A kind of method for preparing low-density polyethylene
A low-density polyethylene and polyethylene technology, applied in the field of preparing linear low-density polyethylene, can solve problems such as difficult application, and achieve the effects of high melt index and good mechanical properties
Active Publication Date: 2016-05-25
CHINA PETROLEUM & CHEM CORP +1
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Problems solved by technology
However, because the traditional Ziegler-Natta catalyst is a multi-active center catalyst, the product obtained has a wide molecular weight distribution and contains some low-molecular-weight polymers; and this part of low-molecular-weight polymers is easy to precipitate from the product, so some low-density high-density Index resin products (melt index 10~50g / 10min) are difficult to apply in food packaging and other fields
Method used
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Embodiment 1~4
[0021] Catalyst preparation
[0022] Add 300g of silica gel carrier activated at 600°C for 4 hours under nitrogen atmosphere, then add 1100g of 10% MAO in toluene solution, and then add 10g of bis(1-butyl-3-methylcyclopentadienyl) chloride The toluene solution of zirconium chloride·2LiCl·THF was reacted for 1 hour, filtered, washed and dried to obtain a powder with good fluidity, that is, a supported metallocene catalyst.
[0023] polymer preparation
[0024] Add ethylene, hexene, hydrogen, nitrogen and the supported metallocene catalyst prepared above into a gas-phase fluidized bed reactor, and react at 85° C. and 2.01 MPa. The parameters of different polymerization process conditions are shown in Table 1, and the properties of different polymers obtained are shown in Table 2.
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Abstract
The invention discloses a low density polyethylene preparation method which is as follows: ethylene and alpha-olefin are polymerized in a single reactor in the presence of hydrogen, an inert gas and a supported metallocene catalyst, the mole ratio of the alpha olefin to the ethylene is 0.02:1-0.2:1, the concentration of the hydrogen in the reactor is 200 to 10000ppv, the polyethylene melt index is 5-50g / 10min, the distribution of molecular weight is 2-10, and the density is 0.910-0.925g / cm<3>. By the method provided by the invention, the ethylene and the alpha olefin can react in the presence of the hydrogen, the inert gas and the supported metallocene catalyst in the single reactor such as a gas phase fluidized bed reactor to directly obtain the linear low density polyethylene, and the obtained polyethylene is high in the melt index, is in single mode distribution, has good mechanical properties, and can be used in the injection molding field.
Description
technical field [0001] The invention relates to a method for preparing polyethylene, in particular to a method for preparing linear low-density polyethylene. Background technique [0002] Linear low density polyethylene (LLDPE) can be widely used in the manufacture of packaging products. The production of LLDPE generally uses traditional Ziegler-Natta catalysts. However, because the traditional Ziegler-Natta catalyst is a multi-active center catalyst, the product obtained has a wide molecular weight distribution and contains some low-molecular-weight polymers; and this part of low-molecular-weight polymers is easy to precipitate from the product, so some low-density high-density Index resin products (melt index 10~50g / 10min) are difficult to apply in food packaging and other fields. [0003] In addition, Ziegler-Natta catalyst needs to add a large amount of hydrogen to produce this low-density high-index product, and its hydrogen / ethylene reaches 0.5. Compared with the pro...
Claims
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IPC IPC(8): C08F210/16C08F4/6592C08L23/08
Inventor 郑刚王伟王洪涛范国强刘长城胡青
Owner CHINA PETROLEUM & CHEM CORP