PBT polyester chip with controllable transparency and preparation method thereof

Abstract

The invention relates to the technical field of PBT polyester, in particular to a PBT polyester chip with controllable transparency and a preparation method thereof. The preparation method comprises the following steps: firstly adding dimethyl terephthalate and dimethyl isophthalate, then adding butanediol and 1, 4-cyclohexanedimethanol, then adding a manganese acetate catalyst and a dispersing agent, mixing, and after mixing, sequentially carrying out ester exchange reaction and polycondensation reaction to prepare the PBT polyester chip. According to the preparation method disclosed by the invention, DMT, DMI, BDO and CHDM are synchronously subjected to ester exchange to produce BHBT (Bis (4-hydroxybutyl) phthalate), and the PBT slices with controllable transparency are prepared through polymerization, so that the preparation method is few in side reaction, and the prepared product is high in quality. The transparency of the slice is adjusted by adjusting the mass ratio of the raw materials, and yarns with excellent gloss and transparency can be obtained after conventional spinning and stretching.

Description

Technical Field

[0001] The present invention relates to the technical field of PBT polyesters, and specifically relates to a PBT polyester chip with controllable transparency and a preparation method thereof. Background Art

[0002] PBT (polybutylene terephthalate) has high strength, good electrical insulation, and good chemical corrosion resistance, and is widely used in clothing, electronic appliances, and chemical environments. In some specific applications, strict requirements are imposed on the transparency of the yarn, and the polyester fiber needs to be treated to improve transparency.

[0003] Currently, the methods for improving the transparency of fabrics mainly include the following: ① Reducing or not adding titanium dioxide to prepare highly lustrous polyester fibers. For example, the Chinese utility model patent with the publication number CN217455241U discloses that a polyester film without added sunscreen additives has a transparent characteristic; the polyester fibers prepared by this method are relatively conventional, but the improvement in transparency is limited. ② Thinning the fabric, reducing the fiber linear density, or reducing the number of weaving fiber filaments. Although these methods improve transparency, as the fabric is thinned, the linear density is reduced, and the number of fabric filaments is reduced, the physical properties of the finished product will also be correspondingly reduced. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: to provide a PBT polyester chip with controllable transparency and a preparation method thereof, and the chip can achieve high transparency.

[0005] To solve the above technical problem, the technical solution adopted by the present invention is: a preparation method of a PBT polyester chip with controllable transparency, comprising the following steps: first adding dimethyl terephthalate (DMT) and dimethyl isophthalate (DMI), then adding butanediol (BDO) and 1,4 - cyclohexanedimethanol (CHDM), and then adding manganese acetate catalyst and dispersant for mixing. After mixing, transesterification reaction and polycondensation reaction are carried out in sequence to prepare the PBT polyester chip.

[0006] Another technical solution adopted by the present invention is: a PBT polyester chip prepared by using the above preparation method of the PBT polyester chip with controllable transparency.

[0007] The beneficial effects of the present invention are as follows: The preparation method of the present invention can simultaneously carry out transesterification of DMT, DMI, BDO, and CHDM to produce BHBT (bis(4 - hydroxybutyl) terephthalate) and obtain a PBT chip with controllable transparency through polymerization. This preparation method has few side reactions and the prepared product has high quality. The transparency of the chip can be adjusted by adjusting the mass ratio of raw materials, and yarns with excellent gloss and transparency can be obtained after conventional spinning and stretching. Description of the Drawings

[0008] Figure 1 This is the finished product diagram of slices with different transparencies in the embodiments of the present invention. From left to right, they are the opaque state, the semi-transparent state, and the transparent state. Detailed implementation manners

[0009] To describe the technical content, achieved objectives, and effects of the present invention in detail, the following is described in conjunction with the implementation manners and accompanied by the drawings.

[0010] A method for preparing PBT polyester slices with controllable transparency includes the following steps: First, dimethyl terephthalate and dimethyl isophthalate are added, then butanediol and 1,4-cyclohexanedimethanol are added, and then manganese acetate catalyst and dispersant are added for mixing. After mixing, transesterification reaction and polycondensation reaction are carried out in sequence to prepare PBT polyester slices.

[0011] As can be seen from the above description, the beneficial effects of the present invention are as follows: The preparation method of the present invention uses dimethyl terephthalate, dimethyl isophthalate, butanediol, and 1,4-cyclohexanedimethanol as raw materials, and carries out transesterification reaction and polycondensation reaction in sequence to prepare PBT polyester slices. By adjusting the raw material ratio, the transparency of the slices can be controlled, and yarns with high permeability and high brightness can be prepared. The present invention uses the DMT method to produce modified BHBT to replace the conventional PTA (terephthalic acid) method process for producing BHBT. The transesterification in the DMT method can be achieved under normal pressure, the side reactions generated are reduced, and the product quality and production safety are improved, and the production cost is saved.

[0012] Among them, two raw materials, DMI and CHDM, are copolymerized, and the dispersant can promote the dispersion of DMI reactants in the polymer and improve the reaction efficiency.

[0013] Further, the mass ratio of dimethyl terephthalate to dimethyl isophthalate ≥ 7 / 3.

[0014] Further, the mass ratio of butanediol to 1,4-cyclohexanedimethanol ≥ 7 / 3.

[0015] Further, the ratio of the total molar number of dimethyl terephthalate and dimethyl isophthalate to the total molar number of butanediol and 1,4-cyclohexanedimethanol is 1:1.1 - 2. That is, n(DMT + DMI):n(BDO + CHDM) = 1:1.1 - 2. As can be seen from the above description, excessive addition of DMI will affect the thermal stability of PBT, and may lead to a decrease in the thermal stability of the material during the processing. The addition of DMI and CHDM will reduce the crystallization ability of PBT and affect its mechanical properties and heat resistance. From the perspective of cost-effectiveness, excessive addition of CHDM will also increase the production cost without correspondingly improving the product performance, thus affecting the economy of the product.

[0016] Furthermore, the temperature of the transesterification reaction is 180 - 230 °C.

[0017] As can be seen from the above description, the catalyst tetrabutyl titanate for the polycondensation reaction reacts with water, rendering the catalyst ineffective. The conventional PTA method will generate water during the reaction, while the DMT method of the present invention does not produce water, and the temperature of the transesterification reaction is set at 180 - 230 °C. Residual water during the reaction process is evaporated completely to avoid the formation of titanium dioxide due to the inactivation of tetrabutyl titanate, further improving transparency.

[0018] Furthermore, the temperature of the polycondensation reaction is 250 - 260 °C.

[0019] As can be seen from the above description, too high a polycondensation temperature will lead to intensified thermal degradation, and too low a temperature cannot carry out polymerization.

[0020] Furthermore, the addition amount of the dispersant is 250 - 350 ppm.

[0021] As can be seen from the above description, the dispersant can be any commercially available model. Adding a dispersant can better promote the dispersion of the solution and improve the reaction rate. If too much dispersant is added, it will lead to a relatively high content of polyester impurities, affecting the slice hue and spinnability.

[0022] Furthermore, the addition amount of the manganese acetate catalyst is 350 - 450 ppm.

[0023] Furthermore, tetrabutyl titanate and trimethyl phosphate are added after the transesterification reaction is completed, and then the polycondensation reaction is carried out.

[0024] As can be seen from the above description, tetrabutyl titanate is used as a catalyst, and trimethyl phosphate is used as a stabilizer.

[0025] Furthermore, the addition amount of tetrabutyl titanate is 300 - 700 ppm, and the addition amount of trimethyl phosphate is 50 - 500 ppm.

[0026] Another technical solution adopted by the present invention is: a PBT polyester slice prepared by using the preparation method of the PBT polyester slice with controllable transparency described above.

[0027] As can be seen from the above description, the yarn prepared from the PBT polyester slice of the present invention can have high transparency, opacity or semi - transparency.

[0028] Example 1 of the present invention is: a preparation method of a PBT polyester slice with controllable transparency, and the steps are as follows: S1: Charge DMT and DMI into a 100 L polymerization kettle, then add BDO and CHDM into the polymerization kettle, and further add 300 ppm manganese acetate catalyst and 400 ppm dispersant 7902 (manufacturer: Shanghai Puzhan Industrial Co., Ltd.). The mass ratio of DMT to DMI is 19 / 1, the mass ratio of BDO to CHDM is 19 / 1, and n(DMT + DMI):n(BDO + CHDM) = 1:1.3.

[0029] S2: Raise the temperature. When the reaction temperature rises to 180°C, start the stirrer (frequency: 30 HZ); when the reaction temperature rises to 180 - 190°C, remove water. As the temperature in the kettle rises, the temperature in the transesterification process tower and the top temperature increase. When it rises to 70°C, turn on the top cooling water to cool the rising methanol and BDO mixed gas, which goes out through the top of the tower and is condensed and collected. The boiling points of BDO and CHDM are relatively high, so they are cooled and refluxed back to the reaction kettle. When the temperature of the materials in the kettle rises to 225°C, the transesterification reaction ends, and weigh the discharge amount of methanol.

[0030] S3: After the transesterification reaction ends, control the kettle pressure at atmospheric pressure, add 400 ppm tetrabutyl titanate and 200 ppm trimethyl phosphate into the kettle, increase the stirrer frequency from 30 HZ to 50 HZ, continue to heat up to 255°C, and then reduce the frequency to 30 HZ until discharging when the power rises to 2.2 KW.

[0031] S4: After the polycondensation reaction is completed, close the vacuum extraction valve and the polycondensation outlet valve of the reaction kettle, and charge nitrogen into the reaction kettle to break the vacuum to atmospheric pressure; then open the outlet valve. When the melt flows out, cool the melt ester strips through chilled water and then introduce them into the cutting chamber for pelletizing, and then charge nitrogen at 0.2 Mpa for slicing. The obtained slices are observed to be opaque to the naked eye, see Figure 1 Left side view.

[0032] Example two of the present invention is as follows: The difference between example two and example one is only that: the mass ratio of DMT to DMI is 9 / 1, and the mass ratio of BDO to CHDM is 9 / 1; the obtained slices are observed to be translucent to the naked eye, see Figure 1 Middle view.

[0033] Example three of the present invention is as follows: The difference between example two and example one is only that: the mass ratio of DMT to DMI is 17 / 3, and the mass ratio of BDO to CHDM is 17 / 3; the obtained slices are observed to be translucent to the naked eye.

[0034] Example four of the present invention is as follows: Example 4 is only different from Example 1 in that the mass ratio of DMT to DMI is 4 / 1, and the mass ratio of BDO to CHDM is 4 / 1; the obtained slices are semi-transparent when observed with the naked eye.

[0035] Example 5 of the present invention is as follows: Example 5 is only different from Example 1 in that the mass ratio of DMT to DMI is 3 / 1, and the mass ratio of BDO to CHDM is 3 / 1; the obtained slices are transparent when observed with the naked eye, as shown in Figure 1 the right side view.

[0036] Example 6 of the present invention is as follows: Example 6 is only different from Example 1 in that the mass ratio of DMT to DMI is 7 / 3, and the mass ratio of BDO to CHDM is 7 / 3; the obtained slices are transparent when observed with the naked eye.

[0037] Comparative Example 1 of the present invention is as follows: Comparative Example 1 is only different from Example 1 in that DMI and CHDM are not added, and the obtained slices are opaque when observed with the naked eye.

[0038] Comparative Example 2 of the present invention is as follows: Comparative Example 2 is only different from Example 1 in that DMI is not added, and the obtained slices are opaque when observed with the naked eye.

[0039] Comparative Example 3 of the present invention is as follows: Comparative Example 3 is only different from Example 1 in that CHDM is not added, and the obtained slices are opaque when observed with the naked eye.

[0040] The products of Examples 1-6 and Comparative Examples 1-3 were tested, and the test results are shown in Table 1.

[0041] Table 1

[0042] Among them, the measurement method of viscosity was tested according to the provisions of GB / T14190-2017 capillary viscometer, and the solvent used was a phenol / tetrachloroethane solution with a mass ratio of 1:1.

[0043] The melting point was measured by the method specified in GB / T 14190-2017. Differential scanning calorimetry was used, and a DSC differential scanning calorimeter was employed to analyze the melting and crystallization behaviors of the polymer at a nitrogen flow rate of 50 mL / min and a mass of 3.5 mg. The sample was rapidly heated to 280 °C and held at this temperature for 3 min to eliminate the thermal history. Then, the sample was cooled from 280 °C to 25 °C at a rate of 10 °C / min to obtain the cooling curve. Finally, the sample was heated from 25 °C to 280 °C at the same temperature change rate to obtain the second heating curve, and the melting point value was read from the DSC curve.

[0044] The tensile strength was measured by the method specified in GB / T 1040.1-2018.

[0045] Example 7 of the present invention is as follows: The difference between Example 7 and Example 1 is only that: 250 ppm of manganese acetate catalyst and 350 ppm of dispersant were added, with n(DMT + DMI):n(BDO + CHDM) = 1:1.1; the transesterification reaction ended when the temperature of the materials in the kettle rose to 220 °C; the temperature of the polycondensation reaction was 250 °C.

[0046] Example 8 of the present invention is as follows: The difference between Example 8 and Example 1 is only that: 350 ppm of manganese acetate catalyst and 450 ppm of dispersant were added, with n(DMT + DMI):n(BDO + CHDM) = 1:2; the transesterification reaction ended when the temperature of the materials in the kettle rose to 230 °C; the temperature of the polycondensation reaction was 260 °C.

[0047] Example 9 of the present invention is: PBT polyester chips prepared by the preparation method of Example 1.

[0048] In summary, the PBT polyester chips with controllable transparency and the preparation method provided by the present invention have the following advantages: 1. Using DMT, DMI, BDO, and CHDM as raw materials, the transparency of the chips can be controlled by adjusting the raw material ratio. 2. The DMT method is used to prepare PBT polyester. Compared with the conventional PTA method, there are fewer side reactions and no water is generated, avoiding the inactivation of tetrabutyl titanate to form titanium dioxide, which can further improve the transparency.

[0049] 3. By limiting the addition ratio of DMI and CHDM, the mechanical properties and heat resistance of the product are not affected during the process of adjusting the transparency.

[0050] The above are only embodiments of the present invention, and do not thus limit the patent scope of the present invention. Any equivalent transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in the relevant technical fields, shall equally be included within the patent protection scope of the present invention.

Claims

1. A method for preparing PBT polyester chips with controllable transparency, characterized in that It includes the following steps: first, dimethyl terephthalate and dimethyl isophthalate are added, then butanediol and 1,4-cyclohexanedimethanol are added, and then manganese acetate catalyst and dispersant are added for mixing. After mixing, transesterification reaction and polycondensation reaction are carried out in sequence to prepare PBT polyester chips.

2. The preparation method of the PBT polyester chip with controllable transparency according to claim 1, characterized in that, The mass ratio of dimethyl terephthalate to dimethyl isophthalate ≥ 7 / 3.

3. The preparation method of the PBT polyester chips with controllable transparency according to claim 1, characterized in that, The mass ratio of butanediol to 1,4-cyclohexanedimethanol ≥ 7 / 3.

4. The preparation method of the PBT polyester chip with controllable transparency according to claim 1, characterized in that, The ratio of the total molar amount of dimethyl terephthalate and dimethyl isophthalate to the total molar amount of butanediol and 1,4-cyclohexanedimethanol is 1:1.1 - 2.

5. The preparation method of the PBT polyester chip with controllable transparency according to claim 1, characterized in that, The temperature of the transesterification reaction is 180 - 230 °C.

6. The preparation method of the PBT polyester chip with controllable transparency according to claim 1, characterized in that, The temperature of the polycondensation reaction is 250 - 260 °C.

7. The preparation method of the PBT polyester chip with controllable transparency according to claim 1, characterized in that, The addition amount of the dispersant is 250 - 350 ppm.

8. The method for preparing the PBT polyester chip with controllable transparency according to claim 1, characterized in that, The addition amount of the manganese acetate catalyst is 350 - 450 ppm.

9. The preparation method of the PBT polyester chip with controllable transparency according to claim 1, characterized in that, After the transesterification reaction is completed, tetrabutyl titanate and trimethyl phosphate are added, and then the polycondensation reaction is carried out.

10. PBT polyester chips prepared by using the preparation method of the PBT polyester chips with controllable transparency according to any one of claims 1 - 9.

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