JP6448111B2 - Antifoam for building board manufacturing process - Google Patents

Description

  The present invention relates to an antifoaming agent used in a manufacturing process of a building material board made mainly of an inorganic material. More specifically, the present invention relates to a liquid antifoaming agent that does not delay the setting of the building material board raw material slurry, which is a cause of lowering the strength of the molded product, and has good operability during use.

  The building board is made by mixing and stirring inorganic powders such as cement, calcium silicate, gypsum and calcium carbonate, fiber reinforcing agents (eg bleached pulp, unbleached pulp, pulp such as waste paper and synthetic fibers), and water to make a raw material slurry. It is manufactured by drying and curing the cake after filtration and dehydration.

  Building material boards are formed by papermaking, extrusion, or formwork pouring, but if bubbles are present in the raw material slurry, the bubbles cause voids and the surface properties are impaired and the strength is reduced. The rate increases. Anti-foaming agents are used as countermeasures, and mineral oil-based antifoaming agents, silicone-based antifoaming agents, polyether-based antifoaming agents, wax-based antifoaming agents and the like are known as commercially available antifoaming agents.

  In Patent Document 1, the oil phase of an emulsion that can be used in the building material board manufacturing process is (a) alcohol having 12 to 30 carbon atoms and / or (b) 1 to 6-valent alcohol having 1 to 30 carbon atoms and carbon number. An oil-in-water emulsion antifoam composition containing a fatty acid ester with 12-30 carboxylic acids is disclosed.

  Patent Document 2 discloses an ethylene oxide / alkylene oxide adduct of a higher alcohol, which is a polyether-based antifoaming agent, particularly as a defoaming agent for building material board papermaking process.

  Patent Document 3 discloses that dimethyl silicone and its methyl group are substituted with a hydrocarbon having 2 or more carbon atoms as an antifoaming agent used in a mold casting process of a hardened calcium silicate material that can be used for a building wall material. Silicones such as alkyl-modified silicones, fatty acids such as glycerin fatty acids, fatty acid esters such as glycerin fatty acid esters and sucrose fatty acid esters, higher alcohols such as octyl alcohol, phosphates such as aromatic phosphates and aliphatic phosphates, etc. Among them, it is disclosed that dimethyl silicone and alkyl-modified silicone are preferably used.

  However, since conventional polyether-based and silicone-based antifoaming agents are hydrophobic substances that are liquid at room temperature, in the building material board raw material slurry that is mainly cured by a hydration reaction, It becomes a substance that inhibits the curing reaction and delays the setting of the raw slurry, which causes a reduction in strength of the molded product.

  Further, as a cement extrusion aid, a method has been proposed in which an antifoaming agent is absorbed into silica powder together with a water reducing agent and a nonionic surfactant to form a powder (Patent Document 4). There is a problem that not only the process of making it into a granular form but also the addition by a pump cannot be performed because it is solid, which is not only expensive in terms of cost but also poor in operability.

JP-A-9-234307 JP 11-199291 A Japanese Patent No. 4343108 JP 2006-232651 A

  The present invention has been made in view of the above-described conventional situation, and as a defoaming agent used in a manufacturing process of a building material board using an inorganic material that is cured by a hydration reaction as a defoaming agent, a setting delay that reduces the strength of a molded product. An object of the present invention is to provide a liquid antifoaming agent that does not exhibit the properties and has good operability during use.

  As a result of intensive studies to solve the above problems, the present inventors include an oil phase component containing a higher alcohol that is solid at room temperature and a water-soluble nonionic surfactant as a defoaming agent for building material board manufacturing processes. By adding an oil-in-water (O / W type) emulsion antifoaming agent prepared by mixing and emulsifying an aqueous phase component to a raw material slurry for a building material board composed of an inorganic material that is cured by a hydration reaction, It has been found that rapid curing can be achieved without hindering the hydration reaction and the strength of the molded product can be maintained high, and that the antifoaming agent is a liquid-form emulsion, so that good operability during use can be secured.

  Further, by adding a water-soluble inorganic salt to the oil-in-water (O / W type) emulsion antifoaming agent, the antifoaming performance is improved, and the product antifoaming agent is separated and thickened over time. Since it can be suppressed, it has been found that good operability can be obtained over a long period of time, and the present invention has been completed.

（式中、Ｒ_１は炭素数１０〜２４の脂肪族炭化水素基を示し、ｎは１０〜１００の整数を示す。） That is, the invention according to claim 1 includes an oil phase component containing a higher alcohol having a melting point of 20 ° C. or higher, and a water phase component containing a water-soluble nonionic surfactant and water (however, an anionic surfactant is not included). ) O / W emulsion antifoaming agent for building board manufacturing process (however, self-emulsifying antifoaming agent is not included), and the water-soluble nonionic surfactant is represented by the following general formula (1) An ethylene oxide adduct of an aliphatic alcohol having 10 to 24 carbon atoms, containing 0.01 to 1 part by weight of the ethylene oxide adduct of the aliphatic alcohol with respect to 100 parts by weight of water of the aqueous phase component, W-type emulsion antifoaming agent.

(In the formula, R ₁ represents an aliphatic hydrocarbon group having 10 to 24 carbon atoms, and n represents an integer of 10 to 100.)

In the invention according to claim 2 , the ethylene oxide adduct of an aliphatic alcohol having 10 to 24 carbon atoms represented by the general formula (1) is selected from the group of lauryl alcohol, cetyl alcohol, stearyl alcohol and oleyl alcohol. is one or ethylene oxide adducts of two or more aliphatic alcohols, O / W type emulsion antifoaming agent according to claim 1.

Invention further wherein comprising 0.5 to 5 parts by weight of water-soluble inorganic salt in water 100 parts by weight of the aqueous phase component, O according to any one of claims 1 or 2 according to claim 3 / W type emulsion defoamer.

The invention according to claim 4, wherein the water-soluble inorganic salt is sodium chloride, potassium chloride, calcium chloride, according to claim 3 is one or more selected from the group consisting of sodium sulfate and potassium sulfate O / W-type emulsion antifoaming agent.

  The antifoaming agent of the present invention is very useful as an antifoaming agent in the building material board manufacturing process because it does not hinder the hydration reaction of the raw material slurry for building material board composed of inorganic substances and can achieve rapid curing. In addition, since it is in liquid form, it can be added by a metering pump and has excellent operability.

  The antifoaming agent of the present invention comprises an oil phase component containing a higher alcohol and a water phase component containing a water-soluble nonionic surfactant and water, and is an O / W type (oil-in-water type) emulsion, or The O / W emulsion further contains a water-soluble inorganic salt in the water phase component.

  The higher alcohol solid at room temperature used in the O / W emulsion defoamer of the present invention refers to a higher alcohol having a melting point of about 20 ° C. or higher. For example, natural alcohols include lauryl alcohol, myristyl alcohol, cetyl alcohol, Examples include stearyl alcohol, eicosanol, docosanol, tetracosanol, hexacosanol, octacosanol, and myricyl alcohol. Synthetic alcohols include linear primary alcohols or branched primary alcohols synthesized by the Ziegler method, alcohol mixtures having different carbon numbers, and linear secondary alcohols obtained by air oxidation of paraffin. Etc. In the O / W emulsion defoamer of the present invention, one or more selected from the group of these higher alcohols can be used.

  The blending amount of the higher alcohol in the O / W emulsion defoamer of the present invention is not particularly limited, but is preferably 5 to 50% by weight, and 10 to 40% by weight based on the total amount of the defoamer to be produced. It is more preferable that If the blending amount of the higher alcohol is less than 5% by weight, the antifoaming effect may not be sufficiently exhibited, and if it exceeds 50% by weight, the product viscosity of the obtained antifoaming agent may be increased and the handleability may be lowered. is there.

  The water-soluble nonionic surfactant used in the O / W type emulsion antifoaming agent of the present invention is a nonionic surfactant that dissolves 0.5% by weight or more in water, for example, an alkylene oxide adduct of an aliphatic alcohol. An alkylene oxide adduct of a fatty acid, an alkylene oxide adduct of an alkylphenol, an alkylene oxide adduct of an aliphatic amine, and an alkylene oxide adduct of sorbitan. Among these, an ethylene oxide adduct of an aliphatic alcohol having 10 to 24 carbon atoms is preferable. Examples of the aliphatic alcohol having 10 to 24 carbon atoms include decyl alcohol, lauryl alcohol, cetyl alcohol, stearyl alcohol, oleyl alcohol, eicosanol, docosanol, and tetracosanol. In addition, application of a hydrophobic nonionic surfactant having a solubility in water of less than 0.5% by weight is not preferable because it may cause a setting delay in a raw material slurry for a building material board to which the antifoaming agent is added.

  The blending amount of the water-soluble nonionic surfactant in the O / W emulsion defoaming agent of the present invention is appropriately changed depending on the type and blending amount of the oil phase component. It is preferable to mix 0.01 to 1.0 part by weight with respect to 100 parts by weight of water in the constituent water phase component, and two or more water-soluble nonionic surfactants may be used in appropriate combination. . If the blending amount of the water-soluble nonionic surfactant is less than 0.01 parts by weight with respect to 100 parts by weight of water in the aqueous phase component, there is a possibility that the fine alcohol fine particles may be insufficient, and 1.0 wt. When the amount exceeds 50 parts, foaming of the product antifoaming agent itself increases, and when the storage period of the product antifoaming agent extends for a long period of time, the increase in product viscosity may increase.

  The water used in the O / W emulsion defoamer of the present invention may be clean water that does not contain a suspended substance, and softened water or pure water may be used in addition to normal industrial water.

  In the water phase containing the water-soluble nonionic surfactant and water of the O / W emulsion defoamer of the present invention, a water-soluble inorganic salt is added in an amount of 0.5 to 100 parts by weight based on 100 parts by weight of water of the water phase component. When 5 parts by weight is contained, in the resulting O / W type emulsion, finer oil phase component particles can be obtained and contribute to the suppression of aggregation. Therefore, an antifoaming agent having a higher defoaming effect is produced. In addition, the obtained antifoaming agent is more preferable because it does not exhibit a setting delay in the raw material slurry for building material boards to which the antifoaming agent is added.

  The water-soluble inorganic salt used in the O / W type emulsion antifoaming agent of the present invention is an inorganic salt that dissolves in an amount of 0.5% by weight or more with respect to water, and an arbitrary combination of two or more water-soluble inorganic salts. May be used. Especially, it is preferable that it is a neutral salt in which pH of aqueous solution shows neutrality. For water-soluble inorganic salts other than neutral salts, the product pH of the antifoaming agent after manufacture may not be stable, and the pH of the product antifoaming agent becomes acidic or alkaline, which is preferable from the viewpoint of safety in handling. I can't go wrong.

  Examples of the water-soluble inorganic salt include sodium chloride, potassium chloride, calcium chloride, sodium sulfate, potassium sulfate, sodium nitrate, potassium nitrate, sodium bromide and potassium bromide. Among these, sodium chloride, potassium chloride, calcium chloride, sodium sulfate, and potassium sulfate are more preferable because they are inexpensive and have little environmental load.

  The blending amount of the water-soluble inorganic salt in the O / W emulsion defoamer of the present invention is 0.5 to 5.0 parts by weight based on 100 parts by weight of water in the water phase component constituting the defoamer. It is preferable to do. If the blending amount is less than 0.5 parts by weight, the oil phase component may be insufficiently atomized. If the blending amount exceeds 5.0 parts by weight, the oil phase component may be finely divided to meet the increase in the blending amount. The improvement of the effect cannot be expected, and the difference in specific gravity between the oil phase and the water phase becomes large, so that separation may occur when the storage period of the product antifoaming agent is long.

  There is no restriction | limiting in particular in the manufacturing method of the O / W type | mold emulsion antifoamer of this invention, The well-known method of obtaining an O / W type | mold emulsion can be used. For example, a dispersion method or a condensation method. More specifically, the former is a mechanical emulsification method using a stirrer or a disperser, and the latter is a phase inversion method, a D phase emulsification method, a liquid crystal emulsification method, a solubilization conversion method, or the like. Physical emulsification method. Among them, under stirring and mixing conditions, an oil phase component containing a higher alcohol is added to an aqueous phase component prepared by dissolving a water-soluble nonionic surfactant in water in advance, and the mixture is heated to a temperature higher than the melting point of the oil phase component and emulsified. It is preferable from the operability to combine the mechanical emulsification method and the temperature phase inversion method. When a water-soluble inorganic salt is included, a water-phase component is prepared by previously dissolving a water-soluble inorganic salt and a water-soluble nonionic surfactant in water.

  As the stirring and mixing equipment, known equipment used for normal stirring and mixing and emulsification dispersion, for example, stirrers equipped with stirring blades such as paddle blades, propeller blades, and turbine blades, dissolvers, homomixers, ball mills, sand mills, ultrasonic waves A disperser, a kneader, a line mixer, a high-speed shearing type agitation disperser, a pressure nozzle type emulsifier, a piston type high pressure emulsifier, or the like can be used, and these two or more types of equipment can also be used in combination.

  In the O / W emulsion defoamer of the present invention, the average particle size of the fine particles of the oil phase component containing the higher alcohol is preferably 1 to 15 μm, and more preferably 2 to 10 μm. If it is less than 1 μm, the load for mechanical dispersion increases and the equipment cost increases. Moreover, when it exceeds 15 micrometers, when the storage period of a product antifoamer extends long, there exists a possibility of producing separation.

  The O / W emulsion defoamer of the present invention may use a water-soluble polymer as required for improving stability over time and improving dispersibility. Water-soluble polymers include cellulose, pullulan, gum arabic, guar gum, glucomannan, xanthan gum, welan gum, lanthanum gum, tragacanth gum, locust bean gum, agarose, glycogen, methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxy Ethyl methyl cellulose, polyvinyl alcohol, polyacrylamide, polyacrylic acid, polymethacrylic acid, copolymers of acrylic acid and acrylamide, copolymers of methacrylamide and acrylamide, copolymers of methacrylamide and methacrylic acid, etc. can be used. These water-soluble polymers can be used alone or in combination of two or more.

  In addition, the O / W emulsion antifoaming agent of the present invention can contain a hydrocarbon, an antiseptic, a fungicide, a bactericide, a rust inhibitor, an anti-skinning agent, and the like, if necessary. Since these are all known and are described in, for example, Japanese Patent Laid-Open No. 2000-300909, the details thereof are omitted.

  Although there is no restriction | limiting in particular in the addition amount of the O / W type | mold emulsion antifoamer of this invention, Usually, 0.1-1000 mg / L is added with respect to a process liquid.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited only to a following example. In addition, various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the scope of the claims.

The antifoaming agent to be evaluated (test antifoaming agent) was prepared by the following method.
(Antifoaming agent 1)
In 70 parts by weight of water, 0.07 part by weight of polyoxyethylene lauryl ether (average number of moles of ethylene oxide added = 20 moles) was dissolved, using a 45 ° inclined paddle blade and stirring at a blade tip speed of 8 m / s. Higher alcohol dissolved by heating (Nafol 20 + A (trade name) manufactured by Sasol Japan Co., Ltd.) [Composition: higher alcohol with 16 to 26 carbon atoms, monocarboxylic acid ester, alkyl ether and other by-products 30%], melting point: 54 (~ 58 ° C) 30 parts by weight was added, the temperature was raised to 75 ° C, and the mixture was stirred for 1 hour to make uniform. Subsequently, 0.1 part by weight of xanthan gum was added, and the mixture was cooled to 30 ° C. to obtain an antifoaming agent 1 having an average particle diameter of 12 μm of oil phase component particles and a viscosity of 180 mPa · s. The antifoaming agent contains 0.1 part by weight of a water-soluble nonionic surfactant with respect to 100 parts by weight of water as an aqueous phase component.

(Antifoaming agent 2-5)
By the same method as antifoam 1, antifoams 2 to 5 having the compositions and properties shown in Table 1 were obtained.

(Antifoaming agent 6)
Dissolve 0.35 parts by weight of sodium chloride and 0.07 parts by weight of polyoxyethylene lauryl ether (average number of moles of added ethylene oxide = 20 moles) in 70 parts by weight of water, using 45 ° inclined paddle blades, and tip speed of the blades Higher alcohol (Nasol 20 + A (trade name) manufactured by Sasol Japan Co., Ltd.) [Composition: higher alcohol 70% with 16 to 26 carbon atoms, monocarboxylic acid ester, alkyl ether, and other secondary substances dissolved with heating while stirring at 8 m / s 30% organism, melting point: 54-58 ° C.) was added, and the mixture was heated to 75 ° C. and stirred for 1 hour to homogenize. Subsequently, 0.1 part by weight of xanthan gum was added, and the mixture was cooled to 30 ° C. to obtain an antifoaming agent 6 having an average particle diameter of oil phase component particles of 8 μm and a viscosity of 170 mPa · s. The antifoaming agent contains 0.5 part by weight of a water-soluble inorganic salt and 0.1 part by weight of a water-soluble nonionic surfactant with respect to 100 parts by weight of water as an aqueous phase component.

(Antifoamer 7-10)
By the same method as antifoaming agent 6, antifoaming agents 7 to 10 having the compositions and properties shown in Table 1 were obtained.

(Antifoaming agent 11)
Antifoam 1 Nafo 20 + A was replaced with decyl alcohol (melting point: 7 ° C.) and 0.07 part by weight of polyoxyethylene lauryl ether (average number of moles of ethylene oxide added = 20 moles) was changed to 2.1 parts by weight. An antifoaming agent 11 was obtained in the same manner as the antifoaming agent 1 except that it was replaced. The antifoaming agent contains 3.0 parts by weight of a water-soluble nonionic surfactant with respect to 100 parts by weight of water as an aqueous phase component. In order to emulsify liquid decyl alcohol at room temperature, a large amount of water-soluble nonionic surfactant is required.

(Defoamer 12)
Antifoam 6 Nafo 20 + A is replaced with decyl alcohol (melting point: 7 ° C.), and 0.07 part by weight of polyoxyethylene lauryl ether (average number of moles of added ethylene oxide = 20 moles) is 2.1 parts by weight. An antifoam 12 was obtained in the same manner as the antifoam 6 except that it was replaced. The antifoaming agent contains 0.5 parts by weight of a water-soluble inorganic salt and 3.0 parts by weight of a water-soluble nonionic surfactant with respect to 100 parts by weight of water as an aqueous phase component. In order to emulsify liquid decyl alcohol at room temperature, a large amount of water-soluble nonionic surfactant is required.

(Antifoaming agent 13)
Instead of dissolving 0.07 part by weight of polyoxyethylene lauryl ether (average number of moles of ethylene oxide = 20 moles) in 70 parts by weight of water, polyoxyethylene oleyl ether (average number of moles of added ethylene oxide = 70 parts by weight of water = The antifoaming agent 13 was obtained in the same manner as in Example 1 except that a solution in which 0.07 parts by weight of 6 mol, solubility in water at 25 ° C. was less than 0.5%) was used. The antifoaming agent contains a hydrophobic nonionic surfactant and does not contain a water-soluble nonionic surfactant.

(Defoaming agent 14)
Foam Clean M-65 (trade name, polyether-based antifoaming agent manufactured by Hakuto Co., Ltd.) was used as the antifoaming agent 14.

(Defoaming agent 15)
As the antifoaming agent 15, foam clean G-401 (trade name, mineral oil-based antifoaming agent manufactured by Hakuto Co., Ltd.) was used.

(Antifoaming agent 16)
As the antifoaming agent 16, foam clean S-30 (trade name, silicone-based antifoaming agent manufactured by Hakuto Co., Ltd.) was used.

Table 1 shows the compositions and properties of antifoaming agents 1-13.

Using the antifoaming agents 1 to 16 (test antifoaming agents), an evaluation test was performed by the following method.
(1) Setting retardance evaluation test This test evaluates the effect of an antifoaming agent added to a raw material slurry for a building material board made mainly of an inorganic material that hardens by a hydration reaction, on the hydration / condensation reaction of the slurry. To do. 90 parts by weight of ordinary Portland cement and 10 parts by weight of gypsum were premixed, and 60 parts by weight of wood pulp was mixed therewith. Further, 30 parts by weight of water and 0.1 part by weight of the test defoaming agent were added to 100 parts by weight of this mixture, and kneading was carried out for 5 minutes with a mixer. Thereafter, the setting time was measured according to JIS A6204-1987 Annex 1 “Concrete Setting Time Test Method”.
(2) Defoaming performance evaluation test This test evaluates the defoaming performance of the defoaming agent added to the process water of the building material board manufacturing process. An acrylic cylinder with an inner diameter of 80 mm and a capacity of 2,000 ml is filled with 1,000 ml of foaming test water (ceramic building material board making process white water) to which 4 mg / L of the test defoaming agent is added. The test water is foamed by dropping the test water from the bottom of the cylinder at 4,000 ml / min using the, and dropping it onto the test water surface from the top of the cylinder. After the start of circulation, the foam height (foaming amount) in the cylinder after 1 minute, 2 minutes, 3 minutes, and 5 minutes elapsed was read to evaluate the foaming suppression effect (defoaming performance).
(3) Surface condition evaluation test This test evaluates the influence of an antifoaming agent on the surface condition of a building material board molded product whose main raw material is an inorganic substance that is cured by a hydration reaction. In the building material board manufacturing process, when the aggregation of the raw material slurry for building material board is hindered or the defoaming effect of process water is low, the surface state of the molded product is deteriorated. The kneaded material which added the test defoamer was produced by the method similar to evaluation of the setting delay property of (1). This kneaded product was put into a mold assembled with a press plate and compression molded at 70 ° C. and 20 kg / cm ² . Then, the obtained compression molded product was clamped and compression-cured for 6 hours, followed by natural curing for 7 days to obtain a cement plate having a length of 500 mm × width of 500 mm × thickness of 12 mm.
The surface of the cement board was visually observed, and the surface condition was evaluated according to the following criteria.
○: The surface is smooth and good. Δ: The surface is slightly uneven. ×: The surface has many unevenness or cracks. (4) Bending strength evaluation test. Cement board obtained by the method of (3). Was measured according to JIS R5201-1997 Annex 2 “Cement Test Method—Measurement of Strength” to evaluate bending strength.

  Table 2 shows the results of the setting delay evaluation test, the defoaming performance evaluation test, the surface condition evaluation test, and the bending strength evaluation test. In addition, the comparative example 7 is an example without an antifoamer addition.

  As shown in Table 2, Examples 1 to 10 of the present invention using antifoaming agents 1 to 10 are almost the same as Comparative Example 7 in which the setting time is blank. It became clear that the raw material slurry for building material boards, which is the main raw material, does not exhibit a setting delay property that hinders the strength of the molded product. Moreover, the defoaming performance with respect to the process water of a building material board manufacturing process is high compared with the comparative example 7, Especially, it became clear that the defoaming performance of Examples 6-10 containing water-soluble inorganic salt improves notably. .

  On the other hand, Comparative Examples 1 and 2 and Comparative Examples 4 to 6 using an antifoaming agent having a higher alcohol or a hydrophobic substance which is liquid at room temperature as an antifoaming component, and Comparative Example 3 containing a hydrophobic nonionic surfactant Then, the setting time was clearly longer than that of Comparative Example 7 in which it was blank, showing a clear setting delay, and the test results of the surface condition and bending strength were also inferior to those of Examples 1-10. .

  As described above, the O / W type emulsion antifoaming agent for the building material board manufacturing process of the present invention does not hinder the hydration reaction of the raw material slurry for the building material board whose main raw material is an inorganic substance that is cured by the hydration reaction. , Without delaying the setting of the slurry, can achieve rapid curing, maintain a good surface condition and high bending strength of the molded article, and obtain good defoaming performance in the process water of the building material board manufacturing process The unique effect of the present invention was demonstrated. Furthermore, since the O / W emulsion defoamer of the present invention is a liquid emulsion, the operability during use is also good.

The antifoaming agent of the present invention can be applied to a building material board manufacturing process. The antifoaming agent of the present invention is very useful because it suppresses foaming in the process, maintains the surface state of the molded article well, and maintains high strength.

Claims (4)

An oil phase component containing a higher alcohol having a melting point of 20 ° C. or higher and a water phase component containing a water-soluble nonionic surfactant and water (but not including an anionic surfactant) . W type emulsion antifoaming agent (however, self-emulsifying type antifoaming agent is not included), and the water-soluble nonionic surfactant is a C10-24 aliphatic alcohol represented by the following general formula (1) An O / W emulsion defoamer comprising 0.01 to 1 part by weight of the ethylene oxide adduct of the aliphatic alcohol per 100 parts by weight of water of the aqueous phase component.

(In the formula, R ₁ represents an aliphatic hydrocarbon group having 10 to 24 carbon atoms, and n represents an integer of 10 to 100.) 1 or 2 or more types of fat from which the ethylene oxide adduct of C10-24 aliphatic alcohol represented by the said General formula (1) is chosen from the group of lauryl alcohol, cetyl alcohol, stearyl alcohol, and oleyl alcohol The O / W emulsion defoamer according to claim 1, which is an ethylene oxide adduct of an aromatic alcohol. Furthermore, O / W type | mold emulsion antifoamer of any one of Claim 1 or 2 which contains 0.5-5 weight part of water-soluble inorganic salts with respect to 100 weight part of water of the said water phase component. The O / W emulsion defoamer according to claim 3, wherein the water-soluble inorganic salt is one or more selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, sodium sulfate and potassium sulfate.