JPH0246050B2 - JURISURUPPONSANKIGANJUHORIESUTERUJUSHINOSEIZOHO - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyester resin having excellent low-temperature curability, and this object is achieved by introducing free sulfonic acid groups into the polyester resin by a method completely different from conventional methods. Compared to resins containing free sulfonic acid groups, polyester resins containing free sulfonic acid groups can be mixed with, for example, melamine compounds to improve various properties such as coating hardness, solvent resistance, and chemical resistance, especially for paints. It is useful for resin compositions aimed at improving performance. That is, in this composition, since the free sulfonic acid group-containing polyester resin also serves as a catalyst for the crosslinking reaction with the melamine compound, the baking temperature of the paint can be low, and moreover, it can be used with strong acids such as mineral acids and P-toluenesulfonic acid. Since it does not require any catalyst, there is no fear of corrosion when applied in the metal field, and it is extremely useful industrially. As a method for introducing free sulfonic acid groups into polyester resins, it has been proposed to create a reaction by simultaneously introducing a polybasic acid containing the groups during condensation. However, in reality, the presence of free sulfonic acid groups may cause the polyhydric alcohol component to decompose, and in order to prevent this, strict manufacturing conditions are imposed, making it impossible to avoid industrial disadvantages. Also, a method of post-sulfonation of polyester resin has been considered, but even with this method, the resin itself decomposes and similar measures are required, and a two-step operation of condensation and sulfonation must be performed. Moreover, in either method, the resin produced is colored, and a satisfactory resin is not necessarily obtained. However, the present inventor has conducted extensive research to obtain a polyester resin containing free sulfonic acid groups that exhibits such unique performance using an advantageous method different from conventional methods. The inventors have discovered that it is possible to introduce free sulfonic acid groups into polyester resins, and have achieved the above object. The sultone compound used in the present method is completely different from conventional sulfonating agents and does not decompose the raw material polyester polyol at all, so that free sulfonic acid groups can be efficiently introduced into the resin. The free sulfonic acid group-containing polyester resin targeted in the present invention has a free sulfonic acid group content per 1 g of resin.
0.05 mmol (hereinafter this content is abbreviated as mmol/g) or more, preferably 0.5 to 10 mmol/g, and a hydroxyl value of 15 to 145 KOHmg per 1 g of resin (hereinafter this content is simply abbreviated as KOHmg/g), preferably
It is 30-100 KOHmg/g. Such a specific composition is expected to provide an efficient autocatalytic effect in the crosslinking reaction with the melamine compound and improve the physical properties of the coating film based on this. The polyester polyol used in the present invention is prepared by condensing a polybasic acid and a polyhydric alcohol by a known method. Typical examples of polybasic acids are terephthalic acid,
Saturated acids such as isophthalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and their lower alkyl esters or anhydrides, maleic acid,
Examples include unsaturated acids such as fumaric acid, itaconic acid, citraconic acid, and lower alkyl esters or anhydrides thereof. Ethylene glycol is a polyhydric alcohol,
1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, cyclohexanedimethanol, penta Examples include erythritol and polytetramethylene ether glycol. The polyester polyol can be produced by condensation using a known method as described above, but typically it can be obtained by the following method. That is,
The polyhydric alcohol was charged at a ratio of 1.1 to 2 moles per mole of the polybasic acid together with a catalyst and a stabilizer into a reaction vessel equipped with a stirrer, a total condenser, a partial condenser, and a torque meter, and the temperature was raised to 230 °C. The condensation reaction may be carried out at ~270°C. The polyester polyol has a hydroxyl value of 15 to 170 KOHmg/g, preferably 30 to 170 KOHmg/g.
Must be 150KOHmg/g. A portion of the hydroxyl groups of the polyester polyol having such a hydroxyl value is reacted with a sultone compound to obtain the desired free sulfonic acid group-containing polyester resin of the present invention. The sultone compound referred to in the present invention has -
It refers to an intramolecular ester of oxysulfonic acid having a bonding moiety of SO ₂ -O-, and a four- to six-membered ring is usually used. Specifically, such compounds include:
Examples include 1,2-ethane sultone, 1,3-propane sultone, 1,3-butane sultone, 1,4-butane sultone, naphtha sultone, etc., but the present invention is not limited thereto. The reaction between the polyester polyol and the sultone compound is carried out at a temperature of 20-250°C, preferably 70-150°C. At temperatures below 20°C, the reaction hardly progresses, making it difficult to obtain the desired resin, or even if obtained, the fluidity of the polyester resin is lost, making it difficult to use. Furthermore, temperatures above 250°C are undesirable because gelation may occur. The reaction time is 10 to 60 minutes, and the reaction proceeds almost quantitatively. Although the reaction may be carried out in the absence of a solvent, any solvent may be used as required. By this means, a polyester resin having a free sulfonic acid group content of 0.05 mmol/g or more and a hydroxyl value of 15 to 145 KOH mg/g can be obtained. If the content of free sulfonic acid groups is 0.05 mmol/g or less, the effect of low-temperature curability cannot be obtained, and other catalysts are required for curing. There is no particular upper limit for the content of free sulfonic acid groups, but when used in paints, etc., water resistance is often required, so in that case it should be 1.0 mmol/
It is preferable to use less than g. In addition, the hydroxyl value
If it is less than 15KOHmg/g, the crosslinking density with the melamine compound will be low, and the physical properties of the coating film such as coating film hardness will not be fully exhibited.On the other hand, if it is more than 145KOHmg/g, the polyester resin will have a low molecular weight and the coating film performance will also deteriorate. It tends to be undesirable. As mentioned above, the free sulfonic acid group-containing polyester resin obtained by the method of the present invention is characterized in that it can be catalyzed or baked at low temperatures when a crosslinking agent such as a melamine compound is added. That is, sufficient coating strength can be obtained by heat treatment at about 70 to 90°C, and considering that conventionally such low-temperature treatment required a strong acid catalyst, the excellent performance of the resin of the present invention is confirmed. The above-mentioned melamine compounds include melamine and its derivatives, such as hexamethylol melamine, in which most of the hydrogens in the free amino groups are replaced with methylol groups, and alkoxymethylmelamine having 1 to 6 carbon atoms, i.e., the hexamethylol melamine. Most of the methylol groups of melamine are alkoxylated, such as hexamethoxymethyl melamine,
Examples include hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentyloxymethylmelamine, hexahexacyoxymethylmelamine, and a mixed ether melamine that is a combination of at least two of these. Alkoxymethylmelamine, for example, in the case of hexamethoxymethylmelamine, is obtained by etherifying hexamethylolmelamine obtained by reacting melamine and formaldehyde with methanol, and most of it becomes methoxymethyl groups. Other effective crosslinking agents include amine compounds such as urea compounds. Further, the free sulfonic acid group-containing polyester resin of the present invention may be used with any auxiliary agent depending on its use, and various pigments and other additives such as leveling agents may be added as necessary. can. Pigments include calcium carbonate, kaolin, clay, alumina, titanium oxide, talc, lithopone,
Examples include mica, gypsum, silica, quinacridone red, red red, aniline black, manganese blue, carbon black, cyanine blue, phthalocyanine blue, iron black, ultramarine blue, chrome yellow, and chrome green. Examples of the leveling agent include silicon compounds, cellulose acetate butyrate, and other known commercially available leveling agents. When used, it can be used without a solvent, but it can be used in a solvent such as benzene, toluene, xylene, methyl ethyl ketone, cyclohexanone, isophorone, methyl isobutyl ketone, cellosolve acetate, butyl cellosolve acetate, or water at a concentration of 10 to 60% by weight. It is often used as follows. As mentioned above, the free sulfonic acid group-containing polyester resin advantageously obtained by the method of the present invention is mainly useful in the fields of paints and adhesives by taking advantage of its characteristics, but it is of course also highly effective in other physical properties. Because of its excellent properties, it can be used in a wide range of fields such as textile glues, paper processing agents, fiber processing agents, films, fibers, and binders. Hereinafter, the method of the present invention will be explained in more detail with reference to Examples. Example 1 400 g (2.41 mol) of isophthalic acid, 144 g (0.99 mol) adipic acid, 183 g (1.76 mol) neopentyl glycol, and 183 g diethylene glycol (183 g (1.76 mol) 1.72 mol) Trimethylolpropane 98g (0.92 mol) and zinc acetate dihydrate 0.4g were charged, and heated to 190~ while blowing nitrogen gas.
Condensation was carried out at 230° C. for 5 hours to obtain a polyester polyol having an acid value of 10 KOH mg/g and a hydroxyl value of 130 KOH mg/g. Next, 500 g of this saturated polyester was placed in one flask, 30 g (0.25 mol) of 1,3-propane sultone was added at a temperature of 120°C, and the temperature was further increased to 150°C.
Heated to ℃ and reacted for 1 hour to determine free sulfonic acid group content, 0.47 mmol/g, and hydroxyl value.
A sulfonic acid group-containing polyester resin containing 105 KOHmg/g was obtained. In order to confirm that the resin contains free sulfonic acid groups, under the conditions described below,
It was investigated using high performance liquid chromatography. The chart is shown in Figure 1. Next, prepare a 40% by weight xylene solution of the resin,
Furthermore, Cymeru 303 (melamine resin manufactured by Mitsui Toatsu Co., Ltd.) as a crosslinking agent and other additives were added in the amounts shown in Table 1 and thoroughly dispersed with a paint conditioner containing glass beads of 1 mm in diameter to form a paint. The paint was baked on a 0.5 mm thick polished mild steel plate at various temperatures shown in Table 1, and the hardenability of the paint film, salt spray resistance, and water resistance at 20°C were measured. Analysis of resin by liquid chromatography A 0.1% by weight tetrahydrophthalic acid solution of the produced polyester resin containing free sulfonic acid groups was developed using high performance liquid chromatography (Figure 1). Chart speed 10cm/min, deployment time 20
It's a minute. For confirmation, a sample was prepared by blending the polyester polyol used in Example 1 and the sultone compound without reacting, and the sample was developed in the same manner as above. (Figure 2). In FIG. 1, the peak of the sultone compound (the peak around the development time of 18 minutes in FIG. 2) has disappeared, which suggests that a free sulfonic acid group-containing polyester resin is produced. Comparative Example 1 Performance was evaluated under all the same conditions as in Example 1 except that a polyester resin containing no free sulfonic acid groups (acid value: 10 KOH mg/g, hydroxyl value: 130 KOH mg/g) was used. Comparative Example 2 Polyester polyol containing no free sulfonic acid groups produced in Example 1 (acid value
10KOHmg/g, hydroxyl value 130KOHmg/g) 300g
A 60% by weight aqueous solution containing 26 g (0.15 mol) of P-toluenesulfonic acid was added to a 40% by weight xylene solution containing P-toluenesulfonic acid, and a paint was prepared using the same method as in Example 1.
Performance was evaluated under the same conditions. The results of Comparative Examples 1 and 2 are also shown in Table 1. Example 2 In Example 1, the charged compounds were 400 g (2.41 mol) of terephthalic acid and 164 g of isophthalic acid.
(0.99 mol), ethylene glycol 107 g (1.73 mol), 1.6-hexanediol 208 g (1.76 mol),
A polyester polyol with an acid value of 12 KOH mg/g and a hydroxyl value of KOH mg/g was produced in the same manner except that 75 g (0.55 mol) of pentaerythritol was used.
Below 1,3-propane sultone 30g (0.25mol)
Polyester resin containing free sulfonic acid groups modified with (free sulfonic acid group content 0.47 mmol/
g, hydroxyl value 108 KOHmg/g). A paint was prepared using the same method as in Example 1, and its performance was evaluated under the same conditions. The results are shown in Table 2. Example 3 In Example 1, the charge was changed to maleic anhydride 97
g (0.99 mol), isophthalic acid 400 g (2.41 mol)
A polyester polyol having an acid value of 8 KOH mg/g and a hydroxyl value of 129 KOH mg/g was produced in the same manner except that 109 g (1.76 mol) of ethylene glycol, 183 g (1.73 mol) of diethylene glycol, and 98 g (0.73 mol) of trimethylolpropane were used. Furthermore, 500 g of this resin was modified with 27 g (0.2 mol) of 1,4-butane sultone to produce a polyester resin containing free sulfonic acid groups with a free sulfonic acid group content of 0.4 mmol/g and a hydroxyl value of 110 KOH mg/g. 10S instead of the melamine compound used in Example 1
A paint was produced using the same process as in Example 1, except that -60 (urea resin manufactured by Mitsui Toatsu Co., Ltd.) was used as a crosslinking agent, and its performance was evaluated under the same conditions. The results are shown in Table 2. Comparative Example 3 300 g of the polyester polyol produced in Example 1 was reacted with 24 g (0.2 mol) of acidic sodium sulfite to produce a polyester resin having a sulfonic acid group (hydroxyl value 110 KOH mg/g), and the same formulation as in Example 1 was used. A paint was prepared and its performance was evaluated under the same conditions. The results of Comparative Example 3 are shown in Table 2.

【table】

【table】

[Table] Performance was evaluated using the following method. Curability: After examining the presence or absence of tack when a pressure of 20 g/cm ² was applied from above the coating, the pencil marks were erased with an eraser based on JIS K5401, and the hardness value was determined when there were no scratches. . Salt spray: Carve a cross-shaped scratch mark that reaches the substrate with a single-edged razor on the painted surface, and use JIS
A salt spray test using Z2371 was conducted for 24 hours to check for corrosion, blistering, and peeling. Water resistance: The painted board was immersed in water at 50±2°C for 24 hours, and changes in the painted surface were observed.

[Brief explanation of the drawing]

FIG. 1 shows a chart of a polyester containing free sulfonic acid groups, and FIG. 2 shows a chart of a blend product of a polyester polyol and a sultone compound (1,3-propane sultone). In each figure, the peak around the retention time of about 12 minutes is the peak of the free sulfonic acid group-containing polyester resin or polyester polyol. Moreover, the peak at a retention time of about 18 minutes in FIG. 2 is due to the sultone compound.

Claims (1)

[Claims] 1. Characterized by reacting a sultone compound with a polyester polyol, the content of free sulfonic acid groups is 0.05 mmol or more per 1 g of polyester resin, and the hydroxyl value is 15 per 1 g of polyester resin.
A method for producing a polyester resin containing ~145 KOHmg of free sulfonic acid groups.