Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2002-08-20
2003-10-21
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S739000, C106S757000, C106S823000
Reexamination Certificate
active
06635109
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to grinding aids for cement clinker, and to the use of certain direct process residue gels as grinding aids for pulverizing cement clinker to cement. In particular, the grinding aids are hydrolysis products of alkylhalodisilanes and other chlorosilanes produced in alkylhalosilane manufacturing operations.
The grinding aids are capable of reducing the energy consumption in the cement clinker grinding operation. For example, when the compositions are used in cement clinker grinding, one can reasonably expect about a thirty percent increase in surface area of the cement by the addition of about 1,000 ppm of the grinding aid composition during each batch grinding operation. Also, concrete made from such cements exhibits about a five percent increase in standardized 28-day compressive strength comparisons.
These grinding aid compositions based on hydrolyzed products of methylchlorodisilanes offer significant cost advantages over conventional types of grinding aids, such as triethanolamine and diethylene glycol.
BACKGROUND OF THE INVENTION
The cement produced in the greatest volume and the one most widely used in concrete for construction is Portland cement. Portland cement is a hydraulic cement, i.e., it sets, hardens, and does not disintegrate in water. The term cement, therefore, as used herein is intended to define inorganic hydraulic cements, principally Portland and related cements. The essential feature of such cements is their ability on hydration to form with water relatively insoluble bonded aggregations of considerable strength and dimensional stability.
Hydraulic cements are manufactured by (i) processing and proportioning a number of raw materials, (ii) burning the raw materials, i.e., clinkering them at a suitable temperature, and (iii) grinding the resulting hard nodules called clinker to a fineness required for an adequate rate of hardening by reaction with water.
Most Portland cements consist mainly of tricalcium silicate Ca
3
SiO
5
and dicalcium silicate Ca
2
SiO
4
. Typically, and in this regard, two types of raw materials are required, (a) one being rich in calcium such as limestone, chalk, marl (cement rock), oyster shells, or clam shells; and (b) the other being rich in silica such as clay or shale. The two other most significant phases in any Portland cement are tricalcium aluminate Ca
3
Al
2
O
6
and a ferrite phase. A small amount of calcium sufate CaSO
4
in the form of gypsum or anhydrite is also added during grinding to control the setting time and to enhance the strength development.
Clinker in Portland cements manufactured from raw materials including components such as calcium carbonate, clay, shale, or sand, is formed by passing such raw materials through a kiln at increasing temperatures during their passage through the kiln. In the kiln itself, free water is evaporated, any water combined with clay is released, magnesium carbonate is decomposed, calcium carbonate is decomposed (calcination), and the lime and clay oxides are combined.
Thus, the process of Portland cement manufacturing consists of (i) quarrying and crushing the rock, (ii) grinding carefully proportioned materials to a high fineness, (iii) subjecting a raw mix to pyroprocessing in a rotary kiln, and (iv) grinding the resulting clinker to a fine powder. Typically, the rock or stone is crushed; the various raw materials are then ground to a powder and blended; the raw mix is converted (changed chemically) into cement clinker by burning the raw mix; and the clinker and gypsum are ground into Portland cement and shipped. These hydraulic cements function as intermediate products used for making concrete, mortar, grout, and composite materials such as asbestos-cement products.
It is not unusual for industrial by-products to be used as raw materials for cement, including such by-products as slags containing carbonate-free lime, silica, and alumina; and fly ash from utility boilers containing finely dispersed silica and alumina.
As an example, U.S. Pat. No. 5,374,310 (Dec. 20, 1994) is directed to the addition of certain direct process residue gels to a cement kiln upstream of the grinding operation, to provide part or all of the silica source for the cement by calcining. In contrast, and according to the present invention, however, the direct process residue gels are added directly to the grinding operation in limited amounts, and without calcining, in order to improve the grinding efficiency. Thus, the present invention differs from the '310 patent in the point of addition of the gel, the gel's function, and the purpose of the gel.
SUMMARY OF THE INVENTION
This invention is directed to a process for manufacturing hydraulic cement in which (i) raw materials are crushed and ground, (ii) the crushed and ground raw materials and other components are burned and calcined to prepare a cement clinker, and (iii) the cement clinker is ground to a fine powder. The improvement contributed according to the present invention is that a certain grinding aid is added to the cement clinker before it is ground in (iii). The grinding aid is an uncalcined direct process residue gel, which is an hydrolysis product of alkylhalodisilanes produced as by-products in the manufacture of alkylhalosilanes.
Preferred grinding aids are high boiling residues of the direct process which have been neutralized to form gels. Typically, these gels are aqueous compositions containing from 1 to about 55 percent by weight of solids, and the balance of the composition to 100 percent is water. The solids typically comprise about 1 to about 50 percent by weight of silicon fines, about 1 to about 40 percent by weight of metal salts, and the balance of the solids to 100 percent by weight is the hydrolysis condensation products of mixed alkylhalosilanes and alkylchlorodisilanes.
These and other features of the invention will become apparent from a consideration of the detailed description.
DETAILED DESCRIPTION OF THE INVENTION
Silicon containing compositions useful in this invention, i.e., the direct process residue gels, are described in U.S. Pat. No. 4,408,030 (Oct. 4, 1983), incorporated herein by reference. This invention herein provides a viable avenue for the recovery of value from such chlorosilicon containing by-products as they are generated during commercial production of silicone polymers. These compositions can be obtained from, for example, processes for reacting silicon metalloid with hydrogen chloride to form chlorosilanes. Thus, chlorosilicon by-products can be obtained from what is commonly called the direct process, where an organochloride such as methyl chloride is reacted with silicon metalloid to form organochlorosilanes. These chlorosilicon by-products typically contain distillation residues, off-specification materials, and excess chlorosilanes.
Thus, according to the direct process, silicones are prepared from silica by reducing silica in an electric furnace to elemental silicon:
SiO
2
+2 C→Si+2 CO.
The elemental silicon is then treated with compounds such as RCl, typically methyl chloride, according to the direct process:
Si+2RCl→R
2
SiCl
2
.
While other products are also obtained, the main product is R
2
SiCl
2
.
Hydrolysis of the main product R
2
SiCl
2
organochlorosilanes, typically Me
2
SiCl
2
, provides siloxane structures which are used in the manufacture of a variety of other silicone products:
(n+m) Me
2
SiCl
2
+2(n+m) H
2
O→(Me
2
SiO)
m
+2(n+m) HCl+HO(Me
2
SiO)
n
H.
Chlorosilicon by-products and processes for hydrolyzing the compositions to direct process residue gels which are useful according to this invention can be prepared by preferred processes in which the chlorosilicon by-product has an SiCl functionality of the material to be hydrolyzed greater than or equal to about 2.8. The average SiCl functionality of the material to be hydrolyzed can be maintained within the prescribed limit by determining the average SiCl functionality of the chlorosilicon by-product and blending it with o
da Cunha, Jr. Sebastiao Walter Lopes
Wineland Jonathan David
Dow Corning Corporation
Marcantoni Paul
LandOfFree
Process for making cements with silicon containing grinding... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for making cements with silicon containing grinding..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for making cements with silicon containing grinding... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3138656