Furan no-bake foundry binders and their use

Details Furan no-bake foundry binders and their use Furan no-bake foundry binders and their use

2002-09-10

2003-07-15

Cain, Edward J. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C523S145000, C523S147000

Reexamination Certificate

active

06593397

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to furan no-bake foundry binders comprising (a) furfuryl alcohol and/or a reactive furan resin, (b) an activator selected from the group consisting of resorcinol, resorcinol pitch, and bisphenol A tar (c) a bisphenol compound (d) a polyol selected from the group consisting of polyester polyols, polyether polyols, and mixtures thereof, and preferably (e) a silane. The binders are cured in the presence of the furan curing catalyst. The invention also relates to foundry mixes prepared with the binder, foundry shapes prepared with the foundry mix, and metal castings prepared with the foundry shapes.
BACKGROUND OF THE INVENTION
One of the most commercially successful no-bake binders is the phenolic-urethane no-bake binder. This binder provides molds and cores with excellent strengths that are produced in a highly productive manner. Although this binder produces good cores and molds at a high speed, there is an interest in binders that have less volatile organic compounds (VOC), free phenol level, low formaldehyde, and that produce less odor and smoke during core making and castings. Furan binders have these advantages, but their cure speed is much slower than the cure speed of phenolic urethane no-bake binders. Furan binders have been modified to increase their reactivity, for instance by incorporating with urea-formaldehyde resins, phenol-formaldehyde resins, novolac resins, phenolic resole resins, and resorcinol into the binder. Nevertheless, these modified furan binders system do not provide the cure speed needed in foundries that require high productivity.
U.S. Pat. No. 5,856,375 discloses the use of BPA tar in furan no-bake binders to increase the cure speed of the furan binder. Although the cure speed of the binder is increased by the addition of the BPA tar, the tensile strength of this system does not match that of the phenolic urethane system.
SUMMARY OF THE INVENTION
This invention relates to furan no-bake binders comprising:
(a) furfuryl alcohol and/or a reactive furan resin,
(b) an activator selected from the group consisting of resorcinol, resorcinol pitch, and bisphenol A tar,
(c) a bisphenol compound,
(d) a polyol selected from the group consisting of aromatic polyester polyols, polyether polyols, and mixtures thereof, and preferably
(e) a silane.
The binders display several advantages when compared to a conventional furan no-bake binder. Cores prepared with the binders cure much faster than those prepared with conventional furan no-bake binders. In fact, the cure speed of cores prepared by the binders of this invention is comparable to that of the phenolic urethane no-bake binder, which is used commercially to make cores where high-speed production is needed. Additionally, the cores made with the binder display excellent tensile strength, and are advantageous from an environmental standpoint because they do not contain free phenol, have low formaldehyde, and contain no solvents or isocyanate.
ENABLING DISCLOSURE AND BEST MODE
The binder contains furfuryl alcohol and/or a reactive furan resin, preferably a mixture thereof. Reactive furan resins that can be used in the no-bake binders are preferably low nitrogen furan resins. The furan resins are prepared by the homopolymerization of furfuryl alcohol or the homopolymerization of bis-hydroxymethylfuran in the presence of heat, according to methods well-known in the art. The reaction temperature used in making the furan resins typically ranges from 95° C. to 105° C. The reaction is continued until the percentage of free formaldehyde is less than 5 weight percent, typically from 3 to 5 weight percent, and the refractive index is from 1.500 to about 1.600. The viscosity of the resin is preferably from about 200 cps to 450 cps. The furan resins have an average degree of polymerization of 2-3.
Preferably, a reactive furan resin, diluted with furfuryl alcohol to reduce the viscosity of the reactive furan resin, is used.
Although not necessarily preferred, modified furan resins can also be used in the binder. Modified furan resins are typically made from furfuryl alcohol, phenol, and formaldehyde at elevated temperatures under essentially alkaline conditions at a pH of from 8.0 to 9.0, preferably 8.4 to 8.7. The weight percent of furfuryl alcohol used in making the nitrogen free modified furan resins ranges from 50 to 65 percent; the weight percent of the phenol used in making the nitrogen free modified furan resins ranges from 10 to 25 percent; and the weight percent of the formaldehyde used in making the nitrogen free modified furan resins ranges from 15 to 25 percent, where all weight percents are based upon the total weight of the components used to make the modified furan resin.
Although not necessarily preferred, urea-formaldehyde resins, phenol-formaldehyde resins, novolac resins, and phenolic resole resins may also be used in addition to the furan resin.
The activator, which promotes the polymerization of furfuryl alcohol) is selected from the group consisting of resorcinol, resorcinol pitch, and bisphenol A tar. Preferably used as the activator is resorcinol. Resorcinol pitch is defined as the highly viscous product, which remains on the bottom of the reaction vessel after resorcinol is produced and distilled from the reaction vessel. Resorcinol pitch is a solid at room temperature and has a melting point of about 70° C. to 80° C. Resorcinol pitch is mostly dimers, trimers, and polymeric resorcinol. It may also contain substituted materials. Bisphenol A tar is defined as the highly viscous product, which remains on the bottom of the reaction vessel after bisphenol A is produced and distilled from the reaction vessel. The bisphenol A tar is a solid at room temperature and has a melting point of about 70° C. to 80° C. Bisphenol A tar is mostly dimers, trimers, and polymeric bis phenol A. It may also contain substituted materials.
The bisphenol compound used is bisphenol A, B, F, G, and H, but preferably is bisphenol A.
The polyol is selected from the group consisting of polyester polyols, polyether polyols, and mixtures thereof. Aliphatic polyester polyols can be used in the binder. Aliphatic polyester polyols are well known and prepared by reacting a dicarboxylic acid or anhydride with a glycol. They generally have an average hydroxyl functionality of at least 1.5. Preferably, the average molecular weight of the polyester polyol is from 300 to 800. Typical dicarboxylic acids preferably used to prepare the polyester polyols are adipic acid, oxalic acid, and isophthalic acid. The glycols typically used to prepare the polyester polyols are ethylene glycol, diethylene glycol and propylene glycol.
The polyether polyols that are used are liquid polyether polyols or blends of liquid polyether polyols having a hydroxyl number of from about 200 to about 600, preferably about 300 to about 500 milligrams of KOH based upon one gram of polyether polyol. The viscosity of the polyether polyol is from 100 to 1,000 centipoise, preferably from 200 to 700 centipoise, most preferably 300 to 500 centipoise. The polyether polyols may have primary and/or secondary hydroxyl groups.
These polyether polyols are commercially available and their method of preparation and determining their hydroxyl value is well known. The polyether polyols are prepared by reacting an alkylene oxide with a polyhydric alcohol in the presence of an appropriate catalyst such as sodium methoxide according to methods well known in the art. Any suitable alkylene oxide or mixtures of alkylene oxides may be reacted with the polyhydric alcohol to prepare the polyether polyols. The alkylene oxides used to prepare the polyether polyols typically have from two to six carbon atoms. Representative examples include ethylene oxide, propylene oxide, butylene oxide, amylene oxide, styrene oxide, or mixtures thereof. The polyhydric alcohols typically used to prepare the polyether polyols generally have a functionality greater than 2.0, preferably from 2.5 to 5.0, most preferably from 2.5 to 4.5. Examples include ethylene glycol, diethy

Affiliated with

Also associated with

Rating

Furan no-bake foundry binders and their use does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Furan no-bake foundry binders and their use, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Furan no-bake foundry binders and their use will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3102585