US3806487A - Stabilization of pigmented nylon against actinic radiation - Google Patents

Abstract

AN IMPROVED RESISTANCE TO ACTINIC RADIATION AND WEATHERING IS IMPARTED TO PIGMENTED NYLON COMPOSITIONS BY INCORPORATING THEREIN FROM ABOUT 400-600 PARTS PER MILLION BY WEIGHT BASED ON THE NYLON OF COPPER IN DISSOLVED FORM AND FROM ABOUT 0.4 TO 2.2 PERCENT BY WEIGHT ON THE NYLON OF AN INORGANIC HALIDE, AND WHEREIN THE RATIO OF COPPER IN PARTS PER MILLION TO HALIDE IN WEIGHT PERCENT IS BETWEEN 325:1 AND 1150:1.

Description

United States Patent 3,806,487 STABILIZATION OF PIGMENTED NYLON AGAINST ACTINIC RADIATION Bernard Silverman, Raleigh, N.C., assignor to Monsanto Company, St. Louis, M0. N0 Drawing. Filed July 3, 1972, Ser. No. 268,345 Int. Cl. C08g 51/56 US. Cl. 260-37 N 6 Claims ABSTRACT OF THE DISCLOSURE An improved resistance to actinic radiation and weathering is imparted to pigmented nylon compositions by incorporating therein from about 400-600 parts per million by weight based on the nylon of copper in dissolved form and from about 0.4 to 2.2 percent by weight on the nylon of an inorganic halide, and wherein the ratio of copper in parts per million to halide in weight percent is between 325:1 and 1150:1.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention is directed to fiber-forming nylon compositions and fiber or filament products obtained therefrom which have an improved resistance to degradation resulting from outside weather conditions and sunlight. By the term nylon compositions, there is included both the nylon-6 (polycaproamide) variety and nylon-66 (polyhexamethylene adipamide) In the more conventional end-uses for polymeric nylon, the nylon is not subjected to a continuing and prolonged exposure to the debilitating effects of sunlight and weather. However, when used in the construction of the recently developed outdoor recreational surfaces such conditions prevail. These grass-like synthetic turfs are finding ever increasing'use as a substitute for natural turf in the playing areas ,of football and soccer stadia, baseball parks, tennis courts, childrens playgrounds, golf tees and the surfaces adjoining swimming pools. In addition they are often used outdoors for decorative purposes.

It becomes readily apparent that in such applications, the level of resistance to deterioration from actinic radiation must be far greater than that required for the more conventional nylon end-uses. Because filaments are used in an upright positionsuch as in the pile of a carpetthe surface area exposed is very great. In addition the filaments are pigmented to simulate the color of living grass, and often the pigments tend to accelerate the sunlight induced degradation process. Moreover, because of the costs of fabrication and installation of these synthetic turfs, the initial nylon properties must be preserved over substantial periods of time.

The present invention is directed to the problem of providing nylon filaments with a sufiicient level of resistance against the degrading effects of sunlight and weathering to satisfy the product demands as above-described.

(2) Prior art In US. Pat. 3,565,910 there is described one of the more effective known methods for stabilizing pigmented nylon compositions against heat and light deterioration. This is accomplished by the use of an additive system comprising a copper compound combined with an inorganic halide. The copper compound is of a type which will provide copper in the nylon composition in a dissolved form while the inorganic halide is usually an alkali metal salt of bromine or 'iodine. The copper is employed in an amount of from 20-200 ppm. by weight of the nylon while the halide is present in an amount of from "ice 0.05 to 5 percent by weight based on the nylon. Optionally, a phosphorous containing compound, such as phenyl phosphinic acid, may also be present in an amount of up to 1 percent by weight of the nylon.

Although the afore-mentioned additive system, as de scribed in the prior art, is relatively effective in stabilizing pigmented nylon compositions against the adverse effects of heat, light and weathering; the protection afforded is not sufiicient to adequately satisfy the rigorous requirements of outdoor synthetic turfs.

It is, therefore, an object of this invention to provide a pigmented nylon composition of improved stability against light and heat degradation. It is also a further object of this invention to provide pigmented nylon filaments having suflicient resistance to deterioration from heat, light and weathering to be used for prolonged periods of time as the pile on synthetic turfs employed as outdoor recreational surfaces.

SUMMARY OF THE INVENTION The present invention resides principally in the surprising discovery that the stabilizing efficiency of the copper-halide additive combination, as disclosed in US. Pat. 3,565,910, can be substantially enhanced by increasing the copper concentration over that previously taught while maintaining a specified quantitative relationship with the halide concentration not heretofore recognized or appreciated as eflicacious.

Thus, there is imparted to a pigmented, fiber-forming nylon composition a greatly improved stability against the effects of Weather and sunlight by incorporating therein from about 400-600 parts per million by weight based on the nylon of copper in dissolved form together with from about 0.4 to 2.2 percent by weight based on the nylon of an inorganic halide. The outstanding results are dependent upon the further proviso that the ratio of copper in parts per million based on the nylon to the halide in percent by weight based on the nylon of between 325 :1 and 1150: 1, respectively.

Optionally, there may also be included for incorporation into the pigmented nylon composition a suflicient amount of a phosphorous containing compound to provide up to 1000 parts per million by weight based on the nylon of phosphorous. A particularly preferred source of phosphorous is phenyl phosphinic acid.

DETAILS OF THE INVENTION As previously noted, the nylon compositions contemplated include both the nylon 6 and nylon 66 varieties. Since the intent is to obtain fibers, filaments and particularly monofilament ribbons for use as pile fibers in the fabrication of synthetic turfs, the initial nylon polymer must be fiber-forming, which implies an average molecular weight of at least 10,000.

As also noted, the nylon compositions with which this invention is concerned are pigmented. It will be recognized by those persons skilled in the art that many pigments are available for use in obtaining a wide variety of colors in nylon. In general, the results obtained in the practice of the instant invention are not limited by the choice of pigment or mixtures thereof.

However, in order to acquire a color resembling living grass, it is desirable to use as part of the pigment mixture a member of the class of copper phthalocyanine pigments. These pigments include both the halogenated copper phthalocyanines as well as the blue unhalogenated phthalocyanine pigments. Especially desirable are the chlorinated copper phthalocyanine pigments. In general, the phthalocyanine pigment is employed in an amount of from about 0.1 to about 2 percent on the weight of the nylon.

To obtain a shade of green color more closely simulating that of natural grass, a chrome yellow pigment is employed with the phthalocyanine pigment. These pigments are obtained from either pure lead chromate, or in the case of the lighter shades lead chromate combined with minor amounts of lead sulfate, lead carbonate or lead phosphate. Generally, the amount will be from about 0.5 to about 2 percent based on the weight of the nylon.

In addition to the phthalocyanine green and chrome yellow pigments, the pigmenting mixtures commonly contain carbon black in minor amounts to achieve the desired corporated into nylon compositions are well known to the art. Hence, it is not necessary to burden this specification with the details for which reference may be made to, for example, US. Pat. 3,565,910 among other existing publications.

The copper which is employed in the present invention is present in the pigmented nylon composition in dissolved form. The means whereby copper becomes dissolved in nylon can vary. For example, by milling metallic copper into a nylon composition a reaction occurs whereby a soluble copper compound is formed. Thus, while copper in dissolved form does not include elementary copper, it does include soluble copper derived therefrom.

Copper compounds soluble in polyamides which may be employed are well known and many are set forth in French Pat. 906,893, U.S. Pat. 2,705,227 and US. Pat. 3,565,910. As illustrations, there may be mentioned copper acetate, copper formate, copper carbonate, cupric sulfite; also copper butyrate, citrate, lactate, oleate, oxalate, stearate and tartrate; also copper benzoate and hydroxybenzoic acid salts of copper such as copper salicylate; also the sulfonic acid copper salts including copper salicylate; also the sulfonic acid copper salts including copper p-toluenesulfonate and copper phenolsulfonate; also various copper resin complexes. It has been found that the source of the copper has little or no effect on the ultimate results, it being merely necessary that the copper be present in the pigmented nylon composition in a dissolved form.

An inorganic halide is employed in combination with the copper. Although the various alkaline earth metal, alkali metal and ammonium halidesexcepting fluorides-can be used to advantage, best results are realized when employing the sodium and potassium bromides and iodides.

As indicated, a phosphorous containing compound may as an option be included in the additive mixture. Phosphorous acid is a preferred phosphorous compound, although phosphoric acid may also be used in addition to various other phosphorous and phosphoric compounds which are readily hydrolyzable to the corresponding acid. The aromatic phosphinic acids are particularly suitable, and especially phenyl phosphinic acid.

The stabilizers of the present invention are incorporated into nylon compositions by conventional methods well known in the art. For example, they may be added to the nylon salt prior to the condensation reaction or at any time during the condensation. Addition of the stabilizers to the molten polymer followed by homogenization during extrusion is another acceptable method. Blending of the stabilizing additives with solid particles of nylon, i.e., molding powder, in a tumbler followed by extrusion of the solid particles is a still further method for satisfactorily incorporating the stabilizers into nylon. An one or a combination 'of these methods can be employed with satisfactory results. The pigments may be admixed with the nylon composition before introducing the stabilizers, concurrently therewith or at a later time.

As previously noted, the unexpectedly improved results realizable in the' practice of this invention are brought about by incorporating into the fiber-forming composition from about 400-600 parts per million based on the weight of the nylon of copper in dissolved form together with from about 0.4 to 2.2 percent by weight on the nylon of the inorganic halide, and wherein the ratio of copper in parts per million and the halide in weight percent is between 32511 and 1150: 1; respectively. Preferably, the cop-. per is present in an amount of from 450-550 p.p.m. on the weight of nylon, the halide in an amount of from 0.4 to 2.2 percent by weight of the nylon and with the aforesaid ratio being between 450:1 and 950:1.

When employing an optional phosphorous containing compound it is desirable that the amount be sufiicient to provide up to 1000 parts per million by weight of phosphorous based on the nylon. That is, anywhere from 0-1000 p.p.m. of phosphorous may be present.

PREFERRED EMBODIMENTS Example I A 50 percent by weight aqueous solution of the adipic acid salt of hexamethylene diamine is prepared. To this aqueous solution is added a suflicient amount of cupric acetate monohydrate to provide 50 parts per million of copper based on the weight of the ultimate polymer.

There is still further added an amount of phenylphosphinic acid which will provide 437 p.p.m. of phosphorous on the weight of the final nylon polymer. Nylon-66 polymer is made from the resulting solution in an autoclave by employing the conventional polymerization procedure. The nylon polymer obtained is cast, quenched and chipped into pellets in conventional manner. The thus prepared pellets are dried to a moisture content of less than 0.2 percent moisture as is normal with nylon to be processed in a screw extruder.

The pelleted nylon is then admixed by tumbling with 2.2 percent by weight on the nylon of a pigment containing color concentrate which is also in the form of pellets. The color concentrate had the following ingredients:

Percent Phthalocyanine green pigment (Ramapo Green G,

No. G-755-D, E. I. du Pont de Nemours Co.) 15 Lead chromate (Chrome yellow pigment shading yellow No. X-2801, Imperial ColorChemical and Paper Corp.) 30 Carbon black '(Black Pearls O, Cabot Corp.) 1.2 Mieronized wax (Chemetron Corp.) 0.8

Nylon resin (a product of E. I. du Pont de Nemours Co. bearing the trade name Elvamid8063- used as a carrier vehicle) 53 To a 50 percent by weight aqueous solution of hexamethylene diammonium adipate there is added a suflicient amount of cupric acetate monohydrate to provide parts per million of copper based on the weight of the ultimate polymer. There is also added potassium bromide in an amount sufiicient to provide 1.1 percent by weight based on the polymer to be produced. There is further added 2000 p.p.m. of phenyl phosphinic acid which will provide 437 p.p.m. of phosphorous on the weight of the final polymer. Nylon-'66 is made from the resulting solu tion by employing conventional polymerizing techniques. The nylon obtained is cast, quenched and chipped into pellets which are dried to a moisture content of less than 0.2 percent.

The nylon is then admixed withv the pigment concentrate of Example 1, in the same manner and in the same amount. The pigmented nylon which is brought to the molten state is then extruded through a spinneret to form a plurality of ribbon-like monofilaments. The filaments are quenched in a water'bath, stretched three times their initial length and packaged.

Example III Nylon pellets produced in accordance with Example II above are admixed by tumbling with solid particles of a cationic copper-resin complex (produced by the Sandoz Corp. and marketed under the trade name Cuprofix 52D). The copper-resin complex is employed in an amount sufficient to provide 350 p.p.m. of copper on the weight of the nylon. The purpose is to raise the copper level in the nylon to 500 p.p.m. from the 150 p.p.m. level which had been incorporated previously. It will be noted by reference to Example II that the pelleted nylon additionally had incorporated therein 1.1 percent by weight of potassium bromide and 2000 p.p.m. ofphenyl phosphinic acid which provides 437 p.p.m. of phosphorous.

The color concentrate of Example I in the same amount as set forth therein is blended into the mixture described above. The resulting mixture is then brought to the melt and extruded through a spinneret to form a plurality of ribbon-like monofilaments. These filaments are quenched in a water bath, stretched three times their initial length and wound up on spools.

Example IV Nylon pellets produced in accordance with Example I above are admixed by tumbling with an amount of cupric acetate monohydrate sufficient to provide 450 p.p.m. of copper on the weight of the nylon. The purpose is to raise the copper level in the nylon to 500 p.p.m. from the previous 50 p.p.m. level. By reference to Example I, it will be noted that the nylon pellets also contain 0.55 percent by weight of potassium bromide and 2000 p.p.m. of phenyl phosphiuic acid which provides 437 p.p.m. of phosphorous.

The color concentrate of Example I and in an amount identical to that set forth therein is blended into the abovedescribed mixture. The resulting mixture is then brought to the molten state and extruded through a spinneret to form ribbon-like monofilaments. These filaments are quenched in water, stretched three times their initial length and wound on bobbins.

Table I below presents a comparative summary of the concentration of copper, metal halide, phosphorus and pigment concentrate present in each of the illustrative examples described hereinabove. All parts and percentages are by weight based upon the nylon polymer into which these ingredients have been incorporated. it will be recognized that Examples I and II lie outside the scope of the present invention. They have been included to provide a standard of comparison, since they are representative of the prior art practice as typified by US. Pat. 3,565,910.

TABLE I Percent Phosgment phorus, Cu, Percent Example concentrate p.p.m. p.p.m. KB:

Table II following presents comparative data on physical measurements taken on the monofilament ribbons obtained in each of the illustrative examples prior to test evaluations.

TABLE II- Breaking Elon- Breaking strength, gation, Tenacity, energy, Example Denier grns. percent gins/den. gmsJden.

TESTS. PERFORMED Actual outdoor exposure tests to the weather conditions prevailing in Durham, NC were performed over a test period of 12 continuous months.

The test samples were prepared by winding the monofilament ribbon around rectangular cards of cardboard such that the flat side of the ribbon was exposed throughout the test length of the filament. The'test specimens were taped to the cardboard at opposite ends thereof to hold them firmly in place.

The cards were mounted horizontally on a table-top surface placed outdoors such that one side only of the card was fully exposed to the radiant energy of the sun and general weather conditions.

Following the test period of a full year, the cards were removed and degradation determinations were made on the exposed length of the monofilament ribbons under test.

In making these determinations, measurements were made of the tensile properties of the exposed filament on a standard Instron Tester using a 5 inch gauge length sample. That is, tenacity and elongation measurements were taken in accordance with ASTM method D-2256.

The results of the degradation tests may be expressed in dilferent ways, but it has been found convenient and meaningful to express such results in terms of the energy required to effect a rupture or break in the test specimen. This is referred to as the "Breaking Energy and is expressed in grams per denier. It can be calculated by multiplying the measured tenacity by one-half the measured percent elongation. The Breaking Energy" parameter is used to express degree of degradation in Table III which follows.

In considering Table III below, it will be noted that although phosphorus and pigment are present in each of the comparative examples, their presence is not indicated in the tabulation because the identity and amounts of these ingredients have not been varied. That is, each example contains 437 p.p.m. on the weight of the nylon of phosphorus and 2.2 percent by weight based on the nylon of an identical pigment concentrate.

1 Based on weight 01 nylon.

Referring to Examples I and H above which typify the prior art, it is noted that Example II contains three times as much copper and twice the amount of potassium bromide as does Example I, yet no improvement over Example I is shown in stabilizing effectiveness. This is clear evidence that improved results cannot be obtained in the usual manner by increasing the concentration of components in the stabilizing system.

However, observe that the effectiveness of Examples III and IV in resisting degradation is susbtantially double that of Examples I and II. This result is unexpectedly achieved by increasing the copper level over that taught by the prior art while observing the previously described 7' Although the invention has been described in consider able detail with reference to certain preferred embodiments, it will also be understood that variations. can be effected which come within the-scope of the invention as described hereinabove and as defined in the appended claims. A n i That which is claimed is: 1 3 1. A pigmented, fiber-forming nylon composition hav; ing incorporated therein an improved additive combina tion forimparting stability against the degradati ve effects 8 for imparting stability against the degradativeefiects of actinic radiation and weathering, said stabilizing system comprising; from about450-550 parts per millionby weight (based on the nylon of copper in dissolved form andffrogn about 0.55 to 1.1 percent by weight basedon the nylon of potassium bromide; and wherein the ratio of copper in parts per million to potassium bromide in weight percent is between 450i1 and 950:1. I l 5. A pigmented fiber-forming nylon composition stabiliz ed' against the degradative effects of actinic radiation and weathering by having present therein 500 parts per million by weight based on the nylon of copper in dissolved fo'rm, 0.55 percent by weight based on the nylon of potassium bromide and sufficient phenyl phosphinic acid to provide 437 parts per million by weight based on the nylon of phosphorous.

of actinic radiation and weathering, said additive com-' bination comprising: from about 400-600 parts per million by weight based on the nylon. of dissolved copper and from about 0.4 .to 2.2 percent by weight based .on the nylon of an inorganic halide selected from the group consisting of the sodium and-potassium salts of bromine and iodine; and wherein. the ratio of copper in parts per million to the halide in Weight percent isbetween 325 :1 to 1150: 1.

2. The composition in accordance with claim 1 in which there is additionally included sufiicientphenyl phosphinic acid to provide from 0-1000 parts per million by weight based on the nylon of phosphorous.

3. A monofilament ribbon prepared from the composition of claim 1. A

4. A pigmented fiber-forming nylon composition having incorporated therein an improved stabilizing system A monofilament ribbon prepared from'ithe corn: 29 m ai .References Cited UNITED STATES PATENTS "3,565,910 2/1971- Elbert '26030.8 2,705,227 4/1955 Stamatoif 260 '45.7 3,573,245 4/1971 Mueller 26045.75 3,457,325 "7/1969 Anton 260 '857 3,07s;24s 2/1963 Ben 2603'0."6 3,692,867 0/1972 Mayer 260-1857 ALLAN LlEBERMAN, Primary Examiner R. ZAITLEN, Assis'tantExaminer US. 01. X.R.