JPS6211036B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for preventing dark reaction of ultraviolet curable printing inks. Since UV-curable printing inks contain prepolymers and/or monomers that have radically crosslinkable ethylenically unsaturated double bonds, they cause a dark reaction and gel during storage, making them difficult to use as printing inks. It has a tendency to become incapacitated. Various studies have been conducted to prevent this dark reaction and improve storage stability, but this dark reaction is generally caused by thermal polymerization. Printing inks are usually stored in an atmosphere at a temperature of 10-30°C. Also, in the summer, 40
Temperatures often rise to ~50°C. Therefore, thermal polymerization inhibitors such as hydroquinone, parabenzoquinone, and
A method has been adopted in which tertiary-butylhydroquinone, cuperone, etc., and tetramethylthiuram disulfide, which is a sensitizer but also has the effect of inhibiting thermal polymerization, are blended into ultraviolet curable printing inks.
Furthermore, Japanese Patent Application Laid-open No. 152809/1983 describes a method for preventing dark reaction of ultraviolet curable ink by finely mixing oxygen or oxygen mixed gas into the ink to prevent deterioration of storage stability. A method is disclosed. However, with conventional thermal polymerization inhibitors, sufficient dark reaction prevention effects cannot be obtained, and when irradiated with ultraviolet rays and photocured, they bring about polymerization inhibiting effects and pose hygiene problems for workers. There was something like that. Furthermore, the method of dispersing oxygen gas into ultraviolet curable printing ink has problems in workability. The present invention provides a prepolymer having a radically crosslinkable ethylenically unsaturated double bond and/or
It was developed to prevent dark reactions in UV-curable printing inks containing monomers. That is, the present invention relates to a method for preventing dark reactions in UV-curable printing inks, which comprises adding 0.001 to 1.0% by weight of an aluminum salt or iron salt of N-nitrosophenylhydroxylamine to the UV-curable printing ink. And this N-
Aluminum salts or iron salts of nitrosophenylhydroxylamine exhibit effects of preventing dark reactions and extremely little deterioration in photocurability.
In addition, compared to conventionally known thermal polymerization inhibitors, when added to ultraviolet curable printing inks containing prepolymers and/or monomers having radically crosslinkable ethylenically unsaturated double bonds, they exhibit remarkable storage stability. and has little polymerization inhibition in the photopolymerization reaction. In addition, if the amount added is less than 0.001% by weight, there will be little effect on storage stability, and if it is more than 1.0% by weight, polymerization will be inhibited in the photopolymerization reaction. 0.001-1.0% by weight of printing ink
is the preferable addition amount. The method of adding the compound () is to add it to a prepolymer or monomer in advance and use it to form an ink, or
The prepolymer, monomer, pigment, and sensitizer may be added after being dispersed and kneaded, and the effect of preventing dark reactions does not differ depending on the method of addition. The ultraviolet curable printing ink related to the present invention generally refers to radically crosslinkable ethylenically unsaturated 2
It consists of a prepolymer and/or monomer having a double bond, and also contains a sensitizer, pigment, and other additives. A monomer having a radically crosslinkable ethylenically unsaturated double bond is
ethylene glycol, polyethylene glycol,
Esterification of acrylic acid or methacrylic acid with alcohol such as trimethylolpropane or pentaerythritol; esterification of allyl alcohol with phthalic acid, maleic acid, isocyanuric acid, etc.; esterification of glycidyl acrylate or glycidyl methacrylate. Examples include those obtained by adding ethylene oxide to a phenol such as bisphenol A, catechol, and resorcin, and then esterifying it with acrylic acid or methacrylic acid. A prepolymer having a radically crosslinkable ethylenically unsaturated double bond is an epoxy resin esterified with acrylic acid or methacrylic acid, such as an acrylic acid or methacrylic acid ester of an epichlorohydrin condensate of bisphenol A, or Epoxidized linseed oil esterified with acrylic acid or methacrylic acid, hydroxyl group-containing resin esterified with acrylic acid or methacrylic acid, for example, a copolymer of dicyclopentadiene and allyl alcohol esterified with acrylic acid. Alkyd resin having excess hydroxyl groups is esterified with acrylic acid, Alkyd resin containing hydroxyl groups, polyester resin and acrylic acid ester of polyol having at least one hydroxyl group are crosslinked with diisocyanate. Examples include things. Sensitizers used in the present invention include benzoin, benzoin methyl ether, benzoin isobutyl ether, benzoin sensitizers such as α-allylbenzoin, benzophenone, P-methylbenzophenone, P-chlorobenzophenone, , 4-bisdiethylaminobenzophenone, acetophenone, benzoin sensitizers such as amyl-P-dimethylaminobenzoate, azo sensitizers such as azoisobutyronitrile, quinones such as anthraquinone, 2-chloroanthraquinone, phenanthrene, etc. sensitizers, sulfide sensitizers such as tetramethylthiuram monosulfide, and combinations of various sensitizers are used. The amount of this sensitizer is generally 0.1 to 25% by weight based on the ink.
It is blended in the proportion of According to the present invention, the photocurability of the ultraviolet curable printing ink is hardly deteriorated, and the storage stability is maintained for an extremely long period of time. In addition, N- of the compound () used in the present invention
Metal salts of nitrosophenylhydroxylamine have extremely high safety and hygiene properties compared to conventional dark reaction inhibitors, and are advantageous in this respect as well. The present invention will be explained below with reference to Examples, Reference Examples, and Comparative Examples. Examples "Middle" refers to parts by weight unless otherwise specified. Reference example 1 (Production of prepolymer) Epicote 828 (epoxy resin manufactured by Shell Oil)
71.7 parts, acrylic acid 28.3 parts, hydroquinone 0.1
1 part and 0.2 parts of triethylenediamine were placed in a four-necked flask equipped with a reflux tube and a stirrer, and after reacting for 18 hours at a temperature range of 90 to 120°C while blowing air, the mixture was cooled and pumped out after the acid value became 1 or less. This will be referred to as prepolymer A. Reference Example 2 (Manufacture of prepolymer) 76.2 parts of Adekacizer O-130P (epoxidized soybean oil manufactured by Asahi Denka Co., Ltd.), 23.8 parts of acrylic acid, 0.1 part of hydroquinone, and 0.2 parts of triethylenediamine with a reflux tube and a stirrer. The mixture was placed in a four-necked flask and reacted at 90 to 120°C for 15 to 20 hours while blowing air to give an acid value of 1 or less, which was then pumped out and used as prepolymer B. Reference Example 3 (Production of prepolymer) 72.7 parts of oleic acid, 17.7 parts of pentaerythritol
1 part was reacted in a 4-necked flask under a stream of carbon dioxide gas at 240°C until the acid value reached 5 or less. Thereafter, 9.6 parts of phthalic anhydride is added and the reaction is carried out at the same temperature for about 3 hours to bring the acid value to 5 or less to obtain an alkyd with a hydroxyl equivalent weight of 725. Next, this alkyd 91 with an equivalent weight of 725 hydroxyl groups
and 10 parts of benzene were placed in a four-necked flask equipped with a thermometer, water separator, and air blowing device, and heated to approximately 90°C.
Blow in air while stirring. A solution of 9 parts of acrylic acid, 0.5 part of para-toluenesulfonic acid, and 0.1 part of hydroquinone was added dropwise at 85 to 95°C.
After dropping, gradually raise the temperature and keep it at 115-125℃. The water produced by the reaction is refluxed with benzene,
Remove in water separator. When the acid value falls below 5, collect and pump out the benzene. This resin will be referred to as Prepolymer C. Reference example 4 Equal moles of dicyclopentadiene and allyl alcohol were placed in an autoclave, and the mixture was heated under pressure at 270°C.
C. for 2 hours, and then unreacted monomers were distilled off to obtain a resin with a conversion rate of 53.8% and a softening point of 96.5.degree. The resin
75 parts and 25 parts of acrylic acid and 0.1 part of hydroquinone
1.0 parts of paratoluenesulfonic acid were placed in a four-necked flask, and the mixture was reacted at 100° C. under benzene reflux for about 15 hours, and then the benzene was distilled off to obtain a resin with an acid value of 15. Prepolymer D is prepared by dissolving and mixing 20 parts of trimethylolpropane triacrylate into 80 parts of the resin. Example 1 Using the prepolymers A to D obtained in Reference Examples 1 to 4, ultraviolet curable printing inks were prepared according to the following formulation, and the photocurability and storage stability were measured. The results are shown in Table 1. Carmine 6BH (Azo red pigment manufactured by Toyo Ink Mfg. Co., Ltd.) 15 parts Prepolymer (A to D) 50.8 parts Benzoin ethyl ether 10 parts Triallylisocyanurate 24 parts Q1301 (N-nitrosof manufactured by Wako Pure Chemical Industries, Ltd.) Aluminum salt of enylhydroxylamine) 0.2 parts Example 2 A UV-curable printing ink was prepared using the following formulation in the same manner as in Example-1, and its photocurability and storage stability were measured. The results are shown in Table-1. Titanium White 30 parts Prepolymer (A to D) 43 parts Benzophenone 10 parts 4,4-bisdiethylaminobenzophenone
1 part Q1301 0.2 part Trimethylolpropane triacrylate
15.8 parts Example 3 In the same manner as in Example 1, an ultraviolet curable printing ink was prepared using the following formulation, and its photocurability and storage stability were measured. The results are shown in Table-1. Regal 330R (manufactured by Columbia Carbon) 20 parts Prepolymer (A to D) 46 parts Parachlorobenzophenone 10 parts Amyl-P-dimethylaminobenzoate 5 parts Q1301 1.2 parts Pentaerythritol triacrylate 18.8 parts Comparative example 1 The following ink formulation In this study, UV-curable printing inks were prepared using hydroquinone, P-benzoquinone, tetramethylthiuram disulfide, and cuperone as inhibitors, and the photocurable storage stability was measured. The results are shown in Table-1. Carmine 6BH 15 parts Prepolymer A 50.8 parts Benzoisoethyl ether 10.0 parts Triallylisocyanurate 24.0 parts Inhibitor 0.2 parts Example 4 Titanium White 30 parts Prepolymer B 43 parts Benzoin ethyl ether 10 parts Trimethylolpropane triacrylate 17 parts Above Created with UV curable printing ink base according to the recipe, 0 parts, 0.005 parts, 0.01 parts of Q-1301.
part, 0.1 part. Its photocurability and storage stability were measured. The results are shown in Table 1. Comparative Example 2 In the ink formulation of Example-4, 0 parts, 0.005 parts, and 0.005 parts of P-benzoquinone were added instead of Q-1301.
Inks containing 0.01 part, 0.1 part, and 1.0 part of each were prepared and their photohardness and storage stability were measured. The results are shown in Table-1. Photocurability was determined by testing each ink obtained as described above on a tin plate coated with a vinyl primer using an RI tester (manufactured by Mei Seisakusho Co., Ltd.).
Immediately after printing with a coating amount of 30 mgr/100 cm ²
The material was placed on a conveyor 10 cm below a high-pressure mercury lamp with an intensity of 80 W/cm, and was irradiated with ultraviolet rays to cure the material, and the conveyor speed was such that complete curing could be confirmed by touch with the finger, and it exhibited photocuring properties. In addition, storage stability was determined by placing the ink in a constant temperature bath at 40° C. after making the ink, and observing the state of storage stability. Example 5 Using the prepolymers A to D obtained in Reference Examples 1 to 4, ultraviolet curable printing inks were prepared according to the following formulation, and the photocurability and storage stability were measured. The results are shown in Table 1. Carmine 6BH (Azo red pigment manufactured by Toyo Ink Co., Ltd.) 15 parts Prepolymer (A to D) 48 parts Benzoin isobutyl ether 10 parts Bisphenol A 2.2 mole ethylene oxide adduct diacrylate 26.8 parts N-nitrosophenylhydroxylamine iron salt 0.2 part

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Claims (1)

[Claims] 1. A method for preventing dark reactions in UV-curable printing inks, which comprises adding 0.001 to 1.0% by weight of an aluminum salt or iron salt of N-nitrosophenylhydroxylamine to the UV-curable printing ink.