Note: Descriptions are shown in the official language in which they were submitted.
Solution Polymerization of Acrylic Acid Derived Monomers
Using Tertiary Alkyl(~C5)Hydroperoxides
(IR 2785)
Background of the Invention
This invention relates ~o an improved process for
polymerizing monomers derived from substituted or
unsubstituted acrylic acid/methacrylic acid and esters
thereof using an initiating amoun~ of a tertiary alkyl
hydroperoxide having~at least -five carbons and/or its
derivatives wherein the polymer product has a low
molecular weight and a narrow molecular weight distribution
suitable for high solids coating applica:tions.
G'~
~ - .
': :
.
- : : '.. . .
' ~ ~
. ': ~ '-'
: ' ,
There is a need in the coatings industry to develop
polymers which possess a narrow molecular weight distribution
- ~MWD) for use in high solids coating formulations. Such
polymers must no-~ only have a low molecular weight and a
S low viscosity in order to produce a sprayable solution, but
must also contain chemically active groups (usually hydroxyl
or carboxyl functionality) in order to undergo molecular
weight build up and network formation during the cross-
linking (i.e., curing) reaction. A more uniformed,
homogeneous crosslinked network can be produced if the
polymer possesses a narrow molecular weight distribution
(MWD). Hence, a narrow MWD improves overall film
properties and influences ~he viscosity of the coating
solution. Therefore, it is desirable for polymers used in
lS high solids coating formulations to be of low molecular
weight and to possess a narrow MWD.
Free radical solu~ion polymerization is the most widely
used commercial proc~ss for the preparation of polymers
suitable for use in high soLid coating ormulations.
Aæonitrile compounds, especially symmetrical azonitrile
compounds, are currently being used as the free radical
source in the industry for producing polymers suitable as
high solids coating resins by solution polymerization
technique. Azonitrile initiators generally produce much
narrower M~D polymers in comparison to conventional organic
peroxide ini~iators. (Conventional organic peroxides are
.,
- 3 -
primarily derivatives of tertiary butyl hydroperoxides).
By the ability of the azonitrile compounds to produce n~rrow
~WD polymers, this makes azonitrile compounds preferred
initiators for high solid coating resin production.
Although tertiary alkyl peroxide having at least five
carbon atoms are known in the prior art, no publication was
found which discloses the use of these peroxides for
producing polymers having a narrow molec~llar weight
distribution which polymers will be suitable in high solids
coating formulations. U.S. Patent Nos. 3$686~102, 3,950,432,
and 4,137,105 discloses the use of ~ertiary amyl(C5) and
tertiary octyl (C8) peroxides as free radical initiators for
vinyl polymerization. Also, U.S. Patent No. 4,130 9 700
discloses the use of tertiary amyl diperoxyketals as
finishing catalysts to reduce residual styrene levels fo~
the bulk polymerization o~ styrene.
Summa~y of the Invention
The present invention is directed to an improved
process for the production of polyme.rs suitable for high
solids coating applications. This process comprises
solution polymerizing monomers derived from substituted or
unsubstituted acrylic acid or methacrylic acid or esters
thereof in a temperature range of from about 90 to 200C in
the presence of a solvent suitable for high solids coating
applications and in the presence of an initiating amount of a
. :
.
~. ~4~
tertiary alkyl hydroperoxide having at least five carbons
and/or its derivatives. The derivatives of the hydroperoxide
are selected from peroxyketals, dialkylperoxides, peroxyesters,
and monoperoxy-carbonates. The polymer product has a narrow
MWD and an average molecular weight of 4000 or less.
Detailed Description of the Invention
I. Polymerization
Polymers suitable for high solids coatin~ applications
are prepared by solution polymerization in which select
monomers are blended with solvent, polymerization
initiator(s), aad, optionally, a chain transer agent, and
heated to about 90~200C for 1-10 hours.
Low solvent to monomer (s/m) ratios are used to co~uct
the polymerization in.order to achieve the desired high
solids content required for high solids coating applications,
typically, 25 to 90% solids by weight. The solvent to
monomer ratios generally used are in the range of (3/1) to
(O.1/1).
In order ~o give low viscosity, sprayable solutions with
high solids contents, the polymer's molecular weight has to be
very low. The normal number~average molecular weight (Mn) is
o the order of 4000 or less.
A preferred method~ for preparing the low molecular weight
polymers suitable for high solids coating applications is a
~ - s - ~
~ 6 ~
programmed addition of monomers and initiator(s) at a given
rate into a polymerization vessel containing solvent at the
desired temperature and/or refluxing temperature. Monomer(s)
and initiator(s), alone or in combination, are metered into
reaction solvent at a rate such that the addition time is
about 1-12 hours, preferably 3-10 hours. When the monomer
and initiator are metered separately, the rate of addition of
the two can be the same or different. Typically, at the end
of the monomer/initiator additiong the percent conversion of
monomer to polymer attainable is about 90-95/O or better.
The percent residual monomer(s) at ,the end of the
monomer/initiator addition is generally about 1.0% or higher.
It is desirable to have percent residual monomer(s) levels of
0.1% or less. This can be accomplished by adding
initiator(s) and further polymerization time. This step is
frequently called "chaser catalyst" in the ar~; In the
practice of this invention, it is preferred to use
ter~iary-alkyl (> C5) hydroperoxide derivatives as chaser
catalysts. The chaser catalyst employed can be the same
or different as the one used in conducting the
polymerization. The use of the tertiary-alkyl (> C5)
hydroperoxide derivatives of the present invention as
chaser catalysts results in a reduction in the percent residual
monomer(s) to 0.1% and less without any adverse effects on
polymer molecular weight and MWD.
",
: .
.
II. Monomers
Another requirement of a high solids coatings resin,
other than low molecular weight, is it must contain
chemically active groups (usually hydroxyl or carboxyl
functionality) in order to undergo molecular weighL buildup
and network formation during the final crosslinking (curing)
reaction where compounds such as melamine are used as the
curing agents. Polymers suitable for use in high solids
coating formulations, normally, have a hydroxyl content of
from about 2 to about 7% by weight. To prepare a polymer
which has a hydroxyl content of about 2-7% by weight, a
sufficient amount of hydroxyalkyl acryla~e or me~hacrylate
is used (normally, 20-40% by weigh~ of the monomer
composition).
Examples of hydroxyalkyl acrylates and methacrylates
that can be used to prepare polymers suitable for high
solids coating applications include: 2 hydroxyethyl
acrylate, 2 hydroxypropyl acrylate, 2-hydroxybutyl acrylate,
2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,
2 hydroxybutyl methacrylate, 3 hydroxypropyl acrylate,
4-hydroxybutyl acrylate, and the like.
Examples of alkyl acrylates and methacrylates
that can be used to prepare polymers suitable for high
solids coating applications include: methyl methacrylate,
ethyl me~hacryla~e, butyl methacrylate, isobutyl metha-
,
. . .
~ - 7 - .~
crylate, hexyl methacryla~e, 2-ethylhexyl methacrylate,
lauryl methacrylate, ethyl acrylate, propyl acrylate,
isopropyl acrylate, butyl acrylate, isobutyl acrylate,
hexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate,
and the like.
Other monomers, such as, styrene, para-methyl styrene,
acrylic acid, methacrylic acid, or vinyl acetate, can also
be used in the preparation of polymers suitable for high
solids coating applications (i.e. to control monomer costs
and/or to obtain a balance of film proper~ies).
Adhesion promoting monomers can also be used in the
preparation of polymers suitable for high solids coating
applications, such as diethylaminoe~hyl methacrylate,
di-methylaminoethyl methacrylate, tertiary-butylaminoethyl
methacrylate, 3-(2-methacryloxyethyl)-2,2-spirocyclohexyl
oxazolidene, and the like.
IIIo Solvent
Examples o~ solvents which are used to prepare polymers
suitable for high solids coating applications include:
toluene, xylene, ethyl acetate, acetone, methyl ethyl
ketone, methyl n-amyl ketone, ethyl alcohol, benzyl alcohol,
oxo~hexyl acetate, oxo--heptyl acetate, propylene glycol methyl
ether acetate, mineral spirits, and other aliphatic, cyclo-
aliphatic and aromatic hydrocarbon, esters, ethers, ketones,
and alcohols which are conven~ionally used. Commercially, the
primary considerations in the selection of a suitable solvent
'
-- 8 --
are cost, toxicity, flammability9 vola~ y, and chai~-transer
activity.
XV. Polymer
An Example of a polymer suitable for hi~h solids coating
applications contains 30% by weight methyl methacrylate or
para-methyl styrene, 40~ by weight isobutyl methacrylate,
and 30% by weight hydroxyethyl methacrylate. Other useful
polymers would comprise about 10-30% by weight styrene,
30-60% by weight butyl methacrylate and/or acrylate, and
20-40~ by weight hydroxyethyl methacrylate and/or
acrylate; the polymer should have a number-average
molecular weight (Mn) of the order of 4,000 or less.
V. Molecular Wei~ht and Molecular Weight Distribution
Molecular weight averages of a discrete distribution of
molecular weights can be defined by the generalized
expression:
M = (~ NiMi )/(~ MiMia 1)
where Ni indi6ates the number of molecules wi~h a molecular
weight, Mi, and where the parameter a is a weighing factor.
Those molecular wei~ht averages that are important in
determining polymer properties are the number-average
Mn ~a = 1), the weight-average Mw (~ = 2), and the Z-average
Mz (a = 3), where Mn < Mw ' Mz .
A measure of the breadth of the distribution of
molecular weights can be given by the ratios (M ~ Mn) and
(Mz/Mn). A high (M ~ Mn) ratio indicates the presence of a
. ., ~
- , . ,. :.
. ~ :
. ~
low molecular weight tail and a high (Mz/MN) ratio indicates
the presence of a high molecular weight tail in the distribution.
The molecular weight distribution (MWD) of a polymer is
one of i~s most fundamental characteristics. ~low
5 properties, reactivity, cure characteristics, hardness,
strength, and various other mechanical properties are all
influenced by the MWD. Also, it is observed ~hat
performance-oriented criteria (such as environmenta] stress,
crack resistance, and permeability to gases and liquids)
heavily depend on the MW~.
Broad M~D polymers (i.e., high (MW/Mn) and (Mz/Mn)
ratios) are unsuitable for high solids coating
applicationsO It is desirable for polymers used in high~
solids coating~ formulations to possess a narrow MWD (i.e.,
(Mw/Mn) and (Mz/Mn) ratios).
The primary goal of high solids coatlngs technology is
to increase the solids (i.e., polymer) content (i.e., reduce
the amount of solvent in the system) while maintaining (or
even reducing) the solu~ion ~iscosity. The solution
viscosity is strongly influenced by the MWD of the polymer,
particularly the (Mz/Mn) ra~io. A narrow MWD polymer (i.e.,
low (Mz/Mn) leads to lower solution viscosity. Thus, a
narrow ~WD results in voc-compliant coatings (i.e.,
voc-volatile organic compounds) having low viscosity at high
solids, superior sprayability (even with conventional air
. ~
. ' :~' '
- 10 -
spray at room temperature) and easier control of film
thickness.
Narrow l~WD also provides a more homogenous cross-linked
network in the final cure/bake cycle (i.e., improves overall
film properties). Narrow MWD results in freedom from
non-functional or mono-functional dimers and trimers which
compromise resistance properties 3 cause oven condensation,
and contribute to sagging. It is the intent of this
invention disclosure to teach the use of certain organic
peroxides (i.e., tertiary-alkyl with five or more carbons)
as polymerization initiators to produce low molecular weight
functional polymers suitable for high solids coating
applications which possess a narrow MWD.
A low molecular weight polymer in the practice of this
invention is defined as having a number-average molecular
weight (Mn) of 500 to 4,000. ~ narrow MWD in the practice
of this invention is defined as having a (MW/M~) ratio of 1.5
to 3.0 and a (Mz/Mn) ratio of 2.0 to 5.0~ preferably a (M ~Mn)
ratio of l.S to 2.5 and a (Mz/M~) ratio of 2.0 to 4Ø The
polymer molecular weight,(M~ Mw, and Mz) we-re determined
by standardized gel permeation chromatography (based on
narrow MWD polystyrene calibration).
While molecular weights and MWD of polymers can be
measured by many different methods (e.g.~ vapor phase
osmometry, ultracentrifugation, and light scattering), the
method used in ~he practice of this invention (gel
:
permeation chromatography) is particularly preferred. Gel
permeation chromatography (GPC) is the most widely used
method within the polymer industry to measure the molecular
weights and MWD of polymers. The advantages o~ using (GPC)
for measuring the molecular weights and MWD of polymers
are: (1) moderate cost, (2) fast analysis time, (3)
e~cellent reproducibility of results, (4) can be applied to
a wide variety of solvents and polymers, (5) can be applied
to a wide range of molecular weights, and (6) good agreement
of results, particularly MWD, with results obtained from
other techniques.
VI. Initiators
The tertiary alkyl (> C5) peroxide initiators used in
the practice of this invention are those that have one hour
half-life temperatures in the range of 50 to 190C.,
preferably ~hose in the range of 60 to 170C; (half-life
is defined as the time it takes for one half of a given
quantity of peroxide in dilute solution (i.e;, typically,
0.2 molar in a solvent such as dodecane or toluene) to
decompose).
The initiator concentra~ion used in the practice of
this invention is in the range of about 0.50 to about 10.0
parts by weight per 100 parts of monomer, preferably about
2.0 to about 5.0 parts by weight per 100 parts of monomer.
High initiator concentration facilitates the production of
the desired low molecular weight polymer. Also, high
.
~ ` ~
- 12 -
initiator concentration facilitatas the production of the
desired narrow M~D. A mixture of two or more tertiary-
alkyl (~ C5) peroxides can also be used in the practice of
this invention. Also, a combination of two or more
initiators can be used wherein at least one is a tertiary-
alkyl (~ C5) hydroperoxide`and/or its derivative.
The tertiary-alkyl (> C5) hydroperoxides and/or
derivatives of said hydroperoxides employed in the practice
of this invention as polymerization initiators are of the
formula:
(ROO)nR
where n is 1 or 2, and when n is 1,
R is selected from t-alkyl of 5-20 carbons, t-cycloalkyl of
6-20 carbons, and
R2
Ar-l- where
~3
R2 is selected from lower alkyl of 1 6 carb-ons,
R3 is selected from alkyl of 2-6 carbons, and
Ar is selected from aryl of 6-12 carbons; and
R1 is independently selected rom R, hydrogen, acyl of 2~18
carbons, aroyl of 7-18 carbons, or alkoxycarbonyl of 2-19
carbons; and
when n is 2,
Rl is selected from di-tertiary-alkylene of 7-20 carbons,
di-tertiary alkynylene of 8-20 carbons7 di-t-cycloalkylene
of 12-20 carbons, and
.~
- 13 -
l2 lR2
-C-Ar'-C-
S R2 R2
where R2 is as defined above and Ar' is selected from
arylene of 6-12 carbons,
R4
\C
10- R5/ \
where R4 and R5 are the same or different, alkyl of 1-10
carbons, cycloalkyl of S~10 carbons, cycloalkenyl of S-10
carbons, or aralkyl of 7-10 carbons, and R4 and R5 can join
together to form an alkylene diradical of 5 11 carbons,
- C - R6 ~1~
where R6 is selected from alkylene of 1-20 carbons,
_cycloalkylene of 5-12 carbons, arylene of 6-12 carbons,
20,
OR70 C
where R7 is selected from al~ylene of 2-20 carbons and
cycloalkylene of 5-12 carbons; and
R is selected from the same groups mentioned above when n = 1
and also can be hydrogen9 acyl of 2-18 carbons, aroyl of
7-18 carbons, or alkoxycarbonyl of 2-19 carbons when Rl is
selected from di-t-alkylene9 di-t-alkynylene,
di-t-cycloalkylene 9 or
, -'
- - : - ~. :- .,: :
,
r~ ~ 14 -
~2~j2~
l2 l2
-C-Ar'-C- and
R3 ~3
~ Rl, R2~ R3, R4, ~5~ R6~ R7, Ar, and Ar' can
optionally be substituted, wherein the substituents can be
one or more of lower alkyl (1-4 carbons), cycloalkyl of 5-12
carbons, halo, carboxy, hydroxy, lower acyloxy, epoxy, lower
alkoxy, aryloxy of 6-12 carbons, lower alkoxycarbonyl,
carbamoyl, mono and di lower alkyl carbamoyl, and
dicarboximido of 4-12 carbons; and Ar', R6 and R7 and when
R4 and R5 join together to form an alkylene diradical can
optionally con~ain one or more oxygen or nitrogen.
Representative examples of suitable tertiary-alkyl (> C5)
peroxide initiators used in the practice of this invention
include: -
~,l-Bis(~-amylperoxy)-3~3,5-trimethylcyclohexane, 1~1-
Bis(t-octylperoxy)-3,3,5 trimethylcyclohexane, l,l-Di-(t-
20 amylperoxy)cyclohexane, l,l-Di-(t-octylperoxy)cyclohexane, `~
2,2-Di-(t-amylperoxy~propane, 2,2-di-(t-octylperoxy)propane,
2,2-Di-(t-amylperoxy~butane, 2,2-Di-(t-octylperoxy~butane,
3,3-Di-(t-amylperoxy~pentane, 2,2~Di-(t-amylperoxy~heptane,
2J2-Di-(t-octylperoxy)heptane, n-Butyl 4,4-bis(t-amylperoxy~-
valerate, n-Butyl:4,4-bis(~-octylperoxy~valerate, Ethyl
3,3-di-(t-amylperoxy)butyrate; Ethyl 3,3-di-(t-octylperoxy)-
butyrate, Di-t-amyl peroxide:, Di-t-octyl peroxide,
2,5-Dimethyl-2,5-di-(t-amylperoxy)hexane, 2,5-Dim~thyl-2,5-
,
:
.
;
~ - 15 -
.
~ ?~
di-~t-octylperoxy)hexane, 2,5-Dimethyl-2,5-di-(t-amylperoxy)-
hexyne-3, 2,5-Dimethyl-2,5-di-(t-octylperoxy)hexyne-3,
t-Amyl peroxy-2-ethylhexanoate, t-Octyl peroxy-2-ethyl-
hexanoate, t-Amyl peroxybenzoate, t-Octyl peroxybenzoate,
t-Amyl peroxyisobutyrate, t-Octyl peroxyisobutyrate, t-Amyl
peroxyacetate, t-Octyl peroxyacetate, t~Amyl peroxy-
propionate, t-Octyl peroxypropionate~ Di-t-amyl diperoxy-
azelate, ~i-t-octyl diperoxyazela~e, di-t-amyl diperoxy-
phthalate, Di-t-octyl dlperoxyphthalate, OO-t-Amyl 0-(2-
ethylhexyl) monoperoxycarbonate, OO-t Octyl 0-(2-ethylhexyl)
monoperoxycarbonate, OO-t-amyl O~isopropyl monoperoxy-
carbonate, OO-t-Octyl O-isopropyl monoperoxycarbonate, 0,0'-
Ethylene bis(OO-t-~amyl monoperoxycarbonate), O,O'-Ethylene
bis(OO~t-octyl monoperoxycarbonate), O,O'-Hexylene bis(OO-t-
amyl monoperoxycarbonate~, O,O'-Hexylene bis(OO-t-octyl ~
monoperoxycarbonate), O,`O'-(Oxybisethylene) bis (OO-t-amyl
monoperoxycarbonate), O,O'-(Oxybisethylene) bis(OO-t-octyl
monoperoxycarbonate)~ (etc.).
: :, ., ~
:
`'` ~ . ~-
-\ - 16 -
Examples
Definitions of Materials Used in the Examples
~MA - Methyl methacrylate monomer (inhibited
10 ppm MEH ).
S IBMA - Isobutyl methacrylate monomer.
H~YA - 2-Hydroxyethyl methacrylate (practical).
PMS - Para-methylstyrene monomer.
AEl~A - Dimethylaminoethyl methacrylate.
MAK - Methyl n amyl ke~one (2-heptanone).
t-Octyl - 1,1,3,3-tetramethylbutyl (C8).
Vazo~ 67 ~ 2,2'-Azobis(methylbutyro~itrile), from
DuPont Corp.
Vazo~ 88 - l,1'-Azobis(cyclohexanecarbonitrile),
from DuPont Corp.
15 ' Lupersol~331- l,l'-Di(t'-butylperoxy')cyclohexane,
marketed by the Lucidol Div. of Pennwal-t
Corp .
Lupersol~531- 19 l-di(t-amylperoxy)cyclohexane, marketed
by the Lucidol Division of Pennwalt
Corpora'cionO
Lupersol~553- 2,2-Di(t-amylperoxy)propane, marketed
by the Lucidol Div. of Pennwalt Corp.
Lupersol~520- 2,2-Di-(t-amylperoxy)butane, marketed by
the Lucidol Div. of Pennwalt Corp.
:
' ..,
,,,
- ~ . .: ...
~ 17 -
Lupersol~233- Ethyl 3,3-di(t-butylperoxy)butyrate,
mar~eted by the Lucidol Div. of Pennwalt
Corp.
Lupersol~533- Ethyl 3,3-di(t-amylperoxy)butyrate,
marke~ed by the Lucidol Div. of Pennwalt
Corp.
Dowanol~PMA - Propylene glycol methyl ether acetate,
from the Dow Chemical Company (Midland,
Michigan)
10 BA - Butyl acrylate monomer.
BMA - Butyl methacrylate monomer.
HEA - 2-Hydroxyethyl acryla~e monomer.
Lupersol~TBEC~ OO~t~bu~yl 0-(2-ethylhexyl)monoperoxy-
carbona~e, marketed by the Lucidol ~
Division of~Pennwalt Corp.
Lupersol~TAEC 00-t~amyl 0-(2-ethylhexyl)monoperoxy-
- carbonate, marketed by the Lucidol
Division of Pennwalt Corp.
E~YXATE~700 - oxo-heptyl acetate, from E~xon Chemicals
2Q Corp.
PHM - parts~per hundred parts monomer(s),
PHR - parts per hundred parts resin.
:.. ..
-: ~
E~YAMPLE 1
This example illustrates ~he performance of
conventional tertiary-butyl peroxides in comparison to
peroxides derived from tertiary-alkyl hydroperoxide with
five carbons (i.e. tertiary-amyl peroxides) with respect
to polymer molecular weight, MWD, and polymer solution color.
i) Preparation of Polymer
300 gO of methyl n-amyl ketone is heated to 145C
in a jacketed glass reactor equipped with a
stirrer, thermometer, reflux condenser, and
nitrogen gas sparging 1ine. A mixture
of (a) 40 g. l~MA, (b) 53 g. IB~A, (c) 40 g. HEMA,
and (d) initiator is added uniformly at a rate of
25 g. per hour to the refluxing solvent for four
hours. After the monomer/initiator addition 1s
completed, polymerization is continued further for `
one hour.
ii) Polymer Molecular Weight and MW~ Analysis
The ~olymer molecular weight and distribution was
determined by standardized gel permeation
chromatography (based on narrow ~WD polystyrene
calibration). The reported molecular weight and
distribution include Mn, (Mw/Mn), and (Mz/Mn).
.~ .
''' ~
.
.
~ ~ \
, ~ - 19 -- . ~
Precision of the e~perimental determinations made
is on the order of 5% maximum standard deviation
for Mn and 10% maximum standard deviation for
(Mw/Mn) and (Mz/Mn~.
The polymer molecular weight and MWD results were determined
as follows:
1) Mode: Gel permeation chromatography
2) Unit: Waters Associates ALC-GPC 244 with Model 6000A
solvent delivèring system
3) Detector: Waters Model R401 Refracting Index Detector.
4) Columnso Wa~ers Ultra-StYrag~l 104 A, 103 A, and two
500 A columns.
S) Solvent: THF (tetrahydrouran).
6) Polymer solution concentration 0.5% by weight.5 7) Calibration: TSK narrow MWD polystrene standards
(range 500 106 Mw).
8) Data handlingo Varian Model 401 chromatography data
system interfaced with an Apple- II+
(Varlan GPC Software).
iii) Pol~mer Solution Color Determination
Polymer solution color was determined by APHA
color values based on a color test (ASTM-D2849)
scale of 5 to 500, in increments of 5.. The lower
~ ~ .
: ' ''' ~ ':
'
~ 20 -
the APHL~ color value, the le~s colored the
solution.
able 1
Moles x 103 / _APHA
Initiator (1) 100 parts Monomer Mn (Mw/Mu) (Mz/Mn) Color
t-Butyl Peroctoate 9.3 4,100 2.6 4.6 100
t-Amyl Peroctoate 8.7 3~300 2.1 3.3 70
Di-t-butyl diperoxyazela~e 6.0 2,300 3.6 6.7 40
Di t-amyl diperoxyazelate 5.5 2,500 2.7 4.5 25
Lupersol TBEC 8 1 39500 2.6 4.830
Lupersol TAEC 7.7 3, 8ao 2.5 4.0 15
Di-t-butyl peroxide 13.7 2,600 2.4 5.040
Di-t-am~l peroxide 11.5 2,400 2.1 3.8~ 30
Lupersol~ 331 7.7 49400 3.3 9.570
Lupersol~ 531 6.9 39000 2.3 3.530
.
(1) The.initiators were used a~ a level of 2.0 g. per 100
g. of m~omer9 after correcting for a~y assay
differe~ces.
As shown in Table 1, a significant improveme~t in the
molecular weight distribution (i.e.Mw/Mn and Mz/Mn ratios)
is evident with the use o t-amyl analog peroxides in
comparison to their corresponding conventlonal
t-butyl analogs. Also, ~he results in Table 1 show that
polymer solution color (~PHA) is better using t-amyl analog
peroxides.
,;:,.
:., , : .: . .
. .
, - ~ .. ` :
- 21 -
a~
Further~ the results obtained with the t-amyl analogs
indicate an increase in molar efficiency. Lower molecular
weights were obtained with the t-amyl peroxides, even-by
using less moles of initiator. On the basis of standard
free radical kinetics, it is well known that polymer
molecular weight decreases with increasing initiator
concentration. In view of this, the molecular weight
results in Table 1 are quite unexpected. This is readily
apparent when the initiator concentration is expressed in
moles per 100 parts by we1ght of monomer (see Table 1).
Example 2
This example illustrates the performance of conventional
tertiary-butyl peroxides in comparison to peroxides
derived from tertiary-alkyl hydroperoxide with eight carbons
lS (i.e. tertiary-octyL peroxides) with respec~ to polymer
molecular weight and distribution (MWD).
The procedure was\the same as that used in Example 1.
~. ,
. ~, .
- 22 -
.
Table 2
Initiator Mn (Mw/Mn? (lYæ~Mn~
Di-(t-butylperoxy)propane(1) 2,400 2.5 3.8
Di-(t-Octylperoxy)propane2,800 2O1 3.1
t-Butyl hydroperoxide(2)6,600 2.1 3.9
t-Octyl hydroperoxide 4 9 500 2.0 3.1
The initiators were compared on an equal molar basis, after
correcting for any assay differences.
(1) A concentration level of 9.1 x l0 3 moles per 100 g. of
monomer was used.
(2) A concentration level of 19.2 x 10 3 moles per 100 g.
of monomer was used.
As shown in Table 2, an improvement in ~he molecular
weight distribution (MWD) was also evident with the use of
t-octyl peroxides in comparison with their corresponding
.
conventional t-butyl analogs.
Example 3
This example illustrates the performance of azonitrile
initiators (Vazo~) versus the preferred teritary-
alkyl peroxide initiators of the present invention (i.e.tertiary amyl peroxyketals) with respect to polymer
molecular weight, MWD, and polymer solution c~lor.
A) The procedure was the same as that used in
Example 1.
.. ~ . . -
.
- 23 -
Table 3A
Moles x 103/ _ APHA
Initiator(l) 100 parts monomer Mn ~Mw/Mn) (Mz/Mn) Color
Vazo~-67 10.4 2,200 2.3 3.5 100
Vazo~-88 8.2 4,800 2.0 3.1 200
Lupersol 533 6.25 2,200 2.0 3.0 35
Lupersol 520 7.6 2,900 1.8 2.7 60
(1) The initiators were used at a level of 2.0 g per 100 g.
of monomer, after correcting for any assay diferences.
B) The procedure was the same as ~hat used in Example l,
except xylene was used as the solvent in place of
methyl n-amyl ketone at a temperature of 135C.
Table 3B
Moles x 103/
15 Initiator(l) 100 ~arts monomer Mn (Mw/Mn) (Mz/Mn~
Vazo~-88 8.2 4,400 2.0 3.2
Lupersol~ 533 6~25 3~200 2.1 3.4
(1) The initiators were used at a level of 2.0 g. per 100
2 of monomer, after correcting for any assay
differences.
As shown in Tables 3A and 3B,.the polymer molecular
weight distribution obtained using certain tertiary-alkyl
(> C5) peroxides was comparable to, and in some cases narrower
than, that obtained using azonitirle initiators
(Vazo~). A comparison of the polymer molecular
" `
~ 24 ~
~L r~ Z~
weigh~s also showed that the molecular weights obtained with
the t-amyl peroxides were lower, even when using less moles o
initiator (regardless of the solvent used to conduct the
polymerization or ~he reaction temperature employed).
Further, the polymer solution color was lower using the
t-amyl peroxides versus the use of Vazo~ initiators.
Example 4
Commercially, the preparation of polymers suitable for
'
high solids coating applications is conduc~ed in solution at
low solvent to monomer ra~ios (i.e. solids contents of 60%
or greater). This example illustrates the performance of an
azonitrile initiator used commercially for the production of
high solids coatings resins (i.e. Vazo~67) versus an initiator
of the present invention with respect to polymer molecu~ar
15. weight, MWD, and % conversion of monomer to polymer achieved.
A low solvent ratio was employed; the theoretical percent of
solids attainable at 100% conversion is 63% by weight.
Procedure
- i) Preparation of Pol~mer
lS0 g. of Dowanol~ PMA (propylene glycol methyl
ether acetate) was heated to the specified reaction
temperature (see TabIe 4) in a jacketed glass
reactor equipped with a stirrer, thermometer,
reflu~ condenser, and nitrogen gas sparging line.
'
'~', . `
'.'~ , .
:~'- '.` ' '
..~
-"~ 2S -
A mixture of (a) 90 g. sytrene, (b) 90 g; BA, (c)
60 g. BMA, (d) 60 g. HEA, and (e) initiator was
added uniformly at a rate of 50 g. per hour to the
solvent for five hours. After the
monomer/initiator addition was completed,
polymerization was continued further for one hour.
ii) % Conversion Determination
.
The % conversion of monomer(s) to polymer achieved
was based on a gas chromatographic analysis of %
residual monomer(s) content by weight present in
solution after polymerization.
iii) Polymer molecular weight and MWD analysis were the
same as rhat used in E~ample 1.
' ~ :
- 26 -
~%~
Table 4
Initiator Lupersol~ 533 Va~o~-67
PHM, Pure Basis (1) 2.0 2.0 6.0
Mole~ x 103 per
i Hundred Parts Monomer(s) 6.25 10.4 31.2
Reaction Temperature, oC(2) 142 92 92
% Conversion Achieved 97 89 90
Mn 49000 16,000 5,800
(Mw/Mn) 2.1 2.1 2.1
~Mz/Mn) ~- 3.8 3.4 3.5
(1) PHM Parts per hundred parts monomer(s) by weight,
i.e., grams per 100 grams o monomer(s).
(2) The reaction temperature employed was based on the 20
minute half life temperture of the initiator.
lS As shown in Table 4, employing a reaction temperature
correspo~ding to ~he 20 minu~e half-l~fe of the initiato~,
significantly lower molecular weight (Mn) polymer production
is evident with an initiator of the present invention versus
an azonitrile initiator, even when three times as much of
the azo initiator is used on per weight basis. A comparison
of the polymer MWD (i.e., Mw/Mn and Mz/Mn ratios) shows that
the polymer MWD obtained with each initiator is essentially
the same. A comparison of the percent conversion achieved
for each initiator shows that higher conversion is obtained
with the peroxide initiator of the present invention versus
..
. .. .
~ :,
-
- ~7 -
,s~0~
the azo initiator, resulting in higher polymer productivity and
lower % volatiles present.
Example 5
This example illustrates the performance of an
5 azonitrile initiator (i.e. Vazo~-88) versus an initiator of
the present invention with respect to polymer molecular
wei ht, MWD, percent conversion, and sol-ution color. A low
solvent ratio was employed3 the theoretical percent of
solids attainable at 100% conversion is 77% `by weight.
Procedure
i) Preparation of Polymer
150 ~. of oxo-heptyl acetate solvent was heated to
145C in a jacke~ed glass reactor equipped with a sitrrer,
thermomet~r, reflux condenser, and nitrogen gas sparging
line. A mixture of (a) 180 g styrene, (b) 180 g BA, (c)
120 g BMA9 (d) 120 g HEA, and (e) initiator was added uniformly
at a rate of 100 g. per hour ~o the solvent for five hours.
After the monomer/initiator addition was completed,
polymeri2a-~ion was continued further for one hour.
ii~ Polymer molecular weight and MWD analysis were the same
as that used in Example 1.
iii) Percent Conversion was determined the same as Example 4.
iv) Solution color was determined the same as Example 1.
- 2~ -
.~f~
Table 5
Initiator(1) Vazo~-88 Lupersol~533
% conversion achieved 92/~/6 hrs. 92%/5 hrs.
Mn 6,000 4,800
(Mw/Mn) 2.3 2.0
(Mz/Mn) 4. 5 3 5
Solution color (APHA) 60 30
(yellow) (clear)
(1) Initiators were compared on an equal weight basis, 4.0 g
per 100 g monomer, after correcting for any assay
differences.
As shown in Table 5, ~he same percent conversion was
obtained in less time (5 hrs. vs. 6 hrs.~ with the initiator
of the present invention vs. the azonitrile initiator.
Also, lower molecular weight, narrower MWD, and lower
solution color was obtained with Lupersol~533 ~s. Vazo~-88
while employing a low solvent to monomer ratio. Thus, for
conducting polymerizations at low solvent to monomer ratios,
preferred initiators of the presen~ in~ention, specifically
Lupersol~533 would be favored over azonitrile initiators.
:
: '; ' :' '
' :.
- 2~ ~
Example 6
This example illustrates the relative performance of a
conventional tertiary butyl peroxide and its corresponding
tertiary-alkyl (>C5) analog with respect to polymer
molecular weight, MWD, and solution viscosity at a low
solvent to monomer ratio.
The procedure was the same as that used in Example 1,
except the amount o solvent (MAK) used to conduct the
polymerization was reduced (i.e., 150 g. of solvent was
used). Total solids contènt was 40% by weight.
i) Polymer Solug on Viscosit,y Measurement
Polymer solution viscosity at ambient temperature
(22C) was determined using a Brookfield V~scometer
Model #HBT with a Spindle ~HBl at a speed setting of
100 rpm.
Table 6
Initiator (~) Lupersol~ 233Lupers l~ 533
.
Mn 3'000
(Mw/Mn) 203 2.2
(Mz/Mn) 5.0 4.0
Polymer solids (wt %) 40 40
Solution Viscosity (cps) 96 80
(1) A concentration level of 6.25 x 10 3 moles per 100
g. o monomer was used.
. .
. .
- ~ .
~ 30 -
' ~
The initiators were compared on an equal molar basis,
after correcting for any assay differences.
Example 7
This example illustrates the relative performance of a
conventional tertiary-butyl peroxide and i~s corresponding
tertiary-alkyl (>C5) analog with respect to polymer
molecular weight, MWD, and solution viscosity employing a
low solvent to monomer ratio (S/M = 0.3/1). Total solids
content was 78% by weightO
Procedure
i) Preparation of_Polymer
150 g of oxo heptyl acetate solvent was heated to thè`
specified reaction -ternperature (See Table 7) in a jacketed
gla~s reactor equipped with` a stirrer, thermometer, ref~ux
1.5 condenser, and nitrogen gas sparging line. A mixture of (a) .
180 g styrene, (b) 180 ~ BA9 (c) 120 g BMA, (d) 120 g HEA,
- and (e) ini~iator was added uniformly a~ a ra~e of 100 g per
hour to -the solvent for five hours. After the
monomer/initiator addition was completed, polymerization was
continued for one-half hour. At the end of five and
one-hal hours an additional charge of initiator was added
(i~e. chaser) and polymerization was further continued for
one hour.
. .
~' : -
~ ~ 31 -
ii) Percent Solids Determination
The percent solids (polymer) content was determined based on
a gas chromatographic analysis of percent residual monomer(s) and
solven~ content by weight present in solution after
polymerization.
iii) Polymer Solution Viscosity Measurement
Polymer solution viscosity at ambient temperature
(26C) was determined using a Brookfield viscometer model
~HBT with a spindle ~HB2 at a speed of 10 rpm.
Table 7
Initiator~1) LupersolO233 Lupersol~533
Temperature, oC(2) 147 145
-
Mn 4,600 3,900
Mw/Mn 2.6 1.9
Mz/Mn 6.3 3 3
Solids content 78% 7g%
Solution viscosity (cps.) 31,680 15,420
(1) The initiators were compared on an equal molar basis,
after correcting for any assay di~ferences:
(a) 4.56 phm ~ure basis Lupersol 233 plus 0.456 phr pure
basis Lupersol 233 chaser;
(b) 5O0 phm p~re basis Lupersol~533 plus 0.50 phr pure
basis Lupersol 533 chaser.
(2) The reaction temperature employed was based on the 15
minute half-life temperature of the initiator.
~' As shown in Tables 6 and 7~ an improvement in the
- molecular distribution is evident with the use of the
.
tertiary-alkyl peroxide in comparison to its corresponding
conventional t-butyl analog, even at low solvent content.
Consequently, as a result of a narrower MWD, the solution
viscosity was much lower~ Solution viscosity is an important
consideration at high solids/low solvent contents. Thus, the
use of tertiary-alkyl (>Cs) peroxides would be favored over
their corresponding conventional t-butyl analogs at low
solvent contents.
Example 8
This example illustrates the performance of a mixture of
a conventional t-butyl peroxide and a tertiary-alkyl (>Cs)
peroxide initiator with respect to polymer molecular weight
and M~D.
The procedure was the same as that used in Example 1.
Table 8
Initiator(s) (1) Mn (Mw/Mn~ MzlMn
Luperso ~ 233 2,7002.3 6.0
Lupersol~ 533 2,2002.1 3.0
Luperso ~ (233/533) Blend (2) 1,900 2.4 3.7
(1) The initiators were used at a level of 2.0 g per 100
g. of monomer, after correcting for any assay
differences.
(2) The initiator blend was composed of a (1:1) by
weight mixture of the two.
- 32 -
X
PAT 6951-11
''":
~ 33 - ~
f ~
As shown in Table 8, the use of a conventional t-butyl
peroxide (i.e., Lupersol 233) résulted in a broad MWD
polymer. The use of the corresponding tertiary-alkyl
analog peroxide initiator (i.e., Lupersol 533) resulted in a
much narrower MWD polymer. The use o~ a mixture of the two
initiators resulted in a polymer MWD much narrower than that
obtained with the t-butyl peroxide initiator, but slightly
broader than that obtained with the tertiary-alkyl ~C5)
analog peroxide. A tertiary-alkyl (>C5) peroxide would
represent a slightly higher cos~ product than a t-butyl
peroxide. Thus, blends of t butyl and t-alkyl (>C5) analog
peroxides could be used as a potential cost reducing system,
with the benefit of narrowing ~he MWD versus using a t-butyl
pe~oxide as the sole polymeriæation initiator.
Example_9
This example illustrates the performance of
ter~iary-alkyl (>C5) peroxide initiators with respect to
polymer molecular weight and MWD using various monomer
combinationsO
The procedure was the same as that used in Example 1.
The ratio amounts of each monomer in the polymers tested
are 30/40/30 weight ratios; the polymers tested and results
are set forth in T~ble 9 as follows:
34 -
~ 3~
Table 9
Initiator (1) Polymer Type Mn (Mw/Mn) (Mz/Mn)
Lupersol 553 MMA/IBMA/HEMA 2,300 2.7 4.4
Lupersol 553 MMA~IBMA/AEMA 1,400 2.6 3.4
Lupersol 533 MMA/IBMA/HEMA 2,200 2.0 3.0
Lupersol 533 Styrene/IBMA/HEMA 2,9002.1 3.4
Lupersol 533 PMS/IBMA/HEl~A 3,000 2 2 3.7
(1) The initiators were used a~ a level of 2.0 g. per
100 g. of monome~, af~er correcting for any assay
di f ferences.
Example 10
This example compares the molecular weight and MWD of
suitable high solids coating resins prepared using
initiators of the present invention to a commercial hig~
solids acrylic resin (i.~., Acryloid~ AT-400, Rohm & ~aas)
currently being used by the industry.
The molecular weight and MWD of ~he resins were
determined as described in F.xample 1.
Table 10
20 Resin Mn ~Mw/Mn) (Mz/Mn)
MMA/IBMA/HEMA 2,200 2.0 3.0
Styrene/IBMA/HEMA 2,900 2.1 3.4
S~yrene/BA/B~A/HEA3 9 900 1.9 3.3
Acryloid~ AT-400 4 9 100 3.2 8.3
''
'
'
~ 35 -
As shown in Table 10, suitable coating resins
prepared using initiators of the present invention posssess
a significantly narrower MWD, particularly ~he Mz/Mn
ratio, than commercially used high solids acrylic resins
(i.e. Acryloid~ AT-400). The narrower MWD resins obtained
with initiators of the present invention would allow one to
go to higher solids contents without substantially affecting
the solution viscosity. Also, the narrower MWD resins would
result in achieving superior film properties as previously
discussed in the present inventionO
Example 11
This example illustrates the performance of conventional
tertiary-butyl peroxides in compari~son to peroxi.des derived
from tertiary-alkyl hydroperoxide with five carbons (i.e~,
15 tert.iary-amyl peroxides) as chase.r catalysts (i.e,, ability
to reduce residual monomer withou~ altering Mn and MWD of
Pol~mer) for solution acrylic resins~
- 36 -
Table 11A
Resin ~A) (B) (C) (D)
monomers l.0 <0.1 1.0 <0.1
S Mn 3,800 3,700 4,600 4,200
Mw/Mn 2.0 2.1 2.4 2.9
Mz/~n 3.4 3.8 5.4 6.9
(A) = Acrylic resins (styrene/BA/BMA/HEA) at 76% solids
in oxo-heptyl acetate ~olvent.
(B) = (A) ~ O.S PHR Lupersol~533 + O.S hr. at 145C
(C) = Acrylic resin (styrene/BA/BMA/HEA) at 76% solids
in oxo-heptyl acetate so~vent.
(D) - (C) ~ 0.456 PHR- Lupersol~233 + O.S hr. at 147C.
Ini~iators were compared on an equal molar basis af~er
correcting for any assay differences at a temperature
corresponding to the 15 minute half-life of the initiator.
Percent residual monomers were determined by gas
chromatography.
Resin mo:Lecular weight and distribution were determined
by GPC analysis (See Example 1).
., ~ '
- 37 -
Table llB
Resin (E) (F) (G)
/O Residual
monomers 0.7 <0.1 <0.1
5 Mn 4,300 4,500 4,800
M ~ Mn 2.0 2.2 2.5
M /M 3.7 4.4 5.4
Acrylic~resin (Styrene/BA/BMA/HEA) at 67% solids in
Dowanol PMA solvent.
10 (F) = (E) + 2.0 PHR t~amyl perbenzoate ~ 2.0 hrs. a-t 142C
(G) = (E) + 2.0 PHR t-butyl perbenzoate ~ 210 hrs. at 142C
As shown in Tables llA & B, the use of tertiary-alkyl
(C5) peroxides would be preferred over their conventional
t-butyl analogs as chaser catalysts for solution acry-lic
resins. The use of the tertiary-amyl (C5) peroxide resulted
in a reduction in residual monomer without significantly
. ~ altering the molecular weight and distribution of the
resin. The use of the tertiary-b~tyl peroxide, however,
resulted in an increase (broadening) of the distribution
(MWD) of the resin. It is desirable that a chaser
catalyst reduce the residual monomer level (i.e., for health
toxicity concerns) without altering the molecular weight and
distribution of the resin (i.e., without increasing the
solution viscosity of the resin solution). Thus, initiators
of ~he present invention would be desirable as chaser
catalysts.
WHAT IS CLAIMED:
-
~ . ~
' - '
