Preparation method of modified high-toughness PTT material

Abstract

The application relates to the technical field of high polymer materials, and discloses a preparation method of modified high-toughness PTT material, which comprises the following steps: mixing dihydric alcohol monomers with a catalyst to prepare a third monomer premixing solution, performing ester exchange-polycondensation reaction on terephthalic acid and 1,3-propanediol to prepare PTT melt, sequentially separating and removing free monomers through a combined process of pre-distillation, vacuum rectification and adsorption refining, and performing underwater granulation, cooling and drying to obtain the high-toughness PTT material; through the synergistic effect of introducing flexible chain segments and destroying crystallization regularity, the crystallinity is reduced, and the toughness of the PTT material is significantly improved; the PTT material has good tensile strength and thermal performance, and the elongation at break and impact strength are greatly improved, the toughness and comprehensive use performance of the PTT material are significantly improved, the performance improvement and economy are considered at the same time, the raw material loss and production cost are effectively reduced, and the application has important industrial application value.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a method for preparing a modified high-toughness PTT material. Background Technology

[0002] PTT (polypropylene terephthalate) is a high-performance polyester material, but its high molecular chain regularity and crystallinity result in low elongation at break, insufficient impact resistance, and fatigue resistance. In practical use, carpets woven from PTT fibers are prone to fiber breakage and pilling after repeated walking; PTT clothing is prone to wrinkling and has poor tensile recovery after washing; and seams are easily cracked under external force. Therefore, it fails to meet the durability and comfort requirements of textile products. In the field of engineering plastics, its insufficient impact resistance also limits its application in casings, connectors, and other similar applications.

[0003] To improve toughness, a third monomer copolymerization modification method is often used. This involves introducing flexible segments or disrupting the regularity of the molecular chain to reduce crystallinity, thereby enhancing toughness. Examples include the introduction of flexible segments or structural units such as polyethylene glycol (PEG) and isophthalic acid (IPA). However, existing toughening modification technologies using third monomers have the following significant drawbacks: the reactivity of the third monomer is mismatched with that of the PTT monomer, making it difficult for the third monomer to effectively embed into the PTT backbone during copolymerization. This results in low binding rates and a large amount of unreacted free monomers remaining in the system, which not only fails to provide toughening but also reduces resin purity and mechanical properties. Furthermore, the separation of free monomers is difficult and incomplete. Traditional water washing or simple distillation methods are inefficient, while hot water extraction is time-consuming and incomplete, resulting in residues that do not meet process requirements. Atmospheric distillation, on the other hand, has high temperatures, which can easily lead to PTT resin degradation. The low binding rate results in limited toughening effects. The remaining free monomers not only fail to effectively toughen the material but may also migrate to the material surface, causing yellowing and stickiness, damaging the material's mechanical properties and heat resistance, making it difficult to achieve both high toughness and stable overall performance.

[0004] Therefore, developing a method to significantly improve the binding rate of the third monomer, achieve efficient and mild separation of free monomers, and thus prepare PTT materials with both high toughness and excellent comprehensive properties has important industrial application value. Summary of the Invention

[0005] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a method for preparing modified high-toughness PTT materials, which solves the problems of low third monomer binding rate, high free monomer residue, and poor toughness of PTT materials, while maintaining the material's good mechanical properties and heat resistance.

[0006] (II) Technical Solution To achieve the above objectives, this invention discloses a method for preparing a modified high-toughness PTT material, comprising the following steps: Step (1): Add the diol monomer and catalyst to the mixing tank, stir and mix to form a uniform third monomer premix; Step (2): Add terephthalic acid (PTA) and 1,3-propanediol (PDO) to the reaction vessel, heat up, add the third monomer premix prepared in step (1), and react to obtain PTT melt; Step (3): The PTT melt prepared in step (2) is sent into a pre-distillation tower by a transfer pump for pre-distillation, and then distilled in a vacuum distillation tower. After the treatment is completed, it is purified by adsorption to obtain the separated PTT resin melt. Step (4): The separated PTT resin melt prepared in step (3) is added to a granulator for granulation, cooled and solidified, dried and separated to obtain high-toughness PTT material.

[0007] Preferably, the diol monomer in step (1) includes any one of diethylene glycol, 1,4-butanediol, and 1,6-hexanediol.

[0008] Preferably, the catalyst in step (1) is either tetrabutyl titanate or antimony glycolate.

[0009] Preferably, in step (1), the mass ratio of diol monomer to catalyst is 100:(1-4), the stirring speed is 80-100 r / min, the stirring temperature is 60℃, and the stirring time is 20-50 min.

[0010] Preferably, the specific preparation process of the polymer melt in step (2) includes the following steps: adding terephthalic acid and 1,3-propanediol to a polymerization reactor equipped with pressure control and distillation device, heating to 180°C, adding the third monomer premix prepared in step (1), maintaining the pressure inside the reactor at 0.2 MPa and the stirring speed at 60-80 r / min, and conducting an ester exchange reaction for 2-3 hours, increasing the vacuum degree of the polymerization reactor to ≥0.095 MPa, heating to 240-250°C, and stirring at 30-40 r / min, and conducting a polycondensation reaction for 4-5 hours until the viscosity of the resin melt reaches 0.8-1.2 dL / g, thus obtaining PTT melt.

[0011] Preferably, in step (2), the mass ratio of terephthalic acid, 1,3-propanediol, and the third monomer premix is ​​100:(55-70):(12.4-20.4).

[0012] Preferably, in step (3), during the pre-distillation process, the temperature inside the pre-distillation column is 180-200℃, the pressure is 0.05MPa, and the distillation time is 30-40min. Pre-distillation can effectively remove more than 80% of free PDO and some low-molecular-weight impurities.

[0013] Preferably, in step (3), during the vacuum distillation process, the temperature inside the vacuum distillation column is 200-220℃, the vacuum degree is 0.098MPa, and the distillation time is 40-50min. Vacuum distillation can effectively separate free diol monomers, and the free monomers are collected at the top of the column for recycling.

[0014] Preferably, in step (3), the specific process of adsorption purification is as follows: the distilled melt is passed through a 4A adsorption molecular sieve column for adsorption purification, the amount of 4A adsorption molecular sieve is 2%-3% of the melt mass, and the adsorption temperature is 190℃. Adsorption purification can effectively adsorb residual trace amounts of free monomers. In this invention, a free monomer separation process using pre-distillation-vacuum distillation-adsorption is developed, with mild reaction conditions, effectively avoiding resin degradation caused by high temperature, and controlling the residual amount of free monomers to below 0.5%.

[0015] Preferably, in step (3), the adsorbent used in the adsorption column after distillation can also be 5A adsorption molecular sieve, the amount of 5A adsorption molecular sieve is 2%-3% of the melt mass, and the adsorption temperature is 190℃.

[0016] Preferably, the specific preparation process of the high-toughness PTT material in step (4) includes the following steps: the PTT resin melt separated in step (3) is stably transported to the granulator by a gear pump at a working pressure of 15-20MPa and a speed of 30-50r / min, the melt flow rate fluctuation is controlled to be ≤±2%, and granulation is carried out underwater. The melt is extruded through a die into a cooling water tank at 25-30℃ for cooling. The die diameter in the granulator is 3-5mm, the number of holes is 30-50, and the flow rate is 1500-2000r / min. A high-speed cutter at a rotational speed of 1000 rpm cuts the material into chips 3-5 mm in length. The chips are cooled to below 60°C in a cooling water tank and then transported to a chip dryer via a softened water flow at a velocity of 0.5-1 m / s. Partial crystallization occurs at 40-50°C in the chip dryer, which circulates hot air at 80-90°C and a wind speed of 1.5 m / s to dry the chips, ensuring a moisture content of ≤0.1%. The dried chips fall into an intermediate chip silo via an ultra-long separator and are then transported to storage via a closed screw conveyor and pneumatic conveying system to obtain high-toughness PTT material.

[0017] (iii) Beneficial technical effects Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, by screening diol-based third monomers with reactivity matching that of PTT raw material monomers, and through random copolymerization of the reactivity-matched diol third monomers, precise control of the material structure is achieved at the molecular chain level, and the reaction conditions are optimized to improve the binding rate to over 95%. The third monomer undergoes coesterification and cocondensation reactions with terephthalic acid and 1,3-propanediol under the action of a catalyst, thereby chemically bonding the flexible segments to the PTT backbone. The reaction process mainly produces two synergistic effects: first, the introduced flexible segments directly increase the flexibility and mobility of the molecular chain; second, the third monomer disrupts the original chemical regularity and spatial symmetry of the PTT molecular chain, significantly reducing its crystallinity and crystallinity. This synergy of "increasing flexibility" and "deregulating regularity" fundamentally changes the material's failure mode, enabling it to undergo greater plastic deformation under stress, which is macroscopically manifested as a significant increase in elongation at break and impact strength. At the same time, the controllable reduction in crystallinity reduces light scattering, allowing the material to maintain high light transmittance even after toughening. This ensures that the third monomer is randomly inserted with a binding rate of over 95%, achieving control over molecular weight distribution and reaction equilibrium. This, in turn, enhances toughness while maintaining the stability of fundamental properties such as heat resistance and weather resistance. Furthermore, the efficient distillation recovery process recycles unreacted monomers, demonstrating a balance between economic efficiency and stability from molecular design to process design.

[0018] (2) In this invention, a diol third monomer system is selected, combined with a catalyst, and through a stepwise reaction of transesterification and polycondensation, the binding rate of the third monomer is increased to over 95%, synergistically improving the flexibility of the molecular chain and the regularity of crystallization. A balance between toughening modification and performance stability is achieved, resulting in a modified PTT material with an elongation at break ≥150%, an impact strength increase of over 40%, and no significant decrease in weather resistance, thus achieving a balance between toughness, strength, and heat resistance. By optimizing the parameters of copolymerization and separation, the melt viscosity is controlled at 0.8-1.2 dL / g and the distillation vacuum degree is ≥0.098 MPa during the polycondensation stage, ensuring a balance between toughening effect and resin stability. The free monomer collected at the top of the column can be recycled and reused with a recovery rate ≥90%, taking into account both performance improvement and economy, and reducing raw material loss and production costs. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] Example 1 A method for preparing a modified high-toughness PTT material includes the following steps: Step (1): Add diethylene glycol monomer and tetrabutyl titanate catalyst in a mass ratio of 100:1 to the mixing tank, stir and mix at a stirring speed of 80 r / min, a stirring temperature of 60℃, and a stirring time of 20 min to form a uniform premix of the third monomer. Step (2): Add terephthalic acid and 1,3-propanediol to the polymerization reactor equipped with pressure control and distillation device, heat to 180°C, add the third monomer premix, wherein the mass ratio of terephthalic acid, 1,3-propanediol and the third monomer premix is ​​100:55:12.4, maintain the pressure inside the reactor at 0.2MPa and the stirring speed at 60r / min, and the transesterification reaction occurs. After reacting for 2 hours, increase the vacuum degree of the polymerization reactor to ≥0.095MPa, heat to 240°C, and stir at 30r / min to induce polycondensation reaction. After reacting for 5 hours, until the resin melt viscosity reaches 0.8dL / g, and obtain PTT melt; Step (3): The PTT melt is fed into a pre-distillation column by a transfer pump for pre-distillation. During the pre-distillation process, the temperature inside the pre-distillation column is 180℃, the pressure is 0.05MPa, and the distillation time is 40min. Then, it is subjected to rectification in a vacuum distillation column. During the vacuum distillation process, the temperature inside the vacuum distillation column is 200℃, the vacuum degree is 0.098MPa, and the rectification time is 50min. After the treatment is completed, the rectified melt is passed through a 4A adsorption molecular sieve adsorption column for adsorption purification. The amount of 4A adsorption molecular sieve is 2% of the melt mass, and the adsorption temperature is 190℃ to obtain the separated PTT resin melt. Step (4): The separated PTT resin melt is stably transported to the granulator by a gear pump at a working pressure of 15MPa and a speed of 30r / min. The flow rate fluctuation of the melt is controlled to be ≤±2%. The melt is granulated underwater and extruded through the die into a 25℃ cooling water tank for cooling. The die diameter of the granulator is 3mm and the number of holes is 50. The high-speed cutter at a speed of 1500r / min cuts the melt into 3mm long chips. The chips are cooled to below 60℃ in the cooling water tank and transported to the chip dryer by a softened water flow at a speed of 0.5m / s. Partial crystallization occurs at 40℃. The chip dryer circulates hot air at 80℃ and a wind speed of 1.5m / s to dry the chips, so that the moisture content of the chips is ≤0.1%. The dried chips fall into the intermediate chip silo through an ultra-long separator and are then sent to the storage through a closed screw conveyor and a pneumatic conveying system to obtain high-toughness PTT material.

[0021] Example 2 A method for preparing a modified high-toughness PTT material includes the following steps: Step (1): Add diethylene glycol monomer and tetrabutyl titanate catalyst in a mass ratio of 100:2.5 to the mixing tank, stir and mix at a speed of 90 r / min, a temperature of 60℃, and a mixing time of 30 min to form a uniform premix of the third monomer. Step (2): Add terephthalic acid and 1,3-propanediol to the polymerization reactor equipped with pressure control and distillation device, heat to 180°C, add the prepared third monomer premix, wherein the mass ratio of terephthalic acid, 1,3-propanediol and the third monomer premix is ​​100:60:18, maintain the pressure inside the reactor at 0.2MPa and the stirring speed at 70r / min, and the transesterification reaction occurs. The reaction lasts for 2.5h. Increase the vacuum degree of the polymerization reactor to ≥0.095MPa, heat to 245°C, and the stirring speed at 35r / min, and the polycondensation reaction occurs. The reaction lasts for 4.5h until the viscosity of the resin melt reaches 1dL / g, and PTT melt is obtained. Step (3): The PTT melt is fed into a pre-distillation column by a transfer pump for pre-distillation. During the pre-distillation process, the temperature inside the pre-distillation column is 190℃, the pressure is 0.05MPa, and the distillation time is 35min. Then, it is subjected to rectification in a vacuum distillation column. During the vacuum distillation process, the temperature inside the vacuum distillation column is 210℃, the vacuum degree is 0.098MPa, and the rectification time is 45min. After the treatment is completed, the rectified melt is passed through a 4A adsorption molecular sieve adsorption column for adsorption purification. The amount of 4A adsorption molecular sieve is 2.5% of the melt mass, and the adsorption temperature is 190℃ to obtain the separated PTT resin melt. Step (4): The separated PTT resin melt is stably transported to the granulator by a gear pump at a working pressure of 18MPa and a speed of 40r / min. The flow rate fluctuation of the melt is controlled to be ≤±2%. The melt is granulated underwater and extruded through the die into a 28℃ cooling water tank for cooling. The die diameter of the granulator is 4mm and the number of holes is 40. The high-speed cutter at a speed of 1800r / min cuts the melt into 4mm long chips. The chips are cooled to below 60℃ in the cooling water tank and transported to the chip dryer by a softened water flow at a flow rate of 0.8m / s. Partial crystallization occurs at 45℃. The chip dryer circulates hot air at 85℃ and a wind speed of 1.5m / s to dry the chips, so that the moisture content of the chips is ≤0.1%. The dried chips fall into the intermediate chip silo through an ultra-long separator and are then sent to the storage through a closed screw conveyor and a pneumatic conveying system to obtain high-toughness PTT material.

[0022] Example 3 A method for preparing a modified high-toughness PTT material includes the following steps: Step (1): Add 1,6-hexanediol monomer and antimony ethylene glycol catalyst in a mass ratio of 100:2.5 to the mixing tank, stir and mix at a speed of 90 r / min, a stirring temperature of 60℃, and a stirring time of 30 min to form a uniform premixed solution of the third monomer. Step (2): Add terephthalic acid and 1,3-propanediol to the polymerization reactor equipped with pressure control and distillation device, heat to 180°C, add the third monomer premix, wherein the mass ratio of terephthalic acid, 1,3-propanediol and the third monomer premix is ​​100:60:18, maintain the pressure inside the reactor at 0.2MPa and the stirring speed at 70r / min, and the transesterification reaction occurs. The reaction lasts for 2.5h. Increase the vacuum degree of the polymerization reactor to ≥0.095MPa, heat to 245°C, and the stirring speed at 35r / min, and the polycondensation reaction occurs. The reaction lasts for 4.5h until the viscosity of the resin melt reaches 1dL / g, and PTT melt is obtained. Step (3): The prepared PTT melt is fed into a pre-distillation column by a transfer pump for pre-distillation. During the pre-distillation process, the temperature inside the pre-distillation column is 190℃, the pressure is 0.05MPa, and the distillation time is 35min. Then, it is subjected to rectification in a vacuum distillation column. During the vacuum distillation process, the temperature inside the vacuum distillation column is 210℃, the vacuum degree is 0.098MPa, and the rectification time is 45min. After the treatment is completed, the rectified melt is passed through a 5A adsorption molecular sieve adsorption column for adsorption purification. The amount of 5A adsorption molecular sieve is 2.5% of the melt mass, and the adsorption temperature is 190℃ to obtain the separated PTT resin melt. Step (4): The separated PTT resin melt is stably transported to the granulator by a gear pump at a working pressure of 18MPa and a speed of 40r / min. The flow rate fluctuation of the melt is controlled to be ≤±2%. The melt is granulated underwater and extruded through the die into a 28℃ cooling water tank for cooling. The die diameter of the granulator is 4mm and the number of holes is 40. The high-speed cutter at a speed of 1800r / min cuts the melt into 4mm long chips. The chips are cooled to below 60℃ in the cooling water tank and transported to the chip dryer by a softened water flow at a flow rate of 0.8m / s. Partial crystallization occurs at 45℃. The chip dryer circulates hot air at 85℃ and a wind speed of 1.5m / s to dry the chips, so that the moisture content of the chips is ≤0.1%. The dried chips fall into the intermediate chip silo through an ultra-long separator and are then sent to the storage through a closed screw conveyor and a pneumatic conveying system to obtain high-toughness PTT material.

[0023] Example 4 A method for preparing a modified high-toughness PTT material includes the following steps: Step (1): Add diethylene glycol monomer and tetrabutyl titanate catalyst in a mass ratio of 100:4 to the mixing tank, stir and mix at a speed of 100 r / min, a temperature of 60℃, and a mixing time of 50 min to form a uniform premix of the third monomer. Step (2): Add terephthalic acid and 1,3-propanediol to the polymerization reactor equipped with pressure control and distillation device, heat to 180°C, add the prepared third monomer premix, wherein the mass ratio of terephthalic acid, 1,3-propanediol and the third monomer premix is ​​100:70:20.4, maintain the pressure inside the reactor at 0.2MPa and the stirring speed at 80r / min, and the transesterification reaction occurs. After reacting for 3h, increase the vacuum degree of the polymerization reactor to ≥0.095MPa, heat to 250°C, and the stirring speed at 40r / min, and the polycondensation reaction occurs. After reacting for 4h, until the resin melt viscosity reaches 1.2dL / g, PTT melt is obtained; Step (3): The PTT melt is fed into a pre-distillation column by a transfer pump for pre-distillation. During the pre-distillation process, the temperature inside the pre-distillation column is 200℃, the pressure is 0.05MPa, and the distillation time is 30min. Then, it is subjected to rectification in a vacuum distillation column. During the vacuum distillation process, the temperature inside the vacuum distillation column is 220℃, the vacuum degree is 0.098MPa, and the rectification time is 40min. After the treatment is completed, the rectified melt is passed through a 4A adsorption molecular sieve adsorption column for adsorption purification. The amount of 4A adsorption molecular sieve is 3% of the melt mass, and the adsorption temperature is 190℃ to obtain the separated PTT resin melt. Step (4): The separated PTT resin melt is stably transported to the granulator by a gear pump at a working pressure of 20MPa and a speed of 50r / min. The flow rate fluctuation of the melt is controlled to be ≤±2%. The melt is granulated underwater and extruded through the die into a 30℃ cooling water tank for cooling. The die diameter of the granulator is 5mm and the number of holes is 30. The high-speed cutter at a speed of 2000r / min cuts the melt into 5mm long chips. The chips are cooled to below 60℃ in the cooling water tank and transported to the chip dryer by a softened water flow at a speed of 1m / s. Partial crystallization occurs at 50℃. The chip dryer circulates hot air at 90℃ and a wind speed of 1.5m / s to dry the chips, so that the moisture content of the chips is ≤0.1%. The dried chips fall into the intermediate chip silo through an ultra-long separator and are then sent to the storage through a closed screw conveyor and a pneumatic conveying system to obtain high-toughness PTT material.

[0024] Comparative Example 1 A method for preparing a PTT material includes the following steps: Step (1): Add terephthalic acid and 1,3-propanediol in a mass ratio of 100:60 to a polymerization reactor equipped with pressure control and distillation device. Heat to 180°C, maintain pressure inside the reactor at 0.2 MPa and stirring speed at 70 r / min to induce transesterification reaction. React for 2.5 h. Increase the vacuum degree of the polymerization reactor to ≥0.095 MPa, heat to 245°C, and stir speed at 35 r / min to induce polycondensation reaction. React for 4.5 h until the resin melt viscosity reaches 1 dL / g to obtain PTT melt. Step (2): The PTT melt is fed into a pre-distillation column by a transfer pump for pre-distillation. During the pre-distillation process, the temperature inside the pre-distillation column is 190℃, the pressure is 0.05MPa, and the distillation time is 35min. Then, it is subjected to rectification in a vacuum distillation column. During the vacuum distillation process, the temperature inside the vacuum distillation column is 210℃, the vacuum degree is 0.098MPa, and the rectification time is 45min. After the treatment is completed, the rectified melt is passed through a 4A adsorption molecular sieve adsorption column for adsorption purification. The amount of 4A adsorption molecular sieve is 2.5% of the melt mass, and the adsorption temperature is 190℃ to obtain the separated PTT resin melt. Step (3): The separated PTT resin melt is stably transported to the granulator by a gear pump at a working pressure of 18MPa and a speed of 40r / min. The flow rate fluctuation of the melt is controlled to be ≤±2%. The melt is granulated underwater and extruded through the die into a 28℃ cooling water tank for cooling. The die diameter of the granulator is 4mm and the number of holes is 40. The high-speed cutter at a speed of 1800r / min cuts the melt into 4mm long chips. The chips are cooled to below 60℃ in the cooling water tank and transported to the chip dryer by a softened water flow at a speed of 0.8m / s. Partial crystallization occurs at 45℃. The chip dryer circulates hot air at 85℃ and a wind speed of 1.5m / s to dry the chips so that the moisture content of the chips is ≤0.1%. The dried chips fall into the intermediate chip silo through an ultra-long separator and are then sent to the storage through a closed screw conveyor and a pneumatic conveying system to obtain PTT material.

[0025] Comparative Example 2 A method for preparing a PTT material includes the following steps: Step (1): Add diethylene glycol monomer and tetrabutyl titanate catalyst in a mass ratio of 100:2.5 to the mixing tank, stir and mix at a speed of 90 r / min, a temperature of 60℃, and a mixing time of 30 min to form a uniform premix of the third monomer. Step (2): Add terephthalic acid and 1,3-propanediol to the polymerization reactor equipped with pressure control and distillation device, heat to 180°C, add the prepared third monomer premix, wherein the mass ratio of terephthalic acid, 1,3-propanediol and the third monomer premix is ​​100:60:18, maintain the pressure inside the reactor at 0.2MPa and the stirring speed at 70r / min, and the transesterification reaction occurs. The reaction lasts for 2.5h. Increase the vacuum degree of the polymerization reactor to ≥0.095MPa, heat to 245°C, and the stirring speed at 35r / min, and the polycondensation reaction occurs. The reaction lasts for 4.5h until the viscosity of the resin melt reaches 1dL / g, and PTT melt is obtained. Step (3): The PTT melt is stably pumped to the granulator at a working pressure of 18MPa and a speed of 40r / min by a gear pump. The flow rate fluctuation of the melt is controlled to be ≤±2%. The melt is granulated underwater and extruded through the die into a 28℃ cooling water tank for cooling. The die diameter of the granulator is 4mm and the number of holes is 40. The high-speed cutter at a speed of 1800r / min cuts the melt into 4mm long chips. The chips are cooled to below 60℃ in the cooling water tank and transported to the chip dryer by a softened water flow at a speed of 0.8m / s. Partial crystallization occurs at 45℃. The chip dryer circulates hot air at 85℃ and a wind speed of 1.5m / s to dry the chips so that the moisture content of the chips is ≤0.1%. The dried chips fall into the intermediate chip silo through an ultra-long separator and are then sent to the storage through a closed screw conveyor and a pneumatic conveying system to obtain the PTT material.

[0026] The 1,3-propanediol used in the embodiments and comparative examples of this invention is produced by our company, and the other raw materials are commercially available.

[0027] The PTT materials prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to corresponding tests. The test methods and results are shown in Table 1. Table 1 As shown in Table 1, the PTT materials corresponding to Examples 1-4 exhibit good toughness, significantly improved impact strength, and excellent mechanical properties. The binding rate of the third monomer is increased to over 95%, the residual amount of free monomer is less than 0.5%, and it also possesses excellent heat resistance. After the third monomer is embedded in the main chain, it does not damage the heat-resistant framework structure of the molecular chain. In Comparative Example 1, no third monomer was introduced, resulting in higher crystallinity and greater brittleness. The elongation at break of the PTT material was significantly reduced, and the cantilever beam notched impact strength was also somewhat decreased. In Comparative Example 2, the PTT melt was not subjected to distillation or adsorption treatment, leaving a large amount of residual free monomer, which affected chain segment movement and interfacial bonding, resulting in a decrease in overall performance.

[0028] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for preparing a modified high-toughness PTT material, characterized in that: Includes the following steps: Step (1): Add the diol monomer and catalyst to the mixing tank, stir and mix to form a uniform third monomer premix; Step (2): Add terephthalic acid and 1,3-propanediol to the reaction vessel, heat up, add the third monomer premix prepared in step (1), and react to obtain PTT melt; Step (3): The PTT melt prepared in step (2) is fed into a pre-distillation column for pre-distillation, and then subjected to distillation in a vacuum distillation column. After the treatment is completed, it is purified by adsorption to obtain the separated PTT resin melt. Step (4): The separated PTT resin melt prepared in step (3) is added to a granulator for granulation, cooled and solidified, dried and separated to obtain high-toughness PTT material.

2. The method for preparing a modified high-toughness PTT material according to claim 1, characterized in that: The diol monomer in step (1) includes any one of diethylene glycol, 1,4-butanediol, and 1,6-hexanediol.

3. The method for preparing a modified high-toughness PTT material according to claim 1, characterized in that: The catalyst in step (1) is either tetrabutyl titanate or antimony glycol.

4. The method for preparing a modified high-toughness PTT material according to claim 1, characterized in that: In step (1), the mass ratio of diol monomer to catalyst is 100:(1-4), the stirring speed is 80-100 r / min, the stirring temperature is 60℃, and the stirring time is 20-50 min.

5. The method for preparing a modified high-toughness PTT material according to claim 1, characterized in that: The specific preparation process of the polymer melt in step (2) includes the following steps: adding terephthalic acid and 1,3-propanediol to the polymerization reactor equipped with pressure control and distillation device, heating to 180°C, adding the third monomer premix prepared in step (1), maintaining the pressure inside the reactor at 0.2 MPa and the stirring speed at 60-80 r / min, reacting for 2-3 h, increasing the vacuum degree of the polymerization reactor to ≥0.095 MPa, heating to 240-250°C, stirring at 30-40 r / min, reacting for 4-5 h, until the viscosity of the resin melt reaches 0.8-1.2 dL / g, and obtaining PTT melt.

6. The method for preparing a modified high-toughness PTT material according to claim 1, characterized in that: In step (2), the mass ratio of terephthalic acid, 1,3-propanediol, and the third monomer premix is ​​100:(55-70):(12.4-20.4).

7. The method for preparing a modified high-toughness PTT material according to claim 1, characterized in that: In step (3), during the pre-distillation process, the temperature inside the pre-distillation tower is 180-200℃, the pressure is 0.05MPa, and the distillation time is 30-40min.

8. The method for preparing a modified high-toughness PTT material according to claim 1, characterized in that: In step (3), during the vacuum distillation process, the temperature inside the vacuum distillation column is 200-220℃, the vacuum degree is 0.098MPa, and the distillation time is 40-50min. The specific process of adsorption purification is as follows: the melt after distillation is passed through a 4A adsorption molecular sieve adsorption column for adsorption purification. The amount of 4A adsorption molecular sieve is 2%-3% of the melt mass, and the adsorption temperature is 190℃.

9. The method for preparing a modified high-toughness PTT material according to claim 1, characterized in that: In step (3), the adsorbent used in the adsorption column after distillation can also be 5A adsorption molecular sieve. The amount of 5A adsorption molecular sieve is 2%-3% of the melt mass, and the adsorption temperature is 190℃.

10. The method for preparing a modified high-toughness PTT material according to claim 1, characterized in that: The specific preparation process of the high-toughness PTT material in step (4) includes the following steps: The PTT resin melt separated in step (3) is stably transported to the granulator by a gear pump at a working pressure of 15-20MPa and a speed of 30-50r / min, and the melt flow rate fluctuation is controlled to be ≤±2%. The granulator is granulated underwater, and the melt is extruded through a die into a cooling water tank at 25-30℃ for cooling. The die diameter in the granulator is 3-5mm, and the number of holes is 30-50. The flow rate is 1500-2000r / min. A high-speed cutter cuts the chip into 3-5mm long fragments. The fragments are cooled to below 60°C in a cooling water tank and then transported to a chip dryer via a softened water flow at a speed of 0.5-1m / s. Partial crystallization occurs at 40-50°C in the chip dryer, which circulates hot air at 80-90°C and a wind speed of 1.5m / s to dry the chip, ensuring a moisture content of ≤0.1%. The dried fragments fall into an intermediate chip silo via an ultra-long separator and are then transported to storage via a closed screw conveyor and pneumatic conveying system to obtain high-toughness PTT material.

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