JP2002241674A - Rust-proofing primer coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rust-proofing primer coating composition having excellent edge-covering property and adhesivity and free from chromium. SOLUTION: The rust-proofing primer coating composition is produced by compounding (A) 100 pts.wt. of an acrylic resin having a weight-average molecular weight of 30,000-150,000, a glass transition point of-30 to +20 deg.C, a hydroxy value of 10-80 and an acid value of 2-40 with (B) 5-20 pts.wt. of an epoxy resin having an epoxy equivalent of 210-1,000 and (C) 0.5-20 pts.wt. (based on 100 pts.wt. of the acrylic resin A) of a blocked polyisocyanate containing a blocking agent having a reaction initiation temperature of 120-150 deg.C and further compounding the primer resin obtained by the above process with (D) 3-20 pts.wt. (based on 100 pts.wt. of the solid component of the primer resin) of an organic bentonite and (E) 5-30 pts.wt. (in terms of solid content based on 100 pts. wt. of the organic bentonite D) of an amide-based wetting and dispersing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can exhibit a good rust prevention effect without containing heavy metals such as chromium.
The present invention relates to a rust-preventive primer coating composition.

[0002]

2. Description of the Related Art Generally, an aluminum wheel is formed into a wheel shape by casting or forging, and then subjected to cutting. A paint such as a clear paint is applied on the aluminum wheel after the cutting for the purpose of imparting aesthetics and weather resistance.

[0003] However, it is known that a sharp edge portion exists in the cut portion, and thread-like rust is generated from such an edge portion. For the purpose of preventing the generation of such rust, conventionally, the surface of aluminum wheels has been rust-proofed with chromic acid before painting, or painted with a paint containing rust-preventive pigments such as zinc chromate. are doing.

[0004] However, heavy metals such as chromium are harmful substances, and their use is not preferable from the viewpoint of environmental health. Therefore, a rust-preventive primer coating containing no heavy metal such as chromium is desired. JP-A-1-194797 and JP-A-6-57178 propose a chrome-free rust-preventive primer coating composition.

[0005]

However, in terms of edge coverage, the coating composition disclosed in the above publication is not sufficiently satisfactory, and a better primer coating composition is required. In addition, since the primer coating compositions of the above publications use silica fine powder as an essential component, there is also a problem that dust is easily generated during spray coating.

An object of the present invention is to provide a rust-preventive primer coating composition which does not contain heavy metals such as chromium and has excellent edge cover properties and adhesion.

[0007]

The rust-preventive primer coating composition of the present invention comprises (A) a weight average molecular weight of 30,000-1.
50,000, glass transition point -30 ° C to 20 ° C, hydroxyl value 10 to 80 (mgKOH / g), and acid value 2 to 40 (m
gKOH / g) of 100 parts by weight of an acrylic resin.
(B) Epoxy resin 5 having an epoxy equivalent of 210 to 1000
-20 parts by weight, and the reaction start temperature is 120-1 parts per 100 parts by weight of (C) acrylic resin (A).
(D) 3 to 20 parts by weight of an organic bentonite based on 100 parts by weight of the solid content of the primer resin, and 0.5 to 20 parts by weight of a blocked polyisocyanate having a blocking agent at 50 ° C. (E) 5-30 parts per 100 parts by weight of the organic bentonite (D)
An amide-based wetting and dispersing agent having a solid content of parts by weight is blended.

[0008] The rust-preventive primer coating composition of the present invention comprises:
By having the above-mentioned composition, it is possible to obtain a primer coating composition having excellent edge cover properties and adhesion, and excellent rust prevention effect.

In the present invention, (F) 0.05 to 5.0.
A urea-based rheology-imparting agent having a solid content of 0 parts by weight may be blended.

Such a urea-based rheology-imparting agent (F)
By blending, the adhesion of the coating film can be further improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The primer resin of the primer coating composition of the present invention can be obtained by blending an epoxy resin (B) and a blocked polyisocyanate (C) with an acrylic resin (A).

The acrylic resin (A) can be obtained by polymerizing a compound having two or more radically polymerizable ethylenically unsaturated groups in a molecule by an ordinary method. The compounds having an ethylenically unsaturated group include the following.

(A): having a hydroxyl group such as hydroxylmethyl (meth) acrylate, hydroxylethyl (meth) acrylate, hydroxylpropyl (meth) acrylate, hydroxylbutyl (meth) acrylate, N-methylolacrylamine, etc. Ethylene monomer (b): Ethylene monomer having a carboxyl group such as (meth) acrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, etc. (c): Methyl (meth) acrylate, ethyl (meth) acrylate (Meth) such as propyl (meth) acrylate, butyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, and n-dodecyl acrylate Monomers such as alkyl acrylate d): the weight-average molecular weight of the (a) and (b) and copolymerizable ethylenic monomer, and (e) :( meth) acrylonitrile, styrene and acrylic resin (A) 30000-1
50,000, preferably 40,000 to 10,000
0. If the weight-average molecular weight is too small, the rust-preventing effect is reduced, and if the weight-average molecular weight is too large, the coating workability is reduced.

The glass transition point is -30 ° C to 20 ° C,
Preferably it is -20 to 0 ° C. If the glass transition temperature is too low, the rust-preventive effect is reduced, and if the glass transition point is too high, the chipping resistance at low temperatures is reduced.

The hydroxyl value is from 10 to 80, preferably from 15 to 25. If the hydroxyl value is too low, the adhesion will decrease, and if it is too high, the rust-preventive effect will decrease. The acid value is from 2 to 40, preferably from 10 to 30. If the acid value is too low or too high, the chipping resistance decreases.

The epoxy resin (B) is a general-purpose epoxy resin comprising a compound containing two or more epoxy groups in one molecule. Specifically, for example, bisphenol A, bisphenol F, Glycidyl ether epoxy resin of polyphenol compounds such as 1,2,2-tetrakis (4'-hydroxyphenyl) ethane; glycidyl ether epoxy resin of polyhydric phenols such as catechol, resorcin, hydroquinone, and phloroglucin; ethylene glycol; Butanediol,
Glycidyl ether epoxy resins of polyhydric alcohols such as glycerol, erythritol and polyoxyalkylene glycol; novolak epoxy resins; cycloaliphatic epoxy resins such as vinylcyclohexene dioxide, limonene dioxide, dicyclopentadiene dioxide; Polyglycidyl ester-based epoxy resins of ester condensates of acids and polycarboxylic acids such as cyclohexane-1,2-dicarboxylic acid; and polyglycidylamine-based epoxy resins. Here, a glycidyl ether epoxy resin or a cycloaliphatic epoxy resin having an epoxy equivalent of 210 to 1000 is preferably used.

When the epoxy equivalent falls below the above range,
The chipping resistance decreases, and conversely, the higher the epoxy equivalent, the lower the water resistance. The epoxy resin (B) is blended in an amount of 5 to 20 parts by weight, preferably 8 to 15 parts by weight, based on 100 parts by weight of the acrylic resin (A). When the amount of the epoxy resin (B) decreases, the water-resistant adhesion decreases, and when the amount of the epoxy resin (B) increases, the chipping resistance at low temperatures decreases.

The blocked polyisocyanate (C) is a polyisocyanate blocked by a blocking agent having a reaction initiation temperature of 120 to 150 ° C., and includes hexamethylene diisocyanate, ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate,
Decamethylene diisocyanate, metaphenylene diisocyanate, triphenylmethane triisocyanate,
Various diisocyanates such as cyclohexyl isocyanate, phenylene diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), and adducts, hydrates and condensates of these with polyols are blocked by heat. Phenol-based, lactam-based, active methylene-based, alcohol-based, amine-based, oxime-based, urea-based, and imine-based blocking agents from which is released.

Here, the reaction start temperature means a temperature at which the elastic modulus changes from a decrease (thermoplastic) to an increase (thermosetting) when a constant temperature rise is given in the process of curing the paint as a coating film. . If the reaction initiation temperature is too low, yellowing occurs, and the chipping resistance at low temperatures decreases. Also,
If the reaction start temperature is too high, the water resistance will decrease.

The blocked polyisocyanate (C) is used in an amount of 0.5 to 100 parts by weight of the acrylic resin (A).
20 parts by weight, preferably 1 to 5 parts by weight are blended. If the amount of the blocked polyisocyanate (C) is too small, the water resistance will be poor, and if it is too large, the adhesion to the overcoat film will be poor.

The primer coating composition of the present invention comprises a primer resin comprising the above acrylic resin (A), the above epoxy resin (B) and the above block polyisocyanate (C), and an organic bentonite (D) and an amide. It is characterized by incorporating a system wetting and dispersing agent (E).

The organic bentonite (D) is obtained by intercalating an organic ammonium salt between layers of bentonite. Examples thereof include “Benton 34” (dimethyl dioctadecyl ammonium bentonite / quaternary ammonia-18 bentonite, National Red Co., Ltd.), trade name "Benton 38" (magnesium montmorillonite / quaternary ammonia-18 hectorite, manufactured by National Red Co.), trade name "Organite A" (complex of montmorillonite and trialkylbenzylammonium salt, Nippon Organic Clay Co., Ltd.) and trade name “New D Orben” (dimethyl C ₁₈ H ₃₇ N ^{+ of} bentonite, manufactured by Shiraishi Industry Co., Ltd.).

The amount of the organic bentonite (D) is 3 to 20 parts by weight, preferably 6 to 12 parts by weight, based on 100 parts by weight of the solid content of the primer resin. If the amount of the organic bentonite (D) is too small, the sagging property and the edge covering property deteriorate. If the amount of the organic bentonite (D) is too large, the adhesion will be poor.

The amide wetting and dispersing agent (E) is a wetting and dispersing agent containing a salt of a polyaminoamide and a low molecular weight acid polymer or a polar acid ester. Specifically, trade name “Anti-Terra-U” (a solution of a salt of an unsaturated polyaminoamide and a low molecular weight acid polymer, BYK Ch
emie) and trade name "Disperbyk-1"
01 "(a solution of a salt of a long-chain polyaminoamide and a polar acid ester, manufactured by BYK Chemie) or the like.

The amount of the amide wetting and dispersing agent (E) is
5 to 100 parts by weight of the organic bentonite (D)
The amount is such that the solid content is 30 parts by weight, preferably 10 to 25 parts by weight. If the amount of the amide-based wetting and dispersing agent (E) is too small, the sagging property and the edge covering property deteriorate.
If the amount of the amide-based wetting and dispersing agent (E) is too large, the paint tends to aggregate.

The primer coating composition of the present invention may further contain a urea-based rheology-imparting agent (F). By blending the urea rheology imparting agent (F), the adhesion of the coating film can be further improved.

As the urea-based rheology-imparting agent (F),
Any rheology-imparting agent for a compound having a urea skeleton may be used. Specifically, trade name “BYK-411” (modified urea solution, manufactured by BYK Chemie) or the like can be used.

The amount of the urea-based rheology-imparting agent (F) is 0.05 to 5.0 parts by weight, preferably 0.1 to 2.0 parts by weight, based on 100 parts by weight of the above-mentioned primer resin solids. This is the amount that will be used. If the amount of the urea-based rheology-imparting agent is too small, the adhesion will be poor. If the amount of the urea-based rheology-imparting agent (F) is too large, the water resistance is deteriorated.

The method for producing the primer coating composition of the present invention is not particularly limited. For example, it is preferable to mix and produce the primer coating composition in the following order. First, an organic bentonite and an amide-based wetting and dispersing agent are mixed in the presence of a solvent to prepare a pregel. Next, this pregel is added and dispersed in a primer resin previously dissolved in a solvent. When using a urea rheology-imparting agent, a urea-based rheology-imparting agent is added to this dispersion and mixed.

The primer coating composition of the present invention is used as a coating form after being diluted with a general organic solvent such as toluene or ethyl acetate, and has a solid content of 7 to 4%.
It is preferably prepared to be 0% by weight, preferably 10 to 25% by weight.

As described above, the primer coating composition of the present invention can be applied to a cut aluminum wheel or the like to give a rustproof effect as well as cosmetic and weather resistance. The target object is not limited to the aluminum wheel, and can be widely applied to a base material requiring a rust prevention effect.

After the application of the primer coating composition of the present invention, a top coating such as a clear coating can be applied as necessary.

[0033]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and can be carried out by appropriately changing the scope of the invention without changing its gist. It is something.

[Preparation of Primer Resin] Acrylic Resin 1
9 parts by weight of an epoxy resin and 2 parts by weight of block isocyanate were blended with 00 parts by weight to prepare a primer resin. As the solvent, 103 parts by weight of toluene and 100 parts by weight of ethyl acetate were used. In addition, some of these solvents were used when preparing a pregel of an organic bentonite and an amide-based wetting and dispersing agent as described later. Therefore, the amount of the solvent obtained by subtracting the amount of the solvent used for the preparation of the pregel is used in the preparation of the primer resin.

The acrylic resin has a weight average molecular weight of 80
000-90000, glass transition point -7 ° C, hydroxyl value 1
6. Those having an acid value of 25 were used. The epoxy resin used had an epoxy equivalent of 450 to 500. As the blocked isocyanate, an aliphatic polyisocyanate (trade name “Desmodur BL3175”,
Sumitomo Bayer Urethane Co., Ltd.) was used.

[Preparation Examples 1 to 9]
An organic bentonite, an amide-based wetting and dispersing agent, and if necessary, a urea-based rheology-imparting agent were added to the primer resin to prepare a primer coating composition. The order of compounding was as follows. An organic bentonite and an amide-based wet swelling agent were previously added and dispersed in a solvent to prepare a pregel, and the pregel was added to and dispersed in a primer resin solution. When a urea-based rheology-imparting agent was blended, it was added and blended thereafter.

The mixing ratios shown in Table 1 are as follows:
The amount of solid content is shown for each of the organic bentonite, the wetting and dispersing agent, and the rheology-imparting agent. In addition, as for the wetting and dispersing agent, the mixing ratio is shown based on 100 parts by weight of the organic bentonite.

The following were used as the organic bentonite, the amide-based wetting and dispersing agent, and the urea-based rheology-imparting agent.・ Organic bentonite: trade name “Benton 38” manufactured by National Red Co., Ltd. ・ Amide wetting and dispersing agent: trade name “Anti-Terr”
aU ", manufactured by BYK Chemie, solid content 50% by weight ・ Urea-based rheology-imparting agent: trade name" BYK-41 "
1 ", BYK Chemie, modified urea solution, solid content 25% by weight

[0039]

[Table 1]

[Examples 1 to 8 and Comparative Example 1] On an aluminum plate (AC4C) as an object to be coated, using a primer coating composition of a preparation example shown in Table 2, coating was performed. The film was baked under the conditions shown below, further coated with a clear paint shown in Table 2, and baked under the conditions shown in Table 2 to form a coating film.

The following paints were used for the top clear coating.・ O-150: Trade name “Super Rack O-150 Clear” (acryl melamine curing type clear paint, manufactured by Nippon Paint Co., Ltd.) ・ nax Superior: brand name “nax Superior Rio”
(Acrylic isocyanate-curable clear paint, manufactured by Nippon Paint Co., Ltd.) PD-A400: trade name "Powax A-400 Clear" (acid epoxy-curable powder clear paint, manufactured by Nippon Paint Co., Ltd.) The coating was performed so that the thickness became 12 μm. The top clear paint is PD-A4 so that the dry film thickness of O-150 is 25 μm, and the dry film thickness of nax Superior is 30 μm.
About 00, it painted so that dry film thickness might be set to 100 micrometers.

The obtained coating film was evaluated for adhesion and rust prevention as follows. -Adhesion: 100 cut lines are formed by forming 11 cuts in the coating film with a cutter knife in the longitudinal direction and the horizontal direction so as to have a width of 2 mm each, and an adhesive tape is stuck thereon. After peeling, the number of grids where the coating film was peeled off was measured. When the number of peeled grids is 0,
That is, 0/100 is ○, 1-3 / 100 is △, 4-10 / 100 is 〜１０,
Those that exceeded × were evaluated as ×.

Rust prevention: After forming a cross cut on the coating film with a cutter knife, put in a salt spray tester according to JIS Z2371 for 24 hours, wash the coating film surface with water, and then heat at 40 ° C. and humidity. A cycle in which the sample was put in an 80-90% constant temperature and humidity box for 120 hours, and then left at room temperature for 24 hours was defined as one cycle, and after repeating this cycle for 12 cycles, the maximum length of the thread rust generated in the cut portion was measured. Was evaluated.

A sample having a rust length of 2 mm or less was evaluated as ◎, a sample having a rust length of 4 mm or less was evaluated as ○, and a sample having a rust length exceeding 4 mm was evaluated as ×. The edge coating properties of the primer coating compositions of Preparation Examples 1 to 9 were evaluated as follows.

FIG. 1 is a front view showing a test apparatus for evaluating the edge cover property, and FIG. 2 is a side view. The blade 2 of the cutter knife is provided on the side surface 1b of the support base 1 with a blade edge 2a.
Is mounted vertically upright. The reason that the side surface of the blade 2 of the cutter knife is attached so as to be in contact with the side surface 1b of the support 1 is that the contact area between the blade 2 of the cutter knife and the support 1 is increased, and the blade 2 of the cutter knife and the support 1 By improving the heat transfer between
This is to make the temperature of the blade 2 of the cutter knife close to the temperature of the support base 1. Further, by making the material of the support base 1 the same as the material of the object to which the paint is actually applied, a temperature change close to the temperature change of the object at the time of baking the coating film can be obtained.
Can be applied to the blade 2 of the cutter knife. Support table 1
Under the base plate 4 having a larger area than the support 1
Is provided.

The coating gun 3 is arranged on the blade 2 of the cutter knife, and the paint to be measured is sprayed from the coating gun 3 and adhered onto the cutting edge 2a. At this time,
Coating is performed by adjusting the discharge amount or the number of coatings so that the thickness of the coating film changes stepwise. Here, the thickness of the coating film is 8 to
Overcoating was performed while changing the coating area so as to change stepwise within a range of 15 μm.

The thickness of the coating film adhered on the cutting edge 2a can be measured by measuring the thickness of the coating film applied on the upper surface 1a of the support 1. When the support 1 has irregularities on the surface, such as an aluminum casting, it may be difficult to measure the thickness of the coating film on the upper surface 1a of the support 1. In such a case, the thickness of the coating film applied on the cutting edge 2a can be obtained by measuring the thickness of the coating film applied on the upper surface 4a of the base plate 4 under the support base 1.

The primer paint applied on the cutting edge 2a is as follows:
In the same manner as in the above Examples and Comparative Examples, baking was performed at 140 ° C. for 20 minutes. As the blade 2 of the cutter knife, a trade name "replaceable blade for NT cutter BA-150" (A blade, blade thickness 0.38 mm, material SK2, manufactured by Nippon Transfer Paper Co., Ltd.) was used.

One terminal of the tester was brought into contact with the conductive portion of the blade 2 and the other terminal was brought into contact with a portion having a thickness of 12 μm, and the edge coverage was evaluated based on the presence or absence of electrical conduction. Specifically, when there was no electrical conduction even when the other terminal was moved along the cutting edge at a portion having a predetermined film thickness, it was judged as “no line conduction” and was evaluated as “○”. Also, when the other terminal is moved, electrical continuity is recognized in certain parts in some places,
It was judged that there was “point conduction”, and was evaluated as △. When electrical continuity was observed in all portions having a predetermined film thickness, it was judged as "conducted" and rated as "x".

Table 2 shows the evaluations of the edge cover properties, adhesion properties and rust prevention properties as described above.

[0051]

[Table 2]

As is clear from the results shown in Table 2, in Examples 1 to 8 using the primer coating compositions of Preparation Examples 2 to 9 according to the present invention, good edge coverage was obtained. In Examples 4 to 8 using the primer coating compositions of Preparation Examples 5 to 9 in which a urea-based rheology-imparting agent was added, good adhesion of the coating film was obtained.

[0053]

According to the present invention, a chromium-free rust-preventive primer coating composition having excellent edge cover properties and adhesiveness can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view showing an edge cover property evaluation test apparatus used in an example of the present invention.

FIG. 2 is a side view showing an edge cover property evaluation test apparatus used in an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Support stand 1a ... Upper surface of a support stand 1b ... Side surface of a support stand 2 ... Blade of a cutter knife 2a ... Blade edge of a cutter knife 3 ... Painting gun 4 ... Base plate 4a ... Top surface of a base plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J038 CG031 CG141 CH121 DB062 DB092 DB122 DB132 DG302 GA01 GA03 GA06 GA07 HA456 HA466 JB01 JB14 JC05 KA09 LA06 MA13 MA14 NA03 NA04 NA23 PA07 PA19 PB05 PB07 PC02

Claims (2)

[Claims] (A) a weight average molecular weight of 30,000 to 15
0000, glass transition point -30 ° C to 20 ° C, hydroxyl value 1
(B) an epoxy resin 5 having an epoxy equivalent of 210 to 1000 based on 100 parts by weight of an acrylic resin having an acid value of 0 to 80 and an acid value of 2 to 40;
To 20 parts by weight, and 0.5 to 20 parts by weight of a blocked polyisocyanate having a blocking agent having a reaction initiation temperature of 120 to 150 ° C. based on (C) 100 parts by weight of the acrylic resin (A). (D) 3 to 20 parts by weight of organic bentonite based on 100 parts by weight of the solid content of the primer resin; and (E) 5 to 30 parts by weight of organic bentonite based on 100 parts by weight of the organic bentonite (D). A rust-preventive primer coating composition comprising an amide-based wetting and dispersing agent having a solid content. 2. (F) The primer resin solids content of 100
The rust preventive primer coating composition according to claim 1, further comprising a urea-based rheology-imparting agent having a solid content of 0.05 to 5.0 parts by weight with respect to parts by weight.