KR101194663B1 - Automotive water-borne primer surfacer composition with low curing temperature to lower co2 and usage of energy - Google Patents

Abstract

The present invention relates to a water-soluble intermediate coating composition for automobiles comprising a resin prepared by the reaction with two kinds of melamine resins using polyester as a secondary resin as a main resin to improve chipping resistance. By such a configuration, the coating composition according to the present invention reduces the general curing temperature (150 ~ 160 ℃) of the water-soluble intermediate paint for automobiles by lowering to 140 ℃ to save fuel energy for forming a coating film and CO ₂ It reduces water generation and acts as an eco-friendly water-soluble intermediate paint. The composition of the present invention can also minimize the use of toxic substances by eliminating the block isocyanate curing agent and secure a price competitiveness through reducing raw material costs.

Description

Aqueous intermediate composition for low temperature curing type automotive to reduce CO2 generation and fuel energy use {AUTOMOTIVE WATER-BORNE PRIMER SURFACER COMPOSITION WITH LOW CURING TEMPERATURE TO LOWER CO2 AND USAGE OF ENERGY}

The present invention relates to a urethane-modified polyester (polyurethane dispersion) -melamine resin and a water-soluble waterborne coating composition for automobiles comprising the same. More specifically, the coating composition according to the present invention includes a resin prepared by the reaction with two kinds of melamine resin using a polyester dispersant as a main resin and a polyester for improving chip resistance.

Water-soluble intermediate paints for automobiles, which are spreading in Europe, are obviously eco-friendly technologies compared to useful intermediate paints, but require a lot of fuel energy to obtain final coatings with baking temperatures of 150 to 160 ° C. Moreover, the use of block isocyanates, which are classified as toxic substances, to secure chipping resistance, which is one of the important roles of middle paints, has a problem of inadvertently harming the health of paint producers and paint workers.

The present invention is to improve the problems with the existing water-soluble middle paint for automobiles as described above. For this purpose, a composition comprising a resin obtained by reacting two kinds of melamine resins as a main component was developed by using a polyurethane dispersion resin as a main resin and a polyester for improving chip resistance as an auxiliary resin. By using this composition, the curing rate could be accelerated by lowering the baking temperature. In other words, by reducing the general curing temperature (150 ~ 160 ℃) of automotive water-soluble intermediate paint to 140 ℃ by reducing the fuel energy for forming a coating film and CO ₂ By reducing the occurrence, we developed a more eco-friendly water-soluble middle paint for automobiles. At the same time, by eliminating the block isocyanate hardeners that are generally used in intermediate coatings, it is possible to minimize the use of toxic substances and secure price competitiveness by reducing raw material costs.

In the present invention, by reducing the crosslinking density that may occur during the reaction of a single curing agent by designing a network structure by reacting the polyurethane dispersion resin and the polyester resin with excellent elastic force and flexibility with a partial or full butoxy, methoxy-based multi- melamine resin The mechanical properties of the intermediate coating were supplemented and improved by supplementing weaknesses and forming a more dense crosslinked coating. At the same time, through the optimum composition ratio study, the baking temperature is lowered up to 140 ° C, thereby realizing the economic benefit of reducing the heat energy consumption required for baking.

First, in the present invention, the polyurethane dispersing resin is used as the main resin, and the polyester has excellent elasticity and flexibility for securing chipping resistance, which occupies the largest proportion in the material properties of the middle paint, and improving the appearance quality and hardness of the coating film. Resin was used as auxiliary resin. In addition, by using multi-component melamine resins of all butoxy and methoxy-based, a multi-component network structure was realized to increase the crosslinking density of the cured coating film and to secure mechanical durability, p-TSA (p-Toluene Sulfonic Acid) and DNNDSA (Dinonylnaphthalene). Strong acid catalyst such as Disulfonic Acid) was used to increase the reaction rate and lower the baking temperature of 150 ° C to 140 ° C.

Specifically, the present invention includes a polyurethane disperse main resin and a polyester auxiliary resin having a hydroxyl group based on the total solids 30 to 60% by weight, and the melamine weight ratio (based on the solids) to the main resin + auxiliary resin is 9: 1 to It relates to a water-soluble coating composition for automobiles, characterized by containing a melamine resin to be 1: 2.

More specifically, the water-soluble coating composition according to the present invention includes a polyurethane disperse main resin and a polyester auxiliary resin having a hydroxyl group in a weight ratio of 10: 1 to 3: 1 (based on solids), and the main resin and the auxiliary resin 30 to 60% by weight based on total solids. In the present invention, the ratio of the methoxy-based melamine resin and the hybrid (butoxy / methoxy) melamine resin is maintained at a weight ratio of 1: 2 to 2: 1, and the melamine weight ratio (based on solids) to the main resin and the auxiliary resin is 9: 1 to Include 1: 2. By such a configuration, the present invention provides a water-soluble intermediate coating composition having improved appearance quality, hardness, and cold resistance chipping performance.

Hereinafter, the present invention will be described in detail.

1. Experiment process and equipment

1.1. Paint manufacturing equipment

DISPERMAT: High speed dissolver

Balance: 0.01 g of measurement unit

DISPERSION EQUIPMENT: Ring Mill

HOT AIR BLOW ZONE: PRE HEATING EQUIPMENT

CONVECTION OVEN: Soburo

DURR ’s ECO BELL (ROBOT): Sprayer

SAMES's CARTRIDGE BELL (ROBOT): Sprayer

MANUAL GUN

1.2. measuring equipment

FORD CUP # 4: Viscosity Measurement

HAAKE ROTOVICO: Rotational type viscometer

Specific gravity cup

Others: pH meter, thermometer, stopwatch

1.3. Quality evaluation device

WAVE SCAN DOI: Appearance Quality Measurement

GLOSS METER: Gloss Measurement Instrument

X-RITE: Color Difference Meter

FILM BUILD GUAGE: film thickness gauge

The polyurethane dispersion resin used in the present invention is synthesized according to the following method. Put a polyester polyol, dimethylpropionic acid (DMPA), N-methylpyrrolidine (NMP) and dibutyltin dilaurate (DBTDL) in a 2-liter three-necked flask and hold at 90-120 ° C until the DMPA is dissolved. Cool to 60 ~ 80 ℃. Hexamethylene diisocyanate (HMDI) and acetone are mixed and added for 30 minutes, followed by reaction at 50-80 ° C. for at least 5 hours. When the NCO content is 0.05% or less, the reaction is terminated and cooled to 40 ° C. Dimethylethanolamine (DMEA) is added for 20 minutes and dispersed with water at 100-500 rpm for 1 hour, followed by raising the temperature to 60-80 ° C. to remove acetone under reduced pressure.

The hydroxyl value of the polyurethane dispersion resin thus produced is 70 to 170, preferably 80 to 150. If the hydroxyl value is less than 70, the hardness is lowered, and if it is more than 170, the impact resistance and cold resistance chipping resistance is lowered. The nonvolatile component is 30 to 55% by weight, preferably 35 to 50% by weight. If the nonvolatile component is less than 30% by weight, the sagging becomes weak at the time of vertical coating, and if it exceeds 55% by weight, the leveling is reduced due to the decrease in flowability. Glass transition temperature is -30-30 degreeC, Preferably it is -20-10 degreeC. If the glass transition temperature is lower than -30 ° C, the coating film hardness is lowered. If the glass transition temperature is higher than 30 ° C, impact resistance and cold resistance chipping resistance are lowered. The weight average molecular weight is 2,000 to 20,000, preferably 5,000 to 15,000. If the weight average molecular weight is less than 2,000, the weather resistance decreases and the coating film hardness decreases. If the weight average molecular weight exceeds 20,000, workability problems such as poor wettability and leveling property due to the deterioration of flowability are caused. In addition, the acid value is 15-40 mgKOH, the degree of neutralization is 5-100%, the VOC content is 1-15%, and the pH is 6-9.

The main resin + auxiliary resin content used in the present invention is 30 to 60% by weight, preferably 35 to 55% by weight based on the total resin (including hardener) solids. Less than 30% by weight causes problems of impact resistance and chipping resistance due to reduced flexibility, and more than 60% by weight results in reduced hardness. The weight ratio of the polyurethane disperse resin and the polyester resin is 10: 1 to 3: 1, and preferably 9: 1 to 6: 1. If it is less than 10: 1, the chipping resistance problem occurs, and if it exceeds 3: 1, the appearance quality decreases due to the loss of gloss after baking.

Preferred as the auxiliary resin polyester resin is Worleepol1181 / 09 manufactured by Worlee, which has a solid content of 100%.

Preferred curing agents used in the present invention are methoxy-based melamine resins and hybrid (butoxy / methoxy) melamine resins. The selective application of melamine resins allows the design of various reaction rates and the cost savings of 20-50% of the block isocyanate curing agent. However, the high hardness of the cured coating film may cause a decrease in chipping resistance, thereby limiting its use. However, in this study, the chipping resistance can be minimized by studying the optimum composition with various melamine resins based on the elasticity and flexibility of the urethane water dispersion resin used as the main resin.

The content of melamine resin is 9: 1 ~ 1: 2 when the weight ratio of the main resin to the secondary resin exceeds 1: 2 and the chipping resistance decreases due to the increase in hardness of the coating film. If included, the hardness of the coating film and the water resistance decrease due to uncured.

Melamine resins usable in the present invention include Cymel 325, Cymel 370, Cymel 323, Cymel 303, Cymel 328, Resimine 717 from INEOS, Luwipal 052 from BASF, Luwipal LR 8955, and the like. In particular, it is preferable to use Luwipal 052 or Luwipal LR 8955 from BASF as the methoxy / butoxy hybrid melamine resin. The use of melamine as an auxiliary curing agent enables the formation of a more dense coating structure because curing is possible at relatively lower temperatures compared to blocked isocyanates.

The water-soluble coating composition according to the present invention may further include an acid catalyst for controlling the baking temperature at the time of curing, and in addition, a leveling agent, an ultraviolet absorber, an alkaline agent which is a neutralizing agent, a buffer, a solvent mixture for forming an azeotrope, a pigment, a thickener. Wetting agent (wetting agent), dispersing agent, antifoaming agent may be further included.

Leveling agents usable in the present invention include polyether modified dimethylpolysiloxane, 2,4,7,9-tetramethyl-5-dekin-4,7-diol, modified urea mixture, and the amount is 0.05 to 10% by weight Preferably it is 0.1-5 weight%. If the leveling agent is used at less than 0.05% by weight, the high surface tension of water causes wetting and appearance deterioration, and when the leveling agent is used at more than 10% by weight, the adhesion with the top coat is caused.

Dimethylethylamine or 2-aminomethyl-1-propanol can be used as a neutralizing agent, and the usage-amount is 0.1-10 weight%, Preferably it is 0.5-5 weight%. If the neutralizing agent is used at less than 0.1% by weight, storage problems such as gelling of the paint may occur, and if it exceeds 10% by weight, workability problems such as sagging may occur due to a decrease in paint non-volatile content due to an increase in paint viscosity. .

Barium sulfate or titanium dioxide may be used as the buffer, and the amount used is 0.1 to 10% by weight, preferably 0.5 to 5% by weight. If the content of the buffer is less than 0.1% by weight, the chipping resistance and the sandmark hiding power is lowered. When the content of the buffer exceeds 10% by weight, the appearance decreases.

The solvent mixture may be selected from butyl cellosolve, hexyl cellosolve, pennitro methyl pyrrolidone, 2-ethyl hexanol, normal butyl alcohol and normal propyl alcohol, and the content is 1 to 20% by weight, preferably 5 to 15% by weight. If the solvent mixture is used at less than 1% by weight, the resin dissolving power in the paint is lowered, resulting in a deterioration in appearance such as clearness and gloss of the paint, and exceeding 20% by weight violates VOC regulation.

As a pigment, TiO ₂ White Pigment, Carbon Black FW285, Raven Ultra 5000, Raven 3500, Blanc Fixe Micro, Hostaperm Violet RL-S, Heliogen Green L8730, Manstral Blue FNX, Sicopal Yellow L1100, Paliotan Yellow L1945, Irgazin DPP BO, Hostaperm Red E3B In addition to these, both organic and inorganic pigments that may be used in automotive paints may be used. The content of the pigment used is 1 to 20% by weight, preferably 5 to 18% by weight. If less than 1% by weight, the undercoat concealment failure occurs, and if it exceeds 20% by weight, the leveling and clearness of the paint, and the impact resistance chipping resistance due to the brittle coating properties.

Thickeners to have the acrylic copolymer emulsion such as VISCALEX HV30, VISCALEX LO30, SOLTHIX A100 and the Laponite RD ^ⓡ cradle type can be used. The amount of thickener used is 0.5-20%, preferably 1-15%. If the amount of use is less than 0.5%, the control of paint rheology becomes difficult, resulting in a drop in sagging.

The undercoat which can be used together with the water-soluble coating composition according to the present invention is an electrodeposition coating used for automobile coating, and the expandability applicable to almost all electrodeposition paints using epoxy as the main resin as a characteristic of the composition according to the present invention. There is a number. Basecoat paints include carboxylic acid-containing acrylic acid and hydroxy-containing acrylic and melamine curing agents or polyester resins, and polyester resins and melamine curing agents, and oil-based automotive paints, polyurethane dispersions and acrylic urethane dispersants. Water-soluble automotive paints that use perfusion, acrylic emulsion as a single or hybrid type of main resin, and selectively use melamine as a curing agent can be used, and transparent coatings for top coats include acrylic acid containing epoxy or carboxyl groups and hydroxyl or siloxane groups. A one-component automotive topcoat made using a thermosetting acrylic resin composition containing a group and a block isocyanate as a curing agent and a two-component automotive topcoat paint using an isocyanate as a curing agent can be used.

Hereinafter, the present invention will be described using examples, but the present invention is only for understanding of the present invention, and the scope of the present invention is not limited thereto in any sense.

Example  1 to 4 and Comparative example  1 to 2

According to the composition shown in Table 1 below, the water-soluble intermediate coating compositions of Examples 1 to 4 and Comparative Examples 1 and 2 were prepared. In Table 1, the unit of each component is g.

* 1 Polyurethane Dispersion Resin: (120 hydroxyl value, 43% by weight of nonvolatile content, glass transition temperature (Tg) -5 ° C, weight average molecular weight 11,000)

* 2 Polyester Resin: Worleepol 1181/09

* 3 Melamine Resin A: Cymel303

* 4 melamine resin B: Luwipal052

* 5 Additive Mixture: Includes all common surface additives, wetting agents, dispersants, and antifoams used in water soluble intermediates for automobiles.

Example: Surfynol 104 / Hydropalat 3216 / Additol VXW 4971 / BYK-381 / BYK-346 / DMEA = 0.5 / 0.5 / 0.4 / 1 / 0.5 / 0.1

* 6 Solvent Mixture: Contains all common solvents used in automotive waterborne paints.

Example: n-methylpyrrolidone / butyl di-glycol / Exxol D60 / hexyl cellosolve = 0.5 / 5 / 0.5 / 1

* 7 Pigment Mixture: Contains all pigments that can be applied to automotive waterborne paints.

Example: Micro Talc IT Extra / CR-97 / BFM / ASP-200 = 3.5 / 17/10 / 2.5

* 8 Acid catalyst: Nacure155 (DNNDSA, dinonylnaphthalene disulfonic acid) from King Industry

Test Example  1: Evaluation of Paint Properties of Water-Soluble Coating Composition (Medium Paint Coating)

Medium coating is discharged by 170 ~ 250cc / min using electrostatic bell sprayer, external voltage -60kv, shaping air 0.5 ~ 1kg / cm ² , Bell rpm 40000 ~ 55000, Head target distance (HTD) is 200 ~ 250mm. In order to stabilize the coating film, it was set for 1 to 2 minutes, and pre-dried for 3 to 5 minutes in a hot air section at 60 to 80 ° C. to evaporate water. The air pressure at this time was 3-4 kg / cm <^2> . Then, after baking at 140 degreeC for 20 minutes, glossiness, adhesiveness, hardness, and smoothness were evaluated by the intermediate coating material only by the following method. The results are shown in Table 2.

Glossiness: Horizontal film is measured with a polisher.

2. Adhesion: Check whether the film is attached after cross cut (2 * 2mm, 100ea)

          Good: Maintain adhesion without falling off coating

          Medium: 1-2 drops

          Poor: When there is a fall of 3 or more coatings

3. Hardness: measured by pencil hardness method

          Pencils with hardness of 3B, 2B, B, HB, F, H, 2H and 3H are used to measure hardness that does not damage the coating

4. Smoothness: The smoothness of the coating film was confirmed by the long wave value measured by Wave scan D.O.I.

          Good: less than 7

          Middle: 7-10

          Poor: greater than 10

Test Example  2: evaluation of paint properties of water-soluble coating composition (base coat and Cree  Coat seal)

After applying a water-soluble water base WT3060 metallic or solid color) onto the cured mid-film, it is subjected to a setting process for stabilization of the coating for about 2 minutes, and then pre-dried to evaporate water in a hot air section at 80 ° C. for about 3 minutes. Followed the process. Subsequently, the cobakryl top coat TT6830 was applied, set in 5 to 10 minutes, and cured in a 140 ° C. oven for about 25 minutes to form a dry coating film, and then evaluated physical properties according to the following method.

1. Appearance: Measure the horizontal film by Wave Scan DOI and check CF value

* The Wave Scan DOI is a device for measuring objective quality by measuring and combining gloss, image sharpness, and smoothness with the instrument rather than subjective evaluation of the exterior paint quality by visual observation. It is used as a quality measuring instrument.

2. Water resistance: After immersing the coating film in hot water at 40 ℃ for 240 hours, discoloration, parts sound, blister (Blister) occurrence, adhesion abnormality is measured.

3. Acid resistance: After dropping 2 cc of sulfuric acid pH 1, 2 and 2 cc of phosphoric acid pH 1 and 2 solution onto the coating film, it is judged whether the coating film is damaged after maintaining at 50 ° C, 60 ° C, and 70 ° C for 30 minutes, respectively.

4. Cold resistance chipping test: -40 ℃ X 3 hours

    Poor: 1-6

    Good: 7 ~ 9 (8: Excellent, 9: Best)

5. Solvent resistance: No abnormality in nail hardness of xylene coatings over time (more than 10 minutes) during xylene spot test.

6. Scratch resistance: 20 ° gloss measurement after 10 round trips with CAR WASH SCRATCH TEST facility with reduced automatic car wash and check gloss retention rate before and after test

    Good: over 60%

    Normal: 50 to 60%

    Poor: less than 50%

7. Soline resistance: No softening, swelling, or discoloration of the coating film during 1 hour deposition test of automobile gasoline spot.

8. Impact resistance: 50g weight was dropped at 20, 30, 40, and 50 cm using a Dupont Tester, and the height of the coating film was measured.

    Good: 30 cm or more

    Normal: 20 cm

    Poor: less than 20 cm

9. Hardness: Measured by pencil hardness method.

10. Adhesion: Check the coating film after cross cut

11. Brake oil resistance: There should be no softening, swelling or discoloration of the coating film during 1 hour deposition test of automobile brake oil spot.

According to the results of Tables 2 and 3, the water-soluble coating composition according to the present invention includes a polyurethane dispersant having a hydroxyl group and a polyester resin in a specific composition ratio with a methoxy-based melamine resin and a hybrid (butoxy / methoxy) melamine resin. By reducing the general curing temperature (150 ~ 160 ℃) of water-soluble intermediate paints to 140 ℃ can save the fuel energy to form a coating film and reduce the generation of CO ₂ . In addition, it is an eco-friendly water-soluble water-based paint that can minimize the use of toxic substances by eliminating block isocyanate hardeners. It also ensures stable curing behavior, better appearance quality and cold resistance against lower temperature and time, and improves the degree of curing of coatings. As a result, there is an effect of providing improved mechanical properties.

Claims (6)

Polyurethane disperse main resin and polyester auxiliary resin which has hydroxyl group include 30-60 weight% of total solids basis,
Melamine resin is included so that the weight ratio (based on solids) of melamine to main resin and auxiliary resin is 9: 1 to 1: 2,
The melamine resin is a water-soluble coating composition for automobiles, characterized in that it comprises a methoxy-based melamine resin and a hybrid (butoxy / methoxy) melamine resin in a weight ratio of 1: 2 to 2: 1. The composition according to claim 1, comprising a polyurethane dispersion main resin and a polyester auxiliary resin in a weight ratio of 10: 1 to 3: 1 (based on solids). delete The polyurethane dispersant main resin according to claim 1, wherein the hydroxyl value is 70 to 170, the nonvolatile component is 30 to 55% by weight, the glass transition temperature (Tg) is -30 ~ 30 ℃, the acid value is 15 ~ 40mgKOH, the degree of neutralization 5 ~ 100%, VOC content 1 ~ 15%, pH 6 ~ 9, weight average molecular weight of 2,000 to 20,000, characterized in that the composition. The composition of claim 1, wherein the polyester auxiliary resin is Worleepol1181 / 09 manufactured by Worlee and has 100% solids. The composition of claim 1 wherein Luwipal 052 or Luwipal LR 8955 from BASF is used as the hybrid (butoxy / methoxy) melamine resin.