KR940011781B1 - Process for preparation of polyurethane used with magnetic media - Google Patents

Abstract

The polyurethane resin for a magnetic recording medium is produced by reacting: (a) a diol of 200-5000 molecular wt. contg. COOX [X = alkali metal or H at the molecular chain; (B) a triol of formula (I) [R = R' = -(CH2)n-(OCH2CH2)m-; n = m = 0-6; R" = -(CH2)l-CH(CH3)-; l = 0-3 having a tertiary amino and a secondary hydroxy gp.; and (c) an organic diisocyanate in the presence of a catalyst or in the organic solvent. The diol is pref. polyester polyol or polyether polyol, and the diisocyanate is pref. 4,4'-diphenylmethane diisocyanate, cyclohexane diisocyanate and/or hexamethylene diisocyanate. The polyurethane resin has a good adhesiveness and dispersibility.

Description

Manufacturing method of polyurethane resin for magnetic recording medium

The present invention relates to a method for producing a polyurethane resin for a magnetic recording medium, and more particularly, to a polyurethane resin for a magnetic recording medium which improves abrasion resistance and durability of a magnetic layer by administering a component having excellent adhesion and dispersibility of a magnetic component. It relates to a manufacturing method.

In recent years, the demand performance of magnetic recording media such as audio tapes and VTR tapes for home use has changed in various ways. In particular, when recording and reproducing, the demand for high reliability is increased, Improving productivity is also one of the big challenges.

Examples of high reliability include high recording density for reproducing clear images and sounds, high speed, high temperature and high humidity, and long-term driving, and magnetic components in the magnetic layer due to severe friction with the head during long-term running of the tape. Drop-out phenomenon due to desorption and wear of the powder and the occurrence of false signals are prevented.

As an example of productivity improvement, productivity improvement of the magnetic recording medium obtained by shortening the time required for dispersing the magnetic component and smoothing the surface of the magnetic recording medium is mentioned. In other words, improving the characteristics, physical properties and productivity of the magnetic layer is an important task of the binder, and it is possible to produce excellent magnetic paints and high performance magnetic recording media by uniform dispersion of magnetic components in a shorter time, thereby providing high sensitivity and high sensitivity. While good electronic properties such as SN ratio and high CN ratio are obtained, a binder having excellent durability such as wear resistance is required.

Fiber binders (nitrocellulose, etc.) and vinyl chloride-vinyl acetate copolymers are used as binders for magnetic recording media. Recently, thermoplastic polyurethane resins and polyisocyanates have been used to improve the durability of magnetic recording media by providing wear resistance to magnetic layers. A binder made from is proposed.

Thermoplastic polyurethane resin has various properties such as injection molding, ejection molding, synthetic leather, elastic fiber, paint, adhesive or ABS resin, AS resin due to its excellent properties such as high elasticity, flexibility, wear resistance, cold resistance and strength. And polymers such as PVC, its derivatives, and cellulose acetate, which are widely used, but have weak disadvantages in heat resistance, hydrolysis resistance, and heat and moisture resistance, and are used for printing inks, magnetic paints, conductive resins, and magnetic rubbers. Although active, the dispersibility of the magnetic component is poor at the time of use, and this causes the satisfactory electronic properties not to be obtained, and it is difficult to smooth the surface of the magnetic recording medium, thereby improving the productivity.

Therefore, the present invention is a method for improving the above disadvantages, COOX group (wherein X is a hydrogen atom or an alkali metal atom) in the molecular chain of the polyurethane resin and at least one tertiary amino group and side chain in the main chain and at least one By introducing a secondary hydroxyl group, a polyurethane resin having a molecular weight of 10,000 to 60,000 having excellent adhesion and dispersibility of magnetic components is prepared, and the resin is used to provide a magnetic recording medium with remarkably improved wear resistance and durability of a magnetic layer. The purpose is.

The present invention is described in detail as follows.

The present invention improves the dispersibility of magnetic components and the electronic properties of the magnetic layer by introducing 0,5 or more preferably 0.5 to 2 COOX groups, which are hydrophilic polar groups, in the molecular chain in the molecular chain used as an average value. to be. If the number of COOX groups in one molecule of polyurethane is less than 0.5, the concentration is too small to improve the dispersibility of the magnetic components. In the case of two or more, the hydrophilicity of the COOX groups increases, resulting in deterioration of solubility and water resistance in organic solvents. It is not suitable as a polyurethane resin for magnetic recording media.

Diol which has a COOX group in a molecular chain can use dimethylol propionic acid (DMPA) and its sodium salt. Furthermore, glycols having 2 to 10 carbon atoms, that is, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2,3-butylene glycol, 1,4-butane diol, and 2,2-dimethyl- Glycol alone or dimethylol propionic acid or its sodium salt, such as 1,3-propane diol, 1,6-hexane diol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, diethylene glycol Mixtures with those, such as malonic acid, adipic acid, glutaric acid, pimeric acid, schweric acid, azeline acid, succinic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, hexahydro terephthalic acid, hexahydroisophthalic acid, etc. Polyester diols having a molecular weight of 200 to 5,000 synthesized by polycondensation with a mixture of dibasic acids and esters thereof can be used.

Moreover, the thing which introduce | transduced 0.01 to 1 weight%, especially 0.03 to 0.7 weight% of COOX group in polyether diol, polyester diol, and polycaprolactone diol can be used.

The polyurethane resin has affinity with a magnetic component by introducing a triol having a structure represented by the following formula (I) having at least one or more tertiary amino groups and at least one secondary hydroxyl group as a side chain in the main chain. That is, the dispersibility of the magnetic component can be improved.

Wherein R is-(CH ₂ ) _n- (OCH ₂ CH ₂ ) _m- (where n and m are integers from 0 to 6 and n and m cannot be 0 at the same time) R 'is- (CH ₂ ) _{n '} -(OCH ₂ CH ₂ ) _m' -(where n ', m' is an integer from 0 to 6, and n 'and m' cannot be 0 at the same time. (Where ℓ is an integer from 0 to 3)

In general, coating agents, i.e. pigments that are contained for various binder, a magnetic powder is sufficiently dried even when the adsorbed water on the surface, since it represents a hydrophilic chemical can have a combination of tertiary amino group and the side chain hydroxyl group, -SO ₃ X group, a group -COOX Affinity with the compound to be contained improves dispersibility and greatly shortens the dispersing time. In addition, when the side chain hydroxyl group reacts with the polyisocyanate, a urethane bond between the side chain hydroxyl group and the isocyanate occurs, thereby forming a warning coating film, thereby improving wear resistance and mechanical strength of the magnetic layer. Improves the durability of the media and improves solubility and solution stability.

The structure of the formula (I) in the molecular chain of the polyurethane resin is an average value of 1 or more, 1 to 10 is suitable, but less than 1 is not effective in improving the dispersibility of the magnetic component, and in the case of more than 10 to the secondary hydroxyl group Network structure is formed, and solubility falls.

As the triol represented by the formula (I), N-isopropanol diethanolamine, propylene oxide adduct of diethanolamine, ethylene oxide adduct of N-isopropanol diethanolamine and the like can be used.

Moreover, if necessary in the said polyurethane resin, it is possible to use the diol of the molecular weight 200-6,000 which has a linear terminal hydroxyl group. Diols having a linear terminal hydroxyl group having a molecular weight of 200 to 6,000 are classified into polyester polyols and polyester polyols. Among them, polyether polyols may be polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like. Furnaces are poly-synthesized by polycondensation of solely or a mixture of glycols having an electric carbon number of 2 to 10 with an electrodibasic acid containing no COOX groups and their esters or acids, such as acid esters and halides. Ester polyols can be used. In addition, polycaprolactone diols in which the ring opening is polymerized with lactones such as ε-caprolactone in the presence of glycol or the like may be used.

Organic diisocyanates (C) used in the present invention include 4,4'-diphenylmethane diisocyanate, lidine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, xylene diisocyanate 2,4- and 2,6-toluene Diisocyanates, p- and m-phenylene diisocyanates, hexa-methylene diisocyanates, 1,5-naphthalene diisocyanates or mixtures thereof are used.

Moreover, the NCO / OH molar ratio of polyol and organic diisocyanate in the said polyurethane resin is 0.8-1.2 / 1, Especially 0.9 / 1.1 is suitable. Outside the range, the excellent performance required by the present invention is not obtained. It is also possible to use catalysts and various stabilizers if necessary.

Examples of the catalyst include tertiary amines such as triethyl amine and triethylene diamine, nitrogen compounds such as morpholine and N-methyl morpholine, metal salts such as potassium acetate and zinc stearate, dibutyltin dilaurate and di Organometallic compounds such as butyl tin oxide can be used.

As a stabilizer, ultraviolet-ray stabilizers, such as substituted benzotriazoles, and thermal oxidation stabilizers, such as a phenol derivative, can be mix | blended and it can remarkably stabilize the said performance of a polyurethane resin.

The molecular weight of the polyurethane resin is preferably 10,000 to 60,000, particularly 15,000 to 50,000, and when the molecular weight is less than 10,000, the dispersibility of the magnetic component is excellent, but the wear resistance of the magnetic layer is weak, resulting in desorption and adhesiveness of the magnetic component. When the molecular weight is 60,000 or more, the wear resistance of the magnetic component is improved, but the dispersibility and solubility of the magnetic component and the solution stability are lowered, which makes it difficult to paint. The end group of the polyurethane resin may be either an isocyanate group or a hydroxyl group at the same time, or an isocyanate group at one end and a hydroxyl group at the other end, but it is preferable to have a hydroxyl group at the sock end.

Conventionally known methods may be used to prepare the polyurethane resins used in the present invention and if necessary, the reactants are sufficiently mixed in the presence of a catalyst, flowed onto a flat or flat surface, heated, cooled and pulverized, dimethyl form. Common production methods such as a solution reaction method for reacting in a single or mixed solvent-based organic solvent such as amide, toluene, xylene, benzene, dioxane, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate and butyl acetate Can be used.

In the present invention, it is necessary to harden the polyurethane resin as a suitable curing agent at the end, and as a curing agent, a low molecular weight polyisocyanate having a molecular weight of 150 to 7,000 is suitable, and the DIC company Banok D-750, D-800, DN-960 , DN-950, CL-2, Desmordue L, Desmordue RF, Desmoroure R, and other equivalents sold by Bayer may be used.

In addition, as block isocyanate, DIC's Banokku D-500, D-504, D-550, etc. may be used.

By adding 3-50 parts by weight of the low molecular weight polyisocyanate to 100 parts by weight of the polyurethane resin of the present invention, the mechanical strength, abrasion resistance, heat resistance, moist heat resistance, solvent resistance, and adhesion to the substrate are greatly improved. You can.

In addition, if necessary in the binder component, a thermoplastic polyurethane resin, a vinyl chloride-vinyl acetate copolymer, a fibrin resin, a polyvinyl butylal resin, a thermoplastic polyester resin, and a vinyl chloride-propionate vinyl are commonly used as binder components of magnetic recording media. By using together a commercial item, such as a system copolymer, an epoxy resin, and a phenoxy resin, as it is, the dispersibility of a magnetic component, the smoothness of the surface of a magnetic layer, etc. can be improved.

As the magnetic component used in the present invention, r-Fe ₂ O ₃ powder Fe ₃ O ₄ powder, Co-containing r-Fe ₂ O ₃ powder, Co-containing Fe ₂ O ₃ powder, CrO ₂ powder, etc. may be used. Various magnetic powders known in the art can be used.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which are only one form and the present invention is not limited to the examples.

Example 1

100 parts of polyester diol having a molecular weight of 2,000 synthesized from adipic acid, 1,4-butane diol, sodium dimethylol propionate, 20 parts of N-isopropanol diethanol amine, and 0.2 parts of dibutyltin dilaurate were stirred at 80 ° C. After removal, 15 parts of 4,4'-diphenyl methane diisocyanate preheated at 50 ° C were added.

After mixing these components for 1 minute, this reaction mixture was flowed on the glass plate, it aged for 24 hours at 100 degreeC, and reaction was completed and the polyurethane resin was obtained. Dispersibility, adhesion, and wear resistance of the magnetic tape of the resin were evaluated, and the results are shown in Tables 1 and 2.

Example 2

100 parts of polyester diol having a molecular weight of 1,500 synthesized from adipic acid, 2,2-dimethyl-1,3-propane diol, dimethylol sodium propionate, 20 parts of N-isopropanol diethanol amine, 0.2 parts of dibutyltin dilaurate, 13 parts of hexamethylene diisocyanate were added, and the polyurethane resin was obtained by the method similar to Example 1. The evaluation results are shown in Table 1 and Table 2.

Comparative Example 1

100 parts of molecular weight 2,000 polyester diol synthesized from adipic acid and 1,4-butane diol, 4 parts of 1,4-butane diol, 0.2 parts of dibutyltin dilaurate, 4,4'-diphenyl methane diisocyanate 23 The polyurethane resin was synthesize | combined by the method similar to Example 1 by adding a part.

Comparative Example 2

Adipic acid 2,2-dimethyl-1,3-propane diol, 100 parts of polyester diol having a molecular weight of 1,500 synthesized from dimethylol sodium propionate, 30 parts of 1,4-butane diol, 0.2 parts of dibutyltin dilaurate, hexa 17 parts of methylene diisocyanates were added to synthesize a polyurethane resin in the same manner as in Example 1.

Assessment Methods

· Dispersibility of magnetic ingredients

20 parts of each of the polyurethane resins obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were taken and mixed with the following materials.

40 cyclohexanone

40 parts methyl ethyl ketone

40 parts r-Fe ₂ O ₃ magnetic powder

After mixing the above mixture for 20 hours using a ball-mill, the obtained magnetic paint was applied and dried on a polyester film having a thickness of 6 µm so as to have a thickness of approximately 12 µm, and then the surface state of the magnetic layer under a microscope (40 times). Was observed to evaluate the dispersibility of the magnetic component.

Adhesiveness with polyester film

After adding 10 parts of Banokku D-750 to the magnetic paint and mixing for 2 hours, the obtained magnetic paint was applied and dried on a polyester film having a thickness of 6 μm so that the thickness after drying was approximately 20 μm, thereby forming a magnetic coating film. After bonding 10 mm of cellophane tape (50 mm in width) onto the magnetic coating film, the adhesiveness with the polyester film was evaluated by the area (peel area) of the magnetic coating film which fell off when the cellophane tape was removed.

Wear resistance of magnetic recording media

50 parts of each of the polyurethane resins obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were taken and mixed with the following materials.

Beanie VAGH (U.S. union carbide company, vinyl chloride- super 50 parts

Vinyl acid copolymer)

Cyclohexanone 280 parts

Methylethyl ketone 280 parts

r-Fe ₂ O ₃ 150 parts

Carbon black eight

Lubricant Part 5

The mixture was mixed for 48 hours using a ball mill, 20 parts of Banocque D-750 (DIC, low molecular weight polyisocyanate) was added and stirred for 5 hours, and the resulting magnetic coating was dried on a 6 μm thick polyester film. The coating was dried to a thickness of 12 m, cut into a predetermined width to make a magnetic recording medium, and then the wear resistance was measured. Abrasion resistance was measured by rubbing the magnetic surface of each tape at the rotary desk to measure the wear amount of the thickness.

TABLE 1

●: Very good, 0% of peeling area

○: Excellent, peeling area less than 10%

▲: Usually, peeling area 10-50%

X: defective or peeled area 50% or more

TABLE 2

○: Example 1 ●: Comparative Example 1

□: Example 2 ■: Comparative Example 2

Claims (2)

A method of producing a polyurethane resin for a magnetic recording medium, comprising adding a mixture of the following components (A), (B), and (C) at the time of producing a polyurethane resin. (A) Diol of molecular weight 200-5,000 which has linear terminal hydroxyl group and contains COOX (however, X is an alkali metal atom or a hydrogen atom) group in a molecular chain. (B) The triol represented by Formula (I) which has a tertiary amino group and a secondary hydroxyl group. Wherein R is-(CH ₂ ) _n- (OCH ₂ CH ₂ ) _m- (where n and m are integers from 0 to 6 and n and m cannot be 0 at the same time) R 'is- (CH ₂ ) _{n '} -(OCH ₂ CH ₂ ) _m' -(where n ', m' is an integer from 0 to 6 and n 'and m' cannot be 0 at the same time) R " Is (Where ℓ is an integer from 0 to 3) (C) organic diisocyanate. The method for producing a polyurethane resin for a magnetic recording medium according to claim 1, wherein the NCO / OH molar ratio of the total polyol (A + B) and the organic diisocyanate (C) is used in the range of 0.8 to 1.2 / 1.