JPS5994803A - Clad magnetic powder layer - Google Patents

Abstract

PURPOSE:To provide a magnetic powder layer having excellent anti-rust property, still stability and durability, by allowing polyamide resin having a reactive functional group and a hardening agent having a group capable of making reaction with the reactive functional group of the polyamide resin so as to harden the resin through bridge formation, in such a manner as to coat the surface of the magnetic powder layer by a film of the hardened polyamide resin. CONSTITUTION:Magnetic powder to which this art pertains may be oxide magnetic powders such as gamma-Fe2O3, metallic magnetic powders such as of Co-Ni-P alloy, and so forth. The polyamide resin having a reactive functional group preferably has a chemical composition as shown by the attached Figure. In this Figure, X<1>-X<3> represent substances which may be same or different. The substances X<1>-X<3> contain either one of hydrogen atom, hydroxy group, amino group, alkyl group, carboxyl group, alkenyl group, and allylic group. At least one of these substances X<1>-X<3> should contain a reactive functional group. Isocyanate compounds, epoxy compounds, acidic anhydride, lactone or the like can be used as the hardening agent having a group capable of making reaction with the reactive functional group of the polyamide resin.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of magnetic powder with excellent dispersibility, and in particular provides a magnetic recording magnetic powder with excellent rust prevention and still stability.

Metal magnetic powder such as iron and cobalt, Fe-Ni, Fe-C
Alloy magnetic powders such as o-Ni have better magnetic properties than oxide-based magnetic powders, but they are used for magnetic recording.
Particles with a particle size of microns or less have poor dispersibility, are easily oxidized in the air and rust, tend to deteriorate saturation magnetization over time, and tend to lack storage stability and methyl stability, that is, still image stability.

In order to eliminate such drawbacks, as described in JP-A No. 50-4122, magnetic powder is pretreated with a compound having free isocyanate groups and then treated with a functional compound containing hydrogen atoms. A method of adding a chemical equivalent or more of a compound having one group to the above-mentioned incyanate compound and reacting it to form a thermoplastic urethane compound, and adding a binder thereto. As described, the magnetic powder is combined with one or two free isocyanate groups.
After pretreatment with a compound having two functional groups containing hydrogen atoms, a chemical equivalent or more of the isocyanate compound is reacted with the isocyanate compound to form a thermoplastic urethane.
' A method of using a compound and blending a binder with it, ■ Also, a method of forming a silicone oil film on the surface of metal magnetic powder as described in JP-A No. 52-155398, ■ Further , A method of providing an outer skin layer made of silicone oil hardened with an amine compound on the surface of metal magnetic powder described in JP-A No. 53-5797;
A method of preparing a magnetic paint by mixing a second solvent, which is a poorer solvent, with a system in which magnetic powder is cross-dispersed with a polymer compound and a good solvent for the polymer compound, as described in Publication No. 55972. ,It has been known.

However, in methods (1) and (2) above, magnetic powder is coated with incyanate and then added or cured with OH or NH-compounds, but the strength of the coating is still not sufficient and the tape performance is Also, the methyl properties are not stable.

In methods ① and ②, the compound that adheres to the magnetic powder (metal powder) is limited to silicone oil, and the binding between the silicone polymer and the binder in the magnetic paint tends to be insufficient. Still stability is not very high. ■What is the method?

As a method for more efficiently adhering a polymer compound to the surface of a magnetic material, it is effective in terms of dispersibility, but since a curing process is not performed, the strength of the resulting film is weak, and the surface of the magnetic material is /Poetry is not good5.Furthermore, when producing a magnetic recording medium (tape) using the magnetic powder obtained by applying each of the above-mentioned known techniques, it is possible to improve the durability and runnability of the recording medium. In order to improve film strength, EB is improved by adding lubricants and abrasives (alumina, etc.) to the magnetic paint composition, increasing the amount of curing agent in the binder, and performing temperature treatment after recording media are manufactured. Although polymerization-based methods are used, the strength of adhering magnetic powder, especially metal magnetic powder (metal magnetic powder and alloy magnetic powder) to the binder is weak (and the work process itself is difficult).

The present invention was made in order to eliminate the above-mentioned drawbacks of conventional magnetic powder for magnetic recording media, and to provide a magnetic powder that has better rust prevention properties, still stability, and durability. The purpose is to

That is, in the present invention, a polyamide resin having a reactive functional group is adhered to or adsorbed on the surface of magnetic powder in advance, and then the polyamide resin is immersed in a curing agent having a group capable of reacting with the functional group. The present invention was achieved based on the knowledge that the polyamide resin coating on the outside of the powder can be cured or crosslinked with a curing agent.

The coated magnetic powder according to the present invention is crosslinked when the polyamide resin is cured and crosslinked by the reaction between the polyamide resin having a reactive functional group and a curing agent having a group capable of reacting with the reactive functional group in the polyamide resin. The surface of magnetic powder is coated with a polyamide resin film.

The magnetic powder used in the present invention includes γ-Fe2O3, C
o Adhesion - Fe20B, Fe50. , coo Fe
,04, Oxide magnetic powder such as CrO2, Fe powder, Ni powder, Co powder, Co-NIF-alloy, Fe-Co-N
i-alloy, Fe-Mn-Zn alloy, Fe-Co-
NIOr alloy, Fe-CoNiP alloy, Fe
-NiZn alloy.

Known metal magnetic powders such as Nl-Co alloys can be used.
No. 8372, Special Publication No. 1972-22062, Special Publication No. 1972-
No. 22513, Special Publication No. 1977-28466, Special Publication No. 1973
-38755, Special Publication No. 47-4286, Special Publication No. 1977
-12422, Special Publication No. 17284, Special Publication No. 47-17284, Special Publication No. 17284
7-18509, Japanese Patent Publication No. 47-18573, US Patent No. 3,026,215; US Patent No. 3,031,341; US Patent No. 3,100,194; US Patent No. 3,242,005
No. 3,389,014; British Patent No. 752,6
No. 59: No. 782,762; No. 1,007,32
No. 3; French Patent No. 1.107,654; West German Published Patent No. 0LS 1.281,334 and other specifications and publications.

A polyamide resin having a reactive functional group has one reactive functional group, for example, a group having at least one reactive hydrogen atom such as -NH2, -NH-1-0B, etc., in the main chain, side chain, or end of the polymer. A compound having a structure represented by a polyamide resin having such a reactive functional group (where xl, x2゜X3 are a hydrogen atom, a hydroxyl group, an amino group, an alkyl group, a carboxyl group, an alkenyl group, respectively) or aryl group, which may be the same or different,
At least one contains a reactive functional group, and po represents a repeating unit of a polymer having an amide bond. ) is preferred.

Here, nine is a positive real number of 600 or less, and is a positive real number such that the average molecular weight of the entire polymer is 30,000 or less.

Among the above compounds, compounds having the structure shown below are more preferable. However, m is a real number of 20 or less, n is a real number of 600 or less, R1 and R2 are organic divalent groups, and may be substituted with -NIL3R4 or -OH.

X4. X6 is H, alkyl, substituted alkyl (e.g. -NR'R', -0H), aryl, one of which has H or a substituted alkyl or substituted aryl group having a reactive functional group, R3, R4 represents H, an alkyl group or an aryl group.

A more preferable compound is a compound having a structure represented by
represents a repeating unit of a polymer having an amide bond,
n is a real number of 600 or less, and the overall average molecular weight is 30.0
It is a positive real number that is less than or equal to 00. Also, A, A'
is an organic divalent group, N, S, 0, etc. may be included in the main chain, X6 and X7 are reactive functional groups, -
It represents OH or -NR'R' (R3 and R4 represent H, an alkyl group or an aryl group).

Examples of polyamide 9 resins having such reactive functional groups are shown in Table 1 below.

Margins below Regarding the molecular weight or average molecular weight (hereinafter simply referred to as molecular weight) of these polyamides, if the molecular weight is less than 500, the strength of the film obtained will be weak and curing will not be sufficient, and if it is more than 30,000, the solubility in solvents will be low. It is preferable to use a compound having a molecular weight of 500 or more and 30,000 or less, and m in the exemplary compound of Cloth-1 is a positive real number that satisfies these conditions.

More preferably, the molecular weight is in the range of 500 to 15,000.

Examples of the curing agent having a group capable of reacting with the reactive functional group of the polyamide resin include incyanate compounds, epoxy compounds, acid anhydrides, lactones, and others.

Examples of isocyanate compounds include those shown in Table 2.

Examples of the margin x4 xy-based compounds include the compounds shown in Table 3 below.

Margin Table 3 Below: Examples of acid anhydrides include (where n+: 2=60:40), and examples of lactones include:

In addition, reactive functional groups such as those mentioned above (-Nco, ON,
9H2-H00n o, etc.)"" There may be several hexagonal numbers.

The average molecular weight of the curing agent is preferably 30,000 or more, and if 9 is greater than 30,000 in the exemplary compound, the solubility will be poor, and the reactive functionality possessed by the compound used as a curing agent Groups such as -CH-0H2-Co, eg -NCOl\07'-Co10, lactone ring, etc., may be present two or more times in the compound. Further, the molecular weight or average molecular weight (hereinafter simply referred to as molecular weight) of the curing agent is preferably 30,000 or less; Preferably, it is a positive real number within the following range. If the molecular weight of the curing agent exceeds 30,000, the coating film formed will become too thick and the entire magnetic powder particles will become large, which is not preferable. For example, it is disadvantageous for high-density recording. Also,
When the molecular weight is less than 100, reaction residues tend to remain in the coated magnetic powder, which deteriorates the performance (especially storage stability) of the magnetic recording medium.
may deteriorate. Among the curing agents, incyanate-based compounds and epoxy-based compounds are preferred, and a coating film formed using an incyanate-based compound is particularly preferred in terms of preservability and strength.

The coated magnetic powder according to the present invention is produced by immersing the magnetic powder to be coated in a solution of polyamide resin dissolved in an organic solvent, then drying or filtering, and after drying, the reactive functional groups in the resin are applied to the surface of the magnetic powder. One method is to add a curing agent having a group capable of reacting with the magnetic powder, and to cure the magnetic powder by crosslinking the functional groups of the polyamide resin that coats the surface of the magnetic powder. In addition, when attaching polyamide resin to the surface of magnetic powder, 4
A well-known so-called coacervation method in which a poor solvent is mixed into a system in which uncoated magnetic powder is mixed and dispersed in a solution of polyamide resin and its good solvent, and a solution of polyamide resin dissolved in an organic solvent is mixed. ``Microcapsule'' published by Sankyo Publishing Co., Ltd. (author: Tamotsu Kondo, Masumi Koishi) ) can be used. Furthermore, it goes without saying that not only these methods but also various other methods can be used.

The coated magnetic powder according to the present invention is (1) dispersed in advance in a polymer (polyamide resin) having a reactive functional group, so that the magnetic powder is well dispersed and a polymer coated powder with good dispersibility can be produced. (2) Because of the curing process, a polymer coating film with better strength than the ferromagnetic powder coating film obtained by conventional methods can be obtained. ■It is also possible to form a coating film entirely in a solvent system, and the workability is good. (2) Furthermore, by using the coated magnetic powder of the present invention, a magnetic recording medium with good durability can be obtained. ■Also. A magnetic recording medium with good oxidation resistance can be obtained. Furthermore, the coated magnetic powder according to the present invention can be used in magnetic recording media, magnetic paints, etc. due to its good dispersibility.
Can be used for magnetic fluids, etc.

Hereinafter, the present invention will be specifically explained with reference to Examples, Comparative Examples, Application Examples, and Comparative Application Examples. In Examples, Comparative Examples, Application Examples, and Comparative Application Examples, "parts" are "parts by weight."
shall mean.

Example 1 100 parts of metal magnetic powder was mixed with 1.5 weight coefficient -1°A (
1) Exemplary compound Tomide #225 solution (toluene/
After dispersing in 670 parts of THF=9575), further n
- Adding 340 parts of hexane and depositing Thomaite 8#225 on the surface of the magnetic powder by a coacervation method, further adding a solution of 3.4 parts of toluylene diisocyanate/60 parts of 7L-hexane to this solution, Heat at 50C for 1 hour. The solution thus obtained is filtered, the resulting residue is dried in a nitrogen atmosphere, and the coated magnetic powder obtained is A.
Let it be I.

Example 2 100 parts of metal magnetic powder was added to 1.5 parts of Tomai 1 by weight.
”#220 solution (methylene chloride/toluene = 70:30
), and after adhering to the polymer, it was filtered and the resulting magnetic powder was redispersed in mineral oil (Isopar) -300M, after which a solution of 22 parts of toluylene diisocyanate/60 parts of Isopar was added, and then, This solution was heated at 50C for 1
After heating for a period of time, the magnetic powder is filtered, washed with 1-hexane, and then dried in a nitrogen atmosphere. The thus obtained coated magnetic powder was designated as 應2.

Examples 3 to 6 Four types of 100 parts of metal magnetic powder were prepared, and each metal magnetic powder was applied to polymers (a), (b), (C), and (d).
) fa) (average molecular weight approximately 1,500) (average molecular weight approximately 3,000 > (average molecular weight approximately 1o,000) and (average molecular weight approximately 5,000) 02 weight ratio methanol/methylene chloride (80/20
) After dispersing in 400 parts of the solution and adhering the polymer, the magnetic powder was filtered out, the obtained magnetic powder was redispersed in 300 ml of Isopar, and then 2 parts of toluylene diisocyanate/60 parts of Aizuno was added to this dispersion. The solution is gradually added, the resulting solution is heated at 50C for 1 hour, and the resulting magnetic powder is filtered and washed with n-hexane, and then dried in a nitrogen atmosphere. Each of the coated magnetic powders thus obtained was
, A4. A5 and A6.

Examples 7-8 Tetraisozolopyrbis(')octylphosphite)
Titanate and tetraoctylbis(ditridecylphosphite 1-)
Each titanate was dissolved in 50 parts of toluene separately, and 100 parts of metal-based magnetic powder was added to the latter solution, mixed and dispersed, filtered, air-dried, and then dried under reduced pressure at 60C to improve the surface of the powder. Magnetic powder treated with a titanate coupling agent was obtained.

This treated magnetic powder was coated with Tomide #225 in the same manner as the metal magnetic powder of Example 1, magnetic powder coated with tolylene diisocyanate was coated with A7, and coated magnetic powder was coated with the metal magnetic powder in the same manner as the metal magnetic powder of Example 2. It was set to A8.

Comparative Example 1 100 parts of metal magnetic powder was mixed and dispersed in 300 parts of lecithin toluene solution of 2 parts by weight, poured into a vat, air-dried, and dried after evaporating toluene to obtain lecithin pre-treated magnetic powder. is defined as comparison A1.

Comparative Example 2 1 weight ratio ethanol solution 2 in which tridecylamine was dissolved
1 grain size in 00d, 0.3μ, axial ratio 7, saturation magnetization σ
*Metal magnetic powder 1001 with 160 emu/y and coercive force of 1080 eelsdead was dispersed and then heated at 80C in a nitrogen atmosphere for 1 hour.

A metal magnetic powder coated with tridecylamine was obtained.

This magnetic powder was mixed with silicone oil (rKF- manufactured by Shin-Etsu Chemical Co., Ltd.).
99J) was dissolved in a 1-weight toluene solution of 200 °C, and then heated at 1500 °C for 2 hours in a nitrogen gas atmosphere to volatilize the toluene, and then allowed to cool in the same atmosphere.
Metal magnetic powder was obtained in which a tridecylamine cured film of silicone oil was formed on the powder surface. This is referred to as comparison A2.

Comparative Example 3 Metal magnetic powder 120 parts Hexamethylene diinocyanate 5 parts Lecithin
2 parts toluene
A composition consisting of 110 parts is kneaded in a ball mill for 3 hours to form a paste. To this, 1 composition 4.4'-methylenebis-2-chloroaniline 10 parts Catalyst (zinc naphthenate) 0.2 parts Methyl ethyl ketone 40 parts Toluene
Add 40 parts and mill with a ball mill to 24 parts.
The mixture was kneaded and reacted for 4 hours, and after the reaction was completed, it was filtered and dried in a nitrogen atmosphere, and the obtained magnetic powder was designated as Comparative A3.

Coated magnetic powders obtained in Examples 1 to 8 &1°2, 3.
The performance of magnetic powders treated according to 4.5.6.7 and 8 and Comparative Examples 1 to 3 (Comparative AI-&3) was examined from both the organic matter residual rate (related) and magnetic tape performance.

(1) Organic matter residual rate The organic matter residual rate is the amount of organic matter (
It is the percentage of the amount of organic matter (y>) adhering to the magnetic powder after stirring the treated magnetic powder with a ball mill for 1).The higher the residual rate, the greater the amount of organic matter adhering to the magnetic powder. The film has strong coating strength, indicating high rust prevention properties.

Magnetic powder AI according to the present invention, 2.3.4.5.6゜7
．． The measurement results of the residual rates for Comparative No. 8 and Comparative A I , Comparative A2 and Comparative A3 are shown in Table 4 below.

Table 4 From the results in Table 4, it can be seen that the amount of residual organic matter in the coated magnetic powder of the present invention is overwhelmingly higher than the amount of residual organic matter in the treated magnetic powder of the comparative example.

Therefore, the coating strength on the surface of the coated magnetic powder according to the present invention indicates that the rust prevention property is higher than that of the uncoated magnetic powder.

In addition, after dispersing 100 parts of metal magnetic powder in 670 parts of 1.5% by weight Tomide #220 (compound exemplified in Table 1, A(1)) solution (methylene chloride/toluene = 70:30), After adhering to the polymer, it is filtered and the obtained magnetic powder is called A9, and the metal magnetic powder made of the same material as this magnetic powder is
Temperature vs. heat absorption and heat change A1, A when magnetic powder 2, which was cured and crosslinked with toluylene diinocyanate on the magnetic powder surface by the same treatment as in Example 2, was heated in a nitrogen atmosphere.
2 and the weight reduction rates B, , B2 are shown in the figure. However, curves A, , and B are respectively magnetic powder/76
9, and curves A2 and B2 are thermal curves showing the endothermic change and weight loss rate change of magnetic powder A2, respectively.

From these thermal curves, magnetic powder A9 causes an endothermic reaction at 80C and an exothermic reaction at 330C, while magnetic powder &9 causes an endothermic reaction at 330C and an exothermic reaction at 410C. .

In addition, the weight loss rate of magnetic powder &9 and A2 decreases rapidly when the exothermic reaction temperature exceeds 330C and 410C, respectively, indicating that the organic matter of these magnetic powders, that is, the coating on the surface of the magnetic powder, is thermally decomposed. It suggests that.

From the above results, it was found that the magnetic powder was not only coated with a holamide resin having a reactive functional group, but also cured and crosslinked with a curing agent having a group capable of reacting with the reactive functional group. It is found to be thermally stable.

(2) Tape performance AI, 2.3.4.5.6.7.8 and comparison j61
For magnetic tapes coated with magnetic paint made from magnetic powder of ゜2.3 on a support, coercive force, residual magnetic flux density, saturation magnetic flux density, squareness ratio (Br/8m), still characteristics, and residual magnetic flux density ( Tape performance was measured in terms of B1) changes over time. The magnetic tape is made of the above magnetic powder &l, 2.3.4
．． 5.6.7.8 and Comparative Boils 1 to &3 were prepared by performing treatments according to the following treatment examples, respectively. Namely.

Application example 1 Treated magnetic powder A I 80 parts VAGH
(Manufactured by Union Carbide, partially hydrolyzed vinyl chloride)
Vinyl acetate copolymer) 7.5 parts King Stan 5701 (manufactured by Gutdrich, polyurethane) 7.5 parts Silicone oil 1.5 parts Methyl ethyl ketone 70 parts Toluene
60 parts cyclohexanone
After 5 parts of the above composition was thoroughly mixed and dispersed in a ball mill, 3 parts of tolylene diisocyanate was added and mixed uniformly to prepare a magnetic paint.

This magnetic paint was applied to one side of a 15 μm thick polyethylene terephthalate film while applying a magnetic field of 1200 Gauss so that the dry film thickness was 5 μm.

The resulting wide sample was supercalendered and then slit into a tape with a width of 12.6577 Lm to create a videotape, which was used as Application 1.

Application Example 2 Application Example 2 was a video tape obtained by applying the same composition and treatment as Application Example 1, except that Treated Magnetic Powder Boiled 2 was used instead of Treated Magnetic Powder A1.

Treatment Examples 3 to 6 Instead of treated magnetic powder A3. A
4. A5. 6. Applications A3, 4°5, 6.7 and 8 were videotapes obtained by the same composition and processing as in Application Example 1, except that A7 and A8 were used.

Comparative Application Examples 1 to 3 Instead of treated magnetic powder A1, magnetic powder comparison points 1.2 and 3 were prepared by the treatment methods according to Comparative Examples 1 to 3, respectively.
Comparative Applications A1 and 2 were prepared using the same composition and processing steps as in Application Example 1, except that
and 3.

Applied AI obtained as above, 2.3,4゜5
, 6.7.8 and Comparative Application/FIILI, the measurement results of tape performance for 2y3 are shown in Table 5.
get the result.

However, in Table 5, (1) He Represents coercive force.

(2) Br Represents residual magnetic flux density.

(3)　Bm Represents saturation magnetic flux density.

(4) Square ratio The squareness ratio is expressed as Br/Bm.

(5) Still characteristics Still characteristics are expressed by the time it takes for one screen of still images to disappear. The larger this value, the higher the durability and abrasion resistance of the recording medium.

(6) Change in residual magnetic flux density of magnetic tape over time under conditions of deterioration temperature 60C and relative humidity 80% (after 10 days) ±,
is shown in texture B, X100 (%). The higher this value is, the smaller the change in residual magnetic flux density over time is.

From the results in Table 5, the steel properties of the magnetic tape using the treated magnetic powder according to the present invention are dramatically improved compared to the magnetic tape using the treated magnetic powder according to the comparative example, and the durability of the tape and This indicates high wear resistance.

Moreover, the deterioration value of the ears is also much higher than that of the magnetic tape using the treated magnetic powder according to the comparative example.

FIG. 3 is a diagram showing an endothermic reaction curve and a thermogravimetric curve between the metal magnetic powder and the metal magnetic powder coated with Tomide #220 and then cured and crosslinked with toluylene diisocyanate.

Patent applicant Konishiroku Photo Industry Co., Ltd. Procedural amendment (voluntary) 1. Display of the case Patent Application No. 205093 of 1982 2 Title of the invention Coated magnetic powder 3 Relationship to the case by the person making the amendment Patent applicant address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name ( Name) (127) Roku Konishi Photo Industry Co., Ltd. 4, Agent 5, Date of amendment order 6 Number of inventions increased by amendment 7 Subject of amendment 8 Contents of amendment (1) 1 in the 3rd line of page 4 of the specification Magnetic recording medium (tape)
Correct the statement "...magnetic recording medium...".

(2) In the 16th line of page 5 of the specification, the statement ``Metal magnetic powder can be used and the ingredients'' has been changed to...Metal magnetic powder can be used, and the present invention is particularly effective for metal magnetic powder,・
...I am corrected.

(3) Page 8 of the specification, line 2, 1, and the statement “Additionally,”
...Again, I corrected myself.

(・1) In the table on page 16 of the specification, in the column /16(17), the statement . ) Corrected as Olestar P-49-75X (contains 12% NCO group).

(5) The statement in column A (18) of the table on page 17 of the specification is as follows: For example, product name manufactured by Mitsui Nikko Urethane Co., Ltd.: Adiprene L-100 (contains 4% NCO group). I am corrected.

, (6) Table on page 17 of the specification, column /16(]9)... For example, manufactured by Mitsui Nisso Ureta/Co., Ltd., product name: Azipleken CI)-123 (NCO group 9 % content)...

(7) In the 7th line of page 30 of the specification, the statement "After being dispersed in 1, after being coated with polymer," is corrected to ``Dispersing in..., and being coated with 1.-Mite #220,...'' .

Procedural amendment (voluntary) 1. Indication of the case 1982 Patent Application No. 205093 2. Name of the invention Coated magnetic powder ((3. Relationship with the case of the person making the amendment Address of the patentee Shinjuku-ku, Tokyo) Nishi-Shinjuku 1-26-2 Name (Name) (127) Konishi Roku Photo Industry Co., Ltd. 4. Representative “Person 102 (1) “…2 units of ownership” on page 2, line 12 of the specification ``...'' is changed to ``...has two pieces...''.

(2) On page 5, lines 12-13 of the specification: “-...Cry,
, oxide magnetic powder such as Fe powder, Ni powder, Co powder...
A certain description is ``...CrQ, iso-oxide magnetic powder, Fe,
"Magnetic powder of simple metals such as Ni and Co..."

(3) Compound N2, 3 in Table 2 on page 12 of the specification is as follows.

Written amendment to the above procedure (voluntary) September 20, 1988 Patent No. 205093 2, Title of invention: Coated magnetic powder 3, Relationship to the case of the person making the amendment Patent applicant address: Shinjuku-ku, Tokyo Nishi-Shinjuku 1-26 Yu 2 Name (Name) (127) Konishiroku Photo Industry Co., Ltd. 4
, Agent 〒102 6. Number of inventions to be increased due to amendment N/A 7. Subject of amendment (1) Procedural amendment filed on January 8, 1980 Alarm bell, page 1, line 5, ``...using magnetic powder '' is changed to ``...magnetic powder is used.''

(2) Procedural amendment record submitted on January 8, 1981, page 12
The entry that says ``...Oreta Star'' in the first line is changed to ``To... Oreta Star''.

(3) Procedural amendment secretary submitted on January 8, 1981, page 2, 15
In the line ``...Azipletan...'', change it to ``・
...Aziprene..."

that's all

Claims (1)

[Claims] Polyamide resin having reactive functional groups and polyamide 9
A coated magnetic powder in which the surface of magnetic powder is coated with a crosslinked polyamide produced when a holamide resin is cured and crosslinked by a reaction between a reactive functional group in the resin and a curing agent having a reactive group.