JPS6358869B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetic coating compositions. Recently, magnetic materials for magnetic recording are required to have increasingly high performance. For this purpose, it is important to improve the magnetic powder, but the binder used when applying the magnetic powder onto a support such as a tape is also an important factor. In general, when manufacturing magnetic tapes and the like, polyurethane resins are often used as surface coating resins, which provide a highly flexible and tough coating film. However, conventional polyurethane has a low ability to disperse magnetic powder, and to compensate for this, soybean lecithin or the like is used as a dispersant, but adverse effects such as bleeding occur during long-term use. To improve such dispersibility, nitrocellulose, polyvinyl butyral,
Resins with good dispersibility such as vinyl chloride/vinyl acetate/vinyl alcohol copolymers have also been used in combination, but this has the drawback of poor abrasion resistance and flexibility. Various studies have been carried out with the aim of resolving these shortcomings, such as (1) Japanese Patent Application Laid-open No. 51-44902, (2) Japanese Patent Publication No. 51-44902,
No. -44903, (3) No. 55-139634, (4) No. 55-139636
No., (5) No. 56-68925, (6) to (9) No. 56-101643 to
Magnetic recording bodies described in No. 101646 and the like are known. However, for example, (1) and (2) use urethane-modified epoxy resins that do not contain OH groups, and (3)
In (9), urethane resins with OH groups are used, but these are not modified with epoxy resins, and the number of OH groups is usually about 1 to 5, resulting in poor dispersibility. Although improvements have been made to some extent, they are still insufficient, and they still have drawbacks such as poor hydrolysis resistance and heat resistance. An object of the present invention is to provide a magnetic coating composition in which the dispersibility of magnetic powder is significantly improved. A further object of the present invention is to provide a magnetic coating composition that has excellent hydrolysis resistance, heat resistance, film hardness, compatibility with other resins, and the like. In the present invention, the epoxy group of a bisphenol-based epoxy resin-modified polyurethane resin is ring-opened using amines and/or carboxylic acids in an amount equal to or less than 1 times the epoxy group to generate an OH group in the molecular chain. The present invention relates to a magnetic coating composition whose main components are a modified polyurethane resin containing 0.1 meq/g or more of functional groups and a functional group number of 3 or more, magnetic powder, and a polyfunctional polyisocyanate compound. In the present invention, the OH group is added to the molecular chain by 0.1meq/
g or more and the number of functional groups (number of OH groups in the molecule) is 3
By using the above-mentioned modified polyurethane resin, due to the synergistic effect of the presence of many OH groups and the presence of the bisphenol skeleton of the epoxy resin, it is possible to improve the dispersibility of magnetic powder, and at the same time improve hydrolysis resistance. Significant improvements were achieved in heat resistance, film hardness, compatibility with other resins, etc. The structure of the present invention will be described in detail below. The modified polyurethane resin having 3 or more functional groups containing OH groups in the molecular chain of the present invention is a polyol,
It is obtained by carrying out a urethanization reaction by a known method using an isocyanate compound and a bisphenol-based epoxy resin, and then reacting with amines or carboxylic acids. In this case it is also optional to use chain extenders. The content of OH groups in the modified polyurethane resin is preferably 0.1 meq/g or more, and the number of functional groups is preferably 3 or more, particularly 6 or more. Here, for example, if the OH group content is 0.2meq/g
If the molecular weight of the polymer is 30,000, then 0.2×
10 ^-3 ×30000=6, and there are 6 OH groups. In the present invention, various polyester polyols, polyether polyols, and other polyols can be used as the polyol. Specific examples of polyester polyols include adipate polyols such as polyethylene adipate polyol, polybutylene adipate polyol, and polyethylene propylene adipate polyol, terephthalic acid polyols (e.g., Toyobo Co., Ltd., trade names Vylon RUX, Vylon RV-200L), and polycaprolactone. Specific examples of polyether polyols include polyoxyethylene glycol, polyoxypropylene polyol, polyoxytetramethylene polyol, and the like. In addition, other polyols include polycarbonate polyols (e.g., Bayer AG, West Germany, product name Desmofene 2020E), polybutadiene polyols (e.g., Nippon Soda, product names G-1000, G-
2000, G-3000, Idemitsu Petrochemical, product name Poly bd
R-45 HT), polypentadiene polyol, castor oil polyol, etc., and one type or two or more types can be used. The isocyanate compound used in the present invention may be any polyisocyanate known in polyurethane chemistry, such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI),
2,4-tolylene diisocyanate (2,4-
TDI), 2,6-tolylene diisocyanate (2,
6-TDI), 4,4'-diphenylmethane diisocyanate (MDI), carbodiimide-modified MDI, polymethylene polyphenyl polyisocyanate (PAPI), orthotoluidine diisocyanate (TODI), naphthylene diisocyanate (NDI),
Examples include xylylene diisocyanate (XDI) and lysine diisocyanate (LDI), and one type or two or more types can be used. As the epoxy resin, a bisphenol type epoxy resin is used, and an epoxy resin represented by the following formula is particularly suitable. (R ¹ and R ² are each hydrogen or methyl group, n is
In the present invention, as described above, epoxy resins having epoxy groups at both ends of the molecule and having no epoxy groups in the molecular chain are preferably used, and specific examples are shown by trade name. For example, Epicote 828,
Examples include 834, 1001, 1002, 1003, 1004, 1007, and 1009 (manufactured by Ciel Chemical). n (average value) is a number of 0.1 or more, preferably 1 or more. As a chain extender, for example, 2 with a molecular weight of 500 or less
~6-functional polyol and 1 with a molecular weight of 500 or less
Diamines having a primary or secondary terminal amino group are mentioned. Suitable chain extenders include (a) ethylene glycol, diethylene glycol, 1,2-propylene glycol, dipropylene glycol, 1,4-butanediol,
2,3-butanediol, 1,3-propylene glycol, 1,6-hexanediol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, metaxylylene Polyols such as glycol and paraxylylene glycol (b) Hydrazine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, 1,
Diamines such as 4-cyclohexanediamine (c) Alkanolamines such as ethanolamine, diethanolamine, and triethanolamine (d) Hydroquinone, pyrogallol, 4,4'-isopropylidene diphenol, aniline, and the above polyols and diamines , polyols with a molecular weight of 500 or less obtained by adding propylene oxide and/or ethylene oxide to alkanolamines in any order. Epoxy-modified polyurethane resin is synthesized using each of the above-mentioned components, and in this case, it is usually preferable to react at an NCO index of about 0.7 to 1.2, preferably about 0.9 to 1.1. The basic structure of the epoxy resin-modified polyurethane resin of the present invention is as follows when compared with a normal polyurethane resin.
That is, polyol is P, polyisocyanate is I,
If the chain extender is S and the epoxy resin is E, the basic structure of general polyurethane resin is -P-I-P-I-S-I-P-I-S-, etc., but the structure of the present invention is The basic structure of epoxy resin-modified polyurethane resin is -P-I-E-I-P-I-S-I-P-I-
E-I etc. In the present invention, a modified polyurethane resin is used in which the epoxy groups of the above-mentioned epoxy-modified polyurethane resin are further reacted with amines and/or carboxylic acids to open the rings and generate OH groups. The amines are preferably compounds containing secondary amino groups, such as dialkylamines such as diethylamine, dipropylamine, and dibutylamine;
Alkanolamines such as N-methylethanolamine, N-butylethanolamine, diethanolamine, and dipropanolamine, and carboxylic acids such as acetic acid, propionic acid, stearic acid, succinic acid, adipic acid, maleic acid, benzoic acid, and phthalic acid. , phenylacetic acid, hydroxyacetic acid (glycolic acid), lactic acid, 2,2-dimethylolpropionic acid, 9,10,12,13-tetraoxyoctadecanoic acid, acetic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, etc. can be mentioned.
These amines and carboxylic acids can be used alone or in combination. In the above-mentioned ring-opening reaction of the present invention, it is preferable to open all the epoxy groups, but it is of course possible to leave a part of the epoxy groups, and usually about 1 part of the amines and/or carboxylic acids is added to the epoxy group. It is preferable to use a double equivalent or less, preferably about 0.2 to 1 times equivalent. The reaction is usually carried out at a temperature of about 20-180°C, preferably about
It is best to do it at 100-150℃. The above ring-opened modified polyurethane resin of the present invention has a large number of OH groups in its molecules and has an extremely good ability to disperse magnetic powder. The number of OH groups is usually preferably 3 or more, generally 6 to 30, particularly preferably 10 to 20.
It is preferable to have OH groups. OH after ring opening above
The groups do not react any further because all of the isocyanate groups have reacted during the polymerization and none remain.
However, if a polyfunctional isocyanate compound is added as a crosslinking agent after dispersing the magnetic powder, it will react and harden. Various types of magnetic powder can be used in the present invention, including iron, chromium, nickel, cobalt, alloys thereof, oxides thereof, and modified products thereof. Specific examples of oxides include γ-
Fe ₂ O ₃ , ferrite, magnetite, CrO ₂ , etc.
Examples of modified products include cobalt-doped γ-Fe ₂ O ₃ and cobalt-doped Fe ₂ O ₃ .
Examples include a bertholide compound of Fe ₃ O ₄ . The amount of magnetic powder blended is preferably about 50 to 2000 ωt parts per 100 ωt parts of the polymer. As the polyfunctional isocyanate compound in the present invention, a polyisocyanate having two or more functional groups can be used. As a preferable specific example,
Various isocyanate compounds that can be used in the production of the epoxy-modified polyurethane resin, trifunctional isocyanate obtained from trimethylolpropane and TDI (product name: Desmodyur L, Bayer AG, West Germany), trifunctional isocyanate (product name: Bayer AG), also available from Bayer AG. Desmodule N75, Desmodule R, Desmodule H, etc.), polymeric polyisocyanate (PPI), and the like. The magnetic coating composition of the present invention can be obtained by mixing the modified urethane resin, magnetic powder, and polyfunctional isocyanate compound. The NCO Index of a magnetic coating composition is normally in the range of about 0.9 to 1.5, but it is preferably higher when considering the active hydrogen contained in the magnetic powder and other additives. In the present invention, vinyl chloride resins, vinylidene chloride resins, vinyl chloride/vinyl acetate/vinyl alcohol copolymer resins (manufactured by UCC,
VAGH, etc.), nitrocellulose, polyvinyl butyral resin, polyester resin, alkyd resin, epoxy resin, acrylonitrile-butadiene rubber, and other resins can be blended. In addition, in the present invention, dispersants, lubricants, abrasives,
Additives such as antistatic agents may also be added. The magnetic coating composition of the present invention can be produced by mixing the above-mentioned components by various methods, for example, it is preferable to use a mixer, roll mill, ball mill, sand mill, high-speed impeller, etc. In particular, it is preferable to add the polyfunctional isocyanate compound after it has been sufficiently dispersed, since the pot life will be longer. Further, it is preferable to use a solvent during the production of the epoxy-modified polyurethane resin of the present invention, during its ring-opening reaction, during the production of the magnetic coating composition, etc. Suitable solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, Ketones such as cyclohexanone, aromatic hydrocarbons such as benzene, toluene, xylene, esters such as ethyl acetate, butyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, 3-methoxybutyl acetate, ethylene glycol diacetate, dimethyl formamide , dimethylacetamide and the like. The magnetic coating composition of the present invention is applied to supports in various forms such as tapes, sheets, cards, disks, and drums. The support typically has a thickness of about 5 to
50μ, preferably about 10 to 40μ, and materials include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene,
Cellulose derivatives such as cellulose acetate, polycarbonate, polyamide, polyimide, polyamideimide, etc. are preferably used. Various methods can be used to apply the magnetic coating composition onto the support, such as impregnation coating, air doctor coating, air knife coating, blade coating, reverse roll coating, gravure coating, cast coating, spray coating, etc. can. After coating, the magnetic powder is subjected to treatment to orient it if necessary, and then dried. The drying temperature is usually about 20 to 100°C, and the drying time is about 5 minutes or more, preferably about 5 minutes or more.
It is best to set it to about 24 hours. Usually 50 ~ after drying
It is preferable to cure at 140°C for about 1 minute to 2 hours. Further, if necessary, the surface can be smoothed or cut into a desired shape. EXAMPLES The present invention will be described in detail below with reference to Examples, Comparative Examples, and Test Examples. Note that parts and % simply indicate parts by weight and % by weight. Example 1 In two separable flasks equipped with a thermometer, a stirrer, a nitrogen gas inlet tube, and a condenser, 280 g (0.14 mol) of Vylon RV-200L, 120 g (0.06 mol) of polycaprolactone diol (molecular weight 2000), and 36 g (0.04 mol) of Epicoat 1001 were added. Weigh out 76.6 g (mol) MDI (0.306 mol) and 156 g cyclohexanone and react at 80°C for 2 hours. Then 1057g of cyclohexanone and 1,6-hexanediol
7.1 g (0.06 mol) was added and the reaction was further carried out at 80°C for 3 hours to obtain an epoxy-modified polyurethane solution. 600 g of this epoxy-modified polyurethane solution and 0.76 g of diethanolamine were reacted at 150° C. for 3 hours. No diethanolamine was detected by gas chromatography. The obtained modified polyurethane solution had a solid content of 30% and a viscosity of 280 mPa.
s/25℃, OH group 0.12 meq/g (OH group number 4.9)
had. 100 parts of the above modified polyurethane solution, magnetic powder (γ
- Ferrite), 4 parts of Desmodyur L, and 100 parts of methyl ethyl ketone were placed in a ball mill and kneaded for 24 hours to obtain a magnetic coating composition. Example 2 Same as Example 1 except that 1.64g of diethanolamine was used, viscosity 270mPa・s/25℃,
A modified polyurethane solution having an OH group content of 0.26 meq/g (OH group number 7.7) was prepared, and a magnetic coating composition was obtained in the same manner as in Example 1. Example 3 Same as Example 1 except that 2.85g of diethanolamine was used, viscosity 270mPa・s/25℃,
A modified polyurethane solution having an OH group content of 0.45 meq/g (OH group number 11.5) was prepared, and a magnetic coating composition was obtained in the same manner as in Example 1. Example 4 A product with a viscosity of 280 mPa·s/25°C and an OH group content of 0.45 meq/g (number of OH groups 11.5) was prepared in the same manner as in Example 1 except that 0.97 g of 2,2-dimethylolpropionic acid was used instead of diethanolamine. A modified polyurethane solution was produced, and a magnetic coating composition was obtained in the same manner as in Example 1. Example 5 In a flask similar to Example 1, add Vyron RV-200L 231g (0.116 mol) Desmofene 2020E 132g (0.066 mol) (molecular weight 2000) Epicote 1001 74.3g (0.083 mol) MDI 41.3g (0.165 mol) IPDI 33.0g ( 0.149 mol) Weigh out 155 g of cyclohexanone and react at 100°C for 3 hours. Next, 1053 g of cyclohexanone and 5.9 g (0.050 mol) of 1,6-hexanediol were added, and the mixture was further reacted at 100° C. for 4 hours to obtain an epoxy-modified polyurethane solution. 600 g of this epoxy-modified polyurethane solution and 6.0 g of diethanolamine were reacted at 150°C for 3 hours, resulting in a viscosity of 310 mPa・s/25°C and an OH group content of 0.96 meq/
A modified polyurethane solution having a weight of 22.0 g (OH group number: 22.0) was prepared, and a magnetic coating composition was obtained in the same manner as in Example 1. Comparative Example 1 A magnetic coating composition was obtained in the same manner as in Example 1 except that the epoxy-modified polyurethane solution before ring opening of Example 1 was used. Comparative Example 2 A magnetic coating composition was prepared in the same manner as in Example 1, except that 0.76 g of diethanolamine was added to 600 g of the epoxy-modified polyurethane solution before ring opening in Example 1, but the solution obtained without performing a heating reaction was used. Obtained. Comparative Example 3 A magnetic coating composition was obtained in the same manner as in Example 5, except that the epoxy-modified polyurethane solution before ring opening of Example 5 was used. Comparative Example 4 A mixture of Vylon RV-200L 280g (0.14mol), polycaprolactone diol 120g (0.06mol) (molecular weight 2000), MDI 65g (0.26mol) and cyclohexanone 142g was reacted at 80°C for 2 hours. Then 960 g of cyclohexanone and 7.1 g (0.06 mol) of 1,6-hexanediol
was added and reacted at 80℃ for 3 hours to reduce the solid content to 30%.
A polyurethane solution with a viscosity of 520 mPa·s/25°C is obtained. A magnetic coating composition was obtained in the same manner as in Example 1 except that this polyurethane solution was used. Comparative Example 5 The same amounts of Vylon RV-200L, polycaprolactone diol and MDI as in Comparative Example 4 were used, and a mixture of these and 141 g of cyclohexanone was reacted at 80°C for 2 hours. Next, 957 g of cyclohexanone and 5.5 g (0.06 mol) of glycerin were added and reacted at 80°C for 3 hours to obtain a solid content of 30% and a viscosity of 500 mPa.
s/25℃, OH group content 0.13meq/g (OH group number 5.4)
A polyurethane solution is obtained. A magnetic coating composition was obtained in the same manner as in Example 1 except that this polyurethane solution was used. Comparative Example 6 600 g of the epoxy-modified polyurethane solution of Example 1 before ring opening and 0.54 g of N-methylethanolamine
were reacted in the same manner as in Example 1, solid content 30%, viscosity 300 mPa・s/25°C, OH group content 0.08 meq/g.
A magnetic coating composition was obtained in the same manner as in Example 1 except that a modified polyurethane solution (OH group number: 3.6) was used. Test Example 1 The obtained magnetic paint was applied onto a polyester film using a doctor blade, dried at room temperature for 2 hours, and then heated and dried in an oven at 100°C for 20 hours to obtain a magnetic coating film. In order to examine the dispersibility of the magnetic coating, the surface gloss of the magnetic coating was measured using a gloss meter (Toyo Seiki S-60). The better the dispersibility, the better the gloss. In addition, in order to examine the strength of the magnetic coating film, the coating film was
After being placed in a constant temperature and humidity chamber adjusted to ℃ and 95% RH for two weeks and humidified, a scratch test was performed using a 2H hardness pencil. The evaluation was ◎ No scratches, △ Scratches, and × Peeling. Note that all samples before the humidification test were rated ◎. The results are shown in Table 1. 【table】

Claims (1)

[Scope of Claims] 1. A molecule in which an OH group is generated by ring-opening the epoxy group of a bisphenol-based epoxy resin-modified polyurethane resin using an amine and/or a carboxylic acid in an amount of 1 or less times the epoxy group. in chains
A magnetic coating composition whose main components are a modified polyurethane resin containing 0.1 meq/g or more of OH groups and a functional group number of 3 or more, magnetic powder, and a polyfunctional isocyanate compound. 2 The epoxy resin component is the formula (R ¹ and R ² are each hydrogen or methyl group, n is
2. The composition according to claim 1, which is a compound represented by the following formula: 0.1 or more.