JPWO2001057108A1 - Polyurethane and waterborne polyurethane resins - Google Patents

Abstract

(57) [Summary] The present invention provides a compound having excellent adhesiveness, adhesion, weather resistance, water resistance, etc., which has the general formula (I) in the molecule. The present invention provides a polyurethane containing a structural unit represented by the formula: (wherein R ¹ and R ² are the same or different and each represent a lower alkyl group), and an acidic group neutralized with a basic compound.

Description

[0001] TECHNICAL FIELD [0002] The present invention relates to aqueous polyurethane resins that have excellent adhesive properties, adhesion, weather resistance, and water resistance, and to polyurethanes used in said resins. BACKGROUND ART [0003] Aqueous polyurethane resins are widely used as resins for paints, adhesives, binders, inks, etc., due to their excellent mechanical properties, abrasion resistance, flexibility, etc. [0004] In particular, with the current trend toward limiting the release of organic solvents into the atmosphere from the perspective of protecting the global environment, it is expected that their application in various applications will expand in the future.

Known aqueous polyurethane resins are those made from diols having acidic groups, such as dimethylolpropionic acid or dimethylolbutanoic acid, whose acidic groups are neutralized with a base (Japanese Patent Publication No. 61-5485, Japanese Patent Publication No. 4-488, Japanese Patent Laid-Open No. 8-27242, and Japanese Patent Laid-Open No. 6-329744).

When used in applications such as paints and adhesives, aqueous polyurethane resins are required to have long-term retention of physical properties such as weather resistance and water resistance in addition to excellent adhesiveness and adhesion, but the aqueous polyurethane resins disclosed in the above publications are not practically satisfactory in terms of these performances.

Furthermore, WO96/09334 discloses a polyurethane using 2,4-diethyl-1,5-pentanediol, but the polyurethane disclosed in the examples of this publication cannot be made into an aqueous polyurethane resin due to its low water solubility, etc. DISCLOSURE OF THE INVENTION An object of the present invention is to provide an aqueous polyurethane resin having excellent adhesiveness, cohesiveness, weather resistance, water resistance, etc., and a polyurethane for use in said resin.

The present invention relates to a compound having the general formula (I) in a molecule. The present invention provides a polyurethane containing a structural unit represented by the formula: (wherein R ¹ and R ² are the same or different and each represent a lower alkyl group), and an acidic group neutralized with a basic compound.

The present invention also provides an aqueous polyurethane resin containing the polyurethane.

In the definition of the groups in general formula (I), the lower alkyl group includes linear or branched groups having 1 to 8 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isoamyl, neopentyl, 2-pentyl, 3-pentyl, hexyl, heptyl, and octyl groups.

Examples of the acidic group include a carboxyl group, a sulfo group, and a phosphono group, with a carboxyl group being preferred.

Examples of the basic compound that neutralizes the acidic group include the basic compounds described below.

The polyurethane of the present invention can be synthesized by known methods (see, for example, JP-A Nos. 8-27242 and 8-259884).

An example of the method for producing the polyurethane of the present invention will be described below in (1) to (3).

(1) Production of polyester polyol: A polyester polyol is produced by reacting 2,4-dialkyl-1,5-pentanediol, which is a diol containing a structural unit represented by general formula (I) in the molecule, with a dicarboxylic acid.

(2) Preparation and neutralization of a urethane prepolymer: The polyester polyol, a compound having an acidic group, and a polyisocyanate are reacted to form a urethane prepolymer having an isocyanate group at its terminal, and the acidic groups of the urethane prepolymer are then neutralized with a basic compound.

(3) Preparation of polyurethane: The polyurethane of the present invention can be obtained by reacting the urethane prepolymer in which the acidic groups have been neutralized with a chain extender.

Steps (1) to (3) will be described in more detail below.

(1) Production of polyester polyol: Polyester polyol can be produced by reacting 2,4-dialkyl-1,5-pentanediol with a dicarboxylic acid by a known method (for example, JP-A-48-101496, W
The polycondensation product can be obtained by, for example, heating under heat or reduced pressure to cause dehydration polycondensation in accordance with the methods described in WO98/44014, WO99/06498, and the like.

Examples of dicarboxylic acids include succinic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, and phthalic acid, which may be used alone or in combination. In place of the dicarboxylic acid, an acid anhydride of the dicarboxylic acid or a lower alkyl ester of the dicarboxylic acid, such as a methyl ester or an ethyl ester, may also be used.

2,4-Dialkyl-1,5-pentanediol can be produced in accordance with the method described in WO97/19904, but can also be purchased as a commercial product.

In addition to 2,4-dialkyl-1,5-pentanediol, other diols may be used in combination. In this case, the proportion of 2,4-dialkyl-1,5-pentanediol in all diols is preferably 30% by weight or more, more preferably 40% by weight or more.

Examples of other diols that can be used in combination include ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol, 1,6-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 1,4-bis(β-hydroxyethoxy)benzene, etc. When other diols are used, polycondensation is carried out randomly.

The molar ratio of diol to dicarboxylic acid in the raw materials is not particularly limited, but is preferably 1.0 to 2.0, more preferably 1.1 to 1.5.

The temperature for producing the polyester polyol is not particularly limited, but is preferably 10
The temperature is 0 to 300°C, more preferably 150 to 250°C.

The number average molecular weight of the polyester polyol is preferably 400 to 8,000, more preferably 600 to 5,000.

The polyester polyol is preferably produced without a solvent.
Any solvent inert to the reaction may be used, for example, ketones such as methyl ethyl ketone and methyl isobutyl ketone, ethers such as tetrahydrofuran, and aromatic hydrocarbons such as benzene, toluene, and xylene.

(2) Production of urethane prepolymer and neutralization: The polyester polyol, which is the raw material for the urethane prepolymer, may be mixed with other polyols such as polycarbonate polyols and polyether polyols to be used as the raw material for the urethane prepolymer. In this case, the proportion of the polyester polyol used in the total polyols is preferably 50% by weight or more, more preferably 70% by weight or more.

Examples of the compound having an acidic group include a compound having an acidic group such as a carboxyl group, a sulfo group, or a phosphono group, preferably a carboxyl group, in the molecule, and having two or more groups having active hydrogen capable of reacting with an isocyanate group, such as hydroxyl groups, in the molecule.

Examples of compounds having an acidic group include dimethylolalkanoic acids such as dimethylolpropionic acid, dimethylolbutanoic acid, dimethylolpentanoic acid, dimethylolheptanoic acid, and dimethyloloctanoic acid; N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid; reaction products of sulfoisophthalic acid and polyfunctional hydroxy compounds; reaction products of 2,3-epoxypropanol and mono-2-ethylhexyl phosphate; and 2,3-dihydroxypropyloctyl phosphate. Among these, dimethylolalkanoic acids such as dimethylolpropionic acid, dimethylolbutanoic acid, dimethylolpentanoic acid, dimethylolheptanoic acid, and dimethyloloctanoic acid are preferred.

The compound having an acidic group is selected so that the acid value of the final polyurethane product is 0.1 to 1.
It is preferable to use it so that it becomes 100 mg KOH/g, and 5 to 40 mg
It is more preferable to use it so that the concentration is KOH/g.

Examples of polyisocyanates include compounds having two or more isocyanate groups, such as aromatic diisocyanates such as diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, 2,4-naphthalene diisocyanate, 1,5-naphthalene diisocyanate, and p-xylylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, 4,4′-diisocyanatodicyclohexane, and 4,4′-diisocyanatodicyclohexylmethane; and aliphatic diisocyanates such as hexamethylene diisocyanate and tetramethylene diisocyanate. These may be used alone or in combination of two or more.

Polyisocyanate is a compound in which the molar ratio of isocyanate groups to hydroxyl groups in the raw material is 1.
It is preferable that the ratio is 1 to 10.0, and more preferably 1.5 to 5.0.
It is more preferable to use it so that

The temperature of the urethane reaction is preferably 20 to 150°C, more preferably 40 to 120°C.
°C is more preferred.

The urethanization reaction can be carried out without a reaction solvent, but if necessary, a solvent such as methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, 1,4
The reaction may be carried out in a reaction solvent such as dioxane, ethyl acetate, toluene, xylene, acetone, dimethylformamide, etc.

Furthermore, during the urethanization reaction, if necessary, a urethanization catalyst such as an organometallic catalyst such as tin octoate or a tertiary amine such as triethylenediamine may be used, and the amount used is usually 0.05 to 5% by weight based on the reaction liquid.

Neutralization of the acidic groups in the urethane prepolymer with a basic compound can be carried out by adding the basic compound to the urethane prepolymer. Furthermore, water is usually added to the neutralized urethane prepolymer to dissolve or disperse the urethane prepolymer in water. Although neutralization can also be carried out after adding water to the urethane prepolymer, it is preferable to add water to the neutralized urethane prepolymer.

The amount of the basic compound used for neutralization is preferably 0.5 to 1.5 equivalents, more preferably 0.8 to 1.2 equivalents, based on the acidic groups in the urethane prepolymer.

The basic compound may be any compound that neutralizes an acidic group to form a salt, such as ammonia, triethylamine, ethylenediamine,
Examples of the organic amines include propylamine, dibutylamine, amylamine, 1-aminooctane, 2-dimethylaminoethanol, ethylaminoethanol, 2-diethylaminoethanol, 1-amino-2-propanol, 2-amino-1-propanol, 3-amino-1-propanol, 1-dimethylamino-2-propanol, 3-dimethylamino-1-propanol, 2-propylaminoethanol, ethoxypropylamine, aminobenzyl alcohol, and morpholine; and hydroxides or carbonates of alkali metals or alkaline earth metals, such as sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. Of these, organic amines are preferably used.

After neutralization with a basic compound, the urethane prepolymer may be emulsified as needed. In this case, 0.1 to 5 parts by weight of an emulsifier may be used relative to the urethane prepolymer. Examples of emulsifiers include anionic surfactants, nonionic surfactants, and polymeric emulsifiers. Specific examples of anionic surfactants and nonionic surfactants include anionic surfactants such as higher alcohol sulfates, alkylbenzene sulfonates, polyoxyethylene alkyl sulfate salts, and polyoxyethylene alkylphenol ether sulfate salts, and nonionic surfactants such as polyoxyethylene alkylphenol ethers, ethylene oxide-propylene oxide block polymers, and sorbitan derivatives. Examples of polymeric emulsifiers include polyvinyl alcohol and hydroxyethyl cellulose.

(3) Production of Polyurethane: In order to increase the molecular weight of the urethane prepolymer, the polyurethane of the present invention is produced by reacting it with a chain extender. In this case, low-molecular-weight diamines, polyols, alkanolamines, hydrazine, etc. are used as the chain extender.

Examples of diamines include ethylenediamine, propylenediamine, tetramethylenediamine, hexamethylenediamine, isophoronediamine, and 1,4-cyclohexanediamine.

Examples of polyols include ethylene glycol, propylene glycol, 1,4-
butanediol, 1,5-pentanediol, 1,6-hexanediol, hydroquinone, and the like.

Examples of alkanolamines include diethanolamine and triethanolamine.

The chain extender is preferably used so that the molar ratio of isocyanate groups in the urethane prepolymer to hydroxyl groups or amino groups in the chain extender is 0.1 to 10, more preferably 0.7 to 1.5.

The reaction between the urethane prepolymer and the chain extender is usually carried out at a temperature of 20 to 100°C, preferably 20 to 50°C.

The polyurethane of the present invention includes not only the polyurethane produced by the above (3) but also the urethane prepolymer produced by the above (2).

The aqueous polyurethane resin containing polyurethane can be prepared by dissolving or dispersing the polyurethane produced as described above in water.Methods for dissolving or dispersing polyurethane in water include, for example, a method in which a urethane prepolymer is produced, and then water is added, if necessary, and an emulsifier is added (which is then reacted with a chain extender to form polyurethane), but it is also possible to dissolve or disperse polyurethane in water by adding water, if necessary, and an emulsifier after the polyurethane is produced.

The solid content of the aqueous polyurethane resin of the present invention is not particularly limited depending on the intended use, but is preferably 30 to 70% by weight.

In addition, when a reaction solvent is used in the urethanization reaction, etc., the reaction solvent may be removed after the production of polyurethane. Examples of methods for removing the reaction solvent include a method of reducing the pressure to below the boiling point of water, and a method of distilling off the solvent using a carrier gas such as nitrogen gas or air.

The aqueous polyurethane resin of the present invention is excellent in adhesiveness, adhesion, weather resistance, water resistance, etc., and is therefore useful for applications such as paints, adhesives, binders, and inks.

When used for the above-mentioned applications, the aqueous polyurethane resin of the present invention may contain, as necessary, an antioxidant, an ultraviolet stabilizer, a colorant, an antifoaming agent, a flow control agent, a water repellent, a lubricant, a filler, and the like.

When the aqueous polyurethane resin of the present invention is used in a paint, the coating method can be a conventional brush coating, spray coating, etc., and the curing conditions can be selected from a wide range of conditions, from room temperature drying to heat drying.
Examples include leather, glass, metal, wood, plastic, inorganic materials, concrete, asphalt, etc. The aqueous polyurethane resin of the present invention may be used as an undercoat, topcoat, one-coat finishing agent, etc. If necessary, other resins such as acrylic, polyester, epoxy, silicone, and fluorine-based resins may be added.

When the aqueous polyurethane resin of the present invention is used as an adhesive, a wide range of curing conditions can be selected, from room temperature drying to heat drying, and the types of adherends include paper, leather, glass, metal, wood, plastic, inorganic materials, concrete, asphalt, etc.

The aqueous polyurethane resin of the present invention may be used for various applications as it is, but may also be used as a two-component composition by using a crosslinking agent, if necessary.

Examples of crosslinking agents include aqueous polyisocyanate crosslinking agents (compounds obtained by reacting an isocyanurate such as hexamethylene diisocyanate with a polyhydric alcohol such as polyethylene glycol), melamine-based crosslinking agents (methoxylated methylol melamine, etc.), and epoxy-based crosslinking agents (ethylene glycol diglycidyl ether, etc.). The amount used is not particularly limited, but is preferably 1 to 40% by weight relative to the solid content of the aqueous polyurethane resin.

Reference examples, working examples, comparative examples and test examples are shown below. Best Mode for Carrying Out the Invention Reference Example 1: Synthesis of polyester polyol (PEPO) using 2,4-diethyl-1,5-pentanediol as a raw material In a flask, 5 mol (730 g) of adipic acid and 2,4-diethyl-1,5-pentanediol were placed.
7.5 mol (1202 g) of pentanediol was charged and mixed at 200 to 220° C. under a nitrogen atmosphere with stirring at 500 to 600 rpm. While removing the generated water, the pressure was gradually reduced when the acid value reached 5 mg KOH/g or less, and finally reduced to 0.4
Further, at 220°C, the acid value was 0.2 mg KOH
When the hydroxyl value reached 0.15/g or less and the hydroxyl value reached a predetermined value, stirring was stopped, the mixture was collected in a container, and then cooled to room temperature to obtain the target polyester polyol (PEPO1).

Reference Example 2: Synthesis of polyester polyol using 3-methyl-1,5-pentanediol as raw material.
The same procedure as in Reference Example 1 was carried out except that pentanediol was used, to obtain the target polyester polyol (PEPO2).

Reference Example 3: Synthesis of polyester polyol using 1,4-butanediol as raw material The same procedure as in Reference Example 1 was carried out except that 1,4-butanediol was used instead of 2,4-diethyl-1,5-pentanediol, to obtain the target polyester polyol (PEPO3).

The molecular properties of the PEPOs obtained in Reference Examples 1 to 3 are shown in Table 1. Here, the number average molecular weight (Mn) of each PEPO is expressed as a function of the hydroxyl value [OHV (mg KOH/g)].
The value was calculated using the following formula (terminal group determination method).

Mn = 1/(OHV/1000/56.1/2) Mn: number average molecular weight OHV: hydroxyl value Example 1: Synthesis of urethane prepolymer and aqueous polyurethane resin. 165.4 g of PEPO1 and 16.9 g of dimethylolbutanoic acid (DMBA) were charged into a 1 L separable flask and heated to 80°C while stirring under a nitrogen atmosphere. Stirring was continued for another 30 minutes while simultaneously supplying nitrogen to the flask and evacuating using a vacuum pump. After evacuating using the vacuum pump was stopped, the temperature inside the flask was lowered to 60°C, and 60 g of acetone was added. After heating again to 80°C, 117.8 g of isophorone diisocyanate (IPDI) was added dropwise over 1 hour. After completion of the dropwise addition, the temperature inside the flask was maintained at 80°C, and stirring was continued until the reaction rate of the hydroxyl groups in the reaction solution reached 95% or more. The reaction mixture was then cooled to 60°C, and 11.6 g of triethylamine was added to neutralize the carboxyl groups in the urethane prepolymer, yielding a urethane prepolymer.

The reaction rate of the hydroxyl groups in the reaction solution was calculated by the following formula.

Reaction rate of hydroxyl groups in the reaction solution = (1 - A/B) x 100 (%), A: number of unreacted hydroxyl groups in the reaction solution, B: number of hydroxyl groups in the raw material. 300g of the obtained urethane prepolymer was placed in a flask, and 388g of distilled water was added little by little while stirring with a homomixer at 3000-4000 rpm, to obtain an aqueous dispersion of urethane prepolymer. While continuing to stir with a homomixer, 16.1g of ethylenediamine (EDA) was added to this aqueous dispersion to obtain the target aqueous polyurethane resin. The solid content of this aqueous polyurethane resin was 50.1% by weight,
The viscosity was 480 mPa·s. The solid content was determined by the following method.

(Method for calculating the solid content of aqueous polyurethane resin) Approximately 1 g of aqueous polyurethane resin was precisely weighed and heated at 105°C under atmospheric pressure for 2 hours, and then the remaining amount was precisely weighed. The solid content of the aqueous polyurethane resin was calculated using the following formula.

Solid content = C/D x 100 (%) C: Weight of aqueous polyurethane resin after heating D: Weight of aqueous polyurethane resin before heating Examples 2-3 and Comparative Examples 1-3 The target aqueous polyurethane resins were produced by the same procedure as in Example 1 using the raw materials shown in Tables 2-1 and 2-2.

In Table 2-1, PTG1000 is a product manufactured by Hodogaya Chemical (a polyether polyol with Mn=996), and DMPA represents dimethylolpropionic acid.

Table 3 shows the physical properties of the aqueous polyurethane resins obtained in each of the Examples and Comparative Examples.

Test Example 1: (Evaluation of aqueous polyurethane resin) (1) Preparation of polyurethane film The films used for measuring the tensile strength and hydrolysis resistance tests were prepared in Examples 1, 3,
The aqueous polyurethane resins obtained in Comparative Examples 1 to 3 were cast onto a glass plate to form a film having a thickness of about 300 μm.

(2) Hydrolysis Resistance Test A test piece of polyurethane film was immersed in warm water at 60°C for 4 days, and the tensile strength was measured. The hydrolysis resistance value was calculated using the following formula.

Hydrolysis resistance = E/F x 100 (%) E: Tensile strength after test F: Tensile strength before test Tensile strength measurements were performed in accordance with JIS K7311.

(3) Adhesion test The adhesion test was carried out in accordance with JIS K6804.
A 25 x 25 mm (30 x 25 x 10 mm) was selected. 0.125 g of aqueous polyurethane resin was evenly applied to the 25 x 25 mm adhesive joint, and birch wood not coated with the aqueous polyurethane resin was attached. The joint was then immediately sealed with a rubber band. The joint was then kept at 23°C for 24 hours. After removing the rubber band, the compressive shear strength was measured 48 hours later using a Shimadzu Autograph AG-1000.

The results of Test Example 1 are shown in Table 4.

Table 4 shows that the polyurethane resin of the present invention has excellent water resistance and adhesion. INDUSTRIAL APPLICABILITY The present invention provides an aqueous polyurethane resin having excellent adhesion, cohesion, weather resistance, water resistance, etc., and a polyurethane used in the resin.

───────────────────────────────────────────────────── Continued from the front page (81) Designated Countries EP(AT,BE,CH,CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE, TR), OA(BF , BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP(GH, G M, KE, LS, MW, MZ, SD, SL, SZ, TZ , UG, ZW), UA(AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, B Z, CA, CH, CN, CR, CU, CZ , DE, DK , DM, DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP P, KE, KG, KR, KZ, LC, LK, LR, LS , LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, MZ, NO, NZ, PL, PT, RO, R U, SD, SE, SG, SI, SK, SL, TJ, TM , TR, TT, TZ, UA, UG, US, UZ, VN, YU, ZA, ZW (Note) This publication is based on the international publication of the International Bureau (WIPO). Please note that the effect of the international publication of the Japanese-language patent application (Japanese-language utility model registration application) related to this publication arises pursuant to Article 184-10, Paragraph 1 of the Patent Act (Article 48-13, Paragraph 2 of the Utility Model Act), and is unrelated to this publication.

Claims (8)

[Claims] Claim 1: A compound having the general formula (I) in a molecule (wherein R ¹ and R ² are the same or different and each represents a lower alkyl group), and a polyurethane containing an acidic group neutralized with a basic compound. 2. The polyurethane according to claim 1, wherein the acidic group is a carboxyl group, a sulfo group, or a phosphono group. 3. The polyurethane according to claim 1, wherein the acidic group is a carboxyl group. 4. The polyurethane according to claim 1, wherein the basic compound is a hydroxide or carbonate of an alkali metal or alkaline earth metal, or an organic amine. 5. An aqueous polyurethane resin containing the polyurethane according to any one of claims 1 to 4. 6. The aqueous polyurethane resin according to claim 5, wherein the weight of the solid content is 30 to 70% by weight. 7. A paint containing the aqueous polyurethane resin according to claim 5. 8. An adhesive comprising the aqueous polyurethane resin according to claim 5.