Process for the preparation of microencapsulated products...

Details Process for the preparation of microencapsulated products... Process for the preparation of microencapsulated products...

1999-03-03

2001-06-26

Hampton-Hightower, P. (Department: 1711)

Plastic and nonmetallic article shaping or treating: processes

Encapsulating normally liquid material

Liquid encapsulation utilizing an emulsion or dispersion to...

C264S004700, C428S329000, C428S402000, C424S400000, C424S405000, C424S408000

Reexamination Certificate

active

06251313

ABSTRACT:

TECHNICAL FIELD
The invention relates to a process for the preparation of microcapsules having shell walls of organopolysiloxane.
BACKGROUND ART
The use of organopolysiloxanes as microcapsule shell wall materials, and processes for their preparation are known. A common feature of all the processes heretofore described, is that the shell walls are formed from already prepared organopolysiloxanes.
The use of solid, thermoplastic organosiloxane polymers for shell walls is described, for example, in U.S. Pat. No. 5,254,656. The organosiloxane polymers must be dissolved in suitable solvents, the solution added under exactly controlled conditions to the material to be encapsulated, and the solvent removed again by a complicated procedure.
The use of liquid organosiloxane polymers for shell walls is described, for example, in U.S. Pat. No. 4,370,160. The liquid organosiloxane polymers must then be converted into the solid state by a separate hardening step.
These known processes for the microencapsulation of organopolysiloxanes require expensive raw materials and are technologically complicated, and thus hinder the practical use of organopolysiloxanes as shell materials in microencapsulation, although organopolysiloxanes are of considerable interest owing to their wide variation and unusual properties.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a process which makes it possible to produce shell walls of organopolysiloxanes in a simple manner and from easily obtainable raw materials.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention relates to a process for the preparation of microcapsules having shell walls of organopolysiloxane surrounding a core material, in which the shell walls are produced in situ by hydrolysis and polycondensation of organosilanes and/or their condensates having not more than 4 silicon atoms.
The organosilanes used in the process preferably have the general formulae Ia to Id
R
1
2
R
2
SiX  (Ia),
R
1
R
2
SiX
2
  (Ib),
R
2
WiX
3
  (Ic),
SiX
4
  (Id),
X
3
Si—R
3
—SiX
3
  (Ie),
in which
R
1
denotes a monovalent, optionally halogen-substituted C
1-18
hydrocarbon radical which is optionally interrupted by ether oxygen atoms or a hydrogen atom,
R
2
has the meaning of R
1
or represents a monovalent C
1-12
hydrocarbon radical which may be interrupted by one or more groups of the formulae —NR
1
—, —S—, —O— or —CO—O— and which may be substituted by one or more groups of the formulae —SH, —OH, —NR
1
2
, —Cl, —COOH,
R
3
is a divalent alkyl radical having 1 to 6 carbon atoms or is the phenylene group and
X denotes a group —OR
4
, an acetoxy, amino, acid amide or oximino group or a chlorine atom,
R
4
denotes a hydrogen atom or a C
1-18
alkyl radical, which may be interrupted by ether oxygen atoms.
Examples of radicals R
1
are alkyl radicals such as the methyl, ethyl, n-propyl, isopropyl, 1-n-butyl, 2-n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl or tert-pentyl radicals; hexyl radicals such as the n-hexyl radical; heptyl radicals such as the n-heptyl radical; octyl radicals such as the n-octyl radical, and isooctyl radicals such as the 2,2,4-trimethylpentyl radical; nonyl radicals such as the n-nonyl radical; decyl radicals such as the n-decyl radical; dodecyl radicals such as the n-dodecyl radical; octadecyl radicals such as the n-octadecyl radical; cycloalkyl radicals such as the cyclopentyl, cyclohexyl and cycloheptyl radicals and methylcyclohexyl radicals; aryl radicals such as phenyl, naphthyl and anthryl and phenanthryl radicals; alkaryl radicals such as o-, m- and p-tolyl radicals, xylyl radicals, and ethylphenyl radicals; and aralkyl radicals, such as the benzyl radical and the &agr;- and the &bgr;-phenylethyl radicals.
The alkyl radicals having 1 to 10, in particular up to 6 carbon atoms are preferred, in particular the methyl and ethyl radicals. Examples of alkyl radicals R
1
which are substituted by an ether oxygen atom are the methoxyethyl and ethoxyethyl radicals.
Examples of halogenated radicals R
1
are haloalkyl radicals, such as the 3,3,3-trifluoro-n-propyl radical, the 2,2,2,2′,2′,2′-hexafluoroisopropyl radical and the heptafluoroisopropyl radical, and haloaryl radicals, such as the o-, m- and p-chlorophenyl radicals.
Examples of aliphatically unsaturated radicals R
1
are alkenyl radicals, such as the vinyl, 5-hexenyl, 2,4-divinylcyclohexylethyl, 2-propenyl, allyl, 3-butenyl and 4-pentenyl radical; and alkynyl radicals, such as the ethynyl, propargyl and 2-propynyl radical.
Preferred radicals R
2
are radicals of the formulae
—(CH
2
)
m
—SH,
—(CH
2
)
m
—OH,
—(CH
2
)
m
—Cl,
 —(CH
2
)
n
—COOH,
—(CH
2
)
m
-NH(C
6
H
11
)
—(CH
2
)
m
—NH
2
,
—(CH
2
)
m
-NH(CH
3
),
—(CH
2
)
m
—NH(CH
2
)
m
NH
2
,
—(CH
2
)
m
—O—(CH
2
)
m
—CH
3
,
—(CH
2
)
m
—[O—(CH
2
)
n
]
m
—O—(CH═CH
2
)
—(CH
2
)
m
—O—CO—CH═CH
2
, where
m denotes the values 1, 2, 3, 4, 5 or 6 and
n denotes the values 1 to 18, in particular 6 to 12.
On average, X has at least the value 2.05, preferably at least 2.1, in particular at least 2.3, calculated per molecule of organosilane of the general formulae Ia to Ie.
The organosilane composition is preferably chosen so that the organopolysiloxane formed as the shell wall corresponds to the general formula II
[R
1
2
R
2
SiO
1/2
]
x
[R
1
R
2
SiO
2/2
]
y
[R
2
SiO
3/2
]
z
[SiO
4/2
]
u
[SiO
3/2
—R
3
—SiO
3/2
]
v
  (II),
in which
x denotes 0 to 60 mol %,
y denotes 0 to 95 mol %,
z denotes 0 to 100 mol %,
u denotes 0 to 50 mol % and
v denotes 0 to 100 mol % and
R
1
, R
2
and R
3
have the abovementioned meanings.
Preferably,
x denotes 0 to 30 mol %,
y denotes 0 to 50 mol %,
z denotes 50 to 100 mol %,
u denotes 0 to 20 mol % and
v denotes 0 to 50 mol %.
The process steps required for producing the shell walls of organopolysiloxanes depend on whether the core material to be encapsulated is water-insoluble or water-soluble.
(A) In the case of water-insoluble, liquid or solid core material to be encapsulated, the organosilanes and/or their condensates are added to an aqueous emulsion, dispersion or suspension of the core material with thorough mixing.
(B) However, the core material to be encapsulated can also be dissolved or dispersed in the organosilanes and/or their condensates and the solution or dispersion mixed into an aqueous phase which optionally contains emulsifier or suspending agent.
In both variants, it is preferable to work with such a large excess of water that the microcapsules formed after production of the shell walls from organosilanes and/or their condensates by hydrolysis and condensation of organosilanes and/or their condensates are present as a dispersion or suspension in the aqueous phase and can be further processed.
(C) In the case of a water-soluble, liquid or solid core material or if water itself is to be microencapsulated, the water-soluble, liquid or solid core material is dissolved in the desired amount of water and the solution or the water itself is dispersed or suspended in a liquid phase which is immiscible with water but miscible with organosilanes and/or their condensates and which optionally contains dispersants or suspending agents.
After the addition of the organosilanes and/or their condensates, the shell walls form. The water-immiscible liquid phase must be chosen so that it is miscible with the organosilanes and/or their condensates but does not act as a solvent for the organopolysiloxane shell walls formed.
For example, solvents customarily used in industry, such as aliphatics, aromatics, esters and alcohols, ketones and ethers, are suitable, provided that they are not water-miscible. Preferably, the solvents have a solubility of less than 1% by weight in water at 20° C. Preferred solvents are hexane, n-heptane, naphtha fractions, toluene and xylene. Furthermore, water must be present in an amount sufficient to enable the hydrolysis to take place. The microcapsules formed are present in the no

Affiliated with

Also associated with

Rating

Process for the preparation of microencapsulated products... 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 the preparation of microencapsulated products..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the preparation of microencapsulated products... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2495021