U.S. patent application number 10/849466 was filed with the patent office on 2005-07-28 for crosslinking agent for a silicone composition which can be crosslinked at low temperature based on a hydrogenated silicone oil comprising si-h units at the chain end and in the chain.
This patent application is currently assigned to RHODIA CHIMIE. Invention is credited to Benayoun, Jean-Paul, Dhaler, Didier, Kieffer, Jacques, White, John.
Application Number | 20050165194 10/849466 |
Document ID | / |
Family ID | 34796771 |
Filed Date | 2005-07-28 |
United States Patent
Application |
20050165194 |
Kind Code |
A1 |
Benayoun, Jean-Paul ; et
al. |
July 28, 2005 |
Crosslinking agent for a silicone composition which can be
crosslinked at low temperature based on a hydrogenated silicone oil
comprising Si-H units at the chain end and in the chain
Abstract
The invention relates to crosslinkable or crosslinked silicone
compositions capable of being used to form a water-repellent and
release coating for a flexible support made of paper or of polymer,
in particular a heat-sensitive flexible support. These compositions
are of the type of those comprising crosslinking
polyorganosiloxanes carrying SiH units and unsaturated, preferably
vinylated, polyorganosiloxanes capable of reacting with the
crosslinking agent by polyaddition in the presence of platinum to
form the release crosslinked coating on the flexible support. The
targeted aim is to make possible the instantaneous crosslinking at
low temperature (85-90.degree. C.) of such silicone compositions
coated on flexible supports at a very high speed. To achieve this
aim, the invention provides for the use of specific crosslinking
agents composed of POSs hydrogenated at the chain end and in the
chain. The invention also relates to the silicone compositions of
solvent-free type or of emulsion type comprising the Si-Vi POS, the
SiH POS crosslinking agent
.alpha.,.omega.-bis(hydrodimethylsiloxyl)poly(hydromet-
hyl)-(dimethyl)siloxane, and the platinum catalyst, inter alia.
Applications: release silicone coatings obtained by
crosslinking/polyaddition for heat-sensitive flexible supports, for
example polymeric films made of polyethylene.
Inventors: |
Benayoun, Jean-Paul; (Lyon,
FR) ; Dhaler, Didier; (Tassin, FR) ; Kieffer,
Jacques; (Neyron, FR) ; White, John; (Chessy
les Mines, FR) |
Correspondence
Address: |
BURNS DOANE SWECKER & MATHIS L L P
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
RHODIA CHIMIE
Boulogne Billancourt Cedex
FR
|
Family ID: |
34796771 |
Appl. No.: |
10/849466 |
Filed: |
May 20, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10849466 |
May 20, 2004 |
|
|
|
PCT/FR02/03952 |
Nov 19, 2002 |
|
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Current U.S.
Class: |
528/10 |
Current CPC
Class: |
C08L 83/04 20130101;
Y10T 428/31786 20150401; C09D 183/04 20130101; C08G 77/12 20130101;
C08G 77/70 20130101; Y10T 428/31855 20150401; D21H 21/16 20130101;
D21H 27/001 20130101; D21H 19/32 20130101; C08L 83/00 20130101;
C08L 83/00 20130101; C08G 77/20 20130101; C08G 77/80 20130101; C09D
183/04 20130101; C08L 83/04 20130101; Y10T 428/31663 20150401 |
Class at
Publication: |
528/010 |
International
Class: |
C08G 077/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 2001 |
FR |
01/14996 |
Claims
What is claimed is:
1. A crosslinking agent used to prepare a water-repellent and
release coating for a fibrous or nonfibrous support comprising: at
least one silicone oil: comprising at least one hydrogenated
(preferably linear) PolyOrganoSiloxane (POS) exhibiting, per
molecule, at least three hydrogen atoms bonded to silicon atoms,
and having the following mean linear formula:
M.sub..alpha.M'.sub..beta.D.sub..gamma.D'.sub..delta.with
M=(R.sup.1).sub.3SiO.sub.1/2 M'=H.sub.a(R.sup.1).sub.bSiO.sub.1/2,
a+b=3, a=1, 2 or 3, b=0 to 3 D=(R.sup.2).sub.2SiO.sub.2/2
D'=HR.sup.3SiO.sub.2/2 0.ltoreq..alpha..ltoreq.2
0<.beta..ltoreq.2 0<.gamma.0<.delta.an- d with:
0<.gamma./.delta.; 15.ltoreq.(.beta./.delta.).times.1000.ltoreq-
.150; the POS or POSs of higher viscosity of the said composition
having a dynamic viscosity .eta. at 25.degree. C. of less than or
equal to 1500 mPa.s.
2. The crosslinking agent according to claim 1, wherein the support
to be coated is made of a heat-sensitive material, comprising
polyethylene and/or polypropylene and/or polyester and/or
poly(vinyl chloride) and/or from thermally printable flexible
supports.
3. The crosslinking agent according to claim 1, wherein, for the
crosslinking of the coating, the support is placed at a temperature
of less than or equal to 110.degree. C.
4. The crosslinking agent according to claim 1, wherein the
silicone composition is a mixture formed of: (I.1) at least one POS
exhibiting, per molecule, at least two alkenyl groups bonded to
silicon atoms, (I.2) at least one crosslinking .ident.SiH POS as
defined above, (II) at least one catalyst (II) comprising at least
one metal belonging to the platinum group.
5. The crosslinking agent according to claim 4, wherein the
crosslinking POS exhibits an .ident.SiH/.ident.Si-alkenyl (Vi)
molar ratio such that: 1.0.ltoreq..ident.SiH/.ident.Si-alkenyl
(Vi).ltoreq.4 preferably 1.4.ltoreq..ident.SiH/.ident.Si-alkenyl
(Vi).ltoreq.3.
6. The crosslinking agent according to claim 5, wherein the POS
(I.1) is a product comprising units of formula: 3 W a Z b SiO 4 - (
a + b ) 2 ( I .1 ) in which: W is an alkenyl group, Z is a
monovalent hydrocarbonaceous group which has no unfavourable effect
on the activity of the catalyst and which is selected from alkyl
groups having from 1 to 8 carbon atoms inclusive, and from aryl
groups, a is 1 or 2, b is 0, 1 or 2 and a+b is between 1 and 3.
7. The crosslinking agent according to claim 1, wherein the release
crosslinkable silicone composition comprises: at least one
adhesion-adjusting system, and/or at least one agent for inhibiting
hydrosilylation.
8. The crosslinking agent according to claim 1, wherein the POS
(I.1) is a blocked linear polydiorganosiloxane comprising
"Si-alkenyl" functional groups, exhibiting a viscosity of the order
of 100 to 1000 mPa.s and a level of alkenyl functional groups La,
expressed as equivalent number of alkenyl functional groups per 100
g of oil, of: 0.010.ltoreq.La.
9. The crosslinking agent according to claim 1, wherein the oil
used as the crosslinking agent comprises at least one POS
comprising .ident.SiH functional groups (I.2) and exhibits a
viscosity of the order of 5 to 150 mPa.s.
10. The crosslinking agent according to claim 1, wherein the
composition is provided in the form of an aqueous
emulsion/dispersion.
11. Silicone composition capable of crosslinking by polyaddition to
form a water-repellent and release coating for a fibrous or
nonfibrous support, wherein: the composition comprises: (I.1) at
least one POS exhibiting, per molecule, at least two alkenyl groups
(preferably C.sub.2-C.sub.6 alkenyl groups) bonded to silicon
atoms, (I.2) at least one silicone oil: comprising at least one
hydrogenated linear PolyOrganoSiloxane (POS) exhibiting, per
molecule, at least three hydrogen atoms bonded to silicon atoms,
and having the following mean linear formula:
M.sub..alpha.M'.sub..beta.D.sub..gamma.D'.sub..delta.with
M=(R.sup.1).sub.3SiO.sub.1/2 M'=H.sub.a(R.sup.1).sub.bSiO.sub.1/2,
a+b=3, a=l, 2 or 3, b=0 to 3 D=(R.sup.2).sub.2SiO.sub.2/2
D'=HR.sup.3SiO.sub.2/2 0.ltoreq..alpha..ltoreq.2
0<.beta..ltoreq.2 0<.gamma.0<.delta.an- d with:
0<.gamma./.delta.; 15.ltoreq.(.beta./.delta.).times.1000.ltoreq-
.150; at least one catalyst (II) comprising at least one metal
belonging to the platinum group; and in that the POS or POSs of
higher viscosity which it comprises has (have) a dynamic viscosity
.eta. at 25.degree. C. of less than or equal to 1500 mPa.s.
12. Support which comprises at least one release coating obtained
from the composition according to claim 11.
Description
[0001] This application is a Continuation-in-Part of PCT
Application No. PCT/FR02/03952 designating the United States and
filed on Nov. 19, 2002, which claims priority from French
Application No. 01/14996 filed on Nov. 20, 2001, the disclosures of
which are incorporated herein in their entirety by reference.
[0002] The field of the invention is that of crosslinkable or
crosslinked silicone compositions capable of being used in
particular to form a water-repellant and release coating or film on
a fibrous or nonfibrous support, for example made of paper or the
like, or alternatively made of natural or synthetic polymers.
[0003] More specifically, the invention relates to silicone
compositions of the type of those comprising:
[0004] functionalized polyorganosiloxanes (POS) carrying, on the
same molecule or not, Si--H and Si--IE units with IE representing a
group comprising at least one ethylenic, preferably vinyl,
unsaturation; the Si--H units being capable of reacting with the
Si--IE units by polyaddition;
[0005] an appropriate metal catalyst, preferably a platinum
catalyst;
[0006] optionally at least one adhesion-adjusting system, for
example based on silicone resin comprising Q (SiO.sub.4/2) and/or T
(RSiO.sub.3/2) siloxyll units;
[0007] optionally other additives (fillers, accelerators,
inhibitors, pigments, surfactants, and the like).
[0008] The invention also relates to the preparation of silicone
compositions of this type.
[0009] The invention also relates to the processes for the
manufacture of articles made of crosslinked silicone, in particular
coatings, e.g. water-repellent and/or release coatings, for fibrous
or nonfibrous flexible supports (paper or polymer film), from the
compositions targeted above.
[0010] For example, these liquid silicone compositions are applied
to support films in industrial coating devices comprising rolls
operating at a very high speed (for example 600 m/min). It is
obvious that, in these very high-speed coating procedures, the
viscosity of the liquid silicone coating composition must be
precisely adapted to the coating operating conditions.
[0011] The liquid silicone coating compositions of more particular
interest in the context of the invention are solvent-free.
[0012] According to an alternative form, the silicone phase of
these liquid silicone coating compositions can be diluted in a
solvent. According to another more advantageous alternative form,
in particular for reasons of health and safety, the liquid silicone
composition is an aqueous dispersion/emulsion.
[0013] In practice, the degree of deposition of release silicone is
between 0.1 and 2 g/m.sup.2, preferably 0.3 and 1 g/m.sup.2, which
corresponds to thicknesses of the order of a micrometre.
[0014] Once applied to the flexible support, the silicone
composition crosslinks to form a firm, release and/or
water-repellent, coating made of silicone (e.g. elastomer).
[0015] In view of the very high-speed industrial coating rates, the
kinetics of crosslinking have to be instantaneous and the
crosslinking has to be correct, that is to say that the release
silicone films have to be sufficiently crosslinked to be able to
fulfil as best as possible their release role and to possess the
desirable mechanical qualities. The assessment of the quality of
the crosslinking of the release silicone film can be carried out in
particular through quantitative determination of the uncrosslinked
extractable compounds, the amount of which must be as small as
possible.
[0016] The ability to release of the free outer face of the
silicone coating is expressed through the detachment force, which
has to be weak and controlled, for the element intended to be
positioned on the support coated by the release silicone film.
Conventionally, this element can be the adhesive face of a label or
of a tape of the same kind.
[0017] Thus, in addition to this weak and controlled detachment
force, the adhesion of the silicone coating to its support has to
be very high. This property of adhesion is assessed, for example,
using the rub off trade test, which consists in rubbing the surface
of the coating with a finger and then measuring the number of
successive passes which result in damage to the coating.
[0018] It is also important for these silicone coating compositions
which can be crosslinked by hydrosilylation, e.g.
.ident.SiH/.ident.SiVi, to have a lifetime at ambient temperature
which is as long as possible, when they are in the form of a
coating bath in industrial coating devices.
[0019] The flexible supports coated with a release silicone film
can be, for example:
[0020] an adhesive tape, the inner face of which is coated with a
layer of pressure-sensitive adhesive and the outer face of which
comprises the release silicone coating;
[0021] or a paper or a polymer film for protecting the adhesive
face of a self-adhesive element or pressure-sensitive adhesive;
[0022] or a polymer film of the Poly(Vinyl Chloride) (PVC),
PolyPropylene, PolyEthylene or PolyEthylene Terephthalate)
type.
[0023] In the case of solvent-free liquid silicone systems which
crosslink by polyaddition (Si--H/Si-alkenyl-Vi-), crosslinking is
carried out under thermal activation. These reaction conditions are
not suitable for some heat-sensitive supports, such as those
comprising polyethylene (PE), such as, for example, PE films or
paper coated with PE, or those of the thermally printable paper
type. These heat-sensitive supports do not withstand being heated
to temperatures of greater than 90.degree. C. All the difficulty
thus lies in obtaining, for these heat-sensitive supports, correct
crosslinking at low temperature, for example of less than or equal
to 110.degree. C. (85-90.degree. C.).
[0024] The use of crosslinking agents of the type of those
comprising siloxyl units: dimethylhydrosiloxyl (M'),
methylhydrosiloxyl (D'), dimethylsiloxyl (D) and trimethylsiloxyl
(M), for liquid silicone compositions which can be crosslinked by
polyaddition (.ident.SiH/SiVinyl), to form release coatings on
flexible supports (coated or uncoated paper, polymer films, and the
like), is generally already disclosed.
[0025] This is thus the case in Patent Application EP A-0 523 660,
which discloses silicone compositions which can be crosslinked in a
few seconds at temperatures below 100.degree. C. and which comprise
network (nonlinear) .ident.Si-Vi POS resins and =-SiH POS
crosslinking agents of MD', MDM' type. It is not at all shown in
this document that the crosslinking of the silicone films obtained
is correct. The level of extractables is not measured in the
examples.
[0026] EP-A-0 523 660 does not relate to a specific .ident.SiH POS
crosslinking agent which confers advantageous properties on the
crosslinked coating in terms of reduced level of extractables and
of duration of stability of the bath of liquid silicone coating
composition, in particular.
[0027] In this context, an essential object of the present
invention is to provide a novel use of specific .ident.SiH POSs as
crosslinking agents in liquid silicone coating compositions which
can be crosslinked instantaneously at low temperature
(.ltoreq.110.degree., preferably .ltoreq.100.degree. C., e.g. of
the order of 85/90.degree. C.) to give a release and/or
water-repellent coating for a flexible support, while resulting in
crosslinked silicone coatings of very good quality characterized by
reduced levels of extractables.
[0028] Another essential object of the invention is to provide a
novel use of specific .ident.SiH POSs as crosslinking agents in
liquid silicone coating compositions which can be crosslinked
instantaneously at low temperature to give a release and/or
water-repellent coating for a flexible support, while exhibiting
long bath lifetimes at ambient temperature.
[0029] Another essential object of the invention is to provide a
novel use of specific .ident.SiH POSs as crosslinking agents in
liquid silicone coating compositions which can be crosslinked
instantaneously at low temperature to give a release and/or
water-repellent coating for a flexible support and which result in
correctly crosslinked silicone coatings having entirely
satisfactory release properties.
[0030] Another essential object of the invention is to provide a
novel use of specific .ident.SiH POSs as crosslinking agents in
liquid silicone coating compositions which can be crosslinked
instantaneously at low temperature to give a release and/or
water-repellent coating for a flexible support and which result in
correctly crosslinked silicone coatings having entirely
satisfactory attachment properties.
[0031] Another essential object of the invention is to provide a
novel use of specific .ident.SiH POSs as crosslinking agents in
liquid silicone coating compositions which can be crosslinked
instantaneously at low temperature to give a release and/or
water-repellent coating for a flexible support and which result in
correctly crosslinked silicone coatings having entirely
satisfactory mechanical properties.
[0032] Another essential object of the invention is to provide a
novel use of specific .ident.SiH POSs as crosslinking agents in
liquid silicone coating compositions which can be
crosslinked-instantaneously at low temperature to give a release
and/or water-repellent coating for a flexible support and which
result in correctly crosslinked silicone coatings having entirely
satisfactory water-repelling properties.
[0033] Another essential object of the invention is to provide a
novel liquid silicone coating composition which can be crosslinked
instantaneously at low temperature to give a release and/or
water-repellent coating for a flexible support, this composition
additionally having the same qualities as those mentioned above for
the use.
[0034] Another essential object of the invention is to provide a
novel liquid silicone coating composition which can be crosslinked
instantaneously at low temperature to give a release and/or
water-repellent coating for a flexible support, this composition
additionally being easy to prepare and economical.
[0035] Another essential object of the invention is to provide a
process for the production at low temperature of release and/or
water-repellent crosslinked silicone coatings on heat-sensitive
flexible supports.
[0036] These objects, among others, are achieved by the present
invention, which relates first to a novel use as crosslinking
agent, in a silicone composition capable of crosslinking by
polyaddition to form a water-repellent and release coating for a
fibrous or nonfibrous support,
[0037] of at least one silicone oil, comprising at least one
hydrogenated (preferably linear) PolyOrganoSiloxane (POS)
exhibiting, per molecule, at least three hydrogen atoms bonded to
silicon atoms,
[0038] and having the following mean linear formula:
M.sub..alpha.M'.sub..beta.D.sub..gamma.D'.delta.
[0039] with M=(R.sup.1).sub.3SiO.sub.1/2
[0040] M'=H.sub.a(R.sup.1).sub.bSiO.sub.1/2, a+b=3, a=1, 2 or
3,
[0041] b=0 to 3
[0042] D=(R.sup.2).sub.2SiO.sub.2/2
[0043] D'=HR.sup.3SiO.sub.2/2
[0044] 0.ltoreq..alpha..ltoreq.2
[0045] 0<.beta..ltoreq.2
[0046] 0<.gamma.
[0047] 0<.delta.
[0048] and with:
[0049] 0<.gamma./67, preferably
0<.gamma./.delta..ltoreq.1.8,
[0050] and more preferably still 0<.gamma./.delta..ltoreq.
[0051] 1.5;
[0052] 15.ltoreq.(.beta./.delta.).times.1000.ltoreq.150,
preferably
[0053] 15.ltoreq.(.beta./.delta.).times.1000.ltoreq.80,
[0054] and more preferably still
[0055] 15.ltoreq.(.beta./.delta.).times.1000.ltoreq.60;
[0056] the POS or POSs of higher viscosity of the said composition
having a dynamic viscosity .eta. at 25.degree. C. of less than or
equal to.1500 mPa.s.
[0057] The use according to the invention of carefully selected
.ident.SiH POS crosslinking agents makes it possible to produce
release coatings on heat-sensitive supports, such as polyethylene
(PE). By virtue of the invention, correct crosslinking of the
coating is provided at a low temperature, for example 90.degree.
C., under industrial coating conditions.
[0058] Furthermore, these novel .ident.SiH POS crosslinking agents
do not modify the Theological behaviour of the silicone
composition, so that it is perfectly capable of being coated on any
support and in particular on any flexible support.
[0059] This final property is all the more advantageous as, in the
context of the invention, the silicone coating compositions can
advantageously be "solvent-free". This means that they are devoid
of solvent and in particular of organic solvent. The advantages
which this provides regarding health and safety are easily
understood.
[0060] The performance achieved by virtue of the invention in terms
of quality of the crosslinking by polyaddition: reactivity/level of
crosslinking/kinetics, are entirely advantageous, as testified
thereto by the low levels of extractables obtained, as regards the
reactivity and the level of crosslinking.
[0061] The formula of the .ident.SiH POS crosslinking agent
indicated above is an overall formula which covers:
[0062] -a- the cases where the .ident.SiH POS crosslinking agent
comprises the MM'DD' units on the same (preferably linear) POS
molecule, it being possible for the crosslinking agent to comprise
one or more different MM'DD' molecules,
[0063] -b- the cases where the .ident.SiH POS crosslinking agent is
formed by a mixture of (preferably linear) POS molecules each
carrying a portion of the MM'DD' units,
[0064] -c- the cases where the .ident.SiH POS crosslinking agent is
formed by a mixture of (preferably linear) .ident.SiH POS
crosslinking agents of -a- and -b- types as described above.
[0065] Mention may be made, as examples of .ident.SiH POS
crosslinking agents of -b- type, of mixtures of .ident.SiH POS
comprising M and D' units and of POS comprising M, D and D' units,
or mixtures of .ident.SiH POS comprising M and D units and of POS
comprising M', D and D' units, or mixtures of .ident.SiH POS
comprising M and D' units and of POS comprising M and D units, or
mixtures of .ident.SiH POS comprising M' and D' units and of POS
comprising M and D units.
[0066] Preferably, the silicone composition involved in the use
according to the invention is composed of .ident.SiH POS and of
.ident.Si-alkenyl (e.g. Vi) POS with a linear, optionally branched,
structure, with the exclusion of .ident.SiH POS and of
.ident.Si-alkenyl (e.g. Vi) POS having a network crosslinked
structure.
[0067] According to an advantageous form of the invention, the
support intended to be coated is made of a heat-sensitive material,
preferably a flexible material, and more preferably still is chosen
from flexible supports comprising polyethylene and/or poly(ethylene
terephthalate) and/or polypropylene and/or poly(vinyl chloride)
and/or from thermally printable flexible supports; polyethylene
films and paper coated with polyethylene being very especially
preferred.
[0068] According to the invention, for the crosslinking of the
coating, the support coated with the polyaddition silicone
composition is placed at a temperature of less than or equal to
110.degree. C., preferably of less than or equal to 100.degree. C.
and more preferably still of between 75 and 95.degree. C., for less
than 60 seconds, preferably less than 10 seconds.
[0069] Advantageously, the silicone composition is a mixture formed
of:
[0070] (I.1) at least one POS exhibiting, per molecule, at least
two alkenyl groups (preferably C.sub.2-C.sub.6 alkenyl groups)
bonded to silicon atoms,
[0071] (I.2) at least one crosslinking .ident.SiH POS as defined
above,
[0072] (I.3) and/or at least one POS carrying Si-alkenyl and Si--H
units,
[0073] (II) at least one catalyst (II) composed of at least one
metal belonging to the platinum group.
[0074] Preferably, use is made of at least one POS (I.1) of
Si-alkenyl type, for example Si-Vi type, and of at least one POS
(I.2) of Si--H type.
[0075] The POS (I.1) is, by weight, one of the essential
constituents of the formulation.
[0076] Advantageously, this POS (I.1) is a product comprising units
of formula: 1 W a Z b SiO 4 - ( a + b ) 2 ( I .1 )
[0077] in which:
[0078] W is an alkenyl group, preferably a vinyl or allyl
group,
[0079] Z is a monovalent hydrocarbonaceous group which has no
unfavourable effect on the activity of the catalyst and which is
preferably chosen from alkyl groups having from 1 to 8 carbon atoms
inclusive, advantageously from the methyl, ethyl, propyl and
3,3,3-trifluoropropyl groups, and from aryl groups, advantageously
from the xylyl, tolyl and phenyl radicals,
[0080] a is 1 or 2, b is 0, 1 or 2 and a+b is between 1 and 3.
[0081] It is advantageous for this polydiorganosiloxane to have a
viscosity (at 25.degree. C.) at least equal to 10 mPa.s, preferably
between 50 and 1000 mPa.s.
[0082] All viscosities concerned with in the present account
correspond to a dynamic viscosity quantity at 25.degree. C.
referred to as "newtonian", that is to say the dynamic viscosity
which is measured, in a way known per se, at a shear rate gradient
which is sufficiently low for the viscosity measured to be
independent of the rate gradient.
[0083] The polyorganosiloxane (I.1) can exhibit a linear, branched
or cyclic structure. Its degree of polymerization is preferably
between 2 and 5000.
[0084] Examples of siloxyll units of formula (I.1) are the
vinyldimethylsiloxane unit, the vinylphenylmethylsiloxane unit and
the vinylsiloxane unit.
[0085] Examples of polyorganosiloxanes (I.1) are
dimethylpolysiloxanes comprising dimethylvinylsilyl ends,
methylvinyldimethylpolysiloxane copolymers comprising
trimethylsilyl ends, methylvinyldimethylpolysiloxan- e copolymers
comprising dimethylvinylsilyl ends, or cyclic
methylvinylpolysiloxanes.
[0086] The polyorganosiloxane (I.2) is preferably of the type of
those comprising siloxyll units of formula: 2 H d L e SiO 4 - ( d +
e ) 2 ( I .2 )
[0087] in which:
[0088] L is a monovalent hydrocarbonaceous group which has no
unfavourable effect on the activity of the catalyst and which is
preferably chosen from alkyl groups having from 1 to 8 carbon atoms
inclusive, advantageously from the methyl, ethyl, propyl and
3,3,3-trifluoropropyl groups, and from aryl groups, advantageously
from the xylyl, tolyl and phenyl radicals,
[0089] d is 1 or 2, e is 0, 1 or 2 and d+e has a value of between 1
and 3.
[0090] The dynamic viscosity .eta..sub.d (at 25.degree. C.) of this
polyorganosiloxane (I.2) is .gtoreq.5, preferably .gtoreq.10, and
more preferably still is between 20 and 1000 mPa.s.
[0091] The polyorganosiloxane (I.2) can exhibit a linear, branched
or cyclic structure. The degree of polymerization is greater than
or equal to 2. More generally, it is less than 5000.
[0092] Examples of units of formula (I.2) are:
M': H(CH.sub.3).sub.2SiO.sub.1/2, D': HCH.sub.3SiO.sub.2/2, D':
H(C.sub.6H.sub.5)SiO.sub.2/2.
[0093] Examples of polyorganosiloxane (I.2) are:
[0094] M'DD': dimethylpolysiloxanes comprising hydrodimethylsilyl
ends, poly(dimethylsiloxane)-(methylhydrosiloxyl)
.alpha.,.omega.-dimethylhydro- -siloxane,
[0095] MDD': copolymers comprising
dimethyl(hydromethyl)polysiloxane (dimethyl) units comprising
trimethylsilyl ends,
[0096] M',DD': copolymers comprising
dimethyl-(hydromethyl)polysiloxane units comprising
hydrodimethylsilyl ends,
[0097] MD': hydromethylpolysiloxanes comprising trimethylsilyl
ends,
[0098] D'.sub.4: cyclic hydromethylpolysiloxanes.
[0099] The polyaddition silicone composition bases may comprise
only linear polyorganosiloxanes (I.1) and (I.2), such as, for
example, those disclosed in Patents: U.S. Pat. No. 3,220,972, U.S.
Pat. No. 3,697,473 and U.S. Pat. No. 4,340,709.
[0100] The catalysts (II) are also well known. Use is preferably
made of platinum and rhodium compounds. It is possible in
particular to use the complexes of platinum and of an organic
product disclosed in patents U.S. Pat. No. 3,159,601, U.S. Pat. No.
3,159,602 and U.S. Pat. No. 3,220,972 and European Patents EP-A-0
057 459, EP-A-0 188 978 and EP-A-0 190 530, or the complexes of
platinum and of vinylated organosiloxanes disclosed in patents U.S.
Pat. No. 3,419,593, U.S. Pat. No. 3,715.334, U.S. Pat. No.
3,377,432 and U.S. Pat. No. 3,814,730. The catalyst generally
preferred is platinum. In this case, the amount by weight of
catalyst (II), calculated as weight of platinum metal, is generally
between 2 and 400 ppm, preferably between 5 and 200 ppm, based on
the total weight of the polyorganosiloxanes (I.1) and (I.2).
[0101] Preferably, the crosslinking POS exhibits an
.ident.SiH/.ident.Si-alkenyl (Vi) molar ratio such that:
1.0.ltoreq..ident.SiH/.ident.Si-alkenyl (Vi).ltoreq.4
preferably 1.4.ltoreq..ident.SiH/.ident.Si-alkenyl
(Vi).ltoreq.3.
[0102] It is advantageous for the POS (I.1) to be a blocked linear
polydiorganosiloxane comprising "Si-alkenyl" functional groups,
preferably located at the chain end, exhibiting a viscosity of the
order of 100 to 1000 mPa.s and a level of alkenyl functional groups
La, expressed as equivalent number of alkenyl functional groups per
100 g of oil, of:
0.01.ltoreq.La
preferably 0.015.ltoreq.La.ltoreq.0.04
and more preferably still 0.015.ltoreq.La.ltoreq.0.1.
[0103] Likewise, the oil of use as crosslinking agent comprising at
least one POS comprising .ident.SiH functional groups (I.2)
exhibits, preferably, a viscosity of the order of 5 to 150
mPa.s.
[0104] The complete curable compositions are fluid at standard
temperature; their viscosity is generally of the order of 50 to 500
mPa.s at 25.degree. C.
[0105] According to an alternative form, the release crosslinkable
silicone composition includes:
[0106] at least one adhesion-adjusting system;
[0107] and/or at least one agent for inhibiting hydrosilylation,
preferably chosen from acetylenic alcohols and/or diallyl maleates
and their derivatives;
[0108] optionally at least one other additive chosen from
bactericides and/or antigelling agents and/or wetting agents and/or
antifoaming agents and/or fillers and/or synthetic latexes and/or
colorants and/or acidifying agents.
[0109] The adhesion-adjusting system is selected from known
systems. It can be those disclosed in French Patent FR-B-2 450 642,
Patent U.S. Pat. No. 3,772,247 or European Patent Application
EP-A-0 601 938. Mention may be made, by way of examples of the
adjusting systems based:
[0110] on 96 to 85 parts by weight of at least one reactive
polyorganosiloxane resin (A) of type: MD.sup.ViQ, MM.sup.ViQ,
MD.sup.ViT, MM.sup.hexenylQ or MM.sup.allyloxypropylQ,
[0111] on 4 to 15 parts by weight of at least one nonreactive resin
(B) of type: MD'Q, MDD'Q, MDT', MQ or MDQ.
[0112] The retardant of the addition reaction (crosslinking
inhibitor) can, for its part, be chosen from the following
compounds:
[0113] polyorganosiloxanes, advantageously cyclic
polyorganosiloxanes, which are substituted by at least one alkenyl,
tetramethylvinyltetrasilox- ane being particularly preferred,
[0114] pyridine,
[0115] organic phosphines and phosphites,
[0116] unsaturated amides,
[0117] alkylated maleates,
[0118] and acetylenic alcohols.
[0119] These acetylenic alcohols (cf. FR-B-1 528 464 and FR-A-2 372
874), which are among the preferred thermal blockers for the
hydrosilylation reaction, have the formula:
R.sup.1--(R.sup.2)C(OH)--C.ident.CH
[0120] in which formula,
[0121] R' is a linear or branched alkyl radical or a phenyl
radical;
[0122] R.sup.2 is H, a linear or branched alkyl radical or a phenyl
radical;
[0123] it being possible for the R.sup.1 and R.sup.2 radicals and
the carbon atoms situated ax to the triple bond optionally to form
a ring;
[0124] the total number of carbon atoms present in R.sup.1 and
R.sup.2 being at least 5, preferably from 9 to 20.
[0125] The said alcohols are preferably chosen from those
exhibiting a boiling point of greater than 250.degree. C. Mention
may be made, by way of examples, of:
[0126] 1-ethynyl-1-cyclohexanol;
[0127] 3-methyl-1-dodecyn-3-ol;
[0128] 3,7,11-trimethyl-1-dodecyn-3-ol;
[0129] 1,1-diphenyl-2-propyn-1-ol;
[0130] 3-ethyl-6-ethyl-1-nonyn-3-ol;
[0131] 3-methyl-1-pentadecyn-3-ol.
[0132] These .alpha.-acetylenic alcohols are commercial
products.
[0133] Such a retardant is present in a proportion of 3000 ppm at
most, preferably in a proportion of 100 to 2000 ppm, with respect
to the total weight of the organopolysiloxanes (I.1) and (I.2).
[0134] According to another implementational route different from
the "solvent-free" one, the composition is provided in the form of
an aqueous emulsion/dispersion and then comprises at least one
surfactant and optionally at least one agent for fixing the pH.
[0135] The agent for fixing and maintaining the pH is preferably a
buffer system comprising HCO.sub.3.sup.-/CO.sub.3.sup.2- and/or
H.sub.2PO.sub.4.sup.-/HPO.sub.4.sup.2-. Thus, in order to obtain
the desired buffer effect, it will be advisable to introduce, in
accordance with the invention, an HCO.sub.3.sup.- and/or
H.sub.2PO.sup.4- salt, such as, for example, NaHCO.sub.3 and/or
Na.sub.2CO.sub.3 and/or NaH.sub.2PO.sub.4 and/or Na.sub.2HPO.sub.4.
It is obvious that any other salt with a different counteranion
(e.g. K) might be suitable. In a particularly preferred way, use is
in practice made of a buffer system composed of NaHCO.sub.3 which
is incorporated in the emulsion.
[0136] The surfactant or surfactants capable of being present in
the emulsion according to the invention as emulsifying agent are
nonionic or ionic in nature.
[0137] According to an advantageous arrangement, the proportion of
water in the emulsion is greater than or equal to 50% by weight,
preferably greater than or equal to 55% by weight and, for example,
in practice of the order of 55-60% by weight or alternatively of 85
to 90% by weight.
[0138] According to another of its subject-matters, the invention
relates to a silicone composition capable of crosslinking by
polyaddition to form a water-repellent and release coating for a
fibrous or nonfibrous support, characterized:
[0139] in that the composition comprises:
[0140] (I.1) at least one POS exhibiting, per molecule, at least
two alkenyl groups (preferably C.sub.2-C.sub.6 alkenyl groups)
bonded to silicon atoms,
[0141] (I.2) at least one silicone oil:
[0142] comprising at least one hydrogenated linear
PolyOrganoSiloxane (POS) exhibiting, per molecule, at least three
hydrogen atoms bonded to silicon atoms,
[0143] and having the following mean linear formula:
M.sub..alpha.M'.sub..beta.D.sub..gamma.D'.sub..delta.
[0144] with M=(R.sup.1).sub.3SiO.sub.1/2
[0145] M'=H.sub.a(R.sup.1).sub.bSiO.sub.1/2, a+b=3, a=1, 2 or 3,
b=0 to 3
[0146] D=(R.sup.2).sub.2SiO.sub.2/2
[0147] D'=HR.sup.3SiO.sub.2/2
[0148] 0.ltoreq..alpha..ltoreq.2
[0149] 0<.beta..ltoreq.2
[0150] 0<.gamma.
[0151] 0.ltoreq..delta.
[0152] and with:
[0153] 0<.gamma./.delta., preferably
0<.gamma./.delta..ltoreq.1.8,
[0154] and more preferably still
0<.gamma./.delta..ltoreq.1.5;
[0155] 15.ltoreq.(.gamma./.delta.).times.1000.ltoreq.150,
preferably
[0156] 15.ltoreq.(.beta./.delta.).times.1000.ltoreq.80,
[0157] and more preferably still
[0158] 15.ltoreq.(.beta./.delta.).times.1000.ltoreq.60;
[0159] at least one catalyst (II) composed of at least one metal
belonging to the platinum group;
[0160] and in that the POS or POSs of higher viscosity which it
comprises has (have) a dynamic viscosity .eta. at 25.degree. C. of
less than or equal to 1500 mPa.s.
[0161] To define the composition according to the invention,
reference is made to the characteristics defined above in the
context of the description of the use.
[0162] According to another of its aspects, the present invention
relates to a process for the preparation of a silicone composition
which can be used in particular as coating base for the preparation
of release and water-repellent coatings, this composition being of
the type of that defined above. According to this process, at least
one (preferably linear) .ident.Si-Vi POS oil (I.1) is mixed with
the crosslinking agent composed of at least one .ident.Si--H POS
oil (I.2) of MM'DD' type and/or of a mixture of oils comprising
(preferably linear) POS molecules each carrying a portion of the
MM'DD' units present in the crosslinking agent. The catalyst (II)
is also incorporated in the silicone phase with the optional other
ingredients, such as the crosslinking inhibitors.
[0163] The mixing means and methodologies are known to a person
skilled in the art, whether solvent-free or emulsion
compositions.
[0164] These compositions can be applied using devices employed on
industrial equipment for the coating of paper, such as a five-roll
coating head, an air knife system or an equalizer bar system, to
flexible supports or materials and can then be cured by moving
through tunnel ovens heated to 70-200.degree. C.; the passage time
in these ovens depends on the temperature; this time is generally
of the order of 5 to 15 seconds at a temperature of the order of
100.degree. C. and of the order of 1.5 to 3 seconds at a
temperature of the order of 180.degree. C.
[0165] The said compositions can be deposited on any flexible
material or substrate, such as paper of various types
(supercalendered, coated, and the like), board, cellulose sheets,
metal sheets, plastic films (polyester, polyethylene,
polypropylene, and the like), and the like.
[0166] The amounts of compositions deposited are of the order of
0.5 to 2 g per m.sup.2 of surface to be treated, which corresponds
to the deposition of layers of the order of 0.5 to 2 .mu.m.
[0167] The materials or supports thus coated can subsequently be
brought into contact with any pressure-sensitive adhesive material
of rubber, acrylic or other nature. The adhesive material is then
easily detachable from the said support or material.
[0168] According to another of its aspects, the present invention
relates to a support, characterized in that it comprises at least
one release coating obtained:
[0169] in accordance with the use as defined above,
[0170] and/or from a composition as defined above.
[0171] The following examples are given by way of indication and
may not be regarded as a limitation on the scope and spirit of the
invention.
DESCRIPTION OF THE FIGURES
[0172] FIG. 1 is a curve giving the level of silicone extractables
(SE) (%) as a function of the temperature of the paper (T) in
.degree. C.:
[0173] -.diamond-solid.- test 1
[0174] -.box-solid.- test 2
[0175] -.tangle-solidup.- test 3
[0176] Z,1 test 4
[0177] FIG. 2 is a curve giving the level of silicone extractables
(SE) (%) as a function of the level (t 1/3) of .ident.SiH POS
crosslinking agent (I.2.1) in the .ident.SiH POS crosslinking agent
(I.2.3), crosslinking at 85.degree. C.
[0178] FIG. 3 is a curve giving the peel strength (PS) as a
function of the peel rate (PR) at crosslinking temperatures of 86
to 95.degree. C.
[0179] FIG. 4 shows histograms at:
[0180] t=0,
[0181] t=3 months and
[0182] t=4 months
[0183] giving the peel strength (PS) for a coating rate of 0.3
m/min and crosslinking temperatures of 86 to 95.degree. C.
EXAMPLES
[0184] The coating of silicone on a Rotomec pilot-scale coating
plant at 100 m/min (residence time of 3.6 s in the ovens) on a
glassine 9564 support or on OPP CR 30 at different oven
temperatures.
[0185] The temperature of the silicone layer is measured in-line
using an infrared camera.
[0186] The coating, after coating and crosslinking, is
characterized by the following tests:
[0187] weight of the silicone coating: the silicon atoms of the
coating are excited using a radioactive source or an X-ray
fluorescence tube and the X-ray intensity reemitted by the coating
is measured. The weight of the silicone coating is thus determined
using a calibration curve. The device used is a Lab X1000 device
sold by Oxford.
[0188] Level of extractables (at the outlet of the coating device:
in-line/4 days after crosslinking: off-line): the test consists in
immersing the coating in toluene and in then quantitatively
determining by atomic absorption spectrophotometry Perkin-Elmer
3100 (APL/AA/T173); on a coating at the outlet of the coating
device (in-line).
[0189] The level of silicone extractable from the coating is
determined using a calibration curve.
[0190] Crosslinking: the level of polymerization of the coating at
the outlet of the coating device is described using a number of
trade tests: the smear test, where the oily nature of the surface
is described by passing the finger over the silicone surface, and
the rub off test, which characterizes the attachment to the
support. In practice, the finger is rubbed over the surface of the
coating and the number of passes starting from which the coating
deteriorates/detaches is recorded. A grading of 10 (10 passes) is
regarded as acceptable for the application.
[0191] Detachment force: the test used corresponds to the Finat No.
3 and 10 standards of edition No. 5 of 1999. This test is' carried
out 4 days after crosslinking (off-line) with adhesive tapes sold
under the Tesa.RTM. 7475 trademark at 23.degree. C. (acrylic base)
and the Tesa.RTM. 7476 trademark at 70.degree. C. (rubber
base).
[0192] Monitoring of the performance of pressure-free instantaneous
adhesion, tack, of the PSA after contact with the silicone coating
according to the No. 9 standard of the Finat edition No. 5 of
1999.
[0193] Products used:
[0194] Oil vinylated at the chain end (I.1): polydimethylsiloxane
oil vinylated in the .alpha. and .omega. positions with 0.022
mol/100 g of Vi and with a viscosity of 25.degree. C. of 200 mPa.s.
This oil comprises 0.15% of ethynylcyclohexanol inhibitor.
[0195] Hydrogenated PDMS silicone oil (I.2.1) having the structure
MD'xDyM with 1 mol of hydrogen/100 g.
[0196] Hydrogenated PDMS oil (I.2.2) having the structure MD'xM and
comprising 1.5 mol of hydrogen per 100 g of structure MD'xM.
[0197] Hydrogenated PDMS oil (I.2.3) having the strucure
M'MD'xDyM'M and comprising 0.7 mol of hydrogen per 100 g.
[0198] Catalyst (II): Karstedt Pt comprising 3000 ppm of Pt, sold
under the Silcolease.RTM. 11091M trademark by Rhodia Silicones.
[0199] The Tests and Their Results:
[0200] -A- Tests 1 TO 11
1TABLE 1 Test POS POS POS POS Catalyst .beta./.delta. .times. 1000
= SE No. (I.1) (I.2.1) (I.2.2) (I.2.3) (II) .gamma./.delta. = D/D'
(M'/D') .times. 1000 (%) 1 100 4.6 -- -- 4.4 1.5 0 27 2 100 -- --
6.9 4.5 1.2 36 3.5 3 100 2.9 -- 2.6 4.4 1.28 22.7 7.5 4 100 -- 1.0
4.8 4.5 0.80 23.2 4.0 5 100 1.0 -- 5.5 4.4 1.08 28 4.5 6 100 2.3 --
3.5 4.4 0.86 17.4 7.5 Counter- 100 3.5 -- 1.7 4.4 0.66 7.96 11.0
test 7 8 100 -- 1.0 4.8 4.5 0.80 23.2 4.0 9 100 -- 1.2 5.9 4.0 0.80
23.2 4.0 10 100 -- 1.4 6.9 4.0 0.80 23.2 4.0 11 100 -- 1.6 8.0 4.0
0.80 23.2 5.0
[0201] 1. Reactivity
[0202] The level of extractables is measured as a function of the
temperature of the paper. The results are given in Table 1 and in
the appended FIG. 1, which shows the level of silicone extractables
as a function of the temperature of the flexible paper support for
Tests 1 to 4, the crosslinking being carried out at a low
temperature of 85.degree. C.
[0203] It is clearly seen that the crosslinking agent according to
the invention with the structure SiH POS (I.2.3): M'MD'D (Tests 2,
3 and 4), makes it possible to obtain the lowest levels of
extractables, the mark of better reactivity. By virtue of the
invention, formulations are accessible which can be crosslinked at
low temperature: 80 to 85.degree. C.
[0204] Test 3, which corresponds to a mixture of the .ident.SiH POS
(I.2.1): MDD', and of the .ident.SiH POS (I.2.3): MM'DD', and Test
4, which corresponds to (I.2.2): MD'M, + (I.2.3): MM'DD', show, in
FIG. 1, that the reactivity (quality of the crosslinking at low
temperature) of the mixtures remains very good, while improving the
attachment to the flexible support. FIG. 2 shows that the level in
the crosslinking agent of structure other than MM'DD', for example
(I.2.1): MDD', must not be too high, preferably less than 30%.
[0205] -B- Tests 12 TO 19
[0206] A new series of crosslinking agents in accordance (Tests 13,
14, 17 and 19) or not in accordance (Countertests 12, 15, 16 and
18) with the invention was evaluated. The characteristics of these
products, ratio .gamma./.delta.=D/D' and
.beta./.delta..times.1000=M'/D'.times.1000, are given in the
following Table 2.
[0207] The vinylated oil used is (I.1) as defined above and the
catalyst is the catalyst (II) as defined above. The SiH/SiVi ratio
is kept constant at 1.8 and the level of Pt is 100 ppm.
2TABLE 2 Extractables Ratio .beta./.delta. .times. 1000 =
Crosslinking agent Rub off in % .gamma./.delta. = D/D' M'/D'
.times. 1000 Countertest 10-OK 10.0 0.208 7.15 12 13 10-OK 4.4 0.52
21.2 14 10-OK 3.4 1.5 57.2 Countertest 10-OK 11.1 0 26.7 15
Countertest 10-OK 9.1 0 10 16 17 10-OK 3.2 1.25 36 POS (1.2.1)
Countertest 10-OK 9.9 0.31 9 18 19 10-OK 4 0.8 23.3
[0208] The crosslinking agents in accordance with the invention
(Tests 13, 14, 17 and 19) have a good hold in the rub off test and
exhibit levels of silicone extractables (SE) of less than 5%, it
being known that, in accordance with the invention, SE <9-10%,
preferably SE.ltoreq.7.5% and more preferably still
SE.ltoreq.5%.
[0209] 2. Detachment Force and Ageing, Tesa 7475 (in-Line)
[0210] The release properties were measured on coatings produced
from a silicone formulation comprising a mixture of POS (1.2.3)
crosslinking agent (82%)/POS (I.2.2) (18%). The peel profiles
obtained and the stabilities towards ageing of these release
properties are shown in FIGS. 3 and 4. It is apparent that the
.ident.SiH POS crosslinking agent according to the invention does
not affect these release properties or their stability over
time.
* * * * *