JPS6317916A - Production of silane-crosslinked polyolefin - Google Patents

Abstract

PURPOSE:To obtain the titled polymer improved in strength at yield point and elongation at break, by modification of polyolefin with a specific silane compound to enable the extrusion energy to be reduced in preparing a silane- modified polyolefin as intermediate product. CONSTITUTION:First, (A) polyolefin and (B) 0.1-10pts.wt. based on the component A, or a trialkoxysilyl butadiene (pref. trimethoxysilyl butadiene) are allowed to react in a kneading extruder in the presence of a free radical generator (pref. dicumyl peroxide) to prepare a silane-modified polyolefin. The resultant modified polyolefin is brought to catalytic reaction with water, normally in the presence of a silanol condensation catalyst such as dibutyltin dilaurate, thus obtaining the objective polymer. The reaction in the kneading extruder mentioned above is preferably carried out at 140-250 deg.C for <10min.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing a silane-modified polyolefin by reacting a polyolefin with a silane compound. More specifically, it provides an economically advantageous method for producing the silane-modified polyolefin, and at the same time, a method for producing a silane-crosslinked polyolefin with improved mechanical properties by treating the silane-modified polyolefin with water in the presence of a silanol condensation catalyst. Regarding.

Traditionally, crosslinked polyethylene has been produced mainly by a crosslinking method using organic peroxides, but this method has not been fully satisfactory in terms of moldability. A method of modifying polyolefins by irradiation with radiation has also been adopted, but this method requires that the molded product be processed as is.
For this reason, the device became large and was not economically efficient.

In order to overcome these difficulties, in recent years, polyolefins have been treated with silane compounds to produce silane-modified polyolefins, which are further treated with water in the presence of a silanol condensation catalyst to achieve heat resistance and ESC resistance.

We manufacture silane cross-linked polyolefins with excellent chemical resistance.
It is already known that it can be applied to electric power cables, medicine bottles, etc. An example of this is 1, for example,
1711 (Misodoland Silicones Limited), olefin polymers and copolymers are treated with a silane compound and a free radical generator, and then treated with a silanol condensation catalyst and water.

A method for producing a silane crosslinked polyolefin is proposed, but this application only describes the method for obtaining the crosslinked polyolefin in principle and does not describe any features from an industrial production perspective.

Another example is a method for producing a silane crosslinked polyolefin disclosed in Japanese Patent Application Laid-Open No. 57-153004 (Nippon Petrochemicals Co., Ltd.). This is because this application limits the manufacturing method of the target polyolefin.

It is considered that the superiority of the silane compounds to be used is not necessarily clear.

Problems to be Solved by the Present Invention The present inventor has examined these prior applications in detail, and as a result of intensive research with the intention of industrialization, the processability of silane-modified polyolefin and the silane obtained as a final product, depending on the type of silane. It was discovered that the mechanical properties of crosslinked polyolefins are different.

In other words, when a silane compound and a free radical generator are added to polyolefin and the two are reacted in a kneading extruder, the silane compound reduces the torque applied to the kneader and reduces the resin pressure, resulting in a reduction in extrusion energy. possible,
We found it to be economically advantageous.

It was also confirmed that a crosslinking reaction had clearly occurred in the final product, the silane crosslinked polyolefin, and it was revealed that the yield point strength and elongation at break were improved in terms of tensile properties.

Problems solved by the present invention The polyolefin used in the present invention is low pressure polyethylene,
High-pressure polyethylene and linear low-density polyethylene are preferred.

The silane compound used in the present invention has the general formula (R is 1 carbon number
It is a specific silane compound represented by ) which shows a hydrocarbon group of ~4, and trimethoxysilylbutadiene is particularly suitable. The proportion of silane used can be arbitrarily changed depending on the reaction conditions or degree of modification, but is generally 0.1 to 10 parts by weight based on the polyolefin to be modified.

Preferably it is 0.5 to 5 parts by weight.

Free radical generators used in the present invention are organic peroxides and peresters, specific examples of which include benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-di(
peroxybenzoate) hexyne-3,L3-bis(
tert-butylperoxyisopropyl)benzene, lauroyl peroxide, tert-butylperacetate 1,3-bis(tert-butylperoxyisopropyl)benzene,
2,5-dimethyl-2,5-di(tert-butylperoxy)hexane-3,2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and tert-butylbarbenzoate Dicumyl peroxide and 1,3-bis(tert-butylperoxyisopropyl)benzene are particularly preferred, and the amount of these free radical generators used is 0.05% based on the polyolefin to be modified.
-0.5 parts by weight, preferably 0.1-0.2 parts by weight.

Examples of the silanol condensation catalyst used in the present invention include:

Dibutyltin dilaurate, stannous acetate, stannous octanoate
Organometallic compounds such as carboxylates, titanate esters and chelates such as tin, stannous caprylate, lead naphthenate, zinc caprylate, iron 2-ethylhexanoate, cobalt naphthenate.

Examples include tetrabutyl titanate, tetranonyl titanate and bis(acetylacetonitrile) di-isopropyltitanate. Suitable catalysts are organotin compounds 9 such as dibutyltin dilaurate.

The silanol condensation catalyst is preferably mixed into the silane-modified polyolefin before contacting with water, i.e., the silanol condensation catalyst is mixed before, during, or after the reaction between the silane compound and the polyolefin. This can be achieved by

The amount of the silanol condensation catalyst added is 0.01 to 0.5 parts by weight, particularly 0.02 parts by weight, based on the unmodified polyolefin.
~0.2 part by weight is preferred.

The method of silane modification of polyolefin adopted in the present invention is as follows:
The polyolefin, silane compound, and free radical generator are mixed in any suitable reactor 8, such as an extruder, Banbury mixer, roll mill, Brabender plasticorder, or the like. in this case.

The reaction temperature is a temperature higher than the melting point of the polyolefin,
The temperature may be selected from any temperature below the decomposition temperature of the polyolefin, but it is preferably carried out at 140 to 250°C for a period of up to 10 minutes. A known method can be used to crosslink the silane-modified polyolefin thus obtained. Namely.

A crosslinked polyolefin can be obtained by molding a silane-modified polyolefin by extrusion or other treatment and then contacting it with water in the presence of a silanol condensation catalyst. Although contact with water to effect silane crosslinking of the resulting composition is usually sufficient due to moisture present in the atmosphere, to increase the rate of crosslinking,
This is done by immersion in water or hot water, or exposure to a steam atmosphere.

In the present invention, the composition before being brought into contact with water may contain other auxiliary agents (3), such as carbon black, talc, calcium carbonate, foaming agents, lubricants, antioxidants, ultraviolet stabilizers (1) heavy metal deterioration. Inhibitor 3 Various additives such as a colorant and a voltage stabilizer can be appropriately blended.

Examples Example 1 (torque comparison) Melt flow rate 4.9 g/10 min and density 0.9
100 parts by weight of high-density polyethylene (manufactured by Nissan Maruzen Polyethylene Co., Ltd., grade 2050) having a density of 62 g/cm3.

A mixture obtained by adding 2 parts by weight of the silane compound shown in Table 1 and 0.15 parts by weight of the free radical generator shown in Table 1 was heated at a jacket temperature of 19
Graft polymerization was carried out for 8 minutes at 0° C. and a rotor rotation speed of 4 Q rpm. Table 1 shows the results of measuring the torque during graft polymerization.

For the obtained samples 1-A, 1-B, and 1-C, sheets produced by heat pressing were extracted with acetone for 5 hours, and then the infrared absorption spectra were measured, and the absorption based on 5i-0 was 1195 cm-' , the absorption based on C-0 is 1
At 090 cm −', the absorption based on 5i-C is 80
It was observed near 0 cm-', and it was confirmed that trimethoxysilylbutadiene was grafted. When the grafting rate was calculated from the ratio DII95/DI303 of the absorbance of 1195 call-' caused by grafting to the absorbance of 1303 cm-' of polyethylene in the infrared absorption spectrum, it was found that about 90χ of the added trimethoxysilylbutadiene had undergone a graft reaction. .

Example 2 (Resin pressure comparison) Melt flow rate 4.9 g/10 min and density 0.9
62 g/cm'' high-density polyethylene (manufactured by Nissan Maruzen Polyethylene Co., Ltd., grade 2050) to 100 parts by weight.

25 parts by weight of a mixture obtained by adding 2 parts by weight of the silane compound shown in Table 2 and 0.15 parts by weight of the free radical generator shown in Table 2.
The mixture was extruded into strands using a 11I/IIlφ extruder (L/D・20) at an extrusion temperature of 200° C. and a screw rotation speed of 25 rpII+ to form pellets. Table 2 shows the results of measuring the resin pressure at this time.

Example 3 (Comparison of silane crosslinked products) Production of catalyst masterbatch Melt flow rate 4.9 g/10 min and density 0.9
100 parts by weight of high-density polyethylene (manufactured by Nissan Maruzen Polyethylene Co., Ltd., grade 2050) having a density of 62 g/cm3.

1 part by weight of dibutyltin dilaurate and 2,2-thiobis(4-methyl-6-tert-butyl-phenol) (manufactured by Ciba Geigy, trade name Irganox 1081) 2
The mixture obtained by adding parts by weight was passed through a 25 m/+iφ extruder (
L/D = 20) at an extrusion temperature of 200° C. and a screw rotation speed of 25 rpm to form a strand and pelletize it.

Production of silane-crosslinked polyolefin A mixture obtained by mixing 95 parts by weight of the pellets of 2-A, 1-B, and 2-C obtained in Example 2 with 5 parts by weight of each of the pellets of catalyst master punch. 25m
/mφ extruder (L/D・20), extrusion temperature 20
It was re-pelletized at 0° C. and a screw rotation speed of 25 rpm. After molding a press plate at 180°C using this re-pelletized product, this press plate was immersed in water at 100°C for 6 hours to perform a crosslinking treatment. The tensile properties of the obtained crosslinked sheet were measured according to JIS K 6760. Further, the degree of crosslinking of the sheet was evaluated using a xylene solution at 90° C. as an extraction medium and the percentage of sheet components that were not extracted even after a 24-hour extraction operation (gel fraction). The results obtained are shown in Table 3.

(Left below) Effects of the invention Torque during production of silane-modified polyolefin (Example 1)
and resin pressure (Example 2).

When using trimethoxysilylbutadiene.

It is clear that the torque and resin pressure are lower than when using vinyltrimethoxysilane.

Furthermore, from a comparison with silane-crosslinked polyolefin (Example 3), it is clear that when trimethoxysilylbutadiene is used, the yield point strength and elongation at break are improved compared to when vinyltrimethoxysilane is used. . Therefore, in all cases, silylbutadiene is superior to vinylsilane and satisfies the original purpose of the present invention.

Patent applicant: Nissan Chemical Industries, Ltd. Nissan Maruzen Polyethylene Co., Ltd.

Claims (1)

[Claims] When manufacturing a silane-modified polyolefin by reacting a polyolefin and a silane compound in the presence of a free radical generator in a kneading extruder, trialkoxysilylbutadiene is used as the silane compound at a concentration of 0.1 to 10% relative to the polyolefin.
A method for producing a silane crosslinked polyolefin, characterized in that part by weight of the silane is used.