Core-shell acrylic binder and manufacturing method therefor

Abstract

The present invention relates to a core-shell acrylic binder used for roof coating, and a manufacturing method therefor. The core-shell acrylic binder of the present invention is characterized in that a core part and a shell part have a specific glass transition temperature, and the core part and the shell part have a specific mass ratio. The core-shell acrylic binder may have excellent elongation, elasticity and durability, and may also have good antifouling properties. In particular, when forming a white-based roof coating layer vulnerable to contamination, a coating layer having an excellent appearance and improved antifouling properties can be formed.

Description

Core-shell acrylic binder and method for producing the same

[0001] The present invention relates to a core-shell acrylic binder and a method for producing the same.

[0002] Conventional roof coatings, often blue in color, lack sufficient thermal insulation, leading to rapid roof temperature increases and subsequent indoor temperature increases. To address this issue, a growing trend has been toward applying white coatings with superior thermal insulation. However, white coatings have poor stain resistance, making them susceptible to contamination. Dust and contaminants can easily adhere, damaging the aesthetics and reducing the coating's performance. To enhance stain resistance, the coating must be smooth and elastic. Accordingly, active development is underway on acrylic binders that enhance elasticity and provide a smooth surface. This development will enable white coatings to offer not only thermal insulation but also stain resistance and durability, reducing long-term maintenance costs and extending the coating's lifespan.

[0003] The present invention provides a core-shell acrylic binder having a core-shell structure, wherein the core and shell portions contain specific monomers in appropriate amounts, each having a glass transition temperature and mass ratio within a specific range, and thus can have excellent elongation and antifouling properties.

[0004] In addition, it is intended to provide a roof coating composition comprising the core-shell acrylic binder and a building having a waterproof coating layer by applying the roof coating composition.

[0005] Another object of the present invention is to provide a method for manufacturing the core-shell acrylic binder.

[0006] Glass transition temperature (T g ) has a core-shell structure having a core portion having a glass transition temperature of -50 to -40 ℃ and a shell portion having a glass transition temperature of -20 to 0 ℃,

[0007] The core portion comprises an acrylic monomer having a carboxylic acid group or a base thereof, and the shell portion comprises a core-shell acrylic binder polymerized with acrylonitrile.

[0008] The core-shell acrylic binder has an elongation of 800% or more and a low-temperature elongation at -20°C of 500% or more.

[0009] In one embodiment, the core portion may be polymerized by including 2 to 10 parts by weight of an acrylic monomer having a carboxylic acid group or a base thereof, based on 100 parts by weight of a C4 to C8 alkyl (meth)acrylate.

[0010] In one embodiment, the shell portion may be polymerized by including 20 to 60 parts by weight of methyl methacrylate and 5 to 25 parts by weight of acrylonitrile for 100 parts by weight of C4 to C6 alkyl (meth)acrylate.

[0011] In one embodiment, the acrylic monomer having the carboxylic acid group or its base may be one selected from acrylic acid and methacrylic acid, or a mixture of the two.

[0012] In one embodiment, the core-shell acrylic binder may contain 20 to 40 wt% of the core portion and 60 to 80 wt% of the shell portion.

[0013] In one embodiment, the difference in transmittance of a 0.1 cm thick film manufactured with the core-shell acrylic binder before contamination and after contamination and washing may be 40% or less.

[0014] Another aspect of the present invention provides a roof coating composition comprising the core-shell acrylic binder.

[0015] Another aspect of the present invention provides a roof coating layer formed by applying a roof coating composition comprising the core-shell acrylic binder.

[0016] Another aspect of the present invention comprises the steps of preparing a core emulsion comprising an acrylic monomer having a carboxylic acid group or a base thereof;

[0017] A method for manufacturing a core-shell acrylic binder is provided, comprising the step of forming a core-shell by adding a shell emulsion containing acrylonitrile to the core emulsion.

[0018] In one embodiment, the core emulsion may be manufactured by including 2 to 10 parts by weight of an acrylic monomer having a carboxylic acid group or a base thereof, relative to 100 parts by weight of a C4 to C8 alkyl (meth)acrylate.

[0019] In one embodiment, the shell emulsion may be prepared by including 10 to 80 parts by weight of methyl methacrylate and 5 to 30 parts by weight of acrylonitrile, based on 100 parts by weight of C4 to C6 alkyl (meth)acrylate.

[0020] In one embodiment, after the step of forming the core-shell, the method may further include a step of neutralizing the pH to a pH of 7.5 to 8.5 to prepare a core-shell acrylic binder.

[0021] A core-shell acrylic binder according to one aspect of the present invention comprises a core portion and a shell portion containing a specific monomer in an appropriate amount, each having a glass transition temperature and mass ratio within a specific range, and thus can have excellent elongation and antifouling properties.

[0022] A white series roof coating layer formed by including the above core-shell acrylic binder not only has heat-insulating properties but also can have improved antifouling properties.

[0023] The present invention will be described in more detail below. However, the following specific examples or examples are merely references for explaining the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

[0024] Additionally, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting.

[0025] Additionally, the singular forms used in the specification and the appended claims are intended to include the plural forms as well, unless the context clearly dictates otherwise.

[0026] Additionally, when a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0027] In addition, the terms “about,” “substantially,” etc. used in this specification are used in a meaning close to or at the numerical value when manufacturing and material tolerances inherent to the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly using the disclosure contents in which exact or absolute values ​​are mentioned to aid in the understanding of the present invention.

[0028] Additionally, the term “(meth)acrylate” as used herein may include both acrylate and methacrylate.

[0029] As the trend shifts from blue-based roof coatings to white-based ones, which offer better thermal insulation properties, the white-based roof coatings are susceptible to contamination. To address this issue, the inventors of the present invention have developed an acrylic binder with a core-shell structure that exhibits excellent elongation, elasticity, and flexibility, thereby enabling the formation of a white-based roof coating with improved stain-repellent properties.

[0030] The present invention will be described below.

[0031] The present invention has a glass transition temperature (T g ) has a core-shell structure having a core portion having a glass transition temperature of -50 to -40°C, or better -45 to -40°C, and a shell portion having a glass transition temperature of -20 to 0°C, or better -15 to -5°C,

[0032] The core portion comprises an acrylic monomer having a carboxylic acid group or a base thereof, and the shell portion comprises a core-shell acrylic binder polymerized with acrylonitrile.

[0033] The core-shell acrylic binder has an elongation of 800% or more and a low-temperature elongation at -20°C of 500% or more.

[0034] A core-shell acrylic binder having a core portion within the above glass transition temperature range may be preferred because it can maintain flexibility and elasticity even at low temperatures.

[0035] A core-shell acrylic binder having a shell portion within the above glass transition temperature range may be preferred because it not only has excellent durability, but also can respond well to microscopic damage and improve antifouling properties.

[0036] The difference in glass transition temperature between the core and shell portions may enable the core-shell acrylic binder and the roof coating composition including the same to maintain durability and elasticity under various temperature conditions, and contaminants do not easily adhere to them and, even if they do adhere, are easily removed.

[0037] The core-shell acrylic binder of the present invention has improved elongation through a core portion having a relatively low glass transition temperature, and may be able to improve the degradation of contamination resistance caused by the core portion having a low glass transition temperature by a shell portion having a relatively high glass transition temperature.

[0038] In one embodiment, the core portion may be polymerized by including 2 to 10 parts by weight, or more preferably 3 to 7 parts by weight, of an acrylic monomer having a carboxylic acid group or a base thereof, relative to 100 parts by weight of a C4 to C8 alkyl (meth)acrylate, but is not limited thereto. A core portion satisfying the above composition range is preferred because it can satisfy the glass transition temperature range of the core portion, but is not limited thereto. In addition, a core portion emulsion having the above composition range can be stably formed, but is not limited thereto.

[0039] In one embodiment, the C4~C8 alkyl(meth)acrylate may be one or a mixture of two or more selected from n-butylacrylate, n-hexylacrylate, n-hexylmethacrylate, 2-ethylhexylacrylate, 2-ethylhexylmethacrylate, and isooctylacrylate, but is not limited thereto.

[0040] In one embodiment, the C4~C8 alkyl(meth)acrylate may be, but is not limited to, a mixture of n-butylacrylate and 2-ethylhexylacrylate.

[0041] In one embodiment, the shell portion may be polymerized by including, but not limited to, 10 to 80 parts by weight of methyl methacrylate, more preferably 15 to 50 parts by weight of methyl methacrylate, and 5 to 30 parts by weight of acrylonitrile, more preferably 7 to 15 parts by weight of methyl methacrylate, based on 100 parts by weight of C4~C6 alkyl(meth)acrylate. A shell portion satisfying the above composition range is preferred because it can satisfy the glass transition temperature range of the shell portion, but is not limited thereto.

[0042] In one embodiment, the C4~C6 alkyl(meth)acrylate may be one or a mixture of two or more selected from n-butylacrylate, n-hexylacrylate, and n-hexylmethacrylate, but is not limited thereto.

[0043] In one embodiment, the acrylic monomer having the carboxylic acid group or its base may be one or a mixture of two selected from acrylic acid and methacrylic acid.

[0044] In one embodiment, the core-shell acrylic binder may comprise 20 to 40 wt% of the core portion, more preferably 25 to 35 wt% of the shell portion, and 60 to 80 wt% of the shell portion, more preferably 65 to 75 wt% of the core portion. A core-shell acrylic binder comprising the core portion and the shell portion in the above composition range may have excellent dispersibility and uniformity, form a smoother surface, and have excellent elongation. In addition, when a coating layer is formed with a roof coating composition comprising the core-shell acrylic binder, antifouling properties may be improved. If the weight ratio of the core portion increases, the shell portion, which is responsible for fouling resistance, may not be able to wrap the core portion, resulting in a decrease in fouling resistance. Conversely, if the weight ratio of the shell portion increases, the effect of the core portion, which is responsible for the elongation of the binder, may become minimal. Therefore, manufacturing a core-shell acrylic binder with an appropriate range of weight ratios of the core portion and the shell portion may be able to well achieve the purpose of the present invention.

[0045] In one embodiment, the elongation of the core-shell acrylic binder may be 700 to 1500%, or more preferably 800 to 1200%. A core-shell acrylic binder having an elongation in the above range is preferred because it has excellent elasticity and flexibility, and a coating layer formed by including the core-shell acrylic binder can prevent cracking due to external stress or temperature changes and improve antifouling properties, but is not limited thereto.

[0046] In one embodiment, the low-temperature elongation at -20°C of the core-shell acrylic binder may be 500 to 1200%, preferably 550 to 1000%, and more preferably 550 to 850%. A core-shell acrylic binder having a low-temperature elongation within the above range is preferred because it has excellent elasticity and flexibility, and a coating layer formed by including the core-shell acrylic binder can prevent cracking due to external stress or temperature changes and improve antifouling properties, but is not limited thereto.

[0047] In one embodiment, the core-shell acrylic binder is in an emulsion state, and the average particle diameter of the core-shell particles may be 200 to 250 nm, more preferably 200 to 220 nm. A core-shell acrylic binder including core-shell particles within the above average particle diameter range may have excellent dispersibility and uniformity, form a smoother surface, and have excellent elongation. In addition, when a coating layer is formed with a roof coating composition including the core-shell acrylic binder, the antifouling property may be improved, but is not limited thereto.

[0048] The core-shell acrylic binder may contain a core-shell particle solid content of 40 to 60 wt%, preferably 45 to 55 wt%, and more preferably 50 to 53 wt%. A core-shell acrylic binder having a solid content within the above range is preferred because it has excellent dispersibility and uniformity, can form a smoother surface, and can have excellent elongation, but is not limited thereto. In addition, when a coating layer is formed with a roof coating composition including the core-shell acrylic binder, antifouling properties may be improved.

[0049] In one embodiment, the difference in transmittance before contamination and after contamination and washing of a 0.1 cm thick film manufactured with the core-shell acrylic binder may be 40% or less, 35% or less, or 30% or less, and the lower limit is not particularly limited, but may be 1% or more, 5% or more, or 10% or more. The range of the difference in transmittance is preferred because it allows for the manufacture of a core-shell acrylic binder film having excellent contamination resistance, but is not limited thereto.

[0050] Another aspect of the present invention provides a roof coating composition comprising the core-shell acrylic binder.

[0051] The above roof coating composition may further include, in addition to the core-shell acrylic binder, fillers such as calcium carbonate and silica, plasticizers such as phthalates and citric acid esters, preservatives, antifoaming agents, and stabilizers, additives such as hardeners, white pigments including TiO2, etc., and may be a roof coating composition typically used in roof coating compositions, and in particular, may be a roof coating composition for forming a white series roof coating layer.

[0052] Another aspect of the present invention provides a building having a waterproof coating layer by applying a roof coating composition comprising the core-shell acrylic binder.

[0053] Another aspect of the present invention comprises the steps of preparing a core emulsion comprising a monomer including an acrylic monomer having a carboxylic acid group or a base thereof;

[0054] A method for manufacturing a core-shell acrylic binder is provided, comprising the step of forming a core-shell by adding a shell emulsion containing acrylonitrile to the core emulsion.

[0055] In one embodiment, the core emulsion may be prepared by including, but is not limited to, 2 to 10 parts by weight, or more preferably 3 to 5 parts by weight, of an acrylic monomer having a carboxylic acid group or a base thereof, relative to 100 parts by weight of a C4 to C8 alkyl (meth)acrylate. The core emulsion polymerized with the above composition range is preferred because it satisfies the glass transition temperature range of the core portion, but is not limited thereto.

[0056] In one embodiment, the core emulsion may be manufactured by further including an emulsifier and distilled water.

[0057] The emulsifier included in the core emulsion is preferably included in an amount of 0.5 to 5% by weight, or better, 1 to 3% by weight, of the sum of the weights of the C4 to C8 alkyl (meth)acrylate and the acrylic monomer having a carboxylic acid group or a base thereof, as this allows for excellent dispersibility of the core-shell particles while forming smaller particles, but is not limited thereto.

[0058] In one embodiment, the shell emulsion may be prepared by including, but not limited to, 20 to 60 parts by weight, more preferably 30 to 50 parts by weight, and 5 to 20 parts by weight, more preferably 10 to 15 parts by weight of methyl methacrylate, based on 100 parts by weight of C4~C6 alkyl(meth)acrylate. The shell emulsion polymerized with the shell emulsion having the above composition range is preferred because it can satisfy the glass transition temperature range of the shell part, but is not limited thereto.

[0059] In one embodiment, the shell emulsion may be manufactured by further including an emulsifier and distilled water.

[0060] The emulsifier included in the above shell emulsion is preferably included in an amount of 0.5 to 5% by weight, or better, 1 to 3% by weight, of the combined weight of the C4 to C6 alkyl (meth)acrylate, methyl methacrylate, and acrylonitrile, as this allows for excellent dispersibility of core-shell particles while forming smaller particles, but is not limited thereto.

[0061] The above emulsifier is not limited to an anionic emulsifier, a nonionic emulsifier, a cationic emulsifier, etc., as long as it can emulsify the monomers of the core and shell parts. The above emulsifier may be any one selected from, or a mixture of two or more selected from, for example, sodium dodecylbenzyl sulfonate, sodium lauryl sulfate, nonylphenol ethoxylate, cetyltrimethylammonium bromide (CTAB), polyoxyethylene sorbitan monooleate (Tween 80), polyoxyethylene sorbitan monostearate (Tween 60), etc., which are nonionic emulsifiers containing a polyoxyethylene structure, but is not limited thereto.

[0062] In one embodiment, the core emulsion may be introduced into a reactor at a constant rate at 60 to 90°C, more preferably 65 to 75°C, and reacted to polymerize the core portion of the core-shell acrylic binder. In addition, the shell emulsion may be introduced into a reactor where the core portion is polymerized at a constant rate at a temperature condition of 60 to 90°C, more preferably 65 to 75°C, and reacted with the core portion to polymerize into a core-shell structure, thereby producing a core-shell binder. Maintaining the temperature condition in the above range is preferred because it may improve the dispersibility of core-shell particles and produce smaller particles, but is not limited thereto. In addition, it may be possible to control the appropriate glass transition temperatures of the core portion and the shell portion to be polymerized.

[0063] In one embodiment, a polymerization initiator may be used during polymerization in the core-shell structure. The polymerization initiator may be any one or a mixture of two or more selected from the group consisting of ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide, etc., and is not particularly limited as long as it is a polymerization initiator capable of initiating polymerization of an acrylic monomer by generating radicals by heat or a reducing agent.

[0064] In one embodiment, after the step of forming the core-shell, the method may further include a step of neutralizing the pH to a pH of 7.5 to 8.5 to prepare a core-shell acrylic binder. The method of adjusting the pH may be, but is not limited to, neutralizing by adding a 28% ammonium hydroxide solution. Adjusting the pH within the above range is preferred because it allows for obtaining a core-shell acrylic binder of uniform core-shell particles, but is not limited thereto.

[0065] The present invention will be described in more detail based on the following examples and comparative examples. However, the following examples and comparative examples are merely illustrative examples for further explaining the present invention, and the present invention is not limited by the following examples and comparative examples.

[0066] [measurement method]

[0067] 1. Measurement of glass transition temperature

[0068] Each of the core and shell emulsions was measured using a DSC device (DSC Q2000; TA instruments) according to ASTM E1356.

[0069] 2. Measurement of average particle diameter of core-shell particles

[0070] The average particle size of the core-shell acrylic binder was measured by the dynamic scattering method using a particle size analyzer (Nicomp nano 380 DLS; Entegris), and the results are shown in Table 3 below.

[0071] 3. Core and shell weight ratio

[0072] The weight ratio of the core and shell parts was calculated according to the following calculation formulas 1 and 2.

[0073] [Calculation Formula 1]

[0074] Core weight ratio (wt%) =

[0075] [Calculation Formula 2]

[0076] Shell weight ratio (wt%) =

[0077] (In the above calculation formulas 1 and 2, the core weight is the sum of the weights of C4~C8 alkyl(meth)acrylate and an acrylic monomer having a carboxylic acid group or a base thereof, and the shell weight is the sum of the weights of C4~C6 alkyl(meth)acrylate, methyl methacrylate, and acrylonitrile.)

[0078] 4. Appearance of the coating

[0079] The coating was visually observed and evaluated as follows, which is shown in Table 3 below.

[0080] ◎: Excellent appearance and no yellowing

[0081] ○: Excellent appearance, but slight yellowing occurs

[0082] △: Poor appearance or yellowing

[0083] ×: Appearance is poor or yellowing occurs significantly

[0084] (The above appearance being excellent means that the coating surface is smooth and free of cracks, and the above appearance being poor means that the coating surface is uneven or cracks have occurred.)

[0085] 5. Elongation of core-shell acrylic binder

[0086] The manufactured core-shell acrylic binder was dried to manufacture a film of 4 cm (1 cm fixed portion at the top and bottom) × 1 cm, and 0.1 cm in thickness, and the elongation was measured using a texture analysis device (TA.XT Plus Texture Analyzer; Stable Micro Systems). The 1 cm upper and lower portions of the manufactured film were fixed to the analysis device, and the elongation for a 2 cm length at the center of the film was calculated using the following Equation 1.

[0087] [Formula 1]

[0088] Elongation (%) = (Elongation length of film just before breakage / Initial film length = 2 cm) × 100 (%)

[0089] 6. Low-temperature elongation of core-shell acrylic binder

[0090] The manufactured core-shell acrylic binder was dried to manufacture a film measuring 4 cm (1 cm each at the top and bottom) × 1 cm and 0.1 cm in thickness. The manufactured film was stored at -20°C for more than one day. The elongation of the stored film was measured using a texture analysis device (TA.XT Plus Texture Analyzer; Stable Micro Systems). The 1 cm upper and lower ends of the film were fixed to the analysis device, and the elongation for a 2 cm length at the center of the film was calculated using the following Equation 1.

[0091] [Formula 1]

[0092] Elongation (%) = (Elongation length of film just before breakage / Initial film length) × 100 (%)

[0093] 7. Contamination resistance

[0094] The manufactured core-shell acrylic binder was dried to produce a film measuring 10 cm × 10 cm and 0.1 cm thick. Carbon powder was added to the manufactured film at 2 g / cm 2The contamination was carried out by applying it. Afterwards, it was washed in running water for 1 minute and dried. The transmittance of the film before contamination and after contamination and washing was measured using a haze meter (NDH-7000; DENSHOKU), and the difference in transmittance is shown in Table 3 below.

[0095] [Example 1]

[0096] A core emulsion was prepared by mixing 29 g of n-butylacrylate, 0 g of 2-ethylhexylacrylate, 0 g of methyl methacrylate, 1 g of acrylic acid, sodium dodecylbenzylsulfonate (2% by weight based on the total weight of n-butylacrylate, 2-ethylhexylacrylate, methyl methacrylate, and acrylic acid), and 12 g of distilled water.

[0097] 55 g of distilled water, 1 g of sodium dodecylbenzylsulfonate, and 0.5 g of sodium bicarbonate were added to a reactor, mixed, and then the core emulsion prepared above and ammonium persulfate (0.2% by weight based on the total weight of n-butylacrylate, 2-ethylhexyl acrylate, methyl methacrylate, and acrylic acid) were simultaneously added at a constant rate for 2 hours under temperature conditions of 75°C. After that, the core emulsion was polymerized by reacting for an additional hour.

[0098] To the core emulsion above, a shell emulsion was prepared by mixing 45 g of n-butylacrylate, 20 g of methyl methacrylate, 5 g of acrylonitrile, sodium dodecylbenzylsulfonate (2% by weight based on the sum of n-butylacrylate, methyl methacrylate, and acrylonitrile), and 28 g of distilled water, and ammonium persulfate (0.2% by weight based on the sum of n-butylacrylate, methyl methacrylate, and acrylonitrile) were simultaneously added at a constant rate for 2 hours. Afterwards, the reaction was further continued for 1 hour to polymerize an emulsion having a core-shell structure. The pH of the polymerized emulsion having a core-shell structure was adjusted to 8.0 using a 28% ammonium hydroxide solution, thereby preparing a core-shell acrylic binder.

[0099] [Examples 2 to 8]

[0100] A core-shell acrylic binder was prepared in the same manner as in Example 1, except that the core and shell emulsions prepared with the ingredients and contents described in Table 1 below were used.

[0101] [Comparative Examples 1 to 5]

[0102] A core-shell acrylic binder was prepared in the same manner as in Example 1, except that the core and shell emulsions prepared with the ingredients and contents described in Table 1 below were used.

[0103] Core emulsion Shell emulsion Component n-butyl acrylate 2-ethylhexyl acrylate Methyl methacrylate Acrylic acid Distilled water Methyl methacrylate n-butyl acrylate Acrylonitrile Distilled water Unit (g) (g) Example 1 2900 11 2 20 45 5 28 Example 2 2900 11 2 10 5 5 5 28 Example 3 3800 230 22 35 335 Example 4 9100 18 19 5 5 6 28 Example 5 2540 11 2 2 5 40 5 28 Example 6 260 31 1 2 1 7 48 5 28 Example 7 4800 22 0 14 3 2 4 20 Example 8 2900 11 2 1 6 44 10 28 Comparative example 129002123233528Comparative Example 2140151122045528Comparative Example 314015112065528Comparative Example 429001122545028Comparative Example 59.5000.5425.5586.536

[0104] [Comparative Example 6]

[0105] An emulsion was prepared by mixing 20 g of methyl methacrylate, 74 g of n-butylacrylate, 1 g of acrylic acid, 5 g of acrylonitrile, sodium dodecylbenzylsulfonate (2% by weight based on the total weight of methyl methacrylate, n-butylacrylate, acrylic acid, and acrylonitrile), and 40 g of distilled water.

[0106] 55 g of distilled water, 1 g of sodium dodecylbenzylsulfonate, and 0.5 g of sodium bicarbonate were added to a reactor and mixed, and then the prepared mixed emulsion and ammonium persulfate (0.2% based on the total weight of methyl methacrylate, n-butylacrylate, acrylic acid, and acrylonitrile) were simultaneously added at a constant rate for 4 hours under temperature conditions of 75°C. After this, the mixture was further reacted for 1 hour to polymerize, and then the pH was adjusted to 8.0 using a 28% ammonium hydroxide solution to prepare an acrylic emulsion.

[0107] Solid content (wt%)Average particle size (nm)Core-shell mass ratio (core / shell)Glass transition temperature (℃)(core / shell)Appearance of coating filmElongation (%)Low temperature elongation (%)Stain resistance (△Transmittance %)Example 151.021030 / 70-45 / -6◎89068020.1Example 250.821230 / 70-45 / -14◎102075028.6Example 351.121340 / 60-40 / 0◎82059017.6Example 450.921020 / 80-50 / -20○113081035.1Example 551.020730 / 70-50 / 0◎83055016.9Example 650.920930 / 70-40 / -20◎105077031.3Example 751.120350 / 50-43 / -6○98069035.3Example 850.119930 / 70-42 / -7△94071019.8Comparative Example 151.221230 / 70-41 / 15○680Not elongatable25.8Comparative Example 251.221730 / 701 / -5○48036018.3Comparative Example 350.921130 / 702 / -43○84047050.3Comparative Example 451.321430 / 70-43 / -5◎48034020.3Comparative example 550.820810 / 90-44 / -6△59037019.1Comparative example 651.0150--20○57043048.3

[0108] In Table 2 above, it was confirmed that examples satisfying the component range and glass transition temperature range of the present invention had excellent elongation and low-temperature elongation. In addition, it was confirmed that the composition could be utilized as a white-colored roof coating composition due to its excellent film appearance and antifouling properties.

[0109] In Table 2 above, Example 8 has a relatively high acrylonitrile content in the shell emulsion, and as the acrylonitrile content increases, the fouling resistance tends to decrease. In addition, because acrylonitrile is toxic and chemically hazardous, its content may be limited.

[0110] As described above, the present invention has been described through specific matters and limited examples, but these are provided only to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and those skilled in the art to which the present invention pertains can make various modifications and variations based on this description.

[0111] Therefore, the idea of ​​the present invention should not be limited to the described embodiments, and all things that are equivalent or equivalent to the following claims as well as the claims are considered to fall within the scope of the idea of ​​the present invention.

Claims

1. Glass transition temperature (T g ) has a core-shell structure having a core portion having a glass transition temperature of -50 to -40 ℃ and a shell portion having a glass transition temperature of -20 to 0 ℃, The core portion comprises an acrylic monomer having a carboxylic acid group or a base thereof, and the shell portion comprises a core-shell acrylic binder polymerized with acrylonitrile. A core-shell acrylic binder having an elongation of 700% or more and a low-temperature elongation at -20°C of 500% or more.

2. In paragraph 1, A core-shell acrylic binder in which the core part is polymerized by including 2 to 10 parts by weight of an acrylic monomer having a carboxylic acid group or a base thereof, relative to 100 parts by weight of a C4 to C8 alkyl (meth)acrylate.

3. In paragraph 1, A core-shell acrylic binder in which the shell portion is polymerized by including 20 to 60 parts by weight of methyl methacrylate and 5 to 25 parts by weight of acrylonitrile relative to 100 parts by weight of C4 to C6 alkyl (meth)acrylate.

4. In paragraph 1, A core-shell acrylic binder wherein the acrylic monomer having the carboxylic acid group or its base is one selected from acrylic acid and methacrylic acid or a mixture of the two.

5. In paragraph 1, The core-shell acrylic binder is a core-shell acrylic binder comprising 20 to 40 wt% of a core portion and 60 to 80 wt% of a shell portion.

6. In paragraph 1, A core-shell acrylic binder having a difference in transmittance of 0.1 cm thick film before contamination and after contamination and washing of 40% or less.

7. A roof coating composition comprising a core-shell acrylic binder selected from any one of claims 1 to 6.

8. A roof coating layer formed by applying a roof coating composition comprising a core-shell acrylic binder selected from any one of claims 1 to 6.

9. A step of preparing a core emulsion containing an acrylic monomer having a carboxylic acid group or a base thereof; A method for manufacturing a core-shell acrylic binder, comprising: a step of forming a core-shell by adding a shell emulsion containing acrylonitrile to the core emulsion.

10. In paragraph 9, A method for producing a core-shell acrylic binder, wherein the core emulsion is produced by including 2 to 10 parts by weight of an acrylic monomer having a carboxylic acid group or a base thereof, relative to 100 parts by weight of a C4 to C8 alkyl (meth)acrylate.

11. In paragraph 9, A method for producing a core-shell acrylic binder, wherein the above-mentioned shell emulsion is produced by including 10 to 80 parts by weight of methyl methacrylate and 5 to 30 parts by weight of acrylonitrile, based on 100 parts by weight of C4 to C6 alkyl (meth)acrylate.

12. In paragraph 9, A method for producing a core-shell acrylic binder, further comprising a step of neutralizing the pH to a pH of 7.5 to 8.5 after the step of forming the core-shell, thereby producing a core-shell acrylic binder.

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