Note: Descriptions are shown in the official language in which they were submitted.
4~7
.1 1
l . .'
BACKGROUND OF TIIE_INVENTION
I Field of the Invention: This invent~on relates to new cross-
linked sulfonated polymers of polystyrene and styrene copolymers
l and to a process for the production thereof. More particularly,
jl the invention relates to a process for producing crosslinked
¦sulfonated polystyrene or styrene copolymers employing selected
¦ crosslinking agents during the sulfonation reaction so as to
~j achieve crosslinking and sulfonation of the polymer simultaneouslyl
¦and efficiently in a homogeneous system. The process yields cross-
l.O I linked sulfonated styrene polymers undisclosed in the prior art. I -
II, Brief Desc~iption of the Prior Art: Prior art procedures
I . ,.
I for preparing crosslinked sulfonated polystyrene or styrene
Il copolymers involve the sulfonation of polymers which have been
¦~previously crosslinked with difunctional reagents or which contain
I copolymeriæed alkenyl halides within the backbone o~ the polymer
itsel~ The crosslinking may then be achieved during formation
,1 of the polymer as i8 the case when styrene divinyl aryl compounds ¦
li are sul~onated, Alternatively, the styrene polymers may contain
therein an alkenyl halide together with a Friedel-Crafts type
0 ~ catalyst, which, upon e~posure to elevated temperatures during
i sulfonation, will effect crosslinking so as to produce the sul-
fonated crosslinked polymer. The latter method is described in
I U.S. Patent 2,628,193,
¦ The methods of the prior art thus, in all cases, require
the presence of specific components within the backbone of the
polymer thereby limiting the choice of molecular weight and final
¦ structure of the sulfonated polymer. Moreover, in cases wherein
~ !I the polymer is crosslinked prior to sulfonation, the degree of
I I! crosslinking desired in the final polymer must be incorporated
O ¦l into the starting polystyrene copolymer. Often, however, a high
: `
- 2 - ~
' :. ' ' -
I4~ J7
; . .
~crosslinking density i6 desired in the final product and this
¦Inecessiates working with a styrene polymer which is insoluble in
,, the sulfonation medium resulting in incomplete or partial
jisulfonation. Similarly, incomplete sulonation is achieved when
alkenyl halides or the like are incorporated into the polymer
since the aromatic sites available for sulfonation are propor-
tionately reduced.
SUMMARY OF_THE INVENTION
~ In following the present invention, polystyrene
L0 ¦ or styrene copolymers of molecular weight 800 to 4,000,000 can
!l be crosslinked to any degree of water solubility during sulfona-
1, tion from a homogeneous reaction mixture by incorporation of from
! 0.1 to 5 mole V/o of specific crosslinking reagents in the styrene
polymer sulfonating solution. These crosslinking reagents are
I not par~ of the polymer backbone and are activated only by the
,~ sulfonating reagent. Consequently, these reagents do not interact
with the styrene polymer until the latter enters the sulfonation
zone, thereby effecting simultaneous sulfonation and crosslinking
a homogeneous system wherein the polymer itself is soluble
~ li throughout the reaction. I
¦1 The resultant crosslinks are covalent carbon bonds which
! are heat-stable, reproducible and not subject to hydrolysis;
properties dificul~ to obtain using procedures of the prior art.
Moreover, since the crosslinking agent is not part of
l the polymer backbone, the same styrene substrate can be used to
Il produce soluble chain extended sulfonates, insoluble sulfonates
; l or sulfonates having any degree of solubility between these
j extremes simply by adjusting the amount of crosslinking reagent
Il used. For the same reason, sulfonated polystyrenes can be
0 ll prepared over a wide range of molecular weights from the same
.
! - 3 -
. ;l I
,,
' ': ' ' ~' -' '''. ',, .
~ 7
styrene substrate by varying the amount of crosslinking reagent.
¦ In addition, since sulfonation occurs in a homogeneous phase
1! simultaneously with crosslinking, virtually complete substitution
¦¦ of the aromatic groups of the polymer with respect to sulfonic
~¦ acid groups can be achieved.
Il Thus, the process of the present inven~ion enables the
I! production of a sulfonated, crosslinked polystyrene or styrene
Il copolymer in which the final molecular weight, degree of cross-
¦l linking and degree of sulfonation can be selected independently
¦¦ of each other. Moreover, the present invention provides a method
¦I for the production of polystyrene and styrene copolymers which
1~ are fully sulfonated with respect to the available aromatic groups;
¦I such fully sulfonated materials could not be produced using the
! methods of the prior art.
BRIEF DESCRIPTION OF T~E DRA~ING
The single FIGURE is a graph illustrating the wide
variety of viscosities (and hence wide range of solubilities)
obtainable from one speci~ic polystyrene substrate using control-
~ led amounts of c~,o-'-dichloro-p-xylene, one of the crosslinking
¦ reagents disclosed herein.
1~ D~TAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
! The homopolymers and copolymers of styrene suitable for
use herein include those polymers having a styrene content of at
leflst about 5% by weight, preferably at ].east 25% by weight,
1, exhibiting solubility in the sulfonation solvent and having a
molecular weight within the range of about 800 to 4,000,000.
~ 1I Copolymerizable comonomers suit:able for use with the
; I; styrene include, for example, alkyl (Cl-C18) acrylates and meth-
11¦ acrylates, maleic anhydride, maleic acid esters, fumaric acid
~¦ esters, acrylonitrile and olefins, e.g, ethyl acrylate, methyl
,i
~ 4 -
- 1. 1
- - . , . , ~. - . ., . . - .
14~7 1 ~
methacrylate, dimethyl meleate, isobutylene, butyl acrylate, etc.
¦; Additionally, aromatic comonomers capable of copoly-
merizing with the styrene may be employed. Such comonomers
include the vinyl aryl compounds such as vinyl naphthalene, vinyl
diphenyl, vinyl fluorene, etc. and their nuclear-substituted
l derivatives such as alkyl, aryl, alkaryl, aralkyl, cycloalkyl,
¦ alkoxy, aryloxy, chloro, fluoro, chloromethyl, fluoromethyl and
trifluoromethyl nuclear derivatives, for example methyl-styrene,
l¦etc; alpha-alkyl-vinyl substituted aromatic compounds such as
I those substituted with isopropenyl or alpha-methyl-vinyl, alpha-
lethyl-vi.nyl, alpha-propyl-vinyl radicals, etc. It will be
¦ recogniæed that when such aromatic comonomers are polymerized with
¦ the styrene and treated''as described, ' ' ''
sulfonation o the aromatic groups of the comonomèrs in addition
to sulfonation of the styrene will also occur. It will also be
' il recognized by those skilled in the art that by requiring the
copolymers to be soluble in the sulfonating reagent, such previous
11 ly cros~linked polymers as-would result from copolymerization with
di'functional compounds, such as diacrylates, divinyl aromatlcs
' ZO I and diallyl compounds, would be excluded from the scope of the
; ' ¦''p'resènt''disclosure.
¦ The specific crosslinking agents'to be employed
are selected aryl compounds having at
; ~ ¦! leas~ two radlcals of the following structure:
wheeein~l~X is selected from the group consisting of -OH, -Cl'
~and~-Br. More particularly, the useful crosslinking agents are
' defined by the following ~eneric structures:
":
5 -
: 1
.::- - . . ., : - ~.
!l !
R
, CH2X
llwherein at least one R is selected from the group consisting of:
-CH~X, ~ and
0 11 . R'~ R'
~¦ -(Q)P-Z-(Q)P' ( ~ CH2X
j¦ R' `R'
~! where X is -OH, -Cl or -Br; Q i9 oxygen or sulfur;
I! P and p' are independently selected integ~rs havlng the.value O or
¦¦ l; Z is a radical containing from 1 to 10 carbon atoms inclusive
~l and is selected from the group consisting of straight and branched
¦¦ chain alkyl radicals; and the remaining R and R' are selected
l from the group consisting of hydrogen, ClC3 alkyl ~dCl-C3 alkoxy
I radicals; and
0 (ii) polynuclear aryl compounds containing at least two
Il -CH2X groups wherein X is as defined.above, which compounds may
I be further substituted with substituent groups selected from the
I A IKy/en~
i S l group consisting of -0~, Cl-C3 nlleyl radicals and Cl-C3 alkoxy¦
radicals.
It is to be noted that the posi.tioning of the functiona~
C~2X groups on the above-described reagents is not critical to the
efficacy of the crosslinkin~ reagent
Illustrative crosslinking reagents include:
- 6 -
- , ~ , - .
a~7
~CH2Cl CH2Cl CH2C
~.6~'-dichloro-xylenes: ~ ~ ~ CH2Cl ~ CH2Cl
CH2Cl
,
CH3
2,4,6-tris-chloromethyl mesitylene ~0 ~
CH3 CH3
CH~Cl
. I
~ C~12Cl
1,4-bis-chloromethyl durene: ~
.1 CH2Cl
I
1,4-bis-hydroxymethyl benzene: HOCH2- @ CH20H
.
4,4'-bis-bromomethyl-diphenoxy ethane:
BrCH~ OCH2CH2-0- ~ CH2Br
.~ .
.
` ix
:
4,4'-bischloromethyl diphenyl methane:
ClCH2 ~CH2~ CH2Cl
4,4'-bis-chloromethyl biphenyl: ClCH2- ~ - ~ CH2C
1,6-bis-chloromethyl naphthalene: ~ CU2Cl
(p-chloromethyl phenyl)-2-(p-chloromethyl thiophenoxy)-ethane:
¦I C1CH2_~(CH2)2-S--~O~H2C1
I 'I Cl H2H
1,6-bLs-hydroxymethyl anthracene:
CH20H
--8--
,
4~7
~;
The a~ount of the crosslinking reagent employed will
vary depending upon a number of factors including thP nature of
the specific reagent and of the copolymer substrate, the
molecular weight desired in the final product and the level of
solubility or insolubility desired in the final product. In
l general, levels of 0.1 to 5 mole V/o of the crosslinking agents
¦ based on the aromatic content of the styrene component may be
employed, although levels of less than about 1.5% are preferred.
The lower levels of crosslinking will result in water-soluble
o ~ polymers while the higher levels will result in water-insoluble
~ulfonated polymers useful, for example, as ion exchange resins.
l Any sulfonation reagent conventionally employed for the
I ~ sulfonation of styrene-containing polymers may be used. Suitable
i ~ reagents include sulfur trioxide, oleum, halosulfonic acids and
sulfur trioxide addition compounds. Among the applicable addi-
tion compounds of sulfur trioxide are included the complexes
of sulfur trioxide with complexing agents such as pyridine,
trialkyl amines, dimethyl formamide, ethers, e.g. bis-2-chloro-
¦ ethyl ether and dioxane, trialkyl phosphates and phosphites.
¦ These reagents are well known to those skilled in the art and
are described in variou~ texts dealing with aromatic sulfonation,
I e.g. E.E. Gilbert "Sulfonation and Related Reactions", Inter-
science Publishers, N.Y. (1965). The preferred class of sulfona-
tion reagents is derived from the addition compounds of sulfur
l trioxide and trialkyl (Cl-C18~ phosphates. The preparation of
I such addition products and the sulfonation therewith are described
in U.S. Patents 3,072,703 and 3,072,618, respectively.
`~ The amount of sulfonating reagent employed will also
vary o~er a wide range dependlng upon a number of factors such
_ 9 _
~ I ~
~4~9~
j¦as the reagents and substrate employed, and the solubility and
jldegree of sulfonation desired in the final product. If a fully
substituted sulfonated styrene polymer or copolymer is desired,
the amount of sulfonating reagent employed mustbe/least e~uimolar
to the number of moles of available aromatic-containing components
The sulfonation and crosslinking conditions are those
conventionally employed in sulfonation reactions. Thus, any
aliphatic hydrocarbons or chlorinated hydrocarbons which are not
l reactive with the sulfonating reagent may be used as solvent. ¦
1 Preferably, 1,2-dichloroethane is used as a solvent medium but
other solvents known to be useful in these sulfonating reactions
may also be employed.
l Although reaction conditions may be ~aried and adapted
i!to parti.cular industrial situations, the ollowing general-
llpreparative procedure may be considered as illustrative. The
; ¦¦polystyrene or copolymer thereof is dissolved in 1,2-dichloro-
¦¦ethane such that the concentration of the polymer in the solvent
; ¦¦is in the range of 1-50% by weight. To this solution is added a
Isuitable amount of the crosslinking agent. The mixture is
20 11 agitated until the polymer and crosslinking agent dissol~e. The
resultant polymer solution is then added simultaneously wlth the
¦sulfonating reagent to a reaction vessel containing precharged
~¦solvent and complexing agent if the sulfonating addition product
is to be formed in situ. The reactions occur immediately and
¦the temperature is maintained at S-25C. by cooling. As the
product forms, it precipitates from the reaction mixture.
The product is then isolated according to any of the
llsuitable procedures described in the art as, for example, by
il filtration or extraction with water if the acid form is desired
11, , 10- 1
. ,. I
,, ~ . . . . . , . . ., .. ~ - -
4~97
;, I
l'or by neutralizatLon ~f the salt form is desired or by s~abiliza-
jltion with alkali metal carbonates and filtration.
Since the chemical nature of the crosslinking agent,
l~the amount of crosslinking agent employed and the styrene substrat~
,lare all variables, it is not possible to represent the cross-
¦¦linked sulfonated polystyrene or styrene copolymers by a single
structure and they may only be considered to be defined by the
process disclosed herein for their production. However, if a
typical cros81inking agent is considered, then the basic type of
structural units involved in the~new practice
llmay be charac~erized.
¦I Thus, if polystyrene of average molecular weight 250,000
jl (degree of polymerization 2404) were crosslinked and sulfonated
llu8ing 0.25 mole percent ~ dichloro-p-xylene in a sulfonating
.. . . .... . .
, medium as here described, a typical
resultant product could be represented by the following structure:
~ (~n-- CH~ (CH~ n
. il S03H ~03H ~S03H
~S03~1
H2
~3So3~1
~CI~ CH~-CH ~CH~ ~n
03H
11
~I I
1 , . ..
~4~7
ll
!
The examples which follow are illustrative and the
scope of the invention is not to be considered as limited thereto.
In the examples, all parts are by weight unless otherwisè noted. I
EXAMPLE I ¦ I
~I This example illustrates a general process used to
! prepare the,new crosslinked ~sulfonated polystyrenes.
~¦ A one liter 3 neck flask equipped with a mechanical
agitator, conden6er and drying tube, was charged with 900 gms. of
Il 1,2-dichloroethane and 0.175 gms.cx,c~'-dichloro-p-xylene. With
1l stirring, 100 gms. o dry powdered polystyrene having a molecular
,I weight of 480,000 was added. The mixture was stirred until all
¦, the polystyrene had dissolved. This was designated solution "A".
The sulfonation vessel, a S-liter Morton flask equipped
¦ with an agitator, thermometer, condenser with drying tube and a
! gas inlet tube, was purged with dry nitrogen for one hour. To
¦ the reactor wa~ added 1250 gms. 1,2-dichloroethane at 0.009%
1~ H20 and 35 gms triethyl phosphate. The temperature of the reaction
¦ mixture was maintained at 15-20C. while 15.82 gms. S03 (liquid,
l stabilized) was slowly added. This amount of S03 was sufficient
I to form a l:l molar complex with the triethyl phosphate.
! When the temperature stabilized, the simultaneous addi-
i tion of solution A (820 ml) and 77.5 gms. (42 ml) stabilized
¦¦ S03 was started. The addition rates were maintained at 20 ml/
minute for "A" and 1 mllminute for the S03. The temperature
l during sulfonation was maintained at 15-21C. The sulfonated
'~ ! polystyrene precipitated as it formed.
¦ As a control, this same procedure was repeated with the
~ ellmination of the 0.175 gms. of ~,C~'-dichloro-p-xylene from
1~ ~ j, the stock solution "A".
i~30 l~ Both polymers were evaluated to determine the extent of
crosslinking by measuring thc Brookfield (RVF) viscosity o~
- 12 - I
, i' , ..
. ~ .. ~ , .
. ,
.
., I .
,,
5% solutions in water: j -
Viscosity De~ree of Sulfonation
Control 100 cps 0.943
Crosslinked2080 cps 0.939
1,
, EXAMPLE II
!j This example illustrates how this process lends itself
!~ to the preparation of sulfonated polystyrenes having widely differ
ent solution properties by simply adjusting the level of cross- !
linking agent used in the sulfonation of the same base polystyrene .
The results obtained in this example are illustrated by the graph
in the FIGURE.
General Procedure
A stock solution for 8ulfonation was prepared by
! dis801ving 220 ~ns . of polystyrene (molecular weight 250,000) and
,¦ the de8ired amount of ~ dichloro-p-xylene in 1980 gms . 1,2-
dichloroethane containing 0.008% water.
A five-liter Morton ve9sel equipped with stainless 9teel
~¦ agitator, thermometer, condenser with drying tube and a gas inlet
'¦ adapter, was purged for one hour with dry nitrogen. Thereupon,
1 2500 gm~ 1,2-dichloroethane and 23.3 gms. triethyl phosphate was
!1 added to the reactor and the temperature lowered to 15C.
¦ With cooling~ 11,14 gms. stabilized S03 was dropped
¦ into the reac`tor in order to form a 1:1 complex with the phosphat~.
When th~ temperature stabilized, the addition of 2000 gms.
¦ (1640 ml) of the stock solution containing polystyrene and
jl crosslinker was started. Simultaneously, the addition of 154.6
i gms~ (83.5 ml) of stabilized S03 was also started. The rate o
¦ the stock solution was 20 ml/min. ancl ~he S03 rate was adjusted
i to 1 ml/min. During the additions, the temperature was maintainec I
i I :
i - 13 - ~
. ' ,~ I .
~: , . . .
l i
Il I .'
at 15-20~C. by cooling. As the crosslinked sulfonated polystyrene~
forms, it precipitated from solution.
When the sulfonation was completed, 143 gms. of
llpulverized sodium carbona~e monohydrate was added to the reactor
¦land the mixture stirred for 1 hour. The stabilized product was
isolated by filtration and drying at 60C. for 2 hours. The
llsulfonated polymer was characterized by preparing a 1~/~ aqueous
'Isolution and measuring the Brookfield viscosity at room temperature.
¦IThe data is tabulated in Table I and plotted in the FIGURE.
ll TABLE I
,¦ Mole % Brookfield
¦'Experiment_ _Crosslinker Viscosity at 1% Type
I
¦ A 0 35 cps Clear Solution
B 0.10 250 ~ Clear Solution
C 0.20 1,350 " Clear Solution .
¦ D 0.25 3,000 " Clear Solution
Il E 0.35 11,680 " Slight Grain
¦¦ F 0,50 5,800 " Moderate Grain
I! G 0.60 590 " Heavily Grained
¦I EXAMPLE III . .
This example illustrates the wide selection in the
choice of polystyrenes and crosslinking agents. - :
. The general procedure described in Example II was
! repeated using a variety o~ polymers and copolymers in the
amounts shown in Table II, The polymers employed were designated -
¦I a~ follows: ~
:~ ~ . .
~' I . .
I - 14 - ! `
jl .
.
;l . . .
,, ~ . . .
!l , I .
Polymer A Polystyrene (MW 250,000)
Polymer B Polystyrene (MW 3 x 106)
Polymer C Polystyrene (MW 30,000)
Polymer D Copolymer of styrene and acrylonitrile (75~/O styrene,
300,000)
IlPolymer E Copolymer of styrene and methylmethacrylate (70%
¦I styrene, MW 287,000)
llPolymer F Copolymer of styrene and maleic anhydride (76. l~/o
¦1 styrene, MW 2,000)
o ~¦Polymer G Polystyrene (MW 500,000)
Polymer H Copolymer of styrene and p-t-butyl styrene (39.6%
' styrene, ~ 750,000)
¦I The viscosity results obtained are tabulated in Table II
EXAMPLE IV
¦ This example illustrates the preparation of an insoluble
!crosslinked sulfonated polystyrene,
i I A stock solution is prepared by dissolving 2~0 gms. of
¦ polystyrene (molecular weight 250,000) and 5 gms. of 2,4,6-tris-
~ ¦ (chloromethyl)-mesitylene in 1980 gms. of 1,2-dichloroethane
,0 containing 0.008% in water.
,; .
five liter reactor as described in Example II is
`~ purged for one hour with dry nitrogen, Thereupon, 2500 gms.,
¦ 1,2-dichloroethane is added to the reactor and the temperature
. ~ . I . , . I
¦ lowered to 15C.
; . , ..
I The addition of 2000 gms. (1640 ml) of the stock
~ solution containing polystyrene and crosslinker is started.
;. , :
; i ~Simultaneously the addition of 1546 gms. (83.5 ml) of stabilized
;;~5O3~is~aLso started. The rate of the stock solution is 20 mllmin.
DurLng the~additions the temperature is maintained at 15-20C. by
~;o~ cooling. A9 the crosslinked sulfonated polystyrene forms, it
! precipitates from solution,
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After the sulfonation the polymer is filtered and washed
once with methanol and then resuspended in water. The polymer
is fully crosslinked and will exhibit no significant solution
viscosity. ~ence, the resultant crosslinked material would be
Il characterized by an appoximate D.S. of 0.90-0.95 which would
,¦ correspond to an exchange capacity of 0.5 meq/gm. (dry basis)
rendering the polymer very well suited for ion exchange uses.
EXAMPLE V
I¦ This example illustrates the use of a diferent sulfonat-
1¦ ing system in the production of the crosslinked sulfonated poly- ¦
¦ styrenes.~
A stock solution is prepared containing 220 gms. Polymer A,
¦ 1980 gms. 1,2-dichloroethane and 0.37 gms. ~ dichloro-p-
xylene.
I A complexed sulfonating reagent is prepared as follows: ¦
; ! A 2 liter round bottom flask fitted with a glass/teflon
¦¦ agitator, nitrogen sweep, thermometer, condenser and drying tube
is charged with 277.4 gms. of bis(beta chloroethylether) and
~1 1000 gms. 1,2-dichloroethane. With cooling so as to maintain the
1l temperature at 15-20C,, 155.3 gms. SO3 is added to the mixture
over a 1 hour period.
A 5-liter Morton flask as described in Example I is
I charged with 1000 gms. of 1,2-dichloroethane. With cooling,
1 2000 gms. of the polymer solution, and the sulfonating reagent
,' solution added simultaneously over a 2 hour period, The reaction
1~ temperature is maintained at 15-20CC. A~-ter the sulfonation, the
¦¦ mixture is stirred 30 minute3 and then 216 gms sodium carbonate
added.
- 1 8
I!
~1 .
.
g7
The stabilized polymer is recovered by filtration and
,j drying. A 1% solution of the final product in water will exhibit
l a Brookfield viscosity of approximately 235 cps compared to 35
¦j cps for the control.
EXAMPLE VI
! Using the general procedure described in Example I the
following polymers can also be sulfonated using the amount of
reagents designated:
ll (a) 200 parts of 90/10 copolymer of methylmethacrylate
¦ and styrene with 2.22 parts 1,4-bis-chloromethyl durene and
22.4 parts of chlorosulfonic acid. The product will be cross-
linked and water swellable.
(b) 100 parts of an 80/20 copolymer of isobutylene and
styrene with 15.4 parts S03, 3.5 parts triethyl phosphate and
1,7 parts 2,2'-dichloro-p-xylene. The product will be crosslink-
ed and water swellable.
As will be reco~nized to those skilled in the art,
1¦ varietions may be made in in~redie~t~, proportions and procedures
¦¦ as long as such variations are within the scope and spirit of the
~ollowing clslms.
1l1 ' .
, 11 . I
19-
