JP2014074099A - Method of producing polyester resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a polyester resin suitable for paint use, excellent in adhesion to metal, workability and the like, and excellent in color tone.SOLUTION: There is provided the method of producing a polyester resin containing an aromatic dicarboxylic acid of 80 to 99 mol% and an unsaturated dicarboxylic acid of 1 to 10 mol% as dicarboxylic acid components, and 1,2-propylene glycol of 60 to 100 mol% as a glycol component. The method includes conducting an esterification reaction at 235°C or lower by adding the dicarboxylic acid components and the glycol component, and further adding an esterification catalyst of 0.5×10to 15.0×10mol based on 1 mol of total acid components.

Description

  The present invention is a polyester resin suitable for paint applications for coating metal steel plates used for home appliances, office supplies, food containers, etc., and is especially applied to metal cans for food and beverages. The present invention relates to the production of a polyester resin that forms a coating film with excellent adhesion.

Conventionally, when coating metal steel plates, polyester resin, epoxy resin, acrylic resin, vinyl resin, etc. are used as paints. Metal steel plates coated with such resins are used for home appliances, office supplies, foodstuffs, etc. It is used for various purposes such as goods containers.
Among them, paints used for food and beverage cans are used for the purpose of preventing the corrosion of can materials caused by a wide variety of foods without impairing the flavor and flavor of the contents, and are therefore non-toxic. In addition, it is required to withstand heat sterilization treatment and to have excellent adhesion, workability, and color tone.

  Conventionally, as a resin for paint used in this application, polyvinyl chloride resin, epoxy-phenolic resin, etc. are often used, but these currently have the following problems. .

  Polyvinyl chloride resin has excellent retort resistance, content resistance, and processability, but the vinyl chloride monomer remaining in the resin may be a substance with serious hygiene problems such as carcinogenicity. It has been pointed out. In addition, when incinerating discarded cans, highly toxic and corrosive chlorine gas and hydrogen chloride gas dioxins are generated from the polyvinyl chloride resin, which may lead to corrosion of the incinerator and environmental pollution. is there.

  Furthermore, the polyvinyl chloride resin has insufficient adhesion to the metal that is a can material, and the coating process is complicated, for example, it is necessary to coat it with an epoxy resin. In addition, with an epoxy-phenolic resin, it is necessary to increase the baking temperature, and appearance defects such as foaming are liable to occur during baking. Furthermore, since it is inferior in workability, it is mainly spray-painted.

  In order to solve such a problem, Patent Document 1 proposes a polyester-based resin excellent in retort resistance, content resistance, metal adhesion, processed part water repellency, and gloss retention. There was a problem that appearance defects such as coloring of the coating film were liable to occur due to the original color tone.

JP 2000-122754 A

  The present invention solves the above problems and provides a method for producing a polyester resin which is a polyester resin suitable for coating applications, which is excellent in metal adhesion, workability and the like, and excellent in color tone. This is a technical issue.

The inventors of the present invention have arrived at the present invention as a result of studies to solve the above problems.
That is, the present invention contains 80 to 99 mol% aromatic dicarboxylic acid and 1 to 10 mol% unsaturated dicarboxylic acid as the dicarboxylic acid component, and 60 to 100 mol% 1,2-propylene glycol as the glycol component. A method for producing a polyester resin, in which a dicarboxylic acid component and a glycol component are added, and an esterification catalyst is added in an amount of 0.5 × 10 ^{−4 to} 15.0 × 10 ⁻⁴ mol with respect to 1 mol of all acid components. Then, the gist is a method for producing a polyester resin, wherein the esterification reaction is performed at a temperature of 235 ° C. or lower.

  According to the method for producing a polyester resin of the present invention, when used in coating applications, it has excellent metal adhesion, workability, retort resistance, content resistance, etc. A suitable polyester resin can be produced with high productivity. The polyester resin obtained by the production method of the present invention can be suitably used for coating applications for coating metal steel plates used in various home appliances, office supplies, food containers and the like.

  The polyester resin obtained by the production method of the present invention contains an aromatic dicarboxylic acid and an unsaturated dicarboxylic acid as the dicarboxylic acid component. It is necessary to contain 80 to 99 mol% of aromatic dicarboxylic acid and 1 to 10 mol% of unsaturated dicarboxylic acid. When the aromatic dicarboxylic acid is less than 80 mol%, the blister resistance and the whitening resistance are inferior. Moreover, if unsaturated dicarboxylic acid is less than 1 mol%, since metal adhesiveness will fall and workability will be aggravated, it is unpreferable. On the other hand, if the unsaturated dicarboxylic acid exceeds 10 mol%, gelation tends to occur in the resin production stage, making it difficult to obtain the target polyester resin.

Examples of the aromatic dicarboxylic acid as described above include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, and the like. Among these, terephthalic acid and isophthalic acid are preferable.
Further, examples of the unsaturated dicarboxylic acid include fumaric acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, unhydrogenated dimer acid, cyclohexene dicarboxylic acid, terpene-maleic acid adduct, etc. Among them, maleic acid is preferable. .

  Moreover, the polyester resin obtained by the manufacturing method of this invention needs to contain 60-100 mol% of 1, 2- propylene glycol as a glycol component, and it must contain 70-100 mol% especially. preferable. When the proportion of 1,2-propylene glycol is less than 60 mol%, the polyester resin has crystallinity and is difficult to handle when used for paint applications. Moreover, it is inferior to metal adhesion, and when it is used as a coating film, it is inferior to retort resistance.

The polyester resin in the present invention as described above may contain the following copolymer components as long as the characteristics are not impaired.
Examples of the copolymerizable dicarboxylic acid component include succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, hydrogenated dimer acid, and other aliphatic dicarboxylic acids, cyclohexanedicarboxylic acid, tetrahydrophthalic acid, hexahydro Aliphatic dicarboxylic acids such as isophthalic acid.

  Examples of copolymerizable glycol components include ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, dimethylolheptane, Dimethylolpentane, 2-ethyl-2-butylpropanediol, 3-methyl-1,5-pentanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 3-methyl -1,6-hexanediol, 4-methyl-1,7-heptanediol, 4-methyl-1,8-octanediol, 4-propyl-1,8-octanediol, diethylene glycol, triethylene glycol, cyclohexanedimethanol , Tricyclodecane glycols, polyethylene glycol , Polypropylene glycol, polytetramethylene glycol, bisphenol ethylene oxide or propylene oxide derivatives, hydrogenated bisphenols, and the like.

  And in the manufacturing method of this invention, it is necessary to add a dicarboxylic acid component and a glycol component, and to make temperature at the time of performing esterification reaction into 235 degrees C or less. When the esterification reaction temperature exceeds 235 ° C., the decomposition of 1,2-propylene glycol proceeds, the coloration of the resin becomes remarkable, and the color tone a value exceeds 1.0, which is to be obtained in the present invention. It becomes difficult to obtain a resin having a good color tone.

Furthermore, in the production method of the present invention, when the esterification reaction is performed, it is necessary to add the esterification catalyst in an amount of 0.5 × 10 ^{−4 to} 15.0 × 10 ⁻⁴ mol with respect to 1 mol of the total acid component. There is.
When the addition amount of the esterification catalyst exceeds 15.0 × 10 ⁻⁴ mol, not only coloring of the resin by the esterification catalyst becomes remarkable but also gelation of the resin may be promoted. On the other hand, if the amount is less than 0.5 × 10 ⁻⁴ , the amount of the esterification catalyst is insufficient, the reaction time of the esterification reaction becomes long, the thermal decomposition of 1,2-propylene glycol is promoted, and the brown resin, The b value exceeds 20.0. In some cases, the polymerization reaction does not proceed and a resin having a target degree of polymerization cannot be obtained.

  As the esterification catalyst in the present invention, it is preferable to use a tin or titanium compound. Since these compounds have a high catalytic ability for esterification reaction, the difference in esterification reactivity between various acid components is reduced, and the effect of suppressing gelation is obtained.

  Examples of the tin compound include mono-n-butyltin oxide, tetrabutyltin, butylchlorotin dihydroxy, butyltris-2-ethylhexaauto, tin oxalate, and dimethyltin malate.

  Examples of titanium compounds include titanium tetraalkoxides such as titanium tetrabutoxide, titanium tetrapropoxide, titanium tetraethoxide, hexaalkyltrititanates, octaalkyldititanates, etc., but titanium tetraalkoxides from the viewpoint of esterification reactivity. Is preferable, and titanium tetrabutoxide is particularly preferable.

  And in the manufacturing method of this invention, after performing transesterification on the above conditions, a polycondensation catalyst is added, and the temperature of 220-240 degreeC under the reduced pressure of 5 hPa or less, Preferably it is 220-235 degreeC. It is preferable to carry out a polycondensation reaction.

  The intrinsic viscosity of the polyester resin obtained by the production method of the present invention is preferably 0.35 or more. When the intrinsic viscosity is less than 0.35, the coating film becomes brittle, and the processability and retort resistance are inferior. The glass transition temperature is preferably 40 ° C or higher, more preferably 60 ° C or higher. When the glass transition temperature is less than 40 ° C., the retort resistance and the content resistance are inferior.

  In the production method of the present invention, if necessary, a heat stabilizer such as phosphoric acid, an antioxidant such as a hindered phenol compound, a pigment such as titanium oxide, a filler, other thermoplastic resins and the like are appropriately used. It may be added.

  The polyester resin obtained by the production method of the present invention may be used alone as a paint, or an amino resin, an epoxy resin, or the like may be added as a paint. At this time, after adding an amino resin or a bisphenol A epoxy resin alone, it is dissolved in a known organic solvent to form a coating composition.

  First, examples of amino resins include formaldehyde adducts such as urea, melamine, and benzoguanamine, and alkyl ether compounds based on alcohols having 1 to 6 carbon atoms. Specific examples include methoxymethylolated urea, methoxylated methylol-N, N-ethyleneurea, methoxylated methylol dicyandiamide, methoxylated methylol melamine, butoxylated methylol benzoguanamine, and the like, preferably methoxylated methylol melamine, butoxylated methylol. Melamine and methylolated benzoguanamine, which can be used alone or in combination.

  As the epoxy resin, a bisphenol A epoxy resin having an epoxy equivalent of 400 to 5000 g / equivalent is preferably used. If the epoxy equivalent is less than 400, sufficient processability cannot be obtained, and if it exceeds 5000, retort resistance cannot be obtained.

  Examples of the organic solvent to be used include toluene, xylene, sorbeso, methyl acetate, butyl acetate, methyl ethyl ketone, cyclohexanone, isophorone, methyl cellosolve, butyl cellosolve, ethylene glycol monoacetate, etc., taking into consideration solubility, evaporation rate, etc. It is selected appropriately.

  Next, the present invention will be specifically described with reference to examples. In addition, the measurement of various characteristic values in an Example and the evaluation method are as follows.

(1) Composition of polyester resin The obtained polyester resin was measured using 1H-NMR spectrometer JNM-LA400 apparatus by JEOL.
(2) Intrinsic viscosity [η]
Measurement was made at a temperature of 20 ° C. using an equal weight mixture of phenol and ethane tetrachloride as a solvent.
(3) Glass transition temperature (Tg)
It measured with the temperature increase rate of 20 degrees C / min. Using the differential scanning calorimeter DSC5200 by Seiko Electronics Industry.

(4) Color tone Measured using a color difference meter ND-Σ80 manufactured by Nippon Denshoku Industries Co., Ltd. The color tone was determined using a Hunter Lab colorimeter. L value is lightness (larger value is brighter), a value is red-green hue (+ is reddish,-is greenish), b value is yellow-blue hue (+ is yellowish,-is Blue).
Here, an a value of 1.0 or less and a b value of 20.0 or less were accepted.

(5) Solubility The obtained polyester resin was dissolved in cyclohexanone to make a 30% by mass solution, and the solubility after standing at 25 ° C was evaluated as solubility.
○: Good ×: Cloudiness, solidification or insolubility

(6) Preparation of test piece After the obtained polyester resin was dissolved in cyclohexanone to make a 40% by mass solution, the film thickness was changed to TFS (Tin-free steel, 70 mm x 150 mm x 0.3 mm) with a bar coater # 38. It apply | coated so that it might become 10-15 micrometers, it dried at 80 degreeC * 30 minutes, and what was obtained was used as the test piece.

(7) Metal adhesion According to JIS K 5400, the test piece obtained in (6) was scratched in a grid pattern with a cutter knife, and the grid area was peeled off with cellophane tape, and the remaining grid in 100 grids Metal adhesion was evaluated according to the number of eyes as follows.
○: The number of remaining grids is 90 or more ×: The number of remaining grids is less than 90

(8) Retort resistance After the test piece obtained in (6) was treated under steam at 130 ° C. for 30 minutes, the whitening of the coating film and the state of the blister were visually determined.
○: Good ×: Whitening or blistering

(9) Content resistance property After the test piece obtained in (6) was treated in an aqueous solution (130 ° C.) containing 3% by mass of sodium chloride and 3% by mass of lactic acid for 30 minutes, the whitening of the coating film and the state of the blister were determined. Judgment was made visually.
○: Good ×: Whitening or blistering

(10) Boiling water resistance After boiling two TFS base materials identical to those used in obtaining the test piece in (6) in a 180 degree direction so as to be sandwiched between the test pieces obtained in (6), boiling distillation is performed. The film was treated in water for 2 hours, the bent part was observed with a loupe, and the presence or absence of cracks in the coating film or the state of the blister was visually determined.
○: Good ×: Crack or blister

Example 1
Terephthalic acid 98.5 mol% (1054 kg), propylene glycol 135 mol% (836 kg), maleic acid 1.5 mol% (7.7 kg) as unsaturated dicarboxylic acid, monobutyltin oxide (manufactured by Yoshitomi Fine Chemical Co., Ltd. FASCAT4100 ") was charged into an esterification reactor so as to be 3.0 × 10 ^-4 mol with respect to 1 mol of all acid components, and an esterification reaction was carried out at normal pressure and a temperature of 235 ° C. for 8 hours.
The obtained reaction product was transferred to a polymerization reactor, and 7.0 × 10 ⁻⁴ mol of tetrabutyl titanate was added as a polycondensation catalyst with respect to 1 mol of all acid components, and then the reaction system was stirred for 90 minutes. The pressure was gradually reduced to 1.0 hpa or less, and finally a polycondensation reaction was performed at a temperature of 230 ° C. for 9 hours to obtain a polyester resin.

Examples 2-5, Comparative Examples 1-3
As shown in Table 1, a polyester resin was obtained in the same manner as in Example 1 except that the esterification temperature and the amount of the esterification catalyst were changed.

  Table 1 shows the characteristic values and evaluation results of the polyester resins obtained in Examples 1 to 5 and Comparative Examples 1 to 3.

As is clear from Table 1, the polyester resins obtained by the methods of Examples 1 to 5 had a good color tone and were excellent in various evaluations when used as a paint.
On the other hand, in Comparative Example 1, since the esterification temperature was 245 ° C., the color tone of the obtained polyester resin was brownish. In Comparative Example 2, since the addition amount of the esterification catalyst was reduced to 0.2 × 10 ⁻⁴ mol with respect to the total acid component, the time required for the esterification reaction was increased, and the obtained polyester resin was brown. there were. In Comparative Example 3, since the addition amount of the esterification catalyst was a large 22.0 × 10 ⁻⁴ mol with respect to the total acid component, the resulting polyester resin had a brown color tone. Moreover, because of the large amount of catalyst, gelation may occur during polymerization, and stable production could not be performed.

Claims (1)

In a method for producing a polyester resin containing 80 to 99 mol% of an aromatic dicarboxylic acid, 1 to 10 mol% of an unsaturated dicarboxylic acid as a dicarboxylic acid component, and 60 to 100 mol% of 1,2-propylene glycol as a glycol component. Then, a dicarboxylic acid component and a glycol component are added, and an esterification catalyst is further added in an amount of 0.5 × 10 ^{−4 to} 15.0 × 10 ⁻⁴ mol with respect to 1 mol of the total acid component, and the temperature is 235 ° C. The manufacturing method of the polyester resin characterized by performing esterification reaction below.