Aqueous emulsions containing organohydropolysiloxanes

Details Aqueous emulsions containing organohydropolysiloxanes Aqueous emulsions containing organohydropolysiloxanes

2000-01-26

2001-02-06

Shaver, Paul F. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Silicon containing

C106S287140

Reexamination Certificate

active

06184406

ABSTRACT:

TECHNICAL FIELD
The invention relates to aqueous stable emulsions which comprise organohydropolysiloxanes and to a process for preparing them.
DESCRIPTION OF THE RELATED ART
Aqueous emulsions comprising organohydropolysiloxanes and the uses thereof are widely known, such as, for example, for the preparation of antiadhesion silicone coatings on paper or film by means of crosslinking reaction (hydrosilylation), the preparation of water-repellent coatings by means of crosslinking reaction (condensation), hydrophobicizing impregnation of textiles, leather or paper, as release agents for bladder coating in tire manufacture, and for the hydrophobicization of building materials.
The stability of organohydropolysiloxane emulsions is a problem, owing to the susceptibility of the Si-H bond to hydrolysis. The reaction with water in this case frequently gives rise to silanol groups and gaseous hydrogen. Measures to improve the stability of organchydropolysiloxane emulsions and to reduce the elimination of hydrogen have already been described.
In Melliand Textilberichte 41, 1125 (1960) it is disclosed that methylhydropolysiloxane emulsions show a stability optimum at an established pH of 3.5-4 depending on the acid used.
The stabilization of specific alkylhydropolysiloxane emulsions prepared using cationic emulsifier, by adding aminocarboxylic acids and establishing a pH at 2.5-5, is described in DE-B 1 161 419 (Bayer AG, issued Jan. 16, 1964). DE-A 21 57 580 (Rhone Poulenc S.A., issued Jun. 22, 1972) and the corresponding GB-A 1336195 claim specific amino acid derivatives for stabilizing alkylhydropolysiloxane emulsions.
The addition of water-soluble, saturated aliphatic aldehydes having at least two C atoms for stabilizing emulsions containing organohydropolysiloxanes is described in DE-B 1 215 929 (Wacker-Chemie GmbH, issued May 5, 1966). EP-B-43 985 (Bayer AG, issued Oct. 3, 1984) discloses alkylhydropolysiloxane emulsions having improved low-temperature and gassing stability, which is achieved by adding trihydric alcohols and mono- or dihydric alcohols.
EP-B 314 955 (General Electric Co., issued Jan. 11, 1995) claims the stabilization of emulsions of organopolysiloxanes containing hydrogen groups by adding hydroxy-functional organopolysiloxanes, preferably at neutral pH.
SUMMARY OF THE INVENTION
Subject matter of the invention are aqueous emulsions comprising
(A) organohydropolysiloxanes alone or in a mixture with organopolysiloxanes free from Si-bonded hydrogen and organyloxy groups,
(B) organopolysiloxanes containing organyloxy groups, as stabilizers,
(C) emulsifiers, and
(D) water.
DETAILED DESCRIPTION OF THE INVENTION
In the context of the present invention the term organopolysiloxanes is intended to embrace polymeric, oligomeric and dimeric siloxanes.
The emulsions of the invention have an average particle diameter of preferably 0.05-10 &mgr;m, with particular preference of 0.1-3 &mgr;m.
As component A it is possible to use all organohydrosiloxanes known to date and also, if desired, further organopolysiloxanes possessing neither Si-bonded hydrogen nor organyloxy groups.
The organohydropolysiloxanes present in the emulsions of the invention preferably comprise those comprising units of the general formula
R
a
H
b
SiO
(4-a-b)/2
  (I)
where
R can be identical or different and denotes SiC-bonded, unsubstituted or substituted hydrocarbon radicals having 1 to 18 carbon atoms,
a is equal to 0, 1, 2 or 3, on average from 0.5 to 2, and
b is equal to 0, 1 or 2, on average from 0.005 to 1,
with the proviso that the sum of a+b is less than or equal to 3 and at least one Si-bonded hydrogen atom is present per molecule.
Examples of R are alkyl radicals, such as the methyl, ethyl, n-propyl, isopropyl, 1-n-butyl, 2-n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, 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, cycloheptyl radical and methylcyclohexyl radicals; alkenyl radicals, such as the vinyl, 1-propenyl and the 2-propenyl radical, aryl radicals, such as the phenyl, naphthyl, anthryl and phenanthryl radical; alkaryl radicals, such as o-, m-, p-tolyl radicals; xylyl radicals and ethylphenyl radicals; and aralkyl radicals, such as the benzyl radical, the &agr;- and the &bgr;-phenylethyl radical.
Examples of substituted radicals R are haloalkyl radicals, such as the 3,3,3-trifluoro-n-propyl radical, the 2,2,2,2′,2′,2′-hexafluoroisopropyl radical, the heptafluoroisopropyl radical and haloaryl radicals, such as the o-, m- and p-chlorophenyl radical.
Radical R preferably comprises the methyl, vinyl and the phenyl radical, the methyl radical being particularly preferred.
Preferably, at least 75% of the Si-bonded radicals R in the organohydropolysiloxane comprising units of the formula (I) are methyl radicals.
The amount of Si-bonded hydrogen in the organohydropolysiloxane used in accordance with the invention is preferably from 0.001 to 2% by weight.
The organohydropolysiloxane which is present in the emulsions of the invention can comprise a resin which is liquid at room temperature or an oil.
The organohydropolysiloxane comprising units of the formula (I) comprises with particular preference those which contain HSiO
1.5
units, HSiCH
3
O units, HSi(CH
3
)
2
O
0.5
units and H
2
SiO units, and also (CH
3
)
3
SiO
0.5
, (CH
3
)
2
SiO and CH
3
SiO
1.5
units.
Preferably, the organohydropolysiloxane present in the emulsions of the invention is essentially linear with a viscosity of preferably from 1 to 100,000. mm
2
/s, with particular preference from 5 to 20,000 mm
2
/s, in each case at 25° C.
Examples of organohydropolysiloxanes comprising units of the formula (I) are:
(CH
3
)
3
SiO—[HSiCH
3
O]
x
—Si(CH
3
)
3
where x=10-200;
(CH
3
)
3
SiO—[HSiCH
3
O]
x
—[(CH
3
)
2
SiO]
y
—Si(CH
3
)
3
where x:y=1:0.5 to 1.25 and with viscosities of 20-1000 mm
2
/s;
H—[Si(CH
3
)
2
O]
n
—Si(CH
3
)
2
H where n=5-200.
Further examples are:
(CH
3
)
3
SiO—[HSiCH
3
O]
50
—Si(CH
3
)
3
;
(CH
3
)
3
SiO—[HSiCH
3
O]
30
—[(CH
3
)
2
SiO]
20
—Si(CH
3
)
3
;
(CH
3
)
3
SiO—[HSiCH
3
O]
5
—[(CH
3
)
2
SiO]
75
—Si(CH
3
)
3
;
H—[Si(CH
3
)
2
O]
15
—Si(CH
3
)
2
H; H—[Si(CH
3
)
2
O]
200
—Si(CH
3
)
2
H.
The organopolysiloxanes which can be used additionally to the organohydropolysiloxanes preferably comprise those comprising units of the formula
R
1
c
R
2
d
SiO
(4-c-d)/2
  (II)
where
R
1
can be identical or different and denotes SiC-bonded, unsubstituted or substituted, aliphatically saturated hydrocarbon radicals having 1 to 18 carbon atoms,
R
2
can be identical or different and denotes SiC-bonded, aliphatically unsaturated hydrocarbon radicals having 2 to 6 carbon atoms,
c is equal to 0, 1, 2 or 3, on average from 1 to 2.1, and
d is equal to 0 or 1, on average from 0 to 1,
with the proviso that the sum of c+d is less than or equal to 3.
Examples of radicals R
1
are the examples specified for R of aliphatically saturated, unsubstituted or substituted hydrocarbon radicals, methyl, ethyl, n- and isopropyl radicals and also the n-hexyl radical being preferred and the methyl radical being particularly preferred.
Examples of radicals R
2
are alkenyl radicals, such as the vinyl, allyl, 1-propenyl, 2-propenyl and 1-hexenyl radical, and also cyclopentenyl and cyclohexenyl radicals, vinyl and 1-hexenyl radicals being preferred and the vinyl radical being particularly preferred.
In particular, at least 75% of the Si-bonded radicals R
1
in the organopolysiloxane comprising units of the formula (II) are methyl radicals.
The organopolysilox

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