A PBS polyester and a preparation method thereof

Abstract

This invention discloses a PBS polyester and its preparation method. The polyester raw materials include succinic acid or its derivatives, zinc 1,4-butanediol, and magnesium salt, wherein the molar ratio of magnesium to succinic acid or its derivative in the magnesium salt is 7.1 × 10⁻⁶. ‑7 ~3.5×10 ‑4 1. The molar ratio of zinc element to succinic acid or its derivatives in the zinc salt is 5.3 × 10⁻⁶. ‑7 ~1.3×10 ‑4 :1; The butanediol ether content in the polyester is 0.4-2.2 wt%; The elongation at break of the polyester is greater than or equal to 250%; The preparation method is as follows: the raw materials are mixed, esterified and polycondensed, and then extruded, pelletized and dried to obtain the PBS polyester; By adding zinc salt and magnesium salt to the raw materials of PBS polyester, the ether content in the polyester is increased, thereby improving the toughness of the polyester.

Description

Technical Field

[0001] This invention relates to a polyester and its preparation method, and particularly to a PBS polyester and its preparation method. Background Technology

[0002] With the increasingly widespread use of plastic products, white pollution is becoming more and more serious. Because biodegradable plastics can replace petroleum-based polymer materials and the products can naturally degrade in the natural environment, biodegradable plastics have recently experienced rapid development.

[0003] Polybutylene succinate (PBS) is one of the fastest-growing fully biodegradable plastics, possessing a high relative molecular weight, high service temperature, and good mechanical properties and water resistance. However, PBS generally has limited toughness, which restricts its application range.

[0004] Chinese patent CN1834139A uses starch-grafted maleic anhydride copolymer to improve the compatibility of starch with aliphatic polyesters. A small amount of natural rubber is added as a toughening agent. Its production process is relatively complex. In addition, the strong irritant and volatility of anhydride can easily cause air pollution, which limits its application range.

[0005] Chinese patent CN1850892A uses starch and aliphatic polyester, with polylactic acid powder grafted onto the surface, to prepare a fully biodegradable starch-based composite with good compatibility through a mixing method. The aliphatic polyester and starch exhibit good compatibility due to the grafting agent, but the product has a low elongation at break and moderate toughness. Summary of the Invention

[0006] Purpose of the invention: The first objective of this invention is to provide a PBS polyester with improved toughness; the second objective of this invention is to provide a method for preparing the polyester.

[0007] Technical solution: The PBS polyester of the present invention comprises succinic acid or its derivatives, 1,4-butanediol, zinc salt and magnesium salt, wherein the molar ratio of magnesium to succinic acid or its derivatives in the magnesium salt is 7.1 × 10⁻⁶. -7 ~3.5×10 -4 1. The molar ratio of zinc element to succinic acid or its derivatives in the zinc salt is 5.3 × 10⁻⁶. -7 ~1.3×10 -4 1; The butanediol ether content in the polyester is 0.4 to 2.2 wt%, and the elongation at break of the polyester is greater than or equal to 250%.

[0008] Preferably, the magnesium salt is one or more of magnesium nitrate, magnesium chloride, magnesium acetate, and magnesium sulfate.

[0009] Preferably, the zinc salt is one or more of zinc sulfate, zinc nitrate, zinc chloride, and zinc acetate.

[0010] By simultaneously adding zinc and magnesium salts and controlling their proportions within a certain range, the catalytic effect of these two metal salts on the ether bond formation of 1,4-butanediol is enhanced, thereby increasing the butanediol ether content. The presence of butanediol ether structures in the polyester improves the toughness of the PBS polyester. The structural formula of the butanediol ether is as follows:

[0011]

[0012] The succinic acid or its derivative reacts with 1,4-butanediol to generate polybutylene succinate (PBS). Preferably, the molar ratio of the succinic acid or its derivative to 1,4-butanediol is 1:1.8 to 2.5, and the succinic acid derivative is succinic anhydride, dimethyl succinate, or diethyl succinate.

[0013] The polyester raw material also includes a titanium catalyst, which is one or more of tetrabutyl titanate, tetraisopropyl titanate, and potassium titanium oxalate. The molar ratio of titanium to succinic acid or its derivative in the titanium catalyst is 3.6 × 10⁻⁶. -5 ~7.2×10 -4 :1.

[0014] The polyester raw material also includes a stabilizer, which is one or more of phosphoric acid, triphenyl phosphate, trimethyl phosphate, phosphorous acid, or triphenyl phosphite. The amount of stabilizer used is based on elemental phosphorus, and the molar ratio of elemental phosphorus to succinic acid or its derivative is 2.7 × 10⁻⁶. -5 ~5.5×10 -4 1. The role of stabilizers is to improve the thermal stability of polymers and reduce thermal degradation side reactions during the reaction process.

[0015] The method for preparing PBS polyester according to the present invention involves mixing succinic acid or its derivative, 1,4-butanediol, titanium source, stabilizer, zinc salt and magnesium salt, performing esterification and polycondensation reactions, and then extruding, pelletizing and drying to obtain the PBS polyester.

[0016] Preferably, the esterification reaction is carried out at a temperature of 160–250°C and a pressure of 40–101 kPa absolute. The esterification reaction is terminated when the esterification rate reaches 95% or higher.

[0017] Preferably, the polycondensation includes a pre-condensation reaction and a final condensation reaction. The pre-condensation reaction temperature is 200-245°C, the pressure is 3-4.5 kPa (absolute pressure), and the reaction time is 0.5-1.5 hours. The final condensation reaction temperature is 200-260°C, the pressure is less than 101 Pa (absolute pressure), and the reaction time is 1.5-3.0 hours, after which the reaction ends.

[0018] Invention Mechanism: By utilizing the catalytic effect of zinc and magnesium ions on the etherification of 1,4-butanediol to butylene glycol ether, a flexible ether bond structure is introduced into the PBS molecular chain, thereby modifying the PBS macromolecular structure, weakening its crystallization ability, and thus improving the toughness of the resin.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) By adding zinc salt and magnesium salt to the raw materials of PBS polyester, the ether content in the polyester is increased, thereby improving the toughness of the polyester and the elongation at break is greater than or equal to 250%; (2) The preparation method is simple to operate and easy to industrialize. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the embodiments.

[0021] Example 1

[0022] The PBS polyester of the present invention comprises 354g (3mol) succinic acid, 675g (7.5mol) 1,4-butanediol, and 0.733g (2.15×10⁻⁶) butylated succinic acid, 1,4-butanediol, and 1,4-butanediol. -3 0.543 g (1.66 × 10⁻⁶) tetrabutyl titanate -3 0.151 g (1.06 × 10⁻⁶) of triphenyl phosphate. -3 mol) magnesium acetate and 0.0363g (1.98×10 -4 mol) zinc acetate.

[0023] The above-mentioned raw materials were added sequentially to a PU2.5 reaction polymerization reactor. Esterification was carried out at a reaction temperature of 250℃ and a reaction pressure of atmospheric pressure until the esterification rate reached over 95%. A pre-condensation reaction was then initiated at a reaction temperature of 245℃ and a pressure of 4.5 kPa (absolute pressure) for 1.5 hours. Subsequently, the pressure was gradually reduced to below 100 Pa, and the temperature was 260℃ for a polycondensation reaction for 1.5 hours. After the reaction was completed, the reactor was evacuated with nitrogen, discharged, granulated, and dried to obtain polyester chips.

[0024] Example 2

[0025] The PBS polyester of the present invention comprises 354g (3mol) succinic acid, 540g (6mol) 1,4-butanediol, and 0.439g (1.29×10⁻⁶) butylated succinic acid, 1,4-butanediol, and 1,4-butanediol. -3 0.109 g (3.33 × 10⁻⁶ mol) tetrabutyl titanate, 0.109 g (3.33 × 10⁻⁶ mol) -4 0.100 g (7.04 × 10⁻⁶ mol) of triphenyl phosphate, 0.100 g (7.04 × 10⁻⁶ mol) -4 mol) magnesium acetate and 0.072 g (3.92 × 10⁻⁶) -4 mol) zinc acetate.

[0026] The above-mentioned raw materials were added sequentially to a PU2.5 reaction polymerization reactor. Esterification was carried out at a reaction temperature of 210℃ and a reaction pressure of atmospheric pressure until the esterification rate reached over 95%. A pre-condensation reaction was then initiated at a temperature of 230℃ and a pressure of 4.0 kPa (absolute pressure) for 1 hour. Subsequently, the pressure was gradually reduced to below 100 Pa (absolute pressure) and the temperature was 245℃ for a polycondensation reaction, which lasted for 2 hours. After the reaction was completed, the reactor was evacuated with nitrogen, discharged, granulated, and dried to obtain polyester chips.

[0027] Example 3

[0028] The PBS polyester of the present invention comprises 354g (3mol) succinic acid, 540g (6mol) 1,4-butanediol, and 0.439g (1.29×10⁻⁶) butylated succinic acid, 1,4-butanediol, and 1,4-butanediol. -3 0.033 g (3.33 × 10⁻⁶ mol) tetrabutyl titanate, 0.033 g (3.33 × 10⁻⁶ mol) -4 0.0509 g (4.23 × 10⁻⁶) mol) phosphoric acid, 0.0509 g (4.23 × 10⁻⁶) - 4 mol) magnesium sulfate and 0.0323g (2.37×10 -4 mol) zinc chloride.

[0029] The above raw materials were added sequentially to a PU2.5 reaction polymerization reactor. Esterification was carried out at a reaction temperature of 160℃ and a reaction pressure of atmospheric pressure until the esterification rate reached over 95%. A pre-condensation reaction was then initiated at a reaction temperature of 200℃ and a pressure of 3.0 kPa (absolute pressure) for 0.5 hours. Subsequently, the pressure was gradually reduced to below 100 Pa, and the temperature was maintained at 200℃ for a polycondensation reaction for 3.0 hours. After the reaction was completed, the reactor was evacuated with nitrogen, discharged, granulated, and dried to obtain polyester chips.

[0030] Example 4

[0031] The PBS polyester of the present invention comprises 354g (3mol) succinic acid, 540g (6mol) 1,4-butanediol, and 0.439g (1.29×10⁻⁶) butylated succinic acid, 1,4-butanediol, and 1,4-butanediol. -3 0.109 g (3.33 × 10⁻⁶ mol) tetrabutyl titanate, 0.109 g (3.33 × 10⁻⁶ mol) -4 0.0021 g (1.42 × 10⁻⁶ mol) of triphenyl phosphate, 0.0021 g (1.42 × 10⁻⁶ mol) -5 mol) magnesium nitrate and 0.0012 g (7.45 × 10⁻⁶) -6 mol) zinc sulfate.

[0032] The above raw materials were added sequentially to a PU2.5 reaction polymerization reactor. Esterification was carried out at a reaction temperature of 180℃ and a reaction pressure of atmospheric pressure until the esterification rate reached over 95%. A pre-condensation reaction was then initiated at a reaction temperature of 245℃ and a pressure of 3.0 kPa (absolute pressure) for 0.75 hours. Subsequently, the pressure was gradually reduced to below 100 Pa, and the temperature was increased to 250℃ for a polycondensation reaction, which lasted 2.2 hours. After the reaction was completed, the reactor was evacuated with nitrogen, discharged, granulated, and dried to obtain polyester chips.

[0033] Example 5

[0034] The PBS polyester of the present invention comprises 354g (3mol) succinic acid, 486g (5.4mol) 1,4-butanediol, and 0.0368g (1.08×10⁻⁶) butylated succinic acid, 1,4-butanediol, and 1,4-butanediol. -4 0.0272 g (8.33 × 10⁻⁶ mol) tetrabutyl titanate, 0.0272 g (8.33 × 10⁻⁶ mol) -5 0.0003 g (2.11 × 10⁻⁶ mol) of triphenyl phosphate, 0.0003 g (2.11 × 10⁻⁶ mol) -6 mol) magnesium acetate and 0.0003 g (1.64 × 10⁻⁶) -6 mol) zinc acetate.

[0035] The above raw materials were added sequentially to a PU2.5 reaction polymerization reactor. Esterification was carried out at a reaction temperature of 220℃ and a reaction pressure of atmospheric pressure. Once the esterification rate reached over 95%, a pre-condensation reaction was initiated at a reaction temperature of 240℃ and a pressure of 3.0 kPa (absolute pressure) for 0.75 hours. Subsequently, the pressure was gradually reduced to below 100 Pa, and the temperature was increased to 250℃ for a polycondensation reaction, which lasted 2.2 hours. After the reaction was completed, the reactor was purged with nitrogen, discharged, granulated, and dried to obtain polyester chips.

[0036] Comparative Example 1

[0037] Based on Example 2, zinc acetate and magnesium acetate were not added, while other conditions remained unchanged.

[0038] Comparative Example 2

[0039] Based on Example 2, zinc acetate was used instead of magnesium acetate in equal molar amounts, while other conditions remained unchanged.

[0040] Comparative Example 3

[0041] Based on Example 2, magnesium acetate was used instead of zinc acetate in equal molar amounts, while other conditions remained unchanged.

[0042] Comparative Example 4

[0043] Based on Example 2, the mass of magnesium acetate was changed to 0.1566 g (1.1 × 10⁻⁶ g). -3The mass of zinc acetate was 0.1651 g (9.0 × 10⁻⁶ mol), and the mass of zinc acetate was 0.1651 g (9.0 × 10⁻⁶ mol). -4 (mol), with other conditions remaining unchanged.

[0044] Performance testing

[0045] Test method for ether content in PBS polyester: PBS polyester is alcoholyzed with excess methanol at 210℃ in the presence of zinc acetate catalyst to release butanediol ethers. The butanediol ether content in the filtrate is then detected by gas chromatography.

[0046] Mechanical property testing method: The test was conducted in accordance with the national standard GB / T 1040.2-2006 "Determination of tensile properties of plastics - Part 2 Test conditions for molded and extruded plastics". Standard specimens of resin were prepared and then tested on a universal tensile testing machine at a speed of 100 mm / min.

[0047] The test results of Examples 1-5 and Comparative Examples 1-4 are shown in Table 1.

[0048] Table 1 Performance Test Results

[0049]

[0050]

[0051] As can be seen from the data in Table 1, as the amount of zinc and magnesium added decreases, the ether content in the polyester decreases, the tensile strength of the polyester increases, and the elongation at break decreases. This indicates that by using a small amount of zinc and magnesium in combination, the toughness of the product can be effectively improved. Under the premise of ensuring basic performance (the mechanical properties are not significantly reduced, and the strength in the examples is basically maintained above 32 MPa), the toughness of the product is well improved.

[0052] As can be seen from Comparative Example 1, without the addition of magnesium and zinc salts, the ether content in polyester decreases sharply, the elongation at break decreases significantly, and the toughness decreases.

[0053] Comparative examples 2 and 3, which only added zinc or magnesium salts, showed that the ether content in the polyester was still very low. This indicates that only by adding both zinc and magnesium salts can the etherification of 1,4-butanediol be promoted to form butanediol ether, thereby improving the toughness of the polyester.

[0054] Comparative Example 4, with the addition of excessive zinc and magnesium salts, further increased the ether content and improved toughness, but significantly reduced its mechanical strength, affecting its performance. Furthermore, due to the acidity of the added substances, excessive addition easily leads to severe 1,4-butanediol side reactions, manifested as a substantial increase in the amount of effluent during esterification, a decrease in the amount of 1,4-butanediol participating in the esterification reaction, and a tendency for insufficient esterification rate, ultimately making it difficult to increase the polymer molecular weight.

Claims

1. A PBS polyester characterized by, The polyester raw material includes succinic acid or its derivatives, 1,4-butanediol, zinc salt, and magnesium salt, wherein the molar ratio of magnesium to succinic acid or its derivative in the magnesium salt is 7.1 × 10⁻⁶. -7 ~3.5×10 -4 1. The molar ratio of zinc element to succinic acid or its derivatives in the zinc salt is 5.3 × 10⁻⁶. -7 ~1.3×10 -4 1; The butanediol ether content in the polyester is 0.4-2.2 wt%; The elongation at break of the polyester is greater than or equal to 250%.

2. The PBS polyester according to claim 1, characterized in that, The magnesium salt is one or more of magnesium nitrate, magnesium chloride, magnesium acetate, and magnesium sulfate.

3. The PBS polyester according to claim 1, characterized in that, Zinc salts are one or more of zinc sulfate, zinc nitrate, zinc chloride, and zinc acetate.

4. The PBS polyester according to claim 1, characterized in that, The polyester raw material also includes a titanium catalyst, which is one or more of tetrabutyl titanate, tetraisopropyl titanate, and potassium titanium oxalate.

5. The PBS polyester according to claim 1, characterized in that, The polyester raw material also includes a stabilizer, which is one or more of phosphoric acid, triphenyl phosphate, trimethyl phosphate, phosphorous acid, or triphenyl phosphite.

6. The PBS polyester according to claim 1, characterized in that, The succinic acid derivative is succinic anhydride, dimethyl succinate, or diethyl succinate, and the molar ratio of succinic acid or its derivative to 1,4-butanediol is 1:1.8 to 2.

5.

7. A process for the preparation of the PBS polyester of claim 1, characterized by, Polyester raw materials are mixed, esterified and polycondensed, and then extruded, pelletized and dried to obtain the PBS polyester.

8. The method of making a PBS polyester according to claim 7, wherein, The esterification reaction is carried out at a temperature of 160–250°C and a pressure of 40–101 kPa.

9. The method of making a PBS polyester according to claim 7, wherein, The polycondensation includes pre-condensation and final condensation reactions. The pre-condensation reaction temperature is 200–245°C, the pressure is 3–4.5 kPa absolute, and the reaction time is 0.5–1.5 hours. The final condensation reaction temperature is 200–260°C, the pressure is less than 100 Pa, and the reaction time is 1.5–3.0 hours.

Images