Furfuryl alcohol-dialdehyde foundry binders

Abstract

Binders for foundry core sands and the like comprising furfuryl alcohol and an aromatic dialdehyde and optionally an aromatic alcohol.

Description

The present invention relates to chemical compositions and methods useful in metal founding, and more particularly, to binders for core sand and the like used in metal foundries.

The expression "core sand" is used herein to include sand used in making shapes of all sorts for foundry purposes, including sand shapes which are to be used as mold cores, sand shapes useful in other casting processes, including sand shapes which are made in patterns and cured therein as well as free standing sand shapes which may be cured in conventional ovens or in microwave ovens for any desirable purpose in foundry work.

While prior art catalyst and binder systems have functioned satisfactorily in many respects, as the cost of labor and the cost of maintaining production facilities have increased, it has become economically important to mix core sand with binders in larger quantities to increase production and reduce costs. Yet, it is highly desired that the binder provide a high tensile strength to the finished components and under high and low humidity conditions.

It is therefore a principal object of this invention to provide compositions which can be advantageously used as binders for core sands and the like used in metal founding operations.

The binder compositions of this invention comprise furfuryl alcohol and an aromatic dialdehyde. In an optional embodiment, an aromatic alcohol can also be included in the binder compositions in partial replacement of the dialdehyde. Representative of the aromatic dialdehyde components of the binder are terephthaldicarboxaldehyde, isophthaldicarboxaldehyde, o-phthalicdicarboxaldehyde, 2,5-dialdehydehydofuran, ##STR1## and the like.

Representative of the aromatic alcohol component of the binder are phenol, resorcinol, bisphenol A, catechol, hydroquinone, xylenols, phlorglucinol, pyrogallol, cresols and the like.

The aromatic dialdehyde component is used in amounts ranging from about 1.0% up to its limit of solubility in furfuryl alcohol. Generally the amount of aromatic dialdehyde used in the binder composition is within the range of about 3 to 10% by weight of furfuryl alcohol.

In the optional embodiment, an aromatic alcohol can be used to replace from 5.0 to 50.0% by weight of the aromatic dialdehyde. It is generally preferred that the amount of aromatic aldehyde in the binder be 5-20% by weight of the dialdehyde.

The binders of this invention are applied to aggregate materials in conventional manner and are catalyzed to form a rigid material by acids such as toluene-sulfonic acid, phosphoric acid, benzene-sulfonic acid, xylene-sulfonic acid, phenolsulfonic acid, methanesulfonic acid and the like, as well as other acid catalysts known and used in the art. The catalysts can be applied to the sand followed by application of the binder thereto or the catalysts can be admixed with the binder and the mixture applied thereto. In any event, the acid catalysts are used in amounts ranging from about 10 to 50% by weight of the binder. Curing of the binders is accomplished at room temperature.

The amount of binder which is used in the acid hardenable mix is any amount which would normally be used in a bound sand mix for foundry purposes; and, for example sand mixes which have incorporated therein the binder of the present invention in an amount from 0.5 to about 3.0 percent are, generally speaking, satisfactory in accordance with the present invention.

When using the binders in producing core sands, it is generally preferred to use with the binders of this invention a silane glass or silica adhesion promoter in an amount ranging from about 0.1% to 3% based on the weight of the binder. Such silane adhesion promoters are well known in the art and include for example, gamma-mercaptopropyltrimethoxysilane, N-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane, beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane, gamma-aminopropyltriphenoxysilane, gamma-aminopropyltribenzoyoxysilane, gamma-aminopropyltrifurfuroxysilane, gamma-aminopropyltri (o-chlorophenoxy)silane, gamma-aminopropyltri (p-chlorophenoxy)silane, gamma-aminopropyltri(tetrahydrofurfuroxy)silane, methyl[2-gamma-triethoxysilypropylamino)ethyl amino]3-propionate in methanol, modified aminoorganosilane, Ureido-silane, mercaptoethyltriethoxysilane, chloropropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, gamma-methacryloxypropyltri(2-methoxyethoxy)silane, gamma-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, gamma-mercaptopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, N-beta(aminoethyl)-gamma-amino-propyltrimethoxysilane.

The advantages of the present invention will be further apparent from the following examples.

EXAMPLE 1

Binder compositions containing 95% by weight of furfuryl alcohol and 5% of various additives were tested as binders for foundry core sand. In these tests a foundry sand mix (Wedron 5025 sand) was prepared by first admixing and mulling 3,000 parts by weigh of the foundry sand and 20% (based on binder) of a 65% solution of toluene sulfonic acid in water until distribution of the acid on the sand was uniform. Then the resulting sand/acid mix and 1.5% of the binder mixture (based on the weight of the sand) was added in each instance and the complete mixture was mulled further until all of the components were uniformly distributed on the grains of sand. Immediately after this final mulling, the mix was packed into four 12-cavity molds to form dumbbell-type bars of one inch cross section. After the bars had been cured enough to be handled without breaking, they were removed from the mold. Twenty-four bars were placed in a high humidity cabinet for storage overnight at 80% relative humidity (RH) and 24 bars were subjected to a low relative humidity (RH) of 40% for overnight storage. After overnight storage the tensile strengths were determined, with the average tensile strength range under the low and high humidity conditions being summarized in the table below. The bench life is determined by the use of a Dietert sand rammer. The bench life is arbitrarily determined as the time at which the number of rams required to reach the present volume is double the number of rams initially required to reach that volume.

TABLE I__________________________________________________________________________ Tensile Strength, p.s.i. Bench 40% RH 80% RH LifeAdditive Average Range Average Range (minutes)__________________________________________________________________________Resorcinol 465 310-600 399 145-575 14Terephthaldehyde 510 250-690 428 300-550 18Bisphenol A 382 325-460 301 190-390 16O-Cresol 328 145-420 294 210-390 16Dimethylol Ethylene Urea 417 310-510 378 250-485 30Dimethoxydihydrofuran 369 225-480 338 170-485 24Dimethoxytetrahydryfuran 398 225-525 363 200-525 26Safrole 343 60-490 323 125-455 19Trimethylolpropane 346 230-450 254 160-375 30Aluminum acetylacetonate 221 175-300 212 125-295 262,4-dihydroxybenzaldehyde 303 175-440 275 140-405 17Furfural 365 255-525 308 170-420 24Furfurylidene ethylene acetal 334 180-470 280 155-375 32Benzophenone tetracarboxylicdianhydride 278 150-390 244 120-370 17Chem Rez-A280* 542 385-740 413 205-550 6__________________________________________________________________________ *A commercially available foundry sand binder which is believed to be a copolymer of furfuryl alcohol and formaldehyde dissolved in furfuryl alcohol (manufactured by Ashland Chemical Company).

EXAMPLE 2

Compositions containing various amounts of terephthaldehyde (TPAL) and furfuryl alcohol were tested as binders for foundry core sands. In these tests a foundry core sand was prepared using 3.0 kilograms of Wedron 5025 sand, 30 grams of the binders shown in the table below containing 0.3% All60* silane and 6.0 grams of a 65% solution of toluene sulfonic acid. Sand bars were prepared and tested as described in Example 1 with the humidity conditions being 25% RH and 89% RH. The test results were as follows:

TABLE II______________________________________Binder % Furfuryl Tensile Strength, psi Bench Life% TPAL Alcohol 25% RH 89% RH (minutes)______________________________________2.5 97.5 345 205 305.0 95.0 360 260 247.5 93.5 395 270 2210.0 90.0 425 230 1612.5 88.5 475 260 13100% Furfuryl Alcohol 295 180 3095% Furfuryl Alcohol+ 5% Resorcinol 340 225 13______________________________________ *All60 silane is a ureido-silane commonly used in foundry binders as an adhesion promoter.

EXAMPLE 3

Following the procedures of Example 2, various amount of 2,5-dialdehydehydofuran and furfuryl alcohol were tested as binders for foundry core sands. The test results were as follows:

TABLE III______________________________________Binder% 2,5-dialdehyde- % Furfuryl Tensile Strength, psi Bench Lifehydrofuran Alcohol 25% RH 89% RH (minutes)______________________________________2.5 97.5 325 250 275.0 95.0 345 220 207.5 93.5 350 210 2210.0 90.0 415 230 1912.5 88.5 420 200 20100% Furfuryl Alcohol 295 180 3095% Furfuryl Alcohol+ 5% Resorcinol 340 225 13______________________________________

EXAMPLE 4

Following the procedures of Example 2, varying amounts of terephthaldehyde (TPAL) were combined with furfuryl alcohol. In this example tensile strengths were determined after storage overnight at relative humidities of 56% and 90%. The data are shown below:

TABLE IV______________________________________Binder % Furfuryl Tensile Strength, psi Bench Life% TPAL Alcohol 56% RH 91% RH (minutes)______________________________________2.5 97.5 295 200 395.0 95.0 420 300 277.5 93.5 370 305 1210.0 90.0 410 295 14100% Furfuryl AlcoholControl 295 212 3995% Furfuryl Alcohol +5% Resorcinol Control 325 272 20______________________________________

EXAMPLE 5

Following the procedure of Example 2, tests were conducted with binders comprising furfuryl alcohol and aromatic aldehydes. Tensile strengths were determined after storage overnight at relative humidities of 34% and 90%. Test results are shown below:

TABLE V______________________________________ Tensile Strength, Bench p.s.i. Life 34% 90% (Min-Binder R.H. R.H. utes)______________________________________10%Terephthaldehyde 90% Furfuryl Alcohol 380 280 1410%2,5-Dialdehydrofuran 90% Furfuryl Alcohol 410 285 1710% Benzaldehyde 90% Furfuryl Alcohol 370 280 2710% Furfural 90% Furfuryl Alcohol 345 265 23100% FurfurylAlcohol Control 260 200 2890%Furfuryl Alcohol+ 5%Resorcinol Control 360 230 17______________________________________

EXAMPLE 6

Following the procedure of Example 2, binder compositions comprising furfuryl alcohol, an aldehyde and an alcohol were tested. Tensile strengths were determined after storage overnight at relative humidities of 59% and 91%. The data are shown below:

TABLE VI______________________________________ Tensile Bench Strength, p.s.i. Life 59% 91% (Min-Composition of Binder* R.H. R.H. utes)______________________________________RES/TPAL/FCH.sub.2 OH(2.5/2.5/95.0) 395 312 18BPA/TPAL/FCH.sub.2 OH(2.5/2.5/95.0) 360 315 24Ph/TPAL/FCH.sub.2 OH(2.5/2.5/95.0) 370 300 24RES/TPAL/FCH.sub.2 OH(3.75/3.75/92.5) 385 305 27BPA/TPAL/FCH.sub.2 OH(3.75/3.75/92.5) 360 250 32Ph/TPAL/FCH.sub.2 OH(3.75/3.75/92.5) 345 235 33RES/TPAL/FCH.sub.2 OH(5.0/5.0/90.0) 420 320 12BPA/TPAL/FCH.sub.2 OH(5.0/5.0/90.0) 380 270 23Ph/TPAL/FCH.sub.2 OH(5.0/5.0/90.0) 380 270 29RES/TPAL/FCH.sub.2 OH(7.5/7.5/85.0) 340 240 5BPA/TPAL/FCH.sub.2 OH(7.5/7.5/85.0) 355 225 20Ph/TPAL/FCH.sub.2 OH(7.5/7.5/85.0) 330 200 24RES/TPAL/FCH.sub.2 OH(10.0/10.0/80.0) 300 250 4BPA/TPAL/FCH.sub.2 OH(10.0/10.0/80.0) 340 250 19Ph/TPAL/FCH.sub.2 OH(10.0/10/0/80.0) 310 220 19FCH.sub.2 OH Control 298 216 40FAR 5 Control 342 266 22FAB 5 Control 315 245 34FAP 5 Control 320 235 26______________________________________ *RES = Resorcinol? TPAL = terephthaldehyde FCH.sub.2 OH = furfuryl alcohol BPA = Bisphenol A Ph = Phenol FAR 5 Control = 95% furfuryl alcohol; 5% resorcinol FAB 5 Control = 95% furfuryl alcohol; 5% Bisphenol A FAP 5 Control = 95% furfuryl alcohol; 5% phenol

EXAMPLE 7

Following the general procedure of Example 2, tests were conducted on binder compositions comprising furfuryl alcohol (FCH.sub.2 OH) and terephthaldehyde (TPAL) and a Novolak resin. The Novolak resin used was Plenco 1617 available from Plastics Engineering Company, Sheboygan, Wis., and was unneutralized and without hexamethylenetetramine. Tensile strengths were determined after storage overnight at relative humidities of 30% and 90%. The results are shown in the table below:

TABLE VII______________________________________ Tensile Strength, Bench% % p.s.i. LifeNovolak % TPAL FCH.sub.2 OH 30% RH 90% RH (Minutes)______________________________________2.5 2.5 95.0 500 315 232.75 3.75 92.5 535 325 205.0 5.0 90.0 555 335 177.5 7.5 85.0 575 330 1010.0 10.0 80.0 560 325 65.0 95.0 465 270 21100%Furfuryl AlcoholControl 435 280 2395%Furfuryl Alcohol+ 5%Resorcinol Control 500 290 15______________________________________

The "no-bake" binders of the invention can be advantageously used as binders for shaped composite articles, such as particle board, fiberglass board, accoustical tile and the like, in which high tensile strength under low and high humidity conditions is desired. Other binder materials can be blended with the binders of the invention for particular applications.

Those modifications and equivalents which fall within the spirit of the invention are to be considered a part thereof.

Claims

1. A binder composition comprising furfuryl alcohol and an aromatic dialdehyde.

2. A binder in accordance with claim 1 wherein the binder also includes an aromatic alcohol.

3. A binder in accordance with claim 1 which also includes a silane.

4. A binder for foundry core sands in accordance with claim 1.

5. A process for manufacturing foundry sand shapes for use as cores and molds comprising placing a sand mix in a shaping element and hardening the mix in the shaping element, the sand mix comprising sand, an acid catalyst and a binder comprising furfuryl alcohol and an aromatic dialdehyde.

6. A process in accordance with claim 5 in which the binder also includes a silane.

7. A process in accordance with claim 5 wherein the binder also includes an aromatic alcohol.