Note: Descriptions are shown in the official language in which they were submitted.
~ W094/04587` 2 1 12 ~ 7 ~ PCT/GB93/017~
Pol~mer ~roducts
.
~ his invention rela~es ~o polymer composl~ions
and` more particularly tO compositions for use in the
manufacture of transparent or reflective articles.
The use of polymer films for improving the Li~ht
transmission through or from transparent or reflective
articles is known. For exampLe, in U.S. Patent No.
a844983 there is descri~ed a glass or plastics
substrate which in use is susceptible to misting which
has on at least one surface an antimist coating of a
hydrophllic polyurethane which when hydrated contains
from 35 to 60% by weight ~ater and which has a
thickness o~ 3 ~m to 50 ~m., Whilst such coatings have
good antimist properties, they are not very scratch or
abrasion resistant. Moreover, the hydrophilic
polyurethanes have tO be employed as coatlngs since
they are not amenaible ~o fabrication as free-slanding
structures such as rilms or sheets.
In US-A-480012~ there are described scratch
resistant coatin~s for peroxide curable polyurethane
elastomers which comprise a polyfunc~ional monomer
having three or more acryloioxy groups per molecule and
at least one ~J-vlnyl imido group con~ain~ng monomer.
~he coatin~s are formed by first coatin~ the inside o~
21~2373
W094/04587 PCT/GB93/017
the mold for the polyurelhane with the
~cryloloxy-N-vinyi/imido group containing monomers,
~uring ~he in-mold coaling, ~as~ing the urethane
composi~ion into ~he mold and curing the urethane.
The surface characteristics of products formed by
this process are stated to include scratch resistance.
However, such coatings ào not confer antimist
properties to the surface.
The invenlion seeks to provide a polymer
composition which not only has the good antimist
properties of the ~nown hydrophilic polyurethane
materials but also has-good scratch and abrasion
resistance and is capable of being formed into free
standing structures sucn as films or sheets as well as
being useful for co~tin~ substrates such as those of
glass or plastic ~ateria~.
The presen~ Lnvenlion ~herefore provides a
composition of matt~r having antifog properties
comprising a hydr~philic polyurethane in admixture wlth
a compatible polymer.
By the term 'compa~ible' is meant that the
polymers will co-exist with the polyurethane componen~
wi~hou~ any phase separa~iQn ~hen the polyurethane and
2142373
.~ke~rnP~a 3
polymer components are admixed. Suitably such
polyurethane polymer mixtures will exhibit good light transmitting
properties.
The compatible polymers may be homopolymers or
copolymers or mixtures of such polymers. Aptly such polymers are
derived from monomers or oligomers having ethylenic unsaturation.
The composition of the invention may be formed by, for
example, drying mixtures of the polyurethane and other polymer
components from a solution thereof or by polymerising the
precursors for compatible polymer in the presence of the hydrophilic
polyurethane component, optionally in the presence of suitable
15 catalysts and/or polymerisation initiators. Suitable precursors include
monomers or oligomers which contain ethylenic saturation.
Thus in accordance with an embodiment of the present
invention there is provided a curable composition comprising a
20 hydrophilic polyurethane and a polymerisable compound containing
polyfunctional acrylic unsaturation
The polymerisable compound containing acryiic unsaturation
(hereinafter called 'acrylic component') may be oligomeric in nature.
25 The component may contain acrylate or methacrylate groups. Aptly
the acrylic component contains at least three acrylically unsaturated
groups. Favoured acrylic components are polyfunctional ether
acrylates, preferably containing at least three acryloloxy groups.
More favoured ether acrylates are penta or hexacrylates. Preferred
30 acrylic components for use in the present invention are
dipentaerithrytol penta- and hexacrylates pentaerithrytol triacrylate
and 1,6 hexane diol - diacrylate.
Suitable hardness and antimist properties may be achieved by
35 the use of less than 50% by weight of the acrylic component.
At~
21~12~7~
The compositions of the invention contain acrylic unsaturation
and are cured by cross-linking through the ethylenic bonds.
Accordingly, the compositions of the invention may desirably contain
initiators to promote cross-linking. The compositions may be cured
5 by radiation including thermal radiation, actinic, infra-red and ultra-
violet radiation and electron beam. Favoured compositions may
contain a photo-initiator reactive to U.V. Iight. Such initiators may be
present in the compositions of the invention or solutions thereof in
conventional amounts.
Ai/lE~JDED SHEET
W094/04587 2 1~ 2 3 7 ~ PCT/GB93/017~
_ 5 _
In addition to c~oss-Lin~Lng of the acrylic
component of the composition, ~he polyurethane
component may also contain ethylenic unsaturation which
may be cross-linkable. For example, the polyurethane
may be a urethane-acr~late bloc~ copolymer.
Oligomeric materials which contain unsaturation
and which are suitable ~or use in the present invention
include hexafunctional aliphatic or aromatic urethane
acrylates, difunctional aliphatic or aromatic urethane
acrylates, epoxy Novalac acrylates, polyester
tetra-acrylates and siloxane di-or hexa acrylates. A
less preferred but still useful component is methyl
methacrylate.
In accordance with another embodiment of the
invention the composition will comprise a mixture of a
hydrophilic polyurethane and a~ least one other
compatible polymer conlaining residues of a monomer
having vinyl unsaturation. Drecursors for compositions
of this type may comprise a mixture of the polyurethane
and =he compatible polymer in a single or mixture of
co-solvents. Suita~ly the compositions of the
invention are formed upon drylng precursor mixture and
evaporating the solvenl thererom.
W094/04587 2 ~ ~ 2 3 7 ~ PCT/GB93/017~ ~
-- 6 --
Apt polymer materials derived from vinyl or
e~hylenically unsa~urated precursors nerein after
referred to as the ~inyl component' include vinyl
~hloride-vinyl acelate copolymers, hydroxy modified
vinyl chloride-vinyl ace~ate copolymers, vinyl
chloride-vinyl acetate copolymers modified with
alpha-beta unsalurated carboxylic acids or epoxy
compounds, polyacrylates and methacrylates, for example
polymethyl methacr~la~es and styrene polymers and
polymer blends such as slyrene-acrylonitrile and
styrene-maleic acid anAydrid polymers. Suitable vinyl
components are available under the trade name UCAR from
Union Carbide.
Aptly, composltions of the present invention
based on hydrophi~i- polyurethanes and vinyl components
will contain at leas~ S~ by wei~ht of the total
composition of vin~ mponent. Favourably, the
composition will conlaln at least 50% by weight of
hydrophilic polyurelhane. Preferably, the compositions
of the present inven~ion will contain at least 10~ by
weight of the vinyl _omponent and typically will
contain about 15~ be weiqht of vinyl component.
The hydrophiLic polyurethane contributes
properties of ~ater-~sorption to the compositions of
the invention. ~uitably, the compositions of the
' ~ W094/~87 2~ 73 PCT/GB93/017
invention, when cured, will contain a~ leas~ 30~ bv
~eight ~ater when nydrated.
Aptly the hyàrophilic polyurethanes for use in
the composition of the invention will contain at leas
35% by weight water when hydrated. Favourably, the
hydrophilic polyurethane will contain at least ~0~ by
weight when hydrated and more favourably may contain up
to 60% or up to 90% waler when hydrated. Suitable
hydrophilic polyurethanes for use in the compositions
of the invention include those described in
US-A-4844983.
Hydrophilic polyurethanes which may be used in
the present invention will be any of those which have
the water content as hereinbefore described. The
saturation water content of the hydrophilic
polyurethane will not however be such as to cause it to
delaminate from a substrate. Favoured hydrophilic
polyurethanes for use in the invention are those which
are linear, that is are substantially free of cross
links and which therefore are soluble in organic
solvents.
The hvdrophilic polyure~hanes suitable for use in
the present invention may be polyether or polyester
polyurethanes. Sui~able p~lyesters which ~ive rise
WOg4/o4582l 12 3 7 ~ PCT/GB93/0l7~ ~
;~
-- 8 --
polyurethanes include polyesters of adipic acid such as
~u~ylene aaipate. However it is preferred to use
hydropnilic polyurethanes which are polyether
polyurethanes. It is particularly preferred therefore
to use hydrophilic Dolyurethanes which are linear
polyether polyure~hanes.
Apt linear polyelher polyurethanes may be random
polymers containina e~her units derived from diolic
compounds which have been reacted with diisocyanates.
Suitable linear polye~her polyurethanes include those
described in European Patent Specification No.050035 at
page 12 line l to page 14 line 10 and at page 32 line 7
to 33 line 12, which are incorporated herein by
cross-reference and which have the required water
content when hydrated.
Particularl~ apl LS a linear polyether
polyurethane which employs poly (ethylene glycol)
derived blocks alon~ ~oge~her with a chain extender and
a diisocyanate. Suitably the poly (ethylene glycol)
may have a molecular weight of between 600 and 6000 and
more suitably or belween 800 and 2000. A particularly
preferred poly (ethyiene glycol) has a molecular weight
of 1540. Suitably the chain extender will be an
aliphatic diol or diamine or amineol containing up to
lO carbon atoms and most suitably up to 4 carbon atoms.
W094/04587 PCT/GB93/017~
~1 21~7~
g
Suitably the aiisocyanate such as toluene diisocyanate,
1, 6-hexamethylene diisocyanate or
4, 4'-dicyclohexyl-methane diisocyanate. A preferred
diisocyanate is 4,4'-dicyclohexylmethane diisocyanate.
The ratio of hydrophilic polyurethane to acrylic
vinyl component as well as the hydrophilic nature of
the polyurethane will affect the physical properties of
the cured composition of the invention. The greater
the amount of polymer component the greater will be the
resistance to abrasion, especially where acrylic
components are employed whereas the greater the amount
of hydrophilic polyurethane and/or the greater the
hydrophilicity of the polyurethane component the better
will be the antimist properties. The concentration o~
hydrophilic polyurethane in the composition may range
from 10% to 99.0% by weight of the total weight of the
composition. Aptly the composition of the present
invention may contain from 10 to 90% by weight of the
hydrophilic polyurethane.
The composition of the invention may be cast, for
example, from solution, to form self supporting sheets
or film coatings. Thus the compositions may also
contain other processing aids such as flow promoters.
Suitable flow aids may include fully reacted materials
such as silicone fluids or reactive materials such as
W094/04587 2 ~ ~ 2 3 ~ ~ PCT/GBg3/017~
o
di-and hexa-func~lonal silicone acrylates.
Both the nature and concentration of the acrylic
or vinyl componenl will also affect the shaping or
forming properties of the composition. The composition
of the invention may be in the form of a solution
suitable for casting or moulding in which the solvents
for each of the resin components are compatible with
each other. Aptly bo~h ~he polyurethane and acrylic or
vinyl componen~s will be dissolved in a common solvent
therefor. Favourably the solvent or solvents will be
chosen to provide a solution having a viscosity
suitable for it to be cast into a sheet or formed into
a film. Apt solvents ~or use in the present invention
are ketones, esters and alcohols as well as mixtures
thereof. Examples of ~uitable organic solvents include
propyl acetate, haloaenated hydrocarbons such as
methylene dichloride, alkanols such as methanol or
ethanol (optionally contalning small amounts of water),
ketones such as ace~one or methyl ethyl ketone, methyl
iso~utylketone, 2-methoxyethanol 2-ethoxyethanol,
diacetone alcohol or ~ixtures of these solvents.
Preferred solvents are Z-ethyoxyethanol, industrial
methylated spirits (IMS) or IMS together with 2
methoxyethanol in a ratio of 3:1. Normally and
prererably the hydrophilic polyurethane component will
be applied in its non-hydrated state.
W O 94/04587 ~ 1 ~ 2~ 7 ~ PC~r/G B93/01744
Those compositions or precursors of the invention
which contain acrylic unsaturation are cured by
cross-linking through the ethylenic bonds.
Accordingly, the compositions of the invention may
desirably contain initiators to promote cross-linking.
The compositions may be cured by radiation including
thermal radiation, actinic, infra-red and ultra-violet
radiation and electron beam.
Favoured compositions may contain a photo-iniator
reactive to U.V. light. Such inhibitors may be present
in the compositions of the invention or solutions
thereof in conventional amounts.
In addition to cross-linking of the acrylic
component of the composition, the polyurethane
component may also contain ethylenic unsaturation which
may be cross-linkable. For example, the polyurethane
may be a urethane-acrylate block copolymer. Preferably
the compositions of the invention are dried to remove
solvent prior to cross linking.
The solids contents of solutions of compositions
of the invention are chosen to provide a balance of
good rheological, drying and film-forming properties.
Aptly, the solids content (polyurethane and acrylic or
W094/04587 2 14 2 3 73 PCT/GBg3/017~ ~
- 12 -
vinyl components) will be less than 50%, ~ore aptly
less than about 25~. ~
Coatings in accordance with the invention may be
prepared by conventional methods of coating surfaces
such as dip coatin~, sprayinq, painting, knife-coating,
on line coating or by printing. In such processes the
composition of the invention is dissolved in a suitable
organic solvent, for exampie having a solids content of
up to 30~ (by wei~nt) or more favourably as a 5 to 15%
solution for dip coating and 5 to 25% for spray
coating.
When the coating is to be used in a high quality
optical product, such as on a lens, it is preferred
that the coating is applied as the result of dip
coating. In this process the solution of the polymer
composition is placed in a suitable container which is
raised mechanically in a controlled manner to immerse
the substrate. Th~ container is then lowered at an
appropriate rate to qive the desired coating thickness.
The thickness of the coating depends upon both the
solution strength, the ~iscosity of the solution and
the rate of withdrawal of the substrate from the
container. Favourably the process is carried out at
between 15 and 30C. The solvent is removed from the
coatina after withdrawal from the solution using a
s~ I A ~ ~ r~ ~ PCI/GB93/01744
WO 94/04587 ~ h
1 3 --
curren~ of air and preferably a current of warm air at
a temperature of ~0 to 70. Drying at this temperature
imparts a qloss to the coating thereby presenting a
better optical appearance to the coated substrate.
It is possible, to apply a coating by preforming
the thin film of the hydrophilic polyurethane - polymer
compositions of the invention and adhering it to the
surface of the glass or plastics substrate which is
required to be rendered antimisting. Aptly, the thin
film may be adhered by means of a transparent adhesive
which is inert to the film and the substrate.
The composition of the invention may be cast,
for example, from solution, to form self supporting
sheets or film coatings. Thus the compositions may
also contain other processing aids such as flow
promoters.
When cast into sheets the compositions may be
used for glazing purposes such as for window panes.
Alternatively, the compositions may be cast as films
onto preformed substrates such as those formed from
glass or plastics materials, e.g. polyacrylic or
polycarbonate resins ~o maintain or improve light
transmission or, if used as mirror, to improve or
maintain reflective properties. When C~st into films
W094/04587 21 ~ 2 ~ 7 3 PCT/GB93/017~ ~ '
the compositions or the invention may be applied from
solutions typically containing greater than 30% by
weight solids e.g. 30-40% by weight solids.
Although the compositions of the present
invention are light transmitting some sacrifice of the
light transmitting properties compared with the base
polyurethane in favour of scratch or abrasion
resistance may occur when the compositions comprise an
acrylic component. We have found however that the
light transmitting properties of the hydrophilic
polurethane can be retained when vinyl component
formations are utilised. Such compositions although
not so scratch resistant as the urethane-acrylic
components may be formulated into free-standing films
for use in multilayer applications such as 'peel-off'
visors for helmets such as those for motor-cycling and
sports activities withoul loss of optical clarity.
The antifogging properties of composition of the
present invention ~ill greatly exceed the performance
specification described in DIN 4646 part 8 (1986) for
'Lenses for eye protectors - Antifogging test'.
Preferred compositions of the invention comprising 10%
of the vinyl based resins when tested to DIN 4646/8
will transmit 80% of the original transmittence for
longer than lO seconds.
~ W094/04587 21 q 2 3 7 3 PCT/GB93/017~
- 15 -
, The present invention will be illustrateà by the
following example.
ExamPle 1
Ninety parts by weight of a hydrophilic
polyurethane, prepared in accordance with the method
described at lines 4 to Z3, column 7 of US-A-4844983
were mixed with nine parts by weight dipentaerithrylol
penta acrylate, 0.5 part of a photo initiator, 0.5
parts of a silicone fluid flow aid and blend of
solvents comprising methylisobutylketone, propyl
acetate 2-ethoxyethanol to produce a solution being a
15% by weight solids content.
The solution was sprayed onto a sheet of
polymethyl methacrylate and cured under a W lamp. A
further sheet was left uncoated.
Both sheets were then placed over a water ba~h
containing water at 45C. After two seconds the
uncoated sheet be~an to mist over and was completely
'opaque' after about ten seconds. The coated sheet did
not start mistinq over until two minutes had elapsed
and then did not completely mist over.
W094/04587 2 1~ 2 ~ 7 3 PCT/GB93/017~ ~
- 16 -
Further samples of both sheets were affixed to a
mirror mounted within a shower cubicle. The shower
unit was operated at maximum temperature. Inspection
of the sheets showed that the uncoated sheet misted
over whereas the reflective properties of the coated
sheet remained intact.
ExamPle 2
A solution of a hydrophilic polyurethane,
prepared in accordance with the procedure described in
Example 1, was found by slowly adding 80 parts by
weight to 2 ethyoxyethanol maintained at room
temperature. 19 parts by weight of dipentaaerithroytol
hexa-acrylate were added slowly with agitation to the
polyurethane solution until dissolved and thereafter a
photo initiator (DAROCURE 1173, available from
CIBA-GEIGY) and liquid flow aid (silicone acrylate)
added. The solids content of the result mixture was
adjusted to 17~ by weight.
The solution was then coated onto a sheet of
perspex and passed through a drying tunnel maintained
at 50C for a period of 5 minutes and then under a W
lamp to cure the resin. After drying and curing, the
coated sheet was subjected to testing according to DIN
4646 part 8. Under the test conditions fogging did not
commence until 15 seconds had elapsed.
~ W094/04587 2 1 ~ ~ 9 7 3 PCT/GBg3/017~
ExamPle 3
A 20% by weight solution was first formed by
dissolving 85 parts by weight in ethoxyethanol. A
hydroxyl modified vinyl chloride-vinyl acetate
copolymer (14.9 parts by weight) was added slowly with
agitation until the mixture was clear and free from
striations. Liquid silicone acrylate (0.1 part by
weight) was then added as a flow aid and the solids
concentration adjusted to 15% by weight. The solution
was then applied as an antimist coating to a motor
cycle helmet visor.
The coated visor was passed through a drying
tunnel, maintained at 50C for a period of 5 minutes.
r~ t ' J ~
