KR20130042714A - Coating transfer improved acryl resin composition for back side coating of thickness film pre-coated automobile steel sheet and paint composition - Google Patents

Abstract

PURPOSE: An acrylic resin composition with excellent releasing force is provided to absolutely improve a releasing agent-transition phenomenon which is a weakness of existing silicon releasing agent. CONSTITUTION: An acrylic resin composition consists of 40-70 weight% of an acrylic monomer copolymer. The acrylic monomer copolymer is obtained by mixing 60-90 weight5 of an alkoxy silane group-containing acrylic monomer and 10-40 weight% of an amide group-containing acrylic monomer. The paint composition consists of 15-35 weight% of the acrylic resin composition, 20-40 weight5 of an epoxy resin composition, 30-54 weight% of an organic solvent, and 1-5 weight% of an additive.

Description

Coating transfer improved acryl resin composition for back side coating of thickness film Pre-coated automobile steel sheet and paint composition}

The present invention relates to an acrylic resin composition for back coating of a thick film pre-coated automotive steel sheet, a method of manufacturing the same, and a coating material comprising the same, and more particularly to a back coating acrylic coating a rear surface of a thick film pre-coated automotive steel sheet. It relates to a resin composition, a method for producing the same, and a paint including the same.

The steel sheet for automotive steel sheet is manufactured by the manufacturer and then reprocessed by grinding, polishing, and cutting at the automobile manufacturer, and then, as a finishing material for the automobile, through pre-treatment electrodeposition coating process, primer coating process, and subsequent mid-high degree painting process. Will be Recently, however, there is an increasing number of cases in which the manufacturing process of the pre-coated metal (PCM) steel sheet is applied to automobile steel sheet manufacturing, and some automotive steel sheet parts are provided to automobile manufacturers with pre-coated paints. After press processing and welding work, research on environment-friendly coating process is being actively conducted in which a medium-definition coating is coated immediately without conventional pruning and primer coating.

The pre-coated steel coating material is coated with the uncoated roll coil on the coater, and then the top surface is coated with a thick film which shows the main properties of the pre-coated steel coating material. In case of rewinding in the form of roll coil, paint the backing paint to prevent integrated contact with the unpainted surface of the coil facing the backcoat, and then pass through the drying duct for drying the coating After forming, it is rewinded in the form of a roll coil, stored and transported and supplied to the end user.

Since precoated automotive steel sheet must be finished with one-time painting of electrostatic coating and primer coating, which is the conventional automotive steel coating process, the thickness of the coating film is more than 80 microns, which is the thickness of the combined film thickness of the existing electrostatic coating and primer coating. A thick film should be formed. In this case, in the case of the back coating used for the back coating of pre-coated metal commonly used in the existing industry, the back coating and the back coating surface for the pre-coated automotive steel sheet are pressed against each other during storage and transportation. In case of re-peeling the roll coil for further processing such as cutting and processing, the back coating surface and the back coating surface are fused to each other so that they are not separated or the top coating surface is transferred to the back coating surface or back coating surface. Transfer phenomenon of the coating film occurs. The transfer phenomenon of the coating film has the disadvantage that the appearance of the overall coating film state and the further progression to the mid-high-level coating process after processing, cutting, welding, which is the main purpose of the pre-coated automotive steel sheet, becomes impossible.

Therefore, in order to improve the film transfer phenomenon to the back coating of the thick film precoated automotive steel sheet, a silicone or acrylic release agent may be formed in the back coating composition to form a coating film, but in this case, the release agent is formed on the surface of the back coating. The release agent transition phenomenon occurs when the release agent is partially cured to the surface of the thick coat, which is the upper surface, when the peeling agent is cured and re-peeled after winding of the roll coil having undergone the top coating and the bottom coating. This release agent transfer phenomenon requires additional polishing process to remove the release agent, or poor adhesion between the middle coat and the thick film when the middle coat is applied on the release agent that has not been removed in the polishing process. It is impossible to achieve the inherent purpose of the medium-definition process after cutting, work welding, which is the main purpose of the pre-coated steel sheet due to the occurrence of defects.

In order to remedy the above drawbacks, the existing pre-coated metal coating industry has been widely used as a release agent for the coating film by simply adding a silicone-based release agent to the paint, improving the disadvantages of the conventional simple addition method The invention of an acrylic resin composition prepared by copolymerizing an acrylic monomer having an alkoxy silane group, which is a self-reactive silicone compound, with an acrylic monomer having an amide group, and a coating including the acrylic resin composition have been completed. As the acrylic monomer to which the alkoxy silane group is added has a low glass transition temperature of the monomer itself, the acrylic resin made of only the acrylic monomer to which the alkoxy silane group is added is fused to a coating film having a low hardness of the final coating film and a relatively high glass transition temperature, thereby transferring the coating film. There is a disadvantage. For this reason, an acrylic monomer having a high glass transition temperature and an amide functional group was formed to improve the disadvantage that could not be used in the existing paint despite the excellent release force, so as to have an appropriate glass transition temperature and a functional group for crosslinking. The acrylic resin composition prepared by copolymerizing the acrylic monomers as described above completely improves the releasing agent transfer phenomenon to the thick film, which is a disadvantage of the conventional silicone releasing agent and excellent release force compared to the conventional silicone releasing agent used by simple addition. By this, the present invention was completed.

A solution-polymerized acrylic resin composition for back coating of a thick film pre-coated automotive steel sheet having improved coating film transition to improve the coating transition of the thick film pre-coated automotive steel sheet to the back coating surface of the steel sheet. It is a subject to offer.

Moreover, another object is to provide the manufacturing method of the acrylic resin composition for back coating of the thick-film precoated automotive steel plate mentioned above.

Another object of the present invention is to provide a coating material including an acrylic resin composition for coating a back coating precoated automotive steel sheet having improved coating film transition.

In order to achieve the above object, the present invention is a solution polymerization type acrylic resin composition,

The solution polymerization type acrylic resin composition is composed of 40% to 70% by weight of the copolymer of the acrylic monomer and 30% to 60% by weight of the organic solvent,

And, the copolymer of the acrylic monomer is characterized in that synthesized by the initiator by mixing 60% to 90% by weight of the acrylic monomer to which the alkoxy silane group is added to the side chain end group and 10% to 40% by weight of the acrylic monomer having an amide group It relates to an acrylic resin composition for coating film pre-coated automotive steel sheet back coating.

It is preferable that the acrylic resin composition has a nonvolatile content of 40 wt% to 70 wt% and a glass transition temperature of 10 to 60 ° C.

The acrylic resin composition is composed of the copolymer of the acrylic monomer 40% to 70% by weight and the organic solvent 30% to 60% by weight. And the copolymer of the acrylic monomer includes 60% to 90% by weight of the alkoxy silane group-containing acrylic monomer and 10% to 40% by weight of the acrylic monomer having an amide group.

The alkoxy silane group acryl monomer is a monomer containing an alkoxy silane group such as mono methoxy, dimethoxy trimethoxy, and mono ethoxy, diethoxy, and triethoxy in the terminal group, and the following compounds can be used. Do.

Specific examples of the alkoxy silane group compound include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i- Selected from the group consisting of propyltrimethoxysilane, i-propyltriethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, n-pentyltrimethoxysilane, n-pentyltriethoxysilane It may be formed using at least one or more materials selected from one or more than one group.

The acrylic monomer having an amide group is a monomer containing an amide group in the terminal group, for example, methyl (meth) acrylamide, ethyl (meth) acrylamide, one or more groups selected from the group consisting of butyl (meth) acrylamide It may be formed using at least one material selected from.

Method for producing a back coating resin composition for a thick film pre-coated automotive steel sheet according to an embodiment of the present invention is to prepare a composition comprising an acrylic monomer comprising an acrylic monomer containing an alkoxy silane group, an acrylic monomer having an amide group copolymerized in an organic solvent Steps.

The paint comprising the acrylic resin composition for back coating for a thick film precoated automotive steel sheet according to an embodiment of the present invention comprises a) an acrylic monomer having an alkoxy silane group added to the side chain terminal, an acrylic monomer having an amide group, and a non-functional acrylic monomer. And an acrylic resin comprising b) an extra organic solvent, wherein the acrylic monomer to which the alkoxy silane group is added is 60 to 90% by weight and the acrylic monomer having an amide is 10% by weight based on the total weight of the acrylic resin. To 40% by weight.

According to the present invention, a thick film coated surface, which is the upper surface of the coated surface, is fused with the rear coating film of the steel sheet during the manufacture and transportation of the finished product, due to the fact that the packaging form of the thick film precoated automotive steel sheet is a roll coil form. In order to prevent this, a fatal defect such as a film transfer between coating surfaces occurs when the roll coil is peeled off again for further processing, and in order to prevent this, a silicone type generally used in the back coating for pre-coated steel sheets in the same industry is used. In the case of using the release agent, the non-reactive silicone release agent is cured on the upper side of the back coating surface. The release agent is transferred to the thick film coating side, which is the opposite top surface. In order to improve the defect caused by the transfer of the coating film or the release agent, a method of suppressing the coating film transition phenomenon using the low surface tension of the release agent composed of the existing non-reactive silicone-based compound is used. The silane group-containing acrylic resin composition thus prepared is prepared by preparing an acrylic resin composition in which an acrylic monomer containing an alkoxy silane group, which is a reactive silicone compound, and an acrylic monomer having an amide group, is added and reacted under solvent conditions to improve the transition phenomenon of the reactive silicone mold release agent. The paints produced using the paints completely eliminate the defects caused by the weak film transfer phenomenon of the back coating of the conventional thick film precoated automotive steel sheet and the transition phenomenon of the non-reactive silicone release agent conventionally formulated in the industry to improve it. Seonhal could.

Hereinafter, preferred embodiments of the present invention will be described in detail, but it should be noted that in the following description, only parts necessary for understanding the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

The present invention is a solution polymerization type acrylic resin composition,

Solution polymerization type acrylic resin composition prepared by the addition reaction of the acrylic monomer containing the silane group and the acrylic monomer containing an amide group is composed of 40 to 70% by weight of the copolymer of the acrylic monomer and 30 to 60% by weight of the organic solvent,

And, the copolymer of the acrylic monomer is a coating film composed of 60% by weight to 90% by weight of the acrylic monomer to which the alkoxy silane group is added to the side chain terminal group and 10% to 40% by weight of the acrylic monomer having an amide group synthesized with an initiator. It is an object of the present invention to provide a method for preparing an acrylic resin composition for back coating precoated automotive steel sheet having improved transition.

When the copolymer of the acrylic monomer to which the alkoxy silane group is added is less than 40% by weight based on the total weight of the acrylic resin composition, the content of the solvent included is increased to satisfy the legal regulations on organic volatile solvents of paint products which are recently strengthened. It is difficult, and when it exceeds 70%, it is difficult to secure an appropriate amount of organic solvent required for the addition reaction, which leads to an increase in the final weight average molecular weight of the resin copolymer thus prepared, which leads to poor workability of the paint, resulting in poor appearance of the final coating. Will occur.

As for the acrylic monomer to which the alkoxy silane group was added in the copolymer of the said acrylic monomer, 60 to 90 weight% of the acrylic monomer to which the alkoxy silane group was added with respect to an acryl monomer copolymer is preferable. If the acrylic monomer added with the alkoxy silane group is included in less than 60% by weight, the content of the silicone compound included in the final back coating composition to function as a releasing agent is relatively low, so that the upper thick film surface is transferred to the back coating surface. When the content exceeds 90% by weight, the content of the acrylic monomer having an amide group formed together to increase the glass transition temperature of the resin composition is relatively low, resulting in a low glass transition temperature of the resin composition and consequently curing of the back coating surface. As the hardness of the coating film is lowered, the back coating is easily fused with the thick film of the upper surface in the state of being wound in the form of a roll coil after coating, thereby causing a defect that is transferred during re-peeling. Therefore, it is preferable that the acrylic monomer to which the alkoxy silane group was added in the copolymer of an acrylic monomer is 60 to 90 weight% with respect to an acrylic monomer copolymer. More preferably, it is 70 to 90 weight%.

The acrylic monomer having an amide group in the copolymer of the acrylic monomer is preferably 10% to 40% by weight of the acrylic monomer having an amide relative to the acrylic monomer copolymer. If the acrylic monomer having an amide group is less than 10% by weight based on the total weight of the acrylic, the acrylic resin composition thus prepared has a disadvantage in that the glass transition temperature is low and thus easily fuses with the thick-film coating surface, and reacts with the amide group to form a cured coating film. There is a lack of sufficient amide groups to react with the epoxy compound further formulated in the paint to form a cured coating film that is insufficient for use in the back coating of thick film precoated automotive steel sheets. If it exceeds 40% by weight, the glass transition temperature of the coating film is too high due to the disadvantages of the adhesion of the coating film and the workability during the additional process such as cutting and processing of the pre-coated automotive steel sheet.

Therefore, the monomer having an amide group in the copolymer of the acrylic monomer is preferably 10% to 40% by weight based on the acrylic monomer copolymer. More preferably, it is 5 weight%-30 weight%.

And the acrylic resin composition of the present invention should ensure a stable compatibility when coating and to form a solvent for the solution polymerization of the acrylic monomer. In the present invention, the amount of the organic solvent used is preferably 30% by weight to 60% by weight, and when the amount of the organic solvent is less than 30% by weight, the viscosity of the acrylic resin composition may be increased and the flowability of the final paint may be deteriorated. And, if it exceeds 60% by weight there is a risk of violating environmental regulations due to the increase in the organic volatile solvent.

In addition, solvents usable in the present invention include acetate solvents such as methyl acetate, ethyl acetate, butyl acetate, cellulose acetate, propylene glycol monomethyl acetate, 3-methoxy butyl acetate, diacetone alcohol, methyl ethyl ketone, cyclohexanone , Ketones such as isophorone, and other solvents such as glycol ethers, glycol ether esters, and aromatic hydrocarbon solvents may be selected and used.

It is preferable to select a solvent having an appropriate boiling point and evaporation rate according to the purpose of use of the paint. In the reaction temperature of the present invention, the solution polymerization was carried out using an aromatic hydrocarbon solvent alone or at least one mixed solvent at 100 to 140 ° C.

Initiators usable in the present invention include benzoyl peroxide, tertiary butyl peroxide, tertiary butyl perbenzoate, tertiary butyl perpirate, tertiary amyl perbenzoate, tertiary amyl peroxy acetate, and tertiary mill peroxide. , Tertiary amylperoxy neodecanoate, tertiary butyl peroxy neodecanoate, tertiary amyl- (2-ethylethyl) monoperoxy carbonate, azobis isobutyl nitrile, 2.2-azobis methylbutyro You may select and use one or more from general polymerization initiators, such as a nitrile.

In the present invention, a general initiator used for acrylic synthesis was used, and the amount of the initiator used is preferably 0.5% to 5.0% by weight (initiator / acrylic monomer copolymer). If the amount is less than 0.5% by weight (initiator / acrylic monomer copolymer), it is unlikely that sufficient radical ions will be generated for the addition reaction of the acrylic monomer, so that an unreacted monomer may remain in the copolymer of the acrylic monomer. In addition, the copolymer of the acrylic monomers thus prepared may be difficult to obtain a sufficient viscosity to be applied to the coating due to the termination of the reaction at a high viscosity, when exceeding 5.0% by weight of radical ions generated more than necessary The overall degree of polymerization of the acrylic monomer copolymer is lowered, and the paint prepared using the low molecular weight acrylic monomer copolymer thus prepared may deteriorate mechanical and chemical properties.

The coating composition produced using the acrylic resin composition of the present invention,

15 wt% to 35 wt% of acrylic resin composition, 20 wt% to 40 wt% of epoxy resin composition, 30 wt% to 54 wt% of organic solvent, and additive 1, which is a copolymer of acrylic monomer to which alkoxy silane group is added and acrylic monomer having amide group Weight percent to 5 weight percent.

The acrylic resin composition is composed of 40 to 70% by weight of the copolymer of acrylic monomer and 30 to 60% by weight of the organic solvent.

And the acrylic monomer copolymer in the acrylic resin composition includes 60% to 90% by weight of the alkoxy silane group-containing acrylic monomer and 10% to 40% by weight of the acrylic monomer having an amide group.

When the acrylic monomer copolymer is less than 15% by weight or more than 40% by weight of the epoxy resin composition in the coating composition, the content of the acrylic monomer becomes relatively low, which makes it difficult to have sufficient release force for the present invention. In addition, when the copolymer of an acrylic monomer exceeds 35 weight%, or when an epoxy resin composition becomes less than 20 weight%, the hardness of a cured coating film may become low and a coating film transition phenomenon may arise.

The amount of the organic solvent used is preferably 30% by weight to 54% by weight, and when the amount of the organic solvent is less than 30% by weight, there is a high possibility that problems such as deterioration of appearance properties such as smoothness of the coating film are likely to occur. The coating property of a coating film etc. may fall, and when it exceeds 54 weight%, there exists a possibility that it may interfere with environmental regulation by the increase of the organic volatile solvent. The organic solvent which can be used by this invention should just use the same organic solvent as the organic solvent used for the acrylic monomer copolymer resin composition of this invention.

In the present invention, a thinner to be additionally applied may be appropriately selected and used when necessary for formation of the coating film.

If the amount of the additive is more than 5% by weight, the use rate of the silicone-based additive is too high, which may seriously affect the appearance, adhesion, and repaintability of the coating.If the amount is less than 1% by weight, the smoothness or flow of the coating The appearance of the castle may be deteriorated, which may cause deterioration of adhesion, which may deteriorate the color or the coating film under exposure to ultraviolet rays. The main types of additives are silicones. BYK-301 of BYK-300 series BYK-Chemie. BYK-306 ?, BYK-307 ?, BYK-308 ?, BYK-310 ?, BYK-320 ?, BYK-322 ?, BYK-323? BYK-325? In order to improve the smoothness and appearance of the coating film, TINUVIN 328 and TINUVIN 400 of Ciba-Geigy were used as UV absorbers, and TINUVIN 123 and TINUVIN 292 genuine grades of the same manufacturer were used as UV stabilizers. It was.

Hereinafter will be described in detail through specific examples and comparative examples of the present invention. Parts in each experiment mean parts by weight.

Preparation of Acrylic Resin Composition

(Example 1)

Put 25 parts of xylene into a 2-liter four-necked flask equipped with a nitrogen gas introduction tube, thermometer, dropping funnel, condenser, heating device, and variable speed agitation device and heat reflux. Dow Corning's trimethoxy silane acrylic as monomer at reaction temperature 135 ~ 140 ℃ 39 parts of monomers (trade name Z-6030), 21 parts of butoxymethyl acrylamide, and 1.5 parts of benzoyl peroxide as an initiator were dropped into the flask uniformly over 3 hours. After dropping for 2 hours, the mixture was diluted with 13.5 parts of butanol to complete polymerization.

The acrylic resin composition thus produced has characteristic values of 25 ° C Gardner viscosity R to T, nonvolatile content 60%, and glass transition temperature of 49 ° C.

(Example 2)

Put 25 parts of xylene into a 2-liter four-necked flask equipped with a nitrogen gas introduction tube, thermometer, dropping funnel, condenser, heating device, and variable speed agitation device and heat reflux. Dow Corning's trimethoxy silane acrylic as monomer at reaction temperature 135 ~ 140 ℃ 45 parts of monomers (brand name Z-6030), 15 parts of butoxymethyl acrylamide, and 1.5 parts of benzoyl peroxide as an initiator were added dropwise to the flask uniformly over 3 hours. After dropping for 2 hours, the mixture was diluted with 13.5 parts of butanol to complete polymerization.

The acrylic resin composition thus produced has characteristic values of 25 ° C Gardner viscosity V to X, nonvolatile content of 60%, and glass transition temperature of 38 ° C.

(Example 3)

Put 25 parts of xylene into a 2-liter four-necked flask equipped with a nitrogen gas introduction tube, thermometer, dropping funnel, condenser, heating device, and variable speed agitation device and heat reflux. Dow Corning's trimethoxy silane acrylic as monomer at reaction temperature 135 ~ 140 ℃ 51 parts of monomers (brand name Z-6030), 9 parts of butoxymethyl acrylamide, and 1.5 parts of benzoyl peroxide were dropped into the flask uniformly over 3 hours by an initiator. After dropping for 2 hours, the mixture was diluted with 13.5 parts of butanol to complete polymerization.

The acrylic resin composition thus produced has characteristic values of 25 ° C Gardner viscosity Z to Z1, nonvolatile content of 60%, and glass transition temperature of 25 ° C.

 (Comparative Example 1)

In the same manner as in Example 1, 60 parts of Dow Corning's trimethoxy silane acrylic monomer (trade name Z-6030) and 1.5 parts of benzoyl peroxide as an initiator were dropped into the flask uniformly over 3 hours. After dropping for 2 hours, the mixture was diluted with 13.5 parts of butanol to complete polymerization.

The acrylic resin composition thus produced has characteristic values of 25 ° C Gardner viscosity Z to Z1, nonvolatile content of 60%, and glass transition temperature of 25 ° C.

(Comparative Example 2)

Put 25 parts of xylene into a 2L four-necked flask equipped with a nitrogen gas introduction tube, thermometer, dropping funnel, condenser, heating device and variable speed agitation device and heat reflux. 1.5 parts of benzoyl peroxide was added dropwise to the flask uniformly over 3 hours as an initiator. After dropping for 2 hours, the mixture was diluted with 13.5 parts of butanol to complete polymerization.

The acrylic resin composition thus produced has characteristic values of 25 ° C. Gardner viscosity Z 4 to Z 6, nonvolatile content of 60%, and glass transition temperature of 78 ° C.

According to the test method described in Examples 1 to 3 and Comparative Examples 1 and 2, the composition is as shown in Table 1 below.

number Ingredients Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 One xylene 25 25 25 25 25 2 Z-6030 39 45 51 60 0 3 Butoxymethyl acrylamide 21 15 9 0 60 4 BPO 1.5 1.5 1.5 1.5 1.5 5 Normal butanol 13.5 13.5 13.5 13.5 13.5 system 100.0 100.0 100.0 100.0 100.0

Film formation

Using the acrylic resin composition prepared in Examples 1 to 3 and Comparative Examples 1 and 2, a coating film was formed in the same manner as in Examples 5 to 7 and Comparative Examples 3 and 4 below.

(Example 5)

30% by weight of the resin composition obtained in Example 1, 30% by weight of epoxy resin (trade name YD-128) supplied by Kukdo Chemical, 35% by weight of solvent, and additives are BYK-306? BYK310? BYK-325? 1% by weight, TINUVIN? 400, TINUVIN? The viscosity (25 ° C.) was adjusted to 15 seconds with Pod Cup No. 4 using toluene and butyl acetate in a paint formulation consisting of 2% by weight and 2% by weight in total. The paint formulation is roll coated on a CRS steel sheet metal specimen, which is a material for precoated automotive sheeting, to have a coating thickness of 30 to 40 μm, and dried at a baking temperature of 241 to 249 ° C. for 40 to 60 seconds to obtain a coating film.

(Example 6)

30 weight% of the resin composition obtained in Example 2, 30 weight% of the epoxy resin (trade name YD-128) supplied by Kukdo Chemical, 35 weight% of the solvent, and the additives were BYK-306? BYK310? BYK-325? 1% by weight, TINUVIN? 400, TINUVIN? The viscosity (25 ° C.) was adjusted to 15 seconds with Pod Cup No. 4 using toluene and butyl acetate in a paint formulation consisting of 2% by weight and 2% by weight in total.

Hereinafter, a coating film was formed in the same manner as in Example 5.

 (Example 7)

30% by weight of the resin composition obtained in Example 3, 30% by weight of epoxy resin (trade name YD-128) supplied by Kukdo Chemical, 35% by weight of solvent, and additives are BYK-306? BYK310? BYK-325? 1% by weight, TINUVIN? 400, TINUVIN? The viscosity (25 ° C.) was adjusted to 15 seconds with Pod Cup No. 4 using toluene and butyl acetate in a paint formulation consisting of 2% by weight and 2% by weight in total.

Hereinafter, a coating film was formed in the same manner as in Example 5.

 (Comparative Example 3)

30% by weight of the resin composition obtained in Comparative Example 1, 30% by weight of epoxy resin (trade name YD-128), 35% by weight of solvent, and additives supplied by Kukdo Chemical were BYK-306? BYK310? BYK-325? 1% by weight, TINUVIN? 400, TINUVIN? The viscosity (25 ° C.) was adjusted to 15 seconds with Pod Cup No. 4 using toluene and butyl acetate in a paint formulation consisting of 2% by weight and 2% by weight in total.

Hereinafter, a coating film was formed in the same manner as in Example 5.

(Comparative Example 4)

30% by weight of the resin composition obtained in Comparative Example 2, 30% by weight of epoxy resin (trade name YD-128), 35% by weight of solvent, and additives supplied by Kukdo Chemical were BYK-306? BYK310? BYK-325? 1% by weight, TINUVIN? 400, TINUVIN? The viscosity (25 ° C.) was adjusted to 15 seconds with Pod Cup No. 4 using toluene and butyl acetate in a paint formulation consisting of 2% by weight and 2% by weight in total.

Hereinafter, a coating film was formed in the same manner as in Example 5.

Test Methods

*One. Polish

It was measured by ASTM-D-523 (a standard for measuring the gloss reflected by non-metallic materials determined by the American Society for Testing and Materials).

2. pencil hardness

Measurement was made by NCCA-II-12 (relative pencil hardness evaluation specification set by the National Coil Coaters Association).

3. Acid and alkali resistance

ASTM-D-1308 was determined by the organic material finish (international standards for household chemicals applied to the American Society for Testing and Materials).

4. Hot water resistance

After immersion in boiling water for 24 hours the specimen formed the coating film, the degree of change of the coating film was visually determined.

5. Adhesiveness

A total of 100 necks were cross-cut into 100 pieces of goggles on the coated film, and when the PE adhesive tape was re-peeled and re-peeled, the total number of goggles of the coating film remaining on the specimens was visually determined.

6. Release force

Attach the 25mm-wide 3M transparent tape to the specimen with the coating film, compress it with a force of 1 kgf / cm ² using a crimping jig, and then apply a force of gf / cm when peeled 180 ° using a tensile strength tester. Displayed in ² units

7. Film transferability

One side of the coated film and one side of the coated film for precoated automotive steel sheet were pressed to face each other, and then the specimen was pressed at 10 kgf / cm ² with a tensile strength tester and then peeled again after 24 hours. Then, the pressed coating surface was peeled off from the original coating material, and the state of transition to the other coating surface was visually determined.

Test result

Test results of Examples 5 to 7 and Comparative Examples 3 and 4 according to the above test method are as shown in Table 2 below.

division Example 5 Example 6 Example 7 Comparative Example 3 Comparative Example 4 Polish
(20 ° / 60 °) 80/88 83/89 87/92 92/96 78/84 Solvent resistance 50 or more times 50 or more times 50 or more times 10 times 50 or more times Processability
(T-Bend) 5 points 5 points 5 points 2 points 2 points Attachment
(Remaining / total) 100/100 100/100 100/100 20/100 70/100 Pencil hardness 1H 2H 2H 2B 4H Release force
(gf / cm ^{2 )} 1,500 1200 900 400 2,000 Coating transition 5 points 5 points 5 points 0 point 0 point

-5 means the best, 0 means poor.

According to the contents of Table 2, the coating film formed by using the coating composition prepared by the method of Examples 5 to 7 of the present invention Comparative Examples 3 and 4 in the items such as workability, adhesion, mold release force, coating film transferability, etc. It showed better performance than the coating film formed using the paint prepared by the method. In Examples 5 to 7 of the present invention, as the content of the acrylic monomer to which the alkoxy silane group is added increases, the gloss and the coating film hardness are observed, but acrylic polymerized with only the acrylic monomer to which the alkoxy silane group is added as in Comparative Example 4 When the coating film was formed by using the resin copolymer, it had high gloss and the best release force, but the physical properties such as solvent resistance, processability, adhesion, and pencil hardness were very weak. This is because when the resin copolymer is prepared using only the alkoxy silane group-containing acrylic monomer, despite the increase of the silicone alkoxy silane compound included in the coating composition, the resin copolymer has a low glass transition temperature and crosslinks with the epoxy resin included in the paint. This is because the overall thermal and mechanical properties are very bad because they do not contain amide functional groups. In addition, when the coating film is formed of a coating material prepared using a resin copolymer polymerized only with an acrylic monomer having an amide group as in Comparative Example 5, it is vulnerable due to high glass transition temperature and excessive crosslinking with the epoxy resin formed in the coating. The overall properties such as processability and film transferability were very poor.

As described above, when the paint is prepared using an acrylic copolymer prepared by using an acrylic monomer having an amide group and an acrylic monomer to which an alkoxy silane group is added as shown in Examples 1 to 3 of the present invention, It was able to completely improve the fragile coating film transferability of the back coating paint of thick film precoated automotive steel plate and use the acrylic monomer copolymer which add-polymerizes the acrylic monomer containing alkoxy silane group. I was able to overcome the technical limitations of the transition between coatings.

As described above, the acrylic resin composition for the back coating of the after-coat pre-coated automotive steel sheet improved coating film transition according to a preferred embodiment of the present invention and the coating material comprising the same are various within the scope without departing from the spirit of the present invention It will be understood by those skilled in the art that variations and modifications are possible.

Claims (8)

In the solution polymerization type acrylic resin composition,
The solution polymerization type acrylic resin composition is made of 40 to 70% by weight of the copolymer of acrylic monomer,
And, the copolymer of the acrylic monomer is a coating film transition, characterized in that synthesized with an initiator by mixing 60% to 90% by weight of the acrylic monomer containing an alkoxy silane group and 10% to 40% by weight of the acrylic monomer containing an amide group Improved acrylic film composition for back coating of precoated automotive steel sheet.
The method of claim 1,
The acrylic resin composition has a non-volatile content of 40% by weight to 70% by weight, the glass transition temperature of 10 ~ 60 ℃ characterized in that the coating film transition improved acrylic film composition for back coating of the coated steel sheet.
The method of claim 1,
The copolymer of the acrylic monomer may include 60% by weight to 90% by weight of the acrylic monomer containing an alkoxy silane group and 10% by weight to 40% by weight of the acrylic monomer containing an amide group. Acrylic resin composition for back coating of coated automotive steel sheets.
The acrylic resin composition of claim 1, wherein the amount of the initiator is in a range of 0.5 wt% to 5.0 wt% (initiator / acrylic monomer copolymer). .
The method according to any one of claims 1 to 3,
The alkoxy silane group acrylic monomers are methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i-propyl One selected from the group consisting of trimethoxysilane, i-propyltriethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, n-pentyltrimethoxysilane and n-pentyltriethoxysilane Or acrylic resin composition for the back coating of the thick film pre-coated automotive steel sheet with improved coating film transition, characterized in using at least one material selected from one or more groups.
The method according to any one of claims 1 to 3,
The acrylic monomer having an amide group is a coating film using at least one material selected from the group consisting of one or more selected from the group consisting of methyl (meth) acrylamide, ethyl (meth) acrylamide, butyl (meth) acrylamide Acrylic resin composition for back coating of thick film precoated automotive steel sheet with improved transition.
The method according to any one of claims 1 to 3,
The initiator is benzoyl peroxide, tertiary butyl peroxide, tertiary butyl perbenzoate, tertiary butyl perpirate, tertiary amyl perbenzoate, tertiary amyl peroxy acetate, tertiary mill peroxide, tertiary amylper General polymerization of oxyneodecanoate, tertiary butylperoxy neodecanoate, tertiary amyl- (2-ethylethyl) monoperoxy carbonate, azobis isobutylnitrile, 2.2-azobis methylbutyronitrile An acrylic resin composition for back coating of a thick film precoated automotive steel sheet having improved coating film transition, characterized in that one or more of the initiators are selected and used.
A coating composition containing an acrylic resin composition for back coating of a thick film precoated automotive steel sheet having improved coating transition,
15% to 35% by weight of the acrylic resin composition of claim 1, 20% to 40% by weight of the epoxy resin composition, 30% to 54% by weight of the organic solvent and 1% to 5% by weight of the additives, characterized in that Coating composition.