JPS6153367A - Resin for magnetic paint - 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 [Field of Industrial Application] The present invention relates to a vinyl chloride resin for magnetic coatings, and particularly to a vinyl chloride resin used as a binder for magnetic recording media.

[Conventional technology]

Magnetic recording media such as magnetic chips and magnetic cards are generally manufactured by coating a magnetic coating containing magnetic powder and its pine paste as a magnetic layer on a substrate such as a preester film. In order to increase the magnetic force and maximum saturation magnetization, and improve the S/N ratio and recording density,
As the above-mentioned magnetic powder, finely divided magnetic powder having a large coercive force and a large specific surface area has come to be used.

However, such fine magnetic powder is a combination of vinyl chloride-vinyl acetate-vinyl alcohol ternary M, vinyl chloride-
When a magnetic paint is prepared using the vinyl acetate-maleic acid terpolymer yanitrocellulose and a conventional binder, there is still a problem in that the paint thickens and its dispersibility is still insufficient.

In addition, low molecular weight surfactants are used as dispersants to improve dispersibility, but the use of large amounts of these dispersants can cause problems such as poor durability of the magnetic recording medium and head stains, so the amount used must be controlled. Naturally, there are limits.

Meanwhile, we are busy working to improve the durability and reliability of magnetic recording media.
? A crosslinking agent that reacts with a part or all of a flexible material such as urethane resin, polyester resin, or acrylonitrile-butadiene rubber and a binder to form a crosslinking bond is added to the magnetic coating material to form a crosslinked coating film on the magnetic layer. However, this is commonly used especially in magnetic recording tapes for recording.

Therefore, the binder is required to be compatible with these flexible materials and to have appropriate reactivity with the crosslinking agent. Furthermore, it has excellent chemical stability;
The reliability of the tape is improved because it is less likely to generate decomposition products that cause deterioration of magnetic powder and corrosion of the head.
This is becoming more and more required.

[Problem that the invention seeks to solve]

As a result of intensive study to develop a binder that can meet the high performance of magnetic recording media, the present inventor found that by using a specific vinyl chloride copolymer, it was possible to maintain and increase the bright dispersibility. It is possible to obtain a magnetic paint that prevents viscosity and has excellent reactivity with a crosslinking agent, and that a magnetic recording medium obtained using the paint has good surface smoothness and durability of the coating film, and The present invention was achieved by discovering that the material has excellent running properties, magnetic properties, and electromagnetic conversion properties.

[Means for solving problems]

That is, a reaction mixture in which an alkali metal salt or ammonium salt of a strong acid containing sulfur or phosphorus is added to a monomer having a nixy group is mixed with vinyl chloride and, if necessary, other monomers that can be copolymerized with these. A copolymer obtained by copolymerization that has a vinyl chloride content of 600% by weight or more, and the amount of strong acid groups containing sulfur or phosphorus bonded to the copolymer is 0.1-4.0% by weight. , the amount of epoxy groups is 0.5
According to the present invention, a resin for magnetic coating material is provided, which is characterized in that the amount of the magnetic paint is at least % by weight.

The reaction between a monomer having an epoxy group and an alkali metal or ammonium salt of a strong acid containing sulfur or phosphorus is usually carried out with stirring at room temperature or under heated conditions. Examples of monomers having a monopoxy group used in this reaction include glycidyl ethers of unsaturated alcohols such as allyl glycityl ether and methacryl glycidyl ether, glycidyl acrylate, glycidyl methacrylate, and glycidyl-p-vinyl Benzoate, methyl glycizol itaconate, glycidyl ethyl maleate,
Examples include glycidyl esters of unsaturated acids such as glycidyl vinyl sulfonate and glycidyl (meth)allylsulfonate, and epoxide olefins such as tutadiene monooxide, vinylcyclohexene monooxide, and 2-methyl-5,6-nipoxyhexene.

Examples of alkali metal salts or ammonium salts of strong acids containing sulfur or phosphorus to be added to the epoxy group-containing monomer include sulfites such as sodium sulfite, sodium thiosulfate, sodium bisulfite, ammonium sulfite, and potassium sulfite; sulfuric acid; Hydrogen sulfates such as sodium hydrogen sulfate, potassium hydrogen sulfate, and ammonium hydrogen sulfate; hydrogen phosphate salts such as dipotassium hydrogen phosphate and disodium hydrogen phosphate; submersible salts such as sodium hydrogen phosphite and ammonium hydrogen phosphite. Acid salts; Tauri/sodium,
Examples include aminosulfonic acid salts such as sodium sulfamino acid and potassium sulfanilate, and heptamine sulfates such as sodium 1-amine ethyl sulfate.

The addition reaction is possible in both an aqueous system and a non-aqueous system, but since the salts used in the addition reaction are water-soluble, an aqueous system or an organic solvent system containing water is preferred.
The reaction is carried out under stirring.

The reaction is usually carried out at room temperature to about 90° C. for 1 to 24 hours, but if the reaction temperature is too high, side reactions will increase. Rather, it is better to react so as to leave unreacted epoxy group-containing monomers so that the epoxy group content in the resin of the present invention is 0.5 weight or more. Catalysts can be used to accelerate addition reactions. Examples of this melting medium include quaternary ammonium salts such as tetrabutylammonium bisal 7ate, tetrabutylammonium bromide, trimethyllauryl ammonium chloride, and pencil triethylammonium chloride, and boron fluorides such as zinc boron tetrafluoride. It will be done.

The reaction mixture thus obtained is copolymerized as it is, or after removing the inorganic salts and addition reaction catalyst, with vinyl chloride and, if necessary, a monomer copolymerizable therewith in the presence of a radical generator.

In addition to vinyl chloride, examples of monomers that can be used as necessary include carboxylic acid vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether, isobutyl vinyl ether, and cetyl vinyl ether; vinylidene chloride, Vinylidene such as vinylidene fluoride; diethyl maleate, butylbenzyl maleate, di-2-hydroxyethyl maleate, dimethyl itaconate, methyl (meth)acrylate, ethyl (meth)acrylate, lauryl (meth)acrylate , unsaturated carbic acid esters such as 2-hydroxypropyl (meth)acrylate; olefins such as ethylene and propylene; allyl alcohol, 3-butene-
Unsaturated alcohols such as 1-ol; unsaturated nitriles such as (meth)acrylonitrile; aromatic vinyls such as styrene, α-methylstyrene, and p-methylstyrene. These monomers are used not only to improve the solubility of the resin by controlling the compatibility and softening point of the resin of the present invention and other resins when mixed, but also to improve the properties of the coating film and the coating properties. Appropriate selection is made depending on needs such as process improvement.

The resin of the present invention can be produced using any known polymerization method, but from the viewpoint of polymer solubility, solution polymerization, lower alcohols such as methanol or ethanol alone, or decomposition with lower alcohols such as methanol or ethanol as the polymerization medium are recommended. Preferably, it is produced by a suspension polymerization method in combination with ionic water. Polymerization initiators used in the production of resins include, for example, lauroyl peroxide, penzoyl oxide,
, 5゜5-trimethylhexanoyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-2-ethoxyethyl-oxydicarbonate, t-butyl-peroxybivalate, t Organic peroxides such as -butyrno-oxyneodecanoate: 2,2'-azobisisobutyronitrile, 2°2'-7 sohysu2,4-dimethylvaleronitrile, 4t4'-azobis- Examples include chiazo compounds such as 4-cyanovaleric acid; inorganic peroxides such as ammonium persulfate, potassium persulfate, and ammonium perphosphate.

Suspension stabilizers include, for example, polyvinyl alcohol,
Partially saponified polyvinyl acetate, methyl cellulose, hydroxyglobil cellulose, Cal? Synthetic polymeric substances such as cellulose derivatives such as oxymethylcellulose, I-rivinylpyrrolidone, polyacrylamide, maleic acid-styrene copolymers, maleic acid-methyl vinyl ether copolymers, maleic acid-vinyl acetate copolymers, and starches; Examples include natural polymeric substances such as gelatin. In addition, as emulsifiers, anionic emulsifiers such as sodium alkylbenzene sulfonate and sodium lauryl sulfate, polyoxyethylene alkyl ether,
Examples include nonionic emulsifiers such as polyoxyethylene sorbitan fatty acid partial ester. Further, a molecular weight regulator such as trichlorethylene or thioglycol can also be used if necessary. The above-mentioned polymerization initiator, reaction mixture of an epoxy group-containing monomer and a salt of a strong acid containing sulfur or phosphorus, vinyl chloride and other monomers, suspending agents, emulsifiers, molecular weight regulators, etc. are added all at once at the start of polymerization. It may be added to the polymerization system, or it may be added in portions during the polymerization. Polymerization is usually carried out at a temperature of 35 to 80°C with stirring.

The resin of the present invention has an average degree of polymerization of 100 to 900, preferably 200 to 500. The content of vinyl chloride is 60% by weight.
That's all. If the degree of polymerization is less than 100, the abrasion resistance of the magnetic layer will be insufficient, and if it exceeds 900, the viscosity of the paint will be high and the magnetic powder will likely be insufficiently dispersed. On the other hand, if the content of vinyl chloride is less than 60% by weight, disadvantages arise, such as a decrease in compatibility with flexible materials and a marked decrease in solvent performance of the coating film.

In addition, l of the strong acid group bonded to the resin is -S03゜-8O
It is necessary that the weight ratio is 0.1 to 4.0 as 4*-PO4 or -po. If it is less than 0.1% by weight, the dispersibility of the magnetic powder will be insufficient, and if it exceeds 4.0% by weight, the hydrophilicity of the strong acid roots will be strong, the solubility in solvents will be insufficient, or the coating will be difficult. The moisture resistance of the film decreases, and furthermore, the magnetic powder agglomerates, resulting in poor dispersibility.

The resin of the present invention obtained in this way is generally a polyurethane resin, ? Lyester resin, acrylonitrile
Flexible materials such as butadiene copolymers, polyinthia,
It is prepared and used as a solution in any solvent together with a crosslinking agent typified by a nate type, magnetic powder, and, if necessary, known materials such as a lubricant, a dispersant, an antistatic agent, and an abrasive.

Note that the resin of the present invention can exhibit excellent heat resistance stability due to the epoxy group in the resin, so that it is possible to manufacture a magnetic recording medium that is highly reliable and is resistant to head corrosion. Furthermore, by utilizing the reactivity of the nixy group, it is possible to crosslink a coating film with a polyamine compound or a carboxylic acid compound.

If desired, the resin of the present invention may also be used in combination with the resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl alcohol-vinyl acetate copolymer resin, cellulose resin, phenoxy resin, amino resin, epoxy resin. It is also possible to use common resin binders for magnetic coatings, such as butyral resin, acrylic resin, etc., as long as the object of the present invention is achieved.

Furthermore, as the magnetic powder, metal magnetic powders such as Fe powder and Co powder are preferably used, but r-Fe2O3*
Fe3O4* Co-containing r -Fe2O3v Co-containing F.304, iron oxide powders such as barium ferrite, and CrO2 powders are also used.

〔Example〕

- The present invention will be specifically explained below with reference to Examples. Note that the number of copies is based on weight.

(Resin Synthesis Example 2 Example 1 15 parts of allylglycidylethyl, 2 parts of sodium bisulfite, and 50 parts of deionized water were stirred at 50°C in an Erlenmeyer flask. After 2 hours, the mixture was colored pale yellow. The oil phase was significantly reduced before and after the reaction.This mixed solution was charged into an autoclave with 5 parts of vinyl acetate, 3 parts of sodium lauryl sulfate, 1 part of potassium persulfate, and 150 parts of deionized water, and degassed. After adding 100 parts of vinyl chloride, 54
Polymerization was initiated at ℃. Autoclave pressure is 5 kl
/cm"K, unreacted vinyl chloride was collected to obtain a copolymer dispersion. This was freeze solidified and thoroughly washed with hot water until no bubbles were generated in the washing water.
After drying, copolymer A was obtained.

Example 2 Copolymer B was obtained in the same manner as in Example 1 except that potassium hydrogen sulfate was used in addition to sodium bisulfite.

Example 3 20 parts of glycidyl methacrylate, 3 parts of ammonium hydrogen phosphate, and 50 parts of deionized water were placed in a glass autoclave, and after degassing, they were mixed at 50°C for 2 hours. In another stainless steel autoclave, 3 parts of 3-buten-1-ol, 1 part of azobisisobutyronitrile, 0.6 part of methylcellulose, and 0.2 parts of polyoxyethylene lauryl ether.
After charging 200 parts of methanol and degassing, 1 part of vinyl chloride was added.
At the same time, the mixture in the glass autoclave was continuously injected into the stainless steel autoclave, and the injection was continued until the pressure in the stainless steel autoclave reached 5'kJ/cns2. Completed. When the pressure further decreased by 3 kl/an''i, unreacted vinyl chloride was collected, dehydrated and washed to obtain copolymer C.

Example 4 A copolymer was obtained in the same manner as in Example 3, except that sodium taurate was used instead of ammonium hydrogen phosphate.

Comparative Example 1 Example 1 except that the amount of sodium bisulfite was increased to 15 parts
Copolymer E was obtained in the same manner as above.

Comparative Example 2 Copolymer F was obtained in the same manner as in Example 1, except that vinyl acetate was 50 parts and vinyl chloride was 65 parts.

Comparative Example 3 Copolymer G was prepared in the same manner as in Example 3 except that glycidyl methacrylate was added to n-globil methacrylate.
I got it.

Comparative Example 4 Copolymer H was obtained in the same manner as in Example 3 except that ammonium hydrogen phosphate was not used.

The properties of these resins are as follows: commercially available vinyl chloride-vinyl acetate-
It is shown in the table together with maleic acid ternary copolymer (I) and vinyl chloride-vinyl acetate-vinyl alcohol ternary co-IT polymer (J).The amount of hydroxyl groups in the resin was determined by infrared absorption analysis by υ, chloride The amount of vinyl is based on the constant fK of the amount of chlorine due to combustion,
The amount of epoxy groups was determined by titration, and the amount of strongly acidic groups was determined by a combination of elemental analysis and infrared absorption spectrometry.

(Evaluation of resin properties) Next, each resin was evaluated as a magnetic coating material and a magnetic recording medium. The results are shown in the table. The evaluation method was as follows.

1) 100 parts of soluble vinyl 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-point scale of ○Δ×.

2) Transfer LO grams of heat-stable vinyl chloride copolymer into a 15CC test tube, plug the opening with absorbent cotton sandwiched with Congo red test paper, and place in an oil path at 150°C to remove the generated hydrochloric acid. The time required for the Congo Red test paper to change color was measured using the following method.

3) 400 parts of dispersion-stable metal iron magnetic powder, 100 parts of vinyl chloride copolymer8
, 300 parts of methyl ethyl ketone, 300 parts of methyl isobutyl ketone, and 300 parts of toluene were 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 generation of glue was observed. The generation of glue was determined by taking a portion of the dispersed paint onto a glass plate, diluting it with about 5 times the amount of methyl ethyl ketone, mixing with a glass rod, and visually observing the mixture. The numbers are indicated by ○Δ× in descending order of del occurrence.

4) Glossiness (1) 400 parts of metallic iron magnetic powder, 70 parts of vinyl chloride copolymer, 30 parts of polyurethane resin (Nipporan 2304 manufactured by Nippon Polyurethane Industries Co., Ltd.), 300 parts of methyl ethyl ketone,
300 parts of methyl isobutyl ketone, 300 parts of toluene,
After dispersing a mixture of 2 parts of silicone oil under high-speed shearing for 90 minutes, 15 parts of polyinocyanate (Corone L manufactured by Nippon Polyurethane Industry Co., Ltd.) and 100 parts of cyclohexanone were added, and the mixture was further dispersed for 90 minutes to form a magnetic paint. did. 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 parts was measured using a glossy needle.

5) Gloss (2) Gloss (1) except that polyamide (Persamide 125 manufactured by General Mills) was used instead of polyincyanate
) A magnetic coating film was obtained and its reflectance was measured.

6) Squareness ratio (Br/Bm) The magnetic coating used for gloss evaluation was 12.5 mm x
A sample of 50 mK was cut out and measured using a magnetic property measuring machine.

7) The magnetic coating used for durability and gloss evaluation was smoothed with a calendar roll and then heat treated at 65°C for 65 hours, then subjected to a load of Zoo and @ and placed on a rotating drum covered with abrasive paper. They were brought into contact and rotated at 150 rpm, and the extent to which the magnetic paint adhered to the abrasive paper was visually observed and judged on a three-point scale of 0Δx.

8) Using the same method as the running resistance durability evaluation, the force generated between the coating film and the rotating drum was measured using Ur-ji in an atmosphere of 65°C and relative humidity of 80°C. I judged it.

Procedural amendment 8 (voluntary) May 5, 1985 2, Name of the invention Resin for magnetic paint 3, Relationship between the person making the amendment and tenancy Patent applicant 4, Details of the invention of the amendment written by Tabimei Ifllll Explanation Structure 5, Contents of Correction (1) Change “900 from room temperature” to “2” on page 6, line 8 of the specification.
Correct it to 0-120CJ.

(2) On page 13, line 12, "in addition" is corrected to "instead."

Claims (1)

[Claims] A reaction mixture in which an alkali metal salt or ammonium salt of a strong acid containing sulfur or phosphorus is added to a monomer having an epoxy group is copolymerized with vinyl chloride and, if necessary, other monomers that can be copolymerized with these. A copolymer with a vinyl chloride content of 60% by weight or more obtained by polymerization, and the amount of strong acid groups containing sulfur or phosphorus bonded to the copolymer is 0.
．． 1 to 4.0% by weight, and the amount of epoxy groups is 0.5% by weight or more.