阅读说明：本技术 一种简单热加工可制得铁电尼龙薄膜的共聚聚酰胺及其制备方法 (Copolyamide capable of preparing ferroelectric nylon film by simple thermal processing and preparation method thereof ) 是由 蔡绪福 黄檑 于 2020-07-10 设计创作，主要内容包括：本发明提供了一种简单热加工可制得铁电尼龙薄膜的共聚聚酰胺及其制备方法,该铁电尼龙薄膜在制备过程中主要包括尼龙盐的制备、缩聚反应和热压或挤出流延成型三个步骤。本发明通过将尼龙11的单体氨基十一酸与戊二胺、十一碳二酸所成的511盐共聚,使其链规整性被破坏,结晶性能降低,热压成型直接得到具有铁电性能的介晶相结构。本发明可以实现铁电尼龙薄膜的大规模、快速制备,具有广阔的应用前景。(The invention provides a copolyamide capable of preparing a ferroelectric nylon film by simple thermal processing and a preparation method thereof. The invention copolymerizes 511 salt formed by monomer amino undecanoic acid of nylon 11, pentanediamine and undecanedioic acid, so that the chain regularity is destroyed, the crystallization performance is reduced, and the mesomorphic phase structure with ferroelectric performance is directly obtained by hot press molding. The invention can realize large-scale and quick preparation of the ferroelectric nylon film and has wide application prospect.)

1. A copolyamide which can be prepared into a ferroelectric nylon film by simple thermal processing is characterized in that: the structural formula is as follows:

wherein x is 0.9-0.5, and y is 0.1-0.5.

2. A process for preparing a copolyamide which can be easily thermally processed to give a ferroelectric nylon thin film as described in claim 1, characterized in that: the method comprises the following steps:

step 1: carrying out a salt forming reaction on undecanedioic acid and pentanediamine in a molar ratio of 1: 1-1.05 to obtain a nylon 511 salt;

step 2: adding the aminoundecanoic acid and 511 salt into an autoclave according to a set ratio, wherein the molecular weight of the aminoundecanoic acid is assumed to be the molecular weight 402 of 1111 salt for convenience of chemical structure composition regulation and control because the dipole density of PA11 is the same as that of PA1111 and the dipole density of PA11-511 is greater than that of PA 11; carrying out pre-polycondensation reaction to obtain a prepolymer; wherein the stirring speed is set to be 100-300 r/min;

and step 3: heating and vacuumizing the prepolymer obtained in the step 2, continuously carrying out melt polycondensation, and timely pumping out the generated micromolecule byproduct H₂O, increasing the molecular weight of the polymer;

and 4, step 4: carrying out hot-pressing or extrusion tape casting on the copolyamide obtained in the step 3 to prepare a copolymerized nylon film; the thickness of the film is controlled to be 40 +/-5 um.

3. The method for preparing the copolyamide capable of preparing the ferroelectric nylon film by simple thermal processing according to claim 2, wherein the method comprises the following steps: the salt-forming reaction in the step 1 takes water as a solvent, the reaction temperature is 80 ℃, and the pH value after the reaction is finished is 7.2.

4. The method for preparing the copolyamide capable of preparing the ferroelectric nylon film by simple thermal processing according to claim 2, wherein the method comprises the following steps: in the step 1, the structural formula of the nylon 511 salt generated by the salifying reaction of the undecanedioic acid and the pentanediamine is as follows:

5. the method for preparing the copolyamide capable of preparing the ferroelectric nylon film by simple thermal processing according to claim 2, wherein the method comprises the following steps: in the step 2, when the nylon 511 salt, the aminoundecanoic acid and the water obtained in the step 1 are added into a polymerization reaction kettle together for pre-polycondensation reaction, the mass of the added water is 2 times of the total mass of the nylon 511 salt and the aminoundecanoic acid, and the molar weight of the added nylon 511 salt is 10-50% of the total molar weight of the nylon 511 salt and the aminoundecanoic acid.

6. The method for preparing the copolyamide capable of preparing the ferroelectric nylon film by simple thermal processing according to claim 2, wherein the method comprises the following steps: in the step 2, the reaction temperature of the pre-polycondensation reaction is 180 ℃, the reaction time is 2 hours, and the reaction pressure is controlled below the saturated vapor pressure of water, specifically 0.3-0.5 MPa.

7. The method for preparing the copolyamide capable of preparing the ferroelectric nylon film by simple thermal processing according to claim 2, wherein the method comprises the following steps: in the step 3, the melt polycondensation reaction adopts a mode of gradually increasing the vacuum degree, the reaction temperature is 235 ℃, and the constant pressure reaction is firstly carried out for 2 hours; then, a circulating water type vacuum pump is adopted for vacuum pumping, the vacuum degree is 0.1Mpa, and the reaction time is 2 hours; and finally, vacuumizing by using a rotary-vane vacuum pump, wherein the vacuum degree is 0.8Mpa, and the reaction time is 2 hours.

8. The method for preparing the copolyamide capable of preparing the ferroelectric nylon film by simple thermal processing according to claim 2, wherein the method comprises the following steps: in the step 4, the nylon film is formed by plasticizing at 225 ℃ for 10 minutes; hot pressing at 225 deg.C for 5 min under 10 MPa; and finally cold pressing at room temperature for 3 minutes under the pressure of 10 MPa.

9. The method for preparing the copolyamide capable of preparing the ferroelectric nylon film by simple thermal processing according to claim 2, wherein the method comprises the following steps: step 1, after obtaining the nylon 511 salt aqueous solution, performing rotary evaporation to obtain a nylon 511 salt concentrated solution, and drying the obtained nylon 511 salt concentrated solution.

Technical Field

The invention belongs to a synthesis technology of ferroelectric polyamide, and particularly relates to copolyamide capable of preparing a ferroelectric nylon film by simple thermal processing and a preparation method thereof.

Background

The ferroelectric polymer film is widely applied to the fields of sensors, piezoelectric brakes, nonvolatile storage materials and the like due to the advantages of high breakdown strength, high piezoelectric sensitivity, light weight, flexibility, large-scale preparation and the like. Polyvinylidene fluoride (PVDF) and PVDF-based copolymers are currently the only commercially available ferroelectric polymers. However, poor ferroelectric stability, high toxicity of the polymerized monomers, and low cost performance limit the use of PVDF as a ferroelectric thin film.

Odd numbered nylons have been reported to have ferroelectricity for nearly 50 years; in recent years, even-numbered nylons also exhibit electric field induced ferroelectricity, and the dipole amide bonds-CO-NH-of nylon have a dipole moment of 3.7D, higher than the dipole moment of dipoles C-F in PVDF (1.52D). Meanwhile, the nylon as an important engineering plastic also has excellent mechanical property, wear resistance and thermal stability. Nylon is therefore a very promising ferroelectric polymer.

Nylon 11(PA11) was the odd numbered nylon with ferroelectricity reported first, and is also the nylon with wide ferroelectric property research. PA11 has alpha, alpha ', gamma and 5 crystal forms, only' has ferroelectricity, because the degree of ordering of hydrogen bonds among nylon molecular chains in the crystal phase is poor, the acting force of the hydrogen bonds among the molecules is weak, the molecular chains are twisted, and dipoles can be oriented under an applied electric field. However, the' phase is not the most thermodynamically stable crystal phase of PA11, so the commonly used method for preparing the ferroelectric nylon film is melt quenching and stretching, and the method has the defects of complicated process, difficult large-scale preparation and the like; the recently reported methods of solution quenching and spin coating film formation also have the defects of expensive solvent, high toxicity, complex process and the like. The difficulty in large-scale, continuous, and rapid preparation of ferroelectric nylon films limits their practical use.

In order to solve the problems, no better solution exists in the current literature reports. The ferroelectric nylon film obtained by simple thermal processing through chemical structure modification is a technical bottleneck of ferroelectric nylon synthesis. The invention copolymerizes 511 salt formed by monomer amino undecanoic acid of nylon 11, pentanediamine and undecanedioic acid, so that the chain regularity is destroyed, the crystallization performance is reduced, and the mesomorphic phase structure with ferroelectric performance is directly obtained by hot press molding. The invention can realize large-scale and quick preparation of the ferroelectric nylon film and has wide application prospect.

Disclosure of Invention

The invention aims to provide a copolyamide capable of preparing a ferroelectric nylon film by simple thermal processing and a preparation method thereof, and solves the technical problems that the ferroelectric crystal phase is difficult to obtain from the existing ferroelectric nylon, and the ferroelectric nylon film is difficult to prepare continuously and rapidly in a large scale. The invention introduces the nylon 511 chain segment into the nylon 11, so that the chain regularity is destroyed, the crystallization performance is reduced, the mesomorphic phase structure with the ferroelectric performance is directly obtained by hot press molding, and the large-scale, continuous and rapid preparation of the ferroelectric nylon film is realized.

In order to achieve the purpose, the invention provides the following technical scheme:

a ferroelectric nylon film which can be prepared by simple thermal processing has a structural formula as follows:

x＝0.9-0.5,y＝0.1-0.5。

the preparation method of the ferroelectric nylon film prepared by simple thermal processing comprises the following steps

The method comprises the following steps:

step 1: carrying out salt forming reaction on undecane diacid and pentanediamine with the molar ratio of 1: 1-1.05 to obtain 511 salt;

step 2: adding the aminoundecanoic acid and 511 salt into an autoclave according to a set ratio, wherein the molecular weight of the aminoundecanoic acid is assumed to be the molecular weight 402 of 1111 salt for convenience of chemical structure composition regulation and control because the dipole density of PA11 is the same as that of PA1111 and the dipole density of PA11-511 is greater than that of PA 11; carrying out pre-polycondensation reaction to obtain a prepolymer; wherein the stirring speed is set to 300 r/min.

And step 3: heating and vacuumizing the prepolymer obtained in the step 2, continuously carrying out melt polycondensation, and timely pumping out the generated micromolecule byproduct H₂O, increasing the molecular weight of the polymer.

And 4, step 4: and (4) carrying out hot-press molding on the nylon copolymer obtained in the step (3) to obtain the copolymerized nylon film. The thickness of the film is controlled to be 40 +/-5 um.

Further, in the salt forming reaction in the step 1, water is used as a solvent, the reaction temperature is 80 ℃, and the pH of the system is controlled to be 7.2 by adding a small amount of reactants in the reaction process.

Further, in step 1, the amino undecanoic acid; the structural formula is as follows:

the structural formula of 511 salt generated by reacting undecanedioic acid with pentamethylene diamine is:

further, in the step 2, the aminoundecanoic acid, the 511 salt obtained in the step 1 and water are added into a polymerization reaction kettle together for pre-polycondensation reaction, the mass of the added water is 2 times of that of the nylon salt, and the molar weight of the 511 salt is 10-50% of the total mass of the aminoundecanoic acid and the 511 salt.

Further, in step 2, the reaction temperature of the pre-polycondensation reaction is 180 ℃, the reaction time is 2 hours, and the reaction pressure is controlled below the saturated vapor pressure of water, specifically 0.3-0.5 MPa.

Specifically, in step 2, a catalyst including phosphorous acid, a salt or an ester of phosphoric acid, etc. should be added in the pre-polycondensation reaction, and sodium hypophosphite is preferred in the present invention. Antioxidant including antioxidant 1076, antioxidant 1098, etc. is also added during the pre-polycondensation reaction, and antioxidant 445 is preferred.

Further, in step 3, the polymerization temperature of melt polycondensation is 100 ℃ higher than the melting point, specifically 235 ℃, the polymerization time is 6 hours, and the vacuum degree is 0.1-0.8 MPa.

Further, the step 1 includes that after the nylon 511 salt water solution is obtained, the nylon 511 salt concentrated solution is obtained after rotary evaporation, and the obtained nylon 511 salt concentrated solution is dried.

Specifically, the drying treatment is carried out for 3-8 h under normal pressure or vacuum at 80-100 ℃, and preferably for 4h under 80 ℃.

Specifically, in the melt polymerization system in the step 3, a circulating water type vacuum pump is adopted for vacuum pumping; and then a rotary-vane vacuum pump is adopted for vacuum pumping.

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

1. according to the invention, amino undecanoic acid and nylon 511 salt are selected for copolymerization, the addition of the chain segment of nylon 511 destroys the crystal structure of PA11, and the 511 chain segment and the 11 chain segment form a eutectic crystal with more defects due to the isomorphous effect; the molecular chain of the copolymerized nylon PA11-511 is in a twisted chain conformation. With the increase of 511 segment content, the hot-pressed PA11-511 film gradually changes from a non-ferroelectric alpha crystal form to a ferroelectric' crystal form; the direct hot processing is realized to prepare the ferroelectric nylon film.

2. The ferroelectric crystal form of the copolyamide PA11-511 is very stable, and the ferroelectric film can not generate crystal form transformation after being annealed near the melting point.

3. The nylon 511 segment contains fewer methylene groups than the nylon 11 segment; that is, as the content of nylon 511 increases, the dipole density of the copolyamide increases. This makes the copolymerized nylon not only directly get the ferroelectric film by hot working, but also the electric function effect is better than nylon 11.

4. The copolyamide prepared by the method has the advantages of adjustable melting point, good toughness, easy processing, good heat resistance, low water absorption and the like, and the preparation process is mature and can be produced in a large scale.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a graph of the infrared spectrum of a ferroelectric polyamide obtained by simple thermal processing in example 1;

FIG. 2 is a DSC of a ferroelectric polyamide as obtained by simple thermal processing in example 1;

FIG. 3 is an XRD pattern of a ferroelectric polyamide as can be obtained by simple thermal processing in example 4;

FIG. 4 is a graph showing the hysteresis loop of a ferroelectric polyamide obtained by simple thermal processing in example 4;

FIG. 5 is a comparison of the infrared spectra of example 1.

Detailed Description

The technical solutions of the present invention will be described clearly and completely below, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.