CA1205793A - Conveyor track lubricant composition employing phosphate esters and method of using same - Google Patents

Abstract

ABSTRACT

It has been found that a conveyor system can be lubricated with dilute [1.0 X 10-3M] aqueous solu-tions of a partially neutralized mono phosphate ester of the formula:

Description

i7~3 BACKGROUND OF THE INVEN~ION

The present invention relates generally to water-based lubricant compositions and a method of uslng such compositions. More particularly, the invention discloses aqueous compositions containing a long chain phosphate ester which are useful for the lubrication of continuously-moving conveyor systems, particularly con-veyor systems used in the packaging of materials intend-ed for human consumption.
~ Continuously-moving conveyor systems employed in food and beverage packaging operations require both cleansing and lubrication to insure that the systems function properly in moving items between packaging stations. ~or example, in those conveyor systems employ-ed in bottling and capping operations, a clean and pro~
perly lubricated conveyor surface permits stoppage of the bottles during the filling and capping operations while the conveyor track continues to move underneath.
If the track is not clean or does not have the proper lubricity, the containers may be knock~d over or fail to stop moving, resulting both in bottle breakage and in disruption of the bottling line. These cleansing and lubricating functions are customarily accomplished by circulating an aqueous dispersion or solution of a water-based material across the track surface.

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various surface active agents have been employ-ed as lubricants in food packaging processes, including long chain fatty acid soaps, sulfonated oils, and alkan-olamides. Of particular interest to the present inven-tion is the water-soluble agent of U.S. Patent 3,574,100 which claims a track lubricant composition comprising a mixture of an imidazoline derivative and an alkali metal salt of the phosphate esters of oleyl alcohol ethoxylate.
The specific phosphate ester salt disc]osed in the 3,574,100 patent is a material manufactured by General Aniline and Film Corpora~ion under the trade name, Gafac GB520. Gafac GB520 is the partial sodium salt of a mixture o mono- and di-alkyl phosphate esters derived from an oleyl alcohol polyethoxylate having eight to nine ethoxy groups, together with 35 percent of unreacted oleyl alcohol ethoxylate, i.e.l H3C-(CH2)7-CH=c~-(cH2)7-cH-(O-cH2c~2)8-9-oH-The mole ratio of phosphate diester to phosphate mono-ester in the Gafac GB520 material is greater than 3 to 1.

DESCRIPTION OF THE INVENTION

The novel lubricants of the present invention are aqueous compositions, at least partially neutralized with a base~ preferably comprising two active components.
The first of these active ingredients is a mono alkyl phosphate ester of the formula ii7~i~

R ~ocH2c~2tno - I - OH
o H
The second of the active ingredients is a synergist taken from the group:
A) an alcohol of the formula R tOCH2CH2tm-OH
B) an amine oxide of the forrnula ,.~
R N ~(CH2CH2O~nH)2r or C) urea.

~ The lubricant compositions also contain minor amounts of di alkyl phosphate ester and phosphoric acidO
In the above formulae R and R are liner saturated primary alkyl groupsl Cl~ through C18, or linear part-ially unsaturated primary alkylene groupsi Cl6 through C20O R and R can also comprise a mixture of saturated or unsaturated alkyl groups C12 through C20, having an average chain length in the range C13 through C18. R
is a mixture of saturated and unsaturated alkyl groups C8 through C18 having an average chain length C12 through Cl8 (i.e., products derived from fatty acids such as coco oil and taIlow). The value of m and n can be zero through three.
We have discovered that while lubricating compositions employing phosphate monoesters as the so~e active ingredient exhibit good lubricity, the use of an alcohol, an amine oxide, or a urea synergist with the phosphate ester greatly improves the performance of the :~?

, .

,3 lubricant compositlon, particularly in the area of dur-ability~ Although the addition of other materials, such as surfactants, can improve the lubricant formula-tions, excellent compositions can be prepared wherein the sole active components comprise a neutralized aqueous dispersion of a two-component system containing a mono-phosphate ester and one of the synergist compositions described above.
These lubricant compositions exhibit excel-lent lubricity at concentrations as low as .01 percent.The use of higher concentrations, (i.e., .05 to .1 per-cent) is generally preferred, however, because it results in greater durability for the applied material.
The phosphate esters of the present invention can be prepared in a conventional manner. For example, a C14 - C15 triethoxyphosphate was synthesized by react-ing a C14 - C15 linear primary alcohol mixture (Neodol R45) with three moles of ethylene oxide and then phosphory-- lating the resultant ethoxylate with polyphosphoric acid at a temperatue of approximately 65-80 C. The product comprised monophosphate ester, unreacted ethoxy-lated alcohol, phosphoric acid, and diester. Other methods of obtaining phosphate esters are illustrated in the prior art, i.e., U.S. Patents 1,970,578, 2,174,271,

2,167,326 and 3,033,889.
It is generally desirable to limit the forma-tion of diester product in the reaction mixture. The diesters are approximately twice the molecular weight of the monoesters and do not add to the system's lubr-icating properties. Thus, based on cost consider-ations, the diester content should be kept to a minimum, preferably less than 15 percent of the active mono ester ingredient. Thi 5 can be accomplished by employing an excess o~ phosphoric acid in the reaction. If de~ired, additional amounts of long-chain alcohol or alcohol ethoxylate can be added to the product after cooling.

~2~3S75~3 In YieW of the fact that the compositions of the present invention typically contain free phosphoric acid as well as the acidic monophosphate ester, the lubricant compositions would have an undesirably low (acid) pH were they not partially neutralized. More-over, it has been found that neutralization results inbetter dispersibility of the compositions in water.
Neutralization can be accomplished by the addition of any suitable base, but the use of NH3, NH40H, or a basic aminofunctional material is generally preferred.
Although the lubricity of the ester composi-tions remains relatively constant over a range of p~
values, the durability of the composition peaks at a pH
~ 5-6, the pK range for neutralization of the first hydroxyl group in mono alkyl phosphate esters. If the neutralization is continued to a pH = 9 (the pK range for the second hydroxyl neutralization), there is a fall-off in product durability. Thus optimum ~ properties in terms of durability are obtained with partial neutralization, whereby the resultant composition has a pH in the range 5.0 to 7.0, ideally pH = 6Ø However, good lubricity can be obtained with compositions of higher p~ values -- in the range 6.5 to 10. Some applications may warrent a partial sacrifice of product durability in order to obtain the benefit of a mildly basic lubricant. For example, formulations having a basic pH can resist acidic beverage spills (e.g., beer) without any major deterioration in lubricity. Moreover, basic (pH 8.0 to 10.0) composi-tions are generally desirable where it is necessary toincorporate a sequestering agent in the lubricant to overcome problems resulting from water hardness.
As previously indicated, the long chain sat-urated alkyl or partially unsaturated alkylene substi tuent groups of the phosphate esters may contain up to ~S7~

three ethoxy groups in the chain. The presence of these groups increases the dispersibility o~ the ester in water but at some sacrifice in lubricity.
Therefore, while the lubricant performance of a typical monophosphate ester increases with the length of the alkyl chain, saturated alkyl groups longer than C15 tend to be too insoluble to be easily formulated, absent some degree of ethoxylatlon. Increasing the ethylene oxide content increases solubility but reduces lubricating ability.
A preferred ester representing a compromise between lubricating performance and solubility (for saturated R groups) is the phosphate ester, R (CH2c 2)2Y4 1 OH

where R is a 50:50 mixture of C14H29 -- and C15H31 --alkyl groups.
The performance of the lubricant compositions is improved by the presence of a free long-chain alco-hol, a long-chain alcohol ethoxylate, a fatty-acid-derived amine oxide, or urea. Although these additives provide no lubricity by themselves, their presence in the lubricating formulation serves as a synergist, im-proving both the lubricity and, in particular, the dur-ability of the compositions. While even a minor amount o~ these additives serves to improve the properties of the lubricants, optimum results are obtained when the long-chain monoester/synergist ratio is in the range of 1:1.5 on a molar basis.
If an alcohol is used as the synergist, the alcohol can be the reactant precursor of the phosphate ~2~7~

ester, and thus R and ~' will be the same. However, this identity is not necessary and desirable lubricant compositions can be formulated utilizing various com-binations o alcohol and phosphate ester which differ either in the length or in the nature (saturated/unsat-urated, ethoxylated/non-ethoxylated) of the linear long-chain substituant group.
The amine oxide synergist employed in certainspecies of the invention is an ethoxylated polyoxyethy-lene fatty aminel characteristically derived from anatural product such as coco oil, tallow, soybean oil, and the like. Particularly useful compounds include bis(2-hydroxyethyl) cocoamine oxide and bis(2-hydroxy-ethyl) tallow amine oxide.
The inclusion of a sequesterant such as ethyl-ene diamine tetra acetic acid (EDTA) in the lubricant composition renders the phosphate ester formulations resistant to the formation of insoluble precipitates `~ when used in hard water formulations.
The phosphate-ester-containing lubricants are generally applied at very low levels of concentration, i.e., between about 1.0 X 10 3 and 3.0 X 10 3 M, based on the monophosphate ester. It is therefore desirable to supply the lubricants in the form of liquid concen-trates which can be further diluted with water prior to use. Concentrates containing about 10 percent by weight of monophosphate ester can be formulated by blending the phosphate ester, synergist and other desired ingre-dients at elevated temperatures (30-50C) in an isopro-panol/water mixture and neutralizing to a pH of 5.0-6~5 with a base. Lower molecular weight phosphate esters so formulated will remain stable at room temperature.
Higher molecular weiyht concentrates may solidify when cooled to ambient temperature, but can be re-liquified by heating to 30-40C. The concentrates are diluted 2f~i;7~3 prior to use, typically in the ratio one part concen-trate to 100 to 200 parts water.
The compositions are applied to the surface of moving conveyor systems so that the surface of the conveyor does not become dry. This may be accomplished by passing the conveyor through a dip or trough con~aining a dilute solution of the lubricant, by brushing or roller coating the lubricant composition on the surface of the conveyor, or by other conventional means. The preferred method of application, however, utilizes spray nozzles spaced along the conveyor track to ensure the proper degree of lubricity. No matter how the material is applied, it is important that the conveyor system remain consistently wet.
As noted above, the lubricant compositions may be improved by use of suractants and/or sequester-ants. Preferred surfactants are long-chain anionic materials such as the sodium salt of sulfonated oleic ` acid.
Should the lubricant concentrate be diluted with hard water, a highly-dispersed suspension may form, giving the product a cloudy appearance. The fine suspension may in time agglomerate and accumulate in the spray nozzles, causing them to block. The use of a ; 25 sequestering agent is desirable to control the hardness. In view of the fact that sequestering agents such as EDTA perform most efficiently at pH of 8.0 or more, it may be desirable to supply the lubricant concentration at a sufficiently high pH ~8.0 ~ 10) to enable the sequestering agent to operate at maximum efficiency~ As has been previously mentioned, however, this increase in pH may result in some loss in the pro-duct's durability.
The lubricity and durability of the lubricant compositions reported in the following examples was ' ' ' 1 .

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measured on a pilot test track, approximately 19 cm wide by 305 cm long. The track, a slat conveyor manu-factured of 304 stainless steel, was operated at a speed of 40 cm/sec. Friction measurements were measured with a 0-5 pound precision load cell manufactured by Trans-ducers, ~nc. (Model C462). The output from the load cell was connected to a Sigma variable speed strip chart recorder, permitting measurements of coefficient of friction (~) vs. time.
A constant load, consisting of eight filled bottles connected to the load cell by a loop of fine wire, was utilized in the experiments. Lubricant com--positions were applied in spurts to the test track with a feed pump, via a fan spray nozzle. The pump and nozzle could be adjusted to vary both the frequency of the spurts and the volume of material delivered. In each of the following examples a spurt rate of 36/minute and a solution volume of 32 mL/minute was employed.
The test was initiated by activating the feed pump and starting the test track and recorder in motion.
The measured coefficient of friction was observed to drop over a period of time to a constant equilibrium value (~), the value depending on the lubricity of the applied material. Because lubricity has an inverse relationship to friction, the lower the value of ~, the better the lubricant.
The pilot test track was also used to measure the durability of the lubricant compositions. This was accomplished by replacing the intermittant stream o~
lubricant applied to the track with a constant stream of water. At the same time, a weighted fiberglass cloth (~5000 gms, width~ll cm) was placed on the track to increase the wear rate. The time required for the co-efficient of friction to increase from the lubricated equilibrium ~alue to the oriyinal friction value re-presents the durability of the test lubricant. The greater the time, the better the durability.
The reported data for coefficients of fric-tion represent meas~rements taken five minutes afterthe initial activation of the feed pump and test track to ensure that a constant equilibrium ha~d been obtainedO
Immediately after making this measurement, the flow of lubricant was replaced with a water stream and the dura-bility test was commenced.
In interpreting the following data, the opti-mum products are those which exhibit both low equil-ibrium coefficients o~ friction and high durability times. Except as otherwise indicated, all formulations were diluted in distilled water to 2.2 X 10 3 M based on the weight of the ester. All ratios are expressed in terms of weight, unless otherwise indicated. Final-ly, although the following examples illustrate the present ~ invention, they should not be construed as limiting the invention to their details.

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C12-C15 non etho~yla~ed monoester A phosphated ester was prepared by reacting a C12 to C1~ linear primary alcohol mixture with polyphosphoric acid at a temperature of approximately 72C. Upon cooling the product was analyzed and found to contain 38.2 perce~t monoester, 11.5 percent ~3P04, 50.3 percent unreacted alcohol, and no measurable di-ester.
The phosphate ester was separated from theunreacted alcohol by dissolving approximately 25 g of the above product in 50 mL of warm isopropyl alcohol and stirring the mixture with heating until a clear solution was obtained. The pH of the solution was adjusted to approximately 6.5 by the addition of con-centrated ~H40H (dilute solutions should be avoi~ed due ~ to the ester's solubility in H20) This resulted in the ~ormation of a white precipitate which was digested at 40C for 45 minutes. The solution was cooled to 20C, filtered throu~h a buchner funnel, washed with cold IPA, and the precipitate dried. The residue --the ammonium salts of the phosphate ester and polyphos-phoric acid -- was dissolved in water to form a 2.2 X
10 3 M lubricant composition based on the phosphate ester, and applied to the test track in the manner pre-viously described. The durability and lubricity of the composition was measured and recorded. The results are set forth at Ex lA in Table I.
A second sample o the phosphate ester/unreact-ed alcohol product of the first reaction was formulated into a lubricant without removal of the unreacted alcohol.
This was accomplished by adding 25 g of material (38 parts ester: 50 parts alcohol) to 2S0 ml of a 10/90 ,~

IPA/H20 solution, and heating the mixture to 35C, with stirringO ~rhe pH of the dispersion was adjusted to 6.5 by the addition of diethanol amine (DEA), and then dil-luted with distilled water to form a 2.2 X 10 3 M
lubricant composition based on the phosphate ester.
~he composition was applied to the test track and it~
durability and lubricity measured and recorded. The results are set forth at ~x lB in Table I.

E~ample II

C12-C15 trietho~ylated mon~e~ter A commercially-available phosphated ester composition (Alkaphos-3, Alkaril Chemicals Ltd.), was formulated into a ~rack lubricant composition. Analy-sis of the product as received revealed it to be a C12 -C15 triethoxyphosphate and that its composition was 45 ` percent monoester, 10 percent phosphoric acid, 40 per-cent unreacted alcohol ethoxylate, and 5 percentdiester.
Twenty-five ~25) grams of the product was dispersed in 250 ml of a 10/90 IPA/H20 solution, neu-tralized to pH 6O5 with DEA, and diluted to 2.2 X 10 3 M with distilled water in the same manner as the ester~alcohol material of Example 1. The results of the composition as a track lubricant a~e set forth at Ex 2 of Table 1.

~ample III

C14C15 non etho~ylated m~noester A phosphated monoester was prepared from a C14C15 linear primary alcohol mixture by ollowing the procedure of Example 1~ Analysis revealed the product 9~

to contain 41.S pereent monoester, 10.7 percent H3PO4, 47.5 percent unreacted alcohol, and no measurable di-ester. A portion of the product was dissolved in 30/70 IPA/H20, neutralized to pH 6.5 with DEA, diluted to 2.2 X 10 3 M in distilled water and testl~d on the pilot track. The results appear at Ex 3A of Table I.
Another portion of the above product was treat-ed 50 as to isolate the phosphate ester from the non-reacted alcohol in accordance with the separation step a of Example 1. The isolated, partially neutraliæed ester/
acid mixture was tested on the pilot track by itself (Ex 3B), and in combination with a number of long chaln alcohols and alcohol ethoxylates (Exs 3C-3H). In all cases, the C14-C15 phosphate ester-containing lubricant was diluted to 2.2 X 10 3 M, based on the ester content, prior to testing.

Example IV

Oleyl dietho~y monoester An oleyl alcohol diethoxylate was prepared by reacting oleyl alcohol [CH3(CH2)7cH=cH(cH2)7c~OH] with ethylene oxide in a 1 to 2 molar ratio. The reaction was carried out by charging the oleyl alcohol and a sodium hydroxide catalyst into an autoclave, heating the autoclave to 140~ C, and gradually adding ethylene oxide gas. The pressure was maintained at 25 to 30 p.s.i. during the reaction.
The resultant oleyl alcohol diethoxylate was reacted with polyphosphoric acid by following the pro-cedure of Example 1. Analysis revealed the product to be 42 percent phosphate monoester, 8 percent H3PO4, and 50 percent alcohol ethoxylate diester. A portion of the product was dissolved in 30/70 IPA/H~0, neutral-ized to pH 6.5 with DEA, diluted to 2.2 X 10 3 M in 7~3 distilled water an2 tested on the pilot track. The results appear at Ex 3A of Table I, Another portion of the product was treated 50 as to isolate the phosphate ester from the alcohol in accordance with the separation step of Example 1. The isolated, partially neutralized ester/acid mixture was tested on the pilot track by itself (Ex 4B), and in combination with a number of long-chain alcohols and alcohol ethoxylates (Exs 4C-4E). In all cases the oleyl diethoxy phosphate-ester-containing lubricant was diluted to 2.2 X 10 3 M based on the ester content, prior to testing.

E ample V
Oleyl polyethoxy ester (Gafac GB5~0~

A commercially-available partially neutralized ` ethoxylated oleyl alcohol ester composition (Gafac GB520, GAF, Inc.) was formulated into a track lubricant. Analy-sis of the product as received revealed the material to be an aqueous dispersion containing a long-chain phos-phate diester, a long-chain phosphate monoester and free oleyl alcohol ethoxylate. The analysis showed the product to be partially neutralized with NaOH.
The degree of ethoxylation of the oleyl alco-hol alkylene substituent was determined to be between 8 and 9, and the ratio of phosphate diester to phosphate monoester to be in excess of 4 to 1. Unreacted ethoxy-lated alcohol was found to constitute approximately 35percent by weight of the solids ingredients.
The GB520 was formulated into a 2.2 X 10 3 M
track lubricant compositionr based on the weight of the total ester. The results of the pilot track test util-izing this material are reported at Ex S of Table 1.

~, As evident from these results, the composition exhibited poor durability and lubricity.

~xample VI

C14-Cl5 (-OE~2Y4 phosphate monoest~r plus ~urfa~tant A lubricant composition was formulated wherein a surfactant was added to improve the hard-water stabil-ity of the composition. A phosphate ester of a C14-C15(EtO)2Y alcohol ethoxylate was prepared in accor-dance with the procedure of Example IV~ Analysis re-vealed the product to be 7 2 . 5 percent monoester~ 9 per-cent diester, 12 percent phosphoric acid, and 6,5 per cent unreac~ed alcohol ethoxylate.
An anionic surfactant -- the sodium salt of - sulfonated oleic acid, 50% active (Sulfonate OA5, Cities Service, Inc.) -- was added to the ester/alcohol blen~
in various amounts, the mixture neutralized to a pH of 6.5 with DEAI and the neùtralized products dispersed in 150 ppm tap water to form track lubricants (2.2 X 10 3 M, based on ester). The results are recorded at Exs 6A-6D in Table I.

~xam~e VII

Cl4Cls(O~t)2Y4 phosphate monoester plus amine O~.iae The Cl4Cl5(OEt)2Y4 alcohol ethoxylate of Example VI was treated so as to isolate the mono-phos-phate ester in accordance with the separation procedure of Example I. Ten Ten ~10) grams of the monoester was 7~

- ~3 -dispersed in 7S grams of 2:13 IPA:H2O, and titrated with N~4Q~ to a pH of 6Ø Five (5) grams of Aromox C/12, bis~2-hydroxyethyl) cocoam.ine oxide (Armak Indus-trial Chemicals), was added to the above solution to form a concentrate, and the material dispersed in tapwater ~100:1) to form a track lubricant (2.2 X 10 3 M, based on ester). The results are recorded at Ex 7 of Table I.

Exam~le VIII

C~ 5 ~o~t) 2Y4 phosphate monoester plus urea The Cl4Cl5~OEt)2Y4 alcohol ethoxylate o~
Example VI was treated so as to isolate the mono-phos-phate ester in accordance with the separation procedure ~ of Example I. Ten ~10) grams of the monoester was dis-persed in 80 grams of 1:8 IPA:H2O and titrated with NH~OH to a pH of 6Ø A concentrate was formulated by dissolving 8 grams of urea in the above solution The concentrate was diluted in distilled water (100:1) to form a track lubricant. The results are reported at EX
8A of Table I.
A second lubricant composition was prepared, as above, but employlng a higher level of urea (20 grams).
The results are recorded at Ex 8B of Table I.

Example IX

Long chain alkylene phosphate esters wereformulated into track lubricant compositions in accor-dance with the procedures of Example 1 through VIII.

The results of the test of these compositions on a pilot test track are summarized in Table I, Exs 9 and 10.

~ a~

Effect of p~

In order to test the effect of pH on lubri-cant properties, a track lubricant concentrate was for-mulated as followso 14-Cl~ triethoxy ' ~ --~
( Monophosphate ester 80% /' Phosphate Ester C14-Cls triethonyl ~ 8.0 alcohol (nonionic) 8 ~phosphoric acid (free) 12% J
No-nionic Alcohol 1.0 ~ Isopropanol 12.0 Urea 15,0 Water (soft) 60.4 Ethylene Diamine Tetra Acetic Acid Disodium.2H2O 1.0 Methanolamine (~EA~ or KOH* 2.6 2~
*The amount and nature of the base was altered to obtain different pH's. With 2.6% MEA, pH = 8.Q.

Track lubricant compositions were prepared ~0 from concentrates having a range of pH from 8.0 through 11.0, and applied to the test track in the manner pre-viously described~ The lubricity and durability of these compositions are set forth in Table II.

~D a ~ 25 --T~LlE: I I

pH pH 1:250 Concentrate Soft Water Example Formula Dilution Dura~ y _~
--~ 8.0 706 6.50 001~5 B 9~0 8.3 6.50 0.147 C 10.0 9~2 5.50 0.155 D10.0 (KOH) 9.2 4.01 0.147 E11.0 tROH) 9.3 3.21 00142 ~ It can be noted that the coefficient of fric-tion (~) stays relatively constant with increase in pH, and that durability decreases with further increase in pH. In certain applications, i.e., where the lubricant is applied substantially constantly to the conveyor track, a relatively low-level of durability may be sat-isfactory.

Exam~le XI
.
Resistance to beverage spills The resistance of the lubricant compositions to acidic beverage spills such as those generally found in beer bottling halls was tested utilizing the formula-tion of ~xample X, partially neutralized with MEA and thereafter diluted with so~t water (250:1) to a pH of7.8.
Forty beer bottles were placed on the clean pilot test track and the test track apparatus adjusted as previously outlined. In an effort to simulate a heavily used track surface as found in a commerical bottling facility, the track was operated at a speed of 40 cm/sec. for a period of two hours with lubricant supplied throughout at a rate of 41 mL/minute.

At the end of the two hour equilibration period, with the track and the lubricant-feed still running, the effect of eight test bottles interconnected with a precision load cell was measured for 4Y2 minutes. The equillbrium coefficient of friction was found to be ~ =
0.154.
After the above equilibrium measurement was completed, the flow of lubricant to the track was supple-mented with a spray of water to determine the effect of dilution on the lubricant composition. Water was sprayed onto the track through a nozzle, upstream of the eight-bottle load, at a rate of 103 mLtminute using a peristal-tic pump. Measurements were taken over a 4Y2 minute period and the water-dilution coefficient of friction was found to be ~ = 0.159. Flow of water was stopped and the coefficient of friction was again measured over a period of 4 minutes: ~ = 0.159.
The effect of a beer spill was determined by applying a supplemental spray of beer (pH 4.1) to the track in the same manner as the water spray in the pre-ceeding water-dilution step, but at a rate of 55 mL/minute. The pH of the combined beer and lubricant spray on the track was determined to be p~ = 4.5. The coefficient of friction, measured over a 7 minute period, was observed initially to rise ~ = 0.167) and then to fall (~ = 0.159). Thereafter, the spray of beer to the test track was stopped and the lubricant alone applied. The lubricity was found to increase somewhat (~ = 0.152).

Claims (15)

What is claimed:

1. In a method for lubricating a continuously-moving conveyor system for transporting packages from a first station to a second station and wherein said packages are temporarily detained at said first station while said conveyor moves beneath said packages, and said conveyor system is wetted with an aqueous lubricant composition:
the improvement wherein said aqueous lubricant composition comprises:
A. a phosphate ester component consisting essentially of:
(i) 51 to 100 percent by weight of a monoalkyl phosphate ester of the formula (ii) 0 to 49 percent by weight of a dialkyl phosphate ester of the formula wherein the concentration of said phosphate ester component in said lubricant composition is in the range 1.0 X 10-3 to 3.0 X 10-3 molar;

B. a synergist component selected from the group consisting of (i) an alcohol of the formula R'?OCH2CH2?m-OH

(ii) an amine oxide of the formula (iii) urea, said synergist present in said lubricant composition in an amount between 10 and 150 percent of the weight of said phosphate ester component;
wherein m and n can have a value of zero through three; R
and R' are selected from the group consisting of (i) linear saturated primary alkyl groups, C14 through C18, (ii) linear partially unsaturated primary alkyl groups C16 through C20, and (iii) a mixture of linear saturated primary alkyl groups C12 through C20, wherein the average length of the alkyl substituant is C13 through C18; and R"
is a mixture of saturated and unsaturated alkyl groups C8 through C18 having an average chain length C12 through C18; and said lubricant composition being at least partially neutralized with a base whereby its pH is in the range 5.0 through 10Ø

2. A method according to claim 1 further including:
applying said lubricant compositions to said conveyor by means of a plurality of spray nozzles spaced along said conveyor system.

3. An Aqueous lubricant composition comprising:
A. a phosphate ester component consisting essentially of:
(i) 51 to 100 percent by weight of a mono alkyl phosphate ester of the formula (ii) 0 to 49 percent by weight of a dialkyl phosphate ester of the formula wherein the concentration of said phosphate ester component in said lubricant composition is in the range 1.0 X 10-3 to 3.0 X 10-3 molar;
B. a synergist component selected from the group consisting of (i) an alcohol of the formula R'(OCH2CH2)m-OH

(ii) an amine oxide of the formula (iii) urea, said synergist present in said lubricant composition in an amount between 10 and 150 percent of the weight of said phosphate ester component;
wherein m and n can have a value of zero through three, R
and R' are selected from the group consisting of (i) linear saturated primary alkyl groups, C14 through C18, (ii) linear partially unsaturated primary alkyl groups C16 through C20, and (iii) a mixture of linear saturated primary alkyl groups C12 through C20, wherein the average length of the alkyl substituant is C13 through C18, and R"
is a mixture of saturated and unsaturated alkyl groups C8 through C18 having an average chain length C12 through C18; and said lubricant composition being at least partially neutralized with a base whereby its pH is in the range 5.0 through 10Ø

4. An aqueous lubricant composition according to claim 3 wherein said base is selected from the group consisting of ammonia, ammonium hydroxide, or a water soluble amine.

5. An aqueous lubricant composition according to claim 3, further including an anionic surfactant.

6. The composition of claim 5 wherein said surfactant is the sodium salt of sulfonated oleic acid.

7. An aqueous lubricant composition according to claim 3, further including a sequestering agent.

8. An aqueous lubricant concentrate comprising:
A. a phosphate ester component consisting essentially of:
(i) 51 to 100 percent by weight of a monoalkyl phosphate ester of the formula (ii) 0 to 49 percent by weight of a dialkyl phosphate ester of the formula wherein the concentration of phosphate ester in said concentrate is in the range 0.2 to 0.5 molar;
B. a synergist component selected from the group consisting of:
(i) an alcohol of the formula R'(OCH2CH2)mOH

(ii) an amine oxide of the formula (iii) urea, said synergist present in an amount between 10 and 150 percent of the weight of said phosphate ester component;
wherein m and n can have a value of zero through three, R
and R' are selected from the group consisting of (i) linear saturated primary alkyl groups, C14 through C18, (ii) linear partially unsaturated primary alkyl groups C16 through C20, (iii) a mixture of linear saturated primary alkyl groups C12 through C20, wherein the average length of the alkyl substituent is C13 through C18, and R" is a mixture of saturated and unsaturated alkyl groups C8 through C18 having an average chain length C12 through C18; and said lubricant concentrate being at least partially neutralized with a base whereby its pH is in the range 5.0 through 10Ø

9. An aqueous lubricant concentrate according to claim 8 wherein said base is selected from the group consisting of ammonia, ammonium hydroxide, or a water soluble amine.

10. An aqueous lubricant concentrate according to claim 8, further including an anionic surfactant.

11. The composition of claim 10 wherein said surfactant is the sodium salt of sulfonated oleic acid.

12. All aqueous lubricant concentrate according to claim 8, further including a sequestering agent.

13. A method according to claim 1 wherein the weight of the mono alkyl phosphate ester comprises at least 85 percent of the total weight of said phosphate ester component.

14. A lubricant composition according to claim 3 wherein the weight of the mono alkyl phosphate ester comprises at least 85 percent of the total weight of said phosphate ester component.

15. An aqueous lubricant concentrate according to claim 8 wherein the weight of the mono alkyl phosphate phospate ester comprises at least 85 percent of the total weight of said phosphate ester component.