JP5766416B2 - Resin composition for paint - Google Patents

Description

  The present invention relates to a resin composition for coatings used in can coatings for cans and lids such as beverage cans and food cans.

  Conventionally, paints using bisphenol A type epoxy resin are often used on the inner surface of cans and lids of beverage cans, food cans, etc., but bisphenol A has an effect on estrogen action and the brains of fetuses and infants. There is a report that there is a possibility of giving.

  The resin composition using the above-described bisphenol A type epoxy resin is widely used because it has excellent processability, retort resistance, corrosion resistance, and the like. For the above reasons, paints that do not use bisphenol A as a raw material are demanded from the market, but the actual situation is that satisfactory performance as a can application cannot be obtained.

  As an example of a bisphenol A-free resin composition, Patent Document 1 discloses a modified resin obtained by reacting a branched thermoplastic polyester resin with a polyhydric acid anhydride compound and / or a polymer containing an acid anhydride group / novolak phenol resin / There is a description that corrosion resistance and processability are improved in a paint composition for cans formed by blending an epoxy resin. However, this does not yet provide sufficient workability, corrosion resistance and impact resistance.

  Patent Document 2 discloses a carboxy-containing polyester resin / novolak type epoxy resin / curing catalyst / phenol having a number average molecular weight in the range of 1,000 to 20,000 and an acid value in the range of 5 to 170 mgKOH / g. A coating composition made of a resin has been proposed, and there is a description that it can form a coating film that has good workability and curability, excellent flavor retention, and does not dissolve bisphenol A, but has corrosion resistance and impact resistance. Still not enough.

  Patent Document 3 discloses a polyester resin having a phenolic hydroxyl group and having an aromatic ring in which at least one of ortho-position and para-position to the hydroxyl group is a hydroxyl group / linear saturated copolymer having no phenolic hydroxyl group A resin composition containing a polyester resin / and a phenol resin has been proposed. Although the curability and retort resistance are improved, the corrosion resistance and impact resistance are insufficient.

  Patent Document 4 proposes a resin composition having a polyester resin / resole type phenol resin having a number average molecular weight in the range of 5,000 to 100,000 and having a specific polycarboxylic acid component and a polyalcohol component. Certainly, the curability and workability are excellent, but the corrosion resistance, impact resistance and retort whitening resistance are still insufficient.

JP 2001-40278 A Japanese Patent Laid-Open No. 2001-72922 JP 2005-126635 A JP 2006-124497 A

  The subject of the present invention is particularly used in paints for can bodies and lids of beverage cans, food cans, etc., and in addition to being excellent in processability, retort resistance and hygiene of the coating film, in particular in corrosion resistance and impact resistance. The object is to provide a resin composition that is excellent and does not contain bisphenol A as a raw material.

  The present inventors cure the polyester resin (A), the phenol resin (B), the metal alkoxide compound and / or the metal chelate compound (C), and are excellent in the processability, retort resistance and hygiene of the coating film. In addition, the present inventors have found a resin composition for use in paints for cans, beverage cans or lids for cans having excellent performance in terms of corrosion resistance and impact resistance, and the present invention has been completed.

  That is, this invention is providing the resin composition characterized by containing a polyester resin (A), a phenol resin (B), a metal alkoxide type compound, and / or a metal chelate type compound (C).

  The resin composition of the present invention is used especially on the inner surface side of can bodies or lids of beverage cans, food cans, etc., does not contain bisphenol A, processability, retort resistance, hygiene, especially corrosion resistance, impact resistance A film having excellent properties can be formed.

  The resin composition of the present invention relates to a resin composition comprising a polyester resin (A), a phenol resin (B), a metal alkoxide compound, and / or a metal chelate compound (C). Hereinafter, the composition of the present invention will be described in more detail.

  The polyester resin (A) used in the resin composition of the present invention preferably has a number average molecular weight of 3,000 to 100,000 and a glass transition temperature of 0 ° C. to 100 ° C. The number average molecular weight is a number average molecular weight in terms of polystyrene of GPC.

  The polyester resin (A) may be any one obtained by esterifying a polybasic acid component and a polyhydric alcohol component. Examples of the polybasic acid component include one or more dibasic acids such as phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, fumaric acid, adipic acid, azelaic acid, sebacic acid, dimer acid, and the like. The lower alkyl esterified product of benzoic acid, crotonic acid, pt-butylbenzoic acid and other monobasic acids, trimellitic anhydride, methylcyclohexeric tricarboxylic acid, pyromellitic anhydride, etc. A tribasic or higher polybasic acid is used in combination.

  Examples of the polyhydric alcohol component include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 3-methylpentanediol, 1,4-hexanediol, 1,6-hexanediol, and cyclohexanedi. A dihydric alcohol such as methanol is mainly used, and a trihydric or higher polyhydric alcohol such as glycerin, trimethylolethane, trimethylolpropane and pentaerythritol can be used in combination as necessary. These polyhydric alcohols can be used alone or in admixture of two or more.

  The polyester resin (A) used in the resin composition of the present invention preferably has a number average molecular weight of 3,000 to 100,000, more preferably 6,000 to 30,000. The glass transition temperature is preferably 0 ° C. to 100 ° C., more preferably 10 to 90 ° C., and still more preferably 30 to 60 ° C. When the number average molecular weight is lower than 3,000, the processability is deteriorated. When the number average molecular weight is higher than 100,000, the viscosity at the time of coating becomes high and appropriate coating cannot be performed. On the other hand, when the glass transition temperature is lower than 0 ° C., the barrier properties such as water vapor and oxygen are inferior, so that the corrosion resistance of the coating film is inferior and the blocking property is also inferior. When the glass transition temperature is higher than 100 ° C., the coating film becomes hard and the workability deteriorates.

  Examples of commercially available products include Byron 300, 500, 560, 600, 630, 650, 670, Byron GK130, 140, 150, 190, 330 manufactured by Toyobo Co., Ltd. 590, 680, 780, 810, 890, 200, 226, 240, 245, 270, 280, 290, 296, 660, 885, Byron GK250, 360, 640, 880, Unitika Co., Ltd. Eritel UE-3220, 3500, 3210, 3215, 3216, 3620, 3240, 3250, 3300, UE-3200, 9200 3201, 3203, 3350, 3370, 3380, 3600, 3600, 3980, 3660, 3690, 960 , The 9800, Toagosei Co., Ltd. Aron Melt PES-310, the 318, the 334, the 316, such as the 360, and the like.

  Among the polyester resins (A) used in the resin composition of the present invention, the polyester resin (A-1) essentially containing diphenolic acid has excellent curability with the phenol resin, and as a result, particularly whitening resistance to retort. It will be excellent. The amount of diphenolic acid introduced in the polyester resin (A-1) is preferably 0.1 to 10% by mass. If it is lower than 0.1% by mass, the effect of improving curability and retort whitening resistance cannot be obtained, and if it exceeds 10% by mass, curing proceeds too much and the workability becomes inferior.

  If only typical examples of the phenol resin (B) used in the resin composition of the present invention are exemplified, carboxylic acid, m-cresol, m-ethylphenol, 3,5-xylenol, m-methoxyphenol, etc. Trifunctional phenolic compounds or various bifunctional compounds such as p-cresol, o-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, 2,5-xylenol, m-methoxyphenol Phenol and formaldehyde are synthesized in the presence of an alkali catalyst. These phenol compounds can be used alone or in admixture of two or more. Moreover, the thing of the form which etherified one part or all part of the methylol group contained in a phenol resin by alcohol with 1-12 carbon atoms can also be used.

  The metal alkoxide compound and / or metal chelate compound (C) that can be used in the resin composition of the present invention are polyester resin (A), phenol resin (B), and epoxy resin having no bisphenol A skeleton (D ) And a curing reaction. A crosslinking reaction proceeds between the functional group of each resin and the metal alkoxide compound and / or metal chelate compound (C). By incorporating a metal into the crosslinked structure in the coating film, the strength of the coating film is improved, and as a result, the function of dramatically improving impact resistance and corrosion resistance is imparted. Further, the metal alkoxide compound and / or metal chelate compound (C) is low-temperature curable compared with conventionally known organic compounds alone, for example, polyester / phenol, polyester / phenol / epoxy, and polyester / melamine resin compositions. It is characterized by being particularly excellent in curability at a high temperature in a short time. By utilizing this feature, it is possible to lower the baking temperature and shorten the time, which has been difficult with only known organic compounds, leading to energy cost reduction and carbon dioxide emission suppression. Examples of the metal alkoxide compound and / or metal chelate compound (C) include alkoxide metal compounds such as zirconium, aluminum, titanium, and tin, and metal chelate compounds in which acetoacetic acid is coordinated to a metal.

  The epoxy resin (D) having no bisphenol A used in the resin composition of the present invention mainly improves the adhesion of the coating film, and is particularly preferably a novolac type epoxy resin. As a commercial product of the novolak type epoxy resin, Epicron N-665, 670, 673, 680, 690, 695, 730, 740, 770, 870, 865, manufactured by DIC Corporation 870, ECN-1273 manufactured by Asahi Kasei Epoxy Co., Ltd., ECN-1299 and the like.

  The blending ratio (mass) of the polyester resin (A) and the phenol resin (B) in the resin composition of the present invention is preferably 75:25 to 95: 5. If the ratio of the polyester resin (A) is lower than 75, the elongation of the coating film is insufficient, so that the workability is deteriorated. If it is higher than 95, the curability is insufficient and the retort whitening resistance is deteriorated. The compounding ratio of the metal alkoxide compound and / or metal chelate compound (C) preferably contains 0.01 to 10% by mass in the total solid content. When the content of the metal alkoxide compound and / or the metal chelate compound (C) is lower than 0.01% by mass, the effect of impact resistance and corrosion resistance cannot be obtained. In addition to being hard and inferior in workability, problems such as thickening or gelation of the paint occur. The compounding ratio of the epoxy resin (D) not having bisphenol A is preferably 0.1 to 30% by mass in the total solid content. When the ratio of the epoxy resin (D) having no bisphenol A is lower than 0.1% by mass, the adhesion of the coating film becomes inferior, and when it exceeds 30% by mass, the retort whitening resistance becomes inferior.

  The resin composition of the present invention can further contain a curing catalyst (E). Examples of the curing catalyst (E) include, in particular, typical ones, inorganic acids such as phosphoric acid, organic acids such as dodecylbenzenesulfonic acid and toluenesulfonic acid, and those blocked with amines or the like. Can be used. The mixing ratio of the curing catalyst (E) is preferably 0.01 to 5% in the total solid content.

  Examples of the organic pigment and / or inorganic pigment (F) that can be used in the resin composition of the present invention include chromate (yellow lead, chromium vermillion) ferrocyanide (bitumen), sulfide (cadmium yellow, cadmium). Red), oxide (titanium oxide, bengara, iron black, zinc oxide) sulfate (barium sulfate, lead sulfate), silicate (ultraviolet, calcium silicate), carbonate (calcium carbonate, magnesium carbonate) phosphate (cobalt violet) ) Metallic powder (aluminum powder, bronze) Inorganic pigments such as carbon (carbon black), azo-based (benzidine yellow, Hansa Yellow, Vulcan Orange, Permanent Red F5R, Carmine 6B, Lake Red C, Chromoval Red, Chromoval Yellow ), Phthalocyanineline (phthalocyanine blue, lid) Sianiline Green), vat dyes (Induslen Blue, Thioindigo Bordeaux) dyed rakes (Eosin Lake, Quinoline Yellow, Rhodamine Lake, Methyl Violet Lake), quinacrines (Sincacia Red, Shinkasia Violet) Organic pigments such as (PV Fast Violet BL) can be mentioned, and these may be used alone or in combination. These pigments make it possible to color the coating film and impart design properties, and arbitrary organic pigments and inorganic pigments can be added to the required design.

  The blending ratio of the organic pigment and / or inorganic pigment (F) is preferably 0.1 to 70 parts by mass with respect to the total solid content.

The resin composition of the present invention can be preferably used particularly for can coatings. Furthermore, it can be used as a coating agent for various metal materials such as aluminum and tin-plated steel sheets or pretreated metals and steel, and other materials and processed products such as wood and films. Good. Hereinafter, the use as a paint for cans will be described.

  The solvent that can be used in the paint using the resin composition of the present invention is not particularly limited, but for example, aromatic hydrocarbons such as toluene, xylene, Solvesso # 100, Solvesso # 150, hexane, heptane, octane, Examples include aliphatic hydrocarbons such as decane, and various ester organic solvents such as methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, amyl acetate, ethyl formate, and butyl propionate. Water-miscible organic solvents such as alcohols such as methanol, ethanol, propanol, and butanol, ketones such as acetone, methyl ethyl ketone, and cyclohaxanone, ethylene glycol (mono, di) methyl ether, ethylene glycol (mono, di) ethyl ether, ethylene Glycol monopropyl ether, ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol (mono, di) methyl ether, diethylene glycol (mono, di) ethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol (mono, di) methyl Ether, propylene glycol (mono, di) methyl ether, propylene glycol monopropyl ether , Propylene glycol monobutyl ether, dipropylene glycol (mono, di) include various organic solvents glycol ether such as methyl ether.

  Conventionally known lubricants, antifoaming agents, leveling agents, lubricants, pigments and the like can be added to the paint for cans using the resin composition of the present invention. In addition, other curing agents such as a melamine resin, a benzoguanamine resin, and an isocyanate resin may be used in combination as a curing auxiliary agent, and these can be used in combination with an appropriate one depending on the drying conditions and lamination conditions of the film.

The paint for cans using the resin composition of the present invention, such as air spray, airless spray or electrostatic spray, by various means such as spray coating, dip coating, roll coater coating, gravure coater and electrodeposition coating, It can be applied as a metal substrate such as a steel plate or an aluminum plate for cans or a paint such as a PET pet film. The coating amount is preferably about 0.1 to 20 μm in terms of dry coating thickness.

  In addition, when the resin composition of the present invention is used as a can coating, it is preferably baked within a range of 100 to 280 ° C. for 1 second to 30 minutes. A coating film can be formed.

  Hereinafter, the present invention will be specifically described with reference to Examples. In the examples, “part” and “%” represent “part by mass” and “% by mass”, respectively.

Example of Synthesis 1 (Synthesis of polyester resin (A-1-1) containing diphenolic acid as an essential component)
As an acid component, 50 parts by mass of terephthalic acid, 112 parts by mass of isophthalic acid, 4.9 parts by mass of diphenolic acid, and 50 parts by mass of 2-ethyl-2-butyl-1,3-butanediol as a polyhydric alcohol component, , 4-butanediol 99 parts by weight, 1,4-cyclohexanedimethanol 48 parts by weight, titanium tetrabutoxide 0.07 parts by weight are charged into a 2 L flask, gradually heated to 220 ° C. over 4 hours, water is retained. Esterification was carried out. After distilling a predetermined amount of water, the polymerization was carried out under reduced pressure to 10 mmHg over 30 minutes, the temperature was raised to 250 ° C., and the latter polymerization was carried out at 1 mmHg or less for 50 minutes. Next, the polymerization under reduced pressure was stopped, the mixture was cooled to 220 ° C. under a nitrogen stream, 1.9 parts by mass of trimellitic anhydride was added, and the mixture was stirred at 220 ° C. for 30 minutes to perform carboxy group modification (post-addition), and then resin The polyester resin (A-1-1) having a number average molecular weight of 22,000, an acid value of 5 (mgKOH / g), and a glass transition temperature of 30 ° C. was obtained. Then, it cooled to 100 degrees C or less, and diluted with the mixed solution of cyclohexanone / solvesso 150 = 50/50, and obtained the polyester resin (A-1-1) solution of 40% of non volatile matters.

The following raw materials were blended and stirred at the ratios shown in Tables 1 and 2 (the numbers in the tables indicate the solid content mass ratios) to prepare paints of Example 1-8 and Comparative Example 1-4.
(1) Polyester resin (A-1-1) Number average molecular weight 22,000 of polyester resin containing diphenolic acid as an essential component, acid value 5 (mgKOH / g), glass transition temperature 30 ° C., cyclohexanone / solvesso 150 = 40% dissolved product of 50/50 mixed solution.
(2) Polyester resin (A-1-2) = Byron GK-360, Toyobo Co., Ltd. number average molecular weight 16,000, acid value 5 (mgKOH / g), glass transition temperature 56 ° C., cyclohexanone / solvesso 150 = 40% dissolved product of 50/50 mixed solution.
(3) Phenolic resin (B-1) = TD2495, DIC paracresol phenolic resin, 50% normal butanol solution (4) Metal alkoxide compound (C-1) = ZA-65, Zirconium butoxide manufactured by Matsumoto Fine Chemical Co., Ltd. (5) Metal chelate compound (C-2) = ZC-150, Matsumoto Fine Chemical Co., Ltd. zirconium acetylacetone chelate (6) Metal chelate compound (C-3) = ALCH-TR, Kawaken Fine Chemical Co., Ltd. aluminum tris Ethyl acetate (7) Epoxy resin (D-1) = Epiclon N-660, Cresol novolac type epoxy resin manufactured by DIC Corporation, 50% methyl ethyl ketone solution (8) Curing catalyst (E-1) NACURE 5925 Enomoto Kasei Co., Ltd. Dodecylbenzenesulfone (Catalyst), 25% solution

[Preparation of evaluation sample]
On the tinplate ET-1 plate, the paints for cans of Examples 1 to 8 and Comparative Examples 1 to 4 were applied by a coater so that the dry film thickness was 10 μm, and the maximum material temperature reached 180 ° C. A baked coated plate was obtained for 10 minutes.

〔Evaluation item〕
1-1. Pencil Hardness Test Test Pencil hardness was measured according to JIS-K-5400 using a high-grade pencil defined in JIS-S-6006.

1-2. Pencil hardness test in hot water Immerse the coated plate in hot water at 80 ° C. and leave it in the hot water 30 minutes later, and then use a high-grade pencil specified in JIS-S-6006 and pencil hardness according to JIS-K-5400. Was measured.

1-3. Workability test test The coated plate was punched into a cap shape with a diameter of about 25 mm and a height of about 17 mm, and then screwed, and then subjected to retort treatment at 125 ° C / 30 minutes to determine the degree of cracking and peeling of the coating film. The determination was made visually according to the following criteria. ○ Above is the practical level.
(Double-circle): There is no crack and peeling at all.
○: There are some cracks and peeling.
Δ: Slightly cracking and peeling
X: Cracking and peeling are remarkable.

1-4. Water resistance test test After the coated plate was retorted at 125 ° C./30 minutes, the degree of whitening of the coating film was visually determined. ○ Above is the practical level.
A: There is no whitening at all.
○: Some whitening is observed. Δ: Whitening is slightly high.
X: Whitening is remarkable.

1-5. Adhesion test test A sample is prepared by punching a painted plate into a cap shape having a diameter of about 25 mm and a height of about 17 mm and then screwing it. A cellophane adhesive tape was affixed to the threaded portion, and the peeled state of the coating film after peeling off was visually determined. After the prototype (before treatment) and the retort treatment at 125 ° C./30 minutes, the degree of cracking and peeling of the coating film was visually determined according to the following criteria. ○ Above is the practical level.
A: No peeling at all.
○: There is some peeling.
Δ: Slightly much peeling.
X: Peeling is remarkable.

1-6. Corrosion resistance test The coated plate was immersed in an aqueous solution containing 3% sodium chloride and 3% citric acid, subjected to a retort treatment at 120 ° C for 90 minutes, and the peeled state of the coating film was visually determined.
(Evaluation method)
○: No peeling.
Δ: There is little peeling.
X: There is much peeling.

1-7. About the one that was subjected to retort treatment at 120 ° C for 90 minutes in tap water after bending the tin plate between three test pieces that were folded in two with the impact-resistant coating on the outside, A current value (mA) of a processed part width of 2 cm when a voltage of 6 V was applied to the bending tip part for 3 seconds was evaluated by the following method. ○ or more is practical level ◎: The energization amount is less than 15 mA.
○: The energization amount is 15 mA or more and less than 30 mA.
Δ: The energization amount is 30 mA or more and less than 45 mA.
X: The energization amount is 45 mA or more.

The evaluation results are shown in Tables 1 and 2. The numbers in the table represent solid weight ratios.

  The resin composition of the present invention does not contain bisphenol A which may adversely affect the human body in terms of estrogen action, etc., and has good workability, coating film hardness, water resistance and curability, and further corrosion resistance. It can be widely used as a paint for various cans with excellent impact resistance.

Claims (4)

Contains polyester resin (A-1), phenol resin (B), metal alkoxide compound and / or metal chelate compound (C), and novolac type epoxy resin (D-1) containing diphenolic acid as an essential component. The polyester resin (A-1) has a number average molecular weight of 3,000 to 100,000, a glass transition temperature of 0 ° C. to 100 ° C., and the polyester resin (A-1) and phenol. The resin composition for paints, wherein the ratio of the resin (B) is 75:25 to 95: 5 by mass ratio.
The resin composition for coatings according to claim 1, wherein the content of the metal alkoxide compound and / or the metal chelate compound (C) is 0.01 to 10% by mass in the total solid content of the resin composition.
The resin composition for coatings according to claim 1 or 2, comprising a curing catalyst (E).
The resin composition for coatings according to any one of claims 1 to 3, comprising an organic pigment and / or an inorganic pigment (F).