Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2002-05-13
2004-06-29
Puttlitz, Karl J. (Department: 1621)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S365000, C562S512000, C562S830000, C562S830000, C526S072000
Reexamination Certificate
active
06756471
ABSTRACT:
The present invention relates to a process for the preparation of water-soluble polymers containing polyalkylene glycol ether side chains and having molecular weights of from 15,000 to 60,000 by solution polymerization of esters of ethylenically unsaturated carboxylic acids and polyalkylene glycols which are masked on the end groups at one end, if desired together with other monomers in at least one hydrocarbon in the presence of free-radical-forming polymerization initiators and, if desired, polymerization regulators at temperatures of up to 200° C., removal of the solvent after the polymerization, and dissolution of the polymers in water to give from 50 to 80% strength by weight solutions, with polymers containing acid groups being neutralized if desired.
DE-A-19 653 524 describes the preparation of copolymers of methylpolyethylene glycol methacrylates and methacrylic acid by polymerization in aqueous medium using water-soluble initiators and water-soluble regulators. The concentrations in the polymerization are about 20% by weight. If the solids concentration in the polymer is increased, polymers having very high polydispersity and a high proportion of high-molecular-weight polymers are formed. Such products are ineffective as dispersants.
Esters of ethylenically unsaturated carboxylic acids and polyalkylene glycols which are masked on the end groups at one end may also be prepared by bulk polymerization or by solution polymerization in an aliphatic or aromatic hydrocarbon, cf. EP-A-753 488. However, polymerization in an aqueous medium, which gives about 25% strength by weight aqueous polymer solutions, is preferred since particularly effective dispersants containing polyalkylene glycol ether side chains are obtained. If the polymerization of the esters of ethylenically unsaturated carboxylic acids and polyalkylene glycols which are masked on the end groups at one end is carried out at high concentration, for example at concentrations of greater than 50% by weight, products which have only low efficacy as dispersants are obtained.
It is an object of the present invention to provide a process for the preparation of highly concentrated, but still readily flowable aqueous solutions of water-soluble polymers which contain polyalkylene glycol ether side chains and which are effective as dispersants for finely divided inorganic substances.
We have found that this object is achieved by a process for the preparation of water-soluble polymers containing polyalkylene glycol ether side chains and having molecular weights of from 15,000 to 65,000 by solution polymerization of esters of ethylenically unsaturated carboxylic acids and polyalkylene glycols which are masked on the end groups at one end, if desired together with other monomers in at least one hydrocarbon in the presence of free-radical-forming polymerization initiators and, if desired, polymerization regulators at temperatures of up to 200° C., removal of the solvent after the polymerization, and dissolution of the polymers in water to give from 50 to 80% strength by weight solutions, with polymers containing acid groups being neutralized if desired, if the concentration of the monomers in the hydrocarbons is from 70 to 95% by weight. The polymerization is preferably carried out at a concentration of the monomers of from 80 to 90% by weight.
Preferably,
(a) esters of the formula
in which
R
1
and R
2
are identical or different and are H or CH
3
,
A is an alkylene group having from 2 to 4 carbon atoms or is —CH
2
—CH
2
—CH
2
—CH
2
—,
is C
1
- to C
50
-alkyl or C
1
- to C
18
-alkylphenyl, and
is a number from 2 to 300,
are copolymerized with
(b) at least one monoethylenically unsaturated carboxylic acid or salts thereof. The monomers (a) and (b) are usually copolymerized in a weight ratio of from 98:2 to 2:98.
Particular preference is given to the copolymerization of
(a) acrylic acid esters or methacrylic acid esters of polyalkylene glycols which are masked on the end groups at one end by C1- to C4-alkyl and have molecular weights of from 200 to 10,000
with
(b) acrylic acid and/or methacrylic acid.
Particularly effective dispersants are obtained if
(a) esters of methacrylic acid and methylpolyethylene glycol having molecular weights of from 350 to 10,000
are copolymerized with
(b) methacrylic acid.
According to a preferred embodiment of the process according to the invention, the copolymerization is carried out in the presence of from 0.1 to 10% by weight of a polymerization regulator. Examples of suitable polymerization regulators are sodium hydrogensulfite, sodium bisulfite, sodium thiosulfate, sodium hypophosphite, phosphorous acid, 2-mercaptoethanol, dodecyl mercaptan, mercaptopropionic acid, mercaptoacetic acid, alkali metal salts of the said acids or mixtures of the polymerization regulators.
The alkylpolyalkylene glycols used can be, for example, compounds of the general formulae
R
1
—(O—CHR
2
—CHR
3
)
n
—OH or R
1
—(O—CH
2
—CH
2
—CH
2
)
n
—OH
where
R
1
=C
1
- to C
50
-alkyl
R
2
and R
3
=H, methyl or ethyl,
n=from 2 to 300.
The molecular weight of the alkylpolyalkylene glycols can be up to 10,000, with a molecular weight of from 200 to 2000 being preferred. This corresponds to up to 230, preferably from 3 to 40, alkylene oxide units per molecule.
Examples of alkylpolyalkylene glycols are methylpolyethylene glycols having molecular weights of 350, 500, 750, 1000, 1500, 2000, 4000 and 10,000.
The alkylpolyalkylene glycols may also contain propylene oxide or butylene oxide units in combination with ethylene oxide units. The alkylene oxide units may be arranged in block form or randomly.
Examples thereof are methylpolyalkylene glycols which are obtainable by adduction of 5 mol of ethylene oxide and 1 mol of propylene oxide, 5 mol of ethylene oxide and 3 mol of propylene oxide, 5 mol of ethylene oxide and 10 mol of propylene oxide and 10 mol of ethylene oxide and 1 mol of propylene oxide, 10 mol of ethylene oxide and 3 mol of propylene oxide, 10 mol of ethylene oxide and 10 mol of propylene oxide, 20 mol of ethylene oxide and 1 mol of propylene oxide, 20 mol of ethylene oxide and 3 mol of propylene oxide, 20 mol of ethylene oxide and 10 mol of propylene oxide, 25 mol of ethylene oxide and 1 mol of propylene oxide, 25 mol of ethylene oxide and 3 mol of propylene oxide and 25 mol of ethylene oxide and 10 mol of propylene oxide ontoin each case 1 mol of methanol.
The polyalkylene glycols which are masked on the end groups at one end may also be polytetrahydrofurans having molecular weights of, for example, from 200 to 10,000 which carry a C
1
- to C
4
-alkyl group as end group.
The unsaturated carboxylic acids employed are preferably acrylic acid, methacrylic acid, maleic acid and maleic anhydride.
Esters of alkylpolyalkylene glycols and unsaturated carboxylic acids can be prepared, for example, by acid-catalyzed esterification of unsaturated carboxylic acids with alkylpolyalkylene glycols by all known processes. The water of reaction can remain in the mixture or be removed from the reaction mixture by, for example, azeotropic distillation using an entraining agent. Thus, the conversion of the alcohol component can be up to 100%, cf. EP-A-0 884 290.
In the esterification, the molar ratio of carboxylic acid to alkylpolyalkylene glycol can be, for example, from 10:1 up to 1:1.
Suitable entraining agents are all organic solvents having a boiling point of from 50 to 300° C. The proportion of entraining agent is, for example, from 5 to 20% by weight, based on the sum of the carboxylic acid and alcohol components. Examples of entraining agents are n-paraffins, such as hexane, decane, undecane, dodecane, octadecane, isoparaffins, such as isooctane, isononane, isodecane, isododecane, isohexadecane, isooctadecane, cycloparaffins, such as cyclohexane, methylcyclohexane, dimethylcyclohexane, aromatics, such as benzene, toluene, o-, m- and p-xylene, xylene mixtures, trimethylbenzene, tetramethylbenzene, mesitylene, ethylbenzene, isopropylbenzene, n-butylbenzene and isobutylbenzene. Preference is given to cyclohexan
Büchner Karl-Heinz
Kroner Matthias
Perner Johannes
BASF Aktiegesellschaft
Oblon, Spivak, McClelland, Maier & Neustadt, P. C.
Puttlitz Karl J.
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