CN-115947898-B - Coating-grade low-density polyethylene and preparation method and application thereof

CN115947898BCN 115947898 BCN115947898 BCN 115947898BCN-115947898-B

Abstract

The present invention relates to a coating grade low density polyethylene. Mainly solves the problem of poor adhesive force in the coating processing process of the low-density polyethylene for the existing coated product. The preparation method is characterized by comprising the following raw materials, by mass, of a prepolymerization raw material, namely, an alpha-olefin, namely, a metallocene catalyst, wherein the mass ratio of the raw materials is 1000-10000:1, the polymerization raw material, namely, a prepolymerization reaction product and ethylene are 1:10-1:500, a chain transfer agent, namely, ethylene is 1:200-1:2000, and a polymerization initiator, namely, ethylene is 1:500-1:5000. The coating-grade low-density polyethylene improves the adhesive force and the peeling strength of a coated product by adding alpha-olefin homopolymer to participate in the reaction, and completely meets the requirements of paper-plastic products.

Inventors

LI CHUANMING
ZHOU CAN
ZHANG YAN
ZHU YAN
YANG JIAN
LI ZHE
YU JIANG
SUN HUI
QI WEI
ZHANG YIMING
LI HONGJIAN
WEI TAO
ZHANG ZHENGYI
XU HAOYANG
CAO JINGLIANG
LI YECHENG
ZHANG ZHANBIN
CHEN LEI
FAN TIESHENG
SUN QIHU

Assignees

中国石油天然气股份有限公司

Dates

Publication Date: 20260508
Application Date: 20211009

Claims (7)

1. The coating-grade low-density polyethylene comprises the following raw materials in percentage by mass The prepolymerization raw material is alpha-olefin and metallocene catalyst, wherein the alpha-olefin and metallocene catalyst are 1000-10000:1; polymerization raw materials, namely a prepolymerization reaction product, ethylene, a polymerization initiator and a chain transfer agent; The prepolymerization reaction product is ethylene in the ratio of 1:10-1:500; chain transfer agent ethylene is 1:200-1:2000; Polymerization initiator ethylene is 1:500-1:5000; The metallocene catalyst is a homogeneous metallocene catalyst; The alpha-olefin is one of 1-propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene and 1-decene; the polymerization initiator is one or a combination of a plurality of peroxyesters RCOOOR', and the chain transfer agent is one of olefin, aldehyde, ketone, alcohol, saturated hydrocarbon and ether; The melt flow rate of the final product is 1-10g/10min by adopting a weight of 2.16Kg, and the density of the final product is 0.915-0.925g/cm 3 ; the preparation method of the coating-grade low-density polyethylene comprises the following steps: S1, firstly preparing an alpha-olefin homopolymer by adopting a metallocene catalyst in a prepolymerization reactor; S2, simultaneously adding the produced alpha-olefin homopolymer, ethylene, an initiator and a chain transfer agent into a reactor operated under high-pressure polymerization conditions, and obtaining a final product after polymerization reaction; The temperature in the prepolymerization reactor is 100-200 ℃, the pressure in the prepolymerization reactor is 0.5-50MPa, and the ratio of aluminum to titanium is 200-2000; The polymerization temperature in each region of the reactor is 300-400 ℃, and the polymerization pressure in each region of the reactor is 150-300MPa.
2. A process for preparing the coating-grade low density polyethylene of claim 1, comprising the steps of: S1, firstly preparing an alpha-olefin homopolymer by adopting a metallocene catalyst in a prepolymerization reactor; S2, simultaneously adding the produced alpha-olefin homopolymer, ethylene, an initiator and a chain transfer agent into a reactor operated under high-pressure polymerization conditions, and obtaining a final product after polymerization.
3. A process for preparing coating-grade low-density polyethylene according to claim 2, wherein the polymerization temperature in each region of the reactor is 300 to 400℃and the polymerization pressure in each region of the reactor is 150 to 300MPa.
4. The method for preparing coating-grade low-density polyethylene according to claim 2, wherein the temperature in the prepolymerization reactor is 100-200 ℃, the pressure in the prepolymerization reactor is 0.5-50MPa, and the ratio of aluminum to titanium is 200-2000.
5. A process for preparing coated low-density polyethylene according to claim 2, wherein the reactor operated under high-pressure polymerization conditions is a tubular reactor or a tank reactor, or a combination of both.
6. A process for preparing coating-grade low-density polyethylene according to claim 2, wherein the reaction product is an ethylene-based polymer, the final product has a melt flow rate of 1 to 10g/10min using a 2.16Kg weight, and the final product has a density of 0.915 to 0.925g/cm 3 .
7. Use of a coating grade low density polyethylene according to claim 1 or obtainable by a process according to any one of claims 2 to 6 in the coating field.

Description

Coating-grade low-density polyethylene and preparation method and application thereof Technical field: the invention relates to the technical field of coated products with high adhesive property, in particular to a coating-grade low-density polyethylene, a preparation method and application thereof. The background technology is as follows: The coating-grade low-density polyethylene has the characteristics of good toughness, strong adhesive force, uniform film formation, good sanitation and the like, and is widely applied to the outer package of products such as food, chemical industry, textiles and the like. With the development of domestic packaging industry, the application range and the consumption of special materials are gradually enlarged, and the market demand is increased. At present, a single high-pressure reactor is adopted for preparing the coating-level low-density polyethylene, and EVA or EMA is added in the coating process, so that on one hand, in a state of coating high-speed coating, the coating effect is affected by uneven mixed resin, and in addition, the effect of physical mixing on coating for enhancing the adhesiveness is poor. The invention comprises the following steps: The invention aims to solve the problem of poor adhesive force of low-density polyethylene for coated products in the background technology in the coating processing process, and provides coating-grade low-density polyethylene which improves the adhesive force and the peeling strength of the coated products and completely meets the requirements of paper-plastic products by adding alpha-olefin homopolymer to participate in the reaction. The invention also provides a preparation method and application of the coating-grade low-density polyethylene. The invention solves the problems by the following technical scheme that the coating-grade low-density polyethylene comprises the following raw materials in parts by mass: the prepolymerization reaction raw material comprises alpha-olefin and metallocene catalyst, wherein the mass ratio of the alpha-olefin to the metallocene catalyst is 1000-10000:1; polymerization raw materials, namely a prepolymerization reaction product, ethylene, a polymerization initiator and a chain transfer agent; the mass ratio of the prepolymerization reaction product to ethylene is 1:10-1:500, preferably 1:50-1:200; the mass ratio of chain transfer agent to ethylene is 1:200 to 1:2000, preferably 1:200 to 1:1000; the mass ratio of the polymerization initiator to the ethylene is 1:500-1:5000. Preferably, the metallocene catalyst is a homogeneous metallocene catalyst, and the adopted homogeneous metallocene catalyst is a catalyst disclosed in a limited geometry metallocene catalyst and a preparation method and application thereof (patent application number 201910909798.4 is published on day 2021, 3 and 26) of the invention filed on day 9 and 25 in 2019. Preferably, the alpha-olefin is one of 1-propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene. Preferably, the polymerization initiator is one or a combination of a plurality of peroxy esters (RCOOOR'), and the chain transfer agent is one of olefin, aldehyde, ketone, alcohol, saturated hydrocarbon and ether. The invention also provides a preparation method of the coating-grade low-density polyethylene, which comprises the following steps: S1, firstly preparing an alpha-olefin homopolymer by adopting a metallocene catalyst in a prepolymerization reactor; S2, simultaneously adding the produced flexible monomer oligomer, ethylene, a polymerization initiator and a chain transfer agent into a reactor operating under high-pressure polymerization conditions, and obtaining a final product after polymerization reaction. Then, the produced alpha-olefin homopolymer, ethylene, an initiator and a chain transfer agent are simultaneously added into a reactor operated under high-pressure polymerization conditions, and a final product is obtained after polymerization. Preferably, the polymerization temperature in the individual regions of the reactor is from 100 to 400℃and preferably from 300 to 400℃and the polymerization pressure in the individual regions of the reactor is from 100 to 400MPa and preferably from 150 to 300MPa. Preferably, the polymerization pressure in each region of the reactor is 100-400MPa, preferably 150-300MPa, the temperature in the prepolymerization reactor is 100-200 ℃, the pressure in the prepolymerization reactor is 0.5-50MPa, and the Al-Ti ratio is 200-2000. Preferably, the reactor operated under high pressure polymerization conditions is a tubular reactor or a tank reactor, or a combination of both, preferably a single tubular process. Preferably, the reaction product produced is an ethylene-based polymer. Preferably, the final product prepared has a melt flow rate of 1-10g/10min using a 2.16Kg weight and a final product density of 0.915-0.925g/cm 3. The invention also provides application of the coating-grade low