Cylindrical molded body and coolant tube

Abstract

To provide a cylindrical molded body having high pressure resistance and excellent flexibility.SOLUTION: A cylindrical molded body comprises a crosslinked polyolefin composition obtained by silane crosslinking of a modified polyolefin composition comprising the following components (A) and (B): component (A): an alkoxysilane-modified ethylene-α-olefin copolymer having a melting peak temperature of 110°C or higher as measured by differential scanning calorimetry (DSC) and a density of less than 0.910 g / cm3; component (B): an alkoxysilane-modified ethylene polymer having a density of 0.910 g / cm3 or more and 0.970 g / cm3 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cylindrical molded body and a coolant tube using the cylindrical molded body. [Background technology]

[0002] Cylindrical molded articles such as tap water pipes and heating pipes used for cold and hot water supply, floor heating, road heating, etc., and industrial cylindrical molded articles such as beverage tubes, tubes for transporting liquid foods, and tubes for delivering compressed air, are required to have a long pipe creep failure time in order to prevent leakage of the contents.

[0003] 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 where a long pipe creep rupture time is required from the viewpoint of durability.

[0004] Patent Document 1 proposes a cylindrical molding that has a good appearance, excellent resistance to hot internal pressure creep, and is flexible and easy to bend, stretch, and work during construction. The cylindrical molding is obtained by molding a polyolefin composition containing 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 a polyolefin different from the ethylene-α-olefin copolymer having a melting end peak temperature of 125°C or higher as measured by a differential scanning calorimeter (DSC). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-81016 Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors' investigations revealed that, since the cylindrical molded body of Patent Document 1 contains a mixture of different olefin-based polymers, fracture may occur originating from the interface between the polymers in a creep test, and therefore, when a higher pressure is applied than under the conditions of Patent Document 1, the pressure resistance is low, and there is room for further improvement in the pressure resistance. In particular, among the uses of cylindrical molded articles, coolant tubes require flexibility to improve workability during bending, and therefore, for such uses, it is necessary to provide pressure resistance while maintaining flexibility.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a cylindrical molded article that has excellent pressure resistance and flexibility. [Means for solving the problem]

[0008] As a result of extensive research into achieving the above-mentioned object, the present inventors have found that the above-mentioned problems can be solved by using a crosslinked polyolefin composition obtained by silane crosslinking a modified polyolefin composition comprising an alkoxysilane-modified ethylene-α-olefin copolymer having a specific melting peak temperature and density, and an alkoxysilane-modified ethylene polymer having a specific density, and have thereby completed the present invention. That is, the gist of the present invention is as follows.

[0009] [1] A cylindrical molded article comprising a crosslinked polyolefin composition obtained by silane crosslinking a modified polyolefin composition containing the following components (A) and (B): Component (A): An alkoxysilane-modified ethylene-α-olefin copolymer, which has a melting peak temperature of 110°C or higher as measured by a differential scanning calorimeter (DSC) and a density of 0.910 g / cm 3 Alkoxysilane-modified ethylene-α-olefin copolymers with a viscosity of less than 1000 ppm Component (B): an alkoxysilane-modified ethylene polymer, the density of which is 0.910 g / cm 3More than 0.970g / cm 3 An alkoxysilane-modified ethylene polymer having the following structure:

[0010] [2] The cylindrical molded article according to [1], wherein the crosslinked polyolefin composition has an A hardness of 86 or more and 95 or less.

[0011] [3] The cylindrical molded article according to [1] or [2], wherein the crosslinked polyolefin composition has a gel fraction of 82% or more.

[0012] [4] The density of the crosslinked polyolefin composition is 0.910 g / cm 3 The cylindrical molded article according to any one of [1] to [3] below.

[0013] [5] The cylindrical molded article according to any one of [1] to [4], wherein the crosslinked polyolefin composition has a flexural modulus of 300 MPa or less.

[0014] [6] A cylindrical molded article made of a crosslinked polyolefin composition obtained by silane crosslinking an alkoxysilane-modified ethylene polymer having an ethylene unit content of 60 mass% or more, and satisfying the following conditions (1) to (3): Condition (1): Density is 0.887 g / cm 3 More than 0.910g / cm 3 Is less than or equal to Condition (2): A hardness is between 86 and 95 Condition (3): Gel fraction must be 82% or more

[0015] [7] A coolant tube using the cylindrical molded article according to any one of [1] to [6]. [Effects of the Invention]

[0016] According to the present invention, a cylindrical molded article is provided which is flexible and has excellent workability during construction, such as bending and stretching, as well as excellent pressure resistance at high pressures, a long pipe creep rupture time, and excellent water flow durability. The cylindrical molded article of the present invention has excellent flexibility and can therefore be suitably used for coolant tubes, which are often bent during installation, particularly coolant tubes for electric vehicles. DETAILED DESCRIPTION OF THE INVENTION

[0017] The following describes in detail an embodiment of the present invention. However, the following description is an example of an embodiment of the present invention, and the present invention is not limited to the contents of the following description as long as it does not go beyond the gist of the present invention.

[0018] The cylindrically shaped article of the present invention is a cylindrically shaped article made of a crosslinked polyolefin composition (hereinafter, sometimes referred to as the "crosslinked polyolefin composition of the present invention") obtained by silane crosslinking a modified polyolefin composition (hereinafter, sometimes referred to as the "modified polyolefin composition of the present invention") containing the following component (A) and component (B): Component (A): An alkoxysilane-modified ethylene-α-olefin copolymer, which has a melting peak temperature of 110°C or higher as measured by a differential scanning calorimeter (DSC) and a density of 0.910 g / cm 3 Alkoxysilane-modified ethylene-α-olefin copolymers with a viscosity of less than 1000 ppm Component (B): an alkoxysilane-modified ethylene polymer, the density of which is 0.910 g / cm 3 More than 0.970g / cm 3 An alkoxysilane-modified ethylene polymer having the following structure:

[0019] The modified polyolefin composition of the present invention can be obtained by mixing component (A) and component (B). However, industrially, it is preferred to prepare a polyolefin composition before alkoxysilane modification (hereinafter, sometimes referred to as "the polyolefin composition of the present invention") by mixing component (A) an ethylene-α-olefin copolymer before alkoxysilane modification, component (B) an ethylene polymer before alkoxysilane modification, an unsaturated silane compound and peroxide for alkoxysilane modification, and further other components used as necessary, and then modify this polyolefin composition with alkoxysilane. Hereinafter, the present invention will be described in detail in accordance with the method for producing the modified polyolefin composition of the present invention according to this method, and then silane-crosslinking this modified polyolefin composition to produce the crosslinked polyolefin composition of the present invention. However, the modified polyolefin composition of the present invention can also be produced by mixing an alkoxysilane-modified ethylene-α-olefin copolymer (component (A)) and an alkoxysilane-modified ethylene polymer (component (B)) that have been separately modified with alkoxysilanes. In this case, the alkoxysilane modification method can be carried out in the same manner as described below, except that an ethylene-α-olefin copolymer and an ethylene polymer are used, respectively, instead of a mixture of an ethylene-α-olefin copolymer and an ethylene polymer.

[0020] [Polyolefin composition] First, the polyolefin composition of the present invention containing an ethylene-α-olefin copolymer and an ethylene-based polymer before alkoxysilane modification, an unsaturated silane compound, a peroxide, etc. will be described.

[0021] (Ethylene-α-olefin copolymer) The ethylene-α-olefin copolymer used in the present invention has the above-mentioned specific melting peak temperature and density, and contains ethylene units and α-olefin units. The type of ethylene-α-olefin copolymer is not particularly limited as long as it satisfies these conditions, and any known ethylene-α-olefin copolymer can be used as appropriate.

[0022] Specific examples of ethylene-α-olefin copolymers include copolymers of ethylene with one or more α-olefins having 3 to 10 carbon atoms, such as ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-1-hexene copolymer, and ethylene-1-octene copolymer. From the viewpoints of improving flexibility and the degree of crosslinking, ethylene-1-octene copolymer is preferred.

[0023] The type of catalyst used in producing the ethylene-α-olefin copolymer is not particularly limited, but examples thereof include Ziegler-Natta catalysts and metallocene catalysts. Among these, ethylene-α-olefin copolymers produced using a metallocene catalyst are preferred.

[0024] The ethylene-α-olefin copolymer used in the present invention has a melting peak temperature of 110°C or higher as measured by differential scanning calorimetry (DSC). When the melting peak temperature of the ethylene-α-olefin copolymer is 110°C or higher, the copolymer can maintain its shape due to crystallization even at high temperatures. From this perspective, the melting peak temperature of the ethylene-α-olefin copolymer is 110°C or higher, and preferably 115°C or higher. However, if the melting peak temperature of the ethylene-α-olefin copolymer is excessively high, there is a risk of unmelted particles occurring during heating during molding or premature crystallization (melt fracture) during cooling during molding, resulting in a poor appearance. Therefore, the melting peak temperature of the ethylene-α-olefin copolymer is usually 145°C or lower. The melting peak temperature of the ethylene-α-olefin copolymer is measured by the method described in the Examples section below.

[0025] The density of the ethylene-α-olefin copolymer used in the present invention (measured according to JIS K6922-1,2:1997) is 0.910 g / cm 3 less than 0.850 g / cm 3 More than 0.910g / cm 3 More preferably, it is 0.860 to 0.900 g / cm3 When the density is less than the upper limit, the flexibility is excellent and the material tends to be easily bent. When the density is equal to or greater than the lower limit, the material tends to be less sticky, can be automatically introduced into a hopper by suction, and does not easily adhere to the hopper, and thus the material tends to have excellent moldability.

[0026] The melt flow rate (MFR) of the ethylene-α-olefin copolymer used in the present invention is preferably 0.1 to 50 g / 10 min, as measured at a temperature of 190°C and a load of 2.16 kg in accordance with JIS K7210 (1999). If the MFR is equal to or less than the upper limit, the molten resin is less likely to drip during molding, improving yield and facilitating molding. If the MFR is equal to or greater than the lower limit, the motor load during modification extrusion is small, preventing excessive resin pressure, improving productivity, and preventing surface roughness after molding. From these viewpoints, the MFR of the ethylene-α-olefin copolymer is preferably 0.1 g / 10 min or more, more preferably 0.5 g / 10 min or more, and is preferably 50 g / 10 min or less, more preferably 30 g / 10 min or less.

[0027] The ethylene-α-olefin copolymer used in the present invention has an A hardness of preferably 40 to 95, as measured at a temperature of 23°C, a humidity of 50%, and after 15 seconds in accordance with JIS K6253. If the A hardness is equal to or less than the upper limit, the cylindrical molded article is easily bent, workability during construction is improved, and distortion is less likely to occur when bent for use, resulting in improved long-term durability. If the A hardness is equal to or greater than the lower limit, the cylindrical molded article is easily solidified during cooling, improving the appearance during molding. In addition, the cylindrical molded article can withstand water pressure and the pressure of the contents, resulting in improved long-term durability. From these viewpoints, the A hardness of the ethylene-α-olefin copolymer is preferably 40 or more, more preferably 50 or more, and on the other hand, it is preferably 95 or less, more preferably 90 or less.

[0028] The ethylene-α-olefin copolymer used in the present invention is commercially available, for example, from the Engage® series manufactured by Dow Chemical Japan, the Kernel® series manufactured by Japan Polyethylene Corporation, the Infuse® series manufactured by Dow Chemical Japan, the Tafmer® series manufactured by Mitsui Chemicals, Inc., and the Evolue® series manufactured by Primer Polymers.

[0029] These ethylene-α-olefin copolymers may be used alone or in combination of two or more types differing in the type of α-olefin, copolymer composition, physical properties, etc.

[0030] Component (A) is produced by alkoxysilane-modifying such an ethylene-α-olefin copolymer with an unsaturated silane compound described below. Alternatively, components (A) and (B) can be produced by alkoxysilane modification with an unsaturated silane compound described below in the coexistence of an ethylene-α-olefin copolymer and an ethylene-based polymer.

[0031] (ethylene polymer) The ethylene polymer used in the present invention has a density of 0.910 to 0.970 g / cm 3 The copolymer may contain monomer units other than ethylene units. The monomer units other than the ethylene units contained in the ethylene-based polymer used in the present invention may be one or more of the α-olefin units contained in the ethylene-α-olefin copolymer described above, but preferably one type. The ethylene polymer may be an ethylene homopolymer containing 100% by mass of ethylene units.

[0032] The density of the ethylene polymer used in the present invention (measured according to JIS K6922-1,2:1997) is 0.910 g / cm 3 More than 0.970g / cm 3 The following is the result. The density of ethylene polymer is 0.910 g / cm3 If the density of the ethylene polymer is 0.970 g / cm or more, the amount of crystalline components in the composition is large, and the pressure resistance is increased, resulting in good pipe creep performance. 3 If the density is less than 0.920, it is possible to prevent poor appearance due to unmelted particles during heating of the molding or premature crystallization (melt fracture) during cooling of the molding. The density of the ethylene polymer is preferably 0.920 to 0.965 g / cm. 3 and more preferably 0.930 to 0.960 g / cm 3 is.

[0033] The ethylene polymer used in the present invention preferably has a melting peak temperature of 125°C or higher as measured by a differential scanning calorimeter (DSC). When the ethylene polymer has a melting peak temperature of 125°C or higher, pressure resistance at higher temperatures can be ensured, resulting in good pipe creep performance. From this perspective, the melting peak temperature of the ethylene polymer is preferably 125°C or higher, more preferably 130°C or higher. However, if the melting peak temperature of the ethylene polymer is excessively high, there is a risk of unmelted particles occurring during heating in molding or premature crystallization (melt fracture) during cooling in molding, resulting in poor appearance such as rough skin. Therefore, the melting peak temperature of the ethylene polymer is usually 180°C or lower.

[0034] Furthermore, the melting peak temperatures of the ethylene-α-olefin copolymer and the ethylene-based polymer are different, and in order to effectively obtain the above-mentioned effects obtained by mixing and using an ethylene-based polymer having a higher melting peak temperature than the ethylene-α-olefin copolymer, the melting peak temperature of the ethylene-based polymer is preferably at least 5°C higher, more preferably at least 10°C higher, than the melting peak temperature of the ethylene-α-olefin copolymer. On the other hand, since an excessively high melting peak temperature of the ethylene-based polymer is undesirable, the difference in the melting peak temperatures is preferably 50°C or less. The melting peak temperature of the ethylene polymer is measured by the method described in the Examples section below.

[0035] The melt flow rate (MFR) of the ethylene polymer used in the present invention is preferably 0.1 to 50 g / 10 min, as measured at a temperature of 190°C and a load of 2.16 kg in accordance with JIS K7210 (1999). If the MFR is equal to or less than the upper limit, the molten resin is less likely to drip during molding, improving yield and facilitating molding. If the MFR is equal to or greater than the lower limit, the motor load during modification extrusion is small, the resin pressure does not become too high, improving productivity and preventing surface roughness after molding. From these viewpoints, the MFR of the ethylene polymer is preferably 0.1 g / 10 min or more, more preferably 0.5 g / 10 min or more, and on the other hand, is preferably 50 g / 10 min or less, more preferably 30 g / 10 min or less.

[0036] The D hardness of the ethylene polymer used in the present invention is preferably 50 to 75, as measured at a temperature of 23°C, a humidity of 50%, and a maximum value according to JIS K7215. If the D hardness is equal to or less than the upper limit, the cylindrical molded article is easily bent, improving workability during construction. If the D hardness is equal to or more than the lower limit, the cylindrical molded article is easily solidified during cooling, improving the appearance during molding, and is able to withstand water pressure and the pressure of the contents, improving long-term durability. From these viewpoints, the D hardness of the ethylene polymer is preferably 50 or more, more preferably 55 or more, and on the other hand, it is preferably 75 or less, more preferably 70 or less.

[0037] The ethylene polymer used in the present invention is commercially available, and can be selected from, for example, the Novatec (registered trademark) series manufactured by Japan Polyethylene Corporation, the Hi-Zex (registered trademark) series, and the Evolue (registered trademark) series manufactured by Prime Polymer Co., Ltd.

[0038] These ethylene polymers may be used alone or in combination of two or more types differing in the type of α-olefin, copolymer composition, physical properties, etc.

[0039] <Unsaturated silane compounds> 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)

[0040] In the above formula (1), R is an ethylenically unsaturated hydrocarbon group, and R' are each independently a hydrocarbon group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms, and at least one of the R' is an alkoxy group having 1 to 10 carbon atoms.

[0041] In formula (1), R is preferably an ethylenically unsaturated hydrocarbon group having 2 to 10 carbon atoms, and more preferably an ethylenically unsaturated hydrocarbon group having 2 to 6 carbon atoms. Specific examples include alkenyl groups such as vinyl, propenyl, butenyl, and cyclohexenyl.

[0042] In formula (1), R' is preferably a hydrocarbon group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, more preferably a hydrocarbon group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. At least one of the 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 represented by R' may be an aliphatic group, an alicyclic group, or an aromatic group, but is preferably an aliphatic group. The alkoxy group having 1 to 10 carbon atoms represented by R' may be linear, branched, or cyclic, but is preferably linear or branched. When R' is a hydrocarbon group, specific examples include alkyl groups such as methyl, ethyl, isopropyl, t-butyl, n-butyl, i-butyl, and cyclohexyl; and aryl groups such as phenyl. When R' is an alkoxy group, specific examples include a methoxy group, an ethoxy group, an isopropoxy group, and a β-methoxyethoxy group.

[0043] When the unsaturated silane compound is represented by the formula (1), at least one of the three R's is an alkoxy group, but it is preferable that two R's are alkoxy groups, and it is more preferable that all R's are alkoxy groups.

[0044] Among the unsaturated silane compounds represented by formula (1), vinyltrialkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, and propenyltrimethoxysilane are preferred. This is because the vinyl group allows modification to ethylene-α-olefin copolymers, and the alkoxy group promotes the crosslinking reaction described below. That is, the alkoxy groups introduced by graft modification onto ethylene-α-olefin copolymers or ethylene-based polymers with unsaturated silane compounds react with water in the presence of a silanol condensation catalyst to hydrolyze and generate silanol groups, and the silanol groups undergo dehydration condensation with each other, bonding between ethylene-α-olefin copolymers, between ethylene-based polymers, or between ethylene-α-olefin copolymers and ethylene-based polymers, resulting in a crosslinking reaction.

[0045] These unsaturated silane compounds may be used alone or in combination of two or more.

[0046] <Peroxide> The peroxide used in the present invention is used to generate carbon radicals to graft-modify the ethylene-α-olefin copolymer and the ethylene-based polymer with the unsaturated silane compound and / or to abstract hydrogen from the ethylene-α-olefin copolymer and the ethylene-based polymer, thereby accelerating the crosslinking reaction of the ethylene-α-olefin copolymer and the ethylene-based polymer.

[0047] As the peroxide, an organic peroxide is preferred from the viewpoint of compatibility with the resin. Examples of organic peroxides include hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide; dialkyl peroxides such as dicumyl peroxide, di-t-butyl peroxide, t-butylperoxy 2-ethylhexanoate, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 2,5-dimethyl-2,5-di-t-butylperoxyhexyne-3, and di(2-t-butylperoxyisopropyl)benzene; diacyl peroxides such as lauryl peroxide and benzoyl peroxide; peroxy esters such as t-butyl peroxyacetate, t-butyl peroxybenzoate, and t-butylperoxyisopropylcarbonate; and ketone peroxides such as cyclohexanone peroxide.

[0048] These organic peroxides may be used alone or in combination of two or more.

[0049] From the viewpoints of grafting efficiency, chain transfer efficiency, and hygiene such as odor, the organic peroxide is preferably t-butylperoxy 2-ethylhexanoate, di(2-t-butylperoxyisopropyl)benzene, or di-t-butyl peroxide.

[0050] <Content of each ingredient> In the polyolefin composition of the present invention, the proportion of the ethylene polymer in the total of 100% by mass of the ethylene-α-olefin copolymer and the ethylene polymer is preferably 2 to 50% by mass, more preferably 5 to 45% by mass. It is preferable that the content of the ethylene polymer in the polyolefin composition of the present invention is within the above range in terms of flexibility, pressure resistance, and appearance. If the content of the ethylene polymer is equal to or less than the above upper limit, the cylindrical molded article is flexible and has good workability during construction. If the content of the ethylene polymer is equal to or more than the above lower limit, the pressure resistance is good, and the cylindrical molded article is easily cured when water-cooled during molding, resulting in an excellent appearance.

[0051] When the polyolefin composition of the present invention contains an unsaturated silane compound, the content of the unsaturated silane compound is preferably 0.1 to 5.0 parts by mass per 100 parts by mass of the ethylene-α-olefin copolymer and the ethylene polymer in total. When the polyolefin composition of the present invention contains a peroxide, the content of the peroxide is preferably 0.01 to 1.00 parts by mass per 100 parts by mass of the total of the ethylene-α-olefin copolymer and the ethylene polymer. When the content of the peroxide and the unsaturated silane compound is equal to or greater than the lower limit, a predetermined modification amount necessary for achieving the effects of the present invention can be obtained, whereas when the content is equal to or less than the upper limit, there is no risk of unreacted substances remaining and adversely affecting performance.

[0052] <Other ingredients> In addition to the above components, the polyolefin composition of the present invention may contain other components such as various additives and resins other than the ethylene-α-olefin copolymer and ethylene-based polymer, within the range that does not impair the effects of the present invention.

[0053] Examples of additives include crosslinking aids, heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, crystal nucleating agents, rust inhibitors, viscosity modifiers, and pigments. Among these, it is preferable to add an antioxidant, particularly a phenol-based 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 relative to 100 parts by mass of the polyolefin composition of the present invention.

[0054] Examples of crosslinking aids include unsaturated cyanurate compounds. Preferred examples of unsaturated cyanurate compounds include triallyl cyanurates, such as triallyloxytriazine and triallyl isocyanurate. This is because the allyl groups allow modification of the ethylene-α-olefin copolymer and component (A), promoting a dynamic crosslinking reaction between the vinyl groups and the allyl groups contained therein. Specifically, the allyl groups grafted onto the modified ethylene-α-olefin copolymer and modified ethylene-based polymer with the unsaturated cyanurate compound undergo an addition reaction with the vinyl groups of the ethylene-α-olefin copolymer, ethylene-based polymer, and their alkoxysilane-modified derivatives via radical chain transfer in the presence of a radical-generating peroxide. This results in crosslinking reactions between alkoxysilane-modified ethylene-α-olefin copolymers, between alkoxysilane-modified ethylene-based polymers, and between alkoxysilane-modified ethylene-α-olefin copolymers and alkoxysilane-modified ethylene-based polymers. These unsaturated cyanurate compounds may be used alone or in combination.

[0055] 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 mass per 100 parts by mass of the ethylene-α-olefin copolymer and the ethylene polymer combined.

[0056] Examples of other resins include polyolefin resins other than ethylene-α-olefin copolymers and ethylene-based polymers, polyester resins, polycarbonate resins, polymethyl methacrylate resins, rosin and its derivatives, terpene resins, petroleum resins and their derivatives, alkyd resins, alkylphenol resins, terpene phenol resins, coumarone-indene resins, synthetic terpene resins, and alkylene resins.

[0057] [Modified polyolefin composition] The modified polyolefin composition of the present invention can be obtained by graft-modifying and / or chemically crosslinking the ethylene-α-olefin copolymer and ethylene-based polymer with the polyolefin composition of the present invention, which contains the unsaturated silane compound, peroxide, and other components blended as needed.

[0058] The method of graft modification and / or chemical crosslinking is not particularly limited and can be carried out according to known techniques, for example, solution modification, melt modification, solid-phase modification by irradiation with electron beams or ionizing radiation, and modification in supercritical fluid are preferably used. Among these, melt modification is preferred because of its excellent equipment and cost competitiveness, and melt-kneading modification using an extruder because of its excellent continuous productivity is more preferred. Examples of devices used for melt-kneading modification include single-screw extruders, twin-screw extruders, Banbury mixers, and roll mixers. Among these, single-screw extruders and twin-screw extruders are preferred because of their excellent continuous productivity.

[0059] Generally, graft modification of ethylene-α-olefin copolymers and ethylene-based polymers with unsaturated silane compounds and / or peroxides is carried out by a graft reaction in which the carbon-hydrogen bonds of the ethylene-α-olefin copolymers and ethylene-based polymers are cleaved to generate carbon radicals, to which unsaturated functional groups are added. As a source of carbon radicals, in addition to the above-mentioned electron beams and ionizing radiation, a method using high temperature or a radical generator such as organic or inorganic peroxides can be used. From the viewpoint of cost and operability, it is preferable to use organic peroxides.

[0060] The radical generator used in producing the modified polyolefin composition of the present invention is not limited, but examples thereof include hydroperoxides, dialkyl peroxides, diacyl peroxides, organic peroxides belonging to the groups of peroxy esters and ketone peroxides, and azo compounds.

[0061] A commonly used melt extrusion modification procedure involves compounding and blending the ethylene-α-olefin copolymer, ethylene polymer, unsaturated silane compound and / or peroxide, and other components as needed, into a kneader or extruder, extruding the mixture while heating, melting, and kneading, and cooling the molten resin emerging from a die in a water tank or the like to obtain a modified polyolefin composition. When the modified polyolefin composition of the present invention is produced by kneading using a single-screw extruder or twin-screw extruder, the composition can be melt-kneaded in a heated state usually at 140 to 240°C, preferably 160 to 220°C.

[0062] The blending ratio of the ethylene-α-olefin copolymer, the ethylene-based polymer, the unsaturated silane compound, and the peroxide is as described above. The blending ratio of the unsaturated silane compound to the peroxide is not particularly limited, but a preferred blending ratio is 1 to 20 parts by mass of peroxide per 100 parts by mass of the unsaturated silane compound. When the amount of peroxide relative to the unsaturated silane compound is at least the above lower limit, a sufficient amount of radicals is generated to easily achieve the required predetermined degree of modification, while when it is at most the above upper limit, deterioration of the ethylene-α-olefin copolymer and the ethylene-based polymer tends to be easily suppressed.

[0063] In the modified polyolefin composition of the present invention, the content ratio of the alkoxysilane-modified ethylene-α-olefin copolymer as component (A) and the alkoxysilane-modified ethylene polymer as component (B) is preferably 2 to 50 mass%, more preferably 5 to 45 mass%, based on the content ratio of the ethylene-α-olefin copolymer and the ethylene polymer in the polyolefin composition of the present invention, with the proportion of component (B) being 100 mass% as the total of component (A) and component (B). It is preferable that the content of component (B) in the modified polyolefin composition of the present invention is within the above range in terms of flexibility, pressure resistance, and appearance. If the content of component (B) is equal to or less than the above upper limit, the cylindrical molded article will be flexible and workable during processing, while if it is equal to or greater than the above lower limit, the pressure resistance will be high, the pipe creep performance will be good, and the cylindrical molded article will be easily cured when water-cooled during molding, resulting in an excellent appearance.

[0064] The modified polyolefin composition of the present invention may contain only one type of component (A), or may contain two or more types, each differing in the type of ethylene-α-olefin copolymer, the unsaturated silane compound used in the alkoxysilane modified product, etc. Similarly, the component (B) may contain only one type, or may contain two or more types, each differing in the type of ethylene polymer, the unsaturated silane compound used in the alkoxysilane modified product, etc. The modified polyolefin composition of the present invention may contain components other than the ethylene-α-olefin copolymer and ethylene polymer contained in the polyolefin composition of the present invention.

[0065] The melt flow rate (MFR) of the modified polyolefin composition of the present invention is preferably 0.2 to 10 g / 10 min, as measured at a temperature of 230°C and a load of 2.16 kg in accordance with JIS K7210 (1999). If the MFR is equal to or less than the upper limit, the molten resin is less likely to drip during molding, improving yield and facilitating molding. If the MFR is equal to or greater than the lower limit, the motor load during modification extrusion is small, the resin pressure does not become too high, improving productivity and preventing surface roughness after molding. From these viewpoints, the MFR of the modified polyolefin composition of the present invention is preferably 0.2 g / 10 min or more, more preferably 0.5 g / 10 min or more, and is preferably 10 g / 10 min or less, more preferably 5 g / 10 min or less.

[0066] [Crosslinked polyolefin composition] When an unsaturated silane compound is used in the polyolefin composition of the present invention, a silanol condensation catalyst can be added thereto, and the resulting mixture can be molded by various molding methods such as extrusion molding, injection molding, and press molding.Then, by exposing the mixture to a water atmosphere, the crosslinking reaction between the silanol groups progresses, and the alkoxysilane-modified compound in the polyolefin composition undergoes an intermolecular crosslinking reaction, thereby producing the crosslinked polyolefin composition of the present invention. Various conditions can be used for the method of exposing to a water atmosphere, and examples thereof include a method of leaving the material in air containing moisture, a method of blowing air containing water vapor, a method of immersing the material in a water bath, and a method of spraying warm water in a mist.

[0067] Examples of silanol condensation catalysts that can be used in the present invention include one or more compounds selected from the group consisting of metal organic acid salts, titanates, borates, organic amines, ammonium salts, phosphonium salts, inorganic acids, organic acids, and inorganic acid esters.

[0068] Examples of metal organic acid salts include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, stannous acetate, stannous octoate, cobalt naphthenate, lead octoate, lead naphthenate, zinc octoate, zinc caprylate, iron 2-ethylhexanoate, iron octoate, and iron stearate. Examples of titanates include tetrabutyl titanate, tetranonyl titanate, and bis(acetylacetonitrile)di-isopropyl titanate. Examples of organic amines include ethylamine, dibutylamine, hexylamine, triethanolamine, dimethylsoya amine, tetramethylguanidine, and pyridine. Examples of ammonium salts include ammonium carbonate and tetramethylammonium hydroxide. An example of the phosphonium salt is tetramethylphosphonium hydroxide. Examples of inorganic acids and organic acids include sulfuric acid, hydrochloric acid, acetic acid, stearic acid, maleic acid, toluenesulfonic acid, and sulfonic acids such as alkylnaphthylsulfonic acid. Examples of inorganic acid esters include phosphate esters such as ethylhexyl phosphate.

[0069] Of these, preferred are metal organic acid salts, sulfonic acids, and phosphates, and more preferred are metal carboxylates of tin, such as dioctyltin dilaurate, alkylnaphthylsulfonic acids, and ethylhexyl phosphate. The silanol condensation catalyst may be used alone or in combination of two or more kinds.

[0070] The amount of the silanol condensation catalyst is not particularly limited, but is preferably 0.0001 to 0.01 parts by mass, and more preferably 0.0001 to 0.005 parts by mass, per 100 parts by mass of the modified polyolefin composition. When the amount of the silanol condensation catalyst is equal to or greater than the lower limit, the crosslinking reaction proceeds sufficiently, which is preferable, and when it is equal to or less than the upper limit, premature crosslinking is less likely to occur in the extruder, which is preferable, as it tends to prevent roughness of the strand surface and the product appearance.

[0071] The silanol condensation catalyst is preferably used as a masterbatch containing a polyolefin, such as polyethylene, polypropylene, or a propylene-ethylene copolymer.

[0072] When the silanol condensation catalyst is used as a masterbatch in which a polyolefin and the silanol condensation catalyst are blended, the content of the silanol condensation catalyst in the masterbatch is not particularly limited, but is preferably 0.1 to 5.0 mass %.

[0073] As the silanol condensation catalyst-containing masterbatch, a commercially available product can be used, for example, "LZ082" manufactured by Mitsubishi Chemical Corporation.

[0074] Furthermore, when a peroxide is used alone in the polyolefin composition of the present invention, there is no need to incorporate the above-mentioned silanol condensation catalyst, and the crosslinking reaction proceeds further during various molding processes such as extrusion molding, injection molding, and press molding due to the radical generator such as the remaining peroxide, thereby producing a crosslinked polyolefin composition.

[0075] When an unsaturated silane compound is used in the polyolefin composition or modified polyolefin composition of the present invention, the hydrolyzable alkoxy groups derived from the unsaturated silane compound used for graft-modifying the ethylene-α-olefin copolymer and the ethylene-based polymer react with water in the presence of a silanol condensation catalyst to hydrolyze and generate silanol groups. The silanol groups then undergo dehydration condensation with each other, causing a crosslinking reaction in which component (A), an alkoxysilane-modified ethylene-α-olefin copolymer, and / or component (B), an alkoxysilane-modified ethylene-based polymer, are bonded to each other to form a crosslinked polyolefin composition.

[0076] The rate at which the crosslinking reaction proceeds depends on the conditions for exposure to the aqueous atmosphere, but typically a temperature range of 20 to 130°C and a period of exposure of approximately 10 minutes to 1 month are sufficient. Preferred conditions are a temperature range of 60 to 100°C and a period of exposure of 1 to 24 hours. When using moist air, the relative humidity is selected from the range of 1 to 100%.

[0077] [Preferable properties of crosslinked polyolefin composition] The crosslinked polyolefin composition of the present invention preferably has the following physical properties in order to achieve the object of the present invention of providing a cylindrical molded article having excellent pressure resistance and excellent flexibility.

[0078] The crosslinked polyolefin composition of the present invention preferably has an A hardness in the range of 86-95. When the crosslinked polyolefin composition of the present invention has an A-hardness of at least the lower limit, the cylindrical molded article is flexible and has good workability during construction, and when it is at most the upper limit, the pressure resistance is high and the pipe creep performance is good. From this viewpoint, the A-hardness of the crosslinked polyolefin composition of the present invention is more preferably in the range of 88 to 94. In the present invention, the density is 0.910 g / cm 3 Ethylene-α-olefin copolymer with a density of less than 0.910 g / cm 3 More than 0.970g / cm 3 By using the following ethylene polymer in combination, the A hardness of the crosslinked polyolefin composition can be set within the above range. The A hardness of the crosslinked polyolefin composition can be measured by the method described in the Examples section below.

[0079] In order for the crosslinked polyolefin composition to exhibit excellent properties over a long period of time, the gel fraction (degree of crosslinking) of the crosslinked polyolefin composition is preferably 82% or more, and more preferably 84% or more. The gel fraction can be adjusted by changing the amount of unsaturated silane compound and / or peroxide added to the polyolefin composition, the type and amount of silanol condensation catalyst added, the conditions for crosslinking (temperature, time), etc. The upper limit of this gel fraction is not particularly limited, but is usually 99%. The gel fraction can be measured by the method described in the Examples section below.

[0080] The density of the crosslinked polyolefin composition of the present invention is 0.910 g / cm 3 If the density of the crosslinked polyolefin composition is equal to or less than the above upper limit, the crosslinked polyolefin composition is flexible and has good workability during application. From this viewpoint, the density of the crosslinked polyolefin composition is preferably 0.905 g / cm 3 On the other hand, from the viewpoint of pressure resistance and appearance, the density of the crosslinked polyolefin composition is preferably 0.887 g / cm or less. 3 It is preferable that the concentration is 0.890 g / cm or more. 3 In the present invention, the density is more preferably 0.910 g / cm or more.3 Ethylene-α-olefin copolymer with a density of less than 0.910 g / cm 3 More than 0.970g / cm 3 A crosslinked polyolefin composition having such a density can be produced by using the following ethylene polymer in combination. The density of the crosslinked polyolefin composition can be measured by the method described in the Examples section below.

[0081] The flexural modulus of the crosslinked polyolefin composition of the present invention is preferably 300 MPa or less. If the flexural modulus of the crosslinked polyolefin composition is not more than the above upper limit, the composition will be excellent in flexibility and workability during application. From this viewpoint, the flexural modulus of the crosslinked polyolefin composition is more preferably 200 MPa or less, further preferably 100 MPa or less, and particularly preferably 70 MPa or less. On the other hand, from the viewpoint of pressure resistance, the flexural modulus of the crosslinked polyolefin composition is preferably 50 MPa or more, more preferably 60 MPa or more. In the present invention, the density is 0.910 g / cm 3 Ethylene-α-olefin copolymer with a low flexural modulus of less than 0.910 g / cm 3 More than 0.970g / cm 3 By using an ethylene polymer having a high flexural modulus in combination, a crosslinked polyolefin composition having such a flexural modulus can be obtained. The flexural modulus of the crosslinked polyolefin composition can be measured by the method described in the Examples section below.

[0082] [Cylindrical molded body] In one embodiment of the present invention, the cylindrically shaped article of the present invention is a cylindrically shaped article made of the crosslinked polyolefin composition of the present invention.

[0083] In another embodiment of the present invention, the cylindrically shaped article of the present invention is a cylindrically shaped article made of a crosslinked polyolefin composition obtained by silane-crosslinking an alkoxysilane-modified ethylene polymer having an ethylene unit content of 60 mass% or more, and satisfying the following conditions (1) to (3): Condition (1): Density is 0.887 g / cm 3 More than 0.910g / cm 3 Is less than or equal to Condition (2): A hardness is between 86 and 95 Condition (3): Gel fraction must be 82% or more When the ethylene unit content of the ethylene polymer used here is 60% by mass or more, the density is high, pressure resistance is good, and pipe creep performance is excellent. From this viewpoint, the ethylene unit content of the ethylene polymer is preferably 70% by mass or more, more preferably 80% by mass or more. On the other hand, from the viewpoint of flexibility, the ethylene unit content of the ethylene polymer is preferably 95% by mass or less, more preferably 90% by mass or less.

[0084] The ethylene polymer preferably contains α-olefin units in addition to ethylene units, and examples of the α-olefin units contained in the ethylene polymer include the α-olefin units contained in the ethylene-α-olefin copolymer used in the present invention. The ethylene polymer may be an ethylene-α-olefin copolymer having such an ethylene unit content, or a mixture of the ethylene-α-olefin copolymer and the above-mentioned ethylene polymer. The alkoxysilane modification and silane crosslinking of the ethylene polymer can be carried out in the same manner as the alkoxysilane modification of the polyolefin composition of the present invention and the silane crosslinking of the modified polyolefin composition of the present invention described above.

[0085] The above conditions (1) to (3) that the crosslinked polyolefin composition in the other embodiments satisfies are the same as those described above as the preferred properties of the crosslinked polyolefin composition of the present invention.

[0086] The layer thickness (wall thickness) of the cylindrical molded article of the present invention is preferably 0.5 to 10 mm. If the layer thickness is equal to or less than the upper limit, it is easily cooled during extrusion cooling and can be easily wound up. On the other hand, if the layer thickness is equal to or more than the lower limit, it is less likely to sag during extrusion, is less likely to crack even when internal pressure is applied, and has excellent durability.

[0087] The outer diameter of the cylindrical molded article of the present invention is preferably 7 to 20 mm. If the outer diameter is equal to or less than the upper limit, it is easily cooled during extrusion cooling and can be easily wound up. On the other hand, if the outer diameter is equal to or more than the lower limit, it is less likely to be crushed and the contents can be efficiently passed through.

[0088] The cylindrical molded article of the present invention may have a single-layer structure or a multi-layer structure.

[0089] [Method for manufacturing cylindrical molded body] There are no particular limitations on the method for producing the cylindrically molded article of the present invention, and examples include a method in which pellets of the modified polyolefin composition of the present invention are blended with the above-mentioned silanol condensation catalyst, fed into a hopper of a pipe manufacturing apparatus, heated and melted in an extruder, extruded into a cylindrical shape through a die, and cooled to form a pipe. More specifically, a mixture of the modified polyolefin composition of the present invention and a silanol condensation catalyst is extruded from an extruder through a die at a temperature of, for example, 150 to 230°C, and after sizing, cooled in a cooling water tank and cut or wound through a take-up machine.

[0090] The extruder may be a single screw extruder, a twin screw extruder, or the like. Any type of die can be used, such as a straight head die, a cross head die, or an offset die. As the sizing method, any of the sizing plate method, outside mandrel method, sizing box method, inside mandrel method, etc. can be used.

[0091] [Application] The uses of the cylindrically molded article of the present invention are not particularly limited, and it can be suitably used as an industrial cylindrically molded article, for example, as an automotive hose component such as an automotive cooling water hose or rubber hose; a water / hot water supply, floor heating, road heating, EcoCute and ENE-FARM piping, a tube and piping for food and various industrial factories, a beverage tube for a vending machine, a compressed air delivery tube, etc.

[0092] In particular, the cylindrical molded article of the present invention is flexible and has excellent workability during installation, such as bending and stretching, and also has excellent creep performance, i.e., water permeability durability, so it can be suitably used for coolant tubes that are often bent during installation, especially coolant tubes for electric vehicles. [Example]

[0093] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples as long as it does not depart from the gist of the invention. Furthermore, the values ​​of various production conditions and evaluation results in the following examples are meant as preferred upper or lower limit values ​​in the embodiments of the present invention, and preferred ranges may be defined by combining the above-mentioned upper or lower limit values ​​with the values ​​in the following examples or values ​​between the examples. In the following description, "parts" means "parts by mass" and "%" means "% by mass".

[0094] [Raw materials] In the following examples and comparative examples, the following raw materials were used.

[0095] <Ethylene-α-olefin copolymer> Ethylene-α-olefin copolymer-1: Infuse® 9010, manufactured by Dow Chemical Japan Metallocene linear low-density polyethylene (ethylene-1-octene copolymer) Ethylene unit content: 60% by mass or more MFR: 0.5g / 10min (190℃, 2.16kg load) Density: 0.877g / cm 3 Melting peak temperature: 122℃ A hardness: 77 Ethylene-α-olefin copolymer-2: Engage® 8842, manufactured by Dow Chemical Japan Metallocene linear low-density polyethylene (ethylene-1-octene copolymer) Ethylene unit content: 60% by mass or more MFR: 1.0g / 10min (190℃, 2.16kg load) Density: 0.857g / cm 3 Melting peak temperature: 38℃ A hardness: 54

[0096] <Ethylene-based polymer> PE-1: Novatec (registered trademark) HY430 manufactured by Japan Polyethylene Corporation High-density polyethylene Ethylene unit content: 95% by mass or more MFR: 0.8g / 10min (190℃, 2.16kg load) Density: 0.954g / cm 3 Melting peak temperature: 135℃ D hardness: 68

[0097] <Propylene polymer> PP-1: Zelas (registered trademark) 7025 manufactured by Mitsubishi Chemical Corporation Propylene-ethylene copolymer Propylene unit content: 60% by mass or more MFR: 2.5g / 10min (230℃, 2.16kg load) Density: 0.89g / cm 3 Melting peak temperature: 162℃ Flexural modulus: 590 MPa PP-2: Adflex® Q300F manufactured by LyondellBasell Propylene-ethylene copolymer Propylene unit content: 60% by mass or more MFR: 0.8g / 10min (230℃, 2.16kg load) Density: 0.89g / cm 3 Melting peak temperature: 162℃ Flexural modulus: 330 MPa PP-3: Novatec PP (registered trademark) EA9, manufactured by Japan Polypropylene Corporation homopropylene polymer Propylene unit content: 100% by mass MFR: 0.5g / 10min (230℃, 2.16kg load) Density: 0.90g / cm 3 Melting peak temperature: 165℃ Flexural modulus: 1850 MPa PP-4: Novatec PP (registered trademark) EG8B, manufactured by Japan Polypropylene Corporation Propylene-ethylene copolymer Propylene unit content: 95% by mass or more MFR: 0.8g / 10min (230℃, 2.16kg load) Density: 0.90g / cm 3 Melting peak temperature: 141℃ Flexural modulus: 900MPa

[0098] <Unsaturated silane compounds> Vinyltrimethoxysilane: KBM-1003 (Shin-Etsu Chemical Co., Ltd.)

[0099] <Peroxide> POX: Di-t-butyl peroxide, Perbutyl D (NOF Corporation)

[0100] <Catalyst Masterbatch (MB)> Silanol condensation catalyst MB: LZ082 manufactured by Mitsubishi Chemical Corporation 1% tin catalyst-containing low density polyethylene MFR: 4g / 10min (190℃, 2.16kg load) Density: 0.91g / cm 3 Melting point: 90℃

[0101] [Measurement and Evaluation Methods for Raw Material (Co)copolymers, Modified Polyolefin Compositions, and Crosslinked Polyolefin Compositions] The measurement and evaluation methods for various physical properties and characteristics of raw material (co)copolymers, modified polyolefin compositions, and crosslinked polyolefin compositions are as follows.

[0102] [Melting Peak Temperature] Using a differential scanning calorimeter manufactured by Hitachi High-Tech Science Corporation, model name "DSC6220", in accordance with JIS K7121, approximately 5 mg of the sample was heated from 20°C to 200°C at a heating rate of 100°C / min, held at 200°C for 3 minutes, then cooled to -10°C at a cooling rate of 10°C / min, and then heated to 200°C at a heating rate of 10°C / min. The melting peak temperature was measured from the thermogram obtained at this time.

[0103] [Melt Flow Rate (MFR)] Measured under the conditions of a measurement temperature of 190°C or 230°C and a load of 2.16 kg, referring to JIS K7210 (1999).

[0104] [Density] Measured with reference to JIS K7112 (1999) for a sheet-shaped molded body formed by molding and crosslinking the modified polyolefin composition.

[0105] [A Hardness] Using a sheet-shaped molded body formed by molding and crosslinking the modified polyolefin composition, the durometer hardness A (maximum value) was measured with reference to JIS K7215:1986.

[0106] [Flexural Modulus] Measured with reference to JIS K7171:2008 using a sheet-shaped molded body formed by molding and crosslinking the modified polyolefin composition.

[0107] [Gel Fraction] A sheet-like molded product (thickness 1 mm) obtained by molding and crosslinking the modified polyolefin composition was subjected to Soxhlet extraction in boiling xylene at 144°C for 10 hours, and the undissolved resin was dried and then measured for mass, which was calculated as a percentage (%) of the sample mass before Soxhlet extraction.

[0108] <Pipe creep failure time> The pipe creep failure time was measured at a temperature of 95°C and circumferential stresses of 0.90 MPa and 1.13 MPa, based on ISO 9080:2012.

[0109] [Example 1] 80 parts of ethylene-α-olefin copolymer-1, 20 parts of PE-1, 2.0 parts of vinyltrimethoxysilane, and 0.03 parts of POX were blended and stirred in a blender. The mixture was then fed into a twin-screw extruder (TEX30α, manufactured by The Japan Steel Works) set at 200°C. The strands emerging from the nozzle were cooled and solidified in a water bath, and then cut into pellets to obtain a modified polyolefin composition. The MFR of the resulting modified polyolefin composition was measured.

[0110] 100 parts of the modified polyolefin composition obtained above was blended with 5 parts of LZ082 as a silanol condensation catalyst MB, and the blend was molded at 200°C using an injection molding machine. The resulting molded product was then left at 85°C and 85% RH for 18 hours to produce a sheet-like molded product made of a crosslinked polyolefin composition. The density, A hardness, flexural modulus, and gel fraction of the resulting crosslinked polyolefin composition were measured. Furthermore, 100 parts of the modified polyolefin composition was blended with 5 parts of LZ082 as a silanol condensation catalyst MB, and molded into a 10A pipe (outer diameter 13 mm, inner diameter 10 mm, thickness 1.5 mm) using an IKG PMS40 pipe molding machine at a set temperature of 200°C. This was then left at 85°C and 85% RH for 18 hours to produce a cylindrical molded article made of the crosslinked polyolefin composition. The pipe creep failure time of the obtained cylindrical molded article was measured. The results of various measurements are shown in Table 1.

[0111] [Comparative Examples 1 to 5] A modified polyolefin composition, a crosslinked polyolefin composition and a cylindrical molded article 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 measurements were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0112] [Table 1]

[0113] The above results reveal the following:

[0114] As shown in Example 1, the melting peak temperature is 110°C or higher, and the density is 0.910 g / cm 3 Ethylene-α-olefin copolymer with a density of less than 0.910-0.970g / cm 3 The crosslinked polyolefin composition using the ethylene polymer having a density of 0.910 g / cm 3 exhibited a longer pipe creep rupture time than those of Comparative Examples 1 to 5 while maintaining flexibility. 3 The melting peak temperature of the flexible ethylene-α-olefin copolymer is 110°C or higher, and the crystalline components do not melt even at the high temperatures used in pipe creep tests, increasing deformation resistance and enabling high pressure resistance while maintaining flexibility. In addition, the density is 0.910-0.970g / cm 3 This is presumably because the use of an ethylene-based polymer with a high crystalline content in the composition increases the amount of crystalline components, resulting in higher deformation resistance and pressure resistance, and also because the ethylene-based polymer has high compatibility with the ethylene-α-olefin copolymer, which is also an ethylene-based polymer (ethylene content of 60% by weight or more), resulting in high interfacial strength and less susceptibility to cracking at the interface.

[0115] Comparative Examples 1 to 4 have a density of 0.89 to 0.90 g / cm 3 Because it uses a propylene polymer, the density is 0.952 g / cm 3It is assumed that the composition contains less crystalline components than Example 1, which uses an ethylene-based polymer of the same type, and the amorphous portion is more susceptible to deformation under high pressure, which makes it unable to withstand the high water pressure during the pipe creep test. Furthermore, while Example 1 uses the same type of ethylene-α-olefin copolymer and ethylene-based polymer as the ethylene-based polymer, this uses an ethylene-α-olefin copolymer and a propylene-based polymer, which results in low compatibility between the polymers and weak interface strength, making it more likely for cracks to initiate at the interface under high water pressure during the pipe creep test. As a result, it is assumed that Comparative Examples 1 to 4 have shorter pipe creep rupture times than Example 1.

[0116] Comparative Example 5 uses an ethylene-α-olefin copolymer with a peak melting temperature lower than 110°C. Therefore, although it has high flexibility, it is prone to deformation at temperatures above the peak melting temperature and has poor pressure resistance. It is therefore presumed that this makes it unable to withstand the water pressure at high temperatures during the pipe creep test, resulting in a shorter pipe creep rupture time than Example 1.

[0117] From the above, it is assumed that the melting peak temperature is 110°C or higher and the density is 0.910 g / cm 3 Alkoxysilane-modified ethylene-α-olefin copolymers with a density of less than 0.910-0.970 g / cm 3 It can be seen that the cylindrical molded body of the present invention, which is made of a crosslinked polyolefin composition using an alkoxysilane-modified ethylene polymer, has low hardness and excellent flexibility, is excellent in workability as a cylindrical molded body, and is a cylindrical molded body having a long pipe creep rupture time.

Claims

1. A cylindrical molded article comprising a crosslinked polyolefin composition obtained by silane crosslinking a modified polyolefin composition containing the following components (A) and (B): Component (A): An alkoxysilane-modified ethylene / α-olefin copolymer, wherein the ethylene / α-olefin copolymer has a melting peak temperature of 110°C or higher and a density of 0.910 g / cm as measured by a differential scanning calorimeter (DSC). ３ Alkoxysilane-modified ethylene / α-olefin copolymer Component (B): an alkoxysilane-modified ethylene polymer, the density of which is 0.910 g / cm ３ 0.970g / cm or more ３ An alkoxysilane-modified ethylene polymer having the following structure:

2. 2. The cylindrical molded article according to claim 1, wherein the crosslinked polyolefin composition has an A hardness of 86 or more and 95 or less.

3. 3. The cylindrically molded article according to claim 1, wherein the crosslinked polyolefin composition has a gel fraction of 82% or more.

4. The density of the crosslinked polyolefin composition is 0.910 g / cm ３ The cylindrical molded body according to claim 1 or 2, wherein:

5. 3. The cylindrical molded article according to claim 1, wherein the crosslinked polyolefin composition has a flexural modulus of 300 MPa or less.

6. A cylindrical molded article comprising a crosslinked polyolefin composition obtained by silane-crosslinking an alkoxysilane-modified ethylene polymer having an ethylene unit content of 60 mass% or more, and satisfying the following conditions (1) to (3): Condition (1): Density is 0.887 g / cm ３ 0.910g / cm or more ３ Is less than or equal to Condition (2): A hardness is 86 or more and 95 or less. Condition (3): Gel fraction is 82% or more

7. A coolant tube using the cylindrical molded article according to claim 1 or 6.

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