GB1559015A - Foundry resin components - Google Patents

Description

PATENT SPECIFICATION

( 21) Application No 41824/78 ( 22) Filed 11 Nov 1976 ( 62) Divided out of No 1 559 013 ( 31) Convention Application No 631 549 ( 32) Filed 13 Nov 1975 ( 31) Convention Application No 733 722 ( 32) Filed 26 Oct 1976 in ( 33) United States of America (US) ( 44) Complete Specification published 9 Jan 1980 ( 51) INT CL' C 08 K 5/06; CO 8 L 61/14, 75/04//C 08 G 8/28, 18/54 ( 52) Index at acceptance C 3 R IC 1 D 1 A 2 1 D 2 C 1 E 2 B 1 E 6 1 E 7 B 1 NIM 1 1 N 1 M 2 1 N 1 MX 1 N 1 X 1 N 2 N 1 N 2 Q 1 1 N 2 Q 3 1 N 2 QX 1 N 4 33 C 33 P C 12 C 25 L 1 B L 2 X L 6 E C 3 N 25 25 K 1 B 4 25 K 1 Y 25 K 3 B 25 L 2 B ( 11) 1559015 ( 54) FOUNDRY RESIN COMPONENTS ( 71) We, INTERNATIONAL MINERALS & CHEMDCAL CORPORATION, a Corporation organised and existing under the laws of the State of New York, United States of America, of IMC Plaza, Libertyville, State of Illinois, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and

by the following statement:-

This invention relates to a core binder useful in the manufacture of foundry cores and molds It also relates in more specific aspects to a resin component of a core binder system.

Cores useful in making metal casings are customarily made by placing a foundry aggregate, usually silica sand which has been admixed with a suitable binder, against a shape or pattern 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 themselves are made by a variety of processes employing a wide variety of binders Three of the many processes in commercial use today are the so-called cold box process, no-bake process, and the rapid nobake process The cold box process is one in which sand is admixed with a suitable resinous binder composition, blown into a core box, and then gassed with a suitable vapor phase catalyst to cure the binder By such process, which is described for example in U S Patent No 3,409,579, a core of sufficient hardness to be stripped from the core box is produced 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 temperatures, 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 employed 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 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 substantially immediately into a core box Processes of this type are described, for example, in U S.

Patent No 3,702,316 The present 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 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.

Accordingly, the present invention provides krs 1,559,015 a binder composition comprising in admixture:

a a phenol-formaldehyde resin characterised by:

(i) (ii) (iii) (iv) (v) (vi) a phenol-formaldehyde mole ratio in the range of 1 0:0 75 to 1 0:2 0, a substituent -(CH 20), R group present at 12 % to 30 % of the substituted phenolic nuclear positions, free phenol in an amount of 5 % to % by weight of the resin, water in an amount of less than 2 % by weight of the resin, an average of 2 i to 3 phenolic nuclei per resin oligomer, and a hydroxymethyl content of less than mole%, a major proportion of the bridges joining phenolic nuclei of the resin being ortho-para with at least 20 % of the bridges being parapara, the bridges being of the formula -CH 2 (OCH 2))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 in an amount of from 80 % to 125 % by weight of the resin, and c a solvent in an amount of 10 % to 40 % by weight of the binder admixture, the solvent being of the formula 1 % R 1 %-O l-_-R 2 R 4 in which R, and R 2 are each independently hydrocarbyl groups having from 3 to 6 carbon atoms and R 1 and R 4 are each independently a hydrogen atom or a methyl, ethyl or phenyl group.

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 invention, both the isocyanate and the phenolic resin will be dissolved or dispersed in the selected solvent The amount of 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 comprises in admixture:

a a phenol-formaldehyde resin characterised by:

(i) a phenol-formaldehyde mole ratio in the range of 1 0:0 75 to 1 0:2 0, (ii) a substituent (CH 2,-O)-R group present at from 12 % to 30 % of the substituted phenolic nuclear positions, (iii) free phenol in an amount of 5 % to % by weight of the resin, (iv) water in an amount of less than 2 % by weight of the resin, (v) an average of 2 to 3 phenolic nuclei per resin oligomer, and (vi) a hydroxymethyl content of less than mole %; a major proportion of the bridges joining phenolic nuclei of the resin being ortho-para with at least about 20 % of the bridges being para-para, the bridges being of the formula -CH 2 (OCH 2)xwhere x is zero in at least 30 % of the bridges and x is an integer in the range of from 1 to 6 in at least 20 % of the bridges, y is an integer in the range of from 1 to 6 and R is a hydrocarbon radical of 3 to 6 carbon atoms; and b a solvent in an amount of 10 % to 40 % by weight of the resin solvent admixture, the solvent being of the formula R 3 1 % O O (O-R 2 R 4 in which R 1 and R% are each independently a hydrocarbyl group having from 3 to 6 carbon atoms and R 3 and R 4 are each independently a hydrogen atom or a methyl, ethyl or phenyl group.

Preferred phenol-formaldehyde resins for use in the present invention are described and claimed in our co-pending Patent Application No 47014/76 (Serial No 1559013), and are those which are prepared by reacting phenol or a substituted phenol with formaldehyde or paraformaldehyde in a phenolto-formaldehyde mole ratio in the range of 1.0:0 75 to 1 0:2 0 in the presence of an alcohol having from 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 p H in the range of from 1.8 to 2 3 for a time sufficient to reduce the free formaldehyde content of the charge to 12 % to 16 % by weight of the total charge, cooling the reaction mixture to 180 F or below, adding a basic metal compound as catalyst in an amount sufficient to raise the p H to 5 0 to 6 5, and continuing the reaction with an exotherm to a free formaldehyde content of 5 % by weight of the total charge, then charging an additional quantity of an alcohol having from 3 to 6 carbon atoms and continuing the reaction while removing water 1,559,015 by azeotropic distillation at a temperature up to 265 F, and recovering a resin product containing less than 2 % by weight free water and less than 1 % by weight free formaldehyde after excess solvent has been removed.

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 diisocyanate, diphenylmethane diisocyanate, and the dimethyl derivatives thereof Other suitable polyisocyanates are 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, xylylene diisocyanate, and the methyl derivatives thereof, polymethylenepolyphenyl isocyanates, and chlorophenylene-2,4-diisocyanate Preferred, however, is the use of commercially available compositions which contain diphenylmethane diisocyanate, and triphenylmethane triisocyanate.

The selected solvents used in accordance with the invention are compounds of the formula RC F in which R 1 and R 2 are the same or different hydrocarbyl groups of three to six carbon atoms, and Rs and R 4 are the same or different methyl, ethyl or phenyl radicals or hydrogen atoms.

Preferred are compounds in which R 3 and R, are hydrogen atoms Especially preferred is dibutoxymethane Useful solvents are dipropoxymethane, diisobutoxymethane, dipentyloxymethane, dihexyloxymethane, and dicyclohexyloxymethane Other solvents which may be used include n-butoxyisopropoxymethane, isobutoxy-butoxymethane and isopropoxypentyloxymethane Among the useful solvents in which R 3 or R 4 is other than hydrogen are acetaldehyde di-n-propyl acetal, benzaldehyde di-n-butyl acetal, acetaldehyde di-n-butyl acetal, acetone di-n-butyl ketal and acetophenone dipropyl ketal.

The aforedescribed materials, while characterised as solvents, 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 acts 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 substrate silica or refractory materials which promote the aforementioned outstanding properties Both the phenol-formaldehyde resin and the polyisocyanate are preferably admixed with the same selected solvent In the preferred practice of this invention, the solvent comprises 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, polyisocyanate 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 amount of about 80 % to 125 % by weight of the resin Preferably, the resin and polyisocyanate are employed in equal amounts by weight.

A preferred polyisocyanate composition which may be admixed with a resin component as hereinbefore described, together with a suitable catalyst to provide a foundry core binder of outstanding properties is described and claimed in our co-pending Patent Application No 41823/78 (Serial No.

1 5509014) and comprises a polyisocyanate composition capable of reaction with a resin component to provide a binder composition comprising in admixture a reactive polyisocyanate and a solvent in an amount of from % to 40 % by weight of the admixture, the solvent being of the formula:

Re where R, and R, are each independently a hydro 100 carbyl group having from 3 to 6 carbon atoms and Re and R 4 are each independently a hydrogen atom or a methyl, ethyl or phenyl group 105 This preferred polyisocyanate component is useful in combination with the preferred phenol-formaldehyde resin component hereinbefore described.

In the preparation of cores suitable for 110 foundry use, the binder (which comprises the resin, polyisocyanate, solvent, and sometimes 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 115 muller or other device suitable for evenly distributing the binder on the sand in keeping with the requirements of the specific processes by which the cores are made These processes are conventional and form no part 120 of the present invention As before described, a catalyst is generally employed and its selec1,559,015 tion will depend upon the specific process 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 substance, 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.

Generally such catalysts are used in amounts from 0 0001 to 0 04 by weight of the resin The catalysts of various resin polyisocyanate binder systems in the foundry art is well known The amount and type of catalyst is adapted to provide the desired 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 for use in this invention, a pilot kettle was charged as follows:

U.S P Phenol 25 lbs 0 2660 lb mols n-Butanol 6 lbs 10 oz 0 0895 lb mols %hypophosphorous acid 35 grams Paraformnaldehyde ( 91 %) 13 lbs 3 oz 0 4000 lb mols Aspirin U S P Powder 8 oz ( 226 grams) The p H was in the range of from 1 8 to 2.3.

The batch was then heated to 235 F to dissolve the para-formaldehyde within an hour, and the temperature was then dropped to 215 F and maintained to a free formaldehyde assay of 12 % by weight ( 16 hours).

The temperature was reduced to 170 F and barium hydroxide ( 8 ounces was added The p H was in the range of from 5 0 to 6 5 An exotherm to 196 F occurred and heating was resumed to 220 F In five and one-half hours, the free formaldehyde content dropped to 4 8 % by weight, and 13 pounds of n-butanol were added, dropping the temperature to F Water begin to collect from the azeotrope boiling at 200 F 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 % by weight was reached as the end point ( 9 5 hours) at 265 F The free formaldehyde content was less than 1 % by weight.

The dehydrated resin was now subjected to vacuum distillation to remove excess butanol and phenol, carried out at 25 inches of vacuum from 200 F to 255 F 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 % by weight 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.

Example 2.

As an example of the use of resins in the so-called cold box process, the resin of Example 1, which made up as described to 77 % by weight resin and 23 % by weight butylal, was used in the manufacture of foundry cores specimens The isocyanate used was a commercially-available isocyanate designated Mondur MR (Registered Trade Mark) 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 % by weight polyisocyanate and 23 % by weight butylal, was then added and mulling continued for another 1-t minutes.

The resin solution and the polyisocyanate solution were both added in the amount of 0.87 % by weight of the sand The bindercoated sand was then blown into a core box 1,559,015 at a blow pressure of 80 p s i and gassed with 12 % by weight 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.

TABLE 1

Gassing Cure Time Test Sec.

Air Purge Time Sec.

Tensile Strength, lbs/sq in.

Time After Draw Min.

60 Min Min.

2 Hr.

3.5 Hr.

Control 6 10 160 157 5 157 5 166 3 Control 3 162 5 6 145 156 3 156 3 152 5 145 151 3 1 6 10 135 147 5 157 5 157 5 145 172 5 173 7 207 5 227 5 210 256 3 2 3 153 5 6 186 3 177 5 226 3 210 191 3 191 3 230 3 1 5 3 180 4 1 6 162 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 Example 1 was again made up as a solution containing 77 % by weight resin and 23 % by weight butylal.

The same polyisocyanate solution used in Example 2 was employed but both the resin component and polyisocyanate component were used in the amount of 1 % by weight each, based on the weight of the Portage 430 sand employed Sand, resin, isocyanate, and catalyst were mixed in a high speed mixing apparatus and transferred into a core box adapted to produce test specimens The catalyst (lead naphthenate) was employed in the percentage indicated, based upon the weight of the binder The core specimen was 157 5 212 5 235 6 1,559,015 6 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-Bake Resin Evaluation Test Catalyst 2.5 % 4.5 % 4.5 % 4.5 % 4.5 % 2.5 % 2.5 % 3 % 3.5 % Sand Temp Set Time Hardness (Dietert 674) OF OF F 94 OF 94 F 76 F 76 F 76 OF 76 OF 3 1/2 min 2 1/2 min.

1 1/2 min.

1 min.

r 1/2 min 2 min 1 min.

sec.

69, 70 45, 80 35, 50 20, 67 Example 4.

In this example a number of acetals were evaluated in the cold box process in which 0 87 % by weight of the resin component 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 % by weight Mondur MR polyisocyanate, the balance being the designated acetal The results are shown in Table 3 Experiments numbers 6, 10, 12 and 14 are comparative and do not illustrate the invention.

1,559,015 -J TABLE 3

Tensiles (psi) Resin Green Solvent Disp 6 rsed Adequately Isocyanate Solubility Strength One Hour Overnight 1) Isobutylal Yes Yes 195 205 225 220 250 210 230 270 2) Normal Butylal Yes Yes 165 180 210 195 235 220 210 3) Amylal Yes Yes 130 165 180 175 215 4) Hexylal Yes Yes 110 120 160 130 180 5) Cyclohexylal Yes Yes 120 170 160 220 250 200 6) Octylal No No 7) Acetaldehyde di-n-Propyl Acetal Yes Yes 189 146 108 8) Benzaldehyde di-n-Butyl Acetal Yes Yes 143 167 224 9) Acetaldehyde di-n-Butyl Acetal Yes Yes 126 149 195 10) Acetaldehyde Diethyl Acetal Yes Yes 108 93 97 11) Acetone Di-n-butyl Ketal Yes Yes 108 88 140 12) Acetone Dimethyl Ketal Yes Yes 27 13) Acetophenone Dipropyl Ketal Yes Yes 178 184 209 14) Isophorone Yes Yes 101 104 84 8 1,559,015 8 Example 5.

The experiment of Example 1 was repeated in all essential details except that aspirin was omitted, although the p H was within the range of from 1 8 to 2 3, and calcium hydroxide, added incrementally, was substituted for barium hydroxide The p H was in the range of from 5 0 to 6 5 When the free formaldehyde content was reduced Material to 12 6 % by weight, the calcium hydroxide was added in five increments, slurried in a little butanol, at 15 minute intervals The first four in increments were of 7 g each and the final one was of 9 g The final increment of butanol ( 17 Ib) was added when the free formaldehyde was dropped to 5 % by weight.

The following formulation was used:

Weight Pound-Moles U.S P Phenol 30 lb 0 31915 n-Butanol 8 lb 0 1111 Hypophosphorous acid, 50 % 42 g Paraformaldehyde ( 911 %) 15 lb 12 oz 0 47775 Calcium hydroxide 37 g n-Butanol 17 lb 0 2361 Example 6.

The experiment of Example 5 was repeated in all essential details except that sodium hydroxide, 50 % by weight, aqueous was substituted in two increments for calcium hydroxide.

The following formulation was used:

Material U.S P Phenol n-Butanol Hypophosphorous acid ( 50 %) Paraformaldehyde, 91 % Sodium hydroxide ( 50 %) n-Butanol Weight g 188 0.6 99 0.8 When the free formaldehyde content reached 13 30 % by weight, 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 described in Example 2 When mixed with the polyisocyanate, it reacted rapidly.

Example 7.

The experiment of Example 6 was repeated in all essential details except that potassium hydroxide, 50 % by weight 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 8.

The experiment of Example 6 was repeated in all essential details except that lithium hydroxide, 15 % by weight 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 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.

Our co-pending Patent Application No.

47012/76 (Serial No 1 559 012) is also directed to a binder system which is suitable for use in the cold box process, the no-bake process and the rapid no-bake process In particular, this co-pending patent application describes and claims a foundry core mix capable of being cured by a catalyst comprising a foundry aggregate and from 1 O/% to 5 % by weight of the aggregate of a binder comprising in admixture:

a) a curable resin which is an epoxy resin.

polyester resin, alkyd resin or an aqueous phenol-formaldehyde resin, b) a reactive liquid polyisocyanate in an amount of 80 % to 125 % by weight of the resin and c) a solvent of the formula 1,559,015 a 1,559,015 9 Rs I R,-O C O-R 2 K 4 in which R, and R, are each independently a hydrocarbyl group having from three to six carbon atoms and R% and R 4 are each independently a hydrogen atom or a methyl, ethyl or phenyl group.

Claims (11)

WHAT WE CLAIM IS:-

1 A resin component capable of reaction with a polyisocyanate in the presence of a catalyst to produce a binder composition comprising in admixture:

a a phenol formaldehyde resin characterised by:

(i) a phenol formaldehyde mole ratio in the range of 1 0:0 75 to 1 0:2 0, (ii) a substituent -(CH 2 O)y R group present at from 12 % to 30 % of the substituted phenolic nuclear positions, (iii) free phenol in an amount of 5 % to % by weight of the resin, (iv) water in an amount of less than 2 % by weight of the resin, (v) an average of 2 to 31 phenolic nuclei per resin oligomer, and (vi) a hydroxymethyl content of less than mole %; a major proportion of the bridges joining phenolic nuclei of the resin being ortho-para with at least about 20 % of the bridges being para-para, the bridges being of the formula -CH 2 (OCH 2)x where x is zero in at least 30 % of the bridges and x is an integer in the range of from 1 to 6 in at least 20 % of the bridges, y is an integer in the range of from 1 to 6 and R is a hydrocarbon radical of 3 to 6 carbon atoms; and b a solvent in an amount of 10 % to 40 % by weight of the resin solvent mixture, the solvent being of the formula R 3 R 1 U C,-O R 2 R 4 in which R 1 and R 2 are each independently a hydrocarbyl group having from 3 to 6 carbon atoms and R 3 and R 4 are each independently a hydrogen atom or a methyl, ethyl or phenyl group.

2 A resin component as claimed in claim 1 in which R 3 and R 4 are both hydrogen atoms.

3 A resin component as claimed in cla;m 1 or claim 2 in which R is a butyl group.

4 A resin component as claimed in any one of claims 1 to 3 in which R, and R 2 are both butyl groups.

A binder composition comprising in admixture:

a a phenol-formaldehyde resin characterised by:

(i) a phenol-formaldehyde mole ratio in the range of 1 0:0 75 to 1 0:2 0, (ii) a substituent -(CH 20)r R group present at 12 % to 30 % of the substituted phenolic nuclear positions, (iii) free phenol in an amount of

5 % to % by weight of the resin, (iv) water in an amount of less than 2 % by weight of the resin, (v) an average of 2 to 3 phenolic nuclei per resin oligomer, and (vi) a hydroxymethyl content of less than mole %, a major proportion of the bridges joining phenolic nuclei of the resin being ortho-para with at least 20 % of the bridges being parapara, the bridges being of the formula -CH 2 (OCH 2)xwhere 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 in an amount of from 80 % to 125 % by weight of the resin, and c a solvent in an amount of 10 % to 40 % by weight of the binder admixture, the solvent being of the formula R 3 I R 1-O-C-O-R 2 R 4 in which R, and R 2 are each independently hydro 95 carbyl groups having from 3 to 6 carbon atoms and R, and R 4 are each independently a hydrogen atom or a methyl, ethyl or phenyl group 100 6 A composition as claimed in claim 5 in which R 3 and R 4 are both hydrogen atoms.

7 A composition as claimed in claim 6 in which R is a butyl group.

8 A composition as claimed in claim 6 or 105 claim 7 in which R, and R 2 are both butyl groups.

9 A composition as claimed in any one of 1,559,015 Q 1,559,015 claims 6 to 8 in which the solvent is present in an amount of about 23 % by weight of the resin.

A binder composition as claimed in claim 5 substantially as hereinbefore described with reference to any one of Examples 2 to 4.

11 A binder composition as claimed in claim 5 substantially as hereinbefore described with reference to any one of Examples 6 to 8.

BOULT, WADE & TENNANT, Chartered Patent Agents, 34 Cursitor Street, London, EC 4 A 1 PQ.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1980.

Published by the Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.