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Description  |
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TECHNICAL FIELD
The present invention is within the field of surface coating of a
substrate, for instance a polymeric substrate, with a polymeric coating
containing ethylene oxide units as primary structural units thereof. The
new surface coating according to the invention imparts to the substrate
outstanding properties which make it possible to utilize the surface
coated articles obtained in novel applications as compared to previously
known surface coated articles in this field. More specifically the
invention relates to a surface coated article comprising a substrate with
a curved polyethylene oxide-based coating thereupon, to a special process
for the preparation of such a surface coated article, to a special coating
composition for the preparation of said surface coated article and to use
of the article as an antifouling or antistatic article or as an article
with friction-reducing properties. A new, very interesting application of
the article according to the invention is within the biomedical field,
which is primarily due to the protein-repellent properties of the surface
coating as will be described more in detail below.
BACKGROUND TO THE INVENTION
DT-PS No. 10 28 524 discloses a method of coating or impregnating textiles
with a coating of polyalkylene oxide and the use of said coating as an
antistatic, soil-repellent and water absorbing coating. A similar method
is disclosed in DT-AS No. 22 39 592, which is specifically directed to a
method of improving the stability of the coating by adding a cationic
antistatic agent in the form of a reactive alkyl ethylene-urea and by
performing the curing operation at elevated temperatures in the presence
of moisture as a catalyst. According to both these references the
preferred method for obtaining a cured coating seems to be the use of a
polyalkylene oxide having at least two unsaturated groups in the form of
acrylic, methacrylic and/or vinyl groups at the ends of the molecule or in
side chains which groups are crosslinked by means of thermally activated
initiators at elevated temperatures. Furthermore, these previously known
methods require several process steps. It is true that DT-AS No. 22 39 592
mentions as an alternative the use of a mixture of a polyalkylene glycol
with a polymerizable vinyl group in one end thereof and a vinyl monomer
with at least two vinyl groups, but said alternative is in no way
disclosed as any preferred alternative. Furthermore, said German citation
neither discloses nor suggests the essential combination of features
necessary according to the present invention or even less the outstanding
combination of properties obtained by the present invention. Finally, no
stabilization treatment is required in connection with the present
invention as is required according to DT-AS No. 22 39 592.
Thus, as will be described more in detail below the present invention
relates merely to polyethylene oxide as a coating material, which means
essential advantages as compared to the use of other polyalkylene oxides,
primarily thanks to the structural compatibility between the ethylene
oxide units and the water molecules. However, the major difference
relative to the prior art is not the use of polyethylene oxide per se but
rather the following combination of features: the presence of
ethylenically unsaturated groups at one end of the polyethylene oxide
chains only, the way of accomplishing the cross-linking of the
polyethylene oxide chains to obtain a stable coating on the substrate to
be coated, viz. by radiation curing, and the swelling of the substrate
prior to cross-linking. These major differences relative to the prior art
impart to the manufactured article a unique structure of densely packed
non-modified polyethylene oxide chains pendant from the substrate as well
as a firm anchoring of the coating to the substrate.
As to the radiation curing this is a curing technique known per se, as is
disclosed e.g. in EP, No. A1, 0 057 906. However, as was mentioned above
the present invention is based on a combination of features, of which
radiation curing is one only, giving results which are not in any way
disclosed or suggested in the prior art.
SE Patent Application Ser.No. 8202524-8 discloses a method of applying to a
polymeric substrate a hydrophilic coating of polyethylene oxide and its
use in medical articles to be inserted into the human body. The
polyethylene oxide is applied to the surface by swelling and curing at
elevated temperature and in the presence of steam. Said known method
differs from the present invention in that there are no unsaturated groups
in the polyethylene oxide and that the cross-linking reactions are
accomplished by means of a compound containing at least two non-reacted
isocyanate groups and in the presence of a catalyst. A major drawback with
this known method and with other prior art not utilizing the polyethylene
oxide chain structure used according to the preesnt invention is, however,
that during the cross-linking reaction the polyethylene oxide chains form
loops at several reaction sites which means a poor degree of coating and
an article that is less useful for practical purposes. This drawback is
definitely eliminated by the present invention in that the structures of
the reactions do not enable the formation of such loops. Furthermore, the
process according to the present invention is much simpler than the method
disclosed in the Swedish citation, as said method comprises several
lengthy steps.
In connection with the prior art it should also be noted that the
water-binding ability of polyethylene oxide is known per se and that said
ability is utilized e.g. when impregnating wood to prevent dessication and
the formation of cracks. Polyethylene oxide is also utilized when
impregnating synthetic materials to impart antistatic properties thereto
and in nonionic dispersants which adsorb and hydrophilize the surfaces of
those particles and drops to be dispersed.
DISCLOSURE 0F THE INVENTION
According to one aspect of the invention there is provided a surface coated
article comprising a substrate and a cured polyethylene oxide-based
coating thereupon. The essential features of said article are that:
(A) the coating consists essentially of polyethylene oxide chains, each of
which has one end that is unmodified, free and pendant from said substrate
and another that has been cross-linked, via one or more, preferably one,
radiation curable, ethylenically unsaturated group(s) as part of said
polyethylene oxide chain, to other chains by a cross-linking agent with
two or more, preferably two or three, radiation curable, ethylenically
unsaturated groups reactive with the ethylenically unsaturated groups of
the polyethylene oxide chains,
(B) the cross-linking operation has been performed by means of radiation,
and
(C) the substrate has been swollen prior to said cross-linking operation,
the productions between polyethylene oxide and cross-linking agent being
such that an adherent, cured coating is obtained.
The structure of the coating as well as the reactants to be utilized when
preparing the coating will be described more in detail below but already
here it should be noticed that the unique structure of the article,
especially a very high surface concentration of freely movable
polyethylene oxide chains, makes it useful especially as a
protein-repellent article.
According to a second aspect of the invention there is provided a process
for the preparation of a surface coated article of the above-mentioned
type which process comprises applying to the substrate a solution
containing
(a) a polyethylene oxide having chains, each of which has one end that is
free and unmodified and another that is cross-linkable, via one or more,
preferably one, radiation curable, ethylenically unsaturated group(s) as
part of said polyethylene oxide chain, to other chains,
(b) a cross-linking agent with two or more, preferably two or three,
radiation curable, ethylenically unsaturated groups reactive with the
ethylenically unsaturated g4oups of the polyethylene oxide chains,
(c) a solvent for said polyethylene oxide and said cross-linking agent,
said solvent also being a swelling solvent for the substrate, and
optionally
(d) a radiation radical initiator; allowing said solvent to act on the
substrate for a sufficient period of time to swell said substrate;
evaporating said solvent to the formation of a coating on the substrate;
and cross-linking said coating by means of radiation, the radical
initiator being added separately if not already present in first-mentioned
solution.
According to a third aspect of the invention there is provided a coating
composition for the preparation of the surface coated article mentioned
above or for use in the above-mentioned process, which coating composition
comprises:
(a) a polyethylene oxide having chains, each of which has one end that is
free and unmodified and another that is cross-linkable, via one or more,
preferably one, radiation curable, ethylenically unsaturated group(s) as
part of said polyethylene oxide chain, to other chains, and per mole of
said polyethylene oxide,
(b) a cross-linking agent with two or more, preferably two or three,
radiation curable, ethylenically unsaturated groups reactive with the
ethylenically unsaturated groups of the polyethylene oxide chains, the
molar amount of said cross-linking agent being 0.1-10, preferably 0.3-3,
moles thereof in the case when said cross-linking agent does not contain
any significant portion of ethylene oxide units, and 0.02-50 moles thereof
when it contains such ethylene oxide units,
(c) 0-500, preferably 50-150, moles of a solvent for said polyethylene
oxide and said cross-linking agent, said solvent also being a swelling
solvent for the substrate, and
(d) 0.0001-0.05, preferably 0.001-0.01, moles of a radiation radical
initiator.
Accoding to a fourth aspect of the invention there are provided uses of the
above-mentioned article, said uses in general terms being defined as an
antifouling, biocompatible or antistatic article or as an article with
friction-reducing properties. Specific uses within these general
definitions will be described below.
Each and every component or reactant that is utilized according to the
invention has a unique function and by optimizing these functions the
coating can be tailored for almost any substrate surface and use. This in
turn means that the invention is applicable to the coating of any
substrate, e.g. a polymeric material, glass, metals, etc. However, since
widely used polymeric materials are often of the nonpolar type which is
not easily coated in a stable way, the invention is especially interesting
in connection with such substrates.
A more detailed description of the functions referred to above will be
given below.
THE POLYETHYLENE OXIDE
An essential feature of the polyethylene oxide to be used according to the
invention is that generally each chain thereof has one end representing an
unmodified polyethylene oxide terminal group, while the other end of said
chain has at least one radiation curable ethylenically unsaturated group.
That is, in the curing operation merely one end of the polyethylene oxide
chain contains reactive group(s) capable of participating in the
cross-linking reaction, while the other end of the chain does not contain
any group that participates in such a cross-linking reaction. Preferably
the reactive end of the chain contains one single ethylenically
unsaturated group only, but within the scope of the invention are also
such cases where two or three or even more unsaturated groups are present,
the proviso being that such reactive groups are positioned so close to the
end of the chain that no essential loops may be formed during the curing
operation. In other words there should be always be present a free movable
polyethylene oxide chain pendant from the substrate surface and directing
itself towards an aqueous phase in contact with the coated article.
Examples of suitable ethylenically unsaturated groups are acrylic and
methacrylic groups, but groups from any ethylenically unsaturated compound
which can be polymerized or cross-linked by radiation radical initiation
are within the scope of the invention. A preferred sub group of
ethylenically unsaturated groups, including the above-mentioned acrylic
and methacrylic groups, is polarized ethylenically unsaturated groups.
Preferably, however, the unsaturated groups are derived from an
ethylenically unsaturated carboxylic acid with a low molecular weight,
preferably with an average molecular weight below 1000, especially below
200.
The term "unmodified" or similar in connection with the end of the
polyethylene oxide which is pendant from the substrate should be
understood in a broad sense. In other words the requisite according to the
present invention is that said end does not contain any ethylenical
unsaturation that takes part in the cross-linking reaction. Generally this
means a conventionally etherified end of a polyethylene oxide. The other
end, i.e. the reactive end, of the polyethylene oxide can be obtained for
instance by reacting a chemically unmodified hydroxyl end of a
polyethylene oxide by an esterification reaction with a compound
containing the ethylenically unsaturated group(s). If desired, said
compound may also contain different functional groups dependent on the
final utility of the article to be manufactured. Anotehr preferable method
of preparing the polyethylene oxide reactant according to the invention,
however, is to start from a compound containing the ethylenically
unsaturated group(s) and ethoxylating the same, which ethoxylation is
performed in a manenr known per se. A major advantage of such a method is
that the polyethylene oxide chains obtained represent a mixture of chains
with a distribution of molecular weights within a desired range, e.g. the
so-called Poisson distribution.
With reference to the length or molecular weight of the polyethylene oxide
chains a preferable lower limit of the ethylene oxide units, to obtain the
desired hydrophilicity and similar properties, is 10 and especially 30. As
to the upper limit of the number of such units there is no strictly
critical such limit, but generally it can be advisable not to exceed 500
ethylene oxide units, as this may cause crystallinity or other properties
which may be non-advantageous for specific applications. An especially
preferable upper limit as to ethylene oxide units is 200, which means that
the most preferable range in this respect is 30-200.
THE CROSS-LINKING AGENT
As was mentioned above this reactant is an agent with two or more radiation
curable ethylenically unsaturated groups reactive with the ethylenically
unsaturated groups of the polyethylene oxide chains. This means that in
general terms the ethylenically unsaturated groups are of the same nature
as the corresponding groups of the polyethylene oxide chains, i.e. the
preferred sub groups as well as the preferred specific groups are the same
as were mentioned above in connection with the polyethylene oxide. Thus,
interesting groups of the cross-linking agent are allylic, acrylic or
methacrylic groups. Furthermore, said cross-linking agent is preferably a
compound having a low molecular weight, which according to an especially
preferble embodiment of the invention means an average molecular weight
below 1000, especially below 300. Thus, the term compound should be read
in a broad sense and includes polymers or oligomers as well as mixed
polymers or oligomers. As was mentioned in connection with the
polyethylene oxide said compound can also contain different functional
groups if desired for any specific purpose. Thus, it may be chosen in
dependency of the substrate to be coated to improve the adhesion or to
improve the flexibility of the applied coating, etc.
According to anotehr interesting embodiment of the invention the
cross-linking agent contains, in addition to ethylenically unsaturated
groups, one or more polyethylene oxide chains containing 5-500, preferably
3-200, ethylene oxide units having a free, non-reacted end. Finally, it
should be noted that the most preferable number of ethylenically
unsaturated groups of the crosslinking agent is 2 or 3.
A specific example of preferable cross-linking agent is
hexamethylenedioldiacrylate.
The polyethylene oxide and cross-linking reactants are of course used in
such proportions or molar ratios that a cured adherent coating having the
desired properties for the intended end use of the article is obtained.
These ratios are difficult to generalize as they very much depend on the
specific nature of the polyethylene oxide reactant and the cross-linking
agent, respectively, but can be established by routine experiments in each
single case now that the inventive idea has been disclosed. Thus, for
instance, different molar ratios may be required whether the cross-linking
agent contains ethylene units or not. However, some guidance in this
respect is given below in connection with the special coating composition
described below.
With reference to the cross-linking operation and the swelling of the
substrate these essential features have been referred to in general terms
above. More detailed information therabout will be given below in
connection with the disclosure of the process according to the invention.
The essential features of the process according to the invention have been
generally described above. As to the details concerning the polyethylene
oxide and the cross-linking agent reference is made to the details above.
With reference to the solvent, however, the following could be added.
The process according to the invention involves the use of a solvent that
in addition to the desired dissolution, spreading and evaporation
capacities also swells the substrate to be coated. This technique relates
primarily to the case where a polymeric substrate is utilized and means
that an improved anchoring effect can be obtained. Thus, by using a
solvent having such a swelling capacity the subsequent cross-linking
rection can cause bridges or cross-links which are more or less
mechanically anchored to the swollen substrate.
The primary functions of the solvent are:
(1) The solvent should be capable of dissolving the polyethylene oxide and
the cross-linking agent,
(2) it should wet the surface of the substrate so as to obtain a homogenous
spreading of the polyethylene oxide,
(3) it should swell the substrate surface so as to obtain a mechanical
anchoring of the polyethylene oxide to the substrate surface, and
(4) it should have an evaporation rate such that the time will be
sufficient for the substrate surface to be swollen and so that a
homogenous and covering film is obtained (this is promoted by a slow
evaporation of the solvent without any complete sorbtion of the
polyethylene oxide into the polymer).
Generally a mixture of solvents is required to obtain the above-mentioned
functions, which solvents must be compatible with each other, since
otherwise another function is required, namely the ability of bringing
about dissolution capacity. The solvent or solvent mixture to be used in a
specific case is determined by routine experimentation. Factors to be
considered in this respect are e.g. the substrate to be coated, the
evaporation rate and the environmental requirements. As an example it can
be mentioned that for polyvinylchloride a suitable mixture is a mixture in
equal parts of tetrahydrofurane (swells PVC), toluene and ethanol
(dissolves polyethylene oxide and wets the surface and gives a suitable
evaporation rate).
In accordance with the invention the curing of the coating composition is
accomplished by means of radiation initiated polymerization which is a
rapid, easy and effective way of obtaining the desired results. Thus, the
initiators to be used are initiators activated by radiation such a gamma-X
rays, electrone beams or ultra violet radiation. Ultra violet radiation
activation is preferable and can be performed at ordinary room temperature
which of course means great advantages as compared to the prior art. UV
polymerization requires presence of a photo initiator, which can
preferably be of the socalled photo phragmentating type, e.g.
2-hydroxy-2-propiophenone, two reactive radicals being formed directly
when starting the radiation, or preferably of the H-abstraction type,
radicals being generated via h-abstraction from an added tertiary amine
(contains acidic .alpha.-hydrogens, for instance thioxanthone+trimethyl
amine). As last-mentioned type of initiator may also abstract hydrogens to
some extent from the polyethylene oxide as well as from a polymeric
substrate, the adhesion to a polymeric substrate can be improved thereby
through the formation of chemical bonds with the substrate, which means
that this represents an especially preferable embodiment of the process
according to the invention.
According to yet another especially preferable embodiment of the process
the cross-linking operation is performed in two steps, viz.:
(i) a partial cross-linking in air for a short time to the formation of a
polyethylene oxide gel, which is sparingly soluble in water but wherein
the polyethylene oxide segments retain some movability; and
(ii) a final curing of said gel in an aqueous phase whereby the polar
polyethylene oxide segments orient themselves towards the aqueous phase.
This means an essential advantage as compared to the prior art since the
structure of the coating according to the invention is such that the
polyethylene oxide chains will be high-ly concentrated to the surface of
the manufactured article, i.e. essentially all chains will be directed
towards the aqueous phase.
In practice the process according to the invention can be performed by
roller-coating or spraying to the surface of the substrate or immersing
the substrate into the solution containing the polyethylene oxide, the
cross-linking agent and optionally also the radical initiator. Excess of
solvent is then allowed to flow off and evaporate from the surface.
Finally the dry or at least non-flowing coating is cured by radiation, for
instance by passing the substrate with the applied coating thereupon past
the radiation source on a conveyor.
Generally this means that the process according to the invention is
performed in two major stages which are simple and rapid. As compared to
the previously known methods this means significant advantages also as to
operability and costs, i.e. in addition to the advantages obtained by the
coated article per se.
The invention also relates to a special coating composition for the
preparation of a surface coated article as described above or for use in
the special process claimed. The proportions between the different
ingredients of said special composition are as follows. Per mole of the
polyethylene oxide there are used 0.1-10, preferably 0.3-3, moles of the
cross-linking agent in the case when said cross-linking agent does not
contain any significant portion of ethylene oxide units, and 0.02-50 moles
of said cross-linking agent in the case when it contains such ethylene
oxide units; 0-500, preferably 50-150, moles of the solvent; and
optionally 0.0001-0.05, preferably 0.001-0.01, moles of the radiation
radical initiator,
Thus, in the case when no significant proportion of ethylene oxide units is
present in the cross-linking agent the molar ratio of polyethylene oxide:
cross-linking agent should generally be from 1:10 to 10:1, but to obtain
optimum properties in this case said ratio is preferably from 1:3 to 3:1.
Especially preferable is a molar ratio at or near 1:1 for lower molecular
weight polyethylene oxides, said ratio being closer to 1:3 the higher the
molecular weight of the polyethylene oxide is.
For cross-linking agents containing ethylene oxide units the variations as
to molar ratios are greater or more versatile as part of desirable
properties ascribable to ethylene oxide units can be imparted to the
article also by the cross-linking agent. Therefore, the general limits as
concerns the above-mentioned ratio can be expressed as 1:50 and 50:1,
respectively, a more narrow general range being difficult to state
depending on the (very interesting) versatility of this embodiment of the
invention. However, in some cases the above-mentioned ranges of 1:10 to
10:1 and 1:3 to 3:1 are applicable also to this case.
As was mentioned above the invention finally relates to special uses of the
article. Said uses can generally be expressed as an antifouling or
antistatic article or as an article with friction-reducing properties.
More specifically, it has been found that the article according to the
invention possesses excellent protein adsorption-preventing properties,
which open great possibilities within the biomaterial field, especially
the biomedical field. The biocompatibility is especially pronounced for
polyoxyethylene chains with at least 10 or more, preferably at least 25 or
30 ethylene oxide units.
Furthermore, the surface coating according to the invention makes
hydrophobic surfaces completely hydrophilic and water-wetting and
facilitates the cleaning of contaminated areas. It also prevents a static
charging of the substrate surface, is oil-repellent as well as
particle-repellent. Another important property that can be utilized for
special applications is the property to reduce friction between surfaces.
Medical uses for which the article according to the invention can be
expected to be applicable are for instance:
tissue-compatible surfaces to be used within the human body, e.g. in vessel
and bone prostheses to prevent rejection reactions;
blood-compatible surfaces to prevent blood coagulation and protein
depositions, e.g. when utilizing catheters and in extracorporal
circulation, such as oxygenators and artificial kidneys;
dressings for the adsorption of tissue liquids.
If the composition is impreganted with iodine I.sub.2 KI there is also
obtained a disinfecting and wound healing effect;
applications where bacterial growth on surfaces (anti-bacterial effect) is
prevented, are e.g. in connection with urinary catheters and in
contraceptives as a sperm-killing coating.
In connection with the medical uses of the article according to the
invention the radiation curing offers great advantages as it means that at
the same time a sterilization of the product is obtained.
EXAMPLES
The invention will now be described more in detail by means of the
following non-limiting examples of represenattive embodiments of the
invention.
EXAMPLE 1
Monoethyl-etherified polyethylene glycol (PEG) with a molecular weight of
550 was monoacrylated with acrylic acid. After evaporation to obtain a
product designated PEG-A-550 there were added to said product 0.02 moles
of hexamethylene diol diacrylate (HDDA) (difunctional cross-linking
agent), 0.0002 moles of 2-hydroxy-2-propiophenone (photoinitiator) and a
solvent mixture consisting of 1.5 moles of ethanol, 0.75 moles of toluene
and 1.0 mole fo tetrahydrofurane (THF).
Three different samples were prepared, viz.: Sample A containing 0.005
moles of PEG-A-550 Sample B containing 0.02 moles of the same compound,
and Sample C containing 0.4 moles of said compound.
Each of said solutions were dropped onto a PVC plate, and the solvent was
allowed to evapoorate, whereupon the applied coating was cured at a speed
of 6 m/min in a UV cure from Primare, U.S.A., which contains two Hg lamps
giving a power of 100 W/cm.
The samples were rinsed with water for 60 seconds. Only sample B gives a
completely hydrophilic, water-wetting surface.
EXAMPLE 2
To a 0.02 moles of PEG-A-1900 there were added 0.02 moles of HDDA and
0.0002 moles of 2-hydroxy-2-propio-phenone. As a solvent there was used
pure 0.2 moles of p-xylene (swells PE).
This solution (D) as well as solution (B) from Example 1 (prepared with
PEG-A-1900 instead of PEG-A-550) were applied in a thin layer onto a
polyethylene surface. The solvent was allowed to evaporate and the coating
was cured as in Example 1.
The products obtained were rinsed in water for 60 seconds. Only product D
was completely hydrophilic, Coating B scaled off with time.
The product was then dipped into a beaker containing heavy fuel oil. On
both samples a black oily film was observed. If the samples were
re-immersed into water the oil was scaled off from coating (D), which
became completely clean from oil. Sample (B) was still covered by oil and
could not be cleaned by rinsing in water.
EXAMPLE 3
Coating compositions prepared according to (B) in Example 1 and containing
PEG-A-550, PEG-A-1900 and PEG-A-5000, respectively, were evaporation
coated onto a PVC foil and cured in a UV-cure according to Example 1.
All samples were exposed for 6 hours to 1% bovine serum albumine (BSA),
dissolved in a physiologic sodium chloride solution, whereupon the
surfaces were rinsed in a clean physiological sodium salt solution for 60
minutes. The samples were dried and surface analyzed by means of electrone
microscopy for chemical analysis=ESCA with relation to protein nitrogen.
For all PEG:s the protein adsorption was reduced as compared to untreated
PVC. The adhered amount of protein is reduced with increasing molecular
weight of the PEG in the following way:
______________________________________
Coating Mole % of N in the surface
______________________________________
Untreated PVC
5
PEG-A-550 2
PEG-A-1900 0.9
PEG-A-5000 <0.5
______________________________________
EXAMPLE 4
A coating composition prepared according to (B) of Example 1 above but with
PEG-A-1900 was applied to two plates of stainless steel which had
previously been provided with a thin PVC film by evaporating a 0.5% PVC
solution in THF on the steel plate. The coating composition was allowed to
dry in air, and then one of the samples was cured in a normal way with one
stage in air, while the other plate was cured in two stages: firstly a
partial and very rapid (<0.5 m/min), exposure in UV-cure in air, and
secondly covering of the coating composition by a film of water below
which final curing was performed at a speed of 5 m/min in a UV-cure.
The samples were exposed to 1% of BSA with subsequent rinsings as in
Example 3.
The protein contents were determined by means of
______________________________________
Type of cure Mole % of N in the surface
______________________________________
Cure in one stage
0.9
Cure in two stages
<0.5
______________________________________
The proportions of PEG (in the form of -CH.sub.2 O-carbon) in the surface
was analyzed by means of ESCA with the following results:
______________________________________
Type of cure Mole % of PEG
______________________________________
Cure in one stage
60
Cure in two stages
>90
______________________________________
EXAMPLE 5
Trimethylol propane (TMP) that had been ethoxylated with 20 ethylene oxide
units per TMP was diacrylated by charging 2 moles of acrylic acid per mole
of TMP.
To 0.003 moles of the dried product (TMP-(EO).sub.20 -A) there were added.
0.0001 moles of 2-hydroxy-2-propiophenone
0.78 moles of ethanol
0.50 moles of toluene
0.25 moles of TMF
The coating composition was applied to Plexiglas.RTM. (PMMA) and the film
was cured in accordance with the two-stage process of Example 4. One
untreated and one treated PMMA plate were exposed to a power mixture of
iron oxide (Fe.sub.2 O.sub.3) and colloidal carbon (equal parts of each
based on the weights) with shaking in a test chamber at a relative
humidity of 70% for 15 minutes.
The untreated sample had a permanent red-black coating after said test,
while the treated sample was completely free from particles when it was
taken out from the chamber.
EXAMPLE 6
A silicon plate was provided with a PVC film by immersion into a 0.5%
solution of PVC in THF. The plate was then coated with a film having the
following composition:
0.02 moles of PEG-A-5000
0.04 moles of trimethylol propane triacrylate (TMPTA)
0.0002 moles of 2-hydroxy-2-propiophenone
2 moles of ethanol
2 moles of toluene
2 moles of THF
The films were spun onto a rotating plate at 100 rpm dried and cured in one
single stage. The protein adsorption was measured by means of
ellipsometry. The following results wer | | |
