A high-strength modified PBT resin and its preparation method

Abstract

This invention discloses a method for preparing high-strength modified PBT resin, comprising the following steps: S1: esterification reaction of raw materials butanediol and terephthalic acid; S2: addition of a diol modifier and continued reaction for a period of time, followed by the addition of a dicarboxylic acid modifier, and crosslinking reaction to obtain a prepolymer of modified PBT material; S3: continued reaction to a certain intrinsic viscosity, addition of aniline monomer and oxidant, and polymerization reaction under the action of subcritical carbon dioxide; obtaining a primary product of modified PBT material; S4: uniformly mixing with PBT masterbatch and additives, melt extrusion, and granulation to obtain high-strength modified PBT resin. The preparation method of this invention not only significantly improves the mechanical properties and thermal stability of the material, but also endows the material with excellent flame retardant properties and functional characteristics, meeting the stringent requirements for high-performance engineering plastics in high-end fields such as automotive, electronics, and aerospace.

Description

Technical Field

[0001] This invention relates to the technical field of PBT resin, and more particularly to a high-strength modified PBT resin and its preparation method. Background Technology

[0002] PBT (polybutylene terephthalate) resin is an important engineering plastic, widely used in the automotive, electronics, and machinery manufacturing industries due to its excellent mechanical properties, thermal stability, and good processability. However, traditional PBT resin still has some limitations in certain high-end applications. For example, its mechanical strength and toughness are insufficient under extreme conditions, making it difficult to meet the requirements of high strength and high toughness. Furthermore, the thermal stability of PBT resin needs improvement, especially during long-term use in high-temperature environments, where performance degradation is likely. Simultaneously, the flame retardant properties of traditional PBT resin are weak, making it difficult to meet some high safety standards. In terms of functional applications, the electrical conductivity and electromagnetic shielding properties of traditional PBT resin are limited, restricting its application in emerging technology fields. Therefore, developing a high-performance, multifunctional modified PBT resin to overcome the shortcomings of existing technologies has become an important research direction. Summary of the Invention

[0003] In view of the shortcomings of the prior art, this invention provides a method for preparing a high-strength modified PBT resin to overcome the limitations of traditional PBT resin in terms of mechanical properties, thermal stability, flame retardancy, and functional applications. While traditional PBT resin possesses good mechanical and processing properties, its high strength, thermal stability, and flame retardancy still need improvement, especially in some high-end application fields (such as automotive, electronics, and aerospace), where it struggles to meet the stringent requirements for material performance. Furthermore, the functional applications of traditional PBT resin (such as electromagnetic shielding) are relatively limited, restricting its application scope in emerging technology fields. Therefore, this invention aims to prepare a high-strength, high-thermal-stability, excellent flame-retardant, and multifunctional modified PBT resin through innovative modification methods, introducing specific modifiers and optimized preparation processes, to meet the demands of modern industry for high-performance engineering plastics.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a high-strength modified PBT resin, the method comprising the following steps:

[0006] S1: Butanediol, terephthalic acid and catalyst are added to the reactor and esterification reaction is carried out under specific temperature and pressure conditions;

[0007] S2: After the esterification reaction in step S1 has proceeded to a certain extent, a diol modifier is added, and the reaction continues for 15 to 60 minutes. Then, a dicarboxylic acid modifier is added, and the crosslinking reaction is carried out under inert gas protection to obtain the prepolymer of the modified PBT material.

[0008] S3: The prepolymer obtained in step S2 is further reacted at a temperature of 265–270℃ and a pressure of less than 80 Pa. When the intrinsic viscosity of the product reaches 0.6–0.9 dL / g, it is added to a reactor along with aniline monomer and oxidant. Polymerization is carried out under the action of subcritical carbon dioxide. After the reaction, the product is cast into strips and pelletized to obtain the initial product of the modified PBT material. This application utilizes the excellent mass and heat transfer properties of subcritical carbon dioxide to promote the uniform dispersion of aniline monomer in the PBT prepolymer and the efficient progress of the grafting reaction, realizing the in-situ polymerization of polyaniline in the PBT resin matrix, and endowing the material with excellent electrical conductivity and electromagnetic shielding properties. Simultaneously, the green and pollution-free characteristics of carbon dioxide simplify the post-processing steps, reduce production costs, and meet environmental protection requirements.

[0009] S4: The primary product is mixed evenly with unmodified PBT masterbatch and additives, and then melt-extruded and granulated at a temperature of 265-275℃ and a screw speed of 300-500 r / min to finally obtain the high-strength modified PBT resin.

[0010] As a preferred technical solution, in step S1, the molar ratio of butanediol to terephthalic acid is 1.1 to 1.5:1.

[0011] As a preferred technical solution, in step S1, the reaction temperature of the esterification reaction is 180-220°C and the reaction pressure is 0.1-0.2 MPa.

[0012] As a preferred technical solution, in step S2, the diol modifier is a mixture of dihydroxyphenylphosphine and butanediol.

[0013] As a preferred technical solution, in step S2, the dicarboxylic acid modifier is an organic solution of aminophenyl-p-dicarboxylic acid.

[0014] As a preferred technical solution, the aminophenyl para-dicarboxylic acid is at least one of 2-aminoterephthalic acid, 2,5-diaminoterephthalic acid, 3,3-diamino-4,4-dicarboxylic biphenyl, and 2,2'-diamino-[1,1'-biphenyl]-4,4'-dicarboxylic acid.

[0015] As a preferred technical solution, in step S3, the oxidant is at least one of ammonium persulfate, potassium persulfate, or hydrogen peroxide.

[0016] As a preferred technical solution, in step S3, the temperature of the subcritical carbon dioxide is 40-50°C and the pressure is 5-10 MPa.

[0017] As a preferred technical solution, in step S4, the mass ratio of the primary product to the unmodified PBT masterbatch and additives is 60-80:20-40:1-5.

[0018] Another aspect of the present invention is to provide a high-strength modified PBT resin, wherein the PBT resin is prepared by the preparation method of the high-strength modified PBT resin described above.

[0019] The beneficial effects of this invention are:

[0020] This invention discloses a method for preparing high-strength modified PBT resin by innovatively introducing dihydroxyphenylphosphaphenanthrene and aminophenyl-p-dicarboxylic acid into the reaction process. Dihydroxyphenylphosphaphenanthrene, as a special diol modifier, possesses unique electronic and steric hindrance effects in its molecular structure, enabling the formation of effective crosslinking points between polymer chains, significantly improving the crosslinking density and thermal stability of the polymer. Simultaneously, the introduced hydroxyl groups can chemically bond with the polymer chains, further enhancing the polymer's mechanical properties and dimensional stability. Furthermore, the phosphaphenanthrene ring also exhibits important flame-retardant properties, effectively inhibiting the thermal decomposition and combustion reactions of the polymer at high temperatures, significantly improving the material's fire resistance and self-extinguishing properties. Aminophenyl-p-dicarboxylic acid, as a functional dicarboxylic acid modifier, has carboxyl groups in its molecule that can chemically bond with the polymer chains, forming a network structure with higher strength and toughness. In addition, the introduction of the amino group provides active sites for subsequent reactions, creating conditions for the grafting reaction of aniline monomers, thereby achieving in-situ polymerization of polyaniline.

[0021] By introducing dihydroxyphenylphosphaphenanthrene and aminophenyl-p-dicarboxylic acid, the high-strength modified PBT resin of this invention not only exhibits excellent mechanical properties, with higher tensile strength, flexural strength, and impact strength, but also shows significant improvement in thermal stability, better meeting the requirements for use in high-temperature environments. Furthermore, the modified PBT resin possesses better chemical resistance and dimensional stability, maintaining stable performance in complex chemical environments. More importantly, the introduction of dihydroxyphenylphosphaphenanthrene endows the material with excellent flame-retardant properties, giving it significant advantages in fireproofing and safety applications. Simultaneously, the introduction of the amino group provides active sites for the subsequent grafting reaction of aniline monomers, enabling polyaniline to polymerize in situ within the PBT resin matrix, thereby endowing the material with excellent electrical conductivity and electromagnetic shielding properties. This innovative modification method provides strong support for the application of PBT resin in high-end fields such as automotive, electronics, and aerospace, possessing significant practical application value and market prospects. Detailed Implementation

[0022] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0023] Example 1

[0024] The preparation method of high-strength modified PBT resin in this embodiment includes the following steps:

[0025] S1: Add the raw materials butanediol (45g), terephthalic acid (166g) and catalyst (composed of 1.2g zinc acetate and 0.8g tetrabutyl titanate) to the reactor and carry out the esterification reaction at a reaction temperature of 200℃ and a reaction pressure of 0.15MPa.

[0026] S2: After esterification reaction in step S1 for 2.5 hours, a diol modifier (a mixture of 65g dihydroxyphenylphosphaphenanthrene and 72g butanediol) is added. After reacting for another 30 minutes, a dicarboxylic acid modifier (200mL of a 30% dimethylformamide solution of 2-aminoterephthalic acid) is added. The mixture undergoes a crosslinking reaction under nitrogen protection for 2 hours to obtain a prepolymer of the modified PBT material. The dihydroxyphenylphosphaphenanthrene is 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide (ODOPB, CAS number 99208-50-1).

[0027] S3: The prepolymer obtained in step S2 is further reacted at a temperature of 265℃ and a pressure of 50Pa. When the intrinsic viscosity of the product reaches 0.75 dL / g, it is added to a reactor along with aniline monomer (25g) and oxidant (0.8g ammonium persulfate). The polymerization reaction is carried out for 3 hours under the action of subcritical carbon dioxide. After the reaction, the product is cast into strips and granulated to obtain the initial product of modified PBT material. The temperature of the subcritical carbon dioxide is 45℃ and the pressure is 8MPa.

[0028] S4: The primary product with a mass ratio of 70:30:5 is mixed with unmodified PBT masterbatch and additives (benzotriazole ultraviolet absorbers, such as UV-327) evenly. After melt extrusion and granulation at a temperature of 270℃ and a screw speed of 400r / min, the high-strength modified PBT resin is finally obtained.

[0029] Example 2

[0030] The preparation method of high-strength modified PBT resin in this embodiment includes the following steps:

[0031] S1: Add the raw materials butanediol (50g), terephthalic acid (175g) and catalyst (composed of 1.1g zinc acetate and 0.9g tetrabutyl titanate) to the reactor and carry out the esterification reaction at a reaction temperature of 220℃ and a reaction pressure of 0.12MPa.

[0032] S2: After esterification reaction in step S1 for 3.5 hours, a diol modifier (a mixture of 70g dihydroxyphenylphosphazene and 76g butanediol) was added. After reacting for another 30 minutes, a dicarboxylic acid modifier (200mL of a 35% dimethylformamide solution of 2,5-diaminoterephthalic acid) was added. The mixture under nitrogen protection underwent a crosslinking reaction for 2 hours to obtain the prepolymer of the modified PBT material. The dihydroxyphenylphosphazene is the same as in Example 1.

[0033] S3: The prepolymer obtained in step S2 is further reacted at a temperature of 265℃ and a pressure of 50Pa. When the intrinsic viscosity of the product reaches 0.8 dL / g, it is added to a reaction vessel along with aniline monomer (30g) and oxidant (0.8g potassium persulfate). The polymerization reaction is carried out for 3 hours under the action of subcritical carbon dioxide. After the reaction, the product is cast into strips and granulated to obtain the initial product of modified PBT material. The temperature of the subcritical carbon dioxide is 45℃ and the pressure is 8MPa.

[0034] S4: The primary product with a mass ratio of 72:28:3 is mixed evenly with unmodified PBT masterbatch and additives (benzotriazole ultraviolet absorbers, such as UV-327). After melt extrusion and granulation at a temperature of 270℃ and a screw speed of 400r / min, the high-strength modified PBT resin is finally obtained.

[0035] Example 3

[0036] The preparation method of high-strength modified PBT resin in this embodiment includes the following steps:

[0037] S1: Add the raw materials butanediol (55g), terephthalic acid (180g) and catalyst (composed of 1.0g zinc acetate and 1.0g tetrabutyl titanate) to the reactor and carry out the esterification reaction at a reaction temperature of 210℃ and a reaction pressure of 0.18MPa.

[0038] S2: After 3 hours of esterification reaction in step S1, a diol modifier (a mixture of 75g dihydroxyphenylphosphaphenanthrene and 80g butanediol) was added. After continuing the reaction for 30 minutes, a dicarboxylic acid modifier (200mL of a 35% (w / w) dimethylformamide solution of 3,3'-diamino-4,4'-dicarboxylic biphenyl) was added. The crosslinking reaction was carried out under nitrogen protection for 2 hours to obtain the prepolymer of the modified PBT material. The dihydroxyphenylphosphaphenanthrene is the same as in Example 1.

[0039] S3: The prepolymer obtained in step S2 is further reacted at a temperature of 265℃ and a pressure of 50Pa. When the intrinsic viscosity of the product reaches 0.8 dL / g, it is added to a reaction vessel along with aniline monomer (35g) and oxidant (1.0g potassium persulfate). The polymerization reaction is carried out for 3 hours under the action of subcritical carbon dioxide. After the reaction, the product is cast into strips and granulated to obtain the initial product of modified PBT material. The temperature of the subcritical carbon dioxide is 45℃ and the pressure is 8MPa.

[0040] S4: The primary product with a mass ratio of 75:25:4 is mixed evenly with unmodified PBT masterbatch and additives (benzotriazole ultraviolet absorbers, such as UV-327). After melt extrusion and granulation at a temperature of 270℃ and a screw speed of 400r / min, the high-strength modified PBT resin is finally obtained.

[0041] Example 4

[0042] The preparation method of high-strength modified PBT resin in this embodiment is basically the same as that in Example 1 in terms of raw material composition and preparation steps. The difference is that in the preparation method of this embodiment, 2,2'-diamino-[1,1'-biphenyl]-4,4'-dicarboxylic acid is used instead of 2-aminoterephthalic acid in step S2.

[0043] Comparative Example 1

[0044] The preparation method of the high-strength modified PBT resin in this comparative example is basically the same as that in Example 1 in terms of raw material composition and preparation steps. The difference is that dihydroxyphenylphosphaphenanthrene is not added in step S2 of the preparation method in this comparative example.

[0045] Comparative Example 2

[0046] The preparation method of the high-strength modified PBT resin in this comparative example is basically the same as that in Example 1 in terms of raw material composition and preparation steps. The difference is that 2-aminoterephthalic acid is not added in step S2 of the preparation method in this comparative example.

[0047] Comparative Example 3

[0048] The preparation method of the high-strength modified PBT resin in this comparative example is basically the same as that in Example 1 in terms of raw material composition and preparation steps. The difference is that aniline monomer is not added in step S3 of the preparation method in this comparative example.

[0049] The high-strength modified PBT resins prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to performance tests, and the performance results are shown in Table 1:

[0050] The flame retardancy test (UL-94) was conducted according to the UL-94 standard, with a sample size of 125mm × 13mm × 3mm prepared. The sample was vertically fixed to the test stand, a flame was applied for 10 seconds, and then the flame was removed. The burning behavior of the sample was observed and recorded to determine its flame retardancy rating.

[0051] Tensile strength was tested according to ISO 527 standard, using dumbbell-shaped specimens measuring 150 mm × 10 mm × 4 mm. The specimens were mounted on a tensile testing machine, and the tensile speed was set to 50 mm / min. The specimens were stretched until fracture, and the maximum tensile stress was recorded as the tensile strength.

[0052] Bending strength was tested according to GB / T 9341. The specific test steps are as follows: First, a rectangular beam specimen with dimensions of 80mm × 10mm × 4mm was prepared according to the standard requirements. Then, the specimen was mounted on a universal testing machine. Next, the loading speed of the testing machine was set to 2mm / min, the data acquisition frequency to 10Hz, and the maximum load to 10kN, according to the test requirements. The testing machine was started to begin loading, and the machine automatically recorded key data such as the loading force and the bending deformation of the specimen until the specimen failed or reached the required load level. Finally, the bending strength was calculated using the recorded data.

[0053] Impact strength was tested according to ISO 179-1:2010. The specific test steps are as follows: First, a rectangular strip specimen with standard dimensions of 80mm × 10mm × 4mm was prepared. Then, the specimen was placed on the supports of the impact testing machine, forming a simply supported beam, with a support spacing of 64mm. Next, the release height of the pendulum was set to 0.5m, and the impact energy range was set to 50J. The pendulum was released to impact the specimen, and the height the pendulum descended after the specimen broke was recorded. By measuring the height the pendulum descended after the specimen broke, the absorbed impact energy, i.e., the impact strength, was calculated.

[0054] Heat distortion temperature (HDT) was tested according to ISO 75, with a specimen size of 80 mm × 10 mm × 4 mm. The specimen was placed on the test platform, a specified load (0.45 MPa) was applied, and the temperature was increased at a rate of 120 °C / h. The temperature at which the specimen under the load underwent the specified deformation was recorded.

[0055] The electromagnetic shielding performance is tested using electromagnetic shielding effectiveness (EMI), according to the MIL-STD-285 standard. The specific test steps are as follows: First, prepare a sample with dimensions of 100mm × 100mm × 2mm, and then place the sample in an electromagnetic shielding test chamber. Use an electromagnetic shielding tester to test the electromagnetic shielding effectiveness of the sample at different frequencies from 100MHz to 1GHz. Record the electromagnetic field strength E0 when unshielded and the electromagnetic field strength E after shielding, and calculate the electromagnetic shielding effectiveness using the formula: Electromagnetic shielding effectiveness (dB) = 20 * log(E0 / E).

[0056] Table 1 Flame retardant rating V-0 V-0 V-0 V-0 V-1 V-0 V-0 Tensile strength, MPa 75 78 77 76 72 69 67 Bending strength, MPa 101 99 100 98 95 93 96 Impact strength, kJ / m² 12.2 12.6 12.4 12.3 11.4 11.2 11.6 Heat distortion temperature, °C 119 120 118 117 110 112 108 Electromagnetic shielding effectiveness, dB 25.4 26.7 25.8 24.9 25.2 26.1 /

[0057] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a high-strength modified PBT resin, characterized in that, The preparation method includes the following steps: S1: Butanediol, terephthalic acid and catalyst are added to the reactor and esterification reaction is carried out under specific temperature and pressure conditions; S2: After the esterification reaction in step S1 has proceeded to a certain extent, a diol modifier is added, and the reaction continues for 15 to 60 minutes. Then, a dicarboxylic acid modifier is added, and the crosslinking reaction is carried out under inert gas protection to obtain the prepolymer of the modified PBT material. S3: The prepolymer obtained in step S2 is further reacted at a temperature of 265-270℃ and a pressure of less than 80Pa. When the intrinsic viscosity of the product reaches 0.6-0.9dL / g, it is added to the reactor, along with aniline monomer and oxidant. The polymerization reaction is carried out under the action of subcritical carbon dioxide. After the reaction is completed, the product is cast into strips and granulated to obtain the initial product of modified PBT material. S4: The primary product is mixed evenly with unmodified PBT masterbatch and additives, and then melt-extruded and granulated at a temperature of 265-275℃ and a screw speed of 300-500 r / min to finally obtain the high-strength modified PBT resin. In step S1, the reaction temperature of the esterification reaction is 180–220°C, and the reaction pressure is 0.1–0.2 MPa. In step S2, the diol modifier is a mixture of dihydroxyphenylphosphaphenanthrene and butanediol; the dihydroxyphenylphosphaphenanthrene is 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide; the dicarboxylic acid modifier is an organic solution of aminophenyl-p-dicarboxylic acid; the aminophenyl-p-dicarboxylic acid is at least one of 2-aminoterephthalic acid, 2,5-diaminoterephthalic acid, 3,3-diamino-4,4-dicarboxylic biphenyl, and 2,2'-diamino-[1,1'-biphenyl]-4,4'-dicarboxylic acid.

2. The method for preparing the high-strength modified PBT resin as described in claim 1, characterized in that, In step S1, the molar ratio of butanediol to terephthalic acid is 1.1 to 1.5:

1.

3. The method for preparing the high-strength modified PBT resin as described in claim 1, characterized in that, In step S3, the oxidant is at least one of ammonium persulfate, potassium persulfate, or hydrogen peroxide.

4. The method for preparing the high-strength modified PBT resin as described in claim 1, characterized in that, In step S3, the temperature of the subcritical carbon dioxide is 40-50°C and the pressure is 5-10 MPa.

5. The method for preparing the high-strength modified PBT resin as described in claim 1, characterized in that, In step S4, the mass ratio of the primary product to the unmodified PBT masterbatch and additives is 60-80:20-40:1-5.

6. A high-strength modified PBT resin, characterized in that, The PBT resin is prepared using the method for preparing high-strength modified PBT resin as described in any one of claims 1 to 5.