JPH0262892B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic tape binder using a specific polyester resin as a binder. Various resins have been reported as binders for magnetic tapes such as cassette tapes and video tapes. In such applications, the demand for videotapes and audiotapes has increased in proportion to the spread of home video recorders and audiotape recorders, and a higher level of performance is required in various aspects such as image quality and sound quality. By the way, the performance of the binder, which plays the role of uniformly and densely filling the magnetic layer coated on the base film of the tape, plays a large role in the performance of the magnetic tape, so various improvements have been made to the resin. It is something. Among these resins, the demand for polyester resins containing metal salts of sulfonic acid is increasing because they have superior dispersibility to magnetic powder and adhesion to base films compared to conventional binders. In particular, recently, attempts have been made to introduce acrylic double bonds into the resin and irradiate it with electron beams, etc., in order to improve the curing speed after coating the base film and make the work more efficient. ing. However, in the magnetic tape manufacturing process, where differences in curing time in units of several seconds have a very large effect, such attempts cannot necessarily be said to be sufficient, and a satisfactory solution in terms of curing speed has not yet been reached. Furthermore, there is room for improvement in the smoothness of the tape surface after coating and drying, and more precise performance is required, and an immediate solution is desired. However, as a result of extensive research in view of the above-mentioned problems, the present inventors have found that (a) a sulfonic acid group-containing polyfunctional product obtained by reacting an epoxy group-containing compound with an acidic sulfite as a component of a polyester resin; an unsaturated polyester resin using a polyester monomer and an unsaturated dicarboxylic acid, and an acrylic monomer bonded to the resin terminal;
and (b) a binder resin composition for magnetic tapes containing an ethylenically unsaturated monomer as a main ingredient maintains sufficient performance such as dispersibility and adhesion, and is more resistant to radiation, etc. than before. We have found remarkable effects such as rapid curing. Furthermore, in the case of a binder resin composition for magnetic tapes whose main ingredient is an unsaturated polyester resin containing polyhydric alcohol allyl ether as a component of the unsaturated polyester resin, there is no risk of curing failure even in the air, and the coating can be advantageously applied. The present inventors have discovered that the present invention has very useful performance industrially, such as being able to carry out various tasks, and have completed the present invention. In the present invention, first, a polyfunctional monomer obtained by reacting an epoxy group-containing compound with an acidic sulfite must be used as a component of the unsaturated polyester resin. The present invention is characterized in that a sulfonic acid group-containing polyhydric alcohol produced by such a specific method is used as a component of the unsaturated polyester resin. When used, problems remain because the smoothness of the tape surface after manufacturing the magnetic tape is not sufficient. Polyfunctionality as used in the present invention means that the molecule contains at least two or more carboxyl groups or hydroxyl groups in total, and the presence of these functional groups enables the production of polyester resins. The reaction of acidic sulfite with epoxy groups is conventionally known and is as follows. (However, in the formula, M represents an alkali metal.) As is clear from the above formula, one sulfonate and one hydroxyl group are generated for each epoxy group, so the hydroxyl group is used in the condensation reaction of the polyester resin. The greatest feature of the present invention is that it is intended to be utilized. Therefore, if a compound having two or more epoxy groups is reacted with an acidic sulfite, a polyfunctional monomer having the same number of hydroxyl groups as the number of epoxy groups can be obtained. The compound is not limited to compounds having epoxy groups, and even compounds with only one epoxy group may contain one hydroxyl group or carboxyl group in the molecule in addition to the epoxy group.
Compounds having more than 100 monomers, or compounds having groups that can become hydroxyl or carboxyl groups by hydrolysis etc. can be used as raw materials for polyester resins, since polyfunctional monomers can be produced. The content of the polyfunctional monomer is 0.05 to 10 mol%, more preferably 0.05 to 5 mol%, based on the total acidic content in the unsaturated polyester resin, assuming a molecular weight of 1 mol per SO ₃ M group. It is introduced in the range of %.
If it is less than 0.05 mol%, the effect of improving the dispersibility of magnetic powder etc. cannot be obtained, and if it is more than 10 mol%, gelation tends to occur during the production of the unsaturated polyester resin, making stable production impossible, which is not preferable. The reaction between a compound having an epoxy group and an acidic sulfite is usually carried out by simply adding 1 to 4 moles of the latter to 1 mole of the epoxy group in the former and allowing the reaction to occur at a temperature of 20 to 200°C in the presence or absence of a solvent. . If necessary, it is also possible to use catalysts such as amines and imidazole. In addition to water, solvents include alcohol, ether, ester, benzene, toluene,
General-purpose solvents such as xylene, acetone, dioxane, and mixed solvents thereof are used as appropriate. Examples of compounds having such an epoxy group include epichlorohydrin, glycidol, ethylene glycol mono (or di) glycidyl ether, diethylene glycol mono (or di) glycidyl ether, triethylene glycol mono (or di) glycidyl ether, and polyethylene glycol mono (or di) glycidyl ether. Glycidyl ether, propylene glycol mono (or di) glycidyl ether, polypropylene glycol mono (or di) glycidyl ether, butylene glycol mono (or di) glycidyl ether, polybutylene glycol mono (or di) glycidyl ether, neopentyl glycol mono (or di) glycidyl ether di) glycidyl ether,
1,6-hexanediol mono(or di)glycidyl ether, bisphenol A type mono(or di)glycidyl ether, bisphenol A type ethylene oxide adduct mono(or di)glycidyl ether, bisphenol A type propylene oxide adduct mono( or di)glycidyl ether, hydrogenated bisphenol A type mono(or di)glycidyl ether, hydrogenated bisphenol A type ethylene oxide adduct mono(or di)glycidyl ether, hydrogenated bisphenol A type propylene oxide adduct mono(or di) ) Glycidyl ether, oxalic acid mono (or di) glycidyl ester, malonic acid mono (or di) glycidyl ester, succinic acid mono (or di) glycidyl ester, glutaric acid mono (or di) glycidyl ester, adipic acid mono (or di) glycidyl ester ) glycidyl ester, pimelic acid mono (or di) glycidyl ester, suberic acid mono (or di) glycidyl ester, sebacate acid mono (or di) glycidyl ester, phthalic acid mono (or di) glycidyl ester, isophthalic acid mono (or di) glycidyl ester ) Glycidyl ester, terephthalic acid mono (or di) glycidyl ester, o, m, p-hydroxybenzoic acid monoglycidyl ether, o, m, p-hydroxybenzoic acid glycidyl ester, o, m, p-hydroxybenzoic acid diglycidyl ester ester ether, 1.
In addition to 3-diglycidyl-5,5-dimethylhydantoin, alicyclic epoxy compounds such as cyclohexanediol mono(or di)glycidyl ether and cyclohexanedicarboxylic acid mono(or di)glycidyl ester, as well as glycerin, pentaerythritol, triglycidyl ester, etc. Polyhydric alcohols such as methylolpropane in which at least one hydroxyl group is a glycidyl ether group, polybasic acids such as trimellitic acid and pyromellitic acid in which at least one carboxyl group is a glycidyl ester, etc. These are representative examples. Examples of the acidic sulfite to be reacted with the compound having an epoxy group include acidic sodium sulfite, acidic potassium sulfite, etc., but acidic sodium sulfite is more practical. The next essential component of the unsaturated polyester resin used in the present invention is the use of an unsaturated dicarboxylic acid. Unsaturated dicarboxylic acids are
It is used in an amount of 20 to 100 mol%, more preferably 30 to 100 mol%. If it is less than 20 mol%, the curing speed will be slow. As such unsaturated dicarboxylic acids, maleic acid (anhydride) is most preferred, but fumaric acid, itaconic acid,
Unsaturated dicarboxylic acids such as citraconic acid and lower alkyl esters thereof can also be used. Another essential component of the unsaturated polyester resin used in the present invention is that an acrylic monomer is bonded to the terminal end of the resin. Such acrylic monomers are compounds having a carboxyl group or a hydroxyl group and an ethylenically unsaturated bond, such as acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, or their methyl esters, ethyl Alkyl esters such as esters, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and reaction products of polyhydric alcohols, epichlorohydrin adducts, and (meth)acrylic acid (for example, Kyoeisha Yushi Kagaku Kogyo Co., Ltd.) Examples include derivatives such as epoxy ester). Since an ethylenically unsaturated bond and an unsaturated bond based on an unsaturated dicarboxylic acid are simultaneously present at the molecular end of the unsaturated polyester resin, it is possible to obtain a magnetic tape binder with a fast curing speed as in the present invention. . Therefore, the unsaturated polyester resin components other than the sulfonic acid group-containing polyfunctional monomer, unsaturated dicarboxylic acid, and acrylic monomer are acid components and polyhydric alcohol components used in the production of ordinary polyester resins. can be used arbitrarily. Examples of acidic components include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, azelaic acid, sebacic acid, 1,3-
Cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, phthalic acid, terephthalic acid,
Isophthalic acid, 2,5-norbornanedicarboxylic acid, 1,4-naphthalic acid, diphenic acid, 4.
4′-oxybenzoic acid, diglycolic acid, thiodipropion-4・4′-sulfonyldibenzoic acid, 2・
Saturated carboxylic acids such as 5-naphthalene dicarboxylic acid and lower alkyl esters thereof can optionally be used. Polyhydric alcohol components include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, pentaerythritol, trimethylolpropane,
Examples include glycerin and the like. Furthermore, if necessary, 3-butene-1,2 diol,
Olefinic glycols such as 2-butene-1,4 diol, 2,5-dimethyl-3-hexene-2,5-diol, 1,5-hexadiene-3,4
It is also possible to use unsaturated polyhydric alcohols such as -diol and 2,6-octadiene-4,5-diol. In the present invention, it is advantageous to use polyhydric alcohol allyl ether in addition to the above-mentioned essential components in order to further impart air-drying properties to the binder with improved curing speed. The amount of the ether charged is not particularly limited, but
It is usually 0.02 to 40 mol%, more preferably 0.2 to 10 mol% based on the polyhydric alcohol component. 0.02
If it is less than 40 mol%, the purpose of imparting air-drying properties cannot be achieved, and if it is more than 40 mol%, the surface curing of the tape will proceed more than the internal curing, which will easily cause surface distortion, and should be avoided. Examples of polyhydric alcohol allyl ethers include glycerin monoallyl ether, trimethylolpropane monoallyl ether, trimethylolpropane diallyl ether, trimethylolethane monoallyl ether,
Trimethylolethane diallyl ether, pentaerythritol monoallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, 1,2,6-hexanetriol monoallyl ether, 1,2,6-hexanetriol diallyl ether, sorbitan monoallyl ether , sorbitan diallyl ether, etc., but the present invention is not limited to these compounds. When producing an unsaturated polyester resin in this way, the polyfunctional monomer, unsaturated dicarboxylic acid,
Acrylic monomers, acid components other than these, polyhydric alcohol components, and, if necessary, polyhydric alcohol allyl ether are reacted. Note that depending on the type of acrylic monomer, it is necessary to use a polyisocyanate-based compound, and such polyisocyanate-based compounds include tolylene diisocyanate, diphenylmethane-4,4-diisocyanate, 1. 5-naphthylene diisocyanate,
Hexamethylene diisocyanate, isophorone diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, xylylene diisocyanate, triphenylmethane-4,4,4'-triisocyanate,
3,3'-bitrylene-4,4'-diisocyanate, 3,3'dimethylphenylmethane-4,4'-diisocyanate, sulfonyl diisocyanate, and polyhydric alcohol adducts thereof, etc. can be mentioned. Generally, the reaction begins with a polyfunctional monomer,
In the presence of an unsaturated dicarboxylic acid, acid components other than these, polyhydric alcohol, polyhydric alcohol allyl ether if necessary, and an esterification catalyst such as dibutyltin oxide, antimony trioxide, zinc acetate, etc., 170 to 280 After esterification at a temperature of ℃, the condensation reaction is carried out at a temperature of 240 to 280℃ under a vacuum of 0.5 to 300 mmHg in the presence of a condensation catalyst. As a condensation catalyst, germanium oxide, antimony trioxide,
Examples include tetrabutyl titanate and dibutyltin oxide. The acrylic monomer or, if necessary, a polyisocyanate compound is added to the unsaturated polyester resin thus obtained, and the reaction is continued to introduce an ethylenically unsaturated bond at the end of the resin. Another essential condition for the magnetic tape binder of the present invention is to mix the unsaturated polyester resin with an ethylenically unsaturated monomer as a crosslinking agent. The blending amount of the monomer in the unsaturated polyester resin is preferably 10 to 80% by weight, more preferably 20 to 60% by weight, but the present invention is not limited thereto. Typical examples of such monomers include (meth)acrylic acid and its lower alkyl esters, styrene, ethylene glycol, diethylene glycol, triethylene glycol, 1,2 and 1,3-propanediol, 1,2 and 1.・Di(meth)acrylates of glycols such as 4-butanediol and hexamethylene glycol, poly(meth)acrylates corresponding to polyfunctional polyhydric alcohols such as trimethylolpropane and pentaerythritol, as well as adipic acid and pimeline. One or more types of acids, ester reaction products of polycarboxylic acids such as azelaic acid, sebacic acid, and glycidyl (meth)acrylate can be used as desired. Therefore, when applying the magnetic tape binder of the present invention to a base film, the above mixture may be used as it is or after adjusting the concentration as appropriate. No particular solvent is required, but commonly used solvents,
For example, ketones such as acetone, dimethyl ketone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, methyl acetate,
In addition to esters such as ethyl acetate and butyl acetate, ethers such as ethylene glycol mono(or di)methyl ether and ethylene glycol mono(or di)ethyl ether, aromatic hydrocarbons such as benzene, toluene, and xylene, and hexane. , aliphatic hydrocarbons such as heptane may be used in combination. In addition, as the magnetic metal powder to be dispersed, γ-
Fe ₂ O ₃ , γ-Fe ₃ O ₄ or mixtures thereof, doped with cobalt, CrO ₂ , barium ferrite,
Fe-Co, Co-Ni, Fe-Co-B, Fe-Co-B,
Mn-Bi, Mn-Al, Fe-Co-V, etc. can be used arbitrarily. The blending ratio of the metal powder to the unsaturated polyester resin is not particularly limited, but is generally 50 to 90% by weight. In order to take advantage of the curing speed that is a feature of the present invention, curing with electron beams, and in some cases with radiation such as β rays, γ rays, and neutron rays, is employed. The irradiation amount is appropriately selected from the range of 0.5 to 10 Mrad, more preferably 2 to 4 Mrad. Further, the irradiation energy (acceleration voltage) is preferably 100 KV or more. The magnetic tape binder of the present invention may optionally contain any known crosslinking agent, binder, plasticizer, lubricant, antistatic agent, wetting agent, and anti-grooming agent other than the ethylenically unsaturated monomer. can be added. Crosslinking agents include isocyanate compounds, epoxy compounds, melamine resins, etc. Other binders include ordinary polyester resins other than the unsaturated polyester resins mentioned above, ethyl cellulose,
Nitrocellulose, vinyl chloride-vinyl acetate copolymer, etc., and as plasticizers, dibutyl phthalate, triphenyl phosphate, etc. are used. The base material is film, tape, sheet, disk,
It may be a card, a drum, or the like, and various materials are selected depending on the form. For example, if the substrate is in the form of a film or tape, acetylcellulose,
Films or tapes made of polyester, polycarbonate, polyvinyl chloride, polypropylene, polyimide, etc. are used. As a means for applying the composition onto the substrate, a doctor knife method, a blade coating method, a reverse roll method, a gravure method, a cast coating method, a spray coating method, a flow coater method, etc. are all employed. After the composition is applied onto the substrate directly or via an anchor coat layer, a magnetic field alignment treatment is performed using a solenoid coil or the like while the coating film is not dry, and then hardening and drying is performed. The magnetic recording medium thus obtained is used for applications such as magnetic recording tapes, recording (video) tapes, tapes for computers and measuring instruments, magnetic cards, and magnetic disks. Next, the magnetic tape binder of the present invention will be explained in more detail by giving examples. However, unless otherwise specified, "parts" or "%" in the examples are based on weight. Example 1 Diethylene glycol diglycidyl ether
0.5 mol and 1.5 mol of acidic sodium sulfite are reacted at a temperature of 100°C for 6 hours using water as a solvent,
Sulfonic acid group-containing polyfunctional monomer (in this case 2
alcohol) was obtained. Next, 0.7 mol of maleic anhydride, 0.3 mol of adipic acid, 0.5 mol of ethylene glycol, 0.5 mol of 1,2-propylene glycol, 0.2 mol of diethylene glycol, and 0.06 mol of the above sulfonic acid group-containing polyfunctional monomer were added. The temperature was raised at ℃ for about 3 hours, and then reacted at 200℃ for 4 hours to form a 3-5 mm
Unreacted raw materials were removed with Hg, and the reaction reached an acid value of 5 or less. One mole of tolylene diisocyanate was reacted per mole of residual hydroxyl groups of this unsaturated polyester resin (at 60°C for 3 hours), and then 1 mole of 2-hydroxyethyl methacrylate was reacted per mole of residual isocyanate groups (at 60°C). 4 hours) to obtain the desired binder resin. The amount of residual isocyanate groups in this resin is IR
The analysis result was 3.0%. The performance of the unsaturated polyester resin as a binder for magnetic tapes was evaluated as follows. 60 parts of unsaturated polyester resin, 40 parts of isobutyl acrylate, 70 parts of trimethylolpropane triacrylate, and 100 parts of methyl ethyl ketone were dispersed for 70 hours using a ball mill, and then filtered and defoamed to obtain a magnetic paint. This magnetic paint was applied onto a 25μ thick polyethylene terephthalate film (stretched product) using the doctor knife method, and then subjected to orientation treatment in a parallel magnetic field of 1000 oersteds, followed by 150KV,
The curing speed, smoothness of the magnetic tape surface, abrasion resistance, and magnetic properties were measured by irradiating the tape with an electron beam at a dose of 3 Mrad. The evaluation method for each measurement item is as follows. ●Curing speed: Line speed under irradiation conditions of 150KV and 3Mrad (unit: m/min). ●Smoothness: Evaluated by 60°-60° reflection gloss rate. ●Abrasion resistance: The number of rotations until the magnetic layer falls off was determined using a Teed abrasion tester. ●Magnetic properties: saturation magnetism Bs and residual magnetism in the orientation direction
The ratio of Br, Br/Bs (squareness ratio) was measured. The above results are shown in Table 1. Examples 2 to 8 A polyfunctional monomer (Example 2) prepared by reacting adipic acid diglycidyl ester and acidic sodium sulfite in place of the sulfonic acid group-containing polyfunctional monomer used in Example 1, A polyfunctional monomer made by reacting a phenol A type monoglycidyl ester and acidic sodium sulfite (Example 3), a polyfunctional monomer made by reacting a trimethylolpropane triglycidyl ester and acidic sodium sulfite (Example 4) ), a polyfunctional monomer made by reacting succinic acid monoglycidyl ester and acidic sodium sulfite (Example 5), a polyfunctional monomer made by reacting p-hydroxybenzoic acid monoglycidyl ester and acidic sodium sulfite ( Example 6), a polyfunctional monomer obtained by reacting epichlorohydrin and acidic sodium sulfite and further hydrolyzing this with sodium bicarbonate (Example 7), a polyfunctional monomer obtained by reacting glycidol with acidic sodium sulfite An unsaturated polyester resin was prepared using the monomer (Example 8). In each example, the amount of polyfunctional monomer added to the acidic content of the resin was 3 mol%, 3 mol%,
2 mol%, 5 mol%, 5 mol%, 2 mol%, 0.5
It was in mol%. The performance as a binder for magnetic tape was investigated in accordance with Example 1. The results are shown in Table 1. Examples 9 and 10 1,6-hexanediol acrylate/trimethylolpropane triacrylate (Example 9), 2-hydroxyethyl acrylate/trimethylolpropane instead of isobutyl acrylate/trimethylolpropane triacrylate used in Example 1 Triacrylate (Example
The performance was investigated in the same manner as in the same example except that 10) was used. The results are shown in Table 1. Comparative Examples 1 to 3 In Example 1, a saturated polyester resin containing a sulfonic acid group was used without using maleic anhydride and a monomer having an acrylic double bond at the molecular end (Comparative Example 1), maleic anhydride A sulfonic acid group-containing saturated polyester resin in which a monomer having an acrylic double bond was simply bonded to the molecular end without using an acid (Comparative Example 2), and a sulfonic acid group-containing polyester resin in Example 1. The performance as a magnetic tape binder was investigated using 5-sodiosulfoisophthalic acid instead of the functional monomer (Comparative Example 3). These results are summarized in Table 1. Example 11 12 In Example 1, 0.4 mol of glycerin monoallyl ether was added as a glycol component to make an unsaturated polyester resin (Example
11) A binder for magnetic tape was produced using 0.3 mol of trimethylolpropane monoallyl ether (Example 12), and its performance was investigated according to Example 1. As a result, the curing speed was 10 m/min.
(Example 11), 10m/min (Example 12), smoothness is 99
(Example 11), 98 (Example 12), wear resistance is 910 (Example 11), 900 (Example 12), magnetic property is 0.85 (Example 12)
11), 0.85 (Example 12), and this binder does not require vacuum even when irradiated with an electron beam.
It had excellent air drying properties.

【table】

【table】

【table】

Claims (1)

[Scope of Claims] 1 (a) A sulfonic acid group-containing polyfunctional monomer obtained by reacting an epoxy group-containing compound with an acidic sulfite and an unsaturated dicarboxylic acid are used as one component of a polyester resin, and A binder resin composition for a magnetic tape, the main ingredients of which are an unsaturated polyester resin in which an acrylic monomer is bonded to the terminal end of the resin, and (b) an ethylenically unsaturated monomer. 2 (a') Using a sulfonic acid group-containing polyfunctional monomer obtained by reacting an epoxy group-containing compound with an acidic sulfite, an unsaturated dicarboxylic acid, and a polyhydric alcohol allyl ether as one component of the polyester resin, and (b) a binder resin composition for a magnetic tape, the main ingredients of which are an unsaturated polyester resin in which an acrylic monomer is bonded to the terminal end of the resin, and (b) an ethylenically unsaturated monomer.