JPH05295100A - Self-dispersed water-based polyester resin, its production and surface treating agent composition for paper therefrom - Google Patents

Abstract

PURPOSE:To obtain the subject resin capable of giving water-resistant films, useful as e.g. a surface treating agent for paper by dissolving in an organic solvent a resin produced from a specific diol, aliphatic diol and/or polyol, and bifunctional and/or polyfunctional carboxylic acid(s) followed by addition of a neutralizing agent to the system to effect phase reversal to an aqueous system. CONSTITUTION:Firstly, a polyester resin with an acid value of 3-70 KOH mg/g is prepared by copolycondensation between at least one kind of alcohol component among (A) diol components of the formula (R is ethylene or propylene; x and y are each an integer of >=1, (x+y) being 2-7 on average), (B) aliphatic diols and (C) trior more hydric alcohols, and at least one kind of acid component among (D) bifunctional carboxylic acids (anhydrides) or lower alkyl esters thereof and (E) tri- or more functional carboxylic acids (anhydrides) or lower alkyl esters thereof. Then, this polyester is dissolved in a ketone-based solvent followed by addition of a neutralizing agent to ionize the carboxyl groups followed by addition of water and then distilling the solvent off the system to effect phase reversal to an aqueous system, thus obtaining the objective water-based polyester resin.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a self-dispersible water-based polyester resin, a method for producing the resin characterized by a phase inversion method, and electrophotographic paper, electrostatic recording paper, or thermal transfer paper using the water-based polyester resin. And a surface treating agent composition for paper.

[0002]

2. Description of the Related Art A water-based resin dispersion can be used as a property improver for surface coating, adhesion, etc. by applying or impregnating the surface of paper, woven fabric, non-woven fabric or the like. .. Conventionally, most of such aqueous resin dispersions are produced by an emulsion polymerization method, and in order to maintain the stability of the polymerization reaction and the produced aqueous resin dispersion, a few% of an emulsifier is used during production. There is.
Usually, if an attempt is made to obtain an aqueous resin dispersion having a small particle size with this formulation, a relatively large amount of emulsifier is required.

However, the emulsifier exhibits harmful side effects such as reduction in water resistance, adhesion, adhesiveness, weather resistance and mechanical strength of the film after drying. The soap-free emulsion polymerization method has been attracting attention as a method for improving these problems. Details of such a polymerization method are described in many documents, for example, “New Development and Problems of Synthetic Polymer Latex” by Yamazaki et al. [Chemical Industry Data (Tokyo Tech News) vo
l. 13 (4) P3 (1978)], the aqueous resin dispersion obtained by soap-free emulsion polymerization has a problem that the storage stability and mechanical stability are extremely poor, and is not practical. ..

On the other hand, in the conventional electrophotographic method, as described in US Pat. Nos. 2,297,691 and 2,357,809, etc., the photoconductive insulating layer is uniformly charged and then the layer is exposed. , An electric latent image is formed by dissipating the electric charge on the exposed portion, and the latent image is visualized by adhering a fine powder having a colored electric charge called a toner (developing process). ), After transferring the obtained visible image to a transfer material such as transfer paper (transfer step), it is permanently fixed by heating, pressure, or any other suitable fixing method (fixing step). In the fixing step of these steps, by controlling the material and physical properties of the binder resin that constitutes the toner,
Low energy retention is being promoted. However,
Regarding paper and the like on which the toner is fixed, neutral paper and recycled paper are being developed, but attempts to improve it for the purpose of improving fixing property have not been made so much. Therefore, an attempt to improve the fixability of paper or the like by using a surface modifier or the like at the time of production can be considered, but when the above-mentioned aqueous resin dispersion is used, as described above, the water resistance of the film, the mechanical strength, etc. There were problems such as decrease, and there was a need to improve these.

The present invention has been made in order to meet the above-mentioned requirements, and its object is to provide a self-dispersible water-based polyester resin having a high water resistance of a film after drying because an emulsifier is not used, and a method for producing the same. Especially. Another object of the present invention is to provide a surface treating agent composition for paper using the self-dispersible water-based polyester resin for improving the low temperature fixing property of the toner.

[0006]

That is, the present invention provides (1) (a) a diol component represented by the following formula:

[0007]

[Chemical 3]

(In the formula, R represents an ethylene or propylene group, x and y are each an integer of 1 or more, and x +
The average value of y is 2 to 7. ) (B) one or more alcohol components selected from the group consisting of aliphatic diols and (c) trihydric or higher polyhydric alcohols; and (d) divalent carboxylic acids, their acid anhydrides or their lower alkyl esters. And (e) polycarboxylic acid having a valence of 3 or more, an acid anhydride thereof, or one or more acid components selected from the group consisting of lower alkyl esters thereof is copolycondensed to obtain an acid value of 3 to 70 KOHmg / g of the polyester resin is dissolved in a ketone solvent, a neutralizing agent is added to ionize the carboxyl groups of the polyester resin,
Next, water is added, and then the ketone solvent is distilled off to invert the phase into an aqueous system, which is a self-dispersion type aqueous polyester resin, (2) (a) a diol component represented by the following formula,

[0009]

[Chemical 4]

(In the formula, R represents an ethylene or propylene group, x and y are each an integer of 1 or more, and x +
The average value of y is 2 to 7. ) (B) one or more alcohol components selected from the group consisting of aliphatic diols and (c) trihydric or higher polyhydric alcohols; and (d) divalent carboxylic acids, their acid anhydrides or their lower alkyl esters. And (e) polycarboxylic acid having a valence of 3 or more, an acid anhydride thereof, or one or more acid components selected from the group consisting of lower alkyl esters thereof is copolycondensed to obtain an acid value of 3 to 70 KOHmg / g of the polyester resin is dissolved in a ketone solvent, a neutralizing agent is added to ionize the carboxyl groups of the polyester resin,
Next, after adding water, the ketone solvent is distilled off to invert the phase to an aqueous system, and a method for producing a self-dispersible aqueous polyester resin, and (3) as a component of a surface treatment agent for paper as described above. The present invention relates to a surface treatment agent composition for paper, which comprises the self-dispersible water-based polyester resin described in 1).

The polyester resin used for producing the self-dispersible water-based polyester resin of the present invention is produced by using an alcohol component and an acid component such as carboxylic acid, its acid anhydride or its lower alkyl ester as a raw material monomer. As the alcohol component, the dihydric alcohols (a) and (b) described below and the polyhydric alcohol having a valence of 3 or more described in (c) are used. The divalent carboxylic acid of (d) and the polyvalent carboxylic acid of trivalent or more of (e) are used. Examples of the diol of (a) include diols represented by the following formula,

[0012]

[Chemical 5]

(Wherein R represents an ethylene or propylene group, x and y are each an integer of 1 or more, and x +
The average value of y is 2 to 7. ) Specifically, for example, polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.3) -2,2-bis (4-hydroxyphenyl)
Propane, polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0) -polyoxyethylene (2.0)-
Examples thereof include alkylene oxide adducts of bisphenol A such as 2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane.

Examples of the aliphatic diol (b) include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,
3-propylene glycol, 1,4-butanediol,
Neopentyl glycol, 1,4-butenediol,
Examples include 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like.

Examples of the trihydric or higher polyhydric alcohol (c) include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4, -butanetriol, 1,2,5,-
Pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4, -butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene and the like can be mentioned. In the present invention, at least one selected from the group consisting of the alcohol components (a) to (c) is used, and the diol component of (a) is 40% of all alcohol components.
The diol component (b) is used in an amount of less than 20 mol% in all alcohol components. The trihydric or higher alcohols in (c) are used in an amount of less than 60 mol% in all alcohol components. If it is 60 mol% or more, it becomes insoluble in a ketone solvent and phase inversion becomes difficult.

Examples of the divalent carboxylic acid (d), its acid anhydride or its lower alkyl ester include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, Succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid, n
-Octenyl succinic acid, n-octyl succinic acid, isooctenyl succinic acid, isooctyl succinic acid and the like, and anhydrides or lower alkyl esters of these acids and the like.

Examples of the trivalent or higher carboxylic acid (e), its acid anhydride or its lower alkyl ester include, for example, 1,2,4-benzenetricarboxylic acid, 2,5,7,
-Naphthalene tricarboxylic acid, 1,2,4, -naphthalene tricarboxylic acid, 1,2,4, -butane tricarboxylic acid, 1,2,5, -hexane tricarboxylic acid, 1,3-
Dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4, -cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,
Examples include 7,8, -octanetetracarboxylic acid, pyromellitic acid, empol trimer acid, and the like, and anhydrides or lower alkyl esters of these acids. In the present invention, one or more kinds selected from the group consisting of the above-mentioned (d) to (e) acid components are used, and the divalent carboxylic acid or the like of (d) is used in an amount of 40 to 100 mol% based on the total acid components. The
(E) Trivalent or higher polycarboxylic acids are 6 out of all acid components.
Used at less than 0 mol%. When it exceeds 60 mol%,
It becomes insoluble in ketone solvents and phase inversion becomes difficult. (C)
When the polyhydric alcohol having a valence of 3 or more and the polycarboxylic acid derivative having a valence of 3 or more of (e) are used in combination,
Used in less than mol%. If it is 30 mol% or more, it becomes insoluble in a ketone solvent and phase inversion becomes difficult. A monohydric alcohol and a monovalent carboxylic acid derivative can be used in an amount of 10 mol% or less for the purpose of controlling the end groups and controlling the molecular weight.

The polyester resin used in the present invention is
It is obtained by copolycondensing the above raw material monomers. The method of copolycondensation is not particularly limited and a known method may be used. The polyester resin used in the present invention preferably has an acid value (according to JIS K0070) of 3 to 70 KOHmg / g, more preferably 5 to 60 KOHmg / g. 3KOHm
If it is less than g / g, a stable self-dispersing aqueous polyester resin dispersion cannot be obtained. On the other hand, the acid value is 70 KOHmg / g
When it exceeds, the water resistance after coating on the coating film or paper is deteriorated, which is not preferable. Here, the acid value of the resin can be adjusted by changing the composition ratio of the acid component and the alcohol component, using a carboxylic acid ester, or blocking the acid value with a monohydric alcohol. The polyester resin used in the present invention preferably has a glass transition temperature of 25 ° C. or higher measured by DSC (differential scanning calorimeter).
If the temperature is lower than 25 ° C., if the paper is phase-inverted to a water system and applied to the paper, and then the paper is placed under high temperature and high humidity (35 ° C., 80% RH), the polyester resin may be copied, which is not preferable. Here, the glass transition temperature of the resin can be adjusted by changing the composition ratio of the constituent monomers.

The polyester resin used in the present invention is
The number average molecular weight is preferably 2,500 to 70,000. If it is less than 2,500, the physical properties of the coating film formed using the resin after phase inversion will be poor, and if it exceeds 70,000, the viscosity will be high in the phase inversion process, which is not preferable.

In the method for producing a self-dispersible water-based polyester resin of the present invention, a polyester resin having the above-mentioned predetermined acid value is dissolved in a ketone solvent and a neutralizing agent is added to ionize the carboxyl groups of the polyester resin. Then, after water is added, the ketone solvent is distilled off to invert the phase to an aqueous system. More specifically, for example, a reactor equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen gas inlet pipe is prepared, and a polyester resin having a predetermined acid value dissolved in a ketone solvent is used. It can be obtained by adding a solvating agent or the like to ionize the carboxyl group (unnecessary if it is already ionized), then adding water, distilling off the ketone solvent and inversion to the water system. The dissolution in the ketone solvent and the addition of the neutralizing agent are usually performed at a temperature not higher than the boiling point of the ketone solvent, and the water used here includes, for example, ion-exchanged water.

As the ketone solvent used at this time, for example, acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, methyl isobutyl ketone,
Methyl isopropyl ketone and the like, and preferably,
It is methyl ethyl ketone. Examples of the neutralizing agent include aqueous ammonia, an aqueous alkaline solution such as sodium hydroxide, allylamine, isopropylamine, diisopropylamine, ethylamine, diethylamine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3-diethylamino. Propylamine, tri-n-octylamine, t-butylamine, sec-butylamine, propylamine, methylaminopropylamine, dimethylaminopropylamine, n-propanolamine, butanolamine, 2
-Amino-4-pentanol, 2-amino-3-hexanol, 5-amino-4-octanol, 3-amino-
3-methyl-2-butanol, monoethanolamine,
Isopropanolamine, neopentanolamine, diglycolamine, ethylenediamine, 1,3-diaminopropane, 1,2-diaminopropane, 1,6-diaminohexane, 1,9-diaminononane, 1,12-diaminododecane, dimer Body fatty acid diamine, 2, 2, 4,
-Trimethylhexamethylenediamine, 2,4,4,-
Examples thereof include amines such as trimethylhexamethylenediamine, hexamethylenediamine, N-aminoethylpiperazine, N-aminopropylpiperazine, N-aminopropyldipiperidipropane and piperazine.
The amount of these neutralizing agents used may be at least an amount capable of neutralizing the acid value of the polyester resin.

The number average molecular weight of the self-dispersible aqueous polyester resin thus obtained is usually 2,500 to 7.
It is 10,000. This corresponds to the molecular weight of the polyester resin used for phase inversion. The particle size of the obtained self-dispersible water-based polyester resin is preferably 0.001 to 10.0 μm, more preferably 0.1.
001 to 1.0 μm. If it exceeds 10.0 μm, the dispersion stability becomes poor, which is not preferable.

The self-dispersible water-based polyester resin of the present invention is impregnated into woven fabric, non-woven fabric, paper, wood, leather, rubber, plastic, metal, glass, concrete, gypsum, ceramic siding material, ALC plate, or the like. By applying to these surfaces, surface coating, adhesion,
In addition to the effect of improving properties such as texture improvement, filming liquid for cathode ray tube, bar code label (P
It can be advantageously used in fields where coating agents for OS labels), civil engineering and construction related matters, inks, paints, powder emulsions, and rubber latex and resin emulsions are generally applied. Further, since it is a polymeric surfactant structurally, it has a wide range of uses as a general surfactant in addition to its use as a binder. For example, it is used as a protective colloid for emulsion polymerization, a dispersant such as coal and calcium carbonate, a coagulant, a binder, a surface modifier and the like.

Among these applications, it has been found to be particularly effective when the self-dispersible water-based polyester resin is used as a surface treatment agent for paper. That is, by applying the self-dispersible water-based polyester resin of the present invention to the surface of a thermal transfer paper (transfer paper) used in a plain paper copying machine, a plain paper printer, etc., the fixing strength between the toner or the thermal transfer ink and the paper can be improved. It will be possible to improve.

Further, the method of treating the surface of paper using the surface treating agent composition for paper of the present invention is, for example, using a blade coater or the like for the base paper, the coating temperature, the coating pressure, the coating amount, the coating. The coating speed may be adjusted appropriately, and then the coating may be dried using a dryer or the like.

[0026]

EXAMPLES The present invention will be specifically described below with reference to examples, but it goes without saying that the present invention is not limited thereto. The following "parts" and "%" are based on weight unless otherwise specified.

Production Example 1 (Production of Polyester Resin) Polyoxypropylene (2.2) -2,2-bis (4-)
(Hydroxyphenyl) propane (1050 g), fumaric acid (340 g), and hydroquinone (1.5 g) were placed in a glass 2-liter four-necked flask, and a thermometer, a stainless stir bar, a downflow condenser, and a nitrogen inlet tube were attached to the flask.
In a mantle heater, the reaction was carried out while stirring at 210 ° C. under a nitrogen stream. Degree of polymerization is ASTM E28-5
Followed from the softening point of 1T, the softening point is 100 ℃
The reaction was terminated when reached. The obtained resin was a pale yellow solid, and the glass transition temperature by DSC was 61.5 ° C. The acid value (measured by the method according to JIS K0070) of the resin was 21.5 KOHmg / g, and the number average molecular weight (polystyrene conversion by gel permeation chromatography) was 3,500. The polyester resin is referred to as polyester resin A.

Production Example 2 (Production of Polyester Resin) Polyoxypropylene (2.2) -2,2-bis (4-)
Hydroxyphenyl) propane 716 g, 1,4-butanediol 12 g, trimethylolpropane 72 g, fumaric acid 278 g, isododecenylsuccinic acid 127 g,
And 1.5 g of hydroquinone were reacted by the same apparatus and procedure as in Production Example 1, and the reaction was terminated when the softening point reached 120 ° C. The obtained resin was a pale yellow solid, and the glass transition temperature by DSC was 65.0 ° C. The acid value of the resin was 12.0 KOHmg / g and the number average molecular weight was 4,000. The polyester resin is referred to as polyester resin B.

Example 1 300 parts of methyl ethyl ketone was charged into a reactor equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen introducing tube, and the polyester resin A obtained in Production Example 1 was added and dissolved at room temperature. Let 2.7 parts of triethylamine was added to the above polyester solution for neutralization, followed by deionized water 1
After adding 000 parts, under reduced pressure with stirring number of 250 rpm,
Methyl ethyl ketone was distilled off at 50 ° C. or lower to obtain the self-dispersible water-based polyester resin (1) of the present invention. The average particle size was 0.9 μm. Particle size is COULTER EL
COULTER MODEL made by ECTRONICS
It was measured at N4.

Example 2 Using 50 parts of the polyester resin B obtained in Production Example 2,
Using 300 parts of methyl ethyl ketone, 10 parts of a 10% aqueous sodium hydroxide solution for neutralization, and 1,000 parts of ion-exchanged water, the same procedure as in Example 1 was carried out to carry out the self-dispersion type aqueous polyester resin (2) of the present invention. Got The average particle size was 0.5 μm.

Test Example A base paper was prepared according to the procedure of (1) below, and a surface treating agent composition for paper was applied to the base paper according to the procedure of (2) below to prepare a transfer paper for neutral electrophotography. The toner fixing test was conducted with a commercially available copying machine in the same manner as (3). (1) Preparation of base paper A base paper was prepared using the following raw materials in the indicated amounts. Pulp: LBKP (Canadian Standard Freeness) 400 ml Filler: Light calcium carbonate (commercially available) adjusted to 8% calcium carbonate in the paper Fixing agent: Cationic starch (commercially available), solid type relative to pulp weight Min 0.5% Size: Ketene dimer size (Cyrene S9
4, made by Kao), solid content 0.03% relative to pulp weight Yield improver: cationic polyacrylamide polymer (commercially available product), solid content 0.02% relative to pulp weight Pulp, filler, fixing agent, sizing agent, and retention aid were used in this order. The pH at the time of fixing was 8.0. Papermaking was done using a tappy square handmade machine, pressing was performed at 3.5 kgw / cm ² for 2 minutes, drying was performed at 100 ° C. for 40 seconds with a rotary dryer, and calender linear pressure was 30 kg / cm ² . A base paper having an amount of 70 g / m ² was prepared. The basis weight of the base paper thus obtained is 70 g /
It was m ² . (2) Coating Using the base paper obtained above, using a blade coater, coating temperature 70 ° C., coating pressure 0.3 to 0.4 kg / c
The surface treatment agent composition for paper was applied at m ² and a coating speed of 100 m / min so that the surface treatment agent for paper shown in Table 1 had the coating amount in the table. Then, using a rotary dryer, 10
It was dried at 5 ° C. for 40 seconds to produce a neutral electrophotographic transfer paper (coated paper to). Here, for the purpose of comparison, a paper surface treating agent composition comprising oxidized starch was used as the coated paper. The self-dispersible water-based polyester resins (1) and (2) obtained in the above examples were used for coated papers.

[0032]

[Table 1]

(3) Fixing test In a commercially available electrophotographic copying machine, the rotation speed of the fixing roller is set to 2
55 mm / sec, the temperature of the heat roller in the fixing device was made variable, and the oil coating device was removed. Paper coated with only the oxidized starch (coated paper), self-dispersing water-based polyester resin in addition to the oxidized starch were used. Coated paper (coated paper ~
), The image was printed using genuine toner. The fixing temperature was controlled to 100 ° C to 220 ° C, and the fixing property and offset property of the image were evaluated. The results are shown in Table 2.

[0034]

[Table 2]

The minimum fixing temperature here is 15 m at the bottom.
Place a load of 500g on an mx 7.5 mm sand eraser,
The image fixed through the fixing device is rubbed 5 times back and forth, and before and after rubbing, the optical reflection density is measured by a reflection densitometer manufactured by Macbeth Co., and when the fixing rate exceeds 70% according to the definition below, Refers to temperature. Fixing rate = image density after rubbing / image density before rubbing × 10
0

As is clear from Table 2, the paper coated with the self-dispersible water-based polyester resin of the present invention can lower the minimum fixing temperature for a copying machine as compared with the paper not coated. Furthermore, coat paper under high temperature and high humidity (3
Even when left for 1 day under the conditions of 5 ° C. and 85% RH, the paper did not bend.

[0037]

According to the present invention, a polyester resin having a predetermined acid value is ionized in a ketone-based solvent, the solvent is distilled off, and the phase is converted to an aqueous system. A dispersion type water-based polyester resin can be obtained. Further, by using the self-dispersible water-based polyester resin, it is possible to provide a paper surface treatment composition capable of improving low-temperature fixability of toner.

Claims (5)

[Claims] 1. A diol component represented by the following formula: (In the formula, R represents an ethylene or propylene group, and x, y
Are each an integer of 1 or more, and the average value of x + y is 2 to 7. ) (B) one or more alcohol components selected from the group consisting of aliphatic diols and (c) trihydric or higher polyhydric alcohols; and (d) divalent carboxylic acids, their acid anhydrides or their lower alkyl esters. And (e) polycarboxylic acid having a valence of 3 or more, an acid anhydride thereof, or one or more acid components selected from the group consisting of lower alkyl esters thereof is copolycondensed to obtain an acid value of 3 to 70 KOHmg / g of the polyester resin is dissolved in a ketone solvent, a neutralizing agent is added to ionize the carboxyl groups of the polyester resin,
Then, water is added, and then the ketone solvent is distilled off to invert the phase to an aqueous system, which is a self-dispersion type aqueous polyester resin. 2. The polyester resin used for phase inversion is 25
The self-dispersible water-based polyester resin according to claim 1, which has a glass transition temperature of not less than ° C. 3. A diol component represented by the following formula: (In the formula, R represents an ethylene or propylene group, and x, y
Are each an integer of 1 or more, and the average value of x + y is 2 to 7. ) (B) one or more alcohol components selected from the group consisting of aliphatic diols and (c) trihydric or higher polyhydric alcohols; and (d) divalent carboxylic acids, their acid anhydrides or their lower alkyl esters. And (e) polycarboxylic acid having a valence of 3 or more, an acid anhydride thereof, or one or more acid components selected from the group consisting of lower alkyl esters thereof is copolycondensed to obtain an acid value of 3 to 70 KOHmg / g of the polyester resin is dissolved in a ketone solvent, a neutralizing agent is added to ionize the carboxyl groups of the polyester resin,
Next, a method for producing a self-dispersible water-based polyester resin, which comprises adding water and then distilling off a ketone solvent to invert the phase to an aqueous system. 4. The polyester resin used for phase inversion is 25
The method for producing a self-dispersible water-based polyester resin according to claim 1, which has a glass transition temperature of not less than ° C. 5. A surface treating agent composition for paper, comprising the self-dispersible water-based polyester resin according to claim 1 as a component of the surface treating agent for paper.