Antimicrobial additives

Details Antimicrobial additives Antimicrobial additives

2002-03-11

2004-09-14

Nutter, Nathan M. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S206000, C525S217000, C525S218000, C525S222000, C525S239000, C525S240000, C525S241000

Reexamination Certificate

active

06790910

ABSTRACT:

The invention relates to antimicrobial polymers obtained by polymerizing acryloxyalkylamines. The invention further relates to a process for preparing these antimicrobial polymers and to their use.
It is highly undesirable for bacteria to become established or to spread on the surfaces of piping, or of containers or packaging. Slime layers frequently form and permit sharp rises in microbial populations, and these can lead to persistent impairment of the quality of water, drinks or foods, and even to spoilage of the product and harm to the health of consumers.
Bacteria must be kept away from all fields of life where hygiene is important. This affects textiles for direct body contact, especially in the genital area, and those for the care of the elderly or sick. Bacteria must also be kept away from surfaces of the furniture and equipment used in patient-care areas, especially in areas for intensive care or neonatal care, and in hospitals, especially in the areas where medical intervention takes place, and in isolation wards for critical cases of infection, and also in toilets.
A current method of treating equipment, or the surfaces of furniture or of textiles, to resist bacteria either when this becomes necessary or else as a precautionary measure, is to use chemicals or solutions or mixtures of these which are disinfectants and therefore have fairly broad general antimicrobial action. Chemical agents of this type act nonspecifically and are frequently themselves toxic or irritant, or form degradation products which are hazardous to health. In addition, people frequently exhibit intolerance to these materials once they have become sensitized.
Another method of counteracting surface spread of bacteria is to incorporate substances with antimicrobial action into a matrix.
U.S. Pat. No. 4,532,269, for example, discloses a terpolymer made from butyl methacrylate, tributyltin methacrylate, and tert-butylaminoethyl methacrylate. This copolymer is used as an antimicrobial paint for ships, and the hydrophilic tert-butylaminoethyl methacrylate present promotes gradual erosion of the polymer and thus releases the highly toxic tributyltin methacrylate, which is the antimicrobial active ingredient.
In these applications, the copolymer prepared with aminomethacrylates is merely a matrix or carrier for added microbicidal ingredients which can diffuse or migrate out of the carrier material. Sooner or later, polymers of this type loose their activity, once the necessary minimum inhibitor concentration (MIC) at the surface has been lost.
The European patent application 0 862 858 has also disclosed that copolymers of tert-butylaminoethyl methacrylate, a methacrylate with a secondary amino function, has inherent microbicidal properties. Systems developed in the future will again have to be based on novel compositions with improved effectiveness if undesirable resistance phenomena in the microbes are to be avoided, particularly bearing in mind the microbial resistance known from antibiotics research.
The object on which the present invention was based was therefore to develop novel antimicrobial polymers. When used as a coating or covering material, these should prevent bacteria from colonizing surfaces and spreading thereon.
Surprisingly, it has now been found that homopolymerization of acryloxyalkylamines or of methacryloxyalkylamines gives polymers which are lastingly microbicidal, are not damaged by solvents or physical stresses, and exhibit no migration. There is no need here for the use of other biocidal active ingredients. The surface of the polymers is, of course, important for the antimicrobial action of these homopolymers.
The present invention therefore provides antimicrobial polymers which are obtained by polymerizing a monomer of the formula I:
where
R1=—H or —CH
3
R2=branched or unbranched aliphatic hydrocarbon radical having from 1 to 5 carbon atoms,
R3=H, or branched or unbranched aliphatic hydrocarbon radical having from 1 to 7 carbon atoms,
R4=H, or branched or unbranched aliphatic hydrocarbon radical having from 1 to 7 carbon atoms,
R5=H, or branched or unbranched aliphatic hydrocarbon radical having from 1 to 7 carbon atoms, and
X=O, NH, NR5.
Acryloyloxyalkylamines (X=0) and alkylaminoacryl-amides (X=NH) are particularly suitable for preparing the polymers of the invention.
The radicals R3 and R4 may be identical or different. If R3 and/or R4 are hydrocarbon groups, these may in particular be methyl, ethyl, isopropyl, n-propyl, or tert-butyl groups.
Preferred monomers used of the formula I are 2-tert-butylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate, 2-dimethylaminomethyl methacrylate, 2-tert-butylaminoethyl acrylate, 3-dimethylaminopropyl acrylate, 2-diethylaminoethyl acrylate, 2-dimethyl-aminoethyl acrylate, N-3-dimethylaminopropylmeth-acrylamide, N-3-diethylaminopropylmethacrylamide, N-3-dimethylaminopropylacrylamide, or N-3-diethylamino-propylacrylamide.
The antimicrobial polymers of the invention may be obtained by homopolymerizing monomers of the formula I. The free-radical polymerization advantageously takes place by a chemical route by way of a free-radical initiator, or initiated by radiation. The examples describe typical procedures.
The present invention further provides antimicrobial polymer blends which are prepared by mixing one or more antimicrobial polymers each obtainable by polymerizing monomers of the formula I, where R1, R2, R3, R4, R5 and X are as defined above, with at least one other polymer.
Examples of blend material, i.e. other polymer with which the polymer of the invention is mixed, are polyurethanes, PVC, polyolefins, such as polyethylene or polypropylene, polysiloxanes, polystyrenes, polyacrylates, polymethacrylates, and engineering plastics, e.g. polyamides or polyterephthalates. To obtain adequate antimicrobial action of a polymer blend, the proportion of the antimicrobial polymer of the invention should be from 0.2 to 90% by weight, preferably from 40-90% by weight.
In principle, any of the processes known in the art, for example as described in detail by H.-G. Elias, MakromolekUle [Macromolecules], Vol. 2, 5th edition, pp. 620 et seq., may be used to prepare the antimicrobial polymer blends. For example, two previously formed polymers are mixed in the melt by mixing the pelletized or pulverulent polymers on roll mills, in kneaders, or using extruders. In the case of thermoplastics, this is achieved by heating above the glass transition temperatures or melting points. In the case of solution mixing, the starting materials are separately prepared solutions of the two polymers in the same solvent.
In specific embodiments of the present invention, it is possible for the proportion of the one or more antimicrobial polymers of the invention in a blend to be less than 40-90% by weight, e.g. from 0.2 to 70% by weight, preferably from 0.2 to 30% by weight, particularly preferably from 0.2 to 15% by weight, very particularly preferably from 0.2 to 10% by weight.
One preferred process for preparing the antimicrobial polymers and, respectively, polymer blends of the invention is free-radical polymerization of monomers of the formula I in solution, using a free-radical initiator. The resultant antimicrobial polymers may, where appropriate after mixing with other polymers, be applied to a surface by known methods, such as dipping, spraying, or spreading. Solvents which have proven successful are ethanol, methanol, water/alcohol mixtures, methyl ethyl ketone, diethyl ether, dioxane, hexane, heptane, benzene, toluene, chloroform, dichloromethane, tetrahydrofuran, and acetonitrile, but it is also possible to use other solvents as long as they have sufficient capability for dissolving the polymers and give good wetting of the substrate surfaces. Solutions with polymer contents of from 3 to 20% by weight, for example about 5% by weight, have proven successful in practice and generally give, in a single pass, coherent coatings which cover the substrate surface and may have a thickness

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