WO1992005220A1

WO1992005220A1 - Antistatic olefin polymer compositions containing ethylene oxide copolymers and method relating thereto

Info

Publication number: WO1992005220A1
Application number: PCT/US1991/006525
Authority: WO
Inventors: Simon Hsiao-Pao Yu; Thomas Ray Mass
Original assignee: The B.F. Goodrich Company
Priority date: 1990-09-13
Filing date: 1991-09-10
Publication date: 1992-04-02
Also published as: AU8538091A; CA2091461A1; JPH06500817A; EP0548213A1

Abstract

The present invention relates to olefin polymer compositions having improved antistatic properties. More particularly, the olefinic compositions of the present invention comprise an antistatic agent which is preferably a randomly polymerized ethylene oxide copolymer wherein the weight percent of ethylene oxide in the copolymer is about 40 to about 90 weight percent.

Description

ANTISTATIC OLEFIN POLYMER COMPOSITIONS

CONTAINING ETHYLENE OXIDE COPOLYMERS

AND METHOD RELATING THERETO

FIELD OF THE INVENTION

The present invention relates to olefin polymer compositions having improved antistatic properties. More particularly, the olefinic compositions of the present invention comprise an antistatic agent which is preferably a randomly polymerized ethylene oxide copolymer wherein the weight percent of ethylene oxide in the copolymer is about 40 to about 90 weight percent. BACKGROUND OF THE INVENTION

U.S. 3,425,981 to PULETTI et al., is directed to olefin polymer compositions containing ethylene oxide polymers. Although the olefin compositions of PULETTl are taught to exhibit enhanced anti-static properties, the present invention is distinguishable over PULETTl for a number of reasons.

First, PULETTl teaches that "Poly(ethylene oxide) lioinopolymer is however preferred as the ethylene oxide polymer resin and shall be used hereinafter as representative of these resins." Col. 2, lines 64-67. Although ethylene oxide

homopolymers in olefins do provide some antistatic properties, such olefin compositions are not sufficiently antistatic to meet many of the needs in the marketplace.

PULETTl did not appreciate and does not teach or suggest that superior antistatic properties can be obtained by substituting the ethylene oxide homopolymer with a randomly polymerized ethylene oxide copolymer, wherein the comonomers are oxiranes and wherein the amount of ethylene oxide in the copolymer is about 40 to 90 weight percent. PULETTl teaches that the ethylene oxide homopolymer can be substituted with a copolymer, and PULETTI mentions a number of possible comonomers, but the critical copolymer range is not taught or suggested by PULETTI, and PULETTI implies that a copolymer would be a mere alternative to the homopolymer, not a dramatically more effective antistatic additive for olefins.

Furthermore, PULETTI teaches that the ethylene oxide polymer component has "an average molecular weight of from 100,000 to ten million and preferably in the range of from about 200,000 to about 1,000,000" (col..2, lines 52-53). Such a molecular weight limitation is not necessary for the present invention, and therefore, Applicant has eliminated an important element of the PULETTI invention, while nevertheless improving antistatic properties of the resulting composition.

SUMMARY OF THE INVENTION

The present invention is directed to an olefinic composition having antistatic properties and comprising an olefinic component and a random ethylene oxide copolymer component. The ethylene oxide copolymer component preferably comprises about 40 to 90 weight percent of the following polymer unit: (-CH₂-CH₂O-). The resulting composition preferably has a surface resistivity in the range of about (10)¹⁰ to about (10)¹⁴ ohm/sq as determined by ASTM D257, and preferably requires less than about 0.5 seconds to dissipate 90% of a 5 kilovolt charge at 50% relative humidity according to National Fire Protection Association Standard (NFPA Code 56A) or requires less than about 2.0 seconds to dissipate 99% of a 5 kilovolt charge at 15% relative humidity according to U.S. Military Specification (MIL-B-81705C) as determined by Federal Test Method Standard 101 B, Method 4046.1.

The ethylene oxide copolymer preferably comprises about 10 to about 60 weight percent polymer units which are the polymerization product of at least one oxirane comonomer other than ethylene oxide. The oxirane comonomer is most preferably epichlorohydrin or propylene oxide.

In one embodiment of the present invention, the olefinic component is a homopolymer or the copolymerization product of an olefin monomer and one or more copolymerizable monomers. The preferred copolymerizable monomers have vinyl functionality. In another embodiment, the olefinic component is a derivative of a homopolymer or a copolymer. In an alternative embodiment, the olefinic component comprises a blend of an olefin polymer with a second polymer. In yet another alternative embodiment, the olefinic component further comprises a metallic salt functionality.

The composition of the present invention

preferably comprises about 2 to 50 weight parts ethylene oxide copolymer per hundred weight parts olefin polymer resin.

The present invention is also directed to a method of manufacturing an antistatic olefinic composition by means of melt mixing or blending the ethylene oxide copolymer of the present invention with an olefinic component. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of the present invention comprises an olefin component, an ethylene oxide copolymer component, and optionally, any one of a number of conventional additives for olefin type materials.

The Olefin Component

The olefin component is preferably the polymerization product of one or more lower olefin monomers such as those containing from 2 to 8 carbon atoms, most preferably from 2 to 3 carbon atoms. Illustrative of such polymers are high density or linear polyethylene, low density or branched polyethylene, polypropylene, polybutene,

polycycloolefins, copolymers of ethylene/pr opylene, copolymers of propylene/butylene, and the like.

Alternatively, the olefin component can be the copolymerization product of an olefin monomer and one or more copolymerizable monomers. Preferred comonomers include those having vinyl functionality, such as:

1. vinyl aryls, i.e., styrene, o-methoxystyrene, p- methoxystyrene, m-methoxystyrene, o-nitrostyrene, m-nitrostyrene, o-methylstyrene, p-methylstryene, m-methylstyrene, p-phenylstyrene, o-phenylstyrene, m-phenylstyrene, vinylnaphthalene and the like;

2. vinyl and vinylidene halides, i.e., vinyl chloride, vinylidene chloride, vinylidene bromide and the like; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl chloroacetate, vinyl chloropropionate, vinyl benzoate, vinyl chlorobenzoate and the like; 3. acrylic and alpha-alkyl acrylic acids, their alkyl esters, and their amides, i.e., acrylic acid, chloroacrylic acid, methacrylic acid, ethacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, n- octyl acrylate, 2-ethylhexyl acrylate, n-decyl acrylate, methyl methacrylate, butyl methacrylate, methyl ethacrylate, ethyl ethacrylate, acrylamide, N- methyl acrylamide, N,N-dimethyl acrylamide, methacrylamide, N-methyl methacrylamide, N,N- dimethyl methacrylamide, and the like;

4. acrylonitrile, chloroacrylonitrile, methacrylonitrile and the like; 5. alkyl esters of maleic and fumaric acid, i.e., dimethyl maleate, diethyl maleate and the like;

6. vinyl alkyl esters and ketones, i.e., vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, 2- chloroethyl vinyl ether, methyl vinyl ketone, ethyl vinyl ketone, isobutyl vinyl ketone and the like; and

7. vinyl pyridine, N-vinyl carbazole, N-vinyl pyrrolidine, ethyl methylene malonate and the like.

Most preferred olefin copolymer compositions include the polymerization product of the following:

styrene/ethylene; ethylene/ethyl acrylate; ethylene/vinyl acetate; ethylene/vinyl chloride; ethylene/acrylic acid; and the like. The most preferred olefinic polymers and copolymers are those which exhibit thermoplastic properties, although thermosets are also intended to be included within the scope of this invention.

Alternatively, the olefin component can be the product of grafted variations or chemical derivatives of

homopolyolefins or their copolymers. Illustrative of such

variations or derivatives are chlorinated polyethylene, copolymer of ethylene/vinyl alcohol, and the like. The olefin polymer component can be of the film forming type. Such resins generally exhibit melt indices of from .1 to 20 decigrams per minute inclusive.

Also included within the term olefin polymers are the blends of olefin polymers with other polymers. Illustrative of such blends are: polyethylene with polypropylene, low density polyethylene with high density polyethylene, polyethylene with olefin copolymers such as these indicated above, for example, ethylene/acrylic acid copolymer, ethylene/methyl acrylate copolymer, ethylene/ethylacrylate copolymer, ethylene/vinyl acetate copolymer, ethylene/acrylic acid/ethyl acrylate

terpolymer, ethylene/acrylic acid/ vinyl acetate terpolymer, polypropylene/chlorinated polyethylene and the like. Other olefinic blends within the scope of the present invention include the blends of olefin polymers with one or more elastomers, crosslinked or non-crosslinked. Illustrative of such blends are polypropylene/EPDM; polypropylene/NBR;

polyethylene/EPDM; and the like.

Also included within the blend of olefin polymers are the metallic salts of those olefin copolymers or blends which contain free carboxylic acid or sulfonic acid groups. Illustrative of such polymers are ethylene/acrylic acid copolymer,

ethylene/methacrylic acid, ethylene/ethacrylic acid,

styrene/acrylic acid, styrene/methacrylic acid, oxidized

polyolefins, propylene/acrylic acid copolymer, butene/acrylic acid copolymer and the like.

Illustrative of the metals which can be used to provide the salts of said carboxylic acid polymers are the one, two, and three valence metals, such as ammonium, sodium, lithium, potassium, calcium, magnesium, aluminum, barium, zinc, zirconium, beryllium, iron, nickel, cobalt, and the like.

Preferred blends include polypropylene or polyethylene with copolymer of ethylene/vinyl acetate or chlorinated polyethylene, and the like.

Ordinary skill and experimentation may be necessary in selecting any particular olefin component, depending upon the intended use and the performance requirements of the final composition.

The Ethylene Oxide Copolymer Component

The preferred ethylene oxide copolymer component of the compositions of the present invention is selected from ethylene oxide polymeric materials having an average molecular weight of from about 1000 to ten million and more preferably in the range of from about 10,000 to about 500,000, (GPC

molecular weight relative to polystyrene). The term "ethylene oxide copolymers" refers to randomly polymerized copolymers wherein the polymerization product comprises about 40 to 90 weight percent of the following polymer unit:

(-CH₂-CH₂O-).

The balance of the ethylene oxide copolymer component is preferably one or more oxirane comonomers other than ethylene oxide. Virtually any oxirane comonomer can be used, but the preferred comonomers are 1,2-epoxides, the most preferred of which are propylene oxide and/or epichlorohydrin.

Catalyst residues or the like or other comonomers can intentionally or unintentionally become incorporated into the ethylene oxide copolymer and this generally is acceptable, provided the polymerization product is about 40 to 90 weight percent ethylene oxide. Ordinary skill and experimentation may be necessary to determine the optimal comonomer composition, depending upon the desired properties of the final material. The Antistatic Olefin Composition

The ethylene oxide polymer is generally used in an amount sufficient to impart the desired antistatic or electrostatic dissipative properties. These amounts are generally about 2 to 50 weight parts ethylene oxide copolymer per hundred weight parts olefin polymer resin. Amounts of from about 10 to about 40 weight parts by weight are most preferred.

The ethylene oxide polymer can generally be blended with the olefin polymer by general melt blending techniques utilizing conventional equipment. It facilitates blending however if the resinous components are premixed as dry powders before blending in the melt. If desired, solution admixture can be used.

While the polymeric compositions of this invention can be used without filler materials, it should be noted that filled polymer compositions of this invention containing from about 5 to about 50 parts by weight finely divided filler per hundred parts olefin polymer provides excellent antistatic properties. For these reasons and the apparent economic advantages, these filled compositions are preferred for these applications where transparency of the polymer is not required.

When the filled polymer compositions are to be used in making film, a filler particle size of from 0.01μ to 15μ can be used. Film forming compositions containing a filler having a particle size of from 0.2 to 6μ are preferred. In applications other than film, filler size is not critical. Illustrative of the filler materials which can be used in the compositions of this invention are fillers, such as, barium sulfate, calcium sulfate, silica, fibrous asbestos, talc, calcium silicate, magnesium silicate, mica, soapstone, slate flour, pumice, wood flour, soybean flour, tobacco flour, walnut shell flour, sulfur, tripolite, calcium oxide, magnesium oxide, calcite, diatomaceous earth, fuller's earth, alumite, calcium phosphate, magnesium phosphate, bauxite, chalk, magnesite, kaolin clay, bentonite clay, ball clay, fire clay, dolomite muscovite,

paragonite, margarite, vermiculite, pyrophyllite, apatite, tricalcium phosphate, titanium dioxide, volcanic dust and the like. Other possible fillers would include conductive fillers, such as, carbon black, metallic powders and the like.

It should be noted that various additive or modifying compounds as are normally present in the resinous components or normally used in such compositions can be present in the polymer compositions of this invention. Such additives include resin stabilizers to protect the resinous components from degradation caused by shear, heat, light oxidation and the like and which are usually provided in

comm ercially available resins, lubricants, dyes, pigments and the like.

Examples

The following examples are given to further illustrate the present invention. The antistatic properties of polymer blend composition are determined under controlled conditions at 25°C by surface and volume resistivity at 50% R.H. (relative humidity) and static decay time at 15% R.H. The samples were also conditioned at least 48 hours prior to measurement.

Surface and volume resistivity testing is conducted in accordance with ASTM D257 with an Electrometer (model 617) equipped with a high voltage supply (model 247) and a resistivity adapter (model 6105) all from Keithley Instruments, Inc. The adapter comprises an upper circular electrode and a lower circular electrode encircled with a guard ring electrode. A sheet sample (3.5 inches in diameter and 1/8-1/16 inch thick) was placed between the upper and lower electrodes, and a voltage of 500 volts was applied between the electrodes. After 60 seconds, the current was recorded from the Electrometer and converted into surface resistivity in ohms per square or volume resistivity in ohm-cm using the equation derived from the dimensions of the electrodes.

The end use of the polymeric antistatic material will determine the desired antistatic properties. For example, sophisticated electronic equipment would require a higher degree of static protection than carpet or articles for dust prevention. Accordingly, different standards have been developed for specific end use applications. For example, electrostatic behavior has been characterized by the Department of Defense in publication DOD-HDBK-263 in terms of surface resistivity. Materials with a surface resistivity in the range of 10⁹-10¹⁴ ohms per square at 50% R.H. are antistatic. Materials with a surface resistivity greater than 10¹⁴ are generally insulators. In another example, electrostatic behavior has also been characterized by EIA

(Electronic Industries Association) in a publication "EIA Interim Standard EIA-541: Packaging Material Standards for ESD

Sensitive Items", 1988, in terms of surface resistivity. Materials with a surface resistivity in the range of 10⁵- 10¹² ohms per square at 50% R.H. are generally "dissipative". Materials with a surface resistivity equal to or greater than about 10¹² are generally insulative.

Different standards have also been developed for the static decay test. The static decay test is carried out in accordance with Federal Test Method Standard 101 B, Method 4046.1, "Electrostatic Properties of Materials" with a Static Decay Meter, model 406C obtained from Electro-Tech Systems, Inc. Static decay is a measure of the ability of a material, when grounded, to dissipate a known charge that has been induced on the surface of the material. A sheet sample (3" x 6") with 1/8- 1/16 inch thickness is placed between clamp electrodes contained in a Faraday cage. A 5,000 volt charge is applied to the surface of the specimen and the time in seconds required to dissipate the charge to 500 volts (10% of its initial value) or to 50 volts (1% of its initial value), after a ground is provided, is then measured. Highly insulative materials will not accept a full charge of 5,000 volts on their surface or show residual charge before applying a charge. In both instances, a static decay test cannot apply and the materials are indicated in the Table as being insulators. The National Fire Protection Association in NFPA, code 56A, "The Standard for the Use of Inhalation Anesthetics" covers products used in the hospital operating room and in hazardous

environments. It requires that the applied charge drop to 10% of its initial value within 0.5 seconds at 50% relative humidity in order to qualify for use in hospital operating rooms and other hazardous environments. According to the same EIA-541 publication, the material shall be considered acceptable if the decay rate is less than two seconds from 5000 to 50 volts at 15% R.H.

EXAMPLE I

Profax 6323, general purpose injection-mold polypropylene from Himont USA Inc., was mixed with a copolymer of ethylene oxide and epichlorohydrin (EO/ECH) with 80 wt % of EO in a Banbury mixer heated at 195°C with hot oil. After mixing (about 5 min.), a 6" x 6" x 1/8" sheet sample was press-molded at 195°C and 30,000 psi. The results are shown in Table I.

EXAMPLE II

Profax SB 222, propylene copolymer from Himont USA Inc., was mixed with a copolymer of EO/ECH with 80 wt% of EO in a Banbury mixer heated at 190°C with hot oil. After mixing (about 5 min.), a 6" x 6" x 1/8 sheet sample was press- molded at 190°C and 30,000 psi. The results are shown in Table II.

EXAMPLE III

Profax 6323, general purpose injection-mold polypropylene from Himont USA, Inc. and Tyrin 3611, chlorinated polyethylene from Dow Chemical, were mixed with a copolymer of EO/ECH with 80 wt% of EO in a Banbury mixer heated at 195°C with hot oil. After mixing (about 5 min.), a 6" x 6" x 1/8" sheet sample was press-molded at 195°C and 30,000 psi. The presence of chlorinated polyethylene significantly improves antistatic properties. The results are shown in Table III.

EXAMPLE IV

LDPE resin, resin of ethylene/vinyl acetate copolymer, and a copolymer of EO/ECH or EO/PO with 80 wt% of EO were mixed via standard laboratory banbury/mill mixing techniques. The mixed alloys were stripped off a standard 2 roll mill, were injection molded on a 75 ton Arburg injection molding machine. Molding conditions used were those

recommended by the resin supplier.

EXAMPLE V

The alloys were prepared using a 300 mm corotating and in termeshing twin screw compounding extruder. A fairly intensive mixing screw configuration was used to minimize dispersion stock temperatures reached 340 to 350°F (121 to 177°C) during the melt blending operation.

Injection molded test specimens were prepared on a 75 ton Arburg injection molding machine. Melt temperatures for molding were in the 330 to 350°F (166 to 177°C range with the mold temperature set at 110°F (43°C).

Claims

WHAT IS CLAIMED IS:

1. An olefinic composition having antistatic properties, said composition comprising:

an olefinic component and a random ethylene oxide copolymer component, said ethylene oxide copolymer component comprising about 40 to 90 weight percent of the following polymer unit: (-CH₂-CH₂O-).

2. The composition of Claim 1 wherein the resulting composition requires less than about 0.5 seconds to dissipate 90% of a 5 kilovolt charge according to National Fire Protection Association standard (NFPA Code 56A) or requires less than about 2.0 second for a 99% dissipation of a 5 kilovolt at 50% relative humidity charge according to U.S. Military

Specification MIL-B-81705C at 15% relative humidity as determined according to Federal Test Method Standard 101 B, Method 4046.1.

3. The composition of Claim 1 wherein the ethylene oxide copolymer comprises about 10 to about 60 weight percent polymer units which are the polymerization product of an oxirane comonomer other than ethylene oxide.

4. The composition of Claim 3 wherein the oxirane comonomer is epichlorohydrin or propylene oxide.

5. The composition of Claim 1 wherein the olefinic component comprises a homopolymer or a copolymerization product of an olefin monomer and one or more copolymerizable monomers or wherein the olefinic component comprises the product of grafted variations or chemical derivatives of homopolyolefins or their copolymers or wherein the olefinic component comprises a blend of an olefin polymer with a second polymer.

6. The composition of Claim 5 wherein the copolymerizable monomers have vinyl functionality.

7. The composition of Claim 1 wherein the olefinic component further comprises a metallic salt functionality.

8. The composition of Claim 1 wherein the amount of ethylene oxide copolymer is about 2 to 50 weight parts per hundred weight parts olefin polymer resin.

9. A method of manufacturing an antistatic olefinic composition, said method comprising the steps of:

melt mixing or blending an olefinic component with an ethylene oxide copolymer component,

wherein the ethylene oxide copolymer component is about 40 to 90 weight percent of the following polymer unit: (-CH₂-CH₂O-).