WO2017186561A1

WO2017186561A1 - Pipe produced with a polymer composition comprising a polyolefin

Info

Publication number: WO2017186561A1
Application number: PCT/EP2017/059369
Authority: WO
Inventors: Mark Johannes Boerakker; Maria Soliman
Original assignee: Sabic Global Technologies B.V.
Priority date: 2016-04-29
Filing date: 2017-04-20
Publication date: 2017-11-02

Abstract

The invention relates a pipe for the transport of water with improved resistance to chlorinated disinfectants. The pipe is produced with a polymer composition comprising polyolefin and poly(ethylene-co-vinylalcohol).

Description

Pipe produced with a polymer composition

comprising a polyolefin

The present invention relates to a pipe for the transport of water produced with a polymer composition comprising a polyolefin. The pipe has an improved resistance to chlorinated disinfectants.

Pipes for the transport of gas, for sanitation and for water supply may be produced with for example bimodal polyethylene compositions. Pipes have a very good resistance to water however their lifetime is shortened when the pipes come into contact with disinfectants which are often added to water for hygienic reasons. The chlorine dioxide used as disinfectant in water degrades most materials including polyethylene (Colin, Aging of polyethylene pipes transporting drinking water disinfected by chlorine dioxide, part 1, Chemical aspects; Polymer engineering and Science 49(7); 1429-1437; July 2009). Other chlorinated solvents are for example chloramine and chlorine, it is known in the art, fo apply additives for example antioxidants and stabilizers to prevent said degradation. Several types of additives are proposed to protect polymers during processing and to achieve the desired end-use properties. However, appropriate combinations of stabilizers have to be carefully selected, depending on the desired final properties the polymeric article should have.

It is the object of the present invention to provide pipe applications with improved service lifetime for the transportation of water containing chlorinated disinfectants, for example chlorine dioxide, chloramine and chlorine.

The pipe for the transport of water according to the invention is produced with a polymer composition comprising polyolefin and poly(ethylene-co-vinylalcohol) wherein the amount, of poly (ethylene-co-vinylalcohol) in the composition is lower than 2.0 wt% relative to the total weight amount of the composition.

Suitable examples of poly(ethylene-co-vinylalcohol) include for example poly(ethylene-co-vinylalcohol) with an ethylene content ranging between 1 and 99 mol%.

According to a preferred embodiment of the invention the ethylene content of poly(ethylene-co-vinylalcohol) ranges between 10 and 70 mol%.

According to a further preferred embodiment of the invention the ethylene content of pofy(ethylene-co-vinytaicohol) ranges between 25 and 50 mol%.

Most preferably the ethylene content, of poly(eihylene-co-vinyialcohoi) ranges between 28 and 45 mol%.

Preferably the pipe is a drinking water pipe. The drinking water pipe, preferably a pressure pipe, based on this polyolefin grade has an improved protection against for example chlorine dioxide containing cold or hot water and consequently a longer life time. It is also possible to transport waste water or water for cooling,

The polyolefin may be selected from polyethylene such as a multimodal polyethylene for example a bimodal or trimodal polyethylene or polypropylene.

Preferably, the polyolefin is multimodal polyethylene.

More preferably, the polyolefin is bimodal polyethylene.

According to a further preferred embodiment of the invention the pipe is produced with a composition comprising

(a) polyolefin

(b) poly(ethyiene-co-vinyiaicohot)

(c) phenolic compound and/or

(d) organic phosphite and/or phospbonite,

Preferably the weight ratio (bj: (c+d) ranges between 7: 1 and 1 :7.

Suitable examples of phenolic compounds include mono phenolic compounds, bisphenolic compounds and polyphenolic compounds. Suitable phenolic compounds include for example tetrakis[methylene-3-(3',5'-di-t-butyl-4-hydroxyph:enyl)propionate3 methane; 1 ,1 ,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane; 1 ,3,5-trimethyl-2,4,6- tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(3,3-bis(4'-hydroxy-3^,-t- butylphenyljbutanoic acid]-glycol ester; tris(3,5-di-t-butyi-4-hydroxy

benzyl)isocyanurate; 1 ,3,5-tris(4-t-butyl-2,6-dimethyl-3-hydroxy-benzyl)isocyanurate; 5- di-t-butyl-4-hydroxy-hydrocinnamic acid triester with 1 ,3,5-tris(2-hydroxyethyl)-s- triazf.ne-2,4,6(1 H, 3H, 5H)-trione; p-cresol/ dicyclopentadiene butylated reaction product; 2,6-bis(2'-bis-hydroxy-3'-t-butyl-5'-methyl-phenyl-4-methyl-phenol).

A preferred phenolic compound is 1 ,3,5-trimethyJ-2,4,6-tris(3,5-di-t-butyl-4- hydroxybenzyljbenzene (lrganox 1330 supplied by BASF),

Suitable organic phosphites and phosphorites include for example triphenyl phosphite, diphenyl alkyl phosphites, phenyl dialkyi phosphites, tris(nonylphenyi) phosphite, triiauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, bis{2,4-di-tert-butylphenyl) pentaerythritol diphosphate, bts(2,6-di-tert- buty)-4-methylphenyl) pentaerythritol diphosphate, bisisodecyloxy-pentaerythritot diphosphite, bis(2,4-di-tert-butyl- 6-methylphenyl) pentaerythritol diphosphite, bis(2,4,6- tri-tert-butylphenyl) pentaerythritol diphosphite, trtstearyi sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl) 4,4'- biphenylenediphosphonite, 6-isooctyloxy-2,4,8,10- tetra-tert-butyI-12H-dibenzo[d, g]-1 ,3,2-dioxaphosphocin, 6-fluoro-2,4.8,10-tetra-tert- butyl-12-methyfdibenzo[d,g]-1 ,3,2-dioxaphosphocin, bis(2,4-di-tert-butyl-6- methylphenyl) methyl phosphite, bis(2,4-di-tert-butyl- 6-methylphenyl) ethyl phosphite.

A preferred phosphite is tris(2,4-di-tert-butylphenyl) phosphite (Irgafos 168 supplied by BASF).

According to another preferred embodiment, of the invention the pipe is produced with a polyethylene composition comprising

(a) multimodal polyethylene

(b) poty(ethylene-co-vinylalcohol)

(c) phenolic compound and

(d) organic phosphite and/or phosphonate wherein the weight ratio (b): (c+d) ranges between 7:1 and 1 :7.

Preferably (b, (c) and (d) are added during the granulation step of the multimodal, for example bimodal, high density polyethylene powder,

According to a preferred embodiment of the invention the components are added to the polyethylene resin while the polyethylene is in a molten state during extrusion.

The components may be added together and may be added separately.

Preferably the components are added in one step.

Preferably the amount of polyolefin in the composition is higher than 90.0 wt%, more preferably higher than 95.0 wt%,

Preferably the amount of poly(ethylene-co-vinylalcohol) in the composition is lower than 1.0 wt%.

More preferably this amount ranges between 0.05 and 0.9 wt%.

Said amounts poly(ethylene-co-vinylalcohol) in the composition according to the invention protect, the pipe against chlorine dioxide during a long period.

The multimodal ethylene polymer may be an ethylene homo- or copolymer. The multimodal ethylene grades to be applied in pipe applications may comprise additives such as for example carbon black, pigments, stearates, a UV stabilizer for example a sterically hindered amine, fillers, minerals .lubricants and/or other stabilisers.

The production processes for bimodaf high density polyethylene (HDPE) are summarised at pages 16-20 of "PE 100 Pipe systems" (edited by Bromstrup; second edition, ISBN 3-802.7-2728-2).

The production of bimodal high density polyethylene (HDPE) via a low pressure slurry process is described by Alt et al. in "Bimodat polyethylene-Interplay of catalyst and process" (Macromol.Symp. 2001 , 163, 135-143). Bimodal high density

polyethylene may be produced via a low pressure slurry process for the production of comprising a poiymerisation stage, a powder drying stage, an extrusion and pellet handling stage, a recycling stage and a wax removal unit. In a two stage cascade process the reactors may be fed continuously with a mixture of monomers, hydrogen, catalyst/co-catalyst and diluent recycled from the process, in the reactors,

polymerisation of ethylene occurs as an exothermic reaction at pressures in the range between for example 0.5 MPa (5 bar) and 1 MPa ( 10 bar) and at temperatures in the range between for example 75 °C and 88 °C. The heat from the poiymerisation reaction is removed by means of cooling water. The characteristics of the polyethylene are determined amongst others by the catalyst system and by the concentrations of catalyst, co monomer and hydrogen. The production of bimodal high density polyethylene (HDPE) via a low pressure slurry process may also be performed via a three stage process.

The concept of the two stage cascade process is elucidated at pages 137-138 by Alt et a). "Bimodal poiyeihyfene-interplay of catalyst and process" (Macromol. Symp. 2001 , 163). The reactors are set up in cascade with different conditions in each reactor including low hydrogen content in the second reactor. This allows for the production of HDPE with a bimodal molecular mass distribution and defined co monomer content in the polyethylene chains.

Suitable catalysts for the production of multimodal polyethylene include Ziegler Natta catalysts, chromium based catalysts and single site metattocene catalysts. In all potential possible technologies the process and the catalyst have to form a well- balanced system. The catalyst is crucial for the polymerisation reaction of multimodal polyethylene. By cooperation of process and catalyst a definite polymer structure is produced..

According to a preferred embodiment of the invention polyethylene is a.

multimodal high density polyethylene ( HDPE) having a polymer density≥ 940 and≤ 970 kg/m³ and a melt flow rate 190/5≥ 0, 1 and≤ 4.0 g / 10 min.

More preferably, the density is≥ 945 and≤ 965 kg/m³ and even more preferably the density is≥ 945 and≤ 955 kg/m³ and the melt flow rate 190/5≥ 0, 1 and≤ 0, 6 g / 10 min.

The density is measured according to ISO 1 183 A. The melt flow rate MFR 190/5 is measured according to ISO 1 133 -1 (190 °C; 5.0 kg).

HDPE may for example be natural or coloured for example yellow, orange or blue. According to a preferred embodiment of the invention polyethylene is a compound comprising multimodal high density polyethylene and carbon black as pigment, wherein the density is≥ 950 and≤ 970 kg/m³ and MFR (190/5)≥ 0, 1 and≤ 4.0g/10 min, wherein the density is measured according to ISO 1 183 A and the melt flow rate MFR 190/5 is measured according to ISO 1133 -1(190 °C; 5.0 kg)..

More preferably the density is > 958 and≤ 965 kg/m³ and the melt flow rate 190/5 is≥ 0, 1 and≤ 0,6 g / 10 min.

Typically compositions used for black HDPE pressure pipes contain a carbon black content of between 2,0 and 2,5 % by weight relative to the total amount of the composition.

Preferably HDPE without pigments or HDPE with pigments has the following characteristics:

● Tensile modulus between≥ 500 and≤ 1400 MPa (according to ISO 527-2) ● Yield stress between≥ 18 and≤ 32 MPa {according to ISO 527-2}

● Full Notch Creep Test (FNCT): 100 - 20000 h (according to ISO 16770 @ 80 °C 1 4 MPa)

Charpy between≥ 14 and≤ 35 kJ/m^s @ 23 C (according to ISO 179-1 ell). More preferably HDPE without pigments or HDPE with pigments has the following characteristics:

● Tensile modulus between≥ 900 and≤ 1400 MPa (according to ISO 527-2) ● Yield stress between≥ 22 and≤ 32 MPa (according to ISO 527-2)

● Full Notch Creep Test (FNCT): 1000 - 20000 h (according to ISO 16770 @ 80 °C / 4 MPa)

● Charpy between≥ 17 and≤ 35 kJ/rn² @ 23 °C (according to ISO 1.79-1 eU).

Polypropylene to be applied in the present invention is preferably based on at least 70 % by weight of propylene monomer more preferably based on≥ 90 % by weight, and≤ 100 % by weight of propylene monomer.

CN 104877212 discloses a flame retardant. HDPE composition which is intended to be used in pipes for coal mining. The composition comprises 100 parts of HDPE, .2.-8 parts of zinc oxide, 5-25 parts of decabromodiphenyl ether, 15-35 parts of calcium stearate, 10-30 parts of magnesium hydroxide, 0,2-0.8 part of 2,6-butylated hydroxytoluene, 0.1-0.5 part of antioxidant, 20-40 parts of EVA, 0.5-2.5 parts of lead stearate, 15-35 parts of EVOH, 0.3-0.7 part of flame retardant, 15-2.5 parts of CPE, 15- 35 parts of UHMWPE, 10-30 parts of EPDM, and 1-5 parts of organic montmoriHonite. The amount of EVOH is about 7 % by weight relative to the total amount of the composition according to the description of CN 104877212. The composition according to CN 104877212 is unsuitable to be used in the production of pipes for the transport of drinking water because the pipe according to CN 104877212 is intended to be used in coal mines with specific requirements related to flame retardant, antistatic, corrosion, lubricating and abrasion resistant properties,

The invention will be elucidated by means of the following non-limiting examples.

Examples

SABIC Vestoien A5924 (Resin A) used as base polymer in all examples was a bimodal high density polyethylene with fvlFRs of 0.24 g/1 Omin and density 358 kg/m³.

Examples l-llf and Comparative Examples A-P

The Examples l-IIi and Comparative Examples A-D use different additive packages in combination with Resin A to protect the polyethylene from attack by chlorine dioxide (see Table 1 ).. The components as indicated in Table 1 were mixed at 245 degrees Cetctus using a twin screw extruder.

wherein:

· Irganox 1010 iTetrakis [methylen- 3-(3 ",5 ')di-t-butyl-4 -hydroxyphenyl)

propionate] methane commercially available from Ciba Speciality Chemicals,

• poly(ethylene-co-vinylalcohol): DT2904RB, commercially available from. Nippon Gohsei, with an ethylene content of 29 mol%;

• Irganox 1330 : 1 ,3,5"Trimethyl-2,4,6-tris{3,5-di-tert-butyl-=4- hydroxybenzyl)benzene;

• !rgafos 188; Tris(2,4-di-tert-butylprienyl) phosphite ;

• DHT-4A^®, commercially available hydrotalcite from Kisuma Chemicals. • Resin A: SABiC Vestolen A5924; bimodal high density polyethylene with MFRs 0.24 g/10min and density 958 kg/m³.

Compounds were compression molded using IS01872-2 resulting in plaques, which were cut to IS0527-1 A tensile bars (4 mm thick).

Ageing test

The tensile bars were aged in a continuous water flow at a temperature of 40 °C with a chlorine dioxide concentration maintained at 1 mg/L and a pH maintained at 7.2. Flow rate was regulated at 200 L/h. Water hardness was regulated to 20 °F, A consiant fresh water flow was added during testing allowing full renewal of the testing water each 4 hrs.

The compression molded samples were aged for 1000 hrs,

Tensile tests according to Plastics- Determination of tensile properties IS0527- 1 at room temperature at a strain rate of 50 mrn/min on aged tensile bars were performed to determine the residual elongation at break for the aged samples and reported in Table 2.

Table 2

From Table 2 it can be concluded that Examples I_» II and II demonstrate significantly higher elongation at break after being exposed to water containing chlorine dioxide than Comparative Example A,.

Comparing

• Comparative Example B to Example I and

• Comparative Example C to Example II and

· Comparative Example D to Example HI

shows that the effect of adding poly(ethylene-co-vinylalcohol) had an additional profound effect on the elongation at break as obtained after exposure to water containing chlorine dioxide.

Claims

1. Pipe for the transport of drinking water produced with a polymer composition

comprising poiyolefin and poly(elhylene-co-vinylalcohol) wherein the amount of poly(ethyfene-co-vinylalcohol) in the composition is lower than 2.0 wt% relative to the total weight amount of the composition.

2. Pipe according to Claim 1 characterised in thai the poiyolefin is polyethylene or polypropylene.

3. Pipe according to any one of Claims 1-2 characterised in thai the ethylene

content of poly(ethylene-co-vinylalcohoi) ranges between 10 and 70 mol%.

4, Pipe according to any one of Claims 1-3 characterised in that the ethylene

content of poly(ethylene-co-vinylalcohol) ranges between 25 and 50 moI%,

5. Pipe according to any one of Claims 1-4 characterised in that the composition comprises a phenofic compound and/or an organic phosphite and/or phosphonite.

6. Pipe according to any one of Claims 1 -5 characterised in that the poiyolefin is multimodal polyethylene,

7. Pipe according to any one of Claims 1-5 characterised in that multimodal high density polyethylene has a polymer density≥ 940 and≤ 970 kg/ro³ and a melt flow rate 190/5≥ 0,1 and≤ 4.0 g / 10 min wherein the density is measured according to ISO 1 183 A and the melt flow rate MFR 190/5 is measured according to ISO 1 133 -1 (190 X; 5.0 kg).

8. Pipe according to any one of Claims 1-7 characterised in that the poiyolefin is bimodal polyethylene.

9. Pipe according to any one of Claims 1-8 characterised in that the amount of

poly(ethyiene-co-vinySalcohol) in the composition is lower than 1.0 wt%.

10. Pipe according to any one of Claims 5-9 characterised in that the phenolic

compound is 1 ,3,5-trirnethyl 2.,4,6-tris(3_J5-di-t-butyl-4-hydroxybenzyl)benzene.

11. Pipe according to any one of Claims 5-10 characterised in that the phosphite is tris(2,4~di-tert-butylphenyl) phosphite.

12. Pipe according to any one of Claims 1-1 1 characterised in that the pipe is a

drinking water pipe.

13. Pipe according to any one of Claims 1-12 produced with a composition comprising

(a) poiyolefin

(b) poly(ethylene-co-vinyialcohol)

(c) phenolic compound and/or