JP3258299B2 - Method for recovering polyalkylene glycol from water-soluble hydraulic fluid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a water-soluble hydraulic fluid widely used as a flame-retardant hydraulic fluid, which contains water, polyalkylene glycol, and optionally glycols. The present invention relates to a method for treating a liquid.

[0002]

2. Description of the Related Art Flame-retardant hydraulic fluids are widely used as pressure transmission media for hydraulic systems near fire, such as steel and die cast. Among the flame-retardant hydraulic fluids,
Water-soluble hydraulic fluids containing water, glycols and polyalkylene glycols as main components satisfy a good balance of excellent flame retardancy and hydraulic oil performance. , A water-soluble hydraulic fluid is used.

[0003] The composition of a water-soluble hydraulic fluid is generally 30 to 70% of water as a flame retardant, 10 to 50% of polyalkylene glycol as a thickener, and 0 to 10% as glycol as a pour point depressant. -50%, and 0-10% of additives such as a lubricant, a lubricating rust inhibitor, an antifoaming agent, and an anticorrosive. The hydraulic fluid is
During the period of use, it receives shear from the hydraulic equipment, heat, and oxidation due to contact with the outside air, etc., gradually deteriorating the components, and usually its performance will be reduced by use for about 3 to 5 years. It cannot be maintained.

[0004]

With respect to general mineral oil-based hydraulic fluids, used fluids that have deteriorated and cannot maintain their performance as hydraulic fluids can be reused as boiler fuels. However, the water-soluble hydraulic fluid contains a large amount of water, so if you want to reuse the liquid after use as fuel, you need special incineration equipment or pre-treatment such as evaporation of water. However, active reuse has not been attempted due to economics. The working fluid also contains dust and evaporation of moisture and volatile anticorrosives as vaporizable substances.However, since these can be filtered during use, and the amount damaged by evaporation can be additionally adjusted, It has nothing to do with intrinsic degradation. However, in all cases of heat deterioration, oxidation deterioration, and shear deterioration, the compounding raw materials undergo chemical changes.

[0005] Polyalkylene glycols generally used as thickeners are mainly subjected to oxidative deterioration and shear deterioration, polymer chains are sheared, and a relatively low molecular weight modification having a polar functional group (ionic) at a shear site. Things. Fatty acids and fatty acid salts generally used as lubricating rust preventive agents are mainly subject to thermal deterioration and oxidative deterioration,
The carboxylic acid moiety is modified, and an esterified product with an alcohol such as a glycol or a modified polyalkylene glycol whose molecular weight is reduced due to deterioration, and an amidated product with an amine are generated.

[0006] As a result of the above deterioration, the working fluid cannot maintain an appropriate viscosity due to shearing of the polyalkylene glycol, or a decrease in lubricity due to a fatty acid modified product.
Problems such as a reduction in rust prevention, a reduction in anticorrosion ability against non-ferrous metals, a reduction in compatibility with sealing materials, and a deterioration in defoaming properties occur. An object of the present invention is to easily and economically recover a polyalkylene glycol contained in a used liquid as a working liquid raw material in order to effectively use a used liquid of a water-soluble hydraulic liquid that has been treated as waste. It is to provide a method.

[0007]

According to the present invention, a water-soluble flame-retardant hydraulic fluid containing a polyalkylene glycol is subjected to coagulation treatment after use to remove impurities capable of coagulation treatment. An aqueous solution containing a polyalkylene glycol is subjected to a water-washing treatment utilizing a cloud point phenomenon, thereby separating into a polyalkylene glycol layer and an aqueous layer, and recovering the polyalkylene glycol layer. The present invention relates to a method for recovering a polyalkylene glycol.

In the present invention, as a result of intensive studies on the deterioration mechanism of the water-soluble hydraulic fluid, the relationship between the deterioration products and the performance of the hydraulic fluid, and the method of removing the deterioration products, the water-soluble hydraulic fluid is subjected to a coagulation treatment after use. Thereafter, a method for obtaining polyalkylene glycol having inexpensive and reusable quality by performing water washing utilizing the cloud point phenomenon was established. The present invention can be applied not only to a hydraulic fluid containing glycol but also to a hydraulic fluid containing substantially no glycol.

[0009] Here, polyalkylene glycol is a raw material used as a thickener for maintaining an appropriate viscosity of the working fluid, and polyalkylene glycol does not significantly affect other performance items. Therefore, the polyalkylene glycol can be reused as a thickener by removing other active ingredients such as fatty acids, amines, glycols, and the like, and denatured substances due to their deterioration.

More specifically, the polyalkylene glycol is a copolymer of an alkylene oxide such as ethylene oxide, propylene oxide, and butylene oxide, and is a copolymer of ethylene oxide and propylene oxide. Those having a copolymerization ratio of about 75:25 to 50:50 are particularly preferred.

On the other hand, fatty acids, modified fatty acid products and polyalkylene glycols whose molecular weight has been reduced by shearing have been mostly converted into substances having polar functional groups (ionic). Aggregation treatment using an aggregating agent can be performed. Since the coagulation treatment is ineffective for polyalkylene glycol, it can be selectively removed.

Examples of the coagulating agent include inorganic coagulants such as polyaluminum chloride (PAC), aluminum sulfate (sulfuric acid band), ferrous sulfate and ferric chloride (iron salt), polyacrylamide, and sodium polyacrylate. ,
Polymer flocculants such as polyethyleneimine lead sulfate can be used. Examples of the aggregation treatment method include a sedimentation separation method and a pressure flotation method.

Further, the fatty acid and the modified product of the fatty acid have relatively low solubility in water and rather have a high affinity for the polyalkylene glycol. Therefore, they remain in the polyalkylene glycol in the washing treatment described later. Among the modified polyalkylene glycols, most of the components whose molecular weight was maintained to such an extent that they could not be effectively removed by the coagulation treatment, the influence of the hydration power of the terminal polar group was stronger than that of a new product. The water can be efficiently removed by the water washing described in (1).

In addition, water-soluble impurities, such as glycols and amines, and inorganic salts introduced into the system by the coagulation treatment, which are difficult to remove by the coagulation treatment, are efficiently removed by the following water washing. Is possible. Examples of the glycols include ethylene glycol, propylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol, tripropylene glycol, and glycol ethers having a molecular weight of about 400 or less.

Examples of the amines include ethanolamines such as monoethanolamine, diethanolamine and triethanolamine; alkylamines such as monomethylamine, dimethylamine, trimethylamine and cyclohexylamine; polyamines such as ethylenediamine and diethylenetriamine; and morpholine. And the like.

The polyalkylene glycol is soluble in water up to a certain temperature, but becomes insoluble and precipitates at a temperature higher than the certain temperature. This phenomenon is called a cloud point phenomenon, and the temperature at which the cloud point phenomenon is observed is called a cloud point. That is, the polyalkylene glycol is soluble in water below the cloud point due to relatively weak hydration due to the ether bond in the main chain and strong hydration due to the polar functional group at the terminal. The thermal motion of a certain water molecule becomes active, so that water cannot be bound at the ether bond portion of the main chain, and the propylene oxide becomes insoluble as a result of relatively increased hydrophobicity.

That is, the cloud point is determined by the balance between the hydration power of an ether bond contained in the main chain and the strong hydration power of a terminal functional group, and increases as the hydration power of the terminal functional group increases. The water-washing treatment utilizing the cloud point phenomenon means that, by heating a polyalkylene glycol aqueous solution having a cloud point or lower to a temperature higher than the cloud point, the aqueous layer is separated into an aqueous layer and a polyalkylene glycol layer, and the aqueous layer is removed. This is a method for selectively removing water-soluble impurities present in polyalkylene glycol. By repeating this washing, water-soluble components other than the polyalkylene glycol can be removed, and the polyalkylene glycol reduced in molecular weight by shearing can be removed to a level that does not affect the thickening effect. This washing is about 2 hours.
It is preferable to repeat it up to about 6 times, preferably about 4 to 5 times. Further, since the polyalkylene glycol layer obtained by this water washing is premised on reuse as a water-soluble hydraulic fluid raw material, even if it contains water as a washing liquid or a small impurity that cannot be completely removed, these are not affected. This is not a problem because it is originally a working fluid raw material.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 40 parts by weight of water, 42.5 parts by weight of glycol, 15 parts by weight of polyalkylene glycol (copolymer of ethylene oxide / propylene oxide, cloud point 72 ° C.), 1 part by weight of fatty acid, 1.4 amines 1 part by weight of a water-soluble hydraulic fluid containing 0.1 part by weight of other additives such as an anticorrosive and an antifoaming agent.
What was actually circulated for 500 hours using a hydraulic pump was used as a post-use liquid. The kinematic viscosity at 40 ° C. of the working fluid immediately after adjustment and the working fluid after circulating use is 50 mm, respectively.
² / sec and 39 mm ² / sec. The kinematic viscosity of the working fluid after circulating use is lower than the kinematic viscosity immediately after adjustment, and a part of the polyalkylene glycol is subjected to shear,
It is clear that the thickening is reduced. The following treatment was performed using the liquid after circulating use.

First, as a pretreatment for the coagulation treatment, 1N hydrochloric acid was added to the test solution to neutralize the pH of the test solution to around neutrality. Next, 3.0 (weight ratio) of emulsion breaker # 20 (manufactured by Matsumura Petroleum Laboratories: flocculating agent) was added to the test liquid 100 as a flocculating agent, and the mixture was sufficiently stirred.
Further, for pH adjustment, an aqueous solution of potassium hydroxide was added until the pH became nearly neutral with a test paper. As soon as the pH was near neutrality, the stirring speed was reduced and floc growth was promoted by slow stirring for 5 minutes.

After the floc had grown, the filtrate and the filtrate were separated by filtration, the filter was discarded, and the filtrate was subjected to the next water washing treatment. The filtrate was heated to 90 ° C. and allowed to stand for 1 hour. The polyalkylene glycol layer was recovered while visually confirming the interface between the polyalkylene glycol layer precipitated and settled by the cloud point phenomenon and the aqueous layer. Discarded. Subsequently, approximately the same amount of ion-exchanged water as the discarded aqueous layer was added to the polyalkylene glycol layer, and the mixture was stirred until it became sufficiently uniform.
After that, heating, standing (cloud point separation), water layer disposal, water addition,
The operations of stirring, heating, and the like are performed using 10 μS (micro Siemens) in which the electric conductivity of the discarded aqueous layer is almost the same as that of ion-exchanged water.
Repeated until: (A total of four times was required.)

The resulting polyalkylene glycol layer is
Although the working fluid raw material can be recycled even in a state containing water, the water was evaporated to obtain a recovered polyalkylene glycol in order to compare the difference between the recovered polyalkylene glycol and a new product. The recovered polyalkylene glycol had a purity of 99.4% by GPC analysis. The kinematic viscosity at 40 ° C. of the working fluid prepared using the recovered polyalkylene glycol is 48 mm ² / sec, and its performance as a thickener is not inferior to that of a new polyalkylene glycol (PAG). It was clear.

Further, in practice, the working fluid is not prepared using only the recovered polyalkylene glycol, and when the working fluid is actually prepared, the recovered polyalkylene glycol is used in combination with a new polyalkylene glycol. Therefore, the difference from the new PAG working fluid is further reduced. In the present invention, the type and amount of the pH adjusting agent and the coagulating agent, the pH, the method for measuring the electrical conductivity, the filtration method, and whether the washing process is a batch system or a continuous system are not limited. It is not something to be done.

Example 2 57.5 parts by weight of water, polyalkylene glycol (cloud point 7
(3 ° C) 40 hours by weight of fatty acid, 1 part by weight of fatty acid, 1.4 parts by weight of amines, 0.1 part by weight of other additives such as anticorrosive, defoamer, etc. Was used as a liquid after use. New hydraulic fluid, each of 40 ° C. kinematic viscosity of the hydraulic fluid after circulation using 48 mm ² / sec, was 42mm ² / sec. The same treatment as in Example 1 was performed using the working fluid after the circulation use to obtain a recovered polyalkylene glycol. 4 prepared using recovered polyalkylene glycol
The kinematic viscosity at 0 ° C. was 47 mm ² / sec. Thus, it was shown that the polyalkylene glycol recovered from the glycol-free water-soluble hydraulic fluid is not inferior in performance as a thickener as compared with a new product.

[0025]

According to the present invention, the polyalkylene glycol contained in the used liquid is used as the working liquid raw material in order to effectively use the used liquid of the water-soluble hydraulic liquid which has been treated as waste. It is possible to simply and economically recover. The polyalkylene glycol recovered according to the recovery method of the present invention does not pose any problem in performance even if it is reused as a working fluid raw material.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08J 11/06 C08J 11/06 C10M 107/34 C10M 107/34 173/02 173/02 // C10N 40:08 C10N 40:08 (72) Inventor Tamio Akada 10-33, Ashihara-cho, Nishinomiya-shi, Hyogo Pref. Matsumura Oil Research Laboratory Co., Ltd. (56) References JP-A-50-119099 (JP, A) JP-A-60-248286 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) C10M 175/00-175/06 C10M 107/34 C10M 173/00-173/02 B01D 17/02 C02F 1/52 C02F 1/58 C08G 65 / 00-65/48 C08J 11/06 C10N 40:08

Claims (2)

(57) [Claims] 1. An aqueous solution containing a polyalkylene glycol obtained by subjecting a water-soluble flame-retardant working fluid containing a polyalkylene glycol to a coagulation treatment to remove impurities capable of coagulation treatment after use. Is subjected to a water-washing treatment utilizing a cloud point phenomenon, whereby a polyalkylene glycol layer and an aqueous layer are separated, and the polyalkylene glycol layer is recovered. . 2. The method according to claim 1, wherein the washing process utilizing the cloud point phenomenon is repeated a plurality of times.