Modification method of regenerated cationic polyester

Abstract

The invention provides a modification method of regenerated cationic polyester, and relates to the technical field of polyester. The modification method of the regenerated cationic polyester comprises the following steps: preserving heat of the regenerated cationic polyester for 10-20 hours to obtain modified regenerated cationic polyester; the intrinsic viscosity of the regenerated cationic polyester is not more than 0.55 dL / g; the intrinsic viscosity of the modified regenerated cationic polyester is not less than 0.60 dL / g; the heat preservation temperature is set to be T, and T is larger than or equal to 180 DEG C and smaller than the vicat softening temperature of the regenerated cationic polyester. After the regenerated cationic polyester with low intrinsic viscosity is subjected to heat preservation at a certain temperature for a period of time, the intrinsic viscosity of the regenerated cationic polyester can be obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of polyesters and relates to a modification method for regenerated cationic polyester. Background Art

[0002] Polyester, including polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc., is widely used in beverage bottles, shoes and clothing, packaging materials and other fields. Polyester has been recycled and reused in large quantities, and my country's current PET recycling has exceeded 6 million tons per year. Cationic polyester has the characteristics of good dyeability, bright color and high color fastness. Regenerated cationic polyester is mainly prepared by condensation reaction, such as the alcoholysis product ethylene glycol, terephthalic acid and sodium 5-sulfonate obtained by alcoholysis of waste polyester, and the modified components are subjected to polycondensation reaction. However, in practical applications, the molecular weight of the obtained regenerated cationic polyester is not high enough, and the intrinsic viscosity is difficult to reach 0.60 dL / g or above, generally 0.5-0.55 dL / g, which affects its application. Polyester fibers (such as polyester mother yarns) are required to have high mechanical strength. Therefore, when the molecular weight of the regenerated cationic polyester is not high enough, the mechanical strength of the obtained regenerated polyester fiber is not enough, which affects its use. Currently, the main method to increase the molecular weight of polyester is to add chain extenders, such as epoxy compounds, isocyanate compounds, etc. However, there are the following shortcomings: (1) The residual chain extender will affect the application of polyester; (2) It is easy to over-react and cause adverse consequences such as cross-linking.

[0003] Therefore, it is necessary to further study the chain extension process of the existing regenerated cationic polyester resin. Summary of the invention

[0004] The applicant unexpectedly discovered that after treating the regenerated cationic polyester at high temperature for a period of time, the intrinsic viscosity of the polyester increases, and the mother yarn obtained after spinning has a higher mechanical strength. Based on this, the present invention provides a modification method for regenerated cationic polyester.

[0005] The technical solution of the present invention is as follows:

[0006] A method for modifying a regenerated cationic polyester, wherein the regenerated cationic polyester is kept warm for 10-20 hours to obtain a modified regenerated cationic polyester;

[0007] The intrinsic viscosity of the regenerated cationic polyester is no more than 0.55 dL / g;

[0008] The intrinsic viscosity of the modified regenerated cationic polyester is not less than 0.60 dL / g;

[0009] Assuming that the insulation temperature is T, 180°C≤T<the Vicat softening temperature of the regenerated cationic polyester.

[0010] Preferably, the regenerated cationic polyester is selected from regenerated cationic polyethylene terephthalate and / or regenerated cationic polybutylene terephthalate.

[0011] Preferably, the heat preservation is carried out in a rotary drum dryer.

[0012] More preferably, the relative humidity in the drum dryer does not exceed 30%.

[0013] Preferably, the insulation temperature T is 10° C. or more lower than the Vicat softening temperature of the regenerated cationic polyester.

[0014] Preferably, the regenerated cationic polyester is dried in advance at a temperature not exceeding 150° C. to a moisture content not exceeding 50 ppm.

[0015] More preferably, dry gas is introduced into the drum dryer during the heat preservation.

[0016] More preferably, the calculation method of the amount of dry gas introduced is as shown in the following formula (1):

[0017] k=α×M×V (1)

[0018] Where k is the amount of dry gas introduced, in m 3 / h; α is the coefficient, α=0.3-0.6, unit is (h·kg) -1 ; M is the weight of the regenerated cationic polyester, in kg; V is the volume of the drum dryer, in m 3 .

[0019] Further preferably, the temperature of the drying gas is between 180° C. and the insulation temperature T, and the water content of the drying gas does not exceed 50 ppm.

[0020] Further preferably, the drying gas is dry air.

[0021] The beneficial effects of the present invention are:

[0022] (1) In the present invention, after the regenerated cationic polyester is treated at a certain temperature for a period of time, the modified regenerated cationic polyester obtained has a higher intrinsic viscosity than that before the treatment, and the fiber obtained after spinning also has a higher mechanical strength.

[0023] (2) During the heat preservation treatment of the present invention, dry gas may be further introduced, which is beneficial to further improve the treatment effect and further increase the intrinsic viscosity of the modified regenerated cationic polyester. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further illustrated and described below through specific implementation methods.

[0025] In order to improve the intrinsic viscosity of the regenerated cationic polyester, the present invention provides a modification method of the regenerated cationic polyester, wherein the regenerated cationic polyester is kept warm for 10-20 hours to obtain the modified regenerated cationic polyester;

[0026] The intrinsic viscosity of the regenerated cationic polyester is no more than 0.55 dL / g;

[0027] The intrinsic viscosity of the modified regenerated cationic polyester is not less than 0.60 dL / g;

[0028] Assuming the holding temperature is T, 180°C ≤ T < the Vicat softening temperature of the regenerated cationic polyester.

[0029] The present invention unexpectedly found that when the intrinsic viscosity of the regenerated cationic polyester is not high enough, the intrinsic viscosity can be increased after heat preservation treatment at a certain temperature for a period of time, thereby improving the mechanical strength of the spun fiber (such as mother yarn or filament). In the present invention, the Vicat softening temperature can be tested according to the method of GB / T1633-2000 "Determination of Vicat softening temperature (VST) of thermoplastics", and the Vicat softening temperature of the regenerated cationic polyester is 220-240°C. For example, when the softening temperature of the regenerated cationic polyester is 220°C, the insulation temperature T can be any value among 180°C, 190°C, 200°C, 210°C, 220°C, etc., and the insulation time can be any value among 10h, 12h, 15h, 17h, 18h, 20h, etc.; when the softening temperature of the regenerated cationic polyester is 230°C, the insulation temperature T can be any value among 190°C, 200°C, 210°C, 220°C, 230°C, etc., and the insulation time can be any value among 10h, 12h, 15h, 17h, 18h, 20h, etc. The present invention finds that both the insulation temperature and the insulation time must be sufficient to improve the intrinsic viscosity of the regenerated cationic polyester. If the insulation temperature is not enough or the insulation time is insufficient, the effect of improving the intrinsic viscosity of the regenerated cationic polyester is not obvious. For example, when the insulation conditions are 160°C×8h, 160°C×12h, 190°C×5h, 190°C×8h, etc., the effect of improving the intrinsic viscosity of the regenerated cationic polyester is not obvious. If the insulation temperature is too high, it may cause the slices or particles to stick together or thermally degrade (for example, the regenerated cationic polyester on the surface of the slices or particles is thermally degraded, which will further cause adhesion). The effect of continuing to extend the insulation time on continuing to increase the intrinsic viscosity is not obvious, which will cause a waste of resources.

[0030] In the present invention, the preparation method of the regenerated cationic polyester is not particularly limited. It can be obtained by co-condensation reaction of ethylene glycol, terephthalic acid and sodium 5-sulfoisophthalic acid in the presence of a catalyst, wherein the amount of sodium 5-sulfoisophthalic acid can be 1-2% of the weight of the reaction raw materials, or by co-condensation reaction of bis(hydroxyethyl)terephthalate BHET and sodium 5-sulfoisophthalic acid in the presence of a catalyst, wherein the amount of sodium 5-sulfoisophthalic acid can be 1-2% of the weight of the reaction raw materials. For example, Chinese patent CN115141363A discloses the above method. Appropriate amounts of antioxidants and nucleating agents can also be added to the regenerated cationic polyester, which is well known to those skilled in the art.

[0031] In the present invention, the test method for the intrinsic viscosity of the regenerated cationic polyester and the modified regenerated cationic polyester is tested according to T / CCFA00011-2021 "Test Method for Intrinsic Viscosity of Recycled Polyester (PET)", the solvent is composed of phenol and 1,1,2,2-tetrachloroethane in a weight ratio of 1:1, and the heating dissolution temperature is 110°C.

[0032] In some embodiments, the recycled cationic polyester is selected from recycled cationic polyethylene terephthalate (recycled cationic PET) and / or recycled cationic polybutylene terephthalate (recycled cationic PBT). Further, the recycled cationic polyester is selected from recycled cationic PET.

[0033] In some embodiments, the heat preservation is performed in a drum dryer. The regenerated cationic polyester is dried in the drum dryer, and the polyester in the drum dryer can be continuously turned over as the drum rotates, thereby improving the heating and heat preservation effect, making the heating and heat preservation more uniform, and avoiding local overheating caused by local heat accumulation. The rotation speed of the drum can be 5-120 rpm.

[0034] In some embodiments, the relative humidity in the drum dryer does not exceed 30%. If the relative humidity in the drum dryer is too high, the regenerated cationic polyester may be degraded at the holding temperature, thereby reducing the intrinsic viscosity. For example, the relative humidity in the drum dryer may be any value of 30%, 25%, 20%, 15%, etc.

[0035] In some embodiments, the heat preservation temperature T is 10°C or more lower than the Vicat softening temperature of the regenerated cationic polyester, such as 10°C, 12°C, 15°C, etc. The heat preservation temperature T is within the above range, which can avoid the regenerated cationic polyester chips or particles from sticking or agglomerating due to the softening of the regenerated cationic polyester during heat preservation. For example, if the Vicat softening temperature of the regenerated cationic polyester is 230°C, the heat preservation temperature T can be 10°C, 15°C, 20°C, etc. lower than the Vicat softening temperature. For example, the heat preservation temperature T can be any value of 180°C, 185°C, 190°C, 200°C, 210°C, 215°C, etc.

[0036] In some embodiments, the regenerated cationic polyester is pre-dried at a temperature not exceeding 150° C. to a moisture content not exceeding 50 ppm. Pre-drying the regenerated cationic polyester to a certain moisture content can avoid thermal degradation in the subsequent heat preservation stage. For example, the moisture content of the regenerated cationic polyester after pre-drying can be any value of 50 ppm, 40 ppm, 30 ppm, etc.

[0037] In some embodiments, dry gas is introduced into the drum dryer during the heat preservation process. The introduction of dry gas can promote the temperature uniformity of the heating and heat preservation process.

[0038] In some embodiments, the method for calculating the amount of dry gas introduced is as shown in the following formula (1):

[0039] k=α×M×V (1)

[0040] Where k is the amount of dry gas introduced, in m 3 / h; α is the coefficient, α=0.3-0.6, unit is (h·kg) -1 ; M is the weight of the regenerated cationic polyester, in kg; V is the volume of the drum dryer, in m 3 The present invention finds that the amount of drying gas introduced cannot be too large or too small. If it is too large, the regenerated cationic polyester chips or particles may adhere or aggregate due to surface softening, affecting subsequent applications or causing waste of gas; if it is too small, the effect is not obvious.

[0041] In some embodiments, the temperature of the drying gas is between 180°C and the insulation temperature T, and the water content of the drying gas does not exceed 50ppm. The temperature of the drying gas is between 180°C and the insulation temperature T, which is more conducive to the insulation effect. For example, when the insulation temperature T is 200°C, the temperature of the drying gas is between 180-200°C, and can be any value of 180°C, 190°C, 200°C, etc.; when the insulation temperature T is 210°C, the temperature of the drying gas is between 180-210°C, and can be any value of 180°C, 190°C, 200°C, 210°C, etc. Further, the temperature of the drying gas is the insulation temperature T.

[0042] In some embodiments, the dry gas is dry air, which is widely available and has low cost.

[0043] The technical solution of the present invention is further described and illustrated according to various embodiments below. Unless otherwise specified, the parts described in the following embodiments are parts by weight.

[0044] Example 1

[0045] The regenerated cationic polyester chips were prepared according to the method of the example of the prior art CN115141363A. The intrinsic viscosity of the regenerated cationic polyester chips was 0.55 dL / g, and the Vicat softening temperature was 235°C.

[0046] The regenerated cationic polyester chips were dried in advance at 140° C. to a water content of 40 ppm.

[0047] 10 kg of the dried regenerated cationic polyester chips were placed in a 190°C inner cylinder with a volume of 0.5 m 3 The chips were placed in a drum dryer, i.e. the insulation temperature of the chips was 190°C, the drum dryer was filled with dry air with a relative humidity of 20%, the rotation speed was 20 rpm, the insulation time was 15 hours, and then cooled to room temperature to obtain modified regenerated cationic polyester chips. The intrinsic viscosity of the modified regenerated cationic polyester chips was measured to be 0.618 dL / g.

[0048] Example 2

[0049] The difference between this embodiment and embodiment 1 is that in embodiment 1, the holding time is adjusted from 15 hours to 10 hours, and the other steps remain unchanged. The intrinsic viscosity of the obtained modified regenerated cationic polyester chips is 0.611 dL / g.

[0050] Example 3

[0051] The difference between this embodiment and embodiment 1 is that in embodiment 1, the holding time is adjusted from 15 hours to 20 hours, and the other steps remain unchanged. The intrinsic viscosity of the obtained modified regenerated cationic polyester chips is 0.624 dL / g.

[0052] Comparative Example 1

[0053] The difference between this comparative example and Example 1 is that in Example 1, the heat preservation time is adjusted from 15 hours to 8 hours, and the other steps remain unchanged. The intrinsic viscosity of the obtained modified regenerated cationic polyester chips is 0.577 dL / g.

[0054] Comparative Example 2

[0055] The difference between this comparative example and comparative example 1 is that in comparative example 1, the temperature in the drum dryer is adjusted from 190°C to 220°C, that is, the insulation temperature is adjusted from 190°C to 220°C, and the other steps remain unchanged. The intrinsic viscosity of the obtained modified regenerated cationic polyester chips is 0.584 dL / g.

[0056] Comparative Example 3

[0057] The difference between this comparative example and Example 1 is that in Example 1, the temperature in the drum dryer is adjusted from 190°C to 170°C, that is, the insulation temperature is adjusted from 190°C to 170°C, and the other steps remain unchanged. The intrinsic viscosity of the modified regenerated cationic polyester chips obtained is 0.556 dL / g.

[0058] Comparative Example 4

[0059] The difference between this comparative example and Example 1 is that in Example 1, the temperature in the drum dryer is adjusted from 190°C to 235°C, that is, the insulation temperature is adjusted from 190°C to 235°C, and the other steps remain unchanged. The obtained modified regenerated cationic polyester chips have obvious adhesion, and the measured intrinsic viscosity is 0.583 dL / g.

[0060] Example 4

[0061] The difference between this embodiment and embodiment 1 is that in embodiment 1, the temperature in the drum dryer is adjusted from 190°C to 180°C, that is, the insulation temperature is adjusted from 190°C to 180°C, and the other steps remain unchanged. The intrinsic viscosity of the obtained modified regenerated cationic polyester chips is 0.610 dL / g.

[0062] Example 5

[0063] The difference between this embodiment and embodiment 1 is that in embodiment 1, the temperature in the drum dryer is adjusted from 190°C to 220°C, that is, the insulation temperature is adjusted from 190°C to 220°C, and the other steps remain unchanged. The intrinsic viscosity of the modified regenerated cationic polyester chips obtained is 0.625 dL / g.

[0064] Example 6

[0065] The difference between this embodiment and embodiment 1 is that in embodiment 1, the temperature in the drum dryer is adjusted from 190°C to 210°C, that is, the insulation temperature is adjusted from 190°C to 210°C, and the insulation time is adjusted from 15h to 12h, and the other steps remain unchanged. The intrinsic viscosity of the modified regenerated cationic polyester chips obtained is 0.622dL / g.

[0066] Example 7

[0067] The difference between this embodiment and embodiment 6 is that in embodiment 6, the holding time is adjusted from 12 hours to 16 hours, and the other steps remain unchanged. The intrinsic viscosity of the obtained modified regenerated cationic polyester chips is 0.625 dL / g.

[0068] Example 8

[0069] 10 kg of the dried regenerated cationic polyester chips of Example 1 were placed in an inner cylinder with a volume of 0.5 m2 at 205°C. 3 The chips were placed in a drum dryer, i.e., the insulation temperature of the chips was 205°C, the drum dryer was filled with dry air with a relative humidity of 25%, the rotation speed was 20 rpm, the insulation time was 13 h, and then cooled to room temperature to obtain modified regenerated cationic polyester chips. The intrinsic viscosity of the modified regenerated cationic polyester chips was measured to be 0.620 dL / g.

[0070] Example 9

[0071] The difference between this embodiment and embodiment 8 is that in embodiment 8, the dry air filled with a relative humidity of 25% is adjusted to a relative humidity of 25% and 205°C dry air, which is continuously and evenly introduced into the drum dryer at a flow rate of 1.5 m 3 / h, and the other steps remain unchanged. The intrinsic viscosity of the modified regenerated cationic polyester chips is 0.626 dL / g.

[0072] Example 10

[0073] The difference between this embodiment and embodiment 9 is that the amount of dry air introduced is increased from 1.5m 3 / h adjusted to 3m 3 / h, and the other steps remain unchanged. The intrinsic viscosity of the modified regenerated cationic polyester chips is 0.623 dL / g.

[0074] Comparative Example 5

[0075] The difference between this comparative example and Example 10 is that the temperature of the introduced dry air is adjusted from 205°C to room temperature, and the relative humidity is still 25°C. The other steps remain unchanged. The intrinsic viscosity of the modified regenerated cationic polyester chips is 0.536 dL / g, which may be due to the high water content of the room temperature gas introduced, resulting in thermal degradation of the regenerated cationic polyester chips at high temperature.

[0076] The modified regenerated cationic polyester chips obtained in the above Examples 1-10 and Comparative Examples 1-5 were spun using a twin-screw melt extrusion spinning process to obtain 40D×12F mother yarns. The melt spinning temperature was 265-275°C and the winding speed was 3500m / min. The mechanical strength of different mother yarns was tested using an INSTRON-1122 tensile testing machine, and the results are shown in Table 1 below.

[0077] Table 1

[0078]

[0079] Therefore, based on the above embodiments and results, the present invention can improve the intrinsic viscosity and the mechanical strength of the spun fiber by keeping the regenerated cationic polyester with low intrinsic viscosity at a certain temperature for a certain period of time.

[0080] As described above, the basic principles, main features and advantages of the present invention are shown and described. Those skilled in the art should understand that the present invention is not limited by the above embodiments, which are only preferred embodiments of the present invention and cannot be used to limit the scope of the present invention. That is, equivalent changes and modifications made according to the scope of the present invention and the content of the specification should still be within the scope of the present invention. The scope of protection required by the present invention is defined by the attached claims and their equivalents.

Claims

1. A modification method for regenerating cationic polyester, characterized in that: The regenerated cationic polyester is kept warm for 10-20 hours to obtain a modified regenerated cationic polyester; The intrinsic viscosity of the regenerated cationic polyester is no more than 0.55 dL / g; The intrinsic viscosity of the modified regenerated cationic polyester is not less than 0.60 dL / g; Assuming that the insulation temperature is T, 180°C≤T<the Vicat softening temperature of the regenerated cationic polyester.

2. The modification method of regenerated cationic polyester according to claim 1, characterized in that: The regenerated cationic polyester is selected from regenerated cationic polyethylene terephthalate and / or regenerated cationic polybutylene terephthalate.

3. The modification method of regenerated cationic polyester according to claim 1, characterized in that: The heat preservation is carried out in a drum dryer.

4. The modification method of regenerated cationic polyester according to claim 3, characterized in that: The relative humidity in the drum dryer does not exceed 30%.

5. The modification method of regenerated cationic polyester according to claim 1, characterized in that: The insulation temperature T is 10° C. or more lower than the Vicat softening temperature of the regenerated cationic polyester.

6. The modification method of regenerated cationic polyester according to claim 1, characterized in that: The regenerated cationic polyester is previously dried at a temperature not exceeding 150° C. to a moisture content not exceeding 50 ppm.

7. The modification method of regenerated cationic polyester according to claim 3, characterized in that: During the heat preservation, dry gas is introduced into the drum dryer.

8. The modification method of regenerated cationic polyester according to claim 7, characterized in that: The calculation method of the amount of dry gas introduced is as shown in the following formula (1): k=α×M×V (1) Where k is the amount of dry gas introduced, in m 3 / h; α is the coefficient, α=0.3-0.6, unit is (h·kg) -1 ; M is the weight of the regenerated cationic polyester, in kg; V is the volume of the drum dryer, in m 3 .

9. The modification method of regenerated cationic polyester according to claim 7, characterized in that: The temperature of the drying gas is between 180° C. and the insulation temperature T, and the water content of the drying gas does not exceed 50 ppm.

10. The modification method of regenerated cationic polyester according to claim 7, characterized in that: The drying gas is dry air.

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