# Patent

## Title
Resin article

## Abstract

Provided is a resin article having a layer-separated structure. The resin article may include a first resin layer and a second resin layer formed on the first resin layer. Also, the component of the first resin layer is detected on a surface of the second resin layer by infrared spectrometer. The resin article may have improved mechanical and surface characteristics. Further, since coating or plating is not required for manufacturing a resin article, a manufacturing time and/or cost can be reduced, and productivity can be increased.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of U.S. patent application Ser. No. 13/687,714, filed on Nov. 28, 2012, which is a continuation-in-part of International Application PCT/KR2011/003887, with an international filing date of May 26, 2011, which claims priority to and the benefit of Korean Patent Application No. 2010-0050639, filed May 28, 2010, Korean Patent Application No. 2010-0050640, filed May 28, 2010, Korean Patent Application No. 2010-0081084, filed Aug. 20, 2010, Korean Patent Application No. 2010-0081085, filed Aug. 20, 2010, and Korean Patent Application No. 2011-0050135, filed May 26, 2011, the disclosures of which are incorporated herein by reference in their entireties.


BACKGROUND
Resins are used for various applications such as a part of an automobile, a helmet, a part of an electric device, a part of a spinning machine, a toy or a pipe due to their excellent processability and properties such as tensile strength, modulus of elasticity, heat resistance and impact resistance.
Particularly, resins for home interior accessories, parts of automobiles and toys are required to be environment-friendly and have excellent scratch resistance because they are in direct contact with a human body. However, resins are generally decomposed by oxygen in the air, ozone and light and easily changed in color when exposed to an external environment over a certain period of time. In order to improve the poor weather resistance and strength of the resins, a coating or plating process has been applied to the resins. However, such a coating or plating process can degrade efficiency and economic feasibility of a manufacturing process of resins or generate toxic materials during the process or disposal of a resin product.
Accordingly, various methods have been suggested to improve characteristics such as scratch resistance, heat resistance and weather resistance of resins without using a coating or plating process. For example, a method of adding an inorganic particle to resins has been suggested to improve physical properties such as wear resistance and hardness of resins. However, the method may deteriorate the processability of a resin and impact strength and brilliance characteristics.
SUMMARY OF THE INVENTION
The present invention provides a resin article having a layer-separated structure. The resin article may have improved mechanical and surface characteristics. Further, since coating or plating is not required for manufacturing the resin article, a manufacturing time and/or manufacturing cost can be reduced, and productivity can be increased.
In one embodiment, a resin article having a layer-separated structure that includes a first resin layer; and a second resin layer formed on the first resin layer. Here, the component of the first resin layer is detected on a surface of the second resin layer by an infrared (IR) spectrometer.
In another embodiment, a resin article having a layer-separated structure includes a first resin layer; a second resin layer formed on the first resin layer; and an interface layer formed between the first resin layer and the second resin layer. Here, the interface layer includes a first resin and a second resin.



BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:
FIG. 1 is an illustrative schematic diagram showing a resin blend, according to one embodiment of the present invention.
FIG. 2 is an illustrative schematic diagram showing a resin blend, according to another embodiment of the present invention.
FIG. 3 is a SEM image illustrating a cross-sectional view of a layer-separated article prepared according to Example 1.
FIG. 4 is an illustrative schematic diagram showing a resin article having layer-separated structure including a first resin layer, a second resin layer and an interface layer formed between the first and the second resin layer, according to one embodiment of the present invention.
FIG. 5 is an illustrative schematic diagram showing a resin article having a layer-separated structure including a first resin layer and a second resin layer, according to one embodiment of the present invention.
FIG. 6 is an illustrative schematic diagram showing a resin article having a layer-separated structure including a first resin layer, a second resin layer and a third resin layer, according to another embodiment of the present invention.
FIG. 7 is an illustrative schematic diagram showing a resin article having layer-separated structure, according to another embodiment of the present invention.
FIG. 8 is an illustrative schematic diagram showing a pellet having a core and a shell.
FIG. 9 is a SEM image illustrating a cross-sectional view of a resin article treated with a solution capable of selectively dissolving a second resin, when viewed at a 45-degree angle from the surface prepared according to Example 1.



DETAILED DESCRIPTION OF EMBODIMENTS
Hereinafter, a resin article having a layer-separated structure and a method of preparing a resin article according to embodiments of the present invention will be described in detail.
In one embodiment, a resin article having a layer-separated structure that includes a first resin layer; and a second resin layer formed on the first resin layer. Here, the component of the first resin layer is detected on a surface of the second resin layer by an infrared (IR) spectrometer.
A structure of the resin article, that is, a structure in which the component of the first resin layer is detected from the surface of the second resin layer by the IR spectrometer, is novel, and has not been known in the art. Generally, in a coating process, the component of the first resin layer is difficult to detect from the surface of the second resin layer.
The surface of the second resin layer indicates a surface exposed to an ambient air, not to the first resin layer.
In addition, the component of the first resin layer indicates at least one of the components included in the first resin layer.
When a resin blend including specific first and second resins is used, due to different physical properties between the first and second resins, layer separation may occur. Specifically, in the case that the resin blend of the first and second resins is melt-processed, and then the melt-processed resin blend is exposed to an ambient air, the first and second resins can be separated. Therefore, a resin article could have a structure in which a first resin layer may be divided from a second resin layer via an interface layer. Also, the resin article could have a structure in which the second resin layer is exposed to an ambient air without using an additional process.
It is shown that such a structural characteristic of the resin article is caused by applying a resin blend of specific first and second resins. The specific first and second resins may be a resin which has predetermined physical properties and/or a predetermined molecular weight distribution and/or a predetermined weight average molecular weight. Since the resin article has such a structural characteristic, the resin article may have improved mechanical and surface characteristics. Further, since coating or plating is not required for manufacturing the resin article, a manufacturing time and/or cost can be reduced, and productivity can be increased.
A “blend” may be a mixture of two or more different species of resins. A type of blend may include, but is not limited, a mixture of two or more resins in one polymer matrix, or a mixture of two or more kinds of pellets. Particularly, as shown in FIG. 1, the mixture of two or more resins in one matrix may be a pellet 10 including the composition of two or more resins 11. Alternatively, as shown in FIG. 2, the mixture of two or more pellets may be a mixture of two or more kinds of pellets 20, 21 including one resin in one pellet. The resins may have different physical properties from each other. For example, the physical properties may include a surface energy, a melt viscosity or a solubility parameter.
A “melting process” or “melt processing” may indicate a process of melting the resin blend at a melting temperature (Tm) of the resin blend or higher to form a melt blend and forming a desired product by using the melt blend. For example, the melting process may include injection molding, compression molding, transfer molding, thermoforming, blow molding, film blowing, extrusion, calendaring, fiber spinning, expanding molding and the like.
A “resin article” may indicate a pellet or a product which is not treated by coating or plating after a resin blend is melting-processed. The resin article may provide, but is not limited to, a part of an automobile, a household, a part of an electric device, a part of a machine, a functional sheet or film, a toy, or a pipe.
A “layer separation” or “layer-separated” may indicate that one layer substantially formed of one resin is disposed or aligned on another layer substantially formed of another resin. The layer substantially formed of one resin may indicate that one type of resin is continuously present in the entire layer, without forming a sea-island structure in the layer. The sea-island structure may indicate a phase-separated resin is partially distributed in an entire resin blend. Further, the “substantially formed” may indicate that one resin is present or one resin is rich in a layer.
A “first resin” may indicate that a resin which may be included in the first resin layer. The first resin mainly determines physical properties of a desired article, and thus may be selected according to a kind of the desired article and process conditions used herein.
A “second resin” may indicate that a resin which may be included in the second resin layer. The second resin shows the difference in physical properties from the first resin as described above and may provide predetermined functions to a surface of the desired article, and thus is not particularly limited to a kind of the functions.
Meanwhile, the resin article may include an interface layer including a blend of a first resin and a second resin and formed between the first resin layer and the second resin layer. As shown in FIG. 3B, the interface layer may serve as a boundary formed between the layer-separated first and second resin layers, and include the blend of the first and second resins. The blend may be present in such a manner that the first resin is physically or chemically bound to the second resin, and the first resin layer may be bound to the second resin layer by the blend.
To observe the first and second resin layers and the interface layer and measure a thickness of each layer, a sample was cut with a diamond knife using a microtoming device to obtain a smooth cross-section, and the smooth cross-section was etched using a solution capable of more selectively dissolving a second resin than a first resin. The etched cross-section is dissolved to different levels of depth according to contents of the first and second resins, and when the cross-section is viewed at a 45-degree angle from a surface thereof through SEM, the first resin layer, the second resin layer and the interface layer may be observed due to a shade difference and thicknesses thereof may be measured. In the present invention, as the solution more selectively dissolving the second resin, a 1,2-dichloroethane solution (10 volume %, in EtOH) is used, but is merely an example. Therefore, any solution having a higher solubility of the second resin than the first resin may be used without limitation, and the solution may vary according to the kind and composition of the second resin. The thickness of the interface layer may be 0.01 to 95% or 0.1 to 70%, of the total thickness of the second resin layer and the interface layer. When the thickness of the interface layer is 0.01 to 95% to the total thickness of the second resin layer and the interface layer, the interface adhesive strength of the first and second resin layers is excellent. Thus, the first and the second resin layers are not detached, and the surface characteristic caused by the second resin layer may be considerably improved. On the other hand, when the thickness of the interface layer is too smaller than the total thickness of the second resin layer and the interface layer, the adhesive strength between the first and second resin layers is decreased, and thus both layers may be detached. However, when the thickness of the interface layer is very thick, the improvement in a surface characteristic of the second resin layer may be insignificant.
The second resin layer may have a thickness of 0.01 to 60%, 0.1 to 40% or 1 to 20%, of the total thickness of the resin article. As the second resin layer has a thickness in a predetermined range, predetermined functions may be provided to the surface of the resin article. Here, when the second resin layer has a very thin thickness, it may be difficult to sufficiently improve the surface characteristic of the resin article, and when the second resin layer has a very thick thickness, the mechanical property of the second resin may be reflected to the resin article, and thus the mechanical property of the first resin may be changed.
In another embodiment, a resin article having a layer-separated structure includes a first resin layer; a second resin layer formed on the first resin layer; and an interface layer formed between the first resin layer and the second resin layer. Here, the interface layer includes a first resin and a second resin.
The resin article has a novel structure which has not been known in the art. The resin article is formed in such a structure that the first resin layer is separated from the second resin layer by an interface layer and the second resin layer is exposed to an ambient air. This structure may not be formed by extrusion and injection process of a general resin, and thus it is difficult to realize the effects according to the structure.
A structure of the resin article, as described above, may include an interface layer including the first resin and the second resin and formed between the first resin layer and the second resin layer. Here, a thickness of the interface layer may be 0.01 to 95% or 0.1 to 75%, of a total thickness of the second resin layer and the interface layer.
In addition, the second resin layer may have a thickness of 0.01 to 60%, 0.1 to 40% or 1 to 20%, of the total resin article.
As described above, the resin article may have such a structure that the first resin layer is separated from the second resin layer by the interface layer, and the second resin layer is exposed to the ambient air. For example, the resin article may have a structure in which a first resin layer, an interface layer and a second resin layer are sequentially stacked as shown in FIG. 3, or a structure in which the first resin layer is disposed, and the interface layers and the second resin layer are disposed above and below the first resin layer as shown in FIG. 4. Alternatively, the resin article may have such a structure that the first resin layer formed in various three-dimensional shapes, for example, spherical, circular, polyhedral and sheet-type shapes, is sequentially surrounded by the interface and the second resin layer.
A resin article formed of the resin blend by a melting process may have improved mechanical and surface characteristics and may be easily produced with a reduced manufacturing cost and time. For example, the resin blend may be layer-separated by a melting process to form a resin article having a specific function on a surface of the resin article, without an additional process, such as coating and plating.
The layer separation of the resin blend may be caused by a difference in physical properties between a first and second resins and/or a molecular weight distribution of the second resin. Here, the different physical properties may, for example, include surface energy, melt viscosity and a solubility parameter. Although it is illustrated here that two resins are blended for the purpose of explanation of the present invention, it will be apparent to one of skilled in the art that three or more resins having different physical properties may be blended and separated during a melting process.
In one embodiment, a resin article includes a first resin layer and a second resin layer having a difference in surface energy from the first resin layer at 25° C. of 0.1 to 35 mN/m, 1 to 30 mN/m, 1 to 20 mN/m, 1 to 10 mN/m, 0.5 to 10 mN/m, 5 to 35 mN/m, 15 to 35 mN/m or 5 to 30 mN/m. It will be apparent to one of skilled in the art that the listed ranges are only examples for the purpose of the description of the present invention and any values within 0.1 to 35 mN/m can be chosen.
The difference in surface energy may indicate the difference in surface energy between the first resin layer and the second resin layer or between the first resin and the second resin.
When the difference in surface energy is less than 0.1 mN/m, the layer separation of the melt-processed resin blend does not easily occur because the second resin in a mixture of melting state is difficult to move through the polymer matrix of the resin blend. When the difference in surface energy is greater than 35 mN/m, the first and second resins may not be attached to each other due to a high difference of surface energy, and thus may be detached.
The lower and/or upper limits of the difference in surface energy may be any numeric value of 0.1 to 35 mN/m, and be dependent on the properties of the first resin. Particularly, when a first resin is used as a base resin and a second resin is used a functional resin to improve surface properties of a first resin, the second resin may be selected such that a difference in surface energy between the first and second resins is 0.1 to 35 mN/m at 25° C. Since a value of the surface energy of the second resin (e.g., functional resin) may be different based on the properties of the first resin (e.g., base resin), the difference in surface energy may be determined based on the properties of the first resin. The properties of the first resin may include, but is not limited to, a kind of the first resin, or a value of the surface energy of the first resin. In one embodiment, the difference in surface energy may be selected by considering mobility of the second resin in a melting mixture of the first and second resins.
The resin blend of the first and second resins having the difference in surface energy of 0.1 to 35 mN/m at 25° C. can be separated by using the difference in surface energy after the melting process has been performed. By way of an example, in the case that the resin blend of the first and second resins is melt-processed, and then the melt-processed resin blend is exposed to an ambient air, the first and second resins can be separated due to the affinity between the second resin and the ambient air. Particularly, the second resin having a smaller surface energy compared to the first resin may have a hydrophobic property, and move to contact with the ambient air. Thus, the second resin may be positioned adjacent to an ambient air to form a second resin layer. A first resin layer may be positioned on an inner side of the second layer. Accordingly, a layer separation can be occurred between the first and second resins of the resin blend.
The resin blend may be separated into two or more layers. The resin blend including the first resin and the second resin may be layer-separated into three layers, i.e., Second resin layer/First resin layer/Second resin layer, as shown in FIG. 5, when two opposite sides of the melt-processed resin blend are exposed to the ambient air. Alternatively, when only one side of the melt-processed resin blend is exposed to the ambient air, the resin blend may be layer-separated into two layers, i.e., Second resin layer/First resin layer. Further, when a resin blend including a first resin, a second resin and a third resin is melt-processed, the melt-processed resin blend may be layer-separated into five layer, i.e., Third resin layer/Second resin layer/First resin layer/Second resin layer/Third resin layer, as shown in FIG. 6, by using the differences in surface energy among the three resins. Furthermore, when all sides of the melt-processed resin blend are exposed to the ambient air, the resin blend may be layer-separated into all direction to form a core-shell structure, as shown FIG. 7.
In another embodiment, a resin article includes a first resin layer and a second resin layer having a difference in melt viscosity from the first resin layer of 0.1 to 3000 pa*s, 1 to 2000 pa*s, 1 to 1000 pa*s, 100 to 500 pa*s, 500 to 3000 pa*s, 1500 to 3000 pa*s or 500 to 2500 pa*s at a shear rate of 100 to 1000 s−1 and a processing temperature of a resin blend including the first and second resins.
The difference in melt viscosity may indicate the difference in melt viscosity between the first resin layer and the second resin layer or between the first resin and the second resin.
It will be apparent to one of skilled in the art that the listed ranges are only examples for the purpose of description of the present invention and any value within the range of 0.1 to 3000 pa*s at the above shear rate can be selected. When the difference in the melt viscosity is less than 0.1 pa*s at the shear rate, the layer separation of the melt-processed resin blend does not easily occur due to a low difference of melt viscosity of the first and second resins. When the difference in the melt viscosity is greater than 3000 pa*s at the shear rate, the first and second resins may not be attached to each other due to a high difference of the melt viscosity and thus may be detached.
The lower and/or upper limits of the difference in melt viscosity may be any numeric value of 0.1 to 3000 pa*s, and be dependent on the properties of the first resin. Particularly, when a first resin is used as a base resin and a second resin is used as functional resin to improve surface properties of the first resin, the second resin may be chosen such that a difference in a melt viscosity between the first and second resins is 0.1 to 3000 pa*s at a shear rate of 100 to 1000 s−1. Since a value of the melt viscosity of the second resin (e.g., functional resin) may be different based on the properties of the first resin (e.g., base resin), the difference in the melt viscosity may be determined based on the properties of the first resin. The properties of the first resin may include, but is not limited to, a kind of the first resin, or a value of the melt viscosity of the first resin. In one embodiment, the difference in melt viscosity may be selected by considering fluidity of the second resin in a melting mixture of the first and second resins.
The resin blend of the first and second resins having the difference in melt viscosity of 0.1 to 3000 pa*s at a shear rate of 100 to 1000 s−1 and a processing temperature of the resin blend can be separated by using the difference in melt viscosity after the melting process has been performed. By way of an example, in the case that the resin blend of the first and second resins is melt-processed, and then the melt-processed resin blend is exposed to an ambient air, the first and second resins can be separated due to the difference of fluidity between the first resin and second resin. Particularly, the second resin having a smaller melt viscosity compared to the first resin may have a higher fluidity than the first resin, and move to the ambient air. Thus, the second resin may be positioned adjacent to an ambient air to form a second resin layer. A first resin layer may be positioned on an inner side of the second layer. Accordingly, a layer separation can be occurred between the first and second resins of the resin blend.
The melt viscosity may be measured using a capillary flow meter, and indicates a shear viscosity (pa*s) at a predetermined processing temperature and shear rate (/s). The shear rate is a shear rate applied when the resin blend is processed, and may be selected among the value of 100 to 1000 s−1 depending on a processing method. It will be apparent to one of skilled in the art to control the shear rate according to the processing method.
The processing temperature is a temperature at which the resin blend of the first and second resins is processed. For example, when the resin blend is subject to a process such as extrusion or injection, the processing temperature is a temperature at which the extrusion or injection is performed. The processing temperature may be controlled according to a resin subjected to melting processes. It will be apparent to one of skilled in the art to control the processing temperature according to kinds of resins of the resin blend. For example, a temperature for extruding or injecting a resin blend including a first resin composed of an ABS resin and a second resin obtained by polymerizing a methyl methacrylate-based monomer may be 210 to 240° C.
In still another embodiment, a resin article includes a first resin layer and a second resin layer having a difference in solubility parameter from the first resin layer at 25° C. of 0.001 to 10 (J/cm3)1/2, 0.01 to 5 (J/cm3)1/2, 0.01 to 3 (J/cm3)1/2, 0.01 to 2 (J/cm3)1/2, 0.1 to 1 (J/cm3)1/2, 0.1 to 10 (J/cm3)1/2, 3 to 10 (J/cm3)1/2, 5 to 10 (J/cm3)1/2, or 3 to 8 (J/cm3)1/2.
The difference in solubility parameter may indicate the difference in solubility parameter between the first resin layer and the second resin layer or between the first resin and the second resin.
The lower and/or upper limit of the difference in solubility parameter may be any numeric value of 0.001 to 10 (J/cm3)1/2, and be dependent on a solubility parameter of the first resin. It will be apparent to one of skilled in the art that the listed values are only examples for the purpose of description of the present invention and any value within the range of 0.001 to 10 (J/cm3)1/2 at 25° C. can be chosen. A solubility parameter is an inherent characteristic of a resin showing soluble ability according to a polarity of each resin molecule, and the solubility parameter for each resin is generally known. When the difference in the solubility parameter is less than 0.001 (J/cm3)1/2, the layer separation does not easily occur due to a low difference of solubility parameter. When the difference in the solubility parameter is greater than 10 (J/cm3)1/2, the first and second resins may not be attached to each other due to a high difference of solubility parameter, and thus may be detached.
The lower and/or upper limits of the difference in solubility parameter may be any numeric value of 0.001 to 10 (J/cm3)1/2, and be dependent on the properties of the first resin. Particularly, when a first and second resins are used as a base and functional resins, respectively, the second resin may be chosen such that a difference in a solubility parameter between the first and second resins is 0.001 to 10 (J/cm3)1/2 at 25° C. Since a value of the solubility parameter of the second resin (e.g., functional resin) may be different based on properties of the first resin (e.g., base resin), the difference in the solubility parameter may be determined based on the properties of the first resin. The properties of the first resin may include, but is not limited to, a kind of the first resin, or a value of the solubility parameter of the first resin. In one embodiment, the difference in solubility parameter may be selected by considering miscibility between the first resin and the second resin in a melting mixture of the first and second resins.
The resin blend of the first and second resins having the difference in solubility parameter of 0.001 to 10 (J/cm3)1/2 at 25° C. can be separated by using the difference in solubility parameter after the melting process has been performed. By way of an example, in the case that the resin blend of the first and second resins is melt-processed, and then the melt-processed resin blend is exposed to an ambient air, the first and second resins can be separated due to the degree of immiscibility between the first resin and second resin. Particularly, the second resin having a difference in solubility parameter from the first resin at 25° C. of 0.001 to 10 (J/cm3)1/2 may be immiscible with the first resin. Thus, the second resin having additionally lower surface tension or lower melt viscosity than that of the first resin may move and be positioned adjacent to an ambient air to form a second resin layer. A first resin layer may be positioned on an inner side of the second layer. Accordingly, a layer separation can be occurred between the first and second resins of the resin blend.
In still another embodiment, a molecular weight distribution (PDI) of the second resin is 1 to 2.5, 1 to 2.3, 1 to 2, 1.3 to 2.5, 1.5 to 2.5, or 1.3 to 2.3. The lower and/or upper limits of the molecular weight distribution (PDI) of the second resin may be any numeric value of 1 to 2.5. It will be apparent to one of skilled in the art that the listed ranges are only examples for the purpose of the description of the present invention and any value within the range of 1 to 2.5 can be selected. When the molecular weight distribution of the second resin is greater than 2.5, the first resin is easily mixed with the second resin due to the low molecular weight portion of the second resin, or the mobility of the second resin in a mixture of melting state is degraded due to the high molecular weight portion thereof, and thus it is difficult for the second resin to move through the polymer matrix of the resin blend. Therefore, the layer separation between the first resin and the second resin is hardly occurred.
In still another embodiment, the weight average molecular weight (Mw) of the second resin is 30,000 to 200,000, 50,000 to 200,000, 80,000 to 200,000, 50,000 to 150,000, 80,000 to 150,000, 50,000 to 120,000, or 80,000 to 120,000. The lower and/or upper limits of the weight average molecular weight (Mw) of the second resin may be any numeric value of 30,000 to 200,000. It will be apparent to one of skilled in the art that the listed ranges are only examples for the purpose of the description of the invention and any value within the range of 30,000 to 200,000 can be chosen. When the weight average molecular weight is smaller than 30,000, the first resin is easily mixed with the second resin, and when the weight average molecular weight is greater than 200,000, the mobility of the second resin in a mixture of melting state is degraded and thus it is difficult for the second resin to move through the polymer matrix of the resin blend. Therefore, the layer separation between the first and second resin is hardly occurred.
Meanwhile, the first resin may determine the physical properties of a desired resin article and may be selected according to a kind of the desired resin article and process conditions. As the first resin, a synthetic resin may be used without limitation, but may include a styrene-based resin such as an acrylonitrile butadiene styrene (ABS)-based resin, a polystyrene-based resin, an acrylonitrile styrene acrylate (ASA)-based resin or a styrene-butadiene-styrene block copolymer-based resin; a polyolefin-based resin such as a high density polyethylene-based resin, a low density polyethylene-based resin or a polypropylene-based resin; a thermoplastic elastomer such as an ester-based thermoplastic elastomer or olefin-based thermoplastic elastomer; a polyoxyalkylene-based resin such as a polyoxymethylene-based resin or a polyoxyethylene-based resin; a polyester-based resin such as a polyethylene terephthalate-based resin or a polybutylene terephthalate-based resin; a polyvinylchloride-based resin; a polycarbonate-based resin; a polyphenylenesulfide-based resin; a vinyl alcohol-based resin; a polyamide-based resin; an acrylate-based resin; engineering plastics; or a copolymer or mixture thereof.
The engineering plastics are a group of plastics that exhibit superior mechanical and thermal properties. By way of examples, polyetherketone, polysulphone, polyimides and the like may be used as the engineering plastics.
The second resin shows the difference in physical properties from the first resin as described above, and may be chosen to provide specific functions to a surface of a resin article. A kind of the functions is not particularly limited. For example, there is a high surface hardness function, an anti-wear function, an anti-contamination function, an anti-fingerprint function, a color, a pearling function, a high-gloss function, a non-gloss function, a barrier function or a combination thereof.
The second resin may have either or all of a thermal curable functional group and a radiation, such as UV, curable functional group without specific limitation. When a thermal curable functional group is included in the second resin, hardness may be increased due to the crosslinks formed in melting process.
As another examples of the second resin, a (meth)acrylate-based resin, an epoxy-based resin, an oxetane-based resin, an isocyanate-based resin, a silicon-based resin, a fluorine-based resin, or a copolymer or mixture thereof may be included.
The (meth)acrylate-based resin is a resin formed by polymerizing an acryl or methacryl monomer as a main component, which may include, but is not limited to, alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, octyl methacrylate, lauryl methacrylate or stearyl methacrylate; alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, lauryl acrylate or stearyl acrylate; or glycidyl (meth)acrylates such as glycidyl methacrylate or glycidyl acrylate.
The epoxy-based resin is a resin containing an epoxy group, and may be, but is not limited to, a bisphenol type such as bisphenol A, bisphenol F, bisphenol S or a hydro additive thereof; a novolac type such as phenol novolac or cresol novolac; a nitrogen-containing ring type such as triglycidyl isocyanurate or hydantoin; an alicyclic type; an aliphatic type; an aromatic type such as naphthalene or biphenyl; a glycidyl type such as glycidyl ether, glycidyl amine or glycidyl ester; a dicyclo type such as dicyclopentadiene; an ester type; or an ether ester type.
The oxetane-based resin is a resin formed by polymerizing an oxetane monomer having at least one oxetane ring, and may be, but is not limited to, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, di[1-ethyl(3-oxetanyl)]methylether, or a polyoxetane compound such as phenol novolac oxetane, terephthalate bisoxetane or biphenylene bisoxetane.
The isocyanate-based resin is a resin containing an isocyanate group, and may be, but is not limited to, diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI) or isophorone diisocyanate (IPDI).
The silicon-based resin is a resin containing a main chain connected by a siloxane bond which is a silicon-oxygen bond, and may be, but is not limited to, polydimethylsiloxane (PDMS).
The fluorine-based resin is a resin containing a fluorine atom, and may be, but is not limited to, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), or polyvinylfluoride (PVF).
In another embodiment, a resin blend for forming a layer-separated structure includes a base resin and a functional resin. A value of a surface energy of the functional resin is different from that of the base resin, and the value of the surface energy of the functional resin is dependent on properties of the base resin.
The base resin, for example, a first resin, may substantially determine the physical properties of a resin article. The functional resin, for example, a second resin, may provide specific functions to a surface of a resin article. The properties of the base resin and the specific functions of the second resin are the same as described the above.
The present invention further provides a method of preparing a resin article having layer-separated structure. In one embodiment, the method includes forming a resin blend of first and second resins; melting the resin blend to form a melt blend; and processing the melt blend to form a layer-separated structure. The surface energy difference between the first resin and the second resin is 0.1 to 35 mN/m at 25° C.
As described above, since the second resin has a different physical property from the first resin, the layer separation may occur during the melting and processing, that is melting process of the resin blend. Further, since the second resin can be formed to have a function such as gloss or anti-contamination and can be separated from the first resin during the melting process of the resin blend, the resin article in which the first resin constitutes a body and the second resin forms a surface on the body can be easily manufactured without performing additional process. Still further, when the first and second resins are used to form a pellet, the pellet having a core of the first resin and a shell of the second resin can be manufactured by the melting process of the resin blend without performing any additional process. Furthermore, the melting process may be performed under a shear stress, and may include, but is not limited to, injection and extrusion.
When the resin blend is used, layer separation occurs due to the difference in physical properties between the first resin and the second resin. For this reason, it is completely different from the conventional method using a solvent having a low viscosity to easily pick an article out of a mold. In the present invention, since at least two layer-separable resins are used, surface and mechanical characteristics of the final resin article may be improved. However, according to the conventional method using the solvent having a low viscosity, the article can be simply and easily separated from a mold, and it has no effect on a physical property of the final product.
In the formation of the resin blend of the first resin and the second resin, a method or device conventionally known to be used to blend a plastic resin, a polymer or a copolymer may be used without limitation. In one embodiment, the resin blend may be prepared to include a first resin and a second resin that have a difference in physical properties, for example, surface energy, melt viscosity or solubility parameter. The resin blend may be melted to form a melt blend and the melt blend may be further processed to form a layer-separated structure. For example, the melted resin blend may be subject to an extrusion process to prepare a pellet. As described above, the first and second resins may be separated during the melting and extrusion processes. Particularly, the second resin may move to contact with an ambient air due to its hydrophobic property compared to the first resin. A second resin layer may be positioned adjacent to an ambient air, and a layer substantially formed of a first resin layer may be positioned on an opposite side to the ambient air but disposed adjacent to the second resin layer. Accordingly, the resin article may have a body that is formed of the first resin and a surface that is on the body and is formed of the second resin.
The resin blend including the first and second resins may be prepared into a pellet using a melting process. The pellet may have a core having a first resin and a shell having a second resin. As shown in FIG. 8, the first resin is disposed in the middle thereof, and a second resin is layer-separated from the first resin and disposed to surround the first resin and to form a shell of the pellet.
The first resin and the second resin have different properties as described above. That is, the first resin and the second resin may have a difference in surface energy from the first resin at 25° C. of 0.1 to 35 mN/m; a difference in melt viscosity of 0.1 to 3000 pa*s at a shear rate of 100 to 1000 s−1 and a processing temperature of the pellet; or a difference in solubility parameter of 0.001 to 10.0 (J/cm3)1/2 at 25° C. Further, the second resin may have a molecular weight distribution (PDI) of 1 to 2.5 or a weight average molecular weight (Mw) of 30,000 to 200,000. The first and second resins have already been described in detail, and thus further detailed description will be omitted.
In another embodiment, the pellet may be further processed to form a resin article. For example, the pellet having first and second resins of different physical properties may be melted and further processed, for example, injected, to form a final product, for example, a resin article. As described above, due to the difference in various physical properties, for example, surface energy, melt viscosity or solubility parameter, of the first and second resins of the pellets, the resin article formed of the pellets may have separated layers, i.e., a body formed of the first resin and a surface layer formed of the second resin and placed on the body. Although it is illustrated that the pellets of core-shell structure having the first and second resins are melt-processed to form a resin article for the purpose of explanation, it will be apparent to one of skilled in the art that a mixture of two or more pellets or pellets including the composition of two or more resins may be used to form a resin article. Alternatively, the resin blend may be directly prepared into a resin article through the melting process, as described above. The processing temperature to be applied may be changed depend on kinds of the first and second resins used in the melting process of the resin blend.
In some embodiments, the method of preparing a resin article may further include curing a layer-separated structure (for example, a resin article having a body and a surface layer on the body) obtained by melt-processing the resin blend. For example, after an extrusion or injection, either or both of thermal curing and radiation curing, such as UV curing, may be further performed on the layer-separated structure. When necessary, chemical or physical treatment, such as a heat treatment, may be performed after the process.
Meanwhile, the method of preparing a resin article may further include preparing a second resin before the forming the resin blend. The second resin may be selected depending on a first resin, as described above. For example, the second resin may be selected such that a value of a surface energy of the second resin is less than that of the first resin. Further, the second resin may be selected to add specific functions on a surface of the resin article. As examples for the preparation of the second resin, there is bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization.
In the suspension polymerization method, the second resin may be prepared by dispersing a monomer in a reaction medium, adding and blending an additive such as a chain transfer agent, an initiator and a dispersion stabilizer in the reaction solvent and polymerizing the blend at 40° C. or higher. One of skilled in the art can easily select the kind of monomer based on a desired function such as a surface hardness function, an anti-wear function, an anti-contamination function, an anti-fingerprint function, a colored function, a pearl function, a high-gloss function, a non-gloss function and a barrier function. By way of examples of the monomer, there are (meth)acrylate monomers, epoxy monomers, oxetane monomers, isocyanate monomers, silicon monomers, fluorine-based monomers or a copolymer thereof.
The reaction medium may be any medium known to be conventionally used to prepare a synthetic resin, polymer or copolymer without limitation. For example, the reaction medium may be distilled water. The chain transfer agent which can be added to the reaction solvent may be, but is not limited to, an alkyl or aryl mercaptan such as n-butyl mercaptan, n-dodecyl mercaptan, tertiary dodecyl mercaptan, isopropyl mercaptan or aryl mercaptan; a halogen compound such as ketone tetrachloride; or an aromatic compound such as an alpha-methylstyrene dimer or an alpha-ethylstyrene dimer. The initiator is a polymerization initiator, which may be, but is not limited to, a peroxide such as octanoyl peroxide, decanoyl peroxide or lauroyl peroxide, or an azo-based compound such as azobisisobutyronitrile or azobis-(2,4-dimethyl)-valeronitrile. The dispersion stabilizer which can be included in the reaction medium may be, but is not limited to, an organic distribution agent such as polyvinyl alcohol, polyolefin-maleic acid or cellulose, or an inorganic distribution agent such as tricalcium phosphate.
The first and second resins have already been described above in detail, and thus further description thereof will be omitted. The present invention will be described with reference to the following Examples in detail. However, the present invention is not limited to the following Examples.
Measurement of Surface Energy
According to the Owens-Wendt-Rabel-Kaelble (OWRK) method, surface energies of first resins and second resins were measured using a drop shape analyzer (Kruss, DSA100). More specifically, the first resins and second resins were dissolved in a methyl ethyl ketone solvent to have a concentration of 15 wt %, and then coated on a LCD glass by bar coating. The coated LCD glass was pre-dried in an oven at 60° C. for 2 minutes and then dried at 90° C. for 1 minute. After drying (or curing), deionized water and diiodomethane were dropped 10 times on the coated surface at 25° C., respectively, to get an average value of a contact angle, and surface energy was calculated by substituting a numerical value into the OWRK method.
Measurement of Melt Viscosity
Melt viscosities of first resins and second resins were measured using a capillary rheometer 1501 (Gottfert). More specifically, after a capillary die was attached to a barrel, the first resins and second resins were put into the barrel by dividing to 3 parts. A shear viscosity (pa*s) according to a shear rate of 100 to 1000 s−1 was measured at a processing temperature of 240° C.
Measurement of Solubility Parameter
While there are some methods of measuring and calculating solubility parameters, the solubility parameters of first resins and second resins were calculated at 25° C. using a known method, the Van Krevelen method [refer to Bicerano, J., Prediction of Polymer Properties, third edition, Marcel Dekker Inc., New York (2002), the disclosure of which is incorporated herein by reference in its entirety]. According to the Van Krevelen method, the solubility parameter was calculated using a group contribution theory, and defined as the following formula:




  
    δ
    ⁡
    
      (
      
        solubility
        ⁢
        
          
        
        ⁢
        parameter
      
      )
    
  
  =
  
    
      
        e
        coh
      
    
    =
    
      
        
          E
          coh
        
        V
      
    
  




In the formula, Ecoh is a cohesive energy, V is a molar volume, and ecoh is a cohesive energy density. The cohesive energy (Ecoh) is defined as follows:

Ecoh=10570.9×(0Xv−0X)+9072.8×(2×1X−1Xv)+1018.2×NVKH 

In the formula, 0X, 1X, 0Xv and 1Xv are connectivity indices, and NVKH is a correlation term. Each variant was calculated with reference to the disclosed literature [Bicerano, J., Prediction of Polymer Properties, third edition, Marcel Dekker Inc., New York (2002)].
Observation of Feature of Cross-Section
Samples went through a low temperature impact test. Then, fracture surfaces of the samples were etched using THF vapor, and a layer-separated cross-section was observed using an SEM.
Meanwhile, to measure thicknesses of layer-separated first and second resin layers and an interface layer, the samples of the following Examples and Comparative Examples were cut with a diamond knife at −120° C. using a microtoming device (Leica EM FC6), thereby obtaining a smooth cross-section. The part of the sample with the microtomed smooth cross-section was dipped in a 1,2-dichloroethane solution (10 volume %, in EtOH) to etch for 10 seconds, and then washed with distilled water. The etched cross-sectional part was dissolved to different levels of depth according to the contents of the first and second resins, and could be observed using an SEM. That is, when the cross-section was viewed at a 45-degree angle from a surface, due to a shade difference, the first resin layer, the second resin layer and the interface layer could be observed, and a thickness of each layer could be measured.
Experiment for Measuring Pencil Hardness
Pencil hardnesses of samples were measured under a constant load of 500 g using a pencil hardness tester (Chungbuk Tech). Scratches were made on a surface of the samples by standard pencils (Mitsubishi; grade 6B to 9H) with a fixed angle of 45 degrees, and therefore a change rate of the surface was observed (ASTM 3363). The values of pencil hardness are average values of the results obtained from tests performed 5 times.
Measurement of Molecular Weight Distribution (PDI)
Molecular weight distribution was measured using gel permeation chromatography (GPC) under conditions as follows:
Instrument: 1200 series produced by Agilent Technologies
Column: 2 PLgel mixed Bs produced by Polymer Laboratories
Solvent: THF
Column Temperature: 40° C.
Concentration of Sample: 1 mg/mL, 100 L injection
Standard: Polystyrene (Mp: 3900000, 723000, 316500, 52200, 31400, 7200, 3940 or 485)
As an analysis program, ChemStataion provided by Agilent Technologies was used, and a weight average molecular weight (Mw) and a number average molecular weight (Mn) were measured using gel permeation chromatography (GPC), and the molecular weight distribution was then calculated from an equation of Mw/Mn.
Surface Analysis by IR Spectrometer
The experiment was performed using a UMA-600 IR microscope equipped with a Varian FTS-7000 spectrometer (Varian, USA) and a mercury cadmium telluride (MCT) detector, and detection of spectra and data processing were performed using Win-IR PRO3.4 software (Varian, USA). Conditions of the experiment were as follows:

    
    
        Germanium (Ge) ATR crystal having refractive index of 4.0
        Spectral Resolution of Middle Infrared Spectrum obtained by Attenuated Total Reflection: 8 cm−1 and Range of 16 Scans: 4000 cm−1-600 cm−1.
        Internal Reference Band: Carbonyl Group (C═O str., 1725 cm−1) of Acrylate
        Original Component of First Resin: Butadiene Compound [C═C str. ( ̃1630 cm−1) or =C—H out-of-plane vib. ( ̃970 cm−1)]
    
    


Peak intensity ratios [IBD(C═C)/IA(C═O)] and [BD(out-of-plane)/IA(C═O)] were calculated, and the detection of spectra was performed 5 times in different regions of one sample, and an average value and a standard deviation were calculated.
EXAMPLE 1
(1) Preparation of First Resin and Second Resin
As a first resin, a first resin-1 (a thermoplastic resin composed of 60 wt % methyl methacrylate, 7 wt % acrylonitrile, 10 wt % butadiene and 23 wt % styrene) was used. As a second resin, a second resin-1 was prepared as following: 1500 g of distilled water and 4 g of 2% polyvinylalcohol aqueous solution as a dispersing agent were put into a 3-liter reactor and dissolved. Subsequently, 560 g of methyl methacrylate, 240 g of glycidyl methacrylate, 2.4 g of n-dodecyl mercaptan as a chain transfer agent and 2.4 g of azobisisobutyronitrile as an initiator were further added thereto, and mixed while stirring at 400 rpm. The mixture was polymerized by 3-hour reaction at 60° C., and cooled to 30° C., thereby obtaining a bead-type second resin-1. Afterward, the second resin-1 was washed three times with distilled water, dehydrated and dried in an oven.
As the results of measurement of the physical properties of the first resin-1 and the second resin-1, it was shown that a difference in surface energy was 6.4 mN/m, a difference in melt viscosity was 180 pa*s, a difference in solubility parameter was 0.5 (J/cm3)1/2, a weight average molecular weight of the second resin obtained by GPC was 100K, and a molecular weight distribution (PDI) of the second resin was 2.1.
(2) Preparation of Resin Blend and Resin Article Using the Same
After 90 parts by weight of the first resin-1 was blended with 10 parts by weight of the second resin-1, the blend was extruded using a twin-screw extruder (Leistritz) at 240° C., thereby obtaining a pellet. A layer separation was observed in the pellet. Then, the pellet was injected using an EC100Φ30 injector (ENGEL) at 240° C., thereby obtaining a sample 1 having a thickness of 3200 μm. A thickness of the second resin layer was 82 nm and a thickness of an interface layer was 33 μm. A pencil hardness of the sample 1 was 2H, and layer separation occurred. The feature of the cross-section of the sample 1 observed by using SEM is shown in FIG. 3. Also, the feature of the cross-section of the sample 1 observed at a 45-degree angle from the surface is shown in FIG. 9. The peak intensity ratio [IBD(C═C)/IA(C═O)] measured by an IR spectrometer was averagely 0.0122 with a standard deviation of 0.0004, and the peak intensity ratio [IBD(out-of-plane)/IA(C═O)] was averagely 0.411 with a standard deviation of 0.0026.
EXAMPLE 2
(1) Preparation of First Resin and Second Resin
As a first resin, the first resin-1 of Example 1 was used. As a second resin, a second resin-2 was prepared as following: 1500 g of distilled water and 4 g of 2% polyvinylalcohol aqueous solution as a dispersing agent were put into a 3-liter reactor and dissolved. Subsequently, 760 g of methyl methacrylate, 40 g of perfluorohexylethyl methacrylate, 2.4 g of n-dodecyl mercaptan as a chain transfer agent and 2.4 g of azobisisobutyronitrile as an initiator were further added thereto, and mixed while stirring at 400 rpm. The mixture was polymerized by 3-hour reaction at 60° C., and cooled to 30° C., thereby obtaining a bead-type second resin-2. Afterward, the second resin-2 was washed three times with distilled water, dehydrated and dried in an oven.
As the results of measurement of the physical properties of the first resin-1 and the second resin-2, it was shown that a difference in surface energy was 4.2 mN/m, a difference in melt viscosity was 250 pa*s, a difference in solubility parameter was 0.2 (J/cm3)1/2, a weight average molecular weight of the second resin obtained by GPC was 100K, and a molecular weight distribution (PDI) of the second resin was 2.0.
(2) Preparation of Resin Blend and Resin Article Using the Same
A sample 2 having a thickness of 3200 μm was prepared by the same method as Example 1, except that 10 parts by weight of the second resin-2 was used instead of 10 parts by weight of the second resin-1. A thickness of the second resin layer was 102 μm and a thickness of an interface layer was 15 μm. A pencil hardness of the sample 2 was 2H, and layer separation occurred.
EXAMPLE 3
(1) Preparation of First Resin and Second Resin
As a first resin, the first resin-1 of Example 1 was used. As a second resin, a second resin-3 was prepared by the same method as described in Example 1, except that 560 g of methyl methacrylate, 240 g of tertiary butyl methacrylate, 2.4 g of n-dodecyl mercaptan as a chain transfer agent and 3.2 g of azobisisobutyronitrile as an initiator were put into the reactor.
As the results of measurement of the physical properties of the first resin-1 and the second resin-3, it was shown that a difference in surface energy was 1.1 mN/m, a difference in melt viscosity was 360 pa*s, a difference in solubility parameter was 0.7 (J/cm3)1/2, a weight average molecular weight of the second resin obtained by GPC was 80K, and a molecular weight distribution (PDI) of the second resin was 1.9.
(2) Preparation of Resin Blend and Resin Article Using the Same
A sample 3 having a thickness of 3200 μm was prepared by the same method as Example 1, except that 10 parts by weight of the second resin-3 was used instead of 10 parts by weight of the second resin-1. A thickness of the second resin layer was 79 μm and a thickness of an interface layer was 24 μm. A pencil hardness of the sample 3 was 2H, and layer separation occurred.
EXAMPLE 4
(1) Preparation of First Resin and Second Resin
As a first resin, a first resin-2 (a thermoplastic resin composed of 21 wt % of acrylonitrile, 15 wt % of butadiene and 64 wt % of styrene) was used. As a second resin, the second resin-1 of Example 1 was used.
As the results of measurement of the physical properties of the first resin-2 and the second resin-1, it was shown that a difference in surface energy was 6.1 mN/m, a difference in melt viscosity was 120 pa*s, a difference in solubility parameter was 0.7 (J/cm3)1/2, a weight average molecular weight of the second resin obtained by GPC was 100K, and a molecular weight distribution (PDI) of the second resin was 2.1.
(2) Preparation of Resin Blend and Resin Article Using the Same
A sample 4 having a thickness of 3200 μm was prepared by the same method as described in Example 1, except that 90 parts by weight of the first resin-2 was used instead of 90 parts by weight of the first resin-1. A thickness of the second resin layer was 46 μm and a thickness of an interface layer was 23 μm. A pencil hardness of the sample 4 was HB, and layer separation occurred.
EXAMPLE 5
As a first resin, the first resin-1 of Example 1 was used. As a second resin, a second resin-4 was prepared by the same method as described in Example 1, except that 592 g of methyl methacrylate, 160 g of phenyl methacrylate, 48 g of methacrylic acid, 2.4 g of n-dodecyl mercaptan as a chain transfer agent and 2.4 g of azobisisobutyronitrile as an initiator were put into the reactor.
As the results of measurement of the physical properties of the first resin-1 and the second resin-4, it was shown that a difference in surface energy was 2.0 mN/m, a difference in melt viscosity was 350 pa*s, a difference in solubility parameter was 0.6 (J/cm3)1/2, a weight average molecular weight of the second resin obtained by GPC was 100K, and a molecular weight distribution (PDI) of the second resin was 2.2.
(2) Preparation of Resin Blend and Resin Article Using the Same
A sample 5 having a thickness of 3200 μm was prepared by the same method as Example 1, except that 10 parts by weight of the second resin-4 was used instead of 10 parts by weight of the second resin-1. A thickness of the second resin layer was 13 μm and a thickness of an interface layer was 36 μm. A pencil hardness of the sample 5 was 1.5H, and layer separation occurred.
COMPARATIVE EXAMPLE 1
Comparative Example 1 was prepared with only the first resin-1 of Example. Particularly, 100 parts by weight of the first resin-1 of Example 1 was extruded using a twin-screw extruder (Leistritz) at 240° C., thereby obtaining a pellet. Then, the pellet was injected using an EC100Φ030 injector (ENGEL) at 240° C., thereby obtaining a sample 6 having a thickness of 3200 μm.
As the results obtained by measuring physical properties of the sample 6, a pencil hardness was F, and layer separation was not observed.
COMPARATIVE EXAMPLE 2
100 parts by weight of the first resin-2 of Example 4 was extruded using a twin-screw extruder (Leistritz) at 240° C., thereby obtaining a pellet. Then, the pellet was injected using an EC100Φ30 injector (ENGEL) at 240° C., thereby obtaining a sample 7 having a thickness of 3200 μm.
As the results obtained by measuring physical properties of the sample 7, a pencil hardness was 2B, and layer separation was not observed.
COMPARATIVE EXAMPLE 3
(1) Preparation of First Resin and Second Resin
As a first resin, the first resin-1 of Example 1 was used. As a second resin, a second resin-5 was prepared as following: 1500 g of distilled water and 4 g of 2% polyvinylalcohol aqueous solution as a dispersing agent were put into a 3-liter reactor and dissolved. Subsequently, 40 g of methyl methacrylate, 760 g of perfluorohexylethyl methacrylate, 2.4 g of n-dodecyl mercaptan as a chain transfer agent and 2.4 g of azobisisobutyronitrile as an initiator were further added thereto, and mixed while stirring at 400 rpm. The mixture was polymerized by 3-hour reaction at 60° C., and cooled to 30° C., thereby obtaining a bead-type second resin-5. Afterward, the second resin-5 was washed three times with distilled water, dehydrated and dried in an oven.
As the results of measurement of the physical properties of the first resin-1 and the second resin-5, it was shown that a difference in surface energy was 37 mN/m, a difference in melt viscosity was 375 pa*s, a difference in solubility parameter was 3.5 (J/cm3)1/2, a weight average molecular weight of the second resin measured by GPC was 100K, and a molecular weight distribution (PDI) of the second resin was 2.1.
(2) Preparation of Resin Blend and Resin Article Using the Same
A sample 8 having a thickness of 3200 μm was prepared by the same method as described in Example 1, except that 10 parts by weight of a second resin-5 was used instead of 10 parts by weight of the second resin-1. A detachment between the first resin and the second resin in the sample 8 occurred, and thus a pencil hardness was not measured.
COMPARATIVE EXAMPLE 4
(1) Preparation of First Resin and Second Resin
As a first resin, the first resin-1 of Example 1 was used. As a second resin, a second resin-6 was prepared by the same method as described in Example 1, except that 0.8 g of n-dodecyl mercaptan and 1.6 g of azobisisobutyronitrile were used instead of 2.4 g of n-dodecyl mercaptan and 2.4 g of azobisisobutyronitrile.
As the results of measurement of the physical properties of the first resin-1 and the second resin-6, it was shown that a difference in surface energy was 6.3 mN/m, a difference in melt viscosity was 1090 pa*s, a difference in solubility parameter was 0.5 (J/cm3)1/2, a weight average molecular weight of the second resin obtained by GPC was 205K, and a molecular weight distribution (PDI) of the second resin was 3.3.
(2) Preparation of Resin Blend and Resin Article Using the Same
A sample 9 having a thickness of 3200 μm was prepared by the same method as Example 1, except that 10 parts by weight of the second resin-6 was used instead of 10 parts by weight of the second resin-1. A pencil hardness of the sample 9 was H, layer separation was partially observed, and a thickness of separated layer was non-uniform in parts.
COMPARATIVE EXAMPLE 5
(1) Preparation of First Resin and Second Resin
As a first resin, the first resin-1 of Example 1 was used. As a second resin, a second resin-7 was prepared by the same method as described in Example 3, except that 4.8 g of n-dodecyl mercaptan and 2.4 g of azobisisobutyronitrile were used instead of 2.4 g of n-dodecyl mercaptan and 3.2 g of azobisisobutyronitrile.
As the results of measurement of the physical properties of the first resin-1 and the second resin-7, it was shown that a difference in surface energy was 1 mN/m, a difference in melt viscosity was 610 pa*s, a difference in solubility parameter was 0.7 (J/cm3)1/2, a weight average molecular weight of the second resin was 42K, and a molecular weight distribution (PDI) of the second resin was 3.2.
(2) Preparation of Resin Blend and Resin Article Using the Same
A sample 10 having a thickness of 3200 μm was prepared by the same method as described in Example 3, except that 10 parts by weight of a second resin-7 was used instead of 10 parts by weight of the second resin-3. A pencil hardness of the sample 10 was F, and layer separation was not observed.
COMPARATIVE EXAMPLE 6
(1) Preparation of First Resin and Second Resin
As a first resin, the first resin-1 of Example 1 was used. As a second resin, a second resin-8 was prepared by the same method as described in Example 3, except that 0.5 g of n-dodecyl mercaptan and 1.6 g of azobisisobutyronitrile were used instead of 2.4 g of n-dodecyl mercaptan and 3.2 g of azobisisobutyronitrile.
As the results of measurement of the physical properties of the first resin-1 and the second resin-8, it was shown that a difference in surface energy was 1 mN/m, a difference in melt viscosity was 1390 pa*s, a difference in solubility parameter was 0.7 (J/cm3)1/2, a weight average molecular weight of the second resin was 245K, and a molecular weight distribution (PDI) of the second resin was 5.3.
(2) Preparation of Resin Blend and Resin Article Using the Same
A sample 11 having a thickness of 3200 μm was prepared by the same method as described in Example 3, except that 10 parts by weight of the second resin-8 was used instead of 10 parts by weight of the second resin-3. A pencil hardness of the sample 11 was F, and layer separation was not observed.
COMPARATIVE EXAMPLE 7
(1) Preparation of First Resin and Second Resin
As a first resin, the first resin-1 of Example 1 was used. As a second resin, a second resin-9 was prepared by the same method as described in Example 3, except that 0.4 g of n-dodecyl mercaptan and 1.1 g of azobisisobutyronitrile were used instead of 2.4 g of n-dodecyl mercaptan and 3.2 g of azobisisobutyronitrile.
As the results of measurement of the physical properties of the first resin-1 and the second resin-9, it was shown that a difference in surface energy was 1 mN/m, a difference in melt viscosity was 2200 pa*s, a difference in solubility parameter was 0.7 (J/cm3)1/2, a weight average molecular weight of the second resin was 320K, and a molecular weight distribution (PDI) of the second resin was 5.2.
(2) Preparation of Resin Blend and Resin Article Using the Same
A sample 12 having a thickness of 3200 μm was prepared by the same method as described in Example 3, except that 10 parts by weight of the second resin-9 was used instead of 10 parts by weight of the second resin-3. A pencil hardness of the sample 12 was F, and layer separation was not observed.
COMPARATIVE EXAMPLE 8
A hard coating layer was formed on the sample 6 of Comparative Example 1 by forming a layer by coating a hard coating solution prepared by the inventor including a multifunctional acrylate (19 wt % DPHA, 10 wt % PETA, 5 wt % urethane acrylate EB 1290 from SK cytech, 45 wt % methyl ethyl ketone, 20 wt % isopropyl alcohol and 1 wt % IRGACURE 184 as a UV initiator from Ciba) using a Mayer bar #9 and drying the coating at 60 to 90° C. for 4 minutes to form a coating film, and curing the coating film by UV irradiation with an intensity of 3000 mJ/cm2.
A pencil hardness of the hard coating layer was 3H, and average values and standard variations of peak intensity ratios [IBD(C═C)/IA(C═O)] and [IBD(out-of-plane)/IA(C═O)] detected by an IR spectrometer were 0, respectively. As shown in Examples 1-5 and Comparative Examples 1-8, the layer separation was observed in Examples 1 to 5 using the first resin and second resin having the described difference value in surface energy, melt viscosity or solubility parameter. It was further observed that the resin article prepared according to the Examples 1 to 5 had a layer formed of the first resin, a layer formed of the second resin and an interface layer including the first resin and the second resin. Here, the first resin layer constituted the body of the resin article and the second resin layer constituted the surface on the body.
As the second resin layer was formed on a surface of the resin article by the melting process without performing additional process, for example, coating process, a manufacturing step/time of the resin article having the surface on the body was reduced. Further, since the second resin polymerized from a methyl methacrylate-based monomer, as illustrated in Examples 1 to 5, could exhibit an excellent anti-scratch characteristic due to a high pencil hardness of HB or more, the resin article showed an improved hardness property. Although the hardness property was illustrated in the Examples 1-5 for the purpose of the description of the present invention, it will be obvious to one of skilled in the art that any other property can be added to the second resin to improve a property of a resin article.
On the other hand, the resin articles prepared using only the first resin (of Comparative Examples 1 and 2) did not have separated layers and had low surface pencil hardness. Accordingly, to use the resin article obtained in Comparative Examples 1 and 2 for a part of an automobile or a part of an electric device, a coating process was needed to improve a surface characteristic.
Meanwhile, when the difference in surface energy between the first resin and the second resin was greater than 35 mN/m (in Comparative Example 3), the first resin was not attached to the second resin and both resins were detached from each other. Therefore, it was understood that layer separation was occurred in the resin article only when the first resin and the second resin had a certain difference in surface energy (at 25° C.) like Examples 1 to 5.
In addition, it was understood from Comparative Examples 4 to 7 that the layer separation was observed only when the second resin had weight average molecular weight and molecular weight distribution as described the above.
As shown in Example 1 and Comparative Example 8, it was confirmed that according to the analysis of the surface of the second resin layer by an IR spectrometer, components of the first resin layer were detected in Example 1, but were not detected in Comparative Example 8 in which the layer was hard-coated.
While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.

## Claims

1. A resin article, comprising:
a first resin layer including a first resin; and
a second resin layer including a second resin having a molecular weight distribution of 1 to 2.5 formed on the first resin layer,
wherein a component of the first resin layer is detected on the top surface of the second resin layer by infrared spectrometer, and
wherein the resin article has a layer-separated structure,
wherein the first resin layer includes at least one selected from the group consisting of a styrene-based resin, a polyolefin-based resin, a thermoplastic elastomer, a polyoxyalkylene-based resin, a polyester-based resin, a polyvinyl chloride-based resin, a polycarbonate-based resin, a polyphenylene sulfide-based resin, a vinyl alcohol-based resin, an acrylate-based resin, engineering plastics and a copolymer thereof, and
wherein the second resin layer includes at least one selected from the group consisting of a (meth)acrylate-based resin, an epoxy-based resin, an oxetane-based resin, an isocyanate-based resin, a silicon-based resin, a fluorine-based resin and a copolymer thereof, wherein the first resin layer and the second resin layer has a difference in surface energy at 25° C. of 0.1 to 35 mN/m, and wherein the first resin layer and the second resin layer have a difference in solubility parameter at 25° C. of 0.001 to 10.0 (J/cm3)1/2.

2. The resin article according to claim 1, further comprises an interface layer including a first resin and a second resin and formed between the first resin layer and the second resin layer.

3. The resin article according to claim 2, wherein the interface layer has a thickness of 0.01 to 95% based on the total thickness of the second resin layer and the interface layer.

4. The resin article according to claim 1, wherein the second resin layer has a thickness of 0.01 to 60% based on the total thickness of the resin article.

5. The resin article according to claim 1, wherein the second resin has a weight average molecular weight of 30,000 to 200,000.

6. The resin article according to claim 1, wherein the second resin has a molecular weight distribution of 1.9 to 2.2.

7. A resin article, comprising: a first resin layer including a first resin; and a second resin layer including a second resin having a molecular weight distribution of 1 to 2.5 formed on the first resin layer,
wherein a component of the first resin layer is detected on the top surface of the second resin layer by infrared spectrometer, wherein the resin article has a layer-separated structure, wherein the first resin includes at least one selected from the group consisting of a styrene-based resin, a polyolefin-based resin, a thermoplastic elastomer, a polyoxyalkylene-based resin, a polyester-based resin, a polyvinyl chloride-based resin, a polycarbonate-based resin, a polyphenylene sulfide-based resin, a vinyl alcohol-based resin, an acrylate-based resin, engineering plastics and a copolymer thereof, wherein the second resin includes at least one selected from the group consisting of a high surface hardness resin, an anti-wear resin, an anti-contamination resin, an anti-fingerprint resin, a colored resin, a pearl resin, a high-gloss resin, a non-gloss resin and a barrier resin, wherein the first resin layer and the second resin layer has a difference in surface energy at 25° C. of 0.1 to 35 mN/m, and-wherein the first resin layer and the second resin layer have a difference in solubility parameter at 25° C. of 0.001 to 10.0 (J/cm3)1/2.