Antistatic floor polish

Combining a carboxylated acrylic latex binder/surfactant/metal salt premix with a polymer binder/LiCl PEO complex/plasticizer premix produces a storage stable, conductive floor polish composition. Coated on a floor, the composition provides high gloss with a surface resistivity of 10.sup.6 ohm/sq. compared to present commercial antistatic floor polishes with a surface resistivity of 10.sup.9 ohm/sq.

FIELD OF THE INVENTION 
The present invention relates to electronically conductive wax or polish 
compositions. In particular a new process increases antistatic protection 
without sacrifice of composition performance or stability. 
BACKGROUND OF THE INVENTION 
It has long been known that static charges which develop between isolated 
bodies are discharged when those bodies are brought into sufficiently 
close proximity or contact. Potentials as high as 30,000 volts have been 
reportedly generated simply by a person walking on a synthetic carpet. In 
recent years this phenomenon, always regarded as something of a nuisance, 
has become a major concern to the manufacturers of sensitive electronic 
equipment. A static discharge of only a few hundred volts can severely 
damage or ruin expensive electronic circuitry, and such damage can occur 
at any stage of the assembly process or during transportation or storage. 
Static charges can accumulate on production workers, on assembly work 
surfaces, and on any of the tools and containers used in the assembly 
area. The need to prevent static discharge requires that the entire 
assembly environment be constructed from materials which will quickly 
dissipate static charge, effectively interconnecting all workers, surfaces 
and equipment with a common electrical ground. 
An ever increasing demand exists for static free environments in which 
electronic components can be manufactured. Conductive floor waxes or 
polishes are commercially available to maintain antistatic protection in 
manufacturing as well as research areas. Yet, in spite of the desirability 
for such antistatic compositions to provide resistivities of 10.sup.6 
-10.sup.8 ohm/sq., these commercial materials can provide resistivities of 
only 10.sup.8 -10.sup.10 ohm/sq. while maintaining clarity and smoothness. 
It is known from British Patent Application No. 2,148,915, to produce 
electronically-conductive, water-based wax or polish compositions 
containing neutralized carboxylic aminoester groups and quaternary 
ammonium compounds and having a resistivity of about 10.sup.9 ohm/sq. This 
reference discloses the use chemicals with anionic and cationic 
functionalities for electrical conductivity for a composition which 
provides high gloss and up to 60 days of antistatic protection. However, 
when high levels of quaternary ammonium compounds are used in these 
compositions to give resistivities below 10.sup.9 ohm/sq., the moisture 
sensitivity increases to a level where film toughness is jeopardized. 
Antistatic polishes and waxes produced prior to the present invention 
exhibit several deficiencies in appearance and performance. Some give a 
hazy appearance or fail to give a smooth and durable surface in that the 
wax or polish is networked with microcracks. Not only do they have an 
undesirable appearance, but they crack and peel prematurely. Thus, a 
continuing need existed for an antistatic polish which provides lasting 
protection against antistatic discharging without haze or microcracking. 
Within the last decade, extensive studies have been undertaken on metal 
salt/polymer complexes as electrical conductors. With the metal ion 
coordinated within a polymer matrix, the mechanism of conductance has 
sometimes been referred to as charge conductance. While the mechanism may 
be subject to controversy, several factors influencing the conductivity of 
these complexes are: (a) strong acid groups in the complex, (b) mobility 
of the complex, (c) solvent in which the complex is formed. 
Alkali metal salt/polyethylene oxide complexes and their thermal and 
mechanical properties have been reported in references such as: C. 
Robitaille and J. Prud'Lomme, Macromolecules, 16, 665 (1983); J. M. 
Parker, P. V. Wright and C. C. Lee, Polymer, 22, 1305 (1981); and D. R. 
Payne and P. V. Wright, Polymer, 23, 690 (1982). While very good 
conductivity was reported for lithium salt complexes, Bekturov et al., 
Makromol. Chem., Rapid Commun., 6, 515 (1985), reported the stability of 
metal thiocyanate/PEO complexes as Na.sup.+ &gt;K.sup.+ &gt;NH.sub.4 +&gt;Li.sup.+. 
This suggests that the less stable Li.sup.+ /PEO complexes are providing 
the best conductivity. Thus, metal ions which complex too strongly may be 
too immobile to provide the best electrical conductivity. Yet, in spite of 
what was known about conductivity of metal salt/PEO complexes, it remained 
for the present invention to detail the composition and preparation of an 
improved antistatic floor polish. 
SUMMARY OF THE INVENTION 
The present invention provides an improved conductive wax or polish 
composition comprising: at least one metal crosslinking latex binder and a 
metal salt/polymer matrix where the polymer is polyethylene or 
polypropylene oxide, wherein the coated composition has a resistivity of 
10.sup.6 to 10.sup.8 ohm/sq. The composition has excellent shelf-life and 
stability while providing high gloss without cracking or streaking even 
though higher levels of metal ion are incorporated than with prior art 
waxes or polishes. Optionally, the was contains one or more additional 
binders selected from the group consisting of copolymers of acrylate, 
urethane, or styrene. 
A preferred composition comprises: 
(a) a carboxylated acrylic latex binder, (b) a coalescence agent combined 
with the latex binder, (c) a complex of a lithium salt and polyethylene 
oxide, (d) a non-ionic surfactant, (e) at least one plasticizer, (f) at 
least one additional binder selected from the group consisting of 
copolymers of acrylate, urethane or styrene, and (g) a lithium salt; 
wherein (c) and (g) combined are no more than 4% by weight of the total 
composition. 
A method for producing the improved composition comprises the steps: 
(a) combining an acrylic binder with a surfactant and a metal salt to 
produce an aqueous mixture (a); 
(b) combining a binder with a metal salt/polymer matrix where the polymer 
is polyethylene or polypropylene oxide to produce an aqueous mixture (b); 
(c) combining (a) and (b) to produce a polish or wax composition with a 
conductivity of 10.sup.6 to 10.sup.8 ohm/sq. when coated on a surface. 
In a preferred method, the acrylic binder is carboxylated, the metal salt 
is monovalent and the surfactant is non-ionic. 
A preferred composition and method employs: 
______________________________________ 
Carboxylated Acrylic Latex Binder 
25-60% 
Polyethylene Oxide Emulsion 
1-4% 
LiCl .5-4% 
Surfactant 0-2% 
Plasticizer 0-1.5% 
______________________________________ 
where the lithium chloride is added in two separate portions to the acrylic 
binder to give the final composition. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention involves a process and composition of matter for 
producing electrically conductive polish or wax materials useful for areas 
where it is important to prevent electrostatic discharge. These materials 
are formulated to contain sufficient metal salt such as lithium chloride 
or calcium acetate that they exhibit excellent conducting properties 
(10.sup.6 -10.sup.8 ohm/sq.) when coated on a vinyl flooring surface. It 
has been discovered that the new process of the present invention must be 
employed in order to incorporate sufficient metal salt without 
destabilizing the formulation or sacrificing its physical appearance as a 
coating. Separate combinations of metal salt and polymer binder must be 
mixed together to produce the compositions of the present invention. 
Emulsified polymers used in the formulation of a floor polish system are 
generally negative in charge. Adding alkali or alkaline earth salts to 
these negatively charged polymers tends to destabilize the emulsion. Thus, 
prior to the present invention, the polymer would gel and a film of the 
composition would crack and streak when high enough levels of metal salt 
were added to give higher conductivity than existing commercial products. 
Now it has been discovered that past problems can be averted when a metal 
salt is premixed with a polyethylene or polypropylene oxide wax emulsion 
before mixing with other mixtures and/or ingredients to produce a coating 
composition. 
Coalescence agents are employed in wax or polish compositions to convert 
the composition from an emulsion to a film when applied to a surface. Many 
coalescence agents included in the wax emulsions are commercially 
available. Preferred coalescence agents include butyl cellusolve, dialkyl 
glycol ethers and tributoxyethyl phosphate. 
Metal salts comprising Na.sup.+, K.sup.+, Li.sup.+, Ca.sup.++, Ba.sup.++, 
Sr.sup.++ cations with chloride, iodide, bromide, thiocyanate, acetate or 
nitrate anions can be employed for producing the metal salt/polymer 
matrix. Lithium chloride is a preferred metal salt. 
It has been discovered that metal salts such as LiCl and metal salt/polymer 
complex can be employed within the wax or polish composition up to a limit 
of 7% by weight without adversely affecting appearance and performance. 
Thus, with 9.4% by weight LiCl in a test composition, the coating showed 
unacceptable cracking. Added as a conductive polymer complex, the 
coordinated lithium compound conducts without the salt exuding to the 
surface where moisture absorption caused by the hygroscopic metal salt can 
create undesirable dirt pickup and slipperiness. 
While lower quantities are effective in improving conductivity, it is 
preferred to use about 4% lithium chloride added as both salt and polymer 
complex. 
While polyethylene or polypropylene oxides are the wax emulsion polymers 
used to produce a preferred electroconductive metal salt/polymer matrix, 
other emulsion polymers and polymer binders can be usefully incorporated 
along with the metal salt/polymer matrix to provide required physical 
properties for a floor wax composition. Useful polymers include 
polyurethanes, acrylate copolymers, acrylic acid terpolymers, polyvinyl 
alcohol, polyethylene glycol, styrene-maleic anhydride copolymer, 
polyethylene polymers and copolymers which are commercially available from 
Rohm & Haas, American Hoechst, Union Carbide, Allied Chemicals, Eastman 
Chemicals, etc. 
A non-ionic surfactant is employed which is compatible with the 
formulation. While many suitable surfactants are commercially available 
for this purpose, a preferred surfactant is Triton.RTM. N101 
(nonylphenoxypolyethoxy ethanol) available from Rohm & Haas. 
Other components conventionally employed in the wax or polish formulation 
include plasticizers, defoamers, coalesence agents, antistats, and 
crosslinking agents; which can be used as known in the art. 
Useful ranges for various components which can be employed to provide 
conductive, aqueous-based waxes or polishes are as follows: 
______________________________________ 
Carboxylated acrylic latex binder 
25-60% 
Polymer latex binder 0-15% 
(acrylate, urethane, styrene, etc.) 
Polyethylene or polypropylene oxide 
1-4% 
Emulsion 
Metal salt 0.5-4% 
Surfactant 0-2% 
Plasticizer 0-1.5% 
Leveling agent 0-4% 
Coalescence agent 2.5-15% 
Water Up to 100% 
______________________________________ 
In detail, the method of the present invention involves two premixes 
combined with final addition ingredients to form the storage stable 
composition. Procedures for the first premix involve combining acrylic 
binder with surfactant prior to adding the metal salt. 
Procedures for the second premix involve preparing the metal 
salt/polyethylene oxide complex and then combining it with binder and 
plasticizer. 
The two premixes are combined along with other ingredients such as leveling 
agents, defoamers, plasticizers, surfactants, antistats, coalescence 
agents, etc. When these pecautions are taken, it is possible to produce a 
final emulsion which can meet or surpass the requirements of electronic 
industry for a storage stable product with excellent antistatic and floor 
protection properties. 
The process and product of the present invention can be employed wherever a 
transparent and conductive surface coating can provide antistatic 
protection.

The following examples illustrate the practice of the present invention 
wherein Example 1 represents the best mode. Parts indicated are by weight 
and the test conditions are standard ASTM tests. 
EXAMPLE 1 
Composition 
______________________________________ 
Parts 
______________________________________ 
Part A 
H.sub.2 O 30.00 
Acrylic latex binder solution A* (See below) 
40.00 
Nonionic Surfactant (Triton N101 
0.50 
from Rohm & Haas) 
LiCl (25% aqueous solution) 
1.25 
Part B 
H.sub.2 O 7.25 
50/50 mixture of oxidized polyethylene emulsion 
5.00 
and LiCl (25% aqueous solution) 
Acrylic copolymer emulsion (Syntran 1292 
15.00 
from Interpolymer Corp.) 
Plasticizer (dibutyl phthalate) 
1.25 
100.00 
______________________________________ 
*The acrylic binder emulsion Part A was prepared using the 
formulation given below. 
Acrylic copolymer emulsion (Neocryl A-623 
57.14 
from Polyvinyl Chemical Ind.) 
Diethylene glycol monomethylether 
14.29 
H.sub.2 O 28.57 
100.00 
______________________________________ 
Procedure 
In the preparation of this formulation, the acrylic binder Part A was mixed 
first before introducing the other ingredients. In order to avoid the 
coagulation of the acrylic emulsion during the mixing procedure, the LiCl 
solution was added after other components in Part A were homogeneously 
mixed. After Part A and Part B were well mixed separately, they were 
brought together and stirred until a homogeneous mixture was obtained. Two 
coats of the final composition were applied on a glass plate or a vinyl 
tile using a slightly damp sponge floor polish applicator. After air 
drying, the polish coating was conditioned at 50% RH and ambient 
temperatures conditions (70.degree. F.). The surface resistivity of the 
coating measured at 50% RH was 6.0.times.10.sup.6 ohm/sq. Without the 
LiCl, a similar polish system had a resistivity of &gt;10.sup.11 ohm/sq. The 
final coating had absolute clarity and good glossy appearance. 
Comment 
While the concentration of the LiCl was important in determining the 
conductivity of the final polish structure, the process for introducing 
the LiCl (or other metal salts) into the system was important for the 
stability of the emulsion polish composition. This is especially true when 
a relatively large amount of LiCl such as used here is employed. More 
specifically, if the LiCl were added all at once, the polish system would 
be destabilized causing poor film formation, streaks and cloudiness to the 
final polish coating. 
EXAMPLE 2 
Composition 
______________________________________ 
Parts 
______________________________________ 
Part A 
H.sub.2 O 21.43 
Carboxylated acrylic resin emulsion (10% solid) 
14.29 
(Carboset 526 from B. F. Goodrich) 
Modified Carboset XL-11* (20% solid) 
21.43 
Non-ionic Surfactant (Triton N-101 
0.36 
from Rohm & Haas) 
LiCl (25% aqueous solution) 0.71 
Part B 
H.sub.2 O 7.32 
50/50 Mixture of Oxidized Polyethylene Emulsion 
5.00 
and LiCl Solution (25% aqueous solution) 
Acrylic copolymer emulsion (Syntran 1292 
28.57 
from Interpolymer Corp.) 
Tributoxyethylphosphate 0.89 
100.00 
Modified Carboset XL-11* (Solution A) 
Carboset XL-11 (carboxylated acrylic resin 
66.67 
Emulsion from B. F. Goodrich) 
Diethylene glycol monomethylether 
10.66 
H.sub.2 O 22.67 
100.00 
______________________________________ 
Procedure 
The process of preparing this composition was the same as that in Example 
1. The resulting coating had a resistivity of 7.2.times.10.sup.6 ohm/sq. 
measured at 50% RH at room temperature. Just as Example 1, the coating 
from this composition was clear with good gloss. 
As indicated, the systems of Example 1 and Example 2 are more or less 
identical to each other except in the resin binders used in the 
formulation. The behavior of the resulting polish coatings was very 
similar in appearance and in charge dissipative characteristics.