CS240627B1 - Method of Polyalkene Modification - Google Patents

Abstract

Modification of polyalkenes at cationic centers introduced into polyalkenes using low molecular weight dications. Siloxanes containing methyl, vinyl, phenyl, trifluoropropyl or cyanopropyl groups are used for modification. Modified polyalkenes are obtained, which are suitable for the production of composites of polyalkenes with mineral fillers.

Description

The invention relates to a modification of polyalkenes. The industrially produced polyalkenes (polypropylene, polyethylene, their copolymers and copolymers of propene or ethylene with higher 1-alkenes) are filled with mineral fillers for various reasons. A technical problem is to ensure the compatibility of the hydrocarbon polymer and the filler, which is usually more or less polar in nature. Polyalkenes are incompatible with fillers. The problem is usually solved by treating the filler, which essentially consists in forming a layer on the surface of its particles that has a greater affinity for the polymer than the filler itself, and which could eventually amortize the negative forces and stresses caused by various factors at the interface the polymer-filler phase.

Another way to improve the compatibility of the polymer-filler compositions is to treat the polymer itself. By incorporating polar polymer blocks or grafts having filler affinity into the matrix polymer chains, the domains of these blocks or grafts surround the filler particles by the intermolecular forces in the composite processing, thereby creating the desired compatibilizing interlayer.

If the blocks or bolts are bound to the polyalkene by covalent bonds, there can be no separation of heterogeneous materials and the composites are stable over a wide temperature range β of the applied forces. Moreover, if the blocks or screws are elastic in nature, they can effectively dampen the interfacial stresses. This results in better mechanical properties of the composites. Blocks and screws melting at a lower temperature than the crystalline polyalkene or having an elastomeric nature can effectively reduce the melt viscosity of the composite.

This greatly facilitates processing. Also, the potential energy savings in processing well-flowing mixtures are not negligible. It is expected that a relatively small proportion of modified polyalkenes relative to the polymer matrix of the filler will be sufficient to ensure compatibility.

Modification of polyalkenes is generally difficult. The hydrocarbon chains are very unstable to the effects of conventional chemical agents. Only under extreme conditions these agents do not fall. Usually, however, this leads to irreversible destruction of macromolecules with all adverse consequences.

It is known that under very mild conditions, in which no destruction or degradation of the polyalkene macromolecules occurs, cation centers can be generated on the polyalkene chains on which the suitable monomers are polymerized to form block and graft copolymers. (This method is described, for example, in CS 190 127; Cs 192 242; Cs 220 722; Cs 238 488). These possibilities have now been extended to the finding that compatibilizing blocks and grafts can be formed from polysiloxanes.

SUMMARY OF THE INVENTION The present invention provides a process for modifying polyalkenes by graft polymerization of cationic polymerizing monomers at cationic centers introduced into polyalkenes by reaction with dications, wherein the modifying agent is siloxane monomers containing methyl, vinyl, phenyl, trifluoropropyl or cyanopropyl groups.

According to the invention, a polyalkene dispersed in a suitable reagent (e.g. tetrahydrofuran, nitromethane) is treated with an oligomeric dication (e.g. siloxonium - see AO 192 242 or one of the described AO 238 488). By interaction of these components, cation centers are formed on the surface of the polyalkene particles, in which the siloxane monomer (for example octamethylcyclotetrasiloxane, optionally cyclic siloxane monomers with silicon phenyls or methyl and vinyl, methyl and trifluoropropyl, methyl and cyanoalkyl respectively) is polymerized in the next step. or more kinds of siloxane monomers with different substituents.

Optionally, siloxane homopolymers formed from a portion of the monomers due to cationic transfer and exchange reactions are extracted from the products. The separation of homopolymers may not always be necessary. The polyalkene is treated in a non-ionic inactivating medium by a low molecular weight dication and a siloxane monomer is added to the product of the interaction of the polyalkene with the dication (either with one of the listed substituents or several in a suitable ratio) to polymerize to form blocks and / or grafts in anhydrous. environment, or in the presence of a cocatalytic amount of protogenic substances such as water, alcohols, etc.

The following examples illustrate the invention:

Example 1

To 1.5 g of commercial polypropylene dosuěeného high vacuum and suspended in 20 ^cc of THF at room temperature was added 0.18 mmol siloxoniového dication

After 24 hours, 15 cnp of octamethylcyclotetrasiloxane was distilled to the interaction product. After 14 days of storage at room temperature, the product is extracted with n-heptane (in which the non-anchored polysiloxanes and polytetramethylene oxide are dissolved) to give 2.4 g of a copolymer with significant properties of interphase active agents.

Example 2

The procedure is as in Example 1, but instead of polypropylene 3e it modifies polyethylene. Together with the siloxane monomer 0.09 mmol of water are added as a cocatalyst. 1.8 g of a copolymer (polyethylene is less reactive than polypropylene) of an interfacial activity are obtained.

Example 3

Following the procedure of Example 2, the ethylene propylene copolymer was modified. Yield 2.1 g of terpolymer again has strong interfacial activity.

Example 4

The procedure was as in Example 2, but instead of polyethylene, the ethylene-1-butene copolymer was modified. The product 1.8 g terpolymer is also interphase active.

Example 5

The procedure is as in Example 2, but the ternary propylene-ethylene-1,3-butadiene copolymer is modified. The 2.6 copolymer product again exhibits interfacial activity.

Example 6

Following the procedure of Example 1, octaphenylcyclotetrasiloxane was used instead of octamethylcyclotetrasiloxane. The product was extracted with toluene. Yield 1.9 g, product contains 0.4 g polysiloxane component.

Example 7

The procedure is as in Example 1 (with a cocatalytic amount of water as in Example 2), but a mixture of octamethylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane (4: 1 molar) is used for modification. The resulting copolymer (2.1 g) not only has the properties of a polymeric surfactant, but can also be radically crosslinked sufficiently.

Example 8

Proceed as in Example 7, using octamethylcyclotetrasiloxane, tetramethyl tetraftrifluoropropyl) cyclotetrasiloxane and tetramethyltetracyanopropylcyclotetrasiloxane (10: 1 molar) for modification. The resulting copolymer (1.8 g) has compatible properties and is resistant to mineral oils.

Example 9

The procedure was as in Example 1, instead of tetrahydrofuran, nitromethane was used to suspend the polypropylene. The yield and properties of the product correspond to the results of Example 1, but the extraction attempts them in the absence of polytetramethylene oxide.

He did

Proceed as in Example 1, using the same molar amount of p-xylene diylium dichloromethane instead of siloxonium dication.

© Q ch ₂ C1O ₄ .

The copolymer obtained had the properties of the product of Example 1. The polyolefin modification process of the present invention has the following advantages:

Compatible blocks and bolts contain siloxane bonds like most mineral fillers. The relatedness of the composition of the compatibilizing component firmly bound to the hydrocarbon matrix of the filler ensures maximum compatibility of the composite. By suitable choice of siloxene monomers, namely with, for example, vinyl substituents, it is possible to provide additional crosslinking compatibility with the intermediate layer, which is highly desirable for many purposes. The elastomeric properties of the polysiloxanes can dampen the stresses and neutralize the unfavorable forces, which, as a result, once again glued the mechanical properties of the composites. Polysiloxane blocks and grafts act as an internal plasticizer. It allows processing of the composite under milder conditions (at lower temperature and pressure, respectively, the exposure time of these factors will be shortened).

The modification does not degrade or thicken the polyalkenes.

Claims (1)

OBJECT OF THE INVENTION Process for modifying polyalkenes by graft polymerization of cationic polymerizing monomers at cationic centers introduced into polyalkenes by reaction with dications, characterized in that the modifying agent is siloxane monomers containing methyl, vinyl, phenyl, trifluoropropyl or cyanopropyl groups. Severography, n. P., MOST