Abstract: A diquaternary ammonium compound, especially a diquaternary ammonium diacetate in which at least one substituent of nitrogen atom is an alkyl group having at least 14 carbon atoms and the total number of carbon atoms of all nitrogen substituents is at most 44, is an excellent formaldehyde polymerization initiator, which gives large particle size polyformaldehyde in a mixture of aliphatic and aromatic hydrocarbons. Polyformaldehyde is a commercial resin suitable, among others, in applications requiring engineering resins having high strength and wear resistance.

Abstract: Compositions comprising an oligomer which (a) comprises the repeating unit (Ar--CHR), and where Ar is an aromatic group and R is hydrogen or a hydrocarbyl group or hydrogen, (b) has pendant and/or terminal groups which include inter alia acyloxymethyl, hydroxymethyl and carboxyl, and (c) has a functionality between 0.5 and 10, and processes for the preparation thereof are described. These compositions may be used in dental, electrical and electronic applications.

Abstract: The object of the invention are new thermoset polymers and prepolymers, a process for their preparation, and their uses. The new thermoset prepolymers consist, at least in part, of the polycondensation products of one or more pyridine derivatives containing at least two activated methyl groups with one or more aromatic monoaldehydes containing at least one hydroxyl group. These prepolymers are used to prepare composite materials, in particular laminates, that can be used at high temperatures.

Abstract: A prepolymer for use in preparing a binder for low vulnerability gun propellants. The condensation of an alkynediol and formaldehyde produces a prepolymer which is cured with a polyisocyanate. The resulting binder can be combined with 1,3,5,7-tetramethylenetetranitramine (HMX) or 1,3,5-trimethylenetrinitramine (RDX), and is readily extruded as multi-perforated propellant grains, the extruded material having a greatly reduced tendency to slumping, and an enhanced mass impetus value.

Abstract: A liquid formulation containing furfural, para toluene sulfonic acid and tetraethylene glycol is impregnated into fine grained, isotropic graphite bodies and then polymerized and pyrolyzed. That increases the density of the impregnated body and improves its surface finish.

Abstract: A poly(conjugated polymethine-type)dye which is the polycondensation reaction product in the presence of strong protic acid of an aromatic polyamine and a dicarbonyl compound. These polymers are useful in the fabrication of optical recording elements and in other electronic applications.

Abstract: Condensation polymers prepared by reaction of a cyclic diol with a diether or aldehyde, or both, optionally with a branching agent, such as bis(4-hydroxycyclohexyl)propane with paraformaldehyde, or a diether such as methylene-dimethyl ether, or both, optionally with a branching agent such as a pentaethritol, in the presence of an acidic catalyst such as p-toluenesulfonic acid.

Abstract: Aminoplast resin is prepared by reacting urea or melamine with formaldehyde in the presence of a stabilizer compound. Dispersions of the resin in a polyol reacted with a polyisocyanate produce polyurethane products having low flammability properties.

Abstract: Disclosed herein is a process for producing an aromatic sulfide polymer, comprising the step of reacting elementary sulfur, a polyhalogen-substituted aromatic compound, an aldehyde or a condensate thereof and a caustic alkali in an organic solvent.

Abstract: Disclosed is a process for producing fine particles of crosslinked urea-formaldehyde polymer which comprises the steps of synthesizing a precondensate of urea and formaldehyde, allowing the precondensate to react by the addition of an aqueous solution of an acid catalyst, and then neutralizing the reaction mixture, characterized in that the filtrate obtained in the filtration step for separating the polymer particles is recycled to the reaction system at the step of synthesizing a precondensate of urea and formaldehyde and/or the step of allowing the precondensate to react by the addition of an aqueous solution of an acid catalyst and in that the precondensate is obtained by reaction 1 mole of urea with 1.4 to 1.9 moles of formaldehyde at a pH of 6 to 10 and a temperature of 10 to 95.degree. C.

Abstract: Oxymethylene polymers are prepared by a continuous process, by mass polymerization of the monomers with the aid of conventional, preferably cationic, initiators, wherein the monomers as well as the resulting polymer are present substantially in molten form during the polymerization.

Abstract: Trioxane homo-or copolymerizate is produced by continuously feeding the liquid starting material to be polymerized into a mixer in which there is present a powdered to granular oxymethylene homopolymer or copolymer which is fluidized to form a fluidized bed, the speed of feeding, catalyst concentration and polymerization temperature are coordinated to each other in suitable manner and after a polymerization reaction of at least 70 percent polymerizate is continuously or cyclically discharged from the mixer serving as reactor.

Abstract: A process for preparing a urea-formaldehyde base resin having a F/U molar ratio of 1.0:1-1.2:1, that is hydrolytically stable, which comprises adjusting a formaldehyde solution to a pH of 0.5-2.5, slowly charging urea to said formaldehyde solution while maintaining the temperature at 40.degree.-70.degree. C., neutralizing the reaction mixture after obtaining a Gardner viscosity in the range of T+-V+, then adding the final charge of urea and permitting equilibration.

Abstract: There are provided metal containing polymeric coordination compounds which are prepared by a process which comprises reacting metal salts with polydentate ligand molecules obtained by the condensation of aromatic dialdehydes with .beta.-hydroxy-.alpha.,.gamma.-diamines. The above are electrical semiconductors. Such polymers containing platinum have a biological activity.

Abstract: A process for producing a polyacetal copolymer, which comprises copolymerizing formaldehyde and a compound selected from the group consisting of alkylene oxides, poly(alkylene oxides), cyclic formals and poly (cyclic formals) in the presence of a Lewis acid and an anionic polymerization catalyst with the exception of metal chelate compounds.

Abstract: A process for the preparation of etherified or non-etherified aminoplast resins, wherein an aminotriazine of the general formula (I) ##STR1## where X is hydrogen, alkyl, phenyl, alkylphenyl or --NH.sub.2, is reacted with a .beta.-hydroxyaldehyde of the general formula (II) ##STR2## where R', R" and R'" are identical or different and each is hydrogen or alkyl, or R" and R'", together with the .alpha.-carbon atom, are a cyclopentane or cyclohexane ring, and R" and/or R'" can be hydroxyalkyl and R" can be phenyl, the reaction being carried out in the presence of not less than one alcohol and an acid catalyst for the preparation of etherified aminoplast resins and in the presence or absence of an acid catalyst for the preparation of non-etherified aminoplast resins. The aminoplast resins prepared according to the invention can be used as surface-coatings raw materials.

Abstract: A polyacetal resin molded article having reduced water contamination is disclosed. The water contamination reduction feature is provided by the inclusion of a substantially water insoluble substance which forms a hydrophobic film on the molded article. It is furthermore required that the water insoluble substance-included polyacetal molded article be heat treated in air or in an inert gas to provide reduced water contamination.

Abstract: A process for preparing urea-formaldehyde resins is disclosed. The process involves reacting urea and formaldehyde at pH 4.5-5.5 at 90.degree. to 100.degree. C. at a mole ratio of 2.0:1 to 2.2:1 formaldehyde:urea, and adding additional urea under these conditions. The reaction mixture is then neutralized and cooled to 30.degree. to 50.degree. C.and additional urea is reacted. The reaction mixture is then cooled to from 40.degree. to 30.degree. C. and additional formaldehyde and urea added to bring the final mole ratio of formaldehyde:urea to from 1.05:1 to 1.15:1.

Abstract: In a process for preparing polyoxymethylenes by polymerizing formaldehyde in the presence of an anionic polymerization catalyst, the use of a polyhydric alcohol having at least three alcoholic hydroxyl groups in the molecule permits the preparation of polyoxymethylenes which have desired molecular weights along with improved melt fluidity and which are excellent in processability.

Abstract: A polyacetal suitable for moldings which are excellent in lubricity, wear and antistatic properties, which has at least one terminal of its linear polymer molecule capped with an alkylene oxide adduct of an alcohol or a carboxylic acid, which adduct is of the formula ##STR1## wherein R.sub.o is a hydrogen atom, alkyl group, substituted alkyl group, aryl group, or substituted aryl group, R.sub.o 's may be the same or different, R.sub.1 is an alkyl group, substituted alkyl group, aryl group, or substituted aryl group, R.sub.2 is a hydrogen atom, alkyl group, substituted alkyl group, aryl group, or substituted aryl group, m is from 2 to 6, and n is from 1 to 1,000; the number average molecular weight of said polyacetal being in the range from 10,000 to 500,000 excluding the terminal group.

Abstract: Polyacetals and polyketals are prepared by reacting emulsified carbonyl compounds with emulsified polyfunctional alcohols in aqueous media and in the presence of specified polycondensation catalysts. Coherent films of the resultant polymers can be applied to substrates from aqueous or non-aqueous media.

Abstract: Nitropolyformals of the formula H--OCH.sub.2 C(NO.sub.2).sub.2 ZC(NO.sub.sub.2 CH.sub.2 OCH.sub.2 --OCH.sub.2 C(NO.sub.2).sub.2 ZC(NO.sub.2).sub.2 CH.sub.2 OH wherein Z is --CH.sub.2 --, --CH.sub.2 CH.sub.2 --, --CH.sub.2 CH.sub.2 CH.sub.2 --, --CH.sub.2 OCH.sub.2 --, or --CH.sub.2 NHCH.sub.2 -- and wherein the average molecular weight of the nitropolyformal molecules is from about 1,000 to about 50,000. The nitropolyformals are prepared by reacting a diol of the formula HOCH.sub.2 C(NO.sub.2).sub.2 ZC(NO.sub.2).sub.2 CH.sub.2 OH, wherein Z is defined as above, with formaldehyde in the presence of concentrated sulfuric acid. These polymers are useful as energetic binders in explosives and propellants.

Abstract: A method is provided by which thermally stable polyoxymethylene containing polymers are produced. These polymers are prepared by polymerizing trioxane or formaldehyde which has been first treated with micro-wave radiation. Trioxane or formaldehyde treated in this manner is then suitable for homopolymerization or copolymerization with any of the variety of comonomers known to copolymerize with these materials. The resultant polyoxymethylene containing polymers are of exceptional thermal stability without the necessity of added stabilizers.

Abstract: According to the present invention, there is provided an improved method of producing a poly-(amide-imide) resin comprising the steps of:(1) reacting a phenanthrene with formaldehyde or a formaldehyde donor in the presence of an acid catalyst to give a phenanthreneformaldehyde reaction product having substantially only methylene bridges;(2) removing from the reaction product unreacted phenanthrene;(3) treating the reaction product with formaldehyde or a formaldehyde donor in the presence of an acid catalyst to give a high molecular weight product having substantially only methylene bridges;(4) oxidizing the high molecular weight product to break the 9, 10 bond in the phenanthrene moieties to produce a polycarboxylated reaction product;(5) reacting the polycarboxylated reaction product with an aromatic diamine to produce a poly-(amide-imide) resin.

Abstract: A process for producing a polyacetal homopolymer or copolymer which comprises continuously feeding a liquid starting mixture containing molten trioxane and a catalyst and optionally a comonomer through a feed opening of a reactor, said reactor being a continuously stirring-type mixer having two stirring shafts having a plurality of plate-like paddles fixed thereto the cross-section of each of said paddles taken perpendicularly of the axial direction of the stirring shaft having a shape of a convex lens, an ellipse or a quasipolygon inscribing a phantom circle at each vertex, one of said paddles facing another paddle fixed to the other stirring shaft and said one paddle being positioned such that it rotates while the edges thereof keep a slight clearance from the inner surface of the barrel and the other paddle; polymerizing the starting mixture while moving it toward the discharge opening by the rotation of the paddles, the improvement wherein the profiles of the paddles are changed, or the arrangement of the

Abstract: A process for producing high-molecular polyacetals, comprising polymerization of gaseous formaldehyde or copolymerization thereof with cyclic formals or cyclic oxides; formaldehyde is admitted into the reaction zone in a gas mixture which is the product of catalytic oxidative dehydrogenation of methanol, wherefrom H.sub.2 O, CH.sub.3 OH and H COOH contaminants have been preliminarily removed. The process of polymerization or copolymerization is carried out in an inert hydrocarbon solvent in the presence of an ionic-type catalyst at a temperature within the range of from -50.degree. to +120.degree. C. with the formation of a vapor phase which is removed from the reaction zone.

Abstract: Undesirable deposition of polyoxymethylene onto the inner wall of a polymerization vessel and onto a stirrer, which deposition is observed in the slurry polymerization of formaldehyde carried out in an inert organic liquid medium in the presence of a polymerization catalyst, can be minimized by carrying out the slurry polymerization in the presence of at least one polyvalent metal salt selected from polyvalent metal salts of alkylsalicylic acids and polyvalent metal salts of dialkyl esters of sulfosuccinic acid. Optionally, a polyethylene glycol monoether may be used in addition to the polyvalent metal salt.

Abstract: Polymerization method utilizing a three-phase system: water-in-oil-in-water or oil-in-water-in-oil comprising the steps (a) adding the monomer material to be polymerized into the innermost water or oil phase; (b) adding, with mechanical agitation, the product of Step a to the middle oil or water phase, said phase containing appropriate surfactant, whereby an emulsion is formed; (c) adding, with mechanical agitation, the emulsion product of Step b to the outermost water or oil phase, said phase containing appropriate surfactant, wherein polymerization proceeds in the innermost water or oil phase until complete.

Abstract: It is disclosed that, in the process for producing polymethylene polyphenyl polycarbamates through the reaction of N-phenyl carbamate with formaldehyde or a formaldehyde-supplying substance in the presence of an acid catalyst, if the reaction is carried out in the concurrent presence of at least one compound or a mixture of at least two compounds selected from the group consisting of N-carboalkoxy (or cycloalkoxy)-2-oxa-4-aza-naphthalenes, bis(N-carboalkoxy(or cycloalkoxy)-anilino)-methanes and N,N'-dicarboalkoxy (or cycloalkoxy)aminobenzyl-anilines, the object product, polymethylene polyphenyl polycarbamate, can be obtained at a high yield.

Abstract: A polyacetal carboxylate is provided having the following empirical formula: ##STR1## where M is selected from the group consisting of akali metal, ammonium, tetra-alkyl ammonium groups and alkanol ammonium groups, and n averages at least 4. Such polyacetal carboxylates can be used as complexing agents and detergency builders.

Abstract: A process for the production of high molecular weight oxymethylene copolymer in the presence of impurity is provided. The process provides a high molecular weight oxymethylene copolymer having a predetermined comonomer content. The process comprises the steps of determining the optimal catalyst concentration in a first oxymethylene copolymerization system which contains less than approximately 10 p.p.m. impurity; determining the concentration of impurity containing at least one active proton in a second copolymerization system; adjusting the catalyst concentration in the second copolymerization system so that the total concentration of catalyst and impurity in the second copolymerization system is maintained at the optimal concentration of catalyst in the first copolymerization system; and adjusting the concentration of comonomer in the second copolymerization system so as to maintain the predetermined comonomer content in the oxymethylene copolymer product.

Abstract: A novel, water-soluble acetal polymer is prepared by reacting a hydroxyl-containing aldehyde with a glycol in an acid reaction medium. The acetal polymer is useful as a dispersing agent for other polymers and as a reactant for the preparation of polyurethane resins.

Abstract: A polymer having the average structure: ##STR1## wherein Y is a moiety containing 1 to about 20 carbon atoms randomly distributed along the polymer chain derived from a comonomer selected from the group consisting of aldehydes and epoxy compounds; p is 0 or 1; the product of q and n averages at least 4; R.sup.1 and R.sup.2 are individually any chemically stable group which stabilizes the polymer against rapid depolymerization in alkaline solution; and Z is a mixture of H and members selected from the group consisting of alkali metals, ammonium and alkanol amine groups having from 1 to about 4 carbon atoms, is useful for the reversible deflocculation of clay slurries. In the preferred embodiments, p is 0 to provide a homopolymer, the product of q and n averages between about 10 and about 200, and Z is a mixture containing at least 1 percent H, the remainder being alkali metal, e.g., sodium.

Abstract: The alkali metal, ammonium and alkanol amine salts of acetal carboxylate polymers are known to be stable detergent builders and chelating agents which depolymerize in acid media making the polymer fragments more readily biodegradable in waste streams. Now, according to the present invention, the hydrolytic stability of an acetal carboxylate polymer can be controlled by bringing together under polymerization conditions an ester of glyoxylic acid and a polymerization initiator and adding to the termini of the resulting polymer end groups having substituents which are selected to be more electron withdrawing as the desired hydrolytic stability increases.

Abstract: A stable dispersion of an aminoplast which is obtained by a process which comprises condensing ammonia hydrazine or an organic compound having a molecular weight of from about 50 to about 400 and which contains at least two groups selected from the group consisting of --NH.sub.2 and --NH-- with benzoquinone or a compound of the formula R--CO--R' in which R and R' stand for the same or different radicals selected from the group consisting of hydrogen C.sub.1 -C.sub.4 alkyl groups which may carry chlorine substituents, C.sub.2 -C.sub.4 -alkenyl groups, C.sub.6 -C.sub.10 aryl groups, C.sub.7 -C.sub.10 aralkyl groups, C.sub.5 -C.sub.10 cycloalkyl group and semi-acetals obtained by reacting said carbonyl compounds with monohydric or dihydric aliphatic alcohols having one to ten carbon atoms in an organic polyhydroxyl compound having a molecular weight of from about 250 to about 14000 as the reaction medium.

Abstract: A process for the preparation of soft and hard resins, and their use in surface-coating binders are disclosed. According to the invention, soft and hard resins are prepared from a urea, formaldehyde and a CH-acidic aldehyde by reacting a urea of the general formula (I) or (II) ##STR1## where R.sup.1 and R.sup.2 are hydrogen or identical or different alkyl, A is alkylene and X is oxygen or sulfur, with formaldehyde and a CH-acidic aldehyde of the general formula (III) ##STR2## where R.sup.3 and R.sup.4 are identical or different alkyl, aryl or alkylaryl wherein the urea, formaldehyde and CH-acidic aldehyde are employed in a mole ratio of from 1:2:2 to 1:4:4, at from 60.degree. to 150.degree. C., in the presence of an acid and in the presence or absence of a solvent and/or diluent, and then treating the product with a base in an anhydrousmedium.

Abstract: Poly(aldehyde amino silicate) foams are produced by mixing an amino compound, an aldehyde, a silicon oxide compound and a blowing agent; then a curing agent is added, thereby producing a rigid, porous product.

Abstract: The alkali metal, ammonium and alkanol amine salts of polymeric acetal carboxylates are stable detergent builders and chelating agents. Now, in the improved process of the present invention for preparing an acetal carboxylate polymer wherein a glyoxylate ester and a polymerization initiator are brought together under polymerization conditions and a chemically stable end group is added to the termini of the resulting polymer to stabilize the polymer against rapid depolymerization in alkaline solution, the improvement comprises contacting the resulting polymer in the presence of an acid catalyst with a sufficient amount of an acetal having 3 to 20 carbon atoms to stabilize the resulting polymer against rapid depolymerization in alkaline solution, and an agent to remove liberated alcohol.

Abstract: The alkali metal, ammonium and alkanol amine salts of polymeric acetal carboxylates are stable detergent builders under laundry use conditions, but depolymerize in acid media, making the polymer fragments more readily biodegradable in waste streams. Now, in the improved process of the present invention for preparing an acetal carboxylate polymer wherein an ester of glyoxylic acid and a polymerization initiator are brought together under polymerization conditions and a chemically stable end group is added to the termini of the resulting polymer to stabilize the polymer against rapid depolymerization in alkaline solution, the improvement comprises adding to the resulting polymer a sufficient amount of an alkali metal hydride, preferably sodium hydride, and a dialkyl sulfate having 1 to about 20 carbon atoms in each alkyl group, preferably dimethyl sulfate, to add to the termini of the resulting polymer an alkyl group derived from the dialkyl sulfate.

Abstract: The alkali metal, ammonium and alkanol ammonium salts of polymeric acetal carboxylates are stable detergent builders under laundry use conditions but depolymerize in acid media, making the polymer fragments more readily biodegradable in waste streams.

Abstract: A stable dispersion of an aminoplast which is obtained by a process which comprises condensing ammonia, hydrazine or a organic compound having a molecular weight of from about 50 to about 400 and which contains at least two groups selected from the group consisting of --NH.sub.2 and --NH-- with benzoquinone or a compound of the formula R--CO--R' in which R and R' stand for the same or different radicals selected from the group consisting of hydrogen C.sub.1 -C.sub.4 alkyl groups which may carry chlorine substituents, C.sub.2 -C.sub.4 -alkenyl groups, C.sub.6 -C.sub.10 aryl groups, C.sub.7 -C.sub.10 aralkyl groups, C.sub.5 -C.sub.10 cycloalkyl groups or semi-acetals obtained by reacting said carbonyl compounds with monohydric or dihydric aliphatic alcohols having one to ten carbon atoms in an organic polyhydroxyl compound having a molecular weight of from about 250 to about 14000 as the reaction medium.

Abstract: In a method for mixing a trioxane, a polymerization catalyst and a comonomer for producing of oxymethylene copolymers by continuously copolymerizing trioxane with a cyclic ether or a cyclic acetal as a comonomer, the improved method comprises following steps:spouting a comonomer and a polymerization catalyst from nozzle openings which are set adjacent to each other,while washing both openings at the tip end of the nozzles with a flow of trioxane,whereby mixing said comonomer, said polymerization catalyst and said trioxane,and then feeding the mixture to a polymerization reactor to effect copolymerization.The raw materials are mixed together before they are fed to the polymerization reactor, and no clogging trouble at the tip end of the nozzle for feeding a polymerization catalyst occurs. Further the resulting copolymer has a much superior heat stability.

Abstract: A capsule solution is prepared by polymerizing urea and formaldehyde in the presence of gum arabic to thereby form a urea-formaldehyde resin wall around a hydrophobic oily solution. The use of gum arabic reduces the viscosity of the capsule solution, the capsule solution which is obtained is particularly suitable for preparing pressure sensitive recording sheets.

Abstract: A process for the preparation of soft and hard resins, and their use in surface-coating binders.According to the invention, soft and hard resins are prepared from a urea and a CH-acidic aldehyde by reacting a urea of the general formula (I) ##STR1## where X is oxygen or sulfur and R.sup.1 and R.sup.2 are hydrogen or identical or different alkyl, aryl or aralkyl, or may be an alkyleneurea radical, with at least 2 moles of a CH-acidic aldehyde of the general formula (II) ##STR2## where R.sup.3 is hydrogen and R.sup.4 is alkyl, aryl or aralkyl, or R.sup.3 and R.sup.4 are identical or different alkyl, aryl or aralkyl, in the presence of a strong acid, to give a condensation product, and then treating the latter with a base in an anhydrous medium.These soft and hard resins are used, in combination with other film-forming agents, as surface-coating binders.

Abstract: Copolymers of acetal carboxylates are provided which have the following empirical formula ##STR1## where Y is one or more comonomers randomly distributed in the copolymer; the product of n and q averages at least 4; p is at least 1; and M is selected from the group consisting of alkali metal, ammonium, alkyl groups having 1 to about 4 carbon atoms, and alkanol ammonium groups having 1 to about 4 carbon atoms in the alkyl chain. Such copolymers are useful as detergent builders to replace sodium tripolyphosphate (STP) in detergent formulations. The copolymers are stable under laundry use conditions, but depolymerize in acid media, making the fragments more readily biodegradable in waste streams.

Abstract: Ether and acetal carboxylates useful as detergent builders to replace sodium tripolyphosphate (STP) in detergent formulations are known to the art. Certain polymeric polycarboxylates are also known to the art but all of these products suffer from either having poor builder properties or they are not readily biodegradable. According to the present invention, a method is provided for preparing new and novel polymeric acetal carboxylates which are stable under laundry use conditions, but depolymerize in acid media, making the polymer fragments more readily biodegradable in waste streams.

Abstract: Microscopic opacifying particles formed of a formaldehyde condensation product are chemically modified to impart anionic-, cationic- or hydroxy-functional groups thereto in order to provide improved dye receptivity, dispersibility and compatibility properties.

Abstract: A process for polymerizing trioxane made from an aqueous solution of methanol-containing formaldehyde by a conventional method or copolymerizing the trioxane with another monomer, characterized bycooling the trioxane to crystallize it,allowing the trioxane in a crystalline state to stand in an open system in an atmosphere of air or an inert gas to remove polyoxymethylene dimethoxide from the trioxane,melting the trioxane, andpolymerizing the trioxane or copolymerizing the trioxane and the another monomer.

Abstract: Poly(aldehyde amino silicate) foams are produced by mixing an amino compound, an aldehyde, a silicon oxide compound and a blowing agent; then a curing agent is added, thereby producing a rigid, porous product.

Abstract: Aromatic onium salts, such as diaryliodonium salts, have been found to be effective thermal initiators for the polymerization of a variety of cationically polymerizable materials including epoxides, cyclic ethers, phenol formaldehyde resins, etc., when used in combination with various cocatalysts such as organic acids and copper salts.