Preparation method of block copolyester suitable for grafting stretch film

Abstract

The invention belongs to the technical field of composite materials for films, and relates to a preparation method of a block copolyester suitable for a grafted stretch film, which comprises the following steps: mixing a hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isohexitol-based polyester prepolymer and a diisocyanate chain extender and then reacting; the molecular weight ranges of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isohexitol-based polyester prepolymer are controlled to be 3000-5000, and meanwhile, the addition amount of a diisocyanate chain extender is controlled to be 5-8% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isohexitol-based polyester prepolymer, so that the block copolyester suitable for the grafted stretch film is obtained. The problems of an existing grafting film material in the aspects of degradability, mechanical property, water permeability and puncture resistance are solved, and a more environment-friendly, efficient and economical solution is provided for fruit tree seedling grafting.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials for films and relates to a method for preparing a block copolyester suitable for grafted stretch films. Background Art

[0002] Grafting of fruit tree seedlings is a common and effective method to enhance the disease resistance of plants and is widely used in fruit tree cultivation. In the process of grafting, polyethylene (PE) grafting film is usually used to wrap the grafted seedlings to improve the survival rate. It has the advantages of low price, high toughness and good light transmittance, and occupies the main market of this type of product. However, there are many problems when using PE grafting film.

[0003] Specifically, PE grafting film is difficult to degrade naturally in the environment, and the polymer fragments produced during the seedling grafting process are difficult to recycle. If they fall into the soil and the environment, they will cause a lot of pollution. At the same time, PE grafting film has high mechanical properties. After the seedlings survive, the film needs to be removed or broken with tools to allow the seedlings to continue growing, which consumes a lot of manpower. In addition, the water permeability of PE wrapping film is poor, which can easily cause excessive humidity in the grafting site, leading to problems such as bacterial growth and rot.

[0004] In view of the shortcomings of PE grafted membrane, people have begun to pay attention to the development of a new generation of grafted membrane materials. Among them, biodegradable polyester materials such as polylactic acid (PLA), polybutylene terephthalate-adipate (PBAT), polybutylene succinate (PBS) have good development prospects. Among them, PBS, compared with PLA and PBAT, has shown a series of unique advantages in its application as a grafted membrane.

[0005] Although PLA is favored for its excellent biodegradability and environmental friendliness, PLA has a rigid chemical structure, an elongation at break of <10%, and insufficient ductility, making it unsuitable for winding grafted films. The literature (In situ formation of PLA-grafted alkoxysilanes for toughening a biodegradable PLA stereocomplex thin film, RSC Adv. 9(38), 21748-21759) developed a PLA stereocomplex by mixing PLA with organic alkoxysilanes, which increased the elongation at break, but still did not meet the elongation at break standard (>300%) for grafted winding films (BB / T 024-2018 industry standard). In contrast, the elongation at break of PBS can be as high as 400%, which provides significant advantages for winding grafted film applications that require high ductility.

[0006] Although PBAT is also a recognized biodegradable polyester, it degrades slowly in the natural environment and is not suitable for use as a grafting membrane. In contrast, PBS exhibits more balanced degradation performance. The literature (Properties of phosphorus-containing polybutylene succinate / polylactic acid composite film material and degradation process effects on physiological indexes of lettuce cultivation, Polymer Test. 119, 107921) confirmed that PBS blended polymers degraded in soil supernatant for 6 months with a degradation rate of 60% to 70%, which has excellent soil degradation performance, which is an important advantage for grafting membranes that require soil degradation performance.

[0007] Patent CN112048058B provides a method for preparing a high melting point crystalline biodegradable copolyester, which uses isocyanate, epoxy and other chain extension methods to mix PBS prepolymer, isohexitol-based polyester prepolymer and chain extender and then react to prepare block copolyester. However, the interaction between the molecular chains of the block copolyester is weak, and the prepared film cannot form a stable three-dimensional structure of chemical bonds, resulting in insufficient puncture resistance and unable to meet the use requirements of grafted stretch film. Summary of the invention

[0008] The purpose of the present invention is to solve the problems existing in the prior art and provide a method for preparing a block copolyester suitable for grafting stretch film.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a block copolyester suitable for a grafted stretch film comprises the following steps: mixing a hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isohexitol-based polyester prepolymer and a diisocyanate chain extender and reacting the mixture; controlling the molecular weights of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isohexitol-based polyester prepolymer to be in the range of 3000-5000; and controlling the addition amount of the diisocyanate chain extender to be 5-8% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isohexitol-based polyester prepolymer, so as to obtain the block copolyester suitable for a grafted stretch film.

[0011] The present invention prepares the block copolyester by chain extension through the reaction of isocyanate groups and hydroxyl groups. The smaller the molecular weight of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isohexitol-based polyester prepolymer, the more diisocyanate chain extenders are needed, and the more urethane bonds are formed. Since the molecular weight range of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isohexitol-based polyester prepolymer is controlled to be 3000-5000, and the amount of the chain extender added is controlled to be 5-8% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isohexitol-based polyester prepolymer, a large number of urethane bonds exist in the molecular chain of the block copolyester, so that a large number of hydrogen bonds (such as Figure 1 As shown in the figure, the interaction between the molecular chains of the block copolyester is strong, forming a hydrogen bond network structure of the polymer, and the strength and elongation at break of the block copolyester are ideal, thereby improving the puncture resistance of the polymer. Since there is an isohexitol structure in the molecular chain of the block copolyester, the isohexitol structure contains an ether bond, has good hydrophilicity, and is prone to hydrolysis, so the degradation performance of the block copolyester is ideal. Due to the presence of an isohexitol structure in the molecular chain of the block copolyester, the block copolyester has a low crystallinity, a large proportion of amorphous regions, a large permeable area during gas diffusion, and poor gas barrier properties.

[0012] As the preferred technical solution:

[0013] In the method for preparing a block copolyester suitable for grafting a stretch film as described above, the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isohexitol-based polyester prepolymer is 2-8:2-8.

[0014] In the method for preparing a block copolyester suitable for grafting stretch film as described above, the diisocyanate chain extender is hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI).

[0015] As described above, the method for preparing a block copolyester suitable for grafting stretch film has a reaction system that is a melting system. The melting system is simple and solvent-free, does not require dissolution, precipitation, or purification, has a low cost, and the molten product can be directly processed, which is convenient and safe. The reaction temperature is 160-220°C, the reaction time is 0.5-1h, and the reaction pressure is 0.1MPa.

[0016] As described above, a method for preparing a block copolyester suitable for grafting a stretch film, the preparation process of a hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol, and additives (antioxidants, catalysts, thermal stabilizers, etc.), firstly carry out an esterification reaction at a temperature of 180-200°C and a pressure of 0.1MPa for 4-6h, and then heat it to 230-250°C and carry out a condensation reaction at a pressure of ≤50Pa for 1-2h to obtain a hydroxyl-terminated PBS prepolymer; wherein the molar ratio of succinic acid to butanediol is 1:1.1-1.3, and the amount of the additive added is 0.5% of the mass of succinic acid.

[0017] As described above, a method for preparing a block copolyester suitable for grafting a stretch film, the preparation process of a hydroxyl-terminated isohexitol-based polyester prepolymer is as follows: after mixing succinic acid, isohexitol, and additives (antioxidants, catalysts, thermal stabilizers, etc.), firstly carry out an esterification reaction at a temperature of 180-220°C and a pressure of 0.1MPa for 3-4h, and then heat it to 240-260°C and carry out a condensation reaction at a pressure of ≤50Pa for 2-3h to obtain a hydroxyl-terminated isohexitol-based polyester prepolymer; wherein the molar ratio of succinic acid to isohexitol is 1:1.1-1.3, and the amount of the additive added is 0.5% of the mass of succinic acid.

[0018] In the method for preparing a block copolyester suitable for grafting stretch film as described above, the hydroxyl-terminated isohexitol-based polyester prepolymer is a hydroxyl-terminated isosorbide-based polyester prepolymer; when the hydroxyl-terminated isohexitol-based polyester prepolymer is a hydroxyl-terminated isosorbide-based polyester prepolymer, the method for preparing a block copolyester suitable for grafting stretch film is recorded as method A.

[0019] In the method for preparing a block copolyester suitable for grafting stretch film as described above, the hydroxyl-terminated isohexitol-based polyester prepolymer is a hydroxyl-terminated isomannide-based polyester prepolymer; when the hydroxyl-terminated isohexitol-based polyester prepolymer is a hydroxyl-terminated isomannide-based polyester prepolymer, the method for preparing a block copolyester suitable for grafting stretch film is recorded as method B.

[0020] In the method for preparing a block copolyester suitable for grafting stretch film as described above, the hydroxyl-terminated isohexide-based polyester prepolymer is a hydroxyl-terminated isoidol-based polyester prepolymer; when the hydroxyl-terminated isohexide-based polyester prepolymer is a hydroxyl-terminated isoidol-based polyester prepolymer, the method for preparing a block copolyester suitable for grafting stretch film is recorded as method C.

[0021] The present invention also provides a grafted stretch film, which is blow-molded from a block copolyester suitable for the grafted stretch film, wherein the block copolyester suitable for the grafted stretch film is prepared by method A; the grafted stretch film has a thickness of 0.05-0.15 mm, an elongation at break of ≥700%, and a water vapor permeability of ≥400 g·m -2 ·d -1 , disintegration and degradation performance ≤85d, puncture resistance ≥15N.

[0022] The present invention also provides a grafted stretch film, which is blow-molded from a block copolyester suitable for the grafted stretch film, wherein the block copolyester suitable for the grafted stretch film is prepared by method B; the grafted stretch film has a thickness of 0.1-0.15 mm, an elongation at break of ≥600%, and a water vapor permeability of ≥300 g·m -2 ·d -1 , disintegration and degradation performance ≤90d, puncture resistance ≥18N.

[0023] The present invention also provides a grafted stretch film, which is blow-molded by a block copolyester suitable for the grafted stretch film, wherein the block copolyester suitable for the grafted stretch film is prepared by method C; the grafted stretch film has a thickness of 0.1 mm, an elongation at break of ≥900%, and a water vapor permeability of ≥350 g·m -2 ·d -1 , disintegration and degradation performance ≤85d, puncture resistance ≥20N.

[0024] Beneficial Effects

[0025] The present invention not only solves the problems of existing grafting membrane materials in terms of degradability, mechanical properties, water permeability and puncture resistance, but also improves production efficiency and reduces costs, providing a more environmentally friendly, efficient and economical solution for fruit tree seedling grafting. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of forming a large number of hydrogen bonds between the molecular chains of the block copolyester suitable for grafting stretch film of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0028] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0029] Molecular weight: The molecular weight of the sample was determined by gel permeation chromatography (GPC) analysis. During the test, a gel permeation chromatograph produced by Waters was used, hexafluoroisopropanol (HFIP) was used as the mobile phase, the flow rate was set at 0.5 mL / min, and the test temperature was maintained at 35°C.

[0030] Elongation at break: measured in accordance with GB / T1040.3-2006 standard; wherein the width of the specimen is 10 mm, the initial distance between the clamps is 50 mm, and the tensile speed is 500 mm / min.

[0031] Water vapor transmission rate: After the sample is preheated for 1 hour, it is measured at a temperature of 25°C and a relative humidity of 60% in accordance with GB / T 26253-2010 standard.

[0032] Disintegration and degradation performance: measured in accordance with GB / T19811-2005 standard.

[0033] Puncture resistance: Cut the sample to be tested into a size of 180mm×180mm and measure it according to BB / T 0024-2018 standard; the puncture speed of the needle is 250mm / min.

[0034] Example 1

[0035] A method for preparing a grafted stretch film, the specific steps are as follows:

[0036] (1) Preparation of raw materials;

[0037] Succinic acid;

[0038] Butanediol;

[0039] Additives: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:1:1;

[0040] Isosorbide;

[0041] Diisocyanate chain extender: HDI;

[0042] (2) preparing a hydroxyl-terminated PBS prepolymer and a hydroxyl-terminated isosorbide-based polyester prepolymer respectively;

[0043] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 180°C and a pressure of 0.1MPa for 4 hours, then heat the temperature to 230°C and carry out a polycondensation reaction at a pressure of 50Pa for 1 hour to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight of 3000; wherein the molar ratio of succinic acid to butanediol is 1:1.1, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0044] The preparation process of the hydroxyl-terminated isosorbide-based polyester prepolymer is as follows: after mixing succinic acid, isosorbide and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 180° C. and a pressure of 0.1 MPa for 3 hours, then heat the temperature to 260° C. and carry out a condensation reaction at a pressure of 30 Pa for 2 hours to obtain a hydroxyl-terminated isosorbide-based polyester prepolymer with a molecular weight of 3000; wherein the molar ratio of succinic acid to isosorbide is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0045] (3) Preparation of block copolyesters suitable for grafted stretch films;

[0046] A hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isosorbide-based polyester prepolymer and a diisocyanate chain extender are mixed by a melting system, and reacted for 1 hour at a temperature of 160° C. and a pressure of 0.1 MPa to obtain a block copolyester suitable for grafting a stretch film; wherein the amount of the diisocyanate chain extender added is 8% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isosorbide-based polyester prepolymer is 8:2;

[0047] (4) preparing grafted stretched membrane;

[0048] The grafted stretch film is obtained by blow molding the block copolyester suitable for the grafted stretch film; wherein the process parameters of the blow molding are as follows: the film blowing machine temperature is 180°C, the screw speed is 30r / min, the traction speed is 25r / min, and the receiving speed is 35r / min.

[0049] The final grafted stretch film has a thickness of 0.05 mm, an elongation at break of 940%, and a water vapor permeability of 500 g·m -2 ·d -1 The puncture resistance is 15N and the disintegration and degradation performance is 78d.

[0050] Example 2

[0051] A method for preparing a grafted stretch film, the specific steps are as follows:

[0052] (1) Preparation of raw materials;

[0053] Succinic acid;

[0054] Butanediol;

[0055] Additives: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:1:1;

[0056] Isosorbide;

[0057] Diisocyanate chain extender: TDI;

[0058] (2) preparing a hydroxyl-terminated PBS prepolymer and a hydroxyl-terminated isosorbide-based polyester prepolymer respectively;

[0059] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 200°C and a pressure of 0.1MPa for 6 hours, then heat the temperature to 250°C and carry out a polycondensation reaction at a pressure of 40Pa for 2 hours to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight of 4000; wherein the molar ratio of succinic acid to butanediol is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0060] The preparation process of the hydroxyl-terminated isosorbide-based polyester prepolymer is as follows: after mixing succinic acid, isosorbide and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 200° C. and a pressure of 0.1 MPa for 4 hours, then heat the temperature to 250° C. and carry out a polycondensation reaction at a pressure of 20 Pa for 3 hours to obtain a hydroxyl-terminated isosorbide-based polyester prepolymer with a molecular weight of 5000; wherein the molar ratio of succinic acid to isosorbide is 1:1.1, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0061] (3) Preparation of block copolyesters suitable for grafted stretch films;

[0062] A hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isosorbide-based polyester prepolymer and a diisocyanate chain extender are mixed in a melt system, and the mixture is reacted for 0.5 h at a temperature of 170° C. and a pressure of 0.1 MPa to obtain a block copolyester suitable for grafting a stretch film; wherein the amount of the diisocyanate chain extender added is 5% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isosorbide-based polyester prepolymer is 5:5;

[0063] (4) preparing grafted stretched membrane;

[0064] The block copolyester suitable for grafted stretch film is blow-molded to obtain the grafted stretch film; wherein, the process parameters of the blow molding are as follows: the film blowing machine temperature is 190°C, the screw speed is 30r / min, the traction speed is 25r / min, and the receiving speed is 35r / min.

[0065] The final grafted stretch film has a thickness of 0.1 mm, an elongation at break of 820%, and a water vapor permeability of 450 g·m -2 ·d -1 The puncture resistance is 20N and the disintegration and degradation performance is 81d.

[0066] Example 3

[0067] A method for preparing a grafted stretch film, the specific steps are as follows:

[0068] (1) Preparation of raw materials;

[0069] Succinic acid;

[0070] Butanediol;

[0071] Additives: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:1:1;

[0072] Isosorbide;

[0073] Diisocyanate chain extender: MDI;

[0074] (2) preparing a hydroxyl-terminated PBS prepolymer and a hydroxyl-terminated isosorbide-based polyester prepolymer respectively;

[0075] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 190°C and a pressure of 0.1MPa for 5 hours, then heat the temperature to 240°C and carry out a polycondensation reaction at a pressure of 30Pa for 2 hours to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight of 5000; wherein the molar ratio of succinic acid to butanediol is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0076] The preparation process of the hydroxyl-terminated isosorbide-based polyester prepolymer is as follows: after mixing succinic acid, isosorbide and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 220° C. and a pressure of 0.1 MPa for 4 hours, then heat the temperature to 240° C. and carry out a polycondensation reaction at a pressure of 40 Pa for 3 hours to obtain a hydroxyl-terminated isosorbide-based polyester prepolymer with a molecular weight of 4000; wherein the molar ratio of succinic acid to isosorbide is 1:1.3, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0077] (3) Preparation of block copolyesters suitable for grafted stretch films;

[0078] A hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isosorbide-based polyester prepolymer and a diisocyanate chain extender are mixed in a melt system, and the mixture is reacted for 0.75 h at a temperature of 160° C. and a pressure of 0.1 MPa to obtain a block copolyester suitable for grafting a stretch film; wherein the amount of the diisocyanate chain extender added is 6% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isosorbide-based polyester prepolymer is 2:8;

[0079] (4) preparing grafted stretched membrane;

[0080] The grafted stretch film is obtained by blow molding the block copolyester suitable for the grafted stretch film; wherein the process parameters of the blow molding are as follows: the film blowing machine temperature is 180°C, the screw speed is 30r / min, the traction speed is 25r / min, and the receiving speed is 35r / min.

[0081] The final grafted stretch film has a thickness of 0.15 mm, an elongation at break of 700%, and a water vapor permeability of 400 g·m -2 ·d -1 The puncture resistance is 25N and the disintegration and degradation performance is 85d.

[0082] Comparative Example 1

[0083] A method for preparing a grafted stretch film is basically the same as that of Example 3, except that the specific process of step (2) is as follows:

[0084] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 200°C and a pressure of 0.1MPa for 5 hours, then heat the temperature to 240°C and carry out a polycondensation reaction at a pressure of 30Pa for 3 hours to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight range of 6000; wherein the molar ratio of succinic acid to butanediol is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0085] The preparation process of the hydroxyl-terminated isosorbide-based polyester prepolymer is as follows: after mixing succinic acid, isosorbide and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 220° C. and a pressure of 0.1 MPa for 4 hours, then heat the temperature to 250° C. and carry out a condensation reaction at a pressure of 45 Pa for 4 hours to obtain a hydroxyl-terminated isosorbide-based polyester prepolymer with a molecular weight of 6000; wherein, the molar ratio of succinic acid to isosorbide is 1:1.3, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid.

[0086] The final grafted stretch film has an elongation at break of 450% and a puncture resistance of 10N.

[0087] Compared with Example 3, the elongation at break of the grafted stretch film is significantly reduced in Comparative Example 1. This is because in Comparative Example 1, the molecular weight of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer is too high. During the subsequent chain extension reaction, the molecular weight of the initial prepolymer increases, and the number of urethane bonds formed is relatively reduced, which leads to a decrease in the number of hydrogen bonds that can be formed between the molecular chains of the block copolyester and a weakening of the interaction force between the molecular chains. This is manifested in that the elongation at break of the grafted stretch film finally obtained is significantly reduced, and the puncture resistance is significantly reduced.

[0088] Comparative Example 2

[0089] A method for preparing a grafted stretch film is basically the same as Example 3, except that in step (3), the amount of diisocyanate chain extender added is 4% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer.

[0090] The final grafted stretch film has an elongation at break of 300% and a puncture resistance of 5N.

[0091] Compared with Example 3, the elongation at break of the grafted stretch film in Comparative Example 2 is significantly reduced. This is because in Comparative Example 2, the amount of diisocyanate chain extender added is too low, resulting in a relatively insufficient amount of chain extender that can participate in the reaction to form carbamate bonds during the chain extension reaction, and the number of carbamate bonds formed is significantly reduced. Correspondingly, the number of hydrogen bonds that can be formed between the block copolyester molecular chains is also reduced, and the interaction force between the molecular chains is weakened. At the same time, too low an amount of diisocyanate chain extender added will also lead to insufficient chain extension reaction, resulting in insufficient molecular weight of the grafted stretch film and decreased strength, which is ultimately manifested as a significant decrease in the elongation at break of the grafted stretch film obtained and a significant decrease in puncture resistance.

[0092] Comparative Example 3

[0093] A method for preparing a grafted stretch film is basically the same as Example 3, except that the diisocyanate chain extender MDI is replaced by Joncryl® ADR 4468 (manufacturer: BASF).

[0094] The final grafted stretch film has an elongation at break of 350% and a puncture resistance of 5N.

[0095] Compared with Example 3, the elongation at break of the grafted stretch film in Comparative Example 3 is significantly reduced. This is because the Joncryl® ADR 4468 chain extender used in Comparative Example 3 is an epoxy chain extender, and its epoxy group undergoes a ring-opening reaction with the hydroxyl groups in the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer to generate a compound containing ether bonds and carbonyl groups, and the ether bonds and carbonyl groups cannot form hydrogen bonds, resulting in the inability to form interaction between the molecular chains after chain extension, which is manifested as a significant decrease in the elongation at break of the grafted stretch film finally obtained, and a significant decrease in the puncture resistance.

[0096] Example 4

[0097] A method for preparing a grafted stretch film, the specific steps are as follows:

[0098] (1) Preparation of raw materials;

[0099] Succinic acid;

[0100] Butanediol;

[0101] Additives: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:1:1;

[0102] Isomanitol;

[0103] Diisocyanate chain extender: HDI;

[0104] (2) preparing hydroxyl-terminated PBS prepolymer and hydroxyl-terminated isomannide-based polyester prepolymer respectively;

[0105] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 180°C and a pressure of 0.1MPa for 4 hours, then heat the temperature to 250°C and carry out a polycondensation reaction at a pressure of 40Pa for 2 hours to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight of 4000; wherein the molar ratio of succinic acid to butanediol is 1:1.3, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0106] The preparation process of the hydroxyl-terminated isomannide-based polyester prepolymer is as follows: after mixing succinic acid, isomannide and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 200° C. and a pressure of 0.1 MPa for 4 hours, then heat the temperature to 250° C. and carry out a condensation reaction at a pressure of 40 Pa for 3 hours to obtain a hydroxyl-terminated isomannide-based polyester prepolymer with a molecular weight of 5000; wherein the molar ratio of succinic acid to isomannide is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0107] (3) Preparation of block copolyesters suitable for grafted stretch films;

[0108] A hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isomannose-based polyester prepolymer and a diisocyanate chain extender are mixed in a melt system, and reacted for 1 hour at a temperature of 180° C. and a pressure of 0.1 MPa to obtain a block copolyester suitable for grafting a stretch film; wherein the amount of the diisocyanate chain extender added is 7% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isomannose-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isomannose-based polyester prepolymer is 5:5;

[0109] (4) preparing grafted stretched membrane;

[0110] The block copolyester suitable for grafted stretch film is blow-molded to obtain the grafted stretch film; wherein, the process parameters of the blow molding are as follows: the film blowing machine temperature is 200°C, the screw speed is 30r / min, the traction speed is 25r / min, and the receiving speed is 35r / min.

[0111] The final grafted stretch film has a thickness of 0.1 mm, an elongation at break of 800%, and a water vapor permeability of 450 g·m -2 ·d -1 The puncture resistance is 20N and the disintegration and degradation performance is 85d.

[0112] Example 5

[0113] A method for preparing a grafted stretch film, the specific steps are as follows:

[0114] (1) Preparation of raw materials;

[0115] Succinic acid;

[0116] Butanediol;

[0117] Additives: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:1:1;

[0118] Isomanitol;

[0119] Diisocyanate chain extender: TDI;

[0120] (2) preparing hydroxyl-terminated PBS prepolymer and hydroxyl-terminated isomannide-based polyester prepolymer respectively;

[0121] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 200°C and a pressure of 0.1MPa for 4 hours, then heat the temperature to 230°C and carry out a polycondensation reaction at a pressure of 50Pa for 3 hours to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight of 4000; wherein, the molar ratio of succinic acid to butanediol is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0122] The preparation process of the hydroxyl-terminated isomannide-based polyester prepolymer is as follows: after mixing succinic acid, isomannide and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 220° C. and a pressure of 0.1 MPa for 4 hours, then heat the temperature to 250° C. and carry out a condensation reaction at a pressure of 50 Pa for 3 hours to obtain a hydroxyl-terminated isomannide-based polyester prepolymer with a molecular weight of 4000; wherein the molar ratio of succinic acid to isomannide is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0123] (3) Preparation of block copolyesters suitable for grafted stretch films;

[0124] A hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isomannose-based polyester prepolymer and a diisocyanate chain extender are mixed in a melt system, and the mixture is reacted for 0.75 h at a temperature of 190° C. and a pressure of 0.1 MPa to obtain a block copolyester suitable for grafting a stretch film; wherein the amount of the diisocyanate chain extender added is 6% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isomannose-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isomannose-based polyester prepolymer is 6:4;

[0125] (4) preparing grafted stretched membrane;

[0126] The block copolyester suitable for grafted stretch film is blow-molded to obtain the grafted stretch film; wherein, the process parameters of the blow molding are as follows: the film blowing machine temperature is 210°C, the screw speed is 30r / min, the traction speed is 25r / min, and the receiving speed is 35r / min.

[0127] The final grafted stretch film has a thickness of 0.15 mm, an elongation at break of 750%, and a water vapor permeability of 300 g·m -2 ·d -1 The puncture resistance is 24N and the disintegration and degradation performance is 90d.

[0128] Example 6

[0129] A method for preparing a grafted stretch film, the specific steps are as follows:

[0130] (1) Preparation of raw materials;

[0131] Succinic acid;

[0132] Butanediol;

[0133] Additives: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:1:1;

[0134] Isomanitol;

[0135] Diisocyanate chain extender: MDI;

[0136] (2) preparing hydroxyl-terminated PBS prepolymer and hydroxyl-terminated isomannide-based polyester prepolymer respectively;

[0137] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 200°C and a pressure of 0.1MPa for 5 hours, then heat the temperature to 240°C and carry out a polycondensation reaction at a pressure of 30Pa for 2 hours to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight of 5000; wherein the molar ratio of succinic acid to butanediol is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0138] The preparation process of the hydroxyl-terminated isomannide-based polyester prepolymer is as follows: after mixing succinic acid, isomannide and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 200° C. and a pressure of 0.1 MPa for 3 hours, then heat the temperature to 260° C. and carry out a condensation reaction at a pressure of 40 Pa for 2 hours to obtain a hydroxyl-terminated isomannide-based polyester prepolymer with a molecular weight of 5000; wherein the molar ratio of succinic acid to isomannide is 1:1.1, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0139] (3) Preparation of block copolyesters suitable for grafted stretch films;

[0140] A hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isomannose-based polyester prepolymer and a diisocyanate chain extender are mixed in a melt system, and reacted for 1 hour at a temperature of 200° C. and a pressure of 0.1 MPa to obtain a block copolyester suitable for grafting a stretch film; wherein the amount of the diisocyanate chain extender added is 5% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isomannose-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isomannose-based polyester prepolymer is 7:3;

[0141] (4) preparing grafted stretched membrane;

[0142] The grafted stretch film is obtained by blow molding the block copolyester suitable for the grafted stretch film; wherein the process parameters of the blow molding are as follows: the film blowing machine temperature is 220°C, the screw speed is 30r / min, the traction speed is 25r / min, and the receiving speed is 35r / min.

[0143] The final grafted stretch film has a thickness of 0.1 mm, an elongation at break of 600%, and a water vapor permeability of 400 g·m -2 ·d -1 The puncture resistance is 18N and the disintegration and degradation performance is 88d.

[0144] Comparative Example 4

[0145] A method for preparing a grafted stretch film is basically the same as that of Example 6, except that the specific process of step (2) is as follows:

[0146] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 200°C and a pressure of 0.1MPa for 5 hours, then heat the temperature to 240°C and carry out a polycondensation reaction at a pressure of 30Pa for 3 hours to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight range of 6000; wherein the molar ratio of succinic acid to butanediol is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0147] The preparation process of the hydroxyl-terminated isosorbide-based polyester prepolymer is as follows: after mixing succinic acid, isosorbide and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 220° C. and a pressure of 0.1 MPa for 4 hours, then heat the temperature to 250° C. and carry out a condensation reaction at a pressure of 45 Pa for 4 hours to obtain a hydroxyl-terminated isosorbide-based polyester prepolymer with a molecular weight of 6000; wherein, the molar ratio of succinic acid to isosorbide is 1:1.3, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid.

[0148] The final grafted stretch film has an elongation at break of 550% and a puncture resistance of 16N.

[0149] Compared with Example 6, the elongation at break of the grafted stretch film is significantly reduced in Comparative Example 4. This is because in Comparative Example 4, the molecular weight of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer is too high. During the subsequent chain extension reaction, the molecular weight of the initial prepolymer increases, and the number of urethane bonds formed is relatively reduced, which leads to a decrease in the number of hydrogen bonds that can be formed between the molecular chains of the block copolyester and a weakening of the interaction force between the molecular chains. This is manifested in that the elongation at break of the grafted stretch film finally obtained is significantly reduced, and the puncture resistance is significantly reduced.

[0150] Comparative Example 5

[0151] A method for preparing a grafted stretch film is basically the same as Example 6, except that in step (3), the amount of diisocyanate chain extender added is 4% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer.

[0152] The final grafted stretch film has an elongation at break of 450% and a puncture resistance of 15N.

[0153] Compared with Example 6, the elongation at break of the grafted stretch film is significantly reduced in Comparative Example 5. This is because in Comparative Example 5, the amount of diisocyanate chain extender added is too low, resulting in a relatively insufficient amount of chain extender that can participate in the reaction to form carbamate bonds during the chain extension reaction, and the number of carbamate bonds formed is significantly reduced. Correspondingly, the number of hydrogen bonds that can be formed between the block copolyester molecular chains is also reduced, and the interaction force between the molecular chains is weakened. At the same time, too low an amount of diisocyanate chain extender added will also lead to insufficient chain extension reaction, resulting in insufficient molecular weight of the grafted stretch film and decreased strength, which is ultimately manifested as a significant decrease in the elongation at break of the grafted stretch film obtained and a significant decrease in puncture resistance.

[0154] Comparative Example 6

[0155] A method for preparing a grafted stretch film is basically the same as Example 6, except that the diisocyanate chain extender MDI is replaced by Joncryl® ADR 4468 (manufacturer: BASF).

[0156] The final grafted stretch film has an elongation at break of 400% and a puncture resistance of 8N.

[0157] Compared with Example 6, the elongation at break of the grafted stretch film in Comparative Example 6 is significantly reduced. This is because the Joncryl® ADR 4468 chain extender used in Comparative Example 6 is an epoxy chain extender, and its epoxy group undergoes a ring-opening reaction with the hydroxyl groups in the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer to generate a compound containing ether bonds and carbonyl groups, and the ether bonds and carbonyl groups cannot form hydrogen bonds, resulting in the inability to form interaction between the molecular chains after chain extension, which is manifested as a significant decrease in the elongation at break of the grafted stretch film finally obtained, and a significant decrease in the puncture resistance.

[0158] Example 7

[0159] A method for preparing a grafted stretch film, the specific steps are as follows:

[0160] (1) Preparation of raw materials;

[0161] Succinic acid;

[0162] Butanediol;

[0163] Additives: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:1:1;

[0164] Isoidol;

[0165] Diisocyanate chain extender: HDI;

[0166] (2) preparing a hydroxyl-terminated PBS prepolymer and a hydroxyl-terminated isoindrol-based polyester prepolymer respectively;

[0167] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 190°C and a pressure of 0.1MPa for 6 hours, then heat the temperature to 230°C and carry out a polycondensation reaction at a pressure of 40Pa for 2 hours to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight of 4000; wherein the molar ratio of succinic acid to butanediol is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0168] The preparation process of the hydroxyl-terminated isoidol-based polyester prepolymer is as follows: after mixing succinic acid, isoidol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 180° C. and a pressure of 0.1 MPa for 3 hours, then heat the temperature to 250° C. and carry out a condensation reaction at a pressure of 40 Pa for 2 hours to obtain a hydroxyl-terminated isoidol-based polyester prepolymer with a molecular weight of 4000; wherein the molar ratio of succinic acid to isoidol is 1:1.1, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0169] (3) Preparation of block copolyesters suitable for grafted stretch films;

[0170] A hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isoidene alcohol-based polyester prepolymer and a diisocyanate chain extender are mixed in a melt system, and the mixture is reacted at a temperature of 170° C. and a pressure of 0.1 MPa for 1 hour to obtain a block copolyester suitable for grafting a stretch film; wherein the amount of the diisocyanate chain extender added is 8% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isoidene alcohol-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isoidene alcohol-based polyester prepolymer is 3:7;

[0171] (4) preparing grafted stretched membrane;

[0172] The block copolyester suitable for grafted stretch film is blow-molded to obtain the grafted stretch film; wherein, the process parameters of the blow molding are as follows: the film blowing machine temperature is 190°C, the screw speed is 30r / min, the traction speed is 25r / min, and the receiving speed is 35r / min.

[0173] The final grafted stretch film has a thickness of 0.1 mm, an elongation at break of 900%, and a water vapor permeability of 450 g·m -2 ·d -1 The puncture resistance is 26N and the disintegration and degradation performance is 80d.

[0174] Comparative Example 7

[0175] A method for preparing a grafted stretch film is basically the same as that of Example 7, except that the specific process of step (2) is as follows:

[0176] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 200°C and a pressure of 0.1MPa for 5 hours, then heat the temperature to 240°C and carry out a polycondensation reaction at a pressure of 30Pa for 3 hours to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight range of 6000; wherein the molar ratio of succinic acid to butanediol is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0177] The preparation process of the hydroxyl-terminated isosorbide-based polyester prepolymer is as follows: after mixing succinic acid, isosorbide and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 220° C. and a pressure of 0.1 MPa for 4 hours, then heat the temperature to 250° C. and carry out a condensation reaction at a pressure of 45 Pa for 4 hours to obtain a hydroxyl-terminated isosorbide-based polyester prepolymer with a molecular weight of 6000; wherein, the molar ratio of succinic acid to isosorbide is 1:1.3, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid.

[0178] The final grafted stretch film has an elongation at break of 700% and a puncture resistance of 20N.

[0179] Compared with Example 7, the elongation at break of the grafted stretch film is significantly reduced in Comparative Example 7. This is because in Comparative Example 7, the molecular weight of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer is too high. During the subsequent chain extension reaction, the molecular weight of the initial prepolymer increases, and the number of urethane bonds formed is relatively reduced, which leads to a decrease in the number of hydrogen bonds that can be formed between the molecular chains of the block copolyester and a weakening of the interaction force between the molecular chains. This is manifested in that the elongation at break of the grafted stretch film finally obtained is significantly reduced, and the puncture resistance is significantly reduced.

[0180] Comparative Example 8

[0181] A method for preparing a grafted stretch film is basically the same as Example 7, except that in step (3), the amount of diisocyanate chain extender added is 4% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer.

[0182] The final grafted stretch film has an elongation at break of 600% and a puncture resistance of 15N.

[0183] Compared with Example 7, the elongation at break of the grafted stretch film in Comparative Example 8 is significantly reduced. This is because in Comparative Example 8, the amount of diisocyanate chain extender added is too low, resulting in a relatively insufficient amount of chain extender that can participate in the reaction to form carbamate bonds during the chain extension reaction, and the number of carbamate bonds formed is significantly reduced. Correspondingly, the number of hydrogen bonds that can be formed between the block copolyester molecular chains is also reduced, and the interaction force between the molecular chains is weakened. At the same time, too low an amount of diisocyanate chain extender added will also lead to insufficient chain extension reaction, resulting in insufficient molecular weight of the grafted stretch film and decreased strength, which is ultimately manifested as a significant decrease in the elongation at break of the grafted stretch film obtained and a significant decrease in puncture resistance.

[0184] Comparative Example 9

[0185] A method for preparing a grafted stretch film is basically the same as Example 7, except that the diisocyanate chain extender MDI is replaced by Joncryl® ADR 4468 (manufacturer: BASF).

[0186] The final grafted stretch film has an elongation at break of 500% and a puncture resistance of 10N.

[0187] Compared with Example 7, the elongation at break of the grafted stretch film in Comparative Example 9 is significantly reduced. This is because the Joncryl® ADR 4468 chain extender used in Comparative Example 9 is an epoxy chain extender, and its epoxy group undergoes a ring-opening reaction with the hydroxyl groups in the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer to generate a compound containing ether bonds and carbonyl groups, and the ether bonds and carbonyl groups cannot form hydrogen bonds, resulting in the inability to form interaction between the molecular chains after chain extension, which is manifested as a significant decrease in the elongation at break of the grafted stretch film finally obtained, and a significant decrease in the puncture resistance.

[0188] Example 8

[0189] A method for preparing a grafted stretch film, the specific steps are as follows:

[0190] (1) Preparation of raw materials;

[0191] Succinic acid;

[0192] Butanediol;

[0193] Additives: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:1:1;

[0194] Isoidol;

[0195] Diisocyanate chain extender: TDI;

[0196] (2) preparing a hydroxyl-terminated PBS prepolymer and a hydroxyl-terminated isoindrol-based polyester prepolymer respectively;

[0197] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 200°C and a pressure of 0.1MPa for 5 hours, then heat the temperature to 240°C and carry out a polycondensation reaction at a pressure of 50Pa for 2 hours to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight of 5000; wherein the molar ratio of succinic acid to butanediol is 1:1.3, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0198] The preparation process of the hydroxyl-terminated isoidol-based polyester prepolymer is as follows: after mixing succinic acid, isoidol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 200° C. and a pressure of 0.1 MPa for 4 hours, then heat the temperature to 250° C. and carry out a condensation reaction at a pressure of 30 Pa for 3 hours to obtain a hydroxyl-terminated isoidol-based polyester prepolymer with a molecular weight of 4000; wherein the molar ratio of succinic acid to isoidol is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0199] (3) Preparation of block copolyesters suitable for grafted stretch films;

[0200] A hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isoidol-based polyester prepolymer and a diisocyanate chain extender are mixed in a melt system, and the mixture is reacted for 1 hour at a temperature of 180° C. and a pressure of 0.1 MPa to obtain a block copolyester suitable for grafting a stretch film; wherein the amount of the diisocyanate chain extender added is 7% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isoidol-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isoidol-based polyester prepolymer is 5:5;

[0201] (4) preparing grafted stretched membrane;

[0202] The block copolyester suitable for grafted stretch film is blow-molded to obtain the grafted stretch film; wherein, the process parameters of the blow molding are as follows: the film blowing machine temperature is 200°C, the screw speed is 30r / min, the traction speed is 25r / min, and the receiving speed is 35r / min.

[0203] The final grafted stretch film has a thickness of 0.1 mm, an elongation at break of 960%, and a water vapor permeability of 350 g·m -2 ·d -1 The puncture resistance is 23N and the disintegration and degradation performance is 85d.

[0204] Example 9

[0205] A method for preparing a grafted stretch film, the specific steps are as follows:

[0206] (1) Preparation of raw materials;

[0207] Succinic acid;

[0208] Butanediol;

[0209] Additives: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:1:1;

[0210] Isoidol;

[0211] Diisocyanate chain extender: MDI;

[0212] (2) preparing a hydroxyl-terminated PBS prepolymer and a hydroxyl-terminated isoindrol-based polyester prepolymer respectively;

[0213] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: after mixing succinic acid, butanediol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 190°C and a pressure of 0.1MPa for 5 hours, then heat the temperature to 240°C and carry out a polycondensation reaction at a pressure of 30Pa for 2 hours to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight of 5000; wherein the molar ratio of succinic acid to butanediol is 1:1.1, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0214] The preparation process of the hydroxyl-terminated isoidol-based polyester prepolymer is as follows: after mixing succinic acid, isoidol and an auxiliary agent, firstly carry out an esterification reaction at a temperature of 200° C. and a pressure of 0.1 MPa for 4 hours, then heat the temperature to 260° C. and carry out a condensation reaction at a pressure of 40 Pa for 3 hours to obtain a hydroxyl-terminated isoidol-based polyester prepolymer with a molecular weight of 5000; wherein the molar ratio of succinic acid to isoidol is 1:1.2, and the amount of the auxiliary agent added is 0.5% of the mass of succinic acid;

[0215] (3) Preparation of block copolyesters suitable for grafted stretch films;

[0216] A hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isoidene alcohol-based polyester prepolymer and a diisocyanate chain extender are mixed in a melt system, and the mixture is reacted for 0.5 h at a temperature of 190° C. and a pressure of 0.1 MPa to obtain a block copolyester suitable for grafting a stretch film; wherein the amount of the diisocyanate chain extender added is 6% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isoidene alcohol-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isoidene alcohol-based polyester prepolymer is 4:6;

[0217] (4) preparing grafted stretched membrane;

[0218] The block copolyester suitable for grafted stretch film is blow-molded to obtain the grafted stretch film; wherein, the process parameters of the blow molding are as follows: the film blowing machine temperature is 210°C, the screw speed is 30r / min, the traction speed is 25r / min, and the receiving speed is 35r / min.

[0219] The final grafted stretch film has a thickness of 0.1 mm, an elongation at break of 930%, and a water vapor permeability of 400 g·m -2 ·d -1 The puncture resistance is 20N and the disintegration and degradation performance is 83d.

Claims

1. A method for preparing a block copolyester suitable for grafting a stretch film, characterized in that: A hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isohexitol-based polyester prepolymer and a diisocyanate chain extender are mixed and reacted, the molecular weights of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isohexitol-based polyester prepolymer are controlled to be in the range of 3000-5000, and the addition amount of the diisocyanate chain extender is controlled to be 5-8% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isohexitol-based polyester prepolymer, so as to obtain a block copolyester suitable for grafting a stretch film.

2. The method for preparing a block copolyester suitable for grafting stretch film according to claim 1, characterized in that: The mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isohexide alcohol-based polyester prepolymer is (2-8): (2-8).

3. The method for preparing a block copolyester suitable for grafting stretch film according to claim 1, characterized in that: The diisocyanate chain extender is hexamethylene diisocyanate, toluene diisocyanate or diphenylmethane diisocyanate.

4. The method for preparing a block copolyester suitable for grafting stretch film according to claim 1, characterized in that: The reaction system is a melting system, the reaction temperature is 160-220°C, the reaction time is 0.5-1h, and the reaction pressure is 0.1MPa.

5. The method for preparing a block copolyester suitable for grafted stretch film according to any one of claims 1 to 4, characterized in that: The hydroxyl-terminated isohexitol-based polyester prepolymer is a hydroxyl-terminated isosorbide-based polyester prepolymer.

6. A method for preparing a block copolyester suitable for grafted stretch film according to any one of claims 1 to 4, characterized in that: The hydroxyl-terminated isohexide-based polyester prepolymer is a hydroxyl-terminated isomannide-based polyester prepolymer.

7. A method for preparing a block copolyester suitable for grafted stretch film according to any one of claims 1 to 4, characterized in that: The hydroxyl-terminated isohexide-based polyester prepolymer is a hydroxyl-terminated isoidide-based polyester prepolymer.

8. A grafted stretch film, characterized in that: The block copolyester suitable for grafted stretch film is blow-molded, and the block copolyester suitable for grafted stretch film is prepared by the preparation method of the block copolyester suitable for grafted stretch film as claimed in claim 5; the thickness of the grafted stretch film is 0.05-0.15mm, the elongation at break is ≥700%, and the water vapor transmission rate is ≥400g·m -2 ·d -1 , disintegration and degradation performance ≤85d, puncture resistance ≥15N.

9. A grafted stretch film, characterized in that: The block copolyester suitable for grafted stretch film is blow-molded, and the block copolyester suitable for grafted stretch film is prepared by the preparation method of the block copolyester suitable for grafted stretch film as claimed in claim 6; the thickness of the grafted stretch film is 0.1-0.15mm, the elongation at break is ≥600%, and the water vapor transmission rate is ≥300g·m -2 ·d -1 , disintegration and degradation performance ≤90d, puncture resistance ≥18N.

10. A grafted stretch film, characterized in that: The block copolyester suitable for grafted stretch film is blow-molded, and the block copolyester suitable for grafted stretch film is prepared by the preparation method of the block copolyester suitable for grafted stretch film as claimed in claim 7; the grafted stretch film has a thickness of 0.1 mm, an elongation at break ≥ 900%, and a water vapor permeability ≥ 350 g·m -2 ·d -1 , disintegration and degradation performance ≤85d, puncture resistance ≥20N.

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