Polyester material, heat-shrinkable film and preparation method and application thereof

Abstract

This invention discloses a polyester material, a heat-shrinkable film, its preparation method, and its applications. The raw materials for preparing the polyester material include a diacid, a diol, a chain extender, a stabilizer, and a catalyst; wherein the diacid comprises: 90 mol%~95 mol% polyterephthalic acid and 5 mol%~10 mol% isophthalic acid; the diol comprises: 65 mol%~78 mol% ethylene glycol, 18 mol%~28 mol% 1,4-cyclohexanediol, and 4 mol%~12 mol% diethylene glycol; the chain extender is 2,2'-(1,3-phenylene)-dioxazoline, added in an amount of 0.2%~0.8% of the total mass of the diol and the diacid; the molar ratio of carboxyl groups to hydroxyl groups in the diacid and the diol is 1:1~1.05. The polyester material of this invention possesses excellent transparency, shrinkage rate, and strength, and has a low initial shrinkage temperature, making it particularly suitable for applications such as heat-shrinkable films. This invention also provides a heat-shrinkable film, as well as the polyester material, a method for preparing the heat-shrinkable film, and their applications.

Description

Technical Field

[0001] This invention relates to the field of polyester materials technology, specifically to a polyester material, a heat-shrinkable film, its preparation method, and its application. Background Technology

[0002] Heat shrink film is a widely used material in packaging, labeling, and other fields. Its main characteristic is that it can shrink rapidly after heating, tightly wrapping the surface of items and providing protection, marking, and decoration. Polyethylene terephthalate (PET) and its copolymer PETG (polyethylene terephthalate-1,4-cyclohexanediethanol copolymer) have become one of the main raw materials for heat shrink film due to their excellent mechanical properties, transparency, and thermal stability.

[0003] However, existing PETG heat shrink film still faces several challenges in practical applications, mainly in the following aspects: (1) The initial shrinkage temperature is high (usually exceeding 65°C), and the low-temperature shrinkage performance is poor; (2) Although the shrinkage rate of existing PETG film has been improved compared with PET, there is still room for further optimization; (3) Existing PETG heat shrink film is difficult to balance haze and strength: If the transparency of the film is to be improved (i.e., the haze is reduced), the amorphous structure of the polymer is usually optimized, which may lead to a decrease in the mechanical strength of the film; conversely, if the strength is improved by increasing the crystallinity, the transparency of the film may be reduced and the haze may be increased, making it difficult to meet the appearance requirements of the product.

[0004] Therefore, how to reduce the shrinkage temperature, increase the shrinkage rate, and improve transparency without losing strength are the technical challenges that PETG heat shrink film urgently needs to solve. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a polyester material.

[0006] The present invention also provides a method for preparing the above-mentioned polyester material.

[0007] The present invention also provides a heat-shrinkable film.

[0008] The present invention also provides a method for preparing the above-mentioned heat shrink film.

[0009] The present invention also provides the application of the above-mentioned polyester material or heat shrink film.

[0010] Specifically, the first aspect of the present invention relates to a polyester material whose raw materials include diacid, diol, chain extender, stabilizer and catalyst. The dicarboxylic acid comprises, based on a total molar amount of 100 parts, 90 mol% to 95 mol% of polyethylene terephthalic acid and 5 mol% to 10 mol% of isophthalic acid. Based on a total molar amount of 100 parts of the diol, the diol comprises: 65 mol% to 78 mol% ethylene glycol, 18 mol% to 28 mol% 1,4-cyclohexanediethanol, and 4 mol% to 12 mol% diethylene glycol. The chain extender is 2,2'-(1,3-phenylene)-dioxazoline (CAS No.: 34052-90-9), and the amount of the chain extender added is 0.2% to 0.8% of the total mass of the diol and diacid; In the dicarboxylic acid and diol, the molar ratio of carboxyl groups to hydroxyl groups is 1:1 to 1.05.

[0011] The polyester material according to the first aspect of the present invention has at least the following beneficial effects: Using 2,2'-(1,3-phenylene)-dioxazoline as a chain extender can effectively increase the molecular weight of polyester, enhance its melt strength and tensile strength, while maintaining its amorphous structure, ensuring heat shrinkage and transparency. However, excessive addition may cause local microphase separation, affecting optical properties and reducing the shrinkage performance of the polyester. Therefore, rationally controlling the amount of chain extender added can enhance the material's strength and heat shrinkage while ensuring its transparency.

[0012] By rationally selecting 1,4-cyclohexanediethanol and diethylene glycol, crystallinity is effectively suppressed, and the formation of amorphous structures is promoted. The introduction of 1,4-cyclohexanediethanol reduces chain segment regularity, decreases crystallization, and allows the material to better release stress when heated, thereby improving thermal shrinkage performance and transparency.

[0013] Diethylene glycol can promote the relaxation of chain segments at low temperatures and inhibit crystallization, thereby reducing the initial shrinkage temperature and improving heat shrinkage performance.

[0014] By adjusting the ratio of polyethylene terephthalate (PET) to isophthalic acid (IPA), the crystallinity of the material can be further reduced, and its transparency, tensile strength, and shrinkage properties can be improved. Combined with reaction equivalence control and the introduction of stabilizers, the chain growth process and molecular weight distribution can be optimized, thereby improving the polymerization uniformity.

[0015] In summary, by combining components such as dicarboxylic acid, diol, chain extender, and stabilizer, the material possesses excellent properties such as high transparency, high shrinkage rate, and high strength, and has a low initial shrinkage temperature, making it particularly suitable for fields such as heat shrink film where high transparency and shrinkage are required.

[0016] According to some embodiments of the present invention, based on a total molar amount of 100 parts of the diol, the diol comprises: 70 mol% to 75 mol% ethylene glycol, 20 mol% to 25 mol% 1,4-cyclohexanediethanol, and 5 mol% to 10 mol% diethylene glycol. Further, the diol comprises: 70 mol% to 73 mol% ethylene glycol, 20 mol% to 24 mol% 1,4-cyclohexanediethanol, and 5 mol% to 8 mol% diethylene glycol. Even further, the diol comprises: 70 mol% to 72 mol% ethylene glycol, 22 mol% to 24 mol% 1,4-cyclohexanediethanol, and 6 mol% to 8 mol% diethylene glycol.

[0017] According to some embodiments of the present invention, the molar ratio of carboxyl groups to hydroxyl groups in the dicarboxylic acid and diol is 1:1 to 1.03, more specifically 1:1 to 1.02.

[0018] According to some embodiments of the present invention, the amount of chain extender added is 0.4% to 0.7% of the total mass of the diol and diacid, and more specifically 0.4% to 0.6%.

[0019] According to some embodiments of the present invention, the stabilizer is selected from at least one of triphenyl phosphate, pentaerythritol phosphate, trimethyl phosphate, and triethyl phosphate.

[0020] According to some embodiments of the present invention, the amount of stabilizer added is 0.04% to 0.2% of the total mass of the diol and diacid, and more specifically 0.1% to 0.2%.

[0021] According to some embodiments of the present invention, the stabilizer is a compound of triphenyl phosphate and pentaerythritol phosphate, wherein the amount of triphenyl phosphate added is 0.02% to 0.08% of the total mass of the diol and diacid, more specifically 0.04% to 0.08%, and even more specifically 0.05% to 0.08%; and the amount of pentaerythritol phosphate added is 0.02% to 0.12% of the total mass of the diol and diacid, more specifically 0.06% to 0.12%, and even more specifically 0.08% to 0.12%.

[0022] By using a reasonable combination of triphenyl phosphate and pentaerythritol phosphate, the stability and durability of polyester materials can be effectively improved, and the service life of the materials can be extended.

[0023] According to some embodiments of the present invention, the catalyst is a metal-based catalyst.

[0024] According to some preferred embodiments of the present invention, the total amount of metal elements in the catalyst is 100-300 ppm, more specifically 150-250 ppm, and even more specifically 160-220 ppm, based on the mass of the terephthalic acid.

[0025] According to some embodiments of the present invention, the catalyst is selected from at least one of antimony acetate, antimony glycolate, tetrabutyl titanate, tetraethyl titanate, and tetraisopropyl titanate.

[0026] According to some preferred embodiments of the present invention, the catalyst is a combination of antimony acetate and tetrabutyl titanate. Based on the mass of the terephthalic acid, the antimony content in the antimony acetate is 120-220 ppm, more preferably 150-200 ppm, and even more preferably 160-200 ppm; the titanium content in the tetrabutyl titanate is 5-25 ppm, more preferably 8-20 ppm, and even more preferably 10-18 ppm.

[0027] By optimizing the catalyst type, the polymerization rate, molecular weight, and polymerization uniformity of polyester materials can be further improved, thereby enhancing the overall performance of the materials.

[0028] A second aspect of the present invention relates to a method for preparing the polyester material, comprising the following steps: The diacid, diol, stabilizer and catalyst are mixed and subjected to a first esterification reaction to obtain a prepolymer; The prepolymer is mixed with the chain extender and subjected to a second esterification reaction to obtain a polyester material.

[0029] According to some embodiments of the present invention, the temperature of the first esterification reaction is 240~270°C, the reaction time is 60~180 min, and the reaction pressure is 0.1~0.3 MPa. For example, the temperature of the first esterification reaction is 240°C, 245°C, 250°C, 255°C, 260°C, 265°C, or 270°C; the reaction time is 60 min, 80 min, 100 min, 120 min, 140 min, 160 min, or 180 min; and the reaction pressure is 0.1 MPa, 0.2 MPa, or 0.3 MPa.

[0030] According to some embodiments of the present invention, the temperature of the second esterification reaction is 270~285°C, the reaction pressure is 0.05~0.5 kPa, and the reaction time is 80~140 min. For example, the temperature of the second esterification reaction is 270°C, 275°C, 280°C, or 285°C; the reaction time is 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, or 140 min; and the reaction pressure is 0.05 kPa, 0.1 kPa, 0.15 kPa, 0.2 kPa, 0.25 kPa, 0.3 kPa, 0.35 kPa, 0.4 kPa, 0.45 kPa, or 0.5 kPa.

[0031] A third aspect of the present invention relates to a heat-shrinkable film made from the aforementioned polyester material.

[0032] According to some embodiments of the present invention, the thickness of the heat-shrinkable film is 10~100μm, more specifically 20~60μm.

[0033] The fourth aspect of this invention relates to a method for preparing the heat-shrinkable film, comprising the following steps: The polyester material is melt-extruded to form a base film; The base film is biaxially stretched to obtain the heat-shrinkable film.

[0034] This invention does not limit the preparation process of the heat shrink film; a suitable process can be selected according to actual needs.

[0035] According to some embodiments of the present invention, the longitudinal stretching temperature of the biaxial stretching is 80~95℃, and the stretching ratio is 3.5~5:1; the transverse stretching temperature is 100~110℃, and the stretching ratio is 4~6:1. Further, the longitudinal stretching temperature of the biaxial stretching is 85~90℃, and the stretching ratio is 4~5:1; the transverse stretching temperature is 105~110℃, and the stretching ratio is 4.5~5.5:1.

[0036] The fifth aspect of this invention relates to the application of the polyester material or the heat-shrinkable film in product packaging. Specifically, the products include high-end market sectors with high requirements for appearance, such as precision electronic products, medical equipment, luxury goods, and food.

[0037] In this article, the numerical ranges mentioned all include the endpoint values ​​and cover any subranges within that range, such as the ranges obtained by arbitrarily combining the specifically listed numerical values. Detailed Implementation

[0038] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0039] Unless otherwise specified, all raw materials involved are commercially available standard products.

[0040] Example 1 1. Preparation of polyester materials A diacid (95 mol% terephthalic acid, 5 mol% isophthalic acid) and a diol (72 mol% ethylene glycol, 22 mol% 1,4-cyclohexanediol, 6 mol% diethylene glycol) were added to a reaction vessel and mixed. Then, 0.06% (by mass of the diacid and diol) of triphenyl phosphate and 0.1% (by mass of pentaerythritol phosphate) were added. After uniform dispersion, 180 ppm (based on terephthalic acid) of antimony acetate (Sb) and 10 ppm (based on Ti) of tetrabutyl titanate were added and mixed thoroughly. The molar ratio of carboxyl groups in the diacid to hydroxyl groups in the diol was 1:1.01. Under nitrogen protection, the reaction system was heated to 255 ± 5 °C, the reaction chamber pressure was maintained at 0.2 MPa, and the reaction time was 120 min. During the reaction, moisture was removed by distillation to obtain the prepolymer.

[0041] After esterification, the reaction proceeds to the polycondensation stage. A chain extender, 2,2'-(1,3-phenylene)-dioxazoline, is added at 0.5% of the total mass of the diacid and diol. After thorough mixing, the mixture is evacuated to 100 Pa and reacted at 280±5℃ for 110 min. Nitrogen gas is then introduced to restore the reactor pressure to atmospheric pressure. The melt is extruded under nitrogen protection and subsequently cast into strips and granulated to obtain the polyester material.

[0042] 2. Preparation of heat shrink film Polyester material was melt-extruded at 260±5℃ to produce a base film with a thickness of 1.25 mm. The base film was dried at 120℃ for 6 hours, then preheated at 85℃ for 1 hour. Subsequently, longitudinal and transverse stretching were performed: longitudinal stretching temperature was 90℃ with a stretch ratio of 5 times; transverse stretching temperature was 110℃ with a stretch ratio of 5 times. After cooling and setting, a heat-shrinkable film with a thickness of 50 μm was obtained.

[0043] Example 2 1. Preparation of polyester materials A diacid (90 mol% terephthalic acid, 10 mol% isophthalic acid) and a diol (70 mol% ethylene glycol, 24 mol% 1,4-cyclohexanediol, 6 mol% diethylene glycol) were added to a reaction vessel and mixed. Then, 0.07% (by mass of the diacid and diol) of triphenyl phosphate and 0.1% (by mass of pentaerythritol phosphate) were added. After uniform dispersion, 200 ppm (based on terephthalic acid) of antimony acetate (Sb) and 15 ppm (based on Ti) of tetrabutyl titanate were added and mixed thoroughly. The molar ratio of carboxyl groups in the diacid to hydroxyl groups in the diol was 1:1.01. Under nitrogen protection, the reaction system was heated to 260 ± 5 °C, the reaction chamber pressure was maintained at 0.2 MPa, and the reaction time was 130 min. During the reaction, moisture was removed by distillation to obtain the prepolymer.

[0044] After the esterification reaction is completed, the reaction proceeds to the polycondensation stage. A chain extender, 2,2'-(1,3-phenylene)-dioxazoline, is added at 0.5% of the total mass of the diacid and diol. After thorough mixing, the mixture is evacuated to 100 Pa and reacted at 280±5℃ for 120 min. Nitrogen gas is then introduced to restore the reactor pressure to atmospheric pressure. The melt is extruded under nitrogen protection and then sequentially cast into strips and granulated to obtain the polyester material.

[0045] 2. Preparation of heat shrink film Polyester material was melt-extruded at 260±5℃ to produce a base film with a thickness of 1.25 mm. The base film was dried at 120℃ for 6 hours, then preheated at 85℃ for 1 hour. Subsequently, longitudinal and transverse stretching were performed: longitudinal stretching temperature was 90℃ with a stretch ratio of 5 times; transverse stretching temperature was 110℃ with a stretch ratio of 5 times. After cooling and setting, a heat-shrinkable film with a thickness of 50 μm was obtained.

[0046] Example 3 1. Preparation of polyester materials A diacid (90 mol% terephthalic acid, 10 mol% isophthalic acid) and a diol (70 mol% ethylene glycol, 22 mol% 1,4-cyclohexanediol, 8 mol% diethylene glycol) were added to a reaction vessel and mixed. Then, 0.06% (by mass of the diacid and diol) of triphenyl phosphate and 0.08% (by mass of pentaerythritol phosphate) were added. After uniform dispersion, 180 ppm (based on terephthalic acid) of antimony acetate (Sb) and 12 ppm (based on Ti) of tetrabutyl titanate were added and mixed thoroughly. The molar ratio of carboxyl groups in the diacid to hydroxyl groups in the diol was 1:1.01. Under nitrogen protection, the reaction system was heated to 260 ± 5 °C, the reaction chamber pressure was maintained at 0.2 MPa, and the reaction time was 130 min. During the reaction, moisture was removed by distillation to obtain the prepolymer.

[0047] After esterification, the reaction proceeds to the polycondensation stage. A chain extender, 2,2'-(1,3-phenylene)-dioxazoline, is added at 0.5% of the total mass of the diacid and diol. After thorough mixing, the mixture is evacuated to 100 Pa and reacted at 280±5℃ for 120 min. Nitrogen gas is then introduced to restore the reactor pressure to atmospheric pressure. The melt is extruded under nitrogen protection and subsequently cast into strips and granulated to obtain the final polyester material.

[0048] 2. Preparation of heat shrink film Polyester material was melt-extruded at 260±5℃ to produce a base film with a thickness of 1.25 mm. The base film was dried at 120℃ for 6 hours, then preheated at 85℃ for 1 hour. Subsequently, longitudinal and transverse stretching were performed: longitudinal stretching temperature was 90℃ with a stretch ratio of 5 times; transverse stretching temperature was 110℃ with a stretch ratio of 5 times. After cooling and setting, a heat-shrinkable film with a thickness of 50 μm was obtained.

[0049] Comparative Example 1 Compared with Example 3, the only difference is that diethylene glycol is replaced with an equal amount of PEG400.

[0050] Comparative Example 2 Compared with Example 3, the only difference is that diethylene glycol is replaced with an equal amount of neopentyl glycol.

[0051] Comparative Example 3 Compared with Example 3, the only difference is that the amount of chain extender added is 1% of the total mass of the dicarboxylic acid and diol.

[0052] Test case 1. Tensile strength: The test standard is GB / T1040.3-2006. Type 2 specimens are used, with a specimen size of 15mm×150mm. Sampling is performed in the transverse direction (TD) and the tensile rate is 100mm / min.

[0053] 2. Shrinkage rate: The sample size is 10mm × 100mm, sampled along the transverse direction (TD), held at 90℃ for 30 seconds, and the change in transverse length is measured (initial length is recorded as L0, and the length after shrinkage is recorded as L1). The shrinkage rate is calculated using the formula: (L0) L1) / L0×100%.

[0054] 3. Initial shrinkage temperature: The sample is tested for shrinkage rate by heating it in a hot water bath at a rate of 2℃ / min. The temperature at which the shrinkage rate reaches 5% is recorded as the initial shrinkage temperature.

[0055] 4. Transparency: Tested using a spectrophotometer.

[0056] The test results are shown in Table 1.

[0057] Table 1

[0058] The results above show that the polyester materials in Examples 1-3 have a lower initial shrinkage temperature, a higher shrinkage rate, and excellent performance in terms of tensile strength and transparency.

[0059] In Comparative Example 1, diethylene glycol was replaced with PEG400. Due to the higher flexibility of PEG segments, the segments were more prone to relaxation, leading to a decrease in the initial shrinkage temperature. However, the introduction of PEG may have the following adverse effects: on the one hand, its compatibility with the aromatic polyester backbone is poor, which can easily cause uneven phase distribution and inconsistent refractive index, resulting in reduced transparency; on the other hand, the increase in flexible segments and phase inhomogeneity may weaken the orientation carrying capacity of the material, leading to a decrease in tensile strength and shrinkage rate.

[0060] In Comparative Example 2, replacing diethylene glycol with neopentyl glycol increased the initial shrinkage temperature of the material, decreased the shrinkage rate at 90°C, but improved the tensile strength. This is because the rigid structure of neopentyl glycol restricts the free movement of chain segments; although its rigidity enhances tensile strength, it significantly reduces the material's shrinkage performance.

[0061] In Comparative Example 3, the excessive addition of chain extender improved tensile strength but reduced transparency, increased initial shrinkage temperature, and decreased shrinkage rate. This is because excessive chain extender may induce microphase separation, thus affecting optical transparency; at the same time, while increasing molecular weight is beneficial for improving strength, it reduces chain segment relaxation ability, leading to poor low-temperature initiation shrinkage performance and a decrease in shrinkage rate.

[0062] The present invention has been described in detail above with reference to the embodiments, but the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A polyester material, characterized in that, The raw materials for preparing the polyester material include diacids, diols, chain extenders, stabilizers, and catalysts; The dicarboxylic acid comprises, based on a total molar amount of 100 parts, 90 mol% to 95 mol% of polyethylene terephthalic acid and 5 mol% to 10 mol% of isophthalic acid. Based on a total molar amount of 100 parts of the diol, the diol comprises: 65 mol% to 78 mol% ethylene glycol, 18 mol% to 28 mol% 1,4-cyclohexanediethanol, and 4 mol% to 12 mol% diethylene glycol. The chain extender is 2,2'-(1,3-phenylene)-dioxazoline, and the amount of the chain extender added is 0.2% to 0.8% of the total mass of the diol and diacid; In the dicarboxylic acid and diol, the molar ratio of carboxyl groups to hydroxyl groups is 1:1 to 1.

05.

2. The polyester material according to claim 1, characterized in that, Based on a total molar amount of 100 parts of the diol, the diol comprises: 70 mol% to 75 mol% ethylene glycol, 20 mol% to 25 mol% 1,4-cyclohexanediethanol, and 5 mol% to 10 mol% diethylene glycol. And / or, the amount of chain extender added is 0.4% to 0.7% of the total mass of the diol and diacid.

3. The polyester material according to claim 1, characterized in that, The stabilizer is selected from at least one of triphenyl phosphate, pentaerythritol phosphate, trimethyl phosphate, and triethyl phosphate; And / or, the amount of the stabilizer added is 0.04% to 0.2% of the total mass of the diol and diacid; And / or, the catalyst is selected from at least one of antimony acetate, antimony glycolate, tetrabutyl titanate, tetraethyl titanate, and tetraisopropyl titanate; And / or, the catalyst is a metal-based catalyst, and the total amount of metal elements in the catalyst is 100~300 ppm based on the mass of the terephthalic acid.

4. The polyester material according to claim 3, characterized in that, The stabilizer is a compound of triphenyl phosphate and pentaerythritol phosphate, wherein the amount of triphenyl phosphate added is 0.02% to 0.08% of the total mass of the diol and diacid; and the amount of pentaerythritol phosphate added is 0.02% to 0.12% of the total mass of the diol and diacid. And / or, the catalyst is a combination of antimony acetate and tetrabutyl titanate, wherein, based on the mass of the terephthalic acid, the antimony content in antimony acetate is 120~220 ppm, and the titanium content in tetrabutyl titanate is 5~25 ppm.

5. The method for preparing the polyester material according to any one of claims 1 to 4, characterized in that, Includes the following steps: The diacid, diol, stabilizer and catalyst are mixed and subjected to a first esterification reaction to obtain a prepolymer; The prepolymer is mixed with the chain extender and subjected to a second esterification reaction to obtain a polyester material.

6. The preparation method according to claim 5, characterized in that, The temperature of the first esterification reaction is 240~270℃, the reaction time is 60~180min, and the reaction pressure is 0.1~0.3MPa; And / or, the temperature of the second esterification reaction is 270~285℃, the reaction pressure is 0.05~0.5kPa, and the reaction time is 80~140min.

7. A heat-shrinkable film, characterized in that: The heat shrink film is made of the polyester material described in any one of claims 1 to 4.

8. The method for preparing the heat-shrinkable film as described in claim 7, characterized in that, Includes the following steps: The polyester material is melt-extruded to form a base film; The base film is biaxially stretched to obtain the heat-shrinkable film.

9. The preparation method according to claim 8, characterized in that, The longitudinal stretching temperature of the biaxial stretching is 80~95℃, and the stretching ratio is 3.5~5:1; the transverse stretching temperature is 100~110℃, and the stretching ratio is 4~6:

1.

10. The use of the polyester material as described in any one of claims 1 to 4 or the heat shrink film as described in claim 7 in product packaging.

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