MOLD CORROSION INHIBITORS This invention relates to a method for inhibiting th corrosion of metals by polyCarylene sulfide) resin composition ^' s. This invention also relates to a composition comprising polyCarylene sulfide) and a polyacrylamide or polyamide corrosion inhibitor. A problem associated with the molding of polyCarylene sulfide) resins is the occasional tendency of these resins to cause corrosion of the molds -employed in the molding processes. For example, it has been occasionally noted that molds have become corroded during the injection molding of polyCarylene sulfide) resins. The corrosion, when observed, has varied from only a slight attack of the mold after a long molding period to very extensive damage after molding for only a short time. Accordingly, a means for mitigating this corrosion problem represents a substantial and very practical contribution of the art. It has been found that the addition of a small amount of a polyacrylamide or polyamide to a polyCarylene sulfide) resin counteracts the tendency of such a resin to ^' cause the corrosion of metal.

An object of this invention is to provide a method for inhibiting the corrosion of metals that come in contact with polyCarylene sulfide) resins, especially during the molding of such resins.

A further object is to provide a novel polyCarylene sulfide) resin composition that will not cause the corrosion of metals ^' brought in contact with the composition. Other objects, advantages and features of this invention will be apparent to those skilled in the art upon reading this disclosure and the appended claims.

In accordance with the practice of this invention, polyacrylamide or polyamide or a mixture thereof is incorporated into polyCarylene sulfide), i.e., ^" sulfide polymer to inhibit or prevent corrosion of metals that come into contact with the composition. 5 Any normally solid polyCarylene sulfide) resin, whether linear, branched or lightly crosslinked, may be employed. The following patents, which are incorporated herein by reference, disclose the preparation of suitable polyCarylene sulfide) resins:

1. U.S. 2,513,188 Cpolyhalo aromatic compounds reacted 10 with sulfur and metal sulfide at the fusion temperature).

2. British 962,941 Cmetal salts of halothiophenols are heated at a polymerizing temperature).

3. U.S. 3,354,129 Csolution reaction of polyhalo compounds ^■ 15 with alkali metal sulfides).

4. U.S. 3,717,620 Cresins of U.S. 3,354,129 modified to yield resins of lower melt flow).

5. U.S. 3,919,177 Cp-phenylene -sulfide polymers produced by reacting p-dihalobenzene, a sulfur source, an alkali 20 metal carboxylate and an organic amide).

Since the preparation of polyCarylene sulfide) resins is well known to those skilled in the art further description will not be set forth herein. Por more detail one can refer to the above patents.

Molding grade polyCarylene sulfide) -resins are particularly

25 benefitted by the present invention. Generally such polyCarylene sulfide) resins have melting points in the range of about 260°C. to about 400°C The melt flow of such. polyCarylene sulfide) resins, determined by the method of ASTM D 1238-70, modified to a temperature of 316°C. using a 5-kg weight, will generally be within the range of

30 about 0.5 to about 4,000 g/10 in. and preferably within about 10 to about 1000 g/10 min.

The presently preferred polyCarylene sulfide) resin is a linear, branched or lightly crosslinked polyCphenylene sulfide) resin. Molding grade polyCphenylene sulfide) resins can be • molded into a 35 variety of useful articles. The molding techniques are well known in the art. Generally molding is carried out above the melting point or softening point but below the decomposition point of the particular

polymer being molded. Suitable molding techniques include injection molding, compression molding, vacuum molding, extrusion and the like.

While the present invention is especially suited to inhibit corrosion associated with the injection molding of polyCphenylene sulfide) resins, the scope of this invention encompasses any molding or extrusion technique wherein corrosion occurs ^' as a result of the contacting of metal with any polyCarylene sulfide) resin.

The polyamides contemplated to be useful in the practice of this invention include polyamides defined by one of the following generic formulas:

Each R and R independently represents an aliphatic hydrocarbon radical having from about 2 to about 15 carbon atoms, a cycloaliphatic hydrocarbon radical having from about 3 to about 16 carbon atoms, a mixed aliphatic-cycloaliphatic hydrocarbon radical having from about 6 to about 20 carbon atoms, or an aromatic hydrocarbon radical* having from about 6 to about 20 carbon atoms. Each n is a whole number and, preferably, falls within the range of about 10 to about 500,000.

Examples of polyamides suitable as corrosion inhibitors in polyCarylene sulfide), particuarly polyCphenylene sulfide), include those listed in the Encyclopedia of Polymer Science and Technology, Vol. 10, pages 392-411 C1969), incorporated by reference herein, such as polypyrrolidone or nylon-4, polyC -caprolactam) or nylon-6, polyChexamethylene adipa ide) or nylon-6,6, polyCenanthiamide) or nylon-9, polyCaminodecanoic acid) or nylon-10, poly Cc^-undecanamide) or nylon-11, polyClaurolactam) or nylon**-12, polyChexamethylene dodecanamide) or nylon-6,10, polyChexamethylene terephthalamide) or

nylon-6,T. Also suitable are aramides such as polyCp-phenylene terephthalaraide), polyCm-phenylene isophthalamide) and polyCN,N~di- phenyl-p-phenylene isophthalamides) and polyamides derived from bisCp-aminocyclohexyl) methane CPACM) and a dicarboxylic acid such as dodecanedioic acid. The presently preferred polyamide corrosion inhibitors are πylon-6,6, nylon-6 and nylon-12.

The polyacrylamides contemplated to be useful in the practice of this invention include polyacrylamides defined by the following generic formula:

3 4 5 ^' Each R , R ant? R independently represents hydrogen, an aliphatic hydrocarbon radical having from 1 to about 6 carbon atoms, or a cycloaliphatic hydrocarbon radical having from 3 to about 10 carbon atoms. Each R and R independently represents hydrogen, an aliphatic hydrocarbon radical having from about 1 to about 12 carbon atoms, a cycloaliphatic hydrocarbon radical having from about 3 to about 14 carbon atoms, an aromatic hydrocarbon radical.-having from about 6 to about 20 carbon atoms, or an alkylol radical having from about 3 to about 10 carbon atoms. The n represents a whole number, preferably ^" within the range of about 10 to about 500,000.

Examples of polyacrylamides suitable as corrosion inhibitors in polyCphenylene sulfide) and other arylene sulfide polymers include those polymers described in the Encyclopedia of Polymer Science and Technology, Volume 1, pages 177-196 C1964), incorporated by reference herein, such as polyacrylamide, polymethacrylamide, polyCN-isopropylacrylamide) , poly CN-tert-butylacrylamide), polyCN- methylolacrylamide) and poly (ΪT,N ^' -methylene bisacrylamide). Also suitable are ionic derivatives of these polyacrylamides such as Ca) anionic derivatives prepared by partial hydrolysis, sulfomethylation or Hofman degradation of polyacrylamides or by copolymerization of

acrylamides with acrylic acid, methacrylic acid, or sodium vinyl sulfonate and Cb) cationic derivatives prepared by incorporating vinylpyridine, vinylbcnzylammonium compounds or diallylammoniura salts as comonomers in any of the above-described polyacrylamides. The presently preferred polyacrylamide corrosion inhibitor is an anionic polyacrylamide marketed by Betz Corporation under the designation of Betz 100 PAA containing about 2-15 mole percent of hydrolyzed sodium acrylate comonomer. Another suitable, yet less preferred polyacrylamide is PAA WC 160 Calso marketed by Betz Corporation) a cationic polyacrylamide containing less than 10 mole percent of a quaternary ammonium compound as a comonomer.

Any of the above polyamide or polyacrylamide corrosion inhibitors or any combination thereof can be utilized in the practice of this invention. Generally the weight ratio of polyamide or polyacrylamide or mixture thereof to the polyCarylene sulfide) resin is within the range of about 0.2:100 to about 3.0:100.and most preferably in the range of about 0.7:100 to about 1.0:100. However, it should be noted that the scope of this invention is not limited to any specific range but rather requires, only that a finite amount of polyamide or polyacrylamide or mixture thereof, sufficient to -at least partially inhibit metal corrosion, be incorporated into the polyCarylene sulfide) resin.

Incorporation of the corrosion inhibitor into the polyCarylene sulfide) resin may be accomplished, for example, by any known dry-blending means.

- The polyCarylene sulfide) resins of this invention can also include other additives such as fillers, pigments, stabilizers, softeners, extenders and other polymers. In injection molding, for example, it is quite common to prepare polyCarylene sulfide) resin compositions containing about 20 to about 50 weight percent of a conventional glass fiber filler, based on the weight of the polyCarylene sulfide) resin and the... lass fiber filler. Generally glass fibers of about 0.03 to about 0.5 inches in length are employed. However, glass-filled compositions prepared by feeding a continuous glass roving through an extruder along with the thermoplastic are also suitable.

CMr

The following examples 3re presented to further illustrate the practice of my invention. It will be apparent to those skilled in the art that modifications ^* in the procedures described in these examples can be made without departing from the scope and spirit of my invention.

Example I In this example the procedure for preparing and testing certain polyCphenylene sulfide) compositions having good corrosion inhibiting properites is described. 5.0 + 0.05 grams of FS-4 Ryton CTrademark) polyCphenylene sulfide ) CPFS), having a melt flow of about 180 + 40 g/10 min. Cdetermined according to ASTM D 1238 modified by using an effective weight of 5.0 Kg at 316 degrees C), was mixed in an aluminum pan. with about 0.02 to 0.Q5 grams of a polyamide or polyacrylamide corrosion inhibitor. The mixture was ground and more thoroughly mixed with mortar and pestle, and was then poured over an acetone-washed, mild 1" x 1" steel coupon placed in an aluminum pan. The pan and its contents were heated for 3 hours ^* at a temperature ranging from 680 degrees F. to 710 degrees F. The solid mixture was removed from the pan, and the steel coupon was exposed to moisture saturated air for two hours,- and thereafter to ambient air for at least 16 hours. Rust formation was visually rated on a "good-fair-poor" scale.

Example II

In this example, the- corrosion inhibiting utility of nylon-6,6 in polyCphenylene sulfide) is illustrated. The nylon-6,6 used was a Monsanto multifil having a melting point of about 480 degrees F. to 500 degrees F. , a specific gravity of 1.14 and a tenacity of 5.0 to 5.5 grams per denier.

The results are summarized in Table I.

Table I

Run Additive Weight-% of Additive Corrosion Ratin

None Poor CControl)

2 Li ₂ C0 ₃ 1.0 Good

CControl)

3 Nylon-6,6 1.0 Good

Clnvention)

4 Nylon-6,6 0.7 Good

(Invention)

5 Nylon-6,6 0.4 Fair Clnvention)

The data in Table I show that nylon-6,6 at levels of 0.7-1.0 weight percent is as effective as Li ₂ C0_, which is commonly used as a mold corrosion inhibitor in polyCphenylene sulfide) molding compounds..

f CM I

Example III The data in Table II..illustrate the corrosion inhibiting effect of polyacrylamides when incorporated into polyCphenylene sulfide). Table II

Run Additive eight-% of Additive Corrosion Rating

None Poor

CControl)

6 Non-ionic PAA a) 1.0 Fair ^* to Poor (Invention)

7 PAA-WC 160 ^ 1.0 Fair

(Invention)

8 Betz 100 ^C ^ 1.0 Good (Invention)

9 Betz 100 ^c) 0.7 Fair (Invention)

10 Betz 100 ^c) 0.4 Fair

(Invention)

a) a polyacrylamide marketed by Pfaltz and Bauer

^J a cationic polyacrylamide in which less than 10 percent of a quaternary aminoalkylacrylate ester is incorporated as a comonomer; marketed by Betz Corp., Trevose, Pa. c) an anionic polyacrylamide in which from 2 to 15 mole percent of a hydrolyzed sodiumgacrylate is incorpoated as a comonomer; molecular weight: 2-10 x 10 ; marketed by Betz Corporation, Tervose, Pa.

The data in Table II show that within the experimental parameters ionic polyacrylamides are more effective in reducing polyCphenylene sulfide)-caused corrosion than non-ionic polyacrylamides. An anionic polyacrylamide containing from 2 to 15 ^" . mole percent of hydrolyzed sodium acryϊate as monomer was essentially as effective as nylon-6,6 Csee Table I) when added as a mold corrosion inhibitor to polyCphenylene sulfide) at levels of from 0.4 to 1.0 weight percent.

OMFI

Example IV In this example, the corrosion inhibiting effects of equal amounts of three polyamides in -polyCphenylene sulfide) are compared. The polyamides employed were a ground general purpose nylon-6,6 resin (marketed as 10V by Monsanto), a nylon-6 Oπarketed by Rhodiaceta) and a nylon-12 (marketed by Rhodiaceta). Each of the inventive poly(phenylene sulfide) compositions contained 1.0 weight percent of one of the polyamides. The two control runs were repeated.

Table III

Run Additive Weight % of Additive Corrosion Rating-

1 None Poor

(control)

2 Li ₂ C0 ₃ 1.0 Good

(control)

3 Nylon-6,6 1.0 Good

(invention)

4 Nylon-6 1.0 Good

(invention)

5 Nylon-12 1.0 Good

(invention)

The results of runs 1, 2 and 3 were the same as before in Example II, thus confirming the earlier results. The results of runs 4 and 5 show that other polyamides are also effective corrosion inhibitors in polyCphenylene sulfide).

It was the purpose of this disclosure to give a full and complete description of our invention and to set forth the best mode of operation. Reasonable modifications of and variations from this disclosure and the appended claims are, however, contemplated to be within the scope of patent protection desired and sought.