KR20120089936A - Resin coating compositions and its coated steel sheet with high press formability, and blocking and sticking resistance - Google Patents

Abstract

PURPOSE: A resin composition for surface treatment is provided to have excellent lubrication and to have good sticking property and blocking property without using solid wax by having polymer beads imparting excellent texture after resin coating, and by controlling size of quencher. CONSTITUTION: A resin composition for surface treatment comprises a base resin, and polymer beads, in which beads with particle diameter of 1.4-1.8 times thicker than the thickness of a resin coating layer, and polymer beads with particle diameter of 1.0-1.3 times thicker than the thickness of the resin coating layer. The weight ratio of the polymer beads with particle diameter of 1.4-1.8 times and 1.0-1.3 times is 1:1-4. 4-20 parts by weight of the polymer beads based on 100.0 parts by weight of total solid phase is used.

Description

Resin coating compositions and its coated steel sheet with high press formability, and blocking and sticking resistance}

The present invention relates to a resin composition for surface treatment excellent in press formability, sticking, and blocking properties, and a steel sheet using the same.

In order to meet the rapid increase in demand for video appliances such as PDP, LCD TV, DVD player, and set-top box, and the slimming of internal and external materials is proceeding at a very high speed, the plastic injection molding that has been used mainly for internal and external materials is steel It is changing rapidly.

In particular, in the case of the exterior material, by using a resin coated steel sheet having a function of painting in advance and adopting a method of mounting the product immediately after the press working without a separate coating process, rapid productivity and slimming in response to the market demand are proceeding very quickly. .

The required characteristics of the exterior material of the image home appliances are that the resin coating layer is press formed directly on the resin coated sheet in advance so that the resin coating layer prevents damage to the surface of the resin coating under high pressure with the mold required in the pressing process and smooth molding. In order to prevent the damage of the resin coating surface by the high lubricity and tension of the material during processing and to maintain the continuous coating surface, flexibility (extension) and scratch resistance of the coating film should be exhibited.

In addition, the resin coated steel sheet used for image home appliances should be transported and stored in the form of coil or sheet, so that the resin coating layers should not stick to each other during the overall process, and there should be no difference from immediately after production in terms of surface gloss appearance. do.

In general, press workability (lubrication), sticking, and blocking properties are interchangeable, and when wax is added to secure press workability, especially sticking and blocking properties are poor. There is an easy disadvantage. That is, liquid wax or solid wax, which is mainly added to improve the lubricity of the surface of the resin coated steel sheet to improve the press workability, is floated on the surface during the curing process after the resin coating, thereby improving the lubricity of the surface. However, by reducing the degree of curing of the resin coating surface layer, there is a disadvantage that the blocking property is inferior.

Therefore, in order to manufacture a resin coated steel sheet having excellent sticking property and blocking property while improving press workability, it is necessary to design the resin coating layer so that the physical properties represented by the wax can be exhibited without adding solid wax as much as possible.

The present invention is a subject resin; And a polymer bead comprising a bead having a particle diameter of 1.4 to 1.8 times a particle diameter and a bead having a particle diameter of 1.0 to 1.3 times as compared to a dry coating thickness; and a resin composition for surface treatment having excellent lubricity and sticking / blocking properties, and a steel sheet using the same. The purpose is to provide.

The present invention is a subject resin; And polymer beads in which beads having a particle diameter of 1.4 to 1.8 times and beads having a particle diameter of 1.0 to 1.3 times are mixed with respect to the dry coating film thickness of the resin coating layer.

Hereinafter, the present invention will be described in detail.

In order to secure excellent press formability (lubrication) without using the solid wax proposed in the present invention, polymer beads are used, and the polymer bead particles have a particle diameter of 1.4 with respect to the dry coating thickness of the final resin coating layer. By coating a mixture of beads of 1.8 to 1.8 times and beads having a particle diameter of 1.0 to 1.3 times, the ball bearing effect of spherical beads during high-pressure press molding without the addition of a separate solid wax that adversely affects blocking properties By this, excellent lubricity can be exhibited. The polymer beads are preferably a mixture of bead particles having a particle diameter of 1.4 to 1.8 times and bead particles having a particle diameter of 1.0 to 1.3 times relative to the dry coating film thickness of the resin coating layer in a weight ratio of 1: 1 to 4.

In particular, it is more preferable to use 4 to 20 parts by weight of the polymer beads with respect to 100 parts by weight of total solids, and once the beads are used in an amount of less than 4 parts by weight, the lubricity and blocking properties deteriorate. Scratches occur more severely when press molding (can be simulated as scratches occur when measuring the friction coefficient as shown in Figure 4).

The polymer beads are preferably at least one selected from the group consisting of melamine beads, acrylic beads, acrylic-styrene beads, polycarbonate beads, polyethylene beads, vinyl chloride beads, and styrene beads, but are not limited thereto.

Acrylic beads used in the present invention are ethyl acrylate, butyl acrylate, amyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, cyclohexyl acrylate, benzyl acrylate, butyl methacrylate, 2-ethylhexyl meta Acrylate, cyclohexyl methacrylate, benzyl hexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, methyl acrylate, methyl methacrylate, benzyl methacrylate, vinyl acetate, styrene, acrylonitrile, acrylic acid , Methacrylic acid, maleic anhydride, itaconic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, N-methylol acrylamide, acrylamide, methacrylamide, glycidyl Amide, lauryl acrylate, ethoxydiethylene glycol acrylate, methoxy triethylene glycol Acrylate, phenoxyethyl acrylate, tetrahydrofuryl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy-3-phenoxy acrylate, neopentyl Glycol diacrylate, 1,6-hexanediol diacrylate, trimethylol propane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, trimethylolpropane acrylate benzoate , 2-ethylhexyl methacrylate, n-stearyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxybutyl methacrylate, 1 , 6-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, glycerin dimethacrylate It is preferable to use the monomers or oligomers of glycerol dimethacrylate hexamethylene diisocyanate and pentaerythritol triacrylate hexamethylene diisocyanate alone or in combination.

In addition, the styrene beads used in the present invention may be used alone or in combination with styrene, α-methylstyrene, α-ethylstyrene, o-ethylstyrene, p-ethylstyrene, 2,4-dimethylstyrene or vinyl toluene. desirable.

In the present invention, a binder resin that uniformly disperses and supports various additives and plays a major component of the final resin coating layer may use all kinds of resins commonly used in the general PCM (precoated metal) industry. At least one main resin selected from the group consisting of polyester resins, epoxy resins, urethane resins, acrylic resins, and alkyd resins is used, wherein the glass transition temperature of the resin is from 15 to 75 ° C. It is preferable. If the glass transition temperature of the main resin is less than 15 ℃, the lubricity required for press workability is insufficient, and if it exceeds 75 ℃, the lubricity is expected to be improved, but the resin coating layer becomes too brittle. At the gripping site, there is an increased possibility that scratches may be severely generated during the drawing process or the resin layer may be broken to cause dent defects.

In the present invention, the main resin preferably has a number average molecular weight of about 2500 to 30000, and is composed of 60 to 90 parts by weight based on 100 parts by weight of the total solid. The content range of the resin does not need to be specifically proposed in consideration of the type of additives and physical properties, but generally less than 60 parts by weight in the scope of the present invention is insufficient to withstand the friction with the mold while firmly holding the additives as a resin. If the content exceeds 90 parts by weight, it means that the content of the additives effective for improving the physical properties is too small. As a result, it becomes difficult to secure the physical properties such as texture as well as good lubricity and blocking properties. It is preferable to use a melamine-based curing agent together with an acid catalyst because it may be difficult to secure the curability of the coated steel sheet only as the main resin to be a binder. The melamine-based curing agent is used 3 to 30 parts by weight based on 100 parts by weight of total solids, the acid catalyst is preferably 0.3 to 6 parts by weight based on 100 parts by weight of total solids, the content of the acid catalyst is cured to the content of the curing agent In consideration of conditions and degree of curing, the content can be adjusted by a conventional method.

In order to secure excellent lubricity without using the solid wax proposed in the present invention, the glass transition temperature of the resin as well as the polymer bead may be a feature.

In the present invention, it may further include a matting agent to match the gloss required by the customer, using an amorphous silica as a matting agent, because the gloss of the surface is significantly changed by using the particles as described above In this very high case it is more advantageous to choose the content of particles as low as possible in the scope of the invention. If a matte surface is to be made, a matting agent should be used. Conventionally, amorphous amorphous silica was used. As such, when the amorphous silica is used, the diffuse reflectance is increased, so that the gloss can easily be reduced. However, since the solvent content is high, the solution has a disadvantage in that the stable coating process range is reduced due to the decrease in the thixotropy of the solution. By selecting and using near silica, the same silica can be used to achieve ball bearing effect. The amount of silica used is not particularly limited because the gloss required by the customer is different, but in the scope of the present invention, when the gloss is close to 4 to 7 matte, the amount of silica is about 0.8 to 2.0 parts by weight based on 100 parts by weight of the total solids. It is contained. If a relatively high gloss of 20-30 or more is required, the matting agent is not added, and beads exhibiting a ball bearing effect (cloud effect) can be easily changed by slightly modifying them to be somewhat smaller in the scope of the present invention. Gloss can be obtained. In the present invention, it is more preferable that the quencher is mixed with the quencher particle diameter of 0.5 to 1 times and 1.1 to 1.5 times based on the dry coating thickness of the final resin coating layer.

1 is a schematic cross-sectional view of the resin layer of the present invention and shows a mechanism in which press workability (lubrication) is exerted by the rolling effect of particles (beads and matting agents) during press molding.

The cross-sectional view of the resin coating layer and the actual cross-section are taken as an example.The particles whose size and content are well controlled exhibit the effect of rolling effect during press molding, thereby improving the press workability (lubrication), as well as the sticking and blocking properties. Contribute to.

Lubricity as well as sticking and blocking properties can be ensured by the selection and proper mixing of the particles as described above, but at least van der Waals bonds when the polar groups on the surface are stuck together in the blocking mechanism. This may cause the resin coating layers to stick to each other or to cause a change in surface roughness due to hydrogen bonding, etc., thus preventing the blocking property because the steel sheets may stick to each other and cause sticking as well as adversely affect the blocking property that causes a slight difference in gloss. Is an acrylic polymer having a nonpolar site and a reactor (hydroxy group, carboxyl group, etc.) with a chemical structure of the resin coating layer to further prevent blocking properties, and a blocking improving agent designed to form an interface with a polar site in the resin coating layer is added. Can be used as The blocking improving agent is preferably used 0.3 to 3.0 parts by weight based on 100 parts by weight of the total solid. If the blocking improver is used less than 0.3 parts by weight, the effect is not sufficiently exhibited, and when it exceeds 3.0 parts by weight, it is difficult to control the glossiness, so excessive addition is not preferable.

Figure 2 is a diagram illustrating the action mechanism of the acrylic polymer-based additives included to improve the blocking properties of the present invention. As part of the improvement of blocking properties, the addition of acrylic polymer designed to have the non-polar side aligned to the surface prevents the sticking due to the electrostatic or functional period bonding such as van der Waals force or hydrogen bonding, one of the causes of blocking. King shows, of course, a schematic of what is designed for the purpose of improving blocking properties.

On the other hand, in order to exhibit the minimum slip properties of the final dry coating film, a silicone compound may be additionally used, and the silicone compound may be a silicone oil, or polysiloxanes having excellent leveling properties and slip properties are used alone or in combination with each other. . It is preferable to use 0.2-2.0 weight part of said silicone compounds with respect to 100 weight part of total solids. If the silicone compound is used in less than 0.2 parts by weight, the slip property is hardly exhibited. If the silicone compound is used in an amount of more than 2.0 parts by weight, physical properties such as corrosion resistance and blocking property may appear, rather than further improving leveling and slip properties.

Up to now, the components forming the resin coating layer in the resin coated steel sheet are mainly described as components that meet the object of the present invention. In fact, they are used as a coating solution in the resin coating process to express surface textures such as color and gloss desired by customers. Depending on the thermal behavior of the process and the resin coating method, solvents having various volatilization temperatures and polar groups are appropriately selected and used at a predetermined concentration. Solvents mainly used in the present invention are those that can be divided into three main temperature ranges of 100 ~ 150 ℃, 151 ~ 175 ℃, 176 ~ 220 ℃ and those below 150 ℃ alcohols, propylene glycol mono Cyclohexanone and solvent naphtha (Kocosol # 100) were mainly used at 151 to 175 ° C, such as methyl ether acetate and ethoxy ethyl acetate, and solvent naphtha (Kocosol # 150) and dimethyl glutarate at 176 to 220 ° C. Was mainly used. Solvent selection and content ratio should be designed to have excellent surface appearance by sequential volatilization in consideration of securing rheology in coating process and characteristics of curing process. The amount of solvent used in the present invention is preferably 50 to 80% by weight based on the total resin coating solution composition.

In addition, the resin composition for surface treatment of the present invention may further include one or more additives such as pigments, wetting agents, crosslinking agents, lubricants, antifoaming agents, adhesion promoters, dispersion stabilizers, etc. 0.05 to 16 parts by weight of the total solid content Parts by weight may be used.

The present invention also relates to a steel sheet comprising a coating layer containing the cured product of the resin composition for surface treatment.

The steel sheet means a metal used for the purpose of automobile materials, home appliances, building materials, and the like, specifically, a metal such as an iron plate, and may be any steel sheet commonly used in the art for this purpose. Cold rolled steel sheet; Zinc-based electroplating steel sheets such as galvanized steel sheet, zinc nickel plated steel sheet, galvanized steel sheet, zinc titanium plated steel sheet, zinc magnesium plated steel sheet, zinc manganese plated steel sheet and zinc aluminum plated steel sheet; Hot-dip galvanized steel sheet; Aluminum plated steel sheet; Further, plated steel sheets containing, as the dissimilar metals or impurities in these plating layers, for example, cobalt, molybdenum, tungsten, nickel, titanium, aluminum, manganese, iron, magnesium, tin, copper, and the like; Further, plated steel sheet in which inorganic materials such as silica and alumina are dispersed in these plating layers; Or an aluminum alloy plate containing silicon, copper, magnesium, iron, manganese, titanium, zinc or the like; Or galvanized steel sheet coated with phosphate; Alternatively, a hot rolled steel sheet may be used, and a multilayer plated sheet obtained by sequentially treating two or more kinds during the plating may be used as necessary.

The method for treating the steel sheet using the resin composition for surface treatment of the present invention may be performed after washing the surface of the steel sheet by a method generally known in the art in order to remove oil and stains adhered to the steel sheet as necessary. have. Although washing | cleaning is not limited to this, It can carry out using an alkali degreasing agent, an acidic degreasing agent, high temperature water, a solvent, etc. After cleaning, surface adjustment can be performed using acid or alkali.

It is preferable to wash with water after washing so that the cleaning agent does not remain on the surface of the steel sheet as much as possible when cleaning the surface of the steel sheet. Although not limited to this, As an example, it is preferable to surface-treat with the resin composition for surface treatments of this invention, after wash | cleaning, water washing, and surface adjustment of the raw material metal (steel plate) surface as mentioned above.

In treating the metal surface by the method according to the present invention, the resin composition for surface treatment may be applied as a coating layer on the surface of the steel sheet by any coating method generally known in the art. The coating method used in the application is not particularly limited, and known coating methods such as bar coating, dip coating, roll coating, curtain coating, spray coating, slot coating, gravure coating, and the like can be used. At this time, the coating temperature is not particularly limited.

The coating layer is such that the adhesion amount is 3000 ~ 45000 mg / m ² , preferably 5000 ~ 15000 mg / m ² . If the adhesion amount exceeds 45000 mg / m ² , the resin layer may be pushed or the workability may be lowered during press workability. If the adhesion amount is less than 3000 mg / m ² , the coating crack may be generated during press work to expose the base iron. And corrosion resistance is greatly reduced and it is difficult to use for home appliance parts. In addition, the thickness of the coating layer is preferably 5 ~ 15 ㎛.

After applying the surface treatment resin composition of the present invention to the surface pretreated as described above, the solvent is volatilized by applying heat to the steel sheet through various methods such as hot air, induction heating and NIR at 200 to 250 ° C. and curing reaction in the resin coating layer. This progresses to form a dry coating film exhibiting final physical properties. This surface-treated steel sheet was improved in press workability, sticking and blocking properties.

The resin composition of the present invention exhibits excellent lubricating properties without any special solid wax, and exhibits good sticking and blocking properties by controlling the size of the polymer bead and the matting agent controlling gloss after coating the resin. It became.

1 is a schematic cross-sectional view of the resin layer of the present invention and shows a mechanism in which press workability (lubrication) is exerted by the rolling effect of particles (beads and matting agents) during press molding.
Figure 2 is a diagram illustrating the action mechanism of the acrylic polymer-based additives included to improve the blocking properties of the present invention.
Figure 3 is a view showing an example of a defective specimen damaged the coating film evaluated by the Drawbead friction tester and the friction tester used to evaluate the press workability (lubrication) of the present invention.
4 is a hot press apparatus and grading principle for evaluating sticking and blocking properties of the present invention.

Hereinafter, the present invention will be described in more detail by way of examples. It should be noted, however, that the following examples are illustrative of the invention and are not intended to limit the scope of the invention.

Reference Example

The dry film thickness of the final resin coating layer was used as a reference.

One. Resin

1) 35 wt% of the number average molecular weight 7000 ~ 8000 polyester resin (ES-960, SK, Tg 15 ℃),

2) 35 wt% of the number average molecular weight 15000-17000 polyester resin (ES 410, SK, Tg 35 ℃),

3) 21 wt% of the number average molecular weight 15000-20000 polyester resin (ES 910, SK, Tg 65 ~ 75 ℃),

4) 6 wt% of the number average molecular weight 20000 ~ 30000 urethane resin (Desmoudur® BL3272MPA, Bayer),

5) Number average molecular weight 2500 ~ 4300 epoxy resin (YD 019K, YD 020L, Kukdo Chemical) 3% by weight

2. Polymer Bead

15 μm: Methyl methacrylate, LDX150 (Advanced Chemistry)

12 μm: Methyl methacrylate, S120 (Advanced Chemistry)

10 μm: methyl methacrylate, MH10FD (KOLON)

3. silicone compound

Silicone Oil: TSF 451 (Hansol E & C)

Polysiloxane compounds; BYK-322, BYK-323, BYK 320 (BYK)

4. Matting agent

Wax-Coated Silica 6-8 μm: Syloid C907, ED40 (Grace)

Wax-Coated Silica 11-13 μm: SS-SIL 2012 (Schemtech)

5. Blocking Enhancer

Acrylic polymer: BYK 394 (BYK)

6.Others

Acid catalyst: Dinonylnaphthalenesulfonic acid (Nacure 1953, King Industies)

Black pigment: carbon black with average size of 24 nm (MA 100, Mitsubishi)

Curing Agent: Melamine Resin (Cymel 303, 254, 370, Cytec)

7. Solvent

6% by weight of propylene glycol monomethyl ether acetate, 34% by weight of cyclohexanone, 28% by weight of solvent naphtha (Kocosol # 100), 21% by weight of solvent naphtha (Kocosol # 150) and 11% by weight of dimethylglutarate It was.

Example Steel plate manufacturing

[Resin composition]

After dispersing the pigment in a solvent, the solid composition of Table 1 and Table 2 was added to prepare a resin coating paint.

Total solids (NV) was prepared in 35 ± 1% by weight of the resin coating solution composition containing a solvent.

[Resin Composition Coating]

A 0.5 mm thick galvanized steel sheet coated with 0.3 ~ 1.5 μm thick non-chromium coated resin exhibiting physical properties such as adhesion and corrosion resistance to the resin coating layer by using the two-stage / 3-stage roll coating apparatus. Coating was carried out continuously. The coated steel plate was continuously hardened to 220 ~ 235 ℃ PMT (peak metal temperature) using an induction furnace. At this time, the overall line speed of the coating and curing process is very high-speed coating is possible up to 150 mpm, the composition according to this embodiment is a composition capable of high-speed coating up to 150 mpm in the embodiment is fixed to 120 mpm to manufacture a coated steel sheet It was.

The dry film thickness of the final resin coating layer was used as a reference.

Polymer Bead Content Comparison division
(Parts by weight) subject
Suzy black
Pigment Acid catalyst Hardener Polymer beads Matting agent Silicone compound blocking
Improver Particle diameter Particle diameter 15 μm 12㎛ 10 탆 7 ~ 8㎛ 11 ~ 13㎛ silicon
oil Poly
Siloxane Inventory 1 75.3 2 1.1 10 2 - 3 0.5 1.5 0.6 1.0 3.0 Inventory 2 75.9 2 1.1 10 2 - 3 0.5 1.5 0.5 1.0 2.5 Inventory 3 74.9 2.5 1.1 10 3 - 3 1.0 0.5 0.5 1.0 2.5 Honorable 4 71.7 2.5 1.3 12 2 - 5 1.0 0.5 0.5 1.0 2.5 Inventory 5 68.1 2.5 1.3 12 2 - 9 0.8 0.8 0.5 1.0 2.0 Inventory 6 65.4 2.5 1.3 12 5 - 9 0.5 0.8 - 1.5 2.0 Honorable 7 65.9 2.5 1.3 12 5 2 7 0.5 0.8 0.5 0.5 2.0 Honors 8 65.9 2.5 1.3 12 5 - 11 0.5 0.5 0.5 0.5 0.3 Inventive Example 9 63.9 2.5 1.3 12 5 - 11 0.5 0.5 0.5 0.8 2.0 Inventive Example 10 63.6 3 1.3 12 3 - 13 0.3 1.0 0.5 0.8 1.5 Inventive Example 11 63.9 2 1.3 12 2 - 15 - 1.0 0.3 1.0 1.5 Inventive Example 12 70.2 1.5 0.5 5 5 4 10 1.0 - 0.3 1.0 1.5 Comparative Example 1 75.4 2.5 1.3 12 One - One 0.5 1.5 0.8 1.0 3.0 Comparative Example 2 62.1 2.5 1.1 10 5 - 16 0.5 0.5 0.3 0.5 1.5 Comparative Example 3 62.1 2.5 1.1 10 2 - 19 1.0 - 0.3 0.5 1.5 Comparative Example 4 70.7 2.5 1.3 12 10 - - 0.5 0.5 0.5 1.0 1.0 Comparative Example 5 70.7 2.5 1.3 12 - - 10 0.5 0.5 0.5 1.0 1.0

Comparison of additives other than polymer beads division
(Parts by weight) subject
Suzy black
Pigment Acid catalyst circa
anger
My Polymer beads Matting agent Silicone compound blocking
Improver Particle diameter Particle diameter 15 μm 12㎛ 10 탆 7 ~ 8㎛ 11 ~ 13㎛ silicon
oil Poly
Siloxane Inventive Example 13 65.2 2 1.3 12 5 - 9 0.5 1.0 1.0 1.0 2.0 Inventive Example 14 68.2 2.5 1.1 10 3 - 13 0.5 0.3 0.3 0.1 1.0 Honorable Mention 15 68.4 2.5 1.1 10 5 - 10 0.5 0.5 0.5 0.5 1.0 Inventive Example 16 67.9 2.5 1.1 10 5 - 10 0.5 0.5 1.0 0.5 1.0 Comparative Example 6 61.6 3 1.3 12 5 - 15 - 0.5 0.1 - 1.5 Comparative Example 7 60.6 2.5 1.3 12 5 4 10 1.0 - 2.0 0.12 1.5 Comparative Example 8 60.5 2.5 1.3 12 5 4 10 1.0 - 1.2 1.0 1.5 Comparative Example 9 65.5 2.5 1.3 12 5 - 11 0.5 0.5 0.5 One 0.2 Comparative Example 10 64.8 2.5 1.1 10 5 - 11 0.5 0.5 0.5 One 3.1 Comparative Example 11 64.6 3 1.1 10 3 - 15 0.5 0.3 0.5 1.0 1.0 Comparative Example 12 63.6 3 1.1 10 3 - 15 0.8 1.5 0.8 0.2 1.0

Test Example

For the steel sheet produced in the Example, its physical properties were measured by the method given below.

1. Press workability measurement

In order to evaluate the press formability of the resin coated steel sheet manufactured in the above example, the friction coefficient was measured by the following method using a Drawbead tester.

After cutting a resin coated steel plate having a size of 320 mm x 45 mm x 0.5 mm (width × length × thickness), the specimen was mounted on a single-sided friction coefficient measuring instrument (POSCO), and then the size of 25 mm × 40 mm (width × length) was measured. After pressing using a mold having, the specimen was moved horizontally to measure the coefficient of friction. The friction coefficient was measured and evaluated as follows. The lower the coefficient of friction, the better the physical properties for molding, but not necessarily. Too low a friction means that the coil must have friction in order to smoothly wind the coil. Too low a friction coefficient in consideration of the winding tension adds a load to the product production process. It was confirmed empirically. Actually, the coefficient of friction of general resin coated steel sheets distributed in household resin coated steel sheets subjected to a press molding process is 0.240 to 0.330 or more.

Figure 3 shows the friction test equipment and measurement method and the appearance of the sample peeled off the resin as a result of the measurement, the resin is peeled off as shown in the bottom when using too many beads or lack of surface lubricity (press workability) Defects occur.

 [Evaluation standard]

? (Very good): 0.150 or less,

○ (excellent): 0.151 ~ 0.180,

△ (normal): 0.181 ~ 0.200,

× (Not good): 0.201 or more

2. Measuring sticking and blocking

The sticking property and blocking property of the resin coated steel sheet prepared in the above example were cut to 10 × 10 cm using a press capable of heating, and the layers to be evaluated were laminated to each other and then laminated to 80 ° C. and 100 ° C. kg.f / cm ² , after pressing for 8 hours by applying temperature and pressure, the standard method suggested by ASTM D3003-94 was evaluated as 0 (very bad) to 10 (very good). Considering that the test condition is a long-term transport by ship due to the characteristics of the product, the experimental application condition is harsher than the general ASTM standard. Sticking property was taken out of the press and measured after decreasing the temperature to room temperature, and blocking property was evaluated after 24 hours elapsed (see FIG. 4).

[Evaluation standard]

? (Very good): 9 to 10,

○ (excellent): 7 to 8,

△ (usually): 5 to 6,

× (Not good): Less than 5 points

division Quality characteristic Remarks Lubricity Sticking Blocking property Inventory 1 ○ ○ ○ Inventory 2 ○ ○ ○ Inventory 3 ○ ○ ○ Honorable 4 ○ ○ ○ Inventory 5 ○ ? ○ Inventory 6 ○ ? ○ Honorable 7 ? ? ? Honors 8 ? ? ○ Inventive Example 9 ? ? ? Inventive Example 10 ? ? ? Inventive Example 11 ? ? ? Inventive Example 12 ○ ? ? Comparative Example 1 × △ × Comparative Example 2 × ? ? Friction scratches Comparative Example 3 △ ? ? Friction scratches Comparative Example 4 × × △ Comparative Example 5 × △ ×

As can be seen in Table 3, in Comparative Example 4 and Comparative Example 5 in which the polymer beads are not used in the composition of the resin composition for surface treatment according to the present invention, all of the quality characteristics were not good, Even when used too little (Comparative Example 1), the quality characteristics were not all good. In addition, when the bead content was exceeded (Comparative Example 2, Comparative Example 3), the press workability was not excellent.

division Quality characteristic Remarks Lubricity Sticking Blocking property Inventive Example 13 ○ ○ ○ Inventive Example 14 ○ ? ? Honorable Mention 15 ? ? ? Inventive Example 16 ? ? ○ Comparative Example 6 △ ? ? Comparative Example 7 ? ○ × Comparative Example 8 ? ○ △ Comparative Example 9 ○ ? △ Comparative Example 10 △ ? ? Surface stain Comparative Example 11 ○ ? ? Gloss Comparative Example 12 △ ? ? Gloss

As can be seen in Table 4, Comparative Example 11 and Comparative Example 12 when the matting agent is used out of the range of 0.8 to 2 parts by weight was poor in gloss. When a small amount of silicone compound was used (Comparative Example 6), the press formability was lowered, and when used in an excessive amount (Comparative Example 7 and Comparative Example 8), the blocking property was lowered. When a small amount of a blocking improving agent was used (comparative example 9), blocking property fell, and when used excessively (comparative example 10), press workability fell.

Claims (17)

Subject resin; And
Polymer beads in which beads having a particle diameter of 1.4 to 1.8 times and beads having a particle diameter of 1.0 to 1.3 times are mixed with the dry coating film thickness of the resin coating layer;
Resin composition for surface treatment comprising a.
The method of claim 1,
The polymer bead is a resin composition for surface treatment, characterized in that the bead particles having a particle diameter of 1.4 to 1.8 times and the bead particles having a particle diameter of 1.0 to 1.3 times are mixed in a weight ratio of 1: 1 to 4 with respect to the dry coating film thickness of the resin coating layer. .
The method of claim 1,
The polymer beads are at least one selected from the group consisting of melamine beads, acrylic beads, acrylic-styrene beads, polycarbonate beads, polyethylene beads, vinyl chloride beads, and styrene beads. .
The method of claim 1,
The polymer bead is a resin composition for surface treatment, characterized in that 4 to 20 parts by weight based on 100 parts by weight of total solids.
The method of claim 1,
The main resin is at least one selected from the group consisting of polyester resins, epoxy resins, urethane resins, acrylic resins and alkyd resins.
The method of claim 1,
The main resin is a resin composition for surface treatment, characterized in that the glass transition temperature of 15 to 75 ℃.
The method of claim 1,
The main resin is a resin composition for surface treatment, characterized in that 60 to 90 parts by weight based on 100 parts by weight of total solids.
The method of claim 1,
A resin composition for surface treatment, further comprising a matting agent.
The method of claim 8,
The matting agent is a resin composition for surface treatment, characterized in that the wax coated silica.
The method of claim 8,
The matting agent is 0.8 to 2 parts by weight based on 100 parts by weight of total solids, the resin composition for surface treatment.
The method of claim 1,
A resin composition for surface treatment, further comprising a silicone compound.
The method of claim 11,
The silicone compound is a resin composition for surface treatment, characterized in that at least one selected from the group consisting of silicone oil and polysiloxane.
The method of claim 11,
The said silicone compound is 0.2-2 weight part with respect to 100 weight part of total solids, The resin composition for surface treatments characterized by the above-mentioned.
The method of claim 1,
A resin composition for surface treatment, further comprising a blocking improver.
15. The method of claim 14,
The blocking improving agent is a resin composition for surface treatment, characterized in that the acrylic polymer forming an interface with a non-polar site and a polar site.
15. The method of claim 14,
The blocking improving agent is a resin composition for surface treatment, characterized in that 0.3 to 3 parts by weight based on 100 parts by weight of total solids.
A steel sheet comprising a coating layer containing a cured product of the resin composition for surface treatment according to any one of claims 1 to 16.

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