Dimensionally Stable PBT Composite Materials and Their Preparation Methods

Abstract

This invention relates to dimensionally stable PBT composite materials and their preparation method. The dimensionally stable PBT material is made from the following raw materials in parts by weight (%): 78-96% PBT resin, 1-5% AS resin, 2-10% toughening agent, 1-5% compatibilizer, 0.5-2% inorganic nucleating agent, and 0.1-0.5% organic nucleating agent. The preparation method involves weighing the raw materials according to the weight ratio, mixing them, adding them to a twin-screw extruder, and then melt-extruding and granulating. Through a reasonable formulation, this invention yields a PBT composite material with very high dimensional stability, almost no back shrinkage, and excellent physical, mechanical, and processing properties. Its preparation process is simple and low-cost, making it particularly suitable for application in the automotive gasket industry and possessing broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and relates to a dimensionally stable PBT composite material and its preparation method. Background Art

[0002] PBT, also known as polybutylene terephthalate, is one of the five major engineering plastics. It features high crystallinity, rapid molding capability, high heat resistance, toughness, fatigue resistance, self-lubrication, low coefficient of friction, weather resistance, low water absorption, and maintains various physical properties (including electrical properties) even in humid environments. It is resistant to hot water, alkalis, acids, and oils, and has excellent moldability. It is widely used in the electrical, electronics, automotive, and machinery industries for structural components. In my country, the primary consumer of PBT is electronics, mainly for connectors, switches, and automotive parts. With the rapid development of my country's automotive industry, the demand for PBT is also growing rapidly.

[0003] Gaskets are materials made of paper, rubber, or copper sheets, placed between two flat surfaces to enhance the seal. They are sealing elements placed between static sealing surfaces to prevent fluid leakage. Rubber is typically chosen for non-metallic gaskets. Due to PBT's excellent processability and oil resistance, PBT composite materials are currently being used to replace rubber gaskets in some automotive sealing gasket applications, significantly reducing costs. However, PBT suffers from low notched impact strength, high molding shrinkage, and severe post-shrinkage, limiting its application in automotive gaskets.

[0004] Therefore, how to ensure that PBT composite materials maintain dimensional stability and minimal post-shrinkage to meet the application needs of downstream manufacturers has always been an urgent problem to be solved in the industry. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a dimensionally stable PBT composite material by means of a blending extrusion method, which addresses the above-mentioned deficiencies of the prior art.

[0006] The technical solution adopted by this invention to solve its technical problem is: to provide a dimensionally stable PBT composite material, which is made from the following raw materials in parts by weight:

[0007]

[0008] In the dimensionally stable PBT composite material described in this invention, the PBT resin is a PBT resin with an intrinsic viscosity of 0.8-1.2. Preferably, it is a PBT resin with a viscosity of 1.0.

[0009] In the dimensionally stable PBT composite material described in this invention, the AS resin is a commercially available general-purpose resin. Only a small amount of AS resin needs to be added to significantly reduce the initial shrinkage rate of PBT after demolding.

[0010] In the dimensionally stable PBT composite material described in this invention, the toughening agent is a thermoplastic polyester elastomer (TPEE) with a hardness of 30D-90D, preferably 50D-70D TPEE. TPEE and PBT resin have good compatibility, which can ensure physical strength while increasing resilience and flexibility, meeting the toughness requirements of the gasket industry, and has little impact on the crystallization of PBT.

[0011] In the dimensionally stable PBT composite material described in this invention, the compatibilizer is MBS (methyl methacrylate-butadiene-propylene terpolymer). MBS can increase the interfacial compatibility between PBT and AS resin, has good synergistic toughening effect with TPEE, and does not affect the material's post-shrinkage.

[0012] In the dimensionally stable PBT composite material described in this invention, the inorganic nucleating agent is ultrafine talc powder. Preferably, it is talc powder with a mesh size of 5000 or larger, more preferably talc powder with a mesh size of 10000 or larger.

[0013] In the dimensionally stable PBT composite material described in this invention, the organic nucleating agent is a sodium salt ionomer of ethylene-acrylic acid copolymer. This nucleating agent not only has high nucleation efficiency but also excellent dispersing effect on ultrafine talc powder. The combination of the two nucleating agents not only greatly improves the crystallinity of PBT resin but also perfects the crystallization of PBT and effectively prevents post-crystallization of the material, avoiding the problem of post-shrinkage in the finished product.

[0014] A method for preparing a dimensionally stable PBT composite material includes the following steps:

[0015] ① Weigh the raw materials according to the aforementioned weight ratio;

[0016] ② Add PBT resin and AS resin to a high-speed mixer and mix for 3-10 minutes. Then add TPEE, MBS, ultrafine talc powder, and sodium salt ionomer of ethylene-acrylic acid copolymer and mix for 15-30 minutes.

[0017] ③ The mixture obtained in step ② is placed in a twin-screw extruder and granulated by melt extrusion. The length-to-diameter ratio of the screw is 32-48. The process conditions are: zone 1 temperature 170-200℃, zone 2 temperature 180-210℃, zone 3 temperature 180-210℃, zone 4 temperature 200-230℃, die head temperature 210-230℃, barrel residence time 0.5-2 minutes, and melt pressure 10-20MPa.

[0018] The dimensionally stable PBT composite nylon material of this invention fully utilizes the synergistic effects of various additives, not only improving the dimensional stability of the material but also controlling post-shrinkage in a relatively stable manner, solving a problem in the industry. Furthermore, it exhibits excellent overall physical and processing properties. Its raw materials are all commercially available, the preparation process is simple, and the cost is relatively low, meeting various application needs for dimensionally stable PBT in the market. It is particularly suitable for application in the automotive gasket industry and has promising development prospects. Detailed Implementation

[0019] The present invention will be further described below with reference to embodiments.

[0020] For ease of description, the PBT resin used in this invention is brand name KH2100, manufactured by Kanghui Petrochemical Co., Ltd.; the AS resin is brand name A2200NF, manufactured by Ningbo Formosa Chemicals Co., Ltd.; the TPEE toughening agent is brand name TX636, manufactured by Yizheng Chemical Fiber Co., Ltd.; the MBS compatibilizer is brand name EM500, manufactured by LG Corporation of Korea; the inorganic nucleating agent, ultrafine talc powder, is brand name HTP-05L, manufactured by Imfabi Corporation; and the organic nucleating agent is brand name AClyn285P, manufactured by Honeywell Corporation.

[0021] Example 1.

[0022] Premix 92.7% PBT resin and 1.5% AS resin by weight in a mixing tank for 7 minutes. Then add 3% TPEE TX636, 2% EM500, 0.6% talc HTP-05L, and 0.2% AClyn285P, and stir for 20 minutes. Afterward, melt-mix the premixed material in a twin-screw extruder, extrude, and granulate. The twin-screw extruder has a screw diameter of 35mm, a screw length-to-diameter ratio of 3:2, and extrusion temperatures of 180℃ in zone 1, 230℃ in zone 2, 200℃ in zone 3, 220℃ in zone 4, and a die head temperature of 230℃. The residence time is 0.5-2 minutes, and the pressure is 15MPa.

[0023] Example 2.

[0024] Premix 89.7% PBT resin and 2% AS resin by weight in a mixing tank for 8 minutes. Then add 5% TPEE TX636, 2% EM500, 1% talc HTP-05L, and 0.3% AClyn285P, and stir for 22 minutes. Afterward, melt-mix the premixed material in a twin-screw extruder, extrude, and granulate. The twin-screw extruder has a screw diameter of 50 mm, a screw length-to-diameter ratio of 3:6, and extrusion temperatures of 190℃ in zone 1, 235℃ in zone 2, 230℃ in zone 3, 210℃ in zone 4, a die head temperature of 225℃, a residence time of 1-1.5 min, and a pressure of 13 MPa.

[0025] Example 3.

[0026] Premix 87.7% PBT resin and 3% AS resin by weight in a mixing tank for 4 minutes. Then add 5% TPEE TX636, 3% EM500, 1% talc HTP-05L, and 0.3% AClyn285P, and stir for 25 minutes. Afterward, melt-mix the premixed material in a twin-screw extruder, extrude, and granulate. The twin-screw extruder has a screw diameter of 65mm, a screw length-to-diameter ratio of 40, and extrusion temperatures of 195℃ in zone 1, 230℃ in zone 2, 235℃ in zone 3, 220℃ in zone 4, a die head temperature of 220℃, a residence time of 1-2 minutes, and a pressure of 16MPa.

[0027] Example 4.

[0028] Premix 83.1% PBT resin and 3% AS resin by weight in a mixing tank for 5 minutes. Then add 5% TPEE TX636, 3% EM500, 1.5% talc HTP-05L, and 0.4% AClyn285P, and stir for 26 minutes. Afterward, melt-mix the premixed material in a twin-screw extruder, extrude, and granulate. The twin-screw extruder has a screw diameter of 75mm, a screw length-to-diameter ratio of 4:4, and extrusion temperatures of 195℃ in zone 1, 230℃ in zone 2, 235℃ in zone 3, 220℃ in zone 4, a die head temperature of 220℃, a residence time of 1-2 minutes, and a pressure of 13MPa.

[0029] Example 5.

[0030] Premix 81.8% PBT resin and 4% AS resin by weight in a mixing tank for 7 minutes. Then add 8% TPEE TX636, 4% EM500, 1.8% talc HTP-05L, and 0.4% AClyn285P, and stir for 28 minutes. Afterward, melt-mix the premixed material in a twin-screw extruder, extrude, and granulate. The twin-screw extruder has a screw diameter of 52 mm, a screw length-to-diameter ratio of 40, and extrusion temperatures of 190℃ in zone 1, 230℃ in zone 2, 235℃ in zone 3, 215℃ in zone 4, a die head temperature of 225℃, a residence time of 1-1.5 min, and a pressure of 19 MPa.

[0031] Example 6.

[0032] Premix 78.5% PBT resin and 4% AS resin by weight in a mixing tank for 5 minutes. Then add 10% TPEE TX636, 5% EM500, 2% talc HTP-05L, and 0.5% AClyn285P, and stir for 30 minutes. Afterward, melt-mix the premixed material in a twin-screw extruder, extrude, and granulate. The twin-screw extruder has a screw diameter of 40mm, a screw length-to-diameter ratio of 48, and extrusion temperatures of 190℃ in zone 1, 230℃ in zone 2, 235℃ in zone 3, 210℃ in zone 4, a die head temperature of 230℃, a residence time of 0.5-2 minutes, and a pressure of 17MPa.

[0033] Comparative Example 1.

[0034] Add 90.7% PBT resin by weight to 5% TPEE TX636, 3% EM500, 1% talc HTP-05L, and 0.3% AClyn285P, and stir for 25 minutes. Then, melt-blend, extrude, and granulate the mixture in a twin-screw extruder. The twin-screw extruder has a screw diameter of 65mm, a screw length-to-diameter ratio of 40, and extrusion temperatures of 195℃ (zone 1), 230℃ (zone 2), 235℃ (zone 3), 220℃ (zone 4), and a die head temperature of 220℃. The residence time is 1.5-2 minutes, and the pressure is 16MPa.

[0035] Comparative Example 2.

[0036] Premix 92.7% PBT resin and 3% AS resin by weight in a mixing tank for 5 minutes. Then add 3% EM500, 1% talc HTP-05L, and 0.3% AClyn285P, and stir for 25 minutes. Afterward, melt-mix the premixed material in a twin-screw extruder, extrude, and granulate. The twin-screw extruder has a screw diameter of 52 mm, a screw length-to-diameter ratio of 40, and extrusion temperatures of 195℃ in zone 1, 230℃ in zone 2, 235℃ in zone 3, 220℃ in zone 4, and a die head temperature of 220℃. The residence time is 1-1.5 min, and the pressure is 15 MPa.

[0037] Comparative Example 3.

[0038] Premix 90.7% PBT resin and 3% AS resin by weight in a mixing tank for 5 minutes. Then add 5% TPEE TX636, 1% talc HTP-05L, and 0.3% AClyn285P, and stir for 26 minutes. Afterward, melt-mix the premixed material in a twin-screw extruder, extrude, and granulate. The twin-screw extruder has a screw diameter of 52 mm, a screw length-to-diameter ratio of 40, and extrusion temperatures of 190℃ in zone 1, 220℃ in zone 2, 235℃ in zone 3, 220℃ in zone 4, and a die head temperature of 220℃. The residence time is 0.5-2 minutes, and the pressure is 14 MPa.

[0039] Comparative Example 4.

[0040] Premix 90.7% PBT resin and 3% AS resin (by weight) in a mixing tank for 5 minutes. Then add 5% TPEE TX636, 3% EM500, and 0.3% AClyn285P, and stir for 22 minutes. Afterward, melt-mix the premixed material in a twin-screw extruder, extrude, and granulate. The twin-screw extruder has a screw diameter of 35mm, a screw length-to-diameter ratio of 3:2, and extrusion temperatures of 190℃ (zone 1), 215℃ (zone 2), 235℃ (zone 3), 220℃ (zone 4), and a die head temperature of 220℃. The residence time is 1-2 minutes, and the pressure is 13MPa.

[0041] Comparative Example 5.

[0042] Premix 89% PBT resin and 3% AS resin by weight in a mixing tank for 5 minutes, then add 5% TPEE TX636, 3% EM500, and 1% talc HTP-05L, and stir for 24 minutes. Afterward, the mixed material is melt-blended, extruded, and granulated in a twin-screw extruder. The twin-screw extruder has a screw diameter of 75mm, a screw length-to-diameter ratio of 3:6, and extrusion temperatures of 195℃ (zone 1), 215℃ (zone 2), 235℃ (zone 3), 220℃ (zone 4), and a die head temperature of 215℃. The residence time is 1-1.5 minutes, and the pressure is 14MPa.

[0043] The PBT composite materials prepared in the first six examples and five comparative examples were tested, and the performance evaluation methods and implementation standards were as follows:

[0044] The granulated material was dried in a forced-air oven at 110℃ for 3–6 hours. The dried material was then injection molded on an injection molding machine with the mold temperature controlled at 80℃. Tensile strength testing was performed according to ASTM D638, with a specimen size of 180×12.7×3.2mm and a tensile speed of 50mm / min. Flexural performance testing was performed according to ASTM D790, with a specimen size of 128×13×3.2mm, a bending speed of 3mm / min, and a span of 64mm. Cantilever beam impact strength testing was performed according to ASTM D256, with a specimen size of 63.5×12.7×4.2mm and a notch size one-fifth of the specimen thickness. Melt flow index testing was performed according to ASTM D1238, with test conditions of 250℃ and a 2.16 kg weight.

[0045] Shrinkage testing was conducted according to ASTM D955 standard. The dried particles were directly injection molded into five 18×5mm sample molds. The sample length was measured with vernier calipers. The test was repeated three times, and the maximum and minimum values ​​of the individual product diameter range were taken. The shrinkage rate could be calculated as (mold length - sample length) * 100% / mold length. Two weeks later, the previous sample length was tested again, the shrinkage rate was calculated, and then compared with the previous shrinkage rate.

[0046] The comprehensive mechanical properties of the examples and comparative examples were evaluated by testing the tensile strength, flexural strength, impact strength, melt index, and shrinkage rate. The results are shown in Tables 1 and 2.

[0047] Table 1. Formulations and Performance of Examples

[0048]

[0049] Table 2 Comparative formulations and properties

[0050]

[0051] As can be seen from Examples 1-6, the PBT composite material of the present invention has excellent physical properties, low molding shrinkage, and essentially no change in shrinkage after two weeks.

[0052] As can be seen from Comparative Example 1, AS resin has a significant impact on both the initial shrinkage rate and the post-shrinkage rate of the material. Comparative Examples 2-5 show that the PBT composite material not only has a higher shrinkage rate, but also exhibits some post-shrinkage after two weeks, which is not as good as the results of the examples. This indicates that the materials and additives selected in this invention have a good synergistic effect in preventing post-shrinkage, and neither can be omitted.

[0053] In summary, the dimensionally stable PBT composite material prepared by this invention perfectly solves the problem of high shrinkage rate of PBT in automotive gasket applications. Its raw materials are all commercially available, the preparation process is simple, and the cost is relatively low, making it particularly suitable for use in the automotive gasket industry and possessing excellent development prospects.

[0054] The present invention provides a detailed description of a dimensionally stable PBT composite material and its preparation method. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of these examples are merely for the purpose of helping to understand the method and core ideas of the invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A dimensionally stable PBT composite material for automotive sealing gaskets, characterized in that: Made from the following parts by weight of raw materials: The toughening agent is a thermoplastic polyester elastomer (TPEE); The compatibilizer is MBS (methyl methacrylate-butadiene-propylene terpolymer); The inorganic nucleating agent is ultrafine talc powder; The organic nucleating agent is a sodium salt ionomer of ethylene-acrylic acid copolymer.

2. The dimensionally stable PBT composite material for automotive gaskets according to claim 1, characterized in that, The PBT resin is a PBT raw material resin with an intrinsic viscosity of 0.8 to 1.

2.

3. The dimensionally stable PBT composite material for automotive gaskets according to claim 1, characterized in that, The AS resin is an acrylonitrile-styrene copolymer.

4. A dimensionally stable PBT composite material for automotive gaskets according to claim 1, characterized in that, Includes the following steps: ① Weigh the raw materials according to the aforementioned weight ratio; ② Add PBT resin and AS resin to a high-speed mixer and mix for 3-10 minutes. Then add TPEE, MBS, ultrafine talc powder, and sodium salt ionomer of ethylene-acrylic acid copolymer and mix for 15-30 minutes. ③ The mixture obtained in step ② is placed in a twin-screw extruder, melt-extruded, and granulated. The screw length-to-diameter ratio is 32-48, and the process conditions are: zone 1 temperature 170-200℃, zone 2 temperature 180-210℃, zone 3 temperature 180-210℃, zone 4 temperature 200-230℃, die head temperature 210-230℃, barrel residence time 0.5-2 minutes, and melt pressure 10-20 MPa.

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