JPS6356425A - Polyethylene resin pipe with multi-layer structure - Google Patents

Abstract

PURPOSE:To improve the peeling resistance of the title pipe, by a method wherein the polyethylene resin pipe is made by multi-layer structure and the inner layer thereof is made by a resin layer, in which specified linear low density polyethylene is blended with a specified stabilizing agent in addition to carbon black. CONSTITUTION:A polyethylene resin pipe is made by a multi-layer structure. An inner layer is constituted of a resin layer, consisting of a linear low density polyethylene, having the melt index of 2g/10min or less, the density of 0.935g/cm<3> or less and the molecular weight distribution index of 15 or more, blended with 0.005-2wt% of carbon black and 0.05-5wt% of compound shown by a constitutional formula; Mx/n.(AlC2)x.(SiO2)Y/.ZE2O (here; M means the metallic cation of Na, K, Mg, Ca, and Cu, (n) means the valence of metallic cation, X and Y means the number of tetrahedron per unit lattice and Z means the number of mole of moisture). An outer layer is constituted of a resin layer, consisting of the low density polyethylene same as the resin of the inner layer, blended with 2-5wt% of carbon black. According to this method, the polyethylene resin pipe for water feeding (for city-water way), prominent in peeling resistance, may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polyethylene resin pipe with a multilayer structure. Specifically, the present invention is a water supply product with excellent peeling resistance (
This relates to polyethylene resin pipes (for tap water).

[Prior art]

Conventionally, polyethylene resins have high strength, excellent creep properties, environmental stress cracking resistance (ESOR), flexibility, etc., and are therefore widely used for water supply pipes such as waterworks. The above-mentioned polyethylene resin pipe has poor weather resistance, especially resistance to ultraviolet rays. For example, in applications that are exposed to the outdoors for long periods of time, such as tap water pipes, carbon black is added as a weather stabilizer at a weight factor of λ to 3. A combination is used.

[Problem that the invention seeks to solve]

However, if polyethylene resin water supply pipes are used for long periods of time, such as for water supply or air conditioner water supply, blisters may form on the inner wall of the water supply pipe, and in extreme cases, they may peel and close the water supply valve. There was a problem. In particular, the above-mentioned inner wall peeling is likely to occur when it comes into contact with water containing a large amount of chlorine.In recent years, as water quality has deteriorated in urban areas, large amounts of chlorine have been used for sterilization. There is a demand for polyethylene resin pipes for water supply.

[Means for solving problems]

In order to solve the above-mentioned problems of the prior art, the inventors of the present invention have made a multi-layered structure of polyethylene resin pipes, and as a result of intensive studies to solve the problems of the above-mentioned conventional technology, the inner layer is made of a specific linear low-density polyethylene, in addition to a carbon blank, and a specific stable material is added to the inner layer. It was discovered that peeling resistance could be significantly improved compared to K by forming a resin layer containing a compounding agent, and the present invention was completed.

That is, the gist of the present invention is a polyethylene resin pipe formed by extrusion molding a polyethylene resin, the pipe has a multilayer structure, and the melt index of the inner layer is
Under 2iyio min I, the density is o, qJjji/c! Linear low-density polyethylene with a molecular weight distribution index of 11 or less and a molecular weight distribution index of 5 or more, 0.005 to 2% by weight of carbon black and the following structural formula (where M is Na) Ks kLll, Oa, Ou metal In the cation, n is the valence of the metal cation, X and Y are the number of tetrahedra per unit cell, and 2 is the number of moles of water. )
It is composed of a resin layer containing 0.0j-jllfi'% of the compound represented by The present invention relates to a polyethylene resin pipe having a multilayer structure, characterized in that it is constituted by a resin layer formed by blending carbon plank co~j-1f% with linear low-density polyethylene of 75 or more.

To explain the present invention in detail, the linear low-density polyethylene used in the polyethylene resin pipe of the present invention is a copolymer of ethylene and other α-olefins. Different from density polyethylene resin.

Linear low density polyethylene is, for example, ethylene and other α-
It is a product obtained by copolymerizing butene, hexene, octene, decene, dermethylpentene, etc. as olefins in an amount of about 77% by weight, preferably about a j-/j weight ratio, and is used in the production of high-density polyethylene by a medium-low pressure method. It is produced using a Ziegler-type catalyst or a Phillips-type catalyst, and the conventional high-density polyethylene is made into a short branched structure using a copolymer component, and the density is appropriately reduced by utilizing this short chain branching to 0.9/ ~0. It is a polyethylene with a structure that is more linear than conventional low-density polyethylene and more branched than high-density polyethylene.

Linear low-density polyethylene, which is used as a raw material for the inner and outer resin layers of unexploded rio polyethylene resin pipes, has a melt index of 0. // 0 minutes or less,
Preferably 0. The range is from 0 to 7 io minutes, more preferably from 9 to 101710 minutes), and the density is
, y3jll/d or less, preferably Olli/j-0, de3sll/atls, more preferably Olli1t-o,
Octopus, I/c! It is within the range of υ, and the molecular weight distribution index (hereinafter referred to as fluidity ratio) is greater than or equal to is, preferably 3
0-10. Preferably, those in the range of 3j to 70 are suitably used.

If the melt index exceeds the above-mentioned upper limit, it is not preferable because it causes uneven wall thickness of the pipe during extrusion molding. In addition, if the density exceeds the upper limit above, the pipe will become stiff and have poor flexibility.)
, and the impact strength is lowered, which is not preferable. moreover,
If the fluidity ratio is less than the above lower limit, roughness may occur in the pipe during extrusion molding, and the temperature may be raised to prevent this, but if the temperature is raised, uneven wall thickness will occur, which is not preferable.

In the method of the present invention, melt index
sb in accordance with Kttao Ic and measured at 1°C.
, the flow ratio is calculated using the above melt index measuring device,
Shear force 10-dyne/cd (load tlt31) and 10
"Dyne/d (load//7.7/g) extrusion i-(,9
/ / 0 minutes) and is calculated as . Also, the density is J
This is a value measured in accordance with IS KA 6o.

The fluidity ratio is a measure of the molecular weight distribution of the resin used, and the larger the fluidity ratio value, the wider the molecular weight distribution.

The inner resin layer of the polyethylene resin pipe of the present invention is composed of the above-mentioned linear low-density polyethylene mixed with a specific amount of carbon black and a specific stabilizer.

As carbon black, one having an average particle size of Jamμ or more is used, and the amount used is usually o, o o s to cow%, preferably 0% by weight, based on the linear low density polyethylene.
．． It is in the range of 1 to 1% by weight.

If the amount of carbon black exceeds the above range, the chlorine water resistance will be poor, which is not preferable.

In addition, the stabilizer to be blended with the above carbon black has the following structural formula (% formula) (where M is a metal cation such as NIL, KSM, Laa, or Ou, n is the valence of the metal cation, and X and Y are A compound represented by the number of tetrahedrons per unit cell (2 represents the number of moles of water) is used. The compounds include Na1. ((Ago, )B” (Sion)+
1) Φ Rich & OKn ((AA'O*)+*・(
SiOm)+1]・Body & OM, 9@ ((Azom)
u・(Sin,)□〕・BodyH,00am (:(A
zom)+t-(Japanese ion)u)"Core 几0 etc. Among these compounds, M is Na or O.
A compound represented by a is preferably used.

The amount of the compound represented by the above structural formula used is 0.0 with respect to the above linear low density polyethylene! r-j weight value, preferably 0. /-/weight value range.

If the amount of the stabilizer added is less than the above range, the effect of chlorine water resistance will be insufficient, and if it is more than the above range, JlS
KA7A - Unfavorable because it exceeds the specified ash content.

Various known methods can be used to uniformly mix carbon black and the stabilizer into the linear low-density polyethylene.

For example, the components may be mixed using a ribbon blender or Henschel mixer and then pelletized using an extruder, or the components may be directly melt-mixed using a Banbury mixer, continuous mixer, kneader, etc. and then pelletized using an extruder. Can be mentioned.

The outer resin layer of the polyethylene resin pipe of the present invention is composed of the linear low-density polyethylene mixed with the carbon black, usually in a weight ratio of 1 to 3, preferably 1 to 3. If the blending amount of carbon black is within the above-mentioned range (J), it is not desirable because the hardness and mechanical strength decrease.

As a method for uniformly mixing carbon black into the linear low-density polyethylene, the above-mentioned known method is employed.

As a method for molding the polyethylene resin pipe of the present invention, for example, linear low-density polyethylene blended with 170 to 2
Melted at a temperature of 50°C, inside the coextrusion die, and
Unlike other extruders, linear low-density polyethylene blended with carbon black is melted at a temperature of 170 to 230°C, extruded from the outside of the coextrusion die, sized, and then cooled to a water temperature of 10 to 100°C. An example of this method is to take a pipe that has been cooled and solidified in a water tank and then use a take-up device to cut or wind it into a predetermined length. As an extruder, a single metal ring type screw is generally used.

Also, as a guide, there is a straight head type, black and more ~
Examples of the sizing method include a sizing plate method, an outside mandrel method, a sizing box method, and an inside mandrel method.

The polyethylene resin pipe of the present invention has an inner layer thickness of 6
0μ or more, preferably 0. /11 or more, and the thickness of the outer layer is preferably at least IQ times the thickness of the inner layer, preferably at least 10-jO times. If the thickness of the inner layer is less than 40 μm, the chlorine contained in the tap water will permeate through the inner layer and reach the outer layer, which is undesirable because it will cause the bubble generation phenomenon as in the prior art. In addition, when the inner layer has a diameter of 6θμ or more, chlorine in the tap water does not penetrate into the outer layer, and due to the effect of adding the stabilizer, bubble generation does not occur, and the service life of the pipe can be significantly extended.

Examples/and (1) Production of polyethylene resin composition (At) Linear low-density polyethylene (density: O, y coco 1/crd, melt index (abbreviated as M): 0.779/10 min,
Flow ratio: 37, Copolymerization component Nibutene-11 copolymerization amount = 1
0% by weight) 9j, 7jlii parts and a master hatch of carbon black (polyethylene master patch containing 33.3% by weight of channel carbon black with an average particle size of 30-11μ or less) 6.2j After dry blending the ti part, extrusion Using a machine, the mixture was melt-kneaded at a resin temperature of 10° C. and extruded into pellets.

(2) Production of polyethylene resin composition (B) Linear low-density polyethylene (density: O, V coco 11/di, melt index", 0.71/10 min, flow ratio = 17,
Copolymerization to copolymerization component nibutene:! l: lO'M amount%)
9 Deprotection 7 parts by weight, strength, - Pump Sick masterbatch (channel type carbon black with average particle size of 30 mμ or less, polyethylene masterbatch containing 73.j 1lffff%) o, iH precious part and stabilizer O shown in Table / , S weight parts were triblended, and then melt-kneaded using an extruder at a resin temperature of 10° C. to form extrusion pellets.

(3) Manufacture of pipe The above polyethylene resin composition (Al pellet)
X, 0, ≠; Melt at a temperature of 110°C using a co-extruder, and use the outside of a coextrusion die (crosshead type) with an outer diameter of 60% l/inner diameter aSλ da), while the other extruder <ao demon yt
, l=jIlm.The above polyethylene resin composition (Bl
is melted at a temperature of 110°C and extruded through the inside of the above coextrusion die for sizing (sizing plate method).
was carried out at an internal pressure of 0-A kEl/cr/IG, then cooled in a water bath with a water temperature of 15°C, and the solidified pipe was heated to 0.4rr.
Pick-up at a pick-up speed of L1 minute, outer diameter 46%, wall thickness g
mm (outer layer?, jIlm, inner 40.3 my, )
A polyethylene resin layered pipe was obtained.

(4) Chlorine water resistance test ■ Test method - According to KARI 6 from J, the above pipe test piece was immersed in 2000 ppm chlorine water at a water temperature of 29°C.
Take out the test piece every time and check the /OH of the inner surface of the pipe test piece.
It was expressed as the number (ke/d) of the amount of blisters generated (O, + me or more) in X/0M1R (/d). The results are shown in Table 1.

(2) Test method - 2 The same procedure as in the above test method was carried out except that the chlorine concentration was set to /00 ppm and the test piece was immersed in water at a temperature of 70°C.

The results are shown in Table 7.

In Comparative Example 1 and Example 1, except that the thickness of the inner layer of the -layer pipe was set to SOμ (Comparative Example/L or that the above stabilizer was not added to the inner layer of the single-layer pipe (Comparative Example)) I did the same thing.

The results are shown in Table 7.

Comparative Example 3 The same procedure as in Example 1 was carried out except that only the polyethylene resin composition (A) was used and a single layer die was used. The results are shown in Table 7.

Comparative Example Example 1 was carried out in the same manner as in Example 1, except that linear low-density polyethylene with the physical properties shown in Table 1 was used as the raw material for the resin composition, and only the resulting composition was used, and a single layer die was used. I went. The results are shown in Table 7.

〔Effect of the invention〕

The water supply pipe using linear low-density polyethylene containing a specific amount of carbon black and the above-mentioned stabilizer according to the present invention has superior inner wall peeling resistance compared to conventional water supply polyethylene pipes, so it can be used for a long period of time. Moreover, there is no risk of clogging the water supply valve, etc.

Sender: Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Hase - (7 others)

Claims (1)

[Claims] (1) A polyethylene resin pipe made by extrusion molding polyethylene resin, which has a multilayer structure, and the inner layer has a melt index of 2 g/10 minutes or less and a density of 0.935 g/cm^3 or less. , and linear low-density polyethylene with a molecular weight distribution index of 15 or more, 0.005 to 2% by weight of carbon black and the following structural formula Mx/n・[(AlO_2)_X・(SiO_2)_Y
)・ZH_2O (However, M is Na, K, Mg, Ca, C
u is a metal cation, n is the valence of the metal cation, X and Y are the number of tetrahedra per unit cell, and Z is the number of moles of water. ), the outer layer has a melt index of 2 g/10 minutes or less, a density of 0.935 g/cm^3 or less, and A polyethylene resin pipe having a multilayer structure, characterized in that it is constructed of a resin layer made of linear low-density polyethylene having a molecular weight distribution index of 15 or more mixed with 2 to 5% by weight of carbon black.