Method for efficiently producing biodegradable polymer by taking butanediol, dimethyl succinate and like as monomer raw materials

Abstract

The invention relates to a method for producing polybutylene succinate (PBS), the raw materials of which comprise: a) a first starting component: dimethyl succinate (DMS) in monomeric form, and b) a second starting component: 1, 4-butanediol (BDO) in monomeric form.

Description

TECHNICAL FIELD

[0001] The present application relates to a reaction system based on 1,4-butanediol and dimethyl succinate (DMS) as monomer raw materials, belonging to the field of polymer production methods. BACKGROUND

[0002] Traditional polybutylene succinate (PBS) production methods usually use 1,4-butanediol (BDO) and succinic acid (also known as butanedioic acid) as monomers. SUMMARY

[0003] The present application describes a process for producing polymers mainly using 1,4-butanediol (BDO) and dimethyl succinate (DMS) as monomers, which has special advantages in devices that produce these two monomers.

[0004] The present application also describes a special process control method in the process.

[0005] The present application relates to a process for producing polybutylene succinate (PBS), which raw materials include: a) The first starting component: dimethyl succinate (DMS) in monomer form; b) The second starting component: 1,4-butanediol (BDO) in monomer form.

[0006] Preferably, the process is a continuous production method.

[0007] The process preferably includes an ester exchange stage.

[0008] The process preferably includes a pre-polycondensation stage.

[0009] The process preferably includes a final polycondensation stage.

[0010] In addition to dimethyl succinate (DMS), the first starting component preferably also includes a dicarboxylic acid; more preferably, the first starting component includes succinic acid.

[0011] Preferably, the content of dimethyl succinate (DMS) in the first starting component is greater than 50 wt%.

[0012] Preferably, in addition to 1,4-butanediol (BDO), other diols can be optionally added to the second starting component.

[0013] Preferably, the process includes a vacuum section, particularly the polycondensation stage and the pre-polycondensation stage of the process.

[0014] Preferably, the preferred solution is: in the ester exchange stage, first directly meter the component with a large proportion (more than 50 wt%) in the low vapor pressure monomer (BDO, DMS) into the vacuum area, which helps to maintain good vacuum degree; The remaining monomers (i.e. the minor components of the monomer mixture BDO, DMS, which are less than 50wt%) required for chain growth are mixed with the monomers from the other vacuum zones and metered directly into the transesterification stage.

[0015] The vacuum system preferably uses a steam-jet vacuum pump (driven by a propellant), but a mechanical vacuum pump or a combination of a steam-jet vacuum pump and a mechanical vacuum pump can also be used.

[0016] Preferably, the propellant comprises at least one monomer (DMS or BDO).

[0017] In a preferred embodiment, the process further comprises metering an additive during the process.

[0018] Preferably, the additive is metered synchronously with the monomers (DMS, BDO).

[0019] Preferably, the additive can also be metered directly into the transesterification stage, the pre-polycondensation stage and / or the final polycondensation stage.

[0020] The additive preferably comprises at least one of the following components: an additive for improving the degradation (in particular biodegradation) properties of PBS, further comonomers, further polymers, a methanol absorber or adsorber.

[0021] A preferred embodiment of the addition of the additive comprises the following: A first portion of the additive is metered in as a liquid / melt (preferably using an extruder and / or a special mixing element); A second portion of the additive is metered in as a solid (preferably suspended or dispersed in a liquid / melt); A third portion of the additive is metered in as a gas (preferably dissolved or dispersed in a liquid / melt).

[0022] The metering of the catalyst takes place in such a way that it is preferably added together with the monomer mixture into the transesterification stage and / or separately into the transesterification stage and / or into a subsequent reaction stage.

[0023] In order to achieve specific properties of the end product, the metering of the additive or the comonomer into the process preferably takes place in a selected process stage.

[0024] More preferably, the additive and / or the comonomer is added directly into the end product melt downstream of the final reactor.

[0025] The key difference between the process according to the application based on DMS and the conventional process for synthesizing PBS is: 1. Difference in monomer selection Traditional PBS processes typically use 1,4-butanediol (BDO) and succinic acid as monomers. Succinic acid can be obtained from renewable raw materials or through chemical synthesis.

[0026] This invention uses dimethyl succinate (DMS, CAS 106-65-0) – a byproduct of a chemical process – instead of succinic acid.

[0027] 2. Differences in by-products and their impact on the process Traditional process: The main and byproducts are water (with low vapor pressure). The process of this invention: the main and by-products are methanol, with small amounts of tetrahydrofuran and butenol as by-products.

[0028] This difference in byproducts will lead to significant changes in process control and parameters compared to known processes (preparation of PBS from succinic acid), particularly in the following aspects: 1) Internal material flow and its control in process tower systems (single or multiple towers); 2) The layout, size and operating parameters of the vacuum system (external components of the reactor) need to be adjusted.

[0029] 3. Vacuum system optimization methods The byproduct of succinic acid to PBS preparation is water, which has a lower vapor pressure than methanol, a byproduct of DMS to PBS preparation. Therefore, the presence of methanol as a byproduct makes maintaining vacuum in the DMS to PBS preparation process difficult, especially in the final polycondensation stage. This invention addresses this by taking the following measures: Low vapor pressure monomers are preferentially introduced into the vacuum system: 1,4-Butanediol (BDO) (melting point about 20°C, low vapor pressure) is an ideal choice; while DMS (Cas: 106-65-0) (melting point 18~19°C) can also be introduced into the vacuum system, preferably into the vapor injection system of the pre-condensation stage; these monomers purified in the process tower will be returned to the reaction stage and act on the chemical reaction to synthesize molecular chains.

[0030] Vacuum can be created by using a mechanical vacuum pump, a vapor jet pump, or a combination thereof.

[0031] System cleaning optimization: Butylene glycol (especially due to its extremely low vapor pressure) can be preferentially introduced into the vacuum system, which can both improve the vacuum level and achieve system flushing; similarly, any mixture of butylene glycol (especially 1,4-butylene glycol) and DMS is suitable for this purpose.

[0032] 4. Material purification and recycling Impurity-containing stream: The "contaminated" stream discharged from the vacuum system is fed into the process tower system for purification and separation; Methanol treatment: Separate high-purity methanol from the system as thoroughly as possible, and store it temporarily for energy conversion (such as combustion).

[0033] Purified monomer recovery: The “pure” stream, rich in BDO and a small amount of DMS, is discharged from the column system and eventually delivered to the reactor.

[0034] 5. Flexibility in individual application: Monomers purified by the tower system can be added to any node of the process in any order and proportion; Fresh monomers and recycled monomers can be mixed or separately metered and added to each reaction stage (transesterification / pre-condensation / final condensation) to construct molecular chains.

[0035] The molecular structure and process differences between the DMS-based PBS process of this invention and the traditional succinic acid process are as follows: 1. Comparison of molecular structures Final product similarity: PBS prepared using dimethyl succinate (DMS) as a monomer has a macromolecular structure almost identical to that of conventional succinate-based PBS, with the only difference being the terminal groups: 1) Succinate-based PBS: The chain ends with hydrogen atoms (-H); 2) DMS-based PBS: The chain end is methyl (-CH3).

[0036] The essential differences in monomer chemistry: All competing patents describe the use of dicarboxylic acids (such as succinic acid) as monomers, while DMS (C6H 10 O4 (CAS 106-65-0) is not a dicarboxylic acid—its molecule has CH3 groups at both ends and no COOH end groups.

[0037] 2. Core technological innovation Reaction phase: The new process includes at least: 1) Transesterification stage; 2) Pre-condensation / final condensation stage (building polymer chains under vacuum conditions through one or more reactors).

[0038] Chain growth mechanism: molecular chains are extended by gradually increasing temperature and decreasing pressure.

[0039] 3. Vacuum System Design Vacuum generation method: mechanical vacuum pump / vapor jet vacuum pump or any combination of the above devices; The primary monomers of the vapor jet vacuum pump (the power fluid is at least one monomer) are preferably 1,4-butanediol (BDO) and DMS (CAS: 106-65-0), but other aliphatic diols (or mixtures of diols with properties similar to BDO) can also be used instead of BDO.

[0040] 4. Adaptability to different process types Known process: Existing batch / continuous processes all use BDO + succinic acid or adipic acid (CAS 124-04-9) to produce PBS.

[0041] The breakthrough in this process: completely abandoning dicarboxylic acids and using DMS (C6H4) with CH3 terminal groups instead of COOH. 10 O4 (CAS106-65-0) serves as the core component, resulting in a systemic innovation in equipment and process control.

[0042] 5. Key Adjustments Due to the differences in physical properties between DMS and succinic acid (such as melting point: DMS is 18~19℃ vs. succinic acid is 184~190℃), the following aspects need to be optimized: the size and layout of process equipment and process parameters.

[0043] 6. Product performance is converging Despite significant differences in the initial monomer properties, as the process progresses to the final product stage, the chemical and physical properties of DMS-based PBS and succinate-based PBS gradually converge, eventually becoming almost identical.

[0044] The technical validation and comprehensive advantages of the DMS-based PBS process are as follows: 1. Verification of the equivalence of the final product Consistency of physicochemical properties: Tests confirmed that PBS synthesized from DMS and butanediol is completely equivalent to succinate-based PBS in terms of physicochemical properties and processing performance.

[0045] Molecular difference convergence: As the polymer chain grows, the difference between DMS-based PBS and traditional PBS gradually decreases, and the final products converge.

[0046] 2. Innovation in DMS Single-Unit Supply Chain Raw material source: DMS is preferably obtained from the esterification byproduct of the maleic anhydride process (refer to the Johnson Matthey process: DMS is produced from the maleic acid side stream).

[0047] Integration advantages: DMS can be directly diverted from the JM unit, thus seamlessly connecting to the PBS production line; this results in significant cost savings, including energy consumption, equipment, process steps, warehousing and logistics.

[0048] 3. Technological Innovation and Patent Breakthroughs Industry First: This invention is the first to use DMS in commercial (especially continuous) PBS production, filling a technological gap; Patent circumvention: Existing literature / patents only cover monomers with dicarboxylic acid end groups (such as succinic acid), while DMS (containing CH3 end groups) completely circumvents such patents.

[0049] 4. Process adaptability adjustment Parameter and equipment reconfiguration: Due to the differences in physical properties between DMS and succinic acid, the following aspects need to be specifically optimized: 1) Process parameters; 2) Equipment size, layout and design.

[0050] Catalyst system upgrade: Improved catalyst system and injection points are adopted to enhance efficiency.

[0051] Analysis shows that the PBS produced by this process has the same chemical properties as the PBS produced using adipic acid. The longer the PBS macromolecules, the smaller the difference between the two processes.

[0052] 5. Formulation flexibility and functional design Monomer mixing flexibility: Succinic acid / DMS / butanediol can be flexibly combined, and different ratios can be adapted to front-end process equipment.

[0053] Precise addition of additives: 1) Co-doping: Added in combination with the main monomer; 2) Stage-specific dosing: Customized for different stages such as transesterification / polymerization; 3) Terminal compounding: The additives / polymers are melt-blended and granulated using an extruder.

[0054] 6. Enhanced environmental friendliness Degradation optimization: This process meets environmental protection requirements by adding special biodegradation promoters.

[0055] Application-oriented modification: The properties of the final product can be controlled by special additives, comonomers or other polymers.

Claims

1. A method for producing polybutylene succinate, characterized in that, The raw materials for the production method include: a) First starting component: contains dimethyl succinate monomer; b) Second starting component: containing 1,4-butanediol monomer.

2. The method for producing polybutylene succinate according to claim 1, characterized in that, The production method described is a continuous production method.

3. The method for producing polybutylene succinate according to claim 2, characterized in that, The production method includes an ester exchange stage.

4. The method for producing polybutylene succinate according to claim 2 or 3, characterized in that, The production method includes a prepolymerization stage.

5. The method for producing polybutylene succinate according to claim 2, 3 or 4, characterized in that, The production method includes a final polycondensation stage.

6. The method for producing polybutylene succinate as described in any of the preceding claims, characterized in that, In addition to dimethyl succinate monomer, the first starting component also contains dicarboxylic acid.

7. The method for producing polybutylene succinate according to claim 6, characterized in that, The first starting component also includes succinic acid.

8. The method for producing polybutylene succinate according to claim 6 or 7, characterized in that, In the first starting component, the mass percentage of the dimethyl succinate monomer exceeds 50%.

9. The method for producing polybutylene succinate as described in any of the preceding claims, characterized in that, In addition to the 1,4-butanediol monomer, the second starting component also contains other diols.

10. A method for producing polybutylene succinate as described in any of the preceding claims, characterized in that, The production method includes a vacuum step, particularly a vacuum step in the final polycondensation stage.

11. The method for producing polybutylene succinate as described in claim 9 or 10, characterized in that, First, the components with a large proportion of low vapor pressure monomers, namely 1,4-butanediol monomer and / or dimethyl succinate monomer, especially those with a proportion exceeding 50 wt%, are metered and added to the vacuum zone. Subsequently, the smaller components of the 1,4-butanediol monomer and / or dimethyl succinate monomer, especially those with a proportion of less than 50 wt%, are metered and added to the vacuum zone.

12. The method for producing polybutylene succinate according to claim 10 or 11, characterized in that, In the vacuum step, a vapor jet vacuum pump is used to generate a vacuum, which is driven by a kinetic fluid.

13. The method for producing polybutylene succinate according to claim 12, characterized in that, The kinetic fluid contains at least dimethyl succinate monomer and / or 1,4-butanediol monomer.

14. The method for producing polybutylene succinate as described in any of the preceding claims, characterized in that, The production method also includes metered addition of additives.

15. The method for producing polybutylene succinate according to any one of claims 14, characterized in that, The additive is added simultaneously and metered with dimethyl succinate monomer and / or 1,4-butanediol monomer.

16. The method for producing polybutylene succinate according to claim 14, characterized in that, The additive contains at least one of the following components: an additive for improving the degradation performance, especially the biodegradability, of polybutylene succinate; other comonomers; other polymers; methanol absorbents or adsorbents.

17. The method for producing polybutylene succinate according to claim 15 or 16, characterized in that, The first part of the additive is added in liquid or melt form, preferably by injecting it in liquid or melt form using an extruder.

18. The method for producing polybutylene succinate according to any one of claims 15 to 17, characterized in that, The second part of the additives is added in solid form, preferably suspended or dispersed in a liquid or melt.

19. The method for producing polybutylene succinate according to any one of claims 15 to 18, characterized in that, The third part of the additives is added in gaseous form, preferably dissolved or dispersed in a liquid or melt.

20. A method for producing polybutylene succinate as described in any of the preceding claims, characterized in that, The catalyst is added in one of the following ways: 1) Added together with the monomer mixture to the transesterification stage; 2) Add the transesterification stage separately; 3) Add to the subsequent reaction stage.

21. A method for producing polybutylene succinate as described in any of the preceding claims, characterized in that, To ensure that the final product achieves specific properties, additives or comonomers are metered and added to selected process stages.

22. The method for producing polybutylene succinate as described in any of the preceding claims, characterized in that, Downstream of the final reactor, additives and / or comonomers are directly metered into the final product melt.