JPH08157757A - Film-forming assistant for water-base acrylic dispersion and its production - Google Patents

Abstract

PURPOSE: To obtain a film-forming assistant for a water-base acrylic dispersion which is hardly toxic to a living body, is excellent in dryability and film-forming properties, and, when compounded into a latex, gives it an excellent storage stability. CONSTITUTION: This assistant comprises at least one glutaric ester repesented by the formula (wherein R1 and R2 are each independently a 1-8C linear or branched alkyl group or a cycloalkyl group) and gives a 1-wt.% aq. soln. or suspension with a pH of 3.5-12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film-forming auxiliary agent for an acrylic aqueous dispersion, which has low toxicity to the living body, is excellent in drying property and film-forming performance, and is excellent in storage stability when blended with latex. Is.

[0002]

2. Description of the Related Art In recent years, global environment and labor environment problems have been discussed. Among them, for solvents that are directly related to environmental destruction, reduction of their usage and replacement with low toxicity solvents by prohibiting their use or limiting the total amount. There is an urgent need. For example, the ethylene glycol solvent used as a solvent for paints and inks is being replaced by propylene glycol solvent, which has low toxicity, and is etherified with a lower alkyl group such as methyl group, ethyl group, and butyl group. Glycol ethers have been developed. Especially in the field of paints, in order to reduce the amount of solvent, the shift from solvent-based paints to water-based paints is in progress, but with the change to water-based paints, film-forming aids that are not needed in solvent-based paints are needed. Then isobutyric acid ester,
Butyl cellosolve, cellosolve acetate, etc. have been used, but these auxiliaries are drying, hydrolyzing, odor,
There was a problem with toxicity. The substitution was desired.

The performance required for these alternative substances is as follows.
It has good dryness, film-forming property, pigment miscibility, hydrolysis resistance, low toxicity, safety (nonflammable or high flash point), and low odor. As such an alternative substance, there is a dipropylene glycol derivative as disclosed in Japanese Patent Laid-Open No. 4-55479, but these substances have good toxicity and safety and low odor, but they have good drying property. There was a problem with the film properties. In addition, there are methyl esters such as succinic acid and adipic acid as alternative substances that have extremely high performance in film-forming properties and drying properties, but hydrolysis of the ester causes a significant decrease in PH after addition of the acrylic aqueous dispersion, Since it is not used because it impairs storage stability, it has been desired to develop an auxiliary agent having the above-mentioned performance. As a method for suppressing the hydrolysis of the methyl ester of succinic acid or adipic acid, JP-A-57-34166 or Po
ly. Mater. Sci. Eng. , Vol. 58,
As disclosed in 1125 to 1132 (1988), there is a method of converting an ester portion into a branched alkyl, but 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (hereinafter Compared to conventional products such as ester (abbreviated as TPIB), PH due to hydrolysis
The problem of storage stability of the composition was not sufficiently obtained, and it was still an unsolved problem.

[0004]

DISCLOSURE OF THE INVENTION The present invention is excellent in drying property and film-forming performance without producing harmful substances even in metabolic processes in the living body, and is excellent in storage stability when compounded in latex. Another object of the present invention is to provide a film forming aid for an acrylic aqueous dispersion.

[0005]

Means for Solving the Problems That is, the present invention comprises one or more glutaric acid esters represented by the following general formula (1), and a pH of a 1% by weight aqueous solution (or suspension) thereof is used. Is in the range of 3.5 or more and 12 or less, which is a film forming aid for an acrylic aqueous dispersion.

[0006]

Embedded image

However, in the formula (1), R ₁ and R ₂ represent a linear or branched alkyl or alicyclic alkyl group having 1 to 8 carbon atoms. R ₁ and R ₂ may be the same. Hereinafter, the present invention will be described in detail. In the formula (1), R ₁ and R ₂ are linear or branched alkyl groups having 1 to 8 carbon atoms or alicyclic alkyl groups, such as a methyl group, an ethyl group, an isopropyl group, a butyl group, and tertiary butytyl. Group, hexyl group, cyclohexyl group, 2-ethylhexyl group and the like, and R ₁ and R ₂ may be the same or different.

Specific compounds include dimethyl glutarate, diethyl glutarate, diisopropyl glutarate, ditert-butyl glutarate, dibutyl glutarate, dihexyl glutarate, dicyclohexyl glutarate, di (2-ethylhexyl) glutarate, glutarate. There are butyl cyclohexylate and tertiary butyl cyclohexyl glutarate, of which diisopropyl glutarate is preferred.

Further, other esters such as adipic acid ester, succinic acid ester, TPIB, etc., containing these glutaric acid esters as a main component, within the range of not impairing their performance,
It can be used by adding ethers such as butyl cellosolve, propylene glycol butyl ether, dipropylene glycol butyl ether, alcohols such as benzyl alcohol, and hydrocarbons such as hexane, toluene, benzene, specifically, 40% by weight. It is possible to add and use in the following ranges.

Examples of the method for producing the compound of the present invention include an esterification reaction between a dibasic acid and an alcohol, a reaction between an acid chloride and an alcohol, and a transesterification reaction between a dibasic acid ester and an alcohol. As an example, a reaction of glutaric acid (hereinafter abbreviated as GA) and isopropanol (hereinafter abbreviated as IPA) in a method for producing diisopropyl glutarate (hereinafter abbreviated as GIP) will be described as follows. 2 to 10 times the molar amount of IPA is added to GA, heated to 50 to 150 ° C. in the presence of an acid catalyst (mineral acid, resin, etc.), and allowed to react for 3 to 20 hours under atmospheric pressure or pressure, and unreacted raw materials and glutar. An equilibrium composition mixture of mono- and di-isopropyl esters of the acid is obtained. Unreacted IPA and generated water are removed from this mixture, and further unreacted G
Diisopropyl glutarate can be obtained by separating A and the monoester by distillation. Also, when low-purity glutaric acid (impurity; succinic acid 5 to 20%, adipic acid 35 to 10%, etc.) is used as a raw material, the reaction can be carried out in the same manner. Can be done.

Generally, the required performance as a film-forming aid is film-forming and drying storage stability, and the dibasic acid ester as described above was considered to have excellent film-forming and drying properties. Actually, when a dibasic acid ester is used as a film-forming aid, the film-forming property and the drying property depend on the carbon number of the dibasic acid, and particularly the dibasic acid ester having a carbon number of 4 or less such as succinic acid has a poor drying property. Although it is excellent, it is extremely inferior in film forming property, and dibasic acid ester having 6 or more carbon atoms such as adipic acid has excellent film forming property but has a problem in drying property. It becomes more remarkable as the carbon number of the dibasic acid increases. The details of this cause are not clear, but the factors generally involved in the film-forming property of the film-forming aid are latex polymers that are expected to be compatible with the latex polymer and have a water-soluble degree as indicated by the SP value and the like. The reason is that the larger the carbon number of the dibasic acid, the more its hydrophobicity increases, the compatibility with the polymer and the distribution to the polymer, and the more plasticizing the polymer. Conceivable. On the other hand, factors relating to the drying property include the initial drying property depending on the boiling point and vapor pressure of the auxiliary agent and the diffusibility of the auxiliary agent inside the latex film, that is, the late drying property depending on the shape and size of the auxiliary agent. When the number of carbon atoms in the dibasic acid is 4 or less, the initial drying property is improved due to the decrease in boiling point and the increase in vapor pressure, and it is considered that the dibasic acid has excellent drying performance. However, when the number of carbon atoms in the dibasic acid is 6 or more, it is considered that the drying performance is inferior because the late drying property is reduced due to the decrease of the diffusivity in the coating film due to the size of the shape of the molecule. It remains in the latex film.
That is, the film-forming property and the drying property, especially the latter drying property are contradictory factors, and it was difficult to overcome them.

As a result of investigating the contradictory factors in the performance of such a film-forming aid, it was found that the glutaric acid ester, which is a dibasic acid having 5 carbon atoms, is excellent in the contradictory performance, that is, the film-forming property and the late drying property. I found it. The details of the reason why the glutaric acid ester has excellent film-forming property and good late drying property are not clear, but one is that the dibasic acid having a carbon number of 4 or 6 has a high melting point. On the other hand, it can be estimated that glutaric acid having 5 carbon atoms is based on its low melting point (liquid). That is, when glutaric acid is used for polyester, a resin having a low melting point and a low Tg is formed. Therefore, when glutaric acid ester is added to the latex, Tg is lowered (plasticized) as well, and as a result, excellent film forming properties are obtained. it is conceivable that. Also this specific low Tg
It is considered that the improvement (high plasticizing effect) resulted in improving the diffusibility of the auxiliary agent in the latex film, that is, promoting the late drying property.

On the other hand, the storage stability, which is an important factor in practical use as well as the film-forming property and the drying property, is determined by using the glutaric acid ester of the present invention and the film-forming auxiliary having a glutaric acid ester as a main component as an organic amine. Can be improved by treating it with an inorganic alkali and adjusting the pH of its 1% by weight aqueous solution (or suspension) in the range of 3.5 to 12. In the present invention, storage stability means that after the auxiliary agent is added to the latex, 2
Long-term stability of latex PH at 5 ° C. for 6 months and 50 ° C. for 1 month or more. During this time, if the pH of the latex is lowered to 7.0 or less, the polymer is aggregated / precipitated, which makes practical use difficult. For example, even if a method in which a methyl group of a dibasic acid ester is replaced with a bulky alkyl group such as a tert-butyl group, suppression of a decrease in latex PH can be realized in the short term, but particularly when the PH is 7.5 or less. At the present time, the hydrolysis rate is remarkably increased, the PH is rapidly lowered, and the polymer is aggregated / precipitated, which is not practically used at present. That is, in order to obtain the stability of the latex, it is necessary to suppress this rapid decrease in PH, which is an important point. Therefore, we investigated a method that does not lower the latex PH to 7.5, and found that the initial PH of the latex significantly affects the stability of the latex, that is, the hydrolysis rate of the ester, and the initial PH is added. It was found to be highly dependent on the pH of a 1% by weight aqueous solution (suspension) of dibasic acid ester. That is, the fact that the storage stability of the latex can be realized when a glutaric acid ester having a pH of 3.5 to 12 is added to make a 1% by weight aqueous solution does not lower the initial PH of the latex, thereby suppressing the hydrolysis rate of the ester. It is thought to be for the reason. Such high performance in film-forming property, drying property and storage stability, which has not been obtained in the past, can be obtained by adjusting the pH of glutarate to 1
The fact that it was first obtained by adjusting the pH to be in the range of 3.5 to 12 in the form of a weight% aqueous solution was unimaginable by anyone.

Examples of the organic amine or inorganic alkali used for the treatment include trimethylamine, triethylamine, tripropylamine, pyridine, substituted pyridine, ethylenediamine and the like as the organic amine.
Particularly low boiling amines are preferred. Examples of the inorganic alkali include alkali and alkaline earth metal hydroxides, oxides, carbonates, and the like, and specific examples include sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium carbonate, calcium oxide, magnesium oxide and the like. Can be mentioned. Alternatively, a solid base such as an anion exchange resin may be used.

The amount of the organic amine or inorganic alkali used is preferably 0.01% to 10% by weight based on the glutaric acid ester. The treatment temperature and treatment time vary depending on the amount of PH before treatment, the amount of the organic amine and the inorganic alkali used, and the pH is 3.5 to 12, preferably 4 to 10 hours in the range of 10 ° C to 100 ° C. The processing is performed until the range becomes 8.

The treatment with an organic amine or an inorganic alkali may be carried out before the distillation of glutaric acid ester or after the distillation of glutaric acid ester. The treatment method may be a batch method, a semi-batch method, or a continuous method, but it is efficient to fill a tubular reactor with a solid alkali and continuously perform the treatment. When the pH of the glutaric acid ester or the mixture of the glutaric acid ester and the additive is 3.5 or less, the storage stability of the latex is significantly impaired. The details of this cause are not clear, but when the pH is 3.5 or less, the initial P of the latex after addition is increased.
It is considered that H is significantly lowered and the hydrolysis rate of the ester is accelerated. It is also considered that when a pH of 12 or more is used, the initial PH of the latex after addition is remarkably increased, the hydrolysis rate of the ester is accelerated, and the storage stability of the latex is impaired.

The amount of the glutaric acid ester used varies depending on the viscosity of the aqueous dispersion and properties such as MFT, but is preferably in the range of 0.5 to 20% by weight based on the solid content of the aqueous dispersion. When the amount used is less than 0.5% by weight, the effect as a film-forming aid is lost, and when the amount used is more than 20% by weight, the viscosity of the aqueous dispersion remarkably increases and the film forming rate also decreases. Absent.

The acrylic aqueous dispersion in which the film-forming aid of the present invention is used is obtained by emulsion-polymerizing a vinyl monomer,
A powdered resin which is emulsified and dispersed in an aqueous medium consisting of water or a mixture with a small amount of hydroalcohol,
Generally, the resin concentration is 30 to 60% by weight. Among them, those obtained by emulsion-polymerizing vinyl monomers are preferable. In addition, the auxiliary agent of the present invention can be added before emulsion polymerization of the acrylic aqueous dispersion or added to the acrylic aqueous dispersion after polymerization.

Examples of vinyl-based monomers used in emulsion polymerization include acrylic-based monomers such as acrylic acid ester, methacrylic acid ester, acrylic acid, methacrylic acid and acrylonitrile, styrene-based monomers such as styrene and α-methylstyrene, and acetic acid. Vinyl, acrylamide, maleic acid, fumaric acid, itaconic acid and the like,
One kind or a mixture of two or more kinds is used. The above acrylic aqueous dispersion is produced by emulsion polymerization of these monomers by a conventional method.

The acrylic dispersion also contains clay, calcium carbonate, which is added when used as a coating composition.
Inorganic pigments such as titanium oxide and talc, color pigments, thickeners, plasticizers, defoamers, preservatives, release agents, etc. may be added.

[0021]

[Examples] The evaluation methods used in Examples and Comparative Examples are shown below. The film-forming property is evaluated by measuring the MFT with a minimum film-forming temperature measuring device manufactured by Takabayashi Rika Co., Ltd. using a composition prepared by adding a predetermined amount of various film-forming aids to the solid content of the acrylic aqueous dispersion. The sex was evaluated.

The method for evaluating the drying property and stickiness is as follows. A composition prepared by adding 10% by weight of various film-forming aids to the solid content of the acrylic aqueous dispersion is formed into a film having a film thickness of 100 μm at 80 ° C., and then extracted with acetone over time. The residual film-forming auxiliary agent in the coating film was quantified by gas chromatography Shimadzu GC-14B, and the time when it became 1/2 of the initial concentration, that is, 5 wt% was compared. At this time, the drying time in TBIP which is a film forming aid generally used was set to 100, and the time in other film forming aids was shown as a relative value. In addition, the stickiness after 5 hours from the film formation was evaluated by touch as follows: no stickiness at all: ⊚, almost no stickiness: ○, slightly sticky: Δ, sticky: ×.

The appearance of the coating film was evaluated by visually observing the appearance of the coating film formed by coating a composition obtained by adding a predetermined amount of various film-forming aids to the solid content of the acrylic aqueous dispersion on a glass plate and forming a film at room temperature. It forms a uniform coating with excellent surface smoothness:
⊚, a uniform coating film without cracks was formed: ◯, slight cracking occurred: Δ, cracks did not form a coating film: ×

The storage stability evaluation method is as follows. A composition prepared by adding a predetermined amount of various film-forming aids to the solid content of an acrylic aqueous dispersion is stored at 50 ° C. for 1 month, and the change in pH over time during that period is calculated by Toa. It was measured and evaluated with a PH meter HM-205 manufactured by Denpa Kogyo KK

[0025]

[Synthesis Example 1] Glutaric acid 2 was added to a 2-liter 4-necked flask.
50 g (1.89 mol) and 570 g of isopropanol
(9.45 mol) was charged and heated to 80 ° C. to be dissolved, and 165 g of 20% by weight of the sulfonic acid resin catalyst (Amberlyst 15E) was added as a catalyst.
The reaction was allowed to proceed for 1 hour to give a suspension of 1% by weight, and 230 g of diisopropyl glutarate having a pH of 3.1 was obtained.

[0026]

[Synthesis Example 2] Glutaric acid 2 was added to a 2-liter 4-necked flask.
50 g (1.89 mol) and 292 g of methanol (9.
45 mol) and heated to 60 ° C. to dissolve it, 103 g of 20% by weight of the total sulfonic acid resin catalyst (Amberlyst 15E) was added as a catalyst and reacted at 60 ° C. for 4 hours to make a 1% by weight aqueous solution PH3. 210 g of dimethyl glutarate of 0.1 was obtained.

[0027]

[Synthesis Example 3] To a 1 liter autoclave, 260 g (2 mol) of a dibasic acid mixture containing 70% by weight of glutaric acid, 20% by weight of succinic acid and 10% by weight of adipic acid and 360 g (6 mol) of isopropanol were added.
500 ppm of a 0% aqueous solution was added, and the mixture was reacted at 135 ° C. for 5 hours to give a suspension of 1% by weight, 70% by weight of diisopropyl glutarate having a pH of 2.9, and 2% of diisopropyl succinate.
190 g of a mixture of 1 wt% and diisopropyl adipate 9 wt% was obtained.

[0028]

[Synthesis Example 4] A 1% by weight suspension was prepared in the same manner as in Synthesis Example 1 except that 276 g (1.89 mol) of adipic acid was used, and 304 g of diisopropyl adipate having a pH of 3.0 was used.
I got

[0029]

Synthesis Example 5 A 1% by weight suspension was prepared in the same manner as in Synthesis Example 1 except that 223 g (1.89 mol) of succinic acid was used to obtain 260 g of PH3.2 diisopropyl succinate.

[0030]

Example 1 100 g of diisopropyl glutarate of Synthesis Example 1 and 1 g of sodium hydroxide were placed in a 300 ml eggplant flask.
Was added and stirred at room temperature for 3 hours, and sodium hydroxide was filtered to obtain 95 g of diisopropyl glutarate having a PH of 4.6 as a 1 wt% suspension.

[0031]

Example 2 100 g of diisopropyl glutarate of Synthesis Example 1 and 8 g of triethylamine were placed in a 300 ml round-bottomed flask.
Was added, and the mixture was stirred at room temperature for 1 hour, and then triethylamine was collected by distillation to obtain 90 g of diisopropyl glutarate having a pH of 10.1 as a 1 wt% suspension.

[0032]

Example 3 In the same manner as in Example 1 except that the dimethyl glutarate of Synthesis Example 2 was used, 90 g of a 1 wt% aqueous solution of dimethyl glutarate having a pH of 4.0 was obtained.

[0033]

Example 4 90 g of a 1% by weight suspension of a dibasic acid ester mixture having a pH of 4.1 was obtained in the same manner as in Example 1 except that the dibasic acid ester mixture of Synthesis Example 3 was used. It was

[0034]

Example 5 The diisopropyl glutarate of Example 1 was mixed with an acrylic aqueous dispersion (acrylic-styrene type, MFT50).
10% by weight with respect to the solid content of C, pH 8.00) was added at room temperature with stirring. Using this aqueous dispersion composition, film forming properties, drying properties, stickiness, and coating film appearance were evaluated. The results are shown in Table 1. As shown in Table 1, the glutaric acid ester, in addition to the good film-forming property, also gave good results in the evaluation of the drying property, the stickiness and the appearance of the coating film. As compared with Table 2, glutaric acid ester has the same film-forming property as diisopropyl adipate, but shows the same drying property as diisopropyl succinate,
Further, in comparison with TPIB which is generally used at present, diisopropyl glutarate shows extremely excellent characteristics not only in film forming property but also in drying property.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

Example 6 The same evaluation as in Example 5 was carried out using the dimethyl glutarate of Example 3. The results are shown in Table 1.

[0038]

Example 7 Using the dibasic acid ester mixture of Example 4 (hereinafter abbreviated as DBIP), the same evaluation as in Example 5 was performed. The results are shown in Table 1.

[0039]

Example 8 The diisopropyl glutarate of Example 1 was mixed with an acrylic aqueous dispersion (acrylic, MFT 22 ° C., PH
10% by weight based on the solid content of 8.00) was added at room temperature with stirring. Using this aqueous dispersion composition, film forming properties and drying properties were evaluated. The results are shown in Table 1.

[0040]

Comparative Example 1 Diisopropyl adipate (Synthesis Example 4) was added to an acrylic aqueous dispersion (acrylic-styrene type, MFT5).
10% by weight based on the solid content (0 ° C.) was added at room temperature with stirring. Using this aqueous dispersion composition, film forming properties, drying properties, stickiness, and coating film appearance were evaluated. The results are shown in Table 2.

[0041]

[Comparative Examples 2 to 6] Diisopropyl succinate (Synthesis Example 5), TPIB, butyl cellosolve, TPI as a film forming aid
The same evaluation as in Comparative Example 1 was carried out using the B / butyl cellosolve mixture and dipropylene glycol n-butyl ether, and the results are shown in Table 2. Compared to conventional TPIB and dipropylene glycol n-butyl ether, which have relatively good film-forming properties, the dibasic acid esters listed in Table 2 are superior in film-forming properties and drying properties. Among them, diisoprol glutarate It has good performance of both.

[0042]

Example 9 A 1% by weight suspension of diisopropyl glutarate having a pH of 4.6 (Example 1) was used as an acrylic aqueous dispersion (acrylic-styrene type, MFT 50 ° C., PH 8.0).
10% by weight based on the solid content of 0) was added at room temperature with stirring. Storage stability was evaluated using this aqueous dispersion composition. It showed better storage stability than TPIB. Table 3 shows the results.

[0043]

[Table 3]

[0044]

[Example 10] Example 9 using 1% by weight suspension of diisopropyl glutarate (Example 2) having a pH of 10.1
When evaluated in the same manner as above, it showed storage stability equal to or higher than that of isobutyric acid ester. Table 3 shows the results.

[0045]

[Comparative Example 7] Diisopropyl glutarate (Synthesis Example 1) having a pH of 3.10 was stirred at 10% by weight with respect to the solid content of an acrylic aqueous dispersion (acrylic-styrene type, MFT 50 ° C) to prepare a 1% by weight suspension. While being added at room temperature. Storage stability was evaluated using this aqueous dispersion composition. Table 3 shows the results.

[0046]

Comparative Example 8 The same evaluation as in Comparative Example 7 was carried out using 1% by weight suspension of diisopropyl glutarate having a pH of 12.5. Table 3 shows the results.

[0047]

Comparative Examples 9 to 10 The same evaluation as in Comparative Example 7 was carried out using 1% by weight suspension as a film-forming aid and diisopropyl adipate (Synthesis Example 4) having a pH of 3.0 and TPIB. Table 3 shows the results.

[0048]

Example 11 The same evaluation as in Example 1 was carried out after the aqueous dispersion composition used in Example 9 for storage stability evaluation was stored at 50 ° C. for 4 weeks. Film performance was similar to Example 5. The results are shown in Table 4.

[0049]

[Table 4]

[0050]

Example 12 After storing the aqueous dispersion composition used for evaluation of storage stability in Example 10 at 50 ° C. for 4 weeks, the film performance was the same as in Example 5. The results are shown in Table 4.

[0051]

Comparative Example 11 The aqueous dispersion composition used for the evaluation of storage stability in Comparative Example 7 was stored at 50 ° C. for 4 weeks and then evaluated in the same manner as in Example 1. The film performance was not as good as that seen in Example 5, and the film forming properties and the appearance of the coating film were remarkably lowered. The results are shown in Table 4.

[0052]

Comparative Example 12 The same evaluation as in Example 1 was carried out after the aqueous dispersion composition used for evaluation of storage stability in Comparative Example 9 was stored at 50 ° C. for 4 weeks. The film performance was not as good as that seen in Example 5, and the film forming properties and the appearance of the coating film were remarkably lowered. The results are shown in Table 4.

[0053]

INDUSTRIAL APPLICABILITY The present invention provides an acrylic aqueous dispersion which does not produce harmful substances even in the metabolic process in the living body, is excellent in drying property and film forming performance, and is excellent in storage stability when blended with latex. It is a film-forming aid for the body.

Claims (3)

[Claims] 1. A glutarate represented by the following general formula (1), which comprises one or more glutaric esters, and the pH of a 1% by weight aqueous solution (or suspension) thereof is in the range of 3.5 or more and 12 or less. A film-forming aid for an acrylic aqueous dispersion, which is prepared. Embedded image However, in the formula (1), R ₁ and R ₂ represent a linear or branched alkyl group having 1 to 8 carbon atoms or an alicyclic alkyl group. R ₁ ,
R ₂ may be the same. 2. A film forming aid for an acrylic aqueous dispersion, wherein the glutaric acid ester of claim 1 is diisopropyl glutarate. 3. A method for producing a film-forming aid for an acrylic aqueous dispersion, which comprises treating the glutaric acid ester according to claim 1 with an organic amine or an inorganic alkali.