WO2001009265A1 - Plug using a composition or pre-mixture based on volatile corrosion inhibitors - Google Patents

Abstract

The invention concerns a plug based on polymers characterised in that it uses a composition or pre-mixture based on volatile corrosion inhibitors comprising in an efficient amount at least a structuring agent consisting of a solid or pasty substance whereof the melting point is between 40 and 110 °C, preferably between 50 and 90 °C. The invention also concerns the use of said plug for internally protecting hollow metal parts against corrosion.

Description

 PLUG IMPLEMENTING A COMPOSITION OR PREMIX BASED ON VOLATILE CORROSION INHIBITORS

The subject of the invention is plugs based on polymers and one of the components of which consists of a composition or premix based on volatile corrosion inhibitors.

It also relates to the use of the aforesaid plugs for the internal protection of hollow metal parts against corrosion.

In the present invention, by "plugs" is meant any part capable of obstructing the opening of a hollow part, such as plugs, capsules, threaded bodies, used for the localized volatile corrosion protection of certain internal parts, hollow metal parts.

The constituent material of the caps which is based on polymers and one of the components of which is a composition or premix based on volatile corrosion inhibitors, has been used to prepare packaging articles.

It is in fact known to use volatile corrosion inhibitors when it is a question of protecting against corrosion of metal parts sensitive to corrosion, in particular those which are made of mild steel with low carbon content and which, once machined , are shipped as is to their place of destination by sea container for on-site finishing, in particular by painting; corrosion risks are then considerable, especially when the parts in question are routed to hot and humid areas.

For example, when the metal parts to be protected are wrapped in films, the LCIs are incorporated into the material constituting these films; since these films can be in contact direct with the surface of the parts to be protected, corrosion inhibitors acting on contact are also incorporated into the constituent mass of these films. Volatile corrosion inhibitors offer, under these conditions, very good protection against corrosion and have the advantage of making it possible to avoid having to resort to conventional techniques for protecting metal parts; these conventional techniques consist in the application of paints, varnishes, plastics, waxes, greases and oils which must be removed before finishing on site, which leads to additional costs and pollution.

Volatile corrosion inhibitors, generally designated by ICV, use additives whose vapor pressure can be considered to be non-negligible at the temperature of use (for example, of the order of 10 ^"5 to 10 ^{" 1} mm Hg, at 20 ° C), which are capable of inhibiting corrosion of metals.

These LCIs act thanks to the fact that they are transported in the form of vapor to the metal surface to be protected, to be adsorbed there or else dissolved in a possible water of condensation.

Products are also known which are classified by extension in the LCIs due to the fact that one of their reaction products has an adequate vapor pressure. Thus, for example, sodium nitrite, in the presence of ammonium ions, can form ammonium nitrite which is relatively volatile. The starting sodium nitrite is then considered as an LCI. It is sometimes necessary to protect against corrosion only internal parts of hollow metal parts of large dimensions and complex geometry, in particular cavities, threaded parts or tubular holes. Stoppers according to this invention, based on polymers and possibly other structuring agents, shaped by the usual techniques of the polymer industry (extrusion, injection, thermoforming) allow to obstruct the openings of metal parts and provide them with the necessary localized protection, considerably minimizing costs.

To incorporate ICV into the constituent material of packaging, in particular films which are often based on thermoplastic polymers, it is known to make direct mixtures of ICV powders with polymers and to directly form articles by question.

At the extrusion temperature which is around 160 ° C for low density polyethylene and 240 ° C for polypropylene, LCIs have an extremely high volatility which leads, in the case of thin articles, to appearance of a high porosity and a high risk of degradation and / or decomposition with elimination of at least part of the LCIs. The anticorrosion effectiveness of such articles is therefore greatly reduced as a result of the loss of active ingredients.

To remedy this drawback, that is to say to limit the loss of ICV during the actual preparation of the articles, it has been proposed to use premixes containing the ICVs, that is to say to active ingredient concentrates dispersed in carriers such as polymers, solvents and plasticizers; premixes based on polymers (Patent BR-A-9001035) have the general advantage of being homogeneous and easy to handle; these premixes are then incorporated into the polymers for the preparation of the articles.

Given, however, that the temperatures used when preparing the premixes are often greater than 150 ° C., there is at least partial degradation of said premixes; so and as for example, it is reported that the dicyclohexy nitrite laminate, mixed and extruded with polyethylene at 160 ° C., leads to premix granules which have a dark yellow coloration, characteristic of a strong degradation, that is to say say of a loss of activity.

To avoid these excessive degradations with heat, it has been proposed to use liquid premixes, based on oil, which do not require passage to high temperatures during their manufacture (US-A-4,913,874 ).

However, since the LCIs are not frequently soluble in these oily media, it follows a heterogeneity of the premixes obtained and the appearance of difficulties due to local over-concentrations or sub-concentrations during their subsequent incorporation into the polymers. from which the articles are made.

It has also been proposed to remedy this drawback by using liquid premixes in the form of solvent or oily solutions comprising ICVs, premixes which are not incorporated during 1 "extrusion, but applied to films by spraying, thus forming, after evaporation of the solvent, either a powdery layer of ICV (patent DE 3,417,149 Al), or an oily layer containing the ICV (patent GB 2,188,274 A).

The disadvantage of these premixes lies in the fact that the LCIs are not trapped in a matrix requiring slow release, the protection obtained therefore being of short duration. Furthermore, the adhesion of the layers deposited on the articles is weak and leads to losses during handling and to the obligation to clean the parts to be protected, which is precisely to be avoided.

The object of the invention is to provide plugs based on polymers using at least one composition. based on ICV responding better than those that already exist to the various desiderata of the practice.

The invention also aims to propose new uses for these stoppers based on ICV, such as partial and localized protection of certain internal parts of hollow metallic parts.

And the Applicant Company had the merit of finding, after in-depth research, that these aims were achieved when recourse is had to caps based on polymers employing a composition based on inhibitors of volatile corrosion which comprises structuring agents capable of allowing the preparation of a premix at sufficiently low temperatures to limit as much as possible the release and / or degradation of the LCIs during this preparation.

Consequently, the stoppers according to the invention, based on polymers are characterized by the fact that they use a composition based on volatile corrosion inhibitors which comprises an effective amount of at least one structuring agent, consisting by a solid or pasty substance whose melting point is from 40 to 110 ° C, preferably from 50 to 90 ° C, whereby the release and / or degradation of the LCIs at the time of the formation of the composition or premix is limited to the maximum.

According to an advantageous embodiment, the composition used in the stoppers according to the invention comprises from 1 to 90%, preferably from 20 to 60% by weight of at least one volatile corrosion inhibitor and from 10 to 99 %, preferably from 40 to 80% of at least one structuring agent consisting of a solid or pasty substance whose melting point is from 40 to 110 ° C, preferably from 50 to 90 ° C.

According to another advantageous embodiment, the composition used in the stoppers in accordance with 1 the invention comprises at least one structuring agent selected from the group of those comprising aliphatic and / or resinous compounds, solid or pasty, with low melting point between 40 and 110 ° C, preferably between 50 and 90 ° C. According to another advantageous embodiment of the composition used in the stoppers in accordance with the invention, the structuring agent is chosen from the group comprising the aliphatic organic compounds mono- or polyfunctional, linear and / or little branched with chains hydrocarbons with at least 10 carbon atoms, including in particular:

- mono- or dicarboxylic acids, optionally oxidized, saturated or unsaturated, their esters and their salts,

- phosphoric, sulfonic and phosphonic acids, their esters with alcohols and their alkali, alkaline-earth metal, zinc, aluminum and / or organic amine salts,

- cyclic or acyclic compounds of the group comprising lactones, ketones, aldehydes, amides and acetals,

- higher alcohols, primary or secondary, cyclic or acyclic, optionally polyalkoxylated, with a hydrocarbon chain having at least 10 carbon atoms,

- linear and / or slightly branched aliphatic hydrocarbons, in particular paraffins and isoparaffins,

- polyolefins and their copolymers with low molecular weights of 3000 to 20,000 g / mole.

- polyglycols, in particular polyethylene glycols with a molecular weight of 2000 to 10,000 g / mole. According to another advantageous embodiment of the composition used in the stoppers in accordance with the invention, the structuring agent is chosen from the group comprising resinous compounds having a polyric and / or cyclic structure and which may contain, in proportion minority, aromatic derivatives and cyclic terpenes.

According to another advantageous embodiment of the composition according to the invention, the structuring agent is chosen from the group of those identified in Table A below and some of which are waxes or oils of natural or synthetic origin.

According to another advantageous embodiment, the composition used in the stoppers according to the invention comprises at least one corrosion inhibitor volatile chosen from the group comprising: nitrogen derivatives and in particular, on the one hand, aliphatic, aromatic, acyclic or cyclic amines including dicyclohexylamine, cyclohexylamine, orpholine, diisopropylamine and benzylamine, their organic salts including benzoates, carbamates, laurates, caprylates, succinates or minerals including nitrites, nitrates, carbonates, phosphates, phosphites and, on the other hand, heterocycles including imidazole and its derivatives, triazoles and their derivatives, as well as hexamethylene tetramine , the nitrogen-oxide derivatives including the alkali or alkaline-earth metal salts of nitrous acid and

- the benzoic derivatives of these metals such as sodium benzoate.

It is possible to include in the composition used in the stoppers according to the invention and / or in the stoppers one or more adjuvants chosen from the group comprising: - antioxidants and / or degradation inhibitors including bisphenol A, butyl-hydroxy-toluene, di-tert-butyl-phosphite, trinonyl-phenoxy-phosphite, dilauryl-thio-dipropionate, anti-UV absorbing agents including benzotriazoles, triazines, hydroxybenzophenones and radical inhibitors including AES or Hindered Amines Light Stabilizer in English, external antistatic agents including phosphoric ethers of ethoxylated alcohols and ethoxylated amine chlorides, or internal ones including ethoxylated fatty amines, ethoxylated polyols and alkyl sulfonates, external or internal lubricants including paraffins, fatty alcohols, fatty acids, esters of acids and alcohols fatty and amides, - plasticizing agents including dioctylphthalate, tricresylphosphate and diesters of aliphatic acids,

- mineral pigments including PbS0, PbCr0 ₄ , CdS. ZnS, organic pigments including azo, phthalocyanine or antraquinone derivatives and

- flame retardants including brominated and chlorinated phosphorus compounds, hydrides of Al, Mg and Zn compounds, as well as epoxy oligomers, mineral fillers including chalks and carbonates, talcs, clays, silicas.

These adjuvants can also be added only at the time of incorporation of the composition into the polymer from which the plugs are made according to the invention or into the structuring agent from which the plugs are made according to the invention.

These stoppers are characterized in that at least one of their components consists of a composition described above and that they are prepared from at least one polymer which is used for at least 50% by weight in their constitution.

The aforementioned polymers which form at least 50% by mass in the constitution of the stoppers in accordance with the invention can be chosen from those of the group comprising: - polyolefins including polyethylenes, polypropylene, polybutene and their copolymers with one or more unsaturated monomers including vinyl acetate, acrylic acid and its esters with short carbon chain alcohols, - polyvinyl chloride and its copolymers, acrylic copolymers and their derivatives, and polyamides, polystyrenes, polycarbo- nates, polyesters, polyurethanes, rubbers including natural rubber, styrene-butadiene and polychloroprene. 11

10 minutes.

The 333 g of the mixture thus obtained, which constitutes a premix [lb], are poured for cooling on a laboratory scaly machine maintained at 10 ° C., then cut into scales with a size between 0.5 and 10 mm.

300 g of premix [lb] are mixed cold and homogeneously with 5.7 kg of low density polyethylene (d = 0.925 g / cm ³ and melt index IF = 20 g / 10 minutes); the mixture obtained is injected at a temperature varying between 145 and 160 ° C in a nest mold cooled to 40 ° C, mounted on a KRAUSS MAFFEI C-40 t injection machine, with hydraulic closure (400 kN) and which works at a rate of 30 strokes / minute; the residence time of the molten material in each of the six zones of the cylinder is 15.6 seconds.

As a finished article, ICV capsules of yellow color, designated [le], 20 mm in diameter, 1 to 3 mm thick and 1 g in mass, are used, used to protect the cavities and threaded parts of the motors. automobiles.

The volatile anticorrosion efficiency of these ICV capsules [le] was tested on mild steel test pieces, in the form of studs; the test used uses two capsules and corresponds to the North American standard FED-STD 101, method 4031B.

This test method consists in placing a steel pad in a confined atmosphere loaded with ICV released from the film, then in causing controlled cooling to condense on the surface of the pad in order to cause possible oxidation after a time. determined. The degree of rusting indicates the anti-corrosion efficiency of the plug with respect to the material constituting the stud.

At the end of this test, it can be seen that the steel stud protected by the corrosion-inhibiting vapors which have been released from the two ICV capsules [the] does not have 10

The process for preparing these plugs generally comprises successively a step of preparing a composition or premix based on volatile corrosion inhibitors according to the invention and a subsequent step during which the premix is incorporated into a the above polymers, the plugs being obtained in particular by extrusion, molding, injection molding or thermoforming from the mixture comprising the premix and the polymer.

The caps are used for the protection of the internal parts of hollow metallic parts susceptible to corrosion, during their transport or their storage, without a complementary protective treatment being applied to these parts.

The invention can be understood even better with the aid of the nonlimiting examples which follow and which relate to advantageous embodiments.

For the preparation of an LCI, 70 g of sodium nitrite, 17.5 g of benzotriazole and 12.5 g of ammonium benzoate are mixed and then micronized in an air jet icroniser to give 100 g of homogeneous powdery mixture designated by [la] and having an average particle size between 1 and 15 μm; this powder constitutes an ICV. In a heating tank provided with a rotating and scraping stirrer, 226 g of the paraffin defined in table A are melted at 65 ° C., then 100 g of powder [la] are incorporated into the melt and carefully dispersed.

Then added 2 g of anti-UV agent (sold under the brand TINUVIN 622 LD by Ciba Geigy), 2 g of antioxidant - degradation inhibitor (sold under the brand CHIMASSORB 944 LD by Ciba Geigy) and 3 g of Color Index PY10401 / 70 yellow dye.

The dispersion is carried out with stirring at a speed of between 300 and 500 revolutions / minute, for of oxidation on its surface.

The same test was carried out, for comparison, using "control" capsules, designated by [ld], which are identical in all respects to the capsules [le], except that they do not contain the LCI identified above [lb]; the 100 g of powder [la] which are part of the premix composition [lb] have been replaced by 100 g of mineral filler based on calcium carbonate.

At the end of the test, the pad protected by the control capsules [ld] is completely attacked: numerous bites and rust are observed on 100% of its surface.

EXAMPLE 2

For the preparation of an LCI, 300 g of premix [lb] defined in example 1, are mixed cold and homogeneously with 5.7 kg of low density polyethylene (d = 0.925 g / cm ³ and IF index = 20 g / 10 minutes); the mixture obtained is injected at a temperature varying from 135 to 150 ° C in a nest mold cooled to 40 ° C, mounted on a KRAUSS MAFFEI C-40 t injection machine, with hydraulic closure (400 kN) and which works at a rate of 60 strokes / minute; the residence time of the molten material in each of the six zones of the cylinder is 9.9 seconds. As a finished article, yellow ICV stoppers, designated [2c], 55 mm in diameter, 1.5 mm thick and 6.5 g in mass, used to protect the cavities and threaded parts, are obtained. automotive engines. The volatile anticorrosion efficiency of these caps

ICV [2c] was tested on mild steel specimens, in the form of studs; the test used involves a third of the stopper, ie 2.2 g and corresponds to the North American standard FED-STD 101, method 4031B, described in example 1. At the end of this test, it can be seen that the stud in steel protected by corrosion-inhibiting vapors released from the ICV plug [2c] does not have oxidation on its surface.

The same test was carried out, for comparison, using a "control" plug, designated by [2d], which is identical in all respects to the plug [2c], except for the fact that it does not contain the LCI identified above [lb]; the 100 g of powder [la] which are part of the premix composition [lb] have been replaced by 100 g of mineral filler based on calcium carbonate.

At the end of the test, the pad protected by the control plug [2d] is completely attacked: numerous bites and rust are observed on 100% of its surface.

Claims

1. Cap based on polymers characterized in that it uses a composition or premix based on volatile corrosion inhibitors which comprises an effective amount of at least one structuring agent consisting of a solid or pasty substance, the melting point is 40 to 110 ° C, preferably 50 to 90 ° C. 2. Cap according to claim 1, characterized in that it uses a composition or premix comprising from 1 to 90%, preferably from 20 to 60% by weight of at least one volatile corrosion inhibitor and 10 to 99%, preferably from 40 to 80% of at least one structuring agent consisting of a solid or pasty substance whose melting point is from 40 to 110 ° C, preferably from 50 to 90 ° C. 3. Cap according to one of claims 1 and 2, characterized in that it uses a composition or premix whose structuring or pasty agent is chosen from the group comprising aliphatic and / or resinous compounds, solid or pasty, low melting point between 40 and 110 ° C, preferably between 50 and 90 ° C. 4. Stopper according to one of claims 1 to 3, characterized in that it uses a composition or premix whose solid or pasty structuring agent is chosen from the group of those comprising aliphatic compounds, mono- or polyfunctional, linear and / or slightly branched with hydrocarbon chains having at least 10 carbon atoms. 5. Stopper according to claim 4, characterized in that it implements a composition or premix whose structuring agent is chosen from the group comprising: - mono- or dicarboxylic acids, optionally oxidized, saturated or unsaturated, their esters and their salts, - phosphoric, sulfonic and phosphonic acids, their esters with alcohols and their salts of alkali, alkaline-earth metals, zinc, d aluminum and / or organic amines, - cyclic or acyclic compounds of the group comprising lactones, ketones, aldehydes, amides and acetals, - higher alcohols, primary or secondary, cyclic or acyclic, optionally polyalkoxylated, with hydrocarbon chain having at least 10 carbon atoms, - linear and / or slightly branched aliphatic hydrocarbons, in particular paraffins and isoparaffins, - polyolefins and their copolymers with low molecular weights of 3000 to 20,000 g / mole, - polyglycols, in particular polyethylene glycols with a molecular weight of 2000 to 10,000 g / mole. 6. Stopper according to claim 4, characterized in that it uses a composition or premix whose structuring agent is chosen from the group comprising resinous compounds having a polymeric and / or cyclic structure and which may contain, in proportion minority, aromatic derivatives and cyclic terpenes. 7. Stopper according to one of claims 1 to 6, characterized in that it uses a composition or premix, the structuring agent of which is chosen from the group of those identified in table A below and some of which are waxes of natural or synthetic origin: TABLE A

8. Stopper according to one of claims 1 to 7, characterized in that it uses a composition or premix comprising at least one volatile corrosion inhibitor chosen from the group comprising: nitrogen derivatives and in particular of a on the other hand, aliphatic, aromatic, acyclic or cyclic amines, including dicyclohexylamine, cyclohexylamine, morpholine, diisopropylamine and benzylamine, their organic salts, including benzoates, carbamates, laurates, caprylates, succinates or minerals, including nitrites, nitrates, carbonates, phosphates, phosphites and, on the other hand, heterocycles including imidazole and its derivatives, triazoles and their derivatives, as well as hexamethylene tetramine, - nitrogen oxides derivatives including the salts of alkali metals or alkaline earth of nitrous acid and the benzoic derivatives of these metals such as sodium benzoate. 9. Stopper according to one of claims 1 to 8, characterized in that it is constituted by at least one polymer which enters for at least 50% by weight in its constitution and which can be chosen from those of the group comprising: - polyolefins including polyethylenes, polypropylene, polybutene and their copolymers with one or more unsaturated monomers including vinyl acetate, acrylic acid and its esters with short carbon alcohols, - polyvinyl chloride and its copolymers, acrylic copolymers and their derivatives, and - polyamides, polystyrenes, polycarbonates, polyesters, polyurethanes, rubbers including natural rubber, styrene-butadiene and polychloroprene. 10. Stopper according to one of claims 1 to 9, characterized in that it is implemented by any suitable method including molding, injection molding, extrusion or thermoforming. 11. Use of the plugs according to one of claims 1 to 10 for the protection of the internal parts of hollow metal parts against corrosion.