US 2861966 A
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United States Patent CORE MOLDING COMPOSITION Joseph L. Betts, Jr., Westfield, and John P. Thorn, Union,
N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application October 5, 1956 Serial No. 614,050
14 Claims. (Cl. 260-23.7)
The present invention relates to'the manufacture of cores for casting metal and in particular it relates to improved cores used in the manufacture of hollow castings. Specifically, it concerns the use of a core oil comprising a mixture of a polymer oil, resin and vegetable oil.
Because the finely divided matter used in the preparation of cores has no natural binding property, it is necessary to employ a binder or core oil to hold the particles together. Considerable skill is necessary to prepare satisfactory cores. The binder must mix well with the inert material so that each particle is coated and the core has a uniform density, but it must not create a sticky condition which would gum up the core molding boxes nor should it cause the core to swell or crack in baking or in storage. It should not absorb moisture from the atmosphere after it has been set in the mold waiting for the metal to be poured. A satisfactory binder must impart sufficient bond strength to the core before it is baked to permit manual handling, and permit easy removal of the sand core from its mold prior to baking.
During baking, the binder should oxidize and/or polymerize to yield a core having suflicient tensile strength to withstand the weight of metal when the casting is poured and strong enough to resist ordinary handling in the foundry, .both before and after baking. It should decompose, or burn out, after the metal is poured, but not until the metal has hardened sutficiently was not to lose its shape. With a proper binder, when the casting is cooled, the inert ingredients in the core can be easily broken up and shaken free from the casting.
In the prior art, it has been common to use various compositions comprising linseed oil, fish oil, and other fatty, vegetable and animal oils, along with modifiers of various types as the binder in the preparation of cores for metal castings. These oils were chosen because they combine with oxygen in the air during the baking step and are converted into a strong binder cementing the grains of sand to each other and yielding a firm, hard core.--
Commonly, such cores are baked with an optimum amount of the core oil binder, the preferred compositions having the property of polymerizing to a moderate extent to serve as a binder. Baking is conventionally carried out in a ventilated oven at moderately high temperatures, e. g. between 350 and 600 F. At such temperatures,
It has now been discovered that mixtures of a petroleum resin, a clay treated polymer, and linseed oil make outstanding core oils.
The petroleum resin is prepared as follows: A steam cracked distillate boiling largely in the range of about 77 to 86 F. is exposed to a thermal soaker wherein the dimers of cyclic diolefins are converted to the monomeric form. The thermally soaked product is then distilled to remove any cyclopentadiene dimers, the cyclodienes being removed as a concentrated stream from the lower portion of the distillate tower. The undimerized portion, C -C is passed overhead to a receiver and reflux drum where part is removed to the upper part of the fractionator as reflux. This C -C portion is then sent to the reaction zone where it polymerizes in the presence of a Friedel-Crafts catalyst, such as aluminum chloride, at a temperature between --40 and 158 F. The polymer is then passed through a catalyst removal zone and thence to a steam distillation tower. Here the C C is removed 1 The clay treated polymer oil is prepared in a clay treating unit which consists of a furnace having two individual circuits, one of which is used to preheat the.
feed and the other to supply heat to the fractionating tower which separates the polymer from light and heavy naphtha, and a drum charged with about 20 tons of 8 to 15 mesh Attapulgus clay. The highly olefinic feed stream consists of a mixture of depentanized distillate from an isoprene fractionator unit and debutanized bottoms from a steam cracking unit. 500 F. and contains about 10 to 25% conjugated diolefins, 40 to olefins, 20 to 40% aromatics, and 2 to 5% paraffins. The liquid feed stream is generally preheated to about 250 to 300 F. and passed downwardly through the clay drum. A temperature rise of about 30 to 50 F. occurs in the clay bed as a result of the exothermic reaction. The treated distillate leaving the clay drum is transferred to a fractionating tower which separates the clay treated polymer from light and heavy naphtha. A stripper in the bottom of the tower removes any light hydrocarbons that may be mixed with the polymer.
The clay treated polymer oil generally has a Staudinger molecular weight between about 200 and 1000 and a Wijs iodine number between about 240-320, preferably about 260. It has about 82 to 95% by weight non-volatile matter (ASTMD15443) and an ash of about 0.3 to 0.4 wt. percent. The polymers viscosity at 210 F. is usually about 100 to 300 seconds, and preferably about 156 seconds, in a Saybolt Universal viscometer. The maleic anhydride and Gardner Diene numbers are about 109 and volatile constituents of the core oil or hinder are removed I l but the residue polymerizes or thickens without undue charring to bind the sand and into a firm structure. It is a common practice in the art to add a soap of iron, lead, manganese or cobalt to the binder to accelerate baking.
When the actual casting takes place, the temperature of the metal is quite high, ranging from 1200 F. for aluminum to approximately 3000 F. for iron. 'The temperature of the metal and the nature of the binder are preferably such that the binder breaks down as the metal begins to cool and assumes the configuration of the core. The sand can then be freely shaken out of the cast metal product after the metal has solidified.
19, respectively. It boils between about 400 and 1000 F., having 5% and points at about 500 and 910 F.,
respectively. The flash point should be between about and 300 F. Its API at 60 F. is between about 6 and14.
The quantity of clay treated polymer employed in the.
resin, it should be present in an amount between about 20 l and 80 wt. percent, and preferably between about 30 and 40 wt. percent. An especially desirable combination of these two polymers is where there is about 33 wt. percent It boils between about 50 to 3 clay treated polymer and 33 wt. percent petroleum resin. In all of these oils the balance of the NVM in the formula is made up with raw linseed oil, e. g. 20 to 80 wt. percent, preferably 30 to 40 wt. percent. The whole core oil 4 The one part by weight of core oil in the above formula refers to the amount of non-volatile matter (NVM) in the oil and not the total composition. This takes into account any differences in the amount of solvent in the various comprises about 30 to 70 wt. percent volatile matter and 5 oils and places them all on the same basis. about 30 to 70 wt. percent non-volatile matter. The vollatile portion generally comprises a mineral hydrocarbon EXAMPLE 1 so vent. The solvent should have a boiling range between Cores made according to the general formula were about 130 and 00 and conslst of about 15 to 98 VOL prepared using each of the following substances, linseed gercen; aromatics, 0 to 45 vol. percent naphthenes and on CTL A polymer having a viscosity of 154 SSU at 0 to 4 percent paraflins and Y a kaun'butanol F. and an iodine number of 260, and PRLA resin having value between about 35 and 130. It is preferred to use a Softening point of about 0 R The two last named Core 0118 contammg betwemalmut 40 and 60 percent substances contained Varsol which is a solvent having the of a hydrocarbon solvent bo111ng between 200 to 400 F. following Properties. The finely divided inert solid (about 40 to 200 mesh) I which makes up the major proportion of the core must Bolllngffmgei be a material which has a relatively high level of strength hlltlal 322 or structure. Sand is the most common material em- Flnal 404 ployed because of its availability and low cost. However, S ifi gravity, 60/60o F 0800 to 0310 other substances such as coke, silica, alum na, etc. may be Aromatics, v01. percent to 35 used. An excellent source of these finely divided materials Naphthenics, VOL percent 34 to 40 is the spent catalysts used in a number of refining operaparaffinics, v01- percent to 35 Hons Kauri-butanol value 38 to 44 In addition to the core 011, the core m1xture may include oxidation promoters, such as iron, cobalt or manganese 25 Each core was molded and baked at 400 F. for predeternaphthanates; polymerization catalysts, such as benzoyl mined periods of time. The results are set forth. in peroxide, ditertiary butyl peroxide and combinations Table I. thereof may be employed. Table I In the preparation of the core, the ingredients are mixed and. kneaded together to produce a uniform composition. 30 Tensile Strength, p. s. i.- It is imperative that the liquids coat the surface of the Core 96? g g" AfmEach Baking'minfinely divided matter to insure its adhesion after it is Percent 100 F. baked. For example, 100 parts by weight of sand is 30 mixed with between about 0.25 and 5.0 parts by weight (NVM) of core oil containing linseed oil, petroleum resin 35 QE P resin (50% alsol) 50 158 69 -c 69 and clay treated polymer, preferably between 0.75 and Olav Treated Polymer 1.50 parts by weight, and between about 1 and 5 parts 2933 s2.7 70 s7 s5 by Weight of water. If the total weight of the core oil is Linseed oiiLII -II 100 13.3 51 279 283 to be used, then about 0.5 to 10 parts by weight of oil 7 7 must be employed since about to 60% of the core oil 40 1 NVM of polymer. g z ifs; g i f j gi ifig figs g gg g fgg The above dlata show that neither thelclay treated pJlymer and 2.0 parts by weight. The resulting composition is or p eum resm when used a are sans actory then molded into the desired shape and baked from about Core 0113' EXAMPLE 2 a few minutes, e. g. about 30 minutes, up to about 300 minute at an elevated temperature, e. g. between about A core wasprepared according to the general formula 350 and 450 F. During the baking operation, the wherein the oil employed was a combination of PRLA polymers and linseed oil interact to form a substance resin, CTLA polymer and linseed oil. This core was having outstandingly high tensile strength properties. It evaluated for its tensile strength after various periods is also possible, in the case of certain cores, to use an of baking. The results are set forth in Table II.
Table II Tensile Strength, p. s. i.-After Wt. NVM Baking Viscosity, Each Baking, Core Oil Per- (Wt. Temp, SSU min.
cent cent) F. 100 F.
Petroleum Resin (40% Var- 5 2 ciay"'ii ti"i 6i 1i' 63.7 400 132 73 248 319 (82.7%) 25x5 Linseed Oil 21.2
open flame for from a few minutes up to aboutlO minutes instead of baking the core.
The following examples are given so that the present invention will bemore clearly understood. The formula set forth below was employed in the preparation of each ofthe cores used in the examples:
Ingredients: Parts by weight AFS standard test sand 100.0 Core nil g 1.0 Water 3.0
these cores overnight in an oven to cool. When this is done there is a possibility that part, and sometimes all, of the core oil is burned out. Thus the present invention tends to avoid this undesirable result.
Resort may be added to many modifications and variations of the present invention without departing from the spirit of the discovery or the scope of the appended claims.
What is claimed is:
1. A core oil composition composed of about 30 to 70 wt. percent of non-volatile matter which comprises about 20 to 80 wt. percent of a hydocarbon polymer oil boiling between about 400 and 1000 F., having an iodine number between about 240 and 320 and a Staudinger molecular weight between about 200 and 1000, about 20 to 80 wt. percent of a petroleum resin having a softening point between about 158 and 230 R, an iodine number between about 92 and 119 and an intrinsic viscosity between 0.037 and 0.120 and 20 to 80 wt. percent of vegetable oil, and about 70 to 30 wt. percent of volatile matter comprising a hydrocarbon solvent boiling between about 130 and 500 F. and having a kauri-butanol value between about 35 and 130.
2 A core oil composition according to claim 1 in which the amount of non-volatile matter is between 40 to 60 wt. percent and the amount of volatile matter is between 60 and 40 wt. percent.
A core oil composition according to claim 1 in which the vegetable oil is unsaturated.
4. A core oil composition according to claim 1 in which the vegetable oil is linseed oil.
5. A core oil composition having the following formula:
Wt. percent Non-volatile matter 40 to 60 Hydrocarbon-polymer oil having an iodine number between 240 and 320 and a Staudinger molecular weight between 200 and 1000 30 to 40 Petroleum resin having a softening point between about 158 and 230 F., an iodine number between 92 and 119 and an intrinsic viscosity between 0.037 and 0.120 30 to 40 Linseed oil Balance Volatile matter comprising a hydrocarbon solvent boiling between 130 and 500 F. and containing between 15 and 98 vol. percent aromatics 60 to 40 6. A core molding composition which comprises 100 parts by weight of a finely divided solid and about 0.25 to 5 parts by weight of a binder comprising 20 to 80 wt. percent of a hydrocarbon polymer oil boiling between about 400 and 1000 F having an iodine number between about 250 and 320 and a Staudinger molecular weight between about 200 and 1000, 20 to 80 wt. percent of a petroleum resin having a softening point between about 158 and 23 R, an iodine number between 92 and 119 and an intrinsic viscosity between 0.037 and 0.120 and about to 30 wt. percent of volatile matter comprising a hydrocarbon solvent boiling between about 130 and 500 F. and having a kauri-butanol value between about 35 and 130 and the balance linseed oil.
7. A core molding composition according to claim 6 in which the quantity of binder is between 0.75 and 1.5 parts by weight.
8. A core molding composition according to claim 6 in which the finely divided solid is sand.
9. A core molding composition according to claim 6 in which the finely divided solid is fiuid coke.
10. A process for preparing a core suitable for use in the manufacture of hollow castings which comprises mixing parts by weight of a finely divided solid with between about 0.5 and 10 parts by weight of a core oil composed of about 30 to 70 wt. percent of non-volatile matter which comprises about 20 to 80 wt. percent of a hydrocarbon polymer oil boiling between about 400 and 1000 F., having an iodine number between about 240 and 320 and a Staudinger molecular weight between about 200 and 1000, about 20 to 80 wt. percent of a petroleum resin having a softening point between about 158 and 230 F an iodine number between about 92 and 119 and an intrinsic viscosity between 0.037 and 0.120
and 20 to 80 wt. percent of vegetable oil, and about 70 to 30 wt. percent of volatile matter comprising a hydrocarbon solvent boiling between about and 500 F. and having a kauri-butanol value between about 35 and 130, molding the resulting mixture, baking the resulting molded mixture for from a few minutes up to 300 minutes at a temperature between about 350 and 600 F. and recovering a core.
11. A process according to claim 10 in which the baking step is replaced by heating the molded mixture with an open flame for from a few minutes up to about 10 minutes.
12. A process according to claim 10 in which between about 1 to 5 parts by weight water is admixed with the finely divided solid and the core oil.
13. A process according to claim 10 in which the finely divided solid is sand.
14. A process according to claim 10 in which the finely divided solid is fluid coke.
References Cited in the file of this patent UNITED STATES PATENTS 2,047,297 Stahl July 14, 1936 2,274,618 Remy Feb. 24, 1942 2,466,667 Thomas Apr. 12, 1949 2,734,046 Nelson et al. Feb. 7, 1956 2,779,750 Fuqua et al Jan. 29, 1957 OTHER REFERENCES Lee et al.: Paint, Oil and Chem. Rev., pages 16-25, January 8, 1948. (Copy in Scientific Library.)