JPH0411697A - Aqueous lubricant composition - Google Patents

Abstract

PURPOSE:To permit imparting a high viscosity to a water-based fluid even with a small amount of a thickener used, eliminate viscosity reduction in its use and prevent its rotting or the like by blending the fluid with a cross-linkable, highly water-absorbent polymer. CONSTITUTION:The title composition comprises a water-based fluid, 0.005-1wt.% crosslinkable, highly water-absorbent polymer which is fine particles of 150mum or less in size or a viscous material at room temperature, the crosslinking density thereof being 0.001-10mmol/g, the water absorption being 50 times or more, (e.g. an isobutylene/maleate polymer with 4mum of particle size, 2mmol/g of crosslinking density, and 300 times water absorption) and, if necessary, a rust preventive, wear-resistant additive, extreme-pressure agent, anticrossive, antiseptic, etc.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a water-based lubricant composition for use in flame-retardant high water content hydraulic oils, metal working oils such as rolling oils and cutting oils, and also as coolants. Regarding.

[Conventional technology]

Traditionally, water-based lubricant compositions have been used as flame-retardant hydraulic oils, metalworking oils, coolants, etc., but flame-retardant hydraulic oils contain 35% to 45% by weight of glycol in a water-based fluid. %
, water-glycol-based products containing 10% to 20% by weight of polyether thickener and a water content of about 35% to 50% are known, and recently, high molecular weight polyethers have been developed. A flame-retardant high water content hydraulic oil has been developed in which the water content is 95% by weight or more by adding 1% to 5% by weight.

However, the former requires a large amount of glycol or polyether to adjust the viscosity to a specified level, resulting in high costs, and the problem is that it is less dusty than mineral oil-based hydraulic fluids even in terms of wear resistance. In addition, during use, the viscosity of the latter decreases due to cleavage of polyether molecular chains, resulting in a decline in its functionality as a hydraulic fluid.Additionally, a large amount of polyether is used to adjust the viscosity to a specified level. There are problems with cost and poor performance compared to mineral oil-based hydraulic fluids.

Similarly, when it comes to water-based metalworking oils, conventional metalworking oils use surfactants as their main ingredient to make base oils such as mineral oils and synthetic oils water-soluble. Problems have been pointed out, such as the fact that it is easily putrefied and post-processing of the used liquid is difficult.

[Problem to be solved by the invention]

The present invention provides a flame-retardant, highly water-containing hydraulic fluid that can provide high viscosity even with a small amount of thickener used, has almost no decrease in viscosity during use, and has excellent abrasion resistance. An object of the present invention is to provide a water-based lubricant composition such as metal working oil that does not have such problems.

Means for Solving Problem C] The water-based lubricant composition of the present invention is characterized in that a crosslinked superabsorbent polymer is added to a water-based fluid.

Known cross-linked superabsorbent polymers can be used, such as polyacrylate-based, isobutylene/maleate-based, starch/polyacrylate-based, and polyvinyl alcohol/polyacrylate-based polymers. A crosslinked superabsorbent polymer having intramolecular crosslinking such as polyacrylamide, hydrophilic acrylic polymer, polyvinyl alcohol, or polyether is used.

The crosslinking density of such a crosslinked superabsorbent polymer is 0. OO] mmol/g ~I Q+n+n
ol/g N desirably 0,05 mmol/
It is best to use one with a crosslinking density of 0.g to 5 mmol/g, and a crosslinking density of 0.5 mmol/g. If it is less than 0.001 mmol/g, the molecular shape of the polymer becomes close to linear, which is undesirable because the viscosity decreases due to shearing etc. during use as a hydraulic oil or metal processing oil, and if it exceeds IQ mmol/g, the water absorption property decreases. This is not preferable because the viscosity increasing effect is small and it is easy to separate from water.

Such a crosslinked superabsorbent polymer is in the form of fine particles or a viscous substance at room temperature, and in the present invention, either form can be used. However, in the case of fine particles, the particle size is preferably 150 μm or less, and preferably is 0.1 μm to 70 μm
By using particles with a finer particle shape, high shear resistance and abrasion resistance can be achieved.
If it exceeds 50 μm, it is not preferable because it easily aggregates and separates from water.

In addition, the water absorption rate of the crosslinked superabsorbent polymer is 50
It is better to use a product with a water absorption rate of 50 times or more, and a product with a water absorption rate of less than 50 times can be added to water and used as a lubricant, but the water absorption will separate,
The dispersibility required for hydraulic fluids and metal working fluids is not good.

These cross-linked super absorbent polymers have a water content of 0.0
Adding only 0.05% to 1% by weight is enough to function as a hydraulic oil and a metal working oil. If the amount added is less than 0.005% by weight, there will be no addition effect;
Addition amounts exceeding % by weight are meaningless in relation to water absorption.

When the aqueous lubricant composition of the present invention is used as a hydraulic oil, various commonly used additives such as rust preventives, wear-resistant additives, extreme pressure agents, corrosion inhibitors, preservatives, etc. may be added as necessary. can be used.

As rust inhibitors, organic carboxylic acids, carboxylates, sulfonates, esters (alcohols), amines, etc.
As inorganic substances, phosphates, nitrites, borates, etc. can be used.

Examples of wear-resistant additives or extreme pressure additives include chlorine-based, sulfur-based, phosphorus-based, and organometallic compounds.

Nitrogen-based, sulfur/nitrogen-based, and metal salt-based anticorrosive agents are used, and silicone and higher alcohol-based antifoaming agents are used. Colorants and fragrances may also be added.

Examples of preservatives include phenolics (phenylphenol, tetrachlorophenol, p-chloro-m-xylenol, etc.), formaldehyde donors (hexahydrotriazine, etc.), and mixtures of tribromosalicylanilide and dibromosalicylanilide.

In addition to the above, mineral oil, metal processing oil such as cutting oil and rolling oil is used.
Base oils such as synthetic oils (polyolefin oils, ester oils), oils and fats, and anionic or cationic surfactants may be added.

[Action and effect of invention]

Linear polymers such as polyethers, which are currently used in high water content hydraulic fluids, have a small molecular weight and show a certain improvement in lubricity as the viscosity increases, but when the molecular weight is large, lubricity is not improved,
Therefore, when used as a thickener, it is necessary to use a relatively large amount of one with a low molecular weight, and when used for a long time, shearing of the linear polymer occurs, resulting in a decrease in viscosity.

On the other hand, the crosslinked superabsorbent polymer in the present invention is generally known as a polymeric water absorbing agent.
It has been discovered that it has high viscosity, high shear stability, and wear resistance, and can be made suitable as a lubricant composition for hydraulic oils, metal working oils, and the like.

The detailed reason for this is unknown, but the structure of cross-linked superabsorbent polymers has a three-dimensional network structure, and upon contact with water, hydrophilicity develops due to hydroxyl groups, carboxylic acid groups, etc. in the structure. Water is absorbed into the network structure by the action of water and osmotic pressure, but by swelling this cross-linked super absorbent polymer with water and making it into a water-based lubricant composition, it can be used as a hydraulic oil or metal working oil. It was discovered that a crosslinked superabsorbent polymer in a water-absorbed state exhibits excellent dispersion stability and thickening properties, and the viscosity can be easily adjusted. In addition, even when water is absorbed, the crosslinked superabsorbent polymer has strong flexibility due to its network structure, and does not break like linear polymers on friction surfaces such as pistons and cutting surfaces, and has high shear stability and resistance. It is thought to exhibit anti-wear properties and maintain lubricity over a long period of time.

The present invention will be explained below with reference to Examples.

[Example 1] Isobutylene/
Maleate-based polymer (particle size 4 μm, degree of crosslinking 2 mm)
ol/g s water absorption rate 300 times), 0.1% by weight, 0.
A water-based lubricant composition of the present invention was prepared by containing 5% by weight of each.

The viscosity of each sample composition and water was measured according to JIS K2283 at varying temperatures.

The results are shown below.

(Margin below) The unit of viscosity is mm''/s.

It can be seen that the viscosity of the water-based lubricant composition increases depending on the amount of the crosslinked superabsorbent polymer added, and it functions as a thickener.

Claims (3)

[Claims] (1) A water-based lubricant composition characterized in that a crosslinked superabsorbent polymer is added to a water-based fluid. (2) The aqueous lubricant composition according to claim 1, wherein the crosslinked superabsorbent polymer has a water absorption rate of 50 times or more. (3) A water-based lubricant composition characterized in that 0.005% to 1% by weight of the crosslinked superabsorbent polymer is added to a water-based fluid.