JPS58177524A - Binder for magnetic recording body - Google Patents

Abstract

PURPOSE:To provide a binder having superior power of dispersing magnetic powder, by using a copolymer contg. vinyl chloride, a vinyl monomer contg. a hydroxyl group, acrylic tertiary amine, and acrylic ester different from the vinyl monomer and the tertiary amine or vinyl acetate as the constituent units. CONSTITUTION:The vinyl monomer contg. a hydroxyl group is a monomer having the structural formula of the reaction product of acrylic acid or methacrylic acid with polyhydric alcohol, and the amount of the monomer to be used is 0.5-10wt% of the amount of the copolymer. The acrylic tertiary amine is tertiary amine contg. an acryloyl group or a methacryloyl group. The tertiary amine contributes to the improvement of the dispersibility of magnetic powder. The amount of the tertiary amine to be used is 0.1-5wt% of the amount of the copolymer. The acrylic ester is the ester of (meth)acrylic acid with alicyclic alcohol, and it is contained in the copolymer by about 1-20wt% and contributes to the improvement of the solubility and the dispersibility. Vinyl acetate may be used in place of the acrylic ester. Magnetic powder is added to the polymerized and dissolved copolymer, and they are kneaded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a binder for magnetic recording materials that has excellent dispersibility of magnetic powder.

Magnetic recording materials used in magnetic recording tapes, magnetic disks, etc. are made by applying an electric current, applying magnetic powder, and a magnetic paint containing a binder %IJ that binds this powder to a substrate such as polyester, and drying it. It has excellent electrical properties and durability. Therefore, there is a strong demand for binders for magnetic recording media that have excellent dispersibility of magnetic powder in magnetic paints and, as a result, properties that can impart a high squareness ratio to magnetic recording media.
Furthermore, it is possible to form a magnetic layer with excellent wear resistance and heat resistance.

Conventionally, vinyl chloride-vinyl acetate-vinyl alcohol polymers have been used as those with comparatively good properties, and when it is necessary to particularly improve the abrasion resistance of the magnetic layer, F
2-Binding agents for magnetic recording materials containing the above-mentioned polymer and incyanate compound have been degraded, but further improvements have been desired.

In view of the above-mentioned current state of magnetic binders, the present invention has been developed to improve the dispersibility of SO magnetic powder made of magnetic elmium, and to add a small amount of incyanate compound to X64I, resulting in 19 wear resistance and heat resistance. The object of the present invention is to provide a cohesive rule for a magnetic ε-brass body that can form a magnetic layer tube with excellent properties.

However, the present invention! In fact, vinyl chloride, a vinyl monomer containing a hydrogen group, an acrylic ester or a copolymer having vinyl acetate as a constituent unit, and an isocyanate compound with the necessary KEp. A binder for a magnetic recording body is characterized by containing:

Vinyl chloride, which makes up the majority of the copolymer in the present invention, provides appropriate hardness and flexibility to the magnetic layer together with other structural units, and the amount used is not specified. It is usually 60 to 92% by weight.

Examples of the hydroxyl group-containing vinyl monomer in the present invention include those having a structural formula as a reaction product of acrylic acid or methacrylic acid and a polyhydric alcohol, acrylamide or methacryl Ili thread amide, etc.
Specific examples of rJ4 include 2- and droxyethyl (meth)
Acrylate (this represents both Fi2-hydroxyethyl acrylate and 2-hydroxyethyl acrylate).

(same hereinafter), 2-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, polyethylene glycol 7-(meth)acrylate expressed by the following formula: CHz ”CR
-COO(' CIt CHz O+B H (Crow is IE& of 2 to 9, R is a water column or methyl group), polyglobylene glycol mono(meth)acrylade-roxyethyl-2'-acryloyloxy 7 Sauce 4 - It is Tami who mentions (meth)acrylic acid esters.
A specific example of the latter is N-methylol (meth)acrylamide.

These can be used alone or in appropriate combinations as a constituent unit of a copolymer, and in particular, polyethylene glycol monomethacrylate in which n in the above formula is 7 to 9, polypropylene glycol monomethacrylate in which n in the above formula is 5 or 6. 2-hydroxypropyl (meth)acrylate and the like are preferably used.

When the amount of vinyl powder containing hydroxyl groups is too large, the solubility of the copolymer in a solvent tends to decrease, and when it is too small, the dispersibility of the magnetic powder tends to decrease.
Anti-i6 with incyanate compounds voiced by llK
Since the flex bond is not sufficiently formed and hardening by heating is difficult, the amount is usually 11 to 30% by weight of the copolymer, preferably α5 to 10% by weight.

51 The acrylic tertiary amine in the present invention refers to a tertiary amine containing an acryloyl group or a methacryloyl group,
specifically? 1 dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, etc.
Suitable examples include meth)acrylic acid ester and dimethylacrylamide, and dimethylaminoethyl acrylate is particularly preferred for the ridged eaves of +Iflu8 wood. The tertiary amine greatly contributes to the fractional property of magnetic powder, but if it is too large, the water resistance of the copolymer becomes a problem, and if it is too small, the fractional properties of the magnetic powder are accelerated. Therefore, it is difficult for the copolymer to produce 1F1 vermilion, which promotes cross-linkage warping between the incyanate compound contained in the copolymer and the above-mentioned copolymer. 05 to 15% by weight, preferably #-1CLl to srcms.

In the present invention, the acrylic ester refers to an ester of (meth)acrylic acid and an aliphatic alcohol, and an ester of (meth)acrylic acid and alicyclic alfur 6-.
I! Fish body and acrylic tertiary amines are various monomers, and specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, and hexyl (meth)acrylate. ) acrylate, cyclohexyl (meth)acrylate, hegetyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate (dodecyl (meth)acrylate, tetradodecyl (
Examples include meth)acrylate, glycidyl (methacrylate, etc.), which may be used alone or in combination,
Generally, Kl to 20% by weight*@% is contained in the copolymer, contributing to improving the solubility in solvent WC% and dispersibility of the magnetic powder, and imparting flexibility to the magnetic layer.

In the present invention, KW! is used instead of the acrylic ester as a constituent unit of the copolymer! #ll vinyl 7- # may be used, and of course may be combined, and the content of vinyl acetate in the copolymer is usually 1 to 20
In terms of weight percent, it contributes to the solubility in bath K and the dispersibility of magnetic powder, and to imparting flexibility to magnetism.

For copolymers containing each of the above-mentioned monomers as constituent units, additionally required #
1C16 also contains other polymerizable vinyl monomers such as ethylene and styrene! It may be added as L4L,
The preferred range of the degree of polymerization is 20.about.600, and the copolymer can be obtained by a known one-machine method, such as the fg liquid polymerization method, the 1L polymerization method, and the suspension polymerization method.

Incyanate compounds to be kneaded with the magnetic powder together with the above copolymer when particularly enhancing the abrasion resistance and heat resistance of the magnetic layer include (c) tolylene diincyanate, diphenylmethane diisocyanate, dianisidithi diisocyanate,
Examples include toridene diisocyanate, hexamethylene diisocyanate, metaxylylene diisocyanate, 1 mole of l-hydromethylolpropane, tolylene di-8-isocyanate 4#, and the like.
If the amount of the incyanate compound used is too large, the final coating will become brittle, so the amount of the incyanate compound used is preferably less than the weight of the above-mentioned co-electropolymer lOO weight IIKjlLiO, and usually it is a
s parts by weight or more.

To prepare a magnetic coating material from the binder K of the present invention, the above-mentioned copolymer (magnetic powder such as T-acetate) is polymerized, for example, by S liquid polymerization and dissolved in an O#l agent such as toluene. Materials are added, kneaded and dispersed to improve the magnetic abrasion resistance.
A magnetic paint is obtained by adding an incyanate compound according to the characteristics of the pigeon coop, etc., and adding a catalyst such as triethylamine in some cases, although it is usually not necessary.

However, the order of addition of the copolymer incyanate compound and the magnetic material powder O, the dispersion means, etc. in the present invention are not limited at all. The solvent used to dissolve the copolymer 9- to form the binder of the present invention may be one or more of toluene, methylethylgtone, methylisobutylgtone, isopropyl alcohol, cyclohexylne, etc. Mixtures of are commonly used. The above copolymer is used in an amount of 1.25 to 1@e parts by weight per 100 weight TIIK magnetic material powders, and is used in the magnetic layer lllll.
4Fi, usually K11ml to have 10-30% by weight of the above copolymer.

The binder for magnetic recording materials of the present invention has the above-mentioned structure, and in particular, the copolymer contains a hydroxyl group-containing vinyl monomer, an acrylic tertiary amine, and two different acrylic esters. contains vinyl acetate as a constituent unit, so the resulting magnetic paint has excellent dispersibility of magnetic powder, and therefore a magnetic layer with a high squareness ratio is formed, and the copolymer also contains vinyl chloride. Therefore, a magnetic layer having appropriate hardness and flexibility is formed by competing with the material.

Furthermore, in the case where the binder of the present invention contains an incyanate compound, the KJII hydroxyl group in the copolymer contributes to the crosslinking reaction between the copolymer and the incyanate compound, resulting in improved wear resistance. The active nitrogen introduced into the acrylic copolymer by the acrylic tertiary amine promotes the crosslinking reaction, so after applying the magnetic paint to the substrate, it forms a magnetic layer with excellent heat resistance. It can be sufficiently cured to form a magnetic layer even at low temperatures, and it is possible to form a magnetic layer in this way (because there is no need to add a low molecular weight catalyst, the catalyst will not bleed and deteriorate the magnetic properties, and In addition, the obtained magnetic paint Pot Lie 7 does not become a waste of food.

Below is 91. The present invention will be explained with reference to examples. In addition, below (hereinafter, "Zheng" and "1%" refer to iris weight and weight %, respectively.
shows.

Example 1 Stirring bar, monomer introduction tube, IL element blowing tube, vacuum twin,
In an autoclave equipped with a thermometer, dissolve 92 parts of polyvinyl alcohol Q32il, which is a suspension 92 fixing agent, and add 9 parts of aO, then add 13 parts of vinyl acetate monomer, 2-human U, in which 06 parts of peroxybenzoyl carbide was dissolved. A mixture of 2 parts of xyethyl methacrylate monomer and 2 parts by weight of dimethylaminoethyl acrylate monomer was added, and after purging with nitrogen, degassing was performed in a vacuum line to remove oxygen from the reaction system, and vinyl chloride 83 was added.
parts by weight were introduced and polymerized at 80° C. for 18 hours with stirring to obtain a copolymer.

The obtained copolymer was centrifuged in a centrifugal Jllli machine, washed with water, thoroughly dehydrated, and air-dried at 50°C for 24 hours to obtain a white powdery polymer. This powder copolymer was dissolved in a mixture of toluene and methyl imptyl ketone (weight ratio 1:1) to prepare a 15-O copolymer II moat. Next, T-iron oxide was added in an amount such that 47 parts of T-iron oxide was added to 20 parts of the copolymer, and the mixture was mixed and dispersed for 10 hours in a l-lumil to obtain a magnetic paint. Circle.

9. Apply magnetic paint to a 257-thick polyester film so that the dry thickness is 6 mm, leave it at a warm temperature for 48 hours, dry it to make a magnetic recording body, measure the squareness ratio, and make it round. .

The result of 7 is shown in Table 1〉Q, an excellent game exceeding 8 and 9.

Examples 2 and 3 In the same manner as in Example 1, the moderate O-silver O copolymer shown in Table 1 was prepared, a magnetic paint was prepared, a magnetic recording material was obtained, and the O
Measure the squareness ratio and make a circle. The results are shown in Table 1).

Comparative Example 1 In the same manner as in Example 1, vinyl chloride-vinyl acetate-vinyl alcohol lk19w-(11 amount Jt, ko011[
K91:3:6) was used to prepare a magnetic paint, and the squareness ratio of the resulting round magnetic recording matrix was measured.

Please refer to the 1110th letter for the results.

1s- @1 Table f: Comparison of sprouting properties Same as Example 1, vinyl chloride-vinyl acetate-acdalic acid ester-vinyl alcohol system II! IJ-r-
Create a magnetic paint using Kakuken Hihiro 1L77
It can be.

Example 4 A white O powder copolymer was obtained in exactly the same manner as in Example 1 regarding the type and amount of raw materials and the operating method. This copolymer was dissolved in toluene-methyl isobutyl ketone (weight ratio 1"l) and 1
A copolymer solution of 5- was prepared, and to the total amount of the 0III case was added an amount of iron oxide such that the amount of T-iron oxide was 47 parts based on 2 parts of copolymer II, and the mixture was heated in a ball mill for 1 G hour. After 90 days of ink dispersion, 65 parts of an incyanate compound (Corone L, manufactured by Nippon Polyurethane Industries, Ltd.) was added and stirred to obtain a magnetic paint.

This magnetic paint was prepared and its viscosity was measured after 24 hours and 48 hours using a B-type viscosity needle to determine the stability of pot-ripe.

Step 1: Magnetic paint was applied onto a polyethylene terephthalate film with a thickness of 25 cm to a dry thickness of 67 cm, and left at room temperature for 4"8 hours to dry and harden, producing a magnetic brass body. , squareness ratio, heat adhesion, and gel fraction were investigated.

These results are shown in Table 2. Heat adhesion refers to whether or not the formed magnetic layers are heated at 120°C for 15 minutes and the magnetic layers adhere to each other by IK. (does not occur), and × indicates adhesion.・ Gel fraction refers to copolymerization without mixing magnetic powder - fat 11 fill 5 to F luene - methyl inoptyl ketone (weight ratio 1:1
) It is the value obtained by dividing the weight of the O film after immersing it in a mixed solvent by the weight of the film before immersion, and is a guideline for determining the reaction efficiency of the crosslinking reaction between the copolymer and the incyanate compound. be.

Examples 5 to 6 In the same manner as in Example 4, 1 lll of a copolymer with a moderate O composition as shown in Table 2 was obtained to obtain a binder, and the viscosity increase rate of the magnetic paint and the squareness ratio of the magnetic layer were determined. , heat adhesion and gel fraction were investigated. The results were in accordance with Table 2.

Comparative Example 3 In the same manner as in Example 4, various O copolymers with O compositions as shown in Table 2 were prepared to obtain binders, and magnetic paints and magnetic layers were evaluated. The results are shown in Table 11.

Comparative Example 4 Example 4 except that 0.82 parts of triethylamine was added as a catalyst to 100 parts of the nine copolymer obtained in Comparative Example 1.
A binder is obtained and the magnetic paint and magnetic layer are evaluated. The results are shown in Table 2.

Comparative Example 5 151 il of vinyl chloride-vinyl acetate-vinyl alcohol 4-polymerotoluene-methylyptyl ketone (weight ratio 1:1) shown in No. 2114 was prepared, and a binder was obtained in the same manner as in Example 4. A magnetic paint was prepared.

These O evaluation results are shown in Table 2.

Comparative Example 6 A binder was obtained and a magnetic paint was prepared in the same manner as in Comparative Example 5, except that 0.41 part of triethylamine was added as a 11γ-catalyst to 100 parts of the vanguard polymer.

These O evaluation results are shown in Table 2.

−18=

Claims (1)

[Claims] Lm vinyl, hydroxyl group-containing vinyl monomer, acrylic 1
1. A binder for a magnetic recording medium, comprising a copolymer having a 13 amine and an acrylic ester or vinyl acetate as a constituent unit, and an incyanate compound as necessary. 1. The binder according to No. 1 JJI, wherein the water-group-containing vinyl monomer is polyethylene glycol monomethacrylate. 1 The hydroxyl group-containing vinyl monomer is 2-hydroxyglobin ν
- The binder according to item 1, which is a methacrylate. Table: The binder according to any one of Items 1 to 3, which is an acrylic tertiary amine or dimethylaminoethyl acrylate. The content of the isocyanate compound is 6 per 1 kilo for copolymer 1-10011iiB (13-301)@the binder described in any of Items 1 to 4JJ.