JPS60101161A - Magnetic paint resin - Google Patents

Abstract

PURPOSE:To provide the titled resin which can retain high dispersibility, is prevented from gelling and gives a magnetic coating film having improved surface smoothness and durability, consisting of a specified vinyl chloride copolymer. CONSTITUTION:A magnetic paint resin is obtd. by copolymerizing 75-95wt% vinyl chloride, 5-20wt% vinyl ester of a carboxylic acid (e.g. vinyl acetate) and 0.5-5wt% unsaturated sulfonic acid or its alkali metal salt (e.g. 2-acrylamide- 2-methylpropanesulfonic acid or its sodium salt). The resin is used as a binder to provide a magnetic paint which can retain high dispersibility, is stable, is prevented from gelling and gives a magnetic coating film having improved surface smoothness and durability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic layer comprising vinyl chloride, carboxylic acid vinyl ester, unsaturated sulfonic acid, or an alkali metal salt thereof copolymerized in a specific ratio, and which is used in a magnetic recording medium. Used as a binder. It concerns vinyl chloride copolymers.

Magnetic recording media such as magnetic tape and magnetic cards.

Generally on a substrate such as polyester film.

Magnetic J-kan is manufactured by applying magnetic paint containing magnetic powder and its binder.

In recent years, in order to increase the coercive force and maximum saturation magnetization, and improve the S/N ratio and recording density, fine gold scrap magnetic powder with a large specific surface area has been used as the magnetic powder5. However, as a binder for this metal magnetic powder, vinyl chloride-vinyl acetate-vinyl alcohol terpolymer,
A product in which a low molecular weight polyester resin is added to a terpolymer of hinyl chloride, vinyl acetate, and maleic acid has been proposed.

However, these binders still cannot be said to have sufficiently satisfactory properties, and since the surface activity of the metal magnetic powder is particularly high, when preparing magnetic paint, the binder and the metal magnetic powder may react and form a gel. As a result, the dispersibility of the magnetic coating material is significantly reduced, and the surface smoothness and durability of the magnetic coating film are impaired.

As a result of intensive studies to improve these difficulties, the present invention has developed a stable magnetic invention that maintains high dispersibility and prevents gelation by using a specific vinyl chloride copolymer as a binder. reached.

That is, the copolymer composition is vinyl chloride weight - 95 weight ratio,
The present invention provides a resin for magnetic coatings characterized by comprising 5 to 20% by weight of carboxylic acid vinyl ester and 0.5 to 5% by weight of unsaturated sulfonic acid or its alkali metal salt.

Specific examples of comonomers with vinyl chloride used in the present invention include carboxylic acid vinyl esters:
Examples include vinyl acetate and vinyl propionate. Examples of unsaturated sulfonic acids or their alkali metal salts include vinylsulfonic acid, methylvinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, and Ac! J” acid ethyl 2-sulfonate, ethyl methacrylate-2-sulfonate, 2-acrylamide-2-
Examples include methylpropane sulfo/acid and alkali metal salts thereof. Here, as an alkali metal atom,
Sodium, potassium, etc. are preferred.

The vinyl chloride copolymer of the present invention has an average degree of polymerization of 100 to
600. Preferably it is from 200 to 500, and the vinyl chloride content is in the range from 75 to 95% by weight. 9
If the amount exceeds 5% by weight, the viscosity of the paint will increase during the preparation of the magnetic paint, causing coating problems such as air entrainment. Furthermore, adding more solvent to reduce the viscosity of magnetic paint is
This not only increases the effort required to recover the solvent, but also causes a decrease in the gloss of the magnetic coating. Further, the content of carboxylic acid vinyl ester needs to be in the range of 5 to 20% by weight. If the content is less than 5% by weight, the solubility in the solvent used in the preparation of the magnetic coating will be insufficient, and if the content exceeds 20% by weight, it will cause peeling of the magnetic coating and decrease in durability. Regarding unsaturated sulfonic acid or its alkali metal salt, if the content is less than 0.5% by weight, the dispersibility of the magnetic powder will be insufficient, and if it exceeds 5% by weight, the hydrophilicity of the sulfonic acid group will become strong. This is undesirable because it will not be able to be sufficiently dissolved in a solvent during paint preparation, and furthermore, agglomeration of metal magnetic powder will occur.

In addition to the above components, it is also possible to use monomers copolymerizable with vinyl chloride in a range of 0 to 10% by weight. The monomers include alkyl vinyl ethers such as methyl vinyl ether, inbutyl vinyl ether, diuryl vinyl ether, and cetyl vinyl ether, ethylene,
α-monoolefins such as clopyrene, vinylidene halides such as vinylidene chloride, alkyl acrylates such as methyl acrylate and methyl methacrylate, unsaturated nitriles such as acrylonitrile and methacrylonitrile, and styrene.

Examples include aromatic vinyls such as α-methylstyrene.

The resin for magnetic coatings of the present invention can be produced by a bulk polymerization method that does not use a monopolymer or by a suspension polymerization method that uses a lower alcohol such as methanol or ethanol alone or in combination with deionized water as a polymerization medium. Ru. In addition, examples of the polymerization initiator used in the production of the resin of the present invention include lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl oxydicarbonate, t-butyl peroxypivalate, and the like. Examples include organic peroxides such as t35-)limethylhexanoyl peroxide, azo compounds such as α5αt-azobisisobutyronitrile, ammonium persulfate, potassium persulfate, and the like. As a suspending agent,
For example, polyvinyl alcohol, partially saponified polyvinyl acetate, cellulose derivatives such as methylcellulose,
synthetic polymeric substances such as polyvinylpyrrolidone, maleic anhydride-vinyl acetate copolymer, and polyacrylamide;
and natural polymer substances such as Denzo/, Gelate/, etc. Examples of the emulsifier include sodium alkylbenzene sulfonate, sodium lauryl sulfate, anionic emulsifier, and nonionic emulsifiers such as polyoxyethylene alkyl ether and polyoxyethylene sorbitan fatty acid partial ester. Further, a molecular weight regulator such as trichlorethylene or thioglycol may be used as necessary. The above-mentioned polymerization initiator, vinyl chloride and other monomers, suspending agents, emulsifiers, molecular weight regulators, etc. may be added all at once or added to the polymerization system at the start of polymerization, or they may be added in portions during polymerization. You can also do that. The unsaturated sulfonic acid or its alkali metal salt may be added all at once at the start of polymerization, but it is preferable to add a portion in the 5th polymerization stage and add the rest in portions as the 1st polymerization progresses. In addition, when charging 1j4 kM of unsaturated sulfonic acid or its alkali gold, a method is used in which it is sufficiently dissolved in a lower alcohol such as methanol or ethanol.

Polymerization is usually carried out in the presence of 35 to so"c with stirring.

The vinyl chloride copolymer obtained in this 5KL process is generally used together with polyurethane resin, curing agent typified by polyisocyanate, and magnetic powder, etc., just like ordinary vinyl chloride resin bi/resin for magnetic coatings. Prepared and used as a solution in any solvent.

Typical examples of polyurethane resins include those obtained by reacting polyester polyols or polyether polyols with incyanates, and those with residual hydroxyl groups are particularly preferred. If desired, ordinary resin binders for magnetic coatings such as vinyl chloride-vinyl acetate copolymer resins, cellulose resins, phenoxy resins, epoxy resins, butyral resins, acrylic resins, and acrylonitrile-butadiene combs can be added to the present invention. It is also possible to use them together as long as the purpose of the above is achieved.

Further, as the magnetic powder, metal magnetic powder such as PE powder and Co powder is more preferably used, but rFe2O3
% Fe3O4% CO containing r-Fe,03,C
Iron oxide powders such as o-containing Fe, O, etc. and Cry powders are also used.

The present invention will be specifically explained below using examples. Note that the number of parts and coefficients on each side are based on weight. In addition, the evaluation of the resin for magnetic paint was based on the following.

1) 100 parts of soluble hinyl chloride copolymer, 20 parts of methyl ethyl ketone
A solution consisting of 0 parts of toluene and 200 parts of toluene was prepared, and the degree of transparency of this solution was visually observed and judged on a three-grade scale of O△x.

2) 400 parts of shiny metallic iron magnetic powder, 100 parts of vinyl chloride copolymer, polyurethane resin (Nipporan 2304 manufactured by Nippon Polyurethane Industry Co., Ltd.) 3oJ Methyl Etyl Ketone 300
parts, methyl isobutyl keto/300 parts, toluene 300 parts
15 parts of polyinocyanate (Coronate L manufactured by Nippon Polyurethane Industries Co., Ltd.) was dispersed by high-speed shearing for 90 minutes.
was added and further dispersed for 15 minutes to obtain a magnetic paint. The obtained magnetic paint was applied onto a polyester film to a film thickness of 5 μm, subjected to magnetic field orientation treatment, and then dried. The reflectance of the magnetic coating film at a reflection angle of 60° was measured using a gloss meter.

3) Gelation/Note: A mixture consisting of 400 parts of metal iron magnetic powder, 100 parts of vinyl chloride conjugate, 300 parts of methyl ethyl ketone, 300 parts of methyl isobutyl ketone, and 300 parts of toluene was dispersed under high-speed shearing for 90 minutes.

This dispersed paint was collected in a sample bottle and stored in a constant temperature bath at 25° C., and the time taken until gel formation was evaluated as gelling property. To determine whether gel is generated, take out a portion of the 5-dispersion paint onto a glass plate and dilute it with approximately 5 times the amount of methyl ethyl ketone.

A glass rod was used and the mixture was mixed and visually observed.

4) After heat-treating the magnetic coating film used for durability and gloss evaluation at 65°C for 65 hours, a load of 100 g was applied, the film was brought into contact with a rotating drum covered with abrasive paper, and rotated at 150 rpm.
The extent to which the magnetic paint adhered to the abrasive paper was visually observed and judged on a three-point scale of ○△x.

Example 1 In a polymerization vessel, 130 parts of deionized water, 1/7 part of methanol, 0.6 part of methyl cellulose, 0.2 part of polyoxyethylene sorbitan fatty acid partial ester, 0 part of trichlorethylene
．． Pour 52 parts, seal the can, degas under reduced pressure, and add 8 parts of vinyl chloride.
7 parts and 10 parts of vinyl acetate were charged, and the mixture was stirred at 58°C.

Thereafter, 0.42 parts of 33s-)J methylhexanoyl peroxide was charged to start polymerization, and at the same time, it was dissolved in 40 parts of methanol. 3 parts of 2-acrylamido-2-methylpropanesulfonic acid was continuously introduced at a constant rate until the entire amount was consumed in 8 hours. After 12 hours of reaction time, when the pressure in the polymerization vessel reached 3 kg/(po), it was cooled to obtain a vinyl chloride copolymer.As a result of analysis, this polymer contained 9.2% vinyl chloride and vinyl acetate. 8.5
%, 2-acrylamido-2-methylpropanesulfonic acid 2.3%, and a polymerization degree of 390. As a result of testing this vinyl chloride copolymer using the above-mentioned evaluation method, it was found that the solubility is ○, and the light when used as a magnetic paint? The R property was 91%, the gelling property was 5 days or more, and the durability was 0.

Example Z and Comparative Example 1 A copolymer was obtained in the same manner as in Example 1, except that the types and amounts of the monomer, unsaturated sulfonic acid, and its alkali metal salt were varied. The composition and evaluation results are shown in the table.

Comparative Example 2 Polymerization was started in the same manner as in Example 1, except that 89 parts of vinyl chloride, 11 parts of vinyl acetate, and 3.0 parts of trichlorethylene were used instead of 2-acrylamide-2-methylpropa/sulfonic acid. , a vinyl chloride copolymer was obtained. As a result of one analysis, this polymer was found to be a copolymer containing 90.7% vinyl chloride, 9.3% vinyl acetate, and a degree of polymerization of 380. As a result of evaluating this vinyl chloride copolymer in the same manner as in Example 1, the solubility Q and glossiness were 1% or less, and a magnetic coating material with sufficient dispersion for physical property evaluation was not obtained.

Comparative Example 3 The same evaluation as in Example was carried out except that a mixture of 100 parts of the copolymer obtained in Comparative Example 2 and 2.5 parts of 2-acrylamido-2-methylpropanesulfonic acid was used. , 2-acrylamide-2-methylpropane sulfo/ec does not dissolve in the solvent, so the solubility x and glossiness are less than 1%, and there is no addition effect. .

Example 3 After degassing under reduced pressure without charging anything into the polymerization vessel, vinyl chloride 90
10 parts of vinyl acetate and stirred at 58°C.
a5-to! j 0.5 part of methylhexanoyl peroxide was charged to start polymerization, and at the same time, it was dissolved in 40 parts of methanol. 3 parts of 2-acrylamido-2-methylpropanesulfonic acid was continuously charged at a constant rate so that the entire amount was consumed in 8 hours. After a reaction time of 9 hours, when the pressure in the polymerization vessel reached 7.4 ky/tyl, it was cooled to obtain a vinyl chloride copolymer. This combination is the result of one analysis.
Vinyl chloride 82.0%, vinyl acetate 13+5%, 2-acrylamido-2-methylpropa/sulfone f114.
It was a copolymer with a polymerization degree of 240. As a result of testing this vinyl chloride copolymer using the above-mentioned evaluation method, the solubility was ○, the gloss when used as a magnetic paint was 96 excellent, and the gelling property was 5.
The durability was good for more than 1 day.

Patent applicant Nippon Zeon Co., Ltd. Procedural amendment August 24, 1980 Director General of the Japan Patent Office T Indication of the case 2, Name of the invention Resin for magnetic paint 5 Person making the amendment 4, Number of inventions increased by the amendment 0 5 , Column for detailed explanation of the invention in the specification to be amended & contents of amendment ill Correct “adjustment” in line 12 of page 2 of the specification to “preparation” 〇(2) Line 18 of member 5 of the same specification ``--Mere Kunsulfonic Acid''
Next, add "3-aryloki 7-2-hydroxyglopanesulfonic acid".

(3) On page 5, line 9, next to “vinylidene rhodanide,” “acrylic acid, methacrylic acid, maleic acid,
Unsaturated Cal H like itaconic acid? Add an unsaturated carboxylic acid anhydride J such as phosphoric acid or maleic anhydride.

(4) “1” next to “Examples” on page 14, line 15
Add 〇

Claims (1)

[Claims] A magnetic paint characterized in that the copolymer composition is 75 to 95% by weight of vinyl chloride, 5 to 20% by weight of vinyl carboxylate 1, 0.5 to 5% by weight of unsaturated sulfonic acid or its alkali metal salt. Resin for use.