KR101412758B1 - Two component aqueous polyurethane coating composition - Google Patents

Abstract

More particularly, the present invention relates to a two-component aqueous polyurethane coating composition comprising a first polyurethane water-dispersible resin containing a free hydroxyl group and a second polyurethane water-dispersible resin different from the first polyurethane water- An aqueous first component comprising a urethane water-dispersible resin, and a second component comprising a crosslinking agent. In particular, the composition exhibits excellent appearance and adhesion performance when applied to a thermoplastic material, and exhibits excellent scratch resistance, chemical resistance, abrasion resistance and durability Component aqueous polyurethane coating composition which is excellent in physical properties of the coating film.

Two component type, aqueous, polyurethane, paint, composition

Description

2-COMPONENT TYPE AQUEOUS POLYURETHANE COATING COMPOSITION [0002]

More particularly, the present invention relates to a two-component aqueous polyurethane coating composition comprising a first polyurethane water-dispersible resin containing a free hydroxyl group and a second polyurethane water-dispersible resin different from the first polyurethane water- An aqueous first component comprising a urethane water-dispersible resin, and a second component comprising a crosslinking agent. In particular, the composition exhibits excellent appearance and adhesion performance when applied to a thermoplastic material, and exhibits excellent scratch resistance, chemical resistance, abrasion resistance and durability Component aqueous polyurethane coating composition which is excellent in physical properties of the coating film.

In general, steel has excellent rigidity according to its inherent properties, but has a problem of rusting when exposed to water. Plastics are vulnerable to chemicals, erosion, ultraviolet rays, or discoloration, It has a surface defect. In order to solve these problems, a solvent type or a water-soluble paint is conventionally coated on the surface of these materials to compensate for drawbacks of iron or plastic materials, and the appearance has been improved by imparting color to the materials.

However, as the society develops, the demand level of the consumer's products is increasing. In recent years, for the material frequently encountered in the real life, the consumer who wants to have a soft and luxurious texture in the surface characteristics, Is increasing.

In the case of automobile interior materials, ABS (acrylonitrile-butadiene-styrene resin), MPPO (modified polyphenylene oxide), PP (polypropylene), PVC (polyvinyl chloride) or TPO (thermoplastic polyolefin) TPU (thermoplastic polyurethane), which has advantages such as shortness of existing materials (scratch resistance, release agent flow, deterioration, etc.), low injection temperature, long life of injection mold, Materials are being introduced. Due to these advantages, the application of TPU material is expected to be expanded despite the disadvantage that TPU material is more expensive than typical TPO material.

In the case of coating an automobile interior material made of TPU material, it is recently required to apply water-soluble paint in terms of VOC regulation of interior paint and odor of vehicle interior.

As a water-soluble paint to be applied to the TPU material, a two-component type in which a one-component type or water-dispersed hydroxyl intermediate using a polyester-based polyurethane water-dispersible resin as a binder and a water-dispersible isocyanate having excellent miscibility are mixed and used to be. The polyurethane water-dispersible resin is widely used for automotive plastic coatings because it exhibits excellent physical properties in terms of abrasion resistance, impact resistance, scratch resistance, and the like. ) Effect and high coalescence.

The polyurethane water-dispersible resin can be variously manufactured from hard and hard to soft and flexible polymers. In view of improving the physical properties of various plastics used in the automobile industry and improving the appearance quality, the use of polyurethane water- The area is expanding.

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

The properties of the coating film formed from the two-component aqueous polyurethane coating are comparable to those of the conventional coating and can be somewhat superior in general hard plastic materials. However, since the TPU material needs to have a high flexibility of the coating film, it may cause problems in mechanical properties such as abrasion resistance.

Therefore, in order to apply the two-component aqueous polyurethane paint to the TPU material, the amount of the hydroxyl intermediate (for example, polyol) should be increased to some extent even if the hydrolytic stability is lowered in order to impart flexibility and elasticity to the coating film , It is necessary to maximize the cross-linking density of the coating film, whether by hydrogen bonding or covalent bonding, in order to impart mechanical properties at the same time. However, a crosslinked polymer having a high crosslinking density has a high glass transition temperature, has poor coalescence, and is difficult to form a continuous film under normal drying temperature. Therefore, when conventional conventional two-component aqueous polyurethane coatings are applied to soft plastics such as TPU, they show a disadvantage that the chemical resistance and abrasion resistance are lowered.

DISCLOSURE OF THE INVENTION The present inventors have conducted studies to solve the above problems and found that a water-soluble hydroxyl group intermediate which is generally used as a binder of a polyurethane-based coating material is replaced by a polyurethane water-dispersible resin containing a free hydroxyl group Component type polyurethane coating composition composed of an aqueous first component and a second component comprising a cross-linking agent can be used to achieve excellent coating film properties, thus completing the present invention.

Accordingly, the present invention has been made in view of the above problems, and it is therefore an object of the present invention to provide a water-soluble coating material which is excellent in physical properties such as scratch resistance, chemical resistance, abrasion resistance and durability, and excellent slip property and appearance property, And which is particularly suitable for a flexible plastic material such as TPU. The present invention also provides a two-component aqueous polyurethane coating composition.

Disclosure of the Invention In order to solve the above technical problems, the present invention provides a polyurethane resin composition comprising a first polyurethane water-dispersible resin containing a free hydroxyl group and a second polyurethane water-dispersible resin different from the first polyurethane water- And a second component comprising a cross-linking agent. The present invention also provides a two-component aqueous polyurethane coating composition comprising:

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

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

When the two-component aqueous polyurethane coating composition according to the present invention is applied to a soft plastic material such as TPU, it exhibits excellent workability, excellent appearance and adhesion performance, and is excellent in scratch resistance, chemical resistance, abrasion resistance and durability It is possible to obtain an effect of controlling the thixotropy without using a separate acrylic or urethane thickener in order to impart thixotropy for improving the spraying workability.

Hereinafter, the present invention will be described in more detail.

The first polyurethane water-dispersible resin contained in the two-component aqueous polyurethane coating composition according to the present invention is an aqueous polyurethane water-dispersible resin containing a free hydroxyl group, and examples thereof include poly Ester-based, polyether-based, polycarbonate-based or polyurea-based polyurethane water-dispersible resins may be used alone or in combination, and in view of texture properties, a free hydroxyl group-containing polyester-based polyurethane water- Is used. From the viewpoint of balance of texture and physical properties of the coating film, it is preferable that the number-average molecular weight of the first polyurethane water-dispersible resin is 10,000 to 30,000 and the elongation is 400 to 1000%. In the first polyurethane water- The content of the alkyl group is preferably 1 to 5% by weight. The free hydroxyl group is preferably introduced into the chain of the first polyurethane water-dispersible 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-dispersible resin per 100 parts by weight of the composition, more preferably 13 to 20 parts by weight. If the content of the first polyurethane water-dispersible resin is less than 13 parts by weight per 100 parts by weight of the two-component composition, there may be a problem of adhesion to the material, and when the content is more than 28 parts by weight, the paint price and hiding power may be lowered.

The second polyurethane water-dispersible resin contained in the two-component aqueous polyurethane coating composition according to the present invention is a polyurethane water-dispersible resin of a different kind from the first polyurethane water-dispersible resin, and examples thereof include polyether- Or a polycarbonate-based polyurethane water-dispersible resin may be used singly or in combination, and a polyether-based polyurethane water-dispersible resin is preferably used in view of the hydrolysis resistance of the coating film or the coating material. The number average molecular weight is preferably from 50,000 to 100,000, the elongation is from 500 to 1,000%, the tensile strength is from 3,000 to 6,000 psi, and the particle size is from 50 to 300 nm. If the molecular weight of the second polyurethane water-dispersible resin is less than 50,000, the solvent resistance and water resistance of the coating film may deteriorate. If the molecular weight exceeds 100,000, viscosity may increase and handling property may deteriorate. When the elongation percentage of the second polyurethane water-dispersible resin is lower than 500%, the characteristics of the textured paint are easily lost. When the elongation of the second polyurethane water-dispersible resin is higher than 1000%, the coating film remains viscous and the properties such as stain resistance, scratch resistance and abrasion resistance are deteriorated .

The two-component aqueous polyurethane coating composition of the present invention preferably contains 6 to 12 parts by weight of the second polyurethane water-dispersible resin per 100 parts by weight of the composition, more preferably 8 to 12 parts by weight. If the content of the second polyurethane water-dispersible resin is less than 6 parts by weight per 100 parts by weight of the two-component composition, a high-quality texture is difficult to obtain. If the content is more than 12 parts by weight,

The crosslinking agent contained in the two-component aqueous polyurethane coating composition according to the present invention has a functional group capable of binding with a hydroxyl group in order to form a coating film. For example, a polyisocyanate, aziridine or carbomide crosslinking agent may be used, A water-dispersible polyisocyanate (for example, hexamethylene diisocyanate (HDI)) is preferably used in consideration of the physical properties such as sensibility by densification (touch felt on the hand), light fastness and chemical resistance. The preferred water-dispersible polyisocyanate has an NCO content of 16 to 18% and a number of NCO functional groups per molecule of 3.5 to 4.5.

Since the crosslinking of the aqueous polyurethane resin accompanies the addition reaction, the reaction ratio (NCO: OH) of the isocyanate group of the polyisocyanate to the hydroxyl group of the first polyurethane water-dispersible resin is preferably in the range of 1: 1.3 to 1.8 Do. When the reaction ratio of the hydroxyl group to the isocyanate group is less than 1.3, deterioration of physical properties such as abrasion resistance and chemical resistance tends to occur. If the ratio is more than 1.8, the coating film becomes hard and the texture may be deteriorated.

The two-component aqueous polyurethane coating composition of the present invention preferably contains 4 to 8 parts by weight of the crosslinking agent per 100 parts by weight of the composition. If the content of the crosslinking agent per 100 parts by weight of the two-component type composition is less than 4 parts by weight, sufficient physical reaction with the free hydroxyl groups in the first polyurethane water-dispersible resin can not be performed and the physical properties such as abrasion resistance tends to deteriorate. There is a fear that the quality of the sensibility may deteriorate due to the hard coating film.

The two-component aqueous polyurethane coating composition of the present invention may contain, in addition to the above-mentioned essential components, a quencher such as amorphous synthetic silica, a dimethylsiloxane-based silicone additive, a polysiloxane- It is preferable that an additive such as an ionic hydrophobic surfactant is further included.

When the aqueous polyurethane coating composition of the present invention is used as an indoor paint, a low gloss of 1 to 2% is apparently required on a 60 degree gloss basis. The degree of gloss is affected by factors such as surface roughness, solvent evaporation and film shrinkage, coating process, temperature and humidity conditions, composition of solvent and additive, and is 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 used in paints generally include silica, talc, or calcium carbonate. After the paint is applied to the material, the quencher is uniformly distributed in the wet film, and as the solvent or water evaporates, the thickness of the film decreases and the film shrinks and the rough surface of the quencher appears. The diffused and scattered light can be reflected on the rough surface and the gloss can be lowered.

As the quenching agent for attenuating the gloss of the coating film, micronized silica is preferably used, and its average particle size is preferably 5 to 10 microns. Micronized silica can be classified into heat treatment, sedimentation type, organic coating, fumed silica, wax-coated silica and gel according to the production method. In order to secure properties such as transparency, quenching efficiency and scratch resistance of the dried film, It is advantageous to use micronized silica excellent in hardness characteristics. When wax-treated silica is used, the surface texture may be improved, but the sharpness of the dried coating film may be lowered.

The two-component aqueous polyurethane coating composition of the present invention preferably contains 1 to 5 parts by weight of the light extinguishing agent per 100 parts by weight of the composition. When the amount of the quencher is less than 1 part by weight per 100 parts by weight of the two-component composition, the quenching effect can not be sufficiently obtained. When the amount of the quencher exceeds 5 parts by weight, And may form an irregular film on the surface due to its amorphous shape, so that there is a concern that the film exhibits weak characteristics to scratches.

In general, an acrylic type or silica type thickening agent is added to the coating composition in order to improve the spraying workability of the coating material. However, acrylic type alkali wettable emulsion thickeners are difficult to apply to coatings of soft plastics such as thermoplastic polyurethanes due to their brittle nature. In addition, the inorganic layered silica type thickener has a high viscosity in a low shear region, so that bubbles are easily generated, the smoothness of the coating surface is poor, and the storage stability may be problematic. Therefore, a urethane-based thickener having a similar surface property is often used as a thickener for a polyurethane coating material. However, the urethane thickener is excellent in the thickening effect irrespective of the pH, but in general, the spraying workability is poor and the abrasion resistance of the coating film is also poor.

On the other hand, when 0.1 to 1 part by weight of DMEA (N, N-dimethylethanolamine) is added to the two-component aqueous polyurethane coating composition of the present invention per 100 parts by weight of the composition, thixotropy is controlled by the pH, Excellent spraying workability can be achieved without using the same thickener separately. If the amount of the DMEA is less than 0.1 parts by weight, the effect of increasing the viscosity is insignificant. If the amount of the DMEA is more than 1 part by weight, the storage stability of the paint and the smell may be a problem.

In addition to the above-mentioned components, conventional paints and additives known in the art may be used in the coating composition of the present invention as needed.

According to one embodiment of the present invention, the two-component aqueous polyurethane coating composition of the present invention is a two-component aqueous polyurethane coating composition comprising an aqueous dispersion of the first polyurethane resin having an appropriate solid content and an aqueous dispersion of the second polyurethane resin The mixture is mixed with ionized water, and if necessary, an additive component such as a quencher, a surfactant, a surface lubricant, a defoamer, a DMEA and a coloring agent is further mixed and stirred to prepare an aqueous first component, The second component may be obtained by preparing a second component which further comprises conventional additives and / or solvents in the two components or, if necessary, in the crosslinking agent, and then mixing the first component and the second component.

Therefore, according to the present invention, there is provided a two-component aqueous polyurethane resin composition comprising a first polyurethane water-dispersible resin containing a free hydroxyl group and a second polyurethane water-dispersible resin different from the first polyurethane water- An aqueous composition for a polyurethane coating is also provided.

There are no particular restrictions on the equipment and manufacturing conditions used in the production of the first component and the second component, and it is possible to manufacture them under the generally applicable conditions by equipment commonly used in this field.

The two-component aqueous polyurethane coating composition of the present invention can be applied to any material such as iron and plastic materials, but is suitably applied to soft plastic products, particularly thermoplastic polyurethane (TPU) products. TPU products include, but are not limited to, automotive interior and exterior parts, in particular trim, panel, console, seat, top sealer or airbag cover.

Therefore, according to the present 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 embodiments are provided for the purpose of helping understanding of the present invention, but the present invention is not limited thereto.

Example  1 to 2 and Comparative Example  1-3

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

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

The composition and content of the concrete paint compositions described in the respective Examples are as shown in Table 1 below.

A) Aliphatic polyester polyurethane resin water dispersion containing hydroxyl group (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 diameter about 180 nm, elongation about 750%, tensile strength about 4500 PSI

C) Water-dispersible polyisocyanate (HDI TRIMER)

D) wax-modified micronized silica

E) acetylenic diol type nonionic surfactant

F) Polysiloxane-based surface lubricant

G) Defoamer

H) DMEA

I) Deionized water

J) Concentrate (black)

Test Example

The primer-coated TPU specimens were spray coated at a dry film thickness of 15 to 20 microns using the respective compositions prepared in the above Examples and Comparative Examples, dried at 80 ° C for 20 minutes, and left for 72 hours The properties of the following items were evaluated using specimens.

1) Appearance

After drying the painted samples at 80 ° C for 20 minutes, it is necessary to compare the bubble, foreign matter, spots, grooves, and smoothness of the surface with the specifications of 1.5 ~ 2.0% It was judged to be excellent.

2) Adhesiveness

Based on the ASTM D3359 tape adhesion test method, the degree of the peeled portion was observed after the tape adhesion test among 100 pieces of 1 mm x 1 mm scale.

3) Chemical resistance

A 75% aqueous solution was prepared using isobutyl alcohol, ethanol, and methanol, respectively. The resultant was wetted with a soft cloth and subjected to 20 reciprocating rub tests. As a result of the test, it was judged to be excellent when the film was peeled off or discolored.

4) Weatherability

The test was carried out at a temperature of 83 ± 3 ℃ for 500 hours with a panel temperature of accelerated weathering test using a Xenon light source. (100/100), color difference (ΔE 2.0 or less) and gloss change (± 0.3).

5) Abrasion resistance

The abrasion test was carried out 500 times perpendicular to the surface of the film with a load of 1000 g using an abrasion tester moving 100 mm of stroke and 30 mm per second. The result of the test shows the number of round trips until the coating is peeled off. It was judged to be excellent when the film was not peeled off in the test of 500 times or more.

6) Solvent resistance

Toluene was rubbed on the cloth and rubbed with a 500 g load ten times. As a result of the test, it was judged to be excellent when the film was peeled off or discolored.

7) Smell

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

8) Sleepiness

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

The physical properties of the above items and the measurement results are shown in Table 2 below.

As can be seen from Table 2, the coating film prepared using the coating composition according to the present invention has excellent appearance, has a small odor after drying, has excellent properties such as adhesion, chemical resistance, abrasion resistance and solvent resistance Respectively.

Claims (6)

An aqueous first component comprising a first polyurethane water-dispersible resin containing a free hydroxyl group and a second polyurethane water-dispersible resin different from the first polyurethane water-dispersible resin, and a second component comprising a crosslinking agent In addition, From here, The first polyurethane water-dispersible resin is a polyester-based polyurethane water-dispersible resin containing 1 to 5 wt% of a free hydroxyl group, a number average molecular weight of 10,000 to 30,000, and an elongation of 400 to 1000% Is 13 to 28 parts by weight per 100 parts by weight of the two-component aqueous polyurethane coating composition, The second polyurethane water-dispersible resin is a polyether-based polyurethane water-dispersible resin having a number average molecular weight of 50,000 to 100,000, an elongation of 500 to 1000%, a tensile strength of 3000 to 6000 psi, and a particle size of 50 to 300 nm , The content thereof is 6 to 12 parts by weight per 100 parts by weight of the two-component aqueous polyurethane coating composition, The crosslinking agent is an aqueous dispersion type polyisocyanate, and the content thereof is 4 to 8 parts by weight per 100 parts by weight of the two-component aqueous polyurethane coating composition, A two component aqueous polyurethane coating composition. The method according to claim 1, wherein the reaction ratio (NCO: OH) of the isocyanate group of the water-dispersible polyisocyanate crosslinking agent to the hydroxyl group of the first polyurethane water-dispersible resin is 1: 1.3 to 1.8, Polyurethane coating composition. The two-component aqueous polyurethane coating composition according to claim 1, which does not contain a separate thickener. A thermoplastic polyurethane product coated with a two-component aqueous polyurethane coating composition according to any one of claims 1 to 3. delete delete