JP2001106836A - Crosslinking thermoplastic polyethylene resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the elastic modulus, heat resistance, shrinking rate, stress cracking resistance, or the like of a polyethylene resin composition. Without losing the thermoplastic property of polyethylene by dynamically crosslinking the composition. SOLUTION: An ethylene/α-olefin copolymer is melted and blended, in the presence of a peroxide and a multifunctional monomer as necessary, with a high-density polyethylene homopolymer or a polymer matrix in which polyethylene is copolymerized with a small amount of an α-olefin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a thermoplastic crosslinkable polyethylene composition. More specifically, peroxide / polymerization of ethylene / α-olefin copolymers in a matrix of a high-density polyethylene homopolymer or a copolymer of a small amount of α-olefin having a melt flow within a specific range The present invention relates to a resin composition in which the entire resin retains fluidity and is thermoplastic by being dynamically crosslinked using a monomer or the like.

[0002]

2. Description of the Related Art Polyethylene has excellent electrical, mechanical and chemical properties, but has a heat distortion temperature of HDPE.
At 132 to 135 ° C., and has drawbacks in creep performance, stress crack resistance, dimensional stability, and the like. These disadvantages can be significantly improved by crosslinking. However, crosslinking causes loss of thermoplasticity, making it impossible to recycle such as melt molding, which has hindered widespread use.

It is known to modify the properties of said polymers by crosslinking polyethylene and / or other polyolefins under the action of free radical generators, such as organic peroxides. However, the processing method is very difficult and difficult. If the treatment is carried out excessively, it gels in a treatment device such as an extruder, which makes it difficult to extrude and takes a great deal of labor to take out the treated product. Further, it has serious disadvantages such as difficulty in processing into a desired shape because the product does not have thermoplasticity.

[0004]

SUMMARY OF THE INVENTION The present invention does not lose the thermoplasticity of polyethylene by dynamic crosslinking,
The purpose is to improve high elastic modulus, heat resistance, low shrinkage, and stress crack resistance.

[0005]

According to the present invention, the crosslinking reaction is strictly controlled by controlling a crosslinking reaction factor to disperse a crosslinked product as a rubber component in a matrix resin so that the matrix resin maintains fluidity. It is a resin composition obtained.

That is, the present invention relates to (1) 20 to 80 parts by weight of a polymer obtained by copolymerizing ethylene alone or an α-olefin of less than 10% by weight with a melt flow rate in the range of 0.5 to 60 g / 10 minutes; Flow rate 0.
20 to 80 parts by weight of an ethylene / α-olefin copolymer obtained by copolymerizing 10 to 40% by weight of an α-olefin in the range of 5 to 50 g / 10 minutes and 100 parts by weight of the ethylene / α-olefin copolymer A resin composition obtained by melt-kneading a composition comprising 0.01 to 2.0 parts by weight of an organic peroxide and / or 0.01 to 2.0 parts by weight of a polyfunctional monomer with respect to the composition.

(2) The resin composition according to the above (1), wherein the polymer described in the above (1) and / or the polymer is a polymer obtained by polymerization using a metallocene catalyst. (3) The α-olefin according to (1), wherein the α-olefin is at least one or more α-olefins selected from 1-butene, 1-hexene, 1-octene, and propylene. It is a resin composition according to 1).

The crosslinking reaction for obtaining the thermoplastic polyethylene crosslinked product of the present invention will be described. In general, a copolymer obtained by copolymerizing an α-olefin has tertiary carbon and is easily attacked by a radical, so that a crosslinking reaction easily proceeds. In the present invention, in order for the resulting resin composition to have thermoplasticity, it is required that the polyethylene which forms the matrix of the resin composition at the time of the crosslinking reaction be subjected to α before the crosslinking reaction takes place.
-It is important that the copolymer, which is a rubber component containing a large amount of olefin, consumes a radical initiator and crosslinks, and is dispersed in the form of particles in a matrix to complete the crosslinking reaction.

In the present invention, the crosslinking reaction is carried out using an organic peroxide alone or a combination of an organic peroxide and a polyfunctional monomer. Specific examples of the α-olefin copolymerized with ethylene in the present invention include 1-butene, 1-hexene, 1-octene and propylene.

Specific examples of the organic peroxide referred to in the present invention include lauroyl peroxide, dipropionitrile peroxide, benzoyl peroxide, di-t-
Organic peroxides such as butyl peroxide, t-butylhydroxyperoxide, t-butylperoxyisobutyrate, and azo compounds such as azobisisobutyronitrile and azoisobutylvaleronitrile are exemplified. The amount of the organic peroxide used is α- used in the crosslinking reaction.
It is in the range of 0.01 to 2.0 parts by weight based on 100 parts by weight of the olefin copolymer.

The polyfunctional monomers used in combination with the organic peroxide of the present invention are rubber components EPR (ethylene propylene rubber) and ethylene / α-olefin copolymers such as ethylene / 1-butene copolymer. Has a function to stabilize these polymer radicals and increase the crosslinking efficiency before the polymer radicals generated by the hydrogen abstraction reaction of the organic peroxide are cleaved and degraded. Specific examples of these include ethylene dimethyl acrylate, divinyl benzene, Examples include polyethylene glycol dimethyl acrylate, diallyl itaconate, triallyl isocyanurate, diallyl phthalate, triallyl phosphate and the like.

The polyethylene of the present invention is a homopolymer of ethylene or a copolymer obtained by copolymerizing an α-olefin, which is generally called high-density polyethylene. The above polyethylene is polymerized using a titanium compound / alkylaluminum compound catalyst or a metallocene catalyst generally called a Ziegler catalyst. In the present invention, polyethylene polymerized with these catalysts can be used. More preferably, polyethylene polymerized with a metallocene catalyst is used in the present invention.

The metallocene catalyst generally comprises a complex of a cyclopentadiene derivative and a transition metal and a reducing agent. As transition metal complexes, zirconocene, titanocene, ferrocenehafnocene and the like are well known. Organic aluminum compounds and organic boron compounds are known as reducing agents, and specific examples thereof include methylaluminoxane (MAO) and borate. When ethylene is polymerized using a metallocene catalyst, a polymer having a narrow molecular weight distribution can be obtained as compared with a polymer obtained using a general Ziegler catalyst in HDPE polymerization.

In the copolymer of ethylene and α-olefin, as the molecular weight of the copolymer increases, the composition of the comonomer decreases in the Ziegler system, whereas a polymer having a uniform composition can be obtained in the metallocene system. Has features. In the present invention, a polymer obtained by copolymerizing an α-olefin in a polyethylene matrix is crosslinked as a rubber component. When a dynamic cross-linking reaction is carried out using a copolymer polymerized with a metallocene catalyst as a rubber component, the cross-linking reaction proceeds uniformly, probably because the composition of the ethylene / α-olefin copolymer as the cross-linking component is uniform. The composition obtained has a good balance between the fluidity and the appearance of the molded product, and even if the composition has an increased crosslink density by the crosslinking reaction, the molded product obtained using these compositions is less likely to have rough skin and has a good appearance. Has excellent features.

The matrix component of the present invention, a polymer of ethylene alone or a copolymer of less than 10% by weight of an α-olefin, has a melt flow rate of 0.5 to 5%.
It is important to be within the range of 0 g / 10 minutes. When the melt flow rate is 50 g / 10 minutes or more, no advantage is observed in the physical properties of the obtained resin composition, particularly in the heat resistance.
In addition, when the amount is 0.5 g / 10 minutes or less, the composition does not have thermoplasticity even if the matrix undergoes slight crosslinking, which is outside the gist of the present invention.

The proportion of a polymer of ethylene alone or a copolymer of less than 10% by weight of an α-olefin in the composition forming the matrix of the composition of the present invention is 20%.
~ 80% by weight. More preferably 30 to 70% by weight
It is. If the proportion of the polymer in the composition is less than 20% by weight, it is difficult to form a continuous phase in the composition even if a low-viscosity one having a high melt flow rate is used, and it becomes impossible to form a desirable morphology. On the other hand, if it exceeds 80% by weight, peroxide is consumed for crosslinking of the continuous phase, and it becomes difficult to control the crosslinking reaction.

The kinetic crosslinking of the present invention is to carry out crosslinking at the time of mixing and melting.
PE) to react while giving shear,
In the narrow sense of the present invention, it means that the reactant is reacted with the crosslinking reagent while melt-kneading or stirring using a Brabender, Banbury mixer, kneader, extruder or reactor.

The melt kneading of the present invention means mixing under high shear at a temperature at which the resin melts. The greater the shear applied to the resin, the more the crosslinked rubber component is dispersed in the matrix in the form of small particles. As a device for giving a shear, a Brabender, a kneader, a single screw or a twin screw extruder is used. The reaction temperature is preferably 150 to 280 ° C, more preferably 170 to 250.
° C. Various auxiliary materials can be added to the composition of the present invention, as is often found in resin compositions.

Such auxiliary materials include miscible thermoplastics, stabilizers, lubricants, inorganic fillers, flame retardants, colorants and the like. The thermoplastic crosslinked polyethylene composition produced by the method of the present invention has excellent physical properties, high resistance to strain, resistance to organic solvents,
Since it has tensile strength at high temperatures, it can be advantageously used in various applications to which molded products such as electric insulating materials, high-temperature containers and conduits, and polyolefins are applied.

[0020]

DETAILED DESCRIPTION OF THE INVENTION The melt flow rate of the present invention is:
The test was carried out at 190 ° C. and 2.16 kg by the JIS K7120 method.

[0021]

EXAMPLE 1 Ethylene / 1-polymerized with a metallocene catalyst
To 4 kg of pellets of a butene copolymer (1-butene 50% by weight, melt flow rate 2.0 g / 10 min), 2 kg
5-Dimethyl-2,5-bis (t-butyl
lperoxy) 40 g of hexane and 80 g of P-divinylbenzene were added, and the mixture was uniformly applied to the pellets.
Allowed to absorb for minutes. An ethylene homopolymer polymerized with a metallocene catalyst (Asahi Kasei Creolex prototype SS9901, melt flow rate 15.0 g / 10
min) 4.0 kg pellets were blended and mixed. Using a ZSK 25 mm extruder (two-axis in different directions), the resin was discharged at a resin temperature of 220 ° C. and a discharge amount of 15 kg / hr.
Extruded and pelletized at m.

The melt flow rate was 0.20.
g / 10 min. The dynamically crosslinked product prepared in Example 1 was heated to a resin temperature of 2 using an injection molding machine (Toshiba IS80EPN).
20 ° C. Mold temperature 60 ° C., tensile dumbbell for measuring physical properties, 1/8 ′ tanzaku, 100 × 100 mm thickness 2
mm flat plate was formed. Table 1 shows the physical properties of this product.

[0023]

Example 2 HDPE homopolymer polymerized with Ziegler catalyst, Suntech J310 (injection molding grade, melt flow rate 22 g / 10 min) Linear Loden Mitsubishi Kasei UF330 (A) Melt flow rate 1.0
The same treatment as in Example 1 was performed using g / 10 min and a density of 0.922 to obtain a dynamically crosslinked product.

[0024]

Comparative Example 1 2,5-D using only HDPE homopolymer, Suntech J310 polymerized with Ziegler catalyst
imethyl-2,5-bis (t-butylyl
Example 1 was repeated with the addition of (roxy) hexane and P-divinylbenzene. In the extrusion treatment, the strand did not elongate due to the crosslinking reaction, and the strand was frequently cut, and uniform extrusion could not be performed. This made it impossible to pelletize.

[0025]

[Examples 3 to 5] Asahi Kasei Creolex prototype SS99
Example 1 was repeated by changing the mixing ratio of 01 (metallocene catalyst) and the ethylene / 1-butene copolymer (1-butene 50% by weight) polymerized with the metallocene catalyst. (80
/ 20, 70/30, 40/60)

[0026]

[Example 6] Asahi Kasei Creolex prototype SS9901
Example 1 was repeated using (metallocene catalyst) and an ethylene / 1-octene copolymer (1-octene 50% by weight) polymerized with the metallocene catalyst.

[0027]

Example 7 2,5-Dimethyl used in Example 1
1-2,5-bis (t-butylperoxy) h
Example 1 was repeated by doubling the amount of exane used.

[0028]

[Table 1]

[0029]

According to the present invention, high elastic modulus, improvement in heat resistance, low shrinkage, and stress crack resistance can be achieved without losing the thermoplasticity of polyethylene by dynamic crosslinking.

Claims (3)

[Claims] 1. Melt flow rate 0.5 to 60 g /
20 to 80 parts by weight of a polymer obtained by copolymerizing ethylene alone or less than 10% by weight of α-olefin in the range of 10 minutes, and 10 to 40% by weight of α in the range of 0.5 to 50 g / 10 minutes of the melt flow rate. 20 to 80 parts by weight of an ethylene / α-olefin copolymer obtained by copolymerizing an olefin and 0.01 to 2.0 parts by weight of an organic peroxide with respect to 100 parts by weight of the ethylene / α-olefin copolymer. And / or a resin composition obtained by melt-kneading a composition comprising 0.01 to 2.0 parts by weight of a polyfunctional monomer. 2. The resin composition according to claim 1, wherein the polymer according to claim 1 is a polymer polymerized using a metallocene catalyst. 3. The α- according to claim 1, and / or
The olefin is at least one α- selected from 1-butene, 1-hexene, 1-octene and propylene;
The resin composition according to claim 1, which is an olefin.