JPH0447688B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing crosslinkable polypropylene.

Conventionally, it has been possible to add vinyl alkoxysilane such as vinyltrimethoxysilane to polyethylene together with a radical generator, and graft polymerize the polyethylene in a molten state to produce crosslinkable polyethylene grafted with vinyl alkoxysilane. However, with regard to polypropylene, when a radical generator is used in the atmosphere, the oxidative deterioration of the polypropylene itself takes priority and decomposes, so it is not easy to produce cross-linkable polypropylene in the same way as producing cross-linkable polyethylene from polyethylene. It was difficult to manufacture.

In view of the above-mentioned current situation, the present invention was made with the aim of providing a method for easily producing crosslinkable polypropylene grafted with vinyl alkoxysilane. The present invention relates to a method for producing crosslinkable polypropylene, which comprises graft polymerizing vinyl alkoxysilane to polypropylene in the presence of a radical generator.

The vinyl alkoxysilane used in the present invention refers to a silane compound having a structure in which a vinyl group and at least one alkoxy group are bonded to one silicon atom. Examples include trimethoxysilane, vinyltriethoxysilane, vinyltris-2-methoxyethoxysilane, vinylmethyldiethoxysilane, vinyltriphenoxysilane, and trivinylethoxysilane.

Furthermore, the Lewis acid used in the present invention refers to Lewis acids in a broad sense that do not contain liberable hydrogen in the molecule, such as BF ₃ , BF ₃ .O(C ₂ H ₅ ) ₂ ,
Examples include Alcl ₃ , Zncl ₂ , Fecl ₃ , Sncl ₄ , Ticl ₄ and the like.

The above-mentioned Lewis acids have the property of adding to the oxygen position of the alkoxy group of vinylalkoxysilane, and in order to prepare vinylalkoxysilane to which a Lewis acid has been added, for example, a gas is added to normally liquid vinylalkoxysilane. By adding the solid, liquid, or solid Lewis acids together by an appropriate method and stirring them uniformly, the reaction between the two proceeds even at room temperature, and the above-mentioned adduct is easily produced.

The amount of Lewis acid added to the vinyl alkoxysilane is 1/10 to 1/1 mole of the silane.
Within the range of 4 moles, the effects of the present invention can be sufficiently exhibited.
The formation of the adduct can be confirmed by measuring the magnetic resonance absorption (NMR) or infrared spectral absorption (IR) of the reaction product as described above. In NMR, there is no change in the absorption of vinyl group hydrogen, but alkoxy The hydrogen absorption position of the group has moved,
In IR, this can be done by detecting that the absorption wavelength of the Si--O bond is shifting.

Next, as a radical generator, organic peroxides such as benzoyl peroxide and dicumyl peroxide can be used, and those which decompose at the melting temperature of polypropylene to generate radicals are usually preferably used.

In order to produce crosslinkable polypropylene according to the present invention, the Lewis acid-added vinyl alkoxysilane prepared by the method described above and polypropylene may be added together and heated and kneaded in the presence of the radical generator. This allows you to easily
Graft polymerization occurs at a good grafting rate to produce crosslinkable polypropylene.

More specifically, a mixture of a Lewis acid-added vinyl alkoxysilane and a radical generator is added to polypropylene, or they are added individually and fed to an extruder, heated and kneaded in the extruder, and extruded to produce, for example, Crosslinkable polypropylene can be obtained by pelletizing, and the amount of radical generator used at that time is preferably in the range of 0.1 to 10 parts by weight per 100 parts by weight of the vinyl alkoxysilane used. , the amount of vinyl alkoxysilane used per 100 parts by weight of polypropylene is
It is preferred to apply the Lewis acid-added vinyl alkoxysilane to the polypropylene in a quantitative range of 0.5 to 5 parts by weight.

In this way, crosslinkable polypropylene is obtained, but this crosslinkable polypropylene is made into a molded article by adding dibutyltin dilaurate or other silanol condensation catalyst, and heated in the presence of moisture, in the same way as conventional alkoxysilane grafted polyethylene. By doing so, crosslinking is quickly promoted and molded products with excellent heat resistance can be obtained. However, as mentioned above, the crosslinking is promoted by heat or hot water even without the addition of a silanol condensation catalyst. It has been found that it has

The method for producing crosslinkable polypropylene of the present invention is as described above, and in particular, it is a method that requires graft polymerization of vinyl alkoxysilane to which a Lewis acid has been added to polypropylene in the presence of a radical generator. It has been difficult to graft-polymerize vinylalkoxysilane onto polypropylene by a simple operation and with good grafting efficiency. Furthermore, the crosslinkable polypropylene obtained based on the present invention has the property that crosslinking can be promoted simply by heat, so by using crosslinkable polypropylene, it is possible to simplify the manufacturing process of molded products. .

Next, the present invention will be explained by examples.

Note that in the following, parts mean parts by weight.

Example 1 BF ₃ .O (C ₂
Add 0.15 parts of H ₅ ) ₂ dropwise and stir to dissolve.
Vinyltrimethoxysilane BF ₃ O was removed by removing unreacted substances and free substances under reduced pressure in a 60°C heating bath.
A (C ₂ H ₅ ) ₂ adduct was prepared.

The above adduct formation can be confirmed by checking the reaction product.
When subjected to NMR and IR, the hydrogen position of the vinyl group remained unchanged in NMR, but the hydrogen position of the methoxy group was shifted, and in IR, it was found that the hydrogen position of the vinyl group was shifted.
This was done by confirming that the absorption wavelength of each bond was shifted.

Dicumyl peroxide is added and dissolved in the above adduct at a ratio of 0.05 part per part of the adduct, and this is added in a quantity such that the amount of vinyltrimethoxysilane used is 1 part per 100 parts of polypropylene pellets. They were added and mixed in the same proportions, fed into an extruder, heated and kneaded, and extruded into pellets. Thus, white polypropylene pellets were obtained.

Next, 0.25 parts of dibutyltin dilaurate was added to 100 parts of the above pellets, extruded into a sheet at about 200°C using an extruder, a sample piece was cut out, and the crosslinked gel fraction was measured for the sample piece under the following conditions.
The gel fraction was 79.4%. Crosslinked gel fraction: A sample piece was immersed in hot water at 95°C for 8 hours, then extruded with xylene at 120°C for 24 hours, and the weight ratio of the unextracted resin to the sample piece was expressed in %.

For comparison, a sample was prepared in the same manner as above except that vinyltrimethoxysilane was mixed with dicumyl peroxide in the same quantitative ratio as above and applied to polyethylene without converting it into a Lewis acid adduct. A pellet was prepared from the pellet, but the pellet turned yellow. Also, a sample piece was prepared from the pellet in the same manner as in the above example, and the crosslinked gel fraction was measured for the sample piece, but the insoluble content was There was hardly any left.

Example 2 Polypropylene pellets prepared in Example 1
Add and mix 1 part of talc to 100 parts, feed it to the extruder, pressurize Freon gas as a foaming agent from the middle of the extruder, extrude foaming through a cooling die at a resin temperature of 180 to 200℃, and make a 5mm thick foam. The foaming ratio is about 25.
I made a double foam sheet.

After producing the foam sheet, the tensile strength of the foam sheet was measured after being left in the air for 24 hours.
The weight was 480Kg/cm ² and the bubble rate was 92%.
Also, place the foam sheet in a heated oven at 130°C,
Measuring the time it takes for the volume to shrink to 90%,
It was hot in 24 hours.

For comparison, talc 1 was added to polypropylene pellets to which no alkoxysilane was grafted.
When a test was conducted on a polypropylene foam sheet with a foaming ratio of about 25 times, which was prepared in the same manner as in the above example, the tensile strength was 350 Kg/cm ² and the closed cell ratio was 90%. The time required for the volume to shrink to 90% under heating conditions of 130°C was 15 minutes.

Example 3 Using the polypropylene pellets prepared in Example 1, a pipe with an inner diameter of 50 mm was extruded. When the physical properties of this pipe were measured, the tensile strength was 570Kg/cm ² ,
The elongation rate was 130%, and the Sial Ruby impact value was 25 Kg/cm ² .

On the other hand, for comparison, a pipe was manufactured in the same manner as above using polypropylene to which no alkoxysilane was grafted, and physical property tests were conducted on ^the pipe.
%, and the Sialby impact value was 7 Kg/cm ² .

Claims (1)

[Claims] 1. A method for producing crosslinkable polypropylene, which comprises graft polymerizing vinyl alkoxysilane to which a Lewis acid has been added onto polypropylene in the presence of a radical generator.