US2927031A

US2927031A - Corrosion inhibition

Info

Publication number: US2927031A
Application number: US662602A
Authority: US
Inventors: Arnold J Rosenthal
Original assignee: Celanese Corp
Current assignee: Celanese Corp
Priority date: 1957-05-31
Filing date: 1957-05-31
Publication date: 1960-03-01
Anticipated expiration: 1977-03-01
Also published as: BE634681A

Description

United States Patent() CORROSION INHIBITION Arnold J. Rosenthal, Whippany, NJ assignor to Celanese Corporation of America, New York, N.Y.,a corporation of Delaware No Drawing. Application May 31, 1957 Serial No. 662,602

20 Claims. (Cl. 106-14) The present invention relates to the prevention of corrosion of metals by solutions of organic acid esters of cellulose in halogen-containing organic solvents. More particularly, it relates to novel processes for preventing such corrosion by incorporation in the solution of special stabilizing agents.

In the course of converting organic acid esters of cellulose to filamentary material and the like, these esters may be dissolved in halogen-containing organic solvents. By way of illustration, cellulose triacetate is dissolved in methylene chloride which may also contain minor amounts of co-solvents for the ester such as methanol, ethanol, isopropanol or the like, as well as small amounts of water. This solution or dope is then dry spun into filamentary cellulose triacetate, the solvent being evaporated by a current of warm air followed by recovery and purification prior to re-use. The spinning is effected by passage of the solution through one or more orifices in a metallic member in the art referred to as a jet. It has been found that these jets as well as other metal equipment contacted by the solvent during use and recovery c rrode rapidly and require frequent replacement.

It is accordingly an object of the present invention to minimize or prevent this corrosion of metallic members contacted by halogen-containing organic solvents for organic acid esters of cellulose.

It is a further object to incorporate in solutions of organic acid esters of cellulose in halogen-containing or-, 'ganic solvents a stabilizer which will inhibit or eliminate corrosion of iron or steel contacted therewith.

Another object is to provide a solution of cellulose triacetate in methylene chloride, which solution can be dry spun without rapid corrosion of the spinning jet.

Other objects of this invention will be apparent from the following detailed description and claims.

In accordance with the present invention, to a halogencontaining organic solvent solution of the organic acid ester of cellulose there is added a stabilizer which inhibits corrosion of metallic members. The stabilizers must satisfy certain requirements in order to be suitable for. use, viz., they must themselves be non-corrosive, they.

should not have any particular affinity for the cellulose ester lest they contaminate articles produced therefrom,

understood. While it might be expected that the corrosion is the result of the presence of hydrohalic acids,1stabilizers heretofore used to prevent corrosion in other systems or contaniing organic solvents. The eifective stabilizers in-v 'alone or in admixture. I V p lower alkyl amines and especially hydroxysubstituted .sary'.

' The solvent. of the cellulose ester solution can be any Patented Mar. 1, 1960 systems, e.g., organometal salts or acid binding agents such as triethylamine and triethanolamine, are ineffective 'in'the instant situation. Moreover, the corrosion of the spinning jets is apparently independent of temperature,

"oxidation but 'faces of jets exposed to air are even less corroded than those shielded from air. In addition, antioxidants such as hydroquinone ethers donot exert any appreciable inhibitory effect on solutions of the character herein set forth. j. 3

It has now been found thata limited group of organic compounds is effective in avoiding the corrosion of metals by solutionsof organic acid'esters of cellulose in halogencludeamine nitrites and cadmium saltsofiatty acids, Of the amine nit-rites, nitritesof lower alkyl amines such as 2-hydroxyproplyamine are preferred; of the cadmium salts of fatty acids, those of waterinsoluble fatty acids and especially water-insoluble alskanoic acids such as 2-ethyl hexoic acid are preferred.

The stabilizers will exert some beneficial action even in the smallest amountsbut for appreciable inhibition they should be present in at least about 0.005% by weight ofthe solution. Generally, at least about 0.01% by weight is employed and preferably about 0.05%. As much as 0.5% or even more can be used but since corrosion is substantially completely eliminated with lesser :amounts there is no point in adding more stabilizer than is neceshalogenated organic solvent but the preferred solvents are chloLne-substituted lower alkanes such as methylene chloride, ethylene dichloride, and the like. contain minor amounts of co-solvents or non-solvents for the esters, depending upon the properties desired for the composition and the subsequent treatments to which it will be subjected. When a methylene chloride solution is to be used for'dry-spinning, for example, the methylene chloride solvent may contain as much as 20% 'by weight stabilizing action will be realized even in the presence of water.

Organic acid esters of cellulose which can be' used arepreferably the lower alkanoic acid esters such as the acetate, propionate, butyrate, acetate-propionate, acetatebuty rate, and the like. While the invention is applicable to any esters which will dissolve in the indicated solvents,

' excellent' results are achieved whenusingcellulose acetate having an acetyl content in excess of about 59.5% and preferably 61.5% by weight calculated as acetic acid.

to bind any decomposition products of halogen-containing Such esters are substantially fully acetylated, i.e., free of unreacted hydroxy groups, and are hereinafter referred to as cellulose triacetate although a small residue of unreacted hydroxy-groups may be present. The present invention is particularly useful in the dry spinning of solutions of cellulose triacetate in methylene chloride-methanol, such as are disclosed in copending US. application Serial No. 566,088,..filed February 17, 1956, by Robert K. Davies and'Arnold J. Rosenthal.

The solutions there described comprisecellulose acetates having an acetyl value in excess of 59.5% by weight expressed as acetic acid (herein referred to as cellulose triacetate) dissolved in methylene chloride-methanol to These may a concentration of above 15% and preferably from 17 to 27%. The methylene chloride can range upwards from 80% of the combined weights of methylene chloride and methanol 'with about 90% or more preferred. These solutions generally contain small amounts of water, from about 0.3% of the weight of the solution up to the amount which will create turbidity, although preferably water is present in no more than 60% by weight of the amount which will create turbidity. The amount of water which will create turbidity will vary with the composition of the solution. With the minimum concentration of 15% by weight of cellulose triacetate in the solution and about of methanolin the solvent the turbidity point will correspond to about 1.7% of water.

Following spinning, the amount of stabilizer adhered to the cellulose triacetate is extremely small and any small residual amounts will be removed during the wet treatments to which fabrics made from said filamentary materials are normally subjected.

The following examples are given to illustrate the invention further.

EXAMPLE I Cellulose acetate having an acetyl value of 59.5% is dissolved in a mixture of 91 parts by weight of methylene chloride and 9 parts by weight of methanol to form a solution having a concentration of cellulose acetate of 21.5% by weight based on the weight of the solvent. On spinning this solution at the rate of 100 meters per minute at a temperature of 85 C. through chromium plated stainless steel jets 1 inch in diameter having holes each 0.036 mm. in diameter it is found that the jets corrode and one or more holes thereof become clogged within less than 100 hours. The presence of iron can be detected in the yarn.

EXAMPLE II To compare quantitatively the corrosive action of dopes of different composition, strips of hot rolled mild steel measuring inch by /s inch by 2% inches are immersed in the dopes for 14 days at 50 C. without agitation and the extent of corrosion of the strips is determined. The dopes in this comparison all are initially 15% by weight solutions of cellulose acetate (61.5% acetyl value) in a 91/9 weight mixture of methylene chloride/methanol. Where water or inhibitor is indicated, the percentage is based on the total weight of the dope. The results are shown in the following table:

The dopes containing the Z-hydroxypropylamine nitrite and the cadmium 2-ethyl hexoate are suitable for spinning and solvent recovery with little or no corrosion of metal equipment contacted therewith.

It is to be understood that the foregoing detailed description is merely given by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patent is:

1. A stable composition of matter, non-corrosive on metals contacted therewith, comprising a solution in a 4 halogen-containing organic solvent of a lower alkanoic acid ester of cellulose and a stabilizing proportion of a member selected from the group consisting of a hydroxy lower alkyl amine nitrite and a cadmium salt of a waterinsoluble fatty acid.

2. A composition ofmatter according to claim 1, wherein said solvent contains up to about 20% by weight of a lower alkanol,

3. A stable composition of matter, non-corrosive on iron contacted therewith, comprising a solution in a chlorine-containing organic solvent of a lower alkanoic ester of cellulose, said solution containing at least about 0.005% by weight of a hydroxy lower alkyl amine nitrite as a stabilizer.

4. A stable composition ,of matter, non-corrosive on iron contacted therewith, comprising a solution of cellulose triacetate in methylene chloride, said solution containing about 0.005 to 0.5% by weight of a hydroxy lower alkyl amine nitrite as a stabilizer.

5. A stable composition of matter, non-corrosive on iron contacted therewith, comprising a solution of cellulose triacetate in a concentration of at least 15% by weight in a solvent comprising methylene chloride and a lower alkanol, the methylene chlorideconstituting at least about by weight of thesolvent, said solution containing about 0.005 to 0.5 by weight of Z-hydroxypropylamine nitrite as a stabilizer.

6. A stable composition of matter, non-corrosive on iron contacted therewith, comprising a solution of cellulose triacetate in a concentration ranging from about 17 to 27% by weight in a solvent comprising about by weight of methylene chloride and about 10% by weight of methanol, said solution containing water in an amount between a minimum of about 0.3% by weight and a maximum of the amount which will bring the solution to the turbidity point, said solution further containing about 0.005 to 0.5% by weight of 2-hydroxypropylamine nitrite as a stabilizer.

7. A stable composition of matter, non-corrosive on metals contacted therewith, comprising a solution of cellulose triacetate in methylene-chloride, said solution containing a stabilizing proportion of 2-hydroxypropy1 amine nitrite.

8. The process for stabilizing a solution against corrosion of metal contacted therewith, said solution comprising a lower alkanoic acid ester of cellulose dissolved in a halogen-containing organic solvent, which process comprises incorporating a stabilizing proportion of a hydroxy lower alkyl amine nitrite in said solution.

9. The process for stabilizing a solution against corrosion of metal contacted therewith, said solution comprising cellulose triacetate dissolved in methylene chloride, which process comprises incorporating a stabilizing proportion of Z-hydroxypropylamine nitrite in said solution.

10. In the production of filamentary material wherein a solution of a lower alkanoic acid ester of cellulose in a halogen-containing organic solvent is extruded through an orifice in a metallic member under conditions such that said cellulose ester is converted tofilamentary material, the improvement which comprises incorporating in said solution a stabilizing proportion of a hydroxy lower alkyl amine nitrite, whereby corrosion of said metallic member and transfer of metal to said solution and said filamentary material are inhibited.

11. In the production of filamentary material wherein a solution of cellulose triacetate in methylene chloride is extruded through an orifice in a metallic member under conditions such that said cellulose triacetate is converted to filamentary material, the improvement which comprises incorporating a stabilizing proportion of 2-hydroxypropylamine nitrite in said solution, whereby corrosion of said metallic member and transfer of metal to said solution and said filamentary material are inhibited.

12. A stable composition of matter, non-corrosive on iron contacted therewith, comprising a solution in a chlorine-containing organic solvent of a lower alkanoic ester of cellulose, said solution containing at least about 0.005% by weight of a cadmium salt of a water-insoluble fatty acid as a stabilizer.

13. A stable composition of matter, non-corrosive on iron contacted therewith, comprising a solution of cellulose triacetate in methylene chloride, said solution containing about 0.005 to 0.5% by weight of a cadmium salt of a water-insoluble alkanoic acid as a stabilizer.

14. A stable composition of matter, non-corrosive on iron contacted therewith, comprising a solution of cellulose triacetate in a concentration of at least 15% by weight in a solvent comprising methylene chloride and a lower alkanol, the methylene chloride constituting at least about 80% by weight of the solvent, said solution containing about 0.005 to 0.5% by weight of cadmium 2-ethyl hexoate as a stabilizer.

15. A stable composition of matter, non-corrosive on iron contacted therewith, comprising a solution of cellulose triacetate in a concentration ranging from about 17 to 27% by weight in a solvent comprising about 90% by weight of methylene chloride and about by weight of methanol, said solution containing water in an amount between a minimum of about 0.3% by Weight and a maximum of the amount which will bring the solution to the turbidity point, said solution further containing about 0.005 to 0.5% by weight of cadmium 2-ethyl hexoate as a stabilizer.

16. A stable composition of matter, non-corrosive on metals contacted therewith, comprising a solution of cellulose triacetate in methylene chloride, said solution containing a stabilizing proportion of cadmium 2-ethy1 hexoate.

17. The process for stabilizing a solution against corrosion of metal contacted therewith, said solution com proportion of cadmium Z-ethyl hexoate in said solution.

19. In the production of filamentary material where in a solution of a lower alkanoic acid ester of cellulose in a halogen-containing organic solvent is extruded through an orifice in a metallic member under conditions such that said cellulose ester is converted to filamentary material, the improvement which comprises incorporating in said solution a stabilizing proportion of a cadmium salt of a water-insoluble fatty acid, whereby corrosion of said metallic member and transfer of metal to said solution and said filamentary material are in-' hibited. V s

20; In the production of filamentary material wherein a solution of cellulose triacetate'in methylene chloride is extruded through an orifice in a metallic member under conditions such that said cellulose triacetate is converted to filamentary material, the improvement which comprises incorporating a stabilizing proportion of cadmium 2-ethyl hexoate in said solution, whereby cor-' rosion of said metallic member and transfer of metal to said solution and said filamentary material are inhibited.

References Cited in the file of this patent I UNITED STATES PATENTS 2,278,747 Swezeyet al'. Apr. 7, 1942 2,419,327 Wachter et a1. Apr. 22,1947 2,499,551 White Mar. 7, .1950 2,596,450

Wachter et a1. May 13, 19 52

Claims

1. A STABLE COMPOSITION OF MATTER, NON-CORROSIVE ON METALS CONTACTED THEREWITH, COMPRISING A SOLUTION IN A HALOGEN-CONTAINING ORGANIC SOLVENT OF A LOWER ALKANOIC ACID ESTER OF CELLULOSE AND A STABILIZING PROPORTION OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF A HYDROXY LOWER ALKYL AMINE NITRITE AND A CADMIUM SALT OF A WATERINSOLUBLE FATTY ACID.