RU2284339C1 - Polyolefin modification method - Google Patents

Abstract

FIELD: polymer production.

SUBSTANCE: chemical modification of polyolefins is accomplished by interaction thereof in melt with monomers in presence of initiator, said initiator being schungite used in amount 0.05-0.15 wt parts per 100 wt parts polyolefin. Polyolefins modified in presence of schungite are characterized by improved strength and elastic properties and can be used as adhesive sublayer in protective coatings of pipelines in oil and gas industry.

EFFECT: increased strength and elasticity of polymers.

1 tbl

Description

Introduction

The invention relates to the chemical industry, and in particular to methods for the chemical modification of polyolefins in order to give them useful properties, for example, adhesive ability and elasticity, when used as a thermoplastic solid adhesive called adhesive in three-layer insulating coatings of metal pipes used to transport oil, petroleum products, gas, etc.

State of the art

To ensure safety during transportation of oil, oil products and gas, the adhesives used in the insulation coatings of metal pipes are subject to increased requirements, in particular:

- melt flow index, g / 10 min 0.4-4.0 - stress at yield strength at (20 ± 3) ° С, MPa not less than 8 - elongation at (20 ± 3) ° С,% not less than 400 - water absorption after 1000 hours holding in water at (80 ± 5) ° С,% no more than 3.0

Modified polyolefins are known to possess such properties.

It is also known that the modification of polyolefins is carried out by grafting monomers on them in the presence of initiators. The polymer can be in a solid state, in the melt or in the form of a solution.

As monomers use compounds such as ethylenically unsaturated carboxylic acids, anhydrides, imides, maleimides.

As initiators, radical initiators such as peroxides are used. At the same time, at a temperature of 100-300 ° C, partial destruction of the polyolefins occurs, and then the grafting of monomers takes place.

Thus, there is a known method for modifying polyethylene with acrylic acid in the presence of dicumyl peroxide as an initiator (Plastics, 1990, N 7, p. 77, L.P. Krul, Yu.I. Matusevich, A.M. Nikiforov and others. Modification of HDPE acrylic acid in the presence of dicumyl peroxide).

There is also known a method (RLC, 1979, 24 C 510 P) for the preparation of grafted copolymers (Japanese application, Cl 26 (3) E 11, C 08 F 255/00, N 531130790, claimed 20.04.77). In this case, a mixture of acrylic acid with another polar monomer is sprayed onto a mixture of a solid polymer with a peroxide initiator. When extruding the resulting composition at 100-300 ° C, the polymer and the monomer react and the desired product is obtained, which is washed from the unreacted monomer and dried.

However, the level of strength and elastic properties is low. So, the strength at the yield strength does not exceed 11 MPa, and the relative elongation is 400-500%.

Also known is the closest to the claimed invention method for modifying polymers, in particular polyethylene, in the presence of organic peroxides (Convention application EP 942021353, number and date of international or regional application EP 95/02829 (07.14.95), number and date of international or regional publication - WO 96/03444 (02/08/96).

In this case, monomers suitable for grafting are used - olefin and ethylenically unsaturated monomers such as vinyl aromatic monomers (styrene), ethylenically unsaturated carboxylic acids and their derivatives, including mono- and esters, anhydrides and imides.

The method is implemented by exposing the polymer melt to a mixture of acrylic acid with maleic anhydride in the presence of organic peroxide while co-extruding them at the polymer melt temperature. The ratio of polymer to grafted monomer is from 99: 1 to 1:50.

However, the polyolefin modified by this method does not provide a sufficiently high level of strength and elastic properties. So, the stress at yield strength at 20 ° C is only 12 MPa, and the relative elongation is not more than 400%.

In addition, the use of organic peroxide increases the likelihood of crosslinking of the polyolefin, which leads to poor adhesion.

Thus, a method for modifying polyolefins with monomers in the presence of an initiator is not known, which would improve the strength and elastic properties of the target product while maintaining properties such as water absorption, melt index, and adhesion.

SUMMARY OF THE INVENTION

The inventive task was to find a method for modifying polyolefins by melt-reacting them with monomers in the presence of an initiator, which would improve the strength and elastic properties of the target product while maintaining water absorption, melt index and adhesion.

The problem is solved by the method of modifying polyolefins by their interaction in the melt with monomers in the presence of an initiator, in which shungite is used as an initiator in an amount of 0.05-0.15 wt.h. per 100 parts by weight polyolefin.

Using the invention allows to obtain the following advantages:

- increase the strength properties of the target product.

So, the stress at the yield point increased to 20 MPa;

- improve the plastic properties of the product. Thus, the elongation at break increased to 700%.

At the same time, the rate of water absorption is maintained, and the melt index and adhesion index even exceed the prototype.

An increase in the strength and elastic properties of the obtained product is directly related to an increase in the durability of the three-layer insulating coating of metal pipes in oil and gas pipelines, which means an increase in safety.

Information confirming the reproducibility of the invention

To implement the invention, you can use the following substances.

As polyolefins, for example:

- high-pressure polyethylene GOST 16337-77 m. 15803-020

- polypropylene GOST 26996-86 m.01020

- copolymer of ethylene with propylene GOST 26996-86 m. 22030

As monomers, olefin and ethylenically unsaturated monomers such as vinyl aromatic monomers, ethylenically unsaturated carboxylic acids and their derivatives, including mono - and esters, anhydrides and imides, for example, can be used:

- Acrylic acid tech. 99.5% of TU 2431-001-52470063-2002

- maleic anhydride tech. 99.9% GOST 11153-75

- styrene

- N, N'-m- (phenylene-1,3) bismaleimide

- shungite TU 5714-007-12862296-01 "Crushed and ground shungites of the Zazhoginsky deposit for domestic and industrial use", which is a natural mineral, the main contents of which are oxides of silicon, aluminum, iron, magnesium, calcium, sodium, potassium, and carbon.

The claimed method is implemented as follows. The granular polyolefin is mixed with the required amount of monomer (1-10 parts by weight per 100 parts by weight of polymer), schungite and, while stirring, is heated. In this case, the temperature should be such that the polyolefin is in the form of a melt. After vaccination, the target product is granulated, cooled and dried by known methods. The claimed method can be implemented on conventionally used equipment, for example, in a twin-screw extruder.

To determine the physicomechanical properties of the target product, the samples in the form of plates were cut out from pressed plates formed at a temperature of 200 ° C and a pressure of 0.3 kgf / cm ² for 15 min.

The properties of the target product and prototype were determined identically:

- adhesion to a steel plate according to GOST - P51164-98 by peeling at an angle of 90 °;

- stress at yield strength and elastic properties - according to GOST 11262;

- melt flow index according to ISO 1133;

- water absorption according to GOST 4650.

The table shows the properties of the target product obtained using various monomers, with different quantitative contents of them and the initiator. As can be seen from the table, the claimed method allows to improve the strength and elastic properties of the modified polyolefins, which, when used for an adhesive sublayer of protective coatings of pipelines in the oil and gas industry, increases their durability.

Table
Target Product Properties Reagents, parts by weight one 2 3 four 5 prototype Properties Polyolefin: - polyethylene one hundred - - one hundred one hundred one hundred - polypropylene - one hundred - - - - - copolymer of ethylene with propylene - - one hundred - - - Monomer: - acrylic acid 0.5 1,0 0.7 - - 1,0 - maleic anhydride 8 9 8 8 10 8 - styrene - - - 1,0 - - - N, N'-m- (phenylene-1,3) -bismaleimide - - - - 1,0 - Shungite 0.05 0.1 0.15 0.1 0.1 - Peroxide - - - - - 0.1 Strength at yield strength, MPa 18.1 twenty 19 19.1 19.5 12 Relative extension, % 650 700 620 650 680 450 Melt index, g / 10 min 0.8 0.85 0.82 0.6 0.75 0.4 Water absorption at 1000 hours in water at 80 ° C,% 0.15 0.1 0.1 0.1 0.1 0.1 Adhesion to a steel plate, kgf / cm during delamination twenty twenty twenty 19 19.5 16

Claims (1)

A method of modifying polyolefins by their interaction in the melt with monomers in the presence of an initiator, characterized in that shungite is used as an initiator in an amount of 0.05-0.15 wt.h. per 100 parts by weight polyolefin.