JP2000310360A - Resin composition for silane bridged polyolefine tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition for a silane crosslinked polyolefine tube excellent in appearance of moldings, excellent in mechanical strength, thermal oxidation durability and a hot hydrostatic pressure creeping property and to be favourably used to supply warm water, hot water, etc. SOLUTION: This resin composition is made by melting and mixing silane graftomer to be provided by making organic unsaturated silane react to base polymer in the presence of a free radical generator and a master batch containing a silanol condensed catalyser and an antioxidant. In this case, 0.1-0.5 weight % of a phenolic antioxidant having more than 500 molecular weight and not containing ester bond is contained based on whole polymer in the antioxidant, 0.1-0.5 weight % of a phenol antioxidant having more than 500 molecular weight and containing amide bond is contained based on whole polymer, and 0.6-1.0 weight % of a phenolic antioxidant having more than 500 molecular weight is contained based on whole polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for silane-crosslinked polyolefin pipes, and more particularly, to a resin composition suitable for supplying hot water, hot water or the like to households, buildings, factories, hot springs, and the like. Silane crosslinked polyolefin pipe resin composition to be obtained.

[0002]

2. Description of the Related Art Metal pipes such as copper pipes, galvanized steel pipes, and stainless steel pipes have been used for water supply and hot water supply. However, these metal pipes have been used for a long time, and colored water such as blue water and red water due to rust. In recent years, polyolefin pipes have been used because of the drawbacks of water leakage and poor workability. In addition, since high strength and creep resistance at high temperatures are required for water supply and hot water supply pipe applications, use of a crosslinked polyethylene pipe excellent in these properties is mainly used. Above all, a silane crosslinked polyethylene pipe is preferably used because of its excellent heat resistance and cold resistance. The tap water flowing inside these tubes contains chlorine for sterilization, and this chlorine acts as an oxidizing agent and causes chemical deterioration of the tubes. In particular, deterioration tends to be promoted in piping of a hot water supply facility that receives a high temperature and high pressure load. Metal ions such as copper ions in water also promote chemical degradation. A silane-crosslinked polyolefin pipe resin composition is known in which a stabilizer such as an antioxidant is added to a polyolefin resin in order to prevent such oxidative deterioration accelerated by heat, metal ions such as chlorine and copper.

[0003]

However, since a part or a considerable part of the compounded antioxidant is extracted by water or hot water passing through the inside of the tube, a mechanism for preventing chemical deterioration of the tube is required. There is a problem that it is lowered, and the destruction of the pipe is accelerated. An object of the present invention is to solve the above-mentioned problems in water supply / hot water supply pipes and to provide a resin composition for silane crosslinked polyolefin pipes that can be suitably used as hot water supply equipment piping.

[0004]

[Means for Solving the Problems]

That is, the present invention relates to a method for producing a base polymer having the general formula RR'SiY ₂ (R is a monovalent olefinically unsaturated compound) in the presence of 0.01 to 0.5% by weight of a free radical generator based on the whole polymer. A hydrocarbon group, Y is a hydrolyzable organic group, and R 'is a monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon or the same as Y). 0.1 to 5% by weight of the silane grafter and 0.01 to 5% by weight of the total polymer.
In a silane-crosslinked polyolefin pipe resin composition obtained by melt-mixing a master batch containing 0.2% by weight of a silanol condensation catalyst and an antioxidant, a phenol-based oxidant having a molecular weight of 500 or more in the antioxidant and containing no ester bond is contained. A phenolic antioxidant having a molecular weight of 500 or more and containing an amide bond in an amount of 0.1 to 0.5% by weight based on the total polymer;
It is a silane-crosslinked polyolefin pipe resin composition containing 0.6% to 1.0% by weight of a phenolic antioxidant having a molecular weight of 500 or more based on the whole polymer.
Furthermore, the silane-crosslinked polyolefin pipe resin composition described above, in which the oxidation induction time at a test temperature of 223 ° C. specified in JIS C 3660-4-2 (common test method for insulators and sheath materials of electric cable) is 120 minutes or more. It is.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The polyolefin-based base polymer used in the present invention is not particularly limited, but low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, polypropylene, ethylene and α-olefin And α-olefins of C3 to C12 such as propylene, butene-1, pentene-1, octene-1, 4-methylpentene-1, 4-methylhexene-1,4,4-dimethylpentene- 1, nonene-1, decene-1, undecene-1, dodecene-1 and the like. Alternatively, hydrogenation of ethylene-ethyl acrylate copolymer, ethylene-methacrylate copolymer, ethylene-vinyl acetate copolymer, chlorinated polyethylene, ethylene-propylene-diene terpolymer, styrene-butadiene-block copolymer Derivatives and mixtures thereof can be mentioned.

[0007] The organic unsaturated silane of the present invention is grafted to the base resin so as to be a cross-linking point between the base resins. The organic unsaturated silane used in the present invention is represented by the general formula RR'SiY ₂ (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, and R 'is an aliphatic unsaturated hydrocarbon group. Monovalent hydrocarbon groups other than hydrogen or
The same compound as used for Y) is used. It is preferable to use an organic unsaturated silane represented by the general formula RSiY3 wherein R ′ is the same as Y, for example, vinyltrimethoxysilane,
Vinyl triethoxy silane, vinyl tributoxy silane, allyl trimethoxy silane, allyl triethoxy silane and the like can be mentioned. The amount of these additives is from 0.1 to 5% by weight, preferably from 0.7 to 3% by weight, based on the total weight of the polymer. If the amount is less than 0.1% by weight, sufficient grafting does not occur. If the amount exceeds 5% by weight, extrusion stability is reduced, so that uniform grafting cannot be performed and it is not economical.

[0008] The free radical generator of the present invention acts as an initiator of the silane grafting reaction. Examples of the free radical generator include organic peroxides and peresters having a strong polymerization initiating action, such as dicumyl peroxide, α,
α'-bis (t-butylperoxy-m-isopropyl) benzene, di-t-butyl peroxide, t-butylcumyl peroxide, di-benzoyl peroxide, 2,5-dimethyl-2,5-di ( t-butylperoxy) hexane, t-butylperoxypivalate,
One or more organic peroxides selected from t-butylperoxy-2-ethylhexanoate, di-t-butylperoxyisophthalate and the like are used.
These are added in an amount of 0.01 to 0.5% by weight, preferably 0.015 to 0.5% by weight, based on the total weight of the polymer.
2% by weight. If the amount is less than 0.01% by weight, a sufficient silane grafting reaction does not proceed. If the amount exceeds 0.5% by weight, the extrudability decreases and the molding surface deteriorates.

The silanol condensation catalyst of the present invention includes dibutyltin dilaurate, dioctyltin dilaurate, stannous acetate, dibutyltin diacetate, dibutyltin dioctoate, lead naphthenate, zinc caprylate, cobalt naphthenate, and tetrabutyl titanate. Examples include organic metal compounds such as esters, lead stearate, zinc stearate, cadmium stearate, barium stearate, and calcium stearate. The amount of these additives is 0.01 to 0.2% by weight based on the total weight of the polymer,
Preferably it is 0.02 to 0.1% by weight. If it is less than 0.01% by weight, a sufficient crosslinking reaction does not proceed, and 0.2% by weight
If the ratio exceeds the above range, crosslinking occurs locally in the extruder during extrusion, and the appearance deteriorates.

The antioxidants of the present invention prevent oxidative degradation promoted by heat, metal ions such as chlorine and copper. The antioxidant used in the present invention contains a phenolic antioxidant having a molecular weight of 500 or more and containing no ester bond in an amount of 0.1 to 0.5% by weight based on the whole polymer, and has a molecular weight of 50 or more.
A phenolic antioxidant containing an amide bond and having a molecular weight of not less than 0 to 0.1 to 0.5% by weight based on the whole polymer, and a phenolic antioxidant having a molecular weight of 500 or more is 0.6 to 1 based on the whole polymer. 0.0% by weight. When a phosphorus-based antioxidant or a sulfur-based antioxidant is used, extraction resistance to water or hot water cannot be obtained, so that the effect of preventing oxidation deterioration is reduced. If the amount of the phenolic antioxidant having a molecular weight of 500 or more is less than 0.6% by weight based on the total weight of the polymer, the desired heat and oxidative deterioration promoted by metal ions such as chlorine and copper are not obtained. No effect can be obtained, and if it exceeds 1.0% by weight, bloom or bleed tends to occur. If a phenolic antioxidant having a molecular weight of less than 500 is used, sufficient extraction resistance to water or hot water cannot be obtained, so that the effect of preventing oxidative deterioration is reduced. Further, the molecular weight used in the present invention is 50.
Of the phenolic antioxidants that are 0 or more, the phenolic antioxidants containing no ester bond must be contained in the range of 0.1 to 0.5% by weight based on the total weight of the polymer. When the phenolic antioxidant which does not contain an ester bond and has excellent extraction resistance to water or hot water is less than 0.1% by weight based on the total weight of the polymer, the extraction resistance to water or hot water is obtained. When the content exceeds 0.5% by weight, the dispersibility of a phenolic antioxidant containing no ester bond and having a melting point exceeding 150 ° C. cannot be obtained, and the molding surface is deteriorated. Further, among the phenolic antioxidants having a molecular weight of 500 or more used in the present invention, the phenolic antioxidant containing an amide bond is used in an amount of 0.1 to 100% based on the total weight of the polymer.
It must be contained in the range of 1 to 0.5% by weight. If the amount of the phenolic antioxidant containing an amide bond having metal inactivity is less than 0.1% by weight based on the total weight of the polymer, the oxidative deterioration due to metal ions generated from the metal joint cannot be prevented, and If it exceeds 0.5% by weight, the melting point becomes 15
The dispersibility of the phenolic antioxidant containing an amide bond exceeding 0 ° C. cannot be obtained, and the molding surface deteriorates. Examples of these phenolic antioxidants containing an ester bond and an amide bond include 2,2′-oxamide-bis- [ethyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate. Examples of phenolic antioxidants that contain an ester bond and do not contain an amide bond include pentaerythrityl-tetrakis [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate], 3,9-bis [2- [3- (3-t
-Butyl-4-hydroxy-5-methylphenyl) -propionyloxy] -1,1-dimethylethyl] -2,
4,8,10-tetraoxaspiro [5.5] undecane, 1,6-hexanediol-bis [3- (3,5-
Di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t
-Butyl-5-methyl-4-hydroxyphenyl) propionate], 2- [1- (2-hydroxy-3,5-
Di-t-pentenylphenyl) ethyl] -4,6-di-t
-Penterphenyl acrylate, octadecyl-3-
Examples of (3,5-di-butyl-4-hydroxyphenyl) propionate, which do not include an ester bond of a phenolic antioxidant but include an amide bond,
N, N'-hexaethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide, N, N'-
Bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and the like, and examples of phenolic antioxidants which do not contain an ester bond or an amide bond include tris- (3 , 5-Di-t-butyl-4-hydroxybenzyl) -isocyanurate,
1,3,5-trimethyl-2,4,6-tris (3,5
-Di-t-butyl-4-hydroxybenzyl) benzene, 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid,
1,1,3-tris (2-methyl-4-hydroxy-5
-T-butylphenyl) butane and the like.

The silane-crosslinked polyolefin pipe resin composition of the present invention is used for measuring the oxidation induction time at a test temperature of 223 ° C. specified in JIS C 3660-4-2 (a common test method for insulators and sheath materials of electric cables and cables). The oxidation induction time is preferably 120 minutes or more. If the heating time is less than 120 minutes, the effect of preventing oxidative deterioration promoted by desired heat, chlorine and particularly metal ions such as copper cannot be expected.

As other additives, if desired, additives usually used, for example, phosphorus-based antioxidants, sulfur-based antioxidants, hinderdamine light stabilizers, ultraviolet absorbers,
An antistatic agent, a pigment, a dispersant, a thickener, a fungicide, a flow regulator, a neutralizing agent, other inorganic fillers, and the like, or other synthetic resins can be contained.

[0013]

Embodiments will be described below with reference to embodiments. << Production of Silane Graft Mer >> According to the compounding ratio shown in Tables 1 and 2, the base polymer, the organic unsaturated silane and the free radical generator are mixed, kneaded using a single screw extruder, and granulated. A graftmer was obtained. << Manufacture of Silanol Condensation Catalyst and Antioxidant Masterbatch >> Carrier polymer, silanol condensation catalyst, antioxidant, etc. are kneaded using a twin screw extruder according to the compounding ratios shown in Tables 3, 4 and 5, and are produced. A granulated silanol condensation catalyst and an antioxidant masterbatch were obtained.

The produced silane graft mer, silanol condensation catalyst, and antioxidant masterbatch are mixed in the ratios shown in Tables 6, 7, and 8, a pipe is extruded using an extruder, and further crosslinked by dipping in hot water. Was done. The surface smoothness, bleed, gel fraction, tensile strength, elongation, oxidation induction time, and hot isostatic creep were evaluated using this extruded pipe. Tables 6, 7, and 8 show the evaluation results.

* Raw materials used (1) LDPE: low density polyethylene (density; 0.923 g / c
^{m 3, MI; 2g / 10min} ) (2) HDPE: high-density polyethylene (density; 0.945 g / c
m ³ , MI; 1 g / 10 min) (3) L-LDPE: linear low density polyethylene (density;
0.94 g / cm ³ , MI; 3 g / 10 min) (4) VTMOS: vinyltrimethoxysilane (5) VTEOS: vinyltriethoxysilane (6) Organic peroxide (1): α, α'-bis (t- (7) Organic peroxide (2): Dicumyl peroxide (8) DOTDL: Dioctyl tin dilaurate (9) DBTDL: Dibutyl tin dilaurate (10) Phenol-based oxidation Inhibitor (1): 2,2′-oxamide-bis- [ethyl 3- (3,5-di-t-butyl-)
4-hydroxyphenyl) propionate] (structure; ester bond and amide bond present, molecular weight: 69)
7) (11) Phenolic antioxidant (2): pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-)
(Hydroxyphenyl) propionate] (structure; ester bond present, no amide bond, molecular weight: 1178) (12) Phenolic antioxidant (3): N, N′-bis [3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionyl] hydrazine (structure; no ester bond, amide bond, molecular weight: 553) (13) Phenolic antioxidant (4): 1,3,5-trimethyl-2,4,6 -Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (structure; no ester bond or amide bond, molecular weight: 761) (14) Sulfur-based antioxidant: pentaerthrityltetrakis (3-lauryl) (15) Phosphorus antioxidant: tris (2,4-di-t-butylphenyl) phosphite (16) Phenol antioxidant (5): i -Octyl-3
-(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate (structure; with ester bond, no amide bond, molecular weight: 391) (17) Phenolic antioxidant (6): 3- (N-salicyloyl) amino-1,2,4-triazole (structure; without ester bond) Amide bond, molecular weight: 204) (18) phenolic antioxidant (7): 4,4'-butylidenebis (3-methyl-6-t-butylphenol)
(Structure: No ester bond or amide bond, molecular weight: 3
83) (19) Hindered amine light stabilizer: bis (2,2,6,6)
-Tetramethyl-4-piperidyl) sebacate

* Evaluation method Extruder of 50mmφ (L / D = 20) 120-150-170-180-170 ° C Full flight screw (compression ratio 3.5) Pipe size: Outer diameter 17mm Inner diameter 13mm (20) Surface smoothness ( -): The surface smoothness of the pipe was evaluated. (21) Bleed (-): Evaluate the presence or absence of bleed,
○ indicates no, and X indicates yes. (22) Gel fraction (%): According to JIS K 6769. (23) Tensile strength (MPa) and elongation (%): JIS K 6769
by. (24) Oxidation induction time (min): JIS C 3660-4-2 (test temperature 22
3 ° C). (25) Hot isostatic creep: conforms to ISO 1167, temperature 1
Under conditions of 10 ° C. and hoop stress of 1.6 MPa, 90
The test was performed for 00 hours, and a sample having no abnormality such as leakage was accepted. When a leakage occurred, the time until an abnormality occurred was measured. The pipe joint used was made of brass.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

[Table 4]

[0021]

[Table 5]

[0022]

[Table 6]

[0023]

[Table 7]

[0024]

[Table 8]

As is clear from the table, Examples 1, 2 and
The materials shown in Nos. 3 and 4 have a good appearance of the molded product and show very excellent crosslinking properties, mechanical strength, thermo-oxidative durability and hot isostatic creep. On the other hand, in all of the comparative examples, the appearance, cross-linking properties, mechanical strength, thermal oxidation durability and hot isostatic creep of the molded product are not balanced.

[0026]

According to the present invention, the appearance of a molded article is excellent,
Further, a resin composition for a silane crosslinked polyolefin pipe which is preferably used for supplying hot water, hot water, or the like excellent in crosslinking properties, mechanical strength, thermal oxidation durability and hot isostatic creep properties can be obtained.

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Claims (2)

[Claims] 1. The method of claim 1 wherein the base polymer has a concentration of 0.
01 to 0.5 wt% of free general formula RR'SiY ₂ in the presence of a radical generator (R is a monovalent olefinically unsaturated hydrocarbon group, an organic group Y which can be hydrolyzed, R 'is an aliphatic A silane graftmer obtained by reacting an organic unsaturated silane represented by a monovalent hydrocarbon group other than an unsaturated hydrocarbon or the same as Y) with respect to the total polymer in an amount of 0.1 to 5% by weight; In a silane-crosslinked polyolefin pipe resin composition obtained by melt-mixing a master batch containing 0.01 to 0.2% by weight of a silanol condensation catalyst and an antioxidant, the antioxidant has a molecular weight of 500 or more and an ester bond. Containing 0.1 to 0.5% by weight of the total polymer with no phenolic antioxidant containing
A phenolic antioxidant containing an amide bond and having a molecular weight of not less than 0 to 0.1 to 0.5% by weight based on the whole polymer, and a phenolic antioxidant having a molecular weight of 500 or more is 0.6 to 1 based on the whole polymer. 0.1% by weight of the resin composition for silane cross-linked polyolefin pipes. 2. An oxidation induction time at a test temperature of 223 ° C. specified in JIS C 3660-4-2 (a common test method for an insulator and a sheath material of an electric cable) is 120.
The resin composition for a silane crosslinked polyolefin pipe according to claim 1, wherein the time is at least one minute.