Biodegradable pa6 and preparation method and application thereof

Abstract

The application relates to a biodegradable PA6 and a preparation method and application thereof, the structural formula of the biodegradable PA6 is as follows: in the formula, x, y and z are positive integers, the value range of x is 2-10, the value range of y is 2-6, the value range of z is 10-60, -OC-R1-CO- is a binary acid chain segment, and -O-R2-O- is a binary alcohol chain segment; when being prepared, PA6 prepolymer is subjected to esterification reaction with a binary alcohol to obtain PA6 prepolymer esterification product, then the PA6 prepolymer esterification product is subjected to ester exchange reaction with a carbonic acid diester, and the biodegradable PA6 is obtained; and the biodegradable PA6 is used for spinning to prepare a biodegradable PA6 fiber. The biodegradable PA6 of the application has the advantages of significantly improved degradation efficiency and degradation speed while keeping excellent physical and chemical properties and application performance of PA6, simple preparation process, high production efficiency, wide application prospect and the capability of meeting the requirements of melt processing of injection molding and spinning.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer fiber preparation, and relates to a biodegradable PA6 and a preparation method and application thereof. BACKGROUND

[0002] PA6 (polyamide 6) products have excellent performance, such as PA6 fibers having high breaking strength, good wear resistance, good moisture absorption, good dyeing property, excellent elastic recovery rate and fatigue resistance, and the like, and can be applied to the preparation of tire cord, automotive textiles and filter materials, and the like, and have a wide range of applications. With the continuous development of the PA6 industry in China, the annual output of PA6 exceeds 6 million tons, which also brings environmental pollution problems, and therefore, the biodegradability of PA6 has attracted more and more attention.

[0003] Biodegradable polymer material refers to a polymer that can be completely degraded by organisms such as bacteria, fungi or algae in nature. The biodegradation of a polymer is a very complex process, mainly depending on the size and structure of the polymer molecules, the types of microorganisms and enzymes, and the like. Since there is no specific biodegradable enzyme for PA6 in nature, it is difficult to achieve direct biodegradation. At present, researchers mainly introduce biodegradable chemical bonds into the molecular chain of PA6 to achieve its biodegradability, such as preparing PA6 copolymer.

[0004] Although the prior art has been able to introduce biodegradable chemical bonds through copolymerization method, the chain segment regularity of the prepared copolymer is poor, and part of the molecular chain segment cannot be crystallized, resulting in a low melting point or no fixed melting point of the copolymer, which will affect the application range and processing difficulty of the copolymer, and cannot meet the requirements of melt spinning.

[0005] For example, patent application CN109749079B discloses a biobased degradable polyamide 6 copolymer and a preparation method thereof, and biodegradable PA6 is prepared by copolymerizing biobased dihydric alcohol and biobased polyester segment into PA6, and the biobased segment and biobased dihydric alcohol can realize biodegradation combined with polyester biodepolymerase. Patent application CN114644754B discloses a biodegradable thermoplastic polyamide elastomer and a preparation method thereof, and the preparation of biodegradable polyamide elastomer is realized by copolymerizing biodegradable long-chain polyester segment and modified PA6 segment. However, the biodegradable chemical bonds introduced by the above-mentioned existing copolymerization method are mainly concentrated on ester bonds, although the ester bonds have a certain biodegradation capacity, but the degradation efficiency and degradation speed still need to be improved.

[0006] Therefore, it is of great significance to study a biodegradable PA6 and a preparation method and application thereof, so that it can not only maintain the excellent physical and application performance of PA6, but also significantly improve the degradation efficiency and degradation speed. SUMMARY

[0007] The present application aims to solve the problems in the prior art, and provides a biodegradable PA6, a preparation method and application thereof.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0009] A biodegradable PA6, the structural formula is as follows:

[0010]

[0011] In the formula, x, y, z are all positive integers, -OC-R1-CO- is a diacid segment, and -O-R2-O- is a diol segment.

[0012] As a preferred technical scheme:

[0013] The biodegradable PA6 as described above, the value range of x is 2-10, the value range of y is 2-6, and the value range of z is 10-60; the diacid corresponding to the diacid segment is one or more of terephthalic acid, phthalic acid and HOOC(CH2)nCOOH, and the value range of n is 2-10; the diol corresponding to the diol segment is ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol or sunflower glycol, etc. The carbon chain length of the diol is less than or equal to 10.

[0014] The biodegradable PA6 as described above, the relative viscosity of the biodegradable PA6 is 2.4-4.0, the hot water extract content is 0.05-2wt%, the melting point is 190-250℃, and the number average molecular weight is 14000-33000g / mol.

[0015] The present application also provides a method for preparing the biodegradable PA6 as described in any one of the above, wherein the PA6 prepolymer ester is subjected to an ester exchange reaction with a carbonic acid diester to obtain the biodegradable PA6.

[0016] The structural formula of the PA6 prepolymer ester is as follows:

[0017]

[0018] As a preferred technical scheme:

[0019] The method as described above, the PA6 prepolymer ester is obtained by esterification reaction of the PA6 prepolymer and the diol;

[0020] The structural formula of the PA6 prepolymer is as follows:

[0021]

[0022] The dihydric alcohol has the following structural formula:

[0023] HO-R2-OH;

[0024] In the esterification reaction, the molar ratio of the hydroxyl functional group of the dihydric alcohol to the carboxyl functional group of the PA6 prepolymer is 1.3-1.8:1.

[0025] The carbonic acid diester is one or more of dimethyl carbonate, diethyl carbonate, diphenyl carbonate and ethylene carbonate.

[0026] The ratio of the molar addition amount of the carbonic acid diester in the transesterification reaction to the molar addition amount of the dihydric alcohol in the esterification reaction is 0.9-1.1:1.

[0027] In the method, the temperature of the esterification reaction is 220-260℃, the pressure is 0.01-0.5MPa, and the termination condition is that the water output of the esterification reaction reaches 95-98% of the theoretical water output.

[0028] The temperature of the transesterification reaction is 250-280℃, the pressure is 100Pa or less, and the time is 2-4h.

[0029] In the method, the preparation step of the PA6 prepolymer is as follows:

[0030] (a) mixing caprolactam, diacid, deionized water and catalyst under mechanical stirring to obtain a mixture;

[0031] The diacid has the following structural formula:

[0032]

[0033] The rotation speed of the mechanical stirring is 60-240r / min, the mechanical stirring time is 10-60min, the mixing temperature is 60-100℃, and the addition amounts of the diacid, deionized water and catalyst are 5-30wt%, 2-5wt% and 0.1-1wt% of the addition amount of caprolactam, respectively.

[0034] (b) sequentially performing hydrolysis ring-opening reaction and prepolymerization reaction on the mixture to obtain the PA6 prepolymer;

[0035] The atmosphere of the hydrolysis ring-opening reaction and the prepolymerization reaction is nitrogen or inert gas; the temperature of the hydrolysis ring-opening reaction is 230-250℃, the pressure is 0.1-0.6MPa, and the time is 2-4h; the temperature of the prepolymerization reaction is 240-290℃, the pressure is 0.1-3MPa, and the time is 2-4h.

[0036] In the method, an ester exchange catalyst and an ether inhibitor are also added during the transesterification reaction. ​

[0037] The transesterification catalyst is a titanium-based catalyst and / or an antimony-based catalyst, the titanium-based catalyst is tetrabutyl titanate and / or titanium glycolate, the antimony-based catalyst is one or more of antimony trioxide, antimony acetate and antimony glycolate, and the ether preventing agent is an acetate, specifically sodium acetate and / or potassium acetate;

[0038] The mass addition amount of the transesterification catalyst and the ether preventing agent is 10-500 ppm and 300-500 ppm, respectively, of the mass addition amount of caprolactam in step (a).

[0039] The application also provides the use of the biodegradable PA6 as described in any one of the above in the preparation of biodegradable PA6 fibers by spinning.

[0040] As a preferred technical solution,

[0041] The use as described above, the biodegradable PA6 is dried in a vacuum oven before spinning, the drying temperature is 100-120℃, and the drying time is 5-8h; the spinning adopts melt spinning technology, and the spinning process parameters include: melt temperature 220-260℃, spinning temperature 240-280℃, first godet speed 4000-4500m / min, second godet speed 5000-6000m / min, draw ratio 1.1-1.5 times, cooling air temperature 15-25℃, cooling air speed 0.5-1m / s, and cooling air relative humidity 60%-90%.

[0042] The use as described above, the biodegradable PA6 fiber has a breaking strength of 2.5-3.5cN / dtex, an elongation at break of 30-70%, a carbonate bond breaking rate of 90-95% after being soaked in a lipase aqueous solution, a degradation rate of 70-85% after 6 months of composting experiment, and all the carbonate bonds and ester bonds in the amorphous region are broken after 6 months of composting experiment, the product is small molecule PA6, which can be further mineralized in the soil environment; all the molecules with a molecular weight of not more than 10000 are considered to be small molecules; the structural formula of the small molecule PA6 is as follows:

[0043]

[0044] Invention mechanism:

[0045] At present, the biodegradable PA6 in the prior art is realized by block polymerization (containing copolymerized biodegradable monomers and polyester segments), the randomness of copolymerization is large, and the crystallinity after copolymerization decreases rapidly, and even the melting point is lost.

[0046] The polymerization method of the application is to design the PA6 prepolymer segment into the ester bond end group form of polyester prepolymer, and then to carry out polycondensation by the ester exchange chain growth way of polyester, so as to copolymerize the polyester and the PA6 segment in the macromolecule, and improve the compatibility of the two kinds of high molecular materials.

[0047] The basic physical and chemical properties are regulated by the preparation of the PA6 prepolymer, and the esterification modification ensures that the ester bond and the carbonate bond reaction site are located at the end of the PA6 chain. After the ester bond end group modification of the PA6 prepolymer and the polycondensation (ester exchange reaction) of the carbonate diester, the embedded ester bond and carbonate bond structure design is realized. Due to the difference in bond length and bond angle of chemical bonds, the ester bond and the carbonate bond are exposed in the amorphous region, which further increases the binding ability with water molecules. The biological enzyme transports and directs the depolymerization of the ester bond and the carbonate bond through the water molecules, and the biodegradable PA6 is depolymerized into PA6 segments. The small molecule PA6 is then mineralized and absorbed by the environment. The biodegradability of the ester bond and the carbonate bond can be regulated by the selection of R1 and R2, so that the biodegradation rate can be regulated.

[0048] Advantages:

[0049] (1) The preparation method of the biodegradable PA6 of the application can be prepared by using traditional polyester and PA6 synthesis equipment, and has the advantages of simple process, high production efficiency, embedded ester bond and carbonate bond, no lattice protection, and easy attack by water molecules to realize biodegradation.

[0050] (2) The preparation method of the biodegradable PA6 of the application has controllable PA6 prepolymer molecular weight in the preparation process, and the basic physical and chemical properties of the biodegradable PA6 can be regulated according to the application requirements, and the biodegradability of the ester bond and the carbonate bond can be regulated according to the copolymerization monomer.

[0051] (3) The biodegradable PA6 of the application has the advantages of significantly improved degradation efficiency and degradation speed, can meet the requirements of melt processing of injection molding and spinning, has extremely high application prospect, and can meet the requirements of melt processing of injection molding and spinning. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 The synthesis path diagram of the biodegradable PA6 of the application is shown in the figure.

[0053] Figure 2 The degradation principle schematic diagram of the biodegradable PA6 of the application is shown in the figure. DETAILED DESCRIPTION

[0054] The application will be further described below with reference to the specific embodiments. It should be understood that these embodiments are only used to illustrate the application and not used 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.

[0055] The performance indicators in the examples and comparative examples of the application involve the following test methods:

[0056] (1) Relative viscosity: according to the test method of China Textile Industry Standard FZ / T 51004-2011, the sample is dissolved in concentrated sulfuric acid with a concentration of 96wt% to prepare a 0.01g / ml test solution, and a Ubbelohde viscometer (capillary diameter of 1.03mm) is used to test in a constant temperature water bath with water temperature of 25±0.1℃, and the average value of 5 parallel tests is taken.

[0057] (2) Hot water extractable content: according to the test method of China Textile Industry Standard FZ / T 51004-2011, the sample is placed in a vacuum oven at 105℃ and dried for 24h to constant weight, then a certain mass (m0) of the sample is taken, deionized water is added with a bath ratio of 20:1, and the sample is extracted in boiling water (water bath temperature≥98℃) using a Soxhlet extractor for 8h, then the sample is taken out and placed in a vacuum oven at 105℃ and dried for 24h, then weighed and recorded as mass (m1), the hot water extractable content is shown in the following formula:

[0058] E=(m0-m1) / m0;

[0059] In the formula, E is the hot water extractable content, unit: wt%; m0 and m1 are the sample masses before and after extraction, unit: g.

[0060] (3) Number average molecular weight: the number average molecular weight of the sample is tested by GPC-50 type gel permeation chromatograph of British PL company, which is equipped with a differential refractive detector and a PL gel column (5μm mixed-C), 1,1,1,3,3,3-hexafluoro-2-propanol is used as the eluent with a flow rate of 1mL / min; when the sample is dried and dissolved in hexafluoroisopropanol to prepare a 1.0mg / mL solution, the test is carried out when the column temperature reaches 40±1℃.

[0061] (4)Breaking strength, breaking elongation: the fiber sample is placed in a constant temperature and humidity chamber at 20℃ and 65% relative humidity for 48h according to GB / T 14343-2008; the tensile property of the fiber sample is tested by using A0-3000cN multifilament strength tester; the tensile speed is 200mm / min, the pre-tension is 5cN, the test distance is 200±0.5mm, each sample is tested for 10 times, and the average value is taken.

[0062] (5)Breaking rate of carbonate bond: the molecular structure of the sample is tested by using AVANCE-600 nuclear magnetic resonance spectrometer: 5-10mg of dried sample is weighed before testing, deuterium sulfate (D2SO4) is used as the testing solvent, the testing temperature is 25℃, and the frequency is 600MHz; the integral areas of the characteristic peaks of the ester bond before and after hydrolysis are tested, (1- the characteristic peak area of the carbonate bond after enzymolysis) / the characteristic peak area of the carbonate bond after enzymolysis = the breaking rate of the carbonate bond, the enzymolysis temperature is 40℃, the concentration of the lipase aqueous solution is 0.8mg / ml, the mass ratio of the biodegradable PA6 fiber to the lipase aqueous solution is 1:100, and the enzymolysis time is 6 months.

[0063] (6)Degradation rate after 6 months of composting experiment: GB / T 19277.1-2011 is referred to.

[0064] (7)Polymer molecular structure characterization method

[0065] The molecular structure of the sample is tested by using AVANCE-600 nuclear magnetic resonance spectrometer: 5-10mg of dried sample is weighed before testing, deuterium sulfate (D2SO4) is used as the testing solvent, the testing temperature is 25℃, and the frequency is 600MHz;

[0066] FTIR spectrum analysis is performed by using Nicolet 6700 Fourier transform infrared spectrometer: the sample is made into a potassium bromide sheet before testing, ATR accessory is used for total reflection testing, and the testing scanning range is 4000-600cm -1 ;

[0067] Tests show that the structural formula of the biodegradable PA6 in each of the following embodiments is as follows:

[0068]

[0069] In the formula, x, y, and z are positive integers, -OC-R1-CO- is a dibasic acid segment, and -O-R2-O- is a dibasic alcohol segment.

[0070] Example 1

[0071] A preparation method of a biodegradable PA6, and the specific steps are as follows:

[0072] (1) Preparation of PA6 prepolymer;

[0073] (a) mixing caprolactam, adipic acid, deionized water and 6-aminohexanoic acid under mechanical stirring to obtain a mixture;

[0074] wherein the rotating speed of mechanical stirring is 60 r / min, the time of mechanical stirring is 60 min, the temperature of mixing is 60℃, and the adding amount of adipic acid, deionized water and 6-aminohexanoic acid is 30wt%, 2wt% and 1wt% of the adding amount of caprolactam respectively;

[0075] (b) sequentially performing hydrolysis ring-opening reaction and prepolymerization reaction on the mixture under nitrogen atmosphere to obtain PA6 prepolymer;

[0076] wherein the temperature of hydrolysis ring-opening reaction is 230℃, the pressure is 0.1 MPa, and the time is 4h; the temperature of prepolymerization reaction is 290℃, the pressure is 3 MPa, and the time is 2h;

[0077] The structural formula of the prepared PA6 prepolymer is as follows:

[0078] In the formula, z = 10;

[0079] (2) adding ethylene glycol to the system after step (1) reaction, and performing esterification reaction under the conditions of 220℃ of temperature and 0.5 MPa of pressure to obtain PA6 prepolymer esterification product, and the termination condition is that the water amount of esterification reaction reaches 98% of the theoretical water amount; the structural formula of PA6 prepolymer esterification product is as follows:

[0080]

[0081] wherein the molar ratio of the hydroxyl functional group of ethylene glycol to the carboxyl functional group of PA6 prepolymer in the esterification reaction process is 1.5:1;

[0082] (3) adding tetrabutyl titanate, sodium acetate and dimethyl carbonate to the system after step (2) reaction, and performing ester exchange reaction under the conditions of 250℃ of temperature and 50 Pa of pressure for 3h to obtain biodegradable PA6, and the structural formula is as follows:

[0083]

[0084] In the formula, x = 10, and y = 6;

[0085] wherein the mass adding amount of tetrabutyl titanate and sodium acetate is 10ppm and 300ppm of the mass adding amount of caprolactam in step (a) respectively; and the molar adding amount ratio of dimethyl carbonate in the ester exchange reaction process to the molar adding amount of ethylene glycol in the esterification reaction process is 0.9:1.

[0086] The prepared biodegradable PA6 has a relative viscosity of 3.1, a hot water extract content of 0.05wt%, a melting point of 190℃, and a number average molecular weight of 14000g / mol.

[0087] Example 2

[0088] A preparation method of biodegradable PA6, the specific steps are as follows:

[0089] (1) Preparation of PA6 prepolymer;

[0090] (a) mixing caprolactam, suberic acid, deionized water and 6-aminocaproic acid under mechanical stirring to obtain a mixture;

[0091] Wherein, the rotating speed of mechanical stirring is 120r / min, the mechanical stirring time is 35min, the mixing temperature is 80℃, and the adding amount of suberic acid, deionized water and 6-aminocaproic acid is 16wt%, 3wt% and 0.5wt% of the adding amount of caprolactam respectively;

[0092] (b) under the nitrogen atmosphere, the mixture is sequentially subjected to hydrolysis ring-opening reaction and prepolymerization reaction, and the PA6 prepolymer is obtained;

[0093] Wherein, the temperature of hydrolysis ring-opening reaction is 240℃, the pressure is 0.5MPa, and the time is 3h; the temperature of prepolymerization reaction is 260℃, the pressure is 1.5MPa, and the time is 3h;

[0094] The structural formula of the prepared PA6 prepolymer is as follows:

[0095] In the formula, z=37;

[0096] (2) After adding hexanediol to the system after step (1) reaction, esterification reaction is carried out at a temperature of 240℃ and a pressure of 0.3MPa to obtain PA6 prepolymer esterification product, and the termination condition is that the water amount of esterification reaction reaches 98% of the theoretical water amount; the structural formula of PA6 prepolymer esterification product is as follows:

[0097]

[0098] Wherein, during the esterification reaction, the molar ratio of the hydroxyl functional group of hexanediol to the carboxyl functional group of PA6 prepolymer is 1.4:1;

[0099] (3) After adding antimony trioxide, potassium acetate and diethyl carbonate to the system after step (2) reaction, transesterification reaction is carried out at a temperature of 265℃ and a pressure of 30Pa for 2.5h, and the biodegradable PA6 is obtained, and the structural formula is as follows:

[0100] wherein x = 5, y = 3;

[0101] wherein the mass addition amount of the antimony trioxide and the potassium acetate is 400 ppm and 350 ppm of the mass addition amount of the caprolactam in step (a) respectively; the ratio of the molar addition amount of the diethyl carbonate in the transesterification reaction to the molar addition amount of the hexanediol in the esterification reaction is 1:1.

[0102] The relative viscosity of the finally prepared biodegradable PA6 is 2.7, the hot water extract content is 1.5 wt%, the melting point is 220℃, and the number average molecular weight is 22000 g / mol.

[0103] Example 3

[0104] A preparation method of a biodegradable PA6, the specific steps are as follows:

[0105] (1) Preparation of PA6 prepolymer;

[0106] (a) mixing caprolactam, pimelic acid, deionized water and 6-aminohexanoic acid under mechanical stirring to obtain a mixture;

[0107] wherein the rotation speed of the mechanical stirring is 240 r / min, the mechanical stirring time is 10 min, the mixing temperature is 100℃, and the addition amounts of the pimelic acid, the deionized water and the 6-aminohexanoic acid are 13 wt%, 5 wt% and 0.1 wt% of the addition amount of the caprolactam respectively;

[0108] (b) sequentially performing hydrolysis ring-opening reaction and prepolymerization reaction on the mixture under a nitrogen atmosphere to obtain the PA6 prepolymer;

[0109] wherein the hydrolysis ring-opening reaction temperature is 250℃, the pressure is 0.6 MPa, and the time is 2 h; the prepolymerization reaction temperature is 240℃, the pressure is 0.1 MPa, and the time is 4 h;

[0110] The structural formula of the prepared PA6 prepolymer is as follows:

[0111] wherein z = 35;

[0112] (2) adding pentanediol to the system after step (1) reaction, and performing esterification reaction under the conditions of a temperature of 260℃ and a pressure of 0.01 MPa to obtain a PA6 prepolymer esterification product, and the termination condition is that the water amount of the esterification reaction reaches 96% of the theoretical water amount; the structural formula of the PA6 prepolymer esterification product is as follows:

[0113]

[0114] In the esterification process, the molar ratio of the hydroxyl functional group of pentanediol to the carboxyl functional group of PA6 prepolymer is 1.8:1.

[0115] (3) adding titanium glycol, sodium acetate and diphenyl carbonate to the system after step (2) reaction, and performing ester exchange reaction at a temperature of 270℃ and a pressure of 80Pa for 4h to obtain the biodegradable PA6, and the structural formula is as follows:

[0116]

[0117] In the formula, x=8, y=5;

[0118] In the formula, x=8, y=5;

[0119] The relative viscosity of the finally prepared biodegradable PA6 is 4, the hot water extract content is 2wt%, the melting point is 235℃, and the number average molecular weight is 33000g / mol.

[0120] Example 4

[0121] A method for preparing a biodegradable PA6, and the specific steps are as follows:

[0122] (1) Preparation of PA6 prepolymer;

[0123] (a) mixing caprolactam, phthalic acid, deionized water and 6-aminohexanoic acid under mechanical stirring to obtain a mixture; wherein the stirring speed is 90r / min, the stirring time is 50min, the mixing temperature is 70℃, and the addition amounts of phthalic acid, deionized water and 6-aminohexanoic acid are 24wt%, 4wt% and 0.3wt% of the addition amount of caprolactam, respectively;

[0124] (b) under a nitrogen atmosphere, sequentially performing hydrolysis ring-opening reaction and prepolymerization reaction on the mixture to obtain the PA6 prepolymer;

[0125] In the formula, x=8, y=5;

[0126] The structural formula of the prepared PA6 prepolymer is as follows:

[0127]

[0128] (2) adding propylene glycol to the system after step (1) reaction, and performing esterification reaction under the conditions of a temperature of 235℃ and a pressure of 0.25 MPa to obtain PA6 prepolymer esterification product, and the termination condition is that the water amount of the esterification reaction reaches 98% of the theoretical water amount;

[0129] The structural formula of the PA6 prepolymer esterification product is as follows:

[0130] In the formula, z = 49;

[0131] In the esterification reaction, the molar ratio of the hydroxyl functional group of propylene glycol to the carboxyl functional group of the PA6 prepolymer is 1.3:1;

[0132] (3) adding a mixture of antimony acetate and ethylene glycol antimony with a mass ratio of 1:1, potassium acetate, and ethylene carbonate to the system after step (2) reaction, and performing ester exchange reaction under the conditions of a temperature of 255℃ and a pressure of 100 Pa for 2 h to obtain biodegradable PA6, and the structural formula is as follows:

[0133] In the formula, x = 4 and y = 2;

[0134] In the ester exchange reaction, the mass addition amount of the mixture of antimony acetate and ethylene glycol antimony with a mass ratio of 1:1 is 500 ppm of the mass addition amount of caprolactam in step (a); the mass addition amount of potassium acetate is 500 ppm of the mass addition amount of caprolactam in step (a); and the molar addition amount of ethylene carbonate in the ester exchange reaction to the molar addition amount of propylene glycol in the esterification reaction is 1.05:1.

[0135] The biodegradable PA6 finally prepared has a relative viscosity of 2.4, a hot water extract content of 0.6 wt%, a melting point of 205℃, and a number average molecular weight of 23000 g / mol.

[0136] Example 5

[0137] A method for preparing biodegradable PA6, and the specific steps are as follows:

[0138] (1) preparation of PA6 prepolymer;

[0139] (a) mixing caprolactam, terephthalic acid, deionized water, and 6-aminohexanoic acid under mechanical stirring to obtain a mixture; wherein the stirring speed is 180 r / min, the stirring time is 20 min, the mixing temperature is 90℃, and the addition amounts of terephthalic acid, deionized water, and 6-aminohexanoic acid are 5 wt%, 3 wt%, and 0.7 wt% of the addition amount of caprolactam, respectively;

[0140] (b) under helium atmosphere, the mixture is subjected to hydrolytic ring-opening reaction and prepolymerization reaction in sequence, to obtain PA6 prepolymer;

[0141] wherein the hydrolytic ring-opening reaction is carried out at a temperature of 245℃, a pressure of 0.5 MPa and for a time of 2.5 h; and the prepolymerization reaction is carried out at a temperature of 270℃, a pressure of 2.6 MPa and for a time of 2.5 h;

[0142] The structural formula of the prepared PA6 prepolymer is as follows:

[0143] wherein z = 60;

[0144] (2) After the reaction in step (1), butanediol is added to the system, and esterification reaction is carried out at a temperature of 255℃ and a pressure of 0.1 MPa to obtain PA6 prepolymer esterification product, and the termination condition is that the water amount of the esterification reaction reaches 95% of the theoretical water amount; the structural formula of the PA6 prepolymer esterification product is as follows:

[0145]

[0146] wherein the molar ratio of the hydroxyl functional group of butanediol to the carboxyl functional group of the PA6 prepolymer during the esterification reaction is 1.6:1;

[0147] (3) After the reaction in step (2), a mixture of titanium glycol and antimony glycol with a mass ratio of 1:1, a mixture of sodium acetate and potassium acetate with a mass ratio of 1:1, and a mixture of dimethyl carbonate and diethyl carbonate with a mass ratio of 1:1 are added to the system, and transesterification reaction is carried out at a temperature of 280℃ and a pressure of 20 Pa for 3.5 h, to obtain biodegradable PA6, and the structural formula is as follows:

[0148] wherein x = 2 and y = 2;

[0149] wherein the mass addition amount of the mixture of titanium glycol and antimony glycol with a mass ratio of 1:1 is 250 ppm of the mass addition amount of caprolactam in step (a), the mass addition amount of the mixture of sodium acetate and potassium acetate with a mass ratio of 1:1 is 400 ppm of the mass addition amount of caprolactam in step (a); and the molar addition amount of the mixture of dimethyl carbonate and diethyl carbonate with a mass ratio of 1:1 during the transesterification reaction to the molar addition amount of butanediol during the esterification reaction is 1.1:1.

[0150] The relative viscosity of the finally prepared biodegradable PA6 is 3.5, the hot water extract content is 1.2 wt%, the melting point is 250℃, and the number average molecular weight is 15000 g / mol.

[0151] Example 6

[0152] The specific process of applying a biodegradable PA6 is as follows:

[0153] The biodegradable PA6 obtained in Example 1 was dried in a vacuum oven at 100°C for 8 hours, and then biodegradable PA6 fibers were prepared by melt spinning technology.

[0154] The spinning process parameters include: melt temperature 220℃, spinning temperature 250℃, first guide disc speed 4000m / min, second guide disc speed 6000m / min, drawing ratio 1.5 times, cooling air temperature 15℃, cooling air velocity 1m / s, and cooling air relative humidity 90%.

[0155] The final biodegradable PA6 fiber had a tensile strength of 3.5 cN / dtex and an elongation at break of 30%. Figure 2 As shown, after soaking in an aqueous solution of lipase (Novozymes CALB), the carbonate bond breakage rate was 90%, and the degradation rate after 6 months of composting was 70%. After 6 months of composting, all carbonate and ester bonds in the amorphous region were broken, and the biodegradable PA6 depolymerized into small molecule PA6 segments, which can be further mineralized in the natural soil environment. The structural formula of the small molecule PA6 is as follows:

[0156]

[0157] In the formula, z = 10.

[0158] Example 7

[0159] The specific process of applying a biodegradable PA6 is as follows:

[0160] The biodegradable PA6 obtained in Example 2 was dried in a vacuum oven at 110°C for 6.5 h, and then biodegradable PA6 fibers were prepared by melt spinning technology.

[0161] The spinning process parameters include: melt temperature 230℃, spinning temperature 260℃, first guide disc speed 4200m / min, second guide disc speed 5100m / min, drawing ratio 1.2 times, cooling air temperature 25℃, cooling air velocity 0.5m / s, and cooling air relative humidity 60%.

[0162] The resulting biodegradable PA6 fiber had a tensile strength of 2.7 cN / dtex and an elongation at break of 58%. After soaking in a Novozymes TLIM aqueous solution, the carbonate bond breakage rate was 95%. The degradation rate after 6 months of composting was 82%. After 6 months of composting, all carbonate and ester bonds in the amorphous region were broken, resulting in small-molecule PA6. The structural formula of small-molecule PA6 is as follows:

[0163]

[0164] wherein z = 37.

[0165] Example 8

[0166] An application of the biodegradable PA6 is as follows:

[0167] The biodegradable PA6 prepared in Example 3 was dried in a vacuum oven at 120°C for 5h, and then a biodegradable PA6 fiber was prepared by using a melt spinning technique.

[0168] The spinning process parameters included: a melting temperature of 240°C, a spinning temperature of 270°C, a first godet speed of 4500m / min, a second godet speed of 5000m / min, a draw ratio of 1.1 times, a cooling air temperature of 25°C, a cooling air speed of 0.5m / s, and a cooling air relative humidity of 65%.

[0169] The biodegradable PA6 fiber finally prepared had a breaking strength of 2.5cN / dtex, an elongation at break of 70%, a carbonate bond breaking rate of 93% after immersion in a lipase (Novozymes Palatase) aqueous solution, a degradation rate of 79% after a composting experiment for 6 months, and all the carbonate bonds and ester bonds in the amorphous region were broken after the composting experiment for 6 months, and the product was a small molecule PA6 having the following structural formula:

[0170]

[0171] wherein z = 35.

[0172] Example 9

[0173] An application of the biodegradable PA6 is as follows:

[0174] The biodegradable PA6 prepared in Example 4 was dried in a vacuum oven at 105°C for 6h, and then a biodegradable PA6 fiber was prepared by using a melt spinning technique.

[0175] The spinning process parameters included: a melting temperature of 250°C, a spinning temperature of 280°C, a first godet speed of 4300m / min, a second godet speed of 6000m / min, a draw ratio of 1.4 times, a cooling air temperature of 15°C, a cooling air speed of 1m / s, and a cooling air relative humidity of 80%.

[0176] The final biodegradable PA6 fiber has a breaking strength of 3.3 cN / dtex, an elongation at break of 36%, a carbonate bond breaking rate of 90% after immersion in a lipase (Novozymes NovoCor ADL) aqueous solution, a degradation rate of 74% after 6 months of composting experiment, and all the carbonate bonds and ester bonds in the amorphous region are broken after 6 months of composting experiment, and the product is a small molecule PA6, and the structural formula of the small molecule PA6 is as follows:

[0177]

[0178] In the formula, z = 49.

[0179] Example 10

[0180] An application of the biodegradable PA6 is as follows:

[0181] The biodegradable PA6 prepared in Example 5 is dried in a vacuum oven at 115°C for 7h, and then a biodegradable PA6 fiber is prepared by using a melt spinning technology.

[0182] The spinning process parameters include: a melting temperature of 250°C, a spinning temperature of 260°C, a first godet speed of 4400 m / min, a second godet speed of 5300 m / min, a draw ratio of 1.2 times, a cooling air temperature of 20°C, a cooling air speed of 0.8 m / s, and a cooling air relative humidity of 70%.

[0183] The final biodegradable PA6 fiber has a breaking strength of 3.3 cN / dtex, an elongation at break of 36%, a carbonate bond breaking rate of 90% after immersion in a lipase (Novozymes NovoCor ADL) aqueous solution, a degradation rate of 74% after 6 months of composting experiment, and all the carbonate bonds and ester bonds in the amorphous region are broken after 6 months of composting experiment, and the product is a small molecule PA6, and the structural formula of the small molecule PA6 is as follows:

[0184]

[0185] In the formula, z = 49.

Claims

1. Biodegradable PA6, characterized in that, The structural formula is as follows: ； In the formula, x, y, and z are positive integers, -OC-R1-CO- is a dibasic acid segment, and -O-R2-O- is a dibasic alcohol segment. x is in the range of 2-10, y is in the range of 2-6, and z is in the range of 10-60; the diacid corresponding to the diacid segment is one or more of terephthalic acid, phthalic acid, and HOOC(CH2) n n is in the range of 2-10; the diol corresponding to the diol segment is a diol having a carbon chain length of 10 or less. The melting point of the biodegradable PA6 is 190-250 DEG C.

2. Biodegradable PA6 according to claim 1, characterized in that The biodegradable PA6 has a relative viscosity of 2.4-4.0, a hot water extract content of 0.05-2 wt%, a melting point of 190-250 DEG C, and a number average molecular weight of 14000-33000 g / mol.

3. Process for the preparation of a biodegradable PA 6 as claimed in any of claims 1-2, characterized in that, The biodegradable PA6 is obtained by performing an ester exchange reaction on the PA6 prepolymer esterification product and a carbonic acid diester; The structural formula of the PA6 prepolymer esterification product is as follows: ； The PA6 prepolymer esterification product is obtained by performing an esterification reaction on the PA6 prepolymer and a dibasic alcohol; The structural formula of the PA6 prepolymer is as follows: ； The structural formula of the dibasic alcohol is as follows: ； The molar addition amount ratio of the carbonic acid diester in the ester exchange reaction to the molar addition amount of the dibasic alcohol in the esterification reaction is 0.9-1.1:

1.

4. The method of claim 3, wherein, In the esterification reaction, the molar ratio of the hydroxyl functional groups of the dibasic alcohol to the carboxyl functional groups of the PA6 prepolymer is 1.3-1.8:

1. The carbonic acid diester is one or more of dimethyl carbonate, diethyl carbonate, diphenyl carbonate, and ethylene carbonate.

5. The method of claim 4, wherein, The esterification reaction is performed at a temperature of 220-260 DEG C and a pressure of 0.01-0.5 MPa, and the termination condition is that the water output of the esterification reaction reaches 95-98% of the theoretical water output. The ester exchange reaction is performed at a temperature of 250-280 DEG C, a pressure of 100 Pa or less, and a time of 2-4 h.

6. The method of claim 4, wherein, The preparation steps of the PA6 prepolymer are as follows: (a) mixing caprolactam, a dibasic acid, deionized water, and a catalyst under mechanical stirring to obtain a mixture; The structural formula of the dibasic acid is as follows: ； The stirring speed of the mechanical stirring is 60-240 r / min, the mechanical stirring time is 10-60 min, the mixing temperature is 60-100 DEG C, and the addition amounts of the dibasic acid, deionized water, and catalyst are 5-30 wt%, 2-5 wt%, and 0.1-1 wt% of the addition amount of caprolactam, respectively; (b) sequentially performing a hydrolysis ring-opening reaction and a prepolymerization reaction on the mixture to obtain the PA6 prepolymer; The atmosphere of the hydrolysis ring-opening reaction and the prepolymerization reaction is nitrogen or an inert gas; the temperature of the hydrolysis ring-opening reaction is 230-250 DEG C, the pressure is 0.1-0.6 MPa, and the time is 2-4 h; and the temperature of the prepolymerization reaction is 240-290 DEG C, the pressure is 0.1-3 MPa, and the time is 2-4 h.

7. The method of claim 6, wherein, An ester exchange catalyst and an ether inhibitor are also added during the ester exchange reaction; The ester exchange catalyst is a titanium-based catalyst and / or an antimony-based catalyst, and the ether inhibitor is an acetate; The mass addition amounts of the ester exchange catalyst and the ether inhibitor are 10-500 ppm and 300-500 ppm of the mass addition amount of caprolactam in step (a), respectively.

8. Use of a biodegradable PA6 according to any one of claims 1-2, characterized in that, The biodegradable PA6 is used for spinning to prepare a biodegradable PA6 fiber.

9. Use according to claim 8, characterized in that, The spinning adopts a melt spinning technology, and the spinning process parameters include: a melting temperature of 220-260 DEG C, a spinning temperature of 240-280 DEG C, a first godet speed of 4000-4500 m / min, a second godet speed of 5000-6000 m / min, a draw ratio of 1.1-1.5 times, a cooling air temperature of 15-25 DEG C, a cooling air speed of 0.5-1 m / s, and a cooling air relative humidity of 60-90%; The biodegradable PA6 fiber has a breaking strength of 2.5-3.5 cN / dtex, an elongation at break of 30-70%, a breaking rate of carbonate bonds of 90-95% after being soaked in a lipase aqueous solution, and a degradation rate of 70-85% after a composting experiment for 6 months; after the composting experiment for 6 months, the carbonate bonds and ester bonds in the amorphous region are all broken, and the product is small molecule PA6, and the structural formula of the small molecule PA6 is as follows: 。

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