High-strength modified PBT resin and preparation method thereof

Abstract

The invention discloses a preparation method of high-strength modified PBT (Polybutylene Terephthalate) resin. The preparation method comprises the following steps: S1, carrying out transesterification on raw materials including butanediol and terephthalic acid; s2, adding a dihydric alcohol modifier, continuously reacting for a period of time, adding a dicarboxylic acid modifier, and carrying out a cross-linking reaction to obtain a prepolymer of the modified PBT material; s3, continuously reacting to a certain intrinsic viscosity, adding an aniline monomer and an oxidizing agent, and carrying out polymerization reaction under the action of subcritical carbon dioxide; a primary product of the modified PBT material is obtained; and S4, uniformly mixing the modified PBT resin with PBT master batch and an auxiliary agent, carrying out melt extrusion, and granulating to obtain the high-strength modified PBT resin. According to the preparation method disclosed by the invention, the mechanical property and the thermal stability of the material are remarkably improved, the material is endowed with excellent flame retardant property and functional characteristics, and the strict requirements of high-end fields such as automobiles, electronic appliances, aerospace and the like on high-performance engineering plastics can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of PBT resin, and in particular to a high-strength modified PBT resin and a preparation method thereof. Background Art

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

[0003] In view of the above shortcomings of the existing technology, the present invention provides a method for preparing a high-strength modified PBT resin to address the limitations of traditional PBT resin in terms of mechanical properties, thermal stability, flame retardancy, and functional applications. Although traditional PBT resin has excellent mechanical properties and processing properties, its high strength, thermal stability, and flame retardancy still need to be improved. This is especially true in high-end applications (such as automotive, electronics, aerospace, etc.), where traditional PBT resins struggle to meet the stringent material property requirements. Furthermore, the functional applications of traditional PBT resins (such as electromagnetic shielding performance) are relatively limited, restricting their application in emerging technologies. Therefore, the present invention aims to prepare a modified PBT resin with high strength, high thermal stability, excellent flame retardancy, and multifunctionality through an innovative modification method, the introduction of specific modifiers, and an optimized preparation process, to meet the modern industrial demand for high-performance engineering plastics.

[0004] In order to achieve the above objects, the technical solution adopted by the present invention is: A method for preparing a high-strength modified PBT resin, comprising the following steps: S1: Adding raw materials butanediol, terephthalic acid and catalyst into a reactor, and performing transesterification reaction under specific temperature and pressure conditions; S2: After the transesterification reaction in step S1 proceeds to a certain extent, a diol modifier is added, and the reaction is continued for 15 to 60 minutes, and then a dicarboxylic acid modifier is added. A cross-linking reaction is carried out under the protection of an inert gas to obtain a prepolymer of a modified PBT material; S3: The prepolymer obtained in step S2 is further reacted at a temperature of 265-270°C 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, and aniline monomer and an oxidant are added. A polymerization reaction is carried out under the action of subcritical carbon dioxide. After the reaction is completed, a strip is cast and pelletized to obtain a preliminary 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 grafting reaction, thereby achieving in-situ polymerization of polyaniline in the PBT resin matrix, and endowing the material with excellent electrical conductivity and electromagnetic shielding properties. At the same time, the green and pollution-free nature of carbon dioxide simplifies post-processing steps, reduces production costs, and meets environmental protection requirements. S4: The primary product is mixed evenly with unmodified PBT masterbatch and additives, and melt-extruded and granulated at a temperature of 265-275° C. and a screw speed of 300-500 r / min to finally obtain the high-strength modified PBT resin.

[0005] As a preferred technical solution, in step S1, the molar ratio of butanediol to terephthalic acid is 1.1 to 1.5:1.

[0006] As a preferred technical solution, in step S1, the reaction temperature of the transesterification reaction is 180-220° C., and the reaction pressure is 0.1-0.2 MPa.

[0007] As a preferred technical solution, in step S2, the diol modifier is a mixture of dihydroxyphenylphosphaphenanthrene and butanediol.

[0008] As a preferred technical solution, in step S2, the dicarboxylic acid modifier is an organic solution of aminophenyl para-dicarboxylic acid.

[0009] 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-dicarboxybiphenyl, and 2,2'-diamino-[1,1'-biphenyl]-4,4'-dicarboxylic acid.

[0010] As a preferred technical solution, in step S3, the oxidant is at least one of ammonium persulfate, potassium persulfate or hydrogen peroxide.

[0011] 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.

[0012] As a preferred technical solution, in step S4, the mass ratio of the primary product to the unmodified PBT masterbatch and the additive is 60-80:20-40:1-5.

[0013] Another aspect of the present invention is to provide a high-strength modified PBT resin, which is prepared using the above-mentioned method for preparing the high-strength modified PBT resin.

[0014] Beneficial effects of the present invention: The preparation method of the high-strength modified PBT resin of the present invention innovatively introduces dihydroxyphenylphosphaphenanthrene and aminophenyl para-dicarboxylic acid during the reaction process. Dihydroxyphenylphosphaphenanthrene, as a special diol modifier, has a phosphaphenanthrene ring in its molecular structure with unique electronic effects and steric hindrance effects, which can form effective crosslinking points between polymer chains, significantly improving the crosslinking density and thermal stability of the polymer. At the same time, the introduced hydroxyl groups can chemically bond with the polymer chains, further enhancing the mechanical properties and dimensional stability of the polymer. In addition, the phosphaphenanthrene ring also has an important flame retardant effect, which can effectively inhibit the thermal decomposition and combustion reaction of the polymer at high temperatures, significantly improving the fire resistance and self-extinguishing properties of the material. Aminophenyl para-dicarboxylic acid, as a functional dicarboxylic acid modifier, has a carboxyl group in its molecule that can chemically bond with the polymer chain to form a network structure with higher strength and toughness. In addition, the introduction of the amino group also provides active sites for subsequent reactions, creating conditions for the grafting reaction of aniline monomers, thereby achieving in situ polymerization of polyaniline.

[0015] By introducing dihydroxyphenylphosphaphenanthrene and aminophenyl para-dicarboxylic acid, the high-strength modified PBT resin of the present invention not only exhibits excellent mechanical properties, with higher tensile strength, flexural strength and impact strength, but also has significantly improved thermal stability, which can better meet the requirements of use in high-temperature environments. In addition, the modified PBT resin also has better chemical resistance and dimensional stability, and can maintain stable performance in complex chemical environments. More importantly, the introduction of dihydroxyphenylphosphaphenanthrene gives the material excellent flame retardant properties, giving it significant advantages in fire prevention and safety applications. At the same time, the introduction of amino groups provides active sites for the subsequent grafting reaction of aniline monomers, allowing polyaniline to be polymerized in situ in the PBT resin matrix, thereby giving the material 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 automobiles, electronics, aerospace, etc., and has important practical application value and market prospects. DETAILED DESCRIPTION

[0016] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are merely examples, and those skilled in the art may conceive of other obvious variations.

[0017] Example 1 The preparation method of the high-strength modified PBT resin of this embodiment comprises the following steps: S1: Add the raw materials butanediol (45g), terephthalic acid (166g) and catalyst (composed of 1.2g zinc acetate and 0.8g tetrabutyl titanate) into the reactor, and carry out ester exchange reaction at a reaction temperature of 200℃ and a reaction pressure of 0.15MPa.

[0018] S2: After 2.5 hours of transesterification in step S1, a diol modifier (a mixture of 65 g of dihydroxyphenylphosphaphenanthrene and 72 g of butanediol) was added. The reaction continued for 30 minutes, and then a dicarboxylic acid modifier (200 mL of a 30% solution of 2-aminoterephthalic acid in dimethylformamide) was added. A cross-linking reaction was carried out under nitrogen for 2 hours to obtain a prepolymer of the modified PBT material. The dihydroxyphenylphosphaphenanthrene was 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide (ODOPB, CAS No. 99208-50-1).

[0019] S3: The prepolymer obtained in step S2 is further reacted at a temperature of 265°C and a pressure of 50 Pa. When the intrinsic viscosity of the product reaches 0.75 dL / g, it is added to a reactor. Aniline monomer (25 g) and an oxidant (0.8 g ammonium persulfate) are also added. Polymerization is carried out under the action of subcritical carbon dioxide for 3 hours. After the reaction, a strip is cast and pelletized to obtain a preliminary product of the modified PBT material. The subcritical carbon dioxide temperature is 45°C and the pressure is 8 MPa.

[0020] S4: The primary product with a mass ratio of 70:30:5 is evenly mixed with the unmodified PBT masterbatch and an additive (benzotriazole ultraviolet absorber, such as UV-327), and melt-extruded and granulated at a temperature of 270°C and a screw speed of 400 r / min to finally obtain the high-strength modified PBT resin.

[0021] Example 2 The preparation method of the high-strength modified PBT resin of this embodiment comprises the following steps: S1: Add the raw materials butanediol (50g), terephthalic acid (175g) and catalyst (composed of 1.1g zinc acetate and 0.9g tetrabutyl titanate) into the reactor, and carry out ester exchange reaction under the conditions of reaction temperature of 220℃ and reaction pressure of 0.12MPa.

[0022] S2: After the transesterification reaction in step S1 for 3.5 hours, a diol modifier (a mixture of 70 g of dihydroxyphenylphosphaphenanthrene and 76 g of butanediol) was added. The reaction continued for 30 minutes, and then a dicarboxylic acid modifier (200 mL of a 35% by mass solution of 2,5-diaminoterephthalic acid in dimethylformamide) was added. A cross-linking reaction was carried out under nitrogen for 2 hours to obtain a prepolymer of a modified PBT material. The dihydroxyphenylphosphaphenanthrene was the same as in Example 1.

[0023] S3: The prepolymer obtained in step S2 is further reacted at a temperature of 265°C and a pressure of 50 Pa. When the intrinsic viscosity of the product reaches 0.8 dL / g, it is added to a reactor. Aniline monomer (30 g) and an oxidant (0.8 g potassium persulfate) are also added. Polymerization is carried out under the action of subcritical carbon dioxide for 3 hours. After the reaction, a strip is cast and pelletized to obtain a preliminary product of the modified PBT material. The subcritical carbon dioxide temperature is 45°C and the pressure is 8 MPa.

[0024] S4: The primary product with a mass ratio of 72:28:3 is evenly mixed with an unmodified PBT masterbatch and an additive (benzotriazole ultraviolet absorber, such as UV-327), and melt-extruded and granulated at a temperature of 270°C and a screw speed of 400 r / min to finally obtain the high-strength modified PBT resin.

[0025] Example 3 The preparation method of the high-strength modified PBT resin of this embodiment comprises the following steps: S1: Add the raw materials butanediol (55g), terephthalic acid (180g) and catalyst (composed of 1.0g zinc acetate and 1.0g tetrabutyl titanate) into the reactor, and carry out ester exchange reaction under the conditions of reaction temperature of 210℃ and reaction pressure of 0.18MPa.

[0026] S2: After the transesterification reaction in step S1 for 3 hours, a diol modifier (a mixture of 75 g of dihydroxyphenylphosphaphenanthrene and 80 g of butanediol) was added. The reaction continued for 30 minutes, and then a dicarboxylic acid modifier (200 mL of a 35% solution of 3,3'-diamino-4,4'-dicarboxybiphenyl in dimethylformamide) was added. A cross-linking reaction was carried out under nitrogen for 2 hours to obtain a prepolymer of the modified PBT material. The dihydroxyphenylphosphaphenanthrene was the same as in Example 1.

[0027] S3: The prepolymer obtained in step S2 is further reacted at a temperature of 265°C and a pressure of 50 Pa. When the intrinsic viscosity of the product reaches 0.8 dL / g, it is added to a reactor. Aniline monomer (35 g) and an oxidant (1.0 g potassium persulfate) are also added. Polymerization is carried out under the action of subcritical carbon dioxide for 3 hours. After the reaction, a strip is cast and pelletized to obtain a preliminary product of the modified PBT material. The subcritical carbon dioxide temperature is 45°C and the pressure is 8 MPa.

[0028] S4: The primary product with a mass ratio of 75:25:4 is evenly mixed with an unmodified PBT masterbatch and an additive (benzotriazole ultraviolet absorber, such as UV-327), and melt-extruded and granulated at a temperature of 270°C and a screw speed of 400 r / min to finally obtain the high-strength modified PBT resin.

[0029] Example 4 The raw material composition and preparation steps of the preparation method of the high-strength modified PBT resin of this embodiment are basically the same as those of Example 1, except that in the preparation method of this embodiment, 2,2'-diamino-[1,1'-biphenyl]-4,4'-dicarboxylic acid is used in step S2 instead of 2-aminoterephthalic acid.

[0030] Comparative Example 1 The raw material composition and preparation steps of the preparation method of the high-strength modified PBT resin in this comparative example are basically the same as those in Example 1, except that, in the preparation method of this comparative example, dihydroxyphenylphosphaphenanthrene is not added in step S2.

[0031] Comparative Example 2 The raw material composition and preparation steps of the preparation method of the high-strength modified PBT resin in this comparative example are basically the same as those in Example 1, except that in the preparation method of this comparative example, 2-aminoterephthalic acid is not added in step S2.

[0032] Comparative Example 3 The raw material composition and preparation steps of the preparation method of the high-strength modified PBT resin in this comparative example are basically the same as those in Example 1, except that in the preparation method of this comparative example, aniline monomer is not added in step S3.

[0033] The high-strength modified PBT resins prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to performance tests, and the performance results are shown in Table 1: The flame retardancy test (UL-94) was conducted according to the UL-94 standard. A specimen measuring 125 mm x 13 mm x 3 mm was prepared. The specimen was fixed vertically to a test stand. A flame was applied for 10 seconds, then removed. The burning behavior of the specimen was observed and recorded to determine its flame retardancy rating.

[0034] Tensile strength was tested according to ISO 527 using dumbbell-shaped specimens measuring 150 mm x 10 mm x 4 mm. The specimens were mounted on a tensile testing machine at a speed of 50 mm / min. The specimens were stretched until fracture, and the maximum tensile stress was recorded as the tensile strength.

[0035] Flexural strength is tested according to GB / T 9341. The specific test steps are as follows: First, prepare a rectangular beam specimen with dimensions of 80 mm × 10 mm × 4 mm according to the standard. Then, mount the specimen on a universal testing machine. Next, set the testing machine's loading speed to 2 mm / min, the data acquisition frequency to 10 Hz, and the maximum load to 10 kN, according to the test requirements. Start the testing machine and begin loading. The machine automatically records key data, such as the loading force and specimen bending deformation, until the specimen fails or reaches the required load level. Finally, calculate the flexural strength based on the recorded data.

[0036] Impact strength is tested according to ISO 179-1:2010. The specific test steps are as follows: First, prepare a rectangular strip specimen with standard dimensions of 80 mm × 10 mm × 4 mm. Then, place the specimen on the support of the impact testing machine to form a simply supported beam state, with the support spacing of 64 mm. Next, set the release height of the pendulum to 0.5 m and the impact energy range to 50 J. Release the pendulum to impact the specimen, and record the height to which the pendulum drops after breaking the specimen. By measuring the height to which the pendulum drops after breaking the specimen, the absorbed impact energy, i.e., the impact strength, is calculated.

[0037] Heat deflection temperature (HDT) is tested according to ISO 75 using specimens measuring 80 mm x 10 mm x 4 mm. The specimen is placed on a test platform, a specified load (0.45 MPa) is applied, and the temperature is increased at a rate of 120°C / h. The temperature at which the specimen undergoes the specified deformation under the load is recorded.

[0038] The electromagnetic shielding performance test indicator is electromagnetic shielding effectiveness (EMI), and the test is based on the MIL-STD-285 standard. The specific test steps are as follows: First, prepare a specimen with dimensions of 100mm × 100mm × 2mm and then place the specimen in an electromagnetic shielding test chamber. Using an electromagnetic shielding tester, test the specimen's electromagnetic shielding effectiveness at different frequencies from 100MHz to 1GHz. Record the electromagnetic field strength E0 when unshielded and the electromagnetic field strength E after shielding. Calculate the electromagnetic shielding effectiveness using the formula: Electromagnetic shielding effectiveness (dB) = 20*log(E0 / E).

[0039] Table 1

[0040] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. Various changes and improvements are possible without departing from the spirit and scope of the present invention, and such changes and improvements fall within the scope of the invention as claimed.

Claims

1. A method for preparing high-strength modified PBT resin, characterized in that: The preparation method comprises the following steps: S1: Adding raw materials butanediol, terephthalic acid and catalyst into a reactor, and performing transesterification reaction under specific temperature and pressure conditions; S2: After the transesterification reaction in step S1 proceeds to a certain extent, a diol modifier is added, and the reaction is continued for 15 to 60 minutes, and then a dicarboxylic acid modifier is added. A cross-linking reaction is carried out under the protection of an inert gas to obtain a prepolymer of a modified PBT material; S3: The prepolymer obtained in step S2 is further reacted at a temperature of 265-270° C. 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, and aniline monomer and an oxidant are added to carry out a polymerization reaction under the action of subcritical carbon dioxide. After the reaction is completed, a strip is cast and pelletized to obtain a primary product of the modified PBT material; S4: The primary product is mixed evenly with unmodified PBT masterbatch and additives, and melt-extruded and granulated at a temperature of 265-275° C. and a screw speed of 300-500 r / min to finally obtain the high-strength modified PBT resin.

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

1.

3. The method for preparing the high-strength modified PBT resin according to claim 1, wherein: In step S1, the reaction temperature of the transesterification reaction is 180-220° C., and the reaction pressure is 0.1-0.2 MPa.

4. The method for preparing the high-strength modified PBT resin according to claim 1, wherein: In step S2, the diol modifier is a mixture of dihydroxyphenylphosphaphenanthrene and butanediol.

5. The method for preparing the high-strength modified PBT resin according to claim 1, wherein: In step S2, the dicarboxylic acid modifier is an organic solution of aminophenyl para-dicarboxylic acid.

6. The method for preparing the high-strength modified PBT resin according to claim 5, wherein: The aminophenyl para-dicarboxylic acid is at least one of 2-aminoterephthalic acid, 2,5-diaminoterephthalic acid, 3,3-diamino-4,4-dicarboxybiphenyl, and 2,2'-diamino-[1,1'-biphenyl]-4,4'-dicarboxylic acid.

7. The method for preparing the high-strength modified PBT resin according to claim 1, wherein: In step S3, the oxidant is at least one of ammonium persulfate, potassium persulfate or hydrogen peroxide.

8. The method for preparing the high-strength modified PBT resin according to claim 1, wherein: In step S3, the temperature of the subcritical carbon dioxide is 40-50° C., and the pressure is 5-10 MPa.

9. The method for preparing the high-strength modified PBT resin according to claim 1, wherein: In step S4, the mass ratio of the primary product to the unmodified PBT masterbatch and the additive is 60-80:20-40:1-5.

10. A high-strength modified PBT resin, characterized in that: The PBT resin is prepared by the preparation method of the high-strength modified PBT resin according to any one of claims 1 to 9.

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