AQUEOUS GRAPHITE LUBRICANT COMPOSITIONS COMPRISING DISPERSANTS BACKGROUND

Field of the disclosure

The present disclosure is directed to lubricant compositions and more specifically to lubricant compositions comprising aqueous graphite dispersions.

Introduction

Hot forging is an industrial process where a metal workpiece is placed in a die and is deformed under pressure. The energy applied to the metal workpiece to plastically deform it is converted into heat. Repeated forging of workpieces and generation of heat raises the temperature of the of the die. A lubricant is used during forging at the interface between workpiece and die to reduce friction and to ensure the workpiece can be removed from the die. Good lubrication can improve the workpiece deformation, favor accurate filling of the die cavities, reduce tool wear at those points with free flow movement and high specific pressures, and reduce the forging force. Such features will lessen the stresses induced in the forging tool and prevent direct tool to workpiece contact, which contributes to longer tool life and betterquality control.

In recent years, the lubricant of choice for hot forging has been a water-based lubricant. Water based lubricants typically include water as a carrier and a lubricating particle such as graphite. Water based lubricants adhere the graphite to the die to form a solid coating on the die as the water evaporates. Water based lubricants are advantaged relative to oil-based lubricants as oil -based lubricants tend to run off the die surface and be squeezed out of the work piece/die interface under pressure. Water based lubricants are not without disadvantages though. Graphite dispersions in water are not stable and require continuous agitation otherwise flocculation and sedimentation occur. Flocculation and sedimentation occurring in lubricant holding tanks can result in an incorrect amount of graphite being applied to the die thereby decreasing the useful life of the die. Flocculation and sedimentation can also result in clogged pipes and spray nozzles intended to apply the lubricant to the forging die. Ideally, a graphite dispersion will resist sedimentation for extended periods of time. One measurement of waterbased lubricants examines if the lubricant can maintain 90% dispersion of the graphite after 30 days with the sediment remaining in a dispersible form (“Sedimentation Test”).

There have been attempts at decreasing the flocculation and sedimentation of waterbased graphite dispersions using dispersants. The theoretical explanation for the efficacy of different dispersants on graphite is not agreed upon. For example, United States Patent Application Publication number US20090305052A1 (“the ‘052 publication”) discloses stable aqueous graphite dispersion with high solids content. The ‘052 publication achieves a higher solid loading content in its aqueous graphite dispersion by utilizing a dispersant such as polyethylene glycols, polyelectrolytes, and salts of lignosulfonic acids. The ‘052 publication explains that the dispersants act as spacers which accumulate at the surface of graphite particles and prevent their steric approach. The ‘052 publication does not define a general molecular architecture or features that affect a compound’ s ability to function as a spacer.

In contrast to the ‘052 publication, Chinese patent application publication number CN111925697A (“the ‘697 publication”) provides a graphene and water-soluble polymer dispersant composite material that can be dispersed in water to form a membrane. The ‘697 publication explains that an enhanced aqueous graphene dispersion can be obtained by the inclusion of water-soluble polymer dispersant containing an aromatic ring structure and a hydrophilic group because the dispersant improves the compatibility between the surface inert graphene and the water-soluble polymer due to pi- pi interaction between the dispersant and the graphene. The ‘697 publication is silent with regard to how placement or quantity of aromatic structures affects the dispersion.

In view of the competing theories behind graphite dispersant efficacy, the unclear affect different molecular moieties have on dispersion performance, and the complexity of the intermolecular forces present in aqueous graphene dispersions, it would be surprising to discover a dispersant that is able to pass the Sedimentation Test.

SUMMARY OF THE DISCLOSURE

The present disclosure provides a dispersant that can pass the sedimentation test. The inventor of the present application has discovered that alkylphenol ether sulfate dispersants are able to pass the Sedimentation Test. Alkylphenol ether sulfate dispersants have the distinguishing feature, relative to other dispersants, of having an ether bridge extending between the alkylphenol and the sulfate moieties of the dispersant. Without being bound by theory, it is believed that the spacing between the phenyl and sulfate moieties of the dispersant provided by the ether bridge increases the interaction/wetting of the dispersant with the graphite and also the surrounding aqueous medium. Such a result is surprising as traditional dispersants comprising both phenyl and sulfate moieties, such as sodium dodecyl benzene sulfonate, comprise the phenyl and sulfate groups right next to one another. The present disclosure is particularly useful for the formation of lubricants utilizing graphite.

According to a first feature of the present disclosure, a lubricant composition comprises water, graphite, a thickener, and an alkylphenol ether sulfate dispersant.

According to a second feature of the present disclosure, the lubricant composition comprises 20 wt% to 60 wt% water based on a total weight of the lubricant composition.

According to a third feature of the present disclosure, the lubricant composition comprises 10 wt% to 60 wt% of graphite based on a total weight of the lubricant composition.

According to a fourth feature of the present disclosure, the graphite has a D90 particle diameter of from 0.5 pm to 5.0 pm.

According to a fifth feature of the present disclosure, the thickener is a polysaccharide.

According to a sixth feature of the present disclosure, the lubricant composition comprises 0.01 wt% to 1.0 wt% of the dispersant based on a total weight of the lubricant composition.

According to a seventh feature of the present disclosure, dispersant has Structure (I) wherein the variable R is a C5-C20 alkyl, the variable x is an average value of 1.0 to 7.0, and the variable Z+ is selected from the group consisting of Li, K, NH4 and Na.

According to an eighth feature of the present disclosure, the variable Z+ of Structure (I) is NH ₄ .

According to a ninth feature of the present disclosure, the variable x of Structure (I) has an average value of 4.2.

According to a tenth feature of the present disclosure, the variable R is a C9 alkyl.

DETAILED DESCRIPTION

As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

All ranges include endpoints unless otherwise stated.

As used herein, the term weight percent (“wt%”) designates the percentage by weight a component is of a total weight of the polymeric composition unless otherwise specified. As used herein, Chemical Abstract Services registration numbers (“CAS#”) refer to the unique numeric identifier as most recently assigned as of the priority date of this document to a chemical compound by the Chemical Abstracts Service.

Lubricant composition

The present disclosure is directed to a lubricant composition. The lubricant composition comprises water, graphite, a thickener, and an alkylated diphenyl oxide sulfonate dispersant. The lubricant composition may comprise 20 wt% to 60 wt% water based on a total weight of the lubricant composition. For example, the lubricant composition comprises 20 wt% or greater, or 25 wt% or greater, or 30 wt% or greater, or 35 wt% or greater, or 40 wt% or greater, or 45 wt% or greater, or 50 wt% or greater, or 55 wt% or greater, while at the same time, 60 wt% or less, or 55 wt% or less, or 50 wt% or less, or 45 wt% or less, or 40 wt% or less, or 35 wt% or less, or 30 wt% or less, or 25 wt% or less of water based on a total weight of the lubricant composition. The lubricant composition may comprise one or more other additives designed to alter a property of characteristic of the lubricant composition.

Thickener

The thickener is included in the lubricant composition to aid in the application and retention of the lubricant composition on surfaces. The thickener may comprise a polysaccharide such as agar, sodium alginate, rhamsam gum, locust bean gum, carrageenan, gum arabic, neem gum, gum chatti, caranna, galactomannan, gum tragacanth, karaya gum, guar gum, welan gum, beta-glucan, cellulose, chicle gum, kino gum, dammar gum, glucomannan, acacia gum, cassia gum, mastic gum, spruce gum, pysllium seed husks, gellan gum, xanthan gum, diutan gum, fenugreek gum, ghatti gum, methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, karaya gum, konjac gum, pectin and combinations thereof. Additionally or alternatively, the thickener may also include other viscosity modifying components such as polyethylene glycol, polyacrylic acid, polyethyleneimine, polyvinyl alcohol, polyacrylamides, carboxyvinyl polymers, poly(vinylpyrrolidinone) and copolymers, polyoxypropylene and combinations thereof.

The lubricant composition may comprise 0.1 wt% to 5.0 wt% thickener based on a total weight of the lubricant composition. For example, the lubricant composition may comprises 0.1 wt% or greater, or 0.2 wt% or greater, or 0.4 wt% or greater, or 0.6 wt% or greater, or 0.8 wt% or greater, or 1.0 wt% or greater, or 1.5 wt% or greater, or 2.0 wt% or greater, or 2.5 wt% or greater, or 3.0 wt% or greater, or 3.5 wt% or greater, or 4.0 wt% or greater, or 4.5 wt% or greater, while at the same time, 5.0 wt% or less, or 4.5 wt% or less, or 4.0 wt% or less, or 3.5 wt% or less, or 3.0 wt% or less, or 2.5 wt% or less, or 2.0 wt% or less, or 1.5 wt% or less, or 1.0 wt% or less, or 0.5 wt% or less of the thickener based on the total weight of the lubricant composition.

Graphite

The lubricant composition comprises graphite. The graphite may have spherical shape, a plate like shape, an oblong shape and/or an irregular shape. The particles of the graphite may have a D90 of from 0.5 microns (“pm”) to 10 pm. As used herein, the term “D90” means that 90% of the graphite particles have a diameter or longest length dimension smaller than the indicated value and 10% of the particles have a diameter or longest length dimension greater than the indicated value. The graphite may have a D90 particle size of 0.5 pm or greater, or 1.0 pm or greater, or 1.5 pm or greater, or 2.0 pm or greater, or 2.5 pm or greater, or 3.0 pm or greater, or 3.5 pm or greater, or 4.0 pm or greater, or 4.5 pm or greater, or 5.0 pm or greater, or 5.5 pm or greater, or 6.0 pm or greater, or 6.5 pm or greater, or 7.0 pm or greater, or 7.5 pm or greater, or 8.0 pm or greater, or 8.5 pm or greater, or 9.0 pm or greater, or 9.5 pm or greater, while at the same time, 10 pm or less, or 9.5 pm or less, or 9.0 pm or less, or 8.5 pm or less, or 8.0 pm or less, or 7.5 pm or less, or 7.0 pm or less, or 6.5 pm or less, or 6.0 pm or less, or 5.5 pm or less, or 5.0 pm or less, or 4.5 pm or less, or 4.0 pm or less, or 3.5 pm or less, or 3.0 pm or less, or 2.5 pm or less, or 2.0 pm or less, or 1.5 pm or less, or 1.0 pm or less. The D90 particle size of the graphite is determined using a Malvern Mastersizer™ laser diffraction particle size analyzer.

The lubricant composition comprises 10 wt% to 60 wt% of graphite based on a total weight of the lubricant composition. For example, the lubricant composition comprises 10 wt% or greater, or 15 wt% or greater, or 20 wt% or greater, or 25 wt% or greater, or 30 wt% or greater, or 35 wt% or greater, or 40 wt% or greater, or 45 wt% or greater, or 50 wt% or greater, or 55 wt% or greater, while at the same time, 60 wt% or less, or 55 wt% or less, or 50 wt% or less, or 45 wt% or less, or 40 wt% or less, or 35 wt% or less, or 30 wt% or less, or 25 wt% or less, or 20 wt% or less, or 15 wt% or less of graphite based on a total weight of the lubricant composition.

Dispersant

The lubricant composition comprises a dispersant that is an alkylphenol ether sulfate dispersant. The dispersant may have Structure (I):

Structure (I) wherein the variable R of structure (I) is a C5-C20 alkyl, the variable x is an average value of 1.0 to 7.0, and Z+ is selected from the group consisting of Li, K, NH4 and Na. R may be a C5 alkyl, or a Ce alkyl, or a C7 alkyl, or a Cs alkyl, or a C9 alkyl, or a C10 alkyl, or a Cn alkyl, or a C12 alkyl, or a C13 alkyl, or a C14 alkyl, or a C15 alkyl, or a Cle alkyl, or a C17 alkyl, or a Cis alkyl, or a C19 alkyl, or a C20 alkyl. R may be a linear or a branched alkyl. R may include one or more carbons that are secondary or tertiary.

The variable “x” of Structure (I) describes the average molar units of oxyethylene in Structure (I). As defined herein, the x value is tested and determined by Proton Nuclear Magnetic Resonance Spectroscopy and Carbon- 13 Nuclear Magnetic Resonance Spectroscopy, x may be a value of 1.0 or greater, or 1.2 or greater, or 1.4 or greater, or 1.6 or greater, or 1.8 or greater, or 2.0 or greater, or 2.2 or greater, or 2.4 or greater, or 2.6 or greater, or 2.8 or greater, or 3.0 or greater, or 3.2 or greater, or 3.4 or greater, or 3.6 or greater, or 3.8 or greater, or 4.0 or greater, or 4.2 or greater, or 4.4 or greater, or 4.6 or greater, or 4.8 or greater, or 5.0 or greater, or 5.2 or greater, or 5.4 or greater, or 5.6 or greater, or 5.8 or greater, or 6.0 or greater, or 6.2 or greater, or 6.4 or greater, or 6.6 or greater, or 6.8 or greater, while at the same time, 7.0 or less, or 6.8 or less, or 6.6 or less, or 6.4 or less, or 6.2 or less, or 6.0 or less, or 5.8 or less, or 5.6 or less, or 5.4 or less, or 5.2 or less, or 5.0 or less, or 4.8 or less, or 4.6 or less, or 4.4 or less, or 4.2 or less, or 4.0 or less, or 3.8 or less, or 3.6 or less, or 3.4 or less, or 3.2 or less, or 3.0 or less, or 2.8 or less, or 2.6 or less, or 2.4 or less, or 2.2 or less, or 2.0 or less, or 1.8 or less, or 1.6 or less, or 1.4 or less, or 1.2 or less.

The lubricant composition may comprise 0.1 wt% to 5.0 wt% dispersant based on a total weight of the lubricant composition. For example, the lubricant composition comprises 0.1 wt% or greater, or 0.2 wt% or greater, or 0.3 wt% or greater, or 0.4 wt% or greater, or 0.5 wt% or greater, or 0.6 wt% or greater, or 0.7 wt% or greater, or 0.8 wt% or greater, or 0.9 wt% or greater, or 1.0 wt% or greater, or 1.5 wt% or greater, or 2.0 wt% or greater, or 2.5 wt% or greater, or 3.0 wt% or greater, or 3.5 wt% or greater, or 4.0 wt% or greater, or 4.5 wt% or greater, while at the same time, 5.0 wt% or less, or 4.5 wt% or less, or 4.0 wt% or less, or 3.5 wt% or less, or 3.0 wt% or less, or 2.5 wt% or less, or 2.0 wt% or less, or 1.5 wt% or less, or 1.0 wt% or less, or 0.9 wt% or less, or 0.8 wt% or less, or 0.7 wt% or less, or 0.6 wt% or less, or 0.5 wt% or less, or 0.4 wt% or less, or 0.3 wt% or less, or 0.2 wt% or less of the dispersant based on the total weight of the lubricant composition.

Examples

Materials

The following materials were used in the examples.

Graphite is a powder of graphite particles having a D90 of 5.0 pm and is commercially available from Molygraph Lubricants, Mumbai, India.

Thickener is xanthan gum commercially available from Loba Chemie Mumbai, India.

Dispersant 1 is a solution of an alkylammonium salt of a polycarboxylic acid sold under the tradename ANTI-TERRA® and is commercially available from BYK-Chemie GmbH, Wesel, Germany.

Dispersant 2 is a 97 wt% actives powder having Structure (II), a CAS# of 9084-06-4 and is available from The Dow Chemical Company, Midland Michigan. Structure (II)

Dispersant 3 is pure sodium dodecyl sulfate having a CAS# of 151-21-3 and is available from commercially available from Loba Chemie Mumbai, India.

Dispersant 4 is an acrylic acid homopolymer that is end capped with poly(phthalaldehyde), has a weight average molecular weight of 2000 g/mol, has a 47-49 wt% solids content and is available from The Dow Chemical Company, Midland Michigan.

Dispersant 5 is an aqueous solution of water, Structure (I) and (2- hydroxy ethyl) ammonium nonylphenol ethoxylate sulfate. Dispersant 5 comprises 30 wt% to 54 wt% of Structure (I), 6 wt% to 30 wt% of the (2-hydroxyethyl)ammonium nonylphenol ethoxylate sulfate and 6 wt% to 24 wt% of water. Structure (I) of Dispersant 5 is as follows: the variable R is a C9 alkyl having a tertiary terminal carbon atom, the variable x has an average value of 4.2 and the variable Z+ is NH4. Dispersant 5 is available from The Dow Chemical

Company, Midland Michigan.

Water is distilled water. Sample Preparation

The examples were prepared by first combining the thickener, the dispersant, a portion of the water and then mixing the solution for 1 minute using a stirrer. Next, the graphite powder was added slowly to the solution and mixed until a paste was formed. Next, the graphite paste was diluted with the remaining water and mixed using an overhead stirrer to form a dispersion having the composition listed in the Table 1. The diluted paste was then added to a 100 milliliter (“ml”) volumetric flask and filled to the 100 ml line.

Test Method

Sedimentation Test: The Sedimentation Test determines what percentage of the dispersion remains dispersed after a predetermined period of time. The 100 ml volumetric flask is filled to the 100 ml mark with the example and the flask is left undisturbed for the indicated period of time. The amount of example remaining dispersed is measured by visually observing the phase separation interface between a clear or hazy water phase and a dispersed graphite phase. The phase separation is determined by examining at what ml demarcation the graphite dispersion phase and water phase is at after an identified period of time, dividing by the initial 100 ml and multiplying by 100. For example, if the interface of the graphite dispersion phase and the water phase is at 95 ml, then 95% of the dispersion resisted phase separation. An example is considered to have passed the Sedimentation Test if 90% of the example remains in the graphite dispersion phase after 720 hours (i.e., 30 days).

Results

Table 1 below provides the composition of each comparative example (“CE”) and each inventive example (“IE”) in weight percents of components while Table 2 provides the performance data of each IE and CE. The data of Table 2 provides the percent of the example remaining in the graphite dispersion phase. The entry “nm” indicates that a particular time interval was not measured. Table 1

Table 2

As can be seen from Tables 1 and 2, IE1 and IE2 drastically outperform CE1-CE10 in terms of producing a lubricant composition that passes the Sedimentation Test as indicated IE1 and IE2 all maintaining 90% graphite dispersion after 720 hours. CE1 and CE2 demonstrate a baseline for the stability that can be expected from an aqueous graphite dispersion when no dispersants are included. CE3 though CE10 demonstrate that the inclusion of certain dispersants can actually decrease the stability of graphite in water relative to dispersions having no dispersant as evidenced by lower percentages of retained graphite dispersion phases of CE3- CE10 relative to CE1 and CE2.

Unlike CE1-CE10, each of IE1 and IE2 is able to maintain 90% or greater of the graphite dispersion phase after 30 days of testing and therefore pass the Sedimentation Test. Such a result is surprising because every comparative example utilizing a dispersant demonstrated worse performance than CE1 and CE2 which did not include a dispersant. As explained above, it is believed that the spacing between the phenyl and sulfate moieties of the dispersant provided by the ether bridge of the dispersants used in IE1 and IE2 increase the dispersant’s ability to interact/bond with the surface of the graphite is enhanced relative to other dispersants.