CA1118143A

CA1118143A - Foundry resin components

Info

Publication number: CA1118143A
Application number: CA000264840A
Authority: CA
Inventors: Melville J. Holik
Original assignee: Aristo Corp
Current assignee: Aristo Corp
Priority date: 1975-11-13
Filing date: 1976-11-03
Publication date: 1982-02-09
Also published as: DE2651808B2; BR7607608A; GB1559015A; GB1559013A; DE2651808A1; GB1559014A

Abstract

ABSTRACT OP THE DISCLOSURE

A new foundry binder composition comprises a selected phenol-formaldehyde resin, a polylsocyanate, and a selected solvent therefor. A preferred solvent is ketal or an acetal such as butyl acetal. The resole is essentially anhydrous, should contain about 8% free phenol, and is further preferably characterized by the presence of substituent -(CH2-O)n-R groups replaclng a phenolic hydrogen, R being a hydrocarbon radlcal such as butyl. Methylene and ether bridges linking phenolic nuclei are predominantly ortho-para with some para-para bridges.
Also disclosed is the admixture of a reactive polyisocyanate and a solvent such as butyl acetal.

Description

1118~L3 FOUNDRY RESIN COMPONENTS
This invention relates to a core binder useful in the manufacture of foundry cores and molds. It also relates in more specific aspects to components of a core binder system.
Cores useful in making metal castings are customarily made by placing a foundry aggregate, usually silica sand which has been admixed with a suitable binder, against a shape or pat-tern and then hardening the binder, as by polymerization. The resulting core is a self-supporting structure which forms a part of a mold assembly.
Various sands are used for making cores. The cores them-selves are made by a variety of processes employing a wide va-riety of binders. Three of the many processes in commercial use today are the so-called cold box process, no-bake process, and the rapid no-bake process. The cold box process is one in which sand is admixed with a suitable resinous binder composi-tion, blown into a core box, and then gassed with a suitable vapor phase eatalyst to cure the binder. By such process, which is deseribed for example in U. S. Patent No. 3,409,579, a core of sufficient hardness to be stripped from the core box is pro-duced in a matter of seconds. The no-bake process is one in which a resinous core binder is admixed with a catalyst and sand and placed in a core box. The core cures at ambient tem-peratures but much more slowly than in the cold box process, over a period of hours or even days. After a suitable period of time, such as two hours, the core can generally be stripped from the core box, but requires further cure time. The rapid no-bake process is similar to the no-bake process, but the character of the resin and the amount and type of catalyst em-ployed are such that a core is formed and may be stripped from the core box in a matter of a few minutes. The bench life, or l3 time period during which a sand-resin mixture may be kept before the reaction proceeds to a detrimental extent prior to placing the mixture into the core box, generally decreases rapidly when the catalyst and resin are adjusted to provide very rapid set times. Therefore the development of the rapid no-bake process was dependent upon the availability of foundry machines which were capable of mixing small but accurately controlled amounts of resin, catalyst and sand and transferring the admixture sub-stantially immediately into a core box. Processes of this type are described, for example, in U. S. Patent No. 3,702,316. The subject invention provides a binder system which is suitable for use in all three of these processes. It will be understood that the kind and amount of catalyst employed will be such as to adapt the final binder-sand admixture to the intended purpose.
That is, in the cold box process, the catalyst will typically be a gaseous amine, such as triethylamine, dispersed in a suitable carrier such as carbon dioxide. In the no-bake and rapid no-bake process, amine catalysts may be employed but common metal catalysts such as lead naphthenate or dibutyl tin dilaurate are also employed in amounts adjusted to provide the desired set time.
Briefly, a foundry mix of this invention comprises foundry aggregate and about 1~ to 5~, based upon the weight of the aggregate of a binder comprising:
a) A phenol-formaldehyde resin characterized by:
1) A phenol-formaldehyde ratio in the range of about 1.0:0.75 to 1.0:2.0,

2) Free phenol in the amount of about 5% to 12~ by weight of the resin,

3) Water in an amount less than about 2~ by weight of the resin, and

4) An average of 2 1/2 to 3 1/2 phenolic nuclei per resin oligomer, b) A liquid polyisocyanate reactive with the resin in the amount of about 80% to 125% by weight of the resin, and, c) A solvent of the formula Rl-O-C-O-R2 in which Rl and R2 are the same or different hydrocarbon radicals of three to six carbon atoms and R3 and R4 are the same or different hydrogen, methyl, ethyl or phenyl radicals. The solvent is present in the amount of about 10% to 40% by weight of the binder.
The binder composition is conventionally provided in two components or packages. One contains the phenolic resin, the other the isocyanate. In a preferred embodiment of the in-vention, both the isocyanate and the phenolic resin will be dissolved or dispersed in the selected solvent. The amount of the solvent in each package may vary provided the amount of solvent present in the resin-isocyanate mixture is within the limits specified. Further, in accordance with one embodiment of the invention, a preferred resin component or package com-prises an admixture of solvent as before-defined, together with a select phenol-formaldehyde resin characterized by:
a) A phenol-formaldehyde ratio in the range of 1.0:0.75 to 1.0:2.0, b) A substituent - (CH2 -O)y-R group present at about 12% to 30% of the substituted phenolic nuclear positions, c) Free phenol in the amount of about 5% to 15%

by weight of the resin, d) Water in the amount of less than 2% by weight of the resin~
e) An average of about 2 1/2 to 3 1~2 phenolic nuclei per resin oligomer and f) A hydroxymethyl content of less than about

5 mole %.
The phenol to phenol bridges are predominantly ortho-para, with at least 20~ of the bridges being para-para, the bridges being of the formula --CH2~OCH2)X-- where x is zero in at least 30~ of the bridges, and x is an integer in the range of 1 to

6 in at least 20% of the bridges. The resin is characterized by substituent groups of the formula -(CH2-O)y~R in which y is an integer in the range of 1 to 6 and R is a hydrocarbon radical of three to six carbon atoms.
In a specific aspect, the invention relates to a phenol-formaldehyde resin prepared by the preferred method herein-after described.
The phenol-formaldehyde resins employed in accordance with this aspect of the invention are preferably prepared by react-ing phenol itself, i.e., non-substituted phenol, with formal-dehyde or paraformaldehyde in the presence of an acid catalyst.
The mole ratio of phenol to formaldehyde is in the range of 1.0:0.75 to 1.0:2Ø The reaction is preferably carried out under vacuum in the later stages and water is collected as the reaction proceeds. In any event, the final resin is stripped to a water content of less than 2%, and preferably less than 1% .
While phenol itself is the preferred reactant, substituted phenols may also be employed. They are not preferred, however, because they are generally more éxpensive and provide no 11~81~3 advantage. Neverthele3s, substituted phenols such as meta-and para-cresol may be employed as desired. Numerous other sub-stituted phenols may also be employed, as describe~ for example in the aforementioned U. S. Patent 3,702,316.
In the prepa~ation of the phenol-formaldehyde resins pre-ferred for use in this invention, either phenol itself or a phenol substituted with -CH2-O-R radicals may be employed. Phe-nol itself is the most preferred starting material. The re-action with formaldehyde is carried out in the presence of a suitable alcohol such as butanol, whereby the desired ether substitution takes place concomitantly with the formation of the resin. In the production of the preferred resin, phenol and formaldehyde or paraformaldehyde in amounts to provide the desired mole ratio are first charged to a kettle and a C3 to C6 alcohol such as butanol in the amount of 10% to 20% by weight of the total charge and acid catalyst are then charged to the re-action kettle. Any acid catalyst which will maintain the pre-ferred pH can be used. A preferred catalyst is hypophosphorous acid in amounts such as 0.15% and 0.45% by weight of the total charge, respectively. Also a 50% mixture of hypophosphorous acid and acetylsalicylic acid can be use~. Oxalic acid is another example of a suitable catalyst if used in small amounts. In any event the pH is maintained in the range of 1.8 to 2.3. The mixture is initially heated to a temperature sufficient to dissolve the paraformaldehyde (230F), and the reactio~ is then carried out at a temperature of about 215F to an initial endpoint at which the remaining free formaldehyde is reduced to 12% to 16% by weight of the total charge. The charge is cooled to 180F
and a base such as barium hydroxide octahydrate, preferably calcium hydroxide, added incrementally, or zinc oxide is then added in an amount sufficient to raise the pH to a level of 3~

5 to ~.5. This may be achieved by adding barium hydroxide octa-hydrate in the amount of about 1% of the phenol. Other bases suitable for raising the pH include lithium, sodium or potas-sium hydroxides. The reaction proceeds with an exotherm to 195F. The temperature is brought to 220F and the reaction is terminated at a free formaldehyde content of about 5%. An ad-ditional quantity of butanol (preferably about twice the amount initially charged) is now added, and the reaction is continued with concomitant removal of water under vacuum to 180 - 200F.
Then dehydration continues at atmospheric pressure by azeotropic distillation. Water is removed as formed in the ensuing etheri-fication reactions to 265F, and is reduced to a content of less than 2% by weight of the resin. Finally, almost all of the unreacted butanol is also removed during a terminal vacuum distillation. The free formaldehyde content is reduced to about 1% or less in the resulting product.
It should be appreciated that the character of the sub-stituted -CH2-O-R radical will be determined by the specific alcohol employed as a reaction medium and reactant. N-butyl alcohol is preferred. However, other C3 to C6 alcohols such as n-propyl alcohol, isopropyl alcohol, isobutyl alcohol, sec-butyl alcohol, n-amyl alcohol, n-hexyl alcohol, and cyclohexa-nol may be employed. The resins produced by the aforementioned process are characterized by the presence of about 5~ to 15%
by weight free phenol and by the presence of bridging groups between phenol nuclei of the formula -CH2(OCH2)X-, in which x is an integer in the range of 0 to 6 with 0 predominating.
Nevertheless, superior properties are imparted to the resin by the presence of bridging groups characterized by x being zero in at least 30~ of the bridges, and x being an integer in the range of 1 to 6 in at least 20% of the bridges. It ~13~

has been found that the character of the bridges, together with the aforedescribed alkoxymethylene substituent group, and ~~~ the free phenol content of 5~ to 15% provides a resin of out~
standing properties when used in conjunction with the here-inafter defined solvent or dispersant for the resin.
The polyisocyanates which can be used in accordance with this invention are those known to be useful in the preparation of foundry core binders. Such polyisocyanates, which will hereinafter be called reactive polyisocyanates, include the aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as 4,4'-dicyclohexylmethane diisocyanate and aromatic polyisocyanates such as 3,4- and 2,6-toluene diisocyanatej diphenylmethyl diisocyanate, and the dimethyl derivatives thereof. Other suitable polyiso-cyanates are 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, xylylene diisocyanate, and the methyl deriva-tives thereof, polymethylenepolyphenol isocyanates, and chlorophenylene-2,4-diisocyanate. Preferred, however, is the use of commercially available compositions which contain di-phenylmethane diisocyanate, and triphenylmethane triisocyanate.
The selected solvents used in accordance with the invention are compounds of the formula Rl-O-f-O-R2 in which Rl and R2 are the same or different hydrocarbon radicals of three to six carbon atoms, and R3 and R4 are the same or different methyl, ethyl, phenyl or hydrogen radicals. Preferred are compounds in which R3 and R4 are hydrogen. Especially pre-ferred is dibutoxymethane. Useful solvents are dipropoxy-methane, diisobutoxymethane, dipentyloxymethane, dihexyl-oxymethane, and dicyclohexyloxymethane. Other solvents _~_ which may be used include n-butoxyisopropoxymethane, isobutoxy-butoxymethane and isopropoxypentyloxymethane. Among the use-ful solvents in which R3 or R4 other than hydrogen are acetal-dehyde n-propyl acetal, benzaldehyde n-butyl acetal, acetalde-hyde n-butyl acetal, acetone di-n-butyl ketal and acetophenone dipropyl ketal.
The aforedescribed materials, while characterized as sol-vents, are, at least in some cases, not strictly speaking solvent to the pure resin. Nevertheless, in the presence of the specified free phenol, the selected solvents act as such, or possibly as a dispersant which is not precisely a true solvent; but in any event serve to reduce the viscosity of the resin to a suitable level such as 250 centipoises. It is thought that during the transformation of the resin to the polymeric binder, the presence of the dispersant contributes properties of adhesion to the substrata silica or refractory materials which promote the aforementioned outstanding prop-erties. Both the phenol-formaldehyde resin and the polyiso-cyanate are preferably admixed with the same selected solvent.
In the preferred practice of this invention, the solvent com-prises about 23% by weight of the resin solvent admixture, and about 23% by weight of the polyisocyanate solvent admixture.
Nevertheless, the amount of solvent in both or either of the resin component or polyisocyanate component may be varied to provide on admixture a binder which includes resin, polyiso-cyanate and selected solvent in the amount of 10% to 40% and preferably about 23% by weight of the binder admixture. The polyisocyanate is employed in the amoun~ of about 80~ to 125%
by weight of the resin. Preferably, the resin and polyiso-cyanate are employed in equal amounts by weight.
In another embodiment of the instant invention, a poly-_g _ isocyanate component is provided which is specially adapted foradmixture with a resin component as hereinbefore described, or other resin components as will be illustrated hereafter, together with a suitable catalyst to provide a foundry core binder of outstanding properties. The polyisocyanate com~
ponent comprises a reactive polyisocyanate as hereinbefore described in admixture with 10% to 40%, and preferably about 23% based upon the weight of the admixture, of a selected sol-l3 vent of the formula Rl-O-C-O-R2, and Rl and R2 being the same or different hydrocarbon radicals of three to six carbon atoms, R3 and R4 being hydrogen, methyl, ethyl or phenyl radi-cals, all as hereinbefore described.
This preferred polyisocyanate component is useful in com-bination with the preferred phenol-formaldehyde resin component hereinbefore described but is also useful with many other con-ventional phenol-formaldehyde resins which are characterized generally as of the resole type but which may contain quanti-ties of water in excess of 2% of the resin, and in fact as much as 25% by weight of the resin. Other resins, not of the phenolic type, but which react with polyisocyanates to provide binders, can also be used. In such cases the resin component may include a diluent or solvent different from the selected solvent. The solvent chosen for use in the resin component will of course be one which is compatible with the resin to provide stable compositions. Typical suitable solvents are cyclohexanone, isophorone,2-(2-butoxyethoxy) ethyl acetate, alkylated naphthalene, and other high solvency aromatics.
In the preparation of cores suitable for foundry use, the binder (which comprises the resin, polyisocyanate, solvent, and some-times a catalyst) is employed in an amount in the range of 1~ to 5~ by weight of the foundry sand. The binder and sand are mixed in a ~luller or otller device suitable for evenly dis-tributing the binder on the sand in keeping with the require-ments of ~he specific processes by which the cores are made.
These processes are conventional and form no part of the in-stant invention. As before described, a catalyst is generally employed and its selection will depend upon the specific pro-cess by which the core is made. In the cold box process, the catalyst is generally an amine such as triethylamine, the sand is coated with binder in the absence of catalyst, and placed in a core box. The amine catalyst is vaporized into a gaseous sub-stance, such as carbon dioxide, and blown through the core box to catalyze the reaction of the binder. In a foundry process such as the no-bake process or rapid no-bake process, either liquid amine catalysts or metal catalysts may be employed, separately or in admixture with the resin. Metal catalysts such as lead naphthenate or dibutyl tin dilaurate are preferred.
~enerally such catalysts are used in amounts from 0.0001 to 0.04 by weight of the resin. The catalysis of various resin polyisocyanate binder systems in the foundry art is well known, The amount and type of catalyst is adapted to provide the de-sired speed of reaction in accordance with the parameters of the specific process in which the binder is employed.
The invention will be better understood with reference to the following examples. It is understood, however, that the examples are intended only to illustrate the invention, and it is not intended that the invention be limited thereby.
Example 1 As a specific example of the method of producing preferred resins of this invention, a pilot kettle was charged as follows:

~1~81.~3 U.S.P. Phenol 25 lbs 0.2660 lb mols n-Butanol 6 lbs 10 oz 0.0895 lb mols 50% hypophosphorous acid 35 grams Paraformaldehyde (91%) 13 lbs 3 oz 0.4000 lb mols "Aspirin"* U.S.P. Powder 8 oz (226 grams) The batch was then heated to 235F to dissolve the para-formaldehyde within an hour, and the temperature was then dropped to 215F and maintained to a free formaldehyde assay of 11.9% (16 hours). The temperature was reduced to 170F
and barium hydroxide (8 ounces) was added. An exotherm to 196 F occurred and heating was resumed to 220F. In five and one-half hours, the free formaldehyde content dropped to 4.8%, and 13 pounds of n-butanol were added, dropping the temperature to 185F. Water began to collect from the azeotrope boiling at 200F under 14 inches of vacuum, and 977 grams were collected in three and one-half hours. The vacuum was discontinued, and removal of water by azeotropic atmospheric distillation was continued until a free water content of less than 1% was reached as the end point (9.5 hours) at 265F.
The dehydrated resin was now subjected to vacuum distilla-tion to remove excess butanol and phenol, carried out at 25 inches of vacuum from 200F to 255F in four and one-half hours. The viscosity of the amber liquid was 19,000 cps, the hydroxyl number was 344 mg KOH/gram resin, and the 38 pounds 4.5 ounces of product was equivalent to 153% resin recovery on the phenol basis. The resin was thinned with 7 pounds of butylal to discharge the batch completely from the kettle, and further reduced to 77% in butylal by the addition of 4 pounds 5 ounces supplemental butylal to obtain the desired viscosity.
Specific gravity of the formulation was 1.050. The overall reaction time and preparation totaled 37 hours.

. * Trademark for acetylsalicylic acid.

Example 2 As an example of the use of resins of this invention in the so-called cold box process, the resin of Example 1, which made up as described to 77% resin and 23% butylal, was used in the manufacture of foundry cores specimens. The isocyanate used was a commercially-available isocyanate designated "Mondur MR" which is a mixture of polyisocyanates. In preparing the sand-binder mixture, sand was charged to a muller.
To the muller was then added the resin solution. The resin-sand mixture was mulled for 1 1/2 minutes. The polyisocyanate,which was made up as a solution containing 77% polyisocyanate and 23% butylal, was then added and mulling continued for another 1 1/2 minutes. The resin solution and the polyisocy-anate solution were both added in the amount of 0.87% by weight of the sand. The binder-coated sand was then blown into a core box at a blow pressure of 80 p.s.i. and gassed with 12%
dimethylethylamine in carbon dioxide at 35 p.s.i. for the time indicated. The core box was then purged by blowing with air for the time indicated. The trials designated "control" used a commercial resin-polyisocyanate system. The results of the trials are set forth in Table 1.

*Trademark Table 1 Tensile Strengtll, lbs,~s~. ln.
Time After ~raw GasslngAir Cure Purge Time Time 15 30 60 2 3.5 Test Sec. Sec. Min. Min. Min. Hr. Hr.
Control 6 10 160 157.5 157.5 - -157.5 166.3 165 162.5 156.3 156.3 - -Control 3 6 145 155 152.5 145 - - -151.3 147.5 1 6 10 135 157.5 172.5 207.5 227.5 157.5 145 173.7 210 256.3 153.5 170 177.5 212.5 235 2 3 6 186.3 195 226.3 191.3 191.3 230 20 3 l.S 3 180 162.3 182.5 - - - -0.5 1.0 172.5 167.5 177.5 Example 3 As another example of the use of the binder system of this invention for the manufacture of foundry cores, the resin of :~118143 Example l was again ~ade up as a solution containin~ 77% resin and 23% butylal.
~ h~ ~ame polyisocyanate solution used in Example 2 was em-plo5~ed but both the resin component and polyisocyanate component were used in the amount of 1% each, based on the weight of the ~ortage 430 sand employed. Sand, resin, isocyanate, and cata-lyst were mixed in a high-speed mixing apparatus and transferred into a core box adapted to produce test specimens. The cata-lyst (lead naphthenate) was employed in the percentage indicated, based upon the weight of the binder. The core specimen was removed from the core box after the specified set time and its hardness was determined. In some cases two specimens were made, and the hardness of each was measured. The results of the test are set forth in Table 2.
Table 2 Rapid No-~ake Resin Evaluation Sand Set Hardness Test Catalyst ~ Time (Dietert 674) l 2.5% 70F
2 4.5% 70F 3 1/2 min. 69, 70 3 4.5% 70F 2 1/2 ~in. 45, 80 4 4.5% 94F 1 1/2 min. 68 4.5% 94F 1 min. 65 6 2.5% 76F 1 1/2 min. 56

7 2.5% 76F 2 min. 54

8 3% 76F 1 min. 35, 50

9 3.5~ 76F 55 sec. 20, 67 Example 4 This e~ample illustrates the use of the preferred polyiso-cyanate component of this invention together with a high water content phenol-formaldehyde resin. The resin is a resole *Tradem~rk C

prepared from 1 mole of phenol and 1.3 moles of paraformalde-hyde (100% basis). The paraformaldehyde was standard 91%
formaldehyde content. The reaction proceeded at 75 - 85C
in the presence of sodium hydroxide catalyst. The resin was cooled and neutralized with acetic acid to pH 6.5. The resin had a viscosity of 350 centipoises, a free phenol content of 13.6% and a water content of 16.7%. A silane was added in the amount of 0.25%. The resin was made up as 65.6% resin in isophorone and designated resin component No. 1, and as 65.6%
resin in 2-(2-butoxyethoxy)-ethyl acetate and designated resin component No. 2.
The resin components were employed with polyisocyanate components in a no-bake process using "Portage 430"*sand, 1%
resin component and 1% polyisocyanate component (based on sand weight) and 3% "Kemamine" catalyst (based on resin weight). Kemamine is dimethyl alkylamine wherein the alkyl group is supplied by soya oil. The results were as shown in Table 3.

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, I , 1~ 3 Example 4 The polyisocyanate colllponen~ of this invention was used with a resin component prepared from:
Table 4 ~isphenol A ~.1 g.
Tetraethylene glycol 2.2 y.
Isophorone 5-5 g-in a cold box system, the test core being gassed with triethyl-amine vapor. The binder (isocyanate component and resin com-1~ ponent) was applied to 1200 g. of Portage sand in a muller.
Table 5 Test Polyisocyanate Component Strip Tensile Strength 1 10 g. Mondur MR ~ 2 g.
Isophorone 99, 94, 102 2 9.2 g. Mondur MR + 4.8 g.
Butylal 183, 237, 190 The advantage of the polylsocyanate component of this in-vention is evident.
Example 5 In this example a number of acetals were evaluated in a cold box process in which 0.87% by weight of the resin com-ponent of Example 1 (77% by weight in the designated acetal) and 0.87~ by weight of the polyisocyanate component were applied to Portage 430 sand and gassed with triethylamine.
The polyisocyanate components each comprised 77% Mondur MR
polyisocyanate, the balance being the designated acetal.
The results are shown in Table 6.

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t~ v. Il v v .. w .. . 6 ~ t 6 w ', 1 q w^ ~5 Example 6 The experiment of Example 1 was repeated in all essential details except that"Aspirin"was omitted and calcium hydroxide, added incrementally, was substituted for barium hydroxide.
When the free formaldehyde content was reduced to 12.6%, the calcium hydroxide was added in five increments, slurried in a little butanol, at 15 minute intervals. The first four in-crements were of 7 g. each and the final one was of 9 g. The final increment of butanol (17 lb) was added when the free for-maldehyde had dropped to 5%.The following formulation was used:
Material WeightPound-Moles U.S.P. Phenol 30 lb 0.31915 n-Butanol 8 lb 0.1111 : Hypophosphorous acid, 50% 42 g Paraformaldehyde (91%) 15 lb 12 oz 0.47775 Calcium hydroxide 37 g n-Butanol 17 lb 0.2361 Example 7 The experiment of Example 6 was repeated in all essential details except that sodium hydroxide, 50% aqueous, was sub-stituted in two increments for calcium hydroxide.
The following formulation was used:
Material Weight, g U.S.P. Phenol 188 n-Butanol 50 Hypophosphorous acid (50%) 0.6 Paraformaldehyde, 91% 99 Sodium hydroxide (50%) 0~8 n-Butanol 100 *Trademark for acetylsalicylic acid.20 ~18~3 When the free formaldehyde content reached 13.30~, 0.57 g.
of sodium hydroxide was added. After 25 minutes of heating the remaining sodium hydroxide (0.23 g.) was added.
The resin was used to make a foundry core specimen as des-cribed in Example 2. When mixed with the polyisocyanate, it reacted rapidly.
Example 8 The experiment of Example 7 was repeated in all essential details except that potassium hydroxide, 50% aqueous solution, 1.25 g. was substituted for the sodium hydroxide. It was added in three increments of 0.42 g., 0.40 g., and 0.43 g., respectively. The second increment was added six minutes after the first, and the-third increment was added eight minutes after the second.
The resulting product was used to make a foundry core specimen as described in Example 2. It reacted rapidly when mixed with the polyisocyanate.
Example 9 The experiment of Example 7 was repeated in all essential details except that lithium hydroxide, 15% aqueous solution, 2.7 g. was substituted for the sodium hydroxide. It was added in increments of 0.7 g., 1.0 g. and 1.0 g., respectively. The second increment was added 100 minutes after the first, and the third increment was added 20 minutes after the second.
The resulting product was used to make a foundry core speci-men as described in Example 2. It reacted rapidly when mixed with the polyisocyanate.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A phenol-formaldehyde resin prepared by reacting phenol with aqueous paraformaldehyde in a phenol-to-formalde-hyde mole ratio in the range of 1.0:0.75 to 1.0:2.0 in the presence of alcohol having 3 to 6 carbon atoms at an initial temperature of about 215°F and in the presence of an acid catalyst in an amount to provide a pH in the range of 1.8 to 2.3 for a time sufficient to reduce the free formaldehyde content of the charge to about 12% to 16% by weight of the total charge, cooling the reaction mixture below about 180°F, adding a metal base catalyst in an amount sufficient to raise the pH to about 5.0 to 6.5, and continuing the reaction with exotherm to free formaldehyde content of about 5% by weight of the total charge, then charging an additional quantity of an alcohol having 3 to 6 carbon atoms and continuing the reaction while removing water by azeotropic distillation at a temperature up to 265°F, and recovering a resin product contain-ing less than 2% free water and less than 1% free formaldehyde after excess solvent has been removed.

2. The composition of claim 1 in which the alcohol is n-butanol.

3. The composition of claim 1 in which the acid catalyst comprises hypophosphorous acid.

4. The composition of claim 1 in which the metal base cata-lyst is barium hydroxide.

5. The composition of claim 1 in which the metal base catalyst is calcium hydroxide.

6. The composition of claim 1 in which the metal base catalyst is zinc oxide.

7. A resin component adapted for reaction with a poly-isocyanate in the presence of a catalyst to provide a binder composition comprising in admixture a. A phenol-formaldehyde resin characterized by:
(i) A phenol formaldehyde mole ratio in the range of 1.0:0.75 to 1.0:2.0, (ii) A substituent -(CH2-O)y-R group present at about 12% to 30% of the substituted phenolic nuclear positions, (iii) Free phenol in the amount of about 5% to 15% by weight of the resin, (iv) Water in the amount of less than 2% by weight of the resin, (v) An average of about 2 1/2 to 3 1/2 phenolic nuclei per resin oligomer, and (vi) A hydroxymethyl content of less than about 5 mole %;
the bridges joining phenolic nuclei of said resin be-ing predominantly ortho-para with at least about 20%
of the bridges being para-para, said bridges being of the formula --CH2(OCH2)X-- where x is zero in at least 30% of the bridges and x is an integer in the range of 1 to 6 in at least 20% of the bridges, y is an integer in the range of 1 to 6 and R is a hydro-carbon radical of 3 to 6 carbon atoms; and b. A solvent in the amount of about 10% to 40% by weight of the resin solvent admixture, said solvent being of the formula in which R1 and R2 are the same or different hydrocarbon radicals of 3 to 6 car-bon atoms and R3 and R4 are the same or different hydrogen, methyl, ethyl, or phenyl radicals.

8. The resin component of claim 7 in which R3 and R4 are hydrogen.

9. The resin component in accordance with claim 7 in which R is butyl.

10. The resin component of claim 7 in which R1 and R2 are both butyl.

11. A polyisocyanate component adapted for reaction with a resin component to provide a binder composition comprising in admixture a reactive polyisocyanate and a solvent in the amount of about 10% to 40% by weight of the admixture, said solvent being of the formula where R1 and R2 are the same or different hydrocarbon radicals of 3 to 6 carbon atoms and R3 and R4 are the same or different hydrogen, methyl, ethyl, or phenyl radicals.

12. The composition of claim 11 in which R3 and R4 are hydrogen.

13. The composition of claim 11 in which the polyisocya-nate comprises diphenylmethane diisocyanate.

14. The composition of claim 11 in which the polyisocya-nate comprises triphenylmethane triisocyanate.

15. The composition of claim 13 in which R1 and R2 are butyl.

16. The composition of claim 14 in which R1 and R2 are butyl.

17. The composition of claim 11 in which the solvent com-prises about 23% of the admixture.

18. A binder composition comprising in admixture:
a. A phenol-formaldehyde resin characterized by:
(i) A phenol-formaldehyde mole ratio in the range of 1.0:0.75 to 1.0:2.0, (ii) A substituent -(CH2O)y-R group present at about 12% to 30% of the substituted phenolic nuclear positions, (iii) Free phenol in the amount of about 5% to 15% by weight of the resin, (iv) Water in the amount of less than 2% by weight of the resin, (v) An average of about 2 1/2 to 3 1/2 phenolic nuclei per resin oligomer, and (vi) A hydroxymethyl content of less than about 5 mole %, the bridged joining phenolic nuclei of said resin being predominantly ortho-para with at least about 20% of the bridges being para-para, said bridges being of the formula --CH2(OCH)x-- where x is zero in at least 30% of the bridges and x is an integer in the range of 1 to 6 in at least 20%
of the bridges, y is an integer in the range of 1 to 6 and R is a hydrocarbon radical of 3 to 6 carbon atoms;
b. a reactive liquid polyisocyanate, and, c. a solvent in the amount of about 10% to 40% by weight of the resin solvent admixture, said sol-vent being of the formula in which R1 and R2 are the same or different hydrocarbo radicals of 3 to 6 carbon atoms and R3 and R4 are the same or different hydrogen, methyl, ethyl, or phenyl radicals.

19. The composition of claim 18 in which R3 and R4 are hydrogen.

20. The composition of claim 18 in which R is butyl.

21. The composition of claim 13 in which R1 and R2 are both butyl,

22. The composition of claim 18 in which the solvent is present in the amount of about 23% by weight of the resin.

23. The composition of claim 1 in which the metal base catalyst is lithium hydroxide.

24. The composition of claim 1 in which the metal base catalyst is sodium hydroxide.

25. The composition of claim 1 in which the metal base catalyst is potassium hydroxide.