CS249941B1 - Polyolefinic composition - Google Patents

Abstract

The purpose of the invention is to improve the resistance of polyolefin compositions based on ethylene polymers to stress corrosion. This purpose is achieved by adding propylene polymers and its copolymers. The subject of the invention can be used in irrigation and water management for the production of hoses for strip sprinklers, in the gas industry for the construction of gas distribution systems, in packaging technology for the production of packaging for the transport of corrosive media, in the cable industry for the outer protective layer of cables, in the shoe industry for the production of soles and the like.

Description

249941

The invention relates to polyolefinic compositions! based on ethylene polymers, which exhibit high resistance to stress corrosion.

It is known that the processing and utility properties of ethylene polymers can be adjusted by the addition of ethylene vinyl acetate copolymer. Addition of ethylene-vinyl acetate co-polymer to ethylene polymers greatly reduces the resistance of the polymeric composition to corrosion under tension as shown in Table 1. For some of the more demanding applications in packaging technology, there is a lack of stress corrosion resistance even for polyethylene itself . For correcting the corrosion of the polyethylene compositions! No. 210 555, it is recommended to add purified inorganic filler to ethylene polymers. However, this is not always feasible, either because a suitable inorganic filler is not available or because the resulting composition is not suitable. application.

These drawbacks are eliminated by the polyolefinic composition, which is characterized by the fact that in the treatment of corrosion under tension in the composition! based on ethylene polymers consisting of copolymers of propylene with ethylene of 1 to 20 ° / other ethylene content with a melt index of 0.1 to 4 g / 10 min. in an amount of 1 to 25 wt. With respect to the weight of ethylene in the polymer compositions prepared on the basis of polymer ethylene and ethylene vinyl acetate, there will be significant changes in the morphological structure, as well as a change in the utility properties of the ethylene polymer-based compositions by increasing their resistance to stress corrosion.

The relationship between structure and corrosion resistance under tension is not theoretically explained. It is believed that the action of the active agents will swell the amorphous regions of the polymers, resulting in a reduction in the cohesive intermolecular forces.

The addition of polymers of propylene in an amount of 1 to 25% by weight, preferably 20% by weight, to the polymers of ethylene, respectively. in an amount of 1 to 25% by weight, preferably 5% by weight; a mixture of ethylene and ethylene vinyl acetate polymers containing 1 to 30 wt. % ethylene vinyl acetate, preferably 15% w / w. ethylene-vinyl acetate will affect the surface properties of the polymer composition by reducing the surface! the energy between the phases, what affects the wetting of the present phases in the polymer composition. This promotes the structuring of the polymer blend as it is not possible to expect more complex high-structural forms to be formed at low adhesion between phases. Thus, better dispersion of the components in the process of homogenization is ensured as well as increased adhesion between the polymer composition phases! prepared base of polymers of ethylene.

By reducing the surface energy between the phases and by creating more complex high-structural morphological forms, the adhesion of the present phases is improved by the addition of ethylene-propylene copolymers, respectively. copolymer, which results in an increase in the resistance of the present phases or components of the polymer mixture prepared on the basis of ethylene polymers to stratification, as well as to diffusion molecules of active organic agents. In that the interfacial layer is formed by the present ethylene propylene copolymer, respectively. the copolymers of ethylene-propylene and ethylene-vinyl acetate localize the surface properties of the components present on the surface of the ethylene polymers at the surface of the phase interface. The formed surface interfacial layer with enhanced polyethylene phase adhesion and more complex morphological structure, by increased propylene segmentation, better resists penetration of active corrosive organic molecule molecules and subsequent disruption of the co-exposed polymer samples. -natural environment under mechanical stress, resulting in increased resistance of polyethylene compositions to clogging of the napapathy. We determined the corrosion under tension according to ČSN 64 3010. LISSAPON N, used as corrosive agent, was taken for corrosion under time, when from the nine test bodies it was broken. The advantages are that polyethylene compositions prepared on the basis of polyethylene, evacopolymer and ethylene propylene copolymers find application applications in such areas of the national economy where their application has not been possible. A further advantage of the present invention is that the customized production of the polymer composition is economically unpretentious and technically easy to realize on machine technology commonly found in polymer manufacturers or processors. Examples 1 to 4

Granular polyethylene with melt index0.07 g / 10 min. was mixed with an ethylene vinyl acetate copolymer containing 12 wt. vinyl acetate with a melting index of 4 g / 10 min and a copolymer of propylene methylene with a melt index of 0.07 g / 10 min. with a content of ethylene of 1.8%. The mixture of granules was overcoated in a temperature range of 180-240 ° C. Voltage corrosion was determined by the above standard.

Claims (1)

Polyolefin composition based on polymeric ethylene with improved stress corrosion resistance, characterized in that it consists of ethylene polymers having a melt index of 0.03-0.5 g / 10 min in an amount of 45 to 98% by weight, of ethylene vinyl acetate copolymer containing % vinyl acetate 5 to 15 wt. and a melt index of 1 to 5 g / 10 min in an amount of 1 to 30 wt. and propylene polymers having a melt index of 0.1 to 4 g / 10 min containing 1 to 20 wt. % of ethylene in an amount of 1 to 25 wt.