Modified polylactic acid / poly (butylene adipate-co-terephthalate) blend and preparation method thereof

Abstract

The invention belongs to the technical field of high-performance resin preparation, and particularly relates to a modified polylactic acid / poly (butylene adipate-co-terephthalate) blend and a preparation method thereof. The preparation method of the modified polylactic acid / poly (butylene adipate-co-terephthalate) blend comprises the following steps: carrying out melt blending on a polyol / polylactic acid / poly (butylene adipate-co-terephthalate) co-alcoholysis product, diisocyanate and lignin to obtain the modified polylactic acid / poly (butylene adipate-co-terephthalate) blend, wherein the polyol / polylactic acid / poly (butylene adipate-co-terephthalate) co-alcoholysis product is prepared by taking an antioxidant, polyol, a catalyst and polylactic acid / poly (butylene adipate-co-terephthalate) as raw materials through melt blending. The mechanical strength and toughness of the blend are effectively improved, and the processability is improved. The method is popularized to the recovery of polylactic acid / poly (butylene adipate-co-terephthalate) products, and has stable and reliable universality.

Description

Technical Field

[0001] The invention belongs to the technical field of high-performance resin preparation, and particularly relates to a modified polylactic acid / polybutylene adipate terephthalate blend and a preparation method thereof. Background Art

[0002] The world is currently facing severe environmental pressures and resource shortages. Replacing traditional non-degradable plastics with biodegradable plastics is a key measure to address white pollution and other issues. Biodegradable plastics can be degraded into harmless substances such as carbon dioxide and water under specific composting conditions, but this inevitably results in carbon emissions. Furthermore, a growing number of studies have found that when biodegradable polymers such as polylactic acid (PLA) are introduced into marine or terrestrial ecosystems, they can lead to serious microplastic pollution.

[0003] According to 2021 statistics, PLA and polybutylene adipate terephthalate (PBAT) production capacity accounted for 29.4% and 29.9% of global biodegradable and compostable plastics, respectively. Due to their complementary mechanical properties, they are often blended. Therefore, the combined recycling of PLA and PBAT holds significant economic and environmental value.

[0004] However, the poor compatibility of PLA and PBAT limits the performance of products obtained through mechanical recycling; chemical recycling methods have high energy costs and separation and purification costs, and the use of large amounts of reagents will cause people to worry about the environment.

[0005] Therefore, it is an important task in this technical field to propose a new reaction processing technology with a simple process flow, higher efficiency and the opportunity to achieve rapid large-scale production to prepare reinforced and toughened polylactic acid / polybutylene adipate terephthalate blends and apply this reaction processing technology to the recycling of used products. Summary of the Invention

[0006] To address these shortcomings, the present invention provides a modified polylactic acid / polybutylene adipate terephthalate blend and a method for preparing the same. The blend achieves significant improvements in both strength and toughness, and the method has been extended to the recycling of polylactic acid / polybutylene adipate terephthalate products, demonstrating stable and reliable universal applicability. Furthermore, even for polylactic acid / polybutylene adipate terephthalate products containing large amounts of calcium powder and other additives, the preparation of the blend is not affected, and the resulting blend still achieves significant improvements in toughness and tensile strength.

[0007] The technical solution of the present invention:

[0008] The first technical problem to be solved by the present invention is to provide a method for preparing a modified polylactic acid / polybutylene adipate terephthalate blend, comprising the following steps: melt-blending a polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysate, a diisocyanate, and lignin to obtain a modified polylactic acid / polybutylene adipate terephthalate blend;

[0009] The polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product is prepared by melt blending using an antioxidant, a polyol, a catalyst and polylactic acid / polybutylene adipate terephthalate as raw materials.

[0010] Furthermore, the diisocyanate is isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, terephthalylidene diisocyanate or hexamethylene diisocyanate; preferably isophorone diisocyanate.

[0011] Furthermore, the lignin is at least one of alkali lignin, softwood lignin, hardwood lignin, lignin sulfonate, enzymatically degraded lignin, hydrolyzed lignin and lignin sulfonate.

[0012] Furthermore, in the modified polylactic acid / polybutylene adipate terephthalate blend, the ratio of each raw material is: 100 parts by weight of the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, 2-10 parts by weight of diisocyanate, and 0.2-3 parts by weight of lignin.

[0013] Furthermore, in the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, the ratio of each raw material is: 0.2-1 parts by weight of antioxidant, 1-5 parts by weight of polyol, 0.2-2 parts by weight of catalyst, and 100 parts by weight of polylactic acid / polybutylene adipate terephthalate.

[0014] Furthermore, the polylactic acid / polybutylene adipate terephthalate can be in any weight ratio, preferably 30:70, 10:90, 50:50 or 80:20.

[0015] Furthermore, the antioxidant is antioxidant 300, antioxidant 702, antioxidant 565, antioxidant 5057, antioxidant 3114 or antioxidant 1425; preferably antioxidant 300.

[0016] Furthermore, the polyol is glycerol, ethylene glycol, hexylene glycol or pentaerythritol; preferably glycerol.

[0017] Furthermore, the catalyst is zinc acetate, tin acetate, zinc acetylacetonate, samarium acetylacetonate or lanthanum acetylacetonate; preferably zinc acetate.

[0018] The second technical problem to be solved by the present invention is to provide a modified polylactic acid / polybutylene adipate terephthalate blend prepared by the above-mentioned preparation method. The blend has high strength and toughness.

[0019] The third technical problem to be solved by the present invention is to provide a method for recycling polylactic acid / polybutylene adipate terephthalate products, comprising the following steps: crushing the polylactic acid / polybutylene adipate terephthalate product, then melt-blending it with an antioxidant, a polyol and a catalyst to obtain a polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, and then melt-blending it with a diisocyanate and lignin to obtain a modified polylactic acid / polybutylene adipate terephthalate blend.

[0020] Furthermore, in the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, the ratio of each raw material is: 0.2-1 parts by weight of antioxidant, 1-5 parts by weight of polyol, 0.2-2 parts by weight of catalyst, and 100 parts by weight of polylactic acid / polybutylene adipate terephthalate.

[0021] Furthermore, the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product is 100 parts by weight, diisocyanate is 2-10 parts by weight, and lignin is 0.2-3 parts by weight.

[0022] The fourth technical problem to be solved by the present invention is to provide a method for improving the strength and toughness of polylactic acid / polybutylene adipate terephthalate, comprising the following steps: melt-blending polylactic acid / polybutylene adipate terephthalate with an antioxidant, a polyol and a catalyst to obtain a polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, and then melt-blending the product with a diisocyanate and lignin to obtain a modified polylactic acid / polybutylene adipate terephthalate blend.

[0023] Furthermore, in the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, the ratio of each raw material is: 0.2-1 parts by weight of antioxidant, 1-5 parts by weight of polyol, 0.2-2 parts by weight of catalyst, and 100 parts by weight of polylactic acid / polybutylene adipate terephthalate.

[0024] Furthermore, the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product is 100 parts by weight, diisocyanate is 2-10 parts by weight, and lignin is 0.2-3 parts by weight.

[0025] The present invention has the following beneficial effects:

[0026] 1. This invention utilizes the polyester backbone characteristics shared by PBAT and PLA. Under metal ion catalysis, polyols attack and insert into the ester chains, forming a polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysate with reactive terminal hydroxyl groups. Lignin units and diisocyanate are then introduced through a urethane transcarbamate reaction to form a dynamic multi-stage crosslinked network. This multi-stage network reconstruction achieves refined phase size and effective intra- and interphase stress transfer, thereby strengthening and toughening the PBAT and PLA blend. This method effectively strengthens and toughens the PLA / PBAT blend, addressing the low mechanical strength and toughness of the PLA / PBAT blend and its recycled products, often due to poor compatibility between the two.

[0027] 2. The lignin units employed in this invention effectively improve the thermal stability of the blend, resulting in a blend that exhibits restored thermal stability. Furthermore, the lignin units are bio-based and degradable, without compromising the biodegradability of the system. Due to the excellent light-to-heat conversion properties of the lignin units, the blend is endowed with excellent light-triggered self-healing properties.

[0028] 3. The method of the present invention can be used to recycle PBAT / PLA mixtures of varying proportions. It can also be used to recycle actual mixed products (PBAT / PLA film bags and PLA cups, straws, and lids). Furthermore, the method demonstrates high compatibility with common industrial additives. For example, calcium carbonate filler, widely used to reduce costs, can be uniformly dispersed within the matrix without compromising co-recycling. These results highlight the adaptability and industrial relevance of the proposed method for upcycling diverse and additive-containing PBAT / PLA plastic waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a chemical cross-linking reaction during the preparation of the present invention;

[0030] Figure 2 is a stress-strain curve of the blend obtained in Example 8;

[0031] Figure 3 is a stress-strain curve of the blend obtained in Comparative Example 7;

[0032] Figure 4 is a stress-strain curve of the blend obtained in Example 9;

[0033] Figure 5 This is the stress-strain curve of the blend obtained in Comparative Example 8. DETAILED DESCRIPTION

[0034] The present invention provides a method for preparing a modified polylactic acid / polybutylene adipate terephthalate blend, comprising the following steps: melt-blending a polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, a diisocyanate and lignin to obtain a modified polylactic acid / polybutylene adipate terephthalate blend;

[0035] The polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product is prepared by melt blending using an antioxidant, a polyol, a catalyst and polylactic acid / polybutylene adipate terephthalate as raw materials.

[0036] The ratio of the raw materials in the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product is: 0.2-1 parts by weight of antioxidant, 1-5 parts by weight of polyol, 0.2-2 parts by weight of catalyst, and 100 parts by weight of polylactic acid / polybutylene adipate terephthalate;

[0037] Alternatively, the ratio of the raw materials in the modified polylactic acid / polybutylene adipate terephthalate blend is: 100 parts by weight of the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, 2-10 parts by weight of diisocyanate, and 0.2-3 parts by weight of lignin.

[0038] The modified polylactic acid / polybutylene adipate terephthalate blend obtained by the present invention achieves improved strength and toughness, and the method is also applied to the recycling of products related to the polylactic acid / polybutylene adipate terephthalate blend.

[0039] The present invention utilizes the polyester backbone of polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA), uses glycerol to undergo co-alcoholization reaction to generate reactive hydroxyl groups, and then introduces lignin and isophorone diisocyanate to form a dynamic cross-linked network through urethane exchange reaction. The chemical cross-linking reaction is as follows: Figure 1 As shown. This cross-linked topology, derived from multifunctional lignin nodes, promotes the formation of a multilevel network; the resulting blend exhibits restored thermal stability. Multilevel network reconstruction achieves refined phase morphology and effective intra- and interphase stress transfer. The prepared blend exhibits significant mechanical reinforcement and toughening. This strategy demonstrates excellent universality and enables the co-recycling of real post-consumer products, including single products containing blended PLA / PBAT components as well as mixtures of multiple product types.

[0040] The present invention is further described below with reference to specific examples, which, however, are not intended to limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0041] Example 1:

[0042] A modified polylactic acid / polybutylene adipate terephthalate blend, the preparation method of which comprises the following steps:

[0043] Polylactic acid and polybutylene adipate terephthalate pellets were dried at 50°C for 24 h. 30 parts by weight of the dried polylactic acid and 70 parts by weight of polybutylene adipate terephthalate were mixed uniformly with 1 part by weight of glycerol, 0.5 part by weight of zinc acetate, and 0.3 part by weight of antioxidant 300. The mixture was then transferred to a torque rheometer and melt-blended to obtain a glycerol / polylactic acid / polybutylene adipate terephthalate co-alcoholysate. 1 part by weight of lignin and 4 parts by weight of isophorone diisocyanate were then added and melt-blended to obtain a modified polylactic acid / polybutylene adipate terephthalate blend.

[0044] Example 2:

[0045] A modified polylactic acid / polybutylene adipate terephthalate blend, the preparation method of which comprises the following steps:

[0046] Polylactic acid and polybutylene adipate terephthalate pellets were dried at 50°C for 24 h. 30 parts by weight of the dried polylactic acid and 70 parts by weight of polybutylene adipate terephthalate were mixed uniformly with 1 part by weight of glycerol, 0.5 part by weight of zinc acetate, and 0.3 part by weight of antioxidant 300. The mixture was then transferred to a torque rheometer and melt-blended to obtain a glycerol / polylactic acid / polybutylene adipate terephthalate co-alcoholysate. 1 part by weight of lignin and 4.5 parts by weight of isophorone diisocyanate were then added and melt-blended to obtain a modified polylactic acid / polybutylene adipate terephthalate blend.

[0047] Example 3:

[0048] A modified polylactic acid / polybutylene adipate terephthalate blend, the preparation method of which comprises the following steps:

[0049] Polylactic acid and polybutylene adipate terephthalate pellets were dried at 50°C for 24 h. 30 parts by weight of the dried polylactic acid and 70 parts by weight of polybutylene adipate terephthalate were mixed uniformly with 1 part by weight of glycerol, 0.5 parts by weight of zinc acetate, and 0.3 parts by weight of antioxidant 300. The mixture was then transferred to a torque rheometer and melt-blended to obtain a glycerol / polylactic acid / polybutylene adipate terephthalate co-alcoholysate. 1 part by weight of lignin and 5 parts by weight of isophorone diisocyanate were then added and melt-blended to obtain a modified polylactic acid / polybutylene adipate terephthalate blend.

[0050] Example 4:

[0051] A modified polylactic acid / polybutylene adipate terephthalate blend, the preparation method of which comprises the following steps:

[0052] Polylactic acid and polybutylene adipate terephthalate pellets were dried at 50°C for 24 h. 30 parts by weight of the dried polylactic acid and 70 parts by weight of polybutylene adipate terephthalate were mixed uniformly with 1 part by weight of glycerol, 0.5 parts by weight of zinc acetate, and 0.3 parts by weight of antioxidant 300. The mixture was then transferred to a torque rheometer and melt-blended to obtain a glycerol / polylactic acid / polybutylene adipate terephthalate co-alcoholyzate. 3 parts by weight of lignin and 7 parts by weight of isophorone diisocyanate were then added and melt-blended to obtain a modified polylactic acid / polybutylene adipate terephthalate blend.

[0053] Example 5:

[0054] A modified polylactic acid / polybutylene adipate terephthalate blend, the preparation method of which comprises the following steps:

[0055] Polylactic acid and polybutylene adipate terephthalate pellets were dried at 50°C for 24 h. 10 parts by weight of the dried polylactic acid and 90 parts by weight of polybutylene adipate terephthalate were mixed uniformly with 1 part by weight of glycerol, 0.5 parts by weight of zinc acetate, and 0.3 parts by weight of antioxidant 300. The mixture was then transferred to a torque rheometer and melt-blended to obtain a glycerol / polylactic acid / polybutylene adipate terephthalate co-alcoholysate. 1 part by weight of lignin and 5 parts by weight of isophorone diisocyanate were then added and melt-blended to obtain a modified polylactic acid / polybutylene adipate terephthalate blend.

[0056] Example 6:

[0057] A modified polylactic acid / polybutylene adipate terephthalate blend, the preparation method of which comprises the following steps:

[0058] Polylactic acid and polybutylene adipate terephthalate pellets were dried at 50°C for 24 h. 50 parts by weight of the dried polylactic acid and polybutylene adipate terephthalate were mixed uniformly with 1 part by weight of glycerol, 0.5 part by weight of zinc acetate, and 0.3 part by weight of antioxidant 300. The mixture was then transferred to a torque rheometer and melt-blended to obtain a glycerol / polylactic acid / polybutylene adipate terephthalate co-alcoholysate. 1 part by weight of lignin and 5 parts by weight of isophorone diisocyanate were then added and melt-blended to obtain a modified polylactic acid / polybutylene adipate terephthalate blend.

[0059] Example 7:

[0060] A modified polylactic acid / polybutylene adipate terephthalate blend, the preparation method of which comprises the following steps:

[0061] Polylactic acid and polybutylene adipate terephthalate pellets were dried at 50°C for 24 h. 80 parts by weight of the dried polylactic acid and 20 parts by weight of polybutylene adipate terephthalate were mixed uniformly with 1 part by weight of glycerol, 0.5 parts by weight of zinc acetate, and 0.3 parts by weight of antioxidant 300. The mixture was then transferred to a torque rheometer and melt-blended to obtain a glycerol / polylactic acid / polybutylene adipate terephthalate co-alcoholyzate. 1 part by weight of lignin and 4.5 parts by weight of isophorone diisocyanate were then added and melt-blended to obtain a modified polylactic acid / polybutylene adipate terephthalate blend.

[0062] Example 8:

[0063] A modified polylactic acid / polybutylene adipate terephthalate blend, the preparation method of which comprises the following steps:

[0064] The crushed PBAT / PLA film bags were dried at 50°C for 24 hours. 100 parts by weight of the dried PBAT / PLA film bags were mixed evenly with 1 part by weight of glycerol, 0.5 parts by weight of zinc acetate, and 0.3 parts by weight of antioxidant 300, and then transferred to a torque rheometer for melt blending to obtain a glycerol / polylactic acid / polybutylene adipate terephthalate co-alcoholyzate. 1 part by weight of lignin and 5 parts by weight of isophorone diisocyanate were then added and melt blended to obtain a modified polylactic acid / polybutylene adipate terephthalate blend.

[0065] Example 9:

[0066] A modified polylactic acid / polybutylene adipate terephthalate blend, the preparation method of which comprises the following steps:

[0067] The crushed PBAT / PLA film bags, PLA cups, straws and lids were dried at 50°C for 24 hours. 50 parts by weight of the dried PBAT / PLA film bags, 50 parts by weight of the PLA cups, straws and lids were mixed evenly with 1 part by weight of glycerol, 0.5 parts by weight of zinc acetate and 0.3 parts by weight of antioxidant 300, and then transferred to a torque rheometer and melt-blended to obtain a glycerol / polylactic acid / polybutylene adipate terephthalate co-alcoholyzate. 1 part by weight of lignin and 5 parts by weight of isophorone diisocyanate were then added and melt-blended to obtain a modified polylactic acid / polybutylene adipate terephthalate blend.

[0068] Comparative Example 1:

[0069] A blend, the preparation method of which comprises the following steps:

[0070] Polylactic acid and polybutylene adipate terephthalate particles were dried at 50°C for 24 hours. 30 parts by weight of the dried polylactic acid and 70 parts by weight of polybutylene adipate terephthalate were mixed with 0.3 parts by weight of antioxidant 300, and then transferred to a torque rheometer and melt-blended to prepare a blend.

[0071] Comparative Example 2:

[0072] A blend, the preparation method of which comprises the following steps:

[0073] Polylactic acid and polybutylene adipate terephthalate pellets were dried at 50°C for 24 h. 30 parts by weight of the dried polylactic acid and 70 parts by weight of polybutylene adipate terephthalate were mixed with 1 part by weight of glycerol, 0.5 part by weight of zinc acetate, and 0.3 part by weight of antioxidant 300. The mixture was then transferred to a torque rheometer and melt-blended to prepare a blend.

[0074] Comparative Example 3:

[0075] A blend, the preparation method of which comprises the following steps:

[0076] Polylactic acid and polybutylene adipate terephthalate pellets were dried at 50°C for 24 h. 30 parts by weight of the dried polylactic acid and 70 parts by weight of polybutylene adipate terephthalate were mixed uniformly with 1 part by weight of glycerol, 0.5 part by weight of zinc acetate, and 0.3 part by weight of antioxidant 300. The mixture was then transferred to a torque rheometer and melt-blended to obtain a glycerol / polylactic acid / polybutylene adipate terephthalate co-alcoholyzate. 4.5 parts by weight of isophorone diisocyanate were then added and melt-blended to obtain a blend.

[0077] Comparative Example 4:

[0078] A blend, the preparation method of which comprises the following steps:

[0079] Polylactic acid and polybutylene adipate terephthalate particles were dried at 50°C for 24 hours. 10 parts by weight of the dried polylactic acid and 90 parts by weight of polybutylene adipate terephthalate were mixed with 0.3 parts by weight of antioxidant 300, and then transferred to a torque rheometer and melt-blended to prepare a blend.

[0080] Comparative Example 5:

[0081] A blend, the preparation method of which comprises the following steps:

[0082] Polylactic acid and polybutylene adipate terephthalate particles were dried at 50° C. for 24 h. 50 parts by weight of the dried polylactic acid and polybutylene adipate terephthalate were mixed with 0.3 parts by weight of antioxidant 300, and then transferred to a torque rheometer and melt-blended to prepare a blend.

[0083] Comparative Example 6:

[0084] A blend, the preparation method of which comprises the following steps:

[0085] Polylactic acid and polybutylene adipate terephthalate particles were dried at 50°C for 24 hours. 80 parts by weight of the dried polylactic acid and 20 parts by weight of polybutylene adipate terephthalate were mixed with 0.3 parts by weight of antioxidant 300, and then transferred to a torque rheometer and melt-blended to prepare a blend.

[0086] Comparative Example 7:

[0087] A blend, the preparation method of which comprises the following steps:

[0088] The crushed PBAT / PLA film bags were dried at 50° C. for 24 h. 100 parts by weight of the dried PBAT / PLA film bags were mixed evenly with 0.3 parts by weight of antioxidant 300, and then transferred to a torque rheometer for melt blending to prepare a blend.

[0089] Comparative Example 8:

[0090] A blend, the preparation method of which comprises the following steps:

[0091] The crushed PBAT / PLA film bags, PLA cups, straws, and lids were dried at 50°C for 24 h. 50 parts by weight of the dried PBAT / PLA film bags, 50 parts by weight of the PLA cups, straws, and lids were mixed with 0.3 parts by weight of antioxidant 300, and then transferred to a torque rheometer for melt blending to prepare a blend.

[0092] Test example

[0093] 1. The Young's modulus, tensile strength and toughness of the blends obtained in Examples 1-3 and Comparative Examples 1 and 3 were tested. The results are shown in Table 1.

[0094] Table 1 Comparison of Young's modulus, tensile strength and toughness of the blends obtained in Examples 1-3 and Comparative Examples 1 and 3

[0095] sample Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 3 Young's modulus (MPa) 157.8±4.3 179.3±9.6 178.8±8.7 116.9±2.4 132.5±9.9 Tensile strength (MPa) 22.1±2.4 35.9±2.8 45.0±3.8 13.9±1.2 24.7±1.2 <![CDATA[Toughness (MJ / m 3 )]]> 73.5±21.2 125.3±11.9 160.3±18.6 60.2±30.2 91.4±9.9

[0096] As can be seen from Table 1, the blend of the present invention achieves effective reinforcement and toughening, and while improving the Young's modulus and tensile strength of the blend, it can also take into account and enhance its toughness.

[0097] 2. The initial degradation temperatures of the blends obtained in Examples 3-4 and Comparative Examples 2-3 were tested, and the results are shown in Table 2.

[0098] Table 2 Initial degradation temperature of the blends obtained in Examples 3-4 and Comparative Examples 2-3

[0099] sample Example 3 Example 4 Comparative Example 2 Comparative Example 3 Initial thermal degradation temperature (℃) 269.5 283.3 241.5 249.8

[0100] As shown in Table 2, the blend of the present invention exhibits restored thermal stability. At the same time, when the amount of lignin added is increased, the thermal stability can be further restored.

[0101] 3. The tensile strength and toughness of the blends obtained in Examples 5-7 and Comparative Examples 4-6 were tested, and the results are shown in Table 3.

[0102] Table 3 Comparison of tensile strength and toughness of the blends obtained in Examples 5-7 and Comparative Examples 4-6

[0103] sample Example 5 Comparative Example 4 Example 6 Comparative Example 5 Example 7 Comparative Example 6 Tensile strength (MPa) 51.9±4.7 32.4±1.4 62.9±4 27.4±0.9 69.4±4.4 62.2±2.5 <![CDATA[Toughness (MJ / m 3 )]]> 248.6±22.9 181.3±14.9 162.1±20.7 9.9±2.0 112.2±4.2 14.3±0.5

[0104] As can be seen from Table 3, within a wide range of addition ratios of polylactic acid and polybutylene adipate terephthalate (from 80:20 by weight to 10:90 by weight), the method of the present invention can achieve efficient mechanical reinforcement and toughening.

[0105] In summary, the method of the present invention can prepare a modified polylactic acid / polybutylene adipate terephthalate blend with high strength and high toughness; further broaden the application field of polylactic acid / polybutylene adipate terephthalate blend materials and reduce the production cost of polylactic acid / polybutylene adipate terephthalate blend products.

[0106] 4. The blends obtained from Example 8 and Comparative Example 7, which were recycled as single PBAT / PLA film bag products, were subjected to stress-strain tests. The length and width of the test samples were 35 mm and 2 mm, respectively; the stretching rate was 50 mm / min, and the gauge length was 15 mm. At least three samples were tested for each group of samples, and representative results were reported. The results are shown in the figure below. Figure 2-3 At the same time, the blends obtained from Example 9 and Comparative Example 8 of the recycled mixed products were subjected to stress-strain tests. The length and width of the test samples were 35 mm and 2 mm, respectively; the tensile rate was 20 mm / min, and the gauge length was 15 mm. At least three samples were tested for each group of samples and representative results were reported. The results are shown in Figure 2. Figure 4-5 shown.

[0107] Depend on Figure 2-3 It can be seen that the products recycled using the method of the present invention show higher strength and toughness. At the same time, the calcium carbonate filler and a large amount of additives such as plasticizers in the real products do not affect the implementation of the technical route of the present invention.

[0108] Depend on Figure 4-5 It can be seen that the products recycled using the method of the present invention show significantly improved tensile strength and toughness.

[0109] In summary, the recycling method of the present invention can achieve the upgraded recycling of real mixed polylactic acid / polybutylene adipate terephthalate products, indicating that it has the potential and value for industrial application.

[0110] It should be noted that the preferred embodiments of the present invention are given in the specification and drawings of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments are not intended to be additional limitations on the content of the present invention. The purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. In addition, the above-mentioned technical features can be combined with each other to form various embodiments not listed above, which are all considered to be within the scope of the description of the present invention. Furthermore, it is obvious to those skilled in the art that improvements or changes can be made based on the above description, and all such improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a modified polylactic acid / polybutylene adipate terephthalate blend, characterized in that: The following steps are involved: melt-blending a polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, a diisocyanate, and lignin to obtain a modified polylactic acid / polybutylene adipate terephthalate blend; The polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product is prepared by melt blending using an antioxidant, a polyol, a catalyst and polylactic acid / polybutylene adipate terephthalate as raw materials.

2. The method for preparing the modified polylactic acid / polybutylene adipate terephthalate blend according to claim 1, wherein: The diisocyanate is isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, terephthalylidene diisocyanate or hexamethylene diisocyanate; Alternatively, the lignin is at least one of alkali lignin, softwood lignin, hardwood lignin, lignin sulfonate, enzymatically degraded lignin, hydrolyzed lignin and lignin sulfonate.

3. The method for preparing the modified polylactic acid / polybutylene adipate terephthalate blend according to claim 1, wherein: In the modified polylactic acid / polybutylene adipate terephthalate blend, the ratio of each raw material is: 100 parts by weight of the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, 2-10 parts by weight of diisocyanate, and 0.2-3 parts by weight of lignin.

4. The method for preparing the modified polylactic acid / polybutylene adipate terephthalate blend according to claim 1, wherein: The ratio of the raw materials in the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product is: 0.2-1 parts by weight of antioxidant, 1-5 parts by weight of polyol, 0.2-2 parts by weight of catalyst, and 100 parts by weight of polylactic acid / polybutylene adipate terephthalate.

5. The method for preparing the modified polylactic acid / polybutylene adipate terephthalate blend according to claim 1, wherein: The antioxidant is antioxidant 300, antioxidant 702, antioxidant 565, antioxidant 5057, antioxidant 3114 or antioxidant 1425; Or, the polyol is glycerol, ethylene glycol, hexylene glycol or pentaerythritol; Alternatively, the catalyst is zinc acetate, tin acetate, zinc acetylacetonate, samarium acetylacetonate or lanthanum acetylacetonate.

6. A modified polylactic acid / polybutylene adipate terephthalate blend, characterized in that: The method is prepared according to any one of claims 1 to 5.

7. A method for recycling polylactic acid / polybutylene adipate terephthalate products, characterized in that: The following steps are involved: The polylactic acid / polybutylene adipate terephthalate product is crushed, then melt-blended with an antioxidant, a polyol and a catalyst to prepare a polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, which is then melt-blended with diisocyanate and lignin to prepare a modified polylactic acid / polybutylene adipate terephthalate blend.

8. The method for recycling polylactic acid / polybutylene adipate terephthalate products according to claim 7, characterized in that: The ratio of the raw materials in the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product is: 0.2-1 parts by weight of antioxidant, 1-5 parts by weight of polyol, 0.2-2 parts by weight of catalyst, and 100 parts by weight of polylactic acid / polybutylene adipate terephthalate; Alternatively, the ratio of the raw materials in the modified polylactic acid / polybutylene adipate terephthalate blend is: 100 parts by weight of the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, 2-10 parts by weight of diisocyanate, and 0.2-3 parts by weight of lignin.

9. A method for improving the strength and toughness of polylactic acid / polybutylene adipate terephthalate, characterized in that: The following steps are involved: Polylactic acid / polybutylene adipate terephthalate is melt-blended with an antioxidant, a polyol and a catalyst to prepare a polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, which is then melt-blended with diisocyanate and lignin to prepare a modified polylactic acid / polybutylene adipate terephthalate blend.

10. The method for improving the strength and toughness of polylactic acid / polybutylene adipate terephthalate according to claim 9, characterized in that: The ratio of the raw materials in the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product is: 0.2-1 parts by weight of antioxidant, 1-5 parts by weight of polyol, 0.2-2 parts by weight of catalyst, and 100 parts by weight of polylactic acid / polybutylene adipate terephthalate; Alternatively, the ratio of the raw materials in the modified polylactic acid / polybutylene adipate terephthalate blend is: 100 parts by weight of the polyol / polylactic acid / polybutylene adipate terephthalate co-alcoholysis product, 2-10 parts by weight of diisocyanate, and 0.2-3 parts by weight of lignin.

Images