Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-09-09
2004-01-13
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S302000, C526S336000, C524S808000
Reexamination Certificate
active
06677417
ABSTRACT:
The present invention relates to a process for establishing the particle size of popcorn polymers during popcorn polymerization, reaction mixtures forming popcorn polymers and comprising monoethylenically unsaturated monomers and a crosslinking agent being polymerized in the absence of oxygen and polymerization initiators at up to 200° C.
It is known that the homopolymers of N-vinylpyrrolidone are generally readily soluble in water and in numerous organic solvents. Furthermore, it is known that insoluble, more or less swellable copolymers based on N-vinylpyrrolidone can be prepared by incorporating at least bifunctional vinyl or acryloyl compounds, which act as crosslinking agents, as polymerized units in a conventional manner. However, even when relatively large amounts of bifunctional components are used, it is not possible to prepare polymers having only low swellability and controllable particle size in water. Polymers based on N-vinylpyrrolidone and having low swellability are prepared, for example, by popcorn polymerization, cf. for example DE-A-2059484, DE-A-2255263 and U.S. Pat. No. 3,277,066.
U.S. Pat. No. 4,451,582 discloses a process for the preparation of insoluble, granular polymers which are only slightly swellable in water and comprise basic vinyl heterocycles having a pKa value of more than 4 and their copolymers with up to 30% by weight of copolymerizable monomers, in which the monomers are polymerized in the presence of from 0.1 to 10% by weight, based on the total amount of monomers, of crosslinking agent in the absence of oxygen and polymerization initiators. The polymers are preferably prepared by precipitation polymerization in water. However, they can also be obtained in the absence of solvents for the monomers, by heating the monomers to temperatures of preferably from 150 to 180° C. This reaction is however poorly controllable and gives only low space-time yields and relatively highly contaminated products.
It is also known that insoluble, only slightly swellable polymers of acrylic acid can be prepared by polymerizing acrylic acid in aqueous solution in the presence of small amounts of 2,2′-azobisisobutyronitrile, cf. J. W. Breitenbach et al., Makromol. Chemie 177, (1976), 2787 to 2792. However, this gives polymer blends which contain a glassy polymer (gel) as the main component and popcorn polymers of acrylic acid in minor amounts. The separation of the polymer blends cannot be carried out at an acceptable cost in industry.
Houben-Weyl, Volume 14, Makrom. Stoffe, Part 1 (1961), page 98, discloses that popcorn polymers are formed from mixtures of styrene with divinylbenzene. Popcorn polymers also form in the industrial butadiene/styrene polymerization. Methyl acrylate, too, tends to form popcorn polymers. On contact with the monomers of which they consist or with other monomers, popcorn polymers have the property of being able to convert them into popcorn polymers. They act as a nucleus for the polymerization. However, the activity is lost if they come into contact with oxygen.
Ullmanns Encyklopädie der Techn. Chemie, 4
th
Edition, Volume 19, 1980, page 385, discloses that an insoluble polymer slightly swellable in water is formed on heating N-vinylpyrrolidone with hydroxides and alcoholates of alkali metals and alkaline earth metals. Such substances referred to as popcorn polymers also form on heating N-vinylpyrrolidone with divinyl compounds in the absence of oxygen and polymerization initiators. In the absence of bases as a rule several hours are required before the popcorn polymerization begins at all.
EP-B-0 177 812 discloses a process for the preparation of insoluble, only slightly swellable, polymer powders based on monoethylenically unsaturated carboxamides, carboxylic acids and carboxylic esters, in which the polymerization is initiated using an active popcorn polymer which is obtainable by heating a mixture of from 99.6 to 98.8% by weight of N-vinylpyrrolid-2-one and from 0.4 to 1.2% by weight of a compound having at least two ethylenically unsaturated double bonds, as a crosslinking agent, to a temperature of from 100 to 150° C. in the absence of oxygen and polymerization initiators. As soon as the active popcorn polymer has formed, a mixture of
a) from 99.9 to 90% by weight of at least one compound from the group consisting of the N-vinylcarboxamides, acrylamide, methacrylamide, acrylic acid, methacrylic acid, acrylic esters, methacrylic esters and/or vinyl esters and
b) from 0.1 to 10% by weight, based on the total monomers, of a compound having at least two ethylenically unsaturated double bonds, as a crosslinking agent,
is polymerized therein in a powder bed in the presence of a heat transfer agent which is inert to the reactants, at from 90 to 220° C. while maintaining the powder state, circulating the reaction material and evaporating the heat transfer agent from the polymerization zone, in the absence of oxygen and polymerization initiators. The popcorn polymers thus obtainable are used, for example, for absorbing tannins from beverages, as dissolution accelerators for pharmaceutical tablets and as ion exchangers. Carboxyl-containing popcorn polymers are obtained, for example, by hydrolyzing popcorn polymers containing acrylic ester and acrylamide units.
WO-A-94/11408 discloses insoluble, only slightly swellable polymers having amino groups. These polymers are prepared by polymerizing open-chain N-vinylcarboxamides, such as N-vinylformamide, and, if required, other monomers copolymerizable therewith with from 0.1 to 10% by weight, based on the monomers used in the polymerization, of a compound having at least two ethylenically unsaturated double bonds, as a crosslinking agent, in the absence of oxygen and polymerization initiators to give popcorn polymers and eliminating the formyl or acyl group from at least 2% of the N-vinylcarboxamides incorporated as polymerized units, with formation of amino-containing popcorn polymers, by the action of enzymes, bases or acids. The popcorn polymers are used as ion exchangers or as adsorber resin for metal ions.
The disadvantage of said processes for the preparation of popcorn polymers is that any desired particle size of the polymer material is formed more or less accidentally and can be brought to the particle size required for the particular application only in an inconvenient manner by mechanical comminution or by agglomeration. However, it is essential to establish the particle size for many applications.
It is an object of the present invention to provide a process for establishing the particle size of popcorn polymers during the popcorn polymerization.
We have found that this object is achieved, according to the invention, by a process for establishing the particle size of popcorn polymers during the popcorn polymerization, reaction mixtures forming popcorn polymers and comprising monoethylenically unsaturated monomers and a crosslinking agent being polymerized in the absence of oxygen and polymerization initiators at up to 200° C., if the popcorn polymerization is carried out as a precipitation polymerization in water or in the absence of a solvent and the particle size of the popcorn polymers is controlled in the range from 1 &mgr;m to 10 mm by passing an inert gas stream into the reaction mixture. For example, from 0.01 to 100, preferably from 0.05 to 30, in particular from 0.1 to 20, liters of inert gas per hour per liter of reaction mixture are required for this purpose.
For the preparation of popcorn polymers, for example,
a) N-vinyllactams of the formula
where n is 3-5, and, if required,
b) other monoethylenically unsaturated monomers copolymerizable therewith
are polymerized in the presence of
c) from 0.1 to 10% by weight, based on the monomers a) and b) used in the polymerization, of a compound containing at least two ethylenically unsaturated double bonds, as a crosslinking agent, in the absence of polymerization initiators and oxygen to give popcorn polymers.
Suitable compounds of the formula I are, for example, N-vinylpyrrolidone, N-vinylpiperidone and N-vinylcaprolact
Bertleff Werner
Kerber Michael
Meffert Helmut
Spang Peter
BASF - Aktiengesellschaft
Pezzuto Helen L.
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