JP3074008B2 - Resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application field] The present invention relates to a precoated metal (PCM), which is hard and has excellent workability and forms a good coating film such as stain resistance and weather resistance. The present invention relates to a resin and a resin composition useful for a top coat.

[Prior art and its problems] PCM is a painted metal plate that is pre-painted on an aluminum plate, iron plate, galvanized steel plate, etc., and does not need to be painted after processing, assembly, or construction. It is widely used for equipment, etc., and the use of pre-coated metal is increasing in the future.

Since PCM is processed and assembled after painting, the top coat for PCM requires that the coating film withstand bending, roll forming, embossing press, etc., as well as excellent adhesion and film elongation. You.

Further, scratch resistance and stain resistance are also required. Also, products used outdoors are required to have weather resistance.

In response to such demands for PCM paints, conventional PCM paints containing polyester resin and melamine resin as the main components have insufficient balance between hardness and workability among the above-mentioned performances. It has a defect that its properties are poor. More specifically, it is very difficult to obtain coating films such as “two-con hardness of 10 or more”, “workability OT no crack” and “pass of red felt pen oil-based ink stain resistance”. When the value is improved, the workability decreases. Furthermore, the outdoor weather resistance is also insufficient.

Means for Solving the Problems The present inventors have eagerly developed a paint resin and a composition thereof which solve the above-mentioned defects and form a coating film having excellent hardness, workability and stain resistance. As a result of research, they have found that a polyester resin having a blocked isocyanate group and a composition obtained by mixing the resin with a curing agent can achieve the above object, and have completed the present invention.

That is, the present invention provides: (1) a free (unblocked) isocyanate group of a partially blocked polyisocyanate compound obtained by blocking one of three isocyanate groups in one molecule, and a glass transition temperature of -15 to A polyester resin containing a hydroxyl group and a blocked isocyanate group obtained by subjecting a hydroxyl group of a polyester having a hydroxyl value of 15 to 80 and a number average molecular weight of 3,000 to 25,000 to 40 ° C. and a blocked isocyanate group, and (2) the above (1). The present invention relates to a resin composition containing, as a main component, a composition obtained by blending a curing agent with the above-described polyester resin containing a hydroxyl group and a blocked isocyanate group.

 Each of these components will be described more specifically.

Blocked Isocyanate Group-Containing Polyester Resin: The resin (hereinafter sometimes abbreviated as “B-NCO polyester resin”) is a partially blocked polystyrene obtained by blocking one of three isocyanate groups in one molecule. Isocyanate compound and glass transition temperature -15 to 40
° C, hydroxyl value 15-80 and number average molecular weight 3,000-25,
It can be obtained by subjecting a polyester which is 000 to urethanization reaction.

Specifically, after only one isocyanate group in a triisocyanate compound having three isocyanate groups in one molecule is blocked to form a partially blocked triisocyanate compound, the remaining free (unblocked) isocyanate group is removed. Each is obtained by reacting the above-mentioned specific polyester resin. Basically, the structure of the B-NCO polyester resin is such that the polyester resin and the partially-blocked triisocyanate compound are almost linearly linked by a urethane bond to constitute a main skeleton, and at least one of the terminals has a hydroxyl group. And the blocked isocyanate group exists in a pendant form.

The polyester resin to be reacted with the triisocyanate compound is a polyester resin having a glass transition temperature (Tg) of −15 to 40 ° C., a hydroxyl value of 15 to 80, and a number average molecular weight of 3,000 to 25,000.

Tg is that of the polyester resin itself, -15 to
The temperature is 40C, preferably -5 to 15C. If the Tg is lower than -15 ° C, the hardness is lowered, and if the Tg is higher than 40 ° C, the workability is not sufficient. Hydroxyl value is 15
If it is lower than 15, the crosslinking curing property is not sufficient, and the hardness and stain resistance of the coating film are inferior, and if it is higher than 80, the crosslinking density becomes high, and It is not preferable because the property becomes insufficient. Further, the number average molecular weight is in the range of 3,000 to 25,000, preferably 3,000 to 15,000, and if it is less than 3,000, processability becomes insufficient, and if it is more than 25,000, the reaction system with the triisocyanate compound becomes high in viscosity, and It is not preferable because the surface smoothness is reduced.

The above Tg is a value measured from an endothermic peak using differential thermal analysis (DSC).

Polyester resins having such characteristic values are mainly composed of dibasic acids (for example, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, fumaric acid) Acids and their anhydrides) and dihydric alcohols (eg, ethylene glycol, propylene glycol, butylene glycol, hexanediol, diethylene glycol, neopentyl glycol, etc.), and, if necessary, monovalent or trivalent or higher. A polyester resin having the above properties can be obtained by using an acid or an alcohol in combination. Particularly as trihydric or higher alcohols, for example, glycerin, trimethylolpropane, trimethylolethane, diglycerin, triglycerin,
1,2,6-hexanetriol, pentaerythritol,
Dipentaerythritol, sorbitol, mannitol,
(Trishydroxyethyl isocyanate) and the like, and polylactone polyols obtained by adding a lactone such as ε-caprolactone to these trivalent or higher alcohols are preferably used.

Examples of the triisocyanate compound having three isocyanate groups in one molecule include hexamethylene diisocyanate (HDI), isophorone diisocyanate,
Tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4 '
Burette type adducts such as methylenebis (cyclohexyl isocyanate), isocyanuric ring type adducts, trihydric alcohol adducts, etc .; triphenylmethane-4,4 ', 4 "-triisocyanate, 1,3,5-triisocyanate Benzene, 2,4,6-triisocyanatotoluene, tris (isocyanatephenyl) thiophosphate, bicycloheptanetriisocyanate, 4,4'-diphenylmethanetriisocyanate, and the like;
Among them, particularly preferred is the HDI trimer type (isocyanuric ring type). This type has good heat resistance among isocyanate compounds and has a wide application range.

 Bullet type is also suitable.

As a blocking agent for partially blocking the triisocyanate compound, for example, phenol-based, lactam-based, active methylene-based, alcohol-based, mercaptan-based,
Acid amide-based, imide-based, amine-based, imidazole-based, urea-based, carbamate-based, imine-based, oxime-based and sulfite-based blocks are used.
Oxime blocking agents such as formamidoxime, acetoaldoxime, acetoxime, methylethylketoxime, diacetylmonooxime, benzophenone oxime and cyclohexanone oxime are particularly preferred.

The BNCO polyester resin of the present invention first blocks one of the three isocyanate groups in one molecule of the triisocyanate compound (partially blocked), and then releases two free isocyanates in the partially blocked product. It is obtained by subjecting the above-mentioned polyester resin having a hydroxyl group to an (unblocked) isocyanate to a urethanization reaction.

The partial blocking reaction of the triisocyanate compound can be performed by an ordinary method, and the reaction ratio is most preferably 1 mol of the blocking agent per 1 mol of the triisocyanate compound. The reaction between the partially blocked triisocyanate compound and the polyester resin can also be carried out by a usual urethanization reaction method, and the ratio thereof is 90 to 98% by weight based on the total amount of both components, especially 90 to 98% by weight. 95 to 98% by weight, preferably 10 to 2% by weight, particularly preferably 5 to 2% by weight, of the partially blocked triisocyanate compound. When the content of the partially blocked triisocyanate compound is more than 10% by weight, the reaction product is high. When the content is less than 2% by weight, the effect of the isocyanate is not obtained. Also, based on hydroxyl groups / isocyanate groups (molar ratio), 12/1 to 3 /
A range of 1 is suitable.

Since the BNCO polyester resin of the present invention has both the blocked isocyanate group and the hydroxyl group in the same molecule, it can be used as a self-curing resin that cures alone without using another crosslinking agent. The resin is cured by heating above the dissociation temperature of the blocking agent to regenerate free isocyanate groups and reacting with coexisting hydroxyl groups to effect three-dimensional crosslinking and curing.

The present invention also includes a resin composition obtained by blending a blocked polyisocyanate compound, an amino resin, or the like as a curing agent (crosslinking agent) with the BNCO polyester resin.

The blocked polyisocyanate compound contains 2 per molecule.
A compound obtained by closing all isocyanate groups of a polyisocyanate compound having at least two isocyanate groups with a blocking agent. It is preferable that the blocking agent is dissociated within the range of 80 to 200 ° C.

Examples of the polyisocyanate compound include tolylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, 4,4'-methylenebiscyclohexyl isocyanate, methylcyclohexane-2,
4-diisocyanate, 1,3-isocyanatomethylcyclohexane, isophorone diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, hexamethylene diisocyanate (HDI)
And an HDI burette type and a trimer type. Among them, the HDI trimer type (isocyanurate type) is particularly preferable.

As the blocking agent for these polyisocyanate compounds, those known per se can be used, and specific examples include the above-mentioned ones. Among them, oxime-based blocking agents are particularly preferable.

Further, as a curing agent, a melamine resin, a urea resin (a methylol compound and / or an alkyl ether compound) and the like can be used.

The composition ratio of the BNCO polyester resin and the curing agent is not particularly limited, but based on the total weight of both components, the former /
In the latter, 80/20 to 40/60, particularly 70/30 to 50/50, are preferred.

It is useful to use the BNCO polyester resin of the present invention or the resin composition comprising the resin and a curing agent as a basic resin of a top coat for PCM. Therefore,
In using these as paints, color pigments that can be used in the paint field, for example, organic color pigments such as cyanine blue, cyanine green, organic red pigments such as azo-based and quinacridone-based; titanium white, titanium yellow, red iron, carbon black, graphite, Inorganic color pigments such as various calcined pigments, extenders such as talc, clay, silica, mica, and alumina, fillers, additives, organic solvents, and the like can be blended as necessary.

In addition, cold rolled steel sheets, hot-dip galvanized steel sheets, electro-galvanized steel sheets, alloy-coated steel sheets,
A metal plate such as an aluminum plate, a stainless steel plate, a copper plate, a copper-plated steel plate, and a tin-plated steel plate is preferable, but it is also applicable to plastics, wood, cement, and the like.

The coating method can be curtain coating, roll coating, dip coating, spray coating, and the like. Usually, the coating is performed so that the thickness of the coating after drying is in the range of 5 to 30 microns.

If the metal surface to be coated is not contaminated with contaminants such as oil, the coating may be performed as it is, but the adhesion of the coating film, a known metal surface treatment to improve corrosion resistance, for example, phosphates It is preferable to perform a surface treatment with a chromate-based surface treatment, a chromate-based coating agent, or the like. In order to improve the quality of the coating film, it is preferable to apply a primer coating after the metal surface treatment and then apply the present coating material. Known primers used in the PCM field, industrial machine coating field, metal parts coating field, etc. can be applied as applicable primers, and are appropriately selected according to the type of material to be coated and the type of metal surface treatment. And polyester-based primers and modified primers thereof are preferred. When workability is particularly required, polyester-based primers are preferred.

To manufacture PCM by coil coating, etc., there is no limitation on the coating method, but curtain coating and roll coating are recommended from the economics of pre-coated steel sheet coating. The roll coating method is used to maximize the uniformity of the coated surface.
A top feed or bottom feed system using this roll is recommended, but a practical bottom feed system using two rolls (so-called natural reverse coating or natural coating) may be used in practice.

The curing of the coating film can be arbitrarily selected depending on the blocking agent dissociation temperature. 200-2
A range of 30 to 70 seconds at 30 ° C is preferred.

The coating containing the BNCO polyester resin of the present invention or a resin composition containing the same as a main component is particularly suitable for pre-coated metal, and the coating film is hard and has excellent workability and stain resistance. Partial corrosion resistance, weather resistance, scratch resistance, etc. are also good.

Further, the resin of the present invention and a composition containing the same are PC
Other than M, for example, it can be used as a post coat.

Examples will be described below. All parts and percentages are in principle based on weight.

Example 1 50% Byron 1520V (trade name, manufactured by Toyobo Co., polyester resin, Tg 2.3 ° C, hydroxyl value 42KOHmg / g, number average molecular weight 6
400) 190 parts (solid content 95 parts) and 70 parts XB-72K-018 (Takeda Pharmaceutical Co., Ltd., hexamethylene diisocyanate triisocyanurate, in which one isocyanate group is blocked with methyl ethyl ketone oxime) 7 parts ( Solid content 5
Was reacted at 70 ° C. for 1 hour, and 1 part by weight of methyl ethyl ketone oxime and 3 parts of sorbetso 150 were further added.
Were mixed to obtain a 50% solution of a B-NCO polyester resin.

Example 2 Byron 1520V in Example 1 was replaced with 50% Byron KS-1
620 (Toyobo Company name, polyester resin, Tg-1.7
C., a hydroxyl value of 56.7 KOH mg / g, and a number average molecular weight of 3900) were carried out in the same manner as in Example 1 to obtain a 50% solution of a B-NCO polyester resin.

Example 3 196 parts (98 parts of solid content) and 70% XB-72K- (50% byron 1780V (trade name, manufactured by Toyobo Co., polyester resin, Tg7.6 ° C, hydroxyl value 18.9KOHmg / g, number average molecular weight 11,000)) 018
By reacting 2.8 parts (the same as above) with 2.8 parts (the same as in Example 1) in the same manner as in Example 1, a 50% solution of a B-NCO polyester resin was obtained.

Example 4 50% Byron 1520V (supra) 196 parts (solid content 98 parts)
1 mole of methyl ethyl ketone oxime was reacted with 1 mole of a triisocyanate compound consisting of a buret type of hexamethylene diisocyanate, and 2 parts (solid content) of a partially blocked triisocyanate compound was reacted in the same manner as in Example 1 to obtain a B-NCO polyester. Resin 50
% Solution was obtained.

Comparative Example 1 Byron 1520V in Example 1 was replaced with 40% Byron 23CS
(Toyobo Co., trade name, polyester resin, Tg 62.1 ° C, hydroxyl value 4.9 KOHmg / g, number average molecular weight 17,000) Except for changing to 237 parts, all were carried out in the same manner as in Example 1 to obtain a B-NCO polyester resin 50. % Solution was obtained.

Comparative Example 2 Byron 1520V in Example 1 was replaced with 30% Byron 35CS
(Toyobo Co., Ltd., polyester resin, Tg 6.9 ° C., hydroxyl value 2.5 KOH mg / g, number average molecular weight 23,000) Except for changing to 316 parts, all procedures were the same as in Example 1 to obtain a B-NCO polyester resin 50. % Solution was obtained.

Performance test A curing agent and a pigment were blended into the B-NCO polyester resin solution obtained in Examples 1-4 and Comparative Examples 1-2 (compositions are shown in Table 1), and thinner (cyclohexanone / swazole 1500 = 1/1 weight ratio) and adjusted to a viscosity of 80 seconds (Ford cup # 4/25 ° C), which was treated with a phosphate-based surface treatment and primer-coated electrogalvanized steel sheet based on a cured coating film of 15- The coated film was coated with a roll coater so as to have a thickness of 20 μ, and was heated at 200 to 230 ° C. for 30 to 70 seconds to be cured.

In Table 1, 1) The B-NCO polyester resin solution (Comparative Example 6) is Viron 1520V.

2) The amount is by weight.

3) 80% coronate 2507: isocyanurate block of hexamethylene diisocyanate, manufactured by Nippon Polyurethane Industry, trade name.

4) Cymel 303: trade name of Mitsui Cyanamid Co., Ltd., hexamethoxymethylolmelamine.

5) T-12PJ: Katsuta Kako Tin catalyst (tin laurate) 6) Swazol 1500: trade name of Cosmo Oil Co., Ltd. 7) Hardness: After leaving the coated plate in a constant temperature room at 20 ° C for 4 hours, Americ
TUKON microhardness t made by an Chain & Cable Company
It was measured with ester. The hardness increases as the numerical value increases.

8) Workability: bending at 20 ° C, goby fold test. In the table, T-bent workability causing no cracks.

9) Stain resistance: After 5 minutes have passed after applying the red ink, n
-The gauze impregnated with butanol was wiped off and the coated surface was observed.

Upper: visual judgment ◎: No abnormality ○: Very slight contamination Bottom: Color difference between contaminated part and non-contaminated part

Claims (2)

(57) [Claims] 1. A free (unblocked) isocyanate group of a partially blocked polyisocyanate compound obtained by blocking one of three isocyanate groups in one molecule, a hydroxyl group having a glass transition temperature of -15 to 40 ° C. A polyester resin having a hydroxyl group and a blocked isocyanate group obtained by subjecting a hydroxyl group of a polyester having a valence of 15 to 80 and a number average molecular weight of 3,000 to 25,000 to a urethanization reaction. 2. A resin composition comprising, as a main component, a composition obtained by blending a curing agent with the polyester resin containing a hydroxyl group and a blocked isocyanate group according to claim 1.