A special masterbatch for PLA degradable film and its application

Abstract

The present invention discloses a masterbatch specifically for PLA biodegradable film. The preparation method comprises the following steps: subjecting calcium oxide to a digestion reaction and a carbonation reaction with an aqueous solution containing dissolved lignin sulfonate, followed by modification by adding alkyl glucoside and glycidyl methacrylate, followed by sequential addition of activated calcium carbonate powder, PBAT resin, and a mixed dispersant to obtain a premix, and finally, allowing the mixture to stand for extrusion and granulation to obtain the masterbatch specifically for PLA biodegradable film. The lignin sulfonate, alkyl glucoside, and glycidyl methacrylate added during the preparation process exhibit a synergistic effect, effectively improving the compatibility of PBAT and PLA, enhancing the toughness and transparency of the film, and reducing the undesirable phenomena of fisheyes and crystal points, thus possessing considerable promotional value.

Description

Technical Field

[0001] The present invention relates to a masterbatch preparation technology, in particular to a special masterbatch for PLA degradable film and application thereof. Background Art

[0002] In recent years, plastic waste has had a devastating impact on the environment we rely on. The development of biodegradable plastics is urgent. Biodegradable plastics, such as polylactic acid (PLA) and polybutylene adipate / terephthalate (PBAT), are gradually gaining attention.

[0003] While PLA resin has high strength, it has low toughness, poor impact and tear resistance, and cannot withstand temperatures above 50°C. Therefore, the scope of PLA's use is somewhat limited. On the other hand, PBAT is an aliphatic-aromatic copolyester formed by the polymerization of diols and dibasic acids. It has excellent flexibility and film-forming properties, but its low strength and low Young's modulus have also limited its popularity and use. For this reason, many researchers have prepared PLA and PBAT into blends, but the compatibility between the two during the blending process is poor, which cannot meet the requirements of various plastic preparation processes. In particular, problems such as crystal points and fish eyes are very likely to occur in blown film products.

[0004] To improve the compatibility between PLA and PBAT, some researchers have proposed using glycidyl methacrylate as a compatibilizer. However, this approach presents numerous challenges in actual production. When the glycidyl methacrylate dosage is too high, it tends to self-polymerize in the molten plastic, leading to excessive cross-linking in the later stages of molding. This not only fails to provide any compatibility, but also causes melt instability and susceptibility to breakage during film blowing. When the glycidyl methacrylate dosage is too low, the compatibility issue remains unresolved, and the problems of crystal points and fisheyes in film blowing remain unresolved.

[0005] Filler masterbatches used in blown film biodegradable plastics are typically a new type of masterbatch made by combining calcium carbonate as the filler and the highly fluid PBAT resin as the carrier. As mentioned above, due to compatibility issues between PBAT and PLA, this type of masterbatch cannot be used directly as a filler in PLA resin. Furthermore, as the calcium carbonate particle size decreases, the filler's dispersibility decreases dramatically, contributing to the frequent occurrence of crystallization and fisheye phenomena. Furthermore, as the filler particle size increases, the transparency and mechanical properties of the biodegradable plastic also deteriorate significantly.

[0006] CN114685954A discloses a biodegradable masterbatch for tableware and its preparation method. The masterbatch comprises the following raw materials: PLA, PBS, a natural filler, a wetting agent, and other reagents. The natural filler is a mixture of leaf fiber, wood fiber, and a filler surface modifier. However, leaf fiber and wood fiber are fibrous fillers, which can easily cause film tearing during the film blowing process.

[0007] CN113072786A discloses a nano-calcium carbonate masterbatch, its preparation method, and its application in strengthening and toughening UPVC. The nano-calcium carbonate masterbatch is made from coated modified nano-calcium carbonate, PVC resin, a calcium-zinc composite stabilizer, a polyurethane prepolymer, polytetrahydrofuran polyol, a lubricant, and an ethylene-vinyl acetate copolymer elastomer. However, the nano-calcium carbonate masterbatch is limited to the PVC field and is not applicable to degradable plastics.

[0008] CN114181463A discloses an ultrafine nano-calcium carbonate masterbatch, a pearlescent film, and a method for preparing the same. The masterbatch is primarily composed of first and second homopolypropylenes, first and second dispersing aids, first and second lubricants, an antioxidant, and the remainder of modified nano-calcium carbonate, wherein the modified nano-calcium carbonate is surface-modified with ethylene glycol. The pearlescent film's surface layer is formed from homopolypropylene and an anti-blocking agent masterbatch, while the core layer is formed from homopolypropylene, an ultrafine nano-calcium carbonate masterbatch, and a white masterbatch. The inner layer is also formed from homopolypropylene. Similarly, the nano-calcium carbonate masterbatch prepared using this technology uses polypropylene as a carrier, making it unsuitable for use in the field of degradable plastics.

[0009] In summary, in the field of PLA film degradable plastics, it is urgent to develop a suitable masterbatch technology to avoid various crystal point and mechanical property problems caused by the film blowing molding process. Summary of the Invention

[0010] The purpose of the present invention is to overcome at least one deficiency of the prior art and provide a PLA degradable film-specific masterbatch and its application.

[0011] The technical solution adopted by the present invention is:

[0012] In a first aspect, the present invention provides a PLA biodegradable film masterbatch, the preparation method of which comprises the following steps:

[0013] 1) subjecting calcium oxide to a digestion reaction with an aqueous solution of dissolved lignin sulfonate, and then removing impurities and aging to obtain a calcium hydroxide suspension;

[0014] 2) subjecting the calcium hydroxide suspension obtained in step 1) to a carbonation reaction with CO2 gas to obtain a nano-calcium carbonate suspension;

[0015] 3) adding alkyl glucoside and glycidyl methacrylate to the nano-calcium carbonate suspension obtained in step 2) to carry out a modification reaction, and then dehydrating, drying and pulverizing in sequence to obtain activated calcium carbonate powder;

[0016] 4) heating and stirring the activated calcium carbonate powder obtained in step 3) and the PBAT resin to mix uniformly, then adding a mixed dispersant, discharging the material when the temperature reaches 94.5-95.5° C. to obtain a premix;

[0017] 5) The premix obtained in step 4) is allowed to stand for 24 to 48 hours, and then extruded and granulated to obtain the PLA degradable film masterbatch.

[0018] In some examples, the lignin sulfonate in step 1) is selected from at least one of sodium lignin sulfonate and calcium lignin sulfonate.

[0019] In some examples, the amount of the lignin sulfonate is 0.1 to 0.2% by mass of the calcium oxide.

[0020] In some examples, the alkyl glucoside in step 3) is at least one selected from alkyl glucosides having 12 to 16 alkyl carbon atoms.

[0021] In some examples, the amount of the alkyl glucoside is 1-3% of the mass of the nano-calcium carbonate, and the concentration of the glycidyl methacrylate in the nano-calcium carbonate suspension is 100-500 ppm.

[0022] In some examples, the mixed dispersant in step 4) is composed of maleic anhydride grafted polyethylene, montan wax, and an auxiliary dispersant, wherein the auxiliary dispersant is selected from at least one of titanate coupling agent, aluminate coupling agent, vinyl bisstearamide, PE wax, stearic acid, zinc stearate, calcium stearate, and citrate.

[0023] In some examples, the mass proportion of maleic anhydride grafted polyethylene in the mixed dispersant is 10-20%, the mass proportion of montan wax is 15-18%, and the rest is auxiliary dispersant.

[0024] In some examples, the mass ratio of activated calcium carbonate powder to PBAT in step 4) is (7-8): (3-2), and the mass amount of the mixed dispersant is 2-4% of the total mass of the calcium carbonate powder and PBAT resin.

[0025] In some examples, the modification reaction temperature in step 3) is 50-90° C., and the modification reaction time is 1-2 hours.

[0026] In a second aspect, the present invention provides a blown film degradable plastic, to which the aforementioned PLA degradable film-specific masterbatch is added.

[0027] The beneficial effects of the present invention are:

[0028] The synergistic effect between the lignin sulfonate and alkyl glucoside in this invention enables the nano-calcium carbonate powder to achieve excellent dispersion properties. The synergistic effect between the alkyl glucoside and glycidyl methacrylate effectively improves the compatibility of PBAT and PLA. The nano-calcium carbonate powder prepared in this manner can be directly added to the PLA film formulation after preparing the masterbatch, effectively improving the film's toughness and transparency while reducing the undesirable effects of fisheyes and crystals. DETAILED DESCRIPTION

[0029] The following disclosure provides many different embodiments or examples for implementing different solutions of the present invention.

[0030] Example 1

[0031] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0032] 1) calcining limestone in a vertical kiln at 900-1000° C., digesting the resulting lime with 40° C. tap water containing 0.2% (calculated as calcium oxide) sodium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:5; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing through 80-, 120-, and 200-mesh vibrating screens, followed by aging for 72 hours;

[0033] 2) Adjust the concentration of the aged calcium hydroxide suspension to 10%, adjust the temperature to 23°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2500m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 16.76m 2 / g of nano calcium carbonate suspension;

[0034] 3) transporting the nano-calcium carbonate suspension to a surface activation kettle, heating the temperature to 70° C., adding 2% dodecyl glucoside and 100 ppm glycidyl methacrylate based on the dry weight of the nano-calcium carbonate, and fully reacting for 1.5 hours; then dehydrating, drying, and pulverizing the modified nano-calcium carbonate suspension in sequence to obtain the activated calcium carbonate powder of the present invention;

[0035] 4) The activated calcium carbonate powder and PBAT resin are thoroughly mixed in a high-speed mixer at a ratio of 8:2. The mixture is dehydrated and stirred at 85°C for 25 minutes. Then, a mixed dispersant (3% by weight of the total weight of the calcium carbonate powder and PBAT resin) is added. The mixed dispersant composition is 10% maleic anhydride-grafted polyethylene, 18% montan wax, 50% zinc stearate, and 22% stearic acid. Continue high-speed stirring until the temperature reaches 95°C to obtain a premix.

[0036] 5) After the premix is allowed to stand for 24 hours, it is extruded and granulated through a twin-screw extruder, and the temperature settings of each section of the extruder are sequentially 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) to obtain the PLA degradable film masterbatch of the present invention.

[0037] Example 2

[0038] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0039] 1) calcining limestone in a vertical kiln at 900-1000° C., digesting the resulting lime with 60° C. tap water containing 0.1% (calculated as calcium oxide) sodium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:6; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing through 80-, 120-, and 200-mesh vibrating screens, followed by aging for 36 hours;

[0040] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 26°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2000m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 14.12m 2 / g of nano calcium carbonate suspension;

[0041] 3) transporting the nano-calcium carbonate suspension to a surface activation kettle, heating the temperature to 90° C., adding 1% dodecyl glucoside and 300 ppm glycidyl methacrylate based on the dry weight of the nano-calcium carbonate, and fully reacting for 1.5 hours; then dehydrating, drying, and pulverizing the modified nano-calcium carbonate suspension in sequence to obtain the activated calcium carbonate powder of the present invention;

[0042] 4) The activated calcium carbonate powder and PBAT resin are thoroughly mixed in a high-speed mixer at a ratio of 8:2. The mixture is dehydrated and stirred at 85°C for 25 minutes. Then, a mixed dispersant (2% by weight of the total weight of the calcium carbonate powder and PBAT resin) is added. The mixed dispersant composition is 15% maleic anhydride-grafted polyethylene, 15% montan wax, 40% zinc stearate, and 30% PE wax. Continue high-speed stirring until the temperature reaches 95°C to obtain a premix.

[0043] The premix is allowed to stand for 48 hours and then extruded into pellets through a twin-screw extruder. The temperature of each section of the extruder is set to 160° C.-165° C.-170° C.-170° C.-175° C.-175° C.-180° C.-180° C.-185° C.-180° C. (die temperature) in sequence to obtain the PLA degradable film masterbatch of the present invention.

[0044] Example 3

[0045] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0046] 1) calcining limestone in a vertical kiln at 900-1000° C., subjecting the resulting limestone to a digestion reaction with 50° C. tap water containing 0.15% (calculated as calcium oxide content) calcium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:4; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing it through 80-, 120-, and 200-mesh vibrating screens in sequence, followed by aging for 48 hours;

[0047] 2) Adjust the concentration of the aged calcium hydroxide suspension to 10%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 3000m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 19.03m 2 / g of nano calcium carbonate suspension;

[0048] 3) transporting the nano-calcium carbonate suspension to a surface activation kettle, heating the temperature to 50° C., adding 3% dodecyl glucoside and 500 ppm glycidyl methacrylate based on the dry weight of the nano-calcium carbonate and fully reacting for 2 hours; then dehydrating, drying and pulverizing the modified nano-calcium carbonate suspension in sequence to obtain the activated calcium carbonate powder of the present invention;

[0049] 4) The activated calcium carbonate powder and PBAT resin are thoroughly mixed in a high-speed mixer at a ratio of 8:2. The mixture is dehydrated and stirred at 85°C for 25 minutes. Then, a mixed dispersant (4% by weight of the total weight of the calcium carbonate powder and PBAT resin) is added. The mixed dispersant composition is 20% maleic anhydride-grafted polyethylene, 16% montan wax, 30% EBS dispersant, and 34% aluminate coupling agent. Continue high-speed stirring until the temperature reaches 95°C, and discharge to obtain a premix.

[0050] 5) After the premix is allowed to stand for 24 hours, it is extruded and granulated through a twin-screw extruder, and the temperature settings of each section of the extruder are sequentially 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) to obtain the PLA degradable film masterbatch of the present invention.

[0051] Example 4

[0052] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0053] 1) calcining limestone in a vertical kiln at 900-1000° C., subjecting the resulting limestone to a digestion reaction with 50° C. tap water containing 0.15% (calculated as calcium oxide content) calcium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:4; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing it through 80-, 120-, and 200-mesh vibrating screens in sequence, followed by aging for 48 hours;

[0054] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 17.46m 2 / g of nano calcium carbonate suspension;

[0055] 3) transporting the nano-calcium carbonate suspension to a surface activation kettle, heating the temperature to 65° C., adding 2.5% dodecyl glucoside and 400 ppm glycidyl methacrylate based on the dry weight of the nano-calcium carbonate and fully reacting for 2 hours; then dehydrating, drying and pulverizing the modified nano-calcium carbonate suspension in sequence to obtain the activated calcium carbonate powder of the present invention;

[0056] 4) The activated calcium carbonate powder and PBAT resin are thoroughly mixed in a high-speed mixer at a ratio of 8:2. The mixture is dehydrated and stirred at 85°C for 25 minutes. A mixed dispersant (2.5% by weight of the total weight of the calcium carbonate powder and PBAT resin) is then added. The mixed dispersant composition is 12% maleic anhydride-grafted polyethylene, 15% montan wax, 28% PE wax, and 45% titanate coupling agent. The mixture is stirred at high speed until the temperature reaches 95°C and the mixture is discharged to obtain a premix.

[0057] 5) After the premix is allowed to stand for 24 hours, it is extruded and granulated through a twin-screw extruder, and the temperature settings of each section of the extruder are sequentially 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) to obtain the PLA degradable film masterbatch of the present invention.

[0058] Example 5

[0059] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0060] 1) calcining limestone in a vertical kiln at 900-1000° C., subjecting the resulting limestone to a digestion reaction with 50° C. tap water containing 0.15% (calculated as calcium oxide content) calcium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:4; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing it through 80-, 120-, and 200-mesh vibrating screens in sequence, followed by aging for 48 hours;

[0061] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 17.46m 2 / g of nano calcium carbonate suspension;

[0062] 3) transporting the nano-calcium carbonate suspension to a surface activation kettle, heating the temperature to 65° C., adding 2.5% dodecyl glucoside and 400 ppm glycidyl methacrylate based on the dry weight of the nano-calcium carbonate and fully reacting for 2 hours; then dehydrating, drying and pulverizing the modified nano-calcium carbonate suspension in sequence to obtain the activated calcium carbonate powder of the present invention;

[0063] 4) The activated calcium carbonate powder and PBAT resin were thoroughly mixed in a high-speed mixer at a ratio of 7:3. The mixture was dehydrated and stirred at 85°C for 25 minutes. Then, a mixed dispersant (2.5% by weight, based on the total weight of the calcium carbonate powder and PBAT resin) was added. The mixed dispersant composition was 12% maleic anhydride-grafted polyethylene, 15% montan wax, 28% PE wax, and 45% titanate coupling agent. The mixture was stirred at high speed until the temperature reached 95°C and discharged to obtain a premix.

[0064] 5) After the premix is allowed to stand for 24 hours, it is extruded and granulated through a twin-screw extruder, and the temperature settings of each section of the extruder are sequentially 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) to obtain the PLA degradable film masterbatch of the present invention.

[0065] Example 6

[0066] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0067] 1) calcining limestone in a vertical kiln at 900-1000° C., subjecting the resulting limestone to a digestion reaction with 50° C. tap water containing 0.15% (calculated as calcium oxide content) calcium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:4; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing it through 80-, 120-, and 200-mesh vibrating screens in sequence, followed by aging for 48 hours;

[0068] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 17.46m 2 / g of nano calcium carbonate suspension;

[0069] 3) transporting the nano-calcium carbonate suspension to a surface activation kettle, heating the temperature to 65° C., adding 2.5% dodecyl glucoside and 400 ppm glycidyl methacrylate based on the dry weight of the nano-calcium carbonate and fully reacting for 2 hours; then dehydrating, drying and pulverizing the modified nano-calcium carbonate suspension in sequence to obtain the activated calcium carbonate powder of the present invention;

[0070] 4) The activated calcium carbonate powder and PBAT resin were thoroughly mixed in a high-speed mixer at a ratio of 7.5:2.5. The mixture was dehydrated and stirred at 85°C for 25 minutes. Then, a mixed dispersant (2.5% by weight, based on the total weight of the calcium carbonate powder and PBAT resin) was added. The mixed dispersant composition was 12% maleic anhydride-grafted polyethylene, 15% montan wax, 28% PE wax, and 45% titanate coupling agent. The mixture was stirred at high speed until the temperature reached 95°C and discharged to obtain a premix.

[0071] 5) After the premix is allowed to stand for 24 hours, it is extruded and granulated through a twin-screw extruder, and the temperature settings of each section of the extruder are sequentially 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) to obtain the PLA degradable film masterbatch of the present invention.

[0072] Comparative Example 1 (digestion reaction in step 1 without adding lignin sulfonate)

[0073] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0074] 1) The limestone is calcined in a vertical kiln at 900-1000°C, and the obtained lime is digested with 50°C tap water, with the mass ratio of calcium oxide to water being controlled at 1:4; the tail gas from the vertical kiln calcination is purified and reserved; the resulting calcium hydroxide suspension is sequentially passed through 80, 120, and 200 mesh vibrating screens for impurity removal, and aged for 48 hours;

[0075] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction was completed (pH ≤ 7.0), the BET specific surface area was obtained to be 17.09m 2 / g of nano calcium carbonate suspension;

[0076] 3) The nano-calcium carbonate suspension was transported to a surface activation kettle, heated to 65° C., and 2.5% dodecyl glucoside and 400 ppm glycidyl methacrylate were added based on the dry weight of the nano-calcium carbonate and fully reacted for 2 hours; the modified nano-calcium carbonate suspension was then dehydrated, dried, and pulverized in sequence to obtain the activated calcium carbonate powder of this comparative example;

[0077] 4) The nano-calcium carbonate powder and PBAT resin are thoroughly mixed in a high-speed mixer at a ratio of 8:2. The mixture is dehydrated and stirred at 85°C for 25 minutes. A mixed dispersant (2.5% by weight of the total weight of the calcium carbonate powder and PBAT resin) is then added. The mixed dispersant composition is 12% maleic anhydride-grafted polyethylene, 15% montan wax, 28% PE wax, and 45% titanate coupling agent. The mixture is stirred at high speed until the temperature reaches 95°C, and the mixture is discharged to obtain a premix.

[0078] 5) After the premix was allowed to stand for 24 hours, it was extruded into pellets through a twin-screw extruder, and the temperature of each section of the extruder was set to 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) in sequence to obtain the PLA degradable film masterbatch of this comparative example.

[0079] Comparative Example 2 (modification reaction in step 3 without adding glycidyl methacrylate)

[0080] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0081] 1) calcining limestone in a vertical kiln at 900-1000° C., subjecting the resulting limestone to a digestion reaction with 50° C. tap water containing 0.15% (calculated as calcium oxide content) calcium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:4; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing it through 80-, 120-, and 200-mesh vibrating screens in sequence, followed by aging for 48 hours;

[0082] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 17.40m 2 / g of nano calcium carbonate suspension;

[0083] 3) The nano-calcium carbonate suspension was transported to a surface activation kettle, heated to 65° C., and 2.5% dodecyl glucoside, based on the dry weight of the nano-calcium carbonate, was added and fully reacted for 2 hours; the modified nano-calcium carbonate suspension was then dehydrated, dried, and pulverized in sequence to obtain the activated calcium carbonate powder of this comparative example;

[0084] 4) The activated calcium carbonate powder and PBAT resin are thoroughly mixed in a high-speed mixer at a ratio of 8:2. The mixture is dehydrated and stirred at 85°C for 25 minutes. A mixed dispersant (2.5% by weight of the total weight of the calcium carbonate powder and PBAT resin) is then added. The mixed dispersant composition is 12% maleic anhydride-grafted polyethylene, 15% montan wax, 28% PE wax, and 45% titanate coupling agent. The mixture is stirred at high speed until the temperature reaches 95°C and the mixture is discharged to obtain a premix.

[0085] 5) After the premix was allowed to stand for 24 hours, it was extruded into pellets through a twin-screw extruder, and the temperature of each section of the extruder was set to 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) in sequence to obtain the PLA degradable film masterbatch of this comparative example.

[0086] Comparative Example 3 (modification reaction in step 3 without adding alkyl glucoside)

[0087] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0088] 1) calcining limestone in a vertical kiln at 900-1000° C., subjecting the resulting limestone to a digestion reaction with 50° C. tap water containing 0.15% (calculated as calcium oxide content) calcium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:4; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing it through 80-, 120-, and 200-mesh vibrating screens in sequence, followed by aging for 48 hours;

[0089] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction was completed (pH ≤ 7.0), the BET specific surface area was obtained to be 17.82m 2 / g of nano calcium carbonate suspension;

[0090] 3) The nano-calcium carbonate suspension was transported to a surface activation kettle, heated to 65° C., and 2.5% sodium stearate and 400 ppm glycidyl methacrylate were added based on the dry weight of the nano-calcium carbonate and fully reacted for 2 hours; the modified nano-calcium carbonate suspension was then sequentially dehydrated, dried, and pulverized to obtain the activated calcium carbonate powder of this comparative example;

[0091] 4) The activated calcium carbonate powder and PBAT resin are thoroughly mixed in a high-speed mixer at a ratio of 8:2. The mixture is dehydrated and stirred at 85°C for 25 minutes. A mixed dispersant (2.5% by weight of the total weight of the calcium carbonate powder and PBAT resin) is then added. The mixed dispersant composition is 12% maleic anhydride-grafted polyethylene, 15% montan wax, 28% PE wax, and 45% titanate coupling agent. The mixture is stirred at high speed until the temperature reaches 95°C and the mixture is discharged to obtain a premix.

[0092] 5) After the premix was allowed to stand for 24 hours, it was extruded into pellets through a twin-screw extruder, and the temperature of each section of the extruder was set to 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) in sequence to obtain the PLA degradable film masterbatch of this comparative example.

[0093] Comparative Example 4 (no addition of lignin sulfonic acid, alkyl glucoside, or glycidyl methacrylate)

[0094] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0095] 1) The limestone is calcined in a vertical kiln at 900-1000°C, and the obtained lime is digested with 50°C tap water, with the mass ratio of calcium oxide to water being controlled at 1:4; the tail gas from the vertical kiln calcination is purified and reserved; the resulting calcium hydroxide suspension is sequentially passed through 80, 120, and 200 mesh vibrating screens for impurity removal, and aged for 48 hours;

[0096] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 17.60m 2 / g of nano calcium carbonate suspension;

[0097] 3) The nano-calcium carbonate suspension was transported to a surface activation kettle, heated to 65° C., and 2.5% sodium stearate based on the dry weight of the nano-calcium carbonate was added and fully reacted for 2 hours; the modified nano-calcium carbonate suspension was then sequentially dehydrated, dried, and pulverized to obtain the activated calcium carbonate powder of this comparative example;

[0098] 4) The activated calcium carbonate powder and PBAT resin are thoroughly mixed in a high-speed mixer at a ratio of 8:2. The mixture is dehydrated and stirred at 85°C for 25 minutes. A mixed dispersant (2.5% by weight of the total weight of the calcium carbonate powder and PBAT resin) is then added. The mixed dispersant composition is 12% maleic anhydride-grafted polyethylene, 15% montan wax, 28% PE wax, and 45% titanate coupling agent. The mixture is stirred at high speed until the temperature reaches 95°C and the mixture is discharged to obtain a premix.

[0099] 5) After the premix was allowed to stand for 24 hours, it was extruded into pellets through a twin-screw extruder, and the temperature of each section of the extruder was set to 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) in sequence to obtain the PLA degradable film masterbatch of this comparative example.

[0100] Comparative Example 5 (different order of adding lignin sulfonate)

[0101] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0102] 1) The limestone is calcined in a vertical kiln at 900-1000°C. The resulting lime is then digested with 50°C tap water, with the mass ratio of calcium oxide to water being controlled at 1:4. The tail gas from the vertical kiln calcination is purified and set aside. The resulting calcium hydroxide suspension is sequentially screened through 80, 120, and 200 mesh vibrating screens for impurity removal and aged for 48 hours.

[0103] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 17.36m 2 / g of nano calcium carbonate suspension;

[0104] 3) The nano-calcium carbonate suspension was transported to a surface activation kettle and heated to 65° C., 0.15% by mass of calcium oxide (calcium lignin sulfonate), 2.5% by mass of nano-calcium carbonate dry basis of dodecyl glucoside and 400 ppm of glycidyl methacrylate were added and fully reacted for 2 hours; the modified nano-calcium carbonate suspension was then sequentially dehydrated, dried and pulverized to obtain the activated calcium carbonate powder of this comparative example;

[0105] 4) The activated calcium carbonate powder and PBAT resin are thoroughly mixed in a high-speed mixer at a ratio of 8:2. The mixture is dehydrated and stirred at 85°C for 25 minutes. A mixed dispersant (2.5% by weight of the total weight of the calcium carbonate powder and PBAT resin) is then added. The mixed dispersant composition is 12% maleic anhydride-grafted polyethylene, 15% montan wax, 28% PE wax, and 45% titanate coupling agent. The mixture is stirred at high speed until the temperature reaches 95°C and the mixture is discharged to obtain a premix.

[0106] 5) After the premix is allowed to stand for 24 hours, it is extruded and granulated through a twin-screw extruder, and the temperature settings of each section of the extruder are sequentially 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) to obtain the PLA degradable film masterbatch of the present invention.

[0107] Comparative Example 6 (different order of adding glycidyl methacrylate)

[0108] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0109] 1) calcining limestone in a vertical kiln at 900-1000° C., subjecting the resulting limestone to a digestion reaction with 50° C. tap water containing 0.15% (calculated as calcium oxide content) calcium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:4; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing it through 80-, 120-, and 200-mesh vibrating screens in sequence, followed by aging for 48 hours;

[0110] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 17.40m 2 / g of nano calcium carbonate suspension;

[0111] 3) The nano-calcium carbonate suspension was transported to a surface activation kettle, heated to 65° C., and 2.5% dodecyl glucoside, based on the dry weight of the nano-calcium carbonate, was added and fully reacted for 2 hours; the modified nano-calcium carbonate suspension was then dehydrated, dried, and pulverized in sequence to obtain the activated calcium carbonate powder of this comparative example;

[0112] 4) The activated calcium carbonate powder obtained in step 3) of Comparative Example 2 and PBAT were thoroughly mixed in a high-speed mixer at a ratio of 8:2. Then, 400 ppm of glycidyl methacrylate (based on the mass of the nano-calcium carbonate) was added. The mixture was dehydrated and stirred at 85°C for 25 minutes. Then, a mixed dispersant (2.5% by weight of the total mass of the calcium carbonate powder and PBAT resin) was added. The mixed dispersant composition was 12% maleic anhydride-grafted polyethylene, 15% montan wax, 28% PE wax, and 45% titanate coupling agent. High-speed stirring was continued until the temperature reached 95°C, and the mixture was discharged to obtain a premix.

[0113] 5) After the premix was allowed to stand for 24 hours, it was extruded into pellets through a twin-screw extruder, and the temperature of each section of the extruder was set to 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) in sequence to obtain the PLA degradable film masterbatch of this comparative example.

[0114] Comparative Example 7 (different mixed dispersant formulations)

[0115] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0116] 1) calcining limestone in a vertical kiln at 900-1000° C., subjecting the resulting limestone to a digestion reaction with 50° C. tap water containing 0.15% (calculated as calcium oxide content) calcium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:4; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing it through 80-, 120-, and 200-mesh vibrating screens in sequence, followed by aging for 48 hours;

[0117] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 17.46m 2 / g of nano calcium carbonate suspension;

[0118] 3) transporting the nano-calcium carbonate suspension to a surface activation kettle, heating the temperature to 65° C., adding 2.5% dodecyl glucoside and 400 ppm glycidyl methacrylate based on the dry weight of the nano-calcium carbonate and fully reacting for 2 hours; then dehydrating, drying and pulverizing the modified nano-calcium carbonate suspension in sequence to obtain activated calcium carbonate powder;

[0119] 4) The activated calcium carbonate powder and PBAT resin were thoroughly mixed in a high-speed mixer at a ratio of 8:2. The mixture was dehydrated and stirred at 85°C for 25 minutes. Then, a mixed dispersant (2.5% by weight, based on the total weight of the calcium carbonate powder and PBAT resin) was added. The mixed dispersant composition was 30% maleic anhydride-grafted polyethylene, 15% montan wax, 28% PE wax, and 27% titanate coupling agent. The mixture was stirred at high speed until the temperature reached 95°C and discharged to obtain a premix.

[0120] 5) After the premix was allowed to stand for 24 hours, it was extruded into pellets through a twin-screw extruder, and the temperature of each section of the extruder was set to 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) in sequence to obtain the PLA degradable film masterbatch of this comparative example.

[0121] Comparative Example 8 (different mixed dispersant formulas)

[0122] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0123] 1) calcining limestone in a vertical kiln at 900-1000° C., subjecting the resulting limestone to a digestion reaction with 50° C. tap water containing 0.15% (calculated as calcium oxide content) calcium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:4; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing it through 80-, 120-, and 200-mesh vibrating screens in sequence, followed by aging for 48 hours;

[0124] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 17.46m 2 / g of nano calcium carbonate suspension;

[0125] 3) transporting the nano-calcium carbonate suspension to a surface activation kettle, heating the temperature to 65° C., adding 2.5% dodecyl glucoside and 400 ppm glycidyl methacrylate based on the dry weight of the nano-calcium carbonate and fully reacting for 2 hours; then dehydrating, drying and pulverizing the modified nano-calcium carbonate suspension in sequence to obtain activated calcium carbonate powder;

[0126] 4) The activated calcium carbonate powder and PBAT resin were thoroughly mixed in a high-speed mixer at a ratio of 8:2. The mixture was dehydrated and stirred at 85°C for 25 minutes. Then, a mixed dispersant (2.5% by weight, based on the total weight of the calcium carbonate powder and PBAT resin) was added. The mixed dispersant composition consisted of 5% maleic anhydride-grafted polyethylene, 15% montan wax, 28% PE wax, and 47% titanate coupling agent. The mixture was stirred at high speed until the temperature reached 95°C and discharged to obtain a premix.

[0127] 5) After the premix was allowed to stand for 24 hours, it was extruded into pellets through a twin-screw extruder, and the temperature of each section of the extruder was set to 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) in sequence to obtain the PLA degradable film masterbatch of this comparative example.

[0128] Comparative Example 9 (different mixed dispersant formulations)

[0129] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0130] 1) calcining limestone in a vertical kiln at 900-1000° C., subjecting the resulting limestone to a digestion reaction with 50° C. tap water containing 0.15% (calculated as calcium oxide content) calcium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:4; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing it through 80-, 120-, and 200-mesh vibrating screens in sequence, followed by aging for 48 hours;

[0131] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 17.46m 2 / g of nano calcium carbonate suspension;

[0132] 3) transporting the nano-calcium carbonate suspension to a surface activation kettle, heating the temperature to 65° C., adding 2.5% dodecyl glucoside and 400 ppm glycidyl methacrylate based on the dry weight of the nano-calcium carbonate and fully reacting for 2 hours; then dehydrating, drying and pulverizing the modified nano-calcium carbonate suspension in sequence to obtain activated calcium carbonate powder;

[0133] 4) The activated calcium carbonate powder and PBAT resin were thoroughly mixed in a high-speed mixer at a ratio of 8:2. The mixture was dehydrated and stirred at 85°C for 25 minutes. A mixed dispersant (2.5% by weight of the total weight of the calcium carbonate powder and PBAT resin) was then added. The mixed dispersant composition consisted of 15% maleic anhydride-grafted polyethylene, 20% montan wax, 28% PE wax, and 37% titanate coupling agent. The mixture was stirred at high speed until the temperature reached 95°C, and the mixture was discharged to obtain a premix.

[0134] 5) After the premix was allowed to stand for 24 hours, it was extruded into pellets through a twin-screw extruder, and the temperature of each section of the extruder was set to 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) in sequence to obtain the PLA degradable film masterbatch of this comparative example.

[0135] Comparative Example 10 (different mixed dispersant formulations)

[0136] A method for preparing a special masterbatch for PLA degradable film comprises the following steps:

[0137] 1) calcining limestone in a vertical kiln at 900-1000° C., subjecting the resulting limestone to a digestion reaction with 50° C. tap water containing 0.15% (calculated as calcium oxide content) calcium lignin sulfonate, with the mass ratio of calcium oxide to water being controlled at 1:4; purifying the exhaust gas from the vertical kiln calcination before use; and removing impurities from the resulting calcium hydroxide suspension by passing it through 80-, 120-, and 200-mesh vibrating screens in sequence, followed by aging for 48 hours;

[0138] 2) Adjust the concentration of the aged calcium hydroxide suspension to 12%, adjust the temperature to 24°C, and transport it to 30m 3 The reactor has a filling volume of 24m 3 The purified carbon dioxide-containing tail gas is passed into the calcium hydroxide suspension through an air compressor for carbonation reaction. The gas flow rate is controlled at 2800m 3 / h, after the reaction is completed (pH ≤ 7.0), the BET specific surface area is 17.46m 2 / g of nano calcium carbonate suspension;

[0139] 3) transporting the nano-calcium carbonate suspension to a surface activation kettle, heating the temperature to 65° C., adding 2.5% dodecyl glucoside and 400 ppm glycidyl methacrylate based on the dry weight of the nano-calcium carbonate and fully reacting for 2 hours; then dehydrating, drying and pulverizing the modified nano-calcium carbonate suspension in sequence to obtain activated calcium carbonate powder;

[0140] 4) The obtained activated calcium carbonate powder and PBAT were fully mixed in a high-speed mixer at a ratio of 8:2, dehydrated and stirred at 85°C for 25 minutes, and then 2.5% PE wax dispersant based on the total mass of calcium carbonate powder and PBAT resin was added. The material was discharged when the temperature reached 95°C to obtain a premix;

[0141] 5) After the premix was allowed to stand for 24 hours, it was extruded into pellets through a twin-screw extruder, and the temperature of each section of the extruder was set to 160°C-165°C-170°C-170°C-175°C-175°C-180°C-180°C-185°C-180°C (die temperature) in sequence to obtain the PLA degradable film masterbatch of this comparative example.

[0142] Performance Testing

[0143] The above examples and comparative examples were subjected to film blowing processing according to a formula of 100 parts of PLA resin + 20 parts of nano-calcium carbonate, and the films were tested for mechanical properties according to GB / T 1040.3-2006.

[0144] Film material compatibility testing: A differential scanning calorimeter (DSC) was used with a 5 mg sample, N2 atmosphere, and a flow rate of 50 mL / min. The temperature was first increased from room temperature to 240°C at a rate of 10°C / min. The temperature was then decreased from 240°C to 25°C at a rate of 10°C / min. The temperature was then increased from 25°C to 230°C at a rate of 10°C / min. The lower the glass transition temperature (Tg), the better the compatibility of the system.

[0145] Film crystal point / fish-eye number test: Cut the film into 10*10cm size and use a magnifying glass to observe the number of crystal points / fish-eyes in the cross-sectional area.

[0146] Film transparency test: Cut the film into a size of 5*5cm and a thickness of 75 microns, and use a haze meter for testing.

[0147]

[0148]

[0149] As can be seen from the above table, although the mechanical properties of Examples 1 to 6 of the present invention are similar to those of Comparative Examples 1 to 10, the number of crystal points / fish eyes is much smaller than that of the comparative examples, effectively reducing the undesirable phenomena of fish eyes and crystal points, and the glass transition temperature is relatively low. This shows that the synergistic effect between the added lignin sulfonate and the alkyl glucoside of the present invention can enable the nano-calcium carbonate filler to obtain very excellent dispersion properties, and the synergistic effect between the alkyl glucoside and a certain amount of glycidyl methacrylate can effectively improve the compatibility of PBAT and PLA.

[0150] The above is a further detailed description of the present invention and should not be considered as a limitation on the specific implementation of the present invention. For those skilled in the art, simple deductions or substitutions that do not depart from the concept of the present invention are within the scope of protection of the present invention.

Claims

1. A PLA degradable film masterbatch, characterized in that: The preparation method comprises the following steps: 1) digesting calcium oxide with an aqueous solution of dissolved lignin sulfonate, and then removing impurities and aging to obtain a calcium hydroxide suspension; 2) subjecting the calcium hydroxide suspension obtained in step 1) to a carbonation reaction with CO2 gas to obtain a nano-calcium carbonate suspension; 3) adding alkyl glucoside and glycidyl methacrylate to the nano-calcium carbonate suspension obtained in step 2) for modification reaction, followed by dehydration, drying and pulverization to obtain activated calcium carbonate powder; 4) The activated calcium carbonate powder obtained in step 3) and the PBAT resin are heated and stirred to mix uniformly, and then a mixed dispersant is added. When the temperature reaches 94.5-95.5°C, the material is discharged to obtain a premix; 5) The premix obtained in step 4) is allowed to stand for 24 to 48 hours, and then extruded and granulated to obtain the PLA biodegradable film masterbatch; wherein: The alkyl glucoside in step 3) is selected from at least one of alkyl glucosides having an alkyl carbon number of 12 to 16; The amount of the alkyl glucoside is 1 to 3% of the mass of the nano-calcium carbonate, and the concentration of the glycidyl methacrylate in the nano-calcium carbonate suspension is 100 to 500 ppm; In step 3), the modification reaction temperature is 50-90° C., and the modification reaction time is 1-2 hours; The mixed dispersant in step 4) is composed of maleic anhydride grafted polyethylene, montan wax, and an auxiliary dispersant, wherein the auxiliary dispersant is selected from at least one of titanate coupling agent, aluminate coupling agent, vinyl bisstearamide, PE wax, stearic acid, zinc stearate, calcium stearate, and citrate; The mass proportion of maleic anhydride grafted polyethylene in the mixed dispersant is 10-20%, the mass proportion of montan wax is 15-18%, and the rest is auxiliary dispersant.

2. The PLA degradable film masterbatch according to claim 1, characterized in that: The lignin sulfonate in step 1) is selected from at least one of sodium lignin sulfonate and calcium lignin sulfonate.

3. The PLA degradable film masterbatch according to claim 1 or 2, characterized in that: The amount of the lignin sulfonate used is 0.1-0.2% of the mass of calcium oxide.

4. The PLA degradable film masterbatch according to claim 1, characterized in that: In the step 4), the mass ratio of activated calcium carbonate powder to PBAT is (7-8): (3-2), and the mass amount of the mixed dispersant is 2-4% of the total mass of the calcium carbonate powder and PBAT resin.

5. A blown film degradable plastic, characterized in that: The PLA degradable film masterbatch according to any one of claims 1 to 4 is added thereto.

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