JPH09111159A - Coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating compsn. for overcoating which can form a flexible scratch-resistant coating film. SOLUTION: This compsn. comprises 95-70wt.% reactive resin and 5-30wt.% spherical particles having an average particle size of 3-50μm, subject to the condition that the relation: 0.3t<=d<=2.0t (wherein (d) is the average particle size in μm; and (t) is the average thickness in μm of a coating film) is satisfied.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating composition having excellent scratch resistance. More specifically, paper,
The present invention relates to an overcoat agent that covers the surface of a plastic sheet or film, or a product obtained by printing these.

[0002]

2. Description of the Related Art Conventionally, a thermosetting resin or an ionizing radiation curing agent is used as an overcoating agent for coating the surface of paper, a plastic sheet or film, and a printed product thereof to protect them from scratches caused by friction and scratches. Reactive resins such as reactive resins have been used.

[0003]

However, in order to prevent scratches due to friction or scratching, it is necessary to harden the resin to be coated, and therefore it is necessary to reduce the average molecular weight between crosslinks. As a result, there is a drawback that the flexibility of the resin itself is lowered and the coating film is cracked when the substrate is bent.

[0004]

Means for Solving the Problems As a result of intensive investigations by the present inventors on an overcoating agent capable of forming a flexible film that is not easily scratched, spherical particles having an average particle size specified as a reactive resin Although a certain amount of effect can be obtained by adding a certain amount, it is not enough, and it is necessary to specify the relationship between the average film thickness of the coating layer and the average particle size of the spherical particles. The present invention has been accomplished by finding that a sufficient effect can be obtained when the above constituent requirements are satisfied. That is, the present invention has an average particle size of 3 to 5
It is composed of 0 μm spherical particles (A) and a reactive resin (B), and the content of the (A) is 5 to 30% by weight based on the total amount of (A) and (B), and the (A) Average particle size d (μ
m) is a coating composition characterized by satisfying the following formula (1). 0.3t ≦ d ≦ 2.0t (1) [where, t is the average film thickness (μm) of the coating layer. ]

The shape (A) used in the present invention is spherical or similar. As the (A), fused alumina, Bayer alumina, zirconia, titania or a eutectic mixture thereof having a Knoop hardness of 1300.
Examples include those of kg / mm ² or more. Of these, preferred are those having a Knoop hardness of 1800 kg / mm ² or more, and a specific example thereof is fused alumina.

The Knoop hardness referred to here is a minute indentation hardness measured using a Knoop indenter, and the load when a diamond-shaped indentation is made on the test surface is obtained from the diagonal length of the longer permanent dent. It is a value represented by the quotient divided by the projected area of the recess. This test method is described in ASTM C-849.

As a method for making the shape of the inorganic particles spherical, a method of charging the pulverized amorphous inorganic material into a high-temperature furnace having a melting point or higher and melting it to make it spherical by utilizing surface tension; The method of blowing the molten material at a high temperature into a mist to make it spherical, and the like.

The content of (A) in the composition of the present invention is usually 5 to 30% by weight, preferably 5 to 25% by weight, particularly preferably 5 to 15% by weight.

If the content of (A) is less than 5%, the scratch resistance is insufficient, and if it exceeds 30% by weight, the reactive resin (B) is used.
As a result, the binder effect is deteriorated and the flexibility is deteriorated.

The average particle size of (A) is usually 3 to 50 μm,
It is preferably 8 to 40 μm. If the average particle size is less than 3 μm, the coating becomes opaque, which is not preferable. On the other hand, when the average particle diameter exceeds 50 μm, the film thickness becomes too large as compared with the film thickness of the coating agent that is usually used, and the surface smoothness of the film deteriorates.

When a substrate of the composition of the present invention is coated, its film thickness and the average particle diameter d are represented by the following formula (1).
Need to be satisfied. 0.3t ≦ d ≦ 2.0t (1) [where t is the average film thickness (μm) of the coating layer] When the average particle size exceeds 2.0t, the particles protrude to the surface of the coating layer, The appearance of the coating layer deteriorates, and when it is less than 0.3 t, the scratch resistance of the coating layer deteriorates, which is not preferable.

As the reactive resin (B) used in the present invention, a thermosetting resin and an ionizing radiation curable resin can be used.

The thermosetting resin used in (B) may be a known one, and examples thereof include a two-component urethane resin, an epoxy resin, an alkyd resin and an unsaturated polyester resin.

As the above-mentioned two-pack type urethane resin, a first liquid consisting of a polyol compound having an average of two or more hydroxyl groups in its molecular structure and a second liquid consisting of a polyisocyanate compound are equivalent to the hydroxyl group and the isocyanate group. An example is one in which the ratio is 0.7 to 1.5.

As the above-mentioned epoxy resin, an epoxy resin having an average of two or more epoxy groups in its molecular structure,
The ratio of the epoxy equivalent of the epoxy resin to the mono- or poly-amine having three or more active hydrogens that react with the epoxy group in one molecule is 0.7 to 1.5. Examples of the composition are as follows.

Examples of the ionizing radiation-curable resin used in (B) include compounds having one or more radical-polymerizable double bonds in the molecular structure. Specific examples include unsaturated polyester resins and (meth) acryloyl groups. [Monofunctional (meth) acrylic ester, polyfunctional (meth) acrylic ester, urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, etc.], vinyl compound [styrene, divinylbenzene, etc.], Examples thereof include allyl compounds [diallyl phthalate and the like] and mixtures of two or more thereof.

More preferred as the reactive resin (B) in the present invention is an ionizing radiation curable resin, and particularly preferred is a polyether urethane (meth) acrylate represented by the following general formula (2). is there. ^{_{CH 2 = C (R 1)}} -COOCH 2 CH 2 -OCONH-X-NHCOO - [- CH (R 2) - (CH 2) n -O-] m -CONH-X-NHCOO -CH 2 CH 2 OCOC (R ¹ ) = CH ₂ (2) (In the formula, R ¹ and R ² are each hydrogen or a methyl group, X is a diisocyanate residue, n is an integer of 1 to 3, and m is
Is an integer of 6 to 60. )

As the diisocyanate used in the polyether urethane (meth) acrylate, known ones can be used. Specific examples thereof include isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate and tolylene diisocyanate.

Examples of the polyether diol used for producing the polyether urethane (meth) acrylate include polyoxypropylene glycol, polyoxyethylene glycol and polyoxytetramethylene glycol having a molecular weight of 500 to 3,000. .

The above-mentioned general formula (2) is used as the reactive resin (B).
When the polyether-based urethane (meth) acrylate shown in is used, its amount is 10% by weight in the total amount of (B).
That is all. If it is less than 10% by weight, the flexibility of the resin itself is lowered, and the film may be cracked when the substrate is bent.

In the present invention, the solubility parameter (SP value) of the reactive resin (B) is usually 9.7 to 11.0, preferably 9.9 to 10.5. If the SP value is less than 9.7, the adhesiveness with (A) will be insufficient, so there is a risk that the spherical particles will lack the holding power and the scratch resistance will be insufficient.
When the P value exceeds 11.0, there is a possibility that the adhesiveness with the base material may become insufficient when the base material such as paper, plastic sheet or film is coated.

The SP value here is calculated by "Polymer Engineering and Science, Vol. 14, p. 174 (1974)". Note that (B) is 2
In the case of a mixture of two or more compounds, S of each component
It is a weighted average of P values.

When the composition of the present invention is cured by irradiation with ionizing radiation, examples of the ionizing radiation include ultraviolet rays and electron beams.

In the case of curing with ultraviolet rays, a known ultraviolet irradiation device equipped with a high pressure mercury lamp, a metal halide lamp, etc. can be used. The irradiation amount of ultraviolet rays at the time of curing is preferably 50 to 1,000 mJ / cm ² .
The amount of irradiation curing is insufficient at less than 50 mJ / cm ^2, the coating film was cured exceeds 1,000 mJ / cm ² there is a possibility of yellowing degradation.

In the case of curing with an electron beam, a known electron beam irradiation device can be used. The irradiation dose of the electron beam is preferably 1 to 10 Mrad. If the irradiation dose is less than 1 Mrad, curing will be insufficient, and if it exceeds 10 Mrad, the cured coating film or substrate (paper, plastic sheet, film, etc.) may be damaged and deteriorated.

In the present invention, the average molecular weight between crosslinks after the reaction of the reactive resin (B) is usually 150 to 1,000.
0, preferably 200 to 1,000, particularly preferably 2
50 to 800. If the average molecular weight between crosslinks is less than 150, the flexibility of the resin itself may decrease and the coating may crack when the base material bends. If it exceeds 1,000, the resin itself becomes too soft and spherical particles are retained. Since it lacks strength, scratch resistance is insufficient.

The average molecular weight between crosslinks as used herein means m / [2 × (f-1)] where f is the average number of functional groups of the polymerizable functional groups of the reactive resin (B) and m is the average molecular weight. It is a value represented by.

In order to use the composition of the present invention for coating, it is preferable that the viscosity is low from the viewpoint of workability. The viscosity is preferably 800 centipoise or less, more preferably 500 centipoise or less at the temperature when used for coating. When the viscosity exceeds 800 centipoise, workability is deteriorated and a smooth coated surface may not be obtained.

In coating the composition of the present invention, the reactive resin (B) is dissolved in order to adjust the viscosity,
Further, one or more kinds of solvents having a boiling point of 70 ° C. to 150 ° C. under normal pressure can be used in the range of 30% by weight or less with respect to the total amount of (A) and (B). The amount of solvent used is 30% by weight
If it exceeds, it takes time to dry and the production speed is reduced, which is not preferable.

As the solvent, those commonly used in paints, inks and the like can be used. Specific examples thereof include aromatic hydrocarbons such as toluene and xylene, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone. , Acetic acid esters such as ethyl acetate, isopropyl acetate and amyl acetate, alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol, ethers such as dioxane, tetrahydrofuran and diisopropyl ether, and mixtures of two or more thereof.

If necessary, (B) used in the present invention may optionally contain a thermosetting catalyst, a photopolymerization initiator, a defoaming agent, a leveling agent, a coating agent such as a coupling agent, and an additive usually added to ink. can do.

Examples of the thermosetting catalyst used when (B) is an alkyd resin or an unsaturated polyester resin in the present invention include peroxides such as tertiary butyl peroxybenzoate, benzoyl peroxide and methyl ethyl ketone peroxide. And azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile.

In the present invention, as the thermosetting catalyst used when (B) is an epoxy resin, imidazoles such as 2-methyl-4-ethylimidazole, phenol,
Examples include phenols such as cresol and bisphenol A.

The thermosetting catalyst used when (B) is a two-component urethane resin in the present invention includes dibutyltin dilaurate, tin octylate, triethylamine and the like.

If necessary, the amount of the thermosetting catalyst used is
It is usually 10% by weight or less, preferably 5% by weight or less, based on the weight of (B).

As the photopolymerization initiator used when (B) is an ultraviolet curable resin in the present invention, benzoin alkyl ether, benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1. -Phenylpropan-1-one, benzophenone, methylbenzoyl formate, isopropylthioxanthone and the like can be mentioned.

The amount of the photopolymerization initiator is usually 20% by weight or less, preferably 6% by weight or less, based on the weight of (B).

[0038]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. Parts in Examples are parts by weight.

Example 1 Bisphenol A type epoxy resin [Yukaka Shell Epoxy Co., Ltd., Epicoat 828] 70 parts 1,6-hexamethylene glycol diglycidyl ether [Sakamoto Yakuhin Kogyo Co., Ltd., SR-16H] 14 Part Spherical alumina having average particle diameter: 30 μm, Knoop hardness: 2800 [Alumina beads CB-A30S manufactured by Showa Denko KK] 15 parts Thixotropic agent [Aerosil 200 manufactured by Nippon Aerosil Co., Ltd.] 0.5 part Sedimentation Inhibitor [Oruben, manufactured by Shiraishi Industry Co., Ltd.] 0.5 part These were uniformly mixed with a planetary mixer. This is designated as the main ingredient 1. The viscosity of a mixture of 100 parts of the main agent 1, 17 parts of m-xylylenediamine and 20 parts of toluene uniformly was 400 centipoise. Further, this product was coated on a printed paper so as to have a dry thickness of 25 μm, and cured at 40 ° C. for 20 minutes. When this coated paper was subjected to a Taber abrasion test in accordance with JIS K-6902, the abrasion loss at 200 revolutions was 30 mg.

Production Example 1 A glass reactor equipped with a dropping funnel, a thermometer, a reflux condenser and a stirring rod was charged with 1000 parts of polytetramethylene glycol having a molecular weight of 1,000 and 444 parts of isophorone diisocyanate, and the temperature was 120 ° C. React for 3 hours.
Then, it cooled at 80 degrees C or less, 232 parts of 2-hydroxyethyl acrylates were added, and it reacted at 80 degrees C until the isocyanate group disappeared. This is called urethane acrylate 1.

Example 2 Urethane acrylate 1 20 parts Trimethylolpropane triacrylate 20 parts Bisphenol A (EO) ₄ diacrylate 20 parts Phenol (EO) ₂ acrylate 20 parts Spherical alumina having an average particle diameter of 30 μm and Knoop hardness of 2800 [ Showa Denko KK, Alumina beads CB-A30S 15 parts Photoinitiator [Merck, Darocur 1173] 3 parts Thixotropic agent [Nippon Aerosil Co., Ltd., Aerosil 200] 0.5 part Toluene 5 parts Was uniformly mixed, and the viscosity was 440 centipoise. The average molecular weight between crosslinks of the reactive resin is 2
72. This product is coated on a printed paper to a dry thickness of 25 μm and exposed to UV light of 150 μm.
Irradiation at mJ / cm ² was performed. The abrasion amount in the Taber abrasion test similar to that in Example 1 was 25 mg.

Example 3 Urethane acrylate 1 20 parts Trimethylolpropane triacrylate 20 parts Bisphenol A (EO) ₄ diacrylate 10 parts Phenol (EO) ₂ acrylate 30 parts Spherical alumina having an average particle size of 20 μm and Knoop hardness of 2800 [ Alumina beads CB-A20S manufactured by Showa Denko KK 15 parts Thixotropic agent [Aerosil 200 manufactured by Nippon Aerosil Co., Ltd. 0.5 part] A mixture of these uniformly had a viscosity of 740 centipoise. The average molecular weight between crosslinks of the reactive resin is 2
It was 87. This product was coated on a printed paper to a dry thickness of 20 μm and exposed to an electron beam of 3 Mr.
irradiated with ad. The abrasion amount in the Taber abrasion test similar to that in Example 1 was 18 mg.

Comparative Example 1 Urethane acrylate 1 20 parts Trimethylolpropane triacrylate 20 parts Bisphenol A (EO) ₄ diacrylate 20 parts Phenol (EO) ₂ acrylate 20 parts Photoinitiator [Merck, Darocur 1173] 3 parts Thixotropy Additive [Aerosil 200 manufactured by Nippon Aerosil Co., Ltd.] 0.5 part Toluene 5 parts The viscosity of a homogeneous mixture of these was 400 centipoise. This product is coated on a printed paper to a dry thickness of 25 μm and exposed to UV light of 150 μm.
Irradiation at mJ / cm ² was performed. In the same Taber abrasion test as in Example 1, the coating layer was completely removed and the base material was scraped off.

Comparative Example 2 20 parts of urethane acrylate 1 20 parts of trimethylolpropane triacrylate 20 parts of bisphenol A (EO) ₄ diacrylate 10 parts of phenol (EO) ₂ acrylate 30 parts thixotropic agent [Aerozil 200 manufactured by Nippon Aerosil Co., Ltd.] 0.5 part The viscosity of a mixture of these uniformly was 720 centipoise. This product was coated on a printed paper to a dry thickness of 20 μm and exposed to an electron beam of 3 Mr.
irradiated with ad. In the same Taber abrasion test as in Example 1, the coating layer was completely removed and the base material was scraped off.

[0045]

EFFECT OF THE INVENTION The coating composition of the present invention comprises adding a specific amount of spherical particles having an average particle size within a specific range to the reactive resin, and further determining the relationship between the average film thickness of the coating layer and the spherical particles. By specifying, a coating film having excellent scratch resistance and flexibility as well as excellent transparency and surface smoothness can be obtained. Therefore, the surface of the paper, the plastic sheet or the film coated with the coating composition of the present invention is less likely to be scratched by friction and scratches, and the coating itself is flexible even if the substrate is bent. The film does not crack, and the appearance is good. Because of such effects, the composition of the present invention is extremely useful as a coating agent for protecting the printed surface of printed paper, plastic sheet or film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Haruo Ohno 1-1-1, Ichigayakaga-cho, Shinjuku-ku, Tokyo Within Dai Nippon Printing Co., Ltd. (72) Inventor Makoto Katsukawa 1-11, Hitotsubashi-honcho, Higashiyama-ku, Kyoto Sanyo Chemical Industry Co., Ltd.

Claims (9)

[Claims] 1. A spherical resin (A) having an average particle diameter of 3 to 50 μm and a reactive resin (B), wherein the content of (A) is 5 to the total amount of (A) and (B). 30% by weight, and the average particle diameter d (μm) of the (A) is represented by the following formula (1)
A coating composition, which satisfies: 0.3t ≦ d ≦ 2.0t (1) [where, t is the average film thickness (μm) of the coating layer. ] 2. The spherical particles (A) have a Knoop hardness of 1300 k.
The composition according to claim 1, which is a spherical inorganic particle having a g / mm ² or more. 3. The composition according to claim 1, wherein the spherical particles (A) are spherical alumina-based particles. 4. The composition according to claim 1, wherein the content of aluminum oxide in the spherical particles (A) is 90% by weight or more. 5. The composition according to claim 1, wherein the reactive resin (B) is a thermosetting resin. 6. The composition according to claim 1, wherein the reactive resin (B) is an ionizing radiation curable resin. 7. The method according to claim 1, wherein at least 10% by weight of the reactive resin (B) is a polyether urethane (meth) acrylate represented by the following general formula (2). The composition as described. ^{_{CH 2 = C (R 1)}} -COOCH 2 CH 2 -OCONH-X-NHCOO - [- CH (R 2) - (CH 2) n -O-] m -CONH-X-NHCOO -CH 2 CH 2 OCOC (R ¹ ) = CH ₂ (2) (In the formula, R ¹ and R ² are each hydrogen or a methyl group, X is a diisocyanate residue, n is an integer of 1 to 3, and m is
Is an integer of 6 to 60. ) 8. The average molecular weight between crosslinks after curing the reactive resin (B) with heat or ionizing radiation is 150 to 1,000.
The composition according to any one of claims 1 to 7. 9. One weight or more of a solvent which dissolves the reactive resin (B) and has a boiling point of 70 ° C. to 150 ° C. under normal pressure is 30% by weight with respect to the total amount of (A) and (B). % Or less, The composition according to any one of claims 1 to 8.