JPH05184814A - Silicone anti-forming agent composition - Google Patents

Abstract

PURPOSE:To obtain the composition without the anti-forming performance being deteriorated even under violent agitation and in an alkaline condition and having a durable anti-forming property. CONSTITUTION:A mixture consisting of a dimethylpolysiloxane with both ends of the molecular chain closed by a trimethylsiloxyl group, a dimethylpolysiloxane with both ends of the molecular chain closed by a vinyldimethylsiloxyl group, a dimethylsiloxane-methylhydrogensiloxane copolymer and a trimethylsiloxyl silicate shown by ((CH3)3SiO1/2)x (SiO2)y (where (x) is 1 to 3 and (y) is 0.5 to 8) is heated at 50-200 deg.C to obtain the composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone antifoam composition, and more particularly to a silicone antifoam composition having excellent defoaming durability.

[0002]

2. Description of the Related Art Conventionally, silicone-based defoaming agents have a defoaming effect with a small amount of addition as compared with non-silicone-based defoaming agents such as alcohol-based, ester-based, mineral oil / vegetable oil, and synthetic oil, and chemical industry. It is widely used as a defoaming agent and a defoaming agent in the fields of food industry, petroleum industry, textile industry, plastic industry, cement industry, paint / adhesive industry, etc. However, even if this silicone defoamer is used in the same way as non-silicone defoamer, when it is used in an aeration tank of a wastewater treatment plant or in an agitated system such as jet dyeing or under alkaline conditions. Its defoaming performance decreases rapidly. Therefore, there has been a problem that it is necessary to intermittently add an antifoaming agent, which imposes a heavy burden on work and cost. Conventionally,
Many silicone defoamers have been proposed in order to solve such problems. For example, JP-A-574830
No. 7 discloses a defoaming agent composition comprising dimethylpolysiloxane, organohydrogenpolysiloxane, finely divided silica and a condensation reaction accelerating catalyst. However, with this antifoam composition, the viscosity was likely to change with time, and it was difficult to obtain stable quality. In addition, JP-A-61-1
No. 97007 discloses a defoaming agent comprising trimethylsiloxy group-endcapped dimethylpolysiloxane, vinyldimethylsiloxy group-endcapped dimethylpolysiloxane, hydrogendimethyldimethylsiloxy group-endcapped dimethylpolysiloxane, alkoxyalkylsilane, fine powder silica, and platinum-based catalyst. Agent compositions are disclosed. However, although this composition has excellent defoaming durability as compared with the non-reactive silicone defoaming agent composed of dimethylpolysiloxane and silica, it cannot be said to have been significantly improved, and it was not sufficiently satisfactory. Further, in JP-A-63-147507, trimethylsiloxy group end-capped dimethylpolysiloxane, silanol group end-capped dimethylpolysiloxane, polyethyl silicate, alkali metal catalyst, and surfactant are used.
A method of making a silicone antifoam composition comprising reacting at ~ 300 ° C is disclosed. However, this method requires a long reaction time, and not only the desired reaction but also a re-equilibrium reaction of dimethylpolysiloxane occurs, resulting in an extremely high viscosity and, in an extreme case, gelation.

[0003]

The present inventors have arrived at the present invention as a result of research for solving the above problems.
An object of the present invention is to provide a silicone defoaming composition having excellent defoaming durability without degrading the defoaming performance even under severe use conditions such as vigorous stirring and alkaline conditions.

[0004]

The present invention provides (A) 20 to 98 parts by weight of dimethylpolysiloxane having both ends of a molecular chain blocked with trimethylsiloxy groups and a viscosity at 25 ° C. of 5 to 10,000 centistokes. , (B) Both ends of the molecular chain are blocked with vinyldimethylsiloxy groups, and the viscosity at 25 ° C. is 100 to 50,000 centistokes dimethylpolysiloxane 0.1 to 40.0 parts by weight, (C) in one molecule In addition, 0.1 to 40.0 parts by weight of a dimethylsiloxane-methylhydrogen siloxane copolymer containing 3 or more silicon-bonded hydrogen atoms and having a viscosity of 20 to 10,000 centistokes at 25 ° C. D) formula _{[(CH 3) 3 SiO 1/2} ] x · (SiO 2) y ( where, x is 1 to 3, y is trimethylsiloxy silicate represented by a 0.5-8.) A mixture of 0.1 to 20.0 parts by weight, (E) 1.0 to 40.0 parts by weight of finely divided silica and (F) a catalytic amount of a platinum catalyst, and heat-treated at 50 to 200 ° C. Which relates to a silicone antifoam composition.

This will be explained by using the present invention (A).
The component dimethylpolysiloxane has the general formula

[Chemical 1] The viscosity at 25 ° C. is 5 to 50,000 centistokes, and preferably 100 to 10,000.
It is Centistokes. If the amount of this component used exceeds 98 parts by weight, the defoaming durability becomes poor, and if it is less than 20 parts by weight, the defoaming effect of the composition itself becomes difficult to be exerted, so it is in the range of 20 to 98 parts by weight. ..

The component (B) dimethylpolysiloxane used in the present invention has the general formula

[Chemical 2] The viscosity at 25 ° C. is 100 to 5,000 centistokes. This is because when the viscosity is less than 100 centistokes, when the crosslinked structure with the component (C) is formed, the crosslink density becomes too high and gel is easily generated.
When it exceeds 50,000 centistokes, gel formation does not occur, but the viscosity of this composition becomes extremely high and it is difficult to handle. Although the amount of this component used is determined in relation to the structure of component (C), if the amount used is less than 0.1 parts by weight, the desired defoaming persistence cannot be obtained, and conversely
If it exceeds 40.0 parts by weight, the viscosity of this composition becomes too high, which makes it difficult to use for the intended purpose.
˜40.0 parts by weight.

The dimethylsiloxane-methylhydrogensiloxane copolymer of component (C) used in the present invention has the following general formula (1) or (2):

[Chemical 3]

[Chemical 4] The viscosity at 25 ° C. is 20 to 10,000 centistokes. This is because when the viscosity is less than 20 centistokes, the crosslink density becomes too high when the crosslinked structure with the component (B) is formed, and a gel is easily generated.
This is because, if it exceeds 2,000 centistokes, gel formation does not occur, but the viscosity of the present composition becomes extremely high and it is difficult to handle. Although the amount used is determined in relation to the structure of the component (B), if the amount used is less than 0.1 parts by weight, the desired defoaming persistence cannot be obtained, and conversely 40.0.
If the amount is more than 1 part by weight, the viscosity of the present composition becomes too high or the composition becomes elastomeric and cannot be used for the intended purpose. Therefore, it is in the range of 0.1 to 40.0 parts by weight.

The component (D), trimethylsiloxysilicate, used in the present invention has the formula [(CH ₃ ) ₃ SiO _1/2 ] _x. (SiO ₂ ) _y (where x is 1 to 3 and y is 0.5 to 8)). This compound can be obtained by a method of cohydrolyzing tetraalkoxysilane and trimethylchlorosilane or a method of cohydrolyzing water glass and trimethylchlorosilane in a toluene / water mixed solution. The purpose of using trimethylsiloxysilicate within the scope of the present structure in the present invention is to use the (E) component in the matrix formed from the dimethylpolysiloxane of the (A) component and the reaction-crosslinked structure of the (B) and (C) components. It is used as an auxiliary agent for evenly dispersing a certain fine powder silica. When it is less than 0.1 part by weight, it is difficult to disperse the silica, and when it exceeds 20 parts by weight, the defoaming performance is deteriorated. There is. Regarding the values of X and Y, those outside the above range are too familiar with silica or, on the contrary, are easily dissolved in dimethylpolysiloxane, so that they cannot serve as a dispersion aid and the defoaming property of the final composition. , And its sustainability is compromised.

Examples of the fine powder silica of the component (E) used in the present invention include fumed silica, silica aerogel, precipitated silica, quartz powder, fused silica, and calcined silica. The specific surface area is 100 m in view of the defoaming effect. It is preferably ² / g or more. Examples of the platinum-based catalyst of the component (F) used in the present invention include chloroplatinic acid, alcohol compounds of chloroplatinic acid, complex salts of chloroplatinic acid with various olefins, vinyl siloxane, and the like. -CH = CH ₂ and (C)
It is used for the purpose of addition reaction of the component Si-H. The amount used is a catalytic amount and is usually 0.1 to 1,000 ppm with respect to the total amount of the components (A) to (E).

In the composition of the present invention, the above components (A) to (F) are weighed in predetermined amounts and uniformly mixed, and then the mixture is mixed at 50 to 50%.
It can be obtained by reacting by heating at 200 ° C. Here, the fine powdery silica of the component (E) may be blended in advance with the dimethylpolysiloxane of the component (A) and further dispersed by a homomixer. preferable. Further, the composition of the present invention tends to increase in viscosity when HSi groups remain in the composition after the heat treatment, and in such a case, an alkali catalyst is added to the composition after the heat treatment. In addition, it is preferable that the unreacted HSi group is eliminated by heating. As an alkaline catalyst that can be used, KOH,
Examples include NaOH and alkali metal alkoxides.

The silicone antifoam composition comprising the components (A) to (F) as described above can be obtained in the form of liquid, paste, sticky or powder at room temperature. The excellent foam sustaining effect of the composition is that the component (A) which is a defoaming component in the crosslinked structure produced by the components (B) and (C),
When the (E) component is incorporated and applied to the foaming system, this
It is considered that the components (A) and (E) are gradually released. The silicone antifoam composition of the present invention can be used in various forms depending on the type of foaming system. For example, when the foaming system is an oil system or a solvent system, it can be used by dispersing it in a liquid having a boiling point of 250 ° C. or less at normal pressure. Further, when the foaming system is an aqueous system, the composition can be used as an emulsion type by using a known surfactant and water. The surfactant used here is sorbitan fatty acid ester, glycerin fatty acid ester, propylene glycol fatty acid ester, polyoxyethylene fatty acid ester,
Examples include, but are not limited to, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene castor oil, ethylene oxide and propylene oxide adduct. Further, during emulsification, a protective colloid agent may be used, and this protective colloid agent has a thickening effect, stability improvement, dispersibility or binding property, and examples thereof include methyl cellulose, hydroxymethyl cellulose, hydroxy cellulose and carboxy. Examples thereof include, but are not limited to, vinyl cellulose, lactose, sodium alginate, sucrose fatty acid ester, tragacanth gum, xanthan gum, and polyvinyl alcohol. Further, the present composition may be used as a protective decolloid, a solid defoaming agent in combination with polyethylene glycol or an alkyl ether thereof, which is solid at room temperature, or a fatty acid ester, or a powder defoaming agent obtained by pulverizing it. You can

[0012]

EXAMPLES Examples of the present invention will be described below. In Examples and Comparative Examples, “part” means “part by weight”, the viscosity is a measured value at 25 ° C., and the viscosity unit “cs” is an abbreviation for centistokes. In addition, in the examples, the persistence test of the defoaming effect and the persistence test of the defoaming effect with the alkaline liquid were performed as follows. ○ Persistence test of antifoaming effect A polyoxyethylene (1
0) 100 ml of a 1.0 wt% aqueous solution of octyl phenyl ether [Octapol 100, manufactured by Sanyo Kasei Co., Ltd.] was sampled and used as a foaming liquid. Separately, 0.2 g of the silicone antifoam composition was accurately weighed in a 50 ml volumetric flask, and tertiary butanol was added thereto to make 50 ml. 0.5 ml of this solution was pipetted and added to the foaming solution. Then, set this on a shaker, shake for 10 seconds to force foaming, and then measure the time until the foam disappears,
The time was used as a standard for defoaming property. This operation was repeated, and the test was stopped when the time required for defoaming took 1 minute or more. The number of repetitions up to that time was used as a measure of the sustainability of the defoaming effect. ○ Persistence test of defoaming effect with alkaline solution pH to 225ml glass bottle with lid with sodium hydroxide
Sodium dodecylbenzene sulfonate prepared in 12 [Kao Corporation, Neoperex F-25]
100 ml of an aqueous solution of 0.25% by weight of was collected and used as a foaming liquid. Separately, 0.2 g of the silicone antifoam composition was accurately weighed in a 50 ml volumetric flask, and tertiary butanol was added thereto to make 50 ml. 0.5 ml of this solution was pipetted and added to the foaming solution. Then, set this on a shaker, shake for 10 seconds to force foaming,
The time until the bubbles disappeared was measured, and the time was used as a measure of the defoaming property. This operation was repeated, and the test was stopped when the time required for defoaming took 1 minute or more. The number of repetitions up to that point was used as a measure of defoaming durability.

[0013]

Example 1 3.8 g of dry silica [Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.] having a specific surface area of 300 m ² / g was added to 76 g of dimethylpolysiloxane blocked with trimethylsiloxy groups at both ends and having a viscosity of 1,000 cs, and after rough mixing. After sufficiently dispersing with a homomixer, this dispersion was transferred to a 500 cc 4-necked flask equipped with a condenser. Then average structural formula

[Chemical 5] And an average structural formula of α, ω-divinyldimethylpolysiloxane (viscosity: 372 cs) having

[Chemical 6] Dimethylsiloxane-methylhydrogensiloxane copolymer (viscosity: 2650cs) with 15.5g of formula _{[(CH 3) 3 SiO 1/2} ] 0.8 · and trimethylsiloxy silicate 1.0g represented by (SiO _{2) 1.0} Charge 0.3 cc of 2% isopropyl alcohol chloroplatinate solution,
The temperature was raised to 120 ° C., and the mixture was heated and reacted for 3 hours. Then
The reaction mixture was stripped under the conditions of 30 mmHg for 1 hour to remove low boiling point substances. Then, this was cooled to obtain a silicone antifoam composition having a viscosity of 30,360 cs. This silicone antifoam composition was subjected to a defoaming effect persistence test and an alkaline solution defoaming effect persistence test. The results are shown in Table 1 and Table 2, respectively.

[0014]

Example 2 3.8 g of dry silica [Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.] having a specific surface area of 300 m ² / g was added to 76 g of dimethylpolysiloxane blocked with trimethylsiloxy groups at both ends and having a viscosity of 1,000 cs, and after rough mixing. After sufficiently dispersing with a homomixer, this dispersion was transferred to a 500 cc 4-necked flask equipped with a condenser. Then average structural formula

[Chemical 7] And an average structural formula of α, ω-divinyldimethylpolysiloxane (viscosity: 372 cs) having

[Chemical 8] Dimethylsiloxane-methylhydrogensiloxane copolymer (viscosity: 2650cs) with 15.5g of formula _{[(CH 3) 3 SiO 1/2} ] 0.8 · and trimethylsiloxy silicate 1.0g represented by (SiO _{2) 1.0} Charge 0.3 cc of 2% isopropyl alcohol chloroplatinate solution,
The temperature was raised to 120 ° C., and the mixture was heated and reacted for 3 hours. Then
0.5 g of potassium hydroxide was added dropwise to this reaction mixture, and 1
The temperature was raised to 80 ° C. and kept at that temperature for 3 hours. Then 3
Stripping was carried out for 1 hour under the condition of 0 mmHg to remove low boiling point substances. Then cool it to a viscosity of 13,
000 cs of silicone antifoam composition was obtained. This silicone antifoam composition was subjected to a defoaming effect persistence test and an alkaline solution defoaming effect persistence test. The results are shown in Table 1 and Table 2, respectively.

[0015]

[Comparative Example 1] 5.0 g of dry silica [Nippsil LP, manufactured by Nippon Silica Co., Ltd.] was added to 74 g of dimethylpolysiloxane having a viscosity of 1000 cs, thoroughly mixed and sufficiently dispersed with a homomixer, and then the dispersion was cooled. Set the vessel 500
Transferred to a 4-neck flask of cc. Then the formula

[Chemical 9] 8.7 g of α, ω-divinyldimethylpolysiloxane (viscosity: 372 cs) represented by

[Chemical 10] Dimethyl polysiloxane represented by (viscosity: 2650c
s) 11.3 g and dimethyldimethoxysilane 1.0 g and 2
% Isopropyl chloroplatinate isopropyl alcohol solution 0.3 cc was charged, and the temperature was raised to 120.degree. Further, the temperature was maintained for 3 hours, then, stripping was carried out under the condition of 30 mmHg for 1 hour and then cooled to obtain an antifoam composition having a viscosity of 65,540 cs. This silicone antifoam composition was subjected to a defoaming effect persistence test and an alkaline solution defoaming effect persistence test. These results are also shown in Table 1 and Table 2, respectively.

[0016]

COMPARATIVE EXAMPLE 2 65 g of dimethylpolysiloxane (1,000 cs) and α, ω-dihydroxydimethylpolysiloxane (12,500 cs) were placed in a 500 cc 4-necked flask.
27 g of polyethyl silicate, 2.7 g of polyoxyethylene (10) / polyoxypropylene (40) copolymer were charged, and the mixture was heated and stirred until the temperature reached 130 ° C. At 130 ° C, potassium hydroxide 1.
5 g was added and stirred until it was uniformly dissolved. Next, 2.7 g of dry silica [Aerosil 200 manufactured by Nippon Aerosil Co., Ltd.] having a specific surface area of 200 m ² / g and 4.5 g of α, ω-dimethylpolysiloxane were added and stirred, and then homodispersed using a homomixer. Then, the mixture was reacted at 180 ° C. for 4 hours with stirring. 1 at 180 ° C
The pressure is reduced to 30 mmHg for an hour, cooled, and the viscosity becomes 8
A defoamer composition of 2,000 cs was obtained. This silicone antifoam composition was subjected to a defoaming effect persistence test and an alkaline solution defoaming effect persistence test. These results are also shown in Table 1 and Table 2, respectively.

[0017]

[Comparative Example 3] 100 g of dimethylpolysiloxane blocked with trimethylsiloxy groups at both ends (1000 cs) and dry-process hydrophobic silica [Aerosil R97 manufactured by Nippon Aerosil Co., Ltd.]
2] 6 g was stirred with a Hobart mixer for 30 minutes, transferred to a 500 cc beaker set in a heater, and stirred and mixed at 120 ° C. for 2 hours. Then, it cooled and the antifoam composition was obtained. This silicone antifoam composition was subjected to a defoaming effect persistence test and an alkaline solution defoaming effect persistence test. These results are also shown in Table 1 and Table 2, respectively.

[Table 1] Table 1 Defoaming property and defoaming durability

[Table 2] Table 2 Defoaming property and defoaming durability in alkaline system

[0018]

The silicone antifoam composition of the present invention comprises (A)
Since the mixture consisting of the components (F) is heat-treated at 50 to 200 ° C, the defoaming performance is not deteriorated even under severe conditions such as vigorous stirring or alkaline conditions, and the defoaming durability is excellent. It has characteristics.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location C08L 83/07 LRP 8319-4J (72) Inventor Hidetoshi Kondo 2-2 Chikusaigan, Ichihara-shi, Chiba Toray・ Dow Corning Silicone Co., Ltd.

Claims (1)

[Claims] 1. (A) 20 to 98 parts by weight of dimethylpolysiloxane having both ends of a molecular chain blocked with trimethylsiloxy groups and a viscosity at 25 ° C. of 5 to 10,000 centistokes, (B) both molecular chains A dimethylpolysiloxane having a terminal blocked with a vinyldimethylsiloxy group and a viscosity at 25 ° C. of 100 to 50,000 centistokes 0.1 to 4.0 parts by weight, (C) one molecule has a silicon atom-bonded hydrogen atom. A dimethylsiloxane / methylhydrogensiloxane copolymer having a viscosity of 20 to 10,000 centistokes at 25 ° C. in an amount of 0.1 to 40.0 parts by weight, (D) formula [(CH ₃ ) ₃ SiO _1/2 ] _x · (SiO ₂ ) _y (wherein x is 1 to 3 and y is 0.5 to 8) 0.1 to 20.0 parts by weight of trimethylsiloxysilicate A silicone defoamer composition obtained by heat-treating a mixture of (E) 1.0 to 40.0 parts by weight of finely divided silica and (F) a catalytic amount of a platinum catalyst at 50 to 200 ° C.