US3776992A

US3776992A - Method for producing sleeves or sheets for feeder heads formed in metal casting and an apparatus therefor

Info

Publication number: US3776992A
Application number: US00129778A
Authority: US
Inventors: M Miki
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-09-07
Filing date: 1971-03-31
Publication date: 1973-12-04
Anticipated expiration: 1990-12-04
Also published as: DE2138481C3; FR2106342B1; DE2138481A1; GB1339483A; DE2138481B2; FR2106342A1

Abstract

A METHOD OF PRODUCING SLEEVES OR SHEETS FOR FEEDER HEADS FORMED IN METAL CASTING, WHICH COMPRISES OPTIONALLY BLENDING A RAW MATERIAL MIXTURE OF REFRACTORY MATERIALS WITH LARGE QUANTITIES OF INORGANIC AND ORGANIC FIBROUS MATERIALS AND A BINDING AGENT; COTTON-OPENING AND MIXING THE INORGANIC AND ORGANIC FLOROUS MATERIALS BLENDED IN THE RAW MATERIALS THROUGH AGITATION IN THE DRY STATE WITHOUT ADDING WATER; KNEADING THE RESULTANT MIXTURE WITH LESS THAN 150% BY WEIGHT OF WATER SO AS TO HOLD THE MIXTURE IN THE SOLID FOAM WITH MINIMAL FLUIDITY; MOLDING THE KNEADED MIXTURE INTO A DESIRED SHAPE BY PRESSING IN MOLDS; AND DRYING TO SOLIDIFY THE MOLDED MIXTURE AT A TEMPERATURE OF ABOUT 180*C.

Description

1973 MASAMITSU MIKI 7 ,992

METHOD FOR PRODUCING SLEEVES OR SHEETS FOR FEEDER HEADS FORMED IN METAL CASTING AND AN APPARATUS THERFOR Filed March 31, 1971 2 Sheets-Sheet l HERA INVENTOR. MAsAMiTsu Mini ATTORNEY5 Dec. 1973 MASAMITSU MIKI 76,9 2

FUR FEEDER HEADS MHTHOI) FOR PRODUCING SLEEVES OR SHEETS FORMED 1N METAL Filed March 31, 1971 CASTTNG AND AN APPARATUS THERFOR 2 Sheets-Sheet 2 OO 0m 0m 0% A25 mic. 0m

INVENTOR. MAsAMiTsu Mini 0% 31m #1 rma ATTOR N EYS United States Fatent O 3,776,992 METHOD FOR PRODUCING SLEEVES OR SHEETS FOR FEEDER HEADS FORMED IN METAL CAST- lNG AND AN APPARATUS THEREFOR Masamitsu Miki, 25-15, l-chome, Nakahara, Mitaka, Tokyo, Japan Filed Mar. 31, 1971, Ser. No. 129,778 Claims priority, application Japan, Sept. 7, 1970, 45/77,948, 45/77,949 Int. Cl. F27d N16 US. Cl. 264-122 7 Claims ABSTRACT OF THE DISCLOSURE A method of producing sleeves or sheets for feeder heads formed in metal casting, which comprises optionally blending a raw material mixture of refractory materials with large quantities of inorganic and organic fibrous materials and a binding agent; cotton-opening and mixing the inorganic and organic fibrous materials blended in the raw materials through agitation in the dry state without adding water; kneading the resultant mixture with less than 150% by weight of water so as to hold the mixture in the solid form with minimal fluidity; molding the kneaded mixture into a desired shape by pressing in molds; and drying to solidify the molded mixture at a temperature of about 180 C.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates generally to a method of producing sleeves or sheets for feeder heads formed in metal casting and to an apparatus therefor. More particularly, this invention relates to a method of continuously producing exothermic or heat-insulating sleeves or sheets for feeder heads formed in metal castings in which large quantities of fibrous materials are added, and to an apparatus therefor.

Description of the prior art Various exothermic or heat-insulating materials have been previously used for making feeder head sleeves formed in metal castings, particularly castings of steel, iron or the like. They have also been formed into sheets or slabs for framing feeder heads formed in molds used for steel ingot making. Large volumes of data and knowledge are available regarding the shape, structure and production method of such sleeves, sheets or slabs. However, recently upgraded requirements for such a sleeve or sheet demand a higher heat-insulating effect, lighter weight, higher strength, and particularly higher flexibility in order to obtain more effective and economical feeder heads. Efforts for this purpose have been directed to the development of new materials for making such sleeves or sheets by the addition of inexpensive organic or inorganic fibrous materials, rather than the addition of expensive exothermic materials, as components to the refractory materials, thereby attaining refractory materials of lighter weight, higher strength, and increased porosity However, even when such sleeves or sheets are made by adding said large quantities of fibrous materials to the refractory materials that their apparent specific gravities are below 1 (therefore lighter than water), great difficulties still arise in molding such sleeves or sheets. This is because heretofore a large volume of water had to be used to make a uniform slurry or a pasty or muddy mixture of the powdered or granular refractory materials, with the large quantities of fibrous materials, with or without the addition of an exothermic agent, an oxidizer, or the like. This large quantity of water thereice after had to be removed during the sleeve molding step, which makes that step very complicated and difficult. In conventional molding methods, removal of this large quantity of water was accomplished by use of a vacuum system. According to this method, molding is carried out by using net type molds, while the water is sucked out by the vacuum system. Sleeves or sheets made in this manner, however, are inferior in strength to the sleeves or sheets made by pressing. Moreover, any method using a vacuum water-removal system is unsuitable for the mass production of sleeves or sheets. Therefore, a special mold had to be developed for pressing in the sleeve molding step of the conventional methods. This enabled the production of sleeves of higher strength, but eflicient mass production of such sleeves was still unattainable.

By conventional methods using either a vacuum system or special molds for pressing, molding is difficult because a large volume of water must be removed; particularly difficult is molding with metal molds which are shaped like sleeves, because muddy materials are apt to slip oil? the molds and because product molds themselves tend to break.

Therefore, the addition of large quantities of fibrous materials is difficult, in conventional molding methods, and thus it is very difiicult, using such methods, to produce feeder head sleeves or sheets which have an apparent specific gravity of below 1 and still retain high strength. Even if this were theoretically possible, there is no practical way of applying the so-molded sleeves to commercial metal castings that use a core shooter, molding machine, or the like.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for economical, continuous production of exothermic or heat-insulating feeder head sleeves or sheets formed in metal casting which have an apparent specific gravity of below 1 together with high strength, good heat insulation and moisture repellence and to provide an apparatus therefor.

Another object of the present invention is to provide a method for the continuous production of feeder head sleeves formed in metal casting of sheets or slabs, such as for framing feeder heads formed in molds for steel ingot-making, from a mixture of refractory materials of powder or granular form with large quantities of inorganic and organic fibrous materials in which the molding of such sleeves, sheets or slabs is carried out through pressing by using a core shooter for metal casting, a coreproducing machine, or the like, and to provide an apparatus therefor.

In order to achieve the above-mentioned objects, the present invention is constructed, as follows:

The present invention is so characterized that a refractory material, in powder or granular form, such as silica or brick powder, with or without the addition of an exothermic material and an oxidizing agent, is admixed with at least 15% by weight of inorganic fibrous materials, such as asbestos or ore flakes, and at least 5% by weight of organic fibers such as wood chips or fiber. To this mixture is added 5 to 10% by weight of a binding agent, such as a synthetic resin, without the addition of water and the entire mixture, is subjected to thorough cotton-opening by using a cotton-opening mixer, and then mixed with other materials in powder or granular form. To the so cotton-opened mixture is added less than 150%, preferably between and water and this mixture is kneaded by a kneader or the like, so as to yield a nonfluid non-slurry or non-paste or muddy, like mixture, i.e., the mixture remains'in the powder, granular or solid form. The so kneaded mixture is then placed into molds to be molded into desired shapes; and the molded mix 3 ture is then dried and solidified at about 180 C. in a. drier or the like.

BRIEF DESCRIPTION OF THE DRAWINGS Various other objects, features and attendant advantages of this invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 shows an operation flow-sheet describing the method and apparatus of the present invention;

FIG. 2A shows a diagrammatic sectional view of the molding step in the method of the present invention;

FIG. 2B shows an enlarged view of area IIB in FIG. 2A;

FIG. 3 shows a perspective view of a sleeve and sheet made by the method of the present invention;

FIG. 4 is a curve comparing the heat insulation property of sleeves produced by the method of the present invention with sleeves produced by the conventional methods;

FIG. 5 shows comparative sectional views of feeder heads formed by using sleeves produced by the method of the present invention and feeder heads formed by conventional methods.

DESCRIPTION OF PREFERRED EMBODIMENTS The following is a description of the present invention using a preferred embodiment illustrated in the drawings:

The method of the present invention is explained, as follows, using an operation flow-sheet of a continuous production apparatus shown in FIG. 1. It is noted that practice of the method of the present invention is not limited to the use of such a continuous production apparatus.

The whole process of the method of the present invention is divided into four or five steps: the first step for blending raw materials (if not required, this step may be omitted); the second step for cotton-opening; the third step for kneading; the fourth step for molding; and the fifth step for drying.

In order to obtain heat-insulating sleeves having an apparent specific gravity below 1 according to the method consisting of the above-mentioned steps, blending of the raw materials in the first step is as follows:

Percent by weight (a) Refractory materials -50 (b) Inorganic fibrous material -60 (c) Organic fibrous material 5-30 (d) Binding agent 5-30 Note: In the above case, the total of inorganic fibrous materials (b) and organic fibrous materials (0) should be greater than For producing exothermic and heatinsulating sleeves, the refractory materials should contain an exothermic material and its oxidizing agent.

Whether having been premixed or not, the above-mentioned materials in the above-mentioned ratios are charged to a hopper 2 using a charging bucket 1. The materials are then continuously sliced out of the hopper by a slicer 3 into a lot of the desired amount, and delivered into a cotton-opening mixer 4 at the second step. The first step may be omitted so that the raw materials are charged directly into cotton-opening mixer 4, as shown by the dotted lines.

Cotton-opening mixer 4 is equipped, on its inside, with a screw 5 having blades to cut or cotton-open fibrous materials, and with an agitating bar 6. The cotton-opening mixer, rotated by a motor 7 set above it, minces and well cotton-opens the charged mixture of raw materials, particularly fibrous materials (b) and (c), in the dry state, and well mixes the so-cotton-opened materials with other materials of powder or granular form, such as refractory materials. Cotton-opening at the second step is novel and has not been adopted by any known methods other than the method of the present invention. Then, a mixture containing the so-cotton-opened materials is sent from the bottom of the cotton-opening mixer 4 into an aqueduct shaped hopper 9 set at one end of a kneader 8.

Less than 150%, preferably between 75% and water is supplied to this mixture by a pump 10, and while it is being kneaded, it is sent by a screw-conveyor 11 driven by a motor 12 to the left end of kneader 8 so as to fall from its right end into an alternating hopper 13.

As the mixture has been cotton-opened and well mixed in the second step, it can be kneaded in the kneader 8 by using a small amount of water, such as about so that even though it is kneaded with water, such kneading does not need a great quantity of water, and the kneaded mixture keeps in the original powder or granular form, which is quite different from that obtained according to conventional methods.

The process of making such a mixture hold in the powder, granular, or solid form with water without being a slurry or pasty and muddy, is impossible or quite new to the conventional methods, and constitutes an important characteristic element of the present invention. Moreover, this process makes possible continuous molding of sleeves by pressing at the fourth step.

The mixture of powder or granular form which has been put into said alternating hopper 1-3 is sent to the fourth step, where it is charged by an alternating dumper 14 alternately into a hopper 17 and a hopper 18 set respectively on

molding machines

19 and 20. Molding by the

molding machines

19 and 20 at the fourth step is carried out as shown in FIG. 2A. As the two molding series follow the same operation process, only one series is described in the following explanation. The mixture of powder or granular form 25 in one of the hoppers 18 is charged into molds 22. and 23 as the volume of one lot which has been sliced out from dumper 26. As the molds are filled with the mixture 25, the dumper 26 is shut, and the so charged mixture is pressed from up to down under a pressure of 5 or 6 kg./cm. by compressed air 27.

In the course of such molding, compressed air presses the mixture 25, and then is let out from the mixture 25 through a great number of air-water vent holes 24, 24' provided on

molds

22 and 23. Molding can be done simply and rapidly in the same manner as used in the case of producing cores for metal casting. If there is more Water than necessary in the to-be-pressed mixture, such excess water will be removed together with air through the vent holes 24, but there is very little water to be removed in the case of molding according to the present lnvention. If there should be very much water to be removed, the molding process of the present invention can still be done, but with difficulty. Therefore, according to the present invention, a mixture is kneaded at the kneadlng step so as not to make it slurry, or pasty and muddy, but as holding the powder, granular, or solid form with less than 150% water added, as mentioned above; the somade mixture makes possible continuous molding by pressing with compressed air. As shown in FIG. 2B, an enlarged view of FIG. 2A, each of said vent holes 24 is constructed as a cluster of a great number of minute holes 24, so as to prevent passage of the mixture of powder or granular form.

Such molding is also possible with a light pressing, either manually or with a machine, instead of using compressed air. Also, instead of the abovementioned type slicer B, cotton-opening mixer 4, and kneader 8, any types will meet the purposes of the present invention.

Sleeves which have been molded as mentioned above are dried at about C. in a drier 21 in the fifth step. During this drying process, the mixed blending agent, e.g., phenol resin, melts and covers the powder or granular form materials so as to bind them together and make a solid sleeve. Besides, a cover with the binding agent makes the product sleeve also water-repellant, that is, highly moisture-repellant.

Physical properties of the so-produced heat-insulating sleeve product, as shown in FIG. 3(I) are: A transverse strength of about 20 kg./cm. (nearly the same as that of products of the conventional methods); apparent specific gravity: 0.7-0.9 (against 1.1-1.5 of products of conventional methods); and almost no damp absorption as compared with products of conventional methods. (Note: The products of the conventional methods for the above com parison contained no fibrous materials.)

Needless to say, besides the production of products which could be molded with difliculty anyway, the method of the present invention can be more easily applied to the production of sheets which can be molded without difiiculty by using a device for producing molds for sheets, such as the sheets of FIG. 3 (II).

The following are special characteristics of the abovementioned mixtures according to the present invention:

As refractory materials (a) of granular form contained in the abovementioned mixture are used silica stone, alumina, chamot, brick powder, fly-ash, silica, etc. If necessary, such exothermic materials such as aluminum and its oxidizing agent are added thereto. The granular size of any of these materials should be between 0.2 and 1 mm. As inorganic fibrous materials (b) are used rock wool, glass wool, ore flakes, asbestos, etc., any of which is sized about 3 to 5 mm. in the longitudinal direction. As organic fibrous materials (c) are used wood chips, pulp, fiber, paper, etc., any of which is sized about 0.5 to 5 mm. in the longitudinal direction. As a binding agent (d) is used a water-insoluble synthetic resin such as phenol resin.

The purposes of mixing the abovementioned raw materials are: The refractory materials (a) such as silica and brick powder make the product fireproof and keep its form stable when used; inorganic fibrous materials (b) such as asbestos and ore flakes makes the product strong and light; and organic fibrous materials (e) such as wood powder and pulp make the product light and porous. In order to make the apparent specific gravity below 1, it is necessary to make the total of inorganic and organic fibrous materials at least 30% by weight of the mixture. A binding agent (d) such as phenol resin is added to melt in the molding step and cover the above-mentioned mixture so as to bind the materials of granular form and make the product water-repellent and moisture-proof.

As mentioned above, according to the present invention, large quantities of inorganic and organic fibrous materials are mixed, thereby making the apparent specific gravity of product below 1 (that is, lighter than water), and also making it strong. Because of such lightweight, the product has high heat-insulation, and because of the use of a binding agent, it exhibits good moisture prevention, as mentioned above, thereby not only greatly raising feeder head efiects of the product, but also reducing production costs.

In summary of the above-mentioned, heretofore when large quantities of fibrous materials have been mixed with a powdered or granular refractory material, it has been so difiicult to mold such a mixture that the art has even suggested kneading the refractory-fiber mixture with water glass or the like, instead of water, such kneadin g being customary with the conventional methods, otherwise to restrict the quantity of fibrous materials used. In general, according to the prior art, in order to knead a mixture with a large quantity of fibrous materials by conventional methods, a great quantity of water, e.g., 500- 700%, had to be used to form a fluid mixture to assume proper mixing. However, this makes it necessary to remove such large quantities of water in the molding step, making the molding process complicated and difficult.

According to the present invention, however, a mixture of raw materials is cotton-opened and well mixed in the dry state before being kneaded with water, thus holding itself in nearly the same condition as of a mixture containing only refractory materials according to the conventional methods, that is, in the original powder or granular form of no fluidity, with the addition of less than water, preferably between 75 and 100% when kneaded. This makes it possible to carry out molding without any special process to remove superfluous water, and to use a pressing method for such molding, thereby again making it possible to mass-produce sleeves by using a core producing machine or the like in the molding step, and, moreover, to make such sleeves strong and heat-insulatmg.

As mentioned above, according to the method of the present invention and by using an apparatus therefor, it is possible to easily and continuously produce sleeves or sheets of an apparent specific gravity of below 1. However, the method of the present invention is not limitedly applied to the product of such sleeves or sheets, but is applicable also to the production of sleeves or sheets of an apparent specific gravity of about 1, even with large quantities of fibrous materials added to refractory materials, etc. That is to say, in this case, also the method of the present invention functions in cotton-opening the added fibrous materials to be well mixed in the mixing step with other materials, such as refractory materials, so that the so made mixture may be subjected to molding without the need of removing water in the molding step, though it has been kneaded in the previous kneading step with some water added. Thus, it is possible to mass-produce products by a pressing method, as well as making them stronger than those made otherwise.

However, according to the conventional methods, fibrous materials are mixed, in the original form, with refractory materials of granular form and other materials, so it is necessary to add such a great volume of water, e.g. SOD-700%, in order to make the mixture pasty and muddy for kneading. This makes it necessary to adopt a molding method which requires the removal of a great volume of water by vacuum suction or by centrifugal separation. In comparison with a product according to the present invention, therefore, a product made by conventional methods is recognized to be quite different in appearance and strength as Well as in molding process. That is, a product which has been molded conventionally while water is sucked out under a vacuum system or by any other conventional methods has an irregular surface and low strength, while a product made according to the present invention has a smooth surface and much higher strength.

The following describes an example of the present invention, all percentages being by weight unless otherwise indicated.

In addition to the above mixture:

Phenol resin 6% of the above mixture. Water 75% of the above mixture.

Mixture (B) (for making adiabatic, exothermic sleeves Percent Silica 25 Aluminum powder 18 Manganese dioxide 15 Asbestos (less than 3-5 mm. dia. and long) 42 In addition to the above mixture:

Phenol resin 6% of the above mixture. Water 100% of the above mixture.

By using mixtures (A) and (B) and the method of the present invention, a sleeve I shown in FIG. 3 having an outside diameter of mm., an inside diameter of 120 mm. and a height of 120 mm. was produced. The added volume of water for use in kneading at the third step was 75-100%, and the molding at the fourth step could be carried out by using a core producing machine at the same rate as in the production of cores of conventional type using the same machine. By drying in a gas dryer at 180 C. for 2 hours, a heat-insulating sleeve (A) and an exothermic, heat-insulating sleeve (B) were produced with sufiicient solidness. These results are compared with those obtained from tests conducted on sleeves made by conventional methods, as follows:

Table I compares the apparent specific gravity of these materials, calculated by using a formula:

Weight of sleeve/volume of sleeve NoTE.(1) Sleeve (C) made by a conventional method contained no added fibrous materials, but was heat-insulating, exothermic, and of nearly the same size as the sleeve of the present invention. (2) Sleeve (D) was also devoid of fibrous materials, and was heat-insulating, exothermic, and of nearly the same size as the sleeve of the present invention. (3) Mixture for the sleeve (C): Aluminum powder 20%, aluminum ash 33%, iron oxide 9%, potassium nitrate 9%, silica powder 26%, cryolite powder 3%.

In addition to the above mixture: Water glass 10% by weight, solidified by the carbonic acid gas process and dried at about 120 C.

(4) Mixture for the sleeve (D): Aluminium powder 15%, aluminum foil and powder 5%, aluminum ash 42%, iron oxide 15%, potassium nitrate perlite powder 10%, cryolite powder 3%.

In addition to the above mixture: Water glass 10% by weight, solidified by the carbonic acid gas process, and dried at about 120 C.

Table 2 presents data comparing moisture resistance of these materials.

TABLE 2 heated at 900-1,000 C., and the rise of temperature of the other surface side was measured, taking time into account as a factor. The test results are shown in FIG. 4, as follows: The test pieces (A) and (B) of the present invention had much slower rise of temperature than the test pieces (C) and (D) of the conventional methods, proving that the sleeve of the present invention has good heat insulation.

In FIG. 4, the curves at the upper part indicate respectively the temperature of the heated side of test pieces, and those at the lower part indicate respectively the temperature rise on the other side.

(7) Results of other tests: The result of use of the sleeve (B) of the present invention for casting cast steel was so good that, as shown in FIG. 5, a feeder head (F) produced as a result of using this sleeve (B) had almost no boiling of molten cast steel, with levelled surface and small size shrinkage cavities as shown at 28 of (F) in FIG. 5. No sintering occurred as compared with the feeder heads (E) and (G) produced respectively by using the sleeves (D) and (C), both made by conventional methods.

These feeder heads (E), (F) and (G) had been cut off the castings.

As mentioned above, sleeves or sheets of the present invention are poorly water-absorbent, thus requiring no cover for moisture prevention. They canbe used as molds as they are, or stocked for a long time. Besides, because of their light weight, they can be handled or transported without difficulty. Because of good heat insulation due to such light weight, a feeder head can maintain its temperature for a long period of time. Also, because of the very low heat absorption, they may be very slow in heat generation, making it possible to obtain an almost smokeless mixture, which is very effective in preventing air pollution. The present invention is characterized by such a great advantage as continuous and automatic production of sleeves for great reduction of production costs.

As used in the appended claims, the term sheets for feeder heads is intended to encompass such sheets in either slab or sleeve form.

Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit and scope of the invention as set forth in the appended claims.

Test items Moisture prevention when exposed to air: by water ab sorption, percent Right 5 hours 1 day 2 days 7 days 30 days Water repellenee (in water) after after after after after alter Samples drying drying drying drying drying drying State when placed on water Present invention:

0 0 0. 7 1. 5 2. 0 2. 0 Floated for more than 48 hours.

0 0 0. 8 1. 5 2. 0 2. 0 Floeted for more than 24 hours.

0 0. 5 1. l5 2. 0 Bank when placed on water.

0 0. 7 2. 0 2. 0 Same as above.

K Above 2.0%. i Strength lowered. Deeomposed.

(5) Strength: A test piece of 25 mm. 'wide and 25 mm.

thick x 140 mm. long, was made from each of the sample 20-25 kg./cm.

: 20-25 kg./cm.

from each of the sample sleeves. Heat insulation was measured of these four test pieces. One surface side was Accordingly, what is claimed as new and intended to be secured by Letters Patent of the United States is:

1. A method of producing sheets for feeder heads formed in metal casting, which consists essentially of (a) blending a raw material mixture comprising (i) from 10 to 50% by weight of at least one refractory material in granular or powder form of a particle size of 0.2-1 mm. and being selected from the group consisting of silica, alumina, chamot, brick powder, fly ash, silica stone, and mixtures thereof; (ii) 15 %-60% by weight of at least one inorganic fibrous material being selected from the group consisting of asbestos, rock wool, glass wool, ore flakes and mixtures thereof;

(iii) at least %-30% by Weight of at least one organic fibrous material selected from the group consisting of wool chips, pulp, paper and mixtures thereof; and

(iv) from 5 to 30% by weight of a synthetic resin water-insoluble binding agent;

(b) cotton-opening and mixing said inorganic and organic fibrous materials blended in the raw materials through agitation in the dry state without the addition of water, and mixing said cotton opened fibrous material with said refractory material;

(c) kneading the resultant mixture in the presence of water in an amount such that the mixture remains in a solid form, and less than 150% by weight of the mixture;

(d) molding the kneaded mixture in the solid form into a desired shape by pressing in molds; and

(e) drying the molded mixture at a temperature of about 180 C. to solidify said molder mixture, such that the apparent specific gravity of the resulting product is approximately 1 or below.

2. The method of claim 1, wherein said blending step is carried out concurrently with said cotton-opening and mixing step.

3. The method of claim 1, wherein the total of said inorganic and organic fibrous materials blended at said blending step is greater than 30% by weight.

References Cited UNITED STATES PATENTS 3,004,878 10/1961 Tomlinson 264-122 X 3,345,442 10/1967 OXel 264-122 X 3,326,273 6/1967 Iago et a1. 104-41 X 3,084,130 4/1963 Painter 264-122 X 2,671,496 3/1954 Chavames et a1. 264-122 X 3,123,878 3/1964 Davidson 164-6 JOSEPH L. SCHOFER, Primary Examiner D. A. JACKSON, Assistant Examiner US. Cl. X.R. 164-6, 41; 264-