kuraray Co., Ltd. of Japan with the brand name EVAL™ H171B, an ethylene content of 38 mol%, and a melt flow rate of 1.7 g / 10 min at 190°C / 2.16 kg. Polyvinyl alcohol (PVA) was purchased from Chongqing Chuanwei Chemical Co., Ltd. of Sinopec Group with the brand name 0588, a degree of polymerization of 500, and a degree of alcoholysis of 88%.

[0170] Example 1

[0171] Preparation of the protective layer material: Polybutylene terephthalate-co-adipate (PBAT), polylactic acid (PLA), talc, antioxidant 1010, EBS dispersant, and chain extender ADR 4370 were uniformly mixed in a mass ratio of 80:20:7:0.5:0.2:0.3 and pelletized using a KraussMaffei ZE25 UTXi parallel, co-rotating twin-screw extruder (screw diameter: 25 mm, aspect ratio: 56). The extruder had 14 sections from the feed port to the die, numbered 1-14. Section 1 served only for feeding and was not heated. The temperatures in sections 2-14 were 150°C, 200°C, 200°C, 200°C, 200°C, 220°C, 220°C, 220°C, 200°C, 200°C, and 200°C, respectively. The total feed rate was 15 kg / h, the screw speed was 150 rpm, and the residence time was 3.5 min.

[0172] Preparation of the adhesive layer material: PBAT, di-tert-butyl peroxide isopropyl benzene (BIBP), and maleic anhydride were mixed uniformly in a mass ratio of 100:0.25:5 and then extruded into pellets using a Labtech parallel, co-rotating twin-screw extruder (screw diameter: 20 mm, aspect ratio: 40). The extruder had 11 sections from the feed port to the die, numbered 1-11. Section 1 served only for feeding and did not heat the extruder. The temperatures in sections 2-11 were: 120°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C, 180°C, and 180°C, respectively. The feed rate was 4 kg / h, the screw speed was 200 rpm, and the residence time was 1.5 min.

[0173] Preparation of the barrier layer material: Glycolide (GA), stannous octoate, ethylene-vinyl alcohol copolymer (EVOH), 1,4-butanediol, antioxidant 1010, and antioxidant 626 were uniformly mixed in a mass ratio of 100:0.1:0.015:0.035:0.3:0.6. The mixture was then extruded and pelletized using a Labtech parallel co-rotating twin-screw extruder (screw diameter: 20 mm, aspect ratio: 40) to produce polyglycolic acid particles with a multimodal molecular weight distribution. The extruder consisted of 11 sections from the feed port to the die, numbered 1-11. Section 1 served only for feeding and was not heated. The temperatures in sections 2-11 were 160°C, 200°C, 220°C, 220°C, 220°C, 220°C, 220°C, 230°C, 235°C, and 240°C, respectively. The polyglycolic acid particles with multimodal molecular weight distribution were collected and characterized by GPC. The GPC curve of the polyglycolic acid particles with multimodal molecular weight distribution is shown in FIG. Figure 1 As shown, the weight average molecular weight of the multimodal molecular weight distribution polyglycolic acid is 268200 g / mol, and the molecular weight distribution index is 2.1, wherein the weight average molecular weight of the polyglycolic acid graft copolymer is 2011500 g / mol, the molecular weight distribution index is 1.1, and the mass proportion is 7.4%; the weight average molecular weight of the polyglycolic acid homopolymer is 199200 g / mol, the molecular weight distribution index is 1.6, and the mass proportion is 92.6%; the multimodal molecular weight distribution polyglycolic acid particles are subjected to a melt flow rate test to characterize their melt flow rate at the processing temperature, which is 5.4 g / 10 min; the melt strength at 235°C is 10 cN, and the melt break draw speed is 320 mm / s.

[0174] Preparation of fully biodegradable composite membranes: Figure 2 As shown, a Labtech LCR-33HD multi-layer co-extrusion film blowing machine is used to prepare a composite film. The protective layer material, the adhesive layer material, and the barrier layer material are respectively added to the hopper 10a of the single-screw extruder 20a, the hopper 10b of the single-screw extruder 20b, and the hopper 10c of the single-screw extruder 20c. Then, the protective layer material, the adhesive layer material, and the barrier layer material are respectively added to the hopper 10a of the single-screw extruder 20a, the hopper 10b of the single-screw extruder 20b, and the hopper 10c of the single-screw extruder 20c, and then enter the corresponding single-screw extruder 20a, the single-screw extruder 20b, and the single-screw extruder 20c for melting and extrusion. The materials are respectively pressurized in the melt pump 30a, the melt pump 30b, and the melt pump 30c. Figure 4The structure of the fully biodegradable composite film shown in FIG. 1 shows that the molten material after distribution enters the co-extrusion distributor 40b through the feed pipe 40a for distribution. The molten material after distribution enters the film blowing die 50a, is blown by air through the air ring 50b and pulled upward to cool to form a film bubble 01a. After the film bubble 01a is cooled, it is guided by the herringbone splint 60 and squeezed by the clamping roller 70a to obtain a precursor film 01b. The precursor film 01b is stretched by the unidirectional stretching device 80 to obtain a stretched film 01c. The stretched film 01c is wound and collected. Collected on the winding roller 90; the screw speeds of the single-screw extruder 20a, the single-screw extruder 20b, and the single-screw extruder 20c are set to 40rpm, 30rpm, and 10rpm, respectively; the temperatures of the single-screw extruder 20a, the single-screw extruder 20b, the single-screw extruder 20c, the melt pump 30a, the melt pump 30b, the melt pump 30c, and the casting die 50c are all 230°C; the speeds of the melt pump 30a, the melt pump 30b, and the melt pump 30c are set to 20rpm, 15rpm, and 5rpm, respectively.

[0175] During the preparation process, the blowing ratio is about 2.5, the drawing ratio is about 2, the total thickness of the prepared composite film is about 100 μm, the single layer thickness of the adhesive layer is about 10 μm, the thickness of the barrier layer is about 20 μm, and the single layer thickness of the protective layer is about 30 μm.

[0176] Example 2

[0177] Preparation of protective layer material: The preparation method is similar to that of Example 1, except that the ratio of polybutylene terephthalate-co-adipate (PBAT), polylactic acid (PLA), talc, antioxidant 1010, EBS dispersant and chain extender ADR 4370 is changed to: 60:40:6:0.5:0.1:0.4.

[0178] Preparation of the bonding layer material: The preparation method is similar to that of Example 1, except that the ratio of PBAT, di-tert-butyl peroxide isopropyl benzene (BIBP), and maleic anhydride is changed to 100:0.15:3, and the feed rate and screw speed are changed to 3 kg / h and 150 rpm, respectively, and the residence time is 2 min.

[0179] Preparation of barrier layer material: The preparation method is the same as that in Example 1.

[0180] Preparation of fully biodegradable composite film: The preparation method is similar to that of Example 1, except that the screw speeds of the single-screw extruder 20a, the single-screw extruder 20b, and the single-screw extruder 20c are set to 50 rpm, 40 rpm, and 15 rpm, respectively; the temperatures of the single-screw extruder 20a, the single-screw extruder 20b, the single-screw extruder 20c, the melt pump 30a, the melt pump 30b, the melt pump 30c, and the casting die 50c are all 230°C; the speeds of the melt pump 30a, the melt pump 30b, and the melt pump 30c are set to 30 rpm, 15 rpm, and 10 rpm, respectively. During the preparation process, the blow-up ratio is approximately 1.8, and the draw-down ratio is approximately 1.5.

[0181] The total thickness of the prepared composite film is about 180 μm, the thickness of a single layer of the adhesive layer is about 20 μm, the thickness of the barrier layer is about 30 μm, and the thickness of a single layer of the protective layer is about 55 μm.

[0182] Example 3

[0183] Preparation of protective layer material: The preparation method is the same as that in Example 1.

[0184] Preparation of bonding layer material: The preparation method is similar to that of Example 1, except that PBAT is replaced by PGA, and the feeding rate and screw speed are changed to 2 kg / h and 150 rpm, and the residence time is 4 min.

[0185] Preparation of barrier layer material: The preparation method is the same as that in Example 1.

[0186] Preparation of fully biodegradable composite film: The preparation method is similar to that of Example 1, except that the blowing ratio is about 1.8 and the drawing ratio is about 1.5 during the preparation process.

[0187] The total thickness of the prepared composite film is about 150 μm, the thickness of a single layer of the adhesive layer is about 15 μm, the thickness of the barrier layer is about 30 μm, and the thickness of a single layer of the protective layer is about 45 μm.

[0188] Example 4

[0189] Preparation of protective layer material: The preparation method is similar to that of Example 1, except that PBAT is replaced by PBST.

[0190] Preparation of bonding layer material: The preparation method is the same as that in Example 3.

[0191] Preparation of the barrier layer material: The preparation method is similar to that of Example 1, except that ethylene-vinyl alcohol copolymer (EVOH) is replaced with polyvinyl alcohol (PVA), and the ratio of glycolide, stannous octoate, polyvinyl alcohol (PVA), 1,4-butanediol, antioxidant 1010, and antioxidant 626 is set to 100:0.1:0.02:0.04:0.5:0.3. Polyglycolic acid particles with a multimodal molecular weight distribution were collected and characterized by GPC. The GPC curve of the multimodal molecular weight distribution polyglycolic acid particles is shown in FIG. Figure 1 As shown, the weight average molecular weight of the multimodal molecular weight distribution polyglycolic acid is 204500 g / mol, and the molecular weight distribution index is 1.8, wherein the weight average molecular weight of the polyglycolic acid graft copolymer is 1430800 g / mol, the molecular weight distribution index is 1.1, and the mass proportion is 3.8%; the weight average molecular weight of the polyglycolic acid homopolymer is 173800 g / mol, the molecular weight distribution index is 1.6, and the mass proportion is 96.2%; the multimodal molecular weight distribution polyglycolic acid particles are subjected to a melt flow rate test to characterize that the melt flow rate at the processing temperature is 9.9 g / 10 min; and the melt strength at 235°C is 20 cN.

[0192] Preparation of fully biodegradable composite membrane: The preparation method is the same as that in Example 2.

[0193] The total thickness of the prepared composite film is about 180 μm, the thickness of a single layer of the adhesive layer is about 20 μm, the thickness of the barrier layer is about 30 μm, and the thickness of a single layer of the protective layer is about 55 μm.

[0194] Example 5

[0195] Preparation of protective layer material: The preparation method is similar to that of Example 1, except that talc and EBS dispersant are not added, and the ratio of polybutylene terephthalate-co-adipate (PBAT), polylactic acid (PLA), antioxidant 1010 and chain extender ADR 4370 is changed to 40:60:0.5:0.5.

[0196] Preparation of the adhesive layer material: The preparation method is similar to that of Example 1, except that maleic anhydride (MAH) is replaced by ethyl methacrylate (EMA).

[0197] Preparation of barrier layer material: The preparation method is the same as that in Example 1.

[0198] Preparation of fully biodegradable composite membrane: The preparation method is the same as that in Example 2.

[0199] The total thickness of the prepared composite film is about 180 μm, the thickness of a single layer of the adhesive layer is about 20 μm, the thickness of the barrier layer is about 30 μm, and the thickness of a single layer of the protective layer is about 55 μm.

[0200] Example 6

[0201] Preparation of protective layer material: The preparation method is similar to that of Example 1, except that polylactic acid (PLA) is not added, and polybutylene terephthalate-co-adipate (PBAT), talc, antioxidant 1010, EBS dispersant and chain extender ADR 4370 are mixed in a ratio of 100:7:0.5:0.2:0.3.

[0202] Preparation of adhesive layer material: The preparation method is the same as that in Example 1.

[0203] Preparation of barrier layer material: The preparation method is the same as that in Example 1.

[0204] Preparation of fully biodegradable composite film: The preparation method is similar to that of Example 1, except that the blowing ratio is about 2.4 and the drawing ratio is about 2 during the preparation process.

[0205] The total thickness of the prepared composite film is about 110 μm, the thickness of a single layer of the adhesive layer is about 10 μm, the thickness of the barrier layer is about 20 μm, and the thickness of a single layer of the protective layer is about 35 μm.

[0206] Comparative Example 1

[0207] Preparation of protective layer material: The preparation method is the same as that in Example 1.

[0208] Preparation of barrier layer material: The preparation method is the same as that in Example 1.

[0209] Preparation of composite film: The preparation method is similar to that of Example 1, except that no adhesive layer is used, the material of the 10b screw is changed to a protective layer material, the blowing ratio is about 1.5, and the drawing ratio is about 1.5.

[0210] The total thickness of the prepared composite film is about 200 μm, the thickness of a single layer of the adhesive layer is about 20 μm, the thickness of the barrier layer is about 40 μm, and the thickness of a single layer of the protective layer is about 60 μm.

[0211] Comparative Example 2

[0212] Preparation of protective layer material: The preparation method is the same as that in Example 1.

[0213] Preparation of adhesive layer material: The preparation method is the same as that in Example 1.

[0214] Preparation of barrier layer material: The preparation method is similar to that of Example 1, except that no ethylene-vinyl alcohol copolymer (EVOH) is added, and the ratio of glycolide, stannous octoate, 1,4-butanediol, antioxidant 1010, and antioxidant 626 is changed to 100:0.1:0.5:0.3:0.6, ultimately producing polyglycolic acid particles. The collected polyglycolic acid particles were characterized by GPC for molecular weight. The GPC curve of the polyglycolic acid particles is shown in the figure below. Figure 1 As shown, the polyglycolic acid has only one peak, a number average molecular weight of 124,900 g / mol, a weight average molecular weight of 197,800 g / mol, and a molecular weight distribution index of 1.58; the melt flow rate test of the polyglycolic acid particles is performed to characterize its melt flow rate at the processing temperature, which is 26.2 g / 10 min; and the melt strength at 235°C is 3 cN.

[0215] Preparation of multilayer film: Same as Example 1, film blowing failed during the film blowing process.

[0216] Comparative Example 3

[0217] Preparation of protective layer material: The preparation method is the same as that in Example 1.

[0218] Preparation of adhesive layer material: The preparation method is the same as that in Example 1.

[0219] Preparation of multilayer film: The preparation method is similar to that of Example 1, except that no barrier layer is used, that is, the material used for the 10c screw is changed to a protective layer material, the blowing ratio is about 1.5, and the drawing ratio is about 1.5.

[0220] The total thickness of the prepared composite film is about 200 μm, the thickness of a single layer of the adhesive layer is about 20 μm, the thickness of the barrier layer is about 40 μm, and the thickness of a single layer of the protective layer is about 60 μm.

[0221] Comparative Example 4

[0222] Preparation of pure PBAT hot-pressed film: Polybutylene terephthalate-co-adipate (PBAT) was tightly stacked between two stainless steel plates and hot-pressed at 180°C with a pressure of 100-200 kN for 4 minutes using a LP-S-50 hot press (maximum pressure 500 kN) from Labtech, Thailand, and then cooled to room temperature to obtain a pure PBAT hot-pressed film.

[0223] The thickness of the prepared pure PBAT hot-pressed film is 280 μm.

[0224] Comparative Example 5

[0225] Preparation of pure PLA hot-pressed film: The preparation method is similar to that of Comparative Example 4, except that polybutylene terephthalate-co-adipate (PBAT) is replaced by polylactic acid (PLA).

[0226] The thickness of the prepared pure PLA hot-pressed film is 200 μm.

[0227] Comparative Example 6

[0228] Preparation of Pure PGA Monolayer Blown Film: The barrier layer material from Example 1 was passed through a Dr. Collin E30P single-screw extruder (screw diameter 30 mm, aspect ratio 30:1) and a matching BL 180 / 600 film blowing machine from the same company. After melting, extrusion, drawing, cooling, stretching, and winding, a pure PGA monolayer blown film was obtained. The extruder screw speed was 50 rpm, and the extruder and die temperatures were set at 180°C, 230°C, 230°C, and 230°C, respectively.

[0229] The thickness of the prepared pure PGA single-layer blown film is 25 μm.

[0230]

Test Example 1

[0231] Interlayer peeling force (i.e., used to characterize interlayer peeling strength) was tested on some examples and comparative example 4, with a sample width of 15 mm. The test results are listed in Table 1.

[0232] Table 1

[0233]

[0234]

[0235] The interlayer peeling force (interlayer peeling strength) of other examples not listed in Table 1 is not significantly lower than that of Example 3.

[0236]

Test Example 2

[0237] The heat sealing strength test was performed on Example 1 and Comparative Example 6, with the strip width being 15 mm. The test results are listed in Table 2.

[0238] Table 2

[0239] Protective layer material Heat sealing strength (N / 15mm) Example 1 PBAT / PLA-80 / 20 ≥8.7 Example 2 PBAT / PLA-60 / 40 ≥6.3 Example 4 PBST / PLA-80 / 20 ≥9.0 Example 5 PBAT / PLA-40 / 60 ≥4.4 Example 6 PBAT ≥9.5 Comparative Example 6 none Unable to heat seal (<0.1)

[0240] The heat sealing strength of other embodiments not listed in Table 2 is not significantly lower than that of Example 5.

[0241]

Test Example 3

[0242] Barrier properties of some embodiments and comparative examples were tested. The oxygen barrier performance was tested at a temperature of 23°C and a relative humidity (RH) of 65%. The water vapor barrier performance was tested at a temperature of 38°C and a relative humidity of 90%. The pressure was 1 standard atmosphere (atm), and the test time was 24 hours. The test results are shown in Table 3.

[0243] Table 3

[0244]

[0245] The oxygen transmission rates and water vapor transmission rates of the other examples not listed in Table 3 are not significantly higher than those of Example 3.

[0246] From the results of the above test examples, it can be seen that the fully biodegradable film of the present invention has good interlayer peel strength, and the interaction between the various film layers can make the composite film have excellent heat sealing performance and barrier properties. Specifically, the oxygen and water barrier properties of each example are very good, with the oxygen transmission rate and water vapor transmission rate reaching as low as 1.24cm 3 / (m 2 ·day·atm) and 6.80g / (m 2 ·day·atm), which is on the same order of magnitude as the barrier performance of pure polyglycolic acid, and significantly superior to Comparative Example 3 (without a PGA barrier layer), Comparative Example 4 (pure PBAT), and Comparative Example 5 (pure PLA). The oxygen permeability coefficient and water vapor permeability coefficient of Example 2, compared to Comparative Example 3 without a PGA barrier layer, are both reduced by approximately one order of magnitude, resulting in approximately 8.1 times and 10.4 times higher oxygen and water barriers, respectively. Furthermore, as shown in Table 3, Comparative Example 1 lacks an adhesive layer, resulting in poor adhesion between the PGA layer and the protective layer. This also leads to poor continuity and defects in the PGA barrier layer during blow molding, which in turn reduces the overall barrier performance of the multilayer film. Furthermore, the configuration of the composite film of the present invention can slow its hydrolysis rate, thereby extending the shelf life and service life of the multilayer film.

[0247] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A fully biodegradable composite film, characterized in that: The composite film comprises a barrier layer, a protective layer and an adhesive layer, wherein the surface layer of the composite film is the protective layer, and the barrier layer and the protective layer are bonded to each other via the adhesive layer; The base resin B of the adhesive layer is selected from a degradable resin grafted with a polar monomer and / or a degradable resin grafted with a monomer containing a group capable of reacting with a hydroxyl group; The matrix resin C of the barrier layer contains at least polyglycolic acid with a multimodal molecular weight distribution.

2. The composite film according to claim 1, wherein The multimodal molecular weight distribution polyglycolic acid has a melt strength of not less than 4 cN, preferably not less than 8 cN at 235° C.; and / or The weight average molecular weight of the multimodal molecular weight distribution polyglycolic acid is 200,000 to 1.5 million g / mol, preferably 250,000 to 500,000 g / mol; and / or, The molecular weight distribution index of the multimodal molecular weight distribution polyglycolic acid is 1.5 to 20.0, preferably 2.0 to 3.5; and / or, The melt flow rate of the multimodal molecular weight distribution polyglycolic acid at 230° C. / 2.16 kg is not higher than 20.0 g / 10 min, preferably 0.5 to 10.0 g / 10 min.

3. The composite film according to claim 1 or 2, wherein The multimodal molecular weight distribution polyglycolic acid is a homogeneous continuous phase; and / or, The multimodal molecular weight distribution polyglycolic acid contains 2 to 4 peaks; and / or, The multimodal molecular weight distribution polyglycolic acid comprises a polyglycolic acid graft copolymer and a polyglycolic acid homopolymer; Preferably, The weight average molecular weight of the polyglycolic acid graft copolymer is greater than the weight average molecular weight of the polyglycolic acid homopolymer; More preferably, The weight average molecular weight of the polyglycolic acid graft copolymer is 500,000 to 10 million g / mol, preferably 1 million to 6 million g / mol; and / or the weight average molecular weight of the polyglycolic acid homopolymer is 50,000 to 350,000 g / mol, preferably 100,000 to 200,000 g / mol; and / or, The molecular weight polydispersity index of the polyglycolic acid graft copolymer is 1.01 to 3.0, preferably 1.05 to 1.5; and / or the molecular weight polydispersity index of the polyglycolic acid homopolymer is 1 to 3, preferably 1.4 to 2.9; and / or, The mass ratio of the polyglycolic acid graft copolymer to the polyglycolic acid homopolymer is 2:98 to 60:40, preferably 3:97 to 10:

90.

4. The composite film according to claim 3, wherein The main chain of the polyglycolic acid graft copolymer includes an ethylene-vinyl alcohol copolymer segment from an ethylene-vinyl alcohol copolymer and / or a polyvinyl alcohol segment from polyvinyl alcohol, and the side chain includes a grafted segment from a glycolic acid monomer derivative, a glycolic acid oligomer or a glycolic acid polymer; Preferably, the structure of the polyglycolic acid graft copolymer is shown in structural formula (I): In the structural formula (I), x and m are positive integers, and y1, y2 and z are natural numbers; More preferably, in structural formula (I), the sum of x, y1, y2 and z is not less than 50, preferably 50-6000, more preferably 200-2500; and / or, m is not less than 50, preferably 50-1000; and / or, the proportion of z in x+y1+y2+z is 0% to 50%; and / or, the proportion of y1 in x+y1+y2 is 0% to 32%; and / or, m is an integer greater than 10, preferably m is an integer greater than 50.

5. The composite film according to claim 3 or 4, wherein The structure of the polyglycolic acid homopolymer is shown in structural formula (II): In the structural formula (II), n1, n2, ..., n i are all natural numbers; M1, M2, ..., M i Each is an imino group, a nitro group or an ether bond; i is an integer not less than 1, R is H, an alkane group or an aromatic hydrocarbon group with a molecular weight of 14 to 1000 g / mol; Preferably, i ranges from 1 to 20, preferably from 1 to 6; and / or, n1, n2, ..., n i The sum of is not less than 50, preferably 50 to 5000.

6. The composite film according to any one of claims 1 to 5, wherein The grafting rate of the matrix resin B is 0.1% to 5%; and / or, The matrix resin B includes poly(butylene terephthalate-co-adipate) grafted glycidyl methacrylate, poly(butylene terephthalate-co-adipate) grafted glycidyl acrylate, poly(butylene terephthalate-co-adipate) grafted methyl methacrylate, poly(butylene terephthalate-co-adipate) grafted hydroxyethyl methacrylate, poly(butylene terephthalate-co-adipate) grafted hydroxypropyl methacrylate, poly(butylene terephthalate-co-adipate) grafted hydroxyethyl acrylate, poly(butylene terephthalate-co-adipate) grafted dimethylaminoethyl methacrylate, poly(butylene terephthalate-co-adipate) grafted dodecafluoroheptyl methacrylate, poly(butylene terephthalate-co-adipate) grafted maleic anhydride, poly(butylene terephthalate-co-adipate) grafted hydroxypropyl methacrylate, One or more blends of polybutylene terephthalate grafted onto dibutyl maleate, polybutylene terephthalate-co-adipate grafted onto dimethylmaleic anhydride, polybutylene terephthalate-co-adipate grafted onto itaconic anhydride, polybutylene terephthalate-co-adipate grafted onto acrylamide, polybutylene terephthalate-co-adipate grafted onto acrylonitrile, polybutylene terephthalate-co-adipate grafted onto N-ethylacrylamide, polybutylene terephthalate-co-adipate grafted onto styrenesulfonic acid, polybutylene terephthalate-co-succinate grafted onto maleic anhydride, polylactic acid grafted onto maleic anhydride, polypropylene carbonate grafted onto maleic anhydride, polycaprolactone grafted onto maleic anhydride, starch grafted onto maleic anhydride, polyhydroxyalkanoate grafted onto maleic anhydride and polyglycolic acid grafted onto maleic anhydride.

7. The composite film according to any one of claims 1 to 6, wherein The protective layer is a degradable film layer; and / or The water vapor permeability coefficient of the protective layer is not greater than 20000 g·μm / (m 2 day atm); and / or The base resin A of the protective layer is the same as the degradable resin grafted with a polar monomer / or the degradable resin grafted with a monomer containing a group reactive with a hydroxyl group; and / or, The matrix resin A of the protective layer is selected from polyester biodegradable resins, preferably selected from any one or more of poly(butylene terephthalate-co-adipate), poly(butylene terephthalate-co-succinate), poly(ethylene terephthalate-co-adipate), poly(ethylene terephthalate-co-succinate), poly(butylene succinate), poly(butylene adipate), polylactic acid, polypropylene carbonate, polyhydroxyalkanoate, and thermoplastic starch. Preferably, the matrix resin A contains at least poly(butylene terephthalate-co-adipate) and / or poly(butylene terephthalate-co-succinate).

8. The composite film according to any one of claims 1 to 7, wherein The heat sealing strength of the composite film is not less than 3.0 N / 15 mm, preferably not less than 5.0 N / 15 mm; and / or, The interlayer peel strength of the composite film is not less than 1.0 N / 15 mm, preferably not less than 2.0 N / 15 mm; and / or, The oxygen transmission rate of the composite film is not greater than 6cm at 23±0.5℃ and relative humidity 65%±5%. 3 / (m 2 ·day·atm), preferably no larger than 2cm 3 / (m 2 ·day·atm); and / or, The oxygen permeability coefficient of the composite film is not greater than 1500 cm at 23±0.5°C and relative humidity 65%±5%. 3 μm / (m 2 ·day·atm), preferably not more than 500cm 3 μm / (m 2 ·day·atm); and / or, The water vapor transmission rate of the composite film is not more than 30g / (m 2 ·day·atm), preferably not more than 15g / (m 2 ·day·atm); and / or, The water vapor permeability coefficient of the composite film is not greater than 2000 g·μm / (m 2 ·day·atm), preferably not more than 1500g·μm / (m 2 ·day·atm).

9. The composite film according to any one of claims 1 to 8, wherein The number of the barrier layer is at least one, and the thickness of each single barrier layer is independently 1 to 50 μm, preferably 5 to 40 μm; and / or, The number of the protective layers is at least 2, and the thickness of each protective layer is independently 3 to 80 μm, preferably 20 to 60 μm; and / or, The thickness of each single adhesive layer is independently 0.5 to 30 μm, preferably 3 to 20 μm; and / or, The total thickness of the composite film is 8 to 270 μm, preferably 15 to 200 μm.

10. A method for preparing the fully biodegradable composite film according to any one of claims 1 to 9, characterized in that: The preparation method comprises: The protective layer material, the adhesive layer material containing the matrix resin B, and the barrier layer material containing the matrix resin C are melted, compressed, and extruded, and then formed into films to form the barrier layer, protective layer, and adhesive layer, which are then heat-pressed; or the protective layer material, the adhesive layer material containing the matrix resin B, and the barrier layer material containing the matrix resin C are melted and compressed, and then co-extruded and formed into films; Preferably, the film-making method is blown film or cast film, preferably blown film.

11. Use of the fully biodegradable composite film according to any one of claims 1 to 10 in food packaging bags, agricultural films, medical packaging, and electronic fields.

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