Antistatic plastic materials containing epihalohydrin polymers

Details Antistatic plastic materials containing epihalohydrin polymers Antistatic plastic materials containing epihalohydrin polymers

1987-05-13

2002-04-09

Wilson, Donald R. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S187000, C525S403000, C525S404000

Reexamination Certificate

active

06369159

ABSTRACT:

BACKGROUND OF THE INVENTION
When formed into such articles as molded objects or films, synthetic polymers are known to generate and accumulate electrostatic charges. When charged, such objects tend to accumulate concentrations of dirt and soil which are unsightly in appearance and interfere with the use of such objects. When nylon or polyester polymers are formed into fibers, the electrostatic charges create processing problems whereas in consumer use, carpeting made from such synthetic fibers has a tendency to generate annoying shocks in cold, dry weather, while in apparel, the charged fabric clings embarassingly to the wearer and shocks the wearer when the garment is being removed. Furthermore, such garments have an increased tendency to attract lint and soil.
The problem of electrostatic charge and arcing that it can create, is also of great concern in clean rooms, such as hospital surgery rooms, as well as chemical plants and laboratories, and electronic equipment, in particular. Arcing due to an electrostatic charge can cause an explosion or can damage electronic equipment.
To overcome the static electricity problem, topical antistats have been used to eliminate the electrical charges, however, such treatments have proven to be of little benefit in the consumer applications due to lack of permanency. Other methods used to reduce the electrostatic charges included copolymerization of monomers containing ionizable groups, surface grafted polymerization of antistatic monomers, inclusion of metallic fibers or carbon-coated filaments, incorporation of an antistatic additive in the matrix polymer, and the like.
The prior art is replete with teachings to reduce antistatic charges in various polymeric structures. Certain prior art patents describe the incorporation of antistatic materials in various polymeric structures which are used to mold or extrude rigid objects such as luggage, protective covers, and automobile parts. There is also a vast body of prior art patent literature directed to the elimination of the static charges in fiber and films.
SUMMARY OF THE INVENTION
This invention is directed to plastic materials, which include thermoplastic compositions and thermosets, containing an effective amount of an epihalohydrin-containing polymer as an antistatic agent. Examples of thermoplastic materials include polymers of acrylonitrile, butadiene, and styrene, also known as ABS polymers; polyamides or nylons; polyesters; polyvinyl chloride; chlorinated polyvinyl chloride; and polycarbonates. Examples of thermosetting materials include epoxy and phenolic resins. The plastic materials contain 1 to 50 weight parts of an epihalohydrin polymer antistatic agent per 100 weight parts of the plastic material.
DETAILED DESCRIPTION OF THE INVENTION
The deleterious effects of electrostatic charge is reduced or eliminated by inclusion in a plastic material an epihalohydrin antistatic agent selected from epihalohydrin homopolymers and epihalohydrin copolymers. An effective amount of the antistatic agent is used in the plastic material to induce charge dissipation by at least 50% in less than 10 seconds on application of 1000 volts of direct current at 23.5° C. and 50% Relative humidity. More specifically, the antistatic agent can be used in amount of 1 to 50 weight parts, preferably 2 to 30 weight parts, per 100 weight parts of the plastic material. Therefore the plastic material comprises between 67 and 99 weight percent of the composition and the antistatic agent comprises between 1 and 33 weight percent of the composition.
The antistatic agent can be in liquid or solid form. When in liquid form, it can be blended with the solid plastic material by mixing the two materials together until the plastic material absorbs the liquid antistatic agent. When the antistatic agent is in a solid form, such as powder, it is mixed with the plastic material until it is uniformly distributed throughout the plastic material. It should be apparent that the antistatic agent becomes an integral part of the plastic material after it is molded, however, it can also be used as a surface treatment therefor.
The Dreyfuss U.S. Pat. No. 3,850,856 and 3,850,857 disclose commercially available liquid epihalohydrin polymers prepared by cationic ring-opening polymerization. The epihalohydrin polymers disclosed in these patents can be used as antistatic agents in the manner described herein. The '857 Dreyfus patent discloses a process for polymerizing an epihalohydrin using as a catalyst a trialkyloxonium salt of an HMF
6
acid where M is a Group V element selected from phosphorous, arsenic, and antimony. The '856 Dreyfuss patent discloses an improvement over the '857 patent wherein polymerization of an epihalohydrin is carried out in the presence of water or ethylene glycol. The resulting polymers of an epihalohydrin prepared pursuant to the Dreyfuss patent '856 have hydroxyl termination. Any of the other alkylene glycols can also provide hydroxyl termination.
The liquid antistatic agents referred to herein have Brookfield viscosity below 16,000,000 cps at 25° C. More specifically, such liquid polymers or antistatic agents have viscosity measured at 25° C. in the range of 100 to 10,000,000 cps, preferably 200 to 2,000,000 cps and have number average molecular weight of 200 to 30,000, preferably 300 to 15,000, as determined by gel permeation chromatography using polystyrene as the calibration standard.
Solid epihalohydrin polymers are also well known commercial elastomers which can also be used as antistatic agents. A particularly useful class of these materials are copolymers of an epihalohydrin and an alkylene oxide. These copolymers are readily prepared by polymerization in mass or solution with catalysts normally formed by reacting an organoaluminum compound with water, and optionally, with a small amount of a chelating agent. These copolymers normally have a number average molecular weight greater than about 30,000, preferably in excess of 60,000, as determined by gel permeation chromatography. The Oetzel U.S. Pat. No. 4,251,648 describes such solid polymers of epihalohydrin also containing an unsaturated epoxy comonomer which makes it possible to cure such copolymers with an organic peroxide.
The epihalohydrin monomers useful in preparing polymeric epihalohydrin antistatic agents of this invention include epichlorohydrin, epibromohydrin, epiiodohydrin, and epifluorohydrin, although eipchlorohydrin is preferred. The antistatic agents include the epihalohydrin homopolymers and copolymers thereof with one or more comonomers selected from 1,2-epoxide monomers, particularly alkyl glycidyl ethers and oxirane-containing monomers or alkylene oxides of 2 to 6 carbon atoms, particularly ethylene oxide and propylene oxide and mixtures thereof. In these copolymers, amount of an epihalohydrin can vary from about 5 to 95 weight parts whereas one or more of the comonomers are used in an amount of 95 to 5 weight parts. Particularly preferred copolymers are solid, as in powder form, consisting of 5 to 95 weight parts epihalohydrin, preferably 10 to 60 weight parts, with 95 to 5 weight parts, preferably 90 to 40 weight parts, of one or more comonomers, such as ethylene oxide or propylene oxide, all on the basis of a total of 100 weight parts. Based upon these weight percentages, the ratio by weight of the epihalohydrin to the oxirane-containing monomer is from about 1:19 to about 1:1. The presence of an epihalohydrin in the antistatic agent appears to improve compatibility between the antistatic agent and the plastic material with which it is blended.
Other antistatic agents can also be included in the plastic compositions, along with the antistatic agents already described. Some examples of such other antistatic agents include long chain and ethoxylated amines and amides, and quarternary ammonium salts.
The plastic materials are generally divided into thermoplastics and thermosets. This invention is generally directed to imparting antistatic character to plastic materials, including engineered plastics. Thermos

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