Note: Descriptions are shown in the official language in which they were submitted.
l~Sl~
This invention relates to the preparation of triorganotin
compounds. This invention further relates to the preparation of
polymerizable triorganotin derivatives of unsaturated carboxylic
acids. --
Polymers derived from triorganotin derivatives of
unsaturated monocarboxylic acids, particularly acrylic and
methacrylic acids, have been recognized as effective toxicants
for numerous applications, including antifouling paints. The
use of these polymers for protecting a variety of materials-
against the growth of harmful organisms is disclosed in
U.S. Patent 3,167,473.
Monomeric precursors of the aforementioned polymers
are prepared by reacting an ethylenically unsaturated acid,
such as acrylic acid, or a suitable derivative thereof, such
as the corresponding acid anhydride, with a triorganotin
hydroxide or a bis (triorganotin) oxide. The water formed as
a by-product of the reaction is conventionally removed by
distillation which is conducted under either atmospheric or
reduced pressure~ The reaction of an acid with a triorganotin
hydroxide can be expressed by the following equation:
O O
R3SnOH + R C ~ R2C~ H20
OH OSnRl
In the foregoing equation R represents a hydrocarbon
radical containing from 1 to 20 carbon atoms and R2 represents
an ethylenically unsaturated hydrocarbon radical.
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. . .
i The reaction mixture usually includes an inert li~uid
il diluent such as an aromat;c hydrocarbon, which fonms an
ll azeotropic mixture with water. The acid and triorganotin
¦¦ compound are usually heated to the boiling point of the
! 1 reaction mixture and a distillation apparatus is employed
to remove the water together with a portion of the hydro- ¦
carbon diluent. In addition to facilitating removal of the
relatively small amount of water formed during the reaction,
the diluent lowers the concentration of unsaturated acid and
the triorganotin derivative thereof, thereby reducing the
likelihood of a spontaneous polymerization. This type of
polymerization is undesirable in those instances when the
organotin derivative is to be subsequently reacted with other
I ethylenically unsaturated compounds to form copolymers such
lS as those disclosed in U. S, Patent 3,167,473.
The distillation of hydrocarbon diluent and water is
often conducted under reduced pressure to minimize heating f
the reaction mixture.
The use of an organic diluent and distillation to
remove the diluent and by-product water may be satisfactory
when the total volume of reagents and diluent does not exceed
about 500 c.c. As the volume of the reaction mixture increases,
it becomes more difficult t~ evenly distribute heat from the
walls o~ the reactor throughout the reaction mixture. Localized
overheating may occur, particularly in areas adjacent to that
¦~ portion of ths reaction vessel where heat is being applied The
heat input required to maintain a distillation wherein the vapor
phase remains at ambient temperature is significant. If the
~ heat is not rapidly dissipated within the reaction mixture, the
! resultant localized overheating could ini~iate a spontaneous
¦ polymerization,,
i -2-
44
An objective of this invention is to provide a method
for preparing relatively large amounts of triorganotin carboxylates
derived from ethylenically unsaturated acids with or without
any organic diluent and in the absence of significant polymer
formation.
It has now been found that this objective can be
realized by replacing the conventional distillation step for
the removal of water by the use of certain chemicals which
will effectively remove the water from the liquid phase of
the reaction mixture. - -
This invention provides an improvement in the method
for preparing triorganotin derivatives of ethylenically un-
saturated acids by (1) reacting an ethylenically unsaturated
mono- or dicarboxylic acid or suitable derivative thereof,
such as an ester or anhydride, witha triorganotin hydroxide
or bis (triorganotin) oxide and (2) removing the water formed
as a by-product of said reaction. The reaction mixture may
optionally include a liquid diluent. The improvement provided
by this invention resides in removing the by-product water
by maintaining the reaction mixture in contact with an amount
of a solid, chemically inert dehydrating agent sufficient to
remove substantially all of the water. The reaction mixture
is maintained in contact with the dehydrating agent for a period
of time sufficient to the dehydrating agent to react with or
absorb between 95 and 100% of the water present. Stoichiometric
amounts of the reactants are generally employed since no advantage
is achieved by employing an excess of either reactant.
L~51444
DE~ILED DESCRIPl~ION QF I~E INVENTION
_ _ . __
The present class of dehydrating agents include
l anhydrous salts which react with water to form stable hydrates
¦ or particulate materials such as activated aluminum ~nd
¦ molecular sieves that are insoLuble in the reaction mixture
¦ and selectively absorb water on the surface of the particles,
¦ within the particles or both. Preferred salts yielding stable
hydra~es include the anhydrous forms of magnesium sulfa~e,
calcium sulfate, the calcium halides (fluoride, chloride, bromide
and iodide), potassium carbonate and sodium sulfate. Other
anhydrou~ saLts are suitable if they are competitive in cost and
per~ormance with ~he preferred species and are chemically inert,
in tha~ they are not polymerization catalysts for the unsaturated
Il acid and do not ~ender the resultant reaction mixture so acidic
l or baæic a~ to initiate a polymerization of the unsaturated acid
or the triorganotin derivative thereof. Drying agents which-are
too acidic or basic can aLso decompose the organotin ester. It
i8 this criterion of chemical inertness that excludes both alkali I
metal or aLkaline earth metal hydroxides and phosphorus pentoxide !
from the class of useful dehydrating agents.
Preferred drying agents which remove water by
~bsorption include activated alumina, silica gel and molecular
~ieves, particularly ~e types designated 4A and 5A.
m e amount of de~ydrating agent employed in the method
!~ of this invention is at lea~t suficient to remove between 95
and 100~ of the theoretical amount of water formed during the
~i reac~ion. The number of moles of water is eclual to the number
¦' f ~quivalents o~ carboxylic acid reacted with the triorgano'in
¦¦ compo~nd~ It is preferabl~ to u~e between a 10 and 50~ exces~
¦1 o~ de~ydrating agent over this theoretical amount. Using any
1~ i
Il I
I I _, 4 _ !
514~ I
I
I larger exces~ would add to the cost of the procesx without any
¦l ~ignificant corresponding increase in efficiency or rate of the
dehydration step
I The reaction be~ween the acid and the triorganotin
~ compound can be conducted in any organic liquid wherein the
reactants and product are soluble. It is often desirable to
prepare the monomer in the soLvent in which it will subsequently
be polymerized. If the polymer i8 to be incorporated into a
paint, it is often desirable to prepare the monomer in mineral
spirits, a mixture of liquid hydrocarbons.
An unexpected advantage resulting from use of the
present dehydrating agents is that triorganotin derivatives of
unsaturated acids can be prepared without any solvent or diluent
¦ Heretoore, it has usually been necessary to include a liquid
¦ hydrocarbon that formis an aæeotropic mixture with water in order
to remove the water and dissipate the heat input required to
effect a continuous distillation. The operability of the 3
present method in the absence of a solvent make~ it possible
to decrease the volume of material required to react a given
~mcunt of acid with a triorganotin compound, thereby increasing
volume efficiency and reducing processing costs. Moreover,
certain organic liquids such as mineral spirits, in which it
m~y b~ desired to subsequently polymerize the present tri-
organotin compounds~ may be unsuitable for preparing the monomer
1l using prior art methods requiring removal of water by distillation,
since the hydrocarbon will not form an azeotropic mixture with
water In these instances the monomer must be separated from
the 801vent in which it is prepared and subsequently combined
with the polymerization medium Usually the a~orementioned
separation entails distilling the reaction mixture solvent.
The prolonged heating required to effect such a distillation may
initiate a spontaneOus exothermic polymerization of the monomeric
triorganotin compound.
In accordance with a generally preferred method of this
invention, one or more unsaturated mono- or polycarboxylic acids
are combined with a stoichiometric amount of one or more
triorganotin hydroxides of the formula RlSnOH or the corresponding
bis (triorganotin) oxides of the formula (R3Sn)20, wherein Rl
represents an alkyl radical containing from 1 to 20 carbon atoms,
or a cycloalkyl, aryl, aIkaryl or aralkyl radical containing up
to 20 carbon atoms. The reaction can optionaIly be conducted in the
presence of a suitable organic solvent, as discussed hereinbefore.
When the unsaturated acid is acrylic or methacrylic acid, the
reaction between the acid and the triorganotin compound is often
exothermic and may not require external heating. If desired the
reaction vessel can be cooled by placing it in an ice-water mixture
or other suitable low temperature environment to maintain the reacting
mixture at a temperature of between 0C. and ambient temperature.
Cooling is considered optional, since neither the quality or yield
of product w~ere adversely affected when the temperature of the
reaction mixture spontaneously rose to as high as 57C. due to heat
generated by the exothermic reaction.
The ethylenically unsaturated acid that is reacted with
a triorganotin compound in accordance with the method of this
in~ention is advantageously of the general formula R2(COOH)n wherein
R is a monovalent or divalent hydrocarbon radical containing from
2 to 20 carbon atoms and a double bond between 2 adjacent carbon
atoms that do not form part of an aromatic ring s~ructure, such as
a phenyl ring. The subscript n represents the integer 1 or 2,
and is also equal to the valence of R O In a preferred
51~
embodiment of the present method n is 1, i.e. the acid is a mono-
carboxylic acid, and R is a radical of the formula H2C=CH- or
H2G=C(CH3)-, which corresponds to acrylic acid dnd methacrylic
acid, respectively. Other suitable ethylenically unsaturated
monocarboxylic acids include crotonic, isocrotonic, 3-butenoic,
oleic, l-cyclohexene-l-carboxylic, and cinamic acids, in addition
to unsaturated acids such as abietic acid that are extracted from
rosin and other natural products.
Dicarboxylic acids containing ethylenic unsaturation
include maleic, fumaric, citraconic, itaconic and the isomeric
tetrahydrophthalic acids, among others.
The reaction between the triorganotin compound and un-
saturated acids other than acrylic, methacrylic, maleic or
fumaric acids may be relatively slow, particularly if the acid
is sterically hindered. In these instances it may be necessary
to heat the mixture slightly, i.e. to a temperature between 30
and 50 & ., to achieve a useful reaction rate while avoiding
polymerization of the unsaturated acid.
Using the preferred acrylic or methacrylic acid, the re-
action with the triorganotin compound is substantially complete after
only several minutes at ambient temperature. The yield of desired
product is usually greater than 90% of the theoretical value.
The triorganotin reagent employed in the method of
this invention is a triorganotin hydroxide or a bis (triorgano-
tin) oxide wherein the three hydrocarbon radicals bonded to the
tin atom contain from 1 to 20 carbon atoms. The radicals can
advantageously each be alkyl, cycloalkyl, aryl, alkaryl or aralkyl.
If the polymer which is ultimately prepared from the monomeric
products of the present method is to be employed to
~5~4~ ~
I control undesirable organisms às taught in U.S. Patent
¦l 3,167,473, the radicals represented by R are preferably
propyl, butyl, cyclohexyl or phenyl radicals. The choice of
Ij radicals for R will be in large measure determined by the
¦I desired end use for the ultimate polymer.
i Polymers wherein the R radicals are other than
propyl, butyl, cyclohexyl or phenyl are useful in numerous
applications, including catalysts for many types of reactions,
¦ antioxidants for rubber, and as additives for oils and other
products.
The three R radicals are preferably identical, but
need not be so. Synthetic methods for preparing both sym-
metrically and asymmetrically substituted triorganotin oxides
Il and hydroxides are sufficiently disclosed in the chemical and
li patent literature that a detailed discussion of this subject
¦ is not required as part of the present specification.
, The dehydrating agent is preferably added following
completion of the reaction between the unsaturated acid and
the triorganotin compound. If the dehydrating agent is present
during this reaction, product yleld may be decreased due to
adsorptlon or absorption of the reagents by the solid de-
hydrating agent. The contact time between the drying agent
and reaction mixture should be at least several minutes to
¦ ensure that most, if not all, of the water reacts with or is
! adsorbed by the dehydrating agent. Agitating the mixture of
, dehydrating agent and reaction product together with a liquid
organic diluent, if present, is desirable since this maximizes
~i -the area of contact between the solid dëhydrating agent and the
~i liquid reaction mixture, thereby accelerating the rate at which
¦I water is removed from the liquid phase by the dehydrating agent.
I
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The following examples disclose preferred embodiments
of the present invention and should not be regarded as limit-
ing the scope of the method defined in the accompanying
Claims. All parts and percentages are by weight.
S ll EXAMPLE l
1i This example demonstrates the effect of reaction
¦l temperature on the yield of tributyltin methacrylate prepared
using the method of this invention.
~ A). An 86.l g. portion of methacrylic acid contain-
j ing lO0 parts per million of p~methoxy phenol as a polymeri-
zation inhibitor was gradually added over a lO minute period
¦ to 298 g. of bis-tri-n-butyltin oxide (TBT0). Prior to
addition of the acid, the TBT0 was cooled to 5C. by im-
ll mersing the reaction vessel in an ice-water mixture. The
lS 1~ reaction mixture was stirred and cooled during addition of
the acid, and the temperature of the reaction mixture increased
to 20C. Stirring was continued for five minutes following
completion of the acid addition, at which time 25 g. of
anhydrous magnesium sulfate were added to the reaction mixture.
The resultant two phase mixture was stirred ~or lO minutes
1 and filtered to separate the solid and liquid phases. The
¦ latter was a slightly off-white mobile oil equivalent to a
90% yield, based on TBT0. It was assumed that additional
1~l product was entrapped by the solid phase.
,1 A potentiometric titration of the reaction product
, revealed no free TBT0 and 0.65% of free methacrylic acid.
, The product was found to contain 0.33% water, as determined b~
¦ Karl Fisher analysis, and 31.2% tin (calculated tin content
!~ _9_
!l I
I
. I
i. l
~C~S~4
for tri-n-butyltin methacrylate = 31.7%). The acid number
of the product was 148 (calculated value = 149.5). The
product dissolved in methanol to yield a clear solution,
j, indlcating that no polymer was present.
5 ' B). The procedure described in part A of this
example was repeated using the same amounts of TBT0 and
Il methacrylic acid. The temperature of the reaction mixture
il was allowed to reach a maximum of 28C. during the addition
I of the methacrylic acid, following which 20 g. of anllydrous
l~l magnesium sulfate were added. After being stirred for 30
¦~ minutes, the liquid phase was separated ~rom the resultant
mixture to yield 353.4 g. (94.2% yield) of an off-white oil
¦ that upon analysis was found to contain 31.05% tin, 0.35%
I water, 0.90% free methacrylic acid and no free TBT0. The
l acid nurnber of the product was 148.57.
C). Tributyltin methacrylate was prepared using
the general procedure described in part A of this example
using twice the amounts of TBT0 and methacrylic acid specified
in part A. The reaction vessel was not cooled either prior
to or during the addition of methacrylic acid, which was
added in two portions of approximately 100 cc. each. The
¦I temperature of the reaction mixture increased to 49C.
t following addition of the first portion of acid and reached
i a maximum of 57C. during addition of the second portion.
A 40 g. portion of anhydrous magnesium sulfate was then
added, the resultant two-phase mixture stirred for one hour
and the solid phase removed by filtration to yield 723 g.
1 ~96.4% yield) of an off-white oil which was completely miscible
¦I with methanol. The reaction product contained 30.2% tin,
l; ;
il I
., 11
I
l I
- i
~51~44 ` `
o .21% water and no free TBT0 or methacrylic acid. The acid
number of the product was 152.6.
EXAMPLE 2
!
Il This example demonstrates the use of anhydrous
calcium sulfate. Although this salt does not have the same
water capacity for a given weight as anhydrous magnesium
sulfate, it is more effective in reducing the water content
! of the product.
A). A 172.2 g. portion of methacrylic acid was
1l gradually added over a five minute period~with stirring, to
' 596 g. of TBT0 which had been cooled to 10C. The temperature
¦ of the reaction mixture increased to 36 C . during the addition
¦ of the acid. When the addition was completed, 20 g. of an- !
l hydrous magnesium sulfate were added and stlrring continued
I for 15 minutes. The mobile oil obtained following separation
¦¦ of the solid phase weighed 737.7 g. (equivalent to a yield of
~! 98.3%, based on TBT0) and contained 0. 75% water. The
relatively high water content indicated that 20 g. of an-
hydrous magnesium sulfate was insufficient to absorb all of
the water present in the tributyltin methacrylate. When
this product was combined with 20 g. of anhydrous calcium
jl sulfate and the mixture stirred for30 minutes, the water
content was reduced to 0.44%.
I B). A reaction vessel equipped with a thermometer~
' nitrogen inlet, agitator and condenser was charged with 225 g.
of mineral spirits and 596 g. of TBT0. The solution was
~, purged with nitrogen for 15 minutes following which 17.0 cc.
,~ of methacrylic acid were added dropwise over a 30 minute period,
¦¦ durlng which time the temperature rose from 23C to 27C.
~ ~5~44~
The cloudy reaction mixture was then agitated for
an additional 30 minutes after which 9 g. of anhydrous
magnesium sulfate was added. After agitating for an additional
~j 30 minutes, the mixture was filtered.
S ` The liquid phase weighed 289 g. and was found to
Il contain 0.2% water. An aliquot of the solution was then
¦~ stirred with 10 g. of anhydrous calcium sulfate for 2 hours,
refiltered and analyzed for water content.
l! Found - 0.02% water
!l %Free TBT0 - none found
¦ %Free Methacrylic Acid - none found
EXAMPLE 3
This example illustrates the problems that can
occur when triorganotin derivatives of unsaturated acids
lS are prepared using a prior art method.
A reaction vessel was charged with 5961 g. (10 moles)
Or TBT0, 1722 g. (20 moles) of methacrylic acid containing
100 parts per million of p-methoxy phenol as a polymerization
inhibitor, and 8 liters of heptane. The contents of the
reaction vessel were stirred while under a partial vacuum
(39-65 mm. of mercury) to remove the water formed as a by-
product of the reaction. An azeotropic mixture of water
and heptane was collected in a trap which permitted return
of the heptane to the reaction vessel. The contents of the
vessel were heated to maintain the liquid phase at a tem-
perature of 34C. throughout the distillation, which was
continued until the theoretical amount of water collected
,1 in the trap. The solution in the reaction vessel was miscible
Il with methanol to yield a clear solution, indicative of no
~ ollgomer or polymer formation. An attempt to separate the
~ -12-
' 11 , "~ I
., - , .
li~?~
I tributyltin methacrylate from the heptane by distillation
,~ yielded a rubbery polymer, even though the temperature of
' the mixture did not exceed 23C. during the distillation.
.1.
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