Note: Descriptions are shown in the official language in which they were submitted.
l~o ~ ~,c,~
Back~round of the Invention
m is invention relates to resin compositions having antistatic
characteristics. ~re particularly, this invention relates to resin
cnmpositions co~prising an electron radiation cured product of an
electron radiation curable resin precursor and an electron radiation
reactive antistatic agent. In other aspects, the present invention
relates to a method of making an antistatic resin cGmposition and
further to substrate sheets coated therewith. Plastics such as
polyethylene, polyprcpylene and the like are poor conduct~rs of
electricit~f and have a tendency to develop and retain electrostatic
charges which attract and hold dust particles. This kendency can have a
detrimental ef~ect on the appearance of the plastic, but is especially
detrinental for plastic films which are used as packaging materials for
delicate electronic devi oe s, such as floppy discs for computers, or are
used for hospital operating room .supplies. For these k~nds of uses f
electrostatic charges can have a detrimen~al eff.ect on the function of
the plastic material. It is, of course, also well known that the build
up of eleetrostatie charges in plastic films leads to handling and other
problems in manufacturing or converting prccesses, espeeially where
plastie fil~s are transported at high speed.
One method whieh ean be used to reduee the build u.p of statie
eleetricity in plasties is to add a nonreaetive antistatie additive,
such as a quaternary a~monium compound or earbDn, when compcunding the
pl.astie matrix. The additive exudes to the ~uxface of the plastie
dhring proeessing and re~lees the build up of static electricity at the
"
.
.
,
:, '` , , .
73Z2
surfaoe of the plastic. miS method, however, offers only short term
antistatic protection. Ano~her method for reducing static build-up
involves providLng a light vac~um metallized film on the pla~tic resin.
mis meth~d, however, suffers from the disadvantage of environmental
instability since the metal used to provide the canductivity
characteristics is susceptible to attack by isture and or other
corrosive oonditions.
Thus, it would be highly desirable to provide a resin
composition having a reduced tendency to form static charges both before
and after fabrication and to provide antistatic laminations ccmprising
the resin co~position. It also wDuld be highly desirable to develop a
more permanent method involving copolymerizing or cross-linking an
antistatic agent with a resin to provide long lasting antistatic
characteristics throughout the resin.
In accordance with the present invention, it has been found
that resin compositions h~ving desirable antistatic properties ccan be
provided by electron radiation curing a composition compri~ing an
electron radiation curable resin precursor and an electron radiation
reactive antistatic agent. The antistatic conposition can be used to
coat a substrate sheet to provide an antistatic lamination. Further
understanding of the present invention will be had from the following
disclosure wherein all parts and percentages are by weight unless
otherwise indicated.
Summary of the Invention
~ n accordance with the present invention, an antistatic resin
oomposition comprises the electron radiation cured reaction product of:
lA) an electron radiation curable prepolymer; and (B) an effective
a~ount of an electron radiation reactive antistatic agent soluble in
said prepolymer. In accordance with the me~hQd of the present
invention, an antistatic resin ~omposition is made by: (A) muxing an
. ~ .
~L213~322
electron radiation curable prepolymer and an effective amaunt of an
electron radiation reactive antistatic agent to form a mixture thereof;
and (B) contacting said mixture with electron radiation in an amrunt
sufficient to cure said mixture. Further in accordance with the present
invention the antistatic resin may be provided as an antistatic coating
on a substrate, such as a metallized substrate sheet. Preferably the
antistatic agent is a quaternary ammoniu~ salt.
escri~tion of the Invention
The antistatic resin composition of the present invention
broadly co~prises the reaction product of a radiation cur~ble precursor
and an effective amount of a radiation reactive antistatic agent. In
accordance with the method of the present inventicn, the antistatic
resin composition is made by mixing a radiation curable resin precursor
and a radiation reactive antistatic ag~nt to provide a mixture thereof.
The reacti~e antistatic agent is employed in an amount which is
effective to bbtain the desired antistatic properties. ~he mixture is
then oontacted with electron radiation in sufficient amount to cure the
mLxture. During radiation curing, the antistatic agent reacts with the
radiation curable resin precursor to form a polymerized resin having
long lasting antistatic characteristics.
The antistatic resin compositions of the present invention are
especially useful as coating materials and in one e~bodiment of the
present invention, an antistatic ooating of the present invention is
provided on a substrate material such as paper, polyethylene,
polypropylene or the like. A preferred embodiment of the present
invention comprises a su~strate material having a continuous thin layer
of conductive metal such as aluminum deposited thereon and a oontinuous
thin layer of the antistAtic resin oomposition of the present invention
overcoating the thin la~er of aluminum~
.
~IL2~373~2
Radiation curable resin precursors suitable for use herein are
commercially available and well known in the art. Generally speaking,
the radiation curable precursor comprises a mixture of at least one
oligomer and mono and/or multi-functional mDnomerS. Generally speaking,
the oligoners constitute the backbone of a radiation curable c~at mg and
largely determine the ultimate performance of the finally cured coating.
Mbny oligomers are based on acrylate chemistry because of ease of
synthesis and cost. For exa~ple, suitable oligomers include the
epoxy-acrylate, polvester-urethane-acrylates, polyether-acrylates, and
polyester-acrylates. Acrylated-epoxy resins tend to have gcod adhesion
and chemical resistance properties. Acrylated-urethane-polyesters tend
to cure to hard, tough, flexible chemica}ly resistant coatings.
Acrylated-polyethers tend to cure to tough, abrasion resistant coatings,
and are generally of lower viscosity than pol~rethanes and epoxies.
Arrylated-polyesters tend to have law visoosity and good weather-
ability.
Oligomers, however, when used by themselves, may shrink
excessively on curing and/or have an unworkable application viscosit~.
mus, monomers and other additives, such as flow control agents, will be
generally used in combination with oligomers to provide a ra~iation
curable prepolymer. Backbone oligomers can be us~d in conjunction with
a wide variety of monomers, both mono- and nLlti-functional :Ct will
be appreciated by those skilled in the art that prcper selection of
monomers contributes to the final cured coating properties by
controlling the cross-link densi~y, hardness, flexibility, cure speed,
etc., and, hence, the particular monomers selected will depend upon the
.inal coating properties desired. Generally, comhinations of ~ono- and
mLlti-functional m~ncmers will be preferred ~o achieve the desired
results.
Examples of useful mono-functional nomers include:
n-vinyl-2-pyrollidone, 2~phenoxyethylacrylate, n-isobutoxynethyl-
,i
32~
acrylami~e, i~cobornylac~late, 2-ethoxyethoxyethylacrylate, and
tetrah~drofurfuI~rlacrylate. N-vinyl-2-pyrollidone is especially
useful kecallse of its abrupt viscosity reduction in small a~unts~ and
high response to electron baam radiation.
S~itable multi-functional m~ncmers include: 1,6-hexanediol
diacrylate, tripropyleneglycoldiacrylate, tri~ethylolpropanetri-
acrylate, pentaerythritoltriacrylate, and tetraethyleneglycol-
diacrylate.
P~tistatic agents suitable for use herein are antistaticagents whic~ are electron radiation reactive with the radiation curable
resin precursor and which are soluble in the resin precursor. It has
been foundl that useful agents for use herein are quaternary a~monium
salts such as triaIkylalkyletherammonium salts. A preferred salt is a
trialkylalk~.ethera~.onium salt wherein each of the trialkyl groups has
from 1 to a~out 3 carbon atoms, the alkylether group has an alky] group
having frcm about 4 to about 18 carbon atoms, and the ether group
is selected from the group consisting of ethylene oxide ~nd propylene
o~ide. An exa~ple of a preferred salt is tliethylalkyletherammonium
sulfate, csEo~rcially available as Emerstat 6660*frcm Emery Industries.
The antista~ic agent is muxed with the radiation curable resin precursor
in an amoun~ effective to obtain the desired antistatic characteristics
for the resIn composition upon curing thereof. The exact amourt will
vary from ~esin t~ resin, antistatic agent to antistatic agent, and
intended use for the resultm g product.
One advantage of the antistatic resin compositions o the
present i~venti.on is that they are especially suitable for use as
coatings upon substr~tes. Substrates contemplated for use m
co~bination ~7ith the ccmpositions of the present invention include w~bs,
sheets or films such as paper, glass, polymer coated paper, w wen and
n~n-woven sheets of ~arious materials, various polymeric films such as
polyethylene film, polypropylene film, polyethvleneterephthalate film,
* Trade Mark ~5-
.
'
lL2l3732;2
polyvinyl chloride film, ionomer resin film and the like, and includemetallized substrates.
Coating of the antistatic compositions of the present
invention onto a substrate can be done in any conventional nanner.
Generally speaking, the ooating composition will be applied to the
substrate surface in the form of a prepolymer and antistatic agent
mixture and then cured in situ by means of electron beam radiation.
Generally speaking the coating need be applied and cured on only one
side of the substrate. Both sides of the substrate generally benefit~
in obtaining antistatic characteristics even though the suhstrate has
been coated with the antistatic composition on only one side so long as
the substrate is not too thick and a sufficient dosage of radiation is
employed to cure the coating. miS phenomenon can be observed on
substrates of thicknesses at least as great as 10 mils and can be
observed not only on polymeric films such ~s polyethy]ene film,
polypropylene film, polyethyleneterephthalate fi~m, polyvinyl chloride
film, ionomer resin ~ilm and the like, but also on paper, glass and
other webs such as can be made from various woven and non-w~ven fibrous
materials. Furthermore, these substrates can have a continuous thin
layer of conductive metal such as aluminum deposited thereon as hy a
conventional vacuum metallizing process and the coating can be applied
to the metallized or non-metallized side of the substrate.
e coating can be applied by dip coating, air-knife coating,
roll coating, gravure coatin~, reverse gravure coating, extrusion
coating, bead coating, curtain coating, use of wire wound coatin~ rods,
and so forth. The coating deposited on the subs~rate is effective even
as a thin coating having a thickness on the order of from 0.1 to 0.5
mils. Of course, the viscDsity of the coating composition can vary
widely depending upon the method of coating which is chosen and the
desired end results. Typical viscosity of coatings may ran~e from 50 to
about 1000 centipoise.
~L2~73~2
Apparatus and methods for curing of the radiation curable
antistatic resin co~position are well kncw~ and any suitable radiation
curing process and appa~atus can be used in carrying out this invention.
Suitable apparatus are co~mercially available from Energy &iences, Inc.
of ~burn, ~ssachusetts under thetrade ~ark ~lectrocurtain . EXamples
o~ suitable app2ratus are disclosed in U.S. Patents No. 3,702,412,
Nove~er 7, 1972 to ~uintal; ~o. 3,769,600, October 30, 1973 to Denholm
et al; and No. 3,780,308, December 18, 1973 to Nablo. High energy
ionizing radiation such as electron beam radiation should he used in
sufficient intensity to penetrate substantially all the way through the
coating oGmposition to cure the same. lypically dosaaes in the range
of from about 1 to about 6 megarads are e~,ployed. Upon contacting the
antistatic resin composition with radiation and sufficient intensity to
cure the s~ame, the ccm~osition used in the present invention is sub-
stantially cQmpletely converted to a solid product.
In a preferred e~bodiment of the present invention, a
continuous ~hin laye~ of conductive metal is sandwiched between a
substrate and the antistatic coating of the present invention. Thus, a
metal layer can be first applied onto a surface of a substrate and t~en
a continuous coating of the antistatic co~position is applied to
overcoat the metal layer to provide a lamunate having especially gc~d
antist~tic properties. Generally speaking, the antistatic coating ~ill
be appiie~ to the metal in the form of an uncured muxture of prepolymer
and antistatic agent and then cured m situ on the netallic layer~
Suitable metals include aluminum, copper, gold, silver, ancl t~e like.
lhe metal layer is preferably deposi~ed in a c~n~entional vacuu~
metallizing step. A resin coated paper with metallized layer thereoi
especially suit2ble to be overc~ated with an antistatic resin
composition of this inv~tion is taught in U~S. Patent 4rl77,310
Dece~ker 4, 1979 to Steeves
:'.
.
~28~7322
The antistatic resin compositions of the present invention
are useful in several T~S of products. For example, the coating may
be used as an overcoating for photographic film or as a packaging film
for electronic devi oe s, floppy discs for computers, hospital oper~ting
rocm supplies, and the like.
T~e present invention is further illustrated by the
following ex~ples:
E~D?T,F. I
The following ingredients were muxed with stirring:
InqredientParts by Weight
ra~iation curable uret~hane
acrylate oligomer based
coating ~S-9384*from Raffi
and Swanson) 95 parts
triethylalkvlet:hera~nonium
sulfate (E~erstat 6660*
from Emery Industries~ 5 parts
~ H~r the triethylalkyletherammonium sulfate was completely
dissolved, an about 0.3 mil thick coating of the mixture was applied on
the al~minum ~acuum metallized side of a sheet of 5 nul thick
polyethylene terephthalate film by a no. 4 wire wcund rod. The coating
~as cured by a 2 ~egarad dose of electron beam radiation.
EX~MPLE II
The ~ollowing ingredients were mixed with stirring:
~ Par_ h~ ei~ht
radiation curable urethane
acrylate oligo~er based
coating ~S-9384*from Raffi
and Swanson) 90 parts
triethylaIkyletheramm~nium
sulfate (Emerstat 6660*
fr~n 3~ ry Industries) 10 parts
Afte~ the triethylalk~letherammGnium sulfate was cc~pletely
dissolved, an about 0.3 mil thick coating was ap;plied on the aluminum
* Trade Mark -8-
~L~8~3~2
vacuu~ metallized side of a sheet of 5 mil thick polyethylene
terephthalate and cured as in Exa~ple I.
. EX~MPLE III
The follcwing ingredients were muxed with st~Lrring:
Inqredient Parts Weight
radiation curable urethane
acrylate oligom~r based
ccating (S-9384*fro~ Raffi
and Swanson) 85 parts
triethylalhyletherammonium
sulfate (Emerstat 6660*
fr~m Emery Industries)15 parts
A~ber the triethylalkylethera~monium sulfate was completely
dissolved, an about 0.3 mil thick coating was applied an the aluminum
vacuum metallized side of a sheet of S mil thick polyethylene
terephthalate and cured as ~n Example I.
EX~MPIE IV
A Resistivity half-life test was u~ed to evaluate the products
of EXamples I-III. Each product was suspended between t~o pol~s of an
electrode. A 100 volt charge was placed on cne of the poles and the
ti~e for half of the voltage to discharge was measured. q~,e
follc~nng results were obtained:
Product of TLme to Half Discharge
Exa~ple I 0.4
Example II 0.1
E~a~ple III 0.3
*Trade Mark ~9-
.' , ', - . .
' ~ '
"': ' `
.
' ' '
37322
EX~ V
~ radiation curable coating vehicle w~s preFared f.rom
triprcpylene glycol diacrylate, 70 parts; a diacrylate este~ prepared
~ro~ the di~lycidyl/ether of bis-phenol A and acrylic acid (Celrad 3600*
Celanese Resins Co.) 15 parts; an acrylate urethane ~ased on an
arc~atic i~ocyanate, (CMD 6700* Celanese Resins Co) 14.7 parts; and a
silicone ~ype sNrface active agent ~DC-l9~, ~cw-Corning Corp) 0.3 part.
To 85 parts of the above vehicle there was added ~S parts of
the triethylAlkvletherammonium sulfate of Exa~ple 1. me resultant
clear liquid coating having a viscosity of 120 cps was applied ~y an
offset gravure 03ating station just prior to an electI~n beam
radiation curing unit. The coating was cured with electron bea~
ra~iation on the follcwing substrates at the coati~g weights shcwn.
-
*rrrade Mark -10-
32Z
Substrate Coat ~. (Ibs./3000 ft2)
_
1 1/4 mil low density polyethlyene 1.6
60 Ib. C2S Paper 5
1/2 mil metallized polyethylene 1.3 (Coating on
terephthalate film side)
1/2 mil metallized polyethylene 1.3 (Coating on
terephthalate metal side)
1 1/4 mil metallized lcw density 1.6 (Cbating on
polyethylene metal side)
Resistance measurements made with a megohm meter (General
Radio) shcwed that all coated surfaces had antistatic properties with
readings in the range of 109 to 101 ohms/sq.
A coupling effect was noted when the antistatic coating was
applied over metallized surfaces. Readings on an ohm meter were 1~3-34
ohms/sq. on the coatings on the metal on the metallized 1/2 mil
polyethylene tereph~halate, and 150-200 ohms/sq. on the coating on the
m~tal on metallized low density polye~hylene.
~2~373;~2
E~A~PLE VI
An antistatic electron beam curable coatin~ was preFared by
mixing with stirring the following ingredients:
Inqredient Parts by Weight
triprcpylene-glycol diacrylate 58.6
epoxy acrylate oligomer
(Celrad 3600*) 12.4
urethane acrylate oligomer
(C~6700*,Celanese Specialty
Resins) 12.2
ga~a-Methacryloxypropyl-
trimethoxysilane 1.3
silicone surface active agent
(D~-193*)Dcw Corning) 0.5
triethylalkylether atnm~niunt
sulfate (Emerstat 666~,Emery
Industries) 15.0
.
Ihe above coating was applied by an offset gravure coat~tg
station to a substrate of 1 1~4 mil low density polyethylerte film at a
coatirtg weight of 1.6 Ibs./3000 ft2, and ~ured at a speed of 200
ft./mirl. by electron beam radiation at a dose rate of 3 negarads.
The surface resistivity of the coated side of the abcve coat~d
polyethylene filnt was measured at 8.75 x 108 ohm/sq. at 100 volts and
6.7 x 108 oh~s/s~. at 300 volts. The surface resitivity of the uncc~tted
side o~ the filnt measured 1.2 x 109 ohms/sq~ at 100 volts and 1.0 x 109
ohms/sq. at 300 volts.
*Trade Mark -12-
~287;~22
EXAMPLE VII
The antistatic electron beam curable ccating of Example Vl was
applied by an offset gravure coating station to the metallized side of
0.5 mil polyester film (polyethylene terephthalate which had beæn vacuum
metallized with aluminum) at a coating weight of 1.3 Ibs./3000 ft.2, and
cured at a speea of 100 ft./min. wqth electron keam radiation at a dose
rate of 3 megarads.
Ihe surface resistivity of the coated side was measured at 2.2
x 105 ohms/sq. at 100 volts and overloaded (too conductive) at 300
volts. The Æ face resistivity of the uncoated side measured 1.3 x 1012
ohms/sq. at 100 volts and 1.6 x 1012 ohms/sq. at 300 volts.
EXPME~E VIII
Example Vl was repeated except that the substrate was 60 Lb.
tper 3300 sq. ft.) clay coated both sides paper. ~le surface
resistivity of the coated side was 1.1 x 101 o~ms/ sq. at 100 volts and
1.2 x 101 at 300 volts. The surface resistivity of the unc~ated side
measured 3.8 x 101 ohms/sq. at 100 volts and 3.5 x 101 ohms/sq~ at 300
volts.
EXAMPLE IX
Example VI was repeated except that the polyethylene substrate
was first metallized hy vacuum deposition of aluminum and the coating
was applied over the metal. The surface resistivity of the coated side
was measu~ed at 1.5 x 105 ohn~s/sq. at 100 volts and overloaded ~too
conductive) at 300 vol s. The surface resistivity of the uncoated side
measured 1.9 x 1012 ohms/sq. at 100 volts and 6.2 x 1011 ohms/sq. at 300
volts.
13
.
8732;~
E~E X
Example Vl was repeated except that the substrate was 3 mil
lay flat low density polyeth~lene tubing. The outside of the tubing was
coated at a weight of approximately 1 Ib./3000 ft.2. The inside of the
tubing was found bo have an antistatic surface.
14
