U.S. patent application number 13/296631 was filed with the patent office on 2012-05-17 for aqueous metal quenching medium.
This patent application is currently assigned to BASF SE. Invention is credited to Stephan Bauer, Erik Bohrer, Frank FISCHER, Antonietta Mauri, Ludger Wegmann.
Application Number | 20120118446 13/296631 |
Document ID | / |
Family ID | 46046713 |
Filed Date | 2012-05-17 |
United States Patent
Application |
20120118446 |
Kind Code |
A1 |
FISCHER; Frank ; et
al. |
May 17, 2012 |
AQUEOUS METAL QUENCHING MEDIUM
Abstract
Aqueous metal quenching media comprising vinyllactam/acrylamide
copolymers
Inventors: |
FISCHER; Frank; (Kirchheim,
DE) ; Bauer; Stephan; (Hochheim, DE) ; Bohrer;
Erik; (Maxdorf, DE) ; Wegmann; Ludger;
(Ludwigshafen, DE) ; Mauri; Antonietta;
(Albersweiler, DE) |
Assignee: |
BASF SE
Ludwigshafen
DE
|
Family ID: |
46046713 |
Appl. No.: |
13/296631 |
Filed: |
November 15, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61414439 |
Nov 17, 2010 |
|
|
|
Current U.S.
Class: |
148/713 ;
148/28 |
Current CPC
Class: |
C08F 220/56 20130101;
C21D 1/60 20130101; C08F 226/10 20130101; C21D 1/63 20130101 |
Class at
Publication: |
148/713 ;
148/28 |
International
Class: |
C21D 1/00 20060101
C21D001/00 |
Claims
1. An aqueous metal quenching medium, comprising a copolymer
comprising in polymerized form: (a) .gtoreq.0.1 and .ltoreq.70% by
weight of a monomer (a) consisting of at least one acrylamide,
methacrylamide, or both, of formula (I)
CH.sub.2.dbd.C(R.sup.1)--C(.dbd.O)--NR.sup.2R.sup.3 (I); (b)
.gtoreq.30 and .ltoreq.99.9% by weight of a monomer (b) consisting
of at least one N-vinyllactam of formula (II) ##STR00003## and (c)
.gtoreq.0 and .ltoreq.50% by weight of a monomer (c) consisting of
at least one further ethylenically unsaturated compound which is
different from the monomer (a) and the monomer (b) wherein the
total amount of the monomer (a) +the monomer (b) +the monomer (c)
equals 100% by weight in copolymerized form, R.sup.1 to R.sup.5 are
each, independently of one another, hydrogen or a linear or
branched, optionally substituted, C.sub.1-C.sub.10-alkyl radical,
and x is an integer from 2 to 8.
2. The medium of claim 1, comprising a copolymer comprising in
polymerized form: (a) .gtoreq.5 and .ltoreq.40% by weight of the
monomer (a); and (b) .gtoreq.60 and .ltoreq.95% by weight of the
monomer (b).
3. The medium of claim 1, wherein R.sup.1, R.sup.4 and R.sup.5 are
each hydrogen, x is an integer from 3 to 5, and R.sup.2 and R.sup.3
are not both hydrogen.
4. The medium of claim 1, wherein at least one of R.sup.2 and
R.sup.3 is an unsubstituted C.sub.2-C.sub.4-alkyl radical.
5. The medium of claim 1, wherein at least one of R.sup.2 and
R.sup.3 is a tert-butyl radical or an isopropyl radical.
6. The medium of claim 1, comprising a copolymer comprising in
polymerized form the monomer (a) consisting of
N-tert-butylacrylamide, N-isopropylacrylamide, or both.
7. The medium of claim 1, wherein the copolymer has a Fikentscher K
value of .gtoreq.30 and .ltoreq.150.
8. The medium of claim 1, wherein a total amount of the copolymer
is .gtoreq.0.1 and .ltoreq.10% by weight.
9. A process for cooling a metal object, the process comprising
contacting a metal object with the aqueous metal quenching medium
of claim 1.
10. An aqueous metal quenching bath, comprising the aqueous metal
quenching medium of claim 1.
11. The medium of claim 2, wherein R.sup.1, R.sup.4 and R.sup.5 are
each hydrogen, x is an integer from 3 to 5, and R.sup.2 and R.sup.3
are not both hydrogen.
12. The medium of claim 2, wherein at least one of R.sup.2 and
R.sup.3 is an unsubstituted C.sub.2-C.sub.4-alkyl radical.
13. The medium of claim 3, wherein at least one of R.sup.2 and
R.sup.3 is an unsubstituted C.sub.2-C.sub.4-alkyl radical.
14. The medium of claim 2, wherein at least one of R.sup.2 and
R.sup.3 is a tert-butyl radical or an isopropyl radical.
15. The medium of claim 2, comprising a copolymer comprising in
polymerized form the monomer (a) consisting of
N-tert-butylacrylamide, N-isopropylacrylamide, or both.
16. The medium of claim 2, wherein the copolymer has a Fikentscher
K value of .gtoreq.30 and .ltoreq.150.
17. The of claim 2, wherein a total amount of the copolymer is
.gtoreq.0.1 and .ltoreq.10% by weight.
18. A process for cooling a metal object, the process comprising
contacting a metal object with the aqueous metal quenching medium
of claim 2.
19. An aqueous metal quenching bath, comprising the aqueous metal
quenching medium of claim 2.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under .sctn.119(e) to U.S.
Provisional Application No. 61/414,439, filed Nov. 17, 2010.
[0002] The present invention relates to an aqueous metal quenching
medium comprising a copolymer CP made up of [0003] .gtoreq.0.1 and
.ltoreq.70% by weight of at least one acrylamide and/or
methacrylamide of the general formula (I) [monomers A], [0004]
.gtoreq.30 and .ltoreq.99.9% by weight of at least one
N-vinyllactam of the general formula (II) [monomers B] and [0005]
.gtoreq.0 and .ltoreq.50% by weight of at least one further
ethylenically unsaturated compound which is different from the
monomers A and monomers B [monomers C], where the total amounts of
the monomers A, B and C add up to 100% by weight (total amount of
monomers) in copolymerized form, where [0006] formula (I) is
CH.sub.2.dbd.C(R.sup.1)--C(.dbd.O)--NR.sup.2R.sup.3 [0007] and
[0008] formula (II) is
##STR00001##
[0008] where [0009] R.sup.1 to R.sup.5 are each, independently of
one another, hydrogen or a linear or branched, optionally
substituted C.sub.1-C.sub.10-alkyl radical and [0010] x is an
integer from 2 to 8.
BACKGROUND OF THE INVENTION
[0011] The present invention relates to the use of a copolymer CP
as component in an aqueous metal quenching medium, in particular a
metal quenching bath.
[0012] The hardening of steels is a widespread method of exerting a
targeted influence on the quality of a steel, for example hardness
and toughness. For this purpose, the steel is firstly heated to a
temperature of about 850.degree. C. and then cooled quickly to room
temperature by means of a metal quenching medium. Above a
temperature of about 400.degree. C., the steel transforms from the
face-centered cubic austenite crystal structure into the desired
metastable tetragonally distorted body-centered martensite crystal
structure, resulting in a significant increase in the hardness of
the steel. In addition to a volume increase of up to 1% by volume
in the transformation from the austenite structure into the
martensite structure (with transformation stresses at, in
particular, the surface of a steel workpiece), excessively rapid
cooling, for example when using water as quenching medium, in a
temperature range below about 400.degree. C. at the same time
results in a volume contraction, as a result of which stresses
arise, particularly in the interior of a steel workpiece. In the
case of large components, e.g. crown gears for wind power plants,
these various stresses lead to cracks and undesirable dimensional
and shape changes. For this reason, water alone cannot be used as
quenching medium for these steel components. An alternative is
provided here by hardening oils. They allow rapid cooling down to a
temperature of about 400.degree. C. However, significantly slow
cooling then occurs because of the reduced thermal conductivity of
the oil. The stresses in the steel microstructure can be decreased
in this way and the steel components have the desired hardness
without deformation and cracks after quenching. Disadvantages of
the hardening oils are the severe soot formation and smoke
evolution during the quenching process and the associated risk of
fire. In addition, the components have to be degreased in an
additional working step after quenching. To circumvent these
problems, aqueous metal quenching media which comprise water
together with from about 1 to 25% by weight of a water-soluble
polymer, for example polyvinyl alcohol, polyethylene glycol,
polyacrylic acid sodium salt and in particular polyvinylpyrrolidone
as active component have been developed.
[0013] Thus, U.S. Pat. No. 3,902,929 discloses metal quenching
baths which comprise from 1 to 13% by weight of
polyvinylpyrrolidone having an average molecular weight in the
range from 5000 to 400 000 g/mol as water-soluble polymers.
[0014] U.S. Pat. No. Re 34,119 describes a metal quenching bath
which comprises, as significant water-soluble polymer, up to 25% by
volume of a polyvinylpyrrolidone having an average molecular weight
in the range from 1 270 000 to 2 240 000 g/mol.
[0015] US-A 2009/65107 discloses metal quenching baths which
comprise, as significant components, inorganic nanoparticles having
an average diameter of from 0.2 to 10 .mu.m, in particular sheet
silicates such as talc, mica, montmorillonite, hectorite or
saponite, and a water-soluble polymer such as polyalkylene glycol,
polyvinylpyrrolidone, polyacrylamide or polyvinyl alcohol.
[0016] US-A 2009/95384 relates to metal quenching baths based on
vinylpyrrolidone/vinylcaprolactam copolymers mixed with substituted
oxazoline polymers, polyalkylene glycols and/or
polyvinylpyrrolidones.
[0017] It was therefore an object of the present invention to
provide copolymers as component for aqueous metal quenching media,
which in the case of a metal object having a temperature of about
850.degree. C., lead to significantly slower cooling compared to
polyvinylpyrrolidone at the same concentration.
BRIEF SUMMARY OF THE INVENTION
[0018] The object was achieved by the use of a copolymer CP as
component in an aqueous metal quenching medium and by an aqueous
metal quenching medium comprising a copolymer CP as component.
[0019] The copolymers CP used according to the invention are made
up of [0020] .gtoreq.0.1 and .ltoreq.70% by weight of at least one
acrylamide and/or methacrylamide of the general formula (I)
[monomers A], [0021] .gtoreq.30 and .ltoreq.99.9% by weight of at
least one N-vinyllactam of the general formula (II) [monomers B]
and [0022] .gtoreq.0 and .ltoreq.50% by weight of at least one
further ethylenically unsaturated compound which is different from
the monomers A and monomers B [monomers C], where the total amounts
of the monomers A, B and C add up to 100% by weight (total amount
of monomers) in copolymerized form, where [0023] formula (I) is
CH.sub.2.dbd.C(R.sup.1)--C(.dbd.O)--NR.sup.2R.sup.3 [0024] and
[0025] formula (II) is
##STR00002##
[0025] where [0026] R.sup.1 to R.sup.5 are each, independently of
one another, hydrogen or a linear or branched, optionally
substituted C.sub.1-C.sub.10-alkyl radical, for example methyl,
ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl,
n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl and isomeric
compounds thereof, optionally substituted by one or more functional
group(s) such as hydroxy, amino, alkoxy such as methoxy or ethoxy,
alkoxycarbonyl such as methoxycarbonyl or ethoxycarbonyl, halogen
such as fluorine, chlorine or bromine groups, and [0027] x is an
integer from 2 to 8.
BRIEF DESCRIPTION OF THE DRAWING
[0028] FIG. 1 depicts cooling curves for several quenching media
and hardening oil.
DETAILED DESCRIPTION OF THE INVENTION
[0029] The radicals R.sup.1 to R.sup.5 are each advantageously
hydrogen or an unsubstituted linear or branched
C.sub.1-C.sub.10-alkyl radical.
[0030] In the monomers A, R.sup.1 is advantageously hydrogen and/or
methyl, with R.sup.1 particularly preferably being hydrogen.
R.sup.2 and R.sup.3 are advantageously not both hydrogen. R.sup.2
and/or R.sup.3 are each advantageously an unsubstituted
C.sub.1-C.sub.4-, in particular C.sub.2-C.sub.4-alkyl radical such
as ethyl, n-propyl, isopropyl, n-butyl, isobutyl and tert-butyl,
with isopropyl and tert-butyl being particularly preferred. It is
particularly advantageous for only one of the radicals R.sup.2 and
R.sup.3 to be a C.sub.2-C.sub.4-alkyl radical. Particular
preference is given to using N-isopropylacrylamide and/or
N-tert-butyl-acrylamide as monomers A. Of course, a copolymer CP
can also comprise mixtures of various monomers A in copolymerized
form.
[0031] The total amount of monomers A in the copolymers CP used
according to the invention is .gtoreq.0.1 and .ltoreq.70% by
weight, preferably .gtoreq.5 and .ltoreq.40% by weight and
particularly preferably .gtoreq.10 and .ltoreq.35% by weight, in
copolymerized form.
[0032] N-Vinyllactams of the general formula (II) are used as
monomers B. Here, R.sup.4 and R.sup.5 can each be, independently of
one another, hydrogen and/or C.sub.1-C.sub.10-alkyl. Hydrogen and
methyl are preferred as R.sup.4 and R.sup.5. Particular preference
is given to hydrogen. The monomer B frequently comprises no methyl
group or a total of only one methyl group.
[0033] According to the invention, x is an integer from 2 to 8,
frequently 3, 4, 5, 6 or 7. In particular, x is an integer from 3
to 5, but particularly advantageously 3 or 5.
[0034] Examples of monomers B are the N-vinyl derivatives of the
following lactams: 2-pyrrolidone, 2-piperidone,
.epsilon.-caprolactam and alkyl derivatives thereof, for example
3-methyl-2-pyrrolidone, 4-methyl-2-pyrrolidone,
5-methyl-2-pyrrolidone, 3-ethyl-2-pyrrolidone,
3-propyl-2-pyrrolidone, 3-butyl-2-pyrrolidone,
3,3-dimethyl-2-pyrrolidone, 3,5-dimethyl-2-pyrrolidone,
5,5-dimethyl-2-pyrrolidone, 3,3,5-trimethyl-2-pyrrolidone,
5-methyl-5-ethyl-2-pyrrolidone, 3,4,5-trimethyl-2-pyrrolidone,
3-methyl-2-piperidone, 4-methyl-2-piperidone,
5-methyl-2-piperidone, 6-methyl-2-piperidone, 6-ethyl-2-piperidone,
3,5-dimethyl-2-piperidone, 4,4-dimethyl-2-piperidone,
3-methyl-.epsilon.-caprolactam, 4-methyl-.epsilon.-caprolactam,
5-methyl-.epsilon.-caprolactam, 6-methyl-.epsilon.-capro-lactam,
7-methyl-.epsilon.-caprolactam, 3-ethyl-.epsilon.-caprolactam,
3-propyl-.epsilon.-caprolactam, 3-butyl-.epsilon.-caprolactam,
3,3-dimethyl-.epsilon.-caprolactam or
7,7-dimethyl-.epsilon.-caprolactam. Of course, a plurality of
different monomers B can also be present in copolymerized form in
the copolymer CP.
[0035] N-Vinylpyrrolidone and/or N-vinylcaprolactam are
particularly advantageously used, with N-vinylpyrrolidone being
particularly preferred as monomer B.
[0036] The total amount of monomers B in the copolymers CP used
according to the invention is .gtoreq.30 and .ltoreq.99.9% by
weight, preferably .gtoreq.60 and .ltoreq.95% by weight and
particularly preferably .gtoreq.65 and .ltoreq.90% by weight, in
copolymerized form.
[0037] Possible monomers C are all ethylenically unsaturated
compounds which differ from the monomers A and B and can be
free-radically copolymerized with these in a simple manner, for
example vinylaromatic monomers such as styrene,
.alpha.-methylstyrene, o-chlorostyrene or vinyltoluenes, vinyl
halides such as vinyl chloride or vinylidene chloride, esters of
vinyl alcohol and monocarboxylic acids having from 1 to 18 carbon
atoms, e.g. vinyl acetate, vinyl propionate, vinyl n-butyrate,
vinyl neodecanoate, vinyl laurate and vinyl stearate, esters of
.alpha.,.beta.-monoethylenically unsaturated monocarboxylic and
dicarboxylic acids preferably having from 3 to 6 carbon atoms, in
particular acrylic acid, methacrylic acid, maleic acid, fumaric
acid and itaconic acid, with alkanols generally having from 1 to
12, preferably from 1 to 8 and in particular from 1 to 4, carbon
atoms, especially methyl, ethyl, n-butyl, isobutyl, pentyl, hexyl,
heptyl, octyl, nonyl, decyl and 2-ethylhexyl acrylates and
methacrylates, dimethyl or di-n-butyl fumarate and maleate,
nitriles of .alpha.,.beta.-monoethylenically unsaturated carboxylic
acids, e.g. acrylonitrile, methacrylonitrile, fumaric dinitrile,
maleic dinitrile, ethers derived from vinyl alcohol and alcohols
having from 1 to 18 carbon atoms, for example n-butyl, cyclohexyl,
dodecyl, ethyl, 4-hydroxybutyl or octadecyl vinyl ethers, and also
C.sub.4-8-conjugated dienes such as 1,3-butadiene (butadiene) and
isoprene. These monomers generally have only a moderate to low
solubility in water under normal conditions [20.degree. C., 1 atm
(absolute)]. Normally, the above-mentioned monomers C are only used
as modifying monomers C in amounts of .ltoreq.10% by weight,
preferably .ltoreq.5% by weight and particularly preferably
.ltoreq.3% by weight, in each case based on the total amount of
monomers C. However, it is advantageous not to use any monomers C
of this type.
[0038] Monomers C which have an increased solubility in water under
the abovementioned conditions are those which comprise either at
least one carboxylic acid or sulfonic acid group or the
corresponding anion thereof and/or at least one amino, ureido or
N-heterocyclic group and/or the ammonium derivatives thereof which
are protonated or alkylated on the nitrogen. Examples which may be
mentioned are acrylic acid, methacrylic acid, fumaric acid, maleic
acid and itaconic acid, vinylsulfonic acid, styrenesulfonic acid
and water-soluble salts thereof, advantageously alkali metal or
ammonium salts thereof, and also 2-vinylpyridine, 4-vinyl-pyridine,
2-vinylimidazole, 2-(N,N-dimethylamino)ethyl acrylate,
2-(N,N-dimethylamino)ethyl methacrylate, 2-(N,N-diethylamino)ethyl
acrylate, 2-(N,N-diethylamino)ethyl methacrylate,
2-(N-tert-butylamino)ethyl methacrylate and
2-(1-imidazolin-2-onyl)ethyl methacrylate. Normally, the
abovementioned monomers C are used as main monomers C in amounts of
.gtoreq.50% by weight, preferably .gtoreq.80% by weight and
particularly preferably .gtoreq.90% by weight, in each case based
on the total amount of monomers C. However, it is advantageous not
to use any monomers C of this type.
[0039] Monomers C which usually increase the internal strength of
the films of a polymer matrix normally have at least one hydroxy
group, at least one epoxy group or at least one carbonyl group or
at least two nonconjugated ethylenically unsaturated double bonds.
Examples are monomers having two vinyl radicals, monomers having
two vinylidene radicals and monomers having two alkenyl radicals.
The diesters of dihydric alcohols with
.alpha.,.beta.-monoethylenically unsaturated monocarboxylic acids
are particularly advantageous, and among these acrylic acid and
methacrylic acid are preferred. Examples of such monomers having
two nonconjugated ethylenically unsaturated double bonds are
alkylene glycol diacrylates and dimethacrylates, e.g. ethylene
glycol diacrylate, 1,2-propylene glycol diacrylate, 1,3-propylene
glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butylene
glycol diacrylate and ethylene glycol dimethacrylate, 1,2-propylene
glycol dimethacrylate, 1,3-propylene glycol dimethacrylate,
1,3-butylene glycol dimethacrylate, 1,4-butylene glycol
dimethacrylate and also divinylbenzene, N,N'-divinyl-ethyleneurea,
vinyl methacrylate, vinyl acrylate, allyl methacrylate, allyl
acrylate, diallyl maleate, diallyl fumarate,
methylenebisacrylamide, cyclopentadienyl acrylate,
triallylcyanurate or triallyl isocyanurate. It can also be
advantageous to use hydroxy-functionalized alkyl acrylates or
methacrylates, for example 2-hydroxyethyl, 2-hydroxypropyl or
4-hydroxybutyl acrylate or methacrylate. The abovementioned
crosslinking monomers C are frequently used in amounts of
.ltoreq.10% by weight, but preferably in amounts of .ltoreq.3% by
weight, in each case based on the total amount of monomers C.
However, particular preference is given to using no monomers C of
this type.
[0040] The total amount of monomers C in the copolymers CP used
according to the invention is .gtoreq.0 and .ltoreq.50% by weight,
preferably .gtoreq.0 and .ltoreq.20% by weight and particularly
preferably .gtoreq.0 and .ltoreq.10% by weight, in copolymerized
form. In a preferred embodiment, the copolymers CP do not comprise
any monomers C in copolymerized form.
[0041] Therefore, in the copolymers CP used according to the
invention, R.sup.1, R.sup.4 and R.sup.5 are each preferably
hydrogen, x is an integer from 3 to 5 and R.sup.2 and R.sup.3 are
not both hydrogen. R.sup.2 and/or R.sup.3 are each particularly
advantageously an unsubstituted C.sub.2-C.sub.4-alkyl radical, in
particular a tert-butyl radical or isopropyl radical. The aqueous
quenching media of the invention therefore advantageously comprise
copolymers CP which comprise N-tert-butylacrylamide and/or
isopropylacrylamide as monomers A in copolymerized form.
[0042] The preparation of the copolymers CP used according to the
invention is not critical and is carried out by polymerization,
preferably by free-radical polymerization, of the monomers A and B
and optionally C. Here, the free-radical polymerization of the
monomers A and B and optionally C can be carried out in the form of
a bulk polymerization or in the form of a solution polymerization
(see, for example S. Dincer, Z. Rzaev, E. Piskin, J. Poly. Research
2006, 13, pages 121 to 131; F. Eeckman, A. Moes, K. Amighi, Eur.
Polym. J. 2004, 40, pages 873 to 881, and I. Nam, J. Bae, K. Jee,
J. Lee, K. Park, Macromol. Res. 2002, 10, pages 115 to 121).
[0043] In the preparation of the copolymers CP according to the
invention, it is possible to place, in each case optionally, a
partial amount or the total amount of monomers A and B and
optionally C in the polymerization vessel at the beginning.
However, it is also possible to introduce, in each case, the total
amount or any remaining amount of monomers A and B and optionally C
during the polymerization reaction. The respective total amount or
any remaining amount of monomers A and B and optionally C can be
introduced discontinuously in one or more portions or continuously
at constant or changing flows into the polymerization vessel. Of
course, the invention also encompasses copolymers CP which are
obtained by the stepwise or gradient mode of operation.
[0044] The copolymers CP used according to the invention
advantageously have a K value in the range .gtoreq.30 and
.ltoreq.150 (determined at 25.degree. C. in a 1% strength aqueous
solution). The copolymers particularly advantageously have a K
value in the range .gtoreq.60 and .ltoreq.120. The setting of the K
values in the preparation of the copolymers CP is well known to
those skilled in the art and is advantageously achieved by
free-radically initiated solution polymerization in the presence of
free-radical chain transfer compounds, also known as free-radical
chain regulators. A person skilled in the art will be familiar with
the determination of the K value (see, for example, H. Fikentscher,
"Systematik der Cellulosen aufgrund ihrer Viskositat in Losung" in
Cellulose-Chemie 13 (1932), pages 58 to 64 and pages 71 to 74, or
Encyclopedia of Chemical Technology, Vol. 21, 2nd edition (1970),
pages 427 and 428).
[0045] The copolymers CP used according to the invention generally
have weight-average molecular weights of .gtoreq.30 000 and
.ltoreq.3 000 000 g/mol and advantageously .gtoreq.50 000 and
.ltoreq.2 500 000 g/mol. The weight-average molecular weights are
determined by gel permeation chromatography using defined
polyvinylpyrrolidone standards (for general methods, see, for
example, M. J. R. Cantow et al., Journal of Polymer Science: Part
A-1, Vol. 5, 1967, pages 1391 to 1394).
[0046] The copolymers CP used according to the invention also have
a solubility at 23.degree. C. and 1 atm (1.013 bar absolute) of
.gtoreq.10 g, advantageously .gtoreq.50 g, per 100 g of deionized
water. In a preferred embodiment, copolymers CP which under the
abovementioned conditions give a solution with deionized water in
any ratio are used.
[0047] The copolymers CP used according to the invention are
advantageously used in the form of aqueous solutions and/or
powder.
[0048] The aqueous metal quenching media of the invention comprise,
as significant component, at least one of the abovementioned
copolymers CP. The aqueous metal quenching media of the invention
particularly advantageously comprise copolymers CP which in
copolymerized form are made up of [0049] .gtoreq.5 and .ltoreq.40%
by weight of monomers A and [0050] .gtoreq.60 and .ltoreq.95% by
weight of monomers B.
[0051] The aqueous metal quenching media of the invention comprise
at least one of the abovementioned copolymers CP in a total amount
of 0.1 and 10% by weight, advantageously .gtoreq.0.1 and .ltoreq.5%
by weight and particularly advantageously .gtoreq.0.5 and
.ltoreq.3% by weight.
[0052] Apart from water and at least one copolymer CP, the aqueous
metal quenching media can further comprise customary additives with
which a person skilled in the art will be familiar, in particular
active compounds to combat microorganisms, for example biocides,
bactericides or fungicides, e.g. polyaminopropylbiguanide
(obtainable from Arch under the trade name Cosmocil.RTM. CQ),
paraformaldehyde, glutaraldehyde, phenoxyethanol,
2,4-dichlorobenzyl alcohol, 2,3-dibromo-3-nitrilopropionamide,
5-chloro-2-methyl-2H-isothiozol-3-one, antifoams such as silicone
oils, fatty alcohol alkoxylates, alcohol alkoxylates, carboxylic
esters or phosphoric esters and/or corrosion inhibitors such as
borax, sodium nitrite, amines, ammonium salts of organic acids,
phosphoric esters, alcohol alkoxylates or 2-butyne-1,4-diol, and
also further compounds such as ethanolamine, polyalkylene oxides,
polyethylene glycols. In general, the total content of the
customary additives in the aqueous metal quenching medium is in the
range .gtoreq.0.1 and .ltoreq.20% by weight.
[0053] The aqueous metal quenching media of the invention therefore
advantageously comprise [0054] .gtoreq.70 and .ltoreq.99.8% by
weight of water [0055] .gtoreq.0.1 and .ltoreq.10% by weight of
copolymer CP and [0056] .gtoreq.0.1 and .ltoreq.20% by weight of
customary additives.
[0057] A person skilled in the art will also be familiar with the
way in which the aqueous metal quenching media of the invention are
employed. Thus, for example, a metal object to be cooled (quenched)
can be sprayed or sprinkled with an aqueous metal quenching medium
according to the invention. It is also possible to pass a metal
object to be quenched through a down-flowing liquid film of aqueous
metal quenching medium. However, a metal object to be quenched is
particularly advantageously dipped (quenched) in an aqueous metal
quenching medium according to the invention, as a result of which
heat energy is removed particularly efficiently, which is why the
use of copolymer CP in such metal quenching baths is particularly
preferred.
[0058] The use according to the invention of copolymers CP makes
available aqueous metal quenching media, in particular aqueous
metal quenching baths, by means of which, in comparison with
corresponding metal quenching media/metal quenching baths based on
polyvinylpyrrolidone, metallic objects, in particular objects made
of iron-, aluminum- and/or titanium-comprising alloys, but in
particular steels, can be cooled significantly more slowly, with
the cooling curves being in the region between the cooling curves
obtained in polyvinylpyrrolidone and in hardening oil based on
mineral oil. It is also of importance that the costly addition of
inorganic nanoparticles or other copolymers can be dispensed with.
Furthermore, any residual amounts of copolymers CP adhering to the
metal objects after cooling can be rinsed off with water in a
simple manner.
[0059] The invention is illustrated by the following nonlimiting
examples.
EXAMPLES
1 Preparation of the Copolymers CP
1.1 Copolymer CP1
[0060] 30.0 g of N-isopropylacrylamide, 120 g of N-vinylpyrrolidone
and 570 g of deionized water were placed at 20-25.degree. C. (room
temperature) and under a nitrogen atmosphere (1.013 bar absolute)
in a 2 l four-necked flask equipped with anchor stirrer, reflux
condenser, introduction facility and nitrogen inlet. While
stirring, the initial charge was heated to 75.degree. C., a
suspension comprising 0.3 g of Wako.RTM. V59 (free-radical
initiator from Wako Pure Chemical Industry, Ltd.) and 12.0 g of
deionized water was then added all at once and the polymerization
mixture was stirred at the abovementioned temperature for another 3
hours. The polymerization mixture was subsequently heated to
85.degree. C. and stirred at this temperature for a further 90
minutes. The polymerization mixture was then brought to a pH of
<4 (pH measurement by means of a sensor at room temperature) by
means of formic acid and stirred at 85.degree. C. for another 3
hours. The polymerization mixture was subsequently cooled to room
temperature and brought to a pH of 7 by addition of
triethanolamine. This gave a polymer solution having a solids
content of 17% by weight. The K value of the copolymer CP1 was
95.
[0061] The solids content was generally determined by drying a
defined amount of the aqueous polymer solution (about 1 g) to
constant weight in an aluminum crucible having an internal diameter
of about 5 cm at 120.degree. C. in a drying oven (about 2 hours).
Two separate measurements were carried out in each case. The values
reported in the examples represent the mean of the respective two
measured results.
[0062] The determination of the Fikentscher K value was generally
carried out at 25.degree. C. using an instrument from Schott, Mainz
(capillary: Micro-Ostwald; type: MO-Ic). The aqueous copolymer
solutions obtained were diluted with deionized water in such a way
that the resulting homogeneous solutions had a polymer content of
1.0% by weight.
1.2 Copolymer CP2
[0063] The preparation of the copolymer CP2 was carried out in a
manner analogous to the preparation of the copolymer CP1 except
that 45.0 g of N-isopropylacrylamide, 105 g of N-vinyl-pyrrolidone
and 570 g of deionized water were used.
[0064] This gave an aqueous copolymer solution having a solids
content of 17% by weight. The K value of the copolymer CP2 was
100.
1.3 Copolymer CP3
[0065] 1.5 g of N-tert-butylacrylamide, 13.5 g of
N-vinylpyrrolidone and 570 g of deionized water were placed at room
temperature and under a nitrogen atmosphere (1.013 bar absolute) in
a 2 l four-necked flask equipped with anchor stirrer, reflux
condenser, introduction facility and nitrogen inlet. While
stirring, the initial charge was heated to 75.degree. C. and a
suspension comprising 0.3 g of Wako.RTM. V59 and 12.0 g of
deionized water was then added all at once. Commencing at the same
time, a mixture of 121.5 g of N-vinylpyrrolidone and 13.5 g of
N-tert-butylacrylamide was metered into the initial charge over a
period of 3 hours at a constant flow rate while stirring. The
polymerization mixture was subsequently heated to 85.degree. C. and
stirred at this temperature for a further 90 minutes. A solution
comprising 0.5 g of Wako.RTM. V59 and 2.0 g of isopropanol was
subsequently added all at once to the polymerization mixture and
the mixture was after-polymerized at 85.degree. C. for 2 hours
while stirring. The polymerization mixture was subsequently brought
to a pH of <4 by means of formic acid (pH measurement of a
sample at room temperature) and stirred at 85.degree. C. for
another 3 hours. The polymerization mixture was subsequently cooled
to room temperature and brought to a pH of 7 by addition of
triethanolamine. This gave a copolymer solution having a solids
content of 20% by weight. The K value of the copolymer CP3 was
75.
1.4 Copolymer CP4
[0066] The preparation of copolymer CP4 was carried out in a manner
analogous to the preparation of the copolymer CP3 except that 3.0 g
of N-tert-butylacrylamide, 12.0 g of N-vinylpyrrolidone and 570 g
of deionized water were initially charged and a mixture of 108 g of
N-vinylpyrrolidone and 27.0 g of N-tert-butylacrylamide was metered
in.
[0067] This gave an aqueous copolymer solution having a solids
content of 20% by weight. The K value of the copolymer CP4 was
60.
1.5 Comparative polymer CCP
[0068] A 20% strength by weight aqueous solution of
polyvinylpyrrolidone having a K value of 97 (Luvitec.RTM. K 90;
sales product of BASF SE) was used as comparative polymer CCP.
1.6 Hardening oil
[0069] Likewise for comparison, the reference oil "Bellini FN" was
used as hardening oil based on mineral oil.
2 Determination of the Cooling Behavior
2.1 Production of the Quenching Media QCP1 to QCP4 and
QCCP/Hardening Oil
[0070] The quenching media QCP1 to QCP4 and QCCP were produced by
diluting the aqueous solutions of the corresponding copolymers CP1
to CP4 and CCP with deionized water to a solids content of 1% by
weight. The hardening oil based on mineral oil was used directly
without further treatment.
2.2 Determination of the Cooling Rates
[0071] The cooling rates were determined using the Smart Quench
testing system from Swerea IVF, Sweden. The cylindrical standard
test body of distortion-resistant Inconel.RTM. 600 having a
diameter of 12.5 mm and a length of 60 mm and a thermocouple in the
center of the body was used and was heated to 860.degree. C. and
subsequently dipped into the associated circulation apparatus
comprising 1.5 liters of the appropriate quenching medium QCP1 to
QCP4 and QCCP or hardening oil at a temperature of 23.degree. C.
The stirring rate in the circulation apparatus was set to 1000 rpm
during the measurements. The cooling measurements were started
automatically at 850.degree. C. The total measurement time was in
each case 20 seconds.
[0072] The corresponding cooling curves are summarized in FIG.
1.
[0073] It can clearly be seen from the cooling curves obtained that
use according to the invention of the copolymers QCP1 to QCP4 in
aqueous quenching media results in a cooling behavior which is in a
region between the cooling behavior given by an aqueous quenching
medium based on a polyvinylpyrrolidone homopolymer and a hardening
oil based on mineral oil.
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