JPS59232108A - Production of crosslinkable polyethylene - Google Patents

Abstract

PURPOSE:To produce crosslinkable PE having a high degree of grafting and stable quality with good reproducibility, by grafting a Lewis acid-added vinylalkoxysilane onto PE in the presence of a radical generator. CONSTITUTION:PE is combined with a Lewis acid-added vinylalkoxysilane (e.g., vinyltrimethoxysilane to which 1/10mol, per mol of vinyltrimethoxysilane, of ZnCl2 is added), and the resulting mixture is kneaded by heating in the presence of a radical generator (e.g., dicumyl peroxide), for example, in an extruder and extruded into pellets. It is possible to produce crosslinkable PE having an extremely high degree of grafting and stable quality in good reproducibility by using the Lewis acid-added vinylalkoxysilane.

Description

[Detailed description of the invention] The present invention relates to a method for producing crosslinkable polyethylene.

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. It is being done.

However, in the above method, the ratio of vinyl alkoxysilane that is effectively grafted onto polyethylene, that is, the effective grafting rate, is low, at most 50 to 50%.
60%, which has the disadvantage of wasting expensive vinylalkoxysilane and increasing manufacturing costs.Also, the residual vinylalkoxysilane that has not been effectively grafted onto polyethylene is Or, it is contained as an impurity in polyethylene in the form of a siloxane condensate, etc., which affects the flow characteristics, crosslinking characteristics, etc. of the grafted polyethylene, and makes it difficult to reproducibly produce crosslinkable polyethylene of stable quality. This is a major reason why it is difficult to manufacture.

In view of the current state of the production of crosslinkable polyethylene as described above, the present invention aims to provide a method for producing crosslinkable polyethylene in which the effective grafting rate of the vinyl alkodisilane used is extremely high and the above-mentioned drawbacks are eliminated. The gist lies in a method for producing crosslinkable polyethylene, which is characterized in that a Lewis acid is added and tahinyl alkoxysilane is graft-polymerized onto polyethylene 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, vinylmethyljethoxysilane, vinyltriphenoxysilane, and trihinylethoxysilane.

Further, the Lewis acid used in the present invention refers to a Lewis acid in a broad sense that does not contain liberable hydrogen in its molecule,
For example, BF, (-OC, Hg), AIc1
3, Zncll, Fec13, S n c 14, Ti
Examples include Cl4.

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 added with a Lewis acid, for example, normally liquid vinylalkoxysilane is added to the gaseous state. By adding , liquid or solid Lewis acid by an appropriate method and stirring uniformly, the reaction between the two proceeds even at room temperature, and the above adduct is easily produced.

The effects of the present invention can be sufficiently exerted when the amount of Lewis acid added to the vinyl alkoxysilane is in the range of 1/10 to 1/4 mole per mole of the silane.

The production of the adduct is confirmed by measuring the nuclear magnetic resonance absorption (NMR) or infrared spectral absorption (IR) of the reaction product as described above. In NMR, there is no change in absorption of vinyl group hydrogen, but alkoxy This can be done by detecting that the absorption position of hydrogen in the group has shifted, and in IR, that the absorption wavelength of the S i-0 bond has shifted.

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

In order to produce crosslinkable polyethylene according to the present invention, it is sufficient to add the Lewis acid-added vinyl alkoxysilane prepared by the method described above and polyethylene and heat-knead the mixture in the presence of the radical generator. , this K
Graft polymerization occurs more easily and with a good grafting rate to produce crosslinkable polyethylene.

More specifically, a mixture of a Lewis acid-added vinyl alkoxysilane and a radical generator is added to polyethylene, or they are individually added together and fed to an extruder, heated and kneaded in the extruder, and extruded, for example. Crosslinkable polyethylene is obtained by pelletizing, and the amount of radical generator used in this case is preferably in the range of 1 to 10 parts by weight per 100 parts by weight of the vinyl alkoxysilane used. It is preferable to apply Lewis acid-added vinyl alkoxysilane to polyethylene in a quantitative range of 5 to 5 parts by weight relative to 100 parts by weight of polyethylene.

The crosslinkable polyethylene thus obtained has a higher grafting rate than the crosslinkable polyethylene obtained by simply grafting vinyl alkoxysilane onto polyethylene in the presence of a radical generator as in the conventional 5-method. Due to this, the content of unreacted sulfur, etc. is low, and therefore the content of impurities is low, and when molded and used for example in pipes, there is little elution into water, and permanganese is This results in excellent quality with low acid consumption. In addition, as mentioned above, since there is less waste in the grafting of vinylalfukidisilane, it is advantageous in terms of cost, and in terms of quality, a product with good reproducibility and stable quality can be obtained. I can do it.

Furthermore, the crosslinkable polyethylene obtained by the method of the present invention can be quickly crosslinked by adding dibutyltin silacrate or other silanol condensation catalyst to form a molded product and heating it in the presence of moisture. It is possible to obtain molded products with excellent heat resistance etc.
As mentioned in Section 6 above, crosslinking can be promoted by heat or hot water even without the addition of a silanol condensation catalyst.
It's clear.

The reason why the crosslinkable polyethylene obtained by the method of the present invention has such characteristics is not clear, but as the ratio of Lewis acid added to vinylalkoxysilane and the amount of Lewis acid-added vinylalkoxysilane to polyethylene increase, It has been confirmed that the above characteristics are strengthened, and in particular, Lewis acid-added vinyl alkoxysilane, in which 1/1 mole or more of Lewis acid is added to 1 mole of vinyl alkoxysilane, is added as the amount of vinyl alkoxysilane to 100 parts by weight of polyethylene. Crosslinked polyethylene obtained by graft polymerization using 1 part by weight or more can be rapidly crosslinked by heat or hot water without using a silanol condensation catalyst. It is effective in simplifying the process.

Next, the present invention will be explained by examples.

In addition, in the following, parts mean parts by weight.

Example 1 BF3(QC2H,)2 in vinyltrimethoxysilane
was added dropwise in the range of 10 to 115 moles per mole of vinylsilane, stirred and dissolved, and unreacted substances and free substances were removed under reduced pressure in a 60°C heating bath to obtain vinyltrimethoxysilane. BF.

(OC2H5)2 adduct was prepared.

The formation of the above adduct was confirmed by subjecting the reaction product to NMR and IR, and in NMR it was found that the hydrogen position of the vinyl group was unchanged, but the hydrogen position of the methoxy group was shifted, and in IR it was found that the hydrogen position of the methoxy group was shifted. This was done by confirming that the absorption wavelength of the 5i-0 bond was shifted.

Add dicumyl oxide to the above adduct at a ratio of 0.03 parts per part of the adduct, dissolve it, and add it in a quantity such that the amount of vinyltrimethoxysilane used is 1 part per 100 parts of polyethylene. They were added and mixed in the same proportions, fed to an extruder, heated and mixed, and extruded into pellets. The residual silane monomer amount of the pellets thus obtained was measured under the following conditions, and the results shown in Table 1 were obtained.

Next, 105 parts of digityltin silaclay) was added to 100 parts of the above pellets and extruded into a sheet at about 150°C using an extrusion method, a sample piece was cut out, and the crosslinked gel fraction was When measured, the results shown in Table 1 were obtained.

Next, a mixture of 100 parts of the above pellets and 05 parts of digityltin silacrate α was extruded using an extruder to
+w pipe was manufactured and the consumption of potassium permanganate was measured for the pipe under the following conditions, and the results shown in Table 4!11 were obtained.

Amount of residual monomer: The extruded pellet was extracted with acetone in a sealed tube, and the extract was subjected to gas chromatography K to quantify the amount of residual monomer in the pellet.

Crosslinked gel fraction: A sample piece was immersed in hot water at 85°C for 4 hours, then extracted with xylene at 120°C and cut into a 9-length piece, and the pipe was filled with distilled water.

For comparison, the procedure was the same as above except that 1-vinyltrimethoxysilane was not made into a Lewis acid adduct but was mixed with dicumyl peroxide in the same quantitative ratio as above and applied to polyethylene. The results of the tests are also shown in Table 1.

Example 2 A zinc chloride adduct of vinyltrimethoxysilane was prepared in the same manner as in Example 1 by adding zinc chloride (Znc12) to vinyltrimethoxysilane in an amount of 1/1 mole per mole of vinylsilane.

The adduct was applied to polyethylene in the same manner as in Example 1, and the same tests as in Example 1 were carried out with the results shown in Table 1-10=.

Table 1 Example 3 In the same manner as in Example 1, BF3 (QC, H5) was added to 3 parts of vinyltrimethoxysilane, and 1/1 mole of silane was added.
(equivalent to 4 moles), dicumyl and 0.05 part of Q-oxide were dissolved therein, and the total amount was mixed with 100 parts of polyethylene, supplied to an extruder, heated and kneaded, and extruded. I made 1 pellet.

When this pellet was measured for residual upper clumps in the same manner as in Example 1, no residual upper clumps were detected.

Next, the pellet was molded into a plate at 140°C using a press, and the obtained plate was used as a sample and extracted with xylene at 120°C for 24 hours, and the unextracted resin content (crosslinked gel content) The measured value was 97%. In addition, when the above pellet was soaked in hot water at 85°C for 4 hours and extracted with xylene using the same method as above, the crosslinked gel content was 97%.
Met.

Furthermore, the pellets may be directly processed without adding any crosslinking catalyst such as dibutyltin dilaurate to the pellets.
Formed into a pipe with an inner diameter of 13 mm, the patent applicant Motoli Fujinuma, representative of Sekisui Chemical Co., Ltd. Amendment to the procedure (Own ship July 13, 1980 To the Commissioner of the Japan Patent Office 1, Indication of the case 1988 Patent application no. 107426 No. 2, Name of the invention Process for producing cross-linked polyethylene 3, Relationship with the amended case Patent applicant Postal code 530 Address Patent Department Tokyo, 2-4-4 Nishitenma, Kita-ku, Osaka (03) 434 -95524, column for detailed description of the invention in the specification subject to amendment Contents of the amendment (1) In the eighth line from the bottom of page 3 of the specification, "BF3-(-OCzHs)2 J" was replaced with "BF3-(-OCzHs)2 J".
Correct it as 3.0(CxHs)z J.

(2) Specification page 8, line 4, same page @ lines 8-9 and 11
In the 8th line from the bottom of the page, replace [BF3(OC2H5)2 J with "BF, ・0
(Corrected as C2Hsh J.

(31FJI detailed work, page 11, 1st r BF3 (OCzHs h ・1/io mole)
・1/7 mole・115 mole” is replaced with [BF3・0 (C2Us) 2・1/10 mole・
1/7 mole, 115 mole,” he corrected.

that's all

Claims (1)

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