CA1106521A - Medium density pipe blends and pipe made therefrom - Google Patents
Medium density pipe blends and pipe made therefromInfo
- Publication number
- CA1106521A CA1106521A CA282,318A CA282318A CA1106521A CA 1106521 A CA1106521 A CA 1106521A CA 282318 A CA282318 A CA 282318A CA 1106521 A CA1106521 A CA 1106521A
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- density
- pipe
- weight
- melt index
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Abstract
ABSTRACT OF THE DISCLOSURE
Blend of thermoplastic resin, and pipe made there-from, having a density of 0.926 to 0.940 grams per cubic centimeter, a melt index of 0.10 to 2.0 decigrams per minute;
a high density ethylene polymer having a density of greater than 0.940 to 0.965 grams per cubic centimeter and a melt index of 0.10 to 2.0 decigrams per minute; and a low density ethylene copolymer having a density of 0.910 to 0.925 grams per cubic centimeter and a melt index of 0.10 to 2.0 decigrams per minute.
Blend of thermoplastic resin, and pipe made there-from, having a density of 0.926 to 0.940 grams per cubic centimeter, a melt index of 0.10 to 2.0 decigrams per minute;
a high density ethylene polymer having a density of greater than 0.940 to 0.965 grams per cubic centimeter and a melt index of 0.10 to 2.0 decigrams per minute; and a low density ethylene copolymer having a density of 0.910 to 0.925 grams per cubic centimeter and a melt index of 0.10 to 2.0 decigrams per minute.
Description
~ S ~ ~ 11456 BACKGROUND OF THE INVENTION
1. Field of the Invention The invention relates to blends of thermoplastic ethylene polymers from which medium density grades o pipe may be formed.
1. Field of the Invention The invention relates to blends of thermoplastic ethylene polymers from which medium density grades o pipe may be formed.
2. Descrip~ion of the Prior Art t Plas~ic pipe made from thermoplastic e~hylene polymers is usually characterized, in terms of the density of the resin stock from which the pipe îs formed, as being a low, medium or high density grade. The low density material has a density of about 0.910 to 0.92S grams per cubic centimeter, the medium density material has a density of about 0.926 to 0.940 grams per cubic centimeter, and the high density material has a density of greater than 0.940 ;
to 0.965 grams per cubic centimeter.
Because of the density limitations o each of these grades of pipe, each grade tends to have limitations ~ ,~
in its other physical properties such as s~ress crack ;~
resistance, low temperature embrittlement point, flexlbility~
burst strength, and upper use temperature.
As a result of these differences in physieal properties, although there is some overlap, in utility, between pipe made from each of these three grades of plastic pipe making material, each grade of material ~ends to be used for making one or more types of pipe for which the other two grades of pipe making ma~erial are not suitable.
The mediu~ grade of pipe making material is preferred over low density polyethylene or high density polyethylene for ~ -~3~
, :: . . :, ~
:
~ ~ 6S 2 ~ 11456 making pipe for applications such as water distribution, gas distribution, irrigation and swimming pools because of a better balance of flexibility and performance character-istics. These include burst strength and upper use temperature.
Because low density and high density ethylene polymers can be more readily made, commercially, than medium density ethylene polymers, the manufacture of medium density pipe making compounds has usually been accomplished by blend-ing low density resin with high density resin so as to be able to provide a wider range of physical properties with the resulting blend of resins than could be provided by the use of individual medium density resins.
Despite this versatility, so to speak, of being able to provide a wide range of extrudable medium density pipe making compounds by blending low density resin with high density resin, it has not been readily possible to date, prior to the present invention, to provide an extrud-able medium density pipe making composition from ethylene polyme-rs which is entirely suitable for making extruded medium density pipe therefrom under present day high spead (10 to 100 feet per minute, 100-1000 pounds per hour at temperatures of ~ 200C. and at pressures of ~ S00 psi) pipe extrusion conditions and wherein the resulting pipe would have the following combination of properties:
low temperature embrittlement point of ~ -60C.;
environmental stress-crack resistant (Fso) of 24 hours;
-~ ~ ~
65 ~ ~ 11456 ~ lOOO hours to fail at hoop stress of 1070 psi during burst testing at 100F;
a design stress rating of 630 psi at 73F; and smooth, glossy surfaces. Smooth and glossy surfa~es are important from a fluid ~low considera~ion.
This combination of properties is now essential for medium density potable water pipe being used under the following conditions: Pipe specifications according to ASTM D-2239, PE-2306 classification, and meeting the requirements of ASTM D-1248, P-23 classification (material - specifications for PE-2306) and approved by the laboratory making the evaluation for this purpose.
SUMMARY OF T~E INVENTION
An object of the present invention is to provide a medium density, thermoplastic, ethylene polymer based composition that can be readily extrudable into pipe.
An object of the present invention is to provide such a pipe composition from which extruded pipe having ; high burst strength and stress crack resistance properties may be prepared.
Another object of the present invention is to provide such a pipe composition as can be extruded into such pipe at high production rates.
A further object of the present invention is to provide such pipe made from such compositions.
These and other objects of the prese~t invention are achieved with a thermoplastic composition formed from a selective combination of ethylene polymers.
.
- ; ~ . ... .
~ ~4~ ~ Z~ 11456 DESCRIPTION OF THE PREFERRED EMBODIMENT
The objects of the present i~vention are achieved by employing as an extrudable, pipe forming, composition one h~ving the following ormulation, based on a total weight percent therein of 100;
a) about 40 to 90, and preferably about 60 to 70, :
weight percent of thermoplas~ic high density ethylene poly-mer;
b) abou~ lO to 60, and preferably about 30 to :.
40, weight percent of thermoplastic low density ethylene copolymer;
c~ about 0.01 to 0.20, and preerably about 0.05 to 0.10, weight percent of antioxident for such ethylene polymers.
The pipe forming compositions of the present invention are used in thermoplastic form, that is, they are not cross-linked. The pipe forming compositions of the pres.ent invention have the following properties: :
Density (ASTM D-1505) of 0.926 to 0.940 grams per cubic centimeter and preferably of about 0.935 to 0.940 grams per cubic centimeter;
Melt index (ASTM D-1238) of about 0.10 to 2.0 decigrams per minute and preferably of about 0.50 to 1.0 decigrams per minute.
They can be extruded in pipe at the rate of about 100 to 1000 pounds p~r hour under ~ypical pipe extrusion conditions o~
a stock t~mperat~re of about 200~C.
' ~
:. ~ ,. , ~ 16S~L 11456 The extruded compositions have the Eollowing properties in extruded form:
burst test properties (ASTM D-2239) at 100F. at least 1000 hours to Eailure at a hoop stress of 1070 pounds per square inch.
A minimum instant burst hoop stress of 2520 psi at 730F. conforms to the specified pipe diameter and wall thickness in ASTM D-2239 or other appropriate pipe specifications.
High Density Ethylene Polymer The high density ethylene polymer which is to be used in the compositions of the present invention is a normally solid (i.e., solid at 23C.) thermoplastic resin having a denslty of greater than 0.940 to 0.965 grams per cubic centimeter and preferably of about 0.948 to 0.952 grams per cubic centimeter (as measured by ASTM 1505 with preparation as in ASTM D-1928, Procedure C), at a melt index of about 0.10 to 2.0 decigrams per 20 minute and preferably of about 0.8 to 1.4 decigrams per minute (as neasured by ASTM D-1238 at 44 psi test pressure).
The high density polyethylene can contain C3 to C6 interpolymerized mono-alpha-olefins such as propylene, butene-l and hexene-l.
The high density ethylene polymers may be used individually or in combination with each other in the com-positions of the present invention.
The high density ethylene polymers have a cyclo-hexane extractables (24 hours, at reflux temperature at atmospheric pressure) content o~ 1 to about 20 weight percent.
6.
.
~ ; , ' ' ' , ~ , The high density ethylene polymers may be made under low pressure conditions of about 150 ~o 300 psl with supported chromium compound based catalysts such as chromium oxide ~as disclosed in U.S. 2,825,721) silyl chromate (as disclosed in U.S. 3,023,203) bis (cyclopentadiene) chromium (as disclosed in U.SO 3,687,920 or U.S. 3,709,853).
As disclosed in these patents, the high density ethylene polymers may be homopolymers, or copolymers of a major portion of ethylene and a minor portion of the C3 to C6 alpha mono-olefin comonomer.
Low Density Ethylene Coeo~ymer The low density ethylene copolymer which is to be used in the compositions of the present invention is a normally solid (i.e. solid at 23C.) thermoplastic resin having a density of about O.glO to 0.925, grams per cubic centimeter and preferably of about 0.918 to 0.922, grams per cubic centimeter, a melt index of about 0.10 to 2.0 decigrams per minute and preferably of about 0.70 to 0.90 decigrams per minute.
The low density ethylene copolymer contains C3 to C6 interpolymerized mono-alpha-olefins such as propylene, butene-l and hexene-l.
The low density ethylene copolymers may be used individually or in combination with each other in the compositions of the present invention.
The low density ethylene copolymers may be made under low pressure conditions of about 150 to 300 psi with ~' ~
zi~
supported chromi~ oxide based catalysts that are modified with titanium and, optionally, fluorine, as disclosed in U.S. 3,606,736 and 4,011,382.
As disclosed in these patents the low density ethylene polymers are formed from a major portion of ethylene and a minor portion of the C3 to C6 alpha-mono-olefin comonomers.
Carbon Black The composition of the present invention also can advantageously include carbon black.
The carbon black which may be used herein includes all reinforcing carbon blacks, including furnace blacks, acetylene blacks and channel blacks. The carbon black, for weather resistant end-use applications, should have a particle size of the order of about 15 to 25 millimicrons.
The carbon black is commonly used in the form of a low density polyethylene based master batch to facilitate the admixture of the carbon black with the other components of the composition of the present invention. The master-batch is made using conventional technology and is prepared from about 25 to 35 parts by weight oE the carbon black and about 75 to 65 parts by weight of polyethylene having a density of about 0.90 + 0.02 which is made with free radical catalysts in tubular reactors under pressures of about ~20,000 psi. ~;
Antioxidant The compositions of the present invention also advantageously contain one or more suitable high temperature ~ ; -antioxidants for the polymer systems.
The antioxidants are preferably sterically hindered phenols. Such compounds would include 8.
' ' ' ': . ' r~
65 Z~ 11456 1,3,5-trimethyl-2,4,6-trisC3,5-ditertiary butyl-4-hydroxy benzyl)benzene;
1,3,5-tris(3,5-ditertiary butyl-4-hydro~y benzyl)-S-triazine-2,4,6-(IH,3H,SH)trione;
tetrakis-[methylene-3-(3',5-di-t-butyl-4'-hydroxy phenyl)-propionate] methane; and di(2-methyl-4-hydroxy 5-t-butyl phenyl)sulfide.
Polymerized 2,2,4-trimethyl dihydroquinoline may also be used.
The antioxidants may be used individually, or in combination with one another.
Adjuvants for~ position In addition to the high density ethylene polymer and low den=ity ethylene copolymer, the compositions of the present invention may also contain one or more adjuvaDt materials of the types normally used in resin based pipe or tubing compositions.
These other adjuvants would include carbon black;
antioxidants; water-proofing fillers; inorganic fillers such as clay, talc and calcium carbonate; lubricants; stabilizers;
and processing aids.
These adjuvants would be used in amounts designed to provide their intended effect in the resulting composit-ion. The total amount of such adjuvants will range from 0 to about 10 weight percent based on the total weight of the composition.
ProcessiDL~ ~ . ieL~ns .
All of the components o the compositions of the present invention are usually blended or compounded ~ogether 9.
.' ~
.:
:
65 ~ 11456 ~
! ~ , ~
prior to their introduction into the extrusion device from which they are to be extruded into the form o pipe or tub-ing. The e~hylene polymer and alkylene copolymer of the composition, and the other desired const~tuents thereof> may be blended together by any of the techniques used in the art to blend and compound thermoplastics to homogeneous masses.
For instance, the components may be fluxed on a variety of apparatus including multi-roll mills, screw mills, continuous mixers, compounding extruders and Banbury mixers, or dis-solved in mutual or compatible solvents.
When all the solid components of the composition are available in the form of a powder, or as small particles, the compositions are most conveniently prepared by first making a blend of the components, say in a Banbury mixer or a continuous extruder, and then masticating this blend on a heated mill, ~or instance on a two-roll mill, and the mill-ing continued until an intimate mixture of the components is obtained. AlternativelyJ as previously described, a master batch containing the base polymers and the carbon black and/
or the antioxidant and, if desired, some or all of the other components, may be added to a mass of polymer, Where the base polymers are not available in powder form, the compositions may be made by introducing the polymers to the mill, ;
masticating un~il they form a band around o~e roll, after which a blend of the remai~ing components is added and the I ;~
milling continued until an inti~ate mix~ure is obtained. I
The rolls are prefera~ly maintained at a temperature which is within the range of about 80C. to 150C. The composit-ion, in the form o~ a sheet, is removed from the mill and - .
10.
.. . .
. .
6S ~ ~ 11456 then brought into a form, typically dice-like pieces, suit- -able for subsequent processing.
Aft~r the various co~ponen~s of the compositions are uniformly admixed and blended tog~ther, they are further processed, in accordance with the present invention, in a convention pipe or tubing extrusion apparatus at about 175 to 235C.
The pipe or tubing is usually made with walls that are about 0.060 to 0.50 inches thick, and the inner diameter of the tubing may be of the order of 0.60 to 6.0 inches.
Examples The following examples are merely illustrative of the present invention and are not intended as a limitation on the scope thereof.
The compositions that were evaluated had the following compositions:
Composition A
68.5 parts by weight of high density polyethylene virgin powder of an average diamter of 0.01 to 0.02 inches, having a density of 0.952, and a melt index of 1.4 decigrams per minute and a cyclohexane extractableR content of 6.8 percent;
25.0 parts by weight of low density polyethylene pellets of cylindrical shape and an average size of l/8 inch diameter and 1/8 inch length having a density of 0.918 and a melt index of 0.2V decigrams per minute;
6.5 parts by weight of carbon black (35 percent carbon black in low density-h~gh pressurQ-polyethylene);
11 .
0.1 part by weight o~ an antioxidant (which ~as 4,4'-thio-bis (6-tertiary butyl meta cresol)).
Composition B
68.5 parts by weight of high density polyethylene virgin powder of an average diameter of 0.01 to 0.02 inches, having a density of 0.952, a melt index of 1.4 decigrams per minute and a cyclohexane extractables cont~nt of 6.8 percent;
25.0 parts by weight of an ethylene-butene-l co-: polymer virgin powder of an average diameter of 0.03 to 0.04 inches having a density of 0.918 and a melt index of 0.80 decigrams per minute;
; 6.5 parts by weight of carbon black (35 percent carbon black in low density-high pressure-polyethylene); .
0.1 part of an antioxidant (which was 4,4'-thio-bis (6-tertiary butyl meta cresol?).
: Composition C
,;~
68.5 parts by weight of high density polyethylene i;:
pellets of cylindrical shape and an average size of 1/8 inch diameter and 1/8 inch length having a density of 0.952, a melt index of 0.97 decigrams per minute and a cyclohexane extractables content of 3.7%;
25.0 parts by weight of low density polyethylene ;
pellets of cylindrical shape and an average size of 1/8 ~ ;
inch diameter and 1/8 inch length having a density of 0.918 and a melt of 0.20 decigrams per minute; :~ .
6.5 parts by weight of carbon bla~k (35 percent carbon black in 1QW density-high pressure-polyethylene);
~.~ part by weight of an antio~idant ~which was 4,4'-thio-bis (6-tertiary butyl meta cresol)~
12.
.
~ ;
~ILOG5231. ~1456 Com~osition D
68.5 parts by weight of high density polyethylene peilets of cyllndrical shape and an average size of 1/8 inch diameter and 1/8 inch length having a density of 0.952, a melt index of 0.97 decigrams per min.u~e and a cylohexane extractables conten~ of 3.7 percent;
25.0 parts by weight of an ethylene butene-l co-polymer virgin powder of an average diameter of 0.03 to 0.04 :
inches having a density of 0.918 and a melt index of 0.80 decigrams per minute;
6.5 parts by weight of carbon black (35 percent carbon black in low density-high pressure- polyethylene);
0.1 part of an antioxidant (which was 4,4'-thio-bis (6-tertiary butyl meta cresol)~.
These compositions were subjected to the following tests:
Melt Index ASTM D-1238; Stress crack resistance, - ASTM 1693; Fso is the time in hours for 50 percent of the ~ :
samples to ~ail; Extrusion rate is measured on pipe under extrusion conditions of 45 revolutions per minute in a 2-lt2" diameter - 16/1 length to diameter ratio extruder, for example; Burst testing according to ASTM D-1598 by extruding the compositions under conventional extrusion techniques into pipe of 1 inch inside diameter and a wall thickness of ~ inches.
The results are set forth in the following Table:
' -6~iZ ~ 56 Table Composition A ~ C D
Melt Index 0.80 1.0 0.51 0.74 Stress Crack Resistance, F50, hours 48 216 192 504 Extrusion Ra~e, lbs./hr71 7~ 69 72 Burst Testing at 100F~
hours to fail at Hoop Stress of 1070 psi 696 1328 1312 1903 The results show that there is a significant in-crease in the failure time with Compositions B and D of the present invention and thus they are stress crack resistant ~ .
as compared with Compositions A and C of the prior art. .-The extrusion rate shows a slight improvement for the com-positions o~ the present invention. Additionally, the compositions of the present invention have increased failure ,~
time in burst testing asi.compared with the compositions of the prior art.
Obviously, other modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that changes may be made in the particular embodiments o this invention described which are within the ~ull intended scope o~ the invention as defined by the appended c:laus.
14.
-
to 0.965 grams per cubic centimeter.
Because of the density limitations o each of these grades of pipe, each grade tends to have limitations ~ ,~
in its other physical properties such as s~ress crack ;~
resistance, low temperature embrittlement point, flexlbility~
burst strength, and upper use temperature.
As a result of these differences in physieal properties, although there is some overlap, in utility, between pipe made from each of these three grades of plastic pipe making material, each grade of material ~ends to be used for making one or more types of pipe for which the other two grades of pipe making ma~erial are not suitable.
The mediu~ grade of pipe making material is preferred over low density polyethylene or high density polyethylene for ~ -~3~
, :: . . :, ~
:
~ ~ 6S 2 ~ 11456 making pipe for applications such as water distribution, gas distribution, irrigation and swimming pools because of a better balance of flexibility and performance character-istics. These include burst strength and upper use temperature.
Because low density and high density ethylene polymers can be more readily made, commercially, than medium density ethylene polymers, the manufacture of medium density pipe making compounds has usually been accomplished by blend-ing low density resin with high density resin so as to be able to provide a wider range of physical properties with the resulting blend of resins than could be provided by the use of individual medium density resins.
Despite this versatility, so to speak, of being able to provide a wide range of extrudable medium density pipe making compounds by blending low density resin with high density resin, it has not been readily possible to date, prior to the present invention, to provide an extrud-able medium density pipe making composition from ethylene polyme-rs which is entirely suitable for making extruded medium density pipe therefrom under present day high spead (10 to 100 feet per minute, 100-1000 pounds per hour at temperatures of ~ 200C. and at pressures of ~ S00 psi) pipe extrusion conditions and wherein the resulting pipe would have the following combination of properties:
low temperature embrittlement point of ~ -60C.;
environmental stress-crack resistant (Fso) of 24 hours;
-~ ~ ~
65 ~ ~ 11456 ~ lOOO hours to fail at hoop stress of 1070 psi during burst testing at 100F;
a design stress rating of 630 psi at 73F; and smooth, glossy surfaces. Smooth and glossy surfa~es are important from a fluid ~low considera~ion.
This combination of properties is now essential for medium density potable water pipe being used under the following conditions: Pipe specifications according to ASTM D-2239, PE-2306 classification, and meeting the requirements of ASTM D-1248, P-23 classification (material - specifications for PE-2306) and approved by the laboratory making the evaluation for this purpose.
SUMMARY OF T~E INVENTION
An object of the present invention is to provide a medium density, thermoplastic, ethylene polymer based composition that can be readily extrudable into pipe.
An object of the present invention is to provide such a pipe composition from which extruded pipe having ; high burst strength and stress crack resistance properties may be prepared.
Another object of the present invention is to provide such a pipe composition as can be extruded into such pipe at high production rates.
A further object of the present invention is to provide such pipe made from such compositions.
These and other objects of the prese~t invention are achieved with a thermoplastic composition formed from a selective combination of ethylene polymers.
.
- ; ~ . ... .
~ ~4~ ~ Z~ 11456 DESCRIPTION OF THE PREFERRED EMBODIMENT
The objects of the present i~vention are achieved by employing as an extrudable, pipe forming, composition one h~ving the following ormulation, based on a total weight percent therein of 100;
a) about 40 to 90, and preferably about 60 to 70, :
weight percent of thermoplas~ic high density ethylene poly-mer;
b) abou~ lO to 60, and preferably about 30 to :.
40, weight percent of thermoplastic low density ethylene copolymer;
c~ about 0.01 to 0.20, and preerably about 0.05 to 0.10, weight percent of antioxident for such ethylene polymers.
The pipe forming compositions of the present invention are used in thermoplastic form, that is, they are not cross-linked. The pipe forming compositions of the pres.ent invention have the following properties: :
Density (ASTM D-1505) of 0.926 to 0.940 grams per cubic centimeter and preferably of about 0.935 to 0.940 grams per cubic centimeter;
Melt index (ASTM D-1238) of about 0.10 to 2.0 decigrams per minute and preferably of about 0.50 to 1.0 decigrams per minute.
They can be extruded in pipe at the rate of about 100 to 1000 pounds p~r hour under ~ypical pipe extrusion conditions o~
a stock t~mperat~re of about 200~C.
' ~
:. ~ ,. , ~ 16S~L 11456 The extruded compositions have the Eollowing properties in extruded form:
burst test properties (ASTM D-2239) at 100F. at least 1000 hours to Eailure at a hoop stress of 1070 pounds per square inch.
A minimum instant burst hoop stress of 2520 psi at 730F. conforms to the specified pipe diameter and wall thickness in ASTM D-2239 or other appropriate pipe specifications.
High Density Ethylene Polymer The high density ethylene polymer which is to be used in the compositions of the present invention is a normally solid (i.e., solid at 23C.) thermoplastic resin having a denslty of greater than 0.940 to 0.965 grams per cubic centimeter and preferably of about 0.948 to 0.952 grams per cubic centimeter (as measured by ASTM 1505 with preparation as in ASTM D-1928, Procedure C), at a melt index of about 0.10 to 2.0 decigrams per 20 minute and preferably of about 0.8 to 1.4 decigrams per minute (as neasured by ASTM D-1238 at 44 psi test pressure).
The high density polyethylene can contain C3 to C6 interpolymerized mono-alpha-olefins such as propylene, butene-l and hexene-l.
The high density ethylene polymers may be used individually or in combination with each other in the com-positions of the present invention.
The high density ethylene polymers have a cyclo-hexane extractables (24 hours, at reflux temperature at atmospheric pressure) content o~ 1 to about 20 weight percent.
6.
.
~ ; , ' ' ' , ~ , The high density ethylene polymers may be made under low pressure conditions of about 150 ~o 300 psl with supported chromium compound based catalysts such as chromium oxide ~as disclosed in U.S. 2,825,721) silyl chromate (as disclosed in U.S. 3,023,203) bis (cyclopentadiene) chromium (as disclosed in U.SO 3,687,920 or U.S. 3,709,853).
As disclosed in these patents, the high density ethylene polymers may be homopolymers, or copolymers of a major portion of ethylene and a minor portion of the C3 to C6 alpha mono-olefin comonomer.
Low Density Ethylene Coeo~ymer The low density ethylene copolymer which is to be used in the compositions of the present invention is a normally solid (i.e. solid at 23C.) thermoplastic resin having a density of about O.glO to 0.925, grams per cubic centimeter and preferably of about 0.918 to 0.922, grams per cubic centimeter, a melt index of about 0.10 to 2.0 decigrams per minute and preferably of about 0.70 to 0.90 decigrams per minute.
The low density ethylene copolymer contains C3 to C6 interpolymerized mono-alpha-olefins such as propylene, butene-l and hexene-l.
The low density ethylene copolymers may be used individually or in combination with each other in the compositions of the present invention.
The low density ethylene copolymers may be made under low pressure conditions of about 150 to 300 psi with ~' ~
zi~
supported chromi~ oxide based catalysts that are modified with titanium and, optionally, fluorine, as disclosed in U.S. 3,606,736 and 4,011,382.
As disclosed in these patents the low density ethylene polymers are formed from a major portion of ethylene and a minor portion of the C3 to C6 alpha-mono-olefin comonomers.
Carbon Black The composition of the present invention also can advantageously include carbon black.
The carbon black which may be used herein includes all reinforcing carbon blacks, including furnace blacks, acetylene blacks and channel blacks. The carbon black, for weather resistant end-use applications, should have a particle size of the order of about 15 to 25 millimicrons.
The carbon black is commonly used in the form of a low density polyethylene based master batch to facilitate the admixture of the carbon black with the other components of the composition of the present invention. The master-batch is made using conventional technology and is prepared from about 25 to 35 parts by weight oE the carbon black and about 75 to 65 parts by weight of polyethylene having a density of about 0.90 + 0.02 which is made with free radical catalysts in tubular reactors under pressures of about ~20,000 psi. ~;
Antioxidant The compositions of the present invention also advantageously contain one or more suitable high temperature ~ ; -antioxidants for the polymer systems.
The antioxidants are preferably sterically hindered phenols. Such compounds would include 8.
' ' ' ': . ' r~
65 Z~ 11456 1,3,5-trimethyl-2,4,6-trisC3,5-ditertiary butyl-4-hydroxy benzyl)benzene;
1,3,5-tris(3,5-ditertiary butyl-4-hydro~y benzyl)-S-triazine-2,4,6-(IH,3H,SH)trione;
tetrakis-[methylene-3-(3',5-di-t-butyl-4'-hydroxy phenyl)-propionate] methane; and di(2-methyl-4-hydroxy 5-t-butyl phenyl)sulfide.
Polymerized 2,2,4-trimethyl dihydroquinoline may also be used.
The antioxidants may be used individually, or in combination with one another.
Adjuvants for~ position In addition to the high density ethylene polymer and low den=ity ethylene copolymer, the compositions of the present invention may also contain one or more adjuvaDt materials of the types normally used in resin based pipe or tubing compositions.
These other adjuvants would include carbon black;
antioxidants; water-proofing fillers; inorganic fillers such as clay, talc and calcium carbonate; lubricants; stabilizers;
and processing aids.
These adjuvants would be used in amounts designed to provide their intended effect in the resulting composit-ion. The total amount of such adjuvants will range from 0 to about 10 weight percent based on the total weight of the composition.
ProcessiDL~ ~ . ieL~ns .
All of the components o the compositions of the present invention are usually blended or compounded ~ogether 9.
.' ~
.:
:
65 ~ 11456 ~
! ~ , ~
prior to their introduction into the extrusion device from which they are to be extruded into the form o pipe or tub-ing. The e~hylene polymer and alkylene copolymer of the composition, and the other desired const~tuents thereof> may be blended together by any of the techniques used in the art to blend and compound thermoplastics to homogeneous masses.
For instance, the components may be fluxed on a variety of apparatus including multi-roll mills, screw mills, continuous mixers, compounding extruders and Banbury mixers, or dis-solved in mutual or compatible solvents.
When all the solid components of the composition are available in the form of a powder, or as small particles, the compositions are most conveniently prepared by first making a blend of the components, say in a Banbury mixer or a continuous extruder, and then masticating this blend on a heated mill, ~or instance on a two-roll mill, and the mill-ing continued until an intimate mixture of the components is obtained. AlternativelyJ as previously described, a master batch containing the base polymers and the carbon black and/
or the antioxidant and, if desired, some or all of the other components, may be added to a mass of polymer, Where the base polymers are not available in powder form, the compositions may be made by introducing the polymers to the mill, ;
masticating un~il they form a band around o~e roll, after which a blend of the remai~ing components is added and the I ;~
milling continued until an inti~ate mix~ure is obtained. I
The rolls are prefera~ly maintained at a temperature which is within the range of about 80C. to 150C. The composit-ion, in the form o~ a sheet, is removed from the mill and - .
10.
.. . .
. .
6S ~ ~ 11456 then brought into a form, typically dice-like pieces, suit- -able for subsequent processing.
Aft~r the various co~ponen~s of the compositions are uniformly admixed and blended tog~ther, they are further processed, in accordance with the present invention, in a convention pipe or tubing extrusion apparatus at about 175 to 235C.
The pipe or tubing is usually made with walls that are about 0.060 to 0.50 inches thick, and the inner diameter of the tubing may be of the order of 0.60 to 6.0 inches.
Examples The following examples are merely illustrative of the present invention and are not intended as a limitation on the scope thereof.
The compositions that were evaluated had the following compositions:
Composition A
68.5 parts by weight of high density polyethylene virgin powder of an average diamter of 0.01 to 0.02 inches, having a density of 0.952, and a melt index of 1.4 decigrams per minute and a cyclohexane extractableR content of 6.8 percent;
25.0 parts by weight of low density polyethylene pellets of cylindrical shape and an average size of l/8 inch diameter and 1/8 inch length having a density of 0.918 and a melt index of 0.2V decigrams per minute;
6.5 parts by weight of carbon black (35 percent carbon black in low density-h~gh pressurQ-polyethylene);
11 .
0.1 part by weight o~ an antioxidant (which ~as 4,4'-thio-bis (6-tertiary butyl meta cresol)).
Composition B
68.5 parts by weight of high density polyethylene virgin powder of an average diameter of 0.01 to 0.02 inches, having a density of 0.952, a melt index of 1.4 decigrams per minute and a cyclohexane extractables cont~nt of 6.8 percent;
25.0 parts by weight of an ethylene-butene-l co-: polymer virgin powder of an average diameter of 0.03 to 0.04 inches having a density of 0.918 and a melt index of 0.80 decigrams per minute;
; 6.5 parts by weight of carbon black (35 percent carbon black in low density-high pressure-polyethylene); .
0.1 part of an antioxidant (which was 4,4'-thio-bis (6-tertiary butyl meta cresol?).
: Composition C
,;~
68.5 parts by weight of high density polyethylene i;:
pellets of cylindrical shape and an average size of 1/8 inch diameter and 1/8 inch length having a density of 0.952, a melt index of 0.97 decigrams per minute and a cyclohexane extractables content of 3.7%;
25.0 parts by weight of low density polyethylene ;
pellets of cylindrical shape and an average size of 1/8 ~ ;
inch diameter and 1/8 inch length having a density of 0.918 and a melt of 0.20 decigrams per minute; :~ .
6.5 parts by weight of carbon bla~k (35 percent carbon black in 1QW density-high pressure-polyethylene);
~.~ part by weight of an antio~idant ~which was 4,4'-thio-bis (6-tertiary butyl meta cresol)~
12.
.
~ ;
~ILOG5231. ~1456 Com~osition D
68.5 parts by weight of high density polyethylene peilets of cyllndrical shape and an average size of 1/8 inch diameter and 1/8 inch length having a density of 0.952, a melt index of 0.97 decigrams per min.u~e and a cylohexane extractables conten~ of 3.7 percent;
25.0 parts by weight of an ethylene butene-l co-polymer virgin powder of an average diameter of 0.03 to 0.04 :
inches having a density of 0.918 and a melt index of 0.80 decigrams per minute;
6.5 parts by weight of carbon black (35 percent carbon black in low density-high pressure- polyethylene);
0.1 part of an antioxidant (which was 4,4'-thio-bis (6-tertiary butyl meta cresol)~.
These compositions were subjected to the following tests:
Melt Index ASTM D-1238; Stress crack resistance, - ASTM 1693; Fso is the time in hours for 50 percent of the ~ :
samples to ~ail; Extrusion rate is measured on pipe under extrusion conditions of 45 revolutions per minute in a 2-lt2" diameter - 16/1 length to diameter ratio extruder, for example; Burst testing according to ASTM D-1598 by extruding the compositions under conventional extrusion techniques into pipe of 1 inch inside diameter and a wall thickness of ~ inches.
The results are set forth in the following Table:
' -6~iZ ~ 56 Table Composition A ~ C D
Melt Index 0.80 1.0 0.51 0.74 Stress Crack Resistance, F50, hours 48 216 192 504 Extrusion Ra~e, lbs./hr71 7~ 69 72 Burst Testing at 100F~
hours to fail at Hoop Stress of 1070 psi 696 1328 1312 1903 The results show that there is a significant in-crease in the failure time with Compositions B and D of the present invention and thus they are stress crack resistant ~ .
as compared with Compositions A and C of the prior art. .-The extrusion rate shows a slight improvement for the com-positions o~ the present invention. Additionally, the compositions of the present invention have increased failure ,~
time in burst testing asi.compared with the compositions of the prior art.
Obviously, other modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that changes may be made in the particular embodiments o this invention described which are within the ~ull intended scope o~ the invention as defined by the appended c:laus.
14.
-
Claims (15)
1. A thermoplastic ethylene polymer based pipe forming composition having a density of about 0.926 to 0.940 grams per cubic centimeter, and a melt index of about 0.1 to about 2.0 decigrams per minute, and comprising, based on the total weight of said composition, about 40 to 90 parts by weight of high density ethylene polymer having a density of greater than 0.940 to 0.965 grams per cubic centimeter; and a melt index of about 0.1 to 2.0 decigrams per minute, and about 10 to 60 parts by weight of low density alkylene copolymer having a density of about 0.910 to 0.925 grams per cubic centimeter; and a melt index of about 0.1 to 2.0, and stabilizingly effective quantities of anti-oxidant for said polymers, each of said polymers being formed from at least a major portion of ethylene and no more than a minor portion of interpolymerized C3 to C6 mono-alpha-olefins.
2. A composition as in claim 1 having a density of about 0.935 to 0.940 grams per cubic centimeter, and a melt index of about 0.5 to 1.0 decigrams per minute.
3. A composition as in claim 1 which contains about 60 to about 70 parts by weight of the high density ethylene polymer.
15.
15.
4. A composition as in claim 1 which contains about 30 to 40 parts by weight of the low density alkylene copolymer.
5. A composition as in claim 1 which contains about 0.01 to about 0.2 weight percent of the antioxidant.
6. A composition as in claim 1 wherein the high density ethylene polymer has a density of about 0.948 to 0.952 grams per cubic centimeter.
7. A composition as in claim 6 where the high density ethylene polymer has a melt index of about 0.8 to 1.4 decigrams per minute.
8. A composition as in claim 1 wherein the low density alkylene copolymer has a density of about 0.918 to 0.922 grams per cubic centimeter.
9. A composition as in claim 8 wherein the low density alkylene copolymer has a melt index of about 0.7 to 0.9 decigrams per minute.
10. A composition as in claim 1 wherein the high density ethylene polymer is polyethylene.
11. A composition as in claim l wherein the low density alkylene copolymer is ethylene-butene-1 copolymer.
12. A composition as in claim 1 which contains carbon black.
16.
16.
13. A composition as in claim 12 wherein the carbon black is present in an amount of from about 2.0 to 3.0 parts by weight.
14. Pipe formed from a thermoplastic medium density olefin polymer based composition as claimed in claim 1 and having an environmental stress crack resistance, F50, of ? 24 hours and a burst stress of ? l000 hours to failure at hoop stress of 1070 psi at 100°F.
15. Pipe as in claim 14 having an environ-mental stress crack resistance, F50, of ? 96 hours and a burst stress of ? 1000 hours to failure at hoop stress of 1070 psi at 100°F.
17.
17.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA282,318A CA1106521A (en) | 1977-07-08 | 1977-07-08 | Medium density pipe blends and pipe made therefrom |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA282,318A CA1106521A (en) | 1977-07-08 | 1977-07-08 | Medium density pipe blends and pipe made therefrom |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1106521A true CA1106521A (en) | 1981-08-04 |
Family
ID=4109095
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA282,318A Expired CA1106521A (en) | 1977-07-08 | 1977-07-08 | Medium density pipe blends and pipe made therefrom |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1106521A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5338589A (en) * | 1991-06-05 | 1994-08-16 | Hoechst Aktiengesellschaft | Polyethylene molding composition |
| US5358994A (en) * | 1992-08-31 | 1994-10-25 | Gas Research Institute | Thermoplastic material for production and repair of polymeric products and coating of metals |
| US6822051B2 (en) | 2002-03-29 | 2004-11-23 | Media Plus, Inc. | High density polyethylene melt blends for improved stress crack resistance in pipe |
| US7867588B2 (en) | 2001-12-17 | 2011-01-11 | Media Plus, Inc. | Polyethylene melt blends for high density polyethylene applications |
-
1977
- 1977-07-08 CA CA282,318A patent/CA1106521A/en not_active Expired
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5338589A (en) * | 1991-06-05 | 1994-08-16 | Hoechst Aktiengesellschaft | Polyethylene molding composition |
| US5358994A (en) * | 1992-08-31 | 1994-10-25 | Gas Research Institute | Thermoplastic material for production and repair of polymeric products and coating of metals |
| US7867588B2 (en) | 2001-12-17 | 2011-01-11 | Media Plus, Inc. | Polyethylene melt blends for high density polyethylene applications |
| US6822051B2 (en) | 2002-03-29 | 2004-11-23 | Media Plus, Inc. | High density polyethylene melt blends for improved stress crack resistance in pipe |
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