JPH055852B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyisocyanate compound that can be used as a curing agent for paints, etc., and more particularly relates to a polyisocyanate compound that provides a coating film in which inorganic powder contained in such paints, etc. is well dispersed. Conventionally, various polyisocyanate compounds have been used as curing agents for paints and adhesives. In this case, the polyisocyanate compound is often used in the form of a polyurethane prepolymer obtained by adding diisocyanate to a polyhydric alcohol, since the diisocyanate monomer is toxic and easily volatile. A typical example is trimethylolpropane tris (tolylene diisocyanate), which is obtained by reacting 1 mole of trimethylolpropane with 3 moles of tolylene diisocyanate, and is known under trade names such as Coronate L (Nippon Polyurethane Co., Ltd.). It is being Such polyisocyanate compounds themselves have low volatility and low toxicity. However, since diisocyanate is used in excess relative to polyhydric alcohol during synthesis, free diisocyanate is inevitably mixed into the polyisocyanate compound. It is extremely difficult to completely remove this diisocyanate. When a polyisocyanate compound containing a small amount of diisocyanate is used, for example, as a curing agent for a paint, there are problems in terms of safety and health during the coating process. Further, when obtaining a high molecular weight polyisocyanate compound, a similar problem occurs because an excessive amount of diisocyanate is reacted with a high molecular weight acrylic polyol or the like. On the other hand, attempts have also been made to obtain high molecular weight isocyanate compounds by using triisocyanates instead of diisocyanates. However, in this case, if the reactivities of the three isocyanate groups are equivalent, each isocyanate group will participate in the reaction, resulting in a gel-like polyisocyanate compound in which branched chains have grown. However, such polyisocyanate compounds with branched chains are not suitable for use in paints, etc. because they are difficult to dissolve in general-purpose solvents. On the other hand, when preparing a magnetic paint in the manufacture of magnetic recording media, a curing agent is generally added just before the end of the material mixing process. However, some curing agents impair the dispersion of magnetic powder in magnetic paints, and there is a limit to the amount they can be used. Therefore, an object of the present invention is to provide a polyfunctional isocyanate compound that has low toxicity, good solubility in general-purpose solvents, and provides a coating film with good dispersion of inorganic powder such as magnetic powder. It is. That is, the polyisocyanate compound according to the present invention has the general formula: (In the formula, R represents a divalent hydrocarbon residue having 2 or 3 carbon atoms, and A represents 2 of a copolyester having a hydroxyl group at both ends and a polar group containing no active hydrogen in the side chain.) has a repeating unit represented by (representing a valent organic residue) and has a general formula: Or general formula: (In the formula, R and A each have the same meanings as above.) Number average molecular weight having both end groups
1530-19400 polyisocyanate compound. A in the repeating unit in this invention is
Represents a divalent organic residue of a copolymerized polyester that has a hydroxyl group at its terminal end and a polar group that does not contain active hydrogen in its side chain. The carboxylic acid component of this copolyester includes aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and 1,5-naphthalic acid, succinic acid, adipic acid,
Dicarboxylic acids such as aliphatic dicarboxylic acids such as azelaic acid, sebacic acid and dodecanedicarboxylic acid, aromatic oxycarboxylic acids such as p-oxybenzoic acid and p-(2-hydroxyethoxy)benzoic acid, and the like can be used. Among these, particularly preferred carboxylic acid components include terephthalic acid, isophthalic acid, adipic acid, and sebacic acid. Also,
The polyhydric alcohol component, which is another component of the copolymerized polyester, includes ethylene glycol, propylene glycol, 1,3-propanediol,
1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-
Aliphatic diols such as pentanediol or substituted derivatives thereof, cycloaliphatic diols such as 1,4-cyclohexanedimethanol, diols such as polyalkylene glycols such as diethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. oxides such as ethylene oxide or propylene oxide adducts of bisphenol A, alkylene oxide adducts of aromatic diols such as ethylene oxide adducts or propylene oxide adducts of hydrogenated bisphenol A, and the like. Moreover, this copolymerized polyester has a polar group that does not have active hydrogen. If this polar group has active hydrogen, it is not suitable because it will react with the isocyanate group of the triisocyanate compound described later. As a polar group without active hydrogen,
Examples include polar groups represented by the following general formula. −SO ₃ M, −OSO ₃ M, −COOM, −OM,

[Formula] or −NO ₂ (wherein, M is Li, Na, K, Ba ⁺ , Ca ⁺ or
Represents Mg ⁺ . ) As a method for introducing a polar group having no active hydrogen into a copolymerized polyester as described above, a compound having the aforementioned polar group is used in combination with the aforementioned carboxylic acid and/or polyhydric alcohol, which are the starting materials for the copolymerized polyester. It is preferable to do so. Among the carboxylic acid components having a polar group, the carboxylic acid components having a sulfonic acid metal base (-SO ₃ M) include 2-sodium sulfoterephthalic acid, 2-sodium sulfoterephthalic acid,
Preferred examples include -potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, and 5-potassium sulfoisophthalic acid. In addition, as a carboxylic acid component having a carboxylic acid metal base (-COOM), potassium dihydrogen 1,3,5-benzenetricarboxylate can be used, and a dicarboxylic acid component having a nitro group or (-NO ₂ ) can be used. such as 5-nitroisophthalic acid;
Metal base of alcohol or phenol (−
Potassium-3,5-dicarboxyphenolate, etc. as a carboxylic acid component having OM); phosphate metal base

As the carboxylic acid component having the formula, di-P-carboxyphenyl phosphate metal salt (chemical formula below) can also be used. Representative examples of the polyhydric alcohol component having a polar group include the following compounds. () Di-P-β-hydroxyethoxyphenyl phosphate metal salt () Di-P-hydroxymethoxyphenyl phosphate metal salt () Di-P-hydroxycarbomethoxyphenyl phosphate metal salt () P-hydroxymethoxyphenyl-P-
β-Hydroxyethoxyphenyl phosphate metal salt () Di-β-hydroxyethyl phosphate metal salt Typical examples of carboxylic acid components and polyhydric alcohol components that have polar groups without active hydrogen have been shown above, but in addition to these, the carboxylic acid components and polyhydric alcohol components that were previously exemplified as copolyester polyester carboxylic acid components and polyhydric alcohol components have been shown. Carboxylic acids or polyhydric alcohols having the aforementioned polar groups can also be used. 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, when comparing the reactivity of the isocyanate group, it becomes as follows: 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. Specifically, the compound represented by the general formula (1) includes 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. The polyisocyanate compound of the present invention, which is composed of a copolymerized polyester and a triisocyanate compound as described above, has a molar ratio M of isocyanate groups of the triisocyanate compound to hydroxyl groups of the copolymerized polyester of 1.5. It is obtained by reacting so that <M≦3. This reaction is carried out with preferential participation of two isocyanate groups excluding the less reactive isocyanate group among the three isocyanate groups of the triisocyanate compound. Therefore, in the polyisocyanate compound of the present invention, the copolymerized polyester is two-dimensionally chain-lengthened by the triisocyanate compound via urethane bonds, and has a chain structure, and when the molar ratio M is 3, is a tetrafunctional polyisocyanate compound having two unreacted isocyanate groups at both ends, and the molar ratio M is 1.5<M<
In the case of No. 3, it is a polyisocyanate compound having five or more functionalities and having isocyanate groups at both ends and side chains. However, when the molar ratio M is 1.5 or less, such a polyfunctional polyisocyanate compound cannot be obtained, and it is substantially impossible to synthesize a compound where the molar ratio M is larger than 3. However, it is possible to carry out the synthesis in a reaction system in which the molar ratio M is larger than 3, that is, in which the triisocyanate compound is present in excess. If a triisocyanate compound in which all three isocyanate groups have the same reactivity is used, the chains grow three-dimensionally and gel, which is disadvantageous both in terms of synthesis and use. In addition, the polyisocyanate compound of the present invention has as one component a copolymerized polyester having a polar group having no active hydrogen in its side chain.
It itself has this polar group in its side chain. Only one type of this polar group may be contained in one molecule of the polyisocyanate compound, or a plurality of types may be contained. Moreover, it is preferable that this polar group is contained in an amount of 0.02 mmol to 1.0 mmol per 1 g of the polyisocyanate compound. If there are too few polar groups, inorganic powders with hydrophilic groups on the surface, such as γ-
Affinity for magnetic powder such as Fe ₂ O ₃ becomes insufficient. Furthermore, if there are too many polar groups, the solubility in general-purpose solvents will deteriorate. The polyisocyanate compound according to the present invention cures the resin by thermal crosslinking and has a polar group in the side chain, so it is useful as a curing agent for paints containing inorganic powder. In that case, the isocyanate group concentration of the polyisocyanate compound is 2% or more, and the molecular weight is usually in the range of 1,530 to 19,400. That is, if the isocyanate group concentration is less than 2%, the crosslinking density will be low, resulting in insufficient hardness of the cured film and slow curing speed. molecular weight
If it is larger than 19400, the curing performance similarly deteriorates, which is not preferable. Note that the isocyanate group concentration here is defined by formula (5). Isocyanate group concentration (%) = Number of isocyanate groups in one molecule of polyisocyanate compound x 42 / Molecular weight of polyisocyanate compound... (5) The molecular weight and isocyanate group concentration of the polyisocyanate compound are determined by appropriately selecting the molecular weight of each component. Therefore, it can be arbitrary. Further, as shown in Table 1, these depend on the value of M, so polyisocyanate compounds having various physical properties can be obtained depending on the blending ratio of the triisocyanate compound and copolymerized polyester during synthesis. In Table 1, polyisocyanate compounds consisting of copolymerized polyester (molecular weight 1500) and T-100 (triisocyanate compound manufactured by Toray Industries, Inc., molecular weight 267) are exemplified.

[Table] When the polyisocyanate compound of this invention is used as a curing agent for a paint, the resins contained in the paint and cured include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer. , vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacryl Acid ester-vinylidene chloride copolymer, methacrylic acid 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, phenolic resin, epoxy resin, thermosetting polyurethane resin, urea resin, melamine resin, Examples include alkyd resins, urea-formaldehyde resins, and mixtures thereof. Among these, resins having hydroxyl groups at the terminals and/or side chains are particularly preferred since they can form urethane bonds with the polyisocyanate compound of the present invention, and mixtures of resins having hydroxyl groups and resins having no hydroxyl groups are also preferred. Equally effective. The polyisocyanate compound according to this invention is
As mentioned above, it can be used as a hardening agent for paints, but it is particularly suitable for use as a hardening agent for magnetic paints when manufacturing magnetic recording media. Any of the above-mentioned resins can be used as a binder for magnetic recording media. In addition to the binder, magnetic paints contain ferromagnetic powder and organic solvents as basic constituent materials. As this ferromagnetic powder, ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder, etc. can be used. As ferromagnetic iron oxide particles, when expressed by the general formula 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 Cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. Cobalt-containing magnetic iron oxide can be broadly divided into two types: doped type and coated type, and it may be either of these types. As the ferromagnetic chromium dioxide, CrO ₂ or CrO 2 to which at least one of Ru, Sn, Te, Sb, Fe, Ti, V, Hn, etc. is added for the purpose of improving Hc can be used. Ferromagnetic alloy powders include Fe, Co, Ni, Fe-Co,
Fe-Ni or Fe-Co-Ni, etc. can be used, and in order to improve various properties, Al, Si, Ti, Cr,
Some contain metal components such as 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, magnetic paints also contain abrasive materials such as aluminum oxide, chromium oxide, and silicon oxide.
Carbon black or the like may be added as an antistatic agent, and molybdenum disulfide, graphite, silicone oil, olive oil, or the like may be added as a lubricant. After the polycyanate compound of the present invention is mixed into a magnetic paint made of the above-mentioned materials, the magnetic paint 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; plastics such as polycarbonate, polyimide, and polyamideimide, as well as non-magnetic materials such as aluminum, copper, tin, zinc, or non-magnetic alloys containing these, depending on the application. Metals: Ceramics such as glass, pottery, and porcelain; Paper, baryta, or paper coated with or laminated with α-polyolefins having 2 to 10 carbon atoms such as polyethylene, polypropylene, and ethylene-butene copolymers. Can be used. These non-magnetic carriers may be transparent or opaque depending on the intended use. Further, the form of the nonmagnetic carrier may be any film, tape, sheet, disk, card, drum, etc., and various materials are selected as necessary depending on the form. The thickness of these nonmagnetic carriers is about 1 to 50 μm, preferably 1 to 30 μm in the case of films, tapes, and sheets.
It is. In addition, in the case of disks and cards, 0.5
The diameter is approximately 10 mm, and if it is drum-shaped, it is cylindrical, and its shape is determined depending on the recorder used. Further, the magnetic recording medium is completed through various processes such as surface treatment, orientation, thermosetting, and cutting. The characteristics of the polyisocyanate compound of this invention are summarized as follows. (1) The number and concentration of isocyanate groups can be selected over a wide range. (2) Use triisocyanate compounds, which are less toxic than diisocyanates, during synthesis. (3) Products with arbitrary molecular weights can be obtained. (4) During synthesis, the side chain isocyanate group has low reactivity, so it does not gel and has a chain structure. (5) Since it has a polar group, it has good affinity with inorganic powders. In particular, when used as a curing agent for paints such as magnetic paints, the following advantages can be obtained for each of the above-mentioned items. (1) Since the number and concentration of isocyanate groups can be increased, a cured film with high crosslinking density is formed.
The cured film has good strength, durability, and solvent resistance. It also has a fast curing speed. (2) Concerns about diisocyanate toxicity during the coating process can be avoided. (3) Since it has a high molecular weight, it is advantageous in terms of the smoothness and gloss of the surface of the cured film. (4) Solubility in solvents used in paints. (5) When added to a paint, the dispersion state of the inorganic powder (magnetic powder) contained therein is not deteriorated, and the paint can be cured while maintaining a good dispersion state. The present invention will be explained below with reference to Examples. Example 1: Synthesis of polyisocyanate compound In a reaction vessel equipped with a thermometer, a stirrer, and a partial reflux condenser, 73 parts by weight of methyl ethyl ketone, 73 parts by weight of toluene, 50 parts of copolymerized polyester (molecular weight: 1500, nuclear magnetic resonance (NMR)) Identified from the results of composition analysis.The components are as follows.Carboxylic acid component: 20 mol% of terephthalic acid, 15 mol% of isophthalic acid, 5 mol% of sodium 5-sulfoisophthalate, 60 mol% of sebacic acid.Diol component: 50 mol% of ethylene glycol, 50 mol% of propylene glycol) and 104 parts by weight of a triisocyanate compound (T-100, manufactured by Toray Industries, Inc.) were added and reacted at 70 to 90°C for 3 hours. The number average molecular weight of the produced polyisocyanate compound is 10900,
The isocyanate group concentration was 3.5% and the number of isocyanate groups was 9. The repeating unit consisted of one molecule of copolymerized polyester and one molecule of triisocyanate. Comparative Example 1: Synthesis of a polyisocyanate compound having no polar group As a copolymerized polyester, the carboxylic acid component is 20 mol% of terephthalic acid, 20 mol% of isophthalic acid, 60 mol% of sebacic acid, and the polyhydric alcohol component is 50 mol% of ethylene glycol. A polyisocyanate compound was synthesized in the same manner as in Example 1, except that a polyisocyanate compound containing 50 mol% of propylene glycol was used. The obtained polyisocyanate compound had no polar groups, had a number average molecular weight of 10,900, an isocyanate group concentration of 3.5%, and a number of isocyanate groups of 9. Example 2 and Comparative Examples 2 and 3: Formation of cured film 20 parts by weight of the polyisocyanate compound obtained in Example 1 and polyester polyurethane (paraprene)
225 (manufactured by Nippon Polyurethane Kogyo Co., Ltd.) was dissolved in a mixed solvent of 50 parts by weight of methyl ethyl ketone and 50 parts by weight of toluene. Then, apply this solution on a glass plate using a doctor blade,
A film was formed. After naturally drying at room temperature for one day, the film was cured by placing it in a vacuum dryer at 80° C. for 48 hours to prepare a cured film (Example 2). Similarly, a cured film was produced using the polyisocyanate compound of Comparative Example 1 (Comparative Example 2). Furthermore, a cured film was prepared in the same manner as in Example 2, except that 20 parts by weight of Coronate L (a triisocyanate compound manufactured by Nippon Polyurethane Co., Ltd.) was used in place of the polyisocyanate compound in Example 1 (Comparative Example 3). Table 2 shows the results of measuring the pencil hardness, gloss, and solvent resistance of the cured films obtained in Example 2 and Comparative Examples 2 and 3.

[Table] As shown in Table 2, the polyisocyanate compound of the present invention, when used as a curing agent, had performance equivalent to or better than that of a conventionally used curing agent (Coronate L). Example 3 and Comparative Examples 4 and 5: Production of magnetic tape 40 parts by weight of polyester polyurethane (same as above) 40 parts by weight of vinyl chloride-vinyl acetate copolymer (YAGH: manufactured by UCC) and 2 parts by weight of lecithin, 80 parts by weight of methyl ethyl ketone After dissolving γ-Fe ₂ O ₃ in a mixed solvent of 80 parts by weight and 80 parts by weight of toluene,
A magnetic paint was prepared by adding 25 parts by weight and mixing in a ball mill for 24 hours. Further, 20 parts by weight of the polyisocyanate compound obtained in Example 1 was added to this magnetic paint and mixed for 30 minutes. Next, magnetic paint was applied onto the polyester film using a doctor blade method, and the film was left standing in a parallel magnetic field of 900 oersted for about 1 second to orient the magnetic powder, and then left in a hot air dryer at 90°C for about 30 minutes. to remove the solvent, and
The coating was cured at 80°C for 48 hours. Finally, the film was cut to obtain magnetic tape. (Example 3) The polyisocyanate compound of Comparative Example 1 and Coronate L (same as above) were used instead of the polyisocyanate compound of Example 1, respectively.
Magnetic tapes were produced in the same manner as in Example 3 (Comparative Examples 4 and 5). Table 3 shows the results of measuring powder shedding, solvent resistance, and squareness ratio for the magnetic tapes of Example 3 and Comparative Examples 4 and 5.

【table】

[Table] From Table 3, the magnetic tape of Example 3 shows no difference from the magnetic tapes of Comparative Examples 4 and 5 in terms of powder fallout and solvent resistance, but is superior in terms of squareness ratio. It can be seen that the magnetic powder is well dispersed.

Claims (1)

[Claims] 1. General formula: (In the formula, R represents a divalent hydrocarbon residue having 2 or 3 carbon atoms, and A represents 2 of a copolyester having a hydroxyl group at both ends and a polar group containing no active hydrogen in the side chain.) has a repeating unit represented by (representing a valent organic residue) and has a general formula: Or general formula: (In the formula, R and A each have the same meanings as above.) Number average molecular weight having both terminal groups
Polyisocyanate compounds from 1530 to 19400.