CN1058932C - Irradiation dilatation process for preparing polyethylene material with high separation effect and high density - Google Patents

Abstract

A high-barrier high-density polyethylene (HDPE) material prepared by irradiation compatibilization method, which is characterized in that HDPE and nylon 6 (PA6) irradiated by ultraviolet rays with a wavelength of 280-400mm are processed at an extruder head temperature of 210- Blending and extrusion molding at 240°C. Due to the introduction of polar groups on the HDPE molecular chain during the irradiation process, it interacts with nylon 6 (PA6) during the high-pressure extrusion process, causing PA6 to stretch along the extrusion direction, forming an equivalent in the HDPE substrate. There are multiple layers of PA6 barrier. Compared with unirradiated HDPE, the material has excellent high barrier properties to organic solvents.

Description

Preparation of High Barrier High Density Polyethylene Material by Irradiation Compatibility

The invention belongs to the field of polymer processing. This high-barrier material is mainly used in the storage and transportation of automobile fuel tanks or other organic solvents, and in the packaging container manufacturing industry.

The fuel tank is an important functional structural part of the car. Polyethylene (PE) has become the material of choice for automobile fuel tanks due to its small specific gravity, excellent molding processability, and good comprehensive mechanical properties. The penetration rate of PE automobile fuel tanks in Europe has reached 60%, but the fuel tanks made of PE can release up to 20g/24 hours of fuel vapor in hot weather, which greatly exceeds the legal emission standard (5g/24 hours). PE for barrier treatment. Du Pont of the United States added 7% Selar barrier nylon sheet to HDPE. According to reports, the penetration of this product is 97% lower than that of unmodified HDPE fuel tank hydrocarbons. It has been used in Lous Elan cars. The disadvantage is that it is added When nylon and HDPE are mixed, a third component must be added as a compatibilizer, and the product preparation process is complicated and the cost is high.

The purpose of the present invention is to provide a high barrier high density polyethylene material prepared by irradiation compatibilization method, which is characterized in that the wavelength is 280 ~ 400nm ultraviolet radiation HDPE and nylon-6 (PA6) with excellent barrier properties to organic solvents ), the temperature of the head of the extruder is 210-240°C for blending and molding. Due to the introduction of polar groups on the HDPE molecular chain during the irradiation process, it interacts with PA6 during the high-pressure extrusion process, making PA6 stretch along the extrusion direction, forming a multi-layer PA6 in the HDPE substrate. The barrier layer has excellent barrier properties to organic solvents.

The purpose of the present invention is achieved by the following technical solutions:

1 Preparation of UV-irradiated HDPE (u-HDPE)

Using a UV lamp with a wavelength of 280-400nm, in air at room temperature, irradiate PE powder for 48-150 hours to introduce polar groups such as COOH, OH, C=O, OOH or C-O into its molecular chain.

2 Preparation of high barrier products

After mechanically mixing 95-80 parts of u-HDPE and 5-20 parts of PA6, use an extruder to process and shape, or extrude the parison first and then use vacuum or hollow molding. The temperature of the extrusion head is 210-240 ° C, the screw speed 10-60rpm.

Figure 1 shows the HDPE/PA6 (90/10) packaging bag with a thickness of 0.08mm formed by this method, and the test results for toluene barrier performance at a temperature of 40°C. The barrier performance of HDPE to toluene is poor, 100% of toluene leaks out in about 6.8 hours, and the leakage rate of u0-HDPE/PA6 (90/10) material packaging bags to toluene is higher than that of HDPE, 100% of toluene leaks out in about 6.2 hours At 6.8 hours, 72% and 80% of the toluene in the u72-HDPE/PA6 (90/10) and u144-HDPE/PA6 (90/10) material packaging bags did not leak, until 12 hours later in the packaging bag Still 48% and 60% toluene respectively. Toluene is an excellent solvent for HDPE, so HDPE has poor barrier properties to toluene. In the u0-HDPE/PA6 (90/10) blend material, due to the poor compatibility between HDPE and PA6, twin-screw mixing, extrusion film blowing process , PA6 is distributed into spherical particles (Figure 2), the particle diameter is large, and the toluene leakage channel is formed at the interface of the two phases, so the leakage of toluene in u0HDPE/PA6 (90/10) material is larger than that of HDPE. After the polar group is introduced into the HDPE molecular chain, it has a strong interaction with the PA6 phase interface, and the PA6 particles stretch along the extrusion direction to form a layered distribution state (Figure 3, Figure 4), with good barrier properties. Table 1 lists the mechanical properties of the products.

Table 1 Mechanical properties of u-HDPE/PA6 (90/10) blends

    Tensile Strength Tensile Modulus Notched Izod Impact Elongation at Break

           MPa         MPa       强度，J/m     ％HDPE           17.2        651       153.0         401.1u0-HDPE/PA6    13.2        801       47.8          4.8u24-HDPE/PA6   21.9        1309      53.6          99.7u48-HDPE/PA6   25.2        1421      61.7          254.5u72-HDPE/PA6   23.0        1387      102.6         440.4

Fig.1 Comparison of toluene leakage between HDPE and uHDPE/PA6 membranes

(a) HDPE (b) u0-HDPE/PA6(90/10)

(c)u72-HDPE/PA6(90/10) (d)u144-HDPE/PA6(90/10)

Fig.2 Scanning electron micrograph of u0-HDPE/PA6(90/10) blend material (×1000)

Fig.3 Scanning electron micrograph of u72-HDPE/PA6(90/10) blend material (×1000)

Fig.4 Scanning electron micrograph of u144-HDPE/PA6(90/10) blend material (×1000)

The above experimental results show that the uHDPE/PA6 blend material is expected to be a high-quality packaging material for organic solvents such as toluene, and can also be developed as a material for automotive fuel tanks.

The present invention has the following advantages:

1. Without adding third components such as compatibilizers, HDPE blend materials with barrier properties to toluene and other organic solvents can be prepared. Compared with HDPE, the barrier properties are greatly improved.

2. The blended material has a low leakage rate, easy molding and processing, and low cost. It is expected to become a high-performance barrier material for automobile fuel tanks.

Example:

1. Using a 500-watt Ga-I ultraviolet lamp, irradiate HDPE (u-48HDPE) in the air at room temperature for 48 hours, introduce oxygen-containing polar groups into its molecular chain, and then irradiate the u48 - HDPE 95 parts and PA6 5 parts are mechanically mixed, using Haake RC 90 torque rheometer twin-screw extruder and its blown film auxiliary machine to blow film, the head temperature is 210-240 ℃, the screw speed is 15-60rpm, the film The inflation ratio is 3-5:1, and the thickness of the film is controlled by adjusting the traction speed.

2. Using a 500-watt Ga-I ultraviolet lamp, in an air atmosphere at room temperature, irradiate HDPE (u72-HDPE) for 72 hours to introduce polar groups into the HDPE molecular chain, and then mix 90 parts of u72-HDPE with PA6 10 After the parts are mechanically mixed, the blown film is extruded by the equipment and conditions of processing and molding in Example 1.

3. Using a 500-watt Ga-I ultraviolet lamp, irradiate HDPE (u144-HDPE) for 144 hours in an air atmosphere at room temperature to introduce polar groups into the HDPE molecular chain, and then mix 80 parts of u144-HDPE with PA6 20 Parts are mechanically mixed, extruded and blown film by the processing and molding equipment and conditions of embodiment 1.

Claims (2)

1. A kind of irradiation compatibilizing method prepares the high barrier high-density polyethylene material, it is characterized in that: the preparation of 1 ultraviolet irradiation HDPE

   Adopting wavelength is 280～400nm ultraviolet lamp, at room temperature in the air, with HDPE material irradiation 48 to 150 hours, introduces COOH, OH, C=O, OOH or C-O polar group on its molecular chain,
2. The preparation of 2 high barrier material

   After 95～80 parts of ultraviolet irradiation HDPE and 5～20 parts of mechanically mixing of PA6, adopt forcing machine machine-shaping, or first extruded parisons adopts vacuum or slush molding, 210～240 ℃ of extruder head temperature, screw speed 10～60rpm again.

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