Method of encapsulating particulate material

Abstract

A method of encapsulating particulate materials. The method of encapsulating particulate materials may be used to multi coat a coated thermoplastic particle. The method includes providing an amount of acidified water in an amount to hydrolyze a pre-determined amount of alkoxysilane. A particulate thermoplastic material is dispersed within the acidified water. Once dispersed, an amount of alkoxysilane having a pre-determined formula is added and an amount of time is allowed to pass thereby allowing the alkoxysilane to hydrolyze and build a particle having a pre-determined particle size. Once the particle with pre-determined particle size has been obtained, the particles may be combined with alkoxysilane having a pre-determined formula and an amount of time is allowed to pass thereby allowing the alkoxysilane to hydrolyze and build a particle having a pre-determined particle size. This provides an encapsulated particulate material having one or more coatings thereon.

Claims

1. A method of encapsulating particulate materials, said method consisting of: a. providing acidified water at least sufficient for hydrolyzing a predetermined amount of alkoxysilane; b. thereafter, dispersing at least one type of particulate material in said acidified water; c. thereafter, slowly adding a predetermined amount of alkoxysilane having the general formula:
R.sub.xSi(OR′).sub.4-x wherein R is selected from the group consisting essentially of alkyl groups, substituted alkyl groups, aryl groups, substituted aryl groups, vinyl, allyl, and hydrogen, wherein the substituents are selected from the group consisting of fluorine, amino, hydroxy, and combinations thereof, and wherein R′ is selected from hydrogen and alkyl groups of 1 to 4 carbon atoms; d. thereafter, allowing sufficient time for said alkoxysilane to hydrolyze and build a predetermined particle size; e. thereafter, treating said product from d. by slowly adding a predetermined amount of alkoxysilane having the general formula:
R.sub.xSi(OR′).sub.4-x wherein R is selected from the group consisting essentially of alkyl groups, substituted alkyl groups, aryl groups, substituted aryl groups, vinyl, allyl, and hydrogen, wherein the substituents are selected from the group consisting of fluorine, amino, hydroxy, and combinations thereof, and wherein R′ is selected from hydrogen and alkyl groups of 1 to 4 carbon atoms; f. thereafter, allowing sufficient time for said alkoxysilane to hydrolyze and build a predetermined particle size.

2. The method of claim 1, wherein more than two coats are provided for an encapsulated material.

3. The method of claim 1, wherein said method is performed in the absence of a cross linkers, catalyst, surfactants, solvents, or any other adjuvants to facilitate encapsulation of said particulate material.

4. The method of claim 1, further comprising the step of neutralizing said product of step f. with a base.

5. The method of claim 1, further comprising the steps of removing water from said dispersal and allowing an amount of solids within said dispersion to be dried.

6. The method of claim 5, wherein said dried solids are ground to a pre-determined particle size.

7. The method of claim 1, wherein said steps e. and f. are repeated as needed to provide additional coats onto said encapsulated particulate material.

8. An encapsulated particulate material prepared by the method of claim 1.

Description

DETAILED DESCRIPTION OF THE DISCLOSURE

(1) It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless the claims expressly state otherwise.

(2) It should be further noted that the encapsulation reaction is run at or near room temperature and therefore, there is no need for any heating or cooling equipment.

(3) The reaction of this may be run in less than twenty-four hours and preferred is a reaction time of less than 10 hours, and a most preferred time is a reaction time of less than 3 hours.

(4) There is a requirement that the stoichiometry be observed between the amount of water in the reaction system and the amount of alkoxysilane in the system in order to carefully control the condensation reaction of the sol gel that is being formed, to achieve the desires results.

(5) It is best if the alkoxysilane is added in small portions, that is, “slowly”. Introducing the alkoxysilane too quickly will result in adverse results, i.e. gelation of the reaction mass.

(6) Adding the alkoxysilane in smaller portions will allow the sol gel to build to the appropriate particle size. This is a critical step in the method, as a particle size that is too small will not encapsulate the particle and a particle size that is too large will cause premature precipitation and gelling. Defining the size of the particle can be determined by watching the reaction medium. The building of the particle can be observed and thus if the alkoxysilane is added too slowly, no particles other than the particle to be encapsulated will be visible while elements of gelling can be observed if the addition is too rapid. As long as one observes the reaction carefully, slight amounts of these two conditions can be remedied by adjustment of the addition rate either more or less.

(7) The condensation reaction can be represented by the following chemical equation:
R.sub.xSi(OR′).sub.4-x+H.sub.2O+H+R.sub.xSi(OH).sub.y+R′OH
wherein R is an alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group, vinyl, allyl or hydrogen. Alkyl groups are those such as methyl, ethyl, propyl, amyl, etc. Aryl groups are selected from phenyl and tolyl. Substituted groups are selected from the group consisting of fluorine, amino groups, hydroxyl groups, and combinations thereof. R′ is selected from hydrogen and alkyl groups of 1 to 4 carbon atoms.

(8) The reaction mass is subjected to mild temperatures to remove the water and dry the sample, such as 50° C. or lower, although this temperature is not overly critical. One should take caution not to melt the encapsulated particle.

(9) If one wishes to use the encapsulated particles in an end use formulation that uses water as part of the formulation, it may not be necessary to remove the water, or it may be necessary to remove some of the water but not dry out the sample completely.

(10) Thereafter, the dried sample may be subjected to grinding to reduce the size of the particles. The size of the ground particle is dependent on the users end use, however, it has been found that grinding the encapsulated particles to the size of table salt is the most useful, producing a flowable product.

(11) In an effort to minimize the amount of water used in the method, one must determine the solubility of the particulate solid in water (Ksp).

(12) It is also contemplated within the scope of this disclosure to perform an encapsulation on an encapsulated material of this disclosure in order to produce an added-to coating thereon, much like producing an onion.

EXAMPLES

(13) Various metal salt solid particles were encapsulated by the method described herein in the following manner by first determining their Ksp. (Table I)

(14) TABLE-US-00001 TABLE I Metal Salt Ksp Potassium chloride (KCl) total soluability Copper Chloride (CuCl.sub.2) 70.6 gm/100 ml Lithium Chloride (LiCl) 76.9 gm/100 ml Barium Chloride (BaCl.sub.2)   31 gm/100 ml Zinc Chloride (ZnCl.sub.2)   81 gm/100 ml
It is necessary to determine the solubility constant (Ksp) of each of the metallic particles, as a stoichiometric amount of water is required to properly form the sol gel and the water is also necessary to dissociate the metallic salt in the mixture. Further, it is unknown what effect the free chloride from the dissociation of the metallic salt will have on the sol gel formation.

Example 1

(15) Potassium chloride was dissolve in acidified water. Thereafter, methyltrimethoxysilane was slowly added to allow for the hydrolysis of the alkoxy silane. The methyltrimethoxysilane was added in two equal portions to allow the sol gel to build to the appropriate particle size. After the reaction, the sol gel was neutralized to cause the precipitation of the matrix. The sample was oven dried at 45° C. overnight to remove the water followed by grinding the resulting metallic salt sol gel to a powder about the size of table salt.

Example 2

(16) To a 200 ml beaker, 35 grams of distilled water was added. To this water, 8 grams of lithium chloride was added with agitation. The temperature of the distilled water was measured at 23° C. During dissociation of the lithium chloride the temperature rose to 60 degrees, an exotherm of 37 degrees centigrade. After cooling back to 23 degrees, 2.3 grams of Dow Corning 6070 silane (methyltrimethoxysilane—Dow Corning Corporation, Midland, Mich.) was added drop wise and allowed to mix and hydrolyze. After continuous mixing for 60 minutes, 2.3 grams of Dow Corning 6070 silane was added drop wise and allowed to mix for 120 minutes. The resulting reaction product was filtered through filter paper to collect the encapsulated metal salt. This was dried for 16 hours at 45° C. resulting in a white crystalline powder. This powder was placed in a porcelain crucible and ground to a fine white powder about the size of table salt.

(17) Thereafter, each of the sol gel versions of the salts set forth in TABLE I above, were produced by virtually the same procedure. The results can be found in TABLE II provided below.

(18) TABLE-US-00002 TABLE II SAMPLE # 1 2 3 4 5 Solubility Water 35 35 35 35 35 Potassium 8 INDEFINATE Copper 8 70.6/100 ml Lithium 8 76.9/100 ml Barium 8   31/100 ml Zinc 8   81/100 ml MTM.sup.1 2.3 23 2.3 2.3 2.3 MTM.sup.2 2.3 2.3 2.3 2.3 2.3 NaOH 1.2 1.2 0 1.2 0 Product 3 gms 3 gms 3 gms Water 15 gms 15 gms 15 gms Dry Weight 0.46 g 0.61 g 0.26 g .sup.1first addition of methyltrimethoxysilane .sup.2second addition of methyltrimethoxysilane

(19) Table III shows additional reactions.

(20) TABLE-US-00003 TABLE III 1 2 3 4 5 Water 175 175 175 175 175 K 40 Cu 40 Li 40 Ba 40 Zn 40 RXN.sup.1 ENDO ENDO ENDO ENDO ENDO MTM 11.5 11.5 11.5 11.5 11.5 MTM 11.5 11.5 11.5 11.5 11.5 NaOH 6 6 6 6 6 Solution OPAQUE BLUE/ OPAQUE OPAQUE OPAQUE Color GREEN Exotherm 40 60 17 Temperature ° C.

(21) Table IV has additional reaction data demonstrating a reduction in the amount of water required for the sol gel formation.

(22) TABLE-US-00004 TABLE IV 1 2 3 Water 35 35 35 Cu 28 Li 30.4 Ba 11.7 MTM 8.7 8.7 8.7 MTM 8.7 8.7 8.7 EXO TEMP. ° C. 60 40 17 SOLN pH 2 6

(23) Table V has additional data showing the double coating technique. The encapsulated material from experiment 1 of table V was used herein. The water and lithium chloride was allowed to equilibrate and a sample of the final product was added to this mixture. The product from experiment 1 of table IV was not soluble in the water solution. However, upon the additional of the first quantity of methyltrimethoxysilane, the material was able to go into solution. The second addition of methyltrimethoxysilane completed the final encapsulation product.

(24) TABLE-US-00005 TABLE V 1 Water 17.5 Li 15.7 MTM 4.35 MTM 3.35 SAMPLE 1 FROM TABLE V 5.0 EXO TEMP ° C. 67 SOLUTION pH 4

(25) It is to be understood that the various embodiments described in this specification are simply exemplary embodiments illustrating the inventive concepts as defined in the claims. As a result, it is to be understood that the various embodiments described and illustrated herein may be combined to from the inventive concepts defined in the appended claims.

(26) In accordance with the provisions of the patent statutes, the present invention has been described to represent what is considered to represent the preferred embodiments. However, it should be noted that this invention can be practiced in other ways than those specifically illustrated and described without departing from the spirit or scope of this invention.