U.S. patent application number 13/212573 was filed with the patent office on 2012-07-19 for fibre-based support containing a layer of a functionalized water-soluble polymer, method of production and use thereof.
This patent application is currently assigned to Ahlstrom Corporation. Invention is credited to Diego FANTINI.
Application Number | 20120183771 13/212573 |
Document ID | / |
Family ID | 46490997 |
Filed Date | 2012-07-19 |
United States Patent
Application |
20120183771 |
Kind Code |
A1 |
FANTINI; Diego |
July 19, 2012 |
FIBRE-BASED SUPPORT CONTAINING A LAYER OF A FUNCTIONALIZED
WATER-SOLUBLE POLYMER, METHOD OF PRODUCTION AND USE THEREOF
Abstract
A cellulose and/or synthetic fibre-based support of which at
least one surface is coated with a layer containing at least one
water-soluble polymer comprising hydroxyl or primary-secondary
amino functional groups, at least some of which have been
functionalized beforehand with at least one organic compound
comprising at least one epoxy functional group, and at least one
R.sup.1 group wherein R.sup.1 is a vinyl functional group or at
least one Si(R.sup.2).sub.3 functional group and wherein
R.sup.2=hydrogen atom, hydroxyl, alkoxy, alkyl, and combinations
thereof
Inventors: |
FANTINI; Diego;
(Pont-Eveque, FR) |
Assignee: |
Ahlstrom Corporation
Kelsinki
FI
|
Family ID: |
46490997 |
Appl. No.: |
13/212573 |
Filed: |
August 18, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13060223 |
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PCT/FI11/50039 |
Jan 19, 2011 |
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13212573 |
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Current U.S.
Class: |
428/392 ;
427/243; 427/256; 427/348; 427/358; 427/369; 428/375 |
Current CPC
Class: |
C09D 133/24 20130101;
D21H 19/54 20130101; Y10T 428/2933 20150115; D21H 19/52 20130101;
Y10T 428/2964 20150115; B32B 23/00 20130101; D21H 27/36 20130101;
D21H 19/34 20130101; C08J 5/121 20130101; B32B 5/02 20130101; D21H
19/58 20130101; D21H 19/60 20130101; D21H 19/80 20130101; C09D 7/80
20180101 |
Class at
Publication: |
428/392 ;
428/375; 427/369; 427/358; 427/348; 427/243; 427/256 |
International
Class: |
B32B 9/00 20060101
B32B009/00; B05D 3/12 20060101 B05D003/12; B05D 1/30 20060101
B05D001/30; B05D 5/00 20060101 B05D005/00; B05D 1/02 20060101
B05D001/02; B32B 23/00 20060101 B32B023/00; B05D 3/04 20060101
B05D003/04 |
Claims
1. A cellulose and/or synthetic fibre-based support of which at
least one surface is coated with a layer containing at least one
water-soluble polymer comprising hydroxyl or primary-secondary
amino functional groups, at least some of which have been
functionalized beforehand with at least one organic compound;
wherein said organic compound contains: at least one epoxy
functional group, and at least one R.sup.1 group wherein R.sup.1 is
a vinyl functional group or at least one Si(R.sup.2).sub.3
functional group and wherein R.sup.2=hydrogen atom, hydroxyl,
alkoxy, alkyl, and combinations thereof.
2. The cellulose and/or synthetic fibre-based support as recited in
claim 1, wherein the fibre-based support is a cellulose
support.
3. The cellulose and/or synthetic fibre-based support as recited in
claim 1, wherein the water-soluble polymer having hydroxyl
functional groups is selected from the group comprising natural and
modified polysaccharides such as starch; CMC; alginate; chitosan,
pectine, chtin, glycogen, arabinoxylane, cellulose and synthetic
polymers such as poly(vinyl alcohol), hydrolysed or partially
hydrolysed copolymers of vinyl acetate, which may be obtained for
example by hydrolysing ethylene--vinyl acetate (EVA) or vinyl
chloride--vinyl acetate, N-vinyl pyrrolidone--vinyl acetate, and
maleic anhydride--vinyl acetate copolymers.
4. The cellulose and/or synthetic fibre-based support as recited in
claim 1, wherein the water-soluble polymer having hydroxyl
functional groups is starch.
5. The cellulose and/or synthetic fibre-based support as recited in
claim 1, wherein the water-soluble polymer having primary-secondary
amino functional groups is selected from the group comprising
polyethyleneimine; polyallylamine; chitosan; polyacrylamide;
partially or totally hydrolized polyacrylamide; parlially or
totally hydrolized polyvinylamine and polyamines based on
amino-ethyl-piperazine.
6. The cellulose and/or synthetic fibre-based support as recited in
claim 1, wherein the organic molecule corresponds to any of the
following formulae: H.sub.2C--O--CH-(R)--CH.dbd.CH.sub.2
H.sub.2C--O--CH--(R)--Si--(R.sup.2).sub.3 wherein R=linear,
branched and/or cyclic carbon chain or polydimethylsiloxane chain
that may contain heteroatoms, and R.sup.2=hydrogen atom, hydroxyl,
alkoxy, alkyl, and combinations thereof.
7. The cellulose and/or synthetic fibre-based support as recited in
claim 1, wherein said organic molecule is preferably one of the
following molecules: 2-vinyloxyrane, 1,2-epoxy-4-pentene
1,2-epoxy-5-hexene, 1,2-epoxy-6-heptene, 1,2-epoxy-7-octene,
1,2-epoxy-8-nonene, 1,2-epoxy-9-decene, 1,2-epoxy-10-undecene,
1-allyloxy-2,3-epoxypropane, 1-allyloxy-3,4-epoxybutane,
1-allyloxy-2,3-epoxypentane, 1-allyloxy-2,3-epoxyhexane,
1-allyloxy-2,3-epoxyheptane, 1-allyloxy-2,3-epoxyoctane,
1-allyloxy-2,3-epoxynonane, 1-allyloxy-2,3-epoxydecane,
1-allyloxy-2,3-epoxyundecane, glycidoxypropyl trimethoxysilane,
glycidoxypropyl triethoxysilane, glycidoxypropyl trisiloxane.
8. The cellulose and/or synthetic fibre-based support as recited in
claim 1, wherein said organic molecule represents between 0.1 and
20% by weight of the water-soluble polymer, preferably 1%.
9. The cellulose and/or synthetic fibre-based support as recited in
claim 1, wherein the functionalized water-soluble polymer accounts
for at least 1% by weight of the layer coated onto the fibre-based
support, advantageously between 20 and 100%.
10. The cellulose and/or synthetic fibre-based support as recited
in claim 1, wherein the layer coated onto the fibre-based support
is deposited in a quantity of 0.2 to 20 g/m.sup.2, preferably 1
g/m.sup.2.
11. The cellulose and/or synthetic fibre-based support as recited
in claim 1, wherein the weight of the fibres ranges from 30 to 160
g/m.sup.2, advantageously from 55 to 140 g/m.sup.2, and preferably
in the order of 58 g/m.sup.2.
12. A method for producing a cellulose and/or synthetic fibre-based
support as recited in claim 1, comprising the following steps:
formation of a cellulose and/or synthetic fibre-based sheet with or
without a parchementizing process; functionalization of a least one
water-soluble polymer comprising hydroxyl or primary-secondary
amino functional groups by grafting at least one organic molecule
comprising at least one epoxy group and at least one R.sup.1
functional group wherein R.sup.1 can be chosen from a vinyl group,
or at least one --Si(R.sup.2).sub.3 functional group and wherein
R.sup.2.dbd.hydrogen atom, hydroxyl, alkoxy, alkyl, and
combinations thereof; coating the cellulose and/or synthetic
fibre-based support with at least one functionalized water-soluble
polymer; calendering or supercalendering of the support if
required.
13. The method as recited in claim 11, wherein the organic molecule
is prepared from a chloro-hydrin precursor.
14. The method as recited in claim 11, wherein the water-soluble
polymer is functionalized at a temperature between 20 and
95.degree. C., preferably between 80 and 95.degree. C., in an
aqueous medium and eventually in the presence of an organic or
inorganic acid or base.
15. The method as recited in claim 11, wherein the coating
techniques include size-press, metering-size-press, foulard
coating, rod coating, "Champion" bar coating, "Meyer" bar coating,
air-knife coating, gravure coating, scraper blade coating, sliding
blade coating, single- and multilayer curtain coating, reverse roll
coating, spray coating, atomisation coating, liquid application
system (LAS) coating, kiss coating, foam coating, and any surface
coating application process.
16. The method as recited in claim 11, wherein the coating of the
cellulose and/or synthetic fibre-based support is carried out at a
temperature between 20 and 95.degree. C., preferably between at 50
and 70.degree. C.
17. Use of the cellulose and/or synthetic fibre-based support as
recited in claim 1 for siliconization.
Description
[0001] This application is a Continuation-In-Part of application
Ser. No. 13/060,223, filed Feb. 22, 2011, the entire content of
which is hereby incorporated by reference in this application
FIELD OF THE INVENTION
[0002] The invention relates to a novel functionalized support
based on cellulose and/or synthetic fibres, and to the production
method thereof
[0003] One of the main areas of application of the present
invention relates to supports that are intended for siliconizing
for all self-adhesive products, such as pressure sensitive labels
or adhesive tape, for the envelope industry, weight/price
equipment, feminine hygiene products or graphic applications, for
vegetable parchment and greaseproof products representing a
non-limiting selection of applications.
SURVEY OF THE RELATED ART
[0004] Supports that are to be siliconized must possess certain
properties which are defined in advance according to the final
application for which they are intended. For instance, in release
liner which is one of the most important applications, one or two
sides of the support are coated with a silicone film i.e. a release
agent. The release agent provides a release effect regarding any
type of sticky materials such as an adhesive, a mastic or dietary
pasty (pizza dough for instance). Thus, once they have been
siliconized, such supports must guarantee two primary
functionalities: they must protect the self-adhesive products
before they are used and they must be capable of a perfect adhesive
transfer upon removal.
[0005] These supports generally consist of a cellulose and/or
synthetic fibre based substrate coated with a layer of
water-soluble binding agents, latexes and pigments. They can be
produced by many techniques including coating, size-press or
metering-size-press. One skilled in the art is quite familiar with
these coating methods which can also be followed by a calendering
or supercalendering step.
[0006] The main properties required when manufacturing such
cellulose and/or synthetic fibre fibre-based supports include
mechanical strength, silicone anchorage, silicone hold-out and
transparency.
[0007] Depending on the market that is particularly being targeted,
more or less emphasis may be placed on the transparency of the
support. For example, the weight/price market requires supports
that are more transparent than the market for envelopes.
[0008] The silicone hold-out must provide a good surface coverage
and must afford a uniform protection. This objective is generally
achieved with a quantity of silicone in the range of 0.5 to 2
g/m.sup.2. It is important to limit the quantity of silicone
applied without loss of its coverage capabilities, in order to
avoid uneconomical wastages of silicone and consequent additional
costs. Actually, the silicone price has a significant impact on the
total cost of the final products due to the relative high price of
the silicone formulation as raw material. Moreover, the catalyst
used in the cross-linking reaction of silicone accounts for a large
part of the overall cost of the silicone formulation. For instance,
in the most part of silicone systems, the platinum that is used as
catalyst cannot be recovered after completion of the reaction.
[0009] The cost and the reactivity of the silicones require that
the support, on which they are applied, fulfils a certain number of
criteria. First of all, the chemical structure of the support must
not prevent the silicone system from cross-linking; i.e.--in the
case of the platinum based silicone systems--the polyaddition
reaction between the vinylic functional groups of the silicone
resin and the hydrogen siloxane functional groups of the silicone
cross-linking agent should not be impacted. In other words, the
support must not inibit the crosslinking reaction of the silicone.
Next, the support has to provide a perfect anchorage of the
silicone to the surface thereof. Furthermore, considering the high
cost of silicone, it is important that the amount of silicone
deposited on the support is as low as possible. To do this, the
support has to form a barrier and thus limit as much as possilbe
the penetration of the silicone inside the support. Likewise, the
surface of the support has to be as regular and as smooth as
possible in order to permit a homogenous application of the
silicone.
[0010] In other words, the first problem concerns the development
of a support that allows simultaneously an efficient anchorage and
an optimal cross-linking of the silicone while still reducing as
much as possible the silicone penetration inside the support. The
siliconizing step does not only depend on the support but also on
the silicone and the cross-linking agent used. The siliconizing
methods are defined according to the silicone cross-linking mode,
and these are divided into two categories, the first being
silicones that are cross-linked under UV radiation or electron
beams, and the second being "thermal cross-linking" silicones.
Since the first category is less exploitable from both the
technical and financial points of view, thermally cross-linked
silicones account for the larger market.
[0011] Silicones are thermally cross-linked by passing the support,
coated in silicone beforehand, through a kiln. The kiln temperature
must be such that the surface of the support reaches the
temperature at which the silicone cross-linking reaction takes
place. In order to enable the cross-linking reaction at a lower
temperature, special silicones have been developed. They are
referred to as "LTC silicones" (low temperature curing). Recently,
new silicone systems have been commercialized: fast curing silicone
systems, the peculiarity of such a type of silicones is the fact
that the cross-linking reaction takes place properly in the
presence of a lower amount of catalyst (i.e.: Platinum). In the
field of self-adhesives, the term of "curing" refers to the
cross-linking reaction of silicone. The temperatures at which
cross-linking occurs with LTC silicones ranges from 60 to
100.degree. C. rather than 110 to 150.degree. C. for conventional
silicones. However, up to now the main disadvantage of using LTC
silicones has concerned the fact that the cross-linked silicone
presented a very poor anchorage on the support. This anchorage
deficiency of LTC silicones therefore limits their use on a large
industrial scale.
[0012] In the case of release liner applications, there are four
main types of support that can be siliconized, these being "coated"
papers, vegetable parchment, glassine and greaseproof paper.
[0013] "Coated" papers, so called CCK (Clay Coated Kraft), are
obtained by depositing on a cellulose and/or synthetic fibre-based
support at least one coated layer of a mixture containing pigments
(clay, calcium carbonate for example) and binders (starch,
polyvinyl alcohol, latex). In order to obtain a satisfactory
silicone hold-out, the coated layer is applied in a quantity of 5
to 20 g/m.sup.2. The coated support is then calendered. In general,
coated papers are designed particularly for applications related to
envelopes, office labels, hygiene, and graphic applications.
[0014] Vegetable parchment paper is a paper made by passing a
waterleaf sheet (unsized paper with a low water resistance), made
from chemical wood pulp through a bath of sulfuric acid, or (at
times) zinc chloride, under established conditions of time,
temperature, and the like. The treated paper is then washed
thoroughly so as to remove the acid or zinc salt, after which it is
dried. The chemicals partially dissolve or gelatinize the cellulose
structure of the paper, which is then regenerated when the chemical
is diluted by the washing. This forms a very tough, stiff paper
with an appearance somewhat like that of a genuine parchment.
Because paper treated in this manner has a tendency to become
brittle and to wrinkle upon drying, it is frequently treated with a
plasticizing agent, usually glycerine or glucose.
[0015] Such vegetable parchment can be then coated with silicone
(generally water based silicone system), either on one side, or on
both side. Silicone coating can occur either on the parchmentizing
line, or on an off-line coater, to produce vegetable parchment for
release applications. Due to the fact that such a tipe of paper is
resistant against heat and since other substances do not stick onto
it, this paper can be used in a variety of applications in packing,
storage and restoration, in composite industry, in dry mounting
presses, and as slip sheets for printing.
[0016] Glassine is a more refined support than clay coated paper.
The process by which it is manufactured differs also in the method
used to form the coating. In fact, the film is formed in a
size-press or metering size-press coating process and in the final
step calendering is replaced by supercalendering. As a result, the
product obtained is denser. It also has greater mechanical
resistance and transparency than clay coated paper. Glassine is
less dimensionally stable than clay coated paper. The mixture used
to coat the cellulose support is composed primarily of
water-soluble binders having a film-forming nature (such as starch,
polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC)), and
often of a viscosifying agent and some additives. The weight of the
coating is in the order of 0.5 to 2 g/m.sup.2 on each surfaces.
[0017] Greaseproof paper is similar to glassine in term of machine
process, except that the silicone layer may be applied on paper
machine using water based emulsions of silicone. The final
applications of such a type of paper include packing, storage and
restoration.
[0018] The technical problems encountered in the prior art and in
the research are mainly associated with the improvement in the
anchorage of the silicone on the support, in avoiding the
inhibition of the cross-linking reaction of silicone and in
reducing the quantities of silicone and catalyst (i.e.: Platinum)
applied on the support for relevant reasons concerning the cost
saving.
[0019] In the past, any changes to the siliconizing method, in
particular by reducing the quantity of the catalyst used or by use
of LTC and fast curing silicones in large amounts, have resulted in
difficulties regarding the anchorage of silicone. Actually, it has
been observed that the main limitating step for improvement in the
siliconizing process concerns the poor anchorage of the silicone on
the substrate. Recently, the producers of substrates to be
siliconized, tried to solve the anchorage problems by focusing
their research in the production of supports able to interact or
react with the silicone system; in other words, they tried to
convert the fibre support from an inert substrate to an "active" or
"reactive" substrate for the silicone.
[0020] In order to "activate" the substrate regarding silicone,
researchers tried to apply onto the substrate the functional groups
involved in the cross-linking reaction of silicone: vinyl, silicone
hidryde and silanol functionalities.
[0021] Thanks to this approach, the silicone should be able to
react not only with itself but with the substrate as well, giving
the anchorage to the substrate. It has been demonstrated that this
approach should work but this concept came up against difficulties
in the production of "activated" substrates and products with such
a type of characteristics are not yet available on the market.
[0022] Document WO2005/071161 describes a glassine that is coated
with standard coating formulations. This cellulose-based support is
then functionalized by grafting directly onto it an organic
molecule containing a vinylic function and an acid halide function.
The hydroxyl functionalities of the substrate react with the acid
halide function of the organic molecule to create covalent bonds
between them. The chain-terminal vinylic function enables good
anchorage and excellent cross-linking of the silicone due to the
formation of covalent bonds between the support and the silicone.
This siliconizing step of this glassine may also be performed with
LTC silicones. The results obtained demonstrate an improvement of
the anchorage of silicone on the support.
[0023] The grafting reaction reported in document WO2005/071161 can
be performed either in an organic solvent process or by applying
directly the pure reactant onto the substrate. However, the
grafting cannot be carried out in a water based process due to the
fact that such a type of organic molecules are very sensitive to
water. Actually, the acid halide function (used as reactive
function for the grafting reaction) reacts with water to form
chemicals that do not react with the substrate. As a result, such a
type of organic molecules cannot be used in conventional
water-based coating of substrates.
[0024] Another drawback concerns the production of acids
(hydrochloric acid, hydrobromic acid, etc.) as by-products during
the grafting reaction. The formation of volatile and strong acids
during the process causes serious problems regarding the safety of
the employees, the enviromental system and problems of corrosion of
the industrial machines.
[0025] Although using an organic solvent based process to apply the
grafting molecule on the substrate could solve the problems related
to the inhibition of the grafting molecule, this approach would
significantly increase the problematic aspects related to safety,
environmental and corrosive issues.
[0026] On the other hand, the coating of the pure grafting molecule
directly onto the substrate could solve the problems of inhibition
of the reactant, but in this case as well, the man in the art is
facing safety and corrosive issues. Moreover, up to now, the
technology to apply very low amount of such organic molecules on an
industial machine has been missing.
[0027] Document WO2009/147283 describes a glassine that has been
coated with a modified compound i.e. a functionalized polymer. In
this case, the functionalization is carried out off-line from the
industrial machine and the functionalized compound is applied by
coating. The functionalization of the compound is carried out by
using one of the following grafting functionalities: halogenic
alkene, carboxylic acid, acid chloride, acid anhydride or acid
ester. Even though the functionalized polymers could be applied
onto the substrate by using a water-based process, the grafting
reactions cannot be performed in water as solvent.
[0028] In fact, in the case of halogeno alkenes or acid chloride as
reactive functional groups, they readly react with water to afford
functional groups that do not react with the polymer. Another
drawback is the production of hydrochloric acid as a by-product
during the grafting reaction.
[0029] In the case of carboxylic acids, acid anhydride or acid
ester as reactive functional groups, the reaction of a chemical
containing one of these functional groups with the polymer would
lead to the formation of a molecule of water. Howoever, it is well
known in organic chemistry that such a type of reactions are
reversible and give a chemical equilibrium between reactants and
products. If the solvent is water, the equilibrium is mainly
shifted to the direction of the reactants (Le Chatelier's
principle). As a result, in water, this reaction does not occur or,
if it occurs, it affords a very low yield of reaction.
[0030] Although the grafting technology reported in these prior art
documents are carried out in organic solvents (anhydrous organic
solvents in the case of halogenic alkene or acid chloride as
reactive functional groups), the use of organic solvents for the
grafting reaction presents several disadvantages. In fact, in
addition to safety and environmental issues, the cost of the
organic solvent based grafting technology is very high due to the
multi-steps process required. In particular, the polymer has first
to be solubilized in the organic solvent, the solvent is then
evaporated at the end of the reaction. The modified polymer can
also be precipitated with a non-solvent, the solvent being purified
or substituted for the next step, and the obtained grafted polymer
solubilized again in water to be then coated on the industrial
machine. Such a type of multi-steps process makes the technology
not competitive in comparison with the possible benefits in
performances of the final product for the silicone.
[0031] The problems that the present invention intends to solve
relate to an improved support that does not suffer from the
drawbacks described in the preceding.
BRIEF DESCRIPTION OF THE INVENTION
[0032] The present invention suggests to carry out the grafting of
the polymer in water as solvent, and then to coat the
functionalized polymers onto the cellulose and/or synthetic fibre
substrate by using a water based coating solution. Thanks to the
chemistry related to the present invention, the reaction of polymer
grafting is carried out in a water based process as well, before
the coating on the support. In the present invention, the organic
molecule used comprises an epoxy function, optionally in the form
of a chloro-hydrin, as reactive functional group for the polymer
grafting. In addition to the epoxy functionality, the organic
molecule comprises at least one vinylic or one silicone hydride or
one silanol functional group. The linkage between the water soluble
polymer and the organic molecule depends on the polymer involved in
the reaction. The reaction does not form water as by-product of the
reaction and it is performed in water as solvent with a high yield
of reaction.
[0033] The water soluble polymer functionalized with the method
reported in the present invention is then coated onto a support
based on the cellulose and/or synthetic fibre substrates, using any
kind of surface treatment in the industry.
[0034] As soon as the functionalized water soluble polymer is
applied onto the substrate, vinylic or silicone hydride or silanol
functionalities are present on the surface of the substrate. The
presence of the vinylic function or silicone hydride or silanol
functionality enables the silicone to react with the substrate in
the siliconizing stage generating covalent bounds between the
silicone layer and the substrate. Thanks to the covalent boundings
the adhesion of the silicone layer is significantly improved and no
inhibition of the silicone cross-linking has been observed.
[0035] The present invention provides to the substrate to be
siliconized several improved characteristics obtained by using a
safety, environmental friendly and cheap process; representing a
significant contribution to the search for sustainable technical
and industrial solutions.
[0036] The present invention provides a new approach which improves
cellulose and/or synthetic fibre-based supports that are intended
to be covered with a silicone film. Thanks to the present
invention, the fibre-based support is improved by using a complete
process that can be solely water based. In fact, a water soluble
polymer is modified by a chemical reaction using water as solvent.
The resulting grafted water soluble polymer is then coated on a
substrate by using any water based methods known to one skilled in
coating processes.
[0037] The resulting products exhibit an improved cross-linking of
the silicone and an enhanced anchorage of the silicone on the
substrate as compared to the prior art supports. The improvement of
the cross-linking of silicone and the enhancement in silicone
anchorage, enables the possibility to reduce the amount of catalyst
to be used in the silicone formulation (i.e.: Platinum), to
maintain the silicone adhesion properties when the product is
subject to severe humid conditions, and also to reduce the curing
time of the silicone during the siliconization step (i.e.: it gives
the possibility to increase the speed of the siliconizing machines
without any arrangements of the industrial machines).
[0038] More precisely, the subject matter of the invention concerns
a cellulose and/or synthetic fibre-based support of which at least
one surface is coated with a layer containing at least one
water-soluble polymer comprising hydroxyl or primary-secondary
amino functional groups, at least some of which have been
functionalized beforehand with at least one organic compound;
[0039] wherein said organic compound contains: [0040] at least one
epoxy functional group, and [0041] at least one R.sup.1 group
wherein R.sup.1 is a vinyl functional (CH.sub.2.dbd.CH--) group or
at least one --Si(R.sup.2).sub.3 functional group and wherein
R.sup.2.dbd.hydrogen atom, hydroxyl, alkoxy, alkyl, and
combinations thereof
[0042] As already said, in the support according to the present
invention, the hydroxyl and/or primary-secondary amino functional
groups of the water-soluble polymer have been functionalized
beforehand with at least one organic compound.
[0043] In a preferred embodiment, the epoxy functional group of
said organic compound corresponds to a saturated three-membered
cyclic ether.
[0044] The term cellulose fibre-based support is understood to mean
a support that contains cellulose fibres that have been more or
less adapted in proportions ranging from 50 to 99% by weight for
purposes of their desired characteristics (density, transparency,
mechanical properties).
[0045] The term synthetic fibre-based support, commonly called
nonwoven, is understood to mean as a sheet or web structures bonded
together by entangling fibre or filaments by a mechanical, thermal
or chemical process. Nonwovens are flat, porous sheets that are
made directly from separate fibres (wetlaid process) or from molten
plastic particles (spundbound, meltblown or electrospinning
processes). Typical fibres used in the production of nonwovens are
made of: polyester (for example: polyethylene terephthalate,
polybutylene terephthalate, polylactic acid), polyolefines (for
example: polypropylene, polyethylene), polyamides (for example:
nylon 6, 6-6, 12, 6-12), polyphenylene sulfide, polycarbonate,
viscose and fibreglass.
[0046] Substrates of cellulosic and synthetic fibres can be
produced and adapted in relative proportions ranging from 1 to 99%
by weight for purposes of their desired characteristics. For
instance, some applications may involve or require the addition of
small amounts of synthetic fibres to the cellulose as a
reinforcement material.
[0047] In a particular embodiment, the support is a cellulose
fibre-based support.
[0048] The coating layer that contains the functionalized water
soluble polymer is designed to afford silicone barrier properties
to the surface of the fibre-based support.
[0049] When the water soluble polymer contains hydroxyl functional
groups, the linkage between the polymer and the organic molecule is
made through an ether bond with a hydroxyl functionality in
position 2 (i.e.: 2-hydroxyether) (as in FIG. 1).
[0050] When the water soluble polymer contains primary or secondary
amino functional groups, the linkage between the polymer and the
organic molecule is an alkylated amine (secondary or tertiary
amine) with a hydroxyl function in position 2 (i.e.:
2-hydroxyamine) (as in FIG. 2). In a particular embodiment, the
water soluble polymer may comprise both hydroxyl and
primary-secondary amino functional groups (i.e.: chitosan).
[0051] In both cases (OH and NH/NH.sub.2 containing polymers), the
chemical reaction involved is an alkylation reaction where no other
by-products are produced during the reaction (i.e.: water is not
produced).
[0052] Additionaly, the coating layer comprising the water-soluble
polymer may contain at least one functionalized water-soluble
polymer and at least one water soluble polymer that has not been
functionalized. As a result, functionalized and unfunctionalized
hydroxyl or amino functional groups may be contained in the same
water-soluble polymer, or they may be contained in a mixture of a
least two water-soluble polymers comprising different hydroxyl or
amino functional groups.
[0053] Furthermore, the coating layer that contains the
functionalized water-soluble polymer may also contain other
water-soluble binders, conventional additives, pigments and
latexes. Depending on the nature of the water soluble polymer, a
suitable crosslinker can be advantageously added in the formulation
in order to render the polymer water insoluble after the
application of the polymer on the substrate and the drying of the
product. In fact, once the coated support is dried, the water
soluble polymer can become water insoluble due to its
cross-linking. The skilled man in the art knows that the
hydrosoluble properties of a polymer can be affected when a
crosslinker is added.
[0054] Interestingly, when the organic molecule is not water
soluble, the grafting reaction can still occur in water. In fact,
by vigorous stirring, it is possible to create an emulsion of the
organic molecule in the water solution and the grafting reaction
occurs even if the polymer and the reactant are not in the same
phase.
[0055] In a preferred embodiment of the invention, the
water-soluble polymer containing hydroxyl functional groups can
advantageously be chosen from the group comprising natural and
modified polysaccharides such as starch; CMC (carboxymethyl
cellulose); alginate; chitosan, pectine, chtin, glycogen,
arabinoxylane, cellulose and synthetic polymers such as poly(vinyl
alcohol); hydrolysed or partially hydrolysed copolymers of vinyl
acetate, which may be obtained for example by hydrolysing
ethylene--vinyl acetate (EVA) or vinyl chloride--vinyl acetate,
N-vinyl pyrrolidone--vinyl acetate, and maleic anhydride--vinyl
acetate copolymers.
[0056] In a preferred embodiment, the water-soluble polymer
containing hydroxyl functional groups is advantageously starch.
[0057] In another preferred embodiment, the water-soluble polymer
containing hydroxyl functional groups is advantageously PVA.
[0058] In a preferred embodiment of the invention, the
water-soluble polymer containing primary-secondary amino functional
groups can advantageously be chosen from the group comprising
polyethyleneimine; polyallylamine; chitosan; polyacrylamide;
partially or totally hydrolized polyacrylamide; parlially or
totally hydrolized polyvinylamine, polyamines based on
amino-ethyl-piperazine; and in general big molecules containing
aliphatic or aromatic polyamino functional groups as for example
spermidine, spermine, diethylenetriamine, triethylenetetramine and
tetraethylenepentamine. This water-soluble polymer containing amino
functionalities is advantageously polyethyleneimine, polyallylamine
and parlially or totally hydrolized polyvinylamine.
[0059] Typically, the water soluble polymers that are grafted
correspond to a molecule containing at least one element from the
group of C, H, N, O, non-metals such as the halogens, Si, S, P,
metals such as Na, Li, K, Mg, Pb, etc.
[0060] The molecular weight of the water soluble polymer comprising
primary-secondary amino or hydroxyl functional groups preferably
ranges from 1,000 to 1,000,000 a.m.u, advantageously from 50,000 to
150,000 a.m.u.
[0061] As already stated, the organic molecule enabling the
grafting of the water soluble polymers contains at least one epoxy
functionality (--CH--O--CH.sub.2) as well as at least one
functional group among vinylic (--CH.dbd.CH.sub.2), silicone
hydride (Si--H), and silanol (Si--OH) groups. The epoxy group
enables the organic molecule to be grafted onto the water-soluble
polymer containing hydroxyl or primary-secondary amino functions by
an alkylation reaction.
[0062] In the grafting reaction reported in the present invention,
the organic molecule can contain, in addition to the epoxy
functional group, silanol groups (Si--OH) that are able to react
with silicone after siliconizing. It is familiar to one skilled in
the art that the silanol functionality can be formed from the
hydrolysis of alkoxylated silanols (Si--O--R*, where R* can be a
methyl, ethyl, propyl, isopropyl, butyl, isobutyl etc.
functyonality). The reaction concerns hydrolysis of alkoxylated
silanols in water;
[0063] which can be catalysed in acid or basic pH. This reaction
leads to the formation of by products such as alcohols (methanol,
ethanol, propanol, isopropanol, butanol, isobutanol etc.). Organic
molecules comrprising silanol groups resulting from the in situ
hydrolysis of alkoxylated silanol groups (Si--OR*) exhibit the same
reactivity as organic molecules comprising silanol groups (Si--OH)
that therefore do not require any in situ hydrolysis. However, over
time, alkoxylated silanols are more stable than silanols, and
therefore provide a more convenient raw material reactant for the
grafting reaction of the water soluble polymer.
[0064] With regards to the polymer grafting reaction involving an
alkylation, carrying out the reaction in basic or acidic
condictions can catalyze the alkylation. In fact, aqueous acidic
conditions can enhance the activatation of the oxygen atom of the
epoxy group while basic conditions can enhance the activatation of
the nucleophile that reacts with the epoxy group. Basic pH
conditions are usually preferred to the acid conditions since it
decreases the eventual formation of side-products (such as
dialcohols resulting from the reaction of the epoxy group with
water and subsequent inactivation of the organic molecule for the
grafting reaction). Moreover, basic pH conditions are preferred due
to the nature of some base polymers, such as polysaccharides, which
are more stable in basic conditions compared to acid conditions. In
fact, in acid pH conditions, polysaccharides can undergo hydrolysis
reaction and therefore exhibit different polymer properties, or be
definitely damaged.
[0065] After the grafting reaction of the water soluble polymer
with the organic molecule, such a functionalized water soluble
polymer can then be coated onto the fibre-based support using any
kind of surface treatment from the coating technology. The coating
layer is layed down onto the fibre-based support, thereby
producing, in a single and rapid step on the industrial machine, a
support exhibiting the desired functionality and a barrier between
the silicone and the support.
[0066] Therefore, the product produced by the described process
presents at the web surface vinylic or silicone hydride or silanol
functionalities which enable a better anchorage of the silicone
during the subsequent siliconizing step.
[0067] For the sake of simplicity, the water-soluble polymer
containing hydroxyl or primary-secondary amino functionalities will
be referred to by the abbreviation "PH" in the following. The terms
"functionalized PH" will be used to denote the products of the
reaction between PH and the organic molecule described in the
preceding.
[0068] The formula of the organic molecule selected to
functionalize the water-soluble polymer containing hydroxyl or
primary-secondary amino functionalities is advantageously one of
the following:
H.sub.2C--O--CH--(R)--CH.dbd.CH.sub.2
H.sub.2C--O--CH--(R)--Si--(R.sup.2).sub.3
[0069] wherein R=linear, branched and/or cyclic carbon
--(C).sub.x-- chain or a polydimethylsiloxane chain
(--O--Si(CH.sub.3).sub.2--).sub.y or the combination of the two
(--C--).sub.z--(--O--Si(CH.sub.3).sub.2--).sub.j chains that may
also contains heteroatoms (X) as part of the chain structure
--C--X--C-- or as side group of the chain structure --C(X)--;
[0070] and wherein R.sup.2=hydroxyl (--OH); hydrogen atom (H);
alkyl; alkoxy such as for example methoxy (--O--CH.sub.3), ethoxy
(--O--CH.sub.2--CH.sub.3), propyoxy
(--O--CH.sub.2--CH.sub.2--CH.sub.3)); and combinations thereof.
[0071] In a preferred embodiment, x is comprised between 1 and 25,
and more advantageously between 5 and 12.
[0072] In a preferred embodiment, y is comprised between 1 and 15,
and more advantageously between 1 and 8.
[0073] In a preferred embodiment, z is comprised between 1 and 15,
and more advantageously between 1 and 8.
[0074] In a preferred embodiment, j is comprised between 1 and 15,
and more advantageously between 1 and 8.
[0075] In the two formulae above, "C--O--C" represents a saturated
three-membered cyclic ether.
[0076] In a preferred embodiment, the --Si(R.sup.2).sub.3 group can
be chosen from the group comprising --Si(OH).sub.3,
--Si(OH).sub.2(CH.sub.3), --Si(OH)(CH.sub.3).sub.2,
--Si(H)(CH.sub.3).sub.2, --Si(H).sub.2(CH.sub.3), --SiH.sub.3,
--Si(O R.sup.3).sub.3, --Si(O R.sup.3).sub.2(CH.sub.3), --Si(O
R.sup.3)(CH.sub.3).sub.2, wherein R.sup.3 are groups chosen from
--CH.sub.3, --CH.sub.2--CH.sub.3, --(CH.sub.2).sub.2--CH.sub.3,
--CH(CH.sub.3).sub.2, --(CH.sub.2).sub.3--CH.sub.3,
--CH.sub.2--CH(CH.sub.3).sub.2, --(CH.sub.2).sub.4--CH.sub.3,
--(CH.sub.2).sub.2--CH(CH.sub.3).sub.2, --C.sub.6H.sub.6 and
combinations thereof
[0077] In a preferred embodiment of the invention, the organic
molecules used for the grafting reaction of the water soluble
polymer can be prefererably one of the following compounds:
2-vinyloxyrane, 1,2-epoxy-4-pentene 1,2-epoxy-5-hexene,
1,2-epoxy-6-heptene, 1,2-epoxy-7-octene, 1,2-epoxy-8-nonene,
1,2-epoxy-9-decene, 1,2-epoxy-10-undecene, 1
-allyloxy-2,3-epoxypropane, 1-allyloxy-3,4-epoxybutane,
1-allyloxy-2,3-epoxypentane, 1-allyloxy-2,3-epoxyhexane,
1-allyloxy-2,3-epoxyheptane, 1-allyloxy-2,3-epoxyoctane,
1-allyloxy-2,3-epoxynonane, 1-allyloxy-2,3-epoxydecane,
1-allyloxy-2,3-epoxyundecane, glycidoxypropyl trimethoxysilane,
glycidoxypropyl triethoxysilane, glycidoxypropyl trisiloxane.
[0078] Said organic molecule is advantageously 1,2-epoxy-9-decene
or 1-allyloxy-2,3-epoxypropane.
[0079] In a preferred embodiment, said organic molecule represents
between 0.1% and 20% by weight of the weight of the PH, more
advantageously between 0.1% and 10% and even more advantageously
between 0.1% and 5%. Even more advantageously, the organic molecule
represents 1% by weight of the weight of the PH. The control of the
grafting rate thus enables the silicone anchorage to be controlled
afterwards, and this is assisted by the presence of the vinylic or
silicone hydride or silanol functionality.
[0080] The functionalized PH preferably accounts for at least 1% by
weight of the layer coated onto the cellulose and/or synthetic
fibre-based support, advantageously at least 5%, and even more
advantageously between 20 and 100%.
[0081] The cellulose layer that forms the support according to the
invention typically exhibits a weight ranging from 30 to 160
g/m.sup.2, preferably from 55 to 140 g/m.sup.2, and most
advantageously in the order of 58 g/m.sup.2. In a particular
embodiment, the weight of the support corresponds to the weight of
the fibres. At least one surface of this support is coated with the
described coating layer in a quantity of 0.2 to 20 g/m.sup.2,
preferably 1 g/m.sup.2.
[0082] The support according to the present invention may be
prepared by the following method: [0083] formation of a cellulose
and/or synthetic fibre-based sheet; with or without a
parchementizing process. [0084] functionalization of at least one
water soluble polymer comprising hydroxyl or primary-secondary
amino functional groups, by grafting at least one organic molecule
comprising at least one epoxy group and at least one R.sup.1
functional group wherein R.sup.1 can be chosen from a vinyl group,
or at least one --Si(R.sup.2).sub.3 functional group and wherein
R.sup.2=hydrogen atom, hydroxyl, alkoxy, alkyl, and combinations
thereof. Said organic molecule is able to form covalent bonds with
the hydroxyl or primary-secondary amino functional groups of the
PH. [0085] coating the cellulose and/or synthetic fibre support, by
methods known to one skilled in the art, with at least one
functionalized PH; this step will advantageously be carried out at
a temperature between 20 and 95.degree. C., preferably between 50
and 70.degree. C. [0086] calendering or supercalendering the
support if required.
[0087] In a particular embodiment of the invention, a chloro-hydrin
compound can be used as precursor of the organic molecule. Indeed,
the chloro-hydrin compound reacts in basic conditions to form an
epoxy compound. The water soluble polymer is therefore still
grafted with a molecule containing an epoxy functional group. The
conversion from the chloro-hydrin functional group to the epoxy
group can be carried out before or during the grafting
reaction.
[0088] Still according to this particular embodiment, an organic
molecule comprising an epoxy group can be obtained from a compound
containing a chloro-hydrin group, in aqueous alkaline conditions.
In fact, the chloro-hydrin easily reacts with water in alkaline
conditions. However, it can be converted to epoxy and therefore be
"activated" by a pre-chemical reaction. The chloridric acid which
is a by-product of this pre-reaction and it can be converted to a
salt (for example sodium chloride, thanks to the alkaline
conditions obtained by the addition of sodium hydroxide). The
organic molecule comprising an epoxy group and obtained from the
chloro-hydrin precursor exhibits the same reactivity as an organic
molecule comprising an epoxy group that does need to be
pre-activated. The chloro-hydrin precursor can be advantageous in
that it is more chemically stable over time and it exhibits lower
toxicity as compared to epoxy compounds.
[0089] According to a preferred method, the PH is functionalized at
a temperature between 20 and 95.degree. C., preferably between 80
and 95.degree. C., in aqueous phase, and eventually in the presence
of an organic or an inorganic acid or base as catalyst. In fact,
adding an organic or an inorganic acid or base may be necessary
when the PH is not already acidic or basic.
[0090] Coating techniques known to one skilled in the art further
include size-press, metering-size-press, foulard coating, rod
coating, "Champion" bar coating, "Meyer" bar coating, air-knife
coating, gravure coating, scraper blade coating, sliding blade
coating, single- and multilayer curtain coating, reverse roll
coating, spray coating, atomisation coating, liquid application
system (LAS) coating, kiss coating, foam coating, and any surface
coating application process.
[0091] The present invention relates as well to a cellulose and/or
synthetic fibre-based support of which at least one surface is
coated with a layer containing at least one water-soluble polymer
comprising hydroxyl or primary-secondary amino functional groups,
at least some of which have been functionalized beforehand or after
the step of coating with at least one organic compound. Said
organic compound contains: [0092] at least one epoxy functional
group, and [0093] at least one R.sup.1 group wherein R.sup.1 is a
vinyl group or at least one Si--(R.sup.2).sub.3 functional group
and wherein R.sup.2=hydrogen atom, hydroxyl, alkoxy, alkyl, and
combinations thereof.
[0094] Additionaly, the present invention concerns the process
associated to this support.
[0095] Generally, a cellulose and/or synthetic fibre-based support
according to the invention will be treated in a siliconizing step
for use in supports, for instance, for self-adhesive labels,
adhesive tapes and vegetable parchment for example. It will be
siliconized by any of the methods known to one skilled in the
art.
[0096] In general, the present invention consists in the
functionalization of a water soluble polymer containing amino or
hydroxyl functional groups with a molecule having an epoxy function
by using a water based process, and in applying the functionalized
polymer on a cellulose and/or synthetic fibre-based support by a
water based coating technique. The present invention is in contrast
to the prior art; which consisted in grafting a molecule directly
(or dissolved in organic solvents) onto the cellulosic support or
in the pre-grafting a molecule on a polymers using reactions in
organic solvents and then coating the resulting grafted polymers on
the cellulosic substrate.
EXEMPLARY EMBODIMENTS OF THE INVENTION
[0097] The invention itself and the advantages that it offers will
be explained in greater detail in the following description of
exemplary embodiments and with reference to the following
figures.
[0098] FIG. 1 represents the alkylation reaction, in an aqueous
medium at a basic or acid pH, between a water soluble polymer
containing hydroxyl functionalities and an organic molecule
comprising both an epoxy function and a functional group among, for
instance, Si--H, Si--OH, or vinyl. In this particular case, starch
is the water soluble polymer containing hydroxyl functionalities
while the molecule having an epoxy functionality refers to the
general formula: H.sub.2C--O--CH--(R)--R.sup.1.
[0099] FIG. 2 represents the alkylation reaction, in an aqueous
medium at a basic or acid pH, between a water soluble polymer
containing primary and/or secondary amino functionalities and an
organic molecule comprising both an epoxy function and a functional
group among, for instance, Si--H, Si--OH, or vinyl. In this
particular case, polyethyleneimine is the water soluble polymer
containing primary and secondary amino functionality while the
molecule having an epoxy functionality refers to the general
formula: H.sub.2C--O--CH--(R)--R.sup.1.
Examples
[0100] Method for Preparing the Glassine According to the
Invention:
[0101] A sheet consisting of 100% cellulose fibres is prepared by
methods known to one skilled in the art. The support used in the
examples is the commercial product Silca Classic Yellow 59
g/m.sup.2 (from Ahlstrom); for the production of the samples
described in the examples, the support has not been coated with the
standard formulation but with the formulations reported in the
examples 1 and 2. In the case of the standard paper, the commercial
grade Silca Classic Yellow has been used as such.
[0102] Off-line from the industrial machine, the water soluble
polymer containing primary-secondary amino or hydroxyl
functionalities is functionalized with an organic molecule by using
the methods of examples 1 and 2. After the functionalization
reaction, the polymer solution can be mixed with other products
commonly used in this application (for example: clays, pigments,
latexes, polymers and/or additives), diluted with water to the
desired solid content and sent to the industrial machine for the
coating step.
[0103] The mixture containing the functionalized water soluble
polymer is then applied to a surface of the support by coating (1
g/m.sup.2), preferably by metering-size-press.
[0104] The support is then dried, remoisturized, and
super-calandered.
Example 1
Functionalization Reaction of a Water Soluble Polymer Containing
Primary and/or Secondary Amino Functionalities and Preparation of
the Coating Pecipe
[0105] In the present example, polyethyleneimine is the polymer
containing primary and/or secondary amino functionalities since it
contains both functionalities on the same polymer structure.
[0106] The commercial polyethyleneimine Polymin P (from Basf) is
delivered as a water solution with a solid content of 50% w/w. In
order to decrease the viscosity of the solution, Polymin P is
diluted with water at a solid content of 20%. For the grafting
reaction, an amount of 2% w/w of pure 1,2-epoxy-9-decene (from
Sigma-Aldrich), compared to the weight of dry Polymin P, is slowly
added to the polymer solution under vigorous stirring. The organic
molecule 1,2-epoxy-9-decene is a liquid which is not soluble in
water, so a vortex is required to create an emulsion of
1,2-epoxy-9-decene in the polymer solution, forming a cloudy
solution. Due to the fact that Polymin P in solution already has a
pH between 11 and 13, the addition of a base in order to increase
the pH to catalyze the reaction is not required. The solution is
heated to 90.degree. C. and mainained at this temperature under
stirring for one hour. Subsequently, the pH of the solution is
neutralized by addition of a water solution of sulphuric acid.
Afterwards, 20% w/w of CMC and 5% w/w of glyoxal compared to the
weight of Polymin P are added to the solution. The solution is then
diluted with water to a final solid content of 8% w/w. Finally, the
solution is transfered to the coating apparatus for the coating
step. CMC is added in the coating formulation as a viscosity
modifier to improve the film forming properties and the water
retention of the coating formulation. Glyoxal is added as a
cross-linking agent for the coating formulation.
Example 2
Functionalization Reaction of a Water Soluble Polymer Containing
Hydroxyl Functionalities and Preparation of the Coating Recipe
[0107] In the present example, PVA, Celvol 20/99 (Celanese), is the
representative polymer containing hydroxyl functionalities. Celvol
20/99 is delivered as a powder. A dispersion of PVA is produced in
water by vigorous stirring. It is then heated up to 95.degree. C.
in order to completely dissolve PVA in water. A clear solution with
a solid content of 12% is obtained. A solution of sodium hydroxide
is added to the PVA solution in order to reach a pH value between
11 and 13. For the grafting reaction, an amount of 2.5% w/w of pure
1,2-epoxy-9-decene (from Sigma-Aldrich), compared to the weight of
dry Polymin P, is slowly added to the polymer solution under
vigorous stirring. The organic molecule 1,2-epoxy-9-decene is a
liquid which is not soluble in water, so a vortex is required to
create an emulsion of 1,2-epoxy-9-decene in the polymer solution,
forming a cloudy solution. The solution is heated to 90.degree. C.
and mainained at this temperature under stirring condition for
three hours. Subsequently, the pH of the solution is neutralized by
addition of a water solution of sulphuric acid. Afterwards, 10% w/w
of CMC and 5% w/w of glyoxal compared to the weight of PVA are
added to solution. The solution is then diluted with water to
afford a final solid content of 8% w/w. Finally, the solution is
transfered to the coating apparatus for the coating step.
Example 3
Silicone Anchorage of Low Temperature Curing (LTC) Silicone
Systems
[0108] Standard glassine (STD) and the glassine produced by the
methods reported in examples 1 (EX1) and 2 (EX2) have been
siliconized with LTC silicones. The silicone anchorage results have
been compared. In order to assess the silicone anchorage, a
standard test called rub-off test has been performed; this test is
an abrasion test in which a sample of siliconized paper, pressed
under a weight, is dragged on an abrasive textile. The silicone
layer at the surface of the sample can be removed by the rubbing.
By measuring the amout of silicone onto the samples before and
after the rubb-off test, it is possible to obtain a percentage of
silicone that remains on the samples. The rub-off percentage 0%
indicates that all the silicone has been removed from the sample,
very poor adhesion; the rubb-off percentage 100% indicates that all
the silicone remained on the sample, the adhesion is ideal. For the
release application, the rub-off value of 75% is commonly
considered as the bottom limit for silicone ancohorage. The
following silicone formulation has been used in this example:
[0109] LTC silicone formulation bath:
[0110] Polymer: D920 (from Wacker)--18.07 g
[0111] Cross-linking agent: XV 525 (from Wacker)--1.43 g
[0112] Catalyst: CO5 (i.e.: Platinum based from Wacker)--2.14 g
[0113] Deposit: 0.9 g/m.sup.2
[0114] Cross-linking for 30 seconds at 80.degree. C. in a
ventilated drying kiln
[0115] Table 1 shows that STD has a rub-off value of 18% (very poor
adhesion of the silicone), whereas EX1 and EX2 have respectively
rub-off values of 96% and 97% (both samples have very good adhesion
properties for LTC silicone systems). So, in the case of standard
glassine the LTC silicone cannot be used due to the poor adhesion
of the silicone system to the substrate; on the contrary, LTC
silicone systems can be used on glassine produced by the methods
reported in the present invention.
TABLE-US-00001 TABLE 1 Sample STD EX1 EX2 Rub-off value 18% 96%
97%
Example 4
Silicone Anchorage Dependence on the Amount of Catalyst (i.e.:
Platinum) in the Silicone Formulation
[0116] For thermal cured silicone systems used in release industry,
the catalyst used is an organometallic compound of platinum. Due to
the high price of platinum, there is a strong interest in reducing
its amount in the silicone formulation. The first problem observed
when a reduced amount of catalyst is used is a poor anchorage of
the silicone to the substrate.
[0117] Standard glassine (STD) and the glassine produced by the
methods reported in examples 1 (EX1) and 2 (EX2) have been
siliconized with a standard silicone formulation by using two
different amounts of catalyst in the silicone formulation, and the
silicone anchorage on different substrates has been tested. In
order to evaluate the silicone anchorage, the rub-off test
(described in example 3) has been performed. For the tests the
following silicone formulations have been used:
[0118] Standard silicone formulation bath:
[0119] Polymer: 11367 (from Bluestar)--50 g
[0120] Cross-linking agent: 12031 (from Bluestar)--2.9 g
[0121] Catalyst (60 ppm Platinum): 12070 (from Bluestar)--1.56 g;
or (30 ppm Platinum): 12070-0.78 g
[0122] Deposit: 0.9 g/m.sup.2
[0123] Cross-linking for 10 seconds at 160.degree. C. in ventilated
drying kiln
[0124] As it is possible to observe in table 2, an satisfactory
rate of silicone anchorage is obtained for all samples when the
silicone formulation contains 60 ppm of platinum. On the contrary,
when the amount of platinum is decreased to 30 ppm, the silicone
anchorage of samples EX1 and EX2 remains very good but the
anchorage of STD is poor.
TABLE-US-00002 TABLE 2 STD EX1 EX2 Rub-off 90% 95% 98% (60 ppm of
Platinum) Rub-off 54% 91% 93% (30 ppm of Platinum)
* * * * *