阅读说明：本技术 一种可重复加工的热固性聚合物的合成方法 (Synthetic method of thermosetting polymer capable of being repeatedly processed ) 是由 陈茂 王宗涛 于 2019-09-11 设计创作，主要内容包括：本发明属于聚合物合成技术领域,具体为一种可重复加工的热固性聚合物的合成方法。本发明采用大分子交联剂,利用高分子链与高分子链之间的可逆交联作用,合成可重复加工的交联聚合物；具体包括官能团化共聚物合成和共聚物交联固化两部分；共聚物以(甲基)丙烯酸(酯)、丙烯酰胺、苯乙烯及其衍生物等乙烯基单体为主要成分,具有可交联官能团的乙烯基单体为次要成分；交联固化通过官能团间形成的动态化学键作用实现。与具有类似化学成分的热塑性材料相比,本发明合成的材料具有更好的机械强度、耐溶剂性、抗蠕变性、抗老化性能等。(The invention belongs to the technical field of polymer synthesis, and particularly relates to a synthetic method of a thermosetting polymer capable of being repeatedly processed. The invention adopts macromolecule cross-linking agent, and utilizes reversible cross-linking function between macromolecule chain and macromolecule chain to synthesize cross-linked polymer which can be processed repeatedly; the method specifically comprises two parts of synthesis of a functionalized copolymer and crosslinking and curing of the copolymer; the copolymer comprises a vinyl monomer such as (meth) acrylic acid (ester), acrylamide, styrene or a derivative thereof as a main component and a vinyl monomer having a crosslinkable functional group as a secondary component; crosslinking and curing are realized through dynamic chemical bond interaction formed between functional groups. Compared with thermoplastic materials with similar chemical components, the synthetic material has better mechanical strength, solvent resistance, creep resistance, ageing resistance and the like.)

1. A method for synthesizing a reworkable thermosetting polymer is characterized in that a macromolecular cross-linking agent is adopted to synthesize a reworkable cross-linked polymer (3) by utilizing reversible cross-linking action between a macromolecular chain and a macromolecular chain, and the synthetic route of the reworkable cross-linked polymer is shown as the following formula:

wherein formula (1) represents a first component of a crosslinked polymer, which is a polymer having repeating crosslinking sites on the polymer chain; wherein, -R₁-and-R₂-represents a vinyl polymer; -R₂-and-R₄-represents a vinyl monomer containing a double bond; r represents a functional group as a crosslinking site, and forms a group having a dynamic chemical bond after R' reaction; m and n represent the number of repeating units;

the second component of the crosslinked polymer represented by formula (2) is a polymer having repeating crosslinking sites on the polymer chain; wherein, -R₃-and-R₄-represents a vinyl polymer; -R₂-and-R₄-represents a vinyl monomer containing a double bond; r' represents a functional group as a crosslinking site, and forms a compound having dynamic chemistry after the reaction of RA group of bonds; a and b represent the number of repeating units;

formula (3) represents a crosslinked structure formed by the interaction between functional groups R and R' on the molecular chain of two crosslinked polymers represented by formulas (1) and (2); wherein R … R 'represents a dynamic chemical bond formed upon interaction between the R and R' functional groups; the mechanism of formation of R … R' dynamic chemical bonds includes the formation and reversible mechanisms of Diels-Alder reactions and other dynamic cycloaddition reactions, transamination, carbonate exchange, boronate exchange, sulfur-sulfur bonds, olefin metathesis and other dynamic chemical bonds.

2. The method of synthesizing a reprocessable thermosetting polymer according to claim 1, wherein in formula (1), the alkenyl polymer is selected from the group consisting of polyethylene, poly (meth) acrylate, polyacrylamide, polyacrylonitrile, polystyrene, and derivatives thereof; is two of the same polymer, or is two of different polymers; the double-bond-containing ethylene monomer is selected from ethylene and derivatives thereof, (methyl) acrylic acid (ester) and derivatives thereof, polyacrylamide and derivatives thereof, and polystyrene and derivatives thereof;

in the formula (2), the monomer is selected from polyethylene, poly (meth) acrylic acid (ester), polyacrylamide, polyacrylonitrile, polystyrene and derivatives thereof; is two of the same polymer, or is two of different polymers; the double-bond-containing ethylene monomer is selected from ethylene and derivatives thereof, (methyl) acrylic acid (ester) and derivatives thereof, polyacrylamide and derivatives thereof, and polystyrene and derivatives thereof;

in formula (3), the mechanism of formation of R … R' dynamic chemical bond is the formation and reversible mechanism of Diels-Alder reaction and other dynamic cycloaddition reactions, transamination, transesterification, boronization, sulfur-sulfur bond, olefin metathesis or other dynamic chemical bonds.

3. The method for synthesizing a reworkable thermosetting polymer according to claim 2, wherein the two crosslinked polymers represented by the formula (1) and the formula (2) are synthesized by the following steps: bulk polymerization and polymerization in a solvent, wherein the synthetic reaction is free radical polymerization, anion polymerization, cation polymerization or ring opening reaction, and the formed copolymer is a random copolymer, an isotactic copolymer, a syndiotactic copolymer or a block copolymer.

4. The method of synthesizing a reprocessable thermosetting polymer according to claim 3, wherein the method of synthesizing the crosslinked polymer represented by formula (3) comprises: solvent processes and melt mixing processes; wherein:

when the polymer is synthesized by a solvent method, the solvent is an organic solvent and/or an inorganic solvent; the organic solvent is a single organic solvent or a mixed organic solvent; the solvent is selected from 1, 4-dioxane, toluene,N,N-dimethylformamide,N,N-dimethylacetamide, dimethylsulfoxide, dichloromethane, 1, 2-dichloroethane, chloroform, tetrahydrofuran, acetone, ethyl acetate, methanol, ethanol, acetonitrile and water;

when the polymer is synthesized by a melt mixing method, the used equipment comprises a single screw extruder, a double screw extruder, an internal mixer, a ball mill or an internal mixer; the synthetic thermosetting crosslinked polymer processing methods include injection molding, compression molding or 3D printing.

5. A method of synthesising a reprocessable thermosetting polymer as claimed in any of claims 1 to 4 wherein two functional groups are involved in the system for forming dynamic covalent bonds, the polymer containing one functional group and the polymer containing the other functional group being cross-linking agents for each other, and the mechanical properties of the resulting cross-linked polymer are controlled by adjusting the feed ratio of the two.

Technical Field

The invention belongs to the technical field of polymer synthesis, and particularly relates to a synthetic method of a thermosetting polymer capable of being repeatedly processed.

Background

Generally, polymeric materials can be divided into two categories, thermoplastic polymers and thermosetting polymers. The thermoplastic polymer has excellent processability and solubility, has good fluidity and ductility after the heated temperature reaches the melting temperature, but has poor tolerance to organic solvents and is easily corroded by the organic solvents; the traditional thermosetting polymer has higher stability, mechanical strength, creep resistance and chemical stability, and plays an important role in the fields of aerospace, automobiles, buildings, electronics and the like. However, compared with thermoplastic polymers, the conventional thermosetting materials have a significant disadvantage that the molecules are crosslinked with each other through irreversible covalent bonds, so that the thermosetting materials are insoluble and infusible, and cannot meet the purposes of repeated processing and recycling (chem. Sci.2016,7,30-38), thereby causing waste and pollution inevitably during production and use (Science 2011,334, 965) 968).

In 2011, the Leibler topic group proposed the concept of "Vitrimer", and applied dynamic covalent bonds to a cross-linked polymer system, the obtained thermosetting polymer not only maintained excellent mechanical properties and chemical stability, but also exhibited certain fluidity under heating conditions, similar to the characteristics of glass-like melt flow and repeatable processing (Science 2001,334, 965-. Therefore, it was translated as "glass-like polymer" (Acta polymeric Sinica,2016,6, 685-. The dynamic cross-linked reticular polymer can show self-repairing, repeated processing and recycling characteristics under certain external stimuli (such as light, heat and the like) due to the reversibility of dynamic covalent bonds in the structure, combines the advantages of thermoplastic polymers and thermosetting polymers, and improves the defects of the two polymers (Science 2017,356, 62-65; CN201610051681.3[ P ]. 2016-01-26; CN201510016304.1[ P ]. 2015-01-13; CN201810306131.0[ P ]. 2018-04-08; CN201810355477.X [ P ]. 2018-04-19; CN201424106802. X [ P ]. 2014-11-06). These dynamically crosslinked network polymers are generally based on two network building modes: 1) the functionalized multi-arm small molecule is formed by crosslinking with a small molecule; 2) the functionalized macromolecule is formed by crosslinking with a multi-arm small molecule.

The invention develops a novel crosslinking mode, namely a method for improving the performance of a polymer through dynamic crosslinking of a macromolecular chain and a macromolecular chain. The method has the advantages of simple and easy operation, high synthesis efficiency, easily obtained raw materials and the like, and the polymer material has wide application range. Compared with the prior dynamic cross-linked network polymer, the macromolecular cross-linking agent strategy adopted by the invention not only can lead the obtained polymer material to be repeatedly processed and recycled, but also can lead the mechanical property of the cross-linked polymer network to be obviously enhanced, has larger tensile strength and bending strength, and also obviously improves the solvent resistance, creep resistance and other aspects.

Disclosure of Invention

The invention aims to solve the defects of the prior art and provide a synthetic method of a reworkable thermosetting polymer, which is simple and easy to operate, has high synthetic efficiency and can improve the mechanical property of general plastics.

The synthetic method of the reworkable thermosetting polymer provided by the invention is to synthesize the reworkable thermosetting polymer by utilizing the macromolecular cross-linking agent, and further research the performances of the polymer material synthesized by the method in the aspects of mechanical property, reworking, recycling and the like. The invention has wide practical prospect in the preparation of the thermosetting cross-linked vinyl polymer which can be repeatedly processed, the improvement of the mechanical property of the general polymer and the like.

The invention provides a method for synthesizing a reworkable thermosetting polymer, which adopts a high molecular material as a cross-linking agent and utilizes the reversible cross-linking function between a high molecular chain and a high molecular chain to synthesize the reworkable cross-linked polymer (3), wherein the synthetic route is shown as the following formula:

wherein, the formula (1) isThe first component of the surface cross-linked polymer is a polymer having repeating cross-linking sites in the polymer chain. Wherein, -R₁-and-R₂-represents vinyl polymers including polyethylene, poly (meth) acrylic acid (esters), polyacrylamide, polyacrylonitrile, polystyrene and derivatives thereof, either of the same type or of two different types; -R₂-and-R₄-represents a vinyl monomer containing double bonds, the monomer being ethylene and its derivatives, (meth) acrylic acid (esters) and its derivatives, polyacrylamide and its derivatives, polystyrene and its derivatives; r represents a functional group as a crosslinking site, and R' forms a group having a dynamic chemical bond after reaction. m and n represent the number of repeating units, and are not particularly required.

The second component of the crosslinked polymer represented by formula (2) is a polymer having repeating crosslinking sites on the polymer chain. Wherein, -R₃-and-R₄-represents vinyl polymers including polyethylene, poly (meth) acrylic acid (esters), polyacrylamide, polyacrylonitrile, polystyrene and derivatives thereof, either of the same type or of two different types; -R₂-and-R₄-represents a vinyl monomer containing double bonds, the monomer being ethylene and its derivatives, (meth) acrylic acid (esters) and its derivatives, polyacrylamide and its derivatives, polystyrene and its derivatives; r' represents a functional group as a crosslinking site, and R forms a group having a dynamic chemical bond after reaction. a and b represent the number of repeating units and are not particularly limited.

The formula (3) represents a crosslinked structure formed by the interaction between the functional groups R and R' on the molecular chain of the two crosslinked polymers represented by the formulas (1) and (2). Wherein R … R 'represents a dynamic chemical bond formed upon interaction between the R and R' functional groups; the mechanism of formation of the dynamic chemical bond of R … R' includes Diels-Alder reaction and other dynamic cycloaddition reactions, transamination, carbonate exchange, boronate exchange, sulfur-sulfur bond, olefin metathesis and other dynamic chemical bond formation and reversible mechanism.

Specifically, the method comprises the following steps: the synthesis of the functionalized copolymer and the cross-linking and curing of the copolymer; the copolymer comprises a vinyl monomer such as (meth) acrylic acid (ester), acrylamide, styrene or a derivative thereof as a main component and a vinyl monomer having a crosslinkable functional group as a secondary component; crosslinking and curing are realized through dynamic chemical bond interaction formed between functional groups.

In the invention, the synthesis process of the two crosslinked polymers shown in the formula (1) and the formula (2) comprises the following steps: bulk polymerization and polymerization in a solvent, the synthesis reactions of which include radical polymerization, anion polymerization, cation polymerization, ring-opening reaction, and the like, and the copolymers formed include random copolymers, isotactic copolymers, syndiotactic copolymers, block copolymers, and the like. Taking solution-method radical polymerization as an example, the specific process is that all monomers, initiator, catalyst and solvent are fully dissolved, nitrogen is introduced for 30 minutes to remove oxygen from the solution, then the solution is reacted for a period of time under illumination or heating condition to obtain polymer solution, and the polymer is precipitated in the solvent and dried in vacuum to obtain the polymers of formula (1) and formula (2). The ratio of reactants, reaction temperature, illumination conditions, and the kind of solvent are not particularly limited, and may be variously adjusted according to the characteristics of the reactants.

In the present invention, the method for synthesizing the crosslinked polymer represented by the formula (3) comprises: solvent processes and melt-mixing processes. Solvent method for synthesizing crosslinked polymer: the polymer of formula (1) is dissolved in a solvent and kept under stirring, and solutions of different equivalents (proportions) of the polymer of formula (2) are added rapidly to form a gel. The resulting polymer gel was subjected to vacuum drying after removing the solvent under reduced pressure to obtain polymers of the formula (3) having different crosslinking densities. Synthesis of crosslinked polymers by melt mixing: the polymer of formula (1) is heated to the melting temperature, continuously stirred, and after sufficient melting, the polymer of formula (2) in different equivalent weight ratios is slowly added to the melt of the polymer of formula (1) while stirring is maintained throughout. After the polymer of the formula (2) is added, the viscosity of the polymer in the cavity is obviously increased, the stirring is continuously kept for 30 minutes, and the polymer of the formula (3) with different crosslinking densities is obtained after cooling. In the solution method, the solvent is an organic solvent and/or an inorganic solvent. The organic solvent may be a single organic solvent or a mixed organic solvent. The solvent is selected from one or a mixture of several solvents of 1, 4-dioxane, toluene, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, dichloromethane, 1, 2-dichloroethane, chloroform, tetrahydrofuran, acetone, ethyl acetate, methanol, ethanol, acetonitrile and water. In the melt mixing method, the used equipment comprises a single screw extruder, a double screw extruder, an internal mixer, a ball mill, an internal mixer and the like. The processing method of the synthesized thermosetting crosslinked polymer comprises injection molding, mould pressing, 3D printing and the like.

The method of the invention can improve the mechanical property, thermal stability, solvent resistance, creep resistance and the like of the general plastic, and simultaneously keeps the characteristic of repeatable processing. Specifically, in a solvent or in a molten state, the same or two copolymers in the formula (1) and the formula (2) form dynamic covalent bond crosslinking among polymer chains under heating or other external stimuli.

According to the method, the crosslinking density is improved by improving the crosslinking functional group density of the polymers in the formula (1) and the formula (2) in the polymerization process, so that the mechanical property of the obtained crosslinked polymer is regulated and controlled.

In the method, two functional groups participate in a system for forming a dynamic covalent bond, a polymer containing one functional group and a polymer containing the other functional group are mutually cross-linked, and the mechanical property of the obtained cross-linked polymer can be regulated and controlled by adjusting the charging proportion of the two.

Compared with the prior art, the invention has the advantages that:

the invention can improve the mechanical property of the polymer and avoid phase separation by a macromolecule crosslinking method. The synthetic process is simple, efficient and good in operability, and has certain application in the field of engineering plastics. The synthesis method can be used for preparing the thermosetting cross-linked polymer capable of being repeatedly processed, and can be used for improving the mechanical property of general plastics.

Drawings

FIG. 1 is a schematic diagram of the mechanism for synthesizing a reprocessable thermoset polymer by macromolecular crosslinking.

FIG. 2 is a diagram of the product of example 5.

FIG. 3 is a stress-strain graph of example 6.

FIG. 4 is a stress-strain graph of example 6.

FIG. 5 is a stress-strain graph of example 6.

FIG. 6 is a bending test chart of example 6

Fig. 7 is a dynamic mechanical analysis chart of example 6.

FIG. 8 is a thermogravimetric analysis chart of example 6.

Detailed Description

The present invention will be described in further detail with reference to examples.

It will be appreciated by those skilled in the art that the following examples are illustrative of the invention only and should not be taken as limiting the scope of the invention. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents, instruments and the like used are not indicated by manufacturers, and are all conventional products which can be obtained by purchasing.

The starting materials of the present invention can be prepared by methods well known in the art or obtained as commercially available products.

The general method of synthesizing a reworkable thermoset polymer from the macromolecular crosslinking agent of the present invention is further explained below, but the vinyl monomers, polymerization methods, dynamic covalent bond types, production and processing methods involved in the present invention are not limited thereto.

In the reaction, the monomer is not particularly specified, and is a vinyl monomer including (meth) acrylic acid (ester), acrylamide, styrene and derivatives thereof. The polymerization method is not particularly limited, and radical polymerization, anion polymerization, cation polymerization, and ring-opening polymerization are usually employed. The solvent is not specifically specified, and is usually a mixed solvent of one or more solvents of 1, 4-dioxane, toluene, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, dichloromethane, 1, 2-dichloroethane, chloroform, tetrahydrofuran, acetone, ethyl acetate, methanol, ethanol, acetonitrile and water, the reaction conditions are not specifically specified, and the temperature is usually between room temperature and 140 ℃ according to the types of monomers; the reaction time is not particularly limited, but is usually 0.5 to 24 hours. And after the reaction is completed, precipitating and separating out the polymer in other solvents to obtain the functionalized polymer. The solvent used for washing or precipitating the product is not particularly specified, and is usually methanol, ethanol, water or a mixed solvent. The drying method of the product has no specific requirements, and drying methods such as drying, natural drying, infrared drying, vacuum drying and the like can be adopted.

In the process of synthesizing the dynamic cross-linked polymer, the organic solvent used by the solvent method is not specifically specified, and is usually a mixed solvent of one or more solvents of 1, 4-dioxane, toluene, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, dichloromethane, 1, 2-dichloroethane, chloroform, tetrahydrofuran, acetone, ethyl acetate, methanol, ethanol, acetonitrile and water;

when the cross-linked polymer is synthesized, the feeding proportion of the two polymers is not specified specifically; the melt mixing method is not specifically defined, and generally includes mixing in an internal mixer, ball milling, single screw extrusion, twin screw extrusion and the like, and the cross-linking reaction occurs simultaneously in the melt mixing process.

The material processing method is not specifically defined, and is usually a method such as molding or injection molding, and the specific processing conditions such as temperature, pressure, time and the like are not specifically defined, and are usually at room temperature to 250 ℃ depending on the kind of the polymer.

The invention is described in detail below with reference to some specific embodiments. These examples are intended to illustrate the invention only and are not intended to limit the scope of the invention. The preparation schemes in the examples are only preferred schemes, but the present invention is not limited to the preferred preparation schemes.