U.S. patent application number 13/988101 was filed with the patent office on 2013-11-07 for sulfonic acid-containing binding agent for moulding mixes for the preparation of moulds and cores.
This patent application is currently assigned to Huttenes-Albertus Chemische Werke GMBH. The applicant listed for this patent is Amine Serghini Anbari, Markus Dorschel, Gerard P.M. Ladegourdie, Ursula Wichmann. Invention is credited to Amine Serghini Anbari, Markus Dorschel, Gerard P.M. Ladegourdie, Ursula Wichmann.
Application Number | 20130292083 13/988101 |
Document ID | / |
Family ID | 45319072 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130292083 |
Kind Code |
A1 |
Ladegourdie; Gerard P.M. ;
et al. |
November 7, 2013 |
SULFONIC ACID-CONTAINING BINDING AGENT FOR MOULDING MIXES FOR THE
PREPARATION OF MOULDS AND CORES
Abstract
A polyisocyanate component for a moulding material binding agent
system is described containing at feast one sulfonic acid in a
solution of at least one polyisocyanate, containing at least two
NCO-groups in the molecule.
Inventors: |
Ladegourdie; Gerard P.M.;
(Dusseldorf, DE) ; Dorschel; Markus; (Koln,
DE) ; Anbari; Amine Serghini; (Neukirchen-Vluyn,
DE) ; Wichmann; Ursula; (Neuss, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ladegourdie; Gerard P.M.
Dorschel; Markus
Anbari; Amine Serghini
Wichmann; Ursula |
Dusseldorf
Koln
Neukirchen-Vluyn
Neuss |
|
DE
DE
DE
DE |
|
|
Assignee: |
Huttenes-Albertus Chemische Werke
GMBH
Dusseldorf
DE
|
Family ID: |
45319072 |
Appl. No.: |
13/988101 |
Filed: |
November 21, 2011 |
PCT Filed: |
November 21, 2011 |
PCT NO: |
PCT/EP2011/070600 |
371 Date: |
June 26, 2013 |
Current U.S.
Class: |
164/349 ; 164/16;
164/369; 252/182.17; 524/745 |
Current CPC
Class: |
B22C 1/2273 20130101;
C08G 18/0852 20130101; C08G 18/542 20130101; C08G 18/0847 20130101;
C08G 18/089 20130101 |
Class at
Publication: |
164/349 ;
252/182.17; 524/745; 164/16; 164/369 |
International
Class: |
B22C 1/22 20060101
B22C001/22 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2010 |
DE |
10 2010 044 163.5 |
Claims
1. Polyisocyanate component for a moulding material binding agent
system, containing at least one sulfonic acid in a solution of at
least one polyisocyanate, containing at least two NCO-groups in the
molecule, wherein, the sulfonic acid has the general formula
R--SO.sub.2--OH, in which R denotes C.sub.1-4-alkyl, and the
polyisocyanate component contains methylene diphenyl diisocyanate
or an oligomer or polymer thereof as polyisocyanate.
2. Solution containing polyisocyanate, for a moulding material
binding agent system, comprising of (a) one or a plurality of
polyisocyanates with in each ease two or more NCO-groups in the
molecule, wherein the one polyisocyanate or at least one of the
plurality of polyisocyanates is a methylene diphenyl diisocyanate
or an oligomer or polymer thereof, and (b) one or a plurality of
sulfonic acids, wherein the one sulfonic acid or at least one of
the plurality of sulfonic acids is selected from the group of
sulfonic acids of the formula R--SO.sub.2--OH, in which R denotes
an alkyl group with between 1 and 4 carbon atoms.
3. Solution containing polyisocyanate according to claim 2,
comprising of (a) one or a plurality of polyisocyanates with in
each case two or more NCO-groups in the molecule, wherein the one
polyisocyanate or at least one of the plurality of polyisocyanates
is a methylene diphenyl diisocyanate or an oligomer or polymer
thereof, (b) one or a plurality of sulfonic acids, wherein the one
sulfonic acid or at least one of the plurality of sulfonic acids is
selected from the group of sulfonic acids of the formula
R--SO.sub.2--OH, in which R denotes an alky group with between 1
and 4 carbon atoms, wherein preferably the one sulfonic acid or at
least one of the plurality of sulfonic acids, is methane sulfonic
acid, and additionally (c) one or a plurality of (co)-solvents, not
selected from the group of ingredients (a) and (b) defined above,
and/or (d) one or a plurality of further substances selected from
the group consisting of acid chlorides and chlorosilanes and/or (e)
optionally one or a plurality of further substances selected from
the group of water repellents.
4. Solution containing polyisocyanate according to claim 2 wherein
the solution does not comprise a resin selected from the group
consisting of phenolic resins and furan resins.
5. Solution containing polyisocyanate according to claim 2 wherein
the solution comprises no polyol that is suitable for reacting with
the polyisocyanate(s) contained, in the solution to form a
cold-curing binding agent.
6. Solution containing polyisocyanate according to claim 2, wherein
the solution is either anhydrous or contains water in a maximum
quantity that is selected so that the molar ratio of NCO-groups to
H.sub.2O is greater than 100:1, preferably greater than 1000:1.
7. Solution containing polyisocyanate according to claim 2 wherein
the solution comprises no moulding matrix.
8. Polyisocyanate component according to claim 1 for a moulding
material binding agent system, comprising 0.01 to 5 wt. %, of the
at least one sulfonic acid.
9. Polyisocyanate component according to claim 8 for a moulding
material binding agent system, wherein it contains 55 to 95 wt. %,
of the at least one polyisocyanate.
10. Polyisocyanate component according to claim 1, wherein at least
one organic solvent, selected from among tetraalkyl silicate,
aromatic hydrocarbons, fatty acid alkyl esters, mixtures of these
and mixtures of these with alkylene carbonates or dialkyl esters of
aliphatic dicarboxylic acid.
11. A method of preparing a polyurethane resin, comprising:
providing a polyisocyanate component according to claim 1 as a
polyisocyanate component of a two-component binding agent system
for preparation of a polyurethane resin.
12. Moulding material binding agent system for preparation of
foundry sand cores from a polyol component, containing a solution
of a polyol containing phenol with at least two OH groups in the
molecule, and a polyisocyanate component, as defined in claim 1,
reacting together to form a cold-curing binding agent.
13. Two-component binding agent system for preparation of a
polyurethane resin for casting, comprising of a polyisocyanate
component as defined in claim 1 and separately a polyol component,
wherein the polyol component preferably comprises a
Phenol-formaldehyde resin with two or more methylol groups per
molecule.
14. (canceled)
15. Mixture for preparation of a core or mould for casting,
comprising a moulding matrix and a moulding material binding agent
system according to claim 12.
16. Mould or core for casting, comprising a moulding matrix and the
cured binding agent system resulting either from the curing of a
moulding material binding agent system according to claim 12 or
that can be prepared by moulding a mixture comprising a moulding
matrix and the components of a moulding material binding agent
system according to claim 12 and curing of the binding agent system
in the moulded mixture to form a cured binding agent system.
17. Method for preparation of a core or mould for casting, with the
following steps: mixing a moulding matrix with the components of a
moulding material binding agent system according to claim 12,
moulding of the resultant mixture comprising moulding matrix and
the components of the binding agent system, bringing the resultant
moulded mixture into contact with a gaseous catalyst, preferably
with a gaseous amine, so that the binding agent system cures and
binds the moulding matrix.
18. A method of extending the benchlife of a mixture, comprising:
mixing a sulfonic acid of the general, formula R--SO.sub.2--OH, in
which R denotes C.sub.1-4-alkyl a moulding matrix and a
polyisocyanate component and a polyol component of a two-component
binding agent system for preparation of a polyurethane resin for
casting, wherein the polyisocyanate component comprises one or a
plurality of polyisocyanates with in each case two or more
NCO-groups in the molecule, wherein the one polyisocyanate or at
least one of the plurality of polyisocyanates is a methylene
diphenyl diisocyanate or an oligomer or polymer thereof, and
wherein the polyol component comprises a phenol-formaldehyde resin
with two or more methylol groups per molecule.
19. The polyisocyanate component according to claim 1, wherein R is
methyl.
20. The solution according to claim 2, wherein R is methyl.
21. A solution according to claim 2, comprising a total quantity of
sulfonic acid in the range 0.01 to 5 wt. %., in respect of the
total weight of the solution.
22. A solution containing polyisocyanate according to claim 2,
comprising a total quantity of polyisocyanate in the range 55 to 95
wt. %, with regard to the total mass of the solution.
23. A solution containing polyisocyanate according to claims 2,
comprising as component (c) one or a plurality of (co-)solvents,
selected from group consisting of tetraalkyl silicate, aromatic
hydrocarbons, fatty acid alkyl esters (preferably rapeseed oil
methyl ester), mixtures of these and mixtures of these with
alkylene carbonates or dialkyl esters of aliphatic dicarboxylic
acids, preferably dimethyl esters of adipinic acid, glutaric acid
and/or succinic acid.
24. The method according to claim 17, wherein the method is a
cold-box casting method.
Description
[0001] The invention relates to a polyisocyanate component for a
moulding material binding agent system or a solution containing
polyisocyanate for a moulding material binding agent system or a
two-component binding agent system, the use of these for the
production of foundry sand cores or moulds according to the
cold-box method, corresponding foundry moulding materials and
foundry sand cores or moulds and the preparation of these and the
use of particular sulfonic acids as a means for extending the
benchlife.
[0002] In the preparation of foundry sand cores and moulds the
polyurethane-forming cold-curing binding agent systems are of great
importance. These binding agent systems consist of two components,
a polyol (normally dissolved in a solvent) with at least two
OH-groups in the molecule and a polyisocyanate (usually likewise
dissolved in a solvent) with at least two NCO-groups in the
molecule. Both components which are added separately to the
moulding mixes containing a moulding matrix, preferably sand, react
in the moulding mix to form a cured polyurethane binding agent,
typically in the presence of catalysts, which guarantee a rapid
reaction and thus a sufficiently short curing time. In addition to
other substances such as metal-organic compounds, in the main
tertiary amines are considered as catalysts which after moulding of
the moulding mix are introduced into the moulding tool as highly
volatile amines with a carrier gas.
[0003] The polyol component is usually a condensation product of
(possibly substituted) phenols with aldehydes (hereinafter referred
to as "phenolic resin" for short) dissolved in a solvent, having a
low-to-average degree of condensation and a large number of free
OH-groups in the molecule. In certain cases, in particular with
sand cores for low casting temperatures, the polyol component,
however, can also be a solution of an oligomeric, dimeric or
monomelic phenol body, e.g. of a terphenol, bisphenol or
dihydroxybenzol. For all these polyois a large number of (generally
polar) solvents are available. The solutions are normally set at a
solid content of 40 to 95 wt. % and can further contain normal
additives.
[0004] In principle all polyisocyanates with at least two
NCO-groups in the molecule can be considered as polyisocyanate
components. Preference is for aromatic polyisocyanates, of which
diphenylmethane-4,4'-diisocyanate,
2,2',6,6'tetramethyldiphenylmethane-4,4'-diisocyanate,
diphenyldimethylmethane-4,4'-diisocyanate and
diphenyl-4,4'-diisocyanate are typical examples. The
polyisocyanates can form the polyisocyanate component either in
pure form or dissolved in an organic solvent, e.g. a mixture of
aromatic hydrocarbons with a boiling point of above 150.degree. C.
In the case of a solution the concentration of the polyisocyanate
is generally above 70 wt. %.
[0005] For the preparation of a moulding mix a moulding matrix,
preferably a grainy moulding sand such a quarto sand, chromite
sand, olivine sand, or zircon sand, is mixed with the two binding
agent components, wherein the proportions of the two components can
be approximately in the region of 0.5 to 1.5 parts by weight of
polyisocyanate component to 1 part by weight of polyol component
and preferably can be dimensioned such that an almost
stoichiometric ratio of the NCO-groups to the OH-groups results.
The moulding mix is then processed to form the foundry sand cores
or moulds, e.g. in that they are filled or fired into a moulding
tool, possibly compressed and then cured by a short period of
gasification with a highly volatile tertiary amine such as
dimethyethylamine or trimethylamine. The sand cores or moulds can
then be removed from the moulding tool.
[0006] In the course of gasification the sand cores or moulds will
already achieve a measurable strength ("initial strength"), which
upon completion of the gasification increases slowly to reach the
final strength value. In practice the highest possible initial
strength is desirable here, in order that the sand cores or moulds
as far as possible can be removed from the moulding fool
immediately after gasification and the tool can be freed up for
another work cycle.
[0007] Sufficiently high initial strengths can be achieved with
binding agent systems adjusted to be reactive. However, excessive
reactivity of the system has the result that the period for which
the moulding mix mixed from the two binding agent components can be
stored before being further processed into sand cores or moulds
(the so-called "benchlife"), is as significantly shortened. This is
a serious disadvantage, for there is a practical requirement for
sufficient benchlives, so that a prepared charge of a moulding mix
(moulding sand mixture) does not become prematurely unusable. Good
benchlives are provided by less strongly reactive binding agent
systems, but these in turn result in poorer initial strengths.
[0008] In order to be able to meet the dual requirements of the
highest possible initial strength and the best possible benchlife,
phosphoryl chloride, phthaloyl chloride or chlorosilanes are added
to the polyisocyanate component of the binding agent. DE-A-34 05
180 describes such a moulding material binding agent system
containing chlorosilanes.
[0009] Binding agent systems containing acid chlorides are known
from U.S. Pat. No. 4,540,724.
[0010] The chlorine content of the binding agent system can lead to
disadvantages and health risks during the processing of the binding
agent system and the subsequent metal casting, since as the binding
agent system decomposes, chlorinated compounds, such as dioxins,
which are a health hazard, can result. Thus there is a need for a
substitute for acid chlorides or chlorosilanes, which can extend
the benchlife of a moulding material and which is at the same time
chlorine-free. The substitute should be capable of fully or
partially replacing the acid chlorides or chlorosilanes used to
date, without adversely affecting the benchlife or the strength of
the sand cores (initial strength and final strength).
[0011] The object of the present invention is to provide a
corresponding chlorine-free substitute which meets the above
requirements.
[0012] DE 2921726 discloses special emulsions containing water, an
organic polyisocyanate, possibly a non-ionic, surface-active medium
as an emulsifier and a sulfonic acid. Here the sulfonic acid is a
sulfonic acid of the general formula R--(SO.sub.3H).sub.n, in which
n denotes an integer 1 or 2 and R an aromatic hydrocarbon radical
with 6 to 14 carbon atoms, an aliphatic hydrocarbon radical with 10
to 18 carbon atoms, a cycloaliphatic hydrocarbon radical with 6 to
15 carbon atoms, an araliphatic hydrocarbon radical with 7 to 15
carbon atoms or an alkaramatic hydrocarbon radical with 7 to 24
carbon atoms.
[0013] DE 2921698 A1 discloses a self-releasing, substantially
anhydrous, polyisocyanate-based binding agent for the production of
moulded forms consisting of [0014] A) a polyisocyanate and [0015]
B) a sulfonic acid of the general formula R--(SO.sub.3H).sub.n, in
which [0016] n denotes an integer 1 or 2 and [0017] R an aromatic
hydrocarbon radical with 6 to 14 carbon atoms, an aliphatic
hydrocarbon radical with 10 to 18 carbon atoms, a cycloaliphatic
hydrocarbon radical with 6 to 15 carbon atoms, an araliphatic
hydrocarbon radical with 7 to 15 carbon atoms or an alkaromatic
hydrocarbon radical with 7 to 24 carbon atoms, wherein the
equivalent ratio of components A) and B) is between 100:0.5 and
100:20.
[0018] JP 03-041116 concerns certain polyurethane resin
compositions for orthopedic cast strips comprising a polyurethane
prepolymer comprising a polyol and a polyisocyanate, a catalyst a
stabiliser (e.g. acid chlorides such as benzoyl chloride or
sulfonic acids such as methane sulfonic acid) and an ester compound
polyethylene glycol.
[0019] DE 4213873 describes the use of esters that are liquid at
ambient temperature as a solvent for isocyanates and/or
isocyanurates, whereby the viscosity of the isocyanates and/or
isocyanurates can be drastically reduced.
[0020] DE 19542752 describes the use of vegetable oil methyl ester,
preferably of rapeseed oil methyl ester, as a solvent for
individual or both components of foundry moulding material binding
agents with a polyurethane basis, the components of which comprise
a phenolic resin containing free OH-groups and a polyisocyanate as
the reaction partner.
[0021] JP 53-128526 discloses how, for the preparation of a
self-curing mould mixture, a phenolic resin containing 0.05 to 40%
carboxylic and/or sulfonic acid and sand is mixed with a
polyisocyanate in the presence of a basic catalyst.
[0022] JP 62-104648 discloses how, for the preparation of a sand
mould, foundry sand is kneaded with a binding agent comprising a
furan resin, toluenesulfonic acid, tetraethylsilicate, methyl
diisocyanate, silicon dioxide and boric acid.
[0023] CN 102049463 discloses a method comprising the mixing of a
sodium alkyl sulfonate solution with a phenolic resin, and then
mixing with sand, further mixing with a polyisocyanate-ester, and
the moulding of a casting mould.
[0024] The object posed is achieved according to the invention by
the use of a sulfonic acid of the general formula R--SO.sub.2--OH,
in which R denotes C.sub.1-4-alkyl, preferably methyl, as a means
to extend the benchlife of a mixture, comprising [0025] a moulding
matrix, preferably a moulding sand, and [0026] the polyisocyanate
component and the polyol component of a two-component binding agent
system for preparation of a polyurethane resin for casting,
preferably according to the polyurethane cold-box method, wherein
the polyisocyanate component comprises one or a plurality of
polyisocyanates with in each case two or more NCO-groups in the
molecule, wherein the one polyisocyanate or at least one of the
plurality of polyisocyanates is a methylene diphenyl diisocyanate
or an oligomer or polymer thereof, and wherein the polyol component
preferably comprises a phenol-formaldehyde resin with two or more
methylol groups per molecule, particularly preferably a benzyl
ether resin with ortho-ortho structures.
[0027] Further aspects of the present invention are apparent from
the attached claims and the following description.
[0028] According to the invention it has been discovered that the
sulfonic acids to be used according to the invention can be used to
extend the benchlife of a moulding material and in so doing can
replace in full or in part the known chlorosilanes or acid
chlorides.
[0029] The invention therefore also relates to (i) a polyisocyanate
component for a moulding material binding agent system, and (ii) a
solution containing polyisocyanate (see below).
[0030] The invention further relates to a moulding material binding
agent system for the preparation of foundry sand cores from a
polyol component, containing a solution of a phenol-containing
polyol, such as benzyl ether resin with ortho-ortho structures,
with at least two OH-groups in the molecule, and a polyisocyanate
component, as defined as above, which react with one another to
form a cold-curing binding agent, e.g. for sand cores or moulding
sand. The invention also relates to a moulding material binding
agent system for the preparation of foundry sand cores from [0031]
a polyol component, containing phenol formaldehyde resin, such as
benzyl ether resin with ortho-ortho structures, with at least two
OH-groups in the molecule, and [0032] a polyisocyanate component,
as defined above, which reset with one another to form a
cold-curing binding agent.
[0033] The invention also relates to a two-component binding agent
system for the preparation of a polyurethane resin for casting (see
below).
[0034] The invention also relates to the use of a polyisocyanate
component or a solution containing polyisocyanate, a moulding
material binding agent system according to the invention or a
two-component binding agent system according to the invention for
the preparation of foundry sand cores according to the cold-box
method.
[0035] The invention also relates to a mixture for preparation of a
core or a mould for casting, e.g. a foundry moulding material, and
corresponding foundry sand cores and moulds and a method for the
preparation thereof.
[0036] The foundry moulding material can also be used as a foundry
moulding sand for the preparation of casting moulds, e.g. for the
no-bake method.
[0037] The invention also relates to a polyisocyanate component for
a moulding material binding agent system, containing at least one
sulfonic acid in a solution of at least one polyisocyanate,
containing at least two NCO-groups in the molecule, characterised
in that: [0038] the sulfonic acid has the general formula
R--SO.sub.2--OH, in which R denotes C.sub.1-4-alkyl, preferably
methyl, and [0039] the polyisocyanate component contains methylene
diphenyl diisocyanate (MDI) or an oligomer or polymer thereof.
[0040] A further subject matter of the invention is a solution
containing a polyisocyanate, preferably a polyisocyanate component
as defined above, for a moulding material binding agent system,
wherein the solution containing polyisocyanate consists of [0041]
(a) one or a plurality of polyisocyanates with in each case two or
more NCO-groups in the molecule, wherein the one polyisocyanate or
at least one of the plurality of polyisocyanates is a methylene
diphenyl diisocyanate or an oligomer or polymer thereof, and [0042]
(b) one or a plurality of sulfonic acids, wherein the one sulfonic
acid or at least one of the plurality of sulfonic acids is selected
from the group of sulfonic acids of the formula R--SO.sub.2--OH, in
which R denotes an alkyl group with between 1 and 4 carbon atoms,
wherein preferably the one sulfonic acid or at least one of the
plurality of sulfonic acids, is methane sulfonic acid, or comprises
the components (a) and (b) defined here.
[0043] According to the invention preference is for a solution
containing polyisocyanate comprising or consisting of [0044] (a)
one or a plurality of polyisocyanates with in each case two or more
NCO-groups in the molecule, wherein the one polyisocyanate or at
least one of the plurality of polyisocyanates is a methylene
diphenyl diisocyanate or an oligomer or polymer thereof, and [0045]
(b) one or a plurality of sulfonic acids, wherein the one sulfonic
acid or at least one of the plurality of sulfonic acids is selected
from the group of sulfonic acids of the formula R--SO.sub.2--OH, in
which R denotes an alkyl group with between 1 and 4 carbon atoms,
wherein preferably the one sulfonic acid or at least one of the
plurality of sulfonic acids, is methane sulfonic acid. and
additionally [0046] (c) one or a plurality of (co)-solvents, not
selected from the group of ingredients (a) and (b) defined above,
and/or [0047] (d) one or a plurality of further substances selected
from the group consisting of acid chlorides and chlorosilanes
and/or [0048] (e) one or a plurality of further substances selected
from the group of water repellents.
[0049] Here, preference according to the invention is for solutions
containing polyisocyanate. which contain no substances (d) selected
from the group consisting of acid chlorides and chlorosilanes.
Chlorinated compounds may, however, in individual cases, be
acceptable in small quantities in the solution containing
polyisocyanate according to the invention. Commercial grades of
methylene diphenyl diisocyanate (and other polyisocyanates) in
particular and their oligomers or polymers comprise certain
quantities of chlorinated compounds as an impurity, due to the use
of chlorinated educts during synthesis. These chlorinated compounds
may be acceptable as an impurity in solutions containing
polyisocyanate according to the invention. In order to further
reduce the burden from the release of chlorine during the casting
process, however, it is preferred, for the preparation of the
solution containing polyisocayanate according to the invention, to
use polyisocyanate grades in which the chlorinated impurity content
is as low as possible, or to reduce the content of such chlorinated
impurities in the polyisocyanates to be used as far as possible by
suitable purification processes.
[0050] The (co-)solvents of component (c) can also be based on
commercially available products, which apart from a (preferably
chlorine-free) main ingredient also comprise certain quantities of
chlorinated compounds as an impurity. In this connection, however,
it is preferred, for preparation of the solution containing
polyisocyanate according to the invention to use (co-)solvent
grades in which the content of chlorinated impurities is as low as
possible or to reduce the content of such chlorinated impurities in
the (co-)solvents to be used as far as possible by suitable
purification processes.
[0051] The term (co-)solvent (c) means that the component (c)
either acts as a solvent itself, where none of the ingredients of
components (a) and (b) themselves act as a solvent for the other
ingredients of components (a) and (b), or acts as an additional
solvent, where one or a plurality of ingredients of components (a)
and (b) itself/themselves acts or act as a solvent for the other
ingredients of components (a) and (b).
[0052] Aminosilanes and aminoorganosilanes, such as
gamma-aminopropyltriethoxysilane,
gamma-aminopropyltrimethoxysilane,
bis-(gamma-erimethoxysilylpropyl)amine, polyazamidsilane,
N-beta(amincethyl)-gamma-aminopropytrimethoxysilane,
N-phenyl-gamma-aminopropyltrimethoxysilane, organically modified
polydimethoxysiloxsne, and triamino-functional silanes are often
used as the water repellent (e).
[0053] Here, according to the invention, it is preferred that the
solution containing polyisocyanate defined above does not comprise
a resin selected from the group consisting of phenolic resins and
furan resins.
[0054] Particularly preferably according to the invention the
solution containing polyisocyanate comprises no polyol that is
suitable for reacting with the polyisocyanate(s) contained in the
solution to form a cold-curing binding agent.
[0055] A solution containing polyisocyanate according to the
invention preferably comprises no moulding matrix, in particular no
casting sand.
[0056] The solution containing polyisocyanate according to the
invention is preferably either anhydrous or contains water in a
maximum quantity that is selected so that the molar ratio of
NCO-groups to H.sub.2O is greater than 100:1, preferably greater
than 1000:1.
[0057] The polyisocyanate component according to the invention or
the solution containing polyisocyanate according to the invention
contains one or a plurality of sulfonic acids, wherein the one
sulfonic acid or at least one of the plurality of sulfonic acids is
selected from the group of sulfonic acids of the formula
R--SO.sub.2--OH, in which R denotes an alkyl group with between 1
and 4 carbon atoms, wherein preferably the one sulfonic acid or at
least one of the plurality of sulfonic acids, is methane sulfonic
acid.
[0058] Additionally, the following applies: The sulfonic acid can
be selected from any suitable sulfonic adds. Preferably, the
sulfonic acid has the general formula R--SO.sub.2--OH, in which R
denotes C.sub.1-12-alkyl, phenyl or C.sub.1-12-alkylphenyl, wherein
an H atom in these radicals can be substituted by a hydroxyl group
or amino group, which can be primary, secondary or tertiary, or R
denotes NH.sub.2.
[0059] The sulfonic acid can be used in pure form or as a solution
in a, preferably, organic solvent. Here the sulfonic acid can be
present in the form of a free acid or also partly in the form of a
salt, for example an ammonium, alkaline or alkaline earth metal
salt. The salt content, in respect of the acid groups, should
preferably not exceed 30 mol %. Preferably, only the free acid is
used.
[0060] The use of sulfonic acid leads to a considerable extension
of the benchlife, without this being accompanied by a significant
drop in strength (initial strength and final strength). This effect
is achieved in a range of low added quantities. Preferably, the
polyisocyanate component contains 0.01 to 5 wt. %., particularly
preferably 0.0025 to 2.5 wt. %., preferably 0.025 to 2.5 wt. %., in
particular 0.05 to 1 wt. %, of the minimum of one sulfonic acid, in
respect of the polyisocyanate component.
[0061] A solution containing polyisocyanate according to the
invention (as defined above) preferably comprises a total quantity
of sulfonic acid in the range 0.01 to 5 wt. %., in respect of the
total weight of the solution.
[0062] With the additional use of acid chlorides or chlorosilanes
the weight ratio of sulfonic acid to acid chloride or chlorosilane
is preferably 1:1 to 9:1, particularly preferably 1:1 to 4:1, in
particular approximately 1:1. Preferably no acid chloride or
chlorosilane is also used.
[0063] Unlike phosphoryl chloride, methane sulfonic acid is an
odourless, non-oxidising, biodegradable, non-toxic, aliphatic,
thermally resistant, low TOC (Total Organic Compound) and strong
organic add. Furthermore, the methane sulfonic acid has an
extremely low vapour pressure and is part of the natural sulphur
cycle.
[0064] Here the polyisocyanate component preferably contains 55 to
85 wt. %, particularly preferably 70 to 90 wt. % of the at least
one polyisocyanate. The polyisocyanate component can also contain a
solvent, preferably in a quantity of 4.99 to 44.99 wt. %,
particularly preferably 9.99 to 29.99 wt. %.
[0065] A solution containing polyisocyanate according to the
invention (as defined above) preferably comprises a total quantity
of polyisocyanate in the range 55 to 95 wt. %., in respect of the
total weight of the solution.
[0066] Here, the total quantity of the ingredients of the
polyisocyanate component or the solution according to the invention
comes to 100 wt. %. Preferably the total quantity of
polyisocyanate, sulfonic acid and solvent comes to 100 wt. %.
[0067] The invention is applicable to all polyurethane-based
binding agent systems, and can thus be used in conjunction with all
normal polyol components and polyisocyanate components and also
requires no changes to the preparation and processing of the
moulding mixes (moulding sand mixtures). The optimum quantity of
sulfonic acid in each case is dependent here on the nature and
reactivity of the polyol component and can be determined in each
individual situation through simple manual trials. For suitable
polyol components and polyisocyanate components, reference may be
made, by way of example, to DE-A-34 05 180. DE-A-10 2004 057 671,
EP-A-1 057 557 554, EP-A-0 771 599 and WO 2010/060826. All suitable
phenol-formaldehyde resins can be used, with the use of benzyl
ether resins being particularly advantageous however.
[0068] The polyisocyanate component according to the invention or
the solution containing polyisocyanate according to the invention
comprises one or a plurality of polyisocyanates with in each case
two or more NCO-groups in the molecule, wherein the one
polyisocyanate or at least one of the plurality of polyisocyanates
is a methylene diphenyl diisocyanate (MDI) or an oligomer or
polymer thereof. A mixtures of 4,4'-,2,2'- and 2,4'-isomers may be
involved here or individual isomers or mixtures of two of the
isomers, or also oligomers or polymers of these. This means that
according to the invention use may be made of [0069] an isomer
selected from the group consisting of the 4,4'-, the 2,2'- and
2,4'-isomers of the monomer methylene diphenyl diisocyanate (MDI),
[0070] mixtures consisting of or containing two or all isomers of
the monomer methylene diphenyl diisocyanate (MDI), [0071] oligomers
and polymers of the methylendiphenyldiisocyanate (MDI), [0072]
mixtures consisting of or containing two or a plurality of
oligomers and/or polymers of the methylene diphenyl diisocyanate
(MDI), [0073] mixtures consisting of or containing one or a
plurality of isomers of the monomer methylene diphenyl diisocyanate
(MDI) and one or a plurality of oligomers and/or one or a plurality
of polymers of the methylene diphenyl diisocyanate (MDI).
[0074] The use of oligomers and polymers of the methylene diphenyl
diisocyanate (MDI) is preferred according to the invention.
[0075] Furthermore, the following applies: Here the polyisocyanate
can be selected from any suitable polyisocyanates, which contain at
least NCO-groups in the molecule and with a phenol-containing
polyol produce a cold-curing binding agent for casting sand.
Suitable polyisocyanates are known to a person skilled in the
art.
[0076] As solvents or co-solvents for the polyisocyanate or the
solution according to the invention (as defined above), preferably
tetrasilicates such as tetraethyl silicate, aromatic hydrocarbons,
fatty acid alkyl esters (preferably rapeseed oil methyl ester),
mixtures of these and mixtures of these with alkylene carbonates
such as propylene carbonate or dialkyl esters of aliphatic
dicarboxylic acids, preferably dimethyl esters of adipinic acid,
glutaric acid and/or succinic acid, can be considered. The latter
dialkyl esters are for example sold under the designation DBE
(Dibasic Ester). They are used as co-solvents. in order to improve
the solubility, for example in tetraethyl silicate, aromatic
hydrocarbons or rapeseed oil methyl esters.
[0077] Alkylene carbonate or DBE are added to the first solvent
mentioned preferably in a ratio of weight of 1:1 to 5, preferably
1:1.5 to 3, thus in a clearly low quantity.
[0078] The subject matter of the invention is also the use of a
polyisocyanate component according to the invention (as defined
above) or a solution containing polyisocyanate according to the
invention (as defined above) as a polyisocyanate component of a
two-component binding agent system for preparation of a
polyurethane resin, preferably as a polyisocyanate component of a
two-component binding agent system for preparation of a
polyurethane resin in the polyurethane cold-box method.
[0079] A further subject matter of the present invention is a
two-component binding agent system for preparation of a
polyurethane resin for casting, consisting of [0080] a
polyisocyanate component according to the invention as defined
above or a solution containing polyisocyanate according to the
invention as defined above as a polyisocyanate component, and
separately [0081] a polyol component, wherein the polyol component
preferably comprises a phenol-formaldehyde resin with two or more
methylol groups per molecule, particularly preferably a benzyl
ether resin with ortho-ortho structures.
[0082] Phenol-formaldehyde resins are synthetic resins, which are
obtained by condensation of phenols with formaldehyde and if
necessary by derivatisation of the resultant condensates.
Phenol-formaldehyde resins are normally, depending on the
proportions of the educts (phenol component and formaldehyde), the
reaction conditions and the catalysts used, split into two product
classes, the novolacs (phenol novolacs) and resoles:
[0083] Here novolacs are soluble, fusible, non-self-curing and
stable when stored oligomers with molecular weights in the range of
approximately 500 to 5000 g/mol. They are produced by condensing
formaldehyde and a phenol component in a molar ratio of
approximately 1:1.25 to 2 in the presence of acid catalysts.
Novolacs are generally free of methylol groups, and their aromatic
rings are linked by methylene bridges. Novolacs can be cured by
reactive cross-linkers (curing agents) (e.g. hexamethylene
tetramine, formaldehyde, isocyanates such as methylene didiphenyl
isocyanate, epoxides etc,) at high temperature with cross-linking.
Novolacs are usually insoluble in water.
[0084] Resoles are mixtures of hydroxymethyl phenols, linked by
methylene and methylene ether bridges. They are prepared by an
alkaline catalysed condensation reaction with molar excess of the
aldehyde. Once a certain degree of polymerisation has been reached
here the condensation is interrupted. Resoles are self-curing
through their reactive methylol groups. Depending on the degree of
condensation resoles are liquid and as such have different
viscosities and are as a rule soluble in water and alcohol. Resoles
can be converted into highly cross-linked structures (resites)
under the effect of heat. For particular areas of application it is
sometimes desirable for resoles to have a certain solubility in
organic solvents. In order to achieve this solubility, resoles are
then normally subjected to modification reactions, such as for
example, condensation at higher temperature with unsaturated
compounds (such as for example vegetable oils), esterification or
etherification with mono- or polyfunctional alcohols.
[0085] A particular class of phenol formaldehyde resins are benzyl
ether resins. Benzyl ether resins are the products of condensation
of a phenol component and formaldehyde, obtained under the
catalytic influence of bivalent metal ions, see U.S. Pat. No.
3,485,797. Benzyl ether resins are particularly suitable as a resin
component for casting binding agents for use in the cold-box method
(see U.S. Pat. No. 3,676,392 and U.S. Pat. No. 3,409,579). Benzyl
ether resins are liquid up to a certain degree of condensation.
Benzyl ether resins are as a rule incompatible with wafer, but
compatible with alcohols and other organic solvents. The particular
feature of benzyl ether resins is their structure. They have phenol
bodies which are linked by both methylene groups --CH.sub.2-- and
by ether groups --CH.sub.2--O--CH.sub.2--, wherein the linking of
two bodies takes place predominantly in the ortho-ortho position,
in benzyl ether resins there is a high content of hydroxymethyl
groups (--CH.sub.2OH) and phenolic hydroxyl groups (--OH). The fact
that benzyl ether resins have predominantly o,o-structures
(ortho-ortho-structures) and accordingly have a linear molecular
structure, makes them highly reactive to cross-linkers (see again
U.S. Pat. No. 3,485,797). Their good compatibility with organic
solvents is responsible for their particular suitability as a resin
component for casting binding agents for use in the cold-box
method. Benzyl ether resins usually contain a high concentration of
residual monomers (phenol component; formaldehyde) once the
condensation reaction is complete. In addition to this benzyl ether
resins can only be processed with comparatively high quantities of
solvents, which in view of the ever-stricter directives on handling
products containing solvents, limits their applicability. The great
need for solvents for processing benzyl ether resins is a result of
their comparatively high viscosity which as a rule must be lowered
by the addition of solvent.
[0086] Preferred benzyl ether resins are described in EP-B-1 057
554. Compounds that are preferably used according to the invention
are described there in paragraphs [0004] to [10006], wherein
particular reference may be made to Formulas I and II given
there.
[0087] Special phenol-formaldehyde resins with low viscosity are
described in particular in DE-A-10 2004 057 671.
[0088] According to the invention, the phenol-formaldehyde resins
are preferably used as a polyol component and can be termed a
phenol-containing polyol. Here the viscosity of she polyol
component is in particular 130 to 140 mPa s at 20.degree. C. For
this purpose the polyol component can have a solvent, for example
in a quantity of 30 to 50 wt. %. Suitable solvents are aromatic and
aliphatic hydrocarbons, esters, ketones, alkyl silicates, fatty
acid esters and similar solvents. When low-viscosity
phenol-formaldehydes according to DE-A-10 2004 057 671 are used the
solvent contents can be considerably reduced.
[0089] For other polyol components and polyisocyanate components
reference may be made to that stated in the introduction to the
description. Here both components are used in the proportions
referred to there.
[0090] The subject matter of the present invention is also the use
of a polyisocyanate component according to the invention as defined
above or a solution containing polyisocyanate according to the
invention as defined above or a two-component binding agent system
as defined above [0091] for the preparation of foundry sand cores
or moulds according to the cold-box method and/or [0092] for
preparation of a polyurethane resin preferably using the
polyurethane cold-box method.
[0093] A further subject matter of the invention is a mixture for
the preparation of a core or a mould for casting, comprising [0094]
a moulding matrix, preferably a moulding sand, and [0095] either
the components of a moulding material binding agent system or the
two-components of a two-component binding agent system according to
the invention.
[0096] Such mixtures comprising a (I) moulding matrix, wherein the
moulding matrix preferably is a moulding sand, and (ii) a binding
agent system (in particular the two components of a two-component
binding agent system) are in connection with the present invention
also referred to as (foundry) moulding materials, moulding mixes or
moulding sand mixtures.
[0097] Preferably for the preparation of the foundry moulding
material 100 parts by weight of sand, for example quartz sand, or
another suitable moulding matrix, are mixed with in each case 0.25
to 2 parts by weight, preferably in each case 0.5 to 1.5 parts by
weight of the polyol components and the polyisocyanate component.
Here mixing preferably takes place at room temperature using normal
mixing equipment.
[0098] The foundry moulding materials obtained in this way can be
used in any suitable method for the preparation of foundry sand
cores or moulds.
[0099] Other subject matters of the present invention are thus
a mould or a core for casting, [0100] composing a moulding matrix,
preferably a moulding sand, and the cured binding agent system
resulting either from the curing of a moulding material binding
agent system according to the invention as defined above or the
curing of a two-component binding agent system according to the
invention as defined above or [0101] that can be produced by
moulding a mixture comprising a moulding matrix, preferably a
moulding sand, and the components of a moulding material binding
agent system according to the invention, or the components of a
two-component binding agent system according to the invention and
curing of the binding agent system in the moulded mixture to form a
cured binding agent system, and a method for preparation of a
foundry core or mould, preferably according to the polyurethane
cold-box method, with the following steps: [0102] mixing of a
moulding matrix, preferably a moulding sand, with the components of
a moulding matrix binding agent system according to the invention
or with the components of a two-component binding agent system
according to the invention, [0103] moulding of the resultant
mixture comprising moulding matrix and the components of the
binding agent system. [0104] bringing the resultant moulded mixture
into contact with a gaseous catalyst, preferably (in particular in
the context of the cold-box method) with a gaseous amine, so that
the binding agent system cures and binds the moulding matrix.
[0105] Preferably the foundry sand cores or moulds are produced
according to the cold-box method. In foundries the cold-box method
is one of the most important polyurethane gasification methods. The
designation is that used by the VDG and has also been introduced
into the German casting industry to designate this method. On this
point reference may be made to U.S. Pat. No. 3,409,579. In the
cold-box method an amine gassing agent such as for example dimethyl
isopropylamine serves as an acceleration catalyst, which
considerably accelerates the addition of polyisocyanate to a
phenolic resin, e.g. benzyl ether resin. In the process a
polyurethane is formed. Resins used in the cold-box method are as a
rule anhydrous here, since water would react prematurely with the
polyisocyanate.
[0106] The process normally involves the foundry sand containing
the binding agent system according to the invention (core sand)
initially being fired into core boxes. Then using an amine-air or
amine-nitrogen mixture in gas or aerosol form, it is gasified. The
amines involved are generally triethyl-, dimethylethyl-,
dimethyl-n-propyl- or dimethylisopropylamine, which are in each
case blown into the core boxes at a pressure of 2 to 6 bar. The
residual gases are normally driven out of the core with heated
scavenging air, nitrogen or CO.sub.2 gas and can be disposed of in
an acid scrubber, charged with diluted sulphuric acid or phosphoric
acid.
[0107] Here the binding agent system according to the invention,
depending on the amine, cures at temperatures of preferably 20 to
100.degree. C., particularly preferably 45 to 80.degree. C. In the
cold-box method especially, the curing normally takes place at the
respective ambient temperature normally prevailing in the foundry,
that is to say generally at a temperature in the range 15 to
50.degree. C., in particular at a temperature in the range 15 to
40.degree. C. Therefore the binding agent is referred to as a
cold-curing binding agent for moulding sand.
[0108] The cold-box method has extensive applications, in
particular in metal casting and for example in engine castings.
[0109] The moulding materials according to the invention can also
be used as moulding sand for the preparation of sand moulds for
casting, e.g. in the non-bake method.
[0110] Thanks to the benchlife extender according to the invention
the moulding materials/moulding sands after casting are to the
greatest possible extent chlorine-free, so that corrosion of the
cast parts is avoided and the used sand cores or moulds can be
re-used as used sand. For this purpose the used sand is heat and/or
mechanically treated. Both of these treatment methods result in
insignificant or no burdening with chemicals that are damaging to
health. This re-employment of previously used sand cores or
treatment of used sand is ever possible with systems containing
bentonite or basic systems.
[0111] The invention is explained in more detail by the following
examples.
EXAMPLES
Example 1
Preparation of a Preferred Phenolic Resin of the Benzyl Ether Type
(Precondensate)
[0112] In a reaction vessel equipped with cooling, a thermometer
and a stirrer:
TABLE-US-00001 385.0 PW Phenol 176.0 PW Paraformaldehyde (as the
formaldehyde source) and 0.11 PW Zinc acetate
were placed. The cooler was set to reflux. The temperature was
continuously increased to 105.degree. C. within an hour and
maintained at this temperature for between two and three hours
until a refractive index of 1.550 was reached.
[0113] The cooler was then switched to atmospheric distillation and
the temperature increased within one hour to 125 to 126.degree. C.,
until a refractive index of approximately 1.593 was reached.
[0114] Then vacuum distillation took place until a refractive index
of 1.612.
[0115] The yield was 82 to 83% of the raw materials used.
[0116] The phenolic resin was used for the preparation of test
specimens according to the cold-box method.
Example 2
Preparation of Cold-Box Phenolic Resin Solutions
[0117] From the phenolic resin (precondensate) according to Example
1 once the desired value of the refractive index had been reached,
resin solutions for the cold-box method were prepared having the
compositions indicated in the following:
[0118] Cold-box resin solution AB1
TABLE-US-00002 50 PW Phenol resin (precondensate from Example 1) 19
PW Aromatic hydrocarbons with a boiling point of 165 to 180.degree.
C. 18 PW DBE (Dibasic Ester) 13 PW Rapeseed oil methyl ester
(RME)
Example 3
Preparation of Polyisocyanate Solutions for the Cold-Box Method
[0119] According to the invention: Polyisocyanate solutions BB1 to
BB6
[0120] In each case 100% methane sulfonic acid was used.
[0121] Polyisocyanate solution BB1
TABLE-US-00003 85 PW Diphenylmethane diisocyanate 12.5 PW Aromatic
hydrocarbons with a boiling point of 165 to 180.degree. C. 2 PW
Rapeseed oil methyl ester (RME) 0.1 PW Methane sulfonic acid 0.4 PW
Water repellent
[0122] Polyisocyanate solution BB2
TABLE-US-00004 85 PW Diphenylmethane diisocyanate 12.4 PW Aromatic
hydrocarbons with a boiling point of 165 to 180.degree. C. 2 PW
Rapeseed oil methyl ester (RME) 0.2 PW Methane sulfonic acid 0.4 PW
Water repellent
[0123] Polyisocyanate solution BB3
TABLE-US-00005 85 PW Diphenylmethane diisocyanate 12.3 PW Aromatic
hydrocarbons with a boiling point of 165 to 180.degree. C. 2 PW
Rapeseed oil methyl ester (RME) 0.3 PW Methane sulfonic acid 0.4 PW
Water repellent
[0124] Polyisocyanate solution BB4
TABLE-US-00006 85 PW Diphenylmethane diisocyanate 12.2 PW Aromatic
hydrocarbons with a boiling point of 165 to 180.degree. C. 2 PW
Rapeseed oil methyl ester (RME) 0.4 PW Methane sulfonic acid 0.4 PW
Water repelient
[0125] Polyisocyanate solution BB5
TABLE-US-00007 85 PW Diphenylmethane diisocyanate 12.1 PW Aromatic
hydrocarbons with a boiling point of 165 to 180.degree. C. 2 PW
Rapeseed oil methyl ester (RME) 0.5 PW Methane sulfonic acid 0.4 PW
Water repelient
[0126] Polyisocyanate solution BB6
TABLE-US-00008 85 PW Diphenylmethane diisocyanate 11.6 PW Aromatic
hydrocarbons with a boiling point of 165 to 180.degree. C. 2 PW
Rapeseed oil methyl ester (RME) 1 PW Methane sulfonic acid 0.4 PW
Water repelient
[0127] Polyisocyanate solution BB8
TABLE-US-00009 65 PW Diphenylmethane diisocyanate 12.8 PW Aromatic
hydrocarbons with a boiling point of 165 to 180.degree. C. 2 PW
Rapeseed oil methyl ester (RME) 0.2 PW Methane sulfonic acid
[0128] Conventionally for comparison: Polyisocyanate solution BB
7
[0129] The polyisocyanate solution for comparison BB7 corresponds
to solution BB3, with the difference that instead of methane
sulfonic acid phosphoryl chloride is used to extend the
benchlife.
Example 4
Preparation of Cold-Box Test Specimens and Core Testing of
These
[0130] a) Using the phenolic resin and polyisocyanate solutions
indicated (see Examples 2 and 3) the moulding sand mixtures
indicated in the following Table 1 were prepared, in which
TABLE-US-00010 [0130] 100 PW Quartz sand H 32, 0.7 PW of the
respective phenolic resin solution (Example 2) and 0.7 PW of the
respective polyisocyanate solution (Example 3)
were mixed in a vibratory mixer.
[0131] The mixing time was in each case 60 seconds. With the
mixtures obtained at a firing pressure of 4 bar, test specimens
(+GF+bar) were fired, which were than gasified for 10 seconds at a
gasification pressure of 4 bar with dimethylisopropylamine and then
flushed with air for 10 seconds. The sand quantify per test
specimen was 3 kg, the sand temperature and the ambient temperature
were approximately 25.degree. C., the relative humidity (RH) was
approximately 39%. Then the flexural strengths of the test
specimens obtained in this way were determined according to the GF
method. In the preparation of the test as specimens and the testing
of the flexural strengths the specifications of VDG leaflet P 73 of
February 1996 were applied.
[0132] Table 1 provides a comparison of the strength values of six
cores according to the invention and a conventional core (in
N/cm.sup.2).
[0133] For the results compiled in Table 1 investigations were
firstly performed with a mixture used to prepare a mould test
specimen immediately after mixing ("IMMEDIATE" column) and secondly
with a mixture first stored for three hours after mixing (for
assessing the so-called "benchlife" BL) and then used to prepare a
test specimen ("3 HOURS" column).
[0134] The results summarised in the following Table 1 show how the
test specimens (cores) prepared according to the invention have
strength values that are just as good as the cores prepared in the
conventional manner.
TABLE-US-00011 TABLE 1 Flexural strengths Further processing of the
mixture IMMEDIATE 3 HOURS Phenol Poly- Test time resin isocyanate
immed. 1 h 24 h immed. 1 h 24 h AB1 BB1 215 328 380 229 329 349 AB1
BB2 224 415 435 230 353 367 AB1 BB3 214 359 417 226 333 353 AB1 BB4
194 338 380 215 326 358 AB1 BB5 200 335 391 216 350 367 AB1 BB6 206
338 388 233 356 370 AB1 BB7 227 385 440 220 351 384 AB1 BB8 220 363
430 223 335 388
Example 5
Preparation of Cold-Box Phenolic Resin Solutions
[0135] From the phenolic resin (precondensate) according to Example
1 once the desired value of the refractive index had been reached,
resin solutions for the cold-box method were prepared having the
compositions indicated in the following:
[0136] Cold-box resin solution HA1
TABLE-US-00012 55 PW Phenol resin (precondensate from Example 1) 30
PW Tetraethyl silicate 15 PW DBE (Dibasic Ester)
Example 6
Preparation of Polyisocyanate Solutions for the Cold-Box Method
[0137] According to the invention: Polyisocyanate solutions HB2 to
HB8
[0138] Conventionally for comparison: Polyisocyanate solution
HB1
[0139] Polyisocyanate solution HB1
TABLE-US-00013 80 PW Diphenylmethane diisocyanate (MDI) 10 PW
Tetraethyl silicate 9.3 PW Dioctyl adipate 0.3 PW Phosphoryl
chloride 0.4 PW Water repelient
[0140] Polyisocyanate solution HB2
TABLE-US-00014 80 PW Diphenylmethane diisocyanate (MDI) 10 PW
Tetraethyl silicate 9.5 PW Dioctyl adipate 0.1 PW Methane sulfonic
acid 0.4 PW Water repelient
[0141] Polyisocyanate solution HB3
TABLE-US-00015 80 PW Diphenylmethane diisocyanate (MDI) 10 PW
Tetraethyl silicate 9.4 PW Dioctyl adipate 0.2 PW Methane sulfonic
acid 0.4 PW Water repelient
[0142] Polyisocyanate solution HB4
TABLE-US-00016 80 PW Diphenylmethane diisocyanate (MDI) 10 PW
Tetraethyl silicate 9.3 PW Dioctyl adipate 0.3 PW Methane sulfonic
acid 0.4 PW Water repelient
[0143] Polyisocyanate solution HB5
TABLE-US-00017 80 PW Diphenylmethane diisocyanate (MDI) 10 PW
Tetraethyl silicate 9.2 PW Dioctyl adipate 0.4 PW Methane sulfonic
acid 0.4 PW Water repelient
[0144] Polyisocyanate solution HB6
TABLE-US-00018 80 PW Diphenylmethane diisocyanate (MDI) 10 PW
Tetraethyl silicate 9.1 PW Dioctyl adipate 0.5 PW Methane sulfonic
acid 0.4 PW Water repelient
[0145] Polyisocyanate solution HB7
TABLE-US-00019 80 PW Diphenylmethane diisocyanate (MDI) 10 PW
Tetraethyl silicate 8.6 PW Dioctyl adipate 1 PW Methane sulfonic
acid 0.4 PW Water repelient
[0146] Polyisocyanate solution HB8
TABLE-US-00020 80 PW Diphenylmethane diisocyanate (MDI) 10 PW
Tetraethyl silicate 9.4 PW Dioctyl adipate 0.1 PW Methane sulfonic
acid 0.1 PW Phosphoryl chloride 0.4 PW Water repelient
Example 7
Preparation of Cold-Box Test Specimens and Core Testing of
These
[0147] a) Using the phenolic resin and polyisocyanate solutions
indicated (see Examples 5 and 6) the moulding sand mixtures
indicated in the following Table 2 were prepared, in which in each
case
TABLE-US-00021 [0147] 100 PW Quartz sand H 32, 0.7 PW of the
respective phenolic resin solution (Example 2) and 0.7 PW of the
respective polyisocyanate solution (Exemple 3)
were mixed in a vibratory mixer.
[0148] The mixing time was in each case 60 seconds. With the
mixtures obtained at a firing pressure of 4 bar, test specimens
(+GF+bar) were fired, which were than gasified for 10 seconds at a
gasification pressure of 4 bar with dimethylisopropylamine and then
flushed with air for 10 seconds. The sand quantity per test
specimen was 3 kg, the sand temperature and the ambient temperature
were approximately 25.degree. C. the relative humidity (RH) was
approximately 39%. Then the flexural strengths of the test
specimens obtained in this way were determined according to the GF
method. In the preparation of the test specimens and the testing of
the flexural strengths the specifications of VDG leaflet P 73 of
February 1996 were applied.
[0149] Table 2 provides a comparison of the strength values of
seven cores according to the invention and a conventional core (in
N/cm.sup.2).
[0150] For the results compiled in Table 2 investigations were
firstly performed with a mixture used to prepare a mould test
specimen immediately after mixing ("IMMEDIATE" column) and secondly
with a mixture first stored for three hours after mixing (for
assessing the so-called "benchlife" BL) and then used to prepare a
test specimen ("3 HOURS" column).
[0151] The results summarised in the following Table 2 show how the
test specimens (cores) to prepared according to the invention have
strength values that are just as good as the cores prepared in the
conventional manner.
[0152] The substantial difference between the conventional core and
the cores according to the invention is that in their preparation
and also during casting the latter no longer produce any noticeable
burden on the workplace. Behaviour during casting has been
confirmed by is sample castings performed under laboratory
conditions.
TABLE-US-00022 TABLE 2 Flexural strengths Further processing of the
mixture IMMEDIATE 3 HOURS Phenol Poly- Test time resin isocyanate
immed. 1 h 24 h immed. 1 h 24 h HA1 HB1 309 409 453 273 376 401 HA1
HB2 294 397 461 253 335 365 HA1 HB3 283 368 427 244 332 356 HA1 HB4
286 376 429 250 371 394 HA1 HB5 285 353 409 253 367 400 HA1 HB6 280
367 397 245 359 385 HA1 HB7 179 300 329 165 227 250 HA1 HB8 300 418
471 236 365 397
* * * * *