Biodegradable packaging material and preparation method thereof

Abstract

The present invention belongs to the field of biodegradable materials, and in particular to a biodegradable packaging material and a preparation method thereof. The biodegradable packaging material provided by the present invention includes an inner layer, an intermediate layer and an outer layer in contact with each other in sequence; the components of the inner layer include PCL-PPC-PCL block copolymer, PBAT and calcium carbonate, and the mass ratio of the three is (5-10):80:(10-15); the components of the intermediate layer include calcium carbonate and PBAT, and the mass ratio of the two is (25-40):(60-75); the components of the outer layer include talc, PLA and PBAT, and the mass ratio of the three is (10-20):5:(75-85). The biodegradable packaging material provided by the present invention has good heat sealing strength and puncture resistance, can be completely biodegraded, has low production cost, smooth production process and high production efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of biodegradable materials, and in particular relates to a biodegradable packaging material and a preparation method thereof. Background Art

[0002] The express delivery industry generates approximately 1.8 million tons of plastic waste annually. The disposable and difficult-to-recycle nature of express packaging films makes them unsuitable for recycling. The rapid growth of my country's express delivery industry has led to serious plastic pollution. Developing low-cost biodegradable packaging as an alternative to non-environmentally friendly materials is one of the most effective ways to fundamentally address this "white pollution" of express packaging.

[0003] In the context of environmental protection, more and more scientific research institutions and enterprises have invested in the research and development of biodegradable packaging materials. However, the biodegradable packaging materials currently developed generally have problems such as insufficient heat sealing strength, low puncture resistance, high production costs, and low production efficiency. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a biodegradable packaging material and a preparation method thereof. The biodegradable packaging material provided by the present invention has good heat sealing strength and puncture resistance, can be completely biodegraded, has low production cost, smooth production process and high production efficiency.

[0005] The present invention provides a biodegradable packaging material, the biodegradable packaging material comprising an inner layer, a middle layer and an outer layer in contact with each other in sequence;

[0006] The components of the inner layer include PCL-PPC-PCL block copolymer, PBAT and calcium carbonate, and the mass ratio of the PCL-PPC-PCL block copolymer, PBAT and calcium carbonate is (5-10):80:(10-15);

[0007] The intermediate layer comprises calcium carbonate and PBAT, and the mass ratio of calcium carbonate to PBAT is (25-40): (60-75);

[0008] The outer layer comprises talc, PLA and PBAT, and the mass ratio of the talc, PLA and PBAT is (10-20):5:(75-85).

[0009] Preferably, in the inner layer components, the number average molecular weight of the PCL-PPC-PCL block copolymer is 8000-13000 g / mol, and the molecular weight distribution is 1.8-3; the melt index of the PBAT at a temperature of 190°C and a load of 2.16 kg is 3-5 g / 10 min; and the particle size of the calcium carbonate is 2-8 μm.

[0010] Preferably, in the intermediate layer components, the particle size of the calcium carbonate is 2 to 8 μm; and the melt index of the PBAT at a temperature of 190° C. and a load of 2.16 kg is 8 to 12 g / 10 min.

[0011] Preferably, in the outer layer components, the particle size of the talc powder is 3 to 7 μm; the melt index of the PLA at a temperature of 190°C and a load of 2.16 kg is 3 to 12 g / 10 min; the elastic modulus of the PLA is 3000 to 4000 MPa; and the melt index of the PBAT at a temperature of 190°C and a load of 2.16 kg is 3 to 5 g / 10 min.

[0012] Preferably, the mass ratio of the inner layer, the middle layer and the outer layer is 1:(1-1.5):(0.8-1.2).

[0013] Preferably, the biodegradable packaging material has a thickness of 40 to 80 μm.

[0014] Preferably, the biodegradable packaging material is a biodegradable courier bag.

[0015] The present invention provides a method for preparing the biodegradable packaging material described in the above technical solution, comprising the following steps:

[0016] a) Prepare inner layer masterbatch, middle layer masterbatch and outer layer masterbatch;

[0017] The components of the inner layer masterbatch include PCL-PPC-PCL block copolymer, PBAT and calcium carbonate, and the mass ratio of the PCL-PPC-PCL block copolymer, PBAT and calcium carbonate is (5-10):80:(10-15);

[0018] The components of the intermediate layer masterbatch include calcium carbonate and PBAT, and the mass ratio of the calcium carbonate to PBAT is (25-40): (60-75);

[0019] The outer layer masterbatch comprises talc, PLA and PBAT, wherein the mass ratio of talc, PLA and PBAT is (10-20):5:(75-85);

[0020] b) using the inner layer masterbatch, the middle layer masterbatch and the outer layer masterbatch as raw materials, performing multi-layer co-extrusion blown film to obtain a biodegradable packaging material.

[0021] Preferably, the inner layer masterbatch is prepared according to the following steps:

[0022] a1) melt-blending PCL-PPC-PCL block copolymer, PBAT and calcium carbonate in proportion, and granulating to obtain an inner layer masterbatch;

[0023] The intermediate layer masterbatch is prepared according to the following steps:

[0024] a2) melt-blending calcium carbonate and PBAT in proportion, and granulating to obtain an intermediate layer masterbatch;

[0025] The outer layer masterbatch is prepared according to the following steps:

[0026] a3) melt-blending talcum powder, PLA and PBAT in proportion, and granulating to obtain outer layer masterbatch.

[0027] Preferably, in step a1), the PCL-PPC-PCL block copolymer is prepared according to the following steps:

[0028] In the presence of a catalyst, PPC diol and ε-caprolactone undergo polymerization reaction in a solvent to obtain a PCL-PPC-PCL block copolymer.

[0029] Compared to the prior art, the present invention provides a biodegradable packaging material and a method for preparing the same. The biodegradable packaging material provided by the present invention comprises an inner layer, an intermediate layer, and an outer layer in contact with each other in sequence. The inner layer comprises a PCL-PPC-PCL block copolymer, PBAT, and calcium carbonate, with the mass ratio of the PCL-PPC-PCL block copolymer, PBAT, and calcium carbonate being (5-10):80:(10-15); the intermediate layer comprises calcium carbonate and PBAT, with the mass ratio of the calcium carbonate to PBAT being (25-40):(60-75); and the outer layer comprises talc, PLA, and PBAT, with the mass ratio of the talc, PLA, and PBAT being (10-20):5:(75-85). The biodegradable packaging material provided by the present invention is a three-layer composite structure, wherein the inner layer mainly plays a heat-sealing role. This layer uses PBAT as a base material and has good biodegradability. Adding calcium carbonate as a filler can effectively reduce production costs. Adding PCL-PPC-PCL block copolymer can significantly improve the heat-sealing strength and puncture resistance of this layer, solving the problem of insufficient heat-sealing strength and puncture resistance after inorganic filling; the middle layer mainly plays a role in reducing the overall production cost of the material. It only contains two components, PBAT base material and calcium carbonate filler, and the proportion of filler material is higher than that of the inner and outer layers; the outer layer mainly plays a mechanical support role. This layer also uses PBAT as a base material, adds talcum powder instead of calcium carbonate as a filler, and adds a certain amount of PLA, which increases the overall stiffness of the material, making the production process of the packaging material smoother and more efficient. The three-layer structure of the biodegradable packaging material provided by the present invention has clear functions. Through the synergistic effect of the three-layer structure, it can effectively solve the problems of insufficient heat-sealing strength, low puncture resistance, high production cost, and low production efficiency of existing biodegradable packaging materials, with good environmental and economic benefits. DETAILED DESCRIPTION

[0030] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0031] The invention provides a biodegradable packaging material, comprising an inner layer, a middle layer and an outer layer which are in contact with each other in sequence.

[0032] In the biodegradable packaging material provided by the present invention, the components of the inner layer include PCL-PPC-PCL block copolymer (polycaprolactone and polypropylene carbonate block copolymer), PBAT (polybutylene terephthalate-adipate) and calcium carbonate; wherein the number average molecular weight of the PCL-PPC-PCL block copolymer is preferably 8000-13000 g / mol, specifically 8000 g / mol, 8500 g / mol, 9000 g / mol, 9500 g / mol, l, 10000 g / mol, 10500 g / mol, 11000 g / mol, 11500 g / mol, 12000 g / mol, 12500 g / mol or 13000 g / mol; the molecular weight distribution of the PCL-PPC-PCL block copolymer is preferably 1.8 to 3, specifically 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3; the PBAT at a temperature of The melt index at 190°C and a load of 2.16 kg is preferably 3 to 5 g / 10 min, specifically 3 g / 10 min, 3.1 g / 10 min, 3.2 g / 10 min, 3.3 g / 10 min, 3.4 g / 10 min, 3.5 g / 10 min, 3.6 g / 10 min, 3.7 g / 10 min, 3.8 g / 10 min, 3.9 g / 10 min, 4 g / 10 min, 4.1 g / 10 min, 4.2 g / 10 min in, 4.3 g / 10 min, 4.4 g / 10 min, 4.5 g / 10 min, 4.6 g / 10 min, 4.7 g / 10 min, 4.8 g / 10 min, 4.9 g / 10 min or 5 g / 10 min; the particle size of the calcium carbonate is preferably 2 to 8 μm, specifically 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm or 8 μm.

[0033] In the biodegradable packaging material provided by the present invention, in the inner layer components, the mass ratio of the PCL-PPC-PCL block copolymer, PBAT and calcium carbonate is (5-10):80:(10-15), wherein the mass ratio of the PCL-PPC-PCL block copolymer to PBAT can be specifically 5:80, 6:80, 7:80, 8:80, 9:80 or 10:80, and the mass ratio of the calcium carbonate to PBAT can be specifically 10:80, 11:80, 12:80, 13:80, 14:80 or 15:80.

[0034] In the biodegradable packaging material provided by the present invention, the components of the intermediate layer include calcium carbonate and PBAT; wherein the particle size of the calcium carbonate is preferably 2 to 8 μm, specifically 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm or 8 μm; the melt index of the PBAT at a temperature of 190° C. and a load of 2.16 kg is preferably 8 to 12 g / 10 min, specifically 8 g / 10 m in, 8.3g / 10min, 8.5g / 10min, 8.7g / 10min, 9g / 10min, 9.3g / 10min, 9.5g / 10min, 9.7g / 10min, 10g / 10min, 10 .2g / 10min, 10.5g / 10min, 10.7g / 10min, 11g / 10min, 11.2g / 10min, 11.5g / 10min, 11.7g / 10min or 12g / 10min.

[0035] In the biodegradable packaging material provided by the present invention, in the intermediate layer components, the mass ratio of calcium carbonate and PBAT is (25-40): (60-75), specifically 25:75, 26:74, 27:73, 28:72, 29:71, 30:70, 31:69, 32:68, 33:67, 34:66, 35:65, 36:64, 37:63, 38:62, 39:61 or 40:60.

[0036] In the biodegradable packaging material provided by the present invention, the components of the outer layer include talc, PLA (polylactic acid) and PBAT; wherein the particle size of the talc is preferably 3 to 7 μm, specifically 3 μm, 3.2 μm, 3.5 μm, 3.7 μm, 4 μm, 4.2 μm, 4.5 μm, 4.7 μm, 5 μm, 5.2 μm, 5.5 μm, 5.7 μm, 6 μm, 6.2 μm, 6.5 μm, 6.7 μm or 7 μm; the melt index of the PLA at a temperature of 190°C and a load of 2.16 kg is preferably 3 to 12 g / 10 min , specifically 3g / 10min, 3.5g / 10min, 4g / 10min, 4.5g / 10min, 5g / 10min, 5.5g / 10min, 6g / 10min, 6.5g / 10min, 7g / 10min, 7.5g / 10min, 8g / 10min, 8.5g / 10min, 9g / 10min, 9.5g / 10min, 10g / 10min, 10.2g / 10min, 10.5g / 10min, 11g / 10min, 11.5g / 10min or 12 g / 10min; the elastic modulus of the PLA is preferably 3000-4000 MPa, specifically 3000 MPa, 3022 MPa, 3100 MPa, 3200 MPa, 3300 MPa, 3400 MPa, 3500 MPa, 3600 MPa, 3700 MPa, 3800 MPa, 3900 MPa or 4000 MPa; the melt index of the PBAT at a temperature of 190°C and a load of 2.16 kg is preferably 3-5 g / 10min, specifically 3 g / 10min, 3.1 g / 10min, 3.3 g / 10min, 3.7 g / 10min, 3.9 g / 10min, 4.1 g / 10min, 4.8 g / 10min, 4.9 g / 10min, 4.9 g / 10min, 4.8 ... .2g / 10min, 3.3g / 10min, 3.4g / 10min, 3.5g / 10min, 3.6g / 10min, 3.7g / 10min, 3.8g / 10min, 3.9g / 10min, 4g / 10min, 4.1g / 1 0min, 4.2g / 10min, 4.3g / 10min, 4.4g / 10min, 4.5g / 10min, 4.6g / 10min, 4.7g / 10min, 4.8g / 10min, 4.9g / 10min or 5g / 10min.

[0037] In the biodegradable packaging material provided by the present invention, in the outer layer components, the mass ratio of talc, PLA and PBAT is (10-20):5:(75-85); wherein the mass ratio of talc to PLA can be specifically 10:5, 11:5, 12:5, 13:5, 14:5, 15:5, 16:5, 17:5, 18:5, 19:5 or 20:5; the mass ratio of PBAT to PLA can be specifically 75:5, 76:5, 77:5, 78:5, 79:5, 80:5, 81:5, 82:5, 83:5, 84:5 or 85:5.

[0038] In the biodegradable packaging material provided by the present invention, the mass ratio of the inner layer, the middle layer and the outer layer is preferably 1:(1-1.5):(0.8-1.2); wherein the mass ratio of the inner layer to the middle layer may specifically be 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45 or 1:1.5; the mass ratio of the inner layer to the outer layer may specifically be 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15 or 1:1.2.

[0039] In the biodegradable packaging material provided by the present invention, the thickness of the biodegradable packaging material is preferably 40 to 80 μm, specifically 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm or 80 μm.

[0040] In the biodegradable packaging material provided by the present invention, the biodegradable packaging material is preferably a biodegradable courier bag.

[0041] The biodegradable packaging material provided by the present invention can also be optionally added with various additives to achieve desired properties, depending on the actual situation. For example, antioxidants can be added to improve the material's aging properties; pigments can be added to change the material's color; and epoxy chain extenders can be added to increase the material's tensile strength.

[0042] The present invention also provides a method for preparing the biodegradable packaging material described in the above technical solution, comprising the following steps:

[0043] a) Prepare inner layer masterbatch, middle layer masterbatch and outer layer masterbatch;

[0044] b) using the inner layer masterbatch, the middle layer masterbatch and the outer layer masterbatch as raw materials, performing multi-layer co-extrusion blown film to obtain a biodegradable packaging material.

[0045] In the preparation method provided by the present invention, in step a), the components of the inner layer masterbatch include PCL-PPC-PCL block copolymer, PBAT and calcium carbonate. The specific component ratios and parameter indicators are consistent with the inner layer components described above and are not repeated here. The inner layer masterbatch is preferably prepared according to the following steps:

[0046] a1) melt-blending PCL-PPC-PCL block copolymer, PBAT and calcium carbonate in proportion, and granulating to obtain an inner layer masterbatch.

[0047] In the above-mentioned inner layer masterbatch preparation step provided by the present invention, the PCL-PPC-PCL block copolymer is prepared according to the following steps:

[0048] In the presence of a catalyst, PPC diol (polypropylene carbonate diol) and ε-caprolactone undergo polymerization reaction in a solvent to obtain a PCL-PPC-PCL block copolymer.

[0049] In the preparation step of the PCL-PPC-PCL block copolymer provided by the present invention, the catalyst is preferably stannous octoate; the number average molecular weight of the PPC diol is preferably 2000-5000 g / mol, specifically 2000 g / mol, 2100 g / mol, 2200 g / mol, 2300 g / mol, 2400 g / mol, 2500 g / mol, 2600 g / mol, 2700 g / mol, 2800 g / mol, 2900 g / mol, 3000 g / mol, 3100 g / mol, 3200 g / mol, 3300 g / mol, 3400 g / mol, 3500 g / mol, 3600 g / mol, 3700 g / mol, 3800 g / mol, 3900 g / mol, 4000 g / mol, 4100 g / mol, 4200 g / mol, 4300 g / mol, 4400 g / mol, 4500 g / mol, 4600 g / mol, 4700 g / mol, 4800 g / mol, 4900 g / mol, 5000 g / mol, 5100 g / mol, 5200 g / mol, 5300 g / mol, 5400 g / mol, 5500 g / mol, 5600 g / mol, 5700 g / mol, 5800 g / mol, 5900 g / mol, 6000 g / mol, 6100 g / mol, 6200 g / mol, 6300 g / mol, 6400 g / mol, 6500 g / mol, 6600 g / mol, 6700 g / mol, 6800 g / mol, 6900 g / 00g / mol, 3300g / mol, 3400g / mol, 3500g / mol, 3600g / mol, 3700g / mol, 3800g / mol, 3900g / mol, 4000g / mol, 4100g / mol, 4200g / mol, 4300g / mol, 4400g / mol, 4500g / mol, 4600g / mol, 4700g / mol, 4800g / mol, 4900g / mol or 5000g / mol; the carbonate content of the PPC diol is preferably The molar ratio of the PPC diol, ε-caprolactone and the catalyst is preferably (60-70):2630:(5-10), wherein the PPC diol and ε-caprolactone are preferably 20-60wt%, specifically 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, 32wt%, 34wt%, 36wt%, 38wt%, 40wt%, 42wt%, 44wt%, 46wt%, 48wt%, 50wt%, 52wt%, 54wt%, 56wt%, 58wt% or 60wt%. The molar ratio of the catalyst can be specifically 60:2630, 61:2630, 62:2630, 63:2630, 64:2630, 65:2630, 66:2630, 67:2630, 68:2630, 69:2630 or 70:2630, and the molar ratio of the catalyst to ε-caprolactone can be specifically 5:2630, 5.5:2630, 6:2630, 6.5:2630, 7:2630, 7.5:2630, 8:2630, 8.5:2630, 9:2630, 9.5:2630 or 10:2630.

[0050] In the above-mentioned PCL-PPC-PCL block copolymer preparation steps provided by the present invention, the solvent includes but is not limited to toluene; the temperature of the polymerization reaction is preferably 100-150°C, specifically 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C or 150°C; the time of the polymerization reaction is preferably 24-40h, specifically 24h, 25h, 26h, 27h, 28h, 29h, 30h, 31h, 32h, 33h, 34h, 35h, 36h, 37h, 38h, 39h or 40h.

[0051] In the preparation steps of the PCL-PPC-PCL block copolymer provided by the present invention, after the polymerization reaction is completed, the crude product is dissolved in tetrahydrofuran, precipitated with petroleum ether, and then dried to obtain the PCL-PPC-PCL block copolymer.

[0052] In the above-mentioned inner layer masterbatch preparation step provided by the present invention, the PCL-PPC-PCL block copolymer, PBAT and calcium carbonate are preferably premixed first, mixed evenly and then melt blended; the melt blending is preferably carried out in a twin-screw extruder; the temperature of the melt blending is preferably 140 to 165°C, specifically 140°C, 145°C, 150°C, 155°C, 160°C or 165°C.

[0053] In the preparation method provided by the present invention, in step a), the components of the intermediate layer masterbatch include calcium carbonate and PBAT. The specific component ratios and parameter indicators are consistent with the inner layer components described above and are not repeated here. The intermediate layer masterbatch is preferably prepared according to the following steps:

[0054] a2) melt-blending calcium carbonate and PBAT in proportion and granulating to obtain an intermediate layer masterbatch.

[0055] In the above-mentioned intermediate layer masterbatch preparation step provided by the present invention, the specific process of the melt blending and granulation is preferably: first melt the PBAT, then add calcium carbonate to the PBAT melt, and then send the melt to the extruder for extrusion granulation; wherein the melting of the PBAT is preferably carried out in an internal mixer; the melting temperature is preferably 120-140°C, specifically 120°C, 125°C, 130°C, 135°C or 140°C; the melting speed is preferably 50-70r / min, specifically 50r / min, 55r / min, 60r / min, 65r / min or 70r / min; the base temperature of the extruder is preferably 140-165°C, specifically 140°C, 145°C, 150°C, 155°C, 160°C or 165°C.

[0056] In the preparation method provided by the present invention, in step a), the components of the outer layer masterbatch include talc, PLA and PBAT. The specific component ratios and parameter indicators are consistent with the inner layer components described above and are not repeated here. The outer layer masterbatch is preferably prepared according to the following steps:

[0057] a3) melt-blending talcum powder, PLA and PBAT in proportion, and granulating to obtain outer layer masterbatch.

[0058] In the above-mentioned outer layer masterbatch preparation step provided by the present invention, the talc powder, PLA and PBAT are preferably premixed first, mixed evenly and then melt blended; the melt blending is preferably carried out in a twin-screw extruder; the temperature of the melt blending is preferably 140 to 165°C, specifically 140°C, 145°C, 150°C, 155°C, 160°C or 165°C.

[0059] In the preparation method provided by the present invention, in step b), the multi-layer co-extrusion blown film is preferably carried out in a multi-layer blown film machine; the screw temperature of the multi-layer blown film machine is preferably 140-155°C, specifically 140°C, 145°C, 150°C or 155°C; the head temperature of the multi-layer blown film machine is preferably 150-160°C, specifically 150°C, 155°C or 160°C.

[0060] The biodegradable packaging material provided by the technical solution of the present invention has a three-layer composite structure. Through the synergistic effect of the three-layer structure, it can effectively solve the problems of insufficient heat sealing strength, low puncture resistance, high production cost, low production efficiency and other problems of existing biodegradable packaging materials, and has good environmental and economic benefits.

[0061] More specifically, the technical solution of the present invention includes at least the following advantages:

[0062] 1) The inner layer of the biodegradable packaging material mainly serves as a heat seal. This layer uses PBAT as a base material and has good biodegradability. Adding calcium carbonate as a filler can effectively reduce production costs. Adding PCL-PPC-PCL block copolymer can significantly improve the heat seal strength and puncture resistance of this layer, solving the problem of insufficient heat seal strength and puncture resistance after inorganic filling.

[0063] 2) The middle layer of the biodegradable packaging material primarily serves to reduce the overall production cost of the material. It contains only two components: the PBAT base material and the calcium carbonate filler, with the filler accounting for a higher proportion than the inner and outer layers.

[0064] 3) The intermediate layer substrate of the biodegradable packaging material preferably uses PBAT with a high melt index. On the one hand, it can improve the dispersion of a large amount of calcium carbonate filler in the resin, and on the other hand, it solves the problem of inconsistent melt flow rate during multi-layer co-extrusion blown film, which makes film blowing difficult. In addition, PBAT with a high melt index is more affordable, which can further reduce the raw material cost of the biodegradable packaging material.

[0065] 4) Since the middle layer contains a large amount of calcium carbonate filler, a lubricant or the like is often required to achieve uniform mixing when twin-screw processing is used. However, lubricants are prone to precipitation, resulting in a decrease in heat seal strength. Therefore, in the process of producing the middle layer masterbatch of the present invention, while preferably using PBAT with a high melt index, it is preferred to melt the PBAT first and then add the calcium carbonate to the PBAT melt, thereby achieving uniform mixing without the need for adding a lubricant.

[0066] 5) The outer layer of the biodegradable packaging material mainly plays a mechanical support role. This layer also uses PBAT as the base material, adds talcum powder instead of calcium carbonate as the filler material, and adds a certain amount of PLA to increase the overall stiffness of the material, making the production process of the packaging material smoother and more efficient.

[0067] 6) All raw materials used are completely biodegradable, and no chemical reaction occurs during the processing. Therefore, the biodegradable packaging material provided by the present invention is completely biodegradable and has outstanding environmental benefits.

[0068] For the purpose of greater clarity, the present invention is described in detail with reference to the following examples and comparative examples.

[0069] The PBAT used in the following examples and comparative examples of the present invention was purchased from Zhejiang Huafeng Environmental Protection Materials Co., Ltd.; PLA was purchased from Zhejiang Hisun Biomaterials Co., Ltd.; calcium carbonate filler was purchased from Guangxi Hezhou Kelong Powder Co., Ltd.; talc filler was purchased from Liaoning Jinghua New Materials Co., Ltd.; PCL-PPC-PCL block copolymer was homemade in the laboratory, and the specific preparation process is as follows:

[0070] (1) Preparation of PCL-PPC-PCL block copolymer-1: 0.67 mol of PPC diol (number average molecular weight of 4600 g / mol, carbonate content of 24 wt%), 26.3 mol of ε-caprolactone and 0.1 mol of stannous octoate were placed in a reactor, 2.5 L of toluene was added, and the mixture was stirred and reacted at 120°C under nitrogen protection for 40 hours. The toluene was removed by centrifugation to obtain a crude product, which was dissolved in 2.5 L of tetrahydrofuran and then precipitated with 5 L of petroleum ether. The precipitate was dried to obtain a PCL-PPC-PCL block copolymer with a number average molecular weight of 10512 g / mol and a molecular weight distribution of 2.6, which was recorded as PCL-PPC-PCL block copolymer-1.

[0071] (2) Preparation of PCL-PPC-PCL block copolymer-2: 0.67 mol of PPC diol (number average molecular weight of 2100 g / mol, carbonate content of 46 wt%), 26.3 mol of ε-caprolactone and 0.05 mol of stannous octoate were placed in a reactor, 2.5 L of toluene was added, and the mixture was stirred and reacted at 120°C under nitrogen protection for 24 hours. The toluene was removed by centrifugation to obtain a crude product, which was dissolved in 2.5 L of tetrahydrofuran and then precipitated with 5 L of petroleum ether. The precipitate was dried to obtain a PCL-PPC-PCL block copolymer with a number average molecular weight of 8102 g / mol and a molecular weight distribution of 1.8, which was recorded as PCL-PPC-PCL block copolymer-2.

[0072] Example 1

[0073] 0.5 kg of PCL-PPC-PCL block copolymer-1, 4 kg of PBAT-1 (melt index of 3.6 g / 10 min (190°C, 2.16 kg, the same below)) and 0.5 kg of calcium carbonate filler (average particle size of 4 μm, particle size distribution of 2-8 μm) were placed in a blender at a speed of 50 r / min and stirred for 5 minutes; then added to a twin-screw extruder, the temperature was set to 140°C in zone 1, 140°C in zone 2, 145°C in zone 3, 150°C in zone 4, 155°C in zone 5, 160°C in zone 6, 165°C in zone 7, 160°C in zone 8, 160°C in zone 9, 155°C in zone 10, 150°C in zone 11 and 150°C in die head, extruded and granulated to obtain the inner layer masterbatch.

[0074] 3.75 kg of PBAT-2 (melt index of 9.3 g / 10 min) was placed in a 140 ° C internal mixer at a speed of 50 r / min and melt-processed for 3 minutes. 1.25 kg of calcium carbonate filler (average particle size of 4 μm, particle size distribution of 2 to 8 μm) was added and processed for 3 minutes. Then, it was added to a single screw and the temperature was set to 140 ° C in zone 1, 160 ° C in zone 2, 165 ° C in zone 3, and 165 ° C in the die head. Extrusion granulation was performed to obtain the intermediate layer masterbatch.

[0075] 1 kg of talc filler (average particle size of 5 μm, particle size distribution of 3-6.5 μm), 0.25 kg of PLA (melt index of 10.2 g / 10 min, elastic modulus of 3022 MPa) and 3.75 kg of PBAT-1 (melt index of 3.6 g / 10 min) were placed in a blender at a speed of 50 r / min and stirred for 5 minutes; then added to a twin-screw extruder, the temperatures were set to 140° C. in zone 1, 145° C. in zone 2, 150° C. in zone 3, 155° C. in zone 4, 160° C. in zone 5, 165° C. in zone 6, 165° C. in zone 7, 165° C. in zone 8, 160° C. in zone 9, 160° C. in zone 10, 155° C. in zone 11 and 155° C. in the die head, and extruded and granulated to obtain the outer layer masterbatch.

[0076] The outer layer masterbatch, the middle layer masterbatch and the inner layer masterbatch were respectively added to the corresponding three-layer film blowing machine conveying screw. The conveying screw temperature of the film blowing machine was 140°C in zone 1, 150°C in zone 2, 155°C in zone 3, and the head temperature was 155°C. The mass ratio of the three-layer masterbatch was 1:1:1. The film was blown to prepare a biodegradable express bag with a thickness of 60 μm. The performance test is shown in Table 1.

[0077] Example 2

[0078] 0.25 kg of PCL-PPC-PCL block copolymer-2, 4 kg of PBAT-1 (melt index of 3.6 g / 10 min) and 0.75 kg of calcium carbonate filler (average particle size of 4 μm, particle size distribution of 2-8 μm) were placed in a blender at a speed of 50 r / min and stirred for 5 minutes; then added to a twin-screw extruder, the temperature was set to 140°C in zone 1, 140°C in zone 2, 145°C in zone 3, 150°C in zone 4, 155°C in zone 5, 160°C in zone 6, 165°C in zone 7, 160°C in zone 8, 160°C in zone 9, 155°C in zone 10, 150°C in zone 11 and 150°C in die head, and extrusion granulation was performed to obtain the inner layer masterbatch.

[0079] 3 kg of PBAT-2 (melt index of 9.3 g / 10 min) was placed in a 140 ° C internal mixer at a speed of 50 r / min and melt-processed for 3 minutes. 2 kg of calcium carbonate filler (average particle size of 4 μm, particle size distribution of 2 to 8 μm) was added and processed for 3 minutes. Then, it was added to a single screw and the temperature was set to 140 ° C in zone 1, 160 ° C in zone 2, 165 ° C in zone 3, and 165 ° C in the die head. Extrusion granulation was performed to obtain the intermediate layer masterbatch.

[0080] 1 kg of talc filler (average particle size of 5 μm, particle size distribution of 3-6.5 μm), 0.25 kg of PLA (melt index of 10.2 g / 10 min, elastic modulus of 3022 MPa) and 3.75 kg of PBAT-1 (melt index of 3.6 g / 10 min) were placed in a blender at a speed of 50 r / min and stirred for 5 minutes; then added to a twin-screw extruder, the temperatures were set to 140° C. in zone 1, 145° C. in zone 2, 150° C. in zone 3, 155° C. in zone 4, 160° C. in zone 5, 165° C. in zone 6, 165° C. in zone 7, 165° C. in zone 8, 160° C. in zone 9, 160° C. in zone 10, 155° C. in zone 11 and 155° C. in the die head, and extruded and granulated to obtain the outer layer masterbatch.

[0081] The outer layer masterbatch, the middle layer masterbatch and the inner layer masterbatch were respectively added to the corresponding three-layer film blowing machine conveying screw. The conveying screw temperature of the film blowing machine was 140°C in zone 1, 150°C in zone 2, 155°C in zone 3, and the head temperature was 155°C. The mass ratio of the three-layer masterbatch was 1:1:1. The film was blown to prepare a biodegradable express bag with a thickness of 60 μm. The performance test is shown in Table 1.

[0082] Example 3

[0083] 0.5 kg of PCL-PPC-PCL block copolymer-1, 4 kg of PBAT-1 (melt index of 3.6 g / 10 min) and 0.5 kg of calcium carbonate filler (average particle size of 4 μm, particle size distribution of 2-8 μm) were placed in a blender at a speed of 50 r / min and stirred for 5 minutes; then added to a twin-screw extruder, the temperature was set to 140°C in zone 1, 140°C in zone 2, 145°C in zone 3, 150°C in zone 4, 155°C in zone 5, 160°C in zone 6, 165°C in zone 7, 160°C in zone 8, 160°C in zone 9, 155°C in zone 10, 150°C in zone 11 and 150°C in die head, and extruded and granulated to obtain the inner layer masterbatch.

[0084] 3.75 kg of PBAT-2 (melt index of 9.3 g / 10 min) was placed in a 140 ° C internal mixer at a speed of 50 r / min and melt-processed for 3 minutes. 1.25 kg of calcium carbonate filler (average particle size of 4 μm, particle size distribution of 2 to 8 μm) was added and processed for 3 minutes. Then, it was added to a single screw and the temperature was set to 140 ° C in zone 1, 160 ° C in zone 2, 165 ° C in zone 3, and 165 ° C in the die head. Extrusion granulation was performed to obtain the intermediate layer masterbatch.

[0085] 1 kg of talc filler (average particle size of 5 μm, particle size distribution of 3 to 6.5 μm), 0.25 kg of PLA (melt index of 10.2 g / 10 min, elastic modulus of 3022 MPa) and 3.75 kg of PBAT-1 (melt index of 3.6 g / 10 min) were placed in a blender at a speed of 50 r / min and stirred for 5 minutes; then added to a twin-screw extruder, the temperatures were set to 140° C. in zone 1, 145° C. in zone 2, 150° C. in zone 3, 155° C. in zone 4, 160° C. in zone 5, 165° C. in zone 6, 165° C. in zone 7, 165° C. in zone 8, 160° C. in zone 9, 160° C. in zone 10, 155° C. in zone 11 and 155° C. in the die head, and extruded and granulated to obtain an outer layer masterbatch.

[0086] The outer layer masterbatch, the middle layer masterbatch and the inner layer masterbatch were respectively added to the corresponding three-layer film blowing machine conveying screw. The conveying screw temperature of the film blowing machine was 140°C in zone 1, 150°C in zone 2, 155°C in zone 3, and the head temperature was 155°C. The mass ratio of the three-layer masterbatch was 1:1:1. The film was blown to prepare a biodegradable express bag with a thickness of 50 μm. The performance test is shown in Table 1.

[0087] Comparative Example 1

[0088] 4.5 kg of PBAT-1 (melt index of 3.6 g / 10 min) and 0.5 kg of calcium carbonate filler (average particle size of 4 μm, particle size distribution of 2 to 8 μm) were placed in a mixer at a speed of 50 r / min and stirred for 5 minutes; then added to a twin-screw extruder, the temperature was set to 140°C in zone 1, 140°C in zone 2, 145°C in zone 3, 150°C in zone 4, 155°C in zone 5, 160°C in zone 6, 165°C in zone 7, 160°C in zone 8, 160°C in zone 9, 155°C in zone 10, 150°C in zone 11, and 150°C in die head, and extruded and granulated to obtain the inner layer masterbatch.

[0089] 3.75 kg of PBAT-2 (melt index of 9.3 g / 10 min) was placed in a 140 ° C internal mixer at a speed of 50 r / min and melt-processed for 3 minutes. 1.25 kg of calcium carbonate filler (average particle size of 4 μm, particle size distribution of 2 to 8 μm) was added and processed for 3 minutes. Then, it was added to a single screw and the temperature was set to 140 ° C in zone 1, 160 ° C in zone 2, 165 ° C in zone 3, and 165 ° C in the die head. Extrusion granulation was performed to obtain the intermediate layer masterbatch.

[0090] 1 kg of talc filler (average particle size of 5 μm, particle size distribution of 3 to 6.5 μm), 0.25 kg of PLA (melt index of 10.2 g / 10 min, elastic modulus of 3022 MPa) and 3.75 kg of PBAT-1 (melt index of 3.6 g / 10 min) were placed in a blender at a speed of 50 r / min and stirred for 5 minutes; then added to a twin-screw extruder, the temperatures were set to 140° C. in zone 1, 145° C. in zone 2, 150° C. in zone 3, 155° C. in zone 4, 160° C. in zone 5, 165° C. in zone 6, 165° C. in zone 7, 165° C. in zone 8, 160° C. in zone 9, 160° C. in zone 10, 155° C. in zone 11 and 155° C. in the die head, and extruded and granulated to obtain an outer layer masterbatch.

[0091] The outer layer masterbatch, the middle layer masterbatch and the inner layer masterbatch were respectively added to the corresponding three-layer film blowing machine conveying screw. The conveying screw temperature of the film blowing machine was 140°C in zone 1, 150°C in zone 2, 155°C in zone 3, and the head temperature was 155°C. The mass ratio of the three-layer masterbatch was 1:1:1. The film was blown to prepare a biodegradable express bag with a thickness of 60 μm. The performance test is shown in Table 1.

[0092] Comparative Example 2

[0093] 0.25 kg of PCL-PPC-PCL block copolymer-2, 4 kg of PBAT-1 (melt index of 3.6 g / 10 min) and 0.75 kg of calcium carbonate filler (average particle size of 4 μm, particle size distribution of 2-8 μm) were placed in a blender at a speed of 50 r / min and stirred for 5 minutes; then added to a twin-screw extruder, the temperature was set to 140°C in zone 1, 140°C in zone 2, 145°C in zone 3, 150°C in zone 4, 155°C in zone 5, 160°C in zone 6, 165°C in zone 7, 160°C in zone 8, 160°C in zone 9, 155°C in zone 10, 150°C in zone 11 and 150°C in die head, and extrusion granulation was performed to obtain the inner layer masterbatch.

[0094] 3 kg of PBAT-1 (melt index of 3.6 g / 10 min) was placed in a 140 ° C internal mixer at a speed of 50 r / min and melt-processed for 3 minutes. 2 kg of calcium carbonate filler (average particle size of 4 μm, particle size distribution of 2 to 8 μm) was added and processed for 3 minutes. Then, it was added to a single screw and the temperature was set to 140 ° C in zone 1, 160 ° C in zone 2, 165 ° C in zone 3, and 165 ° C in the die head. Extrusion granulation was performed to obtain the intermediate layer masterbatch.

[0095] 1 kg of talc filler (average particle size of 5 μm, particle size distribution of 3-6.5 μm), 0.25 kg of PLA (melt index of 10.2 g / 10 min, elastic modulus of 3022 MPa) and 3.75 kg of PBAT-1 (melt index of 3.6 g / 10 min) were placed in a blender at a speed of 50 r / min and stirred for 5 minutes; then added to a twin-screw extruder, the temperatures were set to 140° C. in zone 1, 145° C. in zone 2, 150° C. in zone 3, 155° C. in zone 4, 160° C. in zone 5, 165° C. in zone 6, 165° C. in zone 7, 165° C. in zone 8, 160° C. in zone 9, 160° C. in zone 10, 155° C. in zone 11 and 155° C. in the die head, and extruded and granulated to obtain the outer layer masterbatch.

[0096] The outer layer masterbatch, the middle layer masterbatch and the inner layer masterbatch were respectively added to the corresponding three-layer film blowing machine conveying screw. The conveying screw temperature of the film blowing machine was 140°C in zone 1, 150°C in zone 2, 155°C in zone 3, and the head temperature was 155°C. The mass ratio of the three-layer masterbatch was 1:1:1. The melt fluidity of the middle layer was poor during film blowing. The surface of the prepared biodegradable express bag was uneven, and corrugations appeared on the film surface. The film thickness was 60 μm. The performance test is shown in Table 1.

[0097] Table 1 Performance test data of biodegradable courier bags prepared in Example

[0098]

[0099] It can be seen from Table 1 that after adding PCL-PPC-PCL block copolymer, the heat sealing strength of the biodegradable courier bags is greater than 15N / 15mm, which meets the current requirements for heat sealing strength of courier bags; the heat sealing strength of Comparative Example 1 without adding PCL-PPC-PCL block copolymer is significantly reduced, indicating that the method proposed in the present invention can effectively improve the heat sealing performance of biodegradable courier bags; in Comparative Example 2, since the three layers use PBAT with the same melt index, the melt fluidity of each layer of modified material is too different, making film blowing difficult, and the mechanical properties of the composite film are low, and the puncture strength is low and unstable.

[0100] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A biodegradable packaging material, characterized in that: The biodegradable packaging material comprises an inner layer, a middle layer and an outer layer in contact with each other in sequence; The inner layer comprises a PCL-PPC-PCL block copolymer, PBAT, and calcium carbonate, wherein the melt index of the PBAT at a temperature of 190° C. and a load of 2.16 kg is 3 to 5 g / 10 min, and the mass ratio of the PCL-PPC-PCL block copolymer, PBAT, and calcium carbonate is (5 to 10):80:(10 to 15); The intermediate layer comprises calcium carbonate and PBAT, wherein the melt index of the PBAT at a temperature of 190° C. and a load of 2.16 kg is 8 to 12 g / 10 min, and the mass ratio of the calcium carbonate to the PBAT is (25 to 40):(60 to 75); The outer layer comprises talc, PLA and PBAT, wherein the melt index of the PBAT at a temperature of 190° C. and a load of 2.16 kg is 3 to 5 g / 10 min, and the mass ratio of the talc, PLA and PBAT is (10 to 20):5:(75 to 85).

2. The biodegradable packaging material according to claim 1, characterized in that: In the inner layer components, the number average molecular weight of the PCL-PPC-PCL block copolymer is 8000-13000 g / mol, and the molecular weight distribution is 1.8-3; the particle size of the calcium carbonate is 2-8 μm.

3. The biodegradable packaging material according to claim 1, characterized in that: In the intermediate layer component, the particle size of the calcium carbonate is 2 to 8 μm.

4. The biodegradable packaging material according to claim 1, characterized in that: In the outer layer components, the particle size of the talc powder is 3 to 7 μm; the melt index of the PLA at a temperature of 190° C. and a load of 2.16 kg is 3 to 12 g / 10 min; and the elastic modulus of the PLA is 3000 to 4000 MPa.

5. The biodegradable packaging material according to claim 1, characterized in that: The mass ratio of the inner layer, the middle layer and the outer layer is 1:(1-1.5):(0.8-1.2).

6. The biodegradable packaging material according to claim 1, characterized in that: The thickness of the biodegradable packaging material is 40 to 80 μm.

7. The biodegradable packaging material according to claim 1, characterized in that: The biodegradable packaging material is a biodegradable courier bag.

8. A method for preparing the biodegradable packaging material according to any one of claims 1 to 7, characterized in that: The following steps are involved: a) Prepare inner layer masterbatch, middle layer masterbatch and outer layer masterbatch; The components of the inner layer masterbatch include PCL-PPC-PCL block copolymer, PBAT and calcium carbonate, and the mass ratio of the PCL-PPC-PCL block copolymer, PBAT and calcium carbonate is (5-10):80:(10-15); The components of the intermediate layer masterbatch include calcium carbonate and PBAT, and the mass ratio of the calcium carbonate to PBAT is (25-40): (60-75); The outer layer masterbatch comprises talc, PLA and PBAT, wherein the mass ratio of talc, PLA and PBAT is (10-20):5:(75-85); b) using the inner layer masterbatch, the middle layer masterbatch and the outer layer masterbatch as raw materials, performing multi-layer co-extrusion blown film to obtain a biodegradable packaging material.

9. The preparation method according to claim 8, characterized in that The inner layer masterbatch is prepared according to the following steps: a1) melt-blending PCL-PPC-PCL block copolymer, PBAT and calcium carbonate in proportion, and granulating to obtain an inner layer masterbatch; The intermediate layer masterbatch is prepared according to the following steps: a2) melt-blending calcium carbonate and PBAT in proportion, and granulating to obtain an intermediate layer masterbatch; The outer layer masterbatch is prepared according to the following steps: a3) melt-blending talcum powder, PLA and PBAT in proportion, and granulating to obtain outer layer masterbatch.

10. The preparation method according to claim 9, characterized in that In step a1), the PCL-PPC-PCL block copolymer is prepared according to the following steps: In the presence of a catalyst, PPC diol and ε-caprolactone undergo polymerization reaction in a solvent to obtain a PCL-PPC-PCL block copolymer.

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