WO2023051487A1 - Method for improving dyeing performance of polyethylene terephthalate fiber - Google Patents

Abstract

The present invention relates to a method for improving the dyeing performance of polyethylene terephthalate fiber, comprising: first, preparing modified polyethylene terephthalate using dimethyl terephthalate, ethylene glycol, glycerol and 1,2-propanediol isobutyl-POSS as raw materials, and using ethylene glycol antimony as a catalyst; then, producing modified polyethylene terephthalate fiber from the obtained modified polyethylene terephthalate, and finally dyeing the modified polyethylene terephthalate fiber. The molar ratio of dimethyl terephthalate, ethylene glycol, glycerol and 1,2-propanediol isobutyl-POSS is 1:0.960-0.984:0.015-0.035:0.001-0.005, and a dye uptake rate of the modified polyethylene terephthalate fiber during dyeing is 17.02-18.49 mg·g-1. In the method of the present invention, by means of using a certain amount of glycerol and 1,2-propanediol isobutyl-POSS as monomers, which are copolymerized with dimethyl terephthalate to obtain an easily-dyed PET fiber, the use of complex comonomers is avoided. The present invention has a simple process, strong spinnability of the polymer melt, and high potential for large-scale production.

Description

A method for improving the dyeing performance of polyethylene terephthalate fibers technical field

The invention belongs to the technical field of polyester fibers and relates to a method for improving the dyeing performance of polyethylene terephthalate fibers.

Background technique

Polyethylene terephthalate (PET) fiber is widely used because of its high breaking strength and elastic modulus, moderate resilience, good washing resistance, excellent heat setting, heat resistance and light resistance Textile and clothing, film and engineering plastics and other fields. However, due to the tight aggregation of PET molecular chains, high crystallinity and orientation, and the lack of functional groups combined with dyes on the molecular chains, it is difficult for dye molecules to enter the fiber and dyeing is difficult. Starting from improving the fiber structure, using various physical and chemical means to modify the internal and external structure of conventional PET fibers, improving its dyeing performance, and developing functionalized PET fibers with high added value will greatly improve the use of PET in the field of high-end clothing. competitiveness and increase economic benefits for enterprises.

The main chain of the PET molecule contains a rigid benzene ring and a flexible hydrocarbon group, and the ester group directly connected to the benzene ring and the benzene ring form a rigid conjugated system, which restricts the free rotation of its flexible segment. The impact of this structure on the glass transition temperature is obvious, which increases the barriers to the movement of molecular segments. PET has a high glass transition temperature and needs to be dyed at a very high temperature. In addition, PET has regular molecular chains, good crystallinity, tightly arranged molecular chains, and no polar groups that interact with dye molecules on the molecular chains, making it more difficult to color PET fibers. During the dyeing process of PET fiber, dye molecules are first adsorbed to the surface of the fiber, and then diffused into the interior of the fiber. When the dye molecules diffuse into the fiber, they cannot enter the crystalline region of the PET fiber, but can only enter the amorphous region of the fiber. The above shows that the dyeing performance of PET fibers is related to the size of the amorphous region.

In recent years, in order to solve the problem of difficult dyeing of PET fibers, textile scientists have produced easily dyeable PET fibers by adding modified monomers during PET polymerization. For example, cationic dyeable polyesters are developed by adding cationic dyeable raw materials, but when preparing cationic dyeable polyesters, it is often necessary to introduce 5-sodium sulfonate-dimethyl isophthalate or 5-sodium sulfonate-isophthalate Ethylene glycol phthalate, the sulfonate ion dissociated from the sulfonic acid group is easy to form a strong bonded entanglement point with the positively charged part of the macromolecular chain, making the polymer melt gel and difficult to spin Silk. European Patent EP1217024B1 discloses dyeable PET prepared from alkanediol, terephthalic acid and comonomers which may contain metal or alkylphosphonium sulfones, trivalent aromatic rings and ester functional groups, but this method requires the use of relatively Complex comonomers. Chinese patent CN1282775C improves the dyeing performance of PET by adding aromatic dicarboxylic acid with sulfonic acid group and layered silicate, however, this method needs polyester/layered silicate nanocomposite copolymer and p-phenylene Ethylene diformate chips are blended, dried and then melt-spun, and the preparation process is relatively complicated.

Therefore, it is of great significance to design a method that uses simple comonomers, is easy to operate and has strong spinnability of polymer melts, and can effectively improve the dyeing performance of polyethylene terephthalate fibers.

Contents of the invention

In order to overcome the shortcomings of the prior art solutions, the invention provides a method for improving the dyeing performance of polyethylene terephthalate fibers. The method adopts a copolymerization method to obtain modified polyethylene terephthalate by copolymerization of dimethyl terephthalate, ethylene glycol, glycerin, 1,2-propanediol isobutyl-POSS and catalyst ethylene glycol antimony. Alcohol esters. By controlling the content of comonomers, the topological structure of the modified polyethylene terephthalate polymer macromolecules is changed, thereby affecting the crystallization behavior of the polymer, making the modified polyethylene terephthalate The glass transition temperature (T _g ) of the ester decreases, and the free volume in the amorphous region increases, which facilitates the diffusion of dye molecules into the fiber. At the same time, the initial crystallization temperature (T _c,onset ) of the melt cooling process of modified polyethylene terephthalate moves to low temperature, and the crystallization temperature (T _c,peak ) moves to high temperature, which further affects the crystallization morphology , that is, the nucleation density decreases and the crystallization rate increases. The lower nucleation density can avoid the collision of crystals during the growth process, so that the crystals of modified polyethylene terephthalate grow in a relatively complete three-dimensional way, while the unmodified polyethylene terephthalate The crystals of glycol esters tend to grow in a planar two-dimensional manner. The larger grain size indicates that the gaps between crystal particles in the crystallization area are larger, and the amorphous area is relatively concentrated, which is conducive to the diffusion of dye molecules.

In order to achieve the above object, the scheme adopted by the present invention is as follows:

A method for improving the dyeing performance of polyethylene terephthalate fibers, first using dimethyl terephthalate, ethylene glycol, glycerol, 1,2-propylene glycol isobutyl-POSS as raw materials, and Adopt catalyst ethylene glycol antimony to prepare modified polyethylene terephthalate; Produce modified polyethylene terephthalate fiber by the obtained modified polyethylene terephthalate again, finally to Modified polyethylene terephthalate fibers are dyed.

The molar ratio of dimethyl terephthalate, ethylene glycol, glycerol and 1,2-propanediol isobutyl-POSS is 1:0.960-0.984:0.015-0.035:0.001-0.005.

As a preferred technical solution:

A kind of method for promoting the dyeing performance of polyethylene terephthalate fiber as mentioned above, the preparation process of modified polyethylene terephthalate comprises the steps:

(1) Dimethyl terephthalate, ethylene glycol, glycerol, 1,2-propanediol isobutyl-POSS and ethylene glycol antimony carry out transesterification;

(2) When the amount of methanol to be distilled in the transesterification reaction reaches 90% of the theoretical amount, a vacuum is gradually established to carry out polycondensation reaction to obtain modified polyethylene terephthalate.

The step-by-step establishment of vacuum refers to: on the operation steps, due to the low viscosity of the product in the early stage of the polycondensation reaction, during decompression, a small amount of unreacted low-boiling glycol, water and methanol (reaction by-product) in the material are in boiling state. If the decompression is too fast and too strong, a situation similar to bumping will occur in the reactor, and a large amount of low-viscosity reactants will be extracted together with small molecules, which will block the vacuum pipe and affect the quality of the resin product. Therefore, the vacuum degree in the reactor must be Slowly build up, the low vacuum stage should be maintained in the early stage of the polycondensation reaction. In the later stage of the polycondensation reaction, the viscosity of the product increases rapidly, and it is difficult for small molecules to escape. Therefore, a high vacuum is required to remove the small molecule products generated by polycondensation. This stage is called a high vacuum stage.

According to the above method for improving the dyeing performance of polyethylene terephthalate fibers, in step (1), the temperature of the transesterification reaction is 200-220°C. The transesterification reaction of the present invention does not need to control the pressure, and the temperature is required according to the reaction kinetics, and the transesterification reaction will only occur within this temperature range.

A method for improving the dyeing performance of polyethylene terephthalate fibers as described above, in step (2), the polycondensation reaction temperature is 270-280°C, the total time of the polycondensation reaction is 2-4h, and the stepwise Establishing a vacuum refers to maintaining a vacuum degree of 40 Pa for 40-60 minutes, and then adjusting to a vacuum degree of 80 Pa and maintaining a time of 1-3 hours. The parameter setting of the polycondensation reaction in the present invention is to make the number average molecular weight of the final product of the polycondensation reaction, that is, the modified polyethylene terephthalate, be 13000-16000.

A method for promoting the dyeing performance of polyethylene terephthalate fibers as described above, the specific process of the production is: the gained modified polyethylene terephthalate is melted in an extruder and Extrude and wind through the spinneret die;

When melted in the extruder and extruded through the spinneret die, the spinning temperature is 250-280°C, and the spinning speed is 600-900m/min.

A method for improving the dyeing performance of polyethylene terephthalate fibers as described above, the dyeing uses disperse dyes.

A method for improving the dyeing performance of polyethylene terephthalate fibers as described above, the dye uptake rate of the dyeing is 17.02～18.49mg ^g The amount of dye (mg) dyed has increased by 17% to 30% compared with the comparison sample; the comparison sample is made by the same method as the preparation method of the polyethylene terephthalate fiber, The only difference is that glycerol and 1,2-propanediol isobutyl-POSS are not added.

Principle of the present invention is:

Currently, the prior art discloses the use of polyols as a third monomer to improve the thermal and optical properties of PET. For example, Chinese patent CN104987498A discloses adding a third monomer 2-methyl-1,3-propanediol (MPO) or simultaneously adding a third monomer MPO and a fourth monomer isophthalic acid (IPA) during the PET polymerization process to Preparation of copolyesters with low melting points. Chinese patent CN111454438A uses terephthalic acid, ethylene glycol, catalyst ethylene glycol antimony, an ethylene glycol solution of trimethyl phosphate as an auxiliary agent, and a third monomer polyol to prepare a modified PET resin. The alcohols are glycerol, xylitol, and sorbitol, and the amount of the third monomer added is very small, only 500-1500 ppm of the molar amount of ethylene glycol. The patent pointed out that the addition of a small amount of the third monomer polyol can form a three-dimensional branched chain network structure with polyol as the center and low steric hindrance in the PET resin, thereby increasing the inter-molecular chains of PET. Combined with the force, the thermal properties of PET resin are improved; in addition, the crystallinity of PET resin is reduced by adding polyols, and the optical properties of PET resin are improved.

However, the above scheme is to add a very small amount of polyols to form a three-dimensional branched chain network structure centered on polyols in the PET resin with low steric hindrance, thereby increasing the bonding force between PET molecular chains. , Improving the thermal properties of PET resin, on the other hand is to improve the optical properties by reducing the crystallinity. It is different from the idea of this scheme, and what is improved by using the idea of this scheme is the dyeing performance.

The present invention controls the addition of glycerol and 1,2-propanediol isobutyl-POSS, that is, the molar ratio of dimethyl terephthalate, ethylene glycol and glycerol is 1:0.960-0.984:0.015-0.035: 0.001-0.005, the main ideas are as follows:

According to the kinetic theory of polymer crystallization, the Lauritzen-Hoffman equation gives the expression of the crystallization rate constant G and temperature T of the polymer:

where _G0 is the temperature-independent rate constant, u* is the activation energy for the transport of crystallizable segments at the liquid-solid interface, R is the gas constant, _T∞ is the minimum temperature for viscous flow, and _Kg is the nucleation The constant (K _g is proportional to the surface free energy of the chain folding plane

and the surface free energy of the folded sides of the chain

product), T _c is the crystallization temperature, ΔT=T _m ⁰ -T _c , T _m ⁰ is the melting temperature, f=2T _c /(T _m ⁰ +T _c ).

The first term of the Lauritzen-Hoffman equation (ie

) is the contribution of macromolecular segment diffusion to the crystallization rate, the second term (namely

) is the thermodynamic driving force for crystallization. Any factor that can enhance the movement ability of macromolecular chains can increase the crystallization rate constant G, and any factor that can increase the nucleation constant K _g can decrease G. _Only from the perspective of chain diffusion, the branched chain structure reduces the glass transition temperature (T _g ), which means that the free volume increases, the mobility of the macromolecular chain increases, and the activation energy of chain segment diffusion decreases, which is beneficial to On the other hand, the branched chain structure is a kind of damage to the regularity of the macromolecular chain. With the increase of the branched chain structure, the free energy of the folding surface and side of the macromolecular chain increases, that is

The increase of the value is not conducive to chain folding, then the ability to form crystal nuclei through chain folding will become worse, and the crystallization rate will decrease. As a comonomer, glycerol provides three hydroxyl functional groups to facilitate the synthesis of modified polyester with branched chain structure, thereby affecting the crystallization behavior, and the addition of glycerol can only be controlled within a certain range, the first item The promotion of crystallization is dominated by the enhanced mobility of the macromolecular segment, showing that the initial crystallization temperature (T _c,onset ) shifts to a low temperature, the sample begins to crystallize a little later, the nucleation density decreases, and the melt cools The crystallization temperature (T _c,peak ) of the process moves to high temperature, the crystallization growth rate is fast, and the total crystallization rate increases, which eventually leads to three-dimensional growth of spherulites, and larger crystals are generated, and the average free crystallization around each crystal The volume of the shaped area increases, which is conducive to dyeing. However, when the amount of glycerol added was too low, the effect of the first factor favorable to crystallization was not obvious; when the added amount of glycerol was too high, the second factor unfavorable to crystallization dominated, and the total crystallization rate was observed to decrease.

Due to the existence of the branched chain structure, the macromolecular chains are easy to entangle, which increases the drag force between the flow layers when the melt flows, and the momentum is easier to transfer between the flow layers, the melt viscosity increases, and the melt flow Poor performance, difficult to spin. The 1,2-propanediol isobutyl-POSS introduced in the present invention contains two hydroxyl functional groups, which can be introduced to the end groups of the linear polyester during polymerization. Its larger cage structure provides greater steric hindrance at the end group, which can reduce the entanglement between molecular chains caused by glycerol branched chains, improve the fluidity of the melt, and improve spinnability. On the one hand, it can further reduce the nucleation density together with glycerol, so that the grain size increases, and the amorphous area is concentrated, which is beneficial to the diffusion of dye molecules. But the addition of 1,2-propanediol isobutyl-POSS also needs to be controlled in a certain range, when the addition of 1,2-propanediol isobutyl-POSS is too low, it will affect macromolecular chain structure and melt The influence of fluidity is not obvious; when the addition amount of 1,2-propanediol isobutyl-POSS is too high, the steric hindrance of the molecular chain is too large, resulting in slow crystallization rate, which is not conducive to dyeing.

This is essentially different from the prior art in which the crystallinity of the PET resin is reduced by adding polyols, and the optical properties of the PET resin are improved: on the one hand, the prior art uses the reduction of the crystallinity to improve the optical properties, and on the other hand, it is necessary to add a very small amount The polyol avoids increased steric hindrance, thus improving thermal performance. While crystallinity and crystallization rate are two concepts, what this application utilizes is the relationship between crystallization rate, grain size and dyeing performance. In this application, by controlling the amount of polyhydric alcohol added so that the crystallization rate increases and the grain size increases without affecting the crystallinity, it is beneficial to increase the volume of the amorphous region around each grain, thus aiding in staining. The reduction of crystallinity will reduce the modulus and strength of the fiber, thereby reducing the mechanical properties of the fiber, which is not conducive to taking.

Beneficial effect

(1) The preparation method of the modified PET fiber provided by the present invention changes the macromolecular chain structure of the modified polyethylene terephthalate by controlling the content of the comonomer, thereby regulating and controlling its crystallization characteristics, so that the modification The nucleation density of polyethylene terephthalate decreases, the total crystallization rate increases, and the spherulites are mainly three-dimensional growth, resulting in larger crystals; at the same time, the free volume is increased, making the macromolecular chain segment Increased athletic ability. The modified polyethylene terephthalate is produced into fibers, and the increase in the volume of the amorphous region around the fiber crystal is conducive to the diffusion and coloring of dye molecules, so that it has enhanced and uniform dyeability;

(2) The preparation method of the modified polyethylene terephthalate fiber provided by the invention, the method is by using a certain amount of glycerol and 1,2-propanediol isobutyl -POSS is used as a comonomer, and it is copolymerized with dimethyl phthalate to obtain easily dyeable PET fibers, avoiding the use of complex comonomers and complicated processes, and the fibers have strong spinnability and high potential for large-scale production.

Description of drawings

Fig. 1 is the differential scanning calorimetry curve (DSC) in the polyethylene terephthalate cooling process that embodiment 1～3 prepares;

Fig. 2 is the DSC curve of the polyethylene terephthalate glass transition that embodiment 1～3 prepares;

Fig. 3 is a polarizing microscope image (POM) of the polyethylene terephthalate prepared in Example 1 and Comparative Example 1 when it is isothermally crystallized at 220° C. for 300 s.

Detailed ways

The present invention will be further described below in combination with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

A method for improving the dyeing performance of polyethylene terephthalate fibers, the steps are as follows:

(1) dimethyl phthalate, ethylene glycol, glycerin, 1,2-propanediol isobutyl-POSS with a molar ratio of 1:0.960:0.035:0.005, and catalyst ethylene glycol antimony (of catalyst The amount added is 150 ppm based on the weight of terephthalic acid) for transesterification; wherein, the temperature of the transesterification is 200°C.

(2) when the methanol distillate amount in the transesterification reaction in the step (1) reaches 90% of the theoretical amount, a vacuum is gradually established to carry out the polycondensation reaction, and the reaction temperature of the polycondensation reaction is 270 ℃, and the total time of the polycondensation reaction is 4h, obtain modified polyethylene terephthalate (recorded as PET-1); Wherein, establish vacuum step by step and be meant to be 60min at the vacuum degree of 40Pa, then be adjusted to the vacuum degree of 80Pa and the retention time is 3h.

(3) The modified polyethylene terephthalate obtained in step (2) is spun by a spinning machine, melted in a screw extruder and extruded through a spinneret die to obtain a modified polyethylene terephthalate. Polyethylene terephthalate fiber; wherein, the diameter of the screw is 25 mm, the number of spinneret holes is 36, the spinning temperature during extrusion is 250° C., and the spinning speed is 800 m/min.

(4) adopt carrier dyeing method to dye the modified polyethylene terephthalate fiber that step (3) makes respectively;

When dyeing, the selected dye is disperse blue 2BLN, and the bath ratio is 100:1; add disperse blue 2BLN 1% (owf) and carrier (wintergreen oil) to the dyeing bath, raise the temperature to above 60°C, add methyl salicylate to acidify to pH =5, heat up to boiling, and dye for 60 minutes. After dyeing, soap thoroughly.

The dye uptake rates of the above dyeings are shown in Table 1.

Example 2

A method for promoting the dyeing performance of polyethylene terephthalate fibers, the steps are basically the same as in Example 1, the difference is only that the dimethyl phthalate, ethylene glycol, and propylene glycol in the step (1) The molar ratio of triol and 1,2-propanediol isobutyl-POSS is replaced by 1:0.977:0.020:0.003; the prepared modified polyethylene terephthalate is denoted as PET-2, and the obtained The dye uptake rate of fiber dyeing is shown in Table 1.

Example 3

A method for promoting the dyeing performance of polyethylene terephthalate fibers, the steps are basically the same as in Example 1, the difference is only that the dimethyl phthalate, ethylene glycol, and propylene glycol in the step (1) The molar ratio of triol and 1,2-propanediol isobutyl-POSS is replaced by 1:0.984:0.015:0.001; wherein, the prepared branched polyethylene terephthalate is recorded as PET-3, made of The dye uptake of the obtained fibers is shown in Table 1.

Comparative example 1

A method for improving the dyeing performance of polyethylene terephthalate fibers, the steps are basically the same as in Example 1, except that glycerol and 1,2-propylene glycol isobutyl are not added in step (1) -POSS and the molar ratio of dimethyl terephthalate and ethylene glycol is 1:1; the prepared modified polyethylene terephthalate is recorded as PET-0, and the fiber made from it is dyed The dye uptake rate is shown in Table 1.

Table 1

sample	Dye uptake rate/mg·g -1
PET-0	14.40
PET-1	18.44
PET-2	17.92
PET-3	17.15

It can be seen from Table 1 that the dyeing properties of PET-1, PET-2 and PET-3 are significantly improved compared with PET-0, and the dyeing rate can be increased by 28.1%, 24.4% and 19.1% respectively.

The modified polyethylene terephthalate in Examples 1 to 3 and Comparative Example 1 is subjected to DSC testing, the graph of the cooling process is shown in Figure 1, and the DSC curve of its glass transition is shown in Figure 2 . It can be seen from Figures 1 and 2 that the modification makes the initial crystallization temperature (T _c,onset ) of the melt cooling process from the glass state move to a low temperature, the crystallization temperature (T _c,peak ) moves to a high temperature, and the glass transition The temperature (T _g ) moves to low temperature; and based on this, the crystallization rate of the modified polyethylene terephthalate in the present invention increases during spinning, and the free volume in the amorphous region increases, which is more Facilitate the diffusion of dye molecules into the fiber.

The polarized light microscope pictures of the modified polyethylene terephthalate in Example 1 and Comparative Example 1 in the present invention were crystallized isothermally at 220°C for 300s as shown in Figure 3, as can be seen from Figure 3: The branched chain structure affects the crystal morphology, that is, the nucleation density decreases, and the crystal grows in a relatively complete three-dimensional manner. At 300s, the spherulites of PET-1 are significantly larger than those of PET-0. The larger grain size indicates that the gaps between crystal particles in the crystalline region are larger, and the amorphous region is relatively concentrated, which is also conducive to the diffusion of dye molecules.

Comparative example 2

A method for improving the dyeing performance of polyethylene terephthalate fibers, the steps are basically the same as in Example 1, except that 1,2-propylene glycol isobutyl-POSS is not added in step (1) and The molar ratio of dimethyl phthalate, ethylene glycol, and glycerol is 1:0.965:0.035; the obtained modified polyethylene terephthalate has difficulty in melt extrusion during spinning, and is not easy Spun into fibers.

This is because: glycerol, as a comonomer, provides three hydroxyl functional groups to facilitate the synthesis of modified polyesters with branched chain structures. Due to the existence of the branched chain structure, the macromolecular chains are easy to entangle, which increases the drag force between the flow layers when the melt flows, and the momentum is easier to transfer between the flow layers, and the viscosity of the melt increases, which eventually leads to melt flow. It is difficult to extrude the body and it is not easy to spin.

Example 4

A method for improving the dyeing performance of polyethylene terephthalate fibers, the steps are as follows:

(1) dimethyl phthalate, ethylene glycol, glycerin, 1,2-propanediol isobutyl-POSS with a molar ratio of 1:0.960:0.035:0.005, and catalyst ethylene glycol antimony (of catalyst The amount added is 150ppm of the weight of terephthalic acid) to carry out the transesterification reaction; wherein, the temperature of the transesterification reaction is 210°C.

(2) When 90% of the theoretical amount of methanol in the transesterification reaction in the step (1) is distilled off, a vacuum is gradually established to carry out the polycondensation reaction. The reaction temperature of the polycondensation reaction is 275° C., and the total time of the polycondensation reaction is 2h, obtaining Branched polyethylene terephthalate; wherein, gradually establishing a vacuum refers to maintaining a vacuum degree of 40 Pa for 40 minutes, and then adjusting to a vacuum degree of 80 Pa and maintaining a time of 80 minutes.

(3) The modified polyethylene terephthalate obtained in step (2) is spun by a spinning machine, melted in a screw extruder and extruded through a spinneret die to obtain a modified polyethylene terephthalate. Polyethylene terephthalate fiber; wherein, the diameter of the screw is 25 mm, the number of spinneret holes is 36, the spinning temperature during extrusion is 260° C., and the spinning speed is 600 m/min.

(4) The modified polyethylene terephthalate fibers prepared in step (3) were dyed respectively by carrier dyeing method; the dyeing method and its parameters were the same as in Example 1. The uptake rate of this dyeing was 18.49 mg·g ^-1 .

Example 5

A method for improving the dyeing performance of polyethylene terephthalate fibers, the steps are as follows:

(1) dimethyl phthalate, ethylene glycol, glycerin, 1,2-propanediol isobutyl-POSS with a molar ratio of 1:0.984:0.015:0.001, and catalyst ethylene glycol antimony (catalyst The amount added is 150ppm of the weight of terephthalic acid) to carry out the transesterification reaction; wherein, the temperature of the transesterification reaction is 220°C.

(2) when the methyl alcohol in the transesterification reaction in the step (1) distills out 90% of the theoretical amount, gradually establish a vacuum to carry out the polycondensation reaction, the reaction temperature of the polycondensation reaction is 280 ℃, and the total time of the polycondensation reaction is 3h, obtains Branched polyethylene terephthalate; wherein, gradually establishing a vacuum refers to maintaining a vacuum degree of 40 Pa for 50 minutes, and then adjusting to a vacuum degree of 80 Pa and maintaining a time of 130 minutes.

(3) The modified polyethylene terephthalate obtained in step (2) is spun by a spinning machine, melted in a screw extruder and extruded through a spinneret die to obtain a modified polyethylene terephthalate. Polyethylene terephthalate fiber; wherein, the diameter of the screw is 25 mm, the number of spinneret holes is 36, the spinning temperature during extrusion is 280° C., and the spinning speed is 900 m/min.

(4) The modified polyethylene terephthalate fibers prepared in step (3) were dyed respectively by carrier dyeing method; the dyeing method and its parameters were the same as in Example 1. The uptake rate of this dyeing was 17.02 mg·g ^-1 .

Claims (7)

1. A method for improving the dyeing performance of polyethylene terephthalate fibers is characterized in that: first use dimethyl terephthalate, ethylene glycol, glycerol, 1,2-propylene glycol isobutyl-POSS As raw material, and use the catalyst ethylene glycol antimony to prepare modified polyethylene terephthalate; then produce modified polyethylene terephthalate from the obtained modified polyethylene terephthalate fibers, and finally dyeing modified polyethylene terephthalate fibers;

   The molar ratio of dimethyl terephthalate, ethylene glycol, glycerol and 1,2-propanediol isobutyl-POSS is 1:0.960-0.984:0.015-0.035:0.001-0.005.
2. A kind of method promoting polyethylene terephthalate fiber dyeing performance according to claim 1, is characterized in that, the preparation process of modified polyethylene terephthalate comprises the steps:

   (1) Dimethyl terephthalate, ethylene glycol, glycerol, 1,2-propanediol isobutyl-POSS and ethylene glycol antimony carry out transesterification;

   (2) When the amount of methanol distilled in the transesterification reaction reaches more than 90% of the theoretical amount, a vacuum is gradually established to carry out polycondensation reaction to obtain modified polyethylene terephthalate.
3. A method for improving the dyeing performance of polyethylene terephthalate fibers according to claim 2, characterized in that, in step (1), the temperature of the transesterification reaction is 200-220°C.
4. A method for improving the dyeing performance of polyethylene terephthalate fibers according to claim 2, characterized in that, in step (2), the polycondensation reaction temperature is 270 to 280°C, and the total time of the polycondensation reaction is 2 to 4 hours, the step-by-step establishment of vacuum refers to maintaining a vacuum degree of 40 Pa for 40 to 60 minutes, and then adjusting to a vacuum degree of 80 Pa and maintaining a time of 1 to 3 hours.
5. A method for promoting the dyeing performance of polyethylene terephthalate fibers according to claim 1, characterized in that, the specific process of the production is: the gained modified polyethylene terephthalate Melted in the extruder and extruded through the spinneret die;

   When melted in the extruder and extruded through the spinneret die, the spinning temperature is 250-280°C, and the spinning speed is 600-900m/min.
6. A kind of method for promoting the dyeing performance of polyethylene terephthalate fiber according to claim 1, is characterized in that, described dyeing uses disperse dye.
7. A method for improving the dyeing performance of polyethylene terephthalate fibers according to claim 1, characterized in that the dyeing rate of said dyeing is 17.02-18.49 mg·g ^-1 .

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