JP2007238880A - Polyamide resin aqueous dispersion and its preparation process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamide resin aqueous dispersion which is excellent in mixing stability with an acid compound. <P>SOLUTION: The dispersion contains a polyamide resin of which the proportion of a terminal calboxyl group and a terminal amino group is: (terminal calboxyl group)/(terminal amino group)=40/60-0/100 in molar ratio and the acidic material of the proportion of 0.2-3 mol per one mol of the terminal amino group. The number average particle size of particles constituting the dispersion is 0.01-10 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an aqueous polyamide resin dispersion and a method for producing the same.

  Aqueous dispersion of polyamide resin provides oil resistance, solvent resistance, chemical resistance, abrasion resistance, gas barrier properties, adhesion, etc. by forming a coating film of polyamide resin on the base material Can be widely used in water-based inks, fiber treatment agents, fiber sealants, paper treatment agents, binders, lubricants, steel sheet surface treatment agents, surface modifiers, hot melt adhesives such as interlining adhesives, etc. It has been.

  Since a polyamide resin cannot be produced by emulsion polymerization in the production process, an aqueous polyamide resin dispersion in which the polyamide resin is dispersed in an aqueous medium has been obtained. About the manufacturing method of this polyamide resin aqueous dispersion, various proposals are made conventionally.

  For example, a manufacturing method in which a polyamide resin is dissolved in an organic solvent and reprecipitated and then replaced with an aqueous solvent has been proposed (Patent Documents 1 and 2). However, the particles obtained by reprecipitation have a problem that the particle size is large, and the particles are often re-aggregated when replaced with an aqueous solvent, and the production process is complicated.

  On the other hand, a polyamide resin solution dissolved in a water-insoluble organic solvent is stirred and emulsified with a high shear force using a special emulsifier together with an emulsifier in an aqueous medium, and then the so-called post-emulsification method is used. A so-called manufacturing method has also been proposed. However, since the polyamide resin has a low solubility in an organic solvent, the post-emulsification method has very low productivity and is not an economical method. Further, the process such as control of foaming when removing the organic solvent is complicated, which is economically disadvantageous. Furthermore, it is difficult to say that this is an industrially advantageous method because there is a risk that an organic solvent or an emulsifier may remain in the product, the working environment may be deteriorated, or environmental pollution may be caused.

As a countermeasure for the improvement, Patent Document 3 discloses that a polyamide resin having a ratio of terminal carboxyl groups to terminal amino groups of 60/40 to 100/0 is a base having a ratio of 0.2 to 3 moles per mole of terminal carboxyl groups. It is described that a polyamide resin aqueous dispersion containing a polyamide resin having a mass average particle size of 0.1 to 10 μm can be obtained by dispersing in an aqueous dispersion medium containing a functional substance.
JP-A-61-223059 Japanese Unexamined Patent Publication No. 63-186738 JP 2000-302966 A

  However, the aqueous dispersion described in Patent Document 3 is stable in the alkaline region, but gels when an acidic compound is added, and there is a problem in the combined use with the acidic compound.

  Then, an object of this invention is to be able to obtain the polyamide resin aqueous dispersion excellent in mixing stability with an acid compound.

  As a result of intensive studies, the present inventors have found that when a specific polyamide resin is dispersed in an aqueous dispersion medium containing a specific amount of an acidic substance, the terminal amino group in the polyamide resin becomes a hydrophilic salt, resulting in stable An aqueous polyamide resin dispersion having excellent properties was obtained, and furthermore, it was found that mixing stability with an acidic compound was very excellent, and the above problems were solved.

That is, the gist of the present invention is as follows.
(1) The ratio of the terminal carboxyl group to the terminal amino group is a molar ratio of (terminal carboxyl group) / (terminal amino group) = 40/60 to 0/100, and per mole of the terminal amino group A polyamide comprising a dispersion containing an acidic substance in an amount of 0.2 to 3 mol and an aqueous medium, wherein the number-average particle diameter of the particles constituting the dispersion is 0.01 to 10 μm Resin aqueous dispersion.

  (2) The polyamide resin is

The aqueous polyamide resin dispersion according to (1), wherein the structural unit is at least one selected from the group consisting of:

  (3) The ratio between the terminal carboxyl group and the terminal amino group in terms of molar ratio is (terminal carboxyl group) / (terminal amino group) = 40/60 to 0/100, and 0 per mol of terminal amino group. A method for producing an aqueous dispersion of polyamide resin, comprising heating and stirring an acidic substance in a proportion of 2 to 3 mol and an aqueous medium at a temperature of 70 to 280 ° C. in a closed container.

  The aqueous dispersion of polyamide resin of the present invention can finely and stably disperse the resin in the aqueous medium by neutralizing the amino group in the polyamide resin with an acidic substance. An acidic compound and a cationic compound can be mixed and used stably.

The present invention will be described in detail below.
In the polyamide resin used in the present invention, it is necessary that the ratio of the terminal carboxyl group and the terminal amino group is (terminal carboxyl group) / (terminal amino group) = 40/60 to 0/100 in molar ratio. . If the proportion of the terminal carboxyl group is high and the proportion of the terminal amino group is low, the aqueous dispersion of the polyamide resin becomes difficult and a good dispersion cannot be obtained.

  A known method is used as a method for producing such a polyamide resin. For example, methods such as polycondensation of diamine, dicarboxylic acid, ω-amino-ω ′ carboxylic acid or ring-opening polymerization of cyclic lactam can be mentioned. In this case, at the time of polycondensation or ring-opening polymerization, by using a predetermined amount of triamine, diamine, or monoamine as a polymerization regulator, the ratio between the terminal carboxyl group and the terminal amino group can be easily expressed in molar ratio ( A polyamide resin in which (terminal carboxyl group) / (terminal amino group) = 40/60 to 0/100 can be produced.

  Specific examples of the diamine used in the production of the above polyamide resin include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 1,7-diaminoheptane, 1,8-diaminooctane, 1, Examples include 9-diaminononane, 1,10-diaminodecane, phenylenediamine, and metaxylylenediamine.

  Specific examples of the dicarboxylic acid used for producing the polyamide resin include glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, tetradecanedicarboxylic acid, octadecanedicarboxylic acid, Examples thereof include fumaric acid, phthalic acid, xylylene dicarboxylic acid and the like.

  Specific examples of the ω-amino-ω ′ carboxylic acid used in the production of the polyamide resin include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid and the like. Is mentioned.

Specific examples of the cyclic lactam used for the production of the polyamide resin include ε-caprolactam, ω-enantolactam, ω-lauryl lactam, and the like.
Specific examples of the diamine used as the polymerization regulator described above include the same diamines as described above. Specific examples of monoamines include hexylamine, octylamine, dodecylamine and the like.

  As the polyamide resin preferably used in the present invention, among the polyamide resins obtained by the above-described method,

And a polyamide resin having at least one selected from the group consisting of structural units as a structural unit.

  Specific examples thereof include 6-nylon, 66-nylon, 46-nylon, 610-nylon, 11-nylon, 12-nylon, 6/66 copolymer nylon, 6/610 copolymer nylon, and 6/11 copolymer. Nylon, 6/12 copolymer nylon, 6/66/11 copolymer nylon, 6/66/12 copolymer nylon, 6/66/11/12 copolymer nylon, 6/66/610/11/12 copolymer nylon Etc. These polymers or copolymers may be used alone or as a mixture of two or more.

Examples of the acidic substance used in the present invention include organic acids such as formic acid, acetic acid and propionic acid, and inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid.
The amount of the acidic substance used is required to be 0.2 to 3 mol per mol of terminal amino group of the polyamide resin, preferably 0.4 to 2 mol, more preferably 0.6 to 1.5 mol. It is. If the amount of acidic substance used is less than 0.2 mol, it is difficult to obtain an aqueous dispersion of polyamide resin. Conversely, if the amount of acidic substance used exceeds 3 mol, the resulting aqueous dispersion becomes strongly acidic. It becomes impractical.

  The amount of the terminal amino group is not particularly limited, but is preferably in the range of 20 to 3000 mmol, more preferably in the range of 50 to 2000 mmol, and more preferably in the range of 100 to 2000 mmol per kg of the polyamide resin. Is particularly preferred. A more terminal amino group tends to provide a stable aqueous dispersion with a smaller particle size.

  In the aqueous dispersion of polyamide resin of the present invention, additives such as a nonionic emulsifier, an amphoteric emulsifier, a protective colloid compound, etc. may be used in addition to the above-mentioned substances as long as the physical properties are not impaired. Moreover, various additives, such as antioxidant, can also be added.

  Among these, nonionic emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyethylene glycol fatty acid ester, ethylene oxide propylene oxide block copolymer, polyoxyethylene fatty acid amide, ethylene oxide-propylene oxide copolymer. Examples thereof include compounds having a polyoxyethylene structure such as coalescence, sorbitan derivatives such as polyoxyethylene sorbitan fatty acid esters, and the like. Examples of amphoteric emulsifiers include lauryl betaine and lauryl dimethylamine oxide. Protective colloidal compounds include polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, modified starch, polyvinyl pyrrolidone, water-soluble acrylic copolymers having amino groups, gelatin, gum arabic, casein, etc. The compound currently used is mentioned.

  The aqueous medium used in the present invention is a medium mainly composed of water, and is used as a dispersion medium. This aqueous medium may contain an acidic compound and an organic solvent described later. Thus, the amount of water used as the dispersion medium is usually preferably 30 to 1500 parts by mass, more preferably 100 to 500 parts by mass with respect to 100 parts by mass of the polyamide resin. When the amount of water used is less than 30 parts by mass, the polyamide resin cannot be sufficiently dispersed in water, and when used in excess of 1500 parts by mass, the concentration of the resulting polyamide resin aqueous dispersion becomes thin, It is not preferable for its use.

  In the aqueous polyamide resin dispersion of the present invention, the number average particle diameter of the particles constituting the dispersion is required to be 0.01 to 10 μm. When the number average particle diameter of the particles is less than 0.01 μm, the water resistance of the coating film obtained using the dispersion is deteriorated. On the other hand, if the number average particle diameter of the particles exceeds 10 μm, the stability of the aqueous dispersion deteriorates or the smoothness of the coating film deteriorates.

The manufacturing method of the polyamide resin aqueous dispersion of this invention is demonstrated. As this manufacturing method,
(1) A predetermined amount of polyamide resin, an acidic substance, an aqueous medium, and preferably an organic solvent described later for sufficiently dispersing the polyamide resin are collectively fed into a dispersion tank, While stirring at 1000 rpm, the polyamide resin is heated to a temperature at which it softens in an aqueous medium as a dispersion medium. Subsequently, the temperature is maintained at a temperature higher than the temperature at which the polyamide resin is softened in an aqueous dispersion medium. And a method of obtaining an aqueous dispersion by applying a shearing force by stirring for about 10 to 60 minutes,

  (2) The dispersion tank is heated and pressurized to a temperature higher than the temperature at which the polyamide resin softens in the aqueous dispersion medium, and a predetermined amount of the melted polyamide resin, the acidic substance, the aqueous medium, Preferably, the above-mentioned organic solvent is press-fitted while stirring at 100 to 1000 revolutions per minute, and subsequently maintained at a temperature higher than the temperature at which the polyamide resin softens in the aqueous dispersion medium, and 10 to 100 revolutions per minute at 10 to 1000 revolutions. Examples include a method of applying an shearing force by stirring for about 60 minutes to obtain an aqueous dispersion.

  The temperature above the temperature at which the polyamide resin softens in the aqueous dispersion medium needs to be 70 ° C. to 280 ° C. Preferably it is 90 to 230 ° C. Good results can be obtained if the production is carried out under this temperature range. When the temperature is lower than 70 ° C., the polyamide resin is not sufficiently softened in the aqueous dispersion medium, so that uniform dispersion cannot be achieved. Further, at a temperature higher than 280 ° C., the polyamide resin is deteriorated.

  Furthermore, it is necessary to sufficiently disperse the polyamide resin by applying a shearing force with stirring. Examples of the stirring means include a rotary stirring blade. The rotation speed of the stirring blade is usually preferably 100 to 1000 rotations per minute. If the rotation is less than 100 revolutions per minute, the dispersion is not sufficiently performed, and if it exceeds 1000 revolutions, the accompanying effect is not seen, which is economically disadvantageous.

  In the present invention, in order to sufficiently disperse the polyamide resin, it is preferable to add an organic solvent at the time of aqueous dispersion. The amount of the organic solvent used in the aqueous dispersion is preferably 1 to 40 parts by weight, more preferably 2 to 30 parts by weight, and 3 to 20 parts by weight with respect to 100 parts by weight of the aqueous dispersion. Part is particularly preferred. When the addition amount of the organic solvent exceeds 20 parts by mass, it is desirable to reduce the content of the organic solvent after the dispersion by stripping described later. When the addition amount of the organic solvent exceeds 40 parts by mass, problems such as a long stripping time occur. If the addition amount of the organic solvent is less than 1 part by mass, it may be difficult to make the resin water-soluble, or the temperature in the system needs to be raised in order to make the resin water-soluble. It may decompose and lower the molecular weight.

  The organic solvent can be distilled off by heating the aqueous dispersion with stirring under normal pressure or reduced pressure, and part or all of the organic solvent can be removed (stripped) out of the system. The amount of the organic solvent finally remaining in the aqueous dispersion is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, further preferably 10 parts by mass or less, with respect to 100 parts by mass of the aqueous dispersion. Is particularly preferred. When the content of the organic solvent exceeds 30 parts by mass, not only the original purpose of making the aqueous solution is lost, but also the stability of the aqueous dispersion may be lowered. The content of the organic solvent can be less than 0.01 parts by mass (the detection limit of the analytical instrument used for the measurement). For this purpose, the degree of pressure reduction of the apparatus for distilling off the solvent is increased, or the operation time is increased. In view of productivity, the content of the organic solvent may be 0.01% by mass or more.

  As the organic solvent, those having a solubility in water at 20 ° C. of 5 g / L or more are preferably used, and more preferably 10 g / L or more. Those having a solubility of less than 5 g / L have problems in stability such as phase separation. Especially, a thing with a boiling point of 30-250 degreeC is preferable, and a 50-200 degreeC thing is especially preferable. When the boiling point of the organic solvent is less than 30 ° C., the rate of volatilization when the resin is made aqueous increases and the aqueous formation may not proceed completely. An organic solvent having a boiling point exceeding 250 ° C. is difficult to scatter from the resin film by drying, which may deteriorate the water resistance of the film.

  Specific examples of the organic solvent that can be used in the present invention include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, sec. -Alcohols such as amyl alcohol, tert-amyl alcohol, 1-ethyl-1-propanol, 2-methyl-1-butanol, n-hexanol, cyclohexanol, methyl ethyl ketone, methyl isobutyl ketone, ethyl butyl ketone, cyclohexanone, isophorone, etc. Ketones, ethers such as tetrahydrofuran, dioxane, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, acetic acid Esters such as 3-methoxybutyl, methyl propionate, ethyl propionate, diethyl carbonate, dimethyl carbonate, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol Glycosyl such as ethyl ether acetate, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol ethyl ether acetate, propylene glycol, propylene glycol monomethyl ether, propylene glycol monobutyl ether, propylene glycol methyl ether acetate Le derivatives, furthermore, 3-methoxy-3-methylbutanol, 3-methoxybutanol, acetonitrile, dimethylformamide, dimethylacetamide, diacetone alcohol, ethyl acetoacetate, and the like. Among the above organic solvents, ethanol, n-propanol, isopropanol, n-butanol, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, and the like can be easily formed into an aqueous resin and easily removed from the aqueous medium. Ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, and ethylene glycol monobutyl ether are preferred, and isopropanol is particularly preferred from the viewpoint of low temperature drying property. These organic solvents may be used in combination of two or more.

  According to the production method of the present invention, by cooling the obtained aqueous dispersion to room temperature, a fine polyamide resin aqueous dispersion having a number average particle size of 0.01 to 10 μm can be obtained without aggregation in the process. can get.

  As the above-mentioned dispersion tank, particularly if it is a pressure vessel provided with a means capable of heating to a temperature higher than the temperature at which the polyamide resin softens in an aqueous dispersion medium and a stirring means capable of giving a shearing force to the contents, It is not limited. For example, a pressure-resistant autoclave with a stirrer can be used.

  In the present invention, the polyamide resin softened in the aqueous dispersion medium is subjected to shearing force by stirring, and the terminal amino group in the resin becomes a hydrophilic salt by the action of an acidic substance, and is a stable emulsifier in water. Therefore, a dispersion of fine resin droplets having a number average particle diameter of 0.01 to 10 μm is obtained.

  The obtained aqueous polyamide resin dispersion may be adjusted to an arbitrary concentration using an appropriate concentration means such as a semipermeable membrane.

  In order to further improve various coating film performances such as water resistance and solvent resistance, 0.01 to 100 parts by mass, preferably 0.1 to 0.1 parts by mass of the crosslinking agent with respect to 100 parts by mass of the polyamide resin in the aqueous dispersion. -60 mass parts can be added. When the addition amount of the crosslinking agent is less than 0.01 parts by mass, the degree of improvement of the coating film performance is small, and when it exceeds 100 parts by mass, the performance such as workability is deteriorated. As the crosslinking agent, a crosslinking agent having self-crosslinking property, a compound having a plurality of functional groups that react with a carboxyl group in the molecule, a metal complex having a polyvalent coordination site, and the like can be used. Specifically, isocyanate compounds, melamine compounds, urea compounds, epoxy compounds, carbodiimide compounds, oxazoline group-containing compounds, zirconium salt compounds, silane coupling agents and the like are preferable. Moreover, you may use combining these crosslinking agents.

  In the aqueous dispersion of the present invention, various agents such as a leveling agent, an antifoaming agent, an anti-waxing agent, a pigment dispersant, an ultraviolet absorber, a pigment such as titanium oxide, zinc white, and carbon black, or It is also possible to add dyes.

  The obtained aqueous dispersion of polyamide resin can be used as it is, or can be used after being solid-separated by centrifugation or filtration and then pulverized by a drying means such as spray drying.

  The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples.

  In the following examples and comparative examples, the characteristics of the aqueous dispersion were measured or evaluated by the following methods.

(1) Aqueous yield [%]
When the aqueous dispersion after hydrophilization was pressure filtered at a pneumatic pressure of 0.2 MPa using a 300 mesh stainless steel filter (wire diameter 0.035 mm, plain weave), the resin mass remaining on the filter was measured, The yield was calculated from the measured value and the charged resin mass.

(2) Solid content concentration of aqueous dispersion [% by mass]
An appropriate amount of the aqueous dispersion was weighed and heated at 150 ° C. until the mass of the residue (solid content) reached a constant weight to obtain the solid content concentration.

(3) Average particle diameter of the aqueous dispersion [μm]
The number average particle size and the weight average particle size were determined using a Microtrac particle size distribution analyzer UPA150 (MODEL No. 9340, dynamic light scattering method) manufactured by Nikkiso Co., Ltd.

(4) Pot life of aqueous dispersion After the aqueous dispersion was allowed to stand at room temperature for 30 days, its appearance was evaluated in the following three stages.
○: No change in appearance △: Thickening is observed ×: Solidification, aggregation and generation of precipitates are observed

(5) Mixing stability Changes in appearance when 1 g of acetic acid was added to 30 g of the aqueous dispersion and stirred were evaluated in the following three stages.

○: No change in appearance Δ: Thickening is observed ×: Solidification, aggregation and precipitation are observed [Example 1]

In a 1 liter autoclave with a pressure-resistant structure that can be sealed with a heater, 6/66/12 copolymer nylon [the ratio of terminal carboxyl group to terminal amino group is (terminal carboxyl group) / (terminal amino group) in molar ratio = 10/90, terminal amino group 180 mmol / kg] 100.0 g, 2.0 g of 35% hydrochloric acid [1.07 mol times / amino group], ethylene glycol monobutyl ether 50.0 g as an organic solvent, water 348.0 g was charged and sealed. Next, the inside of the autoclave was heated up to 150 ° C. while starting the stirrer and stirring at 300 rpm. Then, the mixture was further stirred for 30 minutes while maintaining the internal temperature at 150 ° C., and then the contents were cooled to 30 ° C. and taken out from the autoclave to obtain an aqueous polyamide resin dispersion of Example 1. Various characteristics of this aqueous dispersion are shown in Table 1.
[Example 2]

6/66/11/12 copolymer nylon [The ratio of terminal carboxyl group to terminal amino group is (terminal carboxyl group) / (terminal amino group) in a molar ratio. Group) = 2/98, terminal amino group 270 mmol / kg] 100.0 g, 35% hydrochloric acid 3.0 g [1.07 mol times / amino group] and water 397.0 g were charged and sealed. Next, the inside of the autoclave was heated up to 170 ° C. while starting the stirrer and stirring at 300 rpm. Then, the mixture was further stirred for 30 minutes while maintaining the internal temperature at 170 ° C., and then the contents were cooled to 30 ° C. and taken out from the autoclave to obtain an aqueous polyamide resin dispersion of Example 2. Various characteristics of this aqueous dispersion are shown in Table 1.
[Example 3]

In a 1 liter autoclave having a pressure-resistant structure that can be sealed with a heater, 12-nylon [the ratio of terminal carboxyl groups to terminal amino groups is (terminal carboxyl group) / (terminal amino group) = 35/65 in terms of molar ratio, Terminal amino group 100 mmol / kg] 100.0 g, 35% hydrochloric acid 1.5 g [1.4 mol times / amino group], ethylene glycol monobutyl ether 50.0 g as an organic solvent, and water 348.5 g Charged and sealed. Next, the inside of the autoclave was heated to 200 ° C. while starting the stirrer and stirring at 300 rpm. The mixture was further stirred for 30 minutes while maintaining the internal temperature at 200 ° C., and then the contents were cooled to 30 ° C. and taken out from the autoclave to obtain an aqueous polyamide resin dispersion of Example 3. Various characteristics of this aqueous dispersion are shown in Table 1.
[Example 4]

20 parts by mass of a melanin compound (Mitsui Cytec Co., Ltd., Cymel 325) as a crosslinking agent is added to 100 parts by mass of the resin of the aqueous dispersion obtained in Example 1, and the aqueous polyamide resin dispersion of Example 4 is added. Got. Various characteristics of this aqueous dispersion are shown in Table 1.
[Comparative Example 1]

In a 1 liter autoclave with a pressure-resistant structure that can be sealed with a heater, 6/66/12 copolymer nylon [the ratio of terminal carboxyl group to terminal amino group is (terminal carboxyl group) / (terminal amino group) in molar ratio = 10/90, terminal amino group 180 mmol / kg] 100.0 g, 35% hydrochloric acid 0.2 g [0.1 mol times / amino group], ethylene glycol monobutyl ether 50.0 g as an organic solvent, water 349.8 g was charged and sealed. Next, the inside of the autoclave was heated up to 150 ° C. while starting the stirrer and stirring at 300 rpm. The mixture was further stirred for 30 minutes while maintaining the internal temperature at 150 ° C., and then the contents were cooled to 30 ° C. and taken out from the autoclave. However, the taken-out polyamide resin was massive and an aqueous dispersion could not be obtained.
[Comparative Example 2]

In a 1 liter autoclave with a pressure-resistant structure that can be sealed with a heater, 6/66/12 copolymer nylon [the ratio of terminal carboxyl group to terminal amino group is (terminal carboxyl group) / (terminal amino group) in molar ratio = 87/13, terminal amino group 19.4 mmol / kg] 100.0 g, 0.3 g of 35% hydrochloric acid [1.5 mol times / amino group], and 50.0 g of ethylene glycol monobutyl ether as an organic solvent And 349.7 g of water were charged and sealed. Next, the inside of the autoclave was heated up to 150 ° C. while starting the stirrer and stirring at 300 rpm. The mixture was further stirred for 30 minutes while maintaining the internal temperature at 150 ° C., and then the contents were cooled to 30 ° C. and taken out from the autoclave. However, the taken-out polyamide resin was massive and an aqueous dispersion could not be obtained.
[Comparative Example 3]

In a 1 liter autoclave with a pressure-resistant structure that can be sealed with a heater, 6/66/12 copolymer nylon [the ratio of terminal carboxyl group to terminal amino group is (terminal carboxyl group) / (terminal amino group) in molar ratio = 92/8, terminal carboxyl group 165 mmol / kg] 100.0 g, 10% sodium hydroxide aqueous solution 7.0 g [1.06 mol times / carboxyl group], and ethylene glycol monobutyl ether 50.0 g as an organic solvent And 343.0 g of water were charged and sealed. Next, the inside of the autoclave was heated up to 150 ° C. while starting the stirrer and stirring at 300 rpm. The mixture was further stirred for 30 minutes while maintaining the internal temperature at 150 ° C., and then the contents were cooled to 30 ° C. and taken out from the autoclave to obtain a polyamide resin aqueous dispersion of Comparative Example 3. Various characteristics of this aqueous dispersion are shown in Table 1.
[Comparative Example 4]

  In Example 1, the amount of hydrochloric acid added was 9.4 g [5 moles / amino group]. Otherwise, the same operation as in Example 1 was performed. However, although an aqueous polyamide surgical dispersion was obtained, its pH was 1 or less (strong acid), which was not practical.

  As shown in Table 1, according to the present invention, an aqueous dispersion finely and stably dispersed in an aqueous medium can be obtained by adding an acidic substance in a specific range to a polyamide resin having a specific range of end groups. did it. Furthermore, the pot life of the obtained aqueous dispersion was good, and the mixing stability with the acidic compound was also good (Examples 1 to 4).

  However, when the amount of the acidic substance added was small outside the range of the present invention, an aqueous dispersion was not obtained (Comparative Example 1). Also, when the terminal composition of the polyamide resin used was outside the scope of the present invention and the terminal carboxyl group was too much, an aqueous dispersion was not obtained (Comparative Example 2). In addition, the polyamide resin having too many carboxyl group ends, which is a resin outside of the present invention, was obtained as an aqueous dispersion by using a conventional method of adding an alkali, but the aqueous dispersion was mixed and stabilized with an acidic compound. The properties were poor and could not be used in combination with acidic compounds (Comparative Example 3). Further, when the amount of the acidic substance to be added was too large outside the range of the present invention, an aqueous dispersion was obtained, but its pH was 1 or less (strong acid), which was not practical.

Claims (3)

The ratio of the terminal carboxyl group and the terminal amino group in terms of molar ratio, (terminal carboxyl group) / (terminal amino group) = 40/60 to 0/100,
An acidic substance in a proportion of 0.2 to 3 mol per mol of the terminal amino group;
A dispersion containing an aqueous medium,
A polyamide resin aqueous dispersion, wherein the number average particle diameter of the particles constituting the dispersion is 0.01 to 10 μm. Polyamide resin

The aqueous polyamide resin dispersion according to claim 1, wherein at least one selected from the group consisting of: The ratio of the terminal carboxyl group and the terminal amino group in terms of molar ratio, (terminal carboxyl group) / (terminal amino group) = 40/60 to 0/100,
0.2 to 3 moles of acidic material per mole of terminal amino groups;
An aqueous medium,
A method for producing an aqueous polyamide resin dispersion, which comprises heating and stirring in a sealed container at a temperature of 70 to 280 ° C.