JPH0536464B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating method using an ultraviolet curable cationic electrodeposition paint having excellent flexibility and adhesion.

As is well known, UV-curable paints were developed with the aim of saving labor in conventional painting lines.
Among these, it has been developed for coating objects unsuitable for high-temperature baking, such as woodwork and plastics.

Painting with such paints is suitable for transparent clear coatings because the UV curing of the coating film depends on its UV transmittance, and it is suitable for flat surfaces where uniform irradiation of UV rays can be easily obtained due to the shape of the object to be coated. ing.

However, ultraviolet-curable coating films have an essential problem in that, because they cure rapidly, they cause stress distortion with the object to be coated, resulting in poor flexibility and adhesion.

The object of the present invention is to improve the above-mentioned problems of ultraviolet curable coatings, and to provide a coating method using ultraviolet curable coatings that can form coatings with excellent flexibility and adhesion. The object of the present invention is to provide a coating method using a paint that can employ a cationic electrodeposition coating method that causes less paint loss during coating, saves labor, and has fewer problems such as elution from the surface of the object to be coated.

In order to achieve the above object, the present inventor first began research by selecting a paint that could be cured by ultraviolet rays, assuming that it could be used for cationic electrodeposition coating, and after extensive research, a specific amount of The present invention was completed based on the discovery that the object of the present invention can be achieved by applying cationic electrodeposition using a paint containing epoxidized polybutadiene and then irradiating it with ultraviolet rays.

That is, the present invention provides a cationic electrodeposition paint containing a water-soluble or water-dispersible resin as a binder resin component, wherein the binder resin contains epoxidized polybutadiene in which a basic amino compound is added to an epoxy group, and the binder resin 35 to 90% by weight of the solid component is epoxidized polybutadiene.Ultraviolet curable cationic electrodeposition, in which cationic electrodeposition is applied using an ultraviolet curable cationic electrodeposition paint that can be cured by ultraviolet irradiation, and then irradiated with ultraviolet rays. It's in the method of applying the paint.

Further, the present invention further provides a coating method in which the object to be coated is preheated at a temperature of 60°C to 100°C after cationic electrodeposition coating and before irradiation with ultraviolet rays, and a coating method in which the irradiation intensity of the ultraviolet rays is sequentially adjusted over time. Provides a coating method that changes.

The present invention will be explained in detail below.

The UV-curable cationic electrodeposition paint used in the present invention uses a binder resin component in which epoxidized polybutadiene accounts for 35 to 90% by weight of the binder resin solid component, as described above.

Although epoxidized polybutadiene itself has UV curability, its crosslinking density is extremely low when used as a composition alone.

However, when a basic amino compound is added to the epoxy group of epoxidized polybutadiene, the ultraviolet curability is significantly improved.

Specifically, the epoxidized polybutadiene used in the present invention is reacted with a basic amino compound to open at least a portion of the epoxy group, and then neutralized with an acid to form a water-soluble or water-dispersible binder resin component. Use as a.

The epoxidized polybutadiene used in the present invention is
It is obtained by epoxidizing liquid polybutadiene, such as 1,2 bonds, 1,4 bonds, or a mixture of 1,2 bonds and 1,4 bonds, using hydrogen peroxide or peracid in a conventional manner. , from the viewpoint of flexibility of the coating film formed according to the present invention, the number average molecular weight is about 700 to
3000 is preferred, and commercially available examples include E-700, E-1500, E-1800 (trade name manufactured by Nippon Petrochemical Co., Ltd.), E _p -LCB-30 (trade name manufactured by Nippon Zeon Co., Ltd.), BF-1000 (product name manufactured by Nippon Soda Co., Ltd.)
etc.

The basic amino compound used in the reaction with the epoxidized polybutadiene is usually a compound having a primary or secondary amino group, such as an alkylamine such as diethylamine or propylamine, or an alkanol such as propanolamine or diethanolamine. Examples include polyalkyl polyamines such as amines, ethylenediamine, and triethylenetriamine.

Acids used to neutralize the reaction product of epoxidized polybutadiene and basic amino compounds include formic acid, acetic acid, acrylic acid, glycolic acid,
Examples include organic or inorganic acids such as lactic acid, phosphoric acid, and hydrochloric acid.

In addition, components other than epoxidized polybutadiene in which a basic amino compound is added to the epoxy group used in the binder resin component of the present invention do not cause any problems when applying cationic electrodeposition coating, and are particularly effective in curing with ultraviolet rays. There are no particular restrictions on the compound as long as it does not cause any trouble.

Therefore, such compounds include various compounds ranging from one molecule state (monomer state) to multimolecular bond state (oligomer state or polymer state).

Examples of such compounds include basic amino compounds such as the above-mentioned amines that react directly with epoxidized polybutadiene, as well as various monomers such as acrylic acid and methacrylic acid, or those that do not directly react with epoxidized polybutadiene. Examples include various polymers such as epoxy resins, acrylic resins, and modified (adducted) products thereof, which exist in a mixed state.
It is used as a binder resin component as shown in .

In the present invention, the epoxidized polybutadiene needs to account for 35 to 90% by weight of the binder resin solid component as described above, and this content is 35 to 90% by weight.
If it is less than 90% by weight, the UV curability and flexibility of the coating film formed will decrease, which is undesirable.On the other hand, if it exceeds 90% by weight, the UV curability will decrease and the binder resin component will be required. This is not preferable because it makes it impossible to obtain good water solubility or water dilubility.

However, the definition of the weight % in the present invention is, for example, in the case of a binder resin in which epoxidized polybutadiene is reacted with an amine and acrylic acid. forms the solid content of the total resin composition at a weight ratio of 10% by weight, the content of the binder resin solid component of the epoxidized polybutadiene is 90% by weight.

In the case of a binder resin in which epoxidized polybutadiene is mixed with other resins, this means that the epoxidized polybutadiene accounts for 35 to 90 parts by weight of the total binder resin solid content.

Although the ultraviolet curable cationic electrodeposition paint of the present invention can sufficiently achieve the object of the present invention with just the binder resin component described above, it may also contain lead-containing pigments, titanium white, carbon black, talc, etc. Inorganic pigments containing inorganic pigments such as calcium carbonate, especially lead, such as the basic lead silicate pigment Eagle Pitcher #202 (trade name of Eagle Pitcher Co., Ltd.), the basic lead silicate pigment Onker M-50 (Industry Co., Ltd.) If more than 1% by weight of the total paint is added, the range of UV curing conditions, e.g. irradiation time, irradiation light amount, irradiation distance etc. This has the effect of widening the range of curing conditions that can be obtained.

In addition, aliphatic organic acids such as lead, zinc, tin, iron, cobalt, manganese, and other metal salts, especially lead salts, should be added to all paints.
A similar effect can be obtained when it is added in an amount of % by weight or more.

Furthermore, in addition to the above-mentioned materials, the UV-curable cationic electrodeposition paint of the present invention contains photosensitizers such as benzoyl, benzyl, benzophenone, acetophenone, benzyl ketal, and benzoin ether, which are used in ordinary UV-curable paints, and styrene. It is possible to add reactive diluents such as α,β-ethylenically unsaturated compounds such as triacrylate or trimethacrylate of trimethylolpropane.

The ultraviolet curable cationic electrodeposition paint of the present invention thus prepared is diluted with water to form an electrodeposition bath with a solid content of about 10 to 20% by weight, and can be applied to conductive materials such as steel plates, plating surfaces, metal-deposited surfaces, conductive plastics, etc. The bath temperature is 25 to 30℃, and the distance between the electrodes is 10.
Cationic electrodeposition coating is possible under electrodeposition conditions of cm or more, applied voltage of 50 to 500 V, and energization time of 15 to 300 seconds.

The coating film formed in this way is washed with water in a conventional manner, and then a conventional ultraviolet irradiation device (e.g.
It is cured by irradiating ultraviolet rays using a 120 W/cm high-pressure mercury lamp or metal halide lamp at an irradiation distance of about 15 to 30 cm and an irradiation time of about 3 to 30 seconds.

In the above-described coating method according to the present invention, the coating film may be preheated after cationic electrodeposition coating and before irradiation with ultraviolet rays.

In other words, after cationic electrodeposition coating, preheating the formed coating film at a temperature of 60°C to 100°C for about 10 minutes will reduce the excessive irradiation of ultraviolet rays, which corresponds to the overbake property of ordinary thermosetting paints. The range of conditions can be expanded.

At this time, if the temperature is less than 60℃, the above-mentioned heating effect will not be exhibited, and if it exceeds 100℃, thermal deformation may occur depending on the coated object, or photosensitizers and reactive diluents may be removed. Volatilization occurs, which is undesirable.

Furthermore, in the present invention, it has been found that the adhesion of the formed coating film can be improved by sequentially changing the irradiation intensity over time during ultraviolet irradiation, regardless of the presence or absence of the preheating step.

For example, when irradiating ultraviolet light, the light intensity can be increased to 80W/
cm to 120W/cm, conveyor speed 20
Change the irradiation time from m/min to 2m/min (change the irradiation time over time), and set the irradiation distance to 300mm or more.
It was found that when the beam was changed to 100 mm, the adhesion and other physical properties of the paint film were improved compared to when the beam was irradiated with a certain amount of light for a certain period of time and from a certain distance.

As explained above, the paint and coating method of the present invention utilizes cationic electrodeposition coating using a binder resin component containing epoxidized polybutadiene in which a basic amino compound is added to an epoxy group and a specific amount of epoxidized polybutadiene. By curing the formed coating film with ultraviolet irradiation, a coating film with excellent flexibility and adhesion and no yellowing unlike ordinary high-temperature baking-cured coatings can be obtained. Benefits such as labor saving and reduced paint loss can be obtained.

Examples of synthesizing the resin used as the binder resin component of the paint of the present invention are shown below.

Synthesis example A (1) E-1800 (trade name of epoxidized polybutadiene manufactured by Nisseki Chemical Co., Ltd. with a molecular weight of 1800) 1800 parts by weight (2) Diethanolamine 315 〃 (3) Ethyl cellosolve 816 〃 (4) ESA-011P (Sumitomo Chemical Co., Ltd.) 250 〃 (5) Hydroquinone 30 〃 (6) Acrylic acid 144 〃 The components (1) to (3) above were heated to 150℃ under N 2 gas and heated to 150℃ under N ₂ gas.
After an hour, component (4) was added and held at 160°C for another 30 minutes, then cooled to 130°C, and then (5) and (6)
The following components were added and reacted until the acid value became 10 or less to obtain a resin containing about 71% by weight of epoxidized polybutadiene having cationic electrodeposition and ultraviolet curing properties.

Synthesis example B (1) E-1500 (trade name of epoxidized polybutadiene manufactured by Nisseki Chemical Co., Ltd. with a molecular weight of 1500) 1500 parts by weight (2) Diethanolamine 190 〃 (3) Butyl cellosolve 576 〃 (4) Hydroquinone 30 〃 (5) Acrylic acid 130 〃 The components (1) to (3) above were reacted at 150℃ for 2 hours under _N2 gas, then cooled to 130℃, and the components (4) and (5) were added until the acid value became 10 or less. The reaction yielded a resin having an epoxidized polybutadiene content of about 81% by weight and having cationic electrodepositability and UV curability.

Synthesis example C (1) E-700 (trade name of epoxidized polybutadiene manufactured by Nisseki Chemical Co., Ltd. with a molecular weight of 700) 700 parts by weight (2) Diethanolamine 157 〃 (3) Ethyl cellosolve 285 〃 Components of (1) to (3) above was reacted for 2 hours at 150° C. under N ₂ gas to obtain a resin containing about 82% by weight of epoxidized polybutadiene.

Synthesis example D (1) E-1800 1800 parts by weight (2) Diethanolamine 200 〃 (3) Ethyl cellosolve 666 〃 The components (1) to (3) above were reacted at 150°C for 2 hours under N ₂ gas and subjected to cationic electrodeposition. A resin having an epoxidized polybutadiene content of about 90% by weight was obtained, which had a property of hardening and UV curability.

Synthesis example E (1) ESA-011P 1000 parts by weight (2) Ethyl cellosolve 300 (3) Hydroquinone 25 (4) Acrylic acid 126 (5) Triethylamine 2 (6) Dimethylbenzylamine 2 (7) Methyl ethyl ketone 41 〃 The ingredients in (1) and (2) above were heated to 130℃, and then
After adding components (3) to (6) and reacting for 3 hours, the mixture was cooled to 75° C., and component (7) was added and diluted to obtain a resin having cationic electrodepositability and ultraviolet curability.

Note that the obtained resin does not contain any epoxidized polybutadiene.

Synthesis example F (1) ESA-011P 1000 parts by weight (2) Ethyl cellosolve 393 〃 (3) Diethanolamine 180 〃 The components (1) and (2) above were heated to 130°C, and the component (3) was added. The mixture was reacted for 2 hours to obtain a resin that had cationic electrodeposition but no ultraviolet curability.

Note that the obtained resin does not contain any epoxidized polybutadiene.

Synthesis example G (1) ESA-011P 1000 parts by weight (2) Ethyl cellosolve 370 〃 (3) Diethanolamine 90 〃 (4) Hydroquinone 14 parts by weight (5) Acrylic acid 62 〃 The above components (1) and (2) Raise the temperature to 130°C, add component (3) and react for 2 hours, then add (4) and (5).
The following components were added and reacted for 3 hours to obtain a resin having cationic electrodeposition properties and ultraviolet curing properties.

Note that the obtained resin does not contain any epoxidized polybutadiene.

Synthesis Example H (1) Tetrahydrophthalic anhydride 100 parts by weight (2) Hydroxyethyl methacrylate 58 〃 (3) Hydroxyethyl acrylate 52 〃 (4) Hydroquinone 0.1 〃 (5) Ethyl glycol acetate 90 〃 (6) Sumiepoxy ELA- 128 (Sumitomo Chemical epoxy resin product name) 200 〃 (7) ESA-011P 500 〃 (8) Ethyl glycol acetate 190 〃 (9) Tolylene diisocyanate 140 〃 (10) Diethylethanolamine 59 〃 (11) Diethanolamine 31 Parts by weight (12) Ethyl glycol acetate 100 〃 The components (1) to (5) above were reacted at 130°C for 3 hours,
Furthermore, components (6) to (8) were added and reacted for 2 hours.
Next, separately, add ingredients (9) to (12) at 10℃ to 20℃ for 2 minutes.
Allowed time to react. After that, the reaction products of the components (1) to (8) and the reaction products of the components (9) to (12) were mixed and heated at 60°C to 70°C for 1 hour to obtain cationic electrodeposition. And a resin having ultraviolet curable properties was obtained.

Note that the obtained resin does not contain any epoxidized polybutadiene.

Example 1 533.2 g of the resin of Synthesis Example D was placed in a circular stainless steel container, 20 g of Darocur 1173 (trade name of a photosensitizer manufactured by Merck) was added, and the mixture was stirred thoroughly to make it homogeneous. next
159.6 g of a 10% acetic acid aqueous solution was added to neutralize the mixture to obtain a binder resin component. The content of epoxidized polybutadiene in this binder resin component was about 90% by weight.

Add 3287.1g of pure water and dilute it with water to make an electrodeposition bath, and apply the coating to a steel plate (0.8 x 70 x 150 mm) with a length of 1 cm.
Place it in a 20cm wide x 20cm high Enbi vat and use normal cationic electrodeposition experimental equipment at a voltage of 100V to 200V.
Cationic electrodeposition coating with energization time of 60 seconds to 120 seconds,
Coating films of various thicknesses were obtained.

Next, after washing these coatings with water, using an ultraviolet curing device (UB0451-5BM manufactured by Agraphix),
Conveyor speed variable from 2m to 20m/min (standard 10
m/min), lamp rating can be switched from 120W/cm to 80W/cm (standard 120W/cm), irradiation distance can be varied from 100mm to 300mm (standard 150mm), Lamp used: UV curing multi-lamp (mercury + halogen), reflector When UV curing was carried out under conditions of a paraboloid shape (parallel light), a coating film was obtained that was cured according to the energy degree in 1 pass (3 seconds irradiation) to 10 passes (total 30 seconds irradiation) under standard conditions. . Dry average film thickness 10μ and 20μ
When I looked at the coating film performance of the objects, all of them had pencil hardness.
2B to B passed the DuPont impact test 500g x 30cm.

Example 2 Cationic electrodeposition coating was carried out in the same manner as in Example 1 except that the resin of Synthesis Example B was used instead of the resin of Synthesis Example D, and then the same ultraviolet curing equipment as in Example 1 was used under standard conditions. Irradiation was performed for 15 seconds to obtain cured coatings with film thicknesses of 10μ and 20μ. When looking at the performance of these coatings, they had a pencil hardness of H and passed a DuPont impact test of 500 g x 50 cm. However, the content of epoxidized polybutadiene in the binder resin component was about 81% by weight.

Example 3 Example 1 except that the resin of Synthesis Example A was used instead of the resin of Synthesis Example D, and a tin plate was used as the object to be coated.
Cationic electrodeposition coating was performed in the same manner as above, and UV irradiation was performed under standard conditions to obtain cured coatings with film thicknesses of 10μ and 20μ.

In both cases, 4 passes (12 seconds of irradiation) passed the DuPont impact test 500g x 50cm, and 10 passes (30 seconds) passed the DuPont impact test.
500 for 15-pass (45-second irradiation)
g x 30cm passed.

However, the content of epoxidized polybutadiene in the binder resin component was about 71% by weight.

Example 4 533.2 g of the resin of Synthesis Example A, 12 g of E _p -202 (trade name of lead-based inorganic pigment manufactured by Eagle Pitcher Co., Ltd.), 16.8 g of diacetone alcohol, Darocur 1116
(trade name of photosensitizer manufactured by Merck) 20g was uniformly mixed and dispersed, then 51.2g of 30% formic acid aqueous solution was added to neutralize it, and further 3438g of pure water was added to dilute with water to prepare an electrodeposition bath. .

Using this electrodeposition bath, cationic electrodeposition coating was carried out in the same manner as in Example 3, and 2 passes (irradiation for 6 seconds) were carried out under standard conditions.
A coating film was obtained under curing conditions of ~30 passes (irradiation for 90 seconds).

A Dupont impact test was conducted on these coatings, and it was found that those irradiated with 4 to 30 passes weighed 500 g.
×50cm passed, 100g for 10-2 passes irradiation
×50cm passed, indicating that not only the range of curing conditions was expanded compared to Example 3, but also the performance was improved.

However, the content of epoxidized polybutadiene in the binder resin component was about 71% by weight.

Example 5 A coating film was prepared in the same manner as in Example 4, except that inorganic pigments such as talc, sulfuric acid, barium, calcium carbonate, titanium white, and carbon black were used instead of Ep- ₂₀₂ (lead-based inorganic pigment). According to what I got, the Dupont impact test was 500g for 6-10 pass irradiation.
×50cm passed.

However, the content of epoxidized polybutadiene in the binder resin component was about 71% by weight.

Example 6 5 g of each aliphatic organic acid metal salt of lead octylate, zinc naphthenate, manganese naphthenate, iron naphthenate, and cobalt naphthenate was added to the electrodeposition bath of Example 3.
A coating film was obtained in the same manner as in Example 3 except that each electrodeposition bath added was used.
It passed the DuPont impact test 500g x 50cm after 10 passes of irradiation.

However, the content of epoxidized polybutadiene in the binder resin component was approximately 70% by weight.

Example 7 The light of the lamp was reduced from 120 W/cm under standard conditions to 80 W/cm, and the irradiation distance was further changed from 150 mm under standard conditions.
A coating film was obtained by performing 6 passes of irradiation in the same manner as in Example 3 except that the distance was 200 mm. The resulting coating film passed the DuPont impact test of 1000 g x 40 cm.

Thus, in the method of the present invention, it has been found that it is more desirable to gradually irradiate light energy little by little than to irradiate a large amount of light all at once.

Example 8 A coating film was obtained in the same manner as in Example 1, except that the steel plate to be coated (coating film) was preheated at 80° C. for 10 minutes after cationic electrodeposition coating and before UV irradiation.

When looking at the performance of this coating film, it had a pencil hardness of B and passed a DuPont impact test of 500 g x 40 cm.

Example 9 A coating film was obtained in the same manner as in Example 3, except that instead of using the resin of Synthesis Example A, a resin obtained by mixing the resin of Synthesis Example A and the resin of Synthesis Example F at a ratio of 50/50 was used. Ta. When the resulting coating film was subjected to a Dupont impact test, the one with 4 passes of irradiation passed 500g x 40cm.
The 10-pass and 15-pass samples passed 500g x 30cm.

However, the content of epoxidized polybutadiene in the binder resin component was 36% by weight.

Comparative Example 1 The mixing ratio of the resin of Synthesis Example A and the resin of Synthesis Example F was
A coating film was obtained in the same manner as in Example 9 except that the coating was changed to 42/58, and all of the films subjected to irradiation of 4 passes, 10 passes, and 15 passes failed the DuPont impact test of 500 g x 10 cm.

However, the content of epoxidized polybutadiene in the binder resin component was 30% by weight.

Example 10 A coating film was obtained in the same manner as in Example 3, except that instead of using the resin of Synthesis Example A, a resin obtained by mixing the resin of Synthesis Example D and the resin of Synthesis Example E at a ratio of 70/30 was used. Ta. When this coating film was subjected to a Dupont impact test,
The one with 4 passes of irradiation passed 500g/30cm.

However, the content of epoxidized polybutadiene in the binder resin component was about 63% by weight.

Example 11 A coating film was obtained in the same manner as in Example 3, except that instead of using the resin of Synthesis Example A, a resin obtained by mixing the resin of Synthesis Example C and the resin of Synthesis Example F at a ratio of 50/50 was used. Ta. The pencil hardness of this paint film is HB, and in the Dupont impact test, it was 500 after 4 passes of irradiation.
g x 30cm passed.

However, the content of epoxidized polybutadiene in the binder resin component was about 41% by weight.

Example 12 An electrodeposition bath was prepared in the same manner as in Example 1, except that the resin in Synthesis Example G was used instead of the resin in Synthesis Example D, and an electrodeposition bath was prepared in the same manner as in Example 3.
A coating film was obtained in the same manner as in Example 3, except that an electrodeposition bath mixed at a ratio of 37/63 was used.

When this coating film was subjected to a Dupont impact test, it passed the 500g x 40cm one with four passes of irradiation.

However, the content of epoxidized polybutadiene in the binder resin component was about 45% by weight.

Comparative Example 2 A coating film was prepared in the same manner as in Example 12 using the electrodeposition bath prepared in the same manner as in Example 1 except that the resin of Synthesis Example G was used instead of the resin of Synthesis Example D as the electrodeposition bath. I got it. When this coating film was subjected to a Dupont impact test, it was found to be unacceptable for 4 passes of irradiation (500 g x 15 cm).

However, the binder resin component does not contain any epoxidized polybutadiene.

Example 13 A coating film was obtained in the same manner as in Example 12 except that the resin in Synthesis Example H was used instead of the resin in Synthesis Example G. The same results as in Example 12 were obtained.

However, the content of epoxidized polybutadiene in the binder resin component was about 45% by weight.

Comparative Example 3 A coating film was obtained in the same manner as Comparative Example 2 except that the resin of Synthetic Example H was used instead of the resin of Synthetic Example G, and the same results as Comparative Example 2 were obtained.

However, the binder resin component does not contain any epoxidized polybutadiene.

Claims (1)

[Scope of Claims] 1. A cationic electrodeposition paint containing a water-soluble or water-dispersible resin as a binder resin component, wherein the binder resin contains epoxidized polybutadiene in which a basic amino compound is added to an epoxy group. , 35~ of the solid component of the binder resin
An ultraviolet curable cationic electrodeposition coating material comprising 90% by weight of epoxidized polybutadiene that can be cured by ultraviolet irradiation is applied to the object by cationic electrodeposition, and then irradiated with ultraviolet rays. How to apply paint. 2. The coating method according to claim 1, wherein the irradiation intensity of the ultraviolet rays is sequentially changed over time. 3. A cationic electrodeposition paint containing a water-soluble or water-dispersible resin as a binder resin component, wherein the binder resin contains epoxidized polybutadiene in which a basic amino compound is added to an epoxy group, and the solid state of the binder resin is 35~ of ingredients
An ultraviolet curable cationic electrodeposition paint that consists of cationically electrodepositing the object to be coated with an ultraviolet curable cationic electrodeposition paint that is 90% by weight epoxidized polybutadiene and can be cured by ultraviolet irradiation, and then irradiated with ultraviolet rays. A coating method characterized in that the object to be coated is preheated at a temperature of 60°C to 100°C before the irradiation. 4. The coating method according to claim 3, wherein the irradiation intensity of the ultraviolet rays is sequentially changed over time.