JPS62283419A - Magnetic composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 6. [Detailed Description of the Invention] The present invention provides magnetic particles (
The present invention relates to magnetic recording media having a magnetic coating composition and a magnetic layer derived from the coating composition.

More particularly, the present invention relates to magnetic coating compositions containing magnetic grains and a combination coupling agent surfaced with a combination coupling agent containing a titanate or zirconate coupling agent and a silane coupling agent.

Magnetic recording media are generally made by applying a coating composition containing magnetic particles, a resin binder, and a solvent to a non-magnetic substrate followed by removal of the solvent. High dispersion of the magnetic coating composition is essential for uniformity of the magnetic layer and optimization of desired magnetic properties such as flatness, high packing density, high signal/noise ratio, high orientation ratio and low switch field distribution. Required.

Attempts that have been proposed to improve the dispersibility of coating formulations containing large amounts of fine inorganic materials such as magnetic particles include adding dispersants to the coating formulation or embedding the particles with dispersants. The process involves modifying its surface properties by

Although relatively large amounts of conventional dispersants are required to obtain sufficient dispersion, the inclusion of such large amounts of dispersants detracts from the desired properties of the finished tape. In order to improve this drawback, Krσ between the particles of the compound and the resin component is
It has been proposed to use catalytic monochemicals or coupling agents that provide a bridge. Coupling agents disclosed for this use are hydrolysable organofunctional silanes or hydrolysable organotitanates. Regarding the use of this type of coupling agent &-17
Mel J Power Patent, JLI 4,076.890; 4,
330,600; 4.397,751; 4,41
5,630; 4,444,850: and 4,4
75,946;
9,244.

Now, in accordance with the present invention, the dispersibility and stability of a magnetic coating composition suitable for recording media is improved by combining the magnetic particles with an organotitanate. It has been found that substantial improvements can be achieved by treatment with combination coupling agents or by including them in coating formulations containing magnetic grains. The discovery that the inclusion of both a titanate or zirconate coupling agent and a seven-run coupling agent in a magnetic coating composition results in a composition that is stable for weeks and in some cases months. This was completely unexpected since the same degree of stability could not be obtained when the coupling agent alone was used in any amount.

Accordingly, the present invention consists essentially of (a) magnetic grains, (b) an organotitanate or organozirconate coupling agent, and a (cl organo7lancanopring agent), wherein the weight ratio of (b):fc) is 0. .2:1-15:
1, and the total weight of tb) + (C) is 0 of the magnetic grains.
．． 1 to about 15% by weight of the magnetic particles, a magnetic composition suitable for magnetic recording media, a method for making the magnetic composition, magnetic grains, a synthetic resin binder, a solvent and a combined coupling agent in an amount of 0.1 to about 15% by weight of the magnetic grains. and a substrate coated with a magnetic layer comprising a magnetic composition and a synthetic resin binder.

The titanate coupling agent used in the present invention has at least one readily hydrolyzable group;
It is an organic tetravalent titanium compound having at least one hydrophobic group. Suitable titanium compounds of this type have the general formula: : % are the same or different monovalent ligands of the formula % (wherein R' is a substituted or unsubstituted alkyl, aralkyl, aryl, alkaryl or alkenyl group);
at least one A group is difficult to hydrolyze;
and n is 1, 2. or 3]. Suitable ligands that A may contain are substituted or unsubstituted with halo, amino, epoxy, ether, thioether, ester, cyan, carbonyl, and nitro groups, and furthermore, the main substituent is ~ - are aryloxy, acyloxy, sulfonyloxy, sulfonyloxy, diester phosphate and diester pyrophosphate groups which can contain intermediate heteroatoms such as sulfur, nitrogen, or oxygen in the pendant substituents; of course creating a cyclic structure. Other titanate coupling agents useful in the present invention are coordination type compounds, with the general formula = (where R' is as defined above). The organotitanate coupling agent is available under the trade name KR or LICA.
ich Petrochemical B.

Commercially available from Inc. U.S. Patent No. 44 for organotitanate coupling agents and methods for producing the same.
, 122,062. Particularly preferred organotitanates are lower alkyl tris(alkylbenzenesulfonyl) titanates; lower alkyl tris(dialkylpyrophosphate) titanates and lower alkyl tris(N-ethylaminoethylamine) titanates. Isopropyl tris(dodecylbenzenesulfonyl) titanate is most suitable.

The zirconium coupling agents used in the present invention are organic zirconium compounds having at least one easily hydrolyzed group and at least one hydrophobic group that is difficult to hydrolyze. Zirconium compounds are represented by the general formula; dodecylbenzenesulfonyl)zirconate) and alkoxytris(dioctylpyrophosphate)zirconate. The zirconate coupling agent is Ketroch8
It is commercially available from micals Inc. under the trade name LZ.

The silane coupling agent used in the present invention is an organofunctional silane containing at least one hydrolyzable group and at least one greasy substituted organic group attached to 31-C bonded silicon. Silanes of this type have the general formula; polyalkyleneoxy or halogen, each B is the same or different, and n is 1, 2, . or 3).

Alcoquine substituent-containing silane coupling agents are, for example, methoxypropyltris(polyethyleneoxy)silane, methoxypropyltris(polypropyleneoxy/)silane and methoxypropyltris(polyethyleneoxy-polypropyleneoxy) 7 run. Epoxide-substituent-containing silane coupling agents include, for example, glycibixymethyltrimethoxysilane, glycibixypropyltrimethoxysilane, glycidoxyethyltriyobisilane, glycidoxy-n-butyltrimethoxysilane, Sidoxyethyltrichlorosilane, 1,2-epoxypropyltrichlorosilane, cis-2,3-epoxybutoxypropyltriethoxysilane, 3,4-epoxycyclohexyl-1-methyltriacetoxysilane, 3,4-epoxycyclo Hexyl-1~ethyltrimethoxysilane, 3,4-epoxycyclohexyl-1~
These include ethoxypropyltribromo7rane, glycidyltripromono2rane, and the like. Halo substituent-containing silanes include, for example, chloroethyltrimethoxysilane, chloropropyltrimethoxysilane, jobiprobiltriethoxysilane, chloromethoxyethyltrimethoxysilane, bromoethoxypropyltrimethoxysilane, 3,4-dichlorocyclohexyl -1 to dithyltrimethoxysilane and the like. Amino-substituted silanes are, for example, aminoethyltriethoxysilane, aminopropyl)IJ ethoxysilane, N,N-dimethylaminopropyltriethoxysilane, aminomethoxypropyldimethoxychlorosilane, aminoethyltriyobisilane, and the like. Mercapto-substituted silanes include, for example, mercaptoethyltrimethoxysilane, mercaptoethertrichlorosilane, mercaptopropyltrimethoxysilane, 3-mercaptocyclohexyl-1-ethyltrimethoxysilane,
These include 3-mercaptocyclohexyl-1 to ethyltrimethoxysilane. A silane of the above type is Tau Corning Corporation 7 (Dow Corning
Corporation) and Union CarbiaeC
It is commercially available from the organization.

Titanates, zirconates and silane coupling agents are soluble or dispersible in non-aqueous or aqueous solvent systems. In some embodiments of the invention, the coupling agents are individually mixed or blended and then mixed with magnetic grains to form surface-treated particles. They can also be added to the coating formulation containing the magnetic grains and binder system separately in any order, simultaneously, or in combination. As already explained, the weight ratio of titanate or zirconate coupling agent to silane coupling agent is from 0.2:1 to 15:1, preferably from 0.4:1 to 12:1. More preferably 2'
The ratio is 10:1. The amount of combined coupling agent desired to provide a highly dispersible and highly stable coating composition will depend on the particular titanate or zirconate and the particular silane, the components of the coating formulation, and the particular type of solids used. It varies depending on the amount and quantity. Generally from 0.1 to about 15 weight percent based on the magnetic grains will provide a good balance of dispersibility and stability without sacrificing all of the desired properties of the coating. Higher amounts can of course be used if desired.

However, in amounts exceeding about 15%, no further improvement is observed and substantially excessive amounts are uneconomical and therefore cannot be promoted. Typically, about 0.2 to 10%, preferably about 0.5 to 5%, by weight of the combined coupling agent, based on the magnetic grains, provides a magnetic recording medium with all the magnetisms acceptable to magnetic tape manufacturers. .

The magnetic grains whose dispersibility is improved according to the present invention are all known oxides or metals commonly used in magnetic recording systems.

A preferred magnetic material is γ-Fe203. Go-containing-F
e2O2°Feas4. Goo Fe, 04. These are magnetic iron oxide acicular particles such as bertolide, barium ferrite, etc., chromium oxide particles, and metal particles such as iron, cobalt, nickel, and alloys thereof.

In a preferred embodiment of the invention, which is a magnetic recording medium such as a magnetic tape or disk, the base or substrate, generally Holly (vinyl chloride),
Polyesters such as polyethylene, polypropylene, polyamide, polyethylene terephthalate, etc. have magnetic particles,
Magnetic coatings consisting of synthetic binders, resins, binder solvents or solvent systems, and combination coupling agents.
After coating with the coating composition, the solvent or solvent system is removed. The binder resin can be any film-forming polymer that is compatible with the base film (preferred are poly(vinyl chloride), vinyl chloride/vinyl acetate copolymers, vinyl chloride/vinyl acetate/hinyl alcohol terpho IJ polymers). , polyurethane resin, epoxy resin, phenoxy resin, polyether resin,
These include nitrocellulose and unacellulose ester. The binder of choice is a mixture of thermoplastic polyurethane and vinyl chloride copolymer or terpolymer. Other ingredients commonly used in coatings and individual magnetic coatings, such as dispersants, emulsifiers, lubricants, antioxidants, plasticizers, crosslinkers, adhesion promoters, etc., can, of course, be used to advantage of the present invention, if desired. It can be added as long as it is added and used in an amount that does not impair properties.

The invention is further illustrated by the following examples which illustrate the best mode of the invention. In the examples, all parts and percentages are by weight unless otherwise indicated.

Example 1゜Isopropyl tris(4-1'decylbenzenesulfonyl) titanate (Kenritz Chemicals, Inc., K
enrich Petrochemicals, In
KRqSD, commercially available from KRqSD) 1.35 parts with an average molecular weight of 1750 and a weight ratio of ethylene oxide to propylene oxide of about 0.6 to 1.
- 0.15 parts of methoxypropyltris(polyalkyleneoxy)silane in a tetrahydroalane solution 1
00 parts into a mixer containing adsorbed cobalt,
and the average length is O, S microns, the length to width ratio is 6:1,
150 parts of acicular γ-Fθ2o3 particles having a specific surface area of 26 m 2 /gBET and a coercivity of 640 Oersteds at a field strength of 3,000 Oersteds were gradually added over 10 minutes. The mixture was stirred for a further 5 hours, then collected and kept at 55°C until less than 0.5% moisture.
It was dried for 12 hours.

Using this dry product (treated 20203 particles), % "Red Devil 5ha using 60d stainless steel balls"
The magnetic coating composition was prepared by grinding in a ker for 1.4 hours. During this time, each component shown in Table 1 below, a vinyl copolymer solution, was added 15 minutes after the grinding time, and a polyurethane solution was added after 1 hour after the grinding time. The resulting resin tube was strained to remove the steel balls, and then diluted with 1072% of cyhalohequinanone/tetrahydrol to prepare a coating composition of about 40% by weight.

Treated Fe2O3 particles 50.5 Toluene 18.5 Cyclohexanone 2.0 Anionic phosphate ester dispersant '2. ．．
O isocetyl stearate 0.3 Toluene:cyclohexanone (5:3) 6.4
A 15% solution of vinyl chloride-acetate-alcohol copolymer dissolved in 20% solution of vinyl chloride-acetate-alcohol copolymer 20% solution of polyurethane 54.4 urethane prepolymer solution dissolved in tetrahydroalane was stored and a portion of the coating composition was examined for storage stability over time. . In this test, first composition sample II
Ll was placed in a graduated container containing 24d of methyl ethyl ketone and gently shaken for 1 minute. Then, under static conditions, disperse F
The precipitation time was determined by measuring the time required for the interface between the e2o3 particles and methyl ethyl ketone to undergo 81 displacement.

After storage for a certain period of time, a portion of the coating composition was manually coated with a knife blade in a magnetic field to orient the magnetic grains to the optical surface of a 0.02 raa thick polyethylene terephthalate film as shown in Table 2. After that, the coated film was air-dried at room temperature for 24 hours to a coating thickness of 0.01 to 0.
．． 03 Tomo. The magnetic properties of this film are magnetic force 3.0
Measured with a 00 Oersted B-H magnetometer. Further control coating compositions and films were made in the same manner as in this example except that 50.5 parts of untreated cobalt-adsorbed γ-Fe 203 particles were used in place of the treated particles. Table 2 below shows the precipitation times and magnetic properties of the films for the compositions of this example and the control example.

Comparative Example A Fe203 particles (isopropyl) l) Tetrahydrofuran solution 100 containing 1.5 parts of su(4-)'decyl(benzenesulfonyl)titanate and containing no silane compound
The procedure of Example 1 was repeated, except that 1 part was added.

The procedure of Example 1 was repeated with the exception that the magnetic properties of the film of this Example and the results of the precipitation test are listed in Table 2 as Comparative Example A. Table 2 shows the magnetic properties and sedimentation test results of the film of this example as Comparative Example B.

Examples 2-5 The procedure of Example 1 was repeated, except that the .gamma.-Fe2O3 particles were treated with tetrahydro7rane solutions containing titanate and silane compounds in varying proportions.

The total throughput in each case was 1% based on γ-Fe 203 particles. The ratios and test results are shown in Table 3.

2 9/1 4 0.84 1
．． 93 7/3 75 0.81
2.14 515 84 0.76
1.75 3/7 88 0.
79 The operation was repeated with the weight ratio of 1.6 titanate to silane compound being 1/9, and the change in precipitation time was substantially higher than that of the particles treated with a single silane compound.

Example 6゜% “Red Devi using stainless steel ball 60mJ
A coating composition was prepared by grinding the following ingredients in an lShakθr for 1.4 hours.

γ-Fe O") 50.0 Monoluene 18.5 Noclohexanone 2.0'Sopropyltris(4-)"Decylban 0,45zenesulfonyl)titanate γ-Methoxypropyltris(Polyal 0.0
5 Kyleneoxy) 7 Run (2) Anionic phosphate ester dispersant 2.0 Isocetyl stearate 0.3 Toluene:cyclohexanone (5:3) K 6.4 Dissolved vinyl chloride acetate 1 Flucol copolymer Polyurethane dissolved in 20% g liquid tetrahydrofuran 54.4 15% prepolymer H (i) Average length O, S microns, length to width ratio 7:1° and surface area 26 m2. /; needle-like particles.

(2) Example 1.

The vinyl copolymer solution was added 15 minutes after the milling time and the polyurethane bath solution was added 1 hour after the milling time.

After measuring the stability of the composition, it was coated onto a film according to the procedure of Example 1. The results are shown in Table 5.

2 26 B 0.87 1.
97 255 0.89 2.2
12 258 0.91 2.2
Example 7゜N,N-dimethylaminopropyl tricetoxysilane 0
．． The procedure of Example 1 was repeated, except that 15 parts were used in place of the 7 runs of Example 1 and the γ-Fe 203 particles of Example 6 were used. The results of the precipitation test and the magnetic properties of the film are shown in Table 6.

1st month 210 0.90 1.96
Day January 204 0.87 2.211th day Day 212 0.88 2.2 Example 8゜Neoalkoxytris (Bidecyl is anze/Sulfonyl)
Zirconate (Kenrich Petrochemi
caxs.

Xnc, commercially available glue, z09) 0145 parts isopropyl)! A coating composition was made according to the procedure of Example 6, except that 7s(4-bidecylbanzenesulfonyl) titanate was substituted and the iron oxide particles were the cobalt adsorbed particles of Example 1. The results of the sedimentation test were 240 seconds after 1 day of storage, and 205 seconds after 4 and 8 days of storage.

(Outside 5ゑ-)

Claims (1)

[Claims] 1. (a) magnetic particles (b) organotitanate coupling agent or organozirconate coupling agent,
and (c) an organosilane coupling agent,
The weight ratio of (b):(c) is from 0.2:1 to 15:1, and the total amount of (b)+(C) is from 0.1 to about 1 % of the magnetic particles.
5% by weight of a magnetic composition suitable for magnetic recording media. 2. Claim 1, wherein the magnetic particles are iron oxide particles
Compositions as described in Section. 3. The composition according to claim 2, wherein component (b) is an organotitanate. 4. The composition according to claim 2, wherein component (b) is an organozirconate. 5. The composition according to claim 2, wherein the component (b) and the component (c) are present as a coating on the surface of the iron oxide particles. 6. A coating composition comprising magnetic particles, a synthetic resin binder, and a solvent or solvent system for the binder, wherein the composition further comprises (i) an organotitanate coupling agent or an organozirconate coupling agent and (ii) an organosilane coupling agent. Contains an agent,
The weight ratio of (i):(ii) is 0.2:1 to 15:1, and the total amount of (i)+(ii) is 0.1 of the magnetic particles.
A coating composition characterized by an improvement of about 15% by weight. 7. Magnetic particles, a synthetic resin binder, and a combination of (i) an organotitanate coupling agent or an organozirconate coupling agent and (ii) an organosilane coupling agent in an amount of 0.1 to about 15% by weight based on the magnetic particles. and the weight ratio of (i) to (ii) is 0.2
1. A magnetic recording medium comprising a non-magnetic substrate coated with a magnetic layer comprising a coupling agent having a ratio of: 1 to 15:1. 8. 0.1 to about 15% by weight based on the magnetic particles of a combination of (i) an organotitanate or organozirconate coupling agent and (ii) an organosilane coupling agent; Weight ratio is 0.2
1. A method for improving the dispersibility of magnetic particles suitable for use in magnetic recording media, the method comprising bringing the magnetic particles into contact with a coupling agent having a ratio of: 1 to 15:1. 9. The method according to claim 8, wherein the contacting is carried out by dry mixing. 10. The method of claim 8, wherein the contacting is carried out by mixing the particles with the coupling agent solution and then drying the mixture. 11. Claim 1 in which the magnetic particles are iron oxide particles
The method described in item 0.