1. A COMPOSITION OF MATTER HAVING LITTLE TENDENCY TO ACQUIRE AND RETAIN A CHARGE OF STATIC ELECTRICITY, THE ESSENTIAL INGREDIENTS OF WHICH ARE A POLYMER IN WHICH VINYLIDENE CHLORIDE PREDOMINATES AND FROM 0.5 TO 5 PER CENT OF THE WEIGHT OF SUCH POLYMER OF A COMPOUND SELECTED FROM THE CLASS CONSISTING OF THE PENTA-ALKYL TRIPOLYPHOSPHATES AND THE HEXA-ALKYL TETRAPOLYPHOSPHATES WHEREIN THE ALKYL GROUPS CONTAIN FROM 3 TO 8 CARBON ATOMS.
Patented Dec. 4, 1951 UNITED STATES PATENT OFFICE POLYMERIC VINYLIDENE CHLORIDE COMPOSITIONS Eugene D. Serdynsky, James S. Gowing, and Ralph M. Wiley, Midland, and Carl B. Havens. Hope, Mich., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Application March 2, 194.1,
Serial No. 79,313
3 Claims. (Cl. 280-401 nates, as well as their plasticized compositions (all being referred to herein as polymeric vinylidene chloride compositions) have the tendency to accumulate and retain charges of static electricity. In the case of molded and extruded articles made from such compositions, this tendency is especially noticeable, and it becomes objectionable in articles such as films and woven fabrics having large areas. This undesirable property causes oppositely charged particles of dust and lint to collect on the polymeric vinylidene chloride articles in which a charge has accumulated. It also 'makes difiicult the sepa ration of one film or fabric sheet from another, as'friction resulting from attempted separation of such sheets generates enough of a charge, of opposite polarity in the opposed surfaces, to cause those surfaces to adhere to one another. Even when handling powdered forms of polymeric vinylidene chloride compositions, it is observed that the powder may be highly charged and that it tends to interfere with such operations as the dry blending of other modifiers, or sifting to separate particles of specific dimensions.
It would be highly desirable, and it is the principal object of the present invention, to provide a means for reducing substantially the tendency of vinylidene chloride polymers and articles made from them to accumulate or to retain charges of static electricity. A related object is to provide such means whereby the said undesirable tendency is substantially permanently reduced. A particular object is to provide polymeric vinylidene chloride compositions substantially free from tendency to acquire or retain static electric charges. Other and related objects may appear hereinafter.
According to the present invention, the tendency of polymeric vinylidene chloride, and of articles made therefrom, to acquire and retain charges ofstatic electricity is reduced to an unobjectionably low level by adding to the polymer composition and uniformly mixing therewith from 0.5 to 5 per cent by weight of a compound selected from the class consisting of the pentaalkyl tripolyphosphates and the hexa-alkyl tetrapolyphosphates, wherein the alkyl groups contain from 3 to 8 carbon atoms. Such compounds 2 have the empirical formula R5P30l0 and RsPqOrsI respectively. Examples are the penta-propyl, penta-n-butyl, penta-n-amyl, penta-hexyl, and penta-octyl, tripolyphosphates and the corresponding hexa-alkyl esters of tetrapolyphos-' phoric acid, and their isomers. when molded. extruded and woven articles of large. surface area per unit weight, including films, filaments and fabrics, are produced from a polymeric vinylidene chloride composition containing from 0.5 to 5 per cent of one of the defined alkyl 7, polyphosphates, the product is noticeably and significantly less prone to acquire and retain static charges than are otherwise identical articles made from the same basic composition but without the polyphosphate.
- noted. The more rapidly it loses its charge, the
more effective is the anti-static agent in or on the sample. In another test, a sample of the polymeric article is fastened about the rim of a rotor which turns at a fixed rate in contact with another rotor turning in the opposite direction at the point of contact (i. e., in the same direction relative to the axis). A strip of paper is drawn continuously between the two rotors, counter to the direction of rotation of the test sample, and in frictional contact therewith. In each rotation of the sample, it rubs momentarily against the paper sheet, tending to build up a charge, and then it is brought into contact with a grounded copper brush, which tends to carry away the charge, through a millivolt meter. At a fixed rate of rotation, the time is noted which is required to build up the charge to some arbitrarily chosen value. The longer the time required, the more effective is the anti-static agent in or on the sample.
Using the second described test method, the time required to build up a predetermined charge of static electricity was noted in tests made on molded compositions containing 3 per cent of the polyphosphate and 97 per cent'of a commercial plasticized copolymer of about per cent vinylidene chloride and 10 per cent vinyl chloride. with those on otherwise identical control samples The values obtained were compared containing none of the polyphosphatef Typical results are given below:
Time re- 'quired to develop standard charge Modifier Similarly advantageous properties are contributed to the compositions by the use of the corresponding propyl, amyl, hexyl and octyl esters.
When using the first test method, to determine the time required to lose completely the static charge acquired in a. fixed period of time, the compositions containing from 0.5 to per cent of one of the defined polyphosphates were discharged in from 5 to 25 per cent of the time required by the control samples.
Each of the defined polyphosphates contributes .the desired property to the polymer compositions, giving effective and substantially permanent protection against static build-up and static retention to articles made from the modified compositions. Y
The invention is applicable to compositions .and articles made from the homopolymer ,of
vinylidene chloride or from any of the copolymers in which vinylidene chloride predominates, whether or not such articles or compositions contain conventional plasticizers, stabilizers and similar modifiers. The most common and commercially useful copolymers of vinylidene chloride are those which contain vinyl chloride, vinyl acetate, acrylonitrile, ethyl acrylate, methyl methacrylate, or styrene as a copolymerized constituent, but the invention is not limited to the treatment of these specific copolymers and articles made from them.
1. A composition of matter having little tend- 4 ency to acquire and retain a charge of static electricity, the essential ingredients of which are a polymer in which vinylidene chloride predominates and from 0.5 to 5 per cent of the weight of such polymer of a, compound selected from the class consisting of the penta-alkyl tripolyphosphates and the hexa-alkyl tetrapolyphosphates wherein the alkyl groups contain from 3 to 8 carbon atoms.
2. A composition of matter having little tendency to acquire and retain a charge of static electricity, the essential ingredients of which are a polymer in which vinylidene chloride predominates and from 0.5 to 5 per cent of penta-n-butyl tripolyphosphate, based on the weight of such polymer.
3. A composition of matter having little tendency to acquire and retain a charge of static electricity, the essential ingredients of which are a polymer in which vinylidene chloride predominates and from 0.5 to 5 per cent of hexa-n-butyl tetrapolyphosphate, based on the weight of such polymer.
EUGENE D. SERDYNSKY. JAMES S. GOWING. RALPH M. WILEY.
CARL B. HAVENS.
' REFERENCES CITED The following references are of record'in the file of this patent:
UNITED STATES PATENTS OTHER REFERENCES Hochwalt et al., Ind. and Eng. Chem.,-vol. 34,
1942, DD. 20 to 25.