Preparation method of block copolyester applicable to grafting stretch film

Abstract

The present invention belongs to the technical field of composite materials for thin films, and relates to a preparation method of a block copolyester applicable to grafted stretch films. A hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isomannide-based polyester prepolymer, and a diisocyanate chain extender are mixed and then reacted. The molecular weight ranges of both the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isomannide-based polyester prepolymer are controlled to be 3000 - 5000, and at the same time, 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 isomannide-based polyester prepolymer, thus obtaining the block copolyester applicable to grafted stretch films. The present invention not only solves the problems existing in the existing grafted film materials in terms of degradability, mechanical properties, water vapor permeability, and puncture resistance, but also provides a more environmentally friendly, efficient, and economical solution for the grafting of fruit tree seedlings.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials for thin films, and relates to a preparation method of a block copolyester suitable for grafting stretch films. Background Art

[0002] Grafting of fruit tree seedlings, as a commonly used and effective method to enhance the disease resistance of plants, is widely applied in fruit tree cultivation. During the grafting process, polyethylene (PE) grafting films are usually used to wrap and cover the grafted seedlings to improve the survival rate. They have the advantages of low price, high toughness, and good light transmittance, occupying the main market of such products. However, there are many problems when using PE grafting films.

[0003] Specifically, PE grafting films are difficult to degrade naturally in the environment, and the polymer fragments generated during the seedling grafting process are difficult to recycle. Falling into the soil and the environment will cause a large amount of pollution. At the same time, PE grafting films have high mechanical properties. After the seedlings survive, tools are needed to remove the film or make a break to allow the seedlings to continue growing, which consumes a lot of manpower. In addition, the water permeability of PE winding films is poor, which easily causes the humidity at the grafting site to be too high, leading to problems such as the growth of bacteria and rot.

[0004] In view of the deficiencies of PE grafting films, people have begun to pay attention to the development of a new generation of grafting film materials. Among them, biodegradable polyester materials such as polylactic acid (PLA), poly(butylene adipate-co-terephthalate) (PBAT), and poly(butylene succinate) (PBS) have good development prospects. Among them, PBS shows a series of unique advantages in the application as a grafting film compared with PLA and PBAT.

[0005] Although PLA is favored for its excellent biodegradability and environmental friendliness, however, PLA has a large chemical structure rigidity, a breaking elongation rate of <10%, and insufficient ductility, which is not suitable for winding grafting 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 organoalkoxysilanes, and the breaking elongation rate increased, but still did not meet the breaking elongation standard (>300%) of the grafting winding film (industry standard BB / T 024-2018). In contrast, the breaking elongation rate of PBS can be as high as 400%, which provides significant advantages for its application in winding grafting films that require high ductility.

[0006] Although PBAT is also a recognized biodegradable polyester, it degrades slowly in the natural environment and is not suitable as a grafting film. 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 the PBS blend polymer degrades in soil supernatant for 6 months, and the degradation rate can reach 60% - 70%, showing excellent soil degradation performance, which is an important advantage for grafting films that require soil degradation performance.

[0007] Patent CN112048058B provides a preparation method of a high melting point crystalline biodegradable copolyester. By using chain extension methods such as isocyanate and epoxy, a PBS prepolymer, an isomannide-based polyester prepolymer, and a chain extender are mixed and then reacted to prepare a block copolyester. However, the intermolecular forces between the molecular chains of this block copolyester are weak, and the resulting film cannot form a stable three-dimensional chemical bond structure, resulting in insufficient puncture resistance and unable to meet the usage requirements of grafting stretch films. Summary of the Invention

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

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

[0010] A preparation method of a block copolyester suitable for grafting stretch films, in which a hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isomannide-based polyester prepolymer, and a diisocyanate chain extender are mixed and then reacted. The molecular weight ranges of both the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isomannide-based polyester prepolymer are controlled to be 3000 - 5000, and at the same time, 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 isomannide-based polyester prepolymer, thus obtaining a block copolyester suitable for grafting stretch films.

[0011] The present invention prepares a block copolyester by chain extension through the reaction of isocyanate groups and hydroxyl groups. The smaller the molecular weights of the PBS prepolymer capped with hydroxyl groups and the isomannide-based polyester prepolymer capped with hydroxyl groups, the more diisocyanate chain extender is required, and the more urethane bonds are formed. Since the molecular weight ranges of the PBS prepolymer capped with hydroxyl groups and the isomannide-based polyester prepolymer capped with hydroxyl groups are both controlled to be 3000 - 5000, and at the same time, the addition amount of the chain extender is controlled to be 5 - 8% of the total mass of the PBS prepolymer capped with hydroxyl groups and the isomannide-based polyester prepolymer capped with hydroxyl groups, a large number of urethane bonds exist in the molecular chain of the block copolyester, enabling a large number of hydrogen bonds to be formed between the molecular chains of the block copolyester (as shown in Figure 1 ), resulting in a relatively strong force between the molecular chains of the block copolyester, forming a hydrogen bond network structure of the polymer. The strength and elongation at break of the block copolyester are relatively ideal, thereby improving the puncture resistance of the polymer. Since there is an isomannide structure in the molecular chain of the block copolyester, the isomannide structure contains an ether bond and has good hydrophilicity and is prone to hydrolysis reaction, so the degradation performance of the block copolyester is relatively ideal. Since there is an isomannide structure in the molecular chain of the block copolyester, the crystallinity of the block copolyester is relatively low, the proportion of the amorphous region is relatively large, the permeable region is relatively large during the gas diffusion process, and the gas barrier performance is poor.

[0012] As a preferred technical solution:

[0013] For the preparation method of a block copolyester applicable to a grafted stretch film as described above, the mass ratio of the PBS prepolymer capped with hydroxyl groups to the isomannide-based polyester prepolymer capped with hydroxyl groups is 2 - 8:2 - 8.

[0014] For the preparation method of a block copolyester applicable to a grafted stretch film as described above, the diisocyanate chain extender is hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), or diphenylmethane diisocyanate (MDI).

[0015] For the preparation method of a block copolyester applicable to a grafted stretch film as described above, the reaction system is a molten system. The molten system is simple and solvent-free, without the need for dissolution, precipitation, and purification, with low cost. 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 - 1 h, and the reaction pressure is 0.1 MPa.

[0016] A preparation method of a block copolyester applicable to grafted stretch film as described above. The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: After mixing succinic acid, butanediol, and additives (such as antioxidants, catalysts, heat stabilizers, etc.), first carry out an esterification reaction at a temperature of 180 - 200 °C and a pressure of 0.1 MPa for 4 - 6 h, then raise the temperature to 230 - 250 °C and carry out a polycondensation reaction at a pressure ≤ 50 Pa for 1 - 2 h to obtain the hydroxyl-terminated PBS prepolymer; wherein, the molar ratio of succinic acid to butanediol is 1:1.1 - 1.3, and the addition amount of the additive is 0.5% of the mass of succinic acid.

[0017] A preparation method of a block copolyester applicable to grafted stretch film as described above. The preparation process of the hydroxyl-terminated isomannide-based polyester prepolymer is as follows: After mixing succinic acid, isomannide, and additives (such as antioxidants, catalysts, heat stabilizers, etc.), first carry out an esterification reaction at a temperature of 180 - 220 °C and a pressure of 0.1 MPa for 3 - 4 h, then raise the temperature to 240 - 260 °C and carry out a polycondensation reaction at a pressure ≤ 50 Pa for 2 - 3 h to obtain the hydroxyl-terminated isomannide-based polyester prepolymer; wherein, the molar ratio of succinic acid to isomannide is 1:1.1 - 1.3, and the addition amount of the additive is 0.5% of the mass of succinic acid.

[0018] A preparation method of a block copolyester applicable to grafted stretch film as described above. The hydroxyl-terminated isomannide-based polyester prepolymer is the hydroxyl-terminated isosorbide-based polyester prepolymer; when the hydroxyl-terminated isomannide-based polyester prepolymer is the hydroxyl-terminated isosorbide-based polyester prepolymer, the preparation method of the block copolyester applicable to grafted stretch film is denoted as Method A.

[0019] A preparation method of a block copolyester applicable to grafted stretch film as described above. The hydroxyl-terminated isomannide-based polyester prepolymer is the hydroxyl-terminated isomannitol-based polyester prepolymer; when the hydroxyl-terminated isomannide-based polyester prepolymer is the hydroxyl-terminated isomannitol-based polyester prepolymer, the preparation method of the block copolyester applicable to grafted stretch film is denoted as Method B.

[0020] A preparation method of a block copolyester applicable to grafted stretch film as described above. The hydroxyl-terminated isomannide-based polyester prepolymer is the hydroxyl-terminated isoiditol-based polyester prepolymer; when the hydroxyl-terminated isomannide-based polyester prepolymer is the hydroxyl-terminated isoiditol-based polyester prepolymer, the preparation method of the block copolyester applicable to grafted stretch film is denoted as Method C.

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

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

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

[0024] Beneficial effects

[0025] The present invention not only solves the problems existing in the degradability, mechanical properties, water permeability, and puncture resistance of existing grafting film materials, 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 a large number of hydrogen bonds formed between the molecular chains of the block copolyester suitable for grafting stretch films of the present invention. Detailed implementation manners

[0027] The present invention will be further described below in conjunction with specific implementation manners. It should be understood that these embodiments are only used to illustrate the present invention and not 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 also fall within the scope defined by the appended claims of this application.

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

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

[0030] Elongation at break: It is determined with reference to the standard of GB / T 1040.3 - 2006; among them, 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 to be tested is preheated and balanced for 1 h, it is determined with reference to the standard of GB / T 26253 - 2010 at a temperature of 25 °C and a relative humidity of 60%.

[0032] Disintegration and degradation performance: It is determined with reference to the standard of GB / T19811 - 2005.

[0033] Puncture resistance: The sample to be tested is cut into a size of 180 mm × 180 mm and determined with reference to the standard of BB / T 0024 - 2018; among them, the puncture speed of the needle is 250 mm / min.

[0034] Example 1

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

[0036] (1) Preparation of raw materials;

[0037] Succinic acid;

[0038] Butanediol;

[0039] Auxiliary agent: It is composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite with a mass ratio of 1:1:1;

[0040] Isosorbide;

[0041] Diisocyanate chain extender: HDI;

[0042] (2) Prepare a PBS prepolymer with a hydroxyl end group and an isosorbide - based polyester prepolymer with a hydroxyl end group respectively;

[0043] The preparation process of the PBS prepolymer with a hydroxyl end group is as follows: After mixing succinic acid, butanediol and the auxiliary agent, first carry out an esterification reaction at a temperature of 180 °C and a pressure of 0.1 MPa for 4 h, then raise the temperature to 230 °C and carry out a polycondensation reaction at a pressure of 50 Pa for 1 h to obtain a PBS prepolymer with a hydroxyl end group and a molecular weight of 3000; among them, the molar ratio of succinic acid to butanediol is 1:1.1, and the addition amount of the auxiliary agent 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, first carry out an esterification reaction at a temperature of 180 °C and a pressure of 0.1 MPa for 3 h, then raise the temperature to 260 °C and carry out a polycondensation reaction at a pressure of 30 Pa for 2 h to obtain a hydroxyl-terminated isosorbide-based polyester prepolymer with a molecular weight of 3000; among them, the molar ratio of succinic acid to isosorbide is 1:1.2, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0045] (3) Prepare a block copolyester suitable for grafting stretch film;

[0046] Using a molten system, after mixing the hydroxyl-terminated PBS prepolymer, the hydroxyl-terminated isosorbide-based polyester prepolymer, and a diisocyanate chain extender, carry out a reaction at a temperature of 160 °C and a pressure of 0.1 MPa for 1 h to obtain a block copolyester suitable for grafting stretch film; among them, the addition amount of the diisocyanate chain extender 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)Prepare a grafting stretch film;

[0048] Blow-mold the block copolyester suitable for grafting stretch film to obtain the grafting stretch film; among them, the process parameters of blow molding: the temperature of the blown film machine is 180 °C, the screw speed is 30 r / min, the traction speed is 25 r / min, and the winding speed is 35 r / min.

[0049] The finally prepared grafting stretch film has a thickness of 0.05 mm, an elongation at break of 940%, a water vapor transmission rate of 500 g·m -2 ·d -1 , a puncture resistance of 15 N, and a disintegration and degradation performance of 78 d.

[0050] Example 2

[0051] A preparation method of a grafting stretch film, the specific steps are as follows:

[0052] (1)Preparation of raw materials;

[0053] Succinic acid;

[0054] Butanediol;

[0055] Auxiliary agent: composed of antioxidant 1010, tetrabutyl titanate, and triphenyl phosphite with a mass ratio of 1:1:1;

[0056] Isosorbide;

[0057] Diisocyanate chain extender: TDI;

[0058] (2) Prepare hydroxyl-terminated PBS prepolymer and 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, first carry out an esterification reaction at a temperature of 200 °C and a pressure of 0.1 MPa for 6 h, then raise the temperature to 250 °C and carry out a polycondensation reaction at a pressure of 40 Pa for 2 h to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight of 4000; among them, the molar ratio of succinic acid to butanediol is 1:1.2, and the addition amount of the auxiliary agent 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, first carry out an esterification reaction at a temperature of 200 °C and a pressure of 0.1 MPa for 4 h, then raise the temperature to 250 °C and carry out a polycondensation reaction at a pressure of 20 Pa for 3 h to obtain a hydroxyl-terminated isosorbide-based polyester prepolymer with a molecular weight of 5000; among them, the molar ratio of succinic acid to isosorbide is 1:1.1, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0061] (3) Prepare a block copolyester suitable for grafting stretch film;

[0062] Using a molten system, after mixing the hydroxyl-terminated PBS prepolymer, the hydroxyl-terminated isosorbide-based polyester prepolymer, and the diisocyanate chain extender, react at a temperature of 170 °C and a pressure of 0.1 MPa for 0.5 h to obtain a block copolyester suitable for grafting stretch film; among them, the addition amount of the diisocyanate chain extender 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) Prepare a grafting stretch film;

[0064] Blow-mold the block copolyester suitable for grafting stretch film to obtain the grafting stretch film; among them, the process parameters of blow molding are: the temperature of the blown film machine is 190 °C, the screw speed is 30 r / min, the traction speed is 25 r / min, and the winding speed is 35 r / min.

[0065] The thickness of the finally obtained grafting stretch film is 0.1 mm, the elongation at break is 820%, the water vapor transmission rate is 450 g·m -2 ·d -1 , the puncture resistance is 20 N, and the disintegration and degradation performance is 81 d.

[0066] Example 3

[0067] A preparation method of grafted stretch film, the specific steps are as follows:

[0068] (1)Preparation of raw materials;

[0069] Succinic acid;

[0070] Butanediol;

[0071] Auxiliary agent: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite with a mass ratio of 1:1:1;

[0072] Isosorbide;

[0073] Diisocyanate chain extender: MDI;

[0074] (2)Prepare PBS prepolymer with hydroxyl end groups and isosorbide-based polyester prepolymer with hydroxyl end groups respectively;

[0075] The preparation process of the PBS prepolymer with hydroxyl end groups is as follows: After mixing succinic acid, butanediol and the auxiliary agent, first carry out an esterification reaction at a temperature of 190 °C and a pressure of 0.1 MPa for 5 h, then raise the temperature to 240 °C and carry out a polycondensation reaction at a pressure of 30 Pa for 2 h to obtain a PBS prepolymer with hydroxyl end groups with a molecular weight of 5000; Among them, the molar ratio of succinic acid to butanediol is 1:1.2, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0076] The preparation process of the isosorbide-based polyester prepolymer with hydroxyl end groups is as follows: After mixing succinic acid, isosorbide and the auxiliary agent, first carry out an esterification reaction at a temperature of 220 °C and a pressure of 0.1 MPa for 4 h, then raise the temperature to 240 °C and carry out a polycondensation reaction at a pressure of 40 Pa for 3 h to obtain an isosorbide-based polyester prepolymer with hydroxyl end groups with a molecular weight of 4000; Among them, the molar ratio of succinic acid to isosorbide is 1:1.3, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0077] (3)Prepare a block copolyester suitable for grafted stretch film;

[0078] Using a molten system, after mixing the PBS prepolymer with hydroxyl end groups, the isosorbide-based polyester prepolymer with hydroxyl end groups and the diisocyanate chain extender, react at a temperature of 160 °C and a pressure of 0.1 MPa for 0.75 h to obtain a block copolyester suitable for grafted stretch film; Among them, the addition amount of the diisocyanate chain extender is 6% of the total mass of the PBS prepolymer with hydroxyl end groups and the isosorbide-based polyester prepolymer with hydroxyl end groups, and the mass ratio of the PBS prepolymer with hydroxyl end groups to the isosorbide-based polyester prepolymer with hydroxyl end groups is 2:8;

[0079] (4)Prepare grafted stretch film;

[0080] The block copolyester applicable to the grafted stretch film is blow-molded to obtain the grafted stretch film; among them, the process parameters of blow molding are as follows: the temperature of the blown film machine is 180 °C, the screw speed is 30 r / min, the traction speed is 25 r / min, and the winding speed is 35 r / min.

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

[0082] Comparative Example 1

[0083] A preparation method of a grafted stretch film is basically the same as that of Example 3, the only difference being 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, first carry out an esterification reaction at a temperature of 200 °C and a pressure of 0.1 MPa for 5 h, then raise the temperature to 240 °C and carry out a polycondensation reaction at a pressure of 30 Pa for 3 h to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight range of 6000; among them, the molar ratio of succinic acid to butanediol is 1:1.2, and the addition amount of the auxiliary agent 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, first carry out an esterification reaction at a temperature of 220 °C and a pressure of 0.1 MPa for 4 h, then raise the temperature to 250 °C and carry out a polycondensation reaction at a pressure of 45 Pa for 4 h to obtain a hydroxyl-terminated isosorbide-based polyester prepolymer with a molecular weight of 6000; among them, the molar ratio of succinic acid to isosorbide is 1:1.3, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid.

[0086] The elongation at break of the finally obtained grafted stretch film is 450%, and the puncture resistance is 10 N.

[0087] Compared with Example 3, the elongation at break of the grafted stretch film in Comparative Example 1 decreased significantly. This is because in Comparative Example 1, the molecular weights of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer were too high. During the subsequent chain extension reaction, due to the increase in the molecular weight of the starting prepolymer, the number of urethane bonds formed was relatively reduced. As a result, the number of hydrogen bonds that could be formed between the molecular chains of the block copolyester decreased, and the force between the molecular chains weakened, manifested as a significant decrease in the elongation at break and a significant decrease in the puncture resistance of the finally obtained grafted stretch film.

[0088] Comparative Example 2

[0089] A preparation method of grafted stretch film is basically the same as that of Example 3, with the only difference being that in step (3), the addition amount of the diisocyanate chain extender is 4% of the total mass of the PBS prepolymer capped with hydroxyl groups and the isosorbide-based polyester prepolymer capped with hydroxyl groups.

[0090] The elongation at break of the finally prepared grafted stretch film is 300%, and the puncture resistance is 5 N.

[0091] Compared with Example 3, the elongation at break of the grafted stretch film in Comparative Example 2 decreased significantly. This is because in Comparative Example 2, the addition amount of the diisocyanate chain extender was too low, resulting in a relative shortage of the chain extender that could participate in the reaction to form urethane bonds during the chain extension reaction. The number of urethane bonds formed decreased significantly. Correspondingly, the number of hydrogen bonds that could be formed between the block copolyester molecular chains also decreased, and the force between the molecular chains weakened accordingly. At the same time, too low an addition amount of the diisocyanate chain extender would also lead to insufficient chain extension reaction, resulting in insufficient molecular weight of the grafted stretch film and a decrease in strength. Finally, it was manifested as a significant decrease in the elongation at break and a significant decrease in the puncture resistance of the finally prepared grafted stretch film.

[0092] Comparative Example 3

[0093] A preparation method of grafted stretch film is basically the same as that of Example 3, with the only difference being that the diisocyanate chain extender MDI is replaced with Joncryl® ADR 4468 (manufactured by BASF).

[0094] The elongation at break of the finally prepared grafted stretch film is 350%, and the puncture resistance is 5 N.

[0095] Compared with Example 3, the elongation at break performance of the grafted stretch film in Comparative Example 3 decreased significantly. This is because the Joncryl® ADR 4468 chain extender used in Comparative Example 3 is an epoxy-based chain extender. Its epoxy group undergoes a ring-opening reaction with the hydroxyl groups in the PBS prepolymer capped with hydroxyl groups and the isosorbide-based polyester prepolymer capped with hydroxyl groups, generating a compound containing ether bonds and carbonyl groups. Since ether bonds and carbonyl groups cannot form hydrogen bonds, no interaction can be formed between the molecular chains after chain extension, resulting in a significant decrease in the elongation at break and a significant decrease in the puncture resistance of the finally prepared grafted stretch film.

[0096] Example 4

[0097] A preparation method of grafted stretch film is as follows:

[0098] (1) Preparation of raw materials;

[0099] Succinic acid;

[0100] Butanediol;

[0101] Auxiliary agent: composed of antioxidant 1010, tetrabutyl titanate, and triphenyl phosphite with a mass ratio of 1:1:1;

[0102] Isomannitol;

[0103] Diisocyanate chain extender: HDI;

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

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

[0106] The preparation process of the hydroxyl-terminated isomannitol-based polyester prepolymer is as follows: After mixing succinic acid, isomannitol, and the auxiliary agent, first carry out an esterification reaction at a temperature of 200 °C and a pressure of 0.1 MPa for 4 h, then raise the temperature to 250 °C and carry out a polycondensation reaction at a pressure of 40 Pa for 3 h to obtain a hydroxyl-terminated isomannitol-based polyester prepolymer with a molecular weight of 5000; among them, the molar ratio of succinic acid to isomannitol is 1:1.2, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0107] (3) Prepare a block copolyester suitable for grafting stretch film;

[0108] Using a molten system, after mixing the hydroxyl-terminated PBS prepolymer, the hydroxyl-terminated isomannitol-based polyester prepolymer, and the diisocyanate chain extender, react at a temperature of 180 °C and a pressure of 0.1 MPa for 1 h to obtain a block copolyester suitable for grafting stretch film; among them, the addition amount of the diisocyanate chain extender is 7% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isomannitol-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isomannitol-based polyester prepolymer is 5:5;

[0109] (4) Prepare a grafting stretch film;

[0110] Blow-mold the block copolyester suitable for grafting stretch film to obtain the grafting stretch film; among them, the process parameters of blow molding are: the temperature of the blown film machine is 200 °C, the screw speed is 30 r / min, the traction speed is 25 r / min, and the winding speed is 35 r / min.

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

[0112] Example 5

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

[0114] (1) Preparation of raw materials;

[0115] Succinic acid;

[0116] Butanediol;

[0117] Auxiliary agent: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite with a mass ratio of 1:1:1;

[0118] Isomannitol;

[0119] Diisocyanate chain extender: TDI;

[0120] (2) Prepare a PBS prepolymer with a hydroxyl end group and an isomannitol-based polyester prepolymer with a hydroxyl end group respectively;

[0121] The preparation process of the PBS prepolymer with a hydroxyl end group is as follows: After mixing succinic acid, butanediol and the auxiliary agent, first carry out an esterification reaction at a temperature of 200 °C and a pressure of 0.1 MPa for 4 h, and then raise the temperature to 230 °C and carry out a polycondensation reaction at a pressure of 50 Pa for 3 h to obtain a PBS prepolymer with a hydroxyl end group and a molecular weight of 4000; Among them, the molar ratio of succinic acid to butanediol is 1:1.2, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0122] The preparation process of the isomannitol-based polyester prepolymer with a hydroxyl end group is as follows: After mixing succinic acid, isomannitol and the auxiliary agent, first carry out an esterification reaction at a temperature of 220 °C and a pressure of 0.1 MPa for 4 h, and then raise the temperature to 250 °C and carry out a polycondensation reaction at a pressure of 50 Pa for 3 h to obtain an isomannitol-based polyester prepolymer with a hydroxyl end group and a molecular weight of 4000; Among them, the molar ratio of succinic acid to isomannitol is 1:1.2, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0123] (3) Prepare a block copolyester suitable for grafted stretch film;

[0124] Using a molten system, a hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isomannide-based polyester prepolymer, and a diisocyanate chain extender are mixed and then reacted at a temperature of 190 °C and a pressure of 0.1 MPa for 0.75 h to obtain a block copolyester suitable for grafting stretch films; wherein, the addition amount of the diisocyanate chain extender is 6% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isomannide-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isomannide-based polyester prepolymer is 6:4;

[0125] (4)Prepare the grafting stretch film;

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

[0127] The finally prepared grafting stretch film has a thickness of 0.15 mm, an elongation at break of 750%, a water vapor transmission rate of 300 g·m -2 ·d -1 , a puncture resistance of 24 N, and a disintegration and degradation performance of 90 d.

[0128] Example 6

[0129] A preparation method of a grafting stretch film, the specific steps are as follows:

[0130] (1)Preparation of raw materials;

[0131] Succinic acid;

[0132] Butanediol;

[0133] Auxiliary agent: composed of antioxidant 1010, tetrabutyl titanate, and triphenyl phosphite with a mass ratio of 1:1:1;

[0134] Isomannide;

[0135] Diisocyanate chain extender: MDI;

[0136] (2)Respectively prepare a hydroxyl-terminated PBS prepolymer and a hydroxyl-terminated isomannide-based polyester prepolymer;

[0137] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: Succinic acid, butanediol, and the auxiliary agent are mixed, and first subjected to an esterification reaction at a temperature of 200 °C and a pressure of 0.1 MPa for 5 h, and then the temperature is raised to 240 °C and a polycondensation reaction is carried out at a pressure of 30 Pa for 2 h 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 addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0138] The preparation process of the hydroxyl-terminated isomannide-based polyester prepolymer is as follows: Succinic acid, isomannide, and an auxiliary agent are mixed, and then subjected to an esterification reaction at a temperature of 200 °C and a pressure of 0.1 MPa for 3 h, and then the temperature is raised to 260 °C and a polycondensation reaction is carried out at a pressure of 40 Pa for 2 h to obtain a hydroxyl-terminated isomannide-based polyester prepolymer with a molecular weight of 5000; among them, the molar ratio of succinic acid to isomannide is 1:1.1, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0139] (3)Prepare a block copolyester suitable for grafting stretch films;

[0140] Using a molten system, after mixing the hydroxyl-terminated PBS prepolymer, the hydroxyl-terminated isomannide-based polyester prepolymer, and a diisocyanate chain extender, react at a temperature of 200 °C and a pressure of 0.1 MPa for 1 h to obtain a block copolyester suitable for grafting stretch films; among them, the addition amount of the diisocyanate chain extender is 5% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isomannide-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isomannide-based polyester prepolymer is 7:3;

[0141] (4)Prepare a grafting stretch film;

[0142] Blow the block copolyester suitable for grafting stretch films to obtain a grafting stretch film; among them, the process parameters of blowing: the temperature of the blown film machine is 220 °C, the screw speed is 30 r / min, the traction speed is 25 r / min, and the winding speed is 35 r / min.

[0143] The finally prepared grafting stretch film has a thickness of 0.1 mm, an elongation at break of 600%, a water vapor transmission rate of 400 g·m -2 ·d -1 , a puncture resistance of 18 N, and a disintegration and degradation performance of 88 d.

[0144] Comparative Example 4

[0145] A preparation method of a grafting stretch film is basically the same as that of Example 6, the only difference being that: the specific process of step (2) is as follows:

[0146] The preparation process of the hydroxyl-terminated PBS prepolymer is as follows: Succinic acid, butanediol, and an auxiliary agent are mixed, and then subjected to an esterification reaction at a temperature of 200 °C and a pressure of 0.1 MPa for 5 h, and then the temperature is raised to 240 °C and a polycondensation reaction is carried out at a pressure of 30 Pa for 3 h to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight range of 6000; among them, the molar ratio of succinic acid to butanediol is 1:1.2, and the addition amount of the auxiliary agent 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, first carry out an esterification reaction at a temperature of 220 °C and a pressure of 0.1 MPa for 4 h, then raise the temperature to 250 °C and carry out a polycondensation reaction at a pressure of 45 Pa for 4 h to obtain a hydroxyl-terminated isosorbide-based polyester prepolymer with a molecular weight of 6000; among them, the molar ratio of succinic acid to isosorbide is 1:1.3, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid.

[0148] The elongation at break of the finally prepared grafted stretch film is 550%, and the puncture resistance is 16 N.

[0149] Compared with Example 6, the elongation at break of the grafted stretch film in Comparative Example 4 decreased significantly. This is because in Comparative Example 4, the molecular weights of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer were too high. During the subsequent chain extension reaction, due to the increase in the molecular weight of the starting prepolymer, the number of urethane bonds formed was relatively reduced. As a result, the number of hydrogen bonds that could be formed between the molecular chains of the block copolyester decreased, and the force between the molecular chains weakened, manifested as a significant decrease in the elongation at break of the finally prepared grafted stretch film and a significant decrease in the puncture resistance.

[0150] Comparative Example 5

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

[0152] The elongation at break of the finally prepared grafted stretch film is 450%, and the puncture resistance is 15 N.

[0153] Compared with Example 6, the elongation at break of the grafted stretch film in Comparative Example 5 decreased significantly. This is because in Comparative Example 5, the addition amount of the diisocyanate chain extender was too low, resulting in a relative shortage of the chain extender that could participate in the reaction to form urethane bonds during the chain extension reaction, and the number of urethane bonds formed decreased significantly. Correspondingly, the number of hydrogen bonds that could be formed between the molecular chains of the block copolyester also decreased, and the force between the molecular chains weakened accordingly; at the same time, the too low addition amount of the diisocyanate chain extender would also lead to insufficient chain extension reaction, resulting in insufficient molecular weight and decreased strength of the grafted stretch film, and finally manifested as a significant decrease in the elongation at break of the finally prepared grafted stretch film and a significant decrease in the puncture resistance.

[0154] Comparative Example 6

[0155] A preparation method of grafted stretch film is basically the same as that of Example 6, with the only difference being that the diisocyanate chain extender MDI is replaced by Joncryl® ADR 4468 (manufactured by BASF).

[0156] The elongation at break of the finally prepared grafted stretch film is 400%, and the puncture resistance is 8 N.

[0157] Compared with Example 6, the elongation at break performance of the grafted stretch film in Comparative Example 6 decreased significantly. This is because the Joncryl® ADR 4468 chain extender used in Comparative Example 6 is an epoxy-based 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 form a compound containing ether bonds and carbonyl groups. Since ether bonds and carbonyl groups cannot form hydrogen bonds, no interaction can be formed between the molecular chains after chain extension, resulting in a significant decrease in the elongation at break and puncture resistance of the finally prepared grafted stretch film.

[0158] Example 7

[0159] A preparation method of grafted stretch film is as follows:

[0160] (1) Preparation of raw materials;

[0161] Succinic acid;

[0162] Butanediol;

[0163] Auxiliary agent: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite with a mass ratio of 1:1:1;

[0164] Isoidide;

[0165] Diisocyanate chain extender: HDI;

[0166] (2) Preparation of hydroxyl-terminated PBS prepolymer and hydroxyl-terminated isoidide-based polyester prepolymer respectively;

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

[0168] The preparation process of the hydroxyl-terminated isoidide-based polyester prepolymer is as follows: After mixing succinic acid, isoidide, and an auxiliary agent, first carry out an esterification reaction at a temperature of 180 °C and a pressure of 0.1 MPa for 3 h, then raise the temperature to 250 °C and carry out a polycondensation reaction at a pressure of 40 Pa for 2 h to obtain a hydroxyl-terminated isoidide-based polyester prepolymer with a molecular weight of 4000; among them, the molar ratio of succinic acid to isoidide is 1:1.1, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0169] (3)Prepare a block copolyester suitable for grafting stretch film;

[0170] Using a molten system, after mixing the hydroxyl-terminated PBS prepolymer, the hydroxyl-terminated isoidide-based polyester prepolymer, and a diisocyanate chain extender, carry out a reaction at a temperature of 170 °C and a pressure of 0.1 MPa for 1 h to obtain a block copolyester suitable for grafting stretch film; among them, the addition amount of the diisocyanate chain extender is 8% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isoidide-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isoidide-based polyester prepolymer is 3:7;

[0171] (4)Prepare a grafting stretch film;

[0172] Blow the block copolyester suitable for grafting stretch film to obtain the grafting stretch film; among them, the process parameters of blow molding: the temperature of the blown film machine is 190 °C, the screw speed is 30 r / min, the traction speed is 25 r / min, and the winding speed is 35 r / min.

[0173] The finally prepared grafting stretch film has a thickness of 0.1 mm, an elongation at break of 900%, a water vapor transmission rate of 450 g·m -2 ·d -1 , a puncture resistance of 26 N, and a disintegration and degradation performance of 80 d.

[0174] Comparative Example 7

[0175] A preparation method of a grafting stretch film is basically the same as that of Example 7, the only difference being 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, first carry out an esterification reaction at a temperature of 200 °C and a pressure of 0.1 MPa for 5 h, then raise the temperature to 240 °C and carry out a polycondensation reaction at a pressure of 30 Pa for 3 h to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight range of 6000; among them, the molar ratio of succinic acid to butanediol is 1:1.2, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0177] The preparation process of the hydroxyl-terminated isosorbide-based polyester prepolymer is as follows: Succinic acid, isosorbide, and an auxiliary agent are mixed, and then subjected to an esterification reaction at a temperature of 220 °C and a pressure of 0.1 MPa for 4 h, and then the temperature is raised to 250 °C and a polycondensation reaction is carried out at a pressure of 45 Pa for 4 h 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 addition amount of the auxiliary agent is 0.5% of the mass of succinic acid.

[0178] The elongation at break of the finally prepared grafted stretch film is 700%, and the anti-puncture ability is 20 N.

[0179] Compared with Example 7, the elongation at break of the grafted stretch film in Comparative Example 7 decreased significantly. This is because in Comparative Example 7, the molecular weights of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer were too high. During the subsequent chain extension reaction, due to the increase in the molecular weight of the starting prepolymer, the number of urethane bonds formed was relatively reduced. As a result, the number of hydrogen bonds that could be formed between the molecular chains of the block copolyester decreased, and the force between the molecular chains weakened, manifested as a significant decrease in the elongation at break and anti-puncture ability of the finally prepared grafted stretch film.

[0180] Comparative Example 8

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

[0182] The elongation at break of the finally prepared grafted stretch film is 600%, and the anti-puncture ability is 15 N.

[0183] Compared with Example 7, the elongation at break of the grafted stretch film in Comparative Example 8 decreased significantly. This is because in Comparative Example 8, the addition amount of the diisocyanate chain extender was too low, resulting in a relative shortage of the chain extender that could participate in the reaction to form urethane bonds during the chain extension reaction, and the number of urethane bonds formed decreased significantly. Correspondingly, the number of hydrogen bonds that could be formed between the molecular chains of the block copolyester also decreased, and the force between the molecular chains weakened accordingly; at the same time, the too low addition amount of the diisocyanate chain extender would also lead to insufficient chain extension reaction, resulting in insufficient molecular weight and decreased strength of the grafted stretch film, and finally manifested as a significant decrease in the elongation at break and anti-puncture ability of the finally prepared grafted stretch film.

[0184] Comparative Example 9

[0185] A preparation method of grafted stretch film is basically the same as that of Example 7, with the only difference being that the diisocyanate chain extender MDI is replaced by Joncryl® ADR 4468 (manufactured by BASF).

[0186] The elongation at break of the finally prepared grafted stretch film is 500%, and the puncture resistance is 10 N.

[0187] Compared with Example 7, the elongation at break performance of the grafted stretch film in Comparative Example 9 decreased significantly. 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 form a compound containing ether bonds and carbonyl groups. Since ether bonds and carbonyl groups cannot form hydrogen bonds, no interaction can be formed between the molecular chains after chain extension, resulting in a significant decrease in the elongation at break and puncture resistance of the finally prepared grafted stretch film.

[0188] Example 8

[0189] A preparation method of grafted stretch film is as follows:

[0190] (1) Preparation of raw materials;

[0191] Succinic acid;

[0192] Butanediol;

[0193] Auxiliary agent: composed of antioxidant 1010, tetrabutyl titanate and triphenyl phosphite with a mass ratio of 1:1:1;

[0194] Isoidide;

[0195] Diisocyanate chain extender: TDI;

[0196] (2) Preparation of hydroxyl-terminated PBS prepolymer and hydroxyl-terminated isoidide-based polyester prepolymer respectively;

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

[0198] The preparation process of the hydroxyl-terminated isoidide-based polyester prepolymer is as follows: After mixing succinic acid, isoidide, and an auxiliary agent, first carry out an esterification reaction at a temperature of 200 °C and a pressure of 0.1 MPa for 4 h, then raise the temperature to 250 °C and carry out a polycondensation reaction at a pressure of 30 Pa for 3 h to obtain a hydroxyl-terminated isoidide-based polyester prepolymer with a molecular weight of 4000; among them, the molar ratio of succinic acid to isoidide is 1:1.2, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0199] (3) Prepare a block copolyester suitable for grafting stretch films;

[0200] Using a molten system, after mixing the hydroxyl-terminated PBS prepolymer, the hydroxyl-terminated isoidide-based polyester prepolymer, and the diisocyanate chain extender, carry out a reaction at a temperature of 180 °C and a pressure of 0.1 MPa for 1 h to obtain a block copolyester suitable for grafting stretch films; among them, the addition amount of the diisocyanate chain extender is 7% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isoidide-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isoidide-based polyester prepolymer is 5:5;

[0201] (4) Prepare a grafting stretch film;

[0202] Blow-mold the block copolyester suitable for grafting stretch films to obtain the grafting stretch film; among them, the process parameters of blow molding are: the temperature of the blown film machine is 200 °C, the screw speed is 30 r / min, the traction speed is 25 r / min, and the winding speed is 35 r / min.

[0203] The thickness of the finally prepared grafting stretch film is 0.1 mm, the elongation at break is 960%, the water vapor transmission rate is 350 g·m -2 ·d -1 , the puncture resistance is 23 N, and the disintegration and degradation performance is 85 d.

[0204] Example 9

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

[0206] (1) Preparation of raw materials;

[0207] Succinic acid;

[0208] Butanediol;

[0209] Auxiliary agent: composed of antioxidant 1010, tetrabutyl titanate, and triphenyl phosphite with a mass ratio of 1:1:1;

[0210] Isoidide;

[0211] Diisocyanate chain extender: MDI;

[0212] (2) Prepare a hydroxyl-terminated PBS prepolymer and a hydroxyl-terminated isoidide-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, first carry out an esterification reaction at a temperature of 190 °C and a pressure of 0.1 MPa for 5 h, then raise the temperature to 240 °C and carry out a polycondensation reaction at a pressure of 30 Pa for 2 h to obtain a hydroxyl-terminated PBS prepolymer with a molecular weight of 5000; among them, the molar ratio of succinic acid to butanediol is 1:1.1, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0214] The preparation process of the hydroxyl-terminated isoidide-based polyester prepolymer is as follows: After mixing succinic acid, isoidide, and an auxiliary agent, first carry out an esterification reaction at a temperature of 200 °C and a pressure of 0.1 MPa for 4 h, then raise the temperature to 260 °C and carry out a polycondensation reaction at a pressure of 40 Pa for 3 h to obtain a hydroxyl-terminated isoidide-based polyester prepolymer with a molecular weight of 5000; among them, the molar ratio of succinic acid to isoidide is 1:1.2, and the addition amount of the auxiliary agent is 0.5% of the mass of succinic acid;

[0215] (3)Prepare a block copolyester suitable for grafting stretch film;

[0216] Using a molten system, after mixing the hydroxyl-terminated PBS prepolymer, the hydroxyl-terminated isoidide-based polyester prepolymer, and a diisocyanate chain extender, react at a temperature of 190 °C and a pressure of 0.1 MPa for 0.5 h to obtain a block copolyester suitable for grafting stretch film; among them, the addition amount of the diisocyanate chain extender is 6% of the total mass of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isoidide-based polyester prepolymer, and the mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isoidide-based polyester prepolymer is 4:6;

[0217] (4)Prepare a grafting stretch film;

[0218] Blow the block copolyester suitable for grafting stretch film to obtain a grafting stretch film; among them, the process parameters of blowing: the temperature of the blown film machine is 210 °C, the screw speed is 30 r / min, the traction speed is 25 r / min, and the winding speed is 35 r / min.

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

Claims

1. A grafted stretch film, characterized in that: The block copolyester suitable for grafted stretch film is blow-molded. The preparation method of the block copolyester suitable for grafted stretch film is as follows: a hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isosorbide-based polyester prepolymer and a diisocyanate chain extender are mixed and reacted, the molecular weight range of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isosorbide-based polyester prepolymer is controlled to be 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 isosorbide-based polyester prepolymer, so as to obtain the block copolyester suitable for grafted stretch film; 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.

2. A grafted stretch film according to claim 1, characterized in that: The mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isosorbide-based polyester prepolymer is (2-8):(2-8).

3. A grafted stretch film according to claim 1, characterized in that: The diisocyanate chain extender is hexamethylene diisocyanate, toluene diisocyanate or diphenylmethane diisocyanate.

4. A grafted 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. A grafted stretch film, characterized in that: The block copolyester suitable for grafted stretch film is blow-molded. The preparation method of the block copolyester suitable for grafted stretch film is as follows: a hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isomannol-based polyester prepolymer and a diisocyanate chain extender are mixed and reacted, the molecular weight range of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isomannol-based polyester prepolymer is controlled to be 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 isomannol-based polyester prepolymer, so as to obtain the block copolyester suitable for grafted stretch film; 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.

6. A grafted stretch film according to claim 5, characterized in that: The mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isomannide-based polyester prepolymer is (2-8):(2-8).

7. The grafted stretch film according to claim 5, characterized in that: The diisocyanate chain extender is hexamethylene diisocyanate, toluene diisocyanate or diphenylmethane diisocyanate.

8. The grafted stretch film according to claim 5, 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.

9. A grafted stretch film, characterized in that: The block copolyester suitable for grafted stretch film is blow-molded. The preparation method of the block copolyester suitable for grafted stretch film is as follows: a hydroxyl-terminated PBS prepolymer, a hydroxyl-terminated isoidene alcohol-based polyester prepolymer and a diisocyanate chain extender are mixed and reacted, the molecular weight range of the hydroxyl-terminated PBS prepolymer and the hydroxyl-terminated isoidene alcohol-based polyester prepolymer is controlled to be 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 isoidene alcohol-based polyester prepolymer, so as to obtain the block copolyester suitable for grafted stretch film; the thickness of the grafted stretch film is 0.1 mm, the elongation at break is ≥900%, and the water vapor permeability is ≥350 g·m -2 ·d -1 , disintegration and degradation performance ≤85d, puncture resistance ≥20N.

10. A grafted stretch film according to claim 9, characterized in that: The mass ratio of the hydroxyl-terminated PBS prepolymer to the hydroxyl-terminated isoidol-based polyester prepolymer is (2-8):(2-8).

11. The grafted stretch film according to claim 9, characterized in that: The diisocyanate chain extender is hexamethylene diisocyanate, toluene diisocyanate or diphenylmethane diisocyanate.

12. The grafted stretch film according to claim 9, 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.

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