High-GWIT polybutylece terephthalate (PBT) / polyamide 6 (PA6) alloy material and preparation method thereof

Abstract

The invention discloses a high-GWIT (glow wire ignition temperature) PBT (polybutylene terephthalate) / PA6 (polyamide 6) alloy material and a preparation method thereof, and the high-GWIT PBT / PA6 alloy material comprises the following raw materials in parts by weight: 30-60 parts of polybutylene terephthalate; 10 to 20 parts of polycaprolactam; 10 to 30 parts of glass fiber; 3 to 5 parts of compatilizer; 0.2 to 0.6 part of an oxazoline graft polymer; 8 to 12 parts of a flame retardant; 3-5 parts of a flame retardant synergist; 0.2 to 0.5 part of an antioxidant; 0.2 to 0.5 part of a lubricant; the polyethylene-acrylic acid and poly (2-ethyl-2-oxazoline) grafted copolymer contains a heterocyclic compound with unsaturated bonds, and can be subjected to ring-opening reaction with terminal carboxyl groups of PBT and PA6 to form chain extension and cross-linking effects. Under the condition that a small amount of flame-retardant additive is added, the vertical combustion of the PBT / PA6 alloy material can reach UL94 V0 grade, and the GWIT can reach 875V. The external cross-linking effect also enables the mechanical property of the material to be obviously improved.

Description

Technical Field

[0001] The present invention relates to a PBT / PA6 alloy material, and in particular to a PBT / PA6 alloy material with high GWIT and a preparation method thereof. Background Art

[0002] Polybutylene terephthalate (PBT) has the advantages of good stiffness, good self-lubrication, good resistance to organic solvents, and high electrical stability. However, it also has disadvantages such as poor notch toughness and easy decomposition under high temperature and high humidity environments. Polyamide 6 (PA6) has excellent mechanical properties, wear resistance, and is easy to form and process. It is a widely used engineering plastic, but PA6 has the disadvantage that its mechanical and electrical properties deteriorate after absorbing water. Making the two into alloys can improve the water absorption of PA6 and the impact brittleness of PBT. However, both PBT and PA6 are partially crystalline polymers, and their blends have poor compatibility and mechanical properties.

[0003] In the household appliance industry, combustion safety has always been a highly-watched issue, with GWIT being one of the important evaluation indicators. With the emphasis on fire safety in recent years, GWIT in the household appliance industry has also shown a gradual upward trend. At present, the main method is to add a high proportion of flame retardants to produce a large amount of inert gas. These gases are enriched on the surface of the resin, isolating oxygen, thereby inhibiting the combustion reaction; or the added inorganic flame retardants release water vapor at high temperatures, absorb a large amount of heat, and reduce the surface temperature of the material, thereby slowing down or preventing combustion. These solutions require the addition of a large amount of flame retardants, and the mechanical properties of the materials drop sharply, which has no practical application value. Therefore, efficiently improving the compatibility of PBT and PA6, which were originally widely used in the household appliance industry, and improving the GWIT value of the alloy can fill the gaps in PBT and PA materials in high-standard and high-requirement fields.

[0004] Chinese patent document CN 107227002 discloses a high glow-wire ignition temperature and high CTI glass fiber reinforced PBT / PA6 alloy material. The invention uses a bromine-based flame retardant compounded with a red phosphorus masterbatch and used together with a compounded flame retardant synergist to achieve a V0 flame retardant effect while making the GWIT reach 875°C and the CTI value reach 425V. However, the addition of up to 40 parts of the additive in the system significantly reduces the mechanical properties of the material. Summary of the invention

[0005] The present invention provides a PBT / PA6 alloy material with high GWIT and a preparation method thereof. The material uses epoxy grafts and oxazoline graft polymers as compatibilizers and crosslinkers to form a three-dimensional network structure, which can effectively limit the movement of molecular chains, thereby improving the thermal stability and flame retardancy of the material. On this basis, brominated flame retardants and inorganic salt masterbatches are compounded to make the PBT / PA6 alloy material have the performance advantages of both PBT and PA, and the GWIT can reach 850°C, which can cover the application range of PBT and PA in the home appliance industry.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: A high GWIT PBT / PA6 alloy material, the raw material composition includes, by weight: The PBT is polybutylene terephthalate, with an intrinsic viscosity of 0.8-1.0 dl / g, and specifically, the GX112 model of Yizheng Petrochemical can be selected.

[0007] The polyamide is polycaprolactam with an intrinsic viscosity of 2.4-2.8 dl / g, and specifically Huajian's 2.45 viscosity PA6 can be selected.

[0008] The glass fiber is alkali-free chopped strands with a diameter of 10-13 μm and a length of 3.0-4.5 mm, and specifically, T435N or T436H of Taishan Fiberglass can be selected.

[0009] The compatibilizer is one or two of glycidyl methacrylate grafted styrene-butadiene-styrene block copolymer and maleic anhydride grafted ethylene vinyl acetate copolymer.

[0010] The oxazoline grafted polymer is a grafted copolymer of polyethylene-acrylic acid and poly (2-ethyl-2-oxazoline).

[0011] The flame retardant is a brominated flame retardant, including one or more of brominated epoxy resin, decabromodiphenylethane, brominated triazine or brominated polystyrene.

[0012] The flame retardant synergist is one or more of antimony trioxide, aluminum hydroxide, zinc borate, and barium silicate. Preferably, the weight ratio of antimony trioxide to at least one of aluminum hydroxide, zinc borate, and barium silicate is 1.5-2.5:2-3.5.

[0013] The antioxidant is selected from a composite mixture of a primary antioxidant and an auxiliary antioxidant: The main antioxidant is one or more of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythritol tetrakis[β-(3,5-tert-butyl-4-hydroxyphenyl) propionate, bis(2,4-di-tert-butylphenyl)tetratertol or 2,6-di-tert-butyl-4-4-cresol, and N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine.

[0014] The processing aid is selected from one or more of calcium stearate, silicon masterbatch, and ethylene bisstearamide.

[0015] On the basis of the preferred raw material varieties mentioned above, it is further preferred that, by weight, the raw material composition of the high GWIT PBT / PA6 alloy material comprises: More preferably, the raw material composition comprises: The present invention also discloses a method for preparing the high GWIT PBT / PA6 alloy material, comprising: After the raw materials are uniformly mixed, they are melt-kneaded and extruded into granules in a twin-screw extruder; the barrel temperatures of each section of the twin-screw extruder are: zone 1 temperature 180-210°C, zone 2 temperature 220-240°C, zone 3 temperature 220-240°C, zone 4 temperature 220-240°C, zone 5 temperature 210-230°C, zone 6 temperature 180-210°C, zone 7 temperature 180-210°C, zone 8 temperature 180-210°C, zone 9 temperature 180-210°C, die head: 220-240°C The main engine speed is 400~450rpm, and the length-to-diameter ratio of the twin screw is 35:1.

[0016] Compared with the prior art, the advantages of the present invention are: The graft copolymer of polyethylene-acrylic acid and poly(2-ethyl-2-oxazoline) can react with the carboxyl groups at the ends of PBT and PA6 to form new chemical bonds, extend the polymer chains or cross-link to form a three-dimensional network structure. This structure can effectively limit the movement of molecular chains, improve the thermal stability and flame retardant properties of the material, and thus reduce the addition of flame retardants and flame retardant synergists. In addition, after PBT and PA are cross-linked, the notched impact strength, tensile strength and elongation at break of the alloy are all improved. DETAILED DESCRIPTION

[0017] Comparative Examples 1 to 4 and Examples 1 to 6 The raw material formulas for preparing the PBT / PA6 alloy material with high GWIT in each embodiment and comparative example are listed in Table 1 below. The preparation method of the material comprises the following steps: Weigh each component according to weight percentage, mix in a high-speed mixer for 1-3 minutes; mix evenly to obtain a premix; place the premix in the main feed port of a twin-screw extruder, and allow the glass fiber to enter from the side feed port, melt co-extrude, and then granulate and cool.

[0018] The specific data of the mechanical strength, flowability and flame retardancy of the antistatic PBT materials prepared in the examples and comparative examples are listed in Table 2 below.

[0019] serial number Comparative Example 1# Comparative Example 2# Example 1# Example 2# Example 3# Example 4# Example 5# Example 6# PBT GX112 61 59.2 59 59 58.8 59.8 59.8 59.3 PA6 2.45 10 10 10 10 10 10 10 10 Glass fiber T435N 10 10 10 10 10 10 10 10 Glycidyl Methacrylate Grafted Styrene-Butadiene-Styrene Block Copolymer 0 2 2 0 2 2 2 2 Maleic anhydride grafted ethylene vinyl acetate copolymer 0 0 0 2 0 0 0 0 Graft copolymer of polyethylene-acrylic acid and poly(2-ethyl-2-oxazoline) 0.2 0 0.2 0.2 0.4 0.4 0.4 0.4 Decabromodiphenylethane 12 12 12 12 12 12 12 12 Antimony trioxide 3 3 3 3 3 2.5 2.5 2.5 Aluminum hydroxide 3.5 3.5 3.5 3.5 3.5 3.0 0 0 Zinc borate 0 0 0 0 0 0 3.0 3.5 Antioxidant / 1076:168(1:1) 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Lubricant / Calcium Stearate 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 serial number Comparative Example 1# Comparative Example 2# Example 1# Example 2# Example 3# Example 4# Example 5# Example 6# Tensile strengthMpa 75.3 78.5 83.9 81.0 87.6 92.1 91.6 90.2 Bending strength MPa 113 127 136 130 148 156 153 151 <![CDATA[Izod impact strength kJ / m 2 > 5.7 6.8 8.1 7.9 8.7 9.1 9.0 8.8 Melt flow rate g / 10min 29.8 22.8 19.6 20.9 14.9 12.5 13.2 13.0 Vertical burning 1.6mm V0 V0 V0 V0 V0 V0 V0 V0 Vertical burning 0.8mm V1 V1 V0 V0 V0 V0 V1 V0 GWIT 750 750 850 850 850 850 850 850 The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A high GWIT PBT / PA6 alloy material, comprising the following raw materials in parts by weight: Polybutylene terephthalate: 30-60 parts; Polycaprolactam: 10-20 parts; Glass fiber: 10-30 parts; Compatibilizer: 3-5 parts; Oxazoline graft polymer: 0.2-0.8 parts; Flame retardant: 8-12 parts; Flame retardant synergist: 3-5 parts; Antioxidant: 0.2-0.5 parts; Lubricant: 0.2-0.5 parts.

2. The high GWIT PBT / PA6 alloy material according to claim 1, characterized in that: The intrinsic viscosity of the polybutylene terephthalate is 0.8-1.0 dl / g.

3. The high GWIT PBT / PA6 alloy material according to claim 1, characterized in that: The polycaprolactam has an intrinsic viscosity of 2.4-2.8 dl / g.

4. The high GWIT PBT / PA6 alloy material according to claim 1, characterized in that: The glass fiber is alkali-free chopped strands with a diameter of 10-13 μm and a length of 3.0-4.5 mm.

5. The high GWIT PBT / PA6 alloy material according to claim 1, characterized in that: The oxazoline grafted polymer is a grafted copolymer of polyethylene-acrylic acid and poly(2-ethyl-2-oxazoline).

6. The high GWIT PBT / PA6 alloy material according to claim 1, characterized in that: The flame retardant is a brominated flame retardant, including one or more of brominated epoxy resin, decabromodiphenylethane, brominated triazine or brominated polystyrene.

7. The high GWIT PBT / PA6 alloy material according to claim 1, characterized in that: The flame retardant synergist is one or more of antimony trioxide, aluminum hydroxide, zinc borate, and barium silicate. Preferably, the weight ratio of antimony trioxide to at least one of aluminum hydroxide, zinc borate, and barium silicate is 1.5-2.5:2-3.

5.

8. The high GWIT PBT / PA6 alloy material according to claim 1, characterized in that: The main antioxidant is one or more of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythritol tetrakis[β-(3,5-tert-butyl-4-hydroxyphenyl) propionate, bis(2,4-di-tert-butylphenyl)tetratertol or 2,6-di-tert-butyl-4-4-cresol, and N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine.

9. The high GWIT PBT / PA6 alloy material according to claim 1, characterized in that: The lubricant is selected from one or more of calcium stearate, silicone masterbatch, and ethylene bisstearamide.