N-Alkylalkanolamine Derivatives for Metalworking

Taminco: M. D. Gernon, G. Verdino; STLE 2015
1
N-Alkylalkanolamines and N-Alkylalkanolamine Derivatives for Metalworking: e.g., Tertiary NAlkylalkanolamine-N-Oxides
Michael D. Gernon & Guy Verdino
Taminco USA, Pace, FL
Abstract:
Certain alkanolamine additives used in metalworking fluids offer significant peripheral benefits in the areas of
corrosion inhibition, coupling, biocide synergy, emulsification and lubricity. In addition to the alkanolamines
themselves, a number of derivatives of the alkanolamines are also useful. Among the many derivatives of
alkanolamines that can be easily produced, the nitrones (derived by oxidation of secondary alkanolamines) and
the tertiary alkanolamine-N-oxides are particularly notable. This talk will focus on tertiary alkanolamines and
derivatives like the alkanolamine-N-oxides as useful heat activated boundary lubricants, antioxidants and
persistent long term fluid stabilizing additives. The properties of the N-alkylalkanolamines will be reviewed,
and the preparation of certain AAA derivatives such as triethanolamine-N-oxide, N-alkyldiethanolamine-Noxides and N,N-dialkylethanolamine-N-oxides will be described. Most importantly, the utility of the Nalkylalkanoalmines and certain alkanolamine derivatives as metalworking fluid additives will be illustrated.
Introduction:
Tertiary amines can be oxidized at nitrogen to form tertiary amine-N-oxides.1,2,3 The oxidants employed for
this reaction are almost exclusively of the peroxide type (i.e., containing an O-O bond; as in peroxides, peracids,
peresters, etc.; the most commonly used oxidant is aqueous hydrogen peroxide). The basic reaction is given
below:
The oxidation of tertiary amines with peroxide type oxidants typically produces the corresponding amine-Noxide rapidly and in good yield. The use of molecular oxygen is far less efficient than is the use of a peroxide
type oxidant, and the air oxidation of a tertiary amine typically yields a variety of products which typically
includes some though not necessarily a majority of the amine-N-oxide. In contrast, the oxidation of primary
amines can lead to a number of products including imines, oximes and nitro compounds. The oxidation of
secondary amines is more predictable than the oxidation of primary amines but not as straightforward as is the
case for tertiary amines. Secondary amines are initially oxidized to hydroxylamines which are usually
immediately further oxidized to nitrones. The nitrone so formed is usually a RedOx stable molecule, but
nitrones are prone to aqueous hydrolysis yielding monoalkylhydroxylamines and aldehyde. So any nitrone
hydrolysis that occurs while strong oxidant is still present will result in further oxidation.
Tertiary amine-N-oxides are used industrially in a number of areas. A concentrated aqueous solution of
N-methylmorpholine-N-oxide (NMMO) is used as a cellulose solvent in the Lenzing Process for producing
renewable textiles. Tertiary amine-N-oxides are the starting materials used in the production of radical/oxygen
scavenging dialkylhydroxylamines via the Cope Elimination. Fatty amine-N-oxides are used as surfactants, and
the conversion of a tertiary amine group to the corresponding N-oxide is a commonly used strategy for
producing a hydrophile within an amphiphilic molecule. Certain amine-N-oxidants are the preferred
Taminco: M. D. Gernon, G. Verdino; STLE 2015
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stoichiometric oxidants for use with toxic catalytic oxidants like osmium tetroxide, and large amounts of amineN-oxides such as NMMO are used in the pharmaceutical and fine chemical intermediates industry. Certain
amine-N-oxides are useful ligands for commercially important organometallic complexes, and a variety of
amine-N-oxides have found use as additives in coatings, fuels, bleaches and functional fluids.
Preparation and Reactions of Tertiary Amine-N-Oxides:
Tertiary amine-N-oxides are usually prepared by the reaction of an equivalent of tertiary amine with an
equivalent of a peroxide type oxidant. For the oxidation of water soluble tertiary amines, aqueous hydrogen
peroxide is most commonly used. For the oxidation of hydrophobic tertiary amines, alternative oxidants such as
peracids may be used. However, owing to the surfactant properties of the amine-N-oxides derived from
hydrophobic tertiary amines, aqueous hydrogen peroxide can usually be used with them as well. The initial
addition of aqueous hydrogen peroxide to the hydrophobic tertiary amine forms an emulsion, but as further
aqueous hydrogen peroxide is added and a larger amount of the surface active amine-N-oxide forms; the
solution becomes a clear and stable micro emulsion. The use of oxidants other than aqueous hydrogen peroxide
is mostly in the realm of academic work and/or for the synthesis of small volume fine chemical intermediates.
The tertiary amine-N-oxides are weak bases (pKa ≈ 5), and initially formed tertiary amine-N-oxides are
sometimes converted to the ammonium form (i.e., N-hydroxyammonium compound) by the addition of an
equivalent of strong acid. The N-hydroxyammonium form of a tertiary amine-N-oxide can be recrystallized,
and thus acidification is oftentimes used as part of a longer purification procedure. In the commercial sector,
tertiary amine-N-oxides are mostly used as produced; typically as a concentrated aqueous solution.
The quintessential reaction of tertiary amine-N-oxides is the Cope Elimination. The Cope Elimination is a
thermally driven β-elimination reaction that converts a tertiary amine-N-oxide into a dialkylhydroxylamine and
an unsaturated compound. The reaction is illustrated for triethylamine-N-oxide (TEAO) below. Generally, the
Cope Elimination is suppressed in more dilute aqueous solutions, but as the water is removed the reaction
occurs more readily. Note that the formation of tertiary amine-N-oxides is exothermic, and, if the temperature
of a tertiary amine oxidation is allowed to rise uncontrolled, then Cope Elimination of the amine-N-oxide may
start to run concurrently with the amine oxidation; degrading the quality of the product. The typical reaction
temperature for a smooth Cope Elimination is ≈ 120 oC; with significant variance possible depending on the
specific tertiary amine-N-oxide and the state of hydration.
Note that the dialkylhydroxylamine formed by Cope Elimination will generally react with the tertiary amine-Noxide starting material to form tertiary amine and nitrone. Thus, practical application of the Cope Elimination
requires that the dialkylhydroxylamine be immediately removed from the reaction zone where tertiary amine-Noxide is present.
Taminco: M. D. Gernon, G. Verdino; STLE 2015
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The tertiary N-alkylalkanolamines (AAA’s) are ideal substrates for N-oxidation. The 2-hydroxyethyl group(s)
present in tertiary AAA’s will hydrogen bond to hydrogen peroxide, and this hydrogen bonding makes the Noxidation of tertiary AAA’s especially convenient. The Cope Elimination of tertiary amine-N-oxides, on the
other hand, is complicated by the fact that at least one of the possible olefinic elimination groups is an enol; and
this eliminated enol will, of course, rapidly rearrange to an aldehyde. Bulk Cope Elimination reactions carried
out with tertiary AAA-N-oxides are tougher to control than those with simple trialkylamine-N-oxides, and the
rearrangement energy of the enol has been known to cause explosions.4 The possible products of Cope
Elimination for dibutylamine-N-oxide (DBAE-N-oxide) and butyldiethanolamine-N-oxide (BDEA-N-oxide)
are shown below.
Tertiary AAA-N-Oxides in Metalworking:
The tertiary AAA-N-oxides produced from selected AAA’s with intermediate length alkyl groups (C4 being
ideal) are particularly useful as additives in metalworking fluids. Longer chain alkyl groups lead to excessive
surface activity and foaming. Shorter chain alkyl groups yield less useful Cope Elimination products. When
certain advantaged AAA-N-oxides undergo slow and continuous Cope Elimination at a hot machined part
surface, then valuable dialkylhydroxylamines and enols are formed. These valuable dialkylhydroxylamines and
enols provide for antioxidant, boundary lubrication and fluid stabilizing properties.
References:
1) Albini, A.; Synthesis 1993, (3), 263-277.
2) Bernier, D.; Wefelscheid, U. K.; Woodward, S.; Organic Preparations and Procedures International
2009, 41(3), 173-210.
3) O’Neil, I.; Science of Synthesis: Houben-Weyl Methods of Molecular Transformations, Volume 40b,
Product Class 3, Amine-N-Oxides 2009, 855-891.
4) Shulman, G. P.; Canadian Journal of Chemistry 1966, 44, 1601-1604.
N-Alkylalkanolamine Derivatives
for Metalworking:
e.g., tertiary N-alkylalkanolamine-N-oxides
STLE 70th annual meeting
Tuesday; April 15; 9:30 am; session 3H
Taminco is a subsidiary of Eastman Chemical Company
Presentation outline
!  Introduction to tertiary AAA-N-oxides
!  AAA-N-oxides as supplementary emulsifiers
!  Tertiary AAA-N-oxides can undergo cope elimination
in-situ; antioxidants; stabilizers
!  MDEA as an ideal complementary amine for
metalworking
!  Synergex® T & MDEA; an all tertiary system boosted by
N-oxides
!  Synergex® amines & metalworking
!  Conclusions
The N-oxidation of amines:
Tertiary amines → amine-N-oxides
Secondary amines → nitrones
Primary amines → hydroxylamine → oxime → nitroalkane → …….
NH3 → HA → H2NNH2 → N2 → N2O → NO → HNO2 → NO2/N2O4 → HNO3
N-oxidation is preferred over
other paths
The N-alkylalkanolamines
N-oxides from tertiary N-alkylalkanolamines
Tertiary amine-N-oxides & basicity
Calculation of an HLB
!  (Hydrophilic MW ÷ total MW) x100/5
!  Hydrophilic MW = 60 for one EO
!  Hydrophilic MW = 104 for two EO
!  Calculation developed for fatty alcohol ethoxylates
!  Calculation provides rough estimate
Alkanolamines & HLB
(round down to integer; floor function)
Hexane:
Synergex® LA
Synergex®:
Synergex® T:
AMP:
MDEA:
MEOA:
HLB = 0
HLB = 7
HLB = 10
HLB = 12
HLB = 13
HLB = 17
HLB = 20
N-oxidation of tertiary amines
creates a less pH sensitive
hydrophilic group
e.g., foam stabilizing DIMLA-N-oxide type surfactants
The Cope elimination
Cope elimination from tertiary
AAA-N-oxides
Antioxidant activity via hydroxylamine formation
Emulsification & surfactant activity
Semi-syn formula
parts
Naphthenic100 oil
50
DBAE-N-OXIDE/MDEA
37.5/62.5
Amide / soap emulsifier
16
BDEA-N-OXIDE/MDEA
34.5/65.5
Unique nonionic oligomeric ester emulsifier
7
DBAE-N-OXIDE/MIPA
70/30
DIPA oleamide 1:1
5
BDEA-N-OXIDE/MIPA
66/34
Palm oleic acid
5
Amine free, vegetable ester, emulsifier and lubricity additive
7.5
Carboxylate rust inhibitor
3
Water
20
TEOA or amine blend
10
Glycol ether DB
0 to 6
Amine blend ratios
DBAE N oxide/MIPA required no
glycol-ether DB – the other three
formulas required 6 parts
Emulsification & surfactant activity
Amine blend ratios
Synthetic formula
parts
DBAE-N-OXIDE/MDEA
37.5/62.5
Water
50
BDEA-N-OXIDE/MDEA
34.5/65.5
Reverse block polymer
25
DBAE-N-OXIDE/MIPA
70/30
TEOA or amine blend
20
BDEA-N-OXIDE/MIPA
66/34
Carboxylate rust inhibitor
5
Isononanoic acid
3
DBAE-N-oxide/MIPA required only 1 part isononanoic acid
– the other four systems required 3 parts
Tertiary AAA-N-oxides undergo
Cope elimination in-situ
Tertiary AAA-N-oxides undergo
Cope elimination in-situ
Tertiary AAA’s don’t readily N-oxidize
and undergo Cope elimination in-situ
Some tertiary AAA’s do N-oxidize and undergo Cope
elimination in-situ when subjected to “machine” conditions
Some tertiary AAA’s do N-oxidize and undergo Cope
elimination in-situ when subjected to “machine” conditions
Tertiary AAA-N-oxides undergo
Cope elimination in-situ
Falex Torque vs
Jaw Load Chart
DBAE N Oxide
EM 706 blend
50% in Oil
DBAE N Oxide
EM 706 blend
25% in Oil
DBAE N Oxide
EM 706 blend
Heated 2 hrs @
250F in Oil at 50%
DBAE N Oxide
EM 706 blend
Heated 2 hrs @
250F in Oil at 25%
250
8.1
10.2
6.9
7.4
350
11.8
12.1
10.6
10.4
450
13.2
15.2
13.0
11.4
550
16.1
17.2
14.4
13.9
650
19.1
18.7
16.7
15.6
750
19.6
19.7
18.0
18.6
850
20.3
23.8
18.3
19.3
950
20.4
23.8
19.2
20.8
1050
22.1
25.1
20.3
20.2
1150
21.0
25.1
21.8
22.4
Average
17.2
19.1
15.9
16.0
Slope
0.0144
0.0175
0.0149
0.0164
Wear in mgs
52
2
Tertiary amine-N-oxides, MDEA & biostability
Synthetic formula
parts
Semi-syn formula
parts
Water
50
Naphthenic 100 oil
50
Reverse block polymer
25
Amide/soap emulsifier
16
TEOA or amine blend
20
Unique nonionic oligomeric ester emulsifier
7
Carboxylate rust inhibitor
5
DIPA oleamide 1:1
5
Isononanoic acid
3
Palm oleic acid
5
Soluble oil formula
parts
Amine free, vegetable ester, emulsifier and
lubricity additive
7.5
Naphthenic 100 oil
77
Carboxylate rust inhibitor
3
Soap sulfonate emulsifier
18
Water
20
TEOA or amine blend
3.5
TEOA or amine blend
10
TOFA 28
1 to 3.5
Amine blend ratios
DBAE-N-OXIDE/MDEA
37.5/62.5
BDEA-N-OXIDE/MDEA
34.5/65.5
DBAE-N-OXIDE/MIPA
70/30
BDEA-N-OXIDE/MIPA
66/34
DBAE-N-OXIDE/MDEA/BDEA
1/3rd each
BDEA-N-OXIDE/MDEA/BDEA
1/3rd each
Glycol ether DB
0 to 6
Tertiary amine-N-oxides, MDEA & biostability
Soluble oil formula
initial pH
pH day 1
pH day 4
pH day 8
pH day 12
TEA
8.55
8.35
7.95
7.35
7.30
MDEA/DBAE-N-OXIDE
8.80
8.55
8.50
8.45
8.25
MDEA/BDEA-N-OXIDE
8.85
8.55
8.50
8.45
8.20
DBAE-N-OXIDE/MIPA
8.85
8.80
8.50
8.10
7.85
BDEA-N-OXIDE/MIPA
8.90
8.60
8.05
7.65
7.55
Tertiary amine-N-oxides, Synergex® T,
MDEA & biostability
Tertiary amine-N-oxides & biostability
initial pH
at 6%
pH day 12
at 6%
CFU
cfu/ml
DBAE-N-OXIDE/MDEA/ Synergex®-T
9.00
8.90
2,700,000
BDEA-N-OXIDE/MDEA/ Synergex®-T
9.00
8.90
1,600,000
initial pH
at 6%
pH day 12
at 6%
CFU
cfu/ml
DBAE-N-OXIDE/MDEA/ Synergex®-T
8.45
8.20
11,000
BDEA-N-OXIDE/MDEA/ Synergex®-T
8.45
8.25
9,900
initial pH
at 6%
pH day 12
at 6%
CFU
cfu/ml
DBAE-N-OXIDE/MDEA/ Synergex®-T
8.80
7.95
6,800,000
BDEA-N-OXIDE/MDEA/ Synergex®-T
8.80
7.75
11,000,000
Synthetic formula
Semi-syn formula
Soluble oil formula
The easiest & most economical
approach is to produce the AAA
derivative in-situ
MDEA as a base molecule to be
elaborated for multiple functions
The following concentrate formula represents a good starting
point for fully synthetic fluids based on Synergex® T & MDEA.
Polartech SGL is a polyalkylene glycol formulated specifically for
use in high performance fully synthetic metalworking fluids.
Synergex® T
MDEA
5%
10% + additional amount needed to reach desired pH in operating fluid
Isononoic acid
8%
Polartech SGL
20%
Phenoxyethanol
Water
Up to 10%
≈ 50%
* The biocontrol system can be changed from phenoxyethanol to 50 ppm BIT (diluted fluid) – use water to
adjust volumes. The phenoxyethanol biocontrol system can be swapped out for BIT (50 ppm effective
concentration operating fluid; adjust concentrate with water).
Tertiary AAA derivatives (ASA/PIBSA adducts)
Tertiary AAA-N-oxides
in-situ oxidation as alternative to H2O2(aq)
Synergex® AAA’s cover a wide
range of HLB
!  HLB = (weight hydrophilic/total weight) x 20
!  HLB = (60/GMW)x20 (for monoalkanolamines)
!  HLB = (104/GMW)x20 (for dialkanolamines)
Hexane:
Synergex® LA:
Synergex®:
Synergex® T:
MDEA:
MEA:
HLB = 0
HLB = 7
HLB = 10
HLB = 12
HLB = 17
HLB = 20
synergexamine.com
Summary
!  Tertiary AAA’s can form N-oxides
!  N-oxides can be manufactured and added to
arbitrary levels
!  N-oxides can be produced in-situ from tertiary AAA’s
!  MDEA is an ideal complementary tertiary AAA
!  Synergex® tertiary AAA’s offer wide range of HLB and
associated functions