KR100409152B1 - Method of Preparing One-component Type Urethane Resin Composition - Google Patents

Abstract

Disclosed is a method for producing a one-pack type urethane resin composition for automobile chipping undercoating and intermediate having excellent low temperature curability and chipping resistance while having good coating performance such as appearance smoothness and water resistance and excellent coating workability. Isocyanate compound, a monomer polyol having a molecular weight of 500 or less and an oligomeric polyol having a molecular weight of 2000 or less are mixed, but the mixing ratio of the monomer polyol and the oligomer polyol is 0.2 to 0.8: 0.8 to 0.2 in equivalent ratio and isocyanate to the resulting mixture Blocking of the isocyanate functional group is carried out by adding and blocking a blocking agent of the functional group to prepare. The paint prepared using the resin composition and the compound having an amino functional group or a resin having a hydroxy functional group, a pigment, an additive, and a solvent can be cured at a temperature of 140 ° C. or lower, and the cured coating film has excellent performance such as appearance smoothness and water resistance. Good and excellent chipping resistance, especially low temperature chipping resistance.

Description

Method of preparing one-component urethane resin composition {Method of Preparing One-component Type Urethane Resin Composition}

The present invention relates to a method for producing a one-component urethane resin composition for automobile anti chipping undercoat and intermediate paint, and particularly excellent in low temperature curability compared to conventional automotive anti chipping undercoat and intermediate paint resins, and jumping from the road while driving a vehicle. The present invention relates to a method for producing a one-pack type urethane resin composition for automobile chipping undercoating which is excellent in chipping resistance capable of signifying a coating film from the impact of sand and small boulder, and for intermediate chipping.

The purpose of the coating is to protect the body and aesthetics. Especially in the automotive industry, the recent requirement for the coating is the appearance quality of the top coat and the durability of the coating, which has four quality characteristics: scratch resistance, chipping resistance and acid resistance. It is strongly demanded. Among these coating performances, chipping resistance is a performance to protect the coating against the impact of sand or bouncing that bounces off the road while the vehicle is running. Particularly, in the cold regions, rock salt, sand and small rocks sprayed to prevent freezing and slipping of winter roads are often thrown up during the driving of the car, impacting the driving car. The durability against coating damage that is reached is determined by the performance of the anti-chipping coating and the intermediate coating.

In addition, the body of the lower part is centered on the door guard line, which is heavily impacted by sand or small bouncing stones from the wheel while driving the car.The lower body is coated with anti-chipping paint as a relatively thick film of 50-200㎛ between the electrodeposition film and the intermediate film. It is painted to ensure chipping resistance.

As a conventional technique, a middle paint has a method of improving chipping resistance by increasing the molecular weight of a polyester resin to give toughness of the coating film, but a polyester resin having a large molecular weight has a high viscosity, which inevitably leads to a low solid content during coating, resulting in poor hiding power. And the appearance smoothness of the intermediate coating film becomes poor. In addition, in order to improve the appearance quality, a high-solid-type low molecular weight resin having excellent flow characteristics such as smoothness and flowability is used. In the coating film manufactured using this, the chipping resistance is poor due to the deterioration of the toughness of the coating film itself. There is this.

As a chipping-resistant paint, polyester resins have relatively good curing properties but poor chipping resistance. Blocked one-component urethane resins have poor curing properties and must be heated to 150 ° C. or higher to ensure satisfactory curing and chipping resistance. There is a disadvantage of high energy consumption. In addition, as a technique for improving chipping resistance, a technique of using inorganic flat pigments such as talc, mica and the like is applied to the anti-chipping paint and intermediate paint. However, when the content thereof is increased, there is a resistance to impact, but when the coating film is damaged, the peeling area becomes large. On the contrary, when the content thereof is small, the effect on the chipping resistance cannot be expected.

Accordingly, an object of the present invention is to provide a method for producing a thermosetting one-component urethane resin composition which is excellent in low temperature curability and chipping resistance but also excellent in coating appearance quality and water resistance, and can be applied to automotive paints as well as intermediate paints. It is.

Another object of the present invention is to provide a coating composition capable of providing a low temperature hardenability by manufacturing using such a method resin composition, the cured coating film can provide a coating film having excellent performance such as appearance smoothness and water resistance and excellent chipping resistance. It is.

In the present invention to achieve the above object

Mixing an isocyanate compound, a monomer polyol having a molecular weight of 500 or less, and an oligomeric polyol having a molecular weight of 2000 or less, and mixing the mixture of the monomer polyol and the oligomer polyol in an equivalent ratio of 0.2 to 0.8: 0.8 to 0.2; And

It provides a method for producing a one-component urethane resin composition comprising the step of blocking the isocyanate functional group by adding and stirring a blocking agent of an isocyanate functional group to the resulting mixture.

In particular, the resin composition has a number average molecular weight of 500 to 5000, and the blocked isocyanate equivalent in the resin is preferably 200 to 2500 based on the resin nonvolatile content.

Another object of the present invention is achieved by the one-component urethane resin composition comprising the one-component urethane resin composition, the resin of the hydroxy functional group or the amino functional group, a pigment, a dispersant, an additive, and a solvent in the above-described method.

The present inventors have studied the one-component urethane resin for solving various problems caused by the anti-chipping paint and the intermediate paint of automobiles, and have excellent low-temperature below 140 ° C even with excellent coating performance and coating workability such as appearance smoothness and water resistance. The present invention is to invent a one-component urethane resin composition for automobile anti-chipping undercoating and intermediate coating having curability and excellent chipping resistance.

In addition, the inventors of the present invention are a one-component urethane resin in which an isocyanate functional group is blocked with a blocking agent in a urethane resin, and an aromatic isocyanate is used as an isocyanate compound of the urethane resin, and as a polyol component, a monomer polyol having a molecular weight of 500 or less and a molecular weight By using this oligomeric polyol of 2000 or less together and synthesizing with an oxime system, especially methyl ethyl ketoxim, as a blocking agent, a thermosetting blocked one-component urethane resin having good low temperature curing property and excellent chipping resistance was produced.

Hereinafter, the present invention will be described in detail.

The isocyanate compounds which can be used in the synthesis of the blocked one-part thermosetting urethane resin of the thermosetting resin composition of the present invention in the synthesis of the resin of the isocyanate functional group underlying the thermosetting one-component urethane resin composition of the present invention include toluene diisocyanate and isophorone di. Isocyanate, hexamethylene diisocyanate, xylene diisocyanate, these trimer type, polyol adduct type, etc. are mentioned.

Among them, aromatic isocyanates such as toluene diisocyanate, xylene diisocyanate, their trimer type and polyol adact type are more preferably used in order to obtain good curing property at a low temperature of 140 ° C or lower.

As the polyol component, a monomer polyol having a molecular weight of 500 or less and an oligomeric polyol of 2000 or less are used, and these are used in a ratio of 0.2 to 0.8 in terms of hydroxy equivalent number. Specific examples of the monomer polyol include ethylene glycol, diethylene glycol, neopentyl glycol, butyl ethyl furopandiol, 1,3-butanediol, 1.4-butanediol, 1,6-hexanediol, trimethylolfuropane, trimethylolethane, and the like. Specific examples of the oligomeric polyol include polyether polyols, polyester polyols, polycaprolactone polyols, polytetramethylene polyols, polycarbonate polyols, and the like.

The amount of the monomer polyol and the oligomeric polyol is to be used in a ratio of 0.2 to 0.8: 0.8 to 0.2 as the ratio of the number of hydroxy equivalents. If the ratio of the hydroxy equivalent number of the low molecular weight monomer polyol having a molecular weight of 500 or less and the oligomeric polyol having a molecular weight of 2000 or less is less than 0.2 or greater than 0.8, the chipping resistance or hardness of the cured coating film is not obtained at a desired level. These mixing ratios are made into the said range. For example, when the ratio of the hydroxy equivalent number of the low molecular weight monomer polyol is less than 0.2, the pencil hardness required by the chipping undercarriage and the intermediate coating film of the automotive coating is not less than B, and on the contrary, when the ratio is more than 0.8, the chipping resistance , Especially at low temperature chipping resistance.

Moreover, in the said polyol compound, it is preferable to mix and use a triol or more polyol and a bifunctional diol in ratio of 0.2-0.8: 0.8-0.2 by the ratio of equivalent number. If the ratio of the equivalent number of hydroxy equivalents of the polyol of the tri- or bi-functional diol and the bi-functional diol is less than 0.2 or more than 0.8, the chipping resistance or hardness of the cured coating film is not sufficiently good under the chipping degree and the middle of the automobile. I can't.

That is, when the ratio of the equivalent number of hydroxy equivalents of the trifunctional or higher polyol among all the polyol components is more than 0.8, the hardness of the cured coating film is better, the flexibility is poor, and the chipping resistance, in particular, the chipping resistance at low temperature is poor. There is concern about quality. If the equivalent number ratio of the hydroxy equivalent of the trifunctional or higher polyol is less than 0.2, the chipping resistance of the cured coating film is good, but there is a fear that the hardness of the cured coating film is poor. On the other hand, if the equivalent number ratio of the hydroxy equivalent of the difunctional diol is less than 0.2, the chipping resistance is poor, and if it is more than 0.8, the hardness may be poor.

In the present invention, a method of reacting an excess isocyanate functional group with a blocking agent after reacting a polyol compound with an excess of isocyanate compound for the synthesis of a blocked one-part thermosetting urethane resin composition is introduced. As a blocking agent for blocking excess isocyanate functional groups, oximes, caprolactams, phenols and lower alcohols may be used, but oximes are preferably used to obtain good curing property at a low temperature of 140 ° C or lower. More preferably, methyl ethyl ketoxime is used.

It is preferable that the number average molecular weights of the blocked thermosetting urethane resin composition of this invention obtained by such a method have the characteristic value of 500-5000, and the isocyanate equivalent of blocked resin has 200-2500 on the basis of resin non volatile matter. When the number average molecular weight is less than 500 or the isocyanate equivalent is less than 200, the crosslinking density is increased in the cured coating film, so the hardness of the coating film is excellent, but chipping resistance may be poor at a low temperature of -20 ° C. In addition, when the number average molecular weight of the resin composition is greater than 5000, the viscosity of the resin is increased, and there is a disadvantage in that a large amount of an organic solvent must be used for proper workability of the paint. When the isocyanate equivalent is greater than 2500, the crosslinking density of the cured coating film is decreased, resulting in hardness and All chipping resistances may be poor and therefore not appropriate. More preferably, the number average molecular weight is in the range of 1000 to 4000, and the isocyanate equivalent weight is in the range of 400 to 1800.

The one-component urethane curing agent resin composition prepared according to the method of the present invention is obtained by blocking an isocyanate functional group with a blocking agent, and has excellent storage stability, which is a polyol resin having a hydroxy functional group used in a conventional thermosetting two-component urethane paint. A thermosetting coating can be prepared by mixing a resin having an amino functional group, and by using this, a thermosetting coating can be formed.

The chipping undercoat and intermediate paint for automobiles manufactured according to this method have excellent low temperature curing property and good coating workability below 140 ° C, and the cured coating film has good coating performance such as appearance smoothness, hardness and water resistance. Not only at room temperature but also at a low temperature of -20 ℃ excellent chipping resistance.

Hereinafter, the present invention will be described in detail with reference to the following examples, but the scope of the present invention is not limited thereto.

Example 1

In a 2-liter flask, 350 g of xylene, 27.3 g of trimethylolfuropane, 304.7 g of polymethylene glycol (molecular weight 1000), and 212 g of toluene diisocyanate were installed, and a thermometer, a dropping funnel, a condenser, and a nitrogen inlet tube were installed. It heated up to 70 degreeC gradually, paying attention to. After raising the temperature to 70 ° C and maintaining the reaction for 3 hours, 106 g of methylethylketoxime was added dropwise through the dropping funnel over an hour while paying attention to the exotherm, and then the reaction was continued at 75 to 80 ° C without infrared unreacted isocyanate functional groups. The reaction was maintained until it was.

The blocked urethane resin thus synthesized had a solid content of 65% and 25 ° C. Gardner viscosity of U to V. The theoretically calculated isocyanate equivalent weight was 535 in the resin nonvolatile content and the number average molecular weight measured in Zippy was 1300.

Example 2-Example 4

It carried out in the same manner as in Example 1, but was carried out by changing the type and amount of raw materials as shown in Table 1. The characteristic values and the synthesis results are shown in Table 1 together.

Dosage amount, characteristic value, synthesis result of resin composition of Example 1 to Example 4 Example 1 Example 2 Example 3 Example 4 xylene 350 400 400 400 Trimethylol furophane 27.3 29 Neopentyl glycol 21.1 63.5 Polytetramethylene glycol ¹⁾ 304.7 323.4 Polycaprolactone polyol ²⁾ 284.3 157 Toluene diisocyanate 212 180.1 206.2 265.6 Methyl ethyl ketoxime 106 67.5 88.4 113.9 Nonvolatile matter 65% 60% 60% 60% Viscosity U-V X-Y T-U S-T Number average molecular weight 1300 2300 1800 1200 Isocyanate Equivalent 535 775 590 460

1) Product of BASF, Part Name: Poly THT-1000, Molecular Weight: 1000

2) Union Carbide's product, product name: TONE Polyol 0310, molecular weight: 900

Comparative Example 1

Put 300 g of xylene and 480.1 g of 1.6-hexamethylene diisocyanate trimer into a 2-liter flask, install a thermometer, a dropping funnel, a condenser, and a nitrogen inlet tube, and slowly raise the temperature to 70 ° C while adding nitrogen gas. 219.9 g of methyl ethyl ketoxime was added dropwise over an hour while paying attention to exotherm, and the reaction was continued at 75 to 80 ° C. until the unreacted isocyanate functional group was lost by infrared spectrum.

The blocked urethane resin thus synthesized had a solid content of 70% and 25 ° C. Gardner viscosity of S to T. The theoretically calculated isocyanate equivalent weight was 280 and the number average molecular weight measured by Zippy was 900.

Comparative Example 2 to Comparative Example 4

The process was carried out in the same manner as in Example 1, but was performed by changing the type and amount of raw materials as shown in Table 2. Raw material inputs, characteristic values, and synthesis results of Comparative Examples 1 to 4 are summarized in Table 2.

Dosage, Characteristic Values, and Synthesis Results of the Resin Composition Raw Materials of Comparative Examples 1 to 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 xylene 300 350 350 400 Trimethylol furophane 27.6 6.3 61 Polytetramethylene glycol ¹⁾ 308.1 120.3 Polycaprolactone polyol ²⁾ 439.7 Toluene diisocyanate 142.8 279.1 Hexamethylene diisocyanate 207 Coronate-HX ³⁾ 480.1 Methyl ethyl ketoxime 219.9 107.3 61.2 139.6 Nonvolatile matter 70% 65% 65% 60% Viscosity U-V X-Y V-W Y-Z Number average molecular weight 900 1300 2200 1000 Isocyanate Equivalent 280 530 930 375

1) Product of BASF, Part Name: Poly THT-1000, Molecular Weight: 1000

2) Union Carbide's product, product name: TONE Polyol 0230, molecular weight: 1250

3) Product made by Nippon Polyurethane Co., Ltd .: trimer type isocyanate compound of coronate-HX, hexamethylene diisocyanate

Comparative Example 5

In Comparative Example 5, urethane-modified polyester and melamine resin-based conventional automotive intermediate paints (our product, product name: H-840) were introduced as they are.

In order to find out the characteristic of the coating film with respect to resin obtained by the Example and the comparative example as mentioned above, the coating composition was manufactured using each resin. As a resin for dispersing pigments, conventional polyol resins for low molecular weight polyester, aric, alkyd, etc. were used. The resin obtained in Examples and Comparative Examples of the present invention was added to a paste in which the pigment was dispersed by adding an additive for improving the appearance and a solvent such as xylene, toluene, cocosol-100, cocosol-150, butyl acetate, and the like. A thermosetting one-component coating composition was prepared by mixing the ratio of the hydroxy equivalent number and the blocked isocyanate equivalent number to 1/1.

The thickness of the dry coating film on the automotive paint test specimen coated with electrodeposited paint was adjusted by applying the paint prepared in this way and adjusting the viscosity to be suitable for coating by the spray coating method with the thinner composed of the above-mentioned solvents. The coating was allowed to cure for 10 minutes in an oven at 140 ° C. In addition, the existing intermediate paint of Comparative Example 5 was also coated with the same coating thickness and cured in an oven at 140 ° C. for 30 minutes. The curability of the coated specimens was evaluated by rubbing the coating film in hot state immediately after removing the specimen from the oven, and the degree of rolling, marks and scratches. The hardness of the coating film was evaluated by a pencil hardness measurement method.

After coating the white base coat with the thickness of 15-20㎛ dry coating as the top coat, the transparent paint was subsequently coated to the thickness of 35-40㎛ dry and dried for 30 minutes at 140 ℃ oven. The water resistance was visually evaluated for abnormality of the coating film after immersion in hot water at 50 ° C. for 10 days. And chipping resistance was made by using a zeolite tester (Japanese Suga Test Co., Ltd.) to collide 250g of No. 6 with a pressure of 4Kgf / cm ² 5 times at -20 ° C test specimens five times and then peel off the coating film and the peeling area. Was evaluated visually, and after 72 hours of saline spray test, the degree of rust in the test piece was visually evaluated.

The test results evaluated by the above method are summarized in the following Tables 3 and 4.

Coating film performance test result using resin of Example 1-4 Suzy Example 1 Example 2 Example 3 Example 4 Pencil hardness B HB B HB Curable ○ ○ ○ ○ Appearance ○ ○ ○ ○ Water resistance ◎ ◎ ○ ◎ Chipping resistance Peeling number ◎ ◎ ◎ ○ Peeling area ○ ◎ ○ ◎ Outgoing degree ○ ○ ○ ○

Coating film performance test result using resin of comparative example Suzy Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 ¹⁾ Pencil hardness B B HB HB Curable × △ ○ ○ △ Appearance ○ ○ ○ △ ○ Water resistance △ △ ○ ○ ○ Chipping resistance Peeling number × △ × △ × Peeling area △ × △ × × Outgoing degree × × △ △ ×

1) In the case of Comparative Example 5, the evaluation of curability was tested by curing 10 minutes at 140 ℃, other performance was tested by curing 30 minutes at 140 ℃

Evaluation criteria indicate that ◎ indicates excellent, ○ indicates good, Δ indicates somewhat poor, and × indicates poor.

As can be seen from Tables 3 and 4 above, the resin compositions according to Examples 1 to 4 were used when the resin compositions of Comparative Examples 1 to 4 were used and the existing automotive intermediate paints of Comparative Example 5 were used. Compared with the case, the appearance smoothness and hardness are good, and it can be seen that the surface smoothness and water resistance after the top coat as well as very excellent performance in the chipping resistance.

According to the present invention as described above it is possible to manufacture a one-component urethane resin composition for low-temperature curing and excellent chipping resistance. The paint produced using this can be cured at a low temperature of 140 ° C. or lower, and the cured coating film has excellent performance such as appearance smoothness and water resistance, but excellent chipping resistance, particularly low temperature chipping resistance.

Although the present invention has been described above according to an embodiment of the present invention, it will be apparent to those skilled in the art that various modifications may be made without departing from the spirit of the present invention.

Claims (10)

a) an isocyanate compound, and ii) a monomer polyol having a molecular weight of 500 or less and 0.2 to 0.8 equivalents and an oligomeric polyol having a molecular weight of 2000 or less and 0.2 to 0.8 equivalents, Preparing an isocyanate-polyol mixture by mixing a polyol mixture having an equivalent ratio of 0.2 to 0.8: 0.8 to 0.2; And b) blocking the isocyanate functional group by adding a blocking agent of an isocyanate functional group to the prepared isocyanate-polyol mixture, followed by stirring to block the isocyanate functional group. The method of claim 1, wherein the monomer polyol is ethylene glycol, diethylene glycol, neopentyl glycol, butyl ethyl furopandiol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, trimethylolfurophane And at least one selected from the group consisting of trimethylol ethane. The method of claim 1, wherein the oligomeric polyol is at least one selected from the group consisting of polyether polyols, polyester polyols, polycaprolactone polyols, polytetramethylene polyols, and polycarbonate polyols. delete The production method according to claim 1, wherein the isocyanate compound is an aromatic isocyanate compound. The method of claim 1, wherein the isocyanate compound is at least one compound selected from the group consisting of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, xylene diisocyanate, their trimer type and polyol adduct type. A manufacturing method characterized by the above-mentioned. The method according to claim 1, wherein the blocking agent comprises an oxime compound. 8. The method according to claim 7, wherein the oxime compound is methyl ethyl ketoxime. The method of claim 1, wherein the resin composition has a number average molecular weight of 500 to 5000, and the blocked isocyanate equivalent in the resin is 200 to 2500 based on the nonvolatile content of the resin. A one-component thermosetting urethane resin coating composition comprising a resin composition according to the method of claim 1, a resin of a hydroxy functional group or a resin of an amino functional group, a pigment, a dispersant, an additive, and a solvent.