JPH11172184A - Printing ink binder for laminated can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject binder excellent in resistance to retort whitening and post-laminating processability. SOLUTION: This printing ink binder for laminated cans contains a polyesterurethaneurea resin which is prepared by reaction between a polyester polyol, an organic dissocyanate and chain extender, wherein acid components derived from the polyester polyol are such that the weight ratio of aromatic discarboxylic acid (s) such as terephthalic acid to aliphatic dicarboxylic acid (s) is (30:70) to (100:0) and urea linkage concentration is 0.05-0.8 mmol/g based on the solid content of the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a printing ink binder for laminated cans. More specifically, the present invention relates to a printing ink binder for laminate cans having excellent retort whitening resistance and workability after lamination.

[0002]

2. Description of the Related Art Conventionally, the outer surface of a metal can, such as a food and drink can, has been painted and printed to impart corrosion resistance, decorativeness and the like. When painting and printing on the outer surface of a metal can, a coating layer made of white paint is formed on the outer surface of the can, and exterior printing and finish varnish coating are applied.

[0003] However, according to these coating methods, the painted surface is easily damaged by an external impact, and the aesthetic appearance may be impaired. Further, in order to store metal formed in the shape of a can, inventory is stored. The disadvantage was that in some cases a very large space was required.

[0004] Therefore, the printing surface is protected from external impact,
In order to make inventory storage compact, conventional painting and printing processes are eliminated, and instead pre-printed film is pre-coated with adhesive and heat lamination is performed on metal plates for metal cans. It is becoming.

Conventionally, printing inks have been used in which a pigment is dispersed in a binder such as a polyester resin, an acrylic resin, an epoxy resin, a polyamide resin, a nitrified cotton, or a vinyl chloride / vinyl acetate copolymer. In recent years, adhesion to the film, residual solvent, blocking resistance, printing suitability, etc., and even under high hot water conditions such as heat sterilization, good adhesion to the film, polyurethane binder resin A series of resins are used.

[0006] However, in the conventional polyurethane-based resin, whitening due to water spots has occurred on the printed surface of the laminate can under the condition of high hot water during heat sterilization, and the whitening remains even after the heat sterilization treatment.
If the aesthetic appearance of the can is impaired, or when the metal plate is processed into a can after the printed film is heat-laminated, the parts that have been subjected to processing such as neck-in processing and flange processing may be delaminated under high hot water conditions. There was a problem that it would.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the occurrence of whitening caused by high-temperature hot water at the time of heat sterilization after heat sterilization.
An object of the present invention is to provide a printing ink binder for laminated cans, in which a portion subjected to flange processing is hardly delaminated.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the problems can be solved by using a specific polyester urethane urea resin. It was completed.

That is, in the present invention, a polyester polyol, an organic diisocyanate and a chain extender are used as reaction components, and the ratio of an aromatic dicarboxylic acid to an aliphatic dicarboxylic acid in the acid component derived from the polyester polyol is determined by weight. Aliphatic dicarboxylic acid / aliphatic dicarboxylic acid = 30/70 to 100/0 and a polyester urethane urea resin having a urea bond concentration of 0.05 to 0.8 mmol / g with respect to the resin solid content. And a printing ink binder for a laminate can.

[0010] The present invention also relates to the printing ink binder for a laminate can described above, wherein the aromatic dicarboxylic acid is terephthalic acid. The present invention further relates to the printing ink binder for a laminate can described above, further comprising a monomer having one or more unsaturated double bonds in the molecule.

In the polyester urethane urea resin of the present invention, an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid are used as an acid component derived from a polyester polyol in a weight ratio of aromatic dicarboxylic acid / aliphatic dicarboxylic acid = 30.
/ 70 to 100/0. As a reaction component, the polyester polyol alone may be used, or the weight ratio of aromatic dicarboxylic acid / aliphatic dicarboxylic acid is adjusted to be 30/70 to 100/0,
Other polyester polyols can be used in combination.
The molecular weight of the polyester polyol is not particularly limited, but is preferably from 1,000 to 6,000 in number average molecular weight. When the number average molecular weight of the polyester polyol is less than 1,000, the obtained urethane urea resin tends to have poor printability and coating suitability, and when it exceeds 6,000, the drying property and the anti-blocking property tend to decrease. There is.

When the weight ratio of the aromatic dicarboxylic acid constituting the acid component derived from the polyester polyol is lower than 30% by weight in the acid component, the portion subjected to neck-in processing and flange processing is subjected to high hot water conditions. It is not preferable because it causes delamination.

As the constituent components of the polyester polyol, the polyol components include ethylene glycol, diethylene glycol, triethylene glycol, 2-propanediol, 1,3-propanediol, and 1,3-propanediol.
Butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-
Saturated and unsaturated low molecular weight glycols such as pentanediol, 1,6-hexanediol, octanediol, bisphenol A, hydrogenated bisphenol A, dipropylene glycol, and the like. As the acid component, phthalic anhydride, Aromatic dicarboxylic acids such as isophthalic acid and terephthalic acid and / or aliphatic acids such as adipic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, azelaic acid, sebacic acid and suberic acid Examples thereof include dicarboxylic acids, and acid anhydrides corresponding to aromatic and aliphatic dicarboxylic acids.

Of these, terephthalic acid is preferred as the aromatic carboxylic acid as the acid component, since the whitening generated under high-hot water conditions during heat sterilization is easily lost after the heat sterilization treatment.

In addition, a low molecular weight glycol may be added as a polyol component during the urethanization reaction as long as the number average molecular weight of the polyester polyol and the low molecular weight glycol does not fall below 1,000. As the low molecular glycol, those described above can be used.

Incidentally, polyether polyols, polybutadiene glycols, and polycarbonate polyols are not suitable for the present invention because they have insufficient adhesiveness to films, especially to polyethylene terephthalate (PET) films, and hot water resistance.

As the organic diisocyanate compound, various known aromatic, aliphatic or alicyclic diisocyanates can be used, but aliphatic or alicyclic diisocyanates are preferred from the viewpoint of resistance to discoloration during thermal lamination. Used. Examples of the aliphatic diisocyanate include butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, xylylene diisocyanate, and m-tetramethyl xylylene diisocyanate. Representative examples include isocyanate and dimer isocyanate obtained by converting a carboxyl group of a dimer acid into an isocyanate group.

Representative alicyclic diisocyanates include cyclohexane-1,4 diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexane diisocyanate and the like. As an example. As the aromatic diisocyanate, 1,5-naphthylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 4,4′-dibenzyl diisocyanate, dialkyldiphenylmethane diisocyanate,
Tetraalkyldiphenylmethane diisocyanate,
Typical examples include 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, and tolylene diisocyanate.

Examples of the chain extender include various known diamines and glycols. Examples of the diamines include ethylenediamine, propylenediamine, hexamethylenediamine, triethylenetetramine, diethylenetriamine, isophoronediamine, dicyclohexylmethane-4,4′-diamine, 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, and di2. -Hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2
Representative examples thereof include diamines having a hydroxyl group in the molecule, such as -hydroxypropylethylenediamine and di-2-hydroxypropylethylenediamine, and dimerdiamines obtained by converting a carboxyl group of dimer acid into an amino group.

Further, in the urethanization reaction, a reaction terminator may be used. Examples of such a reaction terminator include dialkylamines such as di-n-butylamine,
Examples include aromatic amines such as benzylamine and dibenzylamine, alkanolamines such as diethanolamine, and alcohols such as ethanol and isopropyl alcohol.

The polyester urethane urea resin of the present invention is obtained by reacting a prepolymer having terminal isocyanate groups with a chain extender and, if necessary, a reaction terminator in a suitable solvent. The concentration of the urea bond formed in the reaction with the amine and the reaction terminator is 0.05 to 0.8 mmol /
g. It is necessary to adjust the amounts of the chain extender and the amine as a reaction terminator with respect to the prepolymer having both terminal isocyanate groups.

When the urea bond concentration with respect to the resin solid content is 0.
When the amount is less than 05 mmol / g, tackiness occurs and blocking resistance decreases, which is not preferable. Also, 0.8
If the amount is more than mmol / g, whitening that occurs under high hot water conditions during heat sterilization remains even after the heat sterilization treatment, and is undesirable because it impairs the aesthetic appearance of the can.

The urea bond concentration can be calculated based on the following formula from the charged amount in the case of a resin having no amine value. Urea bond concentration (mol / g) = (molar number of amino group) / (prepared amount of resin solid content) × 100

In the printing ink binder for a film laminate can of the present invention, the polyester polyol, the organic diisocyanate compound and the chain extender are preferably used in an equivalent ratio of an isocyanate group of the organic diisocyanate compound to a hydroxyl group of the polyester polyol of 1.0. /1-2.0
/ 1, more preferably 1.1 / 1 to 1.8 / 1.
And a polyester urethane urea resin obtained by reacting within the range described above. If the equivalent ratio of the isocyanate group to the hydroxyl group is less than 1.0 / 1, the formation of a urea bond in the chain extender will not be possible, and the stickiness will be produced, and the blocking resistance will be reduced. On the other hand, when the equivalent ratio between the isocyanate group and the hydroxyl group is more than 2.0 / 1, the discoloration during thermal lamination increases.

The method for producing the polyester urethane urea resin is not particularly limited, and it may be produced according to the same method as a general method for producing a polyester urethane urea resin. For example, a diisocyanate component and a polyol component are reacted at an equivalent ratio of an excess of isocyanate groups to form a prepolymer having isocyanate groups at both ends, and then these are chain-extended in a suitable solvent and, if necessary, a reaction terminator. And the compounds can be reacted at once.

As the solvent used in the above-mentioned production method, there can be mentioned a solvent generally known as a solvent for printing ink. For example, aromatic solvents such as toluene and xylene, alcohol solvents such as methanol, ethanol, isopropanol and n-butanol, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, and ester solvents such as ethyl acetate and butyl acetate. These can be used alone or in a mixture of two or more. The molecular weight of the obtained polyester urethane urea resin is not particularly limited, but is preferably 5,000 to 200,000 by weight average molecular weight, more preferably 10,000 to 150,000. If it is less than 5,000, the drying property, the blocking resistance, the film strength, and the oil resistance tend to be reduced. On the other hand, 20
If it exceeds 000, the viscosity of the resin solution increases,
This is not preferred because the pigment dispersion tends to decrease.

The printing ink binder for a laminate can of the present invention may contain a monomer having one or more unsaturated double bonds in the molecule. By adding the monomer having one or more unsaturated double bonds and irradiating with energy rays, there is an effect that the crosslinking of the printed matter is promoted and the film strength is increased.

Representative examples of the monomer having one or more unsaturated double bonds include aliphatic acrylate, allyl acrylate, allyl methacrylate, allylated cyclohexyl diacrylate, alicyclic diacrylate, and aliphatic diacrylate. Acrylates, aliphatic triacrylates, aliphatic tetraacrylates, benzyl acrylates, benzyl methacrylates, diacrylated isocyanurates, bisphenol A dimethacrylate, diethylene glycol dimethacrylate, dipentaerythrol hexaacrylate, pentaeristol triacrylate, pentaeristol tetraacrylate , Pentaeristol tetramethacrylate, trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, tris (A (Riloxyethyl) isocyanurate, tris (methacryloxyethyl) isocyanurate methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, acrylic acid, 2-hydroxyethyl acrylate, hydroxy acrylate Propyl, acrylamide, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, methacrylic acid, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate , Maleic acid, itaconic acid, N-methylolacrylamide,
Examples include diacetone acrylamide, glycidyl methacrylate, styrene, vinyl toluene, vinyl acetate, acrylonitrile and the like.

When a printing ink for a laminate can is produced, various pigments and the above-mentioned solvent are added to the printing ink binder for a laminate can, and the mixture is ground and dispersed. Further, an additive such as an anti-blocking agent and a plasticizer, a surfactant for improving ink fluidity and dispersibility, or a resin having compatibility may be used within a range that does not cause discoloration during heat lamination. can do. As compatible resins that can be used in combination, nitrified cotton, chlorinated polyethylene,
Chlorinated polypropylene, chlorinated polyolefins such as chlorinated ethylene / propylene, chlorsulfonated polyolefins, ethylene / vinyl acetate copolymers, or chlorinated or chlorsulfonated products thereof, maleic acid resins, vinyl chloride / vinyl acetate copolymers, etc. Is mentioned. In addition, the resin solid component concentration of the printing ink is appropriately determined in consideration of workability at the time of printing, printing effect, and the like, and is not particularly limited, but is usually adjusted to 3 to 50% by weight. Is good.

To manufacture a laminate can, first, the printing ink for a laminate can of the present invention is printed on a synthetic resin film such as polyester such as polyethylene terephthalate or the like, polyethylene, polypropylene or nylon by gravure, flexographic printing or the like, and dried. Then, a printed synthetic resin sheet is manufactured. Next, an adhesive is further applied to the printing surface side of the printed synthetic resin sheet by spray coating, roll coating, gravure coating, or the like, and dried by heating. Next, the printed synthetic resin sheet is applied by coating, gravure coating or the like on the outer surface side of the metal plate forming the can body, and after heating and drying, it is thermocompression-bonded to the outer surface of the metal plate forming the can body. . Thereafter, when a monomer having one or more unsaturated double bonds in the molecule is used, energy beam irradiation is performed. Examples of the material of the metal plate include iron, tinplate, stainless steel, titanium, copper, and aluminum. In addition,
The surface of these metals may be subjected to a surface treatment in advance, or various primers may be formed.

[0031]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" represent "parts by weight" and "% by weight", respectively.

[Production Example 1] In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen gas inlet tube, an acid component of adipic acid / terephthalic acid = 50/50 and 3-methyl-1,5 were added. 256.3 parts of a polyesterdiol having a number average molecular weight (hereinafter, referred to as Mn) of 2,000 obtained from pentanediol and 25 g of isophorone diisocyanate were charged and reacted at 90 ° C. for 15 hours under a nitrogen stream.
Subsequently, 5.0 parts of isophoronediamine, 2.2 parts of di-n-butylamine, 175 parts of toluene, 350 parts of methyl ethyl ketone, and 175 parts of isopropylene alcohol were added, and the mixture was reacted at 40 ° C. for 3 hours under a stirring frame to obtain a resin solid content. A polyester urethane urea resin solution A having a concentration of 30.0%, Gardner viscosity TU3 (25 ° C.), an amine value = 0, Mn = 34,000, and a weight average molecular weight (hereinafter referred to as Mw) 67,000 was obtained. The equivalent ratio of the isocyanate group of the organic diisocyanate compound to the hydroxyl group of the polyester diol (hereinafter referred to as NC0 / 0H equivalent ratio) is 1.3, and the urea bond concentration with respect to the resin solid content is 0.25 mmol / g.

Production Example 2 In the same manner as in Production Example 1, Mn = 2 obtained from an acid component of adipic acid / terephthalic acid = 50/50 and 3-methyl-1,5-pentanediol.
And 262.7 parts of polyester diol and 32.7 parts of isophorone diisocyanate, and reacted at 90 ° C. for 15 hours under a nitrogen stream. Next, 1.1 parts of isophoronediamine, 175 parts of toluene, and methyl ethyl ketone 3
50 parts, 175 parts of isopropylene alcohol are added,
The reaction was carried out at 40 ° C. for 3 hours under stirring, and the resin solid content concentration was 2
A polyester urethane urea resin solution B having 9.5%, Gardner viscosity O2-P (25 ° C.), amine value = 0, Mn = 35,000, and Mw = 68,000 was obtained. Note that NC
The 0 / 0H equivalent ratio is 1.12, and the urea bond concentration with respect to the resin solid content is 0.05 mmol / g.

Production Example 3 In the same manner as in Production Example 1, Mn = 2 obtained from an acid component of adipic acid / terephthalic acid = 10/90 and 3-methyl-1,5 pentanediol.
Then, 229.8 parts of polyester diol and 50.5 parts of isophorone diisocyanate were charged and reacted at 90 ° C. for 15 hours under a nitrogen stream. Then, 17.5 parts of isophoronediamine, 2.1 parts of di-n-butylamine, 175 parts of toluene, 350 parts of methyl ethyl ketone and 175 parts of isopropylene alcohol were added, and the mixture was stirred at 40 ° C. under stirring.
The reaction was carried out for 2 hours at a resin solid content of 29.0%, Gardner viscosity XY2 (25 ° C.), amine value = 0, Mn = 34,
A polyester urethane urea resin solution C having a molecular weight of 000 and Mw = 70,000 was obtained. The NC0 / 0H equivalent ratio is 2.
The urea bond concentration with respect to the resin solid content is 0.77 mmol.
/ G.

Production Example 4 In the same manner as in Production Example 1, Mn = 5 obtained from an acid component of adipic acid / terephthalic acid = 50/50 and 3-methyl-1,5 pentanediol.
237.6 parts of a polyester diol, 12.8 parts of 1,6 hexanediol and 43.6 parts of isophorone diisocyanate were charged and reacted at 90 ° C. for 15 hours under a nitrogen stream. Then 4.4 parts of isophoronediamine, di-
1.7 parts of n-butylamine, 175 parts of toluene, 350 parts of methyl ethyl ketone, isopropylene alcohol 17
5 parts were added, and the mixture was reacted at 40 ° C. for 3 hours under stirring. The resin solid content concentration was 30.4%, and Gardner viscosity VW (25
° C), amine value = 0, Mn = 32,000, Mw = 6
8,000 polyester urethane urea resin solution D was obtained. The NC0 / 0H equivalent ratio was 1.25, and the urea bond concentration with respect to the resin solid content was 0.2 mmol / g.

Production Example 5 Polyester diol having a Mn of 1,000 obtained from adipic acid and 3-methyl-1,5-pentanediol in the same manner as in Production Example 1
1 part and 81.9 parts of isophorone diisocyanate were charged and reacted at 90 ° C. for 15 hours under a nitrogen stream. Next, 28.4 parts of isophoronediamine, 3.7 parts of di-n-butylamine, 175 parts of toluene, and 35 parts of methyl ethyl ketone
0 parts and 175 parts of isopropylene alcohol were added thereto, and reacted at 40 ° C. for 3 hours under stirring.
3%, Gardner viscosity V2-W (25 ° C.), amine value =
A polyester urethane urea resin solution E having 0, Mn = 17,000 and Mw = 38,000 was obtained. Note that NC0 /
The 0H equivalent ratio is 2.00, and the urea bond concentration with respect to the resin solid content is 1.21 mmol / g.

[Production Example 6] Polyester diol of Mn = 2,000 obtained from adipic acid and 3-methyl-1,5-pentanediol in the same manner as in Production Example 1.
7 parts and 50.6 parts of isophorone diisocyanate were charged and reacted at 90 ° C. for 15 hours under a nitrogen stream. Then, 17.5 parts of isophoronediamine, 2.3 parts of di-n-butylamine, 175 parts of toluene, 35 methyl ethyl ketone
0 parts and 175 parts of isopropylene alcohol were added thereto, and reacted at 40 ° C. for 3 hours under stirring.
2%, Gardner viscosity U (25 ° C.), amine value = 0, M
A polyester urethane urea resin solution F having n = 21,000 and Mw = 40,000 was obtained. The NC0 / 0H equivalent ratio was 2.00, and the urea bond concentration with respect to the resin solid content was 0.77 mmol / g.

Examples 1-6 and Comparative Example 1-2 The polyurethane resin solutions 35 of A to D obtained in Production Examples 1 to 6
, A mixture of 30 parts of titanium oxide, 20 parts of toluene and 15 parts of methyl ethyl ketone was ground to prepare a white printing ink. The viscosity of the obtained printing ink was adjusted with a mixture of toluene, methyl ethyl ketone and isopropyl alcohol (50:40:10 in the order of weight ratio), and a plate depth of 35.
Thickness of 1 with a gravure calibrator equipped with a μm gravure plate
It was printed on a 2μ corona-treated stretched polyethylene terephthalate film and dried at 40-50 ° C to obtain a printed film. Next, a two-component urethane resin-based adhesive was applied to the printed surface with a gravure coater so as to have a dry thickness of 2 g / m ² , and was pre-dried.

Next, a teen steel plate was used as the metal plate for the can, and the printed film provided with the adhesive layer and the metal plate for the can were overlapped so that the adhesive layer was in contact with the metal plate for the can, and a test laminator was used. 4k roll pressure
g / cm ² , and roll lamination at a roll temperature of 200 ° C. Further, the laminated metal plate was subjected to a heat treatment at 215 ° C. for 3 minutes, and then subjected to PE treatment with a web-type EB irradiator.
EB irradiation of 30 kGy was performed from the side of the T film. The obtained laminated metal plate was subjected to a retort whitening resistance test and a workability test. Table 1 shows the results. The test was performed by the following method.

[Retort Whitening Resistance Test] The laminated metal plate was retorted in a retort kettle at 125 ° C. for 30 minutes, and the retort whitening resistance was evaluated. The criteria for the determination are as follows. ：: No whitening was observed on the whole. ×: Partial whitening is observed. [Workability test] After processing a laminated metal plate to 8 mm with an Erichsen extruder, 125 ° C in a retort pot.
For 30 minutes to evaluate the workability. ：: No delamination is observed throughout. X: Delamination is partially observed between the film and the ink.

[0041]

[Table 1] The amount of the monomer having an unsaturated double bond was 10 parts with respect to 100 parts of the urethane resin solid content. TMPTA: trimethylolpropane triacrylate DPHA: dipentaeristol hexaacrylate

[0042]

The printing ink binder of the present invention for laminating cans is excellent in retort whitening resistance and processability after heat sterilization.

Claims (3)

[Claims] A polyester polyol, an organic diisocyanate and a chain extender are used as reaction components, and the ratio of aromatic dicarboxylic acid to aliphatic dicarboxylic acid in the acid component derived from the polyester polyol is expressed by weight in terms of aromatic dicarboxylic acid. / Aliphatic dicarboxylic acid = 30 / 70-100 /
0 and the urea bond concentration is 0.0
A printing ink binder for laminate cans, comprising a polyester urethane urea resin in an amount of 5 to 0.8 mmol / g. 2. The binder according to claim 1, wherein the aromatic dicarboxylic acid is terephthalic acid. 3. The binder according to claim 1, further comprising a monomer having one or more unsaturated double bonds in the molecule.