JP3926461B2 - Paint composition - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention mainly includes resin molded products indoors and outdoors; automobile bodies; woodwork products such as stairs, floors, and furniture; products such as aluminum wheels and door mirrors that have been subjected to treatments such as plating, vapor deposition, and sputtering; range hoods, The present invention relates to a coating composition used in a field where scratch resistance is required, such as metal products such as kitchen panels for kitchens, stainless steel sinks and bathtubs; inorganic building materials such as ceramics wall materials and entrance floors.
[0002]
BACKGROUND OF THE INVENTION AND PRIOR ART
Since resin molded products such as polycarbonate and acrylic plates lack various physical properties such as hardness, weather resistance, stain resistance, and solvent resistance, surface treatment is usually applied to supplement these physical properties. Such surface treatment includes metal mirror surface treatment such as plating, vapor deposition, and sputtering. However, when the metal mirror surface treatment is performed, the treated film is easily scratched, and the scratch is easily noticeable.
[0003]
In addition, range hoods, kitchen panels for kitchens, stainless steel sinks, bathtubs, etc. are easily stained and scratched, and woodwork products such as stairs, floors, furniture, etc. are very easily scratched. On the other hand, for automobile topcoats, in recent years, the trend toward high durability has been increasing to maintain the appearance of paints for new vehicles for a long period of time, so scratch resistance that is not damaged by car wash machines or dust is required. ing.
[0004]
Conventionally known as scratch-resistant paints are ultraviolet (UV) curable paints, electron beam energy (EB) curable paints, silica-based hard coat agents, two-component acrylic urethane-based soft paints, and the like. Yes.
[0005]
[Problems to be solved by the invention]
However, in the UV curable paint, EB curable paint, and silica-based hard coat agent, the use of a hard monomer for increasing the hardness and the increase in strain at the time of curing shrinkage by increasing the crosslink density, Problems such as poor adhesion and cracking are likely to occur.
[0006]
On the other hand, the above-mentioned two-component acrylic urethane-based soft paint has no problems of chipping and cracking, but often has a tacky feeling and has a disadvantage that it is inferior in weather resistance and stain resistance. In order to improve the tackiness, it is conceivable to add polydimethylsiloxane oil to the two-component acrylic urethane-based soft paint. However, the stain resistance cannot be improved, and the adhesion to the substrate is not possible. This causes a problem of lowering.
[0007]
Accordingly, an object of the present invention is to provide a coating composition which has excellent scratch resistance, is free from chipping, cracks and the like, and is excellent in weather resistance, stain resistance, adhesion and the like.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a paint comprising a polydimethylsiloxane copolymer having a polydimethylsiloxane portion and a vinyl polymer chain portion , a caprolactone component, and a siloxane component. The present invention provides a composition, and further provides a paint comprising the above-mentioned paint composition and a urethane crosslinking agent and / or a melamine crosslinking agent.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The coating composition of the present invention comprises a polydimethylsiloxane copolymer (A) having a polydimethylsiloxane portion and a vinyl polymer chain portion , a caprolactone component (B), and a siloxane component (C) as essential components. To do .
[0010]
(A) Polydimethylsiloxane-based copolymer The polydimethylsiloxane-based copolymer (A) in the present invention is a copolymer having a polydimethylsiloxane portion and a polymer chain portion of a vinyl monomer. It may be a coalescence or a graft copolymer.
[0011]
The synthesis of the polydimethylsiloxane block copolymer can be carried out by (1) living polymerization method, (2) polymer initiator method or (3) polymer chain transfer method, etc. It is preferably carried out by 2) polymer initiator method or (3) polymer chain transfer method.
[0012]
(2) In the polymer initiator method, for example,
[Chemical 1]
A block copolymer can be efficiently synthesized by copolymerizing with a vinyl monomer using a polymer azo radical polymerization initiator such as Also, a two-stage process in which a peroxy monomer and polydimethylsiloxane having an unsaturated group are copolymerized at a low temperature to synthesize a prepolymer having a peroxide group introduced into a side chain, and the prepolymer is copolymerized with a vinyl monomer. The polymerization can also be carried out.
[0013]
(3) In the polymer chain transfer method, for example,
[Chemical 2]
To silicone oil, such as HS-CH ₂ COOH,
A block copolymer is obtained by adding a HS-CH ₂ CH ₂ COOH or the like to form a silicone compound having an SH group, and then copolymerizing the silicone compound and a vinyl monomer using chain transfer of the SH group. Can be synthesized.
[0014]
On the other hand, for polydimethylsiloxane graft copolymers, for example,
[Chemical 3]
By copolymerizing a methacrylic ester of polydimethylsiloxane and the like with a vinyl monomer, a graft copolymer can be synthesized easily and with a high yield.
[0015]
Examples of vinyl monomers used in the copolymer with polydimethylsiloxane include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, octyl acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, methyl methacrylate, ethyl methacrylate, n -Butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, styrene, α-methyl styrene, acrylonitrile, methacrylonitrile, Vinyl acetate, vinyl chloride, vinylidene chloride, vinyl Vinyl chloride, vinylidene fluoride, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, maleic anhydride, citraconic acid, acrylamide, methacrylamide, N-methylolacrylamide, N , N-dimethylacrylamide, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate, diacetone acrylamide and the like.
Also, vinyl monomers having an OH group such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, and allyl alcohol can be used. A reaction product with acid, itaconic acid, crotonic acid, maleic acid or the like can also be used.
In addition, the above illustration does not limit the present invention.
[0016]
(B) Caprolactone component As the caprolactone component (B) in the present invention, for example,
[Formula 4]
Bifunctional caprolactone diols such as
[Chemical formula 5]
Trifunctional caprolactone triols, other tetrafunctional caprolactone polyols, etc. can be used.
When the caprolactone component (B) is introduced into the skeleton of the polydimethylsiloxane copolymer (A), lactone-modified hydroxyethyl (meth) acrylates are preferably used.
[Chemical 6]
And radically polymerizable caprolactone represented by the structural formula:
[0017]
(C) Siloxane Component Examples of the siloxane component (C) in the present invention include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltoxioxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, and γ-glycidoxy. Propyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyl Triethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropylmethyldi The hydrolysis with or partial hydrolyzate of a silane compound having a hydrolyzable silyl group such as Tokishishiran, organosilica sol was stably dispersing fine particles of silicic anhydride in an organic solvent or a radically polymerizable in the organosilica sol, A product obtained by adding a partial hydrolyzate of a silane compound having a functional silyl group can be used. In addition, the above illustration does not limit the present invention.
The siloxane component (C) plays an important role in imparting heat resistance, stain resistance and the like to the resulting coating composition and improving the surface hardness of the coating film.
[0018]
The polydimethylsiloxane copolymer (A) in the present invention is usually produced by solution polymerization. In this solution polymerization, aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ester solvents such as ethyl acetate, propyl acetate, isobutyl acetate, and butyl acetate, ethanol, isopropanol Alcohol solvents such as butanol and isobutanol are used alone or as a mixed solvent. If desired, oil-soluble polymerization initiators such as benzoyl peroxide, lauryl peroxide, cumene hydroperoxide, and azobisisobutyronitrile are used. Is used.
The reaction temperature for the solution polymerization is preferably 50 to 150 ° C., and the reaction time is preferably 3 to 12 hours.
[0019]
When the caprolactone component (B) and / or the siloxane component (C) are introduced into the skeleton of the polydimethylsiloxane copolymer (A), the polydimethylsiloxane copolymer (A) is polymerized. In this case, the caprolactone component (B) and / or the siloxane component (C) may be added and copolymerized.
[0020]
The amount of the polydimethylsiloxane moiety in the polydimethylsiloxane copolymer (A ) in the present invention is preferably 1 to 30% by weight, particularly preferably 1 to 20% by weight. This polydimethylsiloxane part has a function of imparting lubricity to the coating film surface and imparting scratch resistance by lowering the coefficient of friction, but if the amount of the polydimethylsiloxane part is less than 1% by weight, such an effect is exerted. On the other hand, if the amount of the polydimethylsiloxane portion exceeds 30% by weight, the stain resistance of the coating film decreases.
The molecular weight of the polydimethylsiloxane portion is preferably about 1000 to 30000, and the molecular weight that is effectively oriented on the surface of the coating film and imparts lubricity is particularly preferably about 5000 to 20000.
[0021]
Caprolactone component in the present invention (B) is preferably a paint solid content 5 to 50 wt%. This caprolactone component (B) imparts high rebound resilience and good adhesion to the coating film and, when subjected to a rubbing force, has the function of absorbing the rubbing force by energy elastic deformation. When the amount of (B) is less than 5% by weight, the scratch resistance and chipping resistance of the coating film are lowered. On the other hand, when the amount of the caprolactone component (B) exceeds 50% by weight, the stain resistance of the coating film is reduced. Decreases.
[0022]
Siloxane component (C) in the present invention is preferably a paint solid content 20% by weight. The siloxane component (C) has a function of imparting stain resistance, weather resistance, and heat resistance to the coating film and improving the surface hardness of the coating film, but the amount of the siloxane component (C) is 1 weight. If the amount of siloxane component (C) exceeds 20% by weight, the scratch resistance of the coating film decreases.
[0023]
In order to cure the coating composition of the present invention, the polydimethylsiloxane copolymer (A ) is preferably urethane-crosslinked and / or melamine-crosslinked.
In order to urethane-crosslink the polydimethylsiloxane copolymer (A), methylenebis-4-cyclohexylisocyanate, trimethylol of tolylene diisocyanate is added to the polydimethylsiloxane copolymer (A) having an OH group. Propane adduct, hexamethylene diisocyanate trimethylolpropane adduct, isophorone diisocyanate trimethylolpropane adduct, tolylene diisocyanate isocyanurate, hexamethylene diisocyanate isocyanurate, isophorone diisocyanate isocyanurate, hexamethylene diisocyanate Use urethane crosslinkers such as polyisocyanates such as biuret bodies or block isocyanates of the above polyisocyanates It can be.
On the other hand, in order to melamine crosslink the polydimethylsiloxane copolymer (A), a melamine crosslinking agent such as alkoxymethylol melamine can be used.
[0024]
The coating film obtained by curing the coating composition of the present invention has excellent adhesion to various materials, retains a predetermined surface hardness, and is resistant to scratches, and further self-healing when scratches occur. Also excellent. Moreover, this coating film is excellent also in stain resistance, a weather resistance, heat resistance, etc.
Such coating compositions include resin molded products indoors and outdoors; automobile bodies; woodwork products such as stairs, floors and furniture; products such as aluminum wheels and door mirrors that have been subjected to plating, vapor deposition, sputtering, etc .; range hoods It is suitable as a paint for use in fields where scratch resistance is required, such as metal products such as kitchen panels for kitchens, stainless steel sinks and bathtubs; ceramic building wall materials, inorganic building materials such as entrance floors, and the like.
[0025]
【Example】
EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples.
[Synthesis Example 1]
Synthesis of Siloxane Component A In a 500 ml flask equipped with a stirrer, thermometer, condenser and nitrogen gas introduction tube, 106 parts by weight of ethanol (hereinafter simply referred to as “parts”), 320 parts of tetraethoxysilane, deionized water After 21 parts and 1 part of 1% hydrochloric acid were charged and maintained at 85 ° C. for 2 hours, ethanol was recovered while the temperature was raised and maintained at 180 ° C. for 30 minutes. Thereafter, the mixture was cooled to obtain a viscous siloxane component A (for external addition).
[0026]
[Synthesis Example 2]
Synthesis of Siloxane Component B As in Synthesis Example 1, 106 parts of ethanol, 270 parts of methyltrimethoxysilane, 23 parts of γ-methacryloxypropylmethyldimethoxylane, 100 parts of deionized water, 1 part of 1% hydrochloric acid and hydroquinone monomethyl ether 0.1 part was charged to synthesize siloxane. This was adjusted to 50% with methyl isobutyl ketone to obtain siloxane component B (for copolymerization).
[0027]
[Synthesis Example 3]
Synthesis of Siloxane Component C Using the same equipment as in Synthesis Example 1, 100 parts of organosilica sol (dispersion medium: methyl isobutyl ketone, solid content: 30%), 1.5 parts of γ-methacryloxypropylmethyldimethoxylane, hydroquinone monomethyl ether 0.01 part and 0.01 part formic acid were charged and reacted at 80 ° C. for 3 hours to obtain a siloxane component C (for copolymerization).
[0028]
[Synthesis Example 4]
Synthesis of Polydimethylsiloxane Block Copolymer D Using the same equipment as in Synthesis Example 1, 50 parts of toluene, 50 parts of methyl isobutyl ketone, polydimethylsiloxane polymer polymerization initiator (manufactured by Wako Pure Chemical Industries, Ltd., VPS-0501) 20 parts, 30 parts of methyl methacrylate, 26 parts of butyl methacrylate, 23 parts of 2-hydroxyethyl methacrylate, 1 part of methacrylic acid and 0.5 part of 1-thioglycerin were allowed to react at 80 ° C. for 8 hours. Dimethylsiloxane block copolymer D was obtained. The obtained block copolymer D had a solid content of 50% and a viscosity X (Gardner Holtz).
[0029]
[Synthesis Example 5]
Synthesis of Polydimethylsiloxane Graft Copolymer E Using the same equipment as in Synthesis Example 1, 50 parts of toluene and 50 parts of methyl isobutyl ketone were charged and heated to 80 ° C. Separately, 30 parts of methyl methacrylate, 26 parts of butyl methacrylate, 23 parts of 2-hydroxyethyl methacrylate, 1 part of methacrylic acid and methacrylic modified polydimethylsiloxane (Shin-Etsu Chemical Co., Ltd., X-22-174DX, molecular weight: 5000) 20 parts and 1 part of azobis-2-methylbutyronitrile (manufactured by Nippon Hydrazine Kogyo Co., Ltd., ABN-E) are mixed, and this mixed monomer is dropped into the above mixed solution of toluene and methyl isobutyl ketone over 3 hours. did. Thereafter, reaction was performed for 6 hours to obtain a polydimethylsiloxane graft copolymer E. The obtained graft copolymer E had a solid content of 50% and a viscosity W (Gardner Holtz).
[0030]
[Synthesis Example 6 ]
Synthesis of Polydimethylsiloxane Graft Copolymer F The monomer composition was 20 parts methyl methacrylate, 26 parts butyl methacrylate, 23 parts 2-hydroxyethyl methacrylate, 10 parts siloxane component B, 1 part methacrylic acid and one-end methacryl-modified polydimethyl. Polydimethylsiloxane-based graft copolymer F was synthesized in the same manner as in Synthesis Example 5 except that 20 parts of siloxane (manufactured by Shin-Etsu Chemical Co., Ltd., X-22-174DX, molecular weight: 5000) was used. The obtained graft copolymer F had a solid content of 50% and a viscosity U (Gardner Holtz).
[0031]
[Synthesis Example 7 ]
Except using siloxane component C instead of the synthetic siloxane component B of polydimethylsiloxane graft copolymer G, it was synthesized polydimethylsiloxane graft copolymer G in the same manner as in Synthesis Example 6. The obtained graft copolymer G had a solid content of 50% and a viscosity T (Gardner Holtz).
[0032]
[Synthesis Example 8 ]
Synthesis of Polydimethylsiloxane Graft Copolymer H Using the same equipment as in Synthesis Example 1, 50 parts of toluene and 50 parts of methyl isobutyl ketone were charged and heated to 80 ° C. Separately, methyl methacrylate 27 parts, caprolactone methacrylic ester (manufactured by Daicel Chemical Industries, Plaxel FM-5), single-end methacryl-modified polydimethylsiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., X-22-174DX, molecular weight: 5000) 20 parts, 17 parts of 2-hydroxyethyl methacrylate, 1 part of methacrylic acid and 1 part of azobis-2-methylbutyronitrile (manufactured by Nippon Hydrazine Kogyo Co., Ltd., ABN-E) are mixed. The solution was added dropwise to the isobutyl ketone mixture over 2 hours. Thereafter, the reaction was carried out for 6 hours to obtain a polydimethylsiloxane graft copolymer H. The obtained graft copolymer H had a solid content of 50% and a viscosity Y (Gardner Holtz).
[0033]
Table 1 shows the constituent components of the above polydimethylsiloxane block and graft copolymers D to H.
[Table 1]
[0034]
[Example 1]
D75 parts of the polydimethylsiloxane block copolymer obtained in Synthesis Example 4, 10 parts of the siloxane component A obtained in Synthesis Example 1 and caprolactone triol (Daicel Chemical Industries, Plaxel 308, molecular weight: 850, OH value ( KOHmg / g): 195) 15 parts are added, and 36 parts of HMDI isocyanurate (Takenate D-170N, solid content: 100%, NCO%: 20.7) is added as a crosslinking agent. The obtained paint was polished and coated on a mild steel plate and a glass plate so that the film thickness upon drying was 25-30 μm.
The obtained coated plate was dried at 60 ° C. for 1 hour and then allowed to stand at room temperature for 1 week, which was used as a test plate.
[0035]
[Example 2]
E75 parts of polydimethylsiloxane block copolymer obtained in Synthesis Example 5, 10 parts of organosilica sol (manufactured by Nissan Chemical Industries, MIBK silica sol, dispersion medium: methyl isobutyl ketone, solid content: 30%) and tetrafunctional caprolactone In addition to blending 15 parts of polyol (Daicel Chemical Industries, Plaxel 410D, molecular weight: 1000, OH number: 220), HMDI trimethylolpropane adduct as a cross-linking agent (Dainippon Ink & Chemicals, Vernock DN- 950, solid content: 75%, NCO%: 12) 62 parts were added, and the obtained paint was polished and coated on a mild steel plate and a glass plate so that the film thickness upon drying was 25-30 μm.
The obtained coated plate was dried at 60 ° C. for 1 hour and then allowed to stand at room temperature for 1 week, which was used as a test plate.
[0036]
Example 3
Coating was carried out in the same manner as in Example 2, except that 20 parts of methoxylated methylol melamine (Mitsui Cytec Co., Ltd., Cymel 303, solid content: 100%) was used as a crosslinking agent.
The obtained coated plate was dried at 150 ° C. for 30 minutes, and this was used as a test plate .
[0037]
[Comparative Example 1]
With formulating the same Ka caprolactone triol 15 parts of polydimethylsiloxane block copolymer E85 parts and Example 1 obtained in Synthesis Example 5, similar HMDI isocyanurate 36 parts Example 1 as a crosslinking agent Was added, and the obtained paint was polished and coated on a mild steel plate and a glass plate so that the film thickness upon drying was 25 to 30 μm.
The obtained coated plate was dried at 60 ° C. for 1 hour and then allowed to stand at room temperature for 1 week, which was used as a test plate.
[0038]
[Comparative Example 2]
62 parts of the same HMDI trimethylolpropane adduct as in Example 2 was added as a crosslinking agent to 100 parts of the polydimethylsiloxane block copolymer F obtained in Synthesis Example 6 , and the resulting paint was polished and treated with a mild steel plate and The glass plate was painted so that the film thickness upon drying was 25-30 μm.
The obtained coated plate was dried at 60 ° C. for 1 hour and then allowed to stand at room temperature for 1 week, which was used as a test plate.
[0039]
[Comparative Example 3]
To 100 parts of the polydimethylsiloxane block copolymer G obtained in Synthesis Example 7 , 36 parts of the same HMDI isocyanurate body as in Example 1 was added as a cross-linking agent, and the resulting paint was polished to a mild steel plate and a glass plate. The film was coated so that the film thickness when dried was 25-30 μm.
The obtained coated plate was dried at 60 ° C. for 1 hour and then allowed to stand at room temperature for 1 week, which was used as a test plate.
[0040]
[Comparative Example 4]
To 100 parts of the polydimethylsiloxane block copolymer H obtained in Synthesis Example 8 , 20 parts of a methoxylated methylol melamine similar to that of Example 3 was added as a cross-linking agent, and the resulting paint was polished to a mild steel plate and a glass plate. The film was coated so that the film thickness when dried was 25-30 μm.
The obtained coated plate was dried at 150 ° C. for 30 minutes, and this was used as a test plate.
[0041]
[Comparative Example 5]
As a crosslinking agent I PDI trimethylolpropane adduct blocked isocyanate (manufactured by Mitsubishi Chemical Corporation, Mitec BL-280, solid content: 59.4%, NCO%: 6.1 ) except for using 122 parts, in the same manner as in Comparative Example 4 A test plate was prepared.
[0042]
Table 2 shows the constituent components of the paints in Examples 1 to 3 and Comparative Examples 1 to 5 described above.
[Table 2]
[0043]
[Test example]
About the test plates obtained in Examples 1 to 3 and Comparative Examples 1 to 5, adhesion, water resistance, alkali resistance, acid resistance, solvent resistance, impact resistance, flex resistance, scratch resistance, stain resistance The weather resistance and salt water resistance were evaluated. A glass plate test plate was used only for the scratch resistance, and a polished mild steel plate test plate was used for the others.
[0044]
Adhesion was evaluated by a cross cut cell tape peeling test. The water resistance was evaluated by immersing in water at 40 ° C. for 96 hours. The alkali resistance was evaluated by performing a spot test for 24 hours at 20 ° C. using 0.1 N NaOH. The acid resistance was evaluated by performing a 24 hour spot test at 20 ° C. using 0.1 N H ₂ SO ₄ . Solvent resistance was evaluated by rubbing xylene 100 times. The impact resistance was evaluated by testing using a DuPont impact tester under the conditions of 1/4 φ, 500 g × 50 cm. The bending resistance was evaluated by performing a bending test using a 3 mmφ bar. The scratch resistance was evaluated based on the haze value (%) after rubbing 50 times with a load of 500 g using # 000 steel wool. Contamination resistance was evaluated by exposing the test plate outdoors for 6 months. The weather resistance was evaluated by using a sunshine weatherometer for 2000 hours. The salt water resistance was evaluated by continuously spraying 5% saline at 35 ° C. for 240 hours. The results are shown in Table 3.
[0045]
[Table 3]
[0046]
As is clear from Table 3, the coating film of the coating composition of the present invention has adhesion, water resistance, alkali resistance, acid resistance, solvent resistance, impact resistance, flex resistance, scratch resistance, and stain resistance. Excellent in weather resistance and salt water resistance.
[0047]
【The invention's effect】
According to the coating composition of the present invention, a coating film excellent in various physical properties such as stain resistance and weather resistance and particularly excellent in scratch resistance can be obtained.

Claims (2)

A polydimethylsiloxane copolymer having a polydimethylsiloxane moiety and a vinyl polymer chain moiety, and caprolactone component contains a siloxane component, partially hydrolyzed in the siloxane component is a silane compound containing a hydrolyzable silyl group A coating composition comprising a decomposed product, an organosilica sol, or a hydrolyzable silane compound having radical polymerizability added to the organosilica sol.   A paint comprising the paint composition according to claim 1 and a urethane crosslinking agent and / or a melamine crosslinking agent.