JP2007125745A - Glass fiber reinforced plastic material, glass fiber reinforced plastic prepreg, glass fiber reinforced plastic layer and lng tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass fiber reinforced plastic material and a glass fiber reinforced plastic prepreg both of which are strong against a cold heat shock at an extremely low temperature, excellent in liquidtight reliability and suitable for constituting the secondary barrier layer of a ground LNG tank, a glass fiber reinforced plastic layer formed using them and the LNG tank. <P>SOLUTION: The glass fiber reinforced plastic material includes surface protective layers 41 wherein a reinforcing glass fiber comprises a long fiber glass mat, heat stress support layers 42 wherein the reinforcing glass fiber comprises a glass fiber fabric and a liquidtight layer 43 wherein the reinforcing glass fiber comprises a short fiber glass mat, and the respective layers are impregnated with a synthetic resin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a glass fiber reinforced plastic material, a glass fiber reinforced plastic prepreg, a glass fiber reinforced plastic layer, and an LNG tank that are resistant to thermal shock at extremely low temperatures and have excellent liquid-tight reliability.

  In recent years, natural gas has attracted attention as a clean energy due to global environmental problems, and the demand for it has been increasing. Liquid natural gas (LNG) is a natural gas mainly composed of methane, which is cooled and liquefied at ultra-low temperatures after removing impurities such as moisture, sulfur compounds, and carbon dioxide. The LNG tank is an apparatus for holding and storing liquefied natural gas at −163 ° C. or lower, and an above-ground type LNG tank and an underground type LNG tank are known.

  Among these, in particular, in a ground type LNG tank, a double-shell type LNG tank composed of an inner tank and an outer tank is generally used. In the double shell type LNG tank, 9% Ni steel has usually been used as the material of the inner tank that contacts the LNG. 9% Ni steel has a low coefficient of linear expansion and is a member having excellent strength and toughness without causing brittle fracture even at a low temperature of −163 ° C. or lower that can maintain LNG in a liquid state.

  However, 9% Ni steel has a large specific gravity and is difficult to construct such as welding. Moreover, Ni which is insufficient on a global scale is used for 9% Ni steel, which is not preferable as a material for an LNG tank, for which demand will continue to increase. Further, the 9% Ni steel having sufficient strength and toughness as described above is difficult to manufacture because it requires a special heat treatment technique. For this reason, 9% Ni steel is expensive and there is no situation in which high performance 9% Ni steel is sufficiently supplied. There is a need for new materials that can be used as tanks in LNG tanks instead of 9% Ni steel.

  Non-Patent Document 1 describes an underground LNG tank in which fiber reinforced plastic is applied to an LNG contact surface. In such an underground LNG tank, the inner tank that becomes the LNG contact surface is a panel made of fiber reinforced plastic, the glass wool with aluminum foil is wound around it, the hard polyurethane foam is wound around the outside, and the outside is surrounded by reinforced concrete. The outer side of reinforced concrete has a structure that supports the load with soil.

  However, the above structure can be applied to an underground LNG tank that can support the liquid load of LNG with a water depth of 30 to 40 m and a diameter of 60 to 100 m by earth pressure, but the hydraulic pressure holding strength of the steel material is high. Since it is not sufficient, it cannot be applied to the above ground type LNG tank which needs to support the liquid load of LNG with steel materials.

  Therefore, the present inventors are an above-ground type LNG tank that is composed of a material that has strength, toughness, and cold insulation, and is lightweight and easy to construct, and is characterized by its secondary barrier layer. The LNG tank was developed first (Japanese Patent Application No. 2005-053162).

This ground type LNG tank is composed of a material that replaces 9% Ni steel, and is composed of at least such an inner tank and an outer tank, and a gap between the inner tank and the outer tank is filled with a heat insulating material. Thus, a secondary barrier layer is further provided between the inner tank and the outer tank, and the secondary barrier layer is made of a resin-based barrier material. And the said secondary barrier layer functions as an emergency barrier at the time of LNG leak, can respond to the thermal contraction at the time of LNG leak, and was sufficiently excellent in the liquid pressure holding strength, gas barrier property, and liquid tightness at the time of LNG leak It is a ground type LNG tank.
However, further improvement in performance has been desired for the secondary barrier layer.
Nikkei Sangyo Shimbun, 13 pages, November 30, 1978

  In view of the above circumstances, the present invention is a glass suitable for constituting the secondary barrier layer of the above-mentioned ground type LNG tank by being resistant to thermal shock at extremely low temperatures and having excellent liquid-tight reliability. An object of the present invention is to provide a fiber reinforced plastic material, a glass fiber reinforced plastic prepreg, a glass fiber reinforced plastic layer formed using these, and an LNG tank.

  In order to achieve the above object, the present invention is a glass fiber reinforced plastic material, wherein the reinforcing glass fiber is made of a long fiber glass mat, and the thermal stress supporting layer is made of a glass fiber fabric. And a liquid-tight layer in which the reinforcing glass fiber is made of a short fiber glass mat, and each of the layers is impregnated with a synthetic resin.

  In a preferred embodiment of the glass fiber reinforced plastic material according to the present invention, the liquid-tight layer is a central layer, and the surface protective layer and the thermal stress support layer are provided symmetrically with respect to the stacking direction.

  Moreover, the glass fiber reinforced plastic material which concerns on this invention is the suitable embodiment, The said synthetic resin is a flame-retardant vinyl ester resin.

  In another aspect, the present invention is a glass fiber reinforced plastic prepreg, and the glass fiber reinforced plastic prepreg is obtained by semi-curing the synthetic resin contained in the glass fiber reinforced plastic material according to the present invention.

  In another aspect, the present invention is a glass fiber reinforced plastic layer, and is formed by curing the synthetic resin contained in the glass fiber reinforced plastic material. Further, the synthetic resin contained in the glass fiber reinforced plastic prepreg is completely cured.

  Furthermore, the present invention is an LNG tank according to another aspect, the LNG tank is provided with at least an inner tank and an outer tank, and a ground type is formed by filling a gap between the inner tank and the outer tank with a heat insulating material. The LNG tank further includes a secondary barrier layer between the inner tank and the outer tank, and the secondary barrier layer is configured using the glass fiber reinforced plastic layer according to the present invention.

  Furthermore, the present invention is a glass fiber reinforced plastic material for a secondary barrier layer of an above-ground LNG tank according to another aspect, comprising at least an inner tank and an outer tank, and insulating the gap between the inner tank and the outer tank. It is used for an above-ground LNG tank that is filled with a material and further includes a secondary barrier layer between the inner tank and the outer tank.

  Furthermore, the present invention is a glass fiber reinforced plastic prepreg for a secondary barrier layer of a ground type LNG tank according to another aspect, comprising at least an inner tank and an outer tank, and insulating the gap between the inner tank and the outer tank. It is used for an above-ground LNG tank that is filled with a material and further includes a secondary barrier layer between the inner tank and the outer tank.

  According to the present invention, the glass fiber reinforced plastic material suitable for constituting the secondary barrier layer of the above-mentioned ground type LNG tank by being strong in thermal shock at extremely low temperature and excellent in liquid-tight reliability. And a glass fiber reinforced plastic prepreg, a glass fiber reinforced plastic layer formed using these, and an LNG tank.

  The glass fiber reinforced plastic material and the glass fiber reinforced plastic prepreg according to the present invention, and the glass fiber reinforced plastic layer and the LNG tank formed using them will be described in more detail with respect to preferred embodiments thereof.

  A glass fiber reinforced plastic material according to the present invention includes a long fiber glass mat to be a surface protective layer, a glass fiber fabric to be a thermal stress support layer, and a short fiber glass mat to be a liquid-tight layer, each of these layers. And impregnated with synthetic resin. Synthetic resin can be impregnated by impregnating all of these layers at once, impregnating each layer, impregnating two of these layers and impregnating the remaining layer separately. it can. Even if not impregnated all at once, they adhere to each other by the adhesive strength of the synthetic resin used.

The glass fiber reinforced plastic material according to the present invention can be made into a glass fiber reinforced plastic prepreg with good handling properties by semi-curing the contained synthetic resin.
A glass fiber reinforced plastic layer can be formed by curing a synthetic resin contained in such a glass fiber reinforced plastic material or glass fiber reinforced plastic prepreg.
Such a glass fiber reinforced plastic layer can be employed as a secondary barrier layer of an above-ground LNG tank.

  In the secondary barrier layer, when microcracks or delamination occurs on the surface layer due to thermal shock, the cracks or delamination generated in each part may be combined to form a through crack and leak. The glass fiber reinforced plastic layer according to the present invention is resistant to thermal shock and excellent in liquid-tight reliability as a laminated structure combining fiber types.

  The glass fiber reinforced plastic material according to the present invention preferably has the liquid-tight layer as a central layer, and the surface protective layer and the thermal stress support layer are provided symmetrically with respect to the stacking direction. This prevents warping on one side. In addition, when joining two or more glass fiber reinforced plastic materials, intentionally formed an asymmetric part at the edge, and using a joining slip piece having a cross-sectional shape along the warped edge It is also possible to cover from above.

  The surface protective layer is composed of a long fiber glass mat (surface mat). Since the long fiber glass mat is a dense glass fiber layer with one fiber as a unit, the wettability of the fiber / resin interface is increased. Therefore, the occurrence of microcracks against thermal shock can be prevented. Moreover, it acts also as a protective layer which protects the inside of the glass fiber reinforced plastic layer which makes | forms a laminated structure.

In the long fiber glass mat, a glass long fiber having a diameter of about 3 μm to 13 μm is preferably used.
Glass is roughly divided into alkali-free type and alkali-containing type depending on the alkali content, but the former is excellent in electrical and mechanical properties, and is called E glass because it is used in the field of electrical relations. The latter is called C glass because it has high chemical resistance and is used for chemical applications. In addition, since C glass has a high alkali content, ECR glass using titanium and zinc-based fluxes has been developed at the same time as reducing the alkali content, and is widely used in place of C glass. Furthermore, glasses such as A glass, L glass, and S glass are also known. In general, E glass is suitable as the long glass fiber used in the present invention.

Further, as the long glass fiber, a filament yarn obtained by simply arranging filaments can be preferably used. Usually, the average fiber length is 30Mm～80mm, standard mass is ^{300g / m 2 ~600g / m 2} . Preferably, the standard mass is ^{400g / m 2 ~500g / m 2} . Optimally, the standard mass is 450 g / m ² .
And the long fiber glass mat which orientated such a glass long fiber at random is normally comprised by the thickness (at the time of resin hardening) of 0.1 mm-0.3 mm.

The thermal stress support layer is made of a glass fiber fabric. The glass fiber fabric is a roving fabric having a mechanical isotropy (roving: a bundle of fibers in units of several tens to several hundreds). The thermal stress support layer composed of such a glass fiber fabric strongly resists thermal stress. Further, the thermal stress support layer itself is prevented from being deformed out of the plane and has an effect of preventing delamination from the liquid-tight layer.
As the glass fiber constituting the glass fiber fabric, E glass can be preferably used.
In such a glass fiber, the single fiber constituting the warp or the weft has either a diameter of about 8.5 to 9.5 μm or a single fiber cross-section constituting the warp and the weft. Is approximately 5.5 to 7.5 μm in diameter.

  The warp and weft are produced by aligning a plurality of single fibers. When either of the diameters of the single fibers constituting the warp or the weft is 8.5 to 9.5 μm, about 200 to 800 single fibers are drawn together. Moreover, when the diameter of the cross section of the single fiber constituting the warp and the weft is about 5.5 to 7.5 μm, about 200 to 400 single fibers are aligned to produce each yarn. In addition, as a form of warp and weft, for example, a plurality of single fibers may be arranged and twisted, or a non-twisted yarn obtained by arranging a plurality of single fibers may be used.

  As a yarn in which a plurality of single fibers are aligned and twisted, for example, by twisting a commonly used glass yarn (about 0.7 to 1.0 turns / inch), that is, By setting the number of twists to about 0.5 times / inch or less, preferably about 0 to 0.3 times / inch, the yarn width is more easily expanded, and there is substantially no gap between adjacent warp and weft yarns. It becomes easy to form an arrayed structure. Further, by using a low twist yarn, the yarn is flattened, the cross-sectional shape of the yarn itself approaches the shape of a flat plate from an elliptical shape, and the distribution of the glass fibers in the glass cloth becomes more uniform.

Also, the standard weight of the glass fiber fabric is ^{400g / m 2 ~700g / m 2} . Preferably, the standard mass is ^{500g / m 2 ~600g / m 2} . Optimally, a plain weave cloth with a standard mass of 580 g / m ² is employed. For example, R580 H 100K manufactured by Unitika Glass Fiber can be used.
And a glass fiber fabric is normally comprised by the thickness (at the time of resin hardening) of 0.3 mm-0.6 mm.

  The liquid-tight layer is composed of a short fiber glass mat (chopped strand mat). The short fiber glass mat is easy to introduce a synthetic resin and has a large adhesion area between the synthetic resin and the glass fiber, so that the synthetic resin hardly flows down even when a molding pressure is applied, thereby forming a liquid-tight layer. In addition, because of the increased amount of synthetic resin, it is firmly bonded to the adjacent thermal stress support layer, and by placing such a liquid-tight layer on the neutral surface, it is possible to reduce interlaminar deformation and reduce delamination It has become.

The short fiber glass mat is preferably a glass fiber filament spun from platinum bushing and having a fiber diameter of 10 μm to 13 μm. As the glass to be employed, E glass can be preferably used.
Such a glass fiber filament is preferably coated with a sizing agent after spinning from a platinum bushing. The sizing agent is a product obtained by dispersing an emulsion of a thermoplastic resin and a silane coupling agent made of an organic silane compound or the like in water.
It is preferable that glass fiber filaments coated with a sizing agent having a fiber diameter of 10 μm or more and 13 μm or less are bundled into 70 strands and 200 strands to form strands.

The production of a strand by bundling glass fiber filaments coated with a sizing agent having a fiber diameter of 10 μm or more and 13 μm or less to a number of filaments of 70 or more and 200 or less is a general production condition in strand production, It is possible to use a general cake obtained by winding a strand in a thread form, and it is preferable to use such a cake from the viewpoint of economy.
While pulling a strand from such a cake, it is cut with a cutter and cut to a length of 1 cm to 10 cm, preferably about 5 cm, to form a short fiber.

A short fiber glass mat can be obtained by randomly orienting such short fibers and forming them into a mat material.
Also, the standard weight of the short fiber glass mat is ^{300g / m 2 ~600g / m 2} . Preferably, the standard mass is ^{400g / m 2 ~500g / m 2} . Optimally, a standard mass of 450 g / m ² is employed. For example, EM450 SS manufactured by Unitika Glass Fiber can be used.
And a short fiber glass mat is normally comprised by the thickness (at the time of resin hardening) of 0.2 mm-0.8 mm.

  The synthetic resin impregnated into the glass fiber reinforced plastic material is preferably a flame retardant vinyl ester resin having a flame retardance of 26 or more and an ductility of 2% or more at −163 ° C. . Such a resin has a self-extinguishing property, and is easy to extend even at −163 ° C. and hardly causes cracks. This flame-retarded vinyl ester resin is a resin obtained by blending a brominated vinyl ester resin and a plastic vinyl ester, and a resin made by Nippon Iupika Co., Ltd. can be suitably used.

  The thickness of the glass fiber reinforced plastic layer after curing is preferably 2 mm to 8 mm as a whole, preferably 4 mm to 5 mm. Thermal load is the product of linear expansion coefficient, temperature difference, Young's modulus, and cross-sectional area of the plate. On the other hand, the load that can be supported is the product of the adhesive strength and the lap area. Since there is an upper limit of adhesive strength and lap area, there is a limit to increasing the cross-sectional area of the plate. The layer thickness is therefore limited.

  The glass fiber reinforced plastic layer according to the present invention is most preferably applied to a secondary barrier layer of a ground type double shell LNG tank. The above ground type double-shell LNG tank includes at least an inner tank and an outer tank. LNG is accommodated in the inner tank.

  The embodiment of FIG. 1 shows such a ground type double-shell LNG tank 1, and the outer tub 3 has a cylindrical shape with a circular flat bottom. A cylindrical secondary barrier layer 4 having a circular flat bottom is provided on the inner wall of the outer tub 3 via a gap. The secondary barrier layer 4 has a side wall height lower than the side wall height of the outer tub 3, and is attached to the inner side wall of the outer tub 3 by an anchor portion 9. The gap is provided between the bottom of the outer tub 3 and the bottom of the secondary barrier layer 4 and between the inner wall of the outer tub 3 and the outer wall of the secondary barrier layer 4. The gap between the outer tub 3 and the secondary barrier layer 4 is filled with a secondary cold insulation material 7. Further, a support material 10 is provided at a position between the bottom of the outer tub 3 and the bottom of the secondary barrier layer 4 and located immediately below the side wall of the inner tub 2. The support material 10 transmits a load to a pile (not shown) installed in the soil below the bottom surface of the outer tub.

  A secondary cold insulator 7 is spread on the bottom of the secondary barrier layer 4. The inner tank 2 is installed inside the secondary barrier layer 4 via the secondary cold insulator 7. The inner tank 2 is a cylindrical container having a flat bottom. The inner tank 2 can accommodate LNG therein. The gap between the inner tank 2 and the secondary barrier layer 4 and the gap between the inner tank 2 and the outer tank 3 are filled with a powdered cold insulating material 5.

  Further, the ground type double shell LNG tank 1 is provided with a lid (not shown), piping for LNG carrying-out means, carrying-in means, etc., and the LNG 8 is held in a sealed state in the inner tank 2.

Next, each component which comprises the ground type double shell LNG tank 1 is demonstrated.
The inner tank 2 has a depth of about 30 m to about 40 m, a diameter of about 60 m to about 100 m, and preferably can accommodate about 100 to 200,000 kl of LNG. And it has a cold-retaining function that can store LNG in liquid form at -163 ° C., liquid and air tightness to prevent LNG and gasified LNG from leaking to the outside, and strength that can withstand the load of LNG with the above capacity. Prepare. In the present embodiment, the inner tank 2 is made of a resin-based barrier material in which glass fiber reinforced plastic is applied to the LNG contact surface instead of the conventionally used 9% Ni steel.

The cylindrical inner tub 2 according to the present embodiment includes a side wall portion and a bottom portion. The resin-based barrier material constituting the inner tank 2 is composed of a plurality of layers. The resin-based barrier material is laminated in a direction perpendicular to the LNG contact surface of the inner tank 2 at both the side wall and the bottom.
FIG. 2 is an enlarged conceptual view of a part of the resin-based barrier material. The resin barrier material 2 constituting the inner tank is composed of a glass fiber reinforced plastic layer 21, a foam glass layer 22, a resin layer 23, a polyurethane foam layer 24, a primer layer 25, a general structure in order from the LNG contact surface 20 of the inner tank 2. This is a member in which steel for steel 26 is laminated.

  The glass fiber reinforced plastic material 21 that comes into contact with LNG is a material having a liquid barrier function that hardly causes cracks even when NG is repeatedly carried in and out at -163 ° C. The glass fiber reinforced plastic material 21 in the present embodiment is provided with a glass fiber stitch material on the LNG contact surface, a resin having ductility and flame retardancy, and a glass fiber cloth having at least shrinkage isotropic properties. Is preferably a laminate in which a plurality of layers are alternately laminated. Such a laminate can be manufactured by a vacuum impregnation method.

Specifically, the stitch material is preferably made of glass fiber. The stitch material refers to a material in which a plurality of weft glass fibers are stacked on a plurality of warp glass fibers and the intersections are fastened by an appropriate adhesive means. The stitch material is characterized by having no swell unlike that formed by weaving fibers like cloth. The glass fiber cloth having isotropic shrinkage is preferably a glass fiber plain weave cloth having a standard mass of 400 to 600 g / m ² . Such glass fiber cloth has a relatively small eye and is less likely to be distorted when it comes into contact with LNG at -163 ° C. About both the said stitch material and glass fiber cloth, as glass fiber, the product made from common E glass may be sufficient.

  The resin is preferably a flame retardant vinyl ester resin having flame retardancy with an oxygen index of 26 or higher and ductility with strain at −163 ° C. of 2% or higher. Such a resin has a self-extinguishing property, and is easy to extend even at −163 ° C. and hardly causes cracks.

  If the stitch material is present on the LNG contact surface of the glass fiber reinforced plastic material, the number of repeated laminations of the resin and the glass fiber cloth layer is appropriately determined according to the required thickness of the glass fiber reinforced plastic material. be able to. The glass fiber reinforced plastic material thus obtained has high airtightness because it has few bubbles and has a fiber content of about 65% or more. Moreover, the crack of resin can be prevented by using a stitch material with few waviness for an LNG contact surface.

  In the present embodiment, the glass fiber reinforced plastic material 21 applied to the LNG contact surface may be a molded and completely cured panel or a prepreg sheet. In the case of preparing a prepreg sheet, for example, a thermosetting resin component containing a UV curing agent can be contained in the resin, and the resin can be completely cured after being attached to a target location. The prepreg sheet of glass fiber reinforced plastic material is particularly useful in that it can be completely covered by being cured after being attached to a panel-shaped glass fiber reinforced plastic material joint or the like.

According to another aspect, the glass fiber reinforced plastic material 21 used in the present embodiment is a sheet-like member, and the resin layer is sandwiched between at least two layers of the glass fiber reinforced plastic material. It may be a layered sheet material. Such a sheet material is formed on an NS tape (non-sanding tape) by vacuum impregnating the above-mentioned glass fiber stitch material, a resin having ductility and flame retardancy, and a glass fiber cloth having at least shrinkage isotropic property. To form the first glass fiber reinforced plastic layer, spray the resin on the NS tape side of the first glass fiber reinforced plastic layer before the glass fiber reinforced plastic layer hardens, The second glass fiber reinforced plastic layer that has been molded and cured in advance can be bonded together. The resin layer is preferably composed of a vinyl ester resin excellent in adhesiveness and gas barrier properties.
Such a three-layer sheet material of glass fiber reinforced plastic is particularly advantageous in that it can be formed into a free shape such as a curved surface and can be easily bonded. In addition, the first glass fiber reinforced plastic layer and the second glass fiber reinforced plastic layer protect the resin layer as a thermal relaxation material, and the resin layer prevents the development of micro cracks in the glass fiber reinforced plastic caused by thermal shock. Therefore, gas barrier properties are maintained. Further, since the interface between the glass fiber reinforced plastic layer and the resin layer is a resin, it has good wettability and has an advantage of being strong against interfacial peeling.

Such a glass fiber reinforced plastic material can be used not only as a member constituting a resin-based barrier material, but also as a barrier material for securing liquid-tightness independently. Specifically, it can be used for covering protection of the joint portion of the inner tank of the LNG tank.
In addition, this invention relates to the glass fiber reinforced plastic material suitable for the secondary barrier layer mentioned later. The glass fiber reinforced plastic material 21 of the present embodiment can be replaced by such a glass fiber reinforced plastic material according to the present invention.

  In addition, in this embodiment, when using as a member which comprises a resin-type barrier material, it is preferable that the layer thickness of the glass fiber reinforced plastic material 21 is 2-10 mm. This is to ensure a liquid barrier function.

  The foam glass layer 22 is a first cold insulation layer, and is located on the side opposite to the LNG contact surface of the glass fiber reinforced plastic material 21. Foam glass is a material that has cold-retaining properties and can withstand a thermal shock caused by the penetration of LNG vaporized gas. The foam glass 22 layer preferably has a thickness of 20 to 60 cm. This is to ensure the cold insulation function. In this embodiment, foam glass is used as the first cold insulation layer in contact with the glass fiber reinforced plastic material 21. However, other cold insulation materials having a cold insulation function and a characteristic capable of withstanding the thermal shock of LNG can be used. .

  The resin layer 23 is located on the side opposite to the glass fiber reinforced plastic material of the foam glass layer 22. The resin layer 23 has a function of adhering the foam glass layer 22 and the polyurethane foam layer 24 provided outside the resin layer 23 and a gas barrier function of preventing the LNG vaporized gas from entering the polyurethane foam layer 24. It is preferable to use an adhesive comprising a vinyl ester resin as the resin. Alternatively, a vinyl ester sheet material having an adhesive function can be used as the resin layer. The thickness of the resin layer 23 is preferably 1 to 3 mm.

  The polyurethane foam layer 24 is a second cold insulation layer, has a cold insulation function, and protects the general structural steel 26 located outside thereof from cold heat. The thickness of the polyurethane foam layer 24 is preferably such that the stainless steel material 26 can be sufficiently cooled, and can be, for example, 25 cm to 40 cm. In this embodiment, the polyurethane foam layer is used as the second cold insulation layer. However, other materials that have a layer containing a large amount of an air layer (such as a foam layer), have low thermal conductivity, and are inexpensive. It can also be used. It is preferable that the second cold insulation layer is easy to foam and has easy workability such that no harmful gas is emitted even when burned.

  The primer layer 25 has a function of adhering the polyurethane foam layer 24 and the general structural steel located outside thereof, and a gas barrier function. In particular, as the primer material, it is preferable to use a material having a high low-temperature ductility that can prevent shear peeling between the polyurethane foam 24 layer as a cold insulation layer and the general structural steel 26 as a steel material. Specifically, a vinyl ester primer can be used. The thickness of the primer layer 25 may be about 0.5 mm to 3 mm, and can usually be about 1 mm to 3 mm.

  The general structural steel 26 holds the liquid pressure of LNG accommodated in the inner tank 2 and has a gas barrier function. The general structural steel 26 is preferably used in terms of cost, but other carbon steels can also be used. The layer thickness of the general structural steel 26 is preferably formed with a gradient so that the top portion is thin and the bottom portion is thick in the resin-based barrier material constituting the side wall of the inner tank 2. This is in order to adapt to the hydraulic pressure of the LNG accommodated so as to have a depth of 40 m or more. Specifically, the radial thickness at the top of the side wall is preferably about 10 mm to 20 mm, and the radial thickness near the bottom of the side wall is preferably about 60 mm to 80 mm. Moreover, it is preferable that the general structural steel 26 which comprises the bottom part of the inner tank 2 is about 5 mm-10 mm in thickness.

  Thus, the resin-based barrier material in which the glass fiber reinforced plastic layer 21, the foam glass layer 22, the resin layer 23, the polyurethane foam layer 24, the primer layer 25, and the general structural steel 26 are laminated is combined with the characteristics of each layer, It has liquid barrier properties, gas barrier properties, cold insulation properties, and liquid pressure retention strength. And each layer is fully adhere | attached and the deformation | transformation by peeling etc. can be prevented. For this reason, it can be applied to sufficiently construct the inner tub 2 as a steel material replacing the 9% Ni steel that has been conventionally used. In addition, in this embodiment, although the resin-type barrier material was demonstrated as the said layer structure, it is not limited to the said layer structure. For example, the foam glass layer 22 and the polyurethane foam layer 24 may be a first cold insulation layer and a second cold insulation layer made of different materials having the same cold insulation function, and each cold insulation layer includes a plurality of cold insulation layers. You may be comprised from. In addition, the resin-based barrier material of the present invention can further include another layer as long as the function and adhesiveness of each layer are not impaired.

  When the bottomed cylindrical inner tub 2 in the present embodiment is composed of the resin-based barrier material, both the bottom and side walls of the inner tub 2 have a layer of general structural steel 26 at the outermost portion, and the general structure The primer 25 layer is located on the inner wall of the steel 26, the polyurethane foam 24 is located on the inner wall of the primer 25 layer, the resin layer 23 is located on the inner wall of the polyurethane foam 24, and the foam glass 22 is located on the inner wall of the resin layer 23 The glass fiber reinforced plastic 21 is located on the inner wall of the foam glass 22. The LNG contact surface of the inner tub 2 is covered with the glass fiber reinforced plastic 21.

  In manufacturing the inner tank 2, first, the side wall and the bottom of the inner tank 2 are manufactured by welding with the general structural steel 26. General structural steel can be easily constructed by welding, and gas barrier properties can be ensured by welding construction. A primer 25, a polyurethane foam 24, a resin layer 23, a foam glass 22 layer, and a glass fiber reinforced plastic layer 21 can be sequentially formed inside the side wall and bottom of the general structural steel 26.

  The primer layer 25 can be applied directly to a general structural steel 26 with a liquid primer material. The polyurethane foam layer 24 can be foamed in situ to a desired thickness. The resin layer 2 can be applied directly to the surface of the polyurethane foam layer 24 with a liquid resin adhesive. Alternatively, a vinyl ester sheet material having an adhesive function can be stretched on the surface of the polyurethane foam layer 24.

  The glass fiber reinforced plastic material 21 can be formed by attaching a prepreg sheet of glass fiber reinforced plastic material or a panel of glass fiber reinforced plastic material to the surface of the foam glass layer 22.

  As described above, the inner tub 2 made of the resin-based barrier material to which the glass fiber reinforced plastic material 21 is applied has sufficient liquid tightness, air tightness, and cold insulation and can withstand liquid loads. it can.

  In the above ground type double shell LNG tank 1 according to the present embodiment, the outer tub 3 can be formed from a prestressed concrete material. A prestressed concrete material is a material in which a compressive force is applied in advance by a steel material to increase resistance to tensile force. The prestressed concrete material can be lighter than a reinforced concrete member and has excellent durability and water tightness. The outer tub 3 can be designed such that the side wall height is about 40 m to 50 m and the diameter of the circular bottom is about 80 m to 100 m. However, since the thickness and size of the outer tub 3 vary depending on the amount of LNG accommodated, those skilled in the art can design the size of the outer tub 3 so as to match the desired LNG capacity. In addition, a moisture barrier layer (not shown) made of general structural steel can be provided on the inner wall of the outer tub 3.

  The secondary barrier layer 4 is provided on the inner wall of the outer tub 3 and has liquid tightness. The secondary barrier layer 4 is an emergency barrier when the inner tank 2 is damaged and LNG leaks out. As the secondary barrier layer 4, a glass fiber reinforced plastic layer formed using the glass fiber reinforced plastic material according to the present invention is provided.

FIG. 3 shows an embodiment of such a secondary barrier layer 4.
The secondary barrier layer 4 includes a surface protective layer 41, a thermal stress support layer 42, and a liquid-tight layer 43. The secondary barrier layer 4 includes a long fiber glass mat to be the surface protective layer 41, a glass fiber fabric to be the thermal stress support layer 42, and a short fiber glass mat to be the liquid-tight layer 43. It is formed by impregnating a synthetic resin and curing the synthetic resin. The long fiber glass mat, the glass fiber fabric, the short fiber glass mat, and the synthetic resin are the same as described above.
As shown in FIG. 3, the liquid-tight layer 43 is a central layer, and the surface protective layer 41 and the thermal stress support layer 42 are provided symmetrically with respect to the stacking direction. This prevents warping on one side.

The glass fiber reinforced plastic material is made into a glass fiber reinforced plastic prepreg having good handleability by semi-curing the contained synthetic resin, and a plurality of such prepregs are joined and completely cured, whereby the secondary barrier layer 4 Can be formed.
Then, as shown in FIG. 4, when two or more glass fiber reinforced plastic prepregs are joined, an asymmetric part is intentionally formed at the edge, and the cross-sectional shape along the warped edge 44 is formed. It is also possible to cover the joint from above using the joint slip piece 45.

  And the surface protection layer 41 of FIG. 2 is comprised with the long fiber glass mat (surface mat) as above-mentioned. Since the long fiber glass mat is a dense glass fiber layer with one fiber as a unit, the wettability of the fiber / resin interface is increased. Therefore, the occurrence of microcracks against thermal shock can be prevented. Also, it acts as a protective layer for protecting the inside of the secondary barrier layer 4 having a laminated structure.

  The thermal stress support layer 42 is made of a glass fiber fabric as described above. The glass fiber fabric is a roving fabric having a mechanical isotropy (roving: a bundle of fibers in units of several tens to several hundreds). The thermal stress support layer composed of such a glass fiber fabric strongly resists thermal stress. Further, the thermal stress support layer 42 itself is prevented from being deformed out of plane, and has an effect of preventing delamination from the liquid-tight layer 43.

  The liquid-tight layer 43 is composed of a short fiber glass mat (chopped strand mat) as described above. The short fiber glass mat is easy to introduce a synthetic resin and has a large adhesion area between the synthetic resin and the glass fiber, so that the synthetic resin hardly flows down even when a molding pressure is applied, thereby forming a liquid-tight layer. Further, since the amount of the synthetic resin increases, it is firmly bonded to the adjacent thermal stress support layer 42, and by arranging such a liquid-tight layer 43 on the neutral surface, the interlayer deformation is reduced and the delamination is reduced. It has a laminated structure. That is, the formability as a whole is improved by the presence of the liquid-tight layer 43.

  As described above, the layers appropriately share the attributes that the secondary barrier layer 4 should have. The thermal stress support layer 42 has a fiber structure that is difficult to be impregnated with the synthetic resin. However, the thermal stress support layer 42 is easily impregnated with the synthetic resin by being sandwiched between the surface protective layer 41 and the liquid-tight layer 43 that are easily impregnated with the synthetic resin.

  Here, referring back to FIG. 1, the powder cold insulation material 5 is a powdery cold insulation material that has heat insulating properties and is easily filled in the gap between the secondary barrier layer 4 and the inner tank 2, and does not react with LNG. Things can be used. This is because the LNG 8 accommodated in the inner tank 2 is kept at -163 ° C., and when LNG leaks from the inner tank 2, a dangerous reaction is prevented from occurring. Specifically, pearlite can be used as the powder cold insulator 5.

  The primary cold insulating material 6 is filled in the gap between the bottom of the inner tank 2 and the bottom of the secondary barrier layer 4. As the primary cold insulation material 6, it is preferable to use an inexpensive and firm cold insulation material. This is because a large surface pressure is received from the bottom of the inner tank 2. Specifically, glass wool can be used. As the secondary cooling material 7, it is preferable to use a material having a surface pressure holding function. This is because a large surface pressure is received from the bottom of the inner tank 2. Specifically, a rigid polyurethane foam can be used.

  As the support material 10, a material having a cold insulation function and a load holding function of the outer wall of the inner tank can be used. In particular, pearlite concrete is preferable.

As described above, the above-described double-shell LNG tank 1 according to the embodiment of FIG. 1 includes the inner tank 2 and the secondary barrier layer 4 made of a resin-based barrier material that is inexpensive, lightweight, and excellent in functionality. Therefore, it has sufficient liquid-tightness, airtightness, and cold insulation as a whole, and is advantageous in terms of cost.
In the present embodiment, the ground type double-shell LNG tank is described, but the present invention is not limited to the double-shell LNG tank. A person skilled in the art can produce a multishell LNG tank as required.

Further, the above ground type LNG tank can be configured as a square above ground type double shell type LNG tank.
When a conventional 9% Ni steel material is used for the inner tank, an inner tank having a circular bottom is preferably employed because of problems such as welding technology. However, if the inner tub 2 is formed of a resin-based barrier material, the general structural steel 26 that forms the outer wall of the inner tub 2 can be easily welded, and the inner wall of the inner tub 2 forms the LNG contact surface. Since the glass fiber reinforced plastic material 21 can be stuck in a sheet shape, the rectangular shape is easier to apply. In addition, the square double-shell LNG tank does not require bending and is easy to install. Further, when the inner diameter is the same as compared with a double-shell type LNG tank having a circular bottom surface, the capacity can be increased, so that a single tank can accommodate a high capacity LNG, which is advantageous. is there.

As a long fiber glass mat, a surface mat manufactured by Nittobo Co., Ltd. (standard mass is 450 g / m ² ), as a glass fiber fabric, R580 H 100K manufactured by Unitika Glass Fiber Co., Ltd. (standard mass is 580 g / m ² ), As a short fiber glass mat, EM450 SS (standard mass is 450 g / m ² ) manufactured by Unitika Glass Fiber Co., Ltd. was adopted. Each fiber was impregnated with a blend resin (flame-retardant vinyl ester resin) manufactured by Nippon Iupika Co., Ltd., and pasted in the same manner as in the embodiment of FIG.
As a comparative example, only R810 H 100K (standard mass is 810 g / m ² ) manufactured by Unitika Glass Fiber Co., Ltd. was used as a glass fiber fabric, and impregnated with polyurethane resin manufactured by INOAC Co., Ltd. and cured.
In the example, the initial failure stress was 200 MPa, and the fracture strength was 490 Pa. On the other hand, in the comparative example, the initial failure stress was 70 MPa and the fracture strength was 300 Pa.
The performance of the example was significantly improved.

A description will be given of the initial failure stress.
As a characteristic of the composite material, cracks and separation of fibers and resin (generally referred to as initial failure) occur locally before the final breakage. At the time of occurrence, the load is always reduced, the sound is generated, and the inclination of the load-displacement diagram is changed, so that the initial failure stress can be grasped quantitatively. Under the load before the initial breakage occurs, the composite material is not damaged at all, and thus liquid-tightness is guaranteed (confirmed by the penetration inspection test). In addition, since a liquid-tight test at a low temperature is physically impossible, the initial failure stress can be treated as a measure of the liquid-tight limit at a low temperature.

It is the schematic which shows the cross section of the ground type double shell LNG tank which concerns on one embodiment of this invention. It is the conceptual diagram which expanded a part of resin-type barrier material. It is the schematic which shows the cross section of the glass fiber reinforced plastic layer which concerns on one embodiment of this invention. It is a conceptual sectional view explaining the form which laminates the glass fiber reinforced plastic prepreg concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground type double shell LNG tank 2 Inner tank 3 Outer tank 4 Resin type secondary barrier layer 5 Powder cold insulation material 6 Primary cold insulation material 7 Secondary cold insulation material 20 LNG contact surface 21 Glass fiber reinforced plastic layer 22 Foam glass layer 23 Resin Layer 24 Polyurethane foam layer 25 Primer layer 26 Stainless steel material 27 Polyurethane foam 41 Surface protective layer 42 Thermal stress support layer 43 Liquid tight layer

Claims (9)

  A surface protective layer in which the reinforcing glass fibers are made of a long fiber glass mat, a thermal stress support layer in which the reinforcing glass fibers are made of a glass fiber fabric, and a liquid-tight layer in which the reinforcing glass fibers are made of a short fiber glass mat, A glass fiber reinforced plastic material obtained by impregnating each layer with a synthetic resin.   A glass fiber reinforced plastic material, wherein the liquid-tight layer is a central layer, and the surface protective layer and the thermal stress support layer are provided symmetrically with respect to the stacking direction.   The glass fiber reinforced plastic material according to any one of claims 1 to 4, wherein the synthetic resin is a flame retardant vinyl ester resin.   A glass fiber reinforced plastic prepreg obtained by semi-curing the synthetic resin contained in the glass fiber reinforced plastic material according to any one of claims 1 to 3.   A glass fiber reinforced plastic layer formed by curing the synthetic resin contained in the glass fiber reinforced plastic material according to claim 1.   A glass fiber reinforced plastic layer formed by completely curing the synthetic resin contained in the glass fiber reinforced plastic prepreg according to claim 4.   A ground-type LNG tank comprising at least an inner tank and an outer tank, and a gap between the inner tank and the outer tank is filled with a heat insulating material, and the secondary tank is interposed between the inner tank and the outer tank. An LNG tank, further comprising a barrier layer, wherein the secondary barrier layer is configured using the glass fiber reinforced plastic layer according to claim 5 or 6.   A ground type LNG tank comprising at least an inner tank and an outer tank, a space between the inner tank and the outer tank is filled with a heat insulating material, and a secondary barrier layer is further provided between the inner tank and the outer tank. A glass fiber reinforced plastic material for a secondary barrier layer of the above-mentioned ground type LNG tank, which is a glass fiber reinforced plastic material for a secondary barrier layer used in the above.   A ground type LNG tank comprising at least an inner tank and an outer tank, a space between the inner tank and the outer tank is filled with a heat insulating material, and a secondary barrier layer is further provided between the inner tank and the outer tank. A glass fiber reinforced plastic prepreg for a secondary barrier layer for a secondary barrier layer of a ground type LNG tank, comprising the glass fiber reinforced plastic prepreg for a secondary barrier layer used in the above.

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