JPH11293049A - Polyethylene resin composition for water pipe, water pipe and water pipe joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve resistance to weather and to chlorine-containing water by incorporating at least one blue pigment and at least one piperidine derivative. SOLUTION: A piperidine derivative employed is represented by the formula. In the formula, n represents an integer of 1 or 2; R<1> , R<2> , R<3> and R<4> independently of one another represent 1-4C alkyl, or R<1> and R<2> or R<3> and R<4> join together to form a tetramethylene or pentamethylene group; R<5> represents H or 1-4C alkyl; and R<6> represents H, 1-22C alkyl or the like. Y is H or 1-22C alkyl or the like when n is 1 and 2-22C alkylene or the like when n is 2. As a blue pigment, there can be preferably mentioned inorganic pigments such as cobalt blue, ultramarine blue and the like and organic pigments such as phthalocyanines and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene resin composition for a water distribution pipe and a water distribution pipe joint. More specifically, pipes and fittings that are blue, do not generate water bubbles on the surface of the molded article even when they come into direct contact with chlorine-containing water, and have the weather resistance required for water supply pipes and water pipe fittings The present invention relates to a polyethylene resin composition that can provide a water supply pipe and a water supply pipe joint formed using the same.

[0002]

2. Description of the Related Art Polyethylene pipes can be integrated with pipes and joints by means of highly flexible material characteristics and fusion bonding, so that they can follow soft ground and ground displacement during an earthquake well. Therefore, it has features such as easy handling, flexibility and the possibility of raw bending piping and high construction efficiency, and resistance to acids and alkalis and excellent corrosion resistance.

Conventionally, polyethylene pipes having relatively small diameters up to an outer diameter of 60.0 mmφ are used in accordance with JIS K.
Although it has been standardized to 6762 and used only for water supply pipes (laying on private land), large-diameter pipes have been used for water pipes (laying to private land) for 10 years in Western European countries. Also, the use of large-diameter water distribution pipes and water distribution pipe joints has begun. In 1997, the Water Supply Association Standard (JWWA) K144, 145, and the Polyethylene Pipe Association for Water Distribution (PWA) 001, 0
02 was enacted.

In the conventional water supply pipe application, the color of the pipe was black, but the color of the water distribution pipe and the distribution pipe joint used on the upstream side of the water supply pipe is specified to be dark blue in the above standard. ing. In order to color and mold polyethylene into blue, ultramarine, inorganic pigments such as cobalt blue and organic pigments such as phthalocyanine blue are used.However, when a blue molded product is used for an application that directly contacts chlorine-containing water. Bubbles may form on the surface of the molded article, resulting in peeling. That is, in the water distribution pipe and the water distribution pipe joint, there is a possibility that a problem that a part of the pipe and the pipe joint is peeled and mixed into the clean water may occur, and in the type of the pigment, one having excellent resistance to chlorine-containing water is selected. It is extremely important.

[0005] On the other hand, since water distribution pipes and water distribution pipe joints may be stored outdoors prior to their construction, strict standards are also required for weather resistance. It is indispensable to add a light stabilizer or an ultraviolet absorber in order to impart weather resistance to a dark blue water supply pipe and a water pipe fitting.

However, when a light stabilizer and / or an ultraviolet absorber is added to polyethylene containing a blue pigment, the chlorine-containing water performance inherent in the blue pigment is impaired, that is, the light stabilizer and / or the ultraviolet absorber is added. If not performed, the time until the occurrence of water bubbles is shortened, and the generation of water bubbles is accelerated. In order to prevent fading of a water pipe colored blue, attempts have been made to blend a specific phthalocyanine compound with a phenolic antioxidant, a hindered amine light stabilizer or a benzotriazole ultraviolet light inhibitor (Japanese Unexamined Patent Publication No. -76639), the effect of preventing the occurrence of water bubbles is inferior and not satisfactory. From these facts, a polyethylene resin composition containing a blue pigment and capable of achieving the weather resistance required for water supply pipes and water pipe fittings without impairing the inherent chlorine-containing water resistance of the pigment is desired. .

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the above-mentioned drawbacks and to provide a polyethylene resin composition for blue water distribution pipes and water distribution pipe joints which is excellent in weather resistance and chlorine-containing water resistance, and polyethylene thereof. An object of the present invention is to provide a water distribution pipe and a water distribution pipe joint made of a resin composition.

That is, the present invention relates to a polyethylene resin composition for a water distribution pipe, a water distribution pipe, and a water distribution pipe joint shown below. 1) A polyethylene resin composition for water distribution pipes comprising at least one blue pigment and at least one piperidine derivative represented by the following formula (I):

Embedded image (Wherein, n is an integer of 1 or 2, and R ¹ , R ² , R ³
And R ⁴ either represents independently an alkyl group having 1 to 4 carbon atoms from one another, or R ¹ and R ² or R ³ and R ⁴ represents a tetramethylene group or a pentamethylene group together, R ⁵ is R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms;
An alkyl group, an alkenyl group having 3 to 22 carbon atoms, or an alkyl group having 1 to 4 carbon atoms, a fluorine atom, a chlorine atom, an alkoxyl group having 1 to 4 carbon atoms, a methylenedioxyl group and / or di- A phenylalkyl group having 7 to 12 carbon atoms which may be substituted by an alkyl-amino group having 1 to 4 carbon atoms, an alkanoyl group having 1 to 22 carbon atoms, a cyanoalkyl group having 2 to 3 carbon atoms, A hydroxyalkyl group having 1 to 22 carbon atoms or an aminoalkyl group having 2 to 22 carbon atoms,
Is a hydrogen atom, an alkyl group having 1 to 22 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, when n is 1,
A bicycloalkyl group having 3 to 12 carbon atoms, or an alkyl group having 2 to 22 carbon atoms substituted by a cyano group, a hydroxyl group or an alkoxycarbonyl group having 1 to 4 carbon atoms, or an ether oxygen atom, nitrogen atom or sulfur An alkyl group having 4 to 22 carbon atoms interrupted by an atom, or an alkyl group having 1 to 4 carbon atoms, a fluorine atom, a chlorine atom, an alkoxyl group having 1 to 4 carbon atoms, a methylenedioxyl group, ethylenedioxyl A phenyl- or -diphenylalkyl group having 7 to 22 carbon atoms which may be substituted by a group or a di-alkyl group having 1 to 4 carbon atoms, or an alkyl group having 1 to 4 carbon atoms or carbon atom A phenyl group which may be substituted by an alkoxycarbonyl group of the formulas (1) to (4),

Embedded image (The symbols in the formula have the same meanings as described above.) Represents a residue or a heterocyclic group-containing alkyl group having 1 to 22 carbon atoms, or Y is, when n is 2, Alkylene group having 2 to 22 carbon atoms, 5 to 22 carbon atoms
A phenylalkylene group having 8 to 14 carbon atoms, a phenylene group, or an alkylene having 4 to 30 carbon atoms interrupted by an ether oxygen atom, a nitrogen atom, a sulfur atom or a 5- to 6-membered heterocyclic ring system Represents a group. ).

2) The polyethylene resin composition for a water distribution pipe according to the above 1, wherein the piperidine derivative is a piperidine derivative in which R ¹ , R ² , R ³ and R ⁴ in the formula (I) represent a methyl group.

[0010] 3) The polyethylene resin composition for a water pipe according to the above item 1, wherein the piperidine derivative is a piperidine derivative in which R ⁵ in the formula (I) represents a hydrogen atom.

4) In the piperidine derivative, R ¹ , R ² , R ³ and R ^{4 in the} above formula (I) represent a methyl group, R ⁵ represents a hydrogen atom, n is 2 and Y is 2. The polyethylene resin composition for a water distribution pipe according to the above 1, which is a piperidine derivative representing a hexamethylene group.

5) The polyethylene resin composition for a water distribution pipe according to any one of 1 to 4 above, wherein the blue pigment is a cobalt blue pigment.

6) The polyethylene resin composition for a water distribution pipe according to any one of 1 to 4 above, wherein the blue pigment is an ultramarine blue pigment.

7) The polyethylene resin composition for a water distribution pipe according to any one of 1 to 4 above, wherein the blue pigment is a phthalocyanine blue pigment.

8) The blue pigment is represented by the following formula (III)

Embedded image (Wherein, M represents a hydrogen atom, Cu, Zn, Ni or Fe, X ^{1 to} X ⁴ represent a chlorine atom, a to d are 0 or an integer of 1 to 4, a + b + c + d is 2 to 10 The polyethylene resin composition for water distribution pipes according to any one of the above items 1 to 4, which is a chlorinated phthalocyanine blue pigment represented by the formula:

9) A water distribution pipe extruded from the polyethylene resin composition according to any one of 1 to 8 above.

10) A water distribution pipe joint injection-molded using the polyethylene resin composition according to any one of 1 to 8 above.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The polyethylene used in the present invention includes various types such as high-density polyethylene (HDPE), low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE). And high-density polyethylene (HDP
E) is preferred.

The high-density polyethylene can be prepared by various methods,
For example, Phillips, Ziegler
, Metallocenes or single-site catalysts (SSCs), which can be prepared by catalytic polymerization using a catalyst comprising one or more metals of Groups IVb, Vb, VIb or VIII of the Periodic Table. These metals are usually capable of either π-coordination or σ-coordination, for example coordination such as oxides, halides, alcoholates, esters, ethers, amines, alkyls, alkenyls and / or aryls. Have one or more children. These metal complexes can be used in free form or activated magnesium chloride,
It may be used by being immobilized on a support such as titanium (III) chloride, aluminum oxide or silicon oxide. These catalysts may be soluble or insoluble in the polymerization medium. The catalyst is, for example, a metal alkyl, a metal hydride, a metal alkyl halide, a metal alkyl oxide or a metal alkyloxane (where the metal is a metal of the periodic table Ia or IIa).
And / or elements of group IIIa. )) Can be used in combination. These activators can improve their activity by substituting their functional groups with other ester, ether, amine or silyl ether groups and the like.

As the polymerization reaction system, any one or more of a homogeneous system, a suspension system, and a gas phase system can be selected. The polymerization reaction is carried out using one reactor or a plurality of reactors connected in series and / or in parallel.

Examples of the blue pigment used in the present invention include inorganic pigments such as cobalt blue and ultramarine blue, and organic pigments such as phthalocyanine pigments, and these can be used alone or in combination. Further, a desired hue is adjusted by using pigments generally used for coloring conventional plastics, for example, inorganic pigments such as acid value zinc and titanium oxide, and organic pigments such as quinacridone pigments and dioxazine pigments. be able to.

The cobalt blue pigment preferably used in the present invention is a composite oxide pigment of cobalt oxide and aluminum oxide, and has a CAS registration number (Chemical Abstr.
actsService Registry Number) 1345-16-0 (Pigment Bl
ue 28), 1333-88-6, 37348-50-8, 68187-11-1, etc., and the ultramarine pigment is CAS Registry Number 67053-79-6 (Pigment Blue
29), 39362-18-0, 1302-83-6 and the like.

The phthalocyanine blue pigment preferably used in the present invention is generally used for coloring blue, and a typical example thereof is a copper phthalocyanine compound as a main component. Further, the chlorinated phthalocyanine blue pigment preferably used in the present invention is represented by the formula (III), wherein X ^{1 to} X ⁴ represent a chlorine atom, and ad is an integer of 0 or 1 to 4, a + b +
c + d is a chlorinated phthalocyanine blue pigment with 2 to 10. Phthalocyanine blue pigment has CAS registration number
147-14-8 (Pigment Blue15, 15: 1, 15: 2, 15: 3, 15: 4
Or 15: 6), 574-93-6 (Pigment Blue 16), 3317-67
-7 (Pigment Blue 75), 12239-87-1, 14055-02-8, etc.
Chlorinated phthalocyanine blue pigment has CAS registration number 276
14-71-7 and the like.

The piperidine derivative used in the present invention is a known compound, specifically, a compound used as a polymer light stabilizer described in JP-A-1-160959. Specific compounds preferably used among these include N, N'-bis (2,2,6,6-tetramethyl-4-piperidinyl) -N, N'-bis-formyl-hexamethylenediamine. Can be The amount of these components is preferably 0.005 to 1% by weight, particularly preferably 0.01 to 0.5% by weight, based on the resin component.

The polyethylene resin composition for water distribution pipes and water distribution pipe joints of the present invention may be in the form of pellets (colored pellets) to be directly used for molding, or a so-called pigment containing a pigment in a high concentration. It may be a colorant in the form of a pellet called a master batch. The piperidine derivative may be added in exactly the same manner as a master batch. When the pigment or the piperidine derivative is contained at a high concentration, the master batch may be diluted with a polyethylene resin and subjected to molding to obtain a water supply pipe and a water pipe fitting.

The water supply pipe of the present invention is currently specified by the above-mentioned standards and is required to have weather resistance and chlorine-resistant water resistance. It is molded by general extrusion using a polyethylene resin or a masterbatch containing a coloring agent and a piperidine derivative at a high concentration.

The water distribution pipe joint according to the present invention is used for connecting the water distribution pipes, and is required to have the same weather resistance and chlorine water resistance as the water distribution pipe. Or a master batch containing a coloring agent and a piperidine derivative at a high concentration and a polyethylene resin by injection molding.

In the present invention, other thermoplastic resins, metal soaps used in conventional plastics, dispersants such as medium- and low-molecular-weight polyethylene, antioxidants, etc. are used as long as the effects of the present invention are not impaired. They can be appropriately blended.

[0029]

The present invention will be described below in more detail with reference to examples and comparative examples. In addition, the piperidine derivative and the ultraviolet absorber used in Examples and Comparative Examples are as follows.

Piperidine derivative (1) Uvinul 4050H (trade name; BASF A)
G): N, N'-bis (2,2,6,6-tetramethyl-4-piperidinyl) -N, N'-bis-formyl-
Hexamethylene diamine;

(2) SANOL LS-770 (trade name; manufactured by Sankyo Co., Ltd.): bis (2,2,6,6-tetramethyl-
4-piperidinyl) sebacate;

(3) Sanol LS-765 (trade name; manufactured by Sankyo Co., Ltd.): bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate;

(4) Tinuvin 123 (trade name; Ci)
ba Specialty Chemicals): bis (2,2,6,6-
Tetramethyl-1-octyloxy-4-piperidinyl) sebacate;

(5) Tinuvin 662 (trade name; Ci)
ba Specialty Chemicals): poly- (N-β-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxy-piperidyl succinate);

(6) Chimassorb 944 (trade name; manufactured by Ciba Specialty Chemicals): poly-{[6-
[(1,1,3,3-tetramethylbutyl) -imino-]-1,3-5-triazine-2,4-diyl] [2
-(2,2,6,6-tetramethylpiperidyl) -amino] -hexamethylene- [4- (2,2,6,6-tetramethylpiperidyl) -imino]};

(7) Chimassorb 119 (trade name; manufactured by Ciba Specialty Chemicals): N, N '''-
[1,2-ethane-diyl-bis [[[4,6-bis-
[Butyl (1,2,2,6,6-pentamethyl-4-piperidinyl) amino-]-1,3,5-triazine-2
-Yl] imino] -3,1-propanediyl]] bis-
N ', N "-dibutyl-N', N" -bis (1,2,
2,6,6-pentamethyl-4-piperidinyl) -1,
3,5-triazine-2,4,6-triamine;

(8) Tinuvin 783 (trade name; Ci)
ba Specialty Chemicals): poly- (N-β-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxy-piperidyl succinate) and poly-{[6-
[(1,1,3,3-tetramethylbutyl) -imino-]-1,3-5-triazine-2,4-diyl] [2
A mixture of-(2,2,6,6-tetramethylpiperidyl) -amino] -hexamethylene- [4- (2,2,6,6-tetramethylpiperidyl) -imino]};

(9) Uvinul 5050H (trade name;
BASF AG):

Embedded image

(10) Adekastab LA-57 (trade name;
Asahi Denka Kogyo Co., Ltd.): Tetrakis (2, 2, 6, 6)
-Tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate;

(11) Adekastab LA-52 (trade name;
Asahi Denka Kogyo Co., Ltd.): Tetrakis (1,2,2)
6,6-pentamethyl-4-piperidyl) 1,2,3
4-butanetetracarboxylate.

UV absorber (1) Tinuvin 326 (trade name; Ciba Specialty)
Chemicals): 2- (2'-hydroxy-3'-tert)
-5'-methylphenyl) -5-chloro-benzotriazole; (2) Tinuvin 328 (trade name; Ciba Specialty)
Chemicals): 2- (2'-hydroxy-3 ', 5'
-Di-tert-amylphenyl) -2H-benzotriazole.

Example 1: Polyethylene resin (density 0.948)
g / cm ³ , MFR 0.13 g / 10 min (190 ° C., 2.1
6 kgf)), 0.1% by weight of tetrakismethylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate) methane as an antioxidant, tris (2,4-di-t
ert-butylphenyl) phosphite 0.1% by weight, calcium stearate 0.1% by weight as a neutralizing agent for catalyst residues,
0.06% by weight of a chlorinated phthalocyanine blue pigment prepared according to Production Example 2 in the examples of JP-A-7-76639 as a blue pigment, and titanium oxide (Pi
gment White 6) 0.06% by weight, low molecular weight polyethylene 0.1
2% by weight and N, N'-bis- (2,2,6,6-tetramethyl-4-piperidinyl) -N, N'-bis-formyl-hexamethylenediamine (Uvinul 40)
50H) 0.05% by weight was blended, and this mixture was mixed with 175/1
The mixture was kneaded with a roll mill at 45 ° C. Thereafter, press molding was performed at 170 ° C. to form a plate having a thickness of 2 mm.
A chlorine-containing water resistance test was performed under the following conditions according to SK6762, and the time until the occurrence of water bubbles was confirmed. Test conditions Chlorine concentration: 2,000 ± 100 ppm Temperature: 60 ° C. In addition, a weather resistance test was performed on the above plate according to JIS K6774. Evaluation was made by the residual rate of elongation before and after exposure. However, the exposure time was 600 hours plus 1,00 hours.
The test was also performed for 0 hour. Table 1 shows the results. Both chlorine-containing water resistance and weather resistance were good.

Comparative Example 1: N, N'-bis (2,2,6,
6-tetramethyl-4-piperidinyl) -N, N'-bis-formyl-hexamethylenediamine (Uvinul
A plate was obtained in the same manner as in Example 1 except that 4050H) was not added, and the time for occurrence of water bubbles and the weather resistance test were performed. Table 1 shows the results. The weather resistance was poor.

Comparative Examples 2 to 14: N, N'-bis (2,
2,6,6-tetramethyl-4-piperidinyl) -N,
N'-bis-formyl-hexamethylenediamine (Uv
inul 4050H), a plate was obtained in the same manner as in Example 1 except that the piperidine derivative shown in Table 1 was blended, and the time of blister generation and the weather resistance test were performed.
Table 1 shows the results. The chlorine-containing water content was poor.

[0045]

[Table 1]

Example 2 A plate was obtained in the same manner as in Example 1 except that 0.13% by weight of a commercially available product, cobalt blue (Pigment Blue 28), was used instead of the chlorinated phthalocyanine blue pigment as the blue pigment. And a weather resistance test were conducted. Table 2 shows the results. Both chlorine-containing water resistance and weather resistance were good.

Comparative Example 15: N, N'-bis (2,2,
6,6-tetramethyl-4-piperidinyl) -N, N '
-Bis-formyl-hexamethylenediamine (Uvin
ul 4050H) was obtained, except that no plate was blended. A plate was obtained in the same manner as in Example 2, and the time for occurrence of blisters was confirmed and the weather resistance test was performed. Table 2 shows the results. The weather resistance was poor.

Comparative Examples 16 to 28: N, N'-bis (2,
2,6,6-tetramethyl-4-piperidinyl) -N,
N'-bis-formyl-hexamethylenediamine (Uv
inul 4050H), and a plate was obtained in the same manner as in Example 2 except that the piperidine derivative shown in Table 2 was blended. The time of blister generation and the weather resistance test were performed.
Table 2 shows the results. The weather resistance was poorer than that of Example 2.

[0049]

[Table 2]

[0050]

The present invention provides a weather-resistant, chlorine-resistant aqueous polyethylene resin composition for producing a dark blue water supply pipe and a water pipe fitting, which is formed by extrusion molding from the polyethylene resin composition of the present invention. The obtained water pipe and the water pipe joint obtained by injection molding are excellent in weather resistance and chlorine-containing water resistance.

────────────────────────────────────────────────── ─── Continuing on the front page (51) Int.Cl. ⁶ Identification code FI F16L 11/04 F16L 11/04 (72) Inventor Yozo Nagai 2-3-2 Yoko, Kawasaki-ku, Kawasaki-shi, Kanagawa Japan Polyolefin Co., Ltd. Kawasaki Research Laboratory

Claims (10)

[Claims] 1. A composition comprising at least one blue pigment,
And a polyethylene resin composition for water distribution pipes, characterized by containing at least one piperidine derivative represented by the following formula (I): (In the formula, n is an integer of 1 or 2, and R ¹ , R ² , R ³ and R ⁴ independently have 1 carbon atom.
R ¹ and R ² or R ³ and R ⁴ together represent a tetramethylene group or a pentamethylene group; and R ⁵ is a hydrogen atom or an alkyl having 1 to 4 carbon atoms. R ⁶ represents a hydrogen atom, an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 3 to 22 carbon atoms, or 1 carbon atom
Carbon atom which may be substituted by an alkyl group having 1 to 4 carbon atoms, a fluorine atom, a chlorine atom, an alkoxyl group having 1 to 4 carbon atoms, a methylenedioxyl group and / or an alkyl-amino group having 1 to 4 di-carbon atoms. A phenylalkyl group having 7 to 12 atoms, an alkanoyl group having 1 to 22 carbon atoms,
A cyanoalkyl group having 2 to 3 carbon atoms, 1 to 3 carbon atoms
22 hydroxyalkyl groups or 2 to 22 carbon atoms
Y represents a hydrogen atom or a group having 1 to 22 carbon atoms when n is 1.
An alkyl group, a cycloalkyl group having 3 to 12 carbon atoms, a bicycloalkyl group having 3 to 12 carbon atoms, or a carbon atom having 2 carbon atoms substituted by a cyano group, a hydroxyl group or an alkoxycarbonyl group having 1 to 4 carbon atoms. Alkyl group having 4 to 22 carbon atoms, or an alkyl group having 4 to 22 carbon atoms interrupted by an ether oxygen atom, a nitrogen atom or a sulfur atom, or an alkyl group having 1 to 4 carbon atoms, a fluorine atom, a chlorine atom, a carbon atom number 1-4 alkoxyl groups,
A methylenedioxyl group, an ethylenedioxyl group or a phenyl- or -diphenylalkyl group having 7 to 22 carbon atoms which may be substituted by an alkyl-amino group having 1 to 4 carbon atoms, or 1 carbon atom ~ 4
A phenyl group which may be substituted by an alkyl group or an alkoxycarbonyl group having 1 to 4 carbon atoms, represented by the following formula (II): (The symbols in the formula have the same meanings as described above.) Represents a residue or a heterocyclic group-containing alkyl group having 1 to 22 carbon atoms, or Y is, when n is 2, Alkylene group having 2 to 22 carbon atoms, 5 to 22 carbon atoms
A phenylalkylene group having 8 to 14 carbon atoms, a phenylene group, or an alkylene having 4 to 30 carbon atoms interrupted by an ether oxygen atom, a nitrogen atom, a sulfur atom or a 5- to 6-membered heterocyclic ring system Represents a group. ). 2. The method according to claim 1, wherein said piperidine derivative is R in formula (I).
^The polyethylene resin composition for water distribution pipes according to claim 1, wherein ¹ , R ² , R ³ and R ⁴ are piperidine derivatives each representing a methyl group. 3. The method according to claim 1, wherein said piperidine derivative is represented by R in formula (I).
^{5. The method according} to claim 1, wherein ⁵ is a piperidine derivative representing a hydrogen atom.
Polyethylene resin composition for water distribution pipes described in 4. The piperidine derivative in the formula (I), wherein R ¹ , R ² , R ³ and R ⁴ represent a methyl group, R ⁵ represents a hydrogen atom, n is 2 and Y is The polyethylene resin composition according to claim 1, which is a piperidine derivative representing a hexamethylene group. 5. The polyethylene resin composition for water distribution pipes according to claim 1, wherein the blue pigment is a cobalt blue pigment. 6. The polyethylene resin composition for a water distribution pipe according to claim 1, wherein the blue pigment is an ultramarine blue pigment. 7. The polyethylene resin composition according to claim 1, wherein the blue pigment is a phthalocyanine blue pigment. 8. The blue pigment is represented by the following formula (III): (Wherein, M represents a hydrogen atom, Cu, Zn, Ni or Fe, X ^{1 to} X ⁴ represent a chlorine atom, a to d are 0 or an integer of 1 to 4, a + b + c + d is 2 to 10 The polyethylene resin composition for water distribution pipes according to any one of claims 1 to 4, which is a chlorinated phthalocyanine blue pigment represented by the following formula: 9. A water distribution pipe extruded from the polyethylene resin composition according to claim 1. Description: 10. A water distribution pipe joint injection-molded using the polyethylene resin composition according to any one of claims 1 to 8.