JPS61204826A - Binder for magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent effectively sticking to a calender roll by using chain- extended polyester of which the sulfonic acid base-contg. polyester segment having a specified hydroxyl group value and acid value are specified is coupled via a diisocyanate group to form the titled binder. CONSTITUTION:The binder consists of the chain-extended polyester of which the sulfonic base-contg. polyester segment having 3-20KOHmg/g hydroxyl group value and <=2KOHmg/g acid value is coupled via the diisocyanate compd. (more preferably coupled in 2-5 units). The polyester having <3KOHmg/g hydroxyl group value is not practicable as the severe conditions are required to manufacture such polyester. On the other hand, the effect of preventing the sticking to the calender roll is hardly admitted when the hydroxyl group value exceeds 20KOHmg/g. The reactivity with the diisocyanate compd. in the succeeding state is deteriorated and the chain extension is difficult to be made when the acid value exceeds 2KOHmg/g.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a polyester-based binder for magnetic recording media into which a sulfonic acid group has been introduced.

Conventional technology There are many conventional binders for magnetic recording media.

Recently, high-performance polyester binders into which sulfonic acid groups have been introduced have been proposed. That is, JP-A-54-28603 discloses a binder for magnetic recording media made of polyester that uses a dicarboxylic acid containing a sulfonic acid metal salt as part of the acid component, and JP-A-54-151417 discloses The publication discloses a binder for magnetic recording media made of a mixture of this polyester and a thermoplastic resin and/or a thermosetting resin. Also, JP-A-54-1324
No. 18 discloses a binder for magnetic recording media made of polyester that uses a glycol containing a sulfonic acid group as part of the glycol component.

Problems to be Solved by the Invention However, the binder made of polyester containing a sulfonic acid group as described above cannot be prepared by mixing magnetic particles and a solvent to prepare a magnetic paint, and applying it to a substrate.
After magnetic field orientation treatment and drying, when calendering is performed for polishing or surface smoothing, the magnetic coating tends to stick to the calendar roll, so the conditions during calendering are not strictly controlled. There was a risk that defective products would be produced.

In addition, each of the above-mentioned publications states that when a magnetic paint is prepared by mixing magnetic particles and a solvent with a polyester binder, a crosslinking agent such as an epoxy resin, an isocyanate compound, or a melamine resin is added, and then a magnetic tape is wound. There is a description that it prevents blocking in the magnetic head and prevents the softening of the coating film due to frictional heat between the magnetic head and the tape. This is a technique that is different from the technique used to prevent coatings from adhering to calender coal during calendering.

The object of the present invention is to provide a high-quality binder that effectively prevents adhesion to calender rolls without impairing the various excellent performances of polyester into which sulfonic acid groups have been introduced as a binder for magnetic recording media. It is something to do.

Means for Solving the Problems The binder for magnetic recording media of the present invention has a hydroxyl value of 3 to 2.
0 KOHmg/g, an acid value of 2 KOHmg/g or less, the sulfonic acid group-containing polyester segment is composed of an extended chain polyester bonded via a diisocyanate-1 compound (preferably 2 to 5 units bonded). By discovering the use of such a specific chain-extended polyester as a pinter for magnetic recording media, the above-mentioned problems have been solved.

The present invention will be explained in detail below.

The polyester constituting the sulfonic acid group-containing polyester segment in the present invention is obtained by subjecting an acid component and a glycol component to a condensation reaction in an inert atmosphere at a temperature of about 150 to 260°C.

Here, the acid components include terephthalic acid, isophthalic acid,
Phthalic acid, 2,5-norbornane dicarboxylic acid, 1,4
-Naphthalic acid, 1.5-naphthalic acid, Sifueninchu, 4,4°-oxybenzoic acid, diglycolic acid, thiodipropionic acid, 4,4'-sulfonyldibenzoic acid, 2.
5-naphthalenedicarboxylic acid, oxalic acid, malonic acid, dimethylmalonic acid, succinic acid, geltal resistance, adipic acid, dodecanedicarboxylic acid, pimelic acid, 2.2-dimethylgeltaric acid, azelaic acid, sebacic acid, 1.3 ~
Examples include cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid. In addition, a small amount of unsaturated carboxylic acids such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, and citraconic acid can also be used in combination.

Glycol components include ethylene glycol propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, bisphenol dioxypropyl ether, 1.3-butanediol, 1
, 4-butanediol, 2,3-butanediol, 1.
Examples include 6-hexanediol, 2-ethyl-1,3-hexanediol, 2,2,4-)limethyl-1,3-bentanediol, neopentyl glycol, and 1,4-cyclohexane dimetatool. In addition, trimethylolethane, trimethylolpropane, glycerin,
A small amount of trihydric or higher alcohol such as pentaerythritol can also be used in combination.

Among the above acid components and glycol components, those containing terephthalic acid and/or isophthalic acid and an aliphatic dicarboxylic acid as the main acid components, and ethylene glycol and neopentyl glycol as the main glycol components are particularly preferred. . The optimal composition is as follows: Acid component Terephthalic acid and/or inphthalic acid 40-90 mol% Aliphatic dicarboxylic acid 10-60 mol% Glycol component Ethylene glycol 30-70 mol% Neopentyl glycol 30-70 mol% Other glycols 0-30 It is mole%. By using specific amounts of these specific components, solubility,
A polyester with well-balanced adhesive strength, cohesive strength, non-stick properties, and hardness can be obtained.

As a method for introducing sulfonic acid groups into polyester,
(b) As an acid component, a polycarboxylic tuna containing a sulfonic acid group such as 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2-stria sulfoterephthalic acid, 2-potassium sulfoterephthalic acid, or an ester thereof is used. (b) A method of reacting a polybasic acid having an unsaturated bond with an acidic sulfite to form a sulfonate-containing polybasic acid and using this as an acid component; (c) A method of reacting a polybasic acid having an unsaturated bond with an acidic sulfite and using this as an acid component. A method of reacting an acidic sulfite to form a sulfonate-containing polyhydric alcohol and using this as a glycol component, producing a polyester having unsaturated bonds by using an unsaturated carboxylic acid as part of the (di)acid component, A method of adding an acidic sulfite monosalt to this unsaturated bond, (e) reacting a compound having an epoxy group with an acidic sulfite to form a polyfunctional monomer containing a sulfonic acid group, which is then used as an acid component or a polyhydric alcohol. Methods such as reacting with

The amount of the sulfonic acid group introduced is preferably 0.2 to 10 mol% based on the total amount of the acid component and glycol component constituting the polyester. If the amount is too small, the performance as a binder for magnetic recording media will be poor, while if the amount is too large, the solvent solubility will be insufficient.

In addition to the above components, ethylenediamine, trimethylenediamine, putrescine, cadaverine, hexamethylenediamine, 2-hydroxyethyl-P-)luidine, 2-carpoxyethyl/l/-P-)luidine, β-
Propiolactam, γ-propiolactam, γ-butyrolactam, γ-valerolactam, (-propiolactam,
It is preferable to condense a small amount of a nitrogen-containing compound such as heptolactam (for example, 0.2 to 10 mol % with respect to the total amount of the acid component and glycol component constituting the polyester) because the dispersibility of the magnetic particles is further improved.

A polyester is obtained by the above condensation reaction, but in the present invention, the hydroxyl value of the obtained polyester is 3 to 2.
The amounts of the acid component and glycol component to be charged are selected and the reaction conditions are set so that the acid value is 0 KOHmg/g or less and the acid value is 2 KOHmg/g or less. Hydroxyl value is 3 KOHmg
/gOHm lower polyester is not practical because harsh conditions are required to produce it, and if the -hydroxyl value exceeds 20 KOHmg/g, it is difficult to recognize the effect of preventing adhesion to calender rolls. Become. Also, the acid value is 2
If it exceeds KOHmg/g, the reactivity with the diisocyanate compound in the next step will be poor, making it difficult to extend the chain length.

In the present invention, the chain length of the polyester thus obtained is extended using a diisocyanate compound. Examples of diisocyanate-1 compounds include tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, inphorone diisocyanate, 1
．． Examples include 4-tetramethylene diisocyanate. The diisocyanate compound must have two isocyanate groups in its molecule, and incyanate compounds that have other functional groups than incyanate groups, such as incyanate and trimethylolpropane, triethylene glycol, etc. adduct bodies are inappropriate.

It is desirable to extend the chain length so that the polyester segments are bonded by 2 to 5 units via a diisocyanate compound.If the chain length is less than 2 units, the effect of preventing adhesion to calender rolls will be insufficient, while if it exceeds 5 units, it will become more like a polyester than a polyester. It becomes polyurethane, and the excellent performance of the polyester magnetic recording binder is lost.

In the chain extension reaction, the above polyester and the diisocyanate-1 compound are heated at a temperature of 4°C in the absence of a catalyst or in the presence of an appropriate catalyst.
This can be achieved by reacting at 0 to 120'00 parts. Through this reaction, the desired chain-length-extended polyester, that is, a polyester with a hydroxyl value of 3 to 20 KOHmg/g and an acid value of 2 KOHmg/g or less, bonded via a sulfonic acid group-containing polyester segmentate compound for nosulfo or less is obtained. .

To prepare a magnetic paint, magnetic particles and a solvent may be added to the chain-extended polyester and mixed uniformly.

As magnetic particles, pure iron, y FezO5 (Go),
Cry), Fe2O3(Go), Fe3O4, Fe
, 04 (Go), Go-Fe, Go-Ni, G
o-Ni-Fe, Go-Ni-Zn, Fe-Mn-
Zn, Go-Ni-Fe-B, Go-Ni-P
, Fe-Go-Ni-P, and the like. The blending ratio of chain extended polyester and magnetic particles is 1 by weight.
; Often the ratio is 1 to 1:7.

Examples of the solvent include cellosolve acetate, butyl cellosolve acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, benzene, I.
Luene and xylene can be removed.

In addition, when preparing the magnetic paint, other known binders, plasticizers, wetting agents, antistatic agents, anti-blooming agents, thermoplastic resins, thermosetting resins, etc. can be blended as necessary.

The base material to which the magnetic paint is applied may be any film, tape, sheet, dinuque, card, drum, or the like. Materials used for films and tapes include acetylcellulose, polyester, polycarbonate, polypropylene, polyimide, and polyvinyl chloride.6 Magnetic paint can be applied onto the base material using the doctor knife method, blade coating method, or reverse roll method. Methods such as method, gravure method, cast coating method, and spray coating method are all adopted.

After applying the magnetic paint directly or via an anchor coat layer to the base material, the paint film is subjected to a magnetic field orientation treatment using a solenoid coil or the like while it is still wet, and then dried on a lie.

This is then passed between calender rolls for polishing or smoothing treatment, but when the chain-extended polyester described above is used as a binder, no troubles such as the coating film adhering to the calender rolls occur during this calendering process. Furthermore, it does not soften due to frictional heat between it and the magnetic head, and does not cause blocking even if it is handled while being wrapped in tape.

The magnetic recording medium thus obtained is an audio tape,
Used for video tapes, tapes for computers and measuring instruments, magnetic cards, magnetic disks, etc.

EXAMPLES Next, the present invention will be explained in more detail with reference to examples. below"
Parts are parts by weight.

Example 1 0.5 mol of terephthalic acid, 0.35 mol of isophthalic acid, 0.15 mol of adipic acid, and 0.6 mol of ethylene glycol under a nitrogen stream were placed in a four-hole flask equipped with a thermometer, a pumper, and a backed column. , neopentyl glycol 0.
7 mol, diethylene glycol 0.2 mol, 2-radiosulfo-1,4-butanediol 0.005 mol, and dibutyltin oxide 0.1% (based on the entire system) were charged and the esterification reaction was carried out at 140 to 240°C. Then, 0.1% of antimony trioxide (based on the whole system) was added to
Condensation is carried out at 220 to 260 °C under a reduced pressure of Torr,
Hydroxyl value 6 KOHa+g/g, acid value 0.8 KO)I
A polyester containing mg/g of sulfonic acid groups was obtained.

Next, add 2 toluene to the reactant (polyester) in the flask.
10 parts of hexamethylene diisocyanate and 1.5 parts of hexamethylene diisocyanate were added and reacted for 2 hours at a temperature of 80 to 100°C.
It was aged for 24 hours at 0°C. As a result, a chain-extended polyester in which three units of sulfonic acid group-containing polyester segments were bonded via a diisocyanate compound was obtained.

This chain-lengthened polyester was applied to aluminum sheets 1 and 2 using the doctor knife method, and dried to a thickness of 5.
I1. A coating film was formed.

In order to investigate the thermal activity of the formed coating film, another aluminum sheet was stacked on top of the aluminum sheet described in ``Second Coating Film'' and heated and pressurized with a heat sealing machine, and a softened coating was applied to the upper aluminum sheet. The lowest temperature at which the film adhered was investigated and found to be 110'C.

The temperature of the calendar roll during calendering is 60-1
00°C, the above-mentioned polyester with extended chain length is mixed with magnetic particles and a solvent to prepare a magnetic paint, applied to a base material, orientated, dried, and then calendered. This indicates that the paint film does not adhere to the calender roll even if the The case where the thermal activity of magnetic paint was measured will be described below.

” 130 parts of button length extension polyester, γ-Fe 01
80 parts, 3 parts of dioctyl sulfonodium succinate, 3 parts of silicone oil, 280 parts of methyl ethyl ketone, 180 parts of toluene, 100 parts of methyl isobutyl ketone
and 60 parts of n-butanol were dispersed and mixed for 70 hours using a ball mill, followed by filtration and defoaming to prepare a magnetic paint.

The thermal activity of this magnetic paint was also examined in the same manner as above, and the lowest temperature at which adhesion started was 130°C.

In addition, the above magnetic paint was applied onto a polyethylene terephthalate film with a thickness of 25 μl using a doctor knife method.
Then, it was oriented in a parallel magnetic field of 1000 oersted, dried at 80°C to obtain a magnetic coating film with a thickness of 5 l, and then passed between calender rolls at a temperature of 100°C for polishing. No adhesion of the coating occurred.

The 60°-eo' reflection gloss rate of this magnetic coating film was 88%, and it had excellent smoothness. Further, the value of the squareness ratio, that is, the ratio Mr/Ms of the saturation magnetization Ms to the residual magnetization Mr of the magnetic hysteresis curve, was 0.86, and a favorable result was obtained.

Comparative Example 1 When the thermal activity of the polyester before chain length extension was similarly examined, the lowest temperature at which adhesion started was as low as 70°C.

Comparative Example 2 A binder prepared by blending 100 parts of the above polyester before chain lengthening with 15 parts of Desmodur L (manufactured by Bayer AG, West Germany), which is an incyane-1 compound, and uniformly mixing the mixture was examined for thermal activity. However, the lowest temperature at which adhesion started was 50°C. Further, when the thermal activity of a magnetic paint prepared in the same manner as in Example 1 except for using this binder was examined, the lowest temperature at which adhesion started was 80°C.

Example 2 2-Radiosulfo-1,4-butanediol 0.005
Esterification was carried out in the same manner as in Example 1, except that 0.02 mol of dimethyl 5-sodium sulfoisophthalate was used instead of mol, and the charging ratio of terephthalic acid was 0.48 mol, and the hydroxyl value was 10 KOHmg/ g, acid value 1
．． 2 KO) Img/g of a sulfonic acid group-containing polyester was obtained.

Next, 250 parts of toluene and 2.6 parts of tolu-1phycine diisocyanate were added to this polyester, and the temperature was 80~80.
The reaction was carried out at 100°C for 2 hours, and then aged at 60°C for 24 hours. As a result, a chain-extended polyester in which three units of sulfonic acid group-containing polyester segments were bonded via a diisocyanate compound was obtained.

The thermal activity of this chain-extended polyester was 100°C, and when a magnetic paint was prepared using it in the same manner as in Example 1, the thermal activity was 120°C.

Effects of the Invention The binder of the present invention can be mixed with magnetic particles and a solvent to prepare a magnetic paint, applied to a base material, subjected to magnetic field orientation treatment, dried, and then used for polishing or surface smoothing. During calendering, there is no problem of the magnetic coating film sticking to the calender roll. Therefore, production of magnetic recording media is stabilized because there is no risk of producing defective products even if the conditions during calendering are not strictly controlled.

Moreover, the various excellent performances of the polyester into which a sulfonic acid group has been introduced as a binder for magnetic recording media are not impaired in any way, and there is no fear of softening due to frictional heat between the polyester and the magnetic head.

Claims (1)

[Claims] 1. Hydroxyl value 3-20KOHmg/g, acid value 2KOHm
A binder for magnetic recording media comprising a chain-extended polyester in which polyester segments containing sulfonic acid groups of g/g or less are bonded via a diisocyanate compound. 2. Hydroxyl value 3-20KOHmg/g, acid value 2KOHm
2. The binder according to claim 1, comprising an extended chain polyester in which 2 to 5 units of sulfonic acid group-containing polyester segments are bonded via a diisocyanate compound. 3. The content of sulfonic acid groups in the polyester segment is 0.0% relative to the total amount of acid components and glycol components.
Claim 1 or 2 which is 2 to 10 mol%
Binder described in section. 4. The binder according to claim 1, wherein the polyester segment contains terephthalic acid and/or isophthalic acid and an aliphatic dicarboxylic acid as main acid components, and ethylene glycol and neopentyl glycol as main glycol components. .