CA1247792A - Process for the manufacture of halogenated polymers - Google Patents
Process for the manufacture of halogenated polymersInfo
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- CA1247792A CA1247792A CA000464159A CA464159A CA1247792A CA 1247792 A CA1247792 A CA 1247792A CA 000464159 A CA000464159 A CA 000464159A CA 464159 A CA464159 A CA 464159A CA 1247792 A CA1247792 A CA 1247792A
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Abstract
IMPROVED PROCESS FOR THE MANUFACTURE OF
HALOGENATED POLYMERS
(E-24) ABSTRACT OF THE DISCLOSURE
In a process for the continuous halogenation of polymers by contacting polymer and halogenating agent in a continuous flow device in which means are provided for disengaging reaction by-products and unreacted halogenating agent from the reaction mixture, by deforming and disrupting the halogenated polymer surface and injecting an inert and/or reactive gas into the halogen-ated polymers immediately after reaction thereby neutral-izing the product. In a preferred embodiment the process is carried out in an extruder-reactor and an optional, supplementary inert and/or reactive gas scrubbing zone is included. The process is amenable to saturated and unsaturated polymers.
HALOGENATED POLYMERS
(E-24) ABSTRACT OF THE DISCLOSURE
In a process for the continuous halogenation of polymers by contacting polymer and halogenating agent in a continuous flow device in which means are provided for disengaging reaction by-products and unreacted halogenating agent from the reaction mixture, by deforming and disrupting the halogenated polymer surface and injecting an inert and/or reactive gas into the halogen-ated polymers immediately after reaction thereby neutral-izing the product. In a preferred embodiment the process is carried out in an extruder-reactor and an optional, supplementary inert and/or reactive gas scrubbing zone is included. The process is amenable to saturated and unsaturated polymers.
Description
J~`J
IMPROVED PROCE:SS E`OR THE MANUFRCTtlRE OF HALOGENA~ED PULYMERS
IMPROVED PROCE:SS E`OR THE MANUFRCTtlRE OF HALOGENA~ED PULYMERS
2 This invention relates to a method of modifying
3 polymers with a halogen or halogens; specifically to a
4 process for the production of halogenated polymers. ~ore
5 specifically, it is directed to a continuous process for
- 6 the manufacture of halogenated polymers such as butyl ~a
7 copolymer of a major proportion of an isoolefin and a minor
8 ~roportion of a multi-olefin) EPM (a copolymer of ethylene
9 and propylene~, EPDM (a terpolymer of ethylene, propylene and a nonconjuga~ed diene), SBR (styrene-butadiene rubber3, 11 B~ (polybutadiene rubber), polyisoprene rubber, ~arious 12 types of po}yethylene, includins linear low density poly-13 ethylene; ethylene vinyl acetate copolymer,~tc.
~4 Numerous references teach methods for ~alogena.-lS ing various polymers. Generally, these references are 16 limited to reactions in solution or are batch rather than 17 oontinuous processes~ There are, for example, references 18 that teach the halogenation of butyl rubber, but each suf-19 fers from serious limitations. An early reference, U.S.
Patent 2,944,578, teaches that chlorinated butyl rubber can 21 be produced in a batch process by dissolving butyl rubber 22 in a suitable, nonreactive solvent, e.g., hexane, and in-23 troducing chlorine or a chlorinating agent. By suitable 24 control of the temperature, concentrations of chlorinating agent and rubber, and reaction time, chlorinated rubber 26 containing the desired lëvel of chlorine is produced. How-27 ever, a batch process i5 inherently inefficient and the 28 need to dissolve the rubber in a solvent incurs significant 29 expenses for solvent recovery and environmental control.
An improved, continuous process for chlorination 31 or bromination of butyl rubber was subsequently disclosed 32 in U.S. ~atent 3,099,644. However, that process still -1 required the preparation and use of a solution of butyl ~ rubber, which, in addition to the limitations noted above, 3 is limited as to the concentration of rubber which can be 4 pro~essed, and which requires significant equipment and process control to precipitate the halogenated rubber from 6 solution and then dry the rubber in a controlled manner so 7 as to avoid degradation~ The halogenation of ~8 ethylene-propylene nonconjugated diene elastomers (EPD~
g has also been disclosed; such processes are analogous to those for halo~enatin~ butyl rubber~ For examplet ~.S.
11 4,051,083 describes the solution bromination and chlorina-12 tion of EPDM using N-halosuccinimide; additionally, the 13 ~neat~ halogenation of EPDM is also described. In the 14 latter disclo5ure the halogenating agent is dispersed in the EPDM by blending on a cool rubber mill and halogenation 16 is effected b~ heating the mixture in a hydraulic press.
17 ; Halogenation of EPDM in an aqueou3 batch process 18 is disclosed in U.S. 3,396,095. The process employs the 19 addition of an excess of C12 or Br2 to a polymer slurry to effect halogenation and avoid the expense of- solvent 21 recovery systems previously disclosed for solution halogen-22 ation processes~
23 - Ch:Lorobromination of polymers such as poly-24 butadiene, butadiene-isoprene copolymers and natural or synthetic polyisoprene is disclosed in ~ritish 1,483,063 26 and 1,483,064. The reaction is described as taking place 27 at a low temperature of 0-15-C, preferably in an inert 28 solvent, and the halogenated products are described as 29 containing high levels, e.g., at least 55% by weight of halogen.
31 A close reading of these references indicates 32 the difficulty with which halogenation of elastomers has 33 been conducted prior to the invention disclosed herein. The 34 various limitations of these batch and continuous solution processes are overcome by the improved process of the 37 present invention.
l The possibility of producing a halogenated rub-2 ber such as halogenated butyl rubber continuously ln an 3 extruder-reactor has been recognized, see, e.g., U.S.
4 Patent 4,185,057. However, ~he generali~ed disclosures of 5 that reference do no more than acknowledge the desirability 6 of such a process, but do not teach one ho~ to accompl~sh 7 such a process. The reference suggests that only enough 8 chlorine be introduced into the extruder to react with the g butyl rubber so that no chlorine remains after reaction. It lO then goes on to suggest that another gas, e.g~, nitrogen, -- ll be introduced to effect the production of gas filled pores 12 in the finlshed rubber, which is the primary object of the 13 invention.
14 No examples are disclosed in the patent and no lS conditions disclosed-which would enable one to actually 16 conduct such a butyl halogenation process. The inv~ntion 17 discloged herein provides a teaching suffic`l`e~.t to enable 18 the practice of this unique halogenation proces~ and apply i~ 19 such a teaching to the halogenation of various poly~ers.
Chlorination of butyl rubber-~: using 21 dichloramine-T and a calender has been reported by 22 Bulgaria~ wor~ers (Kh. Tenchev. et al, Chem Abstracts 23 50756u). The disclosed process was not intended to produce 24 neat chlorinated butyl since calendering is carried out on 25 a mixture of butyl rubber, accelerators, prevulcanization 26 inhibitors as well as variable amounts of carbon black and 27 diChloramine-T.
2~ The halogenation, in a kneader or extruder, of 29 polymers containing carboxylic acid groups using reagents 30 that differ from those disclosed herein is described in 31 V.SO Patent 3,364,187. ~he polymers are converted to the 32 acyl halide derivatives using specific halogenating agents.
33 The patent suggests that the kneading step may be carried 34 out in an extruder, a Banbury~mixer, a roll mill or any 35 other apparatus that yields the described kneading action.
~ i~e ~ ,k A British Patent, 1,257,016, discloses a process 2 for treating polymers with halogenating agents such as 3 N-bromosuccinimide under mechanical shear for the purpose 4 of producin~ unsaturation. The patent mentions that halo-5 genation may possibly occur in an intermediate step ~ol-6 lowed by dehydrohalogenation, but production and isolation 7 of a useful halogenated product is not an objective, nor ~s 8 it achleved. The process also requires the use of scaveng-9 ing amounts of a metal oxide or carbonate such as magnesium
~4 Numerous references teach methods for ~alogena.-lS ing various polymers. Generally, these references are 16 limited to reactions in solution or are batch rather than 17 oontinuous processes~ There are, for example, references 18 that teach the halogenation of butyl rubber, but each suf-19 fers from serious limitations. An early reference, U.S.
Patent 2,944,578, teaches that chlorinated butyl rubber can 21 be produced in a batch process by dissolving butyl rubber 22 in a suitable, nonreactive solvent, e.g., hexane, and in-23 troducing chlorine or a chlorinating agent. By suitable 24 control of the temperature, concentrations of chlorinating agent and rubber, and reaction time, chlorinated rubber 26 containing the desired lëvel of chlorine is produced. How-27 ever, a batch process i5 inherently inefficient and the 28 need to dissolve the rubber in a solvent incurs significant 29 expenses for solvent recovery and environmental control.
An improved, continuous process for chlorination 31 or bromination of butyl rubber was subsequently disclosed 32 in U.S. ~atent 3,099,644. However, that process still -1 required the preparation and use of a solution of butyl ~ rubber, which, in addition to the limitations noted above, 3 is limited as to the concentration of rubber which can be 4 pro~essed, and which requires significant equipment and process control to precipitate the halogenated rubber from 6 solution and then dry the rubber in a controlled manner so 7 as to avoid degradation~ The halogenation of ~8 ethylene-propylene nonconjugated diene elastomers (EPD~
g has also been disclosed; such processes are analogous to those for halo~enatin~ butyl rubber~ For examplet ~.S.
11 4,051,083 describes the solution bromination and chlorina-12 tion of EPDM using N-halosuccinimide; additionally, the 13 ~neat~ halogenation of EPDM is also described. In the 14 latter disclo5ure the halogenating agent is dispersed in the EPDM by blending on a cool rubber mill and halogenation 16 is effected b~ heating the mixture in a hydraulic press.
17 ; Halogenation of EPDM in an aqueou3 batch process 18 is disclosed in U.S. 3,396,095. The process employs the 19 addition of an excess of C12 or Br2 to a polymer slurry to effect halogenation and avoid the expense of- solvent 21 recovery systems previously disclosed for solution halogen-22 ation processes~
23 - Ch:Lorobromination of polymers such as poly-24 butadiene, butadiene-isoprene copolymers and natural or synthetic polyisoprene is disclosed in ~ritish 1,483,063 26 and 1,483,064. The reaction is described as taking place 27 at a low temperature of 0-15-C, preferably in an inert 28 solvent, and the halogenated products are described as 29 containing high levels, e.g., at least 55% by weight of halogen.
31 A close reading of these references indicates 32 the difficulty with which halogenation of elastomers has 33 been conducted prior to the invention disclosed herein. The 34 various limitations of these batch and continuous solution processes are overcome by the improved process of the 37 present invention.
l The possibility of producing a halogenated rub-2 ber such as halogenated butyl rubber continuously ln an 3 extruder-reactor has been recognized, see, e.g., U.S.
4 Patent 4,185,057. However, ~he generali~ed disclosures of 5 that reference do no more than acknowledge the desirability 6 of such a process, but do not teach one ho~ to accompl~sh 7 such a process. The reference suggests that only enough 8 chlorine be introduced into the extruder to react with the g butyl rubber so that no chlorine remains after reaction. It lO then goes on to suggest that another gas, e.g~, nitrogen, -- ll be introduced to effect the production of gas filled pores 12 in the finlshed rubber, which is the primary object of the 13 invention.
14 No examples are disclosed in the patent and no lS conditions disclosed-which would enable one to actually 16 conduct such a butyl halogenation process. The inv~ntion 17 discloged herein provides a teaching suffic`l`e~.t to enable 18 the practice of this unique halogenation proces~ and apply i~ 19 such a teaching to the halogenation of various poly~ers.
Chlorination of butyl rubber-~: using 21 dichloramine-T and a calender has been reported by 22 Bulgaria~ wor~ers (Kh. Tenchev. et al, Chem Abstracts 23 50756u). The disclosed process was not intended to produce 24 neat chlorinated butyl since calendering is carried out on 25 a mixture of butyl rubber, accelerators, prevulcanization 26 inhibitors as well as variable amounts of carbon black and 27 diChloramine-T.
2~ The halogenation, in a kneader or extruder, of 29 polymers containing carboxylic acid groups using reagents 30 that differ from those disclosed herein is described in 31 V.SO Patent 3,364,187. ~he polymers are converted to the 32 acyl halide derivatives using specific halogenating agents.
33 The patent suggests that the kneading step may be carried 34 out in an extruder, a Banbury~mixer, a roll mill or any 35 other apparatus that yields the described kneading action.
~ i~e ~ ,k A British Patent, 1,257,016, discloses a process 2 for treating polymers with halogenating agents such as 3 N-bromosuccinimide under mechanical shear for the purpose 4 of producin~ unsaturation. The patent mentions that halo-5 genation may possibly occur in an intermediate step ~ol-6 lowed by dehydrohalogenation, but production and isolation 7 of a useful halogenated product is not an objective, nor ~s 8 it achleved. The process also requires the use of scaveng-9 ing amounts of a metal oxide or carbonate such as magnesium
10 oxide, zin~ oxide or calcium carbonate in addition to the
11 halogenating agent andG<-olefin polymer. The patent dis-
12 closes, as an alternate method, the preblending of the
13 halogenating ag~nt with a solution of the polymer followed
14 by solvent removal. It is stated that very little, if any,
15 reaction oecurs during surh an operation.
16 An extensive disclosure of polymer modifications
17 conducted in an extruder can be found in~U.S. Patent No.
18 3,862,265. This patent is directed to modif~cation of
19 polyolefins using heat, shear and controlled presjsure to
20 induce degradation $n the polyolefin and to co~bine the
21 polyolefin with a free-radical initiator and/or one or more
22 monomers. The broad disclosure is of value for its teach-
23 ings directed to the modification of polyolefins with
24 various monomers especially to form novel grafted polymers.
Canadian Patent 1,121,956 describes the treat-26 ment of blow-molded articles with fluorine gas to impart 27 barrier properties to ~he article. It is achieved by in-28 troducing a mixture of fluorine and an inert gas into the 29 interior surface of i parison before charging the parison 30 into a blow-mold; the parison is then expanded by an inert 31 gas under pressure. Such batchwise surface treatment 32 method is not particularly relevant to the continuous 33 whole-polymer modification process disclosed herein.
-4a-I U.S. Patent 3,51û,416 (Vaccari et al~ teaches 2 an improved metilod of halogenating PVC particles by using 3 gaseous hydrogen in combination with a swelling agent 4 (chlorination carrier). Following reaction, the PVC
particles are transferred to another piece of equipment (a 6 dryer) in which the chlorination carrier is stripped and 7 gaseous by-products are separated. This reference 8 discloses a process based on particle fluidization which 9 relies or- diffusion to accomplish drying; in addition, such a process requires separate pieces of equipment and ll relatively long times for drying.
12 Some polymers are particularly sensitive when 13 exposed to shear and elevated temperatures in the presence 14 of a halogenating agent. For example, butyl rubber is -4a-. _ . . _ . . _ . _ l subject to degradat~on ~nder such conditions and this has 2 made the achievement of a halogenated butyl product using 3 an extruder-reactor a difficult goal, and,until the invention 4 described at the end of this seceion, a goal ehat had not yet been 5 achieved. ~he hzloge..at.on reaction o butyl rubber in 6 solution is described in ~Encyclopedia of Chemical 7 Technology~ r ~irk-Othmer, Third Edition (1979), Volume 8 at 8 page 476 ffO It is noted that the halogenation reaction 9 carried beyond one halogen atom per olefin unit is compli-l0 cated by chain fragmentation~ Indeed, such fragmentation ll or degradation is a persistent problem when halogenation of 12 butyl rubber is attempted; that problem is aggravated under 13 conditi~ns of heat and shear.
l4 ~ An additional difficulty in this field of poly-15 mer modification is the dehydrohalogenation reaction. One 16 means ~f suppressing such a reaction is the addition of 17 stabilizers which can-be added, e.g., to a solution of 18 halogenated butyl to protect against this reaction during l9 processi~g. It is also necessary to avoid other ~ndesir-20 abie side reactions which vary depending OR the particular 21 polymer ~eing halogenated. Such reactions are further 22 aspects of the sensitivity of the polymers to the severe 23 halogenation reaction that has made the achie~Jement of 24 controlled halogenation of neat polymers in an
Canadian Patent 1,121,956 describes the treat-26 ment of blow-molded articles with fluorine gas to impart 27 barrier properties to ~he article. It is achieved by in-28 troducing a mixture of fluorine and an inert gas into the 29 interior surface of i parison before charging the parison 30 into a blow-mold; the parison is then expanded by an inert 31 gas under pressure. Such batchwise surface treatment 32 method is not particularly relevant to the continuous 33 whole-polymer modification process disclosed herein.
-4a-I U.S. Patent 3,51û,416 (Vaccari et al~ teaches 2 an improved metilod of halogenating PVC particles by using 3 gaseous hydrogen in combination with a swelling agent 4 (chlorination carrier). Following reaction, the PVC
particles are transferred to another piece of equipment (a 6 dryer) in which the chlorination carrier is stripped and 7 gaseous by-products are separated. This reference 8 discloses a process based on particle fluidization which 9 relies or- diffusion to accomplish drying; in addition, such a process requires separate pieces of equipment and ll relatively long times for drying.
12 Some polymers are particularly sensitive when 13 exposed to shear and elevated temperatures in the presence 14 of a halogenating agent. For example, butyl rubber is -4a-. _ . . _ . . _ . _ l subject to degradat~on ~nder such conditions and this has 2 made the achievement of a halogenated butyl product using 3 an extruder-reactor a difficult goal, and,until the invention 4 described at the end of this seceion, a goal ehat had not yet been 5 achieved. ~he hzloge..at.on reaction o butyl rubber in 6 solution is described in ~Encyclopedia of Chemical 7 Technology~ r ~irk-Othmer, Third Edition (1979), Volume 8 at 8 page 476 ffO It is noted that the halogenation reaction 9 carried beyond one halogen atom per olefin unit is compli-l0 cated by chain fragmentation~ Indeed, such fragmentation ll or degradation is a persistent problem when halogenation of 12 butyl rubber is attempted; that problem is aggravated under 13 conditi~ns of heat and shear.
l4 ~ An additional difficulty in this field of poly-15 mer modification is the dehydrohalogenation reaction. One 16 means ~f suppressing such a reaction is the addition of 17 stabilizers which can-be added, e.g., to a solution of 18 halogenated butyl to protect against this reaction during l9 processi~g. It is also necessary to avoid other ~ndesir-20 abie side reactions which vary depending OR the particular 21 polymer ~eing halogenated. Such reactions are further 22 aspects of the sensitivity of the polymers to the severe 23 halogenation reaction that has made the achie~Jement of 24 controlled halogenation of neat polymers in an
25 extruder-reactor a previously elusive goal.
26 Other difficulties which are encountered in attempting to
27 halogenate ~eat polymers include: the problem of mixing a highly
28 viscous polymer phase with a low viscosity halogenating agent phase
29 (e.g., where 8 gaseous halogenating agent is used this difference can be as much as ten orders of magnitude); the low probability of the halo-31 genating agent encountering the reactive Siee on the polymer, particularly3~ when a low functionaliey polymer is employed (e.g., butyl rubber, 33 isobutylenetisoprene copolymer); and the difficulty of removing from 34 coneact with the polymer, i.e., disengaging, potentially damaging by-products of the reaction, e.g., hydrogen halide. These problems and 36 others have been overcome by the inveneion disclosed herein.
Conventional processes, which halogenate 2 polymers such as butyl rubber in solution, incur siynifi-3 cant disadvantages. These include hign capitaL investment 4 for the equipment needed to handle, purify, and recycle the solvent, high energy costs For the movement, vaporiza-6 tion, and purification and recycle of the solvent, 7 potential halogenation of the solvent, potential hydro-8 carbon emissions to the atmosphere and the use of con-9 siderable space for the equipment necessary to handle lO large volumes of solutions.
ll A previous patent application, filed by two of ]2 the inventors herein (U.S. Serial No. 306,882, filed 13 September 30, 1981 now U.S. Patent 4,~84,072 issued May 14 17, 1983) disclosed an improved halogenation process in ~5 which neat rubber was halogenated in an extruder. A
16 significant feature of the earlier invention was injection 17 of the halogenating agent at a position filled with rubber 18 and subjecting the rubber and ayent to a highdegree of l9 mixing. The invention disclosed herein is a further, 20 significant improvement over such a process.
22 In accordance with the present invention, an 23 improved process has been discovered for the continuous 24 production of halogenated polymers, the process comprising 25 contacting a cohesive polymer mass and halogenating agent 26 in a continuous flow device cornprising rneans for conveying 27 said polymer through said device wherein by-product of the 28 halogenation reaction and unreacted halogenating agent are 29 disengaged from said halogenated polymer mass, in said
Conventional processes, which halogenate 2 polymers such as butyl rubber in solution, incur siynifi-3 cant disadvantages. These include hign capitaL investment 4 for the equipment needed to handle, purify, and recycle the solvent, high energy costs For the movement, vaporiza-6 tion, and purification and recycle of the solvent, 7 potential halogenation of the solvent, potential hydro-8 carbon emissions to the atmosphere and the use of con-9 siderable space for the equipment necessary to handle lO large volumes of solutions.
ll A previous patent application, filed by two of ]2 the inventors herein (U.S. Serial No. 306,882, filed 13 September 30, 1981 now U.S. Patent 4,~84,072 issued May 14 17, 1983) disclosed an improved halogenation process in ~5 which neat rubber was halogenated in an extruder. A
16 significant feature of the earlier invention was injection 17 of the halogenating agent at a position filled with rubber 18 and subjecting the rubber and ayent to a highdegree of l9 mixing. The invention disclosed herein is a further, 20 significant improvement over such a process.
22 In accordance with the present invention, an 23 improved process has been discovered for the continuous 24 production of halogenated polymers, the process comprising 25 contacting a cohesive polymer mass and halogenating agent 26 in a continuous flow device cornprising rneans for conveying 27 said polymer through said device wherein by-product of the 28 halogenation reaction and unreacted halogenating agent are 29 disengaged from said halogenated polymer mass, in said
30 continuous flow device downstream of said contact between
31 said polymer and said halogenating agent by means compris-
32 ing deForming and disrupting said halogenated polymer,
33 thereby continually generating new polymer surface and
34 injecting an effective amount of inert gas and/or a
35 reactive neutralizing gas in order to neutralize said
36 halogenated polyrner by disengaging halogenation reaction
37 by-products and unreacted halogenating agent. In a
38 preferred embodiment, the improved polymer l halogenation process is conducted in an extruder-reactor comprising a feed zone, a reacton ~one (preferably vented) and a gas injection, neutralization zone. This im-proved process is subject to signiicantly reduced cor-S rosion because of the abse~ce of aqueous streams. ~he products of this process are useful for a wide ranqe of applications including tires, innertubes, mechanical goods, hoses, and electriral products. ~alogenated products con-taining reactive halogen, e.g , halogenated butyl rubber,lO are capable of.being vulcanized with sulfur-free cure sys-tems, for example, zinc oxide in combination with stearic ~cid, this halogenated rubber can alsQ bP vulcanized by standard sulfur and sulfur-donor-containing cure systems.
DESCRIPTION OF THE PREFERRED E~l~SODI~:N~S
Polymers useful in the practice of this in~en-tion can be categorized in various ways and include:
~a) ol.efin polymers, such as ~he various forms of polyethylene, ethylene-propylene co-polymers, other ethylene copolymers with comonomers such as 1-butene, isobutylene, vinyl acetate, maleic anhydride, ethyl acrylate, methyl acrylate;
generally alpha-olefin and cyclic olefin homo-polymers and copolymers;
(b). polymers from dienes, such as styrene-butadiene rubber, polychloroprene (Neoprene), butyl, poly-butadiene, polyIsoprene,, butadiene-acrylo~itrile (Nitrile), ethylene-propylene-diene;
~c) vinyl and vinylidene Dolymers, such as polyvinyl chloride and :its family of copolymers, polyvinyl esters such as polyvinyl acetate, acrylic poly-mers such as polymethylmethacrylate, polystyrene and its family of copoly~ers such as butadiene-styrene, styrene~acrylonitrile, styrene-isoprene, ac~ylonitrile-butadiene-styrene;
8- ~S~ !
~ _ .
l ~d) heterochain thermoplastics, such as polyamides~
polyesters, polyethers, polysulfides, poly-urethanes, polycarbonatesO
Unsaturated polymers useful in the present in-ven~ion include ethylenically unsaturated elastomers, e.g., the several rubbers of commercial significance, fGr exam-ple, butyl rubber, EPDM rubber, styrene butadiene rub~er (SBR), polyisoprene rubber and poly tbutadiene-isoprene) copolymer rubbers.
The butyl rubber copolymers useful in the present invention contain a major proportion, preferably at least 70 wt.%, of isoolefins and a minor proportion, pref-erably not more than about 30 wt.~, of multi-olefins. Co-polymers of this general type, especially where the cQpoly-15 mer contains about 85-99.5% ~preferably 95-99.5~ of a C4-C7 isoolefin, such as isobutylene, with about 15~0.5~
(preferably about 5-0.5 wt.4) of a multi-olefin of about 4-14 carbon atoms, are commonly referred to in patents and literature as "butyl rubber~; see, for example, the text-20 book ~Synthetic Rubber" by G. S. Whitby (1954 edition byJohn Wiley and Sons, Inc.), pages 608-609, ~Encyclopedi~ of Chemical Technoloqy~, Third Edition, Volume ~, (1979), pages 470-484, etc. The expression "butyl rubberN as em-ployed in the specification and claims is intended to in-2~ clude copolymers containing about 80-99~ by weight of an isoolefin of about 4-7 carbon atoms and about 20-1% of conjugated multi-olefin of about 4-10 carbon atoms. The preparation of butyl-type rubbers is amply described in the literature. In general, it consists of the reaction product 3~ of a C4-C7 isoolefin (preferably isobutylene) with a C4-C10 (preferably a C4-C6 conjugated diolefin, such 2S isoprene, butadiene, dimethyl butadiene, piperylene, etc. Tbe reac-_9_ 1 tion product of isobutylene and isoprene is preferred. Thepreparation of butyl rubber is described in U.S. Patent 2,356,128~
Conventional high molecular weight butyl rubber generally has a number average molecular weight of about 25,000 to about 500,000, pre~erably about 80,000 to about 300,000, especially about 100,000 to about 250,000; and a Wijs odine No. of about 0.5 to 50~ preferably 1 to 20.
~ore recently low molecular weight polymers have also been lO prepared which have number average molecular weights of from 5,000 to 2S,000 and unsaturation expressed as mole %, of 2-10.
The term "EPDM" as used in the specification and claims is used in the sense of its AST~ definition and is intended to ~ean a terpolymer containing ethylene and propylene in the backbone and diene enchainment with residual unsaturation in the sidechains~ Illustrative methods for producing these terpolymers are found in ~.S.
Patent 3,280,082, British Patent 1,030,989 and French 2~ Patent 1,386,600.
The preferred polymers contain about 4S to about 80 wt.% ethylene and about 1 to about 10 wt.~ diene monomer. The balance of the polymer is propylene. Prefer-2~ ably, the polymer contains 45 to 70 wt.% ethylene, mos~preferably 50 to 60 wt.% ethylene, e.g., 56 wt.%, and about 2 to about 9 wt.% diene monomer, more preferably about 2 to about 6 wt.~ diene monomer, most preferably 2.6 to 4 wt.%
diene monomer. The diene monomer is a non-conjugated 3t~ diene. Illustrative of these non-conjugated diene monomers which may be used in the terpolymer (EPDM) are hexadiene, dicyclopentadiene, ethylidene norbornene, methylene nor-bornene, propylidene norbornene and methyltetrahydroindene.
A typical EPDM containing ethylidene norbornene as a diene 3~
l monomer is Vista7On 4608 (Exxon Chemical Company, U.S.A.), 2 a polymer having a Mooney viscosity at 260~P of about 62, 3 and an ethylene content of about 56 wt . % .
4 The polyisoprene rubber referred to in this 5 invention may be natural rubber or synthetic polyisoprene 6 prepared by processes well known in the art, and, an 7 general, has a molecular weight of from about 500 to about 8 509,000, preferably about t500 to about 200,000.
9 , The polybutadiene and poly(butadiene-isoprene) 10 copolymer rubbers referred to in thi invention include the ll geometric isomers thereof, all of which may be prepared by 12 pro~esses well known in the art. In general, s~ch polymers 13 and copolymers have a molecular weight of from about 500 to 14 about 500,000, preferably from about 1500 to about 200,000.
15 Generally, polybutadiene rubbers have Mooney viscosity 16 values, measured at 212-F, of from about 25 to about 65, 17 prefer~bly from about 35 to about 5~, most pr~ferably from 18 about 40 to about 50.
l9 ; The styxene butadiene rubber referred to in this 20 inventio~ is also known as poly(butadiene-co-styre~e), and 21 typically a~breviated SBR~ and includes rubbers prepared by 22 the emulsion ~hot and cold) and solution processes well 23 known in the art. Bound styrene levels are from about 3 to ~4 about 50 wt.~! prefer~bly from about 10 to about 45 wt.%, 25 most preferably from about 12 to about 30 wt.%, for 26 example, 23.5 wt.%~ Generally, such polymers have Mooney 27 viscosity values, measured at 212-F, of from about 20 to 28 130 and above, preferably ~rom about 35 to about 80, most 29 preferably from about 40 to about 70, for Example 52.
The butadiene in such copolymers is present as 31 all three geometric isomers, cis-1,4, trans-1,4 and 1,2 or 32 vinyl and the copolymer can be random, block or graft.
33 The elastomers or rubbers referred to above and 34 processes for their preparation are generally described in 35 the ~irk-Othmer ~Encyclopedia of Chemical Technology~, 36 Third Edition, Volume 8, (1979), butyl p. 470 ff, EPDM
. . .
d ~ J.f.../
1 p.492 ff, polybutadiene p. S46 ff, polyisoprene p. 582 ff 2 and poly~hutadiene-co-styrene~ D. 608 ff, 4 Some forms of halogena~ed butyl rubber, prepared 5 in solution according to processes described above, are 6 commercially aYailable, e.g~, chlorinated butyl rubber and 7 brominated butyl rubber. One method used to prepare hal-`8 ogenated butyl rubber is that of halogenating butyl rubber - 9 in a solution ~butyl rubber cement) containing between 1 to 10 60~ by weight o butyl rubber in a substantially inert ll Cs-Cg hydrocarbon solvent such as pentane, hexane, heptane, 12 etc~, and contacting this butyl rubber cement with a halo-13 gen for a period of up to about 25 minutes. There is then 14 formed the halogenated butyl rubber and a hydrogen palide, 15 the polymer containing up to one or somewhat more halogen 16 atoms per double bond initially present in the polymer.
17 Genera~ly, haiogenated butyl rubber compri~es a copolymer 18 of 85 to 99.5 wt.~ of a C4 to ~8 isoolefin, e.~., isobuty-l9 lene, with 15 to Q.S wt.~ of a Ci to C14 multi-olefin, 20 e.g., isoprene, containing at least about 0.5 wt.% combined 21 halogen in its structure. Por example, where butyl is 22 halogenated with bromine, the bromine can be present in the 23 brominated butyl in an amount of from about t.0 to about 24 3.0 wt.%, preferably from about 1.5 to about 2.5 wt.%. A
25 method of preparing conventionally halogenated butyl rubber 26 is described in U.S. Patent 3,099,644 28 The preparation, in solution, of haloqenated 29 butyl rubber containing both bromine and chlorine, i.e., 30 bromochlorinated butyl rubber, is described in U.S. Patent 31 4,254,240~ The potential 32 for molecular weight breakdown of the butyl rubber, noted 33 earlier, is present even where bromine chloride is used as 34 the halogenating agent, as disclosed in this reference (column 4, lines 24-32).
' 1 The in~ention disclosed herein is also particu-2 larly useful for the halogenation of saturated polymers.
3 Such polymers include rubbers such as ethylene-propylene 4 copolymers (EPM~, generally known in the art and similar in 5 their preparation and composition to EPDM terpolymers with 6 the exception of the presence of residual unsaturation 7 also included is polyisobutylene rubber, produced com-8 mercially ln grades varying æs to molecular weight.
~ g Other saturated polymers useful in the practice 10 of the instant invention include olefin polymers such as ~ ;11 high and low density polyethylene (~DPE and LDPE) and 12 linear low density pol~ethylene ~LLDPE~, c~ -~-13 polymers of ethylene such as e~hylene-vinyl acetate, Rod :14 ~olyvinyl and vinyl: polymers, for exa~ple, p~lyvinyl chloride.
;15 BDPE has a density of about 0.941 to about 0.965 16 ~/cc. ~igh density polyethylene is an established product 17 of commerce and its manufacture and general`p~operties are 18 well known in the art. Typically, ~DPE has a ~elatively 19 broad molecular weight distribution, characterized by the 20 ratio of weight average to number average molecula~ weight, 21 of from about 20 to about 40. LDPE is, similarly, an item 22 of commercer and typically includes products with densities 23 in the range of about 0.910 to about 0.925 g/cc. Medium 24 density polyethylene should not be excluded as a useful 25 polymer, e.g., about 0.925 to about 0.940 g/cc.
26 Linear low density polyethylene (LLDPE) is a 27 relatively new class of low density polyethylene character-28 ized by little, if any, long chain branching, in contrast 29 to conventional low density polyethylene. The processes 30 for producing LLDPE are well known in the art and commer-31 cial grades of this polyolefin plastic are available.
32 Generally, it is produced in gas-phase fluidized bed reac-33 tors or liquid-phase solution process reactors; the former 34 process can be carried out at pressures of about 100 to 300 35 psi and temperatures as low as 100-C~ Polymers can be made 1 in the gas phase with melt indices and densities over the 2 ~ull commercial ranqe and with molecular weight distribu-3 tions rom very narrow to very broad.
4 Polyethylene copolymers include copolymers OL
5 ethylene and alpha-olef ins having 3 to 16 carbon atoms, for 6 example, propyleney 1~butene, etc. Also included are 7 copolymers of ethylene with an unsaturated ester of a lower ~ carboxylic acid. In particular, copolymers of ethylene - t g with vinyl acetate or alkyl acrylates, for example, methyl - lO acrylate and ethyl acrylate, are employed. For the pur-11 poses of this invention, polyethylene copolymers are also 12 considered to include blends of polyethylene and poly-13 ethylene copolymers. ~any such ethylene copolymers are -lÇ available as items of commerce and their composition and lS methods for producing them are well known in the art.
Polyvinyl chloride ~PVC) is the most com-mercially significant member of the polyvinxl and vinyl copolymer famîly which comprises varîous polymers based o~
the vinyl radical or vinylidene radical. Vinyl chloride has been copolymerized with materials such as vlnyl ace-tate, acrylic esters and vinylidene chloride. More recently other polymers have been grarted to polyvinyl chloride including ethylene vinyl acetate and EPDM. PVC is manufac ured commercially using various well known poly-merization processes: suspension, mass, emulsion/disper-sion and solution; the first is the dominant method. The product is available in several forms incl~ding particles, fine powders and latexes.
The polymer and halogenating agent are con-tacted, or reacted, in a continuous flow device. Suitable devices include ~neaders, extruders (employing single or multiple screws, e.g., twin screws), continuous mixers and a recently disclosed blending/extrusion device referred to as a cavity transfer mixer (see, e.g., European Rubber Journal, July-August, 1982, pages 29-32 and G.M. Gale, u.s Patent 4,419,014). Althou~h such polymers can attain very high viscosities, even at relatively hi~h temperatures, ~ - l 3 a --1 such devices are capable of subjecting polymers to 2 deformation.
3 The continuous flow device should be capable 4 of initially forming the polymer feed into a cohesive mass and then deforming the polymer, disrupting the polymer 6 surface, thereby exposing fresh, i.e., unreacted, polymer 7 to the halogenating agent. The exposure of new surface 8 does not necessarily require the use of high speeds where, g e.g., an extruder is used. However, surface disrupting means are preferably employed (as will be described in 1I detail below), for example, pins, reverse flow sections, a 12 "Maillefer" screw design, the cavities of a cavity 13 transfer mixer9 multiple flight screw section, interrupted 14 flight sections, e.g., slotted flights, and combinations thereof.
-13a-4 .
- 1 3- b-The defor~ation forces generated in the continuous 2 flow device are adequate when such ~orces generate a degree 3 of mixing of the polymer and halogenating agent such that 4 the scale of segregation is, preferably, less than 50 5 microns, more preferably less than 30 microns, most preer-6 ably less.than .10 microns... Characterizat~on of the degree 7 of mixing in a two-phase system according to scale of 8 segregation is described in the text, "Principles of Poly-~ mer Processing~, Z. Tadmor and C. G. Gogos (John Wiley and }0 Sons, 1979) ! Section 7.5, pages 209 ~f.
-11 When the region in which the polymer and hal~-12 genating agent are brought into c~ntact, e.g., the reactio~
13 zone of an extruder-reactor,.is not filled with polymer, 14 the halogenating agent is present as a eontinuous phase and the polymer 15 i8 present as either a discontinuous or eontinuous phase; the for~er is preferr~d. Whe~ each co~stitute a continuous phase,`~`for ease of reference this i6 referred to as "co-continuous phases"~ Tn this la~ter situation ~f ehe reactior zone was viewed under contitions where tefosmatio~ of the poly~er was stopped, the polymer and halogenating agent~ould each 20 co~prise an independent, continuous phase. A preferred operating mode of the process ut;lizes a reacCion zone which is only partially filled with poly~er; this permits reaction by-products and unreacted halogenaeing agent to disengage from the polymer phsse. Generally, ehe poly~er is prese~t in the reaction zone to the extent that about 5 to about 95%, 25 preferably lO to about 75~, more preferably about 15 to about 50~, for exa~ple 20 to about 35Z of the reaction zone is filled with the polymer.
One means of achiev;ng a partially filled reaction zone is to feed, in a controlled manner, less polymer into the reaction zone than the 30 conveying capacity of the zone. The space above the polymer is occupied by the halogenating agent and, as fresh surface is ex-poset to the halogensting agent and halogenation occurs, hydrogeu halide is released as a by-produce of the reaceion. The hydrogen halide "disengages" from the polymer and enters and is present in 35 ehe halogensting agene phase. In a preferred embodiment, utilization of vent means in che reaction zone facili~ies removal of the 7r3~
`~ -14-l reaction by-product and unreacted halogenating agent.
2 Another preFerred embodiment imposes a vacuum on the vent 3 means 90 as to more efFiciently disengage by-product(s) 4 and unreacted halogenating agent. The vent means com-prises one or more vents in the contacting region.
6 Means are provided for contacting the halo-7 genated polymer with neutralization means, for example a 8 neutralizing agent. This can also be viewed as a means of 9 disengaging unwanted reaction by-products and unreacted halogenating agent from the halogenated polymer. The 11 neutralization means and the halogenated polymer can be 12 conveyed concurrently or countercurrently through the 13 continuous flow device; preferably in a neutralization 14 zone following the contacting or reaction zone. The pH of the neutralized, halogenated polymer is, preferably, 16 greater than about 5.0, more preferably greater than about 17 6.0~ most preferably greater than about 7Ø In the 18 improved process disclosed herein, neutralization is 19 achieved in an aqueous-free manner by injecting an inert gas, e.g., nitrogen, argon, carbon dioxide or air, into 21 said continuous flow device downstream of the contact 22 between said polymer and said halogenating agent, e.g., in 23 the neutralization zone. Also included in the improved 24 process is the use of a reactive gas such as ammonia which functions to chemically neutralize as well as physically 26 disengage unwanted by-products and/or unreacted halogenat-27 ing agent.
f . J
I Kal)irl and complete neutralization, i.e., ' disengagement, i3 effected by employing process Features 3 such as those described earlier with regard to polymer 4 deformation and surface disruption in order to expose fresh polymer surface to the inert gas and/or reactive 6 gas; simi]arly, the discussion of scale oF segregation is 7 relevant here with regard to the inert and/or reactive gas 8 and polymer. In a preferred embodiment, disengagement 9 occurs in a region oF the continuous flow device which is not completely filled with polymer. In a still more 11 preferred embodiment, vent means are provided so that the 12 inert and/or reactive gas, unreacted halogenating agent 13 and reaction by-products are removed from the polymer 14 conveying means. The amount of inert and/or reactive gas employed can be readily determined and should be an amount 16 ef~ective for the disengagement without being unnecessar-17 ily wasteful. Inert and/or reactive gas injection can be 18 achieved using more than one injection port and the l9 halogenated polymer can again be treated in a supple-mentary scrubbing zone following neutralization in order 21 to remove additional by-products and unreacted halogenat-22 ing agent. Another option is a region for injecting a 23 stabilizer into the continuous flow device following the 24 inert and/or reactive gas treatment. In another embodi-ment, the inert and/or reactive gas injection and venting 26 configuration is designed so as to permit explosive 27 release of the injected inert and/or reactive gas from 28 the halogenated polymer in order to facilitate in the 29 removal of unwanted materials. Filter means can also be employed to remove undispersed materia1 from the halogen-31 ated polymer. The absence of -14a-1 aqueous streams in the process results in significantly 2 reduced corrosion of the process equipment. Furthermore, 3 the halogenated product can be used directly or packaged 4 directly without an intermediate drying step because of the absence of water.
Preferably the various zones which have been 7 described are separated from one another in such a manner 8 as to permit maximum independent control 3f conditions in 9 each zone. Details and conditions are described below for 10 a preferred embodiment utilizing an extruder-reactor, but 11 the principles disclosed are broadly applicable to the 12 system just discussed.
13 A preferred embodiment of the process employs 14 an extruder-reactor~ ~he extruder-reactor may be thought 15 of as carrying out .he halogenated polymer manufacture in 16 various operating zones: ;
17 (A) Fe~d Zone - in which polymer is intr~æuced into the 18 e~truder~reactor in convenient form~ This for~ includ~s, 19 for example, particles and pellets of plastics as they are 20 produced-~ommercially, particles fro~ bales of rub~ér which 21 have been comminuted and crumb from the finishing line of a 22 rubber manufacturing plant, each of which i5 preferably 23 dry, but may contain ~ low level, e.g., about 0 to lS
24 wt.%, preferably about 0 to 5 wt.%, most preferably about 0 25 to 1 wt.%, of a solvent or diluent; the latter materials 26 will be described more fully below. In this improved 27 process the use of water as a diluent is to be avoided in 28 order to avoid corrosion.
29 The feed zone is designed to form the polymer 30 feed into a cohesive mass;and convey or pump the mass past 31 ~ restrictive dam which follows the feed zone and distin-32 guishes it. from the reaction zone which follows. This 33 operation should be conducted at low shear and temperature 34 consistent with the desired result and at a pressure suf-35 ficient to convey the mass, typically up to about 600 psig, 36 preferably up to about 400 psig, most preferably up to '~
16~
1 about 200 psig. Lower pressures are preferred in order to 2 avoid overheating the polymer. This can be achieved, e.g., 3 by utilizing an extruder screw with relatively dee2 flights 4 and by keeping the length of the feed zone, i.e., the feed zone screw length, as short as possible commensurate with 6 de~ired production rates. For example, polymer is intro-7 duced at about room temperature and ex~ts fro~ the feed zone 8 at about 60 to 150C.
~ A restrictive dam is used to separate the feed 10 zone from the reaction zone which follows it so as to 11 prevent back leakage of reactants. T~is dam is not 12 restrictive enou~h, however, to cause excessive overheating 13 of the polymer. A restrictive dam can be, for example, a 14 reverse flighted screw section, a filled screw section, a 15 shallow fli~hted screw section, an unflighted screw sec-16 tion, combinations thereof, or other means known in the 17 art. If an unfli~hted screw section is e~pXoyed, it can 18 have a larger diameter than the root diameter ups~ream of 19 it, for example 5-25~ larger, but not greater than the 20 screw flight diameter. The restricti~e dam length should 21 be about 0.5 to about 8 screw diameters, preferably about 1 22 to about 5 screw diameters, more preferably about 1.5 to 23 ~bout 4 screw diameters, most preferably about 2 to about 3 24 screw diameters in length. If a reverse flighted screw 25 section is employed it can be single or multi-flighted, 26 preferably multi-flighted.
27 It should be noted that where the restrictive 28 dam configuration employed is more than a mere separation 29 boundary or region between zones, for example, more than 30 merely an unflighted screw section, the restrictive dam can 31 be considered to be part of the reaction zone itself, for 32 example when a single or multi-flighted reverse flighted 33 screw section is employed. Under such circumstances, the 34 restrictive dam in this region of the extruder-reactor can 35 be a part of or comprise the reaction zone. When ehe reaction 36 zone is operaeed under ~acuum in 8 partially filled mode, ehe reserio-37 tiveness of the dam between the feed and reaction zone can be reduced 33 so as to permit some gas (e.g., air) to flow into the reaction zone
DESCRIPTION OF THE PREFERRED E~l~SODI~:N~S
Polymers useful in the practice of this in~en-tion can be categorized in various ways and include:
~a) ol.efin polymers, such as ~he various forms of polyethylene, ethylene-propylene co-polymers, other ethylene copolymers with comonomers such as 1-butene, isobutylene, vinyl acetate, maleic anhydride, ethyl acrylate, methyl acrylate;
generally alpha-olefin and cyclic olefin homo-polymers and copolymers;
(b). polymers from dienes, such as styrene-butadiene rubber, polychloroprene (Neoprene), butyl, poly-butadiene, polyIsoprene,, butadiene-acrylo~itrile (Nitrile), ethylene-propylene-diene;
~c) vinyl and vinylidene Dolymers, such as polyvinyl chloride and :its family of copolymers, polyvinyl esters such as polyvinyl acetate, acrylic poly-mers such as polymethylmethacrylate, polystyrene and its family of copoly~ers such as butadiene-styrene, styrene~acrylonitrile, styrene-isoprene, ac~ylonitrile-butadiene-styrene;
8- ~S~ !
~ _ .
l ~d) heterochain thermoplastics, such as polyamides~
polyesters, polyethers, polysulfides, poly-urethanes, polycarbonatesO
Unsaturated polymers useful in the present in-ven~ion include ethylenically unsaturated elastomers, e.g., the several rubbers of commercial significance, fGr exam-ple, butyl rubber, EPDM rubber, styrene butadiene rub~er (SBR), polyisoprene rubber and poly tbutadiene-isoprene) copolymer rubbers.
The butyl rubber copolymers useful in the present invention contain a major proportion, preferably at least 70 wt.%, of isoolefins and a minor proportion, pref-erably not more than about 30 wt.~, of multi-olefins. Co-polymers of this general type, especially where the cQpoly-15 mer contains about 85-99.5% ~preferably 95-99.5~ of a C4-C7 isoolefin, such as isobutylene, with about 15~0.5~
(preferably about 5-0.5 wt.4) of a multi-olefin of about 4-14 carbon atoms, are commonly referred to in patents and literature as "butyl rubber~; see, for example, the text-20 book ~Synthetic Rubber" by G. S. Whitby (1954 edition byJohn Wiley and Sons, Inc.), pages 608-609, ~Encyclopedi~ of Chemical Technoloqy~, Third Edition, Volume ~, (1979), pages 470-484, etc. The expression "butyl rubberN as em-ployed in the specification and claims is intended to in-2~ clude copolymers containing about 80-99~ by weight of an isoolefin of about 4-7 carbon atoms and about 20-1% of conjugated multi-olefin of about 4-10 carbon atoms. The preparation of butyl-type rubbers is amply described in the literature. In general, it consists of the reaction product 3~ of a C4-C7 isoolefin (preferably isobutylene) with a C4-C10 (preferably a C4-C6 conjugated diolefin, such 2S isoprene, butadiene, dimethyl butadiene, piperylene, etc. Tbe reac-_9_ 1 tion product of isobutylene and isoprene is preferred. Thepreparation of butyl rubber is described in U.S. Patent 2,356,128~
Conventional high molecular weight butyl rubber generally has a number average molecular weight of about 25,000 to about 500,000, pre~erably about 80,000 to about 300,000, especially about 100,000 to about 250,000; and a Wijs odine No. of about 0.5 to 50~ preferably 1 to 20.
~ore recently low molecular weight polymers have also been lO prepared which have number average molecular weights of from 5,000 to 2S,000 and unsaturation expressed as mole %, of 2-10.
The term "EPDM" as used in the specification and claims is used in the sense of its AST~ definition and is intended to ~ean a terpolymer containing ethylene and propylene in the backbone and diene enchainment with residual unsaturation in the sidechains~ Illustrative methods for producing these terpolymers are found in ~.S.
Patent 3,280,082, British Patent 1,030,989 and French 2~ Patent 1,386,600.
The preferred polymers contain about 4S to about 80 wt.% ethylene and about 1 to about 10 wt.~ diene monomer. The balance of the polymer is propylene. Prefer-2~ ably, the polymer contains 45 to 70 wt.% ethylene, mos~preferably 50 to 60 wt.% ethylene, e.g., 56 wt.%, and about 2 to about 9 wt.% diene monomer, more preferably about 2 to about 6 wt.~ diene monomer, most preferably 2.6 to 4 wt.%
diene monomer. The diene monomer is a non-conjugated 3t~ diene. Illustrative of these non-conjugated diene monomers which may be used in the terpolymer (EPDM) are hexadiene, dicyclopentadiene, ethylidene norbornene, methylene nor-bornene, propylidene norbornene and methyltetrahydroindene.
A typical EPDM containing ethylidene norbornene as a diene 3~
l monomer is Vista7On 4608 (Exxon Chemical Company, U.S.A.), 2 a polymer having a Mooney viscosity at 260~P of about 62, 3 and an ethylene content of about 56 wt . % .
4 The polyisoprene rubber referred to in this 5 invention may be natural rubber or synthetic polyisoprene 6 prepared by processes well known in the art, and, an 7 general, has a molecular weight of from about 500 to about 8 509,000, preferably about t500 to about 200,000.
9 , The polybutadiene and poly(butadiene-isoprene) 10 copolymer rubbers referred to in thi invention include the ll geometric isomers thereof, all of which may be prepared by 12 pro~esses well known in the art. In general, s~ch polymers 13 and copolymers have a molecular weight of from about 500 to 14 about 500,000, preferably from about 1500 to about 200,000.
15 Generally, polybutadiene rubbers have Mooney viscosity 16 values, measured at 212-F, of from about 25 to about 65, 17 prefer~bly from about 35 to about 5~, most pr~ferably from 18 about 40 to about 50.
l9 ; The styxene butadiene rubber referred to in this 20 inventio~ is also known as poly(butadiene-co-styre~e), and 21 typically a~breviated SBR~ and includes rubbers prepared by 22 the emulsion ~hot and cold) and solution processes well 23 known in the art. Bound styrene levels are from about 3 to ~4 about 50 wt.~! prefer~bly from about 10 to about 45 wt.%, 25 most preferably from about 12 to about 30 wt.%, for 26 example, 23.5 wt.%~ Generally, such polymers have Mooney 27 viscosity values, measured at 212-F, of from about 20 to 28 130 and above, preferably ~rom about 35 to about 80, most 29 preferably from about 40 to about 70, for Example 52.
The butadiene in such copolymers is present as 31 all three geometric isomers, cis-1,4, trans-1,4 and 1,2 or 32 vinyl and the copolymer can be random, block or graft.
33 The elastomers or rubbers referred to above and 34 processes for their preparation are generally described in 35 the ~irk-Othmer ~Encyclopedia of Chemical Technology~, 36 Third Edition, Volume 8, (1979), butyl p. 470 ff, EPDM
. . .
d ~ J.f.../
1 p.492 ff, polybutadiene p. S46 ff, polyisoprene p. 582 ff 2 and poly~hutadiene-co-styrene~ D. 608 ff, 4 Some forms of halogena~ed butyl rubber, prepared 5 in solution according to processes described above, are 6 commercially aYailable, e.g~, chlorinated butyl rubber and 7 brominated butyl rubber. One method used to prepare hal-`8 ogenated butyl rubber is that of halogenating butyl rubber - 9 in a solution ~butyl rubber cement) containing between 1 to 10 60~ by weight o butyl rubber in a substantially inert ll Cs-Cg hydrocarbon solvent such as pentane, hexane, heptane, 12 etc~, and contacting this butyl rubber cement with a halo-13 gen for a period of up to about 25 minutes. There is then 14 formed the halogenated butyl rubber and a hydrogen palide, 15 the polymer containing up to one or somewhat more halogen 16 atoms per double bond initially present in the polymer.
17 Genera~ly, haiogenated butyl rubber compri~es a copolymer 18 of 85 to 99.5 wt.~ of a C4 to ~8 isoolefin, e.~., isobuty-l9 lene, with 15 to Q.S wt.~ of a Ci to C14 multi-olefin, 20 e.g., isoprene, containing at least about 0.5 wt.% combined 21 halogen in its structure. Por example, where butyl is 22 halogenated with bromine, the bromine can be present in the 23 brominated butyl in an amount of from about t.0 to about 24 3.0 wt.%, preferably from about 1.5 to about 2.5 wt.%. A
25 method of preparing conventionally halogenated butyl rubber 26 is described in U.S. Patent 3,099,644 28 The preparation, in solution, of haloqenated 29 butyl rubber containing both bromine and chlorine, i.e., 30 bromochlorinated butyl rubber, is described in U.S. Patent 31 4,254,240~ The potential 32 for molecular weight breakdown of the butyl rubber, noted 33 earlier, is present even where bromine chloride is used as 34 the halogenating agent, as disclosed in this reference (column 4, lines 24-32).
' 1 The in~ention disclosed herein is also particu-2 larly useful for the halogenation of saturated polymers.
3 Such polymers include rubbers such as ethylene-propylene 4 copolymers (EPM~, generally known in the art and similar in 5 their preparation and composition to EPDM terpolymers with 6 the exception of the presence of residual unsaturation 7 also included is polyisobutylene rubber, produced com-8 mercially ln grades varying æs to molecular weight.
~ g Other saturated polymers useful in the practice 10 of the instant invention include olefin polymers such as ~ ;11 high and low density polyethylene (~DPE and LDPE) and 12 linear low density pol~ethylene ~LLDPE~, c~ -~-13 polymers of ethylene such as e~hylene-vinyl acetate, Rod :14 ~olyvinyl and vinyl: polymers, for exa~ple, p~lyvinyl chloride.
;15 BDPE has a density of about 0.941 to about 0.965 16 ~/cc. ~igh density polyethylene is an established product 17 of commerce and its manufacture and general`p~operties are 18 well known in the art. Typically, ~DPE has a ~elatively 19 broad molecular weight distribution, characterized by the 20 ratio of weight average to number average molecula~ weight, 21 of from about 20 to about 40. LDPE is, similarly, an item 22 of commercer and typically includes products with densities 23 in the range of about 0.910 to about 0.925 g/cc. Medium 24 density polyethylene should not be excluded as a useful 25 polymer, e.g., about 0.925 to about 0.940 g/cc.
26 Linear low density polyethylene (LLDPE) is a 27 relatively new class of low density polyethylene character-28 ized by little, if any, long chain branching, in contrast 29 to conventional low density polyethylene. The processes 30 for producing LLDPE are well known in the art and commer-31 cial grades of this polyolefin plastic are available.
32 Generally, it is produced in gas-phase fluidized bed reac-33 tors or liquid-phase solution process reactors; the former 34 process can be carried out at pressures of about 100 to 300 35 psi and temperatures as low as 100-C~ Polymers can be made 1 in the gas phase with melt indices and densities over the 2 ~ull commercial ranqe and with molecular weight distribu-3 tions rom very narrow to very broad.
4 Polyethylene copolymers include copolymers OL
5 ethylene and alpha-olef ins having 3 to 16 carbon atoms, for 6 example, propyleney 1~butene, etc. Also included are 7 copolymers of ethylene with an unsaturated ester of a lower ~ carboxylic acid. In particular, copolymers of ethylene - t g with vinyl acetate or alkyl acrylates, for example, methyl - lO acrylate and ethyl acrylate, are employed. For the pur-11 poses of this invention, polyethylene copolymers are also 12 considered to include blends of polyethylene and poly-13 ethylene copolymers. ~any such ethylene copolymers are -lÇ available as items of commerce and their composition and lS methods for producing them are well known in the art.
Polyvinyl chloride ~PVC) is the most com-mercially significant member of the polyvinxl and vinyl copolymer famîly which comprises varîous polymers based o~
the vinyl radical or vinylidene radical. Vinyl chloride has been copolymerized with materials such as vlnyl ace-tate, acrylic esters and vinylidene chloride. More recently other polymers have been grarted to polyvinyl chloride including ethylene vinyl acetate and EPDM. PVC is manufac ured commercially using various well known poly-merization processes: suspension, mass, emulsion/disper-sion and solution; the first is the dominant method. The product is available in several forms incl~ding particles, fine powders and latexes.
The polymer and halogenating agent are con-tacted, or reacted, in a continuous flow device. Suitable devices include ~neaders, extruders (employing single or multiple screws, e.g., twin screws), continuous mixers and a recently disclosed blending/extrusion device referred to as a cavity transfer mixer (see, e.g., European Rubber Journal, July-August, 1982, pages 29-32 and G.M. Gale, u.s Patent 4,419,014). Althou~h such polymers can attain very high viscosities, even at relatively hi~h temperatures, ~ - l 3 a --1 such devices are capable of subjecting polymers to 2 deformation.
3 The continuous flow device should be capable 4 of initially forming the polymer feed into a cohesive mass and then deforming the polymer, disrupting the polymer 6 surface, thereby exposing fresh, i.e., unreacted, polymer 7 to the halogenating agent. The exposure of new surface 8 does not necessarily require the use of high speeds where, g e.g., an extruder is used. However, surface disrupting means are preferably employed (as will be described in 1I detail below), for example, pins, reverse flow sections, a 12 "Maillefer" screw design, the cavities of a cavity 13 transfer mixer9 multiple flight screw section, interrupted 14 flight sections, e.g., slotted flights, and combinations thereof.
-13a-4 .
- 1 3- b-The defor~ation forces generated in the continuous 2 flow device are adequate when such ~orces generate a degree 3 of mixing of the polymer and halogenating agent such that 4 the scale of segregation is, preferably, less than 50 5 microns, more preferably less than 30 microns, most preer-6 ably less.than .10 microns... Characterizat~on of the degree 7 of mixing in a two-phase system according to scale of 8 segregation is described in the text, "Principles of Poly-~ mer Processing~, Z. Tadmor and C. G. Gogos (John Wiley and }0 Sons, 1979) ! Section 7.5, pages 209 ~f.
-11 When the region in which the polymer and hal~-12 genating agent are brought into c~ntact, e.g., the reactio~
13 zone of an extruder-reactor,.is not filled with polymer, 14 the halogenating agent is present as a eontinuous phase and the polymer 15 i8 present as either a discontinuous or eontinuous phase; the for~er is preferr~d. Whe~ each co~stitute a continuous phase,`~`for ease of reference this i6 referred to as "co-continuous phases"~ Tn this la~ter situation ~f ehe reactior zone was viewed under contitions where tefosmatio~ of the poly~er was stopped, the polymer and halogenating agent~ould each 20 co~prise an independent, continuous phase. A preferred operating mode of the process ut;lizes a reacCion zone which is only partially filled with poly~er; this permits reaction by-products and unreacted halogenaeing agent to disengage from the polymer phsse. Generally, ehe poly~er is prese~t in the reaction zone to the extent that about 5 to about 95%, 25 preferably lO to about 75~, more preferably about 15 to about 50~, for exa~ple 20 to about 35Z of the reaction zone is filled with the polymer.
One means of achiev;ng a partially filled reaction zone is to feed, in a controlled manner, less polymer into the reaction zone than the 30 conveying capacity of the zone. The space above the polymer is occupied by the halogenating agent and, as fresh surface is ex-poset to the halogensting agent and halogenation occurs, hydrogeu halide is released as a by-produce of the reaceion. The hydrogen halide "disengages" from the polymer and enters and is present in 35 ehe halogensting agene phase. In a preferred embodiment, utilization of vent means in che reaction zone facili~ies removal of the 7r3~
`~ -14-l reaction by-product and unreacted halogenating agent.
2 Another preFerred embodiment imposes a vacuum on the vent 3 means 90 as to more efFiciently disengage by-product(s) 4 and unreacted halogenating agent. The vent means com-prises one or more vents in the contacting region.
6 Means are provided for contacting the halo-7 genated polymer with neutralization means, for example a 8 neutralizing agent. This can also be viewed as a means of 9 disengaging unwanted reaction by-products and unreacted halogenating agent from the halogenated polymer. The 11 neutralization means and the halogenated polymer can be 12 conveyed concurrently or countercurrently through the 13 continuous flow device; preferably in a neutralization 14 zone following the contacting or reaction zone. The pH of the neutralized, halogenated polymer is, preferably, 16 greater than about 5.0, more preferably greater than about 17 6.0~ most preferably greater than about 7Ø In the 18 improved process disclosed herein, neutralization is 19 achieved in an aqueous-free manner by injecting an inert gas, e.g., nitrogen, argon, carbon dioxide or air, into 21 said continuous flow device downstream of the contact 22 between said polymer and said halogenating agent, e.g., in 23 the neutralization zone. Also included in the improved 24 process is the use of a reactive gas such as ammonia which functions to chemically neutralize as well as physically 26 disengage unwanted by-products and/or unreacted halogenat-27 ing agent.
f . J
I Kal)irl and complete neutralization, i.e., ' disengagement, i3 effected by employing process Features 3 such as those described earlier with regard to polymer 4 deformation and surface disruption in order to expose fresh polymer surface to the inert gas and/or reactive 6 gas; simi]arly, the discussion of scale oF segregation is 7 relevant here with regard to the inert and/or reactive gas 8 and polymer. In a preferred embodiment, disengagement 9 occurs in a region oF the continuous flow device which is not completely filled with polymer. In a still more 11 preferred embodiment, vent means are provided so that the 12 inert and/or reactive gas, unreacted halogenating agent 13 and reaction by-products are removed from the polymer 14 conveying means. The amount of inert and/or reactive gas employed can be readily determined and should be an amount 16 ef~ective for the disengagement without being unnecessar-17 ily wasteful. Inert and/or reactive gas injection can be 18 achieved using more than one injection port and the l9 halogenated polymer can again be treated in a supple-mentary scrubbing zone following neutralization in order 21 to remove additional by-products and unreacted halogenat-22 ing agent. Another option is a region for injecting a 23 stabilizer into the continuous flow device following the 24 inert and/or reactive gas treatment. In another embodi-ment, the inert and/or reactive gas injection and venting 26 configuration is designed so as to permit explosive 27 release of the injected inert and/or reactive gas from 28 the halogenated polymer in order to facilitate in the 29 removal of unwanted materials. Filter means can also be employed to remove undispersed materia1 from the halogen-31 ated polymer. The absence of -14a-1 aqueous streams in the process results in significantly 2 reduced corrosion of the process equipment. Furthermore, 3 the halogenated product can be used directly or packaged 4 directly without an intermediate drying step because of the absence of water.
Preferably the various zones which have been 7 described are separated from one another in such a manner 8 as to permit maximum independent control 3f conditions in 9 each zone. Details and conditions are described below for 10 a preferred embodiment utilizing an extruder-reactor, but 11 the principles disclosed are broadly applicable to the 12 system just discussed.
13 A preferred embodiment of the process employs 14 an extruder-reactor~ ~he extruder-reactor may be thought 15 of as carrying out .he halogenated polymer manufacture in 16 various operating zones: ;
17 (A) Fe~d Zone - in which polymer is intr~æuced into the 18 e~truder~reactor in convenient form~ This for~ includ~s, 19 for example, particles and pellets of plastics as they are 20 produced-~ommercially, particles fro~ bales of rub~ér which 21 have been comminuted and crumb from the finishing line of a 22 rubber manufacturing plant, each of which i5 preferably 23 dry, but may contain ~ low level, e.g., about 0 to lS
24 wt.%, preferably about 0 to 5 wt.%, most preferably about 0 25 to 1 wt.%, of a solvent or diluent; the latter materials 26 will be described more fully below. In this improved 27 process the use of water as a diluent is to be avoided in 28 order to avoid corrosion.
29 The feed zone is designed to form the polymer 30 feed into a cohesive mass;and convey or pump the mass past 31 ~ restrictive dam which follows the feed zone and distin-32 guishes it. from the reaction zone which follows. This 33 operation should be conducted at low shear and temperature 34 consistent with the desired result and at a pressure suf-35 ficient to convey the mass, typically up to about 600 psig, 36 preferably up to about 400 psig, most preferably up to '~
16~
1 about 200 psig. Lower pressures are preferred in order to 2 avoid overheating the polymer. This can be achieved, e.g., 3 by utilizing an extruder screw with relatively dee2 flights 4 and by keeping the length of the feed zone, i.e., the feed zone screw length, as short as possible commensurate with 6 de~ired production rates. For example, polymer is intro-7 duced at about room temperature and ex~ts fro~ the feed zone 8 at about 60 to 150C.
~ A restrictive dam is used to separate the feed 10 zone from the reaction zone which follows it so as to 11 prevent back leakage of reactants. T~is dam is not 12 restrictive enou~h, however, to cause excessive overheating 13 of the polymer. A restrictive dam can be, for example, a 14 reverse flighted screw section, a filled screw section, a 15 shallow fli~hted screw section, an unflighted screw sec-16 tion, combinations thereof, or other means known in the 17 art. If an unfli~hted screw section is e~pXoyed, it can 18 have a larger diameter than the root diameter ups~ream of 19 it, for example 5-25~ larger, but not greater than the 20 screw flight diameter. The restricti~e dam length should 21 be about 0.5 to about 8 screw diameters, preferably about 1 22 to about 5 screw diameters, more preferably about 1.5 to 23 ~bout 4 screw diameters, most preferably about 2 to about 3 24 screw diameters in length. If a reverse flighted screw 25 section is employed it can be single or multi-flighted, 26 preferably multi-flighted.
27 It should be noted that where the restrictive 28 dam configuration employed is more than a mere separation 29 boundary or region between zones, for example, more than 30 merely an unflighted screw section, the restrictive dam can 31 be considered to be part of the reaction zone itself, for 32 example when a single or multi-flighted reverse flighted 33 screw section is employed. Under such circumstances, the 34 restrictive dam in this region of the extruder-reactor can 35 be a part of or comprise the reaction zone. When ehe reaction 36 zone is operaeed under ~acuum in 8 partially filled mode, ehe reserio-37 tiveness of the dam between the feed and reaction zone can be reduced 33 so as to permit some gas (e.g., air) to flow into the reaction zone
39 from the feed zone 7. ~ ~
.
1 In addition to the polymer which is introduced 2 in~o the feed zone, an optional diluent may also be added.
3 A diluent can function to reduce the viscosity of the 4 polymer to a level commensurate with subsequent good mixing 5 and halogenation without the necessity for excessive heat 6 and a ~risk of molecular weiqht brea~down and undesirable 7 side reactions; it can also function to red~ce the tem-8 perature of the polymer. The diluent may be vo~atlle 9 saturated hydrocarbon, chlorohydrocarbon or chlorocarbon 10such as pentane, hexane, methylene chloride, chloroform, or llcarbon ~etrachloride. I~ may also be a non-hydrocarbQn, 12readily removable from the system downstream, but able to 13perform ~he function of temporarily reducing the apparent 14viscosity of ~he rubber in the reaction zone. Examples of 15suitable materials include water, iner~ gases such as 16nitrogen~ and argon, as well ~s gases such as carbon 17dioxide~and air. ~`
--18 The diluent may also be retained wit~ or in the 19 polymer, such as a hydrocarbon oil. Suitable oils ~nclude ~0 saturatea aliphatic oil and rubber process oil~ such as 21 paraffinicr n~phthenic and arom2tic types. Where such oils 22 are utilized, the halogenated polymer would contain oil 23 after recovery and drying and would commonly be referred to 24 as ~oil extendedn. Oil extended rubber is well known in 25 the art and various grades of oil extended EPDM~ SBR, and 26 polybuta~iene made by other means are commercially avail-27 able. Such products are particularly useful where it is 28 desirable, for example, to extend the rubber with high 29 levels of filler, e.g.; carbon black or mineral filler, to 30 obtain properties from high molecular weight polymer which 31 might otherwise be difficult to process because of its 32 inherently high viscosity, etc.
33 The total amount of diluent, including that 34 which may be present in the feed should not be greater than 35 about ;0 wt.~ based on the polymer, preferably less than 36 abou~ 15 wt.%, most preferably about 5 to about 10 ~t.%.
' 7 f ~
1 (3) Reaction Zone - can generally be described as the zone 2 in which the halogenating agent is caused to react with the 3 polymer to completely effect the halogenation reaction 4 while simultaneously minimizing undesired slde reactions.
5 Scr`ew configuration in the reaction zone is important to 6 mixing efficiency and achievement of the overall objectives 7 of the process. ~he co~figuration should be such as to ca~se dis~lption 8 ~nt reorientation of the flo~ o~ poly~er, ~s,.for example,~
9 by the aforementioned use of reverse fiights, multiple 10 re~erse flights, -pin sections, a series of very short 11 alternati~g reverse and forward screw seceions,-~ulciple flight, iuter-12 rupted flight sections and combi~ations thereof;-and other designs X~ow~
13 in tbc ar~_to improve mixing. Vi~cosity conerol of the poly~er, effected, 14 i~ p2rt, by the use of an optio~l diluent and by control of the molecular 15 weight of the polymer ~t the polymer temperature as ie en~erc.the:-16 reaction zone, also determines, to a large extent, defon~r17 ability.~ Selection of the temperature le~eL influences 18 the reaction and along with residence time in the reaction 19 zone, the nature o the end product. For maximum economy 20 and continuity of production the choice of materials of 21 construction of the reactlon zone is particularly ~mpor-22 tant; this also influences the type and level of potential 23 contaminants in ~he finished polymer and their influence on 24 long-term storage stability of the polymer as well as 25 chemical reactivity. ~his is discussed in further detail 26 later in this disclosure.
27 Where a polymer such as butyl rubber is to be 28halogenated this process should preferably halogenate the 29 rubber to the extent of about one halogen atom per double 30bond of olefinic unsaturation originally present in the 31 rubber. Control is required in order to avoid over and 32under halogenation. This can be achieved by, for example, 33controlling the halogen feed rate in comparison to the 34 rubber feed rate, design of the reaction zone tlength, 35screw eatures and configuration, injection means, tem-36perature, etc.) and RPM so as to determine time of reaction t ~ t ' ,`~ ~ ~
1 and to control the relative rates of the desired reaction ~ versus competing side reactions (e.g., halogenation of the 3 olefinic unsaturation as for example the isoprene moiety in 4 butyl versus the isobutylene moiety)~ Additionally, design S of the neutralization zone to effect rapid and complete 6 neutralization is also important in controllinq the nature 7 of the halogenation.
8 ' The halogenating agent can be gaseous, liquid or 9 soiid and may be added either in a pure state or diluted 10 with a suitable inert fluid as noted above. Suitable halo-11 genating agents include chlorine, sulfuryl chloride, 12 N-chlorosuccinimide, 1,3-dichloro-5,5-dimethylhydantoin 13 iodobenzene dichloride, iodine monochloride, bromine, 14 bromine ~hloride, sodiu~ hypobromite, sulfur bromide and 15 N-bromosuccinimide. . Where gaseous chlorine, bromine or 16 bromine chloride is used~ gaseous diluents, e.g., nitrogen, 17 argon,' air, CO2, etc., can be used whe~`~a daluent is }8 desired.
19 At least under some conditions encountered in 20 extruder halogenation, as, for examplep ~here mixing butyl 21 rubber and the halogenation agent are not as efficient as 22 desired, the use of N-chlorosuccinimide may result in 23 predominantly free-radical reactions rather than the pre-24 ferred ionic reactions.
In this improved process alternative reaction 26 zone mixing techniques are feasible. Injecting halogena'-27 ing agent at a point or points filled with polymer can 28 facilitate nearly instantaneous mixing~ Alternativély the 29 reaction can be allowed to occur at the continuously re-30 newing polyer surface generated by the configuration of the 31 reaction zone and conveying means, e.g , the extruder screw 32 and barrel, in a reaction zone partially filled with 33 polymer. Configuration of the screw and chamber walls 34 should not be so restrictive as to cause excessive pressure 35 and excessive shear heating of the poly~er. Pressure at 36 the point of injection need not be very high where the 1 reaccion zone is only partially filled wi~h p~lymer and preferably venced.~ In addieion, injection can be into the space occupiet by the haloge~ating agent, e.g., the vapor space. A moderately positive in-jec~ion psessure is suitable; the pressure selected should ~aintain a posieive flow into the re~ction zone and prevent pl~gging of the line.
She specific pressure chosen i8 8 ~atter of operating convenience.
In the filled syste~, pressure at the point of i~jection is about 15 eo about 440 psig, preferably 100 to about 300 psig.
Also important for achieving efficie~t reaction o~ the polymer and halogenating age~t is the incorporation i~ the reaeti~ zonc of means to produce tbe level of polymer mixing and sur~ace disruption ~ ~ preferred for the practice of this invention. As described earlier, this ca~ be achieved, for`ex~mple, by utili~ing reverse flights on the reaction zone portion of the extruder screw, pins, etc. Other ~eans inelude operation of the serew at`a rotaeion rate of about SO
to about 600 RPM, prefer~bly about 70 to about 400 RP~, most preferabl~
about 90 to ab~ut 200 RPM, and by incorporation of a downstream re-stric~iv~ dam, of the type described above, to separate ~he reaceiouzone from the neutrali7ation zone which follows it. .
Characterization of mixing by reference to the ~scale of segregation~ achieved between the halogenating agent and polymer ~generally, any two-phase system) was noted earlier. A preferred scale of segregation in the 25 practice of this invention is less than 50 microns, more preferably less than 30 microns, most preferably less than 10 microns.
Overall, it is desirable, by control of polymer viscosity, chamber and screw design, screw RPM, and operat-30 ing pressure, to prevent excessive temperatures i~ thereaction zone while maintaining a high level of mixing. It is desirable that a temperature of less than about 170-C be achieved, preferably less than about 140-C, most preferably less than about 120-C.
. _ . . . . .. . ..
~ -21-l (C) Neutralizcltion Zone - in which by-product HC1 and/or 2 ~Br is neutralized to prevent dehydrohalogenation oF the 3 halogenated polymer and to suppress other undesirable side 4 reactions and corrosion of the equipment. Suitable means to effect neutralization and reMove residual unreacted 6 halogenating reagent in this improved process is the 7 injection of an inert and/or reactive gas into the 8 extruder to neutralize and "sweep out" the by-products-9 and residual halogenation agent. This process is effected ~y employing process features such as those just described ll with regard to the reaction zone in order to disrupt the 12 polymer surface and continually expose new surface to the 13 inert and/or reactive gas in the neutralization zone. In 14 a preferred embodiment vent means are provided in the neutralization zone to permit the inert and/or reactive 16 gas and disengaged products to be swept out and ]7 irnmediately removed from the region near the polymer. In 18 a particularly preferred embodiment, the screw configura-19 tion in the region of the vent comprises a deep, single flighted screw with little or no mixing occurring in the 21 vicinity of the vent in order to avoid restricting the 22 exiting flow of inert and/or reactive gas and disengaged 23 materials. In another preferred embodiment various 24 additives and/or stabilizers are added to the polymer in 25 the neutralization zone. As discussed earlier, multiple 26 injection sites can be used as well as a supplementary 27 injection zone. In another embodiment, pressure in the 28 system is controlled in order to explosively rernove the 29 unwanted products.
r ~J ~f~ ~ ? ~r~
-21a-I The neutralization zone is designed so that 2 the inert and/or reactive gas contacts the reaction 3 products from the react,ion zone as soon as possible after 4 the halogenation reaction in order to prevent dehydro-halogenation of the polymer. This is achieved by utiliz-6 ing a dam between the reaction and neutralization zones 7 which is as short as possible consistent with its 8 functioning as a restrictive dam. The nature and con--9 figuration of various alternatives for the restrictive dam are described above in detail for the dam between the feed 11 and reaction zones. The injection port for the inert 12 and/or reactive gas can be located as close as possible to 13 the downstream end of the dam or the neutralizing reagent 14 can be injected so as to flow countercurrent to the flow Of the halogenated product mixture.
16 (D) Scrubbing ~one - To achieve a halogenated polymer end 17 product not containing usually undesirable materials, the 18 neutralized halogenated rubber can be subjected to 19 supplementary inert and/or reactive gas injection in a scrubbing zone. In a particularly preferred embodiment 21 such scrubbing is performed within the extruder-reactor in 22 a scrubbing zone (D) which sequentially follows neutrali-23 zation zone (C) and which is traversed by the extruder 24 screw means. In this zone a stream or several streams of inert and/or reactive gas can be run -21a-7 ~ S J
1 through countercurrent and/or cc current to the flow of 2 neutralized polymer so as to remove the last traces of the 3 products and unreacted halogenating agent.
,4 Polymer stabilizing agents can optionally be added in this zone~ This can be done by incorporating the 6 stabilizers at'an inj-ection point. - , 7 , In the practice of this invention attention 8 should be given to the temperatures of the neutralization 9 and scrubbing streams when they are brought into contact 10 with the halogenated polymer product so as not to subject 11 the polymer to excessive cooling and increase in viscosity;
, ' 12 in extreme circumstances the polymer might be subject to 13 crystallizationO Methods for preheating these s reams and 14 the temperatures and pressures which are required in order 15 to maintain a continuous process are well within the 16 abilities of those skilled in the polymer processing art.
17 ( ~) Exi - Preferably the extruder-reac~o~ comprises a 18 final exit zone (E~ in which the temperature a~ the halo-19 genated ~olymer product is adjusted for delivery t~,~refrom 20 at a temp2rature below about 130-C, more prefera~ly below 21 about 120-C and most preferably below about 100-C, as a ~2 contribution to the stability 4f the polymer. Also in the 23 exit zone, stabilizer(s) may initially be added to the 24 neutralized; halogenated polymer product if not added in 25 the neutralization or scrubbing zone or additional 26 stabilizer(s) can be added.
27 Suitable stabilizers for use in this process 28 include slurries or solutions of butylated hydroxytoluene 29 (BHT), calcium stearate, sodium stearate, multi-component 30 stabilization systems such as those described in U.S.
31 Patent 4,130,519 to Roper et al and other degradation, 32~oxidation and/or d~hydro-33 halogenation inhibitors well known in the art directed to 34 the polymer being halogenated.
' -22-~ 23 1 In addition to the extruder-reactor features just described, ~he process of this invention can also 3 incorporate filter means kno~n in the art to e~fect the 4 separation of undispersed materials from the polymer, screw means o~ suitable configuration, as described above, 6 transversing zones (A~ - (E) inclusive to properly effect 7 the operations disclosed in said zones (includ~nq single 8 and twin screws~, a system for recycling any organic 3 diluent that may be added to the feed zone and/or included 10 with the halogenating agent and, optionally, means for 11 back-mixing the extruded halogenated polymer to assure that 12 the final pac~ag~d polymer is a homogen~ous product.
13 Materials of construction are a significant 14 consideration in the process herein since potentially cor-~5 rosive reagents are employed. In addition to a concern for 16 long equipmen~ life, product stability needs to be con-17 sidere~ if by-products of the corrosion~r~cess be~ome 18 incorporated into the e~lymer. In addition, halogenation 19 chemistry can be affected if metals and corrosion 20 by-products are present during the halo~enation ~eact~on.
21 M~terials of construction in the feed zone, reaction zone 22 and neutralization zone are selected to prevent or minimize 23 reaction of the equipment with the halogenating agent and 24 the reaction by-products. Small amounts of such materials 25 may cause undesirable side reactions to occur with various 26 constituents o~ the polymerO Useful materials include 27 those alloys known commercially as Hastelloy, steels coated 28 with inert e~lymers such as fluorocarbons, ceramics, etc.
29 ~laterials which have been found to be unsatisfactory where 30 aqueous streams are present include series 300 stainless 31 steels, and carbon steel. Due to the low level of corrosion in this 32 process, other suitable materials include commercial alloys comprising 33 nickel, cobalt, molybdenu~, chromium ant iron as major alloying elemenes;
34 commercial alloys in this class include Hastelloy 8 and C, Xaloy~ 306, 35 Seellite~ 6 and Triboloy~. Titanium coated steel is also useful.
36 Another advaneage for this process is that in the absence 37 of aqueous streams, a dry, halogena~ed produce is produced which can be 38 used immediaeely or packaged (after cooling, if required). Additionally, 39 the corrosion noted above is significantly reduced or may be eliminaeed.
.. _ . . .. .
1 The halogPnated polymers of this invention can 2 be processed in standard equipment used for each such 3 polymer, such as internal mixers, mills, extruders, 4 calenders, etc. Said polymers are amenable to convention-al compounding practice and various fillers and extenders 6 can be incorporated, e.g., Yarious carbon blacks, clays, 7 silicas, carbonates, oils, resins, waxes, etc.
8 As described previously, various halogena~ed 9 polymers are produc~d by the process of this invention including halogenated linear low density polyethylene and 11 halogenated butyl rubber. Halogenated butyl rubber of 12 this invention ma~ be ~ured or vulcanized by any of the 13 prior art methods suitable for such halogenated rubbe~s, 14 e.g., ~sing sulfur, sulfur-containing curing agents (such as sulfenamide derivatives, benzothiazyl disulfide, 16 tetramethylthiouram disulfide, alkyl phenol disulfide, 17 etc.), zinc oxide alone or with various promoters, and 18 mixtures thereof. Curing is usually accomplished at a 19 temperature of from about 140C to about 250C, preferably 150C to about 200C, and usually takes from 1 to 150 21 minutes.
22 This invention will be further understood by 23 reference to the following examples which describe 24 equipment dernonstrating the principles of this invention.
In each of the examples, disruption of the halogenated 26 polymer continued in the neutralization zone.
27 Example 1 -28 An extruder with 2" diameter twin screws, 29 counter-rotating and non-intermeshing was set up according to the teachings herein in order to halogenate several 31 polymers. The feed zone was 18 inches long and separated 32 from the reaction zone by a reverse flighted section. The 33 reaction zone was 28 inches long and separated from the 34 neutralization zone with a reverse flighted section. The reaction zone utilized forwarding single, double and triple 36 flights with slots cut in several of the triple flights.
37 Additionally, some forwarding single sections had mixing h 1 pins in the stem. The configuration in the reaction zone 2 was designed to increase mixing, interrupt polymer flow and 3 expose f resh surface to the halogenating agent.
4 ~ The halogenating aqent was chlorine gas diluted with nitrogen (20-45~ alogenating agent was injected 6 at a slight positive pressure into the vapor space of the 7 reaction zone at a point 6 inches downstrea~ from the 8 beginning of the zone. A vent reaction zone was used, with 9 the vent located 24 inches from the beginning of the reac-lO tion zone.
ll Neutralization was achieved using nitrogen 12 njection, counterourrent to polymer flow, at a rate of 0.5 13 R~ per hour,. A second vent was located 15 inches from the 14 end of the extruder~
16 Polymer Maximum Screw Rate 17 (a) ' Cl,~ Temp,'C .~PM
l9 1. ~DPE 0.38-0.72 160-175 300 , 25 20 2. EP~ ~ 0.41-0.61 185-210 160 ~: 55 21 3~ LLDPE 0.62-3.64 145-165 1Q0 25 22 4. PIB 1.50-1.53 175-185 222 83 23 5. EVA 2.55-4.74 140-160 90 45 24 6. EPDM 2046-3.5; 160-220 156 40 (a) Polymer Identification:
26 1. High density polyethylene, Allied Chemical, 27 AA60-003, 0.3 ~I, 0.96 density.
28 2. Ethylene-propylene copolymer rubber, Exxon 29 Chemical, ~'istalon ~503, 50 wt.% ethylene; typical Mooney viscosity at 127-C=30.
31 3. Linear low density polyethylene, Exxon Chemical, 32 LPX-1 gas phase process, 1.0 MI, 0.918 density.
33 4. Polyisobutylene rub~er, Exxon Chemical, Vistanex 34 0L-80, Staudinger molecular weight 64-81,000.
7 ~ ~ ~
. .
5A Ethylene vinyl acetate copolymer, VSI, VE 645, 2 vinyl acetate = 2B wt~, 3.0 MI, O.9S density.
3 6. Ethylene-propylene diene rubber, Exxon Chemical, q Vistalon 6505, high diene level, typical ethylene=50 wt.%, typical Mooney @ 127'C = 50.
6 ; ~ These results demonstrate the broad applic-7 ability of this improved halogenation process.
8 Example 2 g An extruder with 2~ diameter twin screws, 10 counter-rotating and non-intermeshing was set up according 11 to the teachings herein in order to halogenate butyl rubber 12 ~isobutylene-isoprene copolymer). The feed zone was 10 13 inches long and separated from the reaction zone by a 14 reYerse flighted s~ction. The reaction zone was 47 inches 15 long and separated from the neutralization zone with a 16 reverse, flighted section. The reaction zone~utilized for-17 warding single, double and triple flights with slots cut in 18 several of the triple flights. Additionally, some forward-19 ing single sections had mixing pins in the stem. -~The con-20 figuration in the reaction zone was designed to increase 21 mixin~, interrupt polymer flow and expose fresh surface to 22 the halogenating agent.
23 The halogenating aqent was chlorine gas diluted 24 with 5-10 wt.~ nitrogen. Halogenating agent was injected 25 at a slight positive pressure into the vapor space of the 26 reaction zone at a point 2 inches downstream from the be-27 ginning of the reaction zone at a rate of about 4 Rg/hr.
28 The reaction zone contains a vent located 36 inches from 29 the halogenatiny agent injection point and the vent was 30 vacuum supplemented.
31 Neutralization was achieved using nitrogen in-32 jected countercurrently, beginning 3 inches from the end of 33 the extruder at a rate of 3.7 Kg/hr. A second vent was 34 located 18 inches downstream of the reaction zone vent.
-2~--~7-Polymer feed rate was targeted at 40 Kg/hr- Halogenat~d polyDer produced d~ring this run had a chlQrine content of.l. 39 wt.~, viscosi~y average ~Qlecular w~;ght of 391, 000 and a rheo~eeer cure of 10:7 ~Torque at 30 minutes minus ~inimum tor~ue, in-lb; Test Composlt~on (parts by weight): 100~Rubber, 50-~ried IRB ~5 Carbon Black, 3-Zinc: Ox~de, l-Ste~ric Acid. Rheometer Conditions: 160-C, 5' Arc, 30-minu';e test, 100 cycles per minute oscillat~on. ~ Weight measurement taken of the ex-truder screw parts beore and after the run indicated no evidence of corrosionO 'rhe halogenated polymer was com-pounded in the test for~ula'cion directly as produced; no inten~ediate drying w~s required since no wa~er was used ln the process.
.
1 In addition to the polymer which is introduced 2 in~o the feed zone, an optional diluent may also be added.
3 A diluent can function to reduce the viscosity of the 4 polymer to a level commensurate with subsequent good mixing 5 and halogenation without the necessity for excessive heat 6 and a ~risk of molecular weiqht brea~down and undesirable 7 side reactions; it can also function to red~ce the tem-8 perature of the polymer. The diluent may be vo~atlle 9 saturated hydrocarbon, chlorohydrocarbon or chlorocarbon 10such as pentane, hexane, methylene chloride, chloroform, or llcarbon ~etrachloride. I~ may also be a non-hydrocarbQn, 12readily removable from the system downstream, but able to 13perform ~he function of temporarily reducing the apparent 14viscosity of ~he rubber in the reaction zone. Examples of 15suitable materials include water, iner~ gases such as 16nitrogen~ and argon, as well ~s gases such as carbon 17dioxide~and air. ~`
--18 The diluent may also be retained wit~ or in the 19 polymer, such as a hydrocarbon oil. Suitable oils ~nclude ~0 saturatea aliphatic oil and rubber process oil~ such as 21 paraffinicr n~phthenic and arom2tic types. Where such oils 22 are utilized, the halogenated polymer would contain oil 23 after recovery and drying and would commonly be referred to 24 as ~oil extendedn. Oil extended rubber is well known in 25 the art and various grades of oil extended EPDM~ SBR, and 26 polybuta~iene made by other means are commercially avail-27 able. Such products are particularly useful where it is 28 desirable, for example, to extend the rubber with high 29 levels of filler, e.g.; carbon black or mineral filler, to 30 obtain properties from high molecular weight polymer which 31 might otherwise be difficult to process because of its 32 inherently high viscosity, etc.
33 The total amount of diluent, including that 34 which may be present in the feed should not be greater than 35 about ;0 wt.~ based on the polymer, preferably less than 36 abou~ 15 wt.%, most preferably about 5 to about 10 ~t.%.
' 7 f ~
1 (3) Reaction Zone - can generally be described as the zone 2 in which the halogenating agent is caused to react with the 3 polymer to completely effect the halogenation reaction 4 while simultaneously minimizing undesired slde reactions.
5 Scr`ew configuration in the reaction zone is important to 6 mixing efficiency and achievement of the overall objectives 7 of the process. ~he co~figuration should be such as to ca~se dis~lption 8 ~nt reorientation of the flo~ o~ poly~er, ~s,.for example,~
9 by the aforementioned use of reverse fiights, multiple 10 re~erse flights, -pin sections, a series of very short 11 alternati~g reverse and forward screw seceions,-~ulciple flight, iuter-12 rupted flight sections and combi~ations thereof;-and other designs X~ow~
13 in tbc ar~_to improve mixing. Vi~cosity conerol of the poly~er, effected, 14 i~ p2rt, by the use of an optio~l diluent and by control of the molecular 15 weight of the polymer ~t the polymer temperature as ie en~erc.the:-16 reaction zone, also determines, to a large extent, defon~r17 ability.~ Selection of the temperature le~eL influences 18 the reaction and along with residence time in the reaction 19 zone, the nature o the end product. For maximum economy 20 and continuity of production the choice of materials of 21 construction of the reactlon zone is particularly ~mpor-22 tant; this also influences the type and level of potential 23 contaminants in ~he finished polymer and their influence on 24 long-term storage stability of the polymer as well as 25 chemical reactivity. ~his is discussed in further detail 26 later in this disclosure.
27 Where a polymer such as butyl rubber is to be 28halogenated this process should preferably halogenate the 29 rubber to the extent of about one halogen atom per double 30bond of olefinic unsaturation originally present in the 31 rubber. Control is required in order to avoid over and 32under halogenation. This can be achieved by, for example, 33controlling the halogen feed rate in comparison to the 34 rubber feed rate, design of the reaction zone tlength, 35screw eatures and configuration, injection means, tem-36perature, etc.) and RPM so as to determine time of reaction t ~ t ' ,`~ ~ ~
1 and to control the relative rates of the desired reaction ~ versus competing side reactions (e.g., halogenation of the 3 olefinic unsaturation as for example the isoprene moiety in 4 butyl versus the isobutylene moiety)~ Additionally, design S of the neutralization zone to effect rapid and complete 6 neutralization is also important in controllinq the nature 7 of the halogenation.
8 ' The halogenating agent can be gaseous, liquid or 9 soiid and may be added either in a pure state or diluted 10 with a suitable inert fluid as noted above. Suitable halo-11 genating agents include chlorine, sulfuryl chloride, 12 N-chlorosuccinimide, 1,3-dichloro-5,5-dimethylhydantoin 13 iodobenzene dichloride, iodine monochloride, bromine, 14 bromine ~hloride, sodiu~ hypobromite, sulfur bromide and 15 N-bromosuccinimide. . Where gaseous chlorine, bromine or 16 bromine chloride is used~ gaseous diluents, e.g., nitrogen, 17 argon,' air, CO2, etc., can be used whe~`~a daluent is }8 desired.
19 At least under some conditions encountered in 20 extruder halogenation, as, for examplep ~here mixing butyl 21 rubber and the halogenation agent are not as efficient as 22 desired, the use of N-chlorosuccinimide may result in 23 predominantly free-radical reactions rather than the pre-24 ferred ionic reactions.
In this improved process alternative reaction 26 zone mixing techniques are feasible. Injecting halogena'-27 ing agent at a point or points filled with polymer can 28 facilitate nearly instantaneous mixing~ Alternativély the 29 reaction can be allowed to occur at the continuously re-30 newing polyer surface generated by the configuration of the 31 reaction zone and conveying means, e.g , the extruder screw 32 and barrel, in a reaction zone partially filled with 33 polymer. Configuration of the screw and chamber walls 34 should not be so restrictive as to cause excessive pressure 35 and excessive shear heating of the poly~er. Pressure at 36 the point of injection need not be very high where the 1 reaccion zone is only partially filled wi~h p~lymer and preferably venced.~ In addieion, injection can be into the space occupiet by the haloge~ating agent, e.g., the vapor space. A moderately positive in-jec~ion psessure is suitable; the pressure selected should ~aintain a posieive flow into the re~ction zone and prevent pl~gging of the line.
She specific pressure chosen i8 8 ~atter of operating convenience.
In the filled syste~, pressure at the point of i~jection is about 15 eo about 440 psig, preferably 100 to about 300 psig.
Also important for achieving efficie~t reaction o~ the polymer and halogenating age~t is the incorporation i~ the reaeti~ zonc of means to produce tbe level of polymer mixing and sur~ace disruption ~ ~ preferred for the practice of this invention. As described earlier, this ca~ be achieved, for`ex~mple, by utili~ing reverse flights on the reaction zone portion of the extruder screw, pins, etc. Other ~eans inelude operation of the serew at`a rotaeion rate of about SO
to about 600 RPM, prefer~bly about 70 to about 400 RP~, most preferabl~
about 90 to ab~ut 200 RPM, and by incorporation of a downstream re-stric~iv~ dam, of the type described above, to separate ~he reaceiouzone from the neutrali7ation zone which follows it. .
Characterization of mixing by reference to the ~scale of segregation~ achieved between the halogenating agent and polymer ~generally, any two-phase system) was noted earlier. A preferred scale of segregation in the 25 practice of this invention is less than 50 microns, more preferably less than 30 microns, most preferably less than 10 microns.
Overall, it is desirable, by control of polymer viscosity, chamber and screw design, screw RPM, and operat-30 ing pressure, to prevent excessive temperatures i~ thereaction zone while maintaining a high level of mixing. It is desirable that a temperature of less than about 170-C be achieved, preferably less than about 140-C, most preferably less than about 120-C.
. _ . . . . .. . ..
~ -21-l (C) Neutralizcltion Zone - in which by-product HC1 and/or 2 ~Br is neutralized to prevent dehydrohalogenation oF the 3 halogenated polymer and to suppress other undesirable side 4 reactions and corrosion of the equipment. Suitable means to effect neutralization and reMove residual unreacted 6 halogenating reagent in this improved process is the 7 injection of an inert and/or reactive gas into the 8 extruder to neutralize and "sweep out" the by-products-9 and residual halogenation agent. This process is effected ~y employing process features such as those just described ll with regard to the reaction zone in order to disrupt the 12 polymer surface and continually expose new surface to the 13 inert and/or reactive gas in the neutralization zone. In 14 a preferred embodiment vent means are provided in the neutralization zone to permit the inert and/or reactive 16 gas and disengaged products to be swept out and ]7 irnmediately removed from the region near the polymer. In 18 a particularly preferred embodiment, the screw configura-19 tion in the region of the vent comprises a deep, single flighted screw with little or no mixing occurring in the 21 vicinity of the vent in order to avoid restricting the 22 exiting flow of inert and/or reactive gas and disengaged 23 materials. In another preferred embodiment various 24 additives and/or stabilizers are added to the polymer in 25 the neutralization zone. As discussed earlier, multiple 26 injection sites can be used as well as a supplementary 27 injection zone. In another embodiment, pressure in the 28 system is controlled in order to explosively rernove the 29 unwanted products.
r ~J ~f~ ~ ? ~r~
-21a-I The neutralization zone is designed so that 2 the inert and/or reactive gas contacts the reaction 3 products from the react,ion zone as soon as possible after 4 the halogenation reaction in order to prevent dehydro-halogenation of the polymer. This is achieved by utiliz-6 ing a dam between the reaction and neutralization zones 7 which is as short as possible consistent with its 8 functioning as a restrictive dam. The nature and con--9 figuration of various alternatives for the restrictive dam are described above in detail for the dam between the feed 11 and reaction zones. The injection port for the inert 12 and/or reactive gas can be located as close as possible to 13 the downstream end of the dam or the neutralizing reagent 14 can be injected so as to flow countercurrent to the flow Of the halogenated product mixture.
16 (D) Scrubbing ~one - To achieve a halogenated polymer end 17 product not containing usually undesirable materials, the 18 neutralized halogenated rubber can be subjected to 19 supplementary inert and/or reactive gas injection in a scrubbing zone. In a particularly preferred embodiment 21 such scrubbing is performed within the extruder-reactor in 22 a scrubbing zone (D) which sequentially follows neutrali-23 zation zone (C) and which is traversed by the extruder 24 screw means. In this zone a stream or several streams of inert and/or reactive gas can be run -21a-7 ~ S J
1 through countercurrent and/or cc current to the flow of 2 neutralized polymer so as to remove the last traces of the 3 products and unreacted halogenating agent.
,4 Polymer stabilizing agents can optionally be added in this zone~ This can be done by incorporating the 6 stabilizers at'an inj-ection point. - , 7 , In the practice of this invention attention 8 should be given to the temperatures of the neutralization 9 and scrubbing streams when they are brought into contact 10 with the halogenated polymer product so as not to subject 11 the polymer to excessive cooling and increase in viscosity;
, ' 12 in extreme circumstances the polymer might be subject to 13 crystallizationO Methods for preheating these s reams and 14 the temperatures and pressures which are required in order 15 to maintain a continuous process are well within the 16 abilities of those skilled in the polymer processing art.
17 ( ~) Exi - Preferably the extruder-reac~o~ comprises a 18 final exit zone (E~ in which the temperature a~ the halo-19 genated ~olymer product is adjusted for delivery t~,~refrom 20 at a temp2rature below about 130-C, more prefera~ly below 21 about 120-C and most preferably below about 100-C, as a ~2 contribution to the stability 4f the polymer. Also in the 23 exit zone, stabilizer(s) may initially be added to the 24 neutralized; halogenated polymer product if not added in 25 the neutralization or scrubbing zone or additional 26 stabilizer(s) can be added.
27 Suitable stabilizers for use in this process 28 include slurries or solutions of butylated hydroxytoluene 29 (BHT), calcium stearate, sodium stearate, multi-component 30 stabilization systems such as those described in U.S.
31 Patent 4,130,519 to Roper et al and other degradation, 32~oxidation and/or d~hydro-33 halogenation inhibitors well known in the art directed to 34 the polymer being halogenated.
' -22-~ 23 1 In addition to the extruder-reactor features just described, ~he process of this invention can also 3 incorporate filter means kno~n in the art to e~fect the 4 separation of undispersed materials from the polymer, screw means o~ suitable configuration, as described above, 6 transversing zones (A~ - (E) inclusive to properly effect 7 the operations disclosed in said zones (includ~nq single 8 and twin screws~, a system for recycling any organic 3 diluent that may be added to the feed zone and/or included 10 with the halogenating agent and, optionally, means for 11 back-mixing the extruded halogenated polymer to assure that 12 the final pac~ag~d polymer is a homogen~ous product.
13 Materials of construction are a significant 14 consideration in the process herein since potentially cor-~5 rosive reagents are employed. In addition to a concern for 16 long equipmen~ life, product stability needs to be con-17 sidere~ if by-products of the corrosion~r~cess be~ome 18 incorporated into the e~lymer. In addition, halogenation 19 chemistry can be affected if metals and corrosion 20 by-products are present during the halo~enation ~eact~on.
21 M~terials of construction in the feed zone, reaction zone 22 and neutralization zone are selected to prevent or minimize 23 reaction of the equipment with the halogenating agent and 24 the reaction by-products. Small amounts of such materials 25 may cause undesirable side reactions to occur with various 26 constituents o~ the polymerO Useful materials include 27 those alloys known commercially as Hastelloy, steels coated 28 with inert e~lymers such as fluorocarbons, ceramics, etc.
29 ~laterials which have been found to be unsatisfactory where 30 aqueous streams are present include series 300 stainless 31 steels, and carbon steel. Due to the low level of corrosion in this 32 process, other suitable materials include commercial alloys comprising 33 nickel, cobalt, molybdenu~, chromium ant iron as major alloying elemenes;
34 commercial alloys in this class include Hastelloy 8 and C, Xaloy~ 306, 35 Seellite~ 6 and Triboloy~. Titanium coated steel is also useful.
36 Another advaneage for this process is that in the absence 37 of aqueous streams, a dry, halogena~ed produce is produced which can be 38 used immediaeely or packaged (after cooling, if required). Additionally, 39 the corrosion noted above is significantly reduced or may be eliminaeed.
.. _ . . .. .
1 The halogPnated polymers of this invention can 2 be processed in standard equipment used for each such 3 polymer, such as internal mixers, mills, extruders, 4 calenders, etc. Said polymers are amenable to convention-al compounding practice and various fillers and extenders 6 can be incorporated, e.g., Yarious carbon blacks, clays, 7 silicas, carbonates, oils, resins, waxes, etc.
8 As described previously, various halogena~ed 9 polymers are produc~d by the process of this invention including halogenated linear low density polyethylene and 11 halogenated butyl rubber. Halogenated butyl rubber of 12 this invention ma~ be ~ured or vulcanized by any of the 13 prior art methods suitable for such halogenated rubbe~s, 14 e.g., ~sing sulfur, sulfur-containing curing agents (such as sulfenamide derivatives, benzothiazyl disulfide, 16 tetramethylthiouram disulfide, alkyl phenol disulfide, 17 etc.), zinc oxide alone or with various promoters, and 18 mixtures thereof. Curing is usually accomplished at a 19 temperature of from about 140C to about 250C, preferably 150C to about 200C, and usually takes from 1 to 150 21 minutes.
22 This invention will be further understood by 23 reference to the following examples which describe 24 equipment dernonstrating the principles of this invention.
In each of the examples, disruption of the halogenated 26 polymer continued in the neutralization zone.
27 Example 1 -28 An extruder with 2" diameter twin screws, 29 counter-rotating and non-intermeshing was set up according to the teachings herein in order to halogenate several 31 polymers. The feed zone was 18 inches long and separated 32 from the reaction zone by a reverse flighted section. The 33 reaction zone was 28 inches long and separated from the 34 neutralization zone with a reverse flighted section. The reaction zone utilized forwarding single, double and triple 36 flights with slots cut in several of the triple flights.
37 Additionally, some forwarding single sections had mixing h 1 pins in the stem. The configuration in the reaction zone 2 was designed to increase mixing, interrupt polymer flow and 3 expose f resh surface to the halogenating agent.
4 ~ The halogenating aqent was chlorine gas diluted with nitrogen (20-45~ alogenating agent was injected 6 at a slight positive pressure into the vapor space of the 7 reaction zone at a point 6 inches downstrea~ from the 8 beginning of the zone. A vent reaction zone was used, with 9 the vent located 24 inches from the beginning of the reac-lO tion zone.
ll Neutralization was achieved using nitrogen 12 njection, counterourrent to polymer flow, at a rate of 0.5 13 R~ per hour,. A second vent was located 15 inches from the 14 end of the extruder~
16 Polymer Maximum Screw Rate 17 (a) ' Cl,~ Temp,'C .~PM
l9 1. ~DPE 0.38-0.72 160-175 300 , 25 20 2. EP~ ~ 0.41-0.61 185-210 160 ~: 55 21 3~ LLDPE 0.62-3.64 145-165 1Q0 25 22 4. PIB 1.50-1.53 175-185 222 83 23 5. EVA 2.55-4.74 140-160 90 45 24 6. EPDM 2046-3.5; 160-220 156 40 (a) Polymer Identification:
26 1. High density polyethylene, Allied Chemical, 27 AA60-003, 0.3 ~I, 0.96 density.
28 2. Ethylene-propylene copolymer rubber, Exxon 29 Chemical, ~'istalon ~503, 50 wt.% ethylene; typical Mooney viscosity at 127-C=30.
31 3. Linear low density polyethylene, Exxon Chemical, 32 LPX-1 gas phase process, 1.0 MI, 0.918 density.
33 4. Polyisobutylene rub~er, Exxon Chemical, Vistanex 34 0L-80, Staudinger molecular weight 64-81,000.
7 ~ ~ ~
. .
5A Ethylene vinyl acetate copolymer, VSI, VE 645, 2 vinyl acetate = 2B wt~, 3.0 MI, O.9S density.
3 6. Ethylene-propylene diene rubber, Exxon Chemical, q Vistalon 6505, high diene level, typical ethylene=50 wt.%, typical Mooney @ 127'C = 50.
6 ; ~ These results demonstrate the broad applic-7 ability of this improved halogenation process.
8 Example 2 g An extruder with 2~ diameter twin screws, 10 counter-rotating and non-intermeshing was set up according 11 to the teachings herein in order to halogenate butyl rubber 12 ~isobutylene-isoprene copolymer). The feed zone was 10 13 inches long and separated from the reaction zone by a 14 reYerse flighted s~ction. The reaction zone was 47 inches 15 long and separated from the neutralization zone with a 16 reverse, flighted section. The reaction zone~utilized for-17 warding single, double and triple flights with slots cut in 18 several of the triple flights. Additionally, some forward-19 ing single sections had mixing pins in the stem. -~The con-20 figuration in the reaction zone was designed to increase 21 mixin~, interrupt polymer flow and expose fresh surface to 22 the halogenating agent.
23 The halogenating aqent was chlorine gas diluted 24 with 5-10 wt.~ nitrogen. Halogenating agent was injected 25 at a slight positive pressure into the vapor space of the 26 reaction zone at a point 2 inches downstream from the be-27 ginning of the reaction zone at a rate of about 4 Rg/hr.
28 The reaction zone contains a vent located 36 inches from 29 the halogenatiny agent injection point and the vent was 30 vacuum supplemented.
31 Neutralization was achieved using nitrogen in-32 jected countercurrently, beginning 3 inches from the end of 33 the extruder at a rate of 3.7 Kg/hr. A second vent was 34 located 18 inches downstream of the reaction zone vent.
-2~--~7-Polymer feed rate was targeted at 40 Kg/hr- Halogenat~d polyDer produced d~ring this run had a chlQrine content of.l. 39 wt.~, viscosi~y average ~Qlecular w~;ght of 391, 000 and a rheo~eeer cure of 10:7 ~Torque at 30 minutes minus ~inimum tor~ue, in-lb; Test Composlt~on (parts by weight): 100~Rubber, 50-~ried IRB ~5 Carbon Black, 3-Zinc: Ox~de, l-Ste~ric Acid. Rheometer Conditions: 160-C, 5' Arc, 30-minu';e test, 100 cycles per minute oscillat~on. ~ Weight measurement taken of the ex-truder screw parts beore and after the run indicated no evidence of corrosionO 'rhe halogenated polymer was com-pounded in the test for~ula'cion directly as produced; no inten~ediate drying w~s required since no wa~er was used ln the process.
Claims (86)
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED
AS FOLLOWS:
1. A process for the continuous production of halogenated polymer, the process comprising contacting a cohesive polymer mass and halogenating agent in a con-tinuous flow device comprising means for conveying said polymer through said device wherein by-product of the halogenation reaction and unreacted halogenating agent are disengaged from said halogenated polymer mass in said continuous flow device downstream of said contact between said polymer and said halogenating agent by means compris-ing deforming and disrupting said halogenated polymer, thereby continually generating new polymer surface and injecting an effective amount of inert and/or reactive gas thereby neutralizing said halogenated polymer by disengaging halogenation reaction by-products and unreacted halogenating agent.
2. The process of claim 1 wherein said polymer mass is subjected to deformation and disruption and wherein said polymer and said halogenating agent are present during contact as either co-continuous phases or wherein said halogenating agent is present as a continuous phase and said polymer is present as a discontinuous phase or wherein the region in which said polymer and said halo-genating agent are contacted is filled with said polymer.
3. The process of claim 1 wherein said polymer is an ethylenically unsaturated polymer selected from the group consisting of butyl rubber, EPDM rubber, styrene butadiene rubber, polyisoprene rubber, polybuta-diene rubber and poly(butadiene-isoprene) copolymer rubber.
4. The process of claim 1 wherein said polymer is selected from the group consisting of poly-isobutylene, ethylene-propylene copolymer, high density polyethylene, low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer and polyvinyl chloride.
5. The process of claim 3 wherein said rubber is butyl rubber.
6. The process of claim 3 wherein said rubber is EPDM rubber.
7. The process of claim 4 wherein said satur-ated polymer is linear low density polyethylene.
8. The process of claim 5 wherein said butyl rubber is isobutylene-isoprene copolymer.
9. The process of claim 1 wherein said halo-genating agent is selected from the group consisting of chlorine gas, chlorine liquid, sulfuryl chloride, N-chlorosuccinimide, 1,3- dihalo-5, 5-dimethylhydantoin, iodobenzene dichloride, iodine monochloride, bromine gas, bromine liquid, bromine chloride, sodium hypobromite, sulfur bromide and N-bromosuccinimide.
10. The process of claim 1, further comprising adding a diluent to said rubber feed before, at or near the point of addition of said feed.
11. The process of claim 10 wherein said diluent is selected from the group consisting of volatile saturated hydrocarbons, chlorohydrocarbons, chlorocarbons, non-hydrocarbons, and hydrocarbon oils.
12. The process of claim 11 wherein said diluent is selected from the group consisting of pentane, hexane, methylene chloride, chloroform, carbon tetra-chloride, carbon dioxide, and inert gas.
13. The process of claim 12 wherein said diluent is present in an amount less than about 50 percent by weight based on the weight of rubber.
14. The process of claim 8 wherein said halo-genating agent is selected from the group consisting of bromine, chlorine and bromine chloride.
15. The process of claim 8 wherein said halo-genating agent is diluted with diluent.
16. The process of claim 15 wherein said halo-genating agent is chlorine.
17. The process of claim 15 wherein said diluent is a gas selected from the group consisting of nitrogen, argon, air and CO2.
18. The process of claim 10 wherein said halo-genating agent is diluted with a diluent and wherein the total amount of diluent added to said feed and halogenating agent diluent is less than about 50 percent by weight based on the weight of polymer.
19. The process of claim 18 wherein said diluent added to said feed is selected from the group con-sisting of volatile saturated hydrocarbons, chlorohydro-carbons, chlorocarbons and hydrocarbon oils.
20. The process of claim 1 further comprising vent means in the inert and/or reactive gas injection region.
21. The process of claim 1 further comprising pressure control means in the inert and/or reactive gas injection region in order to explosively disengage said halogenation reaction by-products and said unreacted halogenating agent.
22. The process of claim 1 wherein said injected inert and/or reactive gas and said halogenated polymer are conveyed co currently or countercurrently through said device in a neutralization zone following contact between said polymer and halogenating agent.
23. The process of claim 22 wherein said co-current conveyance of said neutralizing means is initiated at the beginning of said neutralization zone or shortly thereafter.
24. The process of claim 20 further compris-ing a supplementary inert and/or reactive gas injection step.
25. The process of claim 24 wherein said supplementary injection step is performed in a separate scrubbing zone.
26. The process of claim 20 further compris-ing a stabilizer addition zone wherein a degradation, oxidation or dehydrohalogenation stabilizer is added to said halogenated polymer.
27. The process of claim 24 wherein a degradation, oxidation or dehydrohalogenation stabilizer is added following said supplementary inert and/or reactive gas injections step.
28. The process of claim 1 further comprising a final exit zone.
29. The process of claim 28 wherein the tem-perature of said halogenated rubber is adjusted for delivery from said exit zone at a temperature lower than about 130°C.
30. The process of claim 28 wherein a degrada-tion, oxidation or dehydrohalogenation stabilizer is added to said exit zone.
31. The process of claim 24 further comprising filter means to effect the separation of undispersed materials from said halogenated polymer.
32. The process of claim 20 wherein said vent means are under vacuum.
33. The process of claim 1 wherein said contact occurs in a vented reaction zone.
34. The process of claim 1 wherein said con-tinuous flow device is selected from the group consisting of a kneader, a single- or multiple screw extruder and a con-tinuous mixer, and a cavity transfer mixer.
35. The process of claim 1 wherein said means for conveying said polymer is screw means.
36. The process of claim 1 wherein said deformation and disruption generates a degree of mixing of said halogenated polymer and inert gas such that the scale of segregation is less than 50 microns.
37. A process for the continuous production of halogenated polymer, the process comprising reacting said polymer and a halogenating agent in an extruder-reactor, said extruder-reactor comprising zones (A), (B) and (B) and conveying means traversing said zones; zone A, feed zone, in which conditions of temperature and pressure are sufficient to generate a cohesive polymer mass; zone (B), reaction zone, in which said halogenating agent and said polymer are contacted, resulting in a product mixture comprising halogenated polymer, reaction by-products and unreacted halogenating agent; and zone (C), neutralization zone, wherein reaction by-products and unreacted halo-genating agent are disengaged from said halogenated polymer mass by means comprising deforming and disrupting said halogenated polymer, thereby continually generating new polymer surface and injecting an effective amount of inert and/or reactive gas thereby neutralizing said halogenated polymer by disengaging halogenation reaction by-products and unreacted halogenting agent.
38. The process of claim 37 further com-prising first flow restriction means between zones A and B, and second flow restriction means between zones B and C.
39. The process of claim 20 wherein a vacuum is applied to said vent means.
40. The process of claim 37 wherein said deformation and disruption generates a degree of mixing of said halogenated polymer and inert gas such that the scale of segregation is less than 50 microns.
41. The process of claim 38 wherein said restriction means following said feed zone is selected from the group consisting of a reverse flighted screw section, a filled screw section, a shallow flighted screw section, and an unflighted screw section.
42. The process of claim 41 wherein said restriction means is about 0.5 to about 8 screw diameters in length.
43. The process of claim 38 wherein said restriction means following said feed zone comprises said reaction zone.
44. The process of claim 37 wherein said means for producing said deformation is selected from the group consisting of a reverse flighted screw section, a multiple reverse flighted screw section, a pin section, a series of very short alternating reverse and forward screw sections, multiple flight screw section, interrupted flight section, a cavity transfer mixer, and combinations thereof.
45. The process of claim 38 wherein said restriction means separating said neutralization zone from said reaction zone is selected from the group consisting of a reverse flighted screw section, a filled screw section, a shallow flighted screw section, and an unflighted screw section.
46. The process of claim 38 wherein each of said restriction means is an unflighted screw section with a diameter of from 5 to 25 percent larger than the root diameter of the upstream screw section, but not greater than the upstream screw flight diameter.
47. The process of claim 37 wherein said conveying means is screw means.
48. The process of claim 47 wherein said screw means is selected from the group consisting of single and multiple screws.
49. The process of claim 47 wherein said shear forces are generated in said reaction zone by operating said screw means at a rotation rate of from 50 to 600 RPM.
50. The process of claim 37 wherein the mate-rial used in the construction of one or more of said zones is selected from the group consisting of alloys comprising nickel, cobalt, molybdenum, chromium and iron as major alloying elements, and steel coated with inert polymer ceramic or titanium.
51. The process of claim 37 wherein the polymer in the feed zone is subjected to a pressure of up to about 600 psig.
52. The process of claim 38 wherein said inert and/or reactive gas is injected at or adjacent the downstream end of said second restriction means.
53. The process of claim 37 wherein said inert and/or reactive gas is injected into said neutral-ization zone so as to flow countercurrent to the flow of said halogenated product mixture.
54. The process of claim 37 further compris-ing a supplementary inert and/or reactive gas injection step.
55. The process of claim 54 wherein said supplementary injection step is performed in a separate scrubbing zone (D) which follows said neutralization zone, prior to delivering said halogenated polymer product.
56. The process of claim 37 further compris-ing a final exit zone (E).
57. The process of claim 37 further compris-ing stabilizer addition wherein a degradation, oxidation or dehydrohalogenation stabilizer is added to said halogenated polymer.
58. The process of claim 56 wherein the temperature of said halogenated polymer is adjusted for delivery from said exit zone at a temperature lower than about 130°C.
59. The process of claim 54 wherein a degradation, oxidation or dehydrohalogenation stabilizer is added in said supplementary inert and/or reactive gas injection step.
60. The process of claim 56 wherein a degradation, oxidation, or dehydrohalogenation stabilizer is added to said exit zone.
61. The process of claim 55 wherein said extruder-reactor further comprises filter means to effect the separation of undispersed materials from said halogen-ated polymer.
62. The process of claim 37 wherein said polymer mass is subjected to deformation and disruption in said reaction zone and wherein said polymer and said halogenating agent form co-continuous phases within said reaction zone or are present during contact as either co-continuous phases or wherein said halogenating agent is present as a continuous phase and said polymer is present as a discontinuous phase or wherein said halogenating agent is injected at a position filled with said polymer.
63. The process of claim 62 wherein said polymer is an ethylenically unsaturated polymer selected from the group consisting of butyl rubber, EPDM rubber, styrene butadiene rubber, polyisoprene rubber, poly-butadiene rubber and poly(butadiene-isoprene) copolymer rubber.
64. The process of claim 37 wherein said polymer is selected from the group of saturated polymers consisting of polyisobutylene, ethylene-propylene copoly-mer, high density polyethylene, low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer and polyvinyl chloride.
65. The process of claim 63 wherein said rubber is butyl rubber.
66. The process of claim 63 wherein said rubber is EPDM rubber.
67. The process of claim 64 wherein said saturated polymer is linear low density polyethylene.
68. The process of claim 65 wherein said butyl rubber is isobutylene-isoprene copolymer.
69. The process of claim 37 wherein said halo-genating agent is selected from the group consisting of chlorine gas, chlorine liquid, sulfuryl chloride, N-chlorosuccinimide, 1,3-dihalo -5,5-dimethylhydantoin, iodobenzene dichloride, iodine monochloride, bromine gas, bromine liquid, bromine chloride, sodium hypobromite, sulfur bromide and N-bromosuccinimide.
70. The process of claim 37 further comprising adding a diluent to said rubber feed before, at or near the point of addition of said feed.
71. The process of claim 70 wherein said diluent is selected from the group consisting of volatile saturated hydrocarbons, chlorohydrocarbons, chlorocarbons, non-hydrocarbons and hydrocarbon oils.
72. The process of claim 71 wherein said diluent is selected from the group consisting of pentane, hexane, methylene chloride, chloroform, carbon tetra-chloride, carbon dioxide, and inert gas.
73. The process of claim 72 wherein said diluent is present in an amount less than about 50 percent by weight based on the weight of rubber.
74. The process of claim 69 wherein said halogenating agent is selected from the group consisting of bromine, chlorine and bromine chloride.
75. The process or claim 69 wherein said halogenating agent is diluted with diluent.
76. The process of claim 75 wherein said halogenating agent is chlorine.
77. The process of claim 75 wherein said diluent is a gas selected from the group consisting of nitrogen, argon, air and CO2.
78. The process of claim 70 wherein said halogenating agent is diluted with a diluent and wherein the total amount of diluent added to said feed and halo-genating agent diluent is less than about 50 percent by weight based on the weight of butyl rubber.
79. The process of claim 70 wherein said diluent added to said feed is selected from the group consisting of volatile saturated hydrocarbons, chloro-hydrocarbons, chlorocarbons and hydrocarbon oils.
80. The process of claim 68 wherein the tem-perature in said reaction zone is less than about 170°C.
81. The process of claim 37 further compris-ing vent means in said neutralization zone.
82. The process of claim 81 wherein said conveying means comprises screw means wherein said screw means is configured so as to avoid restricting the exiting flow of inert and/or reactive gas and disengaged materials.
83. The process of claim 1 wherein said inert and/or reactive gas is selected from the group consisting of nitrogen, argon, carbon dioxide, air and ammonia.
84. The process of claim 37 wherein said inert and/or reactive gas is selected from the group consisting of nitrogen, arton, carbon dioxide, air and ammonia.
85. The process of claims 1 or 37 wherein said gas is inert.
86. The process of claims 1 or 37 wherein said gas is reactive.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000464159A CA1247792A (en) | 1984-09-27 | 1984-09-27 | Process for the manufacture of halogenated polymers |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000464159A CA1247792A (en) | 1984-09-27 | 1984-09-27 | Process for the manufacture of halogenated polymers |
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| CA1247792A true CA1247792A (en) | 1988-12-28 |
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-
1984
- 1984-09-27 CA CA000464159A patent/CA1247792A/en not_active Expired
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