Binder system for anodes, cathodes, and electrodes

Claim 2

A raw batch composition for use in making a shaped self-sustaining article comprising a mixture of a carbonaceous aggregate, a curable resin binder in sufficient quantity when cured to bond said aggregate into a desired shaped that is self-sustaining, and a curing agent effective for curing said resin under curing conditions, said binder comprising a phenol-formaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C. (212° F.) and a total volatiles content at 135° C. (275° F.) of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, the amount of resin solids in said binder being from about 6% to about 15% by weight based on the weight of said carbonaceous aggregate, said curing agent being present in sufficient amount to effect curing of said binder, under curing conditions.

Claim 3

The raw batch composition of claim 1 wherein said carbonaceous aggregate comprises coke particles having a particle size in the range from 4 mesh to 325 mesh.

Claim 4

The raw batch composition of claim 2 for use in making an electrode, wherein said carbonaceous aggregate further comprises powdered material selected from the group consisting of carbon, graphite, and mixtures thereof, wherein said aggregate has particle sizes in the range from 4 mesh to 325 mesh.

Claim 5

The raw batch composition of claim 2 for making an electrode, wherein said carbonaceous aggregate comprises a mixture of fine particles, coarse particles, and an intermediate fraction of particles, wherein said fines comprises about 40% of said mixture and pass through 100 mesh but are retained on 200 mesh, and said coarse particles comprise about 50% of said mixture and are passed by 4 mesh but retained on 14 mesh, and the intermediate fraction of particles comprises the balance thereof.

Claim 6

The raw batch composition of claim 4 for use in making electrodes, wherein said carbonaceous aggregate further comprises carbon powder, graphite powder, or mixtures thereof.

Claim 7

The raw batch composition of claim 3 wherein said carbonaceous aggregate comprises coke particles selected from the group consisting of petroleum coke, anthracite coke, and mixtures thereof.

Claim 8

The raw batch composition of claim 2 wherein said carbonaceous aggreagate further comprises powdered graphite, powdered carbon, or mixtures thereof, said powder having particle sizes predominantly in the range 200 mesh to 325 mesh.

Claim 9

The raw batch composition of claim 1 wherein said novolac resin has a melting point of at least 110° C. (230° F.).

Claim 10

The raw batch composition of claim 1 wherein said novolac resin has a volatiles content of not more than 2%.

Claim 11

The raw batch composition of claim 9 wherein said free phenol content is not more than 2%.

Claim 12

The raw batch composition of claim 8 wherein said novolac resin has a volatiles content of not more than 2% and said volatiles includes a free phenol content of not more than 2%.

Claim 13

The raw batch composition of claim 8 wherein said binder also comprises a liquid phenol formaldehyde resole resin having a viscosity of 50 cps to 450 cps as measured on a Brookfield RVF viscometer, at 25° C. with a #1 spindle at 20 rpm, said resole resin having a free phenol content of not more than 30% by weight.

Claim 14

The raw batch composition of claim 1 wherein said binder also comprises a plasticizer.

Claim 15

The raw batch composition of claim 12 wherein said binder also comprises a plasticizer.

Claim 16

The raw batch composition of claim 12 wherein said resole has a viscosity of 50 cps to 350 cps.

Claim 17

The raw batch composition of claim 15 wherein said resole resin has a viscosity in the range from 150 cps to 350 cps.

Claim 18

The raw batch composition of claim 15 for use in a ramming or tamping mix, wherein said resole has a viscosity in the range from 50 cps to 150 cps.

Claim 19

The raw batch composition of claim 1 wherein said curing agent comprises hexamethylenetetramine.

Claim 20

The raw batch composition of claim 18 wherein said hexamethylenetetramine is present in an amount of from 6%-10% by weight of said resin.

Claim 21

The raw batch composition of claim 12 wherein said curing agent is a Lewis acid.

Claim 22

A raw batch paste composition for use in making a shaped self-sustaining monolithic article comprising a mixture of a carbonaceous aggregate and a binder comprising a curable unthickened liquid resole phenolic resin combined with at least 5% hexamethylenetetramine based on resin solids, said binder being present in sufficient quantity when cured to bond said aggregate into a desired shape that is self-sustaining, said carbonaceous aggregate comprising coke aggregate having particle sizes in the range from 4 mesh to 200 mesh, said liquid phenol formaldehyde resole resin having a viscosity in the range from 50 cps to 500 cps and a free phenol content of not more than 30%, the resin solids of said resole comprising from 6% to 15% by weight of said aggregate.

Claim 23

A raw batch paste composition for use in making a shaped self-sustaining monolithic article comprising a mixture of a carbonaceous aggregate and a binder comprising a curable unthickened liquid resole phenolic resin combined with at least 5% hexamethylenetetramine based on resin solids, said binder being present in sufficient quantity when cured to bond said aggregate into a desired shape that is self-sustaining, said carbonaceous aggregate comprising coke aggregate having particle sizes in the range from 4 mesh to 200 mesh, said liquid phenol formaldehyde resole resin having a viscosity in the range from 50 cps to 500 cps and a free phenol content of not more than 30%, the resin solids of said resole comprising from 6% to 15% by weight of said aggregate.

Claim 24

The raw batch composition of claim 21 wherein said carbonaceous aggregate comprises a mixture of fine particles, coarse particles, and an intermediate fraction of particles, wherein said fines comprise about 40% of said coke and pass through 100 mesh but are retained on 200 mesh, said coarse particles comprise about 50% of said aggregate and are passed by 4 mesh but are retained on 14 mesh, and the intermediate fraction has particles sizes in between those of the fines and coarse particles, and wherein the amount of said binder is from about 6% to about 8% resin solids based on the weight of said carbonaceous aggregate.

Claim 25

A raw batch composition for use in making a self-sustaining shape that can be pyrolized to form a carbonized shape, comprising a mixture of carbonaceous aggregate and a binder, said carbonaceous aggregate comprising coke aggregate having particle sizes in the range from 4 mesh to 200 mesh, said binder comprising a phenolic resin that is selected from the group consisting of the (1) a phenolformaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C. (212° F.) and a total volatiles content at 135° (275° F.) of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, combined with a curing agent, (2) a mixture of a phenol-formaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C. and a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, and liquid phenol-formaldehyde resole resin combined with at least 5% hexamethylene based on resin solids, said liquid resole resin having a viscosity in the range from 50 cps to 500 cps and a free phenol content of not more than 30%, and (3) liquid phenolformaldehyde resole resin that is free of any added thickening agent, combined with at least 5% hexamethylene based on resin solids, said unthickened liquid resole resin having a viscosity in the range from 50 cps to 500 cps and a free phenol content of not more than 30%, the resin solids of said binder comprising from 6% to 15% by weight of said aggregate, wherein said binder provides a weight of residual carbon following pyrolysis basis on the weight of the binder originally present prior to pyrolysis, of at least 35% by weight.

Claim 26

A raw batch composition for use in making a self-sustaining shape that can be pyrolized to form a carbonized shape, comprising a mixture of carbonaceous aggregate and a binder, said carbonaceous aggregate comprising coke aggregate having particle sizes in the range from 4 mesh to 200 mesh, said binder comprising a phenolic resin that is selected from the group consisting of the (1) a phenolformaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C. (212° F.) and a total volatiles content at 135° (275° F.) of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, combined with a curing agent, (2) a mixture of a phenol-formaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C. and a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, and liquid phenol-formaldehyde resole resin combined with at least 5% hexamethylene based on resin solids, said liquid resole resin having a viscosity in the range from 50 cps to 500 cps and a free phenol content of not more than 30%, and (3) liquid phenolformaldehyde resole resin that is free of any added thickening agent, combined with at least 5% hexamethylene based on resin solids, said unthickened liquid resole resin having a viscosity in the range from 50 cps to 500 cps and a free phenol content of not more than 30%, the resin solids of said binder comprising from 6% to 15% by weight of said aggregate, wherein said binder provides a weight of residual carbon following pyrolysis basis on the weight of the binder originally present prior to pyrolysis, of at least 35% by weight.

Claim 27

The raw batch composition of claim 23 wherein said binder has a weight of residual carbon following pyrolysis based on the weight of the binder originally present prior to pyrolysis of at least 50% by weight.

Claim 28

The raw batch composition of claim 24 wherein said residual carbon is in the range from 50% to 60% by weight.

Claim 29

The raw batch composition of claim 23 wherein said binder is said liquid phenol formaldehyde resole resin having a viscosity of 50 cps-500 cps.

Claim 30

The raw batch composition of claim 23 wherein said binder comprises said particulate or hot melt phenol formaldehyde novolac resin.

Claim 31

The raw batch composition of claim 27 wherein said mixture further comprises a curing agent that is effective for curing said binder under curing conditions, in a sufficient amount to effect curing of said binder under curing conditions.

Claim 32

The raw batch composition of claim 27 wherein said binder further comprises a liquid phenol formaldehyde resole resin having a viscosity of 50 cps.-500 cps.

Claim 33

A self-sustaining shape comprising a compacted mass of particles of coke aggregate bonded together by a binder, said binder comprising a cured phenol formaldehyde resin that prior to curing was selected from the group consisting of (a) a phenol formaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C., a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, combined with a curing agent, (b) a mixture of a phenol-formaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C. and a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, and liquid phenol-formaldehyde resole resin combined with at least 5% hexamethylene based on resin solids, said liquid resole resin having a viscosity in the range from 50 cps to 500 cps and a free phenol content of not more than 30%, and (c) a liquid phenol formaldehyde resole that is free of any added thickening agent, having a viscosity of at least 50 cps and a free phenol content not in excess of 30%, combined with at least 5% hexamethylene based on resin solids, said resin solids comprising from 6% to 15% of said aggregate by weight.

Claim 34

A self-sustaining shape comprising a compacted mass of particles of coke aggregate bonded together by a binder, said binder comprising a cured phenol formaldehyde resin that prior to curing was selected from the group consisting of (a) a phenol formaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C., a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, combined with a curing agent, (b) a mixture of a phenol-formaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C. and a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, and liquid phenol-formaldehyde resole resin combined with at least 5% hexamethylene based on resin solids, said liquid resole resin having a viscosity in the range from 50 cps to 500 cps and a free phenol content of not more than 30%, and (c) a liquid phenol formaldehyde resole that is free of any added thickening agent, having a viscosity of at least 50 cps and a free phenol content not in excess of 30%, combined with at least 5% hexamethylene based on resin solids, said resin solids comprising from 6% to 15% of said aggregate by weight.

Claim 35

The self-sustaining shape of claim 30 wherein said coke particles, prior to being bonded together, had particle sizes in the range from 4 mesh to 200 mesh.

Claim 36

The self-sustaining shape of claim 30 wherein said resin is a room temperature cured resin.

Claim 37

The self-sustaining shape of claim 30 wherein said resin has been cured at an elevated temperature in the range 150° C. to 200°0 C. (302° F. to 392° F.).

Claim 38

The self-sustaining shape of claim 30 wherein said binder is a mixture of said novolac resin and said resole resin, and prior to curing contained from 6%-10% by weight based on the weight of the resin of hexamethylenetetramine.

Claim 39

The shape of claim 31 further comprising powdered carbon, powdered graphite, or mixtures thereof, said powder having particle sizes predominantly in the range 200 mesh to 325 mesh.

Claim 40

The shape of claim 31 that is adapted to be carbonized to make an electrode, wherein said liquid resole had a viscosity in the range from 150 cps to 350 cps.

Claim 41

The shape of claim 31, formed from a ramming mix, wherein said liquid resole had a viscosity in the range from 50 cps to 150 cps.

Claim 42

A shaped article formed by carbonizing a self-sustaining shape according to claim 30 comprising a compacted mass of particles of a carbonaceous aggregate bonded together by a resin binder, said resin binder solids providing upon carbonization at least 35% by weight of carbon based on the precured weight of said binder.

Claim 43

The shaped article of claim 38 wherein the binder of said self-sustaining shape, prior to curing, comprised a novolac curable at 150° C. to 200° C., having a melting point of at least 110° C., and a volatiles content at 135° C. of not more than 2% by weight of the resin including free phenol of not more than 2% as measured by gas chromatography analysis.

Claim 44

The shaped article of claim 39 wherein said binder prior to curing comprised a curing agent, and said curing agent was from 6%-10% by weight of hexamethylenetetramine based on the weight of the resin.

Claim 45

The shaped article of claim 38 wherein the binder, prior to curing, comprised a liquid resole resin having a viscosity in the range from 150 cps to 400 cps, containing from 10%-25% by weight of free phenol.

Claim 46

The shaped article of claim 38 wherein the binder, prior to curing, was a mixture of said novolac and said liquid resole, said novolac prior to curing being curable at 150° C. to 200° C., and said resole prior to curing had a viscosity of 50 cps to 400 cps and contained from 10%-25% by weight of free phenol, and wherein said binder prior to curing included a curing agent.

Claim 47

The shaped article of claim 38 formed by hot pressing and carbonizing.

Claim 48

The shaped article of claim 38 formed by cold pressing, curing, and carbonizing.

Claim 49

An electrode formed by carbonizing a self-sustaining shape comprising a compacted mass of particles of a carbonaceous aggregate comprising coke aggregate bonded together by a binder, said binder comprising a cured phenol formaldehyde resin that prior to curing was a phenol formaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C., a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis said binder further comprising, prior to curing, from 6%-10% by weight of the resin of hexamethylenetetramine, the resin solids of said binder comprising from 6% to 15% of said aggregate by weight.

Claim 50

An electrode formed by carbonizing a self-sustaining shape comprising a compacted mass of particles of a carbonaceous aggregate comprising coke aggregate bonded together by a binder, said binder comprising a cured phenol formaldehyde resin that prior to curing was a phenol formaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C., a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis said binder further comprising, prior to curing, from 6%-10% by weight of the resin of hexamethylenetetramine, the resin solids of said binder comprising from 6% to 15% of said aggregate by weight.

Claim 51

The electrode of claim 45 wherein said binder provided a weight of residual carbon from carbonization of said binder, following carbonizing of said shape, and based on the weight of the binder originally present prior to carbonization, of at least 35% by weight of the original binder weight.

Claim 52

The electrode of claim 46 wherein said carbonaceous aggregate comprised coke particles having particle sizes in the range from 4 mesh to 200 mesh in admixture with a powder selected from the group consisting of carbon, graphite, and mixtures thereof, said powder having a particle size in the range 200 mesh to 325 mesh.

Claim 53

The electrode of claim 47 wherein the weight of said residual carbon following carbonization of said self-sustaining shape based on the weight of the binder originally present prior to carbonization, is at least 50% by weight of the original binder weight.

Claim 54

An electrode formed by carbonizing a self-sustaining shape comprising a compacted mass of particles of a carbonaceous aggregate comprising coke aggregate bonded together by a binder, said binder comprising a cured phenol formaldehyde resin that prior to curing was a mixture of (a) a phenol formaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C., a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measure by gas chromatography analysis, and (b) a liquid phenol formaldehyde resole having a viscosity of at least 150 cps and a free phenol content not in excess of 30%, the resin solids of said binder comprising from 6% to 15% of said aggregate by weight.

Claim 55

An electrode formed by carbonizing a self-sustaining shape comprising a compacted mass of particles of a carbonaceous aggregate comprising coke aggregate bonded together by a binder, said binder comprising a cured phenol formaldehyde resin that prior to curing was a mixture of (a) a phenol formaldehyde novolac resin in particulate or hot melt form, having a melting point of at least 100° C., a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measure by gas chromatography analysis, and (b) a liquid phenol formaldehyde resole having a viscosity of at least 150 cps and a free phenol content not in excess of 30%, the resin solids of said binder comprising from 6% to 15% of said aggregate by weight.

Claim 56

The electrode of claim 49, said liquid resole having a viscosity in the range from 150 cps to 400 cps and containing from 10%-25% by weight of free phenol.

Claim 57

The electrode of claim 50 wherein said carbonaceous aggregate in said self-sustaining shape comprised a coke aggregate mixture of fine particles, coarse particles, and particles intermediate in size between said fine particles and said coarse particles, wherein said fines comprised about 40% of said aggregate and passed through 100 mesh but were retained on 200 mesh, and said coarse particles comprised about 50% of said aggregate and passed through 4 mesh but were retained on 14 mesh.

Claim 58

The electrode of claim 50 wherein said binder provided a weight of residual carbon, following carbonization of said self-sustaining shape based on the weight of the binder originally present prior to carbonization, of at least 50% by weight of the original binder weight.

Claim 59

The electrode of claim 52 wherein said carbonaceous aggregate further comprised a powdered carbon, graphite, or mixture thereof, having particle sizes in the range from 200 mesh to 325 mesh.

Claim 60

A process for making a body that can be pyrolyzed to form an electrode suitable for use in the electrolytic production of metal such as aluminum, prepared from carbonaceous aggregate, a resin binder comprising a phenol formaldehyde novolac resin in particulate or hot melt form, and hexamethylene tetramine, said novolac having a melting point of at least 100° C., a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, comprising the steps of: (a) mixing said aggregate with sufficient resin binder that the solids of said resin comprise 6%-15% by weight of said aggregate and with 6%-20% by weight of hexamethylenetetramine based on the weight of said phenol formaldehyde novolac to coat said aggregate until a free flowing aggregate coated material is formed; (b) molding said free flowing aggregate coated material under pressure into the shape of said electrode; and (c) heating said shape to cure the resin.

Claim 61

A process for making a body that can be pyrolyzed to form an electrode suitable for use in the electrolytic production of metal such as aluminum, prepared from carbonaceous aggregate, a resin binder comprising a phenol formaldehyde novolac resin in particulate or hot melt form, and hexamethylene tetramine, said novolac having a melting point of at least 100° C., a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, comprising the steps of: (a) mixing said aggregate with sufficient resin binder that the solids of said resin comprise 6%-15% by weight of said aggregate and with 6%-20% by weight of hexamethylenetetramine based on the weight of said phenol formaldehyde novolac to coat said aggregate until a free flowing aggregate coated material is formed; (b) molding said free flowing aggregate coated material under pressure into the shape of said electrode; and (c) heating said shape to cure the resin.

Claim 62

The process described in claim 54 in which said phenol formaldehyde novolac has a melting point of 110° C. or greater, a volatiles content of not more than 5%, and a free phenol content not more than 2%.

Claim 63

The process of claim 55 wherein said carbonaceous aggregate comprises powdered carbon, graphite, or mixtures thereof, having particle sizes predominantly in the range 200 mesh to 325 mesh.

Claim 64

The process of claim 55 wherein said binder further comprises a liquid resole resin having a viscosity in the range from 30 cps to 400 cps and containing not more than 30% free phenol.

Claim 65

A process for making a body that can be pyrolyzed to form a carbonized shape suitable for use in the electrolytic production of metal such as aluminum, prepared from carbonaceous aggregate comprising coke particles having sizes in the range from 4 mesh to 200 mesh, and a resin binder comprising a liquid phenol formaldehyde resole resin that is free from added thickening agent, and that is combined with at least 5% hexamethylenetetramine based on resin solids, said resole having a viscosity of 150 cps to 400 cps and containing not more than 30% by weight of free phenol, comprising the steps of: (a) mixing said aggregate with sufficient resin binder that the solids of said resin comprise 6%-15% by weight of the weight of said aggregate; (b) molding said mixture under pressure in the shape of said electrode; and (c) heating said shape to cure the resin.

Claim 66

A process for making a body that can be pyrolyzed to form a carbonized shape suitable for use in the electrolytic production of metal such as aluminum, prepared from carbonaceous aggregate comprising coke particles having sizes in the range from 4 mesh to 200 mesh, and a resin binder comprising a liquid phenol formaldehyde resole resin that is free from added thickening agent, and that is combined with at least 5% hexamethylenetetramine based on resin solids, said resole having a viscosity of 150 cps to 400 cps and containing not more than 30% by weight of free phenol, comprising the steps of: (a) mixing said aggregate with sufficient resin binder that the solids of said resin comprise 6%-15% by weight of the weight of said aggregate; (b) molding said mixture under pressure in the shape of said electrode; and (c) heating said shape to cure the resin.

Claim 67

The process of claim 58 wherein said aggregate further comprises powdered carbon, graphite, or mixtures thereof, having particle sizes predominantly from 200 mesh to 325 mesh.

Claim 68

The process of claim 59 wherein said resole contains from 10% to 25% by weight of free phenol.

Claim 69

A composition useful as a tamping and ramming composition suitable for use in monolithic shape construction comprising a mixture of carbonaceous aggregate comprising coke particles having sizes in the range from 4 mesh to 200 mesh, and a material selected from the group consisting of carbon powder, graphite, and mixtures thereof, a binder comprising a phenol formaldehyde novolac resin, said novolac having a melting point of at least 100° C., a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, plasticizer for said resin, and a curing agent, wherein the amount of resin solids in said binder amount to from 6%-15% by weight based on the weight of said carbonaceous aggregate.

Claim 70

A composition useful as a tamping and ramming composition suitable for use in monolithic shape construction comprising a mixture of carbonaceous aggregate comprising coke particles having sizes in the range from 4 mesh to 200 mesh, and a material selected from the group consisting of carbon powder, graphite, and mixtures thereof, a binder comprising a phenol formaldehyde novolac resin, said novolac having a melting point of at least 100° C., a total volatiles content at 135° C. of not more than 5% by weight of said resin including a free phenol content of not more than 4% by weight of said resin as measured by gas chromatography analysis, plasticizer for said resin, and a curing agent, wherein the amount of resin solids in said binder amount to from 6%-15% by weight based on the weight of said carbonaceous aggregate.

Claim 71

The composition of claim 61 wherein said binder further comprises a liquid phenol formaldehyde resole having a viscosity of 30 cps to 150 cps as measured on a Brookfield RVF viscometer, at 25° C. with a #1 spindle at 20 rpm and a free phenol content not in excess of 30% by weight.

Claim 72

The composition of claim 62 which further comprises an acid accelerator selected from toluene sulfonic acid, benzene sulfonic acid, formic acid, boric acid, or sulfuric acid.