U.S. patent number RE32,812 [Application Number 06/860,204] was granted by the patent office on 1988-12-27 for foundry moulds and cores.
This patent grant is currently assigned to Borden (UK) Limited. Invention is credited to Derek W. Baker, Vincent J. Coppock, Peter H. R. B. Lemon, Jeffrey D. Railton.
United States Patent |
RE32,812 |
Lemon , et al. |
December 27, 1988 |
Foundry moulds and cores
Abstract
A foundry moulding composition comprising (a) a granular
refractory material, (b) from 0.25 to 2.5% based on the weight of
the refractory material of an aqueous solution of a potassium
alkali phenol-formaldehyde resin, said aqueous solution having a
solids content of from 50 to 75% and said resin having a weight
average molecular weight (M.sub.wr) of from 700 to 2000, a
formaldehyde:phenol molar ratio of from 1.2:1 to 2.6:1 and a
potassium hydroxide:phenol molar ratio of from 0.5:1 to 1.2:1; (c)
from 0.05 to 3% based on the weight of said aqueous solution, of at
least one silane, and (d) from 20 to 110% based on the weight of
said aqueous solution of at least one ester active to catalyze
curing of said resin.
Inventors: |
Lemon; Peter H. R. B.
(Sherfield, GB2), Railton; Jeffrey D. (Southampton,
GB2), Baker; Derek W. (Southampton, GB2),
Coppock; Vincent J. (Malpas, GB2) |
Assignee: |
Borden (UK) Limited
(Southampton, GB2)
|
Family
ID: |
26281771 |
Appl.
No.: |
06/860,204 |
Filed: |
May 6, 1986 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
434462 |
Oct 14, 1982 |
04474904 |
Oct 2, 1984 |
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Current U.S.
Class: |
523/145;
523/146 |
Current CPC
Class: |
C08G
8/10 (20130101); C08G 8/28 (20130101); C08L
61/14 (20130101) |
Current International
Class: |
C08L
61/14 (20060101); C08L 61/00 (20060101); C08G
8/10 (20060101); C08G 8/00 (20060101); C08G
8/28 (20060101); C08K 003/36 () |
Field of
Search: |
;523/146,144,145 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0027333 |
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Apr 1981 |
|
EP |
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0146499 |
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Feb 1985 |
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EP |
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1065605 |
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Sep 1959 |
|
DE |
|
1171606 |
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Jun 1964 |
|
DE |
|
1252853 |
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Jun 1965 |
|
DE |
|
2829669 |
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Jan 1980 |
|
DE |
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4916793 |
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Feb 1974 |
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JP |
|
50-130627 |
|
Oct 1975 |
|
JP |
|
2059972 |
|
Apr 1981 |
|
GB |
|
Other References
"Fundamentals of Foundry Technology" P. D. Webster published 1980,
pp. 119-167. .
"Molecular Weight Distribution Measurements of Phenolic Resins", J.
J. Gardikes and F. M. Konrad, pp. 130-137. .
Encyclopedia of Polymer Science and Technology, pp. 31-38, vol. 10,
1969. .
Chromatographic Studies of Some Thermosetting Resins, Aldersley et
al., B. Polymer J., 1969, vol. 1, May, pp. 101-109. .
Chemical & Appl of Phenolic Resins, Knop et al., pp. 38, 51,
65, 84, 1979. .
Chem. Abst. 84, 125183c, (1976). .
Ishida, Molecular Weight of Phenolic Resins, 11/82, pp. 137-142.
.
Tobiason et al., Molecular Weight Characterization of Resole
Phenol-Formaldehyde Resins, Polymer Molecular Weight Methods, pp.
194-203, 1/75. .
Foundry Trade Journal, APV Paramount Turn to Boxless Moulding for
Hight-Output Production, 5/85. .
Blackburn et al., "Experience with Alphaset in High Alloy Steel
Prod.", Proceedings of 1983 Annual Conference, Scrata, pp. 1:2-1:7,
1983. .
Stevenson, Recent Developments in Cold Setting Moulding and
Coremaking, The British Foundryman, 10/84..
|
Primary Examiner: Jacobs; Lewis T.
Attorney, Agent or Firm: Robbins; Frank E. Laramie; James R.
Maskas; George P.
Claims
What is claimed is:
1. A foundry moulding composition comprising
(a) a granular refractory material,
(b) from 0.25 to 2.5% based on the weight of the refractory
material of an aqueous solution of a potassium alkali
phenol-formaldehyde resin, said aqueous solution having a solids
content of from 50 to 75% and said resin having a weight average
molecular weight (M.sub.w) of from 700 to 2000, a
formaldehyde:phenol molar ratio of from 1.2:1 to 2.6:1 and a
potassium hydroxide:phenol molar ratio of from 0.5:1 to 1.2:1;
(c) from 0.05 to 3% based on the weight of said aqueous solution,
of at least one silane, and
(d) from 20 to 110% based on the weight of said aqueous solution of
at least one ester active to catalyze curing of said resin.
2. The composition of claim 1 wherein the refractory material is
selected from the group comprising silica sand, quartz, chromite
sand, zircon, olivine sand or beach sands containing shell
fragments.
3. The composition of claim 2 wherein the refractory material is
chromite sand, olivine sand or beach sands containing shell
fragments.
4. The composition of claim 1 wherein the M.sub.w of said resin is
from 800 to 1700.
5. The composition of claim 4 wherein said M.sub.w is from 950 to
1700.
6. The composition of claim 1 or 4 wherein the potassium
hydroxide:phenol molar ratio is from 0.6:1 to 1.2:1.
7. The composition of claim 1 wherein said silane is
.gamma.-aminopropyltriethoxysilane.
8. The composition of claim 1 wherein from 25% to 40% by weight of
said aqueous solution of said ester catalyst is present.
9. The composition of claim 8 wherein said ester is a low molecular
weight lactone or an ester of a C.sub.1-10 alkyl mono- or
polyhydric alcohol with a C.sub.1-10 carboxylic acid.
10. The composition of claim 9 wherein said lactone is selected
from the group comprising .gamma.-butyrolactone, propiolactone and
.xi.-caprolactone.
11. The composition of claim 9 wherein said carboxylic acid is
acetic acid.
12. The composition of claim 11 wherein said ester is glycerol
triacetate.
13. A process for the production of foundry moulds or cores which
comprises,
mixing granular refractory material with a binder, wherein said
binder comprises (a) from 0.25% to 2.5% based on the weight of the
refractory material of an aqueous solution of a potassium alkali
phenol-formaldehyde resin, said aqueous solution having a solids
content of from 50% to 75% and said resin having a weight average
molecular weight (M.sub.w) of from 700 to 2000, a
formaldehyde:phenol molar ratio of from 1.2:1 to 2.6:1 and a
potassium hydroxide:phenol molar ratio of from 0.5:1 to 1.2:1, (b)
from 0.05% to 3% based on the weight of said aqueous solution of at
least one silane, and (c) from 20% to 110% based on the weight of
said aqueous solution of at least one ester active to catalyze
curing of said resin,
discharging the mixture into a corebox or pattern mold, and
allowing the resin to cure.
14. The process of claim 13 wherein the refractory material is
selected from the group comprising silica sand, quartz, chromite
sand, zircon, olivine sand or beach sands containing shell
fragments.
15. The process of claim 14 wherein the refractory material is
chromite sand, olivine sand or beach sands containing shell
fragments.
16. The process of claim 14 wherein the M.sub.w of said resin is
from 800 to 1700.
17. The process of claim 16 wherein the potassium hydroxide:phenol
molar ratio is from 0.6:1 to 1.2:1.
18. The process of claim 13 wherein from 25% to 40% by weight of
said aqueous solution of said ester catalyst is utilized.
19. The process of claim 17 wherein from 25% to 40% by weight of
said aqueous solution of said ester catalyst is present.
20. The process of claim 19 wherein said ester is a low molecular
weight lactone or an ester of a C.sub.1-10 alkyl mono- or
polyhydric alcohol with a C.sub.1-10 carboxylic acid.
21. The process of claim 20 wherein said carboxylic acid is acetic
acid.
22. The process of claim 21 wherein said ester is glycerol
triacetate.
Description
BACKGROUND OF THE INVENTION
This invention relates to the manufacture of foundry moulds and
cores and to moulding compositions useful therein. More
particularly, the invention relates to the use of highly condensed
potassium alkali phenolic resins in the binders for the moulds and
cores.
Phenol-formaldehyde (PF), phenol-formaldehyde/furfuryl alcohol
(PF/FA), urea-formaldehyde/furfuryl alcohol (UF/FA) and furfuryl
alcohol-formaldehyde condensation products, catalyzed with strong
acid catalysts, such as phosphoric acid, sulphuric acid and
paratoluene sulphonic acid and the like, as well known as binders
for sand in the production of cold-setting foundry moulds and
cores. Aromatic sulphonic acids are more commonly employed than all
other types but have the disadvantage that pungent fumes of sulphur
dioxide are evolved on thermal decomposition.
UF/FA condensation products contain nitrogen which can form ammonia
on thermal decomposition and this tends to neutralize the sulphur
dioxide. However, nitrogen in the binder can react with certain
metals, such as, for example, grey and nodular irons and steel,
resulting in the formation of small bubbles in the final casting, a
defect known in the foundry industry as "pinholing". The employment
of UF/FA binders is consequently restricted.
Phosphoric acid may be employed as a catalyst but tends to build up
on the sand on repeated attrition reclamation and this reduces the
refractoriness of the sand. Phosphoric acid is also incompatible
with PF/FA condensation products and, as a result, the moulds and
cores produced exhibit poor bond strengths.
In the foundry moulding art the use of aqueous highly alkaline
phenol-aldehyde resins as binders for sand has not been developed
because they tend to produce weak cores. It is known in other
fields that the curing of phenol-formaldehyde resins can be
catalyzed by esters. The application of this to foundry moulds and
cores has been suggested in Japanese Patent publication (Kokai) No.
130627/1975 and copending U.S. application Ser. No. 224,131, filed
Jan. 12, 1981.Iadd., now U.S. Pat. No. 4,426,467, issued Jan. 17,
1984.Iaddend.. Whilst these specifications show that foundry cores
and moulds having adequate strength and strength increase with time
can be made they require the use of relatively high proportions of
resin which is costly and makes recovery of the sand, after
casting, more difficult.
The present invention is based on the discovery that the use of
highly condensed phenol-formaldehyde resins can give moulds and
cores which have adequate strength and strength increase at much
lower levels of resin. The use of such highly condensed resins in
making foundry moulds and cores has not been considered
practicable, heretofore.
SUMMARY OF THE INVENTION
The present invention accordingly provides a method of making a
foundry mould or core which comprises mixing granular refractory
material with a binder which comprises:
1. from 0.25% to 2.5% by weight of the granular refractory material
of an aqueous solution, having a solids content of from 50% to 75%
by weight, of a potassium alkali-phenol-formaldehyde resin having
the following characteristics:
(a) a weight average molecular weight (M.sub.w) of from 700 to
2000;
(b) a formaldehyde:phenol molar ratio of from 1.2:1 to 2.6:1;
and
(c) a KOH:phenol molar ratio of from 0.5:1 to 1.2:1;
2. from 0.05% to 3% by weight on the weight of the resin solution
of at least one silane; and
3. from 25% to 110% by weight of the resin solution of at least one
ester active to catalyze curing of the resin;
forming the mixture and allowing the mixture to set by curing of
the resin in the binder.
The moulding compositions comprising the mixture of granular
refractory material and binder as set out above is believed to be
novel and, accordingly, forms part of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The granular refractory materials used in the present invention may
be any of the refractory materials commonly employed in the foundry
industry for the production of moulds and cores, such as silica
sand, quartz, chromite sand, zircon or olivine sand. The
compositions of the invention have the particular advantage that
the difficulties commonly associated with the bonding of sands of
alkaline reaction, such as olivine and chromite, or beach sands
containing shell fragments, and which arise from neutralization or
partial neutralization of the acid catalyst used in conventional
systems, are completely overcome, since in this invention the resin
binder is cured under alkaline conditions. The invention is,
therefore, of particular utility where it is necessary or desirable
to employ alkaline sands.
The nature of the phenol-formaldehyde resin used is a most
important feature of the present invention. There are several
features of the resin which are important. Since the present
invention is directed to cold set techniques, the resin binder will
be used as an aqueous solution of the resin. The solids content of
the aqueous solution is in the range 50 to 75% by weight. Solids
contents below 50% are not used because they contain too much water
which reduces the effectiveness of the binder. Solids contents
above 75%, are not used because the viscosity becomes too high.
The phenol-formaldehyde resins used in this invention have a weight
average molecular weight (M.sub.w) of from 700 to 2000 and
preferably from 800 to 1700. Resins with M.sub.w less than 700,
such as were used in copending U.S. Ser. No. 224,131, give products
which are relatively weaker or require significantly more resin to
achieve similar strengths. Resins with M.sub.w greater than 2000
are either not adequately water soluble within the range of KOH
contents used in the invention or precipitate out of solution or
cause the solution to gel before the resin has cured adequately
yielding products with poor strength.
Optimum results may not be obtained within the broad M.sub.w range
at the extreme limits of the ranges of KOH:phenol and
formaldehyde:phenol molar ratios, especially at the lower end of
the KOH:phenol ratio. We have obtained satisfactory results showing
the advantage of the invention throughout the 800 to 1700 M.sub.w
range. We have, to date, obtained optimum results using resins
having M.sub.w greater than 950.
The resins used in this invention are potassium alkaline
phenol-formaldehyde resins by which is meant that the alkali in the
resin is potassium alkali. This alkali can be present in the resin
during manufacture or, more usually, post added to resin as KOH,
preferably in aqueous solution of suitable strength. The alkalinity
of the resin is expressed in terms of its KOH content and
specifically by the molar ratio of KOH to the phenol in the resin.
Other alkalis are not expressly excluded and may be present in
minor amounts but will not be specifically added because they slow
curing of the resin and give products having lower strength. We
have found that substituting the KOH used in the invention by an
equimolar amount of NaOH gives cores which typically have half the
strength after 1 hour and only achieve two third the strength after
24 hours of cores made using KOH as the alkali.
The molar ratio of KOH:phenol in the resin solution is in the range
0.5:1 to 1.2:1 and preferably 0.6:1 to 1.2:1. At ratios less than
0.5 the speed of cure and product strength are much reduced. The
reasons for this are not entirely clear but it seems probable that
at such low ratios resin tends to be insoluble or precipitates from
solution during curing. Also we believe that a relatively high
KOH:phenol ratio increases the concentration of phenolate type
anions which enhances activity of the resin to curing by
cross-linking. Ratios higher than 1.2 are not used because the
excess KOH makes the resins hazardous to handle and inhibits curing
by oversolubilizing the resin and/or reducing the effect of ester
catalysis. The use of KOH:phenol ratios lower than 0.6 is not
preferred with resins having M.sub.w less than 800 because the
speed of cure and product strength is below optimum.
The resins used have a formaldehyde to phenol molar ratio of from
1.2:1 to 2.6:1. Lower ratios are not used because lower strengths
are obtained in use. Higher ratios are not used because they are
either of low molecular weight, or are excessively crosslinked, or
contain undesirably high levels of unreacted formaldehyde.
Especially, within the preferred limits of this ratio suitable
highly condensed resins, with low levels of unreacted formaldehyde
and high reactivity can be obtained.
It is a subsidiary aspect of this invention that the resin used
satisfies the following criteria:
(a) M.sub.w from 800 to 1700;
(b) KOH:phenol molar ratio 0.6:1 to 1.2:1; and
(c) formaldehyde:phenol molar rato 1.2:1 to 2.6:1.
The curing catalyst used in the invention is an ester. Suitable
esters include low molecular weight lactones e.g.,
.gamma.-butyrolactone, propiolactone, and .xi.-caprolactone, and
esters of short and medium chain e.g. C.sub.1 to C.sub.10 alkyl
mono- or polyhydric alcohols, with short or medium chain e.g.
C.sub.1 to C.sub.10 carboxylic acids especially acetic acid. We
have obtained very good results using triacetin (glyceryl
triacetate) as the catalyst.
The amount of catalyst used in the range 20% to 110%, preferably
25% to 40% by weight on the weight of resin solution used,
corresponding approximately to 10% to 80% by weight on the weight
of solid resin in the solution. The optimum in any particular case
will depend on the ester chosen and the properties of the resin.
The mechanism of catalysis is not certain but we believe that it
involves the initial nucleophilic attack by anionic sites in the
resin on the ester which activates the resin to crosslinking
reactions in the presence of the alkali.
A silane is included in the mixture to improve product strength.
Amounts as low as 0.05% by weight on the weight of resin solution
provide a significant improvement in strength. Increasing the
amount of silane gives greater improvements in strength up to about
0.6% by weight of the resin solution. Higher silane concentrations
are not preferred because of added cost. Further, because the
silane typically used is .delta.-aminopropyltriethoxy silane which
contains nitrogen, use of excess silane may increase the risk of
pinholing defects and for these reasons amounts in excess of 3% by
weight on the resin solution are not used.
The following Examples illustrate the invention. The techniques
used in the Examples are described below:
MANUFACTURE OF PHENOL FORMALDEHYDE RESIN SOLUTIONS
100% phenol was dissolved in 50% aqueous KOH in an amount
corresponding to the desired KOH:phenol molar ratio (from 0.5 to
1.2). The solution was heated to reflux and 50% aqueous
formaldehyde was added slowly, whilst maintaining reflux, in an
amount corresponding to the desired formaldehyde:phenol molar ratio
(1.6, 1.8 or 2.0). The reaction mixture was maintained under reflux
until it attained a pre-determined viscosity corresponding to the
desired value of M.sub.w. (If desired the solids content can be
adjusted by distillation, but this is not usually necessary, a
further advantage of the invention. In some cases minor amounts of
KOH solution were added to adjust the KOH:phenol ratio, but this
would not be necessary in full scale production.) The resin
solution was cooled to 40.degree. C. and 0.4% by weight on the
weight of the resin solution of .delta.-aminopropyl triethoxy
silane was added.
TESTING OF RESINS
(a) viscosity--measured using an Ostwald (U-tube) viscometer at
25.degree. C.
(b) solids content--measured by heating a weighed sample
(2.0.+-.0.1 g) in an air circulating oven for 3 hrs at 100.degree.
C.
(c) Molecular weight (M.sub.w)--measured using gel permeation
chromatography. .[.Samples were prepared by precipitating resin
from the resin solution by adding H.sub.2 SO.sub.4 ; separating,
washing and drying the precipitate and dissolving it in
tetrahydrofuran..].
PREPARATION OF TEST FOUNDRY CORES
1 kg of the selected sand was charged to a Fordath laboratory
coremixer. The ester catalyst was added and mixed for 1 min and the
resin solution was then added. Mixing was continued for 1 min and
the mixture then quickly discharged into the test moulds. One
sample was rammed into a waxed paper cup which was squeezed by hand
to assess the bench life and when setting had occurred. Other
samples were formed into 5.times.5 cm cylindrical test cores by the
standard method recommended by I.B.F. working party P. The test
cores were placed in a standard atmosphere, 20.degree. C.; 50%
relative humidity, and samples were tested for compression strength
1 hr, 2 hr, 4 hr and 24 hr after manufacture. All compression test
cores were made within 2 minutes of discharge of the mix.
In the Examples tests designated with a letter (tests A to F) are
comparative tests outside the invention, tests designated with a
number (1 to 22) are of the invention.
EXAMPLE 1
This Example illustrates the effect of phenol-formaldehyde resin
M.sub.w on core performance.
Test cores were made from the following starting materials
Phenol-formaldehyde resin solution
M.sub.w --variable--see Table 1
Formaldehyde:phenol molar ratio 2:1
KOH:phenol molar ratio 0.85:1
Solids 65% by weight
Amount 1.5% by weight on sand.
Sand--Chelford 50
Silane--0.4% by weight on resin solution of
.gamma.-aminopropyltriethoxysilane.
Catalyst 30% by weight on resin solution of triacetin (0.45% on
sand)
The values of M.sub.w and test results are set out in Table 1.
Tests A and B are of resins outside the M.sub.w range of this
invention. The results show that the benefit of the invention is
obtained within a restricted range of M.sub.w.
TABLE 1 ______________________________________ Test No. A 1 2 3 4 5
6 B ______________________________________ --M.sub.w 560 718 849
966 1050 1217 1320 .infin..sup.(3) Viscosity -- 81 111 144 167 321
364 501 (cSt) Bench Life 65 23 19 16 14.sup.(2) 10 10 2 (mins) Set
Time 180 32 28 22 22.sup.(2) 16 15 3 (mins) Com- pression Strength
(kPa).sup.(1) 1 hr 0 690 1580 2070 2050.sup.(2) 2465 2415 0 2 hr 0
1950 2765 2960 2685.sup.(2) 3000 3000 0 4 hr 0 2860 3200 3520
2750.sup.(2) 3300 3300 0 24 hr 1480 4785 4800 5000 4650.sup.(2)
4400 4400 800 ______________________________________ .sup.(1) "0"
figures for Compression strength mean that the resin had not set at
the test time or the core was soft. .sup. (2) Average of 2 runs
.sup.(3) ".infin." means the --M.sub.w is >2000 and was too high
to measure by the method used.
EXAMPLE 2
Example 1 was repeated using resins having a lower KOH:phenol molar
ratio.
Phenol-formaldehyde resin solution
e,ovs/M/ .sub.w --variable--see Table 2
KOH:phenol molar ratio 0.65:1
formaldehyde:phenol molar ratio 2:1
Solids 66% by weight
Amount 1.5% by weight on sand.
Sand--Chelford 50
Silane--0.4% by weight on resin solution of
.gamma.-aminopropyltriethoxysilane
Catalyst 30% by weight on resin solution of triacetin.
The values of M.sub.w and test results are set out in Table 2. The
results are similar to those of Example 1. The result of Test No. 7
could be improved using .gamma.-butyrolactone as the catalyst.
TABLE 2 ______________________________________ Test No. 7 8 9 10
______________________________________ --M.sub.w 718 849 966 1050
Viscosity (cSt) 107 202 320 405 Bench Life (mins) 35 24 18 15 Set
Time (mins) 70 40 30 26 Compression Strength (kPa) 1 hr 0 740 1085
1285 2 hr 590 1600 1875 2200 4 hr 1085 2350 2650 2900 24 hr 3000
4400 4350 5000 ______________________________________
EXAMPLE 3
This Example illustrates the use of different levels of and
different catalysts and gives a comparison with the system of U.S.
Ser. No. 224,131.Iadd., now U.S. Pat. No. 4,426,467, issued Jan.
17, 1984.Iaddend..
TABLE 3 ______________________________________ Test No. 11 12
C.sup.(3) ______________________________________ --M.sub.w 966 966
560 Viscosity (cSt) 144 144 ca 70 KOH:phenol 0.85 0.85 0.52
formaldehyde:phenol 2 2 1.8 Solids (%) 64 64 68.1 Amount of binder
(%).sup.(1) 1.4 1.33 2.1 Catalyst.sup.(2) .gamma.-Bu TAc .gamma.-Bu
Amount of Catalyst (%) 30 25 32 Bench Life (mins) 3 18 5 Set Time
(mins) 5 24 8 Compression Strength (kPa) 1 hr 2320 1725 1725 2 hr
2950 2765 2450 4 hr 3300 3500 3350 24 hr 4500 5000 4800
______________________________________ Test C is Example 6 of U.S.
Ser. No. 224,131 .[...]..Iadd.now U.S. Pat. No. 4,426,467, issued
JAN. 17, 1984 .sup.(1) Amount of Binder is solids content of binder
including resin alkali and catalyst as % by weight on sand .sup.(2)
Bu = butyrolactone TActriacetin .sup.(3) For Test C the data are
based on the resin solution i.e. the combination of the 6 parts of
resin and the 2.4 parts of 50% KOH solution
EXAMPLE 4
This Example illustrates the effect of variation of the KOH:phenol
molar ratio.
Phenol-formaldehyde resin solution.
M.sub.w 966
formaldehyde:phenol molar ratio 2:1
KOH:phenol molar ratio-variable-see Table 4.
Solids 64% by weight
Amount varies to maintain solid organic resin to sand ratio--see
Table 4.
Sand--Chelford 50
Silane 0.4% by weight on resin solution of .gamma.-aminotriethoxy
silane
Catalyst 30% by weight on resin solution of triacetin.
The Results are set out in Table 4.
TABLE 4 ______________________________________ Test No. 13 14 15 16
17 ______________________________________ KOH:phenol molar 0.34
0.51 0.68 0.85 1.02 ratio Wt % resin 1.33 1.41 1.5 1.59 1.67
solution on sand Bench life (mins) 30 18 15 12 9 Set Time (mins)
100 29 23 19 15 Compression Strength (kPa) 1 hr 0 890 2070 2615
2465 2 hr 200 1625 2715 3305 3110 4 hr 440 2220 3355 3550 3395 24
hr 1875 3995 5032 4537 4271
______________________________________
EXAMPLE 5
This Example further illustrates the variation of KOH:phenol molar
ratio at lower formaldehyde:phenol (f:phenol) molar ratios and
values of M.sub.w. The results are set out in Table 5. In all cases
the resin solution was used at 1.5% by weight on the sand and
including 0.4% by weight on the resin solution of
.gamma.-aminopropyltriethoxy silane. The catalyst was triacetin 30%
by weight on the resin solution.
TABLE 5 ______________________________________ Test No. D 18 E 19 F
20 21 22 ______________________________________ --M.sub.w 650 800
720 950 650 900 1100 1603 Viscosity 191 276 478 460 600 414 277 350
(cSt) Solids (%) 62.7 63.2 63.2 66.1 65.4 66.2 60.2 58 f:phenol
ratio 1.8 1.8 1.8 1.8 1.6 1.6 1.6 1.6 KOH:phenol 0.46 0.79 0.46
0.79 0.45 0.79 0.79 0.75 ratio Bench Life 60 14 35 10 45 20 12 11
(mins) Set Time 220 20 90 16 120 35 18 15 (mins) Compression (kPa)
1 hr 0 2465 0 2515 0 1235 1875 2270 2 hr 0 3100 350 3300 150 2200
2860 3060 4 hr 150 3350 790 3300 350 2800 3300 3500 24 hr 1240 4500
2660 4000 2150 4000 4600 4685
______________________________________
While the invention has been disclosed in this patent application
by reference to the details of preferred embodiments of the
invention, it is to be understood that this disclosure is intended
in an illustrative rather than in a limiting sense, as it is
contemplated that modifications will readily occur to those skilled
in the art, within the spirit of the invention and the scope of the
appended claims.
* * * * *