O USOO5405915A United States Patent 19 11 Patent Number: 5,405,915 Hess et al. 45) Date of Patent: Apr. 11, 1995

54 ETHYLENE POLYMER COMPOSITIONS 4,440,893 4/1984 Kallenback et al...... 524/305 4,506,061 3/1985 Makino et al...... 526/142 (75) Inventors: Kevin J. Hess; Kiplin D. Cowan, both 4,525,516 6/1985 Garcia et al...... 524/380 of Bartlesville, Okla. 4,661,552 4/1987 Kalenback ...... 524/433 (73) Assignee: Phillips Petroleum Company, 4,668,4614,788,019 11/19885/1987 NeedhamKallenbach ...... 264/310264/22 Bartlesville, Okla. 4,857,257 8/1989 Chen ...... 264/30 o 4,868,264 9/1989 Evens et al...... 526/336 21 Appl. No.: 266,296 4,900,706 2/1990 Sasaki et al...... 502/116 (22 Filed: Jun. 27, 1994 4,940,682 7/1990 Sasaki et al...... 502/113 (51 int.C.'...... C08F 8/00 5,017,635,017, 5/19911. Senuma et al. ------524/26/269 52 U.S. C...... 525/290; 525/313; Primary Examiner-Bernard Lipman 525/314; 525/315; 525/297 Attorney, Agent, or Firm-Carl D. Corvin (58) Field of Search ...... 525/290, 313, ; : 57 ABSTRACT An ethylene polymer composition is provided that com 56 References Cited prises: (a) an ethylene polymer (b) a crosslinking agent; U.S. PATENT DOCUMENTS and (c) a non-aromatic, cyclic, unsaturated, crosslinking

3,965,054 6/1976 Nojiri et al...... 260/25 HA co-agent. 4,115,508 9/1978 Hughes ...... 264/310 4,267,080 5/1981 Yokoyama et al...... 260/4 R 10 Claims, No Drawings 5,405,915 1. 2 It is another object of this invention to provide a ETHYLENE POLYMER COMPOSITIONS crosslinkable ethylene polymer composition that has consistent tensile properties when comparing one sam BACKGROUND OF THE INVENTION ple of a composition to another sample of a composi This invention is related to the field of ethylene poly tion. mer compositions. In particular, this invention is related In accordance with this invention an ethylene poly to the field of crosslinked ethylene polymer composi mer composition is provided that comprises (a) an eth tions. ylene polymer (b) a crosslinking agent; and (c) a non There has been, and continues to be, considerable aromatic, cyclic, unsaturated, crosslinking co-agent. interest in converting thermoplastic ethylene polymer 10 These and other objects, features, aspects, and advan compositions into thermosetting ethylene polymer com tages of this invention will become better understood positions. This interest is due to the desire to combine with references to the following detailed description of the low cost, easy processing, and good mechanical the invention and the claims. properties of thermoplastic ethylene polymer composi 15 DETALED DESCRIPTION OF THE tions with the enhanced form stability at elevated tem INVENTION peratures, resistance to stress crack, and good tensile The ethylene polymer used in the inventive composi properties of thermosetting ethylene polymer composi tion is selected from the group consisting of homopoly tions. Crosslinked ethylene polymer compositions are mers of ethylene and copolymers of ethylene and an valuable because they can be used in the wire, cable, alpha-olefin hydrocarbon having from 3 to about 18 pipe, hose, and molded article industries. carbon atoms. When the ethylene polymer is a copoly Thermosetting ethylene polymer compositions are mer, it is preferred if the alpha-olefin is selected from crosslinked by either chemical means or by radiation the group consisting of 1-butene, 3-methyl-1-butene, means. Currently, chemical crosslinking with organic 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, peroxides is a preferred commercial approach. How 25 1-hexene, 3-ethyl-1-hexene, 1-heptene, 1-octene, 1 ever, this approach has several drawbacks. One draw nonene, and 1-decene. Additionally, when the ethylene back is that organic peroxides can produce lower mo polymer is a copolymer, it is preferred if the copolymer lecular weight radicals. These radicals can remove hy comprises from about 80 to about 99 percent by weight drogen atoms from an ethylene polymer and form low ethylene. boiling-point compounds. These low-boiling-point 30 The ethylene polymer of the composition preferably compounds can cause bubbles to form during the cross has a density in the range of from about 0.92 to about linking reaction thereby adversely affecting the proper 0.98 g/cm3 as determined by ASTMD 1505. However, ties of the final ethylene polymer. This bubble draw it is more preferred when the ethylene polymer has a back can be overcome to some extent by using a cross density in the range of from about 0.94 to about 0.97 linking co-agent that reduces bubble formation. 35 g/cm3 as determined by the above method. The ethyl Crosslinking co-agents also have drawbacks. Cur ene polymer preferably has a melt index of at least 5, rently, several commercial processes use aromatic-ring more preferably in the range of from about 10 to about containing, crosslinking co-agents. In particular, triallyl 30 dg/min. as determined by ASTM D1238, Condition cyanurate (hereafter "TAC’) has been used in several 190/2.16. Most preferably, the ethylene polymer has a commercial processes. However, the use of TAC as a melt index in the range of from 15 to 30 dg/min. as crosslinking co-agent has several drawbacks. One draw determined by the above method. back is that the use of TAC is undesirable from a qual These ethylene polymers can be polymerized by any ity-control viewpoint. This is because the crosslinking known method in the art. However, it is preferred if the efficiency is not consistent when using TAC. This ethylene polymers are polymerized by using titanium means that a crosslinked product produced by using 45 halide catalysts. Titanium halide catalysts disclosed in TAC can have widely varying physical properties. This U.S. Pat. Nos. 4,325,837; 4,326,988; 4,328,121; is of particular concern in relation to the tensile proper 4,363,746; 4,391,736; 4,406,818; 4,410,671; and 4,461,882 ties of a crosslinked ethylene polymer composition. (the disclosures of which are hereby incorporated by Tensile properties are perhaps the most important references) are particularly preferred because they can indicators of the useful strength of a crosslinked ethyl 50 produce ethylene polymer compositions that have very ene polymer composition. For example, the tensile low amounts of catalyst residues. Typically, these cata property known as "Percent Elongation at Break” is a lyst residuals are less than 50 parts per million by good indicator of the brittleness of an ethylene polymer weight, however, amounts as low as 10 parts per million composition and the tensile property known as the by weight are not difficult to achieve. When titanium "Strain Energy at Break” is a good indicator of the 55 chloride based catalyst systems are used, it is preferred general toughness of an ethylene polymer composition. if the amount of chloride residues is less than 20 parts These properties are widely known and can be deter per million by weight. This eliminates the need for acid mined on commercially available test equipment. When scavengers such as Group IIA or Group IIB metal TAC is used to produce a crosslinked ethylene polymer compounds. These metal compounds are usually metal composition, these two tensile properties can vary 60 stearates, oxides, hydroxides, formates, acetates, al widely thereby causing serious problems, in the area of coholates, and gycolates. The elimination of these metal quality control, for the producer. compounds provides a further cost savings in the ex This invention provides a solution to this problem of tremely competitive world-wide ethylene polymer mar quality control. ket. 65 The crosslinking agent can be any suitable crosslink SUMMARY OF THE INVENTION ing agent for crosslinking ethylene polymers. However, It is an object of this invention to provide an ethylene it is preferred if the crosslinking agent is an organic polymer composition that is crosslinkable. peroxide crosslinking agent. For example, diperoxy 5,405,915 3 4. compounds can be employed as the cross-linking agents of the composition of the present invention. Examples of diperoxy compounds suitable for use as the crosslink H. H. ing agents include acetylenic diperoxy compounds such Hic-CH--CH- CH--CH-CH, as hexynes having the formula O O O O (Hs Hs R R Hic-f-c- c-f-ch, O O 10 wherein R is selected from the group consisting ofter tiary alkyl, alkyl carbonate, and benzoate. The molecu O O lar weights of the compounds are generally in the range R R of from about 200 to about 600. Examples of diperoxy compounds described above include: octynes having the formula 15 3,6-dimethyl-3,6-di(t-butylperoxy) octane; 3,6-dimethyl-3,6-di(peroxyethyl carbonate) octane; 2,5-dimethyl-2,5-di(peroxybenzoate) hexane; H. H. 2,5-dimethyl-2,5-di(peroxy isobutyl carbonate) hexane; Hic-CH--C=C--CH-CH and O O 20 2,5-dimethyl-2,5-di(t-butylperoxy) hexane. Preferably, the diperoxy compound employed as the O O crosslinking agent of the composition of the present R R invention is selected from the group consisting of 2,5- dimethyl-2,5-di(t-butylperoxy) hexyne-3 and 2,5- and octadiynes having the formula 25 dimethyl-2,5-di(t-butylperoxy) hexane. Other suitable examples of crosslinking agents are disclosed in U.S. Pat. Nos. 3,214,422 and 4,440,893 the entire discloses of Hs H. which are hereby incorporated by reference. Hic-f-c- C- =-c-ch, The crosslinking agent is present in the composition O O 30 in an amount in the range of from about 0.1% to about 3% by weight of the composition. Preferably, the cross O O linking agent is present in the composition in an amount R R in the range of from about 0.2% to about 2% by weight of the composition. More preferably, the crosslinking wherein R is selected from the group consisting ofter 35 agent is present in the composition in an amount in the tiary alkyl, alkyl carbonate, and benzoate. The molecu range of from 0.5% to 1% by weight of the composi lar weights of the compounds are generally in the range tion. of from about 200 to about 600. Examples of acetylenic The crosslinking co-agents useful in this invention are diperoxy compounds described above include: those compounds that are: (1) non-aromatic, (2) cyclic, 2,7-dimethyl-2,7-di(t-butylperoxy) octadiyne-3,5; and (3) unsaturated. These compounds usually have 2,7-dimethyl-2,7-di(peroxy ethyl carbonate) octadiyne from 4 to 60 carbon atoms in their structure. However, 3,5; - it is preferred if there are from 6 to 40 carbon atoms in 3,6-dimethyl-3,6-di(peroxyethyl carbonate) octyne-4; their structure. These compounds should have at least 3,6-dimethyl-3,6-di(t-butylperoxy) octyne-4; 45 one unsaturated carbon-carbon bond. However, poly 2,5-dimethyl 2,5-di(peroxybenzoate) hexyne-3; unsaturated compounds are more preferred for cross 2,5-dimethyl-2,5-di(peroxy-n-propyl carbonate) hex linking efficiency. In general, the formula for these yne-3; compounds is CnH2(n-R where “n” is an integer from 2,5-dimethyl-2,5-di (peroxyisobutyl carbonate) hexyne 4 to 60; 'x' is an integer from 1 to (n-1) and 'x' is the 3; 50 number of unsaturated carbon-carbon double bonds; 2,5-dimethyl-2,5-di(alpha-cumyl peroxy) hexyne-3; and R can be any group that does not interfere with the 2,5-dimethyl-2,5-di(peroxyethyl carbonate) hexyne-3; crosslinking reaction. Suitable compounds are cyclo 2,5-dimethyl-2,5-di(peroxy beta-chloroethyl carbonate) pentene, cyclohexene, cycloheptene, cyclooctene, cy hexyne-3; and clononene, cyclodecene, 1,3-cyclohexadiene, 1,4- 2,5-dimethyl-2,5-di(t-butylperoxy) hexyne-3. 55 cyclohexadiene, 1,3-cycloheptadiene, 1,5-cyclooctadi Other diperoxy compounds suitable for use as the ene, 1,5-cyclononadiene, dicyclopentadiene, cyclohep crosslinking agent of the composition of the present tatriene, 1,5,9-cyclododecatriene, and 1,3,5,7 cyclooc invention include hexanes having the formula tatetraene. A particularly preferred non-aromatic, cyc lic, unsaturated crosslinking co-agent compound is 1,5,9,-cyclododecatriene. (Hs Hs The co-agent is present in the composition in an Hic--CH-CH-i-CH, amount in the range of from about 0.1% to about 3% by O O weight of the composition. Preferably, the co-agent is O O present in the composition in an amount in the range of 65 from about 0.2 to about 2% by weight of the composi R R tion. Most preferably, the co-agent is present in the composition in an amount in the range of from about and octanes having the formula 0.3% to about 1% by weight of the composition. 5,405,915 5 6 The ethylene polymer composition preferably con fed, along with the other compounds, into an extruder tains hydroperoxide scavengers examples of which are having either a single mixing screw or twin mixing those compounds comprising one or more thioester screws. The pellets thus produced may be ground and groups. Examples of compounds having a thioester used in powder form. group include dilauryl thiodipropionate and distearyl thiodipropionate. Further examples of such compounds EXAMPLES can be found in U.S. Pat. No. 4,028,332 the entire dis These examples are provided to further assist a per closure of which is hereby incorporated by reference. son skilled in the art with understanding this invention. The antioxidant employed in the composition of the These examples are intended to be illustrative of the present invention is preferably present in the composi O invention and are not meant to be construed as limiting tion in an amount in the range of from about 0.01% to the scope of the invention. about 1%, more preferably in the range of from about The compounds indicated in Table E-1 were con 0.05 to about 0.5% by weight of the composition. Even tacted together to form a contacted composition. This more preferably, the antioxidant is present in the com contacted composition was then contacted with methy position in an amount in the range of from 0.1% to 0.3% 15 lene chloride to form a wetted composition. The methy by weight of the composition. lene chloride was then evaporated from the wetted If desired, an antioxidant such as a hindered phenolic composition to form a residue composition. This evapo antioxidant can be employed in the composition to re ration step was accomplished by using a rotary evapora duce oxidation of the ethylene polymer. Examples of tor. The evaporation took approximately five hours. these antioxidants include 2,6-di-t-butyl-p-cresol 20 The residue composition was then dried in a vacuum (BHT), tetrakis(methylene(3,5-di-t-butyl-4-hydroxyhy oven overnight at about 35 C. to form a crosslinkable drocinnamate)) methane (IRGANOX 1010) and oc ethylene polymer composition. tadecyl-3,5-di-t-butyl-4-hydroxyhydrocinnamate (IR GANOX 1076). When employed, these antioxidants are TABLE E1 present in the composition in an amount in the range of 25 Ethylene Polymer Compositions" from about 0.01% to about 0.05%, more preferably in Sample Number the range of from 0.01% to 0.03%, by weight of the 2 3 4. composition. Compounds Amounts in Grams Ethylene Polymer 488.65 488.65 488.65 488.6S The use of the co-agent in the composition tends to TAC2 3.5125 0 O 0 make the molded pans stick to the mold. If the degree of 30 TATM3 O 3,5018 0 O adhesion is too great, the parts will be difficult to re 1,9-Dec. O O 3.5080 O move from the mold and may be damaged during ex 1,59-Cys O O O 3.5160 2,5-Dis 3.5034 3.5011 3.501.7 3.5034 traction. On the other hand, if the degree of adhesion is SA7 0.5007 0.5002 0.504 0.5020 too low, the parts may separate from the mold prema UV5318 2.5005 2.5001 2.5009 2.5001 turely during the molding cycle, resulting in the forma 35 DLTDP9 13504 13528 1.3503 1.3502 tion of gas pockets between the pans and the mold. Gas Table E-1 Notes: pockets between the parts and the mold typically result This is an ethylene polymer composition that has a melt indexin the range of about 16 to about 22 grams per 10 minutes. It also has a density in the range of about 0.945 in the formation of crater-like defects or “pock marks' to about 0.955 grams per cubic centimeter. This ethylene polymer composition is on the outside surfaces of the parts. Consequently, a available from Phillips Petroleum Company under the registered trademark of Marlex FM 5580. mold release agent is typically used in the ethylene This is triallyl cyanurate also known as 2,4,6triallyloxy 1,3,5-triazine. Compounds polymer composition. Preferably, the mold release in notes 2-5 are crosslinking co-agents also. This is triallyl trimesate also known as triallyl 1,3,5-benzenecarboxylate. agent employed in the composition is a fatty acid. Fatty This is 1,9-decadiene. acids can be saturated or unsaturated, but saturated This is 15,9-cyclododecatriene. fatty acids are preferred. In general, saturated fatty This is 2,5-dimethyl-2,5-di(tert-butylperoxy)-hexyne-3 it is used as a crosslinking agent. acids have the formula CH3(CH2)COOH where “X” 45 This is stearic acid it is used primarily as a mold release agent. is an integer from 2 to 24. Examples of saturated fatty This is 2-hydroxy-4-n-octoxybenzophenone, it is also known as Cyasorb UV531. This compound is available from American Cyanamid Company. It is used primarily acids are butyric, lauric, palmitic and stearic. Examples as an ultraviolet light stabilizer. of unsaturated fatty acids are oleic, linoleic, and linole This is dilaurylthiodipropionate it is used primarily as an antioxidant. nic. A preferred fatty acid is stearic acid. The mold release agent is preferably present in the 50 Sample compositions 1-4 were molded into five inch composition in an amount in the range of from about by five inch by inch slabs by using a heated platen 0.05% to about 1%, more preferably in the range of press according to the following procedure. Each sam from about 0.1 to about 0.5%, by weight of the compo ple was placed into a picture frame mold of the indi sition. Most preferable, the mold release agent is present cated dimensions. This picture frame mold was inserted in the composition in an amount in the range of from 55 between the platens of the press. The platens were at a about 0.1% to about 0.2% by weight of the composi temperature of about 232 C. Slight pressure (1-50 psig) tion. was then applied from the press for about one minute. If desired, other components which do not adversely The pressure was then raised to thirty tons within one affect the crosslinking of the ethylene polymer can be minute. The picture frame mold was subjected to this employed in the composition of the present invention. pressure and temperature for either two or four minutes Examples of such components include corrosion inhibi to allow the crosslinking reaction to proceed. The pic tors, pigments, additional stabilizers such as metal com ture frame mold was then cooled to less than 40 C. at plexing agents, antistatic agents, ultraviolet absorbers a rate of 27 C. per minute. for light stabilization, carbon black, fillers, reinforcing Standard ASTM test bars were cut from the molded materials and the like. 65 and crosslinked ethylene polymer compositions. The The composition of the present invention can be test bars were then measured for their tensile properties formed by a variety of techniques. For example, the according to ASTM D638. The results are presented in ethylene polymer can be compounded into pellets and Table E-2. 5,405,915 7 8 TABLES E-2 A-D It can be seen from Tables E-2 A-D that the non “Tensile Properties of the Ethylene aromatic cyclictriene compound had the best overall Polymer Composition Samples' consistency in test one. This is an unexpected and im Run Crosslinking Time Test 11 Test 22 5 portant result. This result is important because the Per cent Elongation at Break is a good indicator of the TABLE E-2A SAMPLE ONE 1 2 34.67 2906 brittleness of an ethylene polymer composition. Fur 2 2 472.67 98.43 thermore, in this sample, the brittleness of each ethylene 3 2 46.00 3074 polymer sample did not vary by an unacceptable 4 2 42.00 3058 amount thereby providing an ethylene polymer compo 5 2 31.33 2829 10 Mean 20S.33 4342 sition that is better from a quality control viewpoint. Standard Deviation 149.56 3077 It can be seen from Tables E-2 A-D that the non Consistency Factor 73% T1% aromatic cyclictriene compound had the best overall 6 4. 66.00 3505 consistency in test two. This is an unexpected and im 7 4. 88.00 1984 8 4. 03.33 2298 1S portant result. This result is important because the 9 4. 364.00 7472 Strain Energy at Break is a good indicator of the tough 10 4 81.33 84 ness of an ethylene polymer composition. Furthermore, Mean 160.53 345 in this sample, the toughness of each ethylene polymer Standard Deviation 118.57 2363 Consistency Factor 74% 69% sample did not vary by an unacceptable amount thereby TABLE E-2B SAMPLE TWO 20 providing an ethylene polymer composition that is bet 2 687.33 15701 ter from a quality control viewpoint. 12 2 527.33 11197 Although the present invention has been described in 13 2 685.33 15640 detail with reference to certain preferred versions 14 2. 687.33 1594 thereof, other versions are possible. Therefore, the spirit 15 2 688.00 16017 and scope of the appended claims should not be limited Standard Deviation 71.4 206 to the description of the preferred version contained Consistency Factor 12 1.4% herein. 6 4 S23.33 1236 17 4. 613.33 134SO That which is claimed: 18 4. 597.33 13204 1. An ethylene polymer composition that comprises: 19 4 704.67 16273 (a) an ethylene polymer selected from the group con 20 4 739.33 17833 30 Mean 63S.60 4399 sisting of ethylene homopolymers and ethylene Standard Deviation 86.4 2629 copolymers or mixtures thereof, wherein said eth Consistency Factor 14% 18% ylene polymer has a density in the range of about TABLE E-2C SAMPLE THREE 0.92 g/cm to about 0.98 g/cm and a melt index of 21 2 888.67 2206 35 22 2 584.67 12392 at least 5 dg/minute and that comprises a chloride 23 2 550.67 1545 amount of less than 20 parts per million by weight 24 2 452.67 9346 based on the weight of the ethylene polymer; 25 2 534.00 42 (b) a crosslinking agent; and Mean 602.14 13306 Standard Deviation 167.36 5043 (c) a nonaromatic, cyclic, unsaturated, crosslinking Consistency Factor 28% 38% 40 co-agent. 26 4. 448.00 9330 2. A composition according to claim 1 wherein said 27 4. 518.00 10882 ethylene polymer has a density from about 0.94 g/cm3 28 4 476.67 991 29 4 S28.00 040 to about 0.97 g/cm3 and a melt index from about 10 30 4. 560.67 1725 dg/minute to about 30 dg/minute. Mean 506.27 10578 45 3. A composition according to claim 2 wherein said Standard Deviation 44.27 952 crosslinking co-agent that has the general formula Consistency Factor 9% 9% TABLEE-2D SAMPLE FOUR CnH2(-) R where “n” is an integer from 4 to 60; “x” 31 2 398.00 8053 is an integer from 1 to (n-1) and 'x' is the number of 32 2 4.04.00 8190 unsaturated carbon-carbon double bonds; and R can be 33 2 4O6.67 8374 50 any group that does not interfere with the crosslinking 34 2 400.67 8154 reaction. 35 2 416.67 8477 Mean 405.20 8250 4. A composition according to claim 3 wherein said Standard Deviation 7.20 172 crosslinking co-agent is selected from the group consist Consistency Factor 29% 2% ing of cyclopentene, cyclohexene, cycloheptene, cy 36 4 368.00 751. 55 clooctene, cyclononene, cyclodecene, 1,3-cyclohexadi 37 4 434.67 898O 38 4. 385.33 7828 ene, 1,4-cyclohexadiene, 1,3-cycloheptadiene, 1,5- 39 4 394.00 7991 cyclooctadiene, 1,5-cyclononadiene, dicyclopenta 40 4. 392.00 7842 diene, cycloheptatriene, 1,5,9-cyclododecatriene, Mean 394.80 8030 1,3,5,7 cyclooctatetraene and mixtures thereof. Standard Deviation 24.53 559 60 Consistency Factor 6% 7% 5. A composition according to claim 4 wherein said able E-2. Notes: crosslinking co-agent is 1,5,9 cyclododecatriene. This is the "Percent Elongation at Break" it is a good indicator of the brittleness of 6. A composition according to claim 1 wherein said an ethylene polymer composition. This is the "Strain energy at Break” it is a good indicator of the toughness of an ethylene polymer is a copolymer that comprises an ethylene polymer composition. It is equivalent to the total area under the stress alpha-olefin from 3 to 18 carbon atoms. strain curve. The unit of measurement is pounds per square inch. 65 *This is the consistency factor. It is equal to the standard deviation divided by the 7. A composition according to claim 6 wherein said mean. It gives an indication of how consistent the measured property is from sample alphaolefin is selected from the group consisting of run to sample run. 1-butene, 3-methyl-1-butene, 1-pentene, 3-methyl-1- pentene, 4-methyl-1-pentene, 1-hexene, 3-ethyl-1-hex 5,405,915 9 10 ene, i-heptene, 1-octene, 1-nonene, 1-decene and mix the general formula CH2(-x) R where “n” is an inte tures thereof. ger from 4 to 60; “x' is an integer from 1 to (n-1) and 8. A composition according to claim 7 wherein said ''x' is the number of unsaturated carbon-carbon double ethylene copolymer has a density from about 0.94 bonds; and R can be any group that does not interfere g/cm3 to about 0.97 g/cm3 and a melt index from about with the crosslinking reaction. 10 dg/minute to about 30 dg/minute. 10. A composition according to claim 9 wherein said 9. A composition according to claim 8 wherein said crosslinking co-agent is 1,5,9 cyclododecatriene. ethylene copolymer has a crosslinking co-agent that has k is sk

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