JP2017008637A - Building board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a building board, which is an inorganic building plate having a core layer and a skin layer and resistant to freezing damage, specifically is less likely to cause interlayer detachment due to freezing damage.SOLUTION: A building board 1 comprises: a core layer 2 made of molding material containing hydraulic inorganic material; and a skin layer 3, which is made of a molding material containing hydraulic inorganic material and covers the core layer 2. Bone-dry specific gravity of the skin layer 3 is greater than that of the core layer 2. The bone-dry specific gravity of the skin layer 3 is 0.8 or greater and 2.0 or less, and that of the core layer 2 is 0.7 or greater or less than 2.0. Volume of all pores with diameter of 0.056 to 2 μm on the skin layer 3 and the core layer 2 is 0.25 ml/g or less.SELECTED DRAWING: Figure 1

Description

  The present invention generally relates to a building board, and more particularly to a building board formed of a molding material mainly composed of a hydraulic inorganic material and having a core layer and a skin layer covering the core layer.

  Conventionally, building boards made of materials such as cement and plaster are used for various building materials such as outer walls of buildings. Such building boards are formed in various structures from various materials. For example, in Patent Document 1, a base material layer mainly composed of a cement-based inorganic material and a silicic acid-containing substance, and a base material layer mainly composed of a cement-based inorganic material and a silicic acid-containing substance are formed. An inorganic plate consisting of a surface layer is described.

JP 2004-123399 A

  When an inorganic building board is used for an application such as an outer wall in a cold region, the so-called frost damage phenomenon, in which cracks are caused by repeated freezing and thawing of moisture absorbed by the building board, is a problem. In an inorganic plate having a plurality of layers as described in Patent Document 1, delamination due to a frost damage phenomenon is a particular problem.

  The present invention has been made in view of the above points, and provides a building board that has a core layer and a skin layer and is unlikely to cause delamination due to a frost damage phenomenon, that is, has a resistance to frost damage. With the goal.

The building board according to the present invention includes a core layer formed from a molding material containing a hydraulic inorganic material,
A skin layer that is formed from a molding material containing a hydraulic inorganic material and covers the core layer;
The absolute dry specific gravity of the skin layer is greater than the absolute dry specific gravity of the core layer, the absolute dry specific gravity of the skin layer is 0.8 or more and 2.0 or less, and the absolute dry specific gravity of the core layer is 0.7. And less than 2.0,
In each of the skin layer and the core layer, the volume of all pores having a diameter in the range of 0.056 to 2 μm is 0.25 ml / g or less.

  In the present invention, delamination between the skin layer and the core layer due to a frost damage phenomenon can be suppressed.

It is sectional drawing which shows an example of the building board which concerns on this invention. It is sectional drawing which shows the modification of the building board which concerns on this invention. It is sectional drawing which shows the modification of the building board which concerns on this invention. It is sectional drawing which shows the modification of the building board which concerns on this invention. It is an outline top view of the metal mold | die with which the extrusion machine used for manufacture of the building board which concerns on this invention, and the extrusion molding machine was equipped. FIG. 6 is a schematic sectional view of the mold shown in FIG. It is a perspective view of the modification of the core provided in the inside of the metal mold | die shown in FIG. FIG. 8A is a schematic plan view of a hollow formed body used in the present invention. FIG. 8B is a schematic side view of the hollow formed body shown in FIG. 8A. 9A to 9C are schematic cross-sectional views showing a procedure for measuring the adhesion strength between the skin layer and the core layer of the building board.

  Hereinafter, modes for carrying out the present invention will be described.

  First, the building board 1 which concerns on this embodiment is demonstrated.

  Although the shape of the building board 1 is not specifically limited, For example, it is a planar view rectangular shape. The building board 1 may be provided with a fitting portion for fitting with another building board 1 as necessary.

  As shown in FIG. 1, the building board 1 includes a core layer 2 and a skin layer 3 that covers the core layer 2. The thickness of the skin layer 3 is preferably in the range of 1 mm to 1/3 of the thickness of the entire building board 1, for example.

  The core layer 2 is formed from a molding material containing a hydraulic inorganic material. In this specification, the molding material used for forming the core layer 2 is referred to as a core material. The core material can contain, for example, an inorganic main material, an inorganic admixture, an organic admixture, a reinforcing fiber, and water.

  The inorganic main material is made of a compound containing at least one of silicon and calcium. The inorganic main material is mainly composed of cement, which is a hydraulic inorganic material. The inorganic main material can further contain one or more materials selected from the group consisting of fly ash, silica fume, and silica powder.

  Examples of the inorganic admixture include mica and sodium silicate.

  Examples of the organic admixture include methyl cellulose and organic foam particles. The organic foamed particles can contain, for example, one or more materials selected from the group consisting of styrene resins, vinylidene chloride resins, and acrylonitrile resins.

  The reinforcing fiber includes, for example, pulp and polypropylene fiber.

  In addition to the above raw materials, the core material may further contain an inorganic foam. The inorganic foam can contain, for example, one or more materials selected from the group consisting of pearlite, fly ash balloon, and vermiculite.

  The ratio of each substance contained in the core material is not particularly limited. For example, the core material contains 73 to 97% by weight of an inorganic main material, 1 to 20% by weight of an inorganic admixture, It is preferable that the admixture is contained in the range of 1 to 3.5% by weight and the reinforcing fiber is contained in the range of 1 to 3.5% by weight.

  The skin layer 3 is formed from a molding material containing a hydraulic inorganic material. In this specification, the molding material used for forming the skin layer 3 is referred to as a skin material. This skin material can contain, for example, an inorganic main material, an inorganic admixture, an organic admixture, reinforcing fibers, and water. The skin material may further contain an additive.

  The inorganic main material, the inorganic admixture, the organic admixture, and the reinforcing fiber included in the skin material are, for example, the inorganic main material, the inorganic admixture, the organic admixture, and the reinforcing fiber included in the core material. Is the same.

  The ratio of each substance contained in the skin material is not particularly limited. For example, the skin material contains 69.5 to 97.5% by weight of the inorganic main material and 1 to 20% by weight of the inorganic admixture. Of these, the organic admixture is preferably contained in the range of 1 to 3.5% by weight, and the reinforcing fibers are preferably contained in the range of 1 to 7% by weight.

  An uncured molded body (green sheet) is produced by molding the core material and the skin material. By curing and curing the uncured molded body, the building board 1 including the core layer 2 and the skin layer 3 is obtained.

  In the step of curing the uncured molded body, for example, one or more types of curing selected from the group consisting of room temperature curing, steam curing, and autoclave curing are performed. In this embodiment, it is particularly preferable to perform autoclave curing.

  In this autoclave curing, for example, an uncured molded body is cured within a range of 2 to 10 hours under conditions where the temperature is in the range of 150 to 180 ° C. and the atmospheric pressure is in the range of 0.5 to 1.0 MPa. It is preferable. In this case, the cement crystals are stabilized and the quality can be stabilized.

  Comparing the absolute dry specific gravity of the core layer 2 and the absolute dry specific gravity of the skin layer 3, the absolute dry specific gravity of the skin layer 3 is larger than that of the core layer 2, and the absolute dry specific gravity of the skin layer 3 is It is 0.8 or more and 2.0 or less, and the absolute dry specific gravity of the core layer 2 is 0.7 or more and less than 2.0.

  By reducing the weight of the core layer 2 by making the absolute dry specific gravity of the skin layer 3 greater than the absolute dry specific gravity of the core layer 2 and the absolute dry specific gravity of the core layer 2 and the skin layer 3 within the above range. The overall weight of the building board 1 is reduced and the strength of the skin layer 3 is made higher than that of the core layer 2 by making the skin layer 3 higher in density than the core layer 2. Can be improved.

  In particular, the difference in absolute dry gravity between the core layer 2 and the skin layer 3 is preferably 0.1 or more. In this case, the effect of coexistence of the weight reduction of the building board 1 whole by weight reduction of the core layer 2 and the improvement of the intensity | strength of the building board 1 whole by the improvement of the strength of the skin layer 3 is fully acquired.

  The absolute dry specific gravity of the core layer 2 and the skin layer 3 can be adjusted, for example, by changing the amount of water or the weight-reducing material contained in the core material and the skin material.

  Since the core layer 2 and the skin layer 3 are formed by curing a core material containing a hydraulic inorganic material and a skin material containing a hydraulic inorganic material, respectively, the core layer 2 and the skin layer 3 have a plurality of pores. Have. In the present embodiment, the volume of all pores having a diameter in the range of 0.056 to 2 μm in each of the core layer 2 and the skin layer 3 is 0.25 ml / g or less. Water easily enters pores having a diameter in the range of 0.056 to 2 μm, and the water that has entered the pores is difficult to escape. When the freezing and thawing of the water in the pores are repeated, the building board 1 expands and contracts, so that the building board 1 is easily damaged. However, in this embodiment, the core layer 2 and the skin layer 3 each have a diameter of 0.056 to 2 μm and the total pore volume in the core layer 2 and the skin layer 3 is 0.25 ml / g or less. The absorption of moisture in the skin layer 3 can be suppressed, so that the core layer 2 and the skin layer 3 are less likely to expand and contract. Thereby, delamination between the core layer 2 and the skin layer 3 due to a frost damage phenomenon can be suppressed. In addition, the volume of all the pores in the core layer 2 and the skin layer 3 each having a diameter in the range of 0.056 to 2 μm is a pore size distribution test method for a molded product by a mercury intrusion method defined in JIS R 1655. It is calculated from the measurement result by

  In each of the core layer 2 and the skin layer 3, the volume of all pores having a diameter in the range of 0.056 to 2 μm is, for example, the amount of water contained in the core material and the skin material, and the type of the inorganic main material In addition, at least one of the blending amounts can be adjusted by changing the autoclave time, temperature and the like.

  The adhesion strength between the core layer 2 and the skin layer 3 is preferably 0.7 MPa or more. In this case, delamination between the core layer 2 and the skin layer 3 due to a frost damage phenomenon can be further suppressed.

  The adhesion strength between the core layer 2 and the skin layer 3 can be measured, for example, as follows. First, as shown in FIG. 9A, a cut piece 60 of 40 mm × 40 mm is cut out from the building board 1 in plan view. Next, as shown in FIG. 9B, the test piece 61 having the interface 4 between the core layer 2 and the skin layer 3 is produced by cutting the cut piece 60 in a direction orthogonal to the thickness direction. At that time, the hollow holes of the core layer 2 are not included as much as possible. Next, as shown in FIG. 9C, a tensile test in the thickness direction of the test piece 61 is performed by an autograph in a state where the test piece 61 is fixed to the flat tension jig 7. Then, the adhesion strength between the core layer 2 and the skin layer 3 is calculated from the tensile force when the interface 4 between the core layer 2 and the skin layer 3 of the test piece 61 is damaged.

  The adhesion strength between the core layer 2 and the skin layer 3 is, for example, at least one of the amount of water contained in the core material and the skin material, the type and the amount of the lightweight aggregate, and the type and the amount of the inorganic main material. At least one of them can be adjusted by changing autoclave time, temperature and the like.

  The adhesion strength between the core layer 2 and the skin layer 3 can also be adjusted by the shape of the interface 4 between the core layer 2 and the skin layer 3. For example, compared with the case where the building board 1 has the flat interface 4 as shown in FIG. 1, the adhesion strength between the core layer 2 and the skin layer 3 is higher when it has the uneven interface 4 as shown in FIG. 2. improves. The interface 4 of the building board 1 shown in FIG. 2 has a rectangular uneven shape, but is not limited to this. For example, the interface 4 may be a triangular uneven shape (zigzag shape), and the interface 4 has an arc shape. An uneven shape (wave shape) may be used.

  Although the building board 1 of this embodiment is provided with the above-described configuration, delamination between the core layer 2 and the skin layer 3 due to the frost damage phenomenon occurs despite having the core layer 2 and the skin layer 3. Hateful.

  The structure of the building board 1 is not restricted to what is shown in FIG.1 and FIG.2. For example, a plurality of hollow holes 5 may be formed in the core layer 2 as in the building board 1 shown in FIGS. 3 and 4. That is, the building board 1 may have a hollow structure. When the building board 1 has a hollow structure, the building board 1 can be further reduced in weight.

  A sealer and a paint for surface finishing may be applied to the surface of the building board 1, that is, the surface of the skin layer 3, as necessary.

  Hereinafter, the manufacturing method of the building board 1 of this embodiment is demonstrated.

  The building board 1 shown in FIG. 1 is manufactured by, for example, extruding a core material and a skin material with an extruder 10. FIG. 5 shows an outline of the extruder 10.

  The extruder 10 shown in FIG. 5 includes a first extruder 11 and a second extruder 12. The first extruder 11 extrudes the skin material, and the second extruder 12 extrudes the core material. The first extruder 11 and the second extruder 12 are connected to the mold 100.

  As shown in FIG. 5, the mold 100 includes an inlet 103 at the front end and an extrusion port 104 at the rear end. The inlet 103 is connected to the first extruder 11. For this reason, the skin material flows into the inlet 103 from the first extruder 11.

  FIG. 6 shows a schematic sectional view of the mold 100. The mold 100 includes an upper mold 101, a lower mold 102, a core 105, a flow path 106, a flow path 107, and a flow path 108. The upper mold 101 and the lower mold 102 are stacked so as to face each other in the vertical direction.

  A cavity is formed inside the mold 100. A core 105 is provided in the cavity. The flow path 106 is between the lower surface of the upper mold 101 and the upper surface of the core 105 that appear in the sectional view of FIG. 6, and the flow path 107 is between the upper surface of the lower mold 102 and the lower surface of the core 105. It is. The channel 106 and the channel 107 are connected to the inlet 103. For this reason, the skin material flows through the channel 106 and the channel 107.

  As shown in the sectional view of FIG. 6, the core 105 gradually decreases in thickness from the vicinity of the inlet 103 toward the inlet 103. Further, the end of the core 105 on the side of the extrusion port 104 gradually decreases in thickness toward the extrusion port 104. The tip of the core 105 on the extrusion port 104 side is disposed so as to face the extrusion port 104. The upper surface of the tip portion of the core 105 is formed as a flat inclined surface 111 toward the tip, and the lower surface of the tip portion of the core 105 is formed as a flat inclined surface 112 toward the tip.

  As shown in the sectional view of FIG. 6, a flow path 108 is formed inside the core 105. This flow path 108 is connected to the second extruder 12. Specifically, the flow path 108 in the core 105 is connected to the second extruder 12 via the pipe 17. For this reason, the core material kneaded by the second extruder 12 flows into the flow path 108. A rectangular opening 110 that communicates with the flow path 108 is formed at the tip of the core 105.

  As shown in the cross-sectional view of FIG. 6, the flow path 106, the flow path 107, and the flow path 108 are joined at the extrusion port 104 side with respect to the flow path 106 and the flow path 107 in the mold 100. The part 109 joins. For this reason, the extrusion port 104 is connected to the channel 106, the channel 107, and the channel 108.

  Hereafter, the procedure in which the building board 1 is manufactured with said extrusion molding machine 10 is demonstrated.

  First, the skin material is charged into the inlet 13 of the first extruder 11 shown in FIG. 5, and the core material is charged into the inlet 15 of the second extruder 12 shown in FIG. The skin material and the core material are respectively conveyed while being kneaded by the screw 14 provided in the first extruder 11 and the screw 16 provided in the second extruder 12.

  Next, the core material flows from the second extruder 12 into the flow path 108 through the pipe 17. Further, the skin material flows from the first extruder 11 through the inlet 103 into the flow path 106 and the flow path 107.

  Next, the core material that has passed through the flow path 108 reaches the opening 110. The core material discharged from the opening 110 is formed into a plate shape in accordance with the shape of the opening 110. In addition, the skin material that has passed through the flow path 106 and the skin material that has passed through the flow path 107 merge at the merge portion 109. Thereby, the core material shape | molded by plate shape is wrapped with skin material.

  Next, the core material and the skin material are extruded from the extrusion port 104 while the core material is wrapped by the skin material. By cutting the core material and the skin material at an arbitrary length, an uncured molded body (green sheet) is formed. A building board 1 including the core layer 2 and the skin layer 3 is manufactured by curing and curing the uncured molded body.

  When the interface 4 between the core layer 2 and the skin layer 3 has an uneven shape as in the building board 1 shown in FIG. 2, for example, instead of the core 105 shown in FIG. 6, the core 205 shown in FIG. use. In the core 205, a plurality of concave portions 207 and a plurality of convex portions 208 are alternately arranged on portions corresponding to the flat inclined surface 111 and the flat inclined surface 112 of the core 105 shown in FIG. An inclined surface 206 is formed.

  An opening 110 is formed at the tip of the core 205 as the end of the flow path 108. The upper and lower sides of the opening 110 are the leading edges of the inclined surface 206, respectively. For this reason, as for the opening part 110 of the core 205, an upper side and a lower side have uneven | corrugated shape.

  When the building board 1 is manufactured using the mold 100 including the core 205, the core material is discharged from the opening 110 having an uneven shape on the upper side and the lower side. The bottom surface is formed into a shape having a plurality of irregularities. In addition, the skin material passing through the flow path 106 flows along the inclined surface 206 having a plurality of unevennesses, and the skin material passing through the flow path 107 flows along the inclined surface 206 having a plurality of unevennesses. For this reason, the skin material that has passed through the flow path 106 and the skin material that has passed through the flow path 107 merge with the core material at the merging portion 109 with a plurality of irregularities on the lower surface and the upper surface, respectively. The core material and the skin material are discharged from the extrusion port 110 while maintaining this state. By cutting the core material and the skin material at an arbitrary length, an uncured molded body (green sheet) is formed. By curing and curing the uncured molded body, a building board 1 having an uneven shape at the interface 4 between the core layer 2 and the skin layer 3 as shown in FIG. 2 is manufactured.

  In the core 205 illustrated in FIG. 7, the cross-sectional shape of the concave portion 207 and the convex portion 208 is rectangular, but is not limited thereto. For example, the cross-sectional shapes of the concave portion 207 and the convex portion 208 may be triangular. In this case, the interface 4 between the core layer 2 and the skin layer 3 can be formed into a triangular uneven shape (zigzag shape). Further, the cross-sectional shape of the concave portion 207 and the convex portion 208 may be an arc shape. In this case, the interface 4 between the core layer 2 and the skin layer 3 can be formed into an arcuate uneven shape (wave shape).

  When the building board 1 having a hollow structure as shown in FIG. 3 is manufactured, for example, a hollow formed body 300 shown in FIGS. 8A and 8B is used. The hollow forming body 300 includes a main body portion 301 and a plurality of protruding rods 302. The plurality of protruding bars 302 are arranged in a line at a predetermined interval and are provided in parallel to each other. The dimensions of the plurality of protruding bars 302 are the same. The hollow forming body 300 has a dimension that can be disposed inside the flow path 109.

  The hollow forming body 300 is provided, for example, in the flow path 108 of the core 105 shown in FIG. In this case, some of the plurality of protruding bars 302 protrude from the opening 110. A building board 1 having a hollow structure as shown in FIG. 3 is formed by providing a core 105 in which a hollow forming body 300 is provided in a flow path 108 in a mold 100 and performing extrusion molding using the mold 100. Is manufactured.

  Instead of the core 105 shown in FIG. 6, the hollow forming body 300 may be provided in the flow path 108 of the core 205 shown in FIG. 7. The building board 1 as shown in FIG. 4 is manufactured by extrusion molding using the mold 100 provided with the core 205.

  Hereinafter, the present invention will be specifically described by way of examples.

(Examples 1-4)
A core material and a skin material were prepared by blending an inorganic main material, an inorganic admixture, an organic admixture, a reinforcing fiber, and water in the proportions shown in Table 1 below. In addition, the water content in Table 1 is the ratio of water to the total solid content in each of the core material and the skin material.

  Said core material and skin material were shape | molded using the extrusion machine 10 provided with the metal mold 100 shown in the 1st extruder 11, the 2nd extruder 12, and FIG. 6, and the molded object was produced. The molded body was cured and cured at 160 ° C. in an autoclave, and further adjusted to a moisture content of 10% by a dryer, thereby having dimensions of width 200 mm, thickness 20 mm, length 500 mm, and As shown in FIG. 1, the building board 1 provided with the core layer 2 and the skin layer 3 was manufactured. The thickness of the skin layer 3 in this building board 1 is 2 mm.

(Example 5)
A core material and a skin material were prepared by blending an inorganic main material, an inorganic admixture, an organic admixture, a reinforcing fiber, and water in the proportions shown in Table 1 below. And it shape | molded using the 1st extruder 11, the 2nd extruder 12, and the extrusion molding machine 10 provided with the metal mold | die 100 shown in FIG. 7, and produced the molded object. After this molded body was cured by curing at 160 ° C. in an autoclave, the moisture content was further adjusted to 10% by a dryer, thereby having dimensions of width 200 mm, thickness 20 mm, and length 500 mm. As shown in FIG. 2, a building board 1 having a core layer 2 and a skin layer 3 and an interface 4 between the core layer 2 and the skin layer 3 having an uneven shape was manufactured. The thickness of the skin layer 3 in this building board 1 is 2 mm.

(Comparative Examples 1 and 2)
A core material and a skin material were prepared by blending an inorganic main material, an inorganic admixture, an organic admixture, a reinforcing fiber, and water in the proportions shown in Table 1 below. In addition, the water content in Table 1 is the ratio of water to the total solid content in each of the core material and the skin material.

  Said core material and skin material were shape | molded using the extrusion machine 10 provided with the metal mold 100 shown in the 1st extruder 11, the 2nd extruder 12, and FIG. 6, and the molded object was produced. The molded body was cured and cured at 160 ° C. in Comparative Example 1 and 120 ° C. in Comparative Example 2 in an autoclave, and then further adjusted to a moisture content of 10% by a dryer, thereby having a width of 200 mm and a thickness of 20 mm. A building board 1 having a length of 500 mm and having a core layer 2 and a skin layer 3 as shown in FIG. 1 was produced. The thickness of the skin layer 3 in this building board 1 is 2 mm.

(Evaluation)
About the building boards 1 of Examples 1-5 and Comparative Examples 1 and 2, the absolute dry specific gravity of the core layer 2 and the skin layer 3 was measured by the Archimedes method. The results are shown in Table 1 below.

  Moreover, about the construction board 1 of Examples 1-5 and Comparative Examples 1 and 2, the range of 0.056-2 micrometers in diameter of each of the core layer 2 and the skin layer 3 using Shimadzu Autopore IV 9510 The volume of all pores inside was measured. The results are shown in Table 1 below.

  Moreover, about the construction board 1 of Examples 1-5 and Comparative Examples 1 and 2, the adhesion strength between the core layer 2 and the skin layer 3 was measured by the above-mentioned method.

  Furthermore, the freeze-thaw test was done about the building boards 1 of Examples 1-5 and Comparative Examples 1 and 2. The freeze-thaw test was performed for 300 cycles in accordance with the in-frozen water-thaw test method (Method B) among the freeze-thaw test methods specified in JIS A 1148. By this test method, the delamination between the skin layer and the core layer of the building board 1 and the base material destruction of each of the skin layer and the core layer were evaluated. Regarding the delamination between the skin layer and the core layer, the case where many delaminations and breakage occurred was evaluated as x, the case where a small amount of delamination occurred, and the case where delamination did not occur were evaluated as ○. . In addition, regarding the base material destruction of the skin layer and the core layer, in each layer, the case where no breakage occurred was evaluated as ◯, and the case where the breakage occurred was evaluated as x. These results are shown in Table 1 below.

  As shown in Table 1, delamination of the building board 1 of Examples 1 to 5 is suppressed. Among these, since the adhesive strength of the core layer 2 and the skin layer 3 is 0.7 Mpa or more, especially the building board 1 of Examples 1-4 has suppressed delamination. This is the figure used for the production of the building board 1 of Examples 1 to 4 by the junction of the skin layer 3 and the core layer 2 of the mold shown in FIG. 7 used for the production of the building board 1 of Example 5. 6 is located on the exit side of the mold shown in FIG. 6, and the pressure at the time of joining the skin layer 3 and the core layer 2 is low and the distance is short. Therefore, in the building board 1 of Example 5, the core layer 2 and the skin layer 3 This is probably because the adhesion is slightly lowered.

  On the other hand, as for the building board 1 of the comparative example 1 whose absolute dry specific gravity of the core layer 2 is less than 0.7, many delamination has arisen by the freeze thaw test. This is because the core layer has a low absolute specific gravity, which increases the number of voids in the material before drying, making it difficult for pressure to be applied to the core material during extrusion molding. Therefore, the adhesion strength between the core layer and the skin layer is weak. This is thought to be because of this.

  In addition, the building board 1 of Comparative Example 2 in which the volume of all the pores in the diameter range of 0.056 to 2 μm of each of the core layer 2 and the skin layer 3 is 0.25 ml / g or more is frozen. In the melting test, base material destruction of the core layer 2 and the skin layer 3 occurs. This is considered to be because the pore volume of both the core layer 2 and the skin layer 3 is increased due to the low temperature of the autoclave.

  From these facts, “the absolute density of the skin layer 3 is larger than that of the core layer 2 and the absolute density of the skin layer 3 is 0.8 or more and 2.0 or less. Is 0.7 or more and 2.0 or less, and the volume of all pores in the skin layer 3 and the core layer 2 each having a diameter in the range of 0.056 to 2 μm is 0.25 ml / g or less ” The building boards 1 of Examples 1 to 5 that satisfy the above conditions are less likely to cause delamination in the freeze-thaw test than the building boards 1 of Comparative Examples 1 and 2 that do not satisfy these conditions, and the core layer 2 and the skin layer 3. The base material is less likely to break.

1 Building board 2 Core layer 3 Skin layer

Claims (2)

A core layer formed from a molding material containing a hydraulic inorganic material;
A skin layer that is formed from a molding material containing a hydraulic inorganic material and covers the core layer;
The absolute dry specific gravity of the skin layer is greater than the absolute dry specific gravity of the core layer, the absolute dry specific gravity of the skin layer is 0.8 or more and 2.0 or less, and the absolute dry specific gravity of the core layer is 0.7. And less than 2.0,
A building board in which the volume of all pores in the range of 0.056 to 2 μm in diameter in each of the skin layer and the core layer is 0.25 ml / g or less.   The building board according to claim 1, wherein the adhesion strength between the skin layer and the core layer is 0.7 MPa or more.

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