JP2018145258A - Hot rolling oil for aluminum, hot rolling coolant for aluminum, and method of producing rolled aluminum sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot rolling oil for aluminum capable of preventing its oxidation for a long period of time, a hot rolling coolant for aluminum comprising the hot rolling oil, and a method of producing a rolled aluminum sheet carried out by using the coolant.SOLUTION: The hot rolling oil for aluminum comprises a synthetic ester of a polyhydric alcohol and an aliphatic acid. The polyhydric alcohol is one or more selected from neopentyl glycol, trimethylol propane and pentaerythritol. The ratio of a constituent unit derived from a 6-24C saturated aliphatic acid among the constituent units derived from all aliphatic acids present in the synthetic ester is not less than 60 mol%.SELECTED DRAWING: None

Description

  The present invention relates to a hot rolling oil for aluminum, a hot rolling coolant for aluminum, and a method for producing an aluminum rolled sheet.

  In the hot rolling of aluminum materials (including aluminum and aluminum alloys; the same shall apply hereinafter), for the purpose of ensuring lubricity between the rolling rolls and the aluminum material and cooling the rolling rolls and aluminum materials, Rolled coolant is used. This type of coolant is usually an oil-in-water emulsion in which hot rolled oil for aluminum is dispersed in water.

  In hot rolling oil, refined mineral oil as base oil, emulsifier to form oil droplets in water, oiliness agent to reduce friction between rolling roll and aluminum material, and to suppress oxidation of base oil, etc. Primary antioxidants, secondary antioxidants, and the like. As the oil agent, synthetic esters of fatty acids and polyhydric alcohols, natural fats and oils, and the like are used (for example, Patent Document 1). As synthetic esters, esters of unsaturated fatty acids such as oleic acid, which have a large circulation amount and are inexpensive, are frequently used. In addition, natural fats and oils are often used which have unsaturated fatty acids as main constituents for the same reason as synthetic esters.

JP-A-8-170090

  However, when hot rolling is performed using a conventional coolant, the base oil, the emulsifier, the oily agent, and the like are gradually oxidized, leading to generation of lower fatty acids such as formic acid. The coolant is usually recycled for a plurality of times while replenishing the amount reduced during hot rolling. Therefore, repeated hot rolling may cause problems such as accumulation of lower fatty acids in the coolant, corrosion of the steel material of the rolling equipment, or separation of the water phase and the oil phase due to emulsion destabilization. There is.

  As described above, a primary antioxidant or a secondary antioxidant for suppressing such oxidation may be added to the conventional hot rolling oil. However, even when a primary antioxidant or a secondary antioxidant is added to hot-rolled oil, it is difficult to suppress the oxidation of the base oil or oily agent and reduce the amount of lower fatty acids generated. is the current situation.

  This invention is made | formed in view of this background, The hot rolling oil for aluminum which can suppress oxidation over a long period of time, The hot rolling coolant for aluminum containing this hot rolling oil, and this coolant An object of the present invention is to provide a method for producing an aluminum rolled sheet using the above.

One aspect of the present invention is a hot rolled oil for aluminum containing a synthetic ester of a polyhydric alcohol and a fatty acid,
The polyhydric alcohol is one or more selected from neopentyl glycol, trimethylolpropane and pentaerythritol,
It exists in the hot rolling oil for aluminum whose ratio of the structural unit derived from a C6-C24 saturated fatty acid among the structural units derived from all the fatty acids in the said synthetic ester is 60 mol% or more.

Another aspect of the present invention is a hot rolling coolant for aluminum in which the hot rolling oil for aluminum of the above aspect is dispersed in water,
Containing 1 to 10% by volume of the hot rolling oil for aluminum,
The oil droplets of the hot rolling oil for aluminum are in the hot rolling coolant for aluminum having a volume average particle diameter of 1 to 7 μm.

  Still another embodiment of the present invention is a method for producing an aluminum rolled sheet, in which an aluminum material is hot rolled using the hot rolling coolant for aluminum according to the above embodiment.

  The hot rolled oil for aluminum (hereinafter simply referred to as “hot rolled oil”) contains the synthetic ester which is an ester of the specific polyhydric alcohol and a fatty acid. Moreover, the ratio of the structural unit derived from a C6-C24 saturated fatty acid among the structural units derived from all the fatty acids in the said synthetic ester is 60 mol% or more. Thus, by making the ratio of the structural unit derived from the specific saturated fatty acid 60 mol% or more, the amount of lower fatty acid generated is significantly reduced, and thus the oxidation of the hot rolling oil over a long period of time. Can be suppressed. This is because the radical chain reaction is involved in the generation of lower fatty acids, and by increasing the proportion of the structural units derived from the specific saturated fatty acids, the generation of radicals and the progress of the radical chain reaction can be suppressed. Conceivable.

  That is, when a structural unit derived from an unsaturated fatty acid is contained in the synthetic ester, the double bond may be dissociated by heat during rolling to generate an alkyl radical (R.). The alkyl radical reacts with oxygen in the air to generate a peroxy radical (ROO.), And further extracts hydrogen from a hot rolling oil component such as a synthetic ester to generate hydroperoxide (ROOH). This hydroperoxide readily dissociates into an alkoxy radical (RO.) And a hydroxy radical (.OH).

  And the radical which arose by these reaction produces | generates a new radical in a chain | linkage, consuming the component of hot rolling oil. As a result, it is considered that the decomposition of the components of the hot rolling oil proceeds at an accelerated rate and the amount of lower fatty acid generated increases.

  On the other hand, in the hot rolled oil, by setting the ratio of the specific saturated fatty acid within the specific range, the number of double bonds in the synthetic ester that is the starting point of the chain reaction is sufficiently reduced. can do. Therefore, it is considered that the occurrence of the chain reaction can be suppressed, and as a result, the amount of lower fatty acid generated can be significantly reduced.

  As described above, by using the specific synthetic ester, it is possible to suppress the oxidation of the hot rolling oil over a long period of time.

  The hot rolling coolant for aluminum (hereinafter simply referred to as “coolant”) is an emulsion in which the hot rolling oil is dispersed in water. The content of the hot rolling oil in the coolant and the volume average particle diameter of the oil droplets of the hot rolling oil are each within the specific range. By having such a configuration, the coolant is suitable for hot rolling of aluminum.

  The hot rolling oil usually contains a base oil and an emulsifier in addition to the synthetic ester. As the base oil, for example, naphthenic or paraffinic refined mineral oil can be used.

  As the emulsifier, known emulsifiers for hot rolling oils such as fatty acid amine soap, sodium sulfonate, polyethylene glycol type nonionic surfactant can be used. When the content of the emulsifier is excessively small, the hot rolling oil and water may be separated in the coolant. As a result, the lubricity at the time of hot rolling is lowered, and there is a possibility that the plate surface quality of the rolled plate after hot rolling is lowered. Moreover, when there is too much content of an emulsifier, an emulsifier will become easy to oxidize. In some cases, the coolant is a water-in-oil type, that is, an emulsion in which water is dispersed in hot-rolled oil, which may cause a decrease in lubricity.

  From the viewpoint of avoiding these problems, the content of the emulsifier is preferably 0.1 to 20% by mass.

  The content of the synthetic ester in the hot rolling oil is preferably 1 to 30% by mass. By setting the content of the synthetic ester to 1% by mass or more, the lubricity during hot rolling can be appropriately increased. As a result, it is possible to easily avoid a reduction in plate surface quality of the rolled plate after hot rolling.

  On the other hand, since synthetic esters are relatively expensive, an increase in the content causes an increase in the cost of hot rolling oil. On the other hand, if the content of the synthetic ester is excessively high, the lubricity during hot rolling becomes excessively high, which may cause problems such as poor engagement of the aluminum material with the rolling roll. By setting the content of the synthetic ester to 30% by mass or less, these problems can be easily avoided.

  The synthetic ester may be a single compound, but is usually a mixture of two or more compounds having different structural units derived from fatty acids and different numbers of esterified hydroxyl groups. The synthetic ester may be a full ester in which all the hydroxyl groups of the polyhydric alcohol are esterified, or a partial ester in which some of the hydroxyl groups of the polyhydric alcohol are esterified. From the viewpoint of lubricity during hot rolling, it is preferable to increase the ratio of full ester in the synthetic ester.

  As the polyhydric alcohol, one or more selected from the group consisting of neopentyl glycol, trimethylolpropane and pentaerythritol can be employed. These polyhydric alcohols do not have a tertiary CH (carbon-hydrogen) bond with low thermal stability in their molecular structure. Therefore, thermal decomposition of the structural unit derived from the polyhydric alcohol during hot rolling can be suppressed.

  As the fatty acid, one or two or more compounds selected from the group consisting of saturated fatty acids and unsaturated fatty acids can be employed. The structure of the hydrocarbon chain in these compounds may be a straight chain structure, a branched chain structure, or a cyclic structure.

  In the said hot rolling oil, the ratio of the structural unit derived from a C6-C24 saturated fatty acid among the structural units derived from all the fatty acids in a synthetic ester is 60 mol% or more. When the ratio of the structural unit derived from the saturated fatty acid having less than 6 carbon atoms is increased, the lubricity during hot rolling is lowered, and the surface quality of the rolled sheet may be deteriorated.

  In addition, saturated fatty acids having more than 24 carbon atoms are relatively expensive. Therefore, when the ratio of the structural unit derived from such a saturated fatty acid increases, the cost of the synthetic ester increases. When the ratio of the structural unit derived from the unsaturated fatty acid is increased, the amount of lower fatty acid generated is increased as described above.

  Therefore, by making the ratio of structural units derived from saturated fatty acids having 6 to 24 carbon atoms within the above specific range, the generation amount of lower fatty acids is significantly reduced while avoiding a decrease in lubricity and an increase in cost. be able to. From the same viewpoint, the ratio of the structural unit derived from the saturated fatty acid having 6 to 24 carbon atoms is preferably 70 mol% or more, more preferably 80 mol% or more, and further preferably 90 mol% or more. .

  Moreover, the said hot rolling oil may contain the fatty acid and natural fats and oils as an oiliness agent in the range which does not have a bad influence on oxidation resistance.

  The hot rolling oil further contains one or more primary antioxidants selected from the group consisting of phenolic antioxidants and aromatic amine antioxidants, and the primary antioxidants. The total content of is preferably 0.01 to 3.0% by mass. In the radical chain reaction described above, the primary antioxidant has a function of suppressing chain reaction by donating hydrogen to the alkyl radical (R.) or peroxy radical (ROO.) And becoming a stable radical. I think that.

  By setting the content of the primary antioxidant to 0.01% by mass or more, the oxidation of the hot rolling oil can be suppressed for a longer period. On the other hand, when the content of the primary antioxidant is excessively large, improvement in the effect of suppressing oxidation cannot be expected, and the cost of hot rolling oil is increased. Therefore, by making the total content of the primary antioxidant 0.01 to 3.0% by mass, the effect of suppressing oxidation can be further enhanced while suppressing an increase in cost.

  Examples of the phenolic antioxidant include 2,6-di-t-butylparacresol, 4,4′methylenebis (2,6-di-t-butylphenol), 4,4′methylenebis (6-t-butyl). -O-cresol) and the like can be used. In addition, as the aromatic amine-based antioxidant, for example, P, P'-dioctyldiphenylamine, phenyl-α-naphthylamine, phenothiazine, and the like can be used.

  The hot rolling oil further contains a secondary antioxidant containing sulfur, and the content of the secondary antioxidant is preferably 1.0 to 3.0% by mass as sulfur. . That is, the sulfur content of the hot rolling oil is preferably 1.0 to 3.0% by mass. In the radical chain reaction described above, the secondary antioxidant decomposes hydroperoxide (ROOH) into more stable hydroxide (ROH) to suppress the generation of alkoxy radicals (RO.) And hydroxy radicals (.OH). It is thought that it has the effect | action which suppresses a chain reaction by this.

  By setting the content of the secondary antioxidant to 1.0 mass% or more as sulfur, the oxidation of the hot rolling oil can be suppressed for a longer period. On the other hand, when the content of the secondary antioxidant is excessively large, improvement in the effect of suppressing oxidation cannot be expected, and the cost of hot rolling oil is increased. By setting the content of the secondary antioxidant to 1.0 to 3.0% by mass as sulfur, it is possible to further enhance the effect of suppressing oxidation while suppressing an increase in cost.

  As the secondary antioxidant, for example, compounds such as thiourea, thiazole, sulfenamide, thiuram, dithiocarbamate, xanthate, mercaptan, sulfide and the like can be used. In addition, use of mineral oil containing sulfur-containing components in refined mineral oil as a base oil, or using a combination of mineral oil containing sulfur-containing components and mineral oil containing no sulfur-containing components, etc. The component can also be a secondary antioxidant.

  The primary antioxidant and the secondary antioxidant described above may be added to the hot rolling oil alone, but both the primary antioxidant and the secondary antioxidant should be added to the hot rolling oil. Is more preferable. By using a primary antioxidant and a secondary antioxidant in combination, the effect of suppressing oxidation can be increased synergistically, compared to the case where a primary antioxidant or a secondary antioxidant is added alone. The oxidation of hot rolling oil can be suppressed over a long period of time.

  Content of the said hot rolling oil in the said coolant is 1-10 volume%. Thereby, the lubricity at the time of hot rolling can be maintained in an appropriate range. When the content of hot rolling oil is less than 1% by volume, the lubricity is lowered and the surface quality of the rolled sheet may be deteriorated. On the other hand, when the content of hot rolling oil is increased, the cost of the coolant is increased. Furthermore, when the content of hot rolling oil is excessively large, the lubricity becomes excessively high, which may cause problems such as poor engagement of the aluminum material with the rolling roll. From the viewpoint of avoiding these problems, the content of hot rolling oil is set to 10% by volume or less.

  The median diameter of the oil droplets of the hot rolling oil present in the coolant based on the volume-based particle size distribution is 1 to 7 μm. Thereby, while improving lubricity at the time of hot rolling moderately, an emulsion can be stabilized. When the median diameter of the oil droplets is less than 1 μm, a boiling film is likely to form between the oil droplets in the coolant and the surface of the rolling roll during hot rolling. Therefore, the amount of hot rolling oil supplied to the rolling roll is insufficient, and there is a possibility that the lubricity is lowered. On the other hand, when the median diameter of the oil droplets exceeds 7 μm, the oil droplets in the emulsion easily float due to buoyancy, and in some cases, the hot rolling oil and water may be separated.

  The median diameter of the oil droplets described above is the cumulative median diameter in the volume-based particle size distribution obtained by the laser diffraction / scattering method. A laser diffraction / scattering particle size distribution measuring device (for example, “LA-950” manufactured by Horiba, Ltd.) can be used to measure the median diameter of oil droplets.

  Examples of the hot rolling oil will be described. In addition, the hot rolling oil which concerns on this invention is not limited to the following aspects, A structure can be suitably changed in the range which does not impair the summary.

The abbreviations of the compounds used in this example are as follows.
Polyhydric alcohol NPG: Neopentyl glycol TMP: Trimethylolpropane PE: Pentaerythritol Fatty acid C6: Hexanoic acid C8: Octanoic acid C10: Decanoic acid C14: Dodecanoic acid C16: Hexadecanoic acid C18: Octadecanoic acid C20: Eicosanoic acid C22: docosanoic acid C24: tetracosanoic acid C16F1: cis-9-hexadecenoic acid (palmitoleic acid)
C18F1: cis-9-octadecenoic acid (oleic acid)
C18F2: cis-9, cis-12-octadecadienoic acid (linoleic acid)
C18F3: cis-9, cis-12, cis-15-octadecatrienoic acid (linolenic acid)

Example 1
This example is an example in which the ratio of constituent units derived from fatty acids in the synthetic ester and the content of the synthetic ester are variously changed. In this example, it contains 15% by mass of oleic acid, 3% by mass of triethanolamine, 5% by mass of a nonionic emulsifier, and synthetic esters having the contents shown in Tables 1 and 2, with the balance being refined mineral oil. Hot rolled oil (samples 1-42) was produced.

  The synthetic ester of this example is an ester of a polyhydric alcohol and a fatty acid shown in Tables 1 and 2. Moreover, the ratio of the structural unit derived from each fatty acid when the sum total of the structural unit derived from all the fatty acids in a synthetic ester is 100 mol% is as having shown in Table 1 and Table 2. The refined mineral oil does not contain sulfur-containing components.

  Using the samples shown in Table 1 and Table 2, the effect of suppressing oxidation was evaluated by the following procedure. First, 5 g of a sample, 95 g of ion exchange water, and 1 g of electrolytic iron powder were mixed to prepare an emulsion in which oil droplets of the sample were dispersed in ion exchange water. The emulsion was heated in a sealed container at 90 ° C. for 168 hours, and then the amount of formic acid generated in the container was measured. The amount of formic acid generated (mass ppm) in each sample was as shown in Tables 1 and 2.

  As can be understood from the comparison between Table 1 and Table 2, Samples 1 to 28 (see Table 1) were able to significantly reduce the amount of formic acid generated compared to Samples 29 to 42 (see Table 2). . From these results, in the hot rolled oil for aluminum containing a synthetic ester of a polyhydric alcohol and a fatty acid, the amount of the lower fatty acid is significantly reduced by setting the ratio of the specific saturated fatty acid to 60 mol% or more. Thus, it can be easily understood that the oxidation of the hot rolling oil can be suppressed over a long period of time.

(Example 2)
In this example, a primary antioxidant and / or a secondary antioxidant is added to hot rolled oil. In this example, oleic acid 15% by mass, triethanolamine 3% by mass, nonionic emulsifier 5% by mass, synthetic ester 30% by mass, primary antioxidant and / or secondary antioxidant shown in Table 3 The hot-rolled oil (samples 59-86) which contains a chemical | medical agent and the remainder consists of refined mineral oil was produced. As the synthetic ester, the same synthetic ester as used in Sample No. 13 of Example 1 was used.

  Moreover, about the samples 83-86, the mineral oil which does not contain a sulfur containing component, and the mineral oil containing a sulfur containing component were used together as refined mineral oil. In these samples, “Sulfur-containing mineral oil” in the column of the type of secondary antioxidant in Table 3 and the content of mineral oil containing a sulfur-containing component in the column of content are described. belongs to. In practice, the sulfur-containing component in the mineral oil functions as a secondary antioxidant.

  Using the samples shown in Table 3, the effect of suppressing oxidation was evaluated by the same procedure as in Example 1. The amount of formic acid generated in each sample was as shown in Table 3.

  As can be understood from the comparison between Table 1 and Table 3, samples 59 to 86 (see Table 3) containing the above-mentioned specific synthetic ester and further containing a primary antioxidant and / or a secondary antioxidant are those It was possible to further reduce the amount of formic acid generated as compared with the sample containing no antioxidant (see Table 1). Moreover, the amount of formic acid generated was reduced as the sample content of the primary antioxidant and secondary antioxidant increased. From these results, it is possible to oxidize hot rolling oil by adding primary antioxidants such as phenolic antioxidants and amine antioxidants, and secondary antioxidants containing sulfur to hot rolling oils. Can be understood over a longer period of time.

  Further, as shown in Table 3, Samples 71 to 84 to which the secondary antioxidant was added were able to reduce the amount of formic acid generated compared to Samples 59 to 70 to which the primary antioxidant was added. From these results, it can be understood that the secondary antioxidant has a higher effect of suppressing oxidation than the primary antioxidant.

  Furthermore, samples 85 to 86 to which both the primary antioxidant and the secondary antioxidant are added should further reduce the amount of formic acid generated than samples 59 to 84 to which only one of the antioxidants is added. I was able to. From these results, it is possible to synergistically enhance the effect of suppressing oxidation by adding both the primary antioxidant and the secondary antioxidant into the hot rolling oil. It can be understood that the oxidation of the hot rolling oil can be suppressed over a long period of time compared to the case where the secondary antioxidant is added alone.

(Example 3)
This example is an example of a coolant in which the hot rolling oil is dispersed in water. In this example, the hot rolling oil and water shown in Sample No. 13 of Example 1 are mixed, and two kinds of coolants (Table 4, Sample Nos. 87 and 88) having different hot rolling oil contents are mixed. Prepared. And the effect which suppresses oxidation was evaluated by the procedure similar to Example 1 using these coolants. The amount of formic acid generated in each sample was as shown in Table 4.

  As shown in Table 4, the coolant in which the hot rolling oil containing the specific synthetic ester is dispersed in water significantly reduces the amount of lower fatty acids generated, and thus the hot rolling oil is oxidized for a long time. It can be easily understood that it can be suppressed over the whole area.

  Further, when hot rolling was performed using these coolants, it was possible to avoid a defective biting of the aluminum material into the rolling roll and to obtain a rolled plate having a good surface quality.

Claims (6)

A hot rolled oil for aluminum containing a synthetic ester of a polyhydric alcohol and a fatty acid,
The polyhydric alcohol is one or more selected from neopentyl glycol, trimethylolpropane and pentaerythritol,
The hot rolling oil for aluminum whose ratio of the structural unit derived from a C6-C24 saturated fatty acid among the structural units derived from all the fatty acids in the said synthetic ester is 60 mol% or more.   The hot rolling oil for aluminum according to claim 1, comprising 1 to 30% by mass of the synthetic ester.   The hot rolling oil for aluminum further contains one or more primary antioxidants selected from the group consisting of phenolic antioxidants and aromatic amine antioxidants, and the primary oxidation The hot rolling oil for aluminum according to claim 1 or 2, wherein the total content of the inhibitor is 0.01 to 3.0 mass%.   The hot rolling oil for aluminum further contains a secondary antioxidant containing sulfur, and the content of the secondary antioxidant is 1.0 to 3.0% by mass as sulfur. The hot rolling oil for aluminum according to any one of claims 1 to 3. A hot rolling coolant for aluminum in which the hot rolling oil for aluminum according to any one of claims 1 to 4 is dispersed in water,
Containing 1 to 10% by volume of the hot rolling oil for aluminum,
The hot rolling coolant for aluminum whose median diameter of the oil droplet of the said hot rolling oil for aluminum based on the particle size distribution of volume reference | standard is 1-7 micrometers.   The manufacturing method of an aluminum rolled sheet which performs hot rolling of the aluminum material using the hot rolling coolant for aluminum of Claim 5.