KR100774154B1 - A high hardness polyester coating composition for pcm color steel sheet having excellent corrosion resistance for pe bag and a color steel sheet using thereof - Google Patents

Abstract

The present invention fundamentally prevents the problem of frequent contamination stains on the contact surface between the polyethylene (PE) film used as the packaging film in the packaging process, which is the final process of home appliances and the color coated steel sheet forming the appearance of home appliances It is possible to provide a PCM (pre-coated metal) color steel sheet for high polymer home appliances having excellent PE bag corrosion resistance.

Polyethylene film, high polymer, PCM (pre-coated metal) color steel

Description

High hardness polyester paint composition for PCM color steel plate with excellent PE corrosion resistance and color steel plate using the same

The present invention relates to a color steel sheet for high polymer PCM (pre-coated metal, PCM) for PE bag corrosion resistance and relative processability, and more particularly, polyethylene (PE) film used as a packaging film in packaging operations and The present invention relates to a PCM (pre-coated metal) color steel sheet for high polymer home appliances having excellent PE bag corrosion resistance, which essentially prevents a problem of frequent contamination stains on the contact surface with the color coated steel sheet forming the appearance of home appliances.

Contamination problems frequently occur at the site of contact with the color steel sheets forming the exterior of the product by PE bag, which is a packaging film used in the finishing packaging process of home appliances under high temperature, high humidity, or environment. In particular, dark gray-based dark gray However, due to the more severe appearance of black or clear metallic colors, complaints of demand continue to be raised.

Looking at the basic composition of the top coat applied to conventional PCM color steel sheet exhibiting this problem, as a basic resin, a polymer having a weight molecular weight of about 13,000 and low-branched polyester as the main resin and a melamine resin compound as a crosslinking agent And paints containing small amounts of additives such as colored and extender pigments, curing catalysts, antifoaming agents and leveling agents have been generally used.

In other words, since the molecular weight is high and the resin has a small functional group, the resin hardness is relatively low, and thus, the resin has a disadvantage in coating film hardness and chemical resistance.

In order to solve similar problems with different uses, the main resin is epoxy-modified oil-free polyester resin to provide coating hardness and coating film densification of color steel sheet, and complementary processability, which is relatively weak as auxiliary resin. There was also a household PCM color steel sheet (Patent No. 503164) manufactured as a basic resin of isocyanate resin, but since it is a polyester resin modified with epoxy, it contains some ultraviolet resistance and yellowing resistance which are disadvantages of epoxy. This had the disadvantages of falling.

Also, in general, PE bag erosion contaminants can be improved by increasing the surface hardness by adding extender pigments or matting agents, providing slip properties through the use of wax, and using resins with high glass transition temperature. In some cases, raw materials such as styrene allyl alcohol (SAA), which have a rapid surface reaction, may be used. However, such simple hardness improvement has not been a fundamental solution to PE bag erosion contamination.

Accordingly, the present inventors have found that by changing the composition of the resin in the coating composition for top coat, it is possible to develop a PCM color steel sheet for home appliances, which has high density and hardness of the coating film and excellent chemical resistance, in particular, PE bag corrosion resistance. Reached.

According to the invention,

In the coating composition for top coat of PCM (pre-coated metal, PCM) color steel plate which contains resin which is a main component, a crosslinking agent, a curing catalyst, a solvent, and a usual additive,

The resin is a high-polymer polyester resin and has a weight average molecular weight of 9,000 to 11,000, a hydroxyl value of 50 to 80 mgKOH / g, an acid value of 1 to 5 mgKOH / g, a glass transition temperature of 25 to 50 ° C, and 25 to 55% by weight of the total composition. There is provided a coating composition for top coat of PCM color steel sheet for home appliances, which is contained.

According to another aspect of the present invention,

The PCM color steel plate for home appliances obtained by apply | coating the coating composition for top coats of the PCM color steel plate for home appliances by the said viewpoint is provided.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In the present invention, the polymer polyester resin applied to the PCM color steel sheet for home appliances is completely excluded, and the main resin molecular weight is appropriate for the development of a high-polymer polyester resin having excellent coating film strength and durability and excellent corrosion resistance to PE bags. In order to overcome the hardness shortcomings of the existing methoxy melamine monocure in the hardener part, it was introduced and supplemented with butoxy melamine resin to improve the final process of home appliances. High polymer with excellent corrosion resistance of PE bag which fundamentally prevents the problem of frequently causing contamination stains on the contact surface between polyethylene (PE) film used as a packaging film in the packaging process and color coated steel sheet forming the appearance of home appliances Can provide pre-coated metal (PCM) color steel sheet for home appliances Will.

The present invention will be described in more detail for each component as follows.

1. Polyester Resin

It is preferable to use the main polyester resin used for this invention having a weight average molecular weights of 8,000-11,000, a hydroxyl value of 50-80 mgKOH / g, an acid value of 1-5 mgKOH / g, and a glass transition temperature of 25-50 degreeC.

In this case, if the weight average molecular weight is out of the upper range, it is difficult to increase the number of functional groups, and if the weight average molecular weight is out of the range, durability of the coating film cannot be maintained.

In addition, when the number of functional groups is 50 or less, the crosslinking density of the coating is decreased, and the corrosion resistance of the PE bag is decreased.

2. Crosslinking agent

In the present invention, it is preferable to use a melamine resin as a crosslinking agent for forming the resin component and the coating film, but the conventional isocyanate resin is not preferable because a yellowing phenomenon occurs in a high temperature baking type when used in a large amount. Melamine resins include melamine resins containing amino groups or butoxy groups and melamine resins containing methoxy groups.

Melamine containing an amino group or butoxy group is advantageous in hardness of the coating film, but when acid catalyst is used, the reaction rate is slightly slower at high temperature than the methoxy melamine resin, and the processability is lowered, whereas methoxy melamine resin is used. When used with an acid catalyst, the curing reaction rate is fast and the processability of the coating film is excellent. In the present invention, the basic properties such as hardness and processability of the coating film are made of methoxy type melamine and butoxy type in order to make physical properties equivalent to those of conventional paints. Melamine resin of 1: 0.3 ~ 1: 0.5 is preferably used by mixing. At this time, when the mixing ratio of the two curing agent resin is less than 1: 0.3, there is a disadvantage that the hardness of the coating film is poor and the viscosity increases during the storage of the paint, and when it exceeds 1: 0.5, the hardness of the coating film increases but the workability of the coating film is lowered. There is this.

3. Curing catalyst

As the curing catalyst used in the present invention, a neutralized sulfonic acid selected from p-toluene sulfonic acid (p-TSA) or dinonylnaphthalene sulfonic acid (DNNSA), dinaphthalene disulfonic acid (DNNDSA), and fluoro sulfonic acid with amine or epoxy may be used. Can be.

It is sufficient that the curing catalyst is contained in the range of 0.1 to 1.5% by weight based on the total color steel sheet as an additive amount that is usually used.

4. Solvent

The color steel sheet of the present invention contains an appropriate amount of an organic solvent in consideration of characteristics in handling and coating operations. As an organic solvent, it is preferable to mix and use aromatic hydrocarbon type, glycol ester type, glycol ether type, alcohol solvent, etc. suitably.

The aromatic hydrocarbon solvents include Cocosol # 100 and Cocosol # 150 of Yugong Corp., and glycol ester solvents include ethyl acetate, n-butyl acetate, cellosolve acetate, propylene glycol monomethyl acetate, and the like. Methoxy butyl acetate and the like. Examples of glycol ether solvents include methyl cellosolve, ethyl cellosolve, ethylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, and diethylene glycol butyl ether from Union Carbide. Alcohol solvents include ethanol, Isopropanol, n-butanol, amyl alcohol, cyclohexanol and the like.

It is sufficient to contain the above-mentioned solvent in the range of 40 to 45 weight% with respect to the whole color steel sheet as an addition amount normally.

5. Additives (leveling agents, defoamers and pigments)

In the present invention, it is preferable to use an acrylic, vinyl or silicone leveling agent and an antifoaming agent at 0.5 to 1.0% by weight, respectively, in order to maintain the coating film smoothness and to improve the antifoaming property during painting.

Examples of the leveling agent and the antifoaming agent include Disparon L-1980, Disparon L-1984, Disparon AP-30, BYK356 by BYK356, BYK410, etc. of Kusumoto Chemical.

Moreover, although the main resin of this invention is generally used for the paint containing a coloring pigment, it can also be applied to the transparent metallic paint containing no pigment. As coloring pigments, organic and inorganic pigments used in PCM coatings can be used without distinction.An rust preventive pigment applied for anti-corrosion property in paint coatings is toxic or non-toxic rustproof of strontium chromate and zinc phosphate according to demand. Pigments may be optionally used.

In addition, the paint of the present invention may include a sieving pigment, such as talc, clay, silica, mica, alumina, fillers and the like. It is sufficient to contain the pigment in the range of 10 to 40% by weight based on the whole color steel sheet.

The PCM high polymer color steel sheet obtained as a result of coating the above-mentioned top coat composition on a known plated steel sheet introduces rigidity into the molecular structure by slightly reducing the molecular weight and increasing the branching structure compared to the paint applied to the existing high polymer color steel sheet. At the same time, by increasing the number of functional groups to improve the compactness and strength of the coating film can overcome the disadvantages of chemical, physical and mechanical properties coming from low molecular weight.

Example

The following examples are intended to illustrate the invention and are not intended to limit the invention thereto.

< Example  1: resin synthesis and Basic characteristics  Contrast

In this experiment, we present several experimental examples of synthesizing the main resin and at the same time to compare the basic properties with the existing resin, the mixing ratio is shown as Table 1a below, and each of the obtained main resin and the existing resin The basic properties were compared to Table 1b below.

Resin composition             Experimental Item One 2 3 4 Existing Resin Suzy NPG 32 28.5 35 30 32 TMP 4 4.5 5 5.5 1.5 EG 2 4 One One 5 HPHP 2 3 2 5 - AA 18 20 18 17 17.5 IPA 35.0 34.0 33 35.5 36 TPA 7 6 6 6 8 additive DBTO 0.05 0.05 0.05 0.05 0.1 Diluent Solvent K150 / CA = 7/3 30 30 30 30 K150 / CA = 9/1 importance 1.07 1.07 1.07 1.07 1.06 Viscosity X X X X- Y Solid content 59.7 60.2 60.1 60.5 60 Acid 2.5 1.6 2.1 2.2 3.5 Molecular Weight Mw 9500 10000 10500 10000 10500 Hydroxyl value 65 67 65 60 30 NPG: Neopentylglycol TMP: Trimethylolpropane EG: Ethylene glycol 1,6HD: 1,6 hexanediol AA: Adipic acid IPA: Isophthalic acid TPA: Terephthalic acid HPHP: Hydroxy pivalyl hydroxy pibarate Viscosity: 60% solution (25 ° C Gardner) Molecular Weight: Weight average molecular weight (GPC)

Basic Property Comparison Existing Resin Experimental Example 1-4 (High Polymer) Solid content 60 60 Viscosity Y-Z1 V-X Molecular Weight 11000-14000 9000-11000 Hydroxyl value 20-40 50-80 Tg 20-30 ℃ 25-50 ℃

< Example  2: Resin Selection Paint Test>

In this experiment, a clear paint was prepared based on the following examples using the main resins obtained in Example 1, and then a comparative experiment for selecting a main resin was performed. At this time, the standard, test condition, specimen preparation method, etc. of the material used are as follows.

A) Material specification and working condition

-Test Material: Thickness 0.5mm X Width 70mm / Length 150mm GI (hot dip galvanized steel sheet)

- before treatment: non of 80mg / m ² - chromate chemical conversion coating layer

-Dry coating: Undercoat 5㎛ / Topcoat 10㎛

-PMT: 210 ℃ for upper coat, 235 ℃ for upper coat

2) applied paint

   -Anticorrosion Hado for Home Appliances (Samsung Fine Chemical)

-4 types of development resin and 1 type of existing resin synthesized in Example 1 above

Specific methods of performing the resin selection test by making the main resins of Experimental Example 1-4 synthesized in Table 1 above into a clear paint (Clear) are as follows.

That is, examples 1, 2, 3, and 4 were used to form transparent paints without using a high polymer based on the main resins of Experimental Examples 1-4, respectively. The mixing ratios of the resin-selective clear paints used, respectively, are shown in Table 2 below, using the polymers as examples 5, 6, 7, and 8, respectively, and the comparative test results are shown in Table 3 below. .

Compounding ratio of resin selection clear paint Composition (wt%) PE Bag Improvement High Hardness Resin Application Test existing Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Main Resin 1 (Hardness) 64.0 64.0 64.0 64.0 34.0 34.0 34.0 34.0 - Resin 2 (High Polymer) - - - - 30.0 30.0 30.0 30.0 73.0 Aerosol paste 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 Methylated Melamine 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 6.0 Butylated Melamine 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 - Acid catalyst 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Leveling agent 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 Matting agent (silica) 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 CYCLOHEXANONE 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 DBE 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 KOCOSOL 100 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 system 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

수지: Resin 2 (high polymer) is applied to SK Chemical's SKYBON ES-960

Paint selection comparison test result Test Items PE Bag improvement high hardness resin application test existing Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 importance 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 Solid content 55.5 55.5 55.5 55.5 55.5 53.0 53.0 54.5 50.2 Viscosity (sec / 25 ℃) 80 80 80 80 80 80 80 80 80 Polish 72 73 69 74 73 72 70 71 73 Curing degree 30 50 80 5 25 35 5 30 10 Pencil hardness HB HB HB HB HB HB HB HB HB Machinability (2T) ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ Boiling water resistance △ △ ○ X △ △ X △ X Adhesion ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ PE Bag Erosion Contamination △ ○ ◎ X △ △ X △ X

Judging from the test results, it can be confirmed that the PE bag erosion contaminants and various physical properties were the most excellent in the high hardness resin of Example 3 transparently coated without using a high polymer based on the main resins of Experimental Examples 1-4. there was.

< Example  3: Paint Mixing Experiment>

In this experiment, the mixing ratio of the cured resin was changed to the high-hardness resin of Example 3 in Table 2 based on the PCM top coat paint of general color for home appliances.

At this time, the material specifications and working conditions of Example 9-12, coating materials, and the like are as follows, and the respective mixing ratios and their experimental results are shown as Tables 4a and 4b, respectively.

A) Material specification and working condition

-Test material: Thickness 0.5mm × Width 1014mm GI (hot dip galvanized steel sheet)

- before treatment: non of 80mg / m ² - chromate chemical conversion coating layer

-L / Speed: 80mpm

-Dry coating: Undercoat 5㎛, Top coat 20㎛

-PMT: Undercoat 210 ℃, Overcoat 235 ℃

B) Paint applied:

-Hado: Samsung Fine Chemicals' anti-rust primer

-Top coat: Samsung PCC Co., Ltd. home PCM top coat

Example and Comparative Example (Paint Color: GRAY)

Composition (% by weight) Example Comparative Example (Existing) 9 10 11 12 Polyester Hard Hardness Resin 44.0 44.0 44.0 44.0 - General high polymer resin - - - - 44.0 additive Dispersion additive 0.2 0.2 0.2 0.2 0.2 Pigment Titanium oxide 18.0 18.0 18.0 18.0 18.0 COPPER black 6.0 6.0 6.0 6.0 6.0 Iron oxide yellow 4.0 4.0 4.0 4.0 4.0 Iron oxide red 1.0 1.0 1.0 1.0 1.0 additive Fumed silica 0.5 0.5 0.5 0.5 0.5 Curing resin Methylated melamine 5.0 8.0 8.0 4.0 6.0 Butylated Melamine 3.0 - 3.0 5.0 - additive Leveling agent 1.5 1.5 1.5 1.5 1.5 Curing catalyst Acid catalyst 1.5 1.5 1.5 1.5 1.0 solvent CYCLO HEXANONE 4.0 4.0 4.0 4.0 4.0 DBE 6.0 6.0 6.0 6.0 6.0 KOCOSOL 150 5.3 5.3 2.3 4.3 7.8 system 100.0 100.0 100.0 100.0 100.0  Paint appearance importance 1.30 1.31 1.30 1.30 1.29 Solid content 62.5 63.0 62.5 62.3 63.0 Viscosity (sec / 25 ℃) 110 105 110 113 112

Comparison of test results division Example Comparative example 9 10 11 12 One Polish 72 71 73 70 73 Curing degree 100 ↑ 100 ↑ 100 ↑ 100 ↑ 80 ↑ Pencil diameter F degree F F F F F- Machinability (3T) ◎ ◎ ◎ △ ~ ○ ◎ Acid resistance ◎ ◎ ◎ ◎ ◎ Alkali resistance ◎ ◎ ◎ ◎ ◎ Boiling water resistance ◎ ◎ ◎ ◎ ◎ C.E.T ◎ ◎ ◎ ◎ ◎ PE corrosion resistance ○ △ ~ ○ ◎ ◎ △ Corrosion resistance ◎ ◎ ◎ ◎ ◎

-Gloss of 1: Initial value of 60 degree gloss measurement result with Gloss Meter

-Hardness of 2: MEK Rubbing (solvent resistance)

-Pencil hardness of 3: Using the "Uni Pencil" manufactured by Mitsubishi Corporation, Japan

-Workability of 4: Evaluation of crack occurrence on the processed part by T banding at room temperature (20 ℃)

-Acid resistance of 5: Evaluation of coating state after immersion in 5% acetic acid solution at room temperature (20 ℃) for 24 hours

-Alkali resistance of 6: Evaluation of coating state after immersion in 5% caustic soda solution at room temperature (20 ℃) for 24 hours

-Boiling resistance of 7: Evaluation of coating state after immersion in boiling water (more than 98 ℃) for 1 hour

-C.E.T of 8: 6mm extrusion after cross cut to make 100 division by 1mm interval

  After taping and peeling

-9 PE BAG erosion contamination resistance. PE BAG adhered to the 7 x 15 cm specimen coated surface, 55 ℃ × 95% RH (relative humidity) × left for 12 hours, the film was removed and the degree of discoloration of the attached part was evaluated.

-Corrosion resistance of 10: Salt Spray Test 35 ℃, 5% NaCl, 240 hours

As shown in Table 4b, Example 11 was the most excellent in PE bag erosion fouling and general physical properties of the coating applied to the selected resins Example 9-12, the content of butylated melamine in the cured resin In the case of paint, better results were obtained, but it was confirmed in Example 12 that the problem of deterioration in workability caused by excessive injection.

As a result, it was reconfirmed that it is important to satisfy the processability and contaminants with an appropriate blend design of the main resin and butyl and methylated melamine.

As described above, when the paint according to the present invention is used in a precoated steel sheet, it is possible to obtain a fundamental improvement effect on the erosion contamination of PE bag packaging materials while maintaining the same physical properties (durability, chemical resistance, and mechanical properties) as conventional paints. have.

Claims (3)

In the coating composition for top coat of PCM (pre-coated metal, PCM) color steel plate which contains resin which is a main component, a crosslinking agent, a curing catalyst, a solvent, and a usual additive, The resin is a high hardness polyester resin with a weight average molecular weight of 9,000 to 11,000, a hydroxyl value of 50 to 80 mgKOH / g, an acid value of 1 to 5 mgKOH / g, a glass transition temperature of 25 to 50 ℃, containing 25 to 55% by weight of the total composition As the crosslinking agent, a methyl etherified melamine resin having a methoxy group and a butylether melamine resin having a butoxy group are used at a ratio of 1: 0.3 to 1: 0.5, and the phase of the PCM color steel sheet for home appliances Pottery coating composition. delete PCM color steel sheet for household appliances obtained by apply | coating the coating composition for top coat of the PCM color steel sheet for household appliances of Claim 1.