JP5853832B2 - Printing ink composition for styrene film - Google Patents

Description

  The present invention relates to an ink composition suitable for producing a food tray in which designability is imparted by printing on a polystyrene film, and the film and the polystyrene sheet are molded through a thermocompression bonding process.

  In recent years, packages are generally decorated with printing ink for decoration and surface protection. In addition, it is an exaggeration to say that depending on the quality of the printed matter, such as the design characteristics due to the difference in performance of printing ink, the quality of the printed matter, the favorableness and attention to the contents, the consumer's willingness to purchase, and so on, will directly affect the sales of the product. is not.

  Food trays such as sugar beet containers and lunch boxes are printed with a design pattern on a polystyrene film (hereinafter referred to as PS film), and the printed film is a foamed polystyrene sheet or a polystyrene sheet with excellent impact resistance ( The polystyrene sheet is generally referred to as a PS sheet) and is laminated by thermocompression bonding (hereinafter referred to as thermal lamination). As this printing ink, a printing ink composition containing an acrylic resin or a styrene-acrylic copolymer resin as a main component is known.

  Food trays are packed with food as sugar beet containers and sold at convenience stores and supermarkets. In the process of manufacturing food trays, there is a process of heat lamination of PS sheet gravure printed matter (hereinafter referred to as printed matter) and PS sheet, but the thermal lamination strength between the ink used for the printed matter and the PS sheet is not good. If sufficient, bubble-like unbonded parts (hereinafter referred to as blisters) are generated between the printed material and the PS sheet due to the effects of temperature and pressure during the hot laminating process, and bubbles are formed. This is unpreferable as a product because the designability of the product is impaired.

  As a method of improving the generation of blisters, there is a method of printing or coating an adhesive layer called a medium on the upper surface after applying a design such as a pattern by printing on a film, but the printing process is performed by applying the medium. It is difficult to say that the method is practically preferable because it has a problem of increasing complexity and inevitable increase in cost.

Also, if an attempt is made to improve the thermal lamination strength between the ink / PS sheets without applying an adhesive layer, the acrylic resin or styrene-acrylic copolymer resin, which is the main component of the ink, is heated at the temperature of the thermal laminate. There is a method of adjusting the glass transition temperature of the resin so that the sheet adheres, but there is a problem that a problem of blocking (a phenomenon in which the ink film surfaces stick to each other) is likely to occur. In order to further improve blocking, a method using a nitrocellulose resin to reduce adhesion between ink films is known, but storage stability (separation and precipitation during ink storage is not possible due to poor compatibility with acrylic resins. Is not preferable. That is, there is a demand for a printing ink composition that does not cause blocking when an adhesive layer is not used and when an adhesive layer is not used.
The

  Since the ink described in Patent Document 1 does not contain an anti-blocking component in the ink composition, it is blocked during storage of the printed film, and the workability is not good.

  Since the ink described in Patent Document 2 uses a nitrocellulose resin for preventing blocking, it has poor temporal stability due to lack of compatibility with an acrylic resin, and contains a surfactant in the ink component. Therefore, the heat laminate strength is inferior.

JP 2004-285245 A JP 2000-313833 A

  An object of the present invention is a food tray that is printed on a film and heat laminated with a PS sheet, and is an ink that is printed on the film, and has good blocking resistance while maintaining storage stability. It is providing the printing ink composition for styrene films.

  In the present invention, as a resin composition, the binder resin is an acrylic resin and a cellulose acetate butyrate (CAB) resin and / or a cellulose acetate propionate (CAP), and the acrylic resin has a weight average molecular weight of 20,000 to 130,000. And the glass transition point (Tg) is 20 to 80 ° C., the cellulose acetate butyrate (CAB) resin has a number average molecular weight of 60,000 or less, and the cellulose acetate propionate (CAP) resin is several The printing ink composition for styrene film characterized by having an average molecular weight of 60,000 or less satisfies the above characteristics.

That is, the present invention is a printing ink composition for styrene film for thermal lamination , characterized by containing a binder resin, a pigment and a solvent,
Binder resin
Acrylic resin and cellulose acetate butyrate (CAB) resin and / or cellulose
Acetate Propionate (CAP)
Because
Acrylic resin
Weight average molecular weight 20,000-130,000 and glass transition point (Tg) 20-80 ° C.
and
Synthesized from acrylic monomers containing methyl methacrylate and butyl methacrylate,
Dissolved or dispersed in alcoholic and ester organic solvents,
And,
Cellulose acetate butyrate (CAB) resin
The number average molecular weight is less than 60,000,
Cellulose acetate propionate (CAP) resin
The present invention relates to a printing ink composition for a styrene film for thermal lamination, which has a number average molecular weight of 60,000 or less.

The present invention also provides the solid content weight W1 of the acrylic resin, the solid content weight of the cellulose acetate butyrate (CAB) resin, and the cellulose content.
The present invention relates to the above-mentioned printing ink composition for styrene film for thermal lamination , characterized in that the ratio of the weight of solid content of acetate propionate (CAP) resin to the total amount W2 is W1: W2 = 30: 70 to 99: 1. Is.

Furthermore, the present invention relates to the above-mentioned printing ink composition for styrene film for thermal lamination, further comprising at least one selected from a plasticizer, a resin having a phenyl group or a xylyl group, and a tackifier. It is.

  The printing ink composition for styrene film of the present invention has an ink storage stability by using an acrylic resin, cellulose acetate butyrate (CAB) resin and / or cellulose acetate propionate (CAP) as a resin composition. It was possible to provide an ink with good blocking resistance while maintaining the above.

Hereinafter, embodiments of the present invention will be described in more detail.
The acrylic resin that is the binder resin of the printing ink composition is synthesized using (meth) acrylic acid, (meth) acrylic acid ester, or the like as a monomer. (Meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and a hydrocarbon chain number of butyl group or more (meta ) Alkyl acrylate, (meth) acrylic acid ester having a hydroxyl group, (meth) acrylic acid ester having an amino group, (meth) acrylic acid ester having an epoxy group, and the like. One or more of these monomers can be used. In addition, a copolymer with vinyl acetate or butadiene can also be used.
In the present invention, a polymer having an acrylic monomer as a main skeleton containing methyl methacrylate and / or butyl methacrylate is preferable from the viewpoint of physical properties such as thermal laminate strength and cost.

  The weight average molecular weight of the acrylic resin is 20,000 to 130,000, and particularly preferably 30,000 to 110,000. When the polymerization average molecular weight of the acrylic resin is less than 20,000, it tends to decrease the cohesive force with the PS sheet during thermal lamination, and blisters are generated during the molding process, which is not preferable. On the other hand, the weight average molecular weight is 130,000. Exceeding this is not preferable because the viscosity of the resin becomes high and the ink does not transfer well during printing, resulting in a printed matter with poor design.

  Moreover, although Tg of acrylic resin is 20 to 80 degreeC, Preferably it is 30 to 65 degreeC. If the Tg of the acrylic resin is less than 20 ° C., the acrylic resin is in a soft state at room temperature, which is likely to cause blocking. On the other hand, if the Tg exceeds 80 ° C., the heat of thermocompression bonding during thermal lamination is not preferable. This is not preferable because the resin does not become soft and the adhesiveness with the PS sheet decreases.

  Further, the acrylic resin is preferably dissolved or dispersed in an alcohol-based or ester-based organic solvent from the viewpoint of the drying property of the printed matter. The alcohol solvent is preferably one of methanol, ethanol, isopropanol, and normal propanol, or a mixed solvent thereof, and the ester solvent is any one of ethyl acetate or normal propyl acetate, or a mixed solvent thereof. It is preferable.

  The present invention is characterized in that a CAB resin and / or a CAP resin is blended with an acrylic resin, and is a vehicle resin component particularly suitable for PS film printing. Moreover, the printing ink composition of the present invention can be applied to applications other than thermal lamination applications such as a PS film for shrink film.

The number average molecular weight of the CAB resin and the CAP resin is 60,000 or less, but preferably 10,000 to 30,000.
Regarding the number average molecular weight of the CAB resin and CAP resin, the lower the molecular weight, the lower the viscosity of the resin, but the desired blocking resistance does not decrease. If the number average molecular weight exceeds 60,000, the viscosity of the resin increases, and the ink does not transfer well during printing, resulting in a printed matter with poor design.

A plasticizer, a resin having a phenyl group or a xylyl group, and a tackifier are added to the printing ink composition, whereby any one of the resin and / or the PS film and / or the PS sheet in the printing ink composition. The thermal laminate strength is further improved by effects such as plasticization, improvement of intermolecular interaction, and imparting tackiness to the seeds or more.
The plasticizer is preferably added in an amount of 0.01% to 5.0%, more preferably 0.05% to 2% in the printing ink composition. Specific examples of the plasticizer include citric acid ester, phthalic acid type, adipic acid ester type, sebacic acid ester type, phosphoric acid ester type, polyester type, trimellitic acid type and the like.

About resin which has a phenyl group and a xylyl group, the addition amount of 0.05%-15.0% and also 0.1%-5% is preferable in a printing ink composition. Specific examples of the resin having a phenyl group or a xylyl group include styrene resin, styrene-maleic acid resin, styrene-acrylic resin, xylene resin, alkylphenol resin, and the like.
The tackifier is preferably added in an amount of 0.05% to 15.0%, more preferably 0.1% to 5% to the printing ink composition. Specific examples of the tackifier include rosin resins, modified rosin resins, terpene resins, modified terpene resins, aliphatic hydrocarbon resins, and the like.

  As the solvent, polystyrene has low solvent resistance, so lower alcohols and esters such as ethyl acetate, normal propyl acetate, methanol, ethanol, isopropyl alcohol (IPA), and normal propyl alcohol are used, and the ratio of the ester solvent is 30. A mixed solvent in which the ratio of the alcohol solvent is mixed at 30 to 70 parts by mass with respect to ~ 70 parts by mass can be used. Further, as the slow-drying solvent, a small amount of propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, or the like can be used.

  The printing ink composition used in the present invention is blended with extender pigments, waxes, and plastic fine powders for the purpose of maintaining printing ink properties such as viscosity and fluidity, imparting slip properties to the printing surface, polishing, and matting. Can do. As extender pigments, silica, alumina, talc, calcium carbonate, precipitated barium, and the like can be used. As the wax, polyethylene wax, polypropylene wax, and perfluoroethylene wax can be suitably used.

  Printing configurations include PS film / printing ink layer / PS sheet or PS film / printing ink layer / medium layer / PS sheet, PS film / printing ink layer / adhesive layer / PS sheet, etc. From the point of cost, the structure of PS film / printing ink layer / PS sheet is preferable.

In this invention, other resin can be used together as a resin component other than an acrylic resin, CAB, and / or CAP resin in the range which does not impair the said effect of this invention. The resin used in combination is compatible with acrylic resin, CAB and / or CAP resin, and those used in gravure printing or flexographic printing ink can be used in combination as appropriate.
Examples thereof include polyurethane resin, polyvinyl butyral resin, nitrified cotton resin, chlorinated polyolefin resin, nitrified cotton resin, ketone resin, epoxy resin, ethylene-vinyl acetate copolymer resin, and vinyl acetate resin.

  The ratio of the resin component used in the present invention is such that the ratio of the solid content weight W1 of the acrylic resin to the total amount W2 of the solid content weight of the CAB resin and the solid content weight of the CAP resin is W1: W2 = 30: 70 to 99. However, it is preferably in the range of W1: W2 = 60: 40 to 97: 3. When the solid content weight W1 of the acrylic resin is less than 30 parts, the heat laminating property is impaired, and it is not preferable, and when W1 exceeds 99 parts, blocking tends to occur, which is not preferable.

In the printing ink composition for styrene film of the present invention, a pigment usually used for gravure printing ink can be used without particular limitation. Examples include inorganic pigments such as ultramarine, bitumen, petal, iron black, yellow iron oxide, titanium dioxide, carbon black, titanium black, monoazo pigments, disazo pigments, condensed azo pigments, phthalocyanine pigments, anthraquinone pigments Organic pigments such as quinacridone pigments, isoiredoline pigments, thioindigo pigments, dioxazine pigments, and pyrrolopyrrole pigments can be used.
The amount of the colored pigment used varies depending on the target color tone and concentration, but is used in the range of 0 to 50 parts by mass in the total amount of ink including medium.

  In the production of ink, as in the case of ordinary gravure ink, the resin, pigment, solvent and auxiliary agent are weighed and stirred well, and then kneaded with a kneading disperser such as a paint shaker, attritor or sand mill.

  The PS film in which the printing ink composition of the present invention is used for imparting design properties may be subjected to corona treatment, frame treatment, or stretching treatment.

  A thermoplastic plastic is used as the substrate to be laminated. Polystyrene resins are preferable, and extender pigments may be blended. Further, it may be a sheet foamed with carbon dioxide gas, butane gas, air or the like.

  The printing ink can be printed by any method such as general gravure printing, silk screen printing, flexographic printing, etc., but gravure printing is preferred.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In each example, “part” means “part by weight” “%” means “% by weight”.

<Preparation of acrylic resin varnish (acrylic resin varnish A)>
As acrylic monomers, 37 parts of methyl methacrylate [glass transition temperature Tg = + 105 ° C. of homopolymer] and 60 parts of butyl methacrylate [glass transition temperature Tg = + 20 ° C. of homopolymer], acrylic acid [of homopolymer Glass transition temperature Tg = + 106 ° C.] The copolymer was copolymerized so as to have a composition ratio of 3 parts to prepare an acrylic resin having a weight average molecular weight of 50000 and Tg of 50 ° C. The prepared acrylic resin was dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate were mixed in equal amounts to prepare an acrylic resin varnish A having an acrylic resin solid content of 40%.

<Preparation of acrylic resin varnish (acrylic resin varnish B)>
As acrylic monomers, 37 parts of methyl methacrylate [glass transition temperature Tg = + 105 ° C. of homopolymer] and 60 parts of butyl methacrylate [glass transition temperature Tg = + 20 ° C. of homopolymer], acrylic acid [of homopolymer Glass transition temperature Tg = + 106 ° C.] The copolymer was copolymerized so as to have a composition ratio of 3 parts to prepare an acrylic resin having a weight average molecular weight of 25000 and Tg of 50 ° C. The prepared acrylic resin was dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate were mixed in equal amounts to prepare an acrylic resin varnish B having an acrylic resin solid content of 40%.

<Preparation of acrylic resin varnish (acrylic resin varnish C)>
As acrylic monomers, 37 parts of methyl methacrylate [glass transition temperature Tg = + 105 ° C. of homopolymer] and 60 parts of butyl methacrylate [glass transition temperature Tg = + 20 ° C. of homopolymer], acrylic acid [of homopolymer Glass transition temperature Tg = + 106 ° C.] The copolymer was copolymerized so as to have a composition ratio of 3 parts to prepare an acrylic resin having a weight average molecular weight of 125,000 and Tg of 50 ° C. The prepared acrylic resin was dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate were mixed in equal amounts to prepare an acrylic resin varnish C having an acrylic resin solid content of 40%.

<Preparation of acrylic resin varnish (acrylic resin varnish D)>
As acrylic monomers, 10 parts of styrene [glass transition temperature Tg = + 100 ° C. of homopolymer], 27 parts of methyl methacrylate [glass transition temperature Tg = + 105 ° C. of homopolymer], and butyl methacrylate [glass of homopolymer] Styrene-acrylic copolymerized to give a composition ratio of 60 parts of transition temperature Tg = + 20 ° C. and 3 parts of acrylic acid [glass transition temperature of homopolymer Tg = + 106 ° C.] to give a weight average molecular weight of 50,000 and Tg of 50 ° C. A resin was prepared. The prepared acrylic resin was dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate were mixed in equal amounts to prepare an acrylic resin varnish D having an acrylic resin solid content of 40%.

<Preparation of acrylic resin varnish (acrylic resin varnish E)>
As acrylic monomers, 82 parts of methyl methacrylate [glass transition temperature Tg = + 105 ° C. of homopolymer] and 15 parts of butyl methacrylate [glass transition temperature Tg = + 20 ° C. of homopolymer], acrylic acid [of homopolymer Glass transition temperature Tg = + 106 ° C.] The copolymer was copolymerized so as to have a composition ratio of 3 parts to prepare an acrylic resin having a weight average molecular weight of 50000 and Tg of 90 ° C. The prepared acrylic resin was dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate were mixed in equal amounts to prepare an acrylic resin varnish E having an acrylic resin solid content of 40%.

<Preparation of acrylic resin varnish (acrylic resin varnish F)>
As acrylic monomers, 90 parts of butyl methacrylate [glass transition temperature Tg = + 20 ° C. of homopolymer] and 7 parts of butyl acrylate [glass transition temperature Tg = −56 ° C. of homopolymer], acrylic acid [homopolymer] The glass transition temperature of Tg = + 106 ° C.] was copolymerized to a composition ratio of 3 parts to prepare an acrylic resin having a weight average molecular weight of 50000 and Tg of 15 ° C. The prepared acrylic resin was dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate were mixed in equal amounts to prepare an acrylic resin varnish F having an acrylic resin solid content of 40%.

<Preparation of acrylic resin varnish (acrylic resin varnish G)>
As acrylic monomers, 37 parts of methyl methacrylate [glass transition temperature Tg = + 105 ° C. of homopolymer] and 60 parts of butyl methacrylate [glass transition temperature Tg = + 20 ° C. of homopolymer], acrylic acid [of homopolymer Glass transition temperature Tg = + 106 ° C.] The copolymer was copolymerized so as to have a composition ratio of 3 parts to prepare an acrylic resin having a weight average molecular weight of 140000 and Tg of 50 ° C. The prepared acrylic resin was dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate were mixed in equal amounts to prepare an acrylic resin varnish G having an acrylic resin solid content of 40%.

<Preparation of acrylic resin varnish (acrylic resin varnish H)>
As acrylic monomers, 37 parts of methyl methacrylate [glass transition temperature Tg = + 105 ° C. of homopolymer] and 60 parts of butyl methacrylate [glass transition temperature Tg = + 20 ° C. of homopolymer], acrylic acid [of homopolymer Glass transition temperature Tg = + 106 ° C.] The copolymer was copolymerized so as to have a composition ratio of 3 parts to prepare an acrylic resin having a weight average molecular weight of 10,000 and Tg of 50 ° C. The prepared acrylic resin was dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate were mixed in equal amounts to prepare an acrylic resin varnish H having an acrylic resin solid content of 40%.

<Adjustment of cellulose acetate butyrate resin varnish (CAB resin varnish A)>
Cellulose acetate butyrate resin [Kanto Chemical Co., Inc., number average molecular weight 20000, butyryl 36-44%] 20 parts is dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate are mixed in equal amounts to obtain cellulose having a solid content of 20%. An acetate butyrate resin varnish (CAB resin varnish A) was obtained.

<Adjustment of cellulose acetate butyrate resin varnish (CAB resin varnish B)>
Cellulose acetate butyrate resin [Kanto Chemical Co., Ltd., number average molecular weight 5000, butyryl 44-48%] 20 parts is dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate are mixed in equal amounts to obtain cellulose having a solid content of 20%. -An acetate butyrate resin varnish (CAB resin varnish B) was obtained.

<Adjustment of cellulose acetate butyrate resin varnish (CAB resin varnish C)>
Cellulose acetate butyrate resin [Kanto Chemical Co., Ltd., number average molecular weight 57000, butyryl 49-53%] 20 parts is dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate are mixed in equal amounts to obtain cellulose having a solid content of 20%. An acetate butyrate resin varnish (CAB resin varnish C) was obtained.

<Adjustment of cellulose acetate butyrate resin varnish (CAB resin varnish D)>
Cellulose acetate butyrate resin [Kanto Chemical Co., Inc., number average molecular weight 70,000, butyryl 35-39%] 20 parts is dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate are mixed in equal amounts to obtain a cellulose having a solid content of 10%. Acetic acid butyrate resin varnish (CAB resin varnish D) was obtained.

<Adjustment of cellulose acetate acetate propionate resin varnish (CAP resin varnish)>
Cellulose acetate propionate resin [Kanto Chemical Co., Ltd., number average molecular weight 25000, propionyl 43 to 47%] 20 parts is dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate are mixed in equal amounts to obtain a cellulose having a solid content of 20%. -An acetate propionate resin varnish (CAP resin varnish) was obtained.

<Adjustment of nitrocellulose resin varnish>
20 parts of nitrocellulose resin [Inabata Sangyo Co., Ltd., Standard L1 / 2, trade name DLX30-50] is dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate are mixed in equal amounts, and the nitrocellulose resin has a solid content of 20%. A varnish was obtained.

(Examples 1-12, Comparative Examples 1-8)
First, the printing ink composition for styrene films of Examples 1-12 and Comparative Examples 1-8 was prepared with the compounding ratio shown in Table 1.
For pigments, plasticizers, phenyl group-containing resins, and tackifiers, the following are used, and the indicated components are blended in the paint shaker in the indicated amounts and dispersed by stirring to obtain the respective ink compositions. It was.
Pigment Titanics JR603 [Titanium oxide, manufactured by Teika Co., Ltd.]
Plasticizer Sansosizer DOS [Di-2-ethylhexyl sebacate, manufactured by Shin Nippon Chemical Co., Ltd.]
Phenyl group-containing resin Mighty Ace K125 [phenol copolymer, manufactured by Yasuhara Chemical Co., Ltd.] is dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate are mixed in equal amounts to obtain a solid content of 50%.
Tackifier Ester gum 105 [Arakawa Chemical Co., Ltd.] is dissolved in a mixed solvent in which isopropyl alcohol and ethyl acetate are mixed in equal amounts to obtain a solid content of 50%.

<Evaluation test>
The printing ink compositions of the examples (1) to (12) and the comparative examples (1) to (7) prepared in the above-described formulation and procedure were used in a gravure printing machine, the printing speed was 40 m / min, and the number of lines was 175. Printing was carried out on a polystyrene (PS) film (manufactured by Oishi Sangyo Co., Ltd., Styrophane) having a thickness of 25 μm with a screen and a gravure plate having a plate depth of 30 μm. Thereafter, the printing effect (good design quality of the printed matter), blocking resistance, ink storage stability, suitability for heat lamination, laminate strength, and formability were evaluated. The evaluation results are shown in Table 2. In addition, each evaluation method is based on the method described below.

<Print effect>
The transferability of the ink composition with respect to the PS film was visually evaluated.
○ The ink is very uniformly transferred on the film and has a good appearance.
△ Ink transferability is slightly poor, but appearance is not a problem for practical use.
× Ink transferability is poor and the appearance of the product has a practical problem.

<Ink storage stability>
The test ink is allowed to stand at 40 ° C. for 7 days, and the viscosity measurement data according to the elapsed time is measured with a Zaan cup made by Koiso Co., Ltd., and the storage stability of the ink is evaluated from the difference in viscosity immediately after the ink is finished and after the elapsed time. It was.
○ The viscosity with time is less than 1.5 times immediately after finishing.
Δ: Viscosity with time is about 1.5 to 2 times immediately after finishing, and practically no problem.
X The viscosity with time is 2 or more immediately after finishing, or it causes separation / precipitation / separation and has trouble in practical use.

<Blocking resistance>
The gravure printing of the printing ink cut to the same size as the printed material was performed, a load of 0.5 kg was applied, and the ink was allowed to stand in an atmosphere of 40 ° C. and 80% humidity for 24 hours to evaluate blocking resistance.
○ Ink does not peel at all △ Peeling resistance is felt, but there is no practical problem.
× The area taken up by the ink film is 10% or more, and there are practical problems

<Thermal laminate strength>
On a highly foamed PS sheet (manufactured by JSP Co., Ltd.), the printed film surface of the printed material left at room temperature for one day is put together, a polyester film having a thickness of 12 μm is placed on the film surface of the printed material, and a temperature of 180 μm is used using a laminator. Thermal lamination was carried out under the conditions of 5 ° C. and a rate of 5 m / min, and then the polyester film (not thermally laminated) was removed. A kraft tape (Toyo Ink)) is pasted on the PS film surface of the heat-laminated laminate, cut to a width of 25 mm, and peeled at 300 mm / min with a tensile tester (manufactured by Intesco), peel angle 90 The laminate strength was measured under the condition of the degree. Here, the peel strength (interlayer adhesive strength) between the PS film and the PS sheet laminate (width 25 mm) in a state where the printing ink is interposed is measured.
◎ Laminate strength is very strong, and PS film is cut when peeled. ○ Laminate strength is very good. The peeling interface becomes cohesive failure △ Laminate strength is slightly weak, but there is no practical problem × Laminate strength is weak and practically hindered.

  In general, in the peel strength test, when the laminate strength of the laminate is measured, the laminate is peeled off from the portion having the weakest adhesive strength. For example, in the case of a laminate of PS film / ink / PS sheet, when peeling between the PS film / ink, it is an indication that the adhesion of the ink to the PS film is weak. In the case of peeling between the ink and the PS sheet, it becomes a standard that the thermal lamination strength of the ink to the PS sheet is weak. When both the adhesion to the PS film and the thermal laminating strength are strong, the peeling interface is “layer” and the peeling does not occur, and the ink is pulled to both the PS film and the PS sheet. This is a phenomenon called cohesive failure and is considered to be the most preferable peeling.

[Formability test]
The printed film surface of the printed material left for one day at room temperature is placed on the highly foamed P sheet, a polyester film having a thickness of 12 μm is placed on the film surface of the printed material, and a temperature of 180 ° C. and a speed of 5 m / min are used using a laminator. Thermal lamination was performed under the conditions. After that, the laminate from which the polyester film was removed was prepared by using a vacuum forming machine [formech 300X] to produce a container on a square with a width of 50 mm on one side. Displayed as (×). Blister refers to a phenomenon in which the membrane surface partially peels and becomes blistering and blistering.

  As shown in Table 2, the acrylic resins of Examples (1) to (12) and those using CAB or CAP resin satisfy all the required physical properties, whereas Comparative Examples (1) to (8). Then, any of the required physical properties were poor, and none of the required physical properties were satisfactory.

Claims (3)

A printing ink composition for a styrene film for thermal lamination , comprising a binder resin, a pigment and a solvent,
Binder resin
Acrylic resin and cellulose acetate butyrate (CAB) resin and / or cellulose
Acetate Propionate (CAP)
Because
Acrylic resin
Weight average molecular weight 20,000-130,000 and glass transition point (Tg) 20-80 ° C.
and
Synthesized from acrylic monomers containing methyl methacrylate and butyl methacrylate,
Dissolved or dispersed in alcoholic and ester organic solvents,
And,
Cellulose acetate butyrate (CAB) resin
The number average molecular weight is less than 60,000,
Cellulose acetate propionate (CAP) resin
A printing ink composition for a styrene film for thermal lamination, having a number average molecular weight of 60,000 or less. Solid content weight W1 of the acrylic resin and solid content weight of cellulose acetate butyrate (CAB) resin and cellulose
The ratio between the total amount W2 of the solid weight of acetate propionate (CAP) resins W1: W2 = 30: 70~99: 1 a thermal laminate for styrene film for printing ink according to claim 1, characterized in that Composition. The printing ink composition for styrene film for thermal lamination according to claim 1 or 2 , further comprising at least one selected from a plasticizer, a resin having a phenyl group or a xylyl group, and a tackifier.