CN114516950B - Hyperbranched PBAT polyester and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of biodegradable materials, and particularly relates to hyperbranched PBAT polyester and a preparation method thereof. Active terminal hydroxyl of HBPE can participate in esterification and polycondensation reaction, and is used as polyol to extend a linear structure of a molecular chain into a branched structure, so that the crosslinking density of PBAT is improved, and the strength of PBAT is improved; meanwhile, the polycondensation time is shortened, and the acid value of the product is lower; the HBPE molecules have a spherical hyperbranched structure, the molecules are not entangled, the PBAT molecular chains are introduced to ensure that the PBAT molecular chains have the characteristics of low viscosity and high fluidity, and the polyester is particularly suitable for biodegradable products such as special-shaped injection molding parts and thin-wall injection molding parts with complex structures.

Description

Hyperbranched PBAT polyester and preparation method thereof

technical field

The invention belongs to the technical field of biodegradable materials, in particular to a hyperbranched PBAT polyester and a preparation method thereof.

Background technique

The increasingly serious "white pollution" problem has attracted great attention from countries around the world, and it is imperative to develop biodegradable plastics. Polybutylene terephthalate-co-polybutylene adipate (PBAT) combines the degradation properties of aliphatic polyesters and the mechanical properties of aromatic polyesters, and has good ductility and elongation at break. Long rate, has broad application prospects, but the low melt strength and mechanical strength of PBAT make most of them can not be used alone, and need to be blended with PLA and other degradable materials for injection molding. This promotes the popularization and application of degradable materials; the melt viscosity of PBAT is too high and the fluidity is poor. It is easy to form defects such as flow lines when injection molding thin-walled parts and special-shaped parts. If the injection temperature is increased, it is easy to cause degradation.

In order to improve the melt strength, mechanical strength and fluidity of PBAT, related researches are as follows:

Patent CN112321999A uses cyanuric chloride, ethylenediamine and other raw materials to synthesize triazine ring branching agent, and obtains modified PBAT by blending with the finished PBAT product, which improves the melt strength, mechanical properties and thermal properties of the product.

In the patent CN112266589A, by adding 10-25% hyperbranched polyester to increase the crosslinking density, a product with good creep resistance and low zero shear viscosity is obtained.

The patent CN105237750B increases the molecular weight of the product by adding the polyol chain extender trimethylol ethane in the polymerization stage, thereby improving the mechanical strength.

Under the premise of the same structure, the melt strength, mechanical properties and fluidity of the polymer are related to its molecular weight, molecular uniformity and branching degree. The method that prior art reduces and improves the fluidity of PBAT melt is mainly to add flow aids such as hyperbranched polyester after the PBAT polymerization is completed, but the terminal carboxyl group content in the commercially available PBAT product is mostly below 50mol/t, and some products Even within 10 mol/t, these commercially available products have less active carboxyl groups for reaction, low utilization rate of auxiliary agents, and some ungrafted small-molecule polyesters are easy to migrate; moreover, the blending method requires PBAT and flow The secondary heating of the auxiliary agent will easily lead to thermal degradation of PBAT, causing a series of problems such as increased acid value and yellowing; CN105237750B adds polyol trimethylol ethane in the esterification stage to increase the molecular weight of the product, but polyester As the molecular weight increases, the melt viscosity also increases simultaneously. How to improve the melt strength and mechanical properties of PBAT while reducing the viscosity and avoid the risk of multiple heating is an important issue to expand the application of PBAT in the fields of thin-wall injection molding, special-shaped parts, and blown film.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art, to provide a hyperbranched PBAT polyester and a preparation method thereof, which are suitable for biodegradable products such as special-shaped injection molded parts and thin-walled injection molded parts with complex structures.

The present invention adopts the following technical solutions to realize:

The preparation method of hyperbranched PBAT polyester of the present invention, comprises the steps:

(1) Preparation of HBPE (hydroxyl-terminated hyperbranched polyester):

Second-generation HBPE synthesis: put the core unit and branched monomer into the reactor, under the protection of nitrogen, heat up to 130-160 ℃ while stirring, and then put in catalyst A for constant temperature reaction, when the acid value of the reaction system drops to the specified value When the value is reached, the system is evacuated to extract the water produced by the reaction.

Synthesis of third-generation HBPE: continue to introduce nitrogen, add a certain amount of branched monomer and catalyst A, and react at a constant temperature of 130-160 °C. When the acid value of the reaction system drops to the specified value, end capping;

Partially end-capped third-generation HBPE synthesis: continue to introduce nitrogen, add a certain amount of end-capping agent to carry out end-capping reaction, and conduct constant temperature reaction at 130-160 °C. When the acid value of the reaction system drops to the specified value, the system is evacuated, and the extraction reaction produces The water obtained is a partially end-capped three-generation hyperbranched polyester;

(2) Esterification reaction: terephthalic acid, 1,6-adipic acid, 1,4-butanediol and catalyst A were added to the esterification kettle, and after the temperature was raised to the target temperature, the esterification reaction was carried out. When the water output reaches the theoretical value, the esterification reaction ends;

(3) Polycondensation reaction: Mix the esterified product after the reaction, catalyst A, and the partially end-capped third-generation HBPE prepared evenly, add heat stabilizers and antioxidants and raise the temperature to a specified temperature, turn on the vacuum, and carry out the pre-polycondensation reaction and final polycondensation reaction. .

In step (1), the molecular structure of the synthesized partially end-capped third-generation HBPE is as follows:

End-capping process route (m=32, 24; m-n=3-8).

The catalyst A is preferably one or more of tetrabutyl titanate, tetra-n-ethyl titanate or tetraisopropyl titanate.

In step (1), the core unit is one or more of aliphatic trihydric or tetrahydric alcohols such as pentaerythritol, trimethylolpropane, and glycerin; the branched monomer is 2,2-dihydroxypropionic acid; The end agent is a C1-C10 fatty acid, preferably formic acid, acetic acid, and propionic acid.

In step (1), the molar ratio of the core unit to the branched monomer during the synthesis of the second generation HBPE is 1:9-12, and the amount of catalyst A added is 0.01-0.5% of the mass of the monomer; during the synthesis of the third generation HBPE, the core unit and the new The molar ratio of the added branched monomers is 1:12-16, and the added amount of catalyst A is 0.01-0.5% of the mass of the monomers.

In step (1), when the second-generation HBPE and the third-generation HBPE are synthesized, after the acid value of the reaction system drops to 0-5 mgKOH/g, vacuum is evacuated to -0.02- to -0.06 MPa, and the reaction is continued for 1-2 h.

In step (1), when the partial end-capped third-generation HBPE is synthesized, the molar ratio of the added end-capping agent to the branched monomer added during the synthesis of the third-generation HBPE is 24-29:16, and the acid value of the reaction system drops to 0-5mgKOH/ After g, the reaction was terminated.

In step (1), the molecular weight of the partially end-capped third-generation HBPE is 2500-8000, the molecular weight distribution width is 1.0-1.8, the hydroxyl value is 30-200 mg KOH/g, and the branching degree DB _frey =0.39-0.49.

The molar ratio of the two monomers of terephthalic acid and 1,6-adipic acid in step (2) is 1:1.0-2.3. The molar ratio of dibasic acid to dihydric alcohol is 1:1.1-3.0.

In step (3), the amount of partially end-capped third-generation HBPE is 0.1-10‰ of the theoretical yield of PBAT.

In step (2), during esterification, the dosage of catalyst A calculated as titanium element is 15-50 ppm of the theoretical product mass; in step (3), the dosage of catalyst A calculated as titanium element is 45-150 ppm of the theoretical product mass.

In step (2), the esterification reaction is carried out at a temperature of 180-200°C and a reaction time of 1-3h; then the temperature is raised to 200-230°C for 2-3h;

In step (3), the pre-polycondensation reaction temperature is 230-240°C, the reaction pressure is 50-80KPa, and the reaction time is 1-2h;

In step (3), the final polycondensation reaction is carried out at a temperature of 235-250°C and a reaction pressure of 1-50KPa for 0.2-1.5h, and then adjusted to a reaction temperature of 240-270°C, the reaction pressure is less than 100Pa, and the reaction is performed for 0.5-1.5h, End the reaction.

In step (3), the amount of thermal stabilizer is 0.01%-0.2% of the theoretical product mass, and the amount of antioxidant is 0.01%-0.2% of the theoretical product mass.

Antioxidants are 2,6-di-tert-butyl-4-methylphenol, tetrakis[beta-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol, tris[2.4-di-tert- One or more of butylphenyl] phosphite or n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate; heat stabilizer is trisphosphite One or more of phenyl ester, triphenyl phosphate or ethyl phosphate.

Compared with the prior art, the beneficial effects of the present invention are as follows:

1. In the present invention, the synthesized HBPE is aliphatic polyester, which has biodegradability and will not affect the application of PBAT in food and other related fields. The same catalyst as PBAT polymerization is used in the synthesis process, and additional impurity molecules will not be introduced. .

2. Compared with other technologies of blending and modifying PBAT and fluidity aids, the present invention has a higher utilization rate of the hyperbranched polyester due to the fact that the polyhydroxy hyperbranched polyester is copolymerized with the raw materials in the polymerization stage. The hyperbranched polyester can be completely embedded in the PBAT molecular structure, avoiding the migration problem of small molecular flow aids; when the molecular chain is converted from linear to bulk structure, the mechanical properties of the polymer are significantly improved, and the number of hydroxyl groups in the outer layer is reduced to Appropriate degree, will not cause excessive cross-linking, and the product performance is more uniform. After the outermost hydroxyl group reacts with the dibasic acid in the PBAT raw material, the inner layer structure is still spherical, maintaining the high fluidity of the hyperbranched polyester, that is, the patented technology improves the mechanical properties and melt strength of PBAT. At the same time, the viscosity is reduced and the fluidity is improved. And the method of adding the polyhydroxy hyperbranched polyester in the polymerization stage avoids the degradation risk caused by the secondary heating of the blending method.

Detailed ways

In order to facilitate the understanding of the present invention, examples of the present invention are listed below. It should be understood by those skilled in the art that the embodiments are only for helping the understanding of the present invention, and should not be regarded as a specific limitation of the present invention.

The injection molding sample is carried out according to the provisions of GB/T17037.1-1997, and the A-type mold in GB T17037.1-1997 is used to prepare the 1A-type sample in GB/T1040.2-2006.

Pellet pretreatment: Before forming the sample, the pellets are preheated and dried in a vacuum drying oven, the thickness of the plate is less than 4cm, and the pellets are continuously dried at 80°C for 4h.

Sample preparation conditions: FANUC ROBOSHOT ɑ-S100iA Japan FANUC all-electric injection molding machine, screw injection machine process:

Standard environment for condition adjustment and testing of specimens:

The state adjustment of the sample shall be carried out according to the provisions of GB/T2918-1998. The conditions for state adjustment are the temperature of 23℃±2℃ and the adjustment time of 48h. The test is carried out under the standard environment specified in GB/T2918-1998, the temperature of the environment is 23℃±2℃, and the relative humidity is 50%±10%.

Tensile Strength at Break and Tensile Strain at Break

Prepare Type 1A specimens. According to GB / T1040.2 - 2006 regulations. The test speed is 50mm/min.

Flexural strength and flexural modulus

Prepare 80mm×10mm×4mm strip samples. According to GB/T9341-2008, the test speed is 2mm/min.

Spiral flow length test: The injection parameters refer to the injection molding conditions of the mechanical sample, and the mold is an Archimedes spiral semicircular groove.

in Examples 1-5.

The preparation steps of the partially end-capped third-generation HBPE are as follows:

Second-generation HBPE synthesis: put the core unit (pentaerythritol or trimethylolpropane) and 2,2-dihydroxypropionic acid into the reactor, under nitrogen protection, heat up to 130 °C while stirring, and then put in tetrabutyl titanate Ester, constant temperature reaction, when the acid value of the reaction system drops to 5mgKOH/g, the system is evacuated for 1h, and the water produced by the reaction is extracted.

Synthesis of third-generation HBPE: Continue to introduce nitrogen, add weighed 2,2-dihydroxypropionic acid and tetrabutyl titanate, and react at a constant temperature of 130 °C. When the acid value of the reaction system drops to 5 mgKOH/g, end capping is performed. .

Partially end-capped HBPE synthesis: Continue to introduce nitrogen, add a certain amount of propionic acid, and react at a constant temperature of 140 °C. When the acid value of the reaction system drops to 5 mgKOH/g, the system is evacuated for 1 hour, and the water produced by the reaction is extracted. The resulting product is a partially capped third-generation hyperbranched polyester.

Partially end-capped third-generation HBPE formula table in Examples 1-4:

Partially end-capped three-generation HBPE formula table in Example 5:

The index parameters of the partially end-capped third-generation HBPE prepared according to the above formula and steps are as follows:

Specific examples are as follows:

Example 1

Table 1 Example 1 Feeding Table

(1) Esterification reaction:

Add the weighed terephthalic acid, 1,4-butanediol and adipic acid into the esterification kettle, turn on the heating, stir evenly, raise the temperature to 180 °C, carry out the esterification dehydration reaction, and react for 2 hours. The amount of water reached the theoretical value of 799.9g, and no water was distilled out.

(2) Graft polycondensation: the co-esterified product after the reaction, 5.01 g of partially capped third-generation HBPE, tetrabutyl titanate, triphenyl phosphate and 2,6-di-tert-butyl-4-methylphenol were added for polymerization In the kettle, the reaction temperature was 220°C, the reaction pressure was 80KPa, the reaction time was 2h, and then added, the reaction temperature was 235°C, the reaction pressure was 50KPa, and the reaction was 1.5h; then the temperature was raised to 240°C, the reaction pressure was 100Pa, and the reaction time was 1.5h, and the reaction was ended. .

Example 2

Table 2 embodiment 2 feeding table

(1) Esterification reaction:

Add the weighed terephthalic acid, 1,4-butanediol and adipic acid into the esterification kettle, turn on the heating, stir evenly, raise the temperature to 180 °C, carry out the esterification dehydration reaction, and react for 2 hours. The amount of water reached the theoretical value of 799.9g, and no water was distilled out.

(2) Graft polycondensation: the co-esterified product after the reaction, 15.04g of partially end-capped third-generation HBPE, tetrabutyl titanate, triphenyl phosphate and 2,6-di-tert-butyl-4-methylphenol were added for polymerization In the kettle, the reaction temperature was 220°C, the reaction pressure was 80KPa, the reaction time was 2h, and then added, the reaction temperature was 235°C, the reaction pressure was 50KPa, and the reaction was 1.5h; then the temperature was raised to 240°C, the reaction pressure was 100Pa, and the reaction time was 1.5h, and the reaction was ended. .

Example 3

Table 3 embodiment 3 feeding table

(1) Esterification reaction:

Add the weighed terephthalic acid, 1,4-butanediol and adipic acid into the esterification kettle, turn on the heating, stir evenly, raise the temperature to 180 °C, carry out the esterification dehydration reaction, and react for 2 hours. The amount of water reached the theoretical value of 799.9g, and no water was distilled out.

(2) Graft polycondensation: the co-esterified product after the reaction, 25.07g of partially end-capped third-generation HBPE, tetrabutyl titanate, triphenyl phosphate and 2,6-di-tert-butyl-4-methylphenol were added for polymerization In the kettle, the reaction temperature was 220°C, the reaction pressure was 80KPa, the reaction time was 2h, and then added, the reaction temperature was 235°C, the reaction pressure was 50KPa, and the reaction was 1.5h; then the temperature was raised to 240°C, the reaction pressure was 100Pa, and the reaction time was 1.5h, and the reaction was ended. .

Example 4

Table 4 embodiment 4 feeding table

(1) Esterification reaction:

Add the weighed terephthalic acid, 1,4-butanediol and adipic acid into the esterification kettle, turn on the heating, stir evenly, raise the temperature to 180 °C, carry out the esterification dehydration reaction, and react for 2 hours. The amount of water reached the theoretical value of 799.9g, and no water was distilled out.

(2) Graft polycondensation: the co-esterified product after the reaction, 40.11 g of partially end-capped third-generation HBPE, tetrabutyl titanate, triphenyl phosphate and 2,6-di-tert-butyl-4-methylphenol were added to the polymerization In the kettle, the reaction temperature was 220°C, the reaction pressure was 80KPa, the reaction time was 2h, and then added, the reaction temperature was 235°C, the reaction pressure was 50KPa, and the reaction was 1.5h; then the temperature was raised to 240°C, the reaction pressure was 100Pa, and the reaction time was 1.5h, and the reaction was ended. .

Example 5

Table 5 embodiment 5 feeding table

(1) Esterification reaction:

Add the weighed terephthalic acid, 1,4-butanediol and adipic acid into the esterification kettle, turn on the heating, stir evenly, raise the temperature to 180 °C, carry out the esterification dehydration reaction, and react for 2 hours. The amount of water reached the theoretical value of 799.9g, and no water was distilled out.

(2) Graft polycondensation: the co-esterified product after the reaction, 7.39 g of partially capped third-generation HBPE, tetrabutyl titanate, triphenyl phosphate and 2,6-di-tert-butyl-4-methylphenol were added for polymerization In the kettle, the reaction temperature was 220°C, the reaction pressure was 80KPa, the reaction time was 2h, and then added, the reaction temperature was 235°C, the reaction pressure was 50KPa, and the reaction was 1.5h; then the temperature was raised to 240°C, the reaction pressure was 100Pa, and the reaction time was 1.5h, and the reaction was ended. .

Comparative Example 1

No hyperbranched HBPE was added, and other conditions were the same as in Example 3 above.

Comparative Example 2

Uncapped hyperbranched HBPE was added, and other conditions were the same as in Example 3 above.

The rotational flow length and mechanical properties of Examples 1-5 and Comparative Examples 1-2 were tested.

The test results are shown in Table 6.

Table 6 Spiral flow length and mechanical property parameters of the products of Examples 1-5 and Comparative Examples 1-2

It can be seen from the above data that the addition of end-capped hyperbranched polyester HBPE can greatly improve the fluidity and mechanical strength of PBAT.

Of course, the above contents are only preferred embodiments of the present invention, and should not be considered as limiting the scope of the embodiments of the present invention. The present invention is not limited to the above examples, and equivalent changes and improvements made by those of ordinary skill in the technical field within the essential scope of the present invention should all belong to the scope of the patent of the present invention.

Claims (8)

1. A preparation method of hyperbranched PBAT polyester is characterized in that: the method comprises the following steps:

(1) preparation of HBPE:

synthesis of second-generation HBPE: putting the nuclear unit and the branching monomer into a reactor, heating to 130-160 ℃, and adding a catalyst A for reaction;

the third generation HBPE is synthesized: after the synthesis of the second-generation HBPE is finished, adding a branched monomer and a catalyst A, and continuing to react at the temperature of 130-;

synthesizing part of end-blocked HBPE of three generations: adding a blocking agent after the third-generation HBPE synthesis is finished, carrying out blocking reaction at the temperature of 130-;

(2) esterification reaction:

adding terephthalic acid, 1, 6-adipic acid, 1, 4-butanediol and a catalyst A into an esterification kettle, heating, and carrying out esterification reaction, wherein when the water yield of the reaction reaches a theoretical value, the esterification reaction is finished;

(3) and (3) polycondensation reaction:

uniformly mixing an esterification product after the esterification reaction, a catalyst A and the prepared partially-terminated third-generation HBPE, adding a heat stabilizer and an antioxidant, heating, and then starting vacuum to perform a pre-polycondensation reaction and a final polycondensation reaction;

the core unit is one or more of aliphatic ternary or quaternary alcohol; the branched monomer is 2, 2-dihydroxy propionic acid; the end capping agent is C1-C10 fatty acid;

in the step (1), the molar ratio of a core unit to a branched monomer is 1:9-12 during the synthesis of the second-generation HBPE, and the addition amount of the catalyst A is 0.01-0.5% of the mass of the monomer; when the third-generation HBPE is synthesized, the molar ratio of the core unit to the newly added branched monomer is 1:12-16, and the addition amount of the catalyst A is 0.01-0.5% of the mass of the monomer; when partial end capping third-generation HBPE is synthesized, the molar ratio of the added end capping agent to the branched monomer added when the third-generation HBPE is synthesized is 24-29:16, and the reaction is ended after the acid value of the reaction system is reduced to 0-5 mgKOH/g.

2. The method of preparing a hyperbranched PBAT polyester according to claim 1, characterized in that: the catalyst A is one or more of tetrabutyl titanate, tetra-n-ethyl titanate or tetra-isopropyl titanate.

3. The method of preparing a hyperbranched PBAT polyester according to claim 1, characterized in that: in the step (1), when the second-generation HBPE and the third-generation HBPE are synthesized, after the acid value of the reaction system is reduced to 0-5mgKOH/g, the reaction system is vacuumized to-0.02-0.06 MPa, and the reaction is continued for 1-2 h.

4. The method of preparing a hyperbranched PBAT polyester according to claim 1, characterized in that: in the step (1), the molecular weight of the partially blocked third-generation HBPE is 2500-8000, the molecular weight distribution width is 1.0-1.8, the hydroxyl value is 30-200mg KOH/g, and the branching degree DB is_frey=0.39-0.49。

5. The method of preparing a hyperbranched PBAT polyester according to claim 1, characterized in that: the molar ratio of the terephthalic acid to the 1, 6-adipic acid in the step (2) is 1: 1.0-2.3; the molar ratio of the dibasic acid to the dibasic alcohol is 1: 1.1-3.0; in the step (3), the addition amount of the partially blocked third-generation HBPE is 0.1-10 per mill of the theoretical yield of PBAT; in the step (2), during esterification, the dosage of the catalyst A calculated by titanium element is 15-50ppm of the theoretical product mass; in the step (3), the dosage of the catalyst A calculated by titanium element is 45-150ppm of the theoretical product mass.

6. Method for the preparation of a hyperbranched PBAT polyester according to claim 1, characterized in that:

in the step (2): the esterification reaction is carried out at the temperature of 180 ℃ and 200 ℃ for 1-3 h; then heating to 200-230 ℃ for reaction for 2-3 h;

in the step (3), the pre-polycondensation reaction temperature is 230-240 ℃, the reaction pressure is 50-80KPa, and the reaction time is 1-2 h;

in the step (3), the final polycondensation is carried out at the temperature of 235 ℃ and the temperature of 250 ℃ and under the reaction pressure of 1-50Kpa for 0.2-1.5h, then the reaction temperature is adjusted to 240 ℃ and the reaction pressure is less than 100Pa, and the reaction is carried out for 0.5-1.5h, thus finishing the reaction.

7. The method of preparing a hyperbranched PBAT polyester according to claim 1, characterized in that: in the step (3), the heat stabilizer is one or more of triphenyl phosphite, triphenyl phosphate or ethyl phosphate, and the dosage of the heat stabilizer is 0.01-0.2% of the theoretical product mass; the antioxidant is one or more of 2, 6-di-tert-butyl-4-methylphenol, tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, tri [2, 4-di-tert-butylphenyl ] phosphite or beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid n-octadecyl ester, and the amount of the antioxidant is 0.01 to 0.2 percent of the theoretical mass of the product.

8. A hyperbranched PBAT polyester characterized in that: prepared by the method of preparing a hyperbranched PBAT polyester according to any of claims 1 to 7.