阅读说明：本技术 Pet-pa6中pet平均序列长度的控制方法及应用 (Control method and application of PET average sequence length in PET-PA6 ) 是由 江建明 于 2019-07-19 设计创作，主要内容包括：本发明涉及一种PET-PA6中PET平均序列长度的控制方法及应用,在制备PET-PA6的过程中,通过固定M(己内酰胺或PA6预聚物)加入量的同时调整M的分子量以控制共聚物中PET平均序列长度；M的加入量一定时,M的数均分子量与共聚物中PET平均序列长度呈反比；应用为：通过向PET/PA6熔融共混体系中加入定量的PET-PA6并控制其中PET平均序列长度以控制体系中PET和PA6的相容程度；其他条件一定时,PET-PA6中PET平均序列长度与相容程度呈正比。本发明PET-PA6中PET平均序列长度的控制方法,效果显著,可应用于PET/PA6熔融共混体系中PET和PA6相容程度的控制。(The invention relates to a control method and application of PET average sequence length in PET-PA6, in the process of preparing PET-PA6, the average sequence length of PET in a copolymer is controlled by fixing the adding amount of M (caprolactam or PA6 prepolymer) and adjusting the molecular weight of M; when the addition amount of M is fixed, the number average molecular weight of M is inversely proportional to the average sequence length of PET in the copolymer; the application is as follows: the method is characterized in that quantitative PET-PA6 is added into a PET/PA6 melt blending system, and the average sequence length of PET is controlled so as to control the compatibility degree of PET and PA6 in the system; under other conditions, the average sequence length of PET in PET-PA6 is proportional to the degree of compatibility. The method for controlling the average PET sequence length in the PET-PA6 has obvious effect, and can be applied to the control of the compatibility degree of PET and PA6 in a PET/PA6 melt blending system.)

The method for controlling the average PET sequence length in the PET-PA6 is characterized by comprising the following steps: in the process of preparing PET-PA6 from PTA, EG and M, the average sequence length of PET in PET-PA6 is controlled by fixing the addition amount of M and adjusting the molecular weight of M;

m is caprolactam or PA6 prepolymer;

the average sequence length of PET in PET-PA6 is equal to the number of PET repeating units contained in each PET sequence on average;

the adding amount of M accounts for 2-20% of the total feeding mass, the number average molecular weight of M ranges from 113-17500 g/mol, and the average sequence length of PET in PET-PA6 ranges from 5-50;

when the adding amount of M is fixed, the larger the number average molecular weight of M is, the shorter the average sequence length of PET in PET-PA6 is; otherwise, the opposite is true.

2. The method for controlling the average PET sequence length in the PET-PA6 of claim 1, wherein the amount of M added is 5% of the total feed mass, and the average PET sequence length in the PET-PA6 is reduced from 47.6 to 39.6 when the number average molecular weight of M is increased from 113g/mol to 3200 g/mol.

3. A method for controlling the compatibility degree of PET and PA6 in a melt blending system is characterized in that: during the process of preparing a melt blending system by taking PET and PA6 as raw materials, the compatibility degree of PET and PA6 in the melt blending system is controlled by adding quantitative PET-PA6 and controlling the average sequence length of PET in PET-PA 6;

the mass fraction of PA6 in the raw material is 5-50%, the adding amount of PET-PA6 accounts for 0-30% of the total feeding mass, the average sequence length of PET in PET-PA6 is 10-50, and the method is controlled by the method of claim 1;

the compatibility degree of PET and PA6 in the melt blending system is represented by the difference of the crystallization temperature of the PET and PA6 in the temperature reduction process of DSC test, namely △ Tc or the difference of the glass transition temperature of the DMA test, namely △ Tg, wherein the smaller the △ Tc or △ Tg, the higher the compatibility degree is, and the opposite is true;

when the mass fraction of PA6 in the raw material and the adding amount of PET-PA6 are fixed, the longer the average sequence length of PET in PET-PA6 is, the smaller △ Tc or △ Tg is, the higher the compatibility is, otherwise, the reverse is carried out.

4. The method for controlling the compatibility degree of PET and PA6 in the melt blending system according to claim 3, wherein the addition amount of PET-PA6 accounts for 5-20% of the total feeding mass.

5. The method for controlling the compatibility degree of PET and PA6 in the melt blending system according to claim 4, wherein the addition amount of PET-PA6 accounts for 10-15% of the total feeding mass.

6. The method for controlling the compatibility degree of PET and PA6 in the melt blending system according to claim 3, wherein the mass fraction of PA6 in the PET-PA6 is in the range of 2-20%.

7. The method of controlling the degree of compatibilization of PET and PA6 in a melt blending system according to claim 3,

the mass fraction of PA6 in the raw material is 20%, the adding amount of PET-PA6 accounts for 15% of the total feeding mass, and

when the average sequence length of PET in the PET-PA6 is increased from 10 to 26, △ Tc is reduced from 15 ℃ to 9 ℃, and △ Tg is reduced from 28 ℃ to 3 ℃.

Technical Field

The invention belongs to the technical field of high polymer material processing, and relates to a control method and application of PET average sequence length in PET-PA 6.

Background

Polyethylene terephthalate (PET) and polyamide 6(PA6) are two polymer materials that have found widespread use as plastics and fibers, respectively, each of which has its own unique properties and disadvantages, and thus combining the advantages of PET and PA6 by blending them has been of continuing interest to researchers in this field. However, because of the significant difference between the chemical structures of PET and PA6, PET is incompatible with PA6 in the blending system, which is a key technical problem that prevents the PET/PA6 mixing system from exhibiting excellent performance and obtaining practical application. Although the ultra-fine fiber can be obtained by interfacial separation after spinning the PET/PA6 composite fiber by utilizing the incompatibility of the two, in practical application, in order to pursue the diversity and specificity, the separation degree of the two also needs to be controlled, which also requires the compatibility of both PET and PA6 to be controllable in the PET/PA6 composite fiber.

In order to improve the compatibility of PET and PA6, different approaches and methods have been tried at home and abroad. Most of the work has been to add a compatibilizer Reactive with at least one of the components of the PET/PA6 system, and among them, epoxy resins are used in a relatively large number, such as document 1(Reactive compatibility of polyamide-6(PA6)/polybutylene terephthalate (PBT) blends by a multifunctionality epoxy resin, Journal of polymer science part B: polymer physics,2015,38(1):23-33), to add epoxy resins to a polyester and polyamide melt blend system, to reduce the size of the dispersed polyamide phase by the reaction of the epoxy resins with the polyamide terminal amino groups; document 2 (compatibility of epoxy resins on the phase separation and properties of polyurethane 6/polyethylene terephthalate blends, Virology,2014,51(1):174-180) using bisphenol A epoxy resins, melt blending by means of a twin-screw extruder has revealed that the size of the dispersed phase of PET in a matrix of PA6 is reduced. In addition, the compatilizer can be other substances, for example, document 3 (influence of ionomer Surlyn on the compatibility of PET/PA6 blend, plastics, 2005,34(6):14-17) mentions that ionomer zinc polymethylethylacrylate (Surlyn) can also be used as the compatilizer for increasing the adhesive force of two-phase interface, thereby improving the compatibility of the PET/PA6 blend system, and the experimental result shows that the particle size of the dispersed phase PA6 can be reduced and the uniformity of dispersion can be improved after the ionomer Surlyn is added. However, the use of epoxy resins as compatibilizers has the disadvantages of crosslinking between the macromolecular chains, increasing the melt viscosity and reducing the melt flow, and ionomers also increase the melt viscosity, which is very disadvantageous for fiber and plastic molding.

Patent CN109206621A discloses a method for improving compatibility of polyamide and polyester, namely, a copolymer of PET and polyamide is used as a compatibilizer to improve compatibility of polyester and polyamide blend fiber, the method comprises the steps of firstly preparing prepolymers of polyester (PET/PBT/PTT) and polyamide (PA66/PA46/PQ1010/PA1212), and then copolymerizing the two prepolymers to obtain a block polyesteramide copolymer, and the copolymer is used as a compatibilizer to be added into a polyester and polyamide blend system to improve compatibility. Although the polyesteramide copolymer as a compatibilizer avoids the problems of increased melt viscosity and the like caused by epoxy resins and ionomers as compatibilizers, the patent does not provide a quantitative expression for the improvement of compatibility, nor does it give a precise relationship between the block length and compatibility in the compatibilizer. Since if block polyesteramide copolymers are prepared from prepolymers of different molecular weights, when they are used as compatibilizers, they cause differences in the effect of improving compatibility at the same addition amount, which brings about great troubles and obstacles to the production process.

Therefore, the research of a method for improving the compatibility of the PET/PA6 blending system and accurately regulating and controlling the compatibility is of great significance.

Disclosure of Invention

The invention aims to solve the problem that the compatibility of a PET/PA6 blending system is difficult to accurately regulate in the prior art, provides a control method of the average sequence length of PET in PET-PA6, obtains a control method of the compatibility degree of PET and PA6 in a melt blending system based on the control method, and realizes the accurate regulation of the compatibility of the PET/PA6 blending system.

In order to achieve the purpose, the invention adopts the following scheme:

the method for controlling the average PET sequence length in the PET-PA6 is characterized in that in the process of preparing the PET-PA6 from PTA, EG and M (the specific steps and the process parameters are the same as those in the prior art), the average PET sequence length in the PET-PA6 is controlled by fixing the adding amount of M and adjusting the molecular weight of M; the average sequence length of PET in PET-PA6 can be controlled by fixing the molecular weight of M and simultaneously adjusting the addition amount of M, and the problem that the average sequence length of PET in PET-PA6 is smaller and the improvement effect on compatibility is poor exists in comparison with the method for simultaneously adjusting the molecular weight of M and controlling the average sequence length of PET in PET-PA6 by fixing the addition amount of M;

m is caprolactam or PA6 prepolymer, and the PA6 prepolymer can be prepared by the same method as the prior PA6 prepolymer, so that PA6 prepolymers with different molecular weights can be conveniently prepared by shortening the reaction time;

the average sequence length of PET in PET-PA6 is equal to the number of PET repeat units contained on average per PET sequence, and the average sequence length of PET in PET-PA6 is calculated based on C¹³The results of NMR analysis were calculated by reference to the method in the literature (Journal of macroreticular science, part B: physics,2006,45(4), 581-;

the adding amount of M accounts for 2-20% of the total feeding mass (namely the mass of M is 2-20% of the sum of PTA, EG and M), the number average molecular weight of M ranges from 113-17500 g/mol, and the average sequence length of PET in PET-PA6 ranges from 5-50;

when the adding amount of M is fixed, the larger the number average molecular weight of M is, the shorter the average sequence length of PET in PET-PA6 is; otherwise, the opposite is true.

In the process of preparing PET by taking PTA and EG as raw materials through esterification and polycondensation, M with different molecular weights is added to carry out copolymerization to prepare a PET-PA6 copolymer in the esterification finishing time period (judged by the water yield reaching 90 percent of the theoretical amount);

the length of a PET sequence in the PET-PA6 copolymer is influenced by the addition amount of M and the molecular weight of the added M, the sequence length is changed within the range of 5-50, and when the molecular weight of the M is fixed, the length of the PET sequence is reduced along with the increase of the mass percentage of the added M; while when the mass percentage of added M is fixed, the sequence length of PET decreases with increasing M molecular weight;

the reason why the average sequence length of PET in the PET-PA6 copolymer needs to be considered is that when the PET-PA6 copolymer is used as a compatilizer for both PET and PA6, the PET sequence length directly influences the improvement effect on the compatibility when the addition amount of the compatilizer is the same; meanwhile, the sequence length of PET in the PET-PA6 copolymer also determines the melting point of the copolymer, because the average sequence length of PET in the PET-PA6 copolymer directly affects the thickness of formed platelets, while the thickness of the platelets directly determines the melting point of the copolymer, when the sequence length of PET is short, the melting point of the copolymer is low, and too low melting point can bring adverse effect on melt molding processing, thereby weakening the application value of products;

the principle of regulating the length of the PET sequence in the PET-PA6 copolymer by changing the number average molecular weight of M is to utilize the difference in the kinetic equilibrium constants of the two reactions. Both polyesterification and polyamidation are kinetic reversible reactions, but the kinetic equilibrium constant of the polyamidation is 400, while the kinetic equilibrium constant of the polyesterification is 4 (Pandalu, high molecular chemistry, chemical industry Press, first edition 1986, page 221-; when the molecular weight of M is small, the concentration of the end group capable of performing polymerization reaction per se is high, and the reaction rate for forming amide bonds is high, so that the self-polymerization rate of M is higher than the rate for forming the copolymer, and the probability of the occurrence of the amide bonds in the PET-PA6 copolymer is low, which means that PET has longer sequence length; when the molecular weight of M is increased, the concentration of end groups which can be subjected to polymerization reaction per se is reduced, the self-polymerization rate of M is slowed down due to viscosity increase caused by molecular weight increase, the probability of participating in copolymerization reaction and carrying out amide-ester bond transfer reaction is increased, and the probability of appearance of amide bonds in the PET-PA6 copolymer is high, so that the PET sequence length is reduced; especially when the molecular weight of M is extremely large, the self-polymerization probability is small, and the copolymer has more chance to participate in copolymerization and amide-ester bond transfer reaction, so that more amide bonds exist in the PET-PA6 copolymer, and the average sequence length of PET is very small. Therefore, when the amount of M added is the same, the PET sequence length in PET-PA6 increases with the decrease in M molecular weight.

As a preferable scheme:

in the method for controlling the average PET sequence length in the PET-PA6, the adding amount of M accounts for 5 percent of the total feeding mass, and when the number average molecular weight of M is increased from 113g/mol to 3200g/mol, the average PET sequence length in the PET-PA6 is reduced from 47.6 to 39.6.

The invention also provides a method for controlling the compatibility degree of PET and PA6 in the melt blending system, which comprises the steps of adding a certain amount of PET-PA6 into the melt blending system and controlling the average sequence length of PET in PET-PA6 to control the compatibility degree of PET and PA6 in the melt blending system in the process of preparing the melt blending system by taking PET and PA6 as raw materials;

the mass fraction of the PA6 in the raw materials is controlled to be 5-50% (namely the mass of PA6 accounts for 5-50% of the sum of the masses of PA6 and PET), so as to ensure that the main body of the melt blending system is PET, the PET-PA6 average sequence length can be controlled to control the compatibility degree of the PET and the PA6 in the melt blending system, the PET-PA6 addition amount accounts for 0-30% of the total feeding mass (namely the mass of PET-PA6 accounts for 0-30% of the sum of the masses of PET, PA6 and PET-PA 6), the value is set because the use amount of the compatilizer is smaller than the content of the main body component in the blending system, the PET-PA6 compatilizer is a low molecular weight block copolymer, the melting point is low, the melting point of the blending system can be reduced as an additive, and therefore, the melting point of the main body raw materials is ensured by controlling the addition amount to be smaller than the content of the main body, the value range of the average sequence length of PET in the PET-PA6 is 10-50, and the average sequence length is controlled by adopting the method;

the compatibility degree of PET and PA6 in a melt blending system is represented by the difference △ Tc between crystallization temperatures of PET and PA6 in the temperature reduction process of DSC test or the difference △ Tg of glass transition temperatures measured by DMA, the smaller the △ Tc or △ Tg is, the higher the compatibility degree is, and the opposite is true, the specific value of △ Tc or △ Tg shows certain difference due to different testing instruments and testing conditions, but the regularity is not changed;

when the mass fraction of PA6 in the raw material and the adding amount of PET-PA6 are fixed, the longer the average sequence length of PET in PET-PA6 is, the smaller △ Tc or △ Tg is, the higher the compatibility is, otherwise, the reverse is carried out.

The average sequence length of PET in the PET-PA6 influences the compatibility of the PET/PA6 blend system, because the longer sequence length is beneficial to the molecular chain of the compatilizer to better enter the corresponding phase and not to be separated when the two phases slide, because the PET is used as a main component in the PET/PA6 blend system and has higher content, the increase of the average sequence length of PET in the compatilizer PET-PA6 is more beneficial to the contact of PET-PA6 and PET and PA6 components in the blend system, the interface interaction is better improved, and the compatibility is increased.

As a preferable scheme:

according to the method for controlling the compatibility degree of the PET and the PA6 in the melt blending system, the value range of the adding amount of the PET-PA6 in percentage of the total feeding mass is 5-20%.

According to the method for controlling the compatibility degree of the PET and the PA6 in the melt blending system, the value range of the adding amount of the PET-PA6 in percentage of the total feeding mass is 10-15%, the effect of improving the compatibility is improved along with the increase of the adding amount of the compatilizer, but the improvement of the compatibility is not obvious after a certain content is reached, so that the adding amount of the PET-PA6 is most preferably in the range.

According to the method for controlling the compatibility degree of the PET and the PA6 in the melt blending system, the mass fraction of the PA6 in the PET-PA6 is controlled by a simple feeding ratio, and the value range of the mass fraction of the PA6 in the PET-PA6 is 2-20%.

The method for controlling the compatibility degree of PET and PA6 in the melt blending system comprises the following steps that the mass fraction of PA6 in the raw materials is 20%, the addition amount of PET-PA6 accounts for 15% of the total charged mass, and when the average sequence length of PET in the PET-PA6 is increased from 10 to 26, △ Tc is reduced from 15 ℃ to 9 ℃, and △ Tg is reduced from 28 ℃ to 3 ℃.

Has the advantages that:

(1) the method for controlling the average sequence length of the PET in the PET-PA6 controls the average sequence length of the PET in the PET-PA6 by fixing the adding amount of caprolactam or PA6 prepolymer and adjusting the molecular weight of the caprolactam or PA6 prepolymer, and has obvious effect;

(2) the method for controlling the degree of compatibility of PET and PA6 in the melt blending system is based on the control of the average sequence length of PET in PET-PA6, and the degree of compatibility of PET and PA6 in the melt blending system can be quantitatively expressed by the difference △ Tc between the crystallization temperatures of PET and PA6 in the cooling process of DSC test or the difference △ Tg of the glass transition temperature measured by DMA.

Drawings

FIG. 1 shows C of PET-PA6¹³-NMR spectrum;

FIG. 2 shows C of PET-PA6¹³Assignment of characteristic peaks of different chemical shifts in NMR spectra；

FIG. 3 is a schematic representation of the effect of average sequence length of PET in PET-PA6 on compatibility;

FIG. 4 is a DSC curve measured when the mass fraction of PA6 in the raw material is 20%, PET-PA6 is not added and PET-PA6 of which the total charge mass is 15% is added;

FIG. 5 is a DMA curve measured when the mass fraction of PA6 in the raw material is 20%, PET-PA6 is not added and PET-PA6 of which the total charge mass is 15% is added;

wherein a represents PET, b to d represent PET-PA6 with average sequence lengths of 10.1, 19.7 and 29.8 respectively, e represents a system with 20% of PA6 in the raw material and no PET-PA6, and f to h represent a system with 20% of PA6 in the raw material, 15% of PET-PA6 in the total charge and 10.1, 19.7 and 29.8 in the average sequence length of PET-PA 6.

Detailed Description

The invention will be further illustrated with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.