Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-04-26
2003-02-18
Jagannathan, Vasu (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S236000, C524S560000, C524S910000, C252S008910, C548S347100
Reexamination Certificate
active
06521683
ABSTRACT:
FIELD OF INVENTION
The present invention relates to compositions and methods for reducing and eliminating static electric charges on resins, particularly acrylic resins, by adding to or on the resins an antistatic agent that includes an antistatically effective amount of at least one substituted imidazolinium salt of alkylbenzene sulfonic acid. Antistatic articles of manufacture are also contemplated.
BACKGROUND OF TECHNOLOGY
Synthetic polymers have many commercial uses. They can be readily formed and machined to provide a variety of shapes. Their desirable qualities include crystal clarity, good surface hardness, relatively good resistance to scratches, good chemical resistance and excellent weatherability. Synthetic polymers and in particular acrylic polymers, have many applications such as electrical insulators, automotive instrument panel covers, automotive tail lights, paneling, safety glazing, medical application, sanitary and laboratory wear, aircraft canopies and domes, signage, and the like.
Many polymers are essentially electric insulators, that is, they are non-conductors of electricity. A conductor of electricity has the ability to transmit a stream of electrons and thus carry an electrical current. On the other hand, insulators may become negatively or positively charged and cannot easily dissipate the charge. Therefore, articles prepared from such polymers tend to develop static electric charges upon their surfaces when they are subjected to friction during their production and finishing or during their handling or use. Static electric charges on surfaces are undesirable because they readily attract dust and other contaminants, which may interfere with the smooth finish of the article, making it unsightly and difficult to clean. This will cause the article to be cleaned more frequently and increase the tendency for the surface to be scratched. Additionally, static electric charges may accumulate to a level where sparks may occur when the static charge discharges. This spark can act as an ignition source for flammable materials and vapors, creating severe safety hazards. Also, an unpleasant electric shock may be experienced when the article is handled and the electric charge discharges. Additionally, static electric charges may also cause problems in the processing of resins.
To eliminate the undesirable static electric charges on resins, antistatic agents have been added to polymers and other non-conductive materials. Antistatic agents facilitate the transfer of electrons to eliminate static electric charges on the surface of a material and can be added externally or internally. External antistatic agents may also be applied to the surface of a finished product. Such coatings while useful, may be less desirable if they are easily removed when contact is made with the surface. Application of external antistatic agents is generally performed by spraying the surface or dipping the article in an antistatic bath.
Internal antistatic agents, i.e., agents which are added to resin composition often self-migrate or bloom to the surface of the polymer, thereby effectively reducing or eliminating the accumulation of static electric charges on the surface. As the antistatic agent is wiped away from the surface, more of the agent will migrate to the surface, depending on the type of polymer and chemical structure of the antistatic agent. Such agents are often compounded with the polymer before curing the polymer or forming the finished product.
Acrylic polymers, such as poly(methylmethacrylate), are known to readily accumulate a static electric charge. Efforts to reduce surface charge on these polymers have included chemical treatment of the surface to modify the ester functionality, or incorporating antistatic agents into the resin composition. For example, U.S. Pat. No. 4,973,616 and 5,011,937 issued to Govindan discloses p-toulene sulfonate salts of 2-alkyl imidazolines, e.g., 2-undecyl-4, 4, 5, 5-tetramethyl imidazolinium p-toulene sulfonate. These compounds are said to be useful as internal or external antistatic agents for fibers, such as acrylic fibers and synthetic polymers, such as polystyrene. Additionally, U.S. Pat. No. 5,491,187 issued to Ward et al. discloses methods for reducing or eliminating static electric charges on resins by adding to the resins an effective amount of at least one substituted ammonium salt of a alkylbenzene sulfonic acid having the general formula:
wherein R is straight or branched chain alkyl group having 10 to 14 carbon atoms, R
1
is hydroxyethyl or an alkyl group having 1 to 6 carbon atoms, R
2
and R
3
are the same or different and are hydroxyethyl, an alkyl group having from 1 to 6 carbon atoms or hydrogen, and R
4
is hydrogen or an alkyl group having from 1 to 6 carbon atoms. Resins incorporating these agents tend to yellow due to the lack of thermal stability of the agent.
Antistatic compositions desirably possess several important properties including a short decay time, that is, a short time to dissipate a static electric charge. Antistatic agents are desirably compatible with the resin to which they are added so that they will not change the color properties of the resin at processing temperatures. For example, a clear polymer resin may become yellow or opaque if an incompatible antistatic agent is used. Additionally, it is desired that the antistatic agent be thermogravimetrically stable during processing. Many of the prior art antistatic agents and compositions fail to posses one or more of these properties. Accordingly, there is a need for antistatic agents and compositions which possess these attributes.
SUMMARY OF THE INVENTION
One aspect of this invention contemplates an antistatic agent including at least one substituted imidazolinium salt of alkyl benzene sulfonic acid, said salt having the formula:
wherein R
1
and R
2
are the same or different and are alkyl groups having 6 or more carbon atoms.
Another aspect of the invention there is included an antistatic resin composition including:
a) a synthetic or natural resin; and
b) at least one substituted imidazolinium salt of alkyl benzene sulfonic acid; said salt having the formula:
wherein R
1
, and R
2
are the same or different and are alkyl groups having 6 or more carbon atoms. Various other additives such as fatty acids and optical brighteners may also be added to the resin composition.
A further aspect of this invention provides a method for treating an article to reduce accumulation of static electric charge thereon, including the steps of selecting an article to be treated and applying to said article an antistatically effective amount of a composition including at least one substituted imidazolinium salt of alkylbenzene sulfonic acid, said salt having formula (I) wherein R
1
and R
2
are the same or different and are alkyl groups having 6 or more carbon atoms.
Another aspect of this invention includes a method for making an antistatic compositions selecting a resin composition which accumulates static electric charge on its cured surface; and incorporating in said resin composition, prior to curing, an antistatically effective amount of a composition comprising at least one substituted imidazolinium salt of alkyl benzene sulfonic acid said salt having the above-mentioned formula (I) wherein R
1
and R
2
are the same or different and are alkyl groups having 6 or more carbon atoms.
A further aspect of this invention provides an article of manufacture including a cured synthetic or natural resin; having at least one substituted imidazolinium salt of alkylbenzene sulfonic acid; said salt having the formula:
wherein R
1
and R
2
are the same or different and are alkyl groups having 6 or more carbon atoms incorporated therein.
Also included in this invention is an article of manufacture coated with the aforementioned antistatic agent. The antistatic agents of the present invention conforming to the aforementioned formula are also believed to represent novel salts. Thus, another aspect of this invention relates to an antistatic agent including a salt of an alka
Chatham William P.
Simmons Roy
Ward James J.
Whitlock Michael L.
Hoffmann & Baron , LLP
Jagannathan Vasu
Shosho Callie E.
Witco Corporation
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