Long-lasting hydrolysis-resistant radiation-crosslinked pbt composition and method for preparing the same

Abstract

The application discloses a long-acting hydrolysis-resistant radiation crosslinking PBT composition which comprises the following raw material components in parts by mass: PBT resin: 40-90 parts, reinforcing material: 5-50 parts, crosslinking aid: 1-10 parts, hydrolysis-resistant agent: 0.1-2 parts, coupling agent: 0.1-3 parts, toughening agent: 1-15 parts, antioxidant: 0.1-1 part, and lubricant: 0.1-2 parts. In the formula design, specific aliphatic hydrolysis-resistant agent and vinyl-based toughening agent are added, and due to radiation, methylene segments in the two types of aids are also easily bonded to PBT molecular chains to form covalent bonds. Not only the compatibility between the aid and the PBT resin matrix is improved, but also after bonding, the hydrolysis-resistant agent is not easy to migrate to the material surface to cause passive consumption, and the PBT hydrolysis resistance is further improved.

Description

Technical Field

[0001] This invention relates to the field of polymer composite material processing, specifically to a long-lasting hydrolysis-resistant radiation-crosslinked PBT composition and its preparation method. Background Technology

[0002] Polybutylene terephthalate (PBT) is one of the five major general-purpose engineering plastics. Most PBT is modified before use. Modified PBT engineering plastics possess excellent mechanical and electrical properties, dimensional stability, ease of processing, and fatigue resistance, making them widely used in the automotive, electronics, and machinery industries. The conventional modification method for PBT is physical melt blending, which can be specifically divided into fiber reinforcement modification, flame retardant modification, and alloy modification. Modification can improve and enhance the mechanical, flame retardant, and electrical properties of PBT materials. However, with technological advancements, the requirements for materials are becoming increasingly stringent. For certain applications or needs, more stringent requirements are being placed on the performance of PBT materials, such as long-term hydrolysis resistance, high-temperature resistance, and stress cracking resistance.

[0003] PBT macromolecular chains are composed of repeating ester bonds and contain a large number of terminal carboxyl groups, which promote hydrolysis and chain scission reactions in PBT, especially under high temperature, high humidity, or acid / alkali conditions. This further accelerates the hydrolysis reaction, significantly reducing the mechanical properties of PBT materials and affecting their long-term use. A common method to improve the hydrolysis resistance of PBT is to add hydrolysis-resistant agents (such as aziridine, carbodiimide, etc.) to the formulation for modification. The basic principle is that the hydrolysis-resistant agent can react with the carboxyl groups to form a stable structure and inhibit the hydrolysis reaction. However, high amounts of hydrolysis-resistant agents affect material performance, and they are gradually consumed through reaction. At a certain point, PBT will still undergo hydrolysis and chain scission. Current industry applications require PBT materials to withstand more extreme conditions and be used for longer periods, which cannot be met by simply adding hydrolysis-resistant agents. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies for improving the hydrolysis resistance of PBT materials, and to provide a long-lasting hydrolysis-resistant radiation-crosslinked PBT composition and its preparation method. By using radiation crosslinking, the methylene groups within the PBT material molecules are chemically bonded to form a crosslinked structure, which greatly improves the hydrolysis resistance of PBT materials and provides long-lasting hydrolysis resistance.

[0005] The above-mentioned objective of this invention is achieved through the following technical solutions: A long-lasting hydrolysis-resistant radiation-crosslinked PBT composition, comprising the following raw material components in parts by weight: PBT resin: 40-90 parts Reinforcing material: 5-50 parts Crosslinking agent: 1-10 parts Hydrolysis resistant agent: 0.1-2 parts Coupling agent: 0.1-3 parts Toughening agent: 1-15 parts Antioxidant: 0.1-1 part Lubricant: 0.1-2 parts The intrinsic viscosity of the PBT resin is 0.7-1.2 dL / g, preferably 0.8-1.0 dL / g.

[0006] The reinforcing material is short fibers and / or mineral powder. The short fibers are selected from at least one of glass fiber, basalt fiber, carbon fiber, and aramid fiber. The mineral powder is selected from at least one of talc powder, mica powder, calcium carbonate, barium sulfate, kaolin, wollastonite, and glass microspheres.

[0007] The co-crosslinking agent is at least one selected from pentaerythritol tetramethacrylate, pentaerythritol tetraacrylate, trimethylallyl isocyanurate, triallyl cyanurate, 2,4,6-trienylpropoxy-1,3,5-triazine, trimethylolpropane trimethacrylate, and trimethylolpropane triacrylate.

[0008] The hydrolysis-resistant agent is an aliphatic polycarbodiimide; preferably, the aliphatic polycarbodiimide is obtained by polycondensation and end-capping reaction using hexamethylene diisocyanate as the starting reactant.

[0009] The coupling agent is selected from at least one of KH550, KH560, and KH570.

[0010] The toughening agent is selected from at least one of ethylene-glycidyl methacrylate copolymer (E-GMA), ethylene-glycidyl methacrylate-maleic anhydride copolymer (E-GMA-MAH), ethylene-octene-grafted maleic anhydride copolymer (POE-g-MAH), and ethylene-octene-grafted glycidyl methacrylate copolymer (POE-g-GMA).

[0011] The antioxidant is a mixture of hindered phenolic antioxidant and phosphite antioxidant in a mass ratio of 1:1; preferably, the hindered phenolic antioxidant is selected from at least one of 1010 and 1098; and the phosphite antioxidant is selected from at least one of 168 and 608.

[0012] The lubricant is selected from at least one of silicone powder, TAF, and E wax.

[0013] This invention also provides a method for preparing a long-lasting, hydrolysis-resistant, radiation-crosslinked PBT composition. The specific process steps are to prepare radiation-crosslinkable PBT composition particles, mold them by injection molding or extrusion, and then crosslink them using high-energy radiation.

[0014] The radiation-crosslinkable PBT composition particles are prepared by twin-screw melt extrusion. Specifically, PBT resin, hydrolysis-resistant agent, toughening agent, antioxidant, and lubricant are mixed evenly at high speed according to a set ratio and added to the main feed port of a twin-screw extruder. The crosslinking aid is added from the fifth zone side feed port A. The reinforcing material and coupling agent are fully mixed and then added from the eighth zone side feed port B. The mixture is fed and melt-extruded according to a predetermined ratio. The extrusion temperature is 200~250℃, the screw speed is 300-500rpm, and the particles are cooled, pelletized, and dried to obtain the final product.

[0015] The radiation crosslinking is performed by irradiating the PBT composition with an electron beam or gamma rays, with a radiation dose of 100-500 kGy, preferably 200-400 kGy.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes radiation to excite the methylene groups in the PBT molecular chain to bond together, resulting in extensive cross-linking between molecules via numerous C-C covalent bonds. These C-C bonds exhibit excellent hydrolysis resistance and are not easily broken by hydrolysis even under harsh conditions such as high temperature, high humidity, and strong acids and alkalis. Therefore, the hydrolysis resistance of PBT materials can be significantly improved. Due to the presence of cross-linked structures in the PBT molecular chain, only a small amount of hydrolysis-resistant agent needs to be added. The synergistic effect of these two agents gives the PBT material a longer-lasting hydrolysis resistance without reducing its mechanical properties.

[0017] This invention incorporates specific aliphatic hydrolysis-resistant agents and vinyl toughening agents into its formulation design. Due to radiation, the methylene segments in these two types of additives readily form covalent bonds with the PBT molecular chain. This not only improves the compatibility between the additives and the PBT resin matrix but also, after bonding, prevents the hydrolysis-resistant agents from migrating to the material surface and being passively consumed, further enhancing the hydrolysis resistance of PBT. Detailed Implementation

[0018] The following specific embodiments further illustrate the substantive content of the present invention. Unless otherwise specified, the operating methods in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer, and the selected raw materials are all commercially available PBT modified products.

[0019] Examples 1-8 and Comparative Examples 1-4 The raw material composition of a long-lasting hydrolysis-resistant radiation-crosslinked PBT composition, by mass parts, is shown in Table 1.

[0020] Table 1 shows the formulations of the examples and comparative examples.

[0021] formula Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 PBT resin (1.0 dL / g) 63 63 63 63 63 63 63 63 66.2 66 62.8 62.8 63 Co-crosslinking agent / trimethylolpropane triacrylate 3 3 3 3 3 3 3 Crosslinking agent / trimethylallyl isocyanurate 3 3 3 3 Di-tert-butyl-p-cresol 0.2 p-hydroxyanisole 0.2 Hydrolysis resistant agent / aliphatic polycarbodiimide 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Toughening agent / E-GMA 3 3 Toughening agent / POE-g-GMA 3 3 3 3 3 3 3 Toughening agent / POE-g-MAH 3 3 Toughening agent / E-GMA-MAH 3 3 Coupling agent / KH550 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Fiberglass 30 30 30 30 30 30 30 30 30 30 30 30 30 Antioxidant / 1010 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Antioxidant / 168 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Lubricant / Silicone Powder 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 According to the proportions in Table 1, PBT resin, hydrolysis resistant agent, toughening agent, antioxidant, lubricant, etc. are mixed evenly under high-speed stirring and added to the main feed port of a twin-screw extruder. Crosslinking agent and / or stabilizer are added from feed port A in the fifth zone. Reinforcing material and coupling agent are fully mixed and added from feed port B in the eighth zone. The mixture is fed according to the predetermined ratio and melt-extruded at an extrusion temperature of 210~250℃ and a screw speed of 350-400rpm. After cooling, pelletizing, and drying, crosslinkable PBT composition particles are obtained.

[0022] The above-mentioned particles were injection molded or extruded, and then the PBT composition was radioactively crosslinked using an electron beam. The radiation dose of Examples 1-8 and Comparative Examples 3-4 was 300 kGy, while the other comparative examples were not irradiated.

[0023] Performance Evaluation and Testing The tensile strength, simply supported beam impact strength, and hydrolysis resistance of the samples prepared in the above embodiments and comparative examples were tested, and the test data are listed in Table 3.

[0024] Tensile strength: According to GB / T 1040.2 standard, the test temperature is 23℃ and the tensile rate is 10mm / min; Impact strength of simply supported beam: According to GB / T 1043.1 standard, the test temperature is 23℃ and the impact energy is 4J; Hydrolysis resistance: The hydrolysis resistance of the material was characterized by the retention rate of tensile strength and simple beam impact strength of the sample after soaking in hot water at 80℃ for 500h and 3000h.

[0025] Table 2 Performance test results of the examples and comparative examples project Tensile strength (MPa) Impact strength (MPa) Tensile strength retention rate (%) after 500h hydrolysis experiment Impact strength retention rate (%) after 500 hours of hydrolysis experiment Tensile strength retention rate (%) after 3000h hydrolysis experiment Impact strength retention rate (%) after 3000h hydrolysis experiment Example 1 129.8 57.5 91.6 90.1 85.2 80.3 Example 2 146.1 62.3 99.3 95.7 93.0 89.4 Example 3 140.3 60.1 97.2 95.0 82.7 77.1 Example 4 136.7 58.8 92.4 92.0 90.8 87.0 Example 5 128.1 55.9 89.9 90.0 84.8 80.1 Example 6 143.2 60.0 98.7 94.3 91.5 88.2 Example 7 138.2 58.4 96.8 93.9 81.5 76.8 Example 8 135.6 57.7 90.4 90.5 90.0 86.3 Comparative Example 1 118.8 45.0 60.1 38.6 Powdered and untestable Powdered and untestable Comparative Example 2 119.0 46.1 65.5 47.7 Powdered and untestable Powdered and untestable Comparative Example 3 141.2 61.1 97.0 94.7 83.2 79.6 Comparative Example 4 140.8 60.7 96.6 94.5 83.8 79.3 Comparative Example 5 122.0 48.2 70.0 55.7 Powdered and untestable Powdered and untestable The test results show that the stabilizer has no positive effect in this formulation system and has a slight negative effect. Irradiation has a more significant effect on the impact strength retention rate. The type of toughening agent has different effects on hydrolysis performance. After 500h or 3000h hydrolysis experiments, the optimal toughening agent is POE-g-GMA.

Claims

1. A long-lasting hydrolysis-resistant radiation-crosslinked PBT composition, characterized in that, By weight, it contains the following raw material components: PBT resin: 40-90 parts Reinforcing material: 5-50 parts Crosslinking agent: 1-10 parts Hydrolysis resistant agent: 0.1-2 parts Coupling agent: 0.1-3 parts Toughening agent: 1-15 parts Antioxidant: 0.1-1 part Lubricant: 0.1-2 parts.

2. The long-lasting hydrolysis-resistant radiation-crosslinked PBT composition according to claim 1, characterized in that, The intrinsic viscosity of the PBT resin is 0.7-1.2 dL / g.

3. The long-lasting hydrolysis-resistant radiation-crosslinked PBT composition according to claim 1, characterized in that, The reinforcing material is short fiber and / or mineral powder; the short fiber is selected from at least one of glass fiber, basalt fiber, carbon fiber, and aramid fiber; the mineral powder is selected from at least one of talc powder, mica powder, calcium carbonate, barium sulfate, kaolin, wollastonite, and glass microspheres.

4. The long-lasting hydrolysis-resistant radiation-crosslinked PBT composition according to claim 1, characterized in that, The crosslinking agent is selected from at least one of pentaerythritol tetramethacrylate, pentaerythritol tetraacrylate, trimethylallyl isocyanurate, triallyl isocyanurate, 2,4,6-trienylpropoxy-1,3,5-triazine, trimethylolpropane trimethacrylate, and trimethylolpropane triacrylate.

5. The long-lasting hydrolysis-resistant radiation-crosslinked PBT composition according to claim 1, characterized in that, The hydrolysis-resistant agent is an aliphatic polycarbodiimide.

6. The long-lasting hydrolysis-resistant radiation-crosslinked PBT composition according to claim 1, characterized in that, The toughening agent is selected from at least one of ethylene-glycidyl methacrylate copolymer (E-GMA), ethylene-glycidyl methacrylate-maleic anhydride copolymer (E-GMA-MAH), ethylene-octene-grafted maleic anhydride copolymer (POE-g-MAH), and ethylene-octene-grafted glycidyl methacrylate copolymer (POE-g-GMA).

7. The long-lasting hydrolysis-resistant radiation-crosslinked PBT composition according to claim 1, characterized in that, The antioxidant is a mixture of hindered phenolic antioxidant and phosphite antioxidant in a 1:1 mass ratio; the lubricant is selected from at least one of silicone powder, TAF, and E wax; the coupling agent is selected from at least one of KH550, KH560, and KH570.

8. A method for preparing a long-lasting hydrolysis-resistant radiation-crosslinked PBT composition as described in any one of claims 1 to 7, characterized in that, The specific process involves preparing radiation-crosslinkable PBT composition particles, molding them by injection molding or extrusion, and then crosslinking them using high-energy radiation.

9. The method for preparing the long-lasting hydrolysis-resistant radiation-crosslinked PBT composition according to claim 8, characterized in that, The radiation-crosslinkable PBT composition particles are prepared by twin-screw melt extrusion. Specifically, PBT resin, hydrolysis-resistant agent, toughening agent, antioxidant, and lubricant are mixed evenly at high speed according to a set ratio and added to the main feed port of the twin-screw extruder. The crosslinking aid is added from the fifth zone side feed port A. The reinforcing material and coupling agent are fully mixed and then added from the eighth zone side feed port B. The mixture is fed and melt-extruded according to a predetermined ratio. The extrusion temperature is 200~250℃, the screw speed is 300-500rpm, and the particles are cooled, pelletized, and dried to obtain the final product.

10. The method for preparing the long-lasting hydrolysis-resistant radiation-crosslinked PBT composition according to claim 8, characterized in that, The radiation crosslinking is performed by irradiating the PBT composition with an electron beam or gamma rays, with a radiation dose of 100~500kGy.