JPS6129396B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a printing ink composition for printing on cellophane, plastic film, metal foil, and the like. More specifically, the present invention relates to a gravure printing ink composition that has both favorable adhesion and drying properties to plastic films and metal foils. Various industrial nitrocelluloses specified in JISK-6703 are one of the film-forming elements of gravure printing inks. Nitrocellulose has excellent drying properties, anti-blocking properties, and pigment dispersibility.
It has long been used as a raw material suitable for high-speed printing, which is an essential condition for gravure printing. The printing materials for gravure printing are mainly paper, cellophane, plastic film, metal foil, etc. In the case of printing on paper and cellophane, nitrocellulose has suitable adhesive properties, so nitrocellulose alone or nitrocellulose and a plasticizer are used. Although we have been providing practical inks with film-forming elements consisting of plastic films, for example,
For printing on low-density polyethylene, high-medium density polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyester, nylon, and metal foils such as aluminum foil and tin foil, nitrocellulose alone or nitrocellulose and plasticizer alone is not suitable. Since adhesion is clearly insufficient, other resins such as alkyd resins, polyamide resins, chlorinated rubbers, cyclized rubbers, rosins or their derivatives are used in combination as coating film forming elements, and in order to obtain practical adhesive strength, It was necessary to drastically reduce the amount of nitrocellulose and create an ink composition that contained large amounts of other resins. Therefore,
The drying properties required for gravure printing ink are insufficient,
High-speed printing was difficult, and improvements were desired. It is an object of the present invention to provide a gravure printing ink composition that has both suitable adhesion to plastic films and metal foils and high-speed printing properties. As a result of intensive studies, the inventors found that an ink composition containing nitrocellulose with a low degree of polymerization, which is not listed in JIS K 6703 as a coating film-forming element, meets the above objectives, and has thus arrived at the present invention. be. Nitrocellulose with a low degree of polymerization that is not listed in JIS K6703 will be explained. Among the nitrocellulose listed in JIS K6703, nitrocellulose with the lowest degree of polymerization is H1/16, according to a pamphlet (page 26) titled "Industrial Nitrified Cotton" published by Asahi Kasei Corporation. The average degree of polymerization of H1/16 is 35-45. The use of nitrocellulose having an average degree of polymerization of 30 or less is an essential condition for the ink composition of the present invention. For nitrocellulose with an average degree of polymerization of 30 or more,
Although an ink composition with excellent drying properties is provided, the ink composition is insufficient in terms of adhesion. The average degree of polymerization of nitrocellulose referred to here is the "industrial nitrified cotton" published by Asahi Kasei Kogyo Co., Ltd.
It is determined by the method described on pages 48 to 50 of the pamphlet entitled . That is, accurately weigh the required amount (Note 1) of the sample nitrocellulose into a 200 ml Erlenmeyer flask with a co-sensor, add 50 ml of special grade JIS-K3034 [acetone (reagent)] adjusted to 20 ± 0.1°C, and let it stand for about 16 hours. . After that, mix gently for about 5 minutes to make a sample solution, immerse it in water adjusted to 20 ± 0.1°C, leave it for more than 20 minutes, take 5 ml of this solution, and put it in an Ostwald viscometer at 20 ± 0.1°C. After leaving it at ℃ for 20 minutes or more, measure the rate at which the sample solution flows down between the marked lines AB of the capillary of the viscometer. Separately, the flow time of acetone was measured in the same manner as for the sample solution, and the following formula was used:
Calculate the degree of polymerization using (1), (2), and (3). η _SP = t/t ₀ −1 ………(1) where η _SP : Specific viscosity t : Falling time of sample solution (seconds) t ₀ : Falling time of acetone (seconds) [η]=η〓/1+K ′η _SP ………(2) Here [η]: Intrinsic viscosity C: Concentration of sample (g/) K’: 0.315 = [η]/Km ………(3) Here: Average degree of polymerization Km :11×10 ^-4 (Note 1) The required amount of viscosity sample is η _SP 0.1~
Make it 0.2. The present invention also includes the use of a resin and a plasticizer in addition to low polymerization degree nitrocellulose as a coating film forming element. The resin referred to herein may be any resin used as a coating film forming element in gravure printing or flexographic printing ink. Natural and semi-synthetic resins such as shellac, zein, rosin or its derivatives, gilsonite, asphalt; alkyd resins, phenolic resins, maleic resins, urea resins, melamine resins, acrylic resins, epoxy resins, chlorinated rubber, cyclized resins. Examples include synthetic resins such as rubber, polyvinyl acetate, polyvinyl butyral, polyvinyl chloride, polyamide resin, coumaron resin, ketone resin, and chlorinated polyolefin resin. Plasticizers used in the present invention include castor oil, blown castor oil; dibutyl phthalate, dicyclohexyl phthalate, dioctyl (di-ethylhexyl) phthalate; tricresyl phosphate;
Trichloroethyl phosphate; butylphthalyl butyl glycolate; dibutyl sebacate; dioctyl (diethylhexyl) adipate, diisobutyl adipate; acetyl tributyl citrate, and the like. These plasticizers can be selectively used depending on the purpose. The low degree of polymerization nitrocellulose must be contained in the film forming element of the ink composition in an amount of 15% or more. It is less than 15% and an ink composition with good drying properties cannot be obtained. The remaining coating film-forming elements are mainly composed of resins and/or plasticizers, but additives for the purpose of improving printability, abrasion resistance, removing static electricity, and promoting pigment dispersion can also be added as necessary. Incidentally, the film-forming elements of the ink composition as used in the present invention refer to those that essentially form a paint film, excluding pigments and solvents (volatile components). The excellent effects of the present invention will be explained in detail in Examples below. Example 1 Nitrocellulose HIG1/16 manufactured by Asahi Kasei Industries, Ltd.
(Contains 30% isopropyl alcohol) in 10 times the volume of water, stir well, and then dehydrate using a centrifuge. After repeating this 5 times, 5 times the amount of water was added and heated at 150°C for 60 minutes in an autoclave. The average degree of polymerization of the obtained nitrocellulose was measured and found to be 22. This nitrocellulose was made into ink according to the formulation shown in Table 1.

[Table] This ink was applied onto a commercially processed polypropylene film using a bar coater; Rod No. 18 (manufactured by RD Specialties) in an atmosphere of 20°C and 65% RH, and the following drying test was conducted. After drying for several days, the following 180 degree tensile peel test and cellophane tape peel test were conducted. Drying test: The drying time to the touch of the ink film was measured (according to JIS-K5400) ・180 degree tensile peel test: Adcoat 333E (manufactured by Toyo Ink) was applied to a commercially available polypropylene film, air-dried for 5 minutes, and then dried for 2 days. Glue onto the air-dried ink film without creating any air bubbles, and
Leave it in an atmosphere of ℃ and 65%RH for 2 days. Then heat-seal at 100℃ for 0.6Kg/cm ² G2 seconds, cut into 50mm x 10mm strips, and test them in a tensile tester (UTM-4-100 manufactured by Toyo Baudouin Co., Ltd.) at a tensile speed of 10cm/min. The maximum breaking strength was defined as the tensile peel strength.・Cellophane tape peeling test: Cellophane tape (Nichiban No.
405) and pressed it 5 times with the thumb, then rapidly peeled it off and evaluated the peeling state of the ink surface according to the following criteria. Four panelists conducted the evaluation, and the average value of the evaluation scores was taken as the cellophane tape peel strength. 0 points...1 point where all peeled off...2 points where 80% or more peeled off...3 points where 50% or more peeled off...4 points where 20% or more peeled off...5 points where 0 to 20% peeled off...Measurement results without peeling It is shown in Table-2.

[Table] Example 2 Nitrocellulose HIG1/16 manufactured by Asahi Kasei Industries, Ltd. was heated in an autoclave according to Example 1.
The heating temperature is 150℃, but the heating time is 15 minutes, 30 minutes.
Four levels were changed: minutes, 45 minutes, and 100 minutes. The average degree of polymerization of the obtained nitrocellulose was 33 and 33, respectively.
It was 28, 25, 15. The nitrocellulose thus obtained was made into an ink according to the composition of Run No. 2 in Table 1, and a drying test, a 180 degree tensile peel test, and a cellophane tape peel test were conducted using the methods described in Example 1. The results are shown in Table-3.

[Table] Example 3 Using the nitrocellulose (average degree of polymerization 22) produced in Example 1, ink was produced according to the composition of Run No. 2 in Table 1. However, as a resin, versamide
754, the ones listed in the left column of Table 4 were used. The measurement results of this ink's drying test, 180 degree tensile peel test, and cellophane tape peel test are shown below.
It is shown in the left column of 4.

[Table] Example 4 Using the nitrocellulose produced in Example 1 (average degree of polymerization 22), ink was produced according to the recipe shown in Table 5. Table 6 shows the drying rate, 180 degree tensile peel test, and cellophane tape peel test results for this ink.

【table】

[Table] Example 5 Using the nitrocellulose obtained in Example 2 and having an average degree of polymerization of 15, an ink was produced according to the ink formulation of Run No. 20. This ink was applied on high-density polyethylene film, low-density polyethylene film, and polyester film obtained from Yasui Co., Ltd. in the same manner as in Example 1, and a drying test, a 180 degree tensile peel test,
A cellophane tape peel test was conducted. The results are shown in Table 7.

【table】

[Table] Example 6 Using the nitrocellulose obtained in Example 2 and having an average degree of polymerization of 15, an ink was produced according to the ink formulation of Run No. 20. This ink was applied onto aluminum foil and tin oil in the same manner as in Example 1, and a drying test, a 180 degree tensile peel test, and a cellophane tape peel test were conducted. The results are shown in Table 8.

[Table] As is clear from the examples, the ink obtained by containing 15% or more of nitrocellulose with an average degree of polymerization of 30 or less in the film-forming element of the ink is good for plastic films and metal foils. It has both good adhesion and excellent drying properties, and can be said to be an epoch-making product that greatly improves the shortcomings of conventional nitrocellulose-containing ink compositions.

Claims (1)

[Scope of Claims] 1. A printing ink composition characterized by containing 15% or more of nitrocellulose having an average degree of polymerization of 30 or less in a coating film-forming element. 2. The ink composition according to claim 1, comprising nitrocellulose having an average degree of polymerization of 30 or less as coating film-forming elements, and a resin and/or a plasticizer.