CN101816899B - Molecular sieve/polyimide composite film for adsorption separation and preparation method thereof - Google Patents

Abstract

The invention relates to a molecular sieve/polyimide composite film for adsorption separation and a preparation method thereof. Firstly preparing a molecular sieve solution, then adding diamine into the mixed solution, adding diamine and dianhydride after dissolving, continuously stirring to obtain a polyamic acid PAA composite solution with uniformly dispersed molecular sieves, then dipping the PAA molecular sieve composite solution on a nonporous carrier such as a glass flat plate, and placing the nonporous carrier into an oven for step heating, dehydrating and cyclizing to obtain the molecular sieve/PI composite film. The composite film takes polyimide as a matrix, and a molecular sieve filler is embedded in the polyimide matrix, wherein the mass ratio of the molecular sieve to the polyimide is 0.05-0.5. The preparation process is simple and easy to control, the operation is convenient, the uniformity is good, and compared with the traditional powdery, spherical and strip molecular sieves, the molecular sieve composite film is more convenient to store in engineering, is more beneficial to construction, is easier to recover and reduces the production cost; stable thermal performance, high mechanical performance and good wear resistance.

Description

Molecular sieve/polyimide composite film for adsorption separation and preparation method thereof

technical field

The invention relates to a molecular sieve/polyimide (PI) composite film for adsorption and separation and its preparation. In particular, it relates to a composite film for adsorption and separation with PI as a matrix and molecular sieve as a filler and a preparation method thereof.

Background technique

Polyimide (PI) is a kind of aromatic heterocyclic polymer material containing imide groups in the main chain. It is one of the engineering plastic materials with excellent comprehensive performance, and it is easy to process and shape. Its products such as film, adhesive Compounds, coatings, laminates, etc. are widely used in high-tech fields such as aerospace, machinery, and electronics. Due to the aromatic ring in the main chain, PI film has outstanding advantages: (1) heat resistance: it can withstand extremely low temperature, such as in liquid helium at -269 ° C, it will not be brittle; high temperature resistance, the decomposition temperature is generally at About 500°C; (2) The thermal expansion coefficient of PI is 2×10 ^-5 ～3×10 ^-5 ℃; (3) Solvent resistance: excellent resistance to oil and organic solvents, stable to dilute acids; (4) Mechanical properties: The tensile strength of unfilled PI plastics is above 100MPa, and the elastic modulus is usually 3GPa to 4GPa; (5) PI is non-toxic and can be used to make tableware, medical appliances, and packaging materials.

In addition, selecting a suitable molecular structure and selecting a suitable film-forming technology can obtain a PI film that allows small molecules, such as water molecules, to permeate. When the PI matrix is mixed with molecular sieve without bound water, the water molecules can pass through the PI molecular chain and be adsorbed by the molecular sieve, and the molecular sieve can absorb water in the pores, so that a kind of adsorption with high molecular polymer as the matrix and molecular sieve as the filler can be prepared. Composite membranes for separation. In current industrial applications, it is generally necessary to add a binder to the raw molecular sieve powder to form particles with a certain mechanical strength and shape. The shapes of commercially available molecular sieves mainly include spherical and strip shapes. Traditional spherical and bar-shaped molecular sieves are inconvenient to store in engineering, are not conducive to construction, and are not easy to recycle. Moreover, the wear resistance needs to be improved, and dust will be generated, which limits the use of molecular sieves.

CN101380565 Mix molecular sieves and binders in a certain proportion, form them and calcinate them, then perform Li ⁺ exchange on the formed bodies, dry and activate them to prepare an active low-silicon lithium molecular sieve air oxygen-generating adsorbent. Although this invention improves the selectivity and adsorption capacity of the adsorbent to nitrogen, the storage of shaped (spherical or bar-shaped) molecular sieves is inconvenient and needs to be packed in containers; spherical or bar-shaped molecular sieves are not conducive to construction in engineering, and are not easy to recycle. result in an increase in production costs.

US6918948 prepared a highly dispersed attapulgite fiber binder, which was mixed with zeolite powder, and after molding and roasting, a molecular sieve adsorbent blend with improved performance characteristics was prepared, and when doped with zeolite, it tended to occupy zeolite The space between the crystals is not easy to mix with the zeolite interface, but the attapulgite has a large specific surface area and strong adsorption capacity, which may affect the selective adsorption and separation effect of zeolite to a certain extent.

RU2337064 uses acidified aluminum sulfate starch (or carboxymethyl cellulose) suspension and synthetic molecular sieve as raw materials to mix and granulate, disperse and dry at 350°C, and after calcining, obtain A-type molecular sieve crystals through alkali sodium aluminate crystallization, and finally obtain molecular sieves The particles have good wear resistance and adsorption capacity. Although the molecular sieve in this invention has improved wear resistance, the granular molecular sieve will still have a certain degree of powder loss, which will cause blockage in the use of the fixed bed, resulting in a decrease in adsorption performance, and molecular sieve powder loss will also lead to molecular sieve failure. The mechanical strength gradually decreases.

等利用表面改性的天然沸石与聚丙烯材料制备复合薄膜，虽然沸石添加量为2％时的复合材料水蒸汽渗透很小，但4％沸石填充复合薄膜具有相当高的渗透率，而且与天然皮革的水蒸气渗透率非常相近，该复合薄膜可用来制备高水蒸气渗透率的包装材料。但是该发明中制得的挤出聚丙烯/沸石复合薄膜机械性能下降很快，添加4％沸石的复合薄膜屈服应力下降21.1％，屈服应变下降14.3％，所以在保证基体性能的前途下只能添加少量的沸石，这对制备复合薄膜形式的沸石分子筛很不利；聚丙烯耐低温时会变脆，导致冲击性差，不耐磨，较易老化，需通过改性和添加抗氧剂予以克服。turk

etc. used surface-modified natural zeolite and polypropylene materials to prepare composite membranes. Although the water vapor permeability of the composite material was very small when the zeolite content was 2%, the composite membrane filled with 4% zeolite had a very high permeability, and it was similar to natural The water vapor permeability of leather is very similar, and the composite film can be used to prepare packaging materials with high water vapor permeability. However, the mechanical properties of the extruded polypropylene/zeolite composite film produced in this invention decline rapidly, and the yield stress of the composite film added with 4% zeolite drops by 21.1%, and the yield strain drops by 14.3%. Adding a small amount of zeolite is detrimental to the preparation of zeolite molecular sieve in the form of composite film; polypropylene will become brittle when it is resistant to low temperature, resulting in poor impact resistance, no wear resistance, and easy aging, which needs to be overcome by modification and addition of antioxidants.

CN101205306 prepares a PE composite fresh-keeping packaging film for modified atmosphere packaging of food, which uses polymer matrix, molecular sieve (modified by coupling agent) and plasticizer as raw materials. The composite film uses molecular sieves as active inorganic particles, so that the film has good gas permeability, moisture permeability and porosity, thereby adjusting the gas composition inside the package. But the mass percent of modified molecular sieve used in this invention is only 1.5-20%, and the content of molecular sieve has limited the maximum air permeability and moisture permeability of the composite film; the surface modification of molecular sieve needs to be reacted at room temperature under nitrogen protection for 24 hours. The conditions are stricter.

Contents of the invention

The purpose of the present invention is to improve the shortcomings of traditional spherical and strip molecular sieves, such as inconvenient storage, unfavorable construction, and difficult recovery, etc., thereby providing a molecular sieve/polyimide composite film for adsorption and separation. Another aspect of the present invention One purpose is to provide the preparation method of above-mentioned composite film.

The technical scheme of the present invention is: a molecular sieve/polyimide composite film for adsorption and separation, which is characterized in that polyimide is used as a matrix, and molecular sieve fillers are embedded in the polyimide matrix, wherein molecular sieve and polyimide The mass ratio of amine is 0.05-0.5.

The present invention also provides a method for preparing the above molecular sieve/polyimide composite film for adsorption and separation, the specific steps are as follows:

A. Preparation of molecular sieve solution

Add the molecular sieve into the aprotic polar solvent, control the temperature and time and stir until it is completely dispersed;

B, preparation of molecular sieve/polyamic acid PAA composite solution

Add diamine in the mixed solution that makes in the step A, control temperature and stir, after it dissolves completely, add the dianhydride of equimolar amount with diamine again in batches, continuously stir to form polyamic acid (PAA, PAA, molecular sieve dispersed homogeneously, Polycondensation of diamine and dianhydride) composite solution;

C, preparation of molecular sieve/polyimide (PI) composite film

The PAA molecular sieve composite solution is dip-coated on a non-porous carrier such as a glass plate, placed in an oven to raise the temperature stepwise, and dehydrated and cyclized to obtain a molecular sieve/polyimide (PI) composite film.

In the above step A, the molecular sieve is added into the aprotic polar solvent, and the temperature is controlled at 20-30° C.; after adding the molecular sieve, stir for 20-30 minutes; wherein the mass ratio of the molecular sieve to the solvent is 0.005-0.25.

In the above-mentioned small step B, diamine is added to step A to prepare a mixed solution, and the temperature is controlled at 20-30°C; dianhydride in an equimolar amount to diamine is added in 2-4 batches and stirred for 4-8 hours; the molecular sieve and PAA The mass ratio is 0.05-0.5.

In the above step C step heating process, the heating rate is 2-5°C/min; the temperature is raised to 80-120°C for 30-90 minutes; the temperature is raised to 180-220°C for 30-90 minutes; the temperature is raised to 280-350°C for 30-90 minutes .

The order of adding molecular sieves in the above step A can be as follows: directly add to the solvent before preparing the PAA solution, add after the diamine is completely dissolved in the solvent, add after the dianhydride is completely dissolved in the solvent, or add it after the PAA solution is prepared After adding, the preferred order of adding is the first one.

The PAA used in the present invention is obtained by reacting and polymerizing the precursor dianhydride and diamine in the solvent.

The dianhydride used in the present invention is preferably pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxydiphthalic acid dianhydride Anhydride (ODPA), isomeric diphenyl sulfide dianhydride (TDPA), triphenylene tetracarboxylic dianhydride (HQDPA), benzophenone tetracarboxylic dianhydride (BTDA), benzophenone tetracarboxylic dianhydride (BDPA), One of bisphenol A dianhydride (BPADA), hexafluoroisopropylidene diphthalic anhydride (6-FDA), 3,3',4,4'diphenylsulfone tetracarboxylic anhydride (DSDA) or It is a blend of two.

Diamine among the present invention is preferably selected for use: 4,4'-diaminodiphenyl ether (ODA), dimethyl diphenylmethane diamine (DMMDA), 1,3-two (3-aminophenoxy) benzene ( BAPB), 4,4'-bisphenol A diphenyl ether diamine (BAPP), perfluoroisopropylidene bisamine (4-BDAF), 4,4'-bis(4-aminophenoxy)diphenyl Sulfone (BAPS), 4,4'-bis(4-aminophenoxy)diphenyl ether (BAPE), diaminobenzophenone (DABP), 4,4'-diaminotriphenylamine (DATPA) , 4,4'-diaminodiphenylmethane (MDA), diaminodiphenylsulfone (DDS), phenylenediamine (PDA), 3,4'-diaminodiphenyl ether, 4,4'-diamino Diphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 4,4'-diamino-diphenoxy-1",4"-benzene, 4,4 '-Diamino-diphenoxy-1", 3"-benzene, 3,3'-diamino-diphenoxy-1", 3"-benzene, 4,4'-diamino-diphenoxy Base-4”, 4-diphenylisopropane or a blend of two.

The molecular sieve in the present invention is any one of zeolite molecular sieve (including activated zeolite activated powder), mesoporous molecular sieve or carbon molecular sieve raw powder.

The aprotic polar solvent among the present invention is N-methylpyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), dimethylsulfoxide (DMSO) or THF.

Beneficial effect:

1. The molecular sieve in the form of PI composite film prepared by the present invention has good uniformity, and the molecular sieve composite film is more convenient to store than traditional powdery, spherical, and strip-shaped molecular sieves in engineering, more conducive to construction, and easier to recycle, reducing production costs; Stable thermal performance, can be heated to desorb adsorbate, and can be regenerated and reused; chemical properties are stable and non-toxic, molecular sieves are not easy to lose, and have a wide range of applications; PI matrix wraps molecular sieves, and a good interface between PI and molecular sieves can be formed; mechanical High performance, no cracks, long service life, the most important thing is good wear resistance, no dust, not only can meet the needs of fixed beds, but also meet the needs of various applications other than fixed beds, such as packaging, membrane separation or react.

The typical PI (ODA/PMDA) thin film properties prepared by the present invention are shown in Table 1.

Table 1 Basic properties of typical PI films

project unit PI Remark Exterior - transparent, uniform Visual observation Thermal expansion coefficient 10 ^-6 K ^-1 26.63 GB/T 1036-1989 maximum load N 49.13 GB/T 1040-1992 Tensile Strength MPa 196.5 GB/T 1040-1992 Elastic Modulus GPa 3.25 GB/T 1040-1992 elongation at break % 12.94 GB/T 1040-1992

2. The process is convenient: the requirements for the device are low, the operation process is simple, the reaction process is easy to control, and has certain application value.

Description of drawings

Fig. 1 is the SEM figure of example 1 composite film;

Figure 2 is a graph of the desorption rate of water on 3A and 3A/PI prepared in Example 1.

Detailed ways

The following examples will help to understand the present invention, but do not limit the content of the present invention.

Example 1

Weigh 2.25g of 3A zeolite activated powder, dissolve in 40.25g of DMF, stir for 20min, add 3.04g of 4,4'-diaminodiphenyl ether (ODA), after it is completely dissolved, add 4.46g of pyromellitic dianhydride in 2 batches (PMDA), stirred 4h, made 50g 3A zeolite activated powder and PAA composite solution.

Dip-coat the 3A zeolite activated powder/PAA composite solution on a glass plate, put it into an oven to raise the temperature step by step, and control the heating rate to 3°C/min (90°C×0.8h, 190°C×0.8h, 320°C×1h). A dehydration-cyclized 3A activated zeolite composite membrane was obtained.

The internal structure of the composite film of the present invention is shown in Figure 1. It can be seen from the figure that the molecular sieve is embedded in the polyimide matrix, and a good interface bond can be formed between the polyimide matrix and the molecular sieve filler.

The STA 409 PC synchronous thermal analyzer was used to measure the temperature-programmed desorption (TG/DTG) curve of the composite film under the condition that the reaction atmosphere was nitrogen and the heating rate was 10 °C/min, and the relationship between temperature and dehydration amount was calculated. The desorption rate diagram of the present invention is shown in Figure 2, and it can be seen from the diagram that the desorption curves of water on the molecular sieve and the composite film have the same trend in temperature rising and desorption curves, and the difference in maximum dehydration amount is very small.

Example 2

Weigh 3.38g of 5A zeolite activated powder, dissolve in 31.62g of DMF, stir for 20min, add 6.08g of 4,4'-diaminodiphenyl ether (ODA), after it is completely dissolved, add 8.92g of 3,3',4, 4'-biphenyltetracarboxylic dianhydride (BPDA), stirred for 4h to obtain a composite solution of 50g 5A zeolite activated powder and PAA.

Dip-coat the 5A zeolite activated powder/PAA composite solution on a glass plate, put it into an oven to raise the temperature step by step, and control the heating rate to 4°C/min (100°C×1h, 190°C×0.5h, 300°C×0.6h). A dehydration-cyclized 5A activated zeolite composite film was obtained.

Example 3

Weigh 1.00g of 5A molecular sieve, dissolve in 44.00g of DMAc, stir for 30min, add 2.85g of 4,4'-bisphenol A diphenyl ether diamine (BAPP), after it is completely dissolved, add 2.15g of 4,4'-oxygen Diphthalic anhydride (ODPA), stirred for 5 hours to prepare 50g of 5A molecular sieve and PAA composite solution.

Dip-coat the 5A molecular sieve/PAA composite solution on a glass plate, put it into an oven to raise the temperature step by step, and control the heating rate to 5°C/min (110°C×0.5h, 200°C×1h, 280°C×0.9h), and the dehydrated Cyclized 5A activated zeolite composite membrane forms.

Example 4

Weigh 1.5g of X-type molecular sieve, dissolve it in 42.5g of DMF, stir for 30min, add 3.02g of perfluoroisopropylidene bisamine (4-BDAF), after it is completely dissolved, add 2.98g of triphenylenediethene tetraacid in 4 batches Dianhydride (HQDPA) was stirred for 8 hours to prepare 50 g of X-type molecular sieve and PAA composite solution.

Dip-coat the X-type molecular sieve/PAA composite solution on a glass plate, put it into an oven to raise the temperature step by step, and control the heating rate to 3°C/min (120°C×1.1h, 200°C×0.8h, 290°C×1.1h), and prepare A dehydration-cyclized X-type molecular sieve composite film was obtained.

Example 5

Weigh 0.4g of Y-type molecular sieve, dissolve in 45.6g of DMAc, stir for 25min, add 1.97g of 4,4'-bis(4-aminophenoxy)diphenyl sulfone (BAPS), after it is completely dissolved, add 2.03g of Hexafluoroisopropylidene diphthalic dianhydride (6-FDA) was stirred for 6 hours to prepare 50 g of Y-type molecular sieve and PAA composite solution.

Dip-coat the Y-type molecular sieve/PAA composite solution on a glass plate, put it into an oven to raise the temperature step by step, and control the heating rate to 3°C/min, (110°C×1h, 210°C×1.2h, 300°C×1h), and obtained Dehydration and cyclization Y-type molecular sieve composite membrane.

See Table 2 for the maximum dehydration amount at 30-420°C in Examples 1-5.

The maximum dehydration amount of table 2 example 1-5

Claims (4)

1. a molecular sieve/polyimide composite film for adsorption separation is characterized in that with the polyimides being matrix, and the molecular sieve filling intercalation is in polyimide matrix, and wherein the mass ratio of molecular sieve and polyimides is 0.05～0.5; Prepared by following method, concrete steps are following:

The preparation of A, molecular sieve solution

Molecular sieve is added in the aprotic polar solvent, and wherein molecular sieve and aprotic polar solvent mass ratio are 0.005～0.25; The control temperature is at 20～30 ℃; Stir 20～30min, to disperseing fully;

The preparation of B, molecular sieve/polyamic acid PAA composite solution

Add diamines in the mixed solution that in steps A, makes, the control temperature treats to divide after it dissolves fully the dianhydride of 2～4 batches of addings and diamines equimolar amounts 20～30 ℃ of stirrings again, and continuous stirring 4～8h becomes the diffusing uniform polyamic acid PAA composite solution of molecule screening; Wherein molecular sieve and PAA mass ratio are 0.05～0.5;

The preparation of C, molecular sieve/polyimide composite film

With the dip-coating of PAA molecular sieve composite solution on non-porous support such as glass plate; Put into the baking oven ladder-elevating temperature; Wherein the speed of ladder-elevating temperature is 2～5 ℃/min; Be warmed up to 80～120 ℃ of constant temperature 30～90min, be warmed up to 180～220 ℃ of constant temperature 30～90min, be warmed up to 280～350 ℃ of constant temperature 30～90min; Cyclodehydration makes molecular sieve/polyimide composite film.

2. film according to claim 1 is characterized in that described molecular sieve is any in the former powder of zeolite molecular sieve, mesopore molecular sieve or carbon molecular sieve.

3. film according to claim 1 is characterized in that described dianhydride is a pyromellitic acid anhydride, 3,3 '; 4; 4 '-bibenzene tetracarboxylic dianhydride, 4, the two phthalic anhydrides of 4 '-oxygen, isomery diphenyl sulfide dianhydride, triphen diether tetracarboxylic dianhydride, benzophenone tetracarboxylic acid dianhydride, benzophenone tetracarboxylic dianhydride, bisphenol-A dianhydride, hexafluoro isopropylidene two phthalandione dianhydrides or 3,3 '; 4, one or both blend in 4 '-diphenyl sulfone tetracarboxylic anhydride; Described diamines is 4,4 '-diaminodiphenyl ether, dimethyl diphenyl methane diamines, 1, two (3-amino-benzene oxygen) benzene, 4 of 3-; 4 '-bisphenol-A diphenyl ether diamines, perfluor isopropylidene diamine, 4,4 '-two (4-amino-benzene oxygen) diphenyl sulphone (DPS), 4,4 '-two (4-amino-benzene oxygen) diphenyl ether, diaminourea hexichol (first) ketone, 4; 4 '-diaminourea triphenylamine, 4,4 '-MDA, diamino diphenyl sulfone, phenylenediamine, 3,4 '-diaminodiphenyl ether, 4; 4 '-diaminodiphenyl-methane, 3,3 '-dimethyl-4,4 '-diaminodiphenyl-methane, 4; 4 '-diaminourea-hexichol Oxy-1 ", 4 "-benzene, 4,4 '-diaminourea-hexichol Oxy-1 "; 3 "-benzene, 3,3 '-diaminourea-hexichol Oxy-1 ", 3 "-benzene or 4; 4 '-diaminourea-two phenoxy group-4 ", one or both blend in the different propane of 4-diphenyl.

4. film according to claim 1 is characterized in that described aprotic polar solvent is N-methyl pyrrolidone, N, dinethylformamide, N, N-dimethylacetylamide, dimethyl sulfoxide (DMSO) or oxolane.

Images