US20080060778A1 - Binder composition and method of forming foundry sand cores and molds - Google Patents
Binder composition and method of forming foundry sand cores and molds Download PDFInfo
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- US20080060778A1 US20080060778A1 US11/517,995 US51799506A US2008060778A1 US 20080060778 A1 US20080060778 A1 US 20080060778A1 US 51799506 A US51799506 A US 51799506A US 2008060778 A1 US2008060778 A1 US 2008060778A1
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- starch
- sand
- molds
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- 239000011230 binding agent Substances 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title claims abstract description 41
- 239000000203 mixture Substances 0.000 title claims abstract description 30
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 133
- 229920002472 Starch Polymers 0.000 claims abstract description 87
- 239000008107 starch Substances 0.000 claims abstract description 85
- 235000019698 starch Nutrition 0.000 claims abstract description 85
- 239000004576 sand Substances 0.000 claims abstract description 82
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 32
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 29
- 239000000654 additive Substances 0.000 claims abstract description 26
- 240000003183 Manihot esculenta Species 0.000 claims abstract description 16
- 235000016735 Manihot esculenta subsp esculenta Nutrition 0.000 claims abstract description 16
- 235000019832 sodium triphosphate Nutrition 0.000 claims abstract description 11
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 10
- 239000010703 silicon Substances 0.000 claims abstract description 10
- 238000007664 blowing Methods 0.000 claims abstract description 7
- 230000000996 additive effect Effects 0.000 claims description 8
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 5
- 238000012216 screening Methods 0.000 claims description 5
- 239000011248 coating agent Substances 0.000 claims description 3
- 238000000576 coating method Methods 0.000 claims description 3
- 229910052700 potassium Inorganic materials 0.000 claims description 2
- 239000011591 potassium Substances 0.000 claims description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical group [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims 2
- 238000010438 heat treatment Methods 0.000 claims 1
- 230000002860 competitive effect Effects 0.000 abstract description 3
- 108050001922 30S ribosomal protein S17 Proteins 0.000 abstract 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 abstract 1
- 229910052782 aluminium Inorganic materials 0.000 abstract 1
- 235000013339 cereals Nutrition 0.000 description 14
- 238000004519 manufacturing process Methods 0.000 description 7
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 6
- LEQAOMBKQFMDFZ-UHFFFAOYSA-N glyoxal Chemical compound O=CC=O LEQAOMBKQFMDFZ-UHFFFAOYSA-N 0.000 description 6
- 229920000881 Modified starch Polymers 0.000 description 4
- 125000000217 alkyl group Chemical group 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 229920001296 polysiloxane Polymers 0.000 description 4
- 229920000945 Amylopectin Polymers 0.000 description 3
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 3
- 239000004368 Modified starch Substances 0.000 description 3
- 240000008042 Zea mays Species 0.000 description 3
- 235000002017 Zea mays subsp mays Nutrition 0.000 description 3
- 229910052910 alkali metal silicate Inorganic materials 0.000 description 3
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 description 3
- 238000005266 casting Methods 0.000 description 3
- 229940015043 glyoxal Drugs 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 239000003232 water-soluble binding agent Substances 0.000 description 3
- 229910000838 Al alloy Inorganic materials 0.000 description 2
- 229920000856 Amylose Polymers 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229920001353 Dextrin Polymers 0.000 description 2
- 108010010803 Gelatin Proteins 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 235000005822 corn Nutrition 0.000 description 2
- 235000019425 dextrin Nutrition 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- RBLGLDWTCZMLRW-UHFFFAOYSA-K dicalcium;phosphate;dihydrate Chemical compound O.O.[Ca+2].[Ca+2].[O-]P([O-])([O-])=O RBLGLDWTCZMLRW-UHFFFAOYSA-K 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 229920000159 gelatin Polymers 0.000 description 2
- 235000019322 gelatine Nutrition 0.000 description 2
- 235000011852 gelatine desserts Nutrition 0.000 description 2
- 239000008103 glucose Substances 0.000 description 2
- 239000000413 hydrolysate Substances 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- 235000019426 modified starch Nutrition 0.000 description 2
- -1 octyl triethoxi silane Chemical compound 0.000 description 2
- 239000012188 paraffin wax Substances 0.000 description 2
- 235000019809 paraffin wax Nutrition 0.000 description 2
- 235000019271 petrolatum Nutrition 0.000 description 2
- 229910000077 silane Inorganic materials 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000001993 wax Substances 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 229920002261 Corn starch Polymers 0.000 description 1
- 239000004375 Dextrin Substances 0.000 description 1
- 229920002245 Dextrose equivalent Polymers 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 108010009736 Protein Hydrolysates Proteins 0.000 description 1
- 244000061456 Solanum tuberosum Species 0.000 description 1
- 235000002595 Solanum tuberosum Nutrition 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 229920004482 WACKER® Polymers 0.000 description 1
- 235000016383 Zea mays subsp huehuetenangensis Nutrition 0.000 description 1
- 239000004480 active ingredient Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 235000021120 animal protein Nutrition 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000007767 bonding agent Substances 0.000 description 1
- JHLNERQLKQQLRZ-UHFFFAOYSA-N calcium silicate Chemical compound [Ca+2].[Ca+2].[O-][Si]([O-])([O-])[O-] JHLNERQLKQQLRZ-UHFFFAOYSA-N 0.000 description 1
- 235000012241 calcium silicate Nutrition 0.000 description 1
- 229910052918 calcium silicate Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 239000008121 dextrose Substances 0.000 description 1
- 239000004205 dimethyl polysiloxane Substances 0.000 description 1
- 235000013870 dimethyl polysiloxane Nutrition 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 235000013312 flour Nutrition 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000008273 gelatin Substances 0.000 description 1
- 125000002791 glucosyl group Chemical group C1([C@H](O)[C@@H](O)[C@H](O)[C@H](O1)CO)* 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 235000009973 maize Nutrition 0.000 description 1
- 231100000647 material safety data sheet Toxicity 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000006259 organic additive Substances 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000011236 particulate material Substances 0.000 description 1
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 1
- 229920000435 poly(dimethylsiloxane) Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920005862 polyol Polymers 0.000 description 1
- 150000003077 polyols Chemical class 0.000 description 1
- ZLMJMSJWJFRBEC-OUBTZVSYSA-N potassium-40 Chemical compound [40K] ZLMJMSJWJFRBEC-OUBTZVSYSA-N 0.000 description 1
- 229920001592 potato starch Polymers 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 235000000346 sugar Nutrition 0.000 description 1
- 150000005846 sugar alcohols Polymers 0.000 description 1
- 150000008163 sugars Chemical class 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- 239000000080 wetting agent Substances 0.000 description 1
- 229910052845 zircon Inorganic materials 0.000 description 1
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
- B22C1/20—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents
- B22C1/26—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of carbohydrates; of distillation residues therefrom
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
- B22C1/18—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents
- B22C1/185—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents containing phosphates, phosphoric acids or its derivatives
Definitions
- the present invention refers to a binder and a method of forming foundry sand cores and molds, and more particularly to a water-based binder and a method of forming silica sand cores and molds with great economic and environmental advantages over the currently used organic-compound binders.
- One of the preferred processes for manufacturing engine blocks and heads utilizes silica sand molds and cores.
- the molds and cores are most typically made of silica sand grains bound by a heat-curable phenolic binder or a gas activated cold box binder.
- the heat-curable binders have the disadvantage of requiring heat to set the molds and cores, producing foul-smelling vapors, and requiring special anti-pollution equipment to prevent ambient contamination.
- Another disadvantage arises once the cast motor blocks or heads are solidified, since removal of such cores and molds needs additional heat to burn off the binder by contact with hot air (in order to combust the binder and thus loosen the sand to destroy the cores), thus adding further to the fuel cost of the process.
- U.S. Pat. No. 2,508,359 discloses a starch-containing product for use as a core binder, and more particularly to such a binder made from dextrinized corn flour.
- U.S. Pat. No. 5,582,231 discloses a foundry mold member made from a plurality of sand particles bound together with a binder which consists essentially of gelatins (animal protein). The sand particles are coated with a film of a binder of gelatin having Bloom ratings of less than about 175 Bloom grams.
- the present invention provides a starch-based binder composition employable in the widely-used core forming process of blow boxes where it is desired to have a strong setting sand bonding agent and at the same time a sand mix that easily flows into the core molds and fills all the spaces in the geometries of even complex sand molds, such as for automotive parts.
- the binder composition of the invention comprises specific additives which mixed with starch and sand are specially suited for such core making process.
- Binder compositions discloses a binder composition consisting essentially of an aqueous solution of an alkali metal silicate and a stabilized starch hydrolysate having a dextrose equivalent of below 5. The components being present in the weight ratios, calculated as solids, of 0.4 to 35 parts of stabilized starch hydrolysate per 20 to 49.5 parts alkali metal silicate. The mixture is hardened either by gassing with carbon dioxide or by incorporating chemical hardening agents such as esters of polyhydric alcohols.
- U.S. Pat. No. 4,158,574 “Hydrolyzed amylaceous product and process of making same” relates to a foundry binder system employing glyoxal, a polyhydroxyl compound and a unique catalyst comprised of inorganic alkali halides.
- the polyols used are those that react rigidly with glyoxal including sugars, starch, starch hydrolysates, gums and dextrins.
- the general object of the invention is to make it possible for glyoxal to be used as a low-cost resin-forming binder system with control over the rate of setting.
- Applicants have found suitable additives for providing starch-based binder with sufficient fluidity for using the standard method of blowing sand cores while at then same time obtaining cores of sufficient strength and shape definition with the combination of additives in a predefined proportion thus providing a suitable core and mold making process at a competitive cost.
- a binder made from starch having additives to improve flowability, to improve water repellency, and optionally to improve as needed the coating of the sand by the other additives by use of wetting agents.
- silica sand with any kind starch can be a used to make sand cores for some limited foundry purposes. Even insoluble amylopectin can be used when a proper temperature is applied.
- the sand mix can be dumped into any core box with most any geometry and compacted to make the desired cores.
- the sand mix must be able to be blown into, and thereby be compacted in, the mold forms.
- the coated sand typically is pushed through blow pipes of about 1 inch or less in diameter, using air pressure.
- the applicants have been able to achieve this goal of using low cost water soluble starch as a core binder capable of being effectively blown by use of selective additives.
- Such additives that have been found to effectively increase flowability are: sodium tripolyphosphate, sodium hexamethaphosphate, dicalcium phosphate dihydrate, sodium chloride, dimethylpolysiloxane and ethylic alcohol All these additives match very well with the water repellency additives described bellow.
- Such additives that have been found to effectively control water repellency are: Alkyl silicone (Silres BS69050), triethoxi (2,4,4 trimetilpentil) silane, octyl triethoxi silane plus alkyl silicone Silres BS 16, Wax emulsions, paraffin waxes, wax polymers, natural and paraffin wax combinations under different trade names were tested with acceptable results.
- Such water repellency additives that have been found to be particularly useful in this invention are: triethoxi (2,4,4 trimetilpentil) silane, octyl triethoxi silane plus alkyl silicone and Alkyl silicone (Silres BS69050).
- amylose/amylopectin ratio for tapioca is given as 0.22.
- amylose is a linear chain of 500 to 2000 glucose units
- amylopectin is more massive and branched with linear chain lengths of 25-30 glucose units
- Preferred embodiments of a binder according to the present invention comprise about 70%-95% starch (or more preferably 70-90%, or still more preferably 70-85%) plus additive(s) ⁇ such as, for example, preferably sodium tripolyphosphate and silicon or Silres BS 16, or their functional equivalents).
- Silres BS®16 is the tradename of Wacker Chemie, AG for a concentrated water solution of 1-5% potassium hydroxide and 40-70% potassium methyl siliconate (per the list of ingredients in that company's Material Safety Data Sheet for the U.S.); more specifically, that company's product brochure for Silres BS®16 gives the solids content as 54 wt. % and the approximate active ingredients as 34%.
- a preferred method for making a binder coated sand according to the present invention is by forming silica sand cores and molds for foundries utilizing a starchwater-based binder comprising mixing silica sand grains with starch in a suitable mixer, adding water to said sand and starch mixture and continue mixing said sand, starch, and water so that the sand grains are coated with starch (typically in about one minute); drying the starch-coated sand grains and treating them in a mill to break down lumps which might have been formed during the starch-coating step and screening the sand to separate said lumps; adding water to said coated sand grains and screening said sand grains for homogenizing and loosening said grains; adding sodium tripolyphosphate and silicon or Silres® BS 16; optionally adding dispersing additives; and blowing said cores and molds utilizing said starch-coated sand grains.
- binder coated sand can also be made by direct mixing of sand and binder from starch and additives before blowing
- the objects of the invention are also met by providing a core or mold made from the starch/water based binder composition of the present invention.
- FIG. 1 shows a process block diagram illustrating the main steps of a method illustrating one preferred embodiment of the invention for the manufacture of sand molds and cores utilizing an artificially-modified tapioca type starch.
- FIG. 2 shows a second preferred embodiment; being a process, similar to that in FIG. 1 , modified to utilize native tapioca type starch.
- Silica sand cores are made from sand grains bound by a suitable binder which provides a strong bond between such sand grains in such a manner and with a sufficiency to withstand the handling of the cores and the assembled molds without losing the precise dimensions and form needed for impressing the desired geometry and surface quality to the casting under the temperature and pressure of the molten metal used to form said casting.
- sand cores are shaped by mixing sand and a binder, blowing the binder-sand mixture into a mold having the desired shape, and curing or hardening the binder in the mold so that the mold geometry is fixed in the cores after their removal from said mold.
- binders There are a variety of synthetic resins used as binders as is well known in the art. According to the present invention, a water-based binder and a method for forming the sand cores provide a number of advantages over the current state-of-the-art binders regarding manufacturing costs and core qualities.
- the binder of the invention is mainly composed of starch.
- starch has been utilized as an additive to prior-art binders, mostly in proportions of less than 20% of the binder composition, to the best of applicants' knowledge it has not previously been effectively used as the main constituent of a sand core-making binder in mass production foundries.
- two additives are added to the starch, in the proportions and in the form explained below, which in combination with the starch, provide the desired qualities to the formed cores.
- These additives are sodium tripolyphosphate and silicon or Silres BS 16. More broadly, the separate functions of the two additives with certain starches may be found in only one single additive.
- starch suitable to be utilized as the basis of the binder composition of the invention.
- One difference among them is the amount of starch needed to achieve the same mechanical strength.
- potato requires more than 2% weight (based on sand) and for maize close to 2% weight.
- Tapioca starch the core needs significantly less starch content to achieve the same strength.
- Tapioca starch is thus preferably used but other varieties of starch can also be utilized according to broader aspects of the invention.
- silica sand 10 is mixed with the artificially-modified starch 12 in a proportion of from about 0.5% to 3.0% by weight on the basis of the sand weight, in a paddle mixer 14 for a period of time from about 30 seconds to about 120 seconds. This period of time must be sufficient for achieving a good dispersion of the starch over the surface of the sand particles.
- water 16 is slowly added to the sand-starch mixture preferably in a proportion from about 5% to 10% by weight on the basis of the sand weight and the sand-starch-water mixture is mixed in said mixer 14 for at least 1 minute, producing starch-coated sand grains 18 which are then allowed to dry naturally (indicated by dotted line 19 ) or optionally in a suitable drying furnace 20 for accelerating the drying process and thereby increasing the process productivity.
- the furnace 20 can be of the type having forced air 17 .
- the dry starch-coated sand 18 is then treated in a suitable mill 22 (for example, a ball mill or a vibrating shaker) for destroying the sand lumps which may have been formed during the previous step.
- the milled coated sand 23 is screened on a screen 24 , for example utilizing a sieve # 30 for assuring that all the sand grains have a homogeneous particle size.
- Sand lumps 25 separated from the coated loose sand grains, are recycled to mill 22 .
- the starch-coated sand 23 undergoes a second mixing step in a mixer 28 where water 35 is added in a proportion preferably of at least 2% by weight on the basis of the sand weight, also sodium thipolyphosphate 32 is added in a proportion of from 0.1% to about 0.2% by weight on the basis of the sand weight, and silicon 34 from about 0.1% to 0.2% or Silres BS 16 from about 0.02% to 0.08%, resulting in sand ready for core blowing in blower 36 where the final core 38 is formed.
- silica sand 10 is pre-heated to a temperature in the range from about 110° C. to about 130° C. in a furnace 13 .
- the preheated sand is then transferred to the mixer 14 to follow the rest of the method in the same manner as above-described for the artificially modified starch.
- Water 16 is also preferably heated to a temperature of about 70° C. in order to preserve as much as possible the temperature of the sand above about 70° C.
- the amount of water 16 added at this mixing step should be sufficient to reach a humidity level in the range from about 2% to about 4% of the humid sand weight.
- FIG. 2 The rest of the method illustrated in FIG. 2 is the same as in FIG. 1 .
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Abstract
Description
- The present invention refers to a binder and a method of forming foundry sand cores and molds, and more particularly to a water-based binder and a method of forming silica sand cores and molds with great economic and environmental advantages over the currently used organic-compound binders.
- The automotive industry is extremely competitive and demanding regarding manufacturing costs of automobile components. The manufacturers of cylinder engine blocks and heads, mainly made of aluminum alloys, are constantly looking for methods and systems that provide cost savings and simultaneously increase the quality of such engine parts.
- One of the preferred processes for manufacturing engine blocks and heads utilizes silica sand molds and cores. Currently, the molds and cores are most typically made of silica sand grains bound by a heat-curable phenolic binder or a gas activated cold box binder. The heat-curable binders have the disadvantage of requiring heat to set the molds and cores, producing foul-smelling vapors, and requiring special anti-pollution equipment to prevent ambient contamination. Another disadvantage arises once the cast motor blocks or heads are solidified, since removal of such cores and molds needs additional heat to burn off the binder by contact with hot air (in order to combust the binder and thus loosen the sand to destroy the cores), thus adding further to the fuel cost of the process.
- There is a long-felt and ongoing need for a low-cost, energy efficient, and effective water-soluble binder for the molds and cores, particularly useful in the aluminum-alloys foundries, in order to decrease operational costs in the manufacture of engine blocks and heads.
- Several early attempts to meet this need, going back many years, are mentioned below.
- U.S. Pat. No. 2,508,359 discloses a starch-containing product for use as a core binder, and more particularly to such a binder made from dextrinized corn flour.
- U.S. Pat. No. 5,582,231 discloses a foundry mold member made from a plurality of sand particles bound together with a binder which consists essentially of gelatins (animal protein). The sand particles are coated with a film of a binder of gelatin having Bloom ratings of less than about 175 Bloom grams.
- While a number of earlier patents teach the utilization of starch as an ingredient of water-soluble binders in different proportions for forming sand cores, the starch in such patents is used combined with binders like alkaline silicates and organic resins with which starch cooperates for providing the main binding effect. No reference has been found that addresses the problem of using starch as the main constituent of a binder composition which when mixed with the sand provides said sand with good flow characteristics so that it can be effectively utilized to be air-blown into core forming boxes. The present invention provides a starch-based binder composition employable in the widely-used core forming process of blow boxes where it is desired to have a strong setting sand bonding agent and at the same time a sand mix that easily flows into the core molds and fills all the spaces in the geometries of even complex sand molds, such as for automotive parts. The binder composition of the invention comprises specific additives which mixed with starch and sand are specially suited for such core making process.
- The following patents are of general background interest which are not directly related with the invention.
- U.S. Pat. No. 4,070,196 “Binder compositions” discloses a binder composition consisting essentially of an aqueous solution of an alkali metal silicate and a stabilized starch hydrolysate having a dextrose equivalent of below 5. The components being present in the weight ratios, calculated as solids, of 0.4 to 35 parts of stabilized starch hydrolysate per 20 to 49.5 parts alkali metal silicate. The mixture is hardened either by gassing with carbon dioxide or by incorporating chemical hardening agents such as esters of polyhydric alcohols.
- U.S. Pat. No. 4,158,574 “Hydrolyzed amylaceous product and process of making same” relates to a foundry binder system employing glyoxal, a polyhydroxyl compound and a unique catalyst comprised of inorganic alkali halides. The polyols used are those that react rigidly with glyoxal including sugars, starch, starch hydrolysates, gums and dextrins. The general object of the invention is to make it possible for glyoxal to be used as a low-cost resin-forming binder system with control over the rate of setting.
- U.S. Pat. No. 3,642,503 “Process for bonding particulate materials” teaches the use of an aqueous alkali metal silicate, silicon, dicalcium silicate and lime. An organic additive may be added to retard the setting of the binder, for example glucose or dextrose. No starch is mentioned.
- Documents cited in this text (including the foregoing patents), and all documents cited or referenced in the documents cited in this text, are incorporated herein by reference. Documents incorporated by reference into this text or any teachings therein may be used in the practice of this invention.
- Applicants have found suitable additives for providing starch-based binder with sufficient fluidity for using the standard method of blowing sand cores while at then same time obtaining cores of sufficient strength and shape definition with the combination of additives in a predefined proportion thus providing a suitable core and mold making process at a competitive cost.
- It is therefore an object of the present invention to provide a competitively effective water-soluble binder composition for forming sand cores and molds for foundries with several cost and technical advantages plus environmental benefits, as well as the method of making such cores and molds and the cores and molds made with such composition.
- It is another object of the present invention to provide a method of forming sand cores and molds for foundries at a lower cost.
- It is a further object of the invention to provide such a binder for forming sand cores and molds for foundries that do not require enclosed installations for control of foul smelling vapors in foundries.
- It is still a further object of the invention to provide a method, a binder composition, and sand cores and molds for foundries for producing castings with dimensional precision that advantageously avoids the need to use higher-cost zircon sand to obtain comparable results.
- It is yet a further object of the invention to achieve all the foregoing objectives using a starch-based binder and its starch derivatives (dextrines fore example) that is demonstratively more effective than any starch-containing binder taught in the prior art.
- The objects of the invention are generally met according to one aspect of the present invention by a binder made from starch having additives to improve flowability, to improve water repellency, and optionally to improve as needed the coating of the sand by the other additives by use of wetting agents.
- Applicants have determined that the mix of silica sand with any kind starch can be a used to make sand cores for some limited foundry purposes. Even insoluble amylopectin can be used when a proper temperature is applied. The sand mix can be dumped into any core box with most any geometry and compacted to make the desired cores.
- However, to be commercially and competitively useful, the sand mix must be able to be blown into, and thereby be compacted in, the mold forms. In practice, the coated sand typically is pushed through blow pipes of about 1 inch or less in diameter, using air pressure. The applicants have been able to achieve this goal of using low cost water soluble starch as a core binder capable of being effectively blown by use of selective additives.
- Such additives that have been found to effectively increase flowability are: sodium tripolyphosphate, sodium hexamethaphosphate, dicalcium phosphate dihydrate, sodium chloride, dimethylpolysiloxane and ethylic alcohol All these additives match very well with the water repellency additives described bellow.
- Such additives that have been found to effectively control water repellency are: Alkyl silicone (Silres BS69050), triethoxi (2,4,4 trimetilpentil) silane, octyl triethoxi silane plus alkyl silicone Silres BS 16, Wax emulsions, paraffin waxes, wax polymers, natural and paraffin wax combinations under different trade names were tested with acceptable results.
- Such water repellency additives that have been found to be particularly useful in this invention are: triethoxi (2,4,4 trimetilpentil) silane, octyl triethoxi silane plus alkyl silicone and Alkyl silicone (Silres BS69050).
- In addition, the applicants have determined that some starches are better than others when used in commercial applications. As part of their ongoing research, tapioca starch has been found to be superior to corn and potato starch with regard to the amount needed to achieve the same mechanical strength in the core.
- The amylose/amylopectin ratio for tapioca is given as 0.22. Although the amylose is a linear chain of 500 to 2000 glucose units, the amylopectin is more massive and branched with linear chain lengths of 25-30 glucose units
- Preferred embodiments of a binder according to the present invention comprise about 70%-95% starch (or more preferably 70-90%, or still more preferably 70-85%) plus additive(s) {such as, for example, preferably sodium tripolyphosphate and silicon or Silres BS 16, or their functional equivalents).
- Silres BS®16 is the tradename of Wacker Chemie, AG for a concentrated water solution of 1-5% potassium hydroxide and 40-70% potassium methyl siliconate (per the list of ingredients in that company's Material Safety Data Sheet for the U.S.); more specifically, that company's product brochure for Silres BS®16 gives the solids content as 54 wt. % and the approximate active ingredients as 34%.
- A preferred method for making a binder coated sand according to the present invention is by forming silica sand cores and molds for foundries utilizing a starchwater-based binder comprising mixing silica sand grains with starch in a suitable mixer, adding water to said sand and starch mixture and continue mixing said sand, starch, and water so that the sand grains are coated with starch (typically in about one minute); drying the starch-coated sand grains and treating them in a mill to break down lumps which might have been formed during the starch-coating step and screening the sand to separate said lumps; adding water to said coated sand grains and screening said sand grains for homogenizing and loosening said grains; adding sodium tripolyphosphate and silicon or Silres®
BS 16; optionally adding dispersing additives; and blowing said cores and molds utilizing said starch-coated sand grains. - Alternatively, applicants have determined that such binder coated sand can also be made by direct mixing of sand and binder from starch and additives before blowing
- The objects of the invention are also met by providing a core or mold made from the starch/water based binder composition of the present invention.
-
FIG. 1 shows a process block diagram illustrating the main steps of a method illustrating one preferred embodiment of the invention for the manufacture of sand molds and cores utilizing an artificially-modified tapioca type starch. -
FIG. 2 shows a second preferred embodiment; being a process, similar to that inFIG. 1 , modified to utilize native tapioca type starch. - The present invention will be better understood with reference to the following detailed description of certain specific embodiments thereof.
- Silica sand cores are made from sand grains bound by a suitable binder which provides a strong bond between such sand grains in such a manner and with a sufficiency to withstand the handling of the cores and the assembled molds without losing the precise dimensions and form needed for impressing the desired geometry and surface quality to the casting under the temperature and pressure of the molten metal used to form said casting.
- Currently, sand cores are shaped by mixing sand and a binder, blowing the binder-sand mixture into a mold having the desired shape, and curing or hardening the binder in the mold so that the mold geometry is fixed in the cores after their removal from said mold.
- There are a variety of synthetic resins used as binders as is well known in the art. According to the present invention, a water-based binder and a method for forming the sand cores provide a number of advantages over the current state-of-the-art binders regarding manufacturing costs and core qualities.
- The binder of the invention is mainly composed of starch. Though starch has been utilized as an additive to prior-art binders, mostly in proportions of less than 20% of the binder composition, to the best of applicants' knowledge it has not previously been effectively used as the main constituent of a sand core-making binder in mass production foundries. According to a preferred embodiment of the present invention, two additives are added to the starch, in the proportions and in the form explained below, which in combination with the starch, provide the desired qualities to the formed cores. These additives are sodium tripolyphosphate and silicon or
Silres BS 16. More broadly, the separate functions of the two additives with certain starches may be found in only one single additive. - There are several types of starch suitable to be utilized as the basis of the binder composition of the invention. One difference among them is the amount of starch needed to achieve the same mechanical strength. For example potato requires more than 2% weight (based on sand) and for maize close to 2% weight. However, when using Tapioca starch, the core needs significantly less starch content to achieve the same strength.
- Tapioca starch is thus preferably used but other varieties of starch can also be utilized according to broader aspects of the invention. There are two types of tapioca starch: (a) native (i.e. unmodified) starch and (b) artificially-modified starch. Both types have proven effective as binders for the particular application of core making. The method of the invention may have some differences depending on which type of tapioca starch is utilized.
- The core-making method of this embodiment of the invention will be described first as applied to the utilization of artificially-modified tapioca starch. With reference to
FIG. 1 showing a diagram of the method steps for forming such cores,silica sand 10 is mixed with the artificially-modifiedstarch 12 in a proportion of from about 0.5% to 3.0% by weight on the basis of the sand weight, in apaddle mixer 14 for a period of time from about 30 seconds to about 120 seconds. This period of time must be sufficient for achieving a good dispersion of the starch over the surface of the sand particles. After this first mixing step,water 16 is slowly added to the sand-starch mixture preferably in a proportion from about 5% to 10% by weight on the basis of the sand weight and the sand-starch-water mixture is mixed in saidmixer 14 for at least 1 minute, producing starch-coatedsand grains 18 which are then allowed to dry naturally (indicated by dotted line 19) or optionally in asuitable drying furnace 20 for accelerating the drying process and thereby increasing the process productivity. Thefurnace 20 can be of the type having forcedair 17. The dry starch-coatedsand 18 is then treated in a suitable mill 22 (for example, a ball mill or a vibrating shaker) for destroying the sand lumps which may have been formed during the previous step. Thereafter, the milledcoated sand 23 is screened on ascreen 24, for example utilizing a sieve # 30 for assuring that all the sand grains have a homogeneous particle size. Sand lumps 25, separated from the coated loose sand grains, are recycled tomill 22. After screening, the starch-coatedsand 23 undergoes a second mixing step in amixer 28 wherewater 35 is added in a proportion preferably of at least 2% by weight on the basis of the sand weight, alsosodium thipolyphosphate 32 is added in a proportion of from 0.1% to about 0.2% by weight on the basis of the sand weight, andsilicon 34 from about 0.1% to 0.2% orSilres BS 16 from about 0.02% to 0.08%, resulting in sand ready for core blowing inblower 36 where thefinal core 38 is formed. - Referring now to
FIG. 2 , wherein same numerals designate the same elements, the method therein described is the method followed when native-type tapioca starch is used for binding the sand grains in cores and molds.Silica sand 10 is pre-heated to a temperature in the range from about 110° C. to about 130° C. in afurnace 13. The preheated sand is then transferred to themixer 14 to follow the rest of the method in the same manner as above-described for the artificially modified starch. -
Water 16 is also preferably heated to a temperature of about 70° C. in order to preserve as much as possible the temperature of the sand above about 70° C. The amount ofwater 16 added at this mixing step should be sufficient to reach a humidity level in the range from about 2% to about 4% of the humid sand weight. - The rest of the method illustrated in
FIG. 2 is the same as inFIG. 1 . - It is of course to be understood that in the above specification, only certain specific embodiments have been included for purposes of illustrating the principles of the invention and that the invention is not intended to be limited thereto. It will also be evident that numerous changes may be made to the embodiments herein described without departing from the spirit and scope of the invention which is limited only to the extent set forth in the appended claims.
Claims (20)
Priority Applications (7)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US11/517,995 US20080060778A1 (en) | 2006-09-08 | 2006-09-08 | Binder composition and method of forming foundry sand cores and molds |
US12/440,553 US20110042028A1 (en) | 2006-09-08 | 2007-09-10 | Binder composition amd method of forming foundry sand cores and molds |
PCT/IB2007/004242 WO2008029302A2 (en) | 2006-09-08 | 2007-09-10 | Binder composition and method of forming foundry sand cores and molds |
EP07859284A EP2107955A4 (en) | 2006-09-08 | 2007-09-10 | Binder composition and method of forming foundry sand cores and molds |
CA002662844A CA2662844A1 (en) | 2006-09-08 | 2007-09-10 | Binder composition and method of forming foundry sand cores and molds |
MX2009002490A MX2009002490A (en) | 2006-09-08 | 2007-09-10 | Binder composition and method of forming foundry sand cores and molds. |
ARP070103996A AR062728A1 (en) | 2006-09-08 | 2007-09-11 | BINDING COMPOSITION AND METHOD FOR FORMING HEARTS AND SAND MOLDS FOR FOUNDATIONS |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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US11/517,995 US20080060778A1 (en) | 2006-09-08 | 2006-09-08 | Binder composition and method of forming foundry sand cores and molds |
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Publication Number | Publication Date |
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US20080060778A1 true US20080060778A1 (en) | 2008-03-13 |
Family
ID=39157645
Family Applications (2)
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US11/517,995 Abandoned US20080060778A1 (en) | 2006-09-08 | 2006-09-08 | Binder composition and method of forming foundry sand cores and molds |
US12/440,553 Abandoned US20110042028A1 (en) | 2006-09-08 | 2007-09-10 | Binder composition amd method of forming foundry sand cores and molds |
Family Applications After (1)
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US12/440,553 Abandoned US20110042028A1 (en) | 2006-09-08 | 2007-09-10 | Binder composition amd method of forming foundry sand cores and molds |
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US (2) | US20080060778A1 (en) |
EP (1) | EP2107955A4 (en) |
AR (1) | AR062728A1 (en) |
CA (1) | CA2662844A1 (en) |
MX (1) | MX2009002490A (en) |
WO (1) | WO2008029302A2 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20100267153A1 (en) * | 2007-10-04 | 2010-10-21 | William Andregg | Sequencing Nucleic Acid Polymers with Electron Microscopy |
US20140190651A1 (en) * | 2011-06-21 | 2014-07-10 | Jaguar Land Rover Limited | Apparatus and Method for Embedding an Element |
JP2016002574A (en) * | 2014-06-18 | 2016-01-12 | 旭有機材工業株式会社 | Manufacturing method of casting mold |
JP2016002573A (en) * | 2014-06-18 | 2016-01-12 | 旭有機材工業株式会社 | Manufacturing method of casting mold |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
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WO2011073715A1 (en) | 2009-12-18 | 2011-06-23 | Tenedora Nemak, S.A. De C.V. | Binder composition and method of forming foundry sand cores and molds |
JP5249447B1 (en) * | 2012-05-17 | 2013-07-31 | 株式会社木村鋳造所 | Foundry sand for 3D laminate molding |
DE102014109598A1 (en) * | 2014-07-09 | 2016-01-14 | Tenedora Nemak, S.A. De C.V. | Casting core, use of a foundry core and method of making a foundry core |
CN108723285B (en) * | 2018-07-11 | 2019-12-03 | 佛山市杨森化工有限公司 | A kind of preparation method of high green compression strength moulding sand binder material |
CN109465380B (en) * | 2019-01-04 | 2021-08-10 | 山东永创材料科技有限公司 | High-strength binder for cast iron |
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US3462503A (en) * | 1965-06-14 | 1969-08-19 | Atlantic Richfield Co | Telomerization of ethylene |
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US5215143A (en) * | 1992-11-16 | 1993-06-01 | American Colloid Company | Non-porous carbon molding (foundry) sand and method of casting |
US6139619A (en) * | 1996-02-29 | 2000-10-31 | Borden Chemical, Inc. | Binders for cores and molds |
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US6833097B2 (en) * | 2000-01-03 | 2004-12-21 | Japan Corn Starch Co. Ltd. | Biodegradable block for models |
US8490677B2 (en) * | 2003-09-02 | 2013-07-23 | Sintokogio, Ltd. | Method for forming molds and core for casting metal |
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2006
- 2006-09-08 US US11/517,995 patent/US20080060778A1/en not_active Abandoned
-
2007
- 2007-09-10 EP EP07859284A patent/EP2107955A4/en active Pending
- 2007-09-10 WO PCT/IB2007/004242 patent/WO2008029302A2/en active Application Filing
- 2007-09-10 CA CA002662844A patent/CA2662844A1/en not_active Abandoned
- 2007-09-10 US US12/440,553 patent/US20110042028A1/en not_active Abandoned
- 2007-09-10 MX MX2009002490A patent/MX2009002490A/en unknown
- 2007-09-11 AR ARP070103996A patent/AR062728A1/en unknown
Patent Citations (5)
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US2508359A (en) * | 1947-02-21 | 1950-05-23 | Rose C Baker | Core binder |
US3642503A (en) * | 1970-06-08 | 1972-02-15 | Foseco Int | Process for bonding particulate materials |
US4158574A (en) * | 1975-02-21 | 1979-06-19 | Krause Milling Company | Hydrolyzed amylaceous product and process of making the same |
US4070196A (en) * | 1975-09-15 | 1978-01-24 | Foseco International Limited | Binder compositions |
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US20100267153A1 (en) * | 2007-10-04 | 2010-10-21 | William Andregg | Sequencing Nucleic Acid Polymers with Electron Microscopy |
US20140190651A1 (en) * | 2011-06-21 | 2014-07-10 | Jaguar Land Rover Limited | Apparatus and Method for Embedding an Element |
US9724752B2 (en) * | 2011-06-21 | 2017-08-08 | Jaguar Land Rover Limited | Apparatus and method for embedding an element |
JP2016002574A (en) * | 2014-06-18 | 2016-01-12 | 旭有機材工業株式会社 | Manufacturing method of casting mold |
JP2016002573A (en) * | 2014-06-18 | 2016-01-12 | 旭有機材工業株式会社 | Manufacturing method of casting mold |
Also Published As
Publication number | Publication date |
---|---|
CA2662844A1 (en) | 2008-03-13 |
AR062728A1 (en) | 2008-11-26 |
US20110042028A1 (en) | 2011-02-24 |
WO2008029302A3 (en) | 2009-08-27 |
MX2009002490A (en) | 2009-05-11 |
EP2107955A2 (en) | 2009-10-14 |
EP2107955A4 (en) | 2010-08-04 |
WO2008029302A2 (en) | 2008-03-13 |
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