Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/36—Sulfur-, selenium-, or tellurium-containing compounds
  • C08K5/37—Thiols
  • C08K5/375—Thiols containing six-membered aromatic rings
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/16—Halogen-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/13—Phenols; Phenolates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/34—Heterocyclic compounds having nitrogen in the ring
  • C08K5/3412—Heterocyclic compounds having nitrogen in the ring having one nitrogen atom in the ring
  • C08K5/3432—Six-membered rings
  • C08K5/3435—Piperidines
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/36—Sulfur-, selenium-, or tellurium-containing compounds
  • C08K5/37—Thiols
  • C08K5/372—Sulfides, e.g. R-(S)x-R'
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T137/00—Fluid handling
  • Y10T137/0318—Processes

Definitions

• the present invention relates to a polyolefin composition with increased resistance to degradation caused by ClO 2 -containing water and to a pipe made of such a polyolefin composition.
• the present invention further relates to the use of the polyolefin composition for the production of a pipe and to the use of a specific antioxidant for increasing the resistance of the polyolefin composition against degradation caused by contact with ClO 2 -containing water.
• chlorinated water denotes water which contains chlorine, i.e. the following three forms in equation which is dependent on the pH value and known to the person skilled in the art: Cl 2 , HOCl, and ClO ⁇ .
• Chlorinated water can be produced by adding chlorine gas (Cl 2 ) or sodium hypochlorite (NaOCl) to water.
• antioxidants In order to increase the lifetime of polyolefin pipes exposed to chlorinated water, it is known to add various antioxidants to the composition the pipe is made of. Suitable and often used antioxidants are pentaerythrityl-tetrakis(3-(3′,5′-di-t-butyl-4-hydroxyphenyl)propionate (CAS No. 6683-19-8, “Irganox 1010”), 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxyphenyl)benzene (CAS No. 1709-70-2, “Irganox 1330”) and tris(2,4-di-t-butylphenyl)phosphite (CAS No. 31570-04-4, “Irgafos 168”).
• chlorine dioxide a more effective disinfectant used in water is chlorine dioxide, ClO 2 .
• the use of chlorine dioxide has been seen as favourable for pipes made of a polyolefin composition, as it does not react with the carbon-carbon main chain of the polyolefin.
• ClO 2 readily reacts with many antioxidants used in pipe compositions and therefore indirectly increases the aging of the polymers and hence the pipes made thereof.
• antioxidants used in polyolefin compositions for pipes known to provide a good resistance to chlorinated water do not provide satisfactory resistance against water containing chlorine dioxide.
• a more efficient antioxidant which provides a better protection against ClO 2 -containing water to a polyolefin composition, and thus allows for a longer lifetime of e.g. a pipe, made of a polyolefin composition containing such an antioxidant.
• a further important issue as regards the presence of antioxidants in polyolefin compositions is the aim to avoid contamination of media transported e.g. in a pipe made of such a polyolefin composition. This is particularly important in case of a pipe transporting drinking water.
• it is desirable that the antioxidant used has a low tendency to extraction by the water transported in the pipe.
• the object of the present invention to provide a polyolefin composition with increased resistance to degradation caused by ClO 2 -containing water and particularly to provide a pipe with increased lifetime when exposed to ClO 2 -containing water. Still further, it is an object of the invention that the above objects are achieved by using an amount as small as possible of an antioxidant and that the antioxidant used has a low tendency for extraction by the water transported in a pipe made of such a polyolefin composition.
• the present invention is based on the surprising finding that the above mentioned objects can be achieved by a polyolefin composition comprising a polyolefin base resin and a specifically selected antioxidant.
• the present invention provides a polyolefin composition
• a polyolefin composition comprising a polyolefin base resin and an antioxidant characterized in that said polyolefin composition has a lifetime of at least 200 h in a test measuring the resistance against ClO 2 -containing water at 90° C. and at a concentration of ClO 2 of 4 ppm wherein the equipment used is according to ASTM F2263-03.
• compositions of the invention show a superior life time in said ClO 2 water test, and such a superior lifetime and hence improved resistance against water containing ClO 2 is not obtained by the use of common antioxidants used for improving the resistance of a polyolefin composition against chlorine-containing water in usual amounts.
• base resin denotes the entirety of polymeric components in the polyolefin composition according to the invention, usually making up at least 90 wt % of the total composition.
• the favourable effect of the antioxidants according to the present invention is not dependent on the type of olefin base resin used.
• the base resin may therefore be any polyolefin composition.
• the antioxidant is selected from
• At least one of the substituents R, R′ and/or R′′ of the phenol comprises at least one sulphur heteroatom(s).
• At least one of the heteroatoms preferably a sulphur heteroatom, is directly attached to at least one phenol group.
• the heteroatom preferably sulphur
• group R is present in group R, and preferably is directly attached to at least one phenol group.
• X 2 is a hydroxy group.
• R′ is a hydrogen atom or a aliphatic hydrocarbyl radical, preferably with up to 10 carbon atoms. Most preferably, R′ is a hydrogen atom.
• R′′ in formula I preferably is a hydrogen atom or an aliphatic hydrocarbyl radical, preferably with up to 10 carbon atoms. Most preferably, R′′ is a t-butyl group.
• X 1 is a hydrogen atom or an aliphatic hydrocarbyl radical, preferably with up to 10 carbon atoms. Most preferably, X 1 is a methyl radical.
• X 3 in formula I preferably is a hydrogen atom or an aliphatic hydrocarbyl radical, preferably with up to 10 carbon atoms. Most preferably, X 3 is a hydrogen atom.
• R in the phenolic antioxidant according to formula I is an aliphatic hydrocarbyl group, preferably comprising a heteroatom, with preferably up to 10 atoms, or is a heteroatom selected from the group of S, N and P. More preferably, R is a S, N, or P atom, and most preferably, R is a S atom.
• n 2 or 3.
• R 1 , R 2 , R 3 and R 4 are the same.
• R 1 , R 2 , R 3 and R 4 are aliphatic hydrocarbyl radicals with one to ten carbon atoms each. Still more preferably, all four radicals are a methyl group.
• R 6 is hydrogen
• R a or R b independently are an aliphatic hydrocarbyl radical, optionally comprising heteroatoms, preferably comprising from 4 to 50 C-atoms, more preferably from 10 to 30 C-atoms.
• R a or R b comprise at least one ester group.
• the polyolefin composition comprises only antioxidants selected from only one of groups a), b) and c), or any mixture thereof.
• the polyolefin composition comprises only antioxidants of one of groups a), b) or c), and more preferably comprises one antioxidant compound only.
• the amount of the antioxidant in the polyolefin composition is preferably 5000 ppm or less, more preferably 3500 ppm or less, still more preferably 2500 ppm or less and particularly preferred is 1000 ppm or less.
• the composition will contain the antioxidant in an amount of at least 50 ppm, more preferably of at least 100 ppm.
• antioxidants of the phenols of group a) wherein the heteroatom in the aliphatic part is sulphur examples include 2,2′-Thiodiethylene bis(3,5-di-t-butyl-4-hydroxyphenyl)propionate (CAS No. 41484-35-9, “Irganox 1035”), 4,4′-Thiobis(2-t-butyl-5-methylphenol) (CAS No. 96-69-5, “Lowinox TBM-6P”), 6,6′-di-t-butyl-2,2′-thiodi-p-cresol (CAS No. 90-66-4, “Irganox 1081”).
• antioxidants of the phenols of group a) wherein the heteroatom in the aliphatic part is phosphorus are calcium (3,5-di-t-butyl-4-hydroxybenzyl monoethylphosphonate) (CAS No. 65140-91-2, “Irganox 1425”) and 3,5-Bis(1,1-dimethylethyl)-4-hydroxybenzyl diethyl-phosphonate (CAS No. 976-56-7, “Irganox 1222”).
• antioxidants of the phenols of group a) wherein the heteroatom in the aliphatic part is nitrogen are 1,3,5-Tris(3′,5′-di-t-butyl-4′-hydroxybenzyl)isocyanurate (CAS No. 27676-62-6, “Irganox 3114”), N,N′-Hexamethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide] (CAS No. 23128-74-7, “Irganox 1098”) and N,N′-Bis(3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionyl)hydrazine (CAS No. 32687-78-8, “Irganox MD 1024”).
• antioxidants of the amines of group b) are bis(2,2,6,6-tetramethyl-4-piperidyl)decanediate (“Tinuvin 770”, CAS No. 52829-07-9), poly[1-(2′-hydroxyethyl)-4-hydroxy-2,2,6,6-tetra-methylpiperidylsuccinate] (CAS No.
• Tivin 622 and poly((6-((1,1,3,3-tetramethylbutyl)amino)-1,3,5-triazine-2,4-diyl)((2,2,6,6-tetramethyl-4-piperidyl)imino)(1,6-hexanediyl)((2,2,6,6-tetramethyl-4-piperidyl)imino)) (CAS No. 71878-19-8, “Chimassorb 944”).
• An example for a preferred antioxidant of the sulphur-containing compounds of group c) is di-stearyl-thio-di-propionate (CAS No. 693-36-7, “Arenox DS” or “Irganox PS-802 FL”).
• the polyolefin base resin of the composition of the invention comprises a polyethylene, i.e. an ethylene homo- or copolymer.
• the base resin comprises two or more polyolefin, more preferably polyethylene, fractions with different weight average molecular weight.
• Such resins usually are denoted as multimodal resins.
• compositions comprising multimodal resins are frequently used e.g. for the production of pipes due to their favourable physical and chemical properties as e.g. mechanical strength, corrosion resistance and long-term stability.
• Such compositions are described e.g. in EP 0 739 937 and WO 02/102891.
• molecular weight used herein generally denotes the weight average molecular weight M w .
• multimodal a polyethylene composition comprising at least two polyolefin fractions, which have been produced under different polymerization conditions resulting in different weight average molecular weights for the fractions.
• multi relates to the number of different polymer fractions the composition is consisting of.
• a composition consisting of two fractions only is called “bimodal”.
• the form of the molecular weight distribution curve i.e. the appearance of the graph of the polymer weight fraction as function of its molecular weight, of such a multimodal polyethylene will show two or more maxima or at least be distinctly broadened in comparison with the curves for the individual fractions.
• the polymer fractions produced in the different reactors will each have their own molecular weight distribution and weight average molecular weight.
• the individual curves from these fractions are superimposed into the molecular weight distribution curve for the total resulting polymer product, usually yielding a curve with two or more distinct maxima.
• fraction (A) the fraction having a lower weight average molecular weight
• fraction (B) the fraction having a lower weight average molecular weight
• Fraction (A) preferably is an ethylene homopolymer.
• Fraction (B) of the polyethylene composition preferably is an ethylene copolymer, and preferably comprises at least 0.1 mol % of at least one alpha-olefin comonomer.
• the amount of comonomer is preferably at most 14 mol %.
• the base resin of the polyethylene composition preferably comprises at least 0.1 mol %, more preferably at least 0.3 mol %, and still more preferably at least 0.7 mol % of at least one alpha-olefin comonomer.
• the amount of comonomer is preferably at most 7.0 mol %, more preferably at most 6.0 mol %, and still more preferably at most 5.0 mol %.
• an alpha-olefin comonomer preferably an alpha-olefin having from 4 to 8 carbon atoms is used. Still more preferably an alpha-olefin selected from 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene is used.
• the polyolefin base resin preferably has an MFR 5 (190° C., 5 kg) of from 0.1 to 1.2 g/10 min, more preferably from 0.2 to 0.8 g/10 min, and most preferably from 0.25 to 0.6 g/10 min.
• the density of the base resin preferably is from 930 to 960 kg/m 3 , more preferably is from 935 to 958 kg/m 3 , and most preferably is from 938 to 952 kg/m 3 .
• polyolefins for example carbon black
• pigments for example carbon black
• stabilizers for example carbon black
• antacids and/or anti-UVs for example carbon black
• antistatic agents and utilization agents such as processing aid agents
• the amount of such additives usually is 10 wt. % or below.
• the polymerization catalysts for the production of the base resin include coordination catalysts of a transition metal, such as Ziegler-Natta (ZN), metallocenes, non-metallocenes, Cr-catalysts etc.
• the catalyst may be supported, e.g. with conventional supports including silica, Al-containing supports and magnesium dichloride based supports.
• the catalyst is a ZN catalyst, more preferably the catalyst is a non-silica supported ZN catalyst, and most preferably a MgCl 2 -based ZN catalyst.
• the Ziegler-Natta catalyst further preferably comprises a group 4 (group numbering according to new IUPAC system) metal compound, preferably titanium, magnesium dichloride and aluminium.
• the catalyst may be commercially available or be produced in accordance or analogously to the literature.
• reference is made to WO2004055068 and WO2004055069 of Borealis and EP 0 810 235.
• the content of these documents in its entirety is incorporated herein by reference, in particular concerning the general and all preferred embodiments of the catalysts described therein as well as the methods for the production of the catalysts.
• Particularly preferred Ziegler-Natta catalysts are described in EP 0 810 235.
• the composition preferably is produced in a process comprising a compounding step, wherein the base resin which is typically obtained as a base resin powder from the reactor, together with the antioxidant and optionally other additives is extruded in an extruder to yield the composition of the invention.
• the improved resistance of the polyolefin composition against degradation caused by contact with ClO 2 -containing water is measured at 90° C. and at a concentration of ClO 2 of 4 ppm wherein the equipment used is according to ASTM F2263-03.
• a pipe made of the polyolefin composition of the invention is capable of obtaining a lifetime of at least 200 h, more preferably of at least 220 h, in this test.
• the present invention is also directed to a pipe comprising a polyolefin composition according to the invention including any of the preferred embodiments described above.
• the pipe is preferably for transportation of drinking water, especially drinking water containing ClO 2 .
• the present invention is also directed to the use of a polyolefin composition according to the invention for the production of a pipe. Still further, the present invention is directed to the use of such a pipe for drinking water transportation.
• the present invention is also directed to the use of an antioxidant for increasing the resistance of a polyolefin composition against degradation caused by contact with ClO 2 -containing water.
• the antioxidant is defined as described above including the preferred embodiments.
• Density is measured according to ISO 1183. Sample preparation is done in accordance with ISO 1872/2B.
• the melt flow rate is determined according to ISO 1133 and is indicated in g/10 min.
• the MFR is an indication of the flowability, and hence the processability, of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer.
• the MFR is determined at 190° C. for polyethylene and may be determined at different loadings such as 2.16 kg (MFR 2 ), 5.00 kg (MFR 5 ) or 21.6 kg (MFR 21 ).
• FRR flow rate ratio
• a circulation loop is used for water which contains ClO 2 .
• the concentration of ClO 2 in the water is 4.0 ⁇ 0.1 ppm.
• the pH of the water is 6.8 ⁇ 0.2.
• the temperature of the water is 90 ⁇ 1° C.
• the hoop stress applied to the pipe is about 1.7 MPa.
• the oxidation reduction potential (ORP) is 740 mV and is measured frequently.
• the flow volume is 23 l/h at a flow velocity of about 0.13 m/s and a fluid pressure of 6.5 bar.
• the free pipe length is 250 mm, the outer diameter of the pipe is 12 mm and the thickness of the wall is 2 mm. In the tests two pipes of each material are tested in series, the results given are the average of the two values measured.
• the circulation loop used for ClO 2 testing is made from inert materials (e.g. titanium, PVDF (Polyvinylidene difluoride), PTFE (Polytetrafluoro-ethylene) to avoid contamination of the test fluid.
• inert materials e.g. titanium, PVDF (Polyvinylidene difluoride), PTFE (Polytetrafluoro-ethylene) to avoid contamination of the test fluid.
• the fittings are of PVDF.
• the test fluid is continuously purified in three steps to avoid any contamination: 1. active carbon filter, 2. particle filter, 3. reverse osmosis.
• the internal environment is the above-mentioned solution of ClO 2 in water, the external environment is air.
• the ClO 2 is generated directly at the site using a commercial ClO 2 -generator from Prominent following the equation:
• the mechanism for feeding the stock solutions (NaClO 2 and HCl) to the process are monitored to maintain a consistent ratio of chemicals.
• Sample preparation The polymer pellets are ground and 5 g of the ground polymer is extracted in 50 ml of cyclohexane at a temperature of 81° C. for 2 hours. If needed, cyclohexane is then added to exact 50 ml again. The solution is cooled down in room temperature and thereafter the polymer is precipitated with 50 ml iso-propanol. A suitable amount of the solution is filtered and injected into an HPLC equipment.
• the HPLC measurement can e.g. be performed with a reversed phase C-18 column and methanol and water as mobile phase, for example in a ratio of 85:15.
• a UV detector can be used, wavelength 280 nm for Irganox 1010, Irgafos 168 and Irganox 1330 and 220 nm for Lowinox TBM-6P.
• the quantification is made using calibration curves in a conventional manner.
• Polyethylene compositions for the testing of pipes were produced from commercially available polyethylene resins.
• the properties of the base resins used, as well as the additives which were added to the base resins to yield the polyethylene compositions used for pipe production are given in Table 1.
• Table 1 also the results of the lifetime tests in ClO 2 -containing and chlorinated water are given.
• Example 1 as antioxidant 4,4′-Thiobis(2-t-butyl-5-methylphenol) (CAS No. 96-69-5, Lowinox TBM-6P) was used.
• Comparative Example 2 a typical mixture of conventional antioxidants as used to provide pipes with good resistance to chlorinated water in usual amounts has been used.
• Example 1 the total amount of antioxidant is much less in Example 1 than in Comparative Example 2, and that in Example 1 only one antioxidant is used whereas in Comparative Example 2 a mixture of two different antioxidants was used.

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• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Compositions Of Macromolecular Compounds (AREA)
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