Hard board for flooring, flooring material, and method for manufacturing hard board

Abstract

To provide a hard board for flooring that offers excellent continuous formability in extrusion processing, ensures hardness, and exhibits minimal dimensional changes. [Solution] The hard board 2 for flooring material is made of a resin composition containing calcium carbonate, vinyl chloride resin, plasticizer, and glass wool, with a calcium carbonate content of 55% to 75% by mass, a vinyl chloride resin content of 10% to 25% by mass, a plasticizer content of 5% to 15% by mass, and a glass wool content of 0.5% to 3.5% by mass. The flooring material 1 has a soundproofing sheet 5, a hard board 2, a printed sheet 3, and an abrasion-resistant sheet 4 arranged in order from the back side.

Description

Technical Field

[0001] The present invention relates to a rigid board for floor materials, a floor material, and a method for manufacturing the rigid board.

Background Art

[0002] Floor finishing is carried out by laying floor tiles or wooden floor materials such as flooring on the floor base, applying resin, laying carpet, or laying a resin sheet of the floor material.

[0003] As the resin sheet used as a floor material, a sheet of polyvinyl chloride resin excellent in wear resistance, water resistance, and chemical resistance is used. The polyvinyl chloride resin sheet of the floor material is sometimes called a cushion floor (abbreviation: CF).

[0004] When laying the polyvinyl chloride resin sheet of the floor material on the floor base, many steps are required. Specifically, when the floor base is not smooth, unevenness is adjusted, the sheet is allocated, the sheet is roughly cut and arranged, the sheet is temporarily laid to stretch the curl, the sheet is once removed and an adhesive is applied to the floor base, the sheet is laid on the floor base to which the adhesive has been applied, and then crimping and air bleeding are performed with a roller or the like, the ears at the joint of the sheet are overlapped and cut, adhered, the seam is heat welded, and cured for construction. Thus, the construction of the polyvinyl chloride resin sheet of the floor material requires many steps and the skills of a craftsman.

[0005] On the other hand, recently, the concept of DIY (Do It Yourself) has become popular, and there are more opportunities for ordinary people rather than craftsmen to carry out floor material construction. Although the construction of the polyvinyl chloride resin sheet of the floor material requires many steps and techniques as described above, it is particularly difficult for ordinary people to handle adhesives. Therefore, instead of using an adhesive, a floor material having a protrusion structure called a tenon structure, which is constructed by fitting the protrusions and depressions, has been proposed for DIY.

[0006] On the other hand, flooring materials installed without using such adhesives require minimal dimensional changes due to the environment, as dimensional changes caused by the environment can cause the floor surface to lift or gaps to form.

[0007] Here, filler-filled polyvinyl chloride resin is used as a building material. Because this filler-filled polyvinyl chloride resin has a low coefficient of thermal expansion, it exhibits little dimensional change due to the environment in which it is used, and it also has good mechanical properties such as impact resistance. In particular, sheets and laminates made mainly of polyvinyl chloride resin and filler, using inorganic components such as heavy calcium carbonate as the filler, are known as building materials such as flooring.

[0008] In sheets primarily composed of polyvinyl chloride resin and fillers, a large amount of filler is often added to minimize dimensional changes.

[0009] For example, Patent Document 1 proposes a flooring material with a high filler content. Specifically, Patent Document 1 describes a polyvinyl chloride resin sheet for flooring, characterized in that it contains a rigid polyvinyl chloride resin and heavy calcium carbonate powder, and the mass ratio of heavy calcium carbonate powder to the entire polyvinyl chloride resin sheet is 50% by mass or more. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2023-049187 [Overview of the project] [Problems that the invention aims to solve]

[0011] The polyvinyl chloride resin sheet for flooring described in Patent Document 1 has a high concentration of fillers that reduce the coefficient of linear expansion, making it highly likely that good dimensional changes can be obtained. However, the polyvinyl chloride resin sheet for flooring described in Patent Document 1 uses a rigid polyvinyl chloride resin with a low amount of plasticizer, and when continuously molded by extrusion, the frictional heat of the resin is large, which may cause the resin temperature to rise, and there is a risk that the polyvinyl chloride resin will undergo thermal decomposition during molding.

[0012] Furthermore, slowing down the molding speed to suppress the rise in resin temperature during molding reduces the production volume per hour, worsening manufacturing costs. Increasing the amount of plasticizer in the resin can suppress frictional heat generated by the resin, but this can worsen the hardness of the molded resin product, which affects workability and aesthetics, as well as its dimensional stability, which affects quality. Insufficient hardness makes it difficult to lock the joints together without adhesive. Also, insufficient hardness can make it difficult to clearly define the surface texture when a surface layer is applied, compromising the aesthetic appeal.

[0013] This invention has been made in view of the above-mentioned problems, and aims to provide a hard board for flooring that has excellent continuous formability in extrusion processing, ensures hardness, and exhibits minimal dimensional change. [Means for solving the problem]

[0014] The inventors of this invention conducted diligent research to achieve the above objectives. As a result, they found that simply balancing the amount of plasticizer and the amount of calcium carbonate was insufficient to achieve the desired dimensional stability, moldability, and hardness. Therefore, they further investigated the addition of glass fibers and discovered that by adding glass wool as the glass fiber, it was possible to improve dimensional stability and hardness without impairing moldability. Further research led to the completion of the present invention.

[0015] In other words, in order to achieve the above objective, the rigid board according to the first aspect of the present invention includes the following configuration. (1) The rigid board of the present invention is a rigid board for flooring, Containing calcium carbonate, vinyl chloride resin, plasticizer, and glass wool, the content of the calcium carbonate is 55% by mass or more and 75% by mass or less, the content of the vinyl chloride resin is 10% by mass or more and 25% by mass or less, the content of the plasticizer is 5% by mass or more and 15% by mass or less, and the content of the glass wool is 0.5% by mass or more and 3.5% by mass or less, and is composed of a resin composition.

[0016] In addition, the floor material according to the second aspect of the present invention includes the following configuration. (2) The floor material of the present invention has a soundproof sheet, the rigid board described in (1), a printed sheet, and a wear-resistant sheet arranged in this order from the back side.

[0017] In addition, the manufacturing method of the rigid board according to the third aspect of the present invention includes the following configuration. (3) The manufacturing method of the rigid board of the present invention is a manufacturing method of a rigid board for a floor material, a mixing step of mixing calcium carbonate at a ratio of 55% by mass or more and 75% by mass or less, vinyl chloride resin at a ratio of 10% by mass or more and 25% by mass or less, plasticizer at a ratio of 5% by mass or more and 15% by mass or less, and glass wool at a ratio of 0.5% by mass or more and 3.5% by mass or less to obtain a mixture, a kneading step of melt-kneading the mixture to obtain a resin composition, a molding step of extruding the resin composition to obtain a sheet-shaped rigid board, and includes.

Effects of the Invention

[0018] The rigid board of the present invention is excellent in continuous formability in extrusion processing, ensures hardness, and has little dimensional change.

Brief Description of the Drawings

[0019] [Figure 1] A cross-sectional reference view showing a floor material including a rigid board according to an embodiment of the present invention. [Figure 2] A flowchart showing a production example of a rigid board according to an embodiment of the present invention. [Figure 3] Flow chart showing an example of manufacturing a hard board according to an embodiment of the present invention. [Figure 4] Graph measuring formability (kneading torque (N·m)). [Figure 5] Graph measuring formability (resin temperature (°C)).

Mode for Carrying Out the Invention

[0020] The hard board of the present invention contains calcium carbonate, vinyl chloride resin, plasticizer, and glass wool, and the content of calcium carbonate is 55% by mass or more and 75% by mass or less, the content of vinyl chloride resin is 10% by mass or more and 25% by mass or less, the content of plasticizer is 5% by mass or more and 15% by mass or less, and the content of glass wool is 0.5% by mass or more and 3.5% by mass or less. It consists of a resin composition. Hereinafter, each component of the resin composition related to the hard board of the present invention will be described in detail.

[0021] (Calcium Carbonate) The resin composition related to the hard board of the present invention contains calcium carbonate (chemical formula: CaCO3). As the calcium carbonate used in the present invention, heavy calcium carbonate obtained by pulverizing and classifying limestone, calcining limestone, decarbonizing to obtain quicklime (chemical formula: CaO), reacting the quicklime with water to obtain lime milk (calcium hydroxide (chemical formula: Ca(OH)2)), and reacting the lime milk with carbon dioxide to precipitate fine crystals in the liquid, such as light calcium carbonate, can be mentioned. Among them, heavy calcium carbonate is preferable.

[0022] The calcium carbonate used in the present invention is particulate calcium carbonate, and the particle size is not limited as long as it is smaller than the thickness of the hard board, but the average particle size is preferably 1 to 20 μm, more preferably 2 to 10 μm, still more preferably 3 to 7 μm, and particularly preferably 4 to 5 μm. Here, the average particle size is the average particle size of the powder calculated from the following calculation formula using the specific surface area value per 1 g of the powder by the powder specific surface area measuring device SS-100 type manufactured by Shimadzu Corporation. Average particle diameter = 6 / (specific gravity x specific surface area) x 10000 (μm)

[0023] The calcium carbonate used in this invention may be one in which the particle surface has been treated with fatty acids, resin acids, etc., or it may be one in which it is untreated, but the untreated type is preferred.

[0024] The calcium carbonate used in this invention can be commercially available as calcium carbonate or calcium carbonate. For example, calcium carbonate manufactured by Nitto Funka Kogyo Co., Ltd. (heavy calcium carbonate, untreated surface, product name: NN#500, composition details: average particle size; 4.4 μm) can be used.

[0025] In the resin composition relating to the rigid board of the present invention, it is believed that the calcium carbonate particles exist either floating on the vinyl chloride resin, or bound together by the presence of vinyl chloride resin in the gaps between the calcium carbonate particles.

[0026] The calcium carbonate content in the resin composition for the rigid board of the present invention is 55% by mass or more and 75% by mass or less. If the calcium carbonate content is less than 55% by mass, the dimensional stability and hardness of the rigid board will be insufficient, and if the calcium carbonate content exceeds 75% by mass, the moldability when forming the rigid board from the resin composition will be poor. Furthermore, it is preferable that the calcium carbonate content in the resin composition for the rigid board of the present invention is 62% by mass or more and 65% by mass or less. When the calcium carbonate content is within this range, the dimensional change of the rigid board tends to be less and the moldability tends to be better.

[0027] (Vinyl chloride resin) The resin composition for the rigid board of the present invention contains a vinyl chloride resin. The vinyl chloride resin is a resin whose main component is a polymer in which vinyl chloride is the main monomer. Examples of vinyl chloride resins include polyvinyl chloride resin, which is a homopolymer of vinyl chloride, copolymers of vinyl chloride with monomers such as ethylene, vinyl acetate, vinyl ether, maleic acid ester, acrylic acid, methacrylic acid, acrylic acid ester, and methacrylic acid ester, or blends of these with acrylic resins or urethane resins. Among these, polyvinyl chloride resin is preferred.

[0028] The K value of the vinyl chloride resin used in the present invention is not particularly limited, but for example, it is 50 to 80, preferably 61 to 73, and more preferably 65 to 70. Here, the K value is a value defined by JIS K7367-2. The average degree of polymerization of the vinyl chloride resin used in the present invention is not particularly limited, but for example, it is 480 to 3000, preferably 800 to 1400, and more preferably 800 to 1100. Here, the average degree of polymerization is a value calculated from the intrinsic viscosity based on JIS K6720-2:1999. Note that the average degree of polymerization is a value that can be roughly calculated from the K value.

[0029] Examples of vinyl chloride resins that can be used include "Kanevinyl S1001" and "Kanevinyl S1007," both manufactured by Kaneka Corporation, and "Shin-Etsu PVC Straight Polymer TK-1000," manufactured by Shin-Etsu Chemical Co., Ltd.

[0030] The content of vinyl chloride resin in the resin composition for the rigid board of the present invention is 10% by mass or more and 25% by mass or less. If the content of vinyl chloride resin is less than 10%, it is difficult to knead the mixture containing vinyl chloride resin when manufacturing the rigid board. If the content of vinyl chloride resin exceeds 25% by mass, the dimensional change of the rigid board becomes large. Furthermore, the content of vinyl chloride resin in the resin composition for the rigid board of the present invention is preferably 16% by mass or more and 24% by mass or less, and more preferably 22% by mass or more and 24% by mass or less. When the content of vinyl chloride resin is within this range, the dimensional change of the rigid board tends to be smaller and the moldability tends to be better.

[0031] (Plasticizer) The resin composition relating to the rigid board of the present invention contains a plasticizer. The plasticizer is an additive that imparts flexibility to the vinyl chloride resin. Examples of plasticizers used in the present invention include phthalate ester plasticizers such as dioctyl phthalate (abbreviation: DOP (also abbreviated as DNOP, DEHP)) (IUPAC name: bis(2-ethylhexyl) phthalate (abbreviation: BEHP)), diisononyl phthalate (abbreviation: DINP), dibutyl phthalate (abbreviation: DBP), diisodecyl phthalate (abbreviation: DIDP), benzyl butyl phthalate (abbreviation: BBP), and butyl octyl phthalate (abbreviation: BOP), and adipate ester plasticizers such as diisononyl adipate (abbreviation: DINA). Among these, phthalate ester plasticizers are preferred, and dioctyl phthalate (abbreviation: DOP) is more preferred. Dioctyl phthalate has the chemical formula C 24 H 38 O4, formula C6H4(COOC8H 17 It is represented as )2 and is a compound that is liquid at room temperature with a melting point of -50°C and a boiling point of 385°C.

[0032] The plasticizer content in the resin composition for the rigid board of the present invention is 5% by mass or more and 15% by mass or less. If the plasticizer content is less than 5% by mass, the moldability when forming the rigid board from the resin composition will be poor, and if the plasticizer content exceeds 15% by mass, the dimensional stability and hardness of the rigid board will be insufficient. Furthermore, the plasticizer content in the resin composition for the rigid board of the present invention is preferably 6% by mass or more and 10% by mass or less, and more preferably 7% by mass or more and 9% by mass or less. When the plasticizer content in the rigid board is within this range, the dimensional change of the rigid board tends to be less and the moldability tends to be better.

[0033] Furthermore, the amount of plasticizer relative to the vinyl chloride resin is preferably 25 to 125 parts, more preferably 35 to 58 parts, and particularly preferably 35 to 41 parts per 100 parts of the vinyl chloride resin. In this specification, "parts" means "parts by mass" unless otherwise specified.

[0034] Plasticizers are mainly present by penetrating the vinyl chloride resin component in the resin composition of the rigid board, but they are also thought to be present in the pores and on the surface of the calcium carbonate and on the surface of the glass wool.

[0035] (Glass wool (short glass fibers)) The resin composition for the rigid board of the present invention contains glass wool. Glass wool is a cotton-like short glass fiber with a circular cross-sectional shape. The fiber diameter of the glass wool is not particularly limited, but is preferably 0.4 μm to 20 μm, more preferably 4 μm to 15 μm, even more preferably 10 μm to 11 μm, and particularly preferably 10.5 μm. The cut length of the glass wool is also not particularly limited, but is, for example, 6 mm.

[0036] The glass wool content in the resin composition for the rigid board of the present invention is 0.5% by mass or more and 3.5% by mass or less. If the glass wool content is less than 0.5% by mass, dimensional stability and hardness will be insufficient, and if the glass wool content exceeds 3.5% by mass, the torque during molding of the rigid board will increase and moldability will be poor. Furthermore, the glass wool content in the resin composition for the rigid board of the present invention is preferably 1.5% by mass or more and 2.5% by mass or less, and more preferably 1.6% by mass or more and 2.3% by mass or less. When the glass wool content is within this range, dimensional stability, hardness, and moldability tend to be good.

[0037] Glass wool can be made from short glass fibers or crushed glass fiber nonwoven fabric.

[0038] Furthermore, the amount of glass wool relative to the vinyl chloride resin is preferably 2.4 parts or more and 29 parts or less, and more preferably 7 parts or more and 11.5 parts or less, per 100 parts of the vinyl chloride resin.

[0039] (Use of recycled materials as raw materials) In the manufacture of the rigid board of the present invention, recycled raw materials obtained by recycling used products containing calcium carbonate, polyvinyl chloride resin, plasticizer, and / or glass wool can be used. For example, used PVC products can be separated and collected, and recycled back into plastic raw materials using physical methods, which can then be used as recycled raw materials. Examples of PVC products include PVC window frames, PVC flooring, PVC wallpaper and other PVC building materials, refrigerator door packings, PVC pipes, and agricultural vinyl film. Some waste PVC flooring (cushion flooring) contains glass wool (short glass fibers), which is useful as a raw material for manufacturing the rigid board of the present invention.

[0040] When using recycled raw materials in the manufacture of the rigid board of the present invention, it is also possible to analyze the composition of the recycled raw materials and add any deficient components before use.

[0041] (Other ingredients) The resin composition relating to the rigid board of the present invention may contain other components as needed, to the extent that they do not impair the effects of the present invention. Examples of other components include additives and compounding agents commonly added to polymers such as PVC. Specifically, these include stabilizers, lubricants, processing aids, plasticizers, antioxidants, UV inhibitors, flame retardants, fillers, curing agents, and coupling agents. These components may be included individually or in combination.

[0042] (Stabilizer) The resin composition relating to the rigid board of the present invention may further contain a stabilizer. The stabilizer is an auxiliary agent that reduces torque during processing and suppresses thermal decomposition.

[0043] Examples of stabilizers include lead-based, tin-based, and calcium-zinc-based stabilizers. Specifically, commercially available ADEKA stub GR-18, ADEKA stub 593 (manufactured by ADEKA Corporation), and H-6750D (manufactured by Sakai Chemical Industry Co., Ltd.) can be used.

[0044] The stabilizer content in the resin composition for the rigid board of the present invention is preferably 0.1% by mass or more and 1% by mass or less. When the stabilizer content in the rigid board is within this range, it tends to reduce the torque during processing and suppress thermal decomposition.

[0045] Furthermore, the amount of stabilizer relative to the vinyl chloride resin is preferably 1.0 part or more and 5.0 parts or less per 100 parts of vinyl chloride resin, and more preferably 1.5 parts or more and 2.5 parts or less.

[0046] (Lubricant) Lubricants provide slipperiness to the metal surface of the extruder's inner surface and to the vinyl chloride resins during melt mixing in processing. Examples include polyethylene waxes, ester waxes, higher alcohol waxes, and polymer waxes. These lubricants can be used individually or in combination.

[0047] (Hardboard) The rigid board of the present invention is a molded article made from a resin composition containing calcium carbonate, a vinyl chloride resin, a plasticizer, and glass wool.

[0048] The method for manufacturing a rigid board is not particularly limited, but for example, as shown in Figure 2, calcium carbonate, a vinyl chloride resin, a plasticizer, glass wool, and other components as needed are mixed to form a mixture (S1), the mixture is melt-kneaded to form a resin composition (S2), and the resin composition is extruded to form a sheet-like rigid board (S3).

[0049] Here, the mixing is carried out in the following proportions: calcium carbonate at 55% to 75% by mass, vinyl chloride resin at 10% to 25% by mass, plasticizer at 5% to 15% by mass, and glass wool at 0.5% to 3.5% by mass.

[0050] For example, the raw material components are mixed in advance, the mixture is placed in an extruder equipped with a T-die and melted and mixed, a sheet-like resin composition is extruded from the T-die, and then cut to the desired size to produce a rigid board.

[0051] Furthermore, in order to make each component more uniform, the resin composition can be pelletized, and rigid boards can be formed from the pellets. Specifically, as shown in Figure 3, calcium carbonate, vinyl chloride resin, plasticizer, glass wool, and other components as needed are mixed to form a mixture (S1), the mixture is melt-kneaded to form a resin composition (S2), the resin composition is extruded to form pellets (S4), and the pellets of the resin composition are melt-kneaded and extruded to form a rigid board (S5).

[0052] The size of the hardboard is not particularly limited, but for example, the thickness is 4-5 mm.

[0053] The rigid board of the present invention can be provided with a grooved structure called a tongue on its side. By providing tongues on the side of the rigid board, multiple rigid boards can be interlocked and laid without gaps on the floor surface to form a floor.

[0054] The rigid board of the present invention exhibits excellent continuous formability in extrusion processing, ensures hardness, and exhibits minimal dimensional change.

[0055] (Flooring) The flooring material according to the present invention is a plate-shaped building member that includes at least the aforementioned rigid board. The flooring material according to the present invention may have other layers in addition to the rigid board, and in particular, the rigid board may be an inner layer with other layers on the outside. The rigid board may be provided with tongue and groove joints.

[0056] For example, consider flooring material 1, as shown in Figure 1, in which a soundproofing sheet 5, a hard board 2, a printed sheet 3, and an abrasion-resistant sheet 4 are arranged in order from the back side. Preferably, the hard board is provided with tongue and groove joints. Furthermore, this flooring material can be subjected to UV processing and embossing on its surface. Because the hard board of the flooring material according to the present invention has high hardness, the unevenness caused by the embossing is clearly visible and the design is excellent.

[0057] (Examples) The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0058] The rigid board was manufactured using the following materials:

[0059] PVC: Polyvinyl chloride resin, product name "Kanevinyl S1001" (manufactured by Kaneka Corporation) (Composition details: K value; 67, average degree of polymerization; 1050, apparent density; 0.57 (g / ml)) Calcium carbonate: Product name "NN#500 (manufactured by Nitto Funka Kogyo Co., Ltd.) (Composition details: Average particle size; 4.4 μm)" Plasticizer: Product name "DOP" (manufactured by CG Ester Co., Ltd.) Glass wool: Crushed glass short fibers from the product name "MSA Glass Wool" (manufactured by Olivest Co., Ltd.) Stabilizer: ADEKA Stab GR-18 (manufactured by ADEKA Corporation) (Composition details: Zinc stearate is the main component)

[0060] The physical properties of the rigid board were measured and evaluated using the following methods.

[0061] (Moldability (kneading torque (N·m) after 8 minutes)) Using pellets obtained by crushing the raw material mixture, the torque (N·m) value was read when the mixture was kneaded and extruded using a kneading and extrusion testing apparatus (manufactured by Toyo Seiki Co., Ltd., product name "Laboplastmill") under the conditions of a set kneading temperature of 170°C and a screw rotation speed of 70 rpm, and the operating conditions stabilized 8 minutes (480 seconds) after the start of melt kneading. Figure 4 shows an example graph of the torque (N·m) value against the elapsed time from the start of melt kneading (Example 11 and Comparative Example 6), showing that the torque (N·m) value changes rapidly until about 120 seconds after the start of melt kneading, but then begins to stabilize.

[0062] When the torque is high during mixing and extrusion molding, frictional heat is generated due to the friction between the components of the raw material mixture, causing the resin temperature to rise. If the resin temperature rises too high, the polyvinyl chloride resin component is prone to thermal decomposition. Therefore, the lower the torque, the less the resin temperature rises, allowing for an increase in the discharge rate, which is suitable for continuous production. In addition, low torque makes it easier to mix the raw material components and allows for uniform discharge, resulting in superior quality for rigid boards. However, if the torque is too low, mixing will be insufficient and dimensional stability will be compromised, so a torque of 5 or higher is necessary.

[0063] From the above perspectives, moldability (kneading torque) was evaluated according to the following criteria. 5 to 35; particularly good (◎) 35~40 or less; Good (〇) Over 40; Bad (×)

[0064] (Moldability (resin temperature at 8 minutes (°C))) When mixing and extruding pellets obtained by crushing the raw material mixture, the resin temperature (°C) was read from a resin temperature sensor installed inside a mixing and extrusion test apparatus (manufactured by Toyo Seiki Co., Ltd., product name "Laboplastmill") at the point when the operating conditions stabilized 8 minutes after the start of melt mixing, under the conditions of a set mixing temperature of 170°C and a screw rotation speed of 70 rpm. Figure 5 shows an example graph of the resin temperature (°C) value against the elapsed time from the start of melt mixing (Example 11 and Comparative Example 6), showing that the resin temperature (°C) value changes rapidly until about 120 seconds after the start of melt mixing, but then begins to stabilize.

[0065] In an extrusion molding machine used for forming rigid boards, for example, if the time from hopper to T-die discharge is 5 minutes, if the resin temperature reaches 200°C after 5 minutes, degradation of the polyvinyl chloride resin will certainly occur. Therefore, it is necessary that the resin temperature does not reach 200°C for 5 minutes. In the embodiment of this application, with a margin of safety, the resin temperature is measured over a period of 8 minutes, and the resin temperature at the end of 8 minutes (480 seconds) is used for evaluation.

[0066] For continuous extrusion molding of rigid boards, it is preferable that the resin temperature be below a certain value, as high resin temperatures can easily cause thermal decomposition of polyvinyl chloride (PVC) resins. If the resin is polyvinyl chloride, a temperature of 190°C or lower can prevent thermal decomposition of the resin. However, temperatures below 150°C generally fall below the softening point of PVC resins, making mixing impossible. Based on the above considerations, moldability (resin temperature) was evaluated according to the following criteria. 150~190℃; Excellent (◎) 190~195℃ or less; Good (〇) Over 195℃; Defective (×)

[0067] (Dimensional stability (heated dimensions (%))) Test specimens were prepared by cutting a rigid board to 100cm x 100cm. Except for the test specimen size of 100cm x 100cm, the procedure followed Clause 11 (Test of length and width change due to heating) of JIS-A-1454. The test specimens were kept in an 80°C constant temperature incubator with a stirrer for 6 hours, then removed and left to stand at room temperature for 1 hour. The rate of change in length and width relative to the length before the test was measured.

[0068] If this rate of change is 0.15% or less in any direction, dimensional stability is good. Good dimensional stability allows for long-term use. Since the heated dimensions evaluate defects over time, good values ​​indicate long-term usability. Furthermore, when considering construction using tongue and groove joints, the heated dimensions become even more important because no adhesive is used. From the above perspectives, dimensional stability was evaluated according to the following criteria. -0.1 or higher, or 0.1 or lower; particularly good (◎) -0.15 or greater than -0.1 or less than 0.1 or greater than 0.1 and less than or equal to 0.15; Good (〇) - Less than 0.15 or greater than 0.15 (no upper or lower limit); Poor (×)

[0069] (Hardness (D hardness (°)))

[0070] The durometer D hardness (°) was measured on test pieces made by cutting a hard board to 100cm x 100cm, in accordance with JIS K7215-1986 (Test method for durometer hardness of plastics). If the D hardness is 70 or less, the embossing does not work well, and the realism of the surface (wood grain, marble pattern, etc.) is not achieved. Also, if the hardness is not sufficient, it is difficult to lock the tongue and groove. However, if the hardness is too high, the feel underfoot becomes poor, and there is a risk of serious injury in the event of a fall. Furthermore, if the hardness is too high, it tends to break easily, making it difficult to handle. Based on the above considerations, hardness (D hardness) was evaluated according to the following criteria. 70 or more (100 or less); Good (〇) Less than 70; Poor (×)

[0071] (Examples 1-12, Comparative Examples 1-7) Mixtures were obtained by mixing raw materials such as PVC, calcium carbonate, and plasticizer in the proportions shown in Tables 1 to 5. The resulting mixtures were then melt-kneaded for 8 minutes at a mixing temperature of 150°C and a screw rotation speed of 50 rpm using a kneading and extrusion testing apparatus (manufactured by Toyo Seiki Co., Ltd., product name "Labo Plast Mill") to obtain a kneaded material. The resulting kneaded material was then crushed into pellets. Next, the obtained pellets were melt-kneaded for 8 minutes at a mixing temperature of 170°C and a screw rotation speed of 70 rpm using the same kneading and extrusion testing apparatus (manufactured by Toyo Seiki Co., Ltd., product name "Labo Plast Mill"), and then extruded to form a sheet-like rigid board (thickness: 4 mm).

[0072] During the extrusion molding process, moldability (kneading torque after 8 minutes (N·m)) and moldability (resin temperature after 8 minutes (°C)) were measured. Furthermore, the dimensional stability and hardness (D hardness (°)) of the rigid board obtained by extrusion molding were measured. The results are shown in Tables 1 to 5. Note that for Comparative Example 7, kneading could not be performed, so measurements were not taken.

[0073] [Table 1]

[0074] [Table 2]

[0075] [Table 3]

[0076] [Table 4]

[0077] [Table 5]

[0078] The results shown in Tables 1 to 5 indicate the following: When a mixture containing 55% to 75% by mass of calcium carbonate, 10% to 25% by mass of vinyl chloride resin, 5% to 15% by mass of plasticizer, and 0.5% to 3.5% by mass of glass wool is kneaded and extruded, the moldability (kneading torque) and moldability (resin temperature) are good. Furthermore, the rigid board obtained by molding exhibits good hardness and dimensional stability. Because the resin temperature during molding is low, frictional heat of the resin is less likely to occur, allowing for an increase in the discharge rate, resulting in excellent continuous production capabilities. In addition, uniform discharge improves moldability.

[0079] On the other hand, the results from Examples 7 and 8 and Comparative Examples 1 and 2 show that when the calcium carbonate content is less than 55% by mass, dimensional stability and D hardness are poor (Comparative Example 2), and when the calcium carbonate content exceeds 75% by mass, moldability (kneading torque) is poor (Comparative Example 1).

[0080] Furthermore, the results from Examples 9 and 10 and Comparative Examples 3 and 4 show that when the plasticizer content is less than 5% by mass, the moldability (kneading torque) is poor (Comparative Example 3), and when the plasticizer content exceeds 15% by mass, the D hardness is poor (Comparative Example 4).

[0081] Furthermore, the results from Examples 11 and 12, and Comparative Examples 5 and 6 show that when the glass wool content is less than 0.5% by mass, dimensional stability and D hardness are poor (Comparative Example 5), and when the glass wool content exceeds 3.5% by mass, moldability (mixing torque) is poor (Comparative Example 6).

[0082] Furthermore, the results from Comparative Example 7 show that when the polyvinyl chloride resin content was less than 10% by mass, in other words, when the total amount of calcium carbonate, plasticizer, glass wool, and other materials exceeded 90% by mass, mixing was not possible.

[0083] From the above results, it can be seen that the rigid board of the present invention exhibits excellent continuous formability in extrusion processing, maintains hardness, and exhibits minimal dimensional change.

[0084] Furthermore, the hard board of the present invention provides a flooring material that is hard and has minimal dimensional changes, making it possible to provide an inexpensive, high-quality flooring material that is easy for amateurs to handle.

[0085] Furthermore, the present invention is not limited to the embodiments described above. [Explanation of Symbols]

[0086] 1: Flooring 2: Hard board for flooring 3: Print sheet 4: Abrasion-resistant sheet 5: Soundproofing sheet

Claims

1. A hard board for flooring, It contains calcium carbonate, vinyl chloride resin, plasticizer, and glass wool. The calcium carbonate content is 55% by mass or more and 75% by mass or less. The content of the vinyl chloride resin is 10% by mass or more and 25% by mass or less. The plasticizer content is 5% by mass or more and 15% by mass or less. A rigid board made of a resin composition having a glass wool content of 0.5% by mass or more and 3.5% by mass or less.

2. A flooring material comprising a soundproofing sheet, a hard board as described in claim 1, a printed sheet, and an abrasion-resistant sheet arranged in order from the back side.

3. A method for manufacturing a hard board for flooring, A mixing step to obtain a mixture by mixing calcium carbonate in a ratio of 55% to 75% by mass, vinyl chloride resin in a ratio of 10% to 25% by mass, plasticizer in a ratio of 5% to 15% by mass, and glass wool in a ratio of 0.5% to 3.5% by mass. A kneading step in which the mixture is melted and kneaded to obtain a resin composition, A molding step of extruding the resin composition to obtain a sheet-like rigid board, A method for manufacturing rigid boards, including [the specified method].

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