CA1262008A - Solution polymerization of acrylic acid derived monomers using tertiary alkyl ( c.sub.5) hydroperoxides - Google Patents
Solution polymerization of acrylic acid derived monomers using tertiary alkyl ( c.sub.5) hydroperoxidesInfo
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- CA1262008A CA1262008A CA000495783A CA495783A CA1262008A CA 1262008 A CA1262008 A CA 1262008A CA 000495783 A CA000495783 A CA 000495783A CA 495783 A CA495783 A CA 495783A CA 1262008 A CA1262008 A CA 1262008A
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- methacrylate
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Abstract
- i -Abstract A process is provided for the free radical polymerization of monomers derived from substituted or unsubstituted acrylic acid/methacrylic acid and esters thereof for the production of a polymer having a narrow molecular weight distribution and an average molecular weight of less than 4000. These polymers are produced by the solution polymerizing of said monomers in the presence of a solvent system suitable for high solids coating applications and in the presence of an initiating amount of a tertiary alkyl hydroperoxide having at least 5 carbons and/or its derivatives. These polymers are used for high solids coating applications.
Description
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.
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. ': ~ '-' : ' , 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 ., 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 . :
.
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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.
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.
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,
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 ., 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.
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.
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 ' 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 . ~
. ' :~' ' 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 .
~ ` ~
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 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 .~
l2 lR2 -C-Ar'-C-where R2 is as defined above and Ar' is selected from arylene of 6-12 carbons, \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, 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,
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 ' 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 . ~
. ' :~' ' 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 .
~ ` ~
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 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 .~
l2 lR2 -C-Ar'-C-where R2 is as defined above and Ar' is selected from arylene of 6-12 carbons, \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, 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.
.
;
~ - 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.
,;:,.
:., , : .: . .
. .
, - ~ .. ` :
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.
~. , . ~, .
.
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.
.. ~ . . -.
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.
' ~ :
~%~
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
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.
,;:,.
:., , : .: . .
. .
, - ~ .. ` :
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.
~. , . ~, .
.
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.
.. ~ . . -.
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.
' ~ :
~%~
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.
X
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~ 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:
~ 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~
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).
., ~ ' 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:
-~ . ~
' - '
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.
X
''":
~ 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:
~ 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~
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).
., ~ ' 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:
-~ . ~
' - '
Claims (10)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the free-radical polymerization of monomers derived from substituted or unsubstituted acrylic acid or methacrylic acid or esters thereof or styrene or para-methyl styrene comprising solution polymerizing said monomers wherein 20-40% by weight of the monomer composition is hydroxyalkyl acrylate or methacrylate in a temperature range of 90°-200°C, in the presence of a solvent suitable for high solids coating application, wherein the solvent to monomer ratio is 3:1 to 0.1:1, and in the presence of an initiating amount of about 0.50 to about 10.0 parts by weight per 100 parts of monomer of a tertiary-alkyl hydroperoxide and/or its derivative having a one hour half-life temperature in the range of 50°-190°C and having at least 5 carbons in the tertiary alkyl component, said derivatives being selected from peroxyketals, dialkyl peroxides, peroxyesters, and monoperoxy-carbonates, wherein the initiators and monomers, alone or in combination, are added over a period of at least about 3 hours at a controlled rate wherein the rate of addition corresponds approximately to the rate of decomposition of said monomer and initiator.
2. The process of claim 1 wherein the tertiary-alkyl hydroperoxide and/or its derivative is selected from the class of (ROO)nR1 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 where R2 is selected from lower alkyl of 1-6 carbons, R3 is selected from alkyl of 2-6 carbons, and Ar is selected from aryl of 6-12 carbons, and R1 is independently selected from R, hydrogen, acyl of 2-18 carbons, aroyl of 7-18 carbons, or alkoxycarbonyl of 2-19 carbons, and when n is 2, R1 is selected from di-tertiary-alkylene of 7-20 carbons, di-tertiary alkynylene or 8-20 carbons, di-t-cycloalkylene of 12-20 carbons, and where R2 is as defined above and Ar' is selected from arylene of 6-12 carbons, where R4 and R5 are the same or different, alkyl of 1-10 carbons, cycloalkyl of 5-10 carbons, cycloalkenyl of 5-10 carbons, or aralkyl of 7-10 carbons, and R4 and R5 can join together to form an alkylene diradical of 5-11 carbons, where R6 is selected from alkylene of 1-20 carbons, cycloalkylene of 5-12 carbons, arylene of 6-12 carbons, where R7 is selected from alkylene 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 hydrogen, acyl of 2-18 carbons, aroyl of 7-18 carbons, or alkoxycarbonyl of 2-19 carbons when R1 is selected from di-t-alkylene, di-t-alkynylene, di-t-cycloalkylene, or and wherein R, R1, R2, R3, R4, R5, R6, R7, Ar and Ar' can optionally be substituted, wherein the substituents can be one or more of lower alkyl of 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 contain one or more oxygen or nitrogen.
3. The process of claim 2 wherein the tertiary-alkyl hydroperoxide derivative is selected from tertiary-amyl peroctoate, di-tertiary-amyl diparoxyazelate, di-tertiary-amyl peroxide, 1,1-di(t-amylperoxy)cyclohexane, di-(t-octylperoxy)propane, tertiary-octyl hydroperoxide, 2,2-di-(t-amylperoxy)butane, and ethyl 3,3-di(t-amylperoxy)butyrate.
4. The process of claim 3 wherein the monomers are selected from the group consisting of acrylic acid, methacrylic acid, methyl methacrylate, isobutyl methacrylate, butyl acrylate, butyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, styrene, para-methyl styrene, and mixtures thereof.
5. The process of claim 4 wherein the monomers are by weight of monomer composition 30% methyl methacrylate, 40% isobutyl methacrylate, and 30% hydroxyethyl methacrylate.
6. The process of claim 4 wherein the monomers are by weight of monomer composition 10-30% styrene, 30-60% isobutyl methacrylate, and 20-40% hydroxyethyl methacrylate.
7. The process of claim 4 wherein the monomers are by weight of monomer composition 30% para-methyl styrene, 40% isobutyl methaclylate, and 30% hydroxyethyl methacrylate.
8. The process of claim 4 wherein the monomers are by weight of monomer composition 30% styrene, 30% butyl acrylate, 20% butyl methacrylate, and 20% 2-hydroxyethyl acrylate.
9. The process of claim 4 wherein the solvent is selected from the group consisting of 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 and mineral spirits.
10. The process of claim 1 wherein a combination of two or more initiators are used wherein at least one is a tertiary-alkyl (? C5) hydroperoxide and/or its derivative.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US73926585A | 1985-05-30 | 1985-05-30 | |
| US739,265 | 1985-05-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1262008A true CA1262008A (en) | 1989-09-26 |
Family
ID=24971527
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000495783A Expired CA1262008A (en) | 1985-05-30 | 1985-11-20 | Solution polymerization of acrylic acid derived monomers using tertiary alkyl ( c.sub.5) hydroperoxides |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1262008A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114380933A (en) * | 2020-10-21 | 2022-04-22 | 博立尔化工（扬州）有限公司 | Process for preparing thermoplastic styrene-acrylic resin with wide molecular weight distribution by one-step method |
-
1985
- 1985-11-20 CA CA000495783A patent/CA1262008A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114380933A (en) * | 2020-10-21 | 2022-04-22 | 博立尔化工（扬州）有限公司 | Process for preparing thermoplastic styrene-acrylic resin with wide molecular weight distribution by one-step method |
| CN114380933B (en) * | 2020-10-21 | 2023-09-05 | 博立尔化工（扬州）有限公司 | Process for preparing thermoplastic styrene-acrylic resin with wide molecular weight distribution by one-step method |
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