JPH061841A - Block copolyester/amide resin and coating composition for coated steel sheet containing same - Google Patents

Abstract

PURPOSE:To obtain a block copolyester/amide resin having excellent solubility in a coating solvent and comprising units derived from a specified amorphous polyester, units derived from a polyamide and units derived from a polylactone. CONSTITUTION:The title resin comprises 50-90wt.% units derived from an amorphous polyester prepared from a glycol component comprising 10-80mol% ethylene glycol and 90-20mol% other glycols and an acid component comprising 80-100mol% aromatic dibasic acid and 20-0mol% other dibasic acids, 1-40wt.% units derived from a polyamide comprising dodecanamide and/or undecanamide and 5-40wt.% units derived from a polylactone. This resin has a reduced specific viscosity of 0.1-2dl/g as measured in an o-dichlorobenzene/phenol solvent (volume ratio of 4/6) in a concentration of 1% and is desirable for the production of a coating agent for coated steel sheet.

Description

Detailed Description of the Invention

[0001]

The present invention has a novel block copolymerized polyesteramide resin and excellent adhesion to a metal containing it, high gloss and hardness, good bending workability and solvent resistance. In particular, it relates to a coating composition for a coated steel sheet which is excellent in workability at low temperatures.

[0002]

2. Description of the Related Art A precoated steel sheet (hereinafter abbreviated as PCM) obtained by coating a galvanized steel sheet, a cold rolled steel sheet, an aluminum plated steel sheet, etc. before processing has a simple coating process,
Since it has advantages such as a uniform and beautiful coating film and cost reduction, it can be used for roof materials, outer wall materials,
In recent years, its use is increasing in household electric appliances and office supplies. Particularly in recent years, the demand for home appliances such as refrigerators, ovens, and microwave ovens, which have more demanding performance, is growing rapidly.

Since PCM is required to have a high degree of workability, a copolymerized polyester resin having good workability has come to be used as a resin for PCM paints. The following are known as examples of paints using such a copolyester resin. A coating composition in which an alkyl etherified formaldehyde resin is blended with a copolyester resin comprising an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and an alkylene glycol (Japanese Patent Publication No. 61-323).
No. 51), a coating composition in which an alkyl etherified formaldehyde resin is mixed with an aromatic copolyester resin copolymerized with a polyfunctional component (Japanese Patent Publication No. 57-23714), and a hard composition comprising an amorphous copolyester. A coating composition in which an alkyl etherified formaldehyde resin is blended with a block copolymerized polyester resin composed of a soft component composed of a polymer of a component and a lactone (Japanese Patent Application Laid-Open No. HEI-2)
-86669 gazette) etc. are known.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The paint disclosed in Japanese Patent No. 351 is excellent in processability when the amount of the curing agent such as methylated melamine resin added is small, but in this case, the hardness is low and the solvent resistance and stain resistance are low. Is also lacking. When the amount of the curing agent is increased, the hardness is increased, but the workability is greatly reduced, and the balance between the hardness and the workability is limited. The coating disclosed in Japanese Patent Publication No. 57-23714 has high hardness to some extent and has good gloss and the like, but has low workability, and particularly when the temperature during processing is low in winter or cold regions. The sex is extremely insufficient. Furthermore, although the coating material disclosed in Japanese Patent Application Laid-Open No. 2-86669 certainly has good workability at room temperature, it lacks bending workability at low temperatures, and has performances of hardness and stain resistance. Is not enough. As described above, a PCM coating composition that can be used for high-grade products such as home electric appliances and has excellent hardness and excellent workability, particularly at room temperature or lower, has not yet been obtained.

Therefore, the present invention is for a coated steel sheet having a high hardness, good adhesion such as gloss, good solvent resistance, good stain resistance, and excellent workability, especially at room temperature or below. Made for the purpose of providing paint.

[0006]

As a result, the above-mentioned objects are a novel block-copolymerized polyesteramide resin (A) and an amino resin (B) which are excellent in solubility in coating solvents.
It was found to be achieved by a coating composition for a coated steel sheet, which is characterized by containing

That is, the present invention relates to ethylene glycol 10
-80 mol%, other glycol 20-90 mol% glycol component, aromatic dibasic acid 80-100
50% of the amorphous polyester unit (a) formed from an acid component composed of 0 to 20 mol% of other dibasic acid
90% by weight, dodecane amide and / or undecane amide (b) 1 to 40% by weight, and polylactone unit (c) 5 to 40% by weight formed from lactones, and o-dichlorobenzene / phenol (volume: Ratio 4
/ 6) containing a block copolymerized polyester resin having a reduced specific viscosity (ηsp / C) of 0.1 to 2.0 dl / g measured at a concentration of 1.0% and an amino resin. A characteristic coating composition for coated ore plates.

The structure of the present invention will be described in detail below.

The novel block copolymerized polyesteramide resin (A) of the present invention comprises an amorphous polyester unit (a).
And a polyamide unit (b) and a polylactone unit (c).

The amorphous polyester unit (a) comprises 10 to 80 mol% of ethylene glycol, preferably 20 to 70.
Mol%, other glycol 20-90 mol%, preferably a glycol component consisting of 30-80 mol%, and an aromatic dibasic acid 80-100 mol%, preferably 90-10
It is synthesized from an acid component consisting of 0 mol% and another dibasic acid of 20 to 0 mol%, preferably 10 to 0 mol%. The ratio of ethylene glycol in all glycol components is 1
If it is less than 0 mol% or exceeds 80 mol%, the solubility in the coating solvent is insufficient in both cases. If the proportion of the aromatic dibasic acid in all the acid components is less than 80 mol%, sufficient hardness of the coating film cannot be obtained and solvent resistance and stain resistance are insufficient.

Other glycols used in combination with ethylene glycol include 1,2-propanediol, 1,3-propanediol and 2-methyl-1,3-
Propanediol, 1,3-butanediol, 1,4-
Butanediol, 1,5-pentanediol, 1,6-
Hexanediol, diethylene glycol, neopentyl glycol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propane Aliphatic glycols such as diols, alicyclic glycols such as 1,4-cyclohexanedimethanol, ethylene oxide or propylene oxide adducts of bisphenol A, and aromatic glycols such as ethylene oxide or propylene oxide adducts of bisphenol S. It is possible to use one kind or two or more kinds selected from these. Among these, neopentyl glycol, 1,6 hexanediol, 1,4
-Cyclohexanedimethanol, ethylene oxide or propylene oxide adduct of bisphenol A, and ethylene oxide or propylene oxide adduct of bisphenol S are preferable.

As the aromatic dibasic acid, terephthalic acid,
Examples thereof include isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-diphenyldicarboxylic acid, and one or more of these are selected and used. It is also possible to use a lower alkyl ester. In order to obtain sufficient coating film hardness and coating film strength, it is preferable to use terephthalic acid as one of the aromatic dibasic acid components. Examples of the aromatic dibasic acid preferably used in combination with terephthalic acid include isophthalic acid.

Examples of other dibasic acids include aliphatic dibasic acids and alicyclic dibasic acids. Specific examples of the aliphatic dibasic acid include succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, α, ω-octadecanedicarboxylic acid, and dimer acid. One or two or more types are selected from the above and used. It is also possible to use a lower alkyl ester. Among these, adipic acid, sebacic acid, dodecanedioic acid and the like are preferable.

As the alicyclic dibasic acid, hydrogenated terephthalic acid, hydrogenated isophthalic acid, hydrogenated orthophthalic acid, 2,6-
Examples thereof include hydrogenated products of naphthalenedicarboxylic acid and hydrogenated products of 4,4′-diphenyldicarboxylic acid, and one or more selected from these are used. It is also possible to use a lower alkyl ester. Among these, hydrogenated terephthalic acid and hydrogenated isophthalic acid are preferable. It is also possible to use an aliphatic dibasic acid and an alicyclic dibasic acid together.

The amorphous polyester unit (a) of the present invention
Is an amorphous copolyester obtained by combining ethylene glycol, the above-mentioned preferable glycol, a preferable aromatic dibasic acid, and a preferable dibasic acid.

In some cases, it is possible to copolymerize a small amount of a polycarboxylic acid having a valence of 3 or more and / or a polyol having a valence of 3 or more.

Examples of tribasic or higher polybasic acids include trimellitic acid and pyromellitic acid. Examples of trihydric or higher polyols include glycerin, trimethylolpropane, and pentaerythritol. These polybasic acids and polyols are preferably used in the range of 0 to 10 mol% based on the dibasic acid or glycol, respectively.

The polyamide unit (b) is polydodecane amide and / or polyundecane amide, and 1
It is formed from 2-aminododecanoic acid and / or 11-aminoundecanoic acid.

The polylactone unit (C) has 4 to 12 carbon atoms.
Derived from cyclic lactones or aliphatic oxycarboxylic acids. Cyclic lactones include β-propiolactone, β-2,2-dimethylpropiovalerolactone, δ
-Valerolactone, δ-3-methylvalerolactone, ζ
-Enanthlactone, η-caprylolactone, ε-caprolactone, γ-butyrolactone, laurolactone and the like can be mentioned. Examples of the aliphatic oxycarboxylic acid include ε-oxycarboxylic acid. These cyclic lactones or aliphatic oxycarboxylic acids are 1
One kind or two or more kinds are selected and used. Of these, ε-caprolactone and ε-oxycarboxylic acid are preferable.

Polyesteramide resin (A) of the present invention
Is 50 to 90% by weight of the amorphous polyester unit (a),
Preferably from 60 to 85% by weight, polyamide unit (b)
1 to 40% by weight, preferably 5 to 35% by weight, and 5 to 40% by weight of the polylactone unit (C), preferably 10 to 35% by weight. When the content of the polyester unit (a) is less than 50% by weight, the appearance of the coating film is deteriorated, the gloss is lowered, and the solubility in a coating solvent is lowered, so that it cannot be used as a coating resin. When the polyester unit (a) exceeds 90% by weight, bending workability is deteriorated. When the polyamide unit (b) is less than 1% by weight,
The bending workability of the coating film at room temperature and at a low temperature decreases, and when it exceeds 40% by weight, pencil hardness becomes insufficient, and further, the solubility in a coating solvent decreases, and it cannot be used as a coating resin. When the polylactone unit (c) is less than 5%, the bending workability of the coating film at room temperature and at low temperature is deteriorated, and when it exceeds 40% by weight, sufficient hardness cannot be obtained or stain resistance is insufficient.

In the block copolymerized polyesteramide resin of the present invention, the polylactone unit (c) is present as a block. The amorphous polyester unit (a) and the polyamide unit (b) are present in a block unit other than the polylactone unit (c) in a statistical distribution according to the copolymerization ratio.

The block copolymerized polyesteramide resin (A) of the present invention is prepared by first synthesizing a polyesteramide resin from the components excluding the polylactone unit (c), and then opening the cyclic lactone such as ε-caprolactone on the polyesteramide resin. A method of producing a block copolymer by addition,
Alternatively, the polyesteramide resin and polylactone are melt-mixed at a temperature not lower than the melting point of the polyesteramide resin,
It is produced by a method for producing a block copolymerized polyesteramide by a transesterification reaction.

The polyesteramide resin in the previous step for forming the polylactone unit (c) is ethylene glycol 10
.About.80 mol%, other glycol 20 to 90 mol%, aromatic dibasic acid or lower alkyl ester derivative thereof, 12-aminododecanoic acid and / or
Alternatively, it is produced by melt-polymerizing 11-aminoundecanoic acid. As a specific method, aromatic dibasic acid and other dibasic acids were compared with 1.05
~ 2.0 times moles of glycol and 12-aminododecanoic acid and / or 11-aminoundecanoic acid,
About 150-24 in the presence of conventional esterification catalysts
The reaction is carried out by heating at a temperature of 0 ° C. under normal pressure or by heating at a temperature of about 240 to 260 ° C. under pressure without using a catalyst. When a lower alkyl ester compound of an aromatic dibasic acid or another dibasic acid is used as a starting material, it is about 150 in the presence of a usual transesterification catalyst.
The mixture is heated and reacted at a temperature of ~ 240 ° C under normal pressure. Then 10
2 under reduced pressure of less than mmHg, preferably less than 1 mmHg
Heat polycondensation is carried out at 20 to 290 ° C. At this time, it is preferable to use a polymerization catalyst. After carrying out an esterification reaction or a transesterification reaction using only the component forming the polyester unit (a), 12-aminododecanoic acid and / or 11-aminoundecanoic acid forming the polyamide unit (b) are added, Preliminary reaction may be carried out at 200 to 240 ° C. under N 2 seal for 1 to 2 hours, and then polycondensation may be carried out under reduced pressure. In addition, 12 which is a raw material of the polyamide unit (b)
-Aminododecanoic acid is preferably used alone, but a part thereof may be used in the form of laurolactam.

As the esterification catalyst, titanium compounds, tin compounds and lead compounds, etc., and as the transesterification catalyst, zinc compounds, manganese compounds, cobalt compounds, etc.
Examples of the polymerization catalyst include antimony compounds, titanium compounds, zinc compounds, tin compounds and germanium compounds.

When the phosphorus compound is used together with the polymerization catalyst, the polymerization reactivity and the color tone of the polymer are further improved.

The block copolymerized polyesteramide resin (A) of the present invention can be obtained by a ring-opening addition of a cyclic lactone to the polyesteramide resin obtained by the above production method. Specifically, ethylene glycol 10
.About.80 mol%, other glycol 20 to 90 mol%, aromatic dibasic acid or lower alkyl ester derivative thereof, 12-aminododecanoic acid and / or
Alternatively, a polyesteramide resin obtained by melt-polymerizing 11-aminoundecanoic acid is mixed with 200 of ε-caprolactone.
A ring-opening addition is carried out at ˜260 ° C. under a nitrogen stream in the presence of a tin compound and the like, and finally decompression products and low-boiling substances are removed by reducing the pressure. This method can also be carried out using an extruder. The block copolymerized polyesteramide resin (A) of the present invention can also be obtained by melt-mixing the polyesteramide resin obtained by the above-mentioned production method and polylactone at a temperature higher than the melting point of the polyesteramide and transesterifying. . Specifically, ethylene glycol 1
0-80 mol%, other glycols 20-90 mol%
A polyester amide resin obtained by melt-polymerizing glycol, aromatic dibasic acid or lower alkyl ester derivative thereof, 12-aminododecanoic acid and / or 11-aminoundecanoic acid, and polycaprolactone
Melt polymerize at ˜270 ° C. At this time, a transesterification reaction catalyst may be used.

In this way, the reduced specific viscosity is 0.1 to 1.2.
A block copolymerized polyesteramide resin (A) of dl / g, preferably 0.2 to 1.0 dl / g is produced.

In the block copolymerized polyesteramide resin of the present invention, a component composed of a polyester unit having a specific chemical structure and an aliphatic polyamide unit in the molecular chain and a component composed of an aliphatic polyester unit having a specific chemical structure are in a blocked state. And a resin having good solubility in a coating solvent is obtained by this effect, and the balance between the hardness and processability of the coating film, and particularly the processability at low temperatures below room temperature are improved. In addition, the adhesion to metal substrates and solvent resistance were also improved.

The amino resin (B) used in the present invention is a thermosetting resin obtained by addition reaction of formaldehyde or paraformaldehyde with melamine, benzoguanamine, urea and the like, and a part or all of its methylol group is alkyl. It is etherified. Specifically, methylol melamine, methylol benzoguanamine, methylol urea, methoxylated methylol melamine,
Methoxylated methylol benzoguanamine, methoxylated methylol urea, butoxylated methylol melamine, butoxylated methylol benzoguanamine, butoxylated methylol urea and the like can be mentioned. Among these, alkyl etherified ones are preferable, and methoxylated methylol melamine and butoxylated methylol melamine are particularly preferable, and they can be used alone or in combination.

The coating composition of the present invention contains 50 to 95 parts by weight of the polyesteramide resin (A), particularly preferably 60 to
Those containing 90 parts by weight and 5 to 50 parts by weight of the amino resin (B), particularly preferably 10 to 40 parts by weight are preferable.

If necessary, a curing catalyst, a pigment, a coloring agent, a leveling agent, a weathering agent, etc. may be added to the coating composition of the present invention.

The coating composition of the present invention is generally used by dissolving it in an organic solvent. As the organic solvent, toluene, xylene, "Solvesso"# 100, "Solvesso"# 150, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, butyl normal acetate, methyl cellosolve acetate, ethyl cellosolve acetate, isophorone, butanol, octanol, butyl. From carbitol, its solubility, evaporation rate,
It can be arbitrarily selected depending on the economical efficiency.

A mixer such as a ball mill, an impeller disperser, a sand grind mill, a roll mill or a paint conditioner is used for producing the coating composition of the present invention. The coating is performed by a method such as roll coating, roll coater, spray coating, and electrostatic coating. The baking temperature and time are appropriately selected depending on the size and thickness of the steel plate, the curability of the paint, and the like.

[0034]

The present invention will be described below with reference to examples. All parts in the examples are based on weight. In addition, each measurement item shown in Examples and Comparative Examples complies with the following methods.

Glass transition temperature Measured by DSC.

-Reduced specific viscosity: 0.25 g of resin was dissolved in 25 ml of o-dichlorobenzene / phenol (volume ratio: 4/6) and measured at 25 ° C.

60 ° reflectance was measured using a gloss gloss meter.

Adhesion After a scratch was reached on the coating film using a cutter knife to reach a rugged substrate consisting of 100 squares with a side of 1 mm, a cellophane tape was pressure-bonded, and was not peeled off when peeled off vigorously. The number of remaining gobang eyes was measured.

Pencil hardness Measured according to JIS K5410 using Mitsubishi Uni.

Workability In each measurement temperature atmosphere, the coated steel sheet was bent 180 ° by using a bending tester, and cracks generated in the bent portion were 3 times.
It was observed with a magnifying glass of 0 times. At this time, several bent sheets having the same plate thickness were sandwiched and tested, and the number of sandwiched sheets (R) was set to RT.
Was expressed. The result of the observation shows that the number of the sandwiched steel plates is the smallest among those which do not cause cracks. The smaller the R, the better the workability.

Solvent resistance: The coating film was rubbed with a gauze soaked with methyl ethyl ketone, and the number of times until the substrate became glossy was shown.

Contamination resistance The coated surface was colored with red, black, and blue magic ink, and after 24 hours, the degree of coloring was wiped off with gauze impregnated with n-butanol. The results are expressed as follows. ◎: Very good (no ink marks) ○: Good △: Slightly bad ×: Bad (ink marks clearly remain)

Examples 1-8 252 parts terephthalic acid, 252 parts isophthalic acid, 142 parts ethylene glycol, 132 neopentyl glycol
Parts, bisphenol S ethylene oxide adduct 10
Eight parts were placed in a reaction vessel equipped with a stirrer and a rectification tube, and an esterification reaction was carried out at 240 ° C. for 4 hours under pressure. Next, the mixture was transferred to a reaction vessel equipped with a helical ribbon type stirring blade that had been sufficiently replaced with nitrogen, and 88 parts of 12-aminododecanoic acid was added,
Preliminary reaction at 240 ℃ for 1 hour, zinc acetate 0.2
Part, antimony trioxide 0.1 part, and phosphoric acid 0.1 part were added, and then the reaction conditions of 275 ° C. and 1 mmHg or less were reached for about 1 hour according to a temperature rising and depressurizing program. In that state, the polycondensation reaction is performed for 2 hours and 30 minutes. Then, the temperature in the reaction system was set to 240 ° C., and ε-
100 parts of caprolactone and 0.1 part of monobutylmonohydroxytin oxide are added, and after stirring for 30 minutes, the pressure is reduced to remove unreacted components to complete the reaction. The block copolymerized polyesteramide resin (A-1) thus obtained had a glass transition temperature of 41 ° C. and a reduced specific viscosity of 0.65 dl / g. The ratio of the polyamide unit composed of polydodecanamide determined by elemental analysis is 1
It was 0% by weight, and the composition ratio of the polyester unit obtained from the H-NMR spectrum was as follows: acid component was terephthalic acid / isophthalic acid = 50/50 (molar ratio), and glycol component was ethylene glycol / neopentyl glycol / bisphenol S. Ethylene oxide adduct = 50/40/1
0 (molar ratio), and the polylactone unit was 10% by weight.

In the same manner, block copolymerized polyesteramide resins (A-2) to (A-8) having the composition of polyester units shown in Table 1 and the polymer composition shown in Table 2 were produced in the same manner.

[0045]

[Table 1]

[0046]

[Table 2]

Reference Examples 1 to 8 The composition of the polyester unit is shown in Table 3 in the same manner as in Example 1.
In addition, the polymer composition of resin (A
-9) to (A-16) were produced.

[0048]

[Table 3]

[0049]

[Table 4]

Examples 9 to 16 100 parts of the block copolymerized polyesteramide resin (A-1) obtained in Example 1 was dissolved in 150 parts of a mixed solvent of cyclohexanone / "Solvesso"# 150 (weight ratio 50/50). . 90 parts of this solution, 40 parts of titanium oxide, 4 parts of methoxylated methylol melamine ("Cymel" 303, manufactured by Mitsui Cyanamide Co., Ltd., solid content 98% or more), 26 parts of the above mixed solvent and glass beads were added, and a paint conditioner was used. After dispersing the pigment, the glass beads were removed to obtain a coating composition. The block copolymerized polyesteramide resin (A-1) was replaced with (A-2) to (A-8), and "cymel" was obtained as methoxylated methylol melamine.
Using 303 or "Cymel" 325 (manufactured by Mitsui Cyanamide Co., Ltd., solid content: 80%), a coating composition was similarly prepared with the coating composition shown in Table 5. "Cymel" 3
When 03 was used, 0.8% by weight of ρ-toluenesulfonic acid was used as a catalyst, based on "Cymel" 303. Each of the obtained coating compositions is 70 × 150 × 0.5 mm
It was applied to a chromate-treated electrogalvanized steel sheet having a size of 5 to a thickness of about 20 μm by a bar coater, and then baked at 230 ° C. for 5 minutes. Table 5 shows the test results of the obtained coated steel sheet.

[0051]

[Table 5]

As is clear from Table 5, the coated steel sheet using the block copolymerized polyesteramide resin of the present invention has a good balance between hardness and workability, and is particularly excellent in workability at low temperatures.

Comparative Examples 1 to 8 Polyesteramide resins (A-9) to (A-16) were used, and the composition shown in Table 6 was used to prepare a coating composition in the same manner as in Example 1 and the coating film physical properties were evaluated. The results are shown in Table 6.

[0054]

[Table 6]

As is clear from the results of Table 6, Comparative Examples 1 to 1
The resin of No. 3 has a low solvent solubility and cannot be made into a paint, and the coating films of Comparative Examples 4 to 8 have a poor balance of hardness and workability as compared with the coating films of Examples 1 to 8, and particularly low temperature processing. The sex is inferior.

[0056]

INDUSTRIAL APPLICABILITY The novel block-copolymerized polyesteramide resin of the present invention has excellent solubility in a coating solvent, and a copolymer having a preferred degree of polymerization can be obtained by the above-mentioned production method. Furthermore, the coating composition for a coated steel sheet of the present invention forms a coating film having a good balance between hardness and workability, and particularly excellent in low-temperature workability.

Claims (2)

[Claims] 1. A glycol component comprising 10 to 80 mol% of ethylene glycol and 20 to 90 mol% of other glycol, 80 to 100 mol% of aromatic dibasic acid, and 0 to 20 mol% of other dibasic acid. 50 to 90% by weight of an amorphous polyester unit (a) formed from an acid component, and dodecane amide and / or undecane amide (b)
1 to 40% by weight, and 5 to 40% by weight of a polylactone unit (c) formed from lactones, using a mixed solvent of o-dichlorobenzene / phenol (volume ratio 4/6), and a concentration of 1.0. Reduced specific viscosity (ηsp /
Block copolymerized polyesteramide resin having C) of 0.1 to 2.0 dl / g. 2. A coating composition for a coated steel sheet, comprising the block copolymerized polyesteramide resin (A) according to claim 1 and an amino resin (B).