U.S. patent application number 14/651618 was filed with the patent office on 2015-11-05 for production of thin silicone films.
This patent application is currently assigned to Wacker Chemie AG. The applicant listed for this patent is WACKER CHEMIE AG. Invention is credited to Andreas KOELLNBERGER, Alfred SCHWINGHAMMER.
Application Number | 20150315347 14/651618 |
Document ID | / |
Family ID | 49585392 |
Filed Date | 2015-11-05 |
United States Patent
Application |
20150315347 |
Kind Code |
A1 |
KOELLNBERGER; Andreas ; et
al. |
November 5, 2015 |
PRODUCTION OF THIN SILICONE FILMS
Abstract
Thin silicon films of high thickness uniformity and thicknesses
of from 0.1 .mu.m to 200 .mu.m are prepared by applying a
crosslinkable silicone composition to a moving carrier by means of
a slot die, removing solvent, if present, and subsequently
crosslinking the silicone layer formed on the carrier.
Inventors: |
KOELLNBERGER; Andreas;
(Kirchdorf, DE) ; SCHWINGHAMMER; Alfred;
(Pfarrkirchen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WACKER CHEMIE AG |
Munchen |
|
DE |
|
|
Assignee: |
Wacker Chemie AG
Munich
DE
|
Family ID: |
49585392 |
Appl. No.: |
14/651618 |
Filed: |
November 15, 2013 |
PCT Filed: |
November 15, 2013 |
PCT NO: |
PCT/EP2013/073914 |
371 Date: |
June 11, 2015 |
Current U.S.
Class: |
427/379 ;
427/397.7 |
Current CPC
Class: |
H01L 41/45 20130101;
B29L 2007/008 20130101; B29C 48/0021 20190201; B29K 2083/00
20130101; B29C 48/155 20190201; C08J 5/18 20130101; B05D 3/007
20130101; C08J 2383/04 20130101; B29C 41/28 20130101; B29C 48/08
20190201; B29C 41/003 20130101 |
International
Class: |
C08J 5/18 20060101
C08J005/18; B05D 3/00 20060101 B05D003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 12, 2012 |
DE |
10 2012 222 992.2 |
Claims
1-4. (canceled)
5. A method for the continuous production of a thin silicone film
having a film thickness of 0.1 to 200 .mu.m and a thickness
precision of .+-.5% measured over an area of 200 cm.sup.2,
comprising: i) applying a crosslinkable, solvent-containing or
solvent-free silicone composition (X) through the gap of a slot die
onto a moving carrier, ii) subsequently removing solvent, if
present, from a silicone layer which forms on the carrier, and
crosslinking the silicone layer, iii) wherein after crosslinking,
the resulting crosslinked silicone film is partable from the
carrier, and a) the slot die in step i) is at an angle of between
10.degree. and 90.degree. to the carrier; b) the travel speed of
the carrier is between 0.1 and 1000 m/min; and c) the dynamic
viscosity of the silicone composition (X) as measured according to
DIN53019 is between 100 mPas and 100 Pas.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the U.S. National Phase of PCT Appln.
No. PCT/EP2013/073914 filed Nov. 15, 2013, which claims priority to
German Application No. 10 2012 222 992.2 filed Dec. 12, 2012, the
disclosures of which are incorporated in their entirety by
reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method for the continuous
production of thin silicone films, where the film thickness is
between 0.1 and 200 .mu.m and the thickness precision is .+-.5%
measured over an area of 200 cm.sup.2, and also to the silicone
films produced by this method, and to their use.
[0004] 2. Description of the Related Art
[0005] EP0097313A1 describes the production of a thin silicone
elastomer film having a film thickness of one to 500 .mu.m. For
production, the film is applied to a coated paper, using a coating
technique of rollercoating, air doctor or reverse roll coating,
wire-wound bar coating, or spray coating in order to produce thin
films. These techniques lead to silicone films having
unsatisfactory thickness precision, and are therefore of only
limited usefulness.
[0006] DE2408659 describes a method for producing thin, flawless
silicone films, in which the silicone film is produced by casting a
centrifuged silicone material to which solvent has been added. The
costly and inconvenient method is unsuitable, however, for
industrial production in a continuous process. Moreover, the
thickness precisions achieved by means of the casting processes
described are again insufficient.
[0007] EP1661686A2 describes the extrusion or coextrusion of a
silicone layer. In terms of thickness precision, extrusion
processes are unsuitable for layer thicknesses below about 200
.mu.m, this constituting a substantial disadvantage of this
technology. Through the use of a carrier material during the
extrusion, moreover, the fluctuations in thickness of the carrier
are transferred to the silicone film.
[0008] A continuous method for producing thin silicone films is
described in DE2045558. The principal disadvantages of that method
are that the doctor blade coating, on the one hand, requires high
solvent content (ideally 60 wt % solvent is described) and, on the
other hand, the accuracy of the layer thickness, analogously to
extrusion methods, is dependent on the precision of the carrier
used.
[0009] As the prior art shows, silicone films in a thickness range
starting from about 200 .mu.m and up to several mm can be produced
by extrusion methods or molding methods. The respective methods
here exhibit different disadvantages. In the case of discontinuous
molding methods, a reduction in the layer thickness is accompanied
by problems during automatic demolding, and, moreover, the
production costs per square meter (sq. m.) of film are higher than
in the case of continuously operating processes. Extrusion methods
of HTV rubbers have the disadvantage of relatively large variations
in thickness, and also of the limited possibility, owing to plant
design and slot swelling, of reducing the layer thicknesses below
200 .mu.m.
[0010] In addition to the absolute layer thickness, the uniformity
of the layer thickness over the whole of the web produced is a
critical factor for applications of the film as, for example, a
dielectric or a membrane. The requirement of very uniform films
having thicknesses of between one and about 250 .mu.m exists in
particular in the development of dielectric electroactive polymers
(EAP for short), where the film is used as a dielectric.
Applications of the electroactive polymers in actuators, sensors,
or generators are based on the conversion of electrical energy into
mechanical energy or of mechanical energy into electrical energy.
Following application of an electrically conducting coating to one
or both sides of the film, a deformation in the system as a whole
is brought about, for example, by the application of electrical
voltage (actuator principle).
SUMMARY OF THE INVENTION
[0011] An object of the invention, therefore, was to provide a
continuous method for producing thin silicone films having a very
thin and very uniform layer thickness, and also having high surface
quality and high long-term load resistance. These and other objects
were surprisingly achieved by the method of the invention for the
continuous production of thin silicone films having a film
thickness of 0.1 to 200 .mu.m and a thickness precision of .+-.5%
measured over an area of 200 cm.sup.2, characterized in that
[0012] i) a crosslinkable, solvent-containing or solvent-free
silicone composition (X) is applied through the gap of a slot die
to a moving carrier,
[0013] ii) subsequently the solvent, if present, is removed from
the silicone layer which forms on the carrier film, and the
silicone layer is crosslinked,
[0014] iii) after the crosslinking, the resulting silicone film can
be parted from the carrier,
[0015] with the following provisos: [0016] the slot die in step i)
is at an angle of between 10.degree. and 90.degree. to the carrier;
[0017] the travel speed of the carrier is between 0.1 and 1000
m/min; [0018] the dynamic viscosity of the silicone composition (X)
as measured according to DIN53019 is between 100 mPas and 100
Pas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 illustrones one embodiment of a method according to
the invention.
[0020] FIG. 2 illustrates a further embodiment of a method
according to the invention.
[0021] FIG. 3 illustrates a further embodiment of a method
according to the invention.
[0022] FIG. 4 illustrates a further embodiment of a method
according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The preferred embodiments of individual features of the
present invention, disclosed below at different places in the text,
should be understood such that the combinations of these features
in their preferred embodiments are also particularly preferred.
[0024] The method of the invention is carried out as far as
possible in the absence of particles. Absence of particles means
that during the overall process of film production, care must be
taken to ensure that as few as possible of particles, whether in
the form of active or inert fillers possibly incorporated by
mixing, or in the form of extraneous particles, are included that
are greater than about 1/3 of the desired layer thickness. For
example, in a silicone film of the invention with a thickness of 24
.mu.m, there are preferably no particles included with a diameter
exceeding 8 .mu.m. The removal of any particles present from the
silicone composition (X) may take place in principle by all
techniques known to the state of the art. Examples of such
techniques are straining via strainer sieves (wire nets, wire
braid), filter candles made of any of a very wide variety of
materials (metal, plastic, ceramic, etc.), filtration techniques
such as, for example, magnetic filtration, pressure filtration via
filter presses, backflow filters, suction filters, etc., with or
without filter aids such as activated carbon, metal oxides, etc. A
further example of the removal of particles from the silicone
composition (X) is centrifugation, and all of the methods stated or
possible may take place in a batch process or continuously.
[0025] The method for producing the silicone film from the silicone
composition (X) preferably takes place preferably under clean-room
conditions, in which there are no particles larger than 5 .mu.m.
For the design of the production equipment, this means that the
non-crosslinked silicone composition (X), following the removal of
any particles present, is stored and processed only in clean rooms
of class ISO 5 (ISO 1466-1) or better, preferably in clean rooms of
class ISO 4 or better.
[0026] The carrier material used as carrier plays a minor role with
regard to the production of the silicone film. Only the surface
quality is critical, since elevations or depressions in the surface
are taken on directly by the silicone composition (X). For this
reason, carrier materials used are preferably those whose surfaces
are particularly smooth and contain no depressions or elevations
which are greater than 5%, preferably 3%, of the film thicknesses
to be produced. Examples of carrier materials include:
polyethylene, polypropylene, polyvinyl chloride, polystyrene,
cellophane, polyesters (e.g. polyethylene terephthalate,
polybutylene terephthalate, polycarbonate, polyethylene
naphthalate), fluorine-containing polymers (e.g.
polytetrafluoroethylene), metal strips or metal foils (as a
continuous strip or via the feed rolls depicted; all metals are
possible, with or without surface coating). The thickness of the
carrier material used likewise plays only a minor part. Preferred
thicknesses for polymeric carriers or metal foils are 10 .mu.m to
200 .mu.m, while those for metal strips are 200 .mu.m to 2 mm.
Preferred carrier materials are metal foils, metal strips, and
polymeric films of polyethylene, polypropylene, polyethylene
terephthalate, polybutylene terephthalate, and also
polytetrafluoroethylene.
[0027] The travel speed of the carrier for the production of the
silicone films is customarily between 0.1 and 1000 m/min,
preferably between 0.5 and 500 m/min, and more preferably between 1
and 250 m/min. With the method of the invention it is possible to
achieve web widths of between a few centimeters and several meters,
with the preferred width being between 10 cm and 4 m, more
preferably between 20 cm and 3 m.
[0028] As a result of the use of a slot die, the thickness of the
silicone layer produced is dependent only on the flow rate of
material, which is set via the supplying pump; on the web speed;
and on the density of the crosslinkable silicone composition (X)
used. The dynamic viscosity of the silicone composition (X) as
measured according to DIN53019 is between 100 mPas and 100 Pas,
preferably between 200 mPas and 75 Pas, and more preferably between
300 mPas and 50 Pas. Slot dies are known to the skilled person from
the state of the art.
[0029] Described below are a number of embodiments of the method of
the invention in exemplary form, using FIG. 1 to FIG. 4. These
embodiments, however, should not be considered as exclusive for the
design forms of the method of the invention.
[0030] In one simple embodiment, the silicone films of the
invention are produced on a production line according to FIG.
1.
[0031] FIG. 1 serves for the simple illustration of the method of
the invention. In the case of an arrangement as shown in FIG. 1,
the silicone film is produced by the non-crosslinked silicone
composition (X) being conveyed through the gap in the slot die in
step i), with the feed rate and the speed of the carrier being
adapted in such a way as to result in the desired layer thickness.
The gap opening at the head of the slot die is customarily in the
same width range as the layer to be produced, with marked
differences also being possible (as is also evident from the later
examples). The distance of the slot die from the carrier is
somewhat above the desired layer thickness of the film. For a
silicone film 50 .mu.m thick, for example, the distance between the
slot die and the carrier may vary between 55 .mu.m and 500 .mu.m
preferably between 55 .mu.m and 350 .mu.m and more preferably
between 55 .mu.m and 200 .mu.m.
[0032] The positioning of the slot die relative to the carrier may
take place alternatively vertically from above (position A),
horizontally (position B), or from below (position C). The angle
between the slot die and the carrier material in FIG. 1 is
90.degree., but other angles are possible as described later on
below. FIG. 1 depicts the elements 1 to 3 serving for step ii). The
number of elements should be understood merely as an example and
with no restriction on their number. Where silicone compositions
(X) are used which contain no solvent, the use of a single element
(for hot air, IR radiation, or UV radiation, for example) may be
sufficient to bring about the crosslinking in step ii) to form the
silicone film. In the case of silicone compositions (X) which
include solvent, it is advantageous if the removal of the solvent
and the step of crosslinking to give the silicone film are
separated in process step ii), requiring at least two elements,
element 1 and element 2. However, a plurality of elements in
combinations may also be used for step ii). For example, in FIG. 1,
element 1 serves to vent solvent, element 2 serves for
crosslinking, and element 3 serves for aftertreating. When the
silicone film has cured, it is collected or wound up together with
the carrier in FIG. 1. Depending on the web speed and the onset
temperature of the silicone composition (X), the lengths of the
venting, crosslinking, and aftertreatment sections of the elements
1 to 3 may vary.
[0033] In FIG. 2, production takes place in the same way as for
FIG. 1, with the additional process step ia) of a pretreatment of
the carrier. This is a dipping treatment of the carrier. After the
dipping treatment, the carrier is passed through squeezing rolls
and polishing rolls in order to remove excess pretreatment
material.
[0034] In FIG. 3, production takes place in the same way as for
FIG. 2, with the additional process step of the use of a second
carrier, carrier 2, in step iii) after the crosslinking to give the
silicone film. Here, the carrier 2 is applied to the surface of the
silicone film and, with a slight offset (though it may also take
place simultaneously), the silicone film is parted from carrier 1
and collected together with carrier 2.
[0035] In FIG. 4, production takes place in the same way as for
FIG. 2, with the difference that the silicone film is parted from
the carrier as step iii), directly after production in step ii),
and is collected on its own.
[0036] As silicone compositions (X) it is possible in principle to
use all of the silicones known to the state of the art.
Addition-crosslinking, peroxidically crosslinking,
condensation-crosslinking, or radiation-crosslinking compositions
may be used. Preference is given to peroxidically or
addition-crosslinking compositions. Particularly preferred are
addition-crosslinking compositions.
[0037] Addition-crosslinking silicone compositions (X) used in
accordance with the invention are known in the prior art and
comprise, in a basic composition: [0038] (A) at least one compound
having radicals with aliphatic carbon-carbon multiple bonds, [0039]
(B) at least one organopolysiloxane having Si-bonded hydrogen
atoms, [0040] or instead of (A) and (B) [0041] (C) at least one
organopolysiloxane having SiC-bonded radicals with aliphatic
carbon-carbon multiple bonds, and having Si-bonded hydrogen atoms,
and [0042] (D) at least one hydrosilylation catalyst.
[0043] The addition-crosslinking silicone compositions (X) may be
either one-component silicone compositions or two-component
silicone compositions.
[0044] In the case of two-component silicone compositions, the two
components of the addition-crosslinking silicone compositions (X)
of the invention may comprise all constituents in any desired
combinations, generally with the proviso that one component does
not simultaneously comprise siloxanes with aliphatic multiple bond,
siloxanes with Si-bonded hydrogen, and catalyst, in other words
essentially does not simultaneously comprise constituents (A), (B),
and (D), or (C) and (D).
[0045] The compounds (A) and (B) and, respectively, (C) that are
used in the addition-crosslinking silicone compositions (X) of the
invention are selected, as is known, such that crosslinking is
possible. Thus, for example, compound (A) has at least two
aliphatically unsaturated radicals, and (B) has at least three
Si-bonded hydrogen atoms, or compound (A) has at least three
aliphatically unsaturated radicals and siloxane (B) has at least
two Si-bonded hydrogen atoms, or else siloxane (C) is used instead
of compound (A) and (B), this siloxane (C) having aliphatically
unsaturated radicals and Si-bonded hydrogen atoms in the
proportions stated above. Also possible are mixtures of (A) and (B)
and (C) having the above-designated proportions of aliphatically
unsaturated radicals and Si-bonded hydrogen atoms.
[0046] The addition-crosslinking silicone composition (X) of the
invention customarily contains 30-95 wt %, preferably 30-80 wt %,
and more preferably 40-70 wt % of (A). The addition-crosslinking
silicone composition (X) of the invention customarily contains
0.1-60 wt %, preferably 0.5-50 wt %, and more preferably 1-30 wt %
of (B). If the addition-crosslinking silicone composition (X) of
the invention comprises component (C), there is customarily 30-95
wt %, preferably 30-80 wt %, more preferably 40-70 wt % of (C)
present in the formulation.
[0047] The compound (A) used in accordance with the invention may
comprise silicon-free organic compounds preferably having at least
two aliphatically unsaturated groups, and also organosilicon
compounds preferably having at least two aliphatically unsaturated
groups, or else mixtures thereof.
[0048] Examples of silicon-free organic compounds (A) are
1,3,5-trivinylcyclohexane, 2,3-dimethyl-1,3-butadiene,
7-methyl-3-methylene-1,6-octadiene, 2-methyl-1,3-butadiene,
1,5-hexadiene, 1,7-octadiene,
4,7-methylene-4,7,8,9-tetrahydroindene, methylcyclopentadiene,
5-vinyl-2-norbornene, bicyclo[2.2.1]hepta-2,5-diene,
1,3-diisopropenylbenzene, polybutadiene containing vinyl groups,
1,4-divinylcyclohexane, 1,3,5-triallylbenzene,
1,3,5-trivinylbenzene, 1,2,4-trivinylcyclohexane,
1,3,5-triisopropenylbenzene, 1,4-divinylbenzene,
3-methylhepta-1,5-diene, 3-phenylhexa-1,5-diene,
3-vinylhexa-1,5-diene, and 4,5-dimethyl-4,5-diethylocta-1,7-diene,
N,N'-methylenebisacrylamide, 1,1,1-tris(hydroxymethyl)propane
triacrylate, 1,1,1-tris(hydroxymethyl)propane trimethacrylate,
tripropylene glycol diacrylate, diallyl ether, diallylamine,
diallyl carbonate, N,N'-diallylurea, triallylamine,
tris(2-methylallyl)amine, 2,4,6-triallyloxy-1,3,5-triazine,
triallyl-s-triazine-2,4,6(1H,3H,5H)-trione, diallyl malonate,
polyethylene glycol diacrylate, polyethylene glycol dimethacrylate,
poly(propylene glycol) methacrylate.
[0049] As constituent (A), the addition-crosslinking silicone
compositions (X) of the invention preferably comprise at least one
aliphatically unsaturated organosilicon compound, in which case all
aliphatically unsaturated organosilicon compounds used to date in
addition-crosslinking compositions may be employed, such as, for
example, silicone block copolymers having urea segments, silicone
block copolymers having amide segments and/or imide segments and/or
ester-amide segments and/or polystyrene segments and/or silarylene
segments and/or carborane segments, and silicone graft copolymers
having ether groups.
[0050] Organosilicon compounds (A) having SiC-bonded radicals with
aliphatic carbon-carbon multiple bonds are preferably linear or
branched organopolysiloxanes comprising units of the general
formula (I)
R.sup.4.sub.aR.sup.5.sub.bSiO.sub.(4-a-b)/2 (I)
[0051] where [0052] R.sup.4 independently at each occurrence, is an
organic or inorganic radical free from aliphatic carbon-carbon
multiple bonds, [0053] R.sup.5 independently at each occurrence, is
a monovalent, substituted or unsubstituted, SiC-bonded hydrocarbon
radical having at least one aliphatic carbon-carbon multiple bond,
[0054] a is 0, 1, 2, or 3, and [0055] b is 0, 1, or 2,
[0056] with the proviso that the sum a+b is less than or equal to 3
and there are at least 2 radicals R.sup.5 per molecule.
[0057] Radical R.sup.4 may comprise monovalent or polyvalent
radicals, in which case the polyvalent radicals, such as divalent,
trivalent, and tetravalent radicals, for example, join two or more,
such as two, three, or four, for instance, siloxy units of the
formula (I) to one another.
[0058] Further examples of R.sup.4 are the monovalent radicals --F,
--Cl, --Br, OR.sup.6, --CN, --SCN, --NCO, and SiC-bonded,
substituted or unsubstituted hydrocarbon radicals which may be
interrupted by oxygen atoms or by the group --C(O)--, and also
divalent radicals Si-bonded on both sides in accordance with
formula (I). If radical R.sup.4 comprises SiC-bonded, substituted
hydrocarbon radicals, preferred substituents are halogen atoms,
phosphorus-containing radicals, cyano radicals, --OR.sup.6,
--NR.sup.6--, --NR.sup.6.sub.2, --NR.sup.6--C(O)--NR.sup.6.sub.2,
--C(O)--NR.sup.6.sub.2, --C(O) R.sup.6, --C(O) OR.sup.6,
--SO.sub.2-Ph, and --C.sub.6F.sub.5. In that case R.sup.6,
independently at each occurrence, denotes a hydrogen atom or a
monovalent hydrocarbon radical having 1 to 20 carbon atoms, and Ph
is the phenyl radical.
[0059] Examples of radicals R.sup.4 are alkyl radicals such as the
methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl,
n-pentyl, isopentyl, neopentyl, and 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,
and octadecyl radicals, such as the n-octadecyl radical; cycloalkyl
radicals such as the cyclopentyl, cyclohexyl, cycloheptyl, and
methylcyclohexyl radicals; aryl radicals such as the phenyl,
naphthyl, anthryl, and phenanthryl radicals; alkaryl radicals such
as the o-, m-, and p-tolyl radicals, xylyl radicals, and
ethylphenyl radicals; and aralkyl radicals such as the benzyl
radical, and the .alpha.- and the .beta.-phenylethyl radicals.
[0060] Examples of substituted radicals R.sup.4 are haloalkyl
radicals such as the 3,3,3-trifluoro-n-propyl radical, the
2,2,2,2',2',2'-hexafluoroisopropyl radical, the
heptafluoroisopropyl radicals, haloaryl radicals such as the o-,
m-, and p-chlorophenyl radicals,
--(CH.sub.2)--N(R.sup.6)C(O)NR.sup.6.sub.2,
--(CH.sub.2).sub.o--C(O)NR.sup.6.sub.2,
--(CH.sub.2).sub.o--C(O)R.sup.6, --(CH.sub.2).sub.o--C(O)OR.sup.6,
--(CH.sub.2).sub.o--C(O)NR.sup.6.sub.2,
--(CH.sub.2)--C(O)--(CH.sub.2).sub.pC(O)CH.sub.3,
--(CH.sub.2)--O--CO--R.sup.6,
--(CH.sub.2)--NR.sup.6--(CH.sub.2).sub.p--NR.sup.6.sub.2,
--(CH.sub.2).sub.o--O--(CH.sub.2).sub.pCH (OH) CH.sub.2OH,
--(CH.sub.2).sub.o(OCH.sub.2CH.sub.2).sub.pOR.sup.6,
--(CH.sub.2).sub.o--SO.sub.2-Ph, and
--(CH.sub.2).sub.p--O--C.sub.6F.sub.5, where R.sup.6 and Ph
correspond to the definition indicated therefor above, and o and p
are identical or different integers between 0 and 10.
[0061] Examples of R.sup.4 as divalent radicals Si-bonded on both
sides in accordance with formula (I) are radicals which derive from
the monovalent examples stated above for radical R.sup.4 by virtue
of an additional bond taking place through substitution of a
hydrogen atom. Examples of such radicals are --(CH.sub.2)--,
--CH(CH.sub.3)--, --C(CH.sub.3).sub.2--,
--CH(CH.sub.3)--CH.sub.2--, --C.sub.6H.sub.4--,
--CH(Ph)--CH.sub.2--, --C(CF.sub.3).sub.2--,
(CH.sub.2).sub.o--C.sub.6H.sub.4--(CH.sub.2).sub.o--,
--(CH.sub.2).sub.o--C.sub.6H.sub.4--C.sub.6H.sub.4--
(CH.sub.2).sub.o--, --(CH.sub.2O).sub.p, (CH.sub.2CH.sub.2O).sub.o,
and
--(CH.sub.2).sub.o--O.sub.x--C.sub.6H.sub.4--SO.sub.2--C.sub.6H.sub.4--O.-
sub.x--(CH.sub.2).sub.o--, where x is 0 or 1, and Ph, o, and p have
the definitions stated above.
[0062] Preferably, radical R.sup.4 comprises a monovalent,
SiC-bonded, optionally substituted hydrocarbon radical which has 1
to 18 carbon atoms and is free from aliphatic carbon-carbon
multiple bonds, more preferably a monovalent, SiC-bonded
hydrocarbon radical which has 1 to 6 carbon atoms and is free from
aliphatic carbon-carbon multiple bonds, and more particularly the
methyl or phenyl radicals.
[0063] Radical R.sup.5 may comprise any desired groups amenable to
an addition reaction (hydrosilylation) with an SiH-functional
compound.
[0064] If radical R.sup.5 comprises SiC-bonded, substituted
hydrocarbon radicals, preferred substituents are halogen atoms,
cyano radicals, and --OR.sup.6, where R.sup.6 has the above-stated
definition.
[0065] Preferably, radical R.sup.5 comprises alkenyl and alkynyl
groups having 2 to 16 carbon atoms, such as vinyl, allyl,
methallyl, 1-propenyl, 5-hexenyl, ethynyl, butadienyl, hexadienyl,
cyclopentenyl, cyclopentadienyl, cyclohexenyl,
vinylcyclohexylethyl, divinylcyclohexylethyl, norbornenyl,
vinylphenyl, and styryl radicals, with vinyl, allyl, and hexenyl
radicals being particularly preferred.
[0066] The molecular weight of the constituent (A) may vary within
wide limits, for instance between 10.sup.2 and 10.sup.6 g/mol.
Hence, for example, constituent (A) may comprise a relatively low
molecular mass, alkenyl-functional oligosiloxane, such as
1,2-divinyltetramethyldisiloxane, but may also be a high-polymer
polydimethylsiloxane, for example with a molecular weight of
10.sup.5 g/mol (number average determined by means of NMR), that
possesses in-chain or terminal Si-bonded vinyl groups. The
structure of the molecules forming the constituent (A) is also not
fixed; in particular, the structure of a siloxane of relatively
high molecular mass, in other words an oligomeric or polymeric
siloxane, may be linear, cyclic, branched, or else resinous, or
network-like. Linear and cyclic polysiloxanes are preferably
composed of units of the formula R.sup.4.sub.3SiO.sub.1/2,
R.sup.5R.sup.4.sub.2SiO.sub.1/2, R.sup.5R.sup.4SiO.sub.1/2, and
R.sup.4.sub.2SiO.sub.2/2, where R.sup.4 and R.sup.5 have the
definition indicated above. Branched and network-like polysiloxanes
additionally include trifunctional and/or tetrafunctional units,
with preference being given to those of the formulae
R.sup.4SiO.sub.3/2, R.sup.5SiO.sub.3/2, and SiO.sub.4/2. It will be
appreciated that mixtures of different siloxanes satisfying the
criteria of constituent (A) may also be used.
[0067] Particularly preferred as component (A) is the use of
vinyl-functional, substantially linear polydiorganosiloxanes having
a viscosity of 0.01 to 500,000 Pas, more preferably 0.1 to 100,000
Pas, in each case at 25.degree. C.
[0068] As organosilicon compound (B) it is possible to use all
hydrogen-functional organosilicon compounds which are useful in
addition-crosslinkable compositions.
[0069] Organopolysiloxanes (B) which have Si-bonded hydrogen atoms
are preferably linear, cyclic, or branched organopolysiloxanes
composed of units of the general formula (III)
R.sup.4.sub.cH.sub.dSiO.sub.(4-c-d)/2 (III)
where [0070] R.sup.4 has the definition stated above, [0071] c is
0, 1, 2, or 3, and [0072] d is 0, 1, or 2,
[0073] with the proviso that the sum of c+d is less than or equal
to 3 and there are at least two Si-bonded hydrogen atoms per
molecule.
[0074] The organopolysiloxane (B) used in accordance with the
invention preferably contains Si-bonded hydrogen in a range from
0.04 to 1.7 percent by weight (wt %), based on the total weight of
the organopolysiloxane (B).
[0075] The molecular weight of the constituent (B) may likewise
vary within wide limits, for instance between 10.sup.2 and 10.sup.6
g/mol. Thus constituent (B) may comprise, for example, an
SiH-functional oligosiloxane of relatively low molecular mass, such
as tetramethyldisiloxane, or alternatively may comprise a silicone
resin having SiH groups or a high-polymer polydimethylsiloxane that
possesses SiH groups within the chain or terminally.
[0076] The structure of the molecules that form the constituent (B)
is also not fixed; in particular, the structure of an
SiH-containing siloxane of relatively high molecular mass, in other
words oligomeric or polymeric, may be linear, cyclic, branched, or
else resinous, or network-like. Linear and cyclic polysiloxanes (B)
are composed preferably of units of the formula
R.sup.4.sub.3SiO.sub.1/2, HR.sup.4.sub.2SiO.sub.1/2,
HR.sup.4SiO.sub.2/2, and R.sup.4.sub.2SiO.sub.2/2, with R.sup.4
having the definition indicated above. Branched and network-like
polysiloxanes additionally include trifunctional and/or
tetrafunctional units, with preference being given to those of the
formulae R.sup.4SiO.sub.3/2, HSiO.sub.3/2, and SiO.sub.4/2, where
R.sup.4 has the definition indicated above.
[0077] It will be appreciated that mixtures of different siloxanes
satisfying the criteria of constituent (B) may also be used.
Particularly preferred is the use of low molecular mass,
SiH-functional compounds such as tetrakis(dimethylsiloxy)silane and
tetramethylcyclotetrasiloxane, and also of SiH-containing siloxanes
of higher molecular mass, such as poly(hydrogen-methyl)siloxane and
poly(dimethylhydrogenmethyl)siloxane with a viscosity at 25.degree.
C. of 10 to 20,000 mPas, or similar SiH-containing compounds in
which some of the methyl groups have been replaced by
3,3,3-trifluoropropyl or phenyl groups.
[0078] The amount of constituent (B) in the crosslinkable silicone
compositions (X) of the invention is preferably such that the molar
ratio of SiH groups to aliphatically unsaturated groups in (A) is
0.1 to 20, more preferably between 0.3 and 2.0.
[0079] The components (A) and (B) used in accordance with the
invention are commercial products and/or may be prepared by methods
that are common within chemistry.
[0080] Instead of component (A) and (B), the silicone compositions
of the invention may comprise organopolysiloxanes (C),
simultaneously having aliphatic carbon-carbon multiple bonds and
Si-bonded hydrogen atoms. The silicone compositions of the
invention may also comprise all three components (A), (B), and
(C).
[0081] If siloxanes (C) are used, these are preferably composed of
units of the general formulae (IV), (V), and (VI)
R.sup.4.sub.fSiO.sub.4/2 (IV)
R.sup.4.sub.gR.sup.5SiO.sub.3-g/2 (V)
R.sup.4.sub.hHSiO.sub.3-h/2 (VI)
[0082] where [0083] R.sup.4 and R.sup.5 have the definition
indicated for them above, [0084] f is 0, 1, 2, or 3, [0085] g is 0,
1, or 2, and [0086] h is 0, 1, or 2,
[0087] with the proviso that per molecule there are at least 2
radicals R.sup.5 and at least 2 Si-bonded hydrogen atoms.
[0088] Examples of organopolysiloxanes (C) are those comprising
SiO.sub.4/2, R.sup.4.sub.3SiO.sub.1/2,
R.sup.4.sub.2R.sup.5SiO.sub.1/2, and R.sup.4.sub.2HSiO.sub.1/2
units, known as MP resins, and these resins may additionally
contain R.sup.4SiO.sub.3/2 and R.sup.4.sub.2SiO units, and also
linear organopolysiloxanes substantially consisting of
R.sup.4.sub.2R.sup.5SiO.sub.1/2, R.sup.4.sub.2SiO, and R.sup.4HSiO
units, with R.sup.4 and R.sup.5 meeting the aforementioned
definition.
[0089] The organopolysiloxanes (C) preferably possess an average
viscosity of 0.01 to 500,000 Pas, more preferably 0.1 to 100,000
Pas, in each case at 25.degree. C. Organopolysiloxanes (C) are
preparable by techniques that are common within chemistry.
[0090] As hydrosilylation catalysts (D) it is possible to use all
useful hydrosilylaion catalysts. Component (D) may be a platinum
group metal, as for example platinum, rhodium, ruthenium,
palladium, osmium, or iridium, or an organometallic compound
thereof, or a combination thereof. Examples of component (D) are
compounds such as hexachloroplatinic(IV) acid, platinum dichloride,
platinum acetylacetonate, and complexes of these compounds
encapsulated in a matrix or in a core/shell-like structure. The
platinum complexes with low molecular weight of the
organopolysiloxanes include
1,3-diethenyl-1,1,3,3-tetramethyldisiloxane complexes with
platinum. Other examples are platinum-phosphite complexes or
platinum-phosphine complexes. For photocuring or UV-curing
compositions, for example, alkylplatinum complexes such as
derivatives of cyclopentadienyltrimethylplatinum(IV),
cyclooctadienyldimethylplatinum(II), or diketonato complexes, such
as bisacetylacetonatoplatinum(II), for example, may be used in
order to start the addition reaction by means of light. These
compounds may be encapsulated within a resin matrix.
[0091] The concentration of component (D) for catalyzing the
hydrosilylation reaction of components (A) and (B) and (C) on
exposure is sufficient in order to generate the heat required here
in the method described. The amount of component (D) may be between
0.1 and 1000 parts per million (ppm), 0.5 and 100 ppm, or 1 and 25
ppm of the platinum group metal, depending on the total weight of
the components. The curing rate may be low if the constituent of
the platinum group metal is below 1 ppm. The use of more than 100
ppm of the platinum group metal is uneconomical or lowers the
storage stability of the silicone composition (X).
[0092] The addition-crosslinking silicone compositions (X) may
optionally comprise all further additives which are useful for the
production of addition-crosslinkable compositions. Examples of
reinforcing fillers (F), which may be used as a component in the
addition-crosslinking silicone compositions (X) of the invention,
are fumed or precipitated silicas having BET surface areas of at
least 50 m.sup.2/g, and also carbon blacks and activated carbons
such as furnace black and acetylene black, with preference being
given to fumed and precipitated silicas having BET surface areas of
at least 50 m.sup.2/g. The stated silica fillers may have a
hydrophilic character or may have been made hydrophobic by known
methods. The amount of actively reinforcing filler in the
crosslinkable silicone compositions (X) of the invention is within
the range from 0 to 70 wt %, preferably 0 to 50 wt %.
[0093] With particular preference the crosslinkable,
addition-crosslinking silicone compositions (X) are characterized
in that the filler (E) is surface-treated. The surface treatment is
obtained by the methods known in the state of the art for
hydrophobizing finely divided fillers.
[0094] As a result of a surface treatment, preferred fillers (E)
have a carbon content of at least 0.01 up to a maximum of 20 wt %,
more preferably between 0.1 and 10 wt %, and most preferably
between 0.5 to 5 wt %. Particular preference is given to those
crosslinkable, addition-crosslinking silicone compositions (X)
which are characterized in that the filler (E) is a surface-treated
silica having 0.01 to 2 wt % of Si-bonded, aliphatically
unsaturated groups. These groups are, for example, Si-bonded vinyl
groups. In the addition-crosslinking silicone compositions (X) of
the invention, the constituent (E) is preferably used as a single
or likewise preferably as a mixture of two or more finely divided
filler(s).
[0095] The addition-crosslinking silicone composition (X) of the
invention may alternatively include as constituents further
additives in a fraction of up to 70 wt %, preferably 0.0001 to 40
wt %. These additives may be, for example, inert fillers, resinous
polyorganosiloxanes different from the siloxanes (A), (B), and (C),
reinforcing and nonreinforcing fillers, fungicides, fragrances,
rheological additives, corrosion inhibitors, oxidation inhibitors,
light stabilizers, flame retardants, agents for influencing
electrical properties, dispersing assistants, solvents, adhesion
promoters, pigments, dyes, plasticizers, organic polymers, heat
stabilizers, etc. These include additives such as finely ground
quartz, diatomaceous earth, clays, chalk, lithopone, carbon blacks,
graphite, metal oxides, metal carbonates, metal sulfates, metal
salts of carboxylic acids, metal dusts, fibers such as glass fibers
and polymer fibers, polymer powders, metal dusts, etc.
[0096] The fillers, moreover, may be heat-conducting or
electrically conducting. Examples of heat-conducting fillers are
aluminum nitride; aluminum oxide; barium titanate; beryllium oxide;
boron nitride; diamond; graphite; magnesium oxide; particulate
metals such as copper, gold, nickel, or silver; silicon carbide;
tungsten carbide; zinc oxide, and combinations thereof.
Heat-conducting fillers are known in the state of the art and are
available commercially. For example, CB-A20S and Al-43-Me are
aluminum oxide fillers in different particle sizes, available
commercially from Showa-Denko, and AA-04, AA-2, and AAl 8 are
aluminum oxide fillers which are available commercially from
Sumitomo Chemical Company. Silver fillers are available
commercially from Metalor Technologies U.S.A. Corp. of Attleboro,
Mass., U.S.A. Boron nitride fillers are available commercially from
Advanced Ceramics Corporation, Cleveland, Ohio, U.S.A. The
reinforcing fillers include silica and short fibers such as
KEVLAR-Kurzfaser.RTM., for example. A combination may be used of
fillers with different particle sizes and different particle size
distributions.
[0097] The addition-crosslinking silicone compositions (X) may
comprise further optional components. The examples of further
optional components include, among others, (F) one or more
solvents, and (G) one or more inhibitors.
[0098] The addition-crosslinking silicone compositions (X) may
additionally optionally comprise a solvent (F). It should be
ensured, however, that the solvent (F) has no adverse effects on
the system as a whole. Suitable solvents (F) are known in the state
of the art and are available commercially. The solvent (F) may be,
for example, an organic solvent having 3 to 20 carbon atoms. The
examples of solvents (F) include aliphatic hydrocarbons such as
nonane, decalin, and dodecane, for example; aromatic hydrocarbons
such as mesitylene, xylene, and toluene, for example; esters such
as ethyl acetate and butyrolactone, for example; ethers such as
n-butyl ether and polyethylene glycol monomethyl ethers, for
example; ketones such as, for example, methyl isobutyl ketone and
methyl pentyl ketone; silicone fluids such as, for example, linear,
branched, and cyclic polydimethylsiloxanes, and combinations of
these solvents (F). The optimum concentration of a particular
solvent (F) in the addition-crosslinking silicone composition (X)
may be determined easily by means of routine experiments. Depending
on the weight of the compound, the amount of the solvent (F) may be
between 0 and 95 wt % or between 1 and 95 wt %.
[0099] The addition-crosslinking silicone composition (X) may
additionally optionally comprise (G) inhibitors and stabilizers.
Inhibitors and stabilizers (G) serve for the targeted setting of
the processing life, onset temperature, and crosslinking rate of
the addition-crosslinking silicone composition (X) of the
invention. These inhibitors and stabilizers (G) are very well known
within the field of addition-crosslinking compositions. Examples of
commonplace inhibitors are acetylenic alcohols, such as
1-ethynyl-1-cyclohexanol, 2-methyl-3-butyn-2-ol, and
3,5-dimethyl-1-hexyn-3-ol, 3-methyl-1-dodecyn-3-ol,
polymethylvinylcyclosiloxanes such as
1,3,5,7-tetravinyltetramethyltetracyclosiloxane, low molecular mass
silicone oils with methylvinyl-SiO.sub.1/2 groups and/or
R.sub.2vinylSiO.sub.1/2 end groups, such as
divinyltetramethyldisiloxane, tetravinyldimethyldisiloxane,
trialkyl cyanurates, alkyl maleates, such as diallyl maleates,
dimethyl maleate, and diethyl maleate, alkyl fumarates, such as
diallyl fumarate and diethyl fumarate, organic hydroperoxides such
as cumene hydroperoxide, tert-butyl hydroperoxide, and pinane
hydroperoxide, organic peroxides, organic sulfoxides, organic
amines, diamines and amides, phosphates and phosphites, nitriles,
triazoles, diaziridines, and oximes. The activity of these
inhibitor additives (G) is dependent on their chemical structure,
and so the concentration must be determined individually.
Inhibitors and inhibitor mixtures (G) are added preferably in a
quantitative fraction of 0.00001 wt % to 5 wt %, based on the total
weight of the mixture, preferably 0.00005 to 2 wt %, and more
preferably 0.0001 to 1 wt %.
[0100] The following enumeration stands by way of example for
silicone compositions (X) which are available commercially on the
market and which are suitable for the production of thin layers by
the method of the invention. Mostly they are addition-crosslinking
silicone compositions (X). Depending on the viscosity of the
commercial silicone compositions (X), solvent (F) may be added for
better processing properties. Materials from WACKER Chemie AG,
Munich: ELASTOSIL.RTM. P series (7010, 7600, 7613, 7161-160,
7616-195, 7618, 7619, 7622, 7623, 7624, 7628, 7629, 7630, 7633,
7636, 7642-220, 7670, 671, 7676, 7682, 7683/15, 7683/25, 7683/47,
7683/50, 7683/55, 7684/60, 7685, 7686, 7687, 7688, 7700, 7710,
7720, 7731, 7742, 7770, 7707 US, 7915, . . . ), ELASTOSIL.RTM. M
series (4115, 4125, 4370, 4400, 4440, 4441, 4470, 4600, 4601, 4615,
4630, 4635, 4640, 4645, 4641, 4643, 4644, 4670, 4647, 4648, 4670),
ELASTOSIL.RTM. RT series (601, 602, 604, 607, 615, 617, 619, 620,
622, 623, 624, 625, 626, 627, 628, 629, 630, 633, 646, 670, 672,
675, 678, 685, . . . ), ELASTOSIL.RTM. SOLAR series (2000, 2200,
2202, 3210, . . . ), LSR: ELASTOSIL.RTM. LR series (3003/03,
3003/05, 3003/10, 3003/20, 3070/20, 3844/20, 3846/20, 3856/20,
3003/30, 3004/30, 3005/30, 3040/30, 3044/30, 3065/30, 3070/30,
3071/30, 3072/30, 3843/30, 3844/30, 3846/30, 3856/30, 3003/40,
3003/50, 3003/60, 3003/70, 3003/80, 3003/85, 3004/40, 3004/50,
3004/60, 3004/70, 3005/40, 3005/50, 3005/60, 3040/40, 3040/50,
3040/60, 3043/40, 3043/50, 3043/60, 3043/70, 3015/70, 3023/60,
3092/65, 3094/60, 3065/50, 3066/40, 3066/60, 3066/80, 3070/40,
3070/50, 3070/60, 3071/40, 3071/50, 3071/60, 3072/40, 3074/60,
3076/70, 3170/40, 3841/50, 3842/40, 3842/50, 3842/60, 3842/70,
3162, . . . ), ELASTOSIL.RTM. FLR series (3900/40, 3900/60,
3905/40, 3905/60, . . . ), HTV: ELASTOSIL.RTM. R series, WACKER
SILGEL.RTM. series (610, 611, 612, 613, 616, 619, . . . ),
SEMICOSIL.RTM. series, POWERSIL.RTM. series, LUMISIL.RTM. series,
GENIOMER.RTM. series, SILPURAN.RTM. series, DEHESIVE.RTM.
series.
[0101] Sometimes a pretreatment of the carrier is an advantage as
an additional process step ia).
[0102] Where such pretreatment takes place, this step ia) may take
place, for example, via a dip treatment of the carrier. Other
chemical or physical pretreatment techniques are likewise possible,
with examples thereof being as follows: spray treatment, cleaning
methods, degreasing methods, plasma treatment, or the deposition of
layers (e.g.: fluorocarbon layers). Whether a pretreatment step ia)
is necessary or useful depends on the carrier material used. If
excessive chemical or physical attachment of the silicone elastomer
to the carrier material results in the film being unable to be
detached from the carrier after crosslinking, this can be prevented
by a pretreatment of the carrier. In order to facilitate the
parting of the silicone film from the carrier, the carrier is
preferably treated with a release agent, in which case all of the
release agents known to the state of the art may be used, such as
the following, for example: detergents such as nonionic surfactants
(polyalkylene glycol ethers, alkylglucosides, fatty alcohol
propylates, alkylpolyglucosides, octylphenol ethoxylates,
nonylphenol ethoxylates), anionic surfactants (alkyl carboxylates,
alkylbenzenesulfonates, fatty alcohol sulfates), cationic
surfactants (mostly quaternary ammonium compounds such as
tetraalkylammonium halides or ester quats), or amphoteric
surfactants (betaines, sulfobetaines). All commercial surfactants
or surfactant mixtures may be used for a pretreatment, such as, for
example, the Surfynol.RTM. series, the Dynol.TM. series, the
EnviroGem.RTM. series, the Leunapon F series, the Leunapon FU
series, the Leunapon P series, the Metaupon series, the Hansanol AS
240 series, the Hansanol NS-242 series, the Hansanol NS 243 series,
the Hansanol NS 252 series, the Hansanol NS-262 series, the
Hansanyl OS series, the Hansanid CFAD, the Hansanolat FA series,
the Hansanolat NP series, the Hansateric CAPB series, the
Cremophor.RTM. series, the Eusapon.RTM. series, the Jordapon.RTM.
series, the AVANEL series, the Lutensit.RTM. series, the Lutensol
series, the Pluracare.RTM. series, the Plurafac.RTM. series, or the
Pluronic series.
[0103] The release agent or a mixture of different release agents
and additives is used preferably in an aqueous, alcoholic, or
aqueous-alcoholic mixture, with preferred alcohol components used
being linear and branched aliphatic alcohols such as, for example,
methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol,
octanol, isopropanol, isobutanol, etc.
[0104] Prior to the application of the silicone composition (X) to
the carrier it is preferred for the excess pretreatment material to
be removed from the carrier again, which is preferably accomplished
with the aid of squeezing and/or polishing rolls and/or polishing
plates. Arrangement, size, speed, or number of the assemblies play
only a minor part. Preference, moreover, is given to the use of at
least one polishing roll or polishing plate, particular preference
to the use of a combination of squeezing rolls and polishing
rolls.
[0105] The slot die in step i) is at an angle of between 10.degree.
and 90.degree. relative to the carrier. Preferred angles are
between 30.degree. and 90.degree., and particularly preferred
angles are between 50.degree. and 90.degree..
[0106] In one preferred embodiment, the distance of the slot die
from the carrier in step i) is at least 2 .mu.m, preferably at
least 5 .mu.m greater than the layer thickness of the silicone film
produced.
[0107] The mode of operation of the slot die is unimportant for the
layer thickness calculations, since it represents a premetered
method (bead mode, curtain mode, short curtain mode). Where
necessary, a subatmospheric pressure may be applied to the slot die
in order to achieve the mode at the stated speed. The mass flow
rate of the silicone composition (X) is regulated and adjusted via
suitable pumps, such as, for example, gear pumps, piston pumps,
membrane pumps, etc.
[0108] Activation for the crosslinking in step ii) may take place
thermally, via IR radiation, or via UV radiation. In the case of
room-temperature-vulcanizing (i.e., RTV crosslinking) systems, room
temperature is sufficient for curing, and so there need be no
additional supply of energy. Microwave activation or activation by
ultrasound is also possible.
[0109] In the case of UV-crosslinking systems, the catalyst (D) of
the hydrosilylation reaction of the addition-crosslinking silicone
composition (X) is activated by irradiation in order to achieve
crosslinking. All of the light sources known to the state of the
art may be used, such as LEDs, mercury vapor lamps, doped mercury
vapor lamps, xenon lamps, or lasers, for example. Wavelengths
irradiated with preference are between 250 and 800 nm, particular
preference being given to wavelengths of between 300 and 500 nm.
The arrangement of the light sources is arbitrary, and the distance
between the light source and the silicone composition (X) for
crosslinking may vary between a few millimeters and several
centimeters.
[0110] In the simplest case, the silicone film formed in step ii)
is collected directly with the carrier. Further possibilities
include parting the silicone film from the carrier in a step iii)
and then collecting it, or transferring it from the carrier to a
second carrier and then collecting it together with the second
carrier.
[0111] Reasons for the necessity of transfer to another carrier may
be, for example, the deficient thermal or UV stability of the
carrier, price differences between the carrier materials, surface
properties, surface qualities, thickness, weight, etc. The step of
carrier changeover has no influence at all on the other process
steps.
[0112] Subsequently, the silicone film thus collected may either be
further-processed directly or stored pending further use. If the
carrier is removed from the silicone film only as part of further
processing, the point in time (whether before or after further
processing) may play a part. Further processing of the film may
take place with all of the methods known to the state of the art,
for the shaping of the silicone film, for example, in order to be
able to use it in the desired application. Examples thereof,
without restricting the invention, are cutting with diverse
techniques such as knife, laser, water or particle jet, or
punching. Also possible is fixing by means, for example, of
adhesive bonding, etc.
[0113] A further subject of the present invention are silicone
films produced by the method of the invention, having a film
thickness of 0.1 to 200 .mu.m, preferably of 1 to 150 .mu.m, and
more preferably of 2 to 100 .mu.m, and in each case with a
thickness precision of .+-.5% measured over an area of 200
cm.sup.2; preferably a thickness precision of in each case
.+-.3%.
[0114] The silicone films produced by the method of the invention
described have the advantage, furthermore, that they can be used as
dielectric electroactive polymers (EAP) in actuators, sensors, or
generators, since their breakdown voltage is greater than 25 kV/mm,
preferably greater than 30 kV/mm, and more preferably greater than
35 kV/mm.
[0115] In applications of EAPs in the area of actuators or of
generators, in particular, several million oscillation cycles will
be traversed in the course of the lifetime. One advantage of the
silicone films produced by means of the method of the invention is
a very high long-term load resistance, resulting from the
uniformity of and absence of particles from the silicone film. For
designing the operating voltage of the components, the properties
specified above are likewise of utmost importance, since they
possess a direct influence over the breakdown field strength. The
maximum electrical field in turn has a direct influence on the
efficiency and the performance of the actuators or generators.
[0116] Uniformity means that the layer thickness over a particular
area is subject to only minimal variation. In the case of silicone
films produced with the method of the invention, the layer
thickness varies at maximum by .+-.5% within an area of 200
cm.sup.2 (=thickness precision). This would mean that, for example,
a film having an average layer thickness of 100 .mu.m, over an area
of 200 cm.sup.2, has no point at which the layer thickness is less
than 95 .mu.m or greater than 105 .mu.m. Or, put alternatively, a
film having an average layer thickness of 100 .mu.m and a thickness
precision of .+-.5% always has a thickness of at least 95 and not
more than 105 .mu.m over the entire area of 200 cm.sup.2,
irrespective of where on the 200 cm.sup.2 area the layer thickness
is determined.
[0117] The method described can be used to construct not only
silicone films but also multilayer structures where at least one
layer represents a silicone film of the invention.
[0118] Depending on application, a multiplicity of arrangements or
constructions is conceivable for such systems, and can be achieved
through stacking, folding, rolling, etc.
[0119] Further applications of the films produced by the method
claimed are as follows: barrier films in the medical or food
sector, insulating tapes, protective films (keyboards, skin
protection, oral protection, glass/scratch protection for diverse
materials), packaging of all kinds (foods, plants), backing films
for wound contact materials, functional layers in clothing, layer
for substance separation or gas separation (gas separation,
seawater desalination, etc.), backing film, cooking film, films for
display applications, airbags, or wine corks.
EXAMPLES
[0120] In the examples described below, all figures are in parts
and percentages by weight unless otherwise indicated. Unless
otherwise indicated, the examples below are carried out under a
pressure of the surrounding atmosphere, in other words
approximately at 1000 hPa, and at room temperature, in other words
at 25.degree. C., or at a temperature which comes about when the
reactants are combined at room temperature without additional
heating or cooling. All viscosity figures hereinafter relate to a
temperature of 25.degree. C. The examples below illustrate the
invention, without having any restrictive effect.
[0121] The carrier used in the examples was a PET (polyethylene
terephthalate) film from Mitsubishi Polymer Film GmbH
(HOSTAPHAN.RTM.). Films of this kind are also available from other
manufacturers; for example, MYLAR.RTM. (DuPont Teijin Films),
MELINEX.RTM. (DuPont Teijin Films), SCOTCHPAK.RTM. (3M Company, St.
Paul, Minn.).
[0122] A slot die from COATEMA Coating Machinery GmbH was used, the
nature of this slot die having no critical part as far as
production is concerned. Alternatively, slot dies from other
manufacturers (FMP Technology GmbH, Mitsubishi Heavy Industries,
etc.) can also be used.
[0123] The absolute layer thickness is determined by means of an
SEM analysis of a cryosection; the surface quality and roughness
are determined by means of the Leica DCM 3D confocal
microscope.
Abbreviations used are as follows: Ex. Example No. Number
PDMS Polydimethylsiloxane
LSR Liquid Silicone Rubber
[0124] HTV High-temperature vulcanizing (crosslinking) wt % Weight
percent, w/w U.sub.w Substrate or web speed
.rho. Density
[0125] h Wet film thickness B Coating width
[0126] Examples 1 to 5 were carried out by a method according to
FIG. 1, with position A of the slot die being selected. In example
6 (comparative example, not inventive), the silicone composition
was applied by means of a four-way bar applicator. Examples 7 to 10
were carried out by a method according to FIG. 3, with position A
of the slot die being selected.
Example 1
Without Pretreatment
[0127] Production of a 50 .mu.m film from the RTV-2 material
ELASTOSIL.RTM. P 7670 A/B (mixing ratio A:B=1:1, density according
to ISO 2811=1.03 g/cm.sup.3, Shore A hardness according to ISO
868=7, elongation at break according to ISO 37=600%, tensile
strength according to ISO 37=1.8 N/mm.sup.2, viscosity after mixing
the components according to ISO 3219=1800 mPas with shearing of 1
s.sup.-1, tear strength according to ASTM D 624 B=2.1 N/mm).
[0128] In order to establish a wet film thickness of 50 .mu.m at a
web speed of 1 m/min with a layer width of 0.3 m at the density
given, the feed rate is 15.45 ml/min.
[0129] Measured layer thickness/surface roughness: 50.+-.1.5
.mu.m
[0130] Breakdown voltage according to ASTM D 3755: 35 kV/mm
Example 2
Without Pretreatment
[0131] Production of a 20 .mu.m film from the RTV-2 material
ELASTOSIL.RTM. P 7684/60 A/B (mixing ratio A:B=1:1, density
according to ISO 2811=1.08 g/cm.sup.3, Shore A hardness according
to ISO 868=12, elongation at break according to ISO 37=600%,
tensile strength according to ISO 37=3 N/mm.sup.2, viscosity after
mixing the components according to ISO 3219=1500 mPas with shearing
of 1 s.sup.-1, tear strength according to ASTM D 624 B=13
N/mm).
[0132] In order to establish a wet film thickness of 20 .mu.m at a
web speed of 2 m/min with a layer width of 0.3 m at the density
given, the feed rate is 32.4 ml/min.
[0133] Measured layer thickness/surface roughness: 20.+-.1
.mu.m
[0134] Breakdown voltage according to ASTM D 3755: 50 kV/mm
Example 3
Without Pretreatment
[0135] Production of a 100 .mu.m film from the RTV-2 material
ELASTOSIL.RTM. LR 3003/40, diluted, after or before the mixing of
the component, to a solvent fraction of 50 vol % (alkane fraction,
tradename ISOPAR-E), (mixing ratio A:B=1:1, density according to
ISO 2811=1.0 g/cm.sup.3, Shore A hardness according to ISO 868=42,
elongation at break according to ISO 37=610%, tensile strength
according to ISO 37=10 N/mm.sup.2, tear strength according to ASTM
D 624 B=33 N/mm, viscosity after mixing of the components according
to ISO 3219=5300 mPas with shearing of 1 s.sup.-1).
[0136] A layer thickness of the elastomer of 100 .mu.m at 50 vol %
solvent fraction and a wet film thickness of 200 .mu.m with a web
speed of 5 m/min and a layer width of 0.3 m at the given density
requires a feed rate of 300 ml/min. The solvent is removed by
evaporation prior to crosslinking. The detailed procedure for this
process is unimportant with regard to the film to be produced. In
this example, the web is run through a drying oven 3 m long and
with three different temperature zones (first meter=120.degree. C.,
second meter=140.degree. C., third meter=165.degree. C.) in order
first to evaporate off the solvent and thereafter to bring about
crosslinking of the material through the elevated temperature.
[0137] Measured layer thickness/surface roughness: 100.+-.3
.mu.m
[0138] Breakdown voltage according to ASTM D 3755: 40 kV/mm
Example 4
Without Pretreatment
[0139] The material from example 3 was run with a web speed of 30
m/min and, accordingly, with a feed rate of 1800 ml/min. Measured
layer thickness/surface roughness: 100.+-.4 .mu.m Breakdown voltage
according to ASTM D 3755: 40 kV/mm
Example 5
Without Pretreatment
[0140] Production of a 20 .mu.m film of a silicone having the
following composition:
[0141] 49 wt % of a vinyl-terminated, linear polydimethylsiloxane
having an average chain length of approximately 220.
[0142] 23 wt % of an Me.sub.2Si--H-terminated, linear
polydimethylsiloxane having an average chain length of
approximately 220.
[0143] 23 wt % of a hydrophobized, fumed silica having a BET
surface area of 130 m.sup.2/g
[0144] 5 wt % of a linear comb crosslinker having a chain length of
approximately 220 units and an Si--H content of 0.15 wt %
[0145] The mixture further comprises
[0146] 10 ppm of platinum catalyst (divinyltetramethyldisiloxane
complexes, based on the metal)
[0147] 250 ppm of 1-ethynylcyclohexanol for setting the pot
life.
[0148] Shore A hardness according to ISO 868=26, density according
to ISO 2811=1.05 g/cm.sup.3, elongation at break according to ISO
37=490%, tensile strength according to ISO 37=5.9 N/mm.sup.2, tear
strength according to ASTM D 624 B=11.6 N/mm, viscosity according
to ISO 3219=6900 mPas with shearing of 1 s.sup.-1.
[0149] In order to set a wet film thickness of 20 .mu.m with a web
speed of 10 m/min and a layer width of 0.3 m at the density given,
the feed rate is 63 ml/min.
[0150] Measured layer thickness/surface roughness: 20.+-.0.8
.mu.m
[0151] Breakdown voltage according to ASTM D 3755: >75 kV/mm
Example 6
Comparative Example, not Inventive
[0152] Production of a 50 .mu.m film from the RTV-2 material
ELASTOSIL.RTM. P 7670 A/B (mixing ratio A:B=1:1, density according
to ISO 2811=1.03 g/cm.sup.3, Shore A hardness according to ISO
868=7, elongation at break according to ISO 37=600%, tensile
strength according to ISO 37=1.8 N/mm.sup.2, viscosity after mixing
the components according to ISO 3219=1800 mPas with shearing of 1
s.sup.-1, tear strength according to ASTM D 624 B=2.1 N/mm).
[0153] The adjustment of the layer thickness to 50 .mu.m is
accomplished by manually adapting the distance between the four-way
bar applicator used and the web.
[0154] Measured layer thickness/surface roughness: 50.+-.6
.mu.m
[0155] Breakdown voltage according to ASTM D 3755: 22 kV/mm
Example 7
With Pretreatment
[0156] The dipping bath in FIG. 3 is used, with a solution of 2 wt
% of the commercial surfactant mixture Green Care No. 5 from Tana
Chemie GmbH in water. The rotary speed of the squeezing rolls is
the same as the web speed; that of the polishing rolls is five
times the web speed.
[0157] Production of a 50 .mu.m film from the RTV-2 material
ELASTOSIL.RTM. P 7670 A/B (mixing ratio A:B=1:1, density according
to ISO 2811=1.03 g/cm.sup.3, Shore A hardness according to ISO
868=7, elongation at break according to ISO 37=600%, tensile
strength according to ISO 37=1.8 N/mm.sup.2, viscosity after mixing
the components according to ISO 3219=1800 mPas with shearing of 1
s.sup.-1, tear strength according to ASTM D 624 B=2.1 N/mm).
[0158] In order to establish a wet film thickness of 50 .mu.m at a
web speed of 1 m/min with a layer width of 0.3 m at the density
given, the feed rate is 15.45 ml/min.
[0159] Measured layer thickness/surface roughness: 50.+-.1.5
.mu.m
[0160] Breakdown voltage according to ASTM D 3755: 35 kV/mm
Example 8
With Pretreatment
[0161] The dipping bath in FIG. 3 is used, with a solution of 2 wt
% of the commercial surfactant mixture Green Care No. 5 from Tana
Chemie GmbH in water. The rotary speed of the squeezing rolls is
the same as the web speed; that of the polishing rolls is five
times the web speed.
[0162] Production of a 20 .mu.m film of a silicone having the
following composition:
[0163] 35 wt % of a vinyl-terminated, linear polydimethylsiloxane
having an average chain length of approximately 600.
[0164] 15 wt % of a vinyl-terminated, linear polydimethylsiloxane
having an average chain length of approximately 220.
[0165] 50 wt % of a linear comb crosslinker,
Me.sub.2SiH-terminated, having a chain length of approximately 220
units and an Si--H content of 0.015 wt %.
[0166] The mixture further comprises
[0167] 10 ppm of platinum catalyst (divinyltetramethyldisiloxane
complexes, based on the metal)
[0168] 250 ppm of 1-ethynylcyclohexanol for setting the pot
life.
[0169] Shore A hardness according to ISO 868=2, density according
to ISO 2811=0.97 g/cm.sup.3, elongation at break according to ISO
37=350%, tensile strength according to ISO 37=1.9 N/mm.sup.2, tear
strength according to ASTM D 624 B=2.6 N/mm, viscosity according to
ISO 3219=3500 mPas with shearing of 1 s.sup.-1.
[0170] In order to set a wet film thickness of 20 .mu.m with a web
speed of 10 m/min and a layer width of 0.3 m at the density given,
the feed rate is 64.02 ml/min.
[0171] Measured layer thickness/surface roughness: 20.+-.1
.mu.m
[0172] Breakdown voltage according to ASTM D 3755: 35 kV/mm
Example 9
With Pretreatment
[0173] The dipping bath in FIG. 3 is used, with a solution of 2 wt
% of the commercial surfactant mixture Green Care No. 5 from Tana
Chemie GmbH in water. The rotary speed of the squeezing rolls is
the same as the web speed; that of the polishing rolls is five
times the web speed.
[0174] Production of a 0.5 .mu.m film of a silicone having the
following composition:
[0175] 49 wt % of a vinyl-terminated, linear polydimethylsiloxane
having an average chain length of approximately 220.
[0176] 23 wt % of an Me.sub.2Si--H-terminated, linear
polydimethylsiloxane having an average chain length of
approximately 220.
[0177] 23 wt % of a hydrophobized, fumed silica having a BET
surface area of 130 m.sup.2/g
[0178] 5 wt % of a linear comb crosslinker having a chain length of
approximately 220 units and an Si--H content of 0.15 wt %
[0179] The mixture further comprises
[0180] 10 ppm of platinum catalyst (divinyltetramethyldisiloxane
complexes, based on the metal)
[0181] 250 ppm of 1-ethynylcyclohexanol for setting the pot
life.
[0182] Prior to the application, 1 l of mixture is diluted with 3 l
of solvent (alkane fraction, tradename Isopar E); the density of
the solution is 0.98 g/cm.sup.3, the viscosity of the solution
according to ISO 3219=30 mPas with shearing of 1 s.sup.-1.
[0183] Shore A hardness according to ISO 868=26, elastomer density
according to ISO 2811=1.05 g/cm.sup.3, elongation at break
according to ISO 37=490%, tensile strength according to ISO 37=5.9
N/mm.sup.2, tear strength according to ASTM D 624 B=11.6 N/mm,
viscosity according to ISO 3219=6900 mPas with shearing of 1
s.sup.-1.
[0184] In order to set a wet film thickness of 2 .mu.m with a web
speed of 1 m/min and a layer width of 0.3 m at the density given,
the feed rate is 0.588 ml/min.
[0185] Measured layer thickness/surface roughness: 0.5.+-.0.02
.mu.m
[0186] Breakdown voltage according to ASTM D 3755: 85 kV/mm.
* * * * *