JPS60122712A - Surface treated needlelike particle containing iron carbide and magnetic coating composition containing said particle - Google Patents

Abstract

PURPOSE:To provide an improved squareness ratio to needlelike particles contg. iron carbide and a magnetic coating composition by treating the surfaces of the particles with a specified surface treating agent and combining the treated particles with a binder contg. a film forming resin as the principal component to prepare said magnetic coating composition. CONSTITUTION:Needlelike particles contg. iron carbide are suspended in a solvent so that they are contained by <=10wt%, and 0.01-3wt% surface treating agent is added to the suspension and stirred to form films on the surfaces of the needlelike particles. By this surface treatment the squareness ratio of the particles is improved. A silane coupling agent, long-chain org. carboxylic acid, its salt, phosphoric ester, sorbitan fatty acid ester or org. sulfonate is used as the surface treating agent. The needlelike particles are combined with a binder contg. a film forming resin as the principal component to prepare a magnetic coating composition.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to surface-treated sword-shaped particles containing iron carbide and a magnetic coating composition comprising the sword-shaped particles.

The present inventors have filed a patent application (Japanese Patent Application No. 58-171765) regarding acicular particles containing iron carbide, their manufacturing method, and uses.
No.).

The acicular particles containing iron carbide have excellent magnetic properties such as high coercive force, and have magnetic field orientation.

However, when processed into a magnetic recording medium such as a magnetic tape, the squareness ratio was about 0.7, leaving room for improvement.

An object of the present invention is to provide acicular particles containing iron carbide that provide a magnetic recording medium that exhibits an excellent squareness ratio when processed into a magnetic recording medium, and a magnetic coating composition containing the same. It's about doing.

The above-mentioned purpose is to produce a magnetic paint consisting of acicular particles containing iron carbide by surface-treating them with a surface-treating agent, and acicular particles subjected to the surface treatment in this manner and baingu mainly composed of a film-forming paint. This can be achieved by a composition.

This makes it possible to obtain a magnetic recording medium having an improved squareness ratio and therefore a high coercive force and a high residual magnetic flux density.

In the present invention, the iron carbide-containing acicular particles to be surface-treated are those described in Japanese Patent Application No. 58-171 Flo 5 filed by the present applicant. That is, the acicular particles have an average axis ratio (major axis/minor axis) of large particles of usually 3 or more, preferably 3 to 20, and an average particle diameter (long sleeve) of usually 2 μm.
- or less, preferably 0.1 to 2 μm, optimally 0.1 to 1 μm
．． It is 0 μ so. Here, - large particles are:
These are particles that can be observed and identified using an electron microscope (3,000 to 6,000 times magnification).

Further, the iron carbide contained in the acicular particles is Fe5C2,
FezCs FezoCs (Fe, zC), each alone or a mixture of two or more, with FexC (2≦x3
) is appropriate. Generally, the presence of iron carbide is
The X-ray diffraction pattern of iron carbide represented by a known chemical formula (for example, ^STM X-Ray
This can be confirmed by comparing it with the information written in the Powder Date File. However, the differences in the X-ray diffraction patterns between individual iron carbides are
Since the amount is small, it is possible to confirm the main component iron carbide, but it is almost impossible to confirm other iron carbides that exist in trace amounts. However, the small amount of iron carbide that coexists can be ignored because it has no effect on magnetic properties and the like. In a preferred embodiment, an X-ray diffraction pattern (with a surface spacing of 2.2 in the turn)
8.2.20.2.08.2.05 and 1,9zX. Such iron carbide is considered to correspond to Fe5C2, and Fe2C1Fe2oC-(Fe2,2C
), Fe, C, etc. may coexist.

Further, the content of iron carbide in the acicular particles of the present invention is 2
When it is 0% by weight or more, the coercive force of the acicular particles is preferably 4500 C or more, and when it is 50% by weight or more, the coercive force is 8
It is more preferable to have a temperature of 500C or more. As mentioned above, it is almost impossible to confirm all types of iron carbide contained, and furthermore, it is generally impossible to isolate them, so the amount of iron carbide present cannot be determined. Determine the chemical formula for the main component iron carbide that can be confirmed, and if necessary,
Chemical formulas are determined for components other than iron carbide, such as Fe5
Os, etc. can be determined by combining these chemical formulas, elemental analysis, and scorching heat increase.

Further, the acicular particles include not only those containing only iron carbide as a component, but also those containing other components.

Components other than iron carbide include components derived from manufacturing raw materials,
For example, those derived from the manufacturing process such as iron oxide, such as elemental carbon, and other JR compounds such as copper, magnesium, manganese, nickel, cobalt, etc. derived from additives to manufacturing raw materials. and/or oxides of silicon and the like.

A preferred method for preparing the acicular particles is to contact acicular iron oxyhydroxide or acicular oxide with CO or a mixture thereof with H2.

Here, the acicular iron oxyhydroxide or acicular iron oxide usually has an average axial ratio of 3 or more, preferably 3 to 20, and the average particle diameter (long axis) is usually 2 μm or less. , preferably 0
．． 1 to 2 μm, optimally 0.1 to 1.0 μm. As will be described later, the average axial ratio and average particle diameter of the acicular particles produced are slightly smaller than those of these raw materials, but there is almost no difference, and this is usually the case for the acicular particles of the present invention in general. This is because something like this is suitable.

The acicular iron oxyhydroxide is preferably acicular α-Fe001 (5'-site) or acicular γ-Fe00H (lepidocrocite), and the acicular iron oxide is acicular EI Fe203 (hematite), acicular γ -Fezes (magnetite) or acicular Pe3o.

(Magnetite) is preferred.

The particles obtained in the present invention are averagely uniform acicular particles when observed with an electron microscope, and have the same shape as the acicular particles of the raw material acicular iron oxyhydroxide or acicular iron oxide. This is a vestigial particle, and this exists as a large particle. Further, it is clear that the obtained acicular particles contain carbon according to elemental analysis, and further contain iron carbide according to the X-ray diffraction pattern. X#1 diffraction pattern has interplanar spacings of 2.28.2, 2012, 08.2.05 and 1.9
2A is shown. Such a pattern corresponds to Fe5C2,
The iron carbide of the present invention usually mainly consists of Fe5C2, but Fe2C, FezoCs (Fe2.zc), Fe5C
etc. may coexist. Therefore, the iron carbide contained in the acicular particles of the present invention is appropriately expressed as FexC (2≦×<3).

In addition, when carbonization is incomplete, the acicular particles obtained in the present invention also contain iron oxides, mainly Fe*O<.

Generally, for iron oxide, Fe01FeJ< and γ-
Fetu3 is structurally related, and the oxygen atoms in all three have a cubic close-packed structure, and the actually existing Fe5On varies within these widths, so the above iron oxide is It is appropriate to express it as Fe0y (1<y≦1.5).

The resulting acicular particles also contain iron carbide or, in some cases, iron oxide, but when referring to the elemental analysis values for C, H, and N, it is usually determined by the chemical formula of iron carbide, which is confirmed by the X-ray diffraction pattern. W, contains carbon in excess of the amount of carbon.

It is unclear whether such excess carbon exists in combination with iron or as free carbon. In this sense,
Elemental carbon may be present in the resulting acicular particles.

The particles obtained are therefore - acicular particles consisting essentially of iron carbide or of iron carbide, iron oxide and/or elemental carbon, whose shape as large particles has an average axial ratio of 3 or more; .

Further, the average axial ratio and average particle diameter of the obtained acicular particles are slightly smaller than those of the raw material acicular iron oxyhydroxide or acicular iron oxide, but there is almost no difference. Therefore, the average axial ratio of the acicular particles obtained by this production method is usually 3 or more, preferably 3-2o, and the average particle diameter (long axis) is usually 2μ or less, preferably 0.1-2o. 2μ-1 optimally 0.1-1.0
It is μ-kaku.

In the present invention, the surface treatment agent includes (1) a silane coupling agent, such as γ-7 minobrovir F-ethoxysilane, N-(β-7minoethyl)-1-7 minoprobyltrimethoxysilane, γ-ureido Propyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethylsilane, γ-methacryloyloxibyltrimethoxysilane, γ-norcaptopropyltrimethoxysilane , γ-chloropropyltrimethoxysilane,
Vinyltri(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrichlorosilane, vinyltriacetoxinrane, etc.

(2) Long-chain organic carboxylic acids or salts thereof, such as fatty acids having 12 to 20 carbon atoms such as oleic acid, coconut oil fatty acids, and sodium oleate, or their alkali metals (N
(a-K-N II, etc.) salts or alkaline earth metal (calcium, magnesium, etc.) salts (3) Phosphoric esters, such as lecithin, -7Aku [manufactured by Toho Chemical Co., Ltd.], etc. (4) Sorbitan fatty acids esters, such as polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monosterate, polyoxyethylene sorbitan monolaurate, etc. (5) organic sulfonates;
Examples include sodium dialkylsulfosuccinate and sodium alkylbenzenesulfonate.

In the present invention, the method of treating the acicular particles with a surface treatment agent can be carried out as appropriate. For example, acicular particles containing iron carbide are generally suspended in a solvent to a weight of 10 weight or less. A method in which a predetermined amount of a treatment agent is added to the suspension and stirred to cause the treatment agent to be adsorbed onto the surface of the acicular particles to form a coating layer; Examples include a method in which a coating layer is formed by spraying an agent. The amount of the surface treatment agent is generally preferably 0.01 to 3% by weight based on the iron carbide-containing acicular particles. When the amount of the processing agent is within this range, the effects of the present invention can be achieved significantly, and there is less possibility that the processing agent will leak into the magnetic recording medium and adversely affect various properties, so it is preferable.

The present invention also relates to a magnetic coating composition comprising acicular particles containing iron carbide whose surface has been treated with the above-mentioned surface treatment agent and a binder mainly consisting of a film-forming resin. Magnetic paint is manufactured by a known method, for example, by dispersing the above-mentioned acicular particles together with a binder in an organic solvent. At this time, a dispersant, lubricant, abrasive, antistatic agent, etc. are added as necessary. be able to. As the binder, conventionally known thermoplastic resins, thermosetting resins, reactive resins, etc., and mixtures thereof are used.

As a thermoplastic resin, the softening temperature is 150°C or less, the average molecular weight is toooo~200000, and the degree of polymerization is about 200~
2,000 or so, such as vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic ester styrene copolymer,
Methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, Polyvinyl butyral, cellulose derivatives (
(cellulose acetate butyrate, cellulose guiacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene butadiene copolymer, polyester resin, chlorovinyl ether acrylate copolymer, amino resin, various synthetic rubber-based Thermoplastic resins, mixtures thereof, etc. are used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin,
Alkyd resin, silicone resin, acrylic reactive resin,
Epoxy-polyamide resins, mixtures of high molecular weight polyester resins and incyanate prepolymers, mixtures of methacrylate copolymers and noisocyanate prepolymers,
These include mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanates, polyamine resins, and mixtures thereof.

These binders may be used alone or in combination;
Other additives may be added. The mixing ratio of the acicular particles and the binder is 1 part by weight of the acicular particles to 100 parts by weight of the acicular particles.
It is used in an amount of 0 to 400 parts by weight, preferably 30 to 200 parts by weight.

Dispersants include fatty acids with 12 to 18 carbon atoms (RI C00
H1R1 is an alkyl group having 11 to 17 carbon atoms); a metal soap consisting of an alkali metal (Li, Na, K, etc.) or an alkaline earth metal (Mg, Ca, Ba, etc.) of the above-mentioned fatty acids; lecithin, etc. are used. .

In addition to these, higher alcohols having 12 or more carbon atoms and sulfuric esters can also be used. These dispersants are added in an amount of 1 to 20 parts by weight based on 100 parts by weight of the binder.

As a lubricant, silicone oil, graphite, molybdenum disulfide, tungsten disulfide, carbon number 12-16
Fatty acid esters consisting of a monobasic fatty acid and a monohydric alcohol with 3 to 12 carbon atoms, a monobasic fatty acid with 17 or more carbon atoms, and a total of 21 to 2 carbon atoms in the fatty acid.
A fatty acid ester consisting of a monohydric alcohol consisting of 3 can be used. These lubricants are added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the binder.

As the abrasive, commonly used materials such as fused alumina, silicon carbide, chromium oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite) are used.

These abrasives have an average particle size of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm. These abrasives are added in an amount of 7 to 20 parts by weight based on 100 parts by weight of the binder.

Natural surfactants such as saponins as antistatic agents;
Anionic surfactants such as alkylene oxide, glycerin, and glycidol; higher alkylamines,
Quaternary ammonium salts, pyridine and other heterocycles,
Cationic surfactants such as phosphonium or sulfoniums; Anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric ester groups; Sulfuric acid of amino acids, amine/sulfonic acids, amine/alcohols Alternatively, amphoteric activators such as phosphoric acid esters are used. These antistatic agents may be added alone or in combination. Although these are used as antistatic agents, they are sometimes applied for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

The present invention will be described below with reference to Examples.

Reference Example 1 2 g of needle-shaped lepidocrocite particles with an average particle diameter of 0.7 μis (long axis) and an average axial ratio of 10 were placed in a porcelain boat and inserted into a tube furnace, and after replacing the air by flowing nitrogen, The temperature was raised to 340°C, and at that temperature, a mixture of G, O/H2 (30/70 volume ratio) was flowed at a flow rate of 751 per minute, and treated for 5 hours, and then cooled to room temperature to form a black needle. A powder was obtained.

The X-ray diffraction pattern of the product is ^STM X-Ray
Powder Data File 20-509 F
It matched with e5Cz IronCarbide. Table 1 shows the interplanar spacing (d^) and intensity ratio (1/I) of the peaks in the pattern.
Fe5C in r Data File 20-509
A comparison with those of 2Iron Carbide is shown.

Table 1 Reference Example I Fe5C2 (ΔSTM) 2.653 0.10 2.52 0.23 2,506 0.102.41
0.21 2.42+ 0.152.28 0.36
2.287 0.202.20 0,51 2,206
0.452.190 0.30 2.115 0.40 2. +12 0.252.07
8 0,84 2.080 0.702.05 1,0
0 2.049 1,002.015 0.94 2.
011 '0.302.010 (1,4+1 1.92 0,28 1.950 0.451.910
<0.05 1.821 (1,20 1,800,361,8140,25 Note that no Fe3O4 peak was detected.

The magnetic properties of the thus obtained powder were measured using a sample vibrating magnetometer model VSM 3 manufactured by Toei Kogyo Co., Ltd. at a measurement magnetic field of 15 kOe. The results are shown below.

Coercive force (He) 8780e Residual magnetization (σr) 54.7 e-ring u/g Saturation magnetization (σs) 134.4 e-u/g Examples 1 to 6 and Comparative Example 1 Obtained from Reference Example 1 20g of acicular particles to 20 tons
0 g of the suspension, 0.5 g of the surface treatment agent listed in Table 2 was added thereto, stirred for 1 hour, passed through the mouth, and dried under reduced pressure at room temperature to prepare surface-treated acicular particles.

Acicular particles without surface treatment (Comparative Example 1) and acicular particles with various surface treatments were prepared into paints using the following formulations.

Acicular particles 18.25 g Vinyl chloride-vinyl acetate copolymer 5,25° dioctyl 7-talate 1,00° lauric acid 0.28 Toluene 15.0 g Methyl isobutyl ketone 15.0.

Apply the prepared paint with a doctor knife (gap 100μl11)
It was coated on a polyethylene terephthalate film, oriented using a repulsive magnet method, and dried. The magnetic properties of the film thus obtained were measured in the direction perpendicular and parallel to the orientation treatment direction to determine the magnetic field orientation (orientation degree). The results are shown in Table 2.

In addition, in the table, A: γ-Glycidoxypropyltrimethoxysilane B Nioleic acid C: F-7 Atk B^-600 D = Polyoxyethylene sorbitan monooleate E Sodium dioctylsulfosuccinate F Sodium nioleate Table 2 Surface treatment agent Coercive force Residual magnetism Squareness ratio (Oe) East density (, f Tsusun Example I A, 985 2415 0.752 B
963 2350 0,73 3 C97823800,74 4D 947 2320 0,72 5 E 942 2310 0.72 6 F 954 2330 0.72 Comparative Example 1 None 930 2250 0.70 (or more) Patent applicant Daikin Industries, Ltd. agent Patent attorney Iwao Tamura

Claims (4)

[Claims] (1) Acicular particles containing iron carbide that have been surface treated with a surface treatment agent. (2) The particles according to claim 1, wherein the surface treatment agent is a silane coupling agent, a long-chain organic carboxylic acid or a salt thereof, a phosphoric acid ester, a sorbitan fatty acid ester, or an organic sulfonate. (3) A magnetic coating composition comprising acicular particles containing iron carbide that have been surface-treated with a surface treatment agent and a binder mainly consisting of a film-forming resin. (4) The surface treatment agent is a silane coupling agent, a long-chain organic carboxylic acid or its salt, or a phosphoric acid ester. The composition according to claim 3, which is a sorbitan fatty acid ester or an organic sulfonate.