WO2015003654A1

WO2015003654A1 - Prebake process and system for water-based painting without a middle coat

Info

Publication number: WO2015003654A1
Application number: PCT/CN2014/082056
Authority: WO
Inventors: 李晓琳
Original assignee: 安徽江淮汽车股份有限公司
Priority date: 2013-07-12
Filing date: 2014-07-11
Publication date: 2015-01-15
Also published as: BR112016001095A2

Abstract

Provided is a prebake process for water-based painting without a middle coat, comprising the following steps: before a first heating stage, gas sealing at a temperature of 60-80°C; first heating stage at temperature of 70-80°C, wind velocity of 3-5 m/s, and heating time of 3-4 minutes; second heating stage at temperature of 90-100°C, wind velocity of 10-14 m/s, and heating time of 3-4 minutes; after second heating stage, gas sealing at a temperature of 80-100°C; a forced cooling stage in which workpiece surface temperature is reduced to ≤35°C; the first and second heating stages ensure an absolute humidity of 10-15 g/kg. Also provided are a prebake system for implementing the described process, a vehicle body manufactured using the process, and an automobile having the vehicle body. The process significantly improves the appearance of a workpiece after water-based painting without a middle coat.

Description

Water-based free intermediate coating pre-drying process and system

Technical field

The invention relates to the field of automobile painting, and particularly relates to a pre-baking process and a pre-drying system in an aqueous medium-free coating process. Background technique

As the country's environmental requirements continue to increase, more and more car manufacturers choose to use water-based paint. At present, the water-based paint process with many applications is the traditional 3C2B process, in which 3C stands for three coats, which are middle coat, top coat and cover light, and 2B stands for two drying processes, namely, medium coat drying and top coat drying. Dry, including pre-drying of the intermediate coating and pre-drying of the topcoat. The 3C2B production process has a very mature experience, but its disadvantage is that the coating line is long and achieves maximum process reliability and meets all quality requirements at the expense of high cost.

In the "Modern Coatings and Coatings" of the 14th issue of the 14th volume of 2011, the authors are Xing Wenping, Ge Fei, Pi Wei, the article entitled "Application of water-based coating process for automotive coating", introduced The aqueous B 1B2 process flow, in which the pre-baking conditions are 60 to 80 ° C, the time is 3-5 min, and the B 1B2 process is verified, which does not involve the influence of pre-drying conditions on the coating effect. . In the sixth issue of 2012, Electroplating and Finishing, Volume 31, the authors are Xing Wenping, Ge Fei, Qiu Changsheng, the article titled "Water-based Exemption Coating Process Research", for water-free intermediate coating The installation process, taking the B 1B2 process as an example, introduced the technical effects, influencing factors, and existing problems. However, when discussing the influence of the intermediate flashing and leveling time, the two periods of 4.5min and 7min were selected in the pre-drying process for the test, and the different flashing and leveling time were basically no color and vividness. The conclusion of the influence, but did not deeply explore the influence of the comprehensive factors such as pre-baking temperature and time on the appearance quality of the workpiece. In the actual water-free intermediate coating process, the pre-drying process generally uses a two-stage heating and drying method, the heating temperature is controlled at 60 ± 5 °C, and the tuyere wind speed is controlled at 6-10 m/s, heating time. It is l-2min; the heating temperature is controlled at 80 ± 5 degrees Celsius, the tuyere wind speed is not less than 10m/s, and the heating time is 2.5-3min. In actual production, the ratio of the heating period to the heating of the second stage is generally controlled at about 1:2, which means that the heating from the heating stage to the heating of the second stage requires rapid temperature rise. But in fact, after the water-repellent free-coating process, before pre-drying The wet film thickness is larger, which will more than double, and the rapid heating will lead to pinholes and other quality defects. Moreover, the pre-drying time of the traditional aqueous pre-drying system is about 3-4 minutes, and the drying time is too short. The effect is not good, which is not conducive to the next stage of workpiece processing after pre-drying. According to the pre-drying process carried out under the above conditions, some appearance quality parameters may not even meet the standard requirements. Summary of the invention

The object of the present invention is to overcome the above disadvantages, and to provide a pre-baking process which is advantageous for improving the pre-bake quality and the drying effect in the water-free intermediate coating, and provides a pre-drying process for realizing the pre-drying process. A simple pre-drying system.

To achieve the above object, the present invention provides the following technical solutions:

An aqueous free intermediate coating pre-drying process, comprising the following steps:

The gas seal is performed before heating for a period of time, and the gas seal temperature is 60-80 ° C;

Heating for a period, the temperature is 70-80 ° C, the wind speed is 3-5 m / s, the heating time is 3-4 min; the heating is two, the temperature is 90-100 ° C, the wind speed is 10-14 m / s, the heating time is 3 -4min; after two stages of heating, the gas seal is performed at a gas seal temperature of 80-100 °C;

Strong cold section, reduce the surface temperature of the workpiece to 35 °C;

Wherein, the heating section and the heating section ensure an absolute humidity of 10-15 g/kg.

The sum of the heating time of the heating section and the heating time of the heating section

Preferably, the strong cold section has a temperature of 20 ° C and a wind speed of 16-20 m / s.

Preferably, the heating is at a temperature of 75 ° C and the heating at a temperature of 90 ° C. An aqueous medium-free coating pre-drying system, comprising: a pre-drying chamber; a conveying system for conveying the workpiece to the pre-drying chamber; a heating system for supplying air to the pre-drying chamber; In the direction, the pre-drying chamber is arranged with an inlet air curtain, a heating section, a heating section, an outlet air curtain, and a strong cooling chamber, wherein the length of the heating section and the length of the heating section satisfy the following mathematical expression:

Sl=vti; S2=vt ₂ ; 3min < ti <4min; 3min < t ₂ <4min;

Wherein, SI is the length of the heating section, the unit is m; S2 is the length of the heating two sections, the unit is m; V is the advancement speed of the workpiece on the conveying system, the unit is m/min, ^, t ₂ are respectively The time it takes for the workpiece to heat up for a period of time and heat for two stages.

Preferably, the ratio of the length of the heating section to the length of the heating section is 1:1.

Preferably, the length of the heating section and the length of the heating section should also satisfy the following mathematical expression:

6.5 mm.

v

Preferably, the heating system comprises a heating box for providing a circulating wind for the heating section and the inlet air curtain, a two-stage heating box for providing a circulating wind for the heating two sections and the outlet air curtain, and A cold air box that provides a cold air in a strong cold room.

Preferably, the one-stage heating box comprises a fresh air valve, a filter, a surface cooler, a burner and a circulation fan, the wind passing through the fresh air valve, the filter, the air cooler, the burner and the After the circulation fan enters the heating section and the inlet air curtain; the two-stage heating tank includes a circulation fan, a filter and a burner, and the wind from the heating section passes through the filter, the burner and The circulating fan enters the heating second section and the outlet air curtain; the cold air box comprises a blower, an exhaust fan, a filter and a surface cooler, and the wind passes through the filter, the inlet fan, the strong The cold chamber and the exhaust fan realize air exchange with the outdoor.

A vehicle body manufactured by the above-described process and a vehicle using the vehicle body.

In the pre-baking process of the present invention, a better pre-baking effect is obtained by controlling the temperature, time, and wind speed, and the appearance quality of the paint film on the surface of the workpiece is better.

Further, setting the heating time ratio of the heating section to the heating section is set to 1 : 1, which is advantageous for the sufficient evaporation of water and the gentle rise of the heating rate.

Further, the heating temperature is 75 ° C, and the heating temperature is 90 ° C, which is higher than the set temperature of the conventional heating section and the heating section, but the temperature difference is small, and the heating temperature is close to the gas sealing temperature before the heating, heating The temperature of the second stage is close to the air sealing temperature thereafter, so that the higher the drying speed is ensured, the temperature rise is more stable, and defects such as pinholes are reduced.

The pre-drying system of the invention has a simple structure and can meet the above process requirements. Instruction sheet

Figure 1 is a schematic view of the water-free intermediate coating pre-drying system of the present invention;

Figure 2 is a graph showing the body temperature during the passage of the body through the pre-drying system of Figure 1. The mark in the above figure shows: pre-drying chamber 1, heating system 2, one-stage heating box 21, two-stage heating box 22, and cold air box 23. detailed description

Specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Table 1

Table 1 shows the process and process requirements for using a conventional pre-baking process in a conventional aqueous coating process. It can be seen from Table 1 that the heating period is shorter than the heating period, generally the ratio of the heating period to the heating period is 1:2, and the heating time in the heating section and the heating section is generally not More than 4min. This results in a shorter heating time during heating and a shorter overall heating time, and the degree of moisture elimination in the paint film is not satisfactory because of the thick wet film thickness in the water-free intermediate coating. In addition, the temperature difference between the heating section and the heating section is relatively large (generally, the temperature is set to 60 ° C in the heating section, and the temperature is set to 80 ° C in the heating section, and the temperature difference between the two sections generally reaches 20 °C), that is to say, the temperature rises from heating to the second stage of heating, and the speed is increased rapidly, so that defects such as pinholes are easily caused. Heating a higher wind speed is also not conducive to ensuring the quality of the paint film containing more moisture. Table 2

Table 2 shows the pre-drying process in accordance with the present invention. In the present invention, the air seal is used for air sealing before heating for a period of time to ensure stable operation of the heating section. Moreover, the gas seal temperature is set to 60-80 ° C, and the workpiece entering the heating section is preheated. Next, the workpiece enters a heating process, setting the heating temperature to 70-80 ° C, the wind speed to 3-5 m / s, and the heating time to 3-4 min. Comparing with Table 1, it can be seen that the heating time of the heating section becomes longer, so that most of the moisture on the surface of the workpiece can be taken away during the heating period, and the wind speed of the tuyere is lowered, and the surface quality of the paint film is better. After heating for a period of time, the workpiece enters the heating stage, the heating temperature is 90-100 ° C, the wind speed is 10-14 m / s, and the heating time is 3-4 min. Compared with Table 1, the heating time of the heating section is also After being extended, the paint film is further dried. Although increasing the wind speed relative to heating is beneficial to increase the drying speed of the paint film, the wind speed should not be too large, otherwise the film quality will still be affected. Select 10-14m/s. It is suitable. After heating the second stage, the air seal is used for air sealing, and the gas sealing temperature is 80-100 ° C, which is close to the temperature of the second heating stage. It can be seen from the above that from the workpiece through the gas seal into the heating section, heating the second section to the end of the gas seal heating, the heating time becomes longer in the whole process, preferably at least 6.5min, and the temperature change is relatively gentle, by the temperature, the heating time and The comprehensive control of the wind speed achieves better film quality and thus the appearance quality of the workpiece is better. Wherein, it is preferred that the heating time ratio of the heating section to the heating section is 1:1, and the requirement of the dry moisture requirement can be met. The shortest time is now, and labor productivity is high. Preferably, the heating temperature is 75 ° C, the heating temperature is 90 ° C, the temperature is higher than the traditional process, the temperature difference is small, the drying water efficiency is high, and the temperature difference is gentle. After leaving the gas seal, the workpiece enters the strong cold section and reduces the surface temperature of the workpiece to 35 °C in preparation for the next step of the water-free intermediate coating process. Preferably, the strong cold section is carried out at a temperature of 20 ° C and a wind speed of 16-20 m/s. During the above treatment, heating one section and the heating section need to ensure an absolute humidity of 10-15 g/kg.

table 3

Comparative data on the appearance quality of the workpiece obtained by pre-baking. Wherein, the conventional pre-drying process and the pre-drying process of the present invention are respectively performed using the parameters in Table 1 and Table 2, and other parameters are the same. It can be seen from Table 3 that the surface quality obtained by the pre-baking process according to the present invention is superior to the conventional one for the three different color paints in terms of length, short wave, gloss and vividness of the horizontal and vertical planes. The pre-baking process, especially for white, does not meet the requirements in terms of vividness, and the pre-baking process of the present invention can meet the requirements.

It will be understood by those skilled in the art that in the above description, heating one section and heating two sections means a time step, but in the following description, heating one section and heating two sections means the space physics of the pre-drying chamber. component. Referring to FIG. 1, in order to realize the pre-baking process of the present invention, an embodiment of the present invention provides an aqueous medium-free coating pre-drying system, comprising: pre-baking A dry chamber 1, a heating system 2, and a delivery system (not shown) that transports the workpiece to the pre-drying chamber. Wherein, the heating system 2 supplies air to the pre-drying chamber 1 to achieve the process requirements of the present invention in each section of the pre-drying chamber. After the workpiece is carried by the conveying system, after the previous process of pre-drying is completed, the pre-drying chamber 1 enters and moves therein in the advancing direction of the workpiece indicated by the arrow in the figure. In the advancing direction of the workpiece, the pre-drying chamber 1 is sequentially arranged with an inlet air curtain, a heating section, a heating section, an outlet air curtain and a strong cooling chamber, and in order to satisfy the heating time of the process of the invention, heating a section and the heating The length of the second segment should satisfy the following mathematical expression:

Sl=vti; S2=vt ₂ ; 3min < ti <4min; 3min < t ₂ <4min;

Wherein, the SI is heated for a length, in units of m; S2 is a two-stage heating of length, in m; V is the velocity of the advancing workpiece transport system, the unit is m / min, ^, t ₂ respectively workpiece The time elapsed during the heating of one section and heating of the second section. Preferably, the length ratio of the heating section to the heating section is 1:1, since the workpiece is advanced at the conveying system, it means that the time during which the workpiece is heated in the heating section and the heating section is also 1:1. Preferably, the length of the heating section and the length of the heating section should also satisfy the following equation:

^^^6.5 min, that is, the time the workpiece has been in the heating section and the heating section is not less than

V

6.5min.

The heating system 2 includes a section of heating tanks 21 for providing a circulating air for heating a section and an inlet air curtain, a two-stage heating tank 22 for providing circulating air for heating the two sections and the outlet air curtain, and a cold bellows 23 for supplying cold air to the forced cooling chamber. A section of the heating box 21 heats the external fresh air and sends it to the inlet air curtain to provide a gas seal, and feeds the heating section to make the temperature of the air in the heating section reach the process requirement. The two-stage heating box 22 further heats and heats the air in the second stage of heating to reach the requirements of the heating two-stage process, and provides a gas seal to the outlet air curtain. The cold bellows 23 completes the heat exchange between the refrigerating chamber and the outside, thereby cooling the workpiece in the refrigerating chamber. The fresh air from the outside passes through the fresh air valve, filter, air cooler and burner in the heating chamber 21 to reach the required temperature, and then enters the heating section and the inlet air curtain through the circulation fan. The temperature from the heated section passes through the filter and burner in the two-stage heating tank 22, and the temperature is further increased, and the circulating fan enters the heating second section and the outlet air curtain. The outdoor wind passes through the filter in the cold air box 23, enters the strong cold chamber through the inlet fan, and the air in the strong cold chamber exchanges heat with the workpiece, and then exchanges air with the outdoor through the exhaust fan. By controlling the operation of the circulating fan, the inlet fan and the exhaust fan, it is possible to control the tuyere wind speed of each part of the pre-drying chamber. Of course, the prior art It can be easily imagined by the personnel that the heating system 1 can also utilize other heating and cooling systems such as central air conditioning. After the workpiece leaves the forced cooling chamber, enter the transition section to prepare for the next process.

2 is a view showing the temperature probe detection at different positions of the vehicle body in the process of the pre-drying system in the pre-drying room in the process of the pre-drying system of the embodiment of the present invention. The body temperature curve to the arrival. The appearance quality of the body paint film obtained in the process is given in Table 3 and will not be described here. The appearance quality of the car body is improved, and accordingly, the overall appearance quality of the car will be significantly improved.

Although the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments described above. A person skilled in the art can easily modify and change the present invention without departing from the spirit and scope of the invention.

Claims

Rights request

1. A water-based mid-coat-free pre-drying process, characterized in that it includes the following steps: air sealing before heating for a period of time, and the air sealing temperature is 60-80°C;

In the first heating section, the temperature is 70-80°C, the wind speed is 3-5m/s, and the heating time is 3-4min; in the second heating section, the temperature is 90-100°C, the wind speed is 10-14m/s, and the heating time is 3 -4min; Carry out air sealing after the second heating stage, the air sealing temperature is 80-100 °C;

The strong cooling section reduces the surface temperature of the workpiece to 35 °C;

Among them, the first heating stage and the second heating stage ensure that the absolute humidity is 10-15g/kg.

2. The process according to claim 1, characterized in that the sum of the heating time of the first heating stage and the heating time of the second heating stage reaches at least 6.5 minutes.

3. The process according to claim 1, characterized in that the heating time ratio between the first heating stage and the second heating stage is 1:1.

4. The process according to claim 1, characterized in that the temperature of the strong cooling section is 20°C, and the wind speed is 16-20m/s.

5. The process according to any one of claims 1 to 4, characterized in that the temperature of the first heating stage is 75 °C, and the temperature of the second heating stage is 90 °C.

6. A water-based mid-coat-free coating pre-drying system, including:

Pre-drying room;

A conveying system for conveying workpieces to the pre-drying chamber;

A heating system that supplies air to the pre-drying chamber;

It is characterized in that, in the forward direction of the workpiece, the pre-drying chamber is sequentially arranged with an inlet air curtain, a first heating section, a second heating section, an outlet air curtain, and a forced cooling chamber. The first heating section and the second heating section are arranged in sequence. The length satisfies the following mathematical expression:

Sl=vti; S2=vt ₂ ; 3min < ti <4min; 3min < t ₂ <4min;

Among them, SI is the length of the first heating section, the unit is m; S2 is the length of the second heating section, the unit is m; V is the forward speed of the workpiece on the conveying system, the unit is m/min, ^ and t ₂ are the workpiece respectively The time spent in the first heating stage and the second heating stage;

The inlet air curtain provides an air seal with a temperature of 60-80°C, and the heating system is the pre-drying The room supplies air so that the temperature of the first heating section is 70-80°C and the wind speed is 3-5m/s, and the temperature of the second heating section is 90-100°C and the wind speed is 10-14m/s. The outlet The air curtain provides an air seal of 80-100°C, and the first heating section and the second heating section ensure an absolute humidity of 10-15g/kg.

7. The system according to claim 6, characterized in that the length ratio of the first heating section to the second heating section is 1:1.

8. The system according to claim 6, characterized in that the lengths of the first heating section and the second heating section should also satisfy the following mathematical expression:

^6.5 mm

V

9. The system according to any one of claims 6 to 8, characterized in that, the heating system includes a section of heating box that provides circulating air for the heating section and the inlet air curtain. The second section and the outlet air curtain provide a second section heating box for circulating air and a cold air box that provides cold air for the forced cooling room. The first section heating box includes a fresh air valve, a filter, a surface cooler, a burner and a circulating fan. , the air passes through the fresh air valve, the filter, the surface cooler, the burner and the circulating fan and then enters the first heating section and the inlet air curtain; the second section heating box includes a circulating fan , filter and burner, the wind from the first heating section passes through the filter, the burner and the circulation fan and then enters the second heating section and the outlet air curtain; the cold air box includes an air blower , exhaust fan, filter and surface cooler, the air passes through the filter, the air inlet fan, the forced cooling chamber, and the exhaust fan to achieve air exchange with the outdoors.

10. A vehicle body, characterized in that the vehicle body is manufactured using the process described in any one of claims 1 to 5.

11. An automobile, characterized in that, the automobile adopts a body as claimed in claim 10.