JPH01201319A - Binder for magnetic recording medium and magnetic recording medium having magnetic layer bonded therewith - Google Patents

Abstract

PURPOSE:To make it possible to form a binder for a magnetic recording medium, which requires no special equipment for curing and can shorten a curing time without shortening its pot life and without adversely affecting a treatment for surface smoothing, by mixing a hydroxylated resin with a polyisocyanate and a specified salt. CONSTITUTION:This binder contains a hydroxylated resin component (a), a polyisocyanate (b) and a salt (c) of an amide of formula I (wherein n is an integer of 1-3) with an acid of a pKa of 2.5-4 as determined in an aqueous solution. As component (a), a vinyl chloride/vinyl acetate/vinyl alcohol copolymer, a nitrocellulose resin, a polyurethane resin or the lie is particularly desirable. The mixing ratio of component (a) to component (b) is preferably about 9:1-6:4 (by weight). As said salt of component (c), a salt of 1,5-diazabicyclo(4.3.0) nonene-5 with formic acid, for example, is desirable. The amount of component (c) added is desirably about 0.05-1pt.wt. per 100pts.wt. in total of components (a) and (b).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium binder and a magnetic recording medium having a basic structure consisting of a magnetic layer and a nonmagnetic support bonded by the binder.

Conventional technology Generally, as magnetic recording media for audio, video, or computers, a magnetic layer in which ferromagnetic powder (magnetic material) is dispersed in a resin component (binder) is placed on a nonmagnetic support. A magnetic recording medium provided is used.

Magnetic recording media are required to have high levels of characteristics such as running durability, electromagnetic conversion characteristics, and running properties.

Such a magnetic recording medium is manufactured by coating a magnetic paint prepared by mixing and dispersing ferromagnetic powder, a resin component, other additives, and a solvent on a nonmagnetic support, followed by a magnetic field alignment process, a drying process, and a surface drying process. It is generally manufactured through a smoothing process, other processes, and a cutting process.

Recently, polyisocyanate has been increasingly incorporated as a curing agent component into magnetic paints for the purpose of improving the strength of magnetic recording media.

The combined use of polyisocyanate has the advantage that the strength of the magnetic layer is improved because the polyisocyanate reacts and forms a three-dimensional network crosslinked structure with the resin component such as the polyurethane resin. This three-dimensional network crosslinked structure is mainly formed during the curing process of the magnetic recording medium manufacturing process.

However, since the reaction rate of polyisocyanate is low, there is a problem in that it takes a very long time to form a three-dimensional network crosslinked structure with polyisocyanate. That is, in the curing process when manufacturing a magnetic recording medium, the original magnetic recording medium (a laminate including a non-magnetic support and a layer from which the solvent of the magnetic paint coating layer has been removed) is heated at approximately 60°C. This is generally carried out by leaving it at room temperature for 1 to 3 days and then leaving it at room temperature for about 7 days.

Therefore, there is a problem in that it takes a very long time to manufacture the magnetic recording medium itself.

There is also the problem that the characteristics of the product may change depending on the conditions of the curing process, making product management complicated.

Note that polyisocyanate can be added not only to magnetic paints but also to paints that form a back layer on the surface of a non-magnetic support without a magnetic layer for the purpose of imparting strength to magnetic recording media. The number of cases has increased, and similar problems arise in this case as well.

Therefore, in order to shorten the curing process, it has been proposed to add an organotin-based catalyst to the magnetic paint or the paint forming the back layer (Japanese Patent Publication No. 6L-ISSTO). In this case, although the curing time can be shortened, the pot life of the magnetic paint is also shortened, which poses a problem in actual use. In addition, in the production of magnetic recording media...a magnetic paint made by cross-dispersing a fat component and ferromagnetic powder with a solvent is applied onto a non-magnetic support, and after the solvent is distilled off, the surface is smoothed using a super calender roll etc. However, when an organotin-based catalyst is added, the reaction is accelerated even at room temperature, so the hardness of the magnetic layer is already high when smoothing is performed, making it difficult to achieve satisfactory surface smoothing. It also had the disadvantage of not having any.

On the other hand, after drying the magnetic coating layer, a laminate including a non-magnetic support and a magnetic coating layer coated on the non-magnetic support,
It has also been proposed to manufacture magnetic recording media in a short time by performing alkali treatment before the curing reaction is completed (Japanese Patent Laid-Open No. 62-9
Publication No. 5737). However, this method requires equipment for alkali treatment, which increases the size of the manufacturing equipment and costs.

Problems to be Solved by the Invention The present invention provides a magnetic recording medium that does not shorten the pot life, does not adversely affect the surface smoothing process, and does not require any special equipment for curing, reducing only the curing time. An object of the present invention is to provide a magnetic recording medium having a magnetic layer bonded therewith.

Means for Solving the Problems As a result of intensive research, the present inventors found that an amine represented by -Momonena [where n is an integer of 1 to 3] has a pKa of 2.5 to 4 in an aqueous solution. When a binder contains a salt with an acid of Furthermore, it was discovered that a magnetic recording medium having a magnetic layer bonded with this binder has better surface properties and improved durability than conventional media, and based on these findings, the present invention was completed. reached. That is, the present invention comprises (a) a resin component having a hydroxyl group, (b) a polyisocyanate, and (C) an amine represented by the general formula 1, where n is an integer of 1 to 3, and a pKa in an aqueous solution. 2.5 to 4, a binder for magnetic recording media containing a salt with an acid having a hydroxyl group, (a) a resin component having a hydroxyl group, (b) a polyisocyanate, and (c) a general formula 1, where n is 1 A magnetic recording medium having a magnetic layer bonded with a binder for a magnetic recording medium containing a salt of an amine represented by [representing an integer of ~3] and an acid having a pKa of 2.5 to 4 in an aqueous solution. Regarding.

The resin component (a) having a hydroxyl group used in the present invention can be selected from resin components used as binder components of ordinary magnetic paints.

Examples of resin components include vinyl chloride/vinyl acetate copolymer, vinyl chloride/vinyl acetate/vinyl alcohol copolymer, vinyl chloride/vinylidene chloride copolymer, vinyl chloride/acrylonitrile copolymer, and ethylene/vinyl acetate copolymer. Polymers, cellulose derivatives such as nitrocellulose resins, acrylic resins.

Examples include polyvinyl acetal resin, polyvinyl butyral resin, epoxy resin, phenoxy resin, and polyurethane resin.

These resins have carboxyl groups as polar groups.

It may have a sulfonic acid metal base, a phosphoric ester group, etc. Among the above resins, especially vinyl chloride/vinyl acetate/vinyl alcohol copolymers.

It is preferable to use nitrocellulose resin, phenoxy resin, and polyurethane resin alone or in combination of two or more thereof.

(b) Examples of the polyisocyanate include low-molecular polyisocyanates often having two or more isocyanate groups,
Specific examples include tolylene diisocyanate and diphenylmethane diisocyanate.

xylylene diisocyanate, tetramethylxylylene diisocyanate, hexamethylene diisocyanate,
Organic diisocyanates such as isophorone diisocyanate, dicyclohexylmethane diisocyanate, lysine diisocyanate and their polymers, or an excess of organic diisocyanates, such as ethylene glycol, propylene glycol, dipropylene glycol,
Low-molecular active hydrogen such as butylene glycol, trimethylolpropane, hexanetriol, glycerin, sorbitol, pen-taerythritol, castor oil, ethylenediamine, hexamethylenediamine, ethanolamine, jetanolamine, triethanolamine, water, ammonia, urea, etc. Polyisocyanates obtained by reacting compounds or high-molecular active hydrogen compounds such as various polyether polyols, polyester polyols, and acrylic polyols, or their biuret-formed and allophanated products are suitable. Its molecular weight is about 1
50 to 7,000.

Usually, the blending weight ratio of (a) the resin component having a hydroxyl group and (b) the polyisocyanate is set within the range of about 9.1 to 6.4.

The total m9 of the resin component and polyisocyanate is usually about 10-100 parts by weight per 100 parts by weight of the ferromagnetic powder used.

What is the salt of the amine represented by the general formula (C) [wherein n represents an integer of 1 to 3] used in the present invention and an acid in which p is 2.5 to 4 in an aqueous solution? , for example, 1,5-diaza-bicyclo(4,3
, 0) nonene-5, 1,5-diazabisic O where n is 2
(4,4,0)decene-5,1,8-diaza- where n is 3
Bicyclo(5,4,0)undecene-7, halogenated acetic acids such as chloroacetic acid, bromoacetic acid, fluoroacetic acid, phenoxyacetic acid, 0-chlorocyphenoxyacetic acid 9m
-Chlorphenoxyacetic acid, p-chlorophenoxyacetic acid,
0-bromphenoxyacetic acid.

m-bromphenoxyacetic acid, p-bromphenoxyacetic acid, O-fluorophenoxyacetic acid 9m-fluorophenoxyacetic acid, p-fluorophenoquineacetic acid, 0-cyanophenoxyacetic acid 1m-cyanophenoxyacetic acid, p-cyanophenoxyacetic acid, 0-nitro Phenoxyacetic acid.

Phenoxyacetic acids such as m-nitrophenoxyacetic acid and p-nitrophenoxyacetic acid, 0-chlorobenzoic acid.

m-Chlorobenzoic acid, p-chlorobenzoic acid, @, folic acid, 0-bromobenzoic acid 1m-bromobenzoic acid, folic acid, p-bromobenzoic acid, 0-fluorobenzoic acid 1m-fluorobenzoic acid 1
m-acetylbenzoic acid, p-acetylbenzoic acid, 0-isopropylbenzoic acid, 0-ethylbenzoic acid, 0-cyanobenzoic acid, m-cyanosulfuric acid, p-cyanobenzoic acid, 1m-nitrobenzoic acid, Benzoic acids such as p-nitrobenzoic acid, 2.4゜6-trimethylbenzoic acid, 2.4.6-trimethoxyammizoic acid, o-tert-butylbenzoic acid, hydroxy acids such as glycolic acid, lactic acid, glyceric acid, etc. It is a salt with an acid having a pKa of 2.5 to 4 in an aqueous solution, such as formic acid. Among the above salts, salts of 1,5-noazabicyclo(4,3,0)nonene-5 or 1,8-diaza-vinchlo(5,4,0)undecene-7 with formic acid are particularly preferred. .

When a salt with an acid having a pKa greater than 4 in an aqueous solution is used, the pot life will be shortened since it exhibits catalytic activity near room temperature. If the pKa is less than 2.5, the temperature at which the catalyst exhibits catalytic activity will be 80° C. or higher, making it unsuitable for manufacturing magnetic recording media.

The amount of the salt (c) added is preferably in the range of about 0.05 to I parts by weight based on the total weight of (a) the resin component having a hydroxyl group and (b) the polyisocyanate. If the amount of insects is less than about 0.05 parts by weight, the reaction rate will not be accelerated even when heated, and if it exceeds 1 part by weight, the reaction rate will be accelerated even at around room temperature, and the pot life may be shortened.

The binder for magnetic recording media of the present invention comprises (a) a resin component having a hydroxyl group, (b) a polyisocyanate, and (C) an amine represented by -Momona [where n is an integer of 1 to 3]. It is obtained by mixing a salt with an acid having a pKa of 2.5 to 4 in an aqueous solution, and the above (a) to (C) and ferromagnetic powder are usually used when preparing magnetic paints. A magnetic coating material can be obtained by cross-dispersing it with a solvent.

Examples of the ferromagnetic powder used in the present invention include ferromagnetic iron oxide particles 9 ferromagnetic chromium dioxide, ferromagnetic alloy powder, hexagonal barium ferrite fine particles, iron nitride, and the like. (
The salt (C) may be cross-dispersed in the mixture of the resin component (a) and the ferromagnetic powder using a solvent, and the polyisocyanate (b) may be added thereto. Alternatively, when adding the polyisocyanate (b) to the mixture of the resin component (a) and the ferromagnetic powder, the salt (C) may be added.

The solvent used during mixing is not particularly limited, but is appropriately selected in consideration of the solubility and compatibility of the binder.

For example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, esters such as ethyl formate, ethyl acetate, and butyl acetate, methanol, ethanol, and isopropanol.

Alcohols such as butanol, aromatic hydrocarbons such as toluene, xylene, and ethylbenzene, ethers such as isopropyl ether, ethyl ether, and dioxane, and furans such as tetrahydrofuran and furfural are used as a single solvent or as a mixed solvent. It will be done.

These solvents are used in a proportion of 10 to 10,000% by weight, particularly 100 to 5,000% by weight, based on the binder.

The magnetic paint may further contain a dispersant, a lubricant, an abrasive, an antistatic agent, a rust preventive, and the like.

Dispersants include fatty acids with 12 to 18 carbon atoms (R -COOH
, R is an alkyl or alkenyl group having 11 to 17+ m carbon atoms), an alkali metal (Li, Na, etc.) or an alkaline earth metal (Mg, ca, B a
), fluorine-containing compounds of the above-mentioned fatty acid esters, amides of the above-mentioned fatty acids, polyalkylene oxide alkyl phosphate esters, trialkyl polyolefin oxy quaternary ammonium salts (alkyl has 1 to 5 carbon atoms) , olefins are ethylene, propylene, etc.). Other higher alcohols having 12 or more carbon atoms and sulfuric esters can also be used.

As a lubricant, dialkylpolysiloxane (alkyl has 1 to 5 carbon atoms), dialkoxypolysiloxane (alkoxy has 1 to 4 carbon atoms), monoalkylmonoalkoxypolysiloxane (alkyl has 1 to 5 carbon atoms, alkoxy (1 to 4 carbon atoms), phenylpolysiloxane,
Fluoroalkylpolysiloxane (alkyl has 1 or more carbon atoms)
conductive fine powder such as graphite, inorganic fine powder such as molybdenum disulfide and tungsten disulfide, fine plastic powder such as polyethylene, polypropylene, polyethylene, vinyl chloride copolymer, polytetrafluoroethylene, etc. α-olefin polymers, unsaturated aliphatic hydrocarbons that are liquid at room temperature (compounds in which an n-olefin double bond is bonded to the terminal carbon, carbon atoms of 20
), monobasic fatty acids with 12 to 20 carbon atoms and monobasic fatty acids with 3 to 20 carbon atoms
Fatty acid esters consisting of 12 monohydric alcohols,
Fluorocarbons and the like can be used.

Commonly used abrasive materials include fused alumina, silicon carbide, chromium oxide (CRTOS), corundum, artificial corundum, diamond, artificial diamond,
Garnet, emery (main ingredients: corundum and magnetite), etc. are used.

Antistatic agents include conductive fine powders such as carbon black and carbon black graft polymers, natural surfactants such as saponin, nonionic surfactants such as alkylene oxide, glycerin, and grindol, higher alkylamines, Cationic surfactants such as quaternary ammonium salts, pyridine and other heterocycles, phosphoniums, anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric acid ester groups; Ampholytic active agents such as amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, etc. are used.

As the above-mentioned rust preventive agent, phosphoric acid, sulfamide, guanidine, pyridine, amine, urea, dicyclochromate, rhumium chromate, strontium chromate, etc. can be used, but in particular, dicyclohexylamine nitrite, cyclohexylamine chromate, etc. , diisopropylamine nitrite, jetanolamine phosphate,
Volatile rust inhibitors (inorganic or organic acid salts of amines, amides or imides) such as cyclohexylammonium carbonate, hexamethylene diamine carbonate, propylene diamine stearate, guanidine carbonate, triethanolamine nitrite, and morpholine stearate. When used, the rust prevention effect improves.

To give an example of a method for manufacturing a magnetic recording medium using the binder for magnetic recording media of the present invention, first, a magnetic paint is prepared and coated on a non-magnetic support. The solvent in the magnetic paint is then removed by heating, leaving a solvent-free magnetic layer on the non-magnetic support.

At this point, almost no curing reaction occurs. Next, a curing reaction is performed at a predetermined temperature for a predetermined time. The curing reaction is approximately 45~
Preferably it is carried out at 75°C, especially about 50-70°C.

Examples of materials for the nonmagnetic support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polyethylene and polypropylene, cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose acetate propionate. In addition to cellulose derivatives such as, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide, and polyamideimide, aluminum, copper, tin, zinc, or non-magnetic alloys containing these, etc. Non-magnetic metals, ceramics such as glass, earthenware, and porcelain, and papers such as paper coated or laminated with baryta or α-polyolefins having 2 to 10 carbon atoms such as polyethylene, polypropylene, and ethylene-butene copolymers. Can be used. The nonmagnetic support may be in any form such as a film, tape, sheet, disk, card, or drum.

The coating volume is such that the dry film thickness is about 1 to 50 microns.

The coating layer of magnetic paint may be provided on one side of the non-magnetic support, but for example, when manufacturing a floppy disk, it is coated on both sides.

Furthermore, in the method for manufacturing a magnetic recording medium of the present invention, a coating layer that will become a back coat layer can also be applied to the surface of the nonmagnetic support that is not coated with the magnetic coating layer.

In general, the cloth layer of the back layer contains a back layer paint which may contain the above-mentioned resin components and polyisocyanate, and optionally also other components such as an abrasive and an antistatic agent (e.g., carbon blank). It is prepared by the same method as the above-mentioned magnetic paint, and applied by applying the same method to the surface of the non-magnetic support that is not coated with the magnetic paint layer.

The blending weight ratio of the resin component and polyisonoanate is usually within the same range as the blending ratio when preparing the Moeki magnetic paint.

The back layer paint can be applied at the same time as the magnetic paint is applied, or it can be applied again after the magnetic paint is applied and the various steps are completed to prepare the magnetic recording medium.

Usually, the coated layer of magnetic paint is subjected to a treatment to orient the ferromagnetic fine powder contained in the coated layer of magnetic paint, that is, a magnetic field orientation treatment, and then dried to become a magnetic coated layer. When a back coating layer is provided, the coating layer of the back layer paint is also dried to become the back coating layer.

Drying is carried out to remove the solvent contained in the coated layer of magnetic paint, and the heating temperature is generally below the boiling point of the solvent used, and the heating time is usually 2 minutes or less.

After drying, it is usually preferable to subject the magnetic coating layer to a surface smoothing treatment. For example, a super calender roll is used for the surface smoothing process.

By performing the surface smoothing treatment, the pores generated by removing the solvent during drying disappear and the filling rate of the ferromagnetic powder in the magnetic layer increases, which further smooths the surface of the magnetic layer. Since the contact with the magnetic head is improved, a magnetic recording medium with high electromagnetic conversion characteristics can be obtained.

Effects of the invention When a magnetic recording medium is manufactured using the binder of the invention,
The conventional method, which required curing time of 24 to 72 hours at a temperature of about 60° C., now takes about one-tenth of the curing time, allowing for extremely efficient production. Furthermore, the obtained magnetic recording medium has good surface properties and is also excellent in durability.

The present invention will be explained in more detail with reference to Examples below.

Example I Co-containing 7-Peso; 400 parts by weight Urethane Wll (N-2304, manufactured by Nippon Polyurethane Co., Ltd.)
50 parts by weight vinyl chloride-vinyl acetate-vinyl alcohol copolymer (VAGH9UCC
') 50mEit part 1,8-diaza-hinculo(5,4,0)undecene-7 formate
02 parts by weight stearic acid ・1
Equal parts Butyl stearate 4 parts by weight Methyl ethyl ketone 400 parts by weight Toluene
500 parts by weight of the above composition was cross-dispersed in a ball mill for 48 hours, filtered through a filter, and then polyisocyanate (Trimethylolpropane tolylene neuson anate adduct Takenate E-31: manufactured by Takeda Pharmaceutical Co., Ltd. (Aji)) was added. 25 parts by weight was added and mixed for 30 minutes. This magnetic paint was applied onto a polyester film, subjected to magnetic field orientation treatment, and after drying, supercalender treatment was performed. This coating was cured at 60°C and 23°C, and the change in reaction rate over time was measured.

The reaction rate was calculated by measuring the peak intensity of isocyanate groups using a Fourier transform infrared spectrometer. The results are shown in Table 1.

Example 2 In Example 1, 60 parts by weight of Takelac E-551T (urethane resin manufactured by Ota Pharmaceutical Co., Ltd.) was used instead of the N-230450 overlapping part, and VAGH was used instead of 50 parts by weight.
The same procedure as in Example 1 was conducted except that 40 parts by weight of GH was used. The results are shown in Table 1.

Comparative Example 1 The same procedure as in Example 1 was conducted except that 0.2 parts by weight of the formate of 1,8-diaza-bicyclo(5,4,O)undecene-7 of Example 1 was not used. The results are shown in Table 1.

Comparative Example 2 Example 1 except that 0.2 parts by weight of butyltin nolaurate was used in place of 02 parts by weight of the formate of 1,8-diazalbicyclo(5,4,0)undecene-7 in Example 1. I did the same thing. The results are shown in Table 1.

Comparative Example 3 The same procedure as in Example 2 was conducted except that 0.2 parts by weight of the formate of 1,8-diazalbicyclo(5,4,0)undecene-7 of Example 2 was not used. The results are shown in Table 1.

Example 3 In place of 0.2 parts by weight of the formate of 1,8-diaza-bicyclo(5,4,0)undecene-7 in Example 1, 1.5-
Diaza-bicyclo(4,3,0)nonene-5 formate 0
．． The same procedure as in Example 1 was conducted except that 2 parts by weight was used.

The results are shown in Table 1.

Table 1 As is clear from the table, it was found that the use of the binder of the present invention significantly shortened the curing time compared to the conventional one, and that the reaction was slow at around room temperature as in the conventional case.

Example 4 A magnetic recording medium was prepared by curing at 60° C. for 9 hours using the same formulation and coating method as in Example 1, and its surface gloss and
Durability was measured. Surface gloss was measured by the amount of reflection of light incident at 60° using a gloss meter (manufactured by Suga Test Instruments Co., Ltd.), and durability was measured using a Hayton surface property measuring device manufactured by Shinraikagaku Co., Ltd. Using this method, we measured the change in the dynamic friction coefficient μ over time, measured the time it took to reach twice the initial value μ, and the results are shown in Table 2.

Example 5 Using the same formulation and coating method as in Example 2, it was cured at 60° C. for 3 hours, and its surface gloss and durability were measured in the same manner as in Example 4. The results are shown in Table 2.

Comparative Example 4 Using the same formulation and coating method as in Comparative Example 1, it was cured at 60° C. for 72 hours, and its surface gloss and durability were measured in the same manner as in Example 4. The results are shown in Table 2.

Comparative Example 5 It was cured at 60° C. for 24 hours using the same formulation and coating method as in Comparative Example 3, and its surface gloss and durability were measured in the same manner as in Example 5. The results are shown in Table 2.

Example 6 Using the same formulation as in Example 3, surface gloss and durability were measured according to the method of Example 4. The results are shown in Table 2.

Table 2 *) As is clear from the time table for the initial value of μ to double, it was found that both surface gloss and durability were improved by using the binder of the present invention.

Claims (1)

[Claims] 1. (a) a resin component having a hydroxyl group, (b) a polyisocyanate, and (c) a general formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼ [In the formula, n is an integer from 1 to 3] A binder for a magnetic recording medium, comprising a salt of an amine represented by the following formula and an acid having a pKa of 2.5 to 4 in an aqueous solution. 2. (a) A resin component having a hydroxyl group, (b) a polyisocyanate, and (c) an amine represented by the general formula ▲ Numerical formula, chemical formula, table, etc. ▼ [In the formula, n represents an integer from 1 to 3] 1. A magnetic recording medium having a magnetic layer bonded with a binder for magnetic recording media comprising a salt of an acid having a pKa of 2.5 to 4 in an aqueous solution.