U.S. patent application number 15/326076 was filed with the patent office on 2017-08-03 for hydraulic fluids in plastic injection molding processes.
This patent application is currently assigned to Evonik Oil Additives GmbH. The applicant listed for this patent is Evonik Oil Additives GmbH. Invention is credited to Michael Alibert, Thorsten Bartels, Robert Kolb, Frank Lauterwasser, Frank-Olaf Mahling, Stefan Maier, Thomas Schimmel.
Application Number | 20170218295 15/326076 |
Document ID | / |
Family ID | 51355474 |
Filed Date | 2017-08-03 |
United States Patent
Application |
20170218295 |
Kind Code |
A1 |
Lauterwasser; Frank ; et
al. |
August 3, 2017 |
HYDRAULIC FLUIDS IN PLASTIC INJECTION MOLDING PROCESSES
Abstract
The present invention relates to the use of hydraulic fluids in
plastic injection molding processes. Thereby it was surprisingly
found that the use of hydraulic fluids with the right combination
of physical parameters like the viscosity grade, the viscosity
index, the density and the dispersancy allows for significant
energy savings in plastic injection molding processes (PIM). The
PIM process is an industrial process to manufacture plastic parts
at well controlled temperatures, pressures and cycle times. The
energy consumption of the process became more important over the
last years, however, other parameters like process stability and
accuracy of plastic part parameters as well as machine protection
and long oil drain intervals have to be satisfying.
Inventors: |
Lauterwasser; Frank;
(Darmstadt, DE) ; Mahling; Frank-Olaf; (Mannheim,
DE) ; Kolb; Robert; (Gro -Umstadt, DE) ;
Bartels; Thorsten; (Weisenheim, DE) ; Schimmel;
Thomas; (Conshohocken, PA) ; Maier; Stefan;
(Darmstadt, DE) ; Alibert; Michael; (Darmstadt,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Evonik Oil Additives GmbH |
Darmstadt |
|
DE |
|
|
Assignee: |
Evonik Oil Additives GmbH
Darmstadt
DE
|
Family ID: |
51355474 |
Appl. No.: |
15/326076 |
Filed: |
August 7, 2015 |
PCT Filed: |
August 7, 2015 |
PCT NO: |
PCT/EP2015/068272 |
371 Date: |
January 13, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 2209/084 20130101;
C10M 145/14 20130101; C10N 2030/18 20130101; C10N 2030/10 20130101;
C10N 2030/06 20130101; C10M 149/06 20130101; C10N 2030/54 20200501;
C10N 2020/02 20130101; C10N 2040/08 20130101; C10N 2030/02
20130101; C10N 2030/00 20130101; C10N 2030/12 20130101; C10M
2209/084 20130101; C10M 2209/086 20130101; C10M 2217/02 20130101;
C10M 2209/084 20130101; C10M 2217/02 20130101; C10M 2209/084
20130101; C10M 2217/028 20130101; C10M 2209/084 20130101; C10M
2217/023 20130101; C10M 2209/084 20130101; C10M 2217/024 20130101;
C10M 2209/084 20130101; C10N 2020/04 20130101; C10M 2209/084
20130101; C10N 2020/04 20130101 |
International
Class: |
C10M 145/14 20060101
C10M145/14 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 18, 2014 |
EP |
14181237.0 |
Claims
1. A hydraulic fluid composition used for reducing the energy
consumption of a hydraulic system, comprising a hydraulic fluid, in
a plastic injection molding process, wherein the hydraulic fluid
composition comprises (i) a polyalkyl(meth)acrylate viscosity index
improver comprising monomer units of a) 5 to 40 wt. % of one or
more ethylenically unsaturated ester compounds of formula (I)
##STR00005## wherein R is equal to H or CH.sub.3, R.sup.1
represents a linear or branched alkyl group with 1 to 6 carbon
atoms, R.sup.2 and R.sup.3 independently represent H or a group of
the formula --COOR', wherein R' is H or an alkyl group with 1 to 5
carbon atoms, b) 50 to 95 wt. % of one or more ethylenically
unsaturated ester compounds of formula (II) ##STR00006## wherein R
is equal to H or CH.sub.3, R.sup.4 represents a linear or branched
alkyl group with 7 to 15 carbon atoms, R.sup.5 and R.sup.6
independently represent H or a group of the formula --COOR'',
wherein R'' is H or an alkyl group with 6 to 15 carbon atoms, c) 0
to 30 wt. % of one or more ethylenically unsaturated ester
compounds of formula (III) ##STR00007## wherein R is equal to H or
CH.sub.3, R.sup.7 represents a linear or branched alkyl group with
16 to 30 carbon atoms, R.sup.8and R.sup.9 independently represent H
or a group of the formula --COOR''', wherein R''' is H or an alkyl
group with 16 to 30 carbon atoms, and d) 0 to 10 wt. % of at least
one N-dispersant monomer, and (ii) a base oil selected from API
group I, II, III or IV base oils or mixture thereof, wherein the
formulated hydraulic fluid has a fresh oil viscosity index of at
least 160, a viscosity at 40.degree. C. of 15 cSt to 51 cSt, a
density at 15.degree. C. of 800 kg/m.sup.3 to 890 kg/m.sup.3.
2. The hydraulic fluid composition according to claim 1, wherein
the industrial hydraulic application is a plastic injection molding
process or is a process carried out in a hydraulic press.
3. The hydraulic fluid composition according to claim 1, wherein
the weight average molecular weight (M.sub.w) of the
polyalkyl(meth)acrylate viscosity index improver (i) is 20,000 to
100,000 g/mol.
4. The hydraulic fluid composition according to claim 3, wherein
the weight average molecular weight (M.sub.w) of the
polyalkyl(meth)acrylate viscosity index improver (i) is 40,000 to
70,000 g/mol.
5. The hydraulic fluid composition according to claim 1, wherein
the hydraulic fluid has a viscosity index of at least 180, a
viscosity at 40.degree. C. of equal or less than 36 cSt and a
density at 15.degree. C. of less than 860 kg/m.sup.3.
6. The hydraulic fluid composition according to claim 5, wherein
the hydraulic fluid has a viscosity index of at least 250, a
viscosity at 40.degree. C. between 19 cSt and 28 cSt and a density
at 15.degree. C. of less than 840 kg/m.sup.3.
7. The hydraulic fluid composition according to claim 1, wherein
said N-dispersant monomer is of the formula ##STR00008## wherein
R.sup.10, R.sup.11 and R.sup.12 independently are H or an alkyl
group with 1 to 5 carbon atoms and R.sup.13 is either a group
C(Y)X--R.sup.14 with X.dbd.O or X.dbd.NH and Y is (.dbd.O) or
(.dbd.NR.sup.15), where R.sup.15 is an alkyl or aryl group, and
R.sup.14 represents a linear or branched alkyl group with 1 to 20
carbon atoms which is substituted by a group NR.sup.16R.sup.17
where R.sup.16 and R.sup.17 independently represent H or a linear
or branched alkyl group with 1 to 8 carbon atoms, or wherein
R.sup.16 and R.sup.17 are part of a 4 to 8 membered saturated or
unsaturated ring containing optionally one or more hetero atoms
chosen from the group consisting of nitrogen, oxygen or sulfur,
wherein said ring may be further substituted with alkyl or aryl
groups, or R.sup.13 is a group NR.sup.18R.sup.19, wherein R.sup.18
and R.sup.19 are part of a 4 to 8 membered saturated or unsaturated
ring, containing at least one carbon atom as part of the ring which
forms a double bond to a hetero atom chosen from the group
consisting of nitrogen, oxygen or sulfur, wherein said ring may be
further substituted with alkyl or aryl groups.
8. The hydraulic fluid composition according to claim 7, wherein
said dispersant monomer e) of polymer (i) is at least one monomer
selected from the group consisting of N-vinylic monomers,
(meth)acrylic esters, (meth)acrylic amides, (meth)acrylic imides
each with dispersing moieties in the side chain.
9. The hydraulic fluid composition according to claim 7, wherein
said N-dispersant monomer is at least one monomer selected from the
group consisting of N-vinyl pyrrolidone, N,N-dimethylaminoethyl
methacrylate, N,N-dimethylaminopropylmethacrylamide.
10. The hydraulic fluid composition according to claim 1, wherein
the polyalkyl(meth)acrylate viscosity index improver comprises a
polydispersity index of between 1.5 and 2.5.
11. The hydraulic fluid composition according to claim 1, wherein
the polyalkyl(meth)acrylate viscosity index improver comprises
monomer units of a) 5 to 20 wt. % of the compounds of formula (I),
b) 70 to 90 wt. % of the compound of formula (II), and c) 5 to 25
wt. % of the compound of formula (III).
12. The hydraulic fluid composition according to claim 1, wherein
the hydraulic fluid composition comprises 70 to 95 wt. % of the
base oil selected from API group I, II, III or IV base oils or
mixture thereof and 5 to 30 wt. % of the polyalkyl(meth)acrylate
viscosity index improver.
13. The hydraulic fluid composition according to claim 12, wherein
the hydraulic fluid composition comprises 80 to 95 wt. % of the
base oil and 5 to 20 wt. % of the polyalkyl(meth)acrylate viscosity
index improver.
14. The hydraulic fluid composition according to claim 1, wherein
the hydraulic fluid composition comprises a Dispersant-Inhibitor
(DI) package, comprising antioxidants, antifoam agents,
anticorrosion agents and/or at least one Phosphorous or Sulfur
containing antiwear agent.
15. The hydraulic fluid composition according to claim 2, wherein
the weight average molecular weight (M.sub.w) of the
polyalkyl(meth)acrylate viscosity index improver (i) is 20,000 to
100,000 g/mol.
16. The hydraulic fluid composition according to claim 2, wherein
the hydraulic fluid has a viscosity index of at least 180, a
viscosity at 40.degree. C. of equal or less than 36 cSt and a
density at 15.degree. C. of less than 860 kg/m.sup.3.
17. The hydraulic fluid composition according to claim 2, wherein
said N-dispersant monomer is of the formula ##STR00009## wherein
R.sup.10, R.sup.11 and R.sup.12 independently are H or an alkyl
group with 1 to 5 carbon atoms and R.sup.13 is either a group
C(Y)X--R.sup.14 with X.dbd.O or X.dbd.NH and Y is (.dbd.O) or
(.dbd.NR.sup.15), where R.sup.15 is an alkyl or aryl group, and
R.sup.14 represents a linear or branched alkyl group with 1 to 20
carbon atoms which is substituted by a group NR.sup.16R.sup.17
where R.sup.16 and R.sup.17 independently represent H or a linear
or branched alkyl group with 1 to 8 carbon atoms, or wherein
R.sup.16 and R.sup.17 are part of a 4 to 8 membered saturated or
unsaturated ring containing optionally one or more hetero atoms
chosen from the group consisting of nitrogen, oxygen or sulfur,
wherein said ring may be further substituted with alkyl or aryl
groups, or R.sup.13 is a group NR.sup.18R.sup.19, wherein R.sup.18
and R.sup.19 are part of a 4 to 8 membered saturated or unsaturated
ring, containing at least one carbon atom as part of the ring which
forms a double bond to a hetero atom chosen from the group
consisting of nitrogen, oxygen or sulfur, wherein said ring may be
further substituted with alkyl or aryl groups.
18. The hydraulic fluid composition according to claim 8, wherein
said N-dispersant monomer is at least one monomer selected from the
group consisting of N-vinyl pyrrolidone, N,N-dimethylaminoethyl
methacrylate, N,N-dimethylaminopropylmethacrylamide.
19. The hydraulic fluid composition according to claim 2, wherein
the polyalkyl(meth)acrylate viscosity index improver comprises a
polydispersity index of between 1.5 and 2.5.
20. The hydraulic fluid composition according to claim 2, wherein
the polyalkyl(meth)acrylate viscosity index improver comprises
monomer units of a) 5 to 20 wt. % of the compounds of formula (I),
b) 70 to 90 wt. % of the compound of formula (II), and c) 5 to 25
wt. % of the compound of formula (III).
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to the use of hydraulic fluids
in plastic injection molding processes. Thereby it was surprisingly
found that the use of hydraulic fluids with the right combination
of physical parameters like the viscosity grade, the viscosity
index, the density and the dispersancy allows for significant
energy savings in plastic injection molding processes (PIM). The
PIM process is an industrial process to manufacture plastic parts
at well controlled temperatures, pressures and cycle times. The
energy consumption of the process became more important over the
last years, however, other parameters like process stability and
accuracy of plastic part parameters as well as machine protection
and long oil drain intervals have to be satisfying.
BACKGROUND OF THE INVENTION
[0002] Injection molding is a manufacturing process for producing
parts by injecting material into a mold at well controlled
temperatures, pressures and cycle times. Injection molding can be
performed with a host of materials, including metals, glasses,
elastomers, confections, and most commonly thermoplastic and
thermosetting polymers. Material for the part is fed into a heated
barrel, mixed, and forced into a mold cavity, where it cools and
hardens to the configuration of the cavity.
[0003] The power required for this process of injection molding
depends on the various movements in the molding machine, but also
varies between materials used. The book Manufacturing Processes
Reference Guide from Robert Todd states that the power requirements
depend on a material's specific gravity, melting point, thermal
conductivity, part size, and molding rate. Injection molding
machine is actuated by hydraulic system, wherein the electrical
energy is transformed into mechanical energy through hydraulic
energy. The energy reaches the actuators in the form of pressure
and volume flow. While transmitting power through hydraulic forces,
a loss of energy is observed due to flow losses and friction. In
addition, the compression of hydraulic fluid develops frictional
heat, which has to be controlled for example by cooling. Pump type
and control of that pump also contribute heavily to how efficient a
molding machine is in processing the plastic.
[0004] In the state of the art some efforts were made to save
energy by modification of the injection molding machines. In EP 0
403 041 for example special alternating-current servo motors for
the pumps which are connected to the hydraulic consumers are used.
In U.S. Pat. No. 4,020,633 a completely new concept for the whole
hydraulic drive system of the injection molding machine is
disclosed. But none of these concepts touches the hydraulic fluid
that is used here. Therefore it must be possible to realize
additional energy savings by optimizing these fluids.
[0005] EP 2337832 discloses a method of reducing noise generation
in a hydraulic system, comprising contacting a hydraulic fluid
comprising a polyalkyl(meth)acrylate polymer with the hydraulic
system. The hydraulic fluid has a Viscosity Index VI of at least
130. The polyalkyl(meth)acrylate has a molecular weight in the
range of 10 000 to 200 000 g/mol and is obtained by polymerizing a
mixture of olefinically unsaturated monomers, said mixture
comprising preferably 50 to 95 wt % C.sub.9 to C.sub.16 and 1 to 30
wt % of C.sub.1 to C.sub.8.
[0006] Target of the invention described in EP 2337832 was the
reduction of noise which is achieved by increasing oil viscosities
at higher temperatures. For this effect high viscosities and high
densities are beneficial and the high VI of the fluids is used to
increase the viscosity at the operating temperature.
[0007] In the present invention a completely different approach is
used to increase the energy efficiency. A high VI is used to enable
a reduction of the base fluid viscosity. This reduced viscosity in
combination with a low density of the hydraulic base fluid
increases the efficiency of the injection molding process. In
comparison to EP 2337832 it is not expected that hydraulic fluids
according to the present invention decrease the noise level.
[0008] EP 2157159 discloses a hydraulic fluid containing, as a base
oil, an ester containing at least two ring structures. It is
described that the hydraulic fluid has low energy loss due to
compression and exhibits excellent responsiveness when being used
in a hydraulic circuit. Consequently, the hydraulic fluid realizes
energy-saving, high-speed operation and high precision of control
in the hydraulic circuit.
[0009] EP 1987118 discloses the use of a fluid with a viscosity
improving index of at least 130 for the use in hydraulic systems
like engines or electric motors. This fluid comprises a copolymer
of C.sub.1 to C.sub.6 (meth)acrylates, C.sub.7 to C.sub.40
(meth)acrylates and optionally further with (meth)acrylates
copolymerizable monomers in a mixture of an API group II or III
mineral oil and a polyalphaolefine with a molecular weight below
10,000 g/mol. It is neither shown here that such a fluid is also
usable in an injection molding machine nor which specific
composition of the fluid would be applicable in such a machine.
[0010] However, there still exists a need to investigate further on
possible alternative hydraulic fluid compositions to be used in a
hydraulic system subject to high working pressure, like in plastic
injection molding processes.
OBJECT
[0011] The improvement of energy efficiency is a common object in
the technical field of injection molding. Usually such objects are
achieved by construction improvements of the unit providing
mechanical energy of the hydraulic system. However, there is still
a need for further improvements with regard to that object.
Accordingly, the purpose of the present invention was to provide a
method for saving energy, increase productivity, avoid heating,
improve air release and avoid cavitation over a broad temperature
operating window in a hydraulic system used in plastic injection
molding processes.
[0012] Especially was the object of the present invention to
improve the performance of a hydraulic system in a plastic
injection molding machine with energy savings of at least 5% and of
up to 10%, compared to the performance of a machine when run with a
standard fluid having a VI around 100 as recommended by the
producers of injection molding machines. It was also object to
realize an energy saving for single, very energy consuming process
steps of more than 10%.
[0013] Especially it was the object of the present invention to
realize this energy saving by providing a new hydraulic fluid for
the use in plastic injection molding machines.
[0014] Further objects not explicitly discussed here may become
apparent herein below from the prior art, the description, the
claims or exemplary embodiments.
DESCRIPTION OF THE INVENTION
[0015] The above-indicated prior art documents relating to
injection molding processes try to reduce energy consumption, but
without changing oil parameters. After an exhaustive investigation,
the inventors have unexpectedly found that the hydraulic fluid
plays a crucial role for saving energy in plastic injection molding
processes, and in particular that some hydraulic fluid compositions
adjusted to the right physical parameters, allow for energy savings
of up to 5% or more in the overall plastic injection molding
process (PIM), or more than 10%, mostly up to 15% for certain step
of the PIM process. Indeed, by adjusting the viscosity grade, the
viscosity index, the density and dispersancy of the hydraulic fluid
as defined in claim 1, the inventors have found that a significant
amount of energy can be advantageously saved, even by operating at
high pressure conditions as it is usual in PIM processes.
[0016] In detail, the objects discussed above have been solved by a
novel method of reducing the energy consumption of a hydraulic
system in an industrial hydraulic application, preferably in a
plastic injection molding process or in a process comprising a
hydraulic press. In this method a hydraulic fluid is used in a
plastic injection molding process. The hydraulic fluid composition
thereby comprises (i) a polyalkyl(meth)acrylate viscosity index
improver and (ii) a base oil.
[0017] The polyalkyl(meth)acrylate viscosity index improver (i)
thereby comprises at least monomer units a) and b) and optionally
monomer units c) and/or d). Preferably the component (i) has a
weight average molecular weight (M.sub.w) from 20,000 to 100,000
g/mol. More preferred the molecular weight M.sub.w is between
30,000 and 85,000 g/mol and especially preferred between 40,000 and
70,000 g/mol. The polydispersity index of the
polyalkyl(meth)acrylate viscosity index improver is between 1 and
4, preferred between 1.2 and 3.0 and most preferred between 1.5 and
2.5.
[0018] The polyalkyl(meth)acrylate viscosity index improver (i)
contains 5 to 40 wt. %, preferred 7 to 30 wt. %, more especially
preferred 10 to 25 wt. % of repeating units that have been obtained
by the copolymerization of monomers a) and 50 to 95 wt. %,
preferred 60 to 93 wt. %, more especially preferred 70 to 90 wt. %
of repeating units that have been obtained by the copolymerization
of monomers b). In a special embodiment of the invention the amount
of the compound of formula (II) is between 75 and 90 wt. %,
especially preferred between 70 and 80 wt. %.
[0019] Monomers a) thereby are one or more ethylenically
unsaturated ester compounds of formula (I)
##STR00001##
[0020] wherein R is equal to H or CH.sub.3, R.sup.1 represents a
linear or branched alkyl group with 1 to 6 carbon atoms and R.sup.2
and R.sup.3 independently represent H or a group of the formula
--COOR', wherein R' is H or an alkyl group with 1 to 5 carbon
atoms.
[0021] Examples of component a) are, among others, (meth)acrylates,
fumarates and maleates, which derived from saturated alcohols such
as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl
(meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate,
tert-butyl (meth)acrylate and/or pentyl (meth)acrylate; cycloalkyl
(meth)acrylates, like cyclopentyl (meth)acrylate. Methacrylates are
even preferred over acrylates.
[0022] Monomers b) are one or more ethylenically unsaturated ester
compounds of formula (II)
##STR00002##
[0023] wherein R is equal to H or CH.sub.3, R.sup.4 represents a
linear or branched alkyl group with 7 to 15 carbon atoms and
R.sup.5 and R.sup.6 independently represent H or a group of the
formula --COOR'', wherein R'' is H or an alkyl group with 6 to 15
carbon atoms.
[0024] Among these are (meth)acrylates, fumarates and maleates that
derive from saturated alco-hols, such as n-hexyl (meth)acrylate,
2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate,
2-tert-butylheptyl (meth)acrylate, octyl (meth)acrylate,
3-isopropylheptyl (meth)acrylate, nonyl (meth)acrylate, decyl
(meth)acrylate, undecyl (meth)acrylate, 5-methylundecyl
(meth)acrylate, dodecyl (meth)acrylate, 2-methyldodecyl
(meth)acrylate, tridecyl (meth)acrylate, 5-methyltridecyl
(meth)acrylate, tetradecyl (meth)acrylate and/or pentadecyl
(meth)acrylate.
[0025] The polyalkyl(meth)acrylate viscosity index improver (i) may
also contain further components that are in form of a monomer
copolymerizable with at least one of the components a) and b).
These further monomers are especially the components c) and d),
with c) in a maximal concentration of 30 wt. % and d) in a maximal
concentration of 10 wt. %.
[0026] Monomers c) thereby represent one or more ethylenically
unsaturated ester compounds of formula (III)
##STR00003##
[0027] wherein R is equal to H or CH.sub.3, R.sup.7 represents a
linear or branched alkyl group with 16 to 30 carbon atoms and
R.sup.8 and R.sup.9 independently represent H or a group of the
formula --COOR''', wherein R''' is H or an alkyl group with 16 to
30 carbon atoms.
[0028] Examples of component c) are, among others, (meth)acrylates,
fumarates and maleates, which derived from saturated alcohols such
as 2-methylhexadecyl (meth)acrylate, heptadecyl (meth)acrylate,
5-isopropylheptadecyl (meth)acrylate, 4-tert-butyloctadecyl
(meth)acrylate, 5-ethyloctadecyl (meth)acrylate,
3-isopropyloctadecyl (meth)acrylate, octadecyl (meth)acrylate,
nonadecyl (meth)acrylate, eicosyl (meth)acrylate, cetyleicosyl
(meth)acrylate, stearyleicosyl (meth)acrylate and/or docosyl
(meth)acrylate.
[0029] Optionally, the polyalkyl(meth)acrylate viscosity index
improver (i) contains 5 to 20 wt. % of the monomers a), 70 to 90
wt. % of the monomers b) and 2 to 25 wt. % of the monomers c) in
polymerized form.
[0030] Monomers d) are at least one N-dispersant monomer. Preferred
this N-dispersant monomer is of the formula (IV)
##STR00004##
[0031] wherein R.sup.10, R.sup.11 and R.sup.12 independently are H
or an alkyl group with 1 to 5 carbon atoms and R.sup.13 is either a
group C(Y)X--R.sup.14 with X.dbd.O or NH and Y is (.dbd.O) or
(.dbd.NR.sup.15), where R.sup.15 is an alkyl or aryl group.
R.sup.14 represents a linear or branched alkyl group with 1 to 20
carbon atoms which is substituted by a group NR.sup.16R17, where
R.sup.16 and R.sup.17 independently represent H or a linear or
branched alkyl group with 1 to 8 carbon atoms, or wherein R.sup.16
and R.sup.17 are part of a 4 to 8 membered saturated or unsaturated
ring containing optionally one or more hetero atoms chosen from the
group consisting of nitrogen, oxygen or sulfur, wherein said ring
may be further substituted with alkyl or aryl groups.
[0032] Alternatively R.sup.13 is a group NR.sup.18R.sup.19, wherein
R.sup.18 and R.sup.19 are part of a 4 to 8 membered saturated or
unsaturated ring, containing at least one carbon atom as part of
the ring which forms a double bond to a hetero atom chosen from the
group consisting of nitrogen, oxygen or sulfur, wherein said ring
may be further substituted with alkyl or aryl groups.
[0033] Preferably, said dispersant monomer d) of polymer (i) is at
least one monomer selected from the group consisting of N-vinylic
monomers, (meth)acrylic esters, (meth)acrylic amides, (meth)acrylic
imides each with N-containing, dispersing moieties in the side
chain. In particular it is preferred that the N-dispersant monomer
is at least one monomer selected from the group consisting of
N-vinyl pyrrolidone, N,N-dimethylaminoethyl methacrylate and
N,N-dimethylaminopropylmethacrylamide.
[0034] Optionally the polyalkyl(meth)acrylate viscosity index
improver (i) contains 5 to 25 wt. % of the monomers c) and 1 to 7
wt. % of the monomers d), both in polymerized form. Especially the
viscosity index improver (i) contains 10 to 20 wt. % of the
monomers c) and 2 to 5 wt. % of at least one N-dispersant monomer
d) in polymerized form.
[0035] For this invention the base oil (ii) is selected from API
group I, II, III or IV base oils or a mixture thereof. By using one
of these base oils or mixtures of at least two of these base oils
together with the viscosity index improver (VII) described above
the formulated hydraulic fluid of this invention has a fresh oil
viscosity index of at least 160, a viscosity at 40.degree. C. of 15
cSt to 51 cSt and a density at 15.degree. C. of 800 kg/m.sup.3 to
890 kg/m.sup.3. Especially preferred are API group IV base oils in
form of polyalphaolefin (PAO) or mixtures of API group I to IV base
oils containing at least 50 wt. % polyalphaolefins.
[0036] Synthetic hydrocarbons, especially polyolefins are well
known in the art as API group IV base oils. These compounds are
obtainable by polymerization of alkenes, especially alkenes having
3 to 12 carbon atoms, like propene, 1-hexene, 1-octene, 1-decene
and 1-dodecene, or mixtures of these alkenes. Preferred PAOs have a
number average molecular weight in the range of 200 to 10000 g/mol,
more preferably 500 to 5000 g/mol.
[0037] In particular the hydraulic fluid composition comprises 70
to 95 wt. %, more preferably 80 to 95 wt. % and even more
preferably 80 to 90 wt. % of the base oil (ii) selected from API
group I, II, III or IV base oils or mixture thereof and 5 to 30 wt.
%, more preferably 5 to 20 wt. % and even more preferred 10 to 20
wt. % of the polyalkyl(meth)acrylate viscosity index improver (i).
Especially suitable are hydraulic fluids corresponding to this
invention having a viscosity index of at least 180, preferred of at
least 200, especially preferred of at least 250 and a viscosity at
40.degree. C. of 15 cSt to 36 cSt, preferred between 15 cSt and 28
cSt, especially preferred between 19 cST and 28 cST. Furthermore it
is advantageous, if the hydraulic fluid has a density at 15.degree.
C. of 800 kg/m.sup.3 to 860 kg/m.sup.3, preferred of 800 kg/m.sup.3
to 840 kg/m.sup.3.
[0038] By calculating the hydraulic fluid composition it has to be
considered that the viscosity index improver (VII) might be added
in a solvent. In a preferred embodiment of this invention this
solvent is also an API group I, II, III or IV oil. It is especially
preferred that this solvent is identical to the base oil of the
composition. Independently from the solvent that is used here it
has to be calculated as part of the base oil in the composition.
Usually the VII solution that is added contains 20 to 40 wt. %
solvent.
[0039] The viscosity index can be determined according to ASTM D
2270.
[0040] The hydraulic fluid composition according to this invention
may also contain a Dispersant-Inhibitor package (DI package) to
improve parameters like foam, corrosion, oxidation, wear and
others. This DI package may comprise antioxidants, antifoam agents,
anticorrosion agents and/or at least one Phosphorous or Sulfur
containing antiwear agent.
Technical Benefits of This Invention
[0041] High VI hydraulic fluids are typically applied in mobile
applications such as excavators. In these applications the
hydraulic fluid has to deal with a broad variety of
temperatures--very low starting temperatures in winter and very
high temperatures under heavy load conditions. The high VI of the
fluid is required to keep the viscosity as close as possible to the
optimum. The optimum is defined by the balance between mechanical
efficiency which requires a thin oil and volumetric efficiency
which requires a thick oil to minimize losses by internal leakage
in the pump. In regular operating conditions and especially under
heavy load conditions volumetric efficiency becomes the dominant
factor and the viscosity index improver can greatly improve the
efficiency by increasing the viscosity of the fluid.
[0042] The injection molding application is completely different
compared to an excavator. The outside temperature is constant, the
work cycle is well defined and heavy load conditions are avoided if
possible. For this reason the oil temperature is rather constant
and high VI base fluids are generally not used. Usually ISO46
monograde fluids are recommended by the producers of injection
molding machines.
[0043] For these reasons it would not be expected to see an
advantage of high VI fluids in an application as injection molding,
but surprisingly we found significant energy savings when
low-viscosity hydraulic fluids with high VI were used. Completely
opposed to the well-described energy savings with high VI fluids in
excavators the efficiency increase in injection molding is largest
under low load conditions.
[0044] Surprisingly said method as defined above respectively in
claim 1 not only achieves the above-mentioned objectives, but also
advantageously provides an increased oil life time with consequent
longer drain intervals for the hydraulic system.
[0045] Furthermore, the system performance of the hydraulic system
can be improved. The expression system performance means the work
productivity being done by the hydraulic system within a defined
period of time. Particularly, the system performance can be
improved at least 5%, more preferably at least 10%. In preferred
systems, the work cycles per hour can be improved.
Synthesis of the Viscosity Index Improver
[0046] For the synthesis of the polyalkyl(meth)acrylate viscosity
index improver (i) the monomer mixtures described above can be
polymerized by any known method. Conventional radical initiators
can be used to perform a classic radical polymerization. These
initiators are well known in the art. Examples for these radical
initiators are azo initiators like 2,2'-azodiisobutyronitrile
(AIBN), 2,2'-azobis(2-methylbutyronitrile) and 1,1
azo-biscyclohexane carbonitrile; peroxide compounds, e.g. methyl
ethyl ketone peroxide, acetyl acetone peroxide, dilauryl peroxide,
tert.-butyl per-2-ethyl hexanoate, ketone peroxide, me-thyl
isobutyl ketone peroxide, cyclohexanone peroxide, dibenzoyl
peroxide, tert.-butyl per-benzoate, tert.-butyl peroxy isopropyl
carbonate, 2,5-bis(2-ethylhexanoyl-peroxy)-2,5-dimethyl hexane,
tert.-butyl peroxy 2-ethyl hexanoate, tert.-butyl
peroxy-3,5,5-trimethyl hexanoate, dicumene peroxide, 1,1 bis(tert.
butyl peroxy) cyclohexane, 1,1 bis(tert. butyl peroxy)
3,3,5-trimethyl cyclohexane, cumene hydroperoxide and tert.-butyl
hydroperoxide.
[0047] Poly(meth)acrylates with a lower molecular weight can be
obtained by using chain transfer agents. This technology is
ubiquitously known and practiced in the polymer industry and is
described in Odian, Principles of Polymerization, 1991.
[0048] Furthermore, novel polymerization techniques such as ATRP
(Atom Transfer Radical Polymerization) and or RAFT (Reversible
Addition Fragmentation Chain Transfer) can be applied to obtain
useful polymers derived from alkyl esters. These methods are well
known. The ATRP reaction method is described, for example, by J-S.
Wang, et al., J. Am. Chem. Soc., Vol. 117, pp. 5614-5615 (1995),
and by Matyjaszewski, Macromolecules, Vol. 28, pp. 7901-7910
(1995). Moreover, the patent applications WO 96/30421, WO 97/47661,
WO 97/18247, WO 98/40415 and WO 99/10387 disclose variations of the
ATRP explained above to which reference is expressly made for
purposes of the disclosure. The RAFT method is extensively
presented in WO 98/01478, for example, to which reference is
expressly made for purposes of the disclosure.
[0049] The polymerization can be carried out at normal pressure,
reduced pressure or elevated pressure. The polymerization
temperature is also not critical. However, in general it lies in
the range of -20 to 200.degree. C., preferably 60 to 120.degree.
C., without any limitation intended by this. The polymerization can
be carried out with or without solvents. The term solvent is to be
broadly understood here. According to a preferred embodiment, the
polymer is obtainable by a polymerization in API Group I, II or III
mineral oil or in API group IV synthetic oil.
EXAMPLES
[0050] The invention is illustrated further in the following
non-limiting example and the comparative example (reference oil).
The example below serves for further explanation of preferred
embodiments according to the present invention, but are not
intended to restrict the invention. All results are shown in Table
1 and Table 2.
Testing and Oils
[0051] For determining the energy consumption, different test oils
were compared with a reference (ISO VG 46 monograde Castrol Hyspin
DF Top 46, VI=100).
[0052] The following hydraulic fluids are used:
TABLE-US-00001 TABLE 1 Hydraulic fluid formulations density
KV.sub.40 KV.sub.100 @15.degree. C. Formulation [mm.sup.2/s]
[mm.sup.2/s] VI [kg/L] Comparative 0.85% Hitec 521 Fresh oil: 46.6
7.6 131 0.847 Example 1 8% Nexbase 3060 Fill for trial: 46.6 7.6
130 91.15% Nexbase 3080 After trial: 46.5 7.6 130 Comparative Aral
Forbex SE Fresh oil: 47.2 8.2 148 0.973 Example 2 Fill for trial:
47.0 8.2 149 After trial: 46.9 8.2 149 Reference Castrol Hyspin
Fresh oil: 45.7 6.7 100 0.873 Oil DF Top 46 Fill for trial: 45.7
6.7 100 After trial: 45.7 6.7 100 Example 1 5.8% PAMA-1 Fresh oil:
46.3 8.4 160 0.851 0.85% Hitec 521 Fill for trial: 46.3 8.4 160 21%
Nexbase 3080 After trial: 46.1 8.3 158 72.35% Nexbase 3060 Example
2 14.2% PAMA-1 Fresh oil: 46.6 9.8 203 0.853 0.85% Hitec 521 Fill
for trial: 46.2 9.7 201 17.45% Nexbase 3060 After trial: 46.0 9.6
200 67.5% Nexbase 3043 Example 3 8.8% PAMA-1 Fresh oil: 32.0 7.0
189 0.842 DI package Fill for trial: 32.1 7.0 189 Nexbase 3043 +
3060 After trial: 32.3 7.0 189 Example 4 20% PAMA-2 Fresh oil: 25.7
7.5 285 0.831 DI package Fill for trial: 25.8 7.5 283 PAO-2 After
trial: 25.7 7.4 281
[0053] The polyalkylmethacrylate viscosity index improver PAMA-1
consists of 13 wt. % of methyl methacrylate and 87 wt. % of
C.sub.12-14 alkyl methacrylates (M.sub.w=52,000 g/mol, PDI=2.1),
dissolved in highly refined mineral oil.
[0054] The polyalkylmethacrylate viscosity index improver PAMA-2
consists of 10 wt. % of methyl methacrylate and 90 wt. % of
C.sub.12-15 alkyl methacrylates (M.sub.w=58,000 g/mol, PDI=2.0),
dissolved in highly refined mineral oil.
TABLE-US-00002 Properties Method Kinematic viscosity at 40.degree.
C., ASTM D445 mm.sup.2/s Kinematic viscosity at 100.degree. C.,
ASTM D445 mm.sup.2/s VI ASTM D2270 Density at 15.degree. C., kg/L
ASTM D1298
[0055] The injection molding machine that was used to create the
data was Krauss Maffei KM 80/380 CX. The energy consumption of the
hydraulic pump was calculated by measuring voltage and current of
the pump motor with external test equipment (measuring amplifier MX
840 PAKAP; element for voltage recording MX 403 B, 1000V; both from
Hottinger Baldwin Messtechnik GmbH). Before testing the system was
flushed with the hydraulic fluid to be used and the oil parameters
were checked to ensure that the previous oil was properly purged
and no mixing with previous oils occurred. Table 1 shows
viscometric data for fresh oils, oil fill for trial and for the oil
collected after the trial.
[0056] During testing, molding cycles were run with a
PLEXIGLAS.RTM.-molding compound which was, in cycle A, covered with
CoverForm.RTM. Reactive-Liquid cf30OA monomer mixture.
[0057] The evaluation of data has focused on process steps without
polymer to avoid any influence of polymer properties on the
results.
[0058] FIG. 1: Description of a typical injection molding cycle
[0059] The cycle begins when the mold closes (Step 1), followed by
building up a pressure (Step 2a) which is required to keep the mold
closed during injection. After moving the extruder to the mold
(Step 2b), material is injected (Step 3) and a working pressure is
maintained to compensate material shrinkage during molding (Step
4). Optionally, the work piece can be coated with a CoverForm.RTM.
process step (Step 4.1, applied in Cycle A). The extruder is moved
back when the cooling phase has started (Steps 5 and 6). At the end
of the cooling phase the mold is opened (Step 7) and the work piece
can be removed (Step 8).
[0060] Table 2 shows the differences in energy consumption (savings
are negative values) found for cycle A, cycle B and an evaluation
of Step 1 and Step 2 taken from cycle A data.
Step 1+Step 2 (2a+2b)+Step 4.1+Step 7+Step 8 Cycle A
Step 1+Step 2 (2a+2b)+Step 7+Step 8 Cycle B
[0061] Within this cycle, Steps 1, 2, 4.1, 7 and 8 are independent
of the material which is injected. Consequently, the energy savings
are independent on the plastic material properties.
[0062] The coating step 4.1 is optional and part of the CoverForm
process. Cycle A (with coating) and cycle B (without coating)
evaluate the influence of this step on energy savings.
TABLE-US-00003 TABLE 2 Differences in energy consumption with
investigated hydraulic fluids Comparative Comparative Ex 1 Ex 2 Ex
1 Ex 2 Ex 3 Ex 4 .DELTA. energy consumption versus reference oil
[%] Cycle A -- 3.6 -4.9 -7.5 -6.7 -- Cycle B 2.5 5.1 -5.4 -7.9 -5.2
-9.5 Step 1 + Step 2 -- 2.1 -7.0 -8.6 -5.7 -- Cycle A: process
steps which are material independent, with CoverForm .RTM. process
step Cycle B: process steps which are material independent, without
CoverForm .RTM. process step Step 1 +Step 2: fully material
independent steps before material injection
[0063] On the basis of the above results, it is clearly
demonstrated that physical parameters of the base oil in
combination with a viscosity index improver as defined in claim 1
are crucial in order to observe energy savings in an hydraulic
system used under the high pressure conditions of a plastic
injection molding process.
[0064] Although illustrated and described herein with reference to
certain specific embodiments, the present invention is nevertheless
not intended to be limited to the details shown. Rather, various
modifications may be made in the details within the scope of the
claims.
* * * * *