US 5,162,162 AGrant
Magnetic Coating Formulations and Magnetic Recording Media
Issue Date:1992-11-10
•4 Claims
Abstract
A magnetic coating formulation is composed principally of magnetic particles and a binder. At least a portion of the binder is a polyurethane resin synthesized from a reactant mixture of specific phosphorus compound, epoxy compound, isocyanate compound and polyfunctional hydroxy compounds. The reactant mixture may optionally contain a chain extender. The polyurethane resin contains one phosphoric acid group or one residual group derived from phosphoric acid per 3,000-200,000 number average molecular weight of the polyurethane resin, and has a number average molecular weight of 4,000-150,000. A magnetic recording medium with a magnetic coating layer formed from the magnetic coating formulation is also disclosed. The magnetic coating layer features not only excellent dispersion of magnetic particles, in other words, excellent magnetic characteristics but also superb durability.
Metadata
Assignee
- The B. F. Goodrich Company
Inventors
- Masahiko Yasuda
- Shigeo Hosokawa
- Yorozu Yokomori
- Shinichiro Jimbo
Application Information
Application Number:US 6840787
Filing Date:1991-05-09
Priority Date:1988-10-28
Art Unit:153
Classifications
IPC:
C08L 7504
Field of Search:
428252528694;90062.5472;73
Patent Drawings
This patent does not have any drawings.
Description
EXAMPLE 1
A 2-l flask equipped with a thermometer, a stirrer, a nitrogen gas inlet tube and a reflux condenser was charged with 316 g of phenylphosphonic acid (product of Nissan Chemical Industries, Ltd.) and 316 g of methyl ethyl ketone, followed by the dropwise addition of a solution of 372 g of "Epicoat 828" (trade name, product of Yuka Shell Epoxy Kabushiki Kaisha, epoxy equivalent: 186) in the same amount of methyl ethyl ketone at 70.degree. C. over 30 minutes. They were reacted at 70.degree. C. for 5 hours.
Thereafter, the solvent was driven off by a rotary evaporator to obtain a viscous reaction product having an acid value of 160.
EXAMPLE 2
A reaction product having an acid value of 184 was obtained in a similar manner to Example 1 except that 306 g of diglycidyl adipate (trade name: "Dinacol EX701", product of Nagase Chemical, Ltd., epoxy equivalent: 153) were used in place of "Epicoat 828".
EXAMPLE 3
A reaction product having an acid value of 195 was obtained in a similar manner to Example 1 except that 252 g of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (trade name: "Chissonox CX221", product of Chisso Corporation) were used instead of "Epicoat 828".
EXAMPLE 4
A reaction product having an acid value of 42.4 was obtained in a similar manner to Example 1 except that 764 g of "Gafac RE610" (trade name, product of Toho Chemical Industry Co., Ltd.) and 200 g of "Epicoat 1001" (trade name, product of Yuka Shell Epoxy Kabushiki Kaisha, epoxy equivalent: 470) were used in lieu of phenylphosphonic acid and "Epicoat 828", respectively and the reaction was conducted at 60.degree. C. for 3 hours.
EXAMPLE 5
A reaction product having an acid value of 48.5 was obtained in a similar manner to Example 4 except that 321.7 g of a monoester derivative (purity: 95%) of "Gafac RE610" and 200 g of "Epicoat 1001" were charged and the reaction was conducted at 60.degree. C. for 2 hours.
EXAMPLE 6
A reaction product having an acid value of 47.2 was obtained in a similar manner to Example 4 except that 100 g of tetraglycidylbenzophenone were used instead of "Epicoat 1001" and the reaction was conducted at 60.degree. C. for 2 hours.
EXAMPLE 7
A reaction product having an acid value of 45.0 was obtained in a similar manner to Example 4 except that the amount of "Gafac RE610" was reduced from 764 g to 718 g, 144 g of the phenol novolak type "Epicoat 154" (trade name, product of Yuka Shell Epoxy Kabushiki Kaisha, epoxy equivalent: 180) were used in lieu of "Epicoat 1001" and the reaction was conducted at 70.degree. C.
EXAMPLE 8
A reaction product having an acid value of 46.2 was obtained in a similar manner to Example 4 except that 696 g of "Gafac RS610" (trade name, product of Toho Chemical Industry Co., Ltd.) and 50 g of diglycidyl orthophthalate (trade name: "Dinacol EX721", product of Nagase Chemicals, Ltd.) were used in place of "Gafac RE610" and "Epicoat 1001", respectively.
EXAMPLE 9
A reaction product having an acid value of 75.8 was obtained in a similar manner to Example 4 except that 595 g of "Gafac RE410" (trade name, product of Toho Chemical Industry Co., Ltd.) and 75.6 g of glycerol triglycidyl ester (trade name: "Dinacol EX314", product of Nagase Chemicals, Ltd.) were used in place of "Gafac RE610" and "Epicoat 1001", respectively and the reaction was conducted at 50.degree. C. for 2 hours.
EXAMPLE 10
A reaction product having an acid value of 71.3 was obtained in a similar manner to Example 9 except that 102 g of sorbitol polyglycidyl ether (trade name: "Dinacol EX611", product of Nagase Chemicals, Ltd.) were used in lieu of and "Dinacol EX314" and the reaction was conducted at 50.degree. C. for 3 hours.
EXAMPLE 11
A flask as in Example 1 was charged with 595 g of "Gafac RE410" and 93 g of "Epicoat 828". They were reacted at 100.degree. C. for 30 minutes to obtain a reaction product having an acid value of 72.9.
EXAMPLE 12
A reaction product having an acid value of 50.2 was obtained in a similar manner to Example 11 except that 718 g of "Gafac RE610" were used instead of "Gafac RE410", the amount of "Epicoat 828" was reduced from 93 g to 74.4 g, and the reaction was conducted at 70.degree. C. for 2 hours.
EXAMPLE 13
A flask as in Example 1 was charged with 158.1 g of phenylphosphonic acid and 632 g of tetrahydrofuran, followed by the dropwise addition of a solution of 74.1 g of glycidol in 296.4 g of tetrahydrofuran at 50.degree. C. over about 2 hours. They were reacted at 50.degree. C. for 1 hour. After confirming the elimination of a spot of glycidol as the raw material by thin layer chromatography on silica gel ("Merck Art 5715", trade name, developer: 1:1 mixed solvent of chloroform and methanol), the solvent was distilled out under reduced pressure from the reaction mixture to obtain a viscous reaction product having an acid value of 280.
EXAMPLE 14
A 1-l separable flask equipped with a thermometer, a stirrer, a nitrogen gas inlet tube and a reflux condenser was charged with 100.9 g of poly(1,4-butylene adipate) (molecular weight: 1,000), 7.3 g of 1,4-butylene glycol, 9.2 g of the reaction product obtained in Example 4, 45.0 g of MDI, 270 g of tetrahydrofuran and 270 g of toluene. After reacting the at 80.degree.-85.degree. C. for 12 hours, 100 g of methyl ethyl ketone were added to adjust the solid content to 20%.
The resulting phosphoric-acid-modified polyurethane resin had an acid value of 2.2 (polymer) and a number average molecular weight of 39,000.
After mixing and kneading 750 g of the phosphoric-acid-modified polyurethane resin solution, 600 g of cobalt-modified .gamma.-Fe.sub.2 O.sub.3 (trade name: "AX-3000", product of Titan Kogyo K.K., specific surface area: 31 m.sup.2 /g), 350 g of cyclohexanone and 650 g of methyl ethyl ketone for 72 hours in a ball mill, 20 g of "Desmodule L" were added. The resultant mixture was mixed and kneaded for additional 30 minutes, thereby obtaining a magnetic coating formulation.
A polyester film having a thickness of 9 .mu.m was coated with the magnetic coating formulation to give a coating thickness of 4 .mu.m after drying, followed by drying at 90.degree. C. for 8 hours. The film thus coated was then slit 4.0 mm wide into magnetic tapes.
EXAMPLE 15
A 1-l separable flask equipped with a thermometer, a stirrer and a nitrogen gas inlet tube was charged with 294.6 g of "PTG-1000" (trade name for polyether polyol produced by Hodogaya Chemical Co., Ltd., molecular weight: 1,000), 16.3 g of 1,4-butylene glycol, 18.9 g of neopentyl glycol and 24.9 g of the reaction product obtained in Example 12. After heating the contents to 80.degree. C., 162.9 g of MDI which had been heated to 80.degree. C. were added. The resultant mixture was vigorously stirred for 5 minutes and transferred into a vat, in which the mixture was allowed to age at 120.degree. C. for 10 hours.
The resultant resin had an acid value of 1.9 and a number average molecular weight of 45,000 and was in a solid form. It was dissolved in methyl ethyl ketone to give a solid content of 20%, thereby providing a resin solution.
Magnetic tapes were then produced in a similar manner to Example 14.
EXAMPLE 16
A flask as in Example 15 was charged with 318.9 g of poly(1,4-butylene adipate) (molecular weight: 1,000), 23.1 g of 1,4-butylene glycol and 15.7 g of the reaction product obtained in Example 5. The contents were heated to 110.degree. C.
Thereafter, 142.2 g of MDI which had been heated to 110.degree. C. were added into the flask, followed by vigorous stirring for 3 minutes. During the stirring, the reaction temperature arose to 220.degree.-230.degree. C. because of heat of the reaction. The reaction mixture was transferred into a vat, in which it was allowed to age at 60.degree. C. for 10 hours. The resin thus obtained had an acid value of 1.6 and a number average molecular weight of 48,000 and was in a solid form. It was dissolved in methyl ethyl ketone to give a solid content of 20%, thereby providing a resin solution.
Magnetic tapes were then produced in a similar manner to Example 14.
EXAMPLE 17
Using 263.5 g of poly(1,4-butylene adipate) (molecular weight: 2,000), 22.1 g of 1,4-butylene glycol, 22.7 g of 1,6-hexylene glycol, 31.1 g of "Epicoat 828", 6.2 g of the reaction product obtained in Example 1 and 154.4 g of MDI, a solid resin having an acid value of 2.0 and a number average molecular weight of 58,000 was obtained in a similar manner to Example 15. It was dissolved in methyl ethyl ketone to give a solid content of 20%, thereby providing a resin solution. Magnetic tapes were then produced in a similar manner to Example 14.
EXAMPLE 18
A flask as in Example 15 was charged with 297.1 g of poly(1,4-cyclohexane dimethanol adipate) (molecular weight: 1,000), 15.0 g of 1,6-hexylene glycol, 13.2 g of neopentyl glycol, 25.3 g of "Epicoat 1001" and 18.3 g of the reaction product obtained in Example 11. After heating the contents to 110.degree. C., 136.9 g of MDI were added and reacted under similar conditions to Example 16.
The reaction mixture was transferred into a vat and was then allowed to cool down. Thereafter, it was allowed to age at 60.degree. C. for 10 hours. The resin thus obtained had an acid value of 1.8 and a number average molecular weight of 52,000 and was in a solid form. It was dissolved in methyl ethyl ketone to give a solid content of 20%, thereby providing a resin solution.
Magnetic tapes were then produced in a similar manner to Example 14.
EXAMPLE 19
A flask as in Example 15 was charged at 70.degree. C. with 261.4 g of poly(1,4-butylene adipate) (molecular weight: 2,000), 25.9 g of 1,6-hexylene glycol, 22.8 g of neopentyl glycol, 32.4 g of diethylene glycol diglycidyl ether (trade name: "YED 205", product of Yuka Shell Epoxy Kabushiki Kaisha, aliphatic epoxy compound, epoxy equivalent: 140) and 10.1 g of "Gafac RE-410" (phosphoric acid ester produced by Toho Chemical Industry Co., Ltd.). The contents were heated to 110.degree. C. over about 10 minutes.
Thereafter, under similar conditions to Example 16, 147.4 g of MDI were added and reacted and the reaction mixture was allowed to age.
The resin thus obtained had an acid value of 1.8 and a number average molecular weight of 47,000 and was in a solid form. It was dissolved in methyl ethyl ketone to give a solid content of 20%, thereby providing a resin solution.
Magnetic tapes were then produced in a similar manner to Example 14.
EXAMPLE 20
A flask as in Example 14 was charged with 640 g of methyl ethyl ketone, 100.5 g of poly(1,4-butylene adipate) (molecular weight: 1,000), 8.4 g of neopentyl glycol, 0.8 g of "Epicoat 828" and 3.2 g of "Gafac RE410". They were reacted at 78.degree. C. for 3 hours. MDI (47.1 g) was added further, followed by a reaction at 78.degree. C. for 15 hours. The resultant resin solution had a solid content of 20%. The polymer had an acid value of 1.9 and a number average molecular weight of 45,000.
Magnetic tapes were then produced in a similar manner to Example 14.
EXAMPLE 21
A flask as in Example 15 was charged at 70.degree. C. with 290.6 g of polycarbonate polyol (product of Toagosei Chemical Industry Co., Ltd.), 16.1 g of 1,4-butylene glycol, 18.6 g of 1,6-hexylene glycol, 2.5 g of "Epicoat 828" and 11.3 g of "Gafac RS-410" (product of Toho Chemical Industry Co., Ltd.). After heating the contents to 110.degree. C. over 10 minutes, the reaction mixture was allowed to age at 110.degree. C. for 10 minutes.
Similarly to Example 16, 160.8 g of MDI were then added and reacted and the reaction mixture was allowed to age.
The resultant resin had an acid value of 2.0 and a number average molecular weight of 45,000 and was in a solid form. It was dissolved in methyl ethyl ketone to give a solid content of 20%, thereby providing a resin solution.
Magnetic tapes were then produced in a similar manner to Example 14.
EXAMPLE 22
In a similar manner to Example 14, a phosphoric-acid-modified polyurethane resin solution was prepared. It was neutralized with caustic potash in an amount equivalent to the acid value.
The solution was diluted with methyl ethyl ketone to give a solid content of 20%. Magnetic tapes were then produced in a similar manner to Example 14.
EXAMPLE 23
Using 281.1 g of poly(1,4-butylene adipate) (molecular weight: 1,000), 12.2 g of 1,4-butylene glycol, 21.2 g of neopentyl glycol, 29.2 g of the reaction product obtained in Example 11 and 156.2 g of MDI, a solid resin having an acid value of 5.5 and a number average molecular weight of 45,000 was obtained in a similar manner to Example 16.
Magnetic tapes were then produced in a similar manner to Example 14.
EXAMPLE 24
A flask as in Example 14 was charged with 94.6 g of poly(1,4-butylene adipate) (molecular weight: 1,000), 8.0 g of 1,4-butylene glycol, 1.1 g of the reaction product obtained in Example 13, 103.7 g of MDI and 225 g of tetrahydrofuran. After reacting them at 65.degree. C. for 10 hours, 375 g of tetrahydrofuran were added to give a solid content of 20%.
The resultant phosphoric-acid-modified polyurethane resin had an acid value of 1.8 (polymer) and a number average molecular weight of 52,000.
Magnetic tapes were then produced in a similar manner to Example 14.
EXAMPLE 25
A flask as in Example 15 was charged with 226.1 g of poly(1,4-butylene adipate) (molecular weight: 1,000), 60.7 g of neopentyl glycol and 7.1 g of the reaction product obtained in Example 13. The contents were then heated to 110.degree. C.
Under similar conditions to Example 16, 206 g of MDI were then added and reacted and the reaction mixture was allowed to age.
The thus-obtained resin had an acid value of 3.1 and a number average molecular weight of 62,000 and was in a solid form. It was dissolved in methyl ethyl ketone to give a solid content of 20%, thereby providing a resin solution.
Magnetic tapes were then produced in a similar manner to Example 14.
EXAMPLE 26
A flask as in Example 15 was charged with 226.1 g of poly(1,4-butylene adipate) (molecular weight: 1,000), 60.7 g of neopentyl glycol, 7.1 g of the reaction product obtained in Example 13 and 5.7 g of tri-n-butylamine. The contents were then heated to 110.degree. C.
Under similar conditions to Example 16, 206 g of MDI were then added and reacted and the reaction mixture was allowed to age.
The thus-obtained resin had an acid value of 3.0 and a number average molecular weight of 59,500 and was in a solid form. It was dissolved in methyl ethyl ketone to give a solid content of 20%, thereby providing a resin solution.
Magnetic tapes were then produced in a similar manner to Example 14.
EXAMPLE 27
In a similar manner to Example 25, a phosphoric-acid-modified polyurethane resin solution was prepared. It was neutralized with triethylamine in an amount equivalent to the acid value. The solution was diluted with methyl ethyl ketone to give a solid content of 20%.
Magnetic tapes were then produced in a similar manner to Example 14.
COMPARATIVE EXAMPLE 1
"Estane.RTM. 5701F1" (trade name, product of The B.F. Goodrich Company) was dissolved in a 70:30 mixture of tetrahydrofuran and cyclohexanone to give a solid content of 20%.
Using 750 g of the resin solution, 600 g of cobalt-modified .gamma.-Fe.sub.2 O.sub.3 ("A-3000", trade name; product of Titan Kogyo K.K.), 650 g of cyclohexanone and 350 g of methyl ethyl ketone, magnetic tapes were then produced in a similar manner to Example 14.
COMPARATIVE EXAMPLE 2
"Estane.RTM. 5703" (product of The B.F. Goodrich Company) was dissolved in methyl ethyl ketone to give a solid content of 20%.
Magnetic tapes were then produced in a similar manner to Example 14.
COMPARATIVE EXAMPLE 3
A 1-l separable flask equipped with a thermometer, a stirrer and a nitrogen gas inlet tube was charged with 325.4 g of poly(1,4-butylene adipate) (molecular weight: 1,000), 23.4 g of 1,4-butylene glycol and 6.1 g of "Epicoat 1001". After heating the contents to 80.degree. C., 145.1 g of MDI which had been heated to 80.degree. C. were added and the resultant mixture was vigorously stirred. Thereafter, the reaction mixture was transferred into a vat, in which it was allowed to age at 120.degree. C. for 10 hours. A solid resin having a number average molecular weight of 44,000 was obtained.
Magnetic tapes were then produced in a similar manner to Example 14.
COMPARATIVE EXAMPLE 4
A flask as in Example 14 was charged with 118.4 g of poly(1,4-butylene adipate) (molecular weight: 1,000), 2.1 g of 1,4-butylene glycol, 1.4 g of 2,2-dimethylolpropionic acid, 38.1 g of MDI, 270 g of tetrahydrofuran and 270 g of toluene. After reacting them at 80.degree.-85.degree. C. for 12 hours, 100 g of tetrahydrofuran were added to give a solid content of 20%.
The resultant carboxyl-modified polyurethane resin had an acid value of 3.5 and a number average molecular weight of 52,000.
Magnetic tapes were then produced in a similar manner to Example 14.
COMPARATIVE EXAMPLE 5
A flask as in Example 14 was charged with 116.6 g of poly(1,4-butylene adipate) (molecular weight: 1,000), 2.5 g of 1,4-butylene glycol, 2.8 g of 5-sodiumsulfo-1,3-di(2-hydroxyethyl) isophthalate (product of Sumitomo Chemical Co., Ltd.), 38.1 g of MDI, 270 g of tetrahydrofuran and 270 g of toluene. After reacting them at 80.degree.-85.degree. C. for 12 hours, 100 g of methyl ethyl ketone were added to give a solid content of 20%.
The resultant sodium sulfonate-modified polyurethane resin had a sodium sulfonate (--SO.sub.3 Na) concentration of 0.05 mg eq/g and a number average molecular weight of 48,000.
Magnetic tapes were then produced in a similar manner to Example 14.
COMPARATIVE EXAMPLE 6
A flask as in Example 14 was charged with 468 g of dimethylformamide and 115 g of a hydroxyl-terminated polyurethane ("Estane.RTM. 5703", trade name; product of The B.F. Goodrich Company). After dissolving the latter in the former at 80.degree. C. over 2 hours, 8.2 g of the compound represented by the following formula: ##STR3## and 1.6 g of pyridine were added. A dehydrochlorination reaction was then conducted at 80.degree. C. for 3 hours, whereby phosphoric acid groups were introduced into both ends of each polyurethane chain, respectively. Subsequent to neutralization with caustic soda, the polymer was poured into a large volume of methanol. Further, the polymer was washed several times with methanol.
After drying the polymer under reduced pressure, methyl ethyl ketone was added to adjust the solid content to 20%.
The sodium-phosphate-modified polyurethane resin thus obtained had a sodium phosphate residuum ##STR4## concentration of 1.8 mg eq/g and a number average molecular weight of 58,000.
Magnetic tapes were then produced in a similar manner to Example 14.
With respect to each of the magnetic tapes obtained in the above examples and comparative examples, its surface gloss (60.degree. reflectivity) and square ratio (Br/Bs) were measured to investigate the dispersion and magnetic characteristics, respectively. In addition, its abrasion resistance was also measured to investigate the durability. The results are summarized in Table 1.
The above properties were measured in accordance with the following testing methods, respectively.
Surface gloss
The surface gloss (60.degree. reflectivity) of the magnetic coating layer of each magnetic tape was measured using a gloss meter ("AU-SCH-2D-GU3", trade name for a digitized automatic colorimetric color difference meter manufactured by Toho Rika Kogyo K.K.).
Better dispersion gives a higher gloss value.
Square ratio
Measurement was conducted using "Model 3257", trade name for an automatic recording apparatus for d.c. magnetization characteristics manufactured by Yokogawa Electric Corporation.
Better dispersion gives a higher square ratio.
Abrasion resistance
A crock testing machine of the JSPSR (Japan Society for Promotion of Scientific Research) type manufactured by Daiei Kagaku Seiki Seisakusho K.K. was used. In an environment of 23.degree. C. and 65% RH, the surface of the magnetic coating layer of each magnetic tape was reciprocated and rubbed 200 times under a load of 100 g against a chromium-plated metal cylinder having a diameter of 15 mm. Then, the percentage of any rubbed-off surface area was determined based on the total surface area subjected to the rubbing.
It is clearly envisaged from Table 1 that the magnetic tapes according to the present invention, namely, those of Examples 14-27 are all excellent in dispersion and especially the magnetic tapes of Examples 16-18 in which phosphoric-acid-modified and epoxy-modified polyurethane resins were used respectively are also excellent in durability.
Claims
We claim:
1. A magnetic coating formulation composed principally of magnetic particles and a binder, characterized in that at least a portion of the binder is a polyurethane resin synthesized from a reactant mixture of components (1), (2), (3) and (4) set out below, containing one phosphoric acid group or one residual group derived from phosphoric acid per 3,000-200,000 number average molecular weight of the polyurethane resin, and having a number average molecular weight of 4,000-150,000: (1) a phosphorus compound (a) represented by a structural formula set out below or a phosphorus compound (b) represented by a structural formula set out below: ##STR5## wherein R.sup.1 is a hydrogen atom, a phenyl group, an alkyl group having 1-40 carbon atoms, or an alkylphenyl group having 1-40 carbon atoms, and n is an integer of 0-30 ##STR6## wherein R.sup.2 is a phenyl group, an alkyl group having 1-40 carbon atoms, or an alkylphenyl group having 1-40 carbon atoms; (2) an epoxy compound having at least two epoxy groups and/or an epoxy compound having one epoxy group and at least one hydroxyl group; (3) a bifunctional isocyanate compound and/or a trifunctional isocyanate compound; and (4) a polyfunctional hydroxy compound having a number average molecular weight of 400-5,000.
2. The magnetic coating formulation according to claim 1, wherein the reactant mixture further comprises a chain extender as component (5).
3. The magnetic coating formulation according to claim 1, wherein phosphoric acid groups or residual groups derived from phosphoric acid, said groups being contained in the polyurethane resin, have been at least partly neutralized with a base.
4. The magnetic coating formulation according to claim 2, wherein phosphoric acid groups or residual groups derived from phosphoric acid, said groups being contained in the polyurethane resin, have been at least partly neutralized with a base.
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