Polyadipic acid-butylene terephthalate-glycollic acid copolymer mulching film

Abstract

The invention discloses a poly (adipic acid)-butylene terephthalate-glycollic acid copolymer mulching film, and belongs to the technical field of degradable materials. PBAT and PGA prepolymers are respectively synthesized through a step-by-step prepolymerization and copolymerization reaction process, and then a molecular chain combined block structure is formed through chemical copolymerization, so that the problem of poor compatibility of two materials in a traditional blending method is solved from the molecular level; wherein the polyglycolic acid chain segment enhances the barrier property and mechanical strength of the mulching film while improving the degradability of the mulching film; wherein the poly (butylene adipate-co-terephthalate) chain segment provides good processability and film-forming property, and avoids the problems of easy crystallization and difficult film blowing when PGA is independently processed; in conclusion, the mulching film prepared by the invention has the processability of PBAT and the rapid degradability of PGA, overcomes the compatibility defect of a traditional blending method, and has important application value in the field of agriculture.

Description

Technical Field

[0001] The invention belongs to the technical field of degradable materials, and in particular relates to a polyadipate-butylene terephthalate-glycolic acid copolymer ground film. Background Art

[0002] Mulch is a covering material placed on the soil surface to retain moisture and temperature, inhibit weed growth, and ultimately increase crop yields. Polyethylene mulch has been used in vegetable production since the 1950s, and its popularity in agriculture continues to grow.

[0003] However, due to its non-degradability, traditional polyethylene mulch films leave large amounts of residue in the soil, causing serious environmental problems. Long-term accumulation leads to soil compaction and reduced air permeability, directly resulting in reduced crop yields. Furthermore, residual film fragments circulate throughout the crop growth cycle, creating "white pollution" that poses a persistent threat to the ecological environment. To address this issue, biodegradable plastic mulch films have become a key alternative to traditional mulch films. Currently, the most widely researched and used type is polybutylene adipate terephthalate (PBAT) mulch film. While biodegradable, this material requires certain composting conditions for complete degradation, and its degradation rate in normal soil environments is moderate. Furthermore, polybutylene adipate terephthalate itself suffers from insufficient mechanical strength.

[0004] Another biodegradable material, polyglycolic acid (PGA), is made from the polymerization of glycolic acid and offers significant advantages: rapid degradation, adapting to the demands of natural environments; excellent barrier properties, effectively maintaining soil moisture; and outstanding mechanical strength, enhancing the durability of mulch films. However, this material has inherent disadvantages, such as difficulty in processing.

[0005] To combine the excellent processing properties of PBAT with the rapid degradation and high mechanical strength of PGA, existing technologies often use physical blending to combine the two. However, due to the significant differences in the molecular structures of PBAT and PGA and their poor compatibility, even with the addition of a compatibilizer, it is difficult to form a uniform and stable blend. This prevents the full utilization of the advantages of both materials, and the resulting mulch films often exhibit uneven mechanical properties and unstable degradation rates, limiting their practical application. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a polyadipate-butylene terephthalate-glycolic acid copolymer ground film.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A polyadipate-butylene terephthalate-glycolic acid copolymer mulch film is prepared by the following steps:

[0009] Step 1: Add glycolic acid into a polymerization reactor, introduce nitrogen, and react under heating and stirring conditions until the reaction is complete to obtain a polyglycolic acid prepolymer;

[0010] Step 2: first add terephthalic acid, adipic acid and 1,4-butanediol into a reactor, stir, then add a catalyst to carry out an esterification reaction, after the esterification is completed, obtain an esterified product, and then carry out a polycondensation reaction under reduced pressure to obtain a polybutylene adipate-terephthalate prepolymer;

[0011] Step 3: adding the polyglycolic acid prepolymer and the polybutylene adipate terephthalate prepolymer into a polymerization kettle, and carrying out a reduced pressure reaction under heating conditions to obtain a polybutylene adipate terephthalate glycolic acid copolymer;

[0012] Step 4: adding poly (butylene adipate-terephthalate-glycolic acid copolymer), chain extender, coupling agent, anti-blocking agent, ultraviolet absorber and antioxidant into a twin-screw extruder, extruding and granulating to obtain a modified mulch film material;

[0013] Step 5: Put the modified mulch film material into a single-screw film blowing machine for film blowing to obtain a polyadipate-butylene terephthalate-glycolic acid copolymer mulch film.

[0014] As a further technical solution, the flow rate of nitrogen in step 1 is 50-300 mL / min.

[0015] As a further technical solution, the reaction temperature in step 1 is 160-230° C., the reaction time is 3-5 h, and the stirring speed is 100-300 rpm.

[0016] As a further technical solution, the weight average molecular weight of the polyglycolic acid prepolymer obtained in step 1 is between 4000 and 10000.

[0017] As a further technical solution, in step 2, the molar ratio of 1,4-butanediol, terephthalic acid and adipic acid is 160-180:48:52.

[0018] As a further technical solution, in step 2, the catalyst is tetrabutyl titanate; the mass ratio of the catalyst to the reactants is 1:1000-5:1000; and the mass of the reactants is the total mass of phthalic acid, adipic acid and 1,4-butanediol.

[0019] As a further technical solution, the temperature of the esterification reaction in step 2 is 225-230° C. and the time is 3-4 hours.

[0020] As a further technical solution, the reaction conditions of the polycondensation reaction in step 2 are a vacuum condition of 2KPa and a temperature of 225-230°C for 2-3h.

[0021] As a further technical solution, in step 3, the mass ratio of polybutylene adipate-terephthalate to polyglycolic acid prepolymer is 1:0.1-0.5.

[0022] As a further technical solution, the temperature of the reduced pressure reaction in step 3 is 220-250° C., the time is 3-6 hours, the pressure is less than 50 Pa, and the stirring speed is 100-300 rpm.

[0023] As a further technical solution, the raw materials in step 4 are calculated in parts by mass as follows: 70-100 parts of poly(butylene adipate-terephthalate-glycolic acid) copolymer, 0.1-5 parts of chain extender, 0.001-5 parts of coupling agent, 0.001-1 parts of opening agent, 0.001-1 parts of ultraviolet absorber, and 0.001-1 parts of antioxidant.

[0024] As a further technical solution, the chain extender in step 4 is at least one of ADR 4468, ADR-4370s, hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, triglycidyl isocyanurate, and pyromellitic anhydride.

[0025] As a further technical solution, the coupling agent in step 4 is at least one of an aluminate coupling agent and a silane coupling agent.

[0026] As a further technical solution, the opening agent in step 4 is at least one of oleamide, talc, and silicon dioxide.

[0027] As a further technical solution, the antioxidant in step 4 is at least one of antioxidants 1010 and 1076.

[0028] As a further technical solution, the ultraviolet absorber in step 4 is at least one of UV-234 and UV-326.

[0029] As a further technical solution, the temperature of each section of the twin-screw extruder in step 4 is set to: 110-130°C for sections 1-2, 130-155°C for sections 3-8, 130-155°C for sections 9-11, and 135-150°C for the die.

[0030] As a further technical solution, in step 5, the temperature of the first section of the single-screw film blowing machine is 130-140°C, the temperature of the second section is 140-165°C, the temperature of the third section is 140-155°C, and the temperature of the die head is 140-165°C.

[0031] As a further technical solution, the thickness of the ground film in step 5 is 8-12 μm.

[0032] The present invention first synthesizes PBAT and PGA prepolymers separately through a step-by-step prepolymerization and copolymerization process, and then forms a block structure with molecular chains through chemical copolymerization, fundamentally solving the problem of poor compatibility in traditional physical blending methods. Subsequently, the performance of the material is further improved through blending modification, and finally the polyadipate-butylene terephthalate-glycolic acid copolymer ground film is produced by film blowing.

[0033] Beneficial effects of the present invention:

[0034] 1. The present invention prepares ground film materials by copolymerizing prepolymers, which solves the problem of poor compatibility between two materials in traditional blending methods at the molecular level;

[0035] 2. The mulch film prepared by the present invention contains polyglycolic acid segments, which not only improves the degradability of the mulch film, but also enhances the barrier properties and mechanical strength of the mulch film;

[0036] 3. The ground film prepared by the present invention has good processability and film-forming properties due to the presence of polybutylene adipate-terephthalate chain segments, thus avoiding the problems of easy crystallization and difficult film blowing when PGA is processed alone;

[0037] In summary, the mulch film prepared by the present invention has both the processing performance of PBAT and the rapid degradation of PGA, while overcoming the compatibility defects of the traditional blending method and meeting the needs of agricultural production. Due to its degradable properties, it avoids the white pollution of traditional plastic mulch films and has important application value in the agricultural field. DETAILED DESCRIPTION

[0038] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0039] Example 1

[0040] A polyadipate-butylene terephthalate-glycolic acid copolymer mulch film is prepared by the following steps:

[0041] Step 1: Glycolic acid was added to a polymerization reactor, nitrogen was introduced at a flow rate of 120 mL / min, and the mixture was stirred at 200° C. and 150 rpm for 5 h. After the reaction was completed, a polyglycolic acid prepolymer with a weight average molecular weight of 6000 was obtained;

[0042] Step 2: First, 31.8 kg of terephthalic acid, 30.2 kg of adipic acid and 57.6 kg of 1,4-butanediol were added to a reactor, and after stirring, 0.35 kg of tetrabutyl titanate was added, and an esterification reaction was carried out at 225 ° C. for 3 hours. After the esterification was completed, an esterified product was obtained, and a polycondensation reaction was carried out at 225 ° C. for 2 hours under a vacuum condition of 2 KPa to obtain a polybutylene adipate terephthalate prepolymer;

[0043] Step 3: 10 kg of polyglycolic acid prepolymer and 100 kg of polybutylene adipate terephthalate prepolymer were added to a polymerization kettle, and the mixture was reacted under reduced pressure at 230° C., 150 rpm, and less than 50 Pa to obtain a polybutylene adipate terephthalate glycolic acid copolymer;

[0044] Step 4, 100kg of poly (adipate - butylene terephthalate - glycolic acid copolymer), 0.2kg of diphenylmethane diisocyanate, 0.2kg of aluminate coupling agent, 0.1kg of oleamide, 0.1kg of ultraviolet absorber UV-234 and 0.1kg of antioxidant 1010 are added to a twin-screw extruder, and the temperature of each section of the twin-screw extruder is set to: 120 and 125°C for sections 1-2, 130, 130, 135, 135, 140, 140°C for sections 3-8, 140, 140, 140°C for sections 9-11, and 140°C for the die; extrusion granulation is performed to obtain a modified mulch film material;

[0045] Step 5: Place the modified mulch film material into a single-screw film blowing machine for film blowing. The temperatures of each zone of the single-screw film blowing machine are: the temperature of the first section is 135°C, the temperature of the second section is 140°C, the temperature of the third section is 145°C, and the temperature of the die head is 145°C; obtain a poly(adipate-butylene terephthalate-glycolic acid) copolymer mulch film with a thickness of 8 μm.

[0046] Example 2

[0047] A polyadipate-butylene terephthalate-glycolic acid copolymer mulch film is prepared by the following steps:

[0048] Step 1: Glycolic acid was added to a polymerization reactor, nitrogen was introduced at a flow rate of 120 mL / min, and the mixture was stirred at 230° C. and 300 rpm for 1 hour. After the reaction was completed, a polyglycolic acid prepolymer with a weight average molecular weight of 6000 was obtained;

[0049] Step 2: First, 31.8 kg of terephthalic acid, 30.2 kg of adipic acid and 57.6 kg of 1,4-butanediol were added to a reactor, and after stirring, 0.35 kg of tetrabutyl titanate was added, and an esterification reaction was carried out at 230 ° C for 3 hours. After the esterification was completed, an esterified product was obtained, and a polycondensation reaction was carried out at 230 ° C for 2 hours under a vacuum condition of 2 KPa to obtain a polybutylene adipate-terephthalate prepolymer;

[0050] Step 3: 30 kg of polyglycolic acid prepolymer and 100 kg of polybutylene adipate terephthalate prepolymer were added to a polymerization kettle, and the mixture was reacted under reduced pressure at 250° C., a stirring speed of 300 rpm, and a pressure controlled to be less than 50 Pa for 6 hours to obtain a polybutylene adipate terephthalate glycolic acid copolymer;

[0051] Step 4, 100kg of poly (adipate - butylene terephthalate - glycolic acid copolymer), 0.2kg of isophorone diisocyanate, 0.2kg of silane coupling agent KH-550, 0.1kg of talc, 0.1kg of ultraviolet absorber UV-326 and 0.1kg of antioxidant 1076 were added to a twin-screw extruder, and the temperatures of each section of the twin-screw extruder were set to: 120 and 125°C for sections 1-2, 130, 130, 135, 135, 140, 140°C for sections 3-8, 140, 140, 140°C for sections 9-11, and 140°C for the die; extrusion granulation was performed to obtain a modified mulch film material;

[0052] Step 5: Place the modified mulch film material into a single-screw film blowing machine for film blowing. The temperatures of each zone of the single-screw film blowing machine are: the temperature of the first section is 135°C, the temperature of the second section is 140°C, the temperature of the third section is 145°C, and the temperature of the die head is 145°C; obtain a poly(adipate-butylene terephthalate-glycolic acid) copolymer mulch film with a thickness of 8 μm.

[0053] Comparative Example 1

[0054] Step 1: First, 31.8 kg of terephthalic acid, 30.2 kg of adipic acid and 57.6 kg of 1,4-butanediol were added to a reactor, and after stirring, 0.35 kg of tetrabutyl titanate was added, and an esterification reaction was carried out at 230 ° C for 3 hours. After the esterification was completed, an esterified product was obtained, and a polycondensation reaction was carried out at 230 ° C under a vacuum condition of 2 KPa for 2 hours to obtain a polybutylene adipate terephthalate prepolymer; then, a reduced pressure reaction was continued at 230 ° C with a stirring speed of 150 rpm and a pressure control of less than 50 Pa for 4 hours to obtain polybutylene adipate terephthalate;

[0055] Step 2, 100kg of polybutylene adipate-terephthalate, 0.2kg of isophorone diisocyanate, 0.2kg of silane coupling agent KH-550, 0.1kg of talc, 0.1kg of ultraviolet absorber UV-326 and 0.1kg of antioxidant 1076 were added to a twin-screw extruder, and the temperatures of each section of the twin-screw extruder were set to: 120 and 125°C for sections 1-2, 130, 130, 135, 135, 140, 140°C for sections 3-8, 140, 140, 140°C for sections 9-11, and a die head of 140°C; extrusion granulation was performed to obtain a modified mulch film material;

[0056] Step 3: Place the modified mulch film material into a single-screw film blowing machine for film blowing. The temperatures of each zone of the single-screw film blowing machine are: 135°C for the first section, 140°C for the second section, 145°C for the third section, and 145°C for the die head; and obtain a poly(adipate-butylene terephthalate-glycolic acid) copolymer mulch film with a thickness of 8 μm.

[0057] The performance tests of the mulch films of Examples 1, 2 and Comparative Example 1 were conducted according to the GB / T 35795-2017 standard. The results are shown in the following table:

[0058]

[0059] As can be seen from the above table, the mechanical properties and water vapor barrier properties of the mulch film prepared in the embodiment of the present invention are higher than those of the comparative example, and the mulch film has important application value in the agricultural field.

[0060] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A poly(adipate-butylene terephthalate-glycolic acid) copolymer ground film, characterized in that: Prepared by the following steps: Step 1: Add glycolic acid into a polymerization reactor, introduce nitrogen, and react under heating and stirring conditions until the reaction is complete to obtain a polyglycolic acid prepolymer; Step 2: first add terephthalic acid, adipic acid and 1,4-butanediol into a reactor, stir, then add a catalyst to carry out an esterification reaction, after the esterification is completed, obtain an esterified product, and then carry out a polycondensation reaction under reduced pressure to obtain a polybutylene adipate-terephthalate prepolymer; Step 3: adding the polyglycolic acid prepolymer and the polybutylene adipate terephthalate prepolymer into a polymerization kettle, and carrying out a reduced pressure reaction under heating conditions to obtain a polybutylene adipate terephthalate glycolic acid copolymer; Step 4: adding poly (butylene adipate-terephthalate-glycolic acid copolymer), chain extender, coupling agent, anti-blocking agent, ultraviolet absorber and antioxidant into a twin-screw extruder, extruding and granulating to obtain a modified mulch film material; Step 5: Put the modified mulch film material into a single-screw film blowing machine for film blowing to obtain a polyadipate-butylene terephthalate-glycolic acid copolymer mulch film.

2. The poly(butylene adipate-terephthalate-glycolic acid) copolymer ground film according to claim 1, characterized in that: In step 1, the flow rate of nitrogen is 50-300 mL / min; the reaction temperature is 160-230° C., the reaction time is 3-5 h; and the stirring speed is 100-300 rpm.

3. The poly(adipate-butylene terephthalate-glycolic acid) copolymer ground film according to claim 1, characterized in that: In step 2, the molar ratio of 1,4-butanediol, terephthalic acid and adipic acid is 160-180:48:

52.

4. The poly(adipate-butylene terephthalate-glycolic acid) copolymer ground film according to claim 1, characterized in that: In step 2, the catalyst is tetrabutyl titanate; the mass ratio of the catalyst to the reactants is 1:1000-5:1000; and the mass of the reactants is the total mass of phthalic acid, adipic acid and 1,4-butanediol.

5. The poly(adipate-butylene terephthalate-glycolic acid) copolymer ground film according to claim 1, characterized in that: The temperature of the esterification reaction in step 2 is 225-230° C. and the time is 3-4 hours.

6. The poly(butylene adipate-terephthalate-glycolic acid) copolymer ground film according to claim 1, characterized in that: The reaction conditions of the polycondensation reaction in step 2 are as follows: under a vacuum condition of 2 KPa, at a temperature of 225-230° C. for 2-3 hours.

7. The poly(adipate-butylene terephthalate-glycolic acid) copolymer ground film according to claim 1, characterized in that: In step 3, the mass ratio of polybutylene adipate-terephthalate to polyglycolic acid prepolymer is 1:0.1-0.

5.

8. The poly(adipate-butylene terephthalate-glycolic acid) copolymer ground film according to claim 1, characterized in that: The temperature of the reduced pressure reaction in step 3 is 220-250° C., the time is 3-6 hours, the pressure is less than 50 Pa, and the stirring speed is 100-300 rpm.

9. The poly(adipate-butylene terephthalate-glycolic acid) copolymer ground film according to claim 1, characterized in that: The raw materials in step 4 are calculated in parts by mass as follows: 70-100 parts of poly (butylene adipate-terephthalate-glycolic acid copolymer), 0.1-5 parts of chain extender, 0.001-5 parts of coupling agent, 0.001-1 parts of opening agent, 0.001-1 parts of ultraviolet absorber, and 0.001-1 parts of antioxidant.

10. The poly(adipate-butylene terephthalate-glycolic acid) copolymer ground film according to claim 1, characterized in that: In step 4, the chain extender is at least one of ADR 4468, ADR-4370s, hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, triglycidyl isocyanurate, and pyromellitic anhydride.

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