JP7342645B2 - Cylindrical molded body and method for manufacturing the same - Google Patents

Description

The present invention relates to a cylindrical molded article made of a polyolefin composition, and in particular to a crosslinked polyolefin cylindrical molded article that has a good appearance, excellent hot internal pressure creep performance, and is flexible and has excellent workability during bending and stretching and construction. .

For cylindrical molded bodies such as tap water pipes and heating pipes used for water supply, floor heating, road heating, etc., and industrial cylindrical molded bodies such as beverage tubes, liquid food transfer tubes, compressed air distribution tubes, etc. In order to prevent leakage of the contents, durability is required with a long pipe creep rupture time.

Conventionally, cross-linked polyethylene pipes made by cross-linking high-density polyethylene and linear low-density polyethylene have been used for cylindrical molded products used in applications that require a long pipe creep rupture time from the viewpoint of durability. However, cross-linked polyethylene pipes have a high density and hardness due to their large number of crystalline parts, making them difficult to bend and posing problems in workability and construction. In addition, cross-linked polyethylene obtained from linear low-density polyethylene, which has a sufficiently low density, has few crystal parts and has a low melting point of crystals, so it cannot withstand the passage of hot water. The problem was that they would burst immediately if water was applied to them under pressure.

Patent Document 1 proposes a crosslinked polyethylene tubular molded body using high-density polyethylene and linear low-density polyethylene having a specific MFR and density. In the example of Patent Document 1, a silane-crosslinked polyethylene tubular molded body is manufactured using polyethylene having a density of 0.940 to 0.943 g/cm ³ .
Since the modified polyolefin composition of Patent Document 1 has a high density of 0.940 to 0.943 g/cm ³ , it has many crystalline parts and high hardness. Badness was the problem. Furthermore, since the modified polyolefin composition described in Patent Document 1 has a high density, it shrinks significantly in the water-cooling process, and has problems such as being easily dented and having a rough appearance, and also requiring a depressurization process.

In order to improve such bending and stretching properties and workability, Patent Document 2 proposes a polyolefin resin composition in which an ethylene/α-olefin copolymer and random polypropylene are modified with silane.
The ethylene/α-olefin copolymer described in Patent Document 2 is soft as an elastomer, but because the crystals of the ethylene/α-olefin copolymer have a low melting point, instantaneous rupture occurs when hot water is passed through the copolymer. Ta.

Japanese Patent Application Publication No. 2018-168229 Japanese Patent Application Publication No. 2016-134312

The present invention has been made in view of the above circumstances, and is a cylindrical molded article made of a polyolefin composition containing an ethylene/α-olefin copolymer, which improves the appearance, uniformity of film thickness, and heat resistance of the molded article. The object of the present invention is to provide a cylindrical molded product that has excellent properties such as flexibility and internal pressure creep performance during heat, and is also flexible and has excellent workability during construction, such as bending and stretching.

As a result of extensive research in order to achieve the above object, the present inventor has discovered an ethylene/α-olefin copolymer with a specific melting point and a specific melting point different from this ethylene/α-olefin copolymer. The inventors have discovered that the above problems can be solved by using a polyolefin composition containing a polyolefin having the following properties, and have completed the present invention.
That is, the gist of the present invention is as follows.

[1] An ethylene/α-olefin copolymer whose melting end peak temperature measured by a differential scanning calorimeter (DSC) is 115°C or higher, and a differential scanning calorimeter (DSC) that is different from the ethylene/α-olefin copolymer. A cylindrical molded article obtained by molding a polyolefin composition containing a polyolefin having a melting end peak temperature of 125° C. or higher as measured by a calorimeter (DSC).

[2] The cylindrical molded article according to [1], wherein the polyolefin accounts for 2 to 50% by mass in a total of 100% by mass of the ethylene/α-olefin copolymer and the polyolefin.

[3] The cylindrical molded article according to [1] or [2], wherein the polyolefin is a propylene-based polymer containing propylene units as a main component.

[4] The cylindrical molded article according to any one of [1] to [3], wherein the polyolefin composition further contains a peroxide and is crosslinked with the peroxide.

[5] The cylindrical molded article according to [4], wherein the polyolefin composition further contains an unsaturated silane compound, and is crosslinked with the unsaturated silane compound and the peroxide.

[6] An ethylene/α-olefin copolymer whose melting end peak temperature measured by a differential scanning calorimeter (DSC) is 115°C or higher, and a differential scanning calorimeter different from the ethylene/α-olefin copolymer. 0.01 to 1.00 parts by mass of peroxide is blended with a total of 100 parts by mass of the polyolefin whose melting end peak temperature is 125°C or higher as measured by a calorimeter (DSC), and this is molded. A method for manufacturing a cylindrical molded body.

[7] Further blending 0.1 to 5.0 parts by mass of an unsaturated silane compound to a total of 100 parts by mass of the ethylene/α-olefin copolymer and the polyolefin, and molding the mixture; [6 ] The method for manufacturing a cylindrical molded body.

According to the present invention, a cylindrical molded body is provided which is flexible and has excellent workability during construction such as bending and stretching, and has excellent heat-resistant internal pressure creep performance, that is, high-temperature water passage durability.
The cylindrical molded article of the present invention does not have problems with poor product appearance or poor film thickness due to slow solidification, and can also prevent bursting due to high-temperature water pressure, so it has an excellent appearance and has excellent high-temperature durability. Excellent.

Embodiments of the present invention will be described in detail below, but the following description is an example of the embodiments of the present invention, and the present invention is limited to the following description unless it exceeds the gist thereof. isn't it.

The cylindrical molded article of the present invention comprises an ethylene/α-olefin copolymer having a melting end peak temperature of 115°C or higher as measured by a differential scanning calorimeter (DSC), and the ethylene/α-olefin copolymer. A polyolefin composition containing a polyolefin having a melting end peak temperature of 125° C. or higher as measured by a differential scanning calorimeter (DSC) (hereinafter sometimes referred to as the "polyolefin composition of the present invention"). It uses

[Polyolefin composition]
First, the polyolefin composition of the present invention will be explained.

The polyolefin composition of the present invention comprises an ethylene/α-olefin copolymer having a melting end peak temperature of 115°C or higher as measured by a differential scanning calorimeter (DSC), and the ethylene/α-olefin copolymer. contains a polyolefin having a melting end peak temperature of 125° C. or higher as measured by a differential scanning calorimeter (DSC), and may further contain a peroxide, and may also contain an unsaturated silane compound and a peroxide. May include things. Furthermore, the following component (A), or component (A) and a hydrocarbon rubber softener may be included.

Component (A): a block copolymer having at least two polymer blocks P derived from a vinyl aromatic compound and at least one polymer block Q derived from a conjugated diene and/or isobutylene, and the block At least one block copolymer from the group consisting of block copolymers formed by hydrogenating copolymers. Hereinafter, component (A) may be referred to as a "styrenic thermoplastic elastomer."

In the polyolefin composition of the present invention, the proportion of the polyolefin in the total 100% by mass of the ethylene/α-olefin copolymer and polyolefin is 2 to 50% by mass, preferably 5 to 45% by mass.
It is preferable from the viewpoint of flexibility and appearance that the polyolefin content in the polyolefin composition of the present invention is within the above range. If the polyolefin content is below the above upper limit, the cylindrical molded product is easy to bend, and when it is above the above lower limit, it is easy to harden when water-cooled during molding, resulting in an excellent appearance as a cylindrical molded product.

When the polyolefin composition of the present invention contains a peroxide, the content of the peroxide is 0.01 to 1.00 parts by mass based on a total of 100 parts by mass of the ethylene/α-olefin copolymer and the polyolefin. is preferred.
Further, when the polyolefin composition of the present invention contains an unsaturated silane compound, the content of the unsaturated silane compound is 0.1 to 5 parts by mass based on the total of 100 parts by mass of the ethylene/α-olefin copolymer and the polyolefin. .0 part by mass is preferred.
When the content of the peroxide and the unsaturated silane compound is at least the above lower limit, a predetermined amount of modification necessary to achieve the effects of the present invention can be obtained. On the other hand, if it is below the above upper limit, there is no possibility that unreacted substances will remain and adversely affect the performance.

When the polyolefin composition of the present invention contains component (A), the content of component (A) is preferably 2 to 50 parts by mass based on a total of 100 parts by mass of the ethylene/α-olefin copolymer and polyolefin. , more preferably 3 to 45 parts by weight, and even more preferably 5 to 40 parts by weight.
When the content of component (A) is at least the above lower limit, crosslinking tends to reduce compression set and improve the appearance during extrusion molding. On the other hand, when the content of component (A) is below the above upper limit, no load is placed on the extruder and extrusion workability becomes good.

It is preferable to use 5 to 300 parts by mass, especially 50 to 200 parts by mass, of the softener for hydrocarbon rubber per 100 parts by mass of component (A) in order to fully obtain the effect of the softener for hydrocarbon rubber. This is preferable from the viewpoint of reducing bleed-out of the softener for hydrocarbon rubber after molding.

Each component contained in the polyolefin composition of the present invention will be explained below. Note that hereinafter, the ethylene/α-olefin copolymer, polyolefin, component (A) used as necessary, and the softener for hydrocarbon rubber described below may be referred to as "elastomer component."
Moreover, a peroxide, an unsaturated silane compound, and an unsaturated cyanurate compound described below may be referred to as a "crosslinking aid component".
Moreover, what is obtained by graft modification and/or crosslinking treatment of the polyolefin composition of the present invention may be referred to as "the modified polyolefin composition of the present invention".

<Ethylene/α-olefin copolymer>
The ethylene/α-olefin copolymer contains ethylene units and α-olefin units, and the content of ethylene units is 50% by mass or more based on the total of its constituent units. The type of ethylene/α-olefin copolymer is not particularly limited as long as it is such a copolymer, and any known ethylene/α-olefin copolymer can be used as appropriate.

Specific examples of ethylene/α-olefin copolymers include ethylene/propylene copolymer, ethylene/1-butene copolymer, ethylene/4-methyl-1-pentene copolymer, and ethylene/1-hexene copolymer. Examples include copolymers of ethylene and one or more α-olefins having 3 to 10 carbon atoms, such as ethylene/1-octene copolymers.

The type of catalyst used in producing the ethylene/α-olefin copolymer is not particularly limited, and examples thereof include Ziegler-Natta catalyst and metallocene catalyst. Among these, ethylene/α-olefin copolymers produced using metallocene catalysts are preferred.

The ethylene/α-olefin copolymer used in the present invention has a melting end peak temperature (hereinafter sometimes referred to as "melting end point") of 115°C or higher as measured by a differential scanning calorimeter (DSC). It is. When the melting end point of the ethylene/α-olefin copolymer is 115° C. or higher, the shape can be maintained by crystals even at high temperatures. From this point of view, the melting end point of the ethylene/α-olefin copolymer is 115°C or higher, preferably 117°C or higher.
However, if the melting point of the ethylene/α-olefin copolymer is too high, there is a risk of poor appearance due to unmelted lumps during heating up during molding or early crystallization (melt fracture) during cooling during molding. Therefore, the melting end point of the ethylene/α-olefin copolymer is usually 145°C or lower. The melting end point of the ethylene/α-olefin copolymer is measured by the method described in the Examples section below.

The density of the ethylene/α-olefin copolymer used in the present invention (measured according to JIS K6922-1,2:1997) is preferably 0.850 to 0.910 g/cm ³ , more preferably 0.860 g/cm 3 . ~0.900g/ ^cm3 . When the density is below the above upper limit, it tends to have excellent flexibility and be easy to bend. In addition, when the density is equal to or higher than the above lower limit, it tends to be less sticky, can be put into the hopper by automatic suction, is less likely to adhere to the hopper, and has excellent moldability.

The melt flow rate (MFR) of the ethylene/α-olefin copolymer used in the present invention is the melt flow rate (MFR) measured at a temperature of 190°C and a load of 2.16 kg with reference to JIS K7210 (1999). ), preferably 0.1 to 50 g/10 minutes. If the MFR is too large, the molten resin tends to drip during molding, which may reduce yield or make molding difficult. Furthermore, if the MFR is too small, the motor load during modified extrusion will be large, the resin pressure will increase, productivity will deteriorate, and the surface after molding may become rough.
From these viewpoints, the MFR of the ethylene/α-olefin copolymer is preferably 0.1 g/10 minutes or more, more preferably 0.5 g/10 minutes or more. On the other hand, it is preferably 50 g/10 minutes or less, more preferably 30 g/10 minutes or less.

The A hardness of the ethylene/α-olefin copolymer used in the present invention is A hardness measured after 15 seconds at a temperature of 23°C and a humidity of 50%, with reference to JIS K6253, and is preferably 40 to 95. It is. If the A hardness is too high, it will be difficult to bend as a cylindrical molded product, the workability during construction will be reduced, and when it is bent and used, distortion will occur, so there is a risk that long-term durability will be impaired. In addition, if the A hardness is too low, it will be difficult to solidify during molding and cooling, and the appearance during molding will deteriorate.In addition, as a cylindrical molded product, it will not be able to withstand water pressure or the pressure of the contents, and long-term durability will be significantly impaired. It will be done.
From these viewpoints, the A hardness of the ethylene/α-olefin copolymer is preferably 40 or more, more preferably 50 or more. On the other hand, it is preferably 95 or less, more preferably 90 or less.

The ethylene/α-olefin copolymer used in the present invention is preferably one that does not contain any external additives from the viewpoint of hygiene. If talc or PE wax is added to prevent stickiness, it is preferable that no external additives are added, since there is a risk that water or the like may leached into the contents of the cylindrical molded body.

The ethylene/α-olefin copolymer used in the present invention can be obtained as a commercial product. For example, the Engage (registered trademark) series manufactured by DuPont Dowerstomer Co., Ltd., the Kernel (registered trademark) series manufactured by Nippon Polyethylene Co., Ltd., the Infuse (registered trademark) series manufactured by DuPont Dowerstomer Co., Ltd., the Tafmer (registered trademark) series manufactured by Mitsui Chemicals, Inc., the Mitsui Chemicals Co., Ltd. Applicable products can be selected and used from the Evolu (registered trademark) series manufactured by Kagakusha.

These ethylene/α-olefin copolymers may be used alone or in combination of two or more different types of α-olefins, copolymer compositions, physical properties, etc.

<Polyolefin>
The polyolefin used in the present invention consists of ethylene units and/or α-olefin units. However, the polyolefin used in the present invention is different from the above-mentioned ethylene/α-olefin copolymer.

Specific examples of the polyolefin used in the present invention include ethylene homopolymer, ethylene/propylene copolymer, ethylene/1-butene copolymer, ethylene/4-methyl-1-pentene copolymer, ethylene/1-hexene Copolymers, polymers mainly composed of ethylene units such as ethylene/1-octene copolymers; propylene units such as propylene homopolymers, propylene/ethylene copolymers, propylene/ethylene/1-butene copolymers, etc. Examples include polymers containing 1-butene units as a main component, such as 1-butene homopolymer, 1-butene/ethylene copolymer, and 1-butene/propylene copolymer.
Here, the term "main component" indicates that the content is 50% by mass or more.

From the viewpoint of compatibility with the ethylene/α-olefin copolymer, polyolefins include ethylene homopolymer, ethylene/propylene copolymer, ethylene/1-butene copolymer, propylene/ethylene copolymer, propylene - Ethylene/1-butene copolymer is preferred.

In addition, from the viewpoint of flexibility and appearance, the polyolefin is preferably a propylene-based polymer containing propylene units as a main component, and specifically, propylene homopolymer, propylene/ethylene copolymer, propylene/ethylene/ A 1-butene copolymer is preferred.

The polyolefin used in the present invention has a melting end point of 125° C. or higher as measured by a differential scanning calorimeter (DSC). If the melting end point of the polyolefin is 125° C. or higher, it can solidify faster than the ethylene/α-olefin copolymer during cooling during molding. From this point of view, the melting end point of the polyolefin is 125°C or higher, preferably 130°C or higher.
However, if the melting point of the polyolefin is too high, there is a risk of unmelted spots during heating up during molding and early crystallization (melt fracture) during cooling of molding, resulting in poor appearance such as rough skin. The melting end point is usually below 180°C.

In addition, in order to effectively obtain the effects of the present invention, it is possible to effectively obtain the effects of the present invention by mixing and using a polyolefin that has a melting end point different from that of the ethylene/α-olefin copolymer and having a higher melting end point than the ethylene/α-olefin copolymer. The melting end point of the polyolefin is preferably 1° C. or more higher than the melting end point of the ethylene/α-olefin copolymer, more preferably 2° C. or more higher. On the other hand, since it is not preferable that the melting end point of the polyolefin is too high, it is preferable that the difference in the melting end point is 50° C. or less.
The melting end point of the polyolefin is measured by the method described in the Examples section below.

The melt flow rate (MFR) of the polyolefin used in the present invention is a melt flow rate (MFR) measured at a temperature of 230° C. and a load of 2.16 kg with reference to JIS K7210 (1999), and is preferably 0. 1 to 50 g/10 minutes. If the MFR is too large, the molten resin tends to drip during molding, which may reduce yield or make molding difficult. Furthermore, if the MFR is too small, the motor load during modified extrusion will be large, the resin pressure will increase, productivity will deteriorate, and the surface after molding may become rough.
From these viewpoints, the MFR of the polyolefin is preferably 0.1 g/10 minutes or more, more preferably 0.5 g/10 minutes or more. On the other hand, it is preferably 50 g/10 minutes or less, more preferably 30 g/10 minutes or less.

The polyolefin used in the present invention can be obtained as a commercial product. For example, a suitable product can be selected from the Novatec (registered trademark) series manufactured by Nippon Polyethylene Co., Ltd. and the Xelas (registered trademark) series manufactured by Mitsubishi Chemical Corporation.

These polyolefins may be used alone or in combination of two or more different types of α-olefins, copolymer compositions, physical properties, etc.

<Unsaturated silane compound>
The unsaturated silane compound used in the present invention is not particularly limited, but an unsaturated silane compound represented by the following formula (1) is preferably used.
RSi(R') ₃ ...(1)

In the above formula (1), R is an ethylenically unsaturated hydrocarbon group, R' is independently a hydrocarbon group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms, and R' is an ethylenically unsaturated hydrocarbon group; At least one of them is an alkoxy group having 1 to 10 carbon atoms.

In formula (1), R is preferably an ethylenically unsaturated hydrocarbon group having 2 to 10 carbon atoms, more preferably an ethylenically unsaturated hydrocarbon group having 2 to 6 carbon atoms. Specifically, alkenyl groups such as a vinyl group, a propenyl group, a butenyl group, and a cyclohexenyl group can be mentioned.

In formula (1), R' is preferably a C1-6 hydrocarbon group or a C1-6 alkoxy group, more preferably a C1-4 hydrocarbon group or a C1-4 alkoxy group. is an alkoxy group. Further, at least one of R' is preferably an alkoxy group having 1 to 6 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms.
The hydrocarbon group having 1 to 10 carbon atoms for R' may be an aliphatic group, an alicyclic group, or an aromatic group, but an aliphatic group is preferable. Further, the alkoxy group having 1 to 10 carbon atoms in R' may be linear, branched, or cyclic, but is preferably linear or branched.
When R' is a hydrocarbon group, specifically, an alkyl group such as a methyl group, an ethyl group, an isopropyl group, a t-butyl group, an n-butyl group, an i-butyl group, a cyclohexyl group; an aryl group such as a phenyl group; Examples include groups.
When R' is an alkoxy group, specific examples include a methoxy group, an ethoxy group, an isopropoxy group, and a β-methoxyethoxy group.

When the unsaturated silane compound is represented by the above formula (1), at least one of the three R's is an alkoxy group, but preferably two R's are an alkoxy group, and all R' is more preferably an alkoxy group.

Among the unsaturated silane compounds represented by formula (1), vinyltrialkoxysilanes represented by vinyltrimethoxysilane, vinyltriethoxysilane, propenyltrimethoxysilane, etc. are preferred. This is because the vinyl group enables modification to an ethylene/α-olefin copolymer, and the alkoxy group allows the crosslinking reaction described below to proceed.
That is, an alkoxy group introduced by graft modification into an ethylene/α-olefin copolymer with an unsaturated silane compound reacts with water in the presence of a silanol condensation catalyst and is hydrolyzed to produce a silanol group. By dehydration condensation between the groups, the ethylene/α-olefin copolymers bond to each other and a crosslinking reaction occurs.

These unsaturated silane compounds may be used alone or in combination of two or more.

<Peroxide>
The peroxide used in the present invention generates carbon radicals and graft-modifies the unsaturated silane compound onto the ethylene/α-olefin copolymer, and/or extracts hydrogen from the ethylene/α-olefin copolymer. Used to promote the crosslinking reaction of ethylene/α-olefin copolymers.

The peroxide is preferably an organic peroxide from the viewpoint of compatibility with the resin.
Examples of organic peroxides include hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide; dicumyl peroxide, di-t-butyl peroxide, t-butylperoxy 2-ethylhexanoate, and , 5-dimethyl-2,5-di-t-butylperoxyhexane, 2,5-dimethyl-2,5-di-t-butylperoxyhexine-3, di(2-t-butylperoxyisopropyl)benzene dialkyl peroxides such as lauryl peroxide and benzoyl peroxide; peroxy esters such as t-butyl peroxy acetate, t-butyl peroxybenzoate, and t-butyl peroxy isopropyl carbonate; cyclohexanone peroxide and other ketone peroxides.

These organic peroxides may be used alone or in combination of two or more.

From the viewpoint of grafting efficiency, chain transfer efficiency, and sanitary properties such as odor, organic peroxides include t-butylperoxy-2ethylhexanoate, di(2-t-butylperoxyisopropyl)benzene, and di-t-butylperoxy-2ethylhexanoate. -Butyl peroxide is preferred.

<Component (A)>
Component (A) used in the present invention is a block copolymer having at least two polymer blocks P derived from a vinyl aromatic compound and at least one polymer block Q derived from a conjugated diene and/or isobutylene. At least one block copolymer from the group consisting of block copolymers formed by hydrogenating the block copolymers. The olefin composition and modified polyolefin composition of the present invention can further reduce permanent set and improve fluidity by incorporating component (A).

In component (A), the monomeric vinyl aromatic compound constituting block P is not particularly limited, but styrene derivatives such as styrene and α-methylstyrene are preferred. Among these, it is preferable to use styrene as the main ingredient. Here, "consisting mainly" in component (A) means 50% by mass or more. Note that the block P may contain a monomer other than the vinyl aromatic compound as a raw material.

Examples of monomers other than the vinyl aromatic compound include ethylene, α-olefin, and the like. Further, when the block P contains a monomer other than the vinyl aromatic compound as a raw material, the content thereof is less than 50% by mass, preferably 40% by mass or less. When the content of monomers other than the vinyl aromatic compound is within this range, heat resistance and compression set tend to be good.

The monomeric conjugated diene constituting block Q is not particularly limited, but it is preferably mainly composed of butadiene and/or isoprene, more preferably butadiene and isoprene. Note that the block Q may contain a monomer other than the conjugated diene as a raw material.

Monomers other than the above conjugated diene include isobutylene, styrene, and the like. Moreover, when block Q contains a monomer other than the above-mentioned conjugated diene as a raw material, the content is less than 50% by mass, preferably 40% by mass or less. When the content of monomers other than the conjugated diene is within this range, bleed-out tends to be suppressed.

The block copolymer of component (A) is a hydrogenated block copolymer obtained by hydrogenating a block copolymer having at least two of the above polymer blocks P and at least one of the above polymer blocks Q. It may be. More specifically, it may be a hydrogenated block copolymer in which the double bond of the block Q of the block copolymer is hydrogenated. The hydrogenation rate of block Q is not particularly limited, but is preferably 80 to 100% by mass, more preferably 90 to 100% by mass. By hydrogenating Block Q in the above range, the adhesive properties of the resulting polyolefin composition and modified polyolefin composition tend to decrease and the elastic properties tend to increase. The same applies to the case where the block P uses a diene component as a raw material. Further, the hydrogenation rate can be measured by ¹³ C-NMR.

The mass ratio of block P and block Q constituting component (A) is arbitrary, but from the viewpoint of the mechanical strength and thermal fusion strength of the polyolefin composition and modified polyolefin composition of the present invention, block P is large. On the other hand, from the viewpoint of flexibility, profile extrusion moldability, and suppression of bleed-out, it is preferable that the number of blocks P is small.

The mass proportion of block P in component (A) is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 30% by mass or more, and preferably 60% by mass or less, more preferably It is 50% by mass or less, more preferably 45% by mass or less.

Component (A) can be obtained as a commercial product. Commercially available hydrogenated block copolymers include the "KRATON (registered trademark)-G series" and "KRATON (registered trademark)-A series" manufactured by Kraton Polymer Co., Ltd., and the "Septon (registered trademark) series" manufactured by Kuraray Co., Ltd. ”, “Hybler (registered trademark) series”, “Tuftec (registered trademark) series” and “Asaprene (registered trademark) series” manufactured by Asahi Kasei Corporation. Furthermore, commercially available non-hydrogenated block copolymers include "Hyblar (registered trademark) series" manufactured by Kuraray Co., Ltd. and "Tuffrene (registered trademark) series" manufactured by Asahi Kasei Corporation.

Component (A) may be used alone or in combination of two or more.

<Softener for hydrocarbon rubber>
When component (A) is used in the polyolefin composition of the present invention, it is preferable to use a hydrocarbon rubber softener together. The softener for hydrocarbon rubber softens the polyolefin composition and modified polyolefin composition of the present invention, contributing to improvements in flexibility, elasticity, processability, fluidity, and permanent set.

Examples of the softener for hydrocarbon rubber include mineral oil softeners, synthetic resin softeners, etc. Mineral oil softeners are preferred from the viewpoint of compatibility with other components. Mineral oil softeners are generally a mixture of aromatic hydrocarbons, naphthenic hydrocarbons, and paraffinic hydrocarbons, and those in which 50% by mass or more of all carbon atoms are paraffinic hydrocarbons are called paraffinic oils. , those in which 30 to 45% by mass of all carbon atoms are naphthenic hydrocarbons are called naphthenic oils, and those in which 35% or more by mass of all carbon atoms are aromatic hydrocarbons are called aromatic oils. There is. Among these, it is preferable to use paraffin oil in the present invention. In addition, one kind of softener for hydrocarbon rubber may be used alone, or two or more kinds may be used in combination.

The kinematic viscosity at 40° C. of the hydrocarbon rubber softener is not particularly limited, but is preferably 20 centistokes or more, more preferably 50 centistokes or more, and preferably 800 centistokes or less, more preferably 600 centistokes. It is below Stokes. Further, the flash point (COC method) of the softener for hydrocarbon rubber is preferably 200°C or higher, more preferably 250°C or higher.

Softeners for hydrocarbon rubber are commercially available. Applicable commercial products include, for example, the Nippon Polybutene (registered trademark) HV series manufactured by JX Nippon Oil & Energy Corporation and the Diana (registered trademark) process oil PW series manufactured by Idemitsu Kosan. It can be selected and used as appropriate.

<Other ingredients>
In addition to the above-mentioned components, the polyolefin composition of the present invention can contain various additives, resins other than component (A), etc., as long as they do not impair the effects of the present invention.

Examples of additives include crosslinking aids, heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, crystal nucleating agents, rust preventives, viscosity modifiers, and pigments. Among these, it is preferable to include an antioxidant, particularly a phenolic antioxidant, a sulfur-based antioxidant, or a phosphorus-based antioxidant.
The antioxidant is preferably contained in an amount of 0.1 to 1 part by mass based on 100 parts by mass of the polyolefin composition.

Examples of crosslinking aids include unsaturated cyanurate compounds. As the unsaturated cyanurate compound, triallyl cyanurate represented by triallyloxytriazine, triallyl isocyanurate, etc. is preferred. This is because the allyl group makes it possible to modify the ethylene/α-olefin copolymer and component (A), and the dynamic crosslinking reaction between the vinyl group and the allyl group contained therein proceeds. That is, the allyl group graft-modified and introduced into the modified ethylene/α-olefin copolymer with an unsaturated cyanurate compound is introduced into the ethylene/α-olefin copolymer and the component ( By addition reaction with the vinyl group of A) by radical chain transfer, the modified ethylene/α-olefin copolymers and the modified ethylene/α-olefin copolymer and component (A) bond to each other, resulting in a crosslinking reaction. Incidentally, these unsaturated cyanurate compounds may be used alone or in combination of two or more.

When an unsaturated cyanurate compound is used in the polyolefin composition of the present invention, it is preferably used in an amount of 0.01 to 5 parts by weight based on a total of 100 parts by weight of the ethylene/α-olefin copolymer and polyolefin.

Examples of other resins include polyolefin resins, polyester resins, polycarbonate resins, polymethyl methacrylate resins, rosin and its derivatives, terpene resins, petroleum resins and their derivatives, alkyd resins, alkylphenol resins, terpenephenol resins, and coumarons. Examples include indene resin, synthetic terpene resin, and alkylene resin.

[Modified polyolefin composition]
The polyolefin composition of the present invention contains the above-mentioned ethylene/α-olefin copolymer and polyolefin, the above-mentioned unsaturated silane compound, peroxide, and optionally component (A), and further a softener for hydrocarbon rubber. The modified polyolefin composition of the present invention can be obtained by graft modification and/or chemical crosslinking of the polyolefin composition.

The method of graft modification and/or chemical crosslinking is not particularly limited, and can be carried out according to known methods, such as solution modification, melt modification, solid phase modification by irradiation with electron beams or ionizing radiation, or in a supercritical fluid. The modification of is preferably used. Among these, melt modification with excellent equipment and cost competitiveness is preferred, and melt kneading modification using an extruder with excellent continuous productivity is more preferred.
Examples of devices used for melt-kneading modification include a single screw extruder, a twin screw extruder, a Banbury mixer, and a roll mixer. Among these, single-screw extruders and twin-screw extruders are preferred because of their excellent continuous productivity.

Generally, graft modification of an ethylene/α-olefin copolymer with an unsaturated silane compound and/or peroxide cleaves the carbon-hydrogen bonds of the ethylene/α-olefin copolymer to generate carbon radicals. This is carried out by a graft reaction in which an unsaturated functional group is added to this.
As a source for generating carbon radicals, in addition to the above-mentioned electron beams and ionizing radiation, it is also possible to use a high temperature method or a radical generator such as an organic or inorganic peroxide. From the viewpoint of cost and operability, it is preferable to use organic peroxides.

The radical generator used in producing the modified polyolefin composition of the present invention is not limited, but examples include organic radical generators included in the group of hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxy esters, and ketone peroxides. Examples include oxides and azo compounds.

Generally used melt extrusion modification operations include the ethylene/α-olefin copolymer, polyolefin, unsaturated silane compound and/or peroxide, component (A) as necessary, and hydrocarbon rubber. The softener and other ingredients are blended, put into a kneader or extruder, and extruded while being heated and melted and kneaded.The molten resin coming out of the die is cooled in a water tank, etc. to form a modified polyolefin composition. This is what you get.
When producing the modified polyethylene composition of the present invention by kneading it in a single-screw extruder or twin-screw extruder, the melt-kneading is usually carried out at a temperature of 140 to 240°C, preferably 160 to 220°C. I can do it.

The blending ratios of the ethylene/α-olefin copolymer, polyolefin, unsaturated silane compound, and peroxide are as described above.
The blending ratio of the unsaturated silane compound and the peroxide is not particularly limited, but the preferred blending ratio is 1 to 20 parts by weight of the peroxide per 100 parts by weight of the unsaturated silane compound. If the amount of peroxide relative to the unsaturated silane compound is at least the above lower limit, a sufficient amount of radicals will be generated and the required amount of modification will be easily obtained, and if it is below the above upper limit, ethylene/ This tends to make it easier to suppress deterioration of α-olefin copolymers and polyolefins.

[Silanol condensation catalyst]
By blending a silanol condensation catalyst into the polyolefin composition of the present invention, the silane-modified polyolefin in the polyolefin composition can be subjected to an intermolecular crosslinking reaction.

Silanol condensation catalysts that can be used in the present invention are selected from the group consisting of metal organic acid salts, titanates, borates, organic amines, ammonium salts, phosphonium salts, inorganic and organic acids, and inorganic acid esters. One or more kinds of compounds can be mentioned.

Examples of metal organic acid salts include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, stannous acetate, stannous octoate, cobalt naphthenate, lead octylate, lead naphthenate, and octyltin dilaurate. Examples include zinc acid, zinc caprylate, iron 2-ethylhexanoate, iron octylate, and iron stearate.
Examples of the titanate include tetrabutyl titanate, tetranonyl titanate, and bis(acetylacetonitrile) di-isopropyl titanate.
Examples of organic amines include ethylamine, dibutylamine, hexylamine, triethanolamine, dimethylsawyaamine, tetramethylguanidine, and pyridine.
Examples of ammonium salts include ammonium carbonate and tetramethylammonium hydroxide.
Examples of phosphonium salts include tetramethylphosphonium hydroxide.
Examples of inorganic acids and organic acids include sulfonic acids such as sulfuric acid, hydrochloric acid, acetic acid, stearic acid, maleic acid, toluenesulfonic acid, and alkylnaphthylsulfonic acid.
Examples of inorganic acid esters include phosphoric esters such as ethylhexyl phosphate.

Among these, preferred are metal organic acid salts, sulfonic acids, and phosphoric acid esters, and more preferred are tin metal carboxylates, such as dioctyltin dilaurate, alkylnaphthylsulfonic acid, and ethylhexyl phosphate.
One type of silanol condensation catalyst may be used alone, or two or more types may be used in combination.

The amount of the silanol condensation catalyst blended is not particularly limited, but is preferably 0.0001 to 0.01 parts by mass, more preferably 0.0001 to 0.005 parts by mass, based on 100 parts by mass of the polyolefin composition. Part by mass. When the amount of the silanol condensation catalyst is at least the above lower limit, the crosslinking reaction tends to proceed sufficiently and the heat resistance tends to be good, so it is preferable, and when it is below the above upper limit, early crosslinking is difficult to occur in the extruder. This is preferable because it tends to make the strand surface and product appearance less likely to become rough.

The silanol condensation catalyst is preferably used as a masterbatch containing a polyolefin and a silanol condensation catalyst. Polyolefins that can be used in this masterbatch include polyethylene, polypropylene, propylene/ethylene copolymers, and the like.

When a silanol condensation catalyst is used as a masterbatch containing a polyolefin and a silanol condensation catalyst, the content of the silanol condensation catalyst in the masterbatch is not particularly limited, but is preferably 0.1 to 5.0% by mass.

A commercial product can be used as the masterbatch containing the silanol condensation catalyst, and for example, "LZ082" manufactured by Mitsubishi Chemical Corporation can be used.

[Crosslinked polyolefin composition]
In the polyolefin composition of the present invention, when an unsaturated silane compound is used, the above-mentioned silanol condensation catalyst is blended, molded by various molding methods such as extrusion molding, injection molding, press molding, etc., and then exposed to a water atmosphere. This allows the crosslinking reaction between silanol groups to proceed, resulting in a crosslinked polyolefin composition. Various conditions can be used to expose the product to a water atmosphere, including leaving it in air containing moisture, blowing air containing water vapor, immersing it in a water bath, and spraying it with hot water in the form of a mist. For example, the method of

In addition, in the polyolefin composition of the present invention, when a peroxide is used alone, there is no need to blend the aforementioned silanol condensation catalyst, and residual peroxide The crosslinking reaction can further proceed with a radical generator such as a polyolefin, resulting in a crosslinked polyolefin composition.

In the polyolefin composition of the present invention, when an unsaturated silane compound is used, the hydrolyzable alkoxy group derived from the unsaturated silane compound used for graft modification of the ethylene/α-olefin copolymer is dissolved in the presence of a silanol condensation catalyst. Silanol groups are generated by reacting with water and hydrolyzing, and the silanol groups are further dehydrated and condensed with each other, whereby a crosslinking reaction progresses and the modified polyolefins are bonded to each other to produce a crosslinked polyolefin composition.

The rate of progress of the crosslinking reaction is determined by the conditions of exposure to the water atmosphere, but it is usually sufficient to expose at a temperature range of 20 to 130° C. and for a period of 10 minutes to one week. Preferred conditions are a temperature range of 20-130°C and a time range of 1-160 hours. When using air containing moisture, the relative humidity is selected from the range of 1 to 100%.

In order for the crosslinked polyolefin composition to exhibit excellent properties over a long period of time, the gel fraction (crosslinking degree) of the crosslinked polyolefin composition is preferably 0% or more, more preferably 1% or more. preferable. The gel fraction is adjusted by changing the amount of the unsaturated silane compound and/or peroxide in the polyolefin composition, the type and amount of the silanol condensation catalyst, the crosslinking conditions (temperature, time), etc. be able to. The upper limit of this gel fraction is not particularly limited, but is usually 90%. The gel fraction can be measured by the method described in the Examples section below.

[Cylindrical molded body]
The cylindrical molded article of the present invention can be obtained by molding the polyolefin composition of the present invention into a cylindrical shape.
The layer thickness (wall thickness) of the cylindrical molded body is preferably 0.5 to 10 mm. If the layer thickness is below the above upper limit, it will be easy to cool during extrusion cooling and easy to wind up. Moreover, if it is more than the said lower limit, it will be hard to sag during extrusion, hard to break even if internal pressure is applied, and will be excellent in durability.

The outer diameter of the cylindrical molded body is preferably 7 to 20 mm. If the outer diameter is below the above upper limit, it will be easy to cool during extrusion cooling and easy to wind up. Moreover, if it is more than the said lower limit, it will not be easily crushed and the contents can be efficiently passed through.

The cylindrical molded article of the present invention may have a single layer structure or a multilayer structure.

[Method for manufacturing cylindrical molded body]
There are no particular limitations on the method for producing the cylindrical molded article of the present invention. For example, pellets of the polyolefin composition of the present invention are fed into a hopper of a pipe manufacturing device, heated and melted in an extruder, and then passed through a die into a cylindrical molded article. One method is to extrude it and cool it to make a pipe.
More specifically, the polyolefin composition of the present invention is extruded from an extruder through a die at a temperature of, for example, 150 to 230°C, sized, cooled in a cooling water bath, and cut or rolled up through a take-up machine.

As the extruder, a single screw extruder, a twin screw extruder, etc. can be used.
As the die, any type of die such as a straight head die, a cross head die, an offset die, etc. can be used.
As the sizing method, any method such as a sizing plate method, an outside mandrel method, a sizing box method, an inside mandrel method, etc. can be used.

[Application]
Applications of the cylindrical molded product of the present invention are not particularly limited, but include, for example, automotive hose parts such as automotive cooling water hoses and rubber hoses; water supply, hot water supply, floor heating, road heating, EcoCute and Ene-Farm piping, foods, and various other products. It can be suitably used as industrial cylindrical molded bodies such as tubes and piping for industrial factories, beverage tubes for vending machines, and compressed air distribution tubes.

EXAMPLES Hereinafter, the present invention will be specifically explained using examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, the values of various manufacturing conditions and evaluation results in the following examples have the meaning of preferable upper or lower limits in the embodiments of the present invention, and the preferable ranges are different from the above-mentioned upper or lower limits. , it may be a range defined by the values of the following examples or a combination of values of the examples.
In the following description, "part" indicates "part by mass", and "%" indicates "% by mass".

〔material〕
In the examples and comparative examples of the present invention, the following raw materials were used.

<Ethylene/α-olefin copolymer>
・PE-1: Engage (registered trademark) XLT8677
Manufactured by Dow DuPont Elastomers, metallocene linear low density polyethylene (ethylene/1-octene copolymer), MFR: 0.5 g/10 min (190°C, 2.16 kg load), density: 0.87 g/cm ³ , melting end point: 128°C, A hardness: 50, with external talc additive PE-2: Infuse (registered trademark) 9010
Manufactured by Dow DuPont Elastomers, metallocene linear low density polyethylene (ethylene/1-octene copolymer), MFR: 0.5 g/10 min (190°C, 2.16 kg load), density: 0.88 g/cm ³ , melting end point: 128°C, A hardness: 77, no external additives, PE-3: Engage (registered trademark) 7256
Manufactured by Dow DuPont Elastomers, metallocene linear low density polyethylene (ethylene-butene copolymer), MFR: 2.5 g/10 minutes (190°C, 2.16 kg load), density: 0.89 g/cm ³ , melting End point: 90°C, A hardness: 85, no external additives, PE-4: Mitsui EPT (registered trademark) 3072EM
Manufactured by Mitsui Chemicals, metallocene catalyst system EPDM, Mooney viscosity: 51ML (value after 1 minute of preheating and 4 minutes after rotation) 125°C

<Polyolefin>
・PP-1: Novatec PP (registered trademark) FY6
Propylene/ethylene copolymer manufactured by Nippon Polypro Co., Ltd., MFR: 2.5 g/10 minutes (230°C, 2.16 kg load), melting end point: 172°C
・PP-2: Zelas (registered trademark) 7025
Propylene/ethylene copolymer manufactured by Mitsubishi Chemical Corporation, MFR: 2.5 g/10 minutes (230°C, 2.16 kg load), melting end point: 168°C

<Component (A)>
・Styrenic thermoplastic elastomer: Asaprene (registered trademark) T411
Manufactured by Asahi Kasei, polystyrene/butadiene/styrene block polymer, MFR: 0 g/10 min (190°C, 2.16 kg load), density: 0.94 g/cm ³ , mass proportion of block P: 30 mass %

<Softener for hydrocarbon rubber>
・Oil: Diana (registered trademark) process oil PW90
Manufactured by Idemitsu Kosan Co., Ltd., petroleum-based hydrocarbon, kinematic viscosity 380 mm ² /s, density (15°C): 0.88 g/cm ³

<Unsaturated silane compound>
・Vinyltrimethoxysilane: KBM-1003 (manufactured by Shin-Etsu Chemical Co., Ltd.)

<Unsaturated cyanurate compound (crosslinking aid)>
・Triaryl isocyanurate: TAIC (manufactured by Nippon Kasei Co., Ltd.)

<Peroxide>
・POX1: Di(2-t-butylperoxyisopropyl)benzene, Perbutyl P (manufactured by NOF Corporation)
・POX2: di-t-butyl peroxide, Perbutyl D (manufactured by NOF Corporation)

<Catalyst masterbatch (MB)>
・Silanol condensation catalyst MB: LZ082
Manufactured by Mitsubishi Chemical Corporation, linear low-density polyethylene containing 1% tin catalyst (dioctyltin dilaurate), MFR of low-density polyethylene: 3 g/10 minutes (190°C, 2.16 kg load), density of low-density polyethylene: 0.92 g /cm ³ , melting end point of low density polyethylene: 130°C

[Measurement/evaluation method]
The methods for measuring and evaluating various physical properties and characteristics are as follows.

[Measurement and evaluation of ethylene/α-olefin copolymer and polypropylene]
<Melting end point>
Using a differential scanning calorimeter manufactured by Hitachi High-Tech Science Co., Ltd. under the trade name "DSC6220", approximately 5 mg of the sample was heated from 20 °C to 200 °C at a heating rate of 100 °C/min in accordance with JIS K7121. After holding at 200°C for 3 minutes, the temperature was lowered to -10°C at a cooling rate of 10°C/min, and then the temperature was raised to 200°C at a heating rate of 10°C/min. Extrapolated peak end point from the thermogram measured. (°C) was calculated and set as the melting end point.

[Measurement and evaluation of modified polyolefin composition and crosslinked polyolefin composition]
<Melt flow rate (MFR)>
Measured at 190° C. and 10 kg load in accordance with JIS K7210 (1999).

<A hardness>
The produced sheet-like molded product was punched out into a circular shape with a diameter of 30 mm, six sheets were stacked, and the test temperature was measured using ASKER CL150 at a test temperature of 23° C. with reference to JIS K6253.

<Exterior>
Using the materials described below, a 10A pipe (outer diameter 13 mm, inner diameter 10 mm, thickness 1.5 mm) was molded using a PMS40 pipe molding machine manufactured by IKG at a set temperature of 200°C. The appearance of the resulting pipe after water cooling was visually confirmed and evaluated as follows.
OK: The surface is smooth and the film thickness is uniform. NG: The surface is uneven and the film thickness is uneven.

<Gel fraction>
The manufactured cylindrical molded body was cut out into a piece with a length of 5 mm and a width of 5 mm, and after Soxhlet extraction at the boiling point of xylene for 10 hours, the proportion of insoluble matter (% by mass) was measured.

<Pipe creep failure time>
Pipe creep rupture time was evaluated based on ISO9080 under conditions of circumferential stress of 0.8 MPa and temperature of 95°C.

[Example 1]
53 parts of PE-1 as ethylene/α-olefin copolymer, 13 parts of ethylene/propylene/diene copolymer (EPDM), 20 parts of PP-1 as polyolefin, styrene thermoplastic elastomer as component (A) 7 parts of oil as a softener for hydrocarbon rubber, 2.0 parts of vinyltrimethoxysilane, an unsaturated silane compound, per 100 parts of the elastomer component, and an unsaturated cyanurate compound (triallyl isocyanurate). 0.04 part of peroxide, 0.2 part of POX1, and 0.08 part of POX2, which are peroxides, were blended and stirred in a blender.
After that, the strands are fed into a twin-screw extruder (TEM26-SS, manufactured by Toshiba Machine Co., Ltd.) set at a temperature of 200°C, and the strands that come out of the nozzle are cooled and solidified in a water tank, and then cut into pellets and denatured. A polyolefin composition was obtained. Table 1 shows the physical properties of the obtained modified polyolefin composition.

To 100 parts of the modified polyolefin composition obtained above, 5 parts of LZ033 was added as a silanol condensation catalyst MB to obtain a modified polyolefin composition containing catalyst MB. This was molded using an injection molding machine at 200°C and immersed in warm water at 80°C for 24 hours to produce a 2 mm thick sheet-like molded product made of the crosslinked polyolefin composition. The A hardness of the obtained crosslinked polyolefin composition was evaluated.
Further, after producing a 10A pipe using the above-described method, it was immersed in warm water at 80°C for 24 hours to produce a cylindrical molded body made of a crosslinked polyolefin composition. Table 1 shows the evaluation and measurement results of the appearance, gel fraction, and pipe creep rupture time of the pipe made of the obtained crosslinked polyolefin composition.

[Example 2]
Modification was carried out in the same manner as in Example 1, except that PE-2 and PP-2 were used as elastomer components, and an unsaturated silane compound and peroxide POX2 were used as crosslinking aid components in the amounts shown in Table 1. A polyolefin composition and a crosslinked polyolefin composition were obtained, and various evaluations were performed in the same manner as in Example 1.
The results are shown in Table 1.

[Comparative Examples 1 to 3]
A modified polyolefin composition and a crosslinked polyolefin composition were obtained in the same manner as in Example 1, except that the types and compositions of the raw materials used were changed as shown in Table 1, and various evaluations were performed in the same manner as in Example 1. .
The results are shown in Table 1.

The following results can be found from the above results.

As shown in Examples 1 and 2, a crosslinked polyolefin composition using an ethylene/α-olefin copolymer with a melting end point of 128°C and a polyolefin with a melting end point of around 170°C has a melting end point of 170°C. The pipe creep rupture time was longer than that of Comparative Examples 1 to 3, which used an ethylene/α-olefin copolymer containing no nearby polyolefin.
In addition, Examples 1 and 2 had a higher melting point than Comparative Example 3, which used only the ethylene/α-olefin copolymer, so the solidification rate was faster in water cooling, and a good appearance was obtained.

Furthermore, since Examples 1 and 2 had higher A hardness, yield modulus was improved and they could withstand high water pressure, they exhibited a longer pipe creep rupture time than Comparative Example 1 which did not contain polyolefin.
Furthermore, Examples 1 and 2 have a higher melting point than Comparative Example 2, which used the ethylene/α-olefin copolymer alone, so they have excellent durability in hot water at high temperatures, and can be used for long pipes. The creep rupture time is shown.

When the melting end point is low as in Comparative Example 2, the crystals melt in hot water close to the boiling point, so the pipe creep rupture time is short and the pipe cannot withstand the passage of hot water.
Comparative Example 3, which uses an ethylene/α-olefin copolymer alone with a relatively high melting end point, has a low hardness, has many amorphous parts, and has a slow solidification rate by water cooling, resulting in unevenness on the surface. Moreover, the film thickness becomes uneven and the appearance of the cylindrical molded product is poor. If the film thickness is non-uniform, the circumferential stress in the pipe creep test will also be non-uniform, so Comparative Example 3 resulted in a cylindrical molded body that was not worthy of conducting the creep test.

From the above, a cylindrical molded body made of a crosslinked polyolefin composition formed from a modified polyolefin composition containing an ethylene/α-olefin copolymer with a high melting end point and a polyolefin with a higher melting end point is A. It can be seen that the cylindrical molded product has low hardness, has excellent workability as a cylindrical molded product, and has a long pipe creep rupture time.

The cylindrical molded article of the present invention using the polyolefin composition of the present invention containing an ethylene/α-olefin copolymer with a high melting end point and a polyolefin with a higher melting end point has an excellent appearance and is flexible and easy to work with. Excellent in sex. Moreover, the cylindrical molded product of the present invention has a long pipe creep rupture time, so hot water at a temperature close to boiling water can be passed through with a certain amount of water pressure, making it possible to create a cylindrical molded product that is difficult to break even after a short period of use. can give.
Therefore, the cylindrical molded body of the present invention is suitable for automotive hose members such as automotive cooling water hoses and rubber hoses; It can be suitably used as industrial cylindrical molded bodies such as piping, beverage tubes for vending machines, and compressed air delivery tubes.

Claims (4)

An ethylene/α-olefin copolymer whose melting end peak temperature measured by a differential scanning calorimeter (DSC) is 115°C or higher, and a differential scanning calorimeter (DSC) different from the ethylene/α-olefin copolymer A cylindrical molded article formed by molding a polyolefin composition containing a polyolefin having a melting end peak temperature of 125° C. or higher as measured by DSC),
A cylindrical molded article, wherein the polyolefin composition further contains a peroxide and an unsaturated silane compound, and is crosslinked with the peroxide and the unsaturated silane compound. The cylindrical molded article according to claim 1, wherein the polyolefin accounts for 2 to 50% by mass in a total of 100% by mass of the ethylene/α-olefin copolymer and the polyolefin. The cylindrical molded article according to claim 1 or 2, wherein the polyolefin is a propylene-based polymer containing propylene units as a main component. An ethylene/α-olefin copolymer whose melting end peak temperature measured by a differential scanning calorimeter (DSC) is 115°C or higher, and a differential scanning calorimeter (DSC) different from the ethylene/α-olefin copolymer 0.01 to 1.00 parts by mass of peroxide and 0.1 to 5 parts by mass of unsaturated silane compound for a total of 100 parts by mass of polyolefin having a melting end peak temperature of 125° C. or higher as measured by DSC). A method for manufacturing a cylindrical molded body, which comprises blending .0 parts by mass and molding the same.