Aliphatic-aromatic polyesters, process for their preparation and use

Abstract

The present application relates to polyester material, disclose a kind of aliphatic-aromatic polyester and its preparation method and application.The light transmittance of the aliphatic-aromatic polyester is greater than 90% when the thickness is 5-100mm, and the elongation at break of the aliphatic-aromatic polyester is 50-1050%.The preparation method comprises the following steps: (1) under esterification reaction conditions, aliphatic diol monomer containing the structure shown in formula (I), aromatic monomer containing the structure shown in formula (II) and catalyst are mixed to carry out first stage reaction, and obtain prepolymer;(2) under polycondensation reaction conditions, the second stage reaction is carried out to the prepolymer.The aliphatic-aromatic polyester not only has good toughness, but also has good light transmission performance.

Description

TECHNICAL FIELD

[0001] The present application relates to polyester materials, in particular to an aliphatic-aromatic polyester and a preparation method and application thereof. BACKGROUND

[0002] At present, the commonly used optical grade transparent polymers on the market include biaxially oriented polyester film (BOPET), polystyrene (PS), polycarbonate (PC) and polymethyl methacrylate (PMMA), etc. Due to their good transparency (light transmittance greater than 85%), they become the most important strategic materials in the optoelectronic industry chain. However, the BOPET, PS, PC and PMMA materials contain a large number of benzene rings or side methyl rigid groups in the structure, and the toughness of the materials is poor (elongation at break less than 10%), which is difficult to meet the performance requirements in application fields with high toughness requirements. Moreover, ordinary PET is a semi-crystalline polyester, and after special process of biaxial orientation (BO), the orientation and crystallization microstate of the material are changed, so that the light transmittance of BOPET can reach more than 88% to meet the optical requirements of optical base film.

[0003] CN109320699A discloses a thermoplastic aliphatic-aromatic copolyester elastomer, which is obtained by polymerization of 1,4-butanediol monomer, aliphatic diacid monomer and 4,4'-diphenyl ether dicarboxylic acid or 4,4'-diphenyl ether dimethyl ester monomer, but the transparency of the prepared material still needs to be improved.

[0004] Most of the windows and showcases in the prior art still use glass materials. Common glasses are organic glass (polymethyl methacrylate) and inorganic glass. Whether it is organic glass or inorganic glass, the elongation at break is basically low (for example, the elongation at break of organic glass is only 2-3%), which leads to low toughness and brittleness of these glasses, and they are easy to break. When used as windows or showcases, it is easy to break and increase the replacement cost. Although some high molecular materials meet the toughness requirement and are not easy to break, their light transmittance does not meet the requirements and cannot be used for windows and showcases. SUMMARY

[0005] The present application aims to overcome the problem that the polyester material in the prior art is difficult to have both transparency and toughness, and provides an aliphatic-aromatic polyester and a preparation method and application thereof. The aliphatic-aromatic polyester has high toughness and good light transmission performance under high thickness conditions.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present application provides an aliphatic-aromatic polyester, the light transmittance of which is greater than 90% when the thickness is 5-100mm, and the elongation at break of the aliphatic-aromatic polyester is 50-1050%.

[0007] The second aspect of the present application provides a preparation method of the aliphatic-aromatic polyester, comprising the following steps:

[0008] (1) mixing an aliphatic diol monomer containing the structure shown in formula (I), an aromatic monomer containing the structure shown in formula (II) and a catalyst under esterification reaction conditions to perform a first stage reaction to obtain a prepolymer;

[0009]

[0010] R1 is C4-C8 alkylene, and R2, R3, R4, R5, R6, R7, R8 and R9 are each independently C1-C4 alkyl or hydrogen;

[0011] (2) performing a second stage reaction on the prepolymer under polycondensation reaction conditions.

[0012] The third aspect of the present application provides the application of the above-mentioned aliphatic-aromatic polyester or the aliphatic-aromatic polyester prepared by the above-mentioned preparation method in optical films, outer packaging films or polymer glasses.

[0013] The aliphatic-aromatic polyester provided by the present application has a light transmittance of >90% for a 5-100mm thick polyester piece after hot forming, which indicates that the polyester has good light transmittance under high thickness conditions; the aliphatic-aromatic polyester has an elongation at break of 50-1050%, which indicates that the polyester has good toughness. The aliphatic-aromatic polyester can meet the requirements of high transparency and toughness.

[0014] Moreover, the strength and elongation at break of the aliphatic-aromatic polyester can be adjusted by adjusting the number of methylene groups in the aliphatic diol structural unit, so that polyester materials meeting different use requirements can be obtained, which can be used as optical films, packaging bags, window glasses and showcase glasses, etc., further expanding the application space of polyester materials.

[0015] The preparation method provided by the present application prepares the aliphatic-aromatic polyester by performing esterification reaction and polycondensation reaction on the monomers at one time, which is simple in operation, strong in process controllability and easy to realize industrialization of the product. Moreover, the prepared polyester can meet the requirements of light transmittance and toughness, which expands a new method for preparing polyester materials meeting the requirements of light transmittance and toughness. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the infrared spectrum of the aliphatic-aromatic polyester prepared in Example 1;

[0017] Figure 2 is the wide-angle X-ray diffraction spectrum of the aliphatic-aromatic polyester prepared in Example 1;

[0018] Figure 3 is a DSC melting curve of the aliphatic-aromatic polyester prepared in Example 1;

[0019] Figure 4 is a stress-strain curve of the aliphatic-aromatic polyester prepared in Example 1. DETAILED DESCRIPTION

[0020] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numerical value, however, can include any values up to the stated value, or down to the stated value, or up and down to the stated value. For ranges, the endpoints are included in the ranges. For numerical values, the endpoints are included in the numerical values. Numerical values are provided as approximate values that are understood to include values close to the stated value. Numerical values include values approximating the stated value within 10%, 5%, 1%, or 0.5% of the stated value.

[0021] As described above, the first aspect of the present application provides an aliphatic-aromatic polyester, the light transmittance of which is greater than 90% when the thickness is 5-100 mm, and the elongation at break of which is 50-1050%.

[0022] The aliphatic-aromatic polyester provided by the present application has a light transmittance of 5-100 mm thick polyester piece after hot pressing > 90%, which indicates that the polyester has good light transmittance under high thickness conditions; the elongation at break of the aliphatic-aromatic polyester is 50-1050%, which indicates that the polyester has good toughness. It can be used as optical glass.

[0023] Preferably, the light transmittance of the aliphatic-aromatic polyester is greater than 90% when the thickness is 30-100 mm. The polyester meeting this condition can be better applied to window glass and showcase glass.

[0024] In the present application, the polyester is made into a sheet with a thickness of 5-100 mm by hot pressing, and then cut into a size of 2 cm x 5 cm. The light transmittance of the polyester at this thickness is obtained by taking air light transmittance as the reference object and reading the transmittance at a wavelength of 550 nm using a UV-1911i spectrophotometer of Shimadzu Corporation.

[0025] In the present application, the synthetic aliphatic-aromatic polyester is made into a sample sheet with a thickness of 1 mm by hot pressing, and then a sample strip with a thickness of 1 mm and a width of 4 mm in the narrow part is made using a dumbbell-shaped cutting tool (4th dumbbell-shaped cutting tool in GB / T 528-2009 standard). The elongation at break is determined by using a WD-II 10 type electronic universal testing machine of Shenzhen Kaiqiangli according to GB / T 1040-1992 at a tensile rate of 50 mm / min, and the elongation at break of the aliphatic-aromatic polyester is the elongation at break at the time of fracture.

[0026] Preferably, the crystallinity of the aliphatic-aromatic polyester is less than or equal to 0.4%, which indicates that the polyester has good light transmission performance and is more suitable for use as optical glass. In order to further improve the light transmission performance of the aliphatic-aromatic polyester, it is further preferred that the crystallinity of the aliphatic-aromatic polyester is less than or equal to 0.1%. More preferably, the crystallinity of the aliphatic-aromatic polyester is 0.

[0027] According to the present application, the crystallinity is measured according to the method shown in GB / T 17931-1999.

[0028] Preferably, the aliphatic-aromatic polyester provided by the present application has a crystallinity of less than or equal to 0.4% after being stored at 25°C for 300 days. It is further preferred that the crystallinity of the aliphatic-aromatic polyester is less than or equal to 0.1% after being stored at 25°C for 300 days.

[0029] Preferably, the aliphatic-aromatic polyester is an amorphous polymer. Specifically, the aliphatic-aromatic polyester is an amorphous polymer at a temperature of 25°C. The aliphatic-aromatic polyester having an amorphous form has better light transmission performance.

[0030] According to the present application, preferably, the glass transition temperature of the aliphatic-aromatic polyester is 10-55°C. It is further preferred that the tensile strength of the aliphatic-aromatic polyester is 2.5-25 MPa.

[0031] Preferably, the polyester is a copolyester containing structural unit A shown in formula (I) and structural unit B shown in formula (II),

[0032]

[0033] wherein R1 is C4-C8 alkylene, R2, R3, R4, R5, R6, R7, R8 and R9 are each independently C1-C4 alkyl or hydrogen.

[0034] Specifically, R1 can be C4-C8 linear alkylene or C4-C8 branched alkylene. n can be an integer of 90-160. Preferably, the weight average molecular weight of the polyester is 30000-50000 g / mol.

[0035] During the research, the inventors unexpectedly found that the interaction between the structural unit A and the structural unit B without other structural influence can break the crystalline structure of the polyester, so that the polyester exhibits excellent optical performance characteristic of amorphous state, has a high light transmittance, and the light transmittance of the polyester part with a thickness of 5-100 mm or even 30-100 mm after hot-pressing is greater than 90%. Moreover, the polyester can be endowed with good toughness. The polyester achieves high transparency and high toughness, and has good application effect on optical films, outer packaging films or polymer glasses. Moreover, the strength and elongation at break of the polyester can be adjusted by adjusting the number of carbon (C) atoms in the structural unit A, so that polyester materials meeting different use requirements can be obtained, and the application space of the polyester materials is further expanded.

[0036] As a specific embodiment of the present application, each of R2, R3, R4, R5, R6, R7, R8 and R9 is independently methyl or hydrogen.

[0037] Preferably, R1 is a branched alkylene group with 6-8 carbon atoms. The aliphatic-aromatic polyester obtained under the above conditions can better meet the requirements of light transmittance and toughness.

[0038] The inventors unexpectedly found during the research that limiting the mass content of titanium element in the polyester to less than or equal to 0.15% can effectively improve the light transmittance of the polyester. In order to further improve the long-term light transmittance of the polyester, preferably, the mass content of titanium element in the aliphatic-aromatic polyester is less than or equal to 0.05%. The mass content of titanium element in the polyester refers to the mass percentage of titanium element in the polyester.

[0039] The content of titanium element in the aliphatic-aromatic polyester can be measured by elemental analysis. Specifically, a flame atomic absorption spectrophotometer is used to measure the titanium element in the polyester.

[0040] The second aspect of the present application provides a preparation method of an aliphatic-aromatic polyester, comprising the following steps:

[0041] (1) mixing an aliphatic diol monomer containing a structure represented by formula (I), an aromatic monomer containing a structure represented by formula (II) and a catalyst under esterification reaction conditions to perform a first stage reaction to obtain a prepolymer;

[0042] wherein,

[0043]

[0044] R1 is C4-C8 alkylene, R2, R3, R4, R5, R6, R7, R8 and R9 are each independently C1-C4 alkyl or hydrogen;

[0045] (2) the prepolymer is subjected to a second stage reaction under polycondensation reaction conditions.

[0046] According to the present application, the aromatic monomer is an aromatic diacid and / or an aromatic diacid ester. Specifically, the aromatic diacid ester can be an ester of an aromatic diacid and / or an aromatic diacid with any one of C1-C4 diols. When the aromatic diacid is used as the monomer, the end condition of the first stage reaction can be determined by the tester according to the actual situation, and preferably, can be determined according to the amount of water in the product. In one specific embodiment of the present application, the end condition of the first stage reaction is that when the collected amount of water reaches 80% of the theoretical value, the esterification reaction ends. When the aromatic diacid ester is used as the monomer, it can be specifically aromatic diacid dimethyl ester, aromatic diacid diethyl ester, aromatic diacid dipropyl ester, aromatic diacid dibutyl ester or other feasible aromatic diacid ester compounds. Preferably, the aromatic diacid ester is aromatic diacid methyl ester, and the transesterification reaction is easier to proceed. The time of the first stage reaction is generally 3-4h.

[0047] The end condition of the second stage reaction can also be determined by the tester according to the actual situation, and preferably, can be determined according to the viscosity of the reaction system. In one specific embodiment of the present application, the end condition of the second stage reaction is that the viscosity of the system no longer changes after reaction. The time of the second stage reaction is generally 3-4h.

[0048] The inventors found in the research process that the polyester prepared by the above preparation method can have good transparency and high toughness at the same time. Moreover, the method is simple to operate, has strong process controllability, and is easy to realize industrialization of the product. A new method is developed for preparing polyester materials with high transparency and high toughness.

[0049] In one specific embodiment of the present application, R2, R3, R4, R5, R6, R7, R8 and R9 are each independently methyl or hydrogen.

[0050] Preferably, R1 is C6-C8 branched alkylene. The aliphatic-aromatic polyester obtained under the above conditions can better meet the requirements of light transmission and toughness.

[0051] As one specific embodiment of the present application, the aromatic monomer is 3,3'-diphenyl ether dicarboxylic acid and / or 3,3'-diphenyl ether dimethyl dicarboxylate, and the synthesis route is as shown below:

[0052]

[0053] R1 is C4-C8 alkylene; R2, R3, R4, R5, R6, R7, R8 and R9 are each independently C1-C4 alkyl or hydrogen.

[0054] Preferably, the molar ratio of the aliphatic diol monomer and the aromatic monomer is 1-4:1. Under the above molar ratio, the molecular weight of the polyester prepared can be ensured to be within a suitable range, while the conversion rate of the reaction can be improved on the premise of ensuring the cost, and the boiling point of the aliphatic diol is relatively low, facilitating the subsequent separation of the product and the reactant and avoiding waste of raw materials. Further preferably, when the aromatic monomer is an aromatic diacid, the molar ratio of the aliphatic diol monomer and the aromatic diacid is 2-4:1; when the aromatic monomer is an aromatic diacid methyl ester, the molar ratio of the aliphatic diol monomer and the aromatic diacid ester is 1-1.1:1.

[0055] According to the present application, preferably, the catalyst is a titanium-containing catalyst and / or a non-titanium-containing catalyst. Preferably, the molar ratio of the catalyst and the aromatic monomer is 0.5-1:100, which can be specifically 0.5:100, 0.6:100, 0.7:100, 0.8:100, 0.9:100, 1:100, or any value between the foregoing values, under the above molar ratio, the reaction effect of the aliphatic diol monomer and the aromatic monomer can be ensured on the basis of as little cost as possible. Further preferably, the catalyst is a titanium-containing catalyst and a non-titanium-containing catalyst, and the molar ratio of the titanium-containing catalyst and the non-titanium-containing catalyst is 1:1-4. Limiting the molar ratio of the titanium-containing catalyst and the non-titanium-containing catalyst within the above range can further improve the transparency of the polyester material on the premise of ensuring the catalytic effect. In order to further improve the light transmittance of the polyester material, preferably, the mass ratio of the titanium-containing catalyst and the non-titanium-containing catalyst is 1:1-4; the titanium-containing catalyst is tetrabutyl titanate and / or tetraethyl titanate; and the non-titanium-containing catalyst is selected from at least one of stannous chloride, stannous octoate, zinc acetate and p-toluenesulfonic acid.

[0056] Preferably, in step (1), the esterification reaction conditions at least include: oxygen isolation, and the temperature is 160-180℃. Under the above conditions, the aliphatic diol monomer and the aromatic monomer have better esterification effect, which can further enable the polyester prepared subsequently to have higher transparency and toughness. Oxygen isolation is usually achieved by filling inert gases such as nitrogen or helium into the reaction system. The first stage reaction is carried out under stirring, and the stirring rate can be determined by the test personnel according to the actual situation.

[0057] Preferably, in step (2), the polycondensation reaction conditions at least include: temperature of 220-240℃, specifically can be 220℃, 225℃, 230℃, 235℃, 240℃, or any value between the aforementioned values; absolute vacuum degree of 50-80Pa, specifically can be 50Pa, 60Pa, 70Pa, 80Pa, or any value between the aforementioned values. Under the above conditions, the ester monomer obtained by esterification of the aliphatic dihydric alcohol monomer and the aromatic monomer has better polycondensation effect, thereby enabling the prepared polyester to have higher transparency and toughness.

[0058] The third aspect of the present application provides application of the above-mentioned aliphatic-aromatic polyester or the aliphatic-aromatic polyester prepared by the above-mentioned preparation method to optical films, outer packaging films or polymer glasses.

[0059] The above-mentioned aliphatic-aromatic polyester has good light transmission performance and toughness, and has good application effect on optical films, outer packaging films or polymer glasses.

[0060] According to a particularly preferred embodiment of the present application, the preparation method of the aliphatic-aromatic polyester comprises the following steps:

[0061] (1) mixing the aliphatic dihydric alcohol monomer, the aromatic monomer and the catalyst, and performing a first stage reaction under the conditions of nitrogen protection and mechanical stirring at a temperature of 160-180℃, and when the collected amount of water reaches 80% of the theoretical value, the first stage reaction is considered to be completed;

[0062] The structure of the aliphatic dihydric alcohol monomer is shown in formula (I), and the structure of the aromatic monomer is shown in formula (II),

[0063]

[0064] wherein R1 is C4-C8 alkylene; R2, R3, R4, R5, R6, R7, R8 and R9 are each independently C1-C4 alkyl or hydrogen.

[0065] (2) after the first stage reaction is completed, gradually heating the reaction system to 220-240℃, controlling the vacuum degree of the system to be 50-80Pa, and performing a second stage reaction until the viscosity of the system no longer changes, thereby obtaining the aliphatic-aromatic polyester.

[0066] The aliphatic-aromatic polyester prepared by the above-mentioned method has good transparency and better toughness. Moreover, the method is simple to operate, has strong controllability, and is easy to realize industrialization of the product. The present application expands a new method for preparing polyester materials with both light transmission and toughness.

[0067] The present application will be described in detail through examples as follows.

[0068] In the following examples, the raw materials used are commercially available, all of which are of chemical purity.

[0069] (1) Infrared testing: The chemical structure of the copolyester was characterized using an Avatar 370 infrared spectrometer from Nicolet, USA. During the testing process, the full reflection mode was used, and the test wave number range was 500-4000 cm -1 Before infrared testing, the prepared polyester was dissolved in chloroform, and an excess of methanol was added. After stirring thoroughly, the purified polyester was obtained by filtration and drying.

[0070] (2) XRD testing: The crystal structure of the block copolyester sample was tested using an XD-3A ray diffractometer from Shimadzu, Japan. The sample was heat treated, and the test range was 5°-50°.

[0071] (3) DSC testing: The testing was performed using a DSC8500 differential scanning calorimeter from PE, USA. Under nitrogen protection, the temperature was increased from -60°C to 200°C at a rate of 10°C / min.

[0072] (4) Tensile at break: The synthesized aliphatic-aromatic polyester was formed into a sample sheet with a thickness of 1 mm by hot pressing. Then, a dumbbell-shaped cutter (type 4 dumbbell-shaped cutter in GB / T 528-2009 standard) was used to make a sample strip with a thickness of 1 mm and a width of 4 mm in the narrow part. The WD-II 10 electronic universal testing machine from Kaqiang, Shenzhen, was used to determine the stress-strain curve of the breaking process according to GB / T 1040-1992, with a tensile rate of 50 mm / min.

[0073] (5) Light transmittance: The polyester was formed into a sheet with a thickness of 5-100 mm by hot pressing. Then, it was cut into a size of 2 cm x 5 cm. The light transmittance of the polyester material was tested using the UV-1911i spectrophotometer from Shimadzu, Japan, with air transmittance as the reference object, and the transmittance at a wavelength of 550 nm was read.

[0074] Example 1

[0075] 0.25 mol (22.5 g) of 1,4-butanediol and 0.25 mol (78.25 g) of 3,3'-diphenyl ether dimethyl dicarboxylate were added to a reaction vessel, and 0.0025 mol (0.84 g) of catalyst tetrabutyl titanate was added. Under the conditions of N2 protection and mechanical stirring, the esterification reaction was carried out, and the initial temperature during the reaction was 160°C, which was gradually increased to 180°C. When the amount of water collected reached 80% of the theoretical value, the esterification reaction was considered to be complete.

[0076] After the esterification reaction, the reaction system is gradually heated to 240°C, and the vacuum degree of the system is controlled within 50-80 Pa. The polycondensation reaction is carried out until the viscosity of the system no longer changes, and the aliphatic-aromatic polyester is prepared.

[0077] It can be seen from Figure 1 that the infrared spectrum of the aliphatic-aromatic polyester prepared in Example 1 has a characteristic absorption peak of C-H bond in methylene at 2945 cm -1 , a characteristic absorption peak of C=O bond representing the existence of ester at 1710 cm -1 , a peak at 1150 cm -1 , which is a characteristic absorption peak of C-O bond, absorption peaks at 1594 cm -1 and 1499 cm -1 , which correspond to the characteristic skeleton vibration of benzene ring. It can be seen from Figure 2 that the aliphatic-aromatic polyester prepared in Example 1 has only a wide and diffuse absorption peak, indicating that the polyester film is amorphous without crystallization. It can be seen from Figure 3 that the aliphatic-aromatic polyester prepared in Example 1 has a glass transition peak (T g ) at 54°C, but no obvious crystallization peak and melting point peak, indicating that the arrangement inside the polyester system is amorphous, which is a non-crystalline polymer. It can be seen from Figure 4 that the aliphatic-aromatic polyester prepared in Example 1 has a tensile strength of 23.8 MPa and an elongation at break of 50%, which has good toughness.

[0078] Example 2

[0079] 1 mol (104 g) of 1,5-pentanediol and 0.25 mol (64.5 g) of 3,3'-diphenyl ether dicarboxylic acid are added to a reaction container, and 0.00125 mol (0.42 g) of catalyst tetrabutyl titanate is added. Under the conditions of N2 protection and mechanical stirring, the esterification reaction is carried out, and the initial temperature in the reaction process is 160°C, which is gradually increased to 180°C. When the amount of water collected reaches 80% of the theoretical value, it is considered that the esterification reaction is completed.

[0080] After the esterification reaction, the reaction system is gradually heated to 220°C, and the vacuum degree of the system is controlled within 50-80 Pa. The polycondensation reaction is carried out until the viscosity of the system no longer changes, and the aliphatic-aromatic polyester is prepared.

[0081] Example 3

[0082] Into a reaction vessel were added 0.75 mol (88.5 g) of 3-methyl-1,5-pentanediol and 0.25 mol (64.5 g) of 3,3'-diphenyl ether dicarboxylic acid, and 0.00125 mol (0.42 g) of a catalyst, tetrabutyl titanate, was added. The esterification reaction was carried out under N2 protection and mechanical stirring, and the initial temperature during the reaction was 160°C, which was gradually increased to 180°C. When the amount of water collected reached 80% of the theoretical value, the esterification reaction was considered to be complete.

[0083] After the esterification reaction was complete, the reaction system was gradually heated to 220°C, and the system was controlled at a vacuum of 50-80 Pa. The polycondensation reaction was carried out until the viscosity of the system no longer changed, and an aliphatic-aromatic polyester was prepared.

[0084] Example 4

[0085] Into a reaction vessel were added 0.5 mol (66 g) of 3-methyl-1,6-hexanediol and 0.25 mol (64.5 g) of 3,3'-diphenyl ether dicarboxylic acid, and 0.00125 mol (0.42 g) of a catalyst, tetrabutyl titanate, was added. The esterification reaction was carried out under N2 protection and mechanical stirring, and the initial temperature during the reaction was 160°C, which was gradually increased to 180°C. When the amount of water collected reached 80% of the theoretical value, the esterification reaction was considered to be complete.

[0086] After the esterification reaction was complete, the reaction system was gradually heated to 220°C, and the system was controlled at a vacuum of 50-80 Pa. The polycondensation reaction was carried out until the viscosity of the system no longer changed, and an aliphatic-aromatic polyester was prepared.

[0087] Example 5

[0088] An aliphatic-aromatic polyester was prepared according to the method described in Example 4, except that 0.5 mol of 3-methyl-1,6-hexanediol was replaced with 0.5 mol of 2,5-dimethyl-1,6-hexanediol.

[0089] Example 6

[0090] An aliphatic-aromatic polyester was prepared according to the method described in Example 4, except that 0.25 mol of 3,3'-diphenyl ether dicarboxylic acid was replaced with 0.25 mol of 5,5'-dimethyl-3,3'-diphenyl ether dicarboxylic acid.

[0091] Example 7

[0092] An aliphatic-aromatic polyester was prepared according to the method described in Example 4, except that 0.5 mol of 3-methyl-1,6-hexanediol was replaced with 0.5 mol of 1,7-heptanediol.

[0093] Example 8

[0094] The aliphatic-aromatic polyester was prepared according to the method described in Example 1, except that the tetrabutyl titanate was replaced by tetrabutyl titanate and stannous octoate in a molar ratio of 1:1.

[0095] Example 9

[0096] The aliphatic-aromatic polyester was prepared according to the method described in Example 1, except that the tetrabutyl titanate was replaced by tetrabutyl titanate and zinc acetate in a molar ratio of 1:2.

[0097] Example 10

[0098] The aliphatic-aromatic polyester was prepared according to the method described in Example 2, except that the tetrabutyl titanate was replaced by tetrabutyl titanate and p-toluenesulfonic acid in a molar ratio of 1:4.

[0099] Example 11

[0100] The aliphatic-aromatic polyester was prepared according to the method described in Example 2, except that the molar ratio of tetrabutyl titanate and stannous octoate was 1:0.5.

[0101] Example 12

[0102] The aliphatic-aromatic polyester was prepared according to the method described in Example 2, except that the molar ratio of tetrabutyl titanate and p-toluenesulfonic acid was 1:6.

[0103] Comparative Example 1

[0104] 0.48 mol (43.26 g) of 1,4-butanediol, 0.084 mol (16.99 g) of 1,10-decanedioic acid, and 0.036 mol (10.30 g) of 3,3'-diphenyl ether dimethyl acid dimethyl ester were added to a 250 mL three-necked flask equipped with a stirring device, a condensing device, and a nitrogen protection device. 0.0006 mol (0.2 g) of the catalyst tetrabutyl titanate was added dropwise to the three-necked flask. The condensing water was opened, N2 was introduced, and heating was performed to 180°C. After the monomers were completely melted, constant temperature stirring esterification was performed. When the amount of collected water reached 80% of the theoretical value, it was considered that the esterification reaction was completed.

[0105] After the esterification reaction was completed, the condensing device was removed, and a vacuum device equipped with a safety bottle, a McLeod gauge, and an oil pump was used to gradually heat to 220°C, and the reaction was continued for 3 h while the vacuum degree of the system was controlled to 50-80 Pa. After the polycondensation reaction was completed, the aliphatic-aromatic polyester was obtained after cooling to room temperature.

[0106] Comparative Example 2

[0107] 0.5 mol (38 g) of 1,3-propanediol and 0.25 mol (64.5 g) of 3,3'-diphenyl ether dicarboxylic acid were added into a reaction vessel, and 0.00125 mol (0.42 g) of catalyst tetrabutyl titanate was added. Under the conditions of N2 protection and mechanical stirring, the esterification reaction was carried out, and the initial temperature during the reaction was 160°C, which was gradually increased to 180°C. When the collected amount of water reached at least 80% of the theoretical value, the esterification reaction was considered to be completed.

[0108] After the esterification reaction was completed, the temperature was gradually increased to 220°C, and the vacuum degree of the system was controlled within 50-80 Pa. The polycondensation reaction was carried out until the viscosity of the system no longer changed, and thus the aliphatic-aromatic polyester was prepared.

[0109] Comparative Example 3

[0110] 0.5 mol (38 g) of 1,3-propanediol and 0.25 mol (64.5 g) of 3,3'-diphenyl ether dicarboxylic acid were added into a reaction vessel, and 0.00125 mol (0.42 g) of catalyst tetrabutyl titanate was added. Under the conditions of N2 protection and mechanical stirring, the esterification reaction was carried out, and the initial temperature during the reaction was 160°C, which was gradually increased to 180°C. When the collected amount of water reached at least 80% of the theoretical value, the esterification reaction was considered to be completed.

[0111] After the esterification reaction was completed, the temperature was gradually increased to 220°C, and the vacuum degree of the system was controlled within 50-80 Pa. The polycondensation reaction was carried out until the viscosity of the system no longer changed, and thus the aliphatic-aromatic polyester was prepared.

[0112] Comparative Example 4

[0113] The aliphatic-aromatic polyester was prepared according to the method described in Example 4, except that the amount of tetrabutyl titanate added was 0.005 mol (1.68 g).

[0114] Test Example 1

[0115] The aliphatic-aromatic polyesters prepared in the above examples and comparative examples were tested for physical and chemical parameters, and the obtained parameters are shown in Table 1:

[0116] Table 1

[0117]

[0118]

[0119] The weight average molecular weight of the polyesters prepared in Examples 1-12 and Comparative Examples 1-3 was between 30000-50000 g / mol. The weight average molecular weight of the polyester prepared in Comparative Example 4 was less than 30000 g / mol.

[0120] As can be seen from the results of Table 1, the light transmittance (550 nm) of the polyesters obtained in Examples 1-12 is significantly higher than 90% at a thickness of 5-100 mm, indicating that the polyester within the scope of the present application has a high light transmittance.

[0121] Among them, Examples 1, 2 and 7, and Comparative Examples 3 and 4 are polyesters prepared from linear diol monomers, and have a certain degree of crystallinity after being stored at 25℃ for 300 days, indicating that linear monomers have a certain effect on the long-term transparency of the polyester, and therefore C6-C8 branched alkylene is more conducive to forming a polyester with long-term transparency.

[0122] As can be seen from the data of Comparative Example 1, when the monomer contains two linear diols, the glass transition temperature of the prepared polyester is lower than room temperature (-62.3℃), and the strength of the polyester material is lower. As can be seen from the data of Comparative Example 2, the diol monomer is propylene glycol, i.e. R1 is an alkylene group with a carbon number less than 4, the carbon chain of the aliphatic diol is shorter, and the polyester exhibits obvious rigidity characteristics, although the transparency is higher, but the toughness is poor, only 17% (elongation at break less than 20%). As can be seen from the data of Comparative Example 3, the diol monomer is nonanediol, i.e. R1 is an alkylene group with a carbon number greater than 8, the carbon chain of the aliphatic diol is higher, and the increased flexibility of the segment gives the polyester certain toughness, but due to the increase in segment flexibility, the polyester material begins to exhibit a crystalline state, and the transparency is significantly reduced. As can be seen from the data of Examples 7 and Comparative Example 4, when the mass content of titanium element of the catalyst is greater than 0.238%, it will promote the rapid crystallization of the polyester system. As can be seen from Examples 2, 6, 8-12, keeping the mass content of titanium element less than 0.05% is conducive to forming a polyester with long-term transparency.

[0123] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including combining various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. An aliphatic-aromatic polyester, characterized in that, The aliphatic-aromatic polyester has a light transmittance greater than 90% at a thickness of 30-100 mm, and an elongation at break of 252-1050%; the mass content of titanium in the aliphatic-aromatic polyester is less than or equal to 0.063%. The polyester is composed of structural unit A shown in formula (I) and structural unit B shown in formula (II). Equation (I); Formula (II); Wherein, R1 is a C6-C8 branched alkylene group, and R2, R3, R4, R5, R6, R7, R8 and R9 are each independently a C1-C4 alkyl group or hydrogen group.

2. The aliphatic-aromatic polyester according to claim 1, characterized in that, The crystallinity of the aliphatic-aromatic polyester is less than or equal to 0.4%.

3. The aliphatic-aromatic polyester according to claim 2, characterized in that... The crystallinity of the aliphatic-aromatic polyester is less than or equal to 0.1%.

4. The aliphatic-aromatic polyester according to claim 3, characterized in that, The aliphatic-aromatic polyester is an amorphous polymer.

5. The aliphatic-aromatic polyester according to claim 1, characterized in that, The glass transition temperature of the aliphatic-aromatic polyester is 10-55℃; The aliphatic-aromatic polyester has a tensile strength of 2.5-25 MPa.

6. The aliphatic-aromatic polyester according to claim 1, characterized in that, The mass content of titanium in the aliphatic-aromatic polyester is less than or equal to 0.05%.

7. A method for preparing an aliphatic-aromatic polyester as described in claim 1, characterized in that, Includes the following steps: (1) Under esterification reaction conditions, an aliphatic diol monomer containing the structure shown in formula (I), an aromatic monomer containing the structure shown in formula (II) and a catalyst are mixed and subjected to a first-stage reaction to obtain a prepolymer; the catalyst contains a titanium-containing catalyst, and the molar ratio of the catalyst to the aromatic monomer is 0.5-1:100; in, Formula (I); Formula (II); R1 is a C6-C8 branched alkylene group, and R2, R3, R4, R5, R6, R7, R8 and R9 are each independently a C1-C4 alkyl group or hydrogen group; (2) Under polycondensation reaction conditions, the prepolymer is subjected to a second stage reaction.

8. The preparation method according to claim 7, characterized in that, The catalyst is a titanium-containing catalyst and a non-titanium-containing catalyst, and the molar ratio of the titanium-containing catalyst to the non-titanium-containing catalyst is 1:1-4; The titanium-containing catalyst is tetrabutyl titanate and / or tetraethyl titanate; the non-titanium-containing catalyst is selected from at least one of stannous chloride, stannous octoate, zinc acetate, and p-toluenesulfonic acid. In step (1), the esterification reaction conditions include at least: oxygen isolation and a temperature of 160-180°C; In step (2), the polycondensation reaction conditions include at least the following: a temperature of 220-240°C and an absolute vacuum of 50-80 Pa.

9. The use of the aliphatic-aromatic polyester according to any one of claims 1 to 6, or the aliphatic-aromatic polyester prepared according to the method of claim 7 or 8, in optical films, outer packaging films, or polymeric glass.

Images