WO2017012909A1 - Anti-foaming agents - Google Patents

Abstract

The present invention relates to the use of certain (per)fluoropolyether polymers as anti-foam agents in compositions based on hydrogenated or fluorinated oils.

Description

Anti-foaming agents Cross-reference to related applications

This application claims priority to European application No. 15177367.8 and to European application No. 15177365.2, both filed on 17 July 2015, the whole content of these applications being incorporated herein by reference for all purposes.

Technical Field

The present invention relates to the use of certain (per)fluoropolyether polymers as anti-foam agents in compositions based on hydrogenated or fluorinated oils.

Background Art

(Per)fluoropolyether (hereinafter also referred to as ‘PFPE’) oils are widely used as lubricants, hydraulic fluids, and the like as they are essentially immune to degradation by air and corrosive chemical agents, even at high temperatures. To this aim, neutral PFPE are notably used, i.e. PFPE having (per)fluoroalkyl end groups.

However, problems have arisen as neutral PFPE have the tendency to adsorb a lot of air during use, which results in foam formation. This problem is more important as the viscosity of the neutral PFPE increases. Foam formation is influenced by the chemical and physical properties of the oils and also by the operating conditions (e.g. temperature, viscosity, pressure, circulation rate) or can be caused by the presence of additives. However, foam does not circulate in the mechanical equipment and reduces the efficiency of the lubricating oils, resulting in drawbacks such as accelerated wear, overheating, cavitation and noise caused by entrained air in the system. Severe foaming could also lead to breakdown of the normal operation of the mechanical equipment.

Solutions to such a problem have been already proposed in the art. For example, US 3,445,392 E.I. DU PONT DE NEMOURS AND COMPANY discloses that the tendency of perfluorinated polyethers to foam can be overcome by providing a mixture of perfluorinated polyethers of the formula C₃F₇O[CF(CF₃)CF₂O]_nCF₂CF₃ having a narrow molecular weight distribution, as indicated by their volatility range no broader than 140 degrees on the centigrade scale.

As an alternative, foam control additives are conventionally used in industrial processes where foaming occurs. Foam control additives include both anti-foams, i.e. chemical agents that are typically dispersed into the foaming solution to prevent the formation of excessive foam, and defoamers, i.e. substances that are sprayed over and rapidly collapse the existing foam.

Among foam control additives, PFPE polymer derivatives are known in the art.

For example, US 2011/0015420 relates to a perfluoropolyether-modified polysiloxane, which attains a good defoaming effect for organic solvents.

PFPE comprising salified carboxylate chain ends have been disclosed in the art as additives for neutral PFPE oils. For example, EP 0382224 A AUSIMONT S.R.L. discloses perfluoropolyethers having anti-rust properties, suitable for being used as components for lubricating greases or as antirust additives for lubricating oils and greases based on perfluoropolyethers. In particular, the products having antirust properties comprises a mixture of macromolecules having a perfluoropolyether chain of the following structure:
T(CF₂O)_m(CF₂CF₂O)_n[CF₂CF(CF₃)O]_s[CF(CF₃)O]_pCF₂T' (I)
wherein the end groups T and T’, the same or different from each other, are selected from CF₂XO-, C₂F₄XO-, C₃F₆XO-, -COOH, -CONR₁R₂, -COO^-HA⁺ carboxy group salified with an amine R₁R₂HN, -C(=O)CF₃ and its hydroxylated derivative of formula -C(OH)(HO)(CF₃),
wherein X is F or Cl.
However, this patent application only discloses PFPE comprising carboxylate chain ends salified with organic amine, notably morpholine, isobutylamine and triethanolamine.

In addition, metal salts of perfluorinated polyethers having at least one carboxylic acid end group have been disclosed in US 6638622 HITACHI GLOBAL STORAGE TECHNOLOGIES as anti-wetting and corrosion-protective agents for magnetic recording disks and magnetic recording heads. More in particular, said compounds are also referred to as ‘PFPE-COO^-M⁺’ wherein the PFPE is a perfluorinated polyether comprising monomers units having the structure -CF₂O-, -CF₂CF₂O-, CF₂CF₂CF₂O-, -CF(CF₃)O-, -CF(CF₃)CF₂O- or a combination thereof and M⁺ is the metal atom of the salt, preferably an alkali metal, e.g. sodium.

Further to the above, the phase behaviour of perfluoropolyether carboxylates having sodium, potassium or ammonium counter-ions in water to examine the effect of the aqueous binary systems, in terms of hydration and counter-ion binding has been investigated by CABOI, F., et al, Counterion effect on the phase behaviour of perfluoropolyether carboxylates: micelles and liquid crystals in water, Colloids and Surface, 1999, 160, 47-56

However, none of the abovementioned documents discloses or suggests the use of carboxylated PFPE as antifoam agents.

The Applicant perceived that foam formation is also a common problem in functional fluids.

Modern mechanical equipment such as a transmission, hydraulic, engine or gear all require a functional fluid to possess a number of different properties. These properties allow the equipment to operate in different harsh environments, including various regimes of soot/sludge formation, friction, corrosion, thermal decomposition, oxidation, extreme pressure and wear. In many instances the different properties of the functional fluids are unique to a component of the mechanical equipment. This unique properties may depend on chemical interactions between additives, component design, as well as the materials used. Consequently, a number of functional fluids are required to lubricate various components within the mechanical equipment.

Functional fluids are known in the art as compositions comprising at least one oil in admixture with a further ingredient that is selected on the basis of the use intended for the specific functional fluid. However, functional fluids suffer of a number of disadvantages, including notably the formation of foam, which has become more important in the last years, because of the diffusion of functional fluids having low and very low viscosity for energy saving.

US 7098173 GENERAL MOTORS CORPORATION relates to an anti-foam composition to be used in automatic transmission fluids (ATF), said composition comprising perfluoropolyether compounds. Also, US 2004/0121921 GENERAL MOTORS CORPORATION relates to a functional fluid comprising (a) a lubricating oil, (b) an antiwear agent and (c) an antifoam composition comprising a perfluoropolyether compound.

In the abovementioned patent and patent application in the name of General Motors Corporation, suitable PFPE compounds have the following formulae:
R₁-(CF(CF₃)-CF₂-O-)_n-R₂
R₁-(CF₂-CF₂-CF₂-O-)_n-R₂
R₁-(CF₂-CF₂-O-)_n-(CF₂-O-)_m-R₂
R₁-(CF₂-CF(CF₃)-O-)_n-(CF₂-O-)_m-R₂
wherein R₁ and R₂ are functional or non-functional end groups. Among functional end groups, amide, alkoxy, silane, phosphate, carboxyl and -CF₂-CH₂(OCH₂CH₂)_pOH wherein p is from about 1 to about 20 are listed.

None of these documents however discloses PFPE polymers having at least one chain end comprising an acid group and a cationic counter ion as antifoaming additives for hydrogenated oils.

Compositions containing (per)fluoropolyether polymers having two chain ends and comprising at one or both chain ends a carboxylic group in its acid form or in its salt form with monovalent organic and/or inorganic cations have been disclosed in EP 1681339 A SOLVAY SOLEXIS S.P.A. , EP 2025731 A SOLVAY SOLEXIS S.P.A. , EP 0435062 A AUSIMONT S.P.A. and US 5211861 AUSIMONT S.P.A. .

Summary of the invention

The Applicant perceived that there is the industry of lubricants is always looking for novel anti-foam agents.

Thus, the Applicant faced the problem to provide novel anti-foam agents that can be used in both fluorinated and hydrogenated oils, notably in neutral (per)fluoropolyether oils (PFPE) and functional fluids.

The Applicant has surprisingly found that (per)fluoropolyether polymers comprising at least one acid end group salified with organic or inorganic counter-ions can be used as anti-foam additives in neutral PFPE and functional fluids.

Thus, in a first aspect, the present invention relates to the use of a (per)fluoropolyether polymer [polymer (P)] as anti-foam agent, said polymer (P) comprising a (per)fluoropolyether chain [chain (R_pf)] having two chain ends, wherein at least one chain end comprises at least one anionic group [group -A^-] selected from the group comprising, preferably consisting of, carboxylate, sulphate and phosphate, and a cationic group [group C⁺] selected from the group comprising, preferably consisting of, monovalent and divalent inorganic cations and onium compounds.

In a preferred embodiment, said polymer (P) is used as anti-foam agent for neutral (per)fluoropolyether polymers [neutral PFPE].

In another preferred embodiment, said polymer (P) is used as anti-foam agent in a functional fluid composition comprising at least one hydrogenated oil.

In a further aspect, the present invention relates to a method for reducing the formation of foam in a composition comprising at least one neutral PFPE [composition (C)] or in a functional fluid composition [composition (C*)], said method comprising
- providing a composition (C) comprising at least on neutral PFPE and adding at least one polymer (P) to said composition (C), wherein said polymer (P₁) comprises chain (R_pf) as defined above for polymer (P) having two chain ends, wherein at least one chain end comprises at least one group (-A^-) as defined above for polymer (P), and a cationic group [group C⁺] selected from the group comprising, preferably consisting of, monovalent inorganic cations and onium compounds;
or
- providing a composition (C*) comprising at least one hydrogenated oil, and adding at least one polymer (P) to said composition (C*), wherein said polymer (P₂) comprises a chain (R_pf) as defined above for polymer (P) having two chain ends, wherein at least one chain end comprises at least one group (-A^-) as defined above for polymer (P), and a cationic group [group C⁺] selected from the group comprising, preferably consisting of, monovalent and divalent inorganic cations and onium compounds.

Description of embodiments

For the purposes of the present description:
- the term “anti-foam” is intended to indicate the prevention of the formation of foam;
- the acronym “PFPE” is intended to indicate (per)fluoropolyether and, when used as substantive, is intended to mean either the singular or the plural from, depending on the context;
- the term “(per)fluoropolyether” is intended to indicate a fully or partially fluorinated polyether and the prefix "(per)" means that the polyether can be fully or partially fluorinated;
- the expression “neutral PFPE” is intended to indicate PFPE having chain ends comprising neutral groups, such as groups comprising for example (perhalo)alkyl chains;
- the expression “functional fluid composition” is intended to indicate a fluid composition comprising at least one hydrogenated oil in admixture with a further ingredient that is selected on the basis of the intended use, such as for example metal working fluids, such as cutting oils and coolants; engine oils; gear lubricants; hydraulic fluids; automatic transmission fluids; paints coating and inks; compositions for paper industry, oil recovery, construction industry, jet dyeing of textiles, leather processing, chemical processing;
- the expression “monovalent inorganic cations” is intended to indicate an atom or small molecule with a positive charge and a valency of 1, that does not contain carbon in covalent linkage;
- the expression “monovalent and divalent inorganic cations” is intended to indicate an atom or small molecule with a positive charge and a valence of 1 and 2, respectively, that does not contain carbon in covalent linkage;
- the expression “onium compounds” is intended to indicate a cation formally obtained by the protonation of mononuclear parent hydride of a pnictogen (group 15 of the periodic table);
- the expression “composition based on neutral PFPE” is intended to indicate lubricant (or oil) compositions comprising a neutral PFPE as the main component;
- the use of parentheses before and after symbols or numbers identifying compounds, chemical formulae or parts of formulae has the mere purpose of better distinguishing those symbols or numbers from the rest of the text and hence said parentheses can also be omitted.

In a preferred embodiment, said chain (R_pf) is a chain of formula
-(CFX)_aO(R_f)(CFX')_b-
wherein
a and b, equal or different from each other, are equal to or higher than 1, preferably from 1 to 10, more preferably from 1 to 3;
X and X', equal or different from each other, are -F or -CF₃, provided that when a and/or b are higher than 1, X and X’ are -F;
(R_f) comprises, preferably consists of, repeating units R°, said repeating units being independently selected from the group consisting of:
(i) -CFXO-, wherein X is F or CF₃;
(ii) -CFXCFXO-, wherein X, equal or different at each occurrence, is F or CF₃, with the proviso that at least one of X is –F;
(iii) -CF₂CF₂CW₂O-, wherein each of W, equal or different from each other, are F, Cl, H;
(iv) -CF₂CF₂CF₂CF₂O-;
(v) -(CF₂)_j-CFZ-O- wherein j is an integer from 0 to 3 and Z is a group of general formula -O-R_(f-a)-T, wherein R_(f-a) is a fluoropolyoxyalkene chain comprising a number of repeating units from 0 to 10, said recurring units being chosen among the following : -CFXO- , -CF₂CFXO-, -CF₂CF₂CF₂O-, -CF₂CF₂CF₂CF₂O-, with each of each of X being independently F or CF₃ and T being a C₁-C₃ perfluoroalkyl group.

Preferably, chain (R_f) complies with the following formula:
(R_f-I)
-[(CFX¹O)_g1(CFX²CFX³O)_g2(CF₂CF₂CF₂O)_g3(CF₂CF₂CF₂CF₂O)_g4]-
wherein
- X¹ is independently selected from -F and -CF₃,
- X², X³, equal or different from each other and at each occurrence, are independently -F, -CF₃, with the proviso that at least one of X is -F;
- g1, g2 , g3, and g4, equal or different from each other, are independently integers ≥0, such that g1+g2+g3+g4 is in the range from 2 to 300, preferably from 2 to 100; should at least two of g1, g2, g3 and g4 be different from zero, the different recurring units are generally statistically distributed along the chain.

More preferably, chain (R_f) is selected from chains of formula:
(R_f-IIA) -[(CF₂CF₂O)_a1(CF₂O)_a2]-
wherein:
- a1 and a2 are independently integers ≥ 0 such that the number average molecular weight is between 400 and 10,000, preferably between 400 and 5,000; both a1 and a2 are preferably different from zero, with the ratio a1/a2 being preferably comprised between 0.1 and 10;
(R_f-IIB) -[(CF₂CF₂O)_b1(CF₂O)_b2(CF(CF₃)O)_b3(CF₂CF(CF₃)O)_b4]-
wherein:
b1, b2, b3, b4, are independently integers ≥ 0 such that the number average molecular weight is between 400 and 10,000, preferably between 400 and 5,000; preferably b1 is 0, b2, b3, b4 are > 0, with the ratio b4/(b2+b3) being ≥1;
(R_f-IIC) -[(CF₂CF₂O)_c1(CF₂O)_c2(CF₂(CF₂)_cwCF₂O)_c3]-
wherein:
cw = 1 or 2;
c1, c2, and c3 are independently integers ≥ 0 chosen so that the number average molecular weight is between 400 and 10,000, preferably between 400 and 5,000; preferably c1, c2 and c3 are all > 0, with the ratio c3/(c1+c2) being generally lower than 0.2;
(R_f-IID) -[(CF₂CF(CF₃)O)_d]-
wherein:
d is an integer >0 such that the number average molecular weight is between 400 and 10,000, preferably between 400 and 5,000;
(R_f-IIE) -[(CF₂CF₂C(Hal*)₂O)_e1-(CF₂CF₂CH₂O)_e2-(CF₂CF₂CH(Hal*)O)_e3]-
wherein:
- Hal*, equal or different at each occurrence, is a halogen selected from fluorine and chlorine atoms, preferably a fluorine atom;
- e1, e2, and e3, equal to or different from each other, are independently integers ≥ 0 such that the (e1+e2+e3) sum is comprised between 2 and 300.

Still more preferably, chain (R_f) complies with formula (R_f-III):
(R_f-III) -[(CF₂O)_f1(CF(CF₃)O)_f2(CF₂CF(CF₃)O)_f3]-
wherein:
f1, f2 and f3 are independently integers ≥ 0 such that the number average molecular weight is between 400 and 10,000, preferably between 400 and 5,000.

Preferably, said group (A^-) is selected from carboxylate and phosphate. More preferably, said group (A^-) is carboxylate.

Preferably, said monovalent inorganic counter-ion is an alkaline metal, more preferably Li⁺, Na⁺, K⁺, Cs⁺.

Preferably, said divalent cations are selected in the group comprising, more preferably consisting of, alkaline earth metals such as Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺; and transition metals such as Zn²⁺, Cu²⁺, Mn²⁺, Ni²⁺. More preferably, said divalent cations are selected from Mg²⁺, Ca²⁺, Zn²⁺ and Cu^2+.

Preferably, said onium compounds are selected in the group comprising, preferably consisting of, quaternary ammonium cations, quaternary pyridinium cations and quaternary phosphonium cations.

More preferably, said onium compound is an ammonium cation, even more preferably an alkyl-ammonium cation. More preferably, it is selected in the group comprising tetrabutylammonium, tetrapropylammonium, tetraethylammonium, tetramethylammonium.

Preferably, said group (A^-) is bonded to said chain (R_pf) through a bridging group [group (B)], said group (B) being a sigma bond or a linear or branched alkylene chain comprising from 1 to 6 carbon atoms, optionally interrupted by at least one heteroatom, preferably an oxygen atom. More preferably, said group (B) is a sigma bond or a linear or branched alkylene chain comprising from 1 to 3 carbon atom and interrupted by at least one oxygen atom. Even more preferably, said group (B) is a sigma bond or a chain of formula -CH₂-O-CH₂-.

In a preferred embodiment, said polymer (P) comprises one chain end comprising said group (A^-) and said group (C⁺), the other chain end bearing a neutral terminal group (T).

Preferably said group (T) is selected in the group comprising -H, -F, -Cl, -(O)CF₃, a straight or branched (perhalo)alkyl group, more preferably perfluoroalkyl group, comprising from 1 to 3 carbon atoms.

Advantageously, the abovementioned polymer (P) allows to reduce entrained air and hence bubbles formation, thus improving the air release properties of the neutral PFPE or of the functional fluid.

Polymer (P) according to the present invention can be advantageously prepared according to methods known in the art, for example as disclosed in US 4814372 AUSIMONT S.P.A. and in EP 2004722 A SOLVAY SOLEXIS S.P.A. .

The Applicant found that polymer (P₁) comprising chain (R_pf) as defined above for polymer (P) having two chain ends, wherein at least one chain end comprises at least one group (-A^-) as defined above for polymer (P), and a cationic group [group C⁺] selected from the group consisting of, monovalent inorganic cations and onium compounds is particularly useful as anti-foam agent in oils based on neutral PFPEs.

Preferably, said neutral PFPE oils have a kinematic viscosity equal to or higher than 10 cSt at 20°C, more preferably of from 30 to 5000 cSt at 20°C, and even more preferably of from 50 to 1000 cSt at 20°C, measured according to ASTM D445.

Neutral PFPE oils are preferably selected from the following groups:
(1) B-O-[CF(CF₃)CF₂O]_b1'(CFXO)_b2'-B'
wherein:
- X is equal to -F or -CF₃;
- B and B', equal to or different from each other, are selected from -CF₃, -C₂F₅ or -C₃F₇;
- b1' and b2', equal or different from each other, are independently integers ≥0 selected such that the b1'/b2' ratio is comprised between 20 and 1,000 and b1’+b2’ is in the range 5 to 250; should b1’ and b2’ be both different from zero, the different recurring units are generally statistically distributed along the chain. Said products can be obtained by photooxidation of the hexafluoropropylene as described in CA 786877 MONTEDISON S.P.A. 19680406 , and by subsequent conversion of the end groups as described in GB 1226566 MONTECATINI EDISON S.P.A. 19710331 ;
(2) C₃F₇O-[CF(CF₃)CF₂O]_o'-D
wherein
- D is equal to -C₂F₅ or -C₃F_7,
- o' is an integer from 5 to 250,
said products can be prepared by ionic hexafluoropropylene epoxide oligomerization and subsequent treatment with fluorine as described in US 3242218 DU PONT 19660322 ;
(3) {C₃F₇O-[CF(CF₃)CF₂O]_dd’-CF(CF₃)-}₂
wherein
- dd’ is an integer between 2 and 250,
said products can be obtained by ionic telomerization of the hexafluoropropylene epoxide and subsequent photochemical dimerization as reported in US 3214478 DU PONT 19651026 ;
(4) C’-O-[CF(CF₃)CF₂O]_c1'(C₂F₄O)_c2’(CFX)_c3’-C”
wherein
- X is equal to -F or -CF₃;
- C’ and C”, equal to or different from each other, are selected from -CF₃, -C₂F₅ or -C₃F₇;
- c1’, c2’ and c3’ equal or different from each other, are independently integers ≥0, such that and c1’+c2’+c3’ is in the range 5 to 250; should at least two of c1’, c2’ and c3’ be different from zero, the different recurring units are generally statistically distributed along the chain; said products can be manufactured by photooxidation of a mixture of C₃F₆ and C₂F₄ and subsequent treatment with fluorine as described in US 3665041 MONTEDISON S.P.A. 19720523 ;
(5) D-O-(C₂F₄O)_d1'(CF₂O)_d2'-D'
wherein
- D and D', equal to or different from each other, are selected from -CF₃, -C₂F₅ or -C₃F₇;
- d1’ and d2’ equal or different from each other, are independently integers ≥0, such that the d1'/d2' ratio is comprised between 0.1 and 5 and d1’+d2’ is in the range 5 to 250; should d1’ and d2’ be both different from zero, the different recurring units are generally statistically distributed along the chain; said products can be produced by photooxidation of C₂F₄ as reported in US 3715378 MONTEDISON S.P.A. 19730206 and subsequent treatment with fluorine as described in US 3665041 MONTEDISON S.P.A. 19720523 ;
(6) G-O-(CF₂CF₂C(Hal’)₂O)_g1'-(CF₂CF₂CH₂O)_g2'-(CF₂CF₂CH(Hal’)O)_g3'-G'
wherein
- G and G', equal to or different from each other, are selected from -CF₃, -C₂F₅ or -C₃F₇;
- Hal’, equal or different at each occurrence, is a halogen chosen among F and Cl, preferably F;
- g1', g2’, and g’3 equal or different from each other, are independently integers ≥0, such that g1’+ g2’ + g3’ is in the range 5 to 250; should at least two of g1’, g2’ and g3’ be different from zero, the different recurring units are generally statistically distributed along the chain; said products may be prepared by ring-opening polymerizing 2,2,3,3-tetrafluorooxethane in the presence of a polymerization initiator to give a polyether comprising repeating units of the formula: -CH₂CF₂CF₂O-, and optionally fluorinating and/or chlorinating said polyether, as detailed in EP 148482 A DAIKIN INDUSTRIES 19850717 ;
(7) L-O-(CF₂CF₂O)_l'-L'
wherein
- L and L', equal to or different from each other, are selected from -C₂F₅ or-C₃F₇,
- l' is an integer in the range 5 to 250,
said products can be obtained by a method comprising fluorinating a polyethyleneoxide, e.g. with elemental fluorine, and optionally thermally fragmentating the so-obtained fluorinated polyethyleneoxide as reported in US 4523039 THE UNIVERSITY OF TEXAS 19850611 ;
(8) R¹ _f-{C(CF₃)₂-O-[C(R² _f)₂]_kk1’C(R² _f)₂-O}_kk2’-R¹ _f
wherein
- R¹ _f is a perfluoroalkyl group having from 1 to 6 carbon atoms;
- R² _f is equal to -F or perfluoroalkyl group having from 1 to 6 carbon atoms;
- kk1’ is an integer from 1 to 2;
- kk2' represents a number in the range 5 to 250;
said products can be produced by the copolymerization of hexafluoroacetone with an oxygen-containing cyclic comonomer selected from ethylene oxide, propylene oxide, epoxy-butane and/or trimethylene oxide (oxethane) or substituted derivatives thereof and subsequent perfluorination of the resulting copolymer, as detailed in patent application WO WO 87/00538 LAGOW ET AL. 19870129 .

Preferred compositions (C) suitable for the purposes of the invention are lubricant compositions comprising PFPE oils of formulae (1), (4) and (5) cited above.

More preferably, compositions (C) suitable for the purposes of the invention comprise notably:
- lubricants commercially available under the trade name FOMBLIN^® (type Y, M, W, or Z) from Solvay Specialty Polymers Italy, S.p.A..
Lubricants of this family generally comprise at least one oil (i.e. only one or mixture of more than one oil) complying with either of formulae here below:

wherein
m/n is preferably from 20 to 10000, more preferably from 30 to 5000; and
p/q is preferably 0.1/10, more preferably 0.2/5 and even more preferably 0.5/1.5.

Advantageously, said composition (C) or said composition (C*) is a lubricant composition, which can be used for example as metal working fluids, such as cutting oils and coolants; engine oils; gear lubricants; hydraulic fluids; automatic transmission fluids; paints coating and inks; compositions for paper industry, oil recovery, construction industry, jet dyeing of textiles, leather processing, chemical processing.

Even more preferably, said composition (C) comprises the neutral PFPE as the main component, preferably in an amount of at least 60 wt.%, more preferably at least 80 wt %, even more preferably at least 85 wt % based on the total weight of the composition.

Also, the Applicant found that polymer (P₂) comprising a chain (R_pf) as defined above for polymer (P) having two chain ends, wherein at least one chain end comprises at least one group (-A^-) as defined above for polymer (P), and a cationic group [group C⁺] selected from the group comprising, preferably consisting of, monovalent and divalent inorganic cations and onium compounds, is particularly useful as anti-foam agent in hydrogenated oils and notably functional fluids.

Preferably, said composition (C*) comprises at least one hydrogenated base oil, which is preferably a mineral oil or a synthetic oil, such as polyalphaolefins (PAO) and PAGs; esters; silicon oils; polyphenylethers; etc.

Said at least one hydrogenated base oil can be in admixture with different hydrogenated base oils or with water. In the latter case, the composition (C*) is in the form of a water-in-oil emulsion.

Even more preferably, said composition (C*) comprises the hydrogenated base oil(s) as the main component, preferably in an amount of at least 60 wt.%, more preferably at least 80 wt %, even more preferably at least 85 wt % based on the total weight of the composition.

In addition to the neutral PFPE or to the hydrogenated oil, said composition (C) and said composition (C*) can comprise further additives, such as for example antirust agents, antioxidants, thermal stabilizers, pour-point depressants, antiwear agents, including those for high pressures, dispersants, tracers, dyestuffs and fillers.

Examples of dispersants are for example surfactants, preferably non-ionic surfactants, more preferably (per)fluoropolyether surfactants and (per)fluoroalkyl surfactants.

Examples of fillers are organic fillers such as polytetrafluoroethylene (PTFE) and inorganic fillers such as silica and talc.

Embodiments wherein the composition (C) or the composition (C*) are essentially made of the said neutral PFPE in combination with an amount of up to 1 % wt of any of the additives listed above are also encompassed by the present invention.

Preferably, polymer (P) according to the present invention can be added to said composition (C) or to said composition (C*) in an amount of from 0.0001 wt.% (1ppm) to 10 wt.% based on the total weight of said composition,

More preferably, polymer (P₁) is added to composition (C) in an amount of from 0.05 to 8 wt.% and even more preferably from 1 to 5.5 wt.%.

More preferably, polymer (P₂) is added to composition (C*) in an amount of from 0.0001 wt.% (1 ppm) to 10 wt.% based on the total weight of said composition (C), more preferably, from 0.0005 wt.% (5 ppm) to 5 wt.% and even more preferably from 0.001 wt.% (10 ppm) to 1 wt.%.

Preferably, polymer (P) is added to said composition (C) or to said composition (C*) and then a mixing step is performed, for example by high shear mixing.

Thus, in a further aspect, the present invention relates to a composition [composition (C_#)] comprising at least one neutral PFPE oil, at least one polymer (P₁) as defined above and optionally further additives, as defined above.

Preferably, said composition (C_#) comprises the neutral PFPE as the main component, i.e. from 60 to 99.9999 wt.% based on the total weight of the composition, more preferably from 70 to 99.95 wt.% and even more preferably from 90 to 99 wt.%.

Preferably, said composition (C_#) comprises polymer (P₁) in an amount of from 0.0001 wt.% (1ppm) to 10 wt.% based on the total weight of said composition, more preferably from 0.05 to 8 wt.% and even more preferably from 1 to 5.5 wt.%.

When present, said composition (C_#) comprises the further additives in an amount of from 0.1 to 30 wt.% based on the total weight of the composition.

In a further aspect, the present invention relates to a functional fluid composition [composition (C_$)] comprising at least one hydrogenated base oil as defined above, at least one polymer (P₂) as defined above and optionally further additives.

Preferably, said composition (C_$) comprises the hydrogenated base oil(s) as the main component, i.e. from 60 to 99.9999 wt.% based on the total weight of the composition, more preferably from 70 to 99.9995 wt.% and even more preferably from 90 to 99.999 wt.%.

Preferably, said composition (C_$) comprises said polymer (P₂) in an amount of from 0.0001 wt.% (1 ppm) to 10 wt.% based on the total weight of said composition (C), more preferably, from 0.0005 wt.% (5 ppm) to 5 wt.% and even more preferably from 0.001 wt.% (10 ppm) to 1 wt.%.

When present, said composition (C_$) comprises the further additives in an amount of from 0.1 to 30 wt.% based on the total weight of the composition.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

The invention will be now described in more detail with reference to the following examples whose purpose is merely illustrative and not limitative of the scope of the invention.

Examples

MATERIALS

Base oils 1 to 3 and polymers A to C were obtained by Solvay Specialty Polymers Italy S.p.A.

Base oil 1: Fomblin^®M30 PFPE – linear PFPE oil having chemical formula CF₃-[(CF₂CF₂O)_p-(CF₂O)_q]-CF₃ with p/q between 0.9 and 1
average molecular weight about 16,000 Da
kinematic viscosity (measured according to ASTM D445): 280 cSt at 20°C, 45 cSt at 100°C
viscosity index (measured according to ASTM S2270): 338

Base oil 2: Fomblin^®M60 PFPE – linear PFPE oil having chemical formula CF₃-[(CF₂CF₂O)_p-(CF₂O)_q]-CF₃ with p/q between 0.9 and 1
average molecular weight 18,700 Da
kinematic viscosity (measured according to ASTM D445): 550 cSt at 20°C, 86 cSt at 100°C
viscosity index (measured according to ASTM S2270): 343

Base oil 3: Fomblin^®Y25 PFPE – branched PFPE oil having chemical formula
CF₃O-[(CF₂CF(CF₃)O)_n-(CF₂O)_m]-CF₃ with m/n = 40/1
average molecular weight 3,700 Da
kinematic viscosity (measured according to ASTM D445): 250 cSt at 20°C, 10 cSt at 100°C
viscosity index (measured according to ASTM S2270): 108

Polymer A: branched mono-carboxylic acid PFPE having general formula
T(CF₂O)_m(CF₂CF(CF₃)O)_s(CF(CF₃)O)_pCF₂T’
and average molecular weight (Mn) about 3,300 Da.

Polymer B: branched mono-carboxylic acid PFPE having general formula
T(CF₂O)_m(CF₂CF(CF₃)O)_s(CF(CF₃)O)_pCF₂T’
and average molecular weight (Mn) about 2,200 Da.

Polymer C: branched mono-carboxylic acid PFPE having general formula
T(CF₂O)_m(CF₂CF(CF₃)O)_s(CF(CF₃)O)_pCF₂T’
and average molecular weight (Mn) about 1,300 Da.

Commercial RENOLIN UNISYN CLP 320 – fully-synthetic industrial gear and lubricating oil-based on polyalphaolefin (PAO) having low foaming tendency.

Polymer P-I: PFPE carboxylate monofunctional salt of potassium, having the following structure:
CF₃O(CF₂CF(CF₃)O)_p(CF₂O)_qCF₂COO^- K⁺
average molecular weight (Mn) about 3,500 Da by NMR analysis.

Polymer P-II: Commercial Fomblin^® DA305 PFPE obtained from Solvay Specialty Polymers Italy S.p.A - monofunctional carboxylic acid having the following structure:
CF₃O(CF₂CF(CF₃)O)_p(CF₂O)_qCF₂COOH
average molecular weight (Mn) about 3,500 Da by NMR analysis.

METHODS

ASTM D892 – Standard test method for foaming characteristics of Lubricating Oils

This test method is used to determine the foaming characteristics of lubricating oils at 24°C and 93.5°C. The test consists of three sequences performed at different temperatures. A portion of lubricants is aerated by the use of a gas diffuser with air at a flow rate of 94±5 ml/minute (corresponding to 5.64 l /h) at the test temperature of 24°C (Sequence I). The sample is aerated for 5 minutes and the amount of foam generated after disconnecting the gas diffuser is reported. At the end of a 10 minutes settling time, the amount of foam left is recorded. The test is repeated for fresh sample at 93.5°C (Sequence II), and then, after collapsing the foam, at 24°C (Sequence III).

Formulations with good antifoaming performances show sequence foam results in the range of 0 ml/0 ml, and the maximum foam tolerated is 50 ml/0 ml.

Preparation of potassium salts
An aqueous solution containing KOH (1.85 grams, equal to 33.0 mmoles, in 1.85 g of distilled H₂O) was added, under stirring at room temperature to a 100 g of polymer C (32.5 meq of -COOH chain ends). The solution was then heated up to 40°C and this temperature was kept while stirring for 5 hours. The reaction mixture was then cooled to room temperature and the unreacted KOH was carbonated by bubbling carbon dioxide into the solution, until the pH was lower than 7. Water was then evaporated at reduced pressure and the resulting liquid mixture was filtered on PTFE membrane thus removing the potassium carbonate. 99.7 g of liquid product were obtained.
FTIR analysis show a complete conversion of the carboxylic acid groups to the correspondent potassium salt.
The potassium salts of polymers A and B were prepared following the same procedure disclosed above.

Preparation of sodium salts
Sodium salts of polymers A, B and C were prepared following a procedure similar to that described for potassium salt using NaOH instead of KOH, in the same mol amount.

Preparation of c alcium salts
100 g of polymer C (32.5 meq of -COOH chain ends) were diluted with 100 ml of perfluorohexane. Then, 0.91 g (16.2 mmoles) of CaO powder were added under stirring at room temperature. The mixture was then heated up to 40°C and this temperature was kept while stirring for 5 hours. The reaction mixture was then cooled to room temperature and the resulting solution was filtered on PTFE membrane thus removing the unreacted CaO. The solvent was evaporated at reduced pressure and 98.2 g of colourless liquid product were obtained.
The FTIR analysis show a complete conversion of the carboxylic acid groups to the correspondent calcium salt.
The calcium salts of polymers A and B were prepared following the same procedure disclosed above.

Preparati on of magnesium salts
Magnesium salts were prepared following a procedure similar to that described for calcium salts using MgO instead of CaO, in the same mol amount.

Preparation of organic salts with TEA and TBA

Triethanolamine (TEA) salts were prepared following the procedure disclosed in EP 0382224 cited above. TEA salts are representative of EP 0 382 224 cited above.

Following a similar procedure, tetrabutylammonium (TBA) salts were prepared using tetrabutyl ammonium hydroxide.

Example 1

1a) Compositions based on neutral PFPE oils according to the present invention

Each base oil 1, 2 and 3 was added with a PFPE carboxylate comprising monovalent organic and inorganic counter-ions, in the concentration as listed in the following Table 1.

The compositions were then submitted to the test for the evaluation of foam formation, according to ASTM D892.

The results are reported in the following Table 1.

1b) Compositions based on neutral PFPE oils as comparison(*)

Base oils 1, 2 and 3 were submitted to the test for the evaluation of foam formation, according to ASTM D892.

As further comparative examples, base oils 1 to 3 were added with PFPE carboxylate comprising divalent organic and inorganic counter-ions, in the concentrations listed in the following Table 1. These compositions were also submitted to the test for the evaluation of foam formation, according to ASTM D892.

The results of the comparative examples are reported in the following Table 1 and are identified with the symbol (*).
Table 1

No. Ex.	Base oil	Polymer -COO-	Counter ion	Conc. (wt.%)	ASTM D892 (3 cycles, foam volume ml/ml)
					Seq. I	Seq. 2	Seq. 3
1(*)	1	-	-	-	510/190	280/0	520/200
2(*)	1	A	Ca2+	5	0/0	240/0	0/0
3(*)	1	B	Mg2+	5	90/30	20/0	25/0
4(*)	1	B	TEA	5	10/0	500/0	30/0
5	1	B	Na+	5	0/0	0/0	0/0
6	1	B	TBA	5	50/0	25/0	50/0
7	1	B	K+	5	0/0	50/0	20/0
8(*)	2	-	-	-	530/120	270/0	530/130
9(*)	2	C	Ca2+	1.5	205/0	400/0	250/0
10	2	C	K+	1.5	0/0	50/0	0/0
11	2	C	TBA	3	0/0	0/0	0/0
12(*)	2	A	TEA	5	0/0	110/0	0/0
13(*)	3	-	-	-	130/0	0/0	120/0
14	3	B	Na+	5	0/0	0/0	0/0

(*) comparative
TEA: triethanolamine
TBA: tetrabutylammonium

Example 2

2a) Composition No. 15 (comparative)

RENOLIN was left aging for more than 2 years. The properties of this lubricant, including the formation of foam, were evaluated after this aging time.
The kinematic viscosity of the aged oil at 40°C was 325 cSt, measured according to ASTM D445 standard method.
The antifoaming properties of the aged oil were evaluated according to ASTM D892 standard method Sequence I (at 24°C).
This result are reported in Table 1.
The foam volume was 520/250 ml, indicating that probably the antifoaming agent was separated from the composition and loosed its effectiveness.

2b) Composition No. 16

RENOLIN was formulated by adding 50 ppm of polymer P-I.

The antifoaming properties were evaluated according to ASTM D892 standard method Sequence I (at 24°C).
The results are reported in Table 1.

2c) Composition No. 17 (comparative)

RENOLIN was formulated by adding 100 ppm of polymer P-II.

The antifoaming properties were evaluated according to ASTM D892 standard method Sequence I (at 24°C). The results are reported in Table 2.
Table 2

Example No.	Polymer	Amount (ppm)	ASTM D892 – Seq. I 24°C (mL)
15(*)	-	-	520/520
16	P-I	50	0/0
17(*)	P-II	100	40/20

(*) comparative

The above results clearly demonstrate the excellent anti-foam properties of polymer (P₂) according to the present invention, notably when compared to the PFPE having carboxylate end groups. Indeed, while the amount of the foam was acceptable, the foam was dense and it did not decrease even after the end of the test.

Claims (13)

1. A method for reducing the formation of foam in a composition comprising at least one neutral PFPE [composition (C)] or in a functional fluid composition [composition (C*)], said method comprising

   - providing a composition (C) comprising at least on neutral PFPE and adding at least one polymer (P) to said composition (C), wherein said polymer (P₁) comprises a (per)fluoropolyether chain [chain (R_pf)] having two chain ends, wherein at least one chain end comprises at least one anionic group [group -A^-] selected from the group comprising carboxylate, sulphate and phosphate, and a cationic group [group C⁺] selected from the group comprising, preferably consisting of, monovalent inorganic cations and onium compounds;

   or

   - providing a composition (C*) comprising at least one hydrogenated oil, and adding at least one polymer (P) to said composition (C*), wherein said polymer (P₂a (per)fluoropolyether chain [chain (R_pf)] having two chain ends, wherein at least one chain end comprises at least one anionic group [group -A^-] selected from the group comprising carboxylate, sulphate and phosphate, and a cationic group [group C⁺] selected from the group comprising, preferably consisting of, monovalent and divalent inorganic cations and onium compounds.
2. The method according to claim 1, wherein said chain (R_pf) is a chain of formula

   -(CFX)_aO(R_f)(CFX')_b-

   wherein

   a and b, equal or different from each other, are equal to or higher than 1, preferably from 1 to 10, more preferably from 1 to 3;

   X and X', equal or different from each other, are -F or -CF₃, provided that when a and/or b are higher than 1, X and X’ are -F;

   (R_f) comprises, preferably consists of, repeating units R°, said repeating units being independently selected from the group consisting of:

   (i) -CFXO-, wherein X is F or CF₃;

   (ii) -CFXCFXO-, wherein X, equal or different at each occurrence, is F or CF₃, with the proviso that at least one of X is –F;

   (iii) -CF₂CF₂CW₂O-, wherein each of W, equal or different from each other, are F, Cl, H;

   (iv) -CF₂CF₂CF₂CF₂O-;

   (v) -(CF₂)_j-CFZ-O- wherein j is an integer from 0 to 3 and Z is a group of general formula -O-R_(f-a)-T, wherein R_(f-a) is a fluoropolyoxyalkene chain comprising a number of repeating units from 0 to 10, said recurring units being chosen among the following : -CFXO- , -CF₂CFXO-, -CF₂CF₂CF₂O-, -CF₂CF₂CF₂CF₂O-, with each of each of X being independently F or CF₃ and T being a C₁-C₃ perfluoroalkyl group.
3. The method according to claim1 or 2, wherein said group (A^-) is selected from carboxylate and phosphate.
4. The method according to claim 1, wherein said monovalent inorganic cation is an alkaline metal.
5. The method according to claim 4, wherein said alkaline metal is selected from Li⁺, Na⁺, K⁺, Cs⁺.
6. The method according to claim 1, wherein said onium compounds are selected in the group comprising quaternary ammonium cations, quaternary pyridinium cations and quaternary phosphonium cations.
7. The method according to claim 6, wherein said onium compound is an ammonium cation, even more preferably an alkyl-ammonium cation.
8. The method according to claim 1, wherein said divalent inorganic cations is selected from alkaline-earth metals and transition metals.
9. The method according to claim 8, wherein said alkaline earth metal is Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺.
10. The method according to claim 8, wherein said transition metal is Zn²⁺, Cu²⁺, Mn²⁺, Ni²⁺.
11. The method according to any one of claims 1 to 6, wherein said group (A^-) is bonded to said chain (R_pf) through a bridging group [group (B)], said group (B) being a sigma bond or a linear or branched alkylene chain comprising from 1 to 6 carbon atoms, optionally interrupted by at least one heteroatom, preferably an oxygen atom.
12. The method according to claim 1, wherein said polymer (P) comprises one chain end comprising said group (A^-) and said group (C⁺), the other chain end bearing a neutral terminal group (T).
13. The method according to claim 1, wherein said neutral PFPEs oils have a kinematic viscosity equal to or higher than 10 cSt at 20°C, according to ASTM D445.