US3657123A

US3657123A - Lubricant compositions

Info

Publication number: US3657123A
Application number: US21993A
Authority: US
Inventors: Michael A Stram
Original assignee: Atlantic Richfield Co
Current assignee: Atlantic Richfield Co; Pony Industries Inc
Priority date: 1970-03-23
Filing date: 1970-03-23
Publication date: 1972-04-18
Anticipated expiration: 1989-04-18

Abstract

Water-soluble salts (e.g., alkali metal, ammonium or watersoluble amine salts) of styrene-maleic anhydride copolymer halfesters are employed in aqueous solutions as coolants and lubricants for metal-working operations e.g., metal cutting and abrading. The copolymers are esterified with both a fatty alcohol having from 10 to 22 carbon atoms and a lower alkoxy polyethylene glycol. Metal-working lubricant compositions are also formulated which comprise these salts along with extreme pressure agents such as amine salts of fatty acids and organic phosphate esters. Other additives may also be employed in the lubricating compositions of this invention.

Description

United States Patent [15] 3,657,123 [4 1 Apr. 18, 1972 Stram [541 LUBRICANT COMPOSITIONS [72] Inventor: Michael A. Strum, Chicago, Ill.

[73] Assignee: Atlantic Richileld Company, New York,

[22] Filed: Mar. 23, 1970 [21] Appl.No.: 21,993

[52] U.S.Cl. ..252/34.7, 252/34, 252/41, 252/42], 252/493, 252/495 [51] lnt.Cl. ..Cl0rn1l28 [58] Field olSearch ..252/34.7,421,493,495,

[56] Relerences Cited UNITED STATES PATENTS 2,285,853 6/1942 Downing et al ..252/34.7 X

2,753,305 7/1956 Whitbeck 2,999,064 9/1961 Sluhan 3,472,772 10/1969 Chambers etal ..252/34.7

3,527,726 9/1970 Goweret al. ..252/49.3

Primary Examiner-Daniel E. Wyman Assistant ExaminerW. Cannon Attorney-Morton, Bernard, Brown, Roberts & Sutherland, John \V. Behringer, James N. Dresser, Eugene L. Bernard, W. Brown Morton, Jr., Thomas J. Clough, Martin J. Brown, John T. Roberts and Malcolm L. Sutherland [57] ABSTRACT Water-soluble salts (e.g., alkali metal, ammonium or watersoluble amine salts) of styrene-maleic anhydride copolymer half-esters are employed in aqueous solutions as coolants and lubricants for metal-working operations e.g., metal cutting and abrading. The copolymers are esterified with both a fatty alcohol having from 10 to 22 carbon atoms and a lower alkoxy polyethylene glycol. Metal-working lubricant compositions are also formulated which comprise these salts along with extreme pressure agents such as amine salts of fatty acids and organic phosphate esters. Other additives may also be employed in the lubricating compositions of this invention.

20 Claims, No Drawings LUBRICANT COMPOSITIONS This invention is concerned with novel watenbased coolants and lubricants for use in metal-working operations. More specifically, this invention is directed to aqueous solutions of water-soluble alkali metal, ammonium or amine salts of styrene-maleic anhydride copolymer esters, the copolymers having been esterified with both a fatty alcohol having from 10 to 22 carbon atoms and a lower alkoxy polyethylene glycol, which can be employed in aqueous solution as aqueous, metal working lubricants and preferably as metal cutting and abrading lubricants. This invention is also concerned with aqueous lubricating compositions comprising these water-soluble salts of styrene-maleic anhydride copolymer esters, water, and extreme pressure (E?) agents.

Lubricants suitable for use in metal fabrication such as in cutting, abrading, threading, tapping and the like must effectively cool and lubricate both the tool and the worked metal. During such operations an enormous amount of heat is generated at the interface of the tool and work piece which must be quickly dissipated in order to prevent damage either the tool or work piece or both. This is accomplished by flooding the interface with a fluid having a high capacity for heat absorption as well as eflective lubricating properties for reducing friction between the tool and work piece. The lubricants especially formulated for these purposes are known in the art as cutting fluids or cutting oils. Many cutting oils, especially the earliest fonns thereof, consist essentially of an emulsion of a mineral lubricating oil in water. While these mineral oil based cutting fluids exhibit generally good qualities of cooling and lubrication, they have several attendant disadvantages, including instability to bacterial attach and poor corrosion inhibition. For these reasons, cutting fluid formulations have been developed which employ synthetic, rather than mineral oil bases. Many improvements over the mineral oil compositions are realized in the synthetic cutting fluids, such as stability to bacterial decomposition and improved rust inhibition. The synthetic base lubricants heretofore developed, however, have not satisfied all the requirements necessary to provide a generally well-balanced, efficient cutting fluid. For, whereas one may exhibit generally good lubricating and cooling qualities, it may have an objectionable odor, be irritating to the nose and throat of the operator or cause foaming; which obscures the operator's view of the material being worked, another may have an agreeable odor, or none at all, and be nonirritating and safe for the operator, yet fail to produce a good finished surface on the work piece, the finish perhaps being replete with microscopic ridges, grooves and surface cracks.

it is an object of this invention to provide an aqueous coo lant for metal-working which is improved with respect to bacterially promoted or chemically caused odor, germ-forming tendency, irritation of the skin, clarity and ash content. It is a further object of this invention to provide novel emulsifying agents for use in aqueous metal-working lubricating compositions containing synthetic lubricants.

ln copending application, Ser. No. 7l2,965, filed Mar. 18, I965, in the names of Howard D. Gower, Bob G. Gower and David W. Young, there is disclosed a metal-working coolant which comprises a minor, effective amount of an extreme pressure lubricating agent and an amine salt of a copolymer resin, which resin can have a styrene to maleic anhydride whole ratio of about lzl to 5:1. The resin can also be an ester of these polymers, being up to 100 percent half-esters, esterifred with a member selected from the group consisting of alcohols and capped glycols having the structure where R and R are aliphatic hydrocarbon radicals of about two to six carbon atoms, the total number of carbon atoms in R and a single R is less than about seven and x is from to about 10. These coolants have been found to be advantageous.

In accordance with the present invention it has been found that cutting and abrading, including tapping, and other machining operations, of a high degree of efficiency and are obtained when conducted in the presence of aqueous solutions of water-soluble alkali metal, ammonium or amine salts of styrene-maleic anhydride copolymer esters, which copolymers are esterfied with both a fatty alcohol having from 10 to 22 carbon atoms and a lower alkoxy polyethylene glycol. In addition it has been found that these water-soluble salts are particularly effective as emulsifiers in aqueous lubricating compositions containing extreme pressure agents. The salts of this invention have been found to possess long term stability and good shelflife in aqueous lubricating compositions.

The copolymer ester can be made by the esterification of a styrene-maleic anhydride copolymer with both a fatty alcohol containing about 10 to 22 carbon atoms, preferably about [6 to l8 carbon atoms, and a lower alkoxy, e.g., of one to four carbon atoms, polyethylene glycol of an average molecular weight of about 200 to 750, preferably about 500 to 700. The fatty alcohol can be saturated, such as octadecanol, or olefini cally unsaturated, such as oleyl alcohol. isomers of these alcohols, such as isostearyl alcohol are also suitable. The lower alkoxy polyethylene glycol is preferably a methoxy polyethylene glycol. The fatty alcohol and glycol are reacted in proportions such as to provide a fatty alcohol to glycol mole ratio of about 0.3/1 to l.l/l preferably about 0.75/1 to III.

A slight excess of the glycol is desirable since water solubility is thereby increased. The mole ratio of fatty alcohol to anhydride equivalents in the copolymer esters is from about 0.25 to 0.5, preferably 0.4 to 0.5. The mole ratio of glycol to anhydride equivalents is from about 0.5 to 1.0, preferably 0.5 to 0.75. The polymer has ester groups from both the lower alkoxy polyethylene glycol and the fatty alcohol on the same polymer molecules. The ester is thus distinct from a mixture of the corresponding polymers each being esterified with only one of the aforesaid glycol and fatty alcohol. The polymer can be esterified with a mixture of the alcohol and lower alkoxy polyethylene glycol or it can be esterified sequentially with either the alcohol or glycol followed by esterifrcation with the other. In either case, it is important that the polymer contains both the alcohol and glycol groups and not a mixture of ester polymers which are separately and singly esterified with the alcohol or glycol.

Preparation of the styrene-maleic anhydride polymer components of the composition of the present invention can be made by known methods; for example, it can be made in accordance with the teachings of US. Pat. No. 3,342,787, issued Sept. l9, i967. Thus, styrene and maleic anhydride can be first polymerized, for instance, by solution polymerization where the monomers are polymerized in a suitable solvent employing as a polymerization catalyst a free-radical catalyst, such as a peroxide, preferably benzoyl peroxide, dicumyl peroxide or an alkyl peroxy dicarbonate, at a temperature of about 75 to 300 C. or more. Suitable solvents are aromatics such as cumene, p-cymene, xylene, toluene, etc. Other suitable solvents are the ketones, such as methylethyl ketone. A preferred manner of carrying out the polymerization is by what is known as incremental feed addition. By this method the monomers and catalyst are first dissolved in a portion of the solvent in which the polymerization is to be conducted and the resulting solution fed in increments into a reactor containing solvent heated to reaction temperature, usually the reflux temperature of the mixture.

When an aromatic hydrocarbon is employed as the solvent for the polymerization the formation of the copolymer gives a heterogeneous system, the polymer layer being the heavier layer and recoverable by merely decanting the upper aromatic solvent layer and drying. On the other hand, when a ketone is.

the solvent, the formed copolymer is usually soluble in the solvent media so that recovery of the product necessitates a solvent stripping operation. The polymer contains a molar ratio of styrene to maleic anhydride of from about H to about 5:1 and has an average molecular weight, prior to esterification of about 600 to 5,000, preferably about 800 to about 2,500.

The esterification product of the present invention can be formed by esterifying the styrene-maleic anhydride polymer with a lower alkoxy polyethylene glycol, preferably methoxy polyethylene glycol, of an average molecular weight of about 200 to 750, preferably about 500 to 700, in the presence of a fatty alcohol containing to 22 carbon atoms, preferably about 16 to 18 carbon atoms. The esterification can be carried out at any convenient temperatures, e.g., about 100 to 220 C., preferably about 140 to [90 C. Although no catalyst is necessary, the esterification can be carried out in the presence of a catalytic amount of, for instance, a fatty acid metal salt, preferably an alkali metal salt. The alcohol and glycol can be present, as noted above, in a mole ratio of about from 0.3:1 to l.l:l, preferably about 0.75:1 to lzl. A preferred product is prepared by the reaction of approximately one anhydride equivalent weight of a lzl styrene-maleic anhydride copolymer (average molecular weight of l,500) 0.5 moles medroxy polyethylene glycol (average molecular weight of about 550) and 0.5 moles of stearyl alcohol l-octadencanol). The polymer is about 4 to I50 percent, preferably about 40 to 120 percent, half-esterified with the total methoxy polyethylene glycol and alkanol. The water-soluble salts of this invention can be formed by reacting an alkali metal, ammonia or water-soluble amine with the styrene-maleic anhydride or its partial ester to react with free carboxyl groups present in the partial ester.

The water-soluble, salt-forming amines having boiling points above about 200 C. can be employed in the present invention to form the amine salts of the styrene-maleic anhydride copolymer partial ester. Preferred amines are tertiary amines such as, for example, tributylamine and trifurfurylamine; and hydroxyl lower alkyl amines such as, for example, diethanolamines and triethanolamines. Glycol amines or capped glycol amines of molecular weights up to about 5,000 are also suitable. The ethanolamines are preferred.

A preferred method of reacting the amine and the copolymer is to first dissolve the amine in the water and then add the copolymer while keeping the temperature below about 140 F. to minimize evaporation. Sufficient agitation may be employed to insure complete formulation. Similarly, an alkali metal or ammonium salt can be prepared by means known in the art.

The compositions of this invention can contain from about 0.l to 50, preferably from about 0.5 to l0, weight percent of the alkali metal, ammonia or amine component, from about 2 to 40, preferably from about 4 to 20, weight percent of the styrene-maleic anhydride copolymer ester and from about 20 to 95, preferably from about 70 to 90, weight percent water. The amount of alkali metal, ammonia or amine present is often sufficient to neutralize the compositions or make them basic. The compositions of this invention also contain minor, effective amounts of water-soluble extreme pressure lubricat ing agents such as water-soluble amine salts of organic phosphate ester acids or of fatty acids of about l2 to 20 carbon atoms, for example, triethanolamine oleate, diethanolamine oleate, and similar salts of the various watersoluble amines used to form the water-soluble salts of styrenemaleic anhydride polymers of this invention. These extreme pressure agents are generally effective in the composition of the present invention when employed in minor amounts, for instance, about 2 to weight percent, preferably about 4 to it) weight percent, of the solution ofalkali metal, ammonia or amine; styrene-maleic anhydride copolymer ester and water Where the same amine is employed to form the styrene-maleic anhydride salt as is used to form the salt of the fatty acid, the fatty acid may be added directly along with the styrenemaleic anhydride partial ester to the aqueous solution containing an amount of the amine in excess of that needed to form the styrene-maleic saltv The organic phosphate ester acids which may be employed as E.P agents in the present invention can be, for instance, primary. secondary, or tertiary esters of phosphoric acid and a hydroxyl compound which can be exemplified by the ky alkanols, phenols, including the alkyhmonophenols, and monoalkyi, monoaryland monoarylalkyl-esters of poltal kylene glycols. These phosphate compounds preferably include those corresponding to the following general formula:

wherein R is a hydrocarbon radical having about one to 30, preferably eight to l8, carbon atoms, 1: equals 2 to 10, preferably 2, y is 0 to 20, preferably 2 to 8, and n is l to 2. The R groups can be alkyl, aryl or mixed alkyl-aryl radicals.

These phosphate ester acids of this invention may be oil or water-soluble, depending to a degree on the vaiue of y, although the size of R and 1 may also be factors in determining solubility. Generally oil-solubility tends to increase with larger values of R and .1: while water solubility increases with larger values of y, for example, above about y==8 or l0 the esters tend to be watersoluble while below 5 they can generally be oilsoluble. in any event, where the ester acids are water-insoluble, salt'fonning amine, for example, triethanolamine, can be included in the composition to react with and solubilize the ester acid. At least about i part by weight of amine per part of phosphate ester acid can often be required to solubilize the ester acid in water.

Phosphate ester acids useful as the extreme pressure lubricant component in the present invention include, for example, mono and di-octyl and oxo-decyl phosphates, mixtures of monoand dilauryl phosphate, lauryl polyethylenoxy phosphate esters, nonylphenylpolyethyleneoxy phosphate esters and the like. Methods of preparation of the phospahte ester acids suitable for use in the composition of the present invention appear in abundance in the prior art. US. Pat. No. 3,033,889 to Chiddix et al. (herein incorporated by reference), for example, discloses the preparation of phosphate esters of branched chain (Oxo) alcohols suitable as to the phosphate lubricant in the present invention. Similarly, the preparation of suitable alkyl, aryl and mixed alkaryl-alkyl polyethyleneoxy phosphate ester acids is described in U.S. Pat. No. 3,004,056 to Nunn et al. and No. 3,004,057 to Nunn, both patents being herein incorporated by reference.

In addition to the water-soluble salt of the copolymer, the E.P. agent, and the water, the composition of this invention may also contain various additives such as, for example, about I to [0 weight percent of an anti-foaming agent such as hexadecyi alcohol, or other monohydric alcohols of from about six to 20 carbon atoms; about 2- l0 weight percent, preferably about 3-9 weight percent, boric acid or other suitable boron compound, such as borax, which forms boric acid on hydration, or a mixture of such compounds with low molecular weight amines such as methylethyl amine or tributyl amine and sodium nitrite which can provide protection against rust. Water-soluble glycols, such as hexylene glycols and polyethylene glycols of up to about 5,000 molecular weight, or capped glycols and polyglycols, such as diethylene glycol monoethyl ether, have been found to prevent film formation and tackiness on the machinery or product and improve settling of fine solids for recirculation of fluid and may be employed in amounts up to about 30, preferably about l0 to 25, weight percent. Small amounts of water-soluble silicones may be added an anti-foaming agents and sodium nitrite may also be added as a corrosion inhibitor. it is preferred that the lubricant composition have a viscosity of below about poise at 2 5 C in use, the lubricating composition of this invention may be diluted with water, for instance, to a concentration of 1 part by weight of the cutting oil composition to about l to 100, preferably 5 to 50, parts by weight ofwater.

The invention shall be further described in the following examples EXAMPLE l A siyrene-maleic anhydride copolymer ester was prepared by reacting approximately one anhydride equivalent weight following results:

Test Result 1: carbon 64.61 70 hydrogen 8.78 k oxygen 27.09 Acid Number 62.4

This product was assigned sample designation "A".

A second reaction was performed in like manner with one anhydride equivalent of a styrene-maleic anhydride copolymer of an average molecular weight of 1,500, an acid number of 490 and a styrene to maleic anhydride molar ratio of 1:1 with 1 mole (350 g.) of a methoxy polyethylene glycol of an average molecular weight of 350. The product analyzed Test Result 1: carbon 51.7 i hydrogen 7.6 in oxygen 31.82 Acid Number 174.3

This product was assigned sample designation B".

Samples A and B were dissolved in water to make percent aqueous solutions and these solutions were further reacted with sufficient triethanolamine to make solutions of a pH of 7.0. The stoichometrlc amount of triethanolamlne to neutralize Sample A is about 16.6 grams per 100 grams of the styrene maleic anhydride resin ester while this amount for Sample B is about 46.3 grams per 100 grams of the resin ester. These solutions were then subjected to tapping torque tests on various metals. A commercial tapping fluid, designated Composition X, was also evaluated in the tests. Results of the tests are shown in Table 1. As can be seen from these results, Sample A (a composition containing the mixing ester of this invention) yielded lower torque values than the Sample B monoester on every metal tested. From prior testing, it is apparent that tapping torque data can be related to other metal-working operations such as cutting and abrading, including grinding, honing, etc. The invention as herein disclosed can thus be applicable to a variety of other industrial applications.

TABLE I Tapping Torque Test Tap 60% Express Metal 8620 9310 copper 2024 steel steel aluminum Sample 110 H,O dilution In. Lbs. A 300 250 408 184 B 424 272 414 349 Tapping I21 400 350 120 composition EXAMPLE 11 About 100 g. of the 10 percent aqueous solution of Sample A from Example 1 is combined with sufficient triethanolarnine to make a pH of 7.0 in the same manner as in Example I. About 8 g. of an organic phosphate ester acid extreme pressure lubricating agent is added to the resulting solution to yield a composition containing about 7.3 weight percent lubricating agent. The organic phosphate ester acid is a mixture of approximately equal amounts of primary and secondary phosphate esters of the oxyethylene ether of of 0x0 tridecyl alcohol, the ether containing an average of 5 oxyethylene groups. The solution is subjected to tapping torque tests on various metals with similar results as shown per Sample A in Example 1.

It is claimed:

1. A lubricating composition comprising an aqueous solution of an alkali metal, ammonium or water-soluble amine salt of a styrene-maleic anhydride copolymer ester and a minor, effective amount of an extreme pressure lubricating agent, wherein the polymer has a styrene to maleic anhydride molar ratio of about 1:1 to 5:1 and an unesterified molecular weight of about 600 to 5,000, esterified with both of (A) a fatty alcohol containing from about 10 to 22 carbon atoms; and (B) a lower alkoxy polyethylene glycol wherein the alkoxy group contains one to four carbon atoms and having an average molecular weight of about 200 to 750, said (A) and (B) being in a mole ratio of from about 0.3 to 1.1:1, and wherein about 4 to 150 percent of the total number of carboxyl carbon atoms of the polymer are half-esterified with (A) and (B).

2. The composition of claim 1 wherein the polymer has an unesterified molecular weight of about 800 to 2,500.

3. The composition of claim 2 wherein the (A) fatty alcohol contains about 16 to 18 carbon atoms.

4. The composition of claim 3 wherein the (B) lower alkoxy polyethylene glycol has an average molecular weight of about 500 to 700.

5. The composition of claim 4 wherein the said (A) and (B) are present in a mole ratio of 0.75:1 to 1: 1.

6. The composition of claim 5 wherein about 4 to 120 percent of the total number of carboxyl carbon atoms of the polymer are half-esterified with (A) and (B).

7. The composition of claim 6 wherein the amine salt is of a water-soluble amine having a boiling point above about 200 8. The composition of claim 7 wherein the extreme pressure agent is amine salt of a fatty acid of from 12 to 20 carbon atoms.

9. The composition of claim 7 wherein the extreme pressure agent is a phosphate ester acid.

10. The composition ofclaim 1 wherein the copolymer ester salt is of a water-soluble salt-forming amine having a boiling point above about 200 C.

11. The composition of claim 10 wherein the amine is triethanolamine.

12. The composition of claim 11 wherein the polymer has a styrene to maleic anhydride ratio of about 1:1 and an average molecular weight, prior to esterification, of about 800 to 2,500.

13. The composition of claim 12 wherein the (A) fatty alcohol contains 16 to 18 carbon atoms.

14. The composition of claim 13 wherein the lower alkoxy polyethylene glycol is methoxy polyethylene glycol.

15. The composition of claim 14 wherein the mole ratio of (A) to (B) is from about 0.75:1 to 1:].

16. The composition of claim 1 which contains about 2 to 15 weight percent of a water-soluble extreme pressure agent based on the weight of the solution of the alkali metal, ammonia or amine, copolymer ester salt and water.

17. The composition of claim 16 wherein the extreme pressure agent is an amine salt of a fatty acid of from 12 to 20 carbon atoms.

18. The composition of claim 16 wherein the extreme pressure agent is a phosphate ester acid.

19. The composition ofclaim 1 comprising from about 20 to 95 weight percent of water based on the total weight of said salt and water, said copolymer ester component of said salt being from about 2 to 40 weight percent of the total composition and said alkali metal, ammonium or water soluble amine component of said salt being from about 0.01 to 50 weight percent of the total composition.

20. The composition of claim 19 comprising from about 70 to weight percent of water based on the total weight of said salt and water. said copolymer ester component of said salt being from about 4 to 20 weight percent of the total composition and said alkali metal, ammonium or water-soluble amine component of said salt being from about 0.5 to 10 percent of the total composition.

: t n: e t 5

Claims

2. The composition of claim 1 wherein the polymer has an unesterified molecular weight of about 800 to 2,500.
3. The composition of claim 2 wherein the (A) fAtty alcohol contains about 16 to 18 carbon atoms.
4. The composition of claim 3 wherein the (B) lower alkoxy polyethylene glycol has an average molecular weight of about 500 to 700.
5. The composition of claim 4 wherein the said (A) and (B) are present in a mole ratio of 0.75:1 to 1:1.
6. The composition of claim 5 wherein about 4 to 120 percent of the total number of carboxyl carbon atoms of the polymer are half-esterified with (A) and (B).
7. The composition of claim 6 wherein the amine salt is of a water-soluble amine having a boiling point above about 200* C.
8. The composition of claim 7 wherein the extreme pressure agent is amine salt of a fatty acid of from 12 to 20 carbon atoms.
9. The composition of claim 7 wherein the extreme pressure agent is a phosphate ester acid.
10. The composition of claim 1 wherein the copolymer ester salt is of a water-soluble salt-forming amine having a boiling point above about 200* C.
11. The composition of claim 10 wherein the amine is triethanolamine.
12. The composition of claim 11 wherein the polymer has a styrene to maleic anhydride ratio of about 1:1 and an average molecular weight, prior to esterification, of about 800 to 2,500.
13. The composition of claim 12 wherein the (A) fatty alcohol contains 16 to 18 carbon atoms.
14. The composition of claim 13 wherein the lower alkoxy polyethylene glycol is methoxy polyethylene glycol.
15. The composition of claim 14 wherein the mole ratio of (A) to (B) is from about 0.75:1 to 1:1.
16. The composition of claim 1 which contains about 2 to 15 weight percent of a water-soluble extreme pressure agent based on the weight of the solution of the alkali metal, ammonia or amine, copolymer ester salt and water.
17. The composition of claim 16 wherein the extreme pressure agent is an amine salt of a fatty acid of from 12 to 20 carbon atoms.
18. The composition of claim 16 wherein the extreme pressure agent is a phosphate ester acid.
19. The composition of claim 1 comprising from about 20 to 95 weight percent of water based on the total weight of said salt and water, said copolymer ester component of said salt being from about 2 to 40 weight percent of the total composition and said alkali metal, ammonium or water soluble amine component of said salt being from about 0.01 to 50 weight percent of the total composition.
20. The composition of claim 19 comprising from about 70 to 90 weight percent of water based on the total weight of said salt and water, said copolymer ester component of said salt being from about 4 to 20 weight percent of the total composition and said alkali metal, ammonium or water-soluble amine component of said salt being from about 0.5 to 10 percent of the total composition.