JP2000237504A - Defoaming agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defoaming agent which is safe and excellent in dispersibility to water and superior in foam breaking effect and defoaming effect with respect to a water soluble polymer, especially PVA and partially saponified PVA. SOLUTION: This defoaming agent contains a compound expressed by the formula; HO-(BO)l-(AO)m-(BO)n-H. In the formula, AO is a 2-3C oxyalkylene group containing >=20 wt.% oxyethylene group, BO is an oxybutylene group, m=8-210, and l+n=4-20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous solution of a water-soluble polymer, especially polyvinyl alcohol (hereinafter referred to as PVA).
And partially saponified polyvinyl alcohol (hereinafter partially saponified PVA)
The present invention relates to an antifoaming agent having both excellent foam breaking and foam suppressing properties with respect to an aqueous solution of the present invention and a property of being uniformly dispersed in an aqueous solution.

[0002]

2. Description of the Related Art Water-soluble synthetic polymers having hydrophilic substituents such as PVA are widely used in textile industry, dyeing industry, paper pulp industry, paint industry, synthetic resin emulsion, latex industry, and the like. . However, it is known that when these polymers are used as an aqueous solution, foaming occurs when stirring or aeration is performed, and the foams have high stability. Therefore, bubbles generated when the water-soluble polymer is dissolved or when the aqueous solution is used are difficult to disappear, and there is a problem in use such as a work obstacle. In order to solve the problem, it is known that an antifoaming agent can be added when the water-soluble polymer is dissolved, or that a water-soluble polymer to which an antifoaming agent has been added in advance can be used.

[0003] Defoaming agents known so far, for example, defoaming of polyethers comprising oxyethylene groups and oxypropylene groups described in JP-B-61-7847 and JP-B-6-79642. The agent does not have sufficient foam-suppressing properties to suppress the generation of bubbles. Also, Japanese Patent Application Laid-Open No. 7-1852
The antifoaming agent containing silicone disclosed in Japanese Patent Publication No. 12 and the like has a high foam-breaking property for eliminating bubbles and has a high effect, but is expensive, and repelling is observed when an aqueous solution is dried to form a film. There are problems such as. Furthermore, an antifoaming agent obtained by emulsifying a water-insoluble fatty acid ester, mineral oil, or the like with a surfactant tends to generate scum, and when left for a long period of time, separates in an aqueous solution and contaminates the equipment used. However, there is a problem that sufficient foam suppressing property and foam breaking property cannot be obtained.

[0004]

SUMMARY OF THE INVENTION In order to solve the problems in the prior art, the present invention is safe, has good dispersibility in water, and is suitable for water-soluble polymers, particularly PVA and partially saponified PVA. It is intended to provide an antifoaming agent excellent in foam breaking and foam suppressing effects.

[0005]

That is, the present invention is an antifoaming agent characterized by containing a compound represented by the following formula (1). _{HO- (BO) l - (AO} ) m - (BO) n -H (1) [ wherein AO represents an oxyalkylene group having a carbon number of 2-3, including an oxyethylene group 20 wt% or more, BO is oxybutylene group , M = 8 to 210, and l + n = 4 to 20. ]

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The oxyalkylene group having 2 to 3 carbon atoms constituting the antifoaming agent of the present invention is an oxyethylene group or an oxypropylene group. The proportion of the oxyethylene group in the oxyalkylene group having 2 to 3 carbon atoms is preferably 20% by weight, more preferably 40% by weight or more. If the content is less than 20% by weight, it is difficult to disperse in water, and scum may be generated during use and the device may be soiled.

When the oxyalkylene group having 2 to 3 carbon atoms is composed of an oxyethylene group and an oxypropylene group,
The oxyethylene group and the oxypropylene group may be added in a block shape or may be added in a random shape. In the case where the antifoaming agent is dispersed in water in advance and added, it is more preferable that the antifoaming agent is added in random form, because it is rapidly dispersed in water.

M, which is the average number of moles of the oxyalkylene group added, is from 8 to 210, preferably from 16 to 150;
If it is less than water-soluble in a wide temperature range, the effect as an antifoaming agent is small, and if it exceeds 210, the viscosity becomes high,
Production becomes very difficult. When the oxyethylene group and the oxypropylene group are added in the form of a block and when only the oxyethylene group is used, the average number of moles of the oxyethylene group that is an essential component is preferably continuously 45, more preferably Desirably does not exceed 34 continuously. When it is composed of only oxyethylene groups, if the number of moles of added oxyethylene groups exceeds 45, the freezing point is lowered, and it is easy to solidify at room temperature or in winter, so that handling may be difficult.

The sum of the average number of moles of oxybutylene (BO) group added, l + n, is 4 to 20, preferably 6 to 16.
It is. If l + n is less than 4, the foaming resistance is poor, and if it exceeds 20, a gel is easily formed in water, and it is difficult to dilute and use in water.

The compound of the formula (1) constituting the antifoaming agent of the present invention can be obtained by a known method. For example, it can be obtained by adding an oxyalkylene group to a dihydric alcohol. Examples of the starting dihydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol and the like, and any of them may be used. In producing the antifoaming agent of the present invention, the addition temperature of the oxyalkylene group is preferably from 80 to 160C. The catalyst to be used is an alkaline substance, an alkali metal hydroxide, a carbonate or an organic metal which is usually used for an addition reaction of an oxyalkylene group, such as sodium methylate, potassium methylate, sodium hydroxide, and hydroxide. Examples include potassium, cesium hydroxide, sodium carbonate, potassium carbonate, sodium acetate and the like. These catalysts are used in an amount of about 0.01 to 0.5% by weight based on the product. 10kg more than reacting at normal pressure
The reaction is preferably performed under a pressure of f / cm ² (gauge pressure) or less.

The defoaming agent of the present invention may be used for various water-soluble polymers, but when used for PVA or partially saponified PVA, etc., exhibits a very good defoaming effect over a wide temperature range. I do. The antifoaming agent of the present invention may be directly added to an aqueous solution of a water-soluble polymer, or may be diluted with water or an organic solvent and emulsified, dispersed or dissolved for use. May be added when dissolving in water, or may be added in advance to the water-soluble polymer used. The amount of the antifoaming agent of the present invention is 0.0001 to 0.1% by weight based on the aqueous solution, or 0.01 to 0.1% by weight based on the water-soluble polymer before dissolution.
2% by weight is preferred. Further, the antifoaming agent of the present invention is other antifoaming agents as long as the effect is not impaired, such as mineral oil, vegetable oil, aliphatic alcohol, fatty acid, etc., higher alcohol,
It may be used in combination with a nonionic surfactant comprising an oxyalkylene adduct with a polyhydric alcohol, fatty acid, alkylphenol or the like.

[0012]

The present invention will be specifically described below with reference to examples.
Table 1 shows the antifoaming agents used in this example. Example 1 The following evaluation was performed using the compound shown in Sample a of Table 1. Table 2 shows the results.

Evaluation of Dispersibility in Water A sample was placed in a 110 ml sample bottle with a lid.
4 g and 68.6 g of ion-exchanged water were charged to prepare a 2% by weight aqueous solution of the sample. After the temperature of the solution was 25 ° C., the solution was shaken 30 times by hand, and the state at that time was visually observed. Table 2 shows the results.

Evaluation of defoaming properties (foam suppressing properties, foam breaking properties) About 1 kg of ion-exchanged water was placed in a 3 liter four-necked flask equipped with a stirrer and a thermometer, and partially saponified P was stirred.
116.0 g of VA (PVA217 manufactured by Kuraray Co., Ltd.) is charged. The system was heated to 95 ° C. with stirring, and stirring was continued for 30 minutes to dissolve partially saponified PVA. Partially saponified PV
After all A is dissolved, the total amount of the aqueous solution is 2.9 kg,
By stirring for 60 minutes, 4% by weight partially saponified PVA
An aqueous solution was prepared. This aqueous solution was used as a foaming liquid in the subsequent tests.

4-part saponified PVA preheated to a constant temperature in a graduated cylinder with a scale of up to 1 liter
200 ml of an aqueous solution was charged, and 0.8 ml of an antifoaming agent diluted with ion-exchanged water to 2% by weight was added. Furthermore, after setting the air supply pipe with a diffuser stone, it left still for 30 minutes in the thermostat adjusted to 40 degreeC. After confirming that the temperature of the aqueous solution under test became the same
400ml / min via diffuser stone
In the air. The measurement of the bubble height was performed at intervals of 15 seconds, and the difference in performance between the used antifoaming agents was evaluated by the amount of the bubble. In addition, an observation was made on the manner in which bubbles were reduced after the ventilation was stopped, and the foam breaking property was evaluated.

[0016]

[Table 1]

[0017]

[Table 2]

Examples 2 to 5 and Comparative Examples 1 to 6 The samples shown in Table 1 were evaluated in the same manner as in Example 1. In addition, evaluation was also performed on blanks to which no antifoaming agent was added.

[0019]

The antifoaming agent of the present invention has good dispersibility in water, and has excellent foam breaking and foam suppressing properties with respect to a water-soluble polymer aqueous solution, particularly an aqueous solution of PVA or partially saponified PVA. .

Claims (1)

[Claims] 1. An antifoaming agent comprising a compound represented by the following formula (1). _{HO- (BO) l - (AO} ) m - (BO) n -H (1) [ wherein AO represents an oxyalkylene group having a carbon number of 2-3, including an oxyethylene group 20 wt% or more, BO is oxybutylene group , M = 8 to 210, and l + n = 4 to 20. ]