A process for the preparation of a block polyester-polycarbonate

Abstract

The present application belongs to the technical field of polyester copolymerization modification, and relates to a preparation method of block polyester-polycarbonate. Dimethyl carbonate and dihydric alcohol are used as raw materials, and dihydric alcohol and dimethyl dicarboxylate or dicarboxylic acid are used as raw materials. Under the action of a catalyst, esterification and pre-polycondensation reactions are sequentially performed to obtain carbonate esterification products with methoxy end groups and dicarboxylic acid esterification products with hydroxyl end groups, respectively. The carbonate esterification products with methoxy end groups and the hydroxyl-terminated dicarboxylic acid esterification products are mixed and subjected to final polycondensation reaction under negative pressure to obtain block polyester-polycarbonate. The number average molecular weight of the carbonate esterification products with methoxy end groups is 430-4000 g / mol. The number average molecular weight of the carbonate segment in the block polyester-polycarbonate and the number average molecular weight of the carbonate esterification products with methoxy end groups differ by less than 5%. The preparation method is simple and easy to implement, and the obtained block polyester-polycarbonate has excellent thermal and mechanical properties.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyester copolymerization modification, and relates to a preparation method of block polyester-polycarbonate. BACKGROUND

[0002] In the field of chemical materials today, sustainable development and green chemistry concepts have become the core driving force for industry development. With the enhancement of people's environmental protection consciousness and the continuous rise of demand for environmentally friendly materials, it is urgent to develop new, green and efficient polymer preparation processes. Under this background, dimethyl carbonate (DMC) as a "green" chemical raw material with excellent performance and wide application, has shown great potential in the field of polymer preparation, and has gradually become the focus of research. Its unique structure of carbonyl, methyl and methoxy functional groups endows it with multiple chemical reactivity. Due to its low toxicity, biodegradability and other characteristics, dimethyl carbonate is known as the "new cornerstone" of organic synthesis, and has significant advantages such as safety, convenience, less pollution and easy transportation in chemical production, meeting the requirements of modern "clean process". In the synthesis of polymers, dimethyl carbonate is used to synthesize polycarbonates with aliphatic or aromatic diols through ester exchange method, which is an extremely attractive green process. This process not only protects the environment, but also enables the synthesized polycarbonates to have potential biocompatibility, biodegradability and non-toxicity. In addition, dimethyl carbonate can also be used to prepare other types of polymers, greatly enriching the types and properties of polymers.

[0003] However, although dimethyl carbonate has broad prospects in the field of polymer preparation, it still faces some technical challenges. For example, the representative polymer, polyester-polycarbonate, is usually mainly composed of flexible units, and the difference in reaction activity of rigid units is too large, which cannot realize the preparation of polyester-polycarbonate with good thermal properties and mechanical properties such as heat resistance. CN117343296A and CN116102720A both involve the preparation method of polybutylene terephthalate-co-butylene carbonate, the diol unit of which is 1,4-butanediol segment, and the copolymer is a random copolymer. On the one hand, this leads to poor thermal and mechanical properties of the copolymer, because the random polymer generally has random molecular structure distribution, and the disordered arrangement weakens the intermolecular force, and the crystallization performance is also weakened, which comprehensively leads to poor thermal and mechanical properties compared with ordered polymers. On the other hand, it leads to poor regularity of copolyester segments and insufficient crystallization performance, which comprehensively leads to narrow application scenarios, especially lack of high-end applications such as engineering plastics, cosmetics and bottled products.

[0004] Therefore, it is of great significance to study a preparation method of block polyester-polycarbonate to solve the problems existing in the prior art. SUMMARY

[0005] The application aims to solve the problems in the prior art and provide a preparation method of block polyester-polycarbonate.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows:

[0007] A preparation method of block polyester-polycarbonate, which uses dimethyl carbonate and dihydric alcohol as raw materials, and dihydric alcohol and dimethyl dicarboxylate or dicarboxylic acid as raw materials, and sequentially performs esterification and pre-polycondensation reactions under the action of a catalyst to obtain a carbonate ester compound with a methoxy end group and a dicarboxylic acid ester compound with a hydroxyl end group, respectively, mixes the carbonate ester compound with a methoxy end group and the dicarboxylic acid ester compound with a hydroxyl end group, and performs a final polycondensation reaction under negative pressure, in which process the ester compound is prepared into block polyester-polycarbonate through end group ester exchange reaction;

[0008] The number average molecular weight of the carbonate ester compound with a methoxy end group is 430-4000 g / mol; the molecular weight of the carbonate ester compound with a methoxy end group in the application is controlled in this range, and too high or too low molecular weight is not conducive to the construction of block polymers, which will lead to uneven distribution of polymer performance;

[0009] The method of the application has high preparation efficiency, and the block polyester-polycarbonate prepared has good chain regularity and small sequence structure deviation;

[0010] The number average molecular weight of the carbonate segment in the block polyester-polycarbonate and the number average molecular weight of the carbonate ester compound with a methoxy end group differ by less than 5%, which indicates that the sequence structure deviation is small, i.e., the regularity is good, and no significant inter-chain ester exchange reaction has occurred.

[0011] The ester exchange reaction process of the carbonate ester compound is as follows:

[0012] ;

[0013] The ester exchange reaction process of the dicarboxylic acid ester compound is as follows:

[0014] ;

[0015] Among them, R1 is a dihydric alcohol unit not containing a hydroxyl group, and R2 is a dicarboxylic acid unit not containing a carboxyl group.

[0016] The final polycondensation reaction route is as follows:

[0017] .

[0018] As a preferred technical scheme:

[0019] The preparation method of the block polyester-polycarbonate as claimed in claim 1, wherein, when the terminal group of the carbonate ester is methoxy, the molar ratio of dimethyl carbonate to dihydric alcohol is 2-2.5:1, the esterification reaction temperature is 80-160℃, the esterification reaction time is 4-6h, the pre-polycondensation reaction temperature is 160-180℃, and the pre-polycondensation reaction time is 2-4h and the pre-polycondensation reaction pressure is 100-1000Pa.

[0020] The preparation method of the block polyester-polycarbonate as claimed in claim 1, wherein the number average molecular weight of the dihydric acid ester with hydroxyl group as the terminal group is 430-4000g / mol; and when the terminal group of the dihydric acid ester is hydroxyl, the molar ratio of dihydric alcohol to dimethyl dihydric acid ester or dihydric acid is 1.3-2:1, the esterification reaction temperature is 170-240℃, the esterification reaction time is 2-4h, the pre-polycondensation reaction temperature is 240-280℃, the pre-polycondensation reaction time is 1-2h, and the pre-polycondensation reaction pressure is 50-1000Pa.

[0021] The preparation method of the block polyester-polycarbonate as claimed in claim 1, wherein the catalyst is a composite catalyst composition composed 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 ethylene glycol and titanium dioxide.

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

[0025] The preparation method of the block polyester-polycarbonate as claimed in claim 1, wherein the dihydric alcohol is one or more of 1,4-cyclohexane dimethanol, 1,4-cyclohexane diol, isosorbide, 2,2,4,4-tetramethylcyclobutane diol, 2,5-furan dimethanol and spiro diol, the dihydric acid is one or more of terephthalic acid, isophthalic acid, 2,5-furan dicarboxylic acid, 2,4-furan dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, 1,4-butane dicarboxylic acid, 1,6-hexane dicarboxylic acid and 1,10-decanedioic acid, and the dimethyl dihydric acid ester is one or more of terephthalic acid dimethyl ester, isophthalic acid dimethyl ester, 2,5-furan dicarboxylic acid dimethyl ester, 2,4-furan dicarboxylic acid dimethyl ester, 1,4-cyclohexane dicarboxylic acid dimethyl ester, 1,4-butane dicarboxylic acid dimethyl ester, 1,6-hexane dicarboxylic acid dimethyl ester and 1,10-decanedioic acid dimethyl ester.

[0026] The preparation method of the block polyester-polycarbonate as claimed in claim 1, wherein the mass ratio of the dihydric acid ester with hydroxyl group as the terminal group to the carbonate ester with methoxy group as the terminal 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] The present application firstly obtains a carbonate ester with methoxy end group and a diacid ester with hydroxyl end group with certain molecular weight through esterification and pre-polycondensation reaction, wherein the carbonate ester part is obtained by fully reacting excess dimethyl carbonate with dihydric alcohol, and the hydroxyl unit is completely shielded under the catalysis of alkali metal. The co-polycondensation reaction is carried out by using the above two kinds of esters with certain molecular weight and determined end group, the chain growth is mainly carried out by removing methanol through ester exchange, the dihydric alcohol unit of the carbonate ester is in the chain and basically will not cause loss, and the sequence of the carbonate ester block can be stably controlled; the methoxy end group of the carbonate ester can avoid the ester exchange reaction between the dihydric alcohol units of the two kinds of esters, especially the carbonate ester and the diacid ester, and avoid the sequence structure deviation caused by the large difference in reactivity of the esters.

[0035] Advantages:

[0036] (1) The preparation method of the block polyester-polycarbonate of the present application uses a two-step ester exchange reaction method, controls the end group composition of the ester, and realizes the efficient and high-quality preparation of the high-performance block polyester-polycarbonate with rigid structure.

[0037] (2) The preparation method of the block polyester-polycarbonate of the present application carries out the reaction by using the carbonate block with certain molecular weight and methoxy end group and the diacid ester, and avoids the problems of the insufficient reactivity of the rigid carbonate unit and the deviation of the sequence structure of the polymer caused by the multiple side reactions.

[0038] (3) The preparation method of the block polyester-polycarbonate of the present application is simple and easy to implement, and the block polyester-polycarbonate obtained has excellent thermal and mechanical properties. BRIEF DESCRIPTION OF DRAWINGS

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

[0040] Figure 2 The nuclear magnetic resonance spectrum of the block polyester-polycarbonate of Example 1; wherein m is the polymerization degree of the ester unit, and n is the polymerization degree of the carbonate unit. DETAILED DESCRIPTION

[0041] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not used to limit the scope of the present application. In addition, it should be understood that after reading the content taught by the present application, those skilled in the art can make various modifications or modifications to the present application, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

[0042] The test methods related to the performance indicators in the examples and comparative examples of the present application are as follows:

[0043] (1) Number average molecular weight test: Gel permeation chromatography (GPC) is used to test the number average molecular weight of the sample to be tested. Specifically, a solution of the sample to be tested (2 mg / ml) is dissolved in hexafluoroisopropanol solvent, and a polystyrene standard (manufacturer: Scrstandard, model: SCPS) is used for calibration before testing.

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

[0045] (3) End hydroxyl test: The end hydroxyl value of the ester is determined by automatic potentiometric titrator, and the specific reference is GB / T12008.7-2010 standard.

[0046] (4) End carboxyl test: The volumetric titration method in GB / T14190-2017 standard is used for testing.

[0047] (5) Breaking strength test: According to GB / T 1040.1-2006 standard, the block polyester-polycarbonate is processed into 150mm×10mm×4mm dumbbell-shaped tensile sample by injection molding, and the thermal stress is eliminated at room temperature for 2 weeks before the breaking strength test, and the tensile rate is 50mm / min -1 .

[0048] (6) Test of oligomer content: GB / T 27843-2011 standard is used to test the oligomer content.

[0049] (7) Softening temperature test: ASTM D6480 standard is used to test the softening temperature of copolyester.

[0050] (8) Water content: According to ASTM D6869 standard.

[0051] (9) Number average molecular weight of carbonate segment in block polyester-polycarbonate: calculated by nuclear magnetic resonance, the relative integral area of methylene hydrogen connected to hydroxyl in ester segment is I1, the relative integral area of methylene hydrogen connected to hydroxyl in carbonate segment is I3, and the integral area of methylene hydrogen in the transition segment connecting ester segment and carbonate segment is I2; the number average molecular weight of carbonate block is ( +2)×carbonate repeat unit molecular weight+90 (carbonate end groups consumed in the reaction, i.e. -OCH3 and -COOCH3), unit: g / mol.

[0052] Example 1

[0053] A preparation method of a block polyester-polycarbonate, the specific steps are as follows:

[0054] (1) Preparation of raw materials:

[0055] dimethyl carbonate;

[0056] diol: 1,4-cyclohexane dimethanol;

[0057] dimethyl ester of diacid: dimethyl terephthalate;

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

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

[0060] (2) Esterification and pre-polycondensation reactions were sequentially carried out with dimethyl carbonate and diol as raw materials in the presence of catalyst I to obtain a carbonate esterification product with a methoxy end group;

[0061] wherein the molar ratio of dimethyl carbonate to diol was 2:1, the esterification reaction temperature was 80°C, the esterification reaction time was 6h, the pre-polycondensation reaction temperature was 160°C, the pre-polycondensation reaction time was 4h, and the pre-polycondensation reaction pressure was 100Pa;

[0062] The number average molecular weight of the prepared carbonate esterification product with a methoxy end group was 2130g / mol, the terminal hydroxyl group content was 2mgKOH·g -1 , and the diol reaction rate was 99%.

[0063] (3) Esterification and pre-polycondensation reactions were sequentially carried out with diol and dimethyl ester of diacid as raw materials in the presence of catalyst III to obtain a diacid esterification product with a hydroxyl end group;

[0064] wherein the molar ratio of diol to dimethyl ester of diacid was 1.5:1, the esterification reaction temperature was 170°C, the esterification reaction time was 4h, the pre-polycondensation reaction temperature was 240°C, the pre-polycondensation reaction time was 2h, and the pre-polycondensation reaction pressure was 50Pa;

[0065] The number average molecular weight of the prepared diacid esterification product with a hydroxyl end group was 1000g / mol, the terminal carboxyl group content was 2mgKOH·g -1 , the diacid reaction rate was 99%, and the water content was 10ppm.

[0066] (4) The block polyester-polycarbonate was prepared by mixing the carbonate esterification product with a methoxy end group and the hydroxyl-terminated diacid esterification product and then performing a final polycondensation reaction at a temperature of 250°C and a pressure of 1Pa for 6h;

[0067] wherein the mass ratio of the diacid esterification product with a hydroxyl end group to the carbonate esterification product with a methoxy end group was 50:50.

[0068] The intrinsic viscosity of the final block polyester-polycarbonate is 0.8 g / dL, the melt index is 20 g / 10 min, the number average molecular weight is 4 x 10 4 g / mol, the oligomer content is 0.002 wt%, the softening temperature is 70 °C, and the breaking strength is 60 MPa; as shown in the nuclear magnetic spectrum, the number average molecular weight of the carbonate segment in the block polyester-polycarbonate is 2158 g / mol, and the difference between the number average molecular weight of the carbonate segment in the block polyester-polycarbonate and the number average molecular weight of the carbonate ester with a methoxy end group is 1.3%. Figure 2

[0069] As shown in Figure 1 , the carbonate bond 1741 cm -1 and the aromatic ester bond 1712 cm -1 two characteristic peaks, indicating that the block polyester-polycarbonate is successfully prepared.

[0070] Comparative Example 1

[0071] A method for preparing a polyester-polycarbonate, which is basically the same as Example 1, except that the molar ratio of dimethyl carbonate to diol in step (2) is 1:1.5, and the synthesized is a carbonate ester with a hydroxyl end group;

[0072] The intrinsic viscosity of the final polyester-polycarbonate is 0.67 g / dL, the melt index is 17 g / 10 min, the number average molecular weight is 3.0 x 10 4 g / mol, the oligomer content is 1.3 wt%, the softening temperature is 70 °C, and the breaking strength is 42 MPa; the difference between the number average molecular weight of the carbonate segment in the polyester-polycarbonate and the number average molecular weight of the carbonate ester with a hydroxyl end group is 10%.

[0073] Comparing Comparative Example 1 and Example 1, it can be found that the molecular weight of Comparative Example 1 is reduced, the oligomer content and the difference between the number average molecular weight of the carbonate segment and the number average molecular weight of the carbonate ester with a hydroxyl end group are significantly increased. This is because the excess diol forms a carbonate ester with a hydroxyl end group, which is more difficult to react with the diacid ester than the reaction of hydroxyl and methoxyl, resulting in relatively lower molecular weight and increased oligomer content. In addition, the end hydroxyl group is prone to inter-chain ester exchange reaction in the absence of other reactive groups, which destroys the order of the block sequence, resulting in a large increase in the difference between the number average molecular weight of the carbonate segment before and after copolymerization.

[0074] Comparative Example 2

[0075] ​A method for preparing a block polyester-polycarbonate, which is substantially the same as that of Example 1, except that the number average molecular weight of the carbonate compound with a methoxy end group is controlled to be 260 g / mol by shortening the pre-polycondensation time.

[0076] The number average molecular weight of the finally prepared polyester-polycarbonate is 3.5 x 10 4 g / mol, and the oligomer content is 5.0 wt%.

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

[0078] Comparative Example 3

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

[0080] The number average molecular weight of the finally prepared polyester-polycarbonate is 1.0 x 10 4 g / mol.

[0081] Comparing Example 1 with Comparative Example 3, it can be found that the molecular weight is significantly reduced, because when the carbonate segment is too long, the available end group sites are reduced, which makes the copolyester reaction more difficult and reduces the molecular weight.

[0082] Comparative Example 4

[0083] A method for preparing a block polyester-polycarbonate, which is substantially the same as that of Example 1, except that after the esterification reaction of step (2) and step (3), the esterification products of step (2) and step (3) are blended and then sequentially subjected to pre-polycondensation and final polycondensation reactions.

[0084] The softening temperature of the finally prepared polyester-polycarbonate is 50°C, and the breaking strength is 45 MPa.

[0085] Comparing Example 1 with Comparative Example 4, it can be found that the softening temperature and the breaking strength of Comparative Example 4 are both reduced, because the esterification product is not subjected to pre-polycondensation alone but is directly mixed for pre-polycondensation and final polycondensation, and the ester exchange is directly performed between the units, resulting in a random copolymer, which has a lower crystallization performance than the block copolymer, leading to a reduction in the softening temperature and the breaking strength.

[0086] Example 2

[0087] A method for preparing a block polyester-polycarbonate, the specific steps are as follows:

[0088] (1) Preparation of raw materials:

[0089] Dimethyl carbonate;

[0090] Diol: 1,4-cyclohexane diol;

[0091] Dibasic acid: isophthalic acid;

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

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

[0094] (2) Esterification and pre-polycondensation reactions are sequentially carried out with dimethyl carbonate and diol as raw materials under the action of catalyst I to obtain a carbonate ester compound with a methoxy end group;

[0095] Among them, the molar ratio of dimethyl carbonate to diol is 2.1:1, the esterification reaction temperature is 90°C, the esterification reaction time is 5.75h, the pre-polycondensation reaction temperature is 165°C, the pre-polycondensation reaction time is 3.5h, and the pre-polycondensation reaction pressure is 200Pa;

[0096] The number average molecular weight of the prepared carbonate ester compound with a methoxy end group is 430g / mol; the end hydroxyl content is 4.2mgKOH·g -1 , the diol reaction rate is 96%;

[0097] (3) Esterification and pre-polycondensation reactions are sequentially carried out with diol and dibasic acid as raw materials under the action of catalyst III to obtain a dibasic acid ester compound with a hydroxyl end group;

[0098] Among them, the molar ratio of diol to dibasic acid is 1.7:1, the esterification reaction temperature is 180°C, the esterification reaction time is 3.75h, the pre-polycondensation reaction temperature is 250°C, the pre-polycondensation reaction time is 1.75h, and the pre-polycondensation reaction pressure is 100Pa;

[0099] The number average molecular weight of the prepared dibasic acid ester compound with a hydroxyl end group is 2980g / mol; the end carboxyl content is 3.5mgKOH·g -1 , the dibasic acid reaction rate is 99%, and the water content is 20ppm;

[0100] (4) After mixing the carbonate ester compound with a methoxy end group and the hydroxyl-terminated dibasic acid ester compound, a terminal polycondensation reaction is carried out at a temperature of 255°C and a pressure of 10Pa for 5.5h to prepare a block polyester-polycarbonate;

[0101] The mass ratio of the diacid ester with hydroxyl end group to the carbonate ester with methoxyl end group is 10:90.

[0102] The intrinsic viscosity of the prepared block polyester-polycarbonate is 1 g / dL, the melt index is 12 g / 10 min, the number average molecular weight is 6.5 x 10 4 g / mol, the oligomer content is 0.007 wt%, the softening temperature is 50℃, and the breaking strength is 45 MPa; the difference between the number average molecular weight of the carbonate segment in the block polyester-polycarbonate and the number average molecular weight of the carbonate ester with methoxyl end group is 0.2%.

[0103] Example 3

[0104] A preparation method of a block polyester-polycarbonate, the specific steps are as follows:

[0105] (1) Preparation of raw materials:

[0106] Dimethyl carbonate;

[0107] Diol: isosorbide;

[0108] Dimethyl dicarboxylate: dimethyl 2,5-furan dicarboxylate;

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

[0110] Catalyst III: a composite catalyst composition composed of sodium hydroxide and titanium isopropoxide with a molar ratio of 7:1;

[0111] (2) Using dimethyl carbonate and diol as raw materials, esterification and pre-polycondensation reactions are sequentially carried out under the action of catalyst I to obtain a carbonate ester with methoxyl end group;

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

[0113] The number average molecular weight of the prepared carbonate ester with methoxyl end group is 1450 g / mol; the hydroxyl end group content is 7 mgKOH·g -1 , and the diol reaction rate is 99%;

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

[0115] The molar ratio of the dihydric alcohol and the dimethyl dicarboxylate is 1.3:1, the esterification reaction temperature is 190°C, the esterification reaction time is 3.5h, the pre-polycondensation reaction temperature is 260°C, the pre-polycondensation reaction time is 1.5h, and the pre-polycondensation reaction pressure is 200Pa;

[0116] The number average molecular weight of the dihydric acid esterification product with a hydroxyl end group is 430g / mol; the carboxyl end group content is 5mgKOH·g -1 , the dihydric acid reaction rate is 96%, and the water content is 10ppm;

[0117] (4) The carbonate esterification product with a methoxyl end group and the hydroxyl-terminated dihydric acid esterification product are mixed and subjected to a final polycondensation reaction at a temperature of 260°C and a pressure of 20Pa for 5h to obtain a block polyester-polycarbonate;

[0118] The mass ratio of the dihydric acid esterification product with a hydroxyl end group and the carbonate esterification product with a methoxyl end group is 20:80.

[0119] The block polyester-polycarbonate finally obtained has an intrinsic viscosity of 0.9g / dL, a melt index of 15g / 10min, a number average molecular weight of 5×10 4 g / mol, an oligomer content of 0.003wt%, a softening temperature of 150°C, and a breaking strength of 70MPa; the number average molecular weight of the carbonate segment in the block polyester-polycarbonate and the number average molecular weight of the carbonate esterification product with a methoxyl end group differ by 0.7%.

[0120] Example 4

[0121] A preparation method of a block polyester-polycarbonate, and the specific steps are as follows:

[0122] (1) Preparation of raw materials:

[0123] Dimethyl carbonate;

[0124] Dihydric alcohol: 2,2,4,4-tetramethylcyclobutane diol;

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

[0126] Catalyst I: a composite catalyst composition composed of potassium hydroxide and titanium glycolate with a molar ratio of 7:1;

[0127] Catalyst III: a composite catalyst composition composed of potassium hydroxide and titanium glycolate with a molar ratio of 5:1;

[0128] (2) Dimethyl carbonate and dihydric alcohol are used as raw materials, and esterification and pre-polycondensation reactions are sequentially carried out under the action of catalyst I to obtain a carbonate esterification product with a methoxyl end group;

[0129] wherein the molar ratio of dimethyl carbonate to dihydric alcohol is 2.3:1, the esterification reaction temperature is 120°C, the esterification reaction time is 5h, the pre-polycondensation reaction temperature is 175°C, the pre-polycondensation reaction time is 2.5h, and the pre-polycondensation reaction pressure is 600Pa;

[0130] The number average molecular weight of the prepared carbonate ester compound with methoxy end group is 2130g / mol; the end hydroxyl group content is 10mgKOH.g -1 , the dihydric alcohol reaction rate is 95%; and

[0131] (3) using dihydric alcohol and dimethyl dicarboxylate as raw materials, esterification and pre-polycondensation reactions are sequentially carried out under the action of catalyst II to obtain a diacid ester compound with hydroxyl end group;

[0132] wherein the molar ratio of dihydric alcohol to dimethyl dicarboxylate is 1.9:1, the esterification reaction temperature is 200°C, the esterification reaction time is 3h, the pre-polycondensation reaction temperature is 270°C, the pre-polycondensation reaction time is 1.25h, and the pre-polycondensation reaction pressure is 500Pa;

[0133] The number average molecular weight of the prepared diacid ester compound with hydroxyl end group is 2130g / mol; the end carboxyl group content is 7.5mgKOH.g -1 , the diacid reaction rate is 97%, and the water content is 70ppm;

[0134] (4) mixing the carbonate ester compound with methoxy end group and the diacid ester compound with hydroxyl end group, and then performing a final polycondensation reaction at a temperature of 265°C and a pressure of 50Pa for 4h to prepare a block polyester-polycarbonate;

[0135] wherein the mass ratio of the diacid ester compound with hydroxyl end group to the carbonate ester compound with methoxy end group is 40:60.

[0136] The intrinsic viscosity of the finally prepared block polyester-polycarbonate is 0.7g / dL, the melt index is 30g / 10min, the number average molecular weight is 3.5x10 4 g / mol, the oligomer content is 0.008wt%, the softening temperature is 100°C, and the breaking strength is 65MPa; the difference between the number average molecular weight of the carbonate segment in the block polyester-polycarbonate and the number average molecular weight of the carbonate ester compound with methoxy end group is 0.8%.

[0137] Example 5

[0138] A method for preparing a block polyester-polycarbonate, the specific steps of which are as follows:

[0139] (1) preparation of raw materials:

[0140] dimethyl carbonate;

[0141] diol: 2,5-furandimethanol;

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

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

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

[0145] Catalyst I: a composite catalyst composition composed of an alkali metal catalyst and a titanium-based catalyst with a molar ratio of 9:1;

[0146] Catalyst II: a composite catalyst composition composed of an alkali metal catalyst and a titanium-based catalyst with a molar ratio of 3:1;

[0147] (2) using dimethyl carbonate and diol as raw materials, esterification and pre-polycondensation reactions are sequentially carried out under the action of catalyst I to obtain a carbonate ester compound with a methoxy end group;

[0148] wherein the molar ratio of dimethyl carbonate to diol is 2.4:1, the esterification reaction temperature is 140°C, the esterification reaction time is 4.5h, the pre-polycondensation reaction temperature is 178°C, the pre-polycondensation reaction time is 2.25h, and the pre-polycondensation reaction pressure is 800Pa;

[0149] The number average molecular weight of the prepared carbonate ester compound with a methoxy end group is 2980g / mol; the terminal hydroxyl group content is 12mgKOH·g -1 , and the diol reaction rate is 98%;

[0150] (3) using diol and diacid as raw materials, esterification and pre-polycondensation reactions are sequentially carried out under the action of catalyst II to obtain a diacid ester compound with a hydroxyl end group;

[0151] wherein the molar ratio of diol to diacid is 1.6:1, the esterification reaction temperature is 220°C, the esterification reaction time is 2.5h, the pre-polycondensation reaction temperature is 275°C, the pre-polycondensation reaction time is 1h, and the pre-polycondensation reaction pressure is 800Pa;

[0152] The number average molecular weight of the prepared diacid ester compound with a hydroxyl end group is 1450g / mol; the terminal carboxyl group content is 8mgKOH·g -1 , the diacid reaction rate is 99%, and the water content is 50ppm;

[0153] (4) mixing the carbonate ester compound with a methoxy end group and the hydroxyl-terminated diacid ester compound, and then performing a final polycondensation reaction at a temperature of 270°C and a pressure of 80Pa for 3h to obtain a block polyester-polycarbonate;

[0154] The mass ratio of the diacid ester with hydroxyl end group and the carbonate ester with methoxyl end group is 80:20.

[0155] The intrinsic viscosity of the prepared block polyester-polycarbonate is 1.5 g / dL, the melt index is 5 g / 10 min, the number average molecular weight is 1 x 10 5 g / mol, the oligomer content is 0.009 wt%, the softening temperature is 120℃, and the breaking strength is 70 MPa; the difference between the number average molecular weight of the carbonate segment in the block polyester-polycarbonate and the number average molecular weight of the carbonate ester with methoxyl end group is 0.8%.

[0156] Example 6

[0157] A method for preparing a block polyester-polycarbonate, the specific steps are as follows:

[0158] (1) Preparation of raw materials:

[0159] Dimethyl carbonate;

[0160] Diol: a mixture of 1,4-cyclohexane dimethanol and spiro glycol with a mass ratio of 1:1;

[0161] Diacid: a mixture of 1,4-succinic acid and 1,6-hexanedioic acid with a mass ratio of 1:1;

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

[0163] Catalyst III: a composite catalyst composition composed of sodium ethoxide and titanium glycolate with a molar ratio of 1:1;

[0164] (2) Using dimethyl carbonate and diol as raw materials, esterification and pre-polycondensation reactions are sequentially carried out under the action of catalyst I to obtain a carbonate ester with a methoxyl end group;

[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-polycondensation reaction temperature is 180℃, the pre-polycondensation reaction time is 2h, and the pre-polycondensation reaction pressure is 1000Pa;

[0166] The number average molecular weight of the prepared carbonate ester with a methoxyl end group is 4000 g / mol; the hydroxyl end group content is 15 mgKOH·g -1 , and the diol reaction rate is 97%;

[0167] (3) Using diol and diacid as raw materials, esterification and pre-polycondensation reactions are sequentially carried out under the action of catalyst II to obtain a diacid ester with a hydroxyl end group;

[0168] The molar ratio of dihydric alcohol to diacid is 2:1, the esterification temperature is 240°C, the esterification time is 2h, the pre-polycondensation temperature is 280°C, the pre-polycondensation time is 1h, and the pre-polycondensation pressure is 1000Pa;

[0169] The number average molecular weight of the diacid esterification product with a hydroxyl end group is 4000g / mol; the carboxyl end group content is 10mgKOH·g -1 , the diacid reaction rate is 95%, and the water content is 50ppm;

[0170] (4) The hydroxyl-terminated diacid esterification product and the methoxyl-terminated carbonate esterification product are mixed and then subjected to a final polycondensation reaction at a temperature of 280°C and a pressure of 100Pa for 2h to obtain a block polyester-polycarbonate;

[0171] The mass ratio of the hydroxyl-terminated diacid esterification product to the methoxyl-terminated carbonate esterification product is 90:10.

[0172] The final block polyester-polycarbonate has an intrinsic viscosity of 1.2g / dL, a melt index of 8g / 10min, a number average molecular weight of 7×10 4 g / mol, an oligomer content of 0.008wt%, a softening temperature of 100°C, and a breaking strength of 68MPa; the number average molecular weight of the carbonate segment in the block polyester-polycarbonate and the number average molecular weight of the methoxyl-terminated carbonate esterification product differ 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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