KR20190037577A - Clearcoat composition - Google Patents

Abstract

The present invention relates to a clear coat composition having excellent appearance and flowability of a coating film. The clear coat composition comprises: a polyester-urethane copolymer; a urea dispersion acryl resin; and acryl polyol.

Description

Clear coat composition {CLEARCOAT COMPOSITION}

The present invention relates to a clearcoat composition used for coating an automobile exterior.

In the conventional painting process for automobiles, a two-part type paint using an isocyanate-based curing agent for the clear coat or a paint for imparting elasticity to the intermediate layer was used for improving the endurance chipping resistance and impact resistance of the final coat.

In this connection, although the patent literature discloses a technique relating to a primer composition for automotive paint using an epoxy-modified polyester resin and a block isocyanate curing agent, a separate process for forming a middle layer is required in the patent literature, There was a problem.

Therefore, development of a clearcoat composition capable of forming a coating film having excellent mechanical properties such as good coat film appearance, scratch resistance, resistance to chipping, impact and the like is not required, because a separate intermediate layer is not formed.

European Patent Registration No. 152,413

The present invention provides a clearcoat composition capable of forming a coating film having good appearance characteristics and excellent mechanical properties.

In order to achieve the above object, the present invention provides a clearcoat composition comprising a polyester-urethane copolymer, a urea-dispersed acrylic resin and an acrylic polyol.

The clearcoat composition of the present invention in which the polyester-urethane copolymer, the urea-dispersed acrylic resin and the acrylic polyol are mixed together as described above has not only excellent workability, but also has excellent appearance and mechanical properties There is an excellent advantage.

Hereinafter, the present invention will be described in detail.

The present invention provides a clearcoat composition.

The clearcoat composition of the present invention includes a polyester-urethane copolymer, a urea-dispersed acrylic resin, and an acrylic polyol. Each of the above components will be described in detail below.

[Polyester-urethane copolymer]

The clearcoat composition of the present invention comprises a polyester-urethane copolymer.

The polyester-urethane copolymer includes a repeating unit derived from polyester and a repeating unit derived from polyurethane as a constituent unit, and may be in the form of a random copolymer.

The urethane-derived repeating unit is obtained from a caprolactone polyol-derived unit and an aliphatic diisocyanate-derived unit.

The caprolactone polyol is a linear polyester diol derived from caprolactone. Although not particularly limited, the caprolactone polyol may have a weight average molecular weight (Mw) of 500-1,500. If the weight average molecular weight exceeds 1,500, the workability due to the high viscosity and the hardness of the coating film may be lowered. If the weight average molecular weight is less than 500, the mechanical and chemical properties may be deteriorated.

As the aliphatic diisocyanate, aliphatic or alicyclic hydrocarbon compounds having 2 isocyanate groups (-N = C = O) and 4 to 20 carbon atoms or 4 to 16 carbon atoms may be used alone or in combination of two or more. For example, at least one selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and combinations thereof, but is not limited thereto.

The repeating unit derived from the polyester is obtained from an aliphatic polyhydric alcohol and an aliphatic or alicyclic polybasic acid.

The aliphatic polyhydric alcohol can be used alone or as a mixture of two or more aliphatic compounds having 3 to 12 carbon atoms or 4 to 10 carbon atoms and having at least two hydroxyl groups (-OH). Examples thereof include propanediol, butanediol, Neopentyl glycol, trimethylol propane, and combinations thereof, but is not limited thereto.

The aliphatic or alicyclic polybasic acid is preferably an aliphatic polybasic acid having 3 to 12 carbon atoms, specifically 4 to 10 carbon atoms, having at least two carboxylic acid groups (-COOH), or an aliphatic polybasic acid having 5 to 12 carbon atoms, specifically 6 to 10 carbon atoms May be used singly or in combination of two or more. For example, it may be selected from hexane dicarboxylic acid, cyclohexyldicarboxylic acid, and combinations thereof, but is not limited thereto.

The polyester-urethane copolymer may have a solids content of 50-70 wt% based on the total weight, a hydroxyl value of 20-140mgKOH / g, for example 40-120mgKOH / g, or 60-80mgKOH / g Lt; / RTI > The acid value can also be 1-20 mg KOH / g, for example 2-20 mg KOH / g, or 4-10 mg KOH / g. If the hydroxyl value falls outside the above range, the coating film may be decomposed or the chipping resistance may be deteriorated. If the acid value is out of the above range, the overall mechanical and chemical properties of the coating film may be deteriorated due to the decrease in molecular weight.

The weight average molecular weight (Mw) of the polyester-urethane copolymer is not particularly limited, but the weight average molecular weight may be 2,000 to 6,000 in order to optimize the chipping resistance and other physical properties.

[Urea-dispersed acrylic resin]

The clearcoat composition of the present invention comprises a urea-dispersed acrylic resin.

The urea-dispersed acrylic resin may be contained in an amount of 20 to 200 parts by weight based on 100 parts by weight of the polyester-urethane copolymer, and the adhesion and hardness of the clearcoat composition may be prevented from deteriorating and the appearance and flowability of the coating film may be further improved The urea-dispersed acrylic resin may be contained in an amount of 50 to 100 parts by weight.

The urea-dispersed acrylic resin is one in which urea particles are physically dispersed in an acrylic resin, and 90 to 99 parts by weight of urea particles are dispersed and distributed in an acrylic resin based on 100 parts by weight of urea-dispersed acrylic resin . When the urea particles are contained in an amount exceeding the above range, the flowability is improved but the appearance (surface texture) of the coating film may be lowered. When the urea particles are less than the above range and contained in a small amount, There may be a problem that improvement can not be achieved.

By dispersing the urea particles in the acrylic resin as described above, it is possible to form a pseudo-crosslinked network structure in the paint by hydrogen bonding present in the urea particles, whereby the sagging of the composition relative to the vertical part of the coating film There is an effect to be improved. Here, flowability refers to the degree to which the composition flows when the clearcoat composition is applied and then vertically set, and the improvement in flowability means that the composition does not flow downward and the thickness remains uniform.

The acrylic resin is not particularly limited as long as urea particles can be dispersed in the acrylic resin and the appearance of the coating film using the clearcoat composition can be improved by the glass transition temperature (Tg) property. However, the glass transition temperature of the acrylic resin may be 10-50 ° C or 20-40 ° C. If the glass transition temperature is outside the above range, physical properties of the coating film may be deteriorated.

The acrylic resin may be prepared by copolymerizing an ethylenic unsaturated monomer having a hydroxy group and an ethylenic unsaturated monomer having no hydroxy group.

Examples of the ethylenic unsaturated monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, allyl alcohol, methacryloyl, 2-hydroxyethyl Acrylate and caprolactone. Examples of the ethylenic unsaturated monomer having no hydroxy group include methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (meth) (Meth) acrylate, cyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, acrylonitrile, methacrylonitrile and the like.

In addition, the acrylic resin may be one obtained by reacting an aromatic vinyl compound such as styrene, hydroxyalkyl methacrylate, alkyl acrylate and caprolactone.

As a specific preparation method, a known polymerization method such as solution radical polymerization can be used. For example, the monomer mixture and the radical polymerization initiator can be added dropwise while stirring in a solvent at a polymerization temperature of 50 to 200 DEG C for 2 to 10 hours .

The urea particles may be obtained by reacting an aliphatic diisocyanate with an amine compound.

As the aliphatic diisocyanate, aliphatic or alicyclic hydrocarbon compounds having two isocyanate groups and having 4 to 20 carbon atoms, specifically 4 to 16 carbon atoms, may be used alone or in combination of two or more. For example, hexamethylene di Isocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and combinations thereof.

The amine compound may be at least one alicyclic amine compound selected from the group consisting of benzylamine, methylbenzylamine, ethylbenzylamine, methyl aniline, ethyl aniline, diphenylamine and naphthalamine.

The amine compound may be a primary amine such as ethanolamine, methoxypropylamine, 3,4-dimethoxyphenylethylbutylamine, hexylamine, octylamine, decylamine or stearylamine.

The urea-dispersed acrylic resin may have a hydroxyl value of 100-200 mgKOH / g and a glass transition temperature of 10-50 ° C. If the hydroxyl value is less than 100 mgKOH / g, the crosslinking property of the coating film may be deteriorated. On the other hand, if the hydroxyl value is more than 200 mgKOH / g, the water resistance of the coating film may be deteriorated.

[Acrylic polyol]

The clearcoat composition of the present invention comprises an acrylic polyol.

The acrylic polyol may be contained in an amount of 80 to 500 parts by weight based on 100 parts by weight of the polyester-urethane copolymer. In addition to hardness, water resistance and weather resistance of the final coating film, physical properties such as impact resistance and chipping resistance Based on the total weight of the composition.

The acrylic polyol may have a hydroxyl value of 50-150 mgKOH / g, a glass transition temperature of 0-50 ° C, and a solid content of 45-75% by weight. The hydroxyl value of the acrylic polyol is closely related to the crosslinking density of the paint film, which affects the weatherability and hardness, and if it is outside the above range, the weatherability and hardness may be lowered.

[Other ingredients]

The clearcoat composition of the present invention may contain a curing agent. The type of the curing agent is not particularly limited, but examples thereof include hexamethylol melamine, hexamethoxymethylmelamine, hexabutoxymethylmelamine, hexamethoxybutoxymethylmelamine, Nymethoxy methyl melamine, and combinations thereof.

In this case, the curing agent may be 5-30 parts by weight, for example, 10-25 parts by weight or 15-20 parts by weight based on 100 parts by weight of the total composition.

If the curing agent is contained in an amount of less than 5 parts by weight, the coating may be backed off and the hardness and water resistance may be deteriorated. When the curing agent is more than 30 parts by weight, the coating film may become hardened and the impact resistance and chipping resistance may be deteriorated.

In addition, a curing catalyst may be included for accelerating the curing. The type of the curing catalyst is not particularly limited, and examples thereof include dodecylbenzenesulfonic acid, sulfonic acid, dinonylnaphthalene disulfonic acid, dinonylnaphthalenesulfonic acid, paratoluenesulfonic acid, At least one selected from the group consisting of

The curing catalyst may be used in an amount of 0.5-3 parts by weight based on 100 parts by weight of the composition, for example, 1-2.5 parts by weight, or 1.3-2 parts by weight.

If the curing catalyst is contained in an amount of less than 0.5 parts by weight, the crosslinking density may be lowered due to the lowering of the curing rate, and the hardness, water resistance, solvent resistance and the like may be lowered. When the amount is more than 3 parts by weight, It may become hard and cause problems such as impact resistance, chipping resistance, and re-coating adhesion.

Meanwhile, the clear coat composition of the present invention may further include at least one selected from the group consisting of a leveling agent, a light stabilizer, a storage stability improving agent, and a combination thereof in addition to the curing agent.

According to another aspect of the present invention, there is provided a molded article comprising at least one coating layer formed from the clear coat composition, wherein the molded article may be a metal or a non-metallic material, for example, an automobile part.

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, these examples are intended to further illustrate the present invention, and the scope of the present invention is not limited thereto.

[Example]

[Synthesis Example 1-1] Preparation of polyester-urethane copolymer 1

A thermometer and a stirrer, 7 g of butanediol, 7 g of neopentyl glycol, 4 g of trimethylolpropane, 12 g of cyclohexyldicarboxylic acid and 7 g of hexanedicarboxylic acid were added in this order, and then nitrogen gas The temperature was gradually raised to 210 DEG C while being supplied. After the temperature was elevated, the reaction was maintained until the solid material was completely dissolved and kept in a transparent state. When the temperature of the upper portion of the column was lowered, the reaction was carried out at a temperature lower than the acid value of 10 and diluted with 24 g of xylene . After the intermediate polyester resin was prepared, 20 g of caprolactone polyol, 5 g of hexamethylene diisocyanate and 15 g of propylene glycol monomethyl ether acetate were added at 80 占 폚 or lower, and the reaction was carried out at 100 占 폚. When the content of isocyanate reached '0' as the reaction proceeded, the reaction was terminated. The acid value of the synthesized polyester-urethane copolymer was 5 mgKOH / g, the hydroxyl value was 77 mgKOH / g, and the weight average molecular weight was 5,000.

[Synthesis Example 1-2] Preparation of polyester-urethane copolymer 2

10 g of butanediol, 7 g of neopentyl glycol, 4 g of trimethylolpropane, 11 g of cyclohexyldicarboxylic acid and 6 g of hexanedicarboxylic acid were added in this order to a synthetic four-necked flask equipped with a stirrer, a thermometer and a stirrer, The temperature was gradually raised to 210 DEG C while being supplied. After the temperature was elevated, the reaction mixture was maintained until the solid material was completely dissolved and kept in a transparent state. Then, when the temperature of the upper portion of the column was lowered, the xylene was refluxed, cooled at an acid value of 40 or lower and then diluted with 22 g of xylene . After preparing an intermediate polyester resin, 20 g of caprolactone polyol, 3 g of hexamethylene diisocyanate and 15 g of propylene glycol monomethyl ether acetate were added at 80 캜 or lower, and the reaction was carried out at 100 캜. When the content of isocyanate reached '0' as the reaction proceeded, the reaction was terminated. The acid value of the synthesized polyester-urethane copolymer was 30 mgKOH / g, the hydroxyl value was 150 mgKOH / g, and the weight average molecular weight was 7,000.

[Synthesis Example 2-1] Production of urea-dispersed acrylic resin 1

70 g of acrylic polyol, 10 g of butyl acetate, 1.6 g of benzylamine, 1.4 g of hexamethylene diisocyanate and 17 g of cocosol # 100 were put into a synthetic four-necked flask equipped with a stirrer, a thermometer and a stirrer, and the mixture was stirred at 100 rpm . In this case, the appearance of the coating film may be deteriorated due to the competitive reaction of acrylic, isocyanate, and amine. Therefore, nitrogen is injected into the system for suppressing the side reaction and the reaction is carried out at 10 ± 2 ° C using chilled water Let it happen. The temperature rose to 15 ± 2 ℃ due to heat generation. The acrylic polyol used herein had a long chain structure having a hydroxyl group group in the main chain, a hydroxyl value of 140 mgKOH / g and a glass transition temperature of 30 ° C.

[Synthesis Example 2-2] Preparation of urea-dispersed acrylic resin 2

A synthetic four-necked flask equipped with a thermometer and a stirrer was charged with 70 g of acrylic polyol, 10 g of butyl acetate, 0.8 g of benzylamine, 0.7 g of hexamethylene diisocyanate and 18.5 g of cocosol # 100, and the mixture was stirred at 100 rpm do. In this case, since the appearance of the coating film may be lowered due to the competitive reaction of acrylic, isocyanate and amine, nitrogen is injected into the system for suppressing the side reaction and the reaction is performed at 10 ± 2 ° C using cold water. The temperature rose to 15 ± 2 ℃ due to heat generation. The acrylic polyol used herein had a long chain structure having a hydroxyl group group in the main chain, a hydroxyl value of 140 mgKOH / g and a glass transition temperature of 30 ° C.

[Synthesis Example 3] Synthesis of acrylic polyol

19 g of styrene, 34 g of n-butyl methacrylate, 28 g of hydroxyethyl methacrylate, and 2 g of 2-oxepanone, a homopolymer, 2 - [(2-methyl-1-oxo-2-propenyl) 20 g of a peroxide type initiator was added at a temperature of 140-160 DEG C to prepare an acrylic polyol through a copolymerization reaction.

[Examples 1 to 3 and Comparative Examples 1 to 7]

The urethane-urethane copolymer prepared in Synthesis Example [1-1] and Synthesis Example [1-2], urea-dispersed acrylic resin prepared in Synthesis Example [2-1] and Synthesis Example [2-2] The acrylic polyols prepared in Synthesis Example 3 were mixed in the compositions shown in the following Table 1, and the final viscosity was adjusted to 35 seconds with Forod Cup # 4 to prepare clearcoat compositions for automobiles. Specifically, the polyester-urethane copolymer, the urea-dispersed acrylic resin, the acrylic polyol, and the solvent are stirred at 600-800 rpm using a dissolver, melamine, a catalyst, a light stabilizer, At a speed of 30 minutes to prepare a clearcoat composition.

Next, the specimen coated with the electrodeposition paint was painted with a heavy paint, cured at 140 ° C for 20 minutes (film thickness 30-40 microns), and then applied to the first base coat for automobile water-based paint (Dry film thickness: 12-16 microns) and a second base coat (dry film thickness: 10-20 microns) were bell coated, and hot air was blown at 80 DEG C for 5 minutes to evaporate the water remaining in the coating. The clearcoat compositions prepared in Examples and Comparative Examples were respectively coated thereon and cured in a general oven at 140 DEG C for 25 minutes to form a final coating film.

Acrylic polyol resin (KCC) having a solid content of 70% by weight, a weight average molecular weight (Mw) of 8,000, a hydroxyl value of 120 mgKOH / g and a glass transition temperature of 20 캜,

Melamine hardener: Alkylated melamine resin (cymel 1168, Cytec)

Catalyst: acid catalyst of dodecylbenzenesulfonic acid type (NACURE 5225, King Industries)

Leveling agent: silicone leveling agent (BYK-331, BYK)

Light stabilizer 1: benzotriazole series (Tinuvin 384, BASF)

Light stabilizer 2: Hinderd Amine Light Stabilizer (Tinuvin292, BASF)

Aromatic # 100 (solvent): Kocosol # 100, (CAS No. 64742-95-6, KE-31662, SK General Chemical)

The appearance and physical properties of the final coating film were measured by the following methods, and the results are shown in Table 2.

(1) Appearance: Measurement of the CF value of the final coating film by applying Wave Scan DOI (BYK Gardner) which is an automobile appearance measuring instrument. The measurement result is judged as ⊚ - excellent (CF 65 or more), ∘ - good (CF 60-65), △ - normal (CF 55-60), and X-poor (CF 55 or less).

(2) Adhesion: 2 mm Cross cuts After making 100 pieces, use scotch tape to peel off and judge as "good" when there is no problem, and "excellent" when there is no falling on the cross cutting area of the blade.

(3) Scratch resistance: A method of measuring resistance to scratching of a finished film using AMTEC-KISTER in an automobile, measuring the gloss of the coating film at 20 degrees before and after the test, The result of the measurement shows that when the gloss retention ratio (%) is 70% or more, it is ⊚-excellent, when 60-65% is good, when it is good, when it is 55-60% If it is less than 55%, it is judged as X-defective

(4) Chipping resistance: After leaving at -20 ° C for 3 hours, 50g of chipping stone is used to push out 50g of chipping stone at a pressure of 5bar, and the surface of the coated film is priced. "Good" when the damage is less than 10mm, "Good" when the damage is less than 10mm or less, "Normal" when the damage is less than 10mm or less, 2-3mm When the size is more than 10, it is judged as "bad".

(5) Hardness: Measured by the pencil hardness method (hardness measurement not to damage the coating film with each pencil of 3B, 2B, B, HB, F, H, 2H and 3H). The measurement results are shown as ⊚-excellent (HB or more), ∘-good (B), and X-poor (2B or less).

(6) Impact resistance: No cracks and peeling in the coating when dropped from a height of 30cm or more using a weight of 500g. "Good" when there is no coating crack at 50cm or more, "Good" when coating crack occurs at 40-50cm, "Normal" when coating crack occurs at 30-40cm, "Bad" when crack occurs at 30cm or less Judgment.

(7) Water resistance: Adhesion test and discoloration evaluation after immersing the coated film in a constant temperature bath at 40 ° C for 10 days. Good adhesion and good adhesion when there is no adhesion and discoloration, but "Normal" when recovering after discoloration.

Claims (6)

Polyester-urethane copolymers,
Urea-dispersed acrylic resin and
A clearcoat composition comprising an acrylic polyol. The method according to claim 1,
Based on 100 parts by weight of the polyester-urethane copolymer,
50-100 parts by weight of the urea-dispersed acrylic resin and 120-280 parts by weight of the acrylic polyol. The method according to claim 1,
Wherein the polyester-urethane copolymer has an acid value of 2-20 mgKOH / g, a hydroxyl value of 50-100 mgKOH / g, and a weight average molecular weight (Mw) of 2,000-6,000. The method according to claim 1,
Wherein the urea-dispersed acrylic resin has a hydroxyl value of 100-200 mgKOH / g and a glass transition temperature of 10-50 ° C. The method according to claim 1,
The acrylic polyol has a hydroxyl value of 50-150 mgKOH / g, a glass transition temperature of 0-50 ° C, and a solid content of 45-75% by weight. A molded article comprising at least one coating layer formed from the clearcoat composition of claim 1.