JPH055850B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyurethane resins having hydroxyl groups and/or carboxyl groups. Various methods have been proposed for the synthesis of polyurethane resins having polar groups such as hydroxyl groups or carboxyl groups in their molecules. For example, a polyol with a polyester structure or a polyol with a polyether structure is reacted with a diisocyanate to form a urethane prepolymer with isocyanate groups at the ends, and then reacted with a triol to extend the chain, and hydroxyl groups are added to the molecular ends and side chains. There are known methods to introduce On the other hand, when attempting to obtain polyurethane by extending the chain length of a polyol having hydroxyl groups at both ends of the molecule with a common triisocyanate (eg, Desmodyur N), a gel-like polyurethane with extremely high viscosity is produced. This is because the reactivity of the three isocyanate groups in Desmodyur N is almost equal, so that the chain length of the polyol is extended three-dimensionally. When such polyurethane is used as a paint binder, it is inevitable that pigment dispersion becomes poor, making it impractical. Therefore, as a result of extensive research, the present inventor found that by using triisocyanate having isocyanate groups with different reactivities, the chain length of the polyol can be extended without gelation. I found out what I can get. Furthermore, by introducing hydrophilic hydroxyl or carboxyl groups into this polyurethane, we can create inorganic powders with hydrophilic groups on the surface, such as γ.
- To obtain a polyurethane resin that, when used as a binder for a paint containing magnetic particles such as _{Fe 2} O ₃ , has excellent affinity with such inorganic powder and provides good dispersion in the paint. He was successful in this and came up with this invention. That is, this invention has the following general formula: (In the formula, A represents a divalent organic residue of a compound having two hydroxyl groups in the molecule, and B has 1 to 1 carbon atoms.
6 represents a divalent hydrocarbon residue, R represents a divalent hydrocarbon residue having 2 or 3 carbon atoms, and Z represents a hydroxyl group or a carboxyl group), and General formula: Or related to a polyurethane resin having a number average molecular weight of 1700 to 24000 and having both terminal groups represented by the general formula: -O-B-Z (in the formula, B, Z and R each have the same meanings as above). be. A in the repeating unit in this invention is
Represents a divalent organic residue of a compound that has two hydroxyl groups in the molecule. As this compound, a monomer or polymer having two hydroxyl groups in the molecule is used. Monomers having two hydroxyl groups include dihydric monomers such as ethylene glycol, propylene glycol, β, β'-dihydroxy diethyl ether (diethylene glycol), dipropylene glycol, 1,4-butylene glycol, and 1,3-butylene glycol. Alcohols and mixtures thereof can be used, and examples of polymers having two hydroxyl groups include polyesters and polyethers having two hydroxyl groups (hereinafter referred to as polyester polyols and polyether polyols, respectively), mixtures thereof, and the above-mentioned monomers. Mixtures with etc. can be used. The polyether polyols include polyethylene glycol, polypropylene glycol,
Polypropylene-polyethylene glycol, polybutylene glycol, polyoxymethylene, etc. can be used. In addition, the polyester polyol contains terephthalic acid, isophthalic acid,
Aromatic dicarboxylic acids such as orthophthalic acid and 1,5-naphthalic acid; dicarboxylic acids such as aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid; p-
Oxybenzoic acid, p-(2-hydroxyethoxy)
It may be synthesized using aromatic oxycarboxylic acids such as benzoic acid, tricarboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid, and tetracarboxylic acids. Among these, particularly preferred carboxylic acid components include terephthalic acid, isophthalic acid, adipic acid, and sebacic acid. Further, as the polyhydric alcohol component which is another component of the polyester polyol, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-
pentanediol, neopentyl glycol,
Aliphatic diols or substituted derivatives thereof such as 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, alicyclic diols such as 1,4-cyclohexanedimethanol, diethylene glycol, dipropylene glycol , diols such as polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, ethylene oxide adducts or propylene oxide adducts of bisphenol A, ethylene oxide adducts or propylene oxide adducts of hydrogenated bisphenol A Examples include oxides such as alkylene oxide adducts of aromatic diols. Further, the compound corresponding to the portion represented by A in the repeating unit may have a polar group having no active hydrogen represented by the following general formula in its side chain. −SO ₃ M, −OSO ₃ M, −COOM, −OM, −NO ₂
or

[Formula] (In the formula, M represents Li, K, Na, Ba ⁺ , Ca ⁺ or MG ⁺ .) Such a polar group is introduced into the compound corresponding to the part represented by A in the repeating unit. for,
For example, in the case of a polyester polyol, it is possible to use a method such as using in combination the above-mentioned carboxylic acid component and/or polyhydric alcohol component constituting the polyester polyol with one having the polar group. In this invention, the portion represented by m in the repeating unit has the general formula: (In the formula, R represents a divalent hydrocarbon residue having 2 or 3 carbon atoms.) In this general formula, to distinguish the three isocyanate groups, each is conveniently replaced with X, Y, and Z, When rewritten as follows, comparing the reactivity of the isocyanate group, it becomes: X<Y, Z Y≒Z ...(3). More specifically, Y and Z have twice the reactivity of X at room temperature, and this difference in reactivity further increases as the temperature increases. The compound represented by the general formula (1) is specifically 2,6-diisocyanatohexanoic acid-2-isocyanatoethyl ester, 2,6-diisocyanatohexanoic acid-3-isocyanatopropyl ester, and 2,6-diisocyanatohexanoic acid-
2-isocyanato-2-methylethyl ester. All of these can be produced by phosgenating an ester of lysine and an amino alcohol. In the general formula (1), it is difficult to synthesize a compound in which R has 1 carbon atom;
If it is more than that, the reactivity of the isocyanate group Z becomes low, which is not suitable. In this invention, the moiety represented by n in the repeating unit has the general formula: HO-B-Z (in the formula, B
represents a divalent hydrocarbon residue having 1 to 6 carbon atoms, and Z represents a hydroxyl group or a carboxyl group). Compounds that can be used as the compound corresponding to the moiety represented by n in the repeating unit include polyols such as ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol, and hydroxyl compounds such as glycolic acid, lactic acid, and β-hydroxypropionic acid. Preferred examples include acids and mixtures thereof. When a hydroxy acid is used, of the hydroxyl group and carboxyl group of the hydroxy acid, the hydroxyl group preferentially reacts with the isocyanate group, and the carboxyl group is introduced into the polyurethane resin. The polyurethane resin of the present invention comprising the above-mentioned components can be synthesized by the following method. First, a compound corresponding to the portion represented by A in the repeating unit and a triisocyanate compound as component (B) are added to the hydroxyl group of the compound corresponding to the portion represented by A in the repeating unit in the repeating unit. The molar ratio M of isocyanate groups corresponding to the moiety represented by m is 1.5<M
React so that ≦3. At this time, among the three isocyanate groups of the triisocyanate compound corresponding to the part indicated by m in the repeating unit, the isocyanate group with higher reactivity is preferentially reacted, excluding the one with lower reactivity. hand,
A polyisocyanate compound in which a compound corresponding to the part represented by A in the repeating unit is two-dimensionally chain-extended via a urethane bond by a triisocyanate compound corresponding to the part represented by m in the repeating unit. obtain. At this time, when the molar ratio M is 3, it becomes a tetrafunctional polyisocyanate compound having two isocyanate groups at both ends, and the molar ratio M is 1.5<M<3.
In the case of , it becomes a polyisocyanate compound having five or more functional groups which has an isocyanate group not only at both ends but also at the side chain. However, when the molar ratio M is 1.5 or less, such a polyfunctional polyisocyanate compound cannot be obtained, and it is virtually impossible to synthesize a compound where the molar ratio M is greater than 3. However, it is possible to synthesize the polyisocyanate compound of the present invention in a reaction system in which this molar ratio is greater than 3, that is, in which the triisocyanate compound is present in excess. Here, if a triisocyanate compound corresponding to the part indicated by m in the repeating unit is used, in which all three isocyanate groups have the same reactivity, the chain of the polyisocyanate compound will grow three-dimensionally. This is disadvantageous both in terms of synthesis and use, as it gels. Subsequently, the thus obtained polyisocyanate compound is reacted with a compound corresponding to the moiety represented by n in the repeating unit to introduce a carboxyl group and/or a hydroxyl group. This reaction is an addition reaction between the isocyanate group of the polyisocyanate compound and the hydroxyl group of the compound corresponding to the moiety represented by n in the repeating unit. and,
In addition to highly reactive isocyanate groups, which exist one at each end, there is also one at each end.
In order that less reactive isocyanate groups, which may also be present in side chains, may also participate in this reaction.
The reaction may be carried out by controlling the reaction conditions as necessary. The molecular weight and the number of hydroxyl groups and/or carboxyl groups of the polyurethane resin obtained in this way correspond to the compound corresponding to the moiety indicated by A in the repeating unit and the moiety indicated by m in the repeating unit. It can be arbitrarily adjusted by blending with a compound, in other words, by selecting the molar ratio M of isocyanate groups to hydroxyl groups, and thereby resins having various physical properties can be obtained. The molecular weight of polyurethane resin also depends on the molecular weight of each raw material, but is usually in the range of 1,700 to 24,000, and the concentration of hydroxyl and/or carboxyl groups (number of moles in 1 g of resin) is 0.2 to 5 mmol/g. is preferable. If this concentration is too high, the compatibility with general-purpose solvents and other resins will be poor, and if it is too low, sufficient affinity for inorganic powders cannot be expected. Table 1 shows polyester polyols (molecular weight
1500), T-100 (triisocyanate compound manufactured by Toray Industries, Inc., molecular weight 267) and ethylene glycol (molecular weight 62), the molar ratio M and molecular weight (approximate number), number of hydroxyl groups in one molecule, and hydroxyl groups Shows the relationship with concentration.

[Table] The polyurethane resin of the present invention has hydroxyl groups and/or carboxyl groups not only at both ends but also in some cases in side chains, so it has an affinity with inorganic powders having hydrophilic groups on the surface, such as magnetic powders. Good properties. Therefore, if the polyurethane resin of the present invention is applied as a binder for a magnetic recording medium, it is possible to obtain a magnetic layer with good dispersion of magnetic powder and thus with good various properties. When the polyurethane resin according to the present invention is used as a binder for a magnetic recording medium, any commonly used materials can be used for the other materials constituting the magnetic recording medium. First, as the magnetic powder, ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder, etc. can be used. As ferromagnetic iron oxide particles, the general formula
When expressed as FeOx, the value of X is in the range of 1.33≦X≦1.50, that is, maghemite (γ-Fe ₂ O ₃
X=1.50), magnetite (Fe ₃ O ₄ X=1.33),
and solid solutions thereof (FeOx 1.33<X<1.50) can be used. Cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. Cobalt-containing magnetic iron oxide is roughly divided into two types: doped type and coated type.
There are different types, but it can be either one. As ferromagnetic chromium dioxide, CrO ₂ or Hc
Ru, Sn, Te, Sb, Fe,
A material containing at least one of Ti, V, Hn, etc. can be used. Ferromagnetic alloy powders include Fe, Co,
Ni, Fe-Ni or Fe-CO-Ni can be used, and in order to improve various properties, A, Si,
Some contain metal components such as Ti, Cr, Mn, Cu, and Zn. Examples of organic solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol acetate monoethyl ether; ether, glycol dimethyl ether, and glycol monoethyl ether. , glycol ethers such as dioxane; tars (aromatic hydrocarbons) such as benzene, toluene, and xylene; chlorinated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. You can select and use the system etc. In addition, abrasives such as aluminum oxide, chromium oxide, and silicon oxide, antistatic agents such as carbon black, and lubricants such as molybdenum disulfide, graphite, silicone oil, and olive oil can be added to the magnetic paint. . Further, as the binder, a resin conventionally used as a binder for magnetic recording media may be used in combination with the polyurethane resin according to the present invention. Examples of such resins include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-vinylidene chloride copolymer. , vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester-styrene copolymer, thermoplastic polyurethane Resin, phenoxy resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-acrylic acid copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative , styrene-butadiene copolymer, polyester resin, phenol resin, epoxy resin, thermosetting polyurethane resin, urea resin, melamine resin, alkyd resin, urea-formaldehyde resin, or a mixture thereof. A magnetic paint made of these materials is applied to a non-magnetic carrier according to a conventional method. Materials for this non-magnetic carrier include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polyethylene and polypropylene; cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate, etc. Cellulose derivatives; vinyl resins such as polyvinyl chloride and polyvinylidene chloride; polycarbonate,
In addition to plastics such as polyimide and polyamide-imide, non-magnetic metals such as aluminum, copper, tin, zinc, or non-magnetic alloys containing these; ceramics such as glass, earthenware, and porcelain;
Paper, baryta, or polyethylene, polypropylene, ethylene-butene copolymer, etc. with 2 or more carbon atoms
Paper such as paper coated or laminated with α-polyolefins of 10 can also be used. These non-magnetic carriers may be transparent or opaque depending on the intended use. In addition, the form of the non-magnetic carrier is a film,
It may be a tape, sheet, disk, card, drum, etc., and various materials are selected as necessary depending on the form. The thickness of these non-magnetic carriers is approximately 1 to
It is about 50 μm, preferably 1 to 30 μm. In addition, in the case of disks and cards, it is about 0.5 to 10 mm,
If it is drum-shaped, it is cylindrical, and its shape is determined depending on the recorder used. Examples of the present invention will be described below. Note that all "parts" used here indicate "parts by weight." Example 1: Synthesis of polyurethane resin In a reaction vessel equipped with a thermometer, a stirrer and a partial reflux condenser, methyl ethyl ketone 73
73 parts of toluene, 50 parts of polyester polyol (number average molecular weight 1500, identified from the results of nuclear magnetic resonance (NMR) composition analysis.The components are as follows.Carboxylic acid component: 20 mol% of terephthalic acid, isophthalic acid 20 mol%, sebacic acid 60 mol% Polyhydric alcohol component: ethylene glycol 50 mol%,
50 parts of propylene glycol (50 mol%) and 6.25 parts of a triisocyanate compound (T-100, manufactured by Toray Industries, Inc.) were added and reacted at 70 to 90°C for 3 hours to produce a polyisocyanate compound. Next, add 1.86 parts of ethylene glycol and heat at 70 to 90℃ for another 3 minutes.
A polyurethane resin was obtained by reacting for a period of time. The number average molecular weight of this polyurethane resin is 15,500, the concentration of hydroxyl groups in the molecule is 0.65 mmol/g, and the number of hydroxyl groups is 9.
The reduced viscosity was 0.365 (methyl ethyl ketone/toluene = 1/1, 25°C). Repeating unit is polyester polyol molecule, triisocyanate 1
molecule and one molecule of ethylene glycol. Comparative Example 1: Synthesis of polyurethane resin without hydroxyl groups In the same reaction vessel as in Example 1, 50 parts of the polyester polyol used in Example 1, 73 parts of methyl ethyl ketone, 73 parts of toluene, MDI (4,4'-diphenyl 4.25 parts of methane diisocyanate) was added and reacted to synthesize a polyurethane resin. The molecular weight of this polyurethane resin is 19000, and the reduced viscosity is
0.195 (methyl ethyl ketone/toluene = 1/1,
25℃). Example 2: Preparation of magnetic tape A mixture of 10 parts of γ-Fe ₂ O ₃ magnetic particles, 5 parts of methyl ethyl ketone, and 7.5 parts of toluene was mixed for 3 hours using a ball mill. To this mixture was added a separately prepared mixed solution of 2.0 parts of the polyurethane resin of Example 1, 5 parts of methyl ethyl ketone, and 7.5 parts of toluene, and the mixture was again mixed for 24 hours using a ball mill.
Co., Ltd.) and mixed for 30 minutes. After degassing the resulting mixture, it was coated onto a polyethylene terephthalate film using a doctor blade with a gap of 25 μm and subsequently placed in a parallel magnetic field of 900 Oe for approximately 1
It was left in place for a second. Then put it in a hot air dryer at 90℃ for about 30 minutes.
The solvent was removed by standing for a minute. Additionally, 48 at 80℃
The magnetic coating was cured over time. Comparative Example 2 A magnetic tape was produced in the same manner as in Example 2 using the polyurethane resin of Comparative Example 1 instead of the polyurethane resin of Example 1. Table 2 shows the results of examining the squareness ratio, solvent resistance, and powder shedding of the magnetic tapes of Example 2 and Comparative Example 2.

[Table] From Table 2, it is clear that the effect of improving the durability and dispersion of magnetic powder in the magnetic tape using the polyurethane resin of the present invention is clear.

Claims (1)

[Claims] 1. General formula: (In the formula, A represents a divalent organic residue of a compound having two hydroxyl groups in the molecule, and B has 1 to 1 carbon atoms.
6 represents a divalent hydrocarbon residue, R represents a divalent hydrocarbon residue having 2 or 3 carbon atoms, and Z represents a hydroxyl group or a carbosyl group), and General formula: Or a polyurethane resin having a number average molecular weight of 1,700 to 24,000 and having both end groups represented by the general formula: -O-B-Z (in the formula, B, Z and R each have the same meanings as above).