Preparation method of block polyester-polycarbonate

Abstract

The invention belongs to the technical field of polyester copolymerization modification, and relates to a preparation method of block polyester-polycarbonate, which comprises the following steps: by taking dimethyl carbonate and dihydric alcohol as raw materials, and dihydric alcohol and dibasic acid dimethyl ester or dibasic acid as raw materials, sequentially performing esterification and pre-polycondensation reaction under the action of a catalyst, thereby obtaining the block polyester-polycarbonate. The preparation method comprises the following steps: respectively obtaining a carbonic acid ester with a methoxy end group and a dibasic acid ester with a hydroxyl end group, mixing the carbonic acid ester with the methoxy end group and the dibasic acid ester with the hydroxyl end group, and carrying out final polycondensation reaction under a negative pressure condition to prepare block polyester-polycarbonate; the number-average molecular weight of the carbonate ester with the end group being methoxyl is 430-4000 g / mol; and the difference between the number-average molecular weight of the carbonate chain segment in the block polyester-polycarbonate and the number-average molecular weight of the carbonate ester with the end group being methoxyl is less than 5%. The preparation method is simple and easy to implement, and the obtained block polyester-polycarbonate is excellent in thermal performance and mechanical performance.

Description

Technical Field

[0001] This invention belongs to the field of polyester copolymer modification technology, and relates to a method for preparing block polyester-polycarbonate. Background Technology

[0002] In today's chemical materials field, sustainable development and green chemistry have become core driving forces for industry development. With increasing environmental awareness and rising demand for environmentally friendly materials, the development of novel, green, and efficient polymer preparation processes is urgently needed. Against this backdrop, dimethyl carbonate (DMC), as a high-performance and widely used "green" chemical raw material, has shown great potential in polymer preparation and is gradually becoming a research focus. Its unique structure with multiple functional groups (carbonyl, methyl, and methoxy) endows it with diverse chemical reactivity. Due to its low toxicity and biodegradability, DMC is hailed as a "new cornerstone" of organic synthesis, offering significant advantages in chemical production such as safety, convenience, low pollution, and easy transportation, meeting the requirements of modern "clean processes." In polymer synthesis, the transesterification of dimethyl carbonate with aliphatic or aromatic diols to synthesize polycarbonate is a highly attractive green process. This process is not only environmentally friendly but also enables the synthesized polycarbonate to possess potential biocompatibility, biodegradability, and non-toxicity. In addition, dimethyl carbonate can be used to prepare many other types of polymers, greatly enriching the variety and properties of polymers.

[0003] However, despite the promising prospects of dimethyl carbonate in polymer preparation, it still faces some technical challenges. For example, the representative polymer, polyester-polycarbonate, typically involves flexible units in the reaction. When rigid units react, the reactivity of the system varies too much, making it impossible to achieve polyester-polycarbonate with good thermal and mechanical properties such as heat resistance. For instance, CN117343296A and CN116102720A both involve methods for preparing polybutylene terephthalate-co-butylene carbonate, where the diol unit is a 1,4-butanediol segment, and the copolymer is a random copolymer. This results in poor thermal and mechanical properties because random polymers generally have a randomly distributed molecular structure, and the disordered arrangement weakens intermolecular forces. Simultaneously, crystallinity is also weakened, leading to inferior thermal and mechanical properties compared to polymers with ordered molecular structures. Furthermore, the copolyester segments have poor regularity and insufficient crystallinity, resulting in a narrow range of applications, particularly in high-end applications such as engineering plastics, cosmetics, and bottling.

[0004] Therefore, it is of great significance to study a method for preparing block polyester-polycarbonate in order to solve the problems existing in the prior art. Summary of the Invention

[0005] The purpose of this invention is to solve the problems existing in the prior art and provide a method for preparing block polyester-polycarbonate.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing block polyester-polycarbonate involves using dimethyl carbonate and diol as raw materials, and diol and dimethyl diacid or diacid as raw materials, and sequentially carrying out esterification and pre-condensation reactions under the action of a catalyst to obtain carbonates with methoxy-terminated groups and diacids with hydroxyl-terminated groups, respectively. The carbonates with methoxy-terminated groups and the diacids with hydroxyl-terminated groups are mixed and then subjected to a final condensation reaction under negative pressure. In this process, the esterified group undergoes end-group transesterification reaction to obtain block polyester-polycarbonate.

[0008] The number average molecular weight of carbonates with methoxy end groups is 430~4000 g / mol. The molecular weight of carbonates with methoxy end groups in this invention is controlled within this range. Too high or too low a molecular weight is not conducive to the construction of block polymers and will lead to uneven distribution of polymer properties.

[0009] The method of the present invention has high preparation efficiency and produces block polyester-polycarbonate segments with good regularity and small sequence structure deviation.

[0010] The number-average molecular weight of the carbonate segments in block polyester-polycarbonate differs from that of carbonates with methoxy end groups by less than 5%, indicating small sequence structure deviation, i.e. good regularity, and no significant interchain transesterification reaction has occurred.

[0011] The transesterification process of carbonates is shown below:

[0012] ;

[0013] The transesterification process of the diester ester is shown below:

[0014] ;

[0015] Wherein, R1 is a diol unit that does not contain a hydroxyl group, and R2 is a dicarboxylic acid unit that does not contain a carboxyl group.

[0016] The final polycondensation reaction route is shown below:

[0017] .

[0018] As a preferred technical solution:

[0019] In the preparation method of block polyester-polycarbonate as described above, when preparing carbonates with methoxy end groups, the molar ratio of dimethyl carbonate to diol is 2~2.5:1, the esterification reaction temperature is 80~160℃, the esterification reaction time is 4~6h, the pre-condensation reaction temperature is 160~180℃, the pre-condensation reaction time is 2~4h, and the pre-condensation reaction pressure is 100~1000Pa.

[0020] In the block polyester-polycarbonate preparation method described above, the number average molecular weight of the hydroxyl-terminated diester is 430~4000 g / mol; when preparing the hydroxyl-terminated diester, the molar ratio of diol to dimethyl diacid or diacid is 1.3~2:1, the esterification reaction temperature is 170~240℃, the esterification reaction time is 2~4h, the pre-condensation reaction temperature is 240~280℃, the pre-condensation reaction time is 1~2h, and the pre-condensation reaction pressure is 50~1000 Pa.

[0021] In the preparation method of block polyester-polycarbonate as described above, the catalyst is a composite catalyst composition consisting of an alkali metal catalyst and a titanium-based catalyst.

[0022] The alkali metal catalyst is one or more of sodium methoxide, sodium ethoxide, sodium hydroxide, and potassium hydroxide;

[0023] The titanium-based catalyst is one or more of tetraethyl titanate, tetrabutyl titanate, titanium isopropoxide, titanium glycolate, and titanium dioxide;

[0024] The molar ratio of alkali metal catalyst to titanium catalyst is 1~10:1.

[0025] In the method for preparing block polyester-polycarbonate as described above, the diol is one or more selected from 1,4-cyclohexanediol, 1,4-cyclohexanediol, isosorbide, 2,2,4,4-tetramethylcyclobutanediol, 2,5-furandiol, and spirodiol; and the diacid is terephthalic acid, isophthalic acid, 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, etc. The dicarboxylic acid is selected from one or more of 1,4-succinic acid, 1,6-adipic acid, and 1,10-sebacic acid, and the dicarboxylic acid dimethyl ester is selected from one or more of dimethyl terephthalate, dimethyl isophthalate, dimethyl 2,5-furandicarboxylate, dimethyl 2,4-furandicarboxylate, dimethyl 1,4-cyclohexanedicarboxylate, dimethyl 1,4-succinic acid, dimethyl 1,6-adipic acid, and dimethyl 1,10-sebacic acid.

[0026] In the block polyester-polycarbonate preparation method described above, the mass ratio of the diester with hydroxyl end group and the carbonate with methoxy end group is 10:90~90:10.

[0027] In the preparation method of block polyester-polycarbonate as described above, the final polycondensation reaction temperature is 250~280℃. Too low a reaction temperature will prevent the final polycondensation reaction from proceeding; while too high a reaction temperature will enhance the thermal degradation side reaction in the final polycondensation reaction and affect the color of the product. The final polycondensation reaction time is 2~6h, and the final polycondensation reaction pressure is 1~100Pa.

[0028] In the preparation method of block polyester-polycarbonate described above, the end carboxyl group content of the hydroxyl-terminated diester is 2~10 mg KOH·g. -1 The dicarboxylic acid reaction rate is 95-99%, and the water content is <100ppm.

[0029] In the preparation method of block polyester-polycarbonate described above, the content of terminal hydroxyl groups in the methoxy-terminated carbonate is 2~15 mg KOH·g. -1 The diol reaction rate is 95-99%.

[0030] The block polyester-polycarbonate preparation method described above provides a block polyester-polycarbonate with an intrinsic viscosity of 0.7~1.5 g / dL, a melt index of 5~50 g / 10 min, and a number-average molecular weight of 3.5 × 10⁻⁶. 4 g / mol ~ 1×10 5 g / mol, oligomer content less than 0.01wt%, softening temperature of 50~150℃, and tensile strength of 45~70MPa.

[0031] Invention principle:

[0032] In existing technologies, block polyester-polycarbonate is mainly prepared by ring-opening reactions, such as CN120005155A, CN120289958A, CN119875089A, and CN114573799B. However, due to the limited reaction mechanism, this process suffers from low efficiency and high cost in preparing high-performance polymers (high glass transition temperature, high melting point, etc.). To overcome these problems, CN110407991A discloses a method for preparing block polyester-polycarbonate by reacting aliphatic polycarbonate soft segments (hydroxyl-terminated polyols) with furan dicarboxylate esters. Since both the aliphatic polycarbonate soft segments and furan dicarboxylate esters are hydroxyl-terminated, the polycondensation relies on the removal of the diol unit from the diester, resulting in poor reactivity.

[0033] This invention creatively proposes a novel method for preparing block polyester-polycarbonate. By constructing carbonate blocks with methoxy end groups of a certain molecular weight and reacting them with diesters, it avoids the problems of insufficient reactivity and numerous side reactions in rigid carbonate units that lead to deviations in the polymer sequence structure. Specifically:

[0034] This invention first obtains carbonates with methoxy-terminated ends and diesters with hydroxyl-terminated ends through esterification and pre-condensation reactions, respectively. The carbonate portion is obtained by fully reacting excess dimethyl carbonate with a diol, achieving complete shielding of the hydroxyl unit under alkali metal catalysis. Co-condensation is then performed on these two esters with defined end groups and specific molecular weights. Chain growth primarily occurs through transesterification to remove methanol. The diol unit of the carbonate remains in the chain, causing minimal loss, and the sequence of the carbonate block can be stably controlled. The methoxy end groups of the carbonates prevent transesterification between the diol units of the two esters, especially between the carbonates and diesters, avoiding sequence structure deviations caused by significant differences in reactivity between the esters.

[0035] Beneficial effects:

[0036] (1) A method for preparing block polyester-polycarbonate of the present invention uses a two-step transesterification reaction method to control the end group composition of the esterified compound, thereby achieving efficient and high-quality preparation of high-performance block polyester-polycarbonate with rigid structure.

[0037] (2) The present invention provides a method for preparing block polyester-polycarbonate by constructing a carbonate block with a certain molecular weight methoxy end group and reacting it with a diester, thereby avoiding the problem of insufficient reactivity of rigid carbonate units and many side reactions leading to deviations in polymer sequence structure.

[0038] (3) The present invention provides a method for preparing block polyester-polycarbonate, which is simple and easy to implement, and the resulting block polyester-polycarbonate has excellent thermal and mechanical properties. Attached Figure Description

[0039] Figure 1 The infrared spectrum of block polyester-polycarbonate in Example 1;

[0040] Figure 2 The NMR spectrum of block polyester-polycarbonate in Example 1 is shown; where m is the degree of polymerization of the ester unit and n is the degree of polymerization of the carbonate unit. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0042] The test methods involved in the performance indicators in the embodiments and comparative examples of this invention are as follows:

[0043] (1) Number average molecular weight test: The number average molecular weight of the sample to be tested was determined by gel permeation chromatography (GPC). Specifically, the sample to be tested was dissolved in hexafluoroisopropanol solvent (2 mg / ml). Before the test, the sample was calibrated with polystyrene standard (manufacturer: Scrstandard, brand: SCPS).

[0044] (2) Intrinsic viscosity test: The capillary viscometer method in GB / T 14190-2017 standard was used to test the intrinsic viscosity of polyester-polycarbonate using phenol and 2,2,4,4-tetrachloroethane in a mass ratio of 1:1.

[0045] (3) Terminal hydroxyl test: The terminal hydroxyl value of the ester was determined by an automatic potentiometric titrator, referring to GB / T12008.7-2010 standard.

[0046] (4) Terminal carboxyl group test: The test was performed using the volumetric titration method in GB / T14190-2017 standard.

[0047] (5) Tensile strength test: According to GB / T 1040.1-2006 standard, block polyester-polycarbonate was injection molded into dumbbell-shaped tensile specimens of 150mm×10mm×4mm. After relieving thermal stress at room temperature for 2 weeks, the tensile strength test was carried out at a tensile rate of 50mm / min. -1 .

[0048] (6) Testing of oligomer content: The oligomer content was tested according to GB / T 27843-2011 standard.

[0049] (7) Softening temperature test: The softening temperature of the copolyester was tested using the ASTM D6480 standard.

[0050] (8) Moisture content: Tested according to ASTM D6869 standard.

[0051] (9) Number-average molecular weight of carbonate segments in block polyester-polycarbonate: Calculated using NMR, the relative integral area of ​​methylene hydrogen attached to hydroxyl groups in the ester segment is I1, the relative integral area of ​​methylene hydrogen attached to hydroxyl groups in the carbonate segment is I3, and the integral area of ​​methylene hydrogen in the transition segment connecting the ester and carbonate segments is I2; Number-average molecular weight of carbonate blocks = ( +2) × molecular weight of carbonate repeating unit +90 (carbonate end groups consumed in the reaction, i.e. -OCH3 and -COOCH3), unit: g / mol.

[0052] Example 1

[0053] A method for preparing block polyester-polycarbonate, comprising the following specific steps:

[0054] (1) Preparation of raw materials:

[0055] Dimethyl carbonate;

[0056] Diol: 1,4-cyclohexanediethanol;

[0057] Dimethyl dicarboxylate: Dimethyl terephthalate;

[0058] Catalyst I: A composite catalyst composition consisting of sodium methoxide and tetraethyl titanate in a molar ratio of 1:1;

[0059] Catalyst ⅠⅠ: A composite catalyst composition consisting of sodium methoxide and tetraethyl titanate in a molar ratio of 10:1;

[0060] (2) Using dimethyl carbonate and diol as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of catalyst I to obtain carbonates with methoxy end groups;

[0061] The molar ratio of dimethyl carbonate to diol is 2:1, the esterification reaction temperature is 80℃, the esterification reaction time is 6h, the pre-condensation reaction temperature is 160℃, the pre-condensation reaction time is 4h, and the pre-condensation reaction pressure is 100Pa.

[0062] The number-average molecular weight of the carbonates with methoxy-terminated groups was 2130 g / mol, and the content of terminal hydroxyl groups was 2 mg KOH·g. -1 The diol reaction rate is 99%.

[0063] (3) Using diol and dimethyl diacid as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of catalyst ⅠⅠ to obtain a diacid ester with hydroxyl end groups;

[0064] The molar ratio of diol to dimethyl diacid is 1.5:1, the esterification reaction temperature is 170℃, the esterification reaction time is 4h, the pre-condensation reaction temperature is 240℃, the pre-condensation reaction time is 2h, and the pre-condensation reaction pressure is 50Pa.

[0065] The number-average molecular weight of the diesters with hydroxyl groups at the ends was 1000 g / mol, and the content of terminal carboxyl groups was 2 mg KOH·g. -1 The dicarboxylic acid reaction rate is 99%, and the water content is 10 ppm.

[0066] (4) After mixing the methoxy-terminated carbonate and the hydroxy-terminated diester, the final polycondensation reaction was carried out at 250°C and 1Pa for 6 hours to obtain block polyester-polycarbonate.

[0067] The mass ratio of the diester with hydroxyl end group to the carbonate with methoxy end group is 50:50.

[0068] The final block polyester-polycarbonate had an intrinsic viscosity of 0.8 g / dL, a melt index of 20 g / 10 min, and a number-average molecular weight of 4 × 10⁻⁶. 4 g / mol, oligomer content of 0.002 wt%, softening temperature of 70℃, and tensile strength of 60 MPa; Figure 2 The NMR spectrum shown indicates that the number-average molecular weight of the carbonate segments in the block polyester-polycarbonate is 2158 g / mol, which differs from the number-average molecular weight of carbonates with methoxy end groups by 1.3%.

[0069] like Figure 1 As shown, the carbonate bond is 1741 cm⁻¹. -1 Aromatic ester bond 1712cm -1 The two characteristic peaks indicate that the block polyester-polycarbonate was successfully prepared.

[0070] Comparative Example 1

[0071] A method for preparing polyester-polycarbonate is basically the same as in Example 1, except that: in step (2), the molar ratio of dimethyl carbonate to diol is 1:1.5, and the synthesized carbonate compound has hydroxyl end groups.

[0072] The final polyester-polycarbonate had an intrinsic viscosity of 0.67 g / dL, a melt index of 17 g / 10 min, and a number-average molecular weight of 3.0 × 10⁻⁶. 4 g / mol, oligomer content 1.3wt%, softening temperature 70℃, tensile strength 42MPa; the number average molecular weight of carbonate segments in polyester-polycarbonate differs from that of carbonates with hydroxyl end groups by 10%.

[0073] Comparing Comparative Example 1 and Example 1, it can be found that the molecular weight of Comparative Example 1 is reduced, and the oligomer content and the difference between the number-average molecular weight of carbonate segments and the number-average molecular weight of carbonates with hydroxyl end groups are significantly increased. This is because the carbonates formed by excess diols have hydroxyl end groups. When reacting with diols, the terminal diol units undergo transesterification, which is more difficult than the reaction between hydroxyl and methoxy groups, resulting in a relatively lower molecular weight and an increased oligomer content. In addition, the terminal hydroxyl groups are prone to inter-chain transesterification when no other reactive groups are present, which leads to the disruption of the ordered block sequence, manifested as a significant increase in the difference in number-average molecular weight before and after carbonate segment copolymerization.

[0074] Comparative Example 2

[0075] A method for preparing block polyester-polycarbonate is basically the same as in Example 1, except that the number average molecular weight of the carbonate with methoxy end groups is controlled to be 260 g / mol by shortening the pre-polymerization time.

[0076] The final polyester-polycarbonate had a number-average molecular weight of 3.5 × 10⁻⁶. 4 g / mol, with an oligomer content of 5.0 wt%.

[0077] Comparing Comparative Example 2 with Example 1, it can be found that the molecular weight of Comparative Example 2 is lower and the oligomer content is higher. This is because when the carbonate chain segment is too short, there are more end-group reaction sites, which can easily lead to a significant reduction in the final polycondensation reaction time, poor reaction uniformity, and the presence of unreacted carbonate chain segments, resulting in a decrease in molecular weight and an increase in oligomer content.

[0078] Comparative Example 3

[0079] A method for preparing block polyester-polycarbonate is basically the same as in Example 1, except that the number average molecular weight of the carbonate with methoxy end groups is controlled to be 6040 g / mol.

[0080] The final polyester-polycarbonate had a number-average molecular weight of 1.0 × 10⁻⁶. 4 g / mol.

[0081] Comparing Comparative Example 3 and Example 1, it can be found that the molecular weight is significantly reduced. This is because the carbonate chain segment is too long, reducing the number of end groups available for reaction, making the copolyester reaction more difficult and thus reducing the molecular weight.

[0082] Comparative Example 4

[0083] A method for preparing block polyester-polycarbonate is basically the same as in Example 1, except that: after the esterification reaction in steps (2) and (3), the pre-condensation reaction is not carried out directly, but the esterification products of steps (2) and (3) are blended and then subjected to pre-condensation and final condensation reactions in sequence.

[0084] The final polyester-polycarbonate has a softening temperature of 50℃ and a tensile strength of 45MPa.

[0085] Comparing Comparative Example 4 with Example 1, it can be found that the softening temperature and breaking strength of Comparative Example 4 are both reduced. This is because the esterified compounds were not pre-polymerized separately but were directly mixed and then pre-polymerized and finally polymerized. The units directly underwent transesterification, and the resulting product was a random copolymer. The copolyester's crystallinity is not as good as that of the block copolymer, which leads to a decrease in softening temperature and breaking strength.

[0086] Example 2

[0087] A method for preparing block polyester-polycarbonate, comprising the following specific steps:

[0088] (1) Preparation of raw materials:

[0089] Dimethyl carbonate;

[0090] Diol: 1,4-cyclohexanediol;

[0091] Dicarboxylic acid: isophthalic acid;

[0092] Catalyst I: A composite catalyst composition consisting of sodium ethoxide and tetrabutyl titanate in a molar ratio of 3:1;

[0093] Catalyst ⅠⅠ: A composite catalyst composition consisting of sodium ethoxide and tetrabutyl titanate in a molar ratio of 9:1;

[0094] (2) Using dimethyl carbonate and diol as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of catalyst I to obtain carbonates with methoxy end groups;

[0095] The molar ratio of dimethyl carbonate to diol is 2.1:1, the esterification reaction temperature is 90℃, the esterification reaction time is 5.75h, the pre-condensation reaction temperature is 165℃, the pre-condensation reaction time is 3.5h, and the pre-condensation reaction pressure is 200Pa.

[0096] The number-average molecular weight of the carbonates with methoxy-terminated groups was 430 g / mol; the content of terminal hydroxyl groups was 4.2 mg KOH·g. -1 The diol reaction rate is 96%;

[0097] (3) Using diols and diacids as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of catalyst ⅠⅠ to obtain diacid esters with hydroxyl end groups;

[0098] The molar ratio of diol to diacid is 1.7:1, the esterification reaction temperature is 180℃, the esterification reaction time is 3.75h, the pre-condensation reaction temperature is 250℃, the pre-condensation reaction time is 1.75h, and the pre-condensation reaction pressure is 100Pa.

[0099] The number-average molecular weight of the diesters with hydroxyl-terminated groups was 2980 g / mol; the terminal carboxyl group content was 3.5 mg KOH·g. -1 The dicarboxylic acid reaction rate is 99%, and the water content is 20 ppm;

[0100] (4) After mixing the methoxy-terminated carbonate and the hydroxyl-terminated diester, the mixture was subjected to a final polycondensation reaction at 255°C and 10Pa for 5.5 h to obtain block polyester-polycarbonate.

[0101] The mass ratio of the diester with hydroxyl end group to the carbonate with methoxy end group is 10:90.

[0102] The final block polyester-polycarbonate had an intrinsic viscosity of 1 g / dL, a melt index of 12 g / 10 min, and a number-average molecular weight of 6.5 × 10⁻⁶. 4 g / mol, oligomer content of 0.007wt%, softening temperature of 50℃, and tensile strength of 45MPa; the number-average molecular weight of carbonate segments in block polyester-polycarbonate differs from that of carbonates with methoxy end groups by 0.2%.

[0103] Example 3

[0104] A method for preparing block polyester-polycarbonate, comprising the following specific steps:

[0105] (1) Preparation of raw materials:

[0106] Dimethyl carbonate;

[0107] Diol: Isosorbide;

[0108] Dimethyl dicarboxylate: Dimethyl 2,5-furandicarboxylate;

[0109] Catalyst I: A composite catalyst composition consisting of sodium hydroxide and titanium isopropoxide in a molar ratio of 5:1;

[0110] Catalyst ⅠⅠ: A composite catalyst composition consisting of sodium hydroxide and titanium isopropoxide in a molar ratio of 7:1;

[0111] (2) Using dimethyl carbonate and diol as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of catalyst I to obtain carbonates with methoxy end groups;

[0112] The molar ratio of dimethyl carbonate to diol is 2.2:1, the esterification reaction temperature is 100℃, the esterification reaction time is 5.5h, the pre-condensation reaction temperature is 170℃, the pre-condensation reaction time is 3h, and the pre-condensation reaction pressure is 400Pa.

[0113] The number-average molecular weight of the carbonates with methoxy-terminated groups was 1450 g / mol; the content of terminal hydroxyl groups was 7 mg KOH·g. -1 The diol reaction rate is 99%;

[0114] (3) Using diol and dimethyl diacid as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of catalyst II to obtain a diacid ester with hydroxyl end groups;

[0115] The molar ratio of diol to dimethyl diacid is 1.3:1, the esterification reaction temperature is 190℃, the esterification reaction time is 3.5h, the pre-condensation reaction temperature is 260℃, the pre-condensation reaction time is 1.5h, and the pre-condensation reaction pressure is 200Pa.

[0116] The number-average molecular weight of the diesters with hydroxyl-terminated groups was 430 g / mol; the content of terminal carboxyl groups was 5 mg KOH·g. -1 The dicarboxylic acid reaction rate is 96%, and the water content is 10 ppm;

[0117] (4) After mixing the methoxy-terminated carbonate and the hydroxy-terminated diester, the mixture was subjected to a final polycondensation reaction at 260°C and 20Pa for 5 hours to obtain block polyester-polycarbonate.

[0118] The mass ratio of the diester with hydroxyl end group to the carbonate with methoxy end group is 20:80.

[0119] The final block polyester-polycarbonate had an intrinsic viscosity of 0.9 g / dL, a melt index of 15 g / 10 min, and a number-average molecular weight of 5 × 10⁻⁶. 4 g / mol, oligomer content of 0.003wt%, softening temperature of 150℃, and tensile strength of 70MPa; the number-average molecular weight of carbonate segments in block polyester-polycarbonate differs from that of carbonates with methoxy end groups by 0.7%.

[0120] Example 4

[0121] A method for preparing block polyester-polycarbonate, comprising the following specific steps:

[0122] (1) Preparation of raw materials:

[0123] Dimethyl carbonate;

[0124] Diol: 2,2,4,4-Tetramethylcyclobutanediol;

[0125] Dimethyl dicarboxylate: a mixture of dimethyl 1,4-cyclohexanedicarboxylate and dimethyl 1,10-sebacic acid in a mass ratio of 1:1;

[0126] Catalyst I: A composite catalyst composition consisting of potassium hydroxide and titanium glycol in a molar ratio of 7:1;

[0127] Catalyst ⅠⅠ: A composite catalyst composition consisting of potassium hydroxide and titanium glycol in a molar ratio of 5:1;

[0128] (2) Using dimethyl carbonate and diol as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of catalyst I to obtain carbonates with methoxy end groups;

[0129] The molar ratio of dimethyl carbonate to diol is 2.3:1, the esterification reaction temperature is 120℃, the esterification reaction time is 5h, the pre-condensation reaction temperature is 175℃, the pre-condensation reaction time is 2.5h, and the pre-condensation reaction pressure is 600Pa.

[0130] The number-average molecular weight of the carbonates with methoxy-terminated groups was 2130 g / mol; the content of terminal hydroxyl groups was 10 mg KOH·g. -1 The diol reaction rate is 95%;

[0131] (3) Using diol and dimethyl diacid as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of catalyst II to obtain a diacid ester with hydroxyl end groups;

[0132] The molar ratio of diol to dimethyl diacid is 1.9:1, the esterification reaction temperature is 200℃, the esterification reaction time is 3h, the pre-condensation reaction temperature is 270℃, the pre-condensation reaction time is 1.25h, and the pre-condensation reaction pressure is 500Pa.

[0133] The number-average molecular weight of the diesters with hydroxyl-terminated groups was 2130 g / mol; the terminal carboxyl group content was 7.5 mg KOH·g. -1 The dicarboxylic acid reaction rate is 97%, and the water content is 70 ppm;

[0134] (4) After mixing the methoxy-terminated carbonate and the hydroxy-terminated diester, the final polycondensation reaction was carried out at 265°C and 50Pa for 4 hours to obtain block polyester-polycarbonate.

[0135] The mass ratio of the diester with hydroxyl end group to the carbonate with methoxy end group is 40:60.

[0136] The final block polyester-polycarbonate had an intrinsic viscosity of 0.7 g / dL, a melt index of 30 g / 10 min, and a number-average molecular weight of 3.5 × 10⁻⁶. 4 g / mol, oligomer content of 0.008wt%, softening temperature of 100℃, and tensile strength of 65MPa; the number-average molecular weight of carbonate segments in block polyester-polycarbonate differs from that of carbonates with methoxy end groups by 0.8%.

[0137] Example 5

[0138] A method for preparing block polyester-polycarbonate, comprising the following specific steps:

[0139] (1) Preparation of raw materials:

[0140] Dimethyl carbonate;

[0141] Diol: 2,5-furandiethanol;

[0142] Dicarboxylic acid: 2,4-furandicarboxylic acid;

[0143] Alkali metal catalyst: a mixture of sodium hydroxide and potassium hydroxide in a 1:1 mass ratio;

[0144] Titanium-based catalyst: tetraethyl titanate and titanium dioxide in a 1:1 mass ratio;

[0145] Catalyst I: A composite catalyst composition consisting of an alkali metal catalyst and a titanium catalyst in a molar ratio of 9:1;

[0146] Catalyst ⅠⅠ: A composite catalyst composition consisting of an alkali metal catalyst and a titanium catalyst in a molar ratio of 3:1;

[0147] (2) Using dimethyl carbonate and diol as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of catalyst I to obtain carbonates with methoxy end groups;

[0148] The molar ratio of dimethyl carbonate to diol is 2.4:1, the esterification reaction temperature is 140℃, the esterification reaction time is 4.5h, the pre-condensation reaction temperature is 178℃, the pre-condensation reaction time is 2.25h, and the pre-condensation reaction pressure is 800Pa.

[0149] The number-average molecular weight of the carbonates with methoxy-terminated groups was 2980 g / mol; the content of terminal hydroxyl groups was 12 mg KOH·g. -1 The diol reaction rate is 98%;

[0150] (3) Using diols and diacids as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of catalyst ⅠⅠ to obtain diacid esters with hydroxyl end groups;

[0151] The molar ratio of diol to diacid is 1.6:1, the esterification reaction temperature is 220℃, the esterification reaction time is 2.5h, the pre-condensation reaction temperature is 275℃, the pre-condensation reaction time is 1h, and the pre-condensation reaction pressure is 800Pa.

[0152] The number-average molecular weight of the diesters with hydroxyl-terminated groups was 1450 g / mol; the content of terminal carboxyl groups was 8 mg KOH·g. -1 The dicarboxylic acid reaction rate is 99%, and the water content is 50 ppm.

[0153] (4) After mixing the methoxy-terminated carbonate and the hydroxy-terminated diester, the mixture was subjected to a final polycondensation reaction at 270°C and 80Pa for 3 hours to obtain block polyester-polycarbonate.

[0154] The mass ratio of the diester with hydroxyl end group to the carbonate with methoxy end group is 80:20.

[0155] The final block polyester-polycarbonate had an intrinsic viscosity of 1.5 g / dL, a melt index of 5 g / 10 min, and a number-average molecular weight of 1 × 10⁻⁶. 5 g / mol, oligomer content of 0.009wt%, softening temperature of 120℃, and tensile strength of 70MPa; the number-average molecular weight of carbonate segments in block polyester-polycarbonate differs from that of carbonates with methoxy end groups by 0.8%.

[0156] Example 6

[0157] A method for preparing block polyester-polycarbonate, comprising the following specific steps:

[0158] (1) Preparation of raw materials:

[0159] Dimethyl carbonate;

[0160] Diol: A mixture of 1,4-cyclohexanediol and spirodiol in a mass ratio of 1:1;

[0161] Dicarboxylic acid: a mixture of 1,4-succinic acid and 1,6-adipic acid in a mass ratio of 1:1;

[0162] Catalyst I: A composite catalyst composition consisting of sodium methoxide and titanium dioxide in a molar ratio of 10:1;

[0163] Catalyst ⅠⅠ: A composite catalyst composition consisting of sodium ethoxide and titanium glycol in a molar ratio of 1:1;

[0164] (2) Using dimethyl carbonate and diol as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of catalyst I to obtain carbonates with methoxy end groups;

[0165] The molar ratio of dimethyl carbonate to diol is 2.5:1, the esterification reaction temperature is 160℃, the esterification reaction time is 4h, the pre-condensation reaction temperature is 180℃, the pre-condensation reaction time is 2h, and the pre-condensation reaction pressure is 1000Pa.

[0166] The number-average molecular weight of the carbonates with methoxy-terminated groups was 4000 g / mol; the content of terminal hydroxyl groups was 15 mg KOH·g. -1 The diol reaction rate is 97%.

[0167] (3) Using diols and diacids as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of catalyst II to obtain diacid esters with hydroxyl end groups;

[0168] The molar ratio of diol to diacid is 2:1, the esterification reaction temperature is 240℃, the esterification reaction time is 2h, the pre-condensation reaction temperature is 280℃, the pre-condensation reaction time is 1h, and the pre-condensation reaction pressure is 1000Pa.

[0169] The number-average molecular weight of the diesters with hydroxyl-terminated ends was 4000 g / mol; the end-carboxyl group content was 10 mg KOH·g. -1 The dicarboxylic acid reaction rate is 95%, and the water content is 50 ppm;

[0170] (4) After mixing the methoxy-terminated carbonate and the hydroxyl-terminated diester, the final polycondensation reaction was carried out at 280°C and 100Pa for 2 hours to obtain block polyester-polycarbonate.

[0171] The mass ratio of the diester with hydroxyl end group to the carbonate with methoxy end group is 90:10.

[0172] The final block polyester-polycarbonate had an intrinsic viscosity of 1.2 g / dL, a melt index of 8 g / 10 min, and a number-average molecular weight of 7 × 10⁻⁶. 4 g / mol, oligomer content of 0.008wt%, softening temperature of 100℃, and tensile strength of 68MPa; the number-average molecular weight of carbonate segments in block polyester-polycarbonate differs from that of carbonates with methoxy end groups by 0.5%.

Claims

1. A method for preparing block polyester-polycarbonate, characterized in that: Using dimethyl carbonate and diol as raw materials, and diol and dimethyl diacid or diacid as raw materials, esterification and pre-condensation reactions are carried out sequentially under the action of a catalyst to obtain carbonates with methoxy-terminated groups and diacids with hydroxy-terminated groups, respectively. The carbonates with methoxy-terminated groups and the diacids with hydroxy-terminated groups are mixed and then subjected to a final condensation reaction under negative pressure to obtain block polyester-polycarbonate. The number-average molecular weight of carbonates with methoxy end groups is 430~4000 g / mol; The number-average molecular weight of carbonate segments in block polyester-polycarbonate differs from that of carbonate compounds with methoxy end groups by less than 5%.

2. The method for preparing a block polyester-polycarbonate according to claim 1, characterized in that, When preparing carbonates with methoxy end groups, the molar ratio of dimethyl carbonate to diol is 2~2.5:1, the esterification reaction temperature is 80~160℃, the esterification reaction time is 4~6h, the pre-condensation reaction temperature is 160~180℃, the pre-condensation reaction time is 2~4h, and the pre-condensation reaction pressure is 100~1000Pa.

3. The method for preparing a block polyester-polycarbonate according to claim 1, characterized in that, The number-average molecular weight of the hydroxyl-terminated diesters is 430~4000 g / mol. When preparing hydroxyl-terminated diesters, the molar ratio of diol to dimethyl diacid or diacid is 1.3~2:1, the esterification reaction temperature is 170~240℃, the esterification reaction time is 2~4h, the pre-condensation reaction temperature is 240~280℃, the pre-condensation reaction time is 1~2h, and the pre-condensation reaction pressure is 50~1000Pa.

4. The method for preparing a block polyester-polycarbonate according to claim 1, characterized in that, The catalyst is a composite catalyst composition, consisting of an alkali metal catalyst and a titanium-based catalyst. The alkali metal catalyst is one or more of sodium methoxide, sodium ethoxide, sodium hydroxide, and potassium hydroxide; The titanium-based catalyst is one or more of tetraethyl titanate, tetrabutyl titanate, titanium isopropoxide, titanium glycolate, and titanium dioxide; The molar ratio of alkali metal catalyst to titanium catalyst is 1~10:

1.

5. The method for preparing a block polyester-polycarbonate according to claim 1, characterized in that, The diol is one or more selected from 1,4-cyclohexanediol, 1,4-cyclohexanediol, isosorbide, 2,2,4,4-tetramethylcyclobutanediol, 2,5-furandiol, and spirodiol; the dicarboxylic acid is one or more selected from terephthalic acid, isophthalic acid, 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,4-succinic acid, 1,6-adipic acid, and 1,10-sebacic acid; and the dimethyl terephthalate is one or more selected from dimethyl terephthalate, dimethyl isophthalate, dimethyl 2,5-furandicarboxylate, dimethyl 2,4-furandicarboxylate, dimethyl 1,4-cyclohexanedicarboxylate, dimethyl 1,4-succinate, dimethyl 1,6-adipic acid, and dimethyl 1,10-sebacic acid.

6. The method for preparing a block polyester-polycarbonate according to claim 1, characterized in that, The mass ratio of the diester with hydroxyl end group to the carbonate with methoxy end group is 10:90 to 90:

10.

7. The method for preparing a block polyester-polycarbonate according to claim 1, characterized in that, The final polycondensation reaction temperature is 250~280℃, the final polycondensation reaction time is 2~6h, and the final polycondensation reaction pressure is 1~100Pa.

8. The method for preparing a block polyester-polycarbonate according to claim 1, characterized in that, The terminal carboxyl group content of diesters with hydroxyl groups is 2~10 mg KOH·g. -1 The dicarboxylic acid reaction rate is 95-99%, and the water content is <100ppm.

9. The method for preparing a block polyester-polycarbonate according to claim 1, characterized in that, The content of terminal hydroxyl groups in carbonates with methoxy groups is 2~15 mg KOH·g. -1 The diol reaction rate is 95-99%.

10. The method for preparing a block polyester-polycarbonate according to claim 1, characterized in that, The intrinsic viscosity of block polyester-polycarbonate is 0.7~1.5 g / dL, the melt index is 5~30 g / 10 min, and the number average molecular weight is 3.5×10⁻⁶. 4 g / mol ~ 1×10 5 g / mol, oligomer content less than 0.01wt%, softening temperature of 50~150℃, and tensile strength of 45~70MPa.

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