JP2000290380A - Production of corsslinked hollow pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide crosslinked hollow pipes capable of easily providing bending and, simultaneously, having excellent tensile properties and rubber-like properties with low hardness. SOLUTION: A process for producing crosslinked hollow pipes comprises subjecting an ethylene/α-olefin copolymer, a polypropylene and an organic silane compound to graft reaction in the presence of a free radical generator, molding the resulting reaction product into a hollow pipe, then cutting the hollow pipe to a predetermined length, and exposing the cut hollow pipe in the state of providing bending to water in the presence of a silanol condensation catalyst to effect crosslinking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cross-linked hollow pipe having a bend, and more particularly, to a cross-linked hollow pipe which can be easily bent, has low hardness, excellent tensile properties and rubber-like properties. The present invention relates to a manufacturing method capable of realizing a hollow pipe.

[0002]

2. Description of the Related Art Hollow pipes made of ethylene propylene rubber are widely used for automobiles. Since a large number of hollow pipes for automobiles are provided in a narrow space, they are often used after being bent. As a conventional example of manufacturing such a bent hollow pipe, an unvulcanized ethylene propylene hollow pipe cut to a predetermined length has a predetermined bend and a surface releasing agent such as silicone oil on the surface. Insert the coated metal rod (mandrel),
In this state, a method is known in which a vulcanizing process is performed by placing the material in a high-temperature and high-pressure vulcanizing pot and performing vulcanization. After cooling, the mandrel is pulled out and the release agent is further washed.

[0003]

In the prior art, the reason for vulcanizing by inserting a mandrel into a hollow pipe is that ethylene propylene rubber must be vulcanized at a high temperature and a high pressure. This is because deformation or blockage occurs due to thermal softening, which is to be prevented. For this reason, in the conventional example, steps such as insertion and extraction of the mandrel and removal of the release agent are required, and there is a problem that it takes time and labor. In particular, if even a small amount of the release agent remains inside the hollow pipe, the hollow pipe is easily detached after it is mounted on an automobile or the like, and the use of the release agent has a problem on safety.

On the other hand, the ethylene-propylene rubber is subjected to a graft reaction in the presence of an organic silane compound and a free radical generator, and the resulting product is molded and then contacted with moisture in the presence of a silanol condensation catalyst to effect crosslinking (silane). Water crosslinking) is known. However, it is common to add an inorganic substance such as carbon black as a reinforcing agent to ethylene propylene rubber. In this case, scorch occurs due to the effect of moisture contained in the inorganic substance during the graft reaction, and the surface state of the extruded product is reduced. There is a problem that the extrusion workability is deteriorated due to roughness or a baked resin accompanying the scorch, and it is in a situation where practical use is difficult. It is also known to use a crystalline polymer such as polyethylene instead of an inorganic material as a reinforcing agent. However, there is a problem that the hardness is increased and the rubber-like properties are significantly reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can be bent very easily, and has low hardness, excellent tensile properties and rubber-like properties. It is an object of the present invention to provide a manufacturing method capable of realizing a crosslinked hollow pipe.

[0006]

An object of the present invention is to form a composition containing a silane-grafted ethylene-α-olefin copolymer and polypropylene into a hollow pipe, cut it into a predetermined length, and bend the cut hollow pipe. By exposing to water in the presence of a silanol condensation catalyst in the state of having been subjected to the crosslinking.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, ethylene-α olefin copolymers include ethylene-butene-1 copolymer, ethylene-propylene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer and the like. Although it can be mentioned, an ethylene-propylene copolymer is most preferable for achieving the object of the present invention. Although any type of ethylene-propylene copolymer can be used, a high-ethylene type copolymer having a propylene content of 20 to 35% by weight is preferable. The high ethylene type ethylene propylene copolymer can be pelletized, and the automation of the compound production process such as measurement and mixing is easy. Propylene content of 3
If the amount exceeds 5 parts by weight, pelletization tends to be difficult. If the amount is less than 20 parts by weight, rubber elasticity of a molded article tends to be lost.

As the polypropylene, it is preferable to use an ethylene copolymer type obtained by copolymerizing a small amount of an ethylene component, for example, 2 to 9% by weight. As the copolymerization method, either block copolymerization or random copolymerization may be used, but it is preferable to use block copolymerization in order to increase the strength of the crosslinked molded article. When the content of the ethylene component is as small as less than 2% by weight, the compatibility with the ethylene-α-olefin copolymer tends to decrease. The strength tends to decrease.

[0009] The content weight ratio of the ethylene-α-olefin copolymer to the polypropylene in the polymer component (the former / the latter) is preferably in the range of 70 to 85/30 to 15, and when the content of the polypropylene is less than 15% by weight, the crosslinking is not carried out. It tends to be difficult to increase the strength of the molded article, and if it exceeds 30% by weight, the hardness tends to increase and the rubber-like properties tend to decrease.

As a method for obtaining a silane-grafted ethylene-α-olefin copolymer, a method is generally used in which a graft reaction is carried out between an ethylene-α-olefin copolymer and an organic silane compound in the presence of a free radical generator. In the present invention, an ethylene-α olefin copolymer and an organosilane compound may be formed into a pipe by extruding a composition obtained by blending polypropylene with a reaction product obtained by a graft reaction in the presence of a free radical generator, A reaction product obtained by subjecting the ethylene-α-olefin copolymer, polypropylene and the organic silane compound to a graft reaction in the presence of a free radical generator may be extruded to form a pipe.

The organic silane compound is required to have a group which can be connected to a polymer and a group which can be silanol-condensed. Specifically, vinyltrimethoxysilane,
Vinyltriethoxysilane, vinyltriacetoxysilane, γ-methacryloxypropyltrimethoxysilane,
And ethylenically unsaturated silane compounds such as vinyl tris (2-methoxyethoxy) silane.

As the free radical generator, ethylene-
It is required to generate free radical sites in the α-olefin copolymer, and specifically, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2, 5-di (peroxybenzoate) hexyne-
3,1,3-bis (tert-butylperoxyisopropyl) benzene, lauroyl peroxide, tert-butylperacetate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,2.5 -Dimethyl-
Organic peroxides such as 2,5-di (t-butylperoxy) hexane and tert-butylperbenzoate and peresters, and azo compounds such as azobis-isobutyronitrile and dimethylazodiisobutyrate can be mentioned.

Examples of the silanol condensation catalyst include organotin compounds such as dibutyltin dilaurate, dibutyltin diacetate, and dibutyltin dioctate.

[0014] The crosslinked hollow pipe of the present invention comprises ethylene-α
About 2 μm of fine polypropylene component is uniformly dispersed in the olefin copolymer component, and this fine polypropylene acts as a reinforcing component (organic polymer filler), so it has low hardness and excellent tensile properties and rubber-like properties. Product can be realized. In particular, in a production method in which polypropylene is blended with a graft polymer obtained by graft-reaction of an ethylene-α-olefin copolymer and molding and crosslinking are performed, the polypropylene component is dispersed in a finer state,
Excellent tensile properties can be realized.

The cut hollow pipe is made of ethylene-α
When bending is performed in a state of being heated to a temperature equal to or higher than the melting point of the olefin copolymer, even if the bending diameter of the hollow pipe is reduced, the bending can be performed without breaking the hollow pipe.

In the present invention, an antioxidant, a stabilizer, a coloring agent, a lubricant and the like may be appropriately compounded in addition to the above components.
However, in the present invention, since polypropylene acts as a reinforcing component, it is not necessary to add an inorganic reinforcing agent such as carbon black. A small amount of carbon black may be added as a coloring agent. The grafting reaction of the organic silane compound may be performed using any of a kneader, a Banbury, and an extruder, but is most preferably performed using an extruder that can be easily automated.

[0017]

EXAMPLES (1) Blend and silane graft reaction step According to the composition shown in Table 1, each of ethylene propylene copolymer (melting point: 58 ° C.), polypropylene and black color batch was weighed to a total amount of 2.46 kg. Dry-blended well.

The vinyl silane mixed solution is composed of 10 parts by weight of dicumyl peroxide and 2,2-thio-diethylenebis [3-
(3.5 di-t-butyl-4-hydroxyphenyl) propionate] (antioxidant) 10 parts by weight, 4,4'-
It was prepared by mixing and dissolving 1 part by weight of thiobis- (6-tert-butyl-3-methylphenol) (antioxidant).

To 2 kg of the mixed resin pellets of the ethylene propylene copolymer, polypropylene and black color batch, 48.4 g of the vinylsilane mixed solution was absorbed into the mixed resin pellets while thoroughly mixing in a polyethylene bag. Next, a mixture obtained by absorbing and impregnating a mixed resin pellet with a vinylsilane mixed solution was charged into a 30 mm twin-screw extruder, and subjected to a silane graft reaction while being melt-kneaded to produce a graft polymer. The extruder temperature setting conditions are:
Cylinder 1: 160 ° C., Cylinder 2: 200 ° C., Cylinder 3: 220 ° C., Head: 220 ° C.

(2) Catalyst Masterbatch Mixing Step The catalyst masterbatch is an ethylene propylene copolymer 1
A compound in which 1 part by weight of dibutyltin dilaurate was mixed and absorbed in a polyethylene bag with respect to 00 parts by weight was melt-kneaded in the same manner as in the above (1) to produce a catalyst master batch.

(3) Pipe Extrusion Molding Step The graft polymer produced in the above (1) and the catalyst masterbatch produced in the above (2) are mixed in a weight ratio of 1 / l to 1 / l.
The pellets weighed at a ratio of 9/1 were melt-kneaded with a 40 mm extruder to extrude a hollow pipe having an inner diameter of 6 mmφ and an outer diameter of 10 mmφ, and immediately cut to a length of 40 cm after cooling.

(4) Bending hollow pipe forming and cross-linking step The aluminum mold shown in FIGS. 1 and 2 is put in a constant temperature layer set at 80 ° C. and heated sufficiently. A hollow pipe having a length of 40 cm was attached, and in this state, it was placed in a moist heat of 80 ° C. for 16 hours to perform bending and crosslinking. In addition, two kinds of hollow pipes, a normal temperature hollow pipe and a hollow pipe heated to 100 ° C., were mounted on a mold. FIG. 1 is a plan view of the mold, and FIG. 2 is a side view of the mold.
Is a mold body made of aluminum, 2 is a groove for mounting a middle pipe, and a groove is formed in the mold with a plurality of types of curvatures.

With respect to the crosslinked hollow pipe after cooling, the minimum bending radius at which no break occurred was measured. The results are shown in Table 1.

(5) Sheet Forming and Crosslinking Step The graft polymer produced in the above (1) and the catalyst masterbatch produced in the above (2) are mixed in a weight ratio of 1 / l to 1 / l.
The pellets weighed at a ratio of 9/1 were kneaded with a 6-inch test roll heated to a surface temperature of about 180 ° C. for about 10 minutes, and then pressed into a sheet having a thickness of 2 mm (180 ° C.).
After preheating for 3 minutes and pressurizing for 2 minutes), the sheet was placed in a moist heat of 80 ° C. for 16 hours to perform crosslinking.

Various properties of the crosslinked sheet after cooling are shown in Table 1. Tensile strength, elongation, and hardness (JIS.
A) was measured in accordance with the tensile test in Section 3 of JIS K6301. The compression set was measured according to the compression set test of JIS K 6301, section 10. Table 1 also shows, as a reference example, the characteristics of an ethylene propylene rubber (EPR) sheet produced by a high-pressure high-pressure vulcanization method.

[0026]

[Table 1]

As is apparent from Examples 1 to 3, the crosslinked hollow pipe of the present invention has low hardness, excellent tensile properties and rubbery properties, and uses an inorganic reinforcing agent such as carbon black. Therefore, a cross-linked molded product having a smooth surface state can be realized. Further, as compared with the conventional ethylene propylene rubber (EPR), the same or higher characteristics can be realized, but the bending can be performed extremely easily, so that the productivity can be greatly improved.

[0028]

As described above, according to the present invention, a crosslinked hollow pipe which can be easily bent, has low hardness, excellent tensile properties and rubber-like properties can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory plan view of an example of a mold used for bending a hollow pipe.

FIG. 2 is an explanatory side view of an example of a mold used for bending a hollow pipe.

[Explanation of symbols]

 1 Mold body 2 Groove

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Keiichi Kato 1-1-1, Koriyama, Taishiro-ku, Sendai-shi, Miyagi F-term in Tohoku Rubber Co., Ltd. 4F070 AA13 AA16 AB07 AB08 AC59 GA01 GB06 GC04

Claims (6)

[Claims] 1. A silanol condensation catalyst comprising a composition containing a silane-grafted ethylene-α-olefin copolymer and polypropylene, which is formed into a hollow pipe, cut into a predetermined length, and the cut hollow pipe is bent. A method for producing a crosslinked hollow pipe, wherein the pipe is exposed to moisture in the presence of water and crosslinked. 2. The method for producing a crosslinked hollow pipe according to claim 1, wherein the cut hollow pipe is heated to be higher than the melting point of the ethylene-α-olefin copolymer and then bent. 3. The content ratio by weight between the ethylene-α-olefin copolymer and polypropylene (former / latter) is 70-85.
The method for producing a crosslinked hollow pipe according to claim 1, wherein the ratio is / 30 to 15. 4. The method according to claim 1, wherein the ethylene-α olefin copolymer is an ethylene propylene copolymer. 5. The method according to claim 5, wherein the ethylene-propylene copolymer has a propylene content of 20 to 35% by weight. 6. The polypropylene has an ethylene component of 2-9.
The method for producing a crosslinked hollow pipe according to claim 1, which is of an ethylene copolymer type containing 1% by weight.