JPH01318953A - Method for evaluating physical property of surface of particle material for magnetic recording medium - Google Patents

Abstract

PURPOSE:To examine the physical property of the surface of particle material for a magnetic recording medium by analyzing a compound which is formed by aldol condensation reaction of a carbonyl compound and compound which is formed by dehydrating reaction of a beta-hydroxycarbonyl compound. CONSTITUTION:Particle material for magnetic recording medium and a carbonyl compound having hydrogen atoms are brought into contact. At this time, the carbonyl compound and alpha,beta-double bonded carbonyl compound which is formed by the dehydrating reaction of beta-hydroxycarbonyl compound are analyzed. The presence of a base point is found by the formation of the beta-hydroxycarbonyl compound. The presence of an acid point is found by the formation of the alpha,beta-double bonded carbonyl compound.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for evaluating the surface properties of various magnetic recording medium particle materials used in magnetic recording media, such as ferromagnetic powder and abrasives.

[Conventional technology]

Generally magnetic recording media uses ferromagnetic powder as a binder.

A magnetic layer is formed by applying a magnetic paint made by dispersing and kneading additives such as dispersants, lubricants, and abrasives in an organic solvent onto one surface of a non-magnetic support such as a polyester film. There is. This is what is called a coating type magnetic recording medium.

Furthermore, on the other surface of the nonmagnetic support, it is widely practiced to provide a so-called back coat layer in which conductive carbon black or the like is mixed in a binder. This back coat layer is used not only in the above-mentioned coated magnetic recording media, but also in so-called metal flfl, which is a magnetic layer formed by depositing a ferromagnetic metal directly onto a nonmagnetic support by means such as vacuum deposition.
It is also applied to film-type recording media.

Incidentally, the performance of a magnetic recording medium depends not only on the characteristics of the magnetic material itself, but also on the filling properties, orientation, dispersibility, etc. of the particle material in the magnetic layer or back coat layer. For such magnetic recording media, it is important to know the surface properties of various particulate materials, including the ferromagnetic powder, abrasive, etc. used in the magnetic layer, and the carbon black used in the backcoat layer. Accurately understanding interactions between agents and other additives is essential for improving reproducibility in material development and design or manufacturing processes.

From this point of view, various methods have been used to evaluate the surface properties of ferromagnetic powder depending on the purpose.

These include, for example, various thermochemical methods such as liquid absorption measurement, wetting heat measurement, adsorption heat measurement based on adsorption isotherms, measurement of the zero point of charge by potentiometric titration, surface potential measurement (electroosmosis, streaming potential method, sedimentation potential method), or electrochemical methods such as isoelectric point measurement using electrophoresis or zeta potential measurement.

[Problem to be solved by the invention]

However, each of the above-mentioned methods provides so-called macroscopic information regarding the average physical properties of the surface;
Microscopic information cannot be obtained from this. For example, even if the isoelectric point of a certain particulate material is determined by electrophoresis, how strong are the acid and basic points in the particulate material? Understanding such microscopic surface physical properties, for which it is impossible to know in what proportion they are distributed, would be extremely effective in improving reproducibility in material design and manufacturing processes.

Therefore, an object of the present invention is to provide a method that enables microscopic evaluation of the surface properties of particle materials for magnetic recording media.

[Means to solve the problem]

The present inventors have discovered that -II has acid sites and base sites inherent to the material or generated by adsorption of water molecules, oxidation, etc. on the surface of the magnetic recording medium material powder, and these are Brønsted acids or base sites. Focusing on the fact that they act as Brønsted bases, we found a method that allows these to be separately quantified through a series of reactions, leading to the present invention.

That is, the method for evaluating the surface properties of a particle material for a magnetic recording medium according to the first aspect of the present invention involves bringing a carbonyl compound having an α hydrogen atom into contact with a particle material used for a magnetic recording medium, and forming an aldol of the carbonyl compound. A β-hydroxycarbonyl compound produced by a condensation reaction,
This method is characterized in that an α,β-double bond carbonyl compound produced by the dehydration reaction of the β-hydroxycarbonyl compound is separated.

Furthermore, a method for evaluating the surface properties of a particle material for a magnetic recording medium according to a second aspect of the present invention includes bringing a β-hydroxycarbonyl compound into contact with a particle material used for a magnetic recording medium, and It is characterized by the analysis of a carbonyl compound having an α hydrogen atom produced by a reverse aldol condensation reaction and an α,β-double bond carbonyl compound produced by a dehydration reaction of the β-hydroxycarbonyl compound. .

The aldol condensation reaction is a reaction that occurs with aldehydes or ketones that have a hydrogen atom in the α position.

This reaction is expressed as follows.

In this formula, R1 and R2 are each a hydrogen atom,
Represents a hydrocarbon group having a substituent or an unsubstituted hydrocarbon group. Here, if R2 is a hydrogen atom, the carbonyl compound (]) in the above formula is an aldehyde, and if it is another hydrocarbon group, it is a ketone. Furthermore, R1 and R2 may be bonded to each other at the ends to form a cyclic ketone.

According to the above reaction route, first the carbonyl compound (
1) changes into a β-hydroxycarbonyl compound (I[[) through intermediate (II) in the presence of a base catalyst, which is further easily dehydrated in the presence of an acid catalyst to form an α,β-double bond. Carbonyl compound (IV) is produced. In some cases, the β-hydroxycarbonyl compound ([1) and the carbonyl compound (1) react in the presence of a base catalyst to produce a trimer or higher polymer of the carbonyl compound (+). Sometimes.

Here, representative examples of the above compound (1) include acetaldehyde, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Among them, acetone is preferable from an analytical point of view.

According to the first aspect of the present invention, the presence of basic sites is reduced by the formation of the β-hydroxycarbonyl compound (III) when the particle material and the carbonyl compound (1) are brought into contact with each other.
- The presence of acid sites can be determined by the formation of the double-bonded carbonyl compound (IV), and it is also possible to determine the approximate abundance ratio of basic sites and acid sites based on the ratio of these two compounds. However, since this method is catalyzed by basic sites, it cannot be applied to particle materials that have only acid sites without basic sites, or particle materials that have a large excess of acid sites compared to basic sites. , and carbonyl compound (1
) to the β-hydroxycarbonyl compound (III) is a reversible reaction, so it is necessary to use a large excess of the carbonyl compound (1) in order to allow the catalytic action by the base site to proceed completely.

Furthermore, according to the second aspect of the present invention, the presence of a basic site can be detected by the formation of a carbonyl compound (1) when the particle material and the β-hydroxycarbonyl compound (I[l) are brought into contact with each other.
The presence of acid sites can be known by the formation of α, β-double bond carbonyl compounds), and it is also possible to know the approximate abundance ratio of basic sites and acid sites from the formation ratio of these two compounds. be.

There are no restrictions on particle materials to which this method can be applied, as there are in the first invention.

The particle materials for magnetic recording media to which the present invention can be applied can be broadly classified into ferromagnetic particles, abrasive powder, and other additive particles.

Examples of the ferromagnetic particles include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide particles, ferromagnetic alloy particles, hexagonal barium ferrite particles, metal carbides, metal nitrides, and the like.

The above-mentioned ferromagnetic iron oxide particles, when expressed by the general formula FeOx, have a value of
,50), magnetite (F 630at
1.33), and their solid solutions (F e O,, 1
, 33<x<1.50). Furthermore, these materials also include materials in which cobalt is doped or deposited on these ferromagnetic iron oxides for the purpose of improving coercive force.

The ferromagnetic chromium dioxide contains Ru, Sn, Te, Sb, Fe, and Ti for the purpose of improving coercive force.

Also included are materials to which at least one metal element such as V and Mn is added.

The ferromagnetic alloy particles include Fe and Co.

Ni, Fe-Co, Fe-Ni, Fe-Co-Ni, C
o-Ni, Fe-Co-B, Fe-C.

-Cr-B, Mn-B1. Mn-Al, Fe-CQ-V
etc. Additionally, Al, Si, Ti, and Cr are added for the purpose of improving various properties of these materials.

A metal element such as Mn, Cu, or Zn may be added.

Polishing powders include alumina, chromium oxide, silicon carbide,
These include corundum, diamond, garnet, and emery (main ingredients: corundum and magnetite).

Furthermore, other additive particles include polymer gel particles such as epoxy resin, polystyrene resin, benzoguanamine-formaldehyde condensation resin, contact black, channel black, roll black, disk black, furnace black, and thermal black added to the back coat layer. .

Various carbon blacks such as lamp black and CaC0+
Examples include inorganic pigments such as powder, Ba5Oa powder, ZnO powder, α-Fe, O, powder, Tie, powder 1,1tos powder, and CrtOz powder.

The aldol condensation reaction between these particle materials and a carbonyl compound having an α-hydrogen atom can be carried out in either a gas phase system or a liquid phase system.

Further, the product of the aldol condensation reaction can be analyzed by various qualitative and quantitative analysis methods such as gas chromatography (GC), GC/mass spectrometry, liquid chromatography, and high performance liquid chromatography.

[Effect]

Now, considering the case where acetone is used as a carbonyl compound containing an α hydrogen atom, the aldol condensation reaction can be explained as follows.

First, the α-position hydrogen atom of one of the two molecules of acetone is extracted as a proton by the catalytic action of the basic point present on the surface of the particle material for magnetic recording media. It reacts nucleophilically with the carbonyl carbon of acetone to produce diacetone alcohol through an intermediate, and the base site is regenerated.Next, this diacetone alcohol reacts with the acid present on the surface of the particle material for magnetic recording media. It is dehydrated by the catalytic action of the point, and becomes mesityl oxide stabilized by -c=c-c-o type resonance.

The above reaction can be expressed as follows.

As is clear from the above reaction mechanism, according to the evaluation method according to the present invention, products corresponding to the catalytic actions of the basic sites and acid sites of the particle material for magnetic recording media are obtained. For this reason, for example, even if materials are determined to have the same isoelectric point using conventional evaluation methods, from a more microscopic perspective, it is difficult to determine how strong the basic and acidic points are in balance. Differences may become apparent.

It is believed that basic sites and acid sites act as adsorption sites for other material particles. For example, the basic points and acid points present on the surface of the ferromagnetic powder act as adsorption points for various additives including the binder, dispersant, and abrasive to be kneaded. Therefore, if the combination of various particle materials used in magnetic paints and backcoat layer paints is appropriately selected based on the information obtained by applying the present invention, properties such as dispersibility and surface properties can be improved. becomes possible.

[Example] Hereinafter, preferred embodiments of the present invention will be described based on experimental examples.

In this example, various magnetic powders were selected as particle materials for magnetic recording media, and their basic sites and acid sites were experimentally evaluated. First, Table 1 lists the magnetic powders A to J used.

(Leaving space below) Example 1 In this example, acetone was applied to magnetic powder A to magnetic powder J shown in Table 1, and diacetone alcohol was produced by the catalytic action of the base site and diacetone alcohol was produced by the catalytic action of the acid site. This is an analysis of mesityl oxide.

First, 0.5 to 1 g of each magnetic powder shown in Table 1 and 40 g of acetone were weighed into a 100 mff1 Erlenmeyer flask with a stopper, the flask was sealed, and the flask was ultrasonically dispersed. Next, the Erlenmeyer flask was placed in a constant temperature water bath adjusted to 25±0.05℃ for 15 minutes.
Shake for ~20 hours. Approximately 2 ml of the obtained dispersion was placed in a 2 ml glass syringe equipped with a disposable membrane filter, and extrusion filtration was performed to obtain a transparent filtrate. This filtrate was analyzed by gas chromatography. The analysis was carried out using a Shimadzu gas chromatograph GC-8A equipped with a 3 m long PF, G-20 column and a hydrogen flame ionization detector, with a nitrogen gas flow rate of 40 mJ! /
Minutes.

The temperature was 180'C.

A typical gas chromatograph obtained by such an analytical method is shown in FIG. In this figure, the vertical axis represents the relative peak height, and the horizontal axis represents the retention time (minutes). Retention time 0
．． The peak at 83 minutes is unreacted acetone, the peak at 3.05 minutes is diacetone alcohol, which corresponds to a compound dimerized by acetone causing an aldol condensation reaction due to the catalytic action of the base site, and the peak at 1.63 minutes is diacetone alcohol. Mesityl oxide is produced when acetone alcohol is dehydrated by the catalytic action of acid sites.The peak at 8.34 minutes is 4,6-hydroxy-4,6-dimethyl- produced when diacetone alcohol undergoes an aldol condensation reaction with acetone. Identification of each of these compounds, which are 2-heptanone (corresponding to the trimer of acetone), was performed based on comparison with the retention time of a standard substance and mass spectra.

Example 2 In this example, diacetone alcohol was applied to magnetic powder A to magnetic powder J shown in Table 1, and acetone produced by the catalytic action of the base site and mesityl oxide produced by the catalytic action of the acid site were combined. This is an analysis of

The experiment was conducted in accordance with the method described in Example 1, except that the water temperature in the constant temperature water bath was 30.0±O, OSoC.

The results of Example 1 and Example 2 are summarized in Table 2.

(The following is a blank space) Table 2 According to the method for evaluating surface physical properties according to the present invention, it is possible to evaluate microscopic surface physical properties that could not be captured by conventional methods. For example, we previously worked with the Bulletin of Chemical Society of Japan (Bull, Chew, Soc.

Jpn, ) Volume 53, No. 9, Page 2683 (19
(1986) announced that 1-Fe, O, is more acidic than ex-Fe, O, as a whole. But the second
Looking at the amount of diacetone alcohol produced or the amount of acetone produced, which is an indicator of the height of base site activity in the table, y-
Fe□0. The base site activity of (magnetic powder B) is rather α-F.
On the other hand, when looking at the amount of mesityl oxide produced, which is an indicator of high acid site activity, it is higher than that of etus (magnetic powder D).

The acid site activity of (Magnetic Powder B) is higher than that of α-Fezes (Magnetic Powder D), that is, in r Fears, both the base site activity and the acid site activity are high, and furthermore, as a whole, α-Fe, O, More acidic is y-Fear
It can be concluded that this is because the acid site activity of s exceeds the base site activity.

Note that Table 2 shows that overall values in Example 2 are higher than in Example 1, and this is thought to be due to the equilibrium constant of each elementary reaction. Furthermore, magnetic powder A, i
Even if neither acidic nor basic sites are detected by the method of Example 1, such as fibrous powder C or magnetic powder G, they may be detected by the method of Example 2, so the evaluation method depends on the physical properties of the magnetic powder. It is preferable to select it appropriately depending on the situation.

〔Effect of the invention〕

As is clear from the above description, according to the evaluation method according to the present invention, it is possible to evaluate the surface physical properties of a particle material for a magnetic recording medium more microscopically than before.

This makes it possible to know in more detail the interaction of various particulate materials with solvents, the affinity between particulate materials, etc., and improves reproducibility during material design and manufacturing. Particularly in recent years, various polar groups have been introduced into binders and other additives for the purpose of improving various properties such as dispersibility and surface properties. It is extremely useful for understanding the interaction between the base and acid sites.

Another possible application of the evaluation method of the present invention is to diagnose the deterioration of ketone solvents used in preparing magnetic paints. Ketone solvents tend to polymerize through aldol condensation as they disperse material particles such as magnetic powder. The ketone solvent, which has been polymerized in this way, is difficult to evaporate during the coating and drying process of magnetic paint and back coat layer paint, and remains in the magnetic layer and has no adverse effects.By applying the evaluation method of the present invention, , it becomes possible to discover the deterioration of ketone solvents and avoid the above-mentioned adverse effects.

As another application, it is also possible to evaluate cases where aldol condensation of ketone solvents is actively used. For example, JP-A-62-248128 discloses that a condensation product of cyclic ketones has a lubricating effect. Therefore, if cyclohexanone is used as a solvent when preparing magnetic paint, etc., and the progress of the aldol condensation reaction is confirmed by the evaluation method of the present invention while dispersing the material particles, the lubricant can be separated by selecting an appropriate degree of condensation. It is possible to obtain a magnetic paint etc. that exhibits lubricity even without mixing it with the paint.

[Brief explanation of the drawing]

FIG. 1 shows a typical gas chromatography duram in which the present invention is applied to magnetic powder.

Claims (2)

[Claims] (1) A carbonyl compound having an α-hydrogen atom is brought into contact with a particle material used in a magnetic recording medium, and a β-hydroxycarbonyl compound is produced by an aldol condensation reaction of the carbonyl compound, and the β-hydroxycarbonyl compound is dehydrated. 1. A method for evaluating surface properties of particle materials for magnetic recording media, which comprises analyzing α,β-double bond carbonyl compounds produced by the reaction. (2) The β-hydroxycarbonyl compound and the particle material used in the magnetic recording medium are brought into contact, and the carbonyl compound having an α hydrogen atom, which is produced by a reverse aldol condensation reaction of the β-hydroxycarbonyl compound, and the β
- A method for evaluating the surface properties of a particle material for a magnetic recording medium, which comprises analyzing an α,β-double bond carbonyl compound produced by a dehydration reaction of a hydroxycarbonyl compound.