JPH0440392B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is used as a resin vehicle for a coating composition useful as a top coat for automobile bodies, etc.
The present invention relates to a saturated alicyclic acid-modified polyester resin (hereinafter referred to as acid-controlled modified polyester resin) composition in which the type of carboxyl group that exhibits a resin acid value is controlled, and a method for producing the same. In recent years, oil-free polyester/aminoaldehyde resin-based paints have been attracting attention as top coats for automobile bodies and the like have been required to have good weather resistance, coating film properties, and interlayer adhesion. These polyesters generally have a resin acid value within the range of 1 to 20. However, such paints have been considered difficult to apply to automobile bodies, etc., due to the fact that they are difficult to apply due to the tendency of repelling, the gloss of the paint film surface is poor, and the compatibility with amito resin is poor. . Therefore, in an attempt to maintain the advantages of conventional oil-free polyester/amino resin paints while improving the drawbacks such as difficulty in painting, dullness of the paint film, and poor compatibility with amino resins, we developed an oil-free polyester/amino resin paint. Proposals have been made to use a large amount of saturated alicyclic polybasic acid as the acid component of polyel, or to use aromatic polybasic acid together with saturated alicyclic polybasic acid (Japanese Patent Laid-Open No. 56-20068). ). However, even if such a saturated alicyclic acid-modified polyester resin (hereinafter referred to as modified polyester resin) is used,
Occurrence of repellency, dullness, and compatibility with amito resins are only improved to a certain extent, and it is difficult to say that these shortcomings can be overcome. Moreover, there is a new problem of insufficient curability due to saturated alicyclic modification. In addition, it was extremely difficult to put it into practical use. Therefore, the purpose of the present invention is to have the advantages of conventional oil-free polyester/amino resin paints with a resin acid value of 20 or less, improve the lack of curability newly caused by using a modified polyester resin, and Another object of the present invention is to provide a polyester resin composition useful as a resin vehicle for a coating composition that has excellent gloss and weather resistance, and a method for producing the same. According to the research conducted by the present inventors, incorporating a saturated alicyclic polybasic acid as the acid component of polyester resin is an extremely effective means for improving the heat resistance of a coating film, but it has been found that melamine resin When creating a cured coating film, the initial gloss is low and the curability is poor.When aromatic polybasic acids are added, gloss and curability are excellent, but it is difficult to obtain a high degree of weather resistance. thing,
Even though both saturated alicyclic polybasic acids and aromatic polybasic acids are used to obtain a resin with excellent weather resistance, gloss, and hardenability, the saturated alicyclic polybasic acids have low reactivity, and aromatic Acids are more quickly incorporated into polyester chains, and therefore the carboxyl groups that develop the resin acid value are occupied by alicyclic carboxylic acids that have a low degree of dissociation in non-aqueous solvents, resulting in weak acidity and hardening. It turned out that there was no hope of improving the properties and weather resistance. Therefore, in order to achieve the above object of the invention, it is natural to use a modified polyester resin to improve weather resistance, and to control the types of carboxyl groups that express resin acid value, at least some of them have gloss, hardenability, etc. It is necessary to use aromatic carboxylic acids that are effective for improvement. The present invention was completed based on this knowledge. That is, according to the present invention, in a state where (A) a saturated alicyclic polybasic acid and (B) a resin acid value is expressed, the half-equivalent point potential in non-aqueous potential difference is
A modified polyester resin comprising an acid component consisting of an aromatic polybasic acid exhibiting 350 mV or more, and (C) other polybasic acids and/or -basic acids present as desired, and a polyhydric alcohol component,
The resin acid value is 1 to 20, (A) polybasic acid accounts for 10 to 80 mol% of the total acid component, and 10 to 100 mol% (B) of the carboxyl group that expresses the resin acid value is large. Acid-controlled modified polyester resin compositions that are based on basic acids are provided. Therefore, in the resin composition of the present invention, the acid component is (A) a mol of saturated alicyclic polybasic acid, and (B) the half-equivalent point potential in a non-aqueous potential difference setting in a state where the resin acid value is expressed. b mol of aromatic polybasic acid exhibiting -350 mV or more, (C) Other polybasic acids and/or -basic acids c
mol, (a+b+c=1.0 mol, 10≦a/a+b+c ×100≦80 mol%, 0≦c mol), a mol of the polybasic acid of (A), a mol of the polybasic acid of (B) ( b- _b1 ) moles, and C moles of the polybasic acid and/or -basic acid of (C), where _b1 mole is equal to or less than b mole, and is determined by the following formula ( B) Post-injection molar amount b ₁ = x/100 x N x W/56100 x 1/f x 1/1-P/10
0 Here, N is the resin acid value (the number of KOH mg required to neutralize 1 g of resin solid content), W is the weight of the polyester resin, f is the number of functional groups in (B), and P is the reaction rate (%) of (B) at the time of post-addition. X is the mol% of (B) in the carboxyl group that expresses the resin acid value, and is determined within the range of 10≦x≦100.The resin acid value M (where M=N( 1-x/100)), and adding the polyester prepolymer and ₁ mol of the polybasic acid b (B) to a resin acid value N
The resin is advantageously produced by the process of the present invention, in which the resin is esterified by a step of esterification and then varnished. In the specification of this application, the term "carboxyl group that develops resin oxidation" means "the carboxyl group that develops the acid value of polyester resin", and the term "in a state that develops the acid value of the resin" shall mean "carboxylic acid used alone as an acid component to form a polyester resin". Unless otherwise specified, the term polyester resin includes not only oil-free polyester resins but also alkyd resins. Group polyhydrochloric acid is incorporated into the polyester chain through an ester bond, and then a polybasic acid (B) with relatively high acidity is added afterwards, and the esterification reaction is continued to develop the resin acid value of the polyester resin. The aim is to have a specific proportion of the orboxyl groups occupied by the carboxyl groups of the polybasic acid (B).A typical example of the saturated alicyclic polybasic acid (A) in the above acid component is a cyclohexane ring. For example, 1,1-cyclohexanedicarboxylic acid, hexahydrophthalic acid, 1,3
Examples include cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, methylhexahydrophthalic acid (anhydride), hexahydrotrimellitic acid and its acid anhydride, hexahydro-2-methyltrimellitic acid and its acid anhydride, and the like. In the present invention, alicyclic polybasic acid alkyl esters can also be used as the alicyclic polybasic acids.
Examples of such alicyclic polybasic acid alkyl esters include dimethyl 1,4-cyclohexanedicarboxylate (hereinafter referred to as DMCD), tricyclo[ ^{5,21,02'6 ]} decane-3(4), 8(9) )-dicarboxylic acid dimethyl ester (hereinafter referred to as DD-100)
etc. can be mentioned. A polybasic acid that exhibits a half-equivalent point potential of −350 mV or more in wastewater potentiometric titration in a state where the resin acid value is expressed.
Representative examples of (B) include aromatic polybasic acids such as phthalic anhydride, isophthalic acid, terphthalic acid, trimellitic anhydride, and pyromellitic anhydride. Such a polybasic acid itself is usually obtained by non-aqueous potentiometric titration (indicator electrode: glass electrode; reference electrode: Ganba electrode; solvent: pyridine; analyte concentration 0.5 to 3.
%) (New Experimental Chemistry Course 1, Basic Operations [1], 182~
222 Mitsugu, published by Maruzen, Chemical Society of Japan)
When a TBAH (tetrabutylammonium hydroxide) titration curve is obtained, a curve showing multiple inflection points is obtained, but when it is incorporated into the polyester chain, at least one carboxyl group remains, so the inflection point also remains. A correspondingly reduced curve is shown. In this state, the half-equivalent point potential is still −
Any material exhibiting an acid strength of 350 mV or more can be advantageously used in the present invention. If there are two or more half-equivalent point potentials indicated by the curved points, the acid strength of the polyhydrochloric acid can be determined based on the largest half-equivalent point potential. As the acid component, (C) a polybasic acid and/or a -basic acid may be present as desired, but such acids include any polybasic acid commonly used as an acid component of polyester resins, such as Succinic acid (and its anhydrides), adipic acid,
Aliphatic or partially saturated alicyclic polybasic acids such as azelaic acid, sebacic acid, tetrahydrophthalic anhydride, maleic anhydride, fumaric acid, and itaconic acid are used. Furthermore, benzoin sprinkling pt-
Monocarboxylic acids such as butylbenzoic acid can also be added for the purpose of molecular weight adjustment. The polyhydric alcohol component reacted with these acid components is not special at all, and is appropriately selected from those conventionally used for forming polyesters, such as ethylene glycol, diethylene glycol,
Propylene glycol, neopentyl glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol,
1,4-butylene glycol, 1,6-hexanediol, 1,5-pentanediol, 2,5-
Hexanediol, trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, diglycerin, sorbitol, 1,4
- Cyclohexane dimethanol or the like may be used alone or in combination. As already mentioned, in the acid-controlled modified polyester resin of the present invention, 10 to 80 mol % of the total acid component is occupied by the above-mentioned saturated alicyclic polybasic acid (A), and the carboxyl which expresses the resin acid value is The type of carboxyl groups must be controlled, with 50 to 100 mol% of the groups being based on the polybasic acid of (B). This is because if the amount of saturated alicyclic polybasic acid is less than 10 mol% of the acid component, weather resistance will not improve, and if it exceeds 80 mol%, chemical resistance tends to deteriorate, which is undesirable. The amount of polybasic acid exhibiting the specific acid strength as the proportion of carboxyl groups expressing valence is 10
This is because if the amount is less than mol %, the luster and curability will be insufficient and the object of the present invention will not be achieved. In a particularly preferred embodiment, the polyester resin has a resin acid value of 1 to 20, and 50 to 100 mol% of the carboxyl groups expressing the resin acid value have a specific acid strength expressed by the half-equivalent point potential in the above-mentioned non-aqueous potentiometric titration. It should be derived from a polybasic acid exhibiting As mentioned above, in the method of the present invention, (A) a polybasic acid, (C) a polybasic acid and/or a basic acid, and in some cases, (B) a part of a polybasic acid and a polyhydric alcohol. First, a polyester prepolymer is made, and then all or the remaining (B) polybasic acid is
A polybasic acid is added later and esterification is continued to produce an acid-controlled modified polyester resin. The amount of (B) polybasic acid used in the first and second stage reactions is determined by the number of functional groups of (B) polybasic acid (f), the acid value of the resin (N), the weight of the resin (W), and the acid value of the resin. Desired mol% (x) of carboxyl groups derived from polybasic acid (B) in all carboxyl groups expressing and post-inclusion (B)
Although it varies depending on the reaction rate (P) of the polybasic acid, determine the amount of (B) to be added later (b ₁ mol) using the above formula, and then calculate the final amount of (B) from the difference between the final number of moles b of (B) and b ₁ mol. All you have to do is determine the amount of (B) used in one stage. In the above formula, the reaction rate %P of (B) at the time of post-addition is the reaction rate of the carboxyl groups of (B) used for the post-addition to determine the esterification reaction of the polybasic acid. This is a value indicating whether or not it is reliably incorporated into the polyester chain, for example, 50% or more for dibasic acids such as phthalic anhydride, and approximately 34% or more for tribasic acids such as trimellitic acid. The esterification reaction between a polybasic acid and a polyhydric alcohol is carried out by a conventional method and does not itself require any special operation. In a preferred specific example,
In the first stage of the present invention, the polyester prepolymer is reacted to a resin acid value of 0 to 10, and in the second stage of esterification, the reaction is carried out to a resin acid value of 1 to 20. The number average molecular weight of the resin may be within the range of ordinary polyester resins for paints. In this way, 10 to 80 mol% of the acid component is composed of saturated alicyclic polybasic acids, and 50 to 100 mol% of the carboxyl groups that express the resin acid value are An acid-controlled modified polyester resin based on the polybasic acid (B) having a half-equivalent point potential of -350 mV or more in titration is prepared, and this is diluted with a solvent to an appropriate viscosity according to a conventional method to form a varnish. The acid-controlled modified polyester resin composition thus obtained exhibits extremely good curability when blended with melamine resin, and provides a coating film that has all the advantages of oil-free polyester, including weather resistance, making it suitable for automotive paints. Very useful as a resin vehicle. Example 1 A method for producing a composition comprising an acid-controlled modified polyester resin in which 50 mol% of the acid component is hexahydrophthalic anhydride and exhibits a resin acid value of 8, and 75% of the carboxyl groups are based on isophthalic acid. Composition of acid-controlled modified polyester resin A Hexahydrophthalic anhydride 77.4 parts (0.5 mol) Isophthalic acid 66.48 parts (0.4 mol) Adipic acid 14.62 parts (0.1 mol) Trimethylome propane 25.61 parts Neopentyl glycol 52.67 parts 1.6-hexanediol 55.40 Part 292.18 Calculation of the amount of post-added isophthalic acid (b ₁ mol) Resin design value Resin design value N = 8.0 Polyester resin weight W = 259.3 Number of isophthalic acid functional groups f = 2 Reaction rate of post-added isophthalic acid P = 90% Resin acid value Mol% of carboxyl groups derived from isophthalic acid in all carboxyl groups expressing
From x=75, b ₁ =0.139 mol (23.05 parts) was obtained using the above formula. A reaction layer equipped with a heating device, a stirrer, a reflux device, a water separator, a rectification column, and a thermometer contains the above six reaction materials, except for isophthalic acid, which is 66.48−23.05=43.43.
Prepare and heat. Once the raw materials have melted and stirring is possible, start stirring and raise the reactor temperature to 230°C. However, from 160℃ to 230℃, the temperature is raised at a constant rate over 3 hours. The condensed water produced is distilled out of the system. When it reaches 230℃, keep it warm.
After keeping the temperature for 1 hour, 5 parts of xylene was gradually added as a refluxing solvent into the reaction vessel, and the reaction was continued by switching to condensation in the presence of a solvent. Resin acid value 2.0 (M = 8.0 (1-
75/100)), the reaction is terminated, the reaction tank temperature is cooled to 100℃, and the polyester prepolymer A-
I is obtained. Next, post-fill isophthalic acid 23.05
(0.139 mol) was charged into the reaction tank and the temperature of the reaction tank was raised to 210°C. However, the temperature will rise from 190℃ to 210℃. However, the temperature is raised from 190°C to 210°C over a period of 1 hour at a constant temperature increase rate, and the condensed water produced is distilled out of the system. Once it reaches 210℃, keep it warm and continue the reaction. When the resin acid value reaches 8.0, the reaction is terminated and the mixture is cooled. After cooling, 106.1 parts of xylene is added to obtain acid-controlled modified polyester resin solution A. The nonvolatile content of this solution A was 70.1%, the varnish viscosity (Gardner, temperature 25°C) was Z ₁ , and the resin acid value was 8.1.
Non-aqueous potentiometric titration was performed on a pyridine solution of the obtained polyester polymer A-I and acid-controlled modified polyester resin solution A using n-tetrabutylammonium hydroxide as a titration reagent, and the titration curve is shown in FIG. As is clear from the figure, the half-equivalent point (R) potential of polyester prepolymer A-I (2) is -
400 mV, which corresponds to the half-equivalent point potential of the polyester resin in which the acid component in Table 1 is obtained only from hexahydrophthalic anhydride.
Resin acid value of polyester prepolymer A-I: 2.0
It was confirmed that the type of carboxy group that expresses is based on hexanidrophthalic anhydride. However, there are two inflection points in the titration curve 1 of the acid-controlled modified polyester resin solution A, and the half-equivalent points (P, Q) from the higher potential are -
313 mV and 405 mV, which are in good agreement with the half-equivalent point potentials of -310 and -400 mV of polyester resins obtained from only isophthalic acid and hexahydrophthalic anhydride, respectively, as acid components in Table 1. Therefore, the acid species that give the resin acid value of 8.1 in the obtained acid-controlled modified polyester resin solution A consist of isophthalic acid and hexahydrophthalic anhydride, and the ratio is 75/25, which is as per the resin design value (x = 75 %) It was confirmed that the type of carboxyl group that expresses the resin acid value is controlled.

[Table] A clear paint was prepared from this acid-controlled modified polyester resin solution A using the usual method based on the paint formulation shown below, and applied onto the coating material using a bar coater No. 50 and baked in a hot air dryer at 140℃ and 120℃ for 30 minutes each. Table 2 Acid-controlled modified polyester resin solution A 100 parts Yuban 128 (Note 1) 50 (Note 1) Melamine resin manufactured by Mitsui Toatsu Chemical Co., Ltd. Table 1 shows the results of the gel fraction of this coating film. Examples 2 to 5 Acid-controlled modified polyester resin solutions B to F were produced in the same manner as in Example 1 based on the resin compositions shown in Table 1. The characteristic values of those varnishes are shown in Table 1. Using the various acid-controlled modified polyester resin solutions B to F thus obtained, paints were formed in the same manner as in Example 1 based on the paint formulations shown in Table 2, and coated on painted materials. Table 1 shows the results of the gel fraction of each coating film. Comparative Examples 1 to 3 Based on the resin composition shown in Table 1, modified polyester resin solutions G to I in which the type of carboxyl group that develops the resin acid value is not controlled are produced by a conventional esterification reaction using a pre-preparation method. did. The characteristic values of those varnishes are shown in Table 1. Using the obtained various modified polyester solutions G to I, paints were prepared in the same manner as in Example 1 based on the paint formulations shown in Table 2, and painted on coating materials. Table 1 shows the results of the gel fraction of each coating film.

【table】

[Table] Test method Gel fraction: Soxhlet extractor, extraction solvent acetone/methanol = 1/1 (wt ratio), 70℃
Extract for 5 hours, then dry at 120℃
Dry for 30 minutes and cool in a desiccator. After cooling, measure the weight and calculate the gel fraction. Examples 7 to 8 Acid-controlled modified polyester resin solutions J to K were produced in the same manner as in Example 1 based on the resin compositions shown in Table 2. The characteristic values of those varnishes are shown in Table 2. Using the various acid-controlled modified polyester resin solutions J to M obtained, paints were prepared in the same manner as in Example 1 based on the paint formulations shown in Table 2, and painted on materials. Table 2 shows the results of the gel fraction of each coating film. Comparative Example 4 Based on the resin formation shown in Table 2, a modified polyester resin solution N in which the type of carboxyl group expressing the resin acid value was not controlled was produced by a conventional method. Varnish characteristic values are shown in Table 2. Using the obtained modified polyester resin solution N, a paint was prepared in the same manner as in Example 1 based on the paint formulation shown in Table 2, and coated on the material. The results of the gel fraction of this coating film are shown in Table 2.

【table】 [Brief explanation of drawings]

FIG. 1 is a titration curve obtained by nonaqueous potentiometric titration of the polyester prepolymer A-12 obtained in Example 1 and the acid-controlled modified polyester resin solution A1. (The vertical axis shows the potential, and the horizontal axis shows the titration amount using n-tetrabutylammonium hydroxide titration reagent.)

Claims (1)

[Claims] 1. Expressing a resin acid value selected from the group consisting of (A) saturated alicyclic polybasic acid, (B) phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic anhydride, and pyromellitic anhydride. An acid component consisting of an aromatic polybasic acid exhibiting a half-equivalent point potential of -350 mV or more in non-aqueous potentiometric titration in the state of , a polyhydric alcohol component, and an oil-free polyester resin with a resin acid value of 1 to 2, in which (A) polybasic acid accounts for 10 to 80 moly% of the total acid component, and the resin acid value is expressed. carboxyl group
An oil-free polyester resin composition for paints, in which 50 to 100 mol% is based on (B) a polybasic acid. 2. The acid component is selected from the group consisting of (A) a mole of saturated alicyclic polybasic acid, (B) phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic anhydride, and pyromellitic anhydride, and exhibits a resin acid value. The half-equivalent potential in wastewater potentiometric titration is −350 mV or more.
b moles of aromatic polybasic acid, and (C) C moles of other polybasic acids and/or monobasic acids, provided that a+b+
c = 1.0 mol, 10≦a/a+b+c×100≦80 mol%, 0≦C mol, and contains carboxyl groups that express resin acid value.
An oil-free polyester resin for paints in which 50 to 100 mol% is based on (B) polybasic acid, a mol of polybasic acid (A), polybasic acid (b-b ₁ ) of (B),
and C moles of the polybasic acid and/or monobasic acid of (C), provided that b ₁ mole is equal to or less than b mole, and the molar amount b of (B) determined by the following formula is ₁ = x/100 x N x W/56100 x 1/f x 1/1-P/10
0 Here, N is the resin acid value (the number of KOH mg required to neutralize 1 g of resin solid content), W is the weight of the polyester resin, f is the number of functional groups in (B), and P is the reaction rate (%) of (B) at the time of post-addition. X is the mol% of (B) in the carboxyl groups that express the resin acid value, and the resin acid value M (where M =N(1-x/100)) A paint produced by a step of obtaining a polyester prepolymer, and a step of causing an esterification reaction between the polyester prepolymer and ₁ mole of the polybasic acid b of (B) until the resin acid value is N. A method for producing an oil-free polyester resin composition for use. 3 Resin acid value M is 0 to 10, resin acid value N is 1 to 20,
3. The method according to claim 2, wherein p is 25 to 99%.