Copolyester, preparation method thereof and transparent plastic product

Abstract

The invention relates to the field of special copolyesters, in particular to a copolyester, a preparation method thereof and a transparent plastic product. The preparation method of the copolyester comprises the following steps: esterifying binary acid and polyol to form an esterified product; carrying out prepolymerization on the esterification product to form a prepolymer; carrying out first polycondensation on the prepolymer to form a first polycondensation product; adding an anthraquinone coloring agent into the first polycondensation product, and carrying out second polycondensation to form copolyester; the temperature of the first polycondensation and the temperature of the second polycondensation are 260-320 DEG C respectively and independently; the time of the first polycondensation is 1-6 hours; the time of the second polycondensation is 0.5-2 hours. The anthraquinone coloring agent is introduced in the later stage of polycondensation, so that the copolyester with high mechanical strength, low yellowness and high brightness can be prepared, and the application of the polyester in the field with high transparency requirements is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of special copolyesters, in particular to a copolyester and a preparation method thereof, and a transparent plastic product. BACKGROUND

[0002] Transparent polyesters are widely used in various transparent plastic products, such as cosmetic packaging, water cups, medical devices, films, fibers, etc., due to their advantages in transparency, mechanical properties, chemical resistance, processing performance, and environmental performance. However, under high temperature conditions, polyesters are prone to thermal cracking, which leads to intermolecular chain breaks, resulting in a significant decrease in mechanical strength; and initiates side reactions to generate quinone substances and symmetrical diphenyl ethylene, making the product yellow and reducing the color phase, greatly limiting its application in high transparency requirements. Traditional improvement methods include adding phosphoric acid ester and other thermal stabilizers or cobalt salts to control the color phase, but the improvement of phosphoric acid ester and other thermal stabilizers on product yellowness is quite limited, while cobalt can improve yellowness but will cause a significant decrease in brightness, and cobalt as a heavy metal is limited in use, and the addition of phosphoric acid ester and other thermal stabilizers and cobalt salts usually leads to the degradation of the mechanical strength of the polyester. Therefore, the traditional modification method cannot prepare a polyester with high mechanical strength, low yellowness and high brightness at the same time. SUMMARY

[0003] Therefore, the main purpose of the present application is to provide a preparation method of a copolyester with high mechanical strength, low yellowness and high brightness at the same time, so as to realize the application of the polyester in the field of high transparency requirements.

[0004] In a first aspect, the present application provides a preparation method of a copolyester, comprising the following steps:

[0005] esterifying a dibasic acid and a polyhydric alcohol to form an esterification product;

[0006] prepolymerizing the esterification product to form a prepolymer;

[0007] first polycondensing the prepolymer to form a first polycondensation product;

[0008] adding an anthraquinone dyeing agent to the first polycondensation product to form a copolyester by second polycondensation;

[0009] The temperature of the first polycondensation and the second polycondensation is independently 260°C-320°C; the time of the first polycondensation is 1h-6h; and the time of the second polycondensation is 0.5h-2h.

[0010] In some embodiments, one or more of the following features is met:

[0011] (1) The pressure of the first polycondensation and the second polycondensation is independently 10Pa-100Pa;

[0012] (2) the diacid comprises at least one of terephthalic acid, isophthalic acid, phthalic acid, succinic acid, glutaric acid, adipic acid, and pimelic acid;

[0013] (3) the polyol comprises ethylene glycol and / or other polyol;

[0014] (4) the anthraquinone dye comprises one or more of a red anthraquinone dye, a blue anthraquinone dye, and a violet anthraquinone dye;

[0015] (5) the anthraquinone dye is added in an amount of 0.1 pg / g to 5 pg / g relative to the total mass of diacid and polyol.

[0016] In some embodiments, one or more of the following features are satisfied:

[0017] (1) the other polyol comprises one or more of diethylene glycol, 1,2-propanediol, 1,3-propanetriol, 1,4-cyclohexanedimethanol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, terephthalyl alcohol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, neopentyl glycol, isosorbide, isomannide, and polybutylene glycol;

[0018] (2) the polyol comprises ethylene glycol and other polyol; optionally, the molar ratio of ethylene glycol and other polyol is (0.5-10): 1;

[0019] (3) the red anthraquinone dye comprises one or more of solvent red 52, solvent red GS, pigment red 177, and disperse red 60;

[0020] (4) the blue anthraquinone dye comprises one or more of solvent blue 104, solvent blue 45, blue 2B, pigment blue 60, phthalocyanine blue, vat blue 4, blue 3R, solvent blue 136, disperse blue 72, and blue RR;

[0021] (5) the violet anthraquinone dye comprises one or more of violet 13, disperse violet 57, violet 3R, violet B, and solvent violet 31.

[0022] In some embodiments, the anthraquinone dye is a combination of a red anthraquinone dye and a blue anthraquinone dye, or a violet anthraquinone dye.

[0023] In some embodiments, the esterification conditions comprise one or more of the following features:

[0024] (1) the esterification is performed in the presence of a first catalyst;

[0025] (2) the temperature of the esterification is 220 °C to 260 °C;

[0026] (3) the esterification pressure is 200 kPa-300 kPa;

[0027] (4) the esterification time is 2 h-8 h;

[0028] (5) the molar ratio of the diacid to the polyol is 1:(1-2).

[0029] In some embodiments, the first catalyst comprises one or more of stannous octoate, stannous chloride, zinc acetate, cobalt acetate, lithium acetate, potassium acetate, calcium acetate, magnesium acetate, barium acetate, lead acetate, manganese acetate, antimony acetate, ethylene glycol antimony, antimony oxide, germanium dioxide, and phosphoric acid;

[0030] and / or the first catalyst is added in an amount of 5 pg / g-500 pg / g relative to the total mass of diacid and polyol.

[0031] In some embodiments, the pre-polymerization conditions comprise one or more of the following features:

[0032] (1) the pre-polymerization is performed in the presence of a second catalyst and a thermal stabilizer;

[0033] (2) the pre-polymerization temperature is 240 °C-300 °C;

[0034] (3) the pre-polymerization pressure is 150 Pa-250 Pa;

[0035] (4) the pre-polymerization time is 0.5 h-2 h.

[0036] In some embodiments, the pre-polymerization conditions comprise one or more of the following features:

[0037] (1) the second catalyst comprises one or more of antimony acetate, antimony oxide, ethylene glycol antimony, zirconium acetylacetonate, lanthanum acetylacetonate, bismuth (III) hexanoate, germanium dioxide, tetrabutyl titanate, and titanium tetraisopropoxide;

[0038] (2) the heat stabilizer comprises one or more of heat stabilizer 1010, heat stabilizer 1500, heat stabilizer 1076, heat stabilizer 425, heat stabilizer 330, heat stabilizer 1178, heat stabilizer 501, heat stabilizer 618, heat stabilizer 626, heat stabilizer 168, TDD, trimethyl phosphite, triethyl phosphite, triisooctyl phosphite, triisodecyl phosphite, trilauryl phosphite, tristricosyl phosphite, triphenyl phosphite, tri-p-tolyl phosphite, diphenyl tridecyl phosphite, tris (2, 4-di-t-butylphenyl) phosphite, bis (2, 4-di-t-butylphenyl) pentaerythritol diphosphite, bis (2, 4-di-p-isopropylphenyl) pentaerythritol diphosphite, pentaerythritol tetraphenyl tridecyl diphosphite, pentaerythritol dilauryl diphosphite, pentaerythritol diisodecyl diphosphite, pentaerythritol dioctadecyl diphosphite, phosphoric acid, phosphorous acid, polyphosphoric acid and triethyl phosphonoacetate;

[0039] (3) the second catalyst is added in an amount of 1 μg / g-100 μg / g relative to the total mass of the diacid and the polyol;

[0040] (4) the heat stabilizer is added in an amount of 100 μg / g-3000 μg / g relative to the total mass of the diacid and the polyol.

[0041] In a second aspect, the application provides a copolyester prepared by the preparation method of the first aspect.

[0042] In a third aspect, the application provides a transparent plastic product comprising the copolyester of the second aspect.

[0043] It is found that under high temperature conditions, the polyester is prone to thermal cracking, which causes the intermolecular chain to break, resulting in a significant decrease in mechanical strength; and initiates side reactions to generate quinone substances and p-phenylene vinylene, making the product yellow and reducing the color phase, which greatly limits its application in high transparency requirements.

[0044] Traditional improvement methods include adding phosphoric acid ester and other heat stabilizers or cobalt salts to control the color phase, but the improvement of the yellow degree of the product by the phosphoric acid ester and other heat stabilizers is quite limited, and although the yellow degree can be improved by the cobalt salt, the brightness is significantly reduced, and cobalt is a heavy metal, so its use is limited, and the addition of the phosphoric acid ester and other heat stabilizers and the cobalt salt usually causes the mechanical strength of the polyester to deteriorate. Therefore, the traditional modification method cannot prepare a polyester with high mechanical strength, low yellow degree and high brightness.

[0045] In addition, the hue can be adjusted by introducing the anthraquinone dyeing agent in-situ during the polyester polymerization process. However, the applicant has found that the anthraquinone dyeing agent has poor thermal stability, and is easily decomposed after high-temperature and long-time reaction, and the small molecule compounds generated thereby can cause color change, brightness decrease or odor generation, and result in the decrease of the mechanical properties of the polyester.

[0046] Based on this, the anthraquinone dyeing agent can be introduced in-situ into the copolyester by introducing the anthraquinone dyeing agent in the late stage of the polycondensation and continuing the polycondensation, while avoiding the degradation of the anthraquinone dyeing agent to generate small molecule substances, which adversely affect the yellowness, brightness and mechanical properties of the copolyester, so that the copolyester with high mechanical strength, low yellowness and high brightness can be prepared, and the application of the polyester in the field with high transparency requirement can be realized. DETAILED DESCRIPTION

[0047] The copolyester, the preparation method thereof, the transparent plastic product and the transparent plastic product of the present application will be further described in detail below in conjunction with specific examples. The present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein is only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0049] Herein, "one or more" means any one, any two or any two or more of the listed items.

[0050] In the present application, "first aspect", "second aspect", "third aspect", "fourth aspect" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth" and the like only serve the purpose of non-exhaustive enumeration description, and should be understood as not constituting a closed limitation on the quantity.

[0051] In the present application, the technical features described in an open manner include both the closed technical solution consisting of the listed features and the open technical solution containing the listed features.

[0052] In the present application, the numerical range is involved, such as without special instructions, the above numerical range is considered to be continuous, and includes the minimum value and the maximum value of the range, and each value between the minimum value and the maximum value. Further, when the range refers to an integer, each integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0053] In the present application, the percentage content involved, such as without special instructions, refers to mass percentage for solid-liquid mixing and solid-solid mixing, and refers to volume percentage for liquid-liquid mixing.

[0054] In the present application, the percentage concentration involved, such as without special instructions, refers to the final concentration. The final concentration refers to the proportion of the added ingredient in the system after the ingredient is added.

[0055] In the present application, the temperature parameter, such as without special limitation, allows both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument.

[0056] In the present application, the yellowness b* represents the position of the color on the yellow-blue axis, a positive value indicates yellow, the larger the value, the greater the yellowness, a negative value indicates blue, and the larger the absolute value, the bluer; the brightness L* represents the lightness (brightness) of the color, the larger the value, the greater the brightness, and the a* represents the position of the color on the red-green axis, a positive value indicates red, and a negative value indicates green.

[0057] In the present application, the addition amount of anthraquinone dyeing agent, first catalyst, second catalyst and heat stabilizer is relative to the total mass of diacid and polyol.

[0058] In some embodiments, the tensile strength of the copolyester is 45 MPa-52 MPa; the impact strength is 5 kJ / m 2 -12 kJ / m 2 .

[0059] In some embodiments, the copolyester has a light transmittance of 80%-92% and a haze of 0.3%-3.0%.

[0060] In the first aspect, some embodiments of the present application provide a preparation method of a copolyester, comprising the following steps:

[0061] Esterification of diacid and polyol to form an esterification product;

[0062] Prepolymerization of the esterification product to form a prepolymer;

[0063] carrying out a first polycondensation on the prepolymer to form a first polycondensation product;

[0064] adding an anthraquinone dyeing agent to the first polycondensation product, carrying out a second polycondensation to form a copolyester;

[0065] The temperature of the first polycondensation and the second polycondensation is independently 260-320°C; the time of the first polycondensation is 1-6h; the time of the second polycondensation is 0.5-2h.

[0066] The hue can be controlled by introducing the anthraquinone dyeing agent in situ during the polymerization of the polyester. However, the applicant found that the anthraquinone dyeing agent has poor thermal stability, and is easily decomposed after high-temperature and long-time reaction, and the small molecule compounds generated thereby can cause color change, brightness decrease or odor generation, and also cause the mechanical properties of the polyester to decrease.

[0067] The present application introduces the anthraquinone dyeing agent in the late stage of the polycondensation and continues the polycondensation, which can introduce the anthraquinone dyeing agent in situ into the copolyester, and at the same time avoid the degradation of the anthraquinone dyeing agent to generate small molecule substances, which adversely affect the yellowness, brightness and mechanical properties of the copolyester, so that the copolyester with high mechanical strength, low yellowness and high brightness can be prepared, and the application of the polyester in the field with high transparency requirement can be realized.

[0068] In some embodiments, the temperature of the first polycondensation and the second polycondensation can be 260°C, 270°C, 280°C, 300°C, 310°C, 320°C, etc.; the time of the first polycondensation can be 1h, 2h, 3h, 4h, 5h, 6h, etc.; and the time of the second polycondensation can be 0.5h, 1h, 1.5h, 2h, etc.

[0069] In some embodiments, the pressure of the first polycondensation and the second polycondensation is independently 10-100Pa, for example, 10Pa, 20Pa, 40Pa, 80Pa, 100Pa, etc. Controlling the pressure in the above range is beneficial to timely escape of small molecule products, promote the forward reaction, and obtain the copolyester with target molecular weight or degree of polymerization.

[0070] In some embodiments, the diacid includes at least one of terephthalic acid, isophthalic acid, phthalic acid, succinic acid, glutaric acid, adipic acid and pimelic acid. By adjusting the type of diacid, the performance of the polyester can be controlled, and the above diacids are beneficial to obtain the copolyester with better hue and mechanical properties.

[0071] In some embodiments, the polyol includes ethylene glycol and / or other polyols; optionally, the polyol includes ethylene glycol and other polyols; optionally, the other polyols include one or more of diethylene glycol, 1,2-propanediol, 1,3-propanetriol, 1,4-cyclohexanedimethanol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, p-xyleneglycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, neopentyl glycol, isosorbide, isomannide, and polybutylene glycol; the molar ratio of the ethylene glycol and other polyols is (0.5-10):1, such as 0.5:1, 1:1, 2:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc. By adjusting the type and ratio of the polyols, the properties of the polyester can be controlled. The above polyols are conducive to preparing copolyesters with good color and mechanical properties.

[0072] In some embodiments, the anthraquinone dye includes one or more of a red anthraquinone dye, a blue anthraquinone dye, and a purple anthraquinone dye; optionally, the anthraquinone dye is a combination of a red anthraquinone dye and a blue anthraquinone dye, or a purple anthraquinone dye; the anthraquinone dye includes one or more of a red anthraquinone dye, a blue anthraquinone dye, and a purple anthraquinone dye; the red anthraquinone dye includes one or more of solvent red 52, solvent red GS, pigment red 177, and disperse red 60; the blue anthraquinone dye includes one or more of solvent blue 104, solvent blue 45, blue 2B, pigment blue 60, phthalocyanine blue, vat blue 4, blue 3R, solvent blue 136, disperse blue 72, and blue RR; the purple anthraquinone dye includes one or more of violet 13, disperse violet 57, violet 3R, violet B, and solvent violet 31. The above anthraquinone dyes can react with the active groups of the polyester, and be introduced into the polymer structure of the polyester in situ during polymerization, thereby improving the yellowness and brightness of the polyester.

[0073] In some embodiments, the addition amount of the anthraquinone dye is 0.1 μg / g-5 μg / g, such as 0.1 μg / g, 0.2 μg / g, 0.3 μg / g, 0.5 μg / g, 1 μg / g, 1.5 μg / g, 1.8 μg / g, 2 μg / g, 3 μg / g, 4 μg / g, 5 μg / g, etc., relative to the total mass of the diacid and polyol. Controlling the content of the anthraquinone dye in the above range is conducive to balancing the cost and product color.

[0074] In some embodiments, the esterification is carried out in the presence of a first catalyst; the first catalyst comprises one or more of stannous octoate, stannous chloride, zinc acetate, cobalt acetate, lithium acetate, potassium acetate, calcium acetate, magnesium acetate, barium acetate, lead acetate, manganese acetate, antimony acetate, ethylene glycol antimony, antimony oxide, germanium dioxide, and phosphoric acid; the first catalyst is added in an amount of 5 μg / g to 500 μg / g, for example 5 μg / g, 10 μg / g, 50 μg / g, 100 μg / g, 200 μg / g, 300 μg / g, 400 μg / g, 500 μg / g, etc., relative to the total mass of the diacid and the polyol. The above catalysts have suitable catalytic activity, and controlling the amount within the above range can take into account both reaction stability and reaction efficiency.

[0075] In some embodiments, the esterification is carried out at a temperature of 220 °C to 260 °C, for example 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, etc.; a pressure of 200 kPa to 300 kPa; a time of 2 h to 8 h, for example 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, etc.; and a molar ratio of the diacid to the polyol of 1: (1-2), for example 1:1, 1:1.1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, etc. Controlling the esterification conditions within the above ranges is conducive to taking into account both reaction stability and reaction efficiency.

[0076] In some embodiments, the prepolymerization is carried out in the presence of a second catalyst and a thermal stabilizer; the second catalyst comprises one or more of antimony acetate, antimony oxide, ethylene glycol antimony, zirconium acetylacetonate, lanthanum acetylacetonate, bismuth (III) hexanoate, germanium dioxide, tetrabutyl titanate, and titanium tetraisopropoxide; the second catalyst is added in an amount of 1 μg / g to 100 μg / g, for example 1 μg / g, 5 μg / g, 10 μg / g, 30 μg / g, 50 μg / g, 80 μg / g, 90 μg / g, 100 μg / g, etc., relative to the total mass of the diacid and the polyol; the above second catalysts have suitable catalytic activity, and controlling the amount within the above range is conducive to improving reaction efficiency.

[0077] In some embodiments, the heat stabilizer includes one or more of heat stabilizer 1010, heat stabilizer 1500, heat stabilizer 1076, heat stabilizer 425, heat stabilizer 330, heat stabilizer 1178, heat stabilizer 501, heat stabilizer 618, heat stabilizer 626, heat stabilizer 168, TDD, trimethyl phosphite, triethyl phosphite, triisooctyl phosphite, triisodecyl phosphite, trilauryl phosphite, tristricosyl phosphite, triphenyl phosphite, tri-p-tolyl phosphite, diphenyl tridecyl phosphite, tris (2,4-di-t-butylphenyl) phosphite, di (2,4-di-t-butylphenyl) pentaerythritol diphosphite, di (2,4-di-p-isopropylphenyl) pentaerythritol diphosphite, pentaerythritol tetraphenyl diphosphite, pentaerythritol diphosphite tridecyl, pentaerythritol diphosphite diisodecyl, pentaerythritol bis (octadecyl) phosphite, phosphoric acid, phosphorous acid, polyphosphoric acid, and triethyl phosphonoacetate. The heat stabilizer is added in an amount of 100 μg / g to 3000 μg / g, such as 100 μg / g, 200 μg / g, 500 μg / g, 1000 μg / g, 2000 μg / g, 3000 μg / g, 4000 μg / g, 5000 μg / g, etc., relative to the total mass of the diacid and the polyol. The above heat stabilizers have low color and good thermal stability, which is beneficial to the color and stability.

[0078] In some embodiments, the pre-polymerization is performed at a temperature of 240 °C to 300 °C, such as 240 °C, 250 °C, 260 °C, 280 °C, 290 °C, 300 °C, etc., at a pressure of 150 Pa to 250 Pa, and for a time period of 0.5 h to 2 h, such as 0.5 h, 1 h, 1.5 h, 2 h, etc. Controlling the pre-polymerization conditions in the above ranges is beneficial to controlling the reaction degree.

[0079] In a second aspect, some embodiments of the present application provide the copolyester prepared by the method of the first aspect.

[0080] In some embodiments, the copolyester has a yellowness b* of -3 to 1 and a lightness L* of 65 to 70.

[0081] In some embodiments, the copolyester has a tensile strength of 45 MPa to 52 MPa and an impact strength of 5 kJ / m 2 -12 kJ / m 2 .

[0082] In some embodiments, the copolyester has a light transmittance of 80% to 92% and a haze of 0.3% to 3.0%.

[0083] In a third aspect, some embodiments of the present application provide a transparent plastic product comprising the copolyester of the second aspect.

[0084] The experimental parameters not written in the following specific examples are preferably referred to the guidance given in the present application, and can also be referred to the experimental manuals in the art or other experimental methods known in the art, or to the experimental conditions recommended by the manufacturers.

[0085] The raw materials and reagents in the present application can be purchased through the market route if not specially stated.

[0086] Example 1

[0087] Preparation of the copolyester:

[0088] (1) 830 g (5 mol) of terephthalic acid, 310 g (5 mol) of ethylene glycol, 144 g (1 mol) of 1,4-cyclohexane dimethanol, and 180 μg / g of antimony acetate were added into a N2-protected reactor 1, and reacted at 220℃ under a pressure of 250 kPa for 4 h until the water yield reached more than 90%, to obtain an esterification product.

[0089] (2) 400 μg / g of heat stabilizer 1500, 100 μg / g of heat stabilizer 618, and 10 μg / g of tetrabutyl titanate were added into the esterification product, the pressure was reduced to 200 Pa, and the temperature was increased to 250℃, to perform a prepolymerization reaction for 1 h, to obtain a prepolymer.

[0090] (3) The prepolymer was heated to 280℃, the pressure was reduced to 10 Pa, and a first polycondensation reaction was performed for 2 h to form a first polycondensation product.

[0091] (4) 2.0 μg / g of blue RR and 1.0 μg / g of red 135 were added into the first polycondensation product, and the reaction was continued for 1 h. After the reaction was completed, the pressure was restored to normal pressure by nitrogen charging, and the product was discharged and pelletized to form a second polycondensation product.

[0092] Example 2

[0093] Except that 2.0 μg / g of violet B (instead of 2.0 μg / g of blue RR and 1.0 μg / g of red 135) was used as the anthraquinone dyeing agent, the rest was the same as in Example 1.

[0094] Example 3

[0095] Except that in step (3), the prepolymer was heated to 260℃, the reaction pressure was reduced to 100 Pa, and the reaction time was 6 h; and in step (4), the reaction was continued for 2 h, the rest was the same as in Example 1.

[0096] Example 4

[0097] Except that the prepolymer is heated to 320°C in step (3) and the reaction time is 1 h; and step (4) is continued for 0.5 h, the rest is the same as in Example 1.

[0098] Comparative Example 1

[0099] Except that anthraquinone dyeing agent is not added, the rest is the same as in Example 1, as follows:

[0100] (1) 830 g (5 mol) of terephthalic acid, 310 g (5 mol) of ethylene glycol, 144 g (1 mol) of 1,4-cyclohexane dimethanol, and 180 μg / g of antimony acetate were added to a reactor 1 protected by N2, and reacted at 220°C and a pressure of 250 kPa for 4 h until the water take-up reached more than 90%, to obtain an esterification product.

[0101] (2) 400 μg / g of heat stabilizer 1500, 100 μg / g of heat stabilizer 618, and 10 μg / g of tetrabutyl titanate were added to the esterification product, the pressure was reduced to 200 Pa, and the temperature was raised to 250°C to perform prepolymerization for 1 h, to obtain a prepolymer.

[0102] (3) The prepolymer was heated to 280°C, the pressure was reduced to 10 Pa, and polycondensation was performed for 3 h. After the reaction was completed, nitrogen was filled to restore the normal pressure, and the product was discharged and pelletized.

[0103] Comparative Example 2

[0104] Except that anthraquinone dyeing agent is not added, the rest is the same as in Example 1, as follows:

[0105] (1) 830 g (5 mol) of terephthalic acid, 310 g (5 mol) of ethylene glycol, 144 g (1 mol) of 1,4-cyclohexane dimethanol, 180 μg / g of antimony acetate, 2.0 μg / g of blue RR, and 1.0 μg / g of red 135 were added to a reactor 1 protected by N2, and reacted at 220°C and a pressure of 250 kPa for 4 h until the water take-up reached more than 90%, to obtain an esterification product.

[0106] (2) 400 μg / g of heat stabilizer 1500, 100 μg / g of heat stabilizer 618, and 10 μg / g of tetrabutyl titanate were added to the esterification product, the pressure was reduced to 200 Pa, and the temperature was raised to 250°C to perform prepolymerization for 1 h, to obtain a prepolymer.

[0107] (3) The prepolymer was heated to 280°C, the pressure was reduced to 10 Pa, and polycondensation was performed for 3 h. After the reaction was completed, nitrogen was filled to restore the normal pressure, and the product was discharged and pelletized.

[0108] Comparative Example 3

[0109] The rest is the same as Example 2, and specifically as follows:

[0110] (1) 830 g (5 mol) of terephthalic acid, 310 g (5 mol) of ethylene glycol, 144 g (1 mol) of 1,4-cyclohexane dimethanol, 180 μg / g of antimony acetate, 2.0 μg / g of violet B were added to a reactor 1 protected by N2, and reacted at 220°C under a pressure of 250 kPa for 4 h until the water take-up reached 90% or more, to obtain an esterification product.

[0111] (2) 400 μg / g of heat stabilizer 1500, 100 μg / g of heat stabilizer 618, and 10 μg / g of tetrabutyl titanate were added to the esterification product, the pressure was reduced to 200 Pa, and the temperature was raised to 250°C to perform prepolymerization for 1 h, to obtain a prepolymer.

[0112] (3) The prepolymer was raised to 280°C, the pressure was reduced to 10 Pa, and polycondensation was performed for 3 h. After the reaction was completed, nitrogen was filled to restore the normal pressure, and the product was discharged and pelletized.

[0113] Comparative Example 4

[0114] The rest is the same as Example 1, and specifically as follows:

[0115] (1) 830 g (5 mol) of terephthalic acid, 310 g (5 mol) of ethylene glycol, 144 g (1 mol) of 1,4-cyclohexane dimethanol, 180 μg / g of antimony acetate were added to a reactor 1 protected by N2, and reacted at 220°C under a pressure of 250 kPa for 4 h until the water take-up reached 90% or more, to obtain an esterification product.

[0116] (2) 400 μg / g of heat stabilizer 1500, 100 μg / g of heat stabilizer 618, 10 μg / g of tetrabutyl titanate, 2.0 μg / g of blue RR, and 1.0 μg / g of red 135 were added to the esterification product, the pressure was reduced to 200 Pa, and the temperature was raised to 250°C to perform prepolymerization for 1 h, to obtain a prepolymer.

[0117] (3) The prepolymer was raised to 280°C, the pressure was reduced to 10 Pa, and polycondensation was performed for 3 h. After the reaction was completed, nitrogen was filled to restore the normal pressure, and the product was discharged and pelletized.

[0118] Comparative Example 5

[0119] The rest is the same as Example 1, and specifically as follows:

[0120] (1) Into a N2-protected reactor 1, 830 g (5 mol) of terephthalic acid, 310 g (5 mol) of ethylene glycol, 144 g (1 mol) of 1,4-cyclohexane dimethanol, 180 μg / g of antimony acetate, and 20 μg / g of cobalt acetate were added, and the mixture was reacted at 220°C under a pressure of 250 kPa for 4 h until the water take-up reached 90% or more, to obtain an esterification product.

[0121] (2) Into the esterification product, 400 μg / g of heat stabilizer 1500, 100 μg / g of heat stabilizer 618, and 10 μg / g of tetrabutyl titanate were added, the pressure was reduced to 200 Pa, and the temperature was raised to 250°C, to perform a prepolymerization reaction for 1 h, to obtain a prepolymer.

[0122] (3) Into the prepolymer, 2.0 μg / g of blue RR and 1.0 μg / g of red 135 were added, the temperature was raised to 280°C, the pressure was reduced to 10 Pa, and a first polycondensation reaction was performed for 3 h. After the reaction was completed, the pressure was restored to normal pressure by nitrogen charging, and the product was discharged and pelletized.

[0123] Comparative Example 6

[0124] Except that cobalt acetate was added in the esterification stage instead of anthraquinone dyeing agent, the rest was the same as in Example 1, and the details were as follows:

[0125] (1) Into a N2-protected reactor 1, 830 g (5 mol) of terephthalic acid, 310 g (5 mol) of ethylene glycol, 144 g (1 mol) of 1,4-cyclohexane dimethanol, 180 μg / g of antimony acetate, and 20 μg / g of cobalt acetate were added, and the mixture was reacted at 220°C under a pressure of 250 kPa for 4 h until the water take-up reached 90% or more, to obtain an esterification product.

[0126] (2) Into the esterification product, 400 μg / g of heat stabilizer 1500, 100 μg / g of heat stabilizer 618, and 10 μg / g of tetrabutyl titanate were added, the pressure was reduced to 200 Pa, and the temperature was raised to 250°C, to perform a prepolymerization reaction for 1 h, to obtain a prepolymer.

[0127] (3) The prepolymer was raised to 280°C, the pressure was reduced to 10 Pa, and a polycondensation reaction was performed for 3 h. After the reaction was completed, the pressure was restored to normal pressure by nitrogen charging, and the product was discharged and pelletized.

[0128] Test Example

[0129] The copolyesters of the examples and comparative examples were subjected to the following tests, and the results are shown in Table 1:

[0130] 1. L*, a*, and b*: determined by a Hangzhou Caipu table spectrophotometer CS-821N.

[0131] 2. Light transmittance, haze: measured using a light transmittance and haze meter of model haze gard I made by BYK.

[0132] 3. Tensile strength: tested according to standard ISO 527 using a German Zwick / Roell Z005 universal testing machine, sample diameter 12.7 mm, thickness 3 mm;

[0133] 4. Impact strength: tested according to standard ISO 179-2-2018 using an impact testing machine of INSTRON, using a notched sample, radius 0.25 ± 0.05 mm, sample length 80 ± 2 mm, width 10.0 ± 0.2 mm, total thickness 4.0 ± 0.2 mm.

[0134] Table 1. Performance summary of examples and comparative examples

[0135]

[0136] As can be seen from Table 1, the copolyesters of the examples of the present application have high mechanical strength, low yellowness and high brightness at the same time. As can be seen from comparative examples 1-2 and comparative examples 1-6, the addition of cobalt acetate has an adverse effect on the brightness and mechanical strength of the copolyester, and the timing of the addition of the anthraquinone dyeing agent has a great influence on the performance of the product. Among them, the addition of the anthraquinone dyeing agent in the esterification stage, the prepolymerization stage and the first polycondensation stage will all cause the mechanical strength and brightness of the copolyester to deteriorate significantly, while the addition of the anthraquinone dyeing agent in the second polycondensation stage (late polycondensation stage) can improve the mechanical strength of the copolyester while basically maintaining the brightness, and improve the yellowness of the copolyester.

[0137] Any combination of the technical features of the above-described examples can be made. In order to make the description simple, all possible combinations of the technical features in the above-described examples are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present disclosure.

[0138] The above-described examples only express several embodiments of the present application, in order to specifically and in detail understand the technical solutions of the present application, but it should not be understood as a limitation on the scope of patent protection. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. It should be understood that the technical solutions obtained by the skilled person through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are within the scope of protection of the appended claims of the present application. Therefore, the scope of protection of the patent of the present application should be based on the content of the appended claims, and the description can be used to explain the content of the claims.

Claims

1. A method for preparing a copolyester, characterized in that, Includes the following steps: Dicarboxylic acids and polyols are esterified to form esterified products; The esterification product is prepolymerized to form a prepolymer; The prepolymer is subjected to a first polycondensation to form a first polycondensation product; An anthraquinone dye is added to the first polycondensation product to carry out a second polycondensation, forming a copolyester; The temperatures for the first and second condensation polymerizations are independent, ranging from 260℃ to 320℃; the time for the first condensation polymerization is 1h to 6h; and the time for the second condensation polymerization is 0.5h to 2h.

2. The preparation method according to claim 1, characterized in that, It meets one or more of the following characteristics: (1) The pressures of the first and second polycondensation are each independently 10 Pa to 100 Pa; (2) The dicarboxylic acid includes at least one of terephthalic acid, isophthalic acid, phthalic acid, succinic acid, glutaric acid, adipic acid and pimelic acid; (3) The polyols include ethylene glycol and / or other polyols; (4) The anthraquinone staining agent includes one or more of red anthraquinone staining agents, blue anthraquinone staining agents, and purple anthraquinone staining agents; (5) The amount of the anthraquinone staining agent added relative to the total mass of the diacid and polyol is 0.1 μg / g-5 μg / g.

3. The preparation method according to claim 2, characterized in that, It meets one or more of the following characteristics: (1) The other polyols include one or more of diethylene glycol, 1,2-propanediol, 1,3-propanetriol, 1,4-cyclohexanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, terephthalic acid, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, neopentyl glycol, isosorbide, isomannitol and polybutanediol; (2) The polyols include ethylene glycol and other polyols; optionally, the molar ratio of ethylene glycol to other polyols is (0.5-10):1; (3) The red anthraquinone staining agent includes one or more of Solvent Red 52, Solvent Red GS, Pigment Red 177 and Disperse Red 60; (4) The blue anthraquinone staining agents include one or more of Solvent Blue 104, Solvent Blue 45, Blue 2B, Pigment Blue 60, Phthalocyanine Blue, Vat Blue 4, Blue 3R, Solvent Blue 136, Disperse Blue 72 and Blue RR; (5) The purple anthraquinone dyes include one or more of Violet 13, Disperse Violet 57, Violet 3R, Violet B and Solvent Violet 31.

4. The preparation method according to claim 3, characterized in that, The anthraquinone staining agent is a combination of red and blue anthraquinone staining agents, or a purple anthraquinone staining agent.

5. The preparation method according to any one of claims 1-4, characterized in that, Esterification conditions include one or more of the following characteristics: (1) Esterification was carried out in the presence of the first catalyst; (2) The esterification temperature is 220℃-260℃; (3) The esterification pressure is 200kPa-300kPa; (4) The esterification time is 2h-8h; (5) The molar ratio of the diacid to the polyol is 1:(1-2).

6. The preparation method according to claim 5, characterized in that, The first catalyst includes one or more of stannous octoate, stannous chloride, zinc acetate, cobalt acetate, lithium acetate, potassium acetate, calcium acetate, magnesium acetate, barium acetate, lead acetate, manganese acetate, antimony acetate, antimony glycolate, antimony oxide, germanium dioxide, and phosphoric acid. And / or, the amount of the first catalyst added relative to the total mass of the diacid and polyol is 5 μg / g to 500 μg / g.

7. The preparation method according to any one of claims 1-4, characterized in that, The conditions for prepolymerization include one or more of the following characteristics: (1) Prepolymerization is carried out in the presence of a second catalyst and a heat stabilizer; (2) The prepolymerization temperature is 240℃-300℃; (3) The prepolymerization pressure is 150Pa-250Pa; (4) The prepolymerization time is 0.5h-2h.

8. The preparation method according to claim 7, characterized in that, The conditions for prepolymerization include one or more of the following characteristics: (1) The second catalyst comprises one or more of antimony acetate, antimony oxide, antimony glycol, zirconium acetylacetonate, lanthanum acetylacetonate, bismuth(III) hexanoic acid, germanium dioxide, tetrabutyl titanate and titanium tetraisopropoxide; (2) The heat stabilizers include heat stabilizer 1010, heat stabilizer 1500, heat stabilizer 1076, heat stabilizer 425, heat stabilizer 330, heat stabilizer 1178, heat stabilizer 501, heat stabilizer 618, heat stabilizer 626, heat stabilizer 168, TDD, trimethyl phosphite, triethyl phosphite, triisooctyl phosphite, triisodecyl phosphite, trilauryl phosphite, tri(tetranyl) phosphite, tri(octadecyl) phosphite, triphenyl phosphite, tri-p-toluene phosphite, diphenyltridecyl phosphite, tri(2,4-di-tert-butylphenyl) phosphite, pentaerythritol di(2-) One or more of the following: (4-tert-butylphenyl) diphosphite, di(2,4-di-p-isopropylphenyl) pentaerythritol diphosphite phosphoric acid, pentaerythritol tetraphenyl tridecyl phosphite, pentaerythritol didecyl diphosphite, pentaerythritol diisodecyl diphosphite, pentaerythritol di(octadecyl) phosphite, phosphoric acid, phosphorous acid, polyphosphoric acid, and triethyl phosphonoacetate; (3) The amount of the second catalyst added relative to the total mass of the diacid and polyol is 1 μg / g-100 μg / g; (4) The amount of heat stabilizer added relative to the total mass of diacid and polyol is 100 μg / g-3000 μg / g.

9. The copolyester prepared by the preparation method according to any one of claims 1-8.

10. A transparent plastic product, characterized in that, Includes the copolyester described in claim 9.

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