A synergistic biocide comprises a tris(hydroxymethyl)phosphine or a tetrakis (hydroxymethyl)phosphonium salt and at least one non-surfactant biopenetrant, such as a polymer or copolymer having a plurality of quaternary ammonium groups, a hydrotrope or a syntan, together optionally with a surfactant.

The present invention relates to synergistic biocidal mixtures of hydroxymethyl phosphonium biocides with certain non-foaming biopenetrants.
GB 2 145 708 describes biocidal uses of tetrakis (hydroxymethyl) phosphonium salts. which, together with their parent base, tris(hydroxymethyl)phosphine, are referred to herein collectively as xe2x80x9cTHPxe2x80x9d. U.S. Pat. No. 4,778,813 describes the biocidal use of quaternary ammonium polymers. GB 2 178 960 describes synergism between THP and surfactant. GB 2 228 680 describes synergism between THP and certain aldehydes.
THP formulations are increasingly widely used as biocides for water treatment in treating cooling water, process water e.g. in pulp and paper manufacture, drilling fluids and other aerobic water systems, as well as in anaerobic systems such as oil field formation water, injection water, produced water and water used in hydrostatic testing. Advantages include rapid and effective bactericidal activity and environmental acceptability. Particularly in systems where slime forming bacteria proliferate (e.g. in aerobic systems such as cooling water) it has been found desirable to use THP formulations containing synergistic amounts of a surfactant according to GB 2 178 960, in order to improve cost effective biocidal action. It is believed that the surfactant aids the penetration of the biomass by the THP. However such formulations cause foaming problems. Attempts to combine THP with other biocides (e.g. aldehydes), which do not cause foaming, have not been able to provide such effective biocidal action against slime forming bacteria, and/or have detracted from the favourable environmental profile of THP.
We have now discovered that combinations of THP with certain non-surfactant biopenetrants provide strongly synergistic biocidal formulations which give excellent penetration of bacterial slime and improved activity against planktonic bacteria without causing excessive foam. We have further discovered that mixtures of THP with a surfactant, and with a non-surfactant biopenetrant give a marked ternary synergism, permitting improved biocidal efficiency with reduced foaming.
Our invention provides a biocidally synergistic mixture comprising THP and at least one THP-compatible, non-surfactant, biopenetrant synergist together optionally with a surfactant The non-surfactant biopenetrant may be selected from quaternary ammonium polymers and copolymers, hydrotropes and syntans.
According to a second embodiment the invention provides a method of treating aqueous systems contaminated, or liable to contamination, with microbes such as bacteria. fungi or algae which comprises applying thereto separately or together a biocidally active amount of the components of a synergistic mixture as aforesaid.
The aqueous system may, for instance, be contaminated with bacterial slime and/or planktonic bacteria. The invention is of use for treating aerobic systems such as cooling towers and also for anaerobic systems, such as oil wells, e.g. during secondary recovery.
The THP is conveniently present in the formulation as a salt, but is preferably used at a pH sufficient to form the base. The salt is preferably the sulphate, chloride or phosphate. However any water soluble salt may be used including the phosphite, bromide, fluoride, carbonate, acetate, formate, citrate, borate, or silicate In fact any counter ion which is chemically compatible with THP may be used, the main criteria for selection being economic. Oxidation of THP to tris(hydroxymethyl)phosphine oxide (THPO) should be avoided and oxidising agents for THP are preferably substantially absent. The composition may contain oxygen scavengers to minimise oxidation by atmospheric oxygen. The pH of the composition may be below 3.5 to avoid THPO formation during storage but the pH on addition to aqueous systems is preferably between 3.5 and 9 and more preferably less than 8, e.g. 4 to 7.5. High alkalinity, e.g. above 10, is preferably avoided. The pH of the aqueous system may optionally be adjusted by addition of alkali or acid as appropriate.
An essential component of the invention is a non-surfactant biopenetrant. Surfactants are amphiphilic compounds which, even when present in low concentrations in water (e.g. 0.1% by weight), substantially reduce the interfacial free energy of a water/hydrophobe interface. Surfactants may be identified by their effect on surface tension of water. Non-surfactants do not appreciably reduce surface tension at low concentrations. Typically the reduction of surface tension by a non-surfactant at concentrations of the order of 0.1% does not amount to more than about 5% of the value for pure distilled water. At the same concentrations typical surfactants would reduce surface tension by 50% or more. For the purposes of this specification a compound is considered non-surfactant if it lowers the surface tension of water by less than 20% at a concentration of 0.1% by weight. Preferably the reduction is less than 15%, e.g. less than 10%, especially less than 5%.
The non-surfactant biopenetrant may for example be a quaternary ammonium polymer or copolymer. The quaternary ammonium polymer may for example be any of those described in U.S. Pat. No. 4,778,813. Particularly preferred is poly[oxyethylene(dimethyliminio)ethylene (dimethyliminio)ethylene dichloride]. This a copolymer of NNNxe2x80x2Nxe2x80x2-tetramethyl-1,2-diamino ethane with bis (2-chloroethyl) ether, which is referred to herein as xe2x80x9cWSCPxe2x80x9d. The latter is the commercial name of the product used in example 1, which is sold by Buckman Laboratories. However any other water soluble polymer containing a plurality of quaternary ammonium groups may be used. Such compounds typically comprise a polymeric cation of the formula:
wherein: each R is a divalent organic group constituting with the ammonium group a monomeric residue or separately selected from two or more comonomeric residues; each R1 is an alkyl or hydroxy alkyl group, typically having from 1 to 4 carbon atoms and preferably methyl or ethyl; X is hydrogen or a monovalant inorganic or organic end capping group; and n is from 2 to 3000, e.g. 5 to 2000, especially 8 to 1000, e.g. 10 to 500, most preferably 20 to 100. The counter ion may be any convenient THP-compatible anion e.g. chloride, sulphate, phosphate, bromide, fluoride, carbonate, formate, acetate, citrate, lactate, tartrate, methosulphate, borate or silicate.
R may for example be a C1-6 alkylene, oxyalkylene, polyoxyalkylene, haloalkylene, halooxyalkylene, halopolyoxyakylene or a
group wherein R2 may be a C1-6 alkylene, oxyalkylene polyoxyalkylene, haloalkylene, halooxyalkylene or halopolyoxyalkylene group and R3 represents a covalent bond or an R2 group. The polymer may for example be a methylated polyethylene polyamine of the formula
where n is 2 to 10.
Some other typical examples include:
Poly[hydroxyethylene(dimethyliminio)ethylene(dimethyliminio)methylene dichloride]
Poly[hydroxyethylene(dimethyliminio)-2-hydroxypropylene(dimethyliminio)-methylene dichloride]
N-[3-(dimethylammonio)propyl]-N[3-(ethyleneoxyethylenedimethylammonio) propyl]urea dichloride
-4-[1-tris(2-hydroxyethyl)ammonium chloride-2-butenyl]poly[1-dimethyl-ammonium chloride-2-butenyl]tris(2-hydroxyethyl)ammonium chloride
The non-surfactant biopenetrant may alternatively be a hydrotrope. Hydrotropes are sometimes confused with surfactants because they are also amphiphilic. However hydrotropes do not significantly affect surface tension at low concentrations. Hydrotropes act as solubilisers. When present in relatively high concentrations (e.g. greater than about 1%) they increase the water solubility of sparingly or moderately soluble solutes.
A preferred class of hydrotropes includes water soluble glycol ethers. The glycol ether is preferably a water soluble compound of the formula HO[CR2CR2O])nRxe2x80x2 where each R is methyl, ethyl or preferably H, provided that the total number of carbon atoms per [CR2CR2O] group does not exceed 4, more preferably is not more than 3 and most preferably is 2, Rxe2x80x2 is a lower hydrocarbon group such that the compound is water soluble, e.g. butyl, propyl, ethyl or preferably methyl and n is from 1 to 20, preferably 1 to 10, especially 1 to 5, typically 1 to 3, most preferably 2. Preferred examples include diethylene glycol monomethyl ether.
An important class of hydrotropes for use according to our invention comprises the lower alkyl aryl sulphonates. Water soluble salts, e.g. sodium, potassium, ammonium or salts of benzene sulphonic, toluene sulphonic, xylene sulphonic, ethyl benzene sulphonic or cumene sulphonic acids are very effective. Generally, alkylbenzene sulphonic acids having up to four or even five aliphatic carbon atoms show hydrotropicity but not significant surfactancy. Above six aliphatic carbons, e.g. sodium octyl benzene sulphonate, surfactancy predominates over hydrotropicity. Naphthalene sulphonates are also useful as non-surfactant biopenetrants, e.g. alkali metal C1-4 alkyl naphthalene sulphonates. Urea is also an effective hydrotrope.
A further category of non-surfactant biopenetrants comprises syntans. The latter include a variety of resins and prepolymers which are used in the tanning industry as an alternative to tannin or chrome.
Animal skins comprise a layer of collagen, and tanning agents react to cross link reactive sites within the collagen. One effect of this reaction is to increase the minimum temperature at which the leather tends to shrink in hot water.
For the purpose of this specification xe2x80x9csyntanxe2x80x9d is used to refer to synthetic organic compounds capable of reacting with collagen to form cross links so as to increase the shrink temperature of leather. For example the term includes any water soluble polymer prepared by copolymerising formaldehyde, which is capable of increasing the shrink resistance of collagen and which comprises at least two units of the formula
where each M is an aryl group such as a phenyl, naphthyl or aniline group substituted with one or more hydroxyl and/or sulphate, sulphone or sulphonimide groups or a nitrogenous comonomer such as a dicyandiamide, urea or melamine residue. As used herein the term xe2x80x9csyntanxe2x80x9d also includes resin syntans which are homopolyrners and copolymers of unsaturated carboxylic acids or their salts. esters, amides or nitrites, e.g. acrylic acid, methacrylic acid, acrylamide, acrylonitrile, maleic acid, fumaric acid, itaconic acid, aconitic acid, crotonic acid, isocrotonic acid, citraconic acid, mesaconic acid, angelic acid, tiglic acid and cinnamic acid. The copolymers may also comprise other vinylic comonomers such as styrene. Also included are acetone condensates with, for example sulphones and sulphonamides, and dicyandiamide based resins. Particularly preferred are: sulphonated aryl formaldehyde copolymers; condensates of THP with nitrogen compounds; phosphono polyacrylate or maleate telomers such as those described in EP 0 491 391; or phosphono ethyl phosphino telomers as described in EP 0 861 846.
The sulphonated aryl formaldehyde copolymer may for example be sodium naphthalene sulphonate formaldehyde condensate, sodium phenol formaldehyde concentrate, or sodium resorcinol formaldehyde condensate, or a condensate of formaldehyde with a sodium alkyl benzene or naphthalene sulphonate having less than 5 carbon atoms.
THP condensates may contain 2 or more phosphorus atoms, so long as the phosphorus compound is water soluble to a concentration of at least 0.5 g/l at 25xc2x0 C. Such phosphorus compounds contain a total of at least 2 hydroxymethyl groups, usually at least one per phosphorus atom, and preferably at least 2 hydroxymethyl groups per phosphorus atom. The group or groups joining the phosphorus atoms together may be of the formula xe2x80x94Rxe2x80x94, xe2x80x94Rxe2x80x94Oxe2x80x94, xe2x80x94Rxe2x80x94Oxe2x80x94Rxe2x80x94, xe2x80x94Rxe2x80x94NHxe2x80x94R or xe2x80x94Rxe2x80x94Rxe2x80x3xe2x80x94Rxe2x80x94 where R is an alkylene group of 1 to 4 carbon atoms and Rxe2x80x3 is the residue formed by removal of two hydrogen atoms, bonded to nitrogen, from a di or polyamide or an amine or di or polyamine, such as urea, a C1-20alkylamine, dicyandiamide, thiourea or guanidine. Such compounds with 2 or more, e.g. 3, hydroxyalkyl groups per phosphorus atom may be made by self condensation of THP salts with a compound of general formula Rxe2x80x3H2 such as urea, or a C1 to 20alkylamine, e.g. by heating at 40 to 120xc2x0 C.
The THP condensate may be prepared in situ by adding THP and a minor proportion of (for example) a condensable comonomer such as urea, melamine, an amine or dicyandiamide, simultaneously or consecutively to the system to be treated. Thus, for example, urea or aryl sulphonate hydrotrope may function as hydrotropes or comonomers for the in situ formation of syntans or in both capacities, in accordance with our invention.
The phosphono telomer may be a compound of the formula
H[CHRCHR]nxe2x80x94PO3M2
wherein at least one R group in each unit is a COOM, CH2OH, sulphono or phosphono group and the other r group which may be the same as, or different from, the first R group, is hydrogen or a COOM, hydroxyl, phosphono, sulphono, sulphate and/or hydroxy substituted C1-7 alkyl or C1-7 alkenyl group, and each M is a cation such that the phosphonated oligomer is water soluble and n is greater than 1, e.g. up to 10.
It is possible to use cotelomers, e.g. of the above formula, but in which the [CHRCHR]n chain contains at least two [CHRCHR] groups derived from different monomers and in which n has a total value of at least 3. For example we include a phosphonated trimer or higher cooligomer of maleate and acrylate containing at least one [CH2 CHCOOM] and at least one [CHCOOM CHCOOM] group.
Particularly preferred are phosphonated oligomers of maleic acid, of the formula H(CHCO2M.CHCO2M)aPO3M2 where n is greater than 1 and M is a cationic species such that the compound is water soluble, and especially mixtures of such compounds with phosphonosuccinic acid or its water soluble salts.
Particularly preferred are mixtures of phosphonosuccinate salts and an oligomer of the above formula when n=2, such as may be prepared by reacting sodium phosphite with a small molar excess of sodium maleate in a concentrated alkaline aqueous solution at elevated temperatures in the presence of a free radical source such as hydrogen peroxide.
Other phosphono telomers which are used according to the invention include phosphono acrylate telomers, e.g. of the formula:
M2O3P[CH2CHCOOM]nH
where n may be 2 to 60, preferably 3 to 30, e.g. 4 to 20.
1-Phosphono-2-phosphino ethane can be reacted with salts of telomerisable unsaturated acids such as maleic and acrylic to make syntans which are useful in the present invention. Other phosphono carboxylates of use include phosphonosuccinates and salts of 2-phosphono-1,2,4-tricarboxy butane.
The biopenetrant synergist is not usually present in a greater weight concentration than the THP, although higher concentrations by weight based on THP, e.g. up to 10:1 or even 100:1 are technically possible but commercially undesirable. The proportion is preferably less than 50% by weight based on the weight of THP, more usually less than 20%, typically less than 10%, especially less than 5%. Although very small amounts may be effective we prefer to use proportions of biopenetrant greater than 0.1% based on the weight of THP, usually greater than 0.5%, especially greater than 1%.
The biocide is typically supplied as a 10 to 75%, e.g. 20 to 60%, especially 30 to 50% by weight aqueous solution of THP containing from 0.1 to 10% e.g. 0.2 to 5%, especially 0.5 to 2% of the synergist, based on the total weight of the solution.
Alternatively the composition may be supplied as a solid formed by coating THP onto, or absorbing it into, a powdery granular or porous acid substrate such as adipic acid.
The mixture is typically used at a dosage of 1 to 1500 ppm by weight THP based on the weight of water to be treated, usually 2 to 500, especially 5 to 250, e.g. 10 to 150.
According to a particular embodiment it has been found that mixtures of the aforesaid biopenetrant synergists with surfactants and THP salts provide an enhanced synergism. Such mixtures can provide even more effective biocidal activity, at substantially lower levels of both biocide and surfactant than arm required for conventional mixtures of THP salts and surfactant.
Our invention accordingly further provides a biocidally synergistic mixture comprising: (A) THP; (B) at )cast one non-surfactant biopenetrant; and (C) a surfactant.
The invention further provides a method of treating water with a biocidally active amount of said synergistic mixture.
Surfactants for use in our invention typically contain hydrophobic groups such as alkenyl, cycloalkenyl, alkyl, cycloalkyl, aryl, alkyl/aryl or more complex aryl (as in petroleum sulphonates) moieties having from 8 to 22, preferably 10 to 20, typically 12 to 18 carbon atoms and a hydrophilic moiety. Other hydrophobic groups included in the invention are polysiloxane groups.
The surfactant may for example consist substantially of an at least sparingly water-soluble salt of sulphonic or mono esterified sulphuric acids, e.g. an alkylbenzene sulphonate, alkyl sulphate, alkyl ether sulphate, olefin sulphonate, alkane sulphonate, alkylphenol sulphate, alkylphenol ether sulphate, alkylethanolamide sulphate, alkylethanolamidether sulphate, or alpha sulpho fatty acid or its ester each having at least one alkyl or alkenyl group with from 8 to 22, more usually 10 to 20, aliphatic carbons atoms.
The expression xe2x80x9cetherxe2x80x9d hereinbefore refers to compounds containing one or more glyceryl groups and/or an oxyalkylene or polyoxyalkylene group especially a group containing from 1 to 20 oxyethylene and/or oxypropylene groups. One or more oxybutylene groups may additionally or alternatively be present. For example, the sulphonated or sulphated surfactant may be sodium dodecyl benzene sulphonate, potassium hexadecyl benzene sulphonate, sodium dodecyl dimethyl benzene sulphonate, sodium lauryl sulphate, sodium tallow sulphate, potassium oleyl sulphate, ammonium lauryl monoethoxy sulphate, or monoethanolamine cetyl 10 mole ethoxylate sulphate.
Other anionic surfactants useful according to the present invention include alkyl sulphosuccinates, such as sodium di-2-ethylhexylsulphosuccinate and sodium dihexylsulphosuccinate, alkyl ether sulphosuccinates, alkyl sulphosuccinamates, alkyl ether sulphosuccinomates, acyl sarcosinates, acyl taurides, isethionates, soaps such as stearates, palmitates, resinates, oleates, linoleates, and alkyl ether carboxylates. Anionic phosphate esters and alkyl phosphonates, alkyl amino and imino methylene phosphonates may also be used. In each case the anionic surfactant typically contains at least one aliphatic hydrocarbon chain having from 8 to 22, preferably 10 to 20 carbon atoms, and, in the case of ethers, one or more glyceryl and/or from 1 to 20 oxyethylene and/or oxypropylene and/or oxybutylene groups.
Preferred anionic surfactants are sodium salts. Other salts of commercial interest include those of potassium, lithium, calcium, magnesium, ammonium, monoethanolamine, diethanolamine, triethanolamine, alkyl amines containing up to seven aliphatic carbon atoms, and alkyl and/or hydroxyalkyl phosphonium.
The surfactant may optionally contain or consist of nonionic surfactants. The nonionic surfactant may be, e.g. a C10-22 alkanolamide of a mono or di- lower alkanolamine, such a coconut monoethanolamide. Other nonionic surfactants which may optionally be present, include tertiary acetylenic glycols, polyethoxylated alcohols, polyethoxylated mercaptans, polyethoxylated carboxylic acids, polyethoxylated amines, polyethoxylated alkylolamides, polyethoxylated alkylphenols, polyethoxylated glyceryl esters, polyethoxylated sorbitan esters, polyethoxylated phosphate esters, and the propoxylated or ethoxylated and propoxylated analogues of all the aforesaid ethoxylated nonionics, all having a C8-22 alkyl or alkenyl group and up to 20 ethyleneoxy and/or propyleneoxy groups. Also included are polyoxypropylene/polyethylene oxide copolymers, polyoxybutylenelpolyoxyethylene copolymers and polyoxybutylene/polyoxypropylene copolymers. The polyethoxy, polyoxypropylene and polyoxybutylene compounds may be endcapped with, e.g. benzyl groups to reduce the foaming tendency.
Compositions of our invention may contain amphoteric surfactant.
The amphoteric surfactant may for example be a betaine, e.g. a betaine of the formula: R3N+CH2COOxe2x88x92, wherein each R is an alkyl, cycloalkyl, alkenyl or alkaryl group and preferably at least one, and most preferably not more than one R, has an average of from 8 to 20, e.g. 10 to 18 aliphatic carbon atoms and each other R has an average of from 1 to 4 carbon atoms. Particularly preferred are the quaternary imidazoline betaines of the formula:
wherein R and Rxe2x80x2 are alkyl, alkenyl, cycloalkyl, alkaryl or alkanol groups having an average of from 1 to 20 aliphatic carbon atoms and R preferably has an average of from 8 to 20, e.g. 10 to 18 aliphatic carbon atoms and Rxe2x80x2 preferably has 1 to 4 carbon atoms. Other amphoteric surfactants for use according to our invention include alkyl amine ether sulphates, sulphobetaines and other quaternary amine or quaternised imidazoline sulphonic acids and their salts, and Zwitterionic surfactants, e.g. N-alkyl taurines, carboxylated amido amines such as RCONH(CH2)2N+ (CH2CH2CH3)2CH2COxe2x88x922, and amino acids having, in each case, hydrocarbon groups capable of conferring surfactant properties (e.g. alkyl, cycloalkyl alkenyl or alkaryl groups having from 8 to 20 aliphatic carbon atoms). Typical examples include 2-tallow alkyl, 1-tallow amido alkyl, 1-carboxymethyl imidazoline and 2 coconut alkyl N-carboxymethyl 2 (hydroxyalkyl) imidazoline. Generally speaking any water soluble amphoteric or Zwitterionic surfactant compound which comprises a hydrophobic portion including C8-20 alkyl or alkenyl group and a hydrophilic portion containing an amine or quaternary ammonium group and a carboxylate, sulphate or sulphonic acid group may be used in our invention.
Compositions of our invention may also include cationic surfactants.
The cationic surfactant may for example be an alkylammonium salt having a total of at least 8, usually 10 to 30, e.g. 12 to 24 aliphatic carbon atoms, especially a tri or tetra-alkylammonium salt. Typically alkylammonium surfactants for use according to our invention have one or at most two relatively long aliphatic chains per molecule (e.g. chains having an average of 8 to 20 carbon atoms each, usually 12 to 18 carbon atoms) and two or three relatively short chain alkyl groups having 1 to 4 carbon atoms each, e.g. methyl or ethyl groups, preferably methyl groups. Typical examples include dodecyl trimethyl ammonium salts. Benzalkonium salts having one 8 to 20 C alkyl group two 1 to 4 carbon alkyl groups and a benzyl group are also useful.
Another class of cationic surfactant useful according to our invention comprises N-alkyl pyridinium salts wherein the alkyl group has an average of from 8 to 22, preferably 10 to 20 carbon atoms. Other similarly alkylated heterocyclic salts, such as N-alkyl isoquinolinium salts, may also be used.
Alkylaryl dialkylammonium salts, having an average of from 10 to 30 aliphatic carbon atoms are useful, e.g. those in which the alkylaryl group is an alkyl benzene group having an average of from 8 to 22, preferably 10 to 20 carbon atoms and the other two alkyl groups usually have from 1 to 4 carbon atoms, e.g. methyl groups.
Other classes of cationic surfactant which are of use in our invention include alkyl imidazoline or quaternised imidazoline salts having at least one alkyl group in the molecule with an average of from 8 to 22 preferably 10 to 20 carbon atoms. Typical examples include alkyl methyl hydroxyethyl imidazolinium salts, alkyl benzyl hydroxyethyl imidazolinium salts, and 2 alkyl-1-alkylamidoethyl imidazoline salts.
Another class of cationic surfactant for use according to our invention comprises the amido amines such as those formed by reacting a fatty acid having 2 to 22 carbon atoms or an ester, glyceride or similar amide forming derivative thereof, with a di or poly amine, such as, for example, ethylene diamine or diethylene triamine, in such a proportion as to leave at least one free amine group. Quaternised amido amines may similarly be employed.
Alkyl phosphonium and hydroxyalkyl phosphonium salts having one C8-20 alkyl group and three C1-4 alkyl or hydroxyalkyl groups may also be used as cationic surfactants in our invention.
Typically the cationic surfactant may be any water soluble compound having a positively ionised group, usually comprising a nitrogen atom, and either one or two alkyl groups each having an average of from 8 to 22 carbon atoms.
The anionic portion of the cationic surfactant may be any anion which confers water solubility, such as formate, acetate, lactate, tartrate, citrate, chloride, nitrate, sulphate or an alkylsulphate ion having up to 4 carbon atoms such as methosulphate. It is preferably not a surface active anion such as a higher alkyl sulphate or organic sulphonate.
Polyfluorinated anionic, nonionic or cationic surfactant may also be useful in the compositions of our invention. Examples of such surfactants are polyfluorinated alkyl sulphates and polyfluorinated quaternary ammonium compounds.
Compositions our invention may contain a semi-polar surfactant such as an amine oxide, e.g. an amine oxide containing one or two (preferably one) C8-22 alkyl group, the remaining substituent or substituents being preferably lower alkyl groups, e.g. C1-4 alkyl groups or benzyl groups.
Particularly preferred for use according to our invention are surfactants which are effective as wetting agents, typically such surfactants are effective at lowering the surface tension between water and a hydrophobic solid surface. We prefer surfactants which do not stabilise foams to a substantial extent.
Mixtures of two or more of the foregoing surfactants may be used. In particular mixtures of non-ionic surfactants with cationic and/or amphoteric and/or semi polar surfactants or with anionic surfactants may be used. Typically we avoid mixtures of anionic and cationic surfactants, which are often less mutually compatible.
Preferably the THP and the surfactant are present in a relative weight concentration of from 1:1000 to 1000:1, more usually 1:50 to 200:1, typically 1:20 to 100:1, most preferably 1:10 to 50:1, e.g. 1:1 to 20:1 especially 2:1 to 15:1.
Effective doses of the mixture are typically from 0.5 ppm to 2,000 ppm, more usually 2 ppm to 1,000 ppm, e.g. 5 ppm to 500 ppm especially 10 to 250 ppm.
The composition may additionally contain other biocides, water dispersants, antifoams, solvents, scale inhibitors, corrosion inhibitors, oxygen scavengers and/or flocculants.
Our invention includes aqueous solutions containing a biocidally active concentration of a composition of the invention. Such solutions may be water systems or aqueous based products containing functional ingredients as described in GB 2 145 708. Our invention also includes anhydrous, and concentrated aqueous, formulations adapted to provide the aforesaid products on dilution with water.
Scale or corrosion inhibitors which may be added to the water to be treated in conjunction with the present invention include phosphonates, polymaleates, polyacrylates, polymethacrylates, polyphosphates, phosphate esters, soluble zinc salts, nitrite, sulphite, benzoate, tannin, ligninsulphonates, benzotriazoles and mercaptobenzothiazoles all added in conventional amounts. The scale and/or corrosion inhibitors may be added to the water separately from or in association with the phosphonium compound and surfactant. There may be added to the water to be treated oxygen scavengers, flocculants such as polyacrylamide dispersants, antifoams such as silicones or polyethyleneoxylatcd antifoams or other biocides such as tin compounds or isothiazolones.
The mixture according to our invention may be prepared in situ by adding the THP, the biopenetrant synergist, and optionally the surfactant separately to the water system to be treated. Alternatively and preferably the components may be premixed, either alone, provided that they are miscible in the desired proportions, or with water or other solvents including C1-4 monohydric and polyhydric alcohols, ketones. or dispersants such as polyclectrolytes. Typically THP is miscible with cationic surfactants of the quaternary ammonium and phosphonium type, but mixtures with non-ionic surfactants may require dilution with water or solvents.
The microorganisms to be treated are usually bacteria, fungi, yeasts, and algae that grow in aquatic environments,. Included in this classification are sulphate reducing bacteria, e.g. Desulphovibrio, which may occur in oil installations, iron bacteria, e.g. Gallionella and slime forming bacteria, e.g. Pseudomonas, which last are particularly troublesome in aerated aqueous systems.
The water to be treated may be industrial cooling water, e.g. for power stations or chemical plants or for steel or paper or brewing and may be used in closed circuit or in open circuit involving evaporation in cooling towers. Alternatively the water may be process water, especially process water containing significant sources of nutrients for microorganisms such as process water for paper making plants and breweries. Injection water or drilling fluids for oil fields or water produced from oil fields or water used in reverse osmosis plants, e.g. to provide industrial processes or boilers feed water, may be treated.
Other aquatic environments which may be treated with the synergistic biocidal mixtures according to the method for the invention are cooling or process water in board mills. fertiliser manufacture, oil refineries, primary metals manufacture, e.g. steel or copper, petrochemicals, rubber manufacture, textile and fabric industries, industrial gas manufacture, minerals recover, glass and ceramic manufacture, food industry, leather manufacture, heavy and light engineering, including metal fabrication and automotive engineering, furniture manufacture, electronics industry and surface coating and adhesives manufacture and other manufacturing industries.
The process is also applicable to the treatment of geothermal water, water in domestic, industrial and institutional central heating and air conditioning systems and water used for hydrostatic testing of pipelines and vessels, swimming baths and as cooling water for ships and marine engines.
The invention is also applicable to the control of microbial contamination in a wide variety of aqueous based products. For example compositions of the invention may be added to a variety of solutions and emulsion compositions such as paints, cutting oils, bitumen and tar emulsions, adhesives, weedkillers and insecticides, as well as to solid or concentrated compositions for addition to water in the preparation of such products. The invention, therefore, further provides aqueous based products which are subject to microbial spoilage to which has been added a bacteriostatic or bactericidal quantity of a THP salt, a biopenetrant synergist as aforesaid and, optionally, a surfactant. Typically such compositions consist of aqueous solutions, suspensions or emulsions of at least one functional ingredient, together with a minor proportion of a composition of the invention, sufficient to inhibit growth of microorganisms therein.
The systems to which the invention is particularly applicable arc those involving the circulation or storage of substantial quantities of water, under conditions favouring the multiplication of bacteria, especially hardy bacteria such as P Aeruginosa, e.g. conditions involving maintaining or periodically raising the water to super ambient temperatures favouring bacterial proliferation, or maintaining nutrients for the bacteria in the water systems.
The invention will be illustrated by the following examples:


Programmable architecture for implementing a message processing system using an integrated circuit is described. In an example, first attributes are defined for a plurality of threads within the integrated circuit. Second attributes are defined for a memory associated with the integrated circuit. Third attributes are defined for an interconnection topology associated with at least one of the memory and the plurality of threads. Fourth attributes are defined for an interface to at least one of the memory and the plurality of threads.

Programmable logic devices (PLDs) exist as a well-known type of integrated circuit (IC) that may be programmed by a user to perform specified logic functions. There are different types of programmable logic devices, such as programmable logic arrays (PLAs) and complex programmable logic devices (CPLDs). One type of programmable logic device, known as a field programmable gate array (FPGA), is very popular because of a superior combination of capacity, flexibility, time-to-market, and cost.
An FPGA typically includes an array of configurable logic blocks (CLBs) surrounded by a ring of programmable input/output blocks (IOBs). The CLBs and IOBs are interconnected by a programmable interconnect structure. The CLBs, IOBs, and interconnect structure are typically programmed by loading a stream of configuration data (known as a bitstream) into internal configuration memory cells that define how the CLBs, IOBs, and interconnect structure are configured. Additionally, an FPGA may include embedded memory, such as block random access memories (BRAMs), one or more microprocessors, sometimes referred to as embedded cores, and digital clock managers (DCMs). The combination of components on an FPGA may be used for system-level integration, sometimes referred to as "system-on-a-chip" (SOC).
Historically, FGPAs have not been employed in network processing applications. Rather, Network devices, such as routers, employ dedicated, special purpose components for processing packets that propagate through the network. Conventionally, network devices employ network processors or application specific integrated circuits (ASICs) to provide the desirable packet processing/network processing functions. Such processor- or ASIC-based architectures, however, are static in nature, providing a fixed amount of resources for packet processing/network processing functions. Accordingly, there exists a need in the art for more flexible message processing architectures.

Method and apparatus for a programmable interface of a soft platform on a programmable logic device


Improved electrostatographic developer mixtures comprising finely-divided toner particles electrostatically clinging to the surface of carrier particles wherein the carrier particles comprise a core having an outer layer thereon of poly(2-vinyl-pyridine) mixed with polyurethane. The use of said developer mixtures for the development of electrostatic latent images is also described.

This invention relates, in general, to electrostatographic imaging systems, and, in particular, to improved developer materials and their uses.
The formation and development of images on the surface of photoconductive materials by electrostatic means is well-known. The basic electrophotographic process, as taught by C. F. Carlson in U.S. Pat. No. 2,297,691, involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing the layer to a light and shadow image to dissipate the charge on the areas of the layer exposed to the light, and developing the resulting electrostatic latent image by depositing on the image a finely-divided electroscopic material referred to in the art as "toner". The toner will normally be attracted to those areas of the layer which retain a charge, thereby forming a toner image corresponding to the electrostatic latent image. This powder image may then be transferred to a support surface such as paper. The transferred image may subsequently be permanently affixed to the support surface as by heat. Instead of latent image formation by uniformly charging the photoconductive layer and then exposing the layer to a light and shadow image, one may form the latent image by directly charging the layer in image configuration. The powder image may be fixed to the photoconductive layer if elimination of the powder image transfer step is desired. Other suitable fixing means such as solvent or overcoating treatment may be substituted for the foregoing heat fixing step.
Many methods are known for applying the electroscopic particles to the electrostatic latent image to be developed. One development method, as disclosed by E. N. Wise in U.S. Pat. No. 2,618,552, is well-known as "cascade" development. In this method, a developer material comprising relatively large carrier particles having finely-divided toner particles electrostatically clinging to the surface of the carrier particles is conveyed to and rolled or cascaded across the electrostatic latent image bearing surface. The composition of the toner particles is so chosen as to have a triboelectric polarity opposite that of the carrier particles. As the mixture cascades or rolls across the image bearing surface, the toner particles are electrostatically deposited and secured to the charged portion of the latent image and are not deposited on the uncharged or background portions of the image. Most of the toner particles accidentally deposited in the background are removed by the rolling carrier, due apparently, to the greater electrostatic attraction between the toner and the carrier than between the toner and the discharged background. The carrier particles and unused toner particles are then recycled. This technique is extremely good for the development of line copy images. The cascade development process is the most widely used commercial electrostatographic development technique. A general purpose office copying machine incorporating this technique is described in U.S. Pat. No. 3,099,943.
Another technique for developing electrostatic latent images is the "magnetic brush" process as disclosed, for example, in U.S. Pat. No. 2,874,063. In this method, a developer material containing toner and magnetic carrier particles is carried by a magnet. The magnetic field of the magnet causes alignment of the magnetic carriers in a brush-like configuration. This "magnetic brush" is engaged with an electrostatic latent image bearing surface and the toner particles are drawn from the brush to the electrostatic latent image by electrostatic attraction.
Another technique for developing electrostatic latent image is the "touchdown" process as disclosed, for example, in U.S. Pat. Nos. 2,895,847 and 3,245,823 to Mayo. In this method, a developer material is carried to a latent image bearing surface by a support layer such as a web or sheet and is deposited thereon in conformity with said image.
Carrier particles are made from or coated with materials having appropriate triboelectric properties as well as certain other physical characteristics. Thus, the materials employed as the carrier particles or the coatings thereon should have a triboelectric value commensurate with the triboelectric value of the toner to enable electrostatic adhesion of the toner to the carrier particles and subsequent transfer of the toner from the carrier particles to the image on the plate without excessive power requirements. Furthermore, the triboelectric properties of all the carrier particles should be relatively uniform to permit uniform pick-up and subsequent deposition of toner. The materials employed in the carrier particles should have an intermediate hardness so as not to scratch the plate or drum surface upon which the electrostatic image is initially placed while being sufficiently hard to withstand the forces to which they are subjected during recycle. The carrier particles as well as the surface thereof also should not be comprised of materials which are so brittle as to cause either flaking of the surface or particle break-up under the forces exerted on the particles during recycle. The flaking causes undesirable effects in that the relatively small flaked particles will eventually be transferred to the copy surface thereby interfering with the deposited toner and causing imperfections in the copy image. Furthermore, flaking of the carrier particle surface will cause the resultant carrier particles to have non-uniform triboelectric properties when the carrier particle is composed of a core material different from the surface coating thereon. This results in undesirable nonuniform pick-up of toner by the carrier particles and non-uniform deposition of toner on the image. In addition, when the carrier particle size is reduced, the removal of the resultant small particles from the plate becomes increasingly difficult. Thus, the type of materials useful for making carrier particles or for coating carrier particles, although having the appropriate triboelectric properties, are limited because other physical properties which they possess may cause the undesirable results discussed above.
It is highly desirable to alter the triboelectric properties of carrier cores to accommodate the use of desirable toner compositions while retaining the other desirable physical characteristics of the carrier particle. The alteration of the triboelectric properties of carrier particles by applying a surface coating thereon is a particularly desirable technique. With this technique, not only is it possible to alter the triboelectric properties of carrier particles made from materials having desirable physical characteristics, it is also possible to employ materials previously not suitable as carrier particles. Thus, for example, carrier particles having desirable physical properties with the exception of hardness, can be coated with a material having desirable hardness as well as other physical properties, rendering the resultant product useful as carrier particles.
While ordinarily capable of producing good quality images, conventional developing materials suffer serious deficiencies in certain areas. The developing materials must flow freely to facilitate accurate metering and even distribution during the development and developer recycling phases of the electrostatographic process. Some developer materials, though possessing desirable properties such as proper triboelectric characteristics, are unsuitable because they tend to cake, bridge and agglomerate during handling and storage. Adherence of carrier particles to reusable electrostatographic imaging surfaces causes the formation of undesirable scratches on the surfaces during image transfer and surface cleaning steps. The tendency of carrier particles to adhere to imaging surfaces is aggravated when the carrier surfaces are rough and irregular. The coatings of most carrier particles deteriorate rapidly when employed in continuous processes which require the recycling of carrier particles by bucket conveyors partially submerged in the developer supply such as disclosed in U.S. Pat. No. 3,099,943. Deterioration occurs when portions of or the entire coating separates from the carrier core. The separation may be in the form of chips, flakes or entire layers and is primarily caused by fragile, poorly adhering coating materials which fail upon impact and abrasive contact with machine parts and other carrier particles. Carriers having coatings which tend to chip and otherwise separate from the carrier core must be frequently replaced thereby increasing expense and loss of productive time. Print deletion and poor print quality occur when carrier particles having damaged coatings are not replaced. Fines and grit formed from carrier disintegration tend to drift and form undesirable and damaging deposits on critical machine parts. Many carrier coatings having high compressive and tensile strength either do not adhere well to the carrier core or do not possess the desired triboelectric characteristics. The triboelectric and flow characteristics of many carriers are adversely affected when relative humidity is high. For example, the triboelectric values of some carrier coatings fluctuate with changes in relative humidity and are not desirable for employment in electrostatographic systems, particularly in automatic machines which require carriers having stable and predictable triboelectric values. Another factor affecting the stability of carrier triboelectric properties is the susceptibility of carrier coatings to "toner impaction". When carrier particles are employed in automatic machines and recycled through many cycles, the many collisions which occur between the carrier particles and other surfaces in the machine cause the toner particles carried on the surface of the carrier particles to be welded or otherwise forced into the carrier coatings. The gradual accumulation of permanently attached toner material on the surface of the carrier particles causes a change in the triboelectric value of the carrier particles and directly contributes to the degradation of copy quality by eventual destruction of the toner carrying capacity of the carrier. Thus, there is a continuing need for a better material for developing electrostatic latent images.
It is, therefore, an object of this invention to provide developer materials which overcome the above-noted deficiencies and are suitable for use in electrostatographic reproduction processes.
It is another object of this invention to provide carrier particles which possess improved electrostatic and physical properties for efficient and prolonged use in electrostatographic reproduction processes.
It is a further object of this invention to provide carrier particles having an elastic and tough coating which tenaciously adheres to the carrier core whereby the carrier particles are more resistant to toner impaction, chipping and flaking.
It is another object of this invention to provide developer materials which flow more freely.
It is yet another object of this invention to provide carrier materials having more stable triboelectric values.
It is a further object of this invention to provide carrier coatings having higher tensile and compressive strength.
It is yet another object of this invention to provide carrier coatings having greater resistance to disintegration.
It is yet another object of this invention to provide coated carrier materials having greatly increased developer life.
It is still another object of this invention to provide developer materials having physical and chemical properties superior to those of known developer materials.
The above objects and others are accomplished, generally speaking, by providing electrostatographic developer mixtures comprising finely-divided toner particles electrostatically clinging to the surface of carrier particles wherein said carrier particles comprise a core having an outer layer thereon of poly(2-vinyl-pyridine) mixed with polyurethane.
In accordance with this invention, it has been found that mixtures of poly(2-vinyl-pyridine) and polyurethane or poly(2-vinyl-pyridine) with polyurethane and poly(vinylbutyral) provide electrostatographic carrier coating materials which possess desirable triboelectric charging properties and which also possess elastic or viscoelastic properties as to avoid or minimize mechanical degradation of carrier particles coated therewith. It has been generally believed that failure of toner and coated carrier developer mixtures in electrostatographic reproduction devices is at least partially attributed to toner impaction. It has been found that carrier coating materials usually degrade chemically to lower molecular weight species under the repeated stresses of tumbling and recycling in the housing of reproduction machines. This degradation is thought to be aggravated by the high mechanical stress levels created in the machine configuration from carrier-to-carrier, and carrier-to-housing impacts. The degradation of the carrier coating materials results in coating depletion via polymer substrate adhesive failure or polymer failure resulting in undesirably altered carrier coating triboelectric charging characteristics.
It is postulated that the molecular weight changes of the polymer carrier coating materials may be due to the inability of the carrier coating material to store mechanical energy during the numerous aforementioned impacts. Another theory is that prior carrier coating materials are unable to extend under applied mechanical stress and thus fracture due to brittleness and chain scission of the polymer coating occurs. According to this invention, carrier coating materials have been found which substantially eliminate such effects by possessing elastic mechanical properties which allow for deformation and recovery during and following mechanical impact.
It has now been found that the properties desired of carrier coating materials may be attained by solution blending poly(2-vinyl-pyridine) and polyurethane or poly(2-vinyl-pyridine) with polyurethane and polyvinylbutyral. Poly(2-vinyl-pyridine) is the component of the mixtures that provides desirable triboelectric charging properties to the carrier coating materials, while the polyurethane provides the carrier coating materials with tensile strength, modulus, elongation properties, tear strength, and abrasion resistance. These blended systems not only have desirable mechanical properties, but also exhibit low work functions on the triboelectric scale. The polyurethane employed as a component of the carrier coating materials of this invention generally has a tensile strength of between about 5300 psi and about 5700 psi; a tensile modulus of between about 700 psi and about 1700 psi; elongation of between about 300 percent and about 500 percent; and a tear strength of between about 300 pounds and about 400 pounds. In addition, the polyurethane component preferably has a molecular weight of less than about 50,000 as it provides for better compatibility with the aforementioned polymer systems.
In accordance with this invention, satisfactory electrostatographic carrier coating compositions are provided when the materials comprise from between about 10 and about 90 parts by weight of poly(2-vinyl-pyridine) and from between about 90 and about 10 parts by weight of polyurethane. However, it is preferred that the electrostatographic carrier coating compositions of this invention comprise from between about 30 and about 70 parts by weight of poly(2-vinyl-pyridine) and from between about 70 and about 30 parts by weight of polyurethane because these mixtures exhibit good mechanical properties and stable cascade triboelectric charge values. Further, the extremes of composition, particularly of poly(2-vinyl-pyridine) provide for excessive sensitivity to high relative humidities. Optimum results are generally obtained when the electrostatographic carrier coating compositions of this invention comprise from between about 40 and about 60 parts by weight of poly(2-vinyl-pyridine) and from between about 60 and about 40 parts by weight of polyurethane. In addition, mixtures of polyurethane, polyvinylbutyral, and poly(2-vinyl-pyridine) may be employed to obtain the electrostatographic carrier coating compositions of this invention and such mixtures are considered within the scope of this invention. When poly(vinyl-butyral) is employed in the coating compositions of this invention, it may be present in an amount of from between about 5 and about 20 parts by weight based on the total parts of the coating composition.
Ordinarily, the desired blending of two polymers would lead to a solution of one polymer in another. However, few polymer systems exhibit this behavior and generally experience gross phase separation morphology when observed with optical microscopy. When preparing the blended polymer systems of this invention, this problem may be overcome by dissolving the polyurethane and poly(2-vinyl-pyridine) in equal concentrations in tetrahydrofuran and chloroform, respectively. These solutions may then be blended in desired amounts and evaporated. Microscopic examination of dried films of the polymer blend shows little or no phase separation indicating that polymer domain size was at all times less than 2 microns throughout the range of polymer blend concentrations.
In cascade triboelectric charge measurements, it was found that phase separated morphology of the polymer blends of this invention has only a slight effect on the triboelectric characteristics of the mixtures with the more finely-dispersed polymer systems tending toward a linear triboelectric relationship with composition. It was also found that the polymer blend systems of this invention containing up to about 30.0 percent by weight of poly(2-vinyl-pyridine) are relatively insensitive to relative humidity and other ambient conditions while providing the polymer blend the capability of generating high triboelectric charging of toner material. As to the mechanical properties of the polymer blends of this invention, polyurethane exhibits maximum elastomeric behavior and a low modulus with high elongation properties in the absence of poly(2-vinyl-pyridine). It was further found that the tensile modulus as a function of polymer blend composition exhibits a maximum at about 75.0 percent by weight of poly(2-vinyl-pyridine). However, the polymer blends of this invention all exhibit large elongations to break and high moduli at poly(2-vinyl-pyridine) percentages greater than 5.0. Generally speaking, the mechanical properties of the polymer blends show modulus decreasing and elongation to break increasing with increased polyurethane content.
In general, the electrostatographic coated carriers of the present invention may be prepared by coating a solid substrate with a mixture of poly(2-vinyl-pyridine) and polyurethane or poly(2-vinyl-pyridine) with polyurethane and poly(vinylbutyral) and hardening the resulting layer to form a hard substantially continuous coating thereon. Any suitable coating technique may be used to apply the coating to the substrate such as spraying, dipping, or fluidized bed coating. Any suitable coating thickness may be employed. However, a coating having a thickness at least sufficient to form a thin continuous film is preferred because the carrier coating will then possess sufficient thickness to resist abrasion and prevent pinholes which adversely affect the triboelectric properties of the coated carrier. Generally, for cascade and magnetic brush development, the carrier coating may comprise from about 0.1 percent to about 1.0 percent by weight based on the weight of the coated carrier particle. Preferably, the coating should comprise from about 0.2 percent to about 0.7 percent by weight based on the weight of the coated carrier particle because maximum coating durability, toner impaction resistance, and copy quality are achieved.
Any suitable well-known coated or uncoated carrier material may be employed as the substrate for the carriers of this invention. Typical carrier core materials include sodium chloride, ammonium chloride, aluminum potassium chloride, Rochelle salt, sodium nitrate, potassium chlorate, granular zircon, granular silicon, methyl methacrylate, glass, silicon dioxide, flintshot, iron, steel, ferrite, nickel carborundum and mixtures thereof. Typical carrier substrates for "touchdown" donor surfaces include cloth, metal-backed paper, cellophane, aluminum foil, resins such as polyethylene terephthalate and polyvinyl resins, cellulosic derivatives, protein materials, and combinations thereof. Many of the foregoing and other typical carrier materials are described by L. E. Walkup in U.S. Pat. No. 2,618,551; L. E. Walkup et al in U.S. Pat. No. 2,638,416; E. N. Wise in U.S. Pat. No. 2,618,552; and C. R. Mayo in U.S. Pat. Nos. 2,805,847 and 3,245,823. An ultimate coated carrier particle having an average diameter between about 30 microns to about 1,000 microns is preferred in cascade systems because the carrier particle then possesses sufficient density and inertia to avoid adherence to the electrostatic images during the cascade development process. Adherence of carrier beads to an electrostatographic drum is undesirable because of the formation of deep scratches on the drum surface during the image transfer and drum cleaning steps, particularly where cleaning is accomplished by a web cleaner such as the web disclosed by W. P. Graff, Jr. et al, in U.S. Pat. No. 3,186,838.
Any suitable finely-divided toner material may be employed with the coated carriers of this invention. Typical toner materials include gum copal, gum sandarac, rosin, cumaroneindene resin, asphaltum, gilsonite, phenolformaldehyde resins, rosin modified phenolformaldehyde resins, methacrylic resins, polystyrene resins, epoxy resins, polyester resins, polyethylene resins and mixtures thereof. The particular toner material to be employed obviously depends upon the separation of the toner particles from the coated carrier beads in the triboelectric series. Among the patents describing electroscopic toner compositions are U.S. Pat. No. 2,659,670 to Copley; U.S. Pat. No. 2,753,308 to Landrigan; U.S. Pat. No. 3,079,342 to Insalaco; U.S. Pat. No. Re. 25,136 to Carlson and U.S. Pat. No. 2,788,288 to Rheinfrank et al. These toners generally have an average particle diameter between about 1 and about 30 microns.
Any suitable pigment or dye may be employed as the colorant for the toner particles. Toner colorants are well known and include, for example, carbon black, nigrosine dye, aniline blue, Calco Oil Blue, chrome yellow, ultra marine blue, Quinoline Yellow, methylene blue chloride, Monastral Blue, Malachite Green Oxalate, lampblack, Rose Bengal, Monastral Red, Sudan Black BN, and mixtures thereof. The pigment or dye should be present in the toner in a sufficient quantity to render it highly colored so that it will form a clearly visible image on a recording member.
Any suitable conventional toner concentration may be employed with the coated carriers of this invention. Typical toner concentrations include about 1 part toner with about 10 to 200 parts by weight of carrier.
Any suitable well-known electrophotosensitive material may be employed as the photoreceptor with the coated carriers of this invention. Well-known photoconductive materials include vitreous selenium, organic or inorganic photoconductors embedded in a non-photoconductive matrix, organic or inorganic photoconductors embedded in a photoconductive matrix, or the like. Representative patents in which photoconductive materials are disclosed include U.S. Pat. No. 2,803,542 to Ullrich, U.S. Pat. No. 2,970,906 to Bixby, U.S. Pat. No. 3,121,006 to Middleton, U.S. Pat. No. 3,121,007 to Middleton, and U.S. Pat. No. 3,151,982 to Corrsin.
The surprisingly better results obtained with the carrier coating materials of this invention may be due to many factors. For example, the marked durability of the coating materials may be due to the fact that these resins provide improved abrasion resistance with the substrates tested. Greatly improved adhesion over conventional coating materials is obtained when the coating materials of this invention are applied to glass, steel or similar metallic particles. Coatings prepared from the polymer blends of this invention possess smooth outer surfaces which are highly resistant to cracking, chipping, and flaking. The smooth tough surface enhances the rolling action of the carrier particles across the electrostatographic surfaces and reduces the tendency of the carrier particles to adhere to the electrostatographic surfaces. The carrier coatings are easily prepared and exhibit improved stability during extended periods of usage. The carrier coatings employed in the present invention are non-tacky and have sufficient hardness at normal operating temperatures to prevent impaction; form strong adhesive coatings which do not flake under normal operating conditions; and have triboelectric values such that they can be used with a wide variety of presently available toners in present electrostatographic processes. Thus, the coated carrier particles of this invention have desirable properties which permit their wide use in presently available electrostatographic processes.
The carrier coating materials of this invention are further characterized by low apparent contact potentials and thus enhance the triboelectric charging properties of toner materials. When used as electrostatographic carrier coatings, these polymer blends provide coatings having excellent durability due to their mechanical properties and are especially desirable when employed in continuous electrostatographic development processes which require the recycling of carrier particles by bucket conveyors partially submerged in the developer material supply. Further, these resins have good heat and chemical resistance which is also desirable when employed as carrier coatings in the presence of various conventional electroscopic toner materials and at the conditions encountered in electrostatographic machines.