JPS6358871B2 - - 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, polyester resins containing metal salts of sulfonic acid are in high demand because they have superior dispersibility to magnetic powder and adhesion to base films compared to conventional binders. In particular, in recent years, acrylic double bonds have been introduced into the resin in order to improve the performance of magnetic tape by increasing the curing speed after coating on the base film, and to perform more efficient work. However, attempts are being made to irradiate this with electron beams, etc. 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 an immediate solution is desired since more precise performance is required. However, the present inventors have conducted extensive research in view of the above problems, and have found that (a) an acid component in which the proportion of unsaturated dicarboxylic acid in the total acid component is 40 to 100 mol%, and (b) glycol. component, and 0.05 to 10 mol% of the unsaturated polyhydric alcohol based on the glycol component, by condensing a sulfonic acid group-containing polyhydric alcohol with an acidic sulfite added thereto, and (c) an acrylic monomer at the molecular end. A binder for magnetic tape, which is made by blending 20 to 70% by weight of an ethylenically unsaturated monomer with respect to the resin into an unsaturated polyester resin formed by bonding ester or urethane, has excellent performance such as dispersibility and adhesion. We have found remarkable effects such as the ability to maintain sufficient hardness and to be able to cure more quickly than conventional methods using electron beams, radiation, etc. Furthermore, in the case of a magnetic tape binder based on an unsaturated polyester resin containing 0.02 to 40 mol% of polyhydric alcohol allyl ether based on the glycol component as component (b)', there is no risk of curing failure even in air. The present invention was completed based on the discovery that it has extremely useful performance industrially, such as being able to perform coating operations advantageously. The unsaturated polyester resin used in the present invention must simultaneously satisfy the following conditions (a), (b), and (c). First, as (a), an acid component in which the proportion of unsaturated dicarboxylic acid in the total acid component is 40 to 100 mol % is used. If the unsaturated dicarboxylic acid is less than 40 mol %, the curing rate will be slow, which is not preferable. Examples of unsaturated dicarboxylic acids include (anhydrous) maleic acid, fumaric acid, itaconic acid, citraconic acid, etc. Among these, (anhydrous) maleic acid and fumaric acid are particularly preferably used. Acid components other than unsaturated dicarboxylic acids are not particularly limited, but typically 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,
Saturated carboxylic acids such as diglycolic acid, thiodipropion-4,4'-sulfonylbenzoic acid, and 2,5-naphthalene dicarboxylic acid, lower alkyl esters thereof, and lower alkyl esters of the above unsaturated dicarboxylic acids can be used as desired. . Next, as (b), a glycol component and a sulfonic acid group-containing polyhydric alcohol obtained by adding an acidic sulfite to an unsaturated polyhydric alcohol must be used in an amount of 0.05 to 10 mol % based on the glycol component. 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. Furthermore, if the amount of polyhydric alcohol containing sulfonic acid group used is less than 0.05% by mole, no effect of improving dispersibility can be obtained, and if it is more than 10% by mole, gelation tends to occur during the production of unsaturated polyester resin, making stable production impossible. So I don't like it. When adding acidic sulfite to unsaturated polyhydric alcohol, it is done, for example, by heating 2-butene-1,4-diol and acidic sodium sulfite to about 70°C in the presence of a catalyst such as iron oxide. . The unsaturated polyhydric alcohols used in the above method include 3-butene-1,2-diol, 2-butene-1,4-diol, 2,5-dimethyl-3-hexene-2,5
-Olefin glycols such as diols, 1.5
Examples include diolefin glycols such as -hexadiene-3,4-diol and 2,6-octadiene-4,5-diol. As the acidic sulfite, acidic sodium sulfite, acidic potassium sulfite, etc. are practically used. Examples of the glycol component used as component (b) include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, cyclohexanedimethanol, and pentaerythritol. The final condition that must be met by the unsaturated polyester resin used in the present invention is (c) that an acrylic monomer is bonded to an ester or urethane bond at 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 Examples include alkyl esters such as esters, 2-hydroxyethyl acrylate ester, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl (meth)acrylate. 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. . In the present invention, in order to further impart air-drying properties to the binder with improved curing speed, in addition to the above-mentioned essential component (b), polyhydric alcohol allyl ether is added as component (b)'. It is advantageous to use The amount of the ether charged is usually 0.02 to 40 mol%, more preferably 0.2 to 10 mol%, based on the polyhydric alcohol component. If it is less than 0.02 mol%, the purpose of imparting air-drying properties cannot be achieved, and if it is more than 40 mol%, surface curing of the tape precedes internal curing, which tends to cause surface distortion, and should therefore 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, and pentaerythritol diallyl ether. Examples include erythritol triallyl ether, 1,2,6-hexanetriol monoallyl ether, 1,2,6-hexanetriol diallyl ether, sorbitan monoallyl ether, sorbitan diallyl ether, etc. In the present invention, these compounds It is not limited. When producing an unsaturated polyester resin in this manner, the acid component, the glycol component, the sulfonic acid group-containing polyhydric alcohol, the acrylic monomer, and, if necessary, the 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 examples of such isocyanate-based compounds include tolylene diisocyanate and 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. Examples include 3'-dimethylphenylmethane-4,4'-diisocyanate, sulfonyl diisocyanate, and polyhydric alcohol adducts. Generally, the reaction begins with (a) an acid component, (b) a glycol component, and a polyhydric alcohol containing a sulfonic acid group.
After esterification at a temperature of 220℃, further 0.5~1.0
The reaction is carried out at a temperature of 150 to 200°C under a vacuum of mmHg to complete further esterification. The unsaturated polyester resin thus obtained was subjected to the above treatment at a temperature of 50 to 100°C.
(c) The reaction is continued by adding an acrylic monomer and, if necessary, an isocyanate compound, to introduce an ethylenically unsaturated bond at the end of the resin. Another essential component of 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 20 to 70% by weight, more preferably 30 to 50% by weight, but the present invention is not limited thereto. Representative examples of such monomers include (meth)acrylic acid and its lower alkyl esters, ethylene glycol, diethylene glycol, triethylene glycol, 1.2 and 1.3 propanediol, 1.
Di(meth)acrylates of glycols such as 2 and 1,4-butanediol and hexamethylene glycol, poly(meth)acrylates derived from polyfunctional alcohols such as trimethylolpropane and pentaerythritol, adipic acid, and pimeline. One or more of glycidyl (meth)acrylate compounds derived from acids, polycarboxylic acids such as azelaic acid and sebacic acid, styrene, vinylstyrene, and vinyl acetate can be used as desired. 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. Although a solvent is not particularly necessary, commonly used solvents such as acetone, dimethyl ketone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as 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. γ-Fe ₂ O ₃ , γ- as the magnetic powder to be dispersed
Fe ₃ O ₄ or mixed powder thereof, doped with cobalt, CrO ₂ , barium ferrite, Fe-Co, Co
-N, 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 beta rays, gamma rays, and neutron beams, 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 copolymers, etc., and plasticizers. dibutyl phthalate, triphenyl phosphate, etc. are used. The base material is film, tape, sheet, disk,
It may be a card, a drum, etc., and various materials are selected depending on the form. For example, if the substrate is in the form of a film or tape, acetyl cellulose,
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, the coating film is subjected to a magnetic field orientation treatment using a solenoid coil or the like while it is still undried, and then hardened and dried. 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 binder for magnetic tape of the present invention will be explained in more detail with reference to examples. However, unless otherwise specified, "part" or "%" in the examples
It is based on weight. Example 1 70 moles of maleic anhydride, 30 moles of adipic acid as the acid component, 50 moles of ethylene glycol, 50 moles of propylene glycol, 20 moles of diethylene glycol and 6 moles of 2-sodiosulfo-1,4-butanediol as the glycol components were charged.
The temperature was raised at 200℃ for about 3 hours, and then further heated at 200℃ for 4 hours.
After reacting for an hour, under reduced pressure of 5 to 3 mmHg.
Unreacted glycol components were removed at 170°C to obtain an unsaturated polyester resin having an acid value of about 5. Next, 1 mol of tolylene diisocyanate was added to 1 mol of hydroxyl groups in the unsaturated polyester resin, and an addition reaction was carried out at 60°C for 3 hours. The mixture was reacted for 4 hours to obtain the desired resin. The amount of remaining isocyanate at this time is
It was less than 0.5%. The content of 2-sodiosulfo-1,4-butanediol based on the total glycol components was 5 mol%. 2-Sodiosulfo-1,4-butanediol was obtained by reacting 1.0 mol of 1,4-butenediol with 1.0 mol of acidic sodium sulfite. The performance of the unsaturated polyester resin as a binder for magnetic tape was evaluated as follows. 60 parts of unsaturated polyester resin, γ-Fe ₂ O ₃ 200
parts, isobutyl acrylate (IBA) 40 parts, trimethylolpropane triacrylate (TMP・
TA) and 100 parts of methyl ethyl ketone were dispersed for 70 hours using a ball mill, filtered and defoamed to obtain a magnetic paint. This magnetic paint was applied onto a polyethylene terephthalate film (stretched product) with a thickness of 25μ by the doctor knife method, and then subjected to orientation treatment in a parallel magnetic field of 1000 Oersted, and then 150kV and 3Mrad.
The curing speed, smoothness of the magnetic tape surface, abrasion resistance, and magnetic properties were measured by irradiating the magnetic tape with an electron beam at a dose of . The evaluation method for each measurement item is as follows.・Curing speed: Line speed under irradiation conditions of 150kV and 3Mrad. - Smoothness: Evaluated by 60°-60° reflection gloss rate.・Sedimentation test: 2g of binder resin in toluene/
Dissolve in 100 ml of isobutyl ketone = 4/1 mixed solution, and add 20 g of the solution and iron oxide (γ-Fe ₂ O ₃ ).
2 g was weighed into a graduated test tube, dispersed with ultrasonic waves for about 2 hours, left to stand for 24 hours, and the sedimentation volume of iron oxide was read on the test tube scale. - Wear resistance: The number of rotations until the magnetic layer falls off was determined using a Teed abrasion tester. - Magnetic properties: The ratio of saturation magnetism Bs to remanent magnetism Br in the orientation direction, Br/Bs (squareness ratio) was measured. The above results are shown in Table 1. Example 2 2-Sodiosulfo 1,4- used in Example 1
Instead of butanediol, 3-sodiosulfo-1,2-butanediol (Example 2), which was made by reacting 1,2-butanediol with acidic sodium sulfite;
An unsaturated polyester resin was produced using 2,5-dimethyl-3-sodiosulfo-2,5-hexanediol (Example 3) obtained by reacting 2,5-hexanediol with acidic sodium sulfite.
The content of each of the total glycol components was 5 mol% (Example 2). Hereinafter, the performance as a binder for magnetic tape was investigated according to Example 1. The results are shown in Table 1. Examples 3 and 4 1,6 hexanediol diacrylate/instead of IBA/TMP・TA used in Example 1
Performance was investigated according to the same procedure except that TMP·TA (Example 3) and 2-hydroxybutyl acrylic (Example 4) were used. The results are shown in Table 1. Comparative Examples 1 to 3 In Example 1, a sulfonate-containing saturated polyester resin was used without using maleic anhydride and acrylic acid (Comparative Example 1), and acrylic acid was simply added at the molecular end without using maleic anhydride. Regarding the product using a saturated polyester resin containing acid-bound sulfonic acid group (Comparative Example 2) and the product using 5-sodiosulfoisophthalic acid instead of 2-sodiosulfo-1,4-butanediol (Comparative Example 3) The performance as a magnetic tape binder was investigated. These results are summarized in Table 1. Examples 5 and 6 In Example 1, 40 mol% of glycerin monoallyl ether (based on the total glycol component) was further added to make an unsaturated polyester resin (Example 5), and 30 mol% of trimethylolpropane monoallyl ether (based on the total glycol component) was added. A binder for magnetic tape was manufactured using a binder (Example 6) using a total glycol component), and its performance was investigated according to Example 1.The sedimentation test, magnetic properties, curing speed, smoothness, and wear resistance were Although it was almost the same as Example 1,
This binder did not require vacuum even when irradiated with an electron beam, and had excellent air drying properties.

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Claims (1)

[Scope of Claims] 1 (a) an acid component in which the proportion of unsaturated dicarboxylic acids in the total acid component is 40 to 100 mol %, (b) a glycol component, and 0.05 to 10 mol % with respect to the glycol component An unsaturated polyester resin is obtained by condensing a sulfonic acid group-containing polyhydric alcohol with an acidic sulfite added to an unsaturated polyhydric alcohol, and (c) bonding an acrylic monomer to an ester or urethane bond at the molecular end. A binder for magnetic tape comprising 20 to 70% by weight of an ethylenically unsaturated monomer based on the resin. 2 (a) An acid component in which the proportion of unsaturated dicarboxylic acids in the total acid component is 40 to 100 mol%, (b) A glycol component, and an unsaturated polyhydric alcohol in a proportion of 0.05 to 10 mol% relative to the glycol component. For polyhydric alcohols containing sulfonic acid groups with acidic sulfites added to them, as well as for glycol components.
0.02% to 40 mol% of polyhydric alcohol allyl ether is condensed, and (c) an acrylic monomer is bonded to an ester or urethane bond at the end of the molecule to form an unsaturated polyester resin containing 20 to 70% by weight of the resin. A magnetic tape binder containing % of ethylenically unsaturated monomer.