Cold-rolling oils for steel plates.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rolling oil having high lubricating properties and high mill cleanability, that is, a cold-rolling oil for steel plates, which excels in lubricating and annealing properties.

2. Related Art Statement

Cold-rolling oils used for thin steel plates are generally broken down into two types, one based on animal and vegetable oils and fats (such as tallow and lard, soybean oil, colza oil, palm oil and coconut oil) and the other on mineral oils. Recent demands for energy saving and improvements in produc­tivity lead to higher speed rolling, higher reduction-ratio rolling and mill clean rolling. The rolling oils based on animal and vegetable oils and fats are suitable for high-­load and -speed rolling. However, when as cold-rolled steel plates are directly annealed without degreasing oily deposits thereon, it is likely that they may be contaminated on their surfaces in the annealing step. That is, such rolling oils are suitable in view of lubricating properties, but are unsuitable in view of mill cleanability.

When cold rolling is carried out with the rolling oils based on mineral oils, on the other hand, excellent mill cleanability is achievable, since as cold-rolled thin steel plates can be directly annealed without any surface contami­nation. However, such rolling oils lack in high-load and -speed rolling properties.

For use, oilness improvers such as animal and vegetable oils and fats, fatty acids (capric, lauric, myristic, stearic, oleic and linolenic acids) or esters (synthetic esters such as monoesters, diesters or polyol esters wherein the alcoholic components are trimethylolpropane, pentaerythritol and 2-ethylhexyl alcohol) as described in "Oil Chemistry", No. 73-11, pages 695-706 are generally added to the rolling oils based on mineral oils so as to enhance their rolling lubricating properties. However, the amount of such improvers added is regulated to a narrow range of the required minimum limit so as to retain mill cleanability. As mentioned above, various investigations have been made of cold-rolling oils capable of satisfying high lubricating properties and high mill cleanability at the same time (see for instance Japanese Patent Laid-Open Publication Nos. 56-135600 and 59-80498). However, there is not still found any rolling oil meeting both properties in a well-balanced state and at a higher level.

SUMMARY OF THE INVENTION

The present invention provides cold-rolling oils for steel which make a contribution to improvements in productivity as expressed in terms of energy saving and reductions in the number of the steps involved, and which are stable with respect to heat and mechanical shearing occurring at high speeds and pressures and even with respect to chemical reac­tions such as oxidation, decomposition and polymerization. The cold-rolling oils according to the present invention are easily volatilized off in the annealing step without giving rise to thermally decomposed residues, and combine steel-­plate's surface cleanability (mill cleanability) with high lubricating properties.

More specifically, the cold-rolling oils for steel according to the present invention are composed mainly of the esterified products of tri- or higher-valent alcohols selected from amino alcohols having tertiary nitrogen and fatty acids having six or more carbon atoms, have high lubricating properties and high mill cleanability, and make it possible to effectively carry out rolling of thin steel plates and annealing of the steel plates without degreasing the same.

DETAILED DESCRIPTION OF THE INVENTION

The synthetic esters referred to in this disclosure are "molecularly designed" and synthesized to this end. In recent years, synthetic esters have been employed as base oils of, or additives for, rolling oils. However, most of synthetic esters used as cold-rolling oils are not synthesized to this end, and are often selected from existing synthetic esters employed as engine oils, hydraulic working oils or other lubricant. Thus, they fail to meet satisfactorily both high lubricating properties and high mill cleanability.

The synthetic esters according to the present invention have the properties suitable for cold-rolling oils, i.e., combine high lubricating properties with high mill cleanability, and are "molecularly designed", as mentioned below.

For instance, the tri- or higher-valent alcohols having tertiary nitrogen used in the present invention include triethanolamine, triisopropanolamine, N,N-bis(2-hydroxypropyl)­ethanolamine, N,N-bis(2-hydroxyethyl)-isopropanolamine, triethanolamine tris-glycoether, triisopropanolamine tris-­glycoether, tris(2-hydroxyethyl)isocyanurate, N,N,Nʹ,Nʹ-­tetrakis(2-hydroxyethyl)ethylenediamine, and N,N,Nʹ,Nʹ-­tetrakis(2-hydroxypropyl)ethylenediamine.

In accordance with the present invention, particularly preferable tri- or higher-valent alcohols having tertiary nitrogen are isocyanuric derivatives expressed in terms of the general formula (A) to be given later or polyvalent alcohols expressed in terms of the general formula (B) to be given later, wherein the mother nucleus is formed by an alkylene (or phenyl or cyclohexyl) diamine that is a tetra­valent alcohol.

The fatty acids to be used in the present invention may include straight or branched-chain, saturated or unsaturated and natural or synthetic fatty acids having six or more carbon atoms such as those represented by hexanoic, octanoic, decanoic lauric, myristic, palmitic, stearic, arachinic, behenic, mon­tanic, palmitooleic, oleic, erucic, ricinoleic, hydroxystearic, linoleic, linolenic, isooctylic, isodecanoic, isolauric, isomyristic, isopalmitic, isostearic and isoarachinic acids.

It has been found that, with the esterified products of the specific alcohols and fatty acids having 5 or less carbon atoms, it is impossible to enhance to a sufficient degree the lubricating properties in cold-rolling of steel plates. This is because the present invention is limited to fatty acids having six or more carbon atoms. Although no particular limitation is placed upon the upper-limit number of carbon atoms contained in the fatty acids used, on the other hand, fatty acids having 30 or less carbon atoms are preferred in view of commercial availability and price.

The esterified products according to the present inven­tion may be synthesized by esterification of the tri- or higher-valent alcohols having tertiary nitrogen and the fatty acids, which may be effected in the presence or absence of catalysts in any conventional manner.

One preferred esterified products according to the present invention are the esters of the isocyanuric derivatives having the aforesaid general formula (A) and the fatty acids having six or more carbon atoms, that is, the esterified products of the isocyanuric derivatives of the general formula (A) and the fatty acids having six or more carbon atoms, expressed in terms of the following general formula (C): <chemistry id="chem0001" num="0001"><img file="EP0242925A2_D0001.tif" /></chemistry> wherein X is H or CH₃, and n is an integer of 1 to 10, and R₁-COOH .......... (C) wherein R₁ stands for an alkyl, alkenyl, hydroxyalkyl or hydroxyalkenyl group having at least five carbon atoms.

Of the nitrogen-containing polyols (isocyanuric derivatives) having the general formula (A), tris(2-hydroxyethyl)isocyanu­rate wherein n = 1 and X = H is particularly advantageous for the industrial lubricating oils of the present invention, since it is easily commercially available and inexpensive.

No particular limitation is imposed upon the degree of esterification with the fatty acid. It is desired, however, that one mole of tris(2-hydroxyethyl)isocyanurate be esteri­fied with preferably at least 1.5 moles, more preferably at least 2 moles of the fatty acid on the average.

In the nitrogen-containing polyols (isocyanuric deriva­tives) of the general formula (A), n should preferably be an integer of 1 to 10. It is to be noted, however, that the number n is defined in terms of an averaged number of moles. In some cases, the averaged number of 3 may include 4, since there is then a distribution in the number of addition moles of ethylene or propylene oxide. That is, n is strictly an averaged number which should preferably be not more than 10 in the present invention. If n exceeds 10, the lubricating properties to be achieved then deteriorates.

In general, an increased n allows hydrophilic nature to be afforded to lubricants per se, which then acquire self-­emulsifiability or dispersibility.

Another preferred esterified products according to the present invention are the esters of the tetra-valent alcohols of the aforesaid general formula (B) and the fatty acids having six or more carbon atoms, that is, the esterified products of the nitrogen-containing polyols of the general formula (B) and the fatty acids having six or more carbon atoms, expressed by the general formula (C). <chemistry id="chem0002" num="0002"><img file="EP0242925A2_D0002.tif" /></chemistry> wherein X is H or CH₃, n indicates and integer of 1 to 10, and R₂ stands for an alkyl, having 2 to 6 carbon atoms, phenyl or a cyclohexyl group, and R₁-COOH .......... (C)

The nitrogen-containing polyols of the general formula (A) may be obtained by adding the predetermined amount of ethylene or propylene oxide to ethylenediamine, hexylenediamine, phenyldiamine, cyclohexyldiamine and the like. In particular N,N,Nʹ,Nʹ-tetrakis(2-hydroxypropyl)ethylenediamine, wherein R = C₂H₄, n = 1 and X = CH₃, is advantageous for the industrial lubricating oils of the present invention in view of commercial availability and price.

No particular limitation is imposed upon the degree of esterification with the fatty acid. It is desired, however, that one mole of N,N,Nʹ,Nʹ-tetrakis(2-hydroxypropyl)ethylene­diamine be esterified with preferably at least 2 moles, more preferably at least 3 moles of the fatty acid on the average.

It is to be understood that the reasons why the polyols are limited to ethylene or propylene oxide addition products are that higher alkylene oxide addition products such as butylene oxide addition products are so commercially expensive that difficulty is experienced in obtaining them.

In the nitrogen-containing polyols of the general formula (B), n should preferably be an integer of 1 to 10. Polyols, wherein n is more than 10, have an increased molecular weight and decreases in lubricating properties with an increase in the number of ether bonds. It is to be noted, however, that the number n is defined in terms of an averaged number of moles. In some cases, the averaged number of 3 may include 4, since there may then a distribution in the number of addition moles of ethylene or propylene oxide. In short, n is strictly an averaged number which should preferably be not more than 10 in the present invention. If n exceeds 10, the lubricating properties to be achieved then deteriorates.

In general, an increased n allows hydrophilic nature to be afforded to lubricants per se, which then acquire self-­emulsifiability or dispersibility.

The nitrogen-containing polyols, which are the starting material for synthesizing the esterified products of the present invention, are tetra-valent alcohols, and the esterified products thereof with the fatty acids are obtained in the form of monoesters, diesters, triesters or tetraesters. However, the esterified products in the form of di- or higher-­esters are more preferable on the average for the cold-rolling oils for steel plates according to the present invention.

The synthetic esters of the present invention may be used as the rolling oils alone or in admixture with other base oils such as mineral oil or animal and vegetable oils and fats. Further, they may be used in the form of an emulsion obtained by adding an emulsifying agent thereto.

In addition, the synthetic esters of the present invention may be used in combination with emulsifying agents, fatty acids, antioxidants and corrosion inhibitors ordinarily used as additives with mineral oils or animal and vegetable oils and fats or practical rolling oils which are usually used as the base oils.

When the synthetic ester compounds of the present invention are used in admixture with other base oils, stable properties are ahievable by addition thereof in an amount of at least 5 weight %, preferably at least 20 weight %, although they are effective in an amount of as small as 1 weight %.

The materials of the present invention are applicable not only to the cold-rolling oils for steel plates but also to a wide range of industrial lubrication applications inclusive of processing or mechanical lubrication where they are used as cutting or grinding oils.

EXAMPLES

In what follows, the synthesis examples and examples of the present invention will be given for the purpose of illustration alone.

Synthesis Example 1

Into a four-necked flask having a stirrer, a thermometer, a nitrogen gas-feed tube and a water separator, 522 g (2 moles) of tris(2-hydroxyethyl)isocyanurate and 1269 g (5.85 moles) of coconut oil fatty acid were charged together, and xylene was added as a reflux solvent in an amount of 5 % of the starting materials. The mixture was well agitated and allowed to react at 160 to 230°C in the absence of any catalyst until the calculated amount of water was distilled out. The required time was 9 hours. After the completion of the reaction, xylene was distilled off under reduced pressure, followed by decoloring and filtration with activated clay, thereby to obtain a yellow liquid. The yield and acid number was 1661 g and 1.8, respectively. In similar procedures, a number of synthetic esters were prepared. The properties of the obtained synthetic esters are also set forth in Table 1.

Examples 1-7

Estimation was made of the lubricating and annealing properties of the rolling oil compositions obtained by adding to mineral and palm oils used as the base oils for practical rolling oils ordinarily used additives such as emulsifying agents, fatty acids and antioxidants, and the synthetic esters that were the rolling oils of the present invention.

To make estimation of the rolling lubricating properties of each rolled material under test (spcc) of 1.2X20X200 mm, emulsion rolling was carried out with a two-stage roll type rolling mill at an oil concentration of 3 % and bath tempera­ture of 50°C, and a rolling load was then measured at a reduction ratio of 40 %. To make estimation of the annealing properties of each sample, several tens steel plates rolled with the emulsion liquid under test were formed as such into a stack, which was then fixed in place with a narrow steel belt, followed by annealing in an annealing furnace of a small size.

Referring to the heating conditions for annealing, the stack was heated in an atmosphere of 120 mℓ/min of NHX gas (H₂ : 5 %) to 600°C at a heating rate of 10°C/min, retained at that temperature for 1 hours, and was allowed to stand for cooling.

Thereafter, a cellophane tape was applied over the surface of each steel plate to gather surface deposits, and was sticked over white paper to visually observe the degree of contamination and thereby make estimation of the surface cleanability thereof. The results of testing are set forth in Table 2, wherein the marks are the same as those in Table 1. <tables id="tabl0001" num="0001"><img file="EP0242925A2_D0003.tif" /></tables><tables id="tabl0002" num="0002"><img file="EP0242925A2_D0004.tif" /></tables><tables id="tabl0003" num="0003"><img file="EP0242925A2_D0005.tif" /></tables>

Synthesis Example 2

Into a four-necked flask having a stirrer, a thermometer, a nitrogen gas-feed tube and a water separator, 292 g of N,N,Nʹ,Nʹ,-tetrakis(2-hydroxypropyl)ethylenediamine and 840 g of coconut oil fatty acid were charged together with 2.2 g of a catalyst toluensulfonic acid, and xylene was added as a reflux solvent in an amount of 5 % of the starting materials. The mixture was well agitated and allowed to react at 160 to 230°C until the calculated amount of water was distilled out. The required time was 8 hours. After the completion of the reaction, the reaction product was washed with water for removal of the catalyst, and xylene was distilled off under reduced pressure, followed by decoloring and filtration with activated clay, thereby to obtain a yellow liquid. The yield and acid number were 970 g and 2.3, respectively (Sample A). In similar proce­dures, a number of synthetic esters were prepared. The properties of the obtained synthetic esters are also set forth in Table 3. <tables id="tabl0004" num="0004"><img file="EP0242925A2_D0006.tif" /></tables>

Examples 8-13

Estimation was made of the lubricating and annealing properties of the rolling oil compositions obtained by adding to mineral and palm oils used as the base oils for practical rolling oils ordinarily used additives such as emulsifying agents, fatty acids and antioxidants, and the synthetic esters that were the rolling oils of the present invention.

To make estimation of the rolling lubricating properties of each rolled material under test (spcc) of 1.2X20X200 mm, emulsion rolling was carried out with a two-stage roll type rolling mill at an oil concentration of 3 % and a bath tem­perature of 50°C, and a rolling load was then measured at a reduction ratio of 40 %. To make estimation of the annealing properties of each sample, several tens steel plates rolled with the emulsion liquid under test were formed as such into a stack, which was then fixed in place with a narrow steel belt, followed by annealing in an annealing furnace of a small size.

Referring to the heating conditions for annealing, the stack was heated in an atmosphere of 120 mℓ/min of HNX gas (H₂ : 5 %) to 600°C at a heating rate of 10°C/min, retained at that temperature for 1 hours, and was allowed to stand for cooling.

Thereafter, a cellophane tape was applied over the surface of each steel plate to gather surface deposits, and was sticked over white paper to visually observe the degree of contami­nation and thereby make estimation of the surface cleanability thereof. The results of testing are set forth in Table 4, wherein the marks are the same as those in Table 3,. <tables id="tabl0005" num="0005"><img file="EP0242925A2_D0007.tif" /></tables><tables id="tabl0006" num="0006"><img file="EP0242925A2_D0008.tif" /></tables>

In the present invention, the synthetic ester compounds obtainable from tri- or higher-valent alcohols having tertiary nitrogen such as isocyanuric derivatives or ethylene or pro­pylene oxide addition products of ethylenediamine are intended for use as the rolling lubricants for steel plates, and are "molecularly designed" taking into consideration the require­ments to that end. Unlike the existing synthetic esters used as cold-rolling oils or additives, the ester compounds according to the present invention give rise to improvements in the rolling lubricating properties of steel plates, and make a great deal of contribution to energy and material savings such as reductions in the power cost, as compared with the conventional base oils comprising palm oil. In addition, the ester compounds of the present invention excel in mill cleanability, and can dispense with conven­tional electrolytic degreasing, resulting in reductions in the installation cost.