OBPA biocides

Akcros Intercide ABF-2711 is a special formulation of OBPA biocide - 2% solution in di-(heptyl. nonyl. undecyl) phthalate plasticizer - for PVC pool- and pond-liners, tarpaulins, and marine upholstery. 

TABLE 13.10 Activity of an OBPA-based biocide (Intercide ABF-2-DIDP) versus single-test fungi, NSA, and Disk tests (plastisol folmulation)... 

A similar biocide, Intercide ABF-5-DIDP in the amount of 0.05 and 0.1% (w/w) of the active principle (OBPA), that is, 1.0 and 2.0% (w/w) of the commercial biocide, was tested in a woodfiber-PVC composite (data obtained courtesy of Akcros Chemicals). The unprotected composite (no biocides) did not prevent an active... 

The data in Table 13.11 show a certain level of performance of the biocide against all the test fungi, though its level is somewhat below that for OBPA (Table 13.10). 

In the New Jersey test there was also very poor correlation between biocide protection in the environmental chamber and outdoors. Many biocides showed excellent indoors protection, such as OBPA, copper hydroxide, chlorothalonil, bethoguard, but none of them showed fairly noticeable protective activity in the natural conditions (Table 13.17). Only two biocides, IPBC and Folpet, have shown what can be considered as a fair, but still not very good correlation of their biocidal activity in the environmental chamber and outdoors. 

Biocides, also referred to as antimicrobials, preservatives, fungicides, mildewcides, or bactericides, include several types of materials that differ in toxicity. OBPA (10, lO -oxybisphenoxarsine) is the most active preservative of those commonly used for plastics. Amine-neutralized phosphate and zinc-OMADINE (zinc 2-pyridinethianol-1-oxide) have a lower activity level but are also effective. In the United States all biocides are considered pesticides and must be registered for specific applications with the U.S. Environmental Protection Agency (EPA). 

The use level of biocide additives depends on the efficacy of the active ingredient. OBPA, the most active, requires approximately 0.04% concentration in the final product. Less active ingredients, such as n-(trichloro-methylthio) phthalimide, require a loading of 1.0% in the final compound to achieve a similar level of protection. 

Biocides are generally formulated with a carrier into concentrations of 2 to 10% active ingredient. They are available to plastics converters, processors, and other users in powder, hquid, or sohd pellet form. The carrier, as noted previously, is usually a plasticizer, but it can also be a resin concentrate such as PVC/PVA (polyvinyl acetate) copolymer or polystyrene. For example, OBPA, the most common biocide active ingredient, is typically purchased as a dispersion in a plasticizer at a concentration of 2% active ingredient. 

Of the hundreds of chemicals that are effective as biocides, only a few are used in plastic apphcations. After OBPA, the most common group of active ingredients are 2-n-octyl-4-isothiazolin-3-one, 4, 5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), zinc OMADINE, trichlorophenoxyphenol (TCPP or TRICLOSAN), N trichloromethylthio-4-cyclohexene-l,2-dicarboximide (CAPTAN), and AT-itrichloromethylthio) phthalimide (FOLPET). 

Biocides for plastics are growing at about 7% ear. OBPA, which currently holds the largest market share of all the biocides, is a mature market, growing at half that rate. Other biocides, such as isothiazolin and TCPP, will grow at a much faster rate than OBPA. 

The most widely used active ingredient for PVC is OBPA, based on 10, 10 oxybisphenoxarsine. Until recently it had a 50% market share but usage of arsenic compounds is becoming less popular. Other important biocides include OFT (2- -octyl-4-isothiazolin-3-one), 2, 4, 4 -trichloro-2 -hydroxy-diphenyl ether, zinc pyrithione, iV-butyl-1,2-... 

Numerous halogen and zinc compounds are available, such as Folpet (iV-trichloromethylthio), phthalimide, 2,4,4 -trichloro-2 -hydroxy diphenyl ether, zinc borate and zinc pyrithione. The last-mentioned is a broad-spectrum biocide that can be used instead of OBPA in many applications. 

The minimum inhibitory concentration (MIC) of the biocides used in plastics varies enormously. OBPA has a low MIC value for most of the common organisms, but OIT requires mueh less biocide than OBPA for some species, and much more for others. 

The move away from OBPA is evident in the product lines sold by Akcros Chemicals, a company that addresses both the material protection and hygienic surface markets. Akcros sells biocides imder the Intercide name for use in PVC, polyolefins and other polymer types. Between them these products can deal with all the various types of microorganism (fungi, bacteria, yeasts). 

Commercially available biocides include OBPA (10,10-oxybisphenoloxarsine) from Akzo Nobel, Witco, and Morton zinc-omadine (zinc 2-pyridinethanol-l-oxide) from Olin and Triclosan (trichlorophenoloxyphenol) from Allied Resinous Products, Ciba Specialty, and Microban. Major suppliers also include Ferro, Huels, Microban, Ciba, and Rohm and Haas. 

OBPA is a biocide, that means it is not only toxic to microbes but also to fish and other living species. Its antimicrobial effectiveness is similar to that of organo-mercurials covering a broad spectrum of bacteria, yeasts and mould producing fungi (minimum inhibition concentrations approx. 10 mg OBPA/litre). Among the fungal species Scopulariopsis brevicaule is relatively resistant to OBPA under use conditions. 

Biocides or antimicrobial agents inhibit bacterial growth, improving aesthetic and sanitary properties. They are not absolutely necessary in PO composition. However they are incorporated in the formulations of some items (such as packaging). Several examples of such compounds are 10,16-oxybisphenoxy arsine (OBPA-trade name) 2- -octyl-4-isothiazolin-3-one-1,2-dicarboxyimide (Folpet-trade name). 

The most widely used biocide in PVC has been oxybisphenoxarsine, sold as Intercide ABF (Akcros) and Vinyzene OPBA (Rohm Haas). OPBA has high solubiUty in plasticizers and is most often sold as 2 and 5 percent concentrates. The 2 percent concentrates are commonly used at 1.5 phr in indoor, and at 2.5 phr in outdoor appheations the 5 percent concentrates at 0.6 and 1.0 phr, respectively. OBPA poisons a variety of fiingi and bacteria at low concentrations. It is most likely ingested with plasticizer breakdown products and, mistaken for a phosphorus source, destroys ADP-ATP conversion processes (the usual mode of action of arsenic). Apparently, bacteria and fungi have not developed the sophisticated processes used by higher forms of life to sequester and eliminate trace levels of arsenic. The plasticizer concentrates, nevertheless, must be handled with care. OBPA is widely used in shower curtains and in a variety of outdoor applications. 

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