Composite functional pa6, and preparation method and recycling method thereof

Abstract

The application belongs to the technical field of polymer material preparation and recycling, and relates to a composite functional PA6, a preparation method and a recycling method thereof, and a structure formula of the composite functional PA6 is as follows: wherein n, m and x are positive integers; -OC-R1-CO- is a binary acid segment; -O-R2-O- is a binary alcohol segment; -OA-R3-BO- is a binary acid segment, A and B are carbon atoms, or are phosphorus atoms and carbon atoms respectively, or are carbon atoms and phosphorus atoms respectively. The preparation method is that PA6 oligomer ester is subjected to ester exchange reaction with a functional component, and the composite functional PA6 is obtained. The recycling method comprises the following steps: performing ester bond hydrolysis reaction on the composite functional PA6, cooling and precipitating, performing esterification reaction on the collected precipitate and a binary alcohol, and performing ester exchange reaction on the esterification reaction product and the functional component, and the composite functional PA6 is obtained. The method is simple, and is suitable for recycling and utilization of the composite functional PA6 for multiple times.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polymer material preparation and recycling, and particularly relates to a composite functional PA6, a preparation method thereof and a recycling method. BACKGROUND

[0002] PA6 copolymerization modification grafts or blocks non-amide functional groups or high polymers to the PA6 molecular chain to improve the performance of PA6 in various aspects. At present, most of the copolymerized functional PA6 is prepared by chain extension of esterification reaction of polyamide 6 segments terminated by diacid with polyester segments, polyether segments or molecular segments with hydroxyl structure at both ends. CN109706536A discloses a synthesis method of copolymerized PA6-based polymer, which mainly relies on PA6 segments terminated by diacid and modified by ethylene glycol, and then chain extension is realized by ester exchange. It has excellent physical and mechanical properties and processing performance of PA6, and also introduces the characteristics of functional components. CN111440314A discloses a method for preparing copolymerized PA6 by condensation reaction of terephthalic acid diol ester and diaminic acid derivative mixture, which has low b value and good mechanical properties, greatly promoting the development of copolymerized functional PA6.

[0003] However, like other polyesters and polyamides, copolymerized functional PA6 is difficult to degrade in the natural environment, and it is difficult to realize physical and chemical recycling after adding functional components. At present, the main technical means for recycling and application of copolymerized functional PA6 is to re-produce copolymer by waste polyester and polyamide, CN110862535A discloses a method for preparing copolyester amide by depolymerizing waste polyester containing nylon, which mainly uses physical and chemical methods to alcoholize the polyester and nylon mixed waste and then polymerizes PA6-based polymer. CN113150268A discloses a preparation method of micro-alcoholized functional regenerated polyamide 6, which mainly forms reactive groups by alcoholizing PA6 and then prepares PA6 copolymer with other components such as polyester and polyether. However, these methods are focused on copolymerization and regeneration of original PA6 or polyester treated by alcoholysis, which belongs to secondary re-production, and still faces the problem of recycling and reuse after single cycle, which cannot fundamentally solve the long-term recycling and reuse. In the increasingly serious plastic pollution environment, the multiple recycling and reuse of polymers, especially functional polymers, has become a problem that cannot be ignored in the rapid development of plastic and fiber industry.

[0004] Therefore, it is urgent to develop a new composite functional PA6 capable of multiple recycling and reuse to realize micro-plastic management and environmental protection. SUMMARY

[0005] The present application aims to solve the above-mentioned problems existing in the prior art, and provides a composite functional PA6, a preparation method thereof and a recycling method.

[0006] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0007] A composite functional PA6 has a structural formula as follows:

[0008]

[0009] In the formula, n, m, and x are positive integers; -OC-R1-CO- is a dibasic acid segment; -O-R2-O- is a dibasic alcohol segment; -OA-R3-BO- is a dibasic acid segment, wherein A and B are carbon atoms, or phosphorus atoms and carbon atoms, or carbon atoms and phosphorus atoms, respectively.

[0010] As a preferred technical scheme:

[0011] The composite functional PA6 has 8≤n≤70, 4≤m≤20, and 1≤x≤5; the dibasic acid corresponding to the -OC-R1-CO- dibasic acid segment is a linear aliphatic dibasic acid with a carbon chain length of no more than 16, such as adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid (CAS No.: 693-23-2), 1,14-tetradecanedioic acid (CAS No.: 821-38-5), or 1,16-hexadecanedioic acid (CAS No.: 505-54-4); the dibasic alcohol corresponding to the -O-R2-O- dibasic alcohol segment is a linear dibasic alcohol with a carbon chain length of no more than 6, such as ethylene glycol, propylene glycol, butylene glycol, pentanediol, or hexanediol; and the dibasic acid corresponding to the -OA-R3-BO- dibasic acid segment is phthalic acid, sulfonated phthalic acid, 2-carboxyethyl phenyl phosphinic acid, or DDP ([(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl] butanedioic acid).

[0012] The composite functional PA6 has a relative viscosity of 2.4-4.0, a hot water extract content of 0.05-2 wt%, and a melting point of 190-250℃.

[0013] The present application also provides a method for preparing the composite functional PA6, which comprises subjecting a PA6 oligomer esterification product and a functional component to an ester exchange reaction to obtain the composite functional PA6.

[0014] The PA6 oligomer esterification product has a structural formula as follows:

[0015]

[0016] The functional component has a structural formula as follows:

[0017]

[0018] As a preferred technical solution:

[0019] The method as described above, the ester exchange reaction is also added catalyst A (titanium catalyst or / and antimony catalyst, such as tetrabutyl titanate, titanium glycol, antimony trioxide, antimony acetate and antimony glycol) and anti-ether agent (such as sodium acetate and the like).

[0020] The method as described above, the functional component, catalyst A and anti-ether agent are respectively 1-20% of the mass of PA6 oligomer esterification product, 200-500ppm, 200-800ppm; the temperature of the ester exchange reaction is 250-280℃, the pressure of the ester exchange reaction is 100Pa or less, and the time of the ester exchange reaction is 2-4h.

[0021] The method as described above, the preparation process of the PA6 oligomer esterification product is that the dicarboxyl PA6 oligomer is mixed with dihydric alcohol and then esterification reaction is carried out, so that the PA6 oligomer esterification product is obtained;

[0022] The structural formula of the dicarboxyl PA6 oligomer is as follows:

[0023]

[0024] The structural formula of the dihydric alcohol is as follows:

[0025] HO-R2-OH.

[0026] The method as described above, the temperature of the esterification reaction is 220-260℃, the pressure of the esterification reaction is 0.01-0.5MPa, and the time of the esterification reaction is 2-4h; the dihydric alcohol is ethylene glycol, propylene glycol, butanediol, pentanediol or hexanediol; and the molar ratio of the dihydric alcohol to the dicarboxyl PA6 oligomer is 1.3-1.8:1.

[0027] The method as described above, the preparation process of the dicarboxyl PA6 oligomer is that caprolactam, diacid, deionized water and catalyst B (such as 6-aminohexanoic acid) are mixed, and then hydrolysis ring-opening reaction is carried out, so that the dicarboxyl PA6 oligomer is obtained, wherein the structural formula of the diacid is as follows:

[0028]

[0029] The method as described above, the temperature of the hydrolysis ring-opening reaction is 210-260℃, the pressure of the hydrolysis ring-opening reaction is 0.1-3MPa, and the time of the hydrolysis ring-opening reaction is 3-5h; the amount of the diacid, deionized water and catalyst B is respectively 5-30wt%, 2-5wt% and 0.1-1wt% of the amount of caprolactam.

[0030] The application also provides a method for recycling a composite functional PA6 as described in any one of the above, comprising the following steps:

[0031] (1) placing the composite functional PA6 in a neutral or alkaline aqueous solution to perform an ester bond hydrolysis reaction;

[0032] (2) cooling to precipitate, collecting the precipitate, and obtaining recovered double-carboxyl PA6 oligomers, wherein the structure of the recovered double-carboxyl PA6 oligomers is as follows:

[0033]

[0034] (3) performing an esterification reaction of the recovered double-carboxyl PA6 oligomers with a dihydric alcohol to obtain a PA6 oligomer esterification product, and performing an ester exchange reaction of the PA6 oligomer esterification product with a functional component, thereby obtaining regenerated composite functional PA6,

[0035] wherein the dihydric alcohol has the following structure:

[0036] HO-R2-OH,

[0037] the functional component has the following structure:

[0038]

[0039] The ester bond is used to link between the PA6 oligomer segment and the functional component in the present application. Due to the difference in the ester bond angle and the molecular chain structure, it is difficult to form a crystal lattice around the ester bond, so that the hydrolysis conditions of the ester bond and the amide bond are different. The alkaline / neutral aqueous solution can selectively hydrolyze the ester bond at a lower temperature and pressure. The functional component formed is dissolved in the aqueous phase, and the double-carboxyl PA6 oligomer formed is precipitated after cooling. The separation of the double-carboxyl PA6 oligomer and the functional component can be achieved by simple operation methods such as filtration. The present application uses water as a depolymerization agent, without introducing other chemical structures into the molecular chain, which can ensure the purity and structural stability of the double-carboxyl PA6 oligomer after each separation. The recovered double-carboxyl PA6 oligomer can be esterified again to perform an ester exchange reaction with the functional component, thereby realizing the preparation of composite functional PA6 through multiple cycles. In each cycle, the same or different functional component can be selected according to the needs, thereby solving the problem of recycling and utilization of the current functional PA6 material.

[0040] As a preferred technical solution:

[0041] The method described above, in step (1), the weight ratio of the neutral or alkaline aqueous solution to the composite functional PA6 is 1:5-1:20, the pH value of the alkaline aqueous solution is 8-11, the solute in the alkaline aqueous solution is sodium hydroxide, potassium hydroxide, sodium bicarbonate or sodium carbonate, the temperature of the ester bond hydrolysis reaction is 100-140℃, the pressure of the ester bond hydrolysis reaction is 1.0-1.7 MPa, the time of the ester bond hydrolysis reaction is 2-4 h, and the ester bond hydrolysis rate is ≥98%.

[0042] The esterification reaction temperature in step (3) is 220-260℃, and the esterification reaction pressure is 0.01-0.5MPa; the molar ratio of dihydric alcohol to the recovered double-carboxyl PA6 oligomer is 1.3-1.8:1.

[0043] The ester exchange reaction also adds a catalyst A (a titanium-based catalyst or / and an antimony-based catalyst, such as one or more of tetrabutyl titanate, titanium glycol, antimony trioxide, antimony acetate, and antimony glycol) and an ether inhibitor (such as sodium acetate); the ester exchange reaction temperature is 250-280℃, the ester exchange reaction pressure is 100Pa or less, the functional component, the catalyst A, and the ether inhibitor are 1-20%, 200-500ppm, and 200-800ppm, respectively, of the PA6 oligomer esterification product mass;

[0044] The regenerated composite functional PA6 has a relative viscosity of 2.4-4.0, a hot water extract content of 0.05-2wt%, and a melting point of 190-250℃, meeting the processing requirements of injection molding and melt spinning.

[0045] Advantages

[0046] (1) The functional component of the composite functional PA6 of the present application is linked to the PA6 segment by an ester bond structure. Due to the difference in hydrolysis conditions between ester bonds and amide bonds, the ester bonds can be directionally hydrolyzed under mild conditions, the PA6 segment is separated from other functional components, and the PA6 segment is re-esterified and modified to be copolymerized with the functional component again.

[0047] (2) The present application uses water as a depolymerization agent during recycling, without introducing other chemical structures into the molecular chain, which can ensure the purity and structural stability of the PA6 segment after each separation, thereby realizing stable physical and chemical properties of the composite functional PA6 after multiple cycles of preparation.

[0048] (3) In the recycling process, different functional components can be introduced according to actual application requirements, realizing the redesign of functional PA6 materials.

[0049] (4) In the recycling process, the PA6 segment can be separated and recycled by low-temperature hydrolysis and filtration, etc., which is simple in process, low in cost, and easy to mass industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 is a schematic diagram of the preparation method and recycling method of the composite functional PA6 provided by the present application. DETAILED DESCRIPTION

[0051] The application will be further described below in connection with specific embodiments. It should be understood that these embodiments are only used to illustrate the application and not to limit the scope of the application. Furthermore, it should be understood that those skilled in the art can make various modifications or changes to the application after reading the content of the application, and these equivalent forms also fall within the scope defined by the appended claims.

[0052] The following are the test methods of the relevant performance indicators in each embodiment:

[0053] (1) Detection method of relative viscosity

[0054] Referring to the test method of China Textile Industry Standard FZ / T 51004-2011: dissolve the sample in concentrated sulfuric acid with a concentration of 96wt% to prepare a 0.01g / ml test solution, and use an Ubbelohde viscometer (capillary diameter is 1.03mm) to test in a constant temperature water bath with water temperature of 25±0.1℃, repeat 5 parallel tests and take the average value.

[0055] (2) Detection method of hot water extractable content

[0056] Referring to the test method of China Textile Industry Standard FZ / T 51004-2011: place the sample in a vacuum oven at 105℃ and dry for 24h to constant weight, then take a certain mass (m0) of the sample, add deionized water with a bath ratio of 20:1, use a Soxhlet extractor to extract the sample in boiling water (water bath temperature≥98℃) for 8h, after taking out, place the sample in a vacuum oven at 105℃ and dry for 24h, then weigh and record the mass as (m1), the hot water extractable content is shown in the following formula:

[0057] E=(m0-m1) / m0;

[0058] In the formula, E is the hot water extractable content, wt%; m0 and m1 are the sample masses before and after extraction, respectively, g.

[0059] (3) Detection method of melting point

[0060] Use TA-Q20 differential scanning calorimeter to test the crystallization and melting behavior of the sample: heat and cool the dry sample of about 5mg at a rate of 10℃ / min under nitrogen atmosphere.

[0061] (4) Characterization method of polymer molecular structure

[0062] Use AVANCE-600 nuclear magnetic resonance spectrometer to test the molecular structure of the sample: before testing, weigh 5-10mg of dry sample, use deuterated sulfuric acid (D2SO4) as the test solvent, test temperature is 25℃, and frequency is 600MHz;

[0063] FTIR spectrum analysis was performed by using Nicolet 6700 Fourier transform infrared spectrometer: before testing, the sample was made into potassium bromide flake, and ATR accessory was used for total reflection test, and the test scanning range was 4000-600 cm -1 ;

[0064] Tests show that the structural formula of the composite functional PA6 in each of the following embodiments is as follows:

[0065]

[0066] In the formula, n, m, and x are positive integers; -OC-R1-CO- is a diacid segment; -O-R2-O- is a diol segment; -OA-R3-BO- is a diacid segment, wherein A and B are carbon atoms, respectively, or phosphorus atoms and carbon atoms, respectively, or carbon atoms and phosphorus atoms, respectively.

[0067] (5) Detection method of ester bond hydrolysis rate

[0068] The molecular structure of the sample was tested by using AVANCE-600 nuclear magnetic resonance spectrometer: before testing, 5-10 mg of dry sample was weighed, deuterium sulfate (D2SO4) was used as the test solvent, the test temperature was 25°C, and the frequency was 600 MHz; the integral areas of the ester bond position characteristic peaks before and after hydrolysis were tested, and (1-hydrolysis ester bond characteristic peak area) / ester bond characteristic peak area before hydrolysis = ester bond hydrolysis rate.

[0069] Example 1

[0070] A preparation method of a composite functional PA6, as shown in Figure 1 , the specific steps are as follows:

[0071] (1) Preparation of dicarboxyl PA6 oligomer;

[0072] Caprolactam, adipic acid, deionized water and 6-aminohexanoic acid were mixed, incubated at 80°C and mechanically stirred at a speed of 150 r / min for 18 min, and the amount of adipic acid, deionized water and 6-aminohexanoic acid was 30wt%, 3wt% and 1wt% of the amount of caprolactam, respectively, followed by hydrolysis ring-opening reaction, the temperature of the hydrolysis ring-opening reaction was 210°C, the pressure of the hydrolysis ring-opening reaction was 3MPa, and the time of the hydrolysis ring-opening reaction was 3h, to obtain the dicarboxyl PA6 oligomer;

[0073] (2) Preparation of PA6 oligomer ester;

[0074] The PA6 oligomer esterification product is obtained by mixing the PA6 oligomer esterification product, dimethyl terephthalate, tetrabutyl titanate and sodium acetate, and then performing an ester exchange reaction, wherein the dimethyl terephthalate, tetrabutyl titanate and sodium acetate are 20%, 200 ppm and 800 ppm of the mass of the PA6 oligomer esterification product respectively, the ester exchange reaction temperature is 250°C, the ester exchange reaction pressure is 100 Pa, and the ester exchange reaction time is 4 h.

[0075] (3) preparing the composite functional PA6;

[0076] The PA6 oligomer esterification product is obtained by mixing the PA6 oligomer esterification product, dimethyl terephthalate, tetrabutyl titanate and sodium acetate, and then performing an ester exchange reaction, wherein the dimethyl terephthalate, tetrabutyl titanate and sodium acetate are 20%, 200 ppm and 800 ppm of the mass of the PA6 oligomer esterification product respectively, the ester exchange reaction temperature is 250°C, the ester exchange reaction pressure is 100 Pa, and the ester exchange reaction time is 4 h.

[0077] The relative viscosity of the finally prepared composite functional PA6 is 4.0, the hot water extractable content is 0.05 wt%, and the melting point is 190°C; in the structural formula of the composite functional PA6, n is 8, m is 20, and x is 5.

[0078] The recycling method of the composite functional PA6 is shown in the following steps: Figure 1

[0079] (1) placing the composite functional PA6 in an alkaline aqueous solution to perform an ester bond hydrolysis reaction, wherein the mass ratio of the alkaline aqueous solution to the composite functional PA6 is 20:1, the pH value of the alkaline aqueous solution is 8, the solute in the alkaline aqueous solution is sodium carbonate, the ester bond hydrolysis reaction temperature is 100°C, the ester bond hydrolysis reaction pressure is 1.0 MPa, the ester bond hydrolysis reaction time is 3 h, and the ester bond hydrolysis rate is ≥98%;

[0080] (2) cooling to precipitate a precipitate, collecting the precipitate by filtration with a filtration accuracy of 40-200 μm, and drying to obtain the recycled dicarboxyl PA6 oligomer;

[0081] (3) performing an esterification reaction on the recycled dicarboxyl PA6 oligomer and ethylene glycol, wherein the molar ratio of the ethylene glycol to the recycled dicarboxyl PA6 oligomer is 1.5:1, the esterification reaction temperature is 220°C, the esterification reaction pressure is 0.5 MPa, and the esterification reaction time is 2 h to obtain the PA6 oligomer esterification product; then mixing the PA6 oligomer esterification product, dimethyl terephthalate, tetrabutyl titanate and sodium acetate, and performing an ester exchange reaction, wherein the dimethyl terephthalate, tetrabutyl titanate and sodium acetate are 13%, 400 ppm and 350 ppm of the mass of the PA6 oligomer esterification product respectively, the ester exchange reaction temperature is 250°C, the ester exchange reaction pressure is 100 Pa, and the ester exchange reaction time is 3 h to prepare the regenerated composite functional PA6. ​

[0082] The relative viscosity of the regenerated composite functional PA6 prepared finally is 4.0, the hot water extract content is 0.05wt%, and the melting point is 190°C, meeting the processing requirements of injection molding and melt spinning.

[0083] Example 2

[0084] A preparation method of the composite functional PA6, and the specific steps are as follows:

[0085] (1) preparing dicarboxyl PA6 oligomer;

[0086] The caprolactam, 1, 16-hexadecane diacid, deionized water and 6-aminohexanoic acid are mixed, and the mixture is kept at 75°C and mechanically stirred at a speed of 200r / min for 20min. The amounts of 1, 16-hexadecane diacid, deionized water and 6-aminohexanoic acid are 18wt%, 2.5wt% and 0.5wt% of the amount of caprolactam, respectively. Then, a hydrolysis ring-opening reaction is carried out at a temperature of 235°C and a pressure of 1.7MPa for 3.5h, to obtain the dicarboxyl PA6 oligomer;

[0087] (2) preparing PA6 oligomer esterification product;

[0088] The dicarboxyl PA6 oligomer is mixed with hexanediol, and then esterification reaction is carried out at a temperature of 230°C and a pressure of 0.25MPa for 2.5h, with the molar ratio of hexanediol to dicarboxyl PA6 oligomer being 1.6:1, to obtain the PA6 oligomer esterification product;

[0089] (3) preparing composite functional PA6;

[0090] The PA6 oligomer esterification product, isophthalic acid-5-sodium diethyl sulfonate, antimony acetate and sodium acetate are mixed, and then ester exchange reaction is carried out at a temperature of 265°C and a pressure of 50Pa for 3.5h, with the amounts of isophthalic acid-5-sodium diethyl sulfonate, antimony acetate and sodium acetate being 13% of the mass of the PA6 oligomer esterification product, 450ppm and 650ppm, respectively, to obtain the composite functional PA6.

[0091] The relative viscosity of the composite functional PA6 prepared finally is 3.4, the hot water extract content is 1.2wt%, and the melting point is 215°C. In the structural formula of the composite functional PA6, n is 32, m is 7, and x is 3.

[0092] The recycling method of the composite functional PA6 described above, and the specific steps are as follows:

[0093] (1) the composite functional PA6 is placed in an alkaline aqueous solution for ester bond hydrolysis reaction, the mass ratio of the alkaline aqueous solution to the composite functional PA6 is 16:1, the pH value of the alkaline aqueous solution is 8, the solute in the alkaline aqueous solution is sodium carbonate, the temperature of the ester bond hydrolysis reaction is 115℃, the pressure of the ester bond hydrolysis reaction is 1.2 MPa, the time of the ester bond hydrolysis reaction is 4 h, and the ester bond hydrolysis rate is greater than or equal to 98%;

[0094] (2) cooling to precipitate, collecting the precipitate by filtration with a filtration accuracy of 40-200 μm, and drying to obtain the recovered double-carboxyl PA6 oligomer;

[0095] (3) the recovered double-carboxyl PA6 oligomer is subjected to esterification reaction with hexanediol, the molar ratio of the hexanediol to the recovered double-carboxyl PA6 oligomer is 1.6:1, the temperature of the esterification reaction is 240℃, the pressure of the esterification reaction is 0.3 MPa, the time of the esterification reaction is 2.5 h, and the PA6 oligomer esterification product is obtained; then the PA6 oligomer esterification product, sodium 5-sulfoisophthalate diethyl ester, antimony acetate and sodium acetate are mixed and subjected to ester exchange reaction, the sodium 5-sulfoisophthalate diethyl ester, antimony acetate and sodium acetate are 5%, 250 ppm and 700 ppm of the mass of the PA6 oligomer esterification product respectively, the temperature of the ester exchange reaction is 265℃, the pressure of the ester exchange reaction is 50 Pa, and the time of the ester exchange reaction is 2.5 h, and the regenerated composite functional PA6 is prepared.

[0096] The regenerated composite functional PA6 prepared finally has a relative viscosity of 3.4, a hot water extract content of 1.2 wt%, and a melting point of 215℃, and meets the requirements of injection molding and melt spinning processing.

[0097] Example 3

[0098] A preparation method of a composite functional PA6 is provided, and the specific steps are as follows:

[0099] (1) preparing a double-carboxyl PA6 oligomer;

[0100] The caprolactam, 1,12-dodecanedioic acid, deionized water and 6-aminohexanoic acid are mixed, 60℃ is kept and mechanical stirring is performed, the rotating speed of the mechanical stirring is 240 r / min, the time of the mechanical stirring is 5 min, and the dosages of the 1,12-dodecanedioic acid, deionized water and 6-aminohexanoic acid are 14 wt%, 5 wt% and 0.2 wt% of the dosage of the caprolactam respectively, then a hydrolysis ring-opening reaction is performed, the temperature of the hydrolysis ring-opening reaction is 250℃, the pressure of the hydrolysis ring-opening reaction is 0.6 MPa, and the time of the hydrolysis ring-opening reaction is 4.5 h, and the double-carboxyl PA6 oligomer is obtained;

[0101] (2) preparing a PA6 oligomer esterification product;

[0102] The bishydroxy PA6 oligomer is mixed with pentanediol, and then esterification reaction is carried out, the molar ratio of pentanediol to bishydroxy PA6 oligomer is 1.8:1, the esterification reaction temperature is 245℃, the esterification reaction pressure is 0.05MPa, and the esterification reaction time is 2.5h, to obtain PA6 oligomer esterification product;

[0103] (3) preparing the composite functional PA6;

[0104] The PA6 oligomer esterification product, ethylene phthalate, antimony trioxide and sodium acetate are mixed, and then ester exchange reaction is carried out, the mass of ethylene phthalate, antimony trioxide and sodium acetate is 10%, 500ppm and 500ppm respectively based on the mass of PA6 oligomer esterification product, the ester exchange reaction temperature is 270℃, the ester exchange reaction pressure is 100Pa, and the ester exchange reaction time is 2.5h, to obtain the composite functional PA6.

[0105] The relative viscosity of the finally prepared composite functional PA6 is 2.4, the hot water extractable content is 0.65wt%, and the melting point is 225℃; in the structural formula of the composite functional PA6, n is 35, m is 4, and x is 3.

[0106] The recycling method of the above-mentioned composite functional PA6 comprises the following steps:

[0107] (1) The composite functional PA6 is placed in an alkaline aqueous solution to carry out ester bond hydrolysis reaction, the mass ratio of the alkaline aqueous solution to the composite functional PA6 is 11:1, the pH value of the alkaline aqueous solution is 9, the solute in the alkaline aqueous solution is sodium hydroxide, the ester bond hydrolysis reaction temperature is 135℃, the ester bond hydrolysis reaction pressure is 1.5MPa, the ester bond hydrolysis reaction time is 3.5h, and the ester bond hydrolysis rate is ≥98%;

[0108] (2) cooling to precipitate, collecting the precipitate by filtration, the filtration precision is 40-200μm, drying, and obtaining the recycled bishydroxy PA6 oligomer;

[0109] (3) The recycled bishydroxy PA6 oligomer is mixed with pentanediol to carry out esterification reaction, the molar ratio of pentanediol to recycled bishydroxy PA6 oligomer is 1.8:1, the esterification reaction temperature is 260℃, the esterification reaction pressure is 0.01MPa, and the esterification reaction time is 4h, to obtain PA6 oligomer esterification product; then the PA6 oligomer esterification product, ethylene phthalate, antimony trioxide and sodium acetate are mixed to carry out ester exchange reaction, the mass of ethylene phthalate, antimony trioxide and sodium acetate is 1%, 200ppm and 800ppm respectively based on the mass of PA6 oligomer esterification product, the ester exchange reaction temperature is 270℃, the ester exchange reaction pressure is 100Pa, and the ester exchange reaction time is 4h, to obtain the regenerated composite functional PA6.

[0110] The relative viscosity of the finally prepared regenerated composite functional PA6 is 2.4, the hot water extract content is 0.65%, and the melting point is 225 DEG C, meeting the processing requirements of injection molding and melt spinning.

[0111] Example 4

[0112] A preparation method of a composite functional PA6, and the specific steps are as follows:

[0113] (1) preparing dicarboxyl PA6 oligomer;

[0114] The caprolactam, azelaic acid, deionized water and 6-aminohexanoic acid are mixed, and the mixture is kept at 100 DEG C and mechanically stirred at a speed of 60 r / min for 10 min. The amounts of azelaic acid, deionized water and 6-aminohexanoic acid are 23 wt%, 2 wt% and 0.7 wt% of the amount of caprolactam, respectively. Then, a hydrolysis ring-opening reaction is carried out at a temperature of 225 DEG C and a pressure of 0.1 MPa for 5 h, and the dicarboxyl PA6 oligomer is obtained.

[0115] (2) preparing PA6 oligomer esterification product;

[0116] The dicarboxyl PA6 oligomer is mixed with propylene glycol, and an esterification reaction is carried out at a temperature of 225 DEG C and a pressure of 0.4 MPa for 3 h, and the molar ratio of propylene glycol to dicarboxyl PA6 oligomer is 1.3:1, and the PA6 oligomer esterification product is obtained.

[0117] (3) preparing composite functional PA6;

[0118] The PA6 oligomer esterification product, [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl] butanedioic acid dimethyl ester, antimony glycolate and sodium acetate are mixed, and an ester exchange reaction is carried out at a temperature of 255 DEG C and a pressure of 50 Pa for 3 h, and the amounts of [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl] butanedioic acid dimethyl ester, antimony glycolate and sodium acetate are 1%, 370 ppm and 200 ppm of the mass of the PA6 oligomer esterification product, respectively, and the composite functional PA6 is obtained.

[0119] The relative viscosity of the finally prepared composite functional PA6 is 2.9, the hot water extract content is 1.65 wt%, and the melting point is 250 DEG C. In the structural formula of the composite functional PA6, n is 17, m is 9, and x is 1.

[0120] The above-mentioned recycling method of the composite functional PA6, and the specific steps are as follows:

[0121] (1) the composite functional PA6 is placed in an alkaline aqueous solution for ester bond hydrolysis reaction, the mass ratio of the alkaline aqueous solution to the composite functional PA6 is 8:1, the pH value of the alkaline aqueous solution is 11, the solute in the alkaline aqueous solution is potassium hydroxide, the temperature of the ester bond hydrolysis reaction is 125℃, the pressure of the ester bond hydrolysis reaction is 1.4 MPa, the time of the ester bond hydrolysis reaction is 2 h, and the ester bond hydrolysis rate is ≥98%;

[0122] (2) cooling to precipitate, collecting the precipitate by filtration with a filtration precision of 40-200 μm, drying, and obtaining the recovered double-carboxyl PA6 oligomer;

[0123] (3) the recovered double-carboxyl PA6 oligomer is subjected to esterification reaction with propylene glycol, the molar ratio of propylene glycol to the recovered double-carboxyl PA6 oligomer is 1.3:1, the temperature of the esterification reaction is 235℃, the pressure of the esterification reaction is 0.25 MPa, the time of the esterification reaction is 2.5 h, and the PA6 oligomer esterification product is obtained; then the PA6 oligomer esterification product, [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl] butanedioic acid dimethyl ester, antimony glycolate and sodium acetate are mixed and subjected to ester exchange reaction, [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl] butanedioic acid dimethyl ester, antimony glycolate and sodium acetate are 20%, 500 ppm and 200 ppm of the mass of the PA6 oligomer esterification product respectively, the temperature of the ester exchange reaction is 255℃, the pressure of the ester exchange reaction is 50 Pa, and the time of the ester exchange reaction is 2 h, and the regenerated composite functional PA6 is prepared.

[0124] The relative viscosity of the finally prepared regenerated composite functional PA6 is 2.9, the hot water extractable content is 1.65 wt%, and the melting point is 250℃, which meets the requirements of injection molding and melt spinning processing.

[0125] Example 5

[0126] A preparation method of a composite functional PA6, the specific steps are as follows:

[0127] (1) preparing a double-carboxyl PA6 oligomer;

[0128] The lactam, 1,14-tetradecanedioic acid, deionized water and 6-aminohexanoic acid are mixed, 90℃ is kept and mechanical stirring is carried out, the rotating speed of the mechanical stirring is 100 r / min, the time of the mechanical stirring is 15 min, and the dosages of the 1,14-tetradecanedioic acid, deionized water and 6-aminohexanoic acid are 5 wt%, 4 wt% and 0.1 wt% of the dosage of the lactam respectively, then a hydrolysis ring-opening reaction is carried out, the temperature of the hydrolysis ring-opening reaction is 260℃, the pressure of the hydrolysis ring-opening reaction is 2.4 MPa, and the time of the hydrolysis ring-opening reaction is 4 h, and the double-carboxyl PA6 oligomer is obtained;

[0129] (2) preparing PA6 oligomer esterification product;

[0130] The dicarboxyl PA6 oligomer is mixed with butanediol, and then esterification reaction is carried out, the molar ratio of butanediol to dicarboxyl PA6 oligomer is 1.4:1, the temperature of esterification reaction is 260℃, the pressure of esterification reaction is 0.01MPa, and the time of esterification reaction is 2h, so as to obtain the PA6 oligomer esterification product;

[0131] (3) preparing composite functional PA6;

[0132] The PA6 oligomer esterification product, 2-carboxyethyl phenyl phosphinic acid diethyl ester, titanium glycol and sodium acetate are mixed, and then ester exchange reaction is carried out, the mass of 2-carboxyethyl phenyl phosphinic acid diethyl ester, titanium glycol and sodium acetate is 5%, 250ppm and 300ppm respectively based on the mass of PA6 oligomer esterification product, the temperature of ester exchange reaction is 280℃, the pressure of ester exchange reaction is 100Pa, and the time of ester exchange reaction is 2h, so as to obtain the composite functional PA6.

[0133] The relative viscosity of the finally prepared composite functional PA6 is 3.1, the hot water extractable content is 2wt%, and the melting point is 240℃; in the structural formula of the composite functional PA6, n is 70, m is 4, and x is 2.

[0134] The recycling method of the above-mentioned composite functional PA6 comprises the following specific steps:

[0135] (1) The composite functional PA6 is placed in an alkaline aqueous solution to carry out ester bond hydrolysis reaction, the mass ratio of the alkaline aqueous solution to the composite functional PA6 is 5:1, the pH value of the alkaline aqueous solution is 9, the solute in the alkaline aqueous solution is sodium hydroxide, the temperature of ester bond hydrolysis reaction is 140℃, the pressure of ester bond hydrolysis reaction is 1.7MPa, the time of ester bond hydrolysis reaction is 2.5h, and the ester bond hydrolysis rate is ≥98%;

[0136] (2) cooling to precipitate, filtering to collect the precipitate, the filtering precision is 40-200μm, drying, and obtaining the recycled dicarboxyl PA6 oligomer;

[0137] (3) the recovered double carboxyl PA6 oligomer is esterified with butanediol, the molar ratio of butanediol to the recovered double carboxyl PA6 oligomer is 1.4:1, the esterification temperature is 255℃, the esterification pressure is 0.1MPa, the esterification time is 3h, and the PA6 oligomer esterification product is obtained; then the PA6 oligomer esterification product, 2-carboxyethyl phenyl phosphinic acid diethyl ester, titanium glycolate and sodium acetate are mixed and subjected to ester exchange reaction, the 2-carboxyethyl phenyl phosphinic acid diethyl ester, titanium glycolate and sodium acetate are 9%, 300ppm and 450% of the mass of the PA6 oligomer esterification product respectively, the ester exchange temperature is 280℃, the ester exchange pressure is 100Pa, and the ester exchange time is 3.5h, and the regenerated composite functional PA6 is prepared.

[0138] The relative viscosity of the finally prepared regenerated composite functional PA6 is 3.1, the hot water extract content is 2wt%, and the melting point is 240℃, which meets the requirements of injection molding and melt spinning processing.

Claims

1. A recycling method of composite functional PA6, characterized in that, The method comprises the following steps: (1) placing the composite functional PA6 in a neutral or alkaline aqueous solution to perform an ester bond hydrolysis reaction; the structure of the composite functional PA6 is as follows: ； wherein n, m and x are positive integers; -OC-R1-CO- is a diacid segment; -O-R2-O- is a diol segment; -OA-R3-BO- is a diacid segment, wherein A and B are carbon atoms, or phosphorus atoms, or carbon atoms and phosphorus atoms, respectively; The pH value of the alkaline aqueous solution is 8-11, the solute in the alkaline aqueous solution is sodium hydroxide, potassium hydroxide, sodium bicarbonate or sodium carbonate, the temperature of the ester bond hydrolysis reaction is 100-140 DEG C, the pressure of the ester bond hydrolysis reaction is 1.0-1.7 MPa, and the time of the ester bond hydrolysis reaction is 2-4 h; (2) cooling to precipitate a precipitate, collecting the precipitate, and obtaining recovered double-carboxyl PA6 oligomers, wherein the structure of the recovered double-carboxyl PA6 oligomers is as follows: ； (3) performing an esterification reaction of the recovered double-carboxyl PA6 oligomers with a diol to obtain PA6 oligomer esterification products, and performing a transesterification reaction of the PA6 oligomer esterification products with a functional component, thereby obtaining regenerated composite functional PA6; wherein the structure of the diol is as follows: ， The structure of the functional component is as follows: 。 2. The recycling method of a composite functional PA6 according to claim 1, characterized in that, In step (1), the weight ratio of the neutral or alkaline aqueous solution to the composite functional PA6 is 5:1-20:

1.

3. The recycling method of a composite functional PA6 according to claim 1, characterized in that, In step (3), the temperature of the esterification reaction is 220-260 DEG C, the pressure of the esterification reaction is 0.01-0.5 MPa, and the molar ratio of the diol to the recovered double-carboxyl PA6 oligomers is 1.3-1.8:1; A catalyst A and an ether inhibitor are further added during the transesterification reaction; the temperature of the transesterification reaction is 250-280 DEG C, the pressure of the transesterification reaction is 100 Pa or less, the functional component, the catalyst A and the ether inhibitor are 1-20% of the mass of the PA6 oligomer esterification products, 200-500 ppm and 200-800 ppm, respectively; The regenerated composite functional PA6 has a relative viscosity of 2.4-4.0, a hot water extract content of 0.05-2 wt%, and a melting point of 190-250 DEG C.

4. The recycling method of a composite functional PA6 according to claim 1, characterized in that, 8≤n≤70, 4≤m≤20, 1≤x≤5; the diacid corresponding to the -OC-R1-CO- diacid segment is a linear aliphatic diacid with a carbon chain length of not more than 16, the diol corresponding to the -O-R2-O- diol segment is a linear diol with a carbon chain length of not more than 6, and the diacid corresponding to the -OA-R3-BO- diacid segment is phthalic acid, sulfonic acid-based phthalic acid, 2-carboxyethyl phenyl phosphinic acid or DDP.

5. The recycling method of a composite functional PA6 according to claim 1 or 4, characterized in that, The composite functional PA6 has a relative viscosity of 2.4-4.0, a hot water extract content of 0.05-2 wt%, and a melting point of 190-250 DEG C.

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