NO137863B - LATEEX PAINT CONTAINING A BACTERIQUE KILLER - Google Patents

Abstract

Latex paint that contains a bactericidal agent.

Description

The present invention relates to latex paints containing a bromoGetoxy compound as a bactericidal agent, and these paints are characterized by the fact that they contain 0.025 - 1.0% benzyl bromoacetate, and preferably 0.05 - 0.5% benzyl bromoacetate.

One of the most important and difficult problems facing the paint industry is the preservation of latex paints against bacterial fermentation during storage. These paints are mainly based on polyvinyl acetate, butadiene/styrene and acrylic polymers and copolymers. Furthermore, additives that are necessary in the formulation of these paints also contribute considerably

to promote the growth of bacteria. These nutritive agents include thickeners, such as starch, cellulose derivatives, casein and lecithin, and also film plasticizers, jointing agents, stabilizers and dispersants. Monomers, by-product salts and organic liquids are metabolized by bacteria known to attack aqueous paint systems, including Escherichia sp. such as E. coli, Aerobacter sp. such as A. aerogenes, Bacillus sp.

such as B. subtillus and, primarily, Pseudomonas sp. as

P. aeruginosa.

The end result of bacterial attack on aqueous paint systems includes the development of foul odors, marked reduction in viscosity, breakdown of the colloid and a lowering of pH. In addition, gas evolution that results from fermentation often causes large pressure build-ups." - in closed containers - and leads to the blowing off of the lid and the splashing of the contents. It is therefore obvious that bacterial attack on aqueous paint systems during storage causes such systems unusable and is a serious problem for both producer and consumer. The present invention is based, as I said, on the discovery that latex paint can be preserved effectively against bacterial attack by incorporating therein a bactericidally effective amount of benzyl bromoacetate. It has been shown that benzyl bromoacetate is particularly effective in this application It provides effective inhibition of bacterial growth at relatively low and economical concentrations, it has a weak color and relatively low toxicity and low vapor pressure.

It is well known that many bromoacetic acid esters are effective antimicrobial agents. Such compounds, including 1-bromo-acetoxy-ethanol-2, bis-1, h-bromocotoxy-2-butene. and 555-bis-(bromo-acetoxymethyl)-m-dioxaiv, have been proposed for use in combating microbial problems caused by bacteria in industrial water systems. In particular, such compounds have been proposed for use as slimicides in paper factories, e.g. Norwegian patent 130 78I, which also mentions that the agents used as pesticides in water systems can, as a rule, be used to preserve latex paints.) Furthermore, many bromoacetic acid esters are known to be very effective fungicides, and have been suggested for use as paint additives to combat fungal problems.

Surprisingly, benzyl bromoacetate, although a very effective fungicide, has been found to be completely ineffective in controlling fungal problems associated with aqueous paint systems at economically acceptable concentrations. This is confirmed by standard laboratory rudder yoke under application, by the following methods:

- Typical outdoor polyvinyl acetate paints with the formulation shown in table 1 below were used in this assessment.

Samples of this paint formulation were prepared containing benzyl bromoacetate at concentrations of 0.025% (250 dpm), 0.05%

(500 dpm), 0.1% (1,000 dpm), 0.25% (2,500 dpm), 0.5% (5,000 dpm), 1.0% (10,000 dpm), 2.5%.. (25 -000 dpm) and 5.0% (50,000 dpm). One.

sample of. each.. paint .was .placed...in . a sterile container to be used in can preservation studies, and the remainder was reserved for studies of resistance to mildew attack.

To assess the ability of benzyl bromoacetate to act as a fungicide in aqueous paint systems. each of the samples described above which were reserved for this purpose, was well stirred and brushed out evenly on a page of "Whatman" No. 1 filter paper. A second coating was applied quickly on the same side of the filter paper after 2 hours drying time. After 72 hours of drying another coating followed, 38 mm x 38 mm test pieces were cut from the painted paper and subjected to simulated weathering tests using the following .the cycles described by Ramp and Grier, Fungicides in Paint, Official Digest, 33, No. hhO (Sept. 1961). 1. The leached/heated (L/H) sample was leached- for 2k hours in running tap water, then heated for 2<*>+ hours at 65° C. 2. The heated/leached (H/L) sample was heated for 2 hours at 65° C and then leached■for 2 hours in running tap water.

The samples were air-dried for several hours after treatment, dipped in boiling water and then placed on the surface of plates of malt agar. The trial samples and the plates were inoculated with 1.5 ml of a spore suspension of Pullularia pullulans. The plates were incubated at 28-30°C and assessed for fungal growth at the end of k weeks. The results from these trials are shown in Table 2 below. . In order to be considered suitable for outdoor use, paints must not show any growth on the film in either of the two treatment cycles after an incubation period of several weeks. It will therefore be seen that benzyl bromoacetate does not combat the fungus problems in connection with paint systems even in an amount of 5%, or 6 kg/100 1 paint, which is many times the amount that could come into consideration from an economic point of view, although benzyl -bromoacetate is effective at 10 dpm, on Sabourand Maltose Agar, against Pullularia pullulans, the organism most frequently encountered in fungal problems with paint. It can thus be determined that not even a quantity of 5% (50,000 dpm}, or 5000 times the quantity required to combat fungus on agar, is sufficient to combat fungus on paint films.

To assess the ability of benzyl bromoacetate to protect aqueous paint systems against bacterial degradation during storage, each of the samples kept in sterile containers was streaked onto the surface of Tryptone Glucose Extract Agar (TGE) to check its bacterial condition. Each sample was then inoculated with a 2-hour-old nutrient culture of a strain of Pseudomonas aeruginosa known to down-; breaking aqueous coatings (ATCC 1011+5) in an amount of 1 ml.-culture, per 100 g sample. The inoculated samples were incubated at 28~30°C and. the microbiological state of each sample was examined immediately after inoculation and at h, 2h, h8, 72 hours and 7 days after inoculation by smearing on the surface of TGE plates. The plates were incubated at 28-30°C for 7 days and examined for growth after this incubation time.

7 days after the first inoculation each paint sample was again inoculated with Pseudomonas.aeruginosa and after incubation at 28-30°C for 2h, k- QT 72 hours and 7 days after inoculation streaked on TGE plates. These plates were also incubated for 7 days at 28-30°C

and examined for growth.

The samples which achieved sterility within 8 hours after inoculation and re-inoculation, and which were still sterile 7 days after inoculation and re-inoculation, were considered fully preserved. The results of these experiments are shown in Table^ 3.

As can be seen from Table 3, benzyl bromoacetate is completely effective in protecting water-based paint against bacterial attack at concentrations as low as 6.05% (500 dpm) or 60 g per 100 1 measurement, and achieve considerable efficiency at concentrations as low as 0.025% (250 dpm) or 30 g/100 1 paint. Benzyl bromoacetate is thus ineffective in combating the fungus problem in paint at concentrations of 5%, while at 1/100 to 1/200 of this concentration it is effective in preserving aqueous paint systems against bacterial attack.

Benzyl bromoacetate, which is liquid, can be incorporated! aqueous paint and coating systems by simple addition at any stage of the manufacturing process or to the finished product in sufficient quantity so as to provide a bactericidally effective concentration in the finished product. The benzyl bromoacetate can further be added as a component of any of the raw materials used in the production of the finished product. The benzyl bromoacetate can thus be added to resin, clay or starch suspensions to be used as components of aqueous paint- or coating systems, and used in this way not only serves to provide protection against bacterial attack on the finished product, but also serves to protect the raw material against bacterial attack during storage.

Effective protection against bacterial attack in aqueous paint and. coating systems are generally achieved by using from 0.025% to 1.0% by weight of benzyl bromoacetate in the finished formulation, concentrations between 0.05 and 0.5% being preferred. In these concentrations, benzyl bromoacetate is compatible with all the components that are usually used in the production of water-based paints and coatings, and unlike many currently used antimicrobial agents, such as phenylmercury salts, they do not undergo decomposition or other reactions with sulphide-containing pigments as lithopone. Moreover, it is fully active under both acidic and alkaline pH conditions which can be selected in a special formulation to obtain maximum colloidal stability, and it has little tendency to yellow.

Another satisfactory method of adding benzyl bromoacetate to aqueous paint and coating systems is to adsorb the benzyl bromoacetate on finely powdered, solid materials used as dispersants in such systems. Typical dispersants that can be used for this purpose are calcium magnesium silicate, silicon dioxide and various types of clay and talc. From 10 to 50% by weight of benzyl bromoacetate can be adsorbed on such dispersants by carefully mixing the benzyl bromoacetate and the powdered dispersant in a suitable mblie. The adsorbate can then be added to aqueous paint and coating systems at any time, in sufficient quantity to provide the desired concentration of benzyl bromoacetate in the finished product.

In addition, benzyl bromoacetate can be added to aqueous paint and coating systems as solvents. Benzyl bromoacetate is soluble in many organic solvents such as, e.g. xylene, toluene, turpentine, perchlorethylene, 2-ethoxyethanol, 2-ethoxy-ethyl acetate, diethylene glycol monoethyl ether and the acetate of diethylene glycol monoethyl ether. Solutions - of benzyl bromoacetate in organic solvents which can contain from 1 to 50% benzyl bromoacetate - can simply be mixed in aqueous paint and coating systems to obtain the desired final concentration. A small percentage amount of an emulsifier, usually between 2 and 5% by weight, can be added to such solutions if desired.

Claims (2)

1. Latex paint containing a bromoacetoxy compound as a bactericidal agent, characterized in that it contains 0.025 - 1.0% benzyl bromoacetate. 2. Latex paint according to claim 1, characterized in that it contains 0.05 - 0.5% benzyl bromoacetate.