Conductive polymer laminates

A polymeric laminate and packaging material produced therefrom have (a) at least one conductive layer and (b) at least one static dissipative layer comprising a polymer composition having dispersed therein a non-volatile ionizable metal salt, said static dissipative layer being in electrical contact with the conductive layer. Such a laminate is found to provide shielding and static dissipation suitable for packaging of electrostatically sensitive items such as electronic components.

BACKGROUND OF THE INVENTION 
This invention relates to laminates having at least one electrically 
conductive layer. More specifically, it relates to such laminates 
additionally having at least one static dissipative layer. 
With the proliferation of electronic equipment, there has developed a 
rapidly growing market for packaging and other materials which protect 
sensitive electronic components from electrostatic charges and fields. 
Many electronic devices, including printed circuits and microchips, are 
extremely vulnerable to damage from static discharges of as little as 50 
volts. Static discharges on the order of 10,000 volts are commonly 
encountered during the normal handling of these devices such as from 
friction, motion, separation of dissimilar materials, and induction. It 
is, therefore, necessary to protect the devices from electrostatic fields 
and charges during their manufacture, transportation and use. Packaging 
and other materials used in handling or manufacturing electrostatically 
sensitive devices desirably protect against rapid, damaging discharges and 
fields. In addition to packaging, such items as storage containers, 
housings for electronic devices, materials used in environments in which 
the sensitive devices are manufactured and the like advantageously also 
provide such protection. 
Two types of protection are advantageously provided. First, the devices are 
shielded from external electrostatic or radio frequency fields. Shielding 
can be provided by conductive films or foils, for instance, of 
carbon-loaded polyethylene. Carbon-loaded polymers typically have surface 
resistivities between about 10.sup.3 and 10.sup.6 ohms per square. Second, 
induced or applied electrostatic charges are attenuated or dissipated away 
from the devices to avoid areas of high specific charge. Films having 
treatments involving quaternary or tertiary amines are often used to 
dissipate charges. Such films typically have surface resistivities between 
about 10.sup.10 and 10.sup.13 ohms per square, but a somewhat more 
conductive material is desirable. A material as conductive as carbon 
loaded polyethylene or a metal is, however, so conductive that it may 
conduct an electrostatic charge to an electronic device before the charge 
can be dissipated. Such problems encountered in dealing with static are 
further explained by D. C. Anderson in "ESD Control: To Prevent the Spark 
that Kills," Evaluation Engineering, Vol 23, No. 7, Jul. 1984, p. 20. 
Conductive laminates potentially have a number of uses. Each application 
involves a number of desired characteristics. A packaging material, for 
instance, is desirably lightweight, strong, and easily fabricated into a 
configuration which is adapted to the size and shape of an electronic 
device. While polymers, particularly polyolefins, possess the foregoing 
characteristics, they are not generally static dissipative or conductive 
without surface treatment, incorporation of a blooming additive or filling 
with carbon black, graphite or metallic particles. To achieve conductivity 
as required for shielding, a polymer must have a relatively high loading 
of conductive filler therein which loading is believed to provide 
sufficient conductive filler to achieve contact between conductive 
particles. In the case of carbon black, 25-40 percent by weight carbon 
black based on total weight of carbon black and polymer is often required. 
Such a highly carbon black filled polymer is referred to as carbon-loaded. 
Such concentrations of carbon black or other fillers typically render the 
polymers mechanically weak, and thus degrade some of the properties that 
render polymers suitable for packaging. Furthermore, loaded films are 
known to contaminate electronic devices by sloughing filler particles. 
Layers of polymers filled with sloughable materials have been laminated 
between polyethylene layers to render the filled layers more manageable in 
a packaging process and reduce contamination by sloughing. The laminates 
of U.S. Pat. Nos. 4,554,210 and 4,590,741 exemplify laminates having 
filled layers. Such laminates, however, have relatively high surface 
resistivities generally characteristic of the outer layers of the laminate 
because the outer layers electrically insulate the inner layer. Surface 
resistivity can be lowered, for instance, by use of a conductive 
plasticizer or surface treatment on one or both outer layers as 
exemplified, for instance, by the laminate of U.S. Pat. No. 4,363,071. 
When an amine, humectant or surfactant compound is incorporated into a 
polymer or used as a static dissipative surface treatment thereon, such 
surface treatments exude to the surface of the polymer, where they absorb 
atmospheric moisture to form an electrolyte microlayer. The microlayer is 
generally sufficiently conductive to render the polymer static 
dissipative. At least four major problems are encountered with static 
dissipative surface treatments. Since the static dissipative agents are on 
the surface, they are subject to being removed during handling. In this 
manner, the static dissipative effect is reduced or destroyed until more 
of the amine, humectant or surfactant can migrate to the surface. Further, 
since the static dissipative agent is being continually removed, the 
polymer will eventually lose its static dissipative properties. In 
addition, these static dissipative agents depend on a humid environment 
for effective operation. Thus, their static dissipative behavior will vary 
according to the local relative humidity, and will be minimal in arid 
environments. Finally, these static dissipative agents are sometimes 
corrosive or are potential contaminants. 
Accordingly, it would be desirable to provide a system of polymers which 
has conductive and static dissipative properties which are not 
significantly dependent on local humidity, are stable over time, and which 
has physical properties which permit it to be used for a variety of 
packaging and other shielding and static control and conductive 
applications. 
SUMMARY OF THE INVENTION 
In one aspect, the invention is a polymeric laminate comprising 
(a) at least one comprising a conductive layer and 
(b) at least one static dissipative layer comprising an organic polymer 
having dispersed therein a non-volatile ionizable metal salt in an amount 
sufficient to increase the conductivity of the polymer, said layer being 
in electrical contact with the conductive layer. 
In another aspect, the invention is a laminated, antistatic packaging 
material comprising: 
(a) a first outer layer comprising an organic polymer having dispersed 
therein a non-volatile ionizable metal salt in an amount sufficient to 
increase the conductivity of the polymer; and 
(b) in electrical contact with said first outer layer, an inner layer 
comprising a conductive layer. 
It has been found that laminates of conductive layers and static 
dissipative layers in electrical contact have enhanced surface 
conductivity and provide effective shielding for electrostatically 
sensitive items. Isolation of a conductive layer used in packaging from 
direct contact with package contents or an environment can also be 
achieved by interposing a static dissipative layer or other layer between 
the contents and the conducting layer. 
Polymer laminates and packaging materials of the invention advantageously 
have static dissipative and shielding properties that render them suitable 
for protection of electrostatically sensitive items such as electronic 
devices and components as well as photographic film and the like. The 
laminates and packaging materials of the invention, further, have static 
dissipative properties generally independent of humidity and which do not 
significantly decrease over time Advantageously, contamination by 
sloughing of fillers or removal of surface treatments is also reduced.

DETAILED DESCRIPTION OF THE INVENTION 
Laminates of the invention have at least one instance, conductive layer. A 
conductive layer is generally one which conducts electricity. A conductive 
layer suitable for use in the practice of the invention is more conductive 
than a static dissipative layer in electrical contact therewith. To be 
sufficiently conductive to provide shielding, such conductive layers 
advantageously have resistivities less than about 10.sup.5, preferably 
less than about 10.sup.4, more preferably less than about 10.sup.2 ohm*cm. 
Suitable conductive layers include, for instance, conductive metal plates 
or foils such as gold foil, copper foil, aluminum foil and the like: 
carbon loaded polymers, that is polymer compositions having therein 
sufficient carbon fillers to render the polymer composition conductive: 
polymers filled with electroconductive (e.g. metal, metallized, carbon, or 
other electroconductive) particles, including platelets, flakes, fibers, 
powders, granules, spheres and the like: polymer films having metallized 
surfaces, for instance, those treated by vacuum depositon, arc spraying 
and other processes of depositing a thin layer of metal on the polymer and 
the like. When the conductive layer is a polymer composition having 
conductive filler particles therein, the conductivity thereof is suitably 
enhanced according to the teachings of copending application Ser. No. 
242,090 to Knobel et al., filed Sept. 8, 1988, which is incorporated by 
reference herein in its entirety. 
Many conductive films or sheets are commercially available, such as, for 
instance carbon loaded polyolefin films from Pervel Industries, Inc. under 
the trade designation Condulon,.RTM. from 3M Corporation under the trade 
designation Velostat.RTM. or from Quality Packaging Supply Corporation, 
under the trade designation Xerostat.RTM. and the like. Conductive layers 
are alternatively prepared by processes within the skill in the art. 
Generally when the laminate is to be used in packaging, the conductive 
layer is preferably a polymer composition having therein a conductive 
filler. For packaging of electronic components, the conductive layer 
preferably is of sufficient thickness to shield the components from radio 
frequency radiation and/or electrostatic fields, more preferably from 
about 1 mil to about 50 mils, most preferably from about 3 to about 10 
mils. When a transparent laminate is needed, the conductive layer is 
preferably a metallized transparent or translucent polymer film or sheet. 
A metal layer is generally preferable, for instance, when the application 
requires attenuation of radio frequency radiation and/or electrostatic 
fields. 
When the conductive layer has a polymeric component, any polymer with which 
adequate conductive material can be mixed to make the resulting polymer 
composition conductive is suitable. Such polymers include polyolefins such 
as polyethylene, polypropylene and polyisobutylene, ethylene-acrylic acid 
copolymers, polyesters, polyamides, polyvinylhalides, polystyrene and 
copolymers of styrene and other unsaturated monomers such as 
acrylonitrile/butadiene/styrene polymers, polycarbonates, polyurethanes, 
interpolymers of ethylene and carbon monoxide, polyethers, polycarbonates, 
ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers and 
the like. Mixtures of these and other polymers are also suitable. A 
polymer is advantageously selected for its physical properties and for the 
ease with which it can be laminated to an adjacent layer. Those skilled in 
the art can select suitable polymers without undue experimentation. 
In addition to the conductive layer, laminates of the invention also have 
at least one static dissipative layer comprising an organic polymer 
composition having dispersed therein a non-volatile ionizable metal salt 
in an amount sufficient to increase the conductivity of the polymer 
composition over the conductivity of the same polymer not containing the 
salt. Such layers are referred to herein as static dissipative layers. 
The polymer composition suitably comprises any generally non-conductive, 
organic polymer in which an ionizable metal salt can be dispersed. A 
non-conductive polymer is advantageously one having a resistivity greater 
than about 10.sup.12 ohm.multidot.cm. Suitable polymers include 
polyolefins such as polyethylene, polypropylene and polyisobutylene, 
ethylene-acrylic acid copolymers, polyesters, polyamides, 
polyvinylhalides, polystyrene and copolymers of styrene and other 
unsaturated monomers such as acrylonitrile/butadiene/styrene polymers, 
polycarbonates, polyurethanes, interpolymers of ethylene and carbon 
monoxide, polyethers, ethylene-vinyl acetate copolymers, ethylene-vinyl 
alcohol copolymers and the like. Mixtures of these and other polymers are 
also suitable. The polymer is suitably linear or branched, but, with 
either structure, is preferably thermoplastic. A polymer, conductive 
filler and ionizable metal salt are advantageously selected for their 
mutual compatibility and for physical and chemical properties suitable for 
a specific application. 
Polymers having a plurality of oxygen atoms are particularly useful in 
preparing polymer compositions containing ionizable metal salts, which 
compositions exhibit rapid static decay and are referred to herein as 
oxygen-containing polymers. Exemplary of oxygen-containing polymers are 
polyethers, particularly polytetrahydrofuran, poly(alkylene oxides), such 
as poly(ethylene oxide), poly(propylene oxide), poly(butylene oxide) and 
the like; polyesters: polyurethanes, including polyurethane-polyureas and 
the like; interpolymers of carbon monoxide and olefins and the like. In 
most instances, it is preferable that an oxygen-containing polymer contain 
at least about 0.01 mole fraction oxygen atoms. 
For applications in which especially good static dissipative properties are 
desired, when fluoroalkyl sulfonic acid salts are the ionizable salts, or 
when the oxygen-containing polymer is to be blended with another polymer, 
it is preferred that the oxygen-containing polymer contain at least about 
0.05, more preferably from about 0.075 to about 0.5 mole fraction oxygen, 
because polymers having these ranges of oxygen exhibit particularly low 
static decay times in the practice of the invention. In the case of 
interpolymers of olefins and carbon monoxide, these amounts of oxygen 
correspond to approximately at least about 10 weight percent, more 
preferably from about 15 to 45 weight percent carbonyl groups (carbon 
monoxide) in the polymer, respectively. 
It is also preferred that the oxygen atoms be in uncharged covalent 
functional groups like urethane groups, ether groups or ketone groups. 
Functional groups like salts and acid groups which tend to have or develop 
a charge are somewhat less effective. Groups like esters wherein the 
oxygen atoms are believed to have more resonately dispersed electron 
density are of intermediate utility. The polymers having covalent 
oxygen-containing functional groups polymers are referred to herein as 
oxygen-rich polymers. Among the oxygen-rich polymers, polyurethanes, 
polyethers and carbon monoxide interpolymers with- olefins are preferred 
in most instances because the ionizable metal salts are often more 
effective in such polymers. 
Ketone.-containing polymers are more preferred, in most instances, for use 
in the practice of the invention. Such polymers are readily prepared, for 
example, by the oxidation of various polyolefins. However, one preferred 
ketone-containing polymer is an interpolymer of a lower olefin and carbon 
monoxide. The term "lower olefin" is used broadly herein to refer to a 
mono-unsaturated acyclic hydrocarbon having from about 2 to about 12, 
preferably 2-6, more preferably 2-4 carbon atoms, which are either 
unsubstituted or substituted with heteroatoms or groups which are inert, 
i.e., do not undesirably interfere with the interpolymerization of the 
lower olefin with carbon monoxide. 
The interpolymer may be a simple interpolymer of a lower olefin and carbon 
monoxide, or an interpolymer thereof with at least one other 
copolymerizable monomer, a graft or block interpolymer having at least one 
segment of a lower olefin/carbon monoxide interpolymer or a partially 
hydrogenated interpolymer. Such polymer and method of preparing them are 
described, for example, in U.S. Pat. Nos. 2,296,963, 2,436,269, 2,495,255, 
2,495,286, 2,495,292, 2,641,590, 3,083,184, 3,248,359, 3,530,109, 
3,689,460, 3,694,412, 3,780,140, 3,835,123, 3,929,727, 3,948,850, 
3,948,832, 3,968,082, 3,984,388, 4,024,104, 4,024,325, 4,024,326, 
4,139,522, 4,143,096 and 4,304,887, all incorporated by reference in their 
entireties. 
Preferred carbon monoxide-containing interpolymers are random interpolymers 
of carbon monoxide and an unsubstituted or halogen-substituted lower 
olefin having 2-4 carbon atoms, preferably ethylene (including small 
portions of about C.sub.3 -C.sub.8 aliphatic olefins optionally included 
for property modification). 
When a thermoplastic carbon monoxide containing interpolymer is used, it 
preferably has a melt index, as measured according to ASTM D-1238, 
Condition E, of about 0.1 to about 500, preferably from about 2 to about 
150 grams/10 minutes. A polymer having a melt index within these ranges 
provides optimum processing characteristics for most applications and 
often exhibits somewhat more conductivity than a polymer of lower melt 
index having therein the same ionizable salt. 
Many thermoplastic polyurethanes are commercially available including 
Pellethane.RTM. resins from The Dow Chemical Company, Desmopan.RTM. resins 
from Bayer AG and Texin.RTM. resins from Mobay Chemical Corporation. Other 
polyurethanes are prepared by methods within the skill in the art, for 
instance those described in U.S. Pat. Nos. 4,618,630 and 4,617,325 which 
are incorporated by reference herein in their entireties. Among 
polyurethanes, thermoplastic polyurethanes are preferred. They are 
advantageously the reaction products of hydroxyl-terminated relatively 
high equivalent weight polyether or polyester polyols, a diisocyanate and, 
preferably, a difunctional "chain extender". Such polyurethanes are 
described, for instance, in U.S. Pat. Nos. 4,748,195; 4,621,113; 
4,640,949; 4,597,927; 4,306,052; 3,642,964 and copending Application Ser. 
No. 242,090 which are incorporated herein by reference in their 
entireties. 
A third type of preferred oxygen-rich polymers is the polyethers. 
Polyethers are polymers having plural ether groups and include 
polyoxyalkylenes, polyacetals and the like. Commercially available 
polyethers suitable for use in the practice of the invention include 
Carbowax.RTM. polyethylene glycols and Polyox.RTM. resins from Union 
Carbide Corporation. 
For most applications, the polyethers are advantageously solids, although 
semisolids are useful, for instance, in forming electrolytes or 
non-structural components. Thermoformable polyethers are especially useful 
in the practice of the invention. They are readily amenable to manufacture 
of films, for instance by hot rolling or by deposition, e.g. on a support, 
or by solvent evaporation from a solvent. 
Polyoxyalkylenes have alkylene groups alternating with oxygen atoms. Such 
polyethers are formed, for instance by the processes described in U.S. 
Pat. Nos. 3,580,866; 3,624,008; 3,627,702: 3,649,561: 3,654,183; 
3,728,320; 3,728,321: 3,741,916; 3,756,968; 3,776,863; 4,303,782; 
4,359,589; 4,412,063; 4,423,206 4,705,728 and copending U.S. application 
Ser. No. 242,090. High molecular weight polyalkylene ether glycols are 
also suitably coupled according to processes such as those described in 
U.S. Pat. Nos. 4,275,244 and 4,521,586 which are incorporated by reference 
herein in their entireties. 
Polyoxyalkylene polyethers also include polymers having oxymethylene 
repeating units. The preparation of such polyethers is known in the art 
and includes, for instance, processes described in U.S. Pat. Nos. 
3,597,397; 3,639,347; 3,754,053; 3,803,094 and 4,312,977 which are 
incorporated by reference herein in their entireties. In these processes 
oxymethylene group-containing polyethers or formaldehyde are polymerized 
as homopolymers or, optionally, with comonomers copolymerizable therewith. 
Other polyethers suitable for use in the practice of the invention include, 
for instance, polyacetals. Such polymers are known in the art and include 
polymers produced, for instance, by the processes described in U.S. Pat. 
Nos. 3,883,450 and 4,380,610 which are incorporated by reference herein in 
their entireties. 
The static dissipative layers of the laminates of the invention contain a 
non-volatile ionizable metal salt. By ionizable, it is meant that the salt 
is one which provides mobile ions in the presence of an electric field. 
While the ions are mobile to carry electricity, the salt advantageously 
remains in the polymer composition to maintain bulk or volume conductivity 
rather migrating to the surface of the composition. It is preferable that 
the salt be one which is not readily extractable from the polymers or 
blends thereof by contact with water or other solvent. 
The cation can be any metal which forms an ionizable salt with one or more 
anions, including those metals in Row 2, groups IA and IIA:, Row 3, groups 
IA, IIA and IIIA: Row 4, groups IA-IVA and IB-VIIIB: Rows 5 and 6, groups 
IA-VA and IB-VIIIB; and the lanthanide series of the Periodic Table of the 
Elements. Preferably, the metal is an alkali metal, an alkaline earth 
metal, Co, Ni, Fe, Cu, Cd, Zn, Sn, Al or Ag, more preferably alkali and 
alkaline earth metals, most preferably alkali metals, because salts having 
such cations exhibit low static decay times in the practice of the 
invention. 
The anion is one which forms an ionizable salt with the metal cation. To 
achieve low static decay times, the anion is advantageously one having at 
least one delocalizable electron, that is, it is advantageously an anion 
having charge distributed over more than one atom. Such an anion is 
recognizable by those skilled in the art by such characteristics as pi 
bonding, electron withdrawing groups such as halogen atoms, the 
possibility of resonance structures and the like. The anion is preferably 
a relatively large, multiatomic anion having substituents like phenyl 
groups, sulfur atoms, phosphorus atoms and the like that can accept and 
delocalize an electron charge: more preferably the anion has more than 
one, more preferably at least about 4, most preferably at least about 5, 
non-metallic atoms. Non-metallic atoms are generally considered to be 
selected from the group consisting of boron, carbon, silicon, phosphorus, 
arsenic, oxygen, sulfur, selenium, tellurium, fluorine, chlorine, bromine, 
iodine and astatine. Preferred non-metallic atoms are boron, phosphorus, 
sulfur and carbon in aromatic groups: sulfur and carbon in aromatic groups 
are more preferred. The anion is preferably monovalent. The anion is more 
preferably the conjugate base of an inorganic acid having a delocalizable 
electrons, a fluoroalkyl sulfonate or a tetraorganoboron ion. Such 
include, for example, NO.sub.3 -, SCN-, SO.sub.4.sup.2-, HSO.sub.4 -, 
SO.sub.3.sup.2-, HSO.sub.3 -, ClO.sub.4 -, PO.sub.4.sup.3-, H.sub.2 
PO.sub.4 -, HPO.sub.4.sup.2-, PO.sub.3.sup.3- , HPO.sub.3.sup.2-, H.sub.2 
PO.sub.3 -, fluoroalkyl sulfonic acid anions, particularly perfluoroalkyl 
sulfonic acid anions, tetraorganoboron ions, particularly tetraalkyl and 
tetraarylboron ions, and the like. The anion is most preferably not an 
SCN-- anion, when these salts tend to be water extractable, are less 
effective than other salts, and have a noticeable, undesirable odor and 
color. Similarly, most preferably, the anion is not a carboxylate or 
carbonate ion because salts of these anions tend to be less effective than 
other salts. 
Among the preferred anions are fluoroalkyl sulfonic acid anions 
(fluoroalkyl sulfonate) which are suitably any fluoroalkyl sulfonic acid 
anions compatible with specific compositions in which they are used. 
Advantageously, for achieving static dissipation, preferred fluoroalkyl 
sulfonates have from about one to about twenty carbon atoms and are either 
straight chained, branched or cyclic. Fluoroalkyl sulfonates are sulfonate 
anions having an alkyl group having fluorine substitution, that is, 
fluorine atoms bonded to the carbon atoms of the alkyl groups. The alkyl 
groups, optionally, also have hydrogen atoms and/or other halogen atoms 
bonded to the carbon atoms. Preferably, at least about 25%, more 
preferably about 75%, (by number) of the atoms other than carbon which are 
bonded to carbon atoms of the fluoroalkyl groups are halogen, preferably 
fluorine. More preferably, the fluoroalkyl groups are perhaloalkyl groups, 
that is, alkyl groups having only halogen substitution. Suitable halogens 
include fluorine, chlorine, bromine and iodine, preferably fluorine and 
chlorine. Suitable fluoroalkyl sulfonic acid anions include, for instance, 
C.sub.2 HF.sub.4 SO.sub.3.sup.-, C.sub.2 HClF.sub.3 SO.sub.3.sup.-, 
C.sub.3 H.sub.2 F.sub.5 SO.sub.3.sup.-, C.sub.4 H.sub.2 F.sub.7 
SO.sub.3.sup.-, C.sub.5 H.sub.2 F.sub.9 SO.sub.3.sup.-, C.sub.7 ClF.sub.14 
SO.sub.3.sup.-, C.sub.8 Cl.sub.2 H.sub.2 F.sub.13 SO.sub.3.sup.-, C.sub.20 
ClHF.sub.39 SO.sub.3.sup.- and the like. 
The fluoroalkyl groups are most preferably perfluoroalkyl groups. Exemplary 
perfluoroalkyl sulfonic acid anions include, for example CF.sub.3 
SO.sub.3.sup.- (triflate), C.sub.2 F.sub.5 SO.sub.3.sup.-, C.sub.5 
F.sub.11 SO.sub.3.sup.-, C.sub.7 F.sub.15 SO.sub.3.sup.-, C.sub.8 F.sub.17 
SO.sub.3.sup.-, C.sub.9 F.sub.19 SO.sub.3.sup.-, C.sub.20 F.sub.41 
SO.sub.3.sup.- and the like, isomers thereof and mixtures thereof. The 
salts of perfluoroalkyl sulfonates preferably have from about 1 to about 
20, more preferably from about 1 to about 10, carbon atoms for reasons of 
availability and compatibility with polymers. Within that range of 
perfluoroalkyl sulfonic acid salts, a salt or mixture of salts, is 
advantageously chosen for its compatibility with and resistance to 
leaching or extraction from the polymer or blend in which it is used. For 
instance, a mixture of perfluoroalkyl sulfonates having from about 4 to 
about 10 carbon atoms is most preferred for use in polyurethanes, 
especially for use in a polymer composition to be exposed to a moist or 
aqueous environment. In copolymers of ethylene and carbon monoxide and 
blends thereof with other polymers, however, triflates are most preferred 
in most instances. Exemplary salts include NaCF.sub.3 SO.sub.3 (sodium 
triflate), KC.sub.6 F.sub.13 SO.sub.3, LiC.sub.8 F.sub.17 SO.sub.3, 
NaC.sub.9 F.sub.19 SO.sub.3, and the like. Sodium and potassium 
perfluoroalkyl sulfonates having from about one to about 10 carbon atoms 
are most preferred. 
Ferfluoroalkyl sulfonic acid salts are particularly preferred for 
applications in which the composition containing the salts is to be heated 
above about 230.degree. F., especially when the composition is to be 
heated above about 300.degree. F. Compositions containing perfluoroalkyl 
sulfonic acid salts often exhibit greater clarity and retain their static 
dissipative or conductive qualities after such heating, particularly in 
the presence of additives such as colorants or flame retardant additives, 
better than do similar compositions containing other ionizable salts. 
The ionizable metal salt is dispersed in a polymer in an amount sufficient 
to render the polymer composition containing the salt more static 
dissipative than the polymer composition would be without the salt. Static 
dissipation can be measured using a 406C Static Decay Meter from Electro 
Tech Systems, Inc. or according to Federal Test Standard 101C, Method 
4046, omitting the water step as in the Electronics Industry Association 
Interim Standard IS-5A. The time necessary to measure reduction to .+-.50 
volts of a +5000 volt and -5000 volt charge is measured. A polymeric 
material is considered static dissipative if it is capable of dissipating 
99% of a static charge of 5000 volts (direct current) within 30, 
preferably within about 10, more preferably within about 4, and most 
preferably within about 2 seconds or less. The more rapid times are 
preferred because a charge is available for possible damage for shorter 
times. Increased static dissipative ability is also evidenced by increased 
conductivity or decreased surface or volume resistivity. Conductivity is 
advantageously measured according to the procedure of ASTM-D-257-74 or ANS 
Z-41-1983. Characteristics of materials and measurement render direct 
correlation between measurements of static dissipation and conductivity 
very difficult. Increased static dissipation achieved in the practice of 
the invention is suitably measured by any of these methods or other 
methods which one skilled in the art would consider a measurement 
indicative of conductivity or static dissipation. 
Amounts of non-volatile ionizable salts sufficient to render the polymer 
composition containing the salt more static dissipative than the polymer 
composition would be without the salt vary with the polymer composition 
and the salt used. The amounts are advantageously in the range of from 
about 0.003 to about 20 weight percent based on the weight of the total 
polymer composition in which the salt is dispersed. Preferably, about 0.03 
to about 5, and more preferably about 0.3 to about 3 weight percent of the 
non-volatile ionizable metal salt is used to achieve rapid static 
dissipation. In most instances, levels below those indicated impart 
insufficient increase in conductive behavior to the polymer, whereas 
higher levels do not significantly further increase conductivity and are, 
therefore, unnecessary. 
It is noted that, in the case of oxygen-rich polymers, particularly 
ketone-containing polymers, to obtain a specified increase in 
conductivity, the amount of salt needed varies, in most instances, 
inversely with the amount of carbonyl groups contained in the polymer. 
Accordingly, within a single type of oxygen-rich polymer, i.e. 
ketone-containing, urethane-containing or polyether-containing polymer, a 
polymer having relatively higher relative proportions of oxygen atoms, in 
most instances, requires less salt to achieve a desired level of 
conductive behavior than does another polymer having a lesser relative 
proportion of oxygen atoms. 
Polymer compositions containing non-volatile ionizable metal salts in 
amounts suitable for use in the practice of the invention advantageously 
have resistivities of from about 10.sup.6 to about 10.sup.13 
ohm.multidot.cm, preferably from about 10.sup.6 to about 10.sup.11, more 
preferably from about 10.sup.6 to about 10.sup.10 ehm.multidot.cm. 
Compositions having resistivities in these ranges provide successive 
amounts of static dissipation needed for packaging and shielding 
applications. 
The non-volatile, ionizable metal salt is suitably incorporated into the 
polymer in any convenient manner. Advantageously, the salt is dispersed 
such that it ionizes. A particulate polymer can be mixed directly with the 
salt at the desired proportions and blended until the salt is dispersed 
into the polymer. Alternately, the salt can be blended into the melted 
polymer. In a preferred technique, a solution of the salt can be blended 
with the particulate or melted polymer, and the solvent is later removed. 
This process provides especially good dispersion of the salt into the 
polymer. The solvent employed in this last process is any in which the 
salt is soluble and which is readily evaporated from the polymer/salt 
mixture. Suitable solvents include water, acetone, methyl ethyl ketone, 
methyl isobutyl ketone, methanol, ethanol, butanol, dioxane and the like. 
It is often preferable to use one or more enhancers with the ionizable 
metal salts in the practice of the invention. Enhancers are compounds 
which increase the conductivity of an organic polymer in the presence of 
said ionizable metal salt, but do not substantially increase the 
conductivity of said organic polymer in the absence of said ionizable 
metal salt. Enhancers are advantageously carboxylic acid salts, carboxylic 
acid esters, diphosphate or phosphate esters as taught in U.S. Pat. Nos. 
4,618,630 and 4,617,325 to Knobel et al., which patents are incorporated 
herein by reference in their entireties. The salts and esters preferably 
are those of carboxylic acids having from about 6 to about 30, more 
preferably from about 9 to about 23 carbon atoms. The alcohol portion of 
the esters preferably has from about 2 to about 20, more preferably from 
about 2 to about 10 carbon atoms. It is preferable, in most cases, that 
the enhancer be one in which the non-volatile, ionizable metal salt is 
soluble. Additionally, an enhancer is preferably compatible with the 
polymer in which it is dispersed. In most instances, enhancers are not 
needed in oxygen-rich polymer compositions. In such compositions, 
enhancers are preferably substantially absent, that is, there is 
insufficient enhancer compound present to increase the conductivity of the 
polymer composition containing the ionizable salt, but the compounds may 
be present in amounts less than about 2 percent by weight as surfactants, 
for instance. 
When an enhancer is used with the ionizable metal salt as a conductivity 
additive, the ability to disperse the conductivity additive is largely 
dependent on the compatibility of the enhancer and the organic polymer. It 
is, therefore, generally desirable to select the organic polymer and the 
enhancer together so that the two components are compatible. 
Alternatively, the conductivity additive and organic polymer can be 
compatibilized by use of a cosolvent or other material which 
compatibilizes the polymer and the conductivity additive Materials listed 
above for use as solvents or enhancers are examples of suitable 
cosolvents. An admixture of salt and enhancer, optionally with cosolvent, 
is incorporated into an already prepared polymer, e.g. by melt blending, 
extrusion or the like. Alternatively, the admixture is mixed with a 
polymer-forming reaction mixture or component thereof. Processes taught in 
U.S. Pat. Nos. 4,618,630 and 4,617,325, which are incorporated herein by 
reference, further exemplify incorporation of an ionizable salt and 
enhancer into a polymer composition. 
In the laminates of the invention, a static dissipative layer preferably 
contains insufficient conductive filler to slough appreciably: therefore, 
it can protect an item from contamination and corrosion caused by 
sloughing of conductive particles from a conductive layer. 
It is not critical how laminates of the invention are formed so long as the 
static dissipative layer and conductive layer are in electrical contact, 
that is, such that an electric charge is conducted from one layer to the 
other. Advantageously, electrical contact is established by having the 
layers in direct physical contact. Alternatively, there may be an 
intermediate layer or coating, i.e. an adhesive or tielayer, between the 
layers, so long as the intermediate layer is of a composition and 
thickness which permits current to pass between the conductive layer and 
the static dissipative layer. An intermediate layer can, for instance, be 
sufficiently thin to permit tunnelling for the intermediate layer may 
cover only part of the area between the static dissipative and conductive 
layers. Alternatively, the intermediate layer may be conductive or static 
dissipative. 
In general, a static dissipative layer is laminated to a conductive layer 
by procedures suitable for laminating polymer compositions not containing 
ionizable metal salts to conductive layers. Such procedures are within the 
skill in the art. For instance, the layers can be laminated by processes 
such as coextrusion, otherwise extruding one or more layers upon another 
layer, nipping between pressure rollers, use of adhesives, use of hot 
rollers and the like. 
Alternatively, a static dissipative layer may be deposited as a coating on 
the conductive layer, especially when the polymer composition containing 
the ionizable salt is one which has suitable rheological properties in its 
molten state for application as a coating, e.g. a relatively high melt 
index, or is castable from a volatile solvent such as acetone, methyl 
ethyl ketone, methyl iso-butyl ketone, tetrahydrofuran, isopropanol, 
ethanol, water, methylene chloride and the like. In many applications of 
the laminates of the invention, such as for packaging, the static 
dissipative layer is advantageously at least about 0.2 mil, preferably at 
least about 0.5 mil thick. Such a coating is sufficient, for instance, to 
reduce contamination from sloughing of conductive filler particles. 
Deposition of the static dissipative layer as a coating, for instance, as 
a paint, is also advantageous when the conductive layer is sufficiently 
thick or hard to render other methods of lamination difficult. For 
instance, the conductive layer may be a shaped metal structure such as a 
box, and the static dissipative layer can help avoid sloughing of 
particles from the metal surface and avoid direct contact between the 
metal and items which might otherwise contact it. The layer can also 
provide protection from the environment without electrically insulating 
the box. 
Alternatively, especially when only a thin layer of conductive material is 
desirable, the conductive layer may be applied as a coating on the static 
dissipative layer. For instance, a metal such as nickel, tin, zinc and the 
like can be sputtered onto a static dissipative layer by processes within 
the skill in the art. Sputtering can produce conductive layers having a 
thickness on the order of about 500 angstroms. Such thin layers are 
especially useful when a transparent laminate is desirable. 
Use of coating processes which produce continuous layers or of shaping 
processes which maintain continuity is not necessary. For instance, 
discontinuities may arise, especially in thin, conductive layers, in 
processes, such as shaping, that may deform the layers. A static 
dissipative layer in electrical contact with the conductive layer permits 
electrical conduction in spite of the discontinuities. 
The surface resistivity of a static dissipative layer laminated to a 
conductive layer such that there is electrical contact between the layers, 
is advantageously lower than the resistivity of the static dissipative 
layer alone or of the static dissipative layer on a relatively less 
conductive substrate. Such decreased resistivity is exhibited so long as 
the static dissipative layer has a thickness (d.sub.2) such that the total 
resistance through the thickness of the static dissipative layer, through 
the conductive layer and back through the static dissipative layer is less 
than the resistance across the surface of the static dissipative layer. 
The resistance is measured by 2 electrodes a preselected distance 
(d.sub.1) apart on the surface of the static dissipative layer. If the 
static dissipative layer has a resistance R.sub.1 and the conductive layer 
has a resistance R.sub.2, the thickness (d.sub.2) can be determined from 
the equation R.sub.1 (2d.sub.2)+R.sub.2 d.sub.1 =R.sub.1 (d.sub.1). The 
maximum thickness exhibiting this effect varies with polymer, salt and, 
optionally enhancer, composition and is referred to herein as the 37 
maximum portage thickness" . The static dissipative layer is preferably 
thicker than the percolation distance of electrons, that is the distance 
through which electrons travel through a non-conductive medium. More 
preferably, the static dissipative layer has a thickness of greater than 
the percolation distance of electrons in the layer and less than the 
maximum portage thickness, most preferably from about 0.2 to about 50 
mils. 
Surface conductivity is advantageously measured according to the procedure 
of ASTM D-257-74 using concentric electrodes. Alternatively, it is 
measured according to the procedure of ANS Z-41-1983, 3.5 wherein weighted 
electrodes and an ohmmeter are used to measure electrical resistance from 
which conductivity can be calculated. Volume resistivity is measured 
according to the procedure of ASTM D-991-85. Increased conductivity 
achieved in the practice of the invention is suitably measured by either 
of these methods or other methods which one skilled in the art would 
consider a measurement indicative of conductivity. 
Laminates of the invention have at least two layers as has laminate 10 
illustrated in FIG. 1, having a static dissipative layer 14 and a 
conductive layer 15, layer 15 being in electrical contact with said static 
dissipative layer 14. Such laminates are particularly useful for packaging 
electrostatically sensitive items. When the static dissipative layer is 
the inner layer (the layer nearest an object within the packaging), it 
provides improved static dissipative properties; and the conductive layer 
provides shielding. Laminates of the invention may, however, have any 
number of layers. 
FIG. 2 illustrates a preferred embodiment of the invention, laminate 20, 
which has three layers: static dissipative layers 21 and 23; and, between 
and in conductive contact with said static dissipative layers 21 ad 23, 
conductive layer 22. Such an arrangement of laminate layers provides 
additional protection for an electrostatically sensitive item. Layer 21 
may be identical to layer 23 or, alternatively, may differ from layer 23 
by thickness, composition and/or other properties. 
FIG. 3 illustrates another embodiment of the invention having three layers. 
In FIG. 3, laminate 30 has static dissipative layer 31 in electrical 
contact with conductive layer 32. Additionally, laminate 30 has a third 
layer 33 which is not a static dissipative layer and, in the illustrated 
embodiment, is wood. The composition of layer 33 is not critical to the 
invention Rather than providing electrostatic protection, layer 33 
advantageously provides at least one other property desirable for the 
laminate. For instance, in packaging, a third, non conductive is suitably 
of a composition and structure which provides cushioning, toughness, 
reinforcement, sealability, tear strength, dimensional stability, surface 
protection or other quality suitable for packaging. The third layer is 
optionally a polymer composition in the form of a film, a foam, a sheet, a 
shaped object or the like or is another material such as wood, cardboard, 
ceramic, stone or the like. In an alternative embodiment, a third layer in 
contact with a conductive layer may be an additional conductive layer such 
as a metal layer. 
Another preferred embodiment of the invention is illustrated in FIG. 4 
wherein laminate 40 has 5 layers: static dissipative outer layers 41 and 
45; conductive layers 42 and 44 in electrical contact with layers 41 and 
45, respectively: and inner static dissipative layer 43, in electrical 
contact with both 42 and 44. Electrical conduction is possible throughout 
the laminate. Layer 43 may, optionally, additionally provide a quality 
desired in the laminate as outlined for the third layer in a three layer 
laminate as illustrated in FIG. 3. Five layer laminates are particularly 
useful, for instance, when at least one layer which is neither conductive 
nor static dissipative provides additional dimensional stability, tear 
strength or the like. 
FIG. 5 illustrates an alternative embodiment of the invention, laminate 50 
also having 5 layers: static dissipative outer layers 51 and 55, 
conductive layers 52 and 54 in electrical contact with 51 and 55, 
respectively, and inner layer 53 which is not a static dissipative layer. 
Layer 53 may, optionally, provide a quality desired in the laminate as 
outlined for the third layer of a three layer laminate, as illustrated in 
FIG. 3, and has a composition as outlined for that layer. Five layer 
laminates are particularly useful when an inner layer provides a desirable 
physical property like dimensional stability or tear strength. 
Laminates of sheets of relatively transparent static dissipative polymer 
compositions and of sheets of conductive materials having holes, openings, 
gaps, slits and the like (hereinafter "holey") may be formed by known 
processes such that there are relatively transparent portions of a 
laminate. Such laminates may be used to form packaging which affords some 
opportunity for visual inspection. Possible configurations using 
discontinuous conductive layers are illustrated in FIGS. 6-9. 
In FIG. 6, a laminate 60 has a holey conductive layer in the form of 
stripes 61. Laminated over and under the holey conductive layer are 
relatively transparent static dissipative layers 64 and 65. Between the 
stripes 61, the static dissipative layers are laminated to one another in 
the areas designated 62. To maintain conductivity through the layer, the 
stripes are preferably joined in a region 63. Alternatively, stripes are 
sufficiently close to one another to permit conductivity. 
FIG. 7 is a cross sectional view of laminate 60 taken along line 70-70. 
Lamination of the static dissipative layers is shown in regions 62. In an 
alternative embodiment, only one layer of static dissipative material is 
used and has the stripes of conductive material laminated thereto, 
preferably such that there is little movement in the relative positions of 
the stripes. 
FIG. 8 illustrates a cross section of a bag 80 having conductive material 
81 and transparent static dissipative area 82. The bag is open at the top 
and transparent at the bottom. Such a configuration allows optical 
inspection from the bottom of the bag and affords shielding along the 
sides of the bag. 
FIG. 9 illustrates an expanded view of a laminate 90 having a relatively 
transparent static dissipative layer 91 and a holey, relatively opaque, 
conductive layer 72. In laminate 90 there is a third, relatively 
transparent layer 93. Holes in the conductive layer allow optical 
inspection. This configuration has the advantage of avoiding the 
possibility of losing electrical contact among portions of the conductive 
layer. The third layer 93 is optional, but is generally preferred in 
packaging applications to protect objects packaged such that they touch 
the third layer from direct contact with a conductive layer. 
A laminate of the invention can be processed, fabricated or otherwise 
manipulated and used in the same manner as similar laminates which do not 
have static dissipative and conductive layers. 
Packaging may be produced, for instance, 
according to the teachings of U.S. Pat. Nos. 4,554,210 or 4,590,741 which 
are incorporated herein by reference. Heat sealable polymers may be used 
in the static dissipative polymer compositions so that heat sealable 
packaging is produced. Such packaging can also be heatable and sealable 
using radio frequency or microwave radiation, as described in U.S. Pat. 
Nos. 4,600,614 and 4,601,948, which are incorporated herein by reference 
in their entireties. Similarly, the polymers used may be heat shrinkable. 
The following examples are provided to illustrate the invention but are not 
intended to limit the scope thereof. All parts and percentages are by 
weight unless otherwise indicated. Examples (Ex.) of the invention are 
designated numerically, while comparative samples (C.S.) which are not 
examples of the invention are designated by letters. Conductivity is 
measured according to the procedure of ANSI Z41, part 3,5,2,2. 
EXAMPLES 1 AND COMATIVE SAMPLE A 
A blend of 0.97 weight percent sodium tetraphenyl boron (as ionizable salt) 
in a random interpolymer of ethylene and carbon monoxide (ECO) having 10 
weight percent carbonyl groups and a melt index (M.I.) of about 10 grams 
per 10 minutes is prepared in a Werner-Pfleiderer ZSK-53 Twin Screw 
Extruder. The blend is formed by placing the ECO in the extruder and 
injecting a solution of 45 weight percent sodium tetraphenyl boron in 
methyl ethyl ketone. The solution and ECO are compounded at about 
175.degree. to 190.degree. C. for a residence time of 20-45 seconds to 
form an antistatic composition. Liquid injection rates are controlled to 
yield blends having the indicated concentrations of sodium tetraphenyl 
boron. 
Films 2 mils thick are blown on a gloucester film blowing unit having a 215 
inch screw, a 6 inch die and a 2.3 blowing ratio. Laminate structures are 
prepared as follows: 
Comparative Sample A.: Two of 2 mil ECO films prepared as above are pressed 
together with minimum heat to achieve bonding. 
Example 1.: A piece of carbon-loaded polyethylene film (thickness 3.5 mil, 
conductivity greater than 10.sup.5 (ohm-cm).sup.-1) from Maine Poly Inc. 
is sandwiched between 2 pieces of ECO film prepared as above. The piece of 
carbon-loaded film is slightly smaller in size than the ECO sheets so that 
ECO to ECO contact and seal is made at the edges to avoid any direct 
contact of carbon-loaded polymer with measurement electrodes. A 
measurement electrode fits completely within the ECO film area. The 
sandwich is pressed together with minimum heat to produce a laminate for 
measurement. Samples are tested using the Electrotech 406c static decay 
meter following FTS 101C, method 4046.1 for resistivity, and for 
conductivity using ANSI 7-41 immediately at ambient conditions 
(20.degree.-24.degree. C., greater than 30% humidity) and then are 
retested after 114 hours at 23.degree. C. and greater than 2% relative 
humidity. Results are given in Table 1. 
TABLE 1 
______________________________________ 
Sodium 
tetra- Carbon Surface 
phenyl Mon- Initial 
Static Resis- 
boron oxide Charge Decay tivity 
Samples (wt %) (wt %) (Volts) 
(Sec.) (Ohms) 
______________________________________ 
0 hours, 
conditioned 
C.S.A 1.0 10.0 0 0.48 -- 
Ex. 1 1.0 10.0 0 0.02 -- 
114 hours, 
conditioned 
C.S.A 1.0 10.0 0 0.80 8.4* E11 
Ex. 1 1.0 10.0 0 0.06 2.3* E11 
______________________________________ 
The data in Table I show that the example of the invention having a 
conductive layer exhibits a much more rapid static decay time and a lower 
surface resistivity than does a sample of the polymer containing sodium 
tetraphenyl boron but not in electrical contact with a conductive layer. 
EXAMPLES 2 AND 3 AND COMATIVE SAMPLE B 
A sample of ECO containing 10% carbon monoxide and having a melt index of 
10 g/ 10 min. and containing 5 weight percent sodium tetraphenyl boron is 
prepared as in Example 1 and extruded to form pellets. The pellets are 
pressed hydraulically to form plaques approximately 0.1 inch thick. The 
plaques are cut into 5 inch squares. 
A control (designated Comparative Sample B) is a ECO plaque tested 
directly. 
For Example 2 a silver-coated Mylar screen (from Deposition Technology 
Inc.) is sandwiched between 2 plaques avoiding overlap that would expose 
screen to contact with measurement electrodes. The sandwich is pressed 
hydraulically with heat to seal and form a laminate. There is a slight 
reduction in thickness of the sandwich relative to thicknesses of 
individual components. Resulting laminate is 0.16 inch thick. 
For Example 3, a piece of aluminum foil (kitchen grade) is pressed between 
2 plaques of ECO as for Example 2. After heating and pressing the laminate 
thickness is 0.09 inch. 
Static decay and surface resistivity are measured as in Example 1: and 
volume resistivity, according to the procedures of ASTM D-257-74 using a 
Keithley Corp. Model 614 Electrometer and Model 160 Resistivity Cell. 
Results are shown in Table II. 
TABLE II 
______________________________________ 
Total Surface Volume 
Thickness Static decay 
resistivity 
resistivity 
Sample No. 
(inches) (sec.) (ohms) (ohms .multidot. cm) 
______________________________________ 
C.S.B 0.18 0.01 1 .times. 10.sup.11 
.sup. 4 .times. 10.sup.10 
Ex. 2 0.18 0.01 1 .times. 10.sup.11 
6.8 .times. 10.sup.9 
Ex. 3 0.09 0.01 2.4 .times. 10.sup.10 
1.8 .times. 10.sup.9 
______________________________________ 
The static decay data in Table II is the minimum measurable time for all 
samples. Example 2 which has relatively thick static dissipative (ECO) 
layers, has a surface resistivity and volume resistivity near that of 
Comparative Sample B which has no conductive layer. Example 3, however, 
has thinner static dissipative (ECO) layers and has surface and volume 
resistivities lower than those of Comparative Sample B and Example 2. 
EXAMPLE 4 
Films containing 1 weight percent sodium tetraphenyl boron are prepared as 
in Example 1 from ECO having 10 weight percent carbon monoxide, and with a 
melt index of 10 g/ 10 min.. These films are used to make 3 new laminates 
by the procedures outlined in Example 1. Electrical properties are 
measured as in Example 1 and reported in Table 111. 
Comparative Sample C is prepared from 2 layers of the ECO. 
Example 4 is prepared from two layers of the ECO film, each laminated to a 
side of a film of with Teflon.RTM. metalized on both sides with silver 
commercially available from Deposition Technologies Inc. 
Example 5 is prepared from two layers of ECO film, each on one side of a 
layer of Kaptan.RTM. metallized with silver commercially available from 
Deposition Technologies Inc. 
Example 6 is prepared from two layers of the ECO, having between them a 
silvered screen commercially available from Deposition Technologies Inc. 
TABLE III 
______________________________________ 
Surface 
Static decay 
resistivity 
Sample No. time (sec.) 
(ohms) 
______________________________________ 
C.S.C 0.30 5.1 .times. 10.sup.11 
Ex. 4 0.15 1.2 .times. 10.sup.10 
Ex. 5 0.20 3.3 .times. 10.sup.9 
Ex. 6 0.05 1.8 .times. 10.sup.11 
______________________________________ 
The data in Table III shows that Examples 4-6 have faster static decay 
times and lower surface resistivities than those of the ECO containing 
sodium tetraphenyl boron alone (C.S.C). Examples 4 and 5 having continuous 
conductive layers have lower surface resistivities than Example 6 wherein 
the conductive layer is a screen.