Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Capsules
Reexamination Certificate
1999-02-05
2002-01-08
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Capsules
C424S400000, C424S489000, C424S490000, C424S497000, C424S501000
Reexamination Certificate
active
06337089
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microcapsule that contains a core material and a method for producing the same. More particularly, the present invention relates to a microcapsule, which has a capsule wall composed of organopolysiloxane obtained by polycondensation of a specific hydroxysilane, having thermal and mechanical stability and light resistance and which is bio-inactive.
The microcapsule of the present invention is applied, for example, to pharmaceuticals, liquid crystal, chemical products, recording materials, cosmetic compositions, aromatics, enzymes, agriculture, adhesives, fiber, foods, catalysts, detergents, dyes, paints, preservatives, solvents and the like. Specific examples thereof include microcapsules containing aspirin, vitamins or liquid crystals, pressure sensitive manifold paper, a capsule containing ultraviolet ray absorbers, coloring matters, pigments, aromatics, menthol, insecticides or adhesives, a capsule containing a preservative for rivet, and the like, although use of the microcapsule is not limited to the above-mentioned uses.
2. Description of the Related Art
Application of organopolysiloxanes in a wide range of fields is expected since they have excellent properties such as thermal and mechanical stability and light resistance, and bio-inactivity and the like as general basic properties. Also in the field of microcapsules, such as a microcapsule in the narrow sense and a nanocapsule, production of microcapsules has been previously tried using a capsule walls composed of a polysiloxane or an analogous material.
For example, U.S. Pat. No. 3,257,330 discloses a method for producing a colored gel particle comprising organopolysiloxane as a matrix. However, when an alkoxysilane having a hydrophobic organic group, such as methyltriethoxysilane and the like, is used as a starting material of the matrix, is hydrolyzed and then neutralized, the polymer composition forms a deposit in an aqueous solution. As a result, it has been difficult to produce a microcapsule by incorporating a hydrophobic core material with the polymerization of a hydrolyzate of an alkoxysilane in the aqueous solution.
On the other hand, U.S. Pat. No. 3,551,346 teaches a method in which a polysiloxane is synthesized from a trialkoxysilane in the production of a microcapsule. However, the polysiloxane does not have sufficient strength as a capsule wall (as admited by this U.S. patent). Therefore, this U.S. patent discloses a method for producing a microcapsule having a capsule wall of a two-layer structure by further making simultaneously a capsule wall by a conventional coacervation method. In addition, it is believed that any more than a certain amount a trialkoxysilane can not be used for producing a capsule wall since the trialkoxysilane is confined in an inner phase by the newly generated polysiloxane capsule wall. Therefore, this method is not admitted as a general method for producing a microcapsule composed only of the polysiloxane capsule wall.
Further, JP-B-60-25185, JP-B-3-10309, JP-B-5-70496, JP-B-7-62109, etc. disclose examples wherein a wall of a microcapsule is produced by cross-linking a polysiloxane having a functional group which can participate in cross-linking and polymerization. However, it is difficult to handle such a specific polysiloxane having a functional group participating in cross-linking and polymerization.
As described above, it has been difficult to easily produce a microcapsule having a capsule wall composed of organopolysiloxane according to conventional technologies.
It is advantageous also in cost to directly produce a microcapsule by making, from a hydroxysilane precursor having various properties, an organopolysiloxane capsule wall that can utilize such properties. Further, microcapsules suited for an object can be easily designed by combining various hydroxysilane precursors. For example, they can be expected to produce various capsule walls such as a capsule wall having tight compact network, a capsule wall having an appropriate permeation property, or a capsule wall having high strength or being suitably soft. However, it has been difficult to produce a microcapsule while controlling conditions such as polymerization rate, solubility and the like when solely using a hydroxysilane precursor having a low molecular weight.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a microcapsule that contains a core material, wherein the microcapsule contains a capsule wall composed of organopolysiloxane having excellent properties. Another object of the present invention is to provide a method for producing such a microcapsule easily and with high productivity from generally available silicon compounds.
The present inventors have intensively studied a method for producing a microcapsule having a capsule wall composed of organopolysiloxane directly from a hydroxysilane precursor in order to solve the above-described problems. As a result, the inventors have found that the above-described object can be attained if:
one or more compounds (A) selected from the group of compounds represented by the following general formula (I) are hydrolyzed to produce one or more compounds (B) selected from the group of compounds represented by the following general formula (II):
R
n
SiX
(4−n)
Formula (I)
wherein, n represents an integer from 0 to 3; R represents an organic group in which a carbon atom is directly connected to a silicone atom, and when n is greater than 1, each of the R groups may be the same or different; and X represents at least one group selected from the group consisting of a hydroxyl group, hydrogen, alkoxy group, halogen group, carboxyl group, amino group and siloxy group, and when (4−n) is greater than 1, each of the groups X may be the same or different; and
R
n
Si(OH)
m
Y
(4−m−n)
Formula (II)
wherein, m represents an integer from 1 to 4; n represents an integer from 0 to 3; m+n≦4; R represents an organic group in which a carbon atom is directly connected to a silicone atom, and when n is greater than 1, each of the R groups may be the same or different; and Y represents at least one group selected from the group consisting of an alkoxy group, hydrogen and siloxy group, and when (4−m−n) is greater than 1, each of the groups Y may be the same or different; provided that the compound (B) comprises at least one compound of formula(II) wherein m=2 or 3 and at least one of R group possesses affinity for at least one of a continuous phase and a dispersed phase; and the compound (B) is polycondensed to synthesize organopolysiloxane constituting a capsule wall. The present invention was thus completed.
The term “continuous phase” and “dispersed phase” usually represent a dispersing medium and a dispersed phase before formation of a wall of a microcapsule respectively. In this specification, an outer phase and an inner phase after formation of a wall of a microcapsule are also called and referred to as “continuous phase” and “dispersed phase”, respectively.
According to the present invention, organopolysiloxane constituting a wall of a microcapsule can be synthesized directly from the compound (B) belonging to the so-called hydroxysilanes. Further, the above-described organopolysiloxane can constitute a capsule wall necessary for producing a microcapsule containing core material, thus not requiring formation of a capsule wall by a conventional coacervation method.
The present invention provides a microcapsule containing core material and a capsule wall, in which the capsule wall of the microcapsule comprises:
organopolysiloxane synthesized by polycondensing a compound (B), monomer or monomeric mixture, wherein compound (B) contains one or more compounds represented by the general formula (II):
R
n
Si(OH)
m
Y
(4−m−n)
(II)
wherein, m represents an integer from 1 to 4; n represents an integer from 0 to 3; m+n≦4; R represents an organic group in which a carbon atom is direc
Adachi Takashi
Nosaka Koji
Segawa Akihiro
Segawa Emi
Shintani Hiroshi
Birch & Stewart Kolasch & Birch, LLP
Seiwa Kasei Company, Limited
Tran S.
LandOfFree
Microcapsule containing core material and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microcapsule containing core material and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microcapsule containing core material and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2830388