CA1307869C

CA1307869C - Water based anti-static coating composition and polymer film coatedtherewith

Info

Publication number: CA1307869C
Application number: CA 544418
Authority: CA
Inventors: Robert Edward Touhsaent
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1986-09-08
Filing date: 1987-08-13
Publication date: 1992-09-22
Anticipated expiration: 2009-09-22
Also published as: EP0263590A2; PT85660A; ES2031903T3; DE3779716D1; AU7689987A; DE3779716T2; NZ221376A; ATE77097T1; EP0263590B1; JPS6372765A; US4785032A; EG18322A; EP0263590A3; AU599689B2; PT85660B; BR8704580A; US4950544A; GR3004867T3

Abstract

WATER EASED COSTING COMPOSITION AND
POLYMER FILM COATED THEREWITH
ABSTRACT

A water based antistatic coating composition comprising:
a) at least one water soluble antistatic agent which is acceptable for food packaging polymer films;
b) at least one water soluble or water dispersible film-forming polymer; and, c) a solution or dispersion-forming amount of water.
When applied to a polymer film substrate, the foregoing antistatic coating composition forms, upon drying, an adherent antistatic coating.

Description

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WATER BASED COATING_COMPOSITION AND
POLYMER FILM COATED THEREWITH

This invention relates generally to a water based antistatic coating composition and, in particular, to polymer films treated with an antistatic composition.
U.S. Patent No. 2,063,987 describes the acylated and/or esterified derivatives of aliphatic amino carboxylic acids and the salts of these derivates formed on the amino group or the carboxylic acid group9 whichever is frse, as aqueous treatinq agents, in particular, for wetting, cleansing, sizing, de-electrification, prevention of acid fading of dyestuffs, creping and other treatments of textile filaments, threads, yarns, fabrics, etc. At present, N-acyl derivatives of N-methyl glycine (sarcosine) where the acyl group is lauroyl, oleoyl or derived from the combined fatty acids of coconut oil are approved as antistatic and~or as antifogging agents in polyolefin films used for packaging meat, fresh fruits and fresh vegetables t21 C.F.R. 178.3280). Similar approval is given for the use of N,N-bis(2-hydroxyethyl)higher aliphatic amines.
U.S. Patent No. 2,678,285 describes treating the surface of a polymer film with an antistatic agent, specifically, an aqueous solution of a surface active agent such as triethanolamine stearate containing a finely divided polymeric material and, optionally, a wax.
U.S. Patent Nos. 2,832,696, 2,832,697, 2,832,698, 2,832,699 and 2,937,066 each describe antistatic agents for polymeric materials includingg for example, in the case of U.S Patent No. 2,832,696, fatty amide condensate. Still other disclosures of polymer antistatic components are: U.S. Patent Nos. 3,365,435 (N-(2-hydroxyalkyl)ethanolamine), 3,365,437 (hydroxyalkyl fatty acid amide), 3,407,187 (quaternary alkyl ammonium compound~, 3,445,396 (a ~ :: :

, ' .

combination of N,N-bis(2-hydroxyethyl)higher aliphatic amine and higher aliphatic alcohol), 3,485,786 (alkyl propylamine), 3,575,902 (ethoxylated amine), 3,631,162 (a combination o~
N-(2-hydroxy-3_dodecyloxypropyl)ethanolamine and N,N-bis(2-hydroxyethyl)alkylamine), 3,70~,464 ttetrahydropyrimidine), 3,821,184 (tetrahydropyrimidine), 3,975,325 (a combination of a fatty acid salt and tertiary amine), 4tl47,742 (ethoxylated amine), 4,210,556 (ethoxylated amine), 4,234,664 (~uaternary ammonium salt), 4,241,144 (quaternary ammonium sulfate), 4,268,583 (quaternary ammonium salt) and 4,314,040 (ethoxylated amine).
Aqueous film-forming compositions containing, in addition to a water soluble or water dispersible ~ilm forming polymer, one or more ingredients intended to impart a particular property or characteristic to the substrate to which the compositions are applied are known. Thus, U.S. Patent No. 3,252,826 describes a polymer ~ilm coated with an aqueous coating composition containing a water solu~le gum, polyvinyl alcohol, hydroxyethyl cellulose, carboxy methyl cellulose, agar, etc., and an alkali metal salt of a fatty acid to confer clarity, good slip and good anti-block characteristics upon the film. U.S. Patent No. ~,140,822 describes a polyolefin film coated with an aqueous dispersion comprisiny aluminum chlorhydroxide, phosphoric acid and high molecular weight polyvinyl alcohol to enhance the receptivity of the film surface for paint, ink and glue. U.S. Patent No. 4,596,668 discloses an electrically-conductive surface-coating composition ~or use as a floor coating to provide electrostatic discharge protection. The composition comprises an emulsion of a film forming, water soluble, low molecular weight polyampholyte polymer containing free carboxylic groups and carboxylic amino ester groups and an antistatic agent such as a 4uaternary ammonium salt.
lllis invention provides a water based antistatic polymer film coating composition comprising:
~; ~a) at least one water soluble antistatic agent which is acseptable for food packaging polymer films and which is selected from the group '' ~' . ~ , , ~ .,..
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:~3~
.
F~4067 -3-consisting of N-acyl sarcosinates and N,N-bis(2-hydro~yethyl) higber aliphatic arnines;
(b) at least one water soluble or water dispersible film-forming polymer; and (c) a solution or dispersion-forming amount of water.
When applied to a polymer film substrate, the foregoing antistatic coating composition forms, upon drying, an adherent antistatic coating.
Of the water soluble antistatic agents which are acceptable for use with ~ood packaging films and as such can be used to provide the antistatic coating composition of this invention, the N-acyl sarcosinates and their salts and the N,N-bis(2-hydroxyethyl)higher ; aliphatic amines are preferred.
The useful N-acyl sarcosinates can be represented by the general formula:
R1--C-- ~- CH--CO--M
1 ~2 ~3 1~

wherein R is an alkyl radical o~ from B to about 22 carbon atoms, R2 is hydrogen, methyl or ethyl, R3 is hydrogen, alkyl o~ 1 to 4 carbon atoms, hydroxyalkyl of 1 to 4 carbon atoms and M is hydrogen or a salt-~orming moiety such as alkali metal9 ammonium or propanol substituted ammonium.
The N-acyl sarcosinates can be prepared by a variety o~ methods including those described in U.S. Patent No. 2,063,987 referred to above and U.S. Patent Nos. 2,729,657, 3,074,980 and 3,836,551. Some ~; are commercially available such as "Ha~posyl Lr30"* (W.R. Gra oe), a 30%
;~ by weight aqueous solution o~ sodium lauryl sarcosinate which, in addition to its antistatic capabilities, can also function as a slip agent when applied to polymer film surfaces.
The use~ul N,N-bis(2-hydroxyethyl)higher aliphatic amines can be represented by the general ~ormula RNL~
CH CH OH
~ 2 2 ", ~
1~. :: *~ad~mark ':
,~

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F-4067 ~4~

wherein R is an alkyl or alkenyl group of from 8 ~o about 22 carbon atoms. Particularly preferred are N,N-bis(2-hydroxyethyl)alkenyl or mixtures of alkenyl and alkyl ~C12-C~8) amlnes obkained frum distilled coco, soy, oleyl or tsllow, or mlxtures thereof. "Armo6tat 310" (Anoak CarW~, a diethox~lated tallc~w ~mixed alk~yl a~
alkyl) amine has been used with good results.
The polymeric component of the antistatic coating composition of this invention is preferably one which is soluble or dispersible in water at ambient temperature. Suitable polymers include the homopolymers o~ acrylamide and methacrylamide; the copolymers of acrylamide and methacrylamide with each other and~or with one or more other monomers su~h a~s acrylic acid, methacrylic acid, vinyl alcohol (from hydrolysis of interpolymerized vinyl acetate groups), ~ Yinyl acetate, etc.; polyethylene s~lfonate; polyesters such as i~ maleinized polyesters, hydrophilic polyesters and poly0sters modified with high-functionality organic acids; polymethacrylic acid; polyvinylpyrrolidone; polyvinylmethyl ether; cellulose ethers such as methyl cellulose, ethyl methylcellulose, sodium carboxymethylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, carboxymethyl hydroxyethylcellulose; and natural gums, soluble starches and other natural water soluble film-forming polymers. The foregoing recitation is not intended to be exhaustive but merely representative o~ the many kinds of water soluble and water dispersible ~ilm-forming polymers whlch are useful herein. 0~ thsse polymers, the cellulose ethers are pre~erred with hydroxyethylcellulose (HEC~ beiny especially preferred. The preferred cellulose ethers are generally acceptable ~or use in food packaging polymer films.
If desired, once the coating compositions are applied, the polymer oomponent can be insolubilized. Thus, for example, sodium carboxymethylcellulose can be insolubilized by treatment with aluminum sulfate or with other polyvalent metal ions.
The amounts of antistatic agent, water soluble or water dispersible ~ilm-forming polymer, optional ingredients such as natural or synthetic wax, surface active agent, particulate such as *Trad~mark , :.

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talc (an antiblocking agent) and colloidal silica (to reduce the coefficient o~ ~riction), suspending agent, viscosity modifier, pH
adjustor, etc., and water can vary over wide ranges. In general, the amount of antistatic agent should be such that when the coating composition is applied to a polymer ~ilm, a significant reduction in the tendency of the film to accumulate static electricity on a surface thereof will be achieved. Amounts of antistatic agent ranging from about 1% to about 9g%, and preferably from about 25% to about 75%, weight percent o~ the total coating composition are usually suitable. When applied to a ~ilm sur~ace, coatlng compositions containing such amounts of antistatic agent will be sufficient to lay down from .01 to 1 9/0~65 m2 (about .01 to about lg/lûOO in2), and pre~erably ~rom 0.0~ 9 to .lg/0.65m2 about .03 to about .19/1000 in.2~ of the antistatic agent.
The film forming polymer must be employed in at least that amount which will provide a continuous adherent coating ~hen applied to a polymer film surface. The precise amounts will vary depending upon the nature of the polymer, the nature and amount of antistatic agent and other factors readily appreciated by those skilled in the art. From about 1% to about 9S%, and preferably from about 25~ to about 75% weight percent polymer, based on the total coating composition, can be employed with good results.
Optional ingredient(s), when present, can be employed in the customary amounts.
The total sollds content of the coating composition herein can vary widely, e.g., from about 1 to about 20, and prefera~ly from about 2 to 10, weight percent of the total, the balance being water or a mixture of water and a water soluble organic solvent such as methanol, ethanol, etc., to accelerate drying.
The polymer films to be coated with the foregning water based antistatic coating compositions are, of course, those which tend to accumulate surface electric charges during manufacture and~or while in service. Suitable polymer films include olefin polymers, e.g., homopolymers and copolymerQ of ethylene, propylene and butene-l;

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polyvinyl chloride, vinyl chloride/vinylidene chloride copolymers;
polystyrene; styrene/butadiene copolymers; polyvinyl acetate, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-vinyl alcohol terpolymer, and the like.
Films encountered in the packaging and handling of foods, notably9 oriented polypropylene and vinyl acetate-containing homopolymers and copolymers, are especially well suited for coating by the antistatic coating compositions herein. When, however, the polymer film need not be acceptable for food packaging application, the coating composition can contain essentially any antistatic agent which is suitable for application to the surface of a substrate resin. Thus, any of the known antistatic compositions including many of those referred to above can be employed in coating compositions to be applied to films intended for non-food use.
The following examples are illustrative of antistatic coating compositions prepared în accordance with this invention and oriented polypropylene film coated therewith.

Two water based antistatic coating compositions were formulated ~ as shown in Table I and applied to polypropylene film prior to ; ~ orientation in the transverse direction.
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' 13~78r~ ) " F-~067 7 TA~LE I:_Water ~ased ~ntistatic Coating ÇomPositions ,_ _ -- r Wt. ~ Solution ! Dry Wt. % on Component Sol . Wt . (~) Wt . (g) a dry basi~
Ex.l Ex.2 ~3x.1 Ex.2 Ex.l Ex.2 . . _ Hydroxy~thyl 3 . 0 100 . O 100 0 0 3 . 0 3 . O 63 . 2 52 .
c:~llulo~ ("~ell~
~iza WP 3"l ~.c$~ .
Carbide ) ~ ~ ___ __ . .
Diethox~,rlated a~in~ 2 . O 50 . 0 _ 1 0 _ 21 0 ("Arm~ 310"~* . . .
: ArmaX Company ) _ _ ~ _ _ .
Sod~um la royl ~0 . O _ 6 . 7 ~- 2 . 0 _ 34 .
:: sarco~inate : ~ : ("S~l~syl NIr30~l3 ~ ! :Ciba~ gy~
. ,. ........ ,.~._ .
Carnauba wax 25.0 2.G 2.0 OOS 0.5 10.5 8.
e~ulsion ~ .
Talc lt) o O 2 ~ 5 2 ~ 5 ~ ~!5. 25 5 . 3 4 .
1.; . _ .
Wa1:~r _ 50.0 93.3 _ _ _ _ (de~Qineralized) . .. ~ . _ .
Total ~ _ 2 04 . 5 2 04 . 5 4 . 7 55 . 75 100 . 0 100 .
~: ~ . _, . __ : Application, _ 2 . 3 2 . 8 _ _ _ I~ Ilo~l~ _ . .. .

Diluted with water and acetic acid ko pH 5 and 2 wt . 96 solids .
..
~a~rk 2~d~k 3~a~rk . ~,~, -i:
, .-.,.

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The properties of the films coated with the antistatlc coating compositions are set ~orth in Table II as follows:

TABLE II: Properties of Polypropylene Film Coated With Antistatic Compositlon Property ~xample 1 Example 2 : Coefficient o~ .23 .13 Friction Blocking (g/in.~ 0.8 0.8 Haze, % 2.6 3.4 :: ~
Gloss, % 94.3 91.7 ~`~

EX~MPLES 3-20 The antistatic coating compositions o~ these examples were ~ prepared with 0 (control), ~5, 50, 75 and 100 wt.% sodium lauroyl : sarcosinate antistatic agent ('~ p~syl I30''* W.R. Grace3 and ~: : hydroxyethyl cel~ulose t"c~llosize Qp-os~l~* Uhion Carbide) ~nd diluted with ~emineralized water to 27 3.5 and 5 wt.~ solids.
~: The compositions were applied to the base polypropylene ~ilm .- with a 200 Q gravure roll. Static tests, coe~icient of friction and blocking measurements and coating weights are set forth in Table : III as ~ollows:

Tra~emark .......

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~ C
." ~ g ~ ~ O ~ O O ~ O ~ ~ o o ~ ~
~Uo~ C~OOOOOOOOOOOOOOOOO

c O U~ O N O D ~ ;t O O O q~ ~t Cl~ 1~ 0 CO
O 1`~ 0 0 ~ ~-i j O O O Ll~ ~ O O
~OO~ 0_I--`'--u~ o o o o o o o ~ Ll~ o o 3~ ~ C
q- h C O
C r ~ ~ ~ ~ ~ ~ ~ ~ r` O O~ r` N ~ ~ ~ N

h V ~
0 ~ ~0 ~ P ~) a m e:
~ g L~ ~ ao ~ a~ o U~ O O _, ~3 g ~ CO C~ O--~ O O O O O O O O O ~ N O

O NO ~ N CO 8 8 ~ ' _, o o 8 $ ~ o S ~, ~ N t~ J C~i O O O--i O O O O O ~ N O

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~ t~ w o U~ o o ~ o o u~ o c~ u~ o o u~ o u : v C ~ o O O L~O~ ~~ ~ N

Q O ~D 1~ 03 ~ O

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Claims

1. A water based antistatic polymer film coating composition comprising:
(a) at least one water soluble antistatic agent which is acceptable for food packaging polymer films and which is selected from the group consisting of N-acyl sarcosinates and N,N-bis(2-hydroxyethyl) higher aliphatic amines;
(b) at least one water soluble or water dispersible film-forming polymer; and (c) a solution or dispersion-forming amount of water.

2. The water based antistatic coating composition of claim 1 wherein the antistatic agent is a compound of the general formula wherein R1 is an alkyl radical of from 8 to about 22 carbon atoms, R2 is hydrogen, methyl or ethyl, R3 is hydrogen, alkyl of 1 to 4 carbon atoms or hydroxyalkyl of 1 to 4 carbon atoms, and M is hydrogen or a salt-forming moiety.

3. The water based antistatic coating composition of claim 2 wherein the salt-forming moiety is an alkali metal, ammonium or propanol substituted ammonium.

4. The water based antistatic coating composition of claim 1 wherein the antistatic agent is an alkali metal allyl sarcosinate.

5. The water based antistatic coating composition of claim 1 wherein the antistatic agent is sodium lauroyl sarcosinate.

6. The water based antistatic coating composition of claim 1 wherein the antistatic agent is a compound of the general formula wherein R is an alkyl or alkenyl group of from 8 to about 22 carbon atoms.

7. The water based antistatic coating composition of claim 1 wherein the antistatic agent is an N,N-bis(2-hydroxyethyl)alkenyl or mixture of alkenyl and alkyl (C12-18) amines.

8. The water based antistatic coating composition of claim 1 wherein the water soluble or water dispersible film-forming polymer is a cellulose ether.

9. The water based antistatic coating composition of claim 1 wherein the water soluble or water dispersible film-forming polymer is a hydroxyethyl cellulose.

10. The water based antistatic coating composition of claim 1 containing an antistatic-effective amount of antistatic agent and an antistatic agent-carrying amount of water dispersible film-forming polymer.

11