SU617970A1 - Polymeric composition - Google Patents

Description

f

This invention relates to a composition based on polyolefin and additives that sensitize crosslinking under the influence of high energy ionizing radiation. Such compositions are intended for the manufacture of various kinds of products, for example films, fibers, packaging containers.

It is known that the physical and chemical properties of polyolefins, in particular polyethylene, can be modified by treating these poly. measures in the form of powders or in the Form. of products, for example films, fibers, pipes, radiation of high energy. The result is a crosslinking of the polymer chains. The irradiated polyolefins have a significantly higher tensile strength, impact resistance, resistance to cracking in aggressive media, weather resistance and the temperature of the onset of thermal deformation compared to unirradiated polymers, which means that it expands their field of application.

It is also known that crosslinking is promoted by various compounds that are sources of free tissue. These compounds reduce the radiation dose to achieve the desired degree of crosslinking. Such sensitizing additives are, for example, chlorobenzene i. Monomers having a polyfunctional radical, such as esters of acrylic, methacrylic and cyanuric acids, unsaturated acids — acrylic, methacrylic, unsaturated benzene derivatives — divinyl, tri-benzene, and 21.

The common drawbacks of these sensitizing supplements are:

the low technology of their introduction of the additive is introduced by immersing the polyolefin in the form of a powder or an article, for example a film, in a sensitizer or in its solution, after which excess liquid must be removed;

The irradiated material must for a long time preserve the necessary and constant amount of sensitization1: whose additives, it is difficult to avidu the volatility of the above sensitizing substances and requires the use of special ones; : receptions and operations

use of these substances as sensibilizing additives increases the cost of the finished product several times due to the scarcity and high cost of most of the recommended sensitizers. It is also known to use various lead compounds, including lead stearate, as a sensitizing additive for cross-linking chlorinated polyolefins. For this purpose, polyolefins are chlorinated in a supendo state in an autoclave, then washed and dried. The dried chlorinated polyolefins are mixed in a Banbury mixer with lead stearate, the latter being introduced in an amount of 1-10% by weight of the chlorinated polyolefin. Before the introduction and other additives, stabilizers, fillers, etc. . From the composition, sheets are made, which are then irradiated at an electron accelerator (| b - irradiation). The introduction of dibasic lead stearate together with dibasic lead phthalate in the amount of 1 and 3, respectively, weight, h. allows to significantly reduce the dose of radiation to achieve the necessary degree of crosslinking. For example, the content of the fraction that characterizes, the degree of crosslinking (the higher the degree of crosslinking, the higher the content of the gel fraction) when irradiated with a dose of 5 Mrad increases from 45 to 77%. . The disadvantage of sensitizing additives is that lead compounds, including lead stearate, are highly toxic, which creates harmful working conditions and limits the scope of products containing this sensitizer. Thus, products obtained using lead salts as a sensitizing additive cannot be used. contact with food and drugs. The purpose of the invention is to make the product non-toxic and to improve working conditions. For this, the composition is crosslinked with ionizing radiation as the Dependence of soda

different doses of irradiation from the content of sodium stearate in polyethylene.

Table 1 of polyolefin contains polyethylene, and as a sensitizing additive, sodium, calcium or zinc stearate in the following ratio of components, wt.%: Polyethylene 90-99 Sodium, calcium or zinc stearate 1-10 The composition may additionally contain an ethylene-vinylacetate copolymer. It has been established that the introduction of even 1 wt.% Sodium stearate into low density polyethylene with a melt index of 0.3 g / 10 min significantly increases the degree of crosslinking of polyethylene, which manifests itself in an increase in the gel fraction when irradiated to an absorbed dose of 2 Mrad gelfraction increases from 38 to 58%. In the examples, the gel fraction, characterizing the degree of crosslinking: an by iblefin, is determined as follows. About 0.2000 g of the irradiated material placed in a nylon cloth (capsule) are immersed in a 250 ml xylene e flask and boiled under reflux for 12 hours. Then the sample and the nylon capsule are removed from the flask and dried in a vacuum dryer. this weight. The amount of residue remaining after extraction (gel fraction) is expressed in% by weight of the initial sample. . .. . . Example 1. Weights of 100 weight. low density polyethylene with a melt index of 0.3 g / 10 min is mixed on rollers. with various amounts of {0.5-20 parts by weight) sodium stearate at a temperature for 10 minutes. . .. From the obtained compositions pressed plates with a thickness of 1 and 2 mm. Plates are irradiated on a PX-S 30 unit up to absorbed doses of 2,3,5,10 and 20 Mrad. The degree of crosslinking of the irradiated material is characterized by the content of the gel fraction. . The results are shown in Table 1. gel fraction with

As can be seen from the table. 1, the introduction of 2 weight.h. sodium stearate per 100 weight.h. Polyolefin (Sample No. 4) allows, upon irradiation up to the Absorbed dose of 2 Mrad, approximately the same degree of crosslinking of polyethylene, which, upon irradiation in the absence of sodium stearate, is achieved at a dose of 5 Mrad.

Physical and metachic properties of polyethylene.

Physico-mechanical properties of prototypes made from a composition containing 2 parts by weight sodium stearate, irradiated to doses of 5 and 10 Mrad, are given in table. 2 compared to polyethylene without sodium stearate, irradiated to a dose of 10 Mrad and unirradiated.

table 2

152

170

182

165

The test was carried out in accordance with

Note. GOST 1633-70. When d t, as stearate

Example 3. Analogous to example 1, instead of sodium stearate, calcium stearate is added in an amount of 3.95 parts by weight. per 100 weight. h. polyethylene. Its absorbed dose of 2 mR is irradiated. The gel fraction content is 56%.

Example4. 90 weight.h. low density polyethylene mixed with 10 ver.ch. ethylene copolymer with 20 wt.% vinyl acetate (CMEA) and 1 weight.h. sodium stearate. Plates are pressed from the composition and irradiated in an argon atmosphere to an absorbed dose of 2 Mrad, after which they are heated

680

109

516

102

550

113,612,112

for a period of 1 h. Soderkanie; gel fraction is 60.26%, in t; while for low density polyethylene it is 37.74%, & for compositions of 90 parts by weight low density polyethylene and 10 weight.h. CMEA 43.07%.

Measure 5. A KOMPOSITSH compound is prepared in the mixer, wt%: Polyethylene 81.75

Cerechlor7.0

Tymonox7.0

Bisalkofen BP 0.5 Phosphite P-240.75

Last DP-40.5 measures 2. All operations in the amount of 4.06 weight.h. per 100 parts by weight, S of example 1, only instead of 5 polyethylenes. Zinc stearate 10 is irradiated to doses of 2, 3, and sodium. 3. The content of gel fraction in irradiated samples of polyethylene containing and without zinc stearate. T a b l and c a 3

Sodium hydroxide 0.5 Sodium stearate 2.0 The composition is irradiated with b rays to an absorbed dose of 5 and 10 Mrad, the gel fraction is determined. The amount of gel fraction of the composition containing

The content of the gel fraction in the compositions based on polyethylene after radiation exposure

sodium stearate is given in table. 4 in comparison with a composition of the same composition, but without sodium stearate. The amount of gel fraction found in the composition (k) was converted to polyethylene (PE) containing in the composition

Table 4

Claims (1)

Claim A polymer composition capable of crosslinking by ionizing radiation containing a polyolefin and a stearic acid salt c. as a sensitizing additive, characterized in that, in order to make the products non-toxic, it contains polyethylene as a polyolefin, and sodium, 40 calcium or zinc stearate as a sensitizing additive in the following ratio of components, Polyethylene Sodium stearate, calcium or zinc weight. %: 90-99 1-10