CN114516950B

CN114516950B - Hyperbranched PBAT polyester and preparation method thereof

Info

Publication number: CN114516950B
Application number: CN202210417531.5A
Authority: CN
Inventors: 王敏; 岳林; 黄森彪; 高天正; 廖广明
Original assignee: Fuhai Dongying New Material Technology Co ltd
Current assignee: Fuhai Dongying New Material Technology Co ltd
Priority date: 2022-04-21
Filing date: 2022-04-21
Publication date: 2022-07-15
Anticipated expiration: 2042-04-21
Also published as: CN114516950A

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, and particularly relates to hyperbranched PBAT polyester and a preparation method thereof.

Background

The problem of increasingly serious white pollution has attracted high attention of countries all over the world, and the development of biodegradable plastics is imperative. Polybutylene terephthalate-co-polybutylene adipate (PBAT) integrates the degradation performance of aliphatic polyester and the mechanical property of aromatic polyester, has better ductility and elongation at break, has wide application prospect, but the melt strength and the mechanical strength of the PBAT are low, so that most of the PBAT can not be used independently, and needs to be blended with degradable materials such as PLA and the like for injection molding, and the biodegradable polyesters such as PLA and the like have high cost, thus hindering the popularization and application of the degradable materials; the PBAT has the defects of over-high melt viscosity, poor flowability, easy formation of flow lines and the like when thin-walled parts and special-shaped parts are injection-molded, and easy degradation if the injection-molding temperature is increased.

In order to improve the melt strength, mechanical strength and flowability of the PBAT, the relevant studies are as follows:

in patent CN112321999A, raw materials such as cyanuric chloride and ethylenediamine are used to synthesize a triazine ring branching agent, and the modified PBAT is prepared by blending with a finished PBAT product, so that the melt strength, mechanical properties and thermal properties of the product are improved.

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

In patent CN105237750B, the molecular weight of the product is improved by adding the polyol chain extender trimethylolethane in the polymerization stage, and the mechanical strength is further improved.

Under the premise of unchanged structure, the melt strength, mechanical property and fluidity of the polymer are related to the molecular weight, molecular uniformity and branching degree of the polymer. The method for improving the fluidity of PBAT melt in the prior art mainly comprises the steps of adding flow auxiliaries such as hyperbranched polyester and the like after PBAT polymerization is finished, but the end carboxyl content of purchased PBAT products in the market is more than 50mol/t, some products even can reach within 10mol/t, the commercially available products have fewer active carboxyl groups for reaction, the utilization rate of the auxiliaries is low, and part of small molecular polyester which is not grafted is easy to migrate; in addition, the blending mode needs secondary heating of the PBAT and the flow assistant, so that the thermal degradation of the PBAT is easily caused, and a series of problems such as increase of acid value, yellowing and the like are caused; CN105237750B adds the polyol trimethylolethane in the esterification stage to increase the molecular weight of the product, but the melt viscosity is increased simultaneously with the increase of the molecular weight of the polyester. How to improve the melt strength and the mechanical property of the PBAT and simultaneously reduce the viscosity, and avoid the risk of repeated heating is an important problem for expanding the application of the PBAT in the fields of thin-wall injection molding parts, special-shaped parts, film blowing and the like.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: overcomes the defects of the prior art, provides hyperbranched PBAT polyester and a preparation method thereof, and is suitable for biodegradable products with complex structures, such as special-shaped injection parts, thin-wall injection parts and the like.

The invention is realized by adopting the following technical scheme:

the preparation method of the hyperbranched PBAT polyester comprises the following steps:

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

synthesis of second-generation HBPE: putting the nuclear unit and the branched monomer into a reactor, heating to 130-160 ℃ under the protection of nitrogen while stirring, then adding the catalyst A, reacting at constant temperature, vacuumizing the system when the acid value of the reaction system is reduced to a specified value, and extracting water generated by the reaction.

Third-generation HBPE synthesis: continuously introducing nitrogen, adding a certain amount of branched monomer and the catalyst A, reacting at the constant temperature of 160 ℃ at 130-;

synthesizing part of end-capped third-generation HBPE: continuously introducing nitrogen, adding a certain amount of end-capping reagent to perform end-capping reaction, performing constant-temperature reaction at the temperature of 130-160 ℃, vacuumizing the reaction system when the acid value of the reaction system is reduced to a specified value, and extracting water generated by the reaction to obtain a product, namely the partially end-capped third-generation hyperbranched polyester;

(2) esterification reaction: adding terephthalic acid, 1, 6-adipic acid, 1, 4-butanediol and a catalyst A into an esterification kettle, heating to a target temperature, 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: and (3) uniformly mixing the esterification product after the reaction, the catalyst A and the prepared partially-terminated third-generation HBPE, adding a heat stabilizer and an antioxidant, heating to a specified temperature, starting vacuum, and carrying out a pre-polycondensation reaction and a final polycondensation reaction.

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

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

Catalyst a is preferably one or more of tetrabutyl titanate, tetra-n-ethyl titanate or tetra-isopropyl titanate.

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

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

In the step (1), 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 finished after the acid value of the reaction system is reduced to 0-5 mgKOH/g.

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。

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 dihydric 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.

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 temperature of the pre-polycondensation reaction is 230-;

in the step (3), the final polycondensation is carried out for 0.2-1.5h at the temperature of 235-250 ℃ and the reaction pressure of 1-50KPa, and then the reaction temperature is adjusted to be 240-270 ℃ and the reaction pressure is less than 100Pa, the reaction is carried out for 0.5-1.5h, and the reaction is finished.

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

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; the heat stabilizer is one or more of triphenyl phosphite, triphenyl phosphate or ethyl phosphate.

Compared with the prior art, the invention has the following beneficial effects:

1. in the invention, the synthesized HBPE is aliphatic polyester, has biodegradability, cannot influence the application of PBAT in related fields such as food and the like, uses the same catalyst as PBAT polymerization in the synthesis process, and cannot introduce additional impurity molecules.

2. Compared with other technologies for blending and modifying the PBAT and the flow assistant, the invention has the advantages that as the polyhydroxy hyperbranched polyester and the raw material are copolymerized together in the polymerization stage, the utilization rate of the hyperbranched polyester is higher, the hyperbranched polyester can be completely embedded into the PBAT molecular structure, and the migration problem of the small molecular flow assistant is avoided; when the molecular chain is changed from linear to three-dimensional structure, the mechanical property of the polymer is obviously improved, the number of the hydroxyl groups on the outer layer is reduced to a proper degree, excessive crosslinking can not be caused, and the product performance is more uniform. After the outmost hydroxyl reacts with dibasic acid in the PBAT raw material, the inner layer structure still has a spherical structure, and the high fluidity of the hyperbranched polyester is kept, namely the viscosity of the hyperbranched polyester is reduced and the fluidity of the hyperbranched polyester is improved while the mechanical property and the melt strength of the PBAT are improved by the technology. And the method of adding the polyhydroxy hyperbranched polyester in the polymerization stage avoids the degradation risk brought by secondary heating in a blending mode.

Detailed Description

In order to facilitate understanding of the present invention, the present invention will be described below by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Injection molded specimens were prepared as specified in GB/T17037.1-1997 and specimens conforming to type 1A in GB/T1040.2-2006 were prepared using the type A die of GB T17037.1-1997.

Particle material pretreatment: before forming a sample, the granules are subjected to preheating and drying treatment in a vacuum drying oven, the thickness of the loaded granules is less than 4cm, and the granules are continuously dried for 4 hours at 80 ℃.

Sample preparation conditions: adopting a FANUC ROBOSHOT alpha-S100 iA full-electric injection molding machine of Japan Sendai, a screw injection machine process:

conditioning of the samples and standard environment of the test:

the conditioning of the sample was carried out according to the regulations GB/T2918-1998 under the conditions of a temperature of 23 ℃ C. + -. 2 ℃ and a conditioning time of 48 hours. The test was carried out in a standard environment as specified in GB/T2918-1998 at a temperature of 23 ℃ C. + -. 2 ℃ and a relative humidity of 50%. + -. 10%.

Tensile strength at break and tensile strain at break

A type 1A sample was prepared. According to the GB/T1040.2-2006. The test speed was 50 mm/min.

Flexural Strength and flexural modulus

A80 mm by 10mm by 4mm strip specimen was prepared. The test is carried out according to the regulation of GB/T9341-2008, and the test speed is 2 mm/min.

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

Examples 1 to 5.

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

synthesis of the second-generation HBPE: putting a core unit (pentaerythritol or trimethylolpropane) and 2, 2-dihydroxypropionic acid into a reactor, heating to 130 ℃ under the protection of nitrogen while stirring, then adding tetrabutyl titanate, reacting at constant temperature, vacuumizing the system for 1h when the acid value of the reaction system is reduced to 5mgKOH/g, and extracting water generated by the reaction.

Third-generation HBPE synthesis: and (3) continuously introducing nitrogen, adding weighed 2, 2-dihydroxypropionic acid and tetrabutyl titanate, reacting at the constant temperature of 130 ℃, and sealing when the acid value of the reaction system is reduced to 5 mgKOH/g.

Synthesis of partially-terminated HBPE: and (3) continuously introducing nitrogen, adding a certain amount of propionic acid, reacting at the constant temperature of 140 ℃, vacuumizing the reaction system for 1h when the acid value of the reaction system is reduced to 5mgKOH/g, and extracting water generated in the reaction. The obtained product is three-generation hyperbranched polyester with partial end capping.

Examples 1-4 partially end-capped three generations of HBPE formulation table:

example 5 partial end-capping three generations of HBPE formulation table:

the index parameters of the partially blocked third-generation HBPE prepared by the formula and the steps are as follows:

the specific embodiment is as follows:

example 1

Table 1 example 1 feed table

(1) Esterification reaction:

adding weighed terephthalic acid, 1, 4-butanediol and adipic acid into an esterification kettle, starting heating, uniformly stirring, heating to 180 ℃, carrying out esterification dehydration reaction for 2 hours, and distilling off anhydrous when the water yield of the reaction reaches a theoretical value of 799.9 g.

(2) Graft polycondensation: adding a co-esterification product after the reaction, 5.01g of partially end-capped third-generation HBPE, tetrabutyl titanate, triphenyl phosphate and 2, 6-di-tert-butyl-4-methylphenol into a polymerization kettle, wherein the reaction temperature is 220 ℃, the reaction pressure is 80KPa, the reaction time is 2h, then adding, the reaction temperature is 235 ℃, the reaction pressure is 50KPa, and reacting for 1.5 h; the temperature was then raised to 240 ℃ and the reaction pressure 100Pa for 1.5h, ending the reaction.

Example 2

Table 2 example 2 feed table

(1) Esterification reaction:

(2) Graft polycondensation: adding a co-esterification 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 into a polymerization kettle, wherein the reaction temperature is 220 ℃, the reaction pressure is 80KPa, the reaction time is 2h, then adding, the reaction temperature is 235 ℃, the reaction pressure is 50KPa, and reacting for 1.5 h; the temperature was then raised to 240 ℃ and the reaction pressure 100Pa, the reaction time 1.5h, and the reaction was complete.

Example 3

Table 3 example 3 feed table

(1) Esterification reaction:

(2) Graft polycondensation: adding 25.07g of co-esterification product after the reaction, 25.07g of partially-terminated third-generation HBPE, tetrabutyl titanate, triphenyl phosphate and 2, 6-di-tert-butyl-4-methylphenol into a polymerization kettle, wherein the reaction temperature is 220 ℃, the reaction pressure is 80KPa, the reaction time is 2h, then adding, the reaction temperature is 235 ℃, the reaction pressure is 50KPa, and reacting for 1.5 h; the temperature was then raised to 240 ℃ and the reaction pressure 100Pa, the reaction time 1.5h, and the reaction was complete.

Example 4

Table 4 example 4 feed table

(1) Esterification reaction:

(2) Graft polycondensation: adding 40.11g of a co-esterification product after the reaction, partially-terminated third-generation HBPE, tetrabutyl titanate, triphenyl phosphate and 2, 6-di-tert-butyl-4-methylphenol into a polymerization kettle, wherein the reaction temperature is 220 ℃, the reaction pressure is 80KPa, the reaction time is 2h, then adding, the reaction temperature is 235 ℃, the reaction pressure is 50KPa, and reacting for 1.5 h; the temperature was then raised to 240 ℃ and the reaction pressure 100Pa, the reaction time 1.5h, and the reaction was complete.

Example 5

Table 5 example 5 feed table

(1) Esterification reaction:

(2) Graft polycondensation: adding a co-esterification product after the reaction, 7.39g of partially end-capped third-generation HBPE, tetrabutyl titanate, triphenyl phosphate and 2, 6-di-tert-butyl-4-methylphenol into a polymerization kettle, wherein the reaction temperature is 220 ℃, the reaction pressure is 80KPa, the reaction time is 2h, then adding, the reaction temperature is 235 ℃, the reaction pressure is 50KPa, and reacting for 1.5 h; the temperature was then raised to 240 ℃ and the reaction pressure 100Pa for 1.5h, ending the reaction.

Comparative example 1

The hyperbranched HBPE was not added, and other conditions were the same as in example 3 described above.

Comparative example 2

The uncapped hyperbranched HBPE was added under the same conditions as in example 3 above.

The rotational flow length and mechanical properties of examples 1 to 5 and comparative examples 1 to 2 were measured.

The results are shown in Table 6.

TABLE 6 spiral flow Length and mechanical Properties of the products of examples 1-5 and comparative examples 1-2

The data show that the flowability and the mechanical strength of PBAT can be greatly improved by adding the end-capped hyperbranched polyester HBPE, but excessive crosslinking can be caused and the mechanical property of the product is seriously reduced if the end-capped hyperbranched polyester HBPE is not added.

Of course, the foregoing is only a preferred embodiment of the invention and should not be taken as limiting the scope of the embodiments of the invention. The present invention is not limited to the above examples, and equivalent changes and modifications made by those skilled in the art within the spirit and scope of the present invention should be construed as being included in the scope of the present invention.

Claims

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.