SU912735A1 - Process for producing pulverulent cross-linking polyethylene - Google Patents

Description

Whose method of producing powdered cross-linking polyethylene The invention relates to chemical technology, mainly processing plastics, and can be used to obtain cross-linking polyethylene and compositions based on it A method is known to produce cross-linking polyethylene compositions using peroxide materials by mechanical braces. heavy type, on rollers and others at,; temperatures above the flame temperature of polyolefin and close to the decomposition temperatures of peroxide 1. Lack minutes sposoa is to premature crosslinking of the mixture, as well as significant energy cost. Closest to the proposed method is a method for producing crosslinkable polyethylene with the use of peroxide compounds as crosslinking agents, consisting in crosslinking polyethylene and peroxide crosslinking agent in a liquid state. The material is subjected to the peroxide diffusion process (aging) at a temperature below the melting point of the polyolefin (50-70 ° C) for 5-7 h 2. However, in this method, at the stage of aging, sticking and clumping of the powdery material occurs, which makes it difficult to unload it from the apparatus and transport, and does not ensure uniform distribution of the crosslinking agent. The method is not suitable for powdered polyethylene with a particle size of less than 1 mm. In addition, it requires a long time due to the aging of the material, as well as additional energy consumption at the heating stage. The aim of the invention is to simplify the process and obtain a homogeneous crosslinkable polyethylene. This goal is achieved by the fact that according to the method for producing the powder. 91

The co-crosslinked polyethylene, which includes a blend of polyethylene and a peroxide crosslinking agent, the peroxide crosslinking agent is introduced into the polyethylene as a concentrate, consisting of 6-10% by weight of powdered peroxide and 90-9% by weight of polyethylene.

Melting point peroxides such as dicumyl peroxide, Lunersol-type percadox, Warox, etc. are used as cross-linking agents.

The drawing shows a flowchart of the production of cross-linking polyethylene compositions according to the proposed method with feeding the peroxide concentrate to further mixing, as well as the finished product by pneumatic transport.

The polyethylene powder is pneumatically transported to the bunker 1, from where it flows by gravity, to the metering scale 2, then to the powder preheater with filter 3, where it is heated with nitrogen. From the preheater, polyethylene powder enters the Anger Anger or Petzold high-speed mixer. The process flow also provides for the supply of powdered polyethylene to the mixer, mine the heating stage. A peroxide cross-linking agent is fed into this mixer to form a peroxide concentrate. The finished concentrate si comes in a high-speed mixer 5. Powdered additives (stabilizer, dye, fillers, etc.) or their concentrates are supplied. In the mixer 5 from the hopper 1, the weights 2 weigh a portion of polyethylene powder. After mixing the necessary components in the mixer 5, the finished powder composition is sent to the receiving bin 6, and then it is supplied to the consumer by pneumatic transport.

The criteria for the quality of the obtained product are the following indicators: tensile stress (br), elongation at break (, crosslinked fraction content, adhesion strength to metal ((AOA) dispersion) according to selected indicators (G).

The physicomechanical properties of the compositions obtained are determined and the variance calculated. The composition of the compositions is presented in table. 1. Data on the properties are summarized in table 2.

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Samples for physical and mechanical tests are obtained directly from powders by pressing at 1 ° C and pressure of 0 kgf / cm. Destructive stress during stretching and elongation at break are determined according to GOST 16337-77 p.3.17.

Adhesive strength to steel (St 3) is determined on cylindrical

samples of 20 mm with a thickness of glue seam 0.2 mm. Gelfraction is determined by TU 6-05-1547-7i.

Example 1 (control). Low-density powdered natural polyethylene with mastic-hr mm and peroxide-type crosslinking agents are used as starting materials. In a high-speed mixer, mix the polyethylene powder and

crosslinking agent in the liquid state at 50-70 ° C for 20 minutes. The number of revolutions of the agitator mixer I + OO rpm. Then this mixture is kept at this temperature for 5-7 hours.

Examples 2-3 (control). The starting material used is powdered stabilized low density polyethylene with a particle size of 1 mm. In speed

the mixer, the polyethylene powder and the mixing agent are mixed, followed by exposure to the conditions of Example 1. Example i. In a high-speed mixer, a concentrate of powdered peroxide is prepared by mixing the latter with powdered polyethylene at 60-70 0. The number of revolutions of the mixer of the mixer (n) is 1,400 rpm, the mixing time I (g) is 15 minutes. Then

In the same mixer, a mixture is prepared by diluting the peroxide concentrate with polyethylene powder.

Example 5-6. A stabilizer concentrate (antioxidant) (Vi) of 1520 rpm, min. Is prepared in a high speed mixer. Then a mixture consisting of powdered polyethylene, peroxide concentrates and a stabilizer is prepared under the conditions of example 1 in a high-speed mixer.

Examples In a high-speed mixer, prepare | (5.t DG-100 (and) soot concentrate 150 rpm, 20 minutes. Then, in the same mixer, a mixture of powdered polyethylene and a concentration of 59127356

spending peroxide, stabilizer and the proposed method (examples 4-8) in the same conditions. found at the level of control lumps. As can be seen from the table. 2, the properties of the positions, and the homogeneity (an indicator of the cross-linking compositions obtained by dispersion) is better than that of the controls.

Low density polyethylene 11502-070 98.0 97.5 Dicumyl peroxide 2.0 2.0 1,3-di (tert butylperoxyisopropyl) benAntioxy, 5 0.5 dan

Soot DG-100

Table 1 97.5 98 2, 2.0

2.0 2.0, 0 97.5 97.5 95.5 95.5 0 2.0 0.5 0.5 0.5 0.5 0.5

Claims (1)

Claim A method of producing a powdery crosslinkable polyethylene, comprising mixing polyethylene and a peroxide crosslinking agent, characterized in that, in order to simplify the process and obtain a uniform crosslinkable polyethylene, the peroxide crosslinking agent is introduced into the polyethylene linen in the form of a concentrate consisting of 6- 10 wt.% Powdered peroxide and 90-94 wt.% Polyethylene.