CN115572375A

CN115572375A - High-heat-resistance and high-transparency copolyester resin and preparation method thereof

Info

Publication number: CN115572375A
Application number: CN202211287759.3A
Authority: CN
Inventors: 吴林波; 陈妍如; 李伯耿
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2022-10-20
Filing date: 2022-10-20
Publication date: 2023-01-06

Abstract

The invention discloses a high heat-resistant and high transparent copolyester resin and a preparation method thereof, wherein dibasic acid residues in the copolyester resin comprise 80-100% of terephthalic acid residues and 0-20mol% of second aromatic dibasic acid residues; the diol residues comprise 5 to 80 mole% of 2, 4-tetramethyl-1,3-cyclobutanediol residues or isosorbide residues and 20 to 95 mole% of 4, 8-tricyclo [5.2.1.O2,7] decanedimethanol residues, or 10 to 60 mole% of 2, 4-tetramethyl-1,3-cyclobutanediol residues or isosorbide residues, 31 to 85 mole% of 4, 8-tricyclo [5.2.1.O2,7] decanedimethanol residues and 5 to 30 mole% of third diol residues. Compared with PCcBT and PXCcBT copolyester, the PDcBT and PXDcBT copolyester has the advantages of obviously improved glass transition temperature, heat resistance and mechanical property, good transparency and thermal stability, no obvious foaming and expansion phenomena in the melt processing process, no precipitate in the synthesis process, capability of efficiently synthesizing a product with high transparency at a lower temperature and stable reaction.

Description

High-heat-resistance and high-transparency copolyester resin and preparation method thereof

Technical Field

The invention relates to the technical field of copolyester, in particular to high-heat-resistance and high-transparency copolyester resin and a preparation method thereof.

Background

Bisphenol a polycarbonate (abbreviated as PC) is the most commonly used high heat resistant and high transparent polymer material. PC has excellent transparency, heat resistance and toughness, has light transmittance of more than 90 percent and glass transition temperature of about 150 ℃, can be used for a long time at 120 ℃, is important engineering plastic, and is also commonly used for manufacturing water cups, feeding bottles and household utensils. Since PC releases bisphenol a (BPA) at high temperatures and BPA causes endocrine disorders in the human body, PC is concerned about safety and is prohibited from being used in food contact products such as milk bottles.

By copolymerizing high-steric-hindrance diol monomers such as 2, 4-tetramethyl-1,3-Cyclobutanediol (CBDO) and Isosorbide (ISB) with other diols and dibasic acids or diesters thereof, the BPA problem can be avoided, and the copolyester with high heat resistance, high transparency and high safety can be prepared. Among them, PCcBT, a highly heat-resistant and highly transparent copolyester prepared by copolycondensation using CBDO, 1, 4-Cyclohexanedimethanol (CHDM) and dimethyl terephthalate (DMT) as raw materials, is commercially available in the United states under the trade name of Tritan ^TM As a substitute for PC. Tritan ^TM Glass transition temperature (T) of copolyester _g ) Has a heat distortion temperature of 92 to 109 ℃ (0.455 MPa) or 81 to 92 ℃ (1.82 MPa) at a temperature of up to about 120 ℃, has the characteristics of high heat resistance, high transparency, high toughness and no BPA release, and can be used as food contact materials and products including baby bottles.

However, as a safe high heat-resistant high transparent polymer material, PCcBT resin still has the following technical problems in its manufacture, processing and application.

(1) The heat resistance is low. The high glass transition temperature contribution of PCcBT resin comes primarily from the bulky hindered diol monomer CBDO, while the CHDM contribution is relatively low. Due to the low reactivity of CBDO, it is difficult to introduce efficiently into polymers, even if high levels of CBDO residues are introduced to increase T _g It also tends to result in a decrease in molecular weight, lower performance, and a significant increase in cost. So Tritan ^TM The CBDO residue content of the total diol residues of the copolyester commodity is controlled to be low, only about 37mol% at most, when T is _g A maximum of 120 ℃, a heat distortion temperature of 109 ℃ at 0.455MPa, a heat distortion temperature of 92 ℃ at 1.82MPa, and a heat resistance significantly lower than that of polycarbonate.

(2) The thermal stability was insufficient. The PCcBT copolyester is easy to decompose in the high-temperature processes of melt polycondensation, melt processing and the like, generates gas, expands and influences the normal operation of synthesis and processing. For example, chinese patent publication CN101300285A mentions that during the synthesis of PCcBT copolyester, the melt level is extremely unstable when no stabilizer is added, the melt has high porosity due to excessive foaming and foaming, and the melt interface rises rapidly under no stirring or low stirring speed, and easily overflows from the reaction vessel. Even if the stabilizer is added, the gas can be slowly released and a relatively stable melt interface can be maintained only under the specific types and the specific dosage of the catalyst and the stabilizer; chinese patent publication CN104736600A mentions that when PCcBT is extruded at high temperature, CHDM residues and CBDO residues decompose to produce volatile components of carbon monoxide and carbon dioxide, which makes the processing difficult to exhaust and process, and the resulting sheet has trumpet-shaped defects.

(3) In the reaction process, a precipitate with high melting point and opaqueness is easily generated, so that the reaction is difficult to proceed, the molecular weight of the product is difficult to increase, the transparency is obviously reduced, and the generated precipitate can pollute equipment. To avoid the generation of precipitates, chinese patent publication No. CN101679619A proposes a stepwise transesterification method to solve the above problems, i.e. after dimethyl terephthalate is reacted with all or part of CBDO to form polyester oligomer, which is then reacted with all or part of CHDM to obtain oligomer, which is further polymerized to obtain polymer with high molecular weight. This staged addition reaction process can reduce PCT precipitation but still cannot be completely avoided and increases process costs.

Similarly, copolyesters synthesized from ISB or other highly hindered diols, CHDM, dimethyl terephthalate (DMT) as starting materials also suffer from the problems described above.

Therefore, how to synthesize high heat-resistant and high transparent copolyester with higher heat resistance and thermal stability under the condition of the same content of large steric hindrance diol residues based on large steric hindrance diol monomers such as CBDO, ISB and the like, and the high heat-resistant and high transparent copolyester resin has the advantages of low synthesis temperature, no precipitate generated in the synthesis process and still remains the technical problems to be solved in the field of high heat-resistant and high transparent copolyester resin and preparation thereof.

Disclosure of Invention

The inventionAiming at the problems that the copolyester based on large steric hindrance monomers such as CBDO (conjugated diene monomer) or ISB (isocyclo-bis-acylphosphine) and the like in the prior art is not high enough in heat resistance and poor in heat stability, and precipitates are easily generated in the synthetic process to cause the opacity or transparency of a product to be reduced, the copolyester is prepared by mixing 4, 8-tricyclo [ 5.2.1.O2.7 ] with large steric hindrance monomers such as CBDO or ISB and the like]Adding decane dimethanol (TDD) into a system, and copolymerizing to obtain the heat-resistant high-transparency copolyester. The copolyester has a ratio Tritan ^TM Higher heat resistance, more excellent thermal stability and mechanical properties, and high transparency.

In order to achieve the purpose, the invention adopts the technical scheme that:

a copolyester resin with high heat resistance and high transparency comprises dibasic acid residues and dibasic alcohol residues, wherein,

the total amount of the dibasic acid residues is 100mol percent and comprises 80 to 100 percent of terephthalic acid residues and 0 to 20mol percent of second aromatic dibasic acid residues;

the diol residues comprise 5 to 80 mole%, based on 100 mole% of the total, of 2, 4-tetramethyl-1,3-cyclobutanediol residues or isosorbide residues; and 20 to 95 mole% 4, 8-tricyclo [5.2.1.O2,7] decane dimethanol residues;

or, the diol residues comprise, based on 100 mole% total, 10 to 60 mole% 2, 4-tetramethyl-1,3-cyclobutanediol residues or isosorbide residues, 31 to 85 mole% 4, 8-tricyclo [5.2.1.O2,7] decanedimethanol residues, and 5 to 30 mole% third diol residues;

the third dihydric alcohol residue is at least one of aliphatic dihydric alcohol residue with the main chain carbon atom number less than or equal to 5 or alicyclic or heterocyclic dihydric alcohol residue with the carbon atom number less than or equal to 11.

The copolyester is designated as PDcBT or PXDcBT, where "X" refers to a third diol residue. The structural formula of the copolyester is shown as the following formula:

based on the problems of low molecular weight and low mechanical property of large steric hindrance monomers such as CBDO (conjugated diene monomer) or ISB (isocynate) and DMT (dimethyl terephthalate) during copolymerization, the invention adds primary alcohol TDD with a tricyclic structure into a copolymerization system, enhances the reaction activity by utilizing the primary alcohol structure of the TDD, improves the molecular weight, and improves the overall mechanical property of the copolymer by utilizing the tricyclic structure of the TDD.

For copolyesters of DMT, CBDO or ISB with a third glycol (e.g., CHDM, MPO, etc.), due to the flexible chemical structure of the third glycol, the presence of the third glycol residue typically lowers the glass transition temperature of the copolyester even to a large extent, lowering its service temperature and mechanical properties. In the invention, the primary alcohol TDD with a cyclic structure is added to participate in copolymerization, and the tertiary diol is completely or partially replaced, so that the reduction of the glass transition temperature of the copolyester can be obviously inhibited, the mechanical strength of the copolyester is improved, and the ternary copolyester with higher heat resistance, more excellent thermal stability and mechanical property is obtained.

Meanwhile, different from the characteristic that PCT homopolymer ester is easy to crystallize, the PcBT and PDT homopolymer ester are amorphous polymers and do not crystallize, so that the PDcBT binary copolyester is not crystallized; as for the PCDcBT ternary copolyester, although the PCDcBT ternary copolyester contains a CT sequence, the content of the PCDcBT ternary copolyester is low, so that the PCDcBT ternary copolyester is not crystallized in the synthesis process, is not easy to generate precipitates, and has high transparency and good comprehensive performance.

Preferably, the aromatic dibasic acid residue includes at least one of isophthalic acid residue, phthalic acid residue, diphenic acid residue, naphthalenedicarboxylic acid residue, furandicarboxylic acid residue, and thiophenedicarboxylic acid residue.

Preferably, the third diol residue comprises at least one of ethylene glycol residue, 1, 3-propanediol residue, 1, 2-propanediol residue, 2-methyl-1, 3-propanediol residue, 1, 4-butanediol residue, 2, 3-butanediol residue, 1, 5-pentanediol residue, neopentyl glycol residue, 3-methyl-1, 5-pentanediol residue, 2, 4-trimethyl-1, 3-pentanediol residue, diethylene glycol residue, cyclohexanedimethanol residue, and cyclohexanediol residue.

The cyclohexanedimethanol and cyclohexanediol include the various isomers of 1,4-,1,2,1,3-, etc., with 1, 4-Cyclohexanedimethanol (CHDM) and 1, 4-cyclohexanediol being the most common.

Further preferably, the third diol residues are 1, 4-cyclohexanedimethanol residues and 2-methyl-1, 3-propanediol residues. The presence of 1, 4-cyclohexanedimethanol residues can impart better toughness to the copolyester; the presence of 2-methyl-1, 3-propanediol residues may impart better stability to the copolyester during synthesis and processing and better optical properties.

The intrinsic viscosity of the copolyester resin is 0.50-1.0dL/g, the glass transition temperature is 105-170 ℃, and the light transmittance is 85-93%.

Preferably, the intrinsic viscosity of the copolyester resin is 0.60-0.9dL/g, the glass transition temperature is 110-150 ℃, and the light transmittance is 88-93%.

The invention also provides a preparation method of the heat-resistant high-transparency copolyester resin, which comprises the following steps:

step 1, mixing a dibasic acid component and a dibasic alcohol component according to a molar ratio of 1.05-1;

step 2, carrying out polycondensation reaction on the intermediate product under the absolute pressure of 5-200Pa and at the temperature of 250-270 ℃ to obtain the copolyester resin;

the dibasic acid component comprises 80 to 100% by mole of terephthalic acid or a dialkyl ester thereof, based on 100% by mole of the total; and 0 to 20mol% of a second aromatic dibasic acid or a dialkyl ester thereof;

the dihydric alcohol comprises 5 to 90mol% of 2, 4-tetramethyl-1,3-cyclobutanediol or isosorbide in the total amount of 100 mol%; and 10 to 95 mole% 4, 8-tricyclo [5.2.1.O2,7] decane dimethanol;

or, the diols comprise 10 to 64mol% of 2, 4-tetramethyl-1,3-cyclobutanediol or isosorbide, 31 to 85mol% of 4, 8-tricyclo [5.2.1.O2,7] decanediol and 5 to 30mol% of a third diol, based on 100mol% of the total;

the third dihydric alcohol residue comprises at least one of aliphatic dihydric alcohol with the main chain carbon atom number less than or equal to 5 or alicyclic or heterocyclic dihydric alcohol with the carbon atom number less than or equal to 11.

Because CBDO or ISB has large steric hindrance and is secondary alcohol, has low reaction activity and is easy to generate side reaction, CBDO or ISB generates loss in the reaction process, so that the content of CBDO residue or ISB residue in copolyester is lower than that of CBDO or ISB in diol component. Compared with the copolymerization of CHDM, CBDO and DMT, TDD is adopted to completely or partially replace CHDM, CBTO and DMT, so that the sublimation of CBDO can be effectively inhibited in the esterification stage, the phenomenon of pipeline blockage is not observed, the foaming and expansion phenomena of the melt are obviously weakened in the later stage of the melt polycondensation stage, and the stability of the polymerization process is effectively improved.

The second aromatic dibasic acid or the dialkyl ester thereof comprises at least one of isophthalic acid or the dialkyl ester thereof, phthalic acid or the dialkyl ester thereof, biphenyl dicarboxylic acid or the dialkyl ester thereof, naphthalene dicarboxylic acid or the dialkyl ester thereof, furan dicarboxylic acid or the dialkyl ester thereof, and thiophene dicarboxylic acid or the dialkyl ester thereof;

further preferably, the second aromatic dibasic acid dialkyl ester includes at least one of dimethyl isophthalate, dimethyl phthalate, dimethyl bibenzoate, dimethyl naphthalenedicarboxylate, dimethyl furandicarboxylate, and dimethyl thiophenedicarboxylate.

Preferably, the aliphatic diol having a carbon number of the main chain of 5 or less includes at least one of ethylene glycol, 1, 3-propanediol, 1, 2-propanediol, 1, 4-butanediol, 2, 3-butanediol, 1, 5-pentanediol, 2-methyl-1, 5-pentanediol, 3-methyl-1, 5-pentanediol, 2-ethyl-1, 5-pentanediol, 3-dimethyl-1, 5-pentanediol, 3-diethyl-1, 5-pentanediol, 2-methyl-1, 3-propanediol, and 2-ethyl-1, 3-propanediol. These diols are either inexpensive and readily available, or can impart more excellent toughness and optical properties to the copolyester, or can improve the stability of the synthesis and processing.

Further preferably, the third diol is at least one of 1, 4-cyclohexanedimethanol and 2-methyl-1, 3-propanediol. The introduction of 1, 4-cyclohexanedimethanol can endow copolyester with better toughness; the introduction of 2-methyl-1, 3-propanediol can impart better stability and better optical properties to the copolyester synthesis and processing processes.

The catalyst adopted in the invention is a catalyst commonly used in the field for preparing copolyester, and the catalyst is a tin catalyst or a combination of the tin catalyst and one or more selected from n-butyl titanate, isopropyl titanate, lithium acetate, potassium acetate, calcium acetate, magnesium acetate, barium acetate, zinc acetate, cobalt acetate, antimony acetate, lead acetate and manganese acetate; the tin catalyst is one or more selected from dibutyltin oxide, dimethyltin oxide, stannous octoate, stannous oxalate, dibutyl dimethoxytin, dibutyltin diacetate, monobutyl triisotin octoate and dibutyltin dilaurate;

the dosage of the catalyst is 0.01 to 0.5 weight percent of the weight of the dibasic acid component; the catalyst may be supplemented in an appropriate amount depending on the case.

Preferably, a stabilizer is also added into the reaction mixture, and the dosage of the stabilizer is 0.01 to 0.5 weight percent of the weight of the dibasic acid component;

the stabilizer is selected from one or more of an antioxidant 1010, an antioxidant 1076, an antioxidant 1500, an antioxidant 425, a heat stabilizer 330, a heat stabilizer 1178, a heat stabilizer 618, a heat stabilizer 626, a heat stabilizer 168, trimethyl phosphite, triethyl phosphite, triisooctyl phosphite, triisodecyl phosphite, trilauryl phosphite, tridecyl phosphite, trioctadecyl phosphite, triphenyl phosphite, tri-p-tolyl phosphite, ditridecyl phosphite, tri-2, 4-di-tert-butylphenyl phosphite, di-2, 4-di-p-isopropylphenyl) pentaerythritol diphosphite phosphoric acid, pentaerythritol tetrapentaphenyl tridecyl phosphite, pentaerythritol diphosphite, diisodecyl pentaerythritol diphosphite, tetraphenylpropylene glycol diphosphite, phosphoric acid, phosphorous acid, polyphosphoric acid and triethyl phosphonoacetate, a light stabilizer 791, a light stabilizer 700, a light stabilizer 783, a light stabilizer 119, a light stabilizer 944, a light stabilizer 622, a light stabilizer 770, a light stabilizer 1164.

Compared with the prior art, the invention has the following beneficial effects:

(1) The copolyester of the invention improves the heat resistance of the copolyester by introducing 4, 8-tricyclo [5.2.1.O2,7] decane dimethanol residues, and the glass transition temperature of the copolyester can be adjusted within the range of 105-170 ℃; meanwhile, the material has excellent strength and toughness, the tensile yield strength is not lower than 48MPa, and the elongation at break is not lower than 10%.

(2) The copolyester has excellent thermal stability, is beneficial to improving the characteristic viscosity number in the high-temperature polycondensation process, and improves the stability of the synthesis process; foaming, foaming and expansion phenomena caused by thermal decomposition can be effectively avoided in the melt processing process, and the processability is obviously improved.

(3) The copolyester is not easy to crystallize, is favorable for improving the transparency, effectively avoids crystallization and precipitation in the reaction process, and can prepare the copolyester with high molecular weight and light transmittance not lower than 85 percent at the reaction temperature of less than or equal to 270 ℃.

In conclusion, the high-heat-resistance and high-transparency copolyester provided by the invention has excellent comprehensive performance and is beneficial to realizing large-scale production.

Drawings

FIG. 1 shows the glass transition temperatures (T) of the PDcBT and PCcBT copolyesters _g ) With the content of CBDO residues in the copolyester (. Phi.) _cB ) Wherein the data for the PDcBT are from examples 1-4, the data for the PCcBT are from comparative example 2, tritan ^TM EX401 and Chinese patent publication CN101300285A.

FIG. 2 is an appearance diagram of a sheet obtained by molding the copolyesters prepared in examples 2 and 9 and comparative example 2.

FIG. 3 is an appearance chart of samples obtained by heating and holding copolyesters of comparative example 2, comparative example 3, examples 2,3, 6, and 9 at 260 ℃ in a flask for 2 hours, and then cooling to room temperature.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention. Those skilled in the art should understand that they can make modifications and equivalents without departing from the spirit and scope of the present invention, and all such modifications and equivalents are intended to be included within the scope of the present invention.

The raw materials used in the following embodiments are all commercially available.

In the following embodiments, the names, acronyms, and abbreviations for the monomer residues of the diacids and diols used are shown in table 1.

TABLE 1 summary of names and abbreviations of monomers used in the examples

Name of monomer	Abbreviation for monomer	Abbreviation of monomer residue	Source
				Terephthalic acid dimethyl ester	DMT	T	Aladdin
1, 4-cyclohexanedimethanol	CHDM	C	Kailing chemical industry
				2, 4-tetramethyl-1,3-cyclobutanediol	CBDO	cB	Suzhou subfamily
4, 8-tricyclo [5.2.1.O2,7]Decane dimethanol	TDD	D	Sigma
				2-methyl-1, 3-propanediol	MPO	M	Aladdin
Isosorbide	ISB	I	Aladdin
				1, 3-propanediol	PDO	P	Aladdin

In the following embodiments, the copolyesters produced are represented by PXY, where X is an abbreviation for all diol residues and Y is an abbreviation for all diacid residues. The subscript of the residue indicates the copolymer composition, i.e., the percentage of the amount of material of that residue to the sum of the amounts of material of the diol or diacid residues; the presence of residue X in the superscript indicates the presence of cis-trans isomerism in the copolyester, and the superscript indicates the molar percentage of cis-residues φ _cis,X I.e., the percentage of material from the cis residue to the sum of material from the residue (including cis and trans). For example, in the case of a liquid,

represented by 2-methyl-1, 3-propanediol residue (M), 4, 8-tricyclo [5.2.1.O2,7]A copolyester of decane dimethanol residues (D), 2, 4-tetramethyl-1,3-cyclobutanediol residues (cB) and terephthalic acid residues (T), wherein the contents of M, D and cB residues (. Phi. Sup. _M 、φ _D 、φ _cB ) 23mol%, 52mol% and 25mol%, respectively, of cB residues, cis cBThe residues represent 52mol% of all cB residues (including cis and trans). Furthermore, for the sake of simplicity, for copolyesters comprising two diol residues, only the content of one of the diol residues is indicated, the content of the other diol residue being obviously obtained and therefore not indicated. For example, in the case of a liquid,

the content of cB residues was 12mol% and the content of D residues was 88mol%.

In the following specific embodiments, the test assays used are as follows:

characteristic viscosity number: the Intrinsic Viscosity (IV) of the copolyester sample was measured by means of a hounsfield automatic viscometer at 25 ℃ in a solvent of phenol/tetrachloroethane (w/w =3/2 by mass ratio).

And (3) characterizing a chemical structure: the chemical structure of the copolyester is characterized by a Bruker AC-80 400M nuclear magnetic resonance spectrometer, deuterated chloroform is used as a solvent, and tetramethylsilane is used as an internal standard. From the results of nuclear magnetic hydrogen spectroscopy, the copolyester composition can be calculated. It is noted that the copolyester composition (which is the percentage of moles of a diol residue based on the sum of all moles of diol residues) and the monomer composition (which is the percentage of moles of a diol based on the sum of all moles of diol residues) may differ from each other by varying degrees due to volatilization, degradation, or side reactions of different diol monomers, as well as errors in nuclear magnetic hydrogen spectroscopy, and are not exactly equal to each other.

Thermal properties: adopting Q200 of American TA company to measure a DSC curve of a sample, adopting a temperature program of primary heating-cooling-secondary heating, and measuring the temperature range of room temperature to 250 ℃, the heating and cooling rate of 10 ℃/min and the isothermal time of 3min;

heat distortion temperature: a HaakeMeniJet II micro-injection molding machine is adopted to prepare a cuboid sample strip with the length of 80mm, the width of 10mm and the thickness of 4mm, and the cuboid sample strip is placed at room temperature for 48 hours and then measured. The heat distortion temperature was measured according to GB/T1634.2-2004 using a Heat distortion/Vicat tester from Ceast scientific instruments, italy. The testing pressure is 1.8MPa, and the heating rate is 120 ℃/h.

Tensile property: a HaakeMediniJet II micro-injection molding machine is adopted to prepare dumbbell-shaped sample strips with the width of 4mm and the thickness of 2mm, and the dumbbell-shaped sample strips are placed at room temperature for 48 hours and then are measured. Tensile testing was carried out at 25 ℃ and a tensile rate of 10mm/min according to ASTM D638 using a Roell 2020 Universal Material tester from Zwick, germany. 5 specimens were tested for each sample, and the average value was taken as the test result.

Light transmittance: a HaakeMediniJet II micro-injection molding machine is used for preparing a wafer with the diameter of 25mm and the thickness of 1.5 mm. Measuring a light transmission index by adopting a Hangzhou color spectrum desk-type spectral colorimeter CS-821N instrument: light transmittance and haze H.

Example 1

Synthesis of (DMT + CBDO + TDD)

(1) To N ₂ An atmospheric reactor was charged with 67.96g (0.350 mol) DMT, 16.40g (0.114 mol) CBDO (cis content 51%), 66.98g (0.341 mol) TDD and 0.2039g tin catalyst, and 0.068g stabilizer 1010 and 0.034g stabilizer 626 were added and reacted at 220 ℃ for 2.0h to obtain a transesterification product.

(2) Heating to 260 deg.C, reducing pressure to below 200Pa, polycondensing the ester exchange product at 260 deg.C under absolute pressure of less than or equal to 200Pa for 3.0h to obtain product with intrinsic viscosity of 0.68dL/g and phi _cB 12.2mol%, phi _cis,cB 57.4mol%, phi _D 87.8mol% of copolyester poly (4, 8-tricyclo [5.2.1.O2,7] terephthalate]Decane dimethanol-co-2, 4-tetramethyl-1,3-cyclobutanediol ester), described as

。

In the reaction process, the liquid level of the melt is always kept stable, only a small amount of bubbles are generated, the unstable phenomenon that the interface of the melt rises rapidly due to a large amount of bubbles is not generated, and the condition that the final product is opaque due to the generation of precipitates is not seen. The glass transition temperature of the copolyester is 122 ℃, and the heat distortion temperature of the copolyester under 1.8MPa is 103 ℃.

Example 2

Synthesis of (DMT + CBDO + TDD)

(1) To N ₂ An atmospheric reactor was charged with 67.96g (0.350 mol) DMT, 26.24g (0.182 mol) CBDO (cis content 51%), 53.59g (0.273 mol) TDD and 0.2039g tin catalyst, and 0.068g stabilizer 1010 and stabilizer 0.034g stabilizer 626 were added and reacted at 220 ℃ for 2.0h to obtain a transesterified product.

(2) Heating to 260 deg.C, reducing pressure to below 200Pa, polycondensing the ester exchange product at 260 deg.C under absolute pressure of less than or equal to 200Pa for 3.0h to obtain product with intrinsic viscosity of 0.74dL/g and phi _cB 29.8mol%, phi _cis,cB 58.0mol%, phi _D 70.2mol% of copolyester poly (4, 8-tricyclo [5.2.1.O2,7] terephthalate]Decane dimethanol-co-2, 4-tetramethyl-1,3-cyclobutanediol ester), described

In the reaction process, the liquid level of the melt is always kept stable, only a small amount of bubbles are generated, the unstable phenomenon that the interface of the melt rises rapidly due to a large amount of bubbles is not generated, and the condition that the final product is opaque due to the generation of precipitates is not seen. The glass transition temperature of the copolyester was 130 ℃.

Example 3

Synthesis of (DMT + CBDO + TDD)

(1) To N ₂ An atmospheric reactor was charged with 67.96g (0.350 mol) DMT, 32.81g (0.228 mol) CBDO (cis content 51%), 44.66g (0.228 mol) TDD and 0.2039g tin catalyst, and 0.068g stabilizer 1010 and 0.034g stabilizer 626 were added and reacted at 220 ℃ for 2.0 hours to obtain a transesterification product.

(2) Heating to 260 deg.C, reducing pressure to below 200Pa, polycondensing the ester exchange product at 260 deg.C under absolute pressure of less than or equal to 200Pa for 3.0h to obtain product with intrinsic viscosity of 0.72dL/g and phi _cB 37.0mol%, phi _cis,cB 55.0mol%, phi _D Copolyester-poly (4, 8-tricyclo [5.2.1.O2,7] terephthalic acid at 63.0mol%]DecaneDimethanol-co-2, 4-tetramethyl-1,3-cyclobutanediol ester), described as

。

In the reaction process, the liquid level of the melt is always kept stable, only a small amount of bubbles are generated, the unstable phenomenon that the interface of the melt rises rapidly due to a large amount of bubbles is not generated, and the condition that the final product is opaque due to the generation of precipitates is not seen. The glass transition temperature of the copolyester is 136 ℃, and the thermal deformation temperature of the copolyester under 1.8MPa is 113 ℃.

Example 4

Synthesis of (DMT + CBDO + TDD)

(1) To N ₂ An atmospheric reactor was charged with 67.96g (0.350 mol) DMT, 52.49g (0.364 mol) CBDO (cis content 52%), 17.86g (0.091 mol) TDD and 0.2039g tin catalyst, and 0.068g stabilizer 1010 and 0.034g stabilizer 626 were added and reacted at 220 ℃ for 2.0h to give a transesterified product.

(2) Heating to 260 deg.C, reducing pressure to below 200Pa, polycondensing the ester exchange product at 260 deg.C under absolute pressure of less than or equal to 200Pa for 2.0h to obtain product with intrinsic viscosity of 0.61dL/g and phi _cB 70.4mol%, phi _cis,cB Is 54.2mol%, phi _D 29.6mol% of copolyester poly (4, 8-tricyclo [5.2.1.O2,7] terephthalate]Decane dimethanol-co-2, 4-tetramethyl-1,3-cyclobutanediol ester), described as

。

In the reaction process, the liquid level of the melt is always kept stable, only a small amount of bubbles are generated, the unstable phenomenon that the interface of the melt rises rapidly due to a large amount of bubbles is not generated, and the condition that the final product is opaque due to the generation of precipitates is not seen. The glass transition temperature of the copolyester was 165 ℃.

Example 5

Synthesis of (DMT +CBDO+TDD+MPO)

(1) To N ₂ An atmospheric reactor was charged with 67.96g (0.350 mol) DMT, 15.75g (0.109 mol) CBDO (cis content 51%), 35.72g (0.182 mol) TDD, 14.35g (0.159 mol) 2-methyl-1, 3-propanediol MPO and 0.2039g tin catalyst, and 0.068g stabilizer 1010 and 0.034g stabilizer 626 were added and reacted at 220 ℃ for 1.5 hours to obtain a transesterified product.

(2) Heating to 260 deg.C, reducing pressure to below 200Pa, polycondensing the ester exchange product at 260 deg.C under absolute pressure of less than or equal to 200Pa for 2.0h to obtain product with intrinsic viscosity of 0.76dL/g and phi _cB 25.3mol%, phi _cis,cB 51.6mol%, phi _D 52.0mol percent phi, phi _M 22.7mol% copolyester poly (2-methyl-1, 3-propanediol-co-4, 8-tricyclo [5.2.1.O2,7]]Decane dimethanol-co-2, 4-tetramethyl-1,3-cyclobutanediol ester), described as

In the reaction process, the liquid level of the melt is always kept stable, only a small amount of bubbles are generated, the unstable phenomenon that the interface of the melt rises rapidly due to a large amount of bubbles is not generated, and the condition that the final product is opaque due to the generation of precipitates is not seen. The glass transition temperature of the copolyester was 112 ℃.

Example 6

Synthesis of (DMT + CBDO + TDD + MPO)

(1) To N ₂ An atmospheric reactor was charged with 67.96g (0.350 mol) DMT, 16.40g (0.114 mol) CBDO (cis content 51%), 44.66g (0.228 mol) TDD, 10.25g (0.114 mol) 2-methyl-1, 3-propanediol MPO and 0.2039g tin catalyst, and 0.068g stabilizer 1010 and 0.034g stabilizer 626 were added and reacted at 220 ℃ for 1.5 hours to obtain a transesterified product.

(2) Heating to 260 deg.C, reducing pressure to below 200Pa, polycondensing the ester exchange product at 260 deg.C under absolute pressure of less than or equal to 200Pa for 2.0h to obtain product with intrinsic viscosity of 0.76dL/g and phi _cB 25.6mol%, phi _cis,cB 53.2mol%, phi _D Is 55.5mol％、φ _M 18.9mol% copolyester-poly (2-methyl-1, 3-propanediol-co-4, 8-tricyclo [5.2.1.O2,7]]Decane dimethanol-co-2, 4-tetramethyl-1,3-cyclobutanediol ester), described

In the reaction process, the liquid level of the melt is always kept stable, only a small amount of bubbles are generated, the unstable phenomenon that the interface of the melt rises rapidly due to the generation of a large amount of bubbles is not seen, and the condition that the final product is opaque due to the generation of precipitates is also not seen. The glass transition temperature of the copolyester was 117 ℃.

Example 7

Synthesis of (DMT + CBDO + TDD + MPO)

(1) To N ₂ An atmospheric reactor was charged with 67.96g (0.350 mol) DMT, 24.28g (0.168 mol) CBDO (cis content 51%), 26.79g (0.137 mol) TDD, 13.53g (0.150 mol) 2-methyl-1, 3-propanediol MPO and 0.2039g tin catalyst, and 0.068g stabilizer 1010 and 0.034g stabilizer 626 were added and reacted at 220 ℃ for 1.5 hours to obtain a transesterified product.

(2) Heating to 260 deg.C, reducing pressure to below 200Pa, polycondensing the ester exchange product at 260 deg.C under absolute pressure of less than or equal to 200Pa for 2.0h to obtain product with intrinsic viscosity of 0.74dL/g and phi _cB 38.2mol%, phi _cis,cB Is 52.9mol%, phi _D 35.9mol%, phi _M 25.9mol% copolyester-poly (2-methyl-1, 3-propanediol-co-4, 8-tricyclo [5.2.1.O2,7]]Decane dimethanol-co-2, 4-tetramethyl-1,3-cyclobutanediol ester), described as

In the reaction process, the liquid level of the melt is always kept stable, only a small amount of bubbles are generated, the unstable phenomenon that the interface of the melt rises rapidly due to a large amount of bubbles is not generated, and the condition that the final product is opaque due to the generation of precipitates is not seen. The glass transition temperature of the copolyester was 117 ℃.

Example 8

Synthesis of (DMT + CBDO + TDD + MPO)

(1) To N ₂ An atmospheric reactor was charged with 67.96g (0.350 mol) DMT, 23.62g (0.164 mol) CBDO (cis content 51%), 25.90g (0.132 mol) TDD, 14.35g (0.159 mol) 2-methyl-1, 3-propanediol and 0.2039g tin catalyst, and 0.068g stabilizer 1010 and 0.034g stabilizer 626 were added and reacted at 220 ℃ for 1.5 hours to obtain a transesterified product.

(2) Heating to 260 deg.C, reducing pressure to below 200Pa, polycondensing the ester exchange product at 260 deg.C under absolute pressure of less than or equal to 200Pa for 2.0h to obtain product with intrinsic viscosity of 0.75dL/g and phi _cB 39.3mol%, phi _cis,cB 53.9mol%, phi _D 32.4mol%, phi _M 28.3mol% copolyester-poly (2-methyl-1, 3-propanediol-co-4, 8-tricyclo [5.2.1.O2,7]]Decane dimethanol-co-2, 4-tetramethyl-1,3-cyclobutanediol ester), described as

In the reaction process, the liquid level of the melt is always kept stable, only a small amount of bubbles are generated, the unstable phenomenon that the interface of the melt rises rapidly due to the generation of a large amount of bubbles is not seen, and the condition that the final product is opaque due to the generation of precipitates is also not seen. The glass transition temperature of the copolyester was 114 ℃.

Example 9

Synthesis of (DMT + CBDO + TDD + MPO)

(1) To N ₂ An atmospheric reactor was charged with 67.96g (0.350 mol) DMT, 23.62g (0.164 mol) CBDO (cis content 51%), 31.26g (0.159 mol) TDD, 11.89g (0.132 mol) 2-methyl-1, 3-propanediol and 0.2039g tin catalyst, and 0.068g stabilizer 1010 and 0.034g stabilizer 626 were added and reacted at 220 ℃ for 1.5 hours to obtain a transesterified product.

(2) Heating to 260 deg.C, and reducing pressure to below 200Pa to obtain ester exchange productPolycondensing at 260 deg.C under absolute pressure of 200Pa for 2.5h to obtain product with intrinsic viscosity of 0.71dL/g and phi _cB 36.7mol%, phi _cis,cB Is 52.1mol%, phi _D 41.0mol%, phi _M 22.3mol% copolyester poly (2-methyl-1, 3-propanediol-co-4, 8-tricyclo [5.2.1.O2,7]]Decane dimethanol-co-2, 4-tetramethyl-1,3-cyclobutanediol ester), described

In the reaction process, the liquid level of the melt is always kept stable, only a small amount of bubbles are generated, the unstable phenomenon that the interface of the melt rises rapidly due to the generation of a large amount of bubbles is not seen, and the condition that the final product is opaque due to the generation of precipitates is also not seen. The glass transition temperature of the copolyester was 120 ℃.

Example 10PP ₂₈ D ₃₅ I ₃₇ Synthesis of T (DMT + ISB + TDD + PDO)

(1) To N ₂ An atmospheric reactor was charged with 67.96g (0.350 mol) DMT, 26.60g (0.182 mol) ISB, 29.47g (0.150 mol) TDD, 9.35g (0.123 mol) 1, 3-propanediol PDO and 0.2039g tin catalyst, and 0.068g stabilizer 1010 and 0.034g stabilizer 626 were added to react at 220 ℃ for 1.5 hours to obtain a transesterified product.

(2) Heating to 260 deg.C, reducing pressure to below 200Pa, polycondensing the ester exchange product at 260 deg.C under absolute pressure of less than or equal to 200Pa for 2.5h to obtain product with intrinsic viscosity of 0.71dL/g and phi _I 37.0mol%, phi _D 35.0mol%, phi _P 28.0mol% copolyester-poly (1, 3-propanediol-co-4, 8-tricyclo [5.2.1.O2,7] terephthalate]Decane dimethanol-co-isosorbide ester), noted PP ₂₈ D ₃₅ I ₃₇ T。

Example 11

Synthesis of (DMT + CBDO + TDD + CHDM)

(1) To N ₂ An atmospheric reactor was charged with 67.96g (0.350 mol) DMT, 28.21g (0.196 mol) CBDO (cis content 51%), 33.05g (0.168 mol) TDD, 13.12g (0.09 mol) 1, 4-cyclohexanedimethanol and 0.2039g tin catalyst, and 0.068g stabilizer 1010 and 0.034g stabilizer 168 were added and reacted at 240 ℃ for 1.5 hours to obtain a transesterification product.

(2) Heating to 260 deg.C, reducing pressure to below 200Pa, polycondensing the ester exchange product at 260 deg.C under absolute pressure of less than or equal to 200Pa for 2.5h to obtain product with intrinsic viscosity of 0.74dL/g and phi _cB 36.8mol%, phi _cis,cB Is 52.3mol%, phi _D 41.3mol%, phi _C Copolyester-poly (1, 4-cyclohexanedimethanol-co-4, 8-tricyclo [5.2.1.O2,7] terephthalic acid at 21.9mol%]Decane dimethanol-co-2, 4-tetramethyl-1,3-cyclobutanediol ester), described

During the reaction, more foaming is generated, but the liquid level of the melt is still stable, the phenomenon of instability of the sharp rise of the melt interface is not seen, and the condition that the final product is opaque due to the generation of precipitates is not seen. The glass transition temperature of the copolyester was 131 ℃.

Comparative example 1 PCcBT CHDM/CBDO 78/22 (DMT + CBDO + CHDM)

(1) To N ₂ 67.96g (0.35 mol) of dimethyl terephthalate, 14.44g (0.1001 mol) of CBDO (cis content 51%), 51.18g (0.3549 mol) of CHDM (cis content 25%) and 0.2039g of tin catalyst are added into an atmosphere reactor and reacted for 2.5h at 220 ℃ to obtain an esterification product which is white and opaque.

(2) Gradually heating the ester exchange product to 260 ℃, gradually reducing the absolute pressure to less than 200Pa, carrying out polycondensation, and taking out the product, wherein the system becomes an unagitable opaque solid after 1h, and the product is obviously brittle and is an opaque oligomer.

Comparative example 2

(DMT+CBDO+CHDM)

(1) To N ₂ 67.96g (0.35 mol) of CBDO (cis content 50%) 29.53g (0.205 mol), 36.09g (0.250 mol) of CHDM (cis content 26%) and 0.2039g of tin catalyst are added into an atmosphere reactor and reacted for 1.6h at 220 ℃ to obtain a transesterification product which is white and opaque.

(2) Heating the ester exchange product to 260 deg.C, gradually reducing pressure to below 200Pa (absolute pressure, the same below), performing polycondensation to obtain white system with intrinsic viscosity of 0.62dL/g and phi after 3.5 hr _C 64.8mol%, phi _cis,C 29.1mol%, phi _cB 35.2mol%, phi _cis,cB Copolyester poly (1, 4-cyclohexanedimethanol-co-2, 4-tetramethyl-1,3-cyclobutanediol terephthalate) at 52.1 mole%, reported

After 0.5h of reaction, a large amount of gas began to be evolved, excessive foaming and foaming resulted in a high void volume, the melt interface began to fail to maintain a steady state, and it was necessary to break the foam by rapid stirring to prevent the melt from overflowing from the flask. The copolyester is white and opaque, a processed sample still presents white and semitransparent, and the light transmittance is only 66.07%; the glass transition temperature was 118 ℃ and the heat distortion temperature was 97 ℃ (1.8 MPa).

Comparative example 3

In the present invention, a commercial PCcBT copolyester resin, tritan, from Eastman corporation ^TM EX401 for comparison. The intrinsic viscosity is 0.66dL/g, and the glass transition temperature is 120 ℃.

Comparative example 4PcBT homopolyester

(1) To N ₂ 67.96g (0.350 mol) of DMT, 65.52g (0.455 mol) of CBDO (cis content 45%) and 0.2039g of tin catalyst were charged into an atmospheric reactor and reacted at 220 ℃ for 1.5 hours to obtain a transesterified product.

(2) Heating to 260 ℃, reducing the pressure to below 200Pa, and polycondensing the ester exchange product for 2.0h at 260 ℃ under the condition that the absolute pressure is less than or equal to 200Pa to obtain the productThe viscosity-viscosity number is 0.46dL/g, phi _cis,cB 52.0mol% homopolyester-poly (2, 4-tetramethyl-1,3-cyclobutanediol terephthalate) having a glass transition temperature of 192 ℃.

Comparative example 5

(DMT+CBDO+CHDM+MPO)

(1) To N ₂ 67.96g (0.35 mol) of CBDO (cis content 50%) 22.97g (0.159 mol), CHDM (cis content 26%) 20.97g (0.146 mol), MPO 13.53g (0.150 mol) and tin catalyst 0.2039g are added into an atmosphere reactor and reacted for 1.5h at 220 ℃ to obtain a transesterification product.

(2) Heating the ester exchange product to 260 deg.C, gradually reducing pressure to below 200Pa (absolute pressure, the same applies below), performing polycondensation, and obtaining intrinsic viscosity of 0.66dL/g and phi after 3.0h _M 30.0mol%, phi _C 34.1mol%, phi _cis,C 30.0mol%, phi _cB 35.9mol%, phi _cis,cB Copolyester poly (2-methyl-1, 3-propanediol-co-1, 4-cyclohexanedimethanol-co-2, 4-tetramethyl-1,3-cyclobutanediol terephthalate) at 52.1 mole%, reported

During the polycondensation, more foaming is generated, but the liquid level of the melt is more stable, the unstable phenomenon of the rapid rise of the melt interface is not seen, and the condition that the final product is opaque due to the generation of precipitates is also not seen. The glass transition temperature of the copolyester was 105 ℃.

Analysis of copolyester Properties

1. Characteristic viscosity, glass transition temperature, heat distortion temperature

The intrinsic viscosity, glass transition temperature and heat distortion temperature of a portion of the polyester of the copolyesters of the examples and comparative examples are summarized in Table 2.

TABLE 2 intrinsic viscosity, glass transition temperature and Heat distortion temperature of copolyesters in examples and comparative examples

* Commercial Tritan ^TM The copolyester, designated EX401, had a CBDO residue content close to that of example 3. The glass transition temperature and heat distortion temperature data are from the Eastman's official network.

For the PDcBT binary copolyester, the relation between the glass transition temperature and the cB content is shown in FIG. 1. The glass transition temperature of the PCcBT binary copolyester is also compared to the cB content (note: some of the data are from CN 101300285A) in fig. 1.

It can be seen that the glass transition temperature of the PDcBT of the present invention is 122-165 ℃ when the cB residue content is 12-70 mol%; with increasing cB residue content, tg gradually increased. The PcBT homopolyester of comparative example 4, although having the highest glass transition temperature (192 ℃ C.), has a low CBDO reactivity, it is difficult to prepare a PcBT homopolyester having a high intrinsic viscosity, resulting in a lack of mechanical properties and no practical applicability. Compared with PcBT homopolyester, the PDCBT copolyester has the advantages that: the reactivity of TDD is higher than that of CBDO, and the copolymerization of TDD, CBDO and DMT can synthesize high-characteristic-viscosity PDcBT copolyester which not only has high glass transition temperature, but also has high characteristic viscosity and high enough mechanical property, thus being a practical high-heat-resistance high-transparency material.

Compared to the binary copolyester PCcBT, PDcBT has a higher glass transition temperature at the same cB residue content. Tritan ^TM EX401 has a glass transition temperature of 120 ℃ and a heat distortion temperature of 92 ℃ (1.8 MPa); and of similar composition

The glass transition temperature of (example 3) was 136 ℃ and the heat distortion temperature was 113 ℃ (1.8 MPa). It can be seen that the heat resistance of the PDcBT is significantly better than the PCcBT at the same cB content. Therefore, the heat resistance of the copolyester can be obviously improved by replacing CHDM with TDD.

Based on PDcBT, in examples 5-9, a third diol 2-methyl 1, 3-propanediol (MPO) is introduced to participate in copolymerization to obtain the ternary copolyester PMDcBT. When the M residue content does not exceed 30mol%, despite its glass transition temperature relative to the binary copolyester PDcBT is reduced, but still can reach 110-120 ℃ to reach Tritan ^TM The level of (c). Wherein the content of the first and second substances,

(example 9) the glass transition temperature reached 120 ℃ with Tritan ^TM EX401 is equivalent, but the heat distortion temperature reaches 98 ℃ (under 1.8 MPa), which is higher than Tritan ^TM 92 ℃ of EX401 (1.8 MPa).

On the basis of PCcBT, a third glycol MPO is introduced to replace partial CHDM for copolymerization, which can improve melt stability and reduce generation of precipitates, but the glass transition temperature of the copolyester is reduced obviously, for example, compared with comparative example 2, in comparative example 5, after 30mol% of MPO residues are introduced to replace CHDM residues, the glass transition temperature of the copolyester is reduced from 118 ℃ to 105 ℃ and is lower than Tritan ^TM 110-120 ℃. In addition, the

(example 3) introduction of MPO residues in about 30mol% (actually 28 mol%) instead of TDD residues

The glass transition temperature of the glass reaches 114 ℃ and still reaches Tritan ^TM The level of (c). This also demonstrates the significant advantage of TDD over CHDM in increasing the glass transition temperature.

Aiming at an isosorbide, TDD and DMT copolymerization system, a small amount of 1, 3-propylene glycol is introduced as third dihydric alcohol for copolymerization to obtain the ternary copolyester PP ₂₈ D ₃₅ I ₃₇ The glass transition temperature of T can also be up to 120 ℃ in accordance with Tritan (example 10) ^TM EX401 is comparable. It can be seen that TDD is also suitable for the synthesis of high Tg copolyesters based on the bulky hindered monomer isosorbide, etc.

In example 11, a small amount of CHDM was introduced as a third diol to copolymerize with CBDO and TDD to give a terpolymer

Its cB residue content and Tritan ^TM EX401 is equivalent, butThe glass transition temperature reaches 131 ℃, and is obviously higher than Tritan ^TM EX401, again demonstrating that the introduction of TDD structure can significantly improve the heat resistance of the copolyester.

2. Mechanical properties

The mechanical properties of the PDcBT and PMDcBT copolyesters obtained in some of the examples are shown in table 3. For comparison, the commercial Tritan was used ^TM The EX401 resin was subjected to sample preparation and mechanical property test under the same conditions, and the obtained results are also shown in table 3.

TABLE 3 tensile mechanical Properties of copolyesters in the examples and comparative examples

Therefore, the tensile mechanical properties (including Young modulus, yield strength, breaking strength and ductility) of the PDcBT and PMDcBT copolyester obtained by the invention are comprehensively superior to that of Tritan ^TM EX401. Wherein, the one obtained in example 1

With Tritan ^TM EX401 has a comparable glass transition temperature (120 ℃), but a higher strength (yield strength 55MPa vs.38MPa, break strength 37MPa vs. 30MPa) and better ductility (elongation at break 11% v.8%); prepared in example 3

Has the same content of cB residues as EX401, and has higher T _g (136 ℃ vs.120 ℃), while the modulus, strength and elongation at break are all obviously higher than Tritan ^TM EX401 (Young's modulus 1.87GPa vs.1.69GPa, yield strength 53MPa vs.38MPa, breaking strength 39MPa vs.30MPa, elongation at break 17% vs. 8%). It is clear that the copolyester of the present invention compares Tritan ^TM The resin has more excellent heat resistance and mechanical property.

CBDO and ISB are secondary alcohols, have large steric hindrance and low hydroxyl reaction activity, and are difficult to synthesize homopolyester with high intrinsic viscosity with terephthalic acid or diester thereof. For example, a PcBT homopolyester synthesized by Kelsey et al, shell (Shell) as disclosed in K Dr. Et al, "High impact, amophorus terephthalic acid polyesters of rib 2, 4-tetramethyl-1, 3-cyclic with flex diols", starting from dimethyl terephthalate and CBDO, by the transesterification-melt polycondensation process, at a transesterification temperature of 235 to 250 ℃ and a polycondensation temperature of 260 ℃ has an intrinsic viscosity of 0.31dL/g and a Tg of 174 ℃.

In contrast, the PcBT homopolyester synthesized in the comparative example 4 has the intrinsic viscosity of 0.46dL/g and the Tg of 192 ℃, but the intrinsic viscosity is still low, has insufficient mechanical strength, and is difficult to prepare samples and test mechanical properties. However, in the present invention, after TDD is used as a comonomer, since TDD is a primary alcohol and has small steric hindrance, the intrinsic viscosity of the PDcBT copolyester is significantly increased, as in examples 1 to 4, the intrinsic viscosity is increased to 0.61dL/g to 0.74dL/g, and the mechanical properties are excellent (table 3). Therefore, the introduction of TDD can obviously improve the characteristic viscosity of the PcBT homopolyester and improve the mechanical property of the PcBT homopolyester.

3. Polymerization temperature, precipitate and copolyester transparency

In the PCcBT system, because CHDM has high reaction activity and PCT homopolyester is easy to crystallize and has high melting point, when the PCcBT is synthesized at lower temperature, a long CT sequence or even PCT homopolymer is easy to generate, so that a product is easy to crystallize and precipitate at low temperature, the melt polycondensation is difficult to proceed, and a high-molecular-weight product is difficult to obtain, such as the comparative example 1 of the invention; even if melt polycondensation is possible, the melt is not clarified at the lower temperature (260 ℃) all the time, and the final product appears opaque or low in transparency, as in comparative example 2 of the present invention.

In the prior art, the transparent PCcBT with high molecular weight is synthesized by adopting high (more than or equal to 280 ℃) polycondensation reaction temperature, but is easy to discolor. The copolyester provided by the invention adopts TDD to completely or partially replace CHDM monomers, so that a long CT sequence can be avoided, no opaque precipitate is generated in the polymerization process, a polymerization system is always kept in a molten state, and the copolyester with high intrinsic viscosity, colorless and transparent can be prepared at a lower polycondensation reaction temperature (260 ℃).

In the present invention, the copolyesters obtained in comparative example 2, example 2 and example 9 were molded into a sheet, the transparency was visually observed (see fig. 2), and the light transmittance was measured, and the results are shown in table 4.

TABLE 4 light transmittance of copolyester in examples and comparative examples

The PCcBT copolyester prepared in comparative example 2 using low temperature (polycondensation at 260 ℃) had low light transmittance (66.07%) and low transparency to the naked eye ((a) in fig. 2); whereas the PDcBT copolyester of similar composition prepared at low temperature (260 ℃) in example 2 of the present invention has a light transmittance of more than 85% (note: limited by the purity of the TDD monomer raw material, which is obtained in the case of using a lower purity TDD monomer (purity of only 96 wt%), (if a higher purity TDD raw material is obtained, the transparency is further improved ((b) in fig. 2).

When a small amount of the third glycol monomer MPO is introduced for copolymerization, the light transmittance of the obtained copolyester PMDcBT is obviously improved compared with that of PDcBT ((c) in FIG. 2). For example, prepared in example 9

The light transmittance of the copolyester reaches 89%.

In example 11, although a small amount of CHDM was used, no precipitate was formed during the reaction due to the small amount, and the polymerization was always carried out in a molten state, and the final product was transparent.

4. With respect to melt thermal stability

In comparative example 2, the PCcBT copolyester was extremely unstable at the melt interface during polycondensation, and was vigorously surged, requiring the breaking of bubbles by rapid stirring to prevent the melt from overflowing from the flask. The polyesters synthesized in examples 1-10, however, were able to maintain a stable melt interface during the vacuum polycondensation process. In example 11, less than 30mol% CHDM was used, the foaming was greater than in examples 1-10, and the foaming and settling phenomena were significantly less than in comparative example 2 due to the lower CHDM level, and a more stable reaction process was maintained. The results demonstrate that the CBDO and TDD based copolyesters prepared according to the present invention have superior melt stability.

To further evaluate the melt stability of the copolyesters, the copolyester samples synthesized in comparative example 2, example 3, example 6 and example 9 and Tritan were mixed ^TM EX401 commercial products (comparative example 3) 1g each were charged to a 50mL flask in N ₂ Heating to 260 deg.C under atmosphere without stirring, maintaining at 260 deg.C for 2 hr, naturally cooling to room temperature, and observing the final state, as shown in FIG. 3.

As can be seen, the PCcBT copolyester and Tritan prepared in comparative example 2 ^TM The EX401 commercial resins all produced large and dense bubbles, and the foaming phenomenon of the PDcBT copolyesters obtained in examples 2 and 3 was significantly reduced; whereas examples 6 and 9, incorporating a third glycol monomer MPO, produced PMDcBT copolyesters with much weaker blistering and significantly less blistering.

When a MiniJet micro-injection molding machine is adopted for injection molding and sample preparation, the PCcBT copolyester prepared in the comparative example 2 is also found to have very obvious expansion and foaming, and the prepared sample strip has defects; no swelling was observed in the copolyesters of examples 1 to 9, and defect-free bars were obtained. The above results show that the copolyester of the present invention has significantly improved melt stability, and is more favorable for smooth polymerization and processing.

Claims

1. A copolyester resin with high heat resistance and high transparency, which comprises diacid residues and diol residues, wherein:

the diacid residues comprise 80 to 100 mole percent of terephthalic acid residues and 0 to 20 mole percent of second aromatic diacid residues based on 100 mole percent of the total;

2. The high heat resistance and high transparency copolyester resin according to claim 1 wherein the second aromatic dibasic acid residue comprises at least one of isophthalic acid residue, phthalic acid residue, biphenyldicarboxylic acid residue, naphthalenedicarboxylic acid residue, furandicarboxylic acid residue, and thiophenedicarboxylic acid residue.

3. The heat-resistant high-transparency copolyester resin according to claim 1, wherein the third diol residue comprises at least one of ethylene glycol residue, 1, 3-propanediol residue, 1, 2-propanediol residue, 2-methyl-1, 3-propanediol residue, 1, 4-butanediol residue, 2, 3-butanediol residue, 1, 5-pentanediol residue, neopentyl glycol residue, 3-methyl 1, 5-pentanediol residue, 2, 4-trimethyl-1, 3-pentanediol residue, diethylene glycol residue, cyclohexanedimethanol residue, and cyclohexanediol residue.

4. The copolyester resin with high heat resistance and high transparency according to claim 1 or 3, wherein the third diol residue is at least one of 1, 4-cyclohexanedimethanol residue and 2-methyl-1, 3-propanediol residue.

5. The copolyester resin with high heat resistance and high transparency according to claim 1, wherein the intrinsic viscosity of the copolyester resin is 0.50-1.0dL/g, the glass transition temperature is 105-170 ℃, and the light transmittance is 85-93%.

6. A preparation method of copolyester resin with high heat resistance and high transparency is characterized by comprising the following steps:

the total amount of the dibasic acid component is 100mol percent and comprises 80 to 100 percent of terephthalic acid or dialkyl ester thereof; and 0 to 20mol% of a second aromatic dibasic acid or a dialkyl ester thereof;

7. The method for preparing copolyester resin with high heat resistance and high transparency according to claim 6, wherein the aromatic dibasic acid or its dialkyl ester comprises at least one of isophthalic acid or its dialkyl ester, phthalic acid or its dialkyl ester, biphenyl dicarboxylic acid or its dialkyl ester, naphthalene dicarboxylic acid or its dialkyl ester, furan dicarboxylic acid or its dialkyl ester, thiophene dicarboxylic acid or its dialkyl ester.

8. The method for preparing a copolyester resin with high heat resistance and high transparency according to claim 6, wherein the aliphatic diol having carbon atom number of the main chain less than or equal to 5 comprises at least one of ethylene glycol, 1, 3-propanediol, 1, 2-propanediol, 1, 4-butanediol, 2, 3-butanediol, 1, 5-pentanediol, 2-methyl-1, 5-pentanediol, 3-methyl-1, 5-pentanediol, 2-ethyl-1, 5-pentanediol, 3-dimethyl-1, 5-pentanediol, 3-diethyl-1, 5-pentanediol, 2-methyl-1, 3-propanediol, 2-ethyl-1, 3-propanediol, diethylene glycol;

and/or the alicyclic ring with the carbon number less than or equal to 11 is selected from at least one of cyclohexane dimethanol and cyclohexane diol.

9. The method as claimed in claim 6, wherein the second dialkyl aromatic diacid ester includes at least one of dimethyl isophthalate, dimethyl phthalate, dimethyl bibenzoate, dimethyl naphthanate, dimethyl furandicarboxylate, and dimethyl thiophenedicarboxylate.

10. The method for preparing copolyester resin with high heat resistance and high transparency according to claim 6, wherein the catalyst is tin catalyst or comprises tin catalyst and one or more of n-butyl titanate, isopropyl titanate, lithium acetate, potassium acetate, calcium acetate, magnesium acetate, barium acetate, zinc acetate, cobalt acetate, antimony acetate, lead acetate and manganese acetate; the tin catalyst is one or more selected from dibutyltin oxide, dimethyltin oxide, stannous octoate, stannous oxalate, dibutyl dimethoxytin, dibutyltin diacetate, monobutyl triisotin octoate and dibutyltin dilaurate;

and/or the dosage of the catalyst is 0.01 to 0.5 weight percent of the weight of the dibasic acid component;

and/or, also adding a stabilizer into the reaction mixture, wherein the dosage of the stabilizer is 0.01 to 0.5 weight percent of the mass of the dibasic acid component;

and/or, the stabilizer is selected from one or more of an antioxidant 1010, an antioxidant 1076, an antioxidant 1500, an antioxidant 425, a heat stabilizer 330, a heat stabilizer 1178, a heat stabilizer 618, a heat stabilizer 626, a heat stabilizer 168, trimethyl phosphite, triethyl phosphite, triisooctyl phosphite, triisodecyl phosphite, trilauryl phosphite, tris (tridecyl) phosphite, trioctadecyl phosphite, triphenyl phosphite, tri-p-tolyl phosphite, ditridecyl phosphite, tris (2, 4-di-tert-butylphenyl) phosphite, bis (2, 4-di-p-isopropylphenyl) pentaerythritol diphosphite phosphoric acid, pentaerythritol tetrapentaphenyl tridecyl phosphite, pentaerythritol diphosphite, pentaerythritol diisodecyl diphosphite, tetraphenylpropylene glycol diphosphite, phosphorous acid, triethyl polyphosphate and phosphonoacetate, a light stabilizer 791, a light stabilizer 700, a light stabilizer 783, a light stabilizer 119, a light stabilizer 770, a light stabilizer 944 and a light stabilizer 1164.