Corrosion inhibiting mixture

Abstract

A corrosion inhibiting mixture is disclosed comprising a volatile corrosion inhibitor and a binding matrix, wherein the binding matrix comprises a resin selected from the group of a plastisol, a urethane and an epoxy. The mixture is liquid near ambient temperature and irreversibly cured when heated in a temperature range of about 20° C. to 150° C.

Description

FIELD OF THE INVENTION

This invention relates to improvements in volatile corrosion inhibitors, and more particularly to improvements in volatile corrosion inhibitor delivery devices.

BACKGROUND OF THE INVENTION

Corrosion of metal articles is a significant problem. A known technique for reducing the corrosion of metal articles is to package the articles with a material containing a volatile corrosion inhibitor (“VCI”). VCIs function by slowly releasing vapors that contact the surface of the metals. The vapor phase corrosion inhibitors envelop the metal article in a non-corrosive atmosphere and retard moisture and oxygen present in the atmosphere from attacking and reacting with the metal surfaces. Volatile corrosion inhibitors may be applied by spraying the entire surface of the metal article to be protected, or the metal article itself may be enclosed, packaged or surrounded in or with materials containing VCIs. For example, VCIs may be incorporated into a packaging material such as paper and plastic wraps, films, and plastic dunnage. VCIs are also known to be incorporated into an emitting device with a binding matrix. Such emitters can be used within closed spaces such as packaging containers, electrical boxes, storage bags, and other enclosures. Different volatile corrosion inhibitors or combinations of volatile corrosion inhibitors may be selected based on the type of metal to be protected, the size of the enclosure, and the length of time that protection is required.

Known volatile corrosion inhibitor emitting devices have several drawbacks. They are produced in a set shape such as foam strips, compressed pellets, and air permeable containers such as plastic cups with paper tops. The set shape may not “fit” an intended application. For example, an emitter may be placed randomly in a packaging container or enclosure or stuck to a surface within the package or enclosure. Many end users do not want loose articles or articles that do not appear to be part of the packaging in the containers they receive. Moreover, generic shapes do not adequately identify the function of the VCI device. Since it is sometimes difficult to clearly distinguish that the device is purposely part of the packaging or the enclosure, it may be misplaced or mistakenly removed. Further, there is the problem of reinserting the device as part of a pack and having to locate it properly. Also, some enclosures and packaging do not have surfaces readily available for set shape devices. Moreover, VCI packaging devices produced in this way usually contain the active materials in powder or pellet form. These powders and pellets can spill or spread active materials to unwanted areas. In general known emitter devices have insufficient control over the release of the VCIs.

U.S. Pat. No. 4,124,549 to Hashiudo et al discloses a method for making a corrosion protective film which includes a thermoplastic resin and a volatile corrosion inhibitor mixed together and molded or extruded. Such a product is disadvantages for several of the reasons cited above. In addition, such a thermoplastic composition would result in the loss of many VCIs at the high temperatures needed to form the film.

It would be highly desirable to provide a volatile corrosion inhibiting mixture which can be made at relatively low temperatures, which can assume a variety of shapes, and which can provide a controlled release of VCIs.

SUMMARY OF THE INVENTION

In accordance with a first aspect, a corrosion inhibiting mixture is disclosed comprising a volatile corrosion inhibitor and a binding matrix, wherein the binding matrix comprises a resin selected from the group of a plastisol, a urethane and an epoxy. The mixture is liquid near ambient temperature and irreversibly cured when heated in a temperature range of about 20° C. to 150° C.

From the foregoing disclosure and the following more detailed description of various preferred embodiments it will be apparent to those skilled in the art that the present invention provides a significant advance in the technology of volatile corrosion inhibitors. Particularly significant in this regard is the potential the invention affords for providing a high quality, low cost volatile corrosion inhibitor delivery technique. Additional features and advantages of various preferred embodiments will be better understood in view of the detailed description provided below.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

It will be apparent to those skilled in the art, that is, to those who have knowledge or experience in this area of technology, that many uses and design variations are possible for the volatile corrosion inhibiting device disclosed here. The following detailed discussion of various alternative and preferred features and embodiments will illustrate the general principles of the invention with reference to a volatile corrosion inhibiting device suitable for use in an application where it is desired to protect metal. Other embodiments suitable for other applications will be apparent to those skilled in the art given the benefit of this disclosure.

In accordance with a preferred embodiment, a vapor-phase or volatile corrosion inhibitor emitting device comprises a volatile corrosion inhibitor and a binding matrix. This mixture is combined to form a pourable and moldable liquid at relatively low temperatures, most preferably ambient room temperature (about 20° C.). Advantageously, the mixture may be poured into a mold of any desired moldable shape and gently heated to about 20° C. to 150° C. In accordance with a highly advantageous feature, this heating cures the mixture, so that reheating will not result in melting. Also, forming and curing the mixture at low temperatures is advantageous in that loss of volatile corrosion inhibitors is reduced.

In accordance with a highly advantageous feature, a volatile corrosion inhibitor emitting device is provided which can be readily molded or cast, allowing the emitting device to form a shape that fits a particular application. Many current and potential applications for these devices would be substantially improved if the device could be custom fitted to an enclosure, a packaging container or the items being protected from corrosion. For example, the volatile corrosion inhibitor emitting device can be readily molded or caste into shapes that are known symbols or company logos. With addition of an appropriate pigment, a specific color can be used for a specific application. Emitters may be formed as a narrow cylinder to protect gun barrels, fish-shaped to protect tackle boxes, a bolt to protect tool boxes, a blue shield to protect ferrous based metals, a red shield to protect electrical boxes, etc.

Different corrosion inhibitors or combinations of corrosion inhibitors are selected based on the type of metal to be protected, the size of the enclosure, and the length of time that protection is required. Examples of VCIs for incorporation into the binding matrix include benzoic acid and inorganic salts of benzoic acid such as sodium benzoate, inorganic nitrite salts such as sodium nitrite, amine nitrite salts such as dicyclohexylamine nitrite, carboxylic acids such as caprylic acid, salts of amines and carboxylic acids such as cyclohexylamine benzoate, monoethanolamine benzoate, diethylethanolamine caprylate, and diethylethanolamine caprate, azoles such as tolyltriazole, benzotriazole and their salts, and salts of molybdenum such as sodium molybdate or an amine molybdate. Other volatile corrosion inhibitors suitable for use herein will be readily apparent to those skilled in the art given the benefit of this disclosure.

The binding matrix preferably satisfies a number of conditions. It should be processable at temperatures low enough that the volatile corrosion inhibitors are not driven off during processing. The binding matrix should be able to be readily adjusted to control the emission rate of the volatile corrosion inhibitors. It should be capable of being readily molded or cast into various shapes. The binding matrix should have long term durability for extended use applications. It should be permeable enough to allow the corrosion inhibitor(s) to migrate out of a molded shape. The binding matrix should also be relatively inert so that it does not react with the corrosion inhibitors that it is binding.

The binding matrix of the present invention is chosen such that when combined with the VCI components the resulting blend is in liquid form until cured in a mold. Once cured the resulting product will retain the shape of the mold, and the binding matrix will have permeability characteristics sufficient to allow controlled release of the VCI components. The binding matrix can preferably comprise one of several resins, a plastisol, a urethane and an epoxy. Plastisols are dispersions of fine particle size polyvinyl chloride (PVC) or acrylic polymer or copolymer resins in liquid plasticizers which require heat to harden. Organosols may also be used. Organosols are plastisols to which a volatile solvent or thinner has been added. Plastisols typically require a plasticizer, an additive which softens the mixture to which it is are added. Plasticizers work by embedding themselves between the chains of polymers, space them apart (increasing of the “free volume”), and thus significantly lowering the glass transition temperature for the plastic and making it softer. Suitable plasticizers for use with PVC are a phthalate, a benzoate, an adipate, or a polymeric plasticizer, etc. An acrylic monomer may be used with a plastisol as a cross linking resin to adjust the hardness of the resulting mixture.

In addition to the resins and plasticizers, heat or light stabilizers, color pigments, flame retardants, blowing agents, fillers, viscosity control agents, rheology control additives or other additives may be included as determined by the intended end use. The rate of VCI release from the emitter is controlled by adjusting the components the polymer binding matrix to provide a steady, long lasting rate of emission.

With plastisols, the mixture is irreversibly converted from a colloidal suspension to a solid solution upon heating so that, unlike a thermoplastic material, repeated heating will not melt the resulting emitter. Advantageously, the plastisols are heated to a relatively low temperature range of about 20° C. to 150° C., most preferably about 80° C. to 150° C. after the mixture is poured into a mold. Such relatively low temperatures reduce vaporization of the VCIs in the mixture. The same advantageous result can be achieved with epoxies and urethanes. However for these materials, heating of the mixture results in cross linking between two components, again forming an emitter which is irreversibly cured. A two component epoxy or urethane comprises an epoxy or urethane and a hardener.

Listed below is a summary of several compositions with preferred ranges which produce a mixture having suitable properties for use as a volatile corrosion inhibitor emitting device.

Resin (plastisols, urethane, epoxy) 20–80% (by weight)
Plasticizer (for use with plastisols only) 15–35%
Cross Linking Resin (for use with plastisols) 0–10%
Hardener (for use with epoxy and urethane only) 3–10%
Viscosity Control Agent          1–10%
Filler                           0–30% (10–30% with
                                 epoxy and urethane)
VCI                              10–50%

Suitable hardeners for urethane include isocyanates and diisocyanates. Suitable hardeners for epoxies include amines (diamines, triamines, etc.) and amine adducts. Suitable viscosity control agents comprise mineral spirits, texanol diisobutyrate (“TXIB”) and viscosity modifiers from such as BYK Chemie: BYK-3105, BYK-3155, BYK-4040. Suitable fillers comprise calcium carbonate, Kaolin Clay and talk (magnesium silicate). Other hardeners, viscosity control agents and fillers will be readily apparent to those skilled in the art given the benefit of this disclosure.

The invention disclosed here will be better understood with the aid of the following non-limiting examples of certain preferred embodiments.

EXAMPLE 1

Corrosion Inhibitor with PVC Resin

This mixture is particularly suitable for use as a corrosion inhibitor for ferrous and multi-metal materials.

50% Formolon 40 PVC by Formosa Plastics

16% Plasticizer:

• • 8% dibutylphthalate (DBP)
  • 8% Santicizer 278 Benzoate by Ferro Corp.

1% Viscosity Control Agent: BYK-3155 from BYK Chemie

10% Calcium Carbonate

23% VCIs:

• • 10% caprylic acid
  • 7% diethyl ethanol amine
  • 6% benzotriazole

Mix the components together at ambient conditions to form a liquid mixture. Pour the liquid mixture into a mold. Heat the mold to about 110° C. to irreversibly cure the mixture and form VCI emitter devices.

EXAMPLE 2

Corrosion Inhibitor with Acrylic Resin

This mixture is also suitable for use as a corrosion inhibitor for ferrous and multi-metal materials.

40% DEGALAN® PAMA powder resin by Rohm GmbH

20% Plasticizer:

• • 10% dihexylphthalate (DHP)
  • 10% Santicizer 278 Benzoate by Ferro Corp.

1% Viscosity Control Agent: BYK-4040 from BYK Chemie

15% Calcium Carbonate

24% VCIs:

• • 9% Benzoic acid
  • 9% cyclohexylamine
  • 6% benzotriazole

EXAMPLE 3

Corrosion Inhibitor with Two-Component Urethane

This mixture is also suitable for use as a corrosion inhibitor for ferrous and multi-metal materials.

60% Desmodur 1150 Polyesterether Polyol by Bayer

6% Isocyanate hardener

1% Viscosity Control Agent: BYK-3155 from BYK Chemie

5% Calcium Carbonate

28% VCIs:

• • 10% Sodium benzoate
  • 10% Ammonium benzoate
  • 8% Tolytriazole

EXAMPLE 4

Corrosion Inhibitor with Two-Component Epoxy

This mixture is also suitable for use as a corrosion inhibitor for ferrous and multi-metal materials.

60% RENCAST 3209 epoxy resin from Huntsman

6% REN 3209 hardener from Huntsman

1% Viscosity Control Agent: BYK-3155 from BYK Chemie

5% Calcium Carbonate

28% VCIs:

• • 10% carpylic acid
  • 7% diethyl ethanolamine
  • 6% benzotriazole

From the foregoing disclosure and detailed description of certain preferred embodiments, it will be apparent that various modifications, additions and other alternative embodiments are possible without departing from the true scope and spirit of the invention. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to use the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

1. A corrosion inhibiting mixture comprising, in combination:

a volatile corrosion inhibitor; and

a binding matrix, wherein the binding matrix comprises a resin selected from the group of a plastisol, a urethane and an epoxy;

wherein the mixture is liquid near ambient temperature and irreversibly cured when heated in a temperature range of about 20° C. to 150° C.

2. The corrosion inhibiting mixture of claim 1 wherein the volatile corrosion inhibitor is selected from the group consisting of at least one of benzoic acid, a salt of benzoic acid, an inorganic nitrite salt, an amine nitrite salt, a carboxylic acid, a salt of a carboxylic acid, a salt of an amine, an azole, a salt of an azole, a salt of molybdenum and an amine molybdates.

3. The corrosion inhibiting mixture of claim 1 wherein the volatile corrosion inhibitor comprises about 10-50% by weight of the mixture, and the binding matrix comprises about 90-50% by weight of the mixture.

4. The corrosion inhibiting mixture of claim 1 wherein the binding matrix comprises a plastisol formed from a plasticizer and one of a PVC resin and an acrylic co-polymer.

5. The corrosion inhibiting mixture of claim 4 wherein the plastisol is a PVC resin which comprises about 20-60% by weight of the mixture, and the plasticizer comprises about 15-35% by weight of the mixture.

6. The corrosion inhibiting mixture of claim 4 wherein the plastisol is an acrylic copolymer and the resin further comprises a cross linking resin.

7. The corrosion inhibiting mixture of claim 1 further comprising about 1-10% by weight of a viscosity control agent.

8. The corrosion inhibiting mixture of claim 1 further comprising about 1-30% by weight of a mineral filler.

9. The corrosion inhibiting mixture of claim 1 wherein the binding matrix comprises about 3-10% by weight of a hardener and the resin comprises about 50-85% by weight of one of a urethane and an epoxy.