A polyvinyl chloride (PVC)-based flooring material has been widely used in various buildings such as apartments, residential complexes, villas, row houses, detached houses, office buildings, shopping malls, shops, and pensions, etc.
In general, the PVC-based flooring material has a structure in which a surface layer PVC film, a middle layer PVC film including a printing layer, and a back layer PVC sheet are stacked, and has insufficient abrasion resistance but has advantages in that various patterns are capable of being implemented, dimensional stability is excellent, and economic efficiency is good. However, regarding the PVC, when a phthalate plasticizer widely known as an endocrine disruptor that is added in a large amount to impart flexibility, which is a so-called environmental hormone, is used for a flooring material, the plasticizer is eluted, which adversely affects safety of a human body. In addition, there is a serious problem in that a large amount of dioxin, a carcinogen, occurs at the time of incineration and disposal, and thus an environment-friendly flooring material formed of non-PVC (polyvinyl chloride) has been eagerly desired for a long time.
In addition, reduction of greenhouse gas emissions, which is the main cause of global warming, is being forced around the world, and thus countermeasures are urgently needed. Therefore, constitution in which a flooring material is not disposed by incineration, landfill, etc., after being used, but is formed in a pellet form by extrusion processing, which is a so-called recyclable UNI-material, is emerging as a very promising solution in view of enabling reduction of huge amount of greenhouse gas emissions.
In conclusion, an environment-friendly flooring material formed of a non-PVC material while simultaneously being formed of recyclable UNI-material is urgently needed.
In addition, conventional PVC-based flooring materials are poor in abrasion resistance, and thus in general, the poor abrasion resistance is reinforced by introducing a surface layer formed by coating and curing an ultraviolet (UV) curable resin. However, it is a cost increase factor, and due to a very thin thickness with a few μm, the conventional PVC-based flooring materials are easily worn out and are not able to stay long, and thus there are many inconveniences such as frequent waxing, etc., by consumers to compensate. If the material is replaced with a material that is not fundamentally UV-coated but has excellent abrasion resistance compared to the conventional PVC flooring materials, even if cost of the flooring material rises somewhat, a replacement cycle becomes longer, and thus economic efficiency may be rather excellent. From this point of view, it is urgently required to develop a floor material composed of a material excellent in abrasion resistance.
In addition, dimensional stability should be definitely considered when designing a new flooring material. The dimensional stability may be generally deteriorated due to expansion, shrinkage, or the like due to environmental factors such as external temperature and humidity, etc. A phenomenon frequently occurs in that a connection part between the flooring materials becomes open due to shrinkage or that a surface of the flooring material rises like a wave due to expansion, and thus it is difficult to use the material continuously and stably. Further, in the conventional flooring materials in which multilayer films or sheets are stacked, there may be a serious problem that a shape of the flooring material is distorted since coefficients of thermal expansion for interlayer films or sheets are different.
As a solution to the above-described problem, a flooring material that is stacked based on a biomass biodegradable resin such as polylactic acid as a non-PVC material has been proposed as disclosed in Korean Patent No. 10-1302335. However, since a fiber-reinforced resin layer sheet formed of heterogeneous materials having poor abrasion resistance and reinforced dimensional stability is inserted, there is a disadvantage in that recycling by extrusion processing at the time of disposal is impossible.
In addition, as described in Korean Patent No. 10-1395714, a flooring material stacked based on a polyolefin resin as a non-PVC material has been proposed. However, since a polyolefin resin used in an upper layer has very poor abrasion resistance compared to conventional PVCs, a glass fiber impregnated with a thermosetting polyurethane resin, which is a heterogeneous material, is used in a dimensional stability reinforcing layer, is used, and a thermosetting heterogeneous material is used in an UV coating layer, there is a disadvantage in that recycling by extrusion processing at the time of disposal is impossible.
Further, as described in Korean Patent No. 10-0600841, a flooring material stacked based on a thermoplastic polyurethane resin which is expensive but has relatively excellent abrasion resistance as a non-PVC material has been proposed. However, in the case of the thermoplastic polyurethane resin, when a film and a sheet are formed by a calendering method, processing is very difficult since a resin adheres to a metal roll, and thus a softener such as oil, or the like, is added to solve this problem. However, since the softener has a low molecular weight, it is very likely to be slowly eluted when used as a flooring material. In addition, interlayer thermal stability is changed due to a change in the composition caused thereby, and thus there is a great concern that the dimensional stability may gradually decrease. In addition, to compensate for this, a dimensional stability reinforcing layer using a glass fiber impregnated with a thermosetting polyurethane resin as a heterogeneous material is introduced, and a softener is added but causes excessive softness, which deteriorates abrasion resistance. In order to compensate for this, an ultraviolet coating layer using a thermosetting heterogeneous material is also introduced, which makes it impossible to recycle by extrusion processing at the time of disposal, and also there is disadvantage in that economic efficiency is very weak due to many multilayer structures.
As described above, the environment-friendly flooring material formed of non-PVC material has been continuously researched and developed, but a dimensional stability reinforcing layer and a UV curable coating layer formed of heterogeneous materials have been introduced since there are no materials excellent in abrasion resistance, dimensional stability and molding processability at the same time, and thus the flooring material is not able to be recycled by extrusion processing after disposal. As a result, since excessive amounts of sheets or films are stacked to manufacture the flooring material, the economic efficiency is deteriorated, and thus it is very urgently required to have a breakthrough method for solving these problems at one time.
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