CN-122024884-A - Initiator formula design model construction method for high-pressure free radical polymerization reaction and application thereof

CN122024884ACN 122024884 ACN122024884 ACN 122024884ACN-122024884-A

Abstract

The invention belongs to the technical field of initiators, and particularly relates to a method for constructing an initiator formula design model for high-pressure free radical polymerization reaction and application thereof. The model provided by the invention can screen and obtain the initiator combination with forward synergistic effect based on the interaction between free radicals, and the screening method is simple, efficient and low in cost. The invention identifies a synergistic action mechanism through reaction network analysis, realizes structural reconstruction and efficient optimization of an initiator formula on the premise of keeping the industrial working condition and the product performance unchanged, obviously reduces the unit consumption of the initiator, and has good industrial application value.

Inventors

WANG JINGDAI
Ren Liuxuan
YANG YAO
Jia Tinghao
REN CONGJING
FAN XIAOQIANG
YANG YONGRONG

Assignees

浙江大学

Dates

Publication Date: 20260512
Application Date: 20260212

Claims (9)

1. A method of screening an initiator formulation for a high pressure free radical polymerization reaction, comprising the steps of: (1) Constructing a deterministic reactor physical model based on a basic physical model unit, wherein the basic model unit comprises a mass conservation unit, an energy conservation unit and a reaction dynamics model unit, and the reaction dynamics model unit comprises an initiator thermal decomposition model and a free radical reaction model unit; (2) Establishing an initiator database, wherein the initiator database comprises a plurality of initiators and thermal decomposition kinetic parameters corresponding to each initiator; (3) Selecting a plurality of initiators in an initiator database as a mixed initiator system, inputting the mixed initiator system and the mixture ratio thereof and the temperature and the pressure of the high-pressure free radical polymerization reaction into a reaction mechanism automatic generation tool to obtain a free radical reaction network, and solving the free radical reaction network to obtain decomposition data of each initiator; (4) According to the decomposition data of each initiator, carrying out dynamic simulation under a plug flow reactor model to obtain a reaction rate lifting multiple K, a free radical release quantity GI and a free radical survival quantity SI, carrying out normalization processing on the reaction rate lifting multiple K, the free radical release quantity GI and the free radical survival quantity SI, drawing a radar graph, comprehensively evaluating the normalized indexes by taking at least two of K, GI and SI as evaluation indexes, and screening candidate initiator combinations with synergistic potential according to the comprehensive evaluation results, wherein the comprehensive evaluation results can be visually displayed in a radar graph mode; (5) Inputting the candidate initiator combination and the mixture ratio screened in the step (4) into a deterministic reactor physical model, taking the target temperature distribution and the process constraint condition of an industrial device as optimization targets, carrying out iterative calculation by adjusting the mixture ratio of the initiator, enabling the axial temperature distribution T (z) of the reactor obtained by calculation of the deterministic reactor physical model to be consistent with or have minimum deviation from the target temperature distribution of the industrial device, and determining the mixture ratio of the initiator combination; the process constraints include the conversion of the alkenyl monomer and the weight average molecular weight and number average molecular weight of the product.
2. The screening method of claim 1, wherein the reaction rate improvement factor K is calculated according to equation 1, K=k/K Akzo ; in the formula 1, k is the apparent rate constant of the candidate initiator combination; k Akzo is the reference rate constant for a single initiator; The calculation of the K value is to calculate the corresponding lifting times by using the reference rate constants of the single initiator respectively, and take the average value of the lifting times as the lifting times K of the reaction rate, wherein the reference rate constants are derived from an initiator database.
3. The method of constructing an initiator formulation model according to claim 1, wherein the free radical release GI is calculated according to formula 2: Formula 2; In the formula 2, R mix is the total free radical release amount of the mixed initiator system in the axial interval [ z 1 'z 2 ] of the reactor; is the first Total amount of free radical release in the axial interval [ z 1 'z 2 ] of the reactor in the presence of seed initiator alone; To mix the first initiator system Mass fraction of seed initiator, and satisfies ; Z is the reactor axial coordinate; z 1 and z 2 represent the starting and ending positions, respectively, of the free radical action interval; to the mole fraction of free radicals in the i-th of the mixed initiator system at axial position z; To be at an axial position Where only the kth initiator is present and the other initiators are absent, the calculated mole fraction of the ith free radical; is the collection of all the species of the radicals participating in the reaction in the mixed initiator system.
4. The screening method according to claim 1, wherein the free radical release SI is calculated according to formula 3; formula 3; in the axial position of the reactor Where, in the mixed initiator system, the first Mole fraction of species radicals; the method is a set of all the free radical species participating in the reaction in the system; for the axial co-ordinates of the reactor, And Respectively representing the starting and ending positions of the free radical action zone; To mix the first initiator system Mass fraction of seed initiator, and satisfies ; Is the axial length of the reactor; Is the axial average flow velocity of the reactant fluid in the reactor; is the first order decomposition rate constant of initiator k.
5. The screening method according to claim 1, wherein the kind of the initiator includes an organic peroxide-based initiator and/or an azo-based initiator.
6. The screening method of claim 1, wherein the thermodynamic parameters include a pre-finger factor and activation energy.
7. The screening method according to claim 1, wherein the temperature of the polymerization reaction in the step (3) is 100 to 300 ℃, and the pressure of the polymerization reaction is 100 to 350mpa.
8. A composite initiator system is characterized by comprising, by mass, 20-60 parts of di-tert-butyl peroxide, 10-40 parts of tert-butyl peroxyacetate and 10-70 parts of tert-butyl peroxy-2-ethylhexanoate.
9. The use of the composite initiator system according to claim 8 in high-pressure free radical polymerization of ethylene or ethylene copolymers, wherein the high-pressure free radical polymerization of ethylene or ethylene copolymers is carried out in a high-pressure tubular reactor or autoclave reactor at a temperature of 100-300 ℃ and a pressure of 100-350 mpa.

Description

Initiator formula design model construction method for high-pressure free radical polymerization reaction and application thereof Technical Field The invention belongs to the technical field of initiators, and particularly relates to a method for constructing an initiator formula design model for high-pressure free radical polymerization reaction and application thereof. Background Low Density Polyethylene (LDPE) is an important polymer produced mainly by a high pressure radical polymerization process, and is widely used in the fields of films, cable insulation, injection molded articles, and the like. The process is generally carried out in a tubular or kettle reactor at an ultra-high pressure of 100-350 MPa and a high temperature of 150-300 ℃. In this process, the decomposition behavior of the organic peroxide initiators (e.g., DTBP, TBPB, TBPEH, etc.) directly determines the radical supply characteristics, which have a decisive influence on the polymerization rate, the ethylene conversion, the molecular weight distribution of the product and the process economics. However, single organic peroxide initiators have inherent limitations in that the decomposition temperature zone is generally narrow, resulting in concentrated free radical release behavior, and it is difficult to form a broad and continuous temperature distribution within the reactor. Such discontinuous radical supply is liable to cause reaction fluctuations and may lead to local too rapid decomposition of the initiator with reduced utilization, resulting in a higher unit consumption. In order to widen the reaction temperature area and realize a more stable polymerization reaction, a strategy of compounding various peroxides with different decomposition temperatures is generally adopted. At present, the design of an initiator formula in industrial production mainly depends on the experience of engineering technicians, and is searched and optimized by a trial-and-error method in combination with basic data such as half-life temperature, decomposition kinetics and the like of the initiator. Each recipe adjustment requires testing on industrial equipment, is risky, has a long period, consumes a lot of manpower, material resources and raw material costs, and may cause potential safety hazards due to local overheating or reaction runaway. Thus, there is a strong need in the art for a mixed initiator solution designed based on a deep understanding of the synergistic mechanism between initiator molecules, however, prior art studies on mixed initiators have been mostly focused on the decomposition temperature region superposition or half-life matching layer, often assuming that the initiators decompose independently of each other. Therefore, the problem that the synergistic effect is not obvious and even the antagonistic effect often occurs in the practical application of the existing mixed initiator system limits the further optimization of the initiator compounding strategy. Disclosure of Invention The invention provides a method for constructing an initiator formula design model for high-pressure free radical polymerization reaction and application thereof. The model provided by the invention can screen and obtain the initiator combination with forward synergistic effect based on the interaction between free radicals, and the screening method is simple, efficient and low in cost. In order to achieve the above object, the present invention provides the following technical solutions: the invention provides a screening method of an initiator formula for high-pressure free radical polymerization reaction, which comprises the following steps: (1) Constructing a deterministic reactor physical model based on a basic physical model unit, wherein the basic model unit comprises a mass conservation unit, an energy conservation unit and a reaction dynamics model unit, and the reaction dynamics model unit comprises an initiator thermal decomposition model and a free radical reaction model unit; (2) Establishing an initiator database, wherein the initiator database comprises a plurality of initiators and thermal decomposition kinetic parameters corresponding to each initiator; (3) Selecting a plurality of initiators in an initiator database as a mixed initiator system, inputting the mixed initiator system and the mixture ratio thereof and the temperature and the pressure of the high-pressure free radical polymerization reaction into a reaction mechanism automatic generation tool to obtain a free radical reaction network, and solving the free radical reaction network to obtain decomposition data of each initiator; (4) According to the decomposition data of each initiator, carrying out dynamic simulation under a plug flow reactor model to obtain a reaction rate lifting multiple K, a free radical release quantity GI and a free radical survival quantity SI, carrying out normalization processing on the reaction rate lifting multiple K, the free radical release quanti