JPS5933606B2 - Polyester manufacturing method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing polyester.

More specifically, the present invention relates to a method for producing a polyester suitable as a paint resin, which involves depolymerizing a relatively high-molecular polyester with trimellitic anhydride. BACKGROUND ART Conventionally, attempts have been made to use polyesters in paints, especially powder paints, and various methods for producing polyesters useful for such uses have been proposed.

However, polyesters produced by these methods still have some problems. For example, JP-A-47-2
No. 8092 discloses that a low molecular weight polyester having a hydroxyl value of 15 to 50 is treated with a polybasic organic carboxylic acid anhydride having an acid value of 30 to 1 in an amount equal to or less than the number of moles relative to the hydroxyl equivalent of the polyester.
It has been proposed to modify the polyester into 00 polyester and use this polyester as a paint resin, but powder paints using this polyester have poor coating surface smoothness and are difficult to use after adding a curing agent. It has defects such as poor storage stability and curing reaction during storage. As a result of intensive research on a method for producing polyester that does not have such problems, the present inventors have developed a carboxyl product obtained by depolymerizing a relatively high-molecular hydroxyl group-containing polyester with an excess amount of a specific organic carboxylic acid relative to the equivalent amount of the hydroxyl group. It was discovered that group-containing polyester has the property of forming an extremely smooth coating surface when used as a coating material, and the present invention was achieved based on this discovery.

That is, the present invention provides (the octacid component is at least 50 mol%)
of terephthalic acid and/or isophthalic acid, and the glycol component does not contain more than 90 mol% of ethylene glycol, with a reduced viscosity of 0.
A polyester containing 2 to 1.5 hydroxyl groups is expressed by the following formula (1)
, reduced viscosity of 0.05 to 0.0.
This is the method for producing polyester No. 5. 1<X≦20...
・・・・・・・・・・・・・・・・・・(1) [However, in the above formula, Y is the total number of moles of component (3) per equivalent of hydroxyl group of eight components.

In the present invention, at least 50 mol% of the acid component of the hydroxyl group-containing polyester used as component A consists of terephthalic acid and/or isophthalic acid.

Therefore, the acid component may contain other difunctional carboxylic acids in an amount less than 50 mol%. Such other difunctional carboxylic acids include diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethane dicarboxylic acid, dibromoterephthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, and phthalic acid. , Aromatic difunctional carboxylic acids such as P(β-hydroxyethoxy)benzoic acid, P-hydroxybenzoic acid, P-hydroxymethylbenzoic acid, etc.; Aliphatic difunctional carboxylic acids such as adipic acid, sebacic acid, decamethylene dicarboxylic acid, etc. Functional carboxylic acid: 1,4-cyclohexanedicarboxylic acid, 1
- Alicyclic bifunctional carboxylic acids such as 3-cyclohexanedicarboxylic acid and the like can be exemplified. Among these, it is preferable to use aliphatic dicarboxylic acids such as adipic acid and sebacic acid. Moreover, it is preferable that terephthalic acid and/or isophthalic acid account for 70 mol% or more of the total acid components. When terephthalic acid and isophthalic acid are used together, the mutual ratio is arbitrary, but it is preferable that terephthalic acid accounts for 50 mol% or more with respect to the total number of moles of terephthalic acid and isophthalic acid. When the polyester obtained when the ratio of terephthalic acid and isophthalic acid to the total acid components is less than 50 mol% is used as a paint,
This is not preferred because the surface hardness characteristics of the coating film decrease. Further, the glycol component of the hydroxyl group-containing polyester consists of glycol that does not contain more than 90 mol% of ethylene glycol. If the ethylene glycol content is less than 90 mol%, the resulting polyester will have reduced flexibility. Therefore, the glycol component consists of a combination of 90 mol% or less of ethylene glycol and 10 mol% or more of other glycols, or only other glycols. Such other glycols include propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2-methyl-1,4-butanediol,
1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-methyl 1
・5-pentanediol, 3,3-dimethyl 1,5-pentanediol, 2,4-dimethyl-1,5-pentanediol, 2-methyl-1,6-hexanediol, 3
・4-dimethyl-1,6-hexanediol, 2,5-
Aliphatic glycols such as dimethyl-1,6-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, polytetramethylene glycol, cyclohexane-1,4-dimethanol, cyclohexane-1, Examples include alicyclic glycols such as 3-dimethanol, aromatic glycols such as 1,4-xylylene glycol, 2,2-bis[4-(β-hydroxyethoxy)phenyl]propane, etc. .

These can be used alone or in combination of two or more, and among them, aliphatic glycols, particularly neopentyl glycol, are preferred. The hydroxyl group-containing polyester needs to have a reduced viscosity of 0.2 to 1.5, preferably 0.2 to 0.7.

In the case of a hydroxyl group-containing polyester with a reduced viscosity lower than 0.2, when the resulting carboxyl group-containing polyester is used as a paint, the smoothness of the coating film surface is poor, and when using a hydroxyl group-containing polyester with a reduced viscosity of over 1.5. This is not preferable because the resulting carboxyl group-containing polyester has lower fluidity when melted. The amount of hydroxyl groups in the hydroxyl group-containing polyester is preferably a proportion showing a hydroxyl value of 5 to 13.

Specific examples of hydroxyl group-containing polyesters include monoethylene glycol terephthalate-neopentyl glycol copolymer, terephthalic acid-ethylene glycol adipate-neopentyl glycol copolymer, monoethylene glycol isophthalate-neopentyl glycol copolymer, and terephthalate. Examples include isophthalic acid monoethylene glycol-neopentyl glycol copolymer, terephthalic acid-decamethylene dicarboxylic acid-ethylene glycol-neopentyl glycol copolymer, and terephthalic acid monoethylene glycol-hexamethylene glycol copolymer. can.

The compound used as component (B) in the present invention is trimellitic acid anhydride.

This trimellitic anhydride is contained in a small proportion (for example, 10 mol%
(below), it is possible to substitute with other organic carboxylic acids and use both together. Examples of other organic carboxylic acids include monoalkyl esters of promelitic acid monoanhydride (e.g., monoethyl ester, monoethyl ester, monopropyl ester, monoisopropyl ester,
monobutyl ester, etc.), monoamide of pyromellitic acid 1 anhydride (e.g. monomethylamide, etc.), 3, 31, 4
・Polyvalent carboxylic acid anhydrides such as 4'-benzophenone tetracarboxylic acid monoanhydride, hexahydrotrimellitic anhydride, etc.; Monocarboxylic acids such as stearic acid, benzoic acid, tolylic acid, etc.; ε-oxy Oxycarboxylic acids such as caproic acid, P-oxybenzoic acid, P-(β-oxyethoxy)benzoic acid; terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, dibromoterephthal dicarboxylic acids or their acid anhydrides such as diphenyldicarboxylic acid, adipic acid, sebacic acid, decamethylene dicarboxylic acid, succinic anhydride, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid anhydride, etc. Examples include polycarboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid, pyromellitic dianhydride, naphthalene tetracarboxylic acid, benzophenone tetracarboxylic acid, and acid anhydrides thereof. Among these, isophthalic acid, phthalic anhydride, pyromellitic acid monoanhydride, etc. are preferred. The amount of the trimellissotic anhydride to be used is determined by the following formula [wherein, This is the total number of moles of the organic carboxylic acids of the component (B) per equivalent of hydroxyl groups in the hydroxyl group-containing polyester of the component A).

].

More preferably, especially preferably This is the ratio that satisfies the following.

If X or Y is less than 1, the smoothness of the coated film surface will be low when the resulting polyester is used in a paint, and if it exceeds 20, the resulting carboxyl group-containing polyester will be cured with a curing agent. This is not preferable because the mechanical strength of the molded product decreases and the storage stability of the powder is poor. (A) component hydroxyl group-containing polyester and (B)
The depolymerization reaction with trimellitic anhydride as a component may be carried out by heating and mixing both components using a kneader, extruder, etc., but after the polymerization reaction of the hydroxyl group-containing polyester is completed, the melt in the system It is preferable to add trimellitic anhydride to the hydroxyl group-containing polyester in the state and carry out the reaction at a temperature of preferably 200 to 300° C. for 10 to 60 minutes under normal pressure.

Further, it is preferable to carry out a reduced pressure reaction for about 5 to 10 minutes after the normal pressure reaction. Even when the reaction is carried out using a kneader, extruder, etc., it is preferable to carry out the reaction at a temperature of 200 to 300°C. Due to the depolymerization reaction rules, the hydroxyl group-containing polyester becomes a polymer with a low molecular weight, and the terminal hydroxyl group becomes substantially a terminal carboxyl group, and furthermore, the hydroxyl group-containing polyester has a carboxyl group due to trimellitic anhydride in the side chain of the molecule.

It is presumed that the polyester obtained by the present invention has excellent properties because it has a carboxyl group derived from trimerisolic anhydride in the molecular side chain.

The polyester obtained by depolymerizing a hydroxyl group-containing polyester with trimellitic anhydride is a carboxyl group-containing polyester, and its reduced viscosity is O. 05~O. 5
, preferably O. 1 to 0.4, more preferably O. 15
~0.3.

If the reduced viscosity is less than 0.05, the storage stability of the composition obtained after mixing the polyester and curing agent will be poor;
If it exceeds 5, the fluidity during melting will be poor. The polyester obtained by the present invention has the property of exhibiting excellent storage stability when used as a paint, especially a powder coating, a powder adhesive, or a molding powder by adding a curing agent such as an epoxy compound. In paints, it has the property that the resulting coating film has extremely high smoothness.

The polyester of the present invention includes various stabilizers, pigments, dyes,
Additives such as flow control agents can be added as needed.

The present invention will be explained in detail below with reference to Examples.

In addition, in the examples, [parts] means parts by weight. In addition, the reduced viscosity [ηSp/C] in the text and examples is defined by the following formula (where ηRel: relative viscosity, C: polymer concentration 1.2
7/Dll solvent: orthochlorophenol, measurement temperature 3
It is a value calculated from 5° C., ηSp: specific viscosity).

)Furthermore, the softening point, hydroxyl value, flow characteristics, keratin test and Erichsen test were measured by the following methods.

(1) Softening point: Measured using a softening point measuring device using the Vikat method.

(2) Hydroxyl value: Measured by the method of ASTM D1957-61T.

(3) Flow characteristics of powder: Powder 0.17 is placed on an aluminum plate kept at a constant temperature, and the plate is held at an angle of 60° to the horizontal to heat the powder to flow and harden. Measure the flow distance to the point where the flow stopped and display it as a percentage.

(4) Scratch test: Scratches are made on the surface of the coating painted on a metal surface in a grid pattern at intervals of 1 square length and width until the metal surface is reached, and zero tape is applied and peeled off.
Out of 100 goblets, it is expressed as the number of those whose coating film is in close contact with the metal without peeling off.

(5) Erichsen test: A coating film is formed on a metal plate with a thickness of 1 mm, and a punch with a diameter of 20 mm is extruded from the back side, and the extrusion distance is expressed as the extrusion distance when cracks or peeling occur in the coating film.

Examples 1 and 2 Dimethyl terephthalate 174 was added to a purification tower and a reactor equipped with a stirrer.

8 parts, adipic acid dimethyl ester 17.4 parts (10 mol% based on the total acid components), 62.1 parts ethylene glycol (50 mol% based on the total glycol components), 104.2 parts neopentyl glycol, and calcium acetate. Water salt 0.
176 parts of the reactor were charged, and the mixture was heated to react while distilling methanol out of the system, and the transesterification reaction was completed when the distillation of methanol had stopped.

The obtained reaction product was transferred to a polymerization reactor equipped with a stirrer and purged with nitrogen, and 0.175 parts of antimony trioxide and 0.182 parts of trimethyl phosphate were further added thereto, and the reaction was carried out at normal pressure at 250°C for 30 minutes. The reaction was carried out under a reduced pressure of 20 mmHg for 15 minutes and further under a reduced pressure of 0.5 mmHg for the time shown in Table 1.

The hydroxyl group-containing polyester obtained at this stage is called OH type polyester (the same applies hereinafter). Table 1 shows the composition, reduced viscosity, softening point, and hydroxyl value of the OH type polyester obtained here. 9.6 parts of trimellitic acid anhydride was added to 109 parts of 0H type polyester, and a normal pressure reaction was carried out at 250° C. for 20 minutes.

The polyester obtained at this stage is called COO5 polyester (the same applies hereinafter). Table 1 shows the reduced viscosity, softening point, and acid value of the COO type polyester obtained here. The properties of the COOH type polyester as a powder coating were evaluated by the following method, and the results are shown in Table 1.

43 parts of rutile-type titanium oxide was added to 100 parts of COOH-type polyester, and the mixture was heated to 130°C in a small furnace.
After kneading for 5 minutes, a predetermined amount of triglycidyl isocyanurate was added and kneaded for 2 minutes at 130°C. After cooling, the resin composition was crushed and passed through a 150 mesh sieve to obtain a powder coating. .

The powder coating was applied to a steel plate with a thickness of 1 mm and heated at 180°C for 2 hours.
Baked for 0 minutes to create a coating film.

Table 1 shows the flow characteristics of the powder when it is melted (thermal gradient method) and the properties of the cured coating film. Comparative Example 1 An OH type polyester was produced in the same manner as in Example 1 except that the polycondensation time was changed to the time shown in Table 1.

Table 1 shows the composition, reduced viscosity, softening point and hydroxyl value of the 0H polyester. This 0H type polyester 100
A COOH type polyester was produced in the same manner as in Example 1 by adding 9.7 parts of trimellitic acid anhydride to the mixture.

Table 1 shows the reduced viscosity, softening point and acid value of the obtained COOH type polyester. Furthermore, the properties of the COOH type polyester as a powder coating were evaluated in the same manner as in Example 1, and the results are shown in Table 1. As is clear from Table 1, the COOH type polyesters of Examples 1 and 2 have extremely excellent coating film smoothness and provide powder coatings that are useful for practical purposes, whereas the COOH type polyesters of Comparative Example 1 Forms a powder coating that has a peel-like coating and is of little practical use.

Claims (1)

[Scope of Claims] 1(A) A reduced viscosity in which the acid component consists of at least 50 mol% of terephthalic acid and/or isophthalic acid, and the glycol component consists of a glycol that does not contain more than 90 mol% of ethylene glycol. 0.2 to 1.5 hydroxyl group-containing polyester in a proportion satisfying the following formula (B
) A method for producing polyester having a reduced viscosity of 0.05 to 0.5, which comprises depolymerizing with trimellitic anhydride. 1<X≦20 1<Y≦20 [However, in the above formula,
is the total number of moles of component (B) per equivalent of hydroxyl group of component (A). ].