JP4676632B2 - Method for controlling solubility of water-in-oil emulsion - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for controlling the solubility of a water-in-oil emulsion, and particularly to a water-in-oil emulsion having an oily substance composed of at least one hydrocarbon as a continuous phase and a water-soluble polymer aqueous solution as a dispersed phase. The present invention relates to a method for controlling the solubility of a water-in-oil emulsion, wherein an oil-soluble emulsifier and a water-soluble emulsifier are added to the water-in-oil emulsion and mixed, and then dissolved in water.
[0002]
[Prior art]
Water-in-oil emulsions of water-soluble polymers are suitable for applications that require high molecular weight such as polymer flocculants because the water-soluble polymers can be stored in high-concentration product forms and the viscosity of the dispersion is very low. Liquid product. For example, Japanese Patent Publication No. Sho 54-37986 discloses a method for producing a water-in-oil emulsion by emulsifying and dispersing 30 to 70% by weight of an aqueous monomer solution and 70 to 30% by weight of a hydrophobic organic liquid using a surfactant. It is disclosed. However, since it is a water-in-oil type, if it is dispersed in water at the time of dissolution, oil exists around the water droplets and dissolution does not proceed as it is. Therefore, a method of promoting the dissolution by adding a hydrophilic emulsifier called a so-called “phase inversion agent” into an emulsion or dissolved water is employed (Japanese Patent Laid-Open No. 50-43189).
[0003]
Although depending on the properties of the dissolved water, this dissolving operation is one point that determines the performance of the water-in-oil emulsion type flocculant. That is, if the amount of the phase inversion agent added is increased, the solubility is improved, but the storage stability of the emulsion product is lowered, and the coagulation performance or environment is also affected. In order to set the time until complete dissolution, a certain amount of an emulsifier having a certain HLB value is added in advance to the dissolved water, and a certain amount of water-in-oil emulsion is added thereto, and dissolved under stirring. A method for preparing a liquid is disclosed (Japanese Patent Publication No. 3-75568). Furthermore, depending on the use site of the user, the water-in-oil emulsion to which the phase inversion agent is added is dissolved in water to form an aqueous solution, and then water and the water-in-oil emulsion containing the phase inversion agent are added to the residual liquid. In addition, there is an example of preparing an aqueous solution. In such a case, since it is already viscous, it is very difficult to select the type of transfer agent or to determine the amount added.
[0004]
[Problems to be solved by the invention]
The object of the present invention is to prevent the generation of coarse undissolved particles caused by the rapid dissolution and viscosity increase of water-in-oil emulsions due to the addition of emulsifiers with high HLB added as phase inversion agents and their high addition rate. The aim is to develop a safe and efficient dissolution method.
[0005]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the following inventions have been achieved. That is, the invention of claim 1 of the present invention is an oily substance composed of at least one kind of hydrocarbon in a continuous phase, 5 to 100 mol of a cationic monomer represented by the following general formula (1) and / or (2). %, A water-in-oil polymer emulsion in which a water-soluble polymer aqueous solution composed of 0 to 40 mol% of an anionic monomer represented by the following general formula (3) and 0 to 95 mol% of acrylamide is dispersed. In addition, a nonionic oil-soluble emulsifier having an HLB number (hydrophobic lipophilic balance) of 2 to 8 is added and mixed, and then a nonionic water-soluble emulsifier having an HLB number of 8 to 20 is added. This is a method for adjusting the solubility of a water-in-oil emulsion, which is dissolved in water after addition and mixing .
[Chemical 1]
R ₁ is hydrogen or a methyl group, R ₂ and R ₃ are alkyl, alkoxy or benzyl group having 1 to 3 carbon atoms, R ₄ is hydrogen, alkyl, alkoxy group or benzyl group having 1 to 3 carbon atoms, But it may be different. X ₁ represents an anion, respectively
R ₅ represents hydrogen or a methyl group, R ₆ and R ₇ each represent an alkyl, alkoxy group or benzyl group having 1 to 3 carbon atoms, which may be the same or different, and X ₂ represents an anion.
R ₈ is hydrogen, methyl group or carboxymethyl group, R ₉ is hydrogen or carboxyl group, A is SO ₃ , C ₆ H ₄ SO ₃ , CONHC (CH ₃ ) ₂ CH ₂ SO ₃ or COO, Y is hydrogen or positive Represents an ion.
[0006]
The invention of claim 2 comprises an oily substance comprising at least one hydrocarbon as a continuous phase, 2 to 60 mol% of an anionic monomer represented by the following general formula (3), and 40 to 98 mol% of acrylamide. When dissolving a water-in-oil polymer emulsion having a water-soluble polymer aqueous solution as a dispersed phase in water, a nonionic oil-soluble emulsifier having an HLB number (hydrophobic, lipophilic balance) of 2 to 8 is added. After mixing, a nonionic water-soluble emulsifier having an HLB number of 8 to 20 is added, mixed, and then dissolved in water. This is a method for adjusting the solubility of a water-in-oil emulsion.
[Chemical 3]
R ₈ is hydrogen, methyl group or carboxymethyl group, R ₉ is hydrogen or carboxyl group, A is SO ₃ , C ₆ H ₄ SO ₃ , CONHC (CH ₃ ) ₂ CH ₂ SO ₃ or COO, Y is hydrogen or positive Represents an ion.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The method for synthesizing the water-in-oil emulsion is the same as the conventional method. First, a water-soluble vinyl monomer, water, an oily substance composed of at least one type of hydrocarbon, an amount effective for forming a water-in-oil emulsion and at least one type of surfactant having HLB, A water-in-oil emulsion is formed under stirring, and then synthesized by adding a polymerization initiator and polymerizing in a nitrogen atmosphere. Examples of water-soluble vinyl monomers include the following. Examples of the anionic monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, vinyl sulfonic acid, vinyl benzene sulfonic acid, and acrylamide 2-methylpropane sulfonic acid. Non-ionic monomers (meth) acrylamide, N, N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, N-vinyl pyrrolidone, N-vinyl And formamide and N-vinylacetamide.
[0011]
In order to synthesize an amphoteric water-soluble copolymer, a cationic monomer is copolymerized in addition to the anionic monomer and the nonionic monomer. For example, examples of the tertiary amino group-containing monomer include dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, methyl diallylamine, and ethyl diallylamine. Examples of the quaternary ammonium group-containing monomer include (meth) acryloyloxyethyltrimethylammonium chloride which is a quaternized product of (meth) methyl chloride or benzyl chloride of the tertiary amino group-containing monomer, (Meth) acryloyloxy 2-hydroxypropyltrimethylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloyloxy 2-hydroxypropyldimethylbenzylammonium chloride And (meth) acryloylaminopropyldimethylbenzylammonium chloride. Further examples include dimethyl diallylammonium chloride and methylbenzyl diallylammonium chloride.
[0012]
As for the copolymerization molar ratio of these monomers, in the case of a cationic or amphoteric polymer, 5 to 100 mol% of the cationic monomer represented by the general formula (1) and / or (2), The anionic monomer represented by the formula (3) is 0 to 40 mol% and acrylamide is 0 to 95 mol%, preferably 10 to 100 mol%, anionic monomer 0 to 30 mol% and acrylamide. 0 to 90 mol%. In the case of an anionic polymer, the anionic monomer represented by the general formula (3) is 2 to 50 mol% and acrylamide is 50 to 98 mol%, preferably an anionic monomer 5 to 50. The mol% and acrylamide are 50-95 mol%.
[0013]
Examples of oily substances composed of hydrocarbons include paraffins, mineral oils such as kerosene, light oil, and middle oil, or hydrocarbon synthetic oils having characteristics such as boiling point and viscosity in substantially the same range as these, or mixtures thereof. Can be given.
[0014]
Examples of at least one surfactant having an HLB and an effective amount to form a water-in-oil emulsion are HLB 3-6 nonionic surfactants, specific examples of which are sorbitan monooles -Sorbitan monostearate, sorbitan monopalmitate and the like. The amount of these surfactants to be added is 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the total amount of the water-in-oil emulsion.
[0015]
After neutralizing the anionic monomer, the above components were mixed, and after forming a water-in-oil emulsion with an emulsifier, etc., nitrogen substitution was performed, and the water-in-oil emulsion was set to a constant polymerization temperature. Thereafter, polymerization is initiated by a radical polymerization initiator. As the initiator, any azo, peroxide, or redox polymer can be polymerized. Examples of oil-soluble azo initiators are 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2-methylpropionate), 4,4′-azobis (4-methoxyl2,4-dimethyl) valeronitrile and the like.
[0016]
Examples of water-soluble azo initiators include 2,2′-azobis (amidinopropane) dichloride, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] And dihydrochloride, 4,4′-azobis (4-cyanovaleric acid), and the like. Examples of redox systems include a combination of ammonium or potassium peroxodisulfate and sodium sulfite, sodium hydrogen sulfite, trimethylamine, tetramethylethylenediamine, and the like. Examples of peroxides include ammonium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, and t-butylperoxy 2-ethylhexanoate. Can do.
[0017]
The polymerization temperature can be 0 to 80 ° C., but preferably 20 to 60 ° C. The polymerization concentration is generally 10 to 60% by weight, but preferably 20 to 50% by weight easily controls the polymerization reaction, and the production efficiency is good.
[0018]
The water-in-oil emulsion of the present invention comprises the above monomers, that is, anionic monomer, nonionic monomer, tertiary amino group or quaternary ammonium base-containing monomer, as well as a crosslinkable monomer. Copolymer, for example, a polyfunctional monomer such as methylenebisacrylamide and ethylene glycol di (meth) acrylate, or a heat-crosslinkable monomer such as N, N-dimethylacrylamide, and the like. It is also possible to modify the polymer and improve the performance to accommodate various wastewaters.
[0019]
A phase inversion agent is added to the water-in-oil emulsion synthesized as described above to promote dissolution in water. Conventionally, the phase inversion agent uses a water-soluble emulsifier having an HLB of 8-20. However, when a phase inversion agent is added too much, undissolved particles are generated due to a rapid increase in viscosity at the time of dissolution, and environmental concerns arise. Moreover, when there is too little addition amount, solubility will fall. Therefore, in this invention, in addition to a water-soluble emulsifier, an oil-soluble emulsifier is used together. In particular, the emulsifiers used in the present invention are a nonionic water-soluble emulsifier and a nonionic oil-soluble emulsifier. By using in combination, the viscosity of the solution increases in proportion to the time, and the generation of undissolved particles can be suppressed, and it is possible to cope with the case where there is viscosity from the beginning of dissolution by “additional dissolution”. The addition ratio of these nonionic water-soluble emulsifier and nonionic oil-soluble emulsifier is a: b = 9: 1 to 5: 5, where a and b are the weight percentages of the water-soluble emulsifier and the oil-soluble emulsifier, respectively. Preferably, a: b = 8: 2 to 5: 5. The addition method may be a method in which both emulsifiers are mixed or added, and an oil-soluble emulsifier is added and mixed, and then a water-soluble emulsifier is added and mixed, but the order of oil-soluble emulsifier and water-soluble emulsifier is preferred. Add in. If a water-soluble emulsifier is added first, the water-in-oil emulsion may be destroyed, which is not preferable.
[0020]
The nonionic water-soluble emulsifier as used in the present invention refers to one that forms a transparent liquid when dissolved as a 1% by weight solution in pure water. On the other hand, the nonionic oil-soluble emulsifier is a dispersion medium during polymerization. In particular, when it is dissolved in a refined light oil as a 1% by weight solution, it produces a transparent liquid. This property does not necessarily depend on the HLB, and is greatly affected by the chemical structure. Therefore, there is a range that partially intersects with the oil-soluble emulsifiers 2 to 9 and the water-soluble emulsifiers 8 to 20.
[0021]
Specific examples of these emulsifiers include nonionic water-soluble emulsifiers such as polyoxyethylene nonylphenyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene Examples thereof include oxyethylene tridecyl ether and polyoxyethylene oleyl ether. Nonionic oil-soluble emulsifiers are sorbitan monooleate, sorbitan dioleate, sorbitan monostearate, sorbitan distearate, sorbitan monolaurate, sorbitan dilaurate, sorbitan monopalmi Tate, sorbitan dipalmitate, etc.
[0022]
The water-soluble polymer comprising the water-in-oil emulsion of the present invention can be applied to pulp sludge dewatering in the paper industry, other wastewater treatment in the food industry, metal and oil refining, and treatment of gravel washing wastewater related to building materials. It is. The amount added varies depending on the type of waste water, the concentration of the suspension, etc., but is about 0.1 to 1000 ppm with respect to the liquid amount.
[0023]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated in more detail with an Example and a comparative example, this invention is not restrict | limited to a following example, unless the summary is exceeded.
[0024]
(Synthesis Example 1)
A reaction vessel equipped with a stirrer and a temperature controller was charged with 230.0 g of isoparaffin having a boiling point of 190 ° C. to 230 ° C. and 17.0 g of sorbitan monooleate. Separately, 200.0 g of 60% aqueous acrylic acid (AAC) and 360.0 g of 50% aqueous acrylamide (AAM) were mixed, and 155.4 g of 43% aqueous sodium hydroxide solution (equivalent to acrylic acid) had a liquid temperature of 30 ° C. The mixture was neutralized while cooling so as not to become above. The molar ratio of acrylamide to acrylic acid after monomer infiltration is 60:40. Thereafter, the oil phase and the aqueous monomer solution were combined and stirred and emulsified with a homogenizer at 1000 rpm for 5 minutes. To the obtained emulsion, 1.0 g of a 10% aqueous solution of isopropyl alcohol (0.033% by weight based on the monomer) was added, and after nitrogen substitution, 2,2′-azobis [2- (5-methyl-2) was used as an initiator. -Imidazolin-2-yl) propane] 1.0 g of a 10% aqueous solution of dihydrochloride was added (0.033% by weight of monomer), and the polymerization reaction was started while controlling the temperature at 33 ± 1 ° C. After 5 hours, 1.0 g of the initiator was added, and the reaction was further continued for 5 hours to complete the polymerization (referred to as Sample-1). A part of the obtained water-in-oil emulsion was collected, and a polymer was precipitated with acetone, followed by drying under reduced pressure at 25 ° C. for 48 hours to take out the dried polymer. After dissolution, the weight average molecular weight was measured by a molecular weight measuring device (DLS-7000, manufactured by Otsuka Electronics Co., Ltd.) by a static light scattering method. The results are shown in Table 1.
[0025]
(Synthesis Example 2)
In the same manner as in Example 1, a water-in-oil emulsion (referred to as Sample-2) composed of a copolymer of acrylamide / acrylic acid = 90/10 was synthesized. The results are shown in Table 1.
[0026]
(Synthesis Example 3)
In a reaction vessel equipped with a stirrer and a temperature controller, 230.0 g of isoparaffin having a boiling point of 190 ° C. to 230 ° C. and 17.5 g of sorbitan monooleate, 320.7 g of 80% aqueous acryloyloxyethyltrimethylammonium chloride, 50% aqueous acrylamide 188.2 g and 196.1 g of deionized water were introduced. The molar ratio of acryloyloxyethyltrimethylammonium chloride to acrylamide after monomer incorporation is 50:50. Thereafter, the oil phase and the aqueous monomer solution were combined, and stirred and emulsified with a homogenizer at 1000 rpm for 7 minutes. To the obtained emulsion was added 1.0 g of a 10% aqueous solution of isopropyl alcohol (0.033% by weight to the monomer), and after substitution with nitrogen, 2,2′-azobis [2- (5-methyl-2-methyl ester) was used as an initiator. Imidazolin-2-yl) propane] 0.6 g of a 10% aqueous solution of dihydrochloride (0.02% by weight of monomer) was added to start the polymerization reaction while controlling the temperature at 33 ± 1 ° C. After that, 0.6 g of the initiator was added, and the reaction was further continued for 5 hours to complete the polymerization (referred to as Sample-3). After the polymerization, the weight average molecular weight was measured in the same manner. The results are shown in Table 1.
[0027]
(Synthesis Example 4)
A water-in-oil emulsion (referred to as sample-4) composed of a copolymer of acryloyloxyethyltrimethylammonium chloride / acrylamide = 20/80 was synthesized in the same manner as in Example 1. The results are shown in Table 1.
[0028]
(Synthesis Example 5)
A reaction vessel equipped with a stirrer and a temperature controller was charged with 230.0 g of isoparaffin having a boiling point of 190 ° C. to 230 ° C. and 25.0 g of sorbitan monooleate. Separately, 28.6 g of 60% aqueous acrylic acid and 65.9 g of 50% aqueous acrylamide were mixed, and 37.0 g of 43% aqueous sodium hydroxide solution (equivalent to acrylic acid) was cooled so that the liquid temperature did not exceed 30 ° C. While neutralizing. To the neutralized solution was added 320.5 g of an 80% aqueous solution of acryloyloxyethyltrimethylammonium chloride. The molar ratio of acrylamide / acrylic acid / acryloyloxyethyltrimethylammonium chloride after monomer incorporation is 35:15:50. Thereafter, the oil phase and the aqueous monomer solution were combined, and stirred and emulsified with a homogenizer at 1000 rpm for 7 minutes. To the obtained emulsion was added 0.6 g of 10% aqueous solution of isopropyl alcohol (0.02% by weight of monomer), and after nitrogen substitution, 2,2′-azobis [2- (5-methyl-2) was used as an initiator. -Imidazolin-2-yl) propane] 1.2 g of a 10% aqueous solution of dihydrochloride was added (0.04% by weight of monomer), and the polymerization reaction was started while controlling the temperature at 33 ± 1 ° C. After 5 hours, 1.0 g of the initiator was added, and the reaction was further continued for 5 hours to complete the polymerization (referred to as Sample-5). The results are shown in Table 1.
[0029]
(Synthesis Example 6)
In the same manner as in Example 1, a water-in-oil emulsion (sample 6) comprising a copolymer of acrylamide / acrylic acid / acryloyloxyethyltrimethylammonium chloride = 40/20/40 was synthesized. The results are shown in Table 1.
[0030]
Examples 1-2
To the water-in-oil emulsion synthesized in Synthesis Examples 1 and 2, a phase inversion agent having a composition as shown in Table 2 was added in the order of an oil-soluble emulsifier and a water-soluble emulsifier. Thereafter, using a three-one motor, 10 g was sampled and dissolved 200 times in pure water, the viscosity was measured at regular intervals, and the solubility in water was tested. The solution was filtered through a 60 mesh screen and the weight of insoluble particles was measured. Further, 200 ml of a water-in-oil emulsion one month after the addition of the phase inversion agent was collected and stored in a sample bottle having a diameter of 5 cm, and the separation stability was tested. The results are shown in Table 2.
[0031]
[Comparative Examples 1-2]
The solubility and separation stability were tested when only the water-soluble emulsifier was added to the water-in-oil emulsion synthesized in Synthesis Examples 3-6. The results are shown in Table 3.
[0032]
Examples 3 to 6
To the water-in-oil emulsion synthesized in Synthesis Examples 3 to 6, a phase inversion agent having a composition as shown in Table 2 was added in the order of an oil-soluble emulsifier and a water-soluble emulsifier. Thereafter, using a three-one motor, 10 g was sampled and dissolved 100 times in pure water, the viscosity was measured at regular intervals, and the solubility in water was tested. The solution was filtered through a 60 mesh screen and the weight of insoluble particles was measured. Further, 200 ml of a water-in-oil emulsion one month after the addition of the phase inversion agent was collected and stored in a sample bottle having a diameter of 5 cm, and the separation stability was tested. The results are shown in Table 4.
[0033]
[Comparative Examples 3-6]
The solubility and separation stability were tested when only the water-soluble emulsifier was added to the water-in-oil emulsion synthesized in Synthesis Examples 3-6. The results are shown in Table 5.
[0034]
[Table 1]
AAC: acrylic acid, AAM: acrylamide, DMQ: acryloyloxyethyltrimethylammonium chloride, emulsion viscosity: mPa · s
Molecular weight: The unit is 10,000
[Table 2]
(A): Sobitan monooleate (a) -1; 0.6%, (a) -2; 0.6%
(B): Polyoxyethylene nonylphenyl ether (polyoxyethylene chain; molecular weight 500)
(B) -1; 2.3%, (b) -2; 2.3%
Insoluble matter: All solutions were almost zero.
[0036]
[Table 3]
(B): Polyoxyethylene nonylphenyl ether (polyoxyethylene chain; molecular weight 500)
(B) -3; 2.3%, (b) -4; 2.3%
Separation stability: * 1; supernatant 0.5 cm, * 2; supernatant 0.3 cm
Insoluble matter during dissolution: wet weight of swollen particles (g)
[0037]
[Table 4]
(A): Sobitan monooleate (a) -3; 1%, (a) -4; 1%, (a) -5; 1%, (a) -6; 1%
(B): Polyoxyethylene oleyl ether (polyoxyethylene chain; molecular weight 600)
(B) -5; 3.0%, (b) -6; 3.3%, (b) -7; 3.8%,
(B) -8; 3.8%
Insoluble matter: All solutions were almost zero.
[0038]
[Table 5]
(B) -9; 3.0%, (b) -10; 3.3%, (b) -11; 3.8%,
(B) -12; 3.8%
Insoluble matter during dissolution: wet weight of swollen particles (g)

Claims (2)

An oily substance comprising at least one hydrocarbon is a continuous phase, 5 to 100 mol% of a cationic monomer represented by the following general formula (1) and / or (2) , an anion represented by the following general formula (3) In dissolving water-in-oil polymer emulsion in which water-soluble polymer aqueous solution composed of 0 to 40 mol% of ionic monomer and 0 to 95 mol% of acrylamide is dispersed in water, the HLB number (hydrophobic After adding and mixing a nonionic oil-soluble emulsifier having a lipophilic balance of 2 to 8, a nonionic water-soluble emulsifier having an HLB number of 8 to 20 is added and mixed, and then dissolved in water. A method for adjusting the solubility of a water-in-oil emulsion.
R ₁ is hydrogen or a methyl group, R ₂ and R ₃ are alkyl, alkoxy or benzyl group having 1 to 3 carbon atoms, R ₄ is hydrogen, alkyl, alkoxy group or benzyl group having 1 to 3 carbon atoms, But it may be different. X ₁ represents each anion
R ₅ is hydrogen or a methyl group, R ₆ and R ₇ are alkyl, alkoxy group or benzyl group having 1 to 3 carbon atoms, which may be the same or different, and X ₂ represents an anion, respectively.
R ₈ is hydrogen, methyl group or carboxymethyl group, R ₉ is hydrogen or carboxyl group, A is SO ₃ , C ₆ H ₄ SO ₃ , CONHC (CH ₃ ) ₂ CH ₂ SO ₃ or COO, Y is hydrogen or positive Represents ion An oily substance composed of at least one hydrocarbon is dispersed in a continuous phase, and a water-soluble polymer aqueous solution composed of 2 to 60 mol% of an anionic monomer represented by the following general formula (3) and 40 to 98 mol% of acrylamide is dispersed. In dissolving the water-in-oil polymer emulsion as a phase in water, after adding and mixing a nonionic oil-soluble emulsifier having an HLB number (hydrophobic, lipophilic balance) of 2 to 8, the HLB number A method for adjusting the solubility of a water-in-oil emulsion , wherein a nonionic water-soluble emulsifier of 8 to 20 is added and mixed and then dissolved in water.
R ₈ is hydrogen, methyl group or carboxymethyl group, R ₉ is hydrogen or carboxyl group, A is SO ₃ , C ₆ H ₄ SO ₃ , CONHC (CH ₃ ) ₂ CH ₂ SO ₃ or COO, Y is hydrogen or positive Represents an ion.