KR20090026572A - 2-component type aqueous polyurethane coating composition - Google Patents

Abstract

A 2-component type aqueous polyurethane coating composition is provided to ensure scratch resistance, chemical resistance, abrasion resistance and durability with showing excellent appearance and adhesion property. A 2-component type aqueous polyurethane coating composition comprises the first aqueous component and the second component including a cross-linking agent. The first aqueous component comprises the first polyurethane water-dispersible resin containing a liberated hydroxyl group, and the second polyurethane water-dispersible resin different from the first polyurethane water-dispersible resin.

Description

2-component water-based polyurethane coating composition {2-COMPONENT TYPE AQUEOUS POLYURETHANE COATING COMPOSITION}

The present invention relates to a two-component aqueous polyurethane coating composition, and more particularly, a first polyurethane water-dispersion resin containing a free hydroxyl group and a second poly different from the first polyurethane water-dispersion resin. It consists of an aqueous first component containing a urethane water-dispersing resin and a second component containing a crosslinking agent. In particular, it exhibits excellent appearance and adhesion when coated on a thermoplastic material, and at the same time, scratch resistance, chemical resistance, abrasion resistance, and durability. It relates to a two-component aqueous polyurethane coating composition excellent in coating properties such as.

In general, steel has excellent rigidity depending on its inherent properties, but there is a problem that rust occurs when exposed to moisture, and plastics are vulnerable to chemicals, erosion, ultraviolet rays, or discoloration. Has surface defects coming. In order to solve these problems, conventionally, a solvent type or a water-soluble paint is coated on the surface of these materials to compensate for the drawbacks of steel or plastic materials, and at the same time, color has been improved to improve appearance.

However, as the society develops, the demand level of consumers' products is also increasing. Recently, consumers who want to be given a softer and more luxurious texture not only in physical properties and appearance but also in the surface characteristics of the materials are frequently encountered in real life. Needs are increasing.

In the case of automotive interior materials, ABS (acrylonitrile-butadiene-styrene resin), MPPO (modified polyphenylene oxide), PP (polypropylene), PVC (polyvinyl chloride), or TPO (thermoplastic polyolefin) is mainly used. Recently, there are no disadvantages (scratch resistance, release agent flow, deterioration, etc.) of existing materials, and the low injection temperature results in long life of the injection mold and the need for painting. Material is introduced. Due to these advantages, the application of TPU materials is expected to expand despite the disadvantage that they are rather expensive compared to typical TPO materials.

When painting is required for automobile interior materials made of TPU materials, the application of water-soluble paints in recent years in terms of VOC regulation of interior coatings and vehicle interior odors is required.

As a water-soluble paint applied to a TPU material, a one-component type using a polyester-based polyurethane water-dispersion resin as a binder or a two-component type using a water-dispersible hydroxyl intermediate mixed with a water-dispersible isocyanate having excellent miscibility is generally used. to be. Polyurethane water dispersion resins are widely used for automotive plastic paints because they exhibit excellent physical properties in abrasion, impact, or scratch resistance, and these properties are adjacent packing due to small particle size and narrow molecular weight distribution. ) And high coalescence.

Polyurethane water dispersion resins can be manufactured in a variety of materials from hard and hard to soft and flexible polymers, and use of polyurethane water dispersion resins in terms of improving physical properties and appearance quality of various plastic materials used in the automotive industry. The area is expanding.

On the other hand, in terms of toughness and chemical resistance of the coating film, the two-component water dispersion polyurethane coating composition is more effective.

The properties of coatings formed from two-component water-based polyurethane paints are comparable to those of traditional coatings, and some of the superior physical properties of conventional hard plastic materials are possible. However, in the TPU material, a high flexibility of the coating film must be designed, which may cause problems in mechanical properties such as wear resistance.

Therefore, in order to apply the two-component water-based polyurethane paint to the TPU material, the amount of hydroxyl intermediate (eg, polyol) must be increased to some extent even though the hydrolysis stability is reduced in order to give flexibility and elasticity to the coating film. At the same time, in order to impart mechanical properties, the crosslinking density of the coating film should be as high as possible, whether by hydrogen bonding or covalent bonding. However, a crosslinked polymer having a high crosslinking density has a high glass transition temperature, poor coalescence, and thus it is difficult to form a continuous coating film under a normal drying temperature. Therefore, when the conventional two-component water-based polyurethane paint is applied to a soft plastic such as a TPU, chemical resistance and abrasion resistance are deteriorated.

The present inventors have studied to solve the problems described above, and as a result, the polyurethane water-containing resin containing free hydroxyl group in place of the water-soluble hydroxyl group intermediate generally used as a binder of the polyurethane-based paint The present invention was completed by discovering that excellent coating properties can be realized by using a two-component polyurethane coating composition comprising an aqueous first component and a second component including a crosslinking agent.

Therefore, the present invention improves the weak physical properties of the conventional water-soluble paint, and has excellent coating properties such as scratch resistance, chemical resistance, abrasion resistance, and durability, and excellent slip property and appearance characteristics, and less smell after drying the coating film, and workability. It is an object of the present invention to provide a two-component aqueous polyurethane coating composition which is excellent in this and is particularly suitable for soft plastic materials such as TPU.

In order to solve the above technical problem, the present invention includes a first polyurethane water dispersion resin containing a free hydroxyl group and a second polyurethane water dispersion resin different from the first polyurethane water dispersion resin. Provided is a two-component aqueous polyurethane coating composition comprising an aqueous first component and a second component containing a crosslinking agent.

The present invention also provides a two-component aqueous polyurethane comprising a first polyurethane water dispersion resin containing a free hydroxyl group and a second polyurethane water dispersion resin different from the first polyurethane water dispersion resin. It provides an aqueous composition for coating.

The present invention also provides a thermoplastic polyurethane product coated with the two-component aqueous polyurethane coating composition.

When the two-component water-based polyurethane coating composition according to the present invention is applied to a soft plastic material such as a TPU, it has excellent workability and shows excellent appearance and adhesion, and at the same time, a coating film of scratch resistance, chemical resistance, abrasion resistance, and durability. The physical properties can be improved, the smell is less after drying the coating film, it is possible to obtain the effect of controlling the thixotropy without using a separate acrylic or urethane thickener to give thixotropy for improving spray workability.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated more concretely.

The first polyurethane water-dispersion resin contained in the two-component water-based polyurethane coating composition according to the present invention is an aqueous polyurethane water-dispersion resin containing free hydroxyl groups, for example, poly-containing free hydroxyl groups. Ester-based, polyether-based, polycarbonate-based or polyurea-based polyurethane water-dispersion resins may be used alone or in combination, and in view of texture properties, free hydroxyl group-containing polyester-based polyurethane water-dispersion resins are preferably used. Used. In addition, in view of maintaining the balance between the texture and the coating film properties, the number average molecular weight of the first polyurethane water dispersion resin is preferably 10,000 to 30,000 and the elongation is 400 to 1000%, and the glass hydroxide in the first polyurethane water dispersion resin is preferred. The hydroxyl group content is preferably 1 to 5% by weight. Preferably, the free hydroxyl group is introduced into the chain of the first polyurethane water dispersion resin.

The two-component aqueous polyurethane coating composition of the present invention preferably contains 13 to 28 parts by weight of the first polyurethane water dispersion resin per 100 parts by weight of the composition, and more preferably contains 13 to 20 parts by weight. When the content of the first polyurethane water dispersion resin per 100 parts by weight of the two-component composition may be less than 13 parts by weight, there may be a problem of adhesion to the material, and when using more than 28 parts by weight, the paint price may be increased and the hiding power may be reduced.

The second polyurethane water dispersion resin contained in the two-component water-based polyurethane coating composition according to the present invention is a polyurethane water dispersion resin of a different kind from the first polyurethane water dispersion resin, for example, polyether-based or polyester-based Alternatively, polycarbonate-based polyurethane water dispersion resins may be used alone or in combination, and polyether-based polyurethane water dispersion resins are preferably used in view of hydrolysis resistance in coating films or paints. The number average molecular weight is 50,000 to 100,000, the elongation is 500 to 1000%, the tensile strength is 3000 to 6000psi, the particle size is preferably 50 to 300nm, but is not particularly limited thereto. If the molecular weight of the second polyurethane water dispersion resin is less than 50,000, the solvent resistance and water resistance of the coating film may deteriorate. If the amount of the second polyurethane water dispersion resin exceeds 100,000, the viscosity may increase and the handleability may deteriorate. In addition, when the elongation of the second polyurethane water-dispersion resin is lower than 500%, it is easy to lose the characteristic of the texture paint, and when it is higher than 1000%, viscosity remains on the coating film, and physical properties such as stain resistance, scratch resistance, and wear resistance are deteriorated. Can be.

The two-component aqueous polyurethane coating composition of the present invention preferably contains 6 to 12 parts by weight of the second polyurethane water dispersion resin per 100 parts by weight of the composition, and more preferably 8 to 12 parts by weight. If the content of the second polyurethane water-dispersion resin per 100 parts by weight of the two-component composition is less than 6 parts by weight, it is difficult to obtain a luxurious texture, and if it exceeds 12 parts by weight, there may be a problem in material adhesion.

The crosslinking agent included in the two-component aqueous polyurethane coating composition according to the present invention has a functional group capable of bonding with a hydroxyl group to form a coating film. For example, a polyisocyanate-based, aziridine-based or carbodiimide-based crosslinking agent may be used, and the crosslinking agent may be used. In consideration of physical properties such as sensitivity quality (hand feel when touched), light resistance and chemical resistance by density, water dispersible polyisocyanate (eg, hexamethylene diisocyanate (HDI)) is preferably used. The NCO content of the preferred water-dispersible polyisocyanate is 16-18%, and the number of NCO functional groups in one molecule is 3.5-4.5.

Since the crosslinking of the aqueous polyurethane resin is accompanied by an addition reaction, the reaction ratio (NCO: OH) of the isocyanate group of the polyisocyanate group and the hydroxyl group group of the first polyurethane water dispersion resin is preferably in the range of 1: 1.3 to 1.8 in equivalent ratio. Do. When the reaction ratio of the hydroxyl group to the isocyanate group is less than 1.3, it is easy to cause a decrease in coating film properties such as wear resistance and chemical resistance, and when it exceeds 1.8, the coating film becomes hard and the texture may be degraded.

It is preferable that the said crosslinking agent is contained 4-8 weight part per 100 weight part of compositions in the two-component aqueous polyurethane coating composition of this invention. When the content of the crosslinking agent per 100 parts by weight of the two-component composition is less than 4 parts by weight, sufficient reaction with the free hydroxyl groups in the first polyurethane water dispersion resin is not possible, and the coating film properties such as wear resistance tend to be lowered. There is a fear that the quality of the emotion is deteriorated while the coating film is hard.

In addition to the essential components as described above, the two-component aqueous polyurethane coating composition of the present invention contains a matting agent such as amorphous synthetic silica, a dimethyl siloxane-based silicone additive, a polysiloxane-based surface lubricant for improving the appearance and appearance of the coating film, and a non- It is preferable that additives, such as an ionic hydrophobic surfactant, are further contained.

When the water-based polyurethane coating composition of the present invention is used as an indoor paint, a low gloss of 1 to 2% is required on the appearance of 60 ° gloss. The degree of gloss is influenced by factors such as the roughness of the coating surface, the form of solvent evaporation and film shrinkage, the coating process, the temperature and humidity conditions, the composition of the solvent and the additive, and are primarily determined by the roughness of the coating film surface. In order to exhibit the effect of roughening the surface of the coating film, materials generally used in paints include silica, talc, or calcium carbonate. After the paint is applied to the material, the matting agent is uniformly distributed in the wet coating film, and as the solvent or water evaporates, the thickness of the coating film decreases, and as the film shrinks, the rough surface of the matting agent appears. Diffuse light is diffused and scattered on rough surfaces, reducing gloss.

As a matting agent for attenuating the glossiness of a coating film, it is preferable to use micronized silica, and it is preferable that the average particle diameter is 5-10 microns. Micronitrated silica can be classified into heat treatment, precipitation type, organic coating, fumed, wax coated silica, and gel according to the manufacturing method thereof, and heat treatment method for securing physical properties such as transparency, quenching efficiency and scratch resistance of dry coating film. It is advantageous to use micronized silica, which is prepared with excellent hardness properties. The use of waxed silica can improve the surface texture but can also lead to reduced sharpness in the dry coating.

The two-component aqueous polyurethane coating composition of the present invention preferably contains 1 to 5 parts by weight of the quencher per 100 parts by weight of the composition. If the content of the matting agent per 100 parts by weight of the two-component composition is less than 1 part by weight, the matting effect cannot be sufficiently obtained. If the content of the matting agent is more than 5 parts by weight, the porous material of the matting agent such as silica absorbs the resin powder, thereby lowering the adhesion and softening the coating film. It may cause a deterioration of the degree, and there is a concern that the amorphous film is formed on the surface in an amorphous manner, and thus, the scratch property is weak.

In general, an acrylic type or a silica type thickener is added to the coating composition to improve spray workability of the paint. However, acrylic type alkali wetting emulsion thickeners are difficult to apply to coatings of soft plastic materials, such as thermoplastic polyurethanes, due to their brittle characteristics. In addition, the inorganic layered silica type thickener has a high viscosity in a low shear region, and thus bubbles are easily generated, resulting in poor smoothness of the coating surface and problems in storage. Therefore, as the thickener of the polyurethane material paint, many urethane-based thickeners having similar surface characteristics are used. However, urethane thickeners have excellent thickening effects regardless of pH, but generally have poor spray workability and poor wear resistance of the coating film.

On the other hand, when 0.1 to 1 parts by weight of DMEA (N, N-dimethylethanolamine) is added to 100 parts by weight of the composition to the two-component aqueous polyurethane coating composition of the present invention, thixotropy is controlled by pH, Excellent spray workability can be achieved without using the same thickener separately. If the amount of DMEA is less than 0.1 parts by weight, the thickening effect is insignificant, and if it exceeds 1 part by weight, there may be a paint storage deterioration and odor problems.

In addition, in addition to the components as described above, the coating composition of the present invention may be used as necessary conventional pigments and additives known in the art.

According to one embodiment of the present invention, the two-component water-based polyurethane coating composition of the present invention, dehydration of the water dispersion of the first polyurethane resin and the water dispersion of the second polyurethane resin having an appropriate solid content in an appropriate amount. It is mixed with ionic water, and if necessary, additional additive components such as a matting agent, a surfactant, a surface lubricant, an antifoaming agent, a DMEA, a colorant, and the like are mixed, followed by stirring to prepare an aqueous first component, and separately from the crosslinking agent alone. It can be obtained by preparing a second component or a second component in which a conventional additive and / or a solvent is further included in the crosslinking agent as necessary, and then mixing the first component and the second component.

Thus, according to the present invention, a two-component aqueous solution comprising a first polyurethane water dispersion resin containing a free hydroxyl group and a second polyurethane water dispersion resin different from the first polyurethane water dispersion resin Also provided are aqueous compositions for polyurethane paints.

There is no particular limitation on the equipment and manufacturing conditions used in the production of the first component and the second component, it is possible to manufacture under the conditions normally applied by the equipment commonly used in the art.

The two-component aqueous polyurethane coating composition of the present invention can be applied to any material such as steel, plastic, etc., but is suitably applied to soft plastic products, in particular, thermoplastic polyurethane (TPU) products. TPU products include, but are not limited to, automotive interior and exterior components, especially trim, panels, consoles, seats, top sealers or airbag covers.

Thus, according to the invention, there is also provided a thermoplastic polyurethane product coated with the two-component aqueous polyurethane coating composition.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, these examples are only to aid the understanding of the present invention, and the present invention is not limited thereto.

Example  1 and 2 and Comparative example  1 to 3

Resin water products A), B) and deionized water I) as shown in Table 1 were placed in a container, and amorphous synthetic silica D) was added while mixing at a low speed using a stirrer, and dispersed at 1000 rpm for 10 minutes. An acetylenic diol nonionic surfactant E), a polysiloxane surface lubricant F), an antifoaming agent G), a DMEA H) and a colorant J) were added thereto, followed by stirring for 10 minutes.

Next, the water dispersion type polyisocyanate C) was mixed and if necessary, the viscosity was adjusted to 55-65 seconds in a pod cup (NO # 4) using deionized water.

The composition and content of the specific coating composition described in each example are as shown in Table 1 below.

A) hydroxyl group-containing aliphatic polyester-based polyurethane resin water dispersion (solid content: 55% by weight, Bayer): number average molecular weight about 20,000, elongation about 700%, hydroxyl group content 3%

B) Polyether-based polyurethane resin water dispersion (solid content: 40% by weight, Bayer): number average molecular weight about 75,000, average particle size about 180nm, elongation about 750%, tensile strength about 4500 PSI

C) Water Dispersible Polyisocyanate (HDI TRIMER)

D) Wax Modified Micronized Silica

E) Acetylene Diol Nonionic Surfactant

F) Polysiloxane Surface Lubricant

G) defoamer

H) DMEA

I) deionized water

J) colorant (black)

Test Example

Using each of the compositions prepared in Examples and Comparative Examples, spray-coated with a dry coating thickness of 15 to 20 microns to the primer-coated TPU specimens, and then dried for 20 minutes at a temperature of 80 ℃ left for 72 hours The specimens were used to evaluate the following properties.

1) Appearance

After drying the coated sample for 20 minutes at 80 ℃, compare the degree of bubble, foreign matter, spot, groove, and smoothness of surface with 1.5 ~ 2.0% of standard on 60 ° gloss. If not, it was judged to be excellent.

2) adhesion

Based on the ASTM D3359 tape adhesion test method, the degree of peeling after the tape adhesion test in 100 1 mm x 1 mm scales was observed.

3) Chemical resistance

75% aqueous solution was prepared using isobutyl alcohol, ethanol, and methanol, and the result of 20 round trip rub tests was observed after soaking in a soft cloth. The test result was judged to be excellent when the coating film was not peeled off or discolored.

4) Weather resistance

An accelerated weather resistance tester using a xenon light source was tested at a blackboard panel temperature of 83 ± 3 ° C. for 500 hours and observed for defects that were problematic in practical use. It was judged to be excellent when there was no abnormality in adhesion (100/100), color difference (ΔE 2.0 or less), and glossiness change (± 0.3).

5) wear resistance

Abrasion tester 100 mm stroke and 30 mm per second were used to compare the degree of wear when tested 500 times perpendicular to the coating surface at a load of 1000 g. In the test results, the numerical value indicates the number of round trips until the coating peels off. It was judged to be excellent when the coating film did not peel off in more than 500 tests.

6) solvent resistance

Toluene was applied to the cloth and rubbed 10 times with a 500g load. The test result was judged to be excellent when the coating film was not peeled off or discolored.

7) smell

The completely dried coating film was left at room temperature for 7 days, cut into squares of 5 cm x 6 cm, placed in a fully sealed steel container, and heated for 2 hours in a heating furnace adjusted to 100 ° C. When the test was completed, the container was left at room temperature for 1 hour, and then the lid was opened to compare the degree of smell. The odor grade was divided into 1 ~ 5 grade and judged to be excellent when it was above 3 grade.

8) Slip

When rubbed by hand, the degree of texture was evaluated.

Physical property evaluation and measurement results of the above items are shown in Table 2 below.

As can be seen in Table 2, the coating film prepared using the coating composition according to the present invention is excellent in appearance, less smell after drying, and excellent physical properties such as adhesion, chemical resistance, abrasion resistance, solvent resistance, etc. It was.

Claims (6)

It consists of an aqueous 1st component containing the 1st polyurethane water dispersion resin containing a free hydroxyl group, and the 2nd polyurethane water dispersion resin different from the said 1st polyurethane water dispersion resin, and the 2nd component containing a crosslinking agent. Two-component aqueous polyurethane coating composition. The coating composition according to claim 1, wherein the first polyurethane water dispersion resin is a polyester-based polyurethane water dispersion resin containing free hydroxyl groups and having a number average molecular weight of 10,000 to 30,000. The coating material according to claim 1, wherein the crosslinking agent is polyisocyanate, and the reaction ratio (NCO: OH) of the isocyanate group of the polyisocyanate group and the hydroxyl group of the first polyurethane water dispersion resin is 1: 1.3 to 1.8 in equivalent ratio. Composition. The coating composition according to claim 1, which does not contain a separate thickener. An aqueous composition for two-component polyurethane coatings comprising a first polyurethane water dispersion resin containing a free hydroxyl group and a second polyurethane water dispersion resin different from the first polyurethane water dispersion resin. Thermoplastic polyurethane article coated with a two-component aqueous polyurethane coating composition according to any one of claims 1 to 4.